An Introduction to Redox Polymers for Energy-Storage Applications E-Book

Ulrich S. Schubert

• Herausgeber: Wiley-VCH GmbH
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 1054

Veröffentlichungsjahr: 2023

Beschreibung

An Introduction to Redox Polymers for Energy-Storage Applications

Presents a well-founded introduction to the field or Redox Polymers, with didactical features like summary boxes and a Q&A sections

An Introduction to Redox Polymers for Energy-Storage Applications discusses fundamental aspects related to polymer-based batteries, such as types of batteries, their historic development, design and synthesis criteria of the active material, and summarizes the various types of redox polymers and their applications. Each chapter contains learning objectives, summary boxes, and questions to allow for efficient exam preparation.

In An Introduction to Redox Polymers for Energy-Storage Applications, readers will find detailed information on:

• Fundamental aspects of redox-active polymers, along with their historical classification, taking the key applications of the materials into account
• Energy-storage devices, containing polymers as the electrode active materials, and specific material requirements for the desired applications
• Classification of redox-active polymers, e.g., according to the nature of the actual redox-active moieties, their backbone structure, or topology
• Electrical conductivity of conjugated polymers, covering their most prominent representatives (polyaniline, polypyrrole, polythiophene, and polyacetylene)

An Introduction to Redox Polymers for Energy-Storage Applications also covers the synthesis and applications of these materials, making it an excellent book for graduates, PhD students, and professionals who are starting in this field.

Leseprobe

Table of Contents

Cover

Title Page

Copyright

List of Abbreviations

1 The Emergence of “Redox Polymers” in the Field of Energy‐Storage Applications

*

1.1 An Introduction to Battery Systems

1.2 Redox Polymers: A Short View on Their Long History

References

Note

2 Polymer‐Containing Batteries

*

Study Goals

2.1 Introduction

2.2 Working Principles

2.3 Characterization of Energy‐Storage Devices

2.4 Battery Housing

2.5 Solid‐State Batteries Incorporating Polymers, as Active Materials

2.6 Capacitors Incorporating Polymers, as Active Materials

2.7 Redox‐Flow Batteries Incorporating Polymers as Active Materials

2.8 Concluding Remarks

References

Note

3 Redox Polymers: Architectures, Synthesis, and Characterization

*

Study Goals

3.1 Introduction

3.2 Polymer Architecture

vs.

Battery Cell Performance

3.3 Polymer Architectures

3.4 Polymerization Methods

3.5 TEMPO‐Containing Redox Polymers: A Case Study on How the Backbone Structure Influences the Polymeric Properties

3.6 Characterization of Redox Polymers

3.7 Concluding Remarks

References

Note

4 Conjugated Polymers in the Context of Energy‐Storage Applications

Study Goals

4.1 Introduction

4.2 The Classic Conjugated Polymers at a Glance

4.3 Conjugated Polymers, as Active Materials for Battery Systems

4.4 Concluding Remarks

References

5 Redox‐Active, Sulfur‐Containing Polymers

Study Goals

5.1 Introduction

5.2 Fundamentals of Sulfur‐Containing Batteries

5.3 Composite Electrodes Incorporating Sulfur and Conductive Polymers

5.4 Sulfur‐Containing Polymers in Battery Applications

5.5 Concluding Remarks

References

6 Radical‐Containing Polymers for Energy‐Storage Applications

*

Study Goals

6.1 Introduction

6.2 Organic Radical Polymers

6.3 TEMPO‐Containing Polymers for Energy‐Storage Applications

6.4 Beyond TEMPO: Other Nitroxyl Moieties in ORPs

6.5 Miscellaneous Free‐Radical Moieties in ORPs

6.6 Concluding Remarks

References

Note

7 Polymers Equipped with Redox‐Active Quinone Moieties

*

7.1 Introduction

7.2 General Considerations Regarding Carbonyl Compounds, as Active Electrode Materials

7.3 Quinone‐Containing Polymers for Energy‐Storage Applications

7.4 Polyketone‐Containing Polymers for Energy‐Storage Applications

7.5 Polymers, Which Contain Miscellaneous Redox‐Active Carbonyl Moieties

7.6 Concluding Remarks

References

Note

8 Polyimides and Related Polymers in Battery Applications

*

Study Goals

8.1 Introduction

8.2 Conventional PIs, as Active Materials

8.3 Non‐conventional PIs, as Active Materials

8.4 Conjugated Polymers Incorporating the Core of Diimide Moieties

8.5 Multidimensional Polyimides

8.6 Miscellaneous Polymer Structures Incorporating Redox‐Active Imide Moieties

8.7 Concluding Remarks

References

Note

9 Polymers Containing Redox‐Active Viologen‐Type Moieties

9.1 Introduction

9.2 Viologen‐Containing Polymers for Solid‐State Batteries

9.3 Viologen‐Containing Polymers for Supercapacitors

9.4 Viologen‐Containing Polymers for Redox‐Flow Batteries

9.5 Concluding Remarks

References

10 Polymers: Containing Redox‐Active

N

‐Heterocyclic Moieties

10.1 Introduction

10.2 Polymers: Containing Triphenylamine Moieties

10.3 Polymers: Containing Redox‐Active Carbazole Moieties

10.4 Polymers: Containing Redox‐Active 5,10‐Dihydrophenazine Moieties

10.5 Polymers: Containing Redox‐Active Phenazine Moieties

10.6 Polymers: Containing Redox‐Active Phenothiazine or Phenoxazine Moieties

10.7 Concluding Remarks

References

11 Redox‐Active Metallopolymers

Study Goals

11.1 Introduction

11.2 Applications Related to Redox‐Active Metallopolymers

11.3 Ferrocene‐Containing Polymers for Energy‐Storage Applications

11.4 Beyond Ferrocene: Other Types of Redox‐Active Metallopolymers

11.5 Concluding Remarks

References

12 Students' Section: Representative Exercises on Redox Polymers and Their Usage in Energy‐Storage Applications

12.1 Introduction

12.2 Problems

References

Index

End User License Agreement

List of Tables

Chapter 2

Table 2.1 Summary of recent benchmark values for lithium‐ion and organic ba...

Table 2.2 Summary of the physio‐ and electrochemical properties of various ...

Chapter 3

Table 3.1 Summary of the advantages, disadvantages, and monomer requirement...

Table 3.2 Summary of TEMPO‐bearing polymerizable groups with their inherent...

Chapter 4

Table 4.1 The advantages and disadvantages of important conjugated polymers...

Chapter 6

Table 6.1 Overview of free radicals, which have been introduced into ORPs, ...

Table 6.2 The key characteristics of established LIBs compared to those of ...

Chapter 8

Table 8.1 Common dianhydride and diamine monomers for preparing PIs.

Table 8.2 Comparison of some aqueous batteries based on the lithium‐ion tec...

List of Illustrations

Chapter 1

Figure 1.1 Development of the number of large‐scale energy‐storage projects ...

Figure 1.2 Schematic representation of the most relevant parent conjugated p...

Figure 1.3 Timeline with the most noteworthy inventions and scientific miles...

Figure 1.4 (a) Schematic section through a Bridgestone/Seiko coin‐cell batte...

Figure 1.5 Schematic representation of the chemical structure of PEDOT:PSS. ...

Figure 1.6 (a) Schematic representation of PTMA; (b) schematic representatio...

Chapter 2

Figure 2.1 Classification of energy‐storage (ES) technologies.

Figure 2.2 The advantages of polymer‐based batteries.

Figure 2.3 Schematic representation of the discharging and charging process ...

Figure 2.4 Picture of some important types of batteries: a large 4.5 V block...

Figure 2.5 Schematic representation of the discharging and charging process ...

Figure 2.6 Representation of typical voltage–time (

V

–

t

) curves for a dischar...

Figure 2.7 Schematic representation of a coin cell [7].

Figure 2.8 Schematic representation of (a) a Swagelock™ and (b) a Swagelock™...

