Mechano-electrochemical coupling in flexible all-solid-state lithium metal batteries

Bending and stretching are critical mechanical behaviors affecting the electrochemical performance of flexible batteries in wearable electronic devices. Herein, a mechano-electrochemical model is developed for solid-state Li metal batteries under bending deformation. It is found that bending alters ion transport and electric potential in solid polymer electrolytes, and its influence relies on the bending direction. By means of the curvature and coupling coefficient, a phase map is constructed for the critical current density that leads to ion depletion at the Li metal-electrolyte interface. In addition, a positive curvature helps to decrease the overpotential for electro-chemical reactions on the Li metal electrode. Though the direct influence of bending on electrochemical kinetics is limited, the bending deformation could substantially increase the stress and cause potential mechanical failure of electrodes and electrode-electrolyte interfaces, thereby degrading electrochemical performance.