Effect Of Sr Doping And Ag Composite On Electrochemical Properties Of La₂CoMnO₆ Electrode Materials

Supercapacitors with high energy density and high power density are a top priority of new green power supply.The electrode materials are the key factor to determine the electrochemical properties of supercapacitors.Perovskite oxide material is one of the ideal candidates as the electrode material for supercapacitors due to its stable structure,low price and excellent electrochemical performance.However,the serious cations leakage during the process of electrochemical measurement restricts the practical application of perovskite oxide materials.As an important branch of perovskite oxides,double perovskite La₂Co Mn O₆oxide can promote B site cations ordering and effectively solve the problem of structural instability caused by cations leaching effect.Appropriate A-site elements doping for double perovskite oxides can increase the oxygen vacancy concentration and oxygen ion diffusion rate,which results in the improving of the thermodynamic stability and electrochemical performance.In this paper,we successfully prepared A-site Sr doping La_2-2xSr_2xCo Mn O₆and Ag@La_1.2Sr_0.8Co Mn O₆compound.The electrochemical performance of these electrode materials were studied in detail.In addition,we assembled the La_1.2Sr_0.8Co Mn O₆as negative electrode material with the optimal Sr doping ratio and the Ni Co₂O₄as positive electrode material into aqueous asymmetric supercapacitor.The device with high energy density,high power density and excellent cycle stability are obtained.The main research contents of this paper are as follows:Firstly,a series of La_2-2xSr_2xCo Mn O₆（x=0,0.2,0.4,0.6 and 0.8）electrode materials with different Sr doping ratio were synthesized by sol-gel method.Meanwhile,the structure,morphology and electrochemical properties of different samples were investigated.The test results show that,doping ratio with x=0.4,that is,the sample of La_1.2Sr_0.8Co Mn O₆electrode material owned the largest specific surface area（23.37 m²/g）and the best electrochemical performance.Moreover,at a current density of 1 A/g,the specific capacitance of La_1.2Sr_0.8Co Mn O₆sample reaches 507 F/g,which is 1.9 times that of undoped La₂Co Mn O₆electrode material.In addition,the La_1.2Sr_0.8Co Mn O₆as negative electrode material and the Ni Co₂O₄as positive electrode material were assembled into aqueous asymmetric supercapacitor.At 1500Wk/g power density,the device’s energy density reaches 55.3 Wh/kg and the capacitance retention rate is about 88.5%after 10000 cycles.Therefore,the combination of high energy density and good cycle stability makes the electrode material a potential application to energy storage device.In order to further enhance the electrochemical performance of the electrode materials,we loaded the Ag nanoparticles on the La_1.2Sr_0.8Co Mn O₆and obtain Ag@La_1.2Sr_0.8Co Mn O₆composite electrode material.X-ray diffraction and scanning electron microscopy tests proved that we have successfully decorated Ag nanoparticles in the electrode material surface of La_1.2Sr_0.8Co Mn O_6.Meanwhile,electrochemical tests results indicate that the composited Ag nanoparticles can effectively accelerate the charges transfer,shorten the ion and electron transportation path,and then promote the electrochemical kinetic process of the system.At a current density of 1 A/g,the specific capacitance of Ag@La_1.2Sr_0.8Co Mn O₆composite reaches609 F/g,which is approximately increased 20%than the La_1.2Sr_0.8Co Mn O₆electrode material.Therefore,the new type electrode materials with better electrochemical properties can be obtained by decorating Ag nanoparticles.Therefore,the experimental results provide a theoretical and experimental basis for the development of high-performance electrochemical energy storage devices.