Cation Disordered Anti-Perovskite Cathode Materials with Enhanced Lithium Diffusion and Suppressed Phase Transition

摘要

Recently, a new family of anti-perovskite Li2TMSO was discovered aspromising cathode materials for Li-ion batteries (LIBs) with superiorities inhigh specific capacity, low cost, and environmental friendliness. However, theapplications of these anti-perovskite materials meet severe challenges in thecyclability and rate performance. Herein, a cation-disorderedanti-perovskite type solid solution Li_2Fe_(1?x)Mn_xSO (LFMSO, x = 0, 0.2, 0.5)with excellent electrochemical performance is reported. On the basis ofcomprehensive structural characterizations, the role of the cation disorderingin LFMSO is clarified. In comparison with Li_2FeSO (LFSO), the reduced Li-iondiffusion barrier and the increased Li-rich octahedral configurations in LFMSOwith higher configurational entropy imply the facilitated long-range Li-iondiffusion and the suppressed phase transition, which favor the high-ratecapability and cycling stability. In addition, the large lattice distortion andCoulombic interaction between the anions and cations lead to the breathing ofthe unit cell during charge/discharge. The variation of the unit cell volumedecreases to 2.5 upon Li-ion delithiation. A superstructure is observed inLFMSO for the first time. These findings help to pave the way for the researchand development of novel cathode materials for the next generation LIBs.