Atomistic and multiscale simulations of next generation energy storage systems

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Li-ion batteries are central to green energy technologies and have a vast range of applications from mobile phones and laptops to electric vehicles and even storing electricity from renewable resources. However this technology is reaching its limits and our increasing demand for batteries with larger capacity, power output and lifetime means that we have to explore and develop the next generation of energy storage systems such as Li-metal, Li-S and Li-O2 batteries. The practical realisation of these rests on availability of stable Li metal anodes. Suitable anodes can only be made possible by accurate fundamental understanding and control of the interactions of Li metal with its surroundings, starting from Li processing environments and including (solid or liquid) electrolytes. Using recent advances in linear-scaling Density Functional Theory (DFT) in the ONETEP program, for multiscale simulation of metallic systems in the presence of both electrolyte environment and external potentiostatic control, this studentship aims to advance the current fundamental understanding of metal Li anodes and computationally develop suitable solutions. Special focus will be on the role of externally applied voltages in altering the physicochemical properties of the electrodes and their passivation layers. While preliminary work on these subjects has started to appear in the scientific literature, the role of voltage is essential for realistic simulations but is yet to be tackled in detail by the computational Chemistry and Physics communities, so this is the identified research opportunity for the present studentship. The project will use large-scale DFT simulations to explore the role of an externally applied voltage for the structure, relative stability and electronic properties of metal Li-surfaces, the phonons, vibrational stability and elastic properties of metal Li-surfaces. It will also investigate possible degradation mechanisms and voltage-dependent Li-diffusion mechanisms at the passivated metal-Li surfaces. The overarching goal of the studentship is to use simulation to explore optimum solutions for the difficult combination of requirements of suppressed electron conductivity and resilience to mechanical distortions induced by fast Li-ion diffusion, for the passivation layers of metal Li-anodes. Depending on progress with the Li simulations, other chemistries could also be explored such as Na-based electrodes.