Design And Study Of Degradable MXene-based Micro Zinc Ion Energy Storage Devices

As a new kind of energy storage device,zinc ion hybrid supercapacitor（ZHSC）is favored by researchers because of its high theoretical capacity,good safety,low cost and environmental friendliness.And its high theoretical volume capacity and high security make it not only smaller but also wearable when applied to the field of micro devices.However,the traditional ZHSC has many problems in its practical application,such as the formation of electronic waste due to improper treatment,the formation of zinc dendrites,the difficulty of bending and the difficulty of degradation when using zinc metal as the negative electrode,which makes it difficult to apply to the flexible and environmentally friendly miniaturized devices.In this study,Zn Cl₂modified MXene was used as the anode Mn O₂-MWCNTs as the cathode.The interdigital electrode was carved by laser engraving,and then assembled with 2.00 M Zn SO₄ 0.10 M Mn SO₄ gel electrolyte to form a degradable micro zinc ion hybrid supercapacitor（DMZHSC）.The specific research contents are as follows:1.We prepared pure MXene by etching MAX with LiF and HCl,and then modified pure MXene by using the osmotic pressure between 1.00 M Zn Cl₂ and deionized water to obtain MXene/Zn Cl₂.Under the action of osmotic pressure,zinc ions are pre-inserted into the layers of MXene,which not only expands the layer spacing of MXene,but also opens more active sites for the subsequent storage of zinc ions,and the F functional group on MXene that is not conducive to ion transfer is also replaced by Cl.Thanks to the above modifications,the MXene/Zn Cl₂ anode shown a very high capacitance up to 529.1 F g^-1 at 1.00 m V^-1,which is 32.2%higher than pure MXene(400.3 F g^-1 at 1.00 m V s^-1),and the capacity has almost no attenuation after 20,000 charge-discharge cycles.This study not only expanded the layer spacing of MXene,but also removed some F groups that were not conducive to electrochemical reaction,providing a new method for the modification of high-performance MXene.2.We use the modified MXene/Zn Cl₂ as the negative electrode,and the adjusted Mn O₂-MWCNTs as the positive electrode.After capacity matching,we assemble a full capacitor.The full capacitor shows a high capacitance of 194.1 F g^-1 at 1.00 m V s^-1 and a high energy density of 90.1 Wh kg^-1 at a power density of 185.0 W kg^-1,with a capacity retention rate of 86.9%after 12,000 charge-discharge cycles.We also used laser engraving method to carve the positive and negative electrode materials into interdigital electrodes and assemble them into DMZHSC with 2.00 M Zn SO₄0.10 M Mn SO₄ gel electrolyte.DMZHSC not only has flexible and excellent cycle life（capacity retention rate is 83.1%after 8000 charge-discharge cycles）,but also can degrade rapidly in 2.0 h under slight external stimulation（5.0%H₂O₂）in PBS buffer solution,providing a new idea for new environment-friendly capacitors.