In-situ obtained internal strain and pressure of the cylindrical Li-ion battery cell with silicon-graphite negative electrodes

The mechanical failure of the commercial Li-ion battery cell is a critical question that needs to be addressed based on the in-situ changes of the internal mechanical information. In the present work, an in-situ internal deformation measurement method was applied for measuring the circumferential strain of the 18650 LIB cell with a different silicon content of the negative electrode. The circumferential strain changes are dominated by the volume expansion of the negative electrode during the cell operation. The internal strain is not only related to the volume expansion of the electrodes but also determined by the gap between the jelly roll and the steel case. An internal pressure calculation method is proposed based on the circumferential strain. The known in-situ changes of the internal pressure help understand the internal pressure effects on the cell's ageing and performance. To the best of our knowledge, this is the first time the circumferential internal mechanical information was obtained in the cylindrical battery with different negative electrodes.