Tuning Cation (Dis)Order in Cr‐Based Li‐Excess Oxide Cathode Materials to Improve Li+ Transport Properties

Abstract

Li‐excess disordered rocksalts (DRXs) hold promise as next‐generation cathodes for Li‐ion batteries due to their high capacity and energy density, along with the potential to eliminate the need for Co and Ni. However, due to their low Li+ diffusivity, DRXs need to be pulverized into nanoparticles to achieve high performance. Herein, a new strategy for overcoming this limitation is demonstrated, involving the design of as‐synthesized partially disordered oxides with a structure that lies between ordered layered and fully disordered, exhibiting a varying degree of local (dis)order. This unique structure activates new Li+ diffusion channels, improving percolation and transport properties. This strategy allows a large content of Li+ to be accessed in material with large, micron‐sized particles through highly reversible Cr3+/6+ and O redox, yielding a first discharge capacity of 286 mAh g−1 (881 Wh kg−1). The Li+ percolation network is further improved by substituting Ti with a mixture of multiple metals, which appears to locally decrease the migration barrier through lattice distortion. Proper tuning of the chemical composition, especially the content of metals with empty d orbitals, is established as a crucial factor for controlling the degree of disorder and mitigating voltage fade and hysteresis growth upon cycling.