Sodium-ion battery negative electrode composition and negative electrode sheet, sodium-ion battery

Abstract

The application discloses a sodium-ion battery negative electrode composition with good processability and a sodium-ion battery. The negative electrode composition takes hard carbon material as a negative electrode active material, and further adds a first system stabilizer and a second system stabilizer. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer. The sodium-ion battery negative electrode composition with good processability has the characteristics of good processability, excellent electrochemical performance, high safety and green environmental protection.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a sodium-ion battery negative electrode composition with good processability, a negative electrode sheet, and a sodium-ion battery. Background Technology

[0002] Sodium-ion batteries offer advantages such as abundant resources, high safety, and low cost. Biomass, due to its wide availability, abundant resources, and low cost, is widely used in the preparation of hard carbon anode materials for sodium-ion batteries.

[0003] However, biomass itself contains a large number of metal elements, such as K, Na, Ca, Mg, Fe, and Zn, resulting in a certain proportion of metal impurities in the hard carbon materials produced from biomass. If this type of hard carbon material is used directly in sodium-ion batteries, some of these metal impurities have catalytic activity and, if present at the electrode-electrolyte interface, can cause interfacial instability, leading to irreversible electrolyte decomposition and affecting the battery's cycle stability, storage performance, and calendar life. During charging, the reduction of metal ions can easily form metal dendrites, causing short circuits and posing a significant safety hazard. Furthermore, during battery slurry preparation, metal impurities dissolve in the slurry, making it alkaline and unstable, resulting in poor appearance of the coated electrodes and severely impacting processing performance.

[0004] Currently, various acids (hydrochloric acid, nitric acid, hydrofluoric acid, sulfuric acid, etc.) are generally used to dissolve impurities in hard carbon materials, thereby purifying the hard carbon and avoiding the adverse effects of metallic impurities. However, this method consumes a large amount of acid, and waste liquid treatment is also quite difficult, resulting in high costs and severe environmental pollution. Summary of the Invention

[0005] The purpose of this invention is to provide a sodium-ion battery anode composition with good processability, characterized by good processability, excellent electrochemical performance, high safety, and environmental friendliness.

[0006] This invention can be achieved through the following technical solutions: This invention discloses a sodium-ion battery anode composition with good processability, using hard carbon material as the anode active material, and also adding a first system stabilizer and a second system stabilizer. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer.

[0007] In this invention, the carboxylate ion in the system stabilizer possesses a conjugated carbon-oxygen double bond and a hydroxyl group, making it an excellent complexing ligand. During the homogenization process of preparing the negative electrode sheet for a sodium-ion battery, the additive is added to the slurry. The carboxylate (electron donor) can undergo a complexation reaction with metal ions (electron acceptors) on the surface of the hard carbon material to form a stable complex. The complex exhibits strong electrochemical stability and demonstrates electrochemical inertness during the charge and discharge process of the sodium-ion battery; therefore, the presence of metal ions does not affect the battery performance.

[0008] During the homogenization process of preparing the negative electrode sheet for sodium-ion batteries, the leaching of metallic impurities from the surface of the hard carbon material makes the slurry pH alkaline. The purpose of the first system stabilizer is to complex metal ions and neutralize the alkalinity; the purpose of the second stabilizer is to complex metal ions. The combined use of the first and second system stabilizers achieves the goals of neutralizing alkalinity and fully complexing metal ions, thereby improving the slurry processability and enhancing the battery's cycle life, storage performance, and safety.

[0009] Furthermore, the amount of the first system stabilizer added is 0.05-1.5% of the hard carbon material, and the amount of the second system stabilizer added is 0.05-1% of the hard carbon material; the mass ratio of the first system stabilizer to the second system stabilizer is 0.1-2. Specifically, the amount and ratio of stabilizers added depend on the type and content of impurities in the biomass hard carbon material. The total amount of the first system stabilizer and the second system stabilizer added is determined by the product of the number of metallic impurities and the coordination number of the metallic impurities; furthermore, the amount of the first system stabilizer added is determined by the pH of the slurry.

