STATEMENT REGARDING FEDERAL RIGHTS

[0001 ] This invention was made with government support under Contract No. DE-AC52- 06NA25396 awarded by the U.S. Department of Energy. The government has certain rights in the invention.

FIELD OF THE INVENTION

[0002] The present invention relates generally to solid electrolyte compositions and devices such as batteries and capacitors employing the compositions.

BACKGROUND OF THE INVENTION

[0003] Gel-liquid chemical systems are the electrolytes present in lithium batteries and other electrochemical devices. Gel-liquid chemical systems include solvents, and they utilize solvated lithium ions for ion conduction. To deliver energy at a high rate, these electrolytes must be able to sustain a high capacity for rapid transport of lithium ions to and from the electrodes of the batteries over a broad range of temperatures. Solvents in lithium batteries promote rapid lithium transport but they can limit the applied voltage, they allow the formation of lithium dendrites that can short the electronics, they do not allow for operation at high temperatures, and they can leak out of the battery.

Improvements in lithium ion transport in solid electrolytes to reach a super-ionic state would allow the application of a lithium metal anode to improve battery performance in terms of high energy density, high temperature function, no electronics shorting, and no fluid leakage. Enhanced lithium transfer rates would boost ionic conduction and thus improve the battery performance in terms of high power capacity. The development of better lithium ion conductors is expected to lead to better rechargeable batteries for electric vehicles.

SUMMARY OF THE INVENTION

[0004] In accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention includes a solid electrolyte composition of the formula Li ₃ OCl or of the formula Li^M^OA _, wherein 0 < x < 0.8, wherein M is selected from the group consisting of magnesium, calcium, barium, strontium, and mixtures thereof, and wherein A is selected from the group consisting of fluoride, chloride, bromide, iodide, and mixtures thereof.

[0005] The invention also includes an electrochemical device that comprises a solid electrolyte composition of the formula Li ₃ OCl or of the formula wherein 0 < x < 0.8, wherein M is selected from the group consisting of magnesium calcium, barium, strontium, and mixtures thereof, and wherein A is selected from the group consisting of fluoride, chloride, bromide, iodide, and mixtures thereof. Examples of electrochemical devices include, but are not limited to, a battery and a capacitor.

[0006] The invention also includes a solid electrolyte composition of the formula Li(3 _-x )Mx ₃ OA _; wherein 0 < x < 0.90, wherein M is a cation Q ⁺³ , and wherein A is selected from the group consisting of fluoride, chloride, bromide, iodide, and mixtures thereof

DETAILED DESCRIPTION

[0007] The invention is concerned with solid electrolytes that are anti-perovskites. An embodiment solid electrolyte has the formula Li ₃ OCl. Some other embodiments of these solid electrolytes have the general formula wherein M is an alkaline earth cation selected from Mg ²⁺ , Ca ²⁺ , Ba ²⁺ , Sr ²⁺ , and combinations thereof, and A is a halide anion selected from fluoride, chloride, bromide, iodide, and combinations thereof. The value of x in the formula is 0 < x < 0.80. Some non-limiting values of x include, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.60, 0.65, 0.70, and 0.80; x may have a value smaller than 0.10. For example, some values of x that are less than 0.10 include 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, and 0.09. For each of these values of x, M is an alkaline earth cation, or a mixture of alkaline earth cations, and A is a halide or mixture of halides. A can be a mixture of chloride and bromide. A can be a mixture of chloride and fluoride. A can be a mixture of fluoride and chloride. A can be a mixture of chloride and bromide and iodide. It should be understood that A can be a mixture of any two halides, any 3 halides, and also of all four halides. [0008] An explanation of what is meant by an anti-perovskite may be better understood in relation to for following explanation of what a normal perovskite is. A normal perovskite has a composition of the formula ABX ₃ wherein A is a cation A ⁺ , B is a cation B ²⁺ and X is an anion X ^~ . A normal perovskite is also a composition of the formula ABX ₃ wherein A is a cation A ⁺³ , B is a cation B ⁺³ , and X is an anion X ^"2 . A normal perovskite has a perovskite crystal structure, which is a well known crystal structure.

