Preparation And Lithium Storage Properties Of Nano Metal Oxides/nitrides

At present,commercial graphite anode materials can not fully meet the high performance requirements of various energy storage devices for lithium-ion batteries.Metal-based compounds have attracted much attention due to their advantages such as good electrical conductivity and multi-electron transfer reactions of central metal atoms.However,such materials suffer large volume changes during the ion insertion/extraction process,resulting to lattice distortion and increased internal stress,resulting in rapid capacity decay and poor cycle stability.In view of the above problems,this paper takes metal oxygen/nitride as the research object,and improves the volume change and strain accumulation of the material through strategies such as morphology control,structural design and coupling buffering of carbon matrix materials to improve its electrochemical performance.The main contents of this paper are as following parts:(1)Firstly,we have fabricated the as prepared fall sunfower-like GeO₂/C composite as the anode material by static spinning and heat treatment.The ultrafine GeO₂ nanoparticles are uniformly coupled in the carbon nanofiber matrix to form a rich conductive network;and the carbon matrix material provides sufficient buffer space for the volume change of GeO₂ during cycling,effectively suppressing its stress and strain,and enhancing the cycling stability.The experimental results show that the specific capacities of the prepared fall sunfower-like GeO₂/C composite electrode are 1255,1002,828 and 651 m A h g^-1at current densities of 0.2,0.4,0.8 and 1.0 A g^-1,respectively.This work provides a new perspective for the design of new high-performance lithium-ion battery anode materials.(2)In the second work,we have designed and prepared the as prepared Co_3-xO₄@C nanocomposites by hydrothermal method and heat treatment.The material is rich in metal vacancy defects,which can control the electronic orbital structure of the material and enhance the intrinsic electronic conductance of the material.At the same time,the introduction of cobalt vacancies significantly improves the structural stability of the material and the adsorption capacity for ions.Using it as a lithium ion anode material,the Co_3-xO₄@C-400 electrode material still maintains a high reversible discharge specific capacity of 1566.7 m A h g^-1after 1000 cycles at a current density of 15 A g^-1.The nanocomposite preparation method is simple and feasible,and has excellent performance,which has certain guiding significance for the development of next-generation lithium-ion batteries and electrochemical energy storage technology.(3)Finally,we have synthesized a series of 3D honeycomb Fe₃N@NC nanocomposites with different pore size structures by simple carbonization and ammoniation processes.A reasonable heating rate can induce the formation of abundant nanopore structures(especially micropores)inside Fe₃N@NC,while Fe₃N nanoparticles are uniformly and tightly embedded in the carbon matrix framework.The material has high specific surface area and abundant micro/mesopores,which is favorable for the rapid penetration of electrolyte and the transport of Li⁺,while the introduction of nanopores facilitates the additional storage of ions and significantly improves the specific capacity of the material.The results show that at a high current density of 5 A g^-1,the discharge specific capacity of the electrode material remains at 691.6 m A h g^-1 after 2000cycles.Therefore,we believe that this work can provide certain technical reserves for the future synthesis of high-performance energy storage devices with rich nanopore structures.