Hard carbon/graphite composite anode for durable lithium-ion capacitor

Abstract

Li-ion capacitors (LICs), characterized by high energy and power densities, are widely regarded as promising electrochemical energy-storage devices. However, the application of these devices is limited by the poor stability of anode materials and inferior electrochemical performance owing to asymmetrical kinetics between the anode and cathode. To address these concerns, this study aimed at developing a highly stable composite anode material by tuning the mass ratio between graphite (Gr) and hard carbon (HC). When subjected to thrice-repeated deep prelithiation, the composite anode exhibited enhanced cycling performance without significant deterioration in the capacity. The incorporation of HC in the anode effectively improved the cyclability of Gr, and the thrice-repeated deep prelithiation strategy facilitated the increase in LIC capacity. The LIC using the composite anode exhibited an energy density of 48.5 Wh kg−1 at a power density of 2170 W kg−1, surpassing those of Gr (33.8 Wh kg−1 at 2030 W kg−1) and HC (35.7 Wh kg−1 at 2230 W kg−1) LICs. The enhanced LIC retained 80.5 % of its initial energy density after 10,000 cycles, a significantly higher value than those of LICs based on Gr (26.1 %) and HC (73.3 %). In summary, deep prelithiation can enhance the overall performance of LICs to achieve improved cyclability and capacity compared with its semi-shallow prelithiated counterpart. This study provides a cost-effective solution for the design of LIC anode materials with high rate and long cycling performances.