CA3162016A1 - Sulfur cathode - Google Patents

Abstract

A sulfur cathode generated at least in part by in situ electrochemical pulverization of a metallic sulfide compound is provided. The in situ generated sulfur cathode suppresses the unfavorable process of polysulfide shuttling to provide enhanced sulfur cathode performance and is envisioned for use in Li-S, Na-S, K-S, Ca-S, Mg-S or Al-S batteries used to support rechargeable electronic devices and electric vehicles.

Description

Sulfur Cathode FIELD OF THE INVENTION
[0001] The present disclosure relates to batteries and in particular to batteries having sulfur cathodes, such as Li-S, Na-S, K-S, Ca-S, Mg-S or Al-S batteries.
BACKGROUND

[0002] Electric vehicles require efficient, low-cost, and safe energy storage systems with high energy density and high power capability.1 Lithium ion batteries can be used as a power source in many applications ranging from vehicles to portable electronics such as laptop computers, cellular phones and other electronic devices.2 The electric vehicles powered by conventional lithium-cobalt or lithium-iron phosphate batteries often have a driving range of less than 160 km per charge.

[0003] A battery based on Li-S electrochemistry would offer an attractive technology that meets requirements for low cost and high specific density.3 Li-S battery technology has been the subject of intense research and development both in academia and in industry due to its high theoretical specific energy of 2600 VVh/kg as well as the low cost of sulfur.4 The theoretical capacity of sulfur via two-electron reduction (S +
2Li+ + 2e- <=, Li2S), is 1672 mAh/g (elemental sulfur is reduced to 52- anion).5 The discharge process starts from a crown S8 molecule and proceeds through reduction to higher-order polysulfide anions (Li2S8, Li2S6) at a high voltage plateau (2.3-2.4 V), followed by further reduction to lower-order polysulfides (Li2S4, Li2S2) at a low voltage plateau (2.1 V), terminating with the Li2S product.6 During the charge process, Li2S is oxidized back to S8 through the intermediate polysulfide anions S. The Sx polysulfides generated at the cathode are soluble in the electrolyte and can migrate to the anode where they react with the lithium electrode in a parasitic fashion to generate lower-order polysulfides, which diffuse back to the cathode and regenerate the higher forms of polysulfide. This shuttle effect leads to decreased sulfur utilization, self-discharge, poor ability to repeatedly cycle through oxidation and reduction, and reduced Coulombic efficiency of the battery.' The insulating nature of S and Li2S results in poor electrode rechargeability and limited rate capability. In addition, an 80% volume expansion takes place during discharge.13 These factors have precluded the commercialization of Li-S
batteries in electric vehicles.

[0004] To circumvent these obstacles, extensive efforts have been devoted to improvement of sulfur cathodes. Such efforts have included providing conditions for infiltration or in situ growth of sulfur into or onto conductive scaffolds, such as conductive polymers (e.g., polythiophene, polypyrrole, and polyaniline) and porous carbons (e.g., active carbons, mesoporous carbons, hollow carbon spheres, carbon fibers, and graphene).3,8 It has been generally found that incorporation of sulfur within conductive polymers results in sulfur/polymer cathodes with improved capacity and cycling stability.
The sulfur and the polymer may be crosslinked, leading to electrodes with further improved cycling life.7 Compared with polymeric scaffolds, carbon scaffolds offer many advantages, such as enhanced stability and conductivity, low cost, and controllable pore structure, which make them more attractive candidates for sulfur cathodes.
Polymers (e.g., poly(ethylene oxide) and poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)) may be coated on the carbon/sulfur composites to further improve their cycling life and Coulombic efficiency. However, current sulfur cathodes have not proven satisfactory for development of high-performance Li-S batteries. Current sulfur cathodes do not sufficiently retard polysulfide migration to a sufficient extent to prolong cathode cycling life. During discharge of current sulfur/carbon cathodes, the cyclic S8 molecules are converted to polysulfides (Li2Sn, 2 < n <8) that are smaller than the S8 molecules. Driven by the concentration gradient, the polysulfides unavoidably diffuse away from the cathodes, causing rapid loss of capacity and resulting in poor cycling.

