3D nano-micro structured NiCoP/CC as high-performance cathode for hybrid supercapacitor

Abstract

Transition-metal phosphides are desirable candidates for supercapacitors. Herein, bimetallic phosphides NiCoP/CC is obtained with 3D nano-micro structure. This unique as well as the altered electronic structure effectively improved the energy density of NiCoP/CC//AC hybrid supercapacitors (HSCs). As compared to Ni2P/CC, NiCoP/CC shows a metallic conductivity and has more electrons close to the Fermi level, increasing the intrinsic reactivity effectively. Moreover, the 3D nano-micro structure with a 20 nm staggered nanosheet provides a multidirectional pathway for charge transfer. Thus, NiCoP/CC cathode holds the capacity of 3.42 C cm−2 at 4 mA cm−2, which is much higher than that of Ni2P/CC. As a result, the HSC device delivers a greater energy density of 31.8 Wh kg−1 than that of most reported devices. More importantly, the device works well over a wide temperature range. It can still maintain 100% of its initial capacity after 450 cycles under variable temperatures from 5 ℃ to 50 ℃. In summary, this work starts with structural engineering and then analyzes the performance of HSC under variable temperature environments, offering a universal approach for the rational development of high-performance electrode materials in the field of supercapacitors.