Lithium-ion batteries Improve battery production through digitalization strategies

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Mitsubishi Electronic Europe BV

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The future of lithium-ion battery production is golden. But with growing demand, the pressure on manufacturers is also increasing. How can they effectively scale and improve their processes to turn the challenges they face into opportunities?

It is well known that lithium-ion batteries require expensive raw materials and undergo a particularly complex production process with unfortunately very high scrap rates. If manufacturers are to expand their activities and help electric vehicles take their place at the center of the transport sector, they need every possible advantage. They must use all available resources at their disposal.

An approach that can help achieve this advantage is digitalization—the implementation of digital technologies to capture and process the vast amounts of data generated in modern manufacturing. This data serves to gain insights that bring tangible benefits to the production process.

Meeting the increasing demand

It can only be estimated how dramatically the lithium-ion battery sector will grow in the next ten years. The increasing demand from the electric vehicle sector has already helped the global market grow from around 40 billion US dollars in 2018 to more than 60 billion US dollars in 2022. And this is far from the end of the tunnel, as the growth trend is expected to accelerate further. Forecasts suggest that the market will be worth more than a quarter of a trillion dollars by the end of the decade.

However, the sheer scale of this expansion brings with it some demands. Not only will the competition increase incredibly, but the raw materials used for manufacturing lithium-ion batteries will become scarcer and more expensive with rising demand. Lithium, cobalt, and nickel must be mined and processed before they can be used for production. The IEA predicts that the total demand for minerals needed for electric vehicle production will increase 30-fold between 2020 and 2040.

Very high rejection rates

To meet the increasing demand for electric vehicles, production must be made as efficient as possible. A bottleneck in production is the implementation of effective quality control and the reduction of high scrap rates. Despite working with valuable materials, the scrap rates are extremely high. About 10% of finished products do not meet minimum requirements and end up as waste. In many cases, this rate can rise to an incredible 30%. This high rate is not only incredibly costly and one reason why the battery typically accounts for up to 60% of the total cost of an electric vehicle, but it is also unacceptable for sustainability reasons.

However, to be fair, these rates are not due to negligence or irresponsible behavior by manufacturers. Rather, it is because the manufacturing process itself makes it extremely difficult to carry out conventional quality control measures.

Why the production of lithium-ion batteries is so complex

The production of lithium-ion batteries begins with the manufacturing of strips (or foils) of metal—copper for the anode and aluminum for the cathode. The size of these strips can vary greatly depending on the design and specifications of the batteries being produced, but they are typically several hundred meters long—often over a kilometer at larger production sites—and between a few centimeters and over a meter wide.

To convert them into batteries, the foils are coated with a thin layer of active material slurries. For the cathode, materials such as lithium cobalt oxide, lithium iron phosphate, or other lithium metal oxides are typically used, while the anode is coated with graphite or silicon-based materials.

Neither too thick nor too thin coating

Regardless of the materials used, the thickness of these coatings has a significant impact on the energy capacity and ion transport efficiency of the finished battery. Thicker coatings can store more active material, potentially increasing the overall energy storage capacity of the battery. However, this advantage comes with a downside. Coatings that are too thick can impede the movement of lithium ions between the electrodes, reducing the battery's charge and discharge speed.

This balance between thickness for increased energy storage and the need for efficient ion transport is crucial. It directly affects the battery's performance, especially in EV applications that require rapid energy delivery. If a coating is too thick or too thin, large sections of a strip may be unsuitable for use in a finished product.

Challenging: produce a consistently thin foil

Although the ideal thickness varies depending on the manufacturer's exact requirements, cathode coatings typically range from 100 to 200 μm, while anode coatings are usually somewhat thinner, generally around 70 to 120 μm. This is roughly the thickness of a human hair.

It is not surprising that maintaining a consistently thin foil over an area of up to hundreds of square meters is an incredible challenge. Dozens of factors can affect the thickness of the final product, from the temperature of the foil to the humidity in the facility.

Capturing this complex, ever-changing data is nearly impossible for conventional manufacturing facilities. Yet, it is precisely here that the right implementation of digital manufacturing technologies can help companies excel.

From raw data to results

Modern production lines are equipped with a multitude of sensors that generate vast amounts of data. When this data is effectively analyzed, it can lead to significant improvements in the manufacturing process.

A common application is predictive maintenance. By analyzing data trends, it is possible to predict, for example, when a machine needs targeted maintenance because the drive is drawing slightly more power than usual or the amplitude of vibrations is increasing. This allows operators to address the issue long before actual problems arise, preventing unexpected downtime and increasing efficiency.

Companies can use the same principle to improve the state of lithium-ion battery manufacturing. Not only by implementing predictive maintenance but also by identifying which factors correlate with cell quality. This way, it can be determined which parameters can be controlled to achieve high-quality cells. This increases the value of functional batteries and reduces the amount of material that needs to be scrapped.

Mitsubishi Electric has already applied this knowledge to real production lines for lithium-ion batteries—with impressive results. The team focused on the issue of uneven layer thickness, collecting data from 127 different parameters to determine which might be correlated.