Interphases in LithiumâSulfur Batteries: Toward Deployable Devices

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Interphases in Lithium-Sulfur Batteries: Towards Deployable Devices with Competitive Energy Density and Stability Qing Zhao, Jingxu (Kent) Zheng, and Lynden A. Archer ACS Energy Lett., Just Accepted Manuscript • DOI: 10.1021/acsenergylett.8b01001 • Publication Date (Web): 03 Aug 2018 Downloaded from http://pubs.acs.org on August 6, 2018

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ACS Energy Letters

Interphases in Lithium-Sulfur Batteries: Towards Deployable Devices with Competitive Energy Density and Stability Qing Zhao1, Jingxu Zheng2, Lynden Archer1,2* 1

Robert Frederick Smith School of Chemical and Biomolecular Engineering and 2Department

of Materials Science & Engineering, Cornell University, Ithaca, New York 14853, USA. Corresponding Author *[email protected].

ABSTRACT: Lithium sulfur batteries have been studied intensively because of their potential to create high specific energies that meet accepted targets for mobile and stationary storage. Substantial efforts have been devoted to improve the electron/ion conductivity of the sulfur cathode, to suppress dissolution of polysulfide; and to limit parasitic reactions of polysulfide with lithium. Less consideration has addressed the interface stability of lithium, which is critical for long-term stability of cells that utilize high sulfur loadings and minimal electrolyte volume to maximize overall specific energy. Recent emphasis on all solid-state batteries underscore the important role well-formed interphases must play in achieving high material utilization at practical rates. We prospect that advances towards practical Li-S cells will come from strategies for creating durable interphases on lithium that limit active material and electrolyte loss and which provide greater flexibility in electrolyte design.

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Rechargeable batteries that utilize metallic anodes are considered as promising candidates for next generation energy storage/conversion devices, especially when the metal anode is coupled with high capacity conversion cathodes (sulfur, O2, CO2 et al.).1-4 Among these couples, rechargeable lithium-sulfur (Li-S) batteries that combine metallic lithium as anode and elemental sulfur as cathode offer the highest specific energy (2600 Wh/kg) of any solid-state battery. In addition to the intrinsically low cost and high earth abundance of the cathode material, the Li-S battery is an attractive candidate for next-generation storage for several additional reasons. First, Li-S batteries can be manufactured in similar configurations and form factors as commercial Li-ion batteries.5-8 Second, the electrode reactions are spontaneous and their kinetics relatively fast; Li-S cells typically do not require intervention with a catalyst or thermal source to achieve good discharge/charge rates. Finally, recent literatures have shown that Li-S cells exhibit high abuse tolerance.9,

10

This is remarkable considering the high

reactivity and low melting point of the Li metal anode, which makes it especially prone to thermal runaway. Practical Li-S cells with high specific energies and long cycle stability needs the cooperation of each component, especially using low anode-to-sulfur and electrolyte-tosulfur ratio. A typical Li-S battery (Figure 1a) is composed of a lithium anode, a separator soaked with electrolyte, and a sulfur/carbon based composite cathode loaded onto an Al metal current collector. Notwithstanding the many impressive characteristics of Li-S electrochemical cells, a commercially viable Li-S battery does not exist on large scale today because the solution thermodynamics of sulfur and its reduction compounds are complex.11-13 This issue is



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particularly problematic in Li-S cells because any soluble sulfur polymorphs formed at the cathode are able to diffuse to the reactive Li anode to undergo chemical reduction in a parasitic process, which deplete the active mass of the cathode and anode over time.

Figure 1. Illustration of configuration and energy density of Li-S batteries. a) Configuration of Li-S batteries. The vital points related with energy density as well as long cycle stability have been labeled. b) Energy density of Li-S batteries calculated by thickness of Li or electrolyte-to-sulfur ratio at different content of sulfur. The curves in blue colors are the relationship between thickness of Li and energy density, in which the electrolyte-to-sulfur ratio is constant as 4ul/mg. The curves in red colors are the relationship between electrolyte-to-sulfur and energy density, in which the capacity ratio of lithium-to-sulfur set constant as 2.

A large body of research has focused on creating substrates for sulfur cathodes in order to kinetically trap polysulfide species generated in the cathode to limit parasitic losses of active material.14-19 Significant efforts have also been given to developing strategies for sequestering sulfur and polysulfides in hosts that are able to accommodate the volume changes associated with the electrochemical conversion reactions at the Li-S battery cathode.6 As a consequence 4 ACS Paragon Plus Environment

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of these efforts and nearly a decade’s worth of development, the utilization of sulfur in the LiS battery cathode is approaching 100 % and Li-S cells with cycle life approaching thousands of cycles have already been reported.20, 21 An electrolyte-to-sulfur ratio close to 4ul/mg is thought to be the lowest to guarantee sufficient solubility of LiPS to enable such high utilization of sulfur species in the cathode.22 High areal loadings of sulfur (> 50mg/cm2) have likewise been reported, although these results are mostly achieved with thick current collectors (>200 um).23 The continuous advances made over the last decade have accelerated interest in commercializing Li-S batteries.24 This interest has in turn put a spotlight on several practices in the research literature, including the method of reporting the specific energy of Li-S cells in terms of mass of sulfur in the cathode. It is understood, however, that in a practical battery the mass of additional components must be taken into account to fully understand the competitive advantages of the Li-S cell relative to state-of-the-art Li-ion battery technology. These include the mass & thickness of lithium anode (Li-to-sulfur ratio), the amount of electrolyte used in the cell (electrolyte-to-sulfur ratio), and the areal and volume loading to sulfur in the cathode. These effects can be captured more concretely in terms of the practical specific energy of a LiS battery, which can be computed using the expression:

Here we’ve neglected the mass of any packaging material, which can produce an additional lowering of the cell-level energy density, by as much as 10% for pouch cells. Assuming the composition of sulfur in the cathode is 70 wt% of cathode, the areal density of cathode current collector (Al foil) is 4mg/cm2, and that the electrolyte is 1M LiTFSI in DOL/DME with a 5 ACS Paragon Plus Environment


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density of 1.25 mg/ul, the mass of separator is about 1.1 mg/cm2 (celgard 2320), the specific energy of the cells are easily computed (see Figure 1b). The figure also includes practical specific energies (green shaded area) achievable with state-of-the-art Li-ion cells. The blue curves report the effect of Li anode thickness on specific energy in Li-S cells in which the electrolyte-to-sulfur ratio is fixed at 4 ul/mg for varying sulfur mass loading at the cathode (e.g. 8 ul/cm2 for 2 mg(s)/cm2; 20 ul/cm2 for 5 mg(s)/cm2; 40 ul/cm2 for 10 mg(s)/cm2; 80 ul/cm2 for 20 mg(s)/cm2). The results show that the practical specific energy of the Li-S cell increases with increasing sulfur loading, and when a thin (100 µm) Li anode is used, the overall specific energy are close to or higher than 400 Wh/kg; exceeding values accessible in state-of-the-art LiBs at all sulfur mass loadings in the Li-S battery cathode. It should be noticed that for limited or thin lithium, the Li metal anode need to be coated on copper or other light-weight metal current collector, in which the energy density can be further declined. Meanwhile, sulfur utilization close to 100% (1675 mAh/g) is nearly impossible to achieve for thick electrode. So we also add a line for 20 mg/cm2 sulfur cathode (thick blue lines), in which we estimate the capacity of 1000 mAh/g and the energy density are largely reduced to 60%. It is noted, however, that when a more commonly used and thicker commercial lithium (500 µm) is used as anode, sulfur loadings above 5 mg/cm2 are required to achieve competitive specific energy with LIBs. Taking these observations one step further, we compute the practical specific energy of the LiS cell in which 100% excess of Li is present in the anode and the electrolyte-to-sulfur ratio varied for the same sulfur mass loadings as before (see red curves of Figure 1b). It is apparent from the figure that irrespective of the sulfur mass loading, the specific energy increases as a


