A metal lithium battery

Abstract

The present invention provides a metal lithium battery including a negative electrode and other functional components, wherein the negative electrode is a metal lithium strip having a porous solid electrolyte layer on at least one surface, and the porous solid electrolyte layer is formed by an organic polymer with a specific melting range and a specific inorganic salt in a mass ratio of 5-35:65-95. The metal lithium battery of the present invention can be a liquid or semi-solid electrolyte system battery, wherein the pore structure of the porous solid electrolyte layer on the surface of the lithium strip can make the lithium ion flow uniform, thereby suppressing lithium dendrites; the metal lithium battery of the present invention can be an all-solid-state battery system, wherein the porous solid electrolyte layer can directly serve as a transition layer between the metal lithium strip and the solid electrolyte. In addition, due to the presence of the porous solid electrolyte layer, the reaction of the lithium strip with moisture and nitrogen in the atmosphere can be effectively slowed down, thereby protecting the negative electrode of the lithium strip.

Description

Technical Field

[0001] The present invention belongs to the field of battery preparation, and in particular relates to a metal lithium battery using a metal lithium strip as a negative electrode. Background Art

[0002] The metal lithium negative electrode has a lower density (0.534g / cm 3 ), the highest theoretical capacity (3860mAh / g) and the lowest electrochemical potential (-3.04V, relative to the standard hydrogen electrode) have always been a research hotspot, and have provided the possibility for the manufacture of next-generation secondary batteries with high energy density (>300Wh / kg). However, when used as a negative electrode in a battery system, during the cycle of the metallic lithium negative electrode, a large number of lithium dendrites will be generated on the surface of the metallic lithium negative electrode due to the uneven deposition of lithium ions on the surface of the metallic lithium. The presence of lithium dendrites will not only consume active lithium and electrolyte, resulting in a decrease in battery capacity, but also as the lithium dendrites grow, they will pierce the diaphragm, causing an internal short circuit in the battery and a safety accident. Therefore, in order to achieve large-scale application of metallic lithium, the problem of dendrite growth of metallic lithium still needs to be solved. In addition, due to the high activity of metallic lithium, it is easily damaged by oxidation by substances in the atmosphere or the electrolyte.

[0003] Currently, to protect the surface of lithium metal strips, researchers have proposed using solid electrolytes as artificial solid electrolyte layers (SEIs), hoping to prevent dendrites from piercing and protect the lithium metal surface. However, in practical applications, such SEIs contain only a small number of gaps, but lack sufficient pores or through-holes. As a result, during battery cycling, a large amount of lithium metal accumulates in these gaps, ultimately destroying the SEI and causing its physical failure. Furthermore, due to the lack of sufficient pores or through-holes, such SEIs cannot stably conduct lithium ions, making them unsuitable for use in liquid electrolyte system batteries.

[0004] In view of this, there is a need in the art to provide a metal lithium battery using a metal lithium ribbon with an improved protective layer on the surface as a negative electrode. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide a metal lithium battery using a metal lithium ribbon with an improved protective layer on the surface as the negative electrode.

[0006] To achieve the above object of the invention, the present invention provides a metal lithium battery, which includes a positive electrode, a negative electrode, a separator therebetween, and an electrolyte, wherein the negative electrode is a metal lithium strip having a porous solid electrolyte layer on at least one surface, and the porous solid electrolyte layer is formed by an organic polymer and an inorganic salt in a mass ratio of 5-35:65-95, wherein the melting point of the organic polymer is in the range of 120°C to 300°C, wherein the melting point of the organic polymer is in the range of 120°C to 300°C, and the inorganic salt is one or more compounds having a chemical formula of Li a Y b X c or Li m MX n A mixture of a polyhalogen lithium metal salt and one or more thermally decomposable inorganic salts selected from carbonates, oxalates and ammonium salts, wherein Li represents a lithium ion, Y represents a non-halogen anion, X represents a halogen anion, M represents one or more non-lithium metal ions, a and m are each in the range of 1 to 16, b is in the range of 1 to 8, and c and n are each in the range of 2 to 10.