[0005] Efforts to improve Li-S batteries are described, for example, in European Patent EP3170216 and U.S. Patent Publication No. U520180079865, each incorporated herein by reference in entirety.

[0006] There continues to be a need for improvements in cathodes for batteries such as Na-S, K-S, Ca-S, Mg-S or Al-S batteries.

7 SUMMARY
[0007] The present technology provides sulfur cathodes and batteries including sulfur cathodes. In some embodiments, the sulfur cathodes are completely generated in situ or are based on existing cathodes with sulfur added. The added sulfur may be generated in situ using processes described herein.

[0008] In one example embodiment, generation of a sulfur cathode is provided in situ (i-SC) via electrochemical pulverization of tungsten trisulfide (WS3). Bridging or apical disulphide ligand (S22) in WS3 forms lithium sulphide at - 1.9 V vs Li/Lit during the first lithiation cycle. The subsequent electrochemical delithiation/ lithiation allows the formation of thermodynamically favorable products at higher voltages, preferably above 2.4 V vs Li/Li+. This facilitates a pseudo lithium-sulfur reaction mechanism in a long term cycle with higher order and lower order polysulphide displaying voltage plateaus at 2.39 V vs Li/Li+ and 2.12 - 2.2 V vs Li/Lit, respectively. WS2 formed in the preliminary cycle encourages surface adsorption of Li2Sx, suppressing polysulphide shuttling and negligible over-potential for catalytic oxidation of latter. Electrochemical performance of i-SC provides a remarkable initial discharge capacity of - 1300 mAh/g and a reversible capacity of - 1200 mAh/g is obtained in subsequent cycles at 0.5 C. An excellent discharge capacity of 850 mAh/g and 400 mAh/g was demonstrated by i-SC when cycled at rate of 1.5 C and 2 C, respectively, for 150 cycles with a columbic efficiency of 99.8 %.

[0009] In accordance with one aspect of the technology, there is provided a Li-S, Na-S, K-S, Ca-S, Mg-S or Al-S battery which includes a cathode generated at least in part by electrochemical pulverization of a metallic sulfide compound. The electrochemical pulverization of the metallic sulfide may be provided in situ during an electrochemical process.

[0010] The metallic sulfide compound is a tungsten sulfide compound. The tungsten sulfide compound may be W53.

[0011] In some embodiments, the battery is a Li-S battery and the electrochemical pulverization generates W52 and Li2S as active electrochemical species.

[0012] In some embodiments, the electrochemical pulverization occurs at about 1.9 V
vs. Li/Lit.

[0013] The WS3 may be amorphous and/or crystalline WS3 prepared in a process including milling of (NI-14)2WS4, followed by annealing. The annealing may be conducted at a temperature between about 190 C to about 330 C.

[0014] In some embodiments, the milling is performed in the presence of graphene nanoplatelets, carbon sulfides, metal sulfides or metal oxides.

[0015] In some embodiments, the Li2S is converted to Li + and Sx at about 2.4 V vs.
Li/Lit.

[0016] In some embodiments, the Sx and the Li + are converted to Li2Sx.4,6,8 at about 2.4 V vs. Li/Lit.

[0017] In some embodiments, Li2Sx=4,6,8 is converted to Li2S at about 2.1 V
vs. Li/Lit.

[0018] In some embodiments, the WS2 is generated in the form of sheets ranging in length between about 20 nm to about 1500 nm.

[0019] In some embodiments, the electrochemical pulverization occurs continuously during electrochemical cycles.

[0020] Another aspect of the technology is a battery comprising a cathode including WS2 in the form of sheets ranging in length between about 20 nm to about 1500 nm.

[0021] In some embodiments, the WS2 is generated in situ by electrochemical pulverization of WS3.

[0022] In some embodiments, the WS3 is prepared in a process including milling of (NI-14)2WS4, followed by annealing. The annealing may be conducted at a temperature between about 190 C and about 330 C. The milling may be performed in the presence of graphene nanoplatelets to provide a nucleation surface.

[0023] In some embodiments, the electrochemical pulverization occurs continuously during electrochemical cycles.

[0024] Another aspect of the technology is a sulfur cathode generated at least in part by electrochemical pulverization of a metallic sulfide compound in situ during an electrochemical process. The metallic sulfide compound may be a tungsten sulfide compound. The tungsten sulfide compound may be WS3.

