Correlation Between Thermic And Electric Properties And Valence Electron Structure For Metallic Electrodes Of Liquid Metal Battery

Liquid metal battery is the best choice in the field of large-scale energy storage because of its large capacity,long life and simple manufacture.In this article,the valence electron structures and thermal&electric properties of liquid metal battery are systematically studied with solid and molecular empirical electron theory(EET).The research results indicate that the valence electron structures of the metallic electrodes are closely related to its thermal and electric properties.For the cathode alloy of liquid metal battery,two systems of Li1-xIAx(IA=Na,K,Rb,Cs)and Na1-xIAx(IA=K,Rb,Cs)are designed.By alloying the metal electrode,the melting point of the battery electrode is reduced,and then the working temperature of the liquid metal battery is decreared,which is help for reducing cost.The correlation between the melting point,the cohesive energy and the potential of the alloy electrode and the valence electron structure is studied and analyzed.In the Li1-xIAx system,the theoretical studies show decreasing tendency of melting point,cohesive energy and electric potential with increasing doping content x in Li1-xIAx alloys,this phenomenon is due to the modulation on valence electron structure of IA group dopants.According to the analyses of valence structures,the numbers of covalent electrons are going down with increasing the doping content x for the cathodic alloys and cause the declinations of melting points,electric potential and cohesive energies.It reveals that IA group dopant modulate the valence electron structure of cathodic alloy,and induces the electron transformation from covalent electron to lattice electron in s orbital.In the Na1-xIAx system,the numbers of lattice electrons are going down with increasing the doping content x for the cathodic alloys.It reveals that the electron transformation from lattice electron to covalent electron in s orbital.The anode products such as Li2Sb,?-Li3Sb,?-Li3Sb,LiPB(LT),LiPb(HT),Li3Pb,Li8Pb3,LiBi,LiBi,Li3Bi,Li7Sn2 are formed by transporting Li ion into the anode alloy Sb-Pb-Bi-Sn.And the anode products such as NaSb3,NaSn,Na15Sn4 and NaPb are formed by transporting Na ion into the anode alloy Sb-Sn-Pb.The calculated bond-lengths and melting points fit the observed ones well for these anode products.Owing to their complex structures with various atomic occupations in unit cell,the thermal and electric properties are not only relative to lattice electron,but also depend upon the covalent electron.The average lattice electron number of ?-Li3Sb is the lowest,and NaSb has the lowest average lattice electron number and the highest open gate voltage.The results indicate that covalent electrons and lattice electrons play an important role in the liquid metal battery system with Li or Na as the main metal cathode,and they can regulate the thermal and electrical properties of the anode and cathode of the liquid metal battery.