Research On Preparation Of Germanate Nanostructure And Their Lithium/Sodium-storage Properties

Because of the advantages of high power and energy density,long clendar life,low self-discharge,lithium ion batteries（LIBs）have been widely utilized in hunman’s daily life,for example,portable electronic devices,electric vehicles,biomedical,smart grid,aerospace and other fields.However,graphic,the anode for commercial-available LIBs,delivery quite low theoretical capacity,which is unsatisfied the requirement of high performance electronic devices for humans.Even LIBs have been widely used as energy storage devices,the high-cost price,security and limited lithium nature source,LIBs are unsatisfied with the requirement for grid-scale application.Located in same group of periodic table,similar chemical property,wide distribution,abundant resources,sodium ion batteries（NIBs）have attracted the attention among researchers.Electrode materials play an important role in the performance of batteries.Therefore,exploring electrode materials with high specific capacity is the key process in improving the performance of batteries.Due to high theoretical capacity,fast ion diffusivity,high electrical conductivity,Ge-based anode materials draw much more attention as an alternative anode material for advanced LIBs.However,similar with other alloyed-type anodes materials,large volume change of electrodes leads to unstable of electrodes during charge/discharge process,resulting in fast capacity fading,which hinders the practical application of Ge-based anode.In order to solve the volume expansion of the electrode material,improve the performance of batteries,two-dimensional Ge-based nanostructure anodes were prepared anchored on the conductive current collect,and the energy storage mechanism of electrodes were demonstrated,the relationship between the microstructure and the electrochemical performance were researched,the main sections of exploring are as follows:（1）By solvothermal method using the nickel foam（NF）as conductive current collect,commercial GeO₂ as germanium source and Mn（Ac）₂ as manganese source,2D MnGeO₃NSs@NFs was prepared.The electrochemical performance of the NIBs delivered that the capacity of MnGeO₃NSs@NFs maintain 297.1 mAh/g at 100 mA/g after 100 cycles.Even at a higher current density of 300 mA/g,the discharge capacity still up to 200 mAh/g after 100 charge/discharge cycles.The excellent performances are mainly attributed to the synergistic effect between 2D MnGeO₃NSs and NF,improving the cycle stability of electrode during repeated electrochemical cycling.（2）2D MnGeO₃NSs@Cu was successfully obtained with same conditions as（1）except the copper foam as conductive current collect.When used as anodes for LIBs and NIBs,2D MnGeO₃NSs@Cu demonstrated discharge 936 and 300.7 mAh/g after500 and 100 cycles at current density of 100 mAh/g,and after 10 cycles at higher current density of 2.5 A/g,the discharge specific capacities present 509.2 and 204.7mAh/g,respectively.2D MnGeO₃NSs@Cu illustrated excellent cycling performance,rate performance and long lifespan（3）By solvothermal method using the nickel foam（NF）as conductive current collect,commercial GeO₂ as germanium source and BiI₃ as bismuth source,lotus-stalk Bi₄Ge₃O₁₂NSs@NFs electrode was obtained and studied.The influence of solvent components on the morphology of nanosheets was also studied.When applied as anode for LIBs,lotus-stalk Bi₄Ge₃O₁₂NSs@NF showed excellent Li⁺storage performance with a high reversible capacity of 709 mAh/g after 88 cycles at the current density of100 mA/g.For NIBs test,the material exhibited high reversible capacity of 332.3mAh/g at 100 mA/g after 100 cycles.