Cathode and Metal-air battery comprising cathode and Preparing method thereof

Abstract

A metal-air battery is disclosed. The disclosed metal-air battery may include a negative electrode comprising a metal, a positive electrode comprising a metal carbonate used as a positive active material and an aqueous electrolyte material as a positive electrolyte material, and a separator provided between the negative electrode and the positive electrode. The metal carbonate provided in the positive electrode may be decomposed by the aqueous electrolyte, thereby ensuring the battery circulation of the metal-air battery.

Description

Technology Field

[0001] The disclosed embodiments relate to secondary batteries, and more specifically to a positive electrode, a metal-air battery including the same, and a method for manufacturing the positive electrode. Background Technology

[0002] Metal-air batteries include a negative electrode capable of absorbing and releasing ions and a positive electrode using air as an active material. Since metal-air batteries use the metal itself as the negative electrode and do not require the storage of air, which is the positive active material, within the battery, high-capacity batteries are possible. The theoretical energy density per unit weight of metal-air batteries is very high, exceeding 3500 Wh / kg. This energy density is approximately 10 times that of lithium-ion batteries.

[0003] The cathode of conventional metal-air batteries is manufactured by mixing carbon-based conductive materials, organic electrolytes, etc. When carbon-based conductive materials and organic electrolytes are used as described above, lithium carbonate (Li2CO3) may be generated due to the oxidation of the carbon-based conductive material, and there is a problem in that the lifespan of the metal-air battery is reduced due to the irreversible reaction in which lithium carbonate (Li2CO3) must decompose.

[0004] The capacity or performance of metal-air batteries can be significantly affected, for example, by the material and composition of the positive electrode (air electrode). Furthermore, chemical deterioration and deformation of the battery caused by reaction products can act as factors leading to performance degradation and shortened lifespan. The problem to be solved

[0005] Provides a metal-air battery with excellent performance.

[0006] We provide a metal-air battery capable of suppressing problems caused by chemical degradation due to charging and discharging. We provide a metal-air battery having excellent charge and discharge characteristics.

[0007] A metal-air battery is provided that can prevent problems caused by organic electrolytes.

[0008] It provides a metal-air battery that is advantageous in terms of process ease and manufacturing cost. means of solving the problem

[0009] According to one aspect, an anode is provided comprising a metal carbonate and an aqueous electrolyte as the anode electrolyte material.

[0010] The above metal carbonate may include one or more of Li2CO3, Na2CO3, and K2CO3.

[0011] The above aqueous electrolyte material may include one or more of NH4Cl, LiCl, Li2SO4, LiOH, and alkylammonium chloride.

[0012] It may further include an anode carrier that supports the above metal carbonate.

[0013] The above anode carrier may include one or more of carbon, metal oxide, or metal-containing electronic conductors.

[0014] According to another aspect, a metal-air battery can be provided comprising: a cathode comprising a metal; a separator disposed on the cathode; and an anode disposed on the separator and having a metal carbonate and an aqueous electrolyte as an anode electrolyte material.

[0015] The above separator may include a solid electrolyte.

[0016] The above solid electrolyte may include lithium ion conductive glass, lithium ion conductive crystals (ceramic or glass-ceramic), or a mixture thereof.

[0017] The above solid electrolyte may include one or more selected from lithium-aluminum-germanium-phosphate (LAGP), lithium-aluminum-titanium-phosphate (LATP), and lithium-aluminum-titanium-silicon-phosphate (LATSP).

[0018] The above anode may be an organic electrolyte-free electrode that does not contain an organic electrolyte.

[0019] It may further include a gas diffusion layer provided on at least one surface of the anode portion.

[0020] The above metal carbonate may include one or more of Li2CO3, Na2CO3, and K2CO3.

[0021] The above aqueous electrolyte material may include one or more of NH4Cl, LiCl, Li2SO4, LiOH, and alkylammonium chloride.

[0022] It may further include an anode carrier that supports the above metal carbonate.

