Fig. 5: Operando Li-driven stress monitoring in InLix | LPS | LTO cell by an FBG placed at the interface between the anode and the solid-state electrolyte. | Nature Communications

Fig. 5: Operando Li-driven stress monitoring in InLix | LPS | LTO cell by an FBG placed at the interface between the anode and the solid-state electrolyte.

From: Optical sensors for operando stress monitoring in lithium-based batteries containing solid-state or liquid electrolytes

Fig. 5

a Scheme of the modified coin cell with the implemented optical fiber and the external force sensor. The corresponding X-, Y-, and Z-axis are detailed in the different views. For the sake of simplicity, the “longitudinal” and “transversal” axis is used with respect to the optical fiber, and the “axial” axis is only used with respect to the cell. The scheme of the birefringence phenomena is presented. b–d Experimental calibration curve of the FBG sensor when the ASSB is in an OCV status. The externally applied pressure is increased externally from 0 to 9 MPa. Detailed values of λB, λx, and λy vs. the externally applied pressure with the force sensor. The birefringence regime is shadowed in light yellow. Two regions are observed: 1—when only one peak is observed in the spectra (λB, given by λB = 2neffΛ), the calibration is done by λB – λB,0 and 2—the birefringence regime when λx and λy can be followed. The difference between λx and λy is used in order to calibrate internal transverse stresses. In our case, we focused on externally applied pressure of 8 MPa to profit from the birefringence phenomenon. Thus, the slope of the linear fitting in the upper birefringence regime (5–9 MPa) is 0.105 nm MPa−1. e Time-resolved voltage (top), and external cycling pressure (bottom) for the aforementioned ASSB cycled at C/30 (5.83 mA g−1) and 25 °C in an operando mode. f 2D stack view of the operando collected spectra by the FBG sensor, with the corresponding galvanostatic charge/discharge cycle. The charge and discharge processes are plotted in red and blue, respectively. g Galvanostatic cycle (top), λx and λy evolution (middle) and operando stress evolution obtained internally by the FBG sensor and with the experimental calibration of the sensor (bottom). The points at the beginning/middle/end of the charge/discharge are indicated by colored dots, also marked in the corresponding FBG spectra in (f).

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