[0009] An antiperovskite composition also has the formula ABX ₃ , but in contrast to a normal perovskite, A and B in an antiperovskite are the anions and X is the cation. For example, the antiperovskite ABX ₃ having the chemical formula C10Li ₃ has a perovskite crystal structure but the A (i.e. CI ^" ) is an anion, the B (O ² ) is an anion, and X (i.e. Lf ^1" ) is a cation. C10Li ₃ can be rewritten as Li ₃ OCl. Li ₃ OCl is an example of an embodiment antiperovskite.

[0010] This invention is concerned with the solid electrolyte antiperovskite Li ₃ OCl, and also with solid electrolyte antiperovskite compositions that have the chemical formula Li(3-x ₎ M _¾¾ OA.The invention is also concerned with antiperovskite solid electrolytes of the formula Li ₍₃ . _X) M _x/3 OA wherein M is a cation with a +3 charge (e.g. Al ⁺³ ), A is halide (e.g. F, CP, Br ^~ , Γ, and mixtures thereof), and 0 < x < 0.90.

[001 1] Solid electrolytes of this invention may be used as the electrolytes in lithium batteries, capacitors, and other electrochemical devices. These solid electrolytes provide advantages over more conventional gel-liquid systems. These solid electrolytes provide excellent lithium ion conduction without dendrite formation. Also, these solid electrolytes do not leak from the device.

[0012] Solid electrolyte antiperovskites were prepared. In some cases, a wet chemistry method was used to prepare these compositions. The wet chemistry method involved preparing an aqueous solution of various precursors, evaporating the solvent (i.e. water), and heating the resulting solid under a vacuum to form the solid electrolyte. In an embodiment, precursor powders lithium hydroxide (LiOH), calcium hydroxide

(Ca(OH) ₂ ), and lithium chloride (LiCl) were dissolved in deionized water to form a solution. Evaporation of the water produced a solid that was heated under vacuum conditions. The product was an anhydrous antiperovskite electrolyte. In some cases, solids were combined to form a solid mixture that was subjected to conditions of elevated pressure and elevated temperature that resulted in the formation of an embodiment solid electrolyte.

[0013] The EXAMPLES below provide non-limiting embodiments of solid electrolyte antiperovskites of this invention. For these EXAMPLES, high purity powders of precursors LiOH (98% pure) and LiCl (99% pure) were obtained from ACROS, and Mg(OH) ₂ (> 95.0% pure) was obtained from FISHER.

EXAMPLE A

[0014] Preparation of Li ₃ OCl: An aqueous solution was prepared by dissolving an amount of 4.790 grams of LiOH and an amount of 4.239 grams LiCl in a small amount of deionized water. The amounts of these precursors provided the stoichiometric ratio corresponding to the formulas Li ₃ OCl + H ₂ 0. Most of the water from the solution was evaporated within 1-2 hours using a rotary evaporator and a bath temperature of about 90°C. The resulting solid was placed into an alumina boat. The boat was placed inside a furnace and was heated under a vacuum at a temperature of about 280°C for about 48 hours to give the reaction product, which was the solid electrolyte Li ₃ OCl.

[0015] Powder X-ray diffraction was used to confirm the identity of the reaction product. X-ray diffractograms, typically in a 2Θ range from 10° to 70°, were collected using a RIGAKU ULTIMA III diffractometer with a CuK„ source. The step was 0.02° and the exposure time was 10 seconds per bin. An X-ray diffraction pattern of the reaction product was dominated by the anti-perovskite Li ₃ OCl. Some additional, weaker, diffraction lines also appeared that matched those for a monoclinic Li ₄ (OH) ₃ Cl, whose presence is likely a result of rehydration of Li ₃ OCl at ambient conditions during the post heat-treatment handling of the reaction product. [0016] The ionic conductivity of the reaction product Li ₃ OCl was obtained from impedence match measurements. The ionic conductivity (σ) of the reaction product Li ₃ OCl was in the range of approximately 10 ^"4 to 10 ^"3 S/cm at room temperature, indicating super-ionic behavior. The ionic conductivity (σ) increased to approximately 10 ^"2 to 10 ^"1 S/cm as the temperature increased above 525 K, also indicating superionic behavior for Li ₃ OCl.

