Positive electrode supplementing current collector material and sodium ion battery

Abstract

The application discloses a novel positive electrode sodium supplementing current collector material, and belongs to the technical field of sodium ion batteries. The current collector comprises a microporous aluminum foil layer and a positive electrode sodium supplementing material layer coated on the surface of the aluminum foil layer; wherein the positive electrode sodium supplementing material layer comprises a sodium salt (one or more of Na2C2O4, NaN3, Na2S and Na2CO3) which is easy to dissociate within the working voltage range of the battery. The current collector of the application can meet different sodium supplementing requirements according to actual needs by regulating the type of sodium salt, improve the initial coulomb efficiency of the battery, and thus improve the comprehensive performance of the sodium ion battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery materials technology, and in particular to a current collector material for positive electrode replenishment and a sodium-ion battery. Background Technology

[0002] Lithium-ion batteries have been widely used in the new energy vehicle field due to their advantages such as high energy density, long cycle life, and safety. However, due to the scarcity and high cost of lithium resources, they are unlikely to meet all future demands. Therefore, sodium-ion batteries have emerged as a potential alternative to lithium-ion batteries. However, sodium-ion batteries still face many technical challenges in their industrialization process, such as low initial charge-discharge efficiency, short cycle life, and low energy density. Irreversible loss of active sodium is one of the core issues leading to battery capacity decay and shortened cycle life.

[0003] During the charge and discharge process of sodium-ion batteries, sodium ions undergo reversible intercalation and deintercalation reactions between the positive and negative electrodes. However, due to side reactions such as the formation of the solid electrolyte interphase (SEI) film and electrolyte decomposition, some sodium ions are irreversibly consumed, leading to a continuous reduction in the amount of recyclable sodium ions in the electrode active materials. Particularly under conditions of high operating voltage (>4.0 V vs. Na / Na⁺), high temperature (>60°C), or high-current fast charging, the side reactions at the electrode / electrolyte interface are exacerbated, significantly accelerating the loss of active sodium. Furthermore, traditional sodium-ion battery positive electrode materials (such as layered oxides and polyanionic compounds) and negative electrode materials (such as hard carbon) typically exhibit significant irreversible capacity loss during the first charge and discharge cycle (initial coulombic efficiency is generally below 80%), further reducing the battery's actual usable capacity and energy density.

[0004] Current main strategies for addressing sodium loss include pre-sodiuming of electrode materials and optimization of electrolyte additives. Pre-sodiuming technology provides additional sodium ions during the first charge of the battery to compensate for irreversible losses by introducing electrochemical pre-sodiuming (e.g., using metallic sodium foil), chemical pre-sodiuming (using reducing agents such as sodium naphthalene solution), or adding sacrificial sodium sources (e.g., NaN3, Na2C4O4). However, these methods suffer from high process complexity (requiring strict control of the water and oxygen environment), safety risks (some pre-sodiuming reagents are highly reactive), and high costs, which limit their large-scale application. While electrolyte additives (e.g., FEC, CsPF6) can suppress side reactions by optimizing the SEI / CEI interface film, their sodium compensation capacity is limited, and they may introduce new interfacial instabilities such as increased electrolyte viscosity and decreased ionic conductivity.

