Preparation And Sodium Storage Performance Of Hierarchical Porous Hard Carbon Based On Sodium Alginate

With the increasing demand for energy storage,research on energy storage material and devices has attracted more and more attention.Due to its rich resources,wide distribution and low price,sodium ion batteries are considered to be a promising component for large-scale electrochemical energy storage devices.Developing low-cost electrode materials is an important step in the commercialization process.The precursor of hard carbon materials has the advantage of wide range of sources,low cost,good structural stability and high specific capacity,which is a hotspot for anode materials.In this paper,sodium alginate extracted from brown algae was used as a precursor.A variety of graded porous hard carbon materials have been prepared by direct carbonization,crosslinking carbonization and transition metal catalysis.In this thesis,the microstructure and electrochemical properties of carbon materials were studied.The effects of cross-linking reaction and transition metal catalysis on the structure and sodium storage properties of hard carbon materials were also investigated.(1)Obtained a hard carbon material by carbonizing sodium alginate.When used as an anode for sodium ion batteries,it exhibited a capacity of98.4 m Ah/g.After 100 cycles,the capacity retention was 87.6%,showing great cycle stability.(2)A cross-linked reaction of sodium alginate and divalent calcium ions was used to prepare a hard carbon material with a hierarchical porous structure.Mesopores with a diameter of about 10 nm were evenly distributed on the carbon matrix.The graphitized carbon layer and interconnected mesopores provided a channel for the rapid transport of sodium ions.When used as an anode for Sodium ion batteries,it exhibited a high specific capacity of 191.36 m Ah /g at a current density of 0.1 A/g,and a high specific capacity of 134.8 m Ah/g at a high current of 1 A/g.(3)Based on the crosslinking reaction of sodium alginate,a variety of hard carbon materials with high degree of graphitization were prepared by transition metal catalysis.The hard carbon material prepared by divalent iron ion catalysis had a capacity of 236 m Ah / g at 0.1 A / g,and the capacity remains 94.5% after 100 cycles;the capacity was 162 m Ah/g at 1 A/g,cycling After 500 cycles,the capacity retention was 96.3%,which shows good cycle performance and rate performance.