Construction And Performance Of All-solid-state Ionic-liquid-crystal Based Two Dimentional Li-ion Conducting Channels

Liquid crystal is a substance that has both liquid flow and crystal ordering,and ionic liquid as a green solvent with excellent flame retardancy and thermal stability has attracted the interest of many researchers worldwide.Ionic liquid crystal combines the dual characteristics of ionic liquid and liquid crystal,it shows better ionic conductivity,thermal stability,self-assembly performance and flame retardancy.so,great application potential in the fields of energy storage and electronic components such as smart display windows,solar cells,lithium ion secondary batteries,etc.Among many ionic liquids,imidazole-based ionic liquids are a widely studied type,so they are often introduced into the molecular design and construction of ionic liquid crystals.However,as far as we know,there have been no reports about imidazole-based ionic liquid crystals being applied to lithium salts of lithium ion batteries（lithium cations are introduced into ionic liquid crystal molecules to prepare new lithium salts）.In this paper,we use 4,5-dimethylol-2-phenyl-1-H imidazole,C₁₂H₂₅Br,H₃BO₃,and Li OH·H₂O as the main raw materials,three kinds of ionic liquid crystal lithium salts with different anions were synthesized through substitution reaction on the imidazole ring and anion exchange,namely Li-Br,Li-CF₃SO₃,Li-BOB,then according to the two-dimensional ordering of ionic liquid crystals（controllable ion-conducting channels）,isothermal crystallization and self-assembly of synthesized lithium salts at different times are used to construct a series of all-solid-state ionic liquid crystal-based"fast lithium ion conduction channels"with different thicknesses.The physical and electrochemical properties of this series of lithium salts were systematically studied.The following main conclusions were reached:（1）Three kinds of ionic liquid crystal lithium salts also have good thermal stability.The thermal decomposition temperature is above 210°C,and the smaller the anion radius in the lithium salt molecules,the better the thermal stability.（2）Three ionic liquid crystal type lithium salts can successfully build lithium ions in lithium salts“two-dimensional high-speed transmission channels”with self-assembly method by isothermal crystallization.and within a certain temperature range,as the isothermal crystallization temperature decreases and the time increases,the"two-dimensional high-speed transmission channel"of lithium ions becomes thicker.（3）The successful construction of"two-dimensional high-speed transmission channels"for lithium ions in three ionic liquid crystal type lithium salts can improve the electrochemical performance of lithium salt electrolytes.In particular,Improved ionic conductivity and Li-ion transference number and reduced activation energy for lithium ion migration.Among them,the ionic conductivity of lithium salt can reach the order of 10^-4S cm^-1 at 30°C and 10^-3 at 50°C S cm^-1 order of magnitude.The number of lithium ion migration can be increased to 0.6,and the activation energy of lithium ion migration can be reduced to 0.22e V.However,the"two-dimensional high-speed transmission channel"of lithium ions in the lithium salt cannot change the electrochemical stability window,which has been maintained above 5.8V.