[0007] In a preferred embodiment, the porous solid electrolyte layer has a thickness of 1 μm to 50 μm.

[0008] In a preferred embodiment, the thickness of the metal lithium ribbon is 1 μm to 1000 μm.

[0009] In a preferred embodiment, the metallic lithium strip is formed of pure lithium metal, or is formed of a lithium alloy containing one or more selected from Ag, Al, Au, Ba, Be, Bi, B, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Y, Zn, Zr, Pb, Pd, Sb and Cu.

[0010] In a preferred embodiment, the average pore size of the porous solid electrolyte layer is 1 nm to 10 μm.

[0011] In a preferred embodiment, the organic polymer is one or more selected from the group consisting of polyethylene glycol, polyvinyl alcohol, gelatin, guar gum, carboxymethyl cellulose and paraffin.

[0012] In a preferred embodiment, the polyhalogen lithium metal salt is selected from Li9N2Cl3, Li3InCl6, LiAlF6, Li3YBr6, Li3YCl6 and Li 2.5 Y 0.5 Zr0.5 One or more of CL6.

[0013] In a preferred embodiment, the mass fraction of the polyhalogen lithium metal salt in the inorganic salt mixture is 45% to 95%.

[0014] In a preferred embodiment, the negative electrode is formed by: dissolving an organic polymer and an inorganic salt in an organic solvent in a desired mass ratio to form a gel solution having a viscosity in the range of 50 mPa·s to 10,000 mPa·s; coating the obtained gel solution on at least one surface of a metallic lithium ribbon; and baking the coated metallic lithium ribbon at 35°C to 105°C to obtain a metallic lithium ribbon having a porous solid electrolyte layer.

[0015] In a preferred embodiment, the mass solid content of the gel solution is in the range of 6% to 93%.

[0016] In a preferred embodiment, the maximum particle size of the particles in the gel solution is less than 10 μm.

[0017] In a preferred embodiment, the metal lithium battery is a liquid metal lithium battery, a semi-solid metal lithium battery, an all-solid metal lithium battery or a metal lithium fuel cell.

[0018] In a preferred embodiment, the metal lithium battery is a soft pack battery, a wound battery or a steel can battery.

[0019] The advantageous effects of the present invention include but are not limited to the following:

[0020] The present invention forms a porous solid electrolyte layer on the metal lithium ribbon by coating (e.g., spraying or scraping) at least one surface of the metal lithium ribbon with a gel solution formed by a mixture of an organic polymer and a specific inorganic salt having a specific melting range (i.e., 120°C to 300°C) in an organic solvent at a mass ratio of 5-35:65-95, and then baking the solution. The metal lithium ribbon having such a porous solid electrolyte layer is used as the battery negative electrode (working electrode) to assemble a metal lithium battery. The metal lithium battery of the present invention can be not only an all-solid electrolyte battery system, but also a liquid or semi-solid electrolyte battery system.

[0021] Moreover, in an all-solid-state battery system, the porous solid electrolyte layer can not only directly serve as a solid electrolyte layer, but also serve as a transition layer between the metal lithium belt and the solid electrolyte, which can slow down the formation of lithium dendrites; while in a liquid or semi-solid electrolyte battery system, the pores of the porous solid electrolyte layer can make the lithium ion flow uniform, directly playing a role in inhibiting the growth of lithium dendrites.

