Sodium-ion battery cell with high cycle retention rate and preparation method thereof

Abstract

The application relates to the field of H01M10 / 00, in particular to a sodium ion cell with high cycle retention rate and a preparation method thereof, mainly comprising a positive electrode material, a negative electrode material and an electrolyte. A slurry with high stability, suitable viscosity and good fluidity is obtained by selecting specific positive electrode and negative electrode active materials, conductive materials and bonding materials. The positive electrode slurry and the negative electrode slurry are coated on the electrode sheets, then rolling, slitting and winding are carried out to obtain a sodium ion bare cell, and then water-based electrolyte is injected into the sodium ion bare cell to obtain the sodium ion cell. The sodium ion cell has the advantages of low cost, environmental protection, simple production process, high reliability, excellent rate performance, prolonged cycle life of the sodium ion cell, capacity retention rate maintained at more than 90% after 10000-20000 cycles, solved problems of non-environmental protection and hidden dangers of organic solvent type sodium ion cells, and meets the actual use requirements of products such as mobile phones and computers which need multiple charging and discharging.

Description

TECHNICAL FIELD

[0001] The application relates to the field of H01M10 / 00, in particular to a sodium ion battery cell with high cycle retention rate and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries occupy the main market of secondary batteries due to high energy density and long cycle life. At present, most advanced energy storage systems adopt lithium ion battery technology. However, lithium ion batteries are high in price and short in lithium resources. As a new type of chemical power supply, sodium ion batteries have advantages of rich resource reserves and low cost, and have broad application prospects in large-scale energy storage fields.

[0003] Chinese patent CN102544514B discloses a surface carbon modified lithium ion battery positive electrode material and a preparation method thereof. The positive electrode material obtained after carbonization by modifying LiNi0.5Mn1.5O4 with hydroxy aldehyde resin has excellent rate performance, but the raw material cost of the lithium ion battery is high, and the cycle retention rate needs to be improved. Chinese patent CN112563484A discloses a sodium ion battery positive electrode material, a preparation method thereof and a sodium ion battery. The sodium ion battery positive electrode material with a layered structure is obtained by controlling the reaction of the precursor mixed solution under high temperature and high pressure. However, due to the limitation of some intrinsic properties of sodium ions, the cycle life and rate performance cannot meet the needs of current large-scale energy storage technology, and the existing sodium ion battery mostly uses ester organic electrolyte. Since the ester organic electrolyte contains a large amount of organic flammable solvent, when the battery is out of control, explosion and combustion will occur, which brings great safety hazards to the battery.

[0004] Therefore, the application provides a sodium ion battery cell with high cycle retention rate and low cost to solve the problems of non-environmental protection and safety hazards of organic solvent type, effectively improve the cycle life and rate performance of the sodium ion battery, meet the actual use requirements of products such as mobile phones and computers which need multiple charging and discharging, and have important practical research significance and application value. SUMMARY

[0005] In order to solve the above problems, the application provides a sodium ion battery cell with high cycle retention rate, which mainly comprises a positive electrode material, a negative electrode material and an electrolyte.

[0006] As a preferred technical solution, the positive electrode material comprises a positive electrode sheet, a positive electrode active material, a conductive material A, a bonding material A and a solvent A.

[0007] As a preferred technical solution, the positive pole piece is selected from any one of aluminum foil and copper foil; the thickness of the positive pole piece is 5-8 μm; preferably, the positive pole piece is copper foil, and the thickness of the positive pole piece is 6 μm. By adopting the copper foil with a thickness of 6 μm as the positive pole piece, the rebound of the thickness of the pole piece in the processing process is avoided, and the performance of the battery is ensured.

[0008] In the processing of the sodium ion battery cell, the selection of the material affects the processing effect and difficulty, and further affects the performance of the final sodium ion battery cell. The positive electrode material of the sodium ion battery cell is the key to determining the energy density, power density, cycle life and safety performance and other indicators of the sodium ion battery cell. As a preferred technical solution, the positive electrode material includes, by weight, 25-33 parts of positive electrode active material, 5-8 parts of conductive material A, 6-10 parts of bonding material A, 30-40 parts of solvent A, which provides a positive electrode slurry with high stability, suitable viscosity and good flowability, and helps to ensure the capacity, cycle life and safety of the sodium ion battery cell.

