Wilson Greatbatch - The Greatbatch Lithium-iodide Battery Cell

The Greatbatch Lithium-iodide Battery Cell

In 1968, Catalyst Research Corporation of Baltimore, Maryland developed and patented a lithium battery cell (USA patent 4049890). The cell used two elements at near ends of the electrochemical scale, causing a high voltage of 2.8V and an energy density near the physical maximum. Unfortunately, it had an internal impedance which limited its current load to under 0.1 mA and was thus considered useless.

Greatbatch sought to introduce this invention into the pacemaker industry, which could readily utilize a high impedance battery. The early work was conducted in a rented area of the former Wurlitzer Organ Factory in North Tonawanda, New York. Ralph Mead is understood to have headed the early electrochemical development. Greatbatch introduced the developed WG1 cell to pacemaker developers in 1971, and was met with limited enthusiasm. The lithium-iodide cell manufactured by WG is now the standard cell for pacemakers, having the energy density, low self-discharge, small size and reliability needed.

In the cell as developed for cardiac pacemaker application, the anode is lithium and the cathode a proprietary composition of iodine and poly-2-vinyl pyridine, neither of which is electrically conductive, however after processing by mixing and heating to ~ 150 °C for 72 hours the components react with each other to form an electrically conductive viscous liquid which, while still molten, is poured into the cell where it cools to form a solid. When the liquid contacts the lithium anode it creates a monomolecular layer of semiconducting crystalline lithium iodide. As the cell is discharged by the current load of the pacemaker, the reaction between the lithium anode and iodine cathode forms a growing barrier of lithium iodide, which being resistive causes the terminal voltage of the cell to decrease approximately as an inverse function of the volume of the barrier. Pacemaker designers use this characteristic to permit detection of incipient 'end of life' of the pacemaker's lithium cell.