(Digital Presentation) High Energy Density Stable Lithium-Sulfur Batteries Enabled By 3D Bilayer Garnet Electrolytes

Abstract

The cubic-garnet (Li7La3Zr2O12, LLZO) Lithium-Sulfur battery (GLSB) shows great promise in the pursuit of achieving high energy densities. The sulfur used in the cathodes are abundant and inexpensive and possess high specific capacity. As well, LLZO displays excellent chemical stability with Li metal. By using unique porous/dense/porous LLZO “trilayer” and dense/porous LLZO “bilayer” architectures developed by our group, an exceptionally high areal current density of 10 mA/cm2 in Li-Li symmetric cells without applied pressure was achieved. However, instability in the sulfur cathode/LLZO interface can cause cell performance issues. Therefore, it is critical to resolve the sulfur cathode/LLZO interfacial challenge to achieve stable cycling.Here, we created an innovative gel polymer (GPE) buffer layer to stabilize the sulfur cathode/LLZO interface. With a thin bilayer LLZO architecture as a solid electrolyte, stable cycling was achieved with a high initial discharge capacity of 1542 mAh/g corresponding to an energy density of 223 Wh/kg and 769 Wh/L under a discharge current density of 0.87 mA/cm2 without applied pressure. Moreover, the addition of the GPE interlayer also allowed the GLSB cells to maintain an average discharge capacity of 1218 mAh/g over 265 cycles with 80% capacity retention at discharge current density of 1.74 mA/cm2 under a sulfur loading of 5.2 mg/cm2 at 22 (Figure 1). Achieving such stability is a major step in the development of commercial garnet lithium sulfur batteries. Figure 1