Moistureproof sodium ion battery composite positive plate structure

Abstract

The utility model discloses a moisture-proof sodium ion battery composite positive plate structure which comprises a positive current collector, layered oxide positive material layers are coated on the nightside and the sunny side of the positive current collector, moisture-proof positive material layers are coated on the surfaces of the layered oxide positive material layers, and the moisture-proof positive material layers are coated on the surfaces of the layered oxide positive material layers. And the moisture-proof positive electrode material layer and the layered oxide positive electrode material layer are different in material type. The composite positive plate structure of the moisture-proof sodium ion battery has the characteristics of good moisture resistance, excellent conductivity, high safety and simple process.

Description

TECHNICAL FIELD

[0001] The utility model relates to sodium ion battery technical field, specifically point to a kind of moisture-proof type sodium ion battery composite positive plate structure. BACKGROUND

[0002] As a new type of energy storage device, sodium ion battery has become a potential alternative technology in electric vehicles, energy storage systems and other applications due to its wide range of raw materials and low cost. The positive material of sodium ion battery, such as NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2, etc. is of great concern due to its high theoretical capacity and good ionic conductivity. However, layered oxide materials also have inherent disadvantages, especially in humid environments, where water absorption is a serious problem. Layered oxide materials have high hydrophilicity, especially under high humidity conditions, and these materials are prone to water absorption. Water penetration can cause hydration reaction of the material, which in turn affects the cycle performance and capacity decay of the battery. At the same time, water and electrolyte reaction may cause hydrogen evolution, thermal runaway and other safety hazards, which seriously affect the reliability and safety of the battery.

[0003] In order to reduce water absorption, various coating materials are used in the prior art, such as polytetrafluoroethylene (PTFE), polyetherimide (PEI), carbon coating, etc., as follows:

[0004] PTFE coating: Although PTFE has good water resistance, its low electrical conductivity can negatively affect the rate performance of the battery.

[0005] PEI coating: PEI material has good hydrophilic repulsion properties, but its high adhesion and poor mechanical strength can cause the coating to fall off, affecting the long-term stability of the battery.

[0006] Carbon coating: Although carbon coating has good electrical conductivity, its moisture-proof effect is limited, and there may be problems such as uneven coating and poor adhesion.

[0007] In summary, although the existing coating materials can reduce water absorption to some extent, they still have defects that affect battery performance, especially in terms of electrical conductivity, cycle life, rate performance, etc.

[0008] The root cause is that layered oxide materials have a layered structure, with transition metal layers and sodium ion layers stacked alternately. This structure is conducive to the insertion and extraction of sodium ions, but also has some inherent defects;

[0009] Compared with lithium battery materials, the interlayer spacing of layered oxide positive electrode materials is larger due to the larger radius of sodium ions. This makes it easier for water molecules, oxygen, carbon dioxide and other substances in the air to enter the interlayer and react with transition metal ions, leading to the destruction of the material structure and the decline of the performance; During synthesis, due to high temperature, reducing atmosphere and other factors, oxygen vacancies may exist in the material. The existence of oxygen vacancies will destroy the lattice structure of the material, increase the reactivity of the material, and make it more likely to react with oxygen and water in the air. Oxygen vacancies also change the electronic structure of the material, reducing its stability; The transition metal ions (such as Mn, Ni, Fe) in the layered oxide positive electrode material are usually in a high valence state, with high redox activity. These high valence ions are prone to lose electrons and undergo redox reactions with oxygen or water in the air, forming new oxides or hydroxides, thereby reducing the electrochemical performance of the material; There are a large number of active sites on the surface of the material, which can easily adsorb water molecules and oxygen in the air, thereby triggering a series of chemical reactions and causing changes in the structure and performance of the material.

[0010] Therefore, the prior art needs to be further improved for the moisture-proof problem of the sodium ion battery positive electrode sheet. Practical new type content

[0011] The purpose of the present application is to provide a moisture-proof sodium ion battery composite positive electrode sheet structure, which has the characteristics of good moisture-proof, excellent electrical conductivity, high safety and simple process.