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ACS Energy Letters

strong nonlinear function of decreasing electrolyte-to-sulfur ratio, implying that in order to achieve the high specific energies (>500 Wh/kg) promised by the Li-S battery chemistry, in practical cells, electrolyte-to-sulfur ratio values below 3 and a sulfur loading of at least 5 mg(s)/cm2 are required. Therefore, in addition to contemporary efforts to increase the sulfur loading in Li-S cells, efforts to reduce the amount of electrolyte in the cell are also a priority for future work.

Interphases that simultaneously protect Li from parasitic reactions, are able to flex and stretch to accommodate reversible volume change, and which enable fast interfacial transport of Li are a requirement for progress. Beyond their impact on the practical specific energy of a Li-S battery, proper accounting of the mass of all components in the cell introduces additional, quite serious challenges associated with performance. In particular, the commonly used electrolyte composed of DOL (1,3Dioxolane)/DME (1,2-Dimethoxyethane)-LiTFSI (LiN(CF3SO2)2) + LiNO3 is considered a requirement for stable Li-S battery operation because this electrolyte displays good solubility of lithium polysulfides (LiPS) generated at the cathode, which is advantageous for ensuring fast reaction kinetics of sulfur based intermediate products. This same characteristic unfortunately leads to loss of active material in the cathode and to degradation of the Li anode as a consequence of parasitic reactions between dissolved LiPS and the Li metal anode. Inevitable capacity fading due to parasitic reactions between dissolved LiPS species and the Li anode can to an extent be masked in the small cells typically used in research publications, which often employ large excess of Li. In larger cells that meet any of the criteria defined in the last section as requirements for high practical specific energies, particularly those in which the anode/cathode capacity approaches unity, these reactions produce more rapid fading.25 A 7 ACS Paragon Plus Environment


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stable interface between the lithium anode and electrolyte is known to play a crucial role in inhibiting parasitic reactions between electrolyte components and rough/mossy deposition of Li at low current densities.26 Thus, considering the importance of high sulfur loading and low electrolyte-to-sulfur ratios in achieving high practical specific energies, the quality and stability of interfacial phases formed on the Li anode are as important as the more extensively studied capacity of cathode hosts to bind LiPS, particularly in cells that utilize thin lithium foil to achieve an anode-to-cathode ratio near unity.

Figure 2. Typical methods of protecting Li anode in Li-S batteries. Electrolyte additives, and corresponding electron micrographs, a, An organic/inorganic interface generated by using SiCl4 contained ether based electrolyte. Reproduced with permission from refs 34, Copyright 2018 Wiley-VCH. b, A hybrid interface formed by poly(sulfur-random-1,3diisopropenylbenzene) added electrolyte. Reproduced from refs 36, 2018 American Chemical Society. Artificial layer, and corresponding electron micrographs, c, Scheme of fabricating MoS2-coated Li anode and d SEM image of cross-section view. Reproduced with permission


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from refs 37, Copyright 2018 Nature publishing group. Separator modification, and corresponding electron micrographs, e, Optical photographs and SEM cross-section view of G@PC/PP separators. Reproduced with permission from refs 38, Copyright 2018 Elsevier Inc. f. Schematic illustrating working principle of cross-linked PEGDMA membranes using dangling sulfonate groups to regulate Ion transport (up) and corresponding SEM image. Reproduced from refs 41, 2016 American Chemical Society.

The combination of LiNO3 and polysulfides (either generated from discharge of the Li-S cell or produced by sacrificial additives introduced to the electrolyte) has been investigated for its ability to form a stable SEI, which can protect Li surface.27-30 However, the most detailed studies indicate that the NO3- group is gradually exhausted during battery cycling and generates gases, including N2O and N2, which are detrimental to long-term stability of a closed electrochemical cell.31 The reaction is also reported to yield products that accumulate in the cathode to create a material with composition similar to that of Black Gun Powder.32 These observations imply that despite the widespread use of LiNO3 as a potent electrolyte additive for achieving high Coulombic efficiency and stable cycling in small, research-scale cells, use of this additive in larger format, practical Li-S batteries is potentially problematic. Thus, in order to accommodate the thin-Li anode, high sulfur loading cathodes, and low sulfur-toelectrolyte ratios required for high specific energies, stable artificial solid electrolyte interphases (SEI) designs are needed.33 There are typically three approaches for creating such interphases to stabilize a lithium anode: (i) use of electrolyte additives as sacrificial agents to react with Li and electrolyte



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components to form a self-limited coating on the Li anode in-situ;34-36 (ii) depositing a coating layer on metallic lithium ex-situ;37 and (iii) by coating the Li-facing side of the separator.38-42 A preferable SEI on the metallic Li anode should contain both inorganic salts that enable fast Li-ion transport and Li-ion conducting organic molecules (or polymers) that can flex to buffer volume changes at the anode during repeated Li stripping and plating cycles.43, 44 A recent study by the authors showed that a small amount of SiCl4 can react with previous poor SEI and form Si-interlinked OOCOR molecules with inorganic LiCl salts, which exhibit fast kinetics in Li-S batteries and long cycle stability (1000 cycles) (Figure 2a).34 This improvement is caused by the elasticity of Si-interlinked oligomer that can accommodate the volume change of Li stripping/plating, and low diffusion barrier of LiCl enable fast Li transport. Wang’s group also found that an aromatic-based organosulfides and Li salts can be formed on the surface of metal Li using poly(sulfur-random-1,3-diisopropenylbenzene) additive, which enable the high Coulombic efficiency (CE) of 99.1 % after 420 cycles and long cycle life of 1000 cycles in LiS batteries (Figure 2b).36 Both works propose that a hybrid SEI is favorable for achieving high CEs in Li-S batteries. Recently, Cha et al. reported that two-dimensional (2D) MoS2 also provide artificial protective layer on the surface of Li metal to improve the performance of Li-S cells.37 Specifically, these authors found that sputter coating of a thin (~10nm), 2D MoS2 layer on the surface of Li metal can be lithiated to form an artificial SEI that is effective in stabilizing the metal against parasitic reactions with dissolved LiPS, enabling stable cycling of Li-S batteries for over 1200 cycles with a high CE of 98 % and 84 % capacity retention (Figure 2c-d). Analysis by density functional theory (DFT) calculations reveal that the diffusion of Li+ in the