EXAMPLE B

[0017] Preparation of Li ₂ .9 ₀ Cao _.05 0Cl: An aqueous solution was prepared by dissolving an amount of 4.550 grams of LiOH, an amount of 0.370 grams of Ca(OH) ₂ , and an amount of 4.239 grams of LiCl in a small amount of deionized water. The amount of these precursors corresponded to the stoichiometric ratio corresponding to the formula

Li ₂ 9 ₀ Cao o ₅ 0Cl. Most of the water from the solution was evaporated within 1-2 hours using a rotary evaporator and a bath temperature of about 80-90°C. The resulting solid mass was placed into an alumina boat. The boat was placed inside a glass tube furnace and heated under a vacuum at a temperature of about 280°C for about 48 hours to give the reaction product Li ₂ 9 ₀ Cao o ₅ OCl. [0018] Both Li ₃ OCl and Li ₂ 9 ₀ Cao 05OCI are antiperovskites. The latter can be thought of relative to the former as having some of the sites that would have been occupied with Li ⁺ now being replaced with the higher valence cation Ca ²⁺ . This replacement introduces vacancies in the anti-perovskite crystal lattice. Impedence measurements show that Li ₂ .9 ₀ Cao ₀₅ OC1 had a substantially higher (more than one order of magnitude) ionic conductivity than Li ₃ OCl. It is believed that the vacancies created by replacing 2 Li ⁺ for each Ca ²⁺ are responsible for the observed improved ionic conductivity of Li ₂ goCao.osOCl by facilitating Li ⁺ hopping in the lattice.

EXAMPLE C

[0019] Preparation of Li _{2 8} Mgo _l OCl: An aqueous solution was prepared by dissolving an amount of 4.550 grams of LiOH, an amount of 0.614 grams of Mg(OH) ₂ , and an amount of 4.476 grams of LiCl in a small amount of deionized water. The amounts of these precursors corresponded to the stoichiometric ratio corresponding to the formula

Li _{2 8} Mgo IOCI. Most of the water from the solution was evaporated within 1 -2 hours using a rotary evaporator and a bath temperature of about 90°C. The resulting solid mass was placed into an alumina boat. The boat was placed inside a glass tube furnace and heated under a vacuum at a temperature of about 280°C for about 48 hours to give the reaction product Li _{2 8} Mg ₀ .iOCl.

[0020] Both Li ₃ OCl and Li _2.8 Mg _0. iOCl are antiperovskites. The latter can be thought of relative to the former as having some of the sites that would have been occupied with Li ⁺ now being replaced with the higher valence cation Mg ²⁺ . This replacement introduces vacancies in the anti-perovskite crystal lattice. It is believed that replacement of 2 Li ⁺ with a Mg ²⁺ introduced a vacancy in the antiperovskite crystal lattice. Impendence measurements show that Li _{2 8} Mg _{0 1} OCl has a substantially higher ionic conductivity than Li ₃ OCl. It is believed that the creation of these vacancies by replacement a magnesium cation for 2 lithium cations, thus maintaining the charge balance, is responsible for the improved ionic conductivity of Li _{2 8} Mgo iOCI relative to L13OCI. It is believed that these vacancies facilitate Li ⁺ hopping in the lattice. [0021 ] Embodiment anhydrous antiperovskite solid electrolytes of this invention were prepared by subjecting a homogeneous mixture of various solid precursors to elevated pressures and temperatures. This method is sometimes referred to as a sintering method. This sintering method was used to prepare anhydrous antiperovskite electrolytes of the formula Li^M^OA wherein M is an alkaline earth cation (Mg ²⁺ , for example), and wherein A is a halide or a mixture of halides, and wherein 0 < x < 0.8. For example, an embodiment antiperovskite solid electrolyte was prepared by mechanically mixing precursor powders of lithium oxide (Li ₂ 0), calcium oxide (CaO) and lithium halide (e.g. LiCl), ball-milling the powders under a dry argon atmosphere to form a homogeneous mixture, and subjecting the ball-milled mixture to elevated pressures and temperatures. In other embodiments of the sintering method, precursor powders of Li ₂ 0, MgO, and lithium halides (LiF, LiCl, and/or LiBr) were mechanically mixed and then subjected to ball-milling under a dry argon atmosphere to form a homogeneous powder mixture. The homogeneous powders were sent to the National Synchrotron Light Source at

