As one of the strongest and stiffest natural biopolymers, cellulose nanocrystals (CNCs) have been successfully used as efficiently reinforcing nanofillers for improving mechanical properties of various electrospun polymer matrices. One of the most important applications of reinforced electrospun membranes is for batteries such as lithium ion batteries (LIBs), because porous structure is an essential requirement in most batteries. Particularly, a highly porous separator is required to have high permeability and conductivity for ions in batteries.  Currently, most widely used separators in LIBs are fabricated from polyolefins. These polyolefin separators have well-tailored physical and electrochemical properties in terms of practical application. However, their poor thermal stability, low porosity, and insufficient electrolyte wettability often raise serious questions about ionic transport (affecting final cell performance) and electrical isolation (related to cell safety) between electrodes.This work is to fabricate electrospun nanocomposite membranes based on CNCs and polyacrylonitrile (PAN) for separators of LIBs. In addition to reinforce electrospun membranes, CNCs was used to improve the wettability of membranes with electrolyte. While, PAN was chose to overcome the shortcoming of polyolefin separators in thermal stability. Morphologies, porousness, wettability, and thermal and mechanical properties as well as basic electro-chemical properties of electrospun PAN/CNC membranes were characterized. Morphological investigation indicated that electrospun PAN/CNC fibers of approximately 450 nm in diameter comprised the 3D porous nano-composite membranes with porosity greater than 70%. The addition of CNCs improved both the thermal stability and mechanical properties of PAN/CNC nanocomposite membranes. PAN/CNC membranes at the 5 wt % of CNC contents have good tensile strength (more than 20 MPa). More importantly, compared with commercial polyethylene (PE) membranes, PAN/CNC membranes showed higher air permeability and ion conductivity and superior thermal stability. This study preliminarily demonstrates that porous PAN/CNC nano-composite membranes are a potential candidate as separator in LIBs.

Incorporation of cellulose nanocrystals in electrospun polymer membranes for the separators of lithium ion batteries

247th National Meeting (2014)

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