Highly stable garnet solid electrolyte based Li-S battery with modified anodic and cathodic interfaces

A highly cycling stable Li-S battery has been fabricated using a Ta-doped garnet (Li_6.4La₃Zr_1.4Ta_0.6O₁₂, LLZTO) solid electrolyte. The battery has achieved high reversible specific capacity of 805 mA h g⁻¹ after 500 cycles at a charge/discharge current density of 0.5 and 1.5 mA cm⁻², respectively at 25 °C, and the decay rate of 0.0058% (comparing with 20th discharge capacity). The high stability of the battery is attributed to the modifications of both anodic and cathodic interfaces. At the anode side, an Au coating on the LLZTO surface is introduced to reduce the interfacial resistance by improving the Li wetting towards LLZTO. Under semi-solid state mode, it is verified that the Li-Au-garnet based interface could undergo a high current density of 1.5 mA cm⁻². At the cathode side, P₂S₅/Li₂S additive in liquid catholyte enhances the solubility of the Li₂S to increase the sulfur utilization, and also contributes to the construction of Li₃PS₄ based Li-ion conductive SEI on the cathode. Coin cells and pouch cells with high sulfur loadings of 3.2 and 5.3 mg cm⁻² are assembled to validate the potential of practical application. Both cells exhibit high reversible specific capacities of 1088 mA h g⁻¹ and 799 mA h g⁻¹, delivering areal capacity of 3.5 mA h cm⁻², 4.23 mA h cm⁻², respectively.