[0023] The above anode carrier may include one or more of carbon, metal oxide, or metal-containing electronic conductors. Effects of the invention

[0024] It is possible to realize a metal-air battery with excellent performance. It is possible to realize a metal-air battery with excellent charge-discharge characteristics. It is possible to realize a metal-air battery capable of suppressing problems caused by chemical degradation due to charging and discharging. It is possible to realize a metal-air battery capable of preventing problems caused by organic electrolytes. It is possible to realize a metal-air battery that is advantageous in terms of process ease and manufacturing cost reduction. Brief explanation of the drawing

[0025] FIG. 1 is a cross-sectional view schematically illustrating a metal-air battery according to one embodiment. FIG. 2 is an enlarged cross-sectional view schematically illustrating a metal-air battery according to one embodiment. Figure 3 is a cross-sectional view showing a metal-air battery according to a comparative example. FIG. 4 is a schematic diagram showing the structure of a lithium-air battery according to one embodiment. FIG. 5 is a graph showing the results of measuring the charge-discharge characteristics of a metal-air battery having the structure of Example 1 and Comparative Example 1 according to one embodiment of the present invention. FIG. 6 is a graph showing the results of measuring the charge-discharge characteristics of a metal-air battery having the structure of Example 2 and Comparative Example 2 according to one embodiment of the present invention. FIGS. 7 and 8 are graphs showing the results of evaluating cyclability by repeatedly performing charge-discharge experiments on a metal-air battery according to one embodiment of the present invention. Specific details for implementing the invention

[0026] Hereinafter, metal-air batteries according to embodiments will be described in detail with reference to the attached drawings. The widths and thicknesses of the layers or regions depicted in the attached drawings may be slightly exaggerated for the clarity of the specification and convenience of description. Throughout the detailed description, the same reference numerals indicate the same components.

[0027] FIG. 1 is a cross-sectional view schematically illustrating a metal-air battery according to one embodiment. FIG. 2 is an enlarged cross-sectional view schematically illustrating a metal-air battery according to one embodiment.

[0028] Referring to FIGS. 1 and 2, a metal-air battery may include an anode layer (10) containing a metal and a cathode layer (30) spaced apart from the anode layer (10). The cathode layer (30) may include a metal carbonate (31) and, as a cathode electrolyte material, an aqueous electrolyte material (32). The cathode layer (30) will be described in more detail later. A separator (20) may be provided between the anode layer (10) and the cathode layer (30). The metal-air battery may further include a gas diffusion layer (40) in contact with at least one surface of the cathode layer (30). The gas diffusion layer (40) may facilitate the supply of oxygen (O2) and carbon dioxide (CO2) to the cathode layer (30). The anode layer (30) may be a ‘cathode catalyst layer’ or simply referred to as a ‘cathode’. The anode layer (30) and the gas diffusion layer (40) may be said to constitute a single ‘cathode portion’. In other words, the cathode portion of a metal-air battery may include the anode layer (30) and, optionally, may further include the gas diffusion layer (40).

[0029] The negative electrode layer (10) may include a material capable of absorbing and releasing metal ions. Such a material may include, for example, lithium (Li), copper (Cu), sodium (Na), zinc (Zn), potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), aluminum (Al), or an alloy composed of two or more of these. For example, the negative electrode layer (10) may include lithium (Li). In this case, the negative electrode layer (10) may include at least one of lithium, a lithium-based alloy, or a lithium intercalating compound. When the negative electrode layer (10) includes lithium, the metal-air battery according to the present embodiment may be referred to as a 'lithium-air battery'.

[0030] As previously mentioned, the anode layer (30) may include a metal carbonate (31) and an aqueous electrolyte material (32). As an example, the metal carbonate (31) is Li2CO3 , Na2CO3, K2CO3 It may include one or more of the following, but is not limited to:

[0031] In addition, the aqueous electrolyte material (32) may include one or more of NH4Cl, LiCl, Li2SO4, LiOH, and alkylammonium chloride.

[0032] When the metal-air battery according to the present embodiment is a lithium-air battery, the following electrochemical reaction may occur at the positive electrode during discharge.

