A sodium supplement binder, a preparation method thereof, and a sodium ion battery

Abstract

The application provides a sodium-supplementing binder, which is prepared from the following components in a mass ratio: polyethylene oxide: polyvinylpyrrolidone: NaNO3 = (6-8):(2-1):(2-1); the molecular weight of the polyethylene oxide is 200000-5000000; the molecular weight of the polyvinylpyrrolidone is 20000-100000; and the purity of the NaNO3 is 99.0%-99.9%. The application further provides a preparation method of the sodium-supplementing binder and a sodium ion battery containing the sodium-supplementing binder. The sodium-supplementing binder can be added to the positive and negative electrodes of a sodium battery, and a stable SEI film is formed through an electrochemical reaction, so that the excess sodium ions can shuttle in the sodium ion battery, thereby increasing the cycle performance and service life of the sodium ion battery, and the cycle performance, the initial coulomb efficiency and the average coulomb efficiency of the sodium battery are obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a sodium-supplementing binder, a preparation method thereof and a sodium ion battery. BACKGROUND

[0002] Since the development of sodium ion batteries, they have been studied a lot due to their similar electrochemical performance to lithium ion batteries. However, due to the low specific energy density of sodium ion batteries, they have been greatly limited in the application of digital batteries. In recent years, with the large-scale application of lithium ion batteries in the field of electric vehicles, lithium resources have become increasingly scarce, and the price of lithium carbonate, the main raw material of lithium ion batteries, has increased significantly, resulting in a substantial increase in the production cost of enterprises in the industry chain. Sodium ion batteries have once again attracted attention and research from the industry due to their abundant raw material resources and low and stable prices.

[0003] At present, most sodium ion batteries in the industry still use the system of lithium ion batteries, and there are many problems, such as the most obvious problem of matching of the positive and negative electrodes. A large amount of sodium elements are needed for sodium batteries to form SEI films on the surface of the negative electrode, and only the positive electrode can provide the sodium ions required by the positive and negative electrodes of the sodium battery. This easily consumes the sodium elements from the positive electrode, resulting in a low overall volume energy density of the sodium ion battery and affecting the cycle performance and service life of the sodium ion battery. SUMMARY

[0004] Therefore, the present application provides a sodium-supplementing binder, a preparation method thereof and a sodium ion battery, aiming to solve the problems that the existing sodium battery easily consumes sodium elements from the positive electrode, resulting in a low overall volume energy density of the sodium ion battery and affecting the cycle performance and service life of the sodium ion battery. The sodium-supplementing binder of the present application can be added to the positive and negative electrodes of the sodium battery, and a stable SEI film is formed through an electrochemical reaction, allowing the excess sodium ions to shuttle in the sodium battery, thereby increasing the cycle performance and service life of the sodium battery.

[0005] To achieve the above-mentioned purpose, in one aspect, the present application provides a sodium-supplementing binder (PNNA) prepared from the following components in a mass ratio: polyethylene oxide (PEO): polyvinylpyrrolidone (PVP): NaNO3 = (6-8):(2-1):(2-1); the molecular weight (Mw) of the polyethylene oxide is 200000-5000000; the molecular weight (Mw) of the polyvinylpyrrolidone is 20000-100000; and the purity of the NaNO3 is 99.0%-99.9%.

[0006] On the other hand, embodiments of the present invention also provide a method for preparing the sodium-supplementing binder, comprising the following steps: adding polyethylene oxide, polyvinylpyrrolidone and NaNO3 to a solvent in a mass ratio of (6-8):(2-1):(2-1), stirring and mixing at 10°C to 100°C to obtain a gel; and drying the gel in a vacuum to obtain the sodium-supplementing binder (PNNA).

[0007] In a preferred embodiment, the solvent is one or a mixture of at least two of NMP (N-methylpyrrolidone), methanol, ethanol, DMF (dimethylformamide), or acetonitrile; the sum of the masses of the polyethylene oxide, the polyvinylpyrrolidone, and the NaNO3 is 5.0% to 15.0% of the mass of the solvent.

