Flexible Energy Conversion and Storage Devices E-Book

• Herausgeber: Wiley-VCH Verlag GmbH & Co. KGaA
• Kategorie: Fachliteratur
• Sprache: Englisch

Seitenzahl: 951

Veröffentlichungsjahr: 2018

Beschreibung

Provides in-depth knowledge of flexible energy conversion and storage devices-covering aspects from materials to technologies

Written by leading experts on various critical issues in this emerging field, this book reviews the recent progresses on flexible energy conversion and storage devices, such as batteries, supercapacitors, solar cells, and fuel cells. It introduces not only the basic principles and strategies to make a device flexible, but also the applicable materials and technologies, such as polymers, carbon materials, nanotechnologies and textile technologies. It also discusses the perspectives for different devices.

Flexible Energy Conversion and Storage Devices contains chapters, which are all written by top researchers who have been actively working in the field to deliver recent advances in areas from materials syntheses, through fundamental principles, to device applications. It covers flexible all-solid state supercapacitors; fiber/yarn based flexible supercapacitors; flexible lithium and sodium ion batteries; flexible diversified and zinc ion batteries; flexible Mg, alkaline, silver-zinc, and lithium sulfur batteries; flexible fuel cells; flexible nanodielectric materials with high permittivity for power energy storage; flexible dye sensitized solar cells; flexible perovskite solar cells; flexible organic solar cells; flexible quantum dot-sensitized solar cells; flexible triboelectric nanogenerators; flexible thermoelectric devices; and flexible electrodes for water-splitting.

-Covers the timely and innovative field of flexible devices which are regarded as the next generation of electronic devices
-Provides a highly application-oriented approach that covers various flexible devices used for energy conversion and storage
-Fosters an understanding of the scientific basis of flexible energy devices, and extends this knowledge to the development, construction, and application of functional energy systems
-Stimulates and advances the research and development of this intriguing field

Flexible Energy Conversion and Storage Devices is an excellent book for scientists, electrochemists, solid state chemists, solid state physicists, polymer chemists, and electronics engineers.

Leseprobe

Table of Contents

Cover

Preface

Chapter 1: Flexible All‐Solid‐State Supercapacitors and Micro‐Pattern Supercapacitors

1.1 Introduction

1.2 Potential Components and Device Architecture for Flexible Supercapacitors

1.3 Flexible Supercapacitor Devices with Sandwiched Structures

1.4 Flexible Micro‐Supercapacitor Devices with Interdigitated Architecture

1.5 Performance Evaluation and Potential Application of Flexible Supercapacitors

1.6 Conclusions and Perspectives

References

Chapter 2: Fiber/Yarn‐Based Flexible Supercapacitor

2.1 Introduction

2.2 Supercapacitor with Intrinsic Conductive Fiber/Yarn

2.3 Supercapacitors with Intrinsic Nonconductive Fiber/Yarn

2.4 Integrated Electronic Textiles

2.5 Conclusion and Outlook

References

Chapter 3: Flexible Lithium Ion Batteries

3.1 Overview of Lithium Ion Battery

3.2 Planar‐Shaped Flexible Lithium Ion Batteries

3.3 Fiber‐Shaped Flexible Lithium Ion Batteries

3.4 Perspective

References

Chapter 4: Flexible Sodium Ion Batteries: From Materials to Devices

4.1 Introduction to Flexible Sodium Ion Batteries (SIBs)

4.2 The Key Scientific Issues of Flexible SIBs

4.3 Design of Advanced Materials for Flexible SIBs

4.4 Design of Full Cell for Flexible SIBs

4.5 Summary and Outlook

References

Chapter 5: 1D and 2D Flexible Carbon Matrix Materials for Lithium–Sulfur Batteries

5.1 Introduction

5.2 The Working Mechanism and Challenges of Li–S Batteries

5.3 Flexible Cathode Hosts for Lithium–Sulfur Batteries

5.4 Electrolyte Membranes for Flexible Li–S Batteries

5.5 Separator for Flexible Li–S Batteries

5.6 Summary

References

Chapter 6: Flexible Electrodes for Lithium–Sulfur Batteries

6.1 Introduction

6.2 Lithium–Sulfur Battery and Flexible Cathode

6.3 The Flexible Cathode of Lithium–Sulfur Battery

6.4 Summary and Prospect

References

Chapter 7: Flexible Lithium–Air Batteries

7.1 Motivation for the Development of Flexible Lithium–Air Batteries

7.2 State of the Art for Flexible Lithium–Air Batteries

7.3 Challenges and Future Work on Flexible Lithium–Air Batteries

7.4 Concluding Remarks

References

Chapter 8: Nanodielectric Elastomers for Flexible Generators

8.1 Introduction

8.2 Electro‐Mechanical Principles

8.3 Increasing the Performance of Dielectric Elastomers from the Materials Perspective

8.4 Circuits and Electro‐Mechanical Coupling Methods

8.5 Examples of Dielectric Elastomer Generators

8.6 Conclusion and Outlook

Acknowledgments

References

Chapter 9: Flexible Dye‐Sensitized Solar Cells

9.1 Introduction

9.2 Materials and Fabrication of Electrodes for FDSCs

9.3 Sensitizers in FDSCs and Thin Photoactive Film DSCs

9.4 Electrolyte and Hole‐Transporting Materials for FDSCs

9.5 Conclusion and Outlook

References

Chapter 10: Self‐assembly in Fabrication of Semitransparent and Meso–Planar Hybrid Perovskite Photovoltaic Devices

10.1 Introduction

10.2 Summary and Future Perspective

References

Chapter 11: Flexible Organic Solar Cells

11.1 Introduction

11.2 Active Layer

11.3 Flexible Electrode

11.4 Interfacial Layer

11.5 Tandem Organic Solar Cells

11.6 Fabrication Technology for Flexible Organic Solar Cells

11.7 Summary

References

Chapter 12: Flexible Quantum Dot Sensitized Solar Cells

12.1 Introduction

12.2 Basic Concepts

12.3 Development of the Flexible QDSSCs

12.4 Conclusion and Future Outlook

Acknowledgments

References

Chapter 13: Flexible Triboelectric Nanogenerators

13.1 Introduction

13.2 Materials Used for Flexible Triboelectric Nanogenerators

13.3 Flexible Triboelectric Nanogenerators for Harvesting Ambient Energy

13.4 Flexible Triboelectric Nanogenerators for Self‐Powered Sensors

13.5 Flexible Triboelectric Nanogenerators for Self‐Charging Power Units

13.6 Flexible Triboelectric Nanogenerators for Hybrid Energy Cells

13.7 Service Behavior of Triboelectric Nanogenerators

13.8 Summary and Prospects

References

Chapter 14: Flexible Thermoelectric Materials and Devices

14.1 Introduction

14.2 Thermoelectric Energy Conversion Basics

14.3 Flexible Thermoelectric Materials

14.4 Flexible Thermoelectric Energy Harvesters

14.6 Transverse TE Devices

14.8 Thermoelectric Sensors

14.9 Summary and Outlook

References

Chapter 15: Carbon‐based Electrocatalysts for Water‐splitting

15.1 Introduction

15.2 Nonmetal‐doped Carbon for HER

15.3 Metals Embedded in Carbon for HER

15.4 Electrochemistry

15.5 Outlook and Future Challenges

References

Index

End User License Agreement

List of Tables

Chapter 8

Table 8.1 EAPs classification.

Chapter 9

Table 9.1 PCE of FDSCs with different substrates for photo‐electrode.

Table 9.2 Averaged normal and steady state lateral forces of films prepared by different slurries [28].

Table 9.3 The PCE of FDSCs according to the photo‐electrode preparation processes.

Table 9.4 PCE of FDSCs with different counter‐electrode preparation processes.

Table 9.5 Photovoltaic parameters of sensitizers in flexible and conventional DSCs according to sensitizers.

Table 9.6 Photovoltaic parameters of sensitizers in DSCs with various film thicknesses.

Table 9.7 Summary of electrolyte composition for flexible dye‐sensitized solar cells.

Chapter 10

Table 10.1 Photovoltaic parameters, average transparency (%) between 400 and 800 nm, and coverage (%) of the various semitransparent cells.

Table 10.2 Photovoltaic parameters of the various HTM‐free semitransparent cells, resulted from similar assembly‐solution concentration.

Table 10.3 Photovoltaic performance of the best performing cells during the forward scan, the average values from the four cells of each type are provided in parenthesis.

Chapter 14

Table 14.1 Comparison between different energy scavenging mechanisms.

Table 14.2 Material properties: Seebeck coefficient

S

, electrical conductivity

ρ

, and thermal conductivity

κ

at 298 K.

Chapter 15

Table 15.1 Summary of heteroatom‐doped metal‐free catalysts for HER.

Table 15.2 Summary of metal@carbon catalysts for HER.

List of Illustrations

Chapter 1

Figure 1.1 Ragone plot for various types of energy storage devices.

Figure 1.2 (a) Schematic structure of an EDLC. . (b) (i) Helmholtz model, (ii) Gouy–Chapman model, and (iii) Stern model of double layer.

