Integrated Battery–Capacitor Electrodes: Pyridinic N-Doped Porous Carbon-Coated Abundant Oxygen Vacancy Mn–Ni-Layered Double Oxide for Hybrid Supercapacitors
Subin Jiang, Yi Qiao, Ting Fu, Weimin Peng, Tengfei Yu, Baojuan Yang, Rui Xia, Meizhen Gao
Abstract
Integrating the battery behavior and supercapacitor behavior in a single electrode to obtain better electrochemical performance has been widely researched. However, there is still a lack of research studies on an integrated battery–capacitor supercapacitor electrode (BatCap electrode). In this work, an integrated BatCap electrode porous carbon-coated Mn–Ni-layered double oxide (Mn–Ni LDO-C) was fabricated successfully using controllable heat treatment of polypyrrole-precoated Mn–Ni-layered double hydroxide (Mn–Ni LDH@PPy). This Mn–Ni LDO-C electrode was grown on Ni foam directly and possessed a hierarchical structure that consisted of a pyridinic N (N-6)-doped porous carbon shell and a Mn–Ni LDO core within abundant oxygen vacancies. Benefiting from the synergistic effect of N-6-doped porous carbon and increased oxygen vacancies, Mn–Ni LDO-C exhibited excellent electrochemical performance. The capacity of Mn–Ni LDO-C reached 2.36 C cm–2 (1478.1 C g–1) at 1 mA cm–2 and remained at 92.1% of the initial capacity after 5000 cycles at a current density of 20 mA cm–2. The aqueous battery–supercapacitor hybrid device Mn–Ni LDO-C//active carbon (Mn–Ni LDO-C//AC) also presented superior cycle stability: it retained 85.3% of the original capacity after 5000 cycles at 2 A g–1. Meanwhile, Mn–Ni LDO-C//AC could work normally under a wider potential window (2.0 V), so that the device held the highest energy density of 78.2 Wh kg–1 at a power density of 499.7 W kg–1 and retained 39.1 Wh kg–1 at the highest power density of 31.3 kW kg–1. Two Mn–Ni LDO-C//AC devices connected in series could light a light-emitting diode (LED) bulb easily and keep the LED brightly illuminated for more than 10 min. In general, this work synthesized an integrated BatCap electrode Mn–Ni LDO-C; the integrated electrode exhibited high electrochemical performance, thus has a promising application prospect in the field of energy storage.