Regulating Particle Size of Cobalt-Free Single-Crystal Layered Cathodes toward High-Performance Lithium-Ion Battery

The development of cobalt-free cathode materials for lithium-ion batteries is crucial to address the challenges posed by limited availability, uneven distribution, and price volatility of cobalt. Here, a cobalt-free single crystal cathode material, LiNi_0.75Mn_0.25O₂, was successfully synthesized via a simple solid-state method, with particle size modulation achieved by varying the ball milling time of the precursors. The highly dispersed single crystals exhibited superior cycling stability and rate capability, attributed to the effective suppression of intergranular cracks and enhanced Li⁺diffusion across internal grain boundaries. The single crystals subjected to 3 h of ball milling (SC NM-1) showed a capacity retention of 88.7% after 100 cycles at 0.5C, compared to only 77.6% for the polycrystalline. Additionally, the full cell incorporating SC NM-1 retained 80.8% of its capacity after 300 cycles at 0.5C, which was 30.8% higher than that of the polycrystalline. Furthermore, the single-crystal cathode treated with ball milling for 12 h (SC NM-3) also demonstrated superior rate capability, maintaining a stable discharge capacity of 103.0 mAh g^–1at 4C. This study demonstrated that cobalt-free single-crystal cathode materials with uniform morphology, good dispersion, and improved electrochemical performance could be efficiently synthesized and optimized through a simple ball milling and solid-state method, offering potential for the development of other cathode materials.