Carbon Coating Influence on the Formation of Percolating Electrode Networks for Silicon Anodes

Abstract

Previous studies have demonstrated that chemical vapor deposition carbon coating on silicon (Si@C) can enhance the electrochemical performance of lithium-ion batteries with Si-based anodes. However, the underlying mechanisms contributing to this improvement have not been fully explored. We address this knowledge gap by applying a suite of characterization methods to evaluate Si@C anodes prepared by reducing acetylene on ball-milled Si particles. Raman mapping measurements show that the C coating (<5 nm thick) enables a homogeneous Si and carbon distribution during the slurry casting process, thereby promoting Si utilization during cycling. The coating’s microstructure and morphology were evaluated using X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy, and neutron reflectivity experiments. Electrochemical impedance spectroscopy measurements upon cycling indicate that carbon coating also reduces the overall resistance as benchmarked against bare Si anodes. Galvanostatic cycling in half-cell studies revealed higher initial Coulombic efficiency and specific capacities with increasing carbon coating time. However, solid electrolyte interphase (SEI) investigations using XPS showed that the coated and uncoated samples have very similar characteristics, suggesting that the SEI may only play a minor role in enhancing the performance of Si@C. Full-cell evaluation of the Si electrodes was consistent with half-cell results relating to performance and SEI properties, further supporting the conclusion that electronic and ionic percolation, enabled by effective electrode manufacturing, are the dominant factors contributing to the favorable performance of Si@C.

Conductive carbon embedded beneath cathode active material for longevity of solid-state batteries

“…, D-band at 1377 cm −1 and G-band at 1584 cm −1 ), are colored red. 39,40 The average domain size of the carbon-rich area is 10–20 μm, which is consistent with the pc-NMC811 particle size. Since pc-NMC811 particles are decorated on the RGO framework, as confirmed by the SEM images in Fig.…”

Elucidating the Role of Carbon Conductive Additive in the Processing and Electrochemical Behavior of Surface-Modified Si Anodes

“…Super C45 carbon black, Super C65 carbon black, and graphite were chosen to examine the effects of particle size, surface area, and morphology of the additive on the processing and performance of Si. Initially, ζ potential measurements , were performed to gauge the dispersibility or stability of the carbon additives in suspension. This aspect is crucial in electrode manufacturing as it directly impacts the uniformity of the coating on the current collector.…”

“…Initially, ζ potential measurements , were performed to gauge the dispersibility or stability of the carbon additives in suspension. This aspect is crucial in electrode manufacturing as it directly impacts the uniformity of the coating on the current collector. To simulate the conditions of the slurry preparation of the Si electrodes, the experiments were performed in NMP solvent and the measurements were taken immediately after preparation of the suspensions.…”

“…In our earlier studies on Si-based electrodes, ,, we employed Raman mapping to examine the distribution of Si and carbon within the top 1 μm of the cast. Raman mapping lends itself particularly useful to studies related to carbon conductive additives since it does not detect carbon from the polymeric binder, allowing us to determine the relative abundance of Si and the conductive carbon. , The characteristic peaks of Si appear at ∼520 cm –1 (crystalline) and ∼480 cm –1 (amorphous) ,, in the Raman spectra of the pristine electrodes presented in Figure a–c. In addition, the Raman active bands for carbon black show up at ∼1355 cm –1 (D band) and ∼1590 cm –1 (G band) in Figure a,b.…”

“…Solution 2 was used for the measurements, which were performed using phase analysis light scattering (PALS) mode for ζ potential, while dynamic light scattering (DLS) was employed to determine the particle size. Each measurement was the average of 100 cycles. , The same procedure was performed for different carbon powders.…”