Brookhaven National Laboratory. The sintering method was monitored by in-situ and real-time synchrotron x-ray diffraction using a cubic-anvil apparatus at Beamline X17B2 of the National Synchrotron Light Source at Brookhaven National Laboratory. An energy-dispersive x-ray method was employed with diffracted x-rays collected at a fixed Bragg angle of 2Θ = 6.5°. The pressure was determined using a reference standard of NaCl and the temperature was measured using a W/Re25%-W Re3% thermocouple. The uncertainty in pressure measurements is mainly attributed to statistical variation in the position of diffraction lines of NaCl and was typically less than 2% of the cited values. The temperature variations over the entire length of sample container at 1500 K were of the order of 20 K, and the radial temperature gradients were less than 20 at this condition. X-ray diffraction patterns were obtained for the reference NaCl and for the sample in close proximity to the thermocouple junction. The uncertainties in temperature measurements were thus estimated to be approximately ±10°C.

[0022] EXAMPLES D, E, F, G, H, I, and J describe nonlimiting embodiments of antiperovskite electrolytes prepared by subjecting a homogeneous mixture of powder precursors to elevated temperatures and pressures. High purity powders the precursors Li ₂ 0 (98% pure) and LiCl (99% pure) or LiBr (99% pure) were obtained from ACROS, and CaO (> 99% pure) was obtained from FISHER. Table 1 summarizes the formula of the antiperovskite, the formulas of the precursors, their weights in grams, and the molar ratio of the precursors.

Table 1.

G Li ₂ . ₈ Mgo _. ,OCl Li ₂ 0 (0.386), MgO (0.0576), Li ₂ 0:MgO:LiCl =

LiCl (0.636) 0.90:0.10:1.00

H Li2.6Mgb.2OCl Li20 (0.359), MgO (0.121), Li ₂ 0:MgO:LiCl =

LiCl (0.636) 0.80:0.20:1.00

I Li ₃ OBr Li ₂ 0 (0.512), LiBr (1.483) Li ₂ 0:LiBr = 1 : 1

J Li ₃ OBr _{0 5} Cl ₀ . ₅ Li ₂ 0 (0.381 ), LiCl (0.270), Li ₂ 0: LiCl: LiBr =

LiBr (0.552) 1 :0.5:0.5

EXAMPLE D

[0023] For EXAMPLE D, an amount of 0.413 grams Li ₂ 0, and amount of 0.587 grams of LiCl, which corresponds to a molar ratio of Li ₂ 0:LiCl of 1 : 1 , were mixed in a glove box under a dry argon atmosphere. The mixture was then grinded by ball milling for 2 hours inside the glove box using a SPEX SAMPLE PREP, 5100 MIXER MILL in a stainless steel crucible and under the dry argon atmosphere. The ball milled powder was then enclosed inside a container with its cap sealed using high-performance SCOTCH

