Studies On Integratable Self-healing Micro-supercapacitors

As a new type of energy storage device,micro-supercapacitor?MSC?has attracted extensive attention of researchers.Compared with the traditional sandwich structure supercapacitor?SC?,MSC usually uses two-dimensional?2D?interdigitated patterns as conductive path,which not only greatly reduces the size of the device,but also shows excellent charge transfer characteristics due to its minimum internal resistance.In addition,MSC displays long life,high power density,and can easily be integrated into other micro-electronic devices.However,MSC still has many problems in practical application.For example,the manufacturing technology of MSC is costly and complex,the function is single,the energy density is too low,and the reliability and stability are poor.In view of the above problems,this paper carried out the following aspects according to the current research states of MSC.Firstly,an improved inkjet printing technology realizing the large-scale preparation of MSC was developed based on the existing preparation technology.Secondly,with the help of the improved inkjet printing technology,we further developed a wireless charging optical detection system based on the asymmetric MSC,which meets the current demand for integration of devices.Thirdly,considering the problem of low energy density of MSC,the electrode materials with three-dimensional?3D?structure were developed to improve the energy density.Fourthly,aiming at the vulnerable problem of MSC,self-healing MSC was developed via introducing self-healing materials.The main research content of this paper is as follows:1.An improved inkjet printing method was developed to fabricate large-scale solid-state flexible MSC.The composites containing manganese dioxide?MnO₂?and polypyrrole?PPy?with hierarchical porous structure were used as electrode materials.The porous structure of the composite electrodes not only facilitates diffusion of the electrolyte,but also provides more active areas to store energy.The PPy by in-situ polymerization can improve the conductivity of MnO₂,and protect it from electrolyte corrosion.The prepared MnO₂-PPy MSC presented a high area specific capacitance of 7.26 mF cm^-2 at the scanning rate of 1 mV s^-1.Its equivalent series resistance?ESR?was 41?,indicating a rapid transfer/diffusion of electrons or ions,and an ideal capacitive behavior.2.By further extending the improved inkjet printing method,a wireless charging photodetection system with asymmetric MSC was prepared,as the core of energy storage.Since MnO₂ and vanadium pentoxide?V₂O₅?with large work function difference were selected as the active materials to build the asymmetric MSC,a large voltage window of1.6 V was realized.And the maximum energy density of the manufactured asymmetric MSC is 19.81 mWh cm^-3 when the power density is 0.32 W cm^-3,while the energy density is 2.57 W cm^-3 when the energy density is 14.64 mWh cm^-3.The combination of metal oxides with the conductive polymers not only improves the conductivity of metal oxides,but also protects them from electrolyte corrosion,thus their stability has been improved.Therefore,the capacitance retention rate of the asymmetric MSC reaches up to 92%after7000 cycles.The performance of the photodetector driven by the integrated system is similar to that of the photodetector driven by an external power supply,which verifies that the integrated system can operate normally.3.MXene is widely regarded as an ideal electrode material for SC due to its large specific surface area,good hydrophobicity,metal conductivity and other physical and chemical properties.We have prepared high-quality MXene nanosheets by using a mixture of lithium fluoride?LiF?and hydrochloric acid?HCl?as the etching solution.MXene-rGO composite aerogel with 3D structure was prepared by a simple ice template method,which effectively inhibited the self-stacking of MXene.In addition,the composite aerogel has an abundant porous structure,large specific surface area and high mechanical elasticity.The volume of MXene-rGO aerogel can completely recover to the initial state after about its70%volume compression when the load is released.4.The interdigital electrodes based on MXene-rGO?reduced graphene oxide?composite aerogel were fabricated by simple freeze-drying and laser cutting.A self-healing MSC was prepared by wrapping the electrodes with self-healing polyurethane?PU?.At the scanning rate of 1 mV s^-1,MSC showed the area specific capacitance of 34.6mF cm^-2,and the capacitance retention rate was up to 91%after 15,000 cycles.After wrapping a layer of self-healing PU onto the surface of MSC,the device showed an excellent self-healing ability,which maintained 81.7%specific capacitance after five cut-heal processes,and still can drive a perovskite-based photodetector normally.