Fig. 4: Operando Li-driven stress monitoring in InLix | LPS | LTO cell by an FBG embedded in the anode.
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. It is important to note that an axis transverse to the fiber is an axis perpendicular to the main symmetry axis (c∞) and therefore the axis “axial” to the cell is a “transverse” axis to the fiber. To simplify nomenclature, every time we herein mention “longitudinal” or “transversal” will be respected to the fiber and “axial” will only be respected to the cell. b Time-resolved voltage (top), external cycling pressure (middle), and an internal optical signal (bottom) for the aforementioned ASSB cycled at C/30 (5.83 mA g−1) and 25 °C in an operando mode. c 2D stack view of the reflected spectra, with the corresponding galvanostatic charge/discharge cycle. The charge and discharge processes are plotted in red and blue, respectively. d Comparison between operando stress evolution obtained: 1—internally by the FBG sensor and using the mathematical model (green curve) and 2—internally by the FBG sensor and the sensitivity coefficient obtained with the experimental calibration of the sensor (blue curve). The respective galvanostatic charge/discharge is presented (top). The points at the beginning/middle/end of the charge/discharge are indicated by colored dots, also marked in the corresponding FBG spectra in (d). The external cycling pressure was fixed at 2 MPa prior to performing the battery cycling.
