| Rechargeable zinc batteries(RZBs)have attracted extensive attention in the field of large-scale energy storage due to their advantages of abundant resources,low cost,and high safety.As an ion transport carrier,the electrolyte is one of the important components of battery chemistry.Its physicochemical properties and solvation structure directly affect the electrochemical behavior of RZBs.At present,the problems of hydrogen evolution,narrow voltage windows and dissolution of cathode active materials commonly exist in conventional aqueous zinc ion batteries are related to the chemical and electrochemical instability of water-based electrolyte.These could not only affect the reversibility and stability of Zn anode,but also limit the output voltage and energy density,and reduce the service life of RZBs.The above problems can be alleviated by increasing the concentration of electrolyte in the water system.However,the high concentration electrolyte reduces the ionic conductivity,improves viscosity and increases the cost,which limits its application range to some extent.Based on this,from the perspective of non-aqueous electrolytes,we design and optimize several kinds of electrolyte systems of organic and organic/water hybrid electrolyte system for RZBs.To solves the above scientific problems of traditional electrolytes of water-based zinc battery through adjusting the key parameters such as the type,composition,ratio,and solvation structure of electrolyte,reveals the interface chemistry reaction lows between zinc anode and electrolyte,clarifies the microstructure evolution and electrochemical reaction mechanism of several electrode materials(such as graphite,polyanion compound,and vanadium oxide cathode).The novel type of Zn-based battery systems with high specific energy and long life are constructed.The main research contents and results are as follows:1.Design of high voltage organic electrolyte and rechargeable Zn-graphite battery.In this chapter,a non-aqueous electrolyte composed of zinc bis(trifluoromethylsulfonimide)(Zn(TFSI)2)and acetonitrile(AN)was designed.The optimized Zn(TFSI)2/AN electrolyte features high reductive/oxidative stability,good ionic conductivity(?28 m S cm-1),and low viscosity(?0.4 m Pa·s),enabling the unprecedented cycling stability(over 1000 h)of the Zn anode with a dendrite-free morphology,and the ultrafast Zn plating/stripping with a high Coulombic efficiency(CE)up to>99%.By matching the Zn(TFSI)2/AN electrolyte with zinc anode and graphite cathode,a novel zinc-graphite battery system was constructed,exhibitting a high average output voltage(2.2 V),a high energy/power density(86.5 Wh kg-1 at 4400 W kg-1),and a long cycling stability(97.3%capacity retention after 1000 cycles).In addition,combining electrochemical analysis XRD,Raman,FTIR,XPS,SEM,and TEM analysis,the energy storage mechanism of this Zn-graphite battery:during charge and discharge process,TFSI-anions rapidly(de)intercalation from the graphite cathode,while the electrochemical Zn2+plating/stripping at the anode was revealed.This present work offers new insights and opportunities to the Zn-based electrochemistry.2.High safety organic electrolytes for high-performance rechargeable zinc batteries.Here,we report a nonaqueous phosphate-based electrolyte with dual salts of 0.5 M Zn(OTf)2 and 1.0M Na Cl O4 in trimethyl phosphate(TMP)solvent.The formulated dual cations electrolyte features a fire-extinguishing ability,and in which the anions and cations form a stable solvation structure with solvent molecules,which can effectively inhibit the decomposition of the electrolyte at high or low potentials,and expand the stability voltage window up to 3.2 V(vs.Zn2+/Zn),and have good compatibility to both Zn anode and polyanionic cathodes(e.g.,Na3V2(PO4)2O2F(NVPOF),Na3V2(PO4)2F3(NVPF),and Na3V2(PO4)3(NVP)).In this electrolyte,the deposition of Zn2+ions are uniformed,and the coulomb efficiency of Zn plating/stripping is as high as 99.8%.The surface of Zn anode gradually evolves into a cross-linked grid structure,resulting in a dendrite-free and high coulombic efficiency cycling of Zn anode with a high cycling stability(over 5000 h)is characterized.As a proof-of-concept,a new configuration of RZB by employing a high-voltage NVPOF cathode,a Zn anode,and the dual-cation electrolyte shows an average output voltage of 1.8 V with an energy density of 203 Wh kg-1(based on the cathode)and a long-term cyclability with 83.5%retention over 1000 cycles.It is proved that in the 0.5 M Zn(OTf)2+1.0 M Na Cl O4 in TMP electrolyte,the polyanion Zn-based battery can store energy through the reversible extraction/insertion of Na+from/into the NVPOF cathode and electrochemical deposition/dissolution of Zn at the anode.3.Organic/water hybrid electrolyte construction for rechargeable zinc battery.Compared with the organic system in the previous two chapters,Rechargeable aqueous zinc batteries(RAZBs)are promising for large-scale energy storage because of superiority in addressing cost and safety concerns.However,the poor interface stability between zinc anode and aqueous electrolyte,dendrite growth,and low CE hinder the practical realization of RZBs.In this chapter,we report a non-concentrated organic/water hybrid electrolyte system composed of 2.0 m zinc trifluoromethanesulfonate(Zn(OTf)2)and organic dimethyl carbonate(DMC)solvents to stabilize the Zn anode.Through FTIR,17O NMR and Raman spectroscopy analysis,molecular dynamics(MD)simulation and density functional theory(DFT)calculation,it is concluded that,unlike the case in conventional aqueous electrolyte featuring a typical Zn[H2O]62+solvation.In the formulated DMC-H2O electrolyte,the DMC solvents and OTf-anions participate in Zn2+ions solvation sheath,and then forming a new solvate structure of Zn2+[H2O]3.9[DMC]0.7[OTf-]1.4,which helps the formation of a robust,Zn F2 and Zn CO3-rich organic–inorganic hybrid SEI layer.This composite SEI can effectively inhibit the side reaction between the Zn anode and water,thus achieving a high average CE of Zn plating/stripping(99.8%at areal capacity of 2.5 m Ah cm-2)and a dendrite-free cycling over 1000 cycles.Furthermore,The Zn/V2O5 battery in DMC-H2O electrolyte shows high energy density and long cycle stability,indicates a bright application prospect. |
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