[0022] In addition, due to the presence of the porous solid electrolyte layer, the exposure of the surface to the atmosphere is reduced, which can effectively slow down the reaction between the lithium strip and moisture and nitrogen in the atmosphere, and protect the metal lithium strip from damage. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram of a metal lithium ribbon with a porous solid electrolyte layer according to the present invention is shown;

[0024] Figure 2 A scanning electron microscope (SEM) image showing the surface microstructure of the porous solid electrolyte layer of the present invention;

[0025] Figure 3 A scanning electron microscope (SEM) image of a cross section of a metallic lithium ribbon having a porous solid electrolyte layer according to the present invention is shown;

[0026] Figure 4 A scanning electron microscope (SEM) image showing the local microscopic morphology of the porous solid electrolyte layer of the present invention;

[0027] Figure 5 The cycle test curves of batteries assembled using the metal lithium ribbons obtained according to Example 1 and Comparative Example 1 of the present invention are shown. DETAILED DESCRIPTION

[0028] In order to expand the application range of battery systems using metallic lithium strips as battery negative electrodes (working electrodes), while suppressing the growth of lithium dendrites of the metallic lithium strips and protecting the metallic lithium strips from reacting with moisture and nitrogen in the atmosphere, the inventors have discovered through research that a gel solution formed by an organic polymer having a specific melting range (i.e., a melting point or softening point range of 120°C to 300°C) and a specific inorganic salt mixture in an organic solvent in a specific mass ratio is coated on at least one surface of the metallic lithium strip (e.g., sprayed or scraped) and then baked to form a porous solid electrolyte layer on the metallic lithium strip, thereby achieving the desired purpose.

[0029] Based on this, the present invention provides a metal lithium battery, which includes a positive electrode, a negative electrode, a separator therebetween, and an electrolyte, and is characterized in that the negative electrode is a metal lithium strip having a porous solid electrolyte layer on at least one surface.

[0030] In the present invention, the lithium metal ribbon used can be a ribbon-shaped lithium metal ribbon well known in the art. For example, such a lithium metal ribbon can be a thin lithium metal ribbon with a thickness ranging from 1 μm to 1000 μm. Such a lithium metal ribbon is generally considered to have two surfaces, an upper and a lower surface, and the porous solid electrolyte layer described in the present invention can be formed on at least one of these surfaces, or the formed porous solid electrolyte layer can cover the entire surface of the lithium metal ribbon, thereby blocking direct contact between the lithium metal ribbon and the external environment. Such a lithium metal ribbon can be composed of pure lithium metal or a lithium alloy containing one or more selected from Ag, Al, Au, Ba, Be, Bi, B, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Y, Zn, Zr, Pb, Pd, Sb, and Cu.

[0031] In the present invention, the porous solid electrolyte layer covering at least one surface of the metallic lithium strip is formed of an organic polymer and an inorganic salt. The organic polymer used in the present invention has a melting range (i.e., a melting point or softening point range) in the range of 120°C to 300°C, and the inorganic salt used in the present invention is one or more compounds having a chemical formula of Li a Y b X c or Li m MX n A mixture of a polyhalogen lithium metal salt and one or more thermally decomposable inorganic salts selected from carbonates, oxalates and ammonium salts, wherein Li represents a lithium ion, Y represents a non-halogen anion, X represents a halogen anion, M represents one or more non-lithium metal ions, a and m are each in the range of 1 to 16, b is in the range of 1 to 8, and c and n are each in the range of 2 to 10.

[0032] The present inventors unexpectedly discovered that a desired porous solid electrolyte layer can be formed by coating (e.g., spraying or blade coating) a gel solution of the aforementioned organic and inorganic salts (mixture) in an organic solvent at a mass ratio of 5-35:65-95 onto one or both (or even the entire) surface of a lithium metal ribbon and then baking and drying it. Without being bound by any theory, it is believed that after coating the gel solution formed by mixing the aforementioned organic and inorganic salts in the aforementioned mass ratio, during the baking or drying process, the organic polymer and the polyhalogenated lithium metal salt form a stabilization layer on the surface of the lithium metal ribbon that adheres to the surface of the lithium metal ribbon. This layer protects the surface of the lithium metal ribbon from reaction with airborne components such as water and nitrogen due to exposure. Simultaneously, the thermally decomposable inorganic salts contained in the stabilization layer decompose upon exposure to heat, generating gases. These gases not only carry away some heat (preventing excessive temperatures from melting or softening the organic polymer) but also form the desired porous structure within the stabilization layer. The inventors have discovered that when the mass ratio of the above-mentioned organic polymer to inorganic salt (mixture) is less than 5:95, due to too little organic polymer and too much inorganic salt (resulting in too much gas generated), the required stabilization layer cannot be formed, and the surface of the metal lithium strip cannot be covered, thereby failing to achieve the above-mentioned desired effect; conversely, when the mass ratio is greater than 35:65, due to too much organic polymer and too little inorganic salt, insufficient gas will be generated, thereby failing to form the required porous solid electrolyte layer.

