SHEET-BASED FRAMEWORK FOR HIGH-PERFORMANCE HYBRID QUASI-SOLID BATTERY

Abstract

The present invention relates to a material comprising a garnet-type oxide in the form of a powder comprising a plurality of sheet structures, a hybrid quasi-solid electrolyte framework comprising the material, a hybrid quasi-solid electrolyte comprising the hybrid quasi-solid electrolyte framework, and an electrochemical cell comprising the hybrid quasi-solid electrolyte. The present invention also relates to the respective methods for preparing the material, hybrid quasi-solid electrolyte framework, hybrid quasi-solid electrolyte and electrochemical cell. The present invention also relates to the respective methods for preparing the material, hybrid quasi-solid electrolyte framework, hybrid quasi-solid electrolyte and electrochemical cell as described above.

Claims

1. A material comprising a garnet-type oxide in the form of a powder comprising a plurality of sheet structures.

2. The material according to claim 1, wherein the sheet structures are interconnected with each other.

3. The material according to claim 1, wherein the material comprises a solid mixture of at least lithium and oxygen and optionally an element selected from the group consisting of magnesium, aluminum, silicon, calcium, scandium, vanadium, manganese, iron, nickel, gallium, germanium, strontium, yttrium, zirconium, niobium, barium, tantalum, lanthanum, cerium, neodymium, samarium, europium, gadolinium, terbium and any mixture thereof or is further doped with one or more elements selected from the group consisting of hydrogen, beryllium, boron, carbon, sodium, phosphorous, sulfur, chlorine, potassium, titanium, chromium, cobalt, copper, zinc, arsenic, selenium, bromine, rubidium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, iodine, cesium, hafnium, tungsten, iridium, platinum, gold, mercury, thallium, lead, bismuth, and any mixture thereof.

4.-5. (canceled)

6. The material according to claim 1, wherein the sheet structures have a lateral dimension of greater than 1 μm and a thickness in a range of about 100 nm to about 250 nm or the sheet structures are crystalline.

7. (canceled)

8. A method for forming the material according to claim 1, the method comprising the step of: mixing a plurality of precursors of a garnet-type oxide in an aqueous solvent in the presence of a sugar to form a sol, and heating the sol.

9. The method according to claim 8, wherein the method is a sol-gel method.

10. The method according to claim 8, wherein the precursors are selected from at least a lithium salt and oxygen or a compound comprising oxygen and optionally a compound comprising an element selected from the group consisting of magnesium, aluminum, silicon, calcium, scandium, vanadium, manganese, iron, nickel, gallium, germanium, strontium, yttrium, zirconium, niobium, barium, tantalum, lanthanum, cerium, neodymium, samarium, europium, gadolinium, terbium, and any mixture thereof or further comprises the step of incorporating a dopant into the material, the dopant being one or more elements selected from the group consisting of hydrogen, beryllium, boron, carbon, sodium, phosphorous, sulfur, chlorine, potassium, titanium, chromium, cobalt, copper, zinc, arsenic, selenium, bromine, rubidium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony, tellurium, iodine, cesium, hafnium, tungsten, iridium, platinum, gold, mercury, thallium, lead, bismuth, and any mixture thereof.

11.-13. (canceled)

14. The method according to claim 8, wherein the sugar is a monosaccharide, a disaccharide, an oligosaccharide, or any mixture thereof.

15. The method according to claim 9, wherein the sol gel has a pH in a range of about 1 to about 2.

16. The method according claim 8, wherein the heating step comprises a first heating step and a second heating step, wherein the first heating step is performed at a temperature in a range of about 150° C. to about 500° C., and a duration in a range of 0.5 hours to 5 hours, or more than 5 hours, and the second heating step is performed at a temperature in a range of about 600° C. to about 1500° C., and a duration in a range of about 30 minutes to about 10 hours, or more than 10 hours.

17. (canceled)

18. A hybrid quasi-solid electrolyte framework comprising the material according to claim 3 and a polymer.

19. The hybrid quasi-solid electrolyte framework of claim 18, wherein the polymer is selected from the group consisting of polytetrafluoroethylene (PTFE), polyvinylidene fluoride, polyethylene oxide, sodium alginate, sodium carboxymethyl cellulose, polyacrylic acid, poly(acrylonitrile-methyl methacrylate), styrene butadiene rubber/carboxy methyl cellulose (SBR/CMC), a copolymer comprising acrylamide, lithium carboxylate and acrylonitrile, and any mixture thereof.

