Negative-electrode-free sodium ion battery current collector, preparation method and application thereof, and negative-electrode-free sodium ion battery

Abstract

The invention provides a negative-electrode-free sodium ion battery current collector, a preparation method and application thereof, and a negative-electrode-free sodium ion battery, and relates to the technical field of batteries. The negative-electrode-free sodium ion battery current collector provided by the invention comprises a base material, a conductive layer and a carboxylic acid metal salt layer, the conductive layer is coated on the surface of the base material, and the carboxylic acid metal salt layer is coated on the conductive layer. When the current collector is used for a sodium ion battery, in the first sodium plating process of battery formation, a carboxylic acid ligand existing on the negative electrode side current collector can be spontaneously converted into a carboxylic acid-sodium interface layer, and an artificial SEI interface layer with a low ion diffusion barrier and high mechanical strength is formed in situ. The artificial SEI interface layer not only can effectively promote uniform deposition of sodium ions in the current collector, but also ensures the stability of the SEI layer in the cycle process, greatly reduces the side reaction of sodium metal and electrolyte, and improves the cycle life and safety performance of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a current collector for a sodium-ion battery without a negative electrode, a preparation method and application thereof, and a sodium-ion battery without a negative electrode. Background Art

[0002] Sodium metal batteries are considered to be one of the most promising next-generation negative electrode materials due to their high theoretical capacity (1166 mAh g -1 ) and low redox potential (-2.714 V vs standard hydrogen electrode). However, the high activity of metallic sodium makes it difficult to manufacture, store, and transport the battery. The design of a sodium metal battery without a negative electrode not only further improves the energy density of the battery, but also reduces the costs associated with the manufacture and integration of the negative electrode. More importantly, it eliminates the insecurity brought by the high-activity metallic sodium negative electrode during the manufacturing and transportation processes.

[0003] However, during the cycling of a battery without a negative electrode, due to the lack of a material for storing sodium on the negative electrode side, the deposition of metallic sodium is uneven, resulting in an uneven and easily broken SEI (solid electrolyte interface film) being formed, which ultimately affects the electrochemical and safety performance of the battery. An effective strategy is to design an artificial SEI layer on the surface of the negative electrode current collector. Although the organic SEI has a lower ion diffusion energy barrier, its structure is loose and its mechanical strength is low, making it difficult to prevent dendrite formation. Although the inorganic SEI has a higher mechanical strength, it often has a higher ion diffusion energy barrier.

[0004] Therefore, designing an artificial SEI layer that combines the advantages of organic and inorganic materials is expected to construct an SEI that combines fast ion conduction and high stability, which can effectively protect the negative electrode side and is the key to promoting the practical application of sodium metal batteries without a negative electrode.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The first object of the present invention is to provide a current collector for a sodium-ion battery without a negative electrode, so as to achieve uniform and stable deposition of sodium ions on the negative electrode current collector, and improve the Coulomb efficiency and cycle life of the sodium-ion battery without a negative electrode.

[0007] The second object of the present invention is to provide a preparation method for the above-mentioned current collector for a sodium-ion battery without a negative electrode.

[0008] The third object of the present invention is to provide the application of the above-mentioned current collector for a sodium-ion battery without a negative electrode in a sodium-ion battery without a negative electrode.

[0009] The fourth object of the present invention is to provide a sodium-ion battery without a negative electrode.

[0010] In order to achieve the above objects, the following technical solutions are specifically adopted:

[0011] In a first aspect, the present invention provides a current collector for a sodium-ion battery without a negative electrode, comprising a substrate, a conductive layer, and a metal carboxylate layer; the conductive layer is coated on the surface of the substrate, and the metal carboxylate layer is coated on the conductive layer;

[0012] The substrate includes aluminum foil or copper foil;

[0013] The metal carboxylate layer is mainly composed of a metal carboxylate and a binder.

[0014] As a further technical solution, the conductive layer includes carbon black.

[0015] As a further technical solution, the metal carboxylate includes at least one of sodium formate, calcium formate, magnesium formate, sodium acetate, calcium acetate, magnesium acetate, sodium propionate, calcium propionate, or magnesium propionate.

[0016] As a further technical solution, the binder includes at least one of CMC, PEO, or PAA.

[0017] As a further technical solution, the mass ratio of the metal carboxylate in the metal carboxylate layer is 95%-98%.

