Impact of Jellyroll Tapes on Performance of Layered Oxide/Hard Carbon Sodium-Ion Pouch Cells

This study investigates the influence of jellyroll tape materials on the cycle life and self-discharge of layered oxide/hard carbon sodium-ion pouch cells. Jellyroll tapes made of polyethylene terephthalate (PET) or polypropylene (PP) polymer were used in this study. Severe PET tape decomposition was observed in additive-free electrolyte. The use of solid-electrode interphase forming additives suppressed PET tape decomposition effectively and resulted in a competitive performance comparable to that of cells with PP tape. Replacing PET tape with PP tape led to sodium-ion pouch cells with substantial improvements of capacity retention, coulombic efficiency, and charge endpoint slippage. The superior chemical stability of PP tape in sodium-ion batteries allows for long cycle life and low self-discharge even in the absence of additives.