Test & measurement T
he need to reach zero emissions is on everyone’s agenda. Consumers and industry are increasingly looking to electric energy sources to replace fossil fuels. However, success requires
reliable and efficient forms of battery power storage and better ways to store excess power and stabilise global demand. Achieving that evening-out of supply and demand is the ability to offer long life and material composition flexibility coupled with retaining the ability to power everything from small portable electronic devices to heavy electric vehicles. So far, Lithium-Ion (Li-Ion) batteries have emerged as the leading device capable of servicing many such applications.
It is not a pun to say that much of the demand is being driven by automotive and transport industries, which from 2015-2023 has and is projected to require 450 GWh of Li-Ion battery capacity. To meet those demands the battery industry continues to increase production exponentially. China currently has more than 76 per cent of global manufacturing capacity, but many other regions are developing rapidly. For example, Europe will build 850 GWh of capacity by 2030 with Germany accounting for approximately 330 GWh of the total.
MAKING A BATTERY IS NOT A ONE- TRICK PROCESS
Li-Ion battery cells are comprised of an anode, a cathode, a separator, and a liquid electrolyte. Although structurally simple, manufacturing batteries is an extended and involved process. Electrode manufacture begins with mixing a slurry of active materials, binders, and additives and using it coating both sides of its current collectors. Cathodes are formed by webs of aluminum, and copper is used for the anode. The electrodes’ physical properties are adjusted by compressing them in a calendering process, after which they proceed to a slitting and stamping stage to ensure the electrodes are precisely the right dimensions. After going through a subsequent vacuum drying stage to remove any excess water or solvent, electrodes go to a dry room together with dried separators in preparation for cell production. The electrodes and separator are then wound or stacked in layers, forming an empty cell. The final two stages consist of sealing the electrodes and separator in the package, which is then filled with electrolyte. At that stage, a new battery cell has been born.
MEASURING QUALITY
But to get to the finished stage, parameters such as temperature, pressure, force, level, and flow must all be measured accurately throughout the production process to ensure consistency and quality.
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THE BATTERY REVOLUTION IS BEING DRIVEN BY DIGITAL
MEASUREMENT
The drive to make enough batteries to meet demand for everything from automobiles to long-term energy storage is prompting the urgent construction of new battery production facilities around the world. Frenk Withoos of ABB Measurement and Analytics takes a look at the major role measurement plays in the battery production process and why accuracy is crucial to ensure the top quality and consistency.
For example, the slurry must be mixed at 20°C to 40°C, while its homogeneity i.e., particle size, purity, and viscosity - also affecting its quality – must also be closely measured. Coating requires measuring the dry film thickness to an accuracy of +/- 2 g/m2
,
while surface quality and adhesion between the substrate and the coating are also crucial measurement parameters.
The drying process maintains a web speed of between 35m/min and 80m/min, while temperature is maintained between 50°C and 160°C. Other critical quality parameters include residual humidity and measuring adhesion to the substrate. A constant roller speed of 60 to 100m/min is essential during calendaring, and roller temperatures must be maintained between 50°C and 250°C. The process of slitting can introduce burr waste, so the degree of particle contamination during the cutting process is another important quality control parameter.
The vacuum drying stage demands high accuracy measurement. A working pressure of between 0.07 and 1,000 mbar and a temperature of 60°C to 150°C are essential to the process.
After winding and assembly, the final process of electrolyte filling involves
January 2024 Instrumentation Monthly
measuring pressure to approximately 0.01 mbar as well as ensuring the correct electrolyte quantity. Aging of the cell then involves temperature measurements over extended periods.
With so many intricate processes and valuable materials involved, manufacturers need to avoid scrapping parts and materials if quality parameters go out of specification, which is why so many precise measurements are needed at every stage of manufacturing.
DIGITAL IS THE DIRECT ROUTE TO TOP QUALITY Many analogue instruments are still lingering in numerous industries, though the
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