Experimental batteries live mostly in sheltered laboratories, communicating to the outside world through rosy reports generated for investors. Some systems show good potential, but many are years away from becoming commercially viable. Others disappear from the scene and die gracefully in the lab without hearing of their passing. Below are the most promising experimental batteries worth mentioning in alphabetical order.
Li-air batteries borrow the idea from zinc-air and the fuel cell in that they breathe air. The battery uses a catalytic air cathode that supplies oxygen, an electrolyte and a lithium anode. Scientists anticipate an energy storage potential that is 5 to 10 times larger than that of Li-ion but speculate it will take one to two decades before the technology can be commercialized. Depending on materials used, Li-ion-air will produce voltages in between 1.7 and 3.2V/cell. IBM, Excellatron, Liox Power, Lithion-Yardney, Poly Plus, Rayovac and others are developing the technology. The theoretical specific energy of lithium-air is 13kWh/kg; aluminum-air has similar qualities, with an 8kWh/kg theoretical specific energy.
Most lithium-metal batteries are non-rechargeable. Moli Energy of Vancouver was first to mass-produce a rechargeable Li-metal battery for mobile phones, but occasional shorts from lithium dendrites caused thermal runaway conditions and the batteries were recalled in 1989. Li-metal has a very high specific energy. In 2010, a trial Li-metal-polymer with a capacity of 300Wh/kg was tested in an experimental electric vehicle (this compares to 80Wh/kg for the Nissan Leaf). DBM Energy, the German manufacturer of this battery, claims 2,500 cycles, short charge times and competitive pricing if the battery were mass-produced. Safety remains a major issue.
By virtue of the low atomic weight of lithium and the moderate weight of sulfur, lithium-sulfur batteries offer a very high specific energy of 550Wh/kg, about three times that of Li-ion, and a specific power potential of 2,500Wh/kg. During discharge, the lithium dissolves from the anode surface, and reverses itself when charging by plating itself back onto the anode. Li-S has good cold temperature discharge characteristics and can be recharged at –60°C (–76°F). The challenges are limited cycle life of only 40 to 50 charges/discharges and poor stability at high temperature. Since 2007, Stanford engineers have been experimenting with nanowire and this technology offers promise. Li-S has a cell voltage of 2.10V and is environmentally friendly. Sulfur as the main ingredient is abundantly available.
Silicon-carbon Nanocomposite Anodes for Li-ion
Researchers have developed a new high-performance anode structure for lithium-ion batteries based on silicon-carbon nanocomposite materials. The material contains rigid and robust silicon spheres with irregular channels to promote the access of lithium ions into the particle mass. With graphite anodes, researchers have achieved stable performance and capacity gains of five times that of regular Li-ion. Manufacturing is said to be simple and low-cost, and the battery is safe and broadly applicable. However, the cycle life is limited due to structural problems when inserting and extracting lithium-ion at high volume.
Text taken from batteryuniversity.com