Structural transformations in Li2MnSiO4: evidence that a Li intercalation material can reversibly cycle through a disordered phase

摘要: Li2MnSiO4 is a promising high capacity cathode material due to the potential extract two Li ions per formula unit. In practice, however, use of restricted by low discharge capacity, which has been attributed an irreversible structural change in first charge cycle. this work, we density functional theory calculations explore details change, and our results reveal that during delithiation components. First, find undergoes collapse upon partial delithiation, characterized distortion MnO4 tetrahedron. Remarkably, while transformation disordered structure, show it reversible relithiation does not strongly impede de/intercalation. The calculated reversibility phase consistent with recent experimental X-ray diffraction measurements showing peaks associated crystalline order, disappear are restored lithiation. Additional experiments conducted cycling as function charging cutoff voltages. Second, argue that, degradation primarily caused oxygen evolution highly delithiated state; deficient structure can only reincorporate half total when discharged 1.5 V. Experimentally observed voltage profile shifts few cycles well different electrochemical behavior exhibited Li2FeSiO4 be explained two-component model.