20. The hybrid quasi-solid electrolyte framework of claim 18, wherein the ratio between the hybrid quasi-solid electrolyte framework:polymer is in a range of about 20:1 to about 2:1 by weight.

21. (canceled)

22. The hybrid quasi-solid electrolyte framework according to claim 18, wherein the framework is porous.

23. A method for forming the hybrid quasi-solid electrolyte framework according to claim 18, the method comprising the step of mixing said material with a polymer to form a framework mixture.

24.-25. (canceled)

26. A hybrid quasi-solid electrolyte comprising the hybrid quasi-solid electrolyte framework of claim 18 and an electrolyte dissolved in an electrolyte solvent.

27. The hybrid quasi-solid electrolyte according to claim 26, wherein the electrolyte is present in the electrolyte solvent at a concentration in a range of about 0.25 M to about 10 M.

28. The hybrid quasi-solid electrolyte according to claim 26, wherein the electrolyte comprises a lithium compound.

29. The hybrid quasi-solid electrolyte according to claim 26, wherein the electrolyte solvent is selected from the group consisting of ether, carbonate, and any mixture thereof.

30. (canceled)

31. The hybrid quasi-solid electrolyte according to claim 26, wherein the electrolyte further comprises an electrolyte additive.

32. A method for preparing the hybrid quasi-solid electrolyte according to claim 26, the method comprising the step of contacting the hybrid quasi-solid electrolyte framework with the electrolyte.

33. An electrochemical cell comprising the hybrid quasi-solid electrolyte of claim 26, a cathode, and an anode.

34. The electrochemical cell according to claim 33, wherein the cathode is selected from the group consisting of a sulfur cathode, a sulfur carbon/ceramic cathode, and a metal-based cathode.

35.-36. (canceled)

37. The electrochemical cell according to claim 33, wherein the anode comprises a material selected from the group consisting of lithium metal, graphite, hard carbon, silicon, tin, silicon/C composite, tin/C composite, and any mixture thereof.

38. A method of manufacturing an electrochemical cell according to claim 33, the method comprising the step of contacting the hybrid quasi-solid electrolyte with the cathode and the anode.

39. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0119] The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0120] FIG. 1 is a set of images showing a) photographs and b) schematic of the synthesis of LLZO sheets. a) and b) both show the dissolution of metal nitrates and sucrose forming a clear solution, which was then heated at 250° C. to undergo polymerization, followed by foaming due to thermal decomposition. Upon subsequent heating at 850° C., the organic component was decomposed and oxidized as CO.sub.2 and H.sub.2O gases, while the homogeneously distributed metal ions reacted and crystallized into LLZO.

[0121] FIG. 2 is a set of images showing a) to c) SEM images and d) TEM images of LLZO sheets. Scale bar for a) and b) is 10 μm, c) is 1 μm and d) is 5 nm.

[0122] FIG. 3 is a set of FESEM images of LLZO a) without and b) with sucrose use during synthesis. Scale bar is 10 μm.

[0123] FIG. 4 is an FESEM image of LLZO sheets showing intersheet connecting junctions (indicated by circles). Scale bar is 1 μm.

[0124] FIG. 5 is a set of images showing a) a graph showing XRD patterns of LLZO precursor sheets and LLZO sheets and, b) scanning TEM image, and c) to e) EDX elemental maps of LLZO sheets.

[0125] FIG. 6 is a set of images showing a) schematic depciting LLZO HQSE preparation, whereby interconnected LLZO sheets were bound together using polytetrafluoro-ethylene (PTFE), and then processed into discs, which were imbibed with the liquid electrolyte, b) to d) FESEM images and (inset in b) photograph of LLZO HQSE solid framework, and e) electrolyte imbibition test (right is Celgard 2500 membrane and left is inventive LLZO framework) and f) thermal stability (right is Celgard 2500 membrane and left is inventive LLZO framework). Liquid electrolyte volume was 50 μL for the electrolyte imbibition and thermal stability tests. Scale bar for b) and d) is 100 μm and c) is 10 μm.

