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C: Energy Conversion and Storage; Energy and Charge Transport

Functionalized Carbon as Polysulfide Traps for Advanced Lithium-Sulfur Batteries Remith Pongilat, Sylvain Franger, and Kalaiselvi Nallathamby J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.8b00605 • Publication Date (Web): 06 Mar 2018 Downloaded from http://pubs.acs.org on March 7, 2018

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The Journal of Physical Chemistry

Functionalized Carbon as Polysulfide Traps for Advanced Lithium-Sulfur Batteries Remith Pongilat1,2,3†, Sylvain Franger2† and Kalaiselvi Nallathamby1*† 1CSIR-Central

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Electrochemical Research Institute, Karaikudi, INDIA

ICMMO/ERIEE (UMR CNRS 8182), University Paris Sud/University Paris-Saclay, Orsay, FRANCE. 3

Academy of Scientific and Innovative Research, CSIR, INDIA [email protected]

AUTHOR INFORMATION †These authors contributed equally to this work. Corresponding Author: Kalaiselvi Nallathamby (E-mail: [email protected])

ACS Paragon Plus Environment

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ABSTRACT Rechargeable lithium-sulfur batteries could be qualified to solve the energy needs of the present society simply by raising the specific capacity of the battery packs and could be made as a cost effective technology by virtue of the abundant, safe and economically viable sulfur. However, polysulfide dissolution related issue in the lithium-sulfur battery is the major hurdle, which needs to be reduced prior to the acceptance of rechargeable lithium-sulfur technology as a practically viable and feasible strategy to ensure efficient energy storage mechanisms. Towards this direction, we study the effect of oxidative functionalization and effect of temperature on the cycleability of lithium-sulfur battery as a function of their role in reducing the polysulfide dissolution by using EIS technique. The study demonstrates the reversible cycling of lithiumsulfur battery at 40 C, wherein the cell delivers a discharge capacity of 750 mAh g-1 at a high current of 750 mA g -1 and tolerates up to 7.5 A g-1 current rate with the 60 wt % sulfur loaded functionalized carbon cathode. Our findings reflect the advantageous effect of surface functionalization on the performance of lithium-sulfur battery and the importance of EIS spectroscopy in understanding the mechanism associated with the reversible electrochemical process.


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Introduction Ever since its discovery in the 1960s, Li-S batteries provide a promising option for their application in portable electronic devices. However, soon after the emergence of lithium-ion battery, the development of lithium-sulfur system got hampered temporarily, since LIBs bestowed with stable lifespan and high voltage characteristics captured the e-market due to these advantages1-4. However, the substantial increase in the human as well as gadget population aligned with the economic growth poses a pressing need to search for alternative energy storage devices, which in turn triggers the resurgence of Li-S batteries. Basically, lithium-sulfur system deserves to be extensively investigated as an alternative energy storage device, owing to its high theoretical capacity of 1672 mA h g-1 (very high theoretical specific energy density of 2500 Wh kg-1), natural abundance, environment friendliness and low cost of sulfur 5-8. Sulfur, one of the most abundant elements in the earth’s crust is capable of delivering a capacity of 1672 mA h g -1 and a practical energy density of 400 to 600 Wh kg -1, which are far higher than those of commercial LIBs. Despite the said advantages, few hurdles related to Li-S system need to be addressed, prior to its recommendation as a potential and alternative device in meeting out the requirements of most of the futuristic applications. Among the challenges, the solubility of electrically insulating lithium polysulfides (LinSn)9, which are formed during the intermediate redox reactions between lithium and sulfur in the electrolyte, prevents the in-depth discharge of sulfur and thereby reduces the round trip efficiency of the system10-11. The lower order polysulfides formed due to the direct reaction of dissolved polysulfides with lithium anode will deposit over the lithium and will enhance the shuttle mechanism, resulting in low coulombic efficiency and rapid capacity fading12.


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Different strategies are proposed to alleviate the polysulfide dissolution, which include, coating of sulfur particles with carbon13 or metal oxide14, use of polymer electrolytes15 and mesoporous structures16 etc. Recently, the research group of Nazar reported the mechanism involved in the chemical interactions associated with polysulfides namely, polar–polar interactions, Lewis acid–base interactions and sulfur-chain catenation17. The inclusion of polymeric materials containing functional groups in conjunction with carbonaceous materials, metal oxide additives like MnO2, MgO and phosphorene (a monolayer of black phosphorus), etc. have been attempted with a view to reduce the polysulfide dissolution by entrapping or immobilizing them in the matrix. Such an attempt will provide stability and long term cycleability to the lithium-sulfur cells18-20. Yang Hou et. al. presented a novel design of a lightweight carbon-based cathode by confining sulfur in 2D carbon nanosheets with abundant porous structure followed by 3D graphene aerogel wrapping21, wherein porous carbon nanosheets act as the sulfur host and suppress the diffusion of polysulfide, while the graphene conductive networks anchor the sulfur-adsorbed carbon nanosheets, thus providing pathways for rapid electron/ion transport and prevent the polysulfide dissolution. Another method adopted to immobilize polysulfides deals with the chemical deposition strategy22, in which the surface functional groups present on the graphene oxide will effectively reduce the polysulfide dissolution during cycling with the help of their strong adsorbing ability to anchor S atoms. Intrigued by such literature reports, we have deployed yet another strategy of exploiting peroxide oxidized carbon black as a support to load sulfur and to improve the electrochemical properties by reducing the polysulfide dissolution with the help of functional groups available on the surface of carbon nanoparticles. H2O2 functionalized carbons are known to possess porous nature and are reported for their application as catalyst support for oxygen reduction reaction and