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SEI is accelerated by a surface migration pathway that prevents mossy/dendritic deposition during recharge. Although the mentioned high energy density (589 Wh Kg-1) in this work only based on the mass of cathode (sulfur and CNTs), it suggests that 2D materials with semiconductor to metallic transport characteristics are promising SEI candidates for enabling Li-S cells with long-term cycling stability. Functional separators have been reported to play a similar role in Li-S batteries.45 Pei et al. coated 2D N-doped porous carbon nano sheets on commercial polypropylene separators (G@PC/PP), which can be used to trap polysulfide due to the physical absorption caused by porous structures and chemical absorption caused by chemical absorption of N doping (Figure 2e).38 This approach is attractive because the coatings are thin (0.9 um) and enable the use of high loading of sulfur cathodes (12 mg/cm2) with stable cycling performance. Ion selective membranes that facilitate preferential transport of cations have also been investigated for their ability to enable stable cycling of metal batteries.46 Ma et al. reported a UV-cross-linked polyethylene glycol based separator that incorporates dangling sulfonate groups covalently tethered to the network forms a highly conductive membrane that selectively facilitates Li+ transport, while preventing migration of polysulfide due to electrostatic interactions between SO32- and Sx2- and small pores generated from cross-linking (Figure 2f).41 The applied Li-S batteries demonstrate high-efficiency over 98% even without the addition of LiNO3. Another advantage is high cation ion transference number (tLi+) of ion-selective membrane (> 0.9), which can largely reduce the side-reaction on anode side.



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Figure 3. a, Energy density of Li-S batteries calculated by the capacity ratio of Li-alloy anode and sulfur. b, Illustration (up) and SEM image (down) of air stable LixSi nanoparticles anode that is encapsulated by graphene sheets (Foil). c, Corresponding discharge/charge curves of Foil-S and Li-S batteries. Reproduced with permission from refs 52 (b, c), Copyright 2017 Nature publishing group.

Considering the rigorous conditions of handing metallic Li during cell assembly, especially thin Li anodes required to achieve high specific energy, application of Li-alloys has also been considered as possible choice of anode in Li-S batteries. Replacing the Li anode with a Li alloy also provides a mechanism for eliminating parasitic reactions with dissolved LiPS and electrolyte components, enabling smaller sulfur-to-electrolyte ratios. The effectiveness of this approach can be evaluated using the formula below to compute the specific energy of a Lialloy/sulfur cell:

The calculation of cathode and electrolyte is the same as Figure 1b with fixing sulfur loading as 10mg/cm2. For the anode, the current collector is assumed to be a 9μm Cu with areal density of 8mg/cm2. The anode of LiC6, Li4.4Sn and Li4.4Si are designed to take up 90 wt%, 70 wt%, 12 ACS Paragon Plus Environment

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70 wt% of anode, respectively. The mass of anode is determined on the basis of the capacity of sulfur in the battery cathode. The working voltage is defined as 2.0 V (LiC6-S),47 1.5 V (Li4.4Sn-S),48, 49 1.75 V (Li4.4Si-S)50-52 of different battery systems. Other hybrid anodes like Li-Bi, Li-hard carbon, Li-Al are also possible choices. As displayed in Figure 3a, the specific energy of a Li-Alloy-S cell based on LiC6 or Li4.4Sn as anode shows no obvious superiority in comparison to commercial Li-ion batteries due to the low specific capacity (LiC6-S) or low discharge potential (LiSn-S). An alloy anode composed of Lithiated Si on the other hand is potentially quite promising due to its high capacity and low potential (vs Li+/Li), enabling cells with specific energies as high as 500 Wh/kg. In a recent demonstration of this concept, Cui’s group reported an air-stable Li-alloy/graphene foil anode, in which the Li-alloy especially LixSi is encapsulated by graphene sheets (Figure 3b).52 As displayed in Figure 3c, the foil-S battery shows high utilization of sulfur cathode at the lower operation voltage at about 1.75 V.

Solid state electrolytes that provide interface stability and high ionic conductivity are still needed. Solubility of LiPS at the cathode is both a requirement and a problem in the Li-S cell. It is required for achieving practical charge transfer kinetics and high levels of cathode utilization in sulfur and its electronically insulating reduction products. It is problematic on the other hand because it, (a) provides a mechanism for irreversible loss of the active material in the cathode; (b) facilitates transport of soluble, reactive sulfur compounds to the anode which react with Li and provide a mechanism for irreversible loss of the active anode material; (c) dissolved LiPS slows down ion transport at both electrodes – it increases the viscosity of the electrolyte, producing a diffusion boundary layer near the cathode and a passivating layer at the anode.



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Considering these conflicting attributes of the electrolyte in a Li-S cell, it is unsurprising that Li-S cells designed according to the criteria enumerated above to achieve high specific energy rarely meet the cycle life requirements for a practical battery. Li-S cells in which a solid-state electrolyte (SSE) serves to separate the cell into “cathode” and “anode” compartments are the first step to a Li-S battery design that could resolve these conflicting demands. A full solidstate Li-S in which a SSE serves as both the separator and substrate for cation transport between the electrodes would be another alternative. Two types of solid-state electrolytes have been evaluated in Li-S batteries: solid polymer electrolytes; and solid inorganic electrolytes. The polymer based electrolytes usually combine Li salts (LiTFSI,53 LiCF3SO3,54 Li[N(SO2F)2]55) and polymers (like PEO, polysiloxane56) that promote ion-pair dissociation by coordinating with the Li+ cation in the salt. These electrolytes are attractive for their ease of synthesis, low mass densities, compatibility with large-scale rollto-roll manufacturing, flexibility, and stable mechanical properties at the moderate charging potentials in a Li-S cell. They are problematic, however, because the most attractive polymers are semi-crystalline materials, with ion transport principally occurring in the amorphous phase. This means that except in very rate situations (see discussion about filled polymers below) where the amorphous phase percolates throughout the electrolyte, extremely with low ionic conductivity can be expected in room temperature battery operations. A LiTFSI/Poly(ethylene oxide) (PEO) based polymer electrolyte has, for example, been reported to exhibit an ionic conductivity of 6.35×10-7 S/cm at 25 ○C.53 Introduction of nanosized fillers which interact strongly with the polymer and/or salt, provide mechanisms for frustrating crystallization of


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PEO and for ensuring that the amorphous domains percolate to macroscopic length scales to enable higher conductivity at room temperature. There is a large body of work focused on dispersion of naofillers in PEO and its impact on ion transport.57 These studies show that nanofillers based on ZrO2,54, 58 montmorillonite clays,59 corn starch60, and SiO261 are all effective in enhancing room temperature ionic conductivity of PEO. Meanwhile, some fillers such as LiN3 can form a thin and compact passivation layer with high conductivity in all-solid-state Li–S batteries.62 In some cases, the filler particles have also been reported to facilitate ion-pair dissociation and to increase the lithium ion transference number (tLi+). For example, Miller’s group found that the combination of PEO and halloysite nanotubes (HNT) that has typical dimensions of 10-50 nm can largely increase the conductivity (1.11×10-4 S cm at 25 ○C).53 It was described that the opposite surface chemistry of HNT takes critical roles in improving the conductivity. The outer silica surface with negative charge will absorb Li-ion, while the inter aluminum surface with positive charge will adsorb TFSI- ion, which together dissociated LiTFSI. Meanwhile, the EO units of PEO with lone-pairs also absorb Li-ion, which make polymer organized on outer HNT surface. The channels formed by HNT, LiTFSI, PEO can significantly shorten the path of Li-ion transfer and provide fast Li-ion transport (Figure 4a-b). The applied Li-S batteries with the LiTFSIPEO-HNT electrolyte maintain the capacity retention of 87 % after 100 cycles with outstanding CE close to 100% at each cycle.



