β-Ni(OH)(2) was constructed into a three-dimensional mesoporous film on Ni foam with ultra-thin (∼6 nm) primary nanowalls showing ultrahigh specific capacitance (2675 F g(-1)) and excellent cycling performance (>96% for 500 cycles). The capacitance was higher than theoretical value possibly due to the combination of Faradic and electrical double-layer capacitances.
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