During the research stage new materials are typically made and tested in gram quantities. Consequently, the consistency and performance of these materials when produced in the larger batch sizes (e.g. hundreds of grams to kilograms) required for developing to the prototype and industrial scale remains uncertain until the process has been fully developed.

This represents a significant issue in the road from fundamental research to potential commercialisation – particularly as, given the nature of the required time and resource investments, industry is typically wary of the risks associated with process scale-up for untested materials. As a result, many materials reported as having promising properties in the scientific literature remain at the research only level. Hence, scale-up of advanced battery materials represents a critical link between material discovery, market evaluation, and high-volume manufacturing.

To help address this roadblock, CIC energiGUNE is developing both scale-up facilities and know-how to not only transfer our own novel materials to the proof-of-concept level, but also to help industrial and research partners with their own synthesis processes.

Exploring a rich landscape: taking the first steps

For each cathode material there are a wide range of properties to optimise, such as how much energy it may store, how much and how quickly it can charge and discharge, how easily it may be processed into an electrode, as well as a multitude of synthesis conditions which may affect these both directly and indirectly. Synthesis conditions may also interact with each other (e.g. the optimal reactant concentration at one temperature may be different to that at another temperature). Increasing scale can also have unexpected consequences, for example, a slight exothermic reaction might be unnoticeable at the lab scale, but at a much larger scale might become so extreme as to lead to thermal runaway.

It can seem overwhelming when confronted by this complexity, and the task of finding optimal conditions for materials at scale daunting. However, by taking advantage of tools, techniques, and previously established knowledge, CIC energiGUNE is able to overcome these significant challenges.

Firstly, reproducibility is critical when trying to optimise processes – if there are significant variations between syntheses under supposedly the same conditions, it will be then very difficult when varying conditions to determine what has caused any observed changes. Steady-state production via continuous co-precipitation offers a potential solution, as this approach results in product properties (including primary and secondary particle sizes, morphology, size distribution, particle density, etc.) which remain constant during operation.

Thus, by using a precisely controlled continuous stirred tank reactor (CSTR) system (see Figure 1), combined with powerful analytical tools to benchmark all precursors (e.g. the starting solutions) and variations during the process (for example changes in product size distribution, pH, etc.), it is possible to ensure good reproducibility in properties and quality using a typically economically feasible and scalable method.

Figure 1. schematic of CSTR system networked to a computer for improved reproducibility, data collection during the process, and high precision control of the variable factors (such as solution flow rate, stirring speed, temperature, etc.).

Secondly, it is important to establish the key synthesis conditions and how they interact with each other. Typically, initial investigations at the materials level undertaken by the lithium and sodium research lines have generated data on the key conditions at lab scale – providing a good foundation for scale-up.

By using a Design of Experiments (DOE) methodology, it is then possible to vary the controllable factors, such as solution concentrations, flow rate, etc., which affect the synthesis conditions and study the resulting change in measurable product metric (e.g. purity and stoichiometry, primary and secondary particle size, morphology, etc.) in order to optimise the process.

This methodology may also be extended, as it enables us to understand not only primary effects but also inter-factor interactions – leading to a fuller exploration of the experimental factor-response surface. This can be an important point, as it means an improvement in terms of more rapid development of subsequent material syntheses, and potentially also a better understanding of the entire process (see Figure 2).

Figure 2. simplified schematic overview of a typical DOE methodological approach.

While this can represent a significant investment of time and resources, it also offers considerable advantages. For example, the more in-depth understanding of the process allows better tailoring of the product to meet desired specifications, as well as being foundational to any predictive modelling. Moreover, such work also makes it easier transfer to other production lines – even though there may be difference in optimal conditions from line-to-line (for example, due to uncontrollable factors), a factor-response model can often be fitted and the optimal conditions for a new line discovered with much fewer experiments than would otherwise be needed. In this way, this in-depth approach, although requiring greater initial investment, can often save time and resources later on.

By developing a range of approaches from simple experimental investigations to in-depth modelling, CIC energiGUNE can provide a flexible approach to cathode material scale-up– both internally, to support the development of our own materials, and as an external service, tailored to meet a collaborator’s or client’s needs in terms of time, resources, required information, and desired material output.

The path to success: harnessing the diverse expertise

While the scaling up of cathode materials is by no means a simple task, it remains a crucial step on the road to developing battery systems.

At CIC energiGUNE it is possible to make use of expertise all along the value chain and, while upscaling fits neatly between materials development (to help with selection of materials and lab-scale synthesis) and prototyping (to provide feedback on processability, performance, etc.), other areas have strong roles to play - post-mortem may provide information regarding electrode failure mechanisms, analytical platforms can offer critical data, computational simulation may support statistical analysis of data and predictive tool development.

By working with all areas within CIC energiGUNE, it is possible to harness this expertise – enabling us to better meet the challenges of battery development, both internally and in collaboration with key industrial and research partners.

As we look to expand CIC energiGUNE’s portfolio and integrate the understanding at every point along the value chain of new battery research and development targeted towards meeting demand, scale-up will be an important stepping stone on the road to future energy storage.