We’ve all heard the buzz about solid-state lithium batteries being the next big thing in energy storage, right? Well, a recent study is shaking things up a bit. Published in Energy Storage Materials, this research suggests that the expected energy density improvements from using garnet-type solid electrolytes in lithium metal batteries might not be as impressive as we hoped.
Let me break it down for you. The study found that all-solid-state lithium metal batteries (ASSLMBs) using lithium lanthanum zirconium oxide (LLZO) achieve a gravimetric energy density of just 272 Wh/kg. That’s only a slight bump up from the 250–270 Wh/kg we see in today’s lithium-ion batteries. And given LLZO’s high production costs and manufacturing headaches, it’s a bit of a letdown.
Eric Jianfeng Cheng, the study’s lead author from Tohoku University, put it this way: “All-solid-state lithium metal batteries have been seen as the future of energy storage, but our study shows that LLZO-based designs might not deliver the big energy density boost we expected. Even in perfect conditions, the gains are small, and the cost and manufacturing issues are significant.”
While solid-state lithium metal batteries are known for their safety and energy efficiency, LLZO’s potential as a solid electrolyte faces challenges. Its density adds weight, which eats into the expected energy benefits. Sure, the volumetric energy density is about 823 Wh/L, but LLZO’s weight and cost make it hard to apply practically. Plus, its brittleness and the tricky fabrication process—like dealing with lithium dendrite formation at interfaces—don’t help its case for commercial use.
Cheng noted, “LLZO is a great material in terms of stability, but its mechanical limitations and weight are real hurdles for commercialization.” Because of this, the research team is exploring hybrid models that mix LLZO with other materials. Some promising options include LLZO-in-polymer composite electrolytes, which offer high ionic conductivity while being more flexible and easier to make. Another idea is quasi-solid-state LLZO electrolytes that use a bit of liquid electrolyte to boost ionic transport and structural integrity.
“Instead of going all-in on a fully ceramic solid-state battery, we need to rethink our strategy,” Cheng suggested. “By combining LLZO with polymer or gel-based electrolytes, we can make them easier to manufacture, reduce weight, and still keep high performance.” This research, a collaboration among Tohoku University and several international partners, highlights the need for practical engineering solutions that balance energy performance with manufacturability and cost.
