| Germanium-based ternary metal oxide is one of the most potential negative electrode materials for electrochemical energy storage batteries.Zn2GeO4,as a germanium-based ternary metal oxide,has high specific capacity and low cost,but it has some problems such as large volume expansion and agglomeration in the process of charge and discharge,which hinders its wide application.To solve these problems,MXene materials with high conductivity,high ionic conductivity and rich surface functional groups were selected as modified conductive matrix,Zn2GeO4/MXene composites were constructed,and their electrochemical properties as negative electrodes of sodium/lithium ion batteries were studied.The main research contents are as follows:(1)By using a hydrothermal reaction method,the na-Ti3C2Tx MXene material prepared by alkali etching was combined with Zn2GeO4 to obtain Zn2GeO4/naTi3C2Tx composite material.Zn2GeO4 nanorods are uniformly attached to the surface of the na-Ti3C2Tx MXene layer.The sodium ion battery with it as anode material maintains a specific capacity of 75 mAh·g-1 after 100 discharge and charging cycles at a current density of 100 mA·g-1,which is twice the specific capacity of pure Zn2GeO4 material.This is due to the presence of MXene,which reduces the decomposition of Zn2GeO4 during the cycling process and effectively alleviates the aggregation degree of Zn2GeO4 nanorods,buffering the volume expansion during the Na-Ge alloying reaction.(2)The electrochemical performance of Zn2GeO4/na-Ti3C2Tx composite materials with different amounts of na-Ti3C2Tx MXene added as anode for lithiumion batteries was studied.As the content of na-Ti3C2Tx MXene in the composite material increases,the specific capacity of the composite material significantly decreases.This is because the storage effect of na-Ti3C2Tx MXene on Li+in the composite material is much smaller than that of Zn2GeO4.And the phenomenon of battery capacity increase was studied and analyzed.The results showed that due to the pulverization of electrode active materials during the cycle,new active surfaces were constantly exposed,providing more Li+storage active site,which led to the increase of battery capacity.In addition,the generated SEI film can provide additional capacity through pseudocapacitive behavior.(3)The high-purity Zn2GeO4/f-Ti3C2Tx composite material was successfully prepared by combining the f-Ti3C2Tx MXene material prepared by acid etching with Zn2GeO4 using a hydrothermal synthesis method.Using Zn2GeO4/f-Ti3C2Tx as anode material for sodium ion batteries,after 100 discharge and charging cycles at a current density of 100 mA·g-1,it has a specific capacity of 53 mAh.g-1 and a Coulombic efficiency of 99%.The overall low and continuous attenuation of specific capacity is due to an increase in the charge transfer impedance at the electrode material interface as the number of cycles increases,resulting in a decrease in ion transfer rate and a decrease in battery capacity.The Zn2GeO4/f-Ti3C2Tx composite material was used as anode material for lithium-ion batteries.After 200 discharge and charging cycles at a current density of 200 mA·g-1,it maintained a specific capacity of up to 837.2 mAh.g-1.After 1000 long cycles,the specific capacity stabilized at around 1050 mAh·g-1.As the cycle progresses,there is a phenomenon of capacity increase,and the phenomenon of capacity increase has been analyzed and studied. |
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