Preparation And Electrochemical Performance Of Pb_xM_yTe(M=Sr,Ni) Anode Materials

Lead telluride?PbTe?has a face-centered cubic structure,which has widely applications in photovoltaics,infrared photoelectrons,thermoelectric materials and batteries.The theoretical specific capacity of PbTe is 496 mAh/g,which is higher than that of graphite?372 mAh/g?.Furthermore,PbTe has a high volumetric capacity because of its high density?8.164 g/ml?.Therefore,from the basic research point of view,it is still meaningful to probe electrochemical behavior of ternary lead telluride from the viewpoint of basic scientific research.Doping other metal elements is an effective method to improve the electrochemical performance of PbTe.In this paper,a certain amount of Sr and Ni elements were doped into the PbTe matrix successfully by adjusting the chemical reactivity of the metal and the Te precursor.In addition,it was found that the electrochemical performance of PbTe had been improved through the synergistic effect of doping and a special microstructure.The cubic crystal structure Pb_1-xSr_xTe polyhedral microcrystals with unusual stabilized compositions were synthesized using a facile EDTA mediated solvothermal method.The solubility of solid solution SrTe in PbTe reaches 5.2-6.5 mol%,which is beyond its thermodynamic solubility limit of 1 mol%in bulk.The presence of EDTA plays a crucial role in the formation of pure phase polyhedrons,avoiding the formation of SrCO₃ impurity.In the reaction system,the concentration of OH^-and TEA?triethanolamine?affect the chemical state of the Pb and Te precursor,respectively.The electrochemical performance of obtained powder indicated that the cycle performance and rate performance were improved after the Sr element was incorporated.After 200 cycles,the discharge capacity of the material increases to 146.1 mAh/g,which is 86%higher than that of the pure PbTe.The improved cycle stability and better rate capability in the Pb_0.95Sr_0.05Te composite compared to PbTe is attributed to:on the one hand,introduction of heteroatoms Sr into the PbTe matrix,leading to the formation of a disordered crystal structure that further enhances Li intercalation.On the other hand,the presence of Sr within the PbTe host matrix,which improves the electrochemical kinetics and electrical conductivity of the material.NiTe-Pb_1-xNi_xTe heterojunction nanorods were prepared by a two-step method using Te nanorods as the self-sacrificial template.The analysis shows that the addition of Ni source is the key to maintain the nanorod shape product.The complexing agent EDTA acts to simultaneously regulate the release rate of Pb and Ni metal ions.The NiTe-Pb_1-xNi_xTe heterojunction nanorods as electrode material were tested compared to that of NiTe,PbTe,and their mixture.The NiTe-Pb_1-xNi_xTe heterojunction nanorod electrode not only has a higher specific capacity,but also has better rate performance and cycle stability.The NiTe-Pb_1-xNi_xTe nanorod heterojunction has an initial discharge capacity of 760.42 mAh/g at a current density of 0.5 A/g and the discharge capacity is still 206.43 mAh/g after 200 cycles.This behaviour indicates that a small substitution of Pb with Ni and heterostructure nanorod do have profound synergistic effects on the electrochemical performance,owing to their highly accessible sites,electrical conductivity and short ion diffusion length,which facilitate the ion accessibility and improves the charge transport.The novel structure and high performance demonstrated here affords a new way for structural design and the synthesis of ternary metal chalcogenides as LIBs anodes.