RECHARGEABLE LITHIUM-ION BATTERY

Abstract

Disclosed herein is a re-chargeable Li-air battery cell comprising a Li-based garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT) electrolyte and the like. The Li-rich LLBZT is adjacent to a ceramic wall which, in turn, is adjacent to a porous or dense cathode which, in turn, is adjacent to a porous or dense current-collecting layer. Two or more re-chargeable Li-air battery cells comprising LLBZT may be connected in series. The barium component of the LLBZT may be substituted or doped with an alkaline rare earth metal, for example one of beryllium, magnesium, calcium, strontium, and radium. The tantalum component of LLBZT may be substituted or doped with niobium or lanthanum.

Claims

1. A re-chargeable Li-air battery cell comprising a Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte as a separator, wherein the Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte is adjacent to a ceramic wall which in turn, is adjacent to a porous cathode or a dense cathode which in turn, is adjacent to a porous current-collecting layer.

2. (canceled)

3. A re-chargeable Li-air battery comprising two or more re-chargeable Li-air battery cells according to claim 1, wherein said two or more re-chargeable Li-air battery cells are connected in series.

4. A re-chargeable Li-air battery cell according to claim 1, wherein the barium component of the Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte, is doped with an alkaline rare earth metal and/or the Tantalum component is doped with Niobium or Lanthanum.

5. A re-chargeable Li-air battery cell according to claim 4, wherein the alkaline rare earth metal is one of beryllium, magnesium, calcium, strontium, and radium.

6. An aqueous Li-air battery cell comprising a Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte as a Li-protecting layer, wherein the Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte is adjacent to a ceramic wall which in turn, is adjacent to a porous cathode or a dense cathode which in turn, is adjacent to a porous current-collecting layer.

7. A re-chargeable LiS battery cell comprising a Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte as a separator, wherein the Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte is adjacent to a ceramic wall which in turn, is adjacent to a porous cathode or a dense cathode which in turn, is adjacent to a porous current-collecting layer.

8. (canceled)

9. A re-chargeable LiS battery comprising two or more re-chargeable LiS battery cells according to claim 7, wherein said two or more re-chargeable LiS battery cells are connected in series.

10. A re-chargeable LiS battery cell according to claim 7, wherein the barium component of the Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte is doped with an alkaline rare earth metal and/or the tantalum component is doped with niobium or lanthanum.

11. A re-chargeable LiS battery cell according to claim 10, wherein the alkaline rare earth metal is one of beryllium, magnesium, calcium, strontium, and radium.

12. An aqueous LiS battery cell comprising a Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte as a Li-protecting layer, wherein the Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte is adjacent to a ceramic wall which in turn, is adjacent to a porous cathode or a dense cathode which in turn, is adjacent to a porous current-collecting layer.

13. The re-chargeable Li-air battery cell of claim 1, wherein the cell is a tubular cell.

14. The re-chargeable Li-air battery cell of claim 1, wherein the ceramic wall is a ceramic tubular wall.

15. The aqueous Li-air battery cell of claim 6, wherein the ceramic wall is a ceramic tubular wall.

16. The re-chargeable LiS battery cell of claim 7, wherein the cell is a tubular cell.

17. The re-chargeable LiS battery cell of claim 7, wherein the ceramic wall is a ceramic tubular wall.

18. The aqueous LiS battery cell of claim 12, wherein the ceramic wall is a ceramic tubular wall.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0007] The embodiments of the present disclosure will be described with reference to the following drawings in which:

[0008] FIG. 1A illustrates an example of an experimental design for a Li/Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT)/Li cell according to an embodiment of the present disclosure, FIG. 1B illustrates an example of an experimental design for a Li/LLBZT/aqueous solution cell according to another embodiment of the present disclosure, and FIG. 10 illustrates an example of an experimental design for an aqueous/LLBZT/aqueous solution cell used for characterization of Li-rich garnet-type LLBZT for a Li-aqueous battery according to another embodiment of the present disclosure;

[0009] FIG. 2 shows charts generated while plating and stripping Li using a symmetrical LLBZT/Li cell at 39 A cm.sup.2 current density (top panel), at 84 A cm.sup.2 current density (middle panel), and at 169 A cm.sup.2 current density (bottom panel), all at 25 C. and using the experimental design illustrated in FIG. 1A;

