Binder-free C@NiCo₂O₄ on Ni foam with ultra-stable pseudocapacitive lithium ion storage

Carbon-coated nickel cobaltate on nickel foam (C@NCO@NF) with stable pseudocapacitive lithium storage capacity was prepared via a two-step strategy. NiCo hydroxide was initially grown on Ni foam via electrodeposition. Subsequent glucose soaking and annealing converted the intermediate into C@NCO@NF. Carbon coating could significantly improve the cycling stability and rate performance of the binder-free anode. The C@NCO@NF electrode could stably deliver a reversible capacity of 513 mAh · g^-1 after 500 cycles at a current density of 500 mA · g^-1. It could even stably cycle at a high current density of 5000 mA · g^-1 for 3000 cycles, with a reversible capacity of 115 mAh · g^-1. Kinetic analysis revealed that surface-controlled pseudocapacitance plays a dominant role in the lithium ion storage. Improved electrochemical performance is attributed to the synergetic effect of pseudocapacitance and carbon coating.