Paper-based composite separator for high-rate lithium-ion batteries application by highly-connected pore structure and surface coating.

Accelerating the charging speed of lithium-ion batteries (LIBs) is of great importance to boost their applications. Fast Li ion flux during battery working has possessed great challenge on the separator. In order to design highly-connected pore structure for high-rate LIBs application, in this work, paper-based composite separator was prepared by blending bagasse pulp with AlO nanoparticles followed by reverse-coating of polyvinylidene fluoride-co-hexafluoropropylene (PVDF-HFP) for particle adhesion. In particular, multi-range X-ray nano-computed tomography (CT) results showed that each pore of the composite separator was surrounded by an average of 8 throats with a pore-to-throat ratio of 2.32. This indicated that the pore structure of the separator was highly connected, which would be beneficial to the transportation of fast lithium-ion flux. In addition, the AlO nanoparticle coating on the paper due to its over dosage prompted homogeneous Li ion deposition. Accordingly, the assembled LIB displayed good fast-charging behavior with initial discharge capacity of 101 mAh g at 10 C and capacity retention of 88 % after 2000 cycles. The design strategy would offer a novel idea to the development of separators for fast-charge LIB application.