Research On The Preparation And Performance Of Transition Metal (Fe,Mo,Cu) Oxides/Sulfides

As the key part of Li/Na-ion batteries(LIB/SIB),the electrode material determines to electrochemical performance.But the theoretical specific capacity of commercial graphite is low,and Na storage capacity is limited.It is necessary to develop new and high-performance anode system.Transition-Metal oxides(TMO)and transition-metal sulfide(TMS)have high Li/Na-ion storage capacity and considerable cycle performance,which has attracted great interest from researchers and is expected to replace graphite materials in the field of Li/Na-ion batteries.Therefore,this study selects three transition metal(Fe,Mo,Cu)as representatives to prepare TMO and TMS.Moreover,regarding the problems of volume expansion and poor electronic conductivity,this study has accomplished the following research:The iron alkoxide with flower-like morphology was prepared by solvothermal method,and it was explored whether the different concentration of Fe³⁺in the solution would affect the structure and morphology of iron alkoxide.The results show that the iron alkoxide synthesized with 0.02 mol L^-1 of Fe³⁺in the solution has a complete flower-like morphology.The Fe₂O₃ prepared by solid-phase sintering of iron alkoxide at this concentration,keep the best energy storage performance of.SIB.At a current density of 0.2 C,This Fe₂O₃ anode retained the retention rate of 86%after 100cycles.Moreover,Fe S₂ obtained by the iron alkoxide keep a cycle and rate performance.After 100cycles,Fe S₂ anode can deliver a high reversible capacity of 351.6 m Ah g^-1.MoO₃ prepared at 450? with a shape of micron stacked block,could improve the cycle stability and rate performance of the electrode.For the simple reason that the shape of micron stacked block could provide the insertion of sodium ions with more active sites,and its higher aspect ratio reduces ion diffusion distance.At a current density of 0.2 C,the MoO₃ anode retained 86%of its capacity after 100 cycles.Furthermore,MoS₂@r GO composite material(MG)was prepared by hydrothermal,and the effects of heat treatment of the materials on the sodium storage performance were studied.The results show that the MoS₂@r GO materials of heat treatment(t-MG)had excellent cycle performance and rate performance.After 200 cycles,t-MG anode maintained the capacity of246.3 m Ah g^-1.Besides,the cycle performance t-MG anode at high current density was also eminent.There is basically no loss of capacity a current density of 1 C and 2 C after 200 cycles.In addition,this paper discovered a low-cost and ecofriendly method for producing copper oxide(CuO)as anodes with a high capacity and long cycling stability for Li/Na-ion batteries.In our strategy,carbon nanospheres are used as templates to prepare precursor Cu(OH)₂@C.Then,the Cu(OH)₂@C was converted into CuO.The structure and morphology of the as-synthesized materials is characterized by the X-ray diffraction,scanning electron microscopy and transmission electron microscopy.The anode electrochemical performance of the samples was investigated by galvanostatic cycling(vs.Li/Li⁺,Na/Na⁺)at different current rate.Compared to Na-ion batteries,the CuO applied to Li-ion batteries showed better charge/discharge cycle stability and rate performance.Its capacity retention is as high as 128%at a current density of 0.5 C after 200 cycles.