Study On Preparation And Lithium Storage Properties Of （CrMnCoNiZn）₃O₄ High Entropy Oxide Matrix Composites

Lithium-ion batteries（LIBs）are widely used in daily life because of their characteristics such as low self-discharge and friendly energy density.As for the selection of electrode materials,the theoretical specific capacity of commercial anode graphite is low,which can no longer meet the high requirements of large energy storage equipment and power equipment for fast charge-discharge and high energy density batteries.Therefore,it is necessary to develop anode materials with better performance.High entropy oxide is regarded as one of the new energy materials with great potential for research and development due to its stable crystal structure and high theoretical specific capacity.In this paper,a kind of spinel high entropy oxide nanoparticles（CrMnCoNiZn）₃O₄ was prepared by solution combustion method.The effects of grain size and defects on lithium storage properties of nanomaterials were studied by adjusting the grain size and the content of internal oxygen vacancy defects.And with carbon materials and conductive polymer materials composite,study the composite material lithium storage performance.（1）Spinel structure high entropy oxide nanomaterials（CrMnCoNiZn）₃O₄（HEO）were prepared by solution combustion method,and the theoretical specific capacity was calculated to be 855.9 m Ah g^-1.The grain size of（CrMnCoNiZn）₃O₄ nanomaterials has a maximum value with the increase of conductive carbon black,and the lithium storage performance increases with the increase of the grain size.The HEO-10 sample has the largest grain size（36.3 nm）,and the reversible capacity of 338 m Ah g^-1 after 100 cycles at 100 m A g^-1,and the rate performance at2A g^-1 can reach 260 m Ah g^-1.By adding low cost Li⁺to the precursor solution,oxygen vacancy defects are generated in the material by charge compensation mechanism.With the increase of Li⁺content,the number of oxygen vacancies also increased,and the lithium storage performance was enhanced accordingly.The sample of HEO-011 had the most oxygen vacancies,and the reversible capacity of the electrode was 365 m Ah g^-1 after 100 cycles at 100 m A g^-1.At the current density of 2 A g^-1,the rate performance reaches 196 m Ah g^-1.The existence of oxygen vacancy speeds up the transmission rate of Li⁺and electrons,and improves the electrochemical performance of the material.（2）The（CrMnCoNiZn）₃O₄/CNTs composites were prepared by chemical vapor deposition with acetylene as carbon source and spiral-shaped carbon nanotubes（CNTs）were grown around（CrMnCoNiZn）₃O₄ nanoparticles.The reversible capacity and cyclic stability of the composite electrode were significantly better than that of the pure phase（CrMnCoNiZn）₃O₄ anode,in which the reversible capacity of HEO/CNT-10 sample reached 621 m Ah g^-1 after 100 cycles at 100 m A g^-1.The rate performance at 2 A g^-1 can reach 289 m Ah g^-1.Carbon nanotubes not only improve the conductivity of the material,but also prevent excessive agglomeration of HEO particles,which is conducive to better charge transfer during charging and discharging cycles.Moreover,the good mechanical properties of carbon nanotubes can also alleviate the volume expansion during continuous Li⁺embedding/deembedding,which has a favorable effect on the performance of lithium storage.（3）The（CrMnCoNiZn）₃O₄/PPy composite was prepared by in-situ chemical polymerization with pyrrole monomer as raw material on the surface of（CrMnCoNiZn）₃O₄ nanoparticles.The effect of addition of pyrrole monomer on performance of lithium storage was studied.The results show that the lithium storage performance of the composite increases with the increase of pyrrole monomer content.HEO/PPy-0.2 electrode has the best lithium storage performance,with a reversible capacity of 409 m Ah g^-1 after 100 cycles at 100 m A g^-1,and a rate performance of 360m Ah g^-1 at 2 A g^-1 current density.Flexible polypyrrole effectively buffered the volume expansion of HEO nanoparticles and enhanced the electrical conductivity of the composites,which was conducive to the improvement of electrochemical lithium storage performance.