| Rechargeable aqueous metal-ion batteries(RAMB)on a basis of metal-ion intercalation chemistry are perfect devices for grid-scale energy storage because of their good safety,low cost,and eco-friendliness.However,most of the known RAMB suffer the problems of low energy density owning to the low voltage output(<1.2 V)and poor cycle performance.There are two good strategies to effectively improve the electrochemical performace of RAMB.One is to modify the electrolyte for a wider electrochemical window,the other is to investigate new cathode/anode materials of enhanced capacity and stability.In this thesis,aqueous mixed ion battery(AMIB)based on open framework structure CuHCF cathode and NaTi2(PO4)3 anode with high voltage output>1.56 V is assembled.Then XRD?XPS and ICP-OES are employed to investigate the ion-selectivity and storage mechanism of CuHCF.In addition,VHCF is prepared by a simple co-precipitation method,and used as the cathode electrodes for high stable rechargeable sodium-ion battery.A modified electrolyte containing an appropriate amount of polyethylene glycol(PEG)is used as electrolyte.The effect of interface PEG-Na+ on VHCF electrode and storage mechanism of H+and Na+were studied by 1H,23Na solid-state nuclear magnetic resonance and kinetic analysis.Moreover,a new aqueous deep eutectic solvent(DES)based on methylsulfonylmethane(MSM),LiClO4 and H2O as brand-new type aqueous electrolyte for lithium-ion batteries,and their relationship with the battery performance was studied.Raman,FT-IR,170 NMR,1H NMR experiment,as well as theoretical calculations were performed to analyze the structure and the component coordination mechanism of DES electrolyte.The main results included in this thesis are summarized as follows.1.The new type of AMIB based on CuHCF and NaTi2(PO4)3 has a specific energy of 56 Wh kg-1 with Eav of 1.56 V,and can deliver a specific power of 3006 W kg-1.Iron atom in CuHCF is identified as the center that involves the redox reaction accompanying the reversibly(de)intercalation of alkali cations.The intercalation voltage is affected by the ionic radii of inserted alkali cation,which follows the order:K+>Na+>Li+.Meantime,Li+with small size is supposed to be co-inserted into 24d site,while Na+ and K+ prefer to occupy the 8c site.Moreover.CuHCF exhibits specific ion-selectivity:K+>Na+>Li+.2.VHCF/WO3 aqueous sodium battery exhibits an ultra-high stability at a high current density of 1000 mA g-1,and about 90.1%capacity retention after 2000 cycles in NaP-4.6 electrolyte.Both iron and vanadium atoms in VHCF are the centers which involve in the redox reaction accompanying the reversibly storage reaction of Na+ and H+.H+ storage reaction is likely accompanied by the redox of vanadium atoms,and Na+-intercalation is accompanied by the redox of iron atoms.The slightly structural deformations induced by the cation intercalation and PEG-Na+ interphase are the main contributors to both the excellent electrochemical stability and the improved capacity capability.The ssNMR result reveals that most Na+ions(-96%)extract from VHCF during the first 2/3 charging process,and only very small amount of Na+ ions extract during subsequent 1/3 charging process.3.A brand new type of lithium salt deep eutectic solvent(DES)consisted of MSM,LiClO4 and H2O is reported.The Li+ cation is coordinated with oxygens in MSM,H2O and ClO4-to form Li+-coordinated complexes,leading to a super-concentrated Li-salt solvate.The formed DES-1(MSM:LiClO4:H2O=1.8:1:1)shows a satisfying electrochemical stability window(about 3.3 V).The LTO/DES-1/LMO of high-voltage aqueous lithium battery performs a high energy density(>160 Wh Kg-1)and high working voltage of 2.4 V,and have a capacity retention of 72.2%after 1000 cycles at 4.5 C current density.The possible structure of DES-1 solution has one Li+coordinated to oxygen atoms from one H2O,one ClO4-and two MSM,and that one H2O hydrogens are bonded with two MSM.This hydrogen bonding can significantly decrease the melting point to-48?.resulting in a room temperature solution. |
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