Gotta Charge Fast
Sketching the landscape for fast charging strategies
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Fast-charging has been a problem that has received millions of dollars of funding from automakers, battery manufacturers, and startups to crack it. Here we uncover the challenges to fast-charging batteries in general, who the players are in the space, and whether the industry is moving towards or away from it.
Startups and R&D efforts have targeted fast charging from every perceivable scale. We sketched up some of the strategies ranging from the nano to infrastructural scales:
There is an intrinsic maximum rate at which electrons and lithium ions can move through the pure anode, cathode, and electrolyte of the battery. When charging at higher rates, the anode materials with a voltage close to metallic lithium (i.e. graphite) can induce plating and become severely damaged.
Niobium, silicon, and germanium anodes that allow faster lithium diffusion and have a lower risk of Li plating are being developed by startups like Nyobolt, Echion Technologies, Enevate, and StoreDot.
Quantumscape has also claimed fast-charging capability with solid-state Li metal anodes.
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Most actual electrodes are porous coatings of active materials. If the gaps between the coated powders are really small, Li travel is restricted and this slows intercalation. This is common in energy-dense cells where they pack more active material into a cell. Similarly, current collectors which are typically flat foils may be slow to conduct electrons from the electrode particles furthest away from them.
Whether batteries are made in cylindrical, pouch, or prismatic formats, energy density can be improved by making them bigger with relatively less casing. However, thermal management while fast charging becomes an issue as thicker cells have to dissipate more heat that is generated from the center.
Limitations on the intrinsic material, electrode, cell, and thermal scales must be simultaneously optimized for real-world fast charging methods. This requires smart algorithms and power electronics. In modules and packs, if the charge between individual cells isn't balanced well, this can also prevent fast charging from achieving its full potential.
Brill Power also has intelligent BMS technologies which can optimize charging across cells, modules and packs.
For thermal management, Xing Mobility makes cells fully immersed in a safe coolant.
While consumer EV owners are happy to recharge slowly overnight at home, in situations like public transport or delivery fleets that require maximized uptime, the effective charge time may also be limited on an infrastructural level. Level 3 superchargers need to provide 400-850V of DC power and be widely accessible. Significant time can also be saved by eliminating the "kerfuffle" required to connect with a charger and use the right payment network to activate it.
While range anxiety and recharge times are barriers to mass consumer adoption, the shift towards the low-cost saviour LFP (initially relegated to Chinese buses), by majors like Tesla & VW signals shifting priorities.
It’s a classic chicken or egg. Fast-charging and improving infrastructure may also open the door to smaller (and less rare-metal dependent) batteries which can enable new products in new market segments.
The fast-charging landscape is vast, and each of these diverse strategies has varying degrees of exposure to the dynamically changing energy storage field. Which will win out in the end? Well, the only way to know is to continue tuning in to us at Intercalation Station!
The above companies in no way represent an exhaustive list!
🌞 As always, thanks for reading!
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About the writers: Andrew is a PhD researcher at the University of Oxford (@ndrewwang). Nicholas is a business manager at UCL Business and Venture Fellow with Berkeley SkyDeck (@nicholasyiu). Ethan is a battery scientist with experience at startups, research labs, and EV manufacturers across the world (@ethandalter).