Lithium iodide organic electrolyte for lithium iron battery and preparation method thereof

Abstract

The invention discloses lithium iodide organic electrolyte for a lithium iron battery and a preparation method thereof. The organic electrolyte consists of an electrolyte lithium salt, an organic solvent and an additive, wherein the lithium salt is lithium iodide or the mixture of lithium iodide and other lithium salts, the organic solvent is the combination of organic solvents including ethers, sulfones and carbonates, and the additive is the mixture of an additive A and an additive B. The preparation method comprises the following steps of: (1) dehydrating the organic solvent and the additives in a drying environment, and stirring and mixing the organic solvent and the additives into a homogenous liquid; (2) dissolving the lithium salt into the liquid to obtain a semi-finished product; and (3) utilizing a lithium molecular sieve to adsorb and dehydrate the semi-finished product, and filtering the semi-finished product after the adsorption to obtain a finished product. The lithium iron battery which is made of the lithium iodide organic electrolyte not only can reduce the cost, but also can greatly improve the low-temperature discharging performance, high-temperature discharging performance and large-current discharging performance, and can meet the environment-friendly requirement.

Description

technical field [0001] The invention belongs to the field of lithium batteries, and in particular relates to a lithium iodide organic electrolyte and a preparation method thereof. The lithium iodide organic electrolyte is mainly used in lithium-iron batteries (Li / FeS 2 ). Background technique [0002] With the continuous advancement of electronic information technology, consumer electronics products continue to develop toward diversification, miniaturization, and high power, and the performance requirements for batteries are also rapidly increasing. Suitable, easy to use, low self-discharge rate, long storage life, especially put forward higher and higher requirements for the energy density and power density of the battery. [0003] Secondary batteries have been rapidly developed because they can be recharged and reused, but they cannot replace primary batteries because of their low primary capacity, high self-discharge rate, short storage time, poor safety performance, nee...

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Problems solved by technology

[0003] Secondary batteries have been rapidly developed because they can be recharged and reused, but they cannot replace primary batteries because of their low primary capacity, high self-discharge rate, short storage time, poor safety performance, need to be recharged after use, unstandardized models, and poor versatility. , while the primary battery has the advantages of high primary capacity, extremely low self-discharge rate (can be stored at room temperature for 5-10 years), slow discharge level, and good model standardization and versatility. In recent years, due to the increasing market demand, it has developed rapidly , will still occupy a dominant position in the battery market in the 21st century

[0015] Second, due to the low dielectric constant of ethers, higher ether content will lead to low conductivity of the electrolyte, which will lead to a decline in the performance of lithium-iron batteries when they are discharged at high currents. This is also the case with lithium iodide electrolytes. Another reason why the amount of ether solvents used in a solvent blend must be controlled

[0016] Third, in the presence of oxides or in a high-temperature environment, ether solvents are susceptible to oxidation and polymerization. This phenomenon is particularly obvious on ethylene glycol dimethyl ether and 1,3-dioxane, and the colloidal polymerization product It will cause the viscosity of the electrolyte to increase significantly, and the electrolyte will eventually become an oily viscous liquid as time goes by, which will lead to a significant decrease in the conductivity of the electrolyte, a sharp decline in battery performance, or even complete scrapping

[0017] Fourth, the boiling points of ethers are generally low (the boiling point of ethylene glycol diethyl ether is 96°C, the boiling point of ethylene glycol dimethyl ether is 85°C, and the boiling point of 1,3-dioxane is 76°C). When stored or used under high temperature, the ethers in the electrolyte are easy to volatilize and produce a large amount of steam at high temperature, resulting in a significant decline in the high-temperature storage and discharge performance of the lithium-iron battery, and the excessive internal pressure of the battery caused by steam has a negative impact on the safety performance of the lithium-iron battery. will also have some impact

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