Sodium-ion battery positive electrode slurry, positive electrode plate and sodium-ion battery

Abstract

The invention discloses sodium ion battery positive electrode slurry, a positive electrode plate and a sodium ion battery. The sodium ion battery positive electrode slurry is prepared from the following materials in percentage by mass: 93-97% of a positive electrode main material; 1%-3% of a binder; 1%-5% of a conductive agent; 0.1%-0.5% of an alkaline regulator; and the positive electrode main material is a mixture of a layered oxide sodium battery positive electrode and a polyanion sodium battery positive electrode. The positive pole piece prepared from the layered oxide and polyanion mixed positive pole material is high in compaction, and the obtained sodium ion battery has excellent first effect, energy density, cycle performance and safety performance. The method is simple to operate, slurry mixing is performed in a low-humidity environment in a manner of neutralizing residual alkali on the surface of the material by adopting maleic anhydride, and the obtained positive electrode slurry is good in viscosity and stability, excellent in dispersion effect and excellent in gel resistance.

Description

Technical Field

[0001] The invention relates to a sodium ion battery positive electrode slurry, a positive electrode sheet and a sodium ion battery, belonging to the technical field of sodium ion batteries. Background Art

[0002] In recent years, due to the development of lithium-ion batteries, lithium ore resources have become increasingly scarce, upstream material prices have continued to rise, and the cost of lithium batteries has remained high. Sodium-ion batteries have broad application prospects in the fields of energy storage and two-wheeled vehicles due to their abundant sodium resources, lower cost than lithium batteries, and good safety performance. Their working principle is similar to that of lithium-ion batteries, using the reversible insertion and removal of sodium ions between the positive and negative electrodes to achieve energy storage and release.

[0003] The positive electrode of sodium ion batteries is made of polyanion materials, Prussian blue system materials, transition metal layered oxide materials, etc. Among them, transition metal layered oxides have high specific capacity and good processing performance, but their structural stability is poor and the cycle performance needs to be improved. Polyanions have loose ion channels and excellent cycle performance, but their tap density is low, compaction is low, and specific capacity is low. The two materials complement each other, so blending them to make sodium ion batteries is a good direction. Summary of the invention

[0004] The object of the present invention is to provide a sodium ion battery positive electrode slurry, a positive electrode sheet and a sodium ion battery. The positive electrode slurry of the present invention has good viscosity and stability, excellent dispersion effect, excellent anti-gel property, and a simple and efficient preparation process and high production efficiency. The positive electrode sheet of the present invention has high compaction, and the sodium ion battery has excellent first efficiency, energy density, cycle performance and safety performance.

[0005] The sodium ion battery positive electrode slurry provided by the present invention is made of the following materials in percentage by weight: Positive electrode main material 93%~97%; binder 1%~3%; conductive agent 1%~5%; alkaline regulator 0.1%~0.5%; The main material of the positive electrode is a mixture of a layered oxide sodium positive electrode and a polyanion sodium positive electrode; Wherein, the mass ratio of the layered oxide sodium positive electrode to the polyanion sodium positive electrode is 7-9:1-3, preferably 9:1, 8:2 or 7:3; The chemical formula of the layered oxide sodium positive electrode is Na x MO 2 , M is at least one of Ni, Co, Mn, Fe, Cu, Ti, and V, 0<x≤1; The chemical formula of the polyanion positive electrode is Na 4 Fe y (PO 4 ) 2 P2 O 7 , 2<y<3.

[0006] In the present invention, the alkaline regulator may be anhydrous oxalic acid and / or anhydrous maleic anhydride; The conductive agent may be one or more of conductive carbon black, superconducting carbon black, Ketjen black, graphene conductive slurry, and single-walled carbon nanotubes; The binder may be oily polyvinylidene fluoride (PVDF).

