Detailed Explanation of 18650 Lithium Battery Formation Aging Process.

Detailed Explanation of 18650 Lithium Battery Formation Aging Process.

1、 The concept of pre formation is to perform a small current charge and discharge on the manufactured polymer lithium battery. After the production of polymer lithium batteries, it is necessary to charge and discharge the batteries with low current. There are two important goals for pre charging: 1. After the battery is manufactured, the electrical data is not in practical condition, or the physical properties are not suitable (such as particles that are too large, poor contact, etc.), or the phase itself is incorrect (such as negative metal oxides in some alloy mechanisms), which requires charging and discharging to activate it. 2. During the secondary charging process of polymer lithium batteries, Li is released from the positive active material, passes through the electrolyte barrier electrolyte, and is embedded between the negative graphite layers. During this process, electrons migrate from positive to negative along the peripheral circuit. At this point, due to the low negative potential of lithium ions embedded in graphite, electrons will first react with the electrolyte to form SEI film and local gas. What is SEI? What is SEI? The impact on polymer lithium batteries is so significant! During this process, local gas will be generated along with the consumption of a small amount of electrolyte. Some battery manufacturers may perform battery exhaust and replenishment operations after this process, especially for LTO batteries, which will generate a large amount of gas and cause the battery bulge thickness to exceed 10%. For graphite negative, the gas production is relatively low and there is no need for exhaust operation, because the SEI film generated during the secondary charging process hinders further reaction between electrons and electrolyte, and no longer produces gas. This is also the source of irreversible capacity for graphite based batteries, which indeed causes irreversible capacity loss, but also contributes to the stability of the battery.  

2、 Aging and aging refer to the placement of batteries after assembly and injection to achieve secondary charging. There may be room temperature aging or high temperature aging, both of which aim to make the properties and composition of the SEI film formed after charging more stable, ensuring the stability of the battery's electrochemical function. There are three important goals for aging: 1. After the pre formation process of the battery, a certain amount of SEI film will be formed inside the graphite negative of the battery. However, this film has a thoughtful structure and small pores. Aging the battery at high temperatures will help to restructure the SEI structure and form a loose and porous film. 2. After formation, the voltage of the battery is in an unstable stage, slightly higher than the actual voltage. The goal of aging is to make its voltage more accurate and stable. 3. Placing the battery at high temperature or room temperature for a period of time may ensure that the electrolyte can fully infiltrate the sheet, which is beneficial for the stability of the battery function. The formation aging process of batteries is essential. In actual production, the battery charging and discharging process is selected based on the battery's data system and structural system. However, the formation of batteries must be charged and discharged under low current conditions. After these two critical processes, the firmly secured battery can be divided into capacity and packaged before it is ready for production.