The development of cathode materials with excellent electrochemical properties is crucial for the application of hybrid supercapacitors. NiC2O4?2H2O cathode material was synthesized by a precipitation method, and its microstructure, morphology and electrochemical performance were investigated. The results show that NiC2O4?2H2O exhibits a unique polyhedral particle structure, the particle sizes are 0.5?2.0 μm, and each particle is composed of polycrystals, thus achieving a high specific capacity of 1 096.2 F/g at a current density of 1 A/g. The assembled nickel oxalate//activated carbon hybrid supercapacitor still maintains an energy density of 10.2 Wh/kg at a high power density of 3.7 kW/kg. Connecting two hybrid devices in series can light up green and yellow LEDs. This demonstrates that NiC2O4?2H2O has potential application prospects in electrochemical energy storage as a novel, low-cost and environmentally friendly cathode material.