[0007] The present invention further provides a method for preparing the sodium ion battery positive electrode slurry, comprising the following steps: S1, mixing a part of the solvent with the binder, stirring and dispersing to obtain a glue solution; S2, adding the alkaline regulator and the conductive agent to the glue solution in sequence, stirring and dispersing to obtain a conductive glue; S3, adding a part of the positive electrode main material to the conductive glue, stirring and dispersing, then adding the remaining amount of the positive electrode main material, and adding the remaining amount of the solvent to adjust the viscosity.

[0008] Based on the sodium ion battery positive electrode slurry, the present invention also provides a sodium ion battery positive electrode plate, including a current collector and a positive electrode active material layer arranged on at least one side of the current collector, and the positive electrode active material layer is made of the sodium ion battery positive electrode slurry.

[0009] On the basis of the sodium ion battery positive electrode sheet, the present invention further provides a sodium ion battery, comprising the sodium ion battery positive electrode sheet, the sodium ion battery negative electrode sheet and a separator arranged between the sodium ion battery positive electrode sheet and the sodium ion battery negative electrode sheet; The negative electrode plate is a hard carbon or soft carbon negative electrode plate.

[0010] The diaphragm is at least one of polypropylene, polyethylene and glass fiber.

[0011] The present invention has the following beneficial technical effects: 1. The present invention is simple to operate. Maleic anhydride is used to neutralize the residual alkali on the surface of the material. The slurry is mixed in a low-humidity environment. The obtained positive electrode slurry has good viscosity and stability, excellent dispersion effect, and excellent anti-gelling property.

[0012] 2. The positive electrode material is a mixture of layered oxides and polyanions. The prepared positive electrode sheet has high compaction, and the obtained sodium ion battery has excellent first efficiency, energy density, cycle performance and safety performance. DETAILED DESCRIPTION

[0013] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0014] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0015] Example 1. Preparation of positive electrode slurry for sodium ion battery Layered oxide sodium cathode Na 0.91 Ni 0.22 Fe 0.33 Mn 0.33 Cu 0.11 O 2 and polyanion sodium cathode (Na 4 Fe 2.91 (PO 4 ) 2 P 2 O 7 ) are mixed in a ball mill in a ratio of 9:1 and set aside; in a -30°C dew point environment, part of the solvent (NMP) and the binder (PVDF) are mixed, stirred and dispersed to obtain a glue solution; an alkaline regulator (anhydrous maleic anhydride) is added, mixed and dispersed; a conductive agent (conductive carbon black and carbon nanotubes) is added, mixed, stirred and dispersed to obtain a conductive glue; first a part (40% specific amount) of the mixed positive electrode main material is added, stirred and dispersed for a certain time, and then the remaining positive electrode main material is added, and dispersed at high speed for a certain time; a certain amount of solvent is added to adjust the viscosity; after the homogenization is completed, the poured positive electrode slurry is filtered with a 150-mesh filter and set aside.

[0016] In this embodiment, the total amount of the positive electrode main material, the binder, the alkaline regulator and the conductive agent is prepared, and the amount of each raw material is: the positive electrode main material is 96%, the binder is 1.5%, the alkaline regulator is 0.5%, and the conductive agent is 2%.

[0017] Example 2: Preparation of positive electrode slurry for sodium ion battery Layered oxide sodium cathode Na 0.91 Ni 0.22 Fe 0.33 Mn 0.33 Cu 0.11 O 2 and polyanion sodium cathode (Na 4 Fe 2.91 (PO 4 ) 2 P 2 O 7) are mixed in a ball mill in a ratio of 8:2 and set aside; in a -30°C dew point environment, part of the solvent (NMP) and the binder (PVDF) are mixed, stirred and dispersed to obtain a glue solution; an alkaline regulator (anhydrous maleic anhydride) is added, and mixed and dispersed; a conductive agent (conductive carbon black and carbon nanotubes) is added and mixed, and stirred and dispersed to obtain a conductive glue; first a part (40%) of the mixed positive electrode main material is added, stirred and dispersed for a certain time, and then the remaining positive electrode main material is added, and dispersed at high speed for a certain time; a certain amount of solvent is added to adjust the viscosity; after the slurry is completed, the poured positive electrode slurry is filtered with a 150-mesh filter and set aside.

