| Evolving in leaps and bounds for the Internet of Things,the rapid development and modularization of miniaturization self-powered electronics inspire the urgent pursuit of micro-scale electrochemical energy storage devices.As the multifunctional and long-term operating environment of electronics increases,the challenge for high-performance standards of power supplies is proposed.The desired energy storage devices need to own high capacity,energy density,power density and long cycle stability.Furthermore,it needs to be highly compatible with electronic products in terms of functional characteristics such as miniaturization and integration.Among the numerous rechargeable energy storage systems,micro-supercapacitors(MSCs)with in-plane interdigitated configuration have received intense attention for their short ion transfer distance,high power density,fast charge and discharge performance,ultra-long cycle life,convenient integration and reliable electronic security.In recent years,as a class of extremely important potential material for MSCs electrodes,graphene has gained great attention from researchers due to its ultra-thin two-dimensional(2D)structure,excellent physicochemical properties(large specific surface area,good electrical conductivity and mechanical properties),and the highly adaptability to electronics with a planar geometry.Currently,the main research to improve the specific capacitance,energy density and functionality of graphene-based MSCs,which is focused on doping with heterogeneous elements,compounding with carbon-based materials or pseudocapacitive materials,designing three-dimensional(3D)electrode structures and so on.However,there still exist some challenges in the practical applications and system integration.To further improve its performance and potential for practical applications,which require more effort in materials modification and electrode material structure optimization.Based on this,this paper focus on the three aspects:the modification of 2D graphene materials,the construction of 3D structures and the improvement of space utilization,and the main work and research results are listed as follows:1.Based on the laser modification of 2D graphene materials technology,we develop high-performance graphene-based MSCs for micromachining compatibility.In the experiment,the functional group of the graphene was regulated via combined blue violet-laser(BV-laser)exposing and air plasma treating,which is fully compatible with microfabrication techniques.On the one hand,the electrical conductivity has be enhanced by reducing the functional groups through BV-laser exposing treating.On the other hand,the wettability and active sites are guaranteed by air plasma treating create a slightly functional group onto the graphene surface.The obtained graphene materials(PBV-RGO)shows a low resistance(27.2?sq-1),which indicating the superb electron conductivity,the property assure the rapid electron transfer during the electrochemical reactions.The electrode material was drop-casting into a film,then the symmetrical graphene-based in-planar MSCs with metal current collector free be obtained by laser cutting,encapsulated by H2SO4/polyvinyl alcohol(PVA)gel electrolyte.The obtained MSCs exhibit excellent areal capacitance of 21.86 m F cm-2,outstanding areal energy density of 2.49?Wh cm-2 at a power density of 0.05 m Wh cm-2,and superior long-term stability with 99%retention after 10 000 cycles.2.Based on all-graphene electrodes for flexible high-performance MSCs.In this work,the electrochemical activity and conductivity of graphene be improved by compounding graphene oxide(GO)with rich active sites and electrically exfoliated graphene(EG)with excellent conductivity.And the flexible high-performance all-graphene based MSCs by adjusting the ratio between GO and EG.The self-integrated MSCs be achieved by laser cutting,which simplifies the technology for preparing integrated MSCs.At the same time,using graphene as electrode materials,current collector and wire,the obtained integrated all-graphene MSCs exhibit excellent monolithic,flexibility and compatibility with various flexible substrates,which demonstrates that the devices fabricated by this method own excellent repeatability,remarkable modularity and consistent performance.Encapsulated by H2SO4/PVA gel electrolyte with the areal capacitance of 19.90 m F cm-2,and an energy density of 2.76?Wh cm-2 at a power density of 0.05 m Wh cm-2.The area capacitance retention of MSCs with 93%when the bending angle?varied from 30°to 180°after 100 cycles.The integrated MSCs can be reliably charged up to 3 V,which indicates the broad application in smart textiles.3.Based on the construction of 3D micro/nano interconnected scaffold structure,effectively enhance the electrochemical performance of graphene-based MSCs.The practical application of MSCs are greatly hindered by their low capacity and energy density are limited by their area and dimensionality.Therefore,the design and construction of 3D structures are considered as an effective strategy to improve the capacity and energy density of MSCs.The method effectively improved the energy storage capacity of electrode material by enhancing active electrochemical sites and promoting ion dynamics.As an example of in-situ growth of carbon nanotubes(CNTs)on graphene sheets,modulating the 3D architecture by controlling the amount of=CNTs,a rational 3D micro/nano interconnected scaffold graphene-based(3D-CNT@RG)electrode is obtained.The electrochemical mechanism and theoretical simulations show that a homogeneous electric field distribution ensures enhanced accessibility of electrolyte ions and promotes ion kinetics.The decive exhibit excellent electrochemical performance with high areal capacitance(53.49 m F cm-2)and areal energy density(8.82?Wh cm-2),and superior long-term stability with 97%retention after 20 000 cycles,which greatly broaden the potential application scenarios.4.Based on the 3D micro/nano interconnected scaffold graphene-based MSCs for practice application.Increasing the loading is the most straightforward to improve energy performance of MSCs,and increasing the surface area of electrode is also an attractive option.The pseudocapacitor material Mn O2 nanosheets are uniformly coating on the 3D micro/nano carbon scaffold,which own a high theoretical specific capacity(1370 F g-1).The excellent conductive network of the 3D micro/nano carbon scaffold not only provide excellent electron transfer channels,reduce the overall resistance of the electrode material and mitigate the adverse effects of the low electrical conductivity of Mn O2 itself,but also provide a large specific surface area and space,and in-situ growth of the pseudocapacitor material Mn O2 with strong adhesion.The structure design not only ensure the overall stability of the electrode,but also enable the loading of a large amount of active material with a large specific surface area,further improving the energy storage capacity of the MSCs.The obtained MSCs exhibit excellent electrochemical performance in the highly concentrated Na Cl O4 electrolyte.The device exhibits excellent capacity retention from 0 to 50°C,and still has 26%capacity retention in the crystallized electrolyte.This demonstrates that the devices can be applied with widely operating temperatures range. |
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