Figure 1.3 Schematic structures of (a) SWCNT and (b) MWCNT.

Figure 1.4 Schematic structure of one single‐layer graphene.

Figure 1.5 Chemical structures of PPy, PANi, PTh, and PEDOT (undoped form).

Figure 1.6 Schematic diagrams of flexible supercapacitors with (a) conventional sandwiched structure and (b) interdigitated structure.

Figure 1.7 (a) Schematic illustration of the process for fabricating the transparent and stretchable supercapacitor. (b) CV curves (at scan rate of 0.1 V s

−1

), and (c) charge–discharge curves (at constant current density of 0.2 A g

−1

) of the supercapacitor under different states. (d) Normalized specific capacitance of the supercapacitor as a function of tensile strain.

Figure 1.8 (a) Schematic illustration of fabrication of rGO/PVP composite film and the diffusion of the electrolyte onto the surfaces of rGO sheets. (b) Photograph and (c) tensile stress–strain property of the flexible rGO/PVP film. (d) CV curves of the solid‐state device based on the rGO

55

/PVP

45

composite film with a thickness of 2.4 μm in various bending states (scan rate = 100 mV s

−1

).

Figure 1.9 (a) Cross‐sectional SEM image of a porous graphene paper. (b) Photograph of the porous graphene paper demonstrating its flexibility. (c) Schematic procedure to fabricate a solid‐state supercapacitor from porous graphene paper. (d) Photograph of the flexible device at a bending state. (e) CV curves of the flexible device at bending and relaxation state (scan rate = 10 mV s

−1

).

Figure 1.10 (a–d) Schematic illustration of the fabrication of LSG. (e) SEM images of GO and LSG. Schematic of (f) a conventional structured device and (g) a solid‐state device based on LSG (Inset in (g) indicates the flexibility of the device). (h) CV curves of the devices at different bending angles.

Figure 1.11 (a) SEM image of the SWCNT network. (b) Photograph of an SWCNT network based flexible supercapacitor. (c) SEM images of the wrinkled graphene film. (d) Photographs of the wrinkled graphene‐based flexible supercapacitor device at different stretching states.

Figure 1.12 (a) Schematic diagram of the preparation of the PANi‐rGO/cellulose fiber composite paper. (b) Schematic diagram of an all‐solid‐state integrated supercapacitor device. (c) CV curves of the all‐solid‐state supercapacitor under different deformation conditions (scan rate: 2 mV s

−1

). Normalized specific capacitance of the all‐solid‐state supercapacitor under (d) bending and (e) folding states.

Figure 1.13 (a) Photographs of the solid‐state supercapacitor made of carbon nanoparticles/MnO

2

nanorods hybrid electrode and a carbon cloth at normal, bent, and twisted state. The image on the right shows a red LED turned on by three supercapacitors connected in series. (b) CV curves for the solid‐state supercapacitor at different bending angles.

Figure 1.14 A schematic of fabrication process for interdigitated microelectrodes of PANi nanowire arrays on a flexible film.

Figure 1.15 (a–h) Schematic illustrations of the fabrication procedure for the on‐chip fMSCs with AMA stacked hybrid electrodes and single AMA sandwiched hybrid electrode units. (i) Schematic diagram of the ion diffusion pathway in the AMA stacked hybrid electrodes. (j) A photograph of a large area of printed interdigitated patterns on a flexible PET film. (k) A photograph of the as‐prepared on‐chip fMSCs with AMA stacked hybrid electrodes.

Figure 1.16 Schematic diagrams of (a) screen printing, (b) gravure printing, (c) inkjet printing, and (d) micro‐extrusion printing.

Figure 1.17 (a–c) Illustration of the fabrication procedure for an in‐plane fMSC with interdigital fingers. SEM images of (d) a 46 nm thick PANi‐G nanosheet and (e) PPy‐G nanosheet. (f) SEM image and (g) schematic illustration of micrometer‐thick 2D nanohybrid film, showing a layer‐stacked structure. (h,i) Cross‐sectional SEM images of a 2D nanohybrid film. (j) SEM image of the 2D nanohybrid film with a tilt angle of 30°.

Figure 1.18 Fabrication of graphene based MSC (a–c) Schematic diagrams showing the fabrication process for an LSG microsupercapacitor. (d,e) Photographs of more than 100 micro‐devices produced on a single run on a flexible substrate.

Figure 1.19 (a) Schematic diagram of the fabrication of all‐solid‐state rGO‐PEDOT/PSS based planar fMSCs on a flexible PET film using laser‐cutting technique. (b) Photos of laser‐etched fMSCs with different configurations on one rGO‐PEDOT/PSS film. (c) SEM image of an fMSC (20) pattern (top view).

Figure 1.20 Demonstration and measurement of electrical signals of the energy supply devices. (a) Image of the devices applied to a knit shirt and connected by conductive threads (TEGs size: 1.5 cm × 6 cm). (b) Open‐circuit voltage, and (c) rectified current generated by the TEG from arm swings. (d) The generated charge accumulation from TEG at different frequencies. (e) Demonstration of the human activity sensor. The generated electricity was recorded during the illustrated jogging activity. (f) Charging of various capacitors with TEG. (g) Electric circuit diagram for the pressure sensor. (h) Digital photo of the pressure sensor. Side view (top), top view (bottom). (i) Schematic diagram of the pressure sensing mechanism. Original state (top), under pressure (bottom). (j) Resistance change of the pressure sensor. (k) Change of current in the SC as a function of the pressure applied to the pressure sensor.

Figure 1.21 (a) Circuit diagram of an integrated system. (b) Photograph of a fragmentized graphene foam (FGF) sensor attached on the skin of a neck.

Chapter 2

Figure 2.1 (a) Specific power against specific energy, namely Ragone plot, for different electrical energy storage devices. (b) Two categories of electrode materials: electrochemical double‐layer capacitor (EDLC) and pseudocapacitor, with different charge storage process.

Figure 2.2 (a) Illustration of activation steps for CFTs, which can be assembled into a long‐fiber SC and woven into a dragonfly knot. (b) Spinning process for continuous CNTs/PANi yarn. (c) Schematic demonstration of the coaxial spinning process and images of GO@CMC fiber.

Figure 2.3 (a) Schematics of stainless yarn fabrication and modification, photographs of the energy storage textiles made of SC yarns. (b) Schematic illustration of CuO@AuPd@MnO

2

NWs fabrication process and assembly of coaxial SC.

Figure 2.4 (a) Schematics of SMSC fabrication and its shape memory effect. (b) Schematic illustration of SMSCs woven with traditional yarns to form a textile.

Figure 2.5 (a) Photograph of fiber based asymmetric SC and its CV curves. (b) Schematic illustration of the integrated system and incident light intensities under illumination. (c) Architecture of the linear SC based on metal filament and CNT yarn, corresponding SEM images of bare filament Cu, Cu + CNT electrode, and final SC device (from left to right).

Figure 2.6 (a) Schematic of spinning process of UY and its original/stretched state. (b) Schematic of modification process and a complete all‐solid‐state SC, insets are image of stretchable UY based electrodes. (c) Schematic of CT modified by GHs/MWCNTs, a 50 cm long GHs/MWCNTs‐CT, and photographs of an all‐solid‐state SC embedded in a fabric that is bendable.

Figure 2.7 (a) Schematic of fabrication process of rGO/Ni cotton yarn. (b) Image of a 500‐m‐long Ni‐coated cotton yarn. (c) Schematic of the SC yarn. (d) A fabric made by solid‐state SC yarn and pristine cotton yarns. (e) Schematic of PPTA SC fabrication and testing.

Figure 2.8 (a) Schematic of all‐solid‐state yarn SC, photographs of a 1‐m‐long Ni‐coated polyester yarn, comparison between pristine polyester yarn (white), Ni‐coated yarn (silver), and rGO‐Ni‐yarn (black). (b) Photograph of a fabric woven with five yarn SCs and cotton yarns. (c) Schematic of a TENG cloth and its working mechanism. (d) Photograph of a self‐charging textile woven with a TENG fabric and a yarn SC fabric, and a voltage profile of three yarn SCs in series charged by the TENG fabrics.

Figure 2.9 (a) Schematic of all‐solid‐state, coaxial and integrated “energy fiber.” (b) Schematic of the circuit connection in charging and discharging. (c) Charging/discharging curve with a current during the discharging process. (d) Photograph of two “energy fibers” woven into a flexible textile.

Chapter 3

Figure 3.1 Specific energy densities of the different rechargeable batteries.

Figure 3.2 Schematic representation and operating principles of Li ion batteries during discharge process.

Figure 3.3 The dependence of the total capacity of a lithium ion battery (

C

battery

) on the anode capacity (

C

A

). In the battery, LiCoO

2

with the theoretical capacity of 147 mAh g

−1

is taken as cathode.

