Surface chemistry induced robust SEI on graphite surface via soft carbon coating enables fast lithium storage

Abstract

The realization of fast-charging lithium-ion batteries with long cycle life using graphite anode is typically hindered by the uncontrollable lithium plating on graphite surface. Herein we have systematically investigated the effects of soft carbon coating on SEI properties and Li+ storage capability. A variety of analytical studies combined with three-electrode impedance measurement and interface analysis demonstrate that the carbon coating effectively mitigates the formation of resistive films on the graphite surface, leading to facilitated charge transfer and low energy barrier. The depth-profiling XPS analysis clearly shows that the formation of a uniform, robust and LiF-rich SEI plays a dominant role in enhancing the interfacial kinetics, whereas the Li+ diffusion in bulk electrode is merely affected. As a result, the graphite anode with carbon coating exhibits enhanced fast-charging performance and cycle life, including a capacity retention ratio of 98.3 % after 100 cycles at 2C-CV. In general, this work reveals the critical role of coating layer chemistry in regulating the SEI properties and Li+ storage performance, which provides a valuable guidance for the rational design of practical graphite anode for fast-charging.