The discovery is expected to enable widespread application of aluminum-air fuel cells in a number of applications with power requirements from 1 watt to many kilo-watts. The aluminum-air cell is about 75 times more energy dense than conventional lithium ion cells and delivers significantly greater power in portable electronic applications.
The aluminum-air fuel cell is an independent, self-contained, electrical source that can be mechanically recharged by replacing a fuel cartridge. The power source remains environmentally and ecologically clean throughout its full life cycle, including manufacture, use, and recycling or disposal. The final reaction product is crystalline aluminum hydroxide. It will cost less to manufacture and use than many other power sources according to Eontech, Aluminum PowerÂ’s parent company, in US Patent 6,355,369.
The metal-air cell is made of a non-consumable gas diffusion positive electrode; a consumable negative metal electrode; an electrolyte based on water solutions of salts and/or bases; and a housing enclosing the electrolyte. The electrolyte is held in an electrolyte impermeable container. The aluminum-air fuel cell body contains the cathode in which a replaceable cartridge, containing the anode and electrolyte is fitted to form a sealed unit. Replacing the cartridge recharges the power supply.
The cathode housing accepts the cartridge containing the electrolyte and aluminum anode. When the aluminum is consumed, it is removed and a fresh fuel cartridge is inserted replacing the spent unit. The electrolyte impermeable container is penetrated by a puncture means after the cartridge is fully inserted into the cathode unit. The puncture allows the electrolyte to flow between the positive electrode and the negative electrode and the production of electricity.
The electrolyte is made of a salt solution and an alkali solution. The electrolyte contains additions of Sn+4, Pb+4, Ga.+3, In.+3, poly-saccharide based on D-glucose, polyesters including amides, 2-3 C alcohols and halogenides/hydroxides of alkaline metals. The additions provide a decrease in anode corrosion during discharge, and an increase in the elctrolytes electric capacity. The additions decrease the freezing temperature of the electrolyte.
The research carried out by Alexander M. Iarochenko (Toronto, CA) and Evgeny B. Kulakov (Moscow, RU) demonstrated the corrosion of the aluminum anode occurs according to the electrochemical mechanism. The rate of the process is determined by the kinetics of the cathode hydrogen emission. A complex study of the water decomposition mechanism has shown that the limiting stage there is the intermediate chemical stage of the recombination of adsorbed hydrogen atoms into molecules. Corrosion rate is largely determined by the composition, sizes and shapes of the cathode area on the anode's surface. By modifying their characteristics, it is possible to control the rate of the summarizing corrosion process of the aluminum anode in alkaline electrolytes with the purpose of decreasing it.
The electrochemical corrosion takes place at the anode. The process and the conjugate process is the reduction of hydrogen from water at the cathode and the production of electricity.
The simple structure of the metal-air cell can be adapted to almost any size for use in almost any application. A significant advantage of the aluminum air cell is that it can be mechanically recharged in seconds and the cathode reaction uses oxygen, a readily available cost-free gas from the atmosphere.
As a renewable and sustainable source of energy, aluminum-air based fuel cells offer tremendous advantages in many applications. The aluminum-air fuel cell's high-energy output results from the characteristic energy density of aluminum and the fact that three electrons are released for every atom of aluminum reacted (1 mole electrons released per 9 g aluminum compared to 1 mole electrons released per 32.7 g Zn used).
Development efforts of aluminum-air cells faced significant chemistry challenges: activation of the aluminum anode, controlling the aluminum oxidation reaction. It is also necessary to prevent fouling of the reaction anode surface. Other problems include providing a cathode which is active enough to keep pace with the aluminum anode and controlling hydrogen generated through the corrosion side-reaction (a common problem in this industry).
Aluminum-Power has solved these problems and, in its cell designs for portable electronic devices, is achieving energy densities of 800 Wh/kg with nominal current densities of 70 mA/cm2, maximum current densities of 150 mA/cm2, and peak current densities of 250 mA/cm2 at standard operating conditions.
Unlike other carriers of energy such as gasoline, natural gas or hydrogen, aluminum has tremendous advantages including high energy density, light-weight, stability in a wide range of temperatures. In addition, aluminum is not volatile, not explosive and requires no special transport or storage containers. Perhaps most importantly, the aluminum-air fuel cell has no emissions. The overall reaction by-product, principally aluminum-hydroxide, is environmentally benign and recyclable.
Aluminum-Power Inc. is a Canadian-based high-technology company that has developed proprietary technology in the design, chemistry and manufacture of aluminum and oxygen fuel cells that results in significantly higher power output over extended periods. The company is currently focusing on commercializing its technology for the portable electronics industry. Aluminum Power has licensed the rights to the technology for portable electronic applications to the Trimol Group (OTCBB: TMOL).
. . . . . . . . . . . . . . . . . .Alton Parrish is Editor of Fuel Cell Technology News, the leading industry newsletter produced by Business Communications Inc. To find out more information about or subscribe to Fuel Cell Technology News, please visit www.buscom.com