Enhancing Fast-Charging Performance of Graphite Anode via Ionic Conducting Additives in Lithium-Ion Batteries

Abstract

In recent years, there has been an increasing demand for high-performance lithium-ion batteries (LIBs), driven by the rapid expansion of the electric vehicle (EV) market. LIBs offer advantages such as high energy density and reduced CO₂ emissions, yet their commercialization is hindered by challenges such as fast-charging capability. Graphite is widely used as an anode material due to its low cost, high capacity, and good conductivity. However, graphite suffers from low fast-charging performance. This is primarily due to lithium plating induced by the slow intercalation of Li ions and interfacial impedance due to solid electrolyte interphase (SEI) layer. The primary way to address these issues is to enhance the kinetics of Li transport in anode microstructures. To achieve this goal, this study investigates the effect of Li-ion conducting agent in graphite anodes in the fast-charging performance of LIB cells. Based on its good chemical and mechanical stability, nanosized Li₆ . ₇La₃Zr₁ . ₇Ta₀ . ₃O₁₂ (LLZT), a garnet-type solid electrolyte, was incorporated into the graphite anode slurry at various weight ratios ranging from 0 to 7.5%. As a result, the modified graphite anode delivered a discharge capacity of 112 mAh/g after 10C-rate extreme fast-charging (XFC) in NMC/graphite full cells, demonstrating strong potential for fast-charging applications. In stark comparison, the bare graphite anode delivered almost no discharge capacity after the 10C XFC. This improvement is the result of accelerated Li ion transport pathway provided by LLZT Li-ion conductors. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) confirm the uniform distribution of LLZT particles on the surface of graphite particles in anodes. Furthermore, LLZT itself can act as moisture scavenger to prevent side reactions that damage the SEI layer on graphite. For instance, electrochemical impedance spectroscopy (EIS) and X-ray photoelectron spectroscopy (XPS) reveals that performance improvements are due to LLZT suppressing continuous SEI layer reformation and reducing resistance. Our results demonstrate that incorporating Li-ion conducting agents can effectively passivate the SEI layer and enhance Li⁺ kinetics, thereby enabling extreme fast-charging (XFC) capability in conventional graphite anodes. These findings support the advancement of fast-charging EVs and contribute to the development of next-generation battery technologies.