Preparation And Performance Study On Lithium-ion Battery Polymer Ceramic Composite Electrolyte

With the development of science and technology,energy storage devices are widely used in our daily life.All-solid-state battery has a bright future because of its safety,low cost and high energy density.At present,the disadvantages of inorganic solid electrolyte in solid electrolyte are that the interface between electrode and solid electrolyte is brittle and the compatibility between electrode and solid electrolyte is poor,while the mechanical properties of polymer are good and the compatibility between electrode and solid electrolyte is excellent,but the ionic conductivity and migration number are not high.To sum up,the composite solid electrolyte was prepared by combining polymer and inorganic ceramic to obtain the solid electrolyte with soft texture,good electrode/electrolyte interface compatibility and stronger ability of ion transport,promote the commercialization of solid electrolyte and solve its application problems.In this study,we try to add inorganic ceramics to provide more channels for Li⁺transport,and the ceramics are active ceramics,which can introduce more movable Li⁺into solid electrolyte and enhance its ion transport ability,ceramic powders also reduce the crystallinity of polymers and improve the mechanical properties of solid electrolytes.Firstly,the pure PVDF based solid-state battery and its Li₂W₂O₇composite solid-state battery were tested.Li₂W₂O₇is composed of Li O₄tetrahedra and WO₆octahedra,which can provide more channels for Li⁺transport.The addition of Li₂W₂O₇powder can improve the ability of solid-state electrolyte to transport lithium ions.After1500 cycles,the battery still had a specific capacity of 65 m Ah/g,and at the surface current density of 2C,at room temperature,the ionic conductivity was 9.8×10^-4S/cm,and the ionic migration number was increased to 0.31.The addition of LI₂W₂O₇powder can change the crystallinity of polymer,improve the mechanical properties of solid electrolyte,increase the tensile deformation rate to 347%,and the stress at fracture is8.32 Mpa.At the same time,the electrochemical properties of Li₂W₂O₇composite solid electrolyte such as electrochemical window and impedance spectroscopy were also improved.Secondly,the study is carried out around the LiAlSiO₄fast ion conductor,where Al atoms replace some Si atoms in Si O₂,and the spatial structure changes from Si O₄tetrahedra to Si O₄tetrahedra and Al O₄tetrahedra,the LiAlSiO₄powder has good ionic conductivity.When solid electrolyte is added,lithium ions can be used as conductive ions.The ionic conductivity increases with the increase of the amount of conductive ions,the ionic conductivity of LiAlSiO₄solid electrolyte at room temperature is 9×10^-4S/cm,the ionic mobility is 0.27,and the capacity of LiAlSiO₄solid electrolyte is above65 m Ah/g after 500 cycles,and the surface current density of 2C,the specific capacity can be over 100 m Ah/g,the internal polarization impedance increment is small,the charge-discharge performance is stable,and the LiAlSiO₄powder is introduced into the solid electrolyte system,the increase of Li⁺content in the system leads to the improvement of its performance.The addition of powder decreases the crystallinity of polymer,the mechanical properties of solid electrolyte,the tensile deformation rate increases to 234%,the stress at fracture is 7.32 Mpa,and the lithium dendrite can still circulate normally after breaking 400 hours,the ability of lithium dendrite resistance was enhanced obviously,and the mechanical properties of solid electrolyte were improved.