At the recent launch of the BMW i3 lithium-ion battery-electric car, BMW board member Ian Robertson said that in the next three to four years there will be more progress in battery development than in the previous 100 years. He said electric cars will have batteries with twice the current power within four to five years, which will double the range.

We reported back in January that Toyota Motor Corp and BMW AG agreed to jointly research a lithium-air battery. Lithium-air battery has its anode filled with lithium, and cathode with air.

Lithium metal-air batteries can store more than 5,000 watt-hours per kilogram. (A123 M1 cells are around 120 wh/kg) That's more than forty-times as much as today's high-performance lithium-ion batteries, and more than another class of energy-storage devices: fuel cells.

The reduction in battery mass is achieved by eliminating the need for a second reactant inside the cell. Lithium metal batteries react with oxygen in the air that is pulled in through a 'breathing' casing, making them lightweight and compact.

The technology is being studied by researchers including IBM , which is working to develop a lithium-air battery that will let electric vehicles run 500 miles on one charge.

Given the recent news that General Motors is working on an EV that can go 200 miles (320 km) per charge at a cost of about $30,000 to compete with Tesla's as yet un-named 200 mile $30,000 EV due in approx three to four years, the 2016/17 model year promises to be a very exciting year for affordable, long range electric vehicles.

One question asked is: how will the first BMWi customers benefit from more powerful batteries in the future? EV powertrains are expected to have a minium service life of 20,000 hrs which equates to approx 1.2M km or 80 years average annual motoring so the electric motor and power electronics will likely outlast several battery packs. BMW still have a few years to decide how to switch or upgrade to newer battery technology as it becomes commercially available.