Manganese phosphoxide/Ni5P4 hybrids as an anode material for high energy density and rate potassium-ion storage

Abstract

Potassium-ion batteries (PIBs) that serve as low-cost and large-scale secondary batteries are regarded as promising alternatives and a supplement to lithium-ion batteries. Hybrid active materials feature the synergistic merits of individual components to overcome the sluggish kinetics of K⁺ insertion and structural deterioration of electrodes for PIBs. We report herein that a highly stable hybrid anode active material, an amorphous MnO_xP_y (a-MnO_xP_y) overlayer coating on a Ni₅P₄ film, is grown on carbon fabric cloth (CF) through a phosphidation reaction to obtain the integrated a-MnO_xP_y/Ni₅P₄/CF anode by simple phosphidation treatment. The optimized a-MnO_xP_y/Ni₅P₄/CFP anode delivers a high reversible specific depotassiation capacity of 398.8 mA h g⁻¹ at 0.3 A g⁻¹ after 100 cycles and acquires an excellent rate capability together with high cycling stability with capacities of 225.1 and 175.3 mA h g⁻¹ at 5 and 10 A g⁻¹ after 5000 cycles, respectively. The amorphous a-MnO_xP_y-45 overlayer and the porous features of the a-MnO_xP_y-45/Ni₅P₄ provide sufficient stress buffer and thus greatly accommodate large volume changes during potassiation/depotassiation. The hybrid interface between a-MnO_xP_y and Ni₅P₄ and favorable conductivity of the formed phosphides promote the charge transport and K⁺ storage kinetics. Also, the a-MnO_xP_y/Ni₅P₄/CF//K₄Fe(CN)₆ PIB full cell exhibits an initial discharge capacity of 343.9 mA h g⁻¹ at 0.2 A g⁻¹ and maintains 331.9 mA h g⁻¹ after 100 cycles.