Exploration Of Cathode Materials For Aluminum Ion Batteries And Their Electrochemical Properties

With the increasing problems caused by the use of traditional fossil energy,people have begun to focus on the development of secondary batteries as energy storage.Because of its high theoretical capacity,safety and environmental protection,and low cost,aluminum batteries are considered to be one of the ideal options to replace the current lithium battery system in the future.Compared with the deposition-dissolution process of anode Al³⁺,cathode materials involving ion intercalation or phase conversion are the core issues that limit the electrical and electrical properties of aluminum.Therefore,the selection of suitable cathode materials is crucial for the development of the electrochemical performance of aluminum-ion batteries.Due to the characteristics of aluminum ions,the current cathode materials that can efficiently store aluminum ions are still very limited,and there are many problems.The cathode materials and the energy storage mechanism are explored through a series of electrochemical measurements and structural characterization.The main research contents are as following:（1）Aluminum-graphite batteries with graphite nanosheets as cathodes were successfully constructed by the strategy of pencil-drawing.Compared with the traditional electrode preparation process,this method is simple and efficient.The molybdenum current collector was etched by a laser generator to enhance the surface roughness of the metal substrate;the active material layer of graphite nanosheets was obtained by pencil-drawing;finally,a thin layer of polyvinylidene fluoride（PVDF）was dropped on the surface of the graphite layer to enhance the cathode stability during charging and discharging.A discharge specific capacity of 96 m Ah g^-1 at a current density of 0.5 A g^-1was achieved,and the capacity retention rate was still close to 100%after 2000 cycles,indicating that the battery has excellent long-cycle stability.Further increasing the current density to 2 A g^-1 provides a maximum discharge capacity of 72m Ah g^-1 with a capacity retention of 90%after 6000 cycles.Through a series of in-situ and ex-situ characterization tests,the reversible intercalation/deintercalation behavior of aions was found,and a third-stage reaction mechanism was also confirmed.（2）The flower-like Ni Co-LDH composed of nanosheets was prepared by simply treating the precursor solution at room temperature.And the derivative Ni/Co O,as cathode material for aluminum ion batteries,was obtained by further pyrolysis at 500℃.After high temperature calcination,Ni/Co O still maintains the flower-like structure of the precursor.The material has a high specific surface area,and the lamellar structure facilitates ion shuttling,reduces diffusion resistance,and enhances reaction kinetics,thereby providing higher specific capacity.The material exhibits excellent electrochemical performance and superior reaction reversibility,which is a stable discharge specific capacity of 80 m Ah g^-1 and a coulombic efficiency of 98%after the first 20 cycles of decay at a current density of 500 m Ahg^-1.After 1000 cycles,the discharge specific capacity was 72 m Ah g^-1,the capacity retention rate was up to 90%,and the coulombic efficiency was 96.5%.Finally,through XPS characterization,it was confirmed that the reaction mechanism of the aluminum ion battery is through the redox reaction of element to achieve electrochemical energy storage.