[0033] In the present invention, examples of the organic polymer that can be used include, but are not limited to, polyethylene glycol, polyvinyl alcohol, gelatin, guar gum, carboxymethyl cellulose, paraffin, or a combination thereof.

[0034] In the present invention, the thermally decomposable inorganic salt that can be used can be any carbonate, oxalate, and / or ammonium salt that can generate gas during the baking process, and examples thereof include, but are not limited to, sodium bicarbonate, lithium carbonate, lithium oxalate, sodium oxalate, ammonium bicarbonate, ammonium oxalate, ammonium chloride, etc. Such thermally decomposable inorganic salts generate gas when thermally decomposed, and the gas can generate the desired pores or voids in the stabilization layer.

[0035] In the present invention, as defined above, the formula Li a Y b X c or Li m MX nThe polyhalogen lithium metal salt refers to an inorganic salt containing at least lithium cations (Li) and a (molar) number (c or n) of halogen anions (X) of at least 2, and may also contain one or more non-halogen anions (Y) or one or more non-lithium metal cations (M). It should be noted that when there are multiple non-halogen anions (Y), the total (molar) number of these non-halogen anions (Y) satisfies b defined in the above formula; similarly, when there are multiple non-lithium metal cations (M), the total (molar) number of these non-lithium metal cations (M) satisfies the above formula (each can be a fraction or decimal and the sum is 1). Examples of such polyhalogen lithium metal salts that can be used in the present invention include but are not limited to Li9N2Cl3, Li3InCl6, LiAlF6, Li3YBr6, Li3YCl6, Li 2.5 Y 0.5 Zr 0.5 As is well known in the art, such polyhalogen lithium salts can be obtained by mixing two or more salts according to a chemical formula and then ball milling or sintering. For example, Li9N2Cl3 can be easily obtained by mixing 2 moles of Li3N and 3 moles of LiCl according to a chemical formula and then ball milling or sintering.

[0036] Preferably, the mass fraction of the polyhalogen lithium metal salt in the inorganic salt mixture is 45% to 95%. As mentioned above, during the baking process, the organic polymer and the polyhalogen lithium metal salt form a stabilization layer on the surface of the lithium metal ribbon that adheres to the surface. The inventors have discovered that during the stabilization layer formation process, the polyhalogen lithium metal salt stabilizes the coating formed by the organic polymer on the surface of the lithium metal ribbon. When the mass fraction of the polyhalogen lithium metal salt in the inorganic salt mixture is within the aforementioned range of 45% to 95%, not only can the coating formed by the organic polymer on the surface of the lithium metal ribbon be stabilized to form the stabilization layer, but the surface stabilization layer also has a certain lithium ion conductivity. The inorganic salt mixture, comprising one or more thermally decomposable inorganic salts selected from carbonates, oxalates, and ammonium salts, decomposes upon heating to form the desired pores, particularly pores having an average pore size of 1 nm to 10 μm, as described below.

[0037] In the present invention, the average pore size of the formed porous solid electrolyte layer is preferably 1 nm to 10 μm. The inventors have discovered that when the average pore size of the porous solid electrolyte layer is within this range, the pores of the porous solid electrolyte layer can not only effectively serve as a transition layer between the metallic lithium strip and the solid electrolyte, reserving sufficient space for metallic lithium deposition, but also such pores can uniformize the lithium ion flow, further inhibiting the generation and growth of lithium dendrites. At the same time, when the average pore size of the porous solid electrolyte layer is within this range, it can significantly and more effectively slow down the reaction between the lithium strip and moisture and nitrogen in the atmosphere.