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to capture heavy metals. Even though functionalization of carbon black with H 2O2 has been reported by V.K. Pillai et. al. for its use as electrocatalytic support23, the extended application of such functionalized carbon for catalytic as well as energy storage purposes has not been reported by any research group till date. Further, we strongly opine that by exploiting the H 2O2 triggered oxygen functional groups along with the micro/mesopores present in carbon black, one can effectively accommodate the polysulfide and other sulfides formed during the electrochemical reaction. As a result, significantly improved coulombic efficiency and rate capability performance could be realized, especially through the careful manipulation of post functionalization benefits related to carbon black. In this regard, the study assumes importance, wherein a simple and an easy-to-adopt reaction protocol has been implemented to obtain functionalized carbon, bestowed with increased porosity and the presence of flanked functional groups, capable of exhibiting tolerance against polysulfide dissolution through the effective accommodation of electrochemically generated intermediate products. Such an oxidative functionalized carbon has been exploited to address the challenging dissolution issue pertinent to Li-S system. Selection of simple remedial measure to combat the critical issue of polysulfide dissolution is the highlight of the present study that demonstrates remarkably improved electrochemical behavior in Li-S system. Results and Discussions

Scheme 1. Schematics to prepare S@functionalized carbon.


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Scheme 1 illustrates the synthesis protocol used for the preparation of Sulfur@FC composites. Treatment of acetylene black with peroxide oxidizes the surface of carbon atoms and creates – COO functional groups. It has been reported by Pillai et. al. that the H 2O2 treatment can increase the porosity of the carbon surface and the created porosity has been exploited by them to enhance the heavy metal absorption. On the contrary, thus created pores and the porosity related advantages have been exploited effectively in the current study to accommodate the intermediate products, wherein the associated formation of COO groups on the surface of functionalized carbon has been confirmed with the help of FTIR spectroscopy24, displayed in Figure S1. Herein, presence of a peak around 1700 cm-1 corresponds to the oxidized carbon species, involved in forming C-O linkage. Sulfur impregnated functionalized carbon shows three peaks at 803, 1234 and 1362 cm-1, evidencing the formation of sulfur carbon composite. In the same way, X-ray photo electron spectroscopy reveals the formation of C-O bonds, resulting from the oxidation of carbon due to peroxide. Figure S2 shows the high resolution XPS spectrum of Carbon 1s and Oxygen 1s of pristine and functionalized carbon. It can be easily identified from Figure S2b that the functionalized carbon has definite formation of C-O bonds, while comparing with the pristine carbon due to the oxidative functionalization of select carbon with peroxide. The high resolution O 1s spectrum can be fitted to confirm the presence of oxygen atoms in three different environments such as hydroxyl (536.6 eV) carboxyl (533.3 eV) and ketonic (531.4 eV) carbon arrangement25. Detailed analysis of the C1s and O1s spectrum of both pristine and functionalized carbon shows the formation of oxygen functional groups on the surface of the carbon particles. There is a decrease in the percentage of C-C bonds and increase in the C-O bonds, as can be confirmed from Table S1. Similarly, the C=O percentage shows an increment in the case of functionalized carbon in comparison with the pristine carbon. The as-formed oxygen functional


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groups will help in accommodating intermediate polysulfides, thereby improving the electrochemical properties.

