Double‑carbon protected pre-lithiated SiOx anode for lithium-ion storage with high initial Coulombic efficiency and long cycle life

Abstract

Silicon monoxide (SiO_x) is the most prevalent high-capacity anode material because of their relatively low volume change and superior cycling performance in comparison to silicon (Si). Nevertheless, its low initial coulombic efficiency (ICE) acts as a hindrance to the advancement of anode materials for Li-ion batteries. This study proposes a novel strategy for achieving double‑carbon protected homogeneous pre-lithiation of Li-SiO_x/C/C microparticles, utilising in-situ solid phase prelithiation and secondary carbon coating. To enhance the ICE two pre‑lithium strategies were compared, one is in-situ pre‑lithium by direct contact of SiO_x with LiH (Li-SiO_x), and the other is in-situ pre‑lithium by mixing carbon-coated SiO_x with LiH (Li-SiO_x/C). We found that the presence of the carbon coating led to a mild prelithiation reaction between SiOx and LiH, which improved the homogeneity of the prelithiation and reduced the overgrowth of lithium silicate and crystalline Si. The double‑carbon coating improves the electrical conductivity and structural stability of SiO_x electrode. The Li-SiO_x/C/C prepared with up to 87.13 % ICE and excellent cycling stability. The Li-SiO_x/C/C material employed in the NMC811-Li-SiO_x/C/C full battery exhibits a capacity retention of 78.2 % after 100 cycles, in comparison to 70.13 % with the SiO_x/C material. The findings provide a practical solution to be applied in the commercial context of SiO_x-based anode materials.