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What requirements should lithium-ion battery electrolytes meet?

Writer: admin Time:2019-09-18 03:19:22 Browse:103℃

Electrolytes are compounds that are soluble in aqueous solutions or can conduct electricity on their own in a molten state, and can dissociate into freely moving ions when dissolved in water or heated. Electrolytes are an important component of lithium-ion batteries, playing a role in transporting ions and conducting current between the positive and negative poles.

Electrolyte, as a key material in lithium-ion batteries, affects and even determines the specific energy, lifespan, safety performance, and rate charging and discharging performance of the battery. As a practical electrolyte for lithium-ion batteries, the following conditions should be met:

1. Lithium ion conductivity: The electrolyte does not have electronic conductivity, but must have good ion conductivity. Within the general temperature range, the conductivity of the electrolyte is within 1 × 10-3~2 × Between 10-3S/cm. As an electrolyte, it must have excellent ionic conductivity and electronic insulation, so that it can play the role of ion transport medium, and reduce its own self-discharge.

2. Ion migration number: The internal transport charge of a lithium battery depends on the migration of ions. High ion migration numbers can reduce the concentration polarization during electrode reactions, resulting in a high energy density and power density in the battery. The ideal lithium ion migration number should be as close as possible to 1.

3. Stability: When the electrolyte is in direct contact with the electrode, the occurrence of side reactions should be avoided as far as possible, which requires the electrolyte to have certain chemical stability and thermal stability.

4. Mechanical strength: Lithium ion battery electrolytes need to have sufficient mechanical strength to meet the large-scale production and packaging process of batteries. Li et al. used trimethylphosphate (TMP) as an additive in high-voltage electrolytes and Li1.2Mn0.54Ni0.13Co0.13O2 as the positive electrode of the battery. The results showed that adding 1% TMP to the electrolyte can significantly improve the rate performance and cycling performance of the battery.

5. Excellent mechanical properties: Due to direct contact with positive and negative electrodes, polymer lithium battery electrolytes should have strong toughness and be able to withstand stress changes during battery assembly, storage, and use, without brittle cracking. At the same time, as a diaphragm, it should also have considerable mechanical strength to suppress the generation and puncture of lithium dendrites, and prevent short circuits between positive and negative electrodes.