[0008] In a preferred embodiment, the stirring and mixing time is 30 to 150 minutes. This ensures the uniformity of the gel.

[0009] In a preferred embodiment, the drying temperature is 40°C to 120°C.

[0010] In a preferred embodiment, the drying time is 12 to 36 hours. This ensures that the sodium-added binder forms a stable solid state.

[0011] In another aspect, embodiments of the present invention also provide a sodium-ion battery, wherein the sodium-ion battery contains the sodium-replenishing binder.

[0012] In a preferred embodiment, the N / P ratio of the sodium-ion battery is 1.0 to 1.3.

[0013] In a preferred embodiment, the positive electrode material of the sodium-ion battery contains the following components in the following mass ratio: ternary iron-nickel-manganese-sodium positive electrode: carbon black: the sodium-supplementing binder: polyvinylidene fluoride (PVDF, battery grade) = (8.0~9.5): (1.0~0.25): (0.5~0.125): (0.5~0.125).

[0014] In a preferred embodiment, the negative electrode material of the sodium-ion battery contains the following components in the following mass ratio: hard carbon: carbon black: the sodium-supplementing binder: CMC = (9.0~9.5): (0.4~0.25): (0.3~0.125): (0.3~0.125).

[0015] The sodium-replenishing binder of this application can be added to the positive and negative electrodes of sodium-ion batteries. Through electrochemical reactions, it forms a stable SEI film, allowing excess sodium ions to shuttle within the sodium-ion battery, thereby increasing the cycle performance and lifespan of the battery. This effectively solves the problems of existing sodium-ion batteries, which easily consume sodium elements from the positive electrode, resulting in insufficient sodium ions and thus lower overall volumetric energy density, reduced battery capacity and cycle performance, affecting the cycle performance and lifespan of the sodium-ion battery. The sodium-replenishing binder of this application has low preparation cost and can be used for both the positive and negative electrodes of sodium-ion batteries. Experiments have shown that adding the sodium-replenishing binder of this application to the positive and negative electrodes of sodium-ion batteries significantly improves the cycle performance of the entire battery, with a marked increase in both initial coulombic efficiency and average coulombic efficiency.

[0016] The realization of the objective, functional characteristics and advantages of the present invention will be further explained in conjunction with the embodiments. Attached Figure Description

[0017] Figure 1 This is a schematic diagram showing the cycle curves of the sodium-ion battery (containing sodium-added binder) of Embodiment 1 of this application and the cycle curves of the sodium-ion battery without sodium-added binder. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0020] Currently, most sodium-ion batteries in the industry still use the lithium-ion battery system, which has many problems, the most obvious being the matching of positive and negative electrodes. Sodium batteries require a large amount of sodium to form an SEI film on the negative electrode surface, but only the positive electrode provides the sodium ions needed for both the positive and negative electrodes. This easily consumes the sodium from the positive electrode, resulting in a low overall volumetric energy density of the sodium-ion battery, affecting its cycle performance and lifespan, and limiting its application range. Therefore, it is necessary to provide a sodium-compensating binder, its preparation method, and a sodium-ion battery to solve the above-mentioned technical problems.

[0021] To achieve the above objectives, in one aspect, embodiments of the present invention provide a sodium-supplementing binder (PNNA), prepared from the following components in the following mass ratio: polyethylene oxide (PEO): polyvinylpyrrolidone (PVP): NaNO3 = (6-8):(2-1):(2-1); the molecular weight (Mw) of the polyethylene oxide is 200,000-5,000,000; the molecular weight (Mw) of the polyvinylpyrrolidone is 20,000-100,000; and the purity of the NaNO3 is 99.0%-99.9%.

[0022] On the other hand, embodiments of the present invention also provide a method for preparing the sodium-supplementing binder, comprising the following steps: adding polyethylene oxide, polyvinylpyrrolidone and NaNO3 to a solvent in a mass ratio of (6-8):(2-1):(2-1), stirring and mixing at 10°C to 100°C to obtain a gel; and drying the gel in a vacuum to obtain the sodium-supplementing binder (PNNA).