[0010] FIG. 3 is a chart showing Arrhenius plots of bulk Li-ion conductivity for LLBZT with the experimental design illustrated in FIG. 1A using Li-ion blocking Au electrodes;

[0011] FIG. 4 is a chart showing open circuit AC impedance plots obtained for symmetrical cell before and after the cycling test using the experimental design illustrated in FIG. 1A;

[0012] FIG. 5A is a chart showing open circuit impedance plots obtained for H.sub.2O/Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT)/H.sub.2O using the experimental design illustrated in FIG. 1, while FIG. 5C is a chart showing open circuit impedance plots obtained for D.sub.2O/Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT)/D2O using the experimental design illustrated in FIG. 10;

[0013] FIG. 6A is a chart showing open circuit impedance plots obtained for 1M LiOH/Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT)/1M LiOH using the experimental design illustrated in FIG. 10, while FIG. 6B is a chart showing open circuit impedance plots obtained for 1M LiCl/Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT)/1M LiCl for 10 days using the experimental design illustrated in FIG. 10;

[0014] FIG. 7 is a chart showing the variation of electrical conductivity obtained at 1 MHz for Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 under H.sub.2O, D.sub.2O, 1M LiOH and 1M LiCl at room temperature;

[0015] FIG. 8 are charts showing variation of open circuit voltage (OCV) for Li/Li.sub.6.5La.sub.2.5 Ba.sub.0.5ZrTaO.sub.12/0.1 M LiOH (top panel), Li/i.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12/1M LiOH (middle panel), and Li/Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12/1M LiCl (bottom panel) as a function of time using the experimental design illustrated in FIG. 1B,

[0016] FIG. 9A is a chart showing the stability of the OCV of the cell before and after short circuit testing using the experimental design illustrated in FIG. 1B, while FIG. 9B shows the impedance of the cell. The same garnet sample was used in all three measurements for both sets of data while the solutions were varied in the sequence 0.1M LiOH, 1M LiOH, and 1M LiCl using the experimental design illustrated in FIG. 1B;

[0017] FIGS. 10A and 10B are charts illustrating comparisons of TGA curves of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 after the chemical stability test using the solutions employed in AC impedance spectroscopy study. For comparison, TGA of as-prepared sample is also shown. Asterisks (*) indicate temperatures at which variable temperature PXRD were performed;

[0018] FIGS. 11A and 11B are charts illustrating comparisons of TGA curves of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 after the chemical stability test using the solutions employed in AC impedance spectroscopy study. For comparison, TGA of as-prepared sample is also shown. Asterisks (*) indicate temperatures at which variable temperature PXRD were performed;

[0019] FIG. 12 is a chart illustrating a comparison of TGA curves of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 after the chemical stability test using the solutions employed in AC impedance spectroscopy study. For comparison, TGA of as-prepared sample is also shown. Asterisks (*) indicate temperatures at which variable temperature PXRD were performed;

[0020] FIGS. 13A-13F are examples of scanning electron microscopy (SEM) images of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 before and after the chemical stability tests wherein FIGS. 13A and 13B are as prepared samples (FIG. 13B is a 10-fold higher magnification of FIG. 13A), FIGS. 13C and 13D are water samples (FIG. 13D is a 10-fold higher magnification of FIG. 13C), and FIGS. 13E and 13F are D2O samples (FIG. 13F is a 10-fold higher magnification of FIG. 13E);

[0021] FIGS. 14A-14D are examples of scanning electron microscopy (SEM) images of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 after and before the chemical stability tests wherein FIGS. 14A and 14B are 1M LiOH samples (FIG. 14B is a 10-fold higher magnification of FIG. 14A), and FIGS. 14C and 14D are 1M LiCl samples (FIG. 14D is a 10-fold higher magnification of FIG. 140);

[0022] FIG. 15 are charts showing powder X-ray diffraction (PXRD) patterns of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 samples after soaking in as-prepared (top panel), water (2.sup.nd panel), D2O (3rd panel), 1M LiOH (4th panel), and 1 M LiCl for 5 days (5.sup.th panel). For comparison, simulated PXRD of the parent Li.sub.5La.sub.3Nb.sub.2O.sub.12 garnet phase is shown in the bottom panel;

[0023] FIG. 16 are charts illustrating in-situ variable temperature powder X-ray diffraction (PXRD) patterns at different temperatures of a Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 sample after soaking in water;

