JP2012033490A - Lithium air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium air battery.SOLUTION: A lithium air battery containing an aqueous electrolyte includes lithium halide in the aqueous electrolyte, and thus a reaction between a lithium hydroxide and a solid electrolyte membrane is suppressed to enable protection of an anode. Accordingly, an electrical characteristic of the battery can be improved.

Description

  The present invention relates to a lithium-air battery, and more particularly to a lithium-air battery that has a high energy density and maintains electrical characteristics even when used for a long time.

  The lithium-air battery includes a negative electrode capable of occluding / releasing lithium ions, a positive electrode including oxygen redox catalyst using oxygen in the air as a positive electrode active material, and lithium ion conduction between the positive electrode and the negative electrode. Those having a conductive medium are known.

  The theoretical energy density of the lithium-air battery is 3,000 Wh / kg or more, which corresponds to an energy density almost 10 times that of the lithium ion battery. In addition, lithium-air batteries are environmentally safe, can provide improved stability over lithium ion batteries, and have been extensively developed.

  In such a lithium-air battery, an aqueous electrolyte and a non-aqueous electrolyte can be used as the lithium ion conductive medium. The non-aqueous electrolyte can be exemplified by an organic solvent containing a lithium salt, and the aqueous electrolyte can be exemplified by water containing a salt.

  The problem to be solved by the present invention is to provide a lithium-air battery with improved electrical characteristics by preventing electrode damage due to by-products generated from the electrolyte.

  In order to solve the above problems, an embodiment of the present invention includes a negative electrode capable of occluding / releasing lithium ions, a lithium ion conductive solid electrolyte membrane, an aqueous electrolyte, a positive electrode using oxygen as a positive electrode active material, A lithium-air battery in which the aqueous electrolyte contains lithium hydroxide and lithium halide is provided.

  According to one embodiment, the lithium halide includes one or more selected from the group consisting of lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI). be able to.

  According to one embodiment, the lithium ion conductive solid electrolyte membrane is interposed between the negative electrode and the positive electrode and is formed on one surface of the negative electrode.

  According to one embodiment, the lithium ion conductive solid electrolyte membrane includes a glass-ceramic solid electrolyte containing metal ions.

  According to one embodiment, the lithium ion conductive solid electrolyte membrane may further include a polymer solid electrolyte.

  According to one embodiment, the lithium ion conductive solid electrolyte membrane may include a laminate of a glass-ceramic solid electrolyte and a polymer solid electrolyte.

  According to an embodiment, the lithium halide may be included in a range of about 0.1% to about 100% of a saturation concentration with respect to the aqueous electrolyte.

  According to an embodiment, the lithium halide may be included in a range of about 10% to 100% of a saturation concentration with respect to the aqueous electrolyte.

  According to an embodiment, the aqueous electrolyte may include lithium chloride in a content of about 1 to about 83 parts by weight with respect to 100 parts by weight of water.

  The negative electrode may include lithium metal, an alloy based on lithium metal, a lithium intercalating compound, or the like.

  According to an embodiment, the positive electrode may include a porous carbon-based material.

  According to an embodiment, a separator may be further provided between the solid electrolyte membrane and the positive electrode.

  According to an embodiment, the positive electrode may further include a catalyst for oxygen reduction.

  According to an embodiment, the aqueous electrolyte may be interposed between the lithium ion conductive solid electrolyte membrane and a positive electrode using oxygen as a positive electrode active material.

  According to an embodiment, a part or all of the aqueous electrolyte may be present in a form impregnated in the positive electrode.

  According to an embodiment, the lithium air battery may further include a non-aqueous electrolyte between the negative electrode capable of occluding / releasing lithium ions and the lithium ion conductive solid electrolyte membrane.

  The lithium-air battery using the aqueous electrolyte according to the present invention improves the life characteristics of a lithium-air battery having a high energy density by suppressing the decomposition of the solid electrolyte by discharge products and improving the durability of the electrode. Can do.

