Exfoliated MoS2 as Electrode for All Solid State Rechargeable Lithium

Subscriber access provided by UNIV AUTONOMA DE COAHUILA UADEC

C: Energy Conversion and Storage; Energy and Charge Transport 2

Exfoliated MoS as Electrode for All Solid State Rechargeable Lithium-Ion Batteries Aggunda Lingamurthy Santhosha, Prasant Kumar Nayak, Kilian Pollok, Falko Langenhorst, and Philipp Adelhelm J. Phys. Chem. C, Just Accepted Manuscript • DOI: 10.1021/acs.jpcc.9b01816 • Publication Date (Web): 18 Apr 2019 Downloaded from http://pubs.acs.org on April 18, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 20 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

The Journal of Physical Chemistry

Exfoliated MoS2 as Electrode for All Solid State Rechargeable Lithium-ion Batteries A. L. Santhoshaa, b, Prasant Kumar Nayaka, b, Kilian Pollokc, Falko Langenhorstc, Philipp Adelhelma,b* a

Institute of Technical Chemistry and Environmental Chemistry, Friedrich Schiller University Jena, Philosophenweg 7a, 07743 Jena, Germany

b

Center for Energy and Environmental Chemistry Jena (CEEC Jena), Friedrich Schiller University Jena, Philosophenweg 7a, 07743 Jena, Germany

c

Institute of Geosciences, Friedrich Schiller University Jena, Carl-Zeiss-Promenade 10, 07745 Jena, Germany

Abstract:

The electrode behavior of exfoliated MoS2 is studied in an all-solid-state lithium-ion battery. MoS2 nanosheets with a crystallite thickness of about 6 nm are synthesized by chemical exfoliation of bulk MoS2 and characterized by XRD, SEM, and TEM. MoS2 composite electrodes are obtained by uniaxial cold-pressing at 4 tons and contain 60 wt% MoS2, 30 wt% β-Li3PS4 solid electrolyte and 10 wt% carbon black. Solid-state lithium-ion batteries are assembled using β-Li3PS4 as the solid electrolyte and a Li-In alloy as the counter electrode. The electrode performance is well above state-of-the-art with an initial specific capacity of about 439 mAhg-1 when discharged at 67 mAg-1 (C/10) in the potential range of 0.01 to 3.0 V. The initial irreversible capacity is only 9%. The specific capacity retention is excellent with 312 mAhg-1 obtained after 500 cycles. In view of the theoretical capacity of MoS2 (qth=670 mAhg-1), the solid-state reaction in the cell is incomplete yet the end phases of the conversion reaction after discharge (Mo and Li2S) are confirmed by XRD. We also study the behavior of bulk MoS2 (same mass loading) and found that the performance is inferior compared to MoS2 nanosheets. The initial discharge capacity of bulk MoS2 is only 259 mAhg-1 and the initial irreversible capacity is as large as 26%. Overall, the study shows that MoS2 can be effectively cycled in all-solid-state batteries with β-Li3PS4 as solid electrolyte and that the electrode performance can be significantly improved by nanostructuring. Introduction: Among the rechargeable batteries, lithium-ion batteries (LIBs) have been developed as leading energy storage devices because of high energy density, high power density, light weight, and long service life. In the past few years, research efforts are largely driven by the rising markets of battery electric vehicles (EVs), hybrid electric vehicles (HEVs) as well as stationary energy storage. However, there have always been safety issues arising from the flammable organic 1

ACS Paragon Plus Environment

The Journal of Physical Chemistry 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

Page 2 of 20

electrolytes. Hence there is growing attention on all-solid-state lithium ion batteries (SSBs) because the replacement of the flammable liquid electrolyte by an inorganic solid-state electrolyte (less or non-flammable) would lead to safer batteries. Solid-state technology also holds promises for further increasing the battery energy density as well as providing excellent rate performance.1-8 Generally, advantages of inorganic solid electrolytes (SE) over organic liquid ones relate to their single ion conduction property that prevents concentration polarization and the hope that undesired processes such as dendrite growth or electrolyte decomposition might be minimized or even prevented. Among the various solid electrolytes, superionic sulfides are strong candidates for the application in bulk type SSBs.9 High ionic conductivity rivaling to that of organic liquid electrolytes (≈10 mScm-1) has been achieved with several sulfide materials (e.g., Li10GeP2S12 (LGPS, 12 mScm-1) and Li7P3S11 (17 mScm-1)).3, 1012

The Young’s modulus of sulfidic electrolytes (10 to 20 GPa) is much lower compared to

oxides for which values around 100-200 GPa are typically found.13-15 Connected to this, sulfides are generally much softer materials and therefore the densification of particles to compact monolithic structures is eased. Compacting of sulfide powders by pressing is easily possible at room temperature (as also done in this work). The improved mechanical properties of sulfide electrolytes has been studied and reviewed by Sakuda et. al.16 and Lau et. al.17 for example. This is very different from employing more brittle oxide SEs for which high-temperature sintering processes are necessary.15 A comparison between both type of electrolytes can be found in ref

18

, for example. Softness also helps to maintain a much better particle-particle

contact during cycling. As a result, higher current densities, better cycle life and faster charging times are conceivable with sulfide SEs in SSBs. Important drawbacks of sulfide SE are their moisture sensitivity (great care has to be taken during synthesis and cell assembly) as well as their small electrochemical stability window.19 Careful compositional variation of sulfide electrolytes can, however, at least lessen the issue of moisture sensitivity.20 The chemical instability against lithium, however, remains an issue for all sulfide-based electrolytes which is why currently many laboratory cells are assembled with Li-alloys as counter electrode. The use of the intermetallic phase Li-In shifts the redox potential by 0.62 V vs. Li+/Li. This is still not in the stability range, but the driving force for side reactions is smaller and better stability is obtained.21 Another aspect of using a Li-In electrode is that the volume expansion of 53% for the reaction In®InLi is smaller compared to lithium (which helps to maintain sufficient particle-particle contact upon cycling) and that the risk of dendrite growth is minimized. The use of the indium-lithium electrode for solid state batteries has been recently discussed by our 2