Figure 3.4 (a) Schematic illustration of fabricating process for LTO/CNTs or LCO/CNTs hybrid films. (b) (left) LTO/CNTs film coated on stainless steel substrate; (middle) the double layer film being separated from the stainless steel substrate in DI water; and (right) the final dried flexible hybrid film. (c) Schematic illustration of the lamination process. (d) Schematic structure of the final paper Li‐ion battery device and the picture of the un‐encapsulated Li‐ion paper battery. (e) Picture of the paper battery lighting a red LED. (f) Galvanostatic charging/discharging profile of the assembled paper battery in the first cycle. (g) Self‐discharge performance of the LTO–LCO full battery being charged to 2.6 V. The inset is the cyclic performance of the paper full battery.

Figure 3.5 (a) Schematic illustration of the synthesis process of 3D ZnCo

2

O

4

nanowire arrays/carbon cloth. (b–e) SEM images of the ZnCo

2

O

4

nanowire arrays grown on carbon cloth at different magnifications. Scale bars in (b–e) are 200, 20, 5, and 1 µm, respectively. The inset in (b) is the digital image of the produced flexible electrode at rolled state. (f) Schematic illustration for the structure of the flexible full lithium ion battery based on 3D ZnCo

2

O

4

nanowire arrays/carbon cloth, LiCoO

2

and liquid electrolyte. (g) Photographic images of the assembled flexible full lithium ion battery. (h) Charge–discharge profiles of the 1st, 2nd, 20th, and 40th cycles of the flexible full battery. (i) The voltage versus specific capacity profiles of the flexible full battery before and after 30, 60, 90, and 120 cycles of bending.

Figure 3.6 Schematic and characterization of thin, lightweight, and flexible full battery based on Li

4

Ti

5

O

12

/graphene foam and LiFePO

4

/graphene foam hybrid electrodes. (a) Schematic illustration of the full battery containing a cathode and an anode. (b, c) SEM images of Li

4

Ti

5

O

12

/graphene foam at low and high magnifications. (d) TEM image of Li

4

Ti

5

O

12

sheet on graphene foam. (e) Photograph of the

poly(dimethylsiloxane)

(

PDMS

) encapsulated flexible full battery lighting a red LED device under bending state. (f) Galvanostatic charge/discharge profiles of the as‐fabricated flat flexible full battery (red lines) and bent battery after repeatedly bending to a radius of 5 mm 20 times (blue lines), respectively. (g) Cyclic performance of the battery under flat and bent states.

Figure 3.7 (a) SEM image of web‐like Li

4

Ti

5

O

12

anode. (b) Charge–discharge profiles at 2 C of the full battery. (c) Photograph of full battery at bent state lighting an LED.

Figure 3.8 (a) Schematic illustration of the produced c‐GPE composed of ETPTA, liquid electrolyte and Al

2

O

3

nanoparticles. (b) c‐GPE mixture before UV‐crosslinking reaction. (c)

Thermal gravity analysis

(

TGA

) profiles showing difference in thermal stability compared to a conventional liquid electrolyte (1 M LiPF

6

in EC/DEC = 1/1 v/v) and c‐GPE. (d) Cyclic stability containing capacity retention with cycling as well as coulombic efficiency of a cell based on lithium metal/flat‐shaped c‐GPE/LiCoO

2

cathode.

Figure 3.9 (a) Schematic illustration of the fabrication process and chemical structure of N‐PCPE, along with a photograph showing its mechanical flexibility. (b) Time evolution of ionic conductivity for PCE, N‐PCPE, and conventional carbonate‐based liquid electrolyte at 80 °C. (c) SEM image of N‐PCPE (thickness ≈ 25 µm) with the plastic crystal polymer electrolyte matrix successfully impregnated into PET nonwoven skeleton. (d) Photograph of an LED lightened by an N‐PCPE‐based flexible lithium ion battery under severely wrinkled state. (e) Charge/discharge profiles at current density of 0.2 C of the wrinkled N‐PCPE‐based flexible lithium ion battery before and after cycling.

Figure 3.10 (a) Schematic illustration of a general cable battery. (b) Schematic illustration of the cable battery with hollow‐helix anode having multiple helix structure. (c) First charge and discharge profiles of cable batteries. (d) Photographs of a highly flexible cable battery under bent state. (e) The cable battery exhibited stable operation even when bent.

Figure 3.11 (a) Schematic illustration of a stretchable lithium ion battery including its exploded view layout of the various layers in the battery structure and the illustration of “self‐similar” serpentine geometries used for the interconnects. (b) Optical image of the cathode current collector (Al electrode pads) and self‐similar interconnects on a Si wafer. (c) Optical image of the Al electrode after transfer printing on a sheet of silicone. (d) Optical images and corresponding

finite element analysis

(

FEA

) of deformation mode for deferent levels of applied tensile strain (

ε

) and the interconnect structures after releasing the applied strain. The color in the FEA results represents the maximum principal strains of the metal layer. The scale bars in (b–d) are 2 mm. (e) Output power as a function of applied biaxial strain. (f, g) Optical images of a battery connected to a red light‐emitting diodes (LED) while unstretched and biaxially stretched to 300%, respectively.

Figure 3.12 (a) Exploded view of the multilayer structure of conventional

lithium ion batteries

(

LIB

s) in the planar state. (b) Illustration of 45° Miura folding in the unfolded and (c) folded states. (d) Photograph of an unfolded origami battery powering a green LED. (e) Photograph of a completely compressed origami battery powering a green LED. (f) Capacity retention (left axis, black) and coulombic efficiency (right axis, red) as a function of cycle number under planar and completely compressed state at 20 and 40 mA g

−1

, respectively.

Figure 3.13 (a) Schematic illustration to a fiber‐shaped lithium ion battery with lithium wire as anode and CNT/MnO

2

composite fiber as cathode. (b) SEM image of aligned CNT fiber. (c, d) SEM images of CNT/MnO

2

composite fibers with MnO

2

weight contents of 0.5% and 4.1%, respectively. (e) Voltage profiles of the fiber‐shaped lithium ion batteries with 4.1 wt% of the MnO

2

in CNT/MnO

2

composite fiber during charge and discharge process at a current of

5 × 10

−4

 mA. (f) Dependence of specific capacitance for a battery wire derived from the

multi‐walled carbon nanotube

(

MWCNT

)/MnO

2

composite fiber with MnO

2

weight percentage of 4.1.

Figure 3.14 (a) Schematic illustration to the preparation of the aligned CNT/Si composite fiber. (b, c) SEM images of a bare aligned CNT fiber and an aligned CNT/Si composite fiber with Si weight percentage of 38.1%, respectively. (d) Typical charge–discharge curves of a half lithium‐ion battery based on the bare aligned CNT and aligned CNT/Si composite fibers with a Si weight percentage of 38.1% at 1 A g

−1

. (e) Dependence of specific capacity on cycle number for the composite fiber after bending for 100 cycles at 2 A g

−1

.

C

0

and

C

correspond to the specific capacities at the first and following cycle, respectively.

Figure 3.15 (a) Schematic illustrations of the fabrication process of weavable CNT/Si composite fiber and textile. (b) SEM image of CNT/Si composite fibers wrapped round a copper rod, showing excellent flexibility. (c) SEM image of a textile woven from CNT/Si fibers. (d) Voltage profiles of CNT and CNT/Si composite fiber with Li metal as the counter electrode at 1st cycle with an operation voltage range of 0.1–1.0 V and a charge rate of

C

/5.

Figure 3.16 (a) Schematic illustration of the synthesis of high‐performance composite CNT/LMO and CNT–CNT/Si fibers. (b) Schematic illustration to the fabrication of the coaxial fiber full lithium ion battery. Red core stands for a cotton fiber. (c) Voltage profiles of the fiber‐shaped lithium ion battery at 1 C between 2.0 and 4.3 V. (d) Long‐life performance of the fiber‐shaped lithium ion battery between 2.0 and 4.3 V at 1 C. (e) Photograph of a fiber‐shaped lithium ion battery to lighten up a light emission diode. (f) Fiber‐shaped full lithium ion batteries being woven into a textile.

Figure 3.17 (a) Schematic illustration of the flexible wire‐shaped lithium‐ion battery. The aligned CNT/LTO and CNT/LMO composite fibers are paired as the anode and cathode, respectively. (b) Schematic illustration for the stretching and releasing process of a lithium ion battery wrapped on a heat‐shrinkable tube. (c) Photographs of a battery powering a light‐emitting diode at increasing strains. (d) SEM image of a spring‐like fiber under unstretched and stretched states. (e) SEM image of an over‐twisted CNT/LTO composite fiber at high magnification. (f) Evolution of specific capacitance with strain.

Chapter 4

Figure 4.1 Schematic of flexible sodium ion batteries.

Figure 4.2 Classification of flexible electrodes.

Figure 4.3 (a) Schematic representation showing synthesis of rGO/MoS

2

composite paper. (b) Digital picture showing large area composite paper prepared through vacuum filtration. (c) SEM top‐view image of 60MoS

2

paper; inset shows the EDX spectra of spots in the SEM image indicating the material to be rGO (square) and MoS

2

(circle). The scale is 10 μm. (d) Corresponding SEM cross‐sectional images show the morphology of the paper. Average thickness of this paper was observed to be ∼20 μm. (e) TEM image and SAED pattern of 60 MoS

2

. (f) Tensile test setup (1, load cell, fixed; 2, clamps, top clamp not shown; 3, computer‐controlled movable translation stage) with sample after fracture from loading (inset shows zoomed‐in view of two such specimens). (g) Engineering stress strain plot for rGO, 40MoS

2

, and 60MoS

2

free‐standing papers.

