Silicon–air battery

Silicon–air batteries are a new battery technology invented by a team led by Prof. Ein-Eli at the Grand Technion Energy Program at the Technion – Israel Institute of Technology.

Silicon–air batteries are created from oxygen and silicon. Such batteries would be lightweight, and have a high tolerance for both extremely dry conditions and high humidity and would provide significant savings in cost and weight because the built-in cathode of conventional batteries is not present in silicon–air batteries.^[1][2] The experimental cells described in the journal Electrochemistry Communications using a room-temperature ionic liquid as electrolyte produced between 1 and 1.2 volts at a current density of 0.3 millamperes per square centimeter of silicon.^[3]

History

The only research report available to the public was done by its creator, Yair-Ein-Eli. Eli began research in Technion – Israel Institute of Technology with David Starosvetsky, graduate student Gil Cohen of Technion, Digby Macdonald of Pennsylvania State University, and Rika Hagiwara of Kyoto University.^[4] Eli's reasoning for using silicon as a fuel cell is because of its high specific energy, availability as a resource (eighth most plentiful in the universe, second most plentiful in Earth's crust), tolerance of places with high humidity, and non-toxic properties.^[5] In their experiments, they tested for different potential energies and voltages, using different liquid oxygen solutions.^[6] The experimental results and theories on the battery were published online in 2009 in the journal Electrochemistry Communications. This got the attention of organizations such as DARPA and the Pentagon, where they are currently working on military usage of this battery.^[7] The battery is still under research by these organizations and not available for commercial use.

Design

The battery's energy source is made using an Ionic liquid known as EMI·2.3HF·F (classified in the article as an Room Temperature Ionic Liquid [RTIL]) and wafers containing high amounts of silicon. The wafers act as an Anode(fuel source) and the RTIL acts as an Electrolyte which turns the wafers into usable energy. In its idle state, the RTIL dissolves the wafers at a slow rate because there is no semi-conductor to speed up the reaction. When put into use, the RTIL will then react faster to dissolve the silicon wafers, which will produce energy for use in any electronics.^[8] The battery lacks a built-in cathode that most batteries use to balance the anode's charge.^[4] Instead, the membrane of the battery allows oxygen from the atmosphere to flow through it and acts as the cathode.

SPECTRE

A variation of the silicon-air battery, known as the Stressed Pillar-Engineered CMOS Technology Readied for Evanescence(SPECTRE), is currently being researched by DARPA and partially by SRI It works exactly like the silicon-air battery, but with an added feature. The battery will be used in any piece of military equipment and then the a "kill" signal is sent out to the battery which will then prompt the battery to self-destruct along with the device it is powering.^[9][10]

Storage

The storage of the battery is very comparable to the Aluminum-air battery. The specific energy of the silicon-air battery is estimated to be 8.470 W h/kg and the energy density is about 2109.0 W H/l. The voltage of the battery is 1-1.2 V.^[6]

Usage

Prof. Yair-Ein-Eli proposed that the battery should be used for medical devices such as hearing aids or diabetic pumps which can be tedious for people to charge.^[5] The nature of the battery also allows it to be used in places like Singapore or Central America where the humidity is very high. SRI is currently researching ways to use the battery for daily life use.^[7] Different possibilities can include electronics used daily like a laptop or a phone. On higher scales, it is possible the battery can be used to power cars or even space stations. With SPECTRE, lost military equipment, such as drones, can be destroyed with just a simple signal to prevent the devices from getting into the enemy's hands.^[10]

See also

• Metal-air battery
• Silicon
• Oxygen
• Aluminium–air battery
• Battery

References

Galvanic cells Types Voltaic pile Battery Flow battery Trough battery Concentration cell Fuel cell Thermogalvanic cell Primary cell (non-rechargable) Alkaline Aluminium–air Bunsen Chromic acid Clark Daniell Dry Edison-Lalande Grove Leclanché Lithium Mercury Nickel oxyhydroxide Silicon–air Silver oxide Weston Zamboni Zinc–air Zinc–carbon Secondary cell (rechargeable) Automotive Lead–acid gel / VRLA Lithium–air Lithium–ion Lithium polymer Lithium iron phosphate Lithium titanate Lithium–sulfur Dual carbon battery Molten salt Nanopore Nanowire Nickel–cadmium Nickel–hydrogen Nickel–iron Nickel–lithium Nickel–metal hydride Nickel–zinc Polysulfide bromide Potassium-ion Rechargeable alkaline Sodium-ion Sodium–sulfur Vanadium redox Zinc–bromine Zinc–cerium Cell parts Anode Binder Catalyst Cathode Electrode Electrolyte Half-cell Ions Salt bridge Semipermeable membrane