A Low-Cost and High-Capacity SiO_x/C@graphite Hybrid as an Advanced Anode for High-Power Lithium-Ion Batteries

Abstract

Silicon suboxide (SiO x ) is one of the most promising anodes for the next-generation high-power lithium-ion batteries because of its higher lithium storage capacity than current commercial graphite, relatively smaller volume variations than pure silicon, and appropriate working potential. However, the high cost, poor cycling stability, and rate capability hampered its industrial applications due to its complex production process, volume changes during Li + insertion/extraction, and low conductivity. Herein, a low-cost and high-capacity SiO x /C@graphite (SCG) hybrid was designed and synthesized by a facile one-pot carbonization/hydrogen reduction process of the rice husk and graphite. As an advanced anode for lithium-ion batteries, the SiO x /C@graphite hybrid delivers a high reversible capacity with significantly enhanced cycling stability (842 mAh g –1 after 300 cycles at 0.5 A g –1 ) and rate capability (562 mAh g –1 after 300 cycles at 1 A g –1 ). The great improvement in performances could be attributed to the positive synergistic effect of SiO x nanoparticles as lithium storage active materials, the in situ-formed carbon matrix network derived from biomass functioning as an efficient three-dimensional conductive network and spacer to improve the rate capability and buffer the volume changes, and graphite as a conductor to further improve the rate capabilities and cycling stability by increasing the conductivity. The low-cost and high-capacity SCG derived from rice husk synthesized by a facile, scalable synthetic method turns out to be a promising anode for the next-generation high-power lithium-ion batteries.

Effect of Pitch Coating on SiOx Alloy/Spherical Artificial Graphite Composites as Anode Materials for Lithium‐Ion Batteries

“…And from the second cycle, cathodic peaks between 0.1 and 0.2 V representing the alloying of LixSi appeared, and no anodic peak at broad 0.68 V representing the lithium‐desertion section of SiOx appeared. From these results, it was confirmed that dealloying of Li x Si was slowly generated over a wide voltage range due to the pitch coating layer [16,39–40] . The CV curves of SiOx@G and P@SiOx‐10@G‐1100 increased as the cycle progressed and then stabilized after the fourth cycle, which is believed to be due to the low electrical conductivity of SiOx [38] …”

“…From these results, it was confirmed that dealloying of Li x Si was slowly generated over a wide voltage range due to the pitch coating layer. [16,[39][40] The CV curves of SiOx@G and P@SiOx-10@G-1100 increased as the cycle progressed and then stabilized after the fourth cycle, which is believed to be due to the low electrical conductivity of SiOx. [38] In order to investigate the precise electrochemical information of fully charged anode materials depending on different carbonization temperature, coating layer and SiOx contents, C-LSV curves were obtained as shown in Figure S3.…”

Control of cyclic stability and volume expansion on graphite–SiOx–C hierarchical structure for Li-ion battery anodes

“…After the first cycle, the cathodic peak of MSG exhibited two peaks, which corresponded to Li lithiation of graphite (at 0.01 V) and SiO x (at 0.15 V, alloying of Li x Si). 24 In the anodic peaks at 0.25 V corresponding to the delithiation peak of the graphite, 34 the delithiation peak of the SiO x did not appear. It is expected that the direct reaction of SiO x is obscured by the carbon layer on the surface.…”

“…It is expected that the direct reaction of SiO x is obscured by the carbon layer on the surface. 24 For SG, lithiation peaks appear after the first cycle (at 0.01 V of graphite, at 0.15 V of SiO x ), with delilthiation peaks of SiO x (at 0.68 V) (Fig. S11 † ).…”

“…9,23 In spite of these efforts, the SiO x anodes should be blended with commercial graphite anodes due to the low cyclic performance against graphite for industrial applications. 18,[24][25][26] But, in slurry mixing step, characteristic of the SiO x that tends to be aggregated itself interrupts to form uniform slurry. Thus, "integrity" in graphite and SiO x anodes must be considered importantly when constructing electrodes.…”