[CliffordK]

You might try:

Aluminum Anode

Iron Oxide (rusty piece of steel) for Cathode.

You can experiment with different solvents (salt water, Sodium hydroxide, or acid).

[syhprum]

In the fourties before the development of semicondudtor devices it was very difficult to obtain DC from an AC supply one of the devices I tried as a boy was an electrolitic rectifier which used Aluminium plates in a liquid solution, I was surprised to find this also functioned as a battery   

[crimsonknight3]

Europositron Rechargeable Aluminum Batteries.

"Europositron Powerful Aluminum Battery to Hit Market in 2007 - Europositron of Finland has developed an innovative nano scale electrochemistry technology that allows the production of rechargeable aluminum batteries. (Electrifying Times; Spring/Summer 2006; Vol. 10 No. 1)

Giant Aluminium batteries are for real - Ab Europositron Oy has been conferred the prestigious 2005 Frost & Sullivan Technology Innovation of the Year Award in the field of battery technologies. (ZPEnergy; March 23, 2005)

Award for Europositron's Technology Innovation in Battery Technology - Ab Europositron Oy has been conferred the prestigious 2005 Frost & Sullivan Technology Innovation of the Year Award in the field of battery technologies. (Azonano; 23rd March 2005)"

"District court finds fake inventor

The Helsinki district court has taken an inventor, who for years has been collecting money by issuing stocks, under custody, the newspaper Helsingin Sanomat says. Europositron Ab has sold stocks to hundreds of Finns for at least 1.3 million Euro despite the invention the company is marketing is a pure "product of imagination" according to the police. The company have had large advertisements in newspapers during the the years 2001-2007 and has sold stocks in three issues. Europositron has been collecting money from investors for a aluminum battery which was supposed to be developed with the help of "nano chemistry" and which promised to be 20 times lighter and with a much longer durability than today's batteries. According to testimonies the police has collected, the inventor is not real and Europositron has had no other business than issuing stocks. Helsingin Sanomat says six investors finally got tired with the inventor and reported him to the police."

However, saying that, currently there has been improvements in nano scale chemistry, as such in the medical industry, creating 5nm particles and alloys, such as a nano silver nitrate to treat burn victims to prevent infection, so theoretically this idea could be viable in the next few years