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    Lead-Acid: The coolest thing to happen to batteries since Volta
    By Navarre Bartz | February 25th 2009 01:00 AM | 2 comments | Print | E-mail | Track Comments
    About Navarre

    Navarre recently graduated with a degree in Ceramic Engineering from Missouri S&T (formerly the University of Missouri - Rolla). He is primarily...

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    So, it has been quite some time since I've posted a blog. Unfortunately, I am trying to get this pesky degree and do some research on the side. I would like to continue my history of the battery with the development of the first rechargeable battery. Our sojourn takes us now to France; however, the year is now 1859.

    Gaston Planté was a French physicist who conducted a variety of experiments in the field of electricity. He is best known for the invention of the first rechargeable electrochemical cell, the lead-acid battery. A lead acid battery consists of a negative lead terminal ("spongy" lead) and a positive lead oxide terminal with a sulfuric acid electrolyte. Due to the electrochemical reactions involved, both electrodes turn into lead sulfate while the electrolyte becomes water as more sulfate is reacted with the electrodes. Unlike the Volta cell, this reaction is reversible, making the lead-acid a very useful battery, particularly due to its cabability to deal with abuse. The lead-acid's constant usage until the present day is a testament to its simplicity and resiliency. Lead-acid batteries have an energy density of 40 Wh/kg, and a single lead-acid cell has a potential of ~2V depending on charge state. The first lead-acid batteries had a problem generating acceptable amounts of current, however.

    During the course of his experimentation,  Planté found that surface area was key to the current capability of an electrochemical cell. He developed a new plate that increased the surface area of lead in contact with the sulfuric acid electrolyte. This electrode used a lead-based paste impregnated grid made of a lead alloy. The paste was permeable to the acid, allowing the electrolyte to contact a much greater amount of lead than a traditional rectangular plate would be able to do. The plates would be all made identically and stacked together with a separator in between them. By alternating the polarity of each of the plates, a higher voltage battery can be made. This stack was then immersed in sulfuric acid and given an initial charge. This forms brown lead dioxide at the positive electrode and grey "spongy" lead at the negative electrode. This electrode advance allowed lead-acid to become the premier power battery. Only in the past 10 or so years have new power batteries such as lithium iron phosphate made it into the commercial market. The basic layout of the lead-acid battery has not changed for 150 years, although advances in processing and raw materials have allowed it to improve in energy density and cycle life while its simplicity and inexpensive raw materials have kept it common in the marketplace, particularly in applications where high current loads are neccessary and low energy density is not an issue.



    Très intéressant!

    For comparison, what's the energy density of the typical batteries that we use today in torches and music players?  Does Duracell top the league?

    I remember our physics teacher at school shorting a lead-acid battery with a copper wire, which exploded with a flash!  That's low internal resistance for you!

    Robert H. Olley / Quondam Physics Department / University of Reading / England
    Lithium batteries are around 150 to 180 Wh/kg which is pretty high for rechargeable cells. Rechargeable batteries typically have lower energy densities as their reactions are not as strong to the one direction as primary, or non-rechargeable cells. A typical alkaline battery, like a Duracell are typically between 100 and 200 Wh/kg from what I can see (I do research in rechargeables, so I had to do a Google search for that one) and are much less expensive than the high end lithium polymer batteries that can meet or exceed this energy density. One of the things holding electric cars and the such back is the price of the batteries, and not neccessarily the technology in them.