Synthesis And Electrochemical Performances Of Co₃o₄-based Nanomaterials As Anode For Lithium Ion Batteries

Since the last century,lithium-ion batteries（LIBs）,as a major energy storage equipment,have been widely used in mobile phones,laptops and other portable electronic products.Nowadays,electric vehicles also use LIBs as the main power source,which will need more stringent requirements for the performance of LIBs,for example,higher energy density,longer cycling lifespan,and more environmentally friendly.To date,unfortunately,the conventional commercial anode materials,graphite,has struggled to meet these requirements because of its limited theoretical capacity(³70mAh g^-1)and rate capability,which greatly hinders miniaturization.Therefore scientific research workers in the corresponding field in all countries of the world are working to find new high performance electrode materials for the next generation LIBs.Recently,transition metal oxides（TMOs）,especially cobalt-based oxides with a spinel structure,have become a research hotspot to replace the commercial graphite-based anodes materials due to their higher theoretical Li-storage capacities,resulting from their unique electrochemical conversion mechanism.In this study,mesoporous NiCo₂O₄ nanowire arrays（NWAs）and mesoporous CuCo₂O₄ nanowire clusters were successfully synthesized.And the electrochemical performances of them used as anode materials for lithium ion batteries were researched.The main studies are as follows:1.Mesoporous NiCo₂O₄ nanowire arrays were successfully grown on carbon textiles substrates with robust adhesion through a general surfactant-assisted hydrothermal method and combined with a simple post-annealing treatment.The structure and morphology of the materials were characterized by X-ray diffraction,field-emission scanning electron microscopy and transmission electron microscopy.The mesoporous NiCo₂O₄ NWAs supported on carbon textiles are directly served as a binder-free anodes for Li-ion batteries.The as-prepared mesoporous NiCo₂O₄ nanowires consist of numerous highly crystalline nanoparticles,leaving a large number of mesopores to alleviate the volume change during the charge/discharge process.Electrode architectures presented here promise fast electron transport by direct connection to the growth substrate and facile ion diffusion path provided by both the abundant mesoporous structure in nanowires and large open spaces between neighboring nanowires,which ensures every nanowires participates in the ultrafast electrochemical reaction.As an anode for Li-ion batteries,the NiCo₂O₄/carbon textiles exhibits reversible capacity of¹088.3mAh g^-1 at a current density of 500mAh g^-1,retaining 898mAh g^-1 after 50 cycles,demonstrating a high reversible capacity and an excellent cycle life.2.Mesoporous CuCo₂O₄ nanowire clusters were successfully grown on three-dimensional（3D）carbon cloth substrates with robust adhesion through a simple and rapid single-step hydrothermal method and combined with a simple post-annealing treatment,which can be used as a binder-free anodes for lithium-ion batteries（LIBs）.These mesoporous nanowires and clusters interconnected with each other and forming a network with interval voids,which give rise to large surface area and efficient buffering of the volume change during the charge/discharge process.The integrated hierarchical electrode maintains all the advantageous features of directly building two-dimensional（2D）nanostructure on 3D conductive substrate,such as short diffusion length,strain relaxation and fast electron transport.As the LIBs anode,it present a high reversible capacity of992.1mAh g^-1 after 50 cycles at a current of 500mAh g^-1.As demonstrated in this work,the hierarchical mesoporous CuCo₂O₄ nanowire clusters/carbon cloth also shows high flexibility,which can be directly used as the anode to build flexible LIBs.The introduced facile and low-cost method to prepare mesoporous CuCo₂O₄ nanowire clusters on flexible and conductive carbon cloth substrate is promising for the fabrication of high performance energy storage device,especially for next-generation wearable electronic devices.