Figure 2.9 Schematic representation of a pouch cell [7].

Figure 2.10 Schematic representation of the discharging and charging process...

Figure 2.11 Schematic comparison of the discharging behavior of batteries, w...

Figure 2.12 (a) Schematic representation of an aqueous battery. (b) Summary ...

Figure 2.13 Spiderweb diagram of the material requirements for solid‐state b...

Figure 2.14 Ragone plot for typical energy‐storage devices [87].

Figure 2.15 (a) Representation of a Kleistian jar. (b) Picture of a battery ...

Figure 2.16 (a) Schematic representation of the working principle of a pseud...

Figure 2.17 Itemized Ragone plot showing the specific energy and power for d...

Figure 2.18 Comparison of the cyclability of SC containing PAni, graphene na...

Figure 2.19 Schematic representation of a redox‐flow battery.

Figure 2.20 Spiderweb diagrams of the material requirements for (a) aqueous ...

Figure 2.21 Schematic representation of various redox‐active homopolymers an...

Figure 2.22 Schematic representation of the synthesis of a TEMPO‐containing ...

Figure 2.23 (a) Schematic representation of redox‐active PILs. (b) Schematic...

Figure 2.24 Schematic representation of the three different types of SRFB: (...

Figure 2.25 Schematic representation of an aqueous all‐polymer SRFB: polyqui...

Chapter 3

Figure 3.1 Comparison of the cell voltage of batteries, which contain a cond...

Figure 3.2 Schematic representation of the various homopolymer and copolymer...

Figure 3.3 Schematic representation of three representative redox‐active hom...

Figure 3.4 Schematic representation of the synthetic approaches for the sequ...

Figure 3.5 (a) Schematic representation of various chain alignments in the v...

Figure 3.6 Schematic representation of representative diblock copolymers, wh...

Figure 3.7 Schematic representation of the synthesis of graft polymers

via

g...

Figure 3.8 (a) Schematic representation of the SiO

2

nanoparticles, which wer...

Figure 3.9 Schematic representation of the multistep fabrication of a 3D ord...

Figure 3.10 Schematic representation of the various types of star‐shaped pol...

Figure 3.11 Schematic representation of the topologies of a hyperbranched po...

Figure 3.12 (a) Schematic representation of a hyperbranched polymer, which w...

Figure 3.13 Schematic representation of the various strategies applied in de...

Figure 3.14 Schematic representation of the step‐growth polymerization of di...

Figure 3.15 Representation of the evolution of the molar mass (

M

n

) as a func...

Figure 3.16 Schematic representation of the initiation and chain‐propagation...

Figure 3.17 Representation of the characteristics of CRPs: (a) evolution of ...

Figure 3.18 Schematic representation of the mechanism of an NMP, as proposed...

Figure 3.19 Schematic representation of the ATRP mechanism (P, polymer chain...

Figure 3.20 Schematic representation of the mechanism of the RAFT polymeriza...

Figure 3.21 Schematic representation of the mechanism of (a) the anionic and...

Figure 3.22 Schematic representation of the mechanism of the ROMP process.

Figure 3.23 Schematic representation of the mechanism of the chemical polyme...

Figure 3.24 (a) Schematic representation of a typical three‐electrode setup,...

Figure 3.25 Representation of the three common types of CV curves: (a) rever...

Figure 3.26 Representation of typical voltammograms obtained with a RDE elec...

Figure 3.27 Overview of the reversible redox potential of diverse redox syst...

Figure 3.28 (a) Representative Nyquist plot for an electrochemically active ...

Figure 3.29 (a) Schematic representation of the idealized structure of a ani...

Figure 3.30 (a) Representative AFM images (2 × 2 μm, film thickness of

ca

. 1...

Chapter 4

Figure 4.1 (a) Excerpt from the original paper from 1977.(b) Pictures of...

Figure 4.2 Comparison of the conductivity of typical π‐conjugated polymers t...

Figure 4.3 (a) Schematic representation of classical, hydrocarbon‐based, π‐c...

Figure 4.4 Comparison of the cell voltage of batteries, which contain either...

Figure 4.5 The pioneers of aniline chemistry (from the top left to the botto...

Figure 4.6 (a) H. Letheby (1816–1876). (b) Representation of a Grove cell, a...

Figure 4.7 (a) The chemical structure of polyaniline was analyzed first (fro...

Figure 4.8 (a) A. Angeli (1864–1931) [95].(b) Schematic representation o...

Figure 4.9 (a) Donald Weiss (1924–2008).(b) Schematic representation of ...

Figure 4.10 (a) Schematic representation of Yamamoto's original PT synthesis...

Figure 4.11 Schematic representation of the chemical structure of PEDOT:PSS....

Figure 4.12 Evaluation of the three different methods for the synthesis of c...

Figure 4.13 (a) Schematic representation of Shirakawa's synthesis of the all...

Figure 4.14 Schematic representation of

P1–P5

.

Figure 4.15 (a) Cycling stability of

P2

, as the cathode active material in a...

Figure 4.16 (a) Representative scanning‐electron microscopy (SEM) images of ...

Figure 4.17 (a) Rate capability of the LiFePO

4

/PAni composite, as cathode ac...

Figure 4.18 Schematic representation of the electron‐ and charge‐transfer pr...

Figure 4.19 (a) Schematic representation of the reversible redox chemistry o...

Figure 4.20 (a) Schematic representation of sulfonated PAni (

P6

). (b) Schema...

Figure 4.21 Schematic representation of the reversible redox behavior of

P9

....

Figure 4.22 (a) Schematic representation of the proposed redox chemistry of

Figure 4.23 (a) Representative SEM images of the various

N

‐containing carbon...

Figure 4.24 (a) Schematic representation of the configuration of a solid‐sta...

Figure 4.25 (a) Charging/discharging curves of various film electrodes (elec...

Figure 4.26 (a) Representative DSEM images of PPy and a PPy/LiFePO

4

composit...

Figure 4.27 (a) Picture of the flexible composite cathode. (b) Schematic rep...

Figure 4.28 (a) Representative SEM images of V

2

O

5

nanotube – before and afte...

Figure 4.29 (a) Representative SEM image of the PPy/cellulose composite. (b)...

Figure 4.30 (a) Representative SEM images of the non‐coated and PPY‐coated N...

Figure 4.31 (a) Schematic representation of the two‐step synthesis of PPy‐co...

Figure 4.32 (a) Schematic representation of Fc‐functionalized PPy (

P11

). (b)...

Figure 4.33 (a) Schematic representation of the synthesis of

P12

. (b) Repres...

Figure 4.34 Schematic representation of the modified polypyrroles

P13

–

P16

.

Figure 4.35 (a) Cycling stability of various “polythiophene” films (2.4–4.2 ...

Figure 4.36 (a) Schematic representation of the all‐particulate redox‐flow b...

Figure 4.37 Schematic representation of the fabrication of an activated carb...

Figure 4.38 Schematic representation of the preparation of PEDO:PSS‐coated α...

Figure 4.39 (a) Representative SEM image of redox‐doped PEDOT (substrate: co...

Figure 4.40 (a) Schematic representation of the working principle of a Li–O

2

Figure 4.41 (a) Schematic representation of polymers

P17

–

P20

. (b) Ragone plo...

Figure 4.42 (a) Charging/discharging curve of a PPP film better at the curre...

Figure 4.43 (a) Schematic representation of polyindole. (b) Cycling stabilit...

Figure 4.44 (a) Cycling stability and coulombic efficiency of composite cath...

Chapter 5

Figure 5.1 Schematic representation of the working principle of the first LI...

Figure 5.2 (a) Schematic representation of the working principle of a LSB al...

Figure 5.3 (a) Comparison of charging/discharging curves shows a conventiona...

Figure 5.4 (a) Schematic representation of the PPy/

P1

composite with mixed i...

Figure 5.5 Schematic representation of the fabrication of the sandwich‐type ...

Figure 5.6 (a) Schematic representation of the preparation of the three‐comp...