Page 3 of 20 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


group. 21 Nevertheless, it is clear that the high cost of indium restricts its use to the laboratory level. Considering that the solid state concept requires charge transfer over solid-solid particle contacts, one can easily foresee the challenges related to designing interfaces (or interphases) that enable charging/discharging the battery for many times. For example, as the electrode materials undergo volume changes during lithiation/delithiation, particle cracking and decontacting might more easily occur hence leading to growing interface resistance.22 Customizing the interface between the SE and the electrode composite material is therefore crucial to obtain long cycle life and low polarization. Due to its high theoretical capacity of 1,672 mAhg-1 and low cost, the use of sulfur in SSBs is appealing. However, the insulating properties of sulfur (10-15 Ω-1cm-1) and the desired discharge product Li2S are a well-known challenge to realize such a concept.23-24 Transitions metal (TM) sulfides can react with lithium by a conversion-type reaction and therefore show high theoretical specific capacities in the range of 350 – 950 mAhg-1 (when fully converted to TM and Li2S)25 and often exhibit reasonable electronic conductivity.27-28 For example 10-4 Ω-1cm-1 for MoS229 and10-3 to 10-4 Ω1

cm-1 for WS2.30 Moreover, the reduced TM supports electronic conduction in the discharged

state. Theoretical redox potentials for transition metal sulfides are typically between 1.5 and 2 V vs. Li+/Li (1.1 to 1.6 V vs Na+/Na) so that TM sulfides can be used as electrode materials in various battery types (though not for high voltage systems).25, 31 As many transition metal sulfides are soft materials, a suitable interface compatibility with sulfide SEs is conceivable which may further mitigate issues such as particle cracking and contact loss due to volume changes during cycling. Numerous studies have been already published on the use of TM sulfides in lithium-ion batteries and sodium-ion batteries with liquid electrolytes.32-33 As the electrochemical performance of conversion reactions depends on the particle size, morphology and porosity etc. of the electrode materials,34 researchers put tremendous efforts into preparing nanoengineered electrode materials to improve rate capability and storage capacity.32-36 Nanostructuring will shorten the diffusion paths for ionic and electronic transport, resulting in faster kinetics and a more complete reaction.37 The beneficial effect of nanostructuring and nanomaterials as well as their related challenges has been already thoroughly discussed in literature38-41, As a specific example on sulfides, Douglas et al. demonstrated the improved performance of ultrafine iron pyrite (FeS2) with a particle size of about 5 nm for Li and Na ion 3



Page 4 of 20

batteries.42 Thus, reduction of particle size has been demonstrated to be an effective method. Recently, also low-dimensional metal sulfide materials, such as nanosheets,43 nanowires,44 nanorods,45 nanobelts,46 and nanotubes,47 are found to be promising because they not only increase the electrode-electrolyte contact area but also ease charge transport and provide more mechanical stability during lithium ion insertion/extraction. Most recently, also TM polysulfides like tri- and tetrasulfide have been reported for the lithium and sodium ion battery.48-49 These type of materials are amorphous in nature and show complex redox chemistry which involves, when fully converted, reduction and oxidation of both cation and anion species.48 The chemical diversity of TM (poly)sulfides may therefore allow tailoring of electrode properties. Among the transition metal disulfides (MS2), molybdenum disulfide (MoS2) is a promising electrode material for rechargeable lithium ion batteries because of its layered structure with high theoretical capacity of 670 mAhg-1 resulting from the 4 electrons transfer reaction during the charge/discharge process. This is 1.8 times higher than the commonly used graphite material (372 mAhg-1).50 The MoS2 provides the electronic conductivity of 10-4 Ω-1cm-1 29 and theoretical redox potential vs. Li+/Li is 1.54 V. A motivation for using nanosized MoS2 is to alleviate issues related to the volume expansion of the reaction, which is 107 % for the MoS2 electrode and -21.7 % referring to the cell reaction, see table 1. This is still much smaller compared to most alloying reactions, e.g. +280% for the lithiation of Si to form Li15Si4, but it is foreseeable that large volume changes can easily lead to contact losses and high resistance in case of bulk materials. We note that decontacting combined with interface instability has been found for the combination of sulfidic electrolyte with a high voltage (mechanically hard) oxide cathode.51 Overall, the motivation of combining nanosized, soft MoS2 (Mohs hardness of 1 to 1.5) in SSBs with a sulfidic electrolyte is therefore two-fold. Firstly, two soft materials are combined which, combined with the nanostructuring, may be more effective in sustaining mechanical stress and strain during cycling. Secondly, the compared to high voltage oxides lower redox potential of the MoS2 electrode reduces the driving force for electrolyte decomposition. Note that thermodynamic stability window of sulfide electrolytes is very narrow with values around 2.0 to 2.5 V vs. Li+/Li 52-53. The trade-off for decreasing voltage is a decrease in energy density, of course. MoS2 is composed of (S-Mo-S) stacked layers where the adjacent layers are held together by van der Waals interactions. The large interlayer spacing of 0.61 nm54 enables two-dimensional 4


Page 5 of 20 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


diffusion for the intercalation of lithium ions forming the intermediate LixMoS2, which then converts to the Mo metal and Li2S upon full discharge. The overall, idealized electrode reaction can be written as insertion ¾¾¾¾ ® 2 × Li2S + Mo 4 × Li+ + 4 × e - + MoS2 ¬¾¾¾ ¾ deinsertion

(1)

Several experimental and theoretical studies showed that the reaction path is much more complex, however. The discharge reaction proceeds over several intermediate compounds, starting with intercalation to form LixMoS2 (0 < x < 1) at around 1.8 V vs. Li+/Li followed by successive conversion to the end products below around 1.2 V.50,55-56 There was more disagreement on the charging mechanism for which it was disputed whether the reaction is fully or only partially reversible. Zhang et al. recently found that the reversibly capacity during cycling is dominated by the sulfur redox (Li2S « 2Li + S).57 Considering the use of MoS2 in LIBs with liquid electrolyte, Xiao et al.58 reported a specific capacity of about 600 mAhg-1 for non-exfoliated MoS2 in the 1st discharge, which decreased fast to a capacity of about 200 mAhg1

in the 2nd cycle. However, the electrochemical performance was greatly improved by

exfoliation of MoS2. In this way a capacity of about 1,000 mAhg-1 is achieved in the 1st discharge with retention over 500 mAhg-1 after 50 cycles. Note that the excess capacity during first discharge is due to decomposition of the liquid electrolyte, however, the work clearly indicated the benefit of nanostructuring for improving cycle life and capacity in cells with liquid electrolyte. So far, MoS2 has been rarely studied as an electrode material for SSBs. Chen et al.59 reported on the electrochemical performance of MoS2 as electrode material with Li6PS5Br as solid electrolyte. An initial reversible capacity of 450 mAhg-1 was found when cycled at C/5 in the potential range of 0.1-3.0 V vs. Li+/Li-In counter electrode. However, a significant specific capacity drop of 350 mAhg-1 was observed after 5 cycles. From the 6th cycle onwards, the cell was cycled in the potential range of 1.0-3.0 V resulting in a stable specific capacity of 200 mAhg-1 up to 40 cycles. Although the results demonstrate the activity of MoS2 in SSBs, the obtained capacities are much smaller than expected and the cycle life is insufficient indicating that full utilization of MoS2 is hindered in the bulk phase.

