Causes and treatment methods of lithium swollen battery

Causes and treatment methods of lithium swollen battery

Table of Contents

Lithium batteries have been widely used in the market due to their high energy ratio and high safety. Batteries like lithium batteries are not as safe as polymer batteries. However, due to its early development, it is relatively cheap, and many manufacturers can produce it, which leads to unevenness, and the safety of lithium batteries is sometimes not guaranteed.

In addition, if it is used improperly or the production level is limited, there are still certain safety hazards, such as swollen battery. So why does the lithium batteries have a swollen battery phenomenon? Let’s take a look at the causes of a swollen battery and some solutions.

Analysis of the basic structure of lithium battery packs

The main material composition of the lithium battery pack: cathode material, anode material, electrolyte, lithium battery separator (isolation material).

Cathode

From the perspective of battery weight composition, the cathode material occupies a large proportion (generally 70%-80%), because the performance of the cathode material directly affects the performance of the lithium-ion battery, and its cost also directly determines the cost of the battery. Cathode materials account for 30% to 40% of the cost of lithium-ion batteries, and also directly affect the energy density and performance of lithium-ion battery packs.

Anode

The anode material is composed of a material with a lower potential than the cathode, and has a high specific capacity and good charge-discharge reversibility, thereby maintaining good dimensional and mechanical stability during the lithium intercalation process. The anode material mainly affects the efficiency and cycle performance of the lithium battery pack.

The performance of the anode material also directly affects the performance of the lithium battery. The anode material accounts for about 10-20% of the total cost of the lithium battery. In terms of the type of anode materials, it includes carbon-based anodes and non-carbon anodes.

Analysis of the basic structure of lithium battery packs

Electrolyte

The electrolyte plays the role of transporting charges between the cathode and anode (similar to the carrier wave in the radio), and has a high ionic conductivity. It affects the energy density, wide temperature application, cycle life, power density, safety performance and other factors of lithium battery packs.

Lithium battery separator

The lithium battery separator has a certain pore size and porosity to ensure low resistance and high ionic conductivity. It has good permeability to lithium ions, good wettability to electrolyte, sufficient liquid absorption and moisturizing ability, and maintains ion conductivity. At the same time, it has electronic insulation to ensure the mechanical isolation of the cathode and anode.

In addition, it should have sufficient mechanical properties such as puncture strength and tensile strength, as well as electrolyte corrosion resistance and sufficient electrochemical stability. Power batteries have higher requirements for separators, and composite separators are usually used.

Why do lithium battery packs have swollen battery?

There are three main reasons for lithium swollen battery::

First, the manufacturer’s production process issues

Due to the large number of manufacturers, in order to save costs, many manufacturers make the production environment harsh, use equipment and machines that will be eliminated, etc., so that the coating of the battery is uneven, and dust particles are mixed in the electrolyte. All of these may cause the lithium battery pack to swollen battery when the user uses it, and even cause greater danger.

Why do lithium battery packs have swollen battery

Second, the user’s daily usage habits

The second is the user himself. If the user uses lithium battery products improperly, such as overcharging and overdischarging, or continuous use in an extremely harsh environment, it may also cause the lithium battery to appear swollen battery.

Third, if it is not used for a long time and stored improperly

If any product is not used for a long time, the original performance will basically decrease, and the battery will not be used for a long time, and then it has not been properly preserved. It is not used when it is exposed to the air for a long time, and the battery is fully charged. Since air is conductive to a certain extent, if it is placed for too long, it is equivalent to direct contact between the cathode and anode of the battery, and a chronic short circuit occurs. Once the short circuit occurs, it will generate heat, and some electrolytes will decompose or even gasify, resulting in a swollen battery.

The reasons for the swollen battery caused by overcharging and overdischarging are as follows:

Swollen battery caused by overcharging: Overcharging will cause all the lithium atoms in the cathode material to run into the anode material, causing the original full grid of the cathode to deform and collapse, which is also a main reason for the decline in the power of the lithium battery. In this process, the lithium ions in the anode are more and more, and the excessive accumulation makes the lithium atoms grow stump crystals, which makes the lithium battery bulge.

Swollen battery caused by overcharging and overdischarging

Swollen battery caused by overdischarge: During the first charging and discharging process of a liquid lithium-ion battery, the electrode material and the electrolyte react at the solid-liquid phase interface to form a passivation layer covering the surface of the electrode material. The formed passivation layer film can effectively prevent the passage of electrolyte molecules, but Li+ can be freely inserted and extracted through the passivation layer, which has the characteristics of a solid electrolyte. Therefore, this layer of passivation film is called solid electrolyte interface, referred to as SEI.

The SEI film will have a protective effect on the anode material, making the material structure not easy to collapse, and can increase the cycle life of the electrode material. The SEI film is not static, and there will be a little change during the charging and discharging process, mainly because some organic substances will undergo reversible changes. After the battery is overdischarged, the SEI film is reversibly damaged, and the SEI protecting the anode material is destroyed, causing the anode material to collapse, thereby forming swollen battery phenomenon.

These two factors will lead to a violent reaction similar to a short circuit inside the battery during the use of the battery, generating a large amount of heat, which in turn will cause the electrolyte to decompose and gasify, and a swollen battery will occur.

How to safely dispose of swollen battery?

How to safely dispose of swollen battery

● Use up about half of the battery and start to replenish the battery. In rare cases, a complete discharge and full charge maintenance will be performed, which can greatly reduce the amount of crystallization and significantly slow down the phenomenon of swollen battery.
● The lithium swollen battery can be discarded directly, because the power capacity is already very small, and there is no power at all after a short circuit.
● Lithium battery packs generally need to be recycled professionally so as not to cause pollution. If there is no way to dispose of them, they should be thrown into the classified recycling trash can.

The above are the reasons for the swollen battery and how to deal with the swollen battery correctly in the future.

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