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

Abstract

Recently, a new family of anti‐perovskite Li2TMSO was discovered as promising cathode materials for Li‐ion batteries (LIBs) with superiorities in high specific capacity, low cost, and environmental friendliness. However, the applications of these anti‐perovskite materials meet severe challenges in the cyclability and rate performance. Herein, a cation‐disordered anti‐perovskite type solid solution Li2Fe1−xMnxSO (LFMSO, x = 0, 0.2, 0.5) with excellent electrochemical performance is reported. On the basis of comprehensive structural characterizations, the role of the cation disordering in LFMSO is clarified. In comparison with Li2FeSO (LFSO), the reduced Li‐ion diffusion barrier and the increased Li‐rich octahedral configurations in LFMSO with higher configurational entropy imply the facilitated long‐range Li‐ion diffusion and the suppressed phase transition, which favor the high‐rate capability and cycling stability. In addition, the large lattice distortion and Coulombic interaction between the anions and cations lead to the breathing of the unit cell during charge/discharge. The variation of the unit cell volume decreases to 2.5% upon Li‐ion delithiation. A superstructure is observed in LFMSO for the first time. These findings help to pave the way for the research and development of novel cathode materials for the next generation LIBs.

Separating Cationic and Anionic Redox Activity in the Lithium-Rich Antiperovskite (Li2Fe)SO

“…This marks a notable achievement and unequivocally underscores the substantial advantages and potential offered by both the material and the chosen synthesis approach. Compared to the initial capacity achieved by previous measurements on lithium-rich antiperovskite cathodes of 285 mAh g −1 for (Li 2 Fe)SO by Mikhailova et al, 3 220 mAh g −1 for (Li 2 Fe 0.8 Mn 0.2 )SO by Deng et al, 12 245 mAh g −1 for (Li 2 Fe)S 0.7 Se 0.3 O by Mohamed et al, 16 and 164 and 300 mAh g −1 for (Li 2 Fe)SeO by Mohamed et al 17 and Singer et al, 14 this is by far the highest capacity ever achieved. In contrast, in the constrained potential range, BM, BM300, and BM500 all show capacities around 220 mAh g −1 .…”

“…The recent discovery of the lithium-rich antiperovskite compounds characterized by the general formula (Li 2 TM)ChO (with TM = Fe, Mn, Co; Ch = S, Se) has significantly broadened the landscape of potential cathode materials for lithium-ion batteries (LIBs) . This novel class of materials showcases highly favorable attributes in the context of lithium-ion battery application, including cost effectiveness, utilization of environmentally benign raw materials, efficient lithium diffusion, and the ability of multielectron storage per chemical unit. − From the so far investigated antiperovskite materials Li 2 FeSO, ,,− (Li 2 Co)SO, (Li 2 Mn)SO, (Li 2 Fe 1– x Mn x )SO, ,, (Li 2 Fe 0.9 Co 0.1 )SO, (Li 2 Co)SeO, (Li 2 Mn)SeO, (Li 2 Fe)S 1– x Se x O, and (Li 2 Fe)SeO, ,, the (Li 2 Fe)SO compound captivates with the highest theoretical capacity. Despite the promises of lithium-rich antiperovskites and especially (Li 2 Fe)SO, their great potential could not be fully exploited due to poor cycling stability (only 66% capacity retention in (Li 2 Fe)SO at 0.1 C after 50 cycles) …”