AG10 battery.Introduction to lithium-ion battery principles and process flow

　　Introduction to the principle and process flow of lithium-ion batteries 1. Principle 1.0 Positive electrode structure LiCoO2 (lithium cobalt oxide) + conductive agent (acetylene black) + binder (pVDF) + current collector (aluminum foil) positive electrode 2.0 negative electrode structure graphite + conductive agent (acetylene Black) + Thickener (CMC) + Binder (SBR) + Current Collector (Copper Foil) Negative Electrode 3.0 Working Principle 3.1 The charging process is as shown in the picture above. A power supply charges the battery. At this time, the electrons on the positive electrode e run from the external circuit through the external circuit. On the negative electrode, the positive lithium ions Li+ "jump" into the electrolyte from the positive electrode, "crawl" through the winding holes in the separator, "swim" to the negative electrode, and combine with the electrons that have run over long ago. The reaction that occurs on the positive electrode is LiCoO2 = charging = Li1-xCoO2 + Xli++Xe (electrons) and the reaction that occurs on the negative electrode is 6C +

　　Discharge includes constant current discharge and constant resistance discharge. Constant current discharge actually involves adding a variable resistor in the external circuit that changes with the voltage. The essence of constant resistance discharge is to add a resistor to the positive and negative terminals of the battery to allow electrons to pass. It can be seen that as long as the electrons on the negative electrode cannot run from the negative electrode to the positive electrode, the battery will not discharge. Both electrons and Li+ move at the same time, in the same direction but in different paths. During discharge, the electrons run from the negative electrode through the electronic conductor to the positive electrode. The lithium ions Li+ "jump" into the electrolyte from the negative electrode and "climb" across the separator. small hole, "swim" to reach the positive electrode, and combine with the electrons that have run over long ago.

　　2. Process flow

　　3. Battery defective items and causes:

　　1. Reasons for low capacity:

　　a. The amount of attached materials is too small;

　　b. There is a large difference in the amount of material attached to both sides of the pole piece;

　　c. The pole piece is broken;

　　d. Less electrolyte;

　　e. The conductivity of the electrolyte is low;

　　f. The positive and negative electrodes are not matched properly;

　　g. The porosity of the separator is small;

　　h. Adhesive aging → attachment material falls off;

　　i. The roll core is extremely thick (not dried or the electrolyte has not penetrated)

　　j. Not fully charged when dividing the capacity;

　　k. The positive and negative electrode materials have small specific capacity.

　　2. Causes of high internal resistance:

　　a. The negative electrode piece and the tab are welded;

　　b. The positive electrode piece and the tab are weakly welded;

　　c. The positive electrode lug and the cap are weakly welded;

　　d. The negative electrode lug and the shell are welded;

　　e. The internal resistance of the contact between the rivet and the pressure plate is large;

　　f. No conductive agent is added to the positive electrode;

　　g. The electrolyte does not contain lithium salt;

　　h. The battery has experienced a short circuit;

　　i. The separator paper has small porosity.

　　3. Causes of low voltage:

　　a. Side reactions (electrolyte decomposition; impurities in the positive electrode; water);

　　b. Not well formed (the SEI film is not formed safely);

　　c. The customer’s circuit board leaks electricity (referring to the cells sent back after processing by the customer);

　　d. The customer failed to spot weld as required (cells processed by the customer);

　　e. Burr;

　　f. Micro short circuit;

　　g. The negative electrode produces dendrites.

　　4. Super thickness The reasons for super thickness are as follows:

　　a. Weld leakage;

　　b. Decomposition of electrolyte;

　　c. The moisture has not been dried; d. The sealing performance of the cap is poor;

　　e. The shell wall is too thick; f. The shell is too thick;

　　g. The core is too thick (too many attachments; the pole piece is not compacted; the diaphragm is too thick).

　　5. The causes are as follows:

　　a. Not well formed (the SEI film is incomplete and dense);

　　b. The baking temperature is too high → aging of the adhesive → stripping;

　　c. The specific capacity of the negative electrode is low;

　　d. The positive electrode has more attachments and the negative electrode has less attachments;

　　e. The cap is leaking and the weld is leaking;

　　f. The electrolyte decomposes and the conductivity decreases.

　　6. Explosion a. The sub-capacity cabinet is faulty (causing overcharging);

　　b. Poor diaphragm closing effect;

　　c. Internal short circuit 7. Short circuit

　　a.Material dust;

　　b. Broken during installation;

　　c. Scrape with a ruler (the small diaphragm paper is too small or not properly padded);

　　d. Uneven winding;

　　e. Not wrapped well;

　　f. There is a hole in the diaphragm;

　　g. Burr

　　8.Break circuit

　　a) The pole tabs and rivets are not welded properly, or the effective solder joint area is small;

　　b) The connecting piece is broken (the connecting piece is too short or is welded too far down when spot welding with the pole piece)

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