Mahle and Allotrope develop fast-charge lithium-carbon battery system

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A new battery technology has been unveiled by Mahle Powertrain and Allotrope Energy which is said to offer ultra-fast recharging, coupled with good power density. By combining the benefits of super capacitors and traditional lithium-ion batteries, the lithium-carbon technology should enable a full charge to be delivered in a similar time to refueling an internal combustion-powered vehicle. In addition, Li-C cells are free from rare-earth metals, are fully recyclable, and are not susceptible to runaway events.

“Range anxiety is often quoted as the main barrier to electric vehicle adoption, but if the battery could be recharged in the same time it takes to refuel a conventional IC engine vehicle, much of that worry goes away,” said Dr Mike Bassett, Mahle Powertrain’s head of research.

“With the rise of the on-demand economy, there’s been a rapid increase in the use of petrol-powered mopeds for urban deliveries such as take-away meals, and this has contributed to air quality issues in our cities,” said Bassett. “Decarbonizing these deliveries has so far proved difficult without maintaining a stock of expensive interchangeable batteries or switching to a larger, heavier electric vehicle with increased energy consumption.”

However, in a collaborative project with Allotrope Energy, Mahle Powertrain looked at how an electric moped could be used as an urban delivery vehicle powered by an inexpensive small capacity lithium-carbon battery. The study centered around a city-based e-moped fast-food delivery service with a 25km target range. A 500Wh conventional lithium-ion battery would require a recharge mid-shift that, even with a fast-charger, would take more than 30 minutes. In addition, regular fast-charging reduces battery life to the point it would likely need replacing every year or two. A lithium-carbon pack, however, could be recharged at 20kW in just 90 seconds, meaning a full charge could be achieved in the time taken for the next delivery to be collected.

Allotrope Energy’s lithium-carbon technology features a high-rate battery-type anode and a high-capacity electric double layer capacitor-style (EDLC) cathode, separated by an organic electrolyte. The result is a battery cell that apparently suffers none of the thermal degradation effects experienced by traditional lithium-based batteries. Its stability, even at high temperatures, permits high current delivery and fast recharging, all without the need for complex external cooling or elaborate battery management systems.

Additionally, its capacitor-style cathode enables a lifetime of over 100,000 cycles, far greater than conventional batteries, while the elimination of rare-earth metals and the design’s complete recyclability make it better for the environment both during production and long after it.

“With ultra-fast charging, the size of the battery can be optimized to suit the scenarios the vehicle will be used in, and that leads not only to weight savings but also cost reductions that further lower the barriers to decarbonization,” Bassett said. “The real challenge came in designing the electrical architecture capable of absorbing such high rates of charge. Additionally, with no suitable charging systems on the market that can deliver these charge rates from a domestic supply, we created our own bespoke design.”

The solution Bassett’s team came up with uses its own built-in capacitor-based energy store to deliver ultra-fast charging up to 20kW by augmenting the power from a typical 7kW single phase connection, thereby reducing cost and complexity while eliminating the need for expensive power grid connection upgrades.

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Lawrence has been covering engineering subjects – with a focus on motorsport technology – since 2007 and has edited and contributed to a variety of international titles. Currently he is responsible for content across UKI Media & Events' portfolio of websites while also writing for the company's print titles.

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