Published on March 27th, 2019 | by Steve Hanley
March 27th, 2019 by Steve Hanley
OK. That title is a bit tongue in cheek, but only a bit. If you subscribe to Science Daily, you see announcements about new solid state battery technology several times a week each and every week. What’s so great about solid state batteries to cause all that excitement? In theory, they will cost less, last long, and be capable of more charge/discharge cycles than traditional lithium-ion batteries.
In addition, they may have higher energy density, eliminate the need for cobalt, weigh less, and be smaller than traditional lithium-ion batteries. And oh yeah, they won’t explode or catch fire. That’s a pretty long list of advantages, which is why scientists and researchers around the world are focused on figuring out how to manufacture solid state batteries at scale.
A new report by scientists from Japan’s Tohoku University and the High Energy Accelerator Research Organization says their research has resulted in a new complex hydride lithium superionic conductor that could result in all-solid-state batteries with the highest energy density to date.
The researchers say the new material, achieved by designing structures of hydrogen clusters (complex anions), shows markedly high stability against lithium metal, which would make it the ultimate anode material for all-solid-state batteries, according to Phys.org.
The report claims that “all-solid-state batteries incorporating a lithium metal anode have the potential to address the energy density issues of conventional lithium-ion batteries. But until now, their use in practical cells has been limited by the high lithium ion transfer resistance, caused mainly by the instability of the solid electrolyte against lithium metal.
“This new solid electrolyte that exhibits high ionic conductivity and high stability against lithium metal therefore represents a real breakthrough for all-solid-state batteries that use a lithium metal anode.
Sangryun Kim of Tohoku University says.”We expect that this development will not only inspire future efforts to find lithium superionic conductors based on complex hydrides, but also open up a new trend in the field of solid electrolyte materials that may lead to the development of high-energy-density electrochemical devices.”
All-solid-state batteries are promising candidates for resolving the intrinsic drawbacks of current lithium-ion batteries such as electrolyte leakage, flammability, and limited energy density. Lithium metal is widely believed to be the ultimate anode material for all-solid-state batteries because it has the highest theoretical capacity (3860 mAh g-1) and the lowest potential (-3.04 V vs. standard hydrogen electrode) among known anode materials.
Lithium-ion conducting solid electrolytes are a key component of all-solid-state batteries because the ionic conductivity and stability of the solid electrolyte determine battery performance. The problem is that most existing solid electrolytes have chemical/electrochemical instability and/or poor physical contact against lithium metal, inevitably causing unwanted side reactions at the interface. These side reactions result in an increase in interfacial resistance, greatly degrading battery performance during repeated cycling.
“Complex hydrides have received a lot of attention in addressing the problems associated with the lithium metal anode because of their outstanding chemical and electrochemical stability against the lithium metal anode,” says Kim. “But because of their low ionic conductivity, using complex hydrides with the lithium metal anode have never been attempted in practical batteries. So we were very motivated to see if developing complex hydride that exhibit lithium superionic conductivity at room temperature can enable the use of lithium metal anode. And it worked.”
Now the hard work of transferring breakthroughs in the lab to commercial scale production will begin. An old Irish proverb goes like this: “There’s many a slip t’wixt the cup and the lip.” So far, all the solid state battery news in the past few years has been just that — news.
EV manufacturers such as Volkswagen are betting their entire future strategy on low cost, high energy density batteries being available in the next 3 to 5 years. Will their bets pay off? “We’ll see,” said the Zen master.