Effectively raising the rate performance and cyclability of a graphite anode via hydrothermal modification with melamine and its electrochemical derivatives

Abstract

Despite the extensive utilization of graphite anode material in lithium ion batteries, it suffers from instability of solid electrolyte interface (SEI) films, poor rate performance and inferior cyclability. Herein, a simple hydrothermal modification with melamine was adopted to promote the electrochemical performance of graphite. The good compatibility of melamine with graphite boosts the creation of a uniform melamine coating on the surface of graphite particles. The melamine-modified graphite with a mass ratio of 0.5% for melamine/graphite denotes an excellent rate performance (attaining average specific delithiation/lithiation capacities of 389.3/410.8 at 0.1C and 282.9/283.4 mA h g⁻¹ at 0.5C) and cyclability (achieving capacity retention of 109% after 150 cycles at 0.3C). Detailed characterization studies reveal that the melamine coating not only protects graphite from the direct contact with the electrolyte, but also in situ creates Li₃N in the SEI layer during lithiation to elevate Li⁺ ionic conductivity, effectively giving rise to the improvement in the structural stability and rate capabilities of the graphite anode.