Preparation And Performance Study On Poly (Vinylidene Fluoride)-based Composite Solid Electrolyte For Lithium-ion Batteries

The solid electrolyte can effectively avoid the safety issues caused by the inflammable organic electrolytes in lithium-ion batteries.The polymer-ceramic composite solid electrolyte owns the characteristics of high ionic conductivity,easy processing and high flexibility showing a wide range of application prospects for high-performance all-solid-state rechargeable batteries.PVDF-based solid electrolyte has a very low glass transition point（-35°C）,and it has non-flammability,easy-to-process property,wide electrochemical window,etc.PVDF-based solid electrolyte is one of the current research hotspots in the field of solid electrolytes.Firstly,PVDF-based composite solid electrolyte with different solid powders was studied.Comparing the test data,it was found that different types of solid powders have a great impact on the mechanical properties,cycle performance and battery polarization of PVDF-based solid electrolytes.There is a big gap between the adsorption energy of different powders and other components.After cycling for 100 cycles at a room temperature of 0.1C,the discharge capacity of the montmorillonite composite solid-state battery is about 120 m Ah g^-1,and the discharge capacity of the boron nitride composite solid-state battery and the molybdenum sulfide composite solid-state battery is about 90m Ah g^-1.The minimum capacity of the silicon powder composite solid-state battery is about 80 m Ah g^-1.Layer-structured montmorillonite powder can effectively improve the performance of the PVDF-based solid electrolyte,while nanometer silicon powder will reduce its mechanical properties and cycle performance,but will increase battery polarization,providing a basis for subsequent research.This article subsequently used montmorillonite as the main raw material to prepare lithium aluminosilicate powders in different proportions by high-temperature sintering methods commonly used in laboratories.Theβ-LiAlSiO₄/LiTaO₃ powder was sintered in different ratios of lithium aluminosilicate powders and screened out by comparing the XRD data and battery performances.When the mass content ofβ-LiAlSiO₄/LiTaO₃powder in the PVDF-based solid electrolyte is 10wt%,the composite solid-state battery has the best performance.Theβ-LiAlSiO₄/LiTaO₃ composite solid electrolyte,montmorillonite composite solid electrolyte,and additive-free PVDF-based solid electrolyte are compared through microstructure,mechanical properties,electrochemical and battery performances.It is found that theβ-LiAlSiO₄/LiTaO₃ composite solid electrolyte has excellent cycle performance,rate performance and lithium dendrite suppression ability.At room temperature,it shows a reversible cycle capacity of 110 m Ah g^-1 after 600 cycles at 0.5 C and ionic conductivity of 1.28×10^-3 S cm^-1 at 30°C.In the rate test,the discharge capacity at 0.1 C is 147.8 m Ah g^-1,then the discharge capacity becomes 79.2 m Ah g^-1 when the high rate of 4 C is reached,and when it returns to 0.1 C again,the discharge capacity remains at 145 m Ah g^-1.In the lithium dendrite suppression ability test,stable battery polarization was maintained for a test time of up to 60,000minutes.In this paper,the introduction ofβ-LiAlSiO₄/LiTaO₃ powder into PVDF-based polymer electrolytes effectively improves the electrochemical performances and safety of PVDF-based solid electrolytes,and provides a reference for the research of composite solid electrolytes at room temperature.