Operando Observation of Formation and Annihilation of Inhomogeneous Reaction Distribution in a Composite Electrode for Lithium-Ion Batteries

Takashi Nakamura, Kazuki Chiba, Mahunnop Fakkao, Yuta Kimura, Kiyofumi Nitta, Yasuko Terada, Yoshiharu Uchimoto, Koji Amezawa

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)

Abstract

Inhomogeneous reaction distribution in battery electrodes can be a cause of serious capacity loss and degradation. Therefore, it is important to understand the mechanism of the reaction distribution formation. In this study, formation and annihilation of inhomogeneous charge/discharge reaction in a model LiCoO2 composite electrode were directly observed by operando two-dimensional X-ray absorption spectroscopy. The reaction distribution was clearly observed, and it was demonstrated that the reacted area became smaller with increasing the current density. The inhomogeneous charged situation remained even after 20 h of the open-circuit rest and the discharge treatments. These results suggested that it is difficult to remove the inhomogeneity once it is formed in a composite electrode. High-rate charge/discharge cycles may accumulate the inhomogeneity of the state of charge and result in significant capacity losses. The formation of the reaction distribution was strongly affected by the salt concentration in the liquid electrolyte. The expansion and annihilation rates of the charge/discharge reaction did not simply depend on the apparent ionic conductivity of the liquid electrolyte. This suggested that the salt concentration in a composite electrode varies locally by the lithiation/delithiation reactions especially under high-rate operation. Such a local variation of the salt concentration can suppress or facilitate the charge/discharge reactions in a composite electrode.

Original languageEnglish
Pages (from-to)688-694
Number of pages7
JournalBatteries and Supercaps
Volume2
Issue number8
DOIs
Publication statusPublished - 2019 Aug 1

Keywords

  • in-situ analysis
  • lithium-ion batteries
  • operando spectroscopy
  • reaction distribution
  • X-ray absorption spectroscopy

ASJC Scopus subject areas

  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering
  • Electrochemistry

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