[0126] FIG. 7 is a set of images showing a) Nyquits plots of LLZO HQSE, b) ionic conductivity of LLZO HQSE (left in FIG. 6e, 6f) and Celgard (right in 6e, 6f), and Li symmetric cell cycling of c) LLZO HQSE and d) Celgard. Liquid electrolyte volume was 30 μL for ionic conductivity and Li symmetric cell cycling tests.

[0127] FIG. 8 is a set of photographs of LLZO HQSE: a) as prepared, and b) after EIS testing and coin cell disassembly.

[0128] FIG. 9 is a set of graphs showing the linear sweep voltammtery of 30 μL of liquid electrolyte-infused LLZO HQSE and Celgard at 1 mV s.sup.−1 using a) LiTFSI in DME/DOL and b) LiPF.sub.6 in ethylene carbonate/diethyl carbonate electrolyte, as well as c) cycling stability and d) coulombic efficiency of LiCoO.sub.2 using LLZO HQSE and Celgard membrane.

[0129] FIG. 10 is a schematic depicting G/S cathode preparation, whereby a.sup.1), a.sup.2) are FESEM images, a.sup.3), a.sup.4) are EDX elemntal maps of G/S composite, a.sup.5) is a photograph and a.sup.6) is a FESEM image of G/S cathode. Scale bar for a.sup.1) and a.sup.6) is 1 μm, a.sup.2) is 2.5 μm.

[0130] FIG. 11 is a set of graphs showing a) CV curves and b) Nyquist plots of Li—S hybrid quasi-solid battery.

[0131] FIG. 12 is a set of graphs showing a), b) Discharge-charge profiles at 0.1C and c), d) cycling performance at 0.1C and 0.2C, of a), c), d) LLZO HQSE and b) to d) Celgard.

[0132] FIG. 13 is a set of graphs showing the capacity loss over cycling of Li—S battery at 0.1C using liquid electrolyte-infused a) LLZO HQSE and b) Celgard.

[0133] FIG. 14 is a set of graphs showing a), b) Discharge-charge profiles and c), d) capacity loss over cycling of Li—S battery at 0.5C using electrolyte-infused a), c) LLZO HQSE and b), d) Celgard.

[0134] FIG. 15 is a set of images showing disassembled Li—S battery after 0.5C cycling using electrolyte-infused a) LLZO HQSE and b) Celgard.

[0135] FIG. 16 is a set of images showing a) FESEM image and b) XRD pattern of liquid electrolyte-infused LLZO HQSE after cycling. * denotes the PTFE peak. Scale bar is 10 μm.

[0136] FIG. 17 is a set of graphs showing a) rate capability of LLZO HQSE and b) initial discharge-charge profiles of LLZO HQSE and commercial LLZO HQSE.

[0137] FIG. 18 is a set of FESEM images of a), b) commercial nano Al-doped LLZO a) powder and b) solid framework, and d) LLZO sheets solid framework, as well as c) Diassembled Li—S cell produced with commercial LLZO HQSE. Scale bar for a) is 1 μm and b) and d) is 10 μm.

[0138] FIG. 19 is a set of images showing disassembled Li—S batteries produced with a) LLZO HQSE, and b) Celgard after thermal stability test (first scenario); Li—S hybrid quasi-solid battery after thermal stability test (second scenario): c) before and d) after cell disassembly; and e) Li—S battery produced with Celgard after cell explosion from thermal stability test (second scenario).

EXAMPLES

[0139] Non-limiting examples of the invention will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Example 1: Materials and Methods

[0140] Synthesis of LLZO sheets: LLZO sheets were synthesized via the “cupcake” method. 5.55 mmol sucrose (Biorad, Hercules, Calif., USA) was mixed with stoichiometric amounts of LiNO.sub.3 (Merck) (5.14 mmol, with 10% in excess to account for possible Li loss during calcination), La(NO.sub.3).sub.3.6H.sub.2O (Sigma-Aldrich, St. Louis, Mo., USA) (2 mmol), and ZrO(NO.sub.3).sub.2.xH.sub.2O (Strem Chemicals, Newburyport, Mass., USA) (x was calculated based on the product's certificate of analysis supplied by the manufacturer) (1.334 mmol) in deionized water. The sol was heated at 250° C. for 3 hours, followed by 850° C. for at least 1 hour, then cooled to room temperature.

