Effect of Pitch Coating on SiOx Alloy/Spherical Artificial Graphite Composites as Anode Materials for Lithium‐Ion Batteries

SiOx-based anodes are attracting intensive attention with the increasing demand for high-energy-density lithium-ion batteries (LIBs). Since the theoretical capacity of SiOx is superior to that of graphite and its volume deformation is more stable than that of silicon, tremendous efforts are applied to design various SiOx-based anode materials. However, industrially utilizing SiOx-based anodes is still insufficient owing to volume deformation, low initial coulombic efficiency and poor cycle life. Thus, this work develops a pitch-coated SiOx/graphite (P@SiOx@G) composite constructed with the optimal ratio between SiOx and graphite under the collaborative auxiliary of pitch coating to serve as a buffer against volume deformation and to improve the discharge rate performance. The electrode thicknesses of P@SiOx-10@G-900 increases by approximately 18.6 % from 43.32 mu m to 51.36 mu m after 70 cycles, respectively. However, in SiOx@G, the electrode experiences delamination due to volume expansion during lithiation/delithiation of SiOx. Notably, P@SiOx-10@G-1100 shows an outstanding initial coulombic efficiency of 86.4 % and a high capacity retention rate (at 200 mA g(-1) after 100 cycles) of approximately 96 %. This result is mainly due to the uniform and thin solid electrolyte interphase (SEI) layer on the SiOx/graphite composite.