[0012] The present application can be achieved by the following technical solutions:

[0013] The utility model discloses a moisture-proof sodium ion battery composite positive electrode sheet structure, including the positive electrode current collector, the negative surface and the positive surface of positive electrode current collector are all coated with the layer of layered oxide positive electrode material layer, the surface of layered oxide positive electrode material layer is coated with the layer of moisture-proof positive electrode material layer, and the material type of moisture-proof positive electrode material layer and layered oxide positive electrode material layer is different.

[0014] Further, the moisture-proof positive electrode material layer is a polyanion material layer, and the polyanion material layer is a composite sodium iron phosphate material layer.

[0015] Further, the layered oxide positive electrode material layer is a NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 material layer and / or Na 2 / 3 Ni 1 / 3Mn 2 / 3 O2 material layer.

[0016] Further, the positive electrode current collector is a copper foil, a copper mesh, an aluminum foil or an aluminum mesh.

[0017] Further, the thickness of the positive electrode current collector is 0.012-0.016mm, and the areal density of the single-sided coating is 100-200g / m2.

[0018] Further, the layered oxide positive electrode material layer and the moisture-proof positive electrode material layer are coated on the surface of the positive electrode current collector by rolling, spraying, doctor blade coating or extrusion coating.

[0019] Further, the conductive adhesive layer is a silicone-based conductive adhesive layer, an epoxy-based conductive adhesive layer, an acrylic-based conductive adhesive layer or a polyurethane-based conductive adhesive layer.

[0020] Further, the conductive adhesive layer is a silicone-based conductive adhesive layer, an epoxy-based conductive adhesive layer, an acrylic-based conductive adhesive layer or a polyurethane-based conductive adhesive layer.

[0021] Further, the sodium ion battery is a square sodium ion battery or a cylindrical sodium ion battery.

[0022] Further, the square sodium ion battery is an aluminum shell sodium ion battery or an aluminum plastic film sodium ion battery.

[0023] The moisture-proof sodium ion battery composite positive electrode sheet structure has the following beneficial effects:

[0024] First, the moisture resistance is good, by setting the moisture-proof positive electrode material layer outside the layered oxide positive electrode material layer, the contact between the layered oxide positive electrode material layer and the external moisture can be effectively reduced, and the stability and cycle performance of the battery in a high humidity environment are significantly improved.

[0025] Second, the electrical conductivity is excellent: the moisture-proof positive electrode material layer also has the function of the positive electrode active material layer, and will not significantly affect the electrical conductivity of the battery, compared with other materials (such as PTFE, PEI, etc.) of the conventional positive electrode material layer, the moisture-proof positive electrode material layer has less effect on the electrical conductivity of the battery, thereby not significantly reducing the rate performance of the battery.

[0026] Third, the safety is effectively improved, the chemical stability of the moisture-proof positive electrode material layer is high, which can effectively inhibit the thermal runaway reaction inside the battery and enhance the overall safety of the battery. Even in a high humidity or high temperature environment, the stability of the battery is effectively guaranteed.

[0027] Fourth, the process is simple, the coating process of the moisture-proof positive electrode material layer is simple, which can be realized by common spraying, dipping and other methods, and is easy to realize large-scale application in production. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a structure diagram of the moisture-proof sodium ion battery composite positive electrode sheet structure.

[0029] Figure 2The moisture content of the positive plate coated with different surface coatings of layered oxide is measured and compared after the positive plate is dried and then placed in a high temperature and high humidity environment of 60 DEG C / 85 RH for 2H;

[0030] Figure 3 The batteries assembled with the positive plate coated with different surface coatings of layered oxide under the same environment and process are compared in terms of normal temperature 5C rate discharge;

[0031] Figure 4 The batteries assembled with the positive plate coated with different surface coatings of layered oxide under the same environment and process are compared in terms of 1C cycle for 1000 times;

[0032] The marks in the drawings include: 100 is a moisture-proof positive material layer, 101 is a layered oxide positive material layer, and 102 is a positive current collector. DETAILED DESCRIPTION

[0033] In order to make the person skilled in the art better understand the technical scheme of the utility model, the utility model product is further explained in detail below in combination with embodiments.

