Molecular tailoring of pomegranate-like CoMn2O4 via vanadium doping to achieve durable aqueous zinc-ion batteries with enhanced diffusion kinetics

Abstract

Manganese-based binary transition metal oxides (BTMO) emerge as a highly followed cathode for aqueous zinc-ion batteries (AZIBs) in recent years because of the relatively stable structure and exceptional energy density. Nonetheless, the problems of slow electrochemical reaction kinetics and low intrinsic conductivity have limited their development. Herein, V was introduced into pomegranate-like CoMn₂O₄ to form V doped CoMn₂O₄ (V-CMO) with lauxriant oxygen vancancies via a straightforward solvothermal method, followed by a calcination treatment. DFT calculations demonstrate that oxygen vacancies improve the intrinsic conductivity of V-CMO and reduce Zn²⁺ diffusion energy barrier. Simultaneously, the unique pomegranate-like morphology with abundant pores and the void space promotes the exposure of electrochemical active sites and reduces the volume strain of electrode during cycling, which can further improve the long-term cycling and rate performance of V-CMO cathode. Consequently, V-CMO cathode shows a high specific capacity (306.6 mAh g⁻¹ at 0.1 A g⁻¹ after 200 cycles) and outstanding cycling stability (98.6 mAh g⁻¹ at 1 A g⁻¹ after 2000 cycles with a decay of 0.05 % per cycle). Furthermore, the assembled flexible ZIBs based on V-CMO exhibit outstanding mechanical stability and excellent electrochemical properties at different deformations. This work sheds some new light on designing spinel-type Mn-based cathode for high-performance ZIBs.