Gas detection LI-ION BATTERY RISKS REDUCED BY VOC SENSORS P
hotoionisation detection (PID) sensors are able to detect potential problems before they occur in the manufacture and use of lithium-ion (Li-ion) batteries, and the enormous variety of devices that use rechargeable batteries. The safe utilisation of Li-ion batteries is a key concern for the developers of equipment such as electric vehicles, e-bikes, mobile phones and laptops. The risks posed by Li-ion batteries have been highlighted by a number of high-profile incidents. In 2006 and 2007, for example, millions of laptops and mobile phones were recalled due to safety fears relating to their Li-ion batteries, and in 2013, a Boeing 787 was grounded following electrical issues with the Li- ion battery in the aircraft's auxiliary power unit. Famously, in 2016, around 2.5 million mobile phones had to be recalled after complaints of overheating and exploding batteries. Extensive investigations revealed insufficient insulation material within the batteries and a design that did not provide sufficient space to safely accommodate the batteries' electrodes, resulting in thermal runaway, which occurs when temperatures are raised by thermal or mechanical failure, short circuiting, or electrical abuse. In more recent news, there has been a 60 per cent increase in e- bike fires in London in 2023 compared to 2022, and this number will continue to rise. As a result of the magnitude of this problem, and the global publicity which ensues, demand is growing for sensing technology that can detect faulty Li-ion batteries, during both production and operation. The main safety hazards associated with failing Li-ion batteries are the ignition of the battery cell and/or the emissions of toxic gases. These gases include volatile organic compounds (VOCs), meaning sensitive VOC sensors can be used to check the condition of these batteries – either within portable detectors or in process/plant monitoring equipment. The anode in rechargeable Li-ion batteries is typically graphite, the cathode is a metal oxide, and the electrolyte is usually a lithium salt in a
VOC Dimethyl carbonate Ethyl methyl carbonate Diethyl carbonate Vinylene carbonate Butylene carbonate 1,2- Propylene carbonate Ethylene car-bonate
Boiling Point (°C)
91 107 127 162 238 242 243
(flammable) organic solvent. This elec-trolyte includes compounds such as ethyl methyl carbonate (EMC) which is known to be among the gases emitted by a faulty Li-ion battery. Conveniently, EMC can be detected by ION Science’s PID, so the developers of monitoring systems and equipment are able to design technologies that utilise ION’s MiniPID sensors. The Response Factors for VOCs commonly used in Li-ion battery electrolytes are pre-sented in Table 1: Evaluation of chemicals used in lithium-ion batteries. Due to their specificity, PID sensors are the most commonly employed technology for the
RF 65 18 7.5 3.5 18 15 >50
Sat. vapour pressure @ 25 °C bar
0.07 0.035 0.015 0.0033 0.0002 0.0002 0.0003
detection of VOCs, and ION’s MiniPID range includes the most sensitive PID sensor in the world, which makes it ideal for the detection of trace leaks from faulty Li-ion batteries. Summarising, Peter Morris from ION Science
says: “Prospective customers for our PID sensors in Li-ion battery applications include the developers of portable instruments, as well as the designers of monitoring systems for processes within battery manufacturing, as well as in the manufacture of EVs, e-bikes, laptops, tablets, phones and many others.”
ION Science
Prospective maximum rsponse, ppm (IBE)
1000 2000 2000 1000 1 1 0.5
www.ionscience.com
Measured spike response, ppm (IBE)
80 240 390 480 10 80 <1
60
January 2024 Instrumentation Monthly
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