Eco-friendly utilization of sawdust: Ionic liquid-modified biochar for enhanced Li+ storage of TiO2

In China, forestry logging and wood processing produce hundreds of thousands of tons of sawdust every year, which is either discarded or burned. These nonecofriendly practices result in some challenges associated with greenhouse gas emissions. Sawdust-based biochar tailored for anodes of lithium-ion batteries (LIBs) can effectively realize value-added utilization of sawdust. The purpose of the current work is to prepare TiO2/biochar nanocomposites to improve the electrical conductivity and structural stability of the anode. However, poor interfacial interaction between TiO2 and carbon in the TiO2/C composites arising from their heterogeneous nature leads to structural deformation of the composites used as anodes of lithium-ion batteries (LIBs). A strategy of constructing ionic liquid-coupled biochar/TiO2 interfaces is proposed to obtain chemically bonded interfaces between TiO2 and sawdust-derived biochar. In this study, TiO2/C-880 composites are prepared by one-step carbonization of TiO2 nanoparticles (NPs) and sawdust at 880 degrees C previously dissolved in 1-butyl-3-methyl-imidazolium ([Bmim]H2PO4)/dimethyl sulfoxide (DMSO). The morphologies of TiO2/C-880 demonstrate that the TiO2 is encapsulated by porous biochar with intimate interfaces, and the X-ray photoelectron spectroscopy (XPS) results indicate the formation of N-Ti-O/N-O-Ti and Ti-O-P bonds that bridge the two components. TiO2/C-880 electrodes have high reversible specific capacities (404 mAh g(-1) at 0.1 A g(-1)) and desirable long-term cyclic stability (100 mAh g(-1) at 2 A g(-1) throughout 2500 cycles). Moreover, large diffusion coefficients (DLi+) ranging from 5.9 x 10(-11) to 1.2 x 10(-9) cm(2) s(-1) are obtained from galvanostatic intermittent titration (GITT) curves. The N-Ti-O/N-O-Ti and Ti-O-P bonds at the interfaces offer routes for fast Li+/electron transport, which account for the high performance of the TiO2/C-880 electrodes. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

Forestry logging and wood processing in China generate significant amounts of sawdust annually, which can be utilized to produce biochar tailored for lithium-ion battery anodes. Constructing ionic liquid-coupled biochar/TiO2 interfaces enhances the structure and performance of TiO2/C composites, resulting in high reversible specific capacities and long-term cyclic stability of the electrodes. The chemical bonds at the interfaces facilitate fast Li+/electron transport, contributing to the excellent performance of the TiO2/C electrodes.