Sustainable Separators for High‐Performance Lithium Ion Batteries Enabled by Chemical Modifications

Abstract

Natural polymer nanofibers are attractive sustainable raw materials to fabricate separators for high-performance lithium ion batteries (LIBs). Unfortunately, complicated pore-forming processes, low ionic conductivity, and relatively low mechanical strength of previously reported natural polymer nanofiber-based separators severely limit their performances and applications. Here, a chemical modification strategy to endow high performance to natural polymer nanofiber-based separators is demonstrated by grafting cyanoethyl groups on the surface of chitin nanofibers. The fabricated cyanoethyl-chitin nanofiber (CCN) separators not only exhibit much higher ionic conductivity but also retain excellent mechanical strength in comparison to unmodified chitin nanofiber separators. Through density function theory calculations, the mechanism of high Li + ion transport in the CCN separator is unraveled as weakening of the binding of Li+ ions over that of PF 6 − ions with chitin, via the cyanoethyl modification. The LiFePO 4 /Li 4 Ti 5 O 12 full cells using CCN separators show much better rate capability and enhanced capacity retention compared to the cell using commercial polypropylene (PP) separators. Beyond this, the CCN separator can work very well even at an elevated temperature of 120 °C in the LiFePO 4 /Li cell. The proposed strategy chemical modification of natural polymer nanofibers will open a new avenue to fabricate sustainable separators for LIBs with superior performance.

A Durable Gel Polymer Electrolyte with Excellent Cycling and Rate Performance for Enhanced Lithium Storage

“…The electrochemical performances were compared with the data reported previously, showing superior comprehensive performance (Table S1). ,,,− …”

Natural wood-derived free-standing films as efficient and stable separators for high-performance lithium ion batteries

“…Recently, some studies revealed that functional materials derived from biomass were very promising for use as electrodes and/or separators for electrochemical energy storage. [20][21][22][23][24] For instance, Yu et al recently reported a chitin nanober membrane (CNM) derived from prawn shell for use as a separator in LIBs. 22 The electrochemical performance of LiFePO 4 /Li half-cells with CNM separators was comparable to that of devices based on a commercial PP separator (Celgard 2325).…”

Polyethylene porous microsphere coated coaxial fiber composite membrane for high safety lithium‐ion battery

“…The reactions release a large amount of heat, making the battery temperature exceed the critical temperature (about 150°C) that the battery can withstand. The increase in temperature will in turn accelerate these chemical reactions 10–13 . Too much heat and combustible gases will be released into the battery in a short time, causing the battery to rupture, ignite and even explode.…”