Effect of sulfur doping on structural reversibility and cycling stability of a Li₂MnSiO₄ cathode material

Based on the existing calculation reports, sulfur doping is an effective approach to alleviate the structure collapse of Li2MnSiO4 during cycling. Herein, we investigate the feasibility and limitations of S doping in Li2MnSiO4 by experiment. In our work, the solid solubility of S is confirmed and exceeding the threshold results in MnS impurity. The existence state and site of the S element in a Li2MnSiO4 crystal structure is also confirmed. It is found that S doping significantly improves the structural reversibility and cycling stability. Compared with a pristine sample, a 1mol% S doped sample exhibits a much higher initial coulombic efficiency (88.3%), excellent capacity retention (98% at 10th cycles for instance) and enhanced rate performance. Moreover, the 1mol% S doped sample can retain a discharge capacity of 137 mA h g-1 after 30 cycles while the pristine sample only has 61.6 mA h g-1. This study confirms the effectivity of S doping in suppressing the structural distortion in Li2MnSiO4.