Cobalt-free composite-structured cathodes with lithium-stoichiometry control for sustainable lithium-ion batteries

Lithium-ion batteries play a crucial role in decarbonizing transportation and power grids, but their reliance on high-cost, earth-scarce cobalt in commonly employed high-energy layered Li(NiMnCo)O2 cathodes raises supply-chain and sustainability concerns. Eliminating Co typically degrades layering and cycling stability. Here, we report rational stoichiometry control to synthesize Li-deficient, composite-structured LiNi0.95Mn0.05O2 (intergrown layered and rocksalt phases) that outperforms traditional layered counterparts. Multiscale-correlated experiments and computational modeling of the calcination process reveal that Li deficiency suppresses the rocksalt-to-layered transformation and crystal growth, yielding small-sized composites with low anisotropic lattice expansion/contraction during cycling. Consequently, Li-deficient LiNi0.95Mn0.05O2 delivers 90% first-cycle Coulombic efficiency, 90% capacity retention, and near-zero voltage fade over 100 deep cycles, demonstrating potential as a Co-free cathode for sustainable Li-ion batteries.