[0025] In some embodiments, the electrochemical pulverization generates WS2 and Li2s as active electrochemical species.

[0026] Another aspect of the technology is a Li-S battery comprising the sulfur cathode as described herein.
BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Various objects, features and advantages of the invention will be apparent from the following description of particular embodiments of the invention as supported by the drawings.
Figure 1 is a schematic illustration of synthesis of tungsten trisulfide (W53) via an all-solid-state soft synthesis approach.
Figure 2 includes an SEM image of amorphous W53 showing granule-like morphology (left) and images of elemental mapping of the W53 surface confirming uniform distribution of tungsten (right upper panel) and sulfur (right lower panel).
Figure 3 is an SEM image (cross-section) of the cathode before discharge with a thickness of - 25 pm (tungsten trisulfide loading - 3 mg/cm2) (left side) and images of mapping of the cross section validating presence of tungsten, sulfur and carbon support (right side).
Figure 4a is an image of the surface morphology of W53 at 30,000X
magnification.
Figure 4b is an image of the surface morphology of W53 at 100,000X
magnification.
Figure 5 is a thermal gravimetric plot obtained for (NI-14)2W54 indicating the reaction pathway for formation of amorphous W53.

Figure 6 is a schematic representation of generation of the in situ sulfur cathode produced by electrochemical pulverization followed by pseudo lithium-sulfur electrochemistry to provide stable battery performance.
Figure 7a is an SEM image of the in situ cathode produced as illustrated in Figure 2a obtained at 30,000X magnification after an initial cycle.
Figure 7b is an SEM image of the in situ cathode produced as illustrated in Figure 2a obtained at 100,000X magnification after an initial cycle.
Figure 7c is an SEM image of the in situ cathode produced as illustrated in Figure 2a obtained at 200,000X magnification after an initial cycle.
Figure 7d is an elemental mapping image of the in situ cathode showing distribution of tungsten and sulfur after the initial discharge.
Figure 8 shows XRD patterns of the in situ cathode obtained for a cell before initial discharge and for cells disassembled after the 1stand 150th cycles. Evolution of WS2 nanostructure is associated with peaks labelled (002) and (004) and peaks labelled (111), (220)and (311) are attributed to Li2S.
Figure 9a is an EDX spectrum of the in situ cathode obtained after the 1St cycle.
Figure 9b is an EDX spectrum of the in situ cathode obtained after the 1001h cycle.
Figure 9c is an EDX spectrum of the in situ cathode obtained after the 1501h cycle.
Figure 10a is a cyclic voltammetry plot obtained demonstrating the formation of the in situ cathode in an initial reduction reaction at -1.9 V followed by reversible performance of the electrochemically generated in situ cathode for over four cycles.
Figure 10b is a plot showing a series of charge/discharge curves obtained for the stable in situ cathode for first five cycles at 0.5 C.
Figure 10c is a plot showing specific capacity values obtained for varying current rate (0.5 C to 2 C) demonstrating the effective charge/discharge capability of the in situ cathode.

Figure 10d is a plot showing a series of charge/discharge curves obtained at different temperatures with reduced overpotential for catalytic activity of the in situ formed WS2 nanosheets.
Figure 10e is a plot showing the rate capability of the in situ-generated cathode over prolonged cycles at 1.5 C and 2 C, with Coulombic efficiency of -99.8%.
Figure 11a is a S 2p XPS spectrum of the in situ sulfur cathode before discharge.
Figure llb is an S 2p XPS spectrum of the in situ sulfur cathode after discharge.
Figure 12a is a TEM image of the cathode before discharge.
Figure 12b is a TEM image of the cathode after discharge.
Figure 13a is a plot of open circuit voltage (OCV) of in situ sulfur cathode before discharge after several days and on the right initial discharge hour at an applied current load of 800 mA
Figure 13b is a plot of initial specific discharge capacity of in situ sulfur cathode rested after several days.
DETAILED DESCRIPTION
Introduction and Rationale

[0028] The key issue which has prevented wide-scale development of Li-S
batteries is the polysulfide shuttle effect that is responsible for the progressive leakage of active material from the cathode resulting in low life cycle of the battery.
Moreover, the extremely low electrical conductivity of sulfur cathode requires an extra mass for a conducting agent in order to exploit the whole contribution of active mass to the capacity.
The present inventors have recognized that the polysulfide shuttle effect could be mitigated using tungsten trisulfide as cathode precursor material.

