Three-dimensional Hierarchical Ternary Nanostructures for High ...
SUPPORTING INFORMATION
Three-dimensional Hierarchical Ternary Nanostructures for Highperformance Li-ion Battery Anodes Borui Liu†, Paulo Soares†, Constantine Checkles†, Yu Zhao†, Guihua Yu†,* †
Materials Science and Engineering Program and Department of Mechanical Engineering, The
University of Texas at Austin, Austin, TX 78712, United States. *Corresponding Author: E-mail: [email protected]
MATERIALS AND METHODS Materials Synthesis Synthesis of Si/PPy/CNT ternary hybrid electrodes. The typical synthesis process of the 3D hierarchically nanostructured Si/PPy/CNT hybrid material was carried out via the following steps. First, 84 μL pyrrole monomer (98% reagent grade, Sigma Aldrich) and 184 μL phytic acid solution (50% w/w in H2O, Sigma Aldrich) were mixed with 2.5 mL IPA to form a gel (solution A). Solution B was prepared by dissolving 274 mg ammonium persulphate into 2.5 mL deionized water. Afterwards, 900 μL solution A and 300 μL solution B were added into 60 mg silicon nanoparticles (MTI, Inc) and thoroughly mixed at room temperature (20 ) and sonicated for 5 min to produce a homogeneous Silicon-Polypyrrole hydrogel. Next, 400 μL single-walled carbon nanotubes dispersion solution (0.5 mg/mL in water) was added into the hydrogel above and then was sonicated for 5 min to form a homogeneous Si/PPy/CNT liquid product. Finally, 1
the Si/PPy/CNT liquid material was bladed onto a copper foil, dried in air for 3 h and then immersed under DI water for 10 h to completely remove excess phytic acid and inorganic salts in the anode material. The typical electrode material loading was 0.3-0.5 mg/cm2. Characterization Characterization of Materials. Scanning Electron Microscope (SEM, Hitachi S5500) and Scanning Transmission Electron Microscope (STEM, Hitachi S5500) were used to examine the morphologies of the Si/PPy/CNT composite material. The lithiated electrode was washed with acetonitrile and diluted nitric acid to remove impurities and the SEI layer on the material surface, respectively. To prevent air/moisture side-reactions, the cycled electrodes were always stored in parafilm-sealed plastic plates and handled in an argon atmosphere due to the high sensitivity of the lithiated electrodes to O2 and H2O. Electrochemical tests of Si/PPy/CNT and Si/PPy electrodes. Electrochemical tests of Si/PPy/CNT and Si/PPy electrodes versus Li/Li+ were done in 2032-type cells. All cells were assembled in an argon-filled glovebox. The cells used lithium metal as the negative electrode, 1 M LiPF6 in 1:1 v/v EC:DEC with 1% vinyl carbonate (VC) as the electrolyte and Si/PPy/CNT or Si/PPy coated on copper foil as the positive electrode. The galvanostatic charge/discharge measurements, rate performance and constant-capacity cycling tests were conducted using an MTI Battery Testing System at room temperature. The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were carried out by a Biologic Instrument (BioLogic VMP-3 model).
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Figure S1 | a. SEM image of Si/PPy binary composite electrode. b. TEM image of the in situ coated polypyrrole conductive layer on SiNPs.
Figure S2 | Electrochemical performance of Si/PPy binary electrode. a. EIS spectra of the electrode in the frequency range of 0.1 Hz-1 MHz. b. CV profile of the Si/PPy electrode at a scanning rate of 0.1 mV/s between 0.01 V and 1.0 V (versus Li/Li+). c. Voltage profiles of the Si/PPy electrode at 0.4 A/g, 0.8 A/g, 1.6 A/g, 3.2 A/g and 7.1 A/g rates. d. Rate performance of the Si/PPy electrode at 0.4 A/g, 0.8 A/g, 1.6 A/g, 3.2 A/g and 7.1 A/g rates. 3
Figure S3 | More SEM images showing that 3D framework of Si/PPy/CNT ternary electrode was still kept well after long-term cycling.