Figure 5.7 Representation of the various structural designs of S/PAni compos...

Figure 5.8 Representative scanning‐electron microscopy (SEM, a and d) and TE...

Figure 5.9 (a) Schematic representation of the stepwise fabrication of a PAn...

Figure 5.10 (a) Schematic representation of the core–shell PT/S composite pa...

Figure 5.11 (a) Representative TEM image of PEDOT‐coated sulfur nanospheres....

Figure 5.12 Comparison between a PEDOT:PSS‐coated and pristine sulfur cathod...

Figure 5.13 Schematic representation of the fabrication of hollow S nanosphe...

Figure 5.14 Schematic representation of the preparation of PDA‐coated porous...

Figure 5.15 Schematic representation of PVK and Nafion™.

Figure 5.16 (a) Representative SEM images of the pristine S/C cathode (top) ...

Figure 5.17 Schematic representation of (a) the SPPEs

P2–P5

; (b) the s...

Figure 5.18 Schematic representation of the available conductivity window of...

Figure 5.19 (a) Schematic representation of polythiocyanogen. (b) Cycle stab...

Figure 5.20 Schematic representation of polymers

P6–P10

, which contain...

Figure 5.21 Schematic representation of the “aromatic” polydisulfides

P11

an...

Figure 5.22 (a) Schematic representation of the reversible charging/discharg...

Figure 5.23 (a) Schematic representation of the formation of the cross‐linke...

Figure 5.24 (a) Schematic representation of the typical polysulfide synthesi...

Figure 5.25 Schematic representation of the fabrication process of polysulfi...

Figure 5.26 Schematic representation of the synthesis of a sulfurized BOP, a...

Figure 5.27 (a) Schematic representation of the synthesis of poly(PMAT‐

co

‐S)...

Figure 5.28 (a) Schematic representation of the graphene‐supported TTCA‐sulf...

Figure 5.29 (a) Schematic representation of the high‐temperature reaction be...

Figure 5.30 (a) Charge/discharge curves of the 100 mAh prototype LSB at the ...

Figure 5.31 (a) Schematic representation of the idealized synthesis of carby...

Figure 5.32 (a) Schematic representation of the synthesis of poly(S‐r‐DIB)

v

...

Figure 5.33 Schematic representation of the stepwise fabrication of the poly...

Figure 5.34 (a) Schematic representation of the synthesis of a sulfurized, p...

Figure 5.35 (a) Schematic representation of the synthesis of PPTS. (b) Pictu...

Figure 5.36 (a) Schematic representation of the polymers

P14

and

P15

with th...

Figure 5.37 (a) Charging/discharging curves of a polythiophene (actually bei...

Figure 5.38 Schematic representation of (a) the reversible redox behavior of...

Figure 5.39 (a) Charging/discharging curves of

P23

[203]. (b) Cyclability of ...

Figure 5.40 Schematic representation of thianthrene's reversible redox chemi...

Figure 5.41 (a) Schematic representation of the redox chemistry of

P25

. (b) ...

Figure 5.42 Schematic representation of the thianthrene‐containing side‐chai...

Figure 5.43 (a) Charging/discharging curves of a composite electrode (

P26

/am...

Figure 5.44 (a) Schematic representation of the TCNQ‐equipped n‐type polymer...

Chapter 6

Figure 6.1 Schematic representation of persistent (a)

C

‐centered radicals, (...

Figure 6.2 (a) Schematic representation of the TEMPO‐equipped polymers PTA a...

Figure 6.3 Schematic representation of the synthesis of ORPs

via

a direct po...

Figure 6.4 Correlation between the theoretical capacities and molar mass of ...

Figure 6.5 Schematic representation of the three different electron‐transfer...

Figure 6.6 Schematic representation of conjugated/conductive polymers with p...

Figure 6.7 Schematic representation of the various tacticities of polymers....

Figure 6.8 (a) Schematic representation of polyacetylenes with pending free‐...

Figure 6.9 Schematic representation of the synthesis of a bottlebrush polyme...

Figure 6.10 (a) Schematic representation of TEMPO‐equipped, poly(phenylacety...

Figure 6.11 (a) Schematic representation of poly(TEMPO acrylamide)

P18

. (b) ...

Figure 6.12 (a) Schematic representation of the synthesis of a cross‐linked ...

Figure 6.13 Schematic representation of the formation of surface‐bound polym...

Figure 6.14 Schematic representation of the synthesis of surface‐anchored PT...

Figure 6.15 Schematic representation of the two‐step electron transfer in PT...

Figure 6.16 (a) Comparison of the charging/discharging capacities of non‐cro...

Figure 6.17 Representative scanning‐electron microscopy (SEM) image of an OR...

Figure 6.18 Schematic representation of the fabrication of a PTMA‐coated ele...

Figure 6.19 (a) Picture of the PTMA‐containing 100‐mAh Al‐laminated film pac...

Figure 6.20 Schematic representation of the compensation and self‐compensati...

Figure 6.21 Comparison of the cycling stability of PTMA/C composites, which ...

Figure 6.22 Representation of the molar‐mass dependence of the cell performa...

Figure 6.23 (a) Schematic representation of the TEMPO‐equipped polynorbornen...

Figure 6.24 Schematic representation of Nishide's first all‐polymeric batter...

Figure 6.25 (a) Schematic representation of the hydrophilic ORPs

P24–P26

...

Figure 6.26 (a) Charging/discharging curves of the PTPM/

P26

battery, which c...

Figure 6.27 Schematic representation of the configuration of an ultrathin, f...

Figure 6.28 (a) Schematic representation of polydopamine

P28

. (b) Evolution ...

Figure 6.29 (a) Schematic representation of the synthesis of

P29

via

a grafti...

Figure 6.30 (a) Schematic representation of PIPO. (b) Charging/discharge cur...

Figure 6.31 (a) Schematic representation of copolymers

P30

and

P31

. (b) Repr...

Figure 6.32 Schematic representation of a water‐based, hybrid‐flow battery. ...

Figure 6.33 (a) Schematic representation of the diblock copolymer

P32

. (b) C...

Figure 6.34 Representation of the long‐term stability of the water‐based RFB...

Figure 6.35 (a) Schematic representation of the ORPs

P33

–

P35

. (b) Representa...

Figure 6.36 (a) Schematic representation of the phenylnitroxyl‐equipped poly...

Figure 6.37 (a) Schematic representation of the (nitronyl‐nitroxide)‐equippe...

Figure 6.38 (a) Schematic representation of the reversible reduction and oxi...

Figure 6.39 Schematic representation of the phenoxyl‐containing polymers

P44

...

Figure 6.40 (a) Schematic representation of the galvinoxyl‐containing polyme...

Figure 6.41 Schematic representation of polymers equipped with Blatter‐radic...

Figure 6.42 Schematic representation of the assumed development of ORBs – hy...

Chapter 7

Figure 7.1 (a) Schematic representation of important natural quinone derivat...

Figure 7.2 Classification scheme for redox‐active carbonyl compounds; for ea...

Figure 7.3 Schematic representation of the carbonyl compounds, which were st...

Figure 7.4 (a) Schematic representation of

P2–P5

. (b) Charging/dischar...

Figure 7.5 (a) Schematic representation of the methylene‐bridged polymers

P6

Figure 7.6 (a) Schematic representation of the sulfur‐bridged polymers

P9–P1

...

Figure 7.7 (a) Schematic representation of the SIB, which used

P13

and

P10

, ...

Figure 7.8 (a) Schematic representation of the lithium‐ion storage mechanism...

Figure 7.9 (a) Schematic representation of the synthesis of

P15

. (b) Cycling...

Figure 7.10 (a) Schematic representation of

P16

. (b) Rate performance of

P16

Figure 7.11 (a) Schematic representation of the two‐step synthesis of

P17

. (...

Figure 7.12 Schematic representation of polymers

P18–P21

.