[0024] FIG. 17 are charts illustrating in-situ variable temperature powder X-ray diffraction (PXRD) patterns at different temperatures of a Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 sample after soaking in D.sub.2O;

[0025] FIG. 18 are charts illustrating in-situ variable temperature powder X-ray diffraction (PXRD) patterns at different temperatures of a Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 sample after soaking in 1M LiOH;

[0026] FIG. 19 are charts illustrating in-situ variable temperature powder X-ray diffraction (PXRD) patterns at different temperatures of a Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 sample after soaking in 1M LiCl,

[0027] FIG. 20 is a chart illustrating in-situ variable temperature powder X-ray diffraction (PXRD) patterns at different temperatures of an empty sample holder (for reference for FIGS. 17-19);

[0028] FIG. 21A is schematic illustration of a single-cell re-chargeable Li-air or a LiS battery cell according to the present disclosure, with a ceramic tube separating the LLBZT anode from the porous cathode, while FIG. 21B is a close-up cross-sectional view of the configuration of the LLBZT anode next to the ceramic tubular wall which in turn, is next to the porous cathode which in turn, is next to the porous current collecting layer; and

[0029] FIG. 22A is an illustration of another example of a single-cell re-chargeable LLBZT Li-air battery cell according to the present disclosure, FIG. 22B shows two of the re-chargeable LLBZT Li-air or a LiS battery cells shown in FIG. 22A coupled together in series, and FIG. 22C shows four of the re-chargeable LLBZT Li-air or a LiS battery cells shown in FIG. 22A coupled together in series.

DETAILED DESCRIPTION

[0030] The embodiments of the present disclosure relate to garnet-type structures such as Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (also referred to herein as LLBZT) and related compounds, as a separator for elemental lithium and an aqueous electrolyte in an aqueous LiO.sub.2 battery architecture or in an aqueous LiS battery architecture. LLBZT is referred as Lirich or Li-stuffed garnets because it contains more lithium than that can be accommodated in a classical garnet Li.sub.3Ln.sub.3Te.sub.2O.sub.12 (Ln=Y, Pr, Nd, SmLu).

[0031] According to one embodiment, disclosed herein is a Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT) electrolyte suitable for use as a Li-protecting layer in aqueous LiO.sub.2 batteries. AC and DC electrical measurements, in addition to powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), thermogravimetic analysis (TGA), were used to investigate the electrochemical and chemical properties of Li/LLBZT and LLBZT/aqueous interfaces. Stable open circuit voltages (OCV) of 3V were observed for Li/LLBZT/1MLiOH and Li/LLBZT/1MLiCl at 25 C. A DC galvanostatic Li plating/stripping cycle at varying constant current density was performed and the area specific polarization resistance (ASR) for Li-ion charge transfer was found to be 473 cm.sup.2 at 25 C. The impedance of LLBZT garnet was improved after treating the samples with 1 M LiOH, and 1 M LiCl. The LLBZT garnet also retains its crystal structure and electrochemical stability with Li.

[0032] Accordingly, the Li-rich LLBZT garnet disclosed herein can be successfully employed in next-generation beyond Li-ion batteries as a separator in Li-air battery cells and in LiS battery cells. The Li-rich LLBZT garnet is particularly suitable for incorporation into re-chargeable tubular battery cell configurations. Such re-chargeable Li-air battery cells may have up to four times the storage density of conventional Li-ion batteries. Such re-chargeable Li-air battery cells may be useful for incorporation into automotive battery configurations and applications. Such re-chargeable Li-air battery cells and LiS battery cells may be useful for incorporation into portable electronics battery configurations and applications.

[0033] The following examples are provided to more fully describe the disclosure and are presented for non-limiting illustrative purposes.

