The Synthesis, Characterization And Electrochemical Properties Of Nanostructured Electrode Materials For High-capacity Lithium Batteries

The rapid development of mobile application areas such as implantable medical devices,electric vehicles and communications equipment,has brought unprecedented opportunities and challenges for primary and rechargeable lithium batteries. High-capacity,long-life and high-safety electrode materials are the focus of research in the fields of lithium batteries.Currently,the electrochemical performance of lithium batteries is limited due to the low utilization efficiency,slow diffusion of the lithium ion as well as severe polarization problem of the traditional electrode materials.The high reactivity,favourable charge transport properties and novel structural merits of nanomaterials make them suitable alternative to effectively improve the performance of lithium batteries.On the other hand,α-CuV₂O₆ and other transition-metal vanadates,and Si are potential electrode materials for lithium batteries.The relationship between their composition,structure,morphology and properties needs to be further studied.Therefore,this dissertation focuses on the preparation,characterization and electrochemical investigation of transition metal vanadates and Si nano/microstructures.The main content is as follows.The one-dimensional(1D)α-CuV₂O₆ nano/microstructures were successfully synthesized via a simple and facile low-temperature hydrothermal approach based on the "Ostward ripening-splitting" mechanism.The Li-ion intercalation mechanism and electrochemical properties of theα-CuV₂O₆ nanowires were investigated in detail. Electrochemical measurement results demonstrated that the as-preparedα-CuV₂O₆ nanowires displayed a discharge capacity of 514 mAh/g at 20 mA/g,and activation energies of 35.7-39.3 kJ/mol,which are superior to that of theα-CuV₂O₆ mesowires, microrods and bulk particles due to the large surface area and short Li-ion diffusion route of the nanowires.This result indicates that theα-CuV₂O₆ nanowires are promising cathode candidates for primary lithium batteriesPorous FeVO₄ nanorods and nanoparticles were prepared by a two-step process including a hydrothermal route and a calcination process.Electrochemical measurements revealed that the porous FeVO₄ nanomaterials exhibit further improved electrochemical performance.Particularly,the porous FeVO₄ nanorods retain a high discharge capacity of 760 mAh/g after 20 cycles,indicating their potential application in rechargeable Li batteries.Furthermore,the CoV₂O₆ nanowires and Co₂V₂O₇ microflakes were also obtained by hydrothermal method and preliminarily investigated as anode materials in rechargeable Li batteries.Silicon hollow nanospheres were successfully synthesized via a modified solvothermal approach.The growth mechanism and electrochemical properties of the Si hollow nanospheres were further investigated in detail.The results show that the Si hollow nanospheres retain a high capacity of 1095 mAh/g after cycling up to 48 cycles at 2000 mA/g.The superior electrochemical performance rises from the fact that the hollow nanospherical structure can reduce the stress caused by the volume change of the Si electrode during the charge/discharge process and restrain the aggregation of the nanomaterials.This work opens a new route for the performance improvement of rechargeable Li battery.