Plasma-Assisted Sulfur Doping of LiMn₂O₄ for High-Performance Lithium-Ion Batteries

Though considered as one of the most promising materials for rechargeable Li-ion batteries, spinel LiMn 2 O 4 suffers from fast capacity fading during cycling due to the structural instability, Jahn–Teller distortion, and Mn dissolution into the electrolyte. In order to improve the electrochemical performance, in this work, we, for the first time, realize the sulfur doping by the plasma-assisted method in LiMn 2 O 4 . Physical properties of the synthesized materials LiMn 2 O 4– x S x are measured by XRD, SEM, and EDS, which confirm that S atoms have been successfully doped into the structure of LiMn 2 O 4 (LiMn 2 O 4– x S x ) with the high crystalline and uniform morphology. Compared to the pristine LiMn 2 O 4 prepared by the conventional method (800 °C, 8 h), the LiMn 2 O 4– x S x prepared by the plasma-assisted method shows superior performance with higher capacity (125.3 mAh·g –1 ) and significantly improved cycling stability (maintaining 97.76% of its initial discharge capacity after 60 cycles). In addition, the sulfur-doped LiMn 2 O 4 demonstrates dramatically enhanced reversibility and stability even at the elevated temperature due to the improved structural stability and the suppressed Mn dissolution into the electrolyte by the doping of S. The sulfur doping into LiMn 2 O 4 by the plasma-assisted method offers a new strategy for efficient modification of electrode materials for energy storage devices.