Study On Electrochemical Properties And Preparation Of MgCo₂O₄ Electrode Material For Supercapacitor

Supercapacitors,a popular energy storage device,have played an indispensable role in electronic devices,transportation vehicles,and liberation army armored vehicles etc,which brings favorable convenience to people’s life and military field.Supercapacitors are mainly composed of collector,electrode material and electrolyte and so on,of which electrode material is the main factor affecting its performance.Therefore,spinel-type cobalt-based metal oxide MgCo₂O₄is mainly used as the important research electrode material in this paper.The crystal structure,microscopic morphology,and electrochemical properties are simply analyzed.Asymmetric capacitor is assembled with MgCo₂O₄electrode material and activated carbon.This aim is to test the value of the prepared MgCo₂O₄electrode material in practical applications using a two-electrode system.The main results of this paper are classified into 3 aspects as follows:（1）Using a one-step simple hydrothermal method,the lamellar flower-like and urchin-like MgCo₂O₄electrode material are respectively prepared.A lamellar flower-like MgCo₂O₄with a micropore,And 1A/g,its capacitance can be up to 315 F/g.At a high current density,the specific capacitance is maintained at 73.5%.As far as urchin-like MgCo₂O₄electrode material,its micro-morphology is affected by changing the hydrothermal time,and such morphological changes of"accumulation lump→uniform distribution→closed accumulation"are proposed after observed by technical characterization.A standard three-electrode system was used to test the prepared urchin-like MgCo₂O₄electrode materials,the results show that the area specific capacitance of urchin-like MgCo₂O₄electrode with uniform distribution is as high as 6.75 F/cm²at 1m A/cm²,and discharge time is 3030 s.At 20 m A/cm²,the specific capacitance keeps 88.4%after 1000 cycles,showing excellent electrochemical stability.The experimental results have obvious advantages over the area specific capacitance reported by other cobalt mental oxides.（2）In order to further improve specific capacitance performance of MgCo₂O₄material,surfactant sodium dodecyl sulfonate（SDS）is firstly introduced not only to control the growth morphology of MgCo₂O₄material during hydrothermal process,but also to find that when the crystallization strength of MgCo₂O₄material is weaker than that without SDS,the specific capacitance is better.Under the condition,MgCo₂O₄nanowire arrays are successfully synthesized with SDS.both show 1147.5,1021.5 C/g,about 2295,2043 F/g at a current density of 5 A/g,respectively.This result is superior to other cobalt mental composites.At the same time,the addition of SDS to the solution can greatly promote the specific capacitance of MgCo₂O₄,simplifying the composites preparation method used to synthesize high-capacitance electrode material and saving the cost.The asymmetric capacitors are simply assembled with MgCo₂O₄nanowire arrays and activated carbon set as positive and negative electrodes,respectively.The results show that the maximum energy density can reach 25.5 Wh/kg and the maximum power density can be up to 3.5 k W/kg.（3）In continuing to explore innovative research,It is found that high-capacity and high-performance MgCo₂O₄electrode material with nanoneedle arrays and bimorphology of urchins,together with nanosheet arrays can be prepared by one-step facile hydrothermal route.In a three-electrode system,MgCo₂O₄nanoneedle arrays and bimorphological MgCo₂O₄show superior specific capacitance of 729.6,736 C/g at the current density 2,1A/g,respectively.Most notably,After 10000 and 5500 cycles,both specific capacitance is respectively maintained at 98.5%,and 110.12%,showing outstanding electrochemical performance.These experimental results are obviously superior to other reports.In addition,The asymmetric capacitor of bimorphological MgCo₂O₄material possesses a maximum energy density of 29 Wh/kg at power density of 424.45 W/kg.Meanwhile,it has maximum power density of 2057.88 W/kg at energy density of 11.63 Wh/kg.This experimental report proves that MgCo₂O₄material have great application potential,which can be used as reference to promote high-capacity and high-performance research works for supercapacitors.（4）To further enhance the specific capacitance of MgCo₂O₄materials,core-shell structural MgCo₂O₄@Co（OH）₂,and MgCo₂O₄@Ni（OH）₂electrode materials are synthesized based on MgCo₂O₄with the morphology of urchins and nanoneedles,respectively.Both show excellent specific capacitance of 1480.96,1317.7 C/g,about 2962,2635.4 F/g respectively under the condition of 1 A/g.These results suggest that the specific capacitance of MgCo₂O₄electrode material can be effectively enhanced by constructing different component materials to form core-shell structure.Meanwhile the MgCo₂O₄@Co（OH）₂capacitor has a maximum energy density of 34.65 Wh/kg at 815.3 W/kg.The as-obtained results are better than other reported in some literatures,therefore this work has feasible research value and plays a role of promoting the research of MgCo₂O₄electrode materials.