Protection of Li-metal anode by surface coating to enhance the cycling performance of Li-S batteries

The performance of Lithium-Sulphur batteries is dependent on interfacial processes occurring at the positive and negative electrodes. For example, the surface layers that form on the Li-metal anodes are known to affect the kinetics, capacity and overall performance of batteries. Interfacial reactions between the liquid electrolyte and the metal electrodes limit cycle life, voltage window and cause battery degradation. Furthermore, mossy and dendritic growth of Li-metal occurs in the repetitive Li stripping/plating process creating the risk of thermal runaway events, compromising battery safety. Molecular vapor deposition (MVD) is a coating technique which can deposit very thin (few nm) and conformal films on a variety of substrates including those relevant in electrochemical applications such as metallic foils. The chemical nature and thickness of such films can be tuned and tailored for the specific substrate and application. For instance, in the case of metal anodes, the films can be designed in such a way to mitigate the parasitic side reaction at the electrode/electrolyte interface as well as accommodate the volumetric changes helping to maintain the mechanical integrity of the electrode.
The aim of the project is to exploit the capability and flexibility of MVD to grow functional thin films that conform to complex substrates such as Li-metal anodes. In particular, the focus would be on the production of protecting coatings of organic and hybrid organic-inorganic polymers with ad-hoc designed functionalities. The outcomes of the proposed research are multiple and include (i) building a fundamental understanding of the effect of tailored surface coatings on electrochemical and mechanical properties of Li-metal anodes, (ii) to develop functional coatings and their deposition methodology for high performance Li-S batteries, (iii) to widen the applications of MVD techniques to the field of energy storage devices and (iv) provide solutions and improve cycle life of OXIS Ltd Li-S batteries.

The CDT will produce 50 graduates with doctoral level knowledge and research skills focussed on the development and manufacture of functional industrial coatings. Key impact areas are:

Knowledge
- The development of new products and processes to address real scientific challenges existing in industry and to transfer this knowledge into partnering companies. The CDT will enable rapid knowledge transfer between academia and industry due to the co-created projects and co-supervision.
- The creation of knowledge sharing network for partner companies created by the environment of the CDT.
- On average 2-3 publications per RE. Publications in high impact factor journals. The scientific scope of the CDT comprises a mixture of interdisciplinary areas and as such a breadth of knowledge can be generated through the CDT. Examples would include Photovoltaic coatings - Journal of Materials Chemistry A (IF 8.867) and Anti-corrosion Coatings - Corrosion Science (IF 5.245), Progress in Organic Coatings (IF 2.903)
- REs will disseminate knowledge at leading conferences e.g. Materials Research Society (MRS), Meetings of the Electrochemical Society, and through trade associations and Institutes representing the coatings sector.
- A bespoke training package on the formulation, function, use, degradation and end of life that will embed the latest research and will be available to industry partners for employees to attend as CPD and for other PGRs demonstrating added value from the CDT environment.

Wealth Creation
- Value added products and processes created through the CDT will generate benefits for Industrial partners and supply chains helping to build a productive nation.
- Employment of graduates into industry will transfer their knowledge and skills into businesses enabling innovation within these companies.
- Swansea University will support potential spin out companies where appropriate through its dedicated EU funded commercialisation project, Agor IP.

Environment and society
- Functionalised surfaces can potentially improve human health through anti-microbial surfaces for health care infrastructure and treatment of water using photocatalytic coatings.
- Functionalised energy generation coatings will contribute towards national strategies regarding clean and secure energy.
- Responsible research and innovation is an overarching theme of the CDT with materials sustainability, ethics, energy and end of life considered throughout the development of new coatings and processes. Thus, REs will be trained to approach all future problems with this mind set.
- Outreach is a critical element of the training programme (for example, a module delivered by the Ri on public engagement) and our REs will have skills that enable the dissemination of their knowledge to wide audiences thus generating interest in science and engineering and the benefits that investments can bring.

People
- Highly employable doctoral gradates with a holistic knowledge of functional coatings manufacture who can make an immediate impact in industry or academia.
- The REs will have transferable skills that are pertinent across multiple sectors.
- The CDT will develop ethically aware engineers with sustainability embed throughout their training
- The promotion of equality, diversity and inclusivity within our cohorts through CDT and University wide initiatives.
- The development of alumni networks to grow new opportunities for our CDT and provide REs with mentors.