Optofluidic Hollow-Core Fibres as Raman Sensors for Li-ion Battery Chemistry

We demonstrate a fibre-optic sensing method capable of monitoring chemical changes within Li:ion cells under real working conditions. Our technique is based on optofluidic single-ring hollow-core fibres, which uniquely allow light to be guided at the centre of a microfluidic channel. We integrate the fibres into working Li:ion cells, use them to take sub-microlitre samples of the electrolyte liquid, and analyse these by background-free Raman spectroscopy to identify early signs of battery degradation. Our approach complements existing battery monitoring systems and will enable us to identify degradation mechanisms that currently limit the lifetime and capacity of state-of-the-art energy storage systems.