Figure 7.13 (a) Schematic representation of the overall cell reaction. (b) S...

Figure 7.14 (a) Schematic representation of

COF1

and

COF2

. (b) Schematic rep...

Figure 7.15 Cycling performance of the anthraquinone‐triazine COF at 200 mA ...

Figure 7.16 (a) Schematic representation of the preparation of poly(vinyl hy...

Figure 7.17 (a) Schematic representation of a polymer/air battery, which use...

Figure 7.18 (a) Schematic representation of the anthraquinone‐equipped condu...

Figure 7.19 Schematic representation of the side‐chain polymers

P27

and

P28

....

Figure 7.20 (a) Schematic representation of the reversible four‐electron red...

Figure 7.21 (a) Charging/discharging curves of

P29

, LiTi

2

(PO

4

)

3

and LiMn

2

O

4

...

Figure 7.22 (a) Schematic representation of the PYT‐containing polymers

P30

...

Figure 7.23 (a) Schematic representation of the synthesis of boroxine‐based

Figure 7.24 (a) Schematic representation of

P32

. (b) Schematic representatio...

Figure 7.25 Schematic representation of

PET

and

P33

, as examples for a main‐...

Figure 7.26 (a) Schematic representation of the derivatives

P34–P39

, i...

Figure 7.27 (a) Cycling stability and coulombic efficiency of a LIB, which c...

Figure 7.28 Schematic representation of the biomass‐derived polymers

P40

and...

Figure 7.29 (a) Schematic representation of the bioinspired synthesis of pol...

Figure 7.30 Schematic representation of the polyimines

P41

and

P42

.

Figure 7.31 (a) Schematic representation and picture of

P43

. (b) Representat...

Figure 7.32 (a) Schematic representation of the reversible storage of 6 Li

+

...

Figure 7.33 Schematic representation of polymers

P45

, which incorporated red...

Figure 7.34 (a) Schematic representation of the ladder‐type polymers

P46–P48

...

Chapter 8

Figure 8.1 Schematic representation of the two‐step synthesis of polyimides ...

Figure 8.2 Schematic representation of the redox reaction of various diimide...

Figure 8.3 Picture and chemical structure of the industrial PDI dye PR149....

Figure 8.4 Schematic representation of the reversible redox enolation of con...

Figure 8.5 Schematic representation of PI‐type redox polymers

P1

–

P6

.

Figure 8.6 (a) Representative scanning‐electron microscopy image of the

P6

/c...

Figure 8.7 (a) Schematic representation of the formation of the composite PI...

Figure 8.8 Schematic representation of a hybrid sodium‐ion capacitor [40]....

Figure 8.9 (a) Schematic representation of polymers

P7

and

P8

. (b) Discharge...

Figure 8.10 Comparison of the battery performance of three typical aqueous L...

Figure 8.11 (a) Schematic representation of the chain‐extended polyimide

P9

...

Figure 8.12 Schematic representation of the various PDI‐containing polyimide...

Figure 8.13 Schematic representation of the synthesis of PTCLi6 and

P11c

fro...

Figure 8.14 (a) Schematic representation of the slurry RFB incorporating PHQ...

Figure 8.15 (a) Schematic representation of the urea‐ and sulfonyl‐bridged N...

Figure 8.16 (a) Schematic representation of the anthraquinone‐bridged polyme...

Figure 8.17 (a) Schematic representation of anthraquinone‐bridged polyimides...

Figure 8.18 Schematic representation of the cardo polyimides

P23–P25

....

Figure 8.19 (a) Schematic representation of the redox polymer

P26

. (b) Charg...

Figure 8.20 (a) Schematic representation of polymer

P27

. (b) Rate performanc...

Figure 8.21 Schematic representation of polyimides

P28

and

P29

, which could ...

Figure 8.22 Schematic representation of the polyimides

P30

and

P31–P33

Figure 8.23 (a) Schematic representation of the carbonyl‐rich polyimide

P34

....

Figure 8.24 Influence of various core substituents on the redox potentials (...

Figure 8.25 (a) Schematic representation of polymers

P35

and

P36

. (b) Compar...

Figure 8.26 (a) Schematic representation of the polymers

P37

and

P38

. (b) Sc...

Figure 8.27 (a) Schematic representation of the π‐conjugated polymers

P39

wi...

Figure 8.28 Schematic representation of the fabrication of a freestanding an...

Figure 8.29 (a) Schematic representation of a crystalline polyimide COF

via

...

Figure 8.30 (a) Schematic representation of the synthesis of

P41

via

chemical...

Figure 8.31 (a) Schematic representation of the triptycene‐containing 3D pol...

Figure 8.32 (a) Schematic representation of the ladder‐type polymer

P43

. (b)...

Figure 8.33 (a) Schematic representation of the side‐chain NDI‐containing po...

Figure 8.34 Schematic representation of the redox polymers

P45

and

P46

.

Chapter 9

Figure 9.1 (a) Schematic representation of the reversible two‐stage redox ch...

Figure 9.2 Schematic representation of viologen‐containing main‐chain and si...

Figure 9.3 Schematic representation of

P1

,

PSS

, and the electrochromic devic...

Figure 9.4 (a) Schematic representation of the free‐radical polymer

P2

. (b) ...

Figure 9.5 (a) Schematic representation of the main‐chain polyviologens

P3–P

...

Figure 9.6 (a) Schematic representation of the main‐chain polymer

P8

. (b) Cy...

Figure 9.7 Schematic representation of the synthesis of methyl viologen

via

...

Figure 9.8 (a) Schematic representation of the cross‐linked polymer

P9

. (b) ...

Figure 9.9 Schematic representation of the all‐polymeric battery, which cont...

Figure 9.10 (a) Schematic representation of phospha‐MV

2+

. (b) Representation...

Figure 9.11 (a) Schematic representation of polymers

P12

. (b) Cycling stabil...

Figure 9.12 (a) Schematic representation of

P13

. (b) Rate performance of

P5

...

Figure 9.13 Schematic representation of the thiazolo[5,4‐

d

]thiazole‐containi...

Figure 9.14 (a) Representative SEM image of

P15

.(b) N

2

adsorption/desorp...

Figure 9.15 (a) Schematic representation of polymers

P16

, which comprise a c...

Figure 9.16 Ragone plot of different energy‐storage systems [94].

Figure 9.17 (a) Schematic representation of

P17

. (b) Schematic representatio...

Figure 9.18 (a) Schematic representation of cross‐linked

P18

. (b) Charging/d...

Figure 9.19 Schematic representation of an aqueous RFB, which contains

P19

a...

Figure 9.20 (a) Cycling stability and coulombic efficiency of the aqueous RF...

Figure 9.21 (a) Schematic representation of polymers

P20

and

P21

. (b) Rheolo...

Figure 9.22 (a) Charging/discharging curves of the symmetric RFB (the dotted...

Figure 9.23 Schematic representation of polymers

P23

–

P25

.

Figure 9.24 (a) Schematic representation of the synthesis of the viologen‐lo...

Chapter 10

Figure 10.1 (a) Schematic representation of a

N

‐doped graphene layer, in whi...

Figure 10.2 (a) Schematic representation of the p‐type, one‐electron redox b...

Figure 10.3 (a) Schematic representation of PTPA; the background shows repre...

Figure 10.4 (a) Schematic representation of the reversible redox behavior of...

Figure 10.5 (a) Schematic representation of polymers

P1

and

P2

. (b) Represen...

Figure 10.6 (a) Schematic representation of polymer

P3

. (b) Representative S...

Figure 10.7 (a) Representative SEM images of PTPA microfibers (left) and par...

Figure 10.8 (a) Schematic representation of the polymers

P4

–

P6

. (b) Cycling ...

Figure 10.9 (a) Schematic representation of

P7

. (b) Schematic representation...

Figure 10.10 (a) Schematic representation of the polymers

P8

and

P9

. (b) Rep...

Figure 10.11 (a) Schematic representation of hyperbranched

P10

. (b) Represen...

