How to solve the problem between the high nickel material of the lithium battery and the electrolyte?

These problems arising from the use of high-nickel materials in combination with electrolytes are complicated to solve and have high technical thresholds. If the company does not have sufficient research and development capabilities, it is difficult to make electrolyte products that match high nickel materials.

1. High specific energy electrolyte

The pursuit of high specific energy is currently the biggest research direction of lithium-ion batteries, especially when mobile devices occupy more and more people's lives, and the battery life is the most critical performance of batteries.

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Image 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 positive electrodes and silicon negative electrodes. The negative silicon has a large gram capacity and has attracted attention. However, due to its own swelling effect, it has not been applied. In recent years, the research direction has been changed to a silicon carbon negative electrode, which has a relatively high gram capacity and a small volume change. The film forming additive has different cycling effects in the silicon carbon negative electrode.

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Image source: Beijing Institute of Chemical Reagents

2, high power type electrolyte

At present, it is difficult to achieve high-rate continuous discharge of commercial lithium-ion batteries. The main reason is that the battery ear is extremely hot, and the internal resistance of the battery is too high, which is prone to thermal runaway. Therefore, it is required that the electrolyte can suppress the temperature rise of the battery too fast while maintaining high conductivity. For power batteries, achieving fast charging is also an important direction for the development of electrolytes.

High-power batteries not only require high solid-phase diffusion, nano-imprinting, short ion migration path, control electrode thickness and compaction, but also put forward higher requirements for electrolyte: 1. High dissociation electrolyte Salt; 2, solvent compounding - lower viscosity; 3, interface control - lower membrane impedance.

3, wide temperature electrolyte

When the battery is at a high temperature, the decomposition of the electrolyte itself and the side reaction of the material and the electrolyte are prone to increase; at low temperatures, electrolyte salt precipitation may occur and the impedance of the negative SEI film may be multiplied. The so-called wide temperature electrolyte is to make the battery have a wider working environment. The figure below shows the boiling point comparison chart and solidification comparison chart of various solvents.

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Image source: Beijing Institute of Chemical Reagents

4, safety electrolyte

The safety of the battery is mainly reflected in the burning or even the explosion. Firstly, the battery itself is flammable. Therefore, when the battery is overcharged, overdischarged, or short-circuited, when the external acupuncture and extrusion are received, when the outside temperature is too high, all may cause a security incident. Therefore, flame retardancy is a major direction in the study of safe electrolytes.

The flame retardant function is obtained by adding a flame retardant additive to a conventional electrolyte. Generally, a phosphorus-based or halogen-based flame retardant is used, and the flame-retardant additive is required to be reasonably priced and does not impair the electrolyte performance. In addition, the use of room temperature ionic liquids as electrolytes has also entered the research stage, and the use of flammable organic solvents in batteries will be completely eliminated. And the ionic liquid has the characteristics of extremely low vapor pressure, good thermal stability/chemical stability, and non-flammability, which will greatly improve the safety of the lithium ion battery.

5, long circulating electrolyte

Due to the current technical difficulties in the recovery of lithium batteries, especially the recovery of power batteries, improving battery life is one way to alleviate this situation.

There are two main research ideas for long-circulating electrolytes. One is the stability of the electrolyte, including thermal stability, chemical stability, and voltage stability. Second, the stability with other materials requires stable film formation with the electrode. No oxidation with the diaphragm, no corrosion with the current collector.

The page contains the contents of the machine translation.