[0010] Furthermore, the first system stabilizer is one or more of oxalic acid, citric acid, maleic anhydride (HPMA), polyacrylic acid (PAA), polyhydroxyacrylic acid, maleic acid-acrylic acid copolymer, ethylenediaminetetraacetic acid (EDTA), and aminotriacetic acid.

[0011] Furthermore, the second system stabilizer is a sodium and / or potassium salt of the organic acid of the first system stabilizer.

[0012] Furthermore, the negative electrode composition is homogenized with a binder, dispersant, and conductive agent to form a negative electrode slurry; in the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 85-98:1.0-4.0:1.0-4.5:1.0-4.5.

[0013] Furthermore, the binder is one or more of SBR, PAA, and sodium alginate; the dispersant is CMC; and the conductive agent is one or more of Super P, carbon nanotubes, and graphene.

[0014] Furthermore, the hard carbon material is un-acid-washed and unpurified biomass hard carbon material with an ash content of 0.2-4%.

[0015] Another aspect of the present invention is to protect a sodium-ion battery negative electrode sheet, which is prepared by homogenizing the above-mentioned negative electrode composition.

[0016] Another aspect of the present invention is to protect a sodium-ion battery, comprising a positive electrode and a negative electrode, wherein the negative electrode is the aforementioned negative electrode.

[0017] Furthermore, the positive electrode is a polyanionic material positive electrode, a layered oxide material positive electrode, or a Prussian blue material positive electrode.

[0018] The present invention provides a sodium-ion battery negative electrode composition with good processability, a negative electrode sheet, and a sodium-ion battery, which has the following beneficial effects: First, good processability: During the homogenization process of preparing the negative electrode sheet for sodium-ion batteries, the leaching of metallic impurities from the surface of the hard carbon material makes the slurry pH alkaline. The purpose of the first system stabilizer is to complex metal ions and neutralize the alkalinity; the purpose of the second system stabilizer is to complex metal ions. The combined use of the first and second system stabilizers achieves the purpose of neutralizing alkalinity and completely complexing metal ions, thereby improving the processability of the sauce. Second, excellent electrochemical performance: The addition of the first system stabilizer and the second system stabilizer uses carboxylic acid to make the metal ions exist in the form of complexes. The complexes have no catalytic activity, which avoids the irreversible decomposition of the electrolyte and improves the cycle stability of the battery. At the same time, the complexes have no catalytic activity, which avoids the catalytic decomposition of the electrolyte at the negative electrode interface during battery storage and improves the battery's storage life. Third, high safety: By adding the first system stabilizer and the second system stabilizer, carboxylic acid is used to make the metal ions exist in the form of complexes. The complexes have strong electrochemical stability. The complexed metal ions do not show electrochemical inertness during the battery charging and discharging process and will not generate metal dendrites, thus improving the safety of the battery. Fourth, green and environmentally friendly: By adding the first system stabilizer and the second system stabilizer, hard carbon material can be processed into negative electrode sheets as a negative electrode active material without acid washing. There is no need to use the highly polluting acid washing and purification process. The purpose can be achieved simply by adding the first system stabilizer and the second system stabilizer to the negative electrode slurry during the pulping process. The process is simple. Attached Figure Description

[0019] Figure 1 The image shows the appearance of the electrode obtained in Example 1. Figure 2 Appearance of the electrode obtained in Application Example 2. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the product of the present invention will be further described in detail below with reference to embodiments.

[0021] This invention discloses a sodium-ion battery anode composition with good processability, using hard carbon material as the anode active material, and also adding a first system stabilizer and a second system stabilizer. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer.

