Electrochemical performances of LiNi _1−x Mn _x PO ₄ (x = 0.05–0.2) olivine cathode materials for high voltage rechargeable lithium ion batteries

This study demonstrated to synthesis of carbon-free lithium nickel phosphate (LiNiPO ₄ ) and its analogue of manganese doped LiNi _1−x Mn _x PO ₄ (x = 0.05–0.2) cathode materials by a facile polyol method and their suitability for use in high voltage lithium ion batteries (LIBs). The physicochemical properties were analyzed using X-ray diffraction, Fourier transform infra-red, Raman, field emission scanning electron microscopy (FE-SEM), energy dispersive analysis by X-ray (EDX), and electrochemical studies. FE-SEM showed that the spherical shape particles were uniformly distributed on the surface and EDX confirmed the presence of all the elements in the LiNi _1−x Mn _x PO ₄ nanostructure. Substitution of Mn dopants with LiNiPO ₄ significantly improved the electrical and electrochemical performances for LiNi _1−x Mn _x PO ₄ (x = 0.05–0.2) cathodes. The highly conducting LiNi _1−x Mn _x PO ₄ (x = 0.1) cathode exhibited initial discharge capacity of 94.2 mA h g ⁻¹ at C/4 rate, and 62% capacity retention after 100 cycles between 2.8 and 5.6 V. These features promote LiNi _1−x Mn _x PO ₄ as a suitable cathode material for high voltage LIBs.