| The rapid development of consumer electronics,smart grids,and energy-containing microsystems has put forward higher requirements for energy storage systems.Due to the problems of battery structure,electrode materials,and liquid electrolyte,traditional lithium-ion batteries are difficult to meet the requirements of high safety and high energy density for energy storage systems.All-solid-state batteries have the advantages of high safety performance,long cycle life,and high specific energy,and are considered to be the best energy storage battery system in the future.The problem of transport dynamics restricts the performance of all-solid-state batteries.Therefore,in order to realize an all-solid-state lithium battery with high safety and high energy density,it is of great theoretical value and practical significance to modify the electrode-solid electrolyte interface and study the kinetics of charge transport at the heterogeneous interface.In this thesis,a LiCoO2(LCO)-LiPON-Liall-solid-state thin film battery was prepared by physical vapor deposition technology.The discharge capacity of the battery in the first cycle was 0.08m Ah/cm2,and the capacity retention rate in 100 cycles was97.5%(0.2 C).Based on the experiment,a one-dimensional simulation model of an all-solid-state thin-film battery was established through COMSOL,and the relationship between different diffusion coefficients and different thicknesses of the positive electrode and the solid-state ion transport and capacity of the battery was explored.The simulation results show that when the diffusion coefficient of the positive electrode(LCO)is in the order of 1×10-13 m~2/s and the electrode thickness is 25?m,the areal capacity can reach1.39 m Ah/cm~2.Through cathode ion transport and heterointerface solid-phase lithium concentration distribution,it was founded that the capacity development rate of thin-film batteries is closely related to the ion transport performance of cathode materials and the interface ion transport kinetics between cathode and solid electrolyte.In order to improve the transport kinetics at the LCO-LiPON interface,this paper takes the heterointerface between the cathode(LCO)and solid electrolyte(LiPON)of solid-state thin-film batteries as the research object,and introduces a mixed conductive LLTO and LNO thin film layer at the heterointerface to construct the cathode-electrolyte interface ions.Transmission network,reducing heterointerfacial resistance.Specifically,a lithium lanthanum titanium oxide(LLTO)film with a conductivity of 9.02×10-5 S/cm and a lithium niobate(LNO)film with a conductivity of 8.68×10-6 S/cm were successfully prepared by magnetron sputtering.Then,the interface of LCO-LiPON composite film was modified with LLTO and LNO films by magnetron sputtering preparation technology,and the film impedance of the composite film was reduced from 1953.9?to 1175.4 5?and 1224.05?,which reduced the impedance of LCO-LiPON composite film and enhanced its resistance.ion transport capacity.Then,LLTO and LNO were used to modify the cathode and electrolyte interface of LCO-LiPON-Liall-solid-state battery to verify the effect of enhanced charge transport on solid-state ion interface on the performance of solid-state thin-film battery.After layer modification,the interface impedance was reduced by 3 orders of magnitude,the discharge capacity of the first cycle is doubled,the Coulomb efficiency of the battery was higher than 95%in the first 50 cycles,and the cycle stability of the battery was improved. |
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