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 1096.2 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.