Controlled phase separation of regenerated cellulose with super-engineering thermoplastics into porous membranes with hierarchical morphology as high-performance separators for lithium-ion batteries

Abstract

In this work, a highly porous cellulose/polyarylene ether nitrile (CE/PEN) membrane, bearing hierarchical beads-on-string structures, has been fabricated using regenerated cellulose derived from low-cost waste cigarette butts and PEN via the classical phase conversion method. More specifically, the sequential nucleation of CE and PEN macromolecules from dope solution results in adjustable surface segregation behavior during non-solvent induced phase separation (NIPs), leading to the formation of in-situ assembled rough beads-on-string on the external surfaces and inner pore walls of the membranes. The formation mechanism of a porous membrane with selective component distribution is investigated through thermodynamic and molecular dynamics simulations of phase separation. The resulting composite separator not only exhibits optimal physical properties, including improved mechanical strength, prominent liquid electrolyte wettability (electrolyte contact angle of 0°) and high-thermal resistance, but also demonstrates high ionic conductivity and lower interface resistance. Consequently, the CE/PEN separator enables stable lithium metal anode interface and effectively suppresses the growth of lithium dendrites. More significantly, the resulted lithium metal battery displays remarkable enhancement in capacity, cycling stability (98.6 % for 200 cycles), and rate property (101mAh/g at 10C rate).