Although Mg metal features high volumetric energy density and electrochemical dendrite-free deposition, Mg-storage cathode materials with desirable capacity and long-term stability have reached a bottleneck due to large diffusion barrier of Mg²⁺. Herein, we report for the first time Ni-Fe bimetallic diselenides microflowers (Ni_0.75Fe_0.25Se₂, NFS) as cathode materials for rechargeable magnesium batteries. The NFS exhibits a considerable reversible capacity of 190 mAh g⁻¹ and excellent Mg-storage cycling stability (148 mAh g⁻¹ even after 500 cycles). Compared with unary transitional-metal diselenides (NiSe₂, NS), the NFS shows more redox active sites and higher Mg²⁺ diffusion dynamics, contributing to superior reversible capacity and long cycle life. Furthermore, the concept of sequential reaction based on the potential discrepancy for the NFS magnesiation/demagnesiation process at steady stage was put forward and evidenced by electrochemical measurement and structural characterization. This paper paves the way for constructing advanced high-performance cathode materials of rechargeable magnesium batteries.

尽管Mg金属具有高的体积能量密度和无电化学枝晶沉积的特性，但由于Mg ^2+的扩散势垒较大，因此具有理想容量和长期稳定性的Mg储存阴极材料已成为瓶颈。在此，我们首次报道了Ni-Fe双金属二硒化物微花（Ni _0.75 Fe _0.25 Se ₂，NFS）作为可再充电镁电池的正极材料。NFS表现出可逆的190 mAh g ^-1容量和极好的Mg储存循环稳定性（即使经过500次循环也达到148 mAh g ^-1）。与一元过渡金属二硒化物（NiSe ₂，NS），NFS显示出更多的氧化还原活性位点和更高的Mg ²⁺扩散动力学，从而有助于实现卓越的可逆容量和长循环寿命。此外，提出了基于NFS放大/缩小过程在稳态阶段的潜在差异的顺序反应的概念，并通过电化学测量和结构表征得到证明。本文为构造可充电镁电池的高级高性能正极材料铺平了道路。