How to realize a small series production of customized battery cells

Fill the gap between Gigafactories and R&D production lines

Current battery cell production lines are designed to produce predefined battery cells with a high level of automation and maximum output at highest quality. Any changes in shape or size of the product entail high changeover costs and times, due to narrow flexibility corridors, if they exist at all. The flexible production of customer specific battery variants in varying and adaptable quantities poses major obstacles for existing factories.

But if the requested quantities do not utilize a whole production line, Production as a Service (PaaS) provides a solution to expand the existing ecosystem by enabling customized battery cell production. Focusing on small to medium production volumes, the implementation of a PaaS concept represents a promising approach to fully exploit flexibility while strengthening operational resilience.

Degrees of specification in battery cell production

Looking at the current battery market, we find a nearly infinite number of product variants, which differ considerably in terms of format, chemistry, and other product features. So there is no such thing as the perfect battery or standard cell for a multitude of possible applications.

Consequently we have certain decisions to make, when choosing the right battery cell concept for a specific need. The relevant specifications can be clustered in four categories with each combination serving different market requirements:

· Cell chemistry (materials)

· Cell format

· Cell shape & size

· Cell connections (terminals & tabs)

A closer look at the market reveals that no strictly preferred and dominant variant has emerged yet. Each combines advantages and disadvantages that are carefully considered for the intended purpose of use.

In an ideal world we would design a highly flexible factory which would be capable of producing batteries with full freedom in all four categories and a lot size of one. Unfortunately, with the current technologies, this is not possible, so we need to find a way to decrease the possible degrees of freedom until the ratio between flexibilization costs and flexibility gains fits our need.

Which format to choose: Pouch vs. prismatic vs. cylindric

The cell production process consists of three main steps: electrode production, cell assembly and cell finishing. From a production process perspective the biggest process differences between the cell types lie in the area of cell assembly and are mainly driven by the cell format.

If we now decide on a specific cell format (e.g. prismatic) and at the same time limit the option space for length and width, we will gain nearly full freedom in the two other categories: cell chemistry and cell connections. The overall process complexity (especially within the cell assembly) can be significantly reduced.

Cylindric cells are the cell type with the highest standardization in Size & Shape, combined with a high availability in the market. So they are the go to solution, if customization can be achieved with module and pack design and not with the cell itself. This and some other factors leave pouch and prismatic cell formats as perfect candidates for a highly flexible production line, with each having pros and cons and thus the selection should be made on individual criteria.

By combining the technical approach for flexible cell production with our PaaS concept, we gain the flexibility which is necessary for a shared production. And thus we are opening up this growth market for alternative investments and enable fast scaling.