It is a photograph which shows the surface of the solid electrolyte membrane which is not processed. It is a photograph which shows the surface of the solid electrolyte membrane processed with lithium chloride. It is a photograph which shows the surface of the solid electrolyte membrane processed with lithium hydroxide. It is the schematic which shows the structure of the lithium air battery by one implementation example. 6 is a graph showing a result of electrical characteristics of a cell measured in Experimental Example 2.

  A lithium-air battery according to one aspect includes a negative electrode capable of inserting and extracting lithium ions, a lithium ion conductive solid electrolyte membrane, a water-based electrolyte, and a positive electrode using oxygen as a positive electrode active material, and the water-based electrolyte. Includes lithium hydroxide and lithium halide.

  Lithium-air batteries can use an aqueous electrolyte and a non-aqueous electrolyte as the electrolyte. When an aqueous electrolyte is used, a reaction mechanism represented by the following reaction formula is shown.

(Reaction Formula 1)
4Li + O ₂ + 2H ₂ O → 4LiOH E ^o = 3.45V

  That is, in the process in which lithium generated from the negative electrode encounters and oxidizes with oxygen of the positive electrode, water supplied from the aqueous electrolyte participates in the reaction to generate lithium hydroxide.

  The lithium hydroxide thus produced exists in a dissolved state in the aqueous electrolyte, and the concentration gradually increases in the aqueous electrolyte as the depth of discharge increases.

  The hydroxyl group dissociated by the generated lithium hydroxide is a metal ion contained in the lithium ion conductive solid electrolyte membrane used to protect the negative electrode as shown in the following chemical formula 1. And the structure of the electrolyte membrane is damaged.

  In the above chemical formula, M represents a metal ion contained in the solid electrolyte membrane.

  That is, the lithium ion conductive solid electrolyte membrane serves as a protective film that protects water contained in the aqueous electrolyte so that it cannot directly react with lithium contained in the negative electrode. In such a protective film, the interface structure is changed by lithium hydroxide, which is a reaction product of the battery, and the resistance of the solid electrolyte film is increased by changing the components. As a result, a decrease in conductivity is induced, resulting in a decrease in battery performance.

  However, if lithium halide is dissolved in the aqueous electrolyte, the degree of dissociation of LiOH decreases and the pH of the solution decreases.

  FIG. 1 shows the surface of lithium-aluminum-titanium-phosphate (LATP) which is a kind of lithium ion conductive solid electrolyte membrane, and FIG. 2 shows that the solid electrolyte is left in a 1M LiCl solution for 3 weeks. FIG. 3 shows the surface state after the solid electrolyte was left in a 1M LiOH solution for 3 weeks. In the LATP solid electrolyte left in the LiOH solution, the hydroxyl group of LiOH reacts with the metal ions of the solid electrolyte to generate a large amount of by-products on the surface. However, the LATP solid electrolyte left in LiCl It can be seen that almost no by-products are generated.

  Therefore, it can be seen that the decomposition of the lithium ion conductive solid electrolyte membrane can be suppressed by including lithium halide in the aqueous electrolyte. Thus, lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI) can be exemplified as the lithium halide contained in the aqueous electrolyte. These can be used alone or in admixture of two or more.

  Since these lithium halides are present in a dissolved state in the aqueous electrolyte, they can be present in a high concentration, for example, a saturated concentration. As an example of the saturated concentration, 0.27 g is dissolved in 100 ml of water at 18 ° C. in the case of lithium fluoride, and 83.2 g is dissolved in 100 ml of water at 20 ° C. in the case of lithium chloride. In this case, 166.7 g can be dissolved in 100 ml of water at 20 ° C., and 433 g can be dissolved in 100 ml of water at 20 ° C. in the case of lithium iodide.

  The lithium halide may be present, for example, at a content of about 0.1% to about 100%, or about 10% to about 100% of the saturation concentration. For example, when lithium chloride is present at a content of 50% of the saturation concentration, it means that 41.6 g is dissolved in 100 ml of water at 20 ° C., and exists at a content of 100% of the saturation concentration. In this case, it means that 83.2 g is dissolved in 100 ml of water at 20 ° C.

