Synthesis And Ionic Conductivity Study Of Quaternary Ammonium Camphorsulfonate,Quinuclidine And Quinuclidinol-Based Plastic Crystals

Advanced energy storage technology is one of the effective solutions to solve the sustainable use of energy and energy shortage.The advanced battery represented by secondary lithium battery is an important direction of energy storage technology research.The traditional lithium-containing organic solvent as electrolyte will cause serious safety problems such as overheating and fire,so the research and development of solid electrolyte is a scientific problem to be solved urgently.Organic ionic plastic crystals（OIPCs）,due to their high thermal stability,wide electrochemical window,plasticity and fast transmission of doped ions,are expected to become the most potential solid ionic conductors that can solve the safety problems of batteries.However,organic ionic plastic crystals have problems such as low ionic conductivity,unclear conduction mechanisms,and unclear key factors that determine ionic conductivity.Therefore,revealing the decisive factors for ionic conductivity of organic ionic plastic crystals and improving ionic conductivity are urgent scientific issues in the research of all solid-state batteries.In this experiment,spherical and near-spherical monovalent anions and cations are used as crystallographic ions to synthesize organic ionic plastic crystals in solution.The structure,thermal behavior,stability,kinetic parameters and ionic conductivity of the synthesized organic ionic plastic crystals are characterized.According to the relationship between them,the formation rules of the plastic crystals are explored,and the ionic conduction mechanism and the methods to improve ionic conductivity are revealed.The main research contents and results are as follows:（1）An organic ionic plastic crystal diethyldimethylammonium 10-camphorsulfonate(L/DL-[N₁₁₂₂][CSA])is synthesized.The results show that there is a solid phase transition in L-and DL-[N₁₁₂₂][CSA].After doping with different concentrations of[N₁₁₂₂]F and[N₁₁₂₂]Cl,the solid-solid phase transition temperature of the doped mixture is similar to that of the undoped material;L-and DL-[N₁₁₂₂][CSA]are monoclinic crystals in the low temperature phase.After entering the high temperature phase,they change into a more symmetrical crystal structure;¹H NMR spectra shows that the half-peak width of L-and DL-[N₁₁₂₂][CSA]is significantly narrowed after entering the plastic crystalline phase,and the crystalline ions rotate at high speed;The mixture of L/DL-[N₁₁₂₂][CSA]doped with[N₁₁₂₂]F and[N₁₁₂₂]Cl shows high ionic conductivity,among which the ionic conductivity of the mixture doped with[N₁₁₂₂]F is significantly improved,4～5 orders of magnitude higher than that of pure materials.（2）An organic ionic plastic crystal quinuclidinium triflate（[HQ]Tf）is synthesized.The results show that[HQ]Tf has a solid-solid phase transition at about 5°C.After doping with different concentrations of Li Tf or[3-O-QH]Cl,the phase transition temperature is similar to that of the pure product;[HQ]Tf has a triclinic structure in the low temperature phase and a cubic structure in the plastic phase;¹H and ¹⁹F NMR show that the crystalline ions of[HQ]Tf move freely in the plastic phase;The conductivity of the mixture doped with Li Tf and[3-O-QH]Cl has increased to varying degrees compared to the pure product,with a maximum increase of 1 order of magnitude.Ion conduction is related to its phase behavior,so the conduction of Li⁺and Cl^-is completed through crystal phase.（3）An organic ionic plastic crystal quinuclidinol hydrochloride（（±）/（–）-[3-OH-QH]Cl）is synthesized.The results show that（±）-[3-OH-QH]Cl and（–）-[3-OH-QH]Cl show different thermal behaviors,and the phase transition temperature of the racemate is obviously reduced.Variable-temperature XRD shows that（±）/（–）-[3-OH-QH]Cl changes into a more symmetrical structure at high temperature;PFG NMR measurement shows that the interaction between anion and cation in（±）-[3-OH-QH]Cl is stronger than that in（–）-[3-OH-QH]Cl,and its anion kinetics and cation kinetics are highly coupled;After doping Li Cl with（±）-and（–）-[3-OH-QH]Cl,the conductivity of the mixture increases to varying degrees,and after doping Li Cl with（–）-[3-OH-QH]Cl,the conductivity increases by 4～10 times compared to the pure product.The conductivity of（±）/（–）-[3-OH-QH]Cl and the mixture doped with Li Cl is related to the phase transition,so the ion conduction is completed through the crystal phase.