BATTERY BASICS

Familiar fuel tank and EV battery pack do exactly the same thing. They’re ways to store chemical energy. Liquid fuels release heat energy through the chemical reaction called combustion. This can be converted to motion by an engine. Batteries release energy by making electrons run from place to place via external circuits. Through a motor, for example. Charging simply sends electrons back to where they started.

Only one of these two energy storage systems is compact and cheap, and it’s not the battery pack...

Batteries are named according to their active chemical constituents. Lead-acid and Nickel-cadmium are examples. Lithium-ion is a catch-all name that covers a variety of lithium battery chemistries. These have come to dominate in EVS, for good reasons.

Lithium-ion delivers superior energy and power density compared to other battery chemistries in commercial production. High energy density extends an EV’S driving range. Power density is a measure of the electric current its battery can supply to an EV’S motor or motors, and so affects performance. All batteries store only DC electricity, so an inverter is needed for the conversion to the AC current required to run EV motors.

The big disadvantage of Lithium-ion batteries is their cost. Between $135 and $200 per kwh are the kind of numbers auto industry execs mention. This means the 432 Lithium-ion cells in the big, 600kg-plus and 90kwh battery of the Jaguar I-pace cost $12,000 to $18,000.

But progress is being made in upping energy density. The BMW i3 went into production in 2013 with a 22kwh battery pack. In 2016 capacity was increased to 33kwh and then, in late 2018, to 42kwh, without any change in the pack’s dimensions.

Reducing the cost of cells is a high priority for manufacturers like LG Chem and Samsung SDI. These Korean leaders in Lithium-ion have recently built massive factories in eastern Europe, which could deliver cost-cutting economies of scale.

Investments like these mean Lithium-ion will continue to be the chemistry of choice for EV manufacturers. While there are frequent reports of alternative chemistries under development, the journey from lab to production line is long and uncertain.

The solid state battery, which is basically Lithium-ion without goopy electrolyte paste inside, seems to be the most promising next step. Probably...