Critical-Point-Dried, Porous, and Safer Aramid Nanofiber Separator for High-Performance Durable Lithium-Ion Batteries

Abstract

Ionically conducting, porous separator membranes with submicrometer size pores play an important role in governing the outcome of lithium-ion batteries (LIBs) in terms of life, safety, and effective transport of ions. Though the polyolefin membranes have dominated the commercial segment for the past few decades, to develop next-generation batteries with high-energy density, high capacity, and enhanced safety, there is a need to develop advanced separators with superior thermal stability, electrolyte interfacial capabilities, high melting temperature, and mechanical stability at elevated temperatures. Here, aramid nanofiber separators with enhanced mechanical and thermal stability dried at the critical point are processed and tested for mechanical strength, wettability, electrochemical performance, and thermal safety aspects in LIBs. These separators outperform Celgard polypropylene in all aspects such as delivering a high Young’s modulus of 6.9 ± 1.1 GPa, and ultimate tensile strength of 170 ± 25 MPa. At 40 and 25 °C, stable 200 and 300 cycles with 10% and 11% capacity fade were obtained at 1 C rate, respectively. Multimode calorimetry, specially designed to study thermal safety aspects of LIB coin cells, demonstrates low exothermicity for critical-point-dried aramid nanofiber separators, and post-diagnosis illustrates preservation of structural integrity up to 300 °C, depicting possibilities of developing advanced safer, high-performance LIBs.

Bioinspired Separator with Ion-Selective Nanochannels for Lithium Metal Batteries

“…It is worth noting that the as-prepared EAA75 separator possesses high dimensional stability. For some porous separators fabricated by either a dry or wet process, pore collapse occurs due to capillary forces acting on the pore surface during the drying–rewetting–drying process, which is a drawback for their application and storage. − Impressively, the EAA75 separators retain their opacity due to remaining pores after the drying–rewetting–drying process (Figure h). The preserved porous structure was further confirmed by SEM images (Figure S4).…”

Preparation of low‐density high‐performance porous aramid films using porosity promoter polymers

“…35 As previously pointed out, the objective of this work is to prepare porous poly(m-phenylene isophthalamide) films using these polymers as porosity promoters in an inexpensive and simple way without impairing their performance, establishing relationships between the porosity former and the properties of the films. The obtention of porous highperformance polymers with controlled pore morphology and outstanding properties plays a key role in the development of separators for ion lithium batteries, [36][37][38][39][40] or osmosis membranes. [41][42][43] In addition, due to their properties and low density, they are promising materials for the transport and aerospace industries, especially considering the ongoing global energy crisis and the need for fuel reduction.…”

Recent Development in Novel Lithium-Sulfur Nanofiber Separators: A Review of the Latest Fabrication and Performance Optimizations

“…Aromatic polyamides, frequently called aramids, are often electrospun from Kevlar into nanofibers that boast excellent mechanical and thermal stability [ 68 ]. Many aramid NF (ANF) separators have been designed as alternatives to polyolefin separators in Li-ion batteries [ 20 , 69 , 70 , 71 , 72 ] and only recently in LSBs [ 58 ]. Liu et al [ 73 ] electrospun a poly(m-phenylene isophthalamide) (PMIA) solution to yield a 3D network of 90 nm fibers.…”

“…Nanofiber (NF) separators are highly porous, thermally stable, low cost, and easily modifiable alternatives to polyolefin separators [ 18 , 19 , 20 ]. Because NFs have high porosity and polar functional groups (in some polymer NFs), they also have higher electrolyte affinity and LiPS-adsorbing properties [ 21 ].…”