3 research outputs found
Si Oxidation and H<sub>2</sub> Gassing During Aqueous Slurry Preparation for Li-Ion Battery Anodes
Si
has the possibility to greatly increase the energy density of Li-ion
battery anodes, though it is not without its problems. One issue often
overlooked is the decomposition of Si during large scale slurry formulation
and battery fabrication. Here, we investigate the mechanism of H<sub>2</sub> production to understand the role of different slurry components
and their impact on the Si oxidation and surface chemistry. Mass spectrometry
and in situ pressure monitoring identifies that carbon black plays
a major role in promoting the oxidation of Si and generation of H<sub>2</sub>. Si oxidation also occurs through atmospheric O<sub>2</sub> consumption. Both pathways, along with solvent choice, impact the
surface silanol chemistry, as analyzed by <sup>1</sup>H–<sup>29</sup>Si cross-polarization magic angle spinning nuclear magnetic
resonance (MAS NMR) and attenuated total reflectance Fourier transform
infrared spectroscopy (ATR FTIR). An understanding of the oxidation
of Si, during slurry processing, provides a pathway toward improving
the manufacturing of Si based anodes by maximizing its capacity and
minimizing safety hazards
Correction to “Si Oxidation and H<sub>2</sub> Gassing during Aqueous Slurry Preparation for Li-Ion Battery Anodes”
Correction to “Si Oxidation and H<sub>2</sub> Gassing during
Aqueous Slurry Preparation for Li-Ion Battery Anodes
Chemical Evolution in Silicon–Graphite Composite Anodes Investigated by Vibrational Spectroscopy
Silicon–graphite
composites are under development for the
next generation of high-capacity lithium-ion anodes, and vibrational
spectroscopy is a powerful tool to identify the different mechanisms
that contribute to performance loss. With alloy anodes, the underlying
causes of cell failure are significantly different in half-cells with
lithium metal counter electrodes compared to full cells with standard
cathodes. However, most studies which take advantage of vibrational
spectroscopy have only examined half-cells. In this work, a combination
of FTIR and Raman spectroscopy describes several factors that lead
to degradation in full pouch cells with LiNi<sub>0.5</sub>Mn<sub>0.3</sub>Co<sub>0.2</sub>O<sub>2</sub> (NMC532) cathodes. The spectroscopic
signatures evolve after longer term cycling compared to the initial
formation cycles. Several side-reactions that consume lithium ions
have clear FTIR signatures, and comparison to a library of reference
compounds facilitates identification. Raman microspectroscopy combined
with mapping shows that the composite anodes are not homogeneous but
segregate into graphite-rich and silicon-rich phases. Lithiation does
not proceed uniformly either. A basis analysis of Raman maps identifies
electrochemically inactive regions of the anodes. The spectroscopic
results presented here emphasize the importance of improving electrode
processing and SEI stability to enable practical composite anodes
with high silicon loadings