Carbon Bipolar Membranes for Solid-State Batteries

In traditional batteries with liquid electrolytes, e.g., lithium-ion, each battery cell must be individually sealed, packaged, and electrically connected to other cells in the pack. The cells in solid-state batteries on the other hand may be stacked on top of one another with only a separation layer in between, called a bipolar plate. These bipolar plates or membranes if thin enough must be electrochemically inert to the electrode and electrolyte materials while providing electrical connectivity between the individual cells. Here, NASA has combined advances in the preparation of carbon nanomaterials and solid-state batteries to create extremely lightweight bipolar plates and membranes. These bipolar membranes will enable high energy density solid-state batteries unachievable with typical bipolar plate materials like stainless steel, aluminum, aluminum-copper, or conductive ceramics. The carbon bipolar membranes may be fabricated in multiple ways including but not limited to directly compressing carbon powders onto an electrode-electrolyte stack or separately making a film of the carbon material and dry pressing the film between other battery layers. The new bipolar membranes have been demonstrated in high energy density solid-state batteries in coin and pouch cells. The carbon bipolar membranes are at technology readiness level TRL-4 (Component and or breadboard validation in laboratory environment)and are available for patent licensing. Innovators from the NASA Langley and NASA Glenn Research Centers have developed materials and processes to use carbon nanomaterials as bipolar membranes or plates for separating solid-state battery unit cells. Using carbon materials over current bipolar plates will be an enabling technology for lightweight, high energy density solid-state batteries. Bipolar membranes or plates provide a chemically inert but electrically conductive layer separating solid-state battery unit cells that allow them to be stacked within a single package. Here, the developed bipolar plate materials include films or membranes of graphene, holey graphene, and carbon nanotubes. These carbon materials provide a significant weight savings over currently used metallic materials while maintaining the necessary performance characteristics of the bipolar plates. These new bipolar membranes or plates may be employed in high energy density solid-state batteries for electrified aircraft, electric vehicles, or a variety of electric devices that require high performance batteries.