High Performance Rechargeable Aluminum Sulfur Battery Materials

The specific capacity of aluminum is 2980 mAh g-1 illustrating advantages in both safety and cost-effectivity,showing its potential to be electrode materials.Sulfur has similar features,which means rechargeable aluminum sulfur battery could be a potential choice for next generation energy storage system.The electrodes are well-matched with high energy density and theoretical discharge voltage(namely,1300 Wh kg-1,and 1.23 V).However,there is still some problems for rechargeable aluminum sulfur battery:sluggish kinetic response,low reversibility and shuttle effect etc.These questions should be responsible for the gap between theoretical and practical performance of the battery and hinder its further development.Therefore,researching mechanism of the reaction and finding suitable cathode materials is pivotal for current research in this realm.Our research is also based on the conclusion above:First,in chapter three,we systematically research the mechanism of aluminum sulfide as the cathode of rechargeable aluminum battery,showing better reversibility and kinetic response through electrochemical performance and spectroscopic characterization.We discovered that sulfide cathode shows no conversion between polysulfide and elemental sulfur,which is beneficial towards the reversibility,While in S cathode the situation is contrary.Moreover,insoluble polysulfides on the surface of cathode should be blamed for sluggish kinetic response of sulfur cathode.In sulfide cathode,however,during the charge process,because no sluggish-reacted elemental sulfur was formed,the main oxidation products are Sn2-,which is kinetically impetus.The insoluble sediment on the cathode is thinner and with more kinetic-beneficial S62-in the system,the kinetic response is also better,with cycle more than 100 and Coulombic efficiency?95%.Then,in chapter 4,we discussed the positive effect of MOFs based carbon network to the sulfur cathode based on HKUST-1.The reversibility and Coulombic efficiency obviously increased after carbonized HKUST-1 become the bearer of sulfur,which can run under 1 A g-1 with initial specific capacity 1200 mAh g-1,with retention of 460 mAh g-1 after 500 cycles and 90%Coulombic efficiency.Further characterization like UV-Vis and XPS indicated that metal particles showed catalytic effect to sulfur conversion and accelerated the kinetic response of polysulfides.Therefore,the conversion and utilization of cathode can be increased.Finally,the kinetic sluggish of polysulfide conversion limited the rate capacity and stability of the cathode.In Chapter 5,we researched the mechanism of transition metal(Co)electrochemical catalyst in rechargeable aluminum sulfur battery.We found with the participation of Co,the kinetic response obviously increased,illustrated by better hysteresis and Coulombic efficiency.The hysteresis reduced from 1.3 V to 0.8 V,and the it can maintain 500 mAh g-1 after 200 cycles at current density of 1 A g-1.Under 3 A g-1,the reversible capacity also reached 300 mAh g-1.And similar results can be observed in sulfide cathode,showing the universality of the method.