Assemble And Optimization Of The Flexible Aqueous-Electrolyte Supercapacitors

With the rapid development of modern technology,people are requiring the electronics to have multifunctional,portable,and even flexible,wearable functions.At the same time,the existing energy storage devices are heavy,rigid,and poorly safe,which cannot meet the demands of portable flexible electronic products in the future.Therefore,a safe,lightweight,flexible energy storage device,with large energy and power densities have become a bottleneck in the development of flexible wearable electronics.At present,because of its low power density and poor safety,Li-ions battery is not suitable for the application in portable electronic products.Supercapacitors?SCs?,also known as electrochemical capacitors,have a much higher energy density than conventional capacitors,while have a simple structure and convenient packaging process.Notably,SCs showed high power density of up to 10,000 W kg^-1,which can be charged and discharged in a few seconds.As a result,SCs are promising for the applications in wearable electronics.In recent years,material synthesis methods and characterization methods have been continuously developed,which promotes the in-depth study of the energy storage mechanism of supercapacitors.Pseudocapacitors,containing redox reactions in the energy storage process,have higher energy density compared with electric double layer capacitors.What's more,their high power density and rate capability make them one of the hotspots area in the field of energy storage.On the other hand,due to the high safety of aqueous electrolytes,it is more suitable for the requirements of wearable electronic products.Based on the above discussion,this focuses on the preparation of flexible pseudocapacitive electrode materials and the modification of their microstructure.The pore design and interface modification are used to control the ionic transportation and charge transfer of the electrode materials.The relationship between microstructure and electrochemical storage performance of the electrode film was investigated systematically.The self-supporting membrane materials are used as electrodes to assemble the asymmetric supercapacitor.What's more,a microchip supercapacitor is prepared through device-structure design.In addition,the energy storage characteristics of the flexible energy storage device is systematically analyzed and studied.The major contents are following:1.The preparation of high packing density electrode materials via the modification of interface.The conductive network is constructed by single-walled carbon nanotubes?SWCNTs?.CuHCF nanoparticles are used as the main pseudocapacitive active material in the conductive network of SWCNTs to improve the capacitance of the system.PEDOT:PSS works as the surfactant and binder to promote dispersion of SWCNTs and CuHCF in water,making the electrode structure tight and improving the mechanical stability and packing density of the film.In addition,the addition of PEDOT:PSS can modify the affinity of the electrode-electrolyte interface,which is beneficial to reduce the interface resistance and improve the charge transfer efficiency during charge and discharge.The ternary film showed a packing density of 2.69 g cm^-3,volumetric capacitance of 775 F cm^-3.The asymmetric device exhibited an energy density of 30.08 Wh L^-1,with a power density of 10.79 W L^-1.2.The assembly of asymmetric microsupercapacitors under the drive of capillary force.High bulk density electrode material makes it possible to store more energy in a small space.Capillary force driving is proposed to realize self-assembly of asymmetric microchip devices to obtain better flexibility and facilitate multi-device integration.The asymmetric Na⁺-ions supercapcitor was fabricated under the.The as prepared asymmetric device exhibits excellent flexibility and multidevice connecting capability.In addition,the aeral specific capacitance of 34 mF cm^-2 was achieved at the scan rate of 10 mV s^-1.3.Widen the operating potential window of electrode materials by the adjustment of enery band.We raise a strategy to control the working potential range of negative electrode by optimizing the atomatic arrangement and the concentration of oxygon vacancy.The operating potential range of the MWO SS is tunable between-0.4 and-1.2 V.The asymmetric supercapacitor device was fabricated by using Mo_0.1W_0.9O_3-x/single-walled carbon nanotubes film as negative electrode and commercial activated carbon film as positive electrode.The optimized device showed a stable working voltage of 2.0 V in 1 M Li₂SO₄ aqueous electrolyte and areal capacitance of 232 mF cm^-2 at 10 mV s^-1.The highest energy density and power density are 112?Wh cm^-2 and 21.5 mW cm^-2,respectively.This study opens up new avenues for developing high voltage window aqueous energy storage devices.4.The enhancement of ionic transportation by the regulation of pore size.The pore-size regulation of electode film was used to eliminate the influence on the rate performance of electrodes by the increased packing density.By using the 2D arrays of NbN nanocrystals as spacer,the high electrode film with a packing density about 3 g cm^-3 was obtained.NbN increases the interlayer spacing of activited materials and facilitate the electrolyte and ion penetration even at extremely high scan rate.Interestingly,the as prepared film shows a thickness-independent rate performance that almost same rate capabilities are acquired for 3?m and 50?m thick electrodes.This method may pave a new way for controlling ion transport in electrodes made of MXene and other 2D materials,which have potential applications in high rate energy storage and beyond.5.The design of high-voltage bi-polar structure device.To enlarge the working voltage window of an energy storage device is the most efficient way for increasing its energy density.2D titanium carbide?MXene?free-standing films are employed to evaluate the dependence of electrochemical performance in aqueous Li and Na-ion electrolytes.By contrast,high surface area porous nanoscale carbide derived carbon?nano-CDC?is employed as a surface electrosorbing electrode at cathodic potentials.Both,2D MXene and zero-dimensional?0D?nano-CDC,with contrasting charge storage mechanisms and complementary potential windows of operation,enable the construction of an aqueous Li-ion capacitor with a 2 V voltage window of operation.Furthermore,we demonstrate here the design of flexible bipolar carbide-carbon devices,showing a voltage window of 4 V.