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Figure 4. General design strategies of solid state (SS) electrolyte. Designing polymer based SS electrolyte with high ionic conductivity. a, a schematic diagram of preparing of HNT (Halloysite nanotube) modified LiTFSI-PEO based electrolyte with enhanced ionic conductivity. b, Ionic conductivity comparison of LiTFSI-PEO and LITFSI-PEO-HNT. Reproduced with permission from refs 53, Copyright 2016 Elsevier Ltd. Designing inorganic compound based SS electrolyte with ideal interface. c, a schematic diagram of Li10GeP2S12 solid-state electrolyte based lithium–sulfur battery. Correspond d, Cyclic voltammogram and e, discharge/charge profiles (0.05 C) of all-solid-state cell at 60 °C. Reproduced with permission from refs 69, Copyright 2017 Wiley-VCH.

The chemical diversity of inorganic solid electrolytes under consideration for Li-S batteries is far larger than that of their organic polymer analogs. Li3PS4,63 Li1.5PS3.3(60Li2S40P2S5),64 LiBH4-LiCl,65 Li2S-P2S566 Al3+/Nb5+ co-doped cubic Li7La3Zr2O12 (LLZO)67 have all been applied in Li-S batteries. Some inorganic solid electrolyte such as Li6PS5Br,68 Li10GeP2S12,69 Li7P2.9Mn0.1S10.7I0.370 display high ionic conductivity even at room temperature, which is comparable to conductivity values associated with liquid electrolytes. In spite of this 16 ACS Paragon Plus Environment

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advantage, the inorganic solid electrolytes are often limited by their high interface resistance, which reduces the overall electrode reaction kinetics. The application of LiIn68 and LiAl71 as the anode appear to provide a route towards lower interface resistance between the battery anode and a solid state electrolyte, but analogous strategies for enabling fast interface transport and high sulfur utilization at the cathode are still lacking. An additional challenge is that many of the most attractive inorganic SSEs are chemically unstable in contact with the Li anode. To solve this problem, Yao et al. report a new structure of solid state Li-S batteries (Figure 4c).69 At cathode side, the reduced graphene oxide (rGO)@sulfur nanocomposite is mixed with Li10GeP2S10-acetylene in order to maintain the high ion conductivity and reduce the stress/strain through discharge/charge process. At anode side, a 75%Li2S-24%P2S5-1%P2O5 layer was pressed on the surface of metal Li anode that can avoid the side reaction of Li10GeP2S10. The results in Figure 4d-e demonstrate that the all solid state Li-S batteries exhibit one reduction peak and one oxidation peak, respectively. And the cell can operate with high capacity and CE (almost 100%) at low current of 0.05 C. The electrolyte layer applied in this work is quite thick (1000 um), relative to typical separator (about 25 um for Celgard). The higher mass density of the electrolytes in reality places quite strong constraints on thickness (sulfur-to-electrolyte ratio), which are rarely considered in evaluating the promise of fully solid-state Li-S batteries. Further efforts are clearly needed to make thinner organic solid-state electrolytes with better interface. Additionally, the all solid state electrolytes in Li-S batteries usually display only one discharge plateau, which has been attributed to a one step solid state conversion (from S to Li2S2 or Li2S). This holds promise for a Li-S enabled by SSE that can



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essentially stop the generation of polysulfide, and maintain high CE with long cycling performance. Unfortunately, the conversion kinetics in solid-state sulfur cathodes are slow, meaning that either low current density or elevated temperature operation are required to achieve full sulfur utilization and high specific energy.

Li-S cells that combine high sulfur loading in the cathode and a polysulfide-based catholyte with low electrolyte-to-sulfur ratios provide a promising route to practical batteries with high specific energies. There are numerous studies in the literature in which stable cycling of Li-S batteries is achieved using simple nanomaterials design strategies for achieving good ion and electron transport in the cathode. The effectiveness of traditional approaches for infiltrating sulfur into the cathode substrate, such as melt-infusion, is largely dependent on the accessible pore volume of porous substrate, with the inevitable consequence that low sulfur loadings are achieved. These limitations can to an extent be avoided using other approaches, including wet chemistry synthesis,72 incorporating the sulfur in the form as a polysulfide catholyte20,

23

and

electrodeposition,73 to achieve high sulfur loading without compromising the nanostructure of the cathode and its beneficial effects on transport. Figure 5a-b reports results from a wet chemistry synthesis that enable the sulfur loading up to 90 wt%. The authors dissolved sulfur in N-Methylpyrrolidine (NMP) and also dispersed ketjen black (KB), carbon nanotube (CNT) and pristine graphene (PG) in NMP to form a colloidal dispersion.72 Addition of water to the dispersion precipitates sulfur in nanoparticulate morphologies on the surface of the carbon particles. In addition to sulfur composites, the Li2S cathodes can also be synthesized with high sulfur contents. Because the reaction from Li2S to S is accompanied by a volume reduction, a highly loaded Li2S cathode can in principle accommodate the volume change at the electrode 18 ACS Paragon Plus Environment

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without any efforts needed to encapsulate Li2S. Recently, Tan and co-workers reported a combustion reaction between lithium and CS2 vapor to prepare Li2S nanocrystals wrapped by graphene (Figure 5c-d).74 This simple procedure enables both in-situ combination with conducive carbon but also high Li2S ratio (88 %). As a testament to the effectiveness of the approach, electrochemical analysis of the materials showed that even at a loading of 10mg/cm2, specific capacity close to 1000 mA h/g are achieved for the first few cycles.

Figure 5. High active materials ratio and loading in Li-S batteries. High sulfur ratio, a, Schematic illustration of preparing KB-CNT-PG/S composite through wet chemical synthesis procedure. b, corresponding thermogravimetric analysis of composite. Reproduced from refs 72, 2015 American Chemical Society. High Li2S ratio, c, Schematic illustration of preparing Li2S@graphene capsules by the reaction of Li and CS2. d, correspond TEM images. Reproduced with permission from refs 75, Copyright 2017 Nature publishing group. High sulfur loading. e, Photograph of prepared hollow carbon fiber foam (HCFF), f, corresponding SEM image with sulfur loading 16.5 mg cm−2. Reproduced with permission from refs 76,



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Copyright 2016 Wiley-VCH. (g, h). High polysulfide loading. g, Schematic illustration of preparing polysulfide/coaxial–graphene -coated cotton-carbon composite, g, corresponding cycling performance. Reproduced with permission from refs 23, Copyright 2018 Elsevier Inc.

