Move to production without a robust process development phase: a common mistake in Battery business

The importance to go through DoE and process development phase before move to production.

Many times we are touch with companies which have troubles in running the production due to high scrap rate in critical process or where the main causes are particular process steps.

In some case there is no history about the process, no indication how the costumer have been done the process development, choosed the technology, design the cell components accordingly to that and defined the working window and quality requirements as well.

Sometimes, the quality requirements are completely no sense, in other case there are not quality requirements or, as already happened, cell makers know that particular competitor is using similar technology so "let's use their quality requirements".

Ahhhhh really?

We know the project timeline are super tight.

We know the investors want to start to see machine running in production and start to delivery products to the costumers

We know the budget is limited and many times who made the business plan and feasibiltiy study didn't consider many activities due to lack of experience or knowledge in this industry.

But we know even what does it mean waste 10% of the products in one single machine just because a welding process is not runnig correclty. Since we are engineers, let's use numbers. If my production line is running at 20ppm and i'm producing pouch cells, i should be able to produce 24-25k cells/day at 85% OEE. but if i have additional 10% of scrap due to a single process steps, I missed a equivalent production of 2'500 cells. With an average manufacturing cost of 20$/cell, it would be equivalent to 50'000€/day of loss!!!

So, go through process development steps and DoE allows to make the right choice in term of process technology:

we need to find an answer to this question for example:

based on my application which welding technology is the best in term of CAPEX, OPEX, Performance and quality?

And then, how can i improve that working on cell design?

Which are the risk connected to this manufacturing process? How can I (and my equipment supplier) manage them into the machine and production?

Which are the quality requirements to achieve and how can I measured them?

Is there anything which allow me to measure 100% of the sample in-line or not?

Based on these questions, the answers allows to establish a robust manufacturing process and quality system which can garantee smooth production and low scrap rate or at least can provide in advance inputs which can help us for troubleshooting.

If we are not able to purchase different equipment and afford the investment to create an R&D laboratory to develop process internally we can get support from laboratories or companies which have the expertise in that particular process and in lithium battery manufacturing and work with them to find solutions.

In many cases, the focus of new camers in lithium battery business is on cell chemistry and very small effort in manufacturing and develop their cell design even for manufacturing.

Usually the absence of these inputs and information will affect the assessment of equipment and equipment suppliers and the bubble will boom immediately with the start of production. But once the production start, is too late. The expectation of the management is to start to produce and delivery product but on production floor engineers and operators fights everyday against process and quality issue pushed by their managers and shift leaders with the only target to produce.

"It's to late to find root cause and make analysis, we need to produce. Just fix it temporary then as soon as we have time we will check"

This is one of the most common sentence we heard in production (our friends and colleagues can confirm).

But in a competitive business like this one, where the safety and quality requirements of battery cells (and pack) are one of the most important KPI to still engaged by premium OEMs, do you really want to take the risk to lose the control what you're manufacturing?

Else, when we are looking for a partner to develop a certain manufacturing process we need to be sure about his expertise and capability. Many time we discuss with costumer which said to us:

Ah don't worry, we already made some test for laser notching.

And when you start to check the report you discover the costumer paid several thousands euro for a couple of trials and few straight cutting lines on electrodes without any indication about process capability and quality requirements.

If we want to use this particular example we could start, for example, trying to get several samples of electrodes and understand how the chemical composition and thickness (even just checking the difference between anode and cathode) affect the cutting quality (burrs, sputters, do-coating, HAZ etc) at the same process parameters. Then replicate a dummy notching pattern and evaluate the quality in transition from foil to coating and viceversa. Evaluate the laser source and scanner head capability and limits and define the limits of technology. All the imputs allows us to define a draft of equipment specification or process requirements.

It's important to understand what is the limit and why: the equipment, the laser source or the scanner head?

The quality inspection is another important KPI to consider. Does your patner have all devices and knowledge to distinguish between a good and bad cut?

And what about sputters and particle management? Which are the solutions we can test at lab level to understand the suction flow rate, the distance between suction units and the products, how to handle the electrode during cutting etc?

So perform a process development campaign is NOT just a matter to make 3 - 4 - 5 test trials with different parameters and say: look, the process works!!

We have to be able to characterize the process through quality inspections, provide all inputs and information how to improve and obtain a very high quality and drive even, if necessary, new players to choose the right quality requirements based on their product and application. The inputs are needs to cell maker to develop cell design and manufacturing process and in-directly to equipment supplier to provide him all inputs to design the equipment based on end user requirements.

Many times, these activities, which for some people are just a waste of time and steal resources/money/time from the project, are the ones which can save the project itself once in production.

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