Chemical homogeneity enables long-term stability of cobalt-free high-voltage spinel cathode materials

Cobalt-free LiNi0.5Mn1.5O4 (LNMO) is a highly competitive spinel cathode material due to the Ni2+/4+ redox couple, which alleviates Jahn-Teller distortion and offers a high redox potential near 5 V. However, its limited cycling life remains a major obstacle to large-scale application, primarily due to severe interfacial instability. Here, we identify chemical inhomogeneity as a limiting factor contributing to this instability, which leads to increased oxygen vacancies and rock-salt phase formation on the particle surface, resulting in poor cycling stability. In contrast, we demonstrate that chemically homogeneous LNMO (CH-LNMO), synthesized via a polyvinylpyrrolidone (PVP)-assisted solid-state method, exhibits a uniform Ni/Mn distribution and improved interfacial stability, which achieves excellent cycling performance, with a capacity retention of 90.32 % after 1000 cycles at 2C. We further reveal that chemical homogeneity enhances Ni/Mn ordering in the structure and decreases the Jahn-Teller effect of Mn3+, thereby mitigating interfacial reactions and transition metal ion dissolution. This work underscores the critical role of chemical homogeneity in large-scale synthesis and provides a viable approach for improving the long-term cycling stability of cathode materials.