Research On Key Materials And Devices For Aluminum-sulfur Secondary Batteries

The fast-growing consumer electronics and electric vehicle industries are calling for a new generation of efficient and inexpensive energy storage devices.Among the metal elements,aluminum,as the most abundant metal element in the earth's crust,is considered to be one of the ideal anode materials for new energy storage batteries because of its high gravimetric capacity(2980 mAh g-1),high volumetric capacity(8040 mAh cm-3)and low price.At the same time,elemental sulfur is also characterized by high capacity and low price when used as a battery cathode material.The aluminumsulfur secondary battery system with aluminum metal as the negative electrode and sulfur as the positive electrode has an operating voltage of 1.23 V and a theoretical energy density of up to 1340 Wh kg-1.Therefore,aluminum-sulfur secondary batteries have the advantages of low price and high energy density.However,the development of aluminum-sulfur battery system is still limited by poor aluminum-sulfur reaction kinetics,shuttle effect of polysulfide and low cycle life,and a series of scientific problems and technical issues still need to be solved before practicalization.In this thesis,the research is carried out from three aspects of the assembly structure,cathode material and electrolyte composition of aluminum-sulfur batteries,and the main research progress is as follows.(1)Aiming at the problem of high corrosiveness of aluminum-sulfur battery electrolyte system,a new non-corrosive organic aluminum electrolyte is developed,the influence of collector,binder and cell shell materials on the electrochemical stability of aluminum-sulfur battery is systematically studied,and auxiliary materials applicable to aluminum-sulfur battery system are obtained,which lay the foundation for further indepth study of aluminum-sulfur battery system.(2)To address the problems of poor sulfur cathode reaction kinetics and severe cell polarization,transition metal single-atom catalysts were developed for lowering the sulfur cathode conversion reaction potential,effectively reducing electrode polarization,and achieving a significant increase in the working potential and energy utilization efficiency of aluminum-sulfur secondary batteries.Further,the electrochemical spectroscopy study reveals the reaction path of sulfur in the anode and the electron migration history of Co,which points out the direction for further improving the performance of aluminum-sulfur batteries.(3)In response to the potential safety hazards of organic electrolytes,a highly concentrated saline aqueous electrolyte system was developed to overcome the decomposition of polysulfide in water and passivation of metallic aluminum in water,realizing for the first time an aqueous aluminum-sulfur battery with reversible charge and discharge cycles.This novel electrolyte system reduces the voltage hysteresis of aluminum-sulfur to 0.85 V without the assistance of positive electrocatalyst,and maintains a specific capacity of 400 mAh g-1 after 30 cycles at a current density of 200 mA g-1,which is the highest among the reported aqueous aluminum-metal batteries.