ARTICLE NUMBER: 16094 DOI: 10.1038/NENERGY.2016.94 Metal organic framework-based separator for lithium sulfur batteries 4 5 Songyan Bai 1,2, Xizheng Liu 1, Kai Zhu 1, Shichao Wu 1,2 Haoshen Zhou 1,2,3* 6 7 8 9 10 11 12 13 14 1 Energy Interface Technology Group, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1, Umezono, Tsukuba 305-8568, Japan; 2 Graduate School of System and Information Engineering, University of Tsukuba, Tennoudai 1-1-1, Tsukuba, 305-8573, Japan; 3 National Laboratory of Solid State Microstructures & College of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China. 15 16 17 18 19 *Corresponding author: Haoshen Zhou, hs.zhou@aist.go.jp or hszhou@nju.edu.cn NATURE ENERGY www.nature.com/natureenergy 1
DOI: 10.1038/NENERGY.2016.94 31 Supplementary Figures: 32 33 34 35 Supplementary Figure 1 (a) MOF thin film. (b) The Precursor MOF@GO separator. (c) The prepared MOF@GO separator. (d) GO separator. (e) The peered-off filter. 2 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 49 50 51 52 Supplementary Figure 2 By SEM images, the GO laminates in lithium sulfur batteries were detached themselves gradually over time. (After 200 th charge/discharge cycles with GO separator) (Scale bar, 1μm) NATURE ENERGY www.nature.com/natureenergy 3
DOI: 10.1038/NENERGY.2016.94 72 a b 73 74 75 Supplementary Figure 3 Characterization of MOF@GO separator. (a) SEM images depicted show that the detachment of GO laminates has been greatly relieved in the side of GO layers. 76 (After 200 th charge/discharge cycles with MOF@GO separator) (Scale bar, 1μm) (b) The 77 78 morphology of MOF particles remains intact in the side of MOF layers. (After 200 th charge/discharge cycles with MOF@GO separator) (Scale bar, 100 nm) 4 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 94 95 96 Supplementary Figure 4 Thermogravimetric analysis. The wt% of sulfur in the CMK-3/S composite was determined to ~70%, respectively. NATURE ENERGY www.nature.com/natureenergy 5
DOI: 10.1038/NENERGY.2016.94 112 113 114 115 116 Supplementary Figure 5 The schematic images of permeating measurements. (a) There exits the polysulfide ions in the left side (Red solutions). (b) The MOF@GO separator lies between these two tubes. (c) The blank electrolyte is in the right side. 6 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 136 137 138 Supplementary Figure 6 Characterization of GO laminates. SEM images depicted show the morphology of the pre-synthesized GO laminates. (Scale bar, 1μm) NATURE ENERGY www.nature.com/natureenergy 7
DOI: 10.1038/NENERGY.2016.94 157 158 159 160 Supplementary Figure 7 (a) Tapping-mode AFM image and (b) the corresponding height profile of GO laminates. 8 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 176 177 178 179 Supplementary Figure 8 The analyses based on the IR spectra. (a) The IR spectra of the dehydrated MOF particles before the electrochemical process. (b) The IR spectra of the MOF particles after the process over 100 charge/discharge cycles. NATURE ENERGY www.nature.com/natureenergy 9
DOI: 10.1038/NENERGY.2016.94 187 188 189 Supplementary Figure 9 The illustration of solid UV-Vis spectra. The MOF particles illustrat no obvious changes before/after the charge/discharge process over 100 cycles. 10 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 202 203 204 205 Supplementary Figure 10 The CVs in lithium sulfur batteries. (a) CV profiles with a pristine separator (Celgard 2400) at a scan rate of 0.1 mv s 1. (b) CV profiles with a MOF@GO separator at a scan rate of 0.1 mv s 1 NATURE ENERGY www.nature.com/natureenergy 11
DOI: 10.1038/NENERGY.2016.94 211 12 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 212 213 214 215 Supplementary Figure 11 CVs at different scan rates of lithium sulfur batteries with (a) pristine separator (Celgard 2400) and (b) MOF@GO separators in lithium sulfur batteries. (c) The linear fits of the CV peak currents for the lithium sulfur batteries with pristine separator (α 1, β 1,γ 1 ) and with MOF@GO separators (α 2, β 2,γ 2 ). 216 217 218 219 220 221 Supplementary Figure 12 Electrical impedance of (a) pristine separator (Celgard) and (b) MOF@GO separator. Ion conductivity of (c) C pristine separator (Celgard) and (d) MOF@GO separator. NATURE ENERGY www.nature.com/natureenergy 13
