Operando strain and temperature measurement of sodium-ion batteries via optical fiber sensors

Sodium-ion batteries (SIBs) are rapidly developed towards large-scale energy storage systems. The ability to quantify and evaluate the strains and temperature variations generated inside a battery during electrochemical processes is crucial to developing an advanced battery management system. Here, we report the operando measurement of the internal strain and temperature evolution of a sodium-ion pouch cell via optical fiber sensors. We leverage the cross-sensitivity of the fiber Bragg grating and Fabry-Pe<acute accent>rot interferometer and achieve the decoupling measurement of the strain and temperature effects during the electrochemical process of a sodiumion cell. By correlating the measured time-resolved profiles of strain and temperature and charge-discharge potential curves, we validated the sodium-ion intercalation dynamics and the accompanying thermal effects. Moreover, we show that operando measurements of strain evolution can be used to characterize SIB cell performance quantitatively. Our work provides a unique perspective for understanding the chemical mechanics of SIBs and may also contribute to the sustainability and monitoring of SIB development.