![]() ![]() Amprius announced its lithium metal cells offered 504 Wh/kg and over 1,321 Wh/l at 25☌ (77✯). As we usually talk about gravimetric energy density, we can only try to guess what ONE achieved with its new cell. ONE's lithium metal cells have a volumetric energy density of 1,007 Wh/l, more than twice as much as what the LFP batteries offer (441 Wh/l). Instead of saving the most precious cells as the Gemini battery pack is designed to do, they save fuel. In a way, that's precisely the principle a hybrid car follows. Still, I suspect that these occasions will invert the process the startup described: the LFP cells will take the fast-charge punch and slowly let the lithium metal batteries recover energy. It would be interesting to have the fast charging data for the Gemini battery pack. If the anode-free cells can charge and discharge at a slower rate than LFP, ONE can ensure they will not be submitted to stress, which could eventually make them develop dendrites more easily. Why not use the lithium metal batteries directly, especially considering there are losses with DC-toDC converters? Simple: to preserve them as much as possible. According to the startup, Gemini "switches to the anode-free cell, using it to charge the LFP cell" after 150 miles. The LFP cells will provide around 150 miles (241.4 km) of range, which is more than enough for the daily driving needs of most drivers. There are several purposes for that, but ONE disclosed the most important one. The battery startup said that the DC-to-DC converters move energy between the LFP cells and anode-free batteries seamlessly. However, they seem to play a more crucial role in ONE's hybrid component. In most BEVs, their role is to keep the 12V battery charged, as an alternator does in combustion-engined vehicles. Perhaps the most critical components in the Gemini battery pack are the DC-to-DC converters. Whether this is as effective as ONE says it is, that's certainly a good idea not to have all high-energy-density cells together should any of them present issues. ONE confirms that by stating it "sharply reduces the risk of thermal runaway." If one lithium metal cell starts a fire, LFP batteries could create a barrier that restricts the damage. Lithium metal cells are also more prone to dendrites, needle-like structures that perforate the separator, connect the anode and the cathode, and cause short circuits. If that is confirmed, it should fit among semi-solid-state cells.Ĭalling this arrangement a "skip-cell safety architecture" suggests it was conceived to minimize thermal runaway events with the anode-free cells, which are lighter and also hold more energy than LFP batteries. Nonetheless, it must have a special separator. QuantumScape's solid-state cell will work in the same way, but ONE did not say its new anode-free battery presents a solid electrolyte. Lithium ions plate on the copper foil on the other side of the separator during the discharge process and migrate back to the cathode when the battery is charged. Honestly, that was the only possible explanation for a cell without an anode. ![]() The company confirmed to Motortrend that they are lithium metal cells. ONE calls it a "skip-cell safety architecture," meaning that lithium iron phosphate (LFP) cells are mixed with the startup's new anode-free batteries. ONE will use a different chemistry in the Gemini, but what deserves more attention is the interesting structure it conceived to have it. In September 2022, a Reuters story led me to believe that the Gemini battery pack would have LFP cells mixed with NMC batteries because they had " cathodes made of nickel, cobalt, and manganese." This new story works to correct this mistake: that was a temporary arrangement. ![]()
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