An In Situ Study of the Electrochemical Reaction of Li with Amorphous∕Nanostructured Cu6Sn5 + C

Abstract

The reaction of lithium with a nanostructured Cu 6 Sn 5 + C alloy having approximate composition Sn 27 Cu 31 C 42 was studied using in-situ x-ray diffraction (XRD) and 119 Sn Mössbauer effect spectroscopy. Lithiation of the Cu 6 Sn 5 + C was found to occur with the formation of an amorphous/nanostructured Li x CuSn-like phase where x increases with decreasing voltage. The formation of amorphous/nanostructured grains of Li 4.4 Sn and/or Li 2 CuSn-like phases contained in a disordered partially lithiated carbon matrix was found at the bottom of discharge. The expulsion of copper from the Li x CuSn-like phase(s) to form nanostructured Li 4.4 Sn is difficult to detect in the present measurements. No crystalline components were found during lithiation and delithiation of the electrode material. The smooth sloping discharge curve during the lithiation of Sn in the amorphous/nanostructured material has resemblance to those previously seen in amorphous Sn 30 Co 30 C 40 and amorphous Sn-Si mixtures. Hyperfine parameters found in the present work at given voltages closely resemble those found in the literature for bulk Cu 6 Sn 5.

In situ methods for Li-ion battery research: A review of recent developments

“…This design does allow penetration of the incident X-ray beam, but this setup is also relatively vulnerable to air and moisture contamination. Therefore normally only a small part of the electrode is exposed by creating a hole in a much thicker protective casing or current collector, which in turn is sealed by an X-ray transparent material such as a Kapton foil [6] or Beryllium [7]. However Be, more particularly Be-oxide, is highly toxic and for the study of cathodes an additional protective layer is required to prevent corrosion of the beryllium at higher potentials.…”

“…Slight variations in the observed resonance frequencies give detailed information about the local electronic environment around the nucleus. The local electronic environment of 7 Li (and 6 Li) can adequately be probed by NMR and, consequently, yields information about the Li environment and electrochemically induced structural changes of electrodes during or after cycling.…”

“…As an alternative a more robust cylindrical cell has been designed by Poli and colleagues [76]. 7 Li NMR has shown to be an adequate technique to investigate anode materials. An elaborate overview has been provided by Blanc et al [77].…”

“…From the measured data, the authors quantified the salt diffusivity and the Li þ transport number on the basis of a physical mass transport model. Krachkovskiy and colleagues [81] applied 1D 7 Li NMR imaging in combination with slice-selective NMR to measure the Li þ self-diffusion coefficients in liquid electrolytes.…”

“…To prevent loss of intensity, isotopically enriched 7 Li electrodes can be applied, as 6 Li species are able to absorb neutrons [99]. To investigate thin films electrodes, custommade electrochemical cells are used [100,101].…”