Controllable synthesis of Co/Ni basic carbonate composite via regulating Co/Ni ratio with super rate performance for asymmetric solid-state supercapacitor

Abstract

Under the high current density, high cyclability and good rate performance are two major challenges for the applications of supercapacitor. How to control the composition and structure of the electrode materials is the key factor to solve these two problems. In this work, the controllable morphology Co/Ni Basic Carbonate Composites (CNBCC) were synthesized by one-step hydrothermal regulating the ratio of Co to Ni. Impressively, benefiting to its special sea urchin structure, the composite with the 1:1 ratio of Co to Ni exhibited remarkable electrochemical performance with specific capacitance (at 1 A g−1, 1682 F g−1), superior rate capability (at 1–30 A g−1, 79.3%) and cycling stability (2000 cycles, 96%). Further, a solid-state asymmetric supercapacitor Co1Ni1//AC (ASC) was constructed with a high voltage window (1.7 V). The ASC displayed a high energy density of 42.5 Wh kg−1 at power density 849.7 W kg−1, while still remained at 20.6 Wh kg−1 at a power density of 25511 W kg−1. In addition, the ASC had good flexibility, and their CV curves hardly changed after being bent into different angles; the two ASC in series could light a yellow LED for 25 min.