  Lithium chloride, which is an example of the lithium halide, is present in the aqueous electrolyte at a content of about 1 to about 83 parts by weight per 100 parts by weight of water, and lithium fluoride is about about 100 parts by weight of water. Present in a content of 0.01 to about 0.27 parts by weight, lithium bromide is present in a content of about 1 to about 166 parts by weight per 100 parts by weight of water, and lithium iodide is present in 100 parts by weight of water. It can be present in a content of about 1 to 433 parts by weight per part.

  The lithium ion conductive solid electrolyte membrane protected by the lithium halide contains metal ions and is located between the negative electrode and the positive electrode. In addition, since only lithium ions are allowed to pass through, it functions as a protective film that protects lithium contained in the negative electrode from water. Examples of such a lithium ion conductive solid electrolyte membrane include an inorganic substance containing lithium ion conductive glass, lithium ion conductive crystal (ceramic or glass-ceramic), or a mixture thereof. In consideration of chemical stability, the lithium ion conductive solid electrolyte membrane can be exemplified by an oxide.

  When the lithium ion conductive solid electrolyte membrane contains a large amount of lithium ion conductive crystal, high ion conductivity can be obtained. For example, the lithium ion conductive crystal is, for example, 50% of the total weight of the solid electrolyte membrane. It can be included in an amount of not less than wt%, not less than 55 wt%, or not less than 55 wt%.

Examples of the lithium ion conductive crystal include Li ₃ N, LISICON, crystal having a perovskite structure having lithium ion conductivity such as La _0.55 Li _0.35 TiO ₃ , and LiTi having a NASICON type structure. ₂ P ₃ O ₁₂ , or a glass-ceramic from which the crystals are deposited can be used.

Examples of the lithium ion conductive crystal include Li _{1 + x + y} (Al, Ga) _x (Ti, Ge) _2-x Si _y P _3-y O ₁₂ (where O ≦ x ≦ 1, O ≦ y ≦ 1). For example, 0 ≦ x ≦ 0.4, 0 <y ≦ 0.6, or 0.1 ≦ x ≦ 0.3, 0.1 <y ≦ 0.4). . In the case where the crystal does not include a grain boundary that inhibits ionic conduction, it is advantageous in terms of conductivity. For example, glass-ceramic has few pores and grain boundaries that hinder ionic conduction, and therefore has high ionic conductivity and can have excellent chemical stability.

  Examples of the lithium ion conductive glass-ceramic include lithium-aluminum-germanium-phosphate (LAGP), lithium-aluminum-titanium-phosphate (LATP), lithium-aluminum-titanium-silicon-phosphate. An example is (LATSP).

For example, when the mother glass has a Li ₂ O—Al ₂ O ₃ —TiO ₂ —SiO ₂ —P ₂ O ₅ -based composition and the mother glass is crystallized by heat treatment, the main crystal phase at this time is _{, Li 1 + x + y Al} x Ti becomes _{2-x Si y P 3-} y O 12 (0 ≦ x ≦ 1, O ≦ y ≦ 1), as this time, x and y are, for example, 0 ≦ x ≦ 0. 4, 0 <y ≦ 0.6, or 0.1 ≦ x ≦ 0.3, 0.1 <y ≦ 0.4.

  Here, pores and grain boundaries that interfere with ion conduction refer to the conductivity of the entire inorganic substance including lithium ion conductive crystals, which is 1/10 of the conductivity of the lithium ion conductive crystal itself in the inorganic substance. It refers to ion conductivity inhibitors such as pores and grain boundaries that are reduced to the following values.

  The glass-ceramic is a material obtained by precipitating a crystalline phase in a glass phase by heat-treating the glass, and refers to a material composed of an amorphous solid and a crystal. A material that has undergone a phase transition from a glass phase to a crystalline phase, for example, a material in which the amount of crystals (crystallinity) in the material is 100% by mass can be included. Even in a 100% crystallized material, in the case of glass-ceramic, there are almost no pores between crystal grains or in crystals.

