3rd Workshop on the Simultaneous Combination of Spectroscopies with X-ray Absorption, Scattering and Diffraction Techniques

Structural investigations of Li2MnO3∙Li(NixCoyMnz)O2 – Neutron diffraction, in situ X-ray diffraction, and in situ Raman spectroscopy

5 Jul 2012, 10:30

1h 30m

Main Hall HG E

Poster contribution Materials / Nanomaterials Poster Session

Speaker

Mr Peter Bleith (Paul-Scherrer-Institute)

Description

LiCoO2 is today’s standard cathode material for Li-ion batteries. Li2MnO3∙Li(NixCoyMnz)O2 (NCM) is a very promising candidate to replace LiCoO2 since it shows an approx. 2 times higher specific charge and is less expensive. We investigated the structural changes of NCM upon charge and discharge with ex situ neutron diffraction, in situ X-ray diffraction, and in situ Raman spectroscopy. The in situ XRD measurements were performed at SLS (X04) in a “coffee bag” cell using an automatic sample changer. The neutron diffraction was performed at SINQ (HRPT). The in situ Raman spectroscopic measurements were performed on a LabRAM HR (HoribaJovinYvon SA), using a He-Ne laser as excitation source (632.8 nm, 18 mW) in a cell which allows for recording of Raman spectra from the backside of the electrode. Data from the diffraction techniques showed the phase transitions during galvanostatic cycling. NCM showed an expansion of the c axis during charging and proved a release of oxygen at 4.5 V which was also detected with Differential Electrochemical Mass Spectrometry (DEMS). NCM also showed changes in Raman spectroscopy according to the processes visible in the galvanostatic curve. The new set of peaks cannot yet be ascribed to a phase and two hypotheses are under investigation: An NCM layer without lithium or MnO2 created by Li2MnO3 activation, which means release of oxygen. In short, the combiniation of these techniques gave the opportunity to understand the reaction mechanism of NCM.