[0023] In a preferred embodiment, the solvent is one or a mixture of at least two of NMP, methanol, ethanol, DMF, or acetonitrile; the sum of the masses of the polyethylene oxide, the polyvinylpyrrolidone, and the NaNO3 is 5.0% to 15.0% of the mass of the solvent. This ensures good uniformity of the gel.

[0024] In a preferred embodiment, the stirring and mixing time is 30 to 150 minutes. This ensures the uniformity of the gel.

[0025] In a preferred embodiment, the drying temperature is 40°C to 120°C.

[0026] In a preferred embodiment, the drying time is 12 to 36 hours. This ensures that the sodium-added binder forms a stable solid state.

[0027] In another aspect, embodiments of the present invention also provide a sodium-ion battery, wherein the sodium-ion battery contains the sodium-replenishing binder.

[0028] In a preferred embodiment, the N / P ratio of the sodium-ion battery is 1.0 to 1.3.

[0029] In a preferred embodiment, the positive electrode material of the sodium-ion battery contains the following components in the following mass ratio: ternary iron-nickel-manganese-sodium positive electrode: carbon black: the sodium-supplementing binder: polyvinylidene fluoride (PVDF, battery grade) = (8.0~9.5): (1.0~0.25): (0.5~0.125): (0.5~0.125).

[0030] In a preferred embodiment, the negative electrode material of the sodium-ion battery contains the following components in the following mass ratio: hard carbon: carbon black: the sodium-supplementing binder: CMC = (9.0~9.5): (0.4~0.25): (0.3~0.125): (0.3~0.125).

[0031] The sodium-replenishing binder of this application can be added to the positive and negative electrodes of sodium-ion batteries. Through electrochemical reactions, it forms a stable SEI film, allowing excess sodium ions to shuttle within the sodium-ion battery, thereby increasing the cycle performance and lifespan of the battery. This effectively solves the problems of existing sodium-ion batteries, which easily consume sodium elements from the positive electrode, resulting in insufficient sodium ions and thus lower overall volumetric energy density, reduced battery capacity and cycle performance, affecting the cycle performance and lifespan of the sodium-ion battery. The sodium-replenishing binder of this application has low preparation cost and can be used for both the positive and negative electrodes of sodium-ion batteries. Experiments have shown that adding the sodium-replenishing binder of this application to the positive and negative electrodes of sodium-ion batteries significantly improves the cycle performance of the entire battery, with a marked increase in both the initial coulombic efficiency (around 96.8%) and the average coulombic efficiency (around 99.9%).

[0032] Example 1

[0033] A sodium-supplementing binder PNNA is prepared from the following components in the following mass ratio: polyethylene oxide: polyvinylpyrrolidone: NaNO3 = 8:1:1.25; the molecular weight (Mw) of the polyethylene oxide is 1,000,000; the molecular weight (Mw) of the polyvinylpyrrolidone is 50,000; and the purity of the NaNO3 is 99.9%.

[0034] The preparation method of the sodium-supplementing binder includes the following steps: adding 0.4g of polyethylene oxide, 0.05g of polyvinylpyrrolidone and 0.0625g of NaNO3 to 10ml of NMP solvent, stirring and mixing at 60°C to obtain a gel; drying the gel in a vacuum to obtain the sodium-supplementing binder (PNNA).

[0035] The solvent is NMP.

[0036] The mixing time is 60 minutes. The drying temperature is 80°C.

[0037] The drying time is 12 hours. A sodium-ion battery, wherein the sodium-ion battery contains the sodium-replenishing binder prepared in this embodiment.

[0038] The N / P ratio of the sodium-ion battery is 1.1.

[0039] The positive electrode material of the sodium-ion battery contains the following components in the following mass ratio: ternary iron-nickel-manganese-sodium positive electrode: carbon black: the sodium-supplementing binder: polyvinylidene fluoride (PVDF, battery grade) = 8.0: 1.0: 0.5: 0.5.

