Operando ambient pressure photoelectron spectroscopy of solid/liquid interfaces in Li-ion batteries

• Ambient pressure photoelectron spectroscopy (APPES) is combined with electrochemistry (EC) to investigate the interface between the liquid electrolyte and the solid electrode in Li-ion battery (LIB) cells. The combination of these techniques is promising for further understanding the functionality of LIB interfaces, but it is also associated with several experimental challenges. In this work a functional EC-cell which allows for probing the solid/liquid interface is achieved by the dip-and-pull method. Two systems consisting of a 1M LiClO4 in propylene carbonate electrolyte and a sputter deposited lithium cobalt oxide (LCO) or lithium nickel manganese cobalt oxide (NMC) thin film electrode are investigated. A methodology for combined EC/APPES measurements is proposed, where continuously changing the measurement spot is necessary to avoid accumulation of surface species during X-ray exposure. The APPES spectra from the LCO and NMC electrodes show binding energy (BE) shifts depending on applied voltage. It is argued that this is related to the lithiation of the material, as the BE shifts are found to coincide with expected phase transitions to more conductive phases. The experimental data is compared to results from supercell DFT calculations modelling the bulk material. The opposite trends observed in the experimental and computational approaches indicate the importance of an accurate treatment of the exchange for a proper description of the oxidation states of the Co atoms and their corresponding core-level shifts. 

Ämnesord

NATURVETENSKAP  -- Kemi -- Materialkemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Materials Chemistry (hsv//eng)

NATURVETENSKAP  -- Fysik -- Den kondenserade materiens fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Condensed Matter Physics (hsv//eng)

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