Synthesis and Characterization of Si-Cu Composite Anode Materials for Lithium-ion Batteries
Date Issued
2006
Date
2006
Author(s)
Wang, Jen-Hao
DOI
en-US
Abstract
The main purpose of this study is to explore new anode materials based on silicon for lithium-ion battery. Although silicon possesses a higher theoretical capacity (~3000 mAh/g) than graphite (372 mAh/g), the dramatic volumetric variation during cycling and intrinsic low conductivity, which resulted in structural instability and poor cyclability, obstruct its commercial application.
Si-Cu composite materials are developed by two different methods to overcome the inherent problems of silicon. One is fluidized-bed type reduction (FB-reduction) with the precursor of CuCl powder, and the other is electroless plating in which formaldehyde was served as a reducing agent. Copper has been successfully reduced by both synthesized routes; however, the quality of coating was not satisfactory for FB-reduction and only a “Si + Cu” mixture was formed. Poor electrochemical performance hence has been observed for Si-Cu composites by FB-reduction due to inability to tolerate the volume expansion of silicon, in spite of the enhancement of electrode conductivity.
Contrarily, scanning electron microscope (SEM) images show that more conformity and uniformity of coating can be achieved by using electroless plating and the cyclability, as compared with pure Si electrode, has been thereby improved. To enhance mechanical strength of the copper layer, fluidized-bed chemical vapor deposition (FB-CVD) technique has been carried out to coat a further carbon film on Si-Cu composites. Results show that the electrode made by electroless plating and heat treatment, comparing with Si electrode (<8 cycles), can be greatly improved to 60 cycles without fading at the discharge capacity of 1000 mAh/g.
A new material copper silicide (Cu3Si) is found for Si-Cu composites after heat treatment in FB-CVD. In-situ X-ray diffraction shows that Cu3Si is a partially inactive material in the reaction of lithium. Moreover, electrochemical performance of single phase Cu3Si electrode has been studied.
Subjects
鋰離子二次電池
矽
流體化床
化學氣相沈積
無電鍍
Lithium-ion batteries
silicon
fluidized-bed
chemical vapor deposition
electroless plating
high energy ball milling
SDGs
Type
thesis
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