[0141] Preparation of LLZO HOSE solid framework: 100 mg of LLZO sheets was suspended in ethanol, to which 20 mg of polytetrafluoroethylene (PTFE) was added. The mixture was mixed well while evaporating the ethanol, leading to the formation of a gummy mass. The gummy mass was rolled into a membrane, which was cut into 16.2 mm-diameter discs. The discs were dried in an oven at 60° C.

[0142] Preparation of G/S and LiCoO.sub.2 cathodes: Graphene (G)/S composite was synthesized according to a known method, with some modifications. Specifically, 200 mg of single layer graphene oxide (SLGO) was dispersed in a mixture of 100 mL of deionized water and 30 mL of absolute ethanol. 200 mg of sulfur, dissolved in 4 mL of CS.sub.2, was added to the SLGO dispersion while stirring. The dispersion was kept stirring for 30 minutes, and then transferred into a 200-mL autoclave, and heated at 180° C. for 18 hours. The product was washed twice using ethanol and deionized water, and then freeze dried.

[0143] To prepare the G/S cathode, the G/S composite, acetylene black (AB), and vapor grown carbon fibers (VGCF) were mixed (at a weight ratio of 7:1.5:1.5) using PTFE as a binder using the membrane rolling method as described above. The membrane was cut into 12.7 mm-diameter discs. The discs were dried in an oven at 60° C.

[0144] LiCoO.sub.2 cathode was prepared using commercial LiCoO.sub.2, reduced graphene oxide, AB and VGCF at a weight ratio of 2.4:4:1:1 using the membrane rolling method as described above. The membrane was cut into 12.7 mm-diameter discs. The discs were dried in an oven at 60° C.

[0145] Materials Characterization: Morphological and structural characterizations were performed using field emission scanning electron microscope (FESEM) (JEOL, JSM-7400F) and TEM (FEI Tecnai F20), both fitted with EDX microanalyser (OXFORD). LLZO crystal structure was analyzed by XRD (Bruker D8 ADVANCE). S content in G/S composite was determined by thermal gravimetric analysis (TGA 55, TA Instruments).

[0146] Electrochemical Measurements: CR2032 coin cells were assembled inside an Ar-filled glove box with O.sub.2 and H.sub.2O levels of <1 ppm. Li metal was used as the anode, LLZO solid framework or commercial Celgard 2500 membrane were employed as the separator, and G/S or LiCoO.sub.2 disc was used as the cathode. For G/S cathode, 1 M LiTFSI in dimethoxyethane (DME):1,3-dioxolane (DOL) (1:1 by volume) and 2 wt % LiNO.sub.3 was used as liquid electrolyte at 35 to 40 μL/mg sulfur. For LiCoO.sub.2 cathode, 1 M LiPF.sub.6 in ethylene carbonate:diethyl carbonate (1:1 by volume) was used at 35 to 40 μL/mg LiCoO.sub.2. CV (0.05 mV s.sup.−1) and EIS (100 kHz-10 mHz, 10 mV amplitude) measurements were performed using AUTOLAB PGSTAT302N potentiostat. Ionic conductivity was calculated according to Equation 1:

σ=L/RA  Eq. 1

[0147] where σ is conductivity in mS cm-1, L is thickness in cm, R is resistance in mΩ, and A is surface area in cm2. Li platting-stripping and galvanostatic discharge-charge measurements were conducted using LAND CT2001A battery cycler.

Example 2: Synthesis and Structure of the LLZO Sheets

[0148] The synthesis process is depicted in FIGS. 1a and b. Metal nitrates and sucrose were dissolved in deionized water, forming a clear solution at a pH of 1.5. Sucrose acted as a polydentate ligand that bound the metal ions to form homogeneous metal ion-sucrose complex solution. When the solution was heated, sucrose underwent polymerization, followed by foaming due to thermal decomposition. Subsequently, a brown “cupcake” was formed whereby the internal structure was composed of large sheets (FIG. 2a). Upon further heating, the organic component was decomposed and oxidized as CO.sub.2 and H.sub.2O gases, while the homogeneously distributed metal ions reacted and crystallized into LLZO, which adopted the sheet morphology of the precursor (FIG. 2b). In the absence of sucrose, only bulk LLZO was obtained (FIGS. 3a and 3b), illustrating the critical role played by sucrose in sheet structure formation.