Figure 1a) XPS survey spectrum of sulfur@carbon composite, b) high resolution spectrum of Sulfur 2p, c) high resolution spectrum of Carbon 1s and d) high resolution spectrum of Oxygen 1s Ex-situ XPS measurements were performed with the sulfur confined microporous carbon and the results are shown in Figure 1. XPS peaks corresponding to those of C 1s, O 1s and S 2p core level of sulfur-carbon black composites are illustrated in Figure 1. As shown in Figure 1d, the de-convoluted O 1s spectrum of 60S@AC composite consists of three peaks corresponding to C=O, O–S and C–O species26, appearing at 531.7, 533.2, and 535.2 eV respectively. Presence of O-S species confirms the combination of fraction of sulfur with the oxygen functional groups found on the surface of functionalized carbon nanoparticles. Similarly, the high resolution S 2p


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spectrum also shows the presence of two peaks at 163.8 and 165.0 eV, which can be attributed to the S 2p3/2 and S 2p1/2 peak components27 respectively. Yet another peak found at 166.3 eV can be attributed to the surface S-O species, thus evidencing the formation of oxygen-sulfur attachment28-29. C1s spectrum shows three peaks at 284.2, 285 and 289.2 eV and confirms the presence of carbon oxygen bonds. The currently observed spectral features are in complete agreement with the results reported in the literature. Notably, oxygen functionalization not only improves the porosity, but also enhances the adsorption of sulfur on the surface of carbon nanoparticles, which will eventually enhance the electrochemical performance of the resulting S@FC composite cathode and thus receives importance. The Brunauer-Emmett-Teller (BET) analysis shows that peroxide functionalized carbon has a surface area of 145 m2 g-1 and pore volume of 0.35 cc g-1. A Langmuir-type (Type I) isotherm (Figure S3) obtained for the functionalized carbon indicates the characteristic behavior of porous carbon. There is an increment in pore volume from 0.05 cc g -1 and the pore size distribution curve also shows an increment in pores in the microporous range, attributing to the advantageous effect of surface oxidation with peroxide. Even though no change in morphology has been observed for the functionalized carbon after sulfur impregnation, there is a significant decrease in the surface area of pristine form of functionalized carbon from 145 to ~40 m2 g-1 (FCS60) and the pore volume changes from 0.35 to 0.1 cc g -1, suggesting that sulfur particles are confined inside the pores of the functionalized carbon. Normally, at high temperature, sulfur assumes a linear chain like configuration and as a result, during the impregnation process, the formed S8 rings and the chains get themselves accommodated inside the pores of functionalized carbon which in fact are expected to eventually reduce the surface area of the porous functionalized carbon.


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Figure 2. Raman spectrum of pristine carbon black, functionalized carbon and composite of sulfur with functionalized carbon XRD pattern of carbon black, peroxide functionalized carbon and sulfur–carbon composite is shown in Fig. S4. Presence of sharp diffraction peaks denotes the existence of sulfur in the crystalline state (JCPDS Card No: 102578), while the broad diffraction peak that appears at about 2= 24 degree, indicates the amorphous nature of functionalized carbon particles30. The crystallographic details of carbon and sulfur in the composite are investigated by Raman spectroscopy (Figure 2). The recorded Raman spectrum of FCS60 (functionalized carbon with 60 wt% sulfur loading) carbon is compared with those of pristine carbon black and functionalized carbon black. Among the chosen samples, carbon black displays 3 peaks at 1350, 1550 and 2800 cm-1, functionalized carbon also displays 3 peaks at 1354, 1560 and 2800 cm-1 (D, G and 2D) and the S@FC composite displays all the characteristic peaks of carbon and sulfur. Further, functionalized carbon is found to get partially graphitized, as evidenced by the


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two strong peaks at 1350 and 1600 cm-1, representing the presence of D and G bands of mesoporous carbon respectively. D-band observed around 1350 cm−1 corresponds to the structural disorder due to the presence of sp3 carbons, while the G-band at 580 cm−1 can be attributed to the E2g mode of sp2-hybridized carbon frameworks31. FCS60 upon comparison with the pristine and functionalized carbon shows a small change in the intensity ratio of D and G bands, which indicates the monolayer deposition of sulfur within the pores of the functionalized carbon during impregnation process. i.e., I D/IG ratio of functionalized carbon increases from 0.98 to 1.05 after sulfur impregnation, indicating an increment in disorder. B. Ding et. al reported that sulfur exists in the highly dispersed state with a low-molecular monolayer coverage inside the mesoporous walls of carbon support. In FCS60 cathode, sulfur exist both as monolayer and in the form of surface adsorbed particles, as understood from the peaks observed in XRD due to the presence of monoclinic sulfur atoms 32. Thermogravimetric analysis confirms that the FCS60 composite contains 60 wt % sulfur and 40 wt % functionalized porous carbon (Figure S5). The weight loss region viz., 200-320 C is associated with the removal of sulfur33-34 by sublimation and the remaining weight loss is due to the degradation of carbon. FESEM images of functionalized carbon and the sulfur impregnated functionalized carbon are shown in Figure S6. After sulfur impregnation, no change in morphology of the spherical carbon nanoparticles has been observed. Figure 3a-c shows the TEM images of FCS60, in which the sphere-like carbon particles are, interconnected with each other and are porous in nature. Figures 3d and e show the TEM images of FCS60 and figure 3f shows the SAED pattern of the corresponding sulfur impregnated functionalized carbon. The contrast difference in the TEM images indicates the presence of porous nature of the carbon nanoparticles. The porous


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structure is generally beneficial for the impregnation of sulfur during the melt diffusion process and the presence of nanochannels improves the ease of electrolyte accessibility, especially during galvanostatic cycling. Further, the micro/meso porous nature is found to restrict the lithium polysulfide dissolution in the electrolyte mixture, thus leading to the improved electrochemical properties.