In addition to a high sulfur/carbon ratio in the cathode, it is already clear that a high areal loading of sulfur is needed to achieve Li-S cells with practical specific energies. A threedimensional (3D) interconnected cathode in which sulfur is dispersed on and in a substrate that also serves as a current collector is an effective method to achieve high sulfur loading without compromising electrode kinetics (Figure 5e-f).75 Such 3D interconnected current collector have been reported by the authors to uptake more than 2000% electrolyte, which is a dramatic improvement relative to the 35% electrolyte uptake in a conventional planar, 2D, case in which the active cathode material is coated on an Al current collector. It means that even at high sulfur loadings, electrode components that facilitate electronic and ionic transport co-exist through the electrode. A consequence is that cathodes with high sulfur loading of 21.2 mg/cm2 on a 0.8 cm2 current collector (electrode density 1.74 g cm-3) can be achieved. With 60 ul of electrolyte (electrolyte-to-sulfur ratio of approximately 3.5 ul/mg), the 3D cathodes deliver an initial areal capacity over 23 mAh cm-2 and maintain about 15 mAh cm-2 after 200 cycles. The polysulfides additives can be used to healing the high-loading sulfur electrodes that enables long cycling life.76 Strategies for augmenting sulfur loading in the cathode using polysulfide (Li2S6, Li2S8) additives in liquid electrolytes is also a choice to achieve high sulfur loading and high specific energies in Li-S batteries. An additional benefit is that the interphases formed when the


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dissolved polysulfides react with the Li anode have been reported to be highly effective in passivating the Li anode against continuous parasitic attack by other electrolyte components. As with approaches that utilize a high sulfur loading, a 3D current collector design is needed to preserve good electrochemical access to the dissolved LiPS. Further modifications including coating functional groups on carbon to increase its affinity with sulfur can be employed to increase the stability of the electrochemical processes at such cathodes in extended cycling studies. Manthiram’s group, for example, reported that a coaxial-graphene-coated cotton carbon (CGCC) collector is a particularly effective catholyte host for Li-S batteries (Figure 5g).23 The authors showed that a cathode created by adding 60 ul 1.5M Li2S6 (containing 17.28 mg S) catholyte on CGCC to obtain a nominal sulfur loading of 57.6 mg/cm2 (0.3 cm2) produces Li-S cells with high electrolyte-to-sulfur ratio (4.2 uL/ mg) and maintain areal capacity of about 20 mAh/cm2 after cycling (Figure 5h). They further found that TiS2 addition is effective as a conductive polysulfide adsorbent in Li polysulfides batteries.77 Most of the reported high loading sulfur or polysulfides loading are based on porous current collectors such as carbon fiber (carbon nanotube, graphene) materials, which would be very problematic in commercial cell assembly, particularly for tab connection and thermal management. Meanwhile, the amount of catholyte is still needed to be elevated to further evaluate the specific capacity

Perspective and Outlook A decade’s worth of research has underscored the promise of Li-S batteries for storing large quantities of electric energy on the basis of the S cathode mass. As a result, Li-S batteries are



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considered the most promising next-generation energy storage/conversion technology, particularly for aerial vehicles. In order to be competitive with state-of-the-art lithium-ion battery technology in any of these applications, multiple advances in the design of the electrodes and electrolyte are required to minimize the mass of enabling materials. Li-S cells that exhibit stable long-term cycling and high active material utilization, but which use thinner Li anodes, high active material loading in the cathode, and low sulfur-to-electrolyte mass ratios are required for further progress. Based on the analysis presented earlier in the review, we believe that a useful short target for research is Li-S cells composed of thin anodes in which the Li excess is 100% or lower. As the Li metal anode is chemically reactive towards the most widely used electrolyte co-solvent (DOL), this choice places stricter demands on the compactness of Li deposits formed during batter recharge and the quality and stability of interphases formed on the Li anode. This in turn means that complementary efforts to understand the origins of — as well as to design materials to prevent — mossy deposition of Li are crucial for progress. Because the overarching goal to achieve practical Li-S batteries also require high specific energy, this places strict limits on the mass and chemistry of any artificial interfacial phases used to facilitate stable and uniform lithium stripping/deposition in Li-S cells. Thus, although cells in which the conventional Li anode is replaced with a Li-alloy anode can reduce the usage of metal Li, these types of anodes introduce new problems associated with their lower overall specific capacity. Efforts to introduce electrostatic shields composed of particulate, polymer, and interlinked coatings that selectively transport cations to the Li electrode are particularly promising when these strategies are coupled with state of the art deposition techniques that achieve high-quality, defect free coatings. Application of such


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ACS Energy Letters

coatings either directly as artificial interphases on the anode or as interlayers on the cathode seems promising for large-scale application combining polymer and coating technology. While initial studies along these lines suggest that application of thin coatings on the separator is more straightforward, transfer of coatings formed on inert substrates onto Li has recently been demonstrated in a scalable process compatible with roll-to-roll manufacturing. A Li-S cell in which a polymer or inorganic solid-state electrolyte is employed offers multiple paths for research that could lead to Li-S batteries that are intrinsically safe. The chemical stability and ease with which ions transport across the interfaces such electrodes form presents significant challenges that are fertile grounds for research. It is understood, however, that the strict mass limitations on all components, except the active sulfur material in the cathode, required to achieve practical Li-S cells place demands on the chemistry and density of SSEs that are well beyond those typically considered in the literature at this point. For now though, the low charge potential, cost, mechanical properties, compatibility with large scale manufacturing, and inherently low mass density offered by SSEs based on organic polymers present the most straightforward path towards practical, all-solid state Li-S batteries. Reference to sulfur cathode, maintaining the high utilization and kinetics after enhancing the sulfur (or polysufides catholyte) loading and lowering the electrolyte-to-sulfur ratio (lowered to 2ul/mg) are significant to increase the entire energy density. The deployable devices with competitive energy density and stability can be further expected after well integrating each part of Li-S batteries.

AUTHOR BIOGRAPHIES



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Qing Zhao received his B.S. (2012) and Ph.D. (2017) degree in Nankai University. Now he is a postdoc in Lynden Archer’s group at Cornell University. His research interest focuses on the preparation of micro/nanostructured hybrid materials and their application in various battery fields. Jingxu Zheng received his B.S. degree in Shanghai Jiao Tong University in 2017. Now he is a PhD student in Lynden Archer’s group at Cornell University. His current research interest focuses on rechargeable metal lithium batteries. Lynden A. Archer is the James A. Friend Family Distinguished Professor of Engineering and Director of the Energy Systems Institute at Cornell University. His research interests center on transport properties in bulk liquids and at electrochemical interfaces. NOTES Professor Archer is a Founder and member of the Board of Directors of NOHMs Technologies. NOHMs is a technology company located in Rochester New York seeking to commercialize electrolytes for lithium-ion batteries and electrodes for lithium-sulfur batteries. ACKNOWLEDGMENT We are grateful to the Department of Energy Basic Energy Sciences Program, through Award#: DE-SC0016082, for financial support.