TAPE®. The bottle and powder inside were shipped to National Synchrotron Light Source at Brookhaven National Laboratory where the container was taken into a glove box under a dry argon atmosphere. The cap was unsealed and the powder was loaded into a high pressure cell that consisted of a cubic mixture of amorphous boron and epoxy resin ("BE"), an amorphous carbon cylinder as a heating element, a cylindrical alumina sleeve that separated the BE from the carbon cylinder, and a hexagonal boron nitride ("BN") sample container of 1 millimeter inner diameter and 2 millimeter length. The powder mixture and the NaCl powder were packed into the BN container, with a thin disk of BN separating the starting powder sample mixture from the NaCl powder. This BN disk prevented the powder mixture from interacting with the NaCl powder (i.e. the pressure standard). The volume ratio for the two powders was approximately 1 : 1. After the pressure cell was completely assembled, all air pathways on the pressure cell were covered by DUCO® cement to isolate the powders from moisture. Before removing the assembly from the glove box, the resulting as-finished pressure cell was placed into a capped plastic tube with both ends sealed by high-performance electrical tape. The pressure cell was removed from the plastic tube, placed into a cubic anvil module inside a hydraulic press, and rapidly pumped up to a pressure of about 0.1 GPa sample pressure. Typically, it took 10-15 minutes to set up the anvil pressure module into the hydraulic press and then pump the oil pressure up so as to reach a sample pressure condition of approximately 0.1 GPa by squeezing the cubic sample assembly with six synchronized anvils. It was believed that these steps isolated the sample contents of the pressure cell from room air. After synchrotron x-ray diffraction data were collected at two different sample positions under ambient conditions for calibration purposes, the sample and NaCl pressure standard were compressed to 0.54 GPa and then heated in a stepwise fashion from 27°C to 279°C. The synchrotron x-ray diffraction were collected for both the sample and the NaCl along a heating path at temperatures of 27°C, 102°C, 152°C, 182°C, 201°C, 225°C, 250°C, and 279°C. The experiment was ended by cooling to room temperature, followed by decompression to ambient conditions. Diffraction data were collected on the recovered sample. EXAMPLE E

[0024] EXAMPLE E was prepared by combining an amount of 0.386 grams Li ₂ 0, an amount of 0.576 grams CaO, and amount of 0.576 grams of LiCl, which corresponds to a molar ratio of Li ₂ 0:CaO:LiCl of 0.95:0.05: 1, were mixed in a glove box under an argon atmosphere. The mixture was then grinded by ball milling for 2 hours inside the glove box using a SPEX SAMPLE PREP, 5100 MIXER MILL in a stainless steel crucible and under the dry argon atmosphere. The ball milled powder was then enclosed inside a container with its cap sealed using high-performance SCOTCH TAPE®. The bottle and powder inside were shipped to National Synchrotron Light Source at Brookhaven National Laboratory where the container was taken into a glove box under a dry argon atmosphere. The cap was unsealed and the powder was loaded into a high pressure cell that consisted of a cubic mixture of amorphous boron and epoxy resin ("BE"), an amorphous carbon cylinder as a heating element, a cylindrical alumina sleeve that separated the BE from the carbon cylinder, and a hexagonal boron nitride ("BN") sample container of 1 millimeter inner diameter and 2 millimeter length. The powder mixture and the NaCl powder were packed into the BN container, with a thin disk of BN separating the starting powder sample mixture from the NaCl powder. This BN disk prevented the powder mixture from interacting with the NaCl powder (i.e. the pressure standard). The volume ratio for the two powders was approximately 1 : 1. After the pressure cell was completely assembled, all air pathways on the pressure cell were covered by DUCO® cement to isolate the powders from moisture. Before removing the assembly from the glove box, the resulting as-finished pressure cell was placed into a capped plastic tube with both ends sealed by high-performance electrical tape. The pressure cell was removed from the plastic tube, placed into a cubic anvil module inside a hydraulic press, and rapidly pumped up to a pressure of about 0.1 GPa sample pressure. Typically, it took 10-15 minutes to set up the anvil pressure module into the hydraulic press and then pump the oil pressure up so as to reach a sample pressure condition of approximately 0.1 GPa by squeezing the cubic sample assembly with six synchronized anvils. It was believed that these steps isolated the sample contents of the pressure cell from room air. After synchrotron x-ray data were collected at two different sample positions under these ambient conditions, the sample and NaCl were compressed to 0.41 GPa and then heated in a stepwise fashion from 27°C to 250°C. Synchrotron x-ray diffraction data were collected for both the sample and the NaCl along the heating path at temperatures of 27°C, 100°C, 150°C, 195°C, 215°C, 227°C, and 250°C. The experiment ended by cooling to room temperature and then decompression to ambient conditions. Afterward, diffraction data were collected on the recovered sample at three different sample conditions.