DOI: 10.1038/NENERGY.2016.94 228 229 230 Supplementary Figure 13 Nitrogen sorption data for MOF@GO separators. N 2 sorption isotherm at 77 K and its analytical pore size distribution. 14 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 247 248 249 250 Supplementary Figure 14 The grown crystal facets at different growth rates on the basis of crystalline growth mechanism. (a) Cubic, along the (001) direction. (b) Octahedron, along the (111) direction. (c) Cuboctahedron, along the (001) direction and (111) direction simultaneously. NATURE ENERGY www.nature.com/natureenergy 15
DOI: 10.1038/NENERGY.2016.94 271 272 273 274 Supplementary Figure 15 The structural properties of binuclear Cu(II) paddlewheel subunits. After dehydration (removing the water in cavities), it provides the only affordable vacancy for the formation of Cu-S bond 16 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 295 296 297 Supplementary Figure 16 The IR spectra of the MOF samples after the charge or discharge over 50 th cycles. (Under the adequate dehydration) NATURE ENERGY www.nature.com/natureenergy 17
DOI: 10.1038/NENERGY.2016.94 316 Supplementary Table 317 318 319 Supplementary Table 1 Comparisons of the linear fitting values with/without MOF@GO separator D(α) (cm 2 /s) D(β) (cm 2 /s) D(γ) (cm 2 /s) Pristine Separator 1.45 10-9 2.0 10-9 2.0 10-9 MOF@GO Separator 1.5 10-9 1.5 10-9 2.1 10-9 320 321 322 323 Supplementary Table 2 Comparisons of the electrochemical performance with serial separators in lithium-sulfur batteries Separator Sulfur/ Sulfur mass Cycles Initial Capacity Fading Current Ref Cathode wt% area ratio Capacity Retention rate density / mah g 1 mah g 1 (per mg/cm 2 cycle) Super P / Sulfur/ 60% 0.5 500 1350 740 0.09% 0.5C 3 Celgard Super P graphene / PP Sulfur/ 70% 1.3 500 933 663 0.064% 1C 4 Carbon Black Graphene Oxide Sulfur/ 63% 0.12 100 920 708 0.23% 0.1 C 1 Carbon naotubes single-wall Sulfur/ 70% 0.13 300 1132 501 0.18% 0.2 C 5 carbon nanotube Super P Carbon coating Sulfur/ 60% 0.2 200 1389 828 0.2% 0.2 C 6 Super P MCNT@PEG Sulfur/ 60% 0.15 500 1250 490 0.12% 1 C 7 18 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION Carbon Paper Nafion Sulfur/ 50% 0.7 500 781 468 0.08% 1 C 8 Carbon Paper Mesoporous carbon Sulfur/ 60% 0.5 500 1059 683 0.071% 1 C 9 Super P PEG/Microporous Sulfur/ 70% 0.15 500 1300 780 0.08% 1 C 10 Carbon Super P MOF@GO Sulfur/ 70% 0.3 1,500 1207 855 0.019% 1 C This CMK3 work 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 Supplementary Note Supplementary Note 1. Calculation of Li + diffusion coefficients The ion conductivity of our MOF@GO separator has been calculated, which indicates the highly transport capability to lithium ions against polysulfide anions. Generally, the MOF@GO separator can introduce no notable influence on the transfer of lithium ions across the separator, and play an important role in blocking the dissolved polysulfide ions simultaneously. Therefore, we have studied impedance properties to gain a better understanding the electrochemical performance due to the diffusion effect on sulfur cathode in cells. Compared with the lithium batteries with/without MOF@GO separators, a series of CVs with different scan rates are used to investigate Li + diffusion coefficients according to the equation, to confirm whether the diffusion from sulfur cathode side to the anode side has to be subjected to great suppression or impediment: NATURE ENERGY www.nature.com/natureenergy 19
DOI: 10.1038/NENERGY.2016.94 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 The equation 1 : I p = 2.69 10 5 n 3/2 SD 1/2 v 1/2 C (Equation S1) where n is the number of electrons per specific reaction, for Li + it is 1; S is the surface area of the electrode which is 1.53 cm 2 in this work; C is the concentration of Li + ions in the material, I p is the current intensity and v is the scan rate. And the diffusion coefficients could be calculated using the slop of fitting line I p and v 1/2. Under the conditions with pristine separators (Celgard 2400 separators), the anodic peak was assigned at around 2.5 V and the cathodic peaks at around 2.0 and 2.3 V as peak α 1, β 