Analysis of five trends in the development of the

2022-10-14
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Analysis of five major trends in the development of lithium battery electrolyte

Abstract: due to the increasingly extensive application fields of lithium batteries, the requirements of all kinds of lithium batteries for their electrolyte are bound to be different

: electrolyte is an ionic conductor that plays a conductive role between the positive and negative electrodes of the battery. It is composed of electrolyte lithium salt, high-purity organic solvent and necessary additives in a certain proportion. It plays a vital role in the energy density, power density, wide temperature application, but also risks, cycle life, safety performance, etc. of the battery

lithium battery is composed of shell, positive electrode, negative electrode, electrolyte and diaphragm, among which electrode material is undoubtedly the focus of attention and research. But at the same time, electrolyte is also an aspect that cannot be ignored. After all, electrolyte, which accounts for 15% of the battery cost, does play a crucial role in the energy density, power density, wide temperature application, cycle life, safety performance and so on

electrolyte is an ionic conductor that plays a conductive role between the positive and negative electrodes of the battery. It is composed of electrolyte lithium salt, high-purity organic solvent and necessary additives in a certain proportion. As the application fields of lithium batteries are more and more extensive, the requirements of various lithium batteries for their electrolyte are bound to be different. Next, we will analyze the development trend of electrolyte, which is the key raw material of lithium battery

1. In the first three quarters, the fixed asset investment was 3.45 billion yuan. The pursuit of high specific energy electrolyte is the largest research direction of lithium-ion batteries at present, especially when mobile devices occupy an increasing proportion in people's lives. Battery life has become the most critical performance of batteries

picture source: Beijing Institute of chemical reagents

as shown in the figure, the development of high-energy density batteries in the future must be high-voltage cathode and silicon cathode. The negative silicon has a huge gram capacity and is concerned by people, but it cannot be applied due to its swelling effect. In recent years, the research direction has changed to silicon carbon negative electrode, which has a relatively high gram capacity and small volume change. Different film-forming additives have different circulating effects on silicon carbon negative electrode

picture source: Beijing Institute of chemical reagents

2. High power electrolyte

at present, commercial lithium electronic batteries are difficult to achieve high rate continuous discharge, mainly due to the serious heating of the battery ears, and the internal resistance leads to the overall temperature of the battery is too high, which is prone to thermal runaway. Therefore, it is necessary that the electrolyte can inhibit the rapid temperature rise of the battery while maintaining high conductivity. For power batteries, fast charging is also an important direction of electrolyte development

high power batteries not only put forward requirements for electrode materials, such as high solid-phase diffusion, short ion migration path due to nanocrystallization, control of electrode thickness and compaction, but also put forward higher requirements for electrolyte: 1. Electrolyte salt with high dissociation; 2. Solvent compounding - lower viscosity; 3. Interface control - lower membrane impedance

3. Wide temperature electrolyte

battery is prone to decomposition of electrolyte itself and aggravation of side reactions between materials and electrolyte parts at high temperature; At low temperature, electrolyte salting out and the impedance of negative SEI membrane may increase exponentially. The so-called wide temperature electrolyte is to make the battery have a broader working environment. The following figure shows the boiling point comparison diagram and solidification comparison diagram of various solvents

picture source: Beijing Institute of chemical reagents

4. Safety electrolyte

the safety of the battery is mainly reflected in combustion and even explosion. First of all, the battery itself is flammable. Therefore, when the battery is overcharged, over discharged and short circuited, when it receives external acupuncture and extrusion, and when the external temperature is too high, safety accidents may be caused. Therefore, flame retardancy is a main research direction of safe electrolyte

the flame retardant function is obtained by adding flame retardant additives to the conventional electrolyte. Generally, phosphorus or halogen flame retardants are used. The flame retardant additives are required to be reasonable in price and do not damage the performance of the electrolyte. In addition, the use of room temperature ionic liquids as electrolyte has also entered the research stage, which will completely eliminate the use of flammable organic solvents in batteries. Moreover, ionic liquids have the characteristics of extremely low vapor pressure (2) backward process technology, good thermal/chemical stability and non flammability of automobile parts manufacturers, which will greatly improve the safety of lithium-ion batteries

5. Long cycle electrolyte

because there are still great technical difficulties in the recovery of lithium batteries, especially power batteries, improving the service life of batteries is a way to alleviate this situation

the research idea of long cycle electrolyte mainly has two points: first, the stability of electrolyte, including the thermal electronic universal experimental machine, which is mainly used for the experimental stability, chemical stability and voltage stability of mechanical properties of metals, nonmetals, composites and products; The second is the stability with other materials, which requires stable film formation with the electrode, no oxidation with the diaphragm, and no corrosion with the collector

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