Silicon Monoxide Anode Research Articles

Comparative Study on the Electrochemical Performances of SiO Anode Materials with Carbon-Coating and Boron-Doping for Lithium-Ion Batteries

Recently, Silicon monoxide (SiO) has been received much attention as an alternative choice instead of pure Si anode materials. When SiO anode undergoes lithiation processes, Li oxide (Li2O) and Li silicates (Li4SiO4) are mainly formed and that act as a more stable phase than the Li-Si alloys during long cycles. Moreover SiO is thermodynamically unstable at all temperatures, it can be easily transformed into nano-crystalline Si (nc-Si) and SiOx during heat treatment, triggering a disproportionation reaction. The nc-Si acts to increase the reversible capacity and the SiOx matrix plays an important role in accommodating the volume expansion of embedded nc-Si during alloying/de-alloying processes. However, the electrical conductivity of heat-treated SiO remains low because of this material’s intrinsic semiconductor nature and inactive phases. Carbon coating has been regarded as one of the most effective and typical ways to improve the electrochemical properties of SiOx. Dispersed carbon particles provide pathways for electron transfer and decrease the resistance of the electrode, thus resulting in improved conductivity and electrochemical properties of the SiO negative electrode. However, the local capacity fading caused by electrical loss between the active materials and the carbon coating is unavoidable during long cycle test. Moreover, carbon coating requires additional processing with carbon sources. In this study, we introduce a comparative study that consists of boron-doped SiO (HB-SiO) and carbon-coated SiO (HC-SiO) to verify the effective way for improving the electrochemical performances of SiO anode materials. From the electrochemical results, HB-SiO electrode exhibits about 1.6 times higher than that of HC-SiO electrode, having 611 mAh g-1 at 0.5 C rate after 500 cycles. Electrochemical impedance spectroscopy (EIS) measurement reveals that the internal resistance of the HB-SiO electrode is superior to that of HC-SiO electrode.

Electrochemical Properties and Thermal Stability of Silicon Monoxide Anode for Rechargeable Lithium-Ion Batteries

Electrochemical Properties and Thermal Stability of Silicon Monoxide Anode for Rechargeable Lithium-Ion Batteries

Nitrogen-doped carbon coating for a high-performance SiO anode in lithium-ion batteries

We report a simple process to coat silicon monoxide (SiO) particles with nitrogen-doped carbon layers (NC-SiO) by using a nitrogen-containing ionic liquid. The nitrogen-doping addresses the moderate electric conductivity of SiO particles as large as 20μm and thus enables NC-SiO to exhibit substantially improved specific capacity and rate performance as compared to those of bare carbon-coated SiO (C-SiO) and bare SiO counterparts. Due to the simplicity of the coating procedure, the current approach should be readily applicable to other lithium battery electrodes that suffer from low electronic conductivities.

Synthesis of SiO<SUB><I>x</I></SUB> Powder Using DC Arc Plasma

SiO(x) was prepared by DC arc plasma and applied to the anode material of lithium ion batteries. A pellet of a mixture of Si and SiO2 was used as the raw material. The ratios of the silicon and silicon dioxide (SiO2) mixtures were varied by controlling the Si-SiO2 molar ratio (Si-SiO2 = 1-4). Hydrogen gas was used as the reduction atmosphere in the chamber. The prepared SiO(x) was collected on the chamber wall. The obtained SiO(x) was characterized by X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). XRD and TEM showed that the phase composition of the prepared particles was composed of amorphous SiO(x) and crystalline Si. The prepared SiO(x) showed wire and spherical morphology. XPS indicated the bonding state and 'x' value of the prepared SiO(x), which was close to one. The result of prepared SiO(x) is discussed from thermodynamic equilibrium calculations. The electrochemical behavior of the silicon monoxide anode was investigated.

Reduction effect of irreversible capacity on SiO anode material heat-reacted with Fe2O3

Silicon monoxide (SiO) has a high-expected capacity and long cycle performance, but the first cycle's charge–discharge efficiency was lower than that of a conventional anode material. Recently, we have reported that the irreversible capacity was able to be suppressed based on the crystallinity of SiO. In order to decrease the oxygen defect and improve the crystallinity of SiO, Fe2O3 was reacted with SiO as an oxygen source then heat-treated at 800 °C. When the sample of the mixed SiO and Fe2O3 at a molar ratio of 1:0.2 was heated, Fe2SiO4 (fayalite) with the Pbnm olivine structure was uniformly formed on the SiO surface. It was confirmed that the efficiency of the first cycle's charge–discharge capacity improved in comparison to the conventional SiO.

