The Research On Long-life Electrochemical Energy Storage Devices Based On Light Metal Elements

Lithium-ion batteries have always dominated the energy storage market as a representative of new energy sources,but with limited lithium reserves and its high price,the search and development of alternative energy storage devices have come into focus.Among them,light metal-based rechargeable aluminium ion batteries,potassium metal batteries and sodium metal batteries are considered as extremely promising energy storage devices for the future.In this thesis,the structure and problems of the aluminium ion batteries and the potassium metal batteries are optimized and the advantages of ion batteries and metal batteries are combined to build a sodium ion/sodium metal hybrid battery to obtain energy storage devices with high capacity and long cycle electrochemical performance.The main studies and results are as follows:（1）In order to solve the problems of low reversible capacity and poor cycle life of aluminum ion batteries,in this thesis,sponge-like conductive polymer polythiophene（PTh）was used as the cathode of aluminum ion batteries,together with AlCl3-Et3NHCl ionic liquid electrolyte with low cost and high cut-off voltage,to achieve good multiplicity performance and cycle stability(20,000 stable cycles at a current density of 10 A g^-1 with a reversible capacity of 100 m Ah g^-1).The electrochemical performances of the PTh cathode were measured at different temperatures,different surface loadings and the charge/discharge process of AlCl₄^-embedded/disengaged PTh.The good electrochemical performance is mainly attributed to the unique sponge structure of PTh,which allows PTh to expose more active sites during the battery charging process,contributing to the achievement of high capacity,facilitating the rapid embedding and exfoliation of AlCl₄^-in the electrolyte.（2）In order to solve the problems of low Coulomb efficiency and poor cycle life caused by the growth of dendrites in the negative electrode of potassium metal batteries,in this thesis,self-supported Fe3O4/GO films were prepared by simple mixing and drying of Fe3O4nanoparticles with graphene oxide（GO）,which were placed on the surface of the metal K negative electrode to inhibit the growth of K dendrites.The symmetric cell/half-cell/full cell assembled using the Fe3O4/GO film modified K cathode had significant electrochemical advantages compared with the unmodified K.This is mainly due to the fact that the Fe3O4/GO film with particular mechanical strength can withstand the volume expansion of the K metal cathode during charging and discharging.Meanwhile,the Fe3O4 nanoparticles dispersed within the film can guide the rapid and uniform dispersion and diffusion of K⁺during the transport process,thus inhibiting the growth of dendrites and prolonging the cell life.（3）Combining the advantages of ion batteries and metal batteries,a sodium ion/sodium metal hybrid battery is proposed to greatly enhance the capacity of the anode material while maintaining its stable safety performance.In this thesis,a three-dimensional cross-linked bismuth metal electrode（denoted as A-100Bi）was prepared by an in situ self-construction method,which was used to construct a sodium ion/sodium metal hybrid cell with mixed alloying/de-alloying and plating/exfoliation mechanisms.The electrochemical performance of the hybrid cell was investigated under different control capacities and different current densities.The unique three-dimensional cross-linked structure of the A-100Bi electrode not only enables Na⁺transport and relieves the volume expansion during alloying,but also facilitates the internal deposition of Na metal in the subsequent alloyed Na3Bi“sodiophilic”skeleton to guide the uniform deposition of Na and inhibit the growth of dendrites.