Fiber optics are emerging as a powerful tool for non-invasive battery sensing, offering real-time, high-resolution monitoring of parameters like temperature, volumetric deformation (e.g. strain), and chemical changes within cells. Unlike many traditional sensor technologies, fiber-optic sensors are chemically inert, immune to electromagnetic interference and can operate safely in harsh or confined battery environments. Using just a single piece of interrogator hardware, they can be multiplexed, allowing for discrete measurements at numerous locations with a single fiber. By analyzing the evolution of their thermo-mechanical evolution, detailed insights into performance and degradation patterns can be achieved. These insights can then be linked to underlying electrochemical phenomena and is valuable for large battery packs in electric vehicles and grid storage, improving safety, efficiency, and lifespan. As demand for reliable energy systems grows, fiber-optic sensing promises a transformative step in battery management innovation. Emerging focus areas beyond thermo-mechanical measurements extend to real-time gas sensing, infrared spectroscopy, and nanoplasmonic methods.

Exemplary works include:

• Towards Long-Term Monitoring of Commercial Lithium-Ion Batteries Enabled by Externally Affixed Fiber Sensors and Strain-Based Prognostic Strategies https://doi.org/10.1149/1945-7111/ad3780
• High-Fidelity Strain and Temperature Measurements of Li-Ion Batteries Using Polymer Optical Fiber Sensors https://doi.org/10.1149/1945-7111/ac957e
• Sensing as the key to battery lifetime and sustainability https://doi.org/10.1038/s41893-022-00859-y

Alloy-type anodes often exhibit high capacities, low potentials, and effective suppression of dendrite growth in Li-ion and Na-ion batteries. However, their intrinsic degradation during cycling makes them less commercially viable compared to graphitic and hard-carbon carbon. Nevertheless, with the recent unprecedented proliferation of lithium-ion batteries and critical concerns for the sourcing and sustainability of carbon anode material, aims to better understand the reversibility of anode materials is warranted. Methods to conduct investigations at NTNU lean heavily on operando and in situ methods, particularly those relying on optical microscopy, intermittent methods (e.g. GITT), and fiber-optic methods noted above.

Exemplary systems include LiAl and NaPb, as noted:

• Lithium aluminum alloy anodes in Li-ion rechargeable batteries: past developments, recent progress, and future prospects https://doi.org/10.1088/2516-1083/acd101
• Identifying Problematic Phase Transformations in Pb Foil Anodes for Sodium-Ion Batteries https://doi.org/10.1149/1945-7111/ad76e0
• Aluminum Foil Anodes for Li-Ion Rechargeable Batteries: the Role of Li Solubility within β-LiAl https://doi.org/10.1021/acssuschemeng.1c07242

Battery safety is both critical to both energy security as well as civil preparedness. Collaborative efforts at NTNU are undertaken in conjunction with the SIMLab group in the Department of Structural Engineering at NTNU. Given the nature of research activities and its sensitivity, interested parties are encouraged to contact Prof. Boles directly for further elaboration and discussion.