Kyle Proffitt
April 7, 2025 | The 2025 International Battery Seminar & Exhibit was held March 18-20, 2025 in Orlando, Fla. For three full days, presentations covered the latest developments and considerations in the battery space, with topics including breakthrough technological developments, manufacturing, supply chain issues, automotive-specific concerns, safety, stationary storage, recycling, and more. A parallel Battery Venture, Innovation, and Partnering track included more intimate discussions around business and investment. Exhibitors and poster presentations filled a large auditorium ready to showcase their products and discoveries, culminating in the Best of Show Award.
Some top-level takeaways:
- EVs aren’t everything. Sales have slowed, but the industry is still growing. In the meantime, demand is soaring for stationary storage, driven by increased renewable energy transition and data centers.
- The fundamentals are still good. Sentiment was strong that electrification is beneficial for everyone and will ultimately win out, even if government incentives disappear.
- LFP has gotten real cheap. $50/kWh was tossed around as the metric to beat. This makes competition for new technologies an uphill battle and investment a little tricky.
- New technologies abound, pushing toward higher energy density, longer lifetimes, and increased safety. Safety and longevity were highlighted over and over, as the first keynote will show.
- Silicon anode technologies were a common refrain (again, starting from the keynotes).
- Some unique newer battery use cases were highlighted—large trucks, satellites, and extreme conditions.
- There’s uncertainty about supply chains, pricing, and the future of government incentives with a new administration in Washington, but hope remains strong, and there is alignment with goals to localize infrastructure.
Before we get to all of that, the plenary keynotes at Florida Battery took center stage. This year, Shirley Meng, professor in molecular engineering at the University of Chicago, chief scientist at the Argonne Collaborative Center for Energy Storage Science, and director of the Energy Storage Research Alliance, was named recipient of the honorary Shep Wolsky award and delivered the first keynote address, posed as a question: Can We Have a Safe Lithium-Metal Battery?
We Need Lithium-Metal Batteries
“If we want to move to ultra-high energy density volumetrically, lithium metal has to be the anode,” Meng said. “If we want to move toward gravimetric high energy density, like the lithium-sulfur system, lithium metal has to be the anode… we don’t have any other option.”
Meng highlighted some of the progress of the last 30+ years, tripling energy density while decreasing cost and extending cycle life 10-fold. She noted several trends— movement away from cobalt and toward more nickel in the cathode, the use of LFP and perhaps LMFP—and she said that “silicon is already coming to the market”, referring to its use in the anode.
Meng rehearsed some of what must happen in the battery space to keep moving forward: high energy density, safety, longevity, recycling, and fast charging. She elaborated on the longevity angle, saying that batteries need to become an asset, or sovereign funds and pension funds will not invest. She made one unique point regarding charging, saying that with robotics and safe batteries, swapping is an option. It’s “not that difficult; I was sitting in the car of NIO, in China, the battery swapping was done in five minutes.”
Pointing at emerging technologies, including solid-state, Li-S or Li-O batteries, sodium-ion, aqueous batteries, organic batteries, and novel architectures, Meng boldly proclaimed, “I will put my money on ALL of these chemistries.” She explained her stance by saying that we need 200-300 TWh of batteries to complete the energy transition, “and that’s provided that hydrogen is successful, modular nuclear is successful.” We need more winners. Meng pointed out that only two battery technologies have reached TWh scale, lead acid, taking 150 years, and lithium-ion, in just 30 years. “Let’s hope one or two of these new chemistries will eventually go to a TWh,” she added.
Critical Issues for Lithium Metal Batteries; More Coulombic Efficiency
But she really wanted to talk about lithium metal batteries and why they aren’t mainstream yet. “For me, the biggest challenge is still the coulombic efficiencies.” Typical lithium ion batteries reach 99.986% coulombic efficiency (CE). This means you get back nearly all of the charge you put in each cycle, and you can cycle about 1500 times before capacity drops to 80%. In what first appears a trivial contrast, the CE for lithium metal batteries is 99.5%; at this CE, Meng says “your cell dies after 50 cycles.” Meng said with one exception, current liquid electrolytes don’t allow us to reach 99.9% CE with lithium metal batteries. A liquefied gas electrolyte technology by South 8 Technologies enables 99.9% CE, but it only works in cylindrical cell format. Meng said that “we must spend all our effort and energy to figure out where is the loss of 0.48%.”