[0033] 4Li + (dis.) + O2 (dis.) + 2CO2 (dis.) + 4e- → 2Li2CO3 (solid)

[0034] Lithium ions (Li) provided from the negative electrode layer (10) + Oxygen (O2) and carbon dioxide (CO2) provided from the atmosphere (air) can combine (react) with electrons (e-) on the surface of the anode layer (30) to produce solid lithium carbonate (Li2CO3). The lithium carbonate (Li2CO3) produced here can be considered an example of a reaction product.

[0035] When the metal-air battery according to the present embodiment is a lithium-air battery, the following electrochemical reaction may occur in the positive electrode during charging.

[0036] 2Li2CO3 (dis.) + 2H2O (dis.) → 4LiOH (dis.) + 2CO 2 (dis.)

[0037] Hydrogen ions (H) provided from the aqueous electrolyte material (32) +By using ), the decomposition of lithium carbonate (Li2CO3) can be promoted, and accordingly, the overvoltage during the charging process is reduced and the charging voltage of the metal-air battery (1) can be lowered.

[0038] In addition, when charging, the following electrochemical reactions may occur in the aqueous electrolyte material (32).

[0039] 4LiOH (dis.) → 4Li + (dis.) + 2H2O (dis.) + O 2(dis.) + 4e -

[0040] Lithium hydroxide (LiOH) generated at the anode is lithium ions (Li + It can be decomposed into water (H2O) and oxygen (O2), and accordingly, the reverse reaction of the discharge reaction can proceed. As described above, by using an aqueous electrolyte material (32) as the positive electrolyte material, the irreversible reaction in which lithium carbonate (Li2CO3) must decompose during the charging process can be carried out more easily. Accordingly, the overvoltage during the charging process is reduced, and by lowering the charging voltage of the metal-air battery (1), the lifespan of the metal-air battery (1) can be improved.

[0041] According to one example, the anode layer (30) may further include an anode carrier (33) capable of supporting a metal carbonate (31). As an example, the anode carrier (33) may include one or more of platinum (Pt), ruthenium oxide (RuO2), ruthenium, gold, and carbon.

[0042] The separator (20) may include an ion-conducting material to enable ion conduction between the negative electrode layer (10) and the positive electrode layer (30). The separator (20) may include a solid electrolyte. As an example, the solid electrolyte may include lithium ion-conducting glass, lithium ion-conducting crystals (ceramic or glass-ceramic), or a mixture thereof. For example, lithium ion-conducting crystals may include, for instance, Li3N, LISICON, La0 . 55 Li0 . 35 Crystals having a perovskite structure with lithium ion conductivity such as TiO3, and LiTi2P3O having a NASICON-type structure 12 , or glass-ceramics that precipitate these crystals, etc. Lithium ion conductive crystals are, for example, Li1 +x+ y (Al, Ga) x (Ti, Ge)2 - x Si y P3 - y O 12 (where O≤x≤1, O≤y≤1, e.g., 0≤x≤0.4, 0<y≤0.6, or 0.1≤x≤0.3, 0.1<y≤0.4). Lithium ion conductive glass-ceramics are, for example, lithium-aluminum-germanium-phosphate (LAGP), lithium-aluminum-titanium-phosphate (LATP), lithium-aluminum-titanium-silicon-phosphate (LATSP), etc.

[0043] The gas diffusion layer (40) can serve to absorb oxygen and carbon dioxide from the atmosphere and supply them to the anode layer (30). To this end, the gas diffusion layer (40) may have a porous structure to facilitate the smooth diffusion of oxygen and carbon dioxide. For example, the gas diffusion layer (40) may be formed using carbon paper, carbon cloth, carbon felt, or sponge-like foamed metal or metal fiber mats made of carbon fiber. Additionally, the gas diffusion layer (40) may be made of a flexible porous material that is non-conductive, such as non-woven fabric. However, the anode layer (30) may also be manufactured with a porous structure or a similar structure so that it can perform the role of the gas diffusion layer. In this case, the gas diffusion layer (40) may be omitted.

