Electrochemical Performance Of Prussian Blue Analogues Electrode Materials For Sodium Ion Batterry

Sodium ion battery(SIB)has aroused great attention due to low cost and abundant sodium resources.The chemical/electrochemical properties of SIB are similar to lithium ion batterry.In the past few years,various SIB advanced electrode materials have rapidly recovered and developed.Reasonably designed nanostructures for SIB electrode lead to high reversible capacity,excellent rate capability and long-term cyclability.Prussian blue analogs(PBA)or its modified materials are an important class of electrodes for SIB.However,the low conductivity of PBA,which leads to poor electrochemical kinetics during sodium storage,is still an obstacle.This thesis focuses on the structural design of Prussian blue analogue electrode materials,discusses the structure-activity relationship between structure and performance,and develops high-performance SIB electrode materials.The main research work is divided into the following two aspects:1.Designed and synthesized an iron-based Prussian blue nano frame/carbon nanotubes(CNTs)composite material for SIB cathode.A simple one-step hydrothermal method is used to synthesize a cubic iron-based Prussian blue nano-frame with regular step-etched along the diagonal direction.This step-etched microstructure increased the contact area between electrode and electrolyte and promoted the ion conductivity.By compounding with CNTs to produce a binder-free SIB cathode,the electronic conductivity of the electrode was increased.After applied to SIB,the composite film showed a high specific capacity of 151.8 mAh g-1((0.1 C).Through hard X-ray absorption spectrum data and ex-situ XRD analysis results,the charge-discharge mechanism of the composite cathode is explained.This design will provide an effective guide for the design of SIB cathode materials.2.Using dopamine-coated PBA as a template,vulcanization and carbonization were completed in one step by calcination,therefore a carbon and nitrogen-coated hollow core-shell structured sulfide cubic nanobox Fe0.4Co0.6S2@NC was synthesized.The coated carbon improves the electrical conductivity of PBA.Compared with the uncoated single disulfide,the cubic nanobox had better electrochemical performance when applied to the SIB anode.This coating method can also be used for other phosphide and fluoride anode materials,which has promoted the development of metal organic frame SIB anode materials.