Recently, with GB/T34015-2017 "Recycling and Utilization of Vehicle Power Battery - Residual Energy Testing", GB/T34013-2017 "Power Battery Product Specifications", GB/T34014-2017 "Automobile Power Battery Coding Rules" The details of the national standards for the three power batteries were officially announced, and the power battery standard that has been in the controversial vortex has finally settled. In response to the promulgation of these new standards, the battery China network reporter has also done detailed analysis before, providing targeted advice for battery companies.
However, the country is not only concerned with the "large direction" of the battery size, but also the "small areas" of battery parts. On July 24, the Ministry of Industry and Information Technology issued a number of industry standards and national standards opinions collection, including battery parts, "Insulation Flame Retardant Adhesive Tape for Power Battery Enclosure" and "Powered Lithium Ion Battery Ceramic Seal". The so-called "thousands of dykes collapsed in the ant hole", the failure of a small part may affect the quality of the entire battery or battery pack, and even cause safety problems for the entire new energy vehicle. The insignificant but vital parts of the battery not only protect the safety of the battery and the user, but also serve as a "life-saving" in the event of an accident.
1. Explosion protection assistant - sealing ring
The sealing ring is located under the battery cap to ensure that the battery has a good seal, which blocks the leakage of the electrolyte and provides a good closed environment for the internal reaction of the battery. At the same time, when the battery cap is pressed down, it can also play a role of decompression buffer to ensure the normal operation of the internal components of the battery, and provide an important guarantee for the life and safety of the battery.
The role of the seal is not only to ensure the battery sealing performance, but also to save lives at critical moments. Generally, at least one weak portion is disposed on the sealing ring, and the strength is lower than other portions of the main body plane. When the gas pressure inside the battery abnormally increases until the explosion pressure of the battery, the weak part of the sealing ring can be broken, the gas inside the battery is released from the break, and the discharge is arranged according to the set gas flow direction, so as to prevent unpredictable Airflow to avoid a strong explosion of the battery.
The material of the sealing ring will have different choices depending on the type, shape and environment of the battery. The most commonly used is the perfluoroelastomer seal, which has the characteristics of high price and high performance. However, the cost of the seal in the lithium battery should not only consider the purchase price of the seal, but also the service life and the failure caused by the repair. Wait. Perfluoroelastomer seals are more expensive, but their use and service life are both **, which is the most cost-effective material in general.
However, most rubber seals will undergo elastic deformation under pressure. As the pressure increases, permanent plastic deformation will occur, which will affect the service life of the battery. For some special batteries, it is obviously not up to the requirements. This requires some new sealing rings of other materials. The ceramic materials have good acid and alkali resistance, corrosion resistance and high temperature resistance, making them a new choice. Nowadays, ceramic sealing rings are also being used more and more in the power battery industry. The Ministry of Industry and Information Technology recently collected the standard of "Powered Lithium Ion Battery Ceramic Seals", which will make more detailed regulations on the specifications and use of ceramic sealing rings.
2. Battery protection umbrella - flame retardant insulation, termination tape
The inside and outside of the battery are wrapped with adhesive tapes of various colors, and some are also printed with trademark codes, but it is not only for "face value", but also an essential part of battery safety. The tape in the battery is generally divided into two types, one is a termination tape existing inside the battery, and the pressure-sensitive adhesive tape for the steps of electrode winding, pole piece protection, and core termination, to ensure the normal operation of the battery reaction. . The other is the "clothes" used on the outside of the battery to provide the most basic protection for the battery: anti-collision, high temperature resistance. In the event of an accidental explosion of the battery, this layer of "coating" will also act as an explosion buffer to prevent combustion, and become a protective umbrella for battery safety.
Lithium battery termination tape, also known as lithium battery special tape, thickness is generally 0.016-0.055cm. The termination tape is a kind of pressure-sensitive adhesive tape. In addition to the general characteristics of the pressure-sensitive adhesive tape, it must also have certain acid resistance, alkali resistance, high temperature resistance and electrolyte resistance. Nowadays, the end tape on the market mainly uses polyester film (PET) or polypropylene film (PP) as the substrate, and is coated with acrylate or rubber special glue for lithium battery electrolyte, which is specially used for lithium battery termination and other. Insulation protection and fixing of the parts.
The battery case is insulated with a flame-retardant adhesive tape to provide the most direct protection for the battery. It has a higher thickness than the termination tape, and acts as a buffer when the battery is impacted. It also has high flame retardant, sealing and high temperature resistance to prevent external forces. Damage to the battery optimizes battery quality and extends battery life. And its most important role is to protect the safety of users. When the battery leaks from the electrolyte, it has a sealing property that can block the damage that the electrolyte may cause to the user. When the battery is accidentally burned or even explodes, it has superior flame retardancy, which can block the burning of the battery, thereby reducing the damage to a limit. The color of the insulating flame-retardant adhesive tape is also more diverse. Some will print the product code and trademark, which will increase the "face value" of the battery, and the side also drives the sales of the battery.
The Ministry of Industry and Information Technology issued the "Insulation Flame Retardant Adhesive Tape for Power Battery Enclosures", which will also make uniform standards for the color, specifications and performance of battery tapes, so that the insulation flame retardant makes the application of tape more standardized, which is beneficial to the battery. The development of the industry has also strengthened our own security.
3. Ultimate barrier - safety valve
Just listen to this name and know its position in the battery parts. The safety valve is located between the cap and the package battery to protect the battery and the user and become the ultimate barrier for battery explosion.
The organic electrolyte or polymer inside the lithium ion battery will be electrolyzed under the conditions of high current and high temperature, and the gas will be generated by electrolysis, and the gas will rapidly expand, causing the internal pressure to rise, which will seriously break through the shell and explode. Most of the batteries are now packaged in a metal case such as a steel case or an aluminum case. In the case of overcharging, short circuit, excessive temperature, or even if the battery is squeezed, the internal pressure will increase suddenly. The battery will explode when it is subjected to the value. This also allows the polymer soft pack to develop rapidly. When the gas inside the battery generates gas bubbles, the gas can break through the soft pack shell earlier, avoiding excessive accumulation and causing a severe explosion, but the polymer soft pack battery is only changed. A battery form does not eliminate the problem of battery explosion.
The safety valve solves this problem well, and it can prevent most of the battery inflation and explosion. The safety valve is standard for every 18650 battery and is the most important explosion-proof barrier. When the internal pressure of the battery rises to 1.0-1.2Mpa, the top safety valve will automatically open the exhaust pressure to avoid explosion. However, when the safety valve is opened, the chemical substance leaked inside the battery will chemically react with the oxygen in the air under high temperature conditions, and there is still a possibility of fire, so the safety cannot be pinned on the safety valve. In addition, some 18650 batteries now also come with a protective plate, with overcharge and over-discharge and short-circuit protection to provide double protection for the battery. Nowadays, the safety performance of regular batteries is very high, and the possibility of explosion is very low. However, if the battery is accidentally, the existence of safety valves will be the key to “lifesavingâ€.
It is the existence of these small parts that guarantees the normal operation of the battery, and also protects the safety of the user. Even in the event of a battery accident, it will become the last straw of “lifesavingâ€, and the state’s attention to this field also promotes the small battery. Parts have become more standardized and standardized.
