介孔硅酸锰镁可充镁电池正极材料的制备及其电化学性能研究

Mesoporous Magnesium Manganese Silicate as a Cathode Material for Rechargeable Magnesium Batteries

采用介孔二氧化硅MCM-41作模板和硅源,合成了具有介孔结构的可充镁电池正极材料硅酸锰镁.分别用XRD、SEM、TEM和氮气吸脱附测试研究了合成材料的介孔结构,并通过循环伏安、恒电流充放电测试比较了介孔与无孔硅酸锰镁材料的电化学性能.由于介孔材料活性表面较大,可增加电解液与活性材料的接触,使材料具有较多的电化学反应位.因而,与相应的无孔材料相比,具有介孔结构的硅酸锰镁材料呈现出较低的充放电极化、较大的放电容量和较高的放电电压平台.在0.25 mol/L Mg(AlCl2EtBu)2/THF电解液中,0.2 C(约62.8 mA/g)充放电速率下,介孔硅酸锰镁材料首次放电容量可达到241.8 mAh/g,放电平台为1.65 V(vs Mg/Mg2+).设计具有介孔结构的材料为提高可充镁电池正极的电化学性能提供了一条有效的途径.

Mesoporous magnesium manganese silicate as a cathode material for rechargeable magnesium batteries was prepared using mesoporous silica MCM-41 as both template and silicon source.X-ray diffraction（XRD）,scan-ning electron microscope（SEM）,transmission electron microscope（TEM） and N2 adsorption-desorption measure-ments were performed to characterize the mesoporous structure of the as-prepared material.Furthermore,the electro-chemical performance of mesoporous and bulk materials were compared by cyclic voltammetry and direct current charge-discharge measurements.The larger surface area of the mesoporous material favors the efficient contact be-tween active material and electrolyte,providing more active sites for the electrochemical reaction.As a result,the mesoporous material exhibits better electrochemical performance with lower polarization for magnesium de-intercalation and intercalation,larger discharge capacity and higher discharge flat plateau compared with corre-sponding bulk material.In 0.25 mol/L Mg（AlCl2EtBu）2/THF electrolyte,the initial discharge capacity and discharge voltage plateau of the mesoporous material can reach 241.8 mAh/g and 1.65V,respectively.The mesoporous struc-ture may provide a new approach to improve the reaction activity of the cathode materials for rechargeable magne-sium batteries.