Material Characteristics-Dependent Solid Electrolyte Interphase Formation Behavior of Artificial Graphite Anodes

Abstract

Artificial graphite anode materials are promising for high-performance Li-ion batteries for electric vehicles. Battery cycle-life and performance are known to rely on the formation and stability of solid electrolyte interphase (SEI) layer, particularly, of the anode. Herein, we report the investigation of material characteristics-dependent SEI formation behavior and stability of model artificial graphite anodes in conventional electrolyte with vinylene carbonate additive, and their correlation to performance. Surface analysis results reveal that artificial graphite composite of Cokes and binder pitch in a relatively smaller particle size at 100% graphitization degree and with higher surface area of edges provides promoted interfacial reactivity and formation of more stable, thinner and softer SEI layer that includes plenty of organic compounds, leading to high structural robustness and improved cycling performance. By contrast, aggregated larger particles and/or lower graphitization degree results in inferior performance. A full-cell with the optimized artificial graphite anode and LiCoO2 cathode delivers initial discharge capacity of 161 mAhg−1 at 0.2C, respectively, and initial coulombic efficiency of 89%, and capacity retention of 91% at the 100th cycle. The data give an insight into the principles of material design, the SEI layer stabilization and performance enhancement of artificial graphite anode for high-energy Li-ion batteries.