Styrene–Butadiene–Styrene Block Copolymer-Li5.5PS4.5Cl1.5 Composite Solid-State Electrolyte Enabling a High-Performance All-Solid-State Lithium Battery

To realize high-energy all-solid-state lithium batteries (ASSLB), it is essential to address the interfacial reaction issue between sulfide solid electrolytes (SSEs) and the lithium anode. While SSEs are known for their high ion conductivity, this reaction hinders their application in ASSLBs. To overcome this challenge, a composite solid electrolyte (CSE) is developed. The CSE consists of sulfide-based SSE Li5.5PS4.5Cl1.5 (LPSCl) and a styrene–butadiene–styrene block copolymer (SBS) aiming to create a stable electrolyte–anode interface. The LPSCl-2%SBS CSE not only improves the mechanical properties and high ionic conductivity but also enhances the stability of the electrolyte–anode interface against lithium metal. Experimental results show that symmetric Li/Li cells with LPSCl-2%SBS exhibit stable Li plating/stripping for 1200 h at 1.0 mA cm–2 with a lower overpotential. Notably, the excellent interface stability of the LPSCl-2%SBS CSEs/Li metal enables high performance in Li(Ni0.8Co0.1Mn0.1)O2/LPSCl-2%SBS/Li batteries, demonstrating a high initial discharge capacity (123.2 mA h g–1 at 0.1C), cycling performance (72.9% capacity retention at the 100th cycle at 0.1C and 42.7% capacity retention at the 500th cycle at 0.5C), and rate capability (62.1 mA h g–1 at 0.5C). These findings underscore the importance of the chemical compatibility between sulfide electrolytes and lithium metal, offering a promising approach to the design of high-energy ASSLBs.