Army

Lithium carbon monofluoride-oxygen battery

Battery has two discharge reactions

Energy

In conventional battery systems, energy is stored by employing a reducing agent (lead) as an anode and an oxidizing agent (lead dioxide) as the cathode or positive electrode. An electrolytic solution such as sulfuric acid in water is used between the electrodes. When energy is withdrawn, the reducing agent gives up electrons which flow through an external circuit and are received by the oxidizing agent at the positive electrode. Ions flow through the electrolytic solution between the electrodes to complete the circuit. Some type of chemical compound (for example, lead sulfate) is produced as a result of the combination of these processes. The compound is usually stored in a porous structure of one or both of the electrodes. Batteries are designed to provide maximum energy storage per unit weight. Other design considerations involve the life of the battery, its cost and, of course, the operating efficiency. Usually, there is some sort of trade-off between these desirable characteristics.

Lithium Carbon Fluoride (Li-CFx) batteries are used in applications where a high-specific energy primary power source is needed. Li-CFx cells have one of the highest practical specific energies of any solid cathode primary battery system. Lithium Oxygen (Li-O2 cells) have a theoretical specific energy even higher than Li-CFx cells but a practical specific energy somewhat lower due to cell construction considerations. The construction of an electrochemical cell that takes advantage of both the Li-CFx chemistry and the Li-O2 chemistry has not been described or demonstrated.

To fill this technical gap in battery technology, Army researchers have developed a sealably-enclosed storage lithium carbon monofluoride-oxygen battery system comprising a lithium metal-containing electroactive anode; an electroactive cathode formed of a carbon monofluoride compound; an electrolyte solution formed of an organic solvent and a lithium salt; a casing surrounding the anode, the cathode, and the electrolyte solution; and a port through the casing, wherein the port allows the flow of an oxygen containing gas into the casing.

The unique feature of this invention is the creation of a product through the discharge of a specific cathode material that then acts as a site for the electrochemical reduction of another electroactive species. In this case, the discharge of a CFx active material produces a carbon byproduct that is then the site for the electrochemical reduction of oxygen and the deposition of Li2O2 and Li2O discharge product onto that carbon material. This combination of cell chemistries results in a specific energy for the total cell being higher than for either chemistry by itself.

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