Preparations And Potassium Storage Properties Of Biomass Carbon Derived From Corn Silk And Willow Leaves

With the wide applications of lithium-ion batteries in the fields of electric vehicles and various smart electronic devices,the uneven distribution of lithium metal and the high price have become increasingly serious.Exploring new energy storage devices to alleviate the problems faced by lithium-ion batteries is imperative.Potassium and lithium belong to the same main group and have similar physical and chemical properties.At the same time,potassium metal is rich in the earth,uniformly distributed and low in price,and therefore potassium-ion batteries（PIBs）have gradually attracted attention by researchers and are expected to become one of the next generation of energy storage equipments.Many researches on PIBs are still in their infancy.The choice of electrode materials is the key to improve battery performance.The researches on anode materials for PIBs mainly focus on carbon-based materials,metal alloys,and conversion anodes.Among them,carbon materials,as one of the anode materials of PIBs,exhibit excellent electrochemical performance,which have received great attention from researchers.As one of the important branches of carbon materials,biomass carbon has become a research hotspot of anode materials for PIBs due to its wide distribution,environmental protection,easy processing,and high reversible capacity.In this thesis,different biomass wastes（corn silk,willow leaves）were used as raw materials,and biomass-derived carbon was prepared through different treatment conditions（hydrothermal temperature,carbonization temperature）.The electrochemical performance of the biomass-derived carbon as an anode material for PIBs was studied.The specific research contents are as follows:（1）Using waste corn silk as raw material,hydrothermal and carbonization processes were used to prepare N/O dual-doped corn silk porous biomass-derived carbon with a specific morphology.Multiple groups of corn silk were subjected to hydrothermal treatment at the same temperature and time to obtain precursors,and then the precursors were subjected to carbonization treatment at different temperatures to obtain biomass-derived carbon with different graphitization degrees.The N and O atoms doping into the carbon material after carbonization can increase the lattice spacing of the carbon material,and provide a large number of electrolyte/ion channels and effective active sites for potassium ions during the insertion/extraction process.The corn silk-derived carbon（NOPC-750）used as an anode material for PIBs shows excellent rate performance(a specific capacity of105.8 m Ah g^-1 at a current density of 20 A g^-1)and relatively stable cycling stability with a specific capacity of 155.6 m Ah g^-1 at 1 A g^-1 over 2600 cycles.（2）Using discarded willow leaves as raw materials,after hydrothermal treatment at different times and carbonization treatment at 800℃,a hard carbon material with a special morphology was prepared.Different hydrothermal time plays an important role in the change of the morphology of materials.After 12 hours hydrothermal treatment,the willow leaf-derived carbon（WWLC-12）obtained by the carbonization treatment has a more uniform morphology and a more stable structure.It is used as an anode material for PIBs.At a current density of 0.1 A g^-1,its capacity can be stabilized at 190 m Ah g^-1 over 100 cycles.At a current density of 1 A g^-1,the capacity can still be stabilized at 103.7 m Ah g^-1 over 1800 cycles.Compared with other electrode materials,the WWLC-12 electrode exhibits excellent electrochemical cycling and rate performance.