Graphite Anode of Lithium-Ion Batteries for Fast Charging Application

Abstract

The rapid growth of electric vehicle (EV) market has demanded lithium-ion batteries (LIBs) with fast charging capability. During fast charging application, the anode plays a crucial role in determining the performance of LIBs. In this report, four graphite materials with particle sizes ranged from 5 to 22.4 μm were investigated as anodes of LIBs. The properties of pristine graphite materials, including crystal phase, morphology, particle size and surface area, were evaluated through X-ray diffraction (XRD), scanning electron microscope (SEM) and nitrogen adsorption. Assembled into cells, these graphite materials were evaluated through a fast charging test protocol. The electrochemical measurements demonstrate that the rate capability of LIBs increases when the particle size of graphite anode decreases, and LIBs with 5 mm graphite exhibits the highest capacity retention of 74% at 2C and 65% at 4C, respectively. Further, 80% capacity is retained in 5 mm graphite anode after 120 cycles. Measurements from galvanostatic intermittent titration technique (GITT) reveal that the particle size has negligible effect on Li-ion diffusion coefficient in graphite materials studied in this project. In further, lower resistance were observed at the surface of graphite with smaller particles, although a thicker solid electrolyte interface (SEI) film was formed. Therefore, all these observations suggest that the particle size is a very important parameter that should be considered for graphite anode for fast charging LIBs. Keywords: Graphite, Particle Size, Fast charging, Li-Ion Batteries