Lithium metal battery ceramics strengthened by ultrathin silver-based coating.

Stanford researchers report that a 3-nanometer silver treatment diffused into LLZO solid electrolyte surfaces and made them about five times more resistant to cracking; so far the experiments used small samples rather than full commercial battery cells.

Researchers report an ultrathin silver-based surface treatment that strengthens brittle ceramic electrolytes used in lithium metal batteries. Solid electrolytes promise safer, higher-energy and faster-charging rechargeable batteries, but microscopic cracks in ceramics like LLZO have limited progress. The Stanford-led team applied a 3-nanometer silver layer and annealed it, producing positively charged silver ions that diffused into the electrolyte surface and altered crack behavior. The work, reported in Nature Materials, so far applies to small test samples rather than complete commercial cells. Key findings: - A 3-nanometer silver layer was deposited on LLZO and heated to about 300°C, during which silver ions diffused roughly 20–50 nanometers into the surface. - The silver remained as positively charged ions (Ag+) rather than metallic silver, and the researchers say this state helps harden the ceramic surface against cracking. - Silver-treated samples required nearly five times the force to fracture compared with untreated material when measured with a specialized probe. - The treatment also reduced the tendency for lithium to intrude into existing surface imperfections, a process that can grow fissures during fast charging. - Experiments so far used small electrolyte samples and not full battery cells; researchers are now applying the surface treatment to complete lithium metal batteries to assess behavior under repeated fast charging and long-term use. - Early tests with other metals such as copper showed encouraging signs, and the team is exploring application to other ceramic electrolytes and possibly sodium-based systems. Summary: The reported silver-based surface modification made LLZO electrolytes less brittle and more resistant to crack growth in laboratory tests, and it also reduced pathways for lithium intrusion. Researchers are extending the method to full lithium metal cells and investigating other metals and electrolyte types to evaluate long-term performance and manufacturing considerations. Validation at commercial scale over thousands of charge cycles is undetermined at this time.