It’s clear to everyone nowadays that the EV market is expanding at an increasing rate. Automotive manufacturing has been with us for over 100 years and by now the manufacturing process has been optimised and streamlined for almost all components. However, one component part is evolving as fast as the technology allows – the Battery cell. This means that the manufacturing process also must evolve to keep up with the changing battery formulations and to eliminate waste in the production of both anodes and cathodes. Currently, losses in the manufacturing of lithium-ion batteries due to scrappage of out-of-specification electrodes can run as high as 2-5% of output, with even higher numbers possible at the ramp-up of new manufacturing runs. This wastage contributes overall battery cost and becomes very significant as production is scaled up in giga factories.
To minimise these losses the Battery Industry is turning to proven solutions from the automotive industry – terahertz based measurement techniques. Non-destructive and non-contact terahertz based solutions have an increasing role to play in both off-line laboratory solutions and in-line production solutions to help manufacturers initially validate their designs and then to optimise production.
There are alternative solutions such as x-ray or laser gauging measurements, However, these techniques do not provide all of the key performance indicators. Off-line techniques such as sampling and weighing a coated electrode vs. uncoated substrate are also used. However, on large scale production, the off-line trial-and-error approach can lead to much additional wastage and equipment downtime. In-line techniques offer the opportunity for real-time process control with cost reduction and insurance-of-supply benefits.
The terahertz technique uses highly accurate time of flight measurements (Figure 1) to determine coating thickness based on multiple reflections of terahertz pulses from different coating interfaces. The technique operates as a high frequency pulsed radar system, where time of flight (delta T) is converted into coating thickness (d) based on the formula where c denotes the light speed and n is the refractive index of the coating terahertz measurements enable us to assess the quality of battery electrodes and detect any deviation from the initial design in the manufacturing process. In figure 1, the measured signal from two separate cathodes shows delta . Since both samples are fabricated from the same material (n=3.5), the difference in time of flight in two waveforms interpreted sample 2 is thicker than sample 1 and thickness of each is calculated Micro metres and Micro metres. In addition to the thickness evaluation, with a bit of mathematical effort, the terahertz technique makes it possible to evaluate key performance indicators of the coating such as conductivity and density simultaneously.
Both anode and cathode electrode coatings can be resolved by use of patented algorithms. TeraView has demonstrated reliable and repeatable measurements for both anode and cathode electrode coatings using the same hardware equipment. Working with leading automotive lithium-ion battery manufacturers as well as academic collaborators, TeraView is extending these capabilities to coatings on battery electrodes.
TeraView (https://teraview.com/) is the world’s first and leading company solely focused on the application of terahertz light to provide solutions to customer issues. A spin out from the Toshiba Corporation and Cambridge University, TeraView has developed its proprietary technology across a number of markets. These include non-destructive inspection of high value coatings used in the automotive, pharmaceutical, food and solar industries as well as fault analysis and quality assurance for semiconductor chips used in mobile computing and communications. With the largest number of systems in the field, as well as applications know-how made available to customers via a team of dedicated engineers using intellectual property and knowledge in peer-reviewed scientific publications, TeraView is uniquely placed to deliver the business benefits of terahertz to customers. Headquartered in Cambridge UK, sales and customer support are available throughout the Far East, North America and Europe either directly or through a network of distributors.