High-Energy Density Li-Ion Capacitor with Layered SnS2/Reduced Graphene Oxide Anode and BCN Nanosheet Cathode

Lithium-ion capacitors (LICs) with capacitor-type cathodes and battery-type anodes are considered a promising next-generation advanced energy storages system that meet the requirements of high energy density and power density. However, the mismatch of charge-storage capacity and electrode kinetics between positive and negative electrodes remains a challenge. Herein, layered SnS2/reduced graphene oxide (RGO) nanocomposites are developed for negative electrodes and a 2D B/N codoped carbon (BCN) nanosheet is designed for the positive electrode. The SnS2/RGO derived from SnS2-bonded RGO of high conductivity exhibits a capacity of 1198 mA h g(-1) at 100 mA g(-1). Boron and nitrogen atoms in BCN are found to promote adsorption of anions, which enhance the pseudocapacitive contribution as well as expanding the voltage of LICs. A quantitative kinetics analysis indicates that the SnS2/RGO electrodes with a dominating capacitive mechanism and a diminished intercalation process, benefit the kinetic balance between the two electrodes. With this particular structure, the LIC is able to operate at the highest operating voltage for these devices recorded to date (4.5 V), exhibiting an energy density of 149.5 W h kg(-1), a power density of 35 kW kg(-1), and a capacity retention ratio of 90% after 10 000 cycles.