Synthesis And Electrochemical Performance Of Binary And Ternary Metal Oxides

In this paper,binary and ternary metal oxides a-MnO2,?-MnO2 as cathode material,CuO,SnO2 and NiCo2O4 as anode materials for lithium ion batteries(LIBs)were investigated.CuO,SnO2 were carbon coated and ?-MnO2 was Cu-doped.The synthesis methods,crystal structure and morphology of the obtained samples were discussed.The main results are listed as follows:(1)a-MnO2 was synthesized by a solution phase method using MnSO4,(NH4)2S2O8 as raw materials,AgNO3 as catalyst.Reaction temperature and reaction time play important roles in controlling the crystal phases.To explore the effect of higher temperature,greaterpressure on crystal structure,morphology and electrochemical performance,?-MnO2 and Cu-doped MnO2 were synthesized by hydrothermal method using the same raw materials.The samples were characterized by X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.The results show that the obtained a-MnO2 samples present microspheres with the diameter of 1-2?m composed of nanowires with the size of 15-25 nm.The obtained P-MnO2 and Cu-doped MnO2 samples are nanorods with the size of 60-80 nm.The electrochemical performance of the samples was characterized by constant current charge/discharge tests,cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The results show that a-MnO2 prepared at 25? for 2 days has the best electrochemical performance,capacity of which is 124 mAh/g at a constant current density of 50 mA/g in the range of 1.5?4.2 V at 100th cycle.The electrochemical performance of the Cu-doped ?-MnO2 is better than that of the undoped ?-MnO2.The reversible specific capacity of the Cu-doped ?-MnO2 prepared at 1200C is 146 mAh/g at a constant current density of 50 mA/g in the range of 1.5?4.2 V at 100th cycle.Meanwhile,the formation mechanism and electrochemical process of a-MnO2 and ?-MnO2 has been conducted the exploration.(2)CuO,SnO2 were synthesized through a facile reflux method using KOH,(NH4)2S2O8,nano Cu(Sn)powders as raw materials,and the products were coated carbon by glucose.The samples were characterized by X-ray diffiraction,scanning electron microscopy,and transmission electron microscopy.The results show that the obtained CuO is flower-like structure composed of nanosheets with the size of 10-20 nm.The obtained SnO2 is ring-like structure with the size of 150-200 nm.The morphology of carbon-coated CuO(SnO2)is similar with the pure samples and carbon membrane is with the particles.The electrochemical performance of the samples was characterized by constant current charge/discharge tests,cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The results show that the reversible capacity of carbon-coated samples has an average of 200 mAh/g higher than pure samples.The capacity of CuO,CuO/C,SnO and SnO2/C are 378,615,83 and 268 mAh/g at a constant current density of 100 mA/g in the range of 0.01?3.0 V at 100th cycle.Meanwhile,the formation mechanism and electrochemical process of the product has been conducted the exploration.(3)The precursor of NiCo2O4 was synthesized by ball-milling solvothermal method using NiSO4·6H2O,CoSO4·7H2O and NH4HCO3 as raw materials,ethylene glycol as solvent.NiCo2O4 was obtained after annealing the precursor.The samples were characterized by X-ray diffraction,scanning electron microscopy,and transmission electron microscopy.The results show that spinel NiCo2O4 was synthesized successfully.The morphologies of samples synthesized by ball-milling solvothermal method are different.The sample prepared at 180?with 30 mL EG shows the microspheres composed of the nanoparticles with the size of 15-20 nm.The electrochemical performance of the samples was characterized by constant current charge/discharge tests,cyclic voltammetry(CV)and electrochemical impedance spectroscopy(EIS).The results show that the capacity of the sample prepared at 180? with 30 mL EG is 522 mAh/g at a constant current density of 100 mA/g in the range of 0.01?3.0 V at 100th cycle.Meanwhile,the formation mechanism and electrochemical process of NiCo2O4 has been conducted the exploration.