88840-42-0

The safety of Li-ion batteries is one of the most important factors, if not the most, determining their practical applications. We have found that free carbonate-based solvent molecules in the hybrid electrolyte system can cause severe safety concerns. Mixing ionic liquids with a carbonate-based solvent as the co-solvent at a fixed salt concentration of 1 M LiPF6 can lead to free carbonate-based molecules causing poor charge storage performance and safety concerns.

The invention discloses a method for preparing piperidine type ionic liquid. The preparation method comprises the following steps of adding bromopropane into ethyl acetate, then adding N-methyl piperidine for a reaction for 8-48 h, eluting a solid phase with acetone, and performing rotary evaporation to obtain an intermediate product; dissolving the intermediate product in water, adding lithium trifluoromethanesulfonimide, washing an organic phase with water after extraction and liquid separation, and conducting rotary steaming and drying to obtain a final product. Meanwhile, the invention also discloses the piperidine type ionic liquid prepared by the method and application of the piperidine type ionic liquid as an electrolyte component of a lithium ion battery. The preparation method isimplemented at the normal temperature and has the advantages of being high in yield, economical and simple in operation. The piperidine type ionic liquid has the advantages of high purity, low water content, low viscosity, high conductivity and wide electrochemical window. The piperidine type ionic liquid prepared by the method is used as the electrolyte component to be applied to an electrolyte of the lithium ion battery and shows better inflammability and chemical stability and lower electrochemical impedance.

A fluoride ion battery includes a substantially lithium-free anode and cathode. At least one of the anode or cathode contains fluorine, and a substantially lithium-free liquid electrolyte is used for charge transport. The electrolyte is liquid at temperatures below about 200 degrees Celsius, and can be formed from an organic-soluble fluoride salt dissolved in selected classes of solvents.

Three analogue N-heterocyclic complexes, 1-propyl-1-methylpiperidinium perchlorate (1, [PMpip][ClO4]), 1-cyanomethyl-1-methylpiperidinium perchlorate (2, [CMpip][ClO4]), and 1-cyanomethyl-1-methylmorpholinium perchlorate (3, [CMmor][ClO4]) are identified as phase transition materials displaying switchable dielectric behaviors. Despite the common [ClO4]- anion and the closely related cations, compound 1 crystallizes in the orthorhombic space group P212121, but compounds 2 and 3 belong to the monoclinic space group P21/n with distinct cell dimensions. Compounds 1, 2 and 3 undergo reversible phase transitions around 199, 387 and 416 K, respectively, accompanied by notable step-like dielectric anomalies which could be switched by the phase transition and be tuned in distinct dielectric states. The respective dielectric constants in the high dielectric states are 1.2, 2.2 and 3.2 times that in the low dielectric states for compounds 1, 2 and 3. Generally, these differences in the phase transitions and dielectric properties are caused by the distinct molecular structures and hydrogen-bonding conformations resulting from the structural variations in the side-chain and the ring structure.

A stable hydrophobic ionic crystalline solid comprised of the N-propyl-N-methylpiperidinium cation and hexafluorophosphate anion PP 13PF6 exhibits a remarkably wide electrochemical window of 7.2 V. This high purity crystalline ionic salt has versatility for use as an electrolyte in the electrodeposition of reactive metals such as tin. Moreover, this ionic salt can be used as a solid state electrolyte in Li-ion batteries. Theoretical calculations indicate that this solid state electrolyte has vacant sites that are preferential for Li-ion conductivity with an energy barrier of 0.4 eV. Further, the ionic crystals exhibit molecular rotations which facilitate facile Li-ion transport.

Ionic liquids based on methylpropylpyrrolidinium (MPPY) and methylpropylpiperidinium (MPPI) cations and bis(trifluoromethanesulfonyl)imide (TFSI) anion have been synthesized and characterized by thermal analysis, cyclic voltammetry, impedance spectroscopy as well as galvanostatic charge/discharge tests. 10 wt% of vinylene carbonate (VC) was added to the electrolytes of 0.5 M LiTFSI/MPPY.TFSI and 0.5 M LiTFSI/MPPI.TFSI, which were evaluated in Li || natural graphite (NG) half cells at 25 °C and 50 °C under different current densities. At 25 °C, due to their intrinsic high viscosities, the charge/discharge capacities under the current density of 80 μA cm-2 were much lower than those under the current density of 40 μA cm-2. At 50 °C, with reduced viscosities, the charge/discharge capacities under both current densities were almost indistinguishable, which were also close to the typical values obtained using conventional carbonate electrolytes. In addition, the discharge capacities of the half cells were very stable with cycling, due to the effective formation of solid electrolyte interphase (SEI) on the graphite electrode. On the contrary, the charge/discharge capacities of the Li || LiCoO2 cells using both ionic liquid electrolytes under the current density of 40 μA cm-2 decreased continually with cycling, which were primarily due to the low oxidative stability of VC on the surface of LiCoO2.

Room temperature ionic liquids (RTILs) with high safety characteristic usually have high viscosity and melting point, which is adverse for the application of RTIL-based electrolytes in Li-ion batteries. In this investigation, a promising RTIL, i.e. PP13TFSI consisting of N-methyl-N-propylpiperidinium (PP13) cation and bis(trifluoromethanesulfonyl)imide (TFSI) anion is synthesized. The effect of the content of Li salt in the electrolytes containing PP13TFSI and LiTFSI on the ionic conductivity and cell performance is investigated. The electrolyte of 0.3 mol kg-1 LiTFSI/PP13TFSI is recommended for its higher lithium transference number and discharge capacity in the LiCoO2/Li cell than other electrolytes. In addition, it is found that, by introducing 20% diethyl carbonate (DEC) as a co-solvent into pure RTIL electrolyte, the rate capability and low-temperature performance of the LiCoO2/Li cells are improved obviously, without sacrificing its safety characteristics. It suggests that a component with low viscosity and melting point, i.e. DEC, is necessary to effectively overcome the shortcomings of RTIL for the application in Li-ion batteries.

The replacement of N-methyl of N-methylpiperidine (1), 4-methylmorpholine (4), 2-methyl-1,2,3,4-tetrahydroisoquinoline (7) and tropine (10) by n-propyl, n-butyl and isopropyl groups (3a-3c, 6c, 9a-9c and 12a-12c) has been achieved in high yields by quaternization of the respective tertiary amine with appropriate alkyl halide and demethylation of the resulting quaternary salt with thiophenoxide.It has been established that demethylation is strongly favoured over the removal of n-propyl and n-butyl groups, whereas deisopropylation occurs to some extent.Surprisingly, in the case of 11c, deisopropylation predominates.This method has been applied to morphine (13b), codeine (13d) and thebaine (14b) for similar replacements.The rapid quaternization of thebaine (14b) has been assigned to the absence of H-14 in this alkaloid.The fact that quaternary salts of thebaine, which are susceptible to aromatization of the nucleus by extrusion of the ethanamine chain, are smoothly demethylated to N-alkylnorthebaines (18a-18c) in good yields indicates that demethylation, a bimolecular nucleophilic displacement, competes very successfully with elimination reaction.

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