[0009] As a preferred technical solution, the positive electrode active material is selected from at least one of layered oxide material, polyanion type positive electrode material and Prussian blue positive electrode material.

[0010] As a preferred technical solution, the positive electrode active material is selected from at least one of MnO2, Na x MnO2, Na3V2(PO4)3, NaFePO4, Na2FeP2O7, Na2NiFe(CN)6; preferably, the positive electrode active material is Na3V2(PO4)3, which has good kinetics and cycle stability, effectively improves the specific capacity of the sodium ion battery cell, makes the sodium ion battery cell have excellent rate performance, and prolongs the cycle life of the sodium ion battery cell. This may be due to the fact that the Na3V2(PO4)3 crystal structure with large volume has high stability, which is beneficial to the reversible insertion / extraction of sodium ions, and the insertion / extraction reaction does not cause structure collapse and amorphization.

[0011] The Na3V2(PO4)3 type is NVP-20 μm, and is purchased from Shenzhen Kexin Zhida Technology Co., Ltd.

[0012] The sodium ion superconductor Na3V2(PO4)3 has a strong ion diffusion rate, but the electronic conductivity is insufficient. As an optimal technical solution, the conductive material A is selected from at least one of single-walled carbon nanotubes, multi-walled carbon nanotubes, multi-walled carbon nanotubes, carboxylated multi-walled carbon nanotubes, and fullerene carbon nanotubes. Preferably, the conductive material A is single-walled carbon nanotubes, which makes up for the insufficient conductivity of the sodium ion superconductor Na3V2(PO4)3. In the exploration process, it is found that when the tube diameter of the single-walled carbon nanotubes is 1-5 nm and the length is 20-50 μm, the conductivity of the positive electrode material is significantly improved, and the ability of sodium ions to re-embed after de-embedding is promoted, thereby improving the cycle retention rate of the sodium ion battery.

[0013] The CAS number of the single-walled carbon nanotubes is 308068-56-6, and the purity is 99.9%. They are purchased from Zhejiang Yamei Nanometer Technology Co., Ltd.

[0014] The selection of the binding material relates to whether the slurry can be well coated on the pole piece. As an optimal technical solution, the binding material A is selected from at least one of styrene-butadiene rubber, polyvinyl alcohol, and sodium alginate. Preferably, the binding material A is a combination of polyvinyl alcohol and sodium alginate. When the mass ratio of the polyvinyl alcohol to the sodium alginate is (0.5-1.2):(2-4), the positive electrode slurry provided by the combination of the positive electrode active material, the conductive material A, and the solvent A has high stability, suitable viscosity, and good fluidity, which helps to ensure the capacity, internal resistance, cycle life, and safety of the sodium ion battery. In addition, the introduction of the biobased degradable material polyvinyl alcohol improves the degradation performance of the battery, making the provided sodium ion battery more environmentally friendly. In the exploration process, it is found that when the viscosity (25°C) of the polyvinyl alcohol is 54.0-66.0 mPa.s and the viscosity (25°C) of the sodium alginate is 200±20 mpa.s, the positive electrode slurry has the most suitable viscosity and fluidity, which helps to coat the pole piece smoothly and avoid cracks and shedding on the surface of the pole piece, thereby ensuring the capacity, internal resistance, cycle life, and safety of the sodium ion battery and meeting the usage requirements of products such as mobile phones and computers that need multiple charging and discharging.

[0015] As an optimal technical solution, the solvent A is deionized water.

[0016] The CAS number of the polyvinyl alcohol is 9002-89-5, and the model number is P139535. It is purchased from Shanghai Aldrich Biochemical Technology Co., Ltd. The CAS number of the sodium alginate is 9005-38-3, and the model number is S817372. It is purchased from Shanghai Maikelin Biochemical Technology Co., Ltd.

[0017] As an optimal technical solution, the negative electrode material includes a negative electrode pole piece, a negative electrode active material, a binding material B, and a solvent B.

[0018] As a preferred technical solution, the negative pole piece is selected from any one of aluminum foil and copper foil; the thickness of the positive pole piece is 5-8 μm; preferably, the negative pole piece is copper foil, and the thickness of the negative pole piece is 6 μm. By adopting the copper foil with a thickness of 6 μm as the negative pole piece, the rebound of the thickness of the pole piece in the processing process is avoided, and the performance of the battery is ensured.

