Life, performance and safety of Grace rechargeable lithium-titanium disulfide cells

W.R. Grace & Co. is developing rechargeable Li-TiS₂ cells. This proprietary process produces thin, flexible TiS₂ cathodes with a life in excess of 500 cycles. TiS₂ utilization of 93% is typically achieved at a C/5 discharge rate. A life of 200 cycles has been achieved for AA-size cells at a C/5 discharge rate and 60 cycles at the C rate. The practical energy density is 115 Wh/kg. Safety testing is underway. Vibration and high altitude did not cause venting. Crushing did not result in ignition or temperature rise. Forced overcharge and overdischarge did not result in skin temperatures above 40°C. The peak skin temperature during the short-circuit test was 120°C. Safety analyses point to the need for careful control of electrolyte volume and the benefits of a fusible separator. Grace is developing such a separator, which would shut down the electrochemical cell reaction at a temperature of 130°C