EXAMPLES

Example 1

[0034] Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT) was prepared using conventional ceramic method using stoichiometric quantities of LiNO.sub.3 (99%, Alfa Aesar), La.sub.2O.sub.3 (99.99%, Alfa Aesar) (dried at 900 C. for 12 h), Ta.sub.2O.sub.5 (99%, Alfa Aesar) ZrO.sub.2 (99%, Alfa Aesar) and Ba(NO.sub.3).sub.2 (98%, Alfa Aesar). 10 wt % excess LiNO.sub.3 was added to compensate for lithium oxide volatilization during high-temperature sintering treatment. The synthesis process involved the conventional heating and ball milling steps. Planetary milling (Pulverisette, Fritsch, Germany) was used at a spinning rate of 200 rpm for 6 h using 2-propanol to ensure homogeneous mixing of the powders. Milling was performed before and after decomposition of metal nitrates. Nitrates were burned off by firing powder at 700 C. for 6 h under ambient conditions. The resultant powders were pressed into pellets using an isostatic press, placed on a powder bed, and covered with mother powder in a clean alumina crucible. Final sintering process involved 2 steps, 900 C. for 24 h and a final sintering of 1100 C. for 6 h in ambient atmosphere.

[0035] Ex-situ

[0036] Powder X-ray diffraction (Powder X-ray Diffractometer, Model: Bruker D8 Advance) (Cu K.sub., 40 kV, 40 mA) confirms the formation of garnet-type LLBZT. Measurements were performed from 2 range 10 to 80 at a count rate of 4 sec per step of 0.025 at room temperature. In-situ PXRD measurements using a high-temperature reactor chamber (Anton Paar XRK 900) in air were acquired from 2 range 10 to 80 at a count rate of 3 sec per step of 0.02. FIGS. 1A-1C shows the schematic representation of the electrochemical cell used to investigate the stability of Li-rich LLBZT in various media and also with elemental Li. AC impedance spectroscopy (Solartron Model No: 1260; 0.1 Hz-1 MHz; 100 mV) was used to investigate the electrical conductivity of the samples. Highly porous gold-blocking electrodes were used as current collectors. Commercially available gold paste obtained from Heraeus Inc., Germany (LP A88-11S) was coated on the surface of pellets and cured at 700 C. for 1 h to remove the organic binder. Porosity of the gold layer was confirmed with scanning electron microscopy (Zeiss Sigma VP), with pores on the order of 10-20 m.

[0037] The stability of LLBZT in contact with Li metal was investigated under an argon-filled glove box (Innovative Technology, Inc.). A crucible-shaped sample of LLBZT was fabricated by isostatically pressing a powder sample of LLBZT inside an in-house-made polymer mold, with a load of 200 kN. The powder was pre-sintered at 900 C. for 12 h in air and then ball-milled for 6 h. The crucible-shaped sample was covered with the same powder and sintered at 1100 C. for 12 h. A schematic of the sample and the setup for stability experiments is shown in FIG. 1A. Lithium granules (99%, Alfa Aesar) were softened on top of a stainless-steel foil at ca. 180 C. and then the crucible-shaped LLBZT filled with Li granules for melting, was placed on top of the softened Li. To ensure that the surface of LLBZT was free of interference from surface contaminants during the preparation, several cycles of melting, removal, and refill of fresh lithium was performed prior to the measurements. DC measurements (galvanostatic cycling), specifically Li plating/stripping at varying constant current at room temperature were performed using a Solartron 1287 electrochemical interface. Impedance spectroscopy was performed at open circuit voltage (OCV) before and after Li plating/stripping using a Solartron 1260 impedance analyzer from 0.1 Hz-1M Hz at an amplitude of 100 mV. For Li/LLBZT/aqueous, a similar crucible shape LLBZT was used. The outside of the crucible was coated with a porous gold layer as shown in FIG. 1B. Conducting carbon electrode was immersed in the solution. OCV between Li and carbon electrode was measured using a potentiostat (PARSTAT 4000, Princeton applied research). Adhering 1 mm pellets to hollow quartz tube cylinders was used to perform aqueous stability of LLBZT in deionized water, D.sub.2O, 1M LiOH and 1 M LiCl. Porous gold electrodes were coated at the surface of a pellet to serve as a current collector. These tubes were suspended in a 20-ml vial; the desired solution was poured into the tube as well as into the vial, as shown in FIG. 10. AC impedance of symmetrical aqueous cells was recorded for 10 days.

Chemical and Electrochemical Stabilities of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT) with Elemental Li.

