Mechanism of Synergistic Modification of Microcrystalline Graphite for Lithium Storage

Abstract A the core component of lithium‐ion batteries, the poor rate performance and cycling stability of graphite negative electrodes severely restrict the power output and service life of batteries. In this study, using microcrystalline graphite as the starting material, high‐purity graphite was prepared via a mixed‐acid method, followed by the preparation of expanded graphite through an intercalation‐oxidation approach. Combined with first‐principles calculations, the interfacial and electronic properties of both the high‐purity and expanded microcrystalline graphite were investigated. The results demonstrate that the expanded microcrystalline graphite anode material for lithium‐ion batteries maintains a reversible capacity of 413 mAh·g −1 after 100 cycles at a current density of 0.1 A·g −1 , with a remarkably high capacity retention of 106.5%. First‐principles calculations reveal that expanded graphite exhibits stronger Li atom adsorption energy. Density of states analyses confirm its enhanced electrical conductivity. The improvement of these performances stems from the modification of the lithium storage mechanism by physical structure and chemical properties: the increase in specific surface area and pore structure optimizes the lithium ion transport channels and enhances the physical structure characteristics of the material. The introduction of functional groups enhances the chemical reactivity of the material.