Solid and liquid phase conversion mixed electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a solid and liquid phase conversion mixed electrolyte, a preparation method thereof and application thereof. The method comprises the following steps of: adding N-methylimidazole and methylbenzene, raising the temperature under the protection of N2, dropwise adding n-propyl bromide slowly, reacting the components continuously, standing the reaction product to be layered, discarding the methylbenzene solution on the upper layer, washing the yellow solution on the lower layer with methylbenzene, and drying the product in vacuum to obtain yellow thick liquid of 1-methyl-3-propylimidazolium; dropwise adding saturated aqueous solution of KPF6 into the yellow thick liquid slowly, stirring at the room temperature, standing the reaction product to be layered, repeatedly washing the crude product of oily liquid on the lower layer until no Br<1-> exists in the aqueous phase, and dehydrating the residual water to obtain pale-yellow 1-methyl-3-methylimidazolium hexafluorophosphate ionic liquid; and weighing LiPF6, and dissolving the LiPF6 in the liquid to prepare the mixed ionic liquid electrolyte. The electrolyte is in solid phase at low temperature and in liquid phase at high temperature, and can be converted between solid phase and liquid phase along with the change of temperature. The energy density of a lithium air battery prepared from the electrolyte can be improved, the corrosion speed of a lithium cathode can be slowed, and the cyclic times of the battery can be increased.

Description

technical field [0001] The invention relates to electrolyte preparation technology, in particular to a solid-liquid phase conversion mixed electrolyte and its preparation method and application. Background technique [0002] A lithium-air battery is a battery that uses lithium as the anode and oxygen in the air as the cathode reactant. Compared with lithium-ion batteries, it has a higher energy density because its cathode active material O 2 It can be obtained directly from the surrounding air without being stored in batteries. Theoretically, since oxygen is used as the cathode and the reactants are not limited, the capacity of the lithium-air battery depends only on the lithium electrode. At the same time, due to the high theoretical specific capacity of Li, the theoretical specific energy of the lithium-air battery can reach 11,140Wh / kg, This theoretical specific energy is higher than all current conventional power systems. Another major factor that determines the perfor...

AI Technical Summary

Problems solved by technology

Another major factor that determines the performance of lithium-air batteries is the electrolyte, of which solid electrolytes and gel electrolytes have good reliability and no electrolyte leakage, high specific energy, and wide cycle voltage, but the conductivity of most solid electrolytes at room temperature And the solubility is low; the organic electrolyte system is easy to cause the corrosion of the negative electrode lithium due to the use of water-containing organic solvents in the preparation, resulting in a decrease in the specific capacity of the lithium-air battery and a decrease in the charge-discharge efficiency; and the ionic liquid has a wide electrochemical window. Volatile, recyclable and other advantages, the application of new ionic liquids in the electrolyte research of lithium-air batteries has become a multidisciplinary research frontier

However, the ionic liquid currently used in lithium-air batteries only stays in the experimental stage, and it cannot be converted between solid phase and liquid phase with temperature changes. The pure liquid electrolyte makes the corrosion rate of the lithium metal negative electrode too fast, reducing the battery life