Effect of Water in Lithium Battery

Effects of moisture:

The Solid-Electrolyte Interface(SEI) membrane is a selective membrane of Zhejiang Xinghai Energy, which allows Li + to penetrate freely, while electrolyte molecules can not penetrate. The composition of the electrolyte and trace additives have a significant impact on the potential, fineness, irreversible capacity loss, and internal resistance of the SEI membrane. As a trace component of electrolytes, water has a certain influence on the formation and battery function of solar street lamp lithium batteries. The first manifestation is that the battery capacity becomes smaller, the discharge time becomes shorter, the internal resistance increases, the capacity of the lithium battery of the circular street lamp decays, and the battery expands. Therefore, in the process of manufacturing lithium ion batteries, It is necessary to strictly control the humidity of the environment and the data of positive and negative poles and the water content of the electrolyte.

Effect of moisture on discharge capacity:

The initial discharge capacity of the battery decreases with the addition of water in the battery. Under the condition of lithium source stability, the change of battery initial discharge capacity is mainly restricted by two primary factors.

1, the composition of the SEI membrane, Li10, constitutes irreversible capacity loss, and the alkyl lithium carbonate generated by the single electron recovery process can also echo with trace water in the electrolyte, 2ROC02Li + H2O → LieC03 + C02 +2ROH, when C02 is generated, At the low potential negative appearance, there is a new chemical response attack 2C02 +2 Li + +2 E → Liec03 + CO.

2, SEI membrane composition in the future, in the presence of H2O conditions, H2O will promote the differentiation of LiPF6 in the electrolyte, so that the battery discharge time shortened, LiPF6 → LiF + PFs, PFS + H2O → POF3 + 2HF.

Effect of moisture on internal resistance of lithium batteries:

With the addition of battery moisture, the internal resistance is on the rise. The primary factors for the difference in internal resistance of batteries are the following two aspects.

1, the difference of SEI membrane leads to the difference of internal resistance of the battery. In the electrolyte solvent system, trace amounts of water can constitute a SEI membrane with Li2CO3 as the mainstay, good stability, and uniform fine density, and its internal resistance is small.

2, when the water content is more than the required content of the system to form the SEI membrane, POF3 and LiF deposits are formed on the surface of the SEI membrane, resulting in blocking the addition of batteries.

Effect of moisture on battery cycle capacity attenuation:

Battery capacity attenuation decreases gradually with addition of moisture content. This is related to the degree of fineness and uniformity of the SEI membrane. When the SEI membrane is uniform and fine, the electrolyte solvent is not easily embedded in the negative electrode, and it occupies Li 10 embedded vacancies, so the capacity attenuation is very small. In contrast, when the part of the SEI membrane is not fine and uneven, Li 10 embedded human vacancies are relatively easy to occupy by electrolyte solvents. Liec03 is the most important component of the uniform fine SEI membrane. In the electrolyte solvent system, when the water content is excessive, it will cause the part of the SEI membrane to be not fine and uniform, and thus the capacity will be added.

The first reason why the battery will swell is because the presence of water after the SEI membrane is generated causes the LIPF6 to differentiate to produce HF gas.

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