Structurally Stable Ni(OH)2 Composite with Super Long‐term Cycling Life for Aqueous High‐performance Supercapacitor

Abstract We synthesized an electrochemical structurally stable composite electrode, containing Ni‐doped Co(CO 3 ) 0.5 OH ⋅ 0.11H 2 O nanoneedles and nanoflake‐/nanofrustum‐like Ni(OH) 2 with highly hydrophilic group, leading to enhanced rare performance. The electrode exhibits an outstanding ultra‐long cycle life of more than 140,000 cycles. Specially, the assembled aqueous hybrid supercapacitor presents more than 80 % capacity retention even after 170,000 cycles and high energy density of 44.5 Wh kg −1 . This work highlights a feasible strategy to design and develop high‐efficiency electrodes via engineering on composition and nanostructure.