A Self-Healing, Flowable, Yet Solid Electrolyte Suppresses Li-Metal Morphological Instabilities

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Lithium metal solid-state batteries face challenges like dendrite formation and interface instability.
• Voids and cracks in solid electrolytes are critical failure points during battery operation.
• Existing electrolytes struggle to balance mechanical integrity with ion conductivity.

Purpose of the Study:

• To develop a self-healing, flowable solid electrolyte for lithium metal batteries.
• To address void/crack formation and electrode volume changes during cycling.
• To enhance the cycling stability and lifespan of lithium metal solid-state batteries.

Main Methods:

• Fabrication of a self-healing electrolyte using mobile ceramic crystals in a reconfigurable polymer network.
• Characterization via operando synchrotron X-ray, in situ transmission electron microscopy (TEM), and solid-state NMR.
• Testing of Li0-Li0 and Li0-NMC811 full cells under various current densities and cycling conditions.

Main Results:

• The electrolyte exhibits a self-healing rate of 5.6 µm h⁻¹ and dynamically switches between liquid and solid states.
• Demonstrated accommodation of electrode volume changes and regulation of lithium deposition with high tensile strength (0.28 MPa).
• Achieved extended cycling life in Li0-Li0 cells (12,000 h at 0.2 mA cm⁻²) and stable cycling in full cells (1100 cycles at 5 mA cm⁻²).

Conclusions:

• The designed self-healing electrolyte effectively mitigates key failure mechanisms in lithium metal solid-state batteries.
• The dual-phase ion conduction and rapid Li+ diffusion contribute to enhanced electrochemical performance.
• This material offers a promising pathway for developing robust and long-lasting solid-state lithium metal batteries.