Facile and controllable one-pot synthesis of nickel-doped LiMn0.8Fe0.2PO4 nanosheets as high performance cathode materials for lithium-ion batteries

Abstract

To improve the kinetic performance of LiMn_0.8Fe_0.2PO₄, a facile and controllable non-stoichiometric one-pot stepwise feeding solvothermal approach is successfully developed for preparing nickel-doped LiMn_0.8Fe_0.2PO₄ nanosheets. LiMn_0.8Fe_0.19Ni_0.01PO₄ nanosheets, with an appropriate particle size, ideal lattice volume, smooth surface morphology and high phase purity, could be fabricated through trace amount of nickel doping, modest lithium hydroxide deficiency and stepwise feeding mode, and exhibit the optimal cycling performance and rate capability after carbon coating. After 200 charge/discharge cycles at 0.5C, the LiMn_0.8Fe_0.19Ni_0.01PO₄ cathode only slightly decreases to 148 mA h g⁻¹, corresponding to the capacity retention of 94.1%. Even if increased to 10C and 20C, 75.7% and 65.2%, respectively, initial capacities at 0.1C can still be maintained. These results demonstrate that a suitable Ni²⁺ content and a rational synthesized route are helpful to improve electronic conductivity and Li-ion mobility.