| The ever-increasing environment pollution and energy crisis have made sustainable energy storage systems(e.g.batteries)more demanding.Over the past decades,some metal elements(K,Ca,Zn,Mg and Al)have been intensively investigated for batteries due to rich materials,low cost and high theoretical capacity.Among these doable battery systems,rechargeable magnesium ion batteries(MIBs)have been regarded as one of the most promising candidates to LIBs due to earthabundant raw materials(Mg in the earth’s crust(2.9%)is much higher than that of Li(0.002%),smooth deposition behavior under suitable conditions and high volumetric specific capacity(3833 mAh cm-3)of Mg metal.Most remarkably,Mg metal is environmentally friendly and has high operational security.In these respects,rechargeable magnesium batteries are attractive for next-generation energy storage systems.However,one of the challenges is the incompatibility between Mg metal and conventional organic electrolytes,resulting in irreversible electroplating/stripping behavior.In order to solve this fatal incompatibility problem,researchers have made many efforts and breakthroughs.Specially-designed electrolytes exhibit reversible plating and stripping of Mg metal.Nevertheless,these electrolytes with free halogen ions normally show high viscosity,strong corrosivity to current collectors and extreme reduction resistant,thus making them run counter to the inherently safe characteristics of Mg and environmental friendliness,which greatly limits their large-scale applications.From another point of view,alloy-type anodes have suitable voltage and high theoretical specific capacity,so replacing magnesium metal with alloy-type anodes is very important for the development and application of building high performance rechargeable magnesium batteries.In this thesis,In-Sn alloy system,triphase Sn-Al-Bi alloy system and Ag3Ga modified Bi electrode were prepared by magnetron sputtering technology,meltingsolidification method and coating method,respectively.The characterization of the phase compositions and microscopic morphology,the electrochemical performance test and the exploration of the magnesium storage mechanism were carried out in APC solution.The main contents of the thesis are as follows:1.Unveiling the magnesium storage mechanisms of co-sputtered indium-tin alloy films using operando X-ray diffraction.First,we prepared self-supporting and additivefree In-Sn alloy films with different compositions(In0.2Sn0.8,In0.2Sn0.8/In3Sn and In3Sn,at.%)via one-step magnetron co-sputtering.Compared to the single-phase Sn,the role of In in facilitating the alloying reaction of Sn with Mg was investigated and it has been found that the electrochemical reactivity of In-Sn alloy electrodes could be improved with the increase of In.In addition,biphase In0.2Sn0.8/In3Sn electrode shows the most excellent electrochemical performance,indicating its faster kinetics of Mg2+ions and higher reversibility of the magnesiation/demagnesiation processes,which may be due to the favorable phase boundaries and biphase buffering matrix improving the electrochemical kinetics and stability.More importantly,the Mg storage mechanisms of the sputtered In0.2Sn0.8,In0.2Sn0.8/In3Sn and In3Sn alloy electrodes were revealed using operando XRD,and it has been found that In0.2Sn0.8 and In3Sn display different Mg storage mechanisms when existing alone or biphase coexisting.2.Deformable triphase tin-aluminium-bismuth anodes for rechargeable magnesium ion batteries.A typical melting-solidification method was adopted to fabricate triphase Sn-Al-Bi alloys with different compositions(Sn60Al35Bi5,Sn65Al30Bi5,Sn60Al30Bi10 and Sn55Al40oBi5,at.%).The active Bi phase could facilitate the alloying reaction of Sn with Mg and the inactive Al phase could improve the cycling stability of the Sn-Al-Bi electrodes.Electrochemical tests indicate that the Mg storage performance of Sn-Al-Bi electrodes is dependent on the synergetic effect of their compositions and alternate phase distributions.Among all electrodes,the Sn60Al30Bi10 electrode shows the highest areal specific capacity of 2.40 mAh cm-2 at the current density of 5 mA g-1 while possesses a poor cycling performance.Besides,the Sn55Al40Bi5 electrode exhibits much improved ductility and cycling stability,delivering a capacity retention of 80.9%after 1000 cycles.Moreover,operando XRD was performed to unveil the Mg storage mechanism of the Sn-Al-Bi electrodes.More importantly,the Sn-Al-Bi electrodes show good compatibility with conventional electrolytes as verified in full cells.3.Preparation of ssm-Ag3Ga-Bi electrode and study on its magnesium storage performance.Alloy-anode materials can hardly meet the demand for battery life due to the dramatic volume change in the magnesiated/demagnesiated processes.In order to deal with this problem,magnesium ion batteries with excellent cyclic stability at room temperature were successfully constructed by sputtering Bi on the current collector interface modified by Ag3Ga.The unique Ag3Ga layer not only improves the binding force between Bi and the substrate of the stainless steel mesh(ssm),but also reacts reversibly with magnesium to provide magnesium storage.Compared with ssm-Bi electrode,ssm-Ag3Ga-Bi anode showed significantly improved electrochemical performance(specific capacity,cycle stability and rate performance)for Mg storage.In addition,operando XRD technique was used to reveal the magnesium storage mechanism.More importantly,the ssm-Ag3Ga-Bi electrode shows good compatibility with conventional electrolyte in full cells. |
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