| As the second most abundant element in the earth crust,silicon provides excellent charge storage capacity during its electrochemical oxidation process（4e/atom）.The non-toxic,easy-to-manufacture,and inexpensive properties make it an electrode material for batteries with ultra-high energy density.However,an oxide layer is easily formed on the surface of silicon,which makes it highly electrochemically inert at room temperature.In order to solve the above problems,it is necessary to use electrolytes such as potassium hydroxide and fluoride derivatives which continuously dissolve the surface oxide layer.However,the alkaline electrolyte will rapidly corrode the silicon electrode,which significantly reduces the energy density and shelf life of the prepared batteries.As a semiconductor material,silicon also shows poor conductivity,which seriously affects the performance of the batteries.In this thesis,we try to solve the above problems and the achievements made are listed as follows:（1）The surface of silicon nanoparticles was coated with a MOF layer,and then mixed with copper chloride uniformly and treated at 900℃in an inert atmosphere to obtain the carbon coated electrode material（CuSi@C）.The CuSi@C material has a porous graphitic carbon cages on the surface,which facilitates the transport of the electrolyte to the silicon surface and increases the conductivity of the electrode.（2）The electrode made of CuSi@C material was paired with platinum for a constant current discharge and impedance tests.The electrode doped with a trace amount of copper could be continuously oxidized to achieve continuous discharge.The CuSi@C electrode was then paired with Mn O2 electrodes and platinum-carbon electrodes,respectively,to fabricate silicon-acid batteries.The Si-air battery can achieve a specific charge storage capacity of 1288 A h kg-1CuSi@C and an energy density of 1226 W h kg-1CuSi@C when discharged at a current density of 0.1 m A cm-2.The CuSi@C-Mn O2 battery also exhibits a specific charge storage capacity of 1.34 m A h cm-2 when discharged at a current density of 0.1 m A cm-2,which corresponds to a specific energy density of 1339 W h kg-CuSi@C1.The batteries also can be mechanically charged without changing the electrolyte,thus showing a good long-term discharge performance.（3）The electrochemical oxidation mechanism of CuSi@C was investigated by STEM measurements,geometric phase analysis（GPA）and density functional theory（DFT）calculations.The uneven distribution of element copper in CuSi@C material promotes the oxidation reaction of silicon and forms a highly defective oxide layer,which reduces the active energy silicon,increases its conductivity and thus enhances the electrochemical reactivity of CuSi@C. |