[0044] Although not illustrated in FIG. 1, an anode current collector in contact with the cathode layer (10) may be further provided. The anode current collector may be provided on the lower surface of the cathode layer (10). Thus, the cathode layer (10) may be disposed between the anode current collector and the separator (20). The anode current collector may include, for example, copper (Cu), stainless steel (SUS), silver (Ag), magnesium (Mg), or other conductors. Additionally, an anode current collector in contact with the gas diffusion layer (40) may be further provided. The anode current collector may be provided on the upper surface of the gas diffusion layer (40). Thus, the gas diffusion layer (40) may be disposed between the anode current collector and the anode layer (30). The anode current collector may include, for example, stainless steel (SUS) or a porous carbon material. In this case, the SUS of the positive current collector may have a mesh structure for the permeation of air (gas). The material of the positive current collector is not limited to stainless steel (SUS) and can be varied. If the gas diffusion layer (40) is not used, the positive current collector may be in contact with the positive layer (30). The negative current collector may be considered as part of the negative part, and similarly, the positive current collector may be considered as part of the positive part.

[0045] Figure 3 is a cross-sectional view showing a metal-air battery according to a comparative example.

[0046] Referring to FIG. 3, a separator (60) is provided on a cathode layer (50), and a porous anode layer (70) containing a metal carbonate material is provided between the separator (60) and the gas diffusion layer (90). An anode electrolyte material (80) is impregnated and exists within the pores of the anode layer (70). The anode electrolyte material (80) may be an organic electrolyte. The porous anode layer (70) acts as an electron conductor, and the anode electrolyte material (80) acts as an ion conductor. That is, electrons (e -) moves through the porous anode layer (70), and lithium ions (Li + ) moves through the anode electrolyte material (80). On the surface of the anode layer (70), oxygen, carbon dioxide, and lithium ions react with electrons to produce lithium oxide, e.g., lithium carbonate. The pores of the anode layer (70) provide a space for the reaction product, lithium oxide, to be located. However, since the decomposition process of the reaction product, lithium oxide (i.e., Li2CO3), is an irreversible process, the overvoltage may increase during the charging process, which can cause the battery to degrade rapidly. This can act as a factor in the degradation of battery performance and shortening of its lifespan.

[0047] However, since the metal-air battery according to the embodiment uses an aqueous electrolyte material as the positive electrode electrolyte material to promote the decomposition of lithium oxide, it can fundamentally block or reduce the problem of overvoltage during the charging process caused by lithium oxide. Therefore, it can be very advantageous for improving / maintaining battery performance and extending its lifespan.

[0048] FIG. 4 is a schematic diagram showing the structure of a lithium-air battery according to one embodiment. FIG. 5 is a graph showing the results of measuring the charge-discharge characteristics of a metal-air battery having the structure of Example 1 and Comparative Example 1 according to one embodiment of the present invention. FIG. 6 is a graph showing the results of measuring the charge-discharge characteristics of a metal-air battery having the structure of Example 2 and Comparative Example 2 according to one embodiment of the present invention.

[0049] According to one example, in a lithium-air battery, a separator (20) is interposed between a positive electrode layer (30) adjacent to a positive electrode current collector (34) and a negative electrode layer (10) containing lithium adjacent to a negative electrode current collector (11). The separator (20) is a separator containing a solid electrolyte. A metal carbonate (31) impregnated with an aqueous electrolyte material (32) can be supported on a positive electrode carrier (33). The positive electrode current collector (34) is porous and can also function as a gas diffusion layer capable of air diffusion. A pressing member (220) capable of delivering air to the positive electrode is disposed on the positive electrode current collector (34). A case (320) made of an insulating resin material is interposed between the positive electrode layer (30) and the negative electrode layer (10) to electrically separate the positive electrode layer (30) and the negative electrode layer (10). Air is supplied through the air inlet (230a) and discharged through the air outlet (230b). The lithium air battery is not limited to air stored in a stainless steel container and may contain a combination of gases including oxygen and carbon dioxide.

[0050] The "air" in a lithium-air battery can be the atmosphere. This broad definition of the term "air" applies to all uses, such as air batteries, air electrodes, etc.

