Industry Focus: Battery Manufacturing and Surface Treatment

Battery Manufacturing Industry and Potential Problems

Working with the battery industry is interesting because of the amount of growth and development currently taking place driven by plans for a green future with smarter energy storage. Facilities like UKBIC in Coventry are looking to lead the way for the UK and generate new technology with industry partners.

As an industry that has been manufacturing vehicle and household batteries on a large scale for more than 100 years, but also an industry that has new challenges and technologies at its disposal and importantly, a will and drive from many around the world as we transition from fossil fuels and move to renewable technologies that need to be harnessed with larger than ever storage devices.

This growth and demand has had many challenges, from supply chain and mining issues, through to manufacturing and then end of life and recycling. There seems to be a problem of some kind at every step of the way, especially when considering that the technology for many is seen as the future, so it cannot have the same harmful and negative effects as fossil fuels.

The specific problems we have seen and worked with have been at the manufacturing stage and have included treatment of raw materials such as powders and foils, as well as packaging, cooling and fixing problems.

We have found many applications to be very interesting because of the approach of the engineers. With many older industries, aerospace being a key one, pushing for newer technologies can be very difficult as revalidation, redesign and replacing old machinery can all be costly, time consuming and generally prohibitive.

However, because a lot of the newer battery technology is being developed with fresh eyes and a focus on the future there seems to be a true desire to use the latest, best and most sensible technologies available.

Possible Solutions To Some Of These Problems

As the battery industry progresses in to opening new giga factories and meeting future demand, these problems need to be addressed and solved. The fact is that many of the problems are solvable and it just needs an engineering team to find the right solution.

Here are a couple of the problems we’ve worked on and some of the possible solutions:

Raw Material Chemistry

Raw materials such as carbon based powders, reactive metals and metal foils all need to be correct to ensure the right chemistry is present and the right performance of each material. This is especially important as manufacturers strive for efficiency as the technologies are pushed to their limits.

Raw material processing as been done for many years and has been refined to be quite sophisticated for many applications. Traditional cleaning and processing using chemicals is often a highly suitable process that delivers excellent results. Even processes that require harsher chemicals are often safer in modern manufacturing due to sealed and automated systems that can reuse or recycle liquids.

The advantage of this is that it’s a highly known and understood area of manufacturing used in many high tech industries such as aerospace and electronics. But it can still have it’s downsides with significant amounts of chemicals needed, including transport and disposal costs and environmental impacts that can add significantly to a battery cells carbon footprint.

Material Processing and Cleaning

One big problem in any industry looking to push the limits of the technology is the level of cleanliness of all critical components. One layer of grease, or particulates in the wrong area can lead to significant losses in efficiencies and give variability to the final product.

This can cause big problems because cleanliness isn’t always a problem that can be solved at source. A foil for electrode manufacturing for example could be perfectly clean leaving it’s manufacturing site in one country, but by the time it has been shipped, stored and processed through rollers it could pick up trace contamination and cause problems.

The only real way to be completely sure of product cleanliness, and avoid issues with variable incoming material quality, is to clean and prepare the foils immediately before use. As with the chemistry of the materials, traditional wet processes can be useful, but similar issues can occur.

For some applications it is essential to have a perfect surface to maximise wetting and flow of liquids over the surface as well as to improve adhesion and lifetime product quality.

Packaging and Cooling

New battery technology can have a range of designs and materials and this can be a problem for adhesion of cooling fins and channels, or for the packaging and cell structure to be bonded together. Thermal cycling and expected lifetime shock due to vibration and in worst case damage, means that the products need to perform higher than traditional household batteries.

Labelling, printing and coating can all face the same challenges of adhesive bonding too and the fact that the lightest, most recyclable and sustainable materials are being targeted for use can mean that adhesion performance comes in secondary to other product specification concerns.

As with many adhesion issues there are solutions and the use of a range of adhesives, use of primers and adhesion promoters, harsher chemical use in the product or manual abrasion can all have a place.

Some of the problems have come about when these processes don’t suit the automated manufacturing techniques being used for manufacturing, or when dissimilar materials are used that require different preparation techniques for all bonding areas.

Plasma and Corona Treatment for Battery Manufacturing

Some more traditional battery manufacturing companies have engaged with Plasma and Corona treatment in the past, however, as expected there has been increased demand during the 2010s and especially in to the 2020s as design engineering increases and genuine implementation of new factories rather than research and low volume facilities start to take shape.

Taking the previous examples; here’s are how we solved the problems using modern surface treatments:

Raw Material Treatment Using Vacuum Plasma

Vacuum plasma is a dry surface treatment system that changes the material surface, this is a contained process that can treat anything from moulded or machined parts down to powders or foils.

Larger parts will be sensible to place inside a large and static chamber, usually with shelves or automation. Powders and small components can be tumbled and rotated in a moving drum system.

The key advantage to using this system is that you can add process gases or use specific parameters to get changes to a material without the need for liquids or drying.

When working with raw materials, especially powders and nano materials, you might want to use treatment to improve the material for powder wetting, improving dispersion speed when creating slurries.

You might also want to use treatment to tailor the surface chemistry of the material and impart specific functional groups that would be useful.

Changing surface chemistry aside, vacuum plasma treatment is also an excellent fine cleaning tool. Vacuum plasma can vaporise and remove organic residues that could be covering or reducing usability of powders and raw materials.

At this level, all of the projects lead in to something else and the finished products could be various, ranging from conductive inks to moulded materials and composites with different properties.

Material Processing and Cleaning Using Corona and Plasma Treatment

Having a clean part for processing can be critical and the level of contamination raises the question of ‘how clean is clean?’ as some of the processes we have been involved in seem to have pristine visual surfaces, but contamination is still present enough to cause problems.