Figure 10.12 (a) Schematic representation of the self‐doped DPPA‐type polyme...

Figure 10.13 Schematic representation of the polymers

P15

–

P18

.

Figure 10.14 (a) Cycling stability and (b) rate performance of

P17

and PTPA,...

Figure 10.15 (a) Schematic representation of

P19

. (b) Representative SEM ima...

Figure 10.16 (a) Schematic representation of polymers

P20

and

P21

. (b) Repre...

Figure 10.17 (a) Schematic representation of side‐chain polymer

P22

. (b) Sch...

Figure 10.18 Schematic representation of poly(3,6‐carbazole) (PCz) and poly(

Figure 10.19 (a) Schematic representation of the aqueous Zn battery, which u...

Figure 10.20 (a) Cyclability of a LIB, which contained PVK, as the cathode a...

Figure 10.21 (a) Representative SEM and TEM images of the PVK/S@rGO composit...

Figure 10.22 (a) Schematic representation of the conjugated polymer networks...

Figure 10.23 (a) Comparison of the electrochemical performance of the PCz/S,...

Figure 10.24 (a) Cycling stabilities and coulombic efficiencies of (a) a pot...

Figure 10.25 (a) Schematic representation of the configuration of the “rocki...

Figure 10.26 (a) Schematic representation of the reversible two‐electron red...

Figure 10.27 (a) Schematic representation of polymers

P24

and

P29

. (b) Rate ...

Figure 10.28 (a) Schematic representation of polymers

P24

and

P30

. (b) Compa...

Figure 10.29 (a) Schematic representation of the dual‐ion‐battery, which use...

Figure 10.30 (a) Schematic representation of the polymer networks (or COFs)

Figure 10.31 (a) Schematic representation of

P33

. (b) Representative SEM ima...

Figure 10.32 (a) Schematic representation of

P34

. (b) Schematic representati...

Figure 10.33 (a) Schematic representation of the ladder‐type polymer

P35

. (b...

Figure 10.34 (a) Schematic representation of benzo‐fused hexaazatriphenylene...

Figure 10.35 Schematic representation of COF

P37

. A representative TEM image...

Figure 10.36 (a) Schematic representation of polymers

P38

. (b) Cycling stabi...

Figure 10.37 Cycling stability and coulombic efficiency of (a) a magnesium‐i...

Figure 10.38 (a) Schematic representation of the simulated molecular structu...

Figure 10.39 (a) Schematic representation and space‐filling model of

P40

. (b...

Figure 10.40 (a) Schematic representation of the formation of a homogeneous ...

Figure 10.41 Schematic representation of the COFs C

2

N, C

3

N, and

P41

[143]....

Figure 10.42 (a) Schematic representation of the merging of battery and supe...

Figure 10.43 Schematic representation of

P43

, which was used as the polymeri...

Figure 10.44 (a) Schematic representation of phenothiazine's reversible redo...

Figure 10.45 (a) Schematic representation of

P47

. (b) Cycling stability and ...

Figure 10.46 (a) Schematic representation of the configuration of a LIB, whi...

Figure 10.47 (a) Schematic representation of the polynorbornene‐based polyme...

Figure 10.48 (a) Schematic representation of polymers

P51–P53

. (b) Cyc...

Figure 10.49 (a) Schematic representation of the cross‐linked polymers

P54

. ...

Figure 10.50 (a) Schematic representation of

P55

and of the proposed charge‐...

Figure 10.51 Schematic representation of the phenothiazine–dihydrophenazine ...

Figure 10.52 Schematic representation of the reversible redox behavior of

N

‐...

Figure 10.53 Schematic representation of the phenoxazine‐containing polymers...

Chapter 11

Figure 11.1 A schematic overview of the diverse applications related to meta...

Figure 11.2 Schematic representation of the various types of metallopolymer ...

Figure 11.3 (a) Picture of ferrocene powder.(b) Schematic representation...

Figure 11.4 (a) Schematic representation of the Fc‐containing polymer, used ...

Figure 11.5 Schematic representation of the fabrication of a layered electro...

Figure 11.6 (a) Schematic representation of the π‐conjugated polymers

1

. (b)...

Figure 11.7 (a) Schematic representation of pristine and Fc‐modified PTPA. (...

Figure 11.8 (a) Schematic representation of the electrochemical switching be...

Figure 11.9 (a) Schematic representation of the PPys

3

and

4

with pending Fc...

Figure 11.10 (a) Schematic representation of Fc‐functionalized aniline monom...

Figure 11.11 (a) Schematic representation of the Fc‐equipped polyheteroacene...

Figure 11.12 (a) Schematic representation of the cobaltocenium‐containing po...

Figure 11.13 Schematic representation of the working principle of a redox‐fl...

Figure 11.14 Schematic representation of the redox‐active polymers

9

and

10

,...

Figure 11.15 (a) Schematic representation of the water‐soluble, Fc‐containin...

Figure 11.16 Schematic representation of the synthesis of a metallo‐supramol...

Figure 11.17 (a) Schematic representation of the reversible charging/dischar...

Figure 11.18 (a) Schematic representation of poly(TEMPO methacrylate), an or...

Figure 11.19 Schematic representation of the polymers

15

and

16

.

Figure 11.20 (a) Schematic representation of the multielectron redox‐switchi...

Figure 11.21 (a) Schematic representation of the CCPs

17

and

18

. (b) Compari...

Figure 11.22 (a) Schematic representation of aqueous Zn battery design. (b) ...

Figure 11.23 (a) Schematic representation of the reversible two‐step, redox‐...

Guide

Cover

Table of Contents

Title Page

Copyright

List of Abbreviations

Begin Reading

Index

End User License Agreement

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531

An Introduction to Redox Polymers for Energy‐Storage Applications

Ulrich S. Schubert, Andreas Winter, and George R. Newkome

Authors

Prof. Dr. Ulrich S. SchubertFriedrich Schiller University JenaGermany

Dr. Andreas WinterFriedrich Schiller University JenaGermany

Dr. George R. NewkomeFlorida Atlantic UniversityUSA

Cover Design: Adam Design, Weinheim, Germany

Cover Image: Polyethylene Terephthalate © Shutterstock, Fondmotif and chip © Getty Images

All books published by WILEY‐VCH are carefully produced. Nevertheless, authors, editors, and publisher do not warrant the information contained in these books, including this book, to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

Library of Congress Card No.: applied for

British Library Cataloguing‐in‐Publication Data:A catalogue record for this book is available from the British Library.

Bibliographic information published by the Deutsche NationalbibliothekThe Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at <http://dnb.d-nb.de>.

© 2023 Wiley‐VCH GmbH, Boschstr. 12, 69469 Weinheim, Germany

All rights reserved (including those of translation into other languages). No part of this book may be reproduced in any form – by photoprinting, microfilm, or any other means – nor transmitted or translated into a machine language without written permission from the publishers. Registered names, trademarks, etc. used in this book, even when not specifically marked as such, are not to be considered unprotected by law.