[0029] Described herein is a process for in situ generation of a sulfur cathode via electrochemical pulverization of tungsten trisulfide (W53). The general term "electrochemical pulverization" is defined herein as a process of breaking a particle into smaller particles as a result of an electrochemical process. In one example of electrochemical pulverization described herein, the bridging or apical disulfide ligand (S22-) of WS3 forms lithium sulfide at - 1.9 V vs Li/Lit during the first lithiation cycle. The subsequent electrochemical delithiation/lithiation allows the formation of thermodynamically favorable higher order polysulfide or sulfur at higher voltages, preferably above 2.4 V vs Li/Li+. This facilitates the pseudo lithium-sulfur reaction mechanism in a long term cycle with higher order and lower order polysulfides displaying voltage plateaus at 2.39 V vs Li/Lit and 2.12 -2.2 V vs Li/Lit, respectively.
WS2, which is formed in the preliminary cycle, promotes surface adsorption of Li2S4<x<8.
This suppresses polysulfide shuttling and minimum over-potential for catalytic oxidation of polysulfides. Electrochemical performance of the in situ generated sulfur cathode is favorable with an initial discharge capacity of - 1300 mAh/g and a reversible capacity of - 1200 mAh/g obtained in following cycles at 0.5 C. An excellent discharge capacity of 850 mAh/g and 400 mAh/g was demonstrated by the system when cycled at rate of 1.5 C and 2 C, respectively, for 150 cycles with a Coulombic efficiency of 99.8%.

[0030] While the example embodiment described below is focused on generating an in situ cathode using a tungsten-based sulfur compound for lithium batteries, the strategy employed is expected to be applicable to other metal batteries such as sodium, potassium, aluminum, calcium and magnesium.
Synthesis and Characterization of the W53 for the In Situ Cathode

[0031] WS3 was prepared using an all-solid-state soft synthesis approach reported elsewhere which is illustrated schematically in Figure 1.9,10 In a typical synthesis, 0.45 g of precursor ammonium tetrathiotungstate, (NH4)2WS4, was roll-milled with 0.05 g of graphene nanoplatelets in a 20 mL sample vial containing 5 mm diameter zirconium balls for 12 hours. The composite was annealed at 250 C under an N2 atmosphere, resulting in a structurally stable amorphous mass of WS3 following the decomposition pathway (NH4)2WS4 WS3 +
H2S + NH3. It was found that 10% (m/m) of graphene provides an excellent nucleation surface for growth of WS3 microstructure. The annealed product (250 C) was used to prepare the cathode. Figure 2 displays the scanning electron microscopy (SEM) image of produced WS3. A granule like morphology was observed, indicating the amorphous nature of WS3. Elemental mapping performed over the surface shows a uniform distribution of tungsten and elemental sulfur (Figure 2, inset). A relatively thick cathode was prepared to ensure improved sulfur loading. Figure 3 shows the cross-section (SEM) of fabricated dense cathode with a thickness of - 25 pm. Tungsten trisulfide loading estimated over the coating area of - 0.5 cm2 was 3 mg/cm2. Elemental mapping conducted over the cross-section confirms uniform distribution of tungsten and sulfur on a carbon current collector (Figure 3, inset).
Additionally, high magnification SEM images of WS3 topology were collected to confirm the coarse surface of produced WS3 (Figure 4a and b). Thermal gravimetric analysis (TGA) demonstrating the formation of thermally stable amorphous WS3 via the aforementioned reaction pathway and percentage sulfur content is shown in Figure 5. An initial weight loss of about 13% (m/m) at - 200 C is associated with production of H2S +
NH3, and thermally stable WS3 is observed in the temperature range between about 250 C - 325 C under the conditions employed. This range may be extended under other conditions to cover about 220 C to about 325 C.
Electrochemical Generation of the In Situ Sulfur Cathode