[0018] As a further technical solution, the thickness of the substrate is 8-12 μm;

[0019] The thickness of the conductive layer is 1-3 μm;

[0020] The thickness of the metal carboxylate layer is 1-5 μm.

[0021] In a second aspect, the present invention provides a method for preparing the above-mentioned current collector for a sodium-ion battery without a negative electrode, comprising the following steps:

[0022] a. Mix a metal carboxylate, a binder, and water to prepare a slurry for the metal carboxylate layer;

[0023] b. Coat a slurry of the conductive layer on the substrate to form a conductive layer, and then coat the slurry prepared in step a on the conductive layer, and dry to prepare a current collector for a sodium-ion battery without a negative electrode.

[0024] In a third aspect, the present invention provides the application of the above-mentioned current collector for a sodium-ion battery without a negative electrode in a sodium-ion battery without a negative electrode.

[0025] In a fourth aspect, the present invention provides a sodium-ion battery without a negative electrode, using the above-mentioned current collector for a sodium-ion battery without a negative electrode as the negative electrode of the sodium-ion battery without a negative electrode.

[0026] Compared with the prior art, the current collector for a sodium-ion battery without a negative electrode provided by the present invention has the following beneficial effects:

[0027] 1. SEI with Fast Ion Conduction and High Stability

[0028] Utilizing the special structure of inorganic carboxylates (metal carboxylates), a metal carboxylate layer with both low ion diffusion barrier of organic SEI and high mechanical strength of inorganic SEI is designed. It can effectively promote the uniform deposition of sodium ions on the current collector, while ensuring the stability of the SEI layer during the cycling process, greatly reducing the side reactions between sodium metal and the electrolyte, and improving the cycle life and safety performance of the battery.

[0029] 2. In-situ Construction of High-performance SEI

[0030] During the first sodium plating process of forming a sodium-ion battery, the carboxylate ligands existing on the current collector side of the negative electrode can spontaneously transform into a carboxylate-sodium interface layer, in-situ forming a metal carboxylate layer with a low ion diffusion barrier and high mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a schematic structural diagram of the current collector of the present invention before and after the first sodium plating. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The following will describe the embodiments of the present invention in detail in combination with the embodiments and examples. However, those skilled in the art will understand that the following embodiments and examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention. Those not specified in specific conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0034] In a first aspect, the present invention provides a current collector for a sodium-ion battery without a negative electrode, comprising a substrate, a conductive layer, and a metal carboxylate layer; the conductive layer is coated on the surface of the substrate, and the metal carboxylate layer is coated on the conductive layer;

[0035] The substrate includes aluminum foil or copper foil;

[0036] The metal carboxylate layer is mainly composed of a metal carboxylate and a binder. Among them, the binder is used for the adhesion and fixation of the metal carboxylate on the conductive layer.

[0037] The current collector for sodium-ion battery without a negative electrode provided by the present invention is used for sodium-ion batteries. During the first sodium plating process of battery formation, as Figure 1 shown, the carboxylic acid ligands present on the current collector on the negative electrode side can spontaneously transform into a carboxylic acid-sodium interfacial layer, in-situ forming a carboxylic acid metal salt layer with a low ion diffusion barrier and high mechanical strength. This carboxylic acid metal salt layer can not only effectively promote the uniform deposition of sodium ions on the current collector, but also ensure the stability of the SEI layer during the cycling process, greatly reducing the side reactions between sodium metal and the electrolyte, and improving the cycle life and safety performance of the battery.

[0038] In some alternative embodiments, the conductive layer includes, but is not limited to, carbon black. Coating carbon on the current collector is a relatively conventional technique in the art and will not be elaborated herein.

[0039] In some alternative embodiments, the carboxylic acid metal salt includes, but is not limited to, at least one of sodium formate, calcium formate, magnesium formate, sodium acetate, calcium acetate, magnesium acetate, sodium propionate, calcium propionate, or magnesium propionate.

[0040] In some alternative embodiments, the binder includes CMC, PEO, or PAA, or other binders well-known to those skilled in the art can be selected.

[0041] In some alternative embodiments, the mass percentage of the carboxylic acid metal salt in the carboxylic acid metal salt layer can be, for example, but not limited to, 95%, 96%, or 98%.

