Superionic composite electrolytes with continuously perpendicular-aligned pathways for pressure-less all-solid-state lithium batteries

Solid electrolytes are promising candidates for safe, high-energy battery systems. Composite solid electrolytes, in particular, hold the potential to combine high ionic conductivity with stable electrode interfaces. However, a fundamental trade-off often exists between ion conduction and mechanical properties. Here we present a composite solid electrolyte design that decouples ion conduction from mechanical flexibility, achieving a high ionic conductivity of 10.2 mS cm−1 at 25 °C while maintaining close mechanical contact with the electrode. The composite architecture consists of alternating layers of perpendicularly aligned (PA) Li0.3Cd0.85PS3 nanosheets, to establish continuous superionic conduction pathways, and Li-containing polyethylene oxide (PEO) layers, to ensure flexibility and interfacial compatibility. At 25 °C, this PA-Li0.3Cd0.85PS3/PEO electrolyte enables Li||LiNi0.8Co0.1Mn0.1O2 coin cells (stack pressure during assembly