[0032] A schematic reaction process for generation of the in situ sulfur cathode via electrochemical pulverization of WS3 is shown in Figure 6. The WS3 precursor is arranged in a lattice forming WS6 polyhedra. At 1.9 V vs. Li/Lit, the bridging disulfide ligand in WS6 polyhedra generates a discharge product Li2S in the initial discharge cycle accompanied by generation of WS2 that can electrochemically catalyze polysulfides.
With reversal of polarity (delithiation), the discharge product Li2S is converted to the higher order polysulfide Liz% or polymeric S8 at - > 2.3 V vs Li/Lit on the electrochemically active WS2 surface.

[0033] Figures 7a-c are SEM images of the in situ-generated cathode after initial discharge at 20,000X, 50,000X and 100,000X magnifications respectively. The granule-like morphology associated with WS3 observed is initially transformed to a layered microstructure with dimensions ranging from 1000 nm - 1500 nm which are typical of crystalline WS2. Elemental mapping conducted over the evolved microstructure confirmed uniform distribution of tungsten and sulfur (Figure 7d).

[0034] Figure 8 shows a series of X-ray diffraction (XRD) patterns indicating evolution of the cathode morphology after several electrochemical cycles. Cells were disassembled after the 1st and 150th discharge cycle. It can be seen in Figure 3a that the XRD pattern is featureless prior to the first cycle. This indicates the amorphous nature of the WS3 precursor material. After the 1st discharge cycle, diffraction peaks observed at 28 = 26 and 52 , labelled (111) and (311) respectively, are associated with formation of Li2S. The characteristic peaks attributed to WS2, were observed at 28 = 14 and 30 respectively.
Diffraction peaks obtained ex situ at the 1501h cycle exhibit dominant presence of Li2S
signals (28 = 26 and 520)11 and WS2 signals (28 = 14 and 300),12 confirming generation of the electrochemically active WS2 catalyst via in situ electrochemical pulverization of amorphous WS3.

[0035] Figures 9a-c are energy dispersive x-ray (EDX) spectra obtained for cells discharged after the 1st cycle, the 1001h cycle and the 150th cycle, respectively. The La and Ka peaks associated with tungsten and sulfur at 1.8 keV and 2.3 keV
respectively, suggest formation of WS2 microstructure after the initial discharge. Eventual appearance of the Ka peak at 8.2 keV observed after the 100th cycle and the 150th cycle indicates breakdown of the layered WS2 structural geometry to elemental tungsten ('AT).
The sheet length of the WS2 nanostructure ranges between about 20 nm to about 1500 nm after the 150th cycle. This is believed to be caused by continued electrochemical pulverization occurring in the cycling window.

[0036] Figure 10a shows a cyclic voltammetry (CV) plot exhibiting electrochemical generation of the in situ cathode. The bridging disulfide ligand (S22) of WS3 forms the final discharge product Li2S in the initial reduction cycle (1.9 V vs Li/Lit).
Within the subsequent cycling window, formation of thermodynamically favored S8 occurs >
2.4 V
vs. Li/Lit (oxidation), and formation of a combination of Li2S8, Li2S6, and Li2S4 occurs at 2.39 V vs. Li/Lit (reduction). Reduction of these species to Li2S occurs at 2.1 V vs. Li/Li+.
The complete set of electrochemical reactions occurring in the CV plot of Figure 4a is provided below.
WS3 + Li+ + e- Li2S + WS2 1.9V
8Li2S 16Li+ + 16e- + S8 >2.4 V II
S8 + XLi+ xe- Li2Sx=4,6,8 2.39 V Ill Li2Sx=4,6,8+ XLi+ + xe- Li2S 2.1 V IV

[0037] To ensure complete stripping of Li + ions, the final charging voltage was capped at - 3.5 V vs Li/Lit, where electrolyte decomposition is initiated (Figure 10a).
However, allowing further lithiation past a reduction potential of Li2S at - 1.9 V vs Li/Lit results in Li+/WS2 insertion chemistry at - 1.25 V vs Li/Lit (LixWS2), followed by irreversible breakdown of WS2 sheets into tungsten metal ('N) at < 0.75 V vs Li/Lit thus limiting the sulfur reaction chemistry observed in the range between 2.1 V and 2.4 V vs Li/Lit. In order to circumvent this issue, the cycling window was restricted to 1.9 V -3.5 V vs Li/Lit to access only Li-S conversion chemistry for stable cell performance.