5



Page 6 of 20

In this work, we exfoliated MoS2 by chemical intercalation of lithium ions to obtain MoS2 nanosheets. The reaction products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM) combined with selected area electron diffraction (SAED) and energy-dispersive X-ray spectroscopy (EDXS). The electrochemical performance of the MoS2 nanosheets is studied in solid state lithium ion battery cells and compared with the behavior of bulk MoS2 powder. The electrochemical tests in the solid-state lithium ion battery demonstrated that the MoS2 nanosheets provide a specific capacity as high as 439 mAhg-1 and excellent cycling stability as compared to 259 mAhg-1 for bulk MoS2. For comparison, we also studied the behavior of MoS2 nanosheets in Li-ion cells with liquid electrolyte. Table 1: Properties of the ideal conversion reaction of MoS2 with Li at 25 °C (Data obtained using HSC Chemistry software database). Volumetric energy density in Wh/l is calculated for the discharged state. Cell reaction

discharge 4 Li + MoS2 ¾¾¾¾ ® 2 Li2S + Mo

DG [kJ mol-1]

-596.1

Number of transferred eVoltage / V vs. Li+/Li

4

qth (MoS2) by volume [mAh.cm ]

1.54 3389

qth (MoS2) by weight [mAhg-1]

670

Volume expansion MoS2 electrode Volume expansion cell

107%

-3

Specific energy density [Wh/kg] Volumetric energy density [Wh/L]

-21.7% 881.5 2530.4

Experimental section: Synthesis of Exfoliated MoS2 nanosheets: The synthesis of MoS2 nanosheets is done by chemical intercalation and exfoliation method. Lithium ion intercalation is achieved by immersing 300 mg of crystalline MoS2 bulk powder (Sigma Aldrich) in 3 ml of 1.6M n-butyl lithium (n-BuLi) (Sigma Aldrich) followed by stirring for 72 h in an argon filled glove box. The LixMoS2 is retrieved by filtration and washed with hexane to remove excess lithium and organic residues. Exfoliation is achieved immediately after this by ultra-sonicating LixMoS2 in water for 1 h. The mixture is washed with water several times to remove excess of lithium in the form of LiOH. Then the material is dried in a vacuum oven for 24 h at 70 °C to remove the 6


Page 7 of 20 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


excess water in the crystal structure and stored inside the glove box to avoid the further reaction with air.54, 60-61 Instrumentation and structural characterization: The interplanar spacings of MoS2 were determined by powder X-ray diffraction (PXRD) in a Bruker D8 Discover diffractometer with Cu-Kα (λ = 1.5406 Å) radiation with accelerating voltage of 40 kV and current of 30 mA, angular range of 10°< 2q< 80° with a step size of 0.02° and scan rate 1 s/step calibrated against corundum standard. The experimental patterns were compared with the standard JCPDS file (37-1492) of MoS2 and the lattice parameters were refined by least square regression using the Unit Cell program.62 For SEM, 5 μL of ultrathin nanosheets ethanol suspension was placed on the silicon substrate and dried overnight at room temperature. Afterwards, samples were investigated by field emission (FE) SEM (Carl-Zeiss AG, Germany). TEM observations were carried out with an FEI Tecnai G2 F20 S-TWIN (Oregon, USA) system operating at an accelerating voltage of 200 kV. Solid state cell and electrochemical measurements: Laboratory scale solid electrolyte (β Li3PS4) was synthesized by using a solution method and subsequent heat treatment (see S1).63 The composite working electrodes were made by gently mixing the bulk MoS2 or MoS2 nanosheets inside a glove box with solid electrolyte (β -Li3PS4) and C-nergy super C65 in a weight ratio of 6:3:1 by using an agate mortar for about 15 minutes. Another option to mix MoS2 and solid electrolyte would be ball milling. However, MoS2 and β-Li3PS4 are very soft materials so that the morphology of the nanosheets would easily be affected. Moreover, βLi3PS4 is extremely moisture sensitive, which aggravates any processing outside the glove box. We chose mixing the materials in a mortar instead of ball milling 70mg of β -Li3PS4 solid electrolyte is placed in a 10 mm die and cold pressed at 3 tons for 3 min using a hand press (Specac). The absolute mass of the working electrode (MoS2 nanosheets or bulk) in every cell was 6 mg. The electrode composite powder and the solid electrolyte powder were pressed under 3 tons to form a bilayer pellet using a hand press (Specac). The lithium-indium counter electrode is prepared by placing Li and In foils in a 1:1 stoichiometric ratio on top of the pellet with the pressure of 1 ton for 2 minutes. The use of the LiIn intermetallic phase as counter electrode shifts the voltage vs. Li+/Li by 0.6 V.21 All the composite preparation and cell construction were performed inside an argon-filled glove box (H2O and O2 levels below 1 ppm, MBraun, Germany).

7



Page 8 of 20

The electrochemical measurements were conducted with the above mentioned battery cell using a home built cell set up. The cyclic voltammetry is performed in the potential range of 0.01-3.00 V with a scan rate of 0.01 mVs-1 vs Li+/Li-In. Galvanostatic charge/discharge cycling is carried out in the voltage range from 0.01 V to 3.00 V vs Li+/Li-In. Specific currents and Crate were calculated based on the mass of MoS2 and its theoretical capacity (670 mAhg-1). For the rate performance test, the cell is charged and discharged with an initial low rate of 0.1C and then continued to cycle with high rates up to 1C rate for 5 cycles at each rate and then brought back to cycling at low rate. All the electrochemical experiments were performed at room temperature.

