Novel high-entropy oxides with ultra-long cycle life as cathode materials for aqueous zinc-ion batteries

Abstract

Aqueous zinc-ion battery (AZIB), as a promising economic and environmentally friendly battery, has been plagued by the instability and structural collapse of cathode materials during charge-discharge process for many years, which has seriously hindered its commercial application. At present, researchers have used intercalation, surface coating and other means to inhibit the dissolution of cathode materials, but they have not achieved satisfactory results. In order to fundamentally improve the stability of AZIB cathode, we prepared a high-entropy oxide cathode material (Co_0.2Cr_0.2Fe_0.2Mn_0.2Ni_0.2)₃O₄ (CCFMnO) derived from the concept of high entropy. Because of the unique entropy stabilization effect and strong lattice distortion effect of high-entropy materials, CCFMnO shows satisfactory structural stability. Compared with the low-entropy material Fe₃O₄, the CCFMnO nanomaterial achieved enhanced electrochemical performance due to the synergistic effect of multiple elements, exhibiting an excellent specific capacity (283 mAh g⁻¹ at 0.1 A g⁻¹), good rate capability, and superior cycle stability (66.61 % capacity retention after 90000 cycles at 2 A g⁻¹). In addition, we reveal the storage mechanism and structural evolution of Zn²⁺ during the intercalation/deintercalation of CCFMnO by a series of in-situ and ex-situ characterization methods. This work opens the way to explore new AZIB cathode materials, which will promote the development of AZIB.