Construction of Nano ZnV2O4/N-Doped Porous Carbon Composites with Optimized Ionic and Electronic Conductivities as Competitive Cathodes toward Zinc-Ion Capacitors

Zinc-ion capacitors (ZICs) have great potential for energy storage applications due to high safety, environmental friendliness, low cost, and high energy density. However, challenges such as poor ion diffusion kinetics and the low conductivity of cathode materials still need to be addressed. Nano ZnV2O4/nitrogen-doped porous carbon (ZVO/N-PC) composites are efficiently synthesized via a simple annealing process. Highly crystalline ZVO nanoparticles are in-situ grown on the three-dimensional N-PC surface by precisely tuning the ratio of the vanadium source, achieving a dual enhancement in electronic and ionic conductivities. Benefiting from the nanoengineering build-up, the optimized ZVO-0.6/N-PC anode exhibits impressive rate performance (405.9/308.8 mAh g–1 at 0.2/5.0 A g–1) and cycling capability (0.0029% capacity drop per cycle at 5.0 A g–1 after 5,800 cycles). Using nitrogen-doped porous activated carbon (N-PAC) as the anode and ZVO-0.6/N-PC as the cathode, the assembled ZICs deliver a high energy density of 27.5 Wh kg–1 at a power density of 450.0 W kg–1. After 10,000 cycles at 1.0 A g–1, the capacity retention rate remains as 72.8%, demonstrating excellent cycling stability. This highlights the promising application of nano ZVO/N-PC composites towards ZICs as competitive cathodes.