The Preparation,Modification And Electrochemical Performance Of Biomass Carbon For Sodium Ion Batteries Anode

Lithium ion batteries?LIBs?are currently the most promising electrical energy storage technologies due to their high energy density and cyclabilty.Considering the large-scale applications of LIB in electrical vehicles and power grids,however,an unbalanced geographical distribution of lithium resource and high cost will be a great concern.Sodium ion batteries?SIBs?are made from rich Na-containing resource and low-cost,is expected to be the next generation of energy storage devices.Hard carbon is a dominate candidate as anode material for SIBs due to relative high reversible capacity and low operative potential.Biomass is easy to carbonization and has the advantage of wide distribution,easy collection,and low cost,which makes it an ideal carbon source for electrical energy storage.In this paper,corn stalks?corn straw rinds and inner pitches?and wheat stalks were selected as carbon sources to synthesize hard carbon materials by high temperature carbonization toward SIBs anode applications.The effects of biomass components,synthesis condition and microstructure to sodium ion storage performance of as-synthesized carbon materials were carefully exmined by electrochemical measurements combined with physical characterizations.The specific research results are as follows:?1?Sodium ion has larger radius compared to lithium ion,so the d-spacing of carbon layer needs to be expanded to allow sodium ion to be de/intercalated.In terms of this strategy,a tailored high temperature carbonization and chemical expansion method was performed to synthesize carbon materials.The morphology and microstructure of as-synthesized carbon material was examined by SEM,HRTEM,XRD,Raman and BET.The results showed that the carbon materials retained the natural honeycomb cross-sectional shape and the longitudinal section of the hollow tubular array structure with rich macro-porous and micro-pores,which accelerated the diffusion of sodium ions and electrolyte.All obtained hard carbon materials exhibited large d-spacing,which was larger than 0.335 nm of graphite,Electrochemical tests indicated that carbonization by higher temperature?1200 °C compared to 900 °C?made sodium ion storage performance enchanced,including low irreversible capacity loss,high cycle stability capacity and rate performance.Corn rind derived carbon?CRCS-1200?material displayed the best sodium ion storage performance among the carbon sources,which exhibited a stable reversible capacity of 231 mAh g-1 at 0.25 C?1C = 200 mA g-1?,a stable reversible capacity of 144 mAh g-1 at 1 C after 200 cycles,and a stable reversible capacity of 46 mAh g-1 after 2000 cycles at a rate of 15 C.?2?By using corn straw rinds as carbon source and ethylenediamine as nitrogen source,nitrogen-doped carbon materials?HCRN?were prepared by hydrothermal pre-carbonization treatment,combined with high temperature carbonization and chemical expansion treatment.The morphologies and microstructures of the HCRN were characterized by SEM,TEM,XRD,Raman and XPS.The results show that the nitrogen doping content is 7.4 %.Morphological studies show that HCRN are mainly micro-carbon balls and a part of carbon sheets,which in favor of diffusion of sodium ions and electrolytes.The electrochemical test showed that the HCRN exhibited a stable reversible capacity of 269 mAh g-1 at 0.25 C after 200 cycles,a stable reversible capacity of 217 mAh g-1 at 5 C,followed by a stable reversible capacity of 108 mAh g-1 after 3000 cycles at a rate of 25 C.In addition,the HCRN showed excellent rate performance.The above electrochemical properties showed that the sodium storage properties of the carbon after nitrogen-doped were significantly improved.?3?On the basis of the successful synthesis of nitrogen doped carbon,N,P dual-doped carbon materials was synthesized by using the cheap ammonium dihydrogen phosphate as nitrogen and phosphorus source via one-step hydrothermal method aimed to enhance the ion and electron transfer efficiency of carbon-based materials?CRNP?and further improve the electrochemical performance and capacity.The morphologies and microstructures of the CRNP were characterized by SEM,TEM,XRD,BET and XPS.Morphological studies showed that the CRNP were composed of carbon sheets.Electrochemical tests showed that the CRNP exhibited a stable reversible capacity of 276 mAh g-1 after 100 cycles at 0.25 C followed by a stable reversible capacity of 201 mAh g-1 after 200 cycles at 1 C.In addition,the CRNP exhibited better rate performance and showed a discharge specific capacity of 128 mAh g-1 after 2000 cycles at 5 C.?4?Using CRNP as the anode and C@NaCrO₂ as the cathode,the full sodium ion battery was assembled and its comprehensive performance was evaluaed.The electrochemical tests showed a stable energy capacity of 64.2 mAh g-1 at a current density of 50 mA g-1 and delivered an energy density of 119.84 W h kg-1.This indicated that the CRNP material has potential application in the full sodium ion battery.