Constructing Densely Compacted Graphite/Si/SiO2 Ternary Composite Anodes for High-Performance Li-Ion Batteries.

Abstract

Graphite has dominated the market of anode materials for lithium-ion batteries in applications such as consumer electronic devices and electric vehicles. As commercial graphite anodes are approaching their theoretical capacity, significant efforts have been dedicated towards higher capacity by blending capacity-enhancing additives (e.g., Si) with graphite particles. In spite of the improved gravimetric capacity, the areal capacity of such composite anodes might decrease due to excess void spaces and an incompatible material size distribution. Herein, a rational design of compact graphite/Si/SiO2 ternary composites has been proposed to address the abovementioned issues. Si/SiO2 clusters with an optimal particle size are homogeneously dispersed in the interstitial spaces between graphite particles to promote the packing density, leading to a higher areal capacity than that of pure graphite with equivalent mass loading or electrode thickness. By taking the full intrinsic advantages of graphite, Si, and SiO2, the composite electrodes exhibit 553.6 mAh g-1 after 700 cycles with a capacity retention of 95.2%. Furthermore, the graphite/Si/SiO2 electrodes demonstrate a high coulombic efficiency with an average of 99.68% from 2nd to 200th cycles and areal capacities above 1.75 mAh cm-2 during 200 cycles with an areal mass loading as high as 4.04 mg cm-2. A packing model has been proposed and verified by experimental investigation as a design principle of densely compacted anodes. The effective strategy of introducing Si/SiO2 clusters into the void spaces between graphite particles provides an alternative solution for implementation of graphite-Si composite anodes in next-generation Li-ion cells.