Figure 4.4 (a) Schematic diagram of partially reduced MoO

3−

x

deposited on flexible carbon cloth to enable facile ion diffusion and electron conduction. (b, c) The rate and cycling performance.

Figure 4.5 (a) Schematic illustration of the preparation process for Sn NDs@PNC nanofibers. (b) Digital photos of the as‐spun PAN/PMMA/SnCl

2

fiber membrane and the calcinated self‐supported Sn NDs@PNC electrode for Na ion batteries. (c) SEM, (d) EDS mapping. (e) Rate capability and cycling performance of Sn NDs@PNC, lower Sn content (L‐Sn@PNC), and higher Sn content (H‐Sn@PNC) electrodes, inset: SEM, TEM, and HRTEM images of Sn NDs@PNC after 300 cycles.

Figure 4.6 (a) Illustrative scheme of the designed novel “butter‐bread”‐like anode structure consisting of amorphous P layer@N‐doped graphene frameworks. (b) SEM image of the cross‐section of a P@GN paper, the inset shows its paper‐like appearance. (c) HRTEM image and the corresponding FFT pattern of the P@GN portion, confirming its amorphous structure. (d) Cyclic performance and Coulombic efficiency of P@GN at 200 and 800 mA g

−1

.

Figure 4.7 (a) Schematic illustration demonstrating the fabrication procedure of the L‐NTO NWs@CC composites. (b) SEM image and corresponding EDX mapping of C, Na, and Ti.

Figure 4.8 (a) The schematic structures of some sodium titanates. SEM (b) and TEM (c) images of sodium titanate nanotube arrays.

Figure 4.9 Fabrication of the alluaudite Na

2+2

x

Fe

2−

x

(SO

4

)

3

@porous carbon nanofiber (PCNF) hybrid film. (a–d) Digital photos, (e–h) SEM images, (i–l) TEM images and (m–p) schematic illustrations of the (e–h) porous carbon nanofiber.

Figure 4.10 Front view and side view of the flexible and binder‐free Na

7

V

4

(P

2

O

7

)

4

(PO

4

)/C nanorod–graphene thin film. (b) Temperature dependence of the electronic conductivity of the Na

7

V

4

(P

2

O

7

)

4

(PO

4

)/C nanorod–graphene film and the Na

7

V

4

(P

2

O

7

)

4

(PO

4

)/C nanorod pellet.

Figure 4.11 (a) Schematic chemical structure of starting molecule sodium benzene‐dicarboxylate (SBDC) and three possible linkages to extend its π‐conjugation, forming 1, SSDC, and 2, respectively. (b) Schematic diagram for the synthesis and reversible Na ion insertion/extraction mechanism of SSDC. (c) Schematic molecular packing of SSDC: the molecules are stacking layer‐by‐layer with strong π–π intermolecular interaction in plane and carboxylate group situated on the surface of the layers, forming a channel exactly at the active center for insertion/extraction of sodium ions between layers. (d) Rate capability of SSDC.

Figure 4.12 Digital picture of P(VDF‐HFP)‐ (PVP)/Sb

2

O

3

composite membrane.

Figure 4.13 (a) The flexible SIB full cell (NDCS//NVP) was linked to a flexible/wearable LED screen. (b) The schematic plan of full cell assembled with NDCS//NVP. (c) Schematic illustration for the fabrication of the flexible Sb/rGO//NVP/rGO SIB full cell. (d) Galvanostatic charge/discharge curves at a current density of 100 mA g

−1

over the voltage range of 0.7–3.5 V.

Figure 4.14 (a) SEM image and digital photo (inset) of the MFO@C electrode charged at 3.0 V after 300 cycles. (b) Charge/discharge curves of flexible SIB full cell with (MFO)@C//NVPF/C. (c) SEM images of NTO/CT composite. (d) Capacitance retention of flexible NIC measured under different bent conditions.

Figure 4.15 (a) Schematic illustration of the structure of the flexible quasi‐solid‐state SIC. (b) Diagram of the flexible QSS‐SIC under various bending conditions. (c) Stability of capacitive performance of the QSS‐SIC collected at different bending conditions. (d) A commercial desk lamp and a UT capacitor logo consisting of 50 red LEDs powered by the assembled QSS‐SIC under rolled state.

Chapter 5

Figure 5.1 (a) The fabrication process of the laminated hybrid sulfur cathode and (b) schematic image of structure of the flexible Li–S battery. (c) Comparison to explain the differences in electronic conductivity between aligned CNTs and random CNTs. (d) The preparation method for the S‐rGO paper. (e) The rate capability of 3D–NGS with current densities ranging from 100–1500 mAh g

−1

and the first discharge–charge profiles at different current densities [12]. (f) The preparation method for synthesizing S‐CNT/G and (g) its electrochemical performance when used as flexible Li–S battery cathode.

Figure 5.2 (a) The preparation process of NPCFs by an electrospinning method. (b) Typical tensile stress–strain curves of the as‐prepared membrane and photograph of the tensile stress–strain testing instrument. (c) The preparation process of the CNT–rGO/S composite. (d). The physical performance of CNT–rGO/S. (e) SEM image of sulfur particles and holder materials. (f) The sulfur particles that are protected by GTS. (g) The preparation process of the 3DGS hydrogel. (h) The electrochemical performance of a Li–S battery using 3DGS hydrogel as cathode material at various current densities.

Figure 5.3 (a) The flexibility of material. (b) The SEM image of porous and inner‐connected structure. (c) The discharging capacity at various current densities. (d) Li–S battery with sandwich‐structured cathode that can be curved or bent. (e) SEM view of sulfur particles that are attached on carbon foam. (f) The charge and discharge curve of the battery. . (g) The structure of 3DCNT/Graphene‐Li

2

S aerogel. (h) Electrochemical performance of scaffold material.

Figure 5.4 (a) Cycling performance of GPE‐based batteries, and those of liquid‐based ones at 0.1 C. (b) Rate performance of GPE‐based batteries and the liquid‐based ones from 0.1 to 1 C. (c) The polysulfide immobilization mechanism of GPE‐based batteries and the liquid‐based ones. Dendrites continually grow on the sulfur electrodes' surface in the liquid electrolyte based batteries while the GPE‐based ones can maintain a smooth morphology. (d) With the increasing weight ratio of sucrose in the sucrose‐PEO electrolyte, the ionic conductivity increases obviously. (e) Cycling performance of Li–S batteries with sucrose‐PEO electrolyte and the

electrochemical impedance spectroscopy

(

EIS

) spectrum of the battery. (f) Specific capacity of cells using the sucrose‐PEO electrolyte. The value remained almost constant after 200 cycles.

Figure 5.5 (a) 50PEO–50SiO

2

composite electrolyte membranes, that were flexible enough to be rolled into a tube. (b) Capacity retention of Li–S battery with (1) common liquid electrolyte and (2) the 50PEO–50SiO

2

‐based electrolyte. (c) Preparation and mechanism of the flexible halloysite nano‐clay electrolyte. Cast and dried after HNF, LiTFSI, and PEO were mixed to obtain a thin film and the ordered 3D channels promoted ionic conduction. (d) Photos of initial and final tension state of the halloysite nanoclay electrolyte film. (e) Discharge and charge curves of a battery with halloysite nano‐clay electrolyte at 25 C. (f) Cycling performance of a battery with the halloysite nanoclay electrolyte at 25 C. (g) Stress–strain of GPE assisted by ETU. (h) Charge and discharge stability test of a battery with ETU‐assisted GPE..

Figure 5.6 (a) SEM images of electrodes with PETEA (3 right) and liquid (3 left) electrolytes' surface after 2 and 50 charge and discharge cycles. (b) The PETEA‐based GPE under serious deformation could power a

light‐emitting diode

(

LED

) lamp while the liquid one could not. Compared with liquid electrolyte, PETEA‐based GPE could maintain its stability when bent and had the same specific capacity as before when returned to a flat shape. (c) How the charge capacity of TiO

2

–SiO

2

‐modified CPE depends on the number of cycles. (d) SEM images of the porous structure of TiO

2

–SiO

2

‐modified CPE.

Figure 5.7 (a) Schematic of electrode configuration illustrating the process of combining sulfur and graphene@PP membrane to form an integrated electrode–separator structure. (b) Cross‐section SEM image of sulfur electrode and corresponding EDS spectrum. (c) Stability of electrode–separator combination in terms of conductivity after 5000 bending cycles. (d) Rate performance of the S‐G@PP separator, G‐S + PP separator and Al foil‐S + PP separator batteries at different current densities. (e) Cross section of MoS

2

‐Celgard layer. (f) Schematic Li–S battery configuration of MoS

2

Celgard™ separator. (g) The cycling performance for Celgard™, GO/Celgard™, and MoS

2

/Celgard™ separators at 0.5 C.

