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- Interview with 24M’s CEO: Test data from 24M’s new battery electrolyte, separator, and packaging technology
Interview with 24M’s CEO: Test data from 24M’s new battery electrolyte, separator, and packaging technology
Lithium-metal batteries promise higher energy densities but the tech is met with a few issues including safety challenges, dendrite formation, and inconsistent cycle life, especially when using a liquid electrolyte.
To solve these, 24M, a licensor of battery technologies, created a new separator technology called Impervio which stops dendrites at the source, and a liquid electrolyte called Eternalyte which minimizes the reaction between the electrolyte and lithium-metal, mitigating the cycle life degradation. The new breakthroughs like 24M ETOP (electrode-to-pack) tech, can be utilized with a 24M SemiSolidTM or conventional electrodes, and when combined, 24M says the suite will help commercialize 1000+ mile lithium-metal battery packs.
Impervio Battery Separator
The promise: Fundamentally improve safety and eliminate mass recalls by suppressing dendrite formation while detecting and preventing internal shorts.
Dendrite prevention: The proprietary separator tech inhibits the growth of dendrites right at the source.
Early fault detection: It also continuously monitors the cell for potential shorts before they occur and if detected, the individual cell is shut down before a thermal event can begin.
24M has run comparison tests of baseline NMC/graphite cells with and without Impervio, and so far it has shown promising results:
In the first test, the cathodes of both cells with/without Impervio were intentionally contaminated with ~1% stainless steel. The baseline cell immediately shorted after formation, while the Impervio cell suppressed the dendrite and pushed past 800 cycles with over 83% capacity retention.
In the second test, 24M intentionally created exposed copper on both cells’ anodes, which led to a rapid soft short of the baseline cell, while the Impervio cell suppressed the dendrites and delivered stable coulombic efficiency while cycling, preventing a soft short between the cathode and anode.
Eternalyte Electrolyte
Lithium-metal batteries, especially those with liquid electrolytes, are known for an inconsistent cycle life caused by lithium or other metal dendrites. 24M has reported that Eternalyte has achieved the highest cycle stability among liquid electrolyte systems under 20mA/cm2 plating/stripping current.
24M’s internal tests are showing promising improvements:
High cycle stability: For a lithium-metal cell cycling at 1C discharge/1C charge, 24M Eternalyte allows the cell to retain 83% capacity over 500+ cycles, approximately 500,000+ miles of total range with 1,000 miles per charge.
Significant rate improvements: Test results for lithium-lithium base cells suggested an equivalent of 3,000+ cycles with 4C continuous cycling without shorting or increasing resistance.
ETOP Electrode-to-Pack Technology
ETOP is 24M’s battery packaging system featuring sealed electrodes packaged directly into the battery pack, removing the need for individual cells and modules.
24M’s CEO, Naoki Ota, explained:
“Sony initially commercialized the lithium-ion battery in 1991, and since then, the industry has largely followed their design lead. The approach involves winding electrodes and placing them into a metal casing to construct a battery cell. However, this design is suboptimal for high-voltage applications such as electric vehicles (EVs), which require a voltage range between 300 and 600 volts.
In conventional lithium-ion cell design, each battery cell provides only 3.2 volts (in the case of lithium-ion phosphate chemistry). To achieve a high voltage like 600 volts, one would need to connect almost 200 of these cans in series, where connecting two cans in series would yield 6.4 volts, and so on. Not only does this consume a significant amount of space, but it’s also inefficient.
At 24M, we innovated by creating sealed electrodes or Unit Cells that can be connected in series within a single package. This means that instead of using 200 cans, we might only need one, two, or three cans. This approach reduces costs and increases energy density through our packaging design.”
The 24M ETOP system is delivering improvements in several key areas:
Performance: Achieve electrode (not cell) packing efficiencies of over 70%, the highest pack-level volumetric efficiency available.
Cost: In addition to its streamlined process and decreased materials usage, it enables electrodes to be connected in a combination of series and parallel — an industry first. By eliminating additional connection components, it also further reduces the overall pack cost.
Range and Cycle Life: Higher packing efficiencies and energy density provide benefits for both EV and ESS applications, boosting range and capacity.
Safety: The 24M SemiSolid Electrode and Unit Cell technology continues to provide unmatched safety when subjected to mechanical abuse.
Pack Design Flexibility: The 24M Unit Cell can be connected in series, parallel, and a combination of series and parallel directly within a pack, enabling configurations that are no longer bound or limited by individual cell voltage (V) and capacity (Ah).
You can learn more about 24M’s battery technology on their site here.
Special thanks to Naoki Ota, CEO of 24M for the interview!