Firstly, to try and address the ‘how clean’ question, we can measure the surface energy of a material and determine whether the material is clean, how much it can be cleaned by and how the numbers correlate to real world performance.

We can measure this by using the less technical, but large area test using dyne test inks, or we can be more technical but usually look at a specific 1mm square and use contact angle. There are other methods but these two tend to be the most sensible.

Understanding the cleanliness level can give key supply chain information and ensure that incoming material quality is high. But achieving the cleanliness level can be difficult, especially for inline processes.

Treatment of foils prior to coating with slurries has been an area of interest with several customers and treatment using inline corona treatment has proven to be highly beneficial at removing the trace levels of contamination that can be found on reels of copper and aluminium in particular.

Cleaning materials in this way can give two key advantages, firstly for poor performing materials it can enhance the product significantly leading to a jump in performance as well as processing ease. Secondly, even if a material performs well under normal circumstances, ensuring pretreatment is done every time keeps consistency high and avoids any unexpected contaminated material from ruining a batch.

Foils is a great example, but any metal can be cleaned using plasma and corona. One other big area where plasma is used is for cleaning wire bonding pads to give strong and consistent bonds, avoiding dry joints and failed components. Treatment takes place in a fraction of a second so can easily be bolted on.

Packaging and Cooling Improvements Using Plasma

Raw material treatment and cleaning during processing are both quite technical stages of manufacture, they demand high performance and the need for very tight and specific requirements.

Cooling and packaging of cells and pouches should be the easy bit! But problems with adhesion at these stages can cause a number of headaches. From bonding on polymer clips that guide cooling pipes, to printing on pipes and cables, even bonding together frame works, fins and other ancillary parts.

These adhesion issues could be very simple and as with many applications we work on, it might be a problem that doesn’t actually occur when parts are handled gently during initial testing.

Problems can start to occur after thermal cycling of parts or general vibration due to real world situations. The issues can start to show themselves as loose parts causing loss of performance, overheating or some other concern, but can also be a big source of noise, vibration and harshness within vehicles due to rubbing and touching of parts that should have been isolated.

Using plasma treatment, especially for polymer components means that their surface energy is high and their adhesion is significantly better. Automotive applications have long been a key part of the Tantec world for Plasma and Corona applications, so this is much more ‘business as usual’ than perhaps other battery industry specific applications.

Once customer in particular had a problem on a limited run vehicle where engine clips that had been bonded became loose due to higher than expected temperatures and excessive vibration. Once the engine clips had come loose it lead to a complete failure of the vehicle.

This became an area of critical interest which is when they began using different adhesives and using plasma treatment so their product had a much wider performance window without the need to redesign the vehicle or add weight and complexity. Since the introduction of plasma they haven’t had any failures from this again.

Materials That Can Be Treated And Any Concerns

Battery materials vary, raw products used to create anode slurries and foils used to create batteries are often technical products, highly pure and well understood. Cell packaging and more general materials may be the same used routinely in other industries and their quality might not be as perfect as the materials used to create the batteries themselves.

Either way, what materials react well with plasma treatment and which can’t be used?

In general plasma and corona treatment will do a few things, firstly clean, secondly treat/ functionalise and lastly start to etch the material. These effects will have more and more on the performance of the cell and perhaps not always in a positive way.

For example, a material that is treated for improving coating flow might be perfect after a short treatment, but an excessive treatment leads to so much spreading of coatings that the coating flows off the edges and is uncontrollable.

Equally etching a material with a long treatment can cause a dust like effect on the surface that can lead to poor adhesion.

The trick for any material treatment is to find the sweet spot, more treatment isn’t especially a good thing. That being said, it’s likely that some treatment is positive for most materials and at the very least will give a consist and repeatable surface that is free from organic contamination.

Other Thoughts and Ideas For The Battery Industry

The applications discussed here are interesting because although they are from specific applications, they also cover a range of problems.

It’s easy to say that surface treatment improves adhesion, as this is what it’s primarily used for and what it’s most frequently used for around the world. But battery manufacturing engineers in their relatively limited use of surface treatment have already been exploring the cleaning, functionalisation, wetting and flow properties that are worked on with plasma treatment.

Because battery manufacturing is really trying to push the limits of what’s currently possible, especially in automotive, we believe that even us the manufacturing experts of the technology will be missing applications that we just don’t know exist because we don’t know the battery industry inside out, as not many people will due to the fast paced nature and continued development.

For this industry to make the most of any technology it should be asking questions of the manufacturers and users to question just what else can be done and is the technology the right tool for the job, which is true of all the tools available.

Image courtesy of SMMT

We’re open when it comes to looking at these problems and appreciate that adhesive bonding isn’t always right, we’re first to concede that technologies like ultrasonic welding can be really smart in the right settings, as can physical fastenings.

Using the right tool for the job, with the right materials at the right time to maximise the products performance is going to be key for any battery manufacturer to really carve out a market leading niche.

Conclusion of Battery Industry and Surface Treatment

Battery manufacturing is at an important stage and with new chemistry and technologies coming through and more demanding applications, it seems that the industry is pushing to use the latest and most appropriate technologies possible to create sustainable products.

The majority of applications that we have worked on have been associated with automotive batteries, but obviously the range from home battery walls to aerospace, off highway, rail and mass transport in general all have their requirements and challenges.

This coupled with the demand for higher density storage, green manufacturing and supply chains and demand for long life time products means that design and development is only at it’s beginning.

The use of plasma and corona treatment in battery manufacturing is growing, but there seems to be a lot more possibilities out there. There’s also leak detection using high voltage for finding leaks and defects in packaging, and the lesser used ozone surface treatment available too which currently get more use in other industries.