Figure 1: Schematic representation of the synthesis of exfoliated MoS2 nanosheets. Results and discussion: A schematic representation of the adopted synthesis procedures for the MoS2 nanosheets is shown in Fig. 1. MoS2 bulk and nanosheets were characterized by powder X-ray diffraction (Fig. 2a). All reflexes can be indexed using hexagonal MoS2 with the P63/mmc (JCPDS file no. =37-1492). Lattice parameters are a=0.3160 nm, c=1.2290 nm for the bulk material and a=0.3162, c=1.2368 nm for the exfoliated MoS2. The increase in c-lattice parameter by about 6% indicates that the exfoliation process leads to an increase in MoS2 interlayer spacing. Broadening of the (002) reflex is used to estimate the crystal thickness of the nanosheets in cdirection from the FWHM using the Scherrer equation. A value of about 10 nm is found which is well in line with results from TEM measurements, which we discuss in the following. The size, shape, structure, and morphology of the MoS2 nanosheets are characterized by SEM and TEM. The SEM images show agglomerates and it is therefore hard to identify “nanosized domains”. Nevertheless, the images reveal a sheet-type morphology with lateral dimensions in the μm range, see Figure S2. The TEM image of the MoS2 nanosheets shows that the sheets consist of about 5 to 10 binary S-Mo-S layers. The average layer distance between the sheets 8


Page 9 of 20 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


layers is around 0.620 nm, which is in line with earlier reports on exfoliated MoS2 (0.615 nm)44, 55

. It is important to remember that SEM and TEM only probe a very small fraction of the

sample. We therefore also used nitrogen physisorption to probe the volume of the samples. The specific surface area of the MoS2 nanosheets (21.4 m2g-1) is five times larger compared to bulk MoS2 (4 m2g-1) respectively, as determined by the BET method. Although this increase is significant, it is less to what would be expected from the SEM and TEM analysis. This shows that the use of N2 physisorption is very helpful in fully characterizing the material. In view of all results, however, it is clear that the exfoliation lead to nanosheets with small average crystallite sizes.

Figure 2: A) XRD patterns of the bulk MoS2 and MoS2 nanosheets B) XRD pattern of MoS2 after one discharge, C and D) High resolution TEM images of crystalline MoS2 nanosheets with lattice fringes (0.27 nm) perpendicular and (002) lattice fringes (0.62 nm) parallel to the basal plane (001). 9



Page 10 of 20

Figure 3: Schematic representation of the solid-state lithium ion battery with MoS2 nanosheets as positive and a Li-In alloy as negative electrode. The MoS2-electrodes contained 60 wt% MoS2, 30 wt% solid electrolyte and 10 wt% carbon black.

A schematic representation of the assembled cell is shown in Figure 3. In the following, we discuss the electrochemical properties of the MoS2 nanosheets when used in solid-state lithiumion battery cells. Figure 4 shows the cyclic voltammograms (CV), which are basically consistent with literature reports using liquid electrolytes, i.e. deviations from the theoretical redox potential are observed.64 Such deviations are typical for most conversion reactions. During the first lithiation process, conversion electrodes always undergo an activation so that the first cathodic sweep looks different from the following ones. The onset of the first cathodic peak starts at 0.79 V, which can be attributed to the insertion of lithium ion into the interlayer of MoS2 resulting in the formation of LixMoS2.65 The increase in current at approximately 0.3 V is indicative for the conversion of the LixMoS2 to Mo and Li2S. The overall reaction during this process can be described as stated in equation-1. In the anodic sweep, the reaction is reversed with a maximum current occurring at about 2.0 V. From the second cycle on, the cathodic sweep shows two maxima at about 1.3 V and 0.65 V indicating a multi-step reaction. The peak positions are reasonable considering the theoretical redox potentials of the possible charging reactions (1.54 V or 2.24 V vs. Li+/Li for the formation of MoS2 or S, respectively). Overall, the cyclic voltammograms show that redox reactions occur in a broad potential range and that the observed features repeatedly occur during cycling. This is in line with what is observed for conversion reactions in general and shows that the reaction mechanism is more 10


Page 11 of 20 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


complex than the ideal situation shown in eq. 1.25,

32, 66

Consequently, the galvanostatic

discharge/charge profiles are sloping (see discussion below) and the first cycle includes and activation of the material. It is well known that large structural changes occur in conversion reactions during the activation cycle and amorphous/nanosized phases form that are difficult to characterize.19 As we discuss below, however, we show that the initial state of MoS2 (exfoliated vs. bulk) has a major influence on the electrochemical performance of the electrode in SSB cells. The post mortem XRD measurements indicate that the end discharge products of the conversion reaction (Mo and Li2S, see reaction-1) indeed form during discharge. In figure-2B, a broad reflex at around 2q = 40° indicates elemental Mo with body centred cubic (BCC) structure, which has its highest intensity at 40.54 °. The reflex is very broad and slightly asymmetric which may also be due to some metastable face centered cubic Mo (most intense reflexes at 37.44 ° and 43.51 °) reflex at 2q = 25° refers to Li2S. We note that a more detailed analysis is complicated by several issues such as the amorphous/nanostructured nature of the electrode, the problem that solid state cell pellets can’t be dismantled and the issue of Li3PS4 being highly moisture sensitive. Rechargeability of the electrode is tested by galvanostatic cycling (charging corresponds to delithiation, discharging to lithiation). Figure 5a shows the discharge-charge profiles of the MoS2 nanosheets of first, second, 10th, 50th, 100th, and 500th cycle at a current density of 0.1C (67.0 mAg-1). The first discharge capacity was 439.1 mAhg-1. This is still below the theoretical value (66% of qth), but much higher compared to conventional intercalation compounds (150 – 180 mAhg-1 for layered oxides and 372 mAhg-1 for graphite). Equally important, the coulombic efficiency of the first cycle was 91.4 %, indicating a high degree in reversibility of the electrode reaction. The capacity decreased continuously during cycling yet 312 mAhg-1 are obtained after 500 cycles. This corresponds to an average capacity loss of only 0.25 mAhg-1 per cycle. On the other hand, the initial discharge capacity for bulk MoS2 is 259.6 mAhg-1, which corresponds only to about 40 % of its theoretical capacity. The coulombic efficiency of the first cycle was 74.1 %, which is much lower compared to the nanosheets. During cycling, the capacity decreased to 251 mAhg-1 after 100 cycles. Thus, the MoS2 nanosheets show a much better performance (note that the same amount of active materials was used for both electrodes).

