Lithium battery and manufacturing method thereof

Abstract

The invention discloses a lithium battery and a manufacturing method thereof, which belong to the field of batteries. The lithium battery comprises a positive pole, a negative pole and a diaphragm arranged between the positive pole and the negative pole. The manufacturing method comprises the following steps: making active matters into a mixed paste; preserving blank positions on the front and back sides of an edge in the lengthwise direction of a positive pole piece, coating the paste on other parts of the positive pole piece completely, preserving blank positions on the front and back sides of an edge in the lengthwise direction of a negative pole piece, and coating the paste on other parts of the negative pole piece completely; covering the pasted positions of the negative pole piece with the diaphragm, placing the positive pole piece, and staggering the blank positions of the positive pole piece and the blank positions of the negative pole piece at two ends respectively to arrange the positive pole with blanks at one end and the negative pole with blanks at the other end; welding the blanks of the positive pole with a positive pole tab and the blanks of the negative pole with a negative pole tab; and placing a battery cell welded with the pole tabs in a packaging shell, packaging the shell, drying the shell under vacuum, filling liquid, sealing the shell, and obtaining the battery after formation, capacity grading and examination. The lithium battery and the method have the advantages of reducing the distance from the pole pieces to pole terminals, internal resistance and heat generated during charge and improving safety, reducing pressure drop caused by internal resistance and discharge platform.

Description

technical field [0001] The invention relates to a lithium battery and a manufacturing method thereof belonging to the field of batteries, in particular to a lithium battery with fast charging and super-high specific power and a manufacturing method thereof. Background technique [0002] At present, square lithium-ion batteries mainly have two structural forms, one is the winding type, which has the advantage of simple structure, only one positive electrode and one negative electrode, and the specific energy of the battery is large. The disadvantage is that the pole piece is long and the battery The internal resistance is large, which is not conducive to high-current charging and discharging, and the specific power is small; the other is the laminated type, which has the advantages of short pole pieces and relatively small internal resistance of the battery, which is conducive to high-current charging and discharging. The disadvantage is that the battery There are many pole p...

AI Technical Summary

Problems solved by technology

[0011] The safety of the battery cycled at a high rate is worse than that of a battery cycled at a small rate: due to the difference in the internal structure of the battery and the different charge and discharge rates, the distribution of current on the pole piece is different, and the battery is not suitable for large rates after a cycle of charge and discharge at a large rate. The place where the rate is charged and discharged will be exposed. In the place where the current distribution is dense, lithium deposition is prone to occur, which makes the safety performance of the battery worse.

Lithium-ion batteries store and release energy through the insertion and removal of lithium ions on the positive and negative electrodes. Lithium ions are embedded on the negative electrode during charging, and the diffusion of lithium ions on the negative electrode is a speed-controlling step. When charging, lithium ions obtain electrons on the negative electrode very quickly, but the diffusion is not timely, and lithium deposition is prone to occur, especially in places where the current distribution is dense

[0012] After many charge and discharge cycles of the lithium-ion battery, although the distribution of the positive active material on the positive sheet is uniform or within an appropriate distribution range, the distribution of the negative active material on the negative sheet is also uniform or within an appropriate distribution range, and the negative electrode It is an appropriate excess, but in the process of repeated charging and discharging cycles, the distribution of current is uneven. In the place where the current distribution is dense, metal lithium will be precipitated on the surface of the negative electrode, and it is accumulated. Lithium-ion batteries are tested for safety, and their safety performance is poor

[0013] The current coiled and stacked lithium batteries have relatively large internal resistance. When discharging with a large current, the battery itself generates a lot of heat, the safety deteriorates, and the potential drop is large. The battery undergoes thermal expansion and contraction, and the electrodes become loose. Material failure, poor cycle life

[0014] The existing winding and laminated lithium batteries have their own shortcomings, which are not conducive to fast charging and high current discharging

Even if the positive and negative electrodes are coated evenly, unreasonable electrode structure and cell design will show uneven distribution of current density during high-current charging and discharging, which will affect the safety performance, fast charging performance and high-current charging and discharging of the battery. cycle life

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