Amorphous AlPO₄ Layer Coating Vacuum Thermal Reduced SiO_x with Fine Silicon Grains to Enhance the Anode Stability

Micrometer-sized silicon monoxide (SiO) is regarded as a high-capacity anode material with great potential for lithium ion batteries (LIBs). However, the problems of low initial Coulombic efficiency (ICE), poor electrical conductivity, and large volume change of SiO inevitably impede further application. Herein, the vacuum thermal reduced SiO_x with amorphous AlPO₄ and carbon double-coating layers is used as the ideal anode material in LIBs. The vacuum thermal reduction at low temperature forms fine silicon grains in the internal particles and maintains the external integrity of SiO_x particles, contributing to mitigation of the stress intensification and the subsequent design of multifunctional coating. Meanwhile, the innovative introduction of the multifunctional amorphous AlPO₄ layer not only improves the ion/electron conduction properties to ensure the fast reversible reaction but also provides a robust protective layer with stable physicochemical characteristics and inhibits the volume expansion effect. The sample of SiO_x anode shows an ICE up to 87.6% and a stable cycling of 200 cycles at 1 A g^-1 with an initial specific capacity of 1775.8 mAh g^-1. In addition, the assembled pouch battery of 1.8 Ah can also ensure a cycling life of over 150 cycles, demonstrating a promising prospect of this optimized micrometer-sized SiO_x anode material for industrial applications.