Baris Key

From Grey Lab Page

I have been working on three projects covering research areas in both negative and positive electrode materials of lithium-ion batteries:

The first project involves the investigation of O₂ loss from Li[Ni_xLi_1/3-2x/3Mn_2/3-x/3]O₂ (0<x<1/2). Techniques such as MAS NMR, X-ray Diffraction and Pair Distribution Function (PDF) analysis, neutron diffraction and PDF analysis, X-ray Absorption Spectroscopy (XAS), and Gas Chromotography-Mass Spectrometry (GC/MS) are used to characterize the samples in the series in an effort to understand and quantify the changes occurring at high voltages upon charging and to explain the gain in capacity for the lithium-excess compounds.

The second project involves an investigation of the changes during the lithiation and delithiation of silicon for lithium-ion battery negative electrodes. This study involves mainly in-situ and ex-situ NMR techniques, X-ray and neutron PDF analysis. We've developed a flexible cell design and setup for static in-situ NMR measurements to capture processes which could not be detected by ex-situ methods. Furthermore, the use of local structure probes allowed us to monitor amorphous phases since crystalline silicon is converted into an amorphous lithiated silicon phase during its first discharge.

The in-situ NMR setup is useful for other systems such as investigation of fast changes in high-rate cathode materials in an actual lithium-ion battery. The sensitivity of in-situ NMR measurements are on the order of a few seconds which is sufficient to detect changes during very fast charging/discharging and subsequent relaxation processes. Thus, as a third project, we've been working with nanoparticulate LiCoO₂, but the method can be applied to a wide range of other systems where the NMR shifts of active materials are not governed by paramagnetism.

RECENT PUBLICATIONS

1- Naoko Yamakawa, Meng Jiang, Baris Key and Clare P. Grey, J. Am. Chem. Soc., 2009, ASAP articles [[1]]

2- Meng Jiang, Baris Key, Ying S. Meng and Clare P. Grey,, Chem. Mater., 2009, 21 (13), pp 2733–2745 [[2]]

3- Baris Key, Rangeet Bhattacharyya, Mathieu Morcrette, Vincent Seznec, Jean-Marie Tarascon and Clare P. Grey, J. Am. Chem. Soc., 2009, 131 (26), pp 9239–9249 [[3]]

Issue cover-art link for this article [[4]] Chemical and Engineering News link for this article [[5]]