[0038] Li garnets can have wide electrochemical stability window (ESW) up to 9 V vs. Li.sup.+/Li. Table 1 shows a summary of the chemical stability of selected Li-rich garnet-type compositions including LLBZT, and their interfacial Li-ion charge transfer area specific polarization resistance (ASR) between Li and garnet. Cyclic voltammetry of the composition Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 revealed Li deposition and dissolution peaks near 0 V vs. Li.sup.+/Li, but indicated no other electrochemical reactions up to 6 V vs. Li.sup.+/Li. FIG. 2 shows the charging and discharging cycles of Li-rich garnet-type LLBZT under different current densities at 25 C. The plating and or stripping time were set to one minute. The ASR value for Li.sup.+ ion charge transfer can be estimated from the initial over-potentials associated with each current density. A linear fit of V vs. I of the data in Table 2 shows resistance (R) of 3200 at 25 C. The bulk resistance of the solid electrolyte LLBZT was obtained from Li.sup.+ ion blocking conductivity (FIGS. 2, 3, 4). The bulk resistance of the electrolyte was found to be 1308 at 25 C. Thus, the ASR for Li ion charge transfer, for symmetrical cell with area of 0.5 cm.sup.2, can be estimated as: {(32001308)/2}0.5=473 cm.sup.2. The factor 2 divided the difference between the Li-reversible electrode and bulk impedance

TABLE-US-00001 TABLE 1 Interfacial Solid resistance electrolyte between Li|garnet|Li preparation .sub.25 C. the Li and (pellet dimension) condition (S cm.sup.1) electrolyte 1 Li.sub.7La.sub.3Zr.sub.2O.sub.12 (LLZ), pellet Ceramic 1.8 4400 dimensions are not reported synthesis; 10.sup.4 1230 C. for 36 h 2 Li.sub.6.75La.sub.3(Zr.sub.1.75Nb.sub.0.25)O.sub.12, Ceramic 8.0 Not (d = 1.3 cm, t = 0.2 cm) synthesis; 10.sup.4 mentioned (Li|garnet|Au) 1200 C. for 36 h 3 Li.sub.6.625La.sub.3Zr.sub.1.625Ta.sub.0.375O.sub.12 Ceramic 5.2 99 cm.sup.2 with 29 mol % Al content synthesis; 10.sup.4 (d = 2.0 cm, t = 0.5 cm) 1000 C. for 20 h 4 Li.sub.6La.sub.3ZrTaO.sub.12 Ceramic 2.6 551 cm.sup.2 (d = 2.0 cm, t = 0.5 cm) synthesis; 10.sup.4 1000 C. for 20 h 5 Li.sub.7La.sub.3Zr.sub.2O.sub.12 with 28 mol % Ceramic 3.5 1398 Al, (d = 2.0 cm, t = 0.5 cm) synthesis; 10.sup.4 cm.sup.2 1230 C. 6 Li.sub.6.75 .sub.xLa.sub.3Zr.sub.1.75Nb.sub.0.25 Sol gel; 5.69 300 to O.sub.12 .sub.0.5x with 0.46 wt % 1150 C. 10.sup.4 492 cm.sup.2 Al.sub.2O.sub.3 (d = 1.0 cm, t = 0.1 for 36 h cm) 7 LLZ (d = 1.0 cm, t = 0.1 Ceramic 2.33 Not cm) synthesis; 10.sup.4 mentioned 1180 C. for 36 h 8 0.5 wt % Al.sub.2O.sub.3-doped LLZ Ceramic 4.12 Not (d = 1.0 cm, t = 0.1 cm) synthesis; 10.sup.4 mentioned 1180 C. for 36 h 9 Li.sub.5.98Al.sub.0.33La.sub.3Zr.sub.1.95O.sub.11.89 Ceramic 2.5 37 cm.sup.2 (d = 0.78 cm, t = 0.1 cm) synthesis; 10.sup.4 (Grain size: 20-40 m) 1100 C. for 12 h 10 Li.sub.5.98Al.sub.0.33La.sub.3Zr.sub.1.95O.sub.11.89 