A conductive flexible carbon nanoyarns embedded with VN quantum dots for highly Kinetics-Compatible Li-Ion capacitors

Lithium-ion capacitors (LICs) with high energy and power density has gained widespread attention. However, the kinetics mismatch between the anode and cathode of LICs limits its further development. Vanadium nitride (VN) with high electrical conductivity is a suitable anode to reduce the kinetic gap between the two electrodes of LICs, but the VN usually undergoes severe volume changes (～240 %) during the electrochemical reaction. Herein, the VN@N-PCYS-0.4 films that ultrafine VN quantum dots uniformly embedded in polyacrylonitrile-derived carbon (PAN-DC) nanoyarns were synthesized by a simple sacrificial silica template-assisted electrostatic spinning technique. Ultra-small particle size of VN (∼1 nm) mitigates the volume expansion and enriches the active sites. The super loose porous structure of PAN-DC nanoyarns shortens ions/electrons diffusion pathways and enhances electrolyte penetration. Correspondingly, on the basis of such free-standing VN@N-PCYS-0.4 anode, a LICs was assembled by matching activated carbon (AC) cathode, which exhibits a high energy density of 99.7 Wh kg−1 and a high power density of 24.0 kW kg−1. Such rational design for carbon-based material can surmount kinetics incompatibility between anode and cathode of LIC and provides a perspective to enhance the electrochemical properties of LIC anode in terms of volume expansion suppression and charge transfer resistance reduction.