As an important part of lithium-ion batteries, the electrolyte lithium salt can not only provide free shuttle ions for lithium-ion batteries and assume the role of transmitting ions inside the battery. At the same time, the electrolyte can also form a protective layer on the surface of the electrode material, which to a large extent determines the capacity, operating temperature, cycle performance, power density, energy density and safety of lithium-ion batteries.

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Components of Lithium Battery Electrolyte

The electrolyte is mainly composed of three parts, mainly solvents, lithium salts, and additives. Among these components, although the amount of additives added is still small compared with other components, there are the largest types of additives that can be added to a serving of electrolyte.

Lithium salt

High-quality lithium salts have a greater impact on the energy density, power density, wide electrochemical window, cycle life, and safety performance of lithium batteries. The elements commonly contained in lithium salts are LiPF6, LiClO4, LiBF4, LiAsF6, etc.

solvent

The role of the solvent in the electrolyte is mainly used to dissolve the lithium salt. The solvents in the electrolyte are mainly cyclic carbonates (PC, EC); chain carbonates (DEC, DMC, EMC); and carboxylates (MF, MA, EA, MA, MP, etc.).

Additive

There are many types of additives, and different additives have different effects. Although the added components are small, they have different effects on the performance of lithium battery packs. The main types of additives are film additives, conductive additives, flame retardant additives, overcharge protection additives, additives that control the content of H2O and HF in the electrolyte, additives that improve low temperature performance, and multifunctional additives.

The electrolyte has a significant impact on the overall performance of lithium batteries. As the blood of lithium-ion batteries, the electrolyte bears the heavy responsibility of transporting lithium-ion batteries. Its quality will directly affect the performance of lithium-ion batteries.

What is Lithium Salt?

Electrolyte lithium salt is an important part of the electrolyte of lithium-ion batteries. At present, lithiumLiPF6-carbonate electrolyte is widely used in the market. LiPF6 has the advantages of good solubility, high ion conductivity, and high ion dissociation, but it has poor thermal stability and is easy to hydrolyze to produce HF, which is an important cause of battery performance attenuation. Therefore, in recent years, people have been working hard to find a new type of lithium salt with better performance to replace the traditional lithium salt LiPF6.

What is the Function of Lithium Salts?

１．Improve the conductivity of the electrolyte and the number of lithium ion migrations
２．Enhance the ion conductivity of the electrolyte
３． Reduce the impedance of the electrode surface film to form a stable film with good ion conductivity

How Many Kinds of Lithium Salts?

Here are mainly eight kinds of lithium salts used in lithium ion battery electrolyte: LiPF6 liBF4 LiClO4 LiBOB LiDFP Liodfb liFSl LiTFSl

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Detailed Introduction on Lithium Salts

LiPF6

Dosage

1. Generally around 1.2M, the electrolyte has the highest electronic conductivity
2. More than 1M is conducive to long life cycle
3. The battery capacity below 0.8M is obviously low
4. Usage: 1.0M-1.4M

LiBOB

Dosage:

1. When added to the electrolyte, the acidity will rise
2. Enhance the circulation of lithium manganese acid and inhibit expansion
3. The negative electrode is stable in film formation and can be used in PC solvents to broaden the battery temperature range.
4. It is conducive to circulation in lithium iron batteries
5. Within 1% of usage

LiBF4

Dosage

1.The high temperature performance is better than that of BOB, and the low temperature performance is better
2.Within 0.5% of usage

LiODFB

３．The negative electrode film formation is stable and the impedance is small. The main reason is that the F atom on the ODFB optimizes the structure of the SEI and shortens the length of the polymer chain formed, forming a SEI that is conducive to lithium ion de-embedding.

Dosage

1.The high-pressure system is used more, and the combination with other additives has a better effect.
2.Affect the acidity test of the electrolyte
3.Within 1% of usage

LiTFSl

Dosage

1. Lithium iron phosphate and ternary system, play a role
2. In the primary high-end battery, the high and low temperature performance, safety performance and capacity are greatly superior to the traditional LICLO II battery.
3. Control usage within 1.5%

LiFSI

Dosage

1. Increase the magnification, and the magnification will not decrease under high temperature storage
2. Improve low temperature performance
3. Within 1.5% of usage

LiDFP

Dosage

1. Increase the ternary high temperature cycle, within 1% of the usage
2. It is better to form a film with DTD, VC, FEC, etc.
3. Improve circulation in high-nickel and silicon-carbon electrolytes

LiClO4

Dosage:

1. Low temperature performance is better than LiPO2F2
2. The general usage is within 1.0%, and it has a similar effect to lithium LiPO2F2.

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Is Lithium Salts safe?

No, it isn’t. It is the most dangerous substance in lithium battery electrolyte, especially LiPF6. If your lithium ions battery leak, please stop using it and let professional people handle it as soon as possible. Try to avoid lithium battery leakage, you’d better choose branded batteries.

Harm of Lithium Battery Electrolyte to Human Body

Lithium electrolyte can be absorbed by mouth, nose and skin.

Once electrolyte is been absorbed, people will get headache, dizziness, nausea and difficulty breathing. Liquids or high-concentration vapors are irritating. Oral stimulation of the gastrointestinal tract. Long-term repeated contact with the skin is irritating.

Harm of Lithium Battery Electrolyte to Environment

In case of open flame and high heat, there is a risk of combustion because it is flammable.

Its vapor is heavier than air. It can spread to a considerable distance at a lower level, which will cause back-burning in case of an open flame.

Emergency treatment of leakage

1. Quickly evacuate personnel from the leaking contaminated area to the safe area, isolate them, and strictly restrict access.
2. Cut off the source of the fire.
3. It is recommended that emergency peoplewear self-contained positive pressure respirators and wear fire-fighting protective clothing.
4. Cut off the source of leakage as much as possible. Prevent access to restricted spaces such as sewers and drainage ditches.

Small amount of leakage: absorbed by water or other inert materials. It can also be scrubbed with an emulsion made of a non-flammable dispersant, and the lotion is diluted and placed in the wastewater system.Large-scale leakage: build an embankment or dig a pit to contain it. Cover with foam to reduce the risk of vapor. Transfer to a tank truck or special collector with an explosion-proof pump, recycle or transport to a waste treatment site for disposal.

First aid measures

Skin contact:Immediately remove contaminated clothing and rinse with plenty of flowing water for at least 15 minutes. Seek medical attention.

Eye contact: Lift the eyelids and rinse with flowing water or saline. Seek medical attention.

Inhalation: Quickly leave the scene to a place with fresh air. Keep the respiratory tract unobstructed. If you have difficulty breathing, give oxygen. If breathing stops, perform artificial respiration immediately. Seek medical attention.

Ingestion:Those who take it by mistake gargle with water and drink milk or egg white. Seek medical attention.

As an important part of lithium batteries, the electrolyte lithium salt not only plays a role in providing and transmitting lithium ions, but also determines the overall performance of this lithium battery to a certain extent. A detailed understanding of the advantages and disadvantages of existing lithium electrolyte salts has a good reference and promotion effect for the development of new lithium electrolyte salts.

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