Boron-doped carbon nano dot anchored thin film coating on cobalt vanadium oxide for ultrafast energy storage devices

Lithium-ion capacitors (LICs) with ultrafast rate capabilities are required to increase the applicability of rechargeable energy storage devices. Considering that the power density of an LIC is primarily determined by the anode properties, carbon coating onto the anode material is a promising method of accelerating electron transfer between particles and alleviating structural collapse during repeated charge–discharge cycles. In this study, a new coating configuration featuring a boron-doped carbon nano dot-anchored thin film on cobalt vanadium oxide (BC-CVO) was demonstrated. The coating morphology, wherein the carbon nano dots were connected by a thin carbon film, induced nano-scale surface roughness on CVO, expanding the contact area between the functional groups on the coating layer and electrolyte. The boron-doped carbon lattice structure provided ultrafast electron transfer inside the CVO particles, which allowed reversible electron transfer even under ultrafast charge–discharge cycles. This morphological and chemical combination significantly improved the ultrafast-rate capability of the LIC anodes (429.6 mAh/g at 4000 mA/g and 534.3 mAh/g after 1000 cycles at 2000 mAh/g) compared to that of bare CVO. Furthermore, an LIC full cell fabricated with a BC-CVO anode and an activated carbon cathode showed high energy and power densities.