Nitrogen-rich nanoporous carbon with MXene composite for high-performance Zn-ion hybrid capacitors

The zinc-ion hybrid capacitor, as a novel energy storage system with outstanding electrochemical performance, low cost, and high safety, has attracted widespread research attention. In this work, we report a hetero-structured composite material, CN@MXene, obtained by alternately stacking porous carbon material CN with MXene nanosheets. Theoretical calculations and a series of characterizations reveal that the introduction of MXene nanosheets not only exposes more active sites of CN, but also significantly enhances the conductivity and stability of the overall composite material, thereby achieving excellent electrochemical energy storage performance. Consequently, as a cathode material for zinc-ion hybrid capacitors, CN @MXene achieves a high specific capacity of 240 mA h/g at 0.1 A/g and exhibits outstanding rate performance from 1 to 20 A/g. And the capacitance retention rate remains as high as 94%, after 10,000 cycles of charge-discharge at a current density of 5 A/g. Moreover, based on the CN @MXene electrode, flexible zinc ion micro-capacitor with high area-specific capacity of 264 mF/cm was fabricated using laser cutting technology. We believe that this work provides new research strategies for developing high-performance zinc-ion hybrid capacitors.