Regulation of morphology evolution and Mn dissolution for ultra-long cycled spinel LiMn2O4 cathode materials by B-doping

Abstract

Electrochemical properties of spinel LiMn2O4 cathode material have been always suffered from Mn dissolution and Jahn-Teller distortion. Herein, various Ni/B dual-doped LiNi0.08BxMn1.92-xO4 (x = 0–0.15) with a truncated octahedral morphology are synthesized via a facile solid-state combustion. The effects of Ni/B co-doping on the morphology, crystal structure, Mn dissolution, Li+ diffusion coefficient and activation energy are investigated. Due to the relatively high Ni–O and B–O bond energy than that of Mn–O bond, the structure stability of the LiMn2O4 is enhanced, whilst restraining the Jahn-Teller distortion. The LiNi0.08Mn1.92O4 shows (111), (110) and (100) facets. In comparison, the B-doping endows the LiNi0.08BxMn1.92-xO4 (x ≥ 0.02) with (111) and (100) facets. This morphology evolution without (110) facets effectively inhibits the Mn dissolution. Owing to the synergistic merits of Ni/B dual-doping and unique truncated octahedron, the optimized LiNi0.08B0.06Mn1.86O4 delivers an initial discharge capacity of 113.9 mAh∙g−1 at 1C and maintains a durable cycling life up to 2000 cycles at 5C. Even at 20C, a capacity retention of 86.3% is still obtained after 2000 cycles. Furthermore, a capacity retention of 70.6% can be retained after 500 cycles at 5C and 55 °C. The truncated octahedral LiNi0.08BxMn1.92-xO4 with excellent electrochemical performance will be a good candidate for developing long-life lithium-ion batteries.