[0040] The negative electrode material of the sodium-ion battery contains the following components in the following mass ratio: hard carbon: carbon black: the sodium-supplementing binder: CMC = 9.0: 0.4: 0.3: 0.3.

[0041] The cycle curves of the sodium-ion battery (with sodium-added binder) in Example 1 and the cycle curves of the sodium-ion battery without sodium-added binder are as follows: Figure 1 As shown. From Figure 1 It can be seen that the sodium-ion battery (containing sodium-added binder) of Example 1 has a significantly improved cycle performance; the sodium-ion battery (containing sodium-added binder) of Example 1 has an initial coulombic efficiency of about 90.8% and an average coulombic efficiency of about 99.7%, which is higher than that of the sodium-ion battery without sodium-added binder (initial coulombic efficiency of about 80.1% and average coulombic efficiency of 99.2%).

[0042] Example 2

[0043] A sodium-supplementing binder PNNA is prepared from the following components in the following mass ratio: polyethylene oxide (PEO): polyvinylpyrrolidone (PVP): NaNO3 = 6:2:2; the molecular weight (Mw) of the polyethylene oxide is 200,000; the molecular weight (Mw) of the polyvinylpyrrolidone is 20,000; and the purity of the NaNO3 is 99.9%.

[0044] The preparation method of the sodium-supplementing binder includes the following steps: adding polyethylene oxide, polyvinylpyrrolidone and NaNO3 to 10 ml of solvent in a mass ratio of 6:2:2, stirring and mixing at 50°C to obtain a gel; drying the gel in a vacuum to obtain the sodium-supplementing binder (PNNA).

[0045] The solvent is methanol.

[0046] The mixing time is 30 minutes. The drying temperature is 40°C.

[0047] The drying time is 16 hours.

[0048] A sodium-ion battery, the sodium-ion battery containing the sodium-supplementing binder.

[0049] The N / P ratio of the sodium-ion battery is 1.0.

[0050] The positive electrode material of the sodium-ion battery contains the following components in the following mass ratio: ternary iron-nickel-manganese-sodium positive electrode: carbon black: the sodium-supplementing binder: polyvinylidene fluoride (PVDF, battery grade) = 8.5: 0.75: 0.325: 0.375.

[0051] The negative electrode material of the sodium-ion battery contains the following components in the following mass ratio: hard carbon: carbon black: the sodium-supplementing binder: CMC = 9.2: 0.3: 0.2: 0.2.

[0052] Example 3

[0053] A sodium-supplementing binder PNNA is prepared from the following components in the following mass ratio: polyethylene oxide (PEO): polyvinylpyrrolidone (PVP): NaNO3 = 8:2:2; the molecular weight (Mw) of the polyethylene oxide is 5,000,000; the molecular weight (Mw) of the polyvinylpyrrolidone is 100,000; and the purity of the NaNO3 is 99.9%.

[0054] The preparation method of the sodium-supplementing binder includes the following steps: adding polyethylene oxide, polyvinylpyrrolidone and NaNO3 to 10 ml of DMF solvent in a mass ratio of 8:2:2, stirring and mixing at 100°C to obtain a gel; drying the gel in a vacuum to obtain the sodium-supplementing binder (PNNA).

[0055] The solvent is DMF.

[0056] The mixing time is 150 minutes. The drying temperature is 120°C.

[0057] The drying time is 36 hours. A sodium-ion battery, the sodium-ion battery containing the sodium-replenishing binder.

[0058] The N / P ratio of the sodium-ion battery is 1.2.

[0059] The positive electrode material of the sodium-ion battery contains the following components in the following mass ratio: ternary iron-nickel-manganese-sodium positive electrode: carbon black: the sodium-supplementing binder: polyvinylidene fluoride (PVDF, battery grade) = 9.5: 0.25: 0.125: 0.125.

[0060] The negative electrode material of the sodium-ion battery contains the following components in the following mass ratio: hard carbon: carbon black: the sodium-supplementing binder: CMC = 9.5: 0.25: 0.125: 0.125.