[0038] In the present invention, the thickness of the formed porous solid electrolyte layer can preferably be 1 μm to 50 μm. The inventors have found that the thickness of the formed porous solid electrolyte layer can be obtained by adjusting the solid content and viscosity of the formed gel solution, and that within such a thickness range, the formed porous solid electrolyte layer can not only fully achieve the above-mentioned desired effects, but also ensure that the overall size of the metal lithium ribbon having such a porous solid electrolyte layer is suitable for use as a battery negative electrode.

[0039] Preferably, the metal lithium ribbon with a porous solid electrolyte layer as a negative electrode of the present invention can be prepared by the following method: first, the organic polymer and the inorganic salt are dissolved in a suitable organic solvent in a desired mass ratio (i.e., a mass ratio of 5-35:65 to 95) to form a gel solution, the viscosity of which is preferably in the range of 50 mPa·s to 10000 mPa·s; secondly, the obtained gel solution is coated on at least one surface of the metal lithium ribbon, for example by spraying or scraping; finally, the coated metal lithium ribbon is baked to obtain a metal lithium ribbon with a porous solid electrolyte layer.

[0040] In the present invention, when the organic polymer and the inorganic salt (mixture) are dissolved in an organic solvent at the aforementioned mass ratio, a gel solution or gel-like solution is formed, preferably having a viscosity in the range of 50 mPa·s to 10,000 mPa·s. Furthermore, preferably, the solids content (by mass, i.e., mass solids content) of the formed gel solution is in the range of 6% to 93%. The inventors have discovered that, with the aforementioned viscosity and solids content, the formed gel solution is easy to apply and easy to dry to form a stabilization layer.

[0041] In the present invention, although particulate matter is generally absent from the gel solution, given the aforementioned suitable composition ratios, it is sometimes possible for the inorganic salt to not completely dissolve, resulting in a supersaturated solution. In such cases, the maximum particle size of the particulate matter or insoluble matter in the resulting gel solution is preferably less than 10 μm. This particle size can be achieved after dissolution, for example, by grinding or micronization methods well known in the art. The present inventors have discovered that ensuring this maximum particle size allows for the formation of a porous solid electrolyte layer with more uniform porosity.

[0042] In the present invention, the example of operable organic solvent includes but is not limited to esters, aliphatic hydrocarbons, ethers, aromatic hydrocarbon solvents or its mixture.Preferably, the organic solvent used is for example ethylene carbonate, methyl ethyl carbonate, n-hexane, hexanaphthene, tetrahydrofuran (THF), p-xylene or its mixture.

[0043] In the present invention, baking can be performed in a forced air drying oven or a baking oven, preferably at a temperature of 35° C. to 105° C., which can ensure the formation of a stabilization layer. Typically, the baking time can be 1 hour to 24 hours.

[0044] In the present invention, there is no particular limitation on the positive electrode active material of the battery. For example, the positive electrode active materials that can be used include: organic positive electrode active materials (polypyrrole and its modified or composite materials, polyacrylonitrile and its modified or composite materials, anthraquinone and its modified or composite materials), inorganic positive electrode active materials (including lithium iron phosphate, lithium iron manganese phosphate, lithium titanate, lithium cobalt oxide, lithium manganese oxide (LiMn2O4), LiMnO2, lithium nickelate, lithium nickel manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, sulfur, carbon and oxygen), etc. These positive electrode active materials can be applied to the positive electrode collector such as aluminum foil by methods well known in the art, such as spraying or blade coating.

[0045] In the present invention, there is no particular limitation on the material of the separator between the positive electrode and the negative electrode. For example, a polypropylene separator can be used.

