Next-generation Li-ion capacitor with high energy and high power by limiting alloying-intercalation process using SnO2@Graphite composite as battery type electrode

Lithium-ion capacitors (LICs) with high energy density at high power capability are ideal for future energy storage applications. Group IV elements, mainly tin (Sn)-based derivatives, are considered as a viable option due to their high reversible capacity, lower redox potential, and moderately lower price. In the present work, we report the assembly of a new type of LIC with high energy and power with long-term stability by pairing SnO2@Graphite nanocomposites (SnO2@G ncs) as battery type electrodes and commercial activated carbon (AC) as capacitor type electrodes. SnO2@G ncs are synthesized by hydrothermal method followed by high-energy ball milling of SnO2 and commercial graphite. The testing potential window of the SnO2 @G ncs half–cells are limited to 1 V vs. Li+/Li to enable only the alloying process and avoid the conversion of Sn0 to SnOx. Among the compositions, the composite with 25% SnO2 and 75% graphite (C1)-based LIC, AC/C1 displayed stable performance with high energy and power. Furthermore, AC/C1-based LIC delivers an energy density of 172.33 Wh kg−1 and retains over 90% capacity after 9000 cycles. This study gives the idea of incorporating an alloying-intercalation-based battery-type electrode, which paves the way further to enhance the electrochemical performance of next-generation LICs.