Research On Doping Modification Of MoO₃ Cathode Materials

As a green energy-saving energy storage device,lithium batteries have obvious advantages,such as high energy density,good cycle stability and small self-discharge.Therefore,lithium batteries have a very large market prospect and are widely used in electronic equipment such as computers,earphones and electric vehicles.The theoretical specific capacity of molybdenum oxide is up to 1000 mAhg^-1,which has a very abundant storage capacity in the country and is environmentally friendly.It is an ideal candidate cathode material.However,metal molybdenum is a transition metal element,its oxides have defects such as low ion or electron conductivity and unstable crystal structure.At the same time,The actual discharge specific capacity of MoO₃ is poor,so more research should be done on oxide MoO₃ as a positive electrode material used in lithium battery industryIn this paper,a two-step synthesis method,namely hydrothermal synthesis and subsequent heat treatment technology,is adopted.In the experimental process,K⁺ions are first introduced,and a K/MoO₃ mixture is prepared to realize the control of the patch structure with gully on the crystal surface.In addition,in order to further improve the electrochemical performance of K/MoO₃,K/MoO₃/C composites were prepared based on the optimization of K/MoO₃.（1）Using hydrothermal synthesis and subsequent heat treatment techniques,K⁺ions are distributed around the oxygen atoms due to the internal binding force of the crystal structure,so that the crystal tends to grow along the c-axis.When the content of KNO₃is 0.05 g,the product MoO₃ is transformed from a porous porous rod structure into a lumpy-like structure on the surface of the crystal,which increases the contact area between the positive electrode material and the electrolyte,and increases the discharge specific capacity of the product MoO₃.From the numerical analysis,the sample with no K doping MoO₃ has a first discharge specific capacity of 200 mAhg^-1 at a current density of 0.1 C,and the capacity retention rate is 40.5%after 100 cycles.Correspondingly,the K/MoO₃ composite with KNO₃ doping amount of 0.05 g has a first discharge specific capacity of 256 mAhg^-1,100 cycles,a specific discharge capacity of103 mAhg^-1,a capacity retention rate of 47%,and its cycle stability and capacity.Have been improved.（2）Based on the optimization of K/MoO₃,the K/MoO₃/C composite was prepared by coating the surface of K/MoO₃ composite with dopamine as carbon source and high temperature heat treatment technology.By compounding K/MoO₃ with C,it is possible to increase the conductivity and reduce the crystal size,so that the product K/MoO₃ has improved the capacity while improving the cycle stability.The research shows that when the dopamine is added in an amount of 0.04 g,the crystal structure of the product K/MoO₃/C is a nano-columnar structure.At a current density of 0.1 C,the first discharge specific capacity is 285 mAhg^-1,after 100 cycles,the discharge ratio The capacity is 140 mAhg^-1,and the capacity retention rate is 53%.The electrochemical performance is improved relative to the carbon-free K/MoO₃ composite.