Relevant technical development trend of lithium battery electrolyte 5 New trend analysis

The electrolyte is a conductive ionic conductor between the positive pole and the positive pole of the battery. It is composed of electrolyte lithium salt, high-purity organic solvent, necessary additives and other raw materials in a certain proportion. It plays an important role in the energy density, power density, extensive temperature applications, cycle life and safety performance of batteries.

The electrode material composed of shell, positive electrode, negative electrode, electrolyte and diaphragm is undoubtedly the focus of people's attention and research. But at the same time, electrolyte is also an aspect that can not be ignored. After all, the electrolyte, which accounts for 15% of the battery cost, plays a crucial role in the energy density, power density, wide temperature application, cycle life, safety performance and other aspects of the battery.

Electrolyte is an ionic conductor used to conduct between the positive and negative electrodes of a battery. It is composed of lithium electrolyte and other raw materials, high-purity organic solvents and necessary additives in a certain proportion. With the application of lithium batteries becoming more and more extensive, the requirements of various lithium batteries for their electrolytes are necessarily different.

At present, the pursuit of high specific energy is the biggest research direction of lithium batteries. Especially when mobile devices account for a growing proportion of people's lives, battery endurance has become the most critical performance of batteries.

Negative silicon has a large gram capacity, which has been paid attention to. However, due to its expansion and use, its application has changed its research direction in recent years to negative silicon carbon, which has a high gram capacity and small volume change. Different film forming additives have different effects on the negative cycle of silicon carbon

2. High power electrolyte

At present, it is difficult for commercial lithium electronic batteries to achieve high continuous discharge rate, mainly because the electrode ear of the battery is seriously heated, and the overall temperature of the battery is too high due to internal resistance, which is easy to thermal control. Therefore, the electrolyte should be able to prevent the battery from overheating too fast while maintaining high conductivity. Rapid filling is also an important direction of electrolyte development.

High power battery requires not only high solid phase diffusion of electrode materials, short ion migration path caused by nano crystallization, control of electrode thickness and compactness, but also higher requirements for electrolyte: 1. High dissociation electrolyte salt; 2.2 Solvent compounding - low viscosity; 3. Interface control - low film impedance.

3. Wide temperature electrolyte

At high temperatures, batteries are prone to the decomposition of electrolyte itself and adverse reactions between materials and electrolyte. At low temperature, electrolyte salting out and double increase of negative SEI membrane impedance may occur. The so-called wide temperature electrolyte enables the battery to have a wider working environment. The following figure shows the comparison of boiling points and solidification properties of various solvents.

4. Safety electrolyte

The safety of battery is reflected in combustion and even explosion. First of all, the battery itself is flammable, so when the battery is overcharged, over discharged, short circuited, when the external pin is squeezed, when the external temperature is too high, safety accidents may be caused. Therefore, flame retardant is an important research direction of safe electrolyte.

Flame retardant function is realized by adding flame retardant in conventional electrolyte. Phosphorus based or halogen based flame retardant is generally used. Its price is reasonable and does not damage the performance of electrolyte. In addition, the use of room temperature ionic liquids as electrolytes has also entered the research stage, which will completely eliminate the use of flammable organic solvents in batteries. In addition, ionic liquids have extremely low vapor pressure, good thermal/chemical stability and non flammable characteristics, which will greatly improve the safety of lithium batteries.

5. Long cycle electrolyte

At present, the recovery of lithium battery, especially the recovery of power, still has great technical difficulties, so improving the battery life is a way to alleviate this situation.

Long period electrolyte has two important research ideas. One is the stability of electrolyte, including thermal stability, chemical stability and voltage stability; The other is the stability with other materials, and the electrode film is stable, and the diaphragm is free of oxidation, and the fluid collection is free of corrosion.