[0005] As a core component of a battery, the current collector plays a crucial role in collecting and conducting current, and its performance directly affects the battery's energy efficiency and cycle stability. Traditional sodium-ion batteries typically use aluminum foil (positive electrode) and copper foil (negative electrode) as current collectors. While these materials provide necessary conductive and mechanical support, they only exist as passive conductive substrates and cannot address the problem of active sodium loss. In recent years, some research has attempted to improve interfacial stability by constructing conductive coatings (such as carbon-based materials or conductive polymers) on the current collector surface. However, these improvements have not yet addressed the realization of sodium compensation functionality. Furthermore, the interfacial contact impedance between traditional current collectors and electrode materials remains high, potentially leading to uneven local current distribution. This non-uniformity can accelerate sodium dendrite growth or cause active material to detach from the electrode. In summary, in existing sodium-ion battery technologies, irreversible loss of active sodium severely restricts the battery's cycle life. Traditional sodium compensation strategies (such as pre-sodium treatment and electrolyte additives) have significant limitations, including complex processes, high costs, and limited effectiveness. Meanwhile, traditional current collectors only serve a conductive function and cannot actively participate in the sodium compensation process. Therefore, there is an urgent need to develop novel composite current collector structures that simultaneously possess efficient charge transport capabilities and active sodium compensation functions. Such innovative designs are expected to overcome the shortcomings of existing technologies and meet the practical application requirements of next-generation sodium-ion batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention proposes a current collector material for sodium replenishment at the positive electrode and a sodium-ion battery. By regulating the composite current collector, different sodium replenishment requirements can be met according to actual needs, thereby improving the initial coulombic efficiency of the battery and enhancing the overall performance of the sodium-ion battery.

[0007] Specifically, in order to achieve the above objectives, the present invention adopts the following technical solution: a current collector material for positive electrode sodium replenishment, comprising: a microporous aluminum foil layer, a positive electrode sodium replenishment material layer coated on the surface of the aluminum foil layer, and a microporous aluminum foil layer further rolled on the sodium replenishment material layer; wherein the positive electrode sodium replenishment material layer comprises sodium salt, conductive carbon and binder.

[0008] Furthermore, the sodium salt mentioned above includes one or more of Na2C2O4, NaN3, Na2S, and Na2CO3; the conductive carbon is one or more of carbon black, conductive graphite, carbon nanotubes, graphene, and acetylene black; and the binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylamide, polyacrylamide, and hydroxyethyl cellulose.

[0009] Furthermore, the aforementioned positive electrode sodium replenishment material layer includes 70wt%-90wt% of positive electrode pre-sodium additive, 1wt%-15wt% of conductive carbon, and 1wt%-15wt% of binder.

[0010] The thickness of the microporous aluminum foil layer is 1~100μm, and micropores are uniformly distributed on the microporous aluminum foil layer, with the pore size being 1~20μm.

[0011] A novel method for preparing a positive electrode current collector includes the following steps:

[0012] (1) Add the adhesive to N-methylpyrrolidone solvent and stir until homogeneous to obtain the adhesive solution;

[0013] (2) Mix and stir the sodium salt, conductive carbon and the adhesive solution obtained in step (1) to obtain a slurry;

[0014] (3) Coat the surface of the microporous aluminum foil with the slurry that has been stirred and homogenized.

[0015] (4) Roll the obtained current collector.

[0016] Furthermore, the roller pressing pressure is 100~900Kg.

[0017] Furthermore, the viscosity of the above slurry is 1000-9000 cp.s.

[0018] Specifically, the preparation method of the above-mentioned positive electrode pre-sodium current collector includes the following steps:

[0019] (1) At room temperature of 25°C, add the adhesive to the solvent and stir for 12-24 hours to prepare a transparent adhesive solution with a solid content of 1%-10%. Take it out and set it aside.

[0020] (2) Add the prepared adhesive solution, positive electrode pre-sodium additive, and conductive carbon to the homogenizer at a certain ratio. The homogenizer rotates at 20-50 rpm and 500-5000 rpm, and stirs for 3-24 hours to make it evenly mixed.

[0021] (3) Adjust the viscosity of the slurry to 1000-9000 cp.s, fill it evenly into the microporous aluminum foil, and then dry and roll it. The drying temperature is 25℃-70℃.

[0022] (4) Another piece of microporous aluminum foil is brought into contact with the positive electrode sodium-replenishing material layer and rolled to obtain a composite current collector material for positive electrode sodium replenishment.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention provides a current collector for sodium replenishment in the positive electrode. Sodium salts with high dissociation potential are preferred as the sodium replenishment material in the positive electrode. The charging cut-off voltage can be intermittently increased according to actual needs, and the charging current and charging time can be controlled to release sodium ions and replenish the irreversibly lost sodium source, thereby improving the battery's first charge and discharge efficiency, energy density and cycle life. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of the structure of a novel positive electrode current collector for sodium replenishment according to the present invention;

[0027] Figure 2 The charge-discharge curves of the sodium-ion battery prepared using the positive electrode sodium current collector of Example 1 at 2-4V are shown.