[0149] The sheets have micron-sized lateral dimensions, typically >10 μm, while their thickness is in the nanometre range, about 190 nm (FIG. 2c). Junctions, which were likely formed by coalescence during calcination, connected the sheets to each other (FIG. 4). The resulting continuous Li ion pathways would facilitate Li ion conductivity.

[0150] Powder X-ray diffraction (XRD) analysis (FIG. 5a) showed that the precursor sheets were amorphous. The LLZO sheets crystallized into the cubic phase (JCPDS #01-080-4947), and matched the cubic phase of commercial nano Al-doped LLZO particles in XRD pattern. The LLZO crystallite size was calculated to be 49.5 nm using the Scherrer equation (based on the highest intensity plane (420)). High-resolution transmission electron microscopy (TEM) imaging showed an interplanar d-spacing of 0.326 nm, which corresponded to (400) plane of cubic LLZO (FIG. 2d). Energy dispersive X-ray spectroscopy (EDX) showed the uniform distribution of elements over the sheets (FIGS. 5b to 5e).

Example 3: Characterisation of LLZO HOSE

[0151] LLZO hybrid quasi-solid electrolyte (HOSE) was constructed using LLZO sheets as building blocks for the 3D solid framework, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethoxyethane (DME)/1,3-dioxolane (DOL) with 2 wt % LiNO.sub.3 as the liquid component. The 3D sheet-based framework readily imbibed the liquid electrolyte, and the HOSE showed fast Li ion diffusion, excellent compatibility with Li metal, and high mechanical and anodic stability.

[0152] FIG. 6a presents the schematic of LLZO HOSE preparation. The interconnected LLZO sheets were bound together using polytetrafluoro-ethylene (PTFE), and then processed into approximately 250 to 350 μm-thick discs (FIG. 6b: inset), which were imbibed with the liquid electrolyte. The LLZO sheets were assembled together as a 3D framework with a porous nature (FIGS. 6b to 6d). The LLZO framework could easily imbibe the liquid electrolyte, providing superior electrolyte infiltration (FIG. 6e, left), as compared to commercial Celgard 2500 membrane having a typical pore size of 64 nm. (FIG. 6e, right). LLZO HQSE displayed excellent thermal stability, with no shrinkage or morphological change, after exposure to a temperature of 150° C. for 10 minutes (FIG. 6f, left). This was due to the high thermal stability of LLZO and PTFE binder. In contrast, the Celgard membrane melted under the testing conditions, showing severe shrinkage and disfigurement (FIG. 6f, right).

[0153] Ionic conductivity of LLZO HQSE was investigated via electrochemical impedance spectroscopy (EIS) at room temperature. The Nyquist plot (FIG. 7a) showed a straight line, whose intercept with the real axis indicated bulk resistance. No semi-circle was observed, indicating the absence of grain boundary resistance, which was attributed to the infiltration of the liquid electrolyte within the LLZO framework. The ionic conductivity of LLZO HQSE was calculated to be 0.7 mS/cm, which was comparable to that obtained using Celgard separator (FIG. 7b), showing the suitability of LLZO HQSE for utilization in lithium batteries.

[0154] Stability of LLZO HQSE against Li metal was studied by galvanostatic cycling of a symmetric Li/LLZO HQSE/Li cell for 200 hours at increasing current densities (FIG. 7c). LLZO HQSE displayed smooth cycling with no significant voltage fluctuation. In contrast, the Celgard separator displayed significant instability during initial cycling, and major hysteresis at the high current density of 1 mA cm.sup.−2 (FIG. 7d). These results demonstrated that the LLZO HQSE has a more stable interface with Li metal, resulting in uniform Li deposition and mitigating dendrite growth.

[0155] LLZO HQSE also exhibited good mechanical stability; its non-rigid structure could tolerate processing during preparation and cell assembly/disassembly, with no cracking or disintegration as shown in FIG. 8, where it can be seen that there is no major change in the LLZO HQSE as prepared (FIG. 8a) and after EIS testing and coin cell disassembly (FIG. 8b).