1, γ 1, respectively. The values are evaluated to be D(α 1 )=1.45 10-9 cm 2 /s; D(β 1 )=2.0 10-9 cm 2 /s; D(γ 1 )=2.68 10-9 cm 2 /s. In contrast, for the MOF-based separators, the corresponding redox peak was assigned as peak α 2, β 2, γ 2, respectively. The diffusion coefficients were calculated to be D(α 2 )= 1.5 10-9 cm 2 /s, D(β 2 )=1.9 10-9 cm 2 /s; D(γ 2 )=2.1 10-9 cm 2 /s (Supplementary Table 1). Therefore, these similar values of D + Li indicated that the introduced MOF@GO separator would not significantly degrade the diffusion of the lithium ion. The average values of D Li+ indicated that the introduced MOF@GO separator did not obviously decrease the diffusion of the lithium ion in lithium batteries. In comparison with pristine separator, the MOF-based separators illustrates negligible effects on the transfer of lithium ions across the separator in cells. Meanwhile, it is still able to provide excellent selectivity to lithium ions against unfavorable polysulfide anions, simultaneously. Despite the introduced MOF@GO separator may cause the subtle increase of lithium-ion transfer resistance, it can still indicate the comparable capability of lithium-ion transport, highly efficient lithium-ion diffusion coefficient and ion conductivity, and the excellent rate performance in lithium sulfur batteries. As mentioned in the manuscript, due to the MOF@GO separator, its effective blocking towards dissolved polysulfide has resulted in great improvement in the cycling performance in lithium sulfur batteries. Moreover, the diffusion-related experiment, as EIS, for the separator alone are our preferred pathway for Li + ion diffusion. What counts is whether the ion diffusion would suffer from increasing hindrance by the MOF-based separator. 369 370 371 Supplementary Note 2. Calculation of ion conductivity 20 NATURE ENERGY www.nature.com/natureenergy
DOI: 10.1038/NENERGY.2016.94 SUPPLEMENTARY INFORMATION 372 373 374 375 376 377 378 379 380 381 382 383 384 To better understand the ion transition in the membranes, the ion conductivity is also calculated. Actually, the permeating capability of MOF@GO separators for lithium ions is also beneficial to know its performance of enhanced rate capability. As usual, the introduced MOF@GO separators would cause the slight increase of lithium-ion transfer resistance. In experimental, cells were prepared by inserting pristine Celgard 2400 separators or the MOF@GO separators between two blocking stainless steel electrodes with the electrolyte. The working temperature was raised from ambient temperature (30 C) to 65 C and all cells were recorded at constant temperatures. Ionic conductivity measurements were performed by electrical impedance spectroscopy (EIS). According the equation 2 : σ=l S -1 R -1 (Equation S2) where σ is the ion conductivity, L is the distance between the two stainless steel electrode, the S is the geometric area of electrode/electrolyte interface and the R is the intercept at the real axis in the impedance Nyqiusit plot. 385 386 387 388 389 390 391 392 393 394 395 396 397 398 Supplementary Note 3. The Nitrogen adsorption behavior of MOF@GO separators The permanent porosity of our self-assembled MOF@GO separators was studied using gas permeation experiments. On the basis of its microporous properties, it is supposed to function as the effective ionic sieve with its highly narrowed pore sizes. For the sake of the gas adsorption, the nitrogen adsorption isotherm has been measured at 77 K and 1 atm. It is noteworthy that its pore size distributions can be precisely measured and calculated due to its adsorption behavior of our MOF based separator. In experimental, Nitrogen adsorption with a typical reversible type I isotherm was performed and analyzed the pore size distribution. The Brunauer Emmett Teller (BET surface area) with a saturated adsorption amount of 368.2 cm 3 (STP) g 1 is consistent with theoretical calculation. Accordingly, it can be regarded that by the non-local density functional theory (NLDFT) model, pore size distribution in our separators can be confirmed as a narrow arrangement below 9 Å. NATURE ENERGY www.nature.com/natureenergy 21
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