Figure 3. TEM images of a-c) functionalized carbon, d-f) Sulfur@functionalized carbon composites and SAED pattern of FCS60 In the HRTEM image of FCS60 (Figure S7), lattice fringes (lamellae) of functionalized carbon are observed with no indication for the presence of crystalline sulfur on the surface. Normally, amorphous carbon particles will not exhibit crystalline stacking or special ordering. The presence of discernible crystalline structure and the special order observed in the HRTEM images confirm that the carbon nanoparticles are not completely amorphous in nature 35, which is noteworthy. Elemental mapping reveals the uniform distribution of sulfur in the pores of functionalized carbon nanoparticle (Figure S8). Figure S7 shows the ABF-STEM image of a selected region with individual mapping of sulfur, oxygen and carbon. The elemental mapping


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images (Figure S7b) show that sulfur is uniformly distributed in the meso/micropores of functionalized carbon nanoparticles. As shown in Fig. S6a, the chosen carbon materials are bestowed with interconnected sphere-like morphology with a size ranging from 50 to 60 nm.

Figure 4. EIS Spectra recorded at different voltages during charge and discharge of the cell. EIS studies have been performed on the ACS60 cathode at different depths of discharge and charge (Figure 4) to understand the mechanism of the electrochemical formation of Li 2S during discharge and their reformation as elemental sulfur during charge. During the first discharge, insulating solid octasulfur (S8) rings in the micropores are solvated in the electrolyte and are transformed into long chain polysulfides, which are dissolved in the electrolyte and on further reduction, the long chain polysulfides will get transformed into highly reduced soluble


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polysulfides and solid products such as Li2S2 and Li2S. The solid products will ultimately get precipitated in the electrode surface36. The chemical equations governing the reaction mechanism and the corresponding voltages are given below, S8 + 2Li+ + 2e Li2 S8 -------- 2.4 V Li2S8 + 2Li+ + 2e  4Li2S6 -------- 2.1 V Li2S8 + 2Li+ + 2e 2Li2S4 -------- 2.1V Li2S4 + 2Li+ + 2e 2Li2S2 -------- 2.0V Li2S2 + 2Li+ + 2e  2Li2S -------- 2.0 V As the intermediate polysulfides are formed, the resistance of the cell gradually decreases due to the solubility and increases the conductivity of these soluble higher order polysulfides like Li 2S8, Li2S6 and Li2S4. When the discharge of the cell was continued, a stable flat potential plateau at 2.0 V is obtained due to the conversion of higher order polysulfides to lower order polysulfides like Li2S2 and Li2S. The resultant lower order sulfides are insoluble, get precipitated over the electrode surface and eventually increase the resistance of the electrode/electrolyte interface. Similarly, during charge, the resistance reduces as the lower order polysulfides are transformed in to higher order polysulfides and at the end of the charge, the resistance increases with the formation of elemental sulfur. Since the change in the cell resistance can be effectively measured with the help of impedance analysis, the same has been were used as a tool to examine the reaction mechanism of the currently studied lithium sulfur system. Figure 4 shows the electrochemical impedance spectra of the lithium sulfur battery with FC@S electrode during charge and discharge at different depths of charge/discharge (or voltage). The cell has been stopped at different discharge and charge states, i.e., at different SOC conditions and the electrochemical impedance measurements were carried out individually. The observed values of


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solution resistance (Rs), charge transfer resistance (R ct) and other related parameters are appended in Table S2. From the figure, it can be found that the Rct value and the solution resistance (Rs) decreases upto 2.1 V, due to the increased conductivity of higher order polysulfides compared with that of elemental sulfur and the dissolution of sulfur. As the discharge continues to 2.1 V, formation/transformation of lower order polysulfides and the dissolution of insoluble and resistive lithium polysulfides gets initiated which in turn increases the resistance37. As a result, the internal resistance rises to 165 ohm at the end of discharge, which is attributable to the complete formation of insoluble lower order polysulfide 38-39, viz., Li2S. Similarly, at the end of charge, (3.0 V) Rct increases when compared with the initial value and is believed to be due to the dissolution of polysulfides in the electrolyte.

Figure 5. a) Cyclic voltammetry of S60@FC b) Charge/Discharge profiles of cell with S60@FC cathode c) Specific discharge/charge capacity and coulombic efficiency profile vs cycle number and d) rate capability of S60@FC cathode.