  Since the lithium ion conductive solid electrolyte membrane can obtain high ionic conductivity by containing a large amount of the glass-ceramic, 80% by weight or more of lithium in the lithium ion conductive solid electrolyte membrane. An ion conductive glass-ceramic can be included, and in order to obtain higher ion conductivity, the lithium ion conductive glass-ceramic can be included in an amount of 85 wt% or more or 90 wt% or more.

The Li ₂ O component contained in the glass-ceramic is a component useful for providing a Li ⁺ ion carrier and obtaining lithium ion conductivity. In order to obtain good ionic conductivity more easily, the content of the Li ₂ O component may be 12% or more, 13% or more, or 14%. On the other hand, when the Li 2 _O content component is too large, it tends to deteriorate the thermal stability of the glass, glass - in order to decrease the ceramic conductivity also easily, the content of the Li 2 _O component The upper limit can have a value of 18%, 17% or 16%.

The Al ₂ O ₃ component contained in the glass-ceramic improves the thermal stability of the mother glass, and at the same time, Al ³⁺ ions are dissolved in the crystalline phase, which is effective in improving lithium ion conductivity. is there. In order to obtain this effect more easily, it can be exemplified that the lower limit of the content of the Al ₂ O ₃ component is 5%, 5.5% or 6%. However, when the amount of the Al ₂ O ₃ component exceeds 10%, rather tends to deteriorate the thermal stability of the glass, the glass - to be easily lowered ceramic conductivity, the Al ₂ O It can be exemplified that the upper limit of the content of the _three components is 10%, 9.5% or 9%.

The TiO ₂ component contained in the glass-ceramic contributes to glass formation, is also a constituent component of the crystal phase, and is a useful component in the glass and the crystal. In order to vitrify and for the crystal phase to be precipitated from the glass as the main phase and to obtain high ionic conductivity more easily, the lower limit of the content of the TiO ₂ component is 35%, 36% or 37 % Can be exemplified. On the other hand, if the content of the TiO ₂ component is too large, the thermal stability is liable to deteriorate the glass, the glass - in order to decrease conductivity of the ceramic is also easily contained in the TiO ₂ component It can be exemplified that the upper limit of the amount is 45%, 43% or 42%.

The SiO ₂ component contained in the glass-ceramic can improve the meltability and thermal stability of the mother glass, and at the same time, Si ⁴⁺ ions are dissolved in the crystalline phase to improve lithium ion conductivity. Also contributes. In order to obtain this effect more fully, the lower limit of the content of the SiO ₂ component can be 1%, 2% or 3%. However, when the content of the SiO ₂ component is too large, the conductivity tends to decrease rather, so the upper limit of the content of the SiO ₂ component is 10%, 8% or 7%. can do.

The P ₂ O ₅ component contained in the glass-ceramic is a component useful for the formation of glass and is also a constituent component of the crystal phase. When the content of the P ₂ O ₅ component is less than 30%, it is difficult to vitrify, so the lower limit of the content of the P ₂ O ₅ component is 30%, 32%, or 33%. Can be illustrated. On the other hand, if the content of the P ₂ O ₅ component exceeds 40%, hardly precipitated from the crystal phase different glasses, in order to become difficult to obtain the desired properties, the content of the P ₂ O ₅ component It can be exemplified that the upper limit is 40%, 39% or 38%.

In the case of the above composition, a molten glass can be cast to easily obtain a glass, and the glass-ceramic having the crystal phase obtained by heat-treating this glass is 1 × 10 ⁻³ S · cm ⁻¹ . High lithium ion conductivity.

In addition to the above composition, if a glass-ceramic having a similar crystal structure is used, an Al ₂ O ₃ component is used as a Ga ₂ O ₃ component and a TiO ₂ component is used as a GeO ₂ component. Part or all may be replaced. In addition, when the glass-ceramic is produced, in order to lower the melting point or improve the stability of the glass, other raw materials can be added in a range that does not greatly deteriorate the ion conductivity.