Figure 5.8 (a) The porous structure of a graphene‐modified separator [69]. (b) The flexibility of a Li–S battery using the separator and metal Li as anode material. (c) The flexibility of the separator. (d) Schematic diagram of a modified Celgard™ separator restricting the polysulfide migration while maintaining good lithium ion transportation. (d) Comparison of hydrophilic separator (before and after modification). (g, h) The structure of the modified membrane [2]. (i) The schematic diagram of the experimental battery.

Chapter 6

Figure 6.1 Flexible sulfur cathode with CNTs. (a) A model and the structure of the S‐CNT cathode; (b) stress–strain curve of a flexible S‐CNT membrane cathode. Inset shows a bent S‐CNT membrane. (c) Schematic illustration of the hierarchical, freestanding electrode with ultrahigh sulfur‐loading capability via a facile bottom‐up approach; (d) photograph of the bottom‐up freestanding electrode in both the extending and bending (inset) states.

Figure 6.2 Flexible all

−

carbon interlinked structure for sulfur cathodes. (a) Schematic of sulfur cathode with CNT/carbon nanocages as scaffold; (b) optical image of the flexible sulfur cathode membrane.

Figure 6.3 Flexible sulfur cathode with combination of CNTs and different units. (a) Fabrication process of the laminated hybrid sulfur cathode; (b,c) photographs of hybrid electrodes being lifted up by a tender flower and being bent into a curved structure, respectively. (d) Schematic of the S/PPy/MWCNT composite preparation.

Figure 6.4 Flexible sulfur cathode with SACNTs and N‐CNTs. (a) Synthesis and characterization of the S–PCNT composites; (b) mechanical properties of the S–PCNT composites. Inset shows the photographs of the S‐PCNT composite. (c) Schematic diagrams of the synthesis of S/N–CNT composite.

Figure 6.5 Flexible sulfur cathode with CNFs. (a,b) Schematic illustration of the synthesis process for S@PCNFs–CNT electrode; (c,d) Photograph of freestanding and flexible PCNFs electrode. (e) A schematic illustration for the preparation of mesoporous graphene paper–sulfur electrodes and application as cathode in lithium–sulfur batteries; (f,g) digital photographs of the MGP paper, exhibiting an intact paper‐like morphology and flexible property.

Figure 6.6 Flexible sulfur cathode with Cu, TiO

2

, and Se‐modified CNFs. (a) Schematic illustration of the synthesis for the S@PCNFs‐Cu electrode; (b) photograph of the freestanding and flexible S@PCNFs‐Cu electrode. (c) Digital photograph of CP@TiO

2

‐S membrane indicating its flexibility, with the inset showing a top view. (d) Schematic illustration of the synthesis for S

1−

x

Se

x

@PCNFs electrode; (e) photograph of free‐standing and flexible S

1−

x

Se

x

@PCNFs electrode.

Figure 6.7 Standalone Flex‐SW battery electrodes. (a) Image showing the yarn‐like nature of the flexible sulfur wires (Flex‐SWs); (b) procedure to prepare flexible sulfur wires (Flex‐SWs), Flex‐SWs‐pellets, and Flex‐SWs‐pellets coated with lithium ion conductor (LIC)‐Flex‐SW‐LIC pellets.

Figure 6.8 Flexible sulfur cathode with graphene paper. (a) Schematic illustration of synthesis process and structure of the designed S‐rGO paper; (b) the cut electrode films in different conditions. (c,d) Photographs of an as‐prepared large‐area GCC strip (width: 6 cm) showing its good flexibility.

Figure 6.9 Freestanding graphene‐based films with functionalized graphene sheets and hollow carbon spheres. (a) Fabrication of freestanding graphene‐based porous carbon (GPC) films; (b,c) optical images of a red LED lightened by the Li–sulfur battery under the bending and folding states, respectively. (d) Schematic illustration of the fabrication of the NDHCS–S composites and G–NDHCS–S hybrid paper. Source: Zhou et al. 2015 [88]. Copyright 2015, John Wiley & Sons.

Figure 6.10 Flexible sulfur cathode with graphene foam. (a) Schematic of the procedure for fabricating PDMS/GF and S‐PDMS/GF electrodes; (b,c) photographs of a PDMS/GF showing its good flexibility; (d,e) photographs of a flexible S‐PDMS/GF electrode with 10.1 mg cm

−2

sulfur loading.

Figure 6.11 Flexible sulfur cathode with three‐dimensional carbon foam. (a) The procedure for preparing the S/CBC cathode and CBC interlayer, and their specific location in the Li–S battery configuration. (b) Structure illustration of the NCF‐CNT/S cathode; (c) NCF bent by fingertips; (d) the NCF‐CNT/S composite electrode, bent by tweezers.

Figure 6.12 Flexible sulfur cathode with carbon/binder composites. (a) Schematic representation of the solvent‐free processing approach; (b) photograph of the as‐prepared freestanding cathode foil (∼80 μm thick) with active material loading of c. 3.0–3.2 mg‐S cm

−2

; (c) electrode foil laminated onto the carbon‐coated, expanded aluminum current collector for improved electrical conductivity and reduced contact resistance. (d) Schematic illustration of a Li–S cell with sandwich‐structured cathode; (e) photo images of sandwich‐structured electrodes at tiled (left) and bended state (right).

Figure 6.13 Flexible sulfur cathode with three‐dimensional metal. (a) A schematic diagram of preparing sulfur nanodots on Ni foam with an electrodeposition method; (b) a facile application of Li–S cells: an “S”‐shaped light that contains 10 LEDs lit by an assembled Li–S battery; (c) a flexible packaging Li–S battery with nano S cathode.

Chapter 7

Figure 7.1 Comparison of gravimetric energy densities of various types of batteries and gasoline. The theoretical density is acquired from the thermodynamics of active materials.

Figure 7.2 Nokia Morph Concept, LG OLED TV panel, Philips Fluid flexible smartphone, and Samsung Youm flexible display.

Figure 7.3 Typical structure of (a) coin cell and (b) Swagelok battery.

Figure 7.4 Schematic cell configurations for the flexible lithium–air battery.

Figure 7.5 Schematic illustrations of the three cathodes morphology with discharge state.

Figure 7.6 Recently used flexible current collector in lithium–air field.

Figure 7.7 Schematic cell configurations for the flexible lithium–air batteries.

Figure 7.8 Flexible energy storage devices packed with (a) aluminum‐plastic film, (b) thermoplastic material, (c) PET, and (d) PDMS.

Figure 7.9 Schematic cell configuration of the planar flexible lithium–air battery.

Figure 7.10 (a) Schematic representations for the design and preparation of the TiO

2

NAs/CT. (b–g) Characterizations of TiO

2

NAs/CT cathode.

Figure 7.11 (a) Schematic of the internal structure of the battery. (b) Cycling performance of batteries with TiO

2

NAs/CT cathode and CT cathode. (c) SEM image and XRD pattern of the recovered TiO

2

NAs/CT cathode. (d) Cycling performance of the battery with recovered TiO

2

NAs/CT cathode.

Figure 7.12 (a,b) The bending properties with the device bent to 0°and 360°. (c) The twisting properties with the device twisted to 360°.

Figure 7.13 (a) Schematic representations for the design and preparation of the CT‐Co

3

O

4

NSs‐Ru cathode. (b) SEM image and photograph of the CT‐Co

3

O

4

NSs‐Ru cathode. (c) TEM image and its corresponding EDS mappings.

Figure 7.14 (a) Cycling performance and (b) rate capability of the planar flexible lithium–air battery. (c,d) Digital images of the red LED equipment turned on with the fabricated planar flexible lithium–air battery under planar and bent conditions.

Figure 7.15 (a) Schematic illustration of the fabrication process of the macroporous hollow active carbon fiber cathode. (b) SEM image and photograph of the MACF cathode. (c) The enlargement of (b). (d) TEM image of the R‐MACF cathode.

Figure 7.16 (a–c) Digital images of the red LED equipment turned on with the fabricated planar flexible lithium–air battery under planar and bent conditions. (d) Cycling performance of battery with R‐MACF cathode under bend condition.

Figure 7.17 (a) Schematic illustration of the fabrication process of the PI cathode. (b) SEM image of a paper substrate. (c) Digital image of the obtained PI cathode. (d) SEM image of the obtained PI cathode.

Figure 7.18 (a) Schematic cell configurations for the planar flexible lithium–air battery with PI cathode. (b) Digital images of the fabricated planar flexible lithium–air battery with plane and bent conditions turning on red LED equipment. (c) Discharge capacity of flexible lithium–air batteries with PI cathode (pristine and 1000 folding cycles). (d) Cycling performance of flexible lithium–air batteries with the two kinds of cathode (pristine and 1000 folding cycles).

Figure 7.19 (a) Schematic of the fabrication and the working mechanism of a foldable lithium–air battery. (b) Photograph depicting the practical application of this battery. (c) Discharge voltage versus time and discharge current versus time, inset is the mass of the assembled foldable lithium–air battery.

Figure 7.20 Schematic cell configurations for the cable‐type air battery.

Figure 7.21 Schematic illustration of the fabrication process of the flexible cathode (a) and freestanding polymer electrolyte (b).

