Spherical spinel NiMn2O4 in-situ grown on MWCNT via solvothermal synthesis for supercapacitors

The spherical spinel NiMn2O4 was successfully in-situ grown on MWCNT by solvothermal (ST) method. Mean-while, NiMn2O4/MWCNT-1.0 was also prepared by sol-gel (SG) method for comparison. The effect of preparation methods and the content of MWCNT-x (x = 0, 0.5, 1.0, 1.5) on the specific capacitance of NiMn2O4/MWCNT was investigated by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD). The results showed that when the addition amount of MWCNT was 1.0 g, the NiMn2O4/MWCNT-1.0 composite prepared by ST method has the most obvious increase in specific capacitance (733.8 F g(-1)) with an energy density of 65.2 Wh kg(-1) and a power density of 400.0 W kg(-1). The diffusion coefficient of OH- ions in NiMn(2)O(4 )are greatly improved after the growth of NiMn2O4 (8.123 x 10-15 m2 s(-1)) onto MWCNT, and that in NiMn2O4/MWCNT-1.0 prepared by SG and ST method are 24.74 x 10(-15) m(2) s(-1) and 7910 x 10-15 m2 s(-1), respectively, which proves that the combination of NiMn(2)O(4 )and MWCNT can improve the ability to conduct OH- ions, and the diffusion coefficient of OH- ions in NiMn2O4/MWCNT-1.0 prepared by ST method is about 320 times that of SG method. Furthermore, the capacitance retention rate is about 64 % after 5000 cycles. Therefore, as far as electrode materials are concerned, the combination of spinel and MWCNT as an ion channel to improve the properties of materials has high research significance and application prospects.

Automated summary

In this study, spherical spinel NiMn2O4 was in-situ grown on MWCNT using solvothermal method, and NiMn2O4/MWCNT-1.0 was prepared by sol-gel method for comparison. The effect of preparation methods and MWCNT content on the specific capacitance of the composite was investigated. The results showed that NiMn2O4/MWCNT-1.0 composite prepared by solvothermal method with an addition of 1.0 g MWCNT exhibited the highest specific capacitance, energy density, and power density. The combination of NiMn2O4 and MWCNT significantly improved the diffusion coefficient of OH- ions, and the diffusion coefficient of NiMn2O4/MWCNT-1.0 prepared by solvothermal method was about 320 times that of sol-gel method. The capacitance retention rate after 5000 cycles was approximately 64%.