The lithium ion conductive solid electrolyte membrane as described above may further include a polymer solid electrolyte component in addition to the glass-ceramic component. Such a polymer solid electrolyte is polyethylene oxide doped with a lithium salt. Examples of the lithium salt include LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiBF ₄ , LiPF ₆ , LiSbF ₆ , LiAsF ₆ , LiClO. ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , LiN (SO ₃ CF ₃ ) ₂ , LiC ₄ F ₉ SO ₃ and LiAlCl ₄ can be exemplified.

  The polymer solid electrolyte can form a laminated structure with the glass-ceramic, and the glass-ceramic is between the first polymer solid electrolyte containing the component and the second polymer solid electrolyte. Can intervene.

  The lithium ion conductive solid electrolyte membrane as described above is formed on one surface of the negative electrode capable of occluding / releasing lithium ions, protects the negative electrode from reacting with the aqueous electrolyte, and allows only lithium ions to pass. .

  As the negative electrode capable of inserting / extracting lithium ions, lithium metal, an alloy based on lithium metal, a lithium intercalating compound, or the like can be used. Examples of the alloy based on the lithium metal include an alloy of lithium, aluminum, tin, magnesium, indium, calcium, titanium, vanadium, and the like.

  A lithium air battery according to an embodiment may further include a non-aqueous electrolyte between the negative electrode capable of inserting / extracting lithium ions as described above and the lithium ion conductive solid electrolyte membrane. The non-aqueous electrolyte can serve as a medium through which ions involved in the electrochemical reaction of the lithium air battery can move.

In addition, as the non-aqueous electrolyte, an organic solvent not containing water can be used. Examples of the non-aqueous organic solvent include carbonate-based solvents, ester-based solvents, ether-based solvents, ketone-based solvents, and organic sulfur-based organic solvents. Solvents, organophosphorous solvents, or aprotic solvents can be used. Examples of the carbonate solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), and methyl ethyl carbonate. (MEC), ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), butylene carbonate (BC), etc. are used. Examples of the ester solvents include methyl acetate, ethyl acetate, and n-propyl acetate. , Dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone ), Such as caprolactone (caprolactone) can be used. Examples of the ether solvent include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, and tetrahydrofuran. Examples of the ketone solvent include dichlorohexanone. Examples of the organic sulfur-based solvent and the organic phosphorus-based solvent include methanesulfonyl chloride and p-trichloro-n-dichlorophosphoryl monophosphazene, and the aprotic solvent includes R-CN ( R is, C ₂ -C ₂₀ linear, a hydrocarbon group branched or cyclic structure, a double bond, an aromatic ring or can contain an ether bond) nitriles such as; amides such as dimethylformamide Dioxolanes such as 1,3-dioxolane; sulfolanes and the like can be used.

  The non-aqueous organic solvents can be used alone or in combination of one or more, and the mixing ratio when using one or more can be appropriately adjusted according to the intended battery performance. This is possible and well known to those skilled in the art.

The non-aqueous organic solvent may include a lithium salt, and the lithium salt may be dissolved in the organic solvent and serve as a lithium ion supply source in the battery. The role which accelerates | stimulates the movement of a lithium ion between conductive solid electrolyte membranes can be performed. Examples of the lithium _{salt, LiPF 6, LiBF 4, LiSbF} 6, LiAsF 6, LiN (SO 2 C 2 F 5) 2, Li (CF 3 SO 2) 2 N, LiC 4 F 9 SO 3, LiClO 4, LiAlO ₂ , LiAlCl ₄ , LiN (C _x F _{2x + 1} SO ₂ ) (C _y F _{2y + 1} SO ₂ ) (where x and y are natural numbers), LiF, LiBr, LiCl, LiI and LiB (C ₂ O ₄ ) ₁ (two or more selected from the group consisting of ₂ (lithium bisoxalate borate (LiBOB)) can be used. The concentration of the lithium salt can be used within a range of 0.1 to 2.0M. If the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so that excellent electrolyte performance can be exhibited, and lithium ions can be effectively transferred.