[0019] As a preferred technical solution, the negative pole material includes, by weight, 18-25 parts of a negative active material, 4-6 parts of a binder material B, and 20-30 parts of a solvent B, so as to provide a negative pole slurry with high stability, suitable viscosity, and good fluidity, which helps to ensure the capacity, cycle life, and safety of the sodium ion battery.

[0020] The negative active material is selected from at least one of MoO3, activated carbon, expandable graphite, NaTi2(PO4)3, lithium titanate, sodium superionic conductor, and manganese-based Prussian blue; preferably, the negative active material is MoO3, activated carbon, and expandable graphite, and preferably, the mass ratio of the MoO3, activated carbon, and expandable graphite is (4-6):(2-3):(1-3), which helps to improve the cycle retention rate of the sodium ion battery, so that the provided sodium ion battery has high cycle stability and capacity retention rate. In the exploration process, it is found that although the layered structure of MoO3 is beneficial to the embedding and extraction of sodium ions, it greatly improves the cycle number and capacity retention rate of the sodium ion battery, but the electronic conductivity of MoO3 is insufficient, and when the activated carbon with a specific surface area of 1982 m 2 / g and the expandable graphite with a particle size of 48 μm are used in combination, the problem of insufficient conductivity of the negative electrode material is compensated, the cycle life and rate performance of the sodium ion battery are ensured, and the sodium ion battery is especially suitable for products such as mobile phones and computers that need to be charged and discharged multiple times.

[0021] The CAS number of the MoO3 is 1313-27-5, the product number is M104354, and it is purchased from Shanghai Aldrin Biochemical Technology Co., Ltd.; the model of the activated carbon is SAC-18, and it is purchased from Shenzhen Kexing Zhida Technology Co., Ltd.; the expandable graphite is purchased from Shenzhen Kexing Zhida Technology Co., Ltd.

[0022] As a preferred technical solution, the bonding material B is selected from at least one of styrene-butadiene rubber, polyvinyl alcohol, and sodium alginate; preferably, the bonding material B is polyvinyl alcohol, preferably, the viscosity (25℃) of the polyvinyl alcohol is 80.0-110.0 mPa.s, which provides a positive electrode slurry with high stability, suitable viscosity, and good fluidity by matching the positive electrode active material and the solvent B, helps the coating of the electrode sheet to be flat, avoids the phenomenon of cracking and falling off of the coating on the surface of the electrode sheet, and ensures the capacity, internal resistance, cycle life, and safety of the sodium-ion battery.

[0023] The polyvinyl alcohol has a CAS number of 9002-89-5, a model number of P139541, and is purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.

[0024] As a preferred technical solution, the solvent B is deionized water.

[0025] The electrolyte is a medium for electrochemical reaction and is one of the important factors affecting the interface reaction thermodynamics and kinetics process of the electrode material. As a preferred technical solution, the electrolyte is selected from any one of carbonate electrolyte, ether electrolyte, aqueous electrolyte, and ionic liquid electrolyte. The film layer generated by the electrolyte on the surface of different electrodes has different compositions and properties, thereby affecting the electrochemical stability of the sodium-ion battery. In order to match the above-mentioned positive electrode material and negative electrode material, the cycle life and rate performance of the sodium-ion battery are maximized. As a preferred technical solution, the electrolyte is an aqueous electrolyte, which has high ionic conductivity, realizes high efficiency and energy density, solves the problem of non-environmental protection and safety hazard of organic flammable solvents in the existing organic electrolyte of sodium-ion battery, is rich in resources, low in cost, simple in production process, and has great potential for large-scale industrial application.

[0026] As a preferred technical solution, the aqueous electrolyte includes an electrolyte and a solvent C; the preparation method of the aqueous electrolyte is to dissolve the electrolyte in the solvent C to obtain the aqueous electrolyte; the electrolyte is selected from at least one of sodium nitrate, sodium sulfate, sodium hypochlorite, and sodium bis(fluorosulfonyl)imide; the solvent C is deionized water; preferably, the electrolyte is sodium nitrate and sodium bis(fluorosulfonyl)imide, preferably, the molar concentration of the sodium nitrate is 0.5-1 mol / L, and the molar concentration of the sodium bis(fluorosulfonyl)imide is 0.1-0.5 mol / L. By controlling the molar concentrations of sodium nitrate and sodium bis(fluorosulfonyl)imide, the cycle stability of the sodium-ion battery is improved, the cycle life of the sodium-ion battery is prolonged, and the rate performance of the sodium-ion battery is improved.

