Unveiling the effect of homogenization degree on electrochemical performance of TEMPO-mediated oxidized cellulose separators for lithium-ion batteries

Abstract

Separator is an essential component for lithium-ion batteries, subtly providing transporting micro-channels for lithium ions and electric insulation between electrodes. In this paper, bleached eucalyptus cellulose pulp is implanted with TEMPO-mediated oxidization and high-pressure homogenization to attain cellulose pulps with both micro- and nano-sized fibers, where the blending ratio is regulated by homogenization times. Then the cellulose pulp is formed into separators through vacuum filtration after uniformly dispersed. Macro-properties, micro-structures, physical properties and electrochemical performance of the cellulosic separators are characterized and analyzed. And t commercial Celgard 2500 polypropylene separator is also investigated as comparison. The influence of homogenizing degree on comprehensive properties of the separators is investigated. Besides, the relationship between micro-structure and electrochemical performance is detailedly discussed. Results show that higher homogenization degree contributes to more nano-sized fibers and less micro-fibers, resulting in smaller porosity, poorer electrolyte uptake and larger contact angle. The nano-sized fibers are effective in promoting mechanical strength of separators, but are negative to the impedance performance. This study has unveiled the impact of high-pressure homogenization on the performance of separators, providing meaningful instruction for further development of qualified cellulose separators.