Study On The Preparation And Electrochemical Energy Storage Properties Of Molybdenum And Manganese Oxides

Lithium-ion batteries have been widely used in portable electronic devices and electric vehicles due to their high energy density,no memory,long cycle life,light weight and so on.Currently,the anode material of commercial lithium ion battery is graphite with low theoretical capacity(372 m A h g^-1).Therefore,it is very important to find electrode materials with excellent cycling performance and good stability for the development of the next generation of lithium ion battery.Transition metal oxide materials have the advantages of high theoretical capacity,abundant reserves,environmental friendliness and so on,and can be used as the novel anode materials to replace the commercial graphite anode materials.However,due to the low first cycle efficiency and poor structural stability of transition metal oxides,their applications as anode of lithium ion batteries are limited.In view of the above problems,the active anode materials with excellent specific capability and rate performance were prepared by optimizing the morphology,structure and composition of products.Relevant content is as follows:1.Study on the preparation and electrochemical properties ofγ-Mn OOH.In this work,a hydrothermal reduction route was utilized for the controlled production of Mn OOH nanohydrangeas and Mn OOH nanorods.As the active anodes,galvanostatic charge-discharge,cyclic voltammogram,rate performance and electrochemical impedance were analyzed to compare the lithium ion energy storage performances of two formed Mn OOH nanostructures.The results indicate thatγ-Mn OOH nanorods possess enhanced cycle and rate capacity comparing with theγ-Mn OOH nanohydrangeas.At a current density of 0.2 A g^-1,a specific capacity of 965 m A h g^-1 is obtained for the formedγ-Mn OOH nanorods after 200 cycles,while the reversible capacity of Mn OOH nanohydrangeas is 380 m A h g^-1,which suggests that morphology variation of as-prepared Mn OOH nanostructures can influence the electrochemical properties.γ-Mn OOH nanorods synthesized by this method present a prospective application for lithium ion batteries.2.Study on the preparation and electrochemical properties ofα-MoO₃ structures.Orthorhombicα-MoO₃ is one thermodynamically multifunctional material and presents significant performance in lithium-ion batteries.It is interesting to synthesize regularα-MoO₃ structures through a facile method that can deliver a high reversible capacity and excellent capacity retention property.In this work,sheet-likeα-MoO₃microstructure and strip-likeα-MoO₃microstructure were prepared and utilized as anodes of Li-ion battery.The Li⁺insertion-extraction process and the Li storage performance were investigated.After 400 cycles,the reversible capacity of sheet-likeα-MoO₃ microstructure and strip-likeα-MoO₃ microstructure maintained at 1064.7 and 1143.4 m A h g^-1 at the current density of0.5 A g^-1.Furthermore,strip-likeα-MoO₃ microstructure can deliver a stable specific capacity of 554.4 m A h g^-1 at the current density of 5.0 A g^-1.The excellent reversible capacity and cycle capability suggested that the strip-likeα-MoO₃ microstructures present promising application in lithium ion batteries.3.Study on preparation and electrochemical properties of binary metal oxideα-Mn MoO₄.α-Mn MoO₄ with a high theoretical specific capacity is a promising lithium-ion battery anode material.Due to the synergic effects of multiple transition metals and the better electrical conductivity than that of single metal oxide,the dual metal oxides exhibit superior performance to single transition metal oxide.In this work,a simple hydrothermal reduction method was applied for the synthesis ofα-Mn MoO₄.Dart-likeα-Mn MoO₄microstructures and nanosheet-based flower-likeα-Mn MoO₄microstructures can be prepared by regulating the content of molybdenum acetylacetone in the initial reactants.The electrochemical measurements show that the dart-likeα-Mn MoO₄microstructures and nanosheet-based flower-likeα-Mn MoO₄microstructures can deliver the specific capacities of 1054 m A h g^-1 and 1027 m A h g^-1at the current density of 0.5 A g^-1 after 100 cycles.Besides,the two formedα-Mn MoO₄ present a stable rate performance under a current density of 0.2-5 A g^-1,which suggests thatα-Mn MoO₄ can be used as a good candidate as an anode material.