Synthesis And Performance Of Biomass Derived Hard Carbon Anode Material For Sodium-ion Battery

Hard carbon is considered as one of the most promising anode materials for sodium-ion batteries?SIBs?.Now it is imperative to develop a proper precursor and preparation method to obtain hard carbon anode particles with high initial Coulombic efficiency and good cycling performance.In this paper,high performance hard carbon anodes for SIBs was successfully prepared,by selecting abundant and low-cost pinecones as biomass precursor and optimizing carbonization temperature,impurity content,particle size and other preparation parameters of PHC.The contents and results of this paper are summarized as follows:?1?In this paper,PHC was firstly prepared by a two-step carbonization method using pinecone as carbon source.The microstructure of PHC was studied by X-ray diffraction?XRD?,Raman spectroscopy,scanning electron microscope?SEM?,high-resolution transmission electron microscopy?HRTEM?as well as nitrogen adsorption-desorption isotherms methods.The electrochemical properties of PHC were studied by galvanostatic discharge and charge,cyclic voltammetry?CV?,electrochemical impedance spectra?EIS?tests.The performance of PHC is highly dependent on the carbonization temperature.Increasing carbonization temperature of pinecone precursor can reduce surface area and thus improve the initial Coulombic efficiency.Varying carbonization temperature can also adjust the slope and plateau capacity of PHC,and then regulate the energy density and power characteristics of PHC in battery operation.The PHC carbonized at 1400?in this work shows the best electrochemical performance delivering a reversible capacity of 370 mAh g^-1at the current density of 30 mA g^-11 and 334 mAh g^-11 after 120 cycles,the capacity retention is 92.7%,with a high initial Coulombic efficiency of 85.4%.?2?The influences of impurities,electrolytes,binders and conductive carbon black on the hard carbon negative electrode material of sodium ion batteries was studied.Studies determined that the sodium storage mechanism of PHC is adsorption-intercalation.The washed PHC1400 exhibits a better cycling performance than unwashed PHC1400.The capacity of washed and unwashed PHC1400 is 328mAh g^-11 and 299 m Ah g^-11 after 100 cycles,corresponding to capacity retention of91.1%and 83.3%.PVDF,CMC and sodium alginate were used as binders for PHC materials.The results showed that CMC binder exhibits the best performance.With the electrolyte NaCl O₄-EC:DEC,the SIBs shows the best capacity and cycle performance.PHC1400 has good electrical conductivity and still exhibits excellent electrochemical performance without the addition of conductive carbon black.?3?The cathode materials of NaCrO₂,Na_2/3Ni_1/3-xMg_xMn_2/3O₂ for SIBs was synthesized by using the sol-gel combustion method,and the full cell was constructed using PHC1400 as negative electrode.NaCrO₂/PHC1400 full cell shows a reversible capacity of 288.9 m Ah g^-11 and 150 mAh g^-11 after 200 cycles at the current density of30 mA g^-1.Na_2/3Ni_1/3-0.1Mg_0.1Mn_2/3O₂/PHC1400 full cell shows a reversible capacity of 225.6 mAh g^-11 at the current density of 18 mA g^-1.It shows that PHC1400 as sodium ion anode material has a very high application value in a full cell.