[0038] Figure 10b demonstrates the charge/discharge curve of the in situ cathode for the first five cycles. An initial discharge capacity of - 1200 mAh/g and a reversible capacity of - 1100 mAh/g were determined at 0.5 C. A plot of specific capacity vs. cycle number for the in situ cathode in the current load range of 0.5 C - 2 C is provided in Figure 10c. An excellent capacity (- 1550 mAh/g) close to theoretical capacity of elemental sulfur (1675 mAh/g) was obtained at 0.5 C. A high capacity of - 600 mAh/g was obtained when cycled at 2 C. This can be attributed to strong catalytic activity of in situ-formed W52 nanosheets. The significant observation that the overpotential for oxidation of polysulfide was reduced to 0.21 V can be attributed to surface catalytic activity of the layered W52 nanostructure (Figure 10d). Furthermore, the assembled cell was subjected to charge/discharge over 150 cycles at 1.5 C and 2 C
respectively. The in situ cathode retained a specific capacity of 950 mAh/g and 500 mAh/g at 1.5 C
and 2 C
respectively with Coulombic efficiency of -99.8% even after a prolonged charge/discharge cycle (Figure 10e).

[0039] The deconvoluted high resolution X-ray photoelectron spectroscopy (XPS) spectra of S 2p show two peaks at 161.80 eV and 162.96 eV respectively, pertaining to S 2p1/2 and S 2p3/2 of apical S2- ligands in W53. Similarly, peaks observed at 162.80 eV
and 163.96 eV respectively, can be attributed to S 2p1/2 and S 2p3/2 of bridging 522-ligands in W53 (Fig. 11a). Fig. 11b display the chemical state of sulfur species in in situ cathode after 1st discharge cycle. The presence of peaks designated at 160.90 eV and 162.06 eV attributed to Sw2- 2p1/2 and S w2- 21D3/2 affirms the electrochemical pulverization of W53 into W52 after initial discharge. Additionally, S 2p spectrum also consist of S 2p1/2 and S 2p3/2 signals originating from bridging sulfur atom (SL) in Li2S at 161.66 eV and 160.50 eV respectively. Figures 12a and 12b show transmission electron microscopy (TEM) images of the in situ sulfur cathode before and after discharge, respectively. A
visible ordered pattern was not observed for the in situ sulfur cathode before discharge.
This indicates the amorphous nature of WS3, whereas the in situ sulfur cathode after discharge exhibits a layered geometry with a d spacing of - 0.62 nm and 0.33 nm associated with crystalline WS2 and Li2S respectively.

[0040] A battery that undergoes self-discharge is of no commercial importance regardless of its high gravimetric capacity. Here we demonstrate that the static electrochemical stability of WS3 presents a remarkable shelf life. The Fig.
13a shows the voltage retention after 1, 3, 7 and 30 days. Very interestingly, no drop-in voltage was observed after several days of resting hours. The WS3 electrode exhibited stable voltage plateau at 2.40, 2.80, 2.79 and 2.80 V after 1, 3, 7 and 30 days respectively.
This can be attributed to electrochemical stability of 522- ligands in WS3. Fig. 13a, right panel demonstrates the initial discharge hours after 1, 3, 7 and 30 days. All the electrodes display a voltage plateau of 2 V pertaining to reduction of 522- bridging disulfide ligands in a-WS3. The initial specific discharge capacity for the latter is also provided in Fig. 13b.
Equivalents and Scope

[0041] Other than described herein, or unless otherwise expressly specified, all of the numerical ranges, amounts, values and percentages, such as those for amounts of materials, elemental contents, times and current rate, ratios of amounts, and others, in the following portion of the specification and attached claims may be read as if prefaced by the word "about" even though the term "about" may not expressly appear with the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0042] Any patent, publication, internet site, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

[0043] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0044] While the technology been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.