[0022] Furthermore, the amount of the first system stabilizer added is 0.05-1.5% of the hard carbon material, and the amount of the second system stabilizer added is 0.05-1% of the hard carbon material; the mass ratio of the first system stabilizer to the second system stabilizer is 0.1-2.

[0023] Furthermore, the first system stabilizer is one or more of oxalic acid, citric acid, maleic anhydride (HPMA), polyacrylic acid (PAA), polyhydroxyacrylic acid, maleic acid-acrylic acid copolymer, ethylenediaminetetraacetic acid (EDTA), and aminotriacetic acid.

[0024] Furthermore, the second system stabilizer is a sodium and / or potassium salt of the organic acid of the first system stabilizer.

[0025] Furthermore, the negative electrode composition is homogenized with a binder, dispersant, and conductive agent to form a negative electrode slurry; in the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 85-98:1.0-4.0:1.0-4.5:1.0-4.5.

[0026] Furthermore, the binder is one or more of SBR, PAA, and sodium alginate; the dispersant is CMC; and the conductive agent is one or more of Super P, carbon nanotubes, and graphene.

[0027] Furthermore, the hard carbon material is un-acid-washed and unpurified biomass hard carbon material with an ash content of 0.2-4%.

[0028] Another aspect of the present invention is to protect a sodium-ion battery negative electrode sheet, which is prepared by homogenizing the above-mentioned negative electrode composition.

[0029] Another aspect of the present invention is to protect a sodium-ion battery, comprising a positive electrode and a negative electrode, wherein the negative electrode is the aforementioned negative electrode.

[0030] Furthermore, the positive electrode is a polyanionic material positive electrode, a layered oxide material positive electrode, or a Prussian blue material positive electrode.

[0031] In the positive electrode, the binder is PVDF; the conductive agent is Super P, carbon nanotubes or graphene; the mass ratio of positive electrode active material, binder and conductive agent is 90-96:2.0-5.0:2.0-5.0.

[0032] The sodium-ion batteries described above include pouch cells, cylindrical cells, and prismatic aluminum-cased cells. The added electrolyte is a carbonate-based electrolyte commonly used in the art.

[0033] Example 1 This embodiment relates to a sodium-ion battery anode composition with good processability. Hard carbon material is used as the anode active material, and a first system stabilizer and a second system stabilizer are added. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer. The amount of the first system stabilizer added is 1.5% of the hard carbon material, and the amount of the second system stabilizer added is 0.75% of the hard carbon material; the mass ratio of the first system stabilizer to the second system stabilizer is 2.

[0034] In this embodiment, the first system stabilizer is oxalic acid and citric acid. The second system stabilizer is a sodium salt of the organic acid of the first system stabilizer.

[0035] In this embodiment, the negative electrode composition is homogenized with a binder, dispersant, and conductive agent to form a negative electrode slurry. In the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 98:3:1:4.5. The binder is SBR or PAA; the dispersant is CMC; and the conductive agent is Super P or carbon nanotubes. The hard carbon material is un-acid-washed and purified biomass hard carbon material with an ash content of 0.2-4%.

[0036] Example 2 This embodiment relates to a sodium-ion battery anode composition with good processability. Hard carbon material is used as the anode active material, and a first system stabilizer and a second system stabilizer are added. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer. The amount of the first system stabilizer added is 0.75% of the hard carbon material, and the amount of the second system stabilizer added is 0.5% of the hard carbon material; the mass ratio of the first system stabilizer to the second system stabilizer is 1.5.

[0037] In this embodiment, the first system stabilizer is maleic anhydride and polyacrylic acid. The second system stabilizer is an organic acid potassium salt of the first system stabilizer.

[0038] In this embodiment, the negative electrode composition is homogenized with a binder, dispersant, and conductive agent to form a negative electrode slurry. In the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 91:1:4.5:3. The binder is PAA (sodium alginate); the dispersant is CMC; and the conductive agent is Super P (graphene). The hard carbon material is un-acid-washed and purified biomass hard carbon material with an ash content of 0.2-4%.

