Safer Battery with Switchable Polymer Coating

Physical Sciences Inc. (PSI) proposes to utilize a switchable polymer (SWP) to prevent catastrophic failure due to internal shorting or overdischarge in lithium-ion batteries. The SWP, applied to both the surface of the cathode particles and the cathode current collector, can be reversibly "switched" from an insulator to a conductor upon oxidation permitting normal battery operation. In Phase I, PSI will demonstrate that upon a short or overdischarge the polymer reversibly switches to an insulator reducing the current flow to the cathode material protecting the system and preventing unsafe operation. This reduced current flow will be demonstrated to decrease the localized heat generation by more than two orders of magnitude. PSI will also demonstrate that insulation of the cathode material limits irreversible degradation of the discharge capacity upon overdischarge maintaining cell balance and improving cycle life. In the Phase II program, we will scale up the coating procedure to a production scale, in order to demonstrate the technology in a 5Ah battery. At the conclusion of Phase II, PSI will have demonstrated the technology in full battery systems and be prepared to partner with NASA's industrial partner SAFT America to have cells built for a mock application demonstration.