Supporting Information Cobalt Disulfide Nanoparticles Embedded in Porous Carbonaceous Micro- Polyhedrons Interlinked by Carbon Nanotubes for Superior Lithium and Sodium Storage Yuan Ma,, Yanjiao Ma,, Dominic Bresser,, Yuanchun Ji, Dorin Geiger, Ute Kaiser, Carsten Streb,, Alberto Varzi,*,, Stefano Passerini*,, Helmholtz Institute Ulm (HIU), Helmholtzstrasse 11, D-89081 Ulm, Germany Karlsruhe Institute of Technology (KIT), P.O. Box 3640, D-76021 Karlsruhe, Germany Institute of Inorganic Chemistry I, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany Central Facility for Electron Microscopy, Group of Electron Microscopy of Materials Science, Ulm University, Albert-Einstein-Allee 11, D-89081 Ulm, Germany * E-mail of corresponding author: stefano.passerini@kit.edu (S. Passerini); alberto.varzi@kit.edu (A. Varzi) S1
Figure S1. XRD pattern of the Co-C/CNT nanocomposite. S2
Figure S2. TEM images of (a) Co-C/CNT and (c) CoS 2 -C/CNT and the corresponding particle size distribution of (b) metallic Co and (d) CoS 2. S3
Figure S3. XPS analysis of CoS 2 -C/CNT, including fitting: (a) S 2p 1-3, and (b) Co 2p 1,4. As discussed in the main text, the XPS analysis reveals that some elemental sulfur remains in the sample and does not react with the cobalt comprised in the Co-C/CNT precursor. Additionally, it is observed that some cobalt remains metallic despite the sulfur excess added during the preparation process. The detected sulfate presumably originates from the sample handling and preparation for the XPS analysis, which was conducted under air, since cobalt sulfide rapidly forms cobalt sulfate in contact with oxygen and water. S4
Figure S4. EDX mapping images of CoS 2 -C/CNT. S5
Figure S5. TGA curve recorded for CoS 2 -C/CNT under air flow (heating rate: 2 C min -1 ). S6
Table S1. Co, C and S content determined by ICP-OES and EDX for CoS 2 -C/CNT. ICP [wt%] EDX [wt%] Co 21.8 20.9 C - 56.3 S - 22.8 S7
Figure S6. Raman spectrum of the CoS 2 -C/CNT nanocomposite. S8
Table S2. Electronic conductivity of various metal oxides/sulfides and composites additionally including carbonaceous materials, as reported in literature. Materials Compound Electronic conductivity (S cm -1 ) Ref. Fe 2 O 3 2.2 10-6 5 Metal oxides or carbonaceous metal oxides Fe 2 O 3 -graphene 0.156 6 NiO-GNS 1.4 10-3 7 GNS-CuO 0.2 8 Metal sulfides or carbonaceous metal sulfides SnS 2 1.0 10-3 5 SnS 2 -RGO 0.037 9 NiS-GNS 0.166 10 MoS 2 /C 0.46 11 CoS/graphene 1.5 12 CoS 2 /RGO-CNT 7.2 10-4 13 CoS 2 -C/CNT 1.2 This work S9
Figure S7. (a) Nitrogen-adsorption isotherm at 77 K recorded for CoS 2 -C/CNT. (b) Pore size distribution for CoS 2 -C/CNT, determined from the adsorption isotherm by using the BJH (Barrett-Joyner-Halenda) method. S10
Figure S8. Galvanostatic cycling of electrodes based on the Co-C/CNT intermediate (applied specific current: 100 ma g -1 ) to determine the capacity contribution of the comprised carbon, assuming that the subsequent sulfidation process does not have a substantial impact on the carbonaceous species. These electrodes provide a reversible capacity of about 500 mah g -1 in the first cycle, which subsequently decreases to about 440 mah g -1 after 15 cycles. As metallic cobalt is considered to be electrochemically inactive in these electrodes, the corresponding weight fraction was not considered when calculating the given capacity values. S11
Figure S9. The ex situ SEM micrographs of the CoS 2 -C/CNT anode for LIBs (a) after 60 cycles and (b) after 120 cycles. S12