[0156] Moreover, LLZO HQSE showed enhanced anodic stability (FIGS. 9a and 9b), rendering it a promising candidate for high-voltage cathode. LiCoO.sub.2 was used as a model cathode operating at relatively high voltage (3-4.3 V vs. Li.sup.+/Li). LLZO HQSE showed a better cycling stability and Coulombic efficiency than Celgard (FIGS. 9c and 9d). Specifically, it was found that the LLZO solid framework could stabilize the liquid electrolyte at high voltage. The LLZO HQSE was stable until 4.70 V and 4.52 V vs. Li.sup.+/Li, as compared to 4.48 V and 4.31 V in the case of Celgard membrane, using LiTFSI in DME/DOL and LiPF.sub.6 in ethylene carbonate/diethyl carbonate electrolytes, respectively. The higher anodic stability imparted by the LLZO solid framework may be due to its interaction with the liquid electrolyte, which improved its oxidation resistance.

Example 4: LLZO HOSE In A Li—S Battery

[0157] LLZO HQSE was applied in Li—S hybrid quasi-solid system, displaying high electrochemical reversibility and enhanced battery performance. A current collector-free cathode was prepared using graphene (G)/S composite, carbon additives and PTFE binder. The carbon additives provided the necessary electrical links within the G/S composite, while PTFE enabled the processing into a flexible free-standing electrode (FIG. 10). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) of Li—S hybrid quasi-solid battery showed high electrochemical reversibility and reduced polarization over cycling (FIGS. 11a and 11b), which indicated good electrode/electrolyte contact.

[0158] The CV showed the typical two cathodic peaks at 2.27 V and 1.94 V, which are attributed to reduction of sulfur (S.sub.8) to long-chain (Li.sub.2S.sub.n, 4≤n≤8), and short-chain (Li.sub.2S.sub.n, 1≤n<4) PS, respectively, as well as two overlapping anodic peaks at 2.46 and 2.51 V, which represent the reverse oxidation back to long-chain PS and S.sub.8 (FIG. 11a). The overlapping of the CV curves after the first cycle showed the high electrochemical reversibility, while the positive and negative cathodic and anodic shifts, respectively, indicated reduced polarization and resistance over cycling. The reduced resistance over cycling was confirmed by EIS (FIG. 11b), whereby the diameter of the semicircle in middle-high frequency region, attributed to charge-transfer resistance, decreased significantly after five cycles. This may be explained by an activation process involving active material redistribution.

[0159] Li—S battery with LLZO HQSE has an initial capacity of 1448.3 mAh/g at 0.1C, which was higher than the 1405.0 mAh/g achieved with Celgard membrane (FIG. 12c). After 10 cycles, their capacities reached 957.2 and 874.2 mAh/g, respectively, with capacity fade/cycle of 2.13% and 3%, respectively, after the first cycle. The discharge-charge profiles were studied to gain further insight into their performance. LLZO HQSE displayed two distinct discharge plateaus and two overlapping charge plateaus (FIG. 12a), which was consistent with the CV profile, and similar to that displayed by Celgard membrane (FIG. 12b). However, LLZO HQSE showed a lower polarization of 0.216 V, as compared to 0.221 V shown by Celgard, which indicated enhanced redox kinetics and better energy efficiency, further confirming the minimized electrode/electrolyte interfacial resistance due to the good contact in the former.

[0160] In addition, the upper plateau capacity (Q.sub.H) loss was ˜50% less with LLZO HQSE (FIG. 13a), as compared to Celgard (FIG. 13b). The significantly reduced Q.sub.H loss by LLZO HQSE indicated its effective role in mitigating PS diffusion, resulting in less active material loss, which reduced the lower plateau capacity (Q.sub.L) and total capacity (Q.sub.T) loss. PS shuttling control by LLZO is known, and is attributed to its chemical affinity to soluble PS, and the physical barrier introduced by the LLZO framework. On the other hand, Celgard displayed high Q.sub.H loss due to its inability to control PS shuttling, which resulted in increased Q.sub.L and Q.sub.T fading.

[0161] The improved performance of LLZO HQSE could be better observed with prolonged cycling. LLZO HQSE retained 730.7 mAh/g when cycled for another 40 cycles at 0.2C, with capacity retention (after the first cycle) of 90.2% and capacity fade/cycle (after the first cycle) of 0.25%, as compared to 542.9 mAh/g, 72.3% and 0.71% shown by Celgard, respectively (FIG. 12c). At 0.5C, LLZO and Celgard have initial capacities of 834.5 and 586.8 mAh/g, which decreased to 431.5 and 220.7 mAh/g after 300 cycles, with capacity retention (after the first cycle) of 60.5% and 41.1%, and capacity fade/cycle (after the first cycle) of 0.13% and 0.2%, respectively (FIG. 12d).

