Artist’s rendering of an atomically thin coating of silver and some silver atoms below the surface protecting the crystalline structure of a solid electrolyte for lithium metal batteries in development.
Credit: Chaoyang Zhao
A nanoscale silver coating could be the key to making ultra-powerful solid-state batteries finally work.
Replacing the liquid electrolyte inside today’s batteries with a solid one could unlock a new generation of rechargeable lithium metal batteries. In theory, these batteries would be safer, store far more energy, and recharge much faster than the lithium-ion batteries now in widespread use. Scientists and engineers have been chasing this goal for decades, but progress has been slowed by a persistent flaw. Solid, crystal-based electrolytes tend to develop microscopic cracks that gradually spread during repeated charging and use, eventually causing the battery to fail.
A Thin Silver Layer With a Big Impact
Building on earlier work published three years ago that revealed how tiny cracks, dents, and surface flaws form and grow, Stanford researchers have now identified a promising solution. By heat-treating an extremely thin layer of silver on the surface of a solid electrolyte, they found that much of this cracking problem can be reduced.
As reported in Nature Materials today (January 16), the silver-treated surface became five times more resistant to cracking under mechanical pressure. Just as importantly, the treatment made existing surface defects far less vulnerable to lithium pushing its way inside. This intrusion is especially damaging during fast charging, when nanoscale cracks can widen into deeper channels that permanently disable the battery.
“The solid electrolytes that we and others are working on are a kind of ceramic that allows the lithium-ions to shuttle back and forth easily, but it’s brittle,” said Wendy Gu, associate professor of mechanical engineering and a senior author of the study. “On an incredibly small scale, it’s not unlike ceramic plates or bowls you have at home that have tiny cracks on their surfaces.”
Gu explained that eliminating every microscopic flaw during manufacturing is unrealistic. “A real-world solid-state battery is made of layers of stacked cathode-electrolyte-anode sheets. Manufacturing these without even the tiniest imperfections would be nearly impossible and very expensive,” she said. “We decided a protective surface may be more realistic, and just a little bit of silver seems to do a pretty good job.”
Building on earlier work published three years ago that revealed how tiny cracks, dents, and surface flaws form and grow, Stanford researchers have now identified a promising solution. By heat-treating an extremely thin layer of silver on the surface of a solid electrolyte, they found that much of this cracking problem can be reduced.
As reported in Nature Materials today (January 16), the silver-treated surface became five times more resistant to cracking under mechanical pressure. Just as importantly, the treatment made existing surface defects far less vulnerable to lithium pushing its way inside. This intrusion is especially damaging during fast charging, when nanoscale cracks can widen into deeper channels that permanently disable the battery.
“The solid electrolytes that we and others are working on are a kind of ceramic that allows the lithium-ions to shuttle back and forth easily, but it’s brittle,” said Wendy Gu, associate professor of mechanical engineering and a senior author of the study. “On an incredibly small scale, it’s not unlike ceramic plates or bowls you have at home that have tiny cracks on their surfaces.”
Gu explained that eliminating every microscopic flaw during manufacturing is unrealistic. “A real-world solid-state battery is made of layers of stacked cathode-electrolyte-anode sheets. Manufacturing these without even the tiniest imperfections would be nearly impossible and very expensive,” she said. “We decided a protective surface may be more realistic, and just a little bit of silver seems to do a pretty good job.”
Silver-Lithium Switch
Earlier studies by other researchers explored coating the same solid electrolyte material with metallic silver. That material, known as “LLZO” for its combination of lithium, lanthanum, zirconium, and oxygen, was also used in the new work. However, the Stanford team took a different approach. Instead of metallic silver, they used a dissolved form of silver that has lost an electron (Ag+).
This charged, dissolved silver behaves very differently from solid metallic silver. According to the researchers, Ag+ ions are directly responsible for strengthening the ceramic structure and making it more resistant to cracking.
To apply the treatment, the team deposited a silver layer just 3 nanometers thick onto the surface of LLZO samples and then heated them to 300 degrees Celsius (572° Fahrenheit). During this heating process, silver atoms diffused into the electrolyte surface, replacing much smaller lithium atoms within the porous crystal structure. This exchange extended roughly 20 to 50 nanometers below the surface.
Crucially, the silver remained in its positively charged ionic form rather than becoming metallic again. The researchers believe this is key to preventing cracks from forming. In areas where tiny flaws already exist, the presence of silver ions also helps block lithium from forcing its way inside and forming destructive internal branches.
“Our study shows that nanoscale silver doping can fundamentally alter how cracks initiate and propagate at the electrolyte surface, producing durable, failure-resistant solid electrolytes for next-generation energy storage technologies,” said Xin Xu, who led the research as a postdoctoral scholar at Stanford and is now an assistant professor of engineering at Arizona State University.
“This method may be extended to a broad class of ceramics, It demonstrates ultrathin surface coatings can make the electrolyte less brittle and more stable under extreme electrochemical and mechanical conditions, like fast charging and pressure,” said Xu, who at Stanford worked in the laboratory of Prof. William Chueh, a senior author of the study and director of the Precourt Institute for Energy, which is part of the Stanford Doerr School of Sustainability.
Measuring Strength at the Nanoscale
To quantify the improvement, the researchers used a specialized probe inside a scanning electron microscope to test how much force was needed to fracture the electrolyte surface. The silver-treated material withstood nearly five times more pressure before cracking than untreated samples.
What Comes Next
So far, the experiments focused on small, localized regions rather than complete battery cells. Whether this silver-based approach can be scaled up, integrated with other battery components, and remain effective over thousands of charging cycles is still unknown.
The research team is now testing full lithium metal solid-state batteries and exploring how different types and directions of mechanical pressure affect long-term performance. They are also investigating other solid electrolyte materials, including sulfur-based versions that may offer improved chemical stability when paired with lithium.
Beyond lithium, the researchers see potential applications for sodium-based batteries as well. These systems could help ease supply-chain pressures tied to lithium demand.
Silver is not the only possible option. The team noted that other metals could work, as long as their ions are larger than the lithium ions they replace within the electrolyte structure. Copper showed promise in early tests, although it was less effective than silver.
So far, the experiments focused on small, localized regions rather than complete battery cells. Whether this silver-based approach can be scaled up, integrated with other battery components, and remain effective over thousands of charging cycles is still unknown.
The research team is now testing full lithium metal solid-state batteries and exploring how different types and directions of mechanical pressure affect long-term performance. They are also investigating other solid electrolyte materials, including sulfur-based versions that may offer improved chemical stability when paired with lithium.
Beyond lithium, the researchers see potential applications for sodium-based batteries as well. These systems could help ease supply-chain pressures tied to lithium demand.
Silver is not the only possible option. The team noted that other metals could work, as long as their ions are larger than the lithium ions they replace within the electrolyte structure. Copper showed promise in early tests, although it was less effective than silver.
The Life of Earth
https://chuckincardinal.blogspot.com/
No comments:
Post a Comment
Stick to the subject, NO religion, or Party politics