[0034] As Figure 1 shown, the utility model discloses a kind of moisture-proof sodium ion battery composite positive plate structure, including positive current collector 102, the negative side and the positive side of positive current collector 102 are all coated with layered oxide positive material layer 101, layered oxide positive material layer 101 surface is coated with moisture-proof positive material layer 100, and the material type of moisture-proof positive material layer 100 and layered oxide positive material layer 101 is different.

[0035] In the utility model, in order to guarantee moisture-proof, on the selection of specific material, moisture-proof positive material layer is polyanion material layer, polyanion material layer is composite sodium iron phosphate material layer, and layered oxide positive material layer is NaNi 1 / 3Fe 1 / 3 Mn 1 / 3 O2 material layer and / or Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2 material layer.

[0036] Further, in the selection of auxiliary material, to effectively reduce cost, select existing material type, for example, positive current collector is copper foil, copper mesh, aluminum foil or aluminum mesh; for example, the thickness of positive current collector is 0.012-0.016mm, and the area density of single side coating is 100-200g / m2.

[0037] In process adaptability, similar to existing process, for example, layered oxide positive material layer and moisture-proof positive material layer are coated on the surface of positive current collector by rolling, spraying, doctoring or extrusion coating.

[0038] In the utility model, in order to improve stability, the conductive adhesive layer is further arranged between the moisture-proof positive material layer and the layered oxide positive material layer. Specifically, the conductive adhesive layer is a silica gel-based conductive adhesive layer, an epoxy resin-based conductive adhesive layer, an acrylic-based conductive adhesive layer or a polyurethane-based conductive adhesive layer.

[0039] The structure of the utility model can satisfy different types of sodium ion batteries, such as square sodium ion batteries or cylindrical sodium ion batteries. Specifically, the square sodium ion battery is an aluminum shell sodium ion battery or an aluminum plastic film sodium ion battery.

[0040] In the utility model, the following considerations are made for the moisture-proof positive material layer:

[0041] I. Selection of the moisture-proof positive material layer:

[0042] 1. NFPP (sodium iron pyrophosphate) is a sodium battery positive material with good chemical stability and thermal stability, especially in a high humidity environment. The molecular structure of the NFPP material is more stable, which can effectively prevent water from penetrating into the positive material, avoid hydration reaction and reduce water absorption. Compared with layered oxide materials, NFPP has stronger moisture resistance and hydration resistance, which can protect the active material inside the battery from moisture.

[0043] II. Coating process:

[0044] 1. The layered oxide positive material selects one or more than two of layered oxides NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2; the conductive agent selects one or more than two of carbon black, acetylene black, conductive graphite and carbon nanotubes; the adhesive selects one or more than two of polyvinylidene fluoride, polytetrafluoroethylene and butadiene rubber; the solvent selects one or more than two of N-methylpyrrolidone, N,N-dimethylformamide and dimethyl sulfoxide; the pulp is prepared according to 95%:2%:3%, and the pulp stirring mode is wet or dry preparation to obtain the positive electrode slurry; the viscosity range of the slurry is 4000-8000CP;

[0045] 2. The prepared positive electrode slurry is coated on 0.012-0.016mm thick aluminum foil, the coating single-sided area density is 100-200g / m2, and the layered oxide positive material layer is obtained after drying;

[0046] 3. Then one or more of the solutions of NFPP, PTFE, PEI, conductive carbon, etc. is coated on both sides of the layered oxide positive electrode material layer, with a coating thickness of 2-4 μm, thereby obtaining the final moisture-proof electrode sheet; the battery is assembled according to the normal process flow and with the negative electrode, separator, electrolyte, etc. Embodiment

[0047] The layered oxide positive electrode material is selected from layered oxides NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2; the conductive agent is selected from carbon black, acetylene black, conductive graphite, carbon nanotubes; the binder is selected from polyvinylidene fluoride; the solvent is selected from N-methylpyrrolidone, N,N-dimethylformamide;

