BATT Awards $731,000 Contract for Development of Novel Electrolyte for Li-ion Batteries Based on New Salt

The Batteries for Advanced Transportation Technologies (BATT) program recently awarded a $731,000 contract to University of Rhode Island chemistry professor Brett Lucht, co-director of the URI Energy Center, for the development of new electrolytes for lithium-ion batteries (LIB). BATT is supported by US Department of Energy’s Office of Vehicle Technologies.

One of the components of the project, said Dr. Lucht, is a novel salt he and his colleagues presented at the 214^th meeting of the Electrochemical Society in October 2008: Lithium Tetrafluorooxalatophosphate (LiPF₄C₂O₄, LiF₄OP).

Lucht and his research group have been studying the mechanism that causes lithium ion batteries to degrade over time.

The most widely used electrolytes for lithium-ion batteries are based on LiPF₆ salt dissolved in organic carbonates or esters. These, however, have poor thermal stability, and significant energy fading can occur after several years at room temperature and after a few months at moderately elevated temperatures.

While there are a number of factors contributing to the limited thermal stability and calendar life of Li-ion batteries, the reactions of the electrolyte with the surface of the electrode materials is critical.

Most of the problems associated with the aging of batteries are due to the electrolyte—the liquid in the battery that contains dissolved salts and that allows the lithium ions to go back and forth between the electrodes

—Brett Lucht

Although a number of different alternative electrolytes have investigated, none of the salts have a superior combination of properties to LiPF₆, according to Lucht in the paper for ECS 214. “An

improved salt would benefit LIB technology.”

Lucht had earlier found that lithium tetrafluorooxalatophosphate is generated during thermal storage of LiPF₆-based electrolytes with added LiBOB (an alternative electrolyte).

Investigation of the new salt revealed that it offers both high conductivity and excellent stability.

The high conductivity, thermal stability, and reversibility of cycling with standard anode and cathode materials suggest that LiF₄OP/carbonate electrolytes are a promising alternative for lithium-ion batteries in PHEV applications.

—Brett Lucht, ECS 214

A patent is pending on the new salt.

The researchers have been working closely on the salt with Yardney Technical Products of Pawcatuck, Conn., which makes specialty batteries for the military and the National Aeronautics and Space Administration. Several Fortune 500 companies will also be conducting tests on the salt.

In addition to the salt discovery, Lucht has also developed additives for lithium-ion batteries that stabilize the salt in the battery electrolytes and inhibit its degradation due to heat. Patents are currently pending on this technology. These additives have been successfully tested in small lithium ion batteries, and testing in larger batteries is now under way.

Resources

• Brett L. Lucht, Ang Xiao, Mengqing Xu, and Li Yang (2008) Novel Electrolyte for Lithium Ion Batteries: Lithium

  Tetrafluorooxalatophosphate (LiPF₄C₂O₄) (ECS 214)

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