Table S3. Comparison of the cycling performance of CoS 2 or CoS 2 -based composites, employed as active material for lithium-ion electrodes. Materials Compound Current density (ma g -1 ) Cycles Capacity (mah g -1 ) Ref. CoS2 or CoS2- based composite CoS2 composites including carbonaceous materials different from carbon nanotubes Carbonaceous CoS2 composite with carbon nanotubes CoS 2 Hollow Spheres 100 40 320 14 CoS 2 NPs/Al 2 O 3 NSs 100 150 626 15 Hierarchical Wormlike CoS 2 100 100 883 16 The Yolk-shell CoS 2 @NG 100 150 882 17 CoS 2 NPs/C 500 120 610 18 CoS 2 -in-wall-ncss 200 500 1080 19 NC/CoS 2 100 50 560 20 CoS 2 NP@G-CoS 2 QD 100 50 1022 21 NC@CoS 2 200 100 657 22 CoS 2 @C 200 200 720 23 CoS 2 /G 500 1000 400 24 CoS 2 /G 100 150 800 25 CoS 2 /graphene 50 40 600 26 CoS 2 /rgo 50 30 644 27 CNTs@C@CoS 2 200 100 916 28 CoS 2 /fcnt 200 180 900 29 CoS 2 /NCNTF 1000 160 937 30 CoS 2 /CNTs/graphene 100 100 368 31 CoS 2 /GCAs 250 100 975 32 CoS 2 /rgo/mwcnts 100 100 885 33 This work 100 120 1030 CoS 2 -C/CNT 1000 500 510 - S13
Table S4. Comparison of the rate capability of CoS 2 or CoS 2 -based composites, employed as active material for lithium-ion electrodes. Materials Compound Specific current (A g -1 ) Capacity (mah g -1 ) Ref. CoS2 or CoS2- based composite CoS 2 NPs/Al 2 O 3 NSs 2.0 480 15 Hierarchical Worm-like CoS 2 2.0 501 16 CoS 2 polyhedrons 1.0 110 34 CoS2 composites including carbonaceous materials Carbonaceous CoS2 composite with carbon different from carbon nanotubes nanotubes CoS 2 NPs/C 2.0 392 18 CoS 2 -in-wall-ncss 1.0 732 19 NC/CoS 2 2.0 340 20 CoS 2 NP@G-CoS 2 QD 10.0 411 21 NC@CoS 2 5.0 448 22 CoS 2 @C 10.0 450 23 CoS 2 /G 3.5 400 24 CoS 2 /G 1.0 641 25 CoS 2 /graphene 0.8 420 26 CNTs@C@CoS 2 5.0 672 28 CoS 2 /fcnt 1.0 338 29 CoS 2 /NCNTF 5.0 439 30 CoS 2 /CNTs/graphene 2.0 212 31 CoS 2 /GCAs 2.0 397 32 1.0 612 This work CoS 2 -C/CNT 1.5 533-2.0 470 S14
Figure S10. CV curves recorded for electrodes based on CoS 2 -C/CNT vs. lithium metal at various scan rates ranging from 0.1 to 10.0 mv s -1. S15
Figure S11. Ex situ obtained (a) SEM and (b) TEM micrographs of the CoS 2 -C/CNT nanocomposite subjected to 200 dis-/charge cycles at a specific current of 100 ma g -1 in 1M NaPF 6 -DME vs. sodium metal. S16
Table S5. Comparison of the cycling performance of CoS 2 or CoS 2 -based composites, employed as active material for sodium-ion electrodes. Materials Compound Current density CoS2 CoS2 composites including carbonaceous materials different from carbon nanotubes (ma g -1 ) Cycles Capacity (mah g -1 ) Capacity retention (%) CoS 2 100 100 190 ~30 35 Hollow CoS 2 100 30 728 86 36 CoS 2 NPs/C 500 60 359 94 18 CoS 2 /C polyhedrons Ref. 100 100 510 90 37 CoS 2 /rgo 100 ~100 376 81 38 CoS 2 @MCNFs 1000 100 508 95 39 CoS 2 /rgo 500 100 249 92 150 251 93 40 Carbonaceous CoS2 composite with carbon nanotubes CoS 2 /GCAs 50 100 258 55 32 CoS 2 -MWCNT 100 100 568 77 35 100 435 98 This work 100 CoS 2 -C/CNT 200 402 91 - S17
Table S6. Comparison of the rate capability of CoS 2 or CoS 2 -based composites, employed as active material for sodium-ion electrodes. Materials Compound Specific current (A g -1 ) Capacity (mah g -1 ) Ref. CoS2 composites including CoS2 carbonaceous materials different Carbonaceous CoS2 composite with from carbon nanotubes carbon nanotubes CoS 2 0.8 394 35 Hollow CoS 2 2.0 684 36 CoS 2 NPs/C 2.0 121 18 CoS 2 /C polyhedrons 2.0 288 37 1.0 297 CoS 2 /rgo 2.0 275 38 2.0 288 CoS 2 @MCNFs 5.0 249 39 1.0 273 CoS 2 /rgo 2.0 203 40 CoS 2 /GCAs 0.8 67 32 CoS 2 -MWCNT 0.8 551 35 1 342 This work 1.5 322 - CoS 2 -C/CNT 2 306 S18
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