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The electrochemical performance of currently prepared Sulfur@Carbon composites were evaluated by using CR 2032 coin type cells with 1 M bis(triflouromethyl sulfonimide) lithium and 1 M lithium nitrate in a mixed solvent of 1,2-dimethoxy ethane and 1,3-dioxalane (50:50 v/v) . Cyclic voltammetry measurements were done at a constant scan rate of 0.1 mV s -1 in order to optimize the sulfur content in the functionalized carbon particles and the results are appended in figure S9. Considering the current value and the extent of reversibility, one can identify the best cathode composition suitable for use in lithium sulfur cell assembly. Functionalized carbon with 50 (FCS50) and 70 % (FCS70) of infused sulfur shows inferior current response and reversibility upon continuous cycles. Figure 5a shows the cyclic voltammetry profile of the asprepared cathode with 60 % infused sulfur (FCS60) in lithium sulfur cell assembly recorded at a scan rate of 0.1 mV/s in the voltage range of 1.5 to 3.0 V vs Li/Li+. In the first cathodic scan, two reduction peaks around 2.4 and 2.0 V are observed, which are in accordance with the reported behavior. The peak around 2.4 V corresponds to the reduction of elemental sulfur to higher order polysulfides of lithium and the peak at 2.0 V is attributed to the formation of lower order polysulfides by the reduction of higher order polysulfide. In the subsequent anodic scan, one sharp doublet peak is observed, owing to the complete single step conversion of lower order polysulfide into elemental sulfur. In the following scans, a slight change in current alone is visible, indicating high stability and reversibility. Collectively, cyclic voltammetry results evidence the advantageous effect of surface oxidation for its contribution towards improved electrochemical performance of S@FC composite cathode. In other words, activation of carbon black with peroxide that leads to the presence of porous nature as well as the functionalized functional groups on the surface of carbon plays a vital role in enhancing the overall electrochemical behavior of Li-S battery as a function of


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functionalized carbon@sulphur cathode. Moreover, the FCS60 shows better reversible cycleability and high current response compared with those of FCS50 and FCS70 cathodes and based on this observation; FCS60 was selected for subsequent and detailed electrochemical analysis. Figure 5b depicts the 1 st to 100th cycle voltage profile of the electrodes recorded at 100 mA g-1 current density conditions. Three plateaus are observed commonly in the voltage profile and are consistent with the peaks in the CV. The sulfur@FC (FCS60) carbon composite delivers a first sulfur-specific discharge capacity of 1660 mA h g -1 at 100 mA g-1 current density, which in turn endorses the high utilization of sulfur. Figure 5c shows the charge/discharge capacity of the same cell cycled at 100 mA g -1 for 100 cycles. The first charge capacity of 1648 mA h g -1 indicates good reversibility behavior. However, after 20 subsequent cycles, the reversible capacity of the cell gets maintained only at 950 mA h g-1 with a progressive coulombic efficiency of 98 %. Even though the capacity drops from 1st -10th cycle is more or less 39 %, the capacity drop from 10th-100th cycle is found to be only 0.06 % per cycle. It has already been reported that the capacity loss in the first few cycles in a lithium sulfur cell may be due to the diffusion loss of sulfur or due to the irreversible formation of Li2 S and hence requires no specific explanations. We have compared the electrochemical performance of FCS50 and FCS70 cathodes with that of FCS60 cathode and found that a steady state capacity value of ~500 mA h g -1 with a high capacity fade is observed with 50 and 70 wt % sulfur loaded functionalized carbon cathodes (Figure S10). The charge discharge capacity of the FCS60 composite cathode at different current densities has been depicted in figure 5d. The cathode delivers specific capacities around 702, 584, 503, 422 and 335 mA h g-1 at 1.0, 1.5, 3.0, 5.0 and 7.5 A g -1 current densities respectively. When the current rate was switched from 7.5 A g-1 to 1.5 and 0.2 A g-1 the recouped capacities


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are 532 and 973 mA h g -1 respectively, thus demonstrating the good rate capability of the FCS60 composite cathode.

Figure 6. a,b) Discharge profiles of cells at 1 A/g current rate at different temperatures and the corresponding EIS spectra and c) Discharge profile of FCS60 cathode at 750 mA g -1 current rate for 150 cycles.


