Electronic Supplementary Material (ESI) for ChemComm. This journal is © The Royal Society of Chemistry 2014
Supplementary Information: Preparation of Ge nanotube arrays from ionic liquid for lithium ion battery anodes with improved cycling stability Xusong Liu, a Jian Hao,a Xiaoxu Liu, Lid,* and Jiupeng Zhaoa,*
a,b
Caixia Chi,a Na Li,a Frank Endres,c Yi Zhang,d Yao
a
School of Chemical Engineering and Technology, Harbin Institute of Technology, 150001, Harbin, China. Fax: 086 45186402345; Tel: 086 451 86402345; E-mail:
[email protected]. b Heilongjiang university of Science and Technology, Harbin 150027, China. c Institute of Particle Technology, Chair of Interface Processes Clausthal University of Technology Arnold-Sommerfeld-Str. 638678 Clausthal-Zellerfeld (Germany) d Center for Composite Material, Harbin Institute of Technology, Harbin, China. E-mail:
[email protected] Experimental 1 Synthesis [Emim]Tf2N with the highest quality available was purchased from Io-li-tec
(Germany) and used after drying under vacuum at 100 ℃ to a water content below 2 ppm. GeCl4 (99.9999%) was purchased from Alfa Aesar. The PC membrane was purchased from (Whatman) Shanghai Mosu scientific equipment Co., Ltd. The GeNT arrays were synthesized by template-assisted electrochemical deposition. For this process, a commercial PC nanofiltration membrane with a thickness of 15μm was used as a template. It has an average pore diameter of either 400 nm (M400) or 100nm (M100), with a pore density of 109 cm2. Before deposition, the membrane was sputtered with a 200 nm thick gold layer on one side as a working electrode. A Pt-wire (99.999%) and an Ag-wire were utilized as counter and quasi-reference electrodes, respectively. The electrochemical cell was made of polytetrafluoroethylene (Teflon) and clamped over a Teflon-covered Viton O-ring onto the substrate. 2 Material Characterization Morphological characterization was performed with a Hita-chi S-4800 scanning electron microscope operating at 20 kV. Transmission electron microscopy (TEM) was performed using an FEI Tecnai G2F30 operated at 300 kV. The electrochemical experiments were performed in an argon-filled glove box with water and oxygen contents below 1 ppm by using a CHI660D electrochemical workstation (Shanghai Chen Hua). The PC membrane was dissolved after electrodeposition by dichloromethane (CH2Cl2). Ge NTs and NWs were obtained. The PC membrane with Ge NTs was bound on a copper substrate. After that, the PC membrane was dissolved by dichloromethane, leaving the Ge NTs on the copper substrate. To characterize the as-prepared samples electrochemically, Ge NT arrays were assembled in a CR 2025-type coin cell contained Ge NT electrodes, Li metal, a
microporous polyethylene separator, and an electrolyte solution of 1.1 mol L-1 LiPF6 in ethylene carbonate-diethyl carbonate (EC-DEC; 1:1 vol%). The cells were assembled in an argon-filled glove box and tested to cutoff potentials between 0.01 and 2.0 V. The cells were charged and discharged at a 0.2C rate for 250 cycles. The cells were also tested over a wide range of current rates (in the order 0.1C, 0.2C, 0.5C, 1C, 2C, and then back down to 0.1C).
Fig. S1 SEM images of Ge nanowire bundles (a) the low resolution SEM image of free
standing Ge nanowire bundles. (b) cross-section the high resolution SEM images of Ge nanotube arrays.
Fig. S2 SEM morphologies of Ge NT and NW arrays electrodeposited for different deposition times. (a) Short Ge NT arrays after deposition for 5 min. (b) Ge NT arrays after deposition for 10 min. (c) Long Ge NT arrays after deposition for 30 min. (d) Ge NW arrays after deposition for 40min.
Fig. S3 HR-TEM image of Ge NT taken from the squared area in Fig.4 (a)
Fig. S4 SEM image of Ge NT anodes after 250 charge/discharge cycles
