Galvanostatic cycling of a micron-sized solid-state battery: Visually linking void evolution to electrochemistry

Area of Science:

• Materials Science
• Electrochemistry
• Battery Technology

Background:

• Interface voids at the metal anode and solid electrolyte (SE) interface are a critical challenge for practical lithium metal solid-state batteries (SSBs).
• Understanding void evolution dynamics is essential for developing stable and long-lasting SSBs.

Purpose of the Study:

• To achieve operando observation of void evolution at the lithium metal anode/solid electrolyte interface with high spatio-temporal resolution.
• To directly correlate void dynamics with electrochemical performance during battery cycling.

Main Methods:

• Utilized in-situ transmission electron microscopy (TEM) to visualize the stripping and plating interfaces of a micron-sized SSB under galvanostatic cycling.
• Correlated voltage responses during charge/discharge with observed void nucleation, growth, and refilling.

Main Results:

• Identified two distinct lithium stripping modes: void-growth stripping and void-free stripping.
• Demonstrated the influence of stack pressure and current density on void evolution.
• Proposed a mechanism for void suppression that does not rely on lithium metal plastic deformation.
• Showcased in-situ void-free cycling in Li|SE|Li symmetric SSBs without applied stack pressure.

Conclusions:

• Operando TEM visualization provides critical insights into void formation and evolution mechanisms in SSBs.
• Void suppression strategies can be developed by controlling parameters like current density and potentially eliminating the need for high stack pressure.
• Void-free cycling is achievable, paving the way for more robust and practical lithium metal solid-state batteries.