Curing process of lead-acid E-BIKE battery plates

In the manufacturing process of lead-acid battery, the uncharged plate curing and drying conditions are very important. The quality of the uncharged plate is closely related to the quality of charged plate and the performance of the battery. Therefore, uncharged plate curing and drying process must not be taken lightly.

Well cured plate can obtain solid active material and good appearance quality after formation, on the contrary, due to the influence of climate change and other conditions in different seasons, it often make the plate curing conditions are not well controlled, resulting in the plate batch waste from time to time. General waste phenomenon: negative plate crack,foaming; positive plate active material loose, paste dropped, peeling etc.

Mechanism of curing

The curing of the plate refers to the oxidation of free lead and the lead on the surface of grid, recrystallization and hardening of basic lead sulfate in the process of lead paste gelation of the pasted plate at a certain temperature and time. The curing of uncharged plate for lead-acid battery is a relatively complex process, with both physical and chemical changes. The effects to achieve are the formation of plate grid corrosion layer, the conversion of free lead, and the recrystallization of basic lead sulfate (dehydration forms micropores).

The curing process can be divided into three inseparable stages in order:

1. In the first stage, let the grid mainly forms a corrosion layer, prompting the lead paste and the grid to have a strong adhesion, and make the 3BS(3PbO.PbSO4.H2O) in the lead paste to generate an appropriate proportion.

The corrosion layer of the grid is constantly dissolved by the oxygen in the air into the water of the lead paste, and then reach the surface of the grid to form a micro battery to complete, water as a catalyst (or medium), the lead of the grid is relatively slow corrosion layer because of its low activity. Therefore, this stage will take a long time, the higher the curing temperature, the faster the grid corrosion speed, but the 3BS in the lead paste will also convert to 4BS. Therefore, at this stage, it is very important to ensure that the lead paste has a higher content of moisture, and that the high curing humidity and the appropriate curing temperature are very important. If the grid corrosion is not good, the adhesion of lead paste is poor, the plate is easy to drop powder, the internal resistance of lead-acid battery will increase, the battery capacity attenuation will be faster, and the battery life will be shortened.

2. In the second stage, the free lead in the lead paste is mainly converted into lead oxide, while the grid is further oxidized and corroded. As the moisture in the lead paste is slowly precipitated in steam form, The moisture content was gradually decreased, Micropores begin to form in the lead paste, The exchange of external air entering into the plate is accelerated, The oxidation of free lead began to accelerate; When the moisture content in the lead paste drops to 7% to 8%, The oxidation rate has reached the fastest, This stage requires a high humidity to ensure that the lead paste does not lose water too quickly, To extend the time of rapid conversion of free lead, to achieve the purpose of a more thorough transformation; If the water is lost too quickly, The time of rapid oxidation of free lead is too short, Free lead may be high after curing, It is bound to cause the utilization rate of active substances to reduce and the positive plate even bending, paste dropping and other serious problems.

3. The third stage is the drying stage of the plate, mainly completing the hardening dehydration of lead paste, recrystallization of basic lead sulfate, the formation of porous electrodes, the former stage dehydration forms large pores, and the later stage dehydration continues to form micropores.