11



Page 12 of 20

Figure 4: Cyclic voltammograms of ultrathin few layer MoS2 samples at a scan rate of 0.01 mV s−1 in potential range of 3.0 to 0.01 V vs. Li+/Li-In. The use of the LiIn intermetallic phase as counter electrode shifts the voltage vs. Li+/Li by 0.6 V. Overall, it is evident that the nanosheets morphology has a very beneficial impact on the capacity. The utilization of active material is drastically increased. The discharge-charge profiles also show that, in line with results from cyclic voltammetry, no defined redox potentials are found. The potential profiles are overall quite sloppy. For comparison, we also studied the behavior of our MoS2 nanosheets in cells with liquid electrolyte (Figure S4). While higher capacities are obtained compared to the solid-state cell, the fading is much stronger, i.e. the capacity drops from 918 mAhg-1 to 605 mAhg-1 during the first 25 cycles. Although for the liquid cells, the observed potential profiles are sloppy, they are somewhat more defined as compared to the solid state cells. In particular, the end of charging is much more defined. Very recently, Xu et al. showed cycling data of MoS2 in solid state cells with lithium as counter electrode and Li7P3S11 as solid electrolyte.67 While we could not reliably cycle cells with lithium as counter electrode and any sulfide electrolyte, presumably due to the chemical instability of these types of solid electrolytes towards lithium, see e.g. Richards et al.19 or Wenzel et al.68, their reported potential profiles are interestingly very similar to our results for liquid cells. Though both studies show promising reversibility of the electrode reaction, further studies on clarifying the shape of the potential profile and the stability of lithium as counter electrode towards sulfide electrolytes are needed. 12


Page 13 of 20 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


The rate performance of the MoS2 nanosheets cycled in solid state cells is shown in Figure 5c and 5d. At current densities of 0.1C, 0.5C, 0.2C, and 1C the specific capacities of the MoS2 nanosheets are 437.8, 404.4, 350.9, and 309.7 mAhg-1, respectively. Achieving such high capacity values in solid state cells at room temperature is quite outstanding. We believe that this behavior is aided by the nanosize dimensions of the MoS2. The improvement compared to the bulk MoS2 might be due to two effects. Firstly, the nanosheets may be less prone to loose contact upon cycling because volume changes can be better accommodated for finely dispersed materials. Secondly, the nanoscopic dimensions support a better utilisation of the active material by better electronic wiring, by decreasing the ion diffusion path length within and by increasing the total interfacial contact area. It is also seen that, after a few cycles, the coulombic efficiency quickly approaches to 100 % irrespective of the different current densities applied. At the end of the rate test, the current was reduced to its starting value of 0.1C and capacities of about 400 mAhg-1 were achieved. This is slightly lower compared to the first cycles at C/10 indicating that the high rate test, might have lead to some additional ageing. The obtained values of about 400 mAhg-1 are nevertheless still very high and the capacity only decreased negligibly during further cycling. Finally, it is important to realize our results clearly demonstrate that the initial form of the material has a major influence on the performance, i.e. exfoliated MoS2 is very much prefereed over bulk MoS2.

13



Page 14 of 20

Figure 5: A, B) Charge-discharge profile and cycling performance of MoS2 nanosheets at the current rate of 0.1C in the potential window of 0.01 V to 3.00 V vs. Li+/Li-In and corresponding the coulombic efficiency. C, D) Rate performance charge-discharge profile and cycling performance of MoS2 nanosheets at the different current densities in the potential window of 0.01V to 3.0V (Li+/Li-In)

Conclusion: MoS2 nanosheets were prepared by chemical exfoliation and studied as electrode material in lithium all-solid-state batteries at room temperature. The nanosheets delivered a high discharge capacity of 439 mAhg-1, which decreased to 312 mAhg-1 after 500 cycles when cycled at current rate of 0.1C. In line with conversion reactions in general, the potential profile (galvanostatic mode) as well as the cyclic voltammograms indicate that the reaction is complex and an activation of the electrode occurs during the first lithiation. The ideal discharge products Mo and Li2S were identified by X-ray diffraction. The excellent kinetic behavior is further supported by rate capability measurements providing 304 mAhg-1 at a current of 1C. A comparison with bulk MoS2 as electrode (same active loading) demonstrated that nanosizing is a very effective strategy in improving the performance of MoS2 as electrode in solid state batteries. Moreover, MoS2 is intrinsically fairly conductive and is soft, which is beneficial for achieving fast kinetics and dense electrodes. Overall, our study shows that, for solid state batteries, the combined use of soft electrolytes (sulfides) with soft and nanosized electrode materials such as exfoliated MoS2 can be an effective strategy to mitigate detrimental effects related to the large volume expansion typically observed for conversion reactions. Associated content: Supporting information: 14


Page 15 of 20 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


Supporting information contains the experimental details on the synthesis of solid electrolyte (β-Li3PS4), XRD results confirming the pure phase of the β-Li3PS4, Arrhenius plot showing high ionic conductivity of the solid electrolyte, SEM images of MoS2 nanosheets, charge/discharge profile of bulk-MoS2 in SSB, electrochemical performance of the MoS2 nanosheets a cell with liquid electrolyte. Author’s information: Corresponding Author *Email: [email protected]

ORCID: A. L. Santhosha: 0000-0002-2422-2703 Philipp Adelhelm: 0000-0003-2439-8802 Conflicts of interest: The authors declare no conflict of interest. Acknowledgements The authors thank B. Fähndrich and G. Gottschalt for technical support (physisorption measurements). The Jena Center for Soft Matter (JCSM) is acknowledged for SEM images. P.A. and A.L.S. thank for fruitful discussion within the project “FELIZIA” funded by the Federal Ministry of Education and Research (BMBF, grant number 03XP0026I). F.L. is grateful for funding of the TEM facility via the Gottfried Wilhelm Leibniz programme of the DFG (LA830/14-1).

Notes and reference 1. 2. 3. 4. 5.