[0042] In some alternative embodiments, the thickness of the substrate can be, for example, but not limited to, 8 μm, 10 μm, or 12 μm;

[0043] The thickness of the conductive layer can be, for example, but not limited to, 1 μm, 2 μm, or 3 μm;

[0044] The thickness of the carboxylic acid metal salt layer can be, for example, but not limited to, 1 μm, 3 μm, or 5 μm.

[0045] In a second aspect, the present invention provides a method for preparing the above-mentioned current collector for sodium-ion battery without a negative electrode, including the following steps:

[0046] a. Mix a carboxylic acid metal salt, a binder, and water to prepare a slurry for the carboxylic acid metal salt layer;

[0047] b. Coat a slurry of the conductive layer on the substrate to form the conductive layer, and then coat the slurry prepared in step a on the conductive layer, and dry to prepare a current collector for sodium-ion battery without a negative electrode.

[0048] This preparation method is simple and convenient, and the prepared current collector for sodium-ion battery without a negative electrode can be used for sodium-ion batteries without a negative electrode.

[0049] In a third aspect, the present invention provides an application of the current collector for the sodium-ion battery without a negative electrode in a sodium-ion battery without a negative electrode.

[0050] The current collector for the sodium-ion battery without a negative electrode provided by the present invention is used for a sodium-ion battery and can effectively improve the Coulombic efficiency, cycle performance and safety of the sodium-ion battery.

[0051] In a fourth aspect, the present invention provides a sodium-ion battery without a negative electrode, using the current collector for the sodium-ion battery without a negative electrode as the negative electrode of the sodium-ion battery without a negative electrode.

[0052] The sodium-ion battery has good safety, high Coulombic efficiency and long cycle life.

[0053] The present invention will be further described below through specific examples and comparative examples. However, it should be understood that these examples are only for more detailed description and should not be construed as limiting the present invention in any way.

[0054] Example 1

[0055] A current collector for a sodium-ion battery without a negative electrode includes a substrate (aluminum foil), a conductive layer (carbon) and a carboxylate metal salt layer; the conductive layer is roll-coated on the surface of the substrate to form carbon-coated aluminum foil, and the carboxylate metal salt layer is coated on the conductive layer;

[0056] The carboxylate metal salt layer is composed of a carboxylate metal salt (sodium formate) and a binder (PAA), wherein the mass ratio of the carboxylate metal salt is 98%.

[0057] The thickness of the substrate is 12 μm;

[0058] The thickness of the conductive layer is 1 μm;

[0059] The thickness of the carboxylate metal salt layer is 1 μm.

[0060] The preparation method is as follows:

[0061] a. Mix the carboxylate metal salt, the binder and water to prepare a slurry for the carboxylate metal salt layer;

[0062] b. Roll-coat the slurry prepared in step a on the carbon black of the carbon-coated aluminum foil, and dry it to prepare a current collector for a sodium-ion battery without a negative electrode.

[0063] Example 2

[0064] A current collector for a sodium-ion battery without a negative electrode includes a substrate (aluminum foil), a conductive layer (carbon) and a carboxylate metal salt layer; the conductive layer is roll-coated on the surface of the substrate to form carbon-coated aluminum foil, and the carboxylate metal salt layer is coated on the conductive layer;

[0065] The carboxylate metal salt layer is mainly composed of a carboxylate metal salt (calcium acetate) and a binder (CMC). Among them, the mass proportion of the carboxylate metal salt is 96%.

[0066] The thickness of the substrate is 12 μm;

[0067] The thickness of the conductive layer is 1 μm;

[0068] The thickness of the carboxylate metal salt layer is 3 μm.

[0069] The preparation method is the same as that of Example 1.

[0070] Example 3

[0071] A current collector for a sodium-ion battery without a negative electrode includes a substrate (aluminum foil), a conductive layer (carbon), and a carboxylate metal salt layer; the conductive layer is roll-coated on the surface of the substrate to form a carbon-coated aluminum foil, and the carboxylate metal salt layer is coated on the conductive layer;

[0072] The carboxylate metal salt layer is mainly composed of a carboxylate metal salt (magnesium propionate) and a binder (PEO). Among them, the mass proportion of the carboxylate metal salt is 95%.

[0073] The thickness of the substrate is 12 μm;

[0074] The thickness of the conductive layer is 1 μm;

[0075] The thickness of the carboxylate metal salt layer is 5 μm.

[0076] The preparation method is the same as that of Example 1.

[0077] Comparative Example 1

[0078] A current collector, which is different from that of Example 1 in that it does not contain a carboxylate metal salt layer.

