Development of in situ stacking pressure transmission x-ray diffractometer for aqueous Zn ion pouch cells.

Stacking pressure is increasingly recognized as an important factor in battery performance. Studies have confirmed its critical role in maintaining Coulombic efficiency and enhancing cycle life. It will facilitate battery research if we can observe the crystal structure evolution during cycling under stacking pressures. In this work, we have developed an in situ stacking pressure transmission x-ray diffractometer to monitor the crystal structure evolution of the Zn ion pouch cell with the stacking pressure of 0-600 kPa. It demonstrates the pressure-modulated co-intercalation of zinc and hydronium ions. The Gibbs free energy required for cation desolvation is reduced at 200 kPa, thereby enhancing the cation intercalation. This leads to a 170% increase in discharge capacity compared to the pouch cell without pressure. These findings highlight the potential application of in situ stacking pressure transmission x-ray diffractometers for other battery electrode materials.