| Li-ion batteries have achieved great commercial success due to their relatively high voltage,high energy density,and long cycle lifespan.However,their flammability,limited Li resources,and ever-increasing price make them unsuitable for use in large-scale energy storage system.Therefore,many researchers have switched their attention to the resourceful Na-ion batteries,K-ion batteries,Ca-ion batteries,Mg-ion batteries,and aqueous Zn-ion batteries(AZIBs).Among these battery systems,AZIBs have recently received considerable attention owing to their high capacity,safety,environmental friendliness,and cost effectiveness.Nevertheless,the traditional vanadium oxide and manganese oxide cathode still have great challenges.For example,vanadium oxide dissolves in water and there is slow kinetics of manganese oxide.The above problems can usually be solved by regulating the electrolyte ingredients and designing materials structure.The main study content of this thesis is the optimization of electrolyte,the design of layered MnO2 cathode materials and the energy storage mechanism of AZIBs.The main contents are as follows:(1)A novel 3 M Zn(CF3SO3)2 electrolyte with a mixture solvent of propylene carbonate(PC)and H2O is adopted for aqueous vanadium-based zinc-ion batteries.With the manipulation of the electrolyte solvation structure,the optimized P20(20%PC in volume ratio)electrolyte enables super-stable cycling performance with high-capacity retention of 99.5%/97%after 100/1000 cycles at 0.1/5 A g-1 at ambient environment in the Zn||Na V3O8·1.5H2O batteries.Systematical electrochemical testing and characterizations illustrate the addition of PC effectively reduces the active water molecule in Zn2+-solvent cations and H+in the electrolyte,thereby suppressing the cathode dissolution caused by the inserted H+and co-inserted H2O during the discharge/charge process.Impressively,the PC addition also enabled the Zn||Na V3O8·1.5H2O batteries present high specific capacity of 183/168 m Ah g-1 and high-capacity retention of 100%/100%over 300/400 cycles at 0.1/0.2 A g-1 at-40°C,thus efficiently broadening the practical application for ZVB.This research may provide a promising strategy for designing high-performance electrolytes for aqueous vanadium-based batteries.(2)In this chapter,Zn dendrite growth and Na V3O8·1.5H2O cathode dissolution in Zn||Na V3O8·1.5H2O cells were simultaneously inhibited by introducing Al2(SO4)3 additives into the non-concentrated aqueous electrolyte 2.5 M Zn(CF3SO3)2.Comprehensive characterization showed that a robust SEI layer(Zn4SO4(OH)6·5H2O and[Zn1-xAlx(OH)2][(SO4)x(H2O)z])with Zn2+conductivity was formed in situ on the Zn anode surface,which inhibiting Zn dendrite growth and corrosion reactions.In addition,the Al3+would be embedded in the NVO to form insolubles during the discharge process,which ensuring the structural stability of the NVO during cycling.As a result,the assembled Zn||Cu,Zn||Zn and Zn||NVO batteries all have excellent cycling stability.This research can provide an advanced strategy for developing electrolytes that are compatible with both positive and negative electrodes.(3)In this part,a unique one-dimensional–three-dimensional(1D–3D)hybrid network with interconnected?-MnO2 nanowires was reported as a cathode material for AZIBs.A distinctive 3D nano network structure resulted in enhancement of electrolyte osmosis and significant increase in contact between electrode and electrolyte,and also provided more active sites and convenient rapid ion transport routes.Moreover,the fine nanowire structure and the optimum layer spacing resulted in easier insertion/deinsertion of ion in the active material.Taking advantage of this feature,the?-MnO2 cathode provides high reversible capacity,fast rate capability and good longevity for cycling.Further kinetic experiments revealed that Zn||??MnO2 system constitutes an electrochemical reaction regulated by the combination of ionic diffusion and pseudo-capacitance;and shows high energy efficiency during the charge/discharge states.This research may provide an advanced cathode material for AZIB development. |
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