[0162] Analysis of the discharge-charge profiles at 0.5C agreed with that of 0.1C profiles. A smaller polarization of 0.349 V was observed with LLZO HQSE, as compared to 0.57 V with Celgard (FIGS. 14a and 14b), indicating better reaction kinetics. Interestingly, LLZO HQSE also showed ˜50% less Q.sub.H loss, as compared to Celgard, which resulted in lower Q.sub.L and Q.sub.T loss (SI FIGS. 14c and 14d), leading to better capacity retention. This confirmed the earlier observation about the role of LLZO in controlling PS shuttling.

[0163] The cycled LLZO HQSE appeared as an orange-colored semi-solid disc with no separate liquid electrolyte observed (FIG. 15a). This showed that the liquid electrolyte was completely imbibed within the LLZO solid framework, and that the battery operated in a hybrid quasi-solid state with no risk of electrolyte leakage. The orange color may be due to the PS anchored to the LLZO sheets. In contrast, the battery operated using Celgard showed a brown-colored liquid (FIG. 15b), implying substantial PS diffusion, which may explain its inferior performance.

[0164] Interestingly, the sheet-like morphology of the cycled LLZO and its cubic crystal structure were stable after cycling (FIGS. 16a and 16b), indicating its stability against the liquid electrolyte and PS. LLZO HQSE was further tested at higher current densities to investigate its rate capability, which is the main limitation for Li—S hybrid quasi-solid systems. LLZO HQSE showed capacities of 1635.0, 707.1, 514.5 and 331.1 mAh V at 0.05C, 0.5C, 10 and 2C, respectively, and could recover to 1068.7 mAh/g at 0.05C (FIGS. 17a and 17b). The Li—S hybrid quasi-solid battery performance was among the best reported in the literature (Table 1).

TABLE-US-00001 TABLE 1 Comparison of the performance of Li—S hybrid quasi- solid battery with previously reported systems. Current Initial Final S loading density capacity No. of capacity HQSE solid component (mg cm.sup.−2) (mA cm.sup.−2) (mAh g.sup.−1) cycles (mAh g.sup.−1) Li.sub.7La.sub.3Zr.sub.2O.sub.12 1.2 0.2-0.4 1448.3 10-40 730.7 (inventive example) 1.3 1.1 834.5 300  431.5 1.5 2.5 514.5 .sup. 10.sup.a 514 Li.sub.6.4La.sub.3Zr.sub.1.4Ta.sub.0.6O.sub.12—MgO 1 0.3 1100 200  685 Li.sub.6.45Ca.sub.0.05La.sub.2.95Ta.sub.0.6Zr.sub.1.4O.sub.12 0.71 0.2 786 50 326.8 Li.sub.6.4La.sub.3Zr.sub.1.4Ta.sub.0.6O.sub.12 2.3  0.04 1100 30 706 0.4 855 40 560 Li.sub.6.4La.sub.3Zr.sub.1.4Ta.sub.0.6O.sub.12 1 0.2-0.3 1366  6-44 841 0.8 649 500  537 1.7 463 .sup. 31.sup.a N/A Li.sub.1+xAl.sub.xTi.sub.2−x(PO.sub.4).sub.3 3 0.2 ~975 150  ~800 0.5 750 N/A N/A LiCoO.sub.2 5.5  0.46 ~700 200  ~460 Li.sub.7La.sub.3Zr.sub.2O.sub.12 1.2 0.2 ~1000 N/A N/A 1   550 50 ~400 Li.sub.7La.sub.2.75Ca.sub.0.25Zr.sub.1.75—Nb.sub.0.25O.sub.12 7.5 0.2 645 30 ~500 Li.sub.1.5Al.sub.0.5Ge.sub.1.5(PO.sub.4).sub.3.sup.b 1 0.2 1253 50 622 Li.sub.1.5Al.sub.0.5Ge.sub.1.5(PO.sub.4).sub.3 2.1 0.2 1128.2 50 770.1 Li.sub.1.3Al.sub.0.3Ti.sub.1.7(PO.sub.4).sub.3 N/A N/A (0.1 C) 978 50 ~750 Li.sub.1.3Al.sub.0.3Ti.sub.1.7(PO.sub.4).sub.3 1.7 0.3 ~1200 300  ~300 Li.sub.1.5Al.sub.0.5Ge.sub.1.5(PO.sub.4).sub.3 N/A N/A (0.2 C) 1386 40 720 .sup.aRate study. .sup.bData obtained using DME/DOL electrolyte solvent.

