When temperatures fall below freezing, cellphones need to be recharged frequently, and electric cars have shorter driving ranges. This is because their lithium-ion batteries’ anodes get sluggish, holding less charge and draining energy quickly. To improve electrical performance in the extreme cold, researchers have replaced the traditional graphite anode in a lithium-ion battery with a bumpy carbon-based material, which maintains its rechargeable storage capacity down to -31 F.