Unveiling the role of Ni doping in the electrochemical performance improvement of the LiMn2O4 cathodes

Ni doping is a commonly used strategy to improve the electrochemical performance of LiMn 2 O 4 . Uncovering the structural changes of Ni-doped LiMn 2 O 4 during electrochemical cycling, particularly at the atomic level, is important to understand the mechanism of the relationship between Ni doping and performance improvement. Herein, we investigate the chemical and structural evolutions of the Ni-doped LiMn 2 O 4 electrodes before and after 1000 cycles at 10 C with atomic resolution and correlate them with changes in the electrochemical properties . We found that Ni 2+ ions doped into the Mn 16d sites to form a more steady LiNi x Mn 2-x O 4 phase construction, which can effectively stabilize the spinel structure by hindering Jahn − Teller distortion. Comprehensive atomic imaging demonstrated that Ni doping can suppress the formation of the unexpected Mn 3 O 4 , and rock-salt MnO phases on the surface and subsurface of LiMn 2 O 4 during cycling, which is conducive to stabilizing the MnO 6 octahedron and inhibiting the migration of Mn. Resultantly, splendid long cycling stability of 88.92 % after 1000 cycles at 10 C (1 C = 148 mAh g −1 ) for the optimized LiNi 0.05 Mn 1.95 O 4 sample is presented. Our study provides an ingenious avenue for regulating the surface optimization and reconstruction of electrode materials .