[0051] (Manufacturing of lithium-air batteries)

[0052] Examples 1: Fabrication of a lithium-air battery (anode / LATP / PEGDME / Li cathode)

[0053] A lithium metal foil was placed as the cathode on a copper thin film serving as the cathode current collector, and a polymer electrolyte was placed as the cathode intermediate layer on the cathode. The polymer electrolyte was prepared by mixing polyethylene glycol dimethyl ether (PEGDME) (Mn=500 Dalton, Celgard) and the lithium salt LiTFSI (Lithium bis(trifluoromethylsulonly)imide) such that the molar ratio of EO / Li was 20. A solid electrolyte film, a lithium aluminum titanium phosphate (LATP) film (thickness 180 μm, Ohara Glass Corp., Japan), was placed on the polymer electrolyte.

[0054] A cathode was prepared by dispersing 15 mg of lithium carbonate (Li2CO3) in 1 ml of ethanol on a platinum (Pt) cathode powder, and then impregnating the dried cathode with an aqueous electrolyte material (H2O).

[0055] A gas diffusion layer (GDL) (SGL, 25BC) was placed on top of the anode, a nickel mesh was placed on the gas diffusion layer, and the cell was fixed by pressing it with a pressing member that allows air to be delivered to the anode. A lithium-air battery was manufactured.

[0057] Examples 2

[0058] A lithium-air battery was manufactured in the same manner as in Example 1, except that the anode carrier was made of ruthenium oxide (RuO2).

[0060] Comparative example 1

[0061] A lithium-air battery was prepared in the same manner as in Example 1, except that 15 mg of lithium carbonate (Li2CO3) was dispersed in 1 ml of ethanol on a positive electrode carrier made of platinum (Pt), and an organic electrolyte material (1 M LiTFSI, PEGDME) was impregnated into the dried positive electrode.

[0063] Comparative example 2

[0064] A lithium-air battery was prepared in the same manner as in Example 2, except that 15 mg of lithium carbonate (Li2CO3) was dispersed in 1 ml of ethanol on a positive electrode carrier made of ruthenium oxide (RuO2), and an organic electrolyte material (1 M LiTFSI, PEGDME) was impregnated into the dried positive electrode.

[0066] Evaluation example 1

[0067] The charge capacity and overvoltage of lithium-air batteries according to Examples 1 and 2 and Comparative Examples 1 and 2 are shown in Table 1 below.

[0069] anode carrier anode electrolyte material Charging capacity Overvoltage Example 1 Pt H2O 770 mAh / g 0.69 V Example 2 RuO2 H2O 1330 mAh / g 1.6 V Comparative Example 1 Pt 1M LiTFSI, PEGDME 11 mAh / g > 2.0 V Comparative Example 2 RuO2 1M LiTFSI, PEGDME 44 mAh / g > 2.0 V

[0070] The discharge capacity of the lithium-air batteries prepared in Example 1 and Comparative Example 1 was measured by discharging them at 40°C, 100% relative humidity, an oxygen atmosphere, and carbon dioxide, and is shown in Fig. 5. The discharge capacity of the lithium-air batteries prepared in Example 2 and Comparative Example 2 was measured by discharging them at 40°C, 100% relative humidity, an oxygen atmosphere, and carbon dioxide, and is shown in Fig. 6.

[0071] Referring to FIGS. 5 and 6, it can be seen that compared to Example 1 and Example 2, which contain an aqueous electrolyte material as the positive electrolyte material, the charging capacity of the lithium-air battery according to Comparative Example 1 and Comparative Example 2 is significantly reduced and the overvoltage is significantly increased.

[0072] FIGS. 7 and 8 are graphs showing the results of evaluating cyclability by repeatedly performing charge-discharge experiments on a metal-air battery according to one embodiment of the present invention.

[0073] Example 3: Fabrication of a Lithium-Air Battery (Cathode / LATP / PEGDME / Li Anode)

[0074] A copper metal foil was placed as the cathode, and a polymer electrolyte, which serves as an intermediate layer of the cathode, was placed on the cathode. The polymer electrolyte was prepared by mixing polyethylene glycol dimethyl ether (PEGDME) (Mn=500 Dalton, Celgard) and the lithium salt LiTFSI (Lithium bis(trifluoromethylsulonly)imide) such that the molar ratio of EO / Li is 20. A solid electrolyte film, a Lithium Aluminum Titanium Phosphate (LATP) film (thickness 260 μm, Ohara Glass Corp., Japan), was placed on the polymer electrolyte.

