Critical stripping current leads to dendrite formation on plating in lithium anode solid electrolyte cells

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Solid-state batteries (SSBs) offer potential advantages over conventional lithium-ion batteries.
• Lithium (Li) metal anodes are desirable for high energy density SSBs.
• Dendrite formation and subsequent cell failure remain significant challenges for Li metal anodes.

Purpose of the Study:

• To identify the critical current density threshold for dendrite formation during lithium stripping in solid-state cells.
• To investigate the mechanisms underlying dendrite formation and cell failure.
• To determine the influence of pressure on lithium stripping and transport.

Main Methods:

• Electrochemical cycling of Li/Li6PS5Cl/Li solid-state cells.
• Analysis of lithium stripping current density and its relation to dendrite formation.
• Investigation of pressure effects on lithium stripping and transport mechanisms.

Main Results:

• A critical stripping current density was identified, below the plating threshold, that triggers dendrite formation and cell failure.
• Void formation at the lithium interface during stripping, exacerbated by cycling, leads to localized current density increase and dendrites.
• Stripping current density is pressure-dependent, with higher pressures increasing the critical value, suggesting creep over diffusion as the dominant Li transport mechanism.

Conclusions:

• The critical stripping current density is a key factor limiting the power density of Li anode solid-state cells.
• Achieving high power densities in SSBs may necessitate substantial applied pressure to suppress dendrite formation during stripping.
• Understanding and mitigating stripping-induced dendrites is crucial for the practical implementation of Li metal solid-state batteries.