Interface-Engineered Nickel Cobaltite Nanowires through NiO Atomic Layer Deposition and Nitrogen Plasma for High-Energy, Long-Cycle-Life Foldable All-Solid-State Supercapacitors

Abstract

The large-scale application of supercapacitors (SCs) for portable electronics is restricted by low energy density and cycling stability. To alleviate the limitations, a unique interface engineering strategy is suggested through atomic layer deposition (ALD) and nitrogen plasma. First, commercial carbon cloth (CC) is treated with nitrogen plasma and later inorganic NiCo₂ O₄ (NCO)/NiO core-shell nanowire arrays are deposited on nitrogen plasma-treated CC (NCC) to fabricate the ultrahigh stable SC. An ultrathin layer of NiO deposited on the NCO nanowire arrays via conformal ALD plays a vital role in stabilizing the NCO nanowires for thousands of electrochemical cycles. The optimized NCC/NCO/NiO core-shell electrode exhibits a high specific capacitance of 2439 F g^-1 with a remarkable cycling stability (94.2% over 20 000 cycles). Benefiting from these integrated merits, the foldable solid-state SCs are fabricated with excellent NCC/NCO/NiO core-shell nanowire array electrodes. The fabricated SC device delivers a high energy density of 72.32 Wh kg^-1 at a specific capacitance of 578 F g^-1 , with ultrasmall capacitance decline rate of 0.0003% per cycle over 10 000 charge-discharge cycles. Overall, this strategy offers a new avenue for developing a new-generation high-energy, ultrahigh stable supercapacitor for real-life applications.

Keywords: atomic layer deposition; electrochemical stability; energy density; nitrogen doping; plasma; pseudocapacitors.