Challenges and advances of organic electrode materials for sustainable secondary batteries

Abstract

Organic electrode materials (OEMs) emerge as one of the most promising candidates for the next-generation rechargeable batteries, mainly owing to their advantages of bountiful resources, high theoretical capacity, structural designability, and sustainability. However, OEMs usually suffer from poor electronic conductivity and unsatisfied stability in common organic electrolytes, ultimately leading to their deteriorating output capacity and inferior rate capability. Making clear of the issues from microscale to macroscale level is of great importance for the exploration of novel OEMs. Herein, the challenges and advanced strategies to boost the electrochemical performance of redox-active OEMs for sustainable secondary batteries are systematically summarized. Particularly, the characterization technologies and computational methods to elucidate the complex redox reaction mechanisms and confirm the organic radical intermediates of OEMs have been introduced. Moreover, the structural design of OEMs-based full cells and the outlook for OEMs are further presented. This review will shed light on the in-depth understanding and development of OEMs for sustainable secondary batteries.

Keywords: advanced strategies; challenges; characterization techniques; organic electrode materials; redox reaction mechanism.

FIGURE 1

Advantages of OEMs in rechargeable secondary batteries

FIGURE 2

The significant works about OEMs for rechargeable secondary batteries during the past few decades. Reproduced with permission.^{[ 171 ]} Copyright 2018, WILEY‐VCH GmbH; Reproduced with permission.^{[ 200 ]} Copyright 2022, Elsevier Inc.

FIGURE 3

Bar chart of the scientific papers related to OEMs between 2010 and 2021. Data were collected from the ISI Web of Science

FIGURE 4

Categories of common OEMs and the corresponding redox reaction mechanisms

FIGURE 5

(A) The ion intercalation/extraction process of C4Q molecule in different rechargeable batteries. (B) The illustration of different ion storage mechanisms for per HAQ‐COF repeating unit

FIGURE 6

Common OEMs with different reaction types

FIGURE 7

Comparison of working voltage window and discharge capacity of different types of OEMs in the organic electrolyte (A) and the aqueous electrolyte (B). The structures or names of most organics can be found in Table 1 and the following sections

FIGURE 8

Challenges (including redox potential, theoretical capacity, solubility, electronic conductivity, and complex redox mechanism) and the corresponding strategies of the OEMs

FIGURE 9

(A) Lithium storage mechanism and (B) rate capability of C₆O₆ electrode within an ionic liquid electrolyte. Reproduced with permission.^{[ 73 ]} Copyright 2019, WILEY‐VCH GmbH. (C) Lithium ion uptake/release mechanism and (D) cycling performance of 3Q electrode. Reproduced with permission.^{[ 75 ]} Copyright 2017, Nature Publishing Group

FIGURE 10

(A) The schematic illustration of exfoliated COFs‐based cathode for LIBs. (B) The discharge curves of these three distinct redox‐active COFs electrodes at 0.02 A g^–1. Reproduced with permission.^{[ 81 ]} Copyright 2017, The American Chemical Society. (C) The redox reaction mechanism of the polyaniline cathode with a polymer‐gel electrolyte. The discharge/charge curves (D) and rate performance (E) of the polyaniline cathode with liquid and polymer electrolytes. Reproduced with permission.^{[ 25 ]} Copyright 2018, WILEY‐VCH GmbH. (F) The redox mechanism of HDC electrode. (G) Working potential of HDC and other reported OEMs. (H) Charge and discharge curves of the full battery with HDC cathode and activated carbon anode. Reproduced with permission.^{[ 82 ]} Copyright 2022, WILEY‐VCH GmbH

