Micro/Nano Structure Design And Electrochemical Performance Investigations Of Electrode Materials In Sodium/Magnesium Ion Battery

In the future,with the large-scale application of electric vehicles and energy storage grids,lithium batteries have several drawbacks associated with their potential safety issues,high cost,and resource scarcity.Conversely,sodium and magnesium ion batteries have been proposed as cheaper,safer next generation advanced battery systems because of their friendliness to the environment,rich global reserves,low cost and other advantages.In the basic composition of battery,the development of electrode materials is a major bottleneck for improving the performances of the sodium/magnesium ion battery and reducing the cost.Therefore,designing and developing high-performance electrode materials and solving problems encountered in various materials have important scientific and practical application values for the development of sodium/magnesium ion batteries.The purpose of this thesis is to utilize reasonable structure design for obtain high performance electrode materials.Simultaneously,based on the deep analysis of the structure-performance relationship in materials,we are hunting for and developing new high-performance electrode materials The main research results include the following aspects:1.A P2-type Na0.7Ni0.18Mn0.64Co0.18O2 with hierarchical ball-in-ball structure was designed and synthesized as cathode material for sodium ion batteries.It is a ball-in-ball hierarchical microsphere assembled from nanosheets with a size of 300-500 nm.In the oxide cathode material,the influence of this micro-nano structure on the battery performance is rarely studied.In fact,this work provides an interesting research model to lay the groundwork for understanding the structure-activity relationship between the structural and electrochemical properties of sodium-based layered oxide materials.At the same time,the electrochemical results show that the micro-nanostructured material not only possesses ultra-high capacity,but also has excellent rate performance.In addition,we studied the whole electrochemical process by using synchrotron-based X-ray absorption spectroscopy.The results show that the material has good reversibility.We believe that this work can provide a new idea for the design of novel high-performance sodium-based layered oxide cathode materials and open up a new window for the development of cathode materials in sodium-ion batteries.2.Single-crystal Prussian blue(FeHCFe)nano-frame/single-wall carbon nanotube(SWCNT)composites were designed and prepared as a cathode material for sodium-ion batteries without binders.The design of Prussian blue hybrid composite structure is an effective method to improve the performance of the material.The experimental results show that the composite exhibits ultra-high rate performance(35.0 mAh g-1 at 100 C)and outstanding cycle stability(with a capacity retention rate of 92%at 5 C after 500 cycles).With the help of soft and hard X-ray absorption spectroscopy,we explained why the as-prepared cathode exhibits so enhanced performances and then described its reaction mechanism.This work provides a good reference for the future development of new high-energy other Prussian blue analogue cathode materials.The Prussian blue hybrid composite is expected to be widely used in the research of Prussian blue analogues.3.On the basis of the above-mentioned synthesis of Prussian blue work,we used the prepared core-shell Prussian blue analog @ dopamine as a template to one-step vulcanization and carbonization.Ultimately,we obtained a Fe0.6Coo.3Ni0.1S2 nanoparticle that was confined into a nitrogen-doped carbon nanobox.As negative electrode of sodium ion battery,the material has higher electron conductivity and richer redox couple;the carbon layer of the shell protects the active particles.In this way,the frame structure can remain intact when the sodium ions are repeatedly deintercalated.The experimental results show that the material has extraordinary electrochemical stability and rate performance because of its special design.The material is a potential high-performance anode material.Our design ideas provide useful inspiration for the development of novel micro-nano-anode materials with higher capacity and better electrochemical performance.Meanwhile,we can expand new ideas for the metal-organic framework compound derived sodium ion battery electrode materials.4.We used layered MoS2 nanosheets as positive electrodes for magnesium ion batteries,and pre-prepared[Mg2Cl3]+·[AlPh2Cl2]-/THF(APC)solutions as electrolyte,high-purity magnesium foil(99.9%)as negative electrodes.Magnesium ion batteries were assembled in the argon-filled glove.The test results show that our battery is working properly.The MoS2 nanosheet releases a capacity of 99.5 mAh g-1.Even at a high current density of 200 mA g-1,it still have 8.9 mAh g-1 capacity.These experiences laid a solid foundation for us to establish a complete magnesium ion battery assembly process.