EXAMPLE F

[0025] EXAMPLE F was prepared by combining an amount of 0.359 grams Li ₂ 0, an amount of 0.075 grams CaO, and amount of 0.566 grams of LiCl, which corresponds to a molar ratio of Li ₂ 0:CaO:LiCl of 0.90:0.1 : 1 , were mixed in a glove box under a dry argon atmosphere. The mixture was then grinded by ball milling for 2 hours inside the glove box using a SPEX SAMPLE PREP, 5100 MIXER MILL in a stainless steel crucible and under the dry argon atmosphere. The ball milled powder was then enclosed inside a container with its cap sealed using high-performance SCOTCH TAPE®. The bottle and powder inside were shipped to National Synchrotron Light Source at Brookhaven

National Laboratory where the container was taken into a glove box under a dry argon atmosphere. The cap was unsealed and the powder was loaded into a high pressure cell that consisted of a cubic mixture of amorphous boron and epoxy resin ("BE"), an amorphous carbon cylinder as a heating element, a cylindrical alumina sleeve that separated the BE from the carbon cylinder, and a hexagonal boron nitride ("BN") sample container of 1 millimeter inner diameter and 2 millimeter length. The powder mixture and the NaCl powder were packed into the BN container, with a thin disk of BN separating the starting powder sample mixture from the NaCl powder. This BN disk prevented the powder mixture from interacting with the NaCl powder (i.e. the pressure standard). The volume ratio for the two powders was approximately 1 : 1. After the pressure cell was completely assembled, all air pathways on the pressure cell were covered by DUCO® cement to isolate the powders from moisture. Before removing the assembly from the glove box, the resulting as-finished pressure cell was placed into a capped plastic tube with both ends sealed by high-performance electrical tape. The pressure cell was removed from the plastic tube, placed into a cubic anvil module inside a hydraulic press, and rapidly pumped up to a pressure of about 0.1 GPa sample pressure. Typically, it took 10-15 minutes to set up the anvil pressure module into the hydraulic press and then pump the oil pressure up so as to reach a sample pressure condition of approximately 0.1 GPa by squeezing the cubic sample assembly with six synchronized anvils. It was believed that these steps isolated the sample contents of the pressure cell from room air. After synchrotron x-ray diffraction data were collected at two different sample positions, the sample and NaCl were compressed to 0.36 GPa and then heated in a stepwise fashion from a temperature of 27°C to 250°C. Synchrotron x-ray diffraction data were collected for both the sample and the NaCl along the heating path at temperatures of 27°C, 75°C, 100°C, 125°C, 150°C, 170°C, 180°C, 190°C, 200°C, 212°C, 220°C, 223°C, and 250°C. The experiment was ended by cooling to room temperature and then decompression to ambient conditions. Afterward, diffraction data were collected on the recovered sample at two different sample conditions.

EXAMPLE G

[0026] An amount of 0.386 grams Li ₂ 0, an amount of 0.576 grams MgO, and an amount of 0.608 grams of LiCl, which corresponds to a molar ratio of Li20:MgO:LiCl of 0.90:0.10:1.00 were mixed in a glove box under an argon atmosphere. The mixture was then grinded by ball-milling for 2 hours inside the glove box using a SPEX SAMPLE PREP, 5100 MIXER MILL in a stainless steel crucible and under the dry argon atmosphere. The ball milled powder was then enclosed inside a container with its cap sealed using high-performance SCOTCH TAPE®. The bottle and powder inside were shipped to National Synchrotron Light Source at Brookhaven National Laboratory where the container was taken into a glove box under a dry argon atmosphere. The cap was unsealed and the powder was loaded into a high pressure cell that consisted of a cubic mixture of amorphous boron and epoxy resin ("BE"), an amorphous carbon cylinder as a heating element, a cylindrical alumina sleeve that separated the BE from the carbon cylinder, and a hexagonal boron nitride ("BN") sample container of 1 millimeter inner diameter and 2 millimeter length. The powder mixture and the NaCl powder were packed into the BN container, with a thin disk of BN separating the starting powder sample mixture from the NaCl powder. This BN disk prevented the powder mixture from interacting with the NaCl powder (i.e. the pressure standard). The volume ratio for the two powders was approximately 1 : 1. After the pressure cell was completely assembled, all air pathways on the pressure cell were covered by DUCO® cement to isolate the powders from moisture. Before removing the assembly from the glove box, the resulting as-finished pressure cell was placed into a capped plastic tube with both ends sealed by high-performance electrical tape. The pressure cell was removed from the plastic tube, placed into a cubic anvil module inside a hydraulic press, and rapidly pumped up to a pressure of about 0.1 GPa sample pressure. Typically, it took 10-15 minutes to set up the anvil pressure module into the hydraulic press and then pump the oil pressure up so as to reach a sample pressure condition of approximately 0.1 GPa by squeezing the cubic sample assembly with six synchronized anvils. It was believed that these steps isolated the sample contents of the pressure cell from room air. After synchrotron x-ray data were collected at two different sample positions under these ambient conditions, the sample and NaCl were compressed to 0.41 GPa and then heated in a stepwise fashion from 27°C to 250°C. Synchrotron x-ray diffraction data were collected for both the sample and the NaCl along the heating path at temperatures of 27°C, 100°C, 150°C, 170°C, 195°C,

