Graphitic carbon nitride (g-C3N4) as an electrolyte additive boosts fast-charging and stable cycling of graphite anodes for Li-ion batteries

Abstract

Graphite is the most popular anode material in lithium-ion batteries (LIBs), however, it suffers from poor reaction kinetics and structural degradation during long-term cycling. Surface modification of the graphite electrode and advanced electrolyte designs have been used to address these challenge. However, the previous efforts either involved multi-step reaction processes or resulted in unsatisfactory performance. In this work, we introduce a facile method to improve the rate and cycle performance of graphite by adding graphitic carbon nitride (g-C₃N₄) to the electrolyte. The additive not only induces anions to participate in the solvation structure with lower desolvation energy but also participates in the SEI formation, which contains Li₃N and high amounts of LiF at the graphite interface. Consequently, the structural integrity and reaction kinetics of graphite improved during cycling. The assembled graphite‖Li cell with modified electrolyte demonstrates excellent cycling and rate performance. A reversible specific capacity of 209 mAh g⁻¹ is achieved over 600 cycles at a high current density of 2000 mA g⁻¹, which is significantly superior to that observed with the pristine electrolyte and outperforms other modified graphite electrodes reported in the literature. Furthermore, the modified electrolyte endows the graphite electrode with outstanding cycle stability, even at 60 °C, with a remarkable capacity of 360 mAh g⁻¹ after 100 cycles at 100 mA g⁻¹. This study provides a facile strategy to design electrolytes for graphite-based lithium-ion batteries with fast charge–discharge behavior and long cycle stability.