Figure 7.22 (a) Cable type lithium–air battery powering a commercial red LED display screen at various bended and twisted conditions. (b) First discharge curves of cable type lithium–air batteries with various conditions. (c) Charge–discharge curves of flexible lithium–air battery after being bended thousands of times. (d) Cable‐type lithium–air battery powering a commercial red LED in water.

Figure 7.23 (a) Schematic illustration of the fabrication of the cable‐type flexible lithium–air battery. (b) SEM image of fabricated gel electrolyte coated on the lithium wire. (c) SEM image of aligned CNT sheet wrapped as the outer layer. (d) Photograph of a cable‐type flexible lithium–air battery.

Figure 7.24 (a) The flexibility of the cable‐type flexible lithium–air battery. (b) Discharge curve under a dynamic bending and releasing process. (c) Photograph of cable‐type flexible lithium–air battery woven into flexible powering textile. (d) Photograph of flexibility of the cable‐type flexible lithium–air battery integrated into a knapsack to power a commercial red LED display screen.

Figure 7.25 Inspired by the ancient bamboo slips, a flexible and wearable woven‐type battery pack was fabricated.

Figure 7.26 (a–f) Optic images of the fabricated woven‐type battery pack powering a commercial red LED under various bending and twisting conditions; (g) first discharge curves of the woven‐type battery pack under various bending and twisting conditions; (h) the contradistinction of mean discharge voltage and discharge capacity of the woven‐type battery pack under various bending and twisting conditions; and (i) woven‐type battery pack powering a commercial red LED immersed in water.

Figure 7.27 A rough comparison of energy densities with various types of lithium–air battery.

Figure 7.28 (a) Schematic illustration of the ultrathin and lightweight battery array pack. (b) Exploded view layout of the layers in the battery structure. (c) Photographs of the fabricated battery array pack integrated with a glove, powering a commercial LED. (d) Held by a branch of the asparagus fern. (e) Tested by a screw micrometer.

Figure 7.29 (a) A battery array pack powering a commercial red LED under various bending and twisting conditions. (b) Discharge–charge curves after being bended thousands of times; inset is the battery at planar and folded in half states. (c) The comparison of gravimetric energy density (left axis) and volumetric energy density (right axis) with four types of lithium–air batteries; insets are the photographs of the assembled lithium–air batteries.

Chapter 8

Figure 8.1 Schema of electric field and strain in different conversion cycles: (a) constant charge, (b) constant field, and (c) constant voltage.

Figure 8.2 Schematic of a DEG energy cycle.

Figure 8.3 Fabrication process of SiO

2

‐PDDA‐GO core–shell hybrid particles.

Figure 8.4 Variation curves of dielectric constant and dielectric loss for SR and SiO

2

‐PDDA‐GO/SR dielectric elastomer.

Figure 8.5 (a) Schematic representation of the direct grafting of a dipole to the cross‐linker of a hydrosilylation reaction of a vinyl‐terminated PDMS. (b) Push–pull dipole (

N

‐allyl‐

N

‐methyl‐

p

‐nitroaniline) with vinyl functionalization.

Figure 8.6 Schematic illustration of the formation of an all‐silicone IPN with locked‐in pre‐strain; (a) solution is drop cast onto treated glass, (b) solvent is allowed to evaporate and the RTV silicone cures at room temperature, (c) film is peeled off the glass substrate, (d) film is stretched biaxially by 100% × 100%, (e) HTV silicone is cured at 180 °C for 30 min, and (f) film is relaxed and some pre‐strain is preserved.

Figure 8.7 (a) The proposed electro‐mechanical harvesting scheme is shown by the triangle A–B–C–A on the voltage‐charge work‐conjugate plane, and the rectangle d–e–f–g–d is the constant‐voltage energy harvesting cycle for comparison. Also, the loci of the possible failure modes is shown by

electrical breakdown

(

EB

),

electro‐mechanical instability

(

EMI

),

loss of tension

(

LT

), and rupture stretch(

λ

rupture

). (b) Circuit diagram used to control the electro‐mechanical cycle, where harvesting circuits block is to collect the electrical energy.

Figure 8.8 The self‐priming circuit is connected in parallel with the DEG (a). A simple self‐priming circuit is illustrated (b) along with its equivalent high voltage (c) and high charge (d) forms. With reference to (e), the circuit is in a high charge form when current flows along the dashed path and high voltage form when it follows the dotted path.

Figure 8.9 Dielectric elastomer ocean wave power generator by SRI International, multibody system buoy at sea trial site (a); concatenated rolls in a generator module (b).

Figure 8.10 Shoe generators of dielectric elastomers from motion: photo of the device installed in boot (a) and a cross‐section of the device (b).

Chapter 9

Figure 9.1 World annual solar photovoltaics cell production from 1990 to 2013, with projection to 2017 (Earth Policy Institute – www.earth‐policy.org).

Figure 9.2 (a) Schematic of a typical

dye‐sensitized solar cell

(

DSSC

) and (b) overview of processes and typical time constants under working conditions (one sun (AM 1.5, 1000  W m

−2

)) in a Ru‐based DSC with I

−

/I

3

−

redox couples.

Figure 9.3 Schematic images of TiO

2

film construction from (a) only TiO

2

nanoparticles (NR18) and from (b) suggested building blocks (B650C), and (c) their J–V curves.

Figure 9.4 Images of (Sb,In)SnO

2

‐P25 ((a,c) SEM, (e) TEM) and only P25 (b,d – SEM, f – TEM) films. Photographs of bending property of SnO

2

‐P25 and only P25 on the plastic substrate. The effect of (Sb,In)SnO

2

additives on the device performance: (i)

I

–

V

curves and (j)

Incident photon to current efficiency

(

IPCE

) spectra.

Figure 9.5 Image of the rheological behavior of ethanol‐based TiO

2

paste containing various water percentages: a = 0%, b = 10%, c = 10%, d = 20%, e = 30%, f = 40%, g = 60%, h = 80%, and i = 100%.

Figure 9.6 SEM image of TiO

2

layer by ultrasonic spray deposition (a) before and (b) after pressing.

Figure 9.7 Relationship between the pressure applied to the TiO

2

film and the performance of the fabricated FDSC.

Figure 9.8 Electro‐spray deposition (ESD) illustration (a) and SEM images of TiO

2

beads deposited by ESD and completed flexible photo‐electrode (b).

Figure 9.9 The fabrication of FDSCs using (a) a combination of dye soaking and ultrasonic spray technology, (b) pre‐dye‐coating method, and (c) co‐deposition method.

Figure 9.10 Schematic of the FDSC structure with the thin TiO

2

film deposited with ALD.

Figure 9.11 Schematic of the fiber DSC structure with (a) CNT counter‐electrode and (b) SEM image of Ti–TiO

2

‐CNT‐wire.

Figure 9.12 Schematic diagram of the fabrication of PEDOT/graphene/PET electrode.

Figure 9.13 Nyquist plots of electrochemical impedance spectra measured on symmetrical dummy cells with (a) VG‐1, VG‐2, VG‐3, Pt/FTO and (b) VG‐4 (frequency sweep range: 100 kHz to 0.1 Hz, DC bias: 0 V).

Chapter 10

Figure 10.1 Schematic presentation of the fabrication process to obtain a transparent and conductive metallic grid.

Figure 10.2 (a) The structure of the semitransparent cell: FTO glass/TiO

2

compact layer/mesoporous TiO

2

/grid of CH

3

NH

3

PbI

3

/spiro‐OMeTAD/gold. (b) The structure of the HTM‐free semitransparent cell: FTO glass/TiO

2

compact layer/mesoporous TiO

2

/grid of CH

3

NH

3

PbI

3

/gold. (c) Optical microscopic image of the wide grid: opening of

∼

200 

µ

m. (d) Optical microscopic image of the dense grid: opening of

∼

60 

µ

m.

Figure 10.3 (a) UHR–SEM image of perovskite dense grid (top view). (b) UHR–SEM cross‐section image of the HTM‐free cell where the grid line of CH

3

NH

3

PbI

3

perovskite can be observed. The mesh opening is

∼

60 

µ

m and the assembly solution concentration is 12.5 wt% (about 40% transparency).

Figure 10.4 The grid dimensions vs the assembly solution concentration (measured by profiler). (a) The average height and width (

µ

m,

full width at half maximum

,

FWHM

) of the grid lines resulting from the use of different concentrations of the assembly solutions (wt%). (b) The average cross‐sectional area of a grid line (calculated by multiplying the average width line with the average height of the same grid line) vs assembly solution concentration.

Figure 10.5 (a) The PCE of the semitransparent cells vs their average transparency calculated in the range of 400–800 nm wavelengths (the different colors represent the different solution concentrations). (b) The average transparency of the perovskite solar cells vs the concentration (wt%) of the assembly solution of the precursors. (c) Images of the semitransparent cells with different average transparencies from left to right, 19%, 28%, 38%, 64%, and 67%. (d) The current–voltage curves of the semitransparent cells with different average transparencies. The PCEs of the cells are 0.83%, 1.04%, 3.79%, and 4.98% for the cells of 64%, 38%, 28%, and 19% transparency, respectively.