In addition to the lithium salt, the non-aqueous organic solvent may further include other metal salts, such as AlCl ₃ , MgCl ₂ , NaCl, KCl, NaBr, KBr, and CaCl ₂ .

  On the other hand, the positive electrode using oxygen as the positive electrode active material can be used without limitation as long as it has porosity and conductivity, for example, a porous carbon-based material can be used. . As such a carbon-based material, carbon blacks, graphites, graphenes, activated carbons, carbon fibers and the like can be used.

  A catalyst for oxygen reduction is added to the positive electrode, and such catalysts include noble metal catalysts such as platinum, gold, silver, palladium, ruthenium, rhodium, osmium; manganese oxide, iron oxide, Oxide catalysts such as cobalt oxide and nickel oxide; organometallic catalysts such as cobalt phthalocyanine can be used.

  A separator may be disposed between the positive electrode and the negative electrode. Such a separator is not limited as long as it has a composition that can withstand the range of use of a lithium-air battery. For example, a polymer nonwoven fabric such as a nonwoven fabric of polypropylene material or a nonwoven fabric of polyphenylene sulfide material; polyethylene Examples thereof include porous films of olefin resins such as polypropylene and polypropylene, and two or more of them can be used in combination.

  An aqueous electrolyte exists between a negative electrode having the lithium ion conductive solid electrolyte membrane formed on one surface and a positive electrode using oxygen as an active material. Such an aqueous electrolyte uses water as a main solvent. And lithium halide is included here. Further, the concentration of lithium hydroxide dissolved in the aqueous electrolyte may change according to the reaction mechanism of the lithium air battery.

  Although such an aqueous electrolyte is described as being interposed between the lithium ion conductive solid electrolyte membrane and the positive electrode, a part or all of the aqueous electrolyte is impregnated in the positive electrode structure due to the characteristics of a non-solid liquid. Needless to say, when a separator is also present, it can also exist in a form impregnated in the separator.

  The term “air” as used herein is not limited to atmospheric air, but may include a combination of gases containing oxygen or pure oxygen gas. Such a broad definition of the term “air” can be applied to any application, such as an air battery, an air cathode, etc.

  The lithium air battery can be used for both a lithium primary battery and a lithium secondary battery. Further, the shape is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a horn type, and the like. Further, it can be applied to a large battery used for an electric vehicle or the like.

  An example of the lithium-air battery is schematically shown in FIG. The lithium-air battery 10 includes a positive electrode 13 using oxygen as an active material formed in a first current collector 12, a negative electrode 15 adjacent to a second current collector 14 and capable of inserting and extracting lithium, and the positive electrode An aqueous electrolyte 18 is interposed between the negative electrodes, and a lithium ion conductive solid electrolyte membrane 16 is formed on one surface of the negative electrode 15. A separator (not shown) may be disposed between the solid electrolyte membrane 16 and the positive electrode 13.

  Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Comparative Example 1
Lithium hydroxide 5M was added to 20 mL of water, and the pH of the solution was measured with a pH meter.

Example 1
After adding 1 M lithium chloride to 20 mL of water, 5 M lithium hydroxide was added, and the pH of the solution was measured with a pH meter.

Example 2
Lithium chloride 3M was added to 20 mL of water, lithium hydroxide 5M was added, and the pH of the solution was measured with a pH meter.

Example 3
Lithium chloride 5M was added to 20 mL of water, lithium hydroxide 5M was added, and the pH of the solution was measured with a pH meter.

Example 4
Lithium chloride 8M was added to 20 mL of water, lithium hydroxide 5M was added, and the pH of the solution was measured with a pH meter.

Example 5
After adding lithium chloride 10M to 20 mL of water, lithium hydroxide 5M was added, and the pH of the solution was measured with a pH meter.