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The cycling performance of lithium sulfur battery containing FCS60 cathode has been carried out at different temperatures ranging from 0 C to 40 C and the corresponding discharge profiles are depicted in Figure 6a. Charging of the cells was done at 150 mA g -1 and discharge was done at 1 A g -1 current rate. From the figure, it can be understood that while increasing the temperature, discharge capacity value also increases due to the increased lithium transportation kinetics at high temperatures. The cathode delivers a high capacity of 596 mA h g -1 at 40 C and 390 mA h g-1 at 0 C. The change in the resistance with respect to temperature has been examined with the EIS spectra and is depicted in figure 6b. From the figure, it can be easily understood that the Rct value increases from 80 to 380  as the temperature reduces from 40 to 0 C40-41. Influenced by the exciting results obtained in the high temperature cycling studies coupled with the impedance measurements, the study has been extended for long term cyclability experiments and the obtained result is shown in figure 6c. The cell when cycled at 750 mA g -1 current and under the influence of 40 C, it exhibits a high capacity of 880 mA h g -1 with an insignificant capacity fade corresponding to 0.2%. Further, a high capacity of 700 mA h g-1 has been observed even at the end of the 150th cycle. On the other hand, when the cell was cycled at the same current density and at room temperature, much reduced capacity of 450 mA h g -1 has been obtained42 (Figure S11).[] Thus, it can be concluded that the active functional groups on the surface of carbon nanoparticles are acting as sulfur immobilizers and the same is responsible to reduce the shuttle mechanism by reducing the polysulfide concentration in the electrolyte. Also, by optimizing the ratio of sulfur to carbon and the temperature of cycling with the help of electrochemical impedance spectroscopy studies, we achieved substantially improved specific capacity and cycleability behavior of the lithium-sulfur battery.


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Conclusion In summary, simple oxidative functionalization of carbon black for the effective immobilization of polysulfide has been demonstrated with the help of electrochemical impedance spectroscopy. The results hold promise in reducing the ‘polysulfide shuttle effect’ owing to the surface functional groups associated with the custom modified functionalized carbon nanoparticles. Moreover, effect of temperature on the cycleability of Sulfur@functionalized carbon composites has been successfully displayed and the mechanism associated with the same has been explained. Results show that it is possible to reversibly cycle the FCS60 composite cathode at high temperatures to the extent that a high specific discharge capacity of 750 mA h g -1 at 750 mA g-1 current density could be extracted. Indeed, the FCS60 cathode can exhibit a high specific capacity value c.a. 1000 mA h g -1 and better rate capability performance up to 7.5 A current. Substantial efforts in translating the all-inclusive information about the surface functional groups towards the development of high temperature lithium-sulfur batteries will be the future prospect of this work. ASSOCIATED CONTENT Supporting Information. : Detailed experimental procedure, FTIR spectra, XPS spectra, FESEM images, STEM elemental mapping images, N2 adsorption-desorption isotherm, XRD patterns, TGA plot, CV curves and cycling performance AUTHOR INFORMATION Notes All authors contributed equally to this work. The authors declare no competing financial interests.


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ACKNOWLEDGMENT Among the authors, Remith P. acknowledges the Department of Science and Technology, New Delhi for the financial support through DST-Inspire Fellowship scheme; French Government for the financial support through Eiffel Excellency Fellowship and Kalaiselvi N. acknowledges DST for financial support through GAP 14/16 and GAP 16/17 projects.. REFERENCES (1) Peled, E.; Gorenshtein, A.; Segal, M.; Sternberg, Y. Rechargeable Lithium Sulfur Battery (Extended Abstract). J. Power Sources 1989, 26, 269–271. (2) Rauh, R. D.; Abraham, K. M.; Pearson, G. F.; Surprenant, J. K.; Brummer, S. B. A Lithium / Dissolved Sulfur Battery with an Organic Electrolyte. J. EIectrochem. Soc. 1979, 126, 523527. (3) Yamin, H.; Peled, E. Electrochemistry of a Nonaqueous Lithium/sulfur Cell. J. Power Sources 1983, 9, 281–287. (4) Herbert, D.; Ulam, J. Electric Dry Cells and Storage Batteries. US Pat. No. 3043986, 1962, 2–4. (5) Nole, D. A.; Moss, V. Battery Employing Lithium-Sulphur Electrodes with Non-Aqueous Electrolyte. US Pat. No. 3532543, 1970, 3–5. (6) Rao, M. L. Organic Electrolyte Cells. US Pat.No. 3413154, 1966, Nov 26. (7) Manthiram, A.; Fu, Y.; Chung, S.; Zu, C.; Su, Y. Rechargeable Lithium−Sulfur Batteries. Chem. Rev. 2014, 114, 11751–11787.


