Novel manufacturing approaches to smarter Na-ion cathodes

Na is more abundant than Li with lower cost, and cathode formulations for Na-ion batteries are less dependent than Li-ion on cost volatile elements such as Co. However, for Na-ion technologies to compete with Li-ion, it is essential that their intrinsic energy storage properties are realised as fully as possible. This project will investigate the role and contribution that novel manufacturing approaches can make to competitive Na ion batteries. The approach is based on smart "structured" electrodes that make use of rationally-designed, controlled spatial arrangements of electrode porosity and solid constituents, such as new layered or graded battery electrodes fabricated by additive manufacture.

We have developed new manufacturing approaches that allow micron-scale control of the local active, carbon and binder fraction in ion battery electrodes. We have shown this approach can reduce Li-ion cell degradation rate, and improve power characteristics. However, the underlying reasons for the observed improvements have not been fully rationalised and captured into generic understanding that will eventually support a priori design of optimised electrode structures. This will be a key aim of the project, based on for the first time, investigating what performance benefits might be achieved by applying these structural design approaches to Na-ion cells. We will study how the range of performance trade-offs provided by structured Na-ion cathodes might provide areas of advantage over current Li-ion performance. In particular, Na ion may have particular advantages in stationary grid scale energy storage applications, and we will study how these advantages can be amplified by the structured electrode approach.

The project will also investigate the application of new solvent free, or "dry", processing to Na ion batteries. Novel opportunities for electrode structuring are provided by this approach in which wet slurry casting and drying is replaced by a controlled shear and then solid-state electrode forming process. Elimination of solvent-based processing offers the potential for significant cost, safety and new cathode chemistry possibilities, and can make a significant contribution to a more sustainable battery industry. As well as manufacturing science research, the project will make use of extensive microstructural techniques including focused ion beam microscopy and X-ray micro-tomography, and electrochemical testing of energy storage performance. Cost comparison studies will also be undertaken.

This project falls within the EPSRC energy and decarbonisation research area.