Example 6
After adding lithium chloride 15M to 20 mL of water, lithium hydroxide 5M was added, and the pH of the solution was measured with a pH meter.

Example 7
After saturating lithium chloride in 20 mL of water, 5M lithium hydroxide was added, and the pH of the solution was measured with a pH meter.

Experimental example 1
The pH measurement results of Comparative Example 1 and Examples 1 to 7 are shown in Table 1 below.

  As can be seen from Table 1, in Examples 1 to 7, it can be confirmed that the pH is lowered by increasing the concentration of LiCl. From this result, it can be seen that the dissociation degree of the 5M sodium hydroxide solution was lowered by the addition of LiCl.

Production Example 1: Lithium ion conductive polymer electrolyte membrane reagent is reagent grade lithium bis (trifluoromethanesulfonyl) imide (Aldrich), polyethylene oxide (PEO) (molecular weight ~ 600,000, Aldrich) and acetonitrile (ACN) (Aldrich) was used. 0.5 g of LiTFSI was dissolved in 50 mL of acetonitrile, and 1.4 g of PEO was added thereto, followed by stirring for 12 hours. Thereafter, the solution is added to a polytetrafluoroethylene (PTFE) plate, and then dried under nitrogen gas at 40 ° C. for 24 hours, and then vacuum dried at 150 ° C. for 24 hours to form a lithium ion conductive polymer electrolyte membrane. After being obtained, it was cut into a size of 1.5 cm × 1.5 cm.

Production Example 2: Protected lithium negative electrode 5 cm × 5 cm size aluminum film (polypropylene-coated aluminum film, 200 μm), a hole having a size of 1 cm × 1 cm was formed in the center and 1.4 cm × 1. The hole was closed with a 4 cm LATP (Li1.4Al0.4Ti1.6 (PO4) 3) film (thickness 150 μm, manufactured by Ohara Corporation) to produce an aluminum film partially composed of LATP. 5 cm × 5 cm new aluminum film, copper current collector (thickness 20 μm), lithium foil (1.4 cm × 1.4 cm, thickness 100 μm), lithium ion conductive polymer electrolyte membrane produced in Production Example 1, and the produced aluminum film Were laminated by vacuum heating to obtain an aluminum pouch-type protected lithium negative electrode.

Example 8
Both lithium hydroxide and lithium chloride were saturated in 20 mL of water. A 1 cm × 1 cm size LATP solid electrolyte membrane was immersed in the saturated solution and allowed to stand at 50 ° C. for 3 weeks.

Example 9
Lithium chloride was saturated by adding 0.01 M lithium hydroxide to 20 mL of water. A 1 cm × 1 cm size LATP solid electrolyte membrane was immersed in the saturated solution and allowed to stand at 50 ° C. for 3 weeks.

Example 10
Lithium chloride was saturated by adding 0.001 M of lithium hydroxide to 20 mL of water. A 1 cm × 1 cm size LATP solid electrolyte membrane was immersed in the saturated solution and allowed to stand at 50 ° C. for 3 weeks.

Comparative Example 2
Lithium hydroxide 0.01M was added to 20 mL of water. A 1 cm × 1 cm size LATP solid electrolyte membrane was immersed in the solution and left at 50 ° C. for 3 weeks.

Comparative Example 3
Lithium hydroxide 0.001M was added to 20 mL of water. A 1 cm × 1 cm size LATP solid electrolyte membrane was immersed in the solution and left at 50 ° C. for 3 weeks.

Comparative Example 4
Lithium hydroxide 1M was added to 20 mL of water. A 1 cm × 1 cm size LATP solid electrolyte membrane was immersed in the solution and allowed to stand at 50 ° C. for 1 week.

Comparative Example 5
Lithium hydroxide 1M was added to 20 mL of water. A 1 cm × 1 cm size LATP solid electrolyte membrane was immersed in the solution and left at 50 ° C. for 6 months.

