Suppressed Volume Change of a Spray-Dried 3D Spherical-like Si/Graphite Composite Anode for High-Rate and Long-Term Lithium-Ion Batteries

Abstract

Morphology plays a vital role in controlling the volume variation in Si-based anode materials and enhances lithium-ion battery performances. Here, we demonstrated advanced techniques that combine electrostatic self-assembly and spray-drying methods to form 3D spherical-like silicon/graphite (denoted “Si/G”) composite anode materials. This spherical morphology alleviates issues relating to silicon volume changes that occur in high-rate lithium-ion batteries. Commercial graphite (G) flakes were initially mixed with silicon nanoparticles (ca. 50 nm) to form a bare-Si/G composite through electrostatic interaction; spherical-like composite particles were then obtained through single and double spray-drying processes, giving samples SD1-Si/G and SD2-Si/G, respectively. We examined the charge/discharge characteristics of the fabricated electrodes (CR2032-type coin cells) in the voltage range 0.02–1.5 V (vs Li/Li+). The as-fabricated bare-Si/G, SD1-Si/G, and SD2-Si/G half-cells provided initial discharge specific capacities of 897, 866, and 1020 mA h g–1, respectively. The SD2-Si/G half-cell shows better cycling stability at a high current rate of 400 mA g–1 than the SD1-Si/G and bare-Si/G half-cells due to effective inhibition of the volume change in the more stable spherical structure of the SD2-Si/G composite, as evidenced through in situ dilatometry. Thus, the spherical Si/G composite material produced through this simple spray-drying process had structural characteristics that could effectively resist silicon’s high expansion rate, lower the production rate of broken silicon particles, and improve the electrochemical performance of the anode.