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(8) Yin, Y. X.; Xin, S.; Guo, Y. G.; Wan, L. J. Lithium-Sulfur Batteries: Electrochemistry, Materials and Prospects. Angew. Chemie - Int. Ed. 2013, 52, 13186–13200. (9) Manthiram, A.; Fu, Y.; Su, Y. S. Challenges and Prospects of Lithium-Sulfur Batteries. Acc. Chem. Res. 2013, 46, 1125–1134. (10) Zhang, S. S. Liquid Electrolyte Lithium/sulfur Battery: Fundamental Chemistry, Problems, and Solutions. J. Power Sources 2013, 231, 153–162. (11) Busche, M. R.; Adelhelm, P.; Sommer, H.; Schneider, H.; Leitner, K.; Janek, J. Systematical Electrochemical Study on the Parasitic Shuttle-Effect in Lithium-Sulfur Cells at Different Temperatures and Different Rates. J. Power Sources 2014, 259, 289–299. (12) Shin, E. S.; Kim, K.; Oh, S. H.; Cho, W. Il. Polysulfide Dissolution Control: The Common Ion Effect. Chem. Commun.. 2013, 49, 2004–2006. (13) Jayaprakash, N.; Shen, J.; Moganty, S. S.; Corona, A.; Archer, L. A. Porous Hollow Carbon@sulfur Composites for High-Power Lithium-Sulfur Batteries. Angew. Chemie Int. Ed. 2011, 50, 5904–5908. (14) Liang, X.; Kwok, C. Y.; Lodi-Marzano, F.; Pang, Q.; Cuisinier, M.; Huang, H.; Hart, C. J.; Houtarde, D.; Kaup, K.; Sommer, H.; et. al.. Tuning Transition Metal Oxide-Sulfur Interactions for Long Life Lithium Sulfur Batteries: The “goldilocks” Principle. Adv. Energy Mater. 2016, 6, 1–9. (15) Park, K.-S. K.; Cho, J. H.; Jang, J.; Yu, B.; Hoz, A. T. D. La; Kevin, M.; Ellison, C. J.; Goodenough, J. B. Trapping Lithium Polysulfides of a Li-S Battery by Forming Lithium Bonds in a Polymer Matrix. Energy Environ. Sci. 2015, 8, 2389–2395.


21


Page 22 of 27

(16) Ji, X.; Lee, K. T.; Nazar, L. F. A Highly Ordered Nanostructured Carbon-Sulphur Cathode for Lithium-Sulphur Batteries. Nat. Mater. 2009, 8, 500–506. (17) Pang, Q.; Liang, X.; Kwok, C. Y.; Nazar, L. F. Advances in Lithium–sulfur Batteries Based on Multifunctional Cathodes and Electrolytes. Nat. Energy 2016, 1, 16132. (18) Liang, X.; Hart, C.; Pang, Q.; Garsuch, A.; Weiss, T.; Nazar, L. F. A Highly Efficient Polysulfide Mediator for Lithium–sulfur Batteries. Nat. Commun. 2015, 6, 5682. (19) Ponraj, R.; Kannan, A. G.; Ahn, J. H.; Kim, D. W. Improvement of Cycling Performance of Lithium-Sulfur Batteries by Using Magnesium Oxide as a Functional Additive for Trapping Lithium Polysulfide. ACS Appl. Mater. Interfaces 2016, 8, 4000–4006. (20) Li, L.; Chen, L.; Mukherjee, S.; Gao, J.; Sun, H.; Liu, Z.; Ma, X.; Gupta, T.; Singh, C. V.; Ren, W.; et. al.. Phosphorene as a Polysulfide Immobilizer and Catalyst in HighPerformance Lithium-Sulfur Batteries. Adv. Mater. 2017, 29, 1602734. (21) Hou, Y.; Li, J.; Gao, X.; Wen, Z.; Yuan, C.; Chen, J. 3D Dual-Confined Sulfur Encapsulated in Porous Carbon Nanosheets and Wrapped with Graphene Aerogels as a Cathode for Advanced Lithium Sulfur Batteries. Nanoscale 2016, 8, 8228–8235. (22) Ji, L.; Rao, M.; Zheng, H.; Zhang, L.; Li, O. Y.; Duan, W. Graphene Oxide as a Sulfur Immobilizer in High Performance Lithium/Sulfur Cells. J. Am. Chem. Soc. 2011, 133, 18522–18525. (23) Carmo, M.; Linardi, M.; Poco, J. G. R. H2O2 Treated Carbon Black as Electrocatalyst Support for Polymer Electrolyte Membrane Fuel Cell Applications. Int. J. Hydrogen Energy 2008, 33, 6289–6297.


