Preparation and controllable prelithiation of core-shell SnO_x@C composites for high-performance lithium-ion batteries

SnO_x is an attractive anode material for lithium-ion batteries (LIBs) with high-energy density. However, large volume variation during lithiation/delithiation leads to its rapid capacity decay. Simultaneously, a low initial coulombic efficiency (ICE) also severely limits its commercial application. Therefore, carbon coated SnO_x (SnO_x@C) with adjustable composition and coating thickness was firstly prepared to improve cycling stability through a phenolic resin condensation polymerization-pyrolysis method. The as-prepared SnO_x@C anode exhibited the best electrochemical performance with a capacity retention of 94.1% after 300 cycles at 1 A g⁻¹. To overcome the large irreversible capacity loss during the first cycle, SnO_x@C plates were immersed in the lithium-4,4′-dimethylbiphenyl reagent for different periods of time, and the ICE of SnO_x@C was increased from 64.3% to 224.86% for 20 min of immersion. The full-cell based on the SnO_x@C anode and commercial LiFePO₄ cathode not only presented good cycling stability with a high capacity of 98.05 mAh g⁻¹ at 2C after 80 cycles but also showed satisfactory rate performance.