Efficiency Threshold of Carbon Layer Growth in Li₄Ti₅O₁₂/C Composites

Abstract

The core-shell morphology study is crucial for composite materials, comprised of a low conductive core with a highly conductive thin carbon shell. The study analyzed carbon morphology evolution for the two series of Li 4 Ti 5 O 12 /C samples with carbon content increasing from 0.9 to 5.6 wt%. The conventional X-Ray Photoelectron Spectroscopy (XPS) study allowed us to conclude about the efficiency threshold of carbon layer growth over lithium titanate core for two carbon deposition methods-both sucrose and acetylene decompositions. Although the carbon layer thickness is increasing with carbon concentration growth in LTO/C composites, the efficiency of carbon coverage was shown to decrease with the threshold carbon concentrations about 1-2%. The chemical bonding analysis based on the same XPS data was used for C@LTO interface characterization. The proposed approach can be used for optimization of producing different composites with core-shell structure (carbon-based composites, materials with protective layers, and materials with gradient core-shell structure).

Statistical Raman spectroscopy characterization of carbon additive in low‐C composites: Toward industrial quality control

“…Herein, we study LTO/C composites and suppose that I C /I LTO value characterizes how carbon additive covers the LTO core particles (carbon layer coverage efficiency). For the same carbon deposition method, the particle with more uniform carbon layer is expected to have a higher I C /I LTO value, less uniform one—lower value.…”

“…The right shift of the histograms is an obvious result, corresponding to carbon content growth, but the histogram broadening (for both samples) is more interesting. In our recent paper, the XPS data analysis has allowed us to conclude about threshold behavior of carbon layer growth . It implies that at concentrations below some threshold value (C th about 1.0–1.5%), the carbon layer coverage efficiency is higher and becomes much lower above C th .…”

“…LTO was sintered by the conventional solid‐state synthesis method using lithium carbonate (Li 2 CO 3 ) and titanium dioxide (TiO 2 ) in anatase form (99.9% chemical purity both). See more details about synthesis in our work . LTO/C composite was obtained by two methods: sucrose and acetylene decompositions.…”

“…High‐resolution transmission electron microscopy is, maybe, the most popular scientific tool for thin carbon layer morphology control, but its usage is complicated for relatively large particles (few hundred nanometers and more) with thin carbon layers (few nanometers and less). Moreover, high‐resolution transmission electron microscopy can hardly provide proper statistical analysis (see discussion, for example, in Pelegov, Koshkina, Pryakhina, and Gorshkov), and it is inconvenient and too expensive for industrial in‐line quality control. X‐ray photoelectron spectroscopy (XPS) combines nanoscale in‐depth probing with averaging over a number of particles, but XPS also needs a high vacuum chamber, which is not typical for electrode material mass‐production lines thus resulting in additional complicated system of sampling and manipulation.…”

“…Moreover, high‐resolution transmission electron microscopy can hardly provide proper statistical analysis (see discussion, for example, in Pelegov, Koshkina, Pryakhina, and Gorshkov), and it is inconvenient and too expensive for industrial in‐line quality control. X‐ray photoelectron spectroscopy (XPS) combines nanoscale in‐depth probing with averaging over a number of particles, but XPS also needs a high vacuum chamber, which is not typical for electrode material mass‐production lines thus resulting in additional complicated system of sampling and manipulation. Therefore, the Raman spectroscopy (RS) with its relatively low cost and applicability for routine quality control (both incoming and outgoing) looks like a good candidate for the industrial low‐C composites quality control tool.…”