High energy all-solid-state lithium batteries with

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1 Supporting Information High energy all-solid-state lithium batteries with ultralong cycle life Xiayin Yao, Deng Liu, Chunsheng Wang, Peng Long, Gang Peng, Yong-Sheng Hu, *, Hong Li, Liquan Chen, and Xiaoxiong Xu *, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo , P. R. China Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, Maryland 20742, United States Key Laboratory for Renewable Energy, Beijing Key Laboratory for New Energy Materials and Devices, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing , P. R. China *Corresponding Authors: s: and X.Y. and D.L. contributed equally to this work. 1

2 Section 1: Experimental section 1.1 Synthesis of cobalt sulfide/li 7 P 3 S 11 nanocomposites and neat Li 7 P 3 S 11 electrolyte The designed cobalt sulfide/li 7 P 3 S 11 (or denoted as cobalt sulfide-li 7 P 3 S 11 ) nanocomposites were prepared by a simple in situ liquid-phase method using cobalt sulfide nanosheets and Li 2 S (99.9%, Alfa Aesar), P 2 S 5 (99.0%, Alfa Aesar) as precursors. Cobalt sulfide nanosheets were firstly synthesized through a solution-based precipitation reaction with polyvinyl alcohol (PVA, DP = 1750±50) as a surfactant. In a typical procedure, 15.0 g of 33.3 wt.% cobalt sulfate heptahydrate (CoSO 4 7H 2 O, 99.5%, Aladdin) aqueous solution was mixed with 30.0 g of 1.0 wt.% PVA aqueous solution under stirring at room temperature, forming Co 2+ -PVA complex with OH ligands. S1 Then, equivalent molar amount of 20.0 wt.% Na 2 S 7H 2 O aqueous solution was introduced into the above solution rapidly. The Co 2+ -PVA complex is immediately transformed into numerous cobalt sulfide-pva crystalline nuclei complex and growth with the confinement of PVA chains, rapid forming a black precipitation. After being stirred for 30 min, the obtained cobalt sulfide was filtered, washed with deionized water for several times and freeze dried. To synthesize cobalt sulfide/li 7 P 3 S 11 nanocomposites, the freeze dried cobalt sulfide (1.0 g) was mixed with Li 2 S and P 2 S 5 (0.15 g, the mole ratio of Li 2 S and P 2 S 5 is 7:3) in acetonitrile (99.8%, Aladdin) solvent under stirring at 50 o C for 24 hours. After that, the obtained slurry was vacuuming distilled to remove the residual solvent and dried at 80 o C for 12 hours to collect solid powders. Finally, the powder was further heat-treated at 260 o C for 1 hour to get the target nanocomposites. All preparation processes were performed in an argon atmosphere. Neat Li 7 P 3 S 11 electrolyte was synthesized by the same procedure mentioned above in the absence of cobalt sulfide nanosheets and further used as the electrolyte within cathode layers. 2

3 The synthesis of tetragonal phase Li 10 GeP 2 S 12 electrolyte with average particle size of about 1 μm can be found elsewhere (Figure S12, Supporting Information). S2 For 70%Li 2 S-29%P 2 S 5-1%P 2 O 5, the preparation method is similar to the reported in previous literature except the change of the dopant. S3 At room temperature, the Li 10 GeP 2 S 12 and 70%Li 2 S-29%P 2 S 5-1%P 2 O 5 sulfide electrolytes exhibit lithium ionic conductivities of and S cm -1, respectively (Figure S13, Supporting Information). And the electrochemical windows for the S4, 34 both solid electrolytes could be as high as 4.0 V. 1.2 Material Characterizations The morphologies of the materials were investigated using a scanning electron microscope (Hitachi S-4800). The X-ray diffraction (XRD) patterns were collected in a reflection mode between using Cu Kα radiation at a Bruker D8 Advance Diffractometer. Raman spectra were measured with a Renishaw in Via-Reflex Raman spectrophotometer using the 532 nm spectra. Microstructure and element mapping was performed on a transmission electron microscope (Tecnai G 2 F20, FEI). Ionic conductivities of the Li 7 P 3 S 11 electrolyte were measured by alternating current (AC) impedance method. The samples were cold pressed at 300 MPa with 10 mm of diameter and ~1.0 mm of thickness. Electrochemical impedance spectroscopy (EIS) was conducted using an impedance analyzer (Solartron, 1470E) at frequencies from 1 MHz to 10 Hz with the amplitude of 15 mv in an argon atmosphere. 1.3 All-solid-state lithium battery assembly Laboratory-scale solid-state cells were constructed by using the cobalt sulfide/li 7 P 3 S 11 nanocomposites or cobalt sulfide nanosheets in combination with the neat Li 7 P 3 S 11 electrolyte and Super P as the cathode, together with a lithium anode and a solid electrolyte bilayer located 3