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Three-dimensional Hierarchical Ternary Nanostructures for Highperformance Li-ion Battery Anodes Borui Liu†, Paulo Soares†, Constantine Checkles†, Yu Zhao†, Guihua Yu†,* †
Materials Science and Engineering Program and Department of Mechanical Engineering, The
University of Texas at Austin, Austin, TX 78712, United States. *Corresponding Author: E-mail: [email protected]
MATERIALS AND METHODS Materials Synthesis Synthesis of Si/PPy/CNT ternary hybrid electrodes. The typical synthesis process of the 3D hierarchically nanostructured Si/PPy/CNT hybrid material was carried out via the following steps. First, 84 μL pyrrole monomer (98% reagent grade, Sigma Aldrich) and 184 μL phytic acid solution (50% w/w in H2O, Sigma Aldrich) were mixed with 2.5 mL IPA to form a gel (solution A). Solution B was prepared by dissolving 274 mg ammonium persulphate into 2.5 mL deionized water. Afterwards, 900 μL solution A and 300 μL solution B were added into 60 mg silicon nanoparticles (MTI, Inc) and thoroughly mixed at room temperature (20 ) and sonicated for 5 min to produce a homogeneous Silicon-Polypyrrole hydrogel. Next, 400 μL single-walled carbon nanotubes dispersion solution (0.5 mg/mL in water) was added into the hydrogel above and then was sonicated for 5 min to form a homogeneous Si/PPy/CNT liquid product. Finally, 1
the Si/PPy/CNT liquid material was bladed onto a copper foil, dried in air for 3 h and then immersed under DI water for 10 h to completely remove excess phytic acid and inorganic salts in the anode material. The typical electrode material loading was 0.3-0.5 mg/cm2. Characterization Characterization of Materials. Scanning Electron Microscope (SEM, Hitachi S5500) and Scanning Transmission Electron Microscope (STEM, Hitachi S5500) were used to examine the morphologies of the Si/PPy/CNT composite material. The lithiated electrode was washed with acetonitrile and diluted nitric acid to remove impurities and the SEI layer on the material surface, respectively. To prevent air/moisture side-reactions, the cycled electrodes were always stored in parafilm-sealed plastic plates and handled in an argon atmosphere due to the high sensitivity of the lithiated electrodes to O2 and H2O. Electrochemical tests of Si/PPy/CNT and Si/PPy electrodes. Electrochemical tests of Si/PPy/CNT and Si/PPy electrodes versus Li/Li+ were done in 2032-type cells. All cells were assembled in an argon-filled glovebox. The cells used lithium metal as the negative electrode, 1 M LiPF6 in 1:1 v/v EC:DEC with 1% vinyl carbonate (VC) as the electrolyte and Si/PPy/CNT or Si/PPy coated on copper foil as the positive electrode. The galvanostatic charge/discharge measurements, rate performance and constant-capacity cycling tests were conducted using an MTI Battery Testing System at room temperature. The electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were carried out by a Biologic Instrument (BioLogic VMP-3 model).
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Figure S1 | a. SEM image of Si/PPy binary composite electrode. b. TEM image of the in situ coated polypyrrole conductive layer on SiNPs.
Figure S2 | Electrochemical performance of Si/PPy binary electrode. a. EIS spectra of the electrode in the frequency range of 0.1 Hz-1 MHz. b. CV profile of the Si/PPy electrode at a scanning rate of 0.1 mV/s between 0.01 V and 1.0 V (versus Li/Li+). c. Voltage profiles of the Si/PPy electrode at 0.4 A/g, 0.8 A/g, 1.6 A/g, 3.2 A/g and 7.1 A/g rates. d. Rate performance of the Si/PPy electrode at 0.4 A/g, 0.8 A/g, 1.6 A/g, 3.2 A/g and 7.1 A/g rates. 3
Figure S3 | More SEM images showing that 3D framework of Si/PPy/CNT ternary electrode was still kept well after long-term cycling.
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