There are increasing cases of lithium-ion battery product recall due to safety problems. The activity and high energy density of Li will bring great problems to the safety of lithium-ion batteries. At present, the screening, inspection methods and standards for the safety performance of lithium-ion batteries, especially the potential safety hazards caused by some potential micro structural defects, lag behind the development of lithium-ion battery technology, and the evaluation method and evaluation system have not yet met the requirements of lithium-ion battery safety performance evaluation. In view of this, this paper summarizes and analyzes some representative standards.
1.Introduction to battery safety performance testing standards
At present, the widely used international standard is the lithium ion battery standard of the International Electrotechnical Commission (IEC). According to their respective needs, the International Air Transport Association (IATA), the United Nations Committee of experts on the transport of dangerous goods and the International Civil Aviation Organization (ICAO) have also formulated relevant lithium-ion battery transportation safety standards and have been widely used. In addition, the safety standards for lithium-ion batteries formulated by some countries and organizations, such as Underwriters Laboratories (UL), American Institute of electrical and Electronic Engineers (IEEE) and Japan National Bureau of standards (JIS), also have a wide impact. The test items of these standards are similar, but the test conditions are different.
There are four international standards that are widely used and have a wide range of influence. The United Nations (UN 38.3) manual of tests and standards for the transport of dangerous goods and IEC62281:2012 “safety of lithium primary batteries and battery packs and lithium batteries and battery packs in transport” both focus on the safety test and safety requirements of lithium-ion batteries in transport, mainly aiming at the simulation test of the external environment and mechanical vibration of lithium-ion batteries during transport, including high simulation 8 requirements for temperature test, vibration, impact, external short circuit, impact, overcharge and forced discharge. During the test, the battery shall ensure that the package does not fall off, deform, lose mass, leak, discharge, short circuit, rupture, explosion and fire.
UL1642:2009 lithium battery is applicable to primary (non rechargeable) and secondary (rechargeable) lithium batteries used as power supply in products. The purpose of the standard is to reduce the risk of ignition or explosion of lithium batteries in the use of products. The electrical performance test of battery in the standard includes short-circuit test, abnormal charging test and forced discharge test; Vibration test, impact test and mechanical test; Environmental tests include thermal abuse temperature cycle test, high-altitude simulation test and projectile test. The test requires that the tested battery shall be free from fire, explosion, liquid leakage, exhaust and combustion during the test, and the package shall not be broken.
IEEE1625:2008 standard for rechargeable batteries for notebook computers and IEEE1725:2006 standard for rechargeable batteries for mobile phones mainly establish unified guidelines for the design, production and development of batteries for portable computers and cellular phones, mainly involving the electronics, physical structure, chemical composition, processing flow Quality control and packaging technology. Compared with other battery standards, which generally pay attention to batteries or battery packs, the above standards comprehensively consider the aspects of cells, batteries, host nodes, power accessories, consumers and the environment. These two standards focus on the design and manufacturing process, and do not involve much in the later use of the battery, especially the safety.
2. Focus analysis of existing standards
The current main standards can be summarized into the following categories:
2.1 It is mainly aimed at the external environment and mechanical vibration during transportation
Such as UN38.3, IEC62281:2012 and others simulate the possible hazards of lithium-ion batteries during transportation through test items such as height simulation, temperature test, vibration, impact, external short circuit and impact, which involves less safety issues during the use of lithium-ion batteries.
2.2 Mainly for the design and manufacturing process
Such as IEEE1625, IEEE1725, etc. Taking IEEE1725 as an example, the standard divides the mobile phone lithium-ion battery system into four parts, namely, the cell battery pack, the host and the battery charger. It comprehensively and clearly requires the design, raw materials, manufacturing process and finished product test and evaluation of the cell, so as to provide a reliable evaluation guarantee for the safety of the cell and even the mobile phone and other communication products. The above standards mainly focus on the design and manufacturing process of batteries, and do not involve much safety issues in the later use of lithium-ion batteries. And such IEEE lithium-ion battery standards, due to the strong pertinence of the design and manufacture of lithium-ion batteries in different equipment, the scope of application is limited to a certain extent.
2.3 It is mainly aimed at the electrical performance and safety of lithium-ion battery
Such as UL1642. Through short circuit, abnormal charging, forced discharge test, extrusion, impact, impact, vibration, thermal abuse, temperature cycle, high-altitude simulation test, projectile and other test items, the tested lithium-ion battery is required to be free from fire, explosion, liquid leakage, exhaust, combustion and packaging rupture during the test. Comparing the above two types of standards, the core of these standards is the safety of lithium-ion batteries, and pay more attention to the battery safety risks caused by temperature. However, the judgment basis is difficult to quantify. Only the explosion, fire, smoke, leakage, rupture and deformation of the tested battery can be used to distinguish the batteries that are not conducive to detecting potential dangers.
Safety performance has become an important indicator of lithium-ion battery and another key indicator restricting the application of lithium-ion battery in addition to the cost factor. Due to the characteristics of lithium-ion battery, it will not show abnormal electrochemical behavior in the initial use stage. These potential defects make it difficult to judge whether the lithium-ion battery is qualified. In this paper, the author summarizes and summarizes the commonly used lithium-ion battery safety performance testing standards at home and abroad. Through analysis, it is found that there is a lack of testing methods and evaluation basis for the potential risks of lithium-ion battery safety at home and abroad, and no fast and effective lithium-ion battery safety testing methods or screening methods have been formed.
With the increasing requirements of consumers for the electrical performance and safety of lithium-ion batteries, it is necessary for battery manufacturers, competent departments and industry associations to study the detection methods of the safety performance of lithium-ion batteries and establish a set of intuitive, rapid effective detection methods improve the requirements within the scope of the existing standard system, further refine the standards, clarify the judgment basis, make up for the shortcomings of the existing lithium-ion battery detection standards and systems, improve the detection level of lithium-ion battery safety performance, ensure the sustainable development of lithium-ion battery industry and protect the safety of consumers in the process of battery use.