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Page 23 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(24) Unni, S. M.; Dhavale, V. M.; Pillai, V. K.; Kurungot, S. High Pt Utilization Electrodes for Polymer Electrolyte Membrane Fuel Cells by Dispersing Pt Particles Formed by a Preprecipitation Method on Carbon “polished” with Polypyrrole. J. Phys. Chem. C 2010, 114, 14654–14661. (25) Park, M.; Ryu, J.; Kim, Y.; Cho, J. Corn Protein-Derived Nitrogen-Doped Carbon Materials with Oxygen-Rich Functional Groups: A Highly Efficient Electrocatalyst for All-Vanadium Redox Flow Batteries. Energy Environ. Sci. 2014, 7, 3727–3735. (26) Wu, F.; Li, J.; Tian, Y.; Su, Y.; Wang, J.; Yang, W.; Li, N.; Chen, S.; Bao, L. 3D Corallike Nitrogen-Sulfur Co-Doped Carbon-Sulfur Composite for High Performance LithiumSulfur Batteries. Sci. Rep. 2015, 5, 13340. (27) Xu, M.; Jia, M.; Mao, C.; Liu, S.; Bao, S.; Jiang, J.; Liu, Y.; Lu, Z. Aspergillus Flavus Conidia-Derived Carbon/Sulfur Composite as a Cathode Material for High Performance Lithium–Sulfur Battery. Sci. Rep. 2016, 6, 18739. (28) Li, X.; Li, X.; Banis, M. N.; Wang, B.; Lushington, A.; Cui, X.; Li, R.; Sham, T-K.; Sun, X. Tailoring Interactions of Carbon and Sulfur in Li–S Battery Cathodes: Significant Effects of Carbon– Heteroatom Bonds. J. Mater. Chem. A, 2014, 2, 12866. (29) Marsh, H.; Sherwood, P.; Augustyn, D. An XPS Study of Binding Energies of Sulphur in Carbon. Fuel 1976, 55, 97–98. (30) Lee, C.-G.; Hur, H.; Song, M.-B. Oxidation Behavior of Carbon in a Coin-Type Direct Carbon Fuel Cell. J. Electrochem. Soc. 2011, 158, B410–B415.


23


Page 24 of 27

(31) Balakumar, K.; Kalaiselvi, N. High Sulfur Loaded Carbon Aerogel Cathode for Lithium– sulfur Batteries. RSC Adv. 2015, 5, 34008–34018. (32) Ding, B.; Yuan, C.; Shen, L.; Xu, G.; Nie, P.; Zhang, X. Encapsulating Sulfur into Hierarchically Ordered Porous Carbon as a High- Performance Cathode for Lithium– Sulfur Batteries. Chem. Eur. J. 2013, 19, 1013 – 1019. (33) Li, G.; Sun, J.; Hou, W.; Jiang, S.; Huang, Y.; Geng, J. Three-Dimensional Porous Carbon Composites Containing High Sulfur Nanoparticle Content for High-Performance Lithium– sulfur Batteries. Nat. Commun. 2016, 7, 10601. (34) Zhang, C.; Wang, W.; Wang, A.; Yuan, K.; Yang, Y.; Lu, Y. Effect of Carbon Core Grafting on the Properties of Carbon-Sulfur Composite for Lithium/Sulfur Battery. J. Electrochem. Soc. 2015, 162, A1067–A1071. (35) Gaddam, C. K.; Huang, C. H.; Vander Wal, R. L. Quantification of Nano-Scale Carbon Structure by HRTEM and Lattice Fringe Analysis. Pattern Recognit. Lett. 2016, 76, 90–97. (36) Wild, M.; O’Neill, L.; Zhang, T.; Purkayastha, R.; Minton, G.; Marinescu, M.; Offer, G. J. Lithium Sulfur Batteries, a Mechanistic Review. Energy Environ. Sci. 2015, 8, 3477–3494. (37) Deng, Z.; Zhang, Z.; Lai, Y.; Liu, J.; Li, J.; Liu, Y. Electrochemical Impedance Spectroscopy Study of a Lithium/Sulfur Battery: Modeling and Analysis of Capacity Fading. J. Electrochem. Soc. 2013, 160, A553–A558. (38) Canas, N. A.; Hirose, K.; Pascucci, B.; Wagner, N.; Friedrich, K. A.; Hiesgen, R. Investigations

of

Lithium-Sulfur

Batteries

Using

Electrochemical

Impedance

Spectroscopy. Electrochim. Acta 2013, 97, 42–51.


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(39) Lang, S.-Y.; Shi, Y.; Guo, Y.-G.; Wang, D.; Wen, R.; Wan, L.-J. Insight into the Interfacial Process and Mechanism in Lithium-Sulfur Batteries: An In Situ AFM Study. Angew. Chem. Int. Ed. 2016, 55, 15835–15839. (40) Zhang, S. S.; Xu, K.; Jow, T. R. Electrochemical Impedance Study on the Low Temperature of Li-Ion Batteries. Electrochim. Acta 2004, 49, 1057–1061. (41) Li, X.; Lushington, A.; Sun, Q.; Xiao, W.; Liu, J.; Wang, B.; Ye, Y.; Nie, K.; Hu, Y.; Xiao, Q.; et. al.. Safe and Durable High-Temperature Lithium-Sulfur Batteries via Molecular Layer Deposited Coating. Nano Lett. 2016, 16, 3545–3549. (42) Zhang, S. S.; Xu, K.; Jow, T. R. The Low Temperature Performance of Li-Ion Batteries. J. Power Sources 2003, 115, 137–140.


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174x99mm (300 x 300 DPI)


Functionalized Carbon as Polysulfide Traps for ... - ACS Publications

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