[0039] Example 3 This embodiment relates to a sodium-ion battery anode composition with good processability. Hard carbon material is used as the anode active material, and a first system stabilizer and a second system stabilizer are added. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer. The amount of the first system stabilizer added is 0.1% of the hard carbon material, and the amount of the second system stabilizer added is 1% of the hard carbon material; the mass ratio of the first system stabilizer to the second system stabilizer is 0.1.

[0040] In this embodiment, the first system stabilizer is oxalic acid, polyhydroxyacrylic acid, and maleic acid-acrylic acid copolymer. The second system stabilizer is the sodium and potassium salts of the organic acid of the first system stabilizer.

[0041] In this embodiment, the negative electrode composition is homogenized with a binder, dispersant, and conductive agent to form a negative electrode slurry. In the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 85:4.0:3:1. The binder is SBR, PAA, or sodium alginate; the dispersant is CMC; and the conductive agent is carbon nanotubes or graphene. The hard carbon material is un-acid-washed and purified biomass hard carbon material with an ash content of 0.2-4%.

[0042] Example 4 This embodiment relates to a sodium-ion battery anode composition with good processability. Hard carbon material is used as the anode active material, and a first system stabilizer and a second system stabilizer are added. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer. The amount of the first system stabilizer added is 1% of the hard carbon material, and the amount of the second system stabilizer added is also 1% of the hard carbon material; the mass ratio of the first system stabilizer to the second system stabilizer is 1:1.

[0043] In this embodiment, the first system stabilizer is oxalic acid, citric acid, maleic acid-acrylic acid copolymer, ethylenediaminetetraacetic acid, and aminotriacetic acid. The second system stabilizer is the sodium and potassium salts of the organic acid stabilizers in the first system.

[0044] In this embodiment, the negative electrode composition is homogenized with a binder, dispersant, and conductive agent to form a negative electrode slurry. In the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 90:3:2:2. The binder is SBR; the dispersant is CMC; and the conductive agents are Super P and graphene. The hard carbon material is un-acid-washed and purified biomass hard carbon material with an ash content of 0.2-4%.

[0045] Example 5 This embodiment relates to a sodium-ion battery anode composition with good processability. Hard carbon material is used as the anode active material, and a first system stabilizer and a second system stabilizer are added. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer. The amount of the first system stabilizer added is 1.2% of the hard carbon material, and the amount of the second system stabilizer added is 0.8% of the hard carbon material; the mass ratio of the first system stabilizer to the second system stabilizer is 1.5.

[0046] In this embodiment, the first system stabilizer is oxalic acid, citric acid, ethylenediaminetetraacetic acid, and aminotriacetic acid. The second system stabilizer is the sodium and potassium salts of the organic acids of the first system stabilizer.

[0047] In this embodiment, the negative electrode composition is homogenized with a binder, dispersant, and conductive agent to form a negative electrode slurry. In the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 88:4:4:4. The binder is SBR, PAA, and sodium alginate; the dispersant is CMC; and the conductive agent is Super P, carbon nanotubes, and graphene. The hard carbon material is un-acid-washed and purified biomass hard carbon material with an ash content of 0.2-4%.

[0048] Application Example 1 This embodiment relates to a sodium-ion battery negative electrode composition with good processability and a sodium-ion battery. The preparation process of the sodium-ion battery includes the following steps: S1. Preparation of negative electrode sheet: Biomass hard carbon material, SBR, CMC, Super P, oxalic acid, and sodium oxalate are homogenized in an aqueous solution, coated onto a current collector, dried, rolled, and sliced ​​to obtain the negative electrode sheet. The ash content of the biomass hard carbon material is 2.0%; the addition amounts of oxalic acid and sodium oxalate are 0.20% and 0.10% of the total hard carbon material addition, respectively; the mass ratio of biomass hard carbon material, SBR, CMC, and Super P is 94.5:2.5:1.5:1.5.