Print ISBN: 9783527350902ePDF ISBN: 9783527839285ePub ISBN: 9783527839292oBook ISBN: 9783527843466

List of Abbreviations

ADMET

acyclic diene metathesis

AFM

atomic‐force microscopy

AIBN

2,2′‐azobis(2‐methylpropionitrile)

aRFID

active radio‐frequency identification

ATRP

atom‐transfer radical polymerization

bdt

1,2‐benzenedithiolate

BHJ

bulk heterojunction

BODIPY

boron‐dipyrromethene (

i.e

. 4,4‐difluoro‐4‐bora‐3

a

,4

a

‐diaza‐

s

‐indacene)

BOP

benzoxazine polymer

BTMAPV

1,1‐bis‐[3‐(trimethylammonium)propyl]‐4,4‐bipyridinium tetrachloride

CC

current collector

CCP

conjugated coordination polymers

CD

circular dichroism

CDSA

crystallization‐driven self‐assembly

CE

coulombic efficiency

CNT

carbon nanotube

COF

covalent organic framework

CONASH

coordination nanosheets

CRP

controlled‐radical polymerization

CSIRO

Commonwealth Scientific and Industrial Research Organization

CuAAC

Cu(I)‐catalyzed alkyne‐azide cycloaddition

CV

cyclovoltammetry

Đ

dispersity

DIB

1,3‐diisopropenylbenzene

DP

degree of polymerization

DPE

1,1‐diphenylethylene

DPV

differential‐pulse voltammetry

EDLC

electrical double‐layer capacitor

EDX

energy‐dispersive X‐ray

EE

energy efficiency

EQCM

electrochemical quartz‐crystal microbalance

ESR

electron‐spin resonance

ETT

ethenetetrathiol

exTTF

π‐extended tetrathiafulvalene

F

Faraday constant (9.6485 × 10

4

 C mol

−1

)

Fc

ferrocene

FRP

free‐radical polymerization

FT‐IR

Fourier transform infrared

GNS

graphene nanosheet

GO

graphene oxide

HER

hydrogen evolution reaction

HFB

half‐flow battery

HFP

hexafluoropropylene

HHTP

2,3,6,7,10,11‐hexahydroxytriphenylene

IEM

ion‐exchange membrane

IoT

internet of things

ITO

indium–tin oxide

LED

light‐emitting device

or

light‐emitting diode

LIB

lithium‐ion battery

LSB

lithium–sulfur battery

METAC

[2‐(methacryloyloxy)ethyl]trimethylammonium chloride

M

n

number‐averaged molar mass

MOF

metal‐organic framework

MRI

magnetic‐resonance imaging

MV

methylviologen

M

w

weight‐averaged molar mass

MWCNT

multi‐walled carbon nanotube

MWCO

molecular weight cut‐off

NDI

1,4,5,8‐naphthalenetetracarboxylic diimide

NIDI

bis(

o

‐diiminobenzosemiquinonato)nickel(II)

NIR

near‐infrared

NMR

nuclear magnetic resonance

NTCDA

1,4,5,8‐naphthalenetetracarboxylic dianhydride

OCP

open‐circuit potential

OCV

open‐circuit voltage

OEG

oligo(ethylene glycol)

OER

oxygen evolution reaction

OFET

organic field‐effect transistor

ORB

organic radical battery

ORP

organic radical polymer

P3HT

poly(3‐hexylthiophene)

PA

polyacetylene

PAMAM

polyamidoamine

PAN

polyacrylonitrile

PAni

polyaniline

PCET

proton‐coupled electron transfer

PDA

polydopamine

PDI

perylenetetracarboxylic diimide

PDPA

polydiphenylamine

PE

polyethylene

PEDOT

poly(3,4‐ethylendioxythiophene)

PEFc

polyethynylferrocene

PEG

poly(ethylene glycol)

PEM

poly(ethylene‐

alt

‐maleic anhydride)

PEO

polyether

PETA

pentaerythritol tetraacrylate

PFc

polyferrocene

PFDS

polyferrocenyldimethylsilane

PFS

polyferrocenylsilanes

PI

poly(imide)

PIB

potassium‐ion battery

PIL

poly(ionic liquid)

PMADA

pyromellitic acid dianhydride

PMAT

poly(

m

‐aminothiophenol)

PMDI

pyromellitic diimide

PP

polyphenylene

or

polypropylene

PPTS

poly(phenylene tetrasulfane)

PPV

poly(phenylene vinylidene)

PPy

polypyrrole

pRFB

polymer‐based RFB

PS

polystyrene

PT

polythiophene

PTA

poly(TEMPO acrylate)

PTCDA

3,4,9,10‐perylenetetracarboxylic acid dianhydride

PTMA

poly(TEMPO methacrylate)

PTPA

polytriphenylamine

PTPM

poly(tripyridiniomesitylene)

PTS

para

‐toluenesulfonate

PVBC

poly(vinylbenzyl chloride)

PVDF

poly(vinylidene fluoride)

PVFc

polyvinylferrocene

PVP

poly(vinyl pyrrolidone)

PVQ

poly(vinyl quinone)

QN

quaternary nitrogen

RAFT

reversible addition–fragmentation chain‐transfer

RDE

rotating‐disc electrode

RFB

redox‐flow battery

rGO

reduced graphene oxide

RI

refractive index

ROMP

ring‐opening metathesis polymerization

ROP

ring‐opening polymerization

salen

N

,

N

′‐ethylenebis(salicylimine)

SC

supercapacitor

SCE

saturated calomel electrode

SEI

solid‐to‐electrolyte interface

SEM

scanning‐electron microscopy

SERS

surface‐enhanced Raman spectroscopy

SHE

standard hydrogen electrode

SIB

sodium‐ion battery

SPAN

sulfurized polyacrylonitrile

SRPE

solid redox polymerization electrodes

SSB

sodium–sulfur battery

STM

scanning‐tunneling microscopy

SWCNT

single‐walled carbon nanotube

SWV

square‐wave voltammetry

TCAQ

7,7,8,8‐tetracyanoanthraquinodimethane

TCI

Tokyo Chemical Industry

TEMPO

2,2,6,6‐tetramethylpiperidin‐1‐oxyl‐4‐yl

TMEDA

N

,

N

,

N

′,

N

′‐tetramethylethylenediamine

TTF

tetrathiafulvalene

TTO

tetrathiooxalate

VE

voltage efficiency

WIS

water‐in‐salt

XPS

X‐ray photoelectron spectra

ZIB

zinc‐ion battery

1The Emergence of “Redox Polymers” in the Field of Energy‐Storage Applications*

Study Goals

Knowledge of the history and development of energy‐storage devices

Knowledge of important redox polymers from the different eras

1.1 An Introduction to Battery Systems

In recent years, the market for stationary energy‐storage systems has experienced a tremendous growth – a trend that is expected to continue almost undamped in the future (Figure 1.1) [1]. Moreover, the society calls for efficient, durable batteries to satisfy their specific wishes: electric vehicles, laptops, cell phones, wearable/portable gadgets, Internet of things (IoT), etc. [2]. To fulfill these as well as projected needs, worldwide research is focused on the improvement and development of tailor‐made, energy‐storage systems. In this respect, the implementation of new redox‐active materials represents one approach, and inter‐alia redox polymers have gained significant attention in recent years [3–7]. Before introducing these materials, the long history of energy‐storage devices will be briefly summarized.

In 1936, numerous items – a ceramic pot, a tube of copper, and a rod of iron – were found in Khujut Rabu, Iraq. These artifacts have been assigned to the Parthian (150 BC–223 AD) or Sasanian era (224–650 AD). Though their actual meaning still remains unclear, it has been speculated that they were used as an “energy‐storage device” (a potential of c. 0.8 V was calculated) [8]. Far later, the term “battery” was coined by Benjamin Franklin, who in 1748 compared multiple, simultaneously acting “Leyden jars” to an artillery battery [9]. The first electrochemical cell, the so‐called ”voltaic pile,” was constructed by Alessandro Volta in 1800 [10]. In subsequent years, various alternatives of this original device have been created. From these, the Daniell cell (initially reported in 1836) represents the first practical and durable power source, which even became an industry standard and was employed by the early British electrical telegraph networks [11]. All these batteries were “wet cells,” which were constructed from glassware and contained liquid electrolytes; however, in many cases, their fragile and dangerous nature prevented any portable applications, and they were superseded by the portable, hence more convenient dry‐cell batteries. In this respect, the Leclanché cell and Gassner's zinc–carbon cell – the first real “dry cell” batteries – have to be explicitly named; these dry cells offered potentials of 1.4 and 1.5 V, respectively [12]. The latter, patented in Germany in 1886, comprised a MnO2 cathode, which was dipped into the NH4Cl/ZnCl2 electrolyte paste; the surrounding Zn shell acted as the anode [13].

