Entropy-induced high-density grain boundaries in Co-free high-entropy spinel oxides for highly reversible lithium storage

Transition metal oxides (TMOs) with high discharge capacity are considered as one of the most promising anodes for lithium-ion batteries. However, the practical utilization of TMOs is largely limited by cycling stability issues arising from volume expansion, structural collapse. In this study, we synthesized a high-entropy spinel oxide material (FeCrNiMnZn)3O4 using a solution combustion method. With the implementation of five cations through high-entropy engineering, the agglomeration and expansion of the electrode materials during charging and discharging are suppressed, and the cycling stability is enhanced. The results demonstrate that entropyinduced high-density grain boundaries and the reversibility of spinel structure contribute to improved capacity and cycling stability. Herein, (FeCrNiMnZn)3O4 provides a high capacity (1374 mAh g- 1) at 0.1 A g- 1 and superior cycling stability (almost 100 %) during 200 cycles with a current density of 0.5 A g- 1. The study provides valuable understanding for designing the high entropy oxides anode electrodes.