| Advanced energy-storage systems with high energy density have attracted tremendous attention due to the ever increasing demand for energy storage technologies in electric vehicles and large-sacle grid energy storage.Most recently,aluminum-ion batteries with multivalent ions have been studied intensively.Aluminum is the most abundant metal and the third most abundant element in the Earths crust.Its lower reactivity and easier handling may offer noteworthy cost saving and safety improvement compared to its counterparts.At present,the specific energy density of lithium-ion batteries is close to the theoretical limit,so it is urgent to develop a new multi-electron reaction battery system to improve the battery energy.In recent years,aluminum-based battery system based on three-electron reaction has attracted extensive attention from researchers at home and abroad due to its advantages of abundant reserves,high energy density and excellent safety performance.However,because of the radius ofAlCl4-anion is much larger than that of lithium ion,the number of ion intercalation is affected,and most of the cathode materials used for lithium-ion batteries can not be suitable for intercalation and deintercalation of AlCl4-anion.Moreover,the electrostatic force of Al3+in solid phase diffusion is larger,which hinders hindering its solid phase diffusion in cathode materials.These two kinds two of key problems lead to the low energy density of aluminum-ion batteries,which hinders impeding the practicality commercial realization of aluminum-ion batteries.Aluminum-sulfur battery system has high theoretical specific capacity,but its cycle performance is poor due to the low reactivity of its the discharge product AlSx,which is difficult to be oxidized.It is still a great challenge to realize reversible charging and discharging of Al-S batteries at room temperature.In this dissertation,in order to develop rechargeable aluminium batteries with high energy density,we present that the addition of a redox mediator enables recharging of the Al-S battery at room tempreture with high capacity and high efficiency.And new types of high specific capacity aluminium ion cathode material were designed and fabricated.The reaction mechanism was studied,providing a insight into the design of high energy density and long cycle life aluminium ion batteries.The main results are summarized as follows:(1)We developed a high specific capacity rechargeable Al-S battery at room temperature.We present that the addition of a redox mediator,b is-(pe ntame thyl-cyclopentadienyl)nickel(NiCP),enables recharging of the AI-S battery at room tempreture even with 88%sulfur content that is impossible for the battery in the absence of the mediator.NiCP is homogeneously dissolved in the electrolyte.On charging process,NiCP is oxidized to NiCP+at the cathode surface;NiCP+ in turn chemically oxidizes the AlSx.The introduction of redox mediator enables a significant enhancement of the cycling stability.Furthermore,the charging mechanisms of Al-S cells with and without NiCP were compared by combining different electrochemical and analytical techniques.The reversible specific capacity was 1673.8 mAh g-1.The sulfur content was twice as high as the highest reported in other literatures.By comparing the charge-discharge performance of the same battery with and without NiCP,and the structural characterization of the product after charge and discharge,the reaction mechanism proposed is verified.As the content of NiCP in the ionic liquid electrolyte increases,the charging platform decreases.The single-walled carbon nanotube modified membrane was designed,reducing the polarization of the battery.The single-walled carbon nanotube modified membrane was designed and manufactured to reduce the polarization of the battery.The method is also applicable to other multi-electron metal-sulfur battery systems,and provides a new avenues for the development of metal-sulfur systems with high specific energy density.(2)We report for the first time,the design of α-MnO2 and β-MnO2 as a novel cathode material for rechargeable aluminum-ion batteries.We explored the charge-discharge reaction mechanism of MnO2 and point out the feasibility of MnO2 as a cathode material for rechargeable aluminum ion batteries.By optimizing the battery electrode system,the reaction efficiency of and the cycle stability of the battery is improved.The cyclic stability of β-MnO2 cathode is better than that of α-MnO2.The three-electrode system has better performance than the two-electrode system.At the current density of 30 mA g-1,the first discharge specific capacity of β-MnO2 cathode is 643.6 mAh g-1 and the voltage platform is 0.59 V,and the second discharge voltage platform is at 0.75 V.Even at a much high current density of 150 mA g-1,the capacity still retains 100 mAh g-1 after 100 cycles.In this chapter,MnO2 was applied to aqueous aluminum secondary batteries for the first time.The high-energy aqueous aluminum-ion batteries were obtained,which providing a new idea for the design of high-capacity aqueous aluminum-ion battery. |
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