Kato, Y.; Hori, S.; Saito, T.; Suzuki, K.; Hirayama, M.; Mitsui, A.; Yonemura, M.; Iba, H.; Kanno, R., High-Power All-Solid-State Batteries Using Sulfide Superionic Conductors. Nat. Energy 2016, 1, 16030. Schnell, J.; Günther, T.; Knoche, T.; Vieider, C.; Köhler, L.; Just, A.; Keller, M.; Passerini, S.; Reinhart, G., All-Solid-State Lithium-Ion and Lithium Metal Batteries – Paving the Way to Large-Scale Production. J. of Power Sources 2018, 382, 160-175. Kamaya, N.; Noriaki K.; Kenji H.; Yuichiro Y.; Masaaki H.; Ryoji K.; Masao Y.; Takashi K.; Yuki K.; Shigenori H.; Koji K.; Akio M., A Lithium Superionic Conductor. Nat. Mater. 2011, 10, 682-686. Han, F.; Zhu, Y.; He, X.; Mo, Y.; Wang, C., Electrochemical Stability of Li10GeP2S12 and Li7La3Zr2O12 Solid Electrolytes. Adv. Energy Mater. 2016, 6, 1501590. Janek, J.; Zeier, W. G., A Solid Future for Battery Development. Nat. Energy 2016, 1, 16141. 15



6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22.

23.

Page 16 of 20

Zhao, C.; Liu, L.; Qi, X.; Lu, Y.; Wu, F.; Zhao, J.; Yu, Y.; Hu, Y.-S.; Chen, L., SolidState Sodium Batteries. Adv. Energy Mater. 2018, 8. Gao, Z.; Sun, H.; Fu, L.; Ye, F.; Zhang, Y.; Luo, W.; Huang, Y., Promises, Challenges, and Recent Progress of Inorganic Solid-State Electrolytes for All-Solid-State Lithium Batteries. Adv. Mater. 2018, 30. Sun, C.; Liu, J.; Gong, Y.; Wilkinson, D. P.; Zhang, J., Recent Advances in All-SolidState Rechargeable Lithium Batteries. Nano Energy 2017, 33, 363-386. Hayashi, A.; Minami, K.; Tatsumisago, M., Development of Sulfide Glass-Ceramic Electrolytes for All-Solid-State Lithium Rechargeable Batteries. J. Solid State Electrochem. 2010, 14, 1761-1767. Wang, Y.; Richards, W. D.; Ong, S. P.; Miara, L. J.; Kim, J. C.; Mo, Y.; Ceder, G., Design Principles for Solid-State Lithium Superionic Conductors. Nat. Mater. 2015, 14, 1026-1031. Kuhn, A.; Duppel, V.; Lotsch, B. V., Tetragonal Li10GeP2S12 and Li7GePS8–Exploring the Li Ion Dynamics in LGPS Li Electrolytes. Energy Environ. Sci. 2013, 6, 3548. Wenzel, S.; Randau, S.; Leichtweiß, T.; Weber, D. A.; Sann, J.; Zeier, W. G.; Janek, J., Direct Observation of the Interfacial Instability of the Fast Ionic Conductor Li10GeP2S12 at the Lithium Metal Anode. Chem. Mater. 2016, 28, 2400-2407. Kato, A.; Nose, M.; Yamamoto, M.; Sakuda, A.; Hayashi, A.; Tatsumisago, M., Mechanical Properties of Sulfide Glasses in All-Solid-State Batteries. J. Ceramic Society of Japan 2018, 126, 719-727. Wolfenstine, J.; Allen, J. L.; Sakamoto, J.; Siegel, D. J.; Choe, H., Mechanical Behavior of Li-Ion-Conducting Crystalline Oxide-Based Solid Electrolytes: A Brief Review. Ionics 2018, 24, 1271-1276. Ni, J. E.; Case, E. D.; Sakamoto, J. S.; Rangasamy, E.; Wolfenstine, J. B., Room Temperature Elastic Moduli and Vickers Hardness of Hot-Pressed LLZO Cubic Garnet. J. Mater. Science 2012, 47, 7978-7985. Sakuda, A.; Hayashi, A.; Tatsumisago, M., Sulfide Solid Electrolyte with Favorable Mechanical Property for All-Solid-State Lithium Battery. Sci. Rep. 2013, 3, 2261. Lau, J.; DeBlock, R. H.; Butts, D. M.; Ashby, D. S.; Choi, C. S.; Dunn, B. S., Sulfide Solid Electrolytes for Lithium Battery Applications. Adv. Energy Mater. 2018, 8, 1800933. Kerman, K.; Luntz, A.; Viswanathan, V.; Chiang, Y.-M.; Chen, Z., Review-Practical Challenges Hindering the Development of Solid State Li Ion Batteries. J. Electrochem. Soc. 2017, 164, A1731-A1744. Richards, W. D.; Miara, L. J.; Wang, Y.; Kim, J. C.; Ceder, G., Interface Stability in Solid-State Batteries. Chem. Mater. 2016, 28, 266-273. Sahu, G.; Lin, Z.; Li, J.; Liu, Z.; Dudney, N.; Liang, C., Air-Stable, High-Conduction Solid Electrolytes of Arsenic-Substituted Li4SnS4. Energy Environ. Sci. 2014, 7, 10531058. Santhosha, A. L.; Medenbach, L.; Buchheim, J. R.; Adelhelm, P., The Indium-Lithium Electrode in Solid-State Lithium Ion Batteries: Phase Formation, Redox Potentials and Interface Stability. Batteries & Supercaps 2019, 10.1002/batt.201800149. Zhang, W.; Dominik A. W.; Harald W.; Tobias A.; Ingo M.; Daniel S.; Raimund K.; Thomas L.; Pascal H.; Wolfgang G. Z.; Jürgen J., Interfacial Processes and Influence of Composite Cathode Microstructure Controlling the Performance of All-Solid-State Lithium Batteries. ACS Appl. Mater. Interfaces 2017, 9, 17835-17845. Manthiram, A.; Yu, X.; Wang, S., Lithium Battery Chemistries Enabled by Solid-State Electrolytes. Nat. Rev. Mater. 2017, 2, 16103. 16


Page 17 of 20 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. 25. 26. 27. 28. 29.

30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42.

