High‐Performance, Flame‐Retardant, Binder‐Free Li‐Hectorite‐Polybenzimidazole Fiber Separator for Li‐Ion Batteries
Sagar A. Joshi, Sivaraj Pazhaniswamy, Christian Plank, Michael A. Danzer, Haoqing Hou, Jun Young Cheong, Josef Breu, Seema Agarwal
Abstract
Abstract Li‐Hectorite (Li‐Hec) clays have inherent 2D diffusion slits offering high lithium (Li + ) ion conductivity. Such Li‐Hec clays spontaneously delaminate into flexible nanosheets, allowing them to be coated on high‐temperature stable polybenzimidazole (PBI) nanofibers laid randomly onto each other in the form of non‐woven membranes. Here such Li‐Hec coated PBI nonwovens are shown to be excellent Li‐ion battery separators. An effective strategy based on electrospinning PBI followed by a filtration‐through coating of delaminated Li‐Hec nanosheets of appropriate diameter is applied to prepare the separators without the use of any binder. The composite separator shows excellent properties, such as superior wettability (solvent uptake 413%), thermostability (>500 °C), superior flame resistance, and interfacial compatibility. Additionally, the presented separator shows excellent ion conductivity, Li‐ion transference number, cycling stability, and a rate performance that outperforms the common commercial separators. In summary, this work allows for a better balance between safety, high performance, and separator functionality.