Battery developments that speed up charging are great but ones that go green at the same time are even better. So this battery that can be recharged using water should make some serious waves.

Japanese company Fuji Pigment has developed an aluminium-air battery which it is calling Alfa. It will charge via water and should be available as soon as spring this year.

The Alfa battery can be filled with salty or non-salty water in order to replenish charge. The company claims the cells work "for minimum 14 days by refilling salty water or normal water occasionally." How often that means isn't clear but since pretty much any water will work this shouldn't be hard to manage. Presumably after 14-days it require a full refill and charge.

The battery capacity for this wonder is theoretically 40 times as large as current lithium-ion batteries. The major problem holding back this battery was corrosion but that has been overcome by placing ceramic and carbonaceous materials between aqueous electrolyte and electrodes.

While the aluminium-air battery has a whopping 8,100W/kg capacity and lithium-ion has 120-200Wh/kg it's still lithium-air that comes out on top with 11,400Wh/kg – although when this will be available isn't clear.

The Alfa aluminium-air batteries are expected to be used in cars soon – imagine recharging with water alone and going hundreds of miles on a charge. The future of battery power just got very exciting for 2015.

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