For several months I’ve been telling readers that emerging lead-carbon battery technologies will be game changers in alternative energy storage.
Last week, The Economist published an article about Axion Power International (AXPW.OB) titled “Lead-acid Batteries Recharged” and I found a recent report from Sandia National Laboratories on its side-by-side testing of lead-acid, lead-carbon and Li-ion batteries. Now that Axion’s management is talking to the press and Sandia is releasing independent data, I feel free to explain more fully why lead-carbon technology is so disruptive. I don’t like table pounding, but this is probably the most important Seeking Alpha article I’ve written.
Lead-carbon batteries are different from other types of batteries because they combine the high energy density of a battery and the high specific power of a supercapacitor in a single low-cost device. The primary goals of lead-carbon research have been to extend the cycle lives of lead-acid batteries and increase their power. Basically, developers start with conventional lead-acid chemistry and add carbon components to the negative electrodes. While the carbon components do not change the basic electrochemistry, they increase specific power and reduce a chemical reaction called “sulfation” that occurs during charging cycles and is the principal reason ordinary lead-acid batteries fail. Over the last several years, lead-carbon researchers have followed three different development paths:
- Blending carbon additives into the lead sulfate paste that is used for negative electrodes;
- Developing split-electrodes where half of the negative electrode is lead and the other half is carbon; and
- Completely replacing the lead-based negative electrode with a carbon electrode assembly.
The DOE’s 2008 Peer Review for its Energy Storage Systems Research Program included a slide presentation from Sandia that summarized the results of its cycle-life tests on five different batteries including a deep-cycle lead-acid battery, two lead-acid batteries with carbon enhanced pastes, a split-electrode lead-carbon battery (the Ultrabattery) and an advanced lithium-ion (Li-FePO4) battery. While the tests performed by Sandia focused on smoothing power output from wind turbines and used a 10% depth of discharge from a 50% initial state of charge, which means more testing will be required before comprehensive comparisons are possible, the following graph highlights the magnitude of the cycle-life improvements that lead-carbon technologies offer today.
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