Excellent stability of spinel LiMn₂O₄-based composites for lithium ion batteries

Spinel LiMn₂O₄-based composites with cation (Li ⁺)/anion (F^-) co-doping and Li₂MnO₃ thin surface coating are synthesized by one-step solid-state reaction. The composites modified with body-doping and surface-coating exhibits excellent cycling performance and high rate capability. The LF04 sample tested at 1 C rate exhibits only 1.2% capacity loss after 1000 cycles at room temperature; and when cycling at 55 °C, the composite still shows 94.3% capacity retention after 100 cycles. As the charge-discharge rate increases to 7 C, the as-prepared LiMn₂O₄-based composites deliver more than 95.5% capacity retention after 300 cycles at room temperature and exhibit an average value of coulombic efficiency more than 99.6%. The improved cycling performance of the composites is ascribed to double doping in the spinel structure and the coating on the surface of the spinel particles. The ionic doping could eliminate the problems with cooperative Jahn-Teller distortion and suppress Li⁺-ion order at 0.5 Li; and the inborn Li₂MnO₃ coating containing only Mn⁴⁺ ions, could prevent the disproportionation of Mn³⁺ on the surface.