| Project Detail |
Using oxygen to harness cumulative cationic and anionic redox processes for rechargeable batteries
Oxidation-reduction (redox) reactions involve the transfer of electrons between two chemical species. The electron(s) donor is ‘oxidised’ and the receiver is ‘reduced’. Redox reactions are ubiquitous in nature and in engineered processes, including electrochemical energy conversion and storage. Anionic redox using oxygen as the anion can boost the capacity of conventional transition metal cationic redox, promising tremendous increases in energy density and leading to a powerful alternative to current lithium-ion batteries. With the support of the Marie Sklodowska-Curie Actions Programme, the OXYPOW project will develop new and improved Li-rich layered oxide cathodes with cumulative cationic and anionic redox processes via crystal engineering and tuning of local cation-cation interactions.
The recent discovery of anionic redox chemistry has unveiled a new transformational paradigm for designing sustainable rechargeable batteries with superior energy density. Li-rich layered oxide (LLO) cathodes exhibiting oxygen redox activity can deliver exceptional capacities (> 40% higher than state-of-the-art NMC811), due to the cumulative cationic and anionic redox processes. However, the LLOs suffer from poor energy efficiency, reduced power density and voltage decay, caused by progressive irreversible migration and trapping of transition metals in intermediate sites in the structure during operation. In this context, the aim of the project is to target new LLO polymorphs with improved stability and performance through crystal engineering of the oxygen stacking sequence and tuning of local cation-cation interactions. First, I will leverage my expertise in in situ X-ray/neutron diffraction and total scattering methods to study the evolution of the atomic structure (average and local) during synthesis of selected LLO compositions. This will (1) dramatically reduce the time needed to cover parameter space, (2) facilitate identification of the optimal reaction conditions for specific LLO polymorphs, and (3) provide fundamental mechanistic insight. Secondly, this information will be used to target LLOs with different structural configurations and systematically examine the relationship between their electrochemical performance and structural evolution during operation. Thirdly, I will investigate the charge compensation mechanisms (cationic and anionic) of the materials, which will be related to the structural changes as well as electrochemical data to yield a complete mechanistic picture of the synthesis-structure-property relationship in the system. This fundamental groundwork will allow development of a fabrication strategy for the next generation of sustainable high-performance cathode materials exploiting the untapped electrochemical potential of oxygen. |
