Analysis and Discussion on the process of powdered lithium ion battery production
The production process of lithium cobalt oxide is basically not powdered. The factors that affect the production process are:
1, improper formulation, such as too few adhesives, less capacity, resulting in uneven mixing.
2, the temperature of adhesive baking is too high, so the structure of the adhesive is destroyed.
3, slurry mixing time is not enough, not fully stirred.
4. The temperature of the coating is too low and the pole is not dried.
5, the coating quantity is not uniform, the thickness difference is too big.
6. The pole piece does not bake before rolling, and absorbs water in the air.
7. When the roller is pressed, the pressure is too high.
8. When the roller is pressed, the way of sending the pole pieces is not correct, resulting in uneven stress of the pole piece.
9. With oil positive pole, water negative pole, no powder?
Three. Bad battery projects and causes:
1. low capacity
Cause:
The amount of A. is less than that of the B. pole; the difference between the two sides of the pole piece is quite different; the C. pole piece is broken.
The electrolyte of D. is less, the conductivity of E. electrolyte is low, and the positive electrode of F. is not matched with the negative electrode.
The porosity of the g. membrane is small, the H. adhesive is aging and the attached material falls off, and the I. core is super thick (not dried or the electrolyte is not permeable), and the J. is not full of electricity, and the K. positive and negative material is smaller than the capacity.
2. high resistance
Cause:
A. negative electrode and polar ear arc welding; B. positive electrode and pole ear welding; C. positive pole and cap virtual welding; D. negative electrode and shell welding; e. rivet and pressure plate contact internal resistance; F. positive pole without conductive agent; g. electrolyte without lithium salt; h. battery has short circuit; I. diaphragm paper porosity is small.
3. low voltage
Cause:
A. side reaction (electrolyte decomposition; positive electrode with impurities; water); B. not good (SEI film is not safe); C. customer's circuit board leakage (refers to the client after processing back of the electric core); D. customer is not required to spot welding (customer processed core);
E. burr; F. micro short circuit; g. negative electrode producing dendrite.
4. the causes of ultra thick over thickness are the following:
A. seam gas leakage; B. electrolyte decomposition; C. not dried water; D. cap sealing poor; e. shell too thick; F. shell too thick; g. coils too thick (too much material; no compacted pole; too thick diaphragm).
The 5. causes have the following points
The A. is not good (SEI film is incomplete and dense); the baking temperature of B. is too high and the binder aging and decharging; C. negative electrode has low specific capacity; D. positive electrode is more material and less negative material; e. cap is leaking, welding seam gas leakage; F. electrolyte decomposition, conductivity decrease.
6. explosion
Failure of A. capacity cabinet (causing overcharge); poor closure effect of B. diaphragm; internal short circuit of C..
7. short circuit
A. material dust; B. shell fashion broken; C. scrape (small diaphragm paper too small or not padded); D. winding is uneven; e. is not wrapped; F. diaphragm has holes; g. burr.
8. circuit breaker
A) the pole ears are not welded well with the rivets, or the area of the effective solder joints is small.
B) the joint piece is broken (the joint is too short or too far down when the spot piece is welded.
Four, the safety characteristics of lithium ion batteries
Li ion battery has been widely used in people's daily life, so its safety performance should definitely be the first assessment index of lithium ion battery. For the evaluation index of the safety performance of lithium ion batteries, a very strict standard has been stipulated in the world. A qualified lithium ion battery should be satisfied with the safety performance.
1) short circuit: no fire, no explosion;
2) overcharge: no fire, no explosion;
3) hot box test: no fire, no explosion (150 10min constant temperature)
4) Needling: non explosion (using a 3mm nail to penetrate the battery);
5) flat plate impact: do not fire, do not explode; (10kg weight from 1 meters high to hit battery)
6) incineration: non explosion (gas flame burning test battery)
In order to ensure the safe and reliable use of lithium-ion batteries, experts have carried out very strict and detailed battery safety design to achieve battery safety assessment indicators.
1, diaphragm 135 degrees automatic shutdown protection: the use of advanced international Celgard2300PE-PP-PE three layer composite membrane.
2. Under the condition of the battery heating up to 120 C, the PE membrane holes on both sides of the composite membrane are closed, the internal resistance of the battery is increased, and the inside of the battery has a large area of circuit breakage, and the battery is no longer heating up.
3, the battery cover composite structure: the battery cover adopts the notch explosion-proof structure, when the battery temperature rises, the pressure reaches a certain degree, the crack breaks and deflate.
4, various kinds of environmental abuse test: carry out various misuse tests, such as external short circuit, overcharge, needle, plate impact, incineration, and so on, to investigate the safety performance of the battery. At the same time, the temperature impact test and vibration, drop and impact tests of the battery were carried out to investigate the performance of the battery in actual use.
- UP：Lithium battery has been favored for more than 10 weeks.
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