Tesla research partnership progresses on new battery chemistry

Enlarge / Here's what the lithium deposited at the anode looks like under a scanning electron microscope. Full charge in top row, depleted charge in bottom row. (credit: Louli et al./Nature Energy)

Electric vehicles have come a long way in terms of going a long way on a charge. But everyone is still seeking the next big jump in battery technology-a battery with significantly higher energy density would mean more range or lower costs to hit the current range. There is always some room for incremental progress on current lithium-ion battery technology, but there is a lithium holy grail that has remained out of reach for decades: ditching its graphite anode to shrink the cell.

A lithium metal battery would simply use solid lithium as the anode instead of requiring a graphite framework for lithium atoms to tuck into as the battery charges. The problem is that the lithium doesn't form an order surface during recharging, so the battery capacity drops drastically-declining to 80 percent within 20 charge cycles in some configurations. Rogue lithium also tends to build up dangerous, branching, needle-like structures that can pierce the separator between the anode and cathode and short-circuit the cell.

Last year, a Dalhousie University lab group with ties to Tesla developed a lithium metal battery with somewhat better performance. Lithium atoms electroplate onto a copper electrode as the battery charges and then move back into a conventional lithium-nickel-manganese-cobalt cathode as charge depletes. Through a new electrolyte, they were able to get this battery to last about 90 cycles before hitting 80 percent capacity to control the nasty short-circuit problem.

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