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 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, which can be facilitated by novel manufacturing.

Ion battery electrodes are fabricated by casting of slurries that comprise the electrochemically active material with binder, conductive additive and solvent. The resulting electrode structures are random mixtures of these materials and porosity. Because of high productivity slurry casting has become ubiquitous but cell performance and trade-offs are constrained by the narrow range of slurry cast structures that can be achieved.

The project will research structured electrodes with designed spatial arrangements of electrode porosity and solid constituents, such as layered or graded electrodes.

First, structured electrodes will be spray printed to provide micron-scale control of the variations in the local active, carbon and binder fraction. We have shown that these spatial variations in electrode structure can reduce Li ion cell degradation rate, and improve C-rate response for some materials. For the first time, we will explore what performance benefits might be achieved by applying this approach for Na-ion cells, why they arise, and how the benefits might be maximized. We will study whether the range of performance trade-offs provided by structured Na-ion cathodes provides advantage over current Li ion. Second, we will investigate the application of new solvent free, or “dry”, processing. 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 also offers the potential for significant cost, safety and new cathode chemistry possibilities that will be explored.

Alongside bespoke spray printing, solvent-free and conventional processing equipment, electrode structures will be characterised by Xe plasma FIB with in situ elemental mapping, and a full range of electrochemical and other characterisation techniques.

Strategic fit with Shell

Shell is an integrated energy company that aims to meet the world’s growing demand for energy in ways that are economically, environmentally and socially responsible. The energy sector is currently undergoing substantial transition, driven by demand for more and cleaner energy and increasing customer choice. Energy storage is playing a growing role in this development of reneable energy. Currently, large-scale electricity storage is not cost-effective for extensive deployments to support wind and solar generation, underpinning the need for research & development to improve its performance and reduce its costs. Shell’s Advanced Energy Storage program invests in research to answer questions about technologies that have the potential to redefine present understanding of electron storage. Topics addressed in the program include solid state electrolytes, flow batteries, novel intercalation & conversion electrodes, interfacial reactions and stability, technoeconomic & supply chain analyses, and long duration stationary storage, among others.

Applicants with Home or Overseas fees status are eligible to apply. However, applicants with overseas fees status should note our ability to offer a studentship to a candidate with this fee status is restricted by the EPSRC stipulation that no more than 30% of students funded by a specific EPSRC iCASE training grant held by an institution may be of overseas fees status. Information on fee status can be found at http://www.ox.ac.uk/admissions/graduate/fees-and-funding/fees-and-other-charges (the current position is that we are unable to offer full funding to Overseas candidates. Please contact [Email Address Removed] for any updated information). 

Applications will be considered in Oxford University’s 2022 Graduate Recruitment Open Field, on an as received basis.

Any questions concerning the project can be addressed to Professor Patrick Grant ([Email Address Removed]). General enquiries on how to apply can be made by e‑mail to [Email Address Removed]. You must complete the standard Oxford University Application for Graduate Studies. Further information and an electronic copy of the application form can be found at https://www.ox.ac.uk/admissions/graduate/applying-to-oxford .