4 between the cathode and anode. The schematic diagram of an all-solid-state lithium battery is shown in Figure S9 (Supporting Information). It has been demonstrated that 70%Li 2 S-29%P 2 S 5-1%P 2 O 5 is compatible with lithium metal, 34 which can effectively suppress the reaction between Li 10 GeP 2 S 12 and lithium metal ensuring the compatibility between electrolyte and metallic lithium. For composite cathodes, the as-synthesized samples were mixed with the neat Li 7 P 3 S 11 electrolyte and Super P in weight ratio of 40:50:10 using an agate mortar. The mass loading of cathode is around mg cm -2. Firstly, the solid electrolyte bilayer was obtained by sequential pressing electrolytes of Li 10 GeP 2 S 12 and 70%Li 2 S-29%P 2 S 5-1%P 2 O 5 under 240 MPa. The thickness of the electrolyte bilayer after press is approximate 1 mm. Secondly, the composite cathodes were uniformly spread on the side of Li 10 GeP 2 S 12 layer and pressed under 240 MPa. Finally, the Li foil (99.9%, thickness, 0.1 mm, Alfa Aesar), used as a counter electrode, was attached to the side of 70%Li 2 S-29%P 2 S 5-1%P 2 O 5 by pressing under 360 MPa. All the processes were performed in an argon-filled glove box. 1.4 Electrochemical measurements Electrochemical performances of the as-synthesized samples in all-solid-state lithium battery were investigated by galvanostatic charge-discharge tests at different current densities by using a multichannel battery test system (Wuhan Rambo Testing Equipment Co., Ltd.) in an argon atmosphere. The cutoff voltage was set in the voltage range of 0.5~3.0 V. The specific charge/discharge capacities were calculated based on the mass of cobalt sulfide/li 7 P 3 S 11 nanocomposites or cobalt sulfide nanosheets, while energy density was calculated based on the total weight of cathode layer including cobalt sulfide/li 7 P 3 S 11 nanocomposites or cobalt sulfide nanosheets and the neat Li 7 P 3 S 11 electrolyte as well as Super P. Cyclic voltammogram measurement was performed on a Solartron 1470E (Solartron Public Co., Ltd.) multi-channel 4

5 potentiostats electrochemical workstation at a scan rate of 0.1 mv s -1 between 0.5 and 3.0 V. EIS was conducted using the same impedance analyzer at frequencies from 1 MHz to 0.01 Hz with the amplitude of 10 mv. 5

6 Section 2: Supplementary Figures Figure S1. (a) SEM, (b) TEM and (c) HRTEM of cobalt sulfide nanosheets. The clear crystal lattices with interplanar distances of about nm and nm match well with the d 311 and d 222 spacings of cubic phase Co 9 S 8 crystal. 6

7 Figure S2. (a) SEM and (b) TEM images of cobalt sulfide/li 7 P 3 S 11 nanocomposites, (c) the statistical particle size distribution of the anchored Li 7 P 3 S 11 electrolyte. 7

8 Figure S3. Raman spectum of the neat Li 7 P 3 S 11 electrolyte. Two characteristic bands at around 403 and 417 cm -1 in the Raman spectrum, corresponding to the ions of P 2 S 7 4- and PS 4 3-, confirms the simple crystal structure of Li 7 P 3 S 11. 8

9 Figure S4. XRD patterns of sulfide electrolyte samples prepared by acetonitrile solvent. (a) solid precursor after dried at 80 o C for 12h, and Li 7 P 3 S 11 sulfide electrolytes under annealing temperatures of (b) 200 o C, (c) 250 o C,(d)260 o C,(e)270 o C and (f) 300 o C for 1h. 9

10 Figure S5. Ionic conductivities of Li 7 P 3 S 11 sulfide electrolytes prepared by acetonitrile solvent at room temperature (r.t.) as a function of heat treatment temperatures. Figure S6. Dependence of conductivities on temperature for the neat Li 7 P 3 S 11 electrolytes. 10

