Electrical Conductivity-Relay between Organic Charge-Transfer and Radical Salts toward Conductive Additive-Free Rechargeable Battery

Yui Fujihara, Yui Fujihara, Hiroaki Kobayashi, Shinya Takaishi, Takaaki Tomai, Masahiro Yamashita, Masahiro Yamashita, Masahiro Yamashita, Itaru Honma

Research output: Contribution to journalArticle

Abstract

In recent years, organic electrode materials have been strongly considered for use in sustainable batteries. However, most organic electrode materials have low electrical conductivity and require a lot of conductive additives, which decrease the effective capacity based on the entire electrode weight/volume. In this study, we propose a novel electrical conductivity-relay system that imparts electrical conductivity to organic small molecular electrodes without any conductive additive throughout the charge/discharge cycles. It consists of the combination of the charge-transfer phenomenon in a pristine state and the formation of organic radical salts in redox states. Herein, we demonstrate this electrical conductivity-relay system using a simply mixed molecular crystal couple of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) as a cathode without any conductive additive and aqueous sodium bromide as an electrolyte. During charge/discharge, the electrical conductivity of the cathode is supported by charge-transfer at the TTF/TCNQ interface and (TTF)Brn (0.7 ≤ n ≤ 0.8) and NaTCNQ radical salts, and the cathode exhibits a specific capacity of 112 mAh g-1 and a retention rate of 80.7% at the 30th cycle. Furthermore, the molecular crystal couple electrode of TTF and TCNQ shows better charge/discharge performance than the pure charge-transfer complex electrode, indicating that this system expands candidates for organic electrode materials to various pairs and mixing ratios of small molecules that do not form charge-transfer complexes.

Original languageEnglish
Pages (from-to)25748-25755
Number of pages8
JournalACS Applied Materials and Interfaces
Volume12
Issue number23
DOIs
Publication statusPublished - 2020 Jun 10

Keywords

  • charge-transfer
  • conductive additive-free cathode
  • organic battery
  • radical salt

ASJC Scopus subject areas

  • Materials Science(all)

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