Synthesis And Sodium Storage Performance Of Calcium Terephthalate And Polydopamine Modified Materials

As the remarkable development of the battery industry,electrochemical energy storage systems have also made great progress.At present,lithium-ion batteries?LIBs?with high energy density and large output power are considered to be the most promising equipment of electrochemical energy storage,which are extensively used in the portable-electronic and electric-vehicle markets.However,with the application of LIBs in the scale energy storage market,the cost of LIBs will gradually increase,due to the limited reserves of lithium.Hence,the exploitation of low-cost sodium-ion batteries?SIBs?is expected to be widely applied in the field of scale energy storage,becaues of the rich resources and worldwide distribution of sodium.Electrode materials such as transition metal oxides and graphite are frequently used as electrodes for SIBs,but their theoretical specific capacity is generally low.Therefore,in recent years,organic electrode materials with diverse structures,high theoretical capacity and low price,have attracted more and more attention and researches.In this paper,we mainly use calcium terephthalate and polydopamine as research objects,to study and analyze them as electrode materials of SIBs through physical characterization and electrochemical performance testing.?1?The study of sodium storage performance for calcium terephthalate coated with polydopamine.In this work,a polydopamine?PDA?coating layer was formed by self-polymerization on the calcium terephthalate?CaTP?surface,to increase the electronic conductivity of CaTP.As anodes of SIBs,the specific capacity and rate performance of CaTP advanced obviously after the surface modification of PDA.Particularly,when the mass ratio of dopamine to CaTP is 20%,the reversible capacity reaches 254 mA h g^-1 at the current density of 25 mA g^-1,while the pure CaTP as electrode has only 164.5 mA h g^-1 under the same condition.?2?The study of electrochemical properties for two-dimensional calcium terephthalate flakes.In this work,discontented reaction kinetics of calcium terephthalate?CaTP?were improved by optimizing the morphology and structure.The two-dimensional?2D?-flakes CaTP was synthesized via hydrothermal method with ethanol solvent exfoliated.When used as anodes for SIBs,compared to the three-dimensional?3D?layered CaTP lumps,2D flakes can display the batter sodium storage properties due to shortening the migration paths of Na⁺ions,attaining the rate capacity of 231 mA h g^-1 at 1000 mA g^-1.?3?The study of sodium storage properties for iron-based Prussian blue?NFF?with polydopamine coating.In this work,the electrochemical properties for NFF were improved by using the structural stability and insolubility of polydopamine?PDA?.As cathodes for SIBs,the NFF with PDA coating displayed a reversible capacity of 93.8 mA h g^-1 at 0.2 A g^-1 after 500 cycles.Besides,the results of first-principle calculations showed that PDA was inclined to couple with Fe²⁺sites in the pure NFF,which effectively promote the diffusion of Na⁺ions to boost the sodium storage property of NFF.