Eos Energy Storage has developped a metal-air battery that they claim has done over 5000 cycles with no physical degradation. They have recently raised $15M which will help them to launch their Aurora system in 2014.
Zinc-air battery company Eos Energy Storage raises $15M http://www.greencarcongress.com/2013/05/eos-20130521.html
The Aurora system is delivered in a standard 40’ container, and comes in 1 >MWh and 6 MWh standard sizes, built, respectively, with 2 kWh and 12 kWh >modules. Initial pricing is expected to be $160/kWh.
The specs look promising and the modular concept appeals a lot. Also their predicted cost per kWh is cheap.