Synthesis Of Ni_xCo_1-xC₂O₄ Solid Solution Electrode Material By Microemulsion And Energy Storage Properties

Oxalate is cheap and readily available.As a positive electrode material for supercapacitors,nickel-cobalt oxalate has lower cost than other nickel-cobalt bimetal materials.In this work,Ni_0.55Co_0.45C₂O₄ solid solution was successfully synthesized by a Microemulsion co-precipitation reaction.The electrochemical measurements show that Ni_0.55Co_0.45C₂O₄ achieves a higher specific capacity of 1124 F/g at a current density of 1A/g than its counterpart NiC₂O₄/Co C₂O₄ hybrids.Ni_0.55Co_0.45C₂O₄ electrodes retains 87.4%of the initial capacity after 4000 cycles.The assembled Ni_0.55Co_0.45C₂O₄//AC hybrid supercapacitor attains an energy density of 38.5 Wh/kg at a power density of 799 W/kg and capacitence retention rate reached 80%after 10,000 cycles.In order to study the effect of reaction temperature on the synthesis of nickel-cobalt under the assistance of diethyl oxalate?DEO?,nickel-cobalt under different reaction conditions was obtained by turning the reaction in the presence of the oxalic acid solution with the concentration of 0.1 mol/L.In this paper,the electrochemical properties of the materials obtained at 65°C,75°C and 85°C are studied.The results show that the obtained Ni-Co-75 sample shows excellent electrochemical as the increase of reaction temperature to 75°C with the oxalate concentration of 0.1 mol/L,exhibiting a large specific capacitance of 1386.7 F/g at 1 A/g,as the rate is maintained at 89.8%,and 85.1%of the initial capacity is maintained after 2000 cycles.After determining the optimal reaction temperature,this paper explores the effect of oxalic acid concentration on the nickel-cobalt oxalate assisted by different oxalate Ester.First,at the reaction temperature of 75°C,the nickel-cobalt oxalate is synthesized under the various condition including 0 mol/L,0.1 mol/L,0.2 mol/L and saturated oxalic acid in the presence of diethyl oxalate?denoted as DEO-0.1,DEO-0.2 and DEO-BH?.Through the morphological characterization,it was found that the four materials all have a layered structure.After electrochemical analysis,the electrochemical performance of electrodes is increased in sequenc of:DEO-0.1>DEO-H>DEO-0.2>DEO-BH.Moreover,the specific capacity of DEO-0.1 can reach 1386.7 F/g at a current density of 1 A/g,as the rate is maintained at 89.8%,and 85.1%of the initial capacity is maintained after 2000 cycles.Futhermore,we use dimethyl oxalate?DMO?and dibutyl oxalate?DBO?to realize the synthesis of materials,and in addition to explore the effect of different oxalic acid concentrations on the synthesized samples.By using dimethyl oxalate?DMO?to participate in the synthesis reaction,the DMO-H sample obtained has the best electrochemical performance in the absent of oxalic acid.At a current density of 1 A/g,the specific capacity can reach 1512.5 F/g.The DMO-H//AC hybrid supercapacitor is assembled using DMO-H as positive electrode material and activated carbon as a negative electrode material,showing high power density and high energy density.When the power density is 800 W/kg,the bybrid supercapcitor can provide a maximum energy density of50.66 Wh/kg.Moreover,as the increase of the current density to 8000 W/kg,the power density can still reach 29.9 Wh/kg.After 12,000 cycles,the capacity retention is still70.8%.Dibutyl oxalate?DBO?was used to participate in the synthesis reaction.When the oxalic acid concentration was 0.1 mol/L,the DBO-BH with excellence electrochemical performance,showing a specific capacitance of 1828 F/g?at a current density of 1 A/g?.