Supercritical CO2-Assisted SiOx/Carbon Multi-Layer Coating on Si Anode for Lithium-Ion Batteries

Supercritical CO2 (SCCO2), characterized by gas-like diffusivity, low surface tension, and excellent mass transfer properties, is applied to create a SiOx/carbon multi-layer coating on Si particles. Interaction of SCCO2 with Si produces a continuous SiOx layer, which can buffer Si volume change during lithiation/delithiation. In addition, a conformal carbon film is deposited around the Si@SiOx core. Compared to the carbon film produced via a conventional wet-chemical method, the SCCO2-deposited carbon has significantly fewer oxygen-containing functional groups and thus higher electronic conductivity. Three types of carbon precursors, namely, glucose, sucrose, and citric acid, in the SCCO2 syntheses are compared. An eco-friendly, cost-effective, and scalable SCCO2 process is thus developed for the single-step production of a unique Si@SiOx@C anode for Li-ion batteries. The sample prepared using the glucose precursor shows the highest tap density, the lowest charge transfer resistance, and the best Li+ transport kinetics among the electrodes, resulting in a high specific capacity of 918 mAh g(-1) at 5 A g(-1). After 300 charge-discharge cycles, the electrode retains its integrity and the accumulation of the solid electrolyte interphase is low. The great potential of the proposed SCCO2 synthesis and composite anode for Li-ion battery applications is demonstrated.