Synthesis Of Ge-based Nanomaterials As Anode Materials For Lithium Ion Batteries

In recent years,the rapid expansion of electronic devices and electric vehicle technology have inspired to the research of a new generation of anode materials for lithium-ion batteries?LIBs?with safe,cheap,long cycle life and high specific capacity.As we know,the commercialized carbon-based materials,such as graphite anode electrode possesses a lower theoretical capacity,and limits the improvement of LIBs with high capacity.Germanium base materials are a kind of high capacity electrode materials,therefore,it is considered to be a promising candidate anode materials for substituting graphite.But high capacity anode materials still run into the bottleneck problems during the research process,mainly include the following two aspects: 1)the low efficiency and complex preparation;2)large volume changes upon Li-ion insertion/extraction,resulted in a rapid irreversibility capacity fade and the poor cyclability.Therefore,many efforts have been trying to solve these problems,such as fabricating low dimensional nanostructure,alloying with metals,designing hollow/porous structure and hybrizing with carbon nanocomposite.The concept of this work is to insight into the materials relationship between structural evolution and battery performance during electrochemical reactions.The main research and innovations of this thesis are as follows:1)Synthesis of amorphous GeO_x hollow spheres and the lithium storage electrochemical properties.The formation of homogeneous amorphous GeO_x hollow spheres were ascribed to the release of lots of H2 bubbles by Na BH4 in reducing process,which regarded as a soft template to form hollow spheres.The discharge capacity of the amorphous GeO_x hollow sphere was approximately 794 m A h g-1 after 100 cycles.2)Synthesis of Ge/C composite and the lithium storage electrochemical properties.We employ a relatively facile sol-gel strategy at room temperature and followed by carbonization/crystallization approach tofabricate porou Ge/C composite materials.The unique 3D structure exhibits high porosity and well-defined network morphology.The Ge/C composite exhibited high reversible capacity and excellent cyclability.As for anode,the Ge/C electrodes exhibited high reversible specific storage capacity(1016 mAhg^-1 at current density of 100mAg^-1)and long cycling life.3)Synthesis of Zn₂GeO₄@C nanorod composite as high-capacity anode for lithium-ion batteries.In this paper,Zn₂GeO₄ nanorods have been synthesized using a hydrothermal method.Using dopamine hydrochloride as carbon source to deposit Zn₂GeO₄ nanorods,and then heated at N₂ atmosphere,Zn₂GeO₄@C nanorod composite could be obtained.The Zn₂GeO₄@C nanorods have much higher reversible specific capacity of 635 m Ahg^-1 after 100 cycles,compared to that of Zn₂GeO₄ nanorods.The Zn₂GeO₄@C nanorods could be used as a candidate as high-capacity anode for lithium batteries.