Design And Preparation Of Ferrosilicon Alloy-based Anode Materials For High Performance Lithium Ion Batteries

With the expansion of the market and the continuous increasing of higher energy and power densities of lithium-ion batteries?LIBs?,the performances of the electrode materials should be improved.As the core component of LIB,investigation on the improvement of the performance of the anode is always one of the hot fields for LIBs.The theoretical specific capacity of commercial graphite is 372 m A h g^-1,which can not meet the requirement of the next LIBs with higher energy densities.Because of their high theoretical specific capacities,silicon-based anode materials are expected to become one of the next generation of commercial anode materials for LIBs.However,there are huge volume changes of silicon-based materials during the discharge-charge processes,which result in their poor cycle stability.This paper firstly focus on the design and preparation of high performance silicon-based anode materials,and then develop the preparation procedures for large-scale production of silicon-based anode materials with superior electrochemical performances,using the cheap and commercial ferrosilicon alloy as the origin silicon source.By exploring the influence of ball milling modes and time,the calcination temperatures and atmosphere,as well as the different amounts of graphite for compositing on the electrochemical performance of the as-prepared samples,the suitable process parameters for the preparation of Si-based material with best electrochemical performance and the fundamental composition-structure-performance relationship are obtained.The main research contents and results are as follows:?1?The effects of different ball-milling modes and calcination times on the structure and properties of ferrosilicon alloy anode materials were studied.It is found that the particle sizes of the anode material are largely reduced by ball-milling process and the thickness of Si O_x layer originated from the calcination process plays important effect on the improvement of the cyclic stability of the final anode materials.The electrochemical results indicate the Fe-Si@Si O_x material,which is obtained from the dry ball-milling process for 10 h with calcination for 4 h at 800 under the air atmosphere,displays the best electrochemical performance,with an initial specific capacity of?1012.0 m A h g^-1 and 59.7%of capacity retention ratio after 400 cycles at a discharge-charge current density of 500 m A g^-1.?2?The effect of ball grinding time on the structure and properties of ferrosilicon alloy anode material was further studied.A series of Fe-Si@Si O_x materials were prepared by dry ball-milling for different time and then the same calcination conditions.It is found that the Fe-Si@Si O_x?FS-S-10@SO?achieved from the dry ball-milling process for 10 h with calcination for 4 h at 800?under the air atmosphere,displays the best electrochemical performance,with an initial specific capacity of?1012.0 m A h g^-1 and 59.7%of capacity retention ratio after 400 cycles at a discharge-charge current density of 500 m A g^-1.?3?The effect of the electrochemical performances of the different amount of graphite?G?for the compositing of FS-S-10@SO were studied.A series of FS-S-10@SO/G composites were prepared by ball-milling of FS-S-10@SO and different amount of graphite.It is found that the FS-S-10@SO/G composite obtained from the compositing of FS-S-10@SO and graphite in a mass ratio of 5:3 exhibits the best cycle and rate performances,with a specific capacity of 500 m A h g^-1 and 89.1%capacity retention after 500 cycle at a discharge-charge current density of 0.5 A g^-1.