Research On Preparation And Performance Of Flexible And Stretchable Energy Storage Devices

With the continuous development of science and technology,the rise of flexible intelligent electronics such as electronic skin,bionic devices and artificial intelligence has rapidly changed our life.However,with the development of these flexible intelligent electronics,flexible energy storage power supply has always been the research direction of our unremitting efforts.In order to achieve the flexibility and comfort of these smart electronics,we must abandon the bulky and rigid external power supply system.This means that flexible,skin-friendly,integrated power supply units will be the focus of our research efforts.Supercapacitors have become one of the choices of integrated energy storage devices due to their small size,high safety and excellent wearing comfort.However,there are still many shortcomings in the application of supercapacitors in the wearable integrated system,which requires us to develop new electrode materials and optimize the device structure to improve its performance and practical application value.In addition,flexible lithium-ion batteries with higher energy density are an important aspect of our research.New materials based on high specific capacity and flexible electrodes with high tensile properties are important parts of the realization of fully stretched lithium-ion batteries.The main research results of this paper are as follows:Firstly,CH3CuS nanowires were synthesized by one-step solution method.The nanowires have uniform structure and stable physical and chemical properties.The average length of the nanowires can reach 50～100 μm and the diameter is about 200～300 nm.The CH3CuS nanowire material can be rapidly reacted within tens of seconds by using one-step hydrothermal method,and then the product solution after the reaction can be directly pumped and filtered by using vacuum filtration equipment,and then the complete precursor of the paper based electrode can be obtained.Then the paper based electrode obtained by this step is vacuum dried to prepare the flexible electrode which can be used in the supercapacitor.The flexible electrode is used as the positive and negative electrode of the supercapacitor,and the PVA/KOH mixed gel solution is used as the electrolyte.The all-solid supercapacitor device assembled by CH3CuS nanowire conducting flexible electrode has excellent electrochemical performance.The measured area-specific capacitance of the device is 90.5 μF/cm2 at the current density of 0.5 mA/cm2,and the calculated energy density of the device is 5.2 μW·h/cm2.The device retains 98%of its original capacity after 10,000 cycles of charge and discharge.In addition,the bending performance test is the necessary means for testing the flexible components,the flexible a super capacitor under different bending Angle almost remain the same,the electrochemical performance capacity loss is just flat out state capacity of 1%～2%,the results fully prove that using CH3CuS flexible electrode assembly of the super capacitor has excellent resistance to bending performance.The flexible electrode without additive,economical,effective and environmental protection has a broad application prospect in the field of flexible energy storage devices.Secondly,in order to broaden the application range of supercapacitors and make new energy devices to meet the needs of flexible intelligent electronics,we will make further innovations in the process.In this part,we use the transfer printing method to produce the supercapacitor array quickly.The output voltage and capacitance can be controlled,and the shape of the supercapacitor array can be controlled.Is simply the capacitor electrode shape,the connection forms of a single capacitor and capacitor array assembly can be artificially controlled,in order to meet the existing electronic field of artificial intelligence and wearable electronic skin areas of the specificity of power demand,the super capacitor array device without losing capacity can be realized under the premise of artistic quality.In this paper,the supercapacitor array obtained on PET substrate by transfer printing technique has excellent electrochemical performance,with an area specific capacitance of 0.32 mF/cm2,ultra fast charge-discharge performance,and an area power density of 66.5 μW/cm2.Notably,the output of the voltage and capacitance can be easily manipulated by directly transferring the print of the miniature ultracapacitor array using series and parallel connections,respectively.In addition,we can achieve beautiful and diverse transfer printing of miniature ultracapacitor arrays on a variety of substrates,such as medical film,cotton and glass sheets.In addition,in this paper,the micro-supercapacitor with dragon pattern made by us is attached to the arm of the human body as the tattoo power supply,which is not only a kind of decoration but also can provide power supply for the electronic skin.In this work,we also realize the intelligent glass assembly,the use of transfer printing technology to design a good flower in the shape of a super capacitor above attached with the household glass,integrated circuits connecting two temperature sensor at the same time,when the water temperature changes in temperature sensor drive the different signal light is lit up,can make the users avoid hot water scald.In this work,the miniature supercapacitor made by this method connects the intelligent electronics and the bridge of the specific power supply,which is the main research direction of the next generation power supply.Finally,considering the disadvantages of low energy density of flexible supercapacitors,flexible lithium-ion batteries with higher energy density are one of the focuses of this paper.As a kind of wearable electronic power source with great development prospects,the stretchable lithium-ion battery has received extensive attention in the emerging field of wearable electronics.Despite recent advances in retractable electrodes,separators,and sealing materials,building a retractable full battery remains a huge challenge.In this work,the PVDF/TPU nanofiber separator was prepared by the electrospinning method.LiFePO4(LFP)-TPU and Si@C-TPU slurries were electrosprayed on the prepared elastic and conductive current collectors,respectively,to prepare stretchable cathode and anode.Then the obtained PVDF/TPU nanofiber separator is thermally sandwiched between the positive electrode and the negative electrode.After electrolyte injection and final packaging process,a fully stretchable lithium-ion battery was successfully assembled.The prepared planar fully stretchable lithium-ion battery has a stable area specific capacity of～6 mA·h/cm2 under unstretched conditions.In addition,when the stretchable lithium ion battery is stretched to～150%of its initial length,the stretchable lithium ion battery still maintains a capacity of 4.3 mA-h/cm2.In addition,after 100 stretch/release cycles,the lithium ion battery still has 70%of the initial area specific capacity.The results show that this fully stretchable lithium-ion battery will have broad application prospects in the field of stretchable electronics in the future.