Halogen chlorine triggered oxygen vacancy-rich Ni(OH)2 with enhanced reaction kinetics for pseudocapacitive energy storage

Two-dimensional (2D) Ni(OH)2 nanosheets can theoretically expose their active sites of 100%. Whereas, their intrinsic easy accumulation and low conductivity lead to weak and unsustainable reaction kinetics. Herein, we propose a novel halogen chlorine-triggered electrochemical etching strategy to controllably manage the reaction kinetics of 2D Ni(OH)2 nanosheets (EE/Cl-Ni(OH)2). It is found that halogen chlorine doping can adjust the interlamellar spacing flexibly and promote the lattice oxygen activation to achieve controlled construction of superficial oxygen defects at the adjustable voltage. The optimal EE/Cl-Ni(OH)2 electrode exhibits a high rate capability and excellent specific capacity of 206.9 mA h g−1 at 1 A g−1 in a three-electrode system, which is more than twice as high as the pristine Ni(OH)2. Furthermore, EE/Cl-Ni(OH)2 cathode and FeOOH@rGO anode are employed for developing an aqueous Ni-Fe battery with an excellent energy density of 83 W h kg−1, a high power density of 17051 W kg−1, and robust durability over 20,000 cycles. This strategy exploits a fresh channel for the ingenious fabrication of high-efficiency and stable nickel-based deficiency materials for energy storage.