Experimental example 2
The LATP films, which are the results of Examples 8 to 10 and Comparative Examples 2 to 5, were washed with clean water and dried, and then 100 nm thick gold was coated on both sides by a sputtering method. Next, an aluminum pouch type symmetrical cell using copper foil as a current collector was manufactured, and its conductivity was measured at 25 ° C. The results are shown in Table 2 below.

  As can be seen from the description in Table 2, in Comparative Examples 2 to 5 in which only lithium hydroxide is present, the conductivity of the solid electrolyte is decreased due to the reaction between lithium hydroxide and the solid electrolyte membrane. In Examples 8 to 10 to which lithium chloride was added, it can be seen that the conductivity was hardly lowered.

Experimental example 3
Using the protected lithium negative electrode obtained in Production Example 2 as the negative electrode, 1M LiCl as the aqueous electrolyte, and platinum black (Pt-Black) as the positive electrode, a temperature of 60 ° C., 0.1, 0.2, 0 The potential difference over time for lithium batteries at current densities of .3, 0.4 and 0.5 mA / cm ² was measured and illustrated in FIG. As shown in FIG. 5, it can be seen that a sufficient potential difference can be obtained at various current densities.

DESCRIPTION OF SYMBOLS 10 Lithium air battery 12 1st electrical power collector 13 Positive electrode which makes oxygen active material 14 2nd electrical power collector 15 Negative electrode which can occlude / release lithium 16 Lithium ion conductive solid electrolyte membrane 18 Aqueous electrolyte

Claims (16)

A negative electrode capable of occluding / releasing lithium ions;
A lithium ion conductive solid electrolyte membrane;
An aqueous electrolyte,
A positive electrode using oxygen as a positive electrode active material,
A lithium-air battery in which the aqueous electrolyte contains lithium hydroxide and lithium halide.   The lithium halide includes one or more selected from the group consisting of lithium fluoride (LiF), lithium chloride (LiCl), lithium bromide (LiBr), and lithium iodide (LiI). 2. The lithium air battery according to 1.   The lithium-air battery according to claim 1, wherein the lithium ion conductive solid electrolyte membrane is interposed between the negative electrode and the positive electrode and formed on one surface of the negative electrode.   The lithium-air battery according to claim 1, wherein the lithium ion conductive solid electrolyte membrane is a glass-ceramic solid electrolyte containing metal ions.   The lithium air battery according to claim 4, wherein the lithium ion conductive solid electrolyte membrane further includes a polymer solid electrolyte.   The lithium-air battery according to claim 1, wherein the lithium ion conductive solid electrolyte membrane includes a laminate of a glass-ceramic solid electrolyte and a polymer solid electrolyte.   The lithium-air battery according to claim 1, wherein the lithium halide is included in a range of about 0.1% to about 100% of a saturation concentration with respect to the aqueous electrolyte.   The lithium-air battery according to claim 1, wherein the lithium halide is included in a range of about 10% to 100% of a saturation concentration with respect to the aqueous electrolyte.   The lithium-air battery according to claim 1, wherein the aqueous electrolyte includes lithium chloride in a content of about 1 to about 83 parts by weight with respect to 100 parts by weight of water.   The lithium-air battery according to claim 1, wherein the negative electrode includes lithium metal, an alloy based on lithium metal, or a lithium insertion compound.   The lithium-air battery according to claim 1, wherein the positive electrode contains a porous carbon-based material.   The lithium air battery according to claim 1, further comprising a separator between the solid electrolyte membrane and the positive electrode.   The lithium-air battery according to claim 1, wherein the positive electrode further includes an oxygen reduction catalyst.   The lithium-air battery according to claim 1, wherein the aqueous electrolyte is interposed between the lithium ion conductive solid electrolyte membrane and a positive electrode using oxygen as a positive electrode active material.   The lithium-air battery according to claim 1, wherein part or all of the aqueous electrolyte is impregnated in the positive electrode.   2. The lithium-air battery according to claim 1, further comprising a non-aqueous electrolyte between the negative electrode capable of occluding / releasing lithium ions and the lithium ion conductive solid electrolyte membrane.