Regulating the pore structure of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) oxidized cellulose membranes: impact of drying method and organic solvent processing

Cellulose‐based membrane is a satisfactory candidate for the separator of lithium‐ion batteries due to its renewability, abundant pore structure and outstanding thermal–chemical stability. In this study, 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) oxidized cellulose fiber (TOCF) membranes with different oxidation degrees were prepared. Membranes with high oxidation degree are faced with a pore closure issue, resulting in low porosity. In order to improve the pore structure, the TOCF membranes were dried differently through air drying, vacuum drying and freeze drying. Furthermore, air‐dried membranes were processed by three organic solvents – n‐butyl alcohol, carbon tetrachloride and n‐heptane. The physical properties, pore structure characteristics, mechanical properties and the electrochemical performance of the membranes were measured and characterized. From the results, freeze drying is found to provide the highest porosity and mean pore diameter. Unfortunately, Young’s modulus of the freeze‐dried membranes is the smallest as well. However, membranes processed by n‐butyl alcohol have weak tensile properties. Compared to non‐processed membranes, membranes processed by organic solvents present better pore structure and significantly better electrochemical performance. With all properties considered, TOCF membranes processed by carbon tetrachloride or n‐heptane are qualified for serving as battery separators as they possess improved pore structure, enhanced Young’s modulus, considerable tensile strength and improved electrochemical properties. © 2020 Society of Chemical Industry