A design of Solid-State Li-S cell with evaporated Lithium anode to eliminate shuttle effects

Transcription

1 Supporting Information A design of Solid-State Li-S cell with evaporated Lithium anode to eliminate shuttle effects Yujie Hao, a Sheng Wang, a Feng Xu, a Yijie Liu, a Ningning Feng, a Ping He, *a Haoshen Zhou. *ab a Center of Energy Storage Materials & Technology, College of Engineering and Applied Sciences, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing , P. R. China. b Energy Technology Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Umezono 1-1-1, Tsukuba , Japan. * pinghe@nju.edu.cn; hs.zhou@aist.go.jp S-1

2 Characterization The scanning electron microscopy (SEM) images were collected on a Hitachi SU The X-ray diffraction (XRD) patterns were got on a Bruker D8-Advaned diffractometer. The nitrogen adsorption-desorption analysis was carried out on an ASAP 2020 instrument. The content of the S-MWCNT was investigated by thermogravimetry (TGA) on a SDT Q600. Galvanostatic discharge-charge test was conducted using HJ1001SD8. Electrochemical-Impedance Spectroscopy (EIS) was investigated on Land 2001A. Results Figure S1. XRD of LAGP plate at room temperature. The diffraction peaks corresponding to NASICON-type LiGe 2 (PO 4 ) 3 phase (JCPDS ) were calculated which can be attributed to the similarity in ionic radii of Ge 4+ (0.053 nm) and Al 3+ (0.050 nm), the diffraction peaks are not significantly shifted though 25% of Ge has been substituted by Al. S-2

3 Figure S2. Nyquist plots of LAGP under room temperature. Inset - equivalent circuit used for fitting. R e and R gb corresponds to the grain resistance and the grain boundary resistance respectively. W o is the Warburg diffusion contribution. CPE1 is the associated capacitance. Total resistance of LAGP pellet should be noted as R= R e + R gb (R e =200Ω, R gb =205Ω). The calculated total lithium ionic conductivity of the sintered LAGP solid-state electrolyte was about S/cm. a) b) Figure S3. SEM of a) LAGP pellet and b) multi-walled carbon nanotubes. The grain size of LAGP is about 1 μm in a cube shape. The diameter of multi-walled carbon nanotubesis about 10~20 nm. S-3

4 Weight (%) Temperature/ Figure S4. TGA measurement of S-MWCNT composites. Before 155 o C, the material quality tended to be stable, and then the quality of the composite material began to be reduced. Until 275 o C, the quality of materials became smoothing. Depending on the different melting point of the sulfur and carbon nanotubes, the mass of sulfur began to be reduced at 155 C, and all of the sulfur is evaporated until 275 C, leaving the mass of carbon. The sulfur content of the composites was estimated to be 80%. Figure S5. a) The cross section SEM of boundary between evaporated lithium and LAGP. b) The morphology of evaporated lithium. he thickness of evaporated lithium is about 2-4 um with molten morphology, and the immersion depth is about 4~6 um. S-4

5 Li foil Evaporated Li Figure S6. CV profiles of battery with lithium foil and evaporated lithium anode. The peaks of battery with lithium foil is shifted than that of battery with evaporated lithium, which can be contributed to the relative high resistance. Figure S7. Discharge-charge curve of the battery with S-MWCNT composites as cathode, lithium foil as anode and ionic liquid as electrolyte at a current density of S-5

6 20mA g -1 During the discharge process of the commonly-used batteries with liquid electrolyte, one S-S covalent bond of cyclooctasulfur (S 8 ) is broken and S8 changes into a chain-structural polysulfide anion (Li 2 S n ). Afterwards, the polysulfide anions undergo multistep reactions (n gradually decreases) and finally are reduced into Li2S. Some polysulfide anions (Li 2 S n, 4<n 8) can dissolve into organic liquid electrolyte, while other polysulfide anions (Li 2 S., n 4) are insoluble. As a result, the reduction from S to Li 2 S 8 shows the first voltage plateau at about 2.2V; the reduction from Li 2 S 8 to Li 2 S 4 indicates the battery s voltage steeply declines; the reduction from Li 2 S 4 to Li 2 S forms the lower voltage plateau at about 2.0V. The Coulombic efficiency of the battery was about 85%, which mean the shuttle mechanism existed in this battery. S-6