Ceramic 2.0 130 cm.sup.2 (d = 0.78 cm, t = 0.1 cm) synthesis, 10.sup.4 (Grain size: 100-200 m) 1100 C. for 12 h 11 Li.sub.6.85La.sub.2.9Ca.sub.0.1Zr.sub.1.75Nb.sub.0.25O.sub.12 Ceramic 2.5 925 cm.sup.2 synthesis, 10.sup.4 1050 C. for 12 h 12 Si-coated Ceramic 2.5 127 cm.sup.2 Li.sub.6.85La.sub.2.9Ca.sub.0.1Zr.sub.1.75Nb.sub.0.25O.sub.12 synthesis, 10.sup.4 1050 C. for 12 h 13 Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 Ceramic 1.5 473 cm.sup.2 (LLBZT) synthesis; 10.sup.4 1100 C. for 12 h Stability testing and comments Reference 1 CV (0.2 to 0.4 V, 10 mV min.sup.1); dissolution and [26] deposition reactions of Li were observed reversibly. Chronopotentiometry (10 to 50 A cm.sup.2); Up to 10 A cm.sup.2, the dissolution and deposition curves gave the mirrored relationship at least until 600 s. 2 CV (0.5 to 9 V, 1 mV s.sup.1); Li deposition and [27] dissolution peaks are observed near 0 V vs. Li.sup.+/Li, 3 CV (0.1 to 0.1 V, 1 mV s.sup.1); Linear behavior [22] indicates reversibility of the electrode process. 4 CV (0.1 to 0.1 V, 1 mV s.sup.1); Linear behavior [22] indicates reversibility of the electrode process. 5 CV (0.1 to 0.1 V, 1 mV s.sup.1); Linear behavior [32] indicates reversibility of the electrode process. 6 EIS monitoring for long-term stored samples (up to [28] 5 months); increase in interfacial resistance suggests that the Nb in the compound that is in contact with Li may be reduced slightly. 7 EIS monitoring for long term stored samples (up to 1 [30] month); The resistance of the cell decreased with storage period for the first one week and then became stable for one month at room temperature Chronopotentiometry (0.5 mA cm.sup.2); Abrupt drop in cell voltage after 122 s of Polarization 8 EIS monitoring for long term stored samples (up to 1 [30] month); The resistance of the cell decreased with storage period for the first one week and then became stable for one month at room temperature Chronopotentiometry (0.5 mA cm.sup.2); Abrupt drop in cell voltage after 1000 s of polarization 9 Galvanostatic cycling (up to 134 A cm.sup.2); The [31] potential of the cell remains constant at different current densities and increased linearly at higher current densities up to 134 A cm.sup.2. Above this value, the cell exhibited voltage instability and shortcircuited. 10 Galvanostatic cycling (up to 90 A cm.sup.2); The cell [31] shorted during the 2 h period at the current density of 90 A cm.sup.2. 11 Galvanostatic cycling (0.05 mA cm.sup.2); Voltage [29] hysteresis is large and the plating/stripping curves are unstable 12 Galvanostatic cycling (up to 0.2 mA cm.sup.2); Voltage [29] profiles exhibited flat and stable plating and stripping curves with small over-potential. Voltage profile remained stable after cycling for 225 h (0.1 or 0.05 mA cm.sup.2) 13 Galvanostatic cycling up to 169 A cm.sup.2 This study

