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The new design *combines lead-acid chemistry with ultracapacitors, energy-*storage devices that can quickly absorb and release a lot of charge, which they store along the *roughened surface of their electrodes. Unlike ordinary lead-acid *batteries, which are slowed by the movement of *chemicals within them, these could *provide quick bursts of power for acceleration and then recharge during braking, a must for hybrid-electric and electric vehicles. A hybrid’s rapid recharging cycles and high currents would destroy the lead electrodes in standard batteries, because lead sulfate would build up on them. The new batteries can go through at least four times as many charging cycles as lead-acid batteries, and, *crucially, would cost about a quarter of NiMH batteries.

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The new batteries’ advantage over standard lead‑acid batteries comes from *simple tweaks of the negative *electrode. Instead of a lead plate, Axion makes the electrode from activated carbon, the highly porous, spongelike material used in *ultracapacitor electrodes. When a *regular battery discharges, the lead electrode reacts with sulfate ions, forming lead sulfate and creating protons and electrons. Axion’s activated carbon electrode directly releases and adsorbs protons from the sulfuric acid electrolyte during discharging and *charging. The batteries recharge four times as fast as conventional ones, Granville says.

The UltraBattery is slightly different, says Lan Lam, *project manager of the *battery work at CSIRO. The *negative electrode is split into two, one half made of lead and the other half of activated *carbon. The two halves are connected in parallel so that their *currents combine. This split*-*electrode design gives the battery the best of both technologies, according to Lam. While activated carbon provides quick energy bursts, it cannot store as much energy as the lead-acid chemistry. The combination gives the UltraBattery an energy *capacity closer to that of a lead-acid battery than an *ultracapacitor could get alone, Lam says.
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