Sustainable Lignin-Based 3D Porous Carbon Nanofibers As a Na-Ion Battery Anode

Abstract

Rechargeable lithium-ion batteries (LIBs) have been increasingly popular in recent years in response to the growing need for large-scale energy storage applications and systems. However, due to the scarcity of lithium resources and their unequal distribution in the earth's crust, the present energy crisis has encouraged research into producing greener and more sustainable alternatives. Due to the relatively high abundance of sodium compared to lithium, sodium-ion batteries (SIBs) raise hope as an alternative and more sustainable chemistry.[1] Unfortunately, it is typically found that anode materials for LIBs are not suited for SIBs. Graphite, which is frequently used as an anode material in commercial LIBs, is incapable of achieving efficient Na+ insertion/extraction due to a lack of interlayer spacing (Na+ has a radius 39% bigger than Li+) and high energy involved in the formation of Na-C bonds..[2] So, to develop mechanically flexible electrode materials that combine high electrochemical performance with low-cost is still a challenge for its applications in a world subjected to severe shortage of resources and various environmental issues. The problem can be solved by selecting "green" and economically viable precursors and synthesis procedures. Carbon nanofibers derived from renewable biomass materials exhibit great potential as electrode materials with obvious cost and environmental benefits. Lignin, a heterogeneous and amorphous polymer found in many plants, and it is estimated that annual natural lignin production is 5-36×108 tons, of which more than 70 million tons are commercialized mainly from the paper industry as a by-product, is a possible choice as the precursor for carbon nanofibers due to its low cost and bio-renewable nature.In this work, mechanically flexible and 3D interconnected lignin/polylactic acid (PLA) carbon nanofibers with different amounts of lignin were prepared by electrospinning, then stabilized and carbonized. The obtained carbon nanofibers were characterized by scanning electron microscopy and transmission electron microscopy to investigate their morphology. To determine the carbon yield thermogravimetric analysis has been performed. Surface area, pore radius and volume values were obtained by performing BET analysis from N2 sorption isotherms. The obtained carbon nanofibers were tested as anode materiasl in 1 mol/L NaCF3SO3 in diethylene glycol dimethyl ether (DEGDME) electrolyte. Results show that lignin derived carbon nanofibers deliver a high reversible capacity of 330 mAhg-1 at the current density of 100 mAg-1 in the first cycle. Additionally, these carbon nanofibers showed excellent cycling and high-rate performance and maintained a capacity of up to 200 mAhg-1 for over 200 cycles. It is therefore, demonstrated that lignin derived carbon nanofibers prepared under appropriate conditions are promising anode material candidates for sodium-ion batteries.