Abstract
The chemical and electrochemical insertion of lithium into the spinel structure of CuCr(2)Se(4) was studied and the chemical reaction pathway was followed by ex situ X-ray diffraction on samples with different Li contents. The electrochemical reaction was investigated by in situ X-ray diffraction and in situ scanning electron microscopy. In the early steps of chemical intercalation, two phases with a different Li content coexist and Cu is extruded from the host material. After 4 days of Li intercalation, a conversion reaction is observed. The overall Li uptake is 8 Li ions per formula unit. The structural behaviour of the two intercalated phases at the early stages of intercalation is totally different. For one phase a strong expansion of the a-axis is observed while for the other phase it is only slightly affected by Li uptake. A three-step mechanism was found consisting of reduction of Se(-) followed by a Cu-Li exchange and finally a complete reduction of Cr(3+) to the metallic state accompanied by the formation of Li(2)Se. The discharge capacity of the first cycle amounts to 530 mAh g(-1) and drops to about 380 mAh g(-1) in the fifth cycle. In in situ SEM images the occurrence of Cu whiskers that partially grow out of the crystallites can be observed.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.