11 Figure S7. Initial charge-discharge curves of Li-In/neat Li 7 P 3 S 11 electrolyte/lico 2 all-solid-state cell under a current density of 0.1C (1C = 120 ma g -1 ) at room temperature. The inset is the cyclic performances at 0.1 C. The synthesized neat Li 7 P 3 S 11 electrolyte was employed in the LiCoO 2 -based all-solid-state lithium batteries. The cathode consisted of LiCoO 2 (Shanshan New Energy Co., Ltd., Shanghai, China) and neat Li 7 P 3 S 11 electrolyte at a weight ratio of 7: 3. In-Li (10 wt% Li) alloy was used as the counter electrode. The initial charge/dischage capacities are 129 and 108mA h g -1, which is much higher than these of all-solid-state lithium cell employing Li 7 P 3 S 11 electrolyte prepared by a high-energy ball milling technique followed with annealing. S3 The improvement of specific capacity can be attributed to the higher ionic conductivity and smaller particle size, resulting faster ion conduction and better interfacial contact between active materials and electrolyte. After ten cycles, a reversible specific capacity of 100 mah g -1 with a capacity retention of 92.6% can be obtained, demonstrating a promising electrolyte for LiCoO 2 - based all-solid-state lithium batteries. 11

12 Figure S8. An SEM image of the neat Li 7 P 3 S 11 electrolyte. 12

13 Figure S9. Schematic diagram of an all-solid-state lithium battery. Figure S10. Nyquist plots of cobalt sulfide/li 7 P 3 S 11 nanocomposites and cobalt sulfide nanosheets after 1st and 1000th cycles at current density of 1.27 ma cm -2. The intercept at the Real Z axis in the high frequency corresponds to the ohmic resistance of the cell, which 13

14 originated from the resistance of the solid electrolyte layer and electrode layers. 12, 34 Both two electrodes exhibit an almost identical intercept due to using the same electrolyte bilayer, i.e. Li 10 GeP 2 S 12 and 70%Li 2 S-29%P 2 S 5-1%P 2 O 5, and similar electrode layers. The semicircle in the middle frequency range corresponds to the interfacial resistance in the cathode layer. Actually, the interfacial resistance in this work mostly originates from the formed interface between cobalt sulfide and Li 7 P 3 S 11 solid electrolytes. For cathode electrode comprised of cobalt sulfide/li 7 P 3 S 11 nanocomposites, neat Li 7 P 3 S 11 electrolyte and Super P, the anchored Li 7 P 3 S 11 coating as a buffer layer not only increases the contact but also endows a uniform volume expansion. As can be seen, the cell employing the cobalt sulfide/li 7 P 3 S 11 nanocomposites exhibits very small interfacial resistance, while that of cobalt sulfide nanosheets shows a larger semicircle resistance after the first cycle. After 1000 cycles, cobalt sulfide/li 7 P 3 S 11 nanocomposite electrode shows a much smaller increase in both ohmic resistance as well as the interfacial resistance than those of cobalt sulfide nanosheets. 14

15 Figure S11. SEM images of (a, b) cobalt sulfide/li 7 P 3 S 11 nanocomposite and (c, d) cobalt sulfide nanosheet electrodes after 1000 cycles. 15

16 Figure S12. (a) XRD pattern and (b) SEM image of Li1 0 GeP 2 S 12 electrolyte. Figure S13. Nyquist plots of the Li 10 GeP 2 S 12 and 70%Li 2 S-29%P 2 S 5-1%P 2 O 5 electrolytes at room temperature. The ionic conductivity (σ, S cm -1 ) is calculated from the following equation: σ = L/(R S), where L (~ 0.1cm) is the thickness of electrolyte, R (Ω) is the sample resistance, and S (0.785 cm 2 ) is the area of the electrode. The resistances for Li 10 GeP 2 S 12 and 70%Li 2 S- 29%P 2 S 5-1%P 2 O 5 electrolytes are 15.4 Ω and 62.4 Ω, corresponding to the ionic conductivities of and S cm -1, respectively. 16

17 Table S1. Ionic conductivities and activation energies of sulfide electrolytes prepared by various solvents for Li + ion conduction. Sample Li 7 P 3 S o C Li 7 P 3 S o C Li 7 P 3 S o C Li 3 PS 4 18 Li 7 P 2 S 8 I 21 Li 7 P 3 S Solvent acetonitrile acetonitrile acetonitrile tetra hydrofuran acetonitrile 1,2- dimethoxyethane σ (10-4 S cm -1 ) E α (kj mol -1 ) Supplementary references: (S1) Yao, X.; Kong, J.; Tang, X.; Zhou, D.; Zhao, C.; Zhou, R.; Lu, X. RSC Adv. 2014, 4, (S2) Yin, J.; Yao, X.; Peng, G.; Yang, J.; Huang, Z.; Liu, D.; Tao, Y.; Xu, X. Solid State Ionics 2015, 274, (S3) Huang, B.; Yao, X.; Huang, Z.; Guan, Y.; Jin, Y.; Xu, X. J. Power Sources 2015, 284, (S4) Han, F. D.; Gao, T.; Zhu, Y. J.; Gaskell, K. J.; Wang, C. S. Adv. Mater. 2015, 27,