Surface reconstructed layer with bulk high-valence Mo doping to achieve long-life LiMn₂O₄ cathode material

Mo doping plays a striking role in the stability enhancement of LiMn₂O₄ cathode materials. However, the underlying microscopic mechanism is still unclear. Here, we elucidate that the relationship between the atomic position of Mo doping in LiMn₂O₄ and the stability enhancement of Mo-doped LiMn₂O₄ by utilizing the spherical aberration-corrected scanning transmission electron microscopy (Cs-STEM). It exhibits that the part of Mo⁶⁺ ions occupy empty Mn 16c site to form a surface reconstructed layer of rock-salt like phase on the outermost surface and other Mo⁶⁺ ions dope into the Mn octahedral 16d sites to form LiMo_xMn_2-xO₄ in bulk, which is beneficial for inhibiting the parasitic side reactions. Concomitantly, this dual modification of bulk structure and surface can significantly enhance electrode reversibility and Li⁺ diffusion. As a result, excellent long cycling stability of the as-designed optimal LiMo_0.01Mn_1.99O₄ after 1500 cycles with 61.61 % capacity retention at 10 C (1 C = 148 mAh g⁻¹) is presented, with an initial discharge capacity of 88.30 mAh g⁻¹. Our research provides a clever approach for regulating the surface structure/bulk architecture in LiMn₂O₄ cathode materials.