Sulfur Polymers as Flexible Interfacial Additives for Low Stack‐Pressure Solid‐State Lithium‐Ion Batteries

PolyS: This article describes a new sulfur polymer that is combined with the argyrodite solid electrolyte Li₆PS₅Cl (LPSC) to produce a composite lithium-ion conducting material. This composite enhances ionic conductivity at cell stack-pressures below 1.6 MPa and is used to produce low pressure solid-state batteries that minimize external pressurization systems and therefore increase volumetric and gravimetric capacities.

Abstract

Solid-state batteries (SSBs) fabricated using sulfide solid electrolytes (SSEs) typically require cell stack-pressures in the range of tens to hundreds of megapascals to maintain effective interfacial contact and lithium-ion mobility across the full cell stack. These relatively high cell stack-pressures necessarily require additional cell components that reduce the delivered volumetric and gravimetric capacities of SSBs. This work has developed a novel sulfur polymer (polyS) that improves lithium-ion conductivity in SSBs at low cell stack-pressures, thereby directly targeting this technological limitation. Specifically, this work shows that polyS can be combined with the argyrodite Li₆PS₅Cl (LPSC) to form a stable composite SSE. By combining LPSC particles with a flexible additive that enhances interfacial contact at low pressures, this new polyS LPSC composite SSE material greatly improves ionic conductivity at cell stack-pressures below 2.0 MPa in comparison to conventional LPSC composites. Furthermore, this polyS LPSC composite can be used to fabricate a full SSB that cycles reversibly at only 1.6 MPa. Finally, this composite SSE exhibits self-healing behavior when combined with a lithium metal electrode, wherein lithium dendrites are oxidized to form passivating Li₂S species that recover the cell from shorting.

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