Agricultural Wastes for Full-Cell Sodium-Ion Batteries: Engineering Biomass Components to Maximize the Performance and Economic Prospects

Abstract

Lignin is one of the most abundant biopolymers in nature. Although lignin-derived hard carbon (L-HC) has potential to be used as a sodium-ion battery (SIB) anode but is limited by its poor electrochemical performance. In nature, lignin normally coexists with cellulose and hemicellulose in agricultural biomass, and studies have applied different agricultural biomasses to make SIB anodes; however, the underlying mechanism, especially the functionality of each component, is still unclear. In this study, we aim to combine lignin with cellulose and/or hemicellulose to produce hard carbons with outstanding electrochemical performance and low cost, and more importantly, unveil the underlying mechanisms. We found that the poor electrochemical performance of L-HC was mainly due to its large surface area with high amount of oxygen-containing functional groups and its unique physical structure that inhibit effective Na diffusion. Combining lignin with either cellulose or hemicellulose led to significantly improved electrochemical performance of the resulting hard carbon, with cellulose mainly contributing to the increase of capacity and hemicellulose mainly contributing to the stability of capacity during cycling and at high current density. Based on the comprehensive consideration of both electrochemical performance (half and full cells) and economic perspectives, lignin combined with cellulose showed great potential. Our study shed light on the contributions of each major biomass component on physical and electrochemical properties of resulting hard carbon and designed a unique way to improve L-HC.

Hydrothermally Assisted Conversion of Switchgrass into Hard Carbon as Anode Materials for Sodium-Ion Batteries

“…This finding agrees well with those of previous studies. 6,19 Low ICE has been considered as the main bottleneck impeding the commercial application of hard carbon. This deficiency is largely caused by SEI formation, which results in an irreversible capacity loss during the first cycle.…”

“…With more hemicellulose and impurities removed, the morphology of the precursors became noticeably rougher (Figure S1). Previous research suggests that hemicellulose and other impurities (e.g., ash, lipid) in raw biomass adversely affect the electrochemical performance of derived hard carbon anodes, including a low specific capacity, reduced cycling stability, increased irreversible capacity loss, and a poor rate capability. , Conversely, cellulose content is positively correlated with the anode’s specific capacity and cycling stability. , Therefore, applying hydrothermal pretreatment to switchgrass to remove hemicellulose and other impurities can potentially enhance its viability for the synthesis of high-quality hard carbon production.…”

“…Previous studies employed an activation process to enhance the properties of the synthesized hard carbon, aiming to increase the initial reversible capacity and improve the cycle stability. − However, the persistently low ICE of hard-carbon anodes remains a main bottleneck. , In addition, this activation process often involves the use of strong acids or bases, such as HCl and KOH, which not only raises environmental concerns but also escalates material and processing expenses. , Hydrothermal pretreatment is an environmentally friendly process to convert various biomass into value-added biochemicals . The process operates at 150–260 °C under high pressures, where water medium is pressurized to sub- and supercritical water, functioning as a solvent, reactant, and catalyst .…”

Closed pore structure engineering from ultra-micropores with the assistance of polypropylene for boosted sodium ion storage

“…5g. The corresponding Na + diffusion coefficients were calculated according to Fick's second law and simplified as follows: 53,54 In this equation, τ , n m , V m and S are the pulse time, moles of active material, the molar volume, and the effective contact area, respectively. In addition, Δ E s is the voltage change due to pulses, and Δ E t is the voltage change for the charge/discharge process, as shown in Fig.…”

“…5g. The corresponding Na + diffusion coefficients were calculated according to Fick's second law and simplied as follows: 53,54…”