[0046] In the present invention, there is no particular limitation on the electrolyte used. For example, a carbonate electrolyte can be used. Furthermore, for example, the carbonate electrolyte that can be used is an electrolyte having a solute of 1 mol / L LiPF6 and a solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (volume ratio of 1:1).

[0047] In addition, as needed, the metal battery of the present invention may also include other necessary functional components such as a housing, an aluminum-plastic film, a steel shell, etc., which are well known to those skilled in the art.

[0048] The metal battery provided by the present invention with a metal lithium ribbon having a porous solid dielectric layer as a negative electrode can be a liquid metal lithium battery, a semi-solid metal lithium battery, an all-solid metal lithium battery or a metal lithium fuel cell.

[0049] The metal battery provided by the present invention, which uses a metal lithium ribbon with a porous solid dielectric layer as a negative electrode, can be a soft-pack battery, a wound battery, or a steel-shell battery.

[0050] In order to more clearly understand the technical features, objectives and beneficial effects of the present invention, the present invention is further described in detail with reference to the following drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0051] Example 1

[0052] In a fume hood, polyethylene glycol was used as the organic polymer, sodium bicarbonate was used as the thermally decomposable inorganic salt, and Li9N2Cl3 (obtained by ball milling 2 moles of Li3N and 3 moles of LiCl according to the chemical formula) was used as the polyhalogen lithium metal salt. These were added to a tetrahydrofuran solution in a mass ratio of 15:35:50 in a beaker to prepare a gel solution with a solid content of 30%. The viscosity of the gel solution was 300 mPa·s as measured by an NDJ-8S digital viscometer.

[0053] Next, the gel solution obtained above was uniformly sprayed onto a commercially available metal lithium ribbon having a thickness of 20 μm using a spray gun.

[0054] Finally, the coated lithium metal ribbon was placed and dried in a forced air drying oven at a baking temperature of 45° C. for 4 hours, thereby obtaining a lithium metal ribbon having a porous solid electrolyte layer.

[0055] Figure 1 Schematic diagram of a metal lithium strip with a porous solid electrolyte layer according to the present invention is shown. Figure 1 The figure shows a metallic lithium strip at the bottom and a solid electrolyte layer with a porous structure at the top.

[0056] Figure 2 The scanning electron microscope (SEM) image of the surface microstructure of the porous solid electrolyte layer of the present invention is shown. Figure 2 It can be seen from the figure that the porous solid electrolyte layer formed as the stabilization layer is a porous structure with an average pore size of less than 500 nm. Figure 2 It can also be seen that the porous solid electrolyte layer formed is of uniform and dense thickness, which can better prevent or isolate the metal lithium strip from direct contact with external substances such as air or moisture, thereby reducing the corresponding reaction.

[0057] Figure 3 Figure 2 shows a cross-sectional scanning electron microscope (SEM) image of a metal lithium ribbon with a porous solid electrolyte layer according to the present invention. Figure 3 It can be seen that in the structure obtained by the present invention, the metallic lithium layer and the porous solid electrolyte layer are tightly fitted or attached together, the upper solid electrolyte layer is a porous structure, and there are pores inside the solid electrolyte layer.

[0058] Figure 4 The scanning electron microscope (SEM) image of the local microscopic morphology of the porous solid electrolyte layer of the present invention is shown. Figure 4 It can be seen from the figure that the porous solid electrolyte layer has porous microstructures both on the surface and inside.

[0059] Example 2

[0060] Except for using polyvinyl alcohol instead of polyethylene glycol, the other steps were the same as in Example 1 to obtain a metal lithium ribbon with a porous solid electrolyte layer. After testing, its microscopic morphology and pore structure were basically the same as those in Example 1.

[0061] Example 3

[0062] Except for using guar gum instead of polyethylene glycol, the other steps were the same as in Example 1 to obtain a metal lithium ribbon having a porous solid electrolyte layer. Testing showed that its microscopic morphology and pore structure were substantially the same as those in Example 1.