FIGURE 11

(A) Schematic redox reaction mechanism of aqueous PTO//Zn battery. (B) CV curve at 1.0 mV s^–1 and (C) galvanostatic discharge/charge profiles at different current densities of PTO electrode. Reproduced with permission.^{[ 88 ]} Copyright 2018, WILEY‐VCH GmbH. (D) Illustration of reversible reaction mechanism of aqueous aluminum battery using PZ cathode. (E) Cycling performance of PZ cathode at the current density of 0.05 A g^–1. Reproduced with permission.^{[ 89 ]} Copyright 2021, WILEY‐VCH GmbH

FIGURE 12

(A) Solvated configurations of PTCDA in 1 and 30 M KFSI electrolyte, respectively. (B) CV curves of PTCDA electrode in a three‐electrode battery at 10 mV s^–1. Reproduced with permission.^{[ 107 ]} Copyright 2020, The Royal Society of Chemistry. (C) The solubility of quinones in different solvents and corresponding cycling stability of C4Q cathode. Reproduced with permission.^{[ 108 ]} Copyright 2019, Elsevier Inc. (D) The potential electrode‐electrolyte interface interaction between PTO cathode materials and Na₃PS₄ electrolyte, and the long‐term cycling performance of PTO cathode with solid‐state electrolyte. Reproduced with permission.^{[ 109 ]} Copyright 2019, Elsevier Inc.

FIGURE 13

(A) Cycling stability of PPTS, PBQS, and PAQS at a current density of 1 A g^–1. Reproduced with permission.^{[ 120 ]} Copyright 2018, Elsevier Inc. (B) The rate capability of PHATN electrode, with a discharge capacity of 100 mAh g^–1 at the current density of 10 A g^–1. Reproduced with permission.^{[ 125 ]} Copyright 2019, WILEY‐VCH GmbH. (C) The redox mechanism and (D) the long‐term cyclability of Zn‐HHTP electrode. Reproduced with permission.^{[ 130 ]} Copyright 2021, WILEY‐VCH GmbH

FIGURE 14

(A) Schematic reaction mechanism and chemical structure of SF‐CTF‐1 composites with high sulfur contents. The first discharge‐charge curves (B) and rate performance (C) of SF‐CTF‐1 cathodes with varying sulfur ratios. Reproduced with permission.^{[ 132 ]} Copyright 2017, WILEY‐VCH GmbH. (D) The schematic of Li₂S _x ‐reactive pathway of CMPs/S cathode. (E) Voltage profiles of CMPs‐Li₂S₆ testing and the first three discharge/charge curves. (F) Long‐term cycling performance of CMPs/S cathode at 1 mA cm^–2 under an electrolyte/sulfur ratio of 5 μl mg^–1. Reproduced with permission.^{[ 133 ]} Copyright 2021, WILEY‐VCH GmbH

FIGURE 15

(A) Schematic synthesis route of C₂N‐h2D crystal. (B) Scanning tunneling microscope image on Cu (111) and (C) CV curve at 0.1 mV s^–1 of the C₂N‐h2D crystal. Reproduced with permission.^{[ 147 ]} Copyright 2015, Nature Publishing Group. (D) Proposed Li⁺ storage mechanism of the Te‐based viologen scaffold electrode. Reproduced with permission.^{[ 154 ]} Copyright 2019, WILEY‐VCH GmbH. (E) The simulated structure of Co‐HAB with three‐electron reversible reaction. (F) Discharge profiles of Co‐HAB electrode at different current densities. (G) Cycling stability of Co‐HAB electrode. Reproduced with permission.^{[ 155 ]} Copyright 2018, The American Chemical Society

FIGURE 16

(A) The polymerization types for connecting small organic molecules. (B) The in situ polymerization process and schematic diagram of PAQS‐GO composites. (C) The rate capability of PAQS‐GO electrode at the current density from 0.1 to 100 C. Reproduced with permission.^{[ 160 ]} Copyright 2012, The American Chemical Society. (D) The in situ electropolymerization illustration and schematic redox chemistry mechanism of carbazole‐based cathode for organic lithium batteries. (E) The rate performance of carbazole‐based cathode during the current density of 0.1–20.0 A g^–1. Reproduced with permission.^{[ 162 ]} Copyright 2020, WILEY‐VCH GmbH

