Design of mesoporous Ni-Co hydroxides nanosheets stabilized by BO2- for pseudocapacitors with superior performance.

The investigation of high-efficiency electrodes is essential for the energy conversion/storage devices. In this work, mesoporous two-dimensional Ni-Co hydroxide nanosheets stabilized by BO2- (denoted as (NixCoy)(OH)2/Co(BO2)2) are prepared via a facile and cost-effective procedure to circumvent the shortage of nickel hydroxide, viz. poor conductivity and fast phase transition. The (NixCoy)(OH)2/Co(BO2)2 materials have high specific surface area and plenty of exposed active sites. As electrode, the optimized (Ni0.5Co0.5)(OH)2/Co(BO2)2 delivers a remarkable specific capacity of 2257 F g-1 at 1 A g-1 with superior rate capability (2071 F g-1 at 20 A g-1). Moreover, the asymmetric supercapacitors assembled by (Ni0.5Co0.5)(OH)2/Co(BO2)2 and active carbon provides high energy density (56.5 Wh kg-1 at 0.8 kW kg-1) and excellent cyclic stability (maintaining 98% of initial capacity over 10 000 cycles), demonstrating the promising potential of (Ni0.5Co0.5)(OH)2/Co(BO2)2 in practical applications.