[0165] It should be noted that none of the comparative examples listed above that are garnet-type oxides were used in the form of a powder comprising a plurality of sheet structures.

[0166] The higher performance of the inventive example may be attributed to the intricate LLZO HQSE design. Unlike the commonly used dense solid pellets/layers, the LLZO sheet structures form a non-rigid 3D solid framework that is infused with liquid electrolyte. This design allows battery operation in a hybrid quasi-solid state, while ensuring high Li ion conductivity and low interfacial resistance, thus achieving high capacity, cycling stability, and rate capability. In addition, PS shuttling was significantly reduced by the LLZO sheets and the solid framework's microstructure, which further improved battery performance.

Example 5: Comparison with Commercial LLZO

[0167] In order to validate the significance of the 3D sheet-based framework structure for battery performance, commercial nano Al-doped cubic LLZO was used as a control. Commercial LLZO showed bulky particles (FIG. 18a) that comprised nanocrystallites of 46.4 nm, as calculated by Scherrer equation using the highest intensity plane (420) (FIG. 5a). Commercial LLZO framework showed a very compact and dense structure (FIG. 18b), as compared to LLZO sheets framework (FIG. 18d), due to the high packing density of the commercial LLZO particles.

[0168] The commercial LLZO has an irregular morphology, mostly showing agglomerated bulky particles (FIG. 18a). At 0.1C, commercial LLZO HQSE showed an initial discharge capacity of 1291.2 mAh g.sup.−1 (FIG. 18b), which was slightly less than that achieved by LLZO HQSE produced according to this disclosure. However, the commercial LLZO HQSE was not able to follow up with the charge process, displaying a highly fluctuating charge voltage. This phenomenon has been reported previously, and was attributed to the failure to conduct Li ions. Such failure may be explained by the very dense and compact structure of commercial LLZO HQSE (FIG. 18b), which may have been completely blocked by the interphase layer formed on the surface of LLZO particles during the initial discharge. The large volume of liquid electrolyte observed upon disassembling the cell (FIG. 18c) also revealed the inability of the commercial LLZO HQSE to imbibe liquid electrolyte due to its compact, non-porous structure. These results illustrated the significance of the LLZO's sheet morphology and the LLZO HQSE's porous architecture for optimal battery operation.

[0169] One of the main advantages of hybrid quasi-solid systems is improved battery safety. Therefore, thermal stability experiments were conducted to evaluate the battery safety profile of LLZO HQSE. Li—S batteries were exposed to two scenarios of extreme temperature conditions. In the first scenario, the cells were heated gradually, initially at 150° C. for 30 min, and then at 180° C. and 210° C. for 10 minutes each. In the second scenario, the cells were exposed to a sudden high temperature of 200° C. for 5 minutes.

[0170] LLZO HQSE was stable in both scenarios (FIG. 19a, 19c, 19d), while Celgard showed very poor stability profile. In the first scenario, the Celgard membrane was damaged, leading to full contact between both electrodes (FIG. 19b). In the second scenario, the cell exploded violently (FIG. 19e). These results demonstrated the superior safety profile of LLZO HQSE-based Li—S battery, and highlighted the potential role of hybrid quasi-solid electrolytes in substantially improving the safety profile of lithium batteries.

INDUSTRIAL APPLICABILITY

[0171] The material as disclosed herein may be incorporated into a hybrid quasi-solid electrolyte framework, which may in turn by used to form a hybrid quasi-solid electrolyte for use in an electrochemical cell. The method for forming the material may be a one-step sol-gel process, facilitating facile and cost-effective generation of sheet structures. The hybrid quasi-solid membrane may be used as a quasi-solid electrolyte for safer lithium rechargeable batteries, such as Li—Si, Li-ion and Li-air batteries.

[0172] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.