Research On The Interfacial Design And Electrochemical Properties Of Electrode Materials For Sustainable Aqueous Batteries

The deterioration of environmental contamination has prompted the development green,low cost,large-scale and efficient electrical energy storage systems.Due to their high energy density,long cyclic life and wide potential window,lithium-ion batteries play a dominant role in commercial fields such as electric vehicles and various portable electronic devices.However,the development of lithium-ion batteries in grid-scale energy storage is impeded by safety risks and cost challenges associated with organic electrolytes that are highly volatile,flammable,toxic and expensive.In contrast,sustainable aqueous batteries with water-based electrolytes are widely recognized by worldwide researchers due to their reliable safety,eco-friendliness and affordable maintenance/operation costs.In fact,most of the current aqueous batteries still face a series of problems.During the electrochemical conversion,the instability of electrode materials and the dissolution and irreversible phase changes of active substances lead to rapid capacity decay and poor cyclic lifespan of electrodes.Therefore,it is urgent to optimize the electrode performances by materials design/engineering.Herein,nickel/iron(Ni/Fe),nickel/bismuth(Ni/Bi)and zinc/iodine(Zn/I₂)batteries are studied from the viewpoint of material interface design and energy storage characteristics.The main research contents are listed as follows:1.An aqueous Ni/Fe battery is built with FeS₂@C anode.The Fe₂O₃ precursors are pre-fabricated from useless rusty wastes by a simple hydrothermal treatment.Subsequently,the Fe₃O₄@C nanospheres with homogeneous size(diameter range:?50nm)are prepared by PDA polymerization/carbonization processes.Finally,the Fe₃O₄@C is converted into FeS₂@C by annealing/sulfurization under a vacuum condition.The exterior intact carbon sheaths can not only enhance the electrical conductivity of total electrodes,but also prevent inner FeS₂ expansion/diffussing losses during the electrode operation period.The synergistic effects between outer carbon shells and inner FeS₂actives result in excellent performance in half-cell or full-cell tests,including outstanding prolonged cyclic lifespan,significant specific capability and remarkable energy/power density.To gain insights into pyrite working mechanism/phase variations,we have performed real-time characterizations of the electrodes at distinct operation stages.A redox reaction working mechanism of“FeS₂OH?FeS₂?Fe⁰”is proposed.In addition,we find that the configured anodes would stepwise undergo three key stages of“retention”,“phase change/coexistence”and“degradation”in a total cyclic period,each of which is closely related to the variations of anode composition/structures.2.An aqueous Ni/Bi battery is well-established with Bi@C anode.The initial materials of NH₄Bi₃F₁₀ nanoparticles are synthesized by a conventional liquid reaction method at room temperature.Subsequently,the hollow Bi@C hybrids are fabricated after the dopamine coating and high temperature carbonization at 400?.Particularly note that the high electrovalent bonding of Bi-F plays an essential role in promoting the bismuthic thermostability.Such Bi@C hybrids own special hollowed-out nanostructural features,with high accessible surface areas,smooth ionic transport channels and strong mechanical properties against electrode degradations.The as-built anodes possess superior specific capacity and rate capability,as well as excellent cyclic lifetime.Our assembled Ni/Bi cells with admirable peak energy/power densities of 82.32 Wh kg^-1/15.7 k W kg^-1 and fast-response/stable enough behaviors may fit well in green energy-harvesting usage.More importantly,we further confirm their unique anodic phase conversions of“Bi?Bi(OH)₃”on basis of real-time in-situ characterizations/post-analysis(like XRD,Raman)at different cycling stages.3.An aqueous Zn/I₂ battery is constructed with I₂@GP-CMTs cathode.Partially graphitic/porous carbon microtubes(GP-CMTs)precursors are evolved from hairs and inherently co-doped by multiple heteroatoms(N,O,S,etc.).I₂@porous carbon microtubes(I₂@GP-CMTs)hybrids are then evenly mixed with I₂ by a heating treatment.The appearing abnormal phenomena in thermogravimetic/spectroscopy detections reflect the formation of strong halogen bonds(-I…Y-,Y refers to N,O,S,etc.)and other extra chemisorptions between I₂ and heteroatoms co-doped carbon matrix.Halogen-based interactions prove beneficial to absorb/immobilize sublimated I₂ molecules,and prevent iodic actives from dissolution/losses into the electrolyte solution during the battery operation.The configured cathodes exhibit high reversible specific capacities over the theoretical one,eminent rate capabilities,and remarkably prolonged cyclic behaviors.Benefiting from intrinsic properties of I₂@GP-CMTs,the packed hydrogel Zn/I₂ cells show prominent battery performances on cyclic life and energy/power densities.In addition,the direct redox reaction of“Zn+I₂?Zn I₂”is also confirmed by in-situ Raman detections and operando microscope observations.