REFERENCES (1) Dunn, B.; Kamath, H.; Tarascon, J. M. Electrical Energy Storage for the Grid: A Battery of Choices. Science 2011, 334, 928-935. (2) Cheng, X. B.; Zhang, R.; Zhao, C. Z.; Zhang, Q. Toward Safe Lithium Metal Anode in Rechargeable Batteries: A Review. Chem. Rev. 2017, 117, 10403-10473. (3) Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J. M. Li-O2 and Li-S Batteries with High Energy Storage. Nat. Mater. 2012, 11, 19-29. (4) Al Sadat, W. I.; Archer, L. A. The O2-assisted Al/CO2 Electrochemical Cell: A System for CO2 Capture/Conversion and Electric Power Generation. Sci. Adv. 2016, 2, e1600968. (5) Manthiram, A.; Fu, Y.; Chung, S. H.; Zu, C.; Su, Y. S. Rechargeable Lithium-Sulfur Batteries. Chem.Rev. 2014, 114, 11751-11787. 24 ACS Paragon Plus Environment

Page 25 of 30 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

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(6) Seh, Z. W.; Sun, Y.; Zhang, Q.; Cui, Y. Designing High-Energy Lithium-Sulfur Batteries. Chem. Soc. Rev. 2016, 45, 5605-5634. (7) Jayaprakash, N.; Shen, J.; Moganty, S. S.; Corona, A.; Archer, L. A. Porous Hollow Carbon@Sulfur Composites for High-Power Lithium-Sulfur Batteries. Angew. Chem. Int. Ed. 2011, 50, 5904-5908. (8) 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. (9) Zheng, S.; Yi, F.; Li, Z.; Zhu, Y.; Xu, Y.; Luo, C.; Yang, J.; Wang, C. CopperStabilized Sulfur-Microporous Carbon Cathodes for Li-S Batteries. Adv. Funct. Mater. 2014, 24, 4156-4163. (10) Zeng, W.; Wang, Z.; Cheng, M. M. C.; Ng, K. Y. S. Structured Titanium Nitride Nanotube Arrays/Sulfur Composite as Cathode Materials for Advanced Lithium Sulfur Battery. J. Electrochem. Soc. 2018, 165, A1011-A1018. (11) Yin, Y. X.; Xin, S.; Guo, Y. G.; Wan, L. J. Lithium-sulfur Batteries: Electrochemistry, Materials, and Prospects. Angew. Chem. Int. Ed.2013, 52, 13186-13200. (12) Manthiram, A.; Fu, Y.; Su, Y.-S. Challenges and Prospects of Lithium–Sulfur Batteries. Acc. Chem. Res. 2013, 46, 1125-1134. (13) Ma, L.; Hendrickson, K. E.; Wei, S.; Archer, L. A. Nanomaterials: Science and Applications in the Lithium–sulfur Battery. Nano Today 2015, 10, 315-338. (14) Ma, L.; Zhuang, H. L.; Wei, S.; Hendrickson, K. E.; Kim, M. S.; Cohn, G.; Hennig, R. G.; Archer, L. A. Enhanced Li-S Batteries Using Amine-Functionalized Carbon Nanotubes in the Cathode. ACS Nano 2016, 10, 1050-1059 . (15) Je, S. H.; Hwang, T. H.; Talapaneni, S. N.; Buyukcakir, O.; Kim, H. J.; Yu, J. S.; Woo, S. G.; Jang, M. C.; Son, B. K.; Coskun, A. et al. Rational Sulfur Cathode Design for LithiumSulfur Batteries: Sulfur-Embedded Benzoxazine Polymers. Acs Energy Lett. 2016, 1, 566-572. (16) Cao, J.; Chen, C.; Zhao, Q.; Zhang, N.; Lu, Q.; Wang, X.; Niu, Z.; Chen, J. A Flexible Nanostructured Paper of a Reduced Graphene Oxide-Sulfur Composite for High-Performance Lithium-Sulfur Batteries with Unconventional Configurations. Adv. Mater. 2016, 28, 96299636. (17) Zhang, K.; Zhao, Q.; Tao, Z.; Chen, J. Composite of Sulfur Impregnated in Porous Hollow Carbon Spheres as the Cathode of Li-S Batteries with High Performance. Nano Res. 2012, 6, 38-46. (18) Patil, S. B.; Kim, H. J.; Lim, H. K.; Oh, S. M.; Kim, J.; Shin, J.; Kim, H.; Choi, J. W.; Hwang, S. J. Exfoliated 2D Lepidocrocite Titanium Oxide Nanosheets for High Sulfur Content Cathodes with Highly Stable Li-S Battery Performance. Acs Energy Lett. 2018, 3, 412-419. (19) Xu, K. L.; Liu, X. J.; Liang, J. W.; Cai, J. Y.; Zhang, K. L.; Lu, Y.; Wu, X.; Zhu, M. G.; Liu, Y.; Zhu, Y. C. et al. Manipulating the Redox Kinetics of Li-S Chemistry by Tellurium Doping for Improved Li-S Batteries. Acs Energy Lett. 2018, 3, 420-427. (20) Pan, H.; Chen, J.; Cao, R.; Murugesan, V.; Rajput, N. N.; Han, K. S.; Persson, K.; Estevez, L.; Engelhard, M. H.; Zhang, J. G. et al. Non-encapsulation Approach for Highperformance Li–S Batteries through Controlled Nucleation and Growth. Nat. Energy 2017, 2, 813-820.



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(21) Qu, H.; Zhang, J.; Du, A.; Chen, B.; Chai, J.; Xue, N.; Wang, L.; Qiao, L.; Wang, C.; Zang, X. et al. Multifunctional Sandwich-Structured Electrolyte for High-Performance Lithium-Sulfur Batteries. Adv. Sci. 2018, 5, 1700503. (22) Qie, L.; Manthiram, A. A Facile Layer-by-Layer Approach for High-Areal-Capacity Sulfur Cathodes. Adv. Mater. 2015, 27, 1694-1700. (23) Chung, S. H.; Manthiram, A. Designing Lithium-Sulfur Cells with Practically Necessary Parameters. Joule 2018, 2, 710-724. (24) Service, R. F. Lithium-Sulfur Batteries Poised for Leap. Science 2018, 359, 10801081. (25) Albertus, P.; Babinec, S.; Litzelman, S.; Newman, A. Status and Challenges in Enabling the Lithium Metal Electrode for High-Energy and Low-Cost Rechargeable Batteries. Nat. Energy 2017, 3, 16-21. (26) Tikekar, M. D.; Choudhury, S.; Tu, Z.; Archer, L. A. Design Principles for Electrolytes and Interfaces for Stable Lithium-Metal Batteries. Nat. Energy 2016, 1, 16114. (27) Aurbach, D.; Pollak, E.; Elazari, R.; Salitra, G.; Kelley, C. S.; Affinito, J. On the Surface Chemical Aspects of Very High Energy Density, Rechargeable Li–Sulfur Batteries. J. Electrochem. Soc. 2009, 156, A694. (28) Li, W.; Yao, H.; Yan, K.; Zheng, G.; Liang, Z.; Chiang, Y. M.; Cui, Y. The Synergetic Effect of Lithium Polysulfide and Lithium Nitrate to Prevent Lithium Dendrite Growth. Nat Commun 2015, 6, 7436. (29) Zhao, C. Z.; Cheng, X. B.; Zhang, R.; Peng, H. J.; Huang, J. Q.; Ran, R.; Huang, Z. H.; Wei, F.; Zhang, Q. Li2S5-based Ternary-salt Electrolyte for Robust Lithium Metal Anode. Energy Storage Mater. 2016, 3, 77-84. (30) Cheng, X. B.; Yan, C.; Chen, X.; Guan, C.; Huang, J. Q.; Peng, H. J.; Zhang, R.; Yang, S. T.; Zhang, Q. Implantable Solid Electrolyte Interphase in Lithium-Metal Batteries. Chem 2017, 2, 258-270. (31) Jozwiuk, A.; Berkes, B. B.; Weiss, T.; Sommer, H.; Janek, J.; Brezesinski, T. The Critical Role of Lithium Nitrate in the Gas Evolution of Lithium-sulfur Batteries. Energy Environ. Sci. 2016, 9, 2603-2608. (32) Qu, C.; Chen, Y.; Yang, X.; Zhang, H.; Li, X.; Zhang, H. LiNO3-free Electrolyte for Li-S Battery: A Solvent of Choice with Low Ksp of Polysulfide and Low Dendrite of Lithium. Nano Energy 2017, 39, 262-272. (33) Tao, T.; Lu, S.; Fan, Y.; Lei, W.; Huang, S.; Chen, Y. Anode Improvement in Rechargeable Lithium-Sulfur Batteries. Adv. Mater. 2017, 29, 1700542. (34) Zhao, Q.; Tu, Z.; Wei, S.; Zhang, K.; Choudhury, S.; Liu, X.; Archer, L. A. Building Organic/Inorganic Hybrid Interphases for Fast Interfacial Transport in Rechargeable Metal Batteries. Angew. Chem. Int. Ed. 2018, 57, 992-996. (35) Zu, C.; Manthiram, A. Stabilized Lithium-Metal Surface in a Polysulfide-Rich Environment of Lithium-Sulfur Batteries. J. Phys. Chem. Lett. 2014, 5, 2522-2527. (36) Li, G.; Huang, Q.; He, X.; Gao, Y.; Wang, D.; Kim, S. H.; Wang, D. Self-Formed Hybrid Interphase Layer on Lithium Metal for High-Performance Lithium-Sulfur Batteries. ACS Nano 2018, 12, 1500-1507.


