Lithium iodide battery

The lithium-iodide battery emerged from Wilson Greatbatch's frustration with the short lives of pacemaker batteries, becoming the power source that would keep millions of hearts beating reliably for a decade at a time. This chemistry transformed cardiac pacing from a risky medical intervention into a routine procedure.

The adjacent possible opened in 1960 when Greatbatch accidentally invented the implantable pacemaker while working on a heart rhythm recorder at the University of Buffalo. The oscillator he built had the wrong resistor value, and it began pulsing at 1.8 millisecond intervals—perfect for pacing a human heart. But the zinc-mercury batteries powering early pacemakers lasted only two years, requiring repeated surgeries to replace them.

By 1968, Greatbatch was searching for better power sources. At Catalyst Research Corporation in Baltimore, researchers had developed a lithium-iodine-polyvinylpyridine cell with promising characteristics: high energy density, low self-discharge, and remarkable stability. Greatbatch acquired the rights and in 1970 founded Wilson Greatbatch Ltd. to develop the technology for medical implants.

The chemistry was elegant. The anode was pure lithium, the most electrochemically active metal. The cathode was a proprietary mixture of iodine and poly-2-vinylpyridine, which reacted at 150°C for 72 hours to form an electrically conductive viscous liquid that cooled into a solid. The solid-state electrolyte meant no liquid to leak—critical for something implanted in a human body.

The first pacemaker powered by a lithium-iodide battery was implanted in 1972. On July 9, 1974, Manuel Villafaña and Anthony Adducci at Cardiac Pacemakers Inc. in St. Paul, Minnesota, began manufacturing pacemakers with this new battery chemistry. The results were transformative: battery life extended from two years to ten or more, while the cells became smaller and more reliable.

Path dependence locked in the technology. By 1978, lithium-iodide had become the standard for pacemakers. The solid-state construction eliminated mechanical failure modes. The predictable voltage decline allowed physicians to monitor remaining battery life through external telemetry. Over three million pacemakers have been implanted using this chemistry.

The cascade extended beyond cardiac pacing. The lithium-iodide cell proved that lithium could power implantable medical devices safely—paving the way for defibrillators, neurostimulators, and drug pumps. Meanwhile, Greatbatch's work on lithium chemistries inspired the broader development of lithium-based batteries, eventually contributing to the lithium-ion batteries that power modern electronics. By 2026, cells exhibit energy densities three to four times greater than those produced in 1972, while maintaining the reliability that makes them trusted inside human bodies.