215°C, 227°C, and 250°C. The experiment was ended by cooling to room temperature and then decompression to ambient conditions. Afterward, diffraction data were collected on the recovered sample at three different sample conditions.

EXAMPLE H

[0027] An amount of 0.359 grams Li ₂ 0, an amount of 0.121 grams MgO, and an amount of 0.636 grams of LiCl, which corresponds to a molar ratio of Li ₂ 0:MgO:LiCl of 0.80:0.20: 1.00, were mixed in a glove box under a dry argon atmosphere. The mixture was then grinded by ball-milling for 2 hours inside the glove box using a SPEX

SAMPLE PREP, 5100 MIXER MILL in a stainless steel crucible and under the dry argon atmosphere. The ball milled powder was then enclosed inside a container with its cap sealed using high-performance SCOTCH TAPE®. The bottle and powder inside were shipped to National Synchrotron Light Source at Brookhaven National Laboratory where the container was taken into a glove box under a dry argon atmosphere. The cap was unsealed and the powder was loaded into a high pressure cell that consisted of a cubic mixture of amorphous boron and epoxy resin ("BE"), an amorphous carbon cylinder as a heating element, a cylindrical alumina sleeve that separated the BE from the carbon cylinder, and a hexagonal boron nitride ("BN") sample container of 1 millimeter inner diameter and 2 millimeter length. The powder mixture and the NaCl powder were packed into the BN container, with a thin disk of BN separating the starting powder sample mixture from the NaCl powder. This BN disk prevented the powder mixture from interacting with the NaCl powder (i.e. the pressure standard). The volume ratio for the two powders was approximately 1 : 1. After the pressure cell was completely assembled, all air pathways on the pressure cell were covered by DUCO® cement to isolate the powders from moisture. Before removing the assembly from the glove box, the resulting as-finished pressure cell was placed into a capped plastic tube with both ends sealed by high-performance electrical tape. The pressure cell was removed from the plastic tube, placed into a cubic anvil module inside a hydraulic press, and rapidly pumped up to a pressure of about 0.1 GPa sample pressure. Typically, it took 10-15 minutes to set up the anvil pressure module into the hydraulic press and then pump the oil pressure up so as to reach a sample pressure condition of approximately 0.1 GPa by squeezing the cubic sample assembly with six synchronized anvils. It was believed that these steps isolated the sample contents of the pressure cell from room air. After synchrotron x-ray data were collected at two different sample positions under these ambient conditions, the sample and NaCl were compressed to 0.36 GPa and then heated in a stepwise fashion from 27°C to 250°C. Synchrotron x-ray diffraction data were collected for both powder mixture and NaCl along the heating path at 27°C, 75°C, 100°C, 125°C, 150°C, 170°C, 180°C, 190°C, 200°C, 212°C, 220°C, 223°C, and 300°C. The experiment was ended by cooling to room temperature and then decompression to ambient conditions. Diffraction data were collected on the recovered sample at three different sample conditions. EXAMPLE I

[0028] EXAMPLE I was prepared by combining an amount of 0.512 grams Li ₂ 0, and amount of 1.483 grams of LiBr, which corresponds to a molar ratio of Li ₂ 0:LiBr of 1 : 1, were mixed in a glove box under an argon atmosphere The mixture was then grinded by ball milling for 2 hours inside the glove box using a SPEX SAMPLE PREP, 5100 MIXER MILL in a stainless steel crucible and under the dry argon atmosphere. The ball milled powder was then enclosed inside a container with its cap sealed using high- performance SCOTCH TAPE®. The bottle and powder inside were shipped to National Synchrotron Light Source at Brookhaven National Laboratory.