Figure 1.1 Development of the number of large‐scale energy‐storage projects in Germany according to battery technology [1].

Source: Figure reproduced with kind permission; © 2020 Elsevier B.V.

Along these primary batteries, the secondary batteries, i.e. rechargeable batteries, were also disclosed in the second half of the nineteenth century. Credit must be given to Gaston Planté, who in 1859 invented the lead–acid battery, which could be recharged by applying an appropriate reverse current. This device can certainly be considered, so far, the most successful secondary battery [14]. Similarly, the first alkaline battery, the Ni–Cd cell, was invented in 1899 [15]. This cell, which then entered the market in 1910, offered a much higher energy density to that of the lead–acid battery but was by far more expensive. Research in the last century culminated in the development of the secondary lithium‐ion batteries (LIBs) [16, 17]. Though initially studied by Lewis in 1912, LIBs were brought to market in the 1970s, and, today, LIBs represent the leading technology in the field of secondary batteries. The outstanding contributions in LIB research by J.B. Goodenough, M.S. Whittingham, and A. Yoshino were honored with the Chemistry Nobel Prize in 2019 [18]. Though LIBs feature distinguished benefits (e.g. low costs, high voltages, increased power densities), some serious downside aspects have to be noted. Firstly, LIBs are nonelastic and mechanically treated, leading to possible leakage and thus serious hazards [19]. Secondly, cobalt raw materials are required for the LIB fabrication. These materials are often mined under unsustainable mining conditions, which involve slavery and/or children labor work [20, 21]. Policies against these unacceptable mining conditions led to a significant increase in the world market prices for cobalt, which has recently led to overproduction stagnation [22]. Finally, large battery packs need reliable temperature‐control systems to guarantee safe conditions and to prevent serious hazards, e.g. fires or explosions [23, 24]. These aspects limit the applicability of LIBs, in particular with respect to small and flexible devices (e.g. smart clothing, and packaging) or other demanding applications, such as grid stabilization and on‐site storage [4].

Regarding their applications, redox polymers that are derived from organic raw materials represent one promising alternative approach [3–7]. For example, organic polymers allow the fabrication of flexible devices, and their use is almost independent from the fluctuating commodity prices of rare metals. Moreover, polymers can be synthesized in a wide range of structures and topologies, thus facilitating the preparation of tailor‐made materials. Today, the field of redox‐active polymers is a result of eight decades of research, which will be briefly summed up next.

1.2 Redox Polymers: A Short View on Their Long History

In 1920, Herman Staudinger published his famous article, in which polymers were defined as “long chains of high molecular weight, which are comprised of covalently linked repeating subunits, the self‐styled monomers” [25]. Though his proposal met heavy opposition at the time, this perception represents the initial spark that ignited modern polymer science. His fundamental research on macromolecules and persistence was honored in 1953, when he received the Nobel Prize in Chemistry [26, 27]. Carothers, a pioneer in the field of synthetic polyesters and polyamides, suggested the first classification scheme for synthetic macromolecules, taking into account the monomer subunit as well as the applied polymerization technique [28]. This about 90‐year‐old material classification remains contemporary and is still commonly used to rationalize the differences between macromolecules synthesized via different polymerization methods (e.g. step‐growth vs. chain‐growth polymerization). The field of polymer chemistry has experienced a tremendous evolution, and a range of reliable controlled/living polymerization techniques (i.e. metathesis, ionic, and radical) has become available, thus enabling the controlled and precise synthesis of polymers of various topologies (i.e. linear, star‐shaped, and branched). However, Carothers' fundamental systematics are generally obeyed in all of these cases.

Concurrent with the fast development in synthesis and characterization, the focus of polymer research has moved away from the traditional areas of interest (e.g. tire technology or packaging materials) toward targets, which address the special needs of today's society [29]. Hence, tailor‐made polymers with sophisticated properties can be offered for a broad range of applications, which have relevance for today's daily life style. The long list of potential applications includes photovoltaics [30–32], light‐emitting devices [33, 34], electrochromic devices [35], smart coatings [36, 37], self‐healing materials [38, 39], shape‐memory materials [40, 41], bioimaging [42], carriers in drug/gene delivery [43–48], biodegradable packages [49, 50], and, last but not least, energy storage [3, 4,51–53].

In 2000, the Nobel Prize in Chemistry was awarded to H. Shirakawa, A.G. MacDiarmid, and A.J. Heeger “for the discovery and development of electrically conductive polymers” [18]. Though it is commonly believed that these authors' collaborative research on polyacetylene (PA) represents the origin of conductive polymers, their history can actually be traced back to the middle of the nineteenth century [54]. The first, fully synthetic polymer, polyaniline (PAni), was already reported by F.F. Runge in 1834 [54–56]. Although pyrrole was discovered in 1834 [56], its oxidative polymerization to afford polypyrrole (PPy), as another type of conjugated polymer, was noticed by Angeli in 1915 [57]. The parent structures of the most relevant conductive polymers, along with their years of discovery, are shown in Figure 1.2. In general, their conductivity results from the (reversible) oxidation or reduction of the parent π‐conjugated polymer.

Figure 1.2 Schematic representation of the most relevant parent conjugated polymers along with their years of discovery.

Source: [55], figure 1 (p.1413)/John Wiley & Sons.

1.2.1 The First Era of Redox Polymers

Due to the tremendous interest in these previously mentioned materials, nonconjugated, redox‐active polymers have been overlooked for some time. The interest in such polymers with respect to energy‐storage applications can be traced back to the early days of ion‐exchange polymers, thus defining the first era of redox‐active polymers (Figure 1.3). Cassidy proposed that polymers – in analogy to the proton‐exchange capacity of acidic polymers – should also be able to exchange electrons, as another “fundamental particle” [58]. Due to the chaos of the World War II era, this conception was realized independently by H. Lauth and H.G. Cassidy. Thus, in 1944, Lauth filed a patent for poly(resorcin‐trihydroxybenzene‐formaldehyde) redox polymers, as water deoxygenation agents [59], whereas Cassidy studied the applicability of poly(vinyl quinone) (PVQ), as electron‐exchange polymers [60]. In subsequent work, Cassidy et al. prepared a wide range of PVQ‐type polymers and studied their properties as well as applicability [61–64]. The following years faced a scientific dualism between the Cassidy and Manecke groups [65], the latter first published a study in 1953 on “electron‐exchange polymers” [66]. These authors mainly focused on polymers, which were equipped with 1,4‐/1,2‐benzoquinone [67–83] or 9,10‐anthraquinone moieties [84]. These early contributions were summarized by Cassidy in his seminal textbook on “oxidation–reduction polymers” [58] as well as in numerous review articles [85]. Noteworthy, a range of other redox‐active polymers was also investigated in this timeframe; these species however remained virtually marginal. During the first era of redox‐active polymers, some prominent redox‐active materials, which are commonly used nowadays, were initially published: polymers containing methylene blue [86], thiol [87], ferrocene [88, 89], indigo [90], and pyridinium or quinolinium moieties [91]. Moreover, Harwood and Cassidy reported polypeptides, which incorporated 2,5‐dihydroxyphenylalanine or 3,4‐dihydroxyphenylalanine (DOPA), as redox‐active sites [92]. One further notable milestone is the synthesis of the first stable, polymer‐bound free N‐radicals. Henglein and Boysen prepared such a polymer by γ‐irradiation of a precursor polymer [93]; more conveniently, Braun et al. obtained similar polymers by oxidizing the precursor polymer with PbO2 or Ag2O2 in solution [94]. In the same context, the first report of poly(TEMPO methacrylate) (PTMA), as a nitroxide‐containing polymer, is worth mentioning (TEMPO: 2,2,6,6‐tetramethyl‐piperidinyloxy‐4‐yl) [95]. Today, this polymer represents one of most used active materials in organic radical batteries (ORBs) [3, 53, 96].

Figure 1.3 Timeline with the most noteworthy inventions and scientific milestones in the field of redox‐active polymers [4].

