Lithium-ion batteries are widely used in various fields such as mobile devices, energy storage and renewable energy vehicles and their advantages are longer life than energy, but more than other types of batteries, their main safety an issue that needs to be addressed. . Lithium-ion batteries cause safety problems usually from the generation of heat, and finally, the nature of heat runaway and the reason for the establishment of thermal runaway is mainly short circuit, connection failure, high temperature baking, water immersion, etc., of short circuits. is a common cause of thermal runaway Short circuit divided into external external circuit and internal external circuit, external circuit can be controlled by the protection of auxiliary components and optimization plan when the internal short circuit is strong in effective way to control.
Short circuit simulation test procedure
Nail insertion, extrusion, drop, impact weight and other tests are short circuit test methods commonly found in standards, such as QC/T743-2006, SAND2005-3123, UL2580 -2011, SAE2464 and other standards.
In order to improve the short-term effect, different test methods are restricted to the standard. Acupuncture test specifies the speed of needle insertion (QC / T743-2006 requires 10 ~ 40mm / s, other standards require 80mm / s) needle diameter (usually 3 ~ 8mm); The extrusion test specifies the amount of deformation of the extrusion pressure (100 kN or 1000 times of the sample) (usually 50% of the deformation) and the shape of the extrusion disk (30 mm extrusion plate with a radius of 75). mm; The fall test specifies the height of the fall (1 to 2 m) and the contact surface (hard or lose ground) during the fall.
The advantage of the above method is that it is easy and convenient to implement, since it only shows the visible signs when there is a short period of time in it, and the collection of heat energy which was developed further into the short internal without barriers. can’t explain the weight for the fire that is given after a short period of time.
Short circuit prevention and detection methods
Short circuit protection
(1) Battery, system configuration
The risk of short circuit can be reduced by using ceramic membrane. If the short circuit is unavoidable, the short current can also be reduced by covering the electrode with a layer of PTC, as it increases the resistance of the PTC layer when the short circuit occurs. does , thereby preventing the generation of heat. . Also, since the current electrolyte is based on the alkyl carbonate system, it quickly burns the battery. Improper use of the heating element will cause combustion or explosion by using an electrolyte such as fire retardant or using liquid ionic electrolyte or adding maleimide oligomer which will reduce the security risks posed by short circuits.
(2) Battery usage
Prevent low evolution lithium chargers. Under low temperature conditions, the amount of ion conductivity and circulation of lithium-ion batteries is greatly reduced, which can lead to the initiation of lithium during transfer, so the battery should be warm to be proper heating when you use it at low temperature, to prevent the battery from forming lithium dendrites and measure the diaphragm when charging at low temperature.
A way to find a short circuit in the battery
Temperature detection: Determine if a short circuit has occurred by placing a thermocouple near the battery wall to detect temperature changes. Since the heat is directed from the inside to the outside when a short time occurs, the temperature shows that there is a break, so it is not possible to return the short state immediately.
Summary
The lithium-ion battery in the small circuit is easy to make it run hot, so through the manual process to understand why it is set up, through the simulation to increase it , so that through a variety of methods to prevent and detect lithium-ion batteries. Short circuit to make, to ensure the safety of the lithium-ion battery during use.
