Construction of multi-channel basic cobalt/nickel phosphate core-shell microsphere for superior hybrid Zn-based supercapacitor performances

Abstract

Although unparalleled power density and life-span are achieved by supercapacitor devices, the related lower energy density and linear decreased output voltage still limit their applications in commercial energy storage equipment. In this work, a high performance multi-channel basic cobalt/nickel phosphate core–shell microsphere (BCNP) is firstly constructed and further fabricated with rGO-Zn negative electrode to form a hybrid BCNP//rGO-Zn supercapacitor device, which delivers an outstanding energy density of 376.5 Wh kg−1 at 1.66 kW kg−1 and a stable cell output voltage at 1.5–1.8 V. The excellent energy storage performance may attribute to the following two reasons: Firstly, the in-situ ions exchanging process between large-sized BTC3− anions and small-sized inorganic anions (OH− and PO43−) can not only make BCNP inherits the high surface area of MOF parents but also produces rich “tree-vein-like” mesoporous multi-channels, which dramatically increased the capacity, ratio and life-span of BCNP core–shell microsphere. Secondly, the introduced rGO-Zn negative electrode dramatically increased the output voltage of BCNP//rGO-Zn for boosted energy density. The as-fabricated BCNP//rGO-Zn device with the loading of 4 mg active BCNP can power a 1.5 V thermometer surpass 3 h by charging about one minute, revealing its outstanding application prospect.