Mechanically driven Li dendrite penetration in garnet solid electrolyte

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• All-solid-state batteries offer enhanced safety and energy density over conventional lithium-ion batteries.
• Lithium dendrite penetration into solid electrolytes is a major challenge for solid-state lithium metal batteries.
• Understanding the fracture mechanism of ceramic electrolytes by lithium dendrites is crucial but difficult to observe.

Purpose of the Study:

• To investigate the mechanism of lithium dendrite-induced fracture in garnet solid electrolytes.
• To visualize the interaction between lithium dendrites and ceramic electrolytes at the nanoscale.
• To identify strategies for mitigating dendrite penetration and short-circuiting.

Main Methods:

• Multiscale cryogenic electron microscopy
• Micromechanical fracture modeling
• Direct visualization of lithium dendrite growth and electrolyte fracture

Main Results:

• Lithium dendrites were observed filling crack tips and extending into microcracks within garnet electrolytes.
• Plated lithium generates significant hydrostatic stress, leading to tensile stress and fracture (intergranular and transgranular) in the solid electrolyte.
• No lithium enrichment or nuclei were detected ahead of the dendrite tip.
• Geometrically engineered voids in the electrolyte successfully redirected lithium penetration.

Conclusions:

• Lithium dendrite penetration causes fracture in solid electrolytes due to high hydrostatic stress, not by pre-nucleation.
• Void engineering in solid electrolytes is a viable strategy to mitigate short-circuiting.
• Grain boundary toughening and defect engineering are promising approaches for developing dendrite-resistant solid electrolytes.