Structured electrodes for improved energy storage

The development of Li ion batteries (LiBs) has progressed through the evolution of improved electrochemically active electrode materials and has provided steady improvements in performance. Every LiB battery comprises two electrodes (anode and cathode), each made up of three materials: the electrochemically active material, a binder (typically a polymer) and an electrical conductivity enhancer (typically carbon black). The relative fractions of these three materials, blended together with a fugitive liquid into a slurry, plus the final electrode porosity that allows the liquid electrolyte to flood into the electrode, are optimized based on exhaustive electrochemical testing. Commercial tools are available to help guide this optimisation but are useful only for the most conventional types of electrode. As new manufacturing approaches that allow for more controlled arrangements of the materials to form "structured electrodes" are invented and the resulting devices show better performance, there arises an exciting opportunity to identify, from the uncountable number of possible 2D and 3D spatial arrangements of the electrode materials, those which offer significant improvements in device performance in particular applications. However, to achieve this optimisation through current empirical approaches is impossibly slow and expensive.

This proposal will develop a suite of modelling tools bridging micro to macro lengths-scales to guide the optimization of the spatial distribution of electrode structure to advance the performance, lifetime and introduction of next generation energy storage devices. This design optimization is especially critical where LiB and other systems are pushed to their limits e.g. high power (rapid charge/discharge) applications for EVs, or where ion mobility is otherwise restricted, such as inherently safe but low ionic mobility solid-state batteries. Insights generated will include the optimal spatial arrangements (in three dimensions) of porosity, particle size, binder, porosity for different materials, device formats and applications, how they could be manufactured, and how their properties vary with time in operation. The novelty of our methodology is: (1) a new approach to describe the dynamics of ion movement in energy storage electrodes efficiently that allows the models to be used in optimisation even when significantly more degrees of freedom are available, and (2) the use of a new manufacturing capability for large scale structured electrodes for model validation. By linking models, design optimisation, manufacture and performance measurements the programme will deliver material-independent and generic tools for optimisation of any Li ion, Na ion, supercapacitor or other electrode-based device, within the context of strong industrial guidance and engagement.

We will expose our work to the UK energy storage supply chain through the EPSRC Supergen Energy Storage Hub, also based at Oxford University. The Hub has the mission and resources to expose industry to latest developments in the science base, and vice-versa, with a profile and reach we could not achieve as a relatively modest stand-alone research project. By publicising our work through this forum (as well as conventional publication in the peer-reviewed literature) we aim to expose industry more broadly to innovations in modelling, optimisation and manufacturing, much of which from the current programme is generic in nature and provides a platform approach that could be exploited by other industries. We will also have the opportunity to showcase our modelling and manufacturing capabilities, which may be currently obscure to potential new collaborators.

Working through the Hub also gives an opportunity for the research to feed into the UK national roadmap in energy storage innovation, which is a key deliverable assigned to the Hub work-programme. This roadmap has the authority and buy-in of the key stakeholders in the UK, and thus our research has the potential to make a contribution to the evolution of policy in energy storage research and technology. The Hub will also facilitate public understanding of energy storage research and technology, including safety, sustainability, cost and performance, and we will engage in Hub-organised policy debates and public engagement activities.

Energy storage (ES) was identified as one of the UK's Eight Great Technologies (Willets, 2013) because of its potential to help the UK meet emission targets. The two principle contributions will be allowing greater penetration of all-electric or hybrid electric vehicles to the mass market, and to reduce life cycle costs in grid-scale energy storage through increased use of renewable energy sources. ES is also increasingly recognized as an enabling technology to reduce local pollution, particularly in urban environments. ES has been suggested to reduce the cost of moving to a low carbon electricity system by £10B per annum by 2050.

We will ensuring the timely recognition and protection of exploitable intellectual property (IP). The primary and fastest route to market for this IP will be through our core collaborator and industrial co-creator. Best efforts will also be made to facilitate industrial exploitation with those most suitably placed to do so in a timely fashion, while providing a balanced return for the public purse and inventors. EPSRC Impact Acceleration Award funds will be used for translational activities and proof of concept data to de-risk industrial take-up of the research findings.