The electrochemical performance of sodium-ion-modified spinel LiMn ₂O₄ used for lithium-ion batteries

The spinel LiMn₂O₄ cathode material has been considered as one of the most potential cathode active materials for rechargeable lithium ion batteries. The sodium-doped LiMn₂O ₄ is synthesized by solid-state reaction. The X-ray diffraction analysis reveals that the Li_1-x Na _x Mn₂O ₄ (0 ≤ x ≤ 0.01) exhibits a single phase with cubic spinel structure. The particles of the doped samples exhibit better crystallinity and uniform distribution. The diffusion coefficient of the Li_0.99Na _0.01Mn₂O₄ sample is 2.45 × 10 ^-10 cm^-2 s^-1 and 3.74 × 10^-10 cm^-2 s^-1, which is much higher than that of the undoped spinel LiMn₂O₄ sample, indicating the Na⁺-ion doping is favorable to lithium ion migration in the spinel structure. The galvanostatic charge-discharge results show that the Na⁺-ion doping could improve cycling performance and rate capability, which is mainly due to the higher ion diffusion coefficient and more stable spinel structure.