[0079] Comparative Example 2

[0080] A current collector, which is different from that of Example 1 in that it does not contain a conductive layer.

[0081] Comparative Example 3

[0082] A current collector, which is different from that of Example 1 in that sodium formate is replaced by sodium citrate.

[0083] Comparative Example 4

[0084] A current collector, which is different from that of Example 1 in that sodium formate is replaced by sodium fluoride.

[0085] Test Example 1

[0086] The current collectors provided in the above embodiments and comparative examples were used as the negative electrode to prepare a sodium-ion battery without a negative electrode. Among them, the positive electrode sheet was: sodium iron pyrophosphate, PVDF, and conductive carbon black in a ratio of 95.4:1.8:2.8;

[0087] The electrolyte was: diglyme containing 1M NaPF 6 ;

[0088] The separator was: a PP separator.

[0089] The sodium-ion battery without a negative electrode was assembled in a glove box under an inert atmosphere according to the same preparation method.

[0090] The initial Coulombic efficiency and cycling performance of the sodium-ion batteries without a negative electrode prepared in each example and comparative example were tested. The specific test methods were as follows:

[0091] Test of the initial Coulombic efficiency of the battery: After the assembled battery was left standing for 10 h, it was charged at a constant current and constant voltage of 0.2C to 3.5V, then left standing for 0.5 h, and then discharged at a constant current of 0.5C to 2.0V. The ratio of the discharge capacity to the charge capacity of the battery was calculated as CE.

[0092] Cycling life test: After the assembled battery was left standing for 10 h, at room temperature of 25 °C, it was charged at a constant current and constant voltage of 0.5C to 3.5V, left standing for 0.5 h, and then discharged at a constant current of 1C to 2.0V for 100 cycles, and the capacity retention rate was recorded. The test results are shown in Table 1.

[0093] Table 1

[0094] Group Initial Coulombic Efficiency (%) Capacity Retention Rate after 100 Cycles (%) Example 1 96.8 98.8 Example 2 89.8 95.4 Example 3 87.3 94.5 Comparative Example 1 86.5 93.6 Comparative Example 2 58.7 52.5 Comparative Example 3 73.5 70.1 Comparative Example 4 84.3 86.7

[0095] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A negative electrode-free sodium ion battery current collector, characterized in that: It comprises a substrate, a conductive layer and a carboxylic acid metal salt layer; the conductive layer is coated on the surface of the substrate, and the carboxylic acid metal salt layer is coated on the conductive layer; The substrate comprises aluminum foil or copper foil; The carboxylic acid metal salt layer is mainly composed of carboxylic acid metal salt and a binder.

2. The negative electrode-free sodium ion battery current collector according to claim 1, characterized in that: The conductive layer includes carbon black.

3. The negative electrode-free sodium ion battery current collector according to claim 1, characterized in that: The carboxylate metal salt includes at least one of sodium formate, calcium formate, magnesium formate, sodium acetate, calcium acetate, magnesium acetate, sodium propionate, calcium propionate or magnesium propionate.

4. The negative electrode-free sodium ion battery current collector according to claim 1, characterized in that: The binder includes at least one of CMC, PEO or PAA.

5. The negative electrode-free sodium ion battery current collector according to claim 1, characterized in that: The mass proportion of the carboxylate metal salt in the carboxylate metal salt layer is 95%-98%.

6. The negative electrode-free sodium ion battery current collector according to claim 1, characterized in that: The thickness of the substrate is 8-12 μm; The thickness of the conductive layer is 1-3 μm; The thickness of the carboxylic acid metal salt layer is 1 to 5 μm.

7. The method for preparing a negative electrode-free sodium ion battery current collector according to any one of claims 1 to 6, characterized in that: The following steps are involved: a. mixing a carboxylate metal salt, a binder and water to prepare a slurry of a carboxylate metal salt layer; b. coating a conductive layer slurry on a substrate to form a conductive layer, and then coating the slurry prepared in step a on the conductive layer, and drying to obtain a negative electrode-free sodium ion battery current collector.

8. Use of the negative electrode-free sodium ion battery current collector according to any one of claims 1 to 6 in a negative electrode-free sodium ion battery.

9. A negative electrode-free sodium ion battery, characterized in that: The negative electrode-free sodium ion battery current collector according to any one of claims 1 to 6 is used as the negative electrode of the negative electrode-free sodium ion battery.

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