Preparation,Modification Of Three-Dimensional Spherical CuO Nanomaterials And Their Lithium Storage Performance

Lithium-ion batteries are widely used as energy storage devices in electronic devices such as electric vehicles and mobile communications,due to their high energy density and environmental friendliness.However,as the current commercial anode material graphite no longer can satisfy people’s needs,transition metal oxide CuO stands out among anode materials due to its high theoretical capacity(674 m Ah g^-1),easy production,eco-friendliness and great capabilities of Li⁺insertion and extraction.However,copper oxide produces remarkable volume changes resulting in the mechanical strain of electrode materials when lithium is stripped or embedded,and the poor electronic conductivity of copper oxide as a transition metal oxide,which in summary restricts the application of copper oxide anode material.The main work of this paper is synthesized three-dimensional spherical CuO nanomaterials by hydrothermal method.We can improve the structure stability,enhance the conductivity by doping zinc ions and coating carbon,so as to improve the cycling and rate performance of electrode materials.The research contents are as follows:（1）Three-dimensional spherical CuO nanomaterials were prepared by hydrothermal method with different reaction time and temperature.The nanomaterials were physically characterized by XRD,SEM and other technologies to investigate the effects of different times and temperatures on the growth and morphological structure of the prepared nanostructured samples.The results showed that the three-dimensional spherical CuO nanomaterials had the best crystallinity at 190°C and 12 h,and the morphology is mostly spherical.In addition,the electrochemical performance was evaluated of the three-dimensional spherical CuO nanomaterials as anode materials,and the discharge specific capacity of the samples prepared at 190℃and 12 h was211.5 m Ah g^-1 after 100 cycles in Li-ion batteries,which was higher than that of the samples under other conditions.（2）The spherical Cu_1-xZn_xO nanomaterials were prepared by doping zinc ions with zinc acetate raw materials of different concentrations.The results of XRD,SEM and XPS confirmed that zinc ions were successfully doped into the three-dimensional spherical CuO nanomaterials to form Cu_1-xZn_xO nanomaterials,and as the znic ion concentration increases to the mole ratio of zinc to copper ion of 1:50 more spherical particles with fluff are obtained for the Zn-2 sample.The charge–discharge tests demonstrated that the discharge specific capacity is 319.1 m Ah g^-1 of the Zn-2electrode material after 100 cycles,which was significantly higher than other samples with zinc ion concentration.Because zinc doping improved the storage capacity of Li⁺and enhanced the structural stability and alleviated the volume changes caused in the process of charge and discharge.（3）According to the above experimental results,Zn-2 samples were coated with different concentrations of glucose as non-in-situ carbon coating.The characterization showed that the spherical Cu_1-xZn_xO nanomaterials Zn-2 samples with a diameter of about 500 nm were coated with ultra-thin carbon of about 5 nm.In addition,it was found that the amount of glucose introduced in the reaction system,that is,the concentration of carbon,played a key role in regulating the microstructure of the sample.The C-20 electrode material had excellent electrochemical performance with a capacity retention of 49.84%after 100 cycles at 0.1 C and a discharge specific capacity of 381.8 m Ah g^-1,which was larger than that of the other carbon layer electrode materials.The results show that suitable carbon coating can effectively increase the electrode conductivity and enhance the structural stability of the electrode material.