In the previous series, as long as the inspection process of the four main materials was introduced, the series will start to trace the source, starting from the preparation process and process of raw materials, and introducing the production process of the four main materials. As the "blood" of lithium-ion battery, the electrolyte, which bears the heavy responsibility of conducting lithium ions, is the key to obtaining high energy density and low impedance of lithium-ion batteries. This series starts from the process of electrolyte production and begins to gradually Expand and introduce the production process of the four main materials.
1, the preparation of the solvent:
For cyclic or chain esters such as EC, DEC, PC, and DMC, the following is a brief introduction to the preparation process of the solvent using EC as an example.
The earliest method for preparing EC was to use ethylene glycol and phosgene reaction, but the process plant, low yield and cost, serious pollution, has been eliminated.
The transesterification method produces EC, the reaction rate is increased, and the yield is also improved.
The halohydrin method, the ethylene and carbon dioxide synthesis methods all have problems such as complicated reaction and complicated process.
Urea alcoholysis method: Because the reaction is simple, the raw materials are cheap, unreacted ethylene glycol can be recycled, and the economy is obvious, which has a good development prospect.
Other chemical raw materials are prepared in a similar manner and are not described in detail herein.
2, purification:
The purification treatment of the organic raw materials used has reached the standard for the use of lithium ion battery electrolytes. Here, the items to be inspected include purity, water content, and main content.
3, LiPF6:
At present, there are mainly four methods, namely gas-solid phase method, hydrogen fluoride solvent method, organic solvent method and ion exchange method.
The gas-solid phase method has high purity, but the raw material cost is high, the process is too much, and continuous production is difficult.
The hydrogen fluoride solvent method has a high reaction speed and high efficiency, but has HF production, and has high requirements on the corrosion resistance of the reaction container.
The organic solvent method avoids the generation of HF, and the operation is relatively safe, but PF5 still needs to be prepared and has strong corrosiveness.
The ion exchange method avoids the disadvantage of using PF6 as a raw material, but the alcohol-based lithium and ammonia used are reacted, and the raw materials are expensive, and it is difficult to achieve industrial production.
For the final use of LiPF6, refining is also required, and the purity requirements of the electrolyte have been reached.
4. Due to the sensitivity of the electrolyte, the packaging drum also needs to be pretreated, washed with water, replaced with argon gas, etc. to ensure its drying and no impurities.
5, the next generation of electrolyte outlook
1) In the 3C field, due to the development of mobile phones, tablets and wearable devices, small battery electrolytes emphasize high energy density and develop toward high voltage;
2) In large areas, it is necessary to balance the requirements of conductivity, high and low temperature, low cost and long life;
3) In other respects, due to the increase of energy density, the high pressure of the anode material is required. Therefore, the wettability, film formation stability and cycle stability of the electrolyte need to be deeply considered. With the wide use of silicon materials, the relevant applies to The electrolyte of silicon system has also become a hot topic in the research of literature; based on safety considerations, flame retardant additives, positive and negative surface protection additives under high voltage and composite functional additives have become hot topics.
Summary: This article mainly introduces the industrial production method of electrolyte and some synthetic methods of raw materials. It should be noted that although the electrolyte production process seems relatively simple, it is environmental, temperature and humidity, and impurities. Control is strictly required. In actual production, this kind of situation often occurs. The composition of several electrolytes is exactly the same, but the electrical performance is very far. The reason is that the raw material purity is a large part. Impure or the electrolyte contains a certain amount of impurities, so in actual production, the environmental control in the production process must be.
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