Layered Oxides such as NCM111 are state-of-the-art cathode active materials (CAMs) for commercial applications as well as promising candidates for even higher energy density batteries by raising the nickel content up to 80% (NCM811) and beyond.¹ However, recent studies^2–4 have demonstrated the high reactivity of Ni-rich CAMs with CO₂ and moisture, which is highly problematic for industrial electrode manufacturing processes. In addition, the electrochemical performance of NCM811 is drastically deteriorated by CO₂ and moisture induced surface contamination.⁵

We present an in-depth surface analysis by X-ray photoelectron spectroscopy (XPS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) of NCM based cathode materials before and after exposure to CO₂-containing atmospheres with high relative humidity. In addition, we study the extent of surface contamination by performing thermogravimetric analysis coupled with mass spectrometry (TGA-MS). The impact on cell performance is revealed by gassing analysis via on-line electrochemical mass spectrometry (OEMS) and full-cell cycling tests. The impact of the Ni content on the surface contamination of NCM type CAMs as well as the role of the Brunauer-Emmet-Teller (BET) surface area will be elucidated. A possible strategy to mitigate the reactivity of CAM surfaces with CO₂ and H₂O might be the chemical modification of active material surfaces using analogous approaches to those proposed in the literature.^6–8 The effectiveness of such surface treatments to prevent surface contamination will be evaluated.

Acknowledgements:

This work is financially supported by the BASF SE Battery Research Network.

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