Preparation And Li-storage Performance Of Spinel-type High-entropy Oxide Anode Materials

Lithium-ion batteries(LIBs),as a brand new energy conversion and storage device,have been widely used in mobile communications,electric vehicles,aerospace and other fields.The development of high specific energy anode materials is one of the key factors to improve battery performance.Currently commonly used graphite-based carbon anode materials have low theoretical specific capacity and poor high-current charge and discharge performance;Single transition metal oxides and silicon-tin-based materials have high theoretical capacity,but the larger volume expansion during cycling leads to poor cycle performance and rate performance.In order to overcome the shortcomings of the above-mentioned anode materials,high-entropy oxides(HEOs),with high configuration entropy and multi-principal element characteristics,have developed in this work.In this work,the spinel-type(Cr_0.2Fe_0.2Mn_0.2Co_0.2Ni_0.2)₃O₄HEO nanocrystalline powder with uniform chemical composition and mesoporous structure were successfully prepared by solution combustion synthesis method(SCS).At 200 m A g^-1,the first discharge specific capacity of this HEO electrode is 1166 m Ah g^-1,and the reversible specific capacity after 50 and 500 cycles are 393 and 239 m Ah g^-1,respectively;At 3000 m A g^-1,the specific capacity is still as high as 392 m Ah g^-1.Compared with the single-element Co₃O₄electrode,the multi-principal HEO electrode with high configuration entropy exhibits excellent cycle stability and significantly enhanced rate performance.Then,(Cr_0.2Fe_0.2Mn_0.2M_0.2N_0.2)₃O₄(M=Co or Ni,N=Mg or Zn)HEOs powders were prepared by replacing the Co and Ni in(Cr_0.2Fe_0.2Mn_0.2Co_0.2Ni_0.2)₃O₄with active metal element Zn and inactive metal element Mg,and both exhibit excellent cycle stability and rate performance.At 200 m A g^-1,the capacity of(Cr_0.2Fe_0.2Mn_0.2M_0.2N_0.2)₃O₄can still be as high as 239 m Ah g^-1after 500 cycles,which are higher than(Cr_0.2Fe_0.2Mn_0.2Co_0.2Ni_0.2)₃O₄.Mg-containing HEOs have superior cycle stability and reversible capacity to Zn-containing HEOs because the inactive material Mg O formed can prevent the agglomeration of active materials during charge/discharge process.At 200 m A g^-1,the specific capacity of Mg-containing HEOs is still above 300 m Ah g^-1after 500 cycles.In particular,the reversible capacity of(Cr_0.2Fe_0.2Mn_0.2Mg_0.2Ni_0.2)₃O₄is still as high as 443 m Ah g^-1when the current density is 3000 m A g^-1.Finally,the spinel-type(Al_xCrFeMnCoNi)_3/(5+x)O₄(x=0.2,0.5 and 1)HEOs nanocrystalline powders were prepared by introducing the inactive metal element Al on the basis of the(Cr_0.2Fe_0.2Mn_0.2Co_0.2Ni_0.2)₃O₄HEO.The introduction of Al can not only increase the configuration entropy and lithium-ion diffusion coefficient of the system,and reduces the charge transfer resistance,but also increase the specific surface area and prevent the agglomeration of active materials,thus exhibiting excellent electrochemical performance.At 200 m A g^-1,the first discharge specific capacity of(Al_xCr Fe Mn Co Ni)_3/(5+x)O₄is above 2000 m Ah g^-1,and the capacity is still as high as about 470 m Ah g^-1after 500 cycles,which is higher than(Cr_0.2Fe_0.2Mn_0.2Co_0.2Ni_0.2)₃O₄.At 3000 m A g^-1,the specific capacity of(Al_xCr Fe Mn Co Ni)_3/(5+x)O₄HEOs electrodes can still reach about 610 m Ah g^-1.In particular,the(Al_0.2Cr Fe Mn Co Ni)_3/5.2O₄HEO electrode has higher reversible capacity and cycle stability.At a current density of 200 m A g^-1,the capacity is still as high as537 m Ah g^-1after 500 cycles.