[0049] S2. Preparation of the positive electrode sheet: The composite sodium iron phosphate, PVDF, and Super P are homogenized in NMP solution, coated onto the current collector, dried, rolled, and sliced ​​to obtain the positive electrode sheet. The mass ratio of the composite sodium iron phosphate, binder, and conductive agent is 94:3.5:2.5.

[0050] S3. Assembly of the sodium-ion battery: The negative electrode, positive electrode, and electrolyte are assembled into a 1Ah soft-pack sodium-ion battery. The electrolyte is a 1M NaPF6 / EC+DEC+PC (1:1:1 vol.%) mixture. Battery performance testing is then conducted.

[0051] Application Example 2 This embodiment relates to a sodium-ion battery negative electrode composition with good processability and a sodium-ion battery. The preparation process of the sodium-ion battery includes the following steps: S1. Preparation of negative electrode sheet: Biomass hard carbon material, SBR, CMC, Super P, citric acid, and sodium citrate are homogenized in an aqueous solution, coated onto a current collector, dried, rolled, and sliced ​​to obtain the negative electrode sheet. The ash content of the biomass hard carbon material is 2.0%; the addition amounts of oxalic acid and sodium oxalate are 0.20% and 0.10% of the total hard carbon material addition, respectively; the mass ratio of biomass hard carbon material, SBR, CMC, and Super P is 94.5:2.5:1.5:1.5.

[0052] S2. Preparation of the positive electrode sheet: The composite sodium iron phosphate, PVDF, and Super P are homogenized in NMP solution, coated onto the current collector, dried, rolled, and sliced ​​to obtain the positive electrode sheet. The mass ratio of the composite sodium iron phosphate, binder, and conductive agent is 94:3.5:2.5.

[0053] S3. Assembly of the sodium-ion battery: The negative electrode, positive electrode, and electrolyte are assembled into a 1Ah soft-pack sodium-ion battery. The electrolyte is a 1M NaPF6 / EC+DEC+PC (1:1:1 vol.%) mixture. Battery performance testing is then conducted.

[0054] Comparative Example 1 This embodiment relates to a sodium-ion battery, and the preparation process of the sodium-ion battery includes the following steps: S1. Preparation of negative electrode sheet: Biomass hard carbon material, SBR, CMC and Super P are homogenized in an aqueous solution, coated onto a current collector, dried, rolled, and sliced ​​to obtain the negative electrode sheet. The ash content of the biomass hard carbon material is 2.0%; the mass ratio of biomass hard carbon material, SBR, CMC and Super P is 94.5:2.5:1.5:1.5.

[0055] S2. Preparation of the positive electrode sheet: The composite sodium iron phosphate, PVDF, and Super P are homogenized in NMP solution, coated onto the current collector, dried, rolled, and sliced ​​to obtain the positive electrode sheet. The mass ratio of the composite sodium iron phosphate, binder, and conductive agent is 94:3.5:2.5.

[0056] S3. Assembly of the sodium-ion battery: The negative electrode, positive electrode, and electrolyte are assembled into a 1Ah soft-pack sodium-ion battery. The electrolyte is a 1M NaPF6 / EC+DEC+PC (1:1:1 vol.%) mixture. Battery performance testing is then conducted.

[0057] The pH of the slurry was tested during the anode homogenization process. The pH values ​​for Application Example 1, Application Example 2, and Comparative Example 1 were 7.5, 7.2, and 9.5, respectively, indicating that the additive effectively reduced the pH of the slurry to near neutral. During the anode coating process, the slurries in Application Example 1 and Application Example 2 exhibited better fluidity, and the coated electrodes showed better appearance. Figure 1 The slurry in Comparative Example 1 had poor fluidity and the coated electrode had a poor appearance with obvious streaks, indicating that the coated electrode was not uniform. Figure 2 ).

