Self-assembly of MOF on MXene nanosheets and in-situ conversion into superior nickel phosphates/MXene battery-type electrode

The low conductivity of nickel phosphate hinders its application as electrode for electrochemical energy storage applications, although its environmental and biological benign, as well as the low cost, are superior advantages compared with other transition metal based electrode materials. Herein, the “bottom-up” self-assembly of Ni-MOF amorphous nanospheres on MXene nanosheets, which provide rich nucleation sites for MOF growth, is achieved, and the MOF nanospheres are subsequently in-situ conversed into hierarchically porous nickel phosphate nanospheres through the “top-down” etching. The porous nickel phosphate nanospheres are therefore anchored on the MXene nanosheets, enabling the fast electron transportation between the nickel phosphate and MXene, addressing the low conductivity issue of nickel phosphate. Meanwhile, the porous nickel phosphate nanospheres prevent the aggregation of MXene nanosheets, and the laminar structure is maintained for fast ionic migration within the electrodes through long charge/discharge cycles. The electrode materials displays high specific capacity of 639C g−1 at 0.5 A g−1 and outstanding cycling stability of 85% capacity retention after 10,000 cycles. Asymmetric supercapacitor fabricated using p-phenylenediamine-functional reduced graphene oxide (PPD-rGO) as cathode exhibits an considerable energy density of 72.6 W h kg−1 at the power density of 932 W kg−1. This design strategy holds great guiding significance for the preparation of high performance electrode materials.