Study On The Preparation Of Ge/C Anode Materials From Organic Hybrid Nano-precursors

Germanium has a high theoretical specific capacity(1600 mAh·g^-1)and volume specific capacity(8500 mAh·cm^-3)to Li/Li⁺,and is a very promising anode material for high-energy lithium-ion batteries.However,huge volume changes during lithiation/delithiation processes,leading to cracking and pulverization of the electrode materials,In this paper,a variety of organic-inorganic hybrid materials were designed and successfully used as precursors for Ge/C composite anode materials.The structure of the precursors was designed to construct a stable,interconnect composite interface inside the anode material to achieve a high stable discharge capacity.The problem is to improve the electrochemical performance such as the capacity of the negative electrode and the stability of the cycle.The paper systematically studied the relationship between material preparation process,microstructure and electrochemical properties.A variety of organic hybrid nano-precursors were synthesized by sol-gel method and hydrothermal method,and a continuous composite interface was prepared by reductive sintering.The Ge/C composite anode material achieves a substantial increase in energy density and cycle stability of the anode material.In this paper,the synthesis process of MXDA-Ge Ox hybrid precursor and the structure and electrochemical properties of the Ge/C composite anode material were studied.Electrochemical studies have shown that the reversible capacity,rate performance and cycle stability of the Ge/C composite anode material prepared by the hybrid precursor have been significantly improved compared with the Pure Ge anode material.In order to obtain better cycle stability,the formation of a protective SEI film can be promoted to stabilize the composite structure by increasing the charge and discharge voltage range or by adding a VC electrolyte additive.In order to study the effect of the composite interface on the electrochemical properties,a continuous Ge/C composite interface with two interpenetrating layers was constructed,and an open framework citrate compound was used as a precursor.Using a stainless steel as the substrate and MXDA as template,a new mesoporous open framework was successfully synthesized,which was named NUDT-1,and nanosheets and nanowires with the structure were obtained.Temperature,time and composition ratio of substrate-assisted hydrothermal method were changed.By using ethylenediamine and isopropanolamine as templats,ASU-14 and PKU-17 were obtained,respectively.The obtained open-frame nano-precursor is subjected to reduction sintering to prepare a ruthenium-carbon composite anode material,and the capacity level,cycle stability and rate performance of the material are greatly improved by optimizing the sintering process.Individual materials exhibit excellent rate performance.Among them,the initial discharge specific capacity of ASU-14 nanowire-derived composite anode material at 0.2C was 1632.7 mAh·g^-1,the first charge specific capacity was 1456.3mAh·g^-1,and the first coulombic efficiency was 89.2%.After 100 cycles,the discharge specific capacity was attenuated to 1202.3 mAh·g^-1,and the capacity retention rate was82.5%.