[0027] The sodium bis(fluorosulfonyl)imide has a CAS number of 100669-96-3 and is purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0028] Another aspect of the present invention provides a method for preparing a sodium ion battery cell with a high cyclability retention rate, the preparation steps of which include:

[0029] (1) Using a vacuum mixer, the positive electrode active material, conductive material A, binder material A, and solvent A are stirred into a slurry to obtain a positive electrode slurry;

[0030] (2) using a vacuum mixer to stir the negative electrode active material, binder material B, and solvent B into a slurry to obtain a negative electrode slurry;

[0031] (3) Apply the positive electrode slurry in step (1) and the negative electrode slurry in step (2) to the upper and lower surfaces of the positive electrode sheet and the negative electrode sheet at a speed of 1.2 m / s;

[0032] (4) rolling, slitting, and winding the electrode sheets with the positive electrode slurry and the negative electrode slurry attached thereto by rollers to obtain a sodium ion bare cell;

[0033] (5) dissolving the electrolyte in solvent C to obtain an electrolyte solution, and injecting the electrolyte solution into a sodium ion bare cell to obtain the sodium ion cell.

[0034] Beneficial effects:

[0035] 1. The present invention provides a low-cost sodium-ion battery cell with high cyclability retention rate to solve the problem that organic solvent-based batteries are environmentally unfriendly and pose safety risks, effectively improve the cycle life and rate performance of sodium-ion batteries, and meet the actual use needs of products that require multiple charge and discharge, such as mobile phones and computers.

[0036] 2. Using Na3V2(PO4)3 as the positive electrode active material, combined with single-walled carbon nanotubes with a diameter of 1-5nm and a length of 20-50μm, while significantly improving the conductivity of the positive electrode material, effectively improves the specific capacity of the sodium ion battery cell, makes the sodium ion battery cell have excellent rate performance, and extends the cycle life of the sodium ion battery cell.

[0037] 3. Polyvinyl alcohol and sodium alginate with a mass ratio of (0.5-1.2): (2-4) are used as the binding material A, and are combined with the positive electrode active material, the conductive material A and the solvent A to provide a positive electrode slurry with high stability, suitable viscosity and good fluidity, which helps to ensure the capacity, internal resistance, cycle life and safety of the sodium ion battery cell, helps to improve the degradation performance of the sodium ion battery cell, and makes the provided sodium ion battery cell more environmentally friendly.

[0038] 4. MoO3, activated carbon and expandable graphite with a mass ratio of (4-6): (2-3): (1-3) are used as negative electrode active materials, and a specific surface area of ​​1982m 2When the active carbon is 0.5g and the expandable graphite has a particle size of 48μm, the problem of insufficient conductivity of the negative electrode material is solved, the cycle life and rate capability of the sodium ion battery are ensured, and the sodium ion battery is particularly suitable for products such as mobile phones and computers that need to be charged and discharged multiple times.

[0039] 5. The water-based electrolyte has high ionic conductivity, realizes high efficiency and energy density, solves the problem of non-environmental protection and safety hazard of organic flammable solvents in the existing sodium ion battery, is rich in resources, low in cost, simple in production process, and has great potential for large-scale industrial application. DETAILED DESCRIPTION

[0040] Embodiment 1

[0041] The embodiment 1 of the present application provides a sodium ion battery with high cycle retention rate, which comprises a positive electrode material, a negative electrode material and an electrolyte.

[0042] The positive electrode material comprises a positive electrode sheet, a positive electrode active material, a conductive material A, a bonding material A and a solvent A.

[0043] The positive electrode sheet is a copper foil, and the thickness of the positive electrode sheet is 6μm.

[0044] The positive electrode material comprises the positive electrode active material 30 parts, the conductive material A 6 parts, the bonding material A 8 parts and the solvent A 36 parts by weight.

[0045] The positive electrode active material is Na3V2(PO4)3.

