| The water-based electrolyte in the aqueous metal ion battery replaces the expensive,flammable and toxic organic electrolyte,so it has the advantages of low cost,high power,high safety and environmental friendliness.However,the electrochemical stability window of water（1.23 V）is narrower than that of traditional organic solvents,which greatly limits the operating output voltage of water-based metal ion batteries and thus exhibits low energy density.Based on the concept of organic matter-inorganic salt-water,this thesis has developed two new high-concentration high-pressure-resistant water-based electrolytes,aiming to solve the problems of low operating voltage and low energy density of water-based metal ion batteries.The important results achieved in this paper are as follows:1.We designed a ternary high pressure resistant aqueous lithium ion electrolyte DMAC-Li Cl O4-H2O in a molar ratio of 2.5:1:1 with a voltage window of 3.1 V and ionic conductivity of 2.7 m S cm-1,which use N,N-dimethylacetamide（DMAC）as a co-solvent for water and lithium perchlorate as a solute.Lithium manganate and phosphoric acid oxygen niobium demonstrate capacity of 91 m Ah g-1 and 70 m Ah g-1with DMAC-Li Cl O4-H2O as electrolyte,and can both achieve coulombic efficiency of98%.We developed a new type water-based lithium ion battery by using lithium manganate as a positive electrode,phosphoric acid oxygen niobium as a negative electrode and DMAC-Li Cl O4-H2O as electrolyte.The working voltage of the cell can reach 1.9 V and the energy density is higher than 70 Wh kg-1.The capacity retention ratio is 88%after 1000 cycles.The results of spectroscopy analysis showed that C=O groups in DMAC solvent molecules have strong complexation with lithium ion.The broadening phenomenon of O-H stretching vibration spectrum in water molecule is weakened and the activity of water decreases obviously with the decrease of DMAC solvent content in the electrolyte.The complexation of Li+with DMAC molecules is closer with the increase of Li+concentration,which hinders the reaction between solvent molecules and electrode material.DMAC-Li Cl O4-H2O electrolyte demonstrates superior high-pressure resistance than the ordinary aqueous lithium ion battery.2.Using N,N-dimethylacetamide or polyethylene glycol（PEG）as co-solvents for water and zinc perchlorate as solute to develop aqueous zinc ionic electrolytes DMAC-Zn（Cl O4）2-H2O and PEG-Zn（Cl O4）2-H2O.The ratio of H2O/Zn2+are 6 in the two electrolytes.The electrochemical research results display that zinc negative electrode is stable in the two electrolytes and highly reversible electrochemical deposition/dissolution reactions can be achieved,which demonstrate high coulombic efficiency of 98.9%and 99.7%respectively.Lithium vanadium phosphate positive material exhibits a capacity of 30-40 m Ah g-1 and decay rapidly with DMAC-Zn（Cl O4）2-H2O electrolyte while show a stable capacity of 70 m Ah g-1 for 400 cycles at 5 C with PEG-Zn（Cl O4）2-H2O electrolyte.We developed an aqueous zinc ion battery with Lithium vanadium phosphate positive electrode and PEG-Zn（Cl O4）2-H2O electrolyte,of which the working voltage is 1.4 V and the energy density is 109 Wh kg-1.The resultant cell shows a capacity retention of 70% after 400 cycles. |
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