| Sodium ion batteries have great application prospects in large-scale energy storage systems,and hard carbon has become one of the most widely studied negative electrode materials for sodium ion batteries in recent years because of its high specific capacity and good cycle stability.However,hard carbon materials still have problems such as low first coulombic efficiency,complex structure difficult to accurately control,and poor rate performance,which affect their practical progress.Phenolic resin is a commonly used hard carbon precursor because of its high residual carbon rate and stable structure.In this paper,phenolic resin is used as the raw material,and cross-linked with sucrose,lignin,and gelatin to form a heterogeneous structure.The effect of different ratios of phenolic resin and sucrose on the morphology and structure of hard carbon was studied,the interlayer spacing and disorder of hard carbon materials were adjusted by adjusting the ratio,and the carbonization temperature was optimized.Based on the composite reaction of phenolic resin and lignin in H2SO4 solution,hard carbon anode materials with large layer spacing and low specific surface were obtained.N/P co-doped phenolic resin/gelatin-based hybrid structure hard carbon was obtained by in-situ doping of phenolic resin and gelatin with H3PO4 activation.(1)Preparation and electrochemical performance of phenolic resin/sucrose-based hybrid structure hard carbon.Phenolic resin was dissolved in anhydrous ethanol and sucrose was dissolved in deionized water.After the two solutions were mixed,they were subjected to solvothermal reaction at 180℃,and the cross-linking reaction occurred during the reaction process.Finally,phenolic resin/sucrose based hard carbon microspheres were obtained by carbonization at high temperature.The micro structure of the hard carbon can be controlled,and the best sample PF-S-55-1200 is obtained,with an interlayer spacing of 3.98 A.The first coulombic efficiency and the first charge specific capacity are 86.4%and 323 mAh g-1(at 30 mA g-1),respectively.After 100 charge and discharge cycles,the capacity is still 316.71 mAh g-1.The pyrolysis temperature of the precursor of phenolic resin/sucrose based hybrid structure hard carbon was optimized.This work provides a new idea for practical application of cathode materials for sodium ion batteries.(2)Preparation and sodium storage properties of phenolic resin/lignin-based hybrid structure hard carbon.Using phenolic resin and lignin-rich functional groups,the reaction between them occurs in boiling solution of high concentration H2SO4.After different high-temperature pyrolysis treatments,hard carbon materials with different microstructures are obtained.The FTIR,TG,and XRD characterization tests show that the two have a chemical reaction,and the interlayer spacing of the(002)crystal plane increases to 3.82 (?).The sodium storage performance of phenolic resin/lignin-based hybrid structure hard carbon has been significantly improved.The reversible capacity under 30 mA g-1 is 308.9 mAh g-1,the first coulombic efficiency is 83.42%,and after 150 cycles,the capacity retention rate is 88.5%.The qualitative structure can significantly improve the sodium storage performance of the material.(3)N/P co-doped phenolic resin/gelatin-based hybrid structure hard carbon and performance research.Gelatin is the nitrogen source,the cross-linked body of gelatin and phenolic resin is the carbon source,and H3PO4 is the phosphorus source.Nitrogen and phosphorus was synthesized by high temperature pyrolysis were doped with phenolic resin/gelatin hard charcoal base hybrid structure it is found that the electrochemical performance of the doped sample is obviously better than that of the undoped PF-G-1200,and the performance reaches the best when C:P=1:7.5%,The reversible capacity at 30 mA g-1 is 316.8 mAh g-1,and the capacity decay is only 3%after 80 cycles,showing the influence of heteroatom doping on the electrochemical performance of the material. |
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