Page 27 of 30 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

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(37) Cha, E.; Patel, M. D.; Park, J.; Hwang, J.; Prasad, V.; Cho, K.; Choi, W. 2D MoS2 as An Efficient Protective Layer for Lithium Metal Anodes in High-performance Li–S Batteries. Nat. Nanotech. 2018, 13, 337-344. (38) Pei, F.; Lin, L.; Fu, A.; Mo, S.; Ou, D.; Fang, X.; Zheng, N. A Two-Dimensional Porous Carbon-Modified Separator for High-Energy-Density Li-S Batteries. Joule 2018, 2, 323-336. (39) Kim, M. S.; Ma, L.; Choudhury, S.; Archer, L. A. Multifunctional Separator Coatings for High-Performance Lithium-Sulfur Batteries. Adv. Mater. Interfaces 2016, 3, 1600450. (40) Kim, M. S.; Ma, L.; Choudhury, S.; Moganty, S. S.; Wei, S.; Archer, L. A. Fabricating Multifunctional Nanoparticle Membranes by A Fast Layer-by-layer Langmuir–Blodgett Process: Application in Lithium–Sulfur Batteries. J. Mater. Chem.A 2016, 4, 14709-14719. (41) Ma, L.; Nath, P.; Tu, Z.; Tikekar, M.; Archer, L. A. Highly Conductive, Sulfonated, UV-Cross-Linked Separators for Li–S Batteries. Chem. Mater. 2016, 28, 5147-5154. (42) Kim, M. S.; Kim, M. S.; Do, V.; Lim, Young R.; Nah, In W.; Archer, L. A.; Cho, W. I. Designing Solid-Electrolyte Interphases for Lithium Sulfur Electrodes Using Ionic Shields. Nano Energy 2017, 41, 573-582. (43) Wei, S.; Choudhury, S.; Tu, Z.; Zhang, K.; Archer, L. A. Electrochemical Interphases for High-Energy Storage Using Reactive Metal Anodes. Acc. Chem. Res. 2018, 51, 80-88. (44) Yu, X.; Manthiram, A. Electrode-Electrolyte Interfaces in Lithium-Sulfur Batteries with Liquid or Inorganic Solid Electrolytes. Acc. Chem. Res.2017, 50, 2653-2660. (45) Pan, Y. D.; Chou, S. L.; Liu, H. K.; Dou, S. X. Functional Membrane Separators for Next-Generation High-Energy Rechargeable Batteries. Nat. Sci. Rev. 2017, 4, 917-933. (46) Zhao, Q.; Huang, W.; Luo, Z.; Liu, L.; Lu, Y.; Li, Y.; Li, L.; Hu, J.; Ma, H.; Chen, J. High-Capacity Aqueous Zinc Batteries Using Sustainable Quinone Electrodes. Sci. Adv. 2018, 4, eaao1761. (47) Agostini, M.; Scrosati, B.; Hassoun, J. An Advanced Lithium-Ion Sulfur Battery for High Energy Storage. Adv. Energy Mater. 2015, 5, 1500481. (48) Hassoun, J.; Scrosati, B. A High-Performance Polymer Tin Sulfur Lithium Ion Battery. Angew. Chem. Int. Ed.2010, 49, 2371-2374. (49) Duan, B.; Wang, W.; Wang, A.; Yu, Z.; Zhao, H.; Yang, Y. A New Lithium Secondary Battery System: the Sulfur/Lithium-ion Battery. J. Mater. Chem. A 2014, 2, 308-314. (50) Yang, Y.; McDowell, M. T.; Jackson, A.; Cha, J. J.; Hong, S. S.; Cui, Y. New Nanostructured Li2S/Silicon Rechargeable Battery with High Specific Energy. Nano Lett. 2010, 10, 1486-1491. (51) Lee, S. K.; Oh, S. M.; Park, E.; Scrosati, B.; Hassoun, J.; Park, M. S.; Kim, Y. J.; Kim, H.; Belharouak, I.; Sun, Y. K. Highly Cyclable Lithium-Sulfur Batteries with a Dual-Type Sulfur Cathode and a Lithiated Si/SiO Nanosphere Anode. Nano Lett. 2015, 15, 2863-2868. (52) Zhao, J.; Zhou, G.; Yan, K.; Xie, J.; Li, Y.; Liao, L.; Jin, Y.; Liu, K.; Hsu, P. C.; Wang, J. et al. Air-Stable and Freestanding Lithium Alloy/Graphene Foil as an Alternative to Lithium Metal Anodes. Nat. Nanotech. 2017, 12, 993-999. (53) Lin, Y.; Wang, X.; Liu, J.; Miller, J. D. Natural Halloysite Nano-Clay Electrolyte for Advanced All-Solid-State Lithium-Sulfur Batteries. Nano Energy 2017, 31, 478-485.



