ISOBEL · In Situ Observation of Batteries for Extending Lifetime

Lithium-ion batteries (LIBs) are a key technology in enabling the transition from a dependence on fossil fuels towards renewable energy sources. However, increased energy density, cycle life, and recyclability are still needed. The different degradation processes in the LIBs are hard to disentangle from post-mortem measurements alone, as intermediate species cannot be detected and changes may occur during cell disassembly. This project aims to apply novel in situ techniques to directly observe the processes involved in transition metal (TM) dissolution, how this affects electrolyte decomposition at the cathode and anode, and the effect on the stability of the solid electrolyte interphase layer. This will be achieved via novel in-situ X-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS) measurements that allow electrodes and electrolyte to be simultaneously observed during cycling. This understanding will be used to develop solutions to mitigate TM-dissolution and its impact on cycle life. The focus will be LiNixMn(1-x)/2Co(1-x)/2O2 (NMC) electrodes used in many commercial LIBs, where larger energy densities can be achieved by increasing the nickel content. However, this is accompanied by higher levels of side-reactions from the more reactive surfaces. The electrolyte degradation products coming from NMC materials with different nickel content will be identified and prevented from reaching the graphite electrode by using lithium-ion conducting glass to separate the electrodes. This will help finding out how Ni-rich NMC materials can be stabilized and the extent to which cross talk products contribute to ageing. The project will also investigate new ways to recycling aged NMC to enable their re-use in new cells, decreasing the energy consumption in the recycling and avoiding the disposal of costly and toxic elements. This will include developing heat treatment protocols for replenishing lithium content and restoring the initial structure.