| Recently,the development of mobile electronic equipment and electric vehicles is changing with each passing day,and lithium secondary batteries are attracting attention as an energy storage element.Organic liquid electrolytes are widely used because of their ultra-high ionic conductivity,which allows lithium ions to shuttle freely between the positive and negative electrodes.However,the potential safety problems of organic liquid electrolytes are difficult to solve.For example,liquid electrolytes are prone to leakage and volatilization,side reactions with lithium metal are prone to produce flammable and explosive substances,and lithium dendritic crystal growth can pierce the diaphragm,etc.The development of solid electrolytes with high energy density and high safety to replace the organic liquid electrolytes has attracted the interest of various researchers.However,some performance indicators of solid electrolytes remain to be explored,such as low ion conductivity,poor interface contact,and stability of metallic lithium.To address the above problems,this paper uses poly（vinylidene fluoride-co-hexafluoropropylene）（PVDF-HFP）as the main matrix for composite modification by introducing poly（propylene carbonate）（PPC）,Li0.33La0.557Ti O3（LLTO）.The main research contents and results are as follows:1.Firstly,LLTO nanorods with diameters and lengths of approximately 200 nm and 1μm were prepared by electrospinning-high temperature calcination method,and then they were combined with PVDF-HFP-based solid electrolyte and coated with a film coater using PE film as a support material.Using XRD,TG/DSC,charge-discharge testing and other methods to explore the effect of different content of LLTO nanorods on the performance of solid composite electrolyte（SCE）.The results show that the electrochemical performance of SCE containing 10 wt%LLTO nanorods is the best.Its ionic conductivity reaches 1.21×10-4 S·cm-1,ion migration number is 0.41,and chemical stability window is 4.7 V.In NCM622 as the anode,metal lithium sheet as the cathode assembly NCM622/SCE（10 wt%LLTO）,the initial discharge capacity is 150.6m Ah·g-1 the 100th discharge capacity is 129.1 m Ah·g-1 at 0.5 C.2.Explore the effect of different proportions of PVDF-HFP and PPC on the performance of composite solid electrolytes,and use the XRD,ionic conductivity,rate and other properties to characterize the experiment.The results show that when the ratio of PVDF-HFP to PPC is 1:1,the disorderly arrangement of the chain segments reaches the maximum and the ion conductivity is the highest.Among them,the ionic conductivity is 0.25×10-4 S·cm-1,a stable potential is as high as 4.8 V The lithium symmetrical battery can be cycled stably for 1300 hours and has strong stability with metallic lithium.At the same time,it is assembled into a solid-state battery NCM622/SCE（1:1）/Li for corresponding test,which has remarkable charging and discharging performance.3.On the basis of PVDF-HFP/PPC matrix,further add different content of active spinning filler LLTO nanorods to prepare organic/inorganic multiphase solid composite electrolyte（MSCE）.The results show that when the ratio of PVDF-HFP to PPC is 1:1and the content of LLTO nanorods is 10 wt%,the ion conductivity rises to a maximum of 2.18×10-4S·cm-1,the ion migration number is 0.47,and Li/MSCE（10 wt%LLTO）/Li battery can be tested stably for 2000 hours without lithium dendrite growth,which improves the cycle stability and is suitable for long cycles.The specific discharge capacity of the NCM622/MSCE（10 wt%LLTO）/Li solid-state battery after 100 cycles of charging and discharging is 142 m Ah·g-1. |
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