The Controllable Synthesis And Electrochemical Performances Study Of Pseudocapacitive Anode Materials For Sodium Ion Battery

Sodium ion batteries?SIBs?are considered as a promising alternatives to lithium ion batteries?LIBs?due to their high energy density and abundant resources.The development of high-performance anode materials is a key element in the commercial production of SIBs.Pseudocapacitive electrode materials have the advantages of high power density and long cycle life.Developing pseudocapacitive energy storage mechanism is an effective method to improve the electrochemical performance of traditional electrode.Hence,this thesis focused on designing electron/ion fast transmission channels,constructing nano-size electrode materials,and heteroatom doping methods to controllable synthesis high-performace pseudocapacitive materials as SIBs anode.The research work includes the following parts:1.Using Zn?NO₃?₂ and glucose as raw material,three-dimensional porous nitrogen-doped carbon nanosheet material is prepared via solution combustion and acid etching method.The nanostructure of the carbon cross-linked network greatly improves the specific surface area of electrode materials,which provides the convenient channel for the electrons and ions transmission,and increases the active site of the pseudocapacitive sodium storage.The obtained material shows a reversible specific capacity of 201.2 m Ah g^-1 at 1 A g^-1 after 2000 cycles with 88.9%capacity retention rate.Even at high rate(10 A g^-1),the prepared sample can delivers high reversible capacity of 105 m Ah g^-1.2.A facile scalable approach is proposed to prepare nanostructured Fe S₂embedded in N-doped carbon nanosheet composite?Fe S₂/CNS?via combined Zn O template with Fe Cl₃ solution impregnation process and solid state sulfuration method.The nanoscale particle size can shorten the ion-diffusion paths during sodiation/desodiation process,which provides a large number of active site for the pseudocapacitive sodium storage.As a result,the obtained composite exhibits high specific capacity of 577 m Ah g^-1 after 350 cycles at 1 A g^-1,and the capacity retention rate is as high as 77.2%.3.Using nano-aluminum powder as a template,a high-temperature gas–solid element doping method combined with the hydrolysis reaction of titanyl sulfate solution has been proposed to prepare nitrogen-sulfur co-doped Ti O₂ as SIBs anode.Nitrogen-sulfur element doping in nanostructure electrode material can regulate the dynamic process of local sodium ion diffusion to enhance non-phase change intercalation/deintercalation of sodium ion on near-suface,and thus improve pseudocapacitive contribution of electrode material.The obtained material delivers a reversible specific capacity of 153.9 m Ah g^-1 at 10 C after 2000 cycles.In summary,this thesis provides new insights into the research of high-performance pseudocapacitive SIBs anode materials.