The answer, she says, lies in the lithium metal morphology, which you need some sophisticated equipment to assess. Cryogenic transmission electron tomography has been used extensively by her group and others to reveal that with a poor electrolyte, the lithium deposits with a porous structure. Improving the electrolyte enables more dense lithium deposition and improves CE. Another option is to squeeze the battery with stack pressure. These options can push CE to 99.5% or 99.6%.
“Metallic dead lithium is always trapped in the insulating SEI [solid electrolyte interphase] layers,” Meng says. “The key here is really to control the morphology of lithium metal, regardless of if you’re using liquid electrolyte or solid electrolyte. If you can have large granular, very dense lithium, you have a higher probability to reach 99.9%.” When the deposited lithium is very porous, there is much more surface area for this SEI formation and opportunity to create “dead lithium”. Meng said anode-free designs can help with avoiding porosity, because “electrochemistry tends to produce some of the most pure and dense liquid metal that we have seen.”
Safety: Solid-State
Another problem with that dead lithium, Meng says, is that if you have a poor NMC cathode that’s giving off oxygen during operation, “you’re heading toward disaster for the safety.” The electrolyte, the cathode stability, the lithium morphology, and the cycling environment are all important parameters influencing overall safety, she says. And she has an idea for improving safety. “Maybe you can predict that I’ll say, ultimately safe lithium metal batteries have to be made with solid state.” Then she showed us how.
Part of the solution involves dealing with volume change while avoiding stack pressure. With lithium metal deposition, the anode grows considerably, straining the system. One solution Meng champions is pairing a conversion cathode with the metal anode. “To make cell pressure much better, under control, we proposed recently pairing lithium metal with a conversion cathode like sulfur.” The idea is that as lithium plates and grows in the anode, the cathode shrinks, offsetting the normal expansion. During discharge, the roles reverse.
This work is not yet published but is available on ChemRxiv. Using solid argyrodite (LPSCl) electrolyte, sulfur cathode, and lithium metal anode, her group produced cells with areal loading up to 10 mAh/cm^2 and cell-level energy density of about 415 Wh/kg. Meng says this was accomplished with only 30% sulfur in the cathode, and she projects that loading 60% sulfur will yield 600 Wh/kg. Once again, she stresses that this is only conceivable with a lithium metal anode. “The cycling is very stable, because in the solid state, lithium metal’s deposition stripping efficiency can be 99.9%.” She showed data with some cells cycling 500 times. Morphology control of the sulfur is also quite important.
Finally, Meng pointed to another direction yielding fruitful results. In a recent report, her group performed theoretical calculations to determine how variability in factors such as temperature, pressure, and deposition substrate would affect the specific “grain” orientations that lithium metal adopts during charging. That work led to experimental confirmation that a thin (500 nm) layer of amorphous silicon on top of the copper current collector promotes a specific and more uniform body-centered cubic (101) lithium orientation, as opposed to a (001) orientation observed on bare copper substrate. In this (101) orientation, “the entire lithium metal layer will have very uniform texturing and density,” Meng said. “With this method, in the solid state, we can achieve 99.9% coulombic efficiencies, and the deposition and stripping are very uniform.” The use of the thin silicon seed layer enabled a ten-fold increase in critical current density, to about C/2, compared with bare copper, and it paves the way for further improvements in cycling rate. Meng highlighted that achieving 99.9% CE is a major achievement.
QuantumScape Would Like a Word
In a separate session at the conference, Alex Louli of QuantumScape gave an update since we last covered their anode-free, solid-state, lithium-ion batteries at the 2024 Solid-State Battery Summit. These batteries are not actually 100% solid-state as they use liquid catholyte; a ceramic separator keeps the electrolyte constrained in the cathode. Louli pointed to a February publication in the Journal of The Electrochemical Society, in which they measured critical current density for their cells and demonstrated other state-of-the-art lithium metal electrolytes falling far short of a 4C 15-minute fast charge target, reaching only about 15 mA/cm^2. Then, the y-axis on his graph contracted as he showed results with their separator, “critical current densities on the order of hundreds of milliamps per centimeter squared.” This indicates that the separator would survive sub-one-minute charging, although other components are apparently limiting. For their latest QSE-5 design, a 5.5 Ah cell with 844 Wh/L and 301 Wh/kg, Louli said they have “demonstrated the ability to cycle at automotive rates for 800 cycles and beyond, while retaining 95% of our total energy.” These numbers suggest a coulombic efficiency of 99.983%. “We can do 10C continuous discharge,” he added. Louli presented several encouraging safety testing results, including thermal stability to 300 °C and no thermal runaway events with various puncture tests. They plan to ship these cells to customers for their “first commercial demonstration, targeted for next year.”
