Stabilized Co3+/Co4+ Redox Pair in In Situ Produced CoSe2−x‐Derived Cobalt Oxides for Alkaline Zn Batteries with 10 000‐Cycle Lifespan and 1.9‐V Voltage Plateau

By Yongchao Tang, Xuejin Li, Haiming Lv, D. Xie, Wenlong Wang, Chunyi Zhi, Hongfei Li. Advanced Energy Materials, 2020

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In aqueous alkaline Zn batteries (AZBs), the Co3+/Co4+ redox pair offers a higher voltage plateau than its Co2+/Co3+ counterpart. However, related studies are scarce, due to two challenges: the Co3+/Co4+ redox pair is more difficult to activate than Co2+/Co3+; once activated, the Co3+/Co4+ redox pair is unstable, owing to the rapid reduction of surplus Co3+ to Co2+. Herein, CoSe2−x is employed as a cathode material in AZBs. Electrochemical analysis recognizes the principal contributions of the Co3+/Co4+ redox pair to the capacity and voltage plateau. Mechanistic studies reveal that CoSe2−x initially undergoes a phase transformation to derived CoxOySez, which has not been observed in other Zn//cobalt oxide batteries. The Se doping effect is conducive to sustaining abundant and stable Co3+ species in CoxOySez. As a result, the battery achieves a 10 000‐cycle ultralong lifespan with 0.02% cycle−1 capacity decay, a 1.9‐V voltage plateau, and an immense areal specific capacity compared to its low‐valence oxide counterparts. When used in a quasi‐solid‐state electrolyte, as‐assembled AZB delivers 4200 cycles and excellent tailorability, a promising result for wearable applications. The presented effective strategy for obtaining long‐cyclability cathodes via a phase transformation‐induced heteroatom doping effect may promote high‐valence metal species mediation toward highly stable electrodes.

Subfields: Electrical and Electronic Engineering

View Paper: https://www.semanticscholar.org/paper/952da981a06d80d34f6ac792fae009b7b5cc9180