[0045] In the claims, articles such as "a," "an," and "the" may mean one or more than one unless indicated to the contrary or otherwise evident from the context.
Claims or descriptions that include "or" between one or more members of a group are considered satisfied if one, more than one, or all of the group members are present in, employed in, or otherwise relevant to a given product or process unless indicated to the contrary or otherwise evident from the context.

[0046] It is also noted that the term "comprising" is intended to be open and permits but does not require the inclusion of additional elements or steps. When the term "comprising" is used herein, the term "consisting of" is thus also encompassed and disclosed. Where ranges are given, endpoints are included. Furthermore, it is to be understood that unless otherwise indicated or otherwise evident from the context and understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value or subrange within the stated ranges in different embodiments of the invention, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise. Where the term "about" is used, it is understood to reflect +/- 10% of the recited value. In addition, it is to be understood that any particular embodiment of the present invention that falls within the prior art may be explicitly excluded from any one or more of the claims. Since such embodiments are deemed to be known to one of ordinary skill in the art, they may be excluded even if the exclusion is not set forth explicitly herein.
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Claims (25)

PCT/CA2020/051587

1. A Li-S, Na-S, K-S, Ca-S, Mg-S or Al-S battery comprising a cathode generated at least in part by electrochemical pulverization of a metallic sulfide compound.

2. The battery of claim 1, wherein the electrochemical pulverization of the metallic sulfide is provided in situ during an electrochemical process.

3. The battery of claim 1 or 2, wherein the metallic sulfide compound is a tungsten sulfide compound.

4. The battery of claim 3, wherein the tungsten sulfide compound is W53.

5. The battery of claim 4, wherein the battery is a Li-S battery and the electrochemical pulverization generates W52 and Li2S as active electrochemical species.

6. The battery of claim 4 or 5, wherein the electrochemical pulverization occurs at about 1.9 V vs. Li/Li+.

7. The battery of any one of claims 3 to 6, wherein the W53 is amorphous and/or crystalline W53 prepared in a process including milling of (NI-14)2W54, followed by annealing.

8. The battery of claim 7, wherein the annealing is conducted at a temperature between about 190 C to about 330 C.

9. The battery of claim 7 or 8, wherein the milling is performed in the presence of graphene nanoplatelets, carbon sulfides, metal sulfides or metal oxides.

10. The battery of any one of claims 4 to 9, wherein the Li2S is converted to Li+ and Sx at about 2.4 V vs. Li/Li+.

11. The battery of claim 10, wherein the Sx and the Li+ are converted to Li2Sx.4,6,8 at about 2.4 V vs. Li/Li+.

12. The battery of claim 11, wherein the Li2S,.4,6,8 is converted to Li2S
at about 2.1 V
vs. Li/Li .

13. The battery of any one of claims 5 to 12, wherein the WS2 is generated in the form of sheets ranging in length between about 20 nm to about 1500 nm.

14. The battery of any one of claims 1 to 13, wherein the electrochemical pulverization occurs continuously during electrochemical cycles.

15. A battery comprising a cathode including WS2 in the form of sheets ranging in length between about 20 nm to about 1500 nm.

16. The battery of claim 15, wherein the WS2 is generated in situ by electrochemical pulverization of W53.

17. The battery of claim 16, wherein the W53 is prepared in a process including milling of (N1-14)2W54, followed by annealing.

18. The battery of claim 17, wherein the annealing is conducted at a temperature between about 190 C and about 330 C.

19. The battery of claim 17, wherein the milling is performed in the presence of graphene nanoplatelets to provide a nucleation surface.

20. The battery of any one of claims 15 to 19, wherein the electrochemical pulverization occurs continuously during electrochemical cycles.

21. A sulfur cathode generated at least in part by electrochemical pulverization of a metallic sulfide compound in situ during an electrochemical process.

22. The sulfur cathode of claim 21, wherein the metallic sulfide compound is a tungsten sulfide compound.

23. The sulfur cathode of claim 22, wherein the tungsten sulfide compound is W53.

24. The sulfur cathode of claim 23, wherein the electrochemical pulverization generates W52 and Li2S as active electrochemical species.

25. A Li-S, Na-S, K-S, Ca-S, Mg-S or Al-S battery comprising the sulfur cathode of any one of claims 21 to 24.