[0048] The pulp is prepared according to 95%:2%:3%, and the stirring mode of the pulp is wet or dry; the viscosity of the pulp ranges from 4000-8000 CP; the layered oxide positive electrode slurry is coated on a 0.012 mm thick aluminum foil, with a coating single-sided area density of 160 g / m2, and dried to prepare an electrode sheet; then the prepared layered oxide positive electrode sheet is coated with a 3 μm thick PTFE coating on both sides; the above positive electrode sheet, negative electrode sheet, separator, electrolyte, etc. are assembled into a 1 Ah soft package sodium ion battery. Embodiment

[0049] The same method and steps as in Embodiment 1 are used for preparation, except that the coating on both sides of the layered oxide positive electrode sheet is a PEI layer. Embodiment

[0050] The same method and steps as in Embodiment 1 are used for preparation, except that the coating on both sides of the layered oxide positive electrode sheet is a carbon coating. Embodiment

[0051] The same method and steps as in Embodiment 1 are used for preparation, except that the coating on both sides of the layered oxide positive electrode sheet is a NFPP material layer. Embodiment

[0052] The same method and steps as in Embodiment 1 are used for preparation, except that the surface of the positive electrode sheet is not coated with any coating.

[0053] The battery assembly is completed under the same process environment, and the comparison results of the specific embodiments are shown in Table 1 and Figures 2-4

[0054] Table 1 Performance test results

[0055]

[0056] From Table 1, Figures 2-4 ​It can be seen that by coating the composite sodium iron phosphate NFPP (Na4Fe3(PO4)2P2O7) moisture-proof positive electrode material layer on the surface of the layered oxide material electrode material layer, the electrode sheet has better moisture-proof and conductive performance, and the overall performance of the battery is improved.

[0057] In the description of the present application, it should be understood that the terms such as "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0058] In addition, the terms "first" and "second" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0059] In the present application, unless otherwise specifically defined and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication or interaction relationship between two elements. For ordinary skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0060] The above embodiments are only specific embodiments of the present application, which are described in more detail and in more detail, but cannot be understood as a limitation on the scope of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, and these obvious alternative forms all belong to the protection scope of the present application.

Claims

1. A moisture-proof sodium-ion battery composite cathode sheet structure, comprising a cathode current collector, characterized in that: The negative and positive surfaces of the positive current collector are both provided with a layered oxide positive material layer, and the surface of the layered oxide positive material layer is provided with a moisture-proof positive material layer, and the moisture-proof positive material layer is different from the layered oxide positive material layer in material type.

2. The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 1, characterized in that: The moisture-proof positive material layer is a polyanion material layer, and the polyanion material layer is a composite sodium iron phosphate material layer. 3.The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 2, characterized in that: The layered oxide cathode material layer is a NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2material layer and / or Na 2 / 3 Ni 1 / 3 Mn 2 / 3 O2material layer.

4. The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 3, characterized in that: The positive current collector is a copper foil, a copper mesh, an aluminum foil or an aluminum mesh.

5. The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 4, characterized in that: The thickness of the positive current collector is 0.012-0.016 mm, and the areal density of the single-sided coating is 100-200 g / m2.

6. The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 5, characterized in that: The layered oxide positive material layer and the moisture-proof positive material layer are coated on the surface of the positive current collector by rolling, spraying, doctor blading or extrusion coating.

7. The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 6, characterized in that: The moisture-proof positive material layer and the layered oxide positive material layer are further provided with a conductive adhesive layer. 8.The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 7, characterized in that: The conductive adhesive layer is a silicone-based conductive adhesive layer, an epoxy-based conductive adhesive layer, an acrylic-based conductive adhesive layer or a polyurethane-based conductive adhesive layer. 9.The moisture-proof sodium-ion battery composite cathode sheet structure of claim 8, characterized in that: The sodium ion battery is a square sodium ion battery or a cylindrical sodium ion battery.

10. The moisture-proof sodium-ion battery composite cathode sheet structure according to claim 9, characterized in that: The square sodium ion battery is an aluminum shell sodium ion battery or an aluminum plastic film sodium ion battery.

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