EXAMPLE J

[0029] An amount of 0.381 grams Li ₂ 0, and an amount of 0.270 grams of LiCl, and an amount of 0.552 grams of LiBr, which corresponds to a molar ratio of Li ₂ 0:LiCl:LiBr of 1 :0.5:0.5, were mixed in a glove box under an argon atmosphere. The mixture was then grinded by ball milling for 2 hours inside the glove box using a SPEX SAMPLE PREP, 5100 MIXER MILL in a stainless steel crucible and under the dry argon atmosphere. The ball milled powder was then enclosed inside a sample bottle with its cap sealed using high-performance SCOTCH TAPE®. The bottle and powder inside were shipped to National Synchrotron Light Source at Brookhaven National Laboratory. At the National Synchrotron Light Source at Brookhaven National Laboratory, the container was taken into a glove box under a dry argon atmosphere. The cap was unsealed and the powder was loaded into a high pressure cell. The high pressure cell consisted of a cubic mixture of amorphous boron and epoxy resin ("BE"), an amorphous carbon cylinder as a heating element, a cylindrical alumina sleeve that separated the BE from the carbon cylinder, and a hexagonal boron nitride ("BN") sample container of 1 millimeter inner diameter and 2 millimeter length. The powder mixture and the NaCl powder were packed into the BN container, with a thin disk of BN separating the powder mixture from the NaCl powder. This BN disk prevented the powder mixture from interacting with the NaCl powder (i.e. the pressure standard). The volume ratio for the two powders was approximately 1 : 1. After the pressure cell was completely assembled, all air pathways on the pressure cell were covered by DUCO® cement to isolate the powders from moisture. Before removing the assembly from the glove box, the resulting as-finished pressure cell was placed into a capped plastic tube with both ends sealed by high-performance electrical tape. The pressure cell was removed from the plastic tube, placed into a hydraulic press, and rapidly pumped up to a pressure of about 1 kilobar sample pressure. Typically, it took 10- 15 minutes to set up the anvil pressure module into the hydraulic press and then pump the oil pressure up so as to reach a sample pressure condition of approximately 0.1 GPa, by squeezing the cubic sample assembly with six synchronized anvils. It was believed that these steps isolated the sample contents of the pressure cell from room air. After synchrotron x-ray diffraction data were collected at three different sample positions under these ambient conditions, the mixture and NaCl were compressed to 1.36 GPa and then heated in a stepwise fashion from 27°C to 300°C. Synchrotron x-ray diffraction data were collected for both powder mixture and NaCl along the heating path at 27°C, 100°C, 150°C, 175°C, 200°C, 213°C, 230°C, 250°C, 275°C, 300°C,. The experiment was ended by cooling to room temperature and then decompression to ambient conditions.

Diffraction data were collected on the recovered sample at five different sample conditions.

[0030] The ionic conductivity of the reaction product Li ₃ OCl _{0 5} Br _{0 5} was obtained from impedence match measurements. The ionic conductivity (σ) was in the range of approximately 10 ^"4 to 10 ^"3 S/cm at room temperature, which means that the ionic conductivity of the reaction product Li ₃ 0Clo _.5 Br ₀ .5 reached super-ionic conduction (i.e. exhibited super-ionic behavior). The ionic conductivity (σ) of increased to approximately 10 ^"2 to 10 ^" ' S/cm as the temperature increased above 525 K indicated that the

Li ₃ OCl _0.5 Br _{0 5} , like Li ₃ OCl, exhibited super-ionic behavior. It is believed that the mixing of large (Br ) anions and small (CI ) anions created interstitial ionic pathways for super- ionic conduction.

[0031] Although the present invention has been described with reference to specific details, it is not intended that such details should be regarded as limitations upon the scope of the invention, except as and to the extent that they are included in the accompanying claims.