Carbon nanocages bridged with graphene enable fast kinetics for dual-carbon lithium-ion capacitors

Abstract

Lithium-ion capacitors (LICs) combining the advantages of lithium-ion batteries and supercapacitors are considered a promising next-generation energy storage device. However, the sluggish kinetics of battery-type anode cannot match the capacitor-type cathode, restricting the development of LICs. Herein, hierarchical carbon framework (HCF) anode material composed of 0D carbon nanocage bridged with 2D graphene network are developed via a template-confined synthesis process. The HCF with nanocage structure reduces the Li+ transport path and benefits the rapid Li+ migration, while 2D graphene network can promote the electron interconnecting of carbon nanocages. In addition, the doped N atoms in HCF facilitate to the adsorption of ions and enhance the pseudo contribution, thus accelerate the kinetics of the anode. The HCF anode delivers high specific capacity, remarkable rate capability. The LIC pouch-cell based on HCF anode and active HCF (a-HCF) cathode can provide a high energy density of 162 Wh kg−1 and a superior power density of 15.8 kW kg−1, as well as a long cycling life exceeding 15,000 cycles. This study demonstrates that the well-defined design of hierarchical carbon framework by incorporating 0D carbon nanocages and 2D graphene network is an effective strategy to promote LIC anode kinetics and hence boost the LIC electrochemical performance.