Medenbach, L.; Adelhelm, P., Cell Concepts of Metal-Sulfur Batteries (Metal = Li, Na, K, Mg): Strategies for Using Sulfur in Energy Storage Applications. Top Curr Chem (Cham) 2017, 375, 81. Klein, F.; Jache, B.; Bhide, A.; Adelhelm, P., Conversion Reactions for Sodium-Ion Batteries. Phys. Chem. Chem. Phys. 2013, 15, 15876-87. Rui, X.; Tan, H.; Yan, Q., Nanostructured Metal Sulfides for Energy Storage. Nanoscale 2014, 6, 9889-924. Etacheri, V.; Marom, R.; Elazari, R.; Salitra, G.; Aurbach, D., Challenges in the Development of Advanced Li-Ion Batteries: A Review. Energy Environ. Sci. 2011, 4, 3243. Goriparti, S.; Miele, E.; De Angelis, F.; Di Fabrizio, E.; Proietti Zaccaria, R.; Capiglia, C., Review on Recent Progress of Nanostructured Anode Materials for Li-Ion Batteries. J. of Power Sources 2014, 257, 421-443. O. E1 Beqqali, I. Z., F. Rogemond, H. Chermette, R. Ben Chaabane, M. Gamoudi, G. Guiilaud, Synthetic Matals, Electrical Properties of Molybdenum Disulfide MoS2. Experimental Study and Density Functional Calculation Results. Synthetic Metals. 1997, 90, 165-172. Zhang, C.; Ning, Z.; Liu, Y.; Xu, T.; Guo, Y.; Zak, A.; Zhang, Z.; Wang, S.; Tenne, R.; Chen, Q., Electrical Transport Properties of Individual WS2 Nanotubes and Their Dependence on Water and Oxygen Absorption. App. Phy. Lett. 2012, 101, 113-112. Jache, B.; Mogwitz, B.; Klein, F.; Adelhelm, P., Copper Sulfides for Rechargeable Lithium Batteries: Linking Cycling Stability to Electrolyte Composition. J. of Power Sources 2014, 247, 703-711. Cabana, J.; Monconduit, L.; Larcher, D.; Palacín, M. R., Beyond Intercalation-Based Li-Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting through Conversion Reactions. Adv. Mater. 2010, 22, E170-E192. Yongming S.; Nian L.; and Yi C., Promises and challenges of nanomaterials for lithium-based rechargeable batteries. Nat. energy 2016, 16071 Bruce, P. G.; Scrosati, B.; Tarascon, J. M., Nanomaterials for Rechargeable Lithium Batteries. Angew. Chem. Int. Ed. 2008, 47, 2930-46. Keppeler, M.; Srinivasan, M., Interfacial Phenomena/Capacities Beyond Conversion Reaction Occurring in Nano-Sized Transition-Metal-Oxide-Based Negative Electrodes in Lithium-Ion Batteries: A Review. ChemElectroChem 2017, 4, 2727-2754. Klein, F.; Jache, B.; Bhide, A.; Adelhelm, P., Conversion Reactions for Sodium-Ion Batteries. Phy. Chem. Chem. Phys. 2013, 15, 15876-15887. Wu, Z.; Li, B.; Xue, Y.; Li, J.; Zhang, Y.; Gao, F., Fabrication of Defect-Rich MoS2 ultrathin Nanosheets for Application in Lithium-Ion Batteries and Supercapacitors. J. Mater. Chem. A 2015, 3, 19445-19454. P. Adelhelm., Editorial: The Energy Challenge, Batteries, and Why Simple Math Matters Angew.Chem.Int.Ed. 2018, 57, 6710–6711 Bruce, P. G.; Scrosati, B.; Tarascon, J. M., Nanomaterials for Rechargeable Lithium Batteries. Angew. Chem. Int. Ed. 2008, 47, 2930-46. Jiang, C.; Hosono, E.; Zhou, H., Nanomaterials for Lithium Ion Batteries. Nano Today 2006, 1, 28-33. Palacín, M. R.; Simon, P.; Tarascon, J. M., Nanomaterials for Electrochemical Energy Storage: The Good and the Bad. Acta Chimica Slovenica 2016, 417-423. Anna Douglas, R. C., Landon Oakes, Keith Share, Adam P. Cohn, and Cary L. Pint, Ultrafine Iron Pyrite (FeS2) Nanocrystals Improve Sodium-Sulfur and Lithium-Sulfur Conversion Reactions for Efficient Batteries. ACS NANO 2015, 9, 11156-11165. 17



43. 44. 45. 46. 47. 48. 49. 50. 51.

52. 53. 54. 55. 56. 57.

58. 59.

