In recent years, with the extensive application of lithium ion battery products, lithium battery has increasingly become the most convenient power source for our daily life, and the safety of lithium battery has attracted more and more attention. The overall safety of lithium battery is composed of many complicated factors, among which thermal runaway caused by short circuit accounts for a considerable proportion. In addition to the common external short circuit, the damage of the internal diaphragm of lithium battery is also one of the important reasons for the internal short circuit.
Lithium dendrite is the target of many analyses and researches among the causes of membrane breakage. In the process of repeated charge and discharge of lithium battery, due to the process, material, overcharge, high current charging, low temperature charging and other reasons, metal lithium will inevitably precipitate, and the precipitated lithium will gradually deposit into lithium dendrites, thus becoming a potential risk of lithium battery. Lithium dendrites have a variety of forms, among which dendritic lithium metal will penetrate the diaphragm during the growth and deposition process to a certain extent, resulting in a short circuit in the battery, which often leads to disastrous consequences.
LLOYD Material Mechanics Testing Machine (LLOYD Material Mechanics Testing Machine) provides complete mechanical properties testing of lithium battery diaphragm, including tensile strength, elongation, puncture strength, peel strength (coating composite film), etc. At the same time, LLOYD Material mechanics testing system (LLOYD Material testing machine) can complete high-precision forced internal short circuit test of lithium battery, to ensure more safety of lithium battery.
Today we will introduce ametek lithium battery material test solution fourth lecture - lithium ion battery forced internal short circuit test.
Forced internal short circuit test for lithium ion batteries.
The forced internal short circuit test can be applied to both cylindrical batteries such as 18650 and 21700, as well as square flexible pack batteries. Before testing, the battery needs to be disassembled in a glove box in a specified environment and packaged with a standard metal nickel sheet that simulates tiny metal particles. After reaching the specified temperature and time conditions, the battery was placed in the forced internal short circuit test system at the speed of 0.1mm/s to put pressure on the position of the nickel plate, and the change of the pressure and surface temperature of the lithium battery was monitored in real time at the same time of reaching the specified pressure at a uniform speed. When a 50mV drop in voltage is observed or when the pressure load reaches 400N (square cell) or 800N (cylindrical cell), stop pressurization and hold for 30 seconds, then withdraw the voltage.
If a voltage drop of 50mV occurs before reaching the specified pressure, the battery does not meet the safety standards for mandatory internal short circuit test. If the voltage drop occurs when the pressure reaches 400N or 800N, it indicates that the battery can greatly avoid internal short circuit caused by external particles.
A high-precision forced internal short circuit test system requires a high-precision, high-sampling rate load application system. This system needs to monitor and record the voltage and temperature changes of lithium batteries at the same time, and can flexibly set test conditions to meet more stringent testing and research and development needs.
Forced internal short circuit test system.
In terms of load application and recording, the LLOYD LD system can achieve load accuracy of 0.5% reading level and record load changes at 1000Hz sampling rate. This system uses 32 bit A/D conversion, with extremely high force resolution. While achieving load accuracy and resolution, its voltage and temperature record can also be up to 250Hz, which is the highest accuracy and the highest sampling rate of the test system in the industry.
This system is equipped with explosion-proof high and low temperature environment box, which can meet the temperature requirements of standard forced internal short circuit test, and can simulate the mechanical properties of batteries at different temperatures by changing the temperature. The temperature chamber itself to explosion-proof level, even in the case of violent combustion, explosion of the battery can still ensure the safety of the test personnel and the system, and with active exhaust system, can be tested in the battery flue gas discharge, effectively ensure the laboratory environment.
Mechanical testing of lithium batteries
In addition to meeting the requirements of forced internal short circuit testing, the LLOYD LD test system can also take into account various high-precision battery mechanical strength testing, such as three-point bending strength, compressive strength, tensile strength and elongation measurement of lithium electric diaphragm, puncture strength of lithium electric diaphragm, tensile and puncture performance of aluminum plastic film, etc.
LLOYD test System focuses on all kinds of customized solutions to help you complete more professional standardized and customized testing, and assist in the testing and research and development of lithium battery products.
For more details, please contact AMETEK China office or local distributors.
LLOYD Material mechanics Testing Machine
LLOYD testing System (LLOYD material Testing machine) originated in the United Kingdom, is a product of AMETEK group. LLOYD materials testing systems are widely used in fortune 500 companies with reading-level accuracy, single-channel data sampling rates up to 8000Hz, and test speeds up to 2032mm/min.
LLOYD material testing system (LLOYD material testing machine) can accurately and conveniently complete material stretching, compression, bending, puncture, peel, tear, friction, creep, relaxation, low frequency fatigue and other test items. Rich jig solutions can ensure the accuracy of data while providing users with great convenience in operation. At the same time, as the core of the measurement and control system, professional Nexygen Plus operating software is widely recognized by the majority of users. The software comes with a huge international standard library, in addition to ASTM, DIN, EN, ISO, JIS and other international standards, users can also easily build their own standard files.