High Sulfur Loading and Capacity Retention in Bilayer Garnet Sulfurized-Polyacrylonitrile/Lithium-Metal Batteries with Gel Polymer Electrolytes

The cubic-garnet (Li7La3Zr2O12, LLZO) lithium-sulfur battery shows great promise in the pursuit of achieving high energy densities. The sulfur used in the cathodes is abundant, inexpensive, and possesses high specific capacity. In addition, LLZO displays excellent chemical stability with Li metal; however, the instabilities in the sulfur cathode/LLZO interface can lead to performance degradation that limits the development of these batteries. Therefore, it is critical to resolve these interfacial challenges to achieve stable cycling. Here, an innovative gel polymer buffer layer to stabilize the sulfur cathode/LLZO interface is created. Employing a thin bilayer LLZO (dense/porous) architecture as a solid electrolyte and significantly high sulfur loading of 5.2 mg cm-2, stable cycling is achieved with a high initial discharge capacity of 1542 mAh g-1 (discharge current density of 0.87 mA cm-2) and an average discharge capacity of 1218 mAh g-1 (discharge current density of 1.74 mA cm-2) with 80% capacity retention over 265 cycles, at room temperature (22 & DEG;C) and without applied pressure. Achieving such stability with high sulfur loading is a major step in the development of potentially commercial garnet lithium-sulfur batteries. Schematic illustration of cell configuration and the in situ formed gel polymer electrolyte (GPE) on bilayer cubic-garnet Li7La3Zr2O12 (LLZO) garnet structure. A thin ZnO atomic layer deposition coating is applied to the bilayer LLZO, followed by the in situ gel polymer electrolyte (GPE) formation on the sulfur cathode side. The in situ GPE is formed through 1,3-dioxolane polymerization, followed by mixing with ether-based liquid electrolyte.image