According to the difference of electrolyte and separator, VRLA battery can be divided into AGM battery and GEL battery. AGM batteries mainly use AGM (glass fiber) separators, and the electrolyte is adsorbed in the pores of the separators. GEL batteries mainly use PVC SiO2 separators, and the electrolyte is a colloidal electrolyte that has been gelled. These two types of batteries have their own advantages and disadvantages. From the perspective of development speed, AGM technology has developed rapidly. At present, the market is basically dominated by AGM batteries. GEL batteries have gradually increased in recent years, mainly because there have been many problems in the service life of AGM batteries in the past few years, and the advantages of GEL batteries such as high cycle life have begun to be recognized and accepted by users.
The chemical reactions of lead-acid batteries during charging and discharging are as follows:
Side reactions associated with lead-acid battery charging:
This reaction causes the water in the battery to gradually lose, and it needs to be replenished with pure water to maintain normal use. For batteries with ordinary AGM fiberglass separators, there is a certain porosity in the separator, and a gas channel is reserved between the positive and negative electrodes. At the same time, a special alloy cast grid is used to increase the hydrogen evolution overpotential of the negative electrode to suppress the hydrogen evolution; the oxygen generated by the positive electrode diffuses to the negative electrode along the channel, and the oxygen is recombined into water, ensuring that the oxygen precipitated by the positive electrode diffuses to the lead negative electrode, and the reaction is completed, thereby realizing the recombination of the oxygen precipitated from the positive electrode into water. For batteries with colloidal electrolytes, PVC-SiO2 separators are used. The establishment of oxygen cycle is due to the three-dimensional porous network structure formed by the gel in the battery with SiO2 particles as the skeleton, which stores the electrolysis required by the battery inside;
After the colloid is poured, under the action of the electric field, the gel is formed. The initial structure is not stable. The skeleton has to shrink further, so that the gel has cracks. These cracks exist between the entire positive and negative plates. aisle. The overall oxygen cycle mechanism of the two types of batteries is the same, but the way of oxygen reaching the negative electrode is different. However, the oxygen cycle of the GEL battery is only established after the gel cracks, so the oxygen recombination efficiency is gradually increased, so that the battery has a sealing effect.