Energy Storage Characteristics And Structural Evolution Of Silicon-based Nano-alloy Particles

In recent decades,lithium-ion batteries have become the best choice for portable electronic products and hybrid vehicles due to their advantages of good stability,high capacity,and environmental friendliness.However,the theoretical capacity of the negative electrode material graphite for commercial lithium-ion batteries is 372 m Ah·g^-1cannot meet the needs of electric vehicles and large-scale energy storage,and there is an urgent need to develop a negative electrode material with a larger specific capacity.The content of silicon is the second in the earth's crust.It has abundant reserves and no pollution to the environment.The theoretical specific capacity at room temperature is 3579 m Ah·g^-1,which is about 10 times that of graphite.It exists in the form of Li₁₅Si₄,and the voltage platform is lower than 0.5V(vs.Li)./Li⁺),has a good application prospect.Nevertheless,due to some technical challenges,silicon anodes have not yet been commercialized.First,pure silicon expands in volume by more than 300%during the lithium-ion insertion/extraction process,causing cracks on the surface of the silicon particles,and the active material is separated from the current collector.In addition,with the occurrence of cracks,a new SEI film is continuously produced between the active material and the electrolyte,resulting in an increase in impedance and a sudden drop in capacity;most importantly,silicon is a semiconductor material with poor electrical conductivity.Therefore,in the actual application process,the silicon anode has a poor cycle life and a low coulombic efficiency.In this context,the good conductivity and ductility of transition metal elements are used to prepare silicon-transition metal alloy nanoparticles by DC arc plasma method,and the mass ratio of silicon to transition metal is changed to prepare alloy nanopowders with different compositions.X-ray diffraction(XRD),transmission electron microscope(TEM),scanning electron microscope(SEM),X-ray electron spectroscopy(XPS)were used to micro-characterize the prepared materials.The results showed that the silicon-transition metal alloy nanoparticles The microscopic morphology is a spherical structure of 20-80 nm.Under constant current charge and discharge conditions,when the current density is 500 m A·g^-1,the first discharge specific capacity is about 2400 m Ah·g^-1,and after 100 cycles,the discharge specific capacity is 1140 m Ah·g^-1,the remaining capacity is about 48%.When the current density is 1 A·g^-1,the first discharge specific capacity is about 2400 m Ah·g^-1,after 100 cycles,the discharge specific capacity is 653 m Ah·g^-1,and the remaining capacity is 27.3%.After the current density is 100 m Ah·g^-1,200 m Ah·g^-1,500 m Ah·g^-1,1 A·g^-1,5 A·g^-1 and the rate performance test,the capacity remaining about 70.2%when the current density returns to 100m Ah·g^-1,performance good reversibility.