The Ni(OH)2 with ultra-long cycling life of ≥200,000 cycles and excellent high-rate performance by a porous carbon-confined strategy

Ni(OH) 2 is a typical battery-type material with high theoretical specific capacity. Its two inherent disadvantages, namely slow electrochemical dynamics and extremely poor cycling life, have become stumbling blocks for its application in supercapacitors (SCs). The hitherto slow advancement in the electrochemical performance of Ni(OH) 2 implies a misunderstanding of its electrochemical mechanism and inappropriate building strategies of the structure. In this work, we build a structure of porous carbon-confined α-Ni(OH) 2 using Mg-MOF-74 as a sacrificial template. The carbon matrix acts as the conductive network and the porous substrate for self-healing the damaged structure caused by the dissolution-precipitation of α-Ni(OH) 2 and suppressing the dissolution-recrystallization behavior of β-Ni(OH) 2 transformed from α-Ni(OH) 2 . Due to the thin sheet morphology and the retention of this morphology throughout cycling, the porous carbon-confined Ni(OH) 2 demonstrates excellent high-rate performance, and an ultra-long cycling life comparable to the carbon materials of electrical double layer capacitors (EDLCs). The assembled SCs also exhibit a high power density of 10.8 kW kg −1 and an energy density of 40.9 Wh kg −1 . The positive result in this work may offer a promising strategy for obtaining SCs with both high energy and power densities.