OVERCHARGE PROTECTION ADDITIVES FOR RECHARGEABLE LITHIUM BATTERIES

HIGH-ENERGY-DENSITY, RECHARGEABLE LITHIUM BATTERIES ARE BEING CONSIDERED BY NASA FOR FUTURE MANNED AND UNMANNED MISSIONS. BECAUSE LITHIUM BATTERIES CONTAINING NON-AQUEOUS ELECTROLYTES ARE HIGHLY SENSITIVE TO OVERCHARGE, ESPECIALLY WHEN INDIVIDUAL CELLS ARE CONNECTED IN SERIES, AN ADEQUATE OVERCHARGE PROTECTION MECHANISM MUST BE INCORPORATED INTO THE CELL DESIGN. PHASE I ADDRESSES THIS NEED BY EXPLORING THE ADDITION OF SEVERAL ROBUST REDOX COUPLES TO THE NON-AQUEOUS ELECTROLYTE. THESE ADDITIVES ARE ELECTROACTIVE JUST POSITIVE OF THE NORMAL CELL CUTOFF VOLTAGE ON CHARGE AND NEGATIVE OF IRREVERSIBLE ELECTROLYTE OXIDATION POTENTIAL. PRELIMINARY TESTS SUGGEST THAT THIS PARTICULAR CLASS OF REDOX COUPLES WILL ALSO ENHANCE THE CYCLEABILITY OFTHE LI ELECTRODE AND SUPPRESS ELECTROLYTE REDUCTION. DURINGPHASE I THE LONG-TERM CHEMICAL AND ELECTRO-CHEMICAL STABILITY OF THESE MATERIALS WILL BE ASSESSED PRIOR TO SUBJECTING THEM TO CYCLING IN LI/TIS2 CELLS AND MULTICELL BATTERIES. HIGH-ENERGY-DENSITY, RECHARGEABLE LITHIUM BATTERIES ARE BEING CONSIDERED BY NASA FOR FUTURE MANNED AND UNMANNED MISSIONS. BECAUSE LITHIUM BATTERIES CONTAINING NON-AQUEOUS ELECTROLYTES ARE HIGHLY SENSITIVE TO OVERCHARGE, ESPECIALLY WHEN INDIVIDUAL CELLS ARE CONNECTED IN SERIES, AN ADEQUATE OVERCHARGE PROTECTION MECHANISM MUST BE INCORPORATED INTO THE CELL DESIGN. PHASE I ADDRESSES THIS NEED BY EXPLORING THE ADDITION OF SEVERAL ROBUST REDOX COUPLES TO THE NON-AQUEOUS ELECTROLYTE. THESE ADDITIVES ARE ELECTROACTIVE JUST POSITIVE OF THE NORMAL CELL CUTOFF VOLTAGE ON CHARGE AND NEGATIVE OF IRREVERSIBLE ELECTROLYTE OXIDATION POTENTIAL. PRELIMINARY TESTS SUGGEST THAT THIS PARTICULAR CLASS OF REDOX COUPLES WILL ALSO ENHANCE THE CYCLEABILITY OFTHE LI ELECTRODE AND SUPPRESS ELECTROLYTE REDUCTION. DURINGPHASE I THE LONG-TERM CHEMICAL AND ELECTRO-CHEMICAL STABILITY OF THESE MATERIALS WILL BE ASSESSED PRIOR TO SUBJECTING THEM TO CYCLING IN LI/TIS2 CELLS AND MULTICELL BATTERIES.