Page 18 of 20

Chang, K.; Geng, D.; Li, X.; Yang, J.; Tang, Y.; Cai, M.; Li, R.; Sun, X., Ultrathin MoS2/Nitrogen-Doped Graphene Nanosheets with Highly Reversible Lithium Storage. Adv. Energy Mater. 2013, 3, 839-844. Yang, L.; Wang, S.; Mao, J.; Deng, J.; Gao, Q.; Tang, Y.; Schmidt, O. G., Hierarchical MoS2/Polyaniline Nanowires with Excellent Electrochemical Performance for Lithium-Ion Batteries. Adv. Mater. 2013, 25, 1180-4. Liu, H.; Su, D.; Zhou, R.; Sun, B.; Wang, G.; Qiao, S. Z., Highly Ordered Mesoporous MoS2 with Expanded Spacing of the (002) Crystal Plane for Ultrafast Lithium Ion Storage. Adv. Energy Mater. 2012, 2, 970-975. Villevieille, C.; Wang, X.-J.; Krumeich, F.; Nesper, R.; Novák, P., MoS2 Coating on MoO3 Nanobelts: A Novel Approach for a High Specific Charge Electrode for Rechargeable Li-Ion Batteries. J. of Power Sources 2015, 279, 636-644. Zhou, X.; Wan, L. J.; Guo, Y. G., Facile Synthesis of MoS2@CMK-3 Nanocomposite as an Improved Anode Material for Lithium-Ion Batteries. Nanoscale 2012, 4, 586871. Ye, H.; Ma, L.; Zhou, Y.; Wang, L.; Han, N.; Zhao, F.; Deng, J.; Wu, T.; Li, Y.; Lu, J., Amorphous MoS3 as the Sulfur-Equivalent Cathode Material for Room-Temperature Li-S and Na-S Batteries. Proc Natl Acad Sci USA 2017, 114, 13091-13096. Doan-Nguyen, V. V. T., et al., Molybdenum Polysulfide Chalcogels as High-Capacity, Anion-Redox-Driven Electrode Materials for Li-Ion Batteries. Chem. Mater. 2016, 28, 8357-8365. Stephenson, T.; Li, Z.; Olsen, B.; Mitlin, D., Lithium Ion Battery Applications of Molybdenum Disulfide MoS2 Nanocomposites. Energy Environ. Sci. 2014, 7, 209-231. Koerver, R.; Aygün, I.; Leichtweiß, T.; Dietrich, C.; Zhang, W.; Binder, J. O.; Hartmann, P.; Zeier, W. G.; Janek, J., Capacity Fade in Solid-State Batteries: Interphase Formation and Chemomechanical Processes in Nickel-Rich Layered Oxide Cathodes and Lithium Thiophosphate Solid Electrolytes. Chem. Mater. 2017, 29, 5574-5582. Richards, W. D.; Miara, L. J.; Wang, Y.; Kim, J. C.; Ceder, G., Interface Stability in Solid-State Batteries. Chem. Mater. 2015, 28, 266-273. Zhu, Y.; He, X.; Mo, Y., Origin of Outstanding Stability in the Lithium Solid Electrolyte Materials: Insights from Thermodynamic Analyses Based on FirstPrinciples Calculations. ACS Appl. Mater. Interfaces 2015, 7, 23685-23693. Matte, H. S.; Gomathi, A.; Manna, A. K.; Late, D. J.; Datta, R.; Pati, S. K.; Rao, C. N., MoS2 and WS2 Analogues of Graphene. Angew. Chem. Int. Ed. Engl. 2010, 49, 405962. Chandramohan G.; Andrew J. M.; Mohammad H. M.; Michael De V., Structural Evolution of Electrochemically Lithiated MoS2 Nanosheets and the Role of Carbon Additive in Li-Ion Batteries. Chem. Mater. 2016, 28, 7304−7310 Wang, L.; Xu, Z.; Wang, W.; Bai, X., Atomic Mechanism of Dynamic Electrochemical Lithiation Processes of MoS2 Nanosheets. J. Am. Chem. Soc. 2014, 136, 6693-6697. Zhang, L.; Sun, D.; Kang, J.; Feng, J.; Bechtel, H. A.; Wang, L. W.; Cairns, E. J.; Guo, J., Electrochemical Reaction Mechanism of the MoS2 Electrode in a Lithium-Ion Cell Revealed by in Situ and Operando X-Ray Absorption Spectroscopy. Nano Lett. 2018, 18, 1466-1475. Xiao, J.; Choi, D.; Cosimbescu, L.; Koech, P.; Liu, J.; Lemmon, J. P., Exfoliated MoS2 nanocomposite as an Anode Material for Lithium Ion Batteries. Chem. Mater. 2010, 22, 4522-4524. Chen, M.; Yin, X.; Reddy, M. V.; Adams, S., All-Solid-State MoS2/Li6PS5Br/In–Li Batteries as a Novel Type of Li/S Battery. J. Mater. Chem. A 2015, 3, 10698-10702. 18


Page 19 of 20 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


60. 61. 62. 63. 64. 65. 66.

67. 68.

Sreedhara, M. B.; Santhosha, A. L.; Bhattacharyya, A. J.; Rao, C. N. R., Composite of Few-Layer MoO3 nanosheets with Graphene as a High Performance Anode for SodiumIon Batteries. J. Mater. Chem. A 2016, 4, 9466-9471. Theerthagiri, J.; Senthil, R. A.; Senthilkumar, B.; Reddy Polu, A.; Madhavan, J.; Ashokkumar, M., Recent Advances in MoS2 Nanostructured Materials for Energy and Environmental Applications – a Review. J. Solid State Chemistry 2017, 252, 43-71. Holland, T. J. B.; Redfern, S. A. T., Unit Cell Refinement from Powder Diffraction Data- the Use of Regression Diagnostics. Mineralogical Magazine, 1997, 61, 65-77. Liu, Z.; Fu, W.; Payzant, E. A.; Yu, X.; Wu, Z.; Dudney, N. J.; Kiggans, J.; Hong, K.; Rondinone, A. J.; Liang, C., Anomalous High Ionic Conductivity of Nanoporous BetaLi3PS4. J. Am. Chem. Soc. 2013, 135, 975-978. Chang, K.; Chen, W., In Situ Synthesis of MoS2/Graphene Nanosheet Composites with Extraordinarily High Electrochemical Performance for Lithium Ion Batteries. Chem. Commum. 2011, 47, 4252-4254. Das, S. K.; Mallavajula, R.; Jayaprakash, N.; Archer, L. A., Self-Assembled MoS2– Carbon Nanostructures: Influence of Nanostructuring and Carbon on Lithium Battery Performance. J.Mater. Chem. 2012, 22, 12988. Ha, D. H.; Ly, T.; Caron, J. M.; Zhang, H.; Fritz, K. E.; Robinson, R. D., A General Method for High-Performance Li-Ion Battery Electrodes from Colloidal Nanoparticles without the Introduction of Binders or Conductive-Carbon Additives: The Cases of MnS, Cu(2-X)S, and Ge. ACS Appl. Mater. Interfaces 2015, 7, 25053-60. Xu, R. C.; Wang, X. L.; Zhang, S. Z.; Xia, Y.; Xia, X. H.; Wu, J. B.; Tu, J. P., Rational Coating of Li7P3S11 Solid Electrolyte on MoS2 Electrode for All-Solid-State Lithium Ion Batteries. J. of Power Sources 2018, 374, 107-112. Wenzel, S.; Weber, D. A.; Leichtweiss, T.; Busche, M. R.; Sann, J.; Janek, J., Interphase Formation and Degradation of Charge Transfer Kinetics between a Lithium Metal Anode and Highly Crystalline Li7P3S11 Solid Electrolyte. Solid State Ionics 2016, 286, 24-33.

19



Page 20 of 20

TOC Graphic

TOC-2017.tif

20


Exfoliated MoS2 as Electrode for All Solid State Rechargeable Lithium

Recommend Documents