li ion 18650 battery pack manufacturer

　　What should be paid attention to in the winding process of 18650 lithium battery? 1. Humidity control 1%RH Purpose: To prevent the positive and negative electrodes from absorbing water during the winding process, resulting in zero voltage, self-discharge, and poor cycle performance; method: calculate the dew point value and temperature value 2. Dust control 100,000pc/ft3 (test particle size is 0.5um) purpose

　　1. Humidity control ≤1%RH Purpose: To guard against water absorption during the winding process of the positive and negative electrodes, resulting in zero voltage, self-discharge, and poor cycle performance;

　　Method: Calculate the dew point value and temperature value to obtain the temperature and humidity value;

　　2. Dust control ≤100,000pc/ft3 (test particle size is 0.5um)

　　Purpose: To guard against dust being involved in the electrode group during winding, which will cause short circuit, overheating, fire, self-discharge and other defects of the battery core;

　　Low temperature lithium iron phosphate battery 3.2V 20A -20°C charge, -40°C 3C discharge capacity ≥ 70%

　　Charging temperature: -20~45°C -Discharging temperature: -40~+55°C -40°C Support maximum discharge rate: 3C -40°C 3C discharge capacity retention rate ≥70%

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　　Method: use a dust detector;

　　3. Abnormal cutting burrs

　　Process requirements: pole piece ≤ 8um; pole ear burr ≤ 12um; test method: randomly select 1PCS battery core for the first inspection of each shift and each machine for dissection, and test the front and rear ends of the positive and negative electrodes and the positive and negative electrodes according to the "burr test operation instruction book" Ear clipping burrs.

　　Adverse effects: If the pole piece or tab burr exceeds the process requirements, it may cause the burr to pierce the diaphragm, short-circuit the positive and negative electrodes, overheat the battery cell, and may explode in serious cases, posing a serious safety hazard.

　　18650 lithium-ion battery winding steps

　　Low temperature high energy density 18650 3350mAh-40℃ 0.5C discharge capacity ≥60%

　　Charging temperature: 0~45℃ Discharging temperature: -40~+55℃ Specific energy: 240Wh/kg -40℃ discharge capacity retention rate: 0.5C discharge capacity ≥ 60%

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　　4. Positive and negative plate overturning difference

　　Process requirements: the alignment of positive and negative plates is 0.75~.55mm

　　Negative plate and diaphragm alignment 1?.5mm

　　Test method: After changing rolls, continue random inspection of 3PCS batteries to test the alignment according to the "X-RAY Operation Instruction Book". Bad effects: 1) The alignment of positive and negative electrodes exceeds the process specification, which may cause the negative electrode to not cover the positive electrode. During the charging process, the lithium ions released from the positive electrode cannot find the corresponding graphite to embed, resulting in free lithium ions in the battery cell accumulating on the negative electrode and forming dendrites. The dendrites penetrate the separator and cause an internal short circuit, which poses a safety hazard.

　　2) If the alignment between the negative electrode and the separator exceeds the process standard, the negative electrode may be squeezed and deformed, and the negative material on the electrode may fall off. During the charging process, the battery cell expands, and the powder penetrates the separator, resulting in an internal short circuit of the positive and negative electrodes and a safety hazard. Hidden danger;

　　5. Pole overturning difference in the winding direction (the length of the outer layer negative electrode exceeds the length of the positive electrode material, and the length of the inner layer negative electrode exceeds the length of the positive electrode material). A tipping difference size.

　　Adverse effects: It may cause the negative electrode sheet not to enclose the positive electrode sheet. During the charging process of the battery, the lithium ions released from the positive electrode cannot find the corresponding graphite to embed, causing free lithium ions in the battery cell to accumulate on the negative electrode and appear dendrites. Dendrites puncture the separator and cause internal short circuit, which poses a safety hazard.

　　18650 lithium-ion battery winding steps

　　6. Short circuit detection

　　Parameter setting (100V, 25nF250V,

　　250uA) Test method: use a short-circuit sample to detect the machine during the first inspection of each shift; adverse effects: self-discharge, heat generation, explosion and other short-circuit factors: cutting particles, metal dust, burrs, etc. cause diaphragm holes;