PolyPlus lithium-air and lithium-water batteries

PolyPlus ( http://www.polyplus.com/) is a Berkeley CA based developer of advanced lithium-air and lithium-water batteries. The technology is a game-changer in battery energy density and could enable electric cars with hundreds or perhaps a thousand miles of range.

The PolyPlus lithium-water battery has achieved the highest recorded energy density of 1,300 Watt-hours/kilogram, or an almost 10x improvement over current lithium-ion batteries. ( http://blog.greentransportation.info/2012/02/polyplus-named-edison-awards-finalist.html) PolyPlus projects the energy density for commercial lithium-air batteries to be 1000 watt-hours per kilogram. (http://www.polyplus.com/technology.html)

The key technology is what they call protected lithium electrodes (PLEs) that are remarkably stable in a broad range of electrolytes, including aqueous and non-aqueous solvents.

The invention of the PLE enables the development of a new class of ultra-high energy density batteries including lithium metal semi-fuel cells. PolyPlus encapsulates the lithium metal core using solid electrolyte membranes and a unique compliant seal. The solid electrolyte is highly conductive to lithium ions, but impervious to liquids and gases. In this way, the lithium core is electrochemically active but chemically isolated from the external electrolyte, allowing the construction of lithium-metal/aqueous batteries including lithium/air and lithium/water with unprecedented energy density.

PolyPlus is developing rechargeable and non-rechargeable Li-Air, and Li-Seawater batteries based on protected Li electrodes. At a nominal potential of about 3 volts, the theoretical specific energy for a lithium/air battery is over 5000 Wh/kg for the reaction forming LiOH and 11,000 Wh/kg for the reaction forming Li2O2 or for the reaction of lithium with dissolved oxygen in seawater, rivaling the energy density for hydrocarbon fuel cells and far exceeding Li-ion battery chemistry that has a theoretical specific energy of about 400 Wh/kg. PolyPlus intends to first commercialize non-rechargeable Li/Air and Li/Seawater batteries followed by the introduction of rechargeable Li/Air. The projected energy density and specific energy for commercial Li-Air batteries is on the order of 1000 Wh/l and 1000 Wh/kg. Lithium/Seawater batteries which use the ocean as the positive electrode are even more energy dense and should be introduced commercially at about 1500 Wh/l and 1500 Wh/kg. Li/Air and Li/Seawater batteries are based on non-toxic materials and are environmentally benign.