The Design,Preparation And Lithium Storage Performances Of Germanium-based Anode Materials For Lithium Ion Batteries

With environment and energy problems becoming more and more seriously,the exploitation of energy storage electronics which have high energy density,long cycle life,high safety coefficient have attracted much interest for scholars in all over the world.Recently,Germanium?Ge?has been supposed to be the greatest potential candidate for new-type composite electrodes for lithium-ion batteries?LIBs?,due to their excellent capacity properties,high energy density and structure characteristics.Based on the above advantages,this paper used commercial GeO₂ microparticles to prepare Germanium-based materials and explored their lithium storage performance as electrode materials for LIBs.The related works are shown as follows:1.Germanium-based materials possess promising potential as novel anode materials for high performance LIBs.However,the considerably huge volume change causes rapid capacity fade during the charge-discharge process.A simple strategy was devised to prepare porous GeO2 nanoparticles via thermal decomposition of?Hbipy?2[Ge?C2O4?3]·2H2O in air atmosphere.As an anode material for LIBs,it shows superior electrochemical performance in comparison with commercial GeO₂ microparticles.The initial discharge capacity of porous GeO₂ nanoparticles is high to 2578.8 mA h g^-1,and it still retained 581.9 mA h g^-1after 100 cycles.Even at 2 A g^-1,a reversible discharge capacity of 184.2 mA h g^-1 is yet obtained.The superior lithium storage performances should be chalked up to the positive synergism of nanoscale,porous structure and low crystalline nature,which effectively retard the huge volume change of GeO₂ and are beneficial for fast diffusion of lithium ions during cycling.2.Germanium oxide,which possesses great potential as a high-capacity anode material for LIBs,has suffered from its poor capacity retention and rate capability due to significant volume changes during lithiation and delithiation.In this study,we introduce a simple synthetic route for producing nanosized GeO₂ anchored into biomass-derived hierachical porous carbon?HPC?with a large specific surface area and porous structure and N-dopping.As a negative electrode material for LIBs,GeO₂/HPC exhibited high specific capacity and excellent cycling performance compared with pure HPC;and exhibited a discharge capacity of 2261.4 mA h g^-1 at 200 mA g^-1.After 100 cycles,the reversible capacity of LIBs reached1014.3 mA h g^-1.The excellent lithium storage performances of GeO₂/HPC is due to the direct contact between the biomass carbon and the well-dispersed GeO₂.Herein,the nitrogen doped-carbon matrix not only strengthens the structure but also promotes the lithium diffusion in the GeO₂/HPC material.The nano-porous structure can buffer large volume expansion and increase electron conductivity at the same time,and solves the main problem of pulverization and poor cycling due to volume expansion in the lithiation/delithiation process of GeO₂.3.To improve the electrical conductivity and cycling stability of germanium compounds as anode materials for LIBs,Zn₂GeO₄ nanorods grown on carbon cloth?Zn₂GeO₄/CC?were designed and fabricated by a simple hydrothermal process combined with a post-annealing treatment.The Zn₂GeO₄/CC composites possess hierarchical porosity and a network structure.Serving as free-standing and binder-free anodes for LIBs,they exhibit high specific capacity and excellent reversibility.A discharge capacity as high as 1851.9 mA h g^-1is attained at a current density of 200 mA g^-1,and the Zn₂GeO₄/CC electrode still maintains a high reversible capacity of 1302.3 mA h g^-1 after 200 cycles.Even at a high specific current of 2000 mA g^-1,it still retains a capacity of 847.5 mA h g^-1.The superior electrochemical performance of the Zn₂GeO₄/CC composites is attributed to the synergistic effects of the hierarchical porosity,Zn₂GeO₄ nanorods,and 3D carbon cloth network structure,which can effectively accommodate the huge volume change of the Zn₂GeO₄nanorods during cycling and maintain perfect electrical conductivity throughout the electrode.Moreover,the excellent mechanical flexibility of the Zn₂GeO₄/CC composites makes the material a promising candidate for self-supported and flexible electrodes for LIBs.