FIGURE 17

(A) Electrochemical redox reaction mechanism and (B) EPR spectra change of radical intermediates during the sodium storage process. Reproduced with permission.^{[ 165 ]} Copyright 2019, The American Chemical Society. (C) CV curves of organic electrode materials consist of TEMPO structure at the scan rate of 2.0 mV s^–1. Reproduced with permission.^{[ 166 ]} Copyright 2021, Elsevier Inc. (D) The coupled EPR/NMR methods for determining redox‐active DHAQ intermediates during electrochemical cycling process. Reproduced under the terms of the CC‐BY license.^{[ 167 ]} Copyright 2021, The American Chemical Society

FIGURE 18

Advanced characterization techniques for real‐time structural and composite changes of OEMs: X‐ray diffraction, solid‐state NMR, in situ FTIR, in situ Raman, in situ UV–vis, EPR, ex situ XPS, Cryo‐electron microscopy. Reproduced with permission from the reported references.^{[ 75} , ¹⁰² , ¹⁰⁸ , ¹⁷¹ , ¹⁷⁶ , ¹⁷⁷ , ¹⁷⁸ , ^{179 ]} Copyright 2017, Nature Publishing Group. Copyright 2019, Elsevier Inc. Copyright 2018 and 2016, WILEY‐VCH GmbH. Copyright 2017 and 2021, The American Chemical Society

FIGURE 19

(A) MESP plots and optimized configurations of TPB molecule and its lithiated structures. Reproduced with permission.^{[ 188 ]} Copyright 2018, The American Chemical Society. (B) Flowchart of the straightforward prediction models to explore high‐performance OEMs. Reproduced with permission.^{[ 199 ]} Copyright 2022, The American Chemical Society. (C) The workflow of the artificial intelligence‐based method enabled high‐throughput screening and the efficient searching for novel organic materials. Reproduced with permission.^{[ 200 ]} Copyright 2022, Elsevier Inc.

FIGURE 20

(A) Redox chemistry mechanism of phenazine‐based bipolar electrode and (B) the charge/discharge profiles of organic symmetric battery. Reproduced with permission.^{[ 207 ]} Copyright 2019, WILEY‐VCH GmbH. (C) Li⁺ ion storage mechanism per electrode of the all‐PDB symmetric full‐cell. (D) The long‐term cycling performance of the all‐PDB symmetric full‐cell. Reproduced with permission.^{[ 208 ]} Copyright 2018, WILEY‐VCH GmbH. (E) The H⁺ uptake/release mechanism of the symmetric all‐organic proton battery. (F) The discharge/charge curves and (G) cycling performance of the all‐organic proton battery. Reproduced with permission.^{[ 209 ]} Copyright 2022, WILEY‐VCH GmbH

FIGURE 21

(A) Illustration of the pathways of electrons and Li ions in the inorganic/organic cathode. (B) Cycling performance of 30 mAh‐level Li/PTCDA‐TiS₂ pouch cell. Reproduced with permission.^{[ 211 ]} Copyright 2021, WILEY‐VCH GmbH. (C) CV curves and redox reactions of the electrochemical redox couples in the alkali−acid hybrid batteries. (D) Voltage profiles and the schematic structure of P14AQ/MnO₂ hybrid battery with a high capacity of 33 mAh. Reproduced with permission.^{[ 212 ]} Copyright 2022, The American Chemical Society

FIGURE 22

(A) Schematics and redox reactions of the polypeptide‐based organic radical battery. (B) The workflow and structural identification for the complete degradation products of viologen and biTEMPO polypeptides. Reproduced with permission.^{[ 52 ]} Copyright 2021, Nature Publishing Group

FIGURE 23

Diagram of advanced strategies to current issues of OEMs for sustainable secondary batteries