Engineering Heterostructured SnMn-based Anode Materials For Li/Na Storage

Lithium-ion batteries（LIBs）have been extensively commercialized in our modern society as secondary energy storage equipment.Owing to abundant sodium resources and low cost,sodium ion batteries（NIBs）have shown attractive prospects in the fields of high specific energy density portable power supplies and power batteries.Engineering a new type of anode material with excellent comprehensive performance is one of the keys to the rapid development of LIBs/NIBs.Sn-based oxides and selenides have attracted extensive attention due to its high theoretical capacity,appropriate potential platform,and long cycling performance.However,the recrystallization and internal stresses caused by the conversion-alloying reaction will result in reduction of active site areas and cause the electrode material to crush and fall off,which limit the application of Sn-based oxides and selenides in LIBs and NIBs.Therefore,we have constructed bimetallic heterostructured Sn O₂/Mn₂Sn O₄@C and Mn Se/Sn Se@C nanoboxes by modification with carbon material,nanostructure engineering,and construction of bimetallic heterostructures and investigated their lithium/sodium storage properties.The main research contents are as follows:（1）The heterostructured Multi-Yolk-Shell Sn O₂/Mn₂Sn O₄@C nanoboxes were prepared by co-precipitation,hydrothermal treatment,annealing and carbonization in argon.The heterostructure can significantly enhance thermodynamic stability by generating lattice distortions and introducing a large number of defects in the material while affording superior electronic/ionic conductivity and electrochemical activity for Li/Na ion storage.The hollow structure of the Sn O₂/Mn₂Sn O₄nanoboxes and the elastic phenolic resin-derived carbon shell can remit the volume expansion and pulverization.The prepared Sn O₂/Mn₂Sn O₄@C nanoboxes display excellent capacity(1293 m A h g^-1at 0.2 A g^-1 after 100 cycles)and superior cycling stability(400 m A h g^-1 at 2A g^-1 over549 cycles)for LIBs as well as a high capacity(203 m A h g^-1 at 0.2 A g^-1 after 100cycles)for NIBs.In the meantime,the Sn O₂/Mn₂Sn O₄@C（MSO）and Li Fe PO₄/Na₃V₂（PO₄）₃（LFP/NVP）were used as anode and cathode material,full cell（Li/Na-full cell）test also shown better performance.（2）The heterostructured Mn Se/Sn Se@C nanoboxes were prepared by co-precipitation,hydrothermal treatment,annealing and selenation in Ar/H₂.The existence of Mn Se/Sn Se heterostructure can efficaciously stabilize the reaction products Sn and Li₂Se/Na₂Se,prevent the coarsening of nanosized Sn⁰,and enhance the reversibility of alloying reaction.Strong electronic coupling Sn–C and Se–C chemical bonds between Sn Se and phenolic resin-based carbon provide the fast electrical transport channels during the charge and discharge process.Carbon coating can alleviate volume expansion,avoid active material falling off,and further enhance the stability of cycling process.The Mn Se/Sn Se@C nanoboxes exhibit excellent electrochemical performance for LIBs(557 m A h g^-1 after 900 cycles at 0.5 A g^-1).