TABLE-US-00002 TABLE 2 Current density (A cm.sup.2) Voltage (V) Current (A) 39 10.sup.6 0.08 1.98 10.sup.5 84 10.sup.6 0.17 4.24 10.sup.5 169 10.sup.6 0.25 8.48 10.sup.5
because a symmetrical cell was used. Another way to estimate the ASR is by looking at difference in the total resistance, obtained through electrochemical ac impedance spectroscopy of Li non-blocking cell: Li|LLBZT|Li (FIG. 5). The total cell resistance of ca. 3500 is comparable to the estimated resistance from the galvanostatic cycling. By subtracting the resistance of the electrolyte (1308), and dividing by a factor of two, the interfacial resistance of Li|LLBZT was 1096, and the ASR was 548 cm.sup.2 which is slightly higher than that of DC ASR value. Also, it is apparent from FIG. 4 that the interfacial resistance significantly increased after galvanostatic cycling. The higher charge transfer ASR value in the present study could be attributed to potential interface reaction products and contact resistance between Li and LLBZT.
Chemical and Electrochemical Stabilities of Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT) with Aqueous Solutions.

[0039] The chemical stability of Li-rich LLBZT in deionized water, D.sub.2O and aqueous Li.sup.+ solutions was studied using AC impedance spectroscopy at room temperature to assess its application in beyond Li-ion batteries. FIGS. 5A, 5B, 6A, 6B show the variation of AC impedance plots of LLBZT in H.sub.2O, D.sub.2O, 1M LiOH, and 1M LiCl for 10 days (using the experimental design shown in FIG. 1C). The shape of the impedance plots was typical for Li garnets with Au-blocking electrodes study. In all the cases, the low-frequency regime showed a tail as a consequence of the blocking nature of the electrodes. The bulk impedance decreased in all solutions after the first day. The studies with 1M LiOH, and 1M LiCl solutions showed a gradual decrease in bulk impedance with increasing time. After 10 days, the bulk impedance of the samples was found to follow the order: 1M LiOH<1MLiCl<D.sub.2O<H.sub.2O at room temperature. The bulk impedance was found to have small variation in LiCl and LiOH compared to H.sub.2O and D.sub.2O. Shown in FIG. 7 is the bulk electrical conductivity value obtained from 1 MHz impedance.

[0040] It is also known that Li-rich garnets tend to undergo fast proton exchange in water and in aqueous LiOH/LiCl and deuterium exchange in D.sub.2O. A slight increase in the impedance in D.sub.2O compared to water indicates that potential proton migration in water since mobility of ions depends on charge and mass of the mobile species. The improvement in the bulk ionic conductivity for LLBZT in the aqueous mediums with time may be considered due to increase in mobile charge carries. We believe that either partial exchange of protons in Li garnets may change the mobile path of Li ions that seem to increase the electrical mobility of Li ions in the garnet-type structure.

[0041] Li-rich garnet structures are known to show reversible Li.sup.+/H.sup.+ ion-exchange in water and organic acids. To further understand the chemical/structural stability of Li-rich garnet-type LLBZT with LiOH and LiCl, variation of open circuit voltage (OCV) of the Li-aqueous cells: Li/LLBZT/0.1 M LiOH, Li/LLBZT/1M LiOH, and Li/LLBZT/1M LiCl, was measured as a function of time at room temperature (25 C.), as seen in FIG. 8. The OCV of the cell (3 vs. Li) was found to be constant over the recorded time and it was found to highly reproducible. The observed voltage was also found to be very reliable and stable when replacing different solutions and returned to original value after intentional short-circuit test (FIG. 9A). The observed voltage of Li aqueous cell can be described using the reaction [41]:

Anode side reaction: 2Li.fwdarw.2Li.sup.++2e.sup.Eq. 1

Cathode side reaction: O.sub.2+H.sub.2O+2e.sup..fwdarw.OH.sup.+HO.sup.2Eq. 2

Overall reaction: 2Li+O.sub.2+H.sub.2O.fwdarw.LiOH+Li.sup.++HO.sup.2Eq. 3

[0042] Depending upon pH and nature of electrode catalysts, the oxygen reduction reaction (ORR) follows two electrons and/or four electrons paths in alkaline solution leading to difference reaction products such as Li.sub.2O.sub.2. The former show OCV of about 3.0 V/Li while the latter show 3.45 V/Li. The four-have different dehydration energy. For compete replacement of Li by protons, i.e.,

##STR00001##

[0043] The total proton exchange is anticipated 6.6 wt % loss for the loss of 3.25 moles of water. The Ta-doped garnets experienced adsorbed water loss around 250 C., H.sup.+ release in the form of H.sub.2O around 400-450 C. and CO.sub.2 loss above 550 C. All weight lost up to 550 C. to be from H.sub.2O. Equations 9-12 show the anticipated ion-exchange reaction after 5 days, based on the TGA weight loss experiments.

##STR00002##

[0044] The as-prepared samples also show ca. 0.5 wt. %. The second heating and cooling cycles do not show any weight loss, which further support the adsorption of CO.sub.2 and moisture (FIGS. 10A, 10B, 11A, 11B, 12). Scanning electron microscopy images (FIGS. 13A-13F, 14A-14D) of LiOH and LiCl treated samples were found to have different morphology than those of the as-prepared and H.sub.2O/D.sub.2O soaked samples. The structural stability of the solution treated samples were studied with in-situ PXRD in the temperature range of 30-650 C. In all cases the garnet-type structure was retained even up to the maximum temperature of 650 C. (FIGS. 16-19). The weak additional peaks in FIGS. 16, 17, 18, 19 appear due to sample holder contribution. For comparison, PXRD of an empty alumina sample holder used for HT-PXRD is shown in FIG. 20. Coupling this with the TGA data, this would enforce that the weight loss was due to adsorbed carbonate and moister rather than the decomposition of the garnet crystal structure.

