• • • ELECTRIC VEHICLES • • •
Powering the EV market with battery purity
The electric vehicle (EV) market is booming with more battery- powered cars sold in 2021 than in the previous five years combined1, says Christophe Goasdoué, fluid technologies and asset protection marketing manager for Asia-Pacific at Pall Corporation
P
redictions indicate that global sales of electric cars will account for more than 30% of new sales in key markets by 2040 – up
from 5% in 20202.
Energy suppliers are also realising they need to tap into this burgeoning market, as seen by the UK’s largest independent chain of petrol stations, Motor Fuel Group, announcing a £50 million programme to install 350 fast electric chargers on its sites in 20223.
Lithium-ion units are acknowledged to be the best battery option for cars when comparing size, weight, total cost of ownership and environmental impact, but we must not overlook how challenging it can be to ensure optimum performance. Impurities in materials used in their production directly affect power densities, cycle life and safety. The ‘cleanliness’ of each individual component has a significant impact on the final product and as components get smaller and more sensitive to contamination, robust quality control becomes increasingly difficult. Battery manufacture needs to be taken to the next level to keep up with rapid growth in the EV market, and that means focusing intently on the materials used and adopting a truly scientific approach to quality control.
The cleanliness challenge There are three components of lithium-ion batteries that are most at risk of contamination during manufacture: separators; cathode active materials; and liquid electrolytes. Even the slightest impurities affect a battery’s performance and can undermine the value of the product and the vehicle it powers.
Separators
Separators are becoming thinner as technologies improve, making production processes and quality control challenging. To ensure separators meet technical specifications for cleanliness, quality and uniformity, polymeric films must not contain any microscopic metal particles because contact with other parts of the battery cell could cause electrical short circuits.
Cathode Active Materials (CAM)
The cathode or positive electrode comprises a mix of metal oxides containing lithium. The more uniform its chemical composition and structure, the better the performance and longevity of the battery. The production process requires multi- chemical transformation stages involving solid, liquid and gaseous products, and quality controls
are becoming more stringent as CAM quality impacts not only the overall performance of the battery itself, but also its cost per KWh.
Liquid electrolytes
Electrolytes must demonstrate stability against both the cathode and anode surface. Different types of electrolytes are used, but there is still a need for developments to improve their performance in lithium-ion batteries.
The need for filtration and
separation solutions Each of the constituent parts of a lithium-ion battery has a different requirement. With process water there needs to be approximately 10-90µm particulate, which can be achieved with a particulate filter. And with the paraffin liquid and plasticizer, there should be protection from an ultra-fine cross-flow system to ensure appropriate quality. For cathode manufacture, the various processing lines need an array of cleanliness and quality controls, from oxygen and nitrogen to solvents and pure/mixed solutions. Sub-micron filter ratings need to be as low as 0.3µm, which requires a combination of filtration technologies including cross-flow, liquid-gas coalescence and particulate filtration technologies.
The acidity in liquid electrolyte requires ethylene tetrafluoroethylene (EFTE) coated stainless-steel vessels. Very fine particulate removal ratings (from 0.45µm to 2µm) must also be achieved to ensure cleanliness.
30 ELECTRICAL ENGINEERING • FEBRUARY 2022
Partnering for success EV production is a complex business, but the purity of a battery’s components is vital to the successful running of the car. In sporting philosophy, the concept of marginal gains advocates that every ‘small’ advantage leads cumulatively to enhanced outcomes and a winning formula. For the EV market, progression will be made as suppliers and OEMs work together more collaboratively. If manufacturers bring materials science experts such as Pall into the design process earlier, we can ensure the right filtration technologies are deployed, eliminating some of the points of failure within EV batteries. Through partnering on strategies and projects, we can minimise risk, improve performance and reduce the costs of EV batteries – driving this thriving industry to future prosperity.
References
1
https://heycar.co.uk/blog/electric-cars- statistics-and-projections
2
https://www.bloomberg.com/news/articles/ 2021-08-09/at-least-two-thirds-of-global-car- sales-will-be-electric-by-2040
3
https://www.autocar.co.uk/car-news/business- environment-and-energy/independent-petrol- forecourt-group-spend-%C2%A350m-charge- points
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