Is the next generation of battery on its way?
As the race to become a nation of all-electric vehicle drivers continues to speed along, research teams are constantly looking for the next best thing, and in-terms of EV batteries, consumers want a fast and reliable product, and they want it now.
Lithium metal batteries with solid electrolytes were hoped to be a top contender for the fast charging battery market due to the fact that they are lightweight, inflammable, hold a lot of energy and they can quickly recharge. However, they are prone to short circuiting and failure which has left research teams stumped, until now.
Scientists from Stanford University and SLAC National Accelerator Laboratory believe they have finally unlocked the key to this perplexing constraint – which means the future of EV battery charging has the potential to get a whole lot quicker.
According to the teams, fast recharging causes a lot of mechanical stress for the battery.
William Chueh, Associate Professor of Materials Science and Engineering in the new Stanford Doerr School of Sustainability, said: “Just modest indentation, bending or twisting of the batteries can cause nanoscopic fissures in the materials to open and lithium to intrude into the solid electrolyte causing it to short circuit.” Continuing, “even dust or other impurities introduced in manufacturing can generate enough stress to cause failure.”
Why are they so fragile, and what can be done?
The cause for these stress fractures has long been theorised without a unanimous conclusion. However, in a study published in Nature Energy, the Stanford scientists undertook 60 experiments which proved the issues were caused by dents, fissures and nanoscopic cracks within the ceramic electrolytes which caused them to fail.
These findings meant that the scientists are able to start to work around the flaws which, if successful, could mean the road to fast-charging, long-lasting, non-flammable lithium metal batteries for EVs are well on their way to being realised.
Why do lithium metal batteries crack?
According to the research team, many of the leading solid electrolytes are ceramic and, much like any ceramics, they can, and will, develop small cracks over their surface area, some so microscopic they are thinner than a sheet of paper.
The process of rapid-charging the batteries leads to these fractures occurring, which allows the lithium to force its way through.
“Given the opportunity to burrow into the electrolyte, the lithium will eventually snake its way through, connecting the cathode and anode,” said Geoff McConohy, who completed his doctorate last year working in Chueh’s lab. “When that happens, the battery fails.”
How do lithium metal batteries move forward?
Chueh and the research team are looking for a way to use the mechanical forces to deliberately toughen the material during manufacturing. They are also planning on coating the surface of the electrolyte to prevent or repair cracks if they emerge.
If successful, the findings could prove a valuable asset for allaying the concerns of consumers who are yet to be convinced of the longevity of electric vehicles.