[0063] Example 4

[0064] Except for using ammonium chloride instead of sodium bicarbonate, the other steps were the same as in Example 1 to obtain a metal lithium ribbon having a porous solid electrolyte layer. Testing showed that its microscopic morphology and pore structure were substantially the same as in Example 1.

[0065] Example 5

[0066] The steps were the same as in Example 1, except that Li3YBr6 was used instead of Li9N2Cl3, to obtain a metallic lithium ribbon having a porous solid electrolyte layer. Testing showed that its microscopic morphology and pore structure were substantially the same as those in Example 1.

[0067] Example 6

[0068] In addition to using Li 2.5 Y 0.5 Zr 0.5 Except for replacing Li9N2Cl3 with CL6, the other steps were the same as those in Example 1 to obtain a metallic lithium ribbon with a porous solid electrolyte layer. Testing showed that its microscopic morphology and pore structure were essentially the same as those in Example 1.

[0069] Example 7

[0070] The steps were the same as in Example 1, except that the mass ratio of the three components was changed to 30:20:50, to obtain a metallic lithium ribbon having a porous solid electrolyte layer. Testing showed that its micromorphology and pore structure were essentially the same as those in Example 1.

[0071] Example 8

[0072] Except for changing the mass ratio of the mixture to 25:15:60, the other steps were the same as in Example 1 to obtain a metal lithium ribbon having a porous solid electrolyte layer. Testing showed that its micromorphology and pore structure were substantially the same as in Example 1.

[0073] Comparative Example 1

[0074] A commercially available metal lithium ribbon having a thickness of 20 μm was used directly without forming the porous solid electrolyte layer of the present invention on the surface thereof.

[0075] Application Example 1

[0076] Coin-type lithium metal batteries were assembled using the lithium metal ribbon with a porous solid electrolyte layer of Example 1 and the lithium metal ribbon of Comparative Example 1 as working electrodes. The batteries used a lithium metal sheet as a counter electrode, a carbonate electrolyte, and a polypropylene separator. The carbonate electrolyte consisted of a solute of 1 mol / L LiPF6 and a solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (in a 1:1 volume ratio).

[0077] After assembling the battery, the cycle performance test was carried out. Cycle performance test steps: The assembled button battery was left for 12 hours and the cycle performance was tested at 1mA / cm 2 The battery was charged at a constant current of 1 mA / cm 2 The battery was discharged at a constant current for 1 hour, and the time and voltage changes during the cycle were recorded. The cycle test results are shown in Figure 2. Figure 5 shown.

[0078] Figure 5 The cycle test curves of batteries assembled using the metal lithium strips obtained in Example 1 and Comparative Example 1 are shown. Figure 5It can be seen that in the initial stage of the battery cycle, due to the presence of the porous solid electrolyte layer, the cycle voltage of the battery of Example 1 is higher. As the cycle progresses, the cycle voltage of the metal lithium strip without the porous solid electrolyte layer increases rapidly. This is because a large amount of "dead lithium" is formed on the surface of the metal lithium strip without the protection of the porous solid electrolyte layer, resulting in an increase in the impedance of the electrode surface. It can also be seen from the local enlarged view of the cycle from 150 to 175 times that the battery cycle voltage of Example 1 is small, and as the cycle progresses, the cycle voltage increases slowly, which shows that the porous solid electrolyte layer has the function of protecting the metal lithium and can delay the change of the surface microstructure of the metal lithium strip, that is, inhibit the formation of dendrites and reduce the presence of "dead lithium".

[0079] Application Examples 2 to 8

[0080] Except for using the metal lithium ribbons with porous solid electrolyte layers prepared in Examples 2 to 8 as working electrodes to assemble metal lithium batteries, the other procedures and processes were the same as those in Application Example 1. After testing, similar cycling test performance was obtained as that of the metal lithium battery using the metal lithium ribbons with porous solid electrolyte layers prepared in Example 1 as working electrodes.

