Preparation Of Silicon-Carbon Materials From Larch Sawdust Via Liquid Phase In Situ Doping Silicon For Supercapacitors

With the depletion of petrochemical resources,more and more researchers have focused their attention on renewable resources.In recent years,China's fast-growing and high-yield forest?hybrid pine?has a wide planting area and a high yield.The cutting and processing process will produce a large amount of waste wood chips,resulting in a waste of wood resources.Using waste wood chips instead of chemical raw materials to prepare new carbon materials and applying them in the field of supercapacitor development could realize the effective transformation and efficient utilization of agricultural and forestry waste resources,which is an important way to solve the issue of resources,energy and environment.By means of liquefaction,wood resources are converted into wood-based liquefaction,and the porous structure of carbon materials is controlled to ordered or hierarchical.The abundant porosity and ordered pore structure can provide the transmission channel and storage space for the charge,and further improve the reversibility and cycle life during charge and discharge.This study not only realize the efficient utilization of sawdust resources,but also has positive significance to environmental protection.In this work,the waste larch sawdust,as raw materials,was converted into wood liquefaction via a simple phenol liquefaction method,furthermore,the silicon sources as the hard template were added by liquid phase in-situ doping technology.What's more,the orderly arrangement and the regulation of the hierarchical porous structure were realized during carbonization process,and broaden on energy storage performance of larch-based carbon materials.The synergistic effect between in-situ doping of different silicon sources and the optimized carbonization conditions for the morphology and pore structure of carbon materials were investigated,the effects of the both on the energy storage characteristics of supercapacitors are revealed,and the co-storage mechanism of double-layer capacitor and pseudo-capacitor in the regulation of supercapacitor energy storage is illustrated.During the liquefaction process,it was found that the larch liquefaction reaction system had obvious phenolization reaction,and the solid sawdust was transformed into small aromatic compounds with a large number of hydroxyl groups and side chains,could increase the functional group reactivity.This provides a favorable doping environment for the effective doping of hard template silicon source and a feasible basis for the preparation of deciduous pine based carbon materials with controllable pore structure.The morphology and pore structure of carbon composites were effectively controlled by SiO₂ doping and carbonization temperature coordination.The Si-C-900shown a main microporous structure and a large number of active sites provided by oxygen-containing functional groups on the surface,which effectively improved its conductivity,multiplier,capacitance and cyclic stability.The specific capacitance value is 260 F/g,energy density is 23.1 Wh/kg,and power density is 640 W/kg at 1.6 A/g current density,meanwhile,after 3000 cycles,the capacitance retention rate was above97%,showing good electrochemical performance.Meanwhile,the effects of filtration treatment for larch liquefaction on the pore structure and electrochemical properties of the material were studied.Filtration treatment increases the complexity of the experimental process,and waste wood sawdust is underutilized,and the electrochemical performance was not improved obviously.Therefore,the Si-Carbon composite with high performance can be prepared by in situ liquid doping method of larch liquefaction without filtration treatment.The regulation effect of in-situ doping of different silicon sources on the ordered pore structure of carbon materials and the influence mechanism of carbonization temperature on the morphology and pore structure of carbon materials were studied.The mechanism of their influence about the energy storage characteristics for supercapacitors is revealed.Different silicon-carbon composites performances were analysis by doped different silicon sources?Tetramethoxysilane,tetraethoxysilane,and tetrapropoxysilane?,the results exhibited TEOS-doped carbon materials had abundantpore structures and large-scale pore size distribution?1-10nm?,and the carbon materials at the carbonization temperature of 900? process the excellent electrochemical performance,and the specific capacitance value was 288 F/g,the energy density was 93.73 Wh/kg,and the power density was 850 W/kg under the current density of 0.2 A/g,as well as good rate performance and cyclic stability?the capacitance remained 97%after 3000 cycles?.