Analysis and Discussion on Pollination of Lithium-ion Battery Production Process

The current production process of lithium cobalt acid in polystyrene powder will not basically fall off the powder. The factors that affect the possibility of falling powder in the production process are:

1, the proportion of formula is not appropriate, such as too few adhesives, less tolerance causes uneven stirring.

2, the adhesive baking temperature is too high, so that the adhesive structure is damaged,.

3, the slurry stirring time is not enough, did not completely stir open.

4, the temperature is too low when coated, the electrode has not been dried.

5, the amount of coating is not uniform, the thickness difference is too large.

6, pole before the pressure of the roller did not bake, in the air to absorb a large amount of water.

7, roll pressure is too large, so that the pole powder and the collection fluid stripping.

8, when the roller pressure is not the right way to deliver the pole, resulting in uneven force of the pole.

9, with oily positive pole, water negative pole, do not drop powder?

III. Bad Battery Projects and Causes:

1. Low capacity

Causes:

A. Low amount of material; B. Large differences in the amount of material on both sides of the electrode; C. Polar fracture;

D. Low electrolytic E. Low conductivity of electrolytes; F. The positive and negative discs were not matched;

G. A low porosity of the diaphragm; H. The adhesive aging → material shedding; I. Over thick core(not dried or not permeated by electrolytic fluid) J. Not fully charged at capacity; K. The positive and negative materials are smaller than the capacity.

2. Internal resistance

Causes:

A. Negative film and polar ear virtual welding; B. Positive film and polar ear virtual welding; C. Positive ear and cap virtual welding; D. Negative ear and shell welding; E. The rivet has a large internal resistance in contact with the press plate; F. Positive electrode without conductive agent; G. The electrolyte is free of lithium salts; H. The battery has been short-circuited; I. Low porosity of diaphragm paper.

3. Low voltage

Causes:

A. Side reactions(electrolyte decomposition; Positive impurity; There is water); B. Not properly formed(the SEI membrane is not safe); C. Leakage of power from the customer's circuit board(referred to as the core returned by the customer after processing); D. The customer failed to spot welding(the customer's machined core) as required;

E. Thorn; F. Micro short circuit; G. The negative pole produces dendrites.

4. The reasons for the excessive thickness are as follows:

A. Weld leakage; B. Electrolytic decomposition; C. Water not dried; D. Poor sealing of the cap; E. The shell walls are too thick; F. The shell is too thick; G. The roll core is too thick(too much material; Polar film is not compacted; The diaphragm is too thick).

5. The causes are the following

A. Not properly formed(the SEI membrane is incomplete and dense); B. High baking temperature → adhesive aging → offloading; C. The negative pole is lower than the capacity; D. More positive and less negative materials; E. The cap leaks and the weld leaks; F. Electrolytic decomposition and reduced conductivity.

6. Explosions

A. Failure of the compartment(causing overcharging); B. Poor diaphragm closure effect; C. Internal short circuit

7. Short circuit

A. Dust; B. Shelling fashion breaks; C. Scratching(small diaphragm paper is too small or uncushioned); D. Inconsistent winding; E. Unwrapped; F. A hole in the diaphragm; G. Thorn

8. Broken roads

A) The ears and rivets are not welded well, or the effective spot area is small;

(b) Break of the splint(the splint is too short or welding too low with the electrode)

Safety characteristics of lithium-ion batteries

Lithium-ion batteries have been widely used in people's daily life, so its safety performance should definitely be the first assessment index of lithium-ion batteries. For the safety performance evaluation index of lithium-ion batteries, the international regulations are very strict, and a qualified lithium-ion battery should meet the safety performance conditions.

1) Short circuit: No fire, no explosion;

2) Overcharge: No fire, no explosion;

3) Hot box test: No fire, no explosion(150 °C constant temperature 10 min)

4) Acupuncture: does not explode(penetration of the battery with a <S> 3 mm nail);

5) Flat impact: no fire, no explosion; (10kg weight hits battery from a height of 1 meter)

6) Incineration: No explosion(gas flame burning battery)

In order to ensure the safe and reliable use of lithium-ion batteries, experts have conducted a very strict and sophisticated battery safety design to meet the battery safety assessment targets.

1, diaphragm 135 °C automatic off protection: using the international advanced Celgard2300PE-PP-PE three-layer composite film.

2, in the case of battery heating up to 120 °C, the PE membrane holes on both sides of the composite membrane are closed, the resistance in the battery increases, and a large area of disconnection is formed inside the battery, and the battery is no longer heated.

3, battery cover composite structure: battery cover adopts indentation explosion proof structure, when the battery heating up, the pressure reaches a certain degree of indentation rupture, air release.

All kinds of environmental abuse tests: Conduct various abuse tests, such as external short circuit, overcharge, acupuncture, plate impact, incineration, etc., to investigate the safety performance of batteries. At the same time, the battery temperature impact test and vibration, drop, impact and other mechanical properties tests were carried out to investigate the performance of the battery in the actual operating environment.

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