High-performance thermally stable lithium metal batteries using bacterial cellulose/poly(p-phenylene benzobisoxazole)...

The thermal shrinkage and material deterioration of commercial polyolefin separators at high temperatures remain substantial barriers to safe lithium metal battery operation. In this work, bacterial cellulose (BC) nanofibers were employed as a matrix, with poly(p-phenylene benzobisoxazole) (PBO) nanofibers (PNFs) prepared via a reported protonation strategy. BC/PNF (BP) nanocomposite separators were fabricated via vacuum filtration. By incorporating 10 wt% PNFs, the BP10 separator retained an intact nanofibrous network and full dimensional stability after thermal treatment at 300 °C for 0.5 h, outperforming commercial PP in structural integrity. BP10 exhibited an ionic conductivity of 0.68 mS·cm^-1 and a lithium-ion transference number of 0.37, both exceeding those of PP. The Li/LiFePO₄ cells assembled with BP10 achieved 122.6 mAh·g^-1 after 200 cycles at 1C, and Li/Li symmetric cells sustained stable cycling for over 1000 h at 1.0 mA cm^-2; elevated-temperature cycling at 55 °C likewise outperformed PP. TG-FTIR analysis showed that PNFs shifted the thermal decomposition pathways of the nanocomposite separator, suppressing small-molecule volatile release such as CO and reducing total volatile products by ∼50%. The findings demonstrated a simple, fast and effective strategy for constructing nanocomposite separators from renewable BC and thermally robust PNFs for high-performance lithium metal battery separators with enhanced ionic transport and thermal stability.