Functionalized Silicon Particles for Enhanced Half- and Full-Cell Cycling of Si-Based Li-Ion Batteries

Abstract

Vinylene carbonate (VC) and polyethylene oxide (PEO) have been investigated as functional agents that mimic the solid electrolyte interphase (SEI) chemistry of silicon (Si). VC and PEO are known to contribute to the stability of Si-based lithium-ion batteries as an electrolyte additive and as a SEI component, respectively. In this work, covalent surface functionalization was achieved via a facile route, which involves ball-milling the Si particles with sacrificial VC and PEO. Thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy indicate that the additives are strongly bound to Si. In particular, MAS NMR shows Si−R or Si−O−R groups, which confirm functionalization of the Si after milling in VC or PEO. Particle size analysis by dynamic light scattering reveals that the additives facilitate particle size reduction and that the functionalized particles result in more stable dispersions based on zeta potential measurements. Raman mapping of the electrodes fabricated from the VC and PEO-coated active material with a polyacrylic acid (PAA) binder reveals a more homogenous distribution of Si and the carbon conductive additive compared to the electrodes prepared from the neat Si. Furthermore, the VC-milled Si strikingly exhibited the highest capacity in both half-and full-cell configurations, with more than 200 mAh g −1 measured capacity compared to the neat Si in the half-cell format. This is linked to an improved electrode processing based on the Raman and zeta potential measurements as well as a thinner SEI (with more organic components for the functionalized Si relative to the neat Si) based on XPS analysis of the cycled electrodes. The effect of binder was also investigated by comparing PAA with P84 (polyimide type), where an increased capacity is observed in the latter case.

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

“…Previous studies demonstrated that structural hetero-geneity can be unveiled by the K-means clustering analysis on the Raman mapping of the object. 24,33,45,46 Briefly, this method groups the total number (denoted as n) of Raman spectra (x 1 ,x 2 ,x 3 ...x n ) within the Raman mapping into K sets (K ≤ n) to minimize the sum of squares within-cluster, defined by the objective function, J, as…”

“…The corresponding Raman maps of the electrodes generated through K-clustering means analysis are presented in Figure c,d. Previous studies demonstrated that structural heterogeneity can be unveiled by the K-means clustering analysis on the Raman mapping of the object. ,,, Briefly, this method groups the total number (denoted as n ) of Raman spectra ( x 1 , x 2 , x 3 ... x n ) within the Raman mapping into K sets ( K ≤ n ) to minimize the sum of squares within-cluster, defined by the objective function, J , as J = arg .25em min ∑ i = 1 k ∑ x ∈ S i ∥ x − c i ∥ 2 in which c i is the mean of points (or centroid), serving as the cluster spectrum in the K set, S i . The value of the centroid is updated iteratively, c i new , based on c i new = 1 false| S i false| ∑ x j ∈ S i x j The n spectra can be grouped into clusters based on their similarities.…”

“…Samples were prepared by making dilute dispersions of the Si powder in n -methyl-2-pyrrolidone (NMP). The details were reported elsewhere . The zeta potential was determined using the phase analysis light scattering (PALS) mode, and each measurement was the average of 100 cycles.…”

“…The electrodes were dried at 100 °C on a hot plate to remove the NMP solvent. Prior to battery assembly, the electrodes were annealed at 350 °C at 1 h under an argon atmosphere using a ramp rate of 10 °C min –1 . The final mass loadings of the electrodes were approximately 1.1–1.2 mg Si cm –2 .…”

One-Pot Controllable Synthesis of Silica Nanocapsules with Encapsulated Osmanthus Fragrance for Durable Odor Improvement of Leather

“…In detail, the first segment of the weight loss occurred at around 130 °C as a result of the complete decomposition of OF. The second phase was in the range of 173–280 °C, which was due to the decomposition of the organic silane. When the temperature rose to 600 °C, the weight losses of SiO 2 NPs and OF-SiO 2 NCs were about 29.2 and 47.4%, dividedly. By calculation, the loading efficiency of OF was determined to be 17.6%.…”