Mitigating the fast-charging limitations of graphite anodes via g-C3N4 surface engineering

Abstract

With the rapid expansion of the electric vehicle (EV) market, the demand for fast-charging lithium-ion batteries (LIBs) has increased considerably to extend the driving range and reduce charging time. However, commercial graphite (Gr) anodes suffer from slow interfacial kinetics under fast-charging conditions, ultimately causing Li plating on their surfaces, which results in significant capacity losses and safety concerns. Herein, a surface engineering approach using graphitic carbon nitride (g-C3N4) is introduced to modify Gr anodes. Three-dimensional electrochemical modeling at particle- and electrode-levels has identified critical requirements for functional surface coatings that effectively improve the fast-charging capability. By conducting a simple chemical exfoliation process followed by a post-heat treatment, g-C3N4 nanoplates form a functional surface layer on Gr particles, which reduces the activation energy for Li⁺ adsorption and migration during charging. Hence, g-C3N4-decorated Gr (g-C3N4@Gr) exhibits a lower overpotential and effectively suppresses Li plating under fast-charging conditions. When paired with a commercial LiNi0.8Co0.1Mn0.1O2 cathode in a full-cell configuration, the g-C3N4@Gr anode demonstrates stable cycling performance for up to 300 cycles, achieving an 80 % state of charge in only 6.8 min. This study clearly describes the fast-charging mechanism in commercial Gr anodes and a practical strategy for advancing fast-charging LIB technology.