Lithium-Ion Capacitor with Improved Energy Density via Perfect Matching Silicon@3D Graphene Aerogel Anode and BCNNTs Cathode

The challenge for current lithium-ion capacitors (LICs) to obtain high energy density is to improve the energy storage performance at high rates. The key lies in balancing the kinetics mismatch between battery-type anode and capacitor-type cathode as well as ensuring high capacity contribution of electrodes. To this end, graphene aerogel (GA) supported high-capacity silicon (Si) nanoparticles 3D conductive framework is designed as anode for LICs, overcoming the notably volume expansion (300%) of Si and contributing to the high energy density. More importantly, a dominating capacitive mechanism lies in the intercalation process of Si@GA anode, which enables its fast charge–discharge capability. So as to match the high capacity anodes, boron carbonitride nanotubes (BCNNTs) with high-rate pseudocapacitive behavior and desirable capacity are used as cathode to construct a novel LIC with high energy density. Benefiting from high-rate capabilities of both anode and cathode, the rational designed 4.5 V Si@GA//BCNNTs LIC exhibits excellent electrochemical performance, delivering a maximum energy density of 197.3 W h kg−1 at the power density of 225 W kg−1. This strategy may widen the application for materials with volume expansion issues and many other material systems in pseudocapacitive advanced high-rate devices.