MAHLE Powertrain and Allotrope Energy have unveiled a new battery technology for small EVs that combines supercapacitors with lithium-ion batteries in order to offer ultra-fast charging coupled with good power density.

The two companies considered how an electric moped could be powered by an inexpensive, small-capacity battery that could be recharged between stops in as little as 90 seconds.

Allotrope’s technology features a high-rate battery-type anode and a high-capacity electric double-layer capacitor (EDLC)-style cathode, separated by an organic electrolyte. The company says its battery cell suffers none of the thermal degradation effects that plague 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.”

Allotrope says the battery’s “capacitor-style cathode” enables a lifetime of over 100,000 cycles, uses no rare-earth metals, and is completely recyclable.

MAHLE Powertrain investigated the scenario of an electric moped used for food delivery, with a range of 25 km. A 500 Wh conventional lithium-ion battery would require a 30-minute recharge mid-shift, and frequent fast charging would shorten battery life. A lithium-carbon pack, however, could be recharged at 20 kW in 90 seconds—just enough time for the next delivery to be collected.

“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,” says Dr. Mike Bassett, MAHLE Powertrain’s Head of Research. “The real challenge came in designing the electrical architecture capable of absorbing such high rates of charge. Also, 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 at up to 20 kW by augmenting the power from a typical 7 kW single-phase connection, thereby reducing cost and complexity while eliminating the need for expensive power grid connection upgrades.

Source: MAHLE Powertrain