Effect of cell pressure on the electrochemical performance of all‐solid‐state lithium batteries with zero‐excess Li metal anode

Abstract

All‐solid‐state cells (ASSCs) typically operate at a specific pressure to ensure good contact between the solid electrolyte and the electrode‐active materials. However, establishing the ideal cell pressure is challenging because of the various cell structures, the mechanical characteristics of solid electrolytes, and the extent to which the volume of the electrodes changes during cycling. In this study, we propose a specially designed cell assembly that adjusts to the changes in volume that occur during cycling while maintaining a constant cell pressure. The evaluations indicate that the spring in the cell assembly effectively reduces the stress incurred from the volume expansion that occurs in the electrode during charging (lithiation) and the volume contraction that occurs during discharging (delithiation) while maintaining the prescribed cell pressure. The capacity fading—as a function of the cycle number—decreases when operating ASSCs comprising a cell assembly that include a spring, compared with those that exclude a spring. Focused ion beam–scanning electron microscope reveals no cracks and delamination in the LiNi0.8Co0.1Mn0.1O3 (NCM811) composite cathode of the ASSCs, operated at 25 MPa, with a spring‐equipped assembly. The Ag nanolayer that deposits on the Cu foil is an effective collector metal, forming a dense lithium plating layer on the Ag/Cu foil anode.

Deformation Mechanism Maps of Pure Lithium: Their Application in Determining Stack Pressure for All-Solid-State Lithium-Ion Batteries

“…Many researchers have investigated the interface stability between the Li metal anode and SSE to identify optimal conditions for suppressing the formation of dendrites and voids. − They all agree that controlling creep deformation of Li metal critically affects their formation at the interface. − Kasemchainan et al reported that the formation of voids and dendrites on Li metal anode in ASSLIBs is significantly influenced by current density and can be suppressed through creep deformation by applying stack pressure. Doux et al studied the failure mechanisms of Li metal in ASSLIBs under different stack pressures and demonstrated that while stack pressure is necessary to establish good initial contact between the Li metal and SSE, thereby preventing the formation of voids, excessive stack pressure can lead to cell short-circuiting.…”