Softening agent for lithium ion battery pole piece

Abstract

The invention belongs to the field of preparation of lithium ion secondary batteries, and particularly relates to a softening agent for a lithium ion battery pole piece. The softening agent is specifically fluorinated hydrocarbon or a retaining agent or a mixture of the two, wherein the fluorinated hydrocarbon can be a mixture or a single substance, and the fluorinated hydrocarbon not only has a certain softening effect, but also has a relatively low boiling point, and is easily volatilized completely in a subsequent drying technology; and the retaining agent can be uniformly distributed on the pole piece under the condition that the using amount is very small, so that residue of the retaining agent component when a battery core is dried is reduced, and influence on a battery is reduced.

Description

technical field [0001] The invention belongs to the field of preparation of lithium-ion secondary batteries, and in particular relates to a softener for lithium-ion battery pole pieces. Background technique [0002] The lithium-ion secondary battery uses lithium ions to move between the positive electrode and the negative electrode to provide electric energy to the outside. The existing lithium-ion battery uses a separator to separate the positive and negative electrodes to avoid electronic conduction. Lithium-ion secondary batteries are divided into cylindrical structure and square structure. Among them, square lithium-ion secondary batteries have the characteristics of high energy density and flexible shape and size. In order to realize this structure, winding or stacking manufacturing processes are usually used . Among them, the winding process has the advantages of simple process and fast production speed. [0003] In order to make a square battery, after the winding p...

AI Technical Summary

Problems solved by technology

[0003] In order to make a square battery, after the winding process, the battery needs to be pressurized to form a square structure. The positive electrode sheet often breaks after winding and pressing, resulting in loss of battery capacity and potential safety hazards, especially as the battery volume increases. The increase in specific energy, the increase in the compaction density and thickness of the positive electrode, the thinning of the aluminum foil, and the occurrence of positive electrode pressure fracture are more serious

[0004] The existing solution is to use high-strength aluminum foil to resist fracture. However, the price of high-strength aluminum foil is relatively high, which will increase the cost of the battery; in addition, high-strength aluminum foil is usually added with other metal or non-metallic elements, which will affect the lithium battery cycle. It will also lead to a decrease in capacity and reduce battery life; in addition, even if high-strength aluminum foil is used, it still cannot solve the problem of positive electrode piece fracture

[0005] If the softener is injected into the bending part (B area) of the wound battery to prevent the electrode active material from falling off and the current collector to break, because the battery is very tight after winding, the softener is difficult to maintain during subsequent heating and baking. Completely volatilized from the pole piece, thus partially remaining in the battery, which will seriously affect the performance and life of the battery

The residue can be reduced by increasing the baking time, but this will also prolong the production time and increase the cost; in addition, reducing the amount of softener can reduce the residue of softener, but it is difficult to achieve uniform coating after reducing the amount

These are greatly restricted in actual production

Images