Synthesis Of Germanium-based Anode Materials And Their Lithium Storage Properties

Germanium-based materials have been proven to have excellent lithium ion storage capabilities and are considered to be one of the most promising candidates to replace graphite anodes for commercial lithium ion batteries?LIBs?.Nevertheless,germanium-based anode materials have huge volume changes during the lithiation/delithiation progress,which seriously affects the cycle performance of the battery and strongly prevents their commercial application.In this paper,Ge/Fe_xGe@C nanowires and Cu₃Ge/Ge@C nanorods were prepared by hydrothermal treatment and subsequent high temperature thermal reduction.At the same time,Li₂Ti Ge O₅,Li₂Ge O₃ and Li₂Ge O₃/G composites were obtained by ball milling and heat treatment.The use of these germanium-based materials as anodes for LIBs showed greatly improved cycle performance and rate capability.The main contents are as follows:1.Ge-Fe-O_x/EDA bimetal oxide nanowires were synthesized by hydrothermal treatment,with Ge O₂,Fe₂O₃ and EDA as raw materials.After coating with carbon,Ge-Fe-O_x/EDA bimetal oxide nanowires were reduced at high temperature,resulting in Ge/Fe Ge/Fe Ge₂@C nanowires.The carbon-coated nanowire design effectively enhances the structural stability of the anode.When Ge/Fe Ge/Fe Ge₂@C is used as anode material for LIBs,it still has a high specific capacity of 547 m Ah g^-1 after cycling400 times at a current density of 1 A g^-1.2.Single crystal Cu Ge O₃ nanorods were obtained by heating Ge O₂,Cu?CH₃COO?₂·H₂O and EDA in a stainless steel reactor at 160°C for 24 h.Then Cu Ge O₃ nanorods were coated with dopamine hydrochloride and reduced under high temperature in H₂/Ar mixed atmosphere to obtain Cu₃Ge/Ge@C nanorods.This peapod-like porous carbon-coated nanorod structure and the introduction of the inactive phase Cu₃Ge can not only accelerate charge transfer,but also effectively limit volume expansion,which greatly improves the cycle life of the material.When Cu₃Ge/Ge@C is used as anode material for LIBs,the specific discharge capacity is 956 m Ah g^-1 after500 cycles at a current density of 0.2 A g^-1.And after 200 cycles at a current density of1 A g^-1,it still has a high capacity of 756 m Ah g^-1.3.Li₂Ti Ge O₅ was prepared from Ge O₂,Ti O₂ and Li₂CO₃ through multiple planetary ball milling and high-temperature heating.When Li₂Ti Ge O₅ is used as anode electrode material for LIBs,the capacity is 190 m Ah g^-1 after 420 cycles at a current density of 5 A g^-1;with two steps of planetary ball milling and high temperature heat treatment,Li₂Ge O₃?with raw materials of Ge O₂,Li₂CO₃?and Li₂Ge O₃/G?with raw materials of Ge O₂,Li₂CO₃and EG?were synthesized.As anode materials for LIBs,the specific discharge capacity of Li₂Ge O₃ is 570 m Ah g^-1 after 100 cycles at a current density of 1 A g^-1;while the capacity of Li₂Ge O₃/G electrode is 632 m Ah g^-1after 150cycles under a higher current density of 2 A g^-1,showing improved stability under high current density.