Analysis and summary of lithium battery forming - aging process

Lithium ion battery manufacturing is a process closely linked by a number of technological steps. As a whole, the production of lithium battery includes wafer manufacturing process, battery assembly process and the final injection, sealing, forming and aging process. In these three stages of the process, each process can be divided into several key processes, and each step will have a great impact on the final performance of the battery.

In the process of polar plate manufacturing, it can be divided into five processes: slurry preparation, slurry coating, polar plate roller pressing, polar plate cutting and polar plate drying. In the battery assembly process, and according to the different battery specifications and models, roughly divided into winding, shell, welding and other processes. The liquid injection process after assembly includes liquid injection and sealing. Finally, the battery into, aging, volume three steps of technology. After the completion of battery production, the battery needs to be pre-  activated and stabilized for the first time, that is, the final conversion - aging - volume division process.

First, Pre - formation

About the concept of Pre - formation, is the formation of lithium-ion batteries that take a small electrical charge and discharge. After the manufacture of lithium battery, it is necessary to charge and discharge the battery with small current. About the purpose of pre- charging, there are mainly two:

1, After the battery has been produced, electrode material and not in the best state, or inappropriate physical properties (such as particle is too large, contact is not close, etc.), or phase itself is wrong (for example, some of the mechanism of alloy metal oxide cathode).It needs to be activated by initial charge and discharge.

2, In the process of lithium battery charge for the first time, Li + emerge from the positive living material, after the electrolyte - diaphragm - electrolyte process, embedded in the negative graphite material layer.In the process, electronic migration along the peripheral circuit from the positive to the negative terminal.At this point, due to the low lithium ion embedded graphite anode potential electronic will react with the electrolyte to generate SEI and part of the gas. About the role of the SEI you can search the formation : What is SEI? It has such an impact on lithium batteries!

Second, the aging

Aging generally refers to the placement of battery assembly liquid injection after the first charge, which can have either normal temperature aging or high temperature aging. Both functions are to make SEI film properties and composition formed after the initial charge forming more stable, so as to ensure the stability of battery electrochemical performance. There are three main purposes of aging:

1, After the preforming process of the battery, a certain amount of SEI film will be formed in the graphite negative electrode of the battery, but the film structure is tight and the pores are small. Aging the battery at high temperature will help the SEI structure restructure and form a loose porous film.

2, The voltage of the converted battery is in an unstable stage, slightly higher than the real voltage. The purpose of aging is to make the voltage more accurate and stable.

3, put the battery in high temperature or room temperature for a period of time, can guarantee the electrolyte can to fully infiltrates of pole piece, is conducive to the stability of the battery performance.

The chemical-aging process of battery is essential. In actual production, the battery charging and discharging process is selected according to the battery material system and structure system. However, the chemical-aging process of battery must be charged and discharged under the condition of low current. After these two key processes, the stabilized battery can be divided into capacitance, packaging and other processes before leaving the factory.

The page contains the contents of the machine translation.