Sea urchin-like CoNi2S4materials derived from nickel hexamyanocobaltate for high-performance asymmetric hybrid supercapacitor.

In this work, a mild chemical precipitation method and simple hydrothermal treatment of the nickel hexamyanocobaltate precursor strategy are developed to prepare a sea urchin-like CoNi2S4compound with remarkable specific capacity and excellent cycling stability. The prepared CoNi2S4has an outstanding specific capacity of 149.1 mA h g-1at 1 A g-1and an initial capacity of 83.1% after 3000 cycles at 10 A g-1. Moreover, the porous carbon nanospheres (PCNs) with exhibit cycling stability (94.7% of initial specific capacity after 10 000 cycles at 10 A g-1) are selected as negative electrode to match CoNi2S4positive electrode for assembly of CoNi2S4//PCNs asymmetric supercapacitor (ASC). Satisfactorily, the as-assembled CoNi2S4//PCNs ASC exhibits an impressive energy density of 41.6 Wh kg-1at 797 W kg-1, as well as the suitable capacity retention of 82.8% after 10 000 cycles. The superior properties of the device demonstrated that the as-prepared material is potential energy storage material.

Core-shell shaped Ni2CoHCF@PPy microspheres from prussian blue analogues for high performance asymmetric supercapacitors.

Recently, prussian blue analogues (PBAs), as the most classical class of metal-organic frameworks, have been widely studied by scientists. Nevertheless, the inferior conductivity of PBAs restricts the application in supercapacitors. In this work, nickel cobalt hexacyanoferrate (Ni2CoHCF) had been produced via a simple co-precipitation approach and coated with polypyrrole on its surface. The conductivity of PBAs was improved by the polypyrrole coating. The Ni2CoHCF@PPy-400 microspheres were demonstrated to the outstanding specific capacity of 82 mAh g-1at 1 A g-1. After 3000 cycles, the Ni2CoHCF@PPy-400 microspheres had a long cycle life and 86% specific capacity retention rate at 5 A g-1. Additionally, it was coupled with activated carbon to build high performance asymmetric supercapacitor (Ni2CoHCF@PPy-400//AC), which displayed a high energy density of 21.7 Wh kg-1at the power density of 888 W kg-1and good cycle stability after 5000 cycles (a capacity retention rate of 85.2%). What is more, the results reveal that the Ni2CoHCF@PPy-400 microspheresare a prospective candidate for exceptional energy storage devices.