[0061] Example 4

[0062] A sodium-supplementing binder PNNA is prepared from the following components in the following mass ratio: polyethylene oxide (PEO): polyvinylpyrrolidone (PVP): NaNO3 = 7:1.5:2; the molecular weight (Mw) of the polyethylene oxide is 2,000,000; the molecular weight (Mw) of the polyvinylpyrrolidone is 100,000; and the purity of the NaNO3 is 99.9%.

[0063] The preparation method of the sodium-supplementing binder includes the following steps: adding polyethylene oxide, polyvinylpyrrolidone and NaNO3 to 10 ml of solvent at a mass ratio of 7:1.5:2, stirring and mixing at 60°C to obtain a gel; and drying the gel in a vacuum to obtain the sodium-supplementing binder (PNNA).

[0064] The solvent is acetonitrile.

[0065] The mixing time is 120 minutes. The drying temperature is 90°C.

[0066] The drying time is 28 hours. A sodium-ion battery, the sodium-ion battery containing the sodium-replenishing binder.

[0067] The N / P ratio of the sodium-ion battery is 1.2.

[0068] The positive electrode material of the sodium-ion battery contains the following components in the following mass ratio: ternary iron-nickel-manganese-sodium positive electrode: carbon black: the sodium-supplementing binder: polyvinylidene fluoride (PVDF, battery grade) = 9.5: 1.0: 0.5: 0.5.

[0069] The negative electrode material of the sodium-ion battery contains the following components in the following mass ratio: hard carbon: carbon black: the sodium-supplementing binder (CMC = 9.0: 0.35: 0.25): 0.15.

[0070] The volumetric energy density of the sodium-ion batteries with sodium-supplemented negative electrodes prepared in Examples 1 to 4 above is approximately 280 Wh / L.

[0071] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A sodium-replenishing binder, characterized by, Prepared from the following components by mass ratio: polyethylene oxide: polyvinylpyrrolidone: NaNO3=(6-8):(2-1):(2-1); the molecular weight of the polyethylene oxide is 200000-5000000; the molecular weight of the polyvinylpyrrolidone is 20000-100000; the purity of the NaNO3 is 99.0%-99.9%; The preparation method of the sodium-supplementing binder comprises the following steps: adding polyethylene oxide, polyvinylpyrrolidone and NaNO3 into a solvent in a mass ratio of (6-8):(2-1):(2-1), stirring and mixing at 10-100 DEG C to obtain a gelatinous substance; and drying the gelatinous substance in a vacuum to obtain the sodium-supplementing binder. The solvent is one or a mixture of at least two of NMP, methanol, ethanol, DMF or acetonitrile; the sum of the mass of the polyethylene oxide, the polyvinylpyrrolidone and the NaNO3 is 5.0%-15.0% of the mass of the solvent.

2. The sodium supplementing binder of claim 1, wherein, The stirring and mixing time is 30-150 minutes.

3. The sodium supplement binder of claim 1, wherein, The drying temperature is 40-120 DEG C.

4. The sodium supplement binder of claim 1, wherein, The drying time is 12-36 hours.

5. A sodium-ion battery, characterized in that, The sodium ion battery contains the sodium-supplementing binder of claim 1.

6. The sodium-ion battery of claim 5, wherein, The N / P ratio of the sodium ion battery is 1.0-1.

3.

7. The sodium-ion battery of claim 6, wherein, The positive electrode material of the sodium ion battery contains the following components by mass ratio: ternary iron-nickel-manganese-sodium positive electrode: carbon black: the sodium-supplementing binder: polyvinylidene fluoride=(8.0-9.5):(1.0-0.25):(0.5-0.125):(0.5-0.125).

8. The sodium-ion battery of claim 7, wherein, The negative electrode material of the sodium ion battery contains the following components by mass ratio: hard carbon: carbon black: the sodium-supplementing binder: CMC=(9.0-9.5):(0.4-0.25):(0.3-0.125):(0.3-0.125).

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