Nano-composite Si particle formation by plasma spraying for negative electrode of Li ion batteries

Abstract

Nano-composite silicon powders have been produced at a maximum process throughput of 6 g/min by plasma spraying with metallurgical grade silicon powder as raw material. The obtained powders are found to be fundamentally composed of crystalline silicon particles of 20-40 nm in diameter, and are coated with an $5-nm-thick amorphous carbonous layer when methane gas is additionally introduced during plasma spraying. The performance of half-cell batteries containing the powders as negative electrodes has shown that the capacity decay observed for the raw Si coarse particles is significantly improved by plasma treatment. The carbonous coating potentially contributes to an improvement in capacity retention, although coexisting SiC particles that inevitably form during high-temperature processing reduce the overall capacity. V C 2014 AIP Publishing LLC.

High throughput production of nanocomposite SiOxpowders by plasma spray physical vapor deposition for negative electrode of lithium ion batteries

“…Crushed raw SiO powders were first sieved to a mean diameter of 165 μ m. These powders were fed from the top of the dc torch such that the powders passed through the highest temperature zone in the plasma jet preferentially. The powder feeding rate was adjusted to 8 g min −1 at the maximum, taking into account of the thermal load for the complete evaporation of the Si powders under the present plasma condition [12]. CH 4 gas was also introduced to the plasma from the top of the plasma torch to maintain overall C/Si molar ratios of 0.25, 1 and 1.5.…”

“…Meanwhile, as an industrial-compatible approach that is capable of production of nanostructured powders at high throughputs, we have employed plasma spraying physical vapor deposition [12]. Nanoparticles of several tens of nm in size were produced at >360 g h −1 from metallurgical-grade Si powders and the improvement in the specific capacity retention was confirmed for batteries with these powders as the negative electrode.…”

Instantaneous formation of SiOx nanocomposite for high capacity lithium ion batteries by enhanced disproportionation reaction during plasma spray physical vapor deposition

“…[32,38–40] In the present work, we employ rather simple model proposed by Ulrich,[40] which is confirmed to reproduce at least the growth of Si nanoparticles in PS-PVD. [30] Compared to the growth of Si, collision between SiO and H 2 molecules in the plasma gas would become important as is found experimentally in the reduction of SiO in the Ar + H 2 plasma. Therefore, the growth inhibition factor, which is the ratio of the collision frequency of SiO particles with respect to that between SiO and H 2 , is introduced in the SiO particle number density evolution, assuming that the SiO molecule that collides with H 2 does not participate in the SiO growth.…”

“…Schematics of the system can be found elsewhere. [30] To modify the nanoparticle structures, two plasma conditions, at which different powder heating and cooling histories are expected, are employed; condition [A] as the typical PS-PVD and [B] for an increased quenching capability. The detailed plasma conditions are listed in Table 1.…”

Modeling and simulation of a turbulent‐like thermal plasma jet for nanopowder production

“…Furthermore, a thermal plasma has a steeply decreasing temperature gradient at its fringe, where the material vapor rapidly changes into nanopowder. Taking advantage of these two characteristics, thermal plasma has achieved the one‐step production of nanopowders with very high yields .…”