A Multifunctional Interlayer Enhancing Water Tolerance in Rechargeable Lithium Batteries

As a protic impurity, water can severely degrade battery life and pose safety risks. Lowering the H2O content in the electrolyte is essential, but it often requires energy-intensive drying technologies. Here, we develop a multifunctional interlayer utilizing dehydrated sepiolite on a commercial polypropylene separator (Sep@PP) to address water-induced challenges in lithium batteries. Its open channel and rich active sites (Si–O–Si, Mg–OH2, and Mg–OH groups) make it effectively absorb harmful impurities (e.g., H2O, HF, and transition metal ions), thereby preventing electrolyte decomposition, stabilizing the electrode interface, and further enhancing cycling stability. Moreover, the inherent thermal stability of dehydrated sepiolite endows the separator with exceptional heat resistance, mitigating thermal runaway risks and significantly enhancing overall battery safety. As a result, the LiNi0.5Mn1.5O4 (LNMO)//Li cell assembled with the Sep@PP separator exhibits excellent cycling stability, retaining 84.1% of its capacity over 500 cycles. Even when cycled in an electrolyte containing ultrahigh water content (1200 ppm), the LNMO//Li cell still maintains 81.7% of its capacity over 500 cycles, demonstrating its strong tolerance to moisture. Furthermore, the LiNi0.6Mn0.2Co0.2O2 (NCM622)//Li cell paired with the Sep@PP separator shows superior stability and maintains 72.3% of the initial capacity after 200 cycles, even at 55 °C. These findings underscore that leveraging the unique structure of dehydrated sepiolite presents a novel approach to mitigating water hazards in the modern battery industry.