Design,Preparation And Energy Storage Performance Of Titanium-Based Metal Organic Compound-Derived Nanostructures

Titanium-based nanomaterials,such as titanium dioxide and lithium titanate,have been widely used in various industries because of their excellent physical and chemical properties,abundant resources,and convenient preparation processes.Especially in the field of electrochemical energy storage fields,including lithium-ion batteries,sodium-ion batteries,and lithium-sulfur batteries,titanium-based nanomaterials have attracted intensive attention of the scientific and industrial fields,because of their excellent rate performance and cycle stability.However,traditional titanium-based nanomaterials also have their own problems,such as high platform voltage and low capacity,which seriously affects the energy density of battery and confined their further promotion and application in the field of small electric vehicles.To overcome these challenges,enrgy scientists are paying more attention to metal titanate anode materials,for example,zinc titanate,nickel titanate,and cobalt titanate,due to their higher capacity,lower operating voltage,as well as the excellent cyclic stability similar to lithium titanate.Based on the above background,titanium-based nanomaterials with a new tubular structure are designed and synthesized by adopting the metal material organic compound derivation strategy in this dissertation.The mechanisms behind the synthesis and assembly of the novel titanium-based binary metal organic crystal materials?M-Ti-EG,M is Ni,Co and Zn,EG is ethylene glycol?,and the energy storage performance of their derivatives for lithium?sodium?ion batteries and lithium-sulfur batteries have been thoroughly studied and discussed.The specific results are as follows:?1?A series of M-Ti-EG are designed and prepared.Their synthesis and assembly mechanism are explored through studying the influences of he synthesis temperature,reaction time and transition metal element properties on the synthesis phenomenon,the size and morphology of the products Ni-Ti-EG,Co-Ti-EG,Zn-Ti-EG micron rod-like metal organic compound by using a series of in-situ optical and Ex-situ electron microscopy.The preliminary research results show that during the assembly process of M-Ti-EG,there are scientific mechanisms and phenomena such as"confined nucleation-filled crystal flower","secondary self-assembly regrowth"and"growth in digestion equilibrium".The nature and type of elements have an important influence on product growth rate,size and thermal stability.Among them,Zn-Ti-EG has the longest nucleation and growth time,and the product size is the longest?up to 40 microns?,but the equilibrium temperature for the growth and digestion of the product during the reaction is low,so that Zn can be achieved by adjusting the reaction temperature.-Controllable preparation of Zn-Ti-EG microtubes.?2?Zinc titanate?A-ZTO?and zinc titanate/carbon?ZTO/C?are obtained by micro-tubular Zn-Ti-EG metal organic compounds as raw materials after low-temperature annealing in air and argon atmosphere,respectively Two porous microtube derivative materials.Thanks to its unique porous tube structure,it can not only provide a fast migration channel for carriers,but also effectively buffer the volume expansion caused by the electrode during the process of charging and discharging.Both exhibit stable and fast lithium and sodium storage performance,especially ZTO/C has a uniform and continuous three-dimensional conductive network,and the stable and fast performance characteristics are more prominent.Electrochemical performance studies have shown that after 5000 cycles at 10 A g^-1,the lithium storage capacity loss rate of both is less than 10%,but the lithium storage performance of ZTO/C is significantly better than that of A-ZTO.At 5 A g^-1,the discharge capacity of ZTO/C is 281 m Ah g^-1at the 50th cycle,which is much higher than the discharge capacity of the A-ZTO anode in the same situation(217 m Ah g^-1).In addition,ZTO/C also exhibits relatively excellent anodic sodium-ion storage performance.At 0.1 A g^-1,the discharge capacity of ZTO/C at the 20th cycle is 278 m Ah g^-1.After 1000 cycles cycle at 5 A g^-1,the capacity can still maintain 108 m Ah g^-1.The observed energy storage performance of ZTO/C are much better than A-ZTO anode and other general transition metal titanate anode materials.?3?Using Zn-Ti-EG microtubes as raw materials,Ti N mesoporous microtubes were successfully synthesized by high-temperature selective evaporation and ammonia high-temperature nitridation.The excellent conductivity of Ti N,the porous tubular structure and the excellent chemical adsorption performance of lithium polysulfide are in line with the requirements of lithium-sulfur batteries for sulfur cathode carriers.Lithium performance.The results of electrochemical studies show that under a sulfur loading of about 1 mg cm^-2,the discharge capacity of the S@Ti N positive electrode at current densities of 0.02 C and 1 C are 954 and 560 m Ah g^-1,respectively.After a long cycle of 500 cycles at the current density of 0.5 C,the capacity retention rate of the S@Ti N positive electrode is 45.5%.In summary,the metal-organic compound-derived porous titanium-based metal oxide or nitride compound developed in this paper exhibits excellent energy storage performance,and has wide application prospects in the field of energy storage as a multifunctional material.In addition,the assembly mechanism of M-Ti-EG binary metal organic crystal compounds disclosed in this paper will provide valuable guidance and reference for the future controllable preparation and morphology control of M-Ti-EG and similar materials.