Batteries are indispensable devices in our everyday lives: so many items we use on a daily basis, from our mobile phones to our laptops, rely on battery power to function. Yet despite its mundanity, battery technology is suddenly hogging the limelight because it is used to power all sorts of different electric vehicles (EVs), from electric cars to e-scooters, which are regularly in the headlines. For true environmentalists, however, battery technology is more interesting as a way of storing electricity as the generation and use of renewable energy - which is intermittent - increases.
Last but not least, battery technology has attracted press coverage but in a less positive way because of the flammable properties of Lithium-ion batteries. During 2018, around 23 electric energy storage accidents at utilities in South Korea were reported due to battery-provoked fires. Short circuits, overcharge, over-discharge, mechanical damage and high temperatures can lead to thermal runaway, fire, and explosion in the batteries. New technologies are being investigated to improve Li-ion battery safety. The College of Engineering of the University of Illinois is studying graphene, as the material that could take oxygen out of lithium battery fires.
IEC International Standards and Conformity Assessment (CA) Systems are therefore more crucial than ever to establish and test the safety specifications and performance requirements for batteries, whether lead-acid, nickel-cadmium (NICad) or, indeed, Li-ion. Several IEC TCs prepare standards for cells and batteries. One of them is IEC TC 21, chaired by Herbert Giess. “IEC TC 21 is the primary TC to deal with battery standardization inside the IEC. It was founded in 1933. In 1965, it was decided to split the work of the TC into two different areas covering different battery technologies. Subcommittee 21A was given the task of preparing standards for batteries with alkaline electrolyte such as NiCad or nickel–metal-hydride and TC 21 was asked to focus on batteries with acid electrolyte called lead-acid. Both now share the work on Li-ion batteries which have become the new kids on the block in recent years,” he explains.
While IEC TC 21 and SC 21A prepare standards for cells and batteries used in multiple fixed and portable applications, IEC TC 120 was set up to publish specifications for their integration into electrical energy storage systems. “TC 120 standards concern the interconnection of batteries with the large energy storage systems and their safe integration into power grids,” Giess says.
IECEE (IEC System of Conformity Assessment Schemes for Electrotechnical Equipment and Components) is one of the four CA systems administered by the IEC. It runs a scheme which tests the safety, performance component interoperability, energy efficiency, electromagnetic compatibility (EMC), hazardous substances, etc. of batteries, chargers and charging stations.
According to a forecast by the International Energy Agency, the number of EVs on the world’s roads will increase from 3 million to 125 million by 2030. In 2018, IEC TC 21 published several important documents, including a second edition of IEC 62660-2 which is part of the IEC 62660 series on secondary Li-ion cells for the propulsion of EVs. “IEC 62660 has three different parts: the first deals with performance testing, the second with reliability tests and the third with safety requirements,” Giess describes.
The purpose of IEC 62660-2 is to provide a basic reliability and abuse testing methodology for Li-ion cells which can be used in a diverse range of automobile battery packs and systems. It is available in a red line version, which means that the changes with the previous edition are highlighted. The new edition specifies a thermal stabilization test which did not exist in the previous edition, for instance.
IEC TC 21 publishes a wide number of lead acid battery specifications. While this technology is still predominant because it is cheaper and safer than Li-ion for now, lead acid batteries are being phased out in a number of applications. “Lead has a bad reputation. Just see the coverage around the fire at Notre Dame de Paris and the lead oxide dust levels it generated. But what people often don’t know is that lead-acid batteries are 98% recyclable. They are recycled both in the US and Europe, using well mastered processes. The lead is used over and over again without losing its properties,” Giess argues.
Weight is also an issue: Li-ion batteries weigh considerably less than their lead-acid counterparts. Li-ion’s low weight is especially impressive when you consider performance. For the same weight as lead-acid, Li-ion batteries have a much higher energy density (energy storage capacity). According to most reports, the energy density of Li-ion is around 3,5 times that of lead acid.
Li-ion batteries can also be recycled, but this process remains expensive and, for the time being, the rates of material recovery rarely top 20%. The raw materials used in Li-ion batteries are generally nickel, cobalt, manganese and lithium which are expensive to get hold of. Some of these raw materials are scarce and can be situated in parts of the word which are difficult to access and politically unstable. Research is progressing fast, however, and some labs have managed to reach 80% recovery levels. Scientists are also looking at Lithium-air chargeable batteries as an alternative to Li-ion.
Another way forward is to reuse these batteries for second life applications. Depending on its chemistry, size, configuration and purpose, according to most reports, a Li-ion battery can perform between 500 to over 10 000 cycles of charging and discharging. This means that a battery that is used every day in a power tool by a professional craft worker might reach the end of its first life in a few months while a battery used in some energy storage applications can last for over 15 years.
Li-ion batteries that have been used in one application can be assessed for their ability to be used in other, less demanding applications. One possible second life for batteries is as a component for flexible charging stations. These are quick charging stations that can be operated autonomously during large-scale events, such as festivals or sporting events. Batteries from electric vehicles could be re-used in everything from back-up power for data centres to energy storage systems. In Europe several vehicle manufacturers, companies which are pioneers in the electric car market, have installed used batteries primarily in different kind of energy storage systems, ranging from small residential devices to larger containerized grid-scale solutions.
IEC TC 21 has issued two essential standards for renewable energy storage systems. The first one, IEC 61427-1, specifies general requirements and methods of test for off-grid applications and electricity generated by PV modules. The second, IEC 61427-2, does the same but for on-grid applications, with energy input from large wind and solar energy parks. “The standards focus on the proper characterization of the battery performance, whether it is used to power a vaccine storage fridge in the tropics or prevent black-outs in power grids nation-wide. As these standards are largely chemistry agnostic, which means that they apply just as well to lead-acid or to Li-ion batteries, they enable utility planners or end-customers to compare apples with apples, even when different battery chemistries are involved,” Giess describes.
The TC is also preparing standards for flow batteries. A typical flow battery consists of two tanks of electrochemically active liquids which are pumped past two electrodes of opposed polarity separated by a membrane. “Flow batteries are an interesting technology that can be used for very large energy storage requirements as the storage tanks can be sized at will,” says Giess.
Looking ahead, Herbert Giess rather surprisingly favours fuel cells for automotive applications. “Several car manufacturers are actively pursuing this avenue. We often forget that this technology was used to send Apollo 11 on the moon all those years ago! But it has a big environmental potential as cars powered by fuel cells do not generate any harmful emissions only water vapour and there are no battery recycling problems. Of all the technologies used to power cars, it is my personal favourite.”