Issue Date: January 24, 2011
Relativity Powers Batteries
Much of the power in lead-acid batteries comes from relativistic effects on lead electrons, according to a theoretical study (Phys. Rev. Lett., DOI: 10.1103/PhysRevLett.106.018301). Rechargeable lead-acid batteries, which use sulfuric acid as the electrolyte between metallic Pb and PbO2 electrodes, are common in vehicles. But just why they work so well has been something of a mystery. Researchers at Sweden’s Uppsala University and Finland’s University of Helsinki investigated the role that relativistic effects might be playing in battery chemistry. Relativity theory holds that electrons in heavier elements must move faster to counter stronger nuclear attractions. Such electrons’ orbitals also shrink, with the overall effect of making the element more electronegative and a stronger oxidant. The researchers calculated that relativistic effects contribute about 1.7 V of a lead battery’s total electromotive force of 2.1 V. They suggest that a better understanding of relativistic effects in heavy elements might lead to new battery materials.
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