[0046] The Na3V2(PO4)3 is of NVP-20μm type and is purchased from Shenzhen Keyi Zhida Technology Co., Ltd.

[0047] The conductive material A is single-walled carbon nanotubes, the tube diameter of the single-walled carbon nanotubes is 1-5nm, and the length is 20-50μm.

[0048] The single-walled carbon nanotubes have a CAS number of 308068-56-6 and a purity of 99.9%, and are purchased from Zhejiang Yame Nanometer Technology Co., Ltd.

[0049] The bonding material A is a combination of polyvinyl alcohol and sodium alginate, the mass ratio of the polyvinyl alcohol and the sodium alginate is 1:3, the viscosity of the polyvinyl alcohol (25℃) is 54.0-66.0mPa.s, and the viscosity of the sodium alginate (25℃) is 200±20mpa.s.

[0050] The solvent A is deionized water.

[0051] The polyvinyl alcohol has a CAS number of 9002-89-5, a model number of P139535, and is purchased from Shanghai Aladdin Biochem Technology Co., Ltd.; the sodium alginate has a CAS number of 9005-38-3, a model number of S817372, and is purchased from Shanghai Macklin Biochemical Technology Co., Ltd.

[0052] The negative electrode material comprises a negative electrode sheet, a negative electrode active material, a bonding material B, and a solvent B.

[0053] The negative electrode sheet is a copper foil, and the thickness of the negative electrode sheet is 6 μm.

[0054] The negative electrode material comprises, by weight parts, 20 parts of a negative electrode active material, 5 parts of a bonding material B, and 22 parts of a solvent B.

[0055] The negative electrode active material is MoO3, activated carbon, and expandable graphite, and the mass ratio of the MoO3, the activated carbon, and the expandable graphite is 5:2.5:2.

[0056] The MoO3 has a CAS number of 1313-27-5, a product number of M104354, and is purchased from Shanghai Aladdin Biochem Technology Co., Ltd.; the activated carbon has a model number of SAC-18 and is purchased from Shenzhen Kexing Zhida Technology Co., Ltd.; and the expandable graphite is purchased from Shenzhen Kexing Zhida Technology Co., Ltd.

[0057] The bonding material B is polyvinyl alcohol, and the viscosity (25°C) of the polyvinyl alcohol is 80.0-110.0 mPa·s.

[0058] The polyvinyl alcohol has a CAS number of 9002-89-5, a model number of P139535, and is purchased from Shanghai Aladdin Biochem Technology Co., Ltd.

[0059] The solvent B is deionized water.

[0060] The electrolyte is an aqueous electrolyte.

[0061] The aqueous electrolyte comprises an electrolyte and a solvent C; the aqueous electrolyte is prepared by dissolving the electrolyte in the solvent C; the solvent C is deionized water; the electrolyte is sodium nitrate and sodium bis(fluorosulfonyl)imide, the molar concentration of the sodium nitrate is 0.8 mol / L, and the molar concentration of the sodium bis(fluorosulfonyl)imide is 0.2 mol / L.

[0062] The sodium bis(fluorosulfonyl)imide has a CAS number of 100669-96-3 and is purchased from Gleen Tai (Shanghai) Chemical Industry Development Co., Ltd.

[0063] The embodiment 1 of the present application provides a preparation method of a sodium ion battery cell with high cycle retention rate, which comprises the following steps:

[0064] (1) a positive electrode active material, a conductive material A, a bonding material A and a solvent A are stirred into a slurry by a vacuum stirrer to obtain a positive electrode slurry;

[0065] (2) a negative electrode active material, a bonding material B and a solvent B are stirred into a slurry by a vacuum stirrer to obtain a negative electrode slurry;

[0066] (3) the positive electrode slurry in step (1) and the negative electrode slurry in step (2) are applied to the upper and lower surfaces of a positive electrode sheet and a negative electrode sheet at a speed of 1.2 m / s;

[0067] (4) the electrode sheets with the positive electrode slurry and the negative electrode slurry attached are rolled, cut and wound by a roller to obtain a sodium ion bare battery cell;

[0068] (5) an electrolyte is dissolved in a solvent C to obtain an electrolyte solution, and the electrolyte solution is injected into the sodium ion bare battery cell to obtain the