[0018] In this embodiment, the total amount of the positive electrode main material, the binder, the alkaline regulator and the conductive agent is prepared, and the amount of each raw material is: the positive electrode main material is 96%, the binder is 1.5%, the alkaline regulator is 0.5%, and the conductive agent is 2%.

[0019] Example 3: Preparation of positive electrode slurry for sodium ion battery Layered oxide sodium cathode Na 0.91 Ni 0.22 Fe 0.33 Mn 0.33 Cu 0.11 O 2 and polyanion sodium cathode (Na 4 Fe 2.91 (PO 4 ) 2 P 2 O 7 ) are mixed in a ball mill in a ratio of 7:3 and set aside; in a -30°C dew point environment, part of the solvent (NMP) and the binder (PVDF) are mixed, stirred and dispersed to obtain a glue solution; an alkaline regulator (anhydrous maleic anhydride) is added, mixed and dispersed; a conductive agent (conductive carbon black and carbon nanotubes) is added, mixed, stirred and dispersed to obtain a conductive glue; first a part (40%) of the mixed positive electrode main material is added, stirred and dispersed for a certain time, and then the remaining positive electrode main material is added, and dispersed at high speed for a certain time; a certain amount of solvent is added to adjust the viscosity; after the homogenization is completed, the poured positive electrode slurry is filtered with a 150-mesh filter and set aside.

[0020] In this embodiment, the total amount of the positive electrode main material, the binder, the alkaline regulator and the conductive agent is prepared, and the amount of each raw material is: the positive electrode main material is 96%, the binder is 1.5%, the alkaline regulator is 0.5%, and the conductive agent is 2%.

[0021] In this embodiment, the total amount of the positive electrode main material, the binder, the alkaline regulator and the conductive agent is prepared, and the amount of each raw material is: the positive electrode main material is 96%, the binder is 1.5%, the alkaline regulator is 0.5%, and the conductive agent is 2%.

[0022] Comparative Example 1: Preparation of positive electrode slurry for sodium ion battery Under a dew point environment of -30°C, part of the solvent (NMP) and the binder (PVDF) were mixed and stirred to obtain a glue solution; an alkaline regulator (anhydrous maleic anhydride) was added and mixed and dispersed; a conductive agent (conductive carbon black and carbon nanotubes) was added and mixed and stirred to obtain a conductive glue; a portion of 40% layered oxide positive electrode main material Na 0.91 Ni 0.22 Fe 0.33 Mn 0.33 Cu 0.11 O 2 , stir and disperse for a certain period of time, then add the remaining positive electrode main materials, and disperse at high speed for a certain period of time; add a certain amount of solvent to adjust the viscosity; after the homogenization is completed, the poured positive electrode slurry is filtered with a 150-mesh filter and set aside.

[0023] In this embodiment, the total amount of the layered oxide positive electrode material, the binder, the alkaline regulator and the conductive agent is 96% of the positive electrode material, 1.5% of the binder, 0.5% of the alkaline regulator, and 2% of the conductive agent. Comparative Example 2: Preparation of positive electrode slurry for sodium ion battery Under a dew point environment of -30℃, part of the solvent (NMP) and the binder (PVDF) were mixed and stirred to obtain a glue solution; a certain amount of alkaline regulator (anhydrous maleic anhydride) was added and mixed and dispersed; a conductive agent (conductive carbon black and carbon nanotubes) was added and mixed and stirred to obtain a conductive glue; a portion of 40% polyanion positive electrode main material (Na 4 Fe 2.91 (PO 4 ) 2 P 2 O 7 ), stir and disperse for a certain period of time, then add the remaining positive electrode main material, and disperse at high speed for a certain period of time; add a certain amount of solvent to adjust the viscosity; after the homogenization is completed, the poured positive electrode slurry is filtered with a 150-mesh filter and set aside.

