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

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 NiCo₂O₄ (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.