Construction of High-Capacitance 3D CoO@Polypyrrole Nanowire Array Electrode for Aqueous Asymmetric Supercapacitor

TLDR

The design exploits the high electrochemical activity of CoO and PPy, the excellent conductivity of PPy, and the short ion diffusion paths in ordered mesoporous nanowires. A supercapacitor electrode was fabricated by growing well‑aligned CoO nanowire arrays on 3D nickel foam and uniformly anchoring polypyrrole onto each nanowire to enhance pseudocapacitance. The hybrid electrode delivers a specific capacitance of 2223 F g⁻¹, retains 99.8 % after 2000 cycles, and enables an aqueous asymmetric device with 1.8 V, 43.5 Wh kg⁻¹ energy density, 5500 W kg⁻¹ power density, 20 000 cycles, and can power LEDs and a motor within 10 s of charging.

Abstract

We have developed a supercapacitor electrode composed of well-aligned CoO nanowire array grown on 3D nickel foam with polypyrrole (PPy) uniformly immobilized onto or firmly anchored to each nanowire surface to boost the pseudocapacitive performance. The electrode architecture takes advantage of the high electrochemical activity from both the CoO and PPy, the high electronic conductivity of PPy, and the short ion diffusion pathway in ordered mesoporous nanowires. These merits together with the elegant synergy between CoO and PPy lead to a high specific capacitance of 2223 F g(-1) approaching the theoretical value, good rate capability, and cycling stability (99.8% capacitance retention after 2000 cycles). An aqueous asymmetric supercapacitor device with a maximum voltage of 1.8 V fabricated by using our hybrid array as the positive electrode and activated carbon film as the negative electrode has demonstrated high energy density (~43.5 Wh kg(-1)), high power density (~5500 W kg(-1) at 11.8 Wh kg(-1)) and outstanding cycleability (~20,000 times). After charging for only ~10 s, two such 4 cm(2) asymmetric supercapacitors connected in series can efficiently power 5 mm diameter red, yellow, and green round LED indicators (lasting for 1 h for red LED) and drive a mini 130 rotation-motor robustly.