[0024] In this embodiment, the total amount of the polyanion positive electrode main material, the binder, the alkaline regulator and the conductive agent is prepared, and the amount of each raw material is: the positive electrode main material is 96%, the binder is 1.5%, the alkaline regulator is 0.5%, and the conductive agent is 2%.

[0025] The slurries prepared in the above-mentioned Examples 1, 2, 3 and Comparative Examples 1 and 2 were coated, rolled, slit and cut to obtain positive electrode sheets for sodium ion batteries. The coating conditions and the compaction conditions of the positive electrode sheets are shown in Table 1 below. Each positive electrode sheet and negative electrode sheet were stacked, packaged, baked, injected, formed, and divided to obtain sodium ion batteries. The first efficiency was calculated, and the results are shown in Table 1. A 0.2C cycle performance test was performed at 2.0-3.95V, and the 2000-week cycle results are shown in Table 1.

[0026] Table 1 Comparison of coating conditions, compaction, first effect, and cycle retention rate between Examples 1-3 and Comparative Examples 1-2

[0027] From the data in Table 1, it can be seen that the positive electrode sheet obtained by mixing the layered oxide sodium positive electrode and the polyanion sodium positive electrode in a ratio of 9:1 has high compaction, and the obtained sodium ion battery has excellent first efficiency, energy density, cycle performance and safety performance.

Claims

1. A sodium ion battery positive electrode slurry, made of the following materials in percentage by mass: Positive electrode main material 93%~97%; binder 1%~3%; conductive agent 1%~5%; alkaline regulator 0.1%~0.5%; The positive electrode main material is a mixture of a layered oxide sodium positive electrode and a polyanion sodium positive electrode, and the mass ratio of the layered oxide sodium positive electrode to the polyanion sodium positive electrode is 7-9:1-3.

2. The sodium ion battery positive electrode slurry according to claim 1, characterized in that: The chemical formula of the layered oxide sodium positive electrode is Na x MO2, M is at least one of Ni, Co, Mn, Fe, Cu, Ti, V, 0<x≤1; The chemical formula of the polyanion positive electrode is Na4Fe y (PO4)2P2O7, 2<y<3.

3. The sodium ion battery positive electrode slurry according to claim 1 or 2, characterized in that: The alkaline regulator is anhydrous oxalic acid and / or anhydrous maleic anhydride; The conductive agent is one or more of conductive carbon black, superconducting carbon black, Ketjen black, graphene conductive slurry, and single-walled carbon nanotubes; The binder is oily polyvinylidene fluoride.

4. The method for preparing the positive electrode slurry for a sodium ion battery according to any one of claims 1 to 3, comprising the following steps: S1, mixing a part of the solvent with the binder, stirring and dispersing to obtain a glue solution; S2, adding the alkaline regulator and the conductive agent to the glue solution in sequence, stirring and dispersing to obtain a conductive glue; S3, adding a part of the positive electrode main material to the conductive glue, stirring and dispersing, then adding the remaining amount of the positive electrode main material, and adding the remaining amount of the solvent to adjust the viscosity.

5. A positive electrode plate for a sodium ion battery, comprising a current collector and a positive electrode active material layer disposed on at least one side of the current collector, wherein the positive electrode active material layer is made of the positive electrode slurry for a sodium ion battery according to any one of claims 1 to 3.

6. A sodium ion battery, comprising the sodium ion battery positive electrode sheet, the sodium ion battery negative electrode sheet and a separator arranged between the sodium ion battery positive electrode sheet and the sodium ion battery negative electrode sheet according to claim 5.

7. The sodium ion battery according to claim 6, characterized in that: The negative electrode plate refers to a hard carbon or soft carbon negative electrode plate.

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