[0075] A cathode was prepared by dispersing 15 mg of lithium carbonate (Li2CO3) in 1 ml of ethanol on a platinum (Pt) cathode powder, and then impregnating the dried cathode with an aqueous electrolyte material (H2O).

[0076] A gas diffusion layer (GDL) (SGL, 25BC) was placed on top of the anode, a nickel mesh was placed on the gas diffusion layer, and the cell was fixed by pressing it with a pressing member that allows air to be delivered to the anode. A lithium-air battery was manufactured.

[0077] The charge-discharge capacity of the lithium-air battery prepared in Example 3 was measured after 20 charge-discharge cycles at 40°C, 100% relative humidity, an oxygen atmosphere, and carbon dioxide, and is shown in FIGS. 7 and 8.

[0078] Referring to FIGS. 7 and 8, it can be seen that the cyclability of the charge-discharge cycle of the metal-air battery according to Example 3 is maintained so that the charge-discharge cycle continues for 20 cycles. FIGS. 7 and 8 are the results of a basic experiment, and depending on the composition of the anode layer and other conditions, the charge-discharge cyclability may be further improved.

[0079] Although many details are described in detail in the foregoing description, they should be interpreted as examples of specific embodiments rather than as limiting the scope of the invention. For instance, a person skilled in the art to which the present invention pertains will understand that the structure of the metal-air battery described above can be modified in various ways. Therefore, the scope of the present invention should not be determined by the described embodiments but by the technical concept described in the patent claims. Explanation of the symbols

[0081] 1: Metal-air battery 10: Cathode layer 11: Cathode current collector 20: Separator 30: Anode layer 31: Metal carbonates 32: Aqueous Electrolytes 33: Anode carrier 40: Gas diffusion layer

Claims

Claim 1 A metal carbonate; an aqueous electrolyte as an anode electrolyte material; and an anode comprising an anode carrier that supports the metal carbonate and includes a metal oxide or a metal. Claim 2 In claim 1, the metal carbonate comprises one or more of Li2CO3, Na2CO3, and K2CO3, forming an anode. Claim 3 The anode according to claim 1, wherein the aqueous electrolyte material comprises one or more of NH4Cl, LiCl, Li2SO4, LiOH, and alkylammonium chloride. Claim 4 delete Claim 5 In claim 1, the anode carrier comprises one or more of platinum, ruthenium oxide, ruthenium, and gold. Claim 6 A metal-air battery comprising: a negative electrode portion containing a metal; a separator disposed on the negative electrode portion; and an anode portion disposed on the separator portion; wherein the anode portion comprises a metal carbonate, an aqueous electrolyte material as an anode electrolyte material, and an anode carrier that supports the metal carbonate and contains a metal oxide or a metal. Claim 7 In claim 6, the separator comprises a solid electrolyte, a metal-air battery. Claim 8 In claim 7, the solid electrolyte comprises a lithium ion conductive glass, a lithium ion conductive crystal (ceramic or glass-ceramic), or a mixture thereof, in a metal-air battery. Claim 9 A metal-air battery according to claim 7, wherein the solid electrolyte comprises one or more selected from lithium-aluminum-germanium-phosphate (LAGP), lithium-aluminum-titanium-phosphate (LATP), and lithium-aluminum-titanium-silicon-phosphate (LATSP). Claim 10 In claim 6, the anode is an organic electrolyte-free electrode that does not contain an organic electrolyte, in a metal-air battery. Claim 11 A metal-air battery according to claim 6, further comprising a gas diffusion layer provided on at least one surface of the anode. Claim 12 In claim 6, the metal carbonate comprises one or more of Li2CO3, Na2CO3, and K2CO3, a metal-air battery. Claim 13 A metal-air battery according to claim 6, wherein the aqueous electrolyte material comprises one or more of NH4Cl, LiCl, Li2SO4, LiOH, and alkylammonium chloride. Claim 14 delete Claim 15 In claim 6, the anode carrier comprises one or more of platinum, ruthenium oxide, ruthenium, and gold, in a metal-air battery.

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