Figure 10.6 The recombination lifetimes that were extracted from the IMVS measurement for the cells with and without HTM vs the

V

OC

.

Figure 10.7 Schematic diagram of (a) mesoporous structure; (b) meso–planar hybrid structure; and (c) planar structure, of perovskite solar cells; the arrows show that the hybrid structure falls in between these two designs.

Figure 10.8 Optical image of the (a) mesoporous‐titania grid deposited with the help of a mesh (mesh size 50 µm), (b) perovskite deposited on TiO

2

grid; (c) top view SEM image, (d) cross‐sectional SEM image of the grid.

Figure 10.9 Cross‐sectional HR‐SEM image of cell showing the planar part without

meso

‐TiO

2

, and mesoporous part with TiO

2

can be clearly seen from left to right part of the image.

Figure 10.10 (a)

J

–

V

characteristics of perovskite solar cells (PSCs) for the different architectures and (b) the comparative EQE curve for these cells.

Figure 10.11 Absorption spectra of mesoporous and planar cells, showing normalized spectra in the range of 400–850 nm.

Figure 10.12 (a–d) show the perovskite density at different locations of grid cells, the much dense perovskite coverage is evident in image (a), the valley region of the titania grid, whereas (b–d) show the enlarged view of the junction of meso–planar area and peaks of titania at mesh junction points. These recombination centers are responsible for some of the performance loss of meso–planar hybrid cell structures.

Figure 10.13 (a) The steps involved in the charge extraction measurements. (b) Charge extraction of different types of cells using white LED, inset shows semilogarithmic graph of the charge extraction, presenting the difference between the cells structure.

Chapter 11

Figure 11.1 Schematic outline of the conversion from photons to electrons in OSCs.

Figure 11.2 Typical

J

–

V

characteristics of a polymer solar cell.

Figure 11.3 Schematic diagram of (a) a conventional device structure and (b) an inverted device structure.

Figure 11.4 Absorption spectra and molecular structures of three representative polymers with different optical bandgaps.

Figure 11.5 Structures of PPV and PT and their derivatives.

Figure 11.6 Structures of some widely used donor and acceptor fragments.

Figure 11.7 Structure of the representative D–A copolymer.

Figure 11.8 Representative fullerenes and non‐fullerene acceptors.

Figure 11.9 (a) Device structure of an all‐plastic solar cell; (b) transfer printing of PEDOT:PSS PH1000 electrode; and (c) photographic picture of a fabricated all‐plastic solar cell.

Figure 11.10 Chemical structures of representative materials to produce low work function interfaces.

Figure 11.11 Schematic representation of an organic tandem device of an organic tandem solar cell in a normal (a) and an inverted configuration (b).

Figure 11.12 (a) Structure of organic tandem solar cells and (b) the

J

–

V

characteristics.

Figure 11.13 (a,b) Tandem solar cells with PEDOT:PSS/PEIE as the ICL and the

J

–

V

characteristics. (c) Conductivity tuning of the PEDOT:PSS/PEI ICL; (d) All‐solution‐processed all‐plastic multijunction (seven junctions, 22 layers) cells displayed

V

oc

of 5.37 V.

Figure 11.14 (a) Chemical structure of low‐bandgap polymer PMDPP3T; (b) Structure of triple‐junction tandem cell based on the PMDPP3T:PC

71

BM junction. (c) Structure of triple‐junction tandem cell with the PMDPP3T:PC

71

BM junction; All the three junctions absorb different spectral regions.

Figure 11.15 (a) Fabrication principle of the slot‐die coating; (b) a photograph of fabricated flexible films and (c) a picture of the roll‐to‐roll machine.

Chapter 12

Figure 12.1 Roll‐to‐roll fabrication of flexible photovoltaic cells.

Figure 12.2 Density states in semiconductor nanocrystals.

Figure 12.3 (a) Absorption spectra of CuInS

2

QDs with different average sizes and (b) size‐dependent optical bandgaps of CuInS

2

QDs determined from absorption (red stars) and 2D

photoluminescence excitation

(

PLE

) spectra (green spheres). The solid line represents the calculation result from finite depth‐well

effective mass approximation

(

EMA

) theory.

Figure 12.4 Illustration of cascade scheme for electron–hole pair multiplication. A high‐energy photon creates an exciton with excess energy,

n

*

1

. The hot exciton can lose energy by cooling or electron–hole pair multiplication to form either

n

1

or a hot biexciton,

n

*

2

, and so on.

Figure 12.5 Ultrafast electron transfer from CdSe nanocrystals to methylviologen (MV

2+

).

Figure 12.6 Surface‐to‐volume atom ratio and chemical potential of nanocrystals calculated using InP lattice parameters.

Figure 12.7 (a) Schematic of QDSSCs and (b) energy‐band diagram of QDSSCs.

Figure 12.8 Typical

I

–

V

cure of QDSSCs.

Figure 12.9 Schematic of QDSSCs based on Zn–Cu–In–Se QDs.

Figure 12.10 (a) Schematic presentation of the steps for the preparation of TiO

2

electrodes by the

cold isostatic pressing

(

CIP

) technique and (b) TiO

2

films on PEN/ITO substrate.

Figure 12.11 Different TiO

2

nanoarray structures: (a) Nanorods. (b) Nanodendrites. (c) Nanowires. (d) Nanotubes.

Figure 12.12 Different ZnO structures: (a) Nanodisks. (b) Nanorods; (c) branched‐nanorods. (d) Microspheres.

Figure 12.13 Schematic of in situ sensitization techniques: (a) CBD method. (b) SILAR method.

Figure 12.14 Schematic of ex situ sensitization techniques: (a) Molecular linker. (b) electrophoretic deposition.

Figure 12.15 (a) Energy‐band diagram and charge separation processes in the CdS/PAPC QDSC system and (b) schematic representation of a mesoscopic sensitized TiO

2

electrode grafted onto a PAPC molecular relay on a CdS surface.

Figure 12.16 (a) Digital photograph and (b)

J

–

V

curve and power density (under AM 1.5 illumination) of the 12.97 cm

2

CdS/CdSe QDSSC module.

Chapter 13

Figure 13.1 Basic working modes of the TENG. The attached‐electrode (a) contact/separation and (b) sliding mode. The single‐electrode (c) contact/separation and (d) sliding mode. The freestanding (e) contact/separation and (f) sliding mode.

Figure 13.2 FTENGs for harvesting energy from human activities such as walking/jogging. (a) A multilayered FTENG to harvest energy from foot motion during walking. (b) A fabric‐structured FTENG and its application of footstep‐driven power mats during walking. (c) An FTENG attached to clothes to scavenge energy from body motion. (d) An FTENG cloth by weaving two kinds of belts to scavenge energy from body motion.

Figure 13.3 FTENGs for harvesting energy from hand or finger motions. (a) An FTENG with checker‐like interdigital electrodes to harvest energy from moving the mouse. (b) A transparent single‐electrode‐mode FTENG to scavenge energy from touching the screen of a cell phone. (c) An FTENG as a keyboard cover to harvest energy from typing motion.

Figure 13.4 FTENGs for harvesting wind energy. A lawn‐structured FTENG to harvest wind energy: (a) schematic illustration of the device structure and (b) photographs showing 60 LEDs lighted up by the FTENG by energy harvested from wind blowing. A flag‐shaped FTENG to scavenge wind energy: (c) schematic illustration of the device structure and (d) output current of the FTENG from wind blowing at various incident angles.

Figure 13.5 FTENGs for harvesting water energy. An FTENG with elastic wavy electrodes to harvest water energy: (a) schematic diagram and photograph of the device and (b) photographs showing the FTENG mounted on a life vest to harvest water wave energy An FTENG with multiple parallel electrodes to scavenge water energy: (c) schematic illustration of the device structure; (d) photograph showing the FTENG during bending; and (e) photograph showing the FTENG interacting with water waves.

Figure 13.6 FTENGs as self‐powered touch/pressure sensors. (a) A transparent FTENG with pyramid microstructures as a touch sensor. The plot shows the output voltage induced by a piece of feather. (b) An FTENG composed of a micropyramid‐structured PDMS and an ITO electrode to detect pressure/touch. The plot shows the output voltage as a function of the applied pressure. (c) An FTENG with nanowire‐structured FEP film as the triboelectric layer to sense pressure/touch. The plot shows the measured output voltage with increasing pressure and the photograph shows a wireless alarm system triggered by finger tapping on an FTENG. (d) An FTENG with nanostructured PTFE film as the triboelectric layer to detect pressure/touch. The plot shows the relationship between the forward output current and pressure. (e) An integrated FTENG sensor array working in the attached‐electrode contact/separation mode for pressure/touch sensing. The plot shows the output voltage as a function of the external pressure.

