| Rechargeable aqueous metal ions batteries(RAMBs),which have the advantages of low cost,high safety,environmentally friendliness and high ionic mobility,are a new kind of green energy storage device and have potential to be applied in the large scale energy storage in the future.In recent years,RAMBs have attracted more and more attention and made certain progress,yet low voltage output,low energy density and limited cycle life hinder their practical applications.So the electrode materials with excellent electrochemical properties become an important factor to design new-type RAMBs.In this thesis,we develop a high voltage and energy density rechargeable aqueous sodium ions battery(RASB)based on a new type aqueous electrolyte and rhombohedral zinc hexacyanoferrate as cathode materials,and its working mechanism are investigated detailedly.In addition,a rechargeable aqueous zinc ions battery(RAZB)also is assembled based on modification of vanadium phosphate as cathode materials.The detailed works are listed as following:1.A new aqueous electrolyte of high performance is created.A ternary Na-H2O-PEG electrolyte is prepared based on sodium perchlorate(NaClO4)with high solubility,polyethylene glycol(PEG)as additive and the molar ratio of NaClO4 to H2O is 1/6.The Na-H2O-PEG electrolyte with high ionic conductivity(2.44 × 10-2 S cm-1)and low activation energy(0.203 eV),can be widely used in broad temperature.The electrochemical properties of ZnHCF in Na-H2O-PEG electrolyte and Na2SO4 electrolyte are explored.It is illustrated that although a same initial capacity(66 mAh g-1)is displayed,ZnHCF shows a higher working voltage(0.97 V vs.Ag/AgCl)and cyclic stability in the Na-H2O-PEG electrolyte.2.A high voltage and rate capability RASB is well-established.First,ZnHCF with regular morphology is synthesized by an improved co-precipitation method,and the effect of different factors on the morphology of ZnHCF particles is discussed.Second,one RASB consisted of ZnHCF as cathode materials,carbon-coated NaTi2(PO4)as anode materials and Na-H2O-PEG as electrolyte,is assembled with an average operating voltage of 1.6 V,which is higher than voltage(<1.5 V)of most RAMBs.Finally,the working mechanism of the battery is studied by Ex situ XRD,XPS and other detection techniques.A reversible phase transformation between rhombohedral Zn3[Fe(CN)6]2 and rhombohedral Na2Zn3[Fe(CN)6]2 that are accompanied by the insertion/extraction of sodium ion in zinc hexacyanoferrate is unveiled and some interphase may occur.3.Utilizing carbon-coated lithium vanadium phosphate as cathode,zinc as anode and Zn-H2O-PEG as electrolyte,the new zinc-ion battery is manufactured and the electrochemical properties of the battery are studied in detail.The battery can deliver a high capacities of 140.9 mAh g-1 and more than 85%of the initial discharge capacity is retained after 500 cycles at 5 C rate,which implies that the battery shows excellent electrochemical properties. |
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