Why do 18650 2000mah battery experience capacity fading in the early stages? What is its production process?

　　1. Early capacity decay

　　Early capacity fading is the fatal flaw of valve-regulated batteries, which is mainly manifested in grids made of antimony-free alloys and low-antimony alloys. After the battery passes through several or dozens of deep rings, the battery capacity suddenly drops and is scrapped. This is caused by the formation of a high-resistance barrier layer between the grid and the active material (this happens during shallow discharge). The phenomenon is not obvious).

　　In 1998, the author introduced cadmium element into low antimony alloy to make super calcium alloy, which can solve this problem. So after it was spread, most manufacturers in Jiangsu, Zhejiang, Anhui, Jiangxi and Fujian now use this alloy. This kind of alloy can effectively avoid the early capacity fading of the deep ring of electric vehicle batteries.

　　However, with the continuous improvement of environmental protection requirements, many scholars have proposed that cadmium is extremely harmful to the human body and the environment.

　　As national environmental protection policies become increasingly tight and most countries in the world ban the import of cadmium-containing batteries, research on cadmium-free batteries is again on the table.

　　2Production process

　　2.1 Composition of alloy

　　Increasing the tin content in the alloy is an effective way to overcome early capacity fading. When the tin content in the alloy is 1.4% to 1.6%, it can significantly prevent the formation of the barrier layer, thus improving the performance of the battery.

　　The best calcium content is between 0.08% and 0.1%. This alloy has low resistance and corrosion resistance. If the calcium content is too much, it will cause serious corrosion.

　　2.2 Composition of active substances

　　¾ After testing and screening, the active material formula commonly used on lead, antimony and cadmium alloys is of little significance when used on lead-calcium alloys. Generally, it will not exceed 150 (DOD%)&NTIlde; rings, so it is used on lead-calcium alloys. The active substance formula is different from the conventional formula.

　　1) The additive formula of the positive plate consists of colloidal graphite, high-priced lead compounds, fibers, water, dilute sulfuric acid and additive M1, adhesive M2. M1 is a composite additive. Its function is to prevent the formation of the barrier layer. M2 can strengthen the active material. inter-firmness.

　　2) The negative plate additives are barium sulfate, humic acid, lignin, acetylene black, fiber, water, stearic acid, dilute sulfuric acid and additive N (N is a single oxide that can prevent the negative plate from being vulcanized). But it should be noted that the amount of additives added to the internal and external formation of the battery is not the same, because some of the additives are dissolved into the electrolyte during external formation. Furthermore, the amount of additives in tall plates and short plates is somewhat different, and there is a difference in quantity between the two.

　　2.3 Curing of raw plate

　　The curing method is directly related to the service life of the electric vehicle battery. A plate that is not cured well is prone to poor binding ability between the active material and the grid. The resistance at this interface is too large, and the resistance becomes larger and larger during use. This shortens the battery life. At the same time, a poorly cured positive plate will cause the positive active material to sludge prematurely, causing the battery life to end early.

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