Topological Synthesis And Electrochemical Properties Of Porous Titanium-Based Anode Materials

With the progress of society and the development of civilization,lithium-ion battery has been vigorously developed in recent years as the mainstream clean energy and has been diffusely used in many fields.Traditional lithium-ion batteries usually use graphite or carbon materials as the anodes.However,their structural stability is generally poor,resulting in bad long-cycle performance and low electrochemical performance at high current density.At the same time,due to their low lithium inlayable potential(≈0 V vs Li+),lithium dendrites are easy to be generated in the battery cycling,which may cause a series of safety problems.Therefore,it is of great significance to develop safe,stable and excellent lithiumion battery anode materials.Titanium-based anode materials usually have more stable crystal structure,so there is no crystal structure collapse during charging and discharging,which greatly improves the cycle stability of the battery.At the same time,they have a higher lithium impingement potential(≈0.5 V or 1.5 V vs Li+),which can effectively avoid the generation of lithium dendrites in the battery cycling.In addition,titanium-based anode materials usually do not change in volume during the charge-discharge cycle of the battery,showing "zero strain" characteristics,so such materials tend to have longer battery life.Compared with graphite materials,although titanium-based anode materials show more excellent stability and safety,they have no obvious advantages in terms of capacity,so relevant modification treatment is required.The study shows that the electrochemical performance of electrode materials can be effectively improved by adjusting their micromorphology and it is a more economical and simple way.Among them,the construction of porous morphology is one of the common schemes.Based on the above research status,this paper takes the preparation of titanium base anode material with low cost and easy operation as the principle,takes the control of favorable microstructure as the policy,and takes effectively improving electrochemical performance as the core research goal to carry out systematic research work,and obtains the following results:(1)Using layered titanate H1.07Ti1.73O4·H2O(HTO)as a precursor,Zn2+was exchanged into the layers of HTO through ion exchange,and porous plate-like Zn2Ti3O8 particles were prepared by the in-situ topological reaction at a certain temperature.At the electrochemical performance measurement of the lithium-ion half-battery,it exceeded most literature reports.What’s more,we conducted a systematic study on the electrochemical reaction mechanism of Zn2Ti3O8 for the first time.The electrochemical reaction type was confirmed(intercalation reaction),and the electrochemical reaction equation was deduced and the theoretical capacity was calculated for the first time by first principles(266 mAh/g).Besides,the correlation analysis confirmed that this special porous platelike morphology can not only introduce a large amount of pseudocapacitance,but also promote the intercalation reaction of Zn2Ti3O8 to the maximum extent,which made Zn2Ti3O8 particles show excellent electrochemical properties.(2)In view of Zn2Ti3O8 as a potential new titanium anode material,further modification of Zn2Ti3O8 was studied.By electrostatic force,the Zn2+ intercalated HTO was laid on the graphene oxide sheet.After subsequent heat treatment,they formed the two-dimensional laminated rGO@Zn2Ti3O8 complex.Due to the introduction of reduced graphene oxide(rGO),its electrical conductivity was significantly improved,and a large number of heterogeneous planes between the two particles induced more pseudocapacitance behavior,which greatly increased its reversible capacity to 668 mAh/g and made its electrochemical properties further enhanced.(3)In view of the proven performance improvement of the anode material brought by the porous plate morphology,we modified the previous preparation process and prepared the porous plate-like Li4Ti5O12.In the half-battery test,its reversible capacity was significantly improved due to the introduction of pseudocapacitance and showed enhanced electrochemical kinetics performance.In the full-battery test,it not only shows good compatibility with commercial lithium iron phosphate LiFePO4,but also shows excellent electrochemical performance and good application prospect.(4)By exploring and summarizing the above-mentioned preparation processes of Zn2Ti3O8 and Li4Ti5O12,porous plate-like Li2ZnTi3O8 particles with similar morphology were prepared successfully and the formation mechanism of their morphology and structure was studied deeply.Through analysis,a large number of pseudocapacitance have been successfully introduced and formed a lithium storage mode that works with intercalation reaction.This coexistence energy storage mode enables the electrode to store more Li+when working,and the porous plate-like Li2ZnTi3O8 reaches the maximum capacity of Li2ZnTi3O8based anode electrode(338 mAh/g).Meanwhile,it makes the anode be abled to maintain excellent performance in long cycle test under high current density.In terms of electrochemical reaction kinetics,the two-dimensional plate structure provides a flat path for electron transport and reduces the charge transfer resistance.At the same time,the micropores on its surface could provide a faster channel for Li+diffusion,greatly increasing the diffusion rate of lithium ions.The simple and high-yield preparation method and its excellent electrochemical performance make it very likely to be a new generation of cathode materials for lithium-ion batteries.(5)In view of the pseudocapacitance characteristics and excellent performance advantages brought by the porous structure for electrode materials,TiO2 particles with porous plate-like morphology were prepared by using HTO as a titanium source and directly by heat treatment.After analysis of the test related to lithium-ion batteries,the porous plate-like TiO2 particles obtained at different heat treatment temperatures have a great improvement in the rate performance,reversible capacity and kinetic characteristics compared with commercial TiO2.As the porous structure can effectively improve the diffusion rate of ions and provide diffusion channels for larger ions,we conducted a performance test for sodiumion batteries here.The results show that porous plate-like TiO2 can still show excellent electrochemical performance when serving as the anode electrode of sodium-ion batteries,and it is a potential multi-purpose anode electrode material for batteries.In this study,a systematic study was carried out on a variety of titanium base anode materials with porous structure prepared by layered titanate H1.07Ti1.73O4·H2O(HTO)as titanium source,exploring the advantages of porous structure for the improvement of electrochemical performance.The synthesis of related materials and the construction method of porous morphology in this work are simple,economic,and excellent electrochemical performance of the products can be achieved,which provides the preparation idea and research basis for the construction of porous electrode materials.