Research On High Performance Nickel-based Electrode Material For Supercapacitor

Nickel-based compounds like nickel oxide and nickel hydroxide are used to fabricate electrode materials for supercapacitors instead of traditional precious metals(Ru O2, Ir O2.etc) owing to their high theoretical specific capacitance, long cycle life, low cost and environmentally benign nature. Anodization, a new type of preparation method, is proved facile and simple to fabricate nickel-based electrode meterials with great performance. Our group fabricated porous Ni(OH)2–Ni F2 composite(PNC) film by anodization previously, demonstrating a high specific capacitance but a low cycle life and slow rate of charge and discharge. In this report, there are two main research objectives as follows:(1) Improving the cycle life of PNC on premise of high specific capacitance;(2) Improving the charge and discharge rate of PNC.Here, morphology, construction and composition changing of anodic film during charge and discharge are studied. The poor adhesion strength between Ni(OH)2 which transformed from Ni F2 and the grains growing are two main reasons resulting in low cycle life of PNC. Poor conductivity of Nickel-based compound is the main reason of slow charge and discharge rate.A series of annealing treatments are carried out to eliminate the bad influence caused by Ni F2. Only when the temperature is not lower than 400℃, Ni F2 can transformed to Ni O completely. The specific capacitance of anodic film has no decay after 2000 cycles of CV tests(at 100 m V/s) after annealed under 400℃ for 1h, yet it’s lower than PNC. When PNC film is annealed under 600℃ for 4min(NNO), Capacitance of NNO is comparable to PNC and has no decay after 2000 times of galvanostatic charge-discharge tests at current density of 33.33A/g.Even though NNO is alrealy with a high specific capacitance and long cycle life, poor conductivity is a key obstacle for rapid charge and discharge rate of nickel-based electrode material. Hence, solvothermal treatment was used for Co-doping to improve conductivity of NNO and nano-sponge Ni-Co compound(NNO/Co) was fabricated consequently. NNO/Co showed a high specific capacitance of 1411.9F/g at 100 m V/s. There was no capacitance decay after 2000 cycles of CV tests, indicating a long cyce life and good capacitance stability. However, the rate capability was improved only at the beginning of the cyclability test. The detailed mechanism and the approach to further enhancement are yet to be investigated.