Boron-based composites anode leads to ultrahigh power and energy density of lithium-ion capacitor

There is an urgent need to find a way to increase the energy density of supercapacitors while preserving their high power. Building lithium-ion hybrid capacitors (LICs) is recognized as a powerful strategy. However, until now, at relatively high power density (around 40 kW kg  1), the energy density of LIC only reaches 15-25 Wh kg  1, which is far from reaching the range of energy density of lithium-ion batteries(50-150 Wh kg  1). Here, a new type of LIC device with amorphous Co-B nanoparticles/graphene composites as anode and nitrogen-doped porous carbon as cathode has been fabricated. Coupling the amorphous Co-B nanoparticles/graphene composites (ACB-G) and nitrogen-doped porous carbon (NPC), the lithium ion capacitors device delivers a high energy density of 139 Wh kg  1 at 200 W kg  1, and an excellent 83% capacity retention after 10,000 cycles. Even at 40 kW kg  1, the energy density can reach 61 Wh kg  1. Such as-prepared LICs mainly benefit from the amorphous boron-based material's ability to embed lithium quickly and in large quantities. The study of amorphous anode material in LICs may reveal a new perspective towards application of high-performance storage devices.