Electrochemical behavior of carbon-coated silicon monoxide electrode with chromium coating in rechargeable lithium cell

The effects of Cr coating are studied with respect to improving the electrochemical characteristics of carbon-coated silicon monoxide anodes in rechargeable Li cells. The Cr coating is applied by ion beam sputtering. Analyses of the coating are carried out by EDX, SEM, TEM, and EPMA. A coin cell (CR2032) with a carbon-coated SiOx anode coated with Cr and a lithium cobalt oxide (LCO) cathode is assembled in an argon-filled glove box. The charged capacity of the Cr-coated SiOx–C/LCO cell is 1127 mAh g−1 in the 1st cycle at 0.1 C, while that of the uncoated SiOx–C/LCO cell is 956 mAh g−1. In addition, the Cr-coated SiOx–C/LCO cell has a discharged capacity of 733 mAh g−1, which is higher than that of the uncoated cell (635 mAh g−1). Furthermore, the discharge capacity retention ratio (100th:2nd) of the Cr-coated cell is 75% while that of the uncoated cell is 69%. The rate capability of the Cr-coated cell is superior to that of the uncoated cell. Cr has good electrical conductivity, enabling more Li ions to be stored in the Cr-coated cell than in the uncoated cell. Investigations into the improved electrochemical characteristics are carried out through the analyses of impedance, voltage profile, and cycle data.

Electrochemical Behaviors of Diamond-Like-Carbon-Coated Silicon Monoxide–Graphite Composite Anode for Li-Ion Battery

The effects of a diamond-like carbon (DLC) coating on a silicon monoxide–graphite composite electrode are studied in order to improve the electrochemical characteristics of silicon monoxide anodes. The DLC is applied through plasma-enhanced chemical vapor deposition and identified by high-resolution transmission electron microscopy, Raman spectroscopy, and electron microprobe analysis. DLC-coated silicon monoxide– graphite composite anode/LiCoO2 full-cells (CR2032) are then assembled in an argon-filled glove-box. The discharge capacity of the coated cell is 523 mA h g−1 at the first cycle and 409 mA h g−1 at the 100th cycle at a 0.5 C rate. The 100-cycle capacity retention is 78.2%, which is greater than that of the bare cell (52%). The improved electrochemical characteristics of the DLC-coated cell are determined through impedance, energy-dispersive X-ray, and scanning electron microscopy analyzes. Because the DLC has a high Young's modulus and chemical stability, the coated silicon monoxide– graphite composite maintains a high capacity during cycling.

High-performance porous silicon monoxide anodes synthesized via metal-assisted chemical etching

We describe a simple process for synthesizing three-dimensional porous silicon monoxide anode materials from bulk silicon monoxide powders by combining a galvanic displacement reaction and metal catalytic etching process. Silver nanoparticles that act as a catalyst were deposited on the surface of silicon monoxide via a galvanic reaction. Subsequently, the silver-deposited silicon monoxide particles were chemically etched to synthesize porous silicon monoxide particles, without changing the chemical and physical properties of SiO. The carbon-coated porous silicon monoxide anodes exhibited excellent electrochemical properties, including a high specific capacity (1520mAhg−1), a stable cycling retention (reversible capacity of 1490mAhg−1, after 50 cycles), and a high rate capability (74% at 3C rate, compared to 0.1C rate). This process may open up an effective way to make other porous semiconducting materials for a rich variety of applications, including lithium-ion batteries.

Electrochemical behavior of SiO anode for Li secondary batteries

The electrochemical behavior of the SiO (silicon monoxide) anode during its reaction with Li has been investigated using solid-state nuclear magnetic resonance (NMR) and high resolution transmission electron microscopy (HRTEM). It was mainly focused on identifying the intermediate and final phases formed with their microstructures of the electrochemically lithiated SiO at various voltage steps during the first cycle. A model for the reaction of SiO with lithium was suggested, which was consistent with the discharge capacity of about 2400mAhg−1.

Electrochemical behavior of a silicon monoxide and Li-powder double layer anode cell

A new technique for synthesizing double layer anodes with silicon monoxide and Li powder has been developed to reduce the initial capacity loss of silicon monoxide anodes. Double layer anode (DLA) cells are fabricated using Li emulsified powders on a Cu foil and silicon monoxide powders on a Cu mesh collector and their electrochemical behaviors are studied. The DLA cells show reduced initial irreversibility and enhanced coulombic efficiency. The coulombic efficiency of the first cycle of the DLA cell is over 100% and its capacity remains as 700 mAh g −1 up to 20 cycles. SEM observation shows that the Li-powder layer in DLA compensated for the initial irreversible loss and vanished after several cycles.

Electrochemical behavior of a lithium-pre-doped carbon-coated silicon monoxide anode cell

Owing to high energy density, silicon monoxide is an attractive anode material for lithium ion secondary batteries. However, its huge irreversible capacity during initial cycling makes it difficult to use in lithium secondary batteries. A new technique for lithiation in the silicon monoxide has been developed using Li powders. The electrochemical behavior of the lithium powder pre-doped carbon-coated silicon monoxide (OG) anode cell was studied. The cells showed reduced initial irreversibility and enhanced coulombic efficiency. The behavior of the cells was analyzed by X-ray diffraction and electrochemical testing methods.

Analysis of SiO Anodes for Lithium-Ion Batteries

The chemical structure of SiO (silicon monoxide) anodes has been analyzed using X-ray photoelectron spectroscopy (XPS). Vapor deposition was used to form SiO anodes on Cu film. XPS analysis was performed on anodes at each of three stages: after deposition, after initial charge, and after discharge. The results of this analysis were then evaluated in terms of the anode’s respective electrochemical characteristics. It has been found that some Si remains oxidized in the full charge state and that lithium silicates are formed. The lithium silicates serve as a buffer with respect to changes in anode volume.