[0081] It should be understood that while the present invention describes in detail the lithium metal battery using a lithium metal ribbon with a porous solid electrolyte layer as an electrode in conjunction with specific embodiments and examples, the above description is merely illustrative and not exhaustive or restrictive, and the present invention is not limited to the embodiments and specific examples provided. Those skilled in the art can modify the lithium metal battery described herein through appropriate operations based on the disclosure and teachings of the specification.

[0082] While the specific embodiments of the present invention have been described in detail, they are not intended to limit the present invention. Any modifications, substitutions, and improvements to those details that fall within the spirit and principles of the present invention are intended to be included within the scope of protection of the present invention. The full scope of the present invention is set forth in the appended claims and any equivalents thereof.

Claims

1. A metal lithium battery comprising a positive electrode, a negative electrode, a separator therebetween, and an electrolyte, characterized in that: The negative electrode is a metallic lithium strip having a porous solid electrolyte layer on at least one surface, and the porous solid electrolyte layer is formed of an organic polymer and an inorganic salt in a mass ratio of 5-35:65~95, wherein the melting point of the organic polymer is in the range of 120°C to 300°C and is one or more selected from the group consisting of polyethylene glycol, polyvinyl alcohol, gelatin, guar gum and carboxymethyl cellulose, and the inorganic salt is one or more of the chemical formula Li a Y b X c or Li m MX n A polyhalogen lithium metal salt and one or more thermally decomposable inorganic salts selected from carbonates, oxalates and ammonium salts, wherein Li represents a lithium ion, Y represents a non-halogen anion, X represents a halogen anion, M represents one or more non-lithium metal ions, a and m are each in the range of 1 to 16, b is in the range of 1 to 8, and c and n are each in the range of 2 to 10, wherein the mass fraction of the polyhalogen lithium metal salt in the inorganic salt mixture is 45% to 95%.

2. The metal lithium battery according to claim 1, characterized in that The thickness of the porous solid electrolyte layer is 1 μm to 50 μm; the thickness of the metal lithium strip is 1 μm to 1000 μm.

3. The metal lithium battery according to claim 1, characterized in that The metallic lithium strip is formed of pure lithium metal, or is formed of a lithium alloy containing one or more selected from Ag, Al, Au, Ba, Be, Bi, B, C, Ca, Cd, Co, Cr, Cs, Fe, Ga, Ge, Hf, Hg, In, Ir, K, Mg, Mn, Mo, N, Na, Nb, Ni, Pt, Pu, Rb, Rh, S, Se, Si, Sn, Sr, Ta, Te, Ti, V, Y, Zn, Zr, Pb, Pd, Sb and Cu.

4. The metal lithium battery according to claim 1, characterized in that The average pore diameter of the porous solid electrolyte layer is 1 nm to 10 μm.

5. A metal lithium battery according to claim 1, characterized in that: The polyhalogen lithium metal salt is selected from Li9N2Cl3, Li3InCl6, LiAlF6, Li3YBr6, Li3YCl6 and Li 2.5 Y 0.5 Zr 0.5 One or more of CL6.

6. The metal lithium battery according to claim 1, characterized in that The negative electrode is formed by the following method: dissolving an organic polymer and an inorganic salt in an organic solvent at a desired mass ratio to form a gel solution having a viscosity in a range of 50 mPa·s to 10,000 mPa·s; coating the obtained gel solution on at least one surface of a metallic lithium ribbon; and The coated lithium metal ribbon is baked at 35° C. to 105° C. to obtain a lithium metal ribbon having a porous solid electrolyte layer.

7. The metal lithium battery according to claim 6, characterized in that The mass solid content of the gel solution is in the range of 6% to 93%; and the maximum particle size of the particles in the gel solution is less than 10 μm.

8. The metal lithium battery according to claim 1, characterized in that The metal lithium battery is a liquid metal lithium battery, a semi-solid metal lithium battery, an all-solid metal lithium battery or a metal lithium fuel cell.

9. The metal lithium battery according to claim 1, characterized in that The metal lithium battery is a soft-pack battery, a wound battery or a steel-shell battery.

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