Page 28 of 30

(54) Hassoun, J.; Scrosati, B. Moving to a Solid-State Configuration: a Valid Approach to Making Lithium-Sulfur Batteries Viable for Practical Applications. Adv. Mater. 2010, 22, 5198-5201. (55) Judez, X.; Zhang, H.; Li, C.; Gonzalez-Marcos, J. A.; Zhou, Z.; Armand, M.; Rodriguez-Martinez, L. M. Lithium Bis(fluorosulfonyl)imide/Poly(ethylene oxide) Polymer Electrolyte for All Solid-State Li-S Cell. J. Phys. Chem. Lett. 2017, 8, 1956-1960. (56) Chen, L.; Fan, L. Z. Dendrite-Free Li Metal Deposition in All-Solid-State Lithium Sulfur Batteries with Polymer-in-Salt Polysiloxane Electrolyte. Energy Storage Mater. 2018, 15, 37-45. (57) Srivastava, S.; Schaefer, J. L.; Yang, Z.; Tu, Z.; Archer, L. A. 25th Anniversary Article: Polymer-Particle Composites: Phase Stability and Applications in Electrochemical Energy Storage. Adv. Mater. 2014, 26, 201-234. (58) Sheng, O. W.; Jin, C. B.; Luo, J. M.; Yuan, H. D.; Fang, C.; Huang, H.; Gan, Y. P.; Zhang, J.; Xia, Y.; Liang, C. et al. Ionic Conductivity Promotion of Polymer Electrolyte with Ionic Liquid Grafted Oxides for All-Solid-State Lithium-Sulfur Batteries. J. Mater. Chem. A 2017, 5, 12934-12942. (59) Zhang, Y.; Zhao, Y.; Gosselink, D.; Chen, P. Synthesis of Poly(ethyleneoxide)/Nanoclay Solid Polymer Electrolyte for All Solid-State Lithium/Sulfur Battery. Ionics 2014, 21, 381-385. (60) Lin, Y.; Li, J.; Liu, K.; Liu, Y.; Liu, J.; Wang, X. Unique Starch Polymer Electrolyte for High Capacity All-Solid-State Lithium Sulfur Battery. Green Chem. 2016, 18, 3796-3803. (61) Choudhury, S.; Mangal, R.; Agrawal, A.; Archer, L. A. A Highly Reversible RoomTemperature Lithium Metal Battery Based on Crosslinked Hairy Nanoparticles. Nat. Commun. 2015, 6, 10101. (62) Eshetu, G. G.; Judez, X.; Li, C.; Bondarchuk, O.; Rodriguez-Martinez, L. M.; Zhang, H.; Armand, M. Lithium Azide as An Electrolyte Additive for All-Solid-State Lithium-Sulfur Batteries. Angew Chem Int Ed. 2017, 56, 15368-15372. (63) Lin, Z.; Liu, Z.; Dudney, N. J.; Liang, C. Lithium Superionic Sulfide Cathode for AllSolid Lithium-Sulfur Batteries. ACS Nano 2013, 7, 2829-2833. (64) Nagata, H.; Chikusa, Y. Activation of Sulfur Active Material in an All-Solid-State Lithium–Sulfur Battery. J. Power Sources 2014, 263, 141-144. (65) Unemoto, A.; Chen, C.; Wang, Z.; Matsuo, M.; Ikeshoji, T.; Orimo, S. Pseudo-Binary Electrolyte, LiBH4-LiCl, for Bulk-Type All-Solid-State Lithium-Sulfur Battery. Nanotechnology 2015, 26, 254001. (66) Yamada, T.; Ito, S.; Omoda, R.; Watanabe, T.; Aihara, Y.; Agostini, M.; Ulissi, U.; Hassoun, J.; Scrosati, B. All Solid-State Lithium-Sulfur Battery Using a Glass-Type P2S5-Li2S Electrolyte: Benefits on Anode Kinetics. J. Electrochem. Soc. 2015, 162, A646-A651. (67) Tao, X.; Liu, Y.; Liu, W.; Zhou, G.; Zhao, J.; Lin, D.; Zu, C.; Sheng, O.; Zhang, W.; Lee, H. W. et al. Solid-State Lithium-Sulfur Batteries Operated at 37 degrees C with Composites of Nanostructured Li7La3Zr2O12/Carbon Foam and Polymer. Nano Lett. 2017, 17, 2967-2972. (68) Chen, M.; Adams, S. High performance All-Solid-State Lithium/Sulfur Batteries Using Lithium Argyrodite Electrolyte. J. Solid State Electrochem. 2014, 19, 697-702.


Page 29 of 30 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

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(69) Yao, X. Y.; Huang, N.; Han, F. D.; Zhang, Q.; Wan, H. L.; Mwizerwa, J. P.; Wang, C. S.; Xu, X. X. High-Performance All-Solid-State Lithium-Sulfur Batteries Enabled by Amorphous Sulfur-Coated Reduced Graphene Oxide Cathodes. Adv. Energy Mater. 2017, 7, 1602923. (70) Xu, R. C.; Xia, X. H.; Li, S. H.; Zhang, S. Z.; Wang, X. L.; Tu, J. P. All-Solid-State Lithium–Sulfur Batteries Based on a Newly Designed Li7P2.9Mn0.1S10.7I0.3 Superionic Conductor. J. Mater. Chem. A 2017, 5, 6310-6317. (71) Nagao, M.; Suzuki, K.; Imade, Y.; Tateishi, M.; Watanabe, R.; Yokoi, T.; Hirayama, M.; Tatsumi, T.; Kanno, R. All-Solid-State Lithium–Sulfur Batteries with Three-dimensional Mesoporous Electrode Structures. J. Power Sources 2016, 330, 120-126. (72) Du, W. C.; Yin, Y. X.; Zeng, X. X.; Shi, J. L.; Zhang, S. F.; Wan, L. J.; Guo, Y. G. Wet Chemistry Synthesis of Multidimensional Nanocarbon-Sulfur Hybrid Materials with Ultrahigh Sulfur Loading for Lithium-Sulfur Batteries. ACS Appl. Mater. Interfaces 2015. (73) Zhao, Q.; Hu, X.; Zhang, K.; Zhang, N.; Hu, Y.; Chen, J. Sulfur Nanodots Electrodeposited on Ni Foam as High-performance Cathode for Li-S Batteries. Nano Lett. 2015, 15, 721-6. (74) Peng, H. J.; Huang, J. Q.; Liu, X. Y.; Cheng, X. B.; Xu, W. T.; Zhao, C. Z.; Wei, F.; Zhang, Q. Healing High-Loading Sulfur Electrodes with Unprecedented Long Cycling Life: Spatial Heterogeneity Control. J. Am. Chem. Soc. 2017, 139, 8458-8466. (75) Tan, G.; Xu, R.; Xing, Z.; Yuan, Y.; Lu, J.; Wen, J.; Liu, C.; Ma, L.; Zhan, C.; Liu, Q. et al. Burning Lithium in CS2 for High-Performing Compact Li2S–Graphene Nanocapsules for Li–S Batteries. Nat. Energy 2017, 2, 17090. (76) Fang, R.; Zhao, S.; Hou, P.; Cheng, M.; Wang, S.; Cheng, H. M.; Liu, C.; Li, F. 3D Interconnected Electrode Materials with Ultrahigh Areal Sulfur Loading for Li-S Batteries. Adv. Mater. 2016, 28, 2274-3382. (77) Chung, S. H.; Luo, L.; Manthiram, A. TiS2-Polysulfide Hybrid Cathode with High Sulfur Loading and Low Electrolyte Consumption for Lithium-Sulfur Batteries. Acs Energy Lett. 2018, 3, 568-573.

Quotes to highlights in paper: 1) Practical Li-S cells with high specific energies and long cycling stability require integration of fundamental knowledge about the interphases formed on the 29 ACS Paragon Plus Environment


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electrochemically active cell components. The needs are particularly acute in cells that utilize low anode-to-sulfur and electrolyte-to-sulfur ratio for maximizing cell-level energy density. 2) Interphases that simultaneously protect Li from parasitic reactions, are able to flex and stretch to accommodate reversible volume change, and which enable fast interfacial transport of Li are a requirement for progress. 3) Solid state electrolytes that provide interface stability and high ionic conductivity are still needed. 4) Li-S cells that combine high sulfur loading in the cathode and a polysulfide-based catholyte with low electrolyte-to-sulfur ratios provide a promising route to practical batteries with high specific energies.


Interphases in LithiumâSulfur Batteries: Toward Deployable Devices

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