China Energy Storage Network News:Shenzhen Kemin has advanced technologies for new energy vehicles (three electric systems) and energy storage batteries (thermal management) sensors, and is a leading technology company that can provide a complete set of sensor solutions. Since 2019, the Scientific Sensor Innovation Research Institute, in collaboration with the Gas Sensor Research Institute of Shanghai Jiaotong University and Shenzhen Fodi Power Co., Ltd., has successfully developed the first power and energy storage battery gas sensor (leakage detection: detecting volatile substances（VOCs）Gas concentration changes).

NO1. Development background

Lithium ion batteries can produce gases such as carbon dioxide (CO2), carbon monoxide (CO), volatile organic compounds (VOCs), and hydrogen (H2) in the early stages of liquid leakage. So, how can we be detected in the bud of danger, safeguarding the safety of life and property?

NO2. Mechanism analysis

2.1. Carbon dioxide (CO2) gas comes from the early stage of battery leakage, that is, when danger occurs, the SEI membrane (main components: lithium carbonate (Li2CO3), lithium methylcarbonate (LMC), and lithium ethylcarbonate (LEDC) inside the battery will decompose under the catalytic action of the electrolyte lithium hexafluorophosphate (LiPF6) to produce carbon dioxide (CO2); Therefore, the detection and identification of initially produced gas under abnormal conditions is crucial for early detection of lithium battery leakage! It is highly feasible to use carbon dioxide (CO2) concentration to monitor power battery leakage. However, due to the presence of carbon dioxide (CO2) in the air at a concentration of about 400 ppm, sensor false positives can occur.

At this point, other "dangerous signal gases" are needed to assist in detection. There are two iconic gases: carbon monoxide (CO) and volatile organic compounds (VOCs).

Carbon monoxide (CO): It mainly comes from the deflagration stage in the later stage of battery leakage and thermal runaway (the gas is generated when electrolyte combustion is not sufficient in the sealed environment of the battery pack). From the perspective of timeliness, using carbon monoxide (CO) concentration detection as a detection item obviously cannot achieve early safety warning!

Volatile Organic Compounds (VOCs): The interior of the battery contains a large number of low boiling point organic electrolytes, such as dimethyl carbonate (DMC), methyl ethyl carbonate (DEC), etc. When the interior temperature of the battery rises, these organic electrolytes are easily vaporized and released through the exhaust valve. Therefore, monitoring the concentration of volatile organic compounds (VOCs) becomes an ideal means for early warning of thermal runaway abnormalities in batteries. At the same time, this has also been confirmed by international authoritative research institutions: When abnormal battery leakage occurs, volatile organic compounds (VOCs) are the fastest gas to precipitate, with a concentration second only to CO2. At this time, the battery temperature does not change significantly. However, in the same way, as the concentration of volatile organic compounds (VOCs) is mainly affected by temperature, when power batteries are used at high rates, the temperature may remain high for a short period of time, resulting in electrolyte vaporization (VOCs) and discharge, which can easily lead to sensor false alarms. It is also necessary to jointly warn with other "dangerous signal gases" to further enhance the accuracy of sensor early warning.

NO3. Successful R&D

KM-CO2/VOCs I with dual detection functions for CO2 and VOCs gas emerged as the times require!

The Scientific Sensor Innovation Research Institute has developed KM-CO2/VOCs I sensors over three years! It is a gas detection sensor with a CAN FD output interface, with dual monitoring functions for CO2 and VOCs gases; It has excellent qualitative and quantitative detection performance for mixed gases, and can provide feedback on whether the battery is operating safely by monitoring the gas generated by battery leakage. Otherwise, the sensor will promptly feed back and cut off the charging circuit, effectively preventing the risk of thermal runaway of the battery.