Three-dimensional Continuous Structure Construction And Optimization Mechanism Of Microscale Energy Storage Device

Energy storage devices are the core components of smart mobile terminals.As the size of terminals is gradually decreased,the demand for microscale energy storage devices is increasing.However,microscale energy storage devices still have the problem of low energy density,and constructing three-dimensional microelectrodes is an effective method to increase the energy density of microscale energy storage devices.At present,there are two scientific problems in this field:(1)three-dimensional construction strategies are commonly complicated.(2)energy density,power density,and cycle stability of three-dimensional microelectrodes are difficult to balance.Therefore,based on these two problems,this thesis proposes the construction strategy of three-dimensional microelectrodes with different thicknesses,optimizes the construction process and electrochemical performance of micro-energy storage devices,and proposes an optimization mechanism to meet the different needs of micro-energy storage devices.The influence of different construction processes on the electrochemical performance of microscale energy storage devices is analyzed.The following results are obtained in this thesis:(1)Aiming at solving the complex of three-dimensional construction strategy,a fast and dry method to construct microsupercapacitor is proposed.This strategy is fully compatible with modern semiconductor microfabrication.The lithography,physical vapor deposition,rapid annealing and magnetron sputtering are used.The Co film was oxidized to Co₃O₄ network structure within 5 minutes.The three-dimensional interconnected nano-network structure provides a continuous electronic conduction path.The holes created by the overlap of nanosheet allow the electrolyte to penetrate and shorten the ion diffusion distance.By adjusting the time of magnetron sputtering,highly electrical conductive Pt nanoparticles were uniformly deposited on the Co₃O₄film to further improve the electrical conductivity of the microelectrode.Therefore,the volume capacity of the microsupercapacitor is 35.1 F cm^-3,1.56 times higher than that of the pure Co₃O₄ microsupercapacitor,and 3.48 times higher at high discharge rate.The capacity retention is 91.9%after 5000 cycles.In addition,due to the short annealing time of this strategy,it can be used in the construction of flexible microsupercapacitor with a capacity of 30.5 F cm^-3.(2)An one-step lithography combined with post anealling is used to obtain three-dimensional interconnected channel pore carbon microsupercapacitors.By mixing Zn O nanowires with photoresist and then pyrolyzing,three-dimensional interconnected channel pores were created inside the pyrolyzed carbon microelectrode.This method decreased the complexity of the three-dimension consctruction of microsupercapacitor.The channel hole can be used as an electrolyte"reservoir"in the microelectrode,and the monolithic electrode provides complete electron conduction paths.Electron/ion bicontinuous conduction paths are realized.The microelectrode is activated uniformly when using the Zn O nanowires as the activation agent.Micropores and mesopores are found on the pore walls of the channel macropores,further increasing the specific surface area of the microelectrodes.The three-dimensional channel pore carbon microsupercapacitor shows an area capacity of 10.01 m F cm^-2,1.48-5.02 times higher than that of conventional nanoparticle-like pore carbon micro-supercapacitor,and is6.63 times higher than that of the unactivated porous carbon microsupercapacitor.The capacity of microsupercapacitor is not attenuated after 10,000 cycles.The high-concentration electrolyte Li TFSi was introduced to constuct high-voltage microsupercapacitor firstly,and the voltage of microsupercapacitor was extended to2.5 V.The energy density of Li TFSi microsupercapacitor is 6.23 times higher than that of microsupercapacitors based on the H₂SO₄ electrolyte.The single Li TFSi microsupercapcitor was assembled with the solar cell as self-charging system and provided energy for the functional device(working potential>1.8 V).(3)Aiming at the problem that energy density,power density and cycle stability of microscale energy storage devices are difficult to balance,a strategy for the complex growth of Cu HCF on three-dimensional dendritic Ni current collectors is proposed.By adjusting the electrodepostion time of the three-dimension current collector,the growth time of the electrochemical active material,the concentration of the complexing agent,etc.,the Cu HCF is grown on the surface and inside of the three-dimensional dendeitic porous nickel current collector.The mass loading of Cu HCF is high.Ion/electron diffusion distance is still short.The electrons are conducted continuously along the dendritic Ni current collectors.The potassium citrate complexing agent enlarges the interplanar spacing of the electrode material.Various kinds of the monovalent alkali metal ions,the divalent alkaline earth metal ions,the trivalent ions and the transition metal ions can be inserted into the electrode material.The capacity of the Cu HCF/three-dimensional dendritic porous nickel microelectrode is 0.61 m Ah cm^-2,and the capacity retention rate is 89%when the current density is increased by 20 times from 2 m A cm^-2 to 100 m A cm^-2.The potassium-zinc hybrid ion microbattery was assembled,showing as capacity of 0.281 m Ah cm^-2 with operating voltage of 1.66 V.The energy density is0.477 m Wh cm^-2,significantly higher than those of other microbatteries and microsupercapacitors reported in the literature.The cycle performance of the interdigital electrode was improved by adding Cu²⁺into the electrolyte.The capacity retention rate was increased from 82.4%to 91.6%after 1000 cycles.At the same time,the spontaneous phase transition of the Cu HCF as the cathode material of Zn ion microbattery or KZn hybrid ion microbattery can be suppressed,and the capacity retention rate of KZn hybrid ion microbattery after 1500 cycles is increased from 39.2%to 76.4%.