Strong synergetic electrochemistry between transition metals of α phase Ni−Co−Mn hydroxide contributed superior performance for hybrid supercapacitors

Electroactive materials with high electrochemical activity, good rate capability and excellent cycling stability are urgently needed for hybrid supercapacitors, but achieving those performances at the same time is still a big challenge. Here, α phase nickel−cobalt−manganese hydroxide (NiCoMn−OH) with a flower-like structure is synthesized and used as the battery materials for hybrid supercapacitor. The NiCoMn−OH exhibits strong synergetic electrochemistry between the transition metals, which contributes better charge storage performances. The NiCoMn−OH shows a specific capacity of 757 C g−1 at 1 A g−1 and retains 369 C g−1 at very high specific current of 50 A g−1, which are both much higher than the corresponding bimetal and nomometal hydroxides. Therefore, both high electrochemical activity and rate capability have been achieved. The α phase NiCoMn−OH also exhibits a long-term cycling stability because the specific role of Co, maintaining 100% of the specific capacity after 1200 cycles. The hybrid supercapacitor based on NiCoMn−OH also shows high specific capacity of 219 C g−1 at 1 A g−1, high rate performance of 53% capacity retention when the specific current increases 25 times and ultralong cycling stability of 83% capacity retention after 12,000 cycles.