High-energy Graphite Microcrystalline Carbon for High-Performance Lithium-Ion Capacitor: Diffusion Kinetics and Lithium-Storage Mechanism

Graphite microcrystalline carbon (GMC) is a potential candidate for lithium storage devices because of its high degree of disorder in the crystalline structure. The mechanism that affects the energy-storage ability of GMC in its capacitive coupling state is still unclear. Herein, high-energy GMC is synthesized through a dual-activation approach, and its kinetics and lithium-storage mechanism to boost lithium-ion diffusion are further investigated. The porous graphite microcrystalline provides the structural advantage in raising the Li' storage capability, promotes the rapid transfer of electrons/ions, and possesses high conductivity. The defective heterostructure stimulates the internal electric field effect, facilitating rapid charge convey and fast diffusion kinetics. The first-principles calculations reveal that the nitrogen vacancies generated in graphite crystallites provide abundant reactive sites and induce excessive electrons around the local nitrogen atoms to form negative charge centers for accelerating the conveyance of Li'. The GMC electrode displays a high capacity of 1195 mAh g-1 at 0.1 A g-1, while the assembled GMC//GMC lithium-ion capacitor device delivers a high energy density of 190.63 Wh kg-1 at 225 W kg-1. This work is expected to offer an in-depth mechanism of electrons/ions diffusion and lithium storage for highenergy carbon electrodes and provide rational ideas for the optimal construction of high-energy carbon-based materials.