Nb-doped and Al₂O₃ + B₂O₃-coated granular secondary LiMn₂O₄ particles as cathode materials for lithium-ion batteries

In this work, to improve the cyclability and high-temperature performance of cubic spinel LiMn₂O₄ (LMO) as cathode materials, Nb⁵⁺-doped LiMn₂O₄ powders coated and uncoated with Al₂O₃ and/or B₂O₃ were synthesized via the modified solid-state reaction method. It was found that Nb⁵⁺-doped and B₂O₃ + Al₂O₃-coated LMO powders comprising 5 μm granular agglomerated fine primary particles smaller than 350 nm in diameter exhibited superior electrochemical properties with initial discharge capacity of 101.68 mA h g^-1; we also observed capacity retention of 96.31% after 300 cycles at room temperature (RT) and that of 98% after 50 cycles at 55 °C and 1C rate.