Source: Figure reproduced with kind permission; © 2021 Elsevier B.V.

In summary, the time was not ready for a significant technological breakthrough during the first era of redox‐active polymers. These materials attracted only interest from a scientific point of view and their use was devoted mainly in water deoxygenation and H2O2 production [59,97–101]. The first battery, which contained a redox‐active polymer as an electrolyte, was invented in 1958 [102]; a few years later, the first secondary LIB using a redox polymer, as cathode, was demonstrated [103]. However, these inventions did not promote the technological breakthrough of redox polymers and were only on the scientific fringes for many years.

1.2.2 The Second Era of Redox Polymers

The second age of redox polymers, which appeared in the groundbreaking research of Heeger, MacDiarmid, and Shirakawa, was dominated by the class of π‐conjugated polymers and notably polymers from the first era almost fell into oblivion. These authors showed that (partially) oxidized PA exhibited a significantly increase in the electric conductivity when compared to the parent all‐trans‐PA [104]. However, the initial goal – replacement of Cu by organic polymers in electric wires – had to be abandoned, and the focus of interest shifted toward an improvement of the polymer's properties. Recently, Rasmussen summarized the fascinating history of PA; the reader is referred to this article for a detailed view on this topic [55]. At about the same time, new redox‐active polymers were synthesized, and the long‐known materials were rediscovered. For example, Yamamoto et al. [105] as well as Koßmehl and Chatzitheodorou [106] pioneered the research on polythiophene (PT, Figure 1.2). Poly(phenylene vinylidene) (PPV) represents one further material, which – similar to PA – can be doped to achieve electric conductivity; thus, the physical and electric properties can be tuned via functional groups on the aromatic rings. Noteworthy, the first polymer‐based, light‐emitting diode (LED), which used PPV as the emissive layer, was reported in 1989 [107]. This discovery boosted the research in light‐emitting π‐conjugated polymers for applications in electroluminescent devices. Since then, a plethora of polymers have been prepared and utilized accordingly [108, 109]; however, a survey of these will not be given within this book. Special credit goes to Diaz, who not only revisited PPy and PAni but also established electropolymerization, as a fast and reliable technique to fabricate conjugated polymer films on conductive surfaces [110]. Finally, the studies by Diaz et al. on PPy [111–113] and PAni [114, 115] enabled one to better understand the physical background, which, in turn, is responsible for the observed phenomena [116–118].

Electropolymerization is a highly versatile method to prepare polymer films directly on substrates, i.e. processing steps from solution become obsolete; however, the latter represented a significant restriction, when aiming for post‐synthetic processing. At that time, the common redox polymers were barely soluble (particularly in water) and, thus far, from being easy to process. In 1991, Epstein and coworkers showed that sulfonated PAni was readily soluble, even in water, thus facilitating its processability; moreover, the self‐doping effect, due to intramolecular acid–base reactions, induced electric conductivity [119]. The improved post‐synthetic processability finally enabled the commercialization of redox polymers. The first generation of commercial products incorporating redox polymers was summarized by Miller in 1993 [120, 121]. In particular, two rechargeable LIBs must be highlighted in this context. In 1987, Bridgestone/Seiko began selling 3 V coin cells, which contained PAni and LiBF4, as cathode material and electrolyte, respectively (Figure 1.4a) [122, 123]. The Varta/BASK coin cell contained partially oxidized (i.e. p‐doped) PPy, as the active material [124]. Miller pointed out that these batteries had lower energies than the conventional batteries available at that time, e.g. NiCd batteries, but could be kept longer in the charged state, hold their charge longer, and were environmentally more compatible [121]. However, these batteries could not compete with e.g. the ones developed by Valence Technologies, which instead utilized a Li+‐conductive polymer (interestingly, in 1992, Motorola ordered $108 worth of this battery [125]). At least in the case of Bridgestone/Seiko battery, their sale was discontinued after only five years.

Figure 1.4 (a) Schematic section through a Bridgestone/Seiko coin‐cell battery. (b) Photograph of a Varta/BASF coin‐cell battery.

Source: (b) [121] Reproduced with permission/John Wiley & Sons, Inc.

The synthesis of PEDOT [poly(3,4‐ethylendioxythiophene)] represents the next mentionable milestone in the context of redox polymers. This particular polymer featured a higher conductivity, stability, and biocompatibility when compared to the parent PT; however, PEDOT and PT have a common downside, which is a restricted processability from solution due to their low solubilities [126]. The solubility problem could be solved by using poly(styrene sulfonic acid) (PSS), as a water‐soluble polyelectrolyte for the charge‐balancing of partially oxidized PEDOT (Figure 1.5) [127]. The resulting PEDOT: PSS, which was commercialized by Bayer under the trade name Baytron‐P®, which featured reasonable solubility in water and, thus, enabled its processing from solution. These homogeneous, flexible films were highly conductive (up to c. 10 S cm−1), transmissive for visible light, and thermally stable [128]; however, the initial target, i.e. the replacement of indium tin oxide (ITO)‐coated glass substrates in polymer LEDs, could, due to the insufficient currents, not be reached. Nonetheless, it was demonstrated that both the performance and stability of such devices could be vastly improved by depositing a thin PEDOT–PSS film onto the ITO‐coated substrate [129].

Figure 1.5 Schematic representation of the chemical structure of PEDOT:PSS. The picture shows a beaker filled with an aqueous solution of PEDOT:PSS.

Source: B. Jewłoszewicz, K. A. Bogdanowicz, W. Przybył, A. Iwan, I. Plebankiewicz, POlymers 2000, 12, article ID 565.

Two further prominent inventions of redox‐active polymers appeared: bulk heterojunction (BHJ) solar cells and organic field‐effect transistors (OFETs). Research on the former was pioneered by Wudl and coworkers [130] as well as by Holmes and coworkers [131]. In BHJ devices, a conductive polymer, as the electron‐donor material, is blended with an acceptor compound, typically a fullerene derivative; however, this application represents a topic of its own and its evaluation is far beyond the scope of this book – the reader is referred to three excellent reviews [132–134]. The same holds true for OFETs, where initially PA‐ and PT‐type polymers were used [135–138].

To conclude, it may be mentioned that substantial progress was made in the second era of redox polymers regarding energy‐storage applications [139, 140]. However, this period was dominated by the class of π‐conjugated polymers and the emergence of cutting‐edge applications, which are commonly referred to as “organic electronics” (e.g. polymer LEDs, BHJ solar cells, and OFETs).

1.2.3 The Third Era of Redox Polymers

The beginning of the third, ongoing era of redox polymers can be marked by the research of Nakahara et al. [141] as well as Nishide et al. [142], who developed the concept of ORBs in the beginning of the twenty‐first century. These authors utilized PTMA, as the nitroxide‐containing, redox‐active polymer in their initial studies (Figure 1.6a). As depicted in Figure 1.6b,c, the TEMPO moiety exhibits a fast and highly reversible one‐electron oxidation to afford a N‐oxoammonium species (the latter is formed in batteries during the discharging process).

Figure 1.6 (a) Schematic representation of PTMA; (b) schematic representation of the reversible one‐electron oxidation of nitroxide radicals; (c) representative cyclic voltammogram (CV) of a composite electrode comprising of PTMA, graphite, and a binder (1 : 8 : 1 ratio) at a scanning rate of 10 mV s−1 (counter electrode: Pt wire; reference electrode: Li/Li+; electrolyte: carbonate mixture containing 1 M LiPF6) [141].

Source: Figure reproduced with kind permission; © 2002 Elsevier B.V.

Starting from these groundbreaking studies, the field of polymer‐based organic batteries literally exploded with diverse research groups joining this field [53]. We have come full circle – the redox‐active polymers, which are commonly used, as active materials, in today's energy‐storage application, are mostly nonconjugated polymers equipped with redox‐active moieties (along with conjugated polymers bearing localized charges) [3]. Accordingly, these materials, which have already been described during the first era of redox polymers (vide supra