Figure 13.7 FTENGs as self‐powered body motion sensors. (a) A stretchable‐rubber‐based FTENG for body motion sensing. The plot shows the voltage responses to the diaphragmatic breathing. (b) A textile‐based FTENG to monitor human respiratory information. The plot shows the processed respiratory signal with datum line and other parameters marked for the respiratory data analysis. (c) An FTENG with serpentine‐patterned electrodes to detect human motion. The plot shows the voltage response to swallowing motion. (d) A hydrogel‐based FTENG to sense joint motion. The plot shows the voltage responses when bending the elbow at different angles. (e) A single‐thread‐based FTENG to monitor body motion. The plot shows the current responses to finger gestures. (f) An implantable FTENG to sense organ motion. The plot shows the output voltage when the FTENG was anchored over the left lateral wall.

Figure 13.8 FTENGs as self‐powered object motion sensors. An FTENG working in the freestanding sliding mode to detect object motion: (a) schematic diagram and photographs of the device; (b) velocity measurement on uniform velocity‐reciprocating motion; (c) velocity measurement on uniform acceleration motion; and (d) velocity measurement on uniform acceleration and deceleration motion. A recyclable FTENG to detect object motion inside a tube: (e) schematic diagram of the device structure and (f) output current response to a moving object inside a tube.

Figure 13.9 FTENGs as self‐powered acoustic sensors. A single‐electrode‐mode FTENG to detect acoustic waves: (a) schematic diagram and photograph of the device; (b) photograph shows the FTENG worn on the neck as a self‐powered throat microphone; (c) plots showing the low‐frequency component (left) and high‐frequency component (right) of the output signals responding to the concrete dynamic change during speaking. An attached‐electrode‐mode FTENG to detect acoustic waves: (d) schematic diagram and photograph of the device and (e) photograph showing the FTENG as a self‐powered microphone for sound recording.

Figure 13.10 FTENGs as self‐powered liquid/gas flow sensors. A self‐recovering FTENG to detect air flow: (a) schematic diagram and photograph of the device; (b) the relationship between the output voltage and the airflow rate at a certain relative humidity and (c) the influence of humidity on the output voltage at a certain airflow rate. An FTENG working in the single‐electrode sliding mode to detect the flow of both water and air: (d) schematic diagram and photograph of the device; (e) dependence of the signal average period time/frequency on liquid flow rate at 1.0 mm capillarity and (f) dependence of the signal average period time/frequency on gas flow rate at 3.0 mm capillarity.

Figure 13.11 FTENGs as self‐powered sensors to detect other kinds of signals. An FTENG as self‐powered liquid volume sensor: (a) schematic illustration showing the device structure and (b) dependence of the output voltage on the delivery volume under different gap distances between the two triboelectric layers. An FTENG as a self‐powered sensor to detect volatile organic compounds in air: (c) schematic diagram and photograph of the device; (d) the output current and response of the FTENG under different ethanol concentration gas flow; (e) responses of the FTENG when detecting methanol, ethanol, propanol, butanol, and chloroform gas flow (210 ppm).

Figure 13.12 FTENGs for SCPUs with self‐charging over a period of time to power electronics. (a) A stretchable, waterproof SCPU integrating a stretchable TENG and stretchable supercapacitors to drive an electronic watch. (b) A transparent SCPU integrating an FTENG and supercapacitors to drive a calculator. (c) A fabric‐based SCPU integrating FTENGs with supercapacitors to drive a pressure sensor. The plot shows various charging rates of the supercapacitor by the FTENG harvesting energy from different human activities. (d) A transparent stretchable sensor system composed of an FTENG, a supercapacitor, and a strain sensor to detect strain. (e) A textile‐based SCPU combining an FTENG and a capacitor to power a liquid crystal display and a remote control.

Figure 13.13 FTENGs for SCPUs to sustainably power electronics. (a) A flexible SCPU combining an FTENG with a Li ion battery to sustainably drive an ultraviolet sensor. (b) An SCPU integrating an FTENG, a capacitor, and a power management circuit to sustainably power numerous electronics with the energy harvested from palm tapping. A shape‐adaptive FTENG combined in an SCPU by integrating with a capacitor and a power management circuit: (c) schematic illustration showing the basic structure of the FTENG; (d) photograph showing a bracelet‐like FTENG worn on the wrist; (e) charging a capacitor by an FTENG harvesting tapping motion; (f) demonstration of the SCPU to sustainably power an electronic watch with the FTENG scavenging energy from tapping motion. A tube‐like FTENG combined in an SCPU with a battery: (g) photographs and schematic illustration of the FTENG; and (h) demonstration of the SCPU to sustainably power an electronic watch with energy harvested by the FTENG during walking.

Figure 13.14 FTENGs for hybrid energy cells. A transparent hybrid energy cell composed of an FTENG, a PiENG, and a PyENG: (a) schematic diagram and photograph of the device and (b) photographs showing two spot lights lighted up by the hybrid energy cell. A textile‐based hybrid energy cell composed of an FTENG and a solar cell: (c) schematic illustration and photograph of the device and (d) photographs showing a capacitor charged by the hybrid energy cell (left) and an electronic watch continuously powered (right) under sunlight with mechanical excitation.

Figure 13.15 Service behavior of TENG: (a) schematic diagram; (b) the fabrication process of the T‐SCs; (c) the output current of TENG before and after damage; and (d) the self‐charging system and the voltage of the T‐SCs charged by the T‐TENG.

Chapter 14

Figure 14.1 Schematic cross‐sections of an n‐type thermoelectric leg (a), a thermoelectric couple (b), and a thermoelectric module (c) comprising individual thermocouples connected electrically in series and thermally in parallel. With application of temperature difference (potential) the output is a voltage (temperature difference) in the power generation (refrigeration) mode.

Figure 14.2 Evolution of maximum ZT over time. Blue dots and red triangles represent the cooling and power generation thermoelectric materials, respectively. Bi

2

Te

3

and PbTe are the basic constituents of alloys of which ZT is reported. References for Nano SiGe: [25], nano PbTe: [26], RI PbTe (PbTe doped with resonant impurity): [27], nano Bi

2

Te

3

: [28], and hierarchical PbTe: [29].

Figure 14.3 Power factors and ZT of emerging polymer and CNT‐based thermoelectric materials over the past decades. ZT values are shown above the symbols along with the type of material (n or/and p type) and Refs 38, [47–57].

Figure 14.4 Molecular structure of typical organic TE materials.

Figure 14.5 Chronological illustration of flexible substrate for TE device (a) from left at bottom 2012 multiple element modules by assembling individual composite films made by multiwalled CNT and PVDF [76]. From left at top 2011 A freestanding flexible nanotube‐PEDOT:PSS thin film [77]. (b) 2013 from left: mixed polystyrene and CNTs together and composites printed on a naphthalate film substrate [78]. Right flexible PPy paper‐like membrane [65]. (c) 2016 devices directly brush‐painted onto curved surfaces by using Bi

2

Te

3

‐based inorganic paints with Sb

2

Te

3

chalcogenidometalate as a sintering aid [75].

Figure 14.6 Chronological illustration of wearable thermoelectric devices both rigid and flexible . (a) From 2004 to 2008 some of the first‐generation wearable TE devices manufactured using Bismuth Telluride as the TE material can be seen. Clockwise from left: assembly of TEG for human body applications, micromachined thermopile chips on a one Euro coin [95], a watch‐size TEG used to power a pulse oximeter [96], TEG of the EEG headset stretchable band and its electronic module [96]. (b) From 2011 to 2014: voltage generated by flexible TE device from KAIST, screen printed n‐ and p‐type TE legs on glass fabric, PDMS‐embedded copper electrodes for connection of the TE legs 45. PP‐PEDOT thermoelectric films [64]. Flexible Si fabric thermoelectric device [97]. (c) 2014–2016 Flexible thermoelectric module from TEGway [98], a spin‐off from KAIST. Flexible uni‐leg organic thermoelectric (OTE) module fabricated using a photo etching process from doped P3HT [99]. Flexible thermoelectric fabric composed based on self‐assembled tellurium nanorods on PVDF substrate [100], TE painting on substrate, fabricated TE device on hemispherical PET substrate [75].

Figure 14.7 Planar TE devices' architecture. (a) A planar TE device printed on a flexible substrate. (b) Printed devices can be used for forming different 3D structures, for example, corrugated TE device. (c) Rolled architecture.

Figure 14.8 Structure of a transverse thermoelectric device.

Figure 14.9 BST/Ni tubular‐type transverse TEG manufactured by Yamada group with a power density of ∼870 W m

−2

at Δ

T

 ∼90 K.

Figure 14.10 (a) A 3D drawing of a transverse TEG comprising BST and nickel layers. BST refers to bismuth antimony telluride (Bi

0.5

Sb

1.5

Te

3

) p‐type bismuth telluride. (b) ANSYS simulation results of transverse TEG device. Temperature distribution at the cross‐section through the different layers of the device. (c) Voltage generated by the transverse TEG device. The dimensions of the device used in the simulation are 16 mm × 20 mm × 2 mm with a tilt angle of 45°.

Figure 14.11 Output open circuit voltage (a) and power output at matched load conditions (b) of the BST/Ni transverse TEG simulated using ANSYS. DT refers to device thickness. The resistances of the devices are calculated as 10.6, 5.3, and 3.5 mΩ for 1, 2, and 3 mm thicknesses, respectively. The temperature difference between the hot and the cold sides varies from 1 to 5 K.

Chapter 15