Preparation And Sodium Storage Performance Of Wood-Derived 3D Carbon Self-supporting Anode Materials

In the context of the current vigorous development of advanced energy storage technologies and devices,carbon-based materials derived from biomass materials are expected to contribute to the industrialization of sodium ion batteries(SIBs)due to their abundant resources,low embedded sodium platform,easy regulation and good stability.However,there are still technical challenges for the preparation of hard carbon with high initial coulombic efficiency,excellent multiplicative performance and good cycling stability.Therefore,the construction of high-performance SIBs hard carbonbased anode materials needs to be further exploration and research.Wood is the most productive renewable biomass resource in nature,which has the advantages of longitudinal grain through straight three-dimensional pore structure,low curvature,good mechanical strength and easy processing,and its structure is hierarchically porous,so its derived carbon becomes one of the most promising and cost-effective SIBs electrode precursor materials.In this study,six biomasses from three types of plants,namely broadleaf,coniferous and herbaceous,were selected as precursors based on a multi-level pore dimensional design strategy to maintain their natural biofine graded morphological structure and morphology.The sodium storage performance of different types of wood-derived 3D carbon self-supported anode materials was first explored by a one-step high-temperature pyrolysis followed by a combination of two modifications,namely heteroatom doping and metal loading,in the expectation of obtaining functional SIBs anode materials with excellent functionality using plant legacy structures.The main research contents and results of the paper are stated as follows:(1)Six wood/bamboo blocks are selected as wood-derived 3D carbon selfsupported anode material precursors,and the biomass-derived 3D carbon selfsupporting materials are prepared by one-step high-temperature carbonization after simple pretreatment with H2SO4.The results of SEM and Image Pro show that all six carbon materials retain the original morphology of the precursors with increased pore patency,and results of TEM and XRD indicate that all six materials have an amorphous structure with layer spacing of more than 0.380 nm.At a current density of 30 mA g-1,the reversible specific capacities of the six materials are distributed in the range of 305.9-354.2 mAh g-1,all with an initial coulomb efficiency of over 70%.The analysis by constant current intermittent titration technique(GITT)combine with electrochemical impedance spectroscopy(EIS)confirmed that all six materials have excellent ion mobility rates and verified stable multiplicity performance.Based on the electrochemical performance results,among the six biomass-derived 3D carbon selfsupported anodes selected,basswood(Bass-SHC)has the best reversible specific capacity(354.2 mAh g-1),ICE(92.4%)and cycling stability(92%capacity retention after 500 weeks of cycling).(2)The sulfur-doped basswood-derived 3D carbon self-supported anode(S-SHC)is constructed by using sulfur powder as the sulfur source.The result of XPS shows the successful doping of sulfur atoms in the Bass-SHC carbon layer,and results of TEM and XRD indicate that the sulfur doping process expands the layer spacing of BassSHC(0.388 nm to 0.406 nm).The S-SHC carbon source was prepared at three pyrolysis temperatures of 1100℃,1300℃ and 1500℃.The electrochemical performance of SSHC showed that the best 3D-derived carbon is obtained at 1300℃ for basswood pyrolysis:the first discharge specific capacity is up to 529.7 mAh g-1,and at a current density of 1 A g-1,a reversible specific capacity of～250 mAh g-1 is still achieved with over 4000 cycles.(3)A composite self-supporting material(Bi/SHC)was obtained by combining hydrothermal and high temperature reduction methods to load nano-Bi on lindenderived 3D carbon.The results of SEM,TG and XRD show that nano-Bi is successfully loaded on Bass-SHC and the loading amount of nano-Bi varied.The electrochemical performance of Bi/SHC with different bismuth loadings was found:Bi/SHC-2 with 0.466 g bismuth oxide addition has the best electrochemical performance,and the first discharge specific capacity of the material reaches 506.6 mAh g-1 at a current density of 30 mA g-1,and the first coulomb efficiency is～75.7%;the specific capacity also returns to the original level when the multiplier performance returns to the current density of 50 mA g-1;the material can be stably cycled for more than 3000 weeks with a coulomb efficiency of>99%and has good cycling stability.(4)A comprehensive comparison of the electrochemical performance of BassSHC,S-SHC-1300,and Bi/SHC-2,which are preferentially selected in the three sections,is performed.Bass-SHC and S-SHC-1300 have similar charge-discharge and cycling characteristics curves,indicating that they have similar sodium storage behavior.S-SHC-1300 has the best multiplicative performance,maintaining a specific capacity of 380 mhA g-1 when the current density returns to 50 mA g-1.