have different dehydration energy. For compete replacement of Li by protons, i.e.,

##STR00003##

[0045] The total proton exchange is anticipated 6.6 wt % loss for the loss of 3.25 moles of water. The Ta-doped garnets experienced adsorbed water loss around 250 C., H.sup.+ release in the form of H.sub.2O around 400-450 C. and CO.sub.2 loss above 550 C. All weight lost up to 550 C. to be from H.sub.2O. Equations 9-12 show the anticipated ion-exchange reaction after 5 days, based on the TGA weight loss experiments.

##STR00004##

[0046] The as-prepared samples also show ca. 0.5 wt. %. The second heating and cooling cycles do not show any weight loss, which further support the adsorption of CO.sub.2 and moisture (FIGS. 10A, 10B, 11A, 11B, 12). Scanning electron microscopy images (FIGS. 13A-13F, 14A-14D) of LiOH and LiCl treated samples were found to have different morphology than those of the as-prepared and H.sub.2O/D.sub.2O soaked samples. The structural stability of the solution treated samples were studied with in-situ PXRD in the temperature range of 30-650 C. In all cases the garnet-type structure was retained even up to the maximum temperature of 650 C. (FIGS. 16-19). The weak additional peaks in FIGS. 16, 17, 18, 19 appear due to sample holder contribution. For comparison, PXRD of an empty alumina sample holder used for HT-PXRD is shown in FIG. 20. Coupling this with the TGA data, this would enforce that the weight loss was due to adsorbed carbonate and moister rather than the decomposition of the garnet crystal structure.

[0047] The present study shows that Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT) was found to be structurally stable after exposure to H.sub.2O, D.sub.2O, 1M LiOH, and 1M LiCl for 10 days at room temperature. TGA analysis showed partial exchange of Li ions by protons in LLBZT after exposed to H2O, 1M LiOH, and 1M LiCl and deuterium exchange in D2O. Tandem temperature variable PXRD measurements show that the garnet structure is retained after solution treatment and heating. After 10 days, the bulk impedance of the samples was found to follow the order: 1M LiOH<1M LiCl<D2O<H2O. The bulk impedance was found to be varying rather small in LiCl and LiOH compared to water and D2O. The open circuit voltage (OCV) of the Li-aqueous cells: Li/LLBZT/0.1MLiOH, Li/LLBZT/1MLiOH, and Li/LLBZT/1MLiCl showed 3 V vs. Li and it was found to be constant over the recorded time and highly reproducible. The lower OCV was explained using poor catalytic activity of electrodes used. The absence of short-circuit voltage suggest that presently investigated garnet-type oxide is stable with elemental Li and LiOH and LiCl solutions.

[0048] It is to be noted that the barium (Ba) component of the Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte may be substituted with another alkaline rare earth metal. For example, beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), or radium (Ra), or lanthanum (La) in varying concentrations. In addition, the tantalum (Ta) component of the Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 electrolyte may be substituted with Niobium (Nb) or Zirconium (Zr) in varying concentrations.

Example 2

[0049] Examples of tubular re-chargeable Li-air battery cells comprising the Li-rich garnet-type Li.sub.6.5La.sub.2.5Ba.sub.0.5ZrTaO.sub.12 (LLBZT) disclosed herein are illustrated in FIGS. 21 and 22. FIG. 21A is a schematic illustration of an example of a single-cell re-chargeable Li-air battery cell according to the present disclosure, with a ceramic tube separating the LLBZT anode from the porous cathode, while FIG. 21B is a close-up cross-sectional view of the configuration of the LLBZT anode next to the ceramic tubular wall which in turn, is next to the porous cathode which in turn, is next to the porous current collecting layer. FIG. 22A is an illustration of another example of a single-cell re-chargeable LLBZT Li-air battery cell or a LLBZT LiS battery cell according to the present disclosure, FIG. 22B shows two of the re-chargeable LLBZT Li-air battery cells or a LLBZT LiS battery cells shown in FIG. 22A coupled together in series, and FIG. 22C shows four of the re-chargeable LLBZT Li-air battery cells or a LLBZT LiS battery cells shown in FIG. 22A coupled together in series.

REFERENCES (FROM TABLE 1)

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