Composition Design And Structure Regulation Of Mo-based Anode Materials And Their Energy Storage Mechanism Research

Efficient energy storage system is essential for humankind to promote the sustainable development.Mo-based anode materials,such as MoO₃,are considered as ideal candidates for battery energy storage systems due to their rich valence,diverse physical and chemical properties.However,the practical application of MoO₃ is limited by its poor intrinsic conductivity and serious volume expansion during discharge-charge.Based on the above analysis,MoO₃ was purposely modified from the composition design and structure regulation,for example,creating oxygen vacancy,special morphologies design,and the introduction of Co ion and NH₄⁺,to prepare MoO_3-x@glucose,MoO₃ nanoplates,Co MoO₄and 3D porous nitrogen-doped carbon(NH₄)₂MoO₄.Subsequently,the electrochemical performance for lithium/sodium storage of Mo-based anode materials were studied.Furthermore,the energy storage mechanism of electrode materials during discharge-charge was revealed.The contents of this thesis are summarized as follows:1.Due to the pulverization issue of MoO₃electrode during discharge-charge,MoO_3-x@glucose composites were designed and synthesized by a green vacuum drying method through crystal structure regulation.The intercalation and reducibility of glucose were used to enlarge the interlayer spacing and create oxygen vacancies of MoO₃.Meanwhile,glucose molecules are connected by hydrogen bonds to form uniform colloid coated on MoO_3-x surface.This unique"encapsulation structure"enables MoO_3-x@glucose to act as a soft frame to firmly hold the powdered electrode material during discharge-charge,which allows the subsequent reactions to proceed in a confined space,thereby ensuring the integrity of the electrode.When used as an anode for lithium ion battery,it remains 607 mAh g^-1 high discharge capacity at 1A g^-1 after 200 cycles.This work is expected to provide some clues for the design of conversion electrode materials for lithium ion battery in the future.2.To improve the pulverization issue of MoO₃electrode during discharge-charge,MoO₃ nanoplates with rigidity and flexibility were successfully synthesized by using Mo-MOFs as self-sacrifice template through microstructure structure regulation.The nanoplates structure can effectively buffer the stress caused by volume change during discharge-charge,which prevents the electrode from pulverization.When used as sodium ion battery electrode,it shows up to154 mAh g^-1high discharge capacity at 50 m A g^-1 after 1200 cycles.This work provides a new insight into the design of structural morphologies to prevent pulverization in other anode materials during discharge-charge.3.Through element composition design,Co MoO₄ nanorods with micro-nano structure were prepared by introducing Co elements with rich valence state into MoO₃ using Mo-Co bimetallic complex as template.This Co MoO₄ nanorods can reduce the side reaction between electrode and electrolyte during discharge-charge and effectively buffer stress,which shows excellent lithium and sodium storage performance.It exhibits 528 mAh g^-1 high discharge capacity for lithium ion battery at 1 A g^-1 after 1000 cycles,and shows 84 mAh g^-1 high discharge capacity for sodium ion battery at 0.1 A g^-1 after 1000 cycles.This work provides a new method which is simple,easy to control and mass preparation of Co MoO₄ nanorods.Meanwhile,it also provides a new experimental idea for preparing other molybdates.4.Based on the template effect of Mo-MOFs and its own characteristics of carbon and nitrogen,and ammonia generated by urea at high temperature.The 3D porous nitrogen-doped carbon(NH₄)₂MoO₄ composites were synthesized by“fumigation reaction”using Mo-MOFs and urea in a closed container.Compared with the structure of MoO₃,the NH₄⁺ions between the layers of(NH₄)₂MoO₄ ensure the stability of the[MoO₄]tetrahedron in the entire structure during the Li insertion process,which can effectively prevent electrode from pulverization.When used as anode for lithium ion battery,it shows 1838 mAh g^-1 high discharge capacity at0.5 A g^-1 after 200 cycles.This work further enriches the Mo-based material system,and promotes ammonium molybdate application and development in lithium ion battery and sodium ion battery.