[0058] The pouch cells were tested within a voltage range of 3.4-1.5V at a 1C@1C rate. The first-cycle efficiencies of Application Example 1, Application Example 2, and Comparative Example 1 were 90.82%, 90.21%, and 89.07%, respectively, indicating that the additive can effectively improve the interface stability of sodium-ion batteries, thereby improving the first-cycle efficiency.

[0059] After 1000 cycles, the capacity retention rates of the pouch cells in Application Example 1, Application Example 2, and Comparative Example 1 were 94.3%, 93.2%, and 92.5%, respectively, indicating that the system stabilizer can effectively improve the cycle stability of sodium-ion batteries. The pouch cells in Application Example 1, Application Example 2, and Comparative Example 1 were stored at 25°C for 60 days at 100% SOC. The capacity retention and recovery rates of the pouch cell in Application Example 1 were 94.62% and 95.62%, respectively; those in Application Example 2 were 94.05% and 95.32%, respectively; and those in Comparative Example 1 were 92.08% and 91.41%, respectively. This indicates that the additive can significantly improve the storage performance of sodium-ion batteries.

[0060] Test results show that the performance of sodium-ion batteries is significantly improved. This is because carboxylic acid reacts with metal ions on the surface of hard carbon materials to form stable complexes. These complexes exhibit strong electrochemical stability and lack catalytic activity, displaying electrochemical inertness during the charge and discharge process of sodium-ion batteries, thus avoiding the adverse effects of metal ions in biomass hard carbon materials.

[0061] Table 1 Performance Test Results The above embodiments are merely specific examples of the present invention, and their descriptions are quite specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these obvious substitutions all fall within the protection scope of the present invention.

Claims

1. A sodium-ion battery negative electrode slurry, characterized in that: the negative electrode slurry is formed by homogenizing a negative electrode composition with a binder, a dispersant, and a conductive agent; The negative electrode composition comprises hard carbon material, a first system stabilizer, and a second system stabilizer. The first system stabilizer is a carboxylic acid organic acid, and the second system stabilizer is an organic acid salt of the first system stabilizer. The amount of the first system stabilizer added is 0.05-1.5% of the mass of the hard carbon material, and the amount of the second system stabilizer added is 0.05-1% of the mass of the hard carbon material. The mass ratio of the first system stabilizer to the second system stabilizer is 0.1-2. The hard carbon material is un-acid-washed and purified biomass hard carbon material with an ash content of 0.2-4%. In the negative electrode slurry, the mass ratio of hard carbon material, binder, dispersant, and conductive agent is 85-98: 1.0-4.0：1.0-4.5：1.0-4.5。 2. The sodium-ion battery negative electrode slurry according to claim 1, characterized in that: The stabilizer of the first system is one or more of oxalic acid, citric acid, maleic anhydride, polyacrylic acid, polyhydroxyacrylic acid, maleic acid-acrylic acid copolymer, ethylenediaminetetraacetic acid, and aminotriacetic acid.

3. The sodium-ion battery negative electrode slurry according to claim 1, characterized in that: The second system stabilizer is a sodium and / or potassium salt of the organic acid of the first system stabilizer.

4. The sodium-ion battery negative electrode slurry according to claim 1, characterized in that: The binder is one or more of SBR, PAA, and sodium alginate; the dispersant is CMC; and the conductive agent is one or more of Super P, carbon nanotubes, and graphene.

5. A sodium-ion battery negative electrode sheet, characterized in that: It is prepared using the sodium-ion battery negative electrode slurry according to any one of claims 1-4.

6. A sodium-ion battery, comprising a positive electrode and a negative electrode, characterized in that: The negative electrode sheet is the negative electrode sheet according to claim 5.

7. The sodium-ion battery according to claim 6, characterized in that: The positive electrode is a polyanionic material positive electrode, a layered oxide material positive electrode, or a Prussian blue material positive electrode.

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