[0028] Figure 3 The charge-discharge curves of the sodium-ion battery prepared using the positive electrode pre-sodium current collector of Example 2 are shown at 2-4V.

[0029] Figure 4 The charge-discharge curves of the sodium-ion battery prepared using the positive electrode pre-sodium current collector of Example 3 are shown at 2-4V.

[0030] Figure 5 The charge-discharge curves of the sodium-ion battery prepared using the positive electrode pre-sodium current collector of Example 4 are shown at 2-4V.

[0031] Figure 6 The charge-discharge curves of the sodium-ion battery prepared using the positive electrode pre-sodium current collector of Comparative Example 1 are shown at 2-4V. Detailed Implementation

[0032] The following detailed description, in conjunction with embodiments of the present invention and accompanying drawings, provides a clear and complete illustration of the technical solutions in these embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] It should be noted that all technical terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0034] Example 1

[0035] S1. Preparation and coating of positive electrode sodium supplementation material

[0036] (1) At room temperature of 25°C, weigh 4 wt% of PVDF adhesive and dissolve it in N-methylpyrrolidone solvent. Stir for 24 hours to prepare a transparent adhesive solution with a solid content of 4%. Take it out and set it aside.

[0037] (2) The positive electrode sodium supplementation additive Na2C2O4 and conductive carbon SP are mixed in a ratio of 7:2 and then mixed evenly using a planetary mixer. During the mixing process, the speed is maintained at 50 rpm for revolution and 5000 rpm for rotation, and the mixing time is 10 h.

[0038] (3) Add an appropriate amount of the prepared adhesive solution and N-methylpyrrolidone solvent to the above mixture and continue stirring and mixing, maintaining a rotation speed of 50 rpm for revolution and 5000 rpm for 10 hours;

[0039] (4) Adjust the viscosity of the slurry to 3000 cp.s and fill it evenly on the porous aluminum foil current collector 100 with a thickness of 12μm and a pore size of 50μm. The thickness of the sodium supplement layer is 12μm and the surface density is 20g / m2.

[0040] S2. Preparation of a current collector containing a positive electrode sodium-supplementing material layer

[0041] After drying at 60℃, the material is rolled to obtain a positive electrode sodium-filling current collector with a smooth surface.

[0042] Example 2

[0043] S1. Preparation and coating of positive electrode sodium supplementation material

[0044] (1) At room temperature of 25°C, weigh 4 wt% of PVDF adhesive and dissolve it in N-methylpyrrolidone solvent. Stir for 24 hours to prepare a transparent adhesive solution with a solid content of 4%. Take it out and set it aside.

[0045] (2) The positive electrode sodium supplement Na2S and conductive carbon SP are mixed in a ratio of 8:1 and then mixed evenly using a planetary mixer. During mixing, the speed is maintained at 50 rpm for revolution and 5000 rpm for rotation, and the mixing time is 10 h.

[0046] (3) Add an appropriate amount of the prepared adhesive solution and N-methylpyrrolidone solvent to the above mixture and continue stirring and mixing, maintaining a rotation speed of 50 rpm for revolution and 5000 rpm for 10 hours;

[0047] (4) Adjust the viscosity of the slurry to 9000 cp.s and fill it evenly on the porous aluminum foil current collector 100 with a thickness of 12μm and a pore size of 50μm. The thickness of the sodium supplement layer is 12μm and the surface density is 20g / m2.

[0048] S2. Preparation of a current collector containing a positive electrode sodium-supplementing material layer

[0049] After drying at 60℃, the material is rolled to obtain a positive electrode sodium-filling current collector with a smooth surface.

[0050] Example 3

[0051] S1. Preparation and coating of positive electrode sodium supplementation material

[0052] (1) At room temperature of 25°C, weigh 4 wt% of PVDF adhesive and dissolve it in N-methylpyrrolidone solvent. Stir for 24 hours to prepare a transparent adhesive solution with a solid content of 4%. Take it out and set it aside.

[0053] (2) The positive electrode sodium supplement additive Na3N and conductive carbon SP are mixed in a ratio of 8:1 and then mixed evenly using a planetary mixer. During mixing, the speed is maintained at 50 rpm for revolution and 5000 rpm for rotation, and the mixing time is 10 h.

[0054] (3) Add an appropriate amount of the prepared adhesive solution and N-methylpyrrolidone solvent to the above mixture and continue stirring and mixing, maintaining a rotation speed of 50 rpm for revolution and 5000 rpm for 10 hours;

[0055] (4) Adjust the viscosity of the slurry to 5000 cp.s and fill it evenly on the porous aluminum foil current collector 100 with a thickness of 12μm and a pore size of 50μm. The thickness of the sodium supplement layer is 12μm and the surface density is 20g / m2.

[0056] S2. Preparation of a current collector containing a positive electrode sodium-supplementing material layer

[0057] After drying at 60℃, the material is rolled to obtain a positive electrode sodium-filling current collector with a smooth surface.

[0058] Example 4

[0059] S1. Preparation and coating of positive electrode sodium supplementation material

[0060] (1) At room temperature of 25°C, weigh 10wt% of adhesive PVDF and dissolve it in N-methylpyrrolidone solvent. Stir for 24 hours to prepare a transparent adhesive solution with a solid content of 10%. Take it out and set it aside.

[0061] (2) The positive electrode sodium supplement Na2CO3 and conductive carbon SP are mixed in a ratio of 7:2 and then mixed evenly using a planetary mixer. During mixing, the speed is maintained at 50 rpm for revolution and 5000 rpm for rotation, and the mixture is stirred for 10 hours.

[0062] (3) Add an appropriate amount of the prepared adhesive solution and N-methylpyrrolidone solvent to the above mixture and continue stirring and mixing, maintaining a rotation speed of 50 rpm for revolution and 5000 rpm for 10 hours;

[0063] (4) Adjust the viscosity of the slurry to 12000 cp.s and fill it evenly on top of the porous aluminum foil current collector 100 with a thickness of 12μm and a pore size of 50μm. The thickness of the sodium supplement layer is 12μm and the surface density is 20g / m2.

[0064] S2. Preparation of a current collector containing a positive electrode sodium-supplementing material layer

[0065] After drying at 60℃, the material is rolled to obtain a positive electrode sodium-filling current collector with a smooth surface.

[0066] Comparative Example 1

[0067] In this comparative example, aluminum foil was used as the current collector, and the substrate aluminum foil was 12μm thick.

[0068] Application examples

[0069] The positive electrode sodium-compensating current collectors prepared in Examples 1-4 and the current collector prepared in Comparative Example 1 were applied to sodium-ion batteries. The specific preparation method of the sodium-ion battery is as follows:

[0070] (1) Preparation of positive electrode sheet: N-methylpyrrolidone (NMP) and polyvinylidene fluoride (PVDF) are prepared into a gel solution, and then mixed with layered oxide positive electrode material, conductive carbon black (SP) and an appropriate amount of NMP solvent. The ratio of each component is NFM111:PVDF:SP = 7:2:1. After stirring for 30 minutes to make it uniform, it is coated onto the positive electrode sodium-supplementing composite current collector or aluminum foil to prepare the positive electrode sheet.

[0071] (2) Battery assembly: The obtained positive electrode and sodium metal electrode are assembled into a sodium-ion coin cell, and the electrochemical performance of the sodium-ion battery prepared above is tested.

[0072] Figure 2 The normal charge-discharge curves of the positive electrode sodium-filled current collector prepared in Example 1 applied to a sodium-ion battery show that the first discharge specific capacity is 116.05 mAh / g and the first charge-discharge efficiency is 90.69%.

[0073] Figure 3 The normal charge-discharge curves of the positive electrode sodium-filled current collector prepared in Example 2 applied to a sodium-ion battery show that the first discharge specific capacity is 113.31 mAh / g and the first charge-discharge efficiency is 91.24%.

[0074] Figure 4 The normal charge-discharge curves of the positive electrode sodium-filled current collector prepared in Example 3 applied to a sodium-ion battery show that the first discharge specific capacity is 112.73 mAh / g and the first charge-discharge efficiency is 90.13%.

[0075] Figure 5The normal charge-discharge curves of the positive electrode sodium-filled current collector prepared in Example 4 applied to a sodium-ion battery show that the first discharge specific capacity is 115.79 mAh / g and the first charge-discharge efficiency is 91.04%.

[0076] Figure 6 The normal charge-discharge curve of the positive electrode sodium-filled current collector prepared in Comparative Example 1 is shown when applied to a sodium-ion battery. It can be seen that the specific capacity of the first discharge cycle is 108.33 mAh / g and the first charge-discharge efficiency is 84.52%.

[0077] Table 1:

[0078] Group Discharge specific capacity / mAh / g First charge / discharge efficiency % Example 1 116.05 90.69 Example 2 113.31 91.24 Example 3 112.73 90.13 Example 4 115.79 91.04 Comparative Example 1 108.33 84.52

[0079] As can be seen from Table 1 above, the present invention coats the positive electrode sodium supplementation additive onto the microporous aluminum foil, which can improve the battery's first charge-discharge efficiency and specific capacity.

[0080] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0081] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0082] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A current collector material for positive electrode sodium supplementation, characterized in that, It includes a microporous aluminum foil layer, a positive electrode sodium-supplementing material layer coated on the surface of the aluminum foil layer, and a microporous aluminum foil layer further rolled on the sodium-supplementing material layer.

2. The current collector material for positive electrode sodium replenishment according to claim 1, characterized in that, The thickness of the microporous aluminum foil layer is 1~100μm.

3. The current collector material for positive electrode sodium replenishment according to claim 1, characterized in that, The microporous aluminum foil layer has micropores uniformly distributed on it, and the pore size is 1~20μm.

4. The current collector material for positive electrode sodium replenishment according to claim 1, characterized in that, The positive electrode sodium-supplementing material layer includes sodium salt, conductive carbon, and binder.

5. The current collector material for positive electrode sodium replenishment according to claim 4, characterized in that, The sodium salt includes one or more of Na2C2O4, NaN3, Na2S, and Na2CO3; the conductive carbon is one or more of carbon black, conductive graphite, carbon nanotubes, graphene, and acetylene black; and the binder is one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylamide, polyacrylamide, and hydroxyethyl cellulose.

6. The current collector material for positive electrode sodium replenishment according to claim 4, characterized in that, The positive electrode sodium replenishment material layer includes 70wt%-90wt% positive electrode pre-sodium additive, 1wt%-15wt% conductive carbon, and 1wt%-15wt% binder.

7. A novel method for preparing a positive electrode current collector, characterized in that, The preparation method includes the following steps: (1) Add the adhesive to N-methylpyrrolidone solvent and stir until homogeneous to obtain the adhesive solution; (2) Mix and stir the sodium salt, conductive carbon and the adhesive solution obtained in step (1) to obtain a slurry; (3) Coat the surface of the microporous aluminum foil with the slurry that has been stirred and homogenized. (4) Roll the obtained current collector.

8. The method for preparing a current collector material for positive electrode sodium supplementation according to claim 7, characterized in that, The roller pressing pressure is 100~900Kg.

9. The method for preparing a current collector material for positive electrode sodium supplementation according to claim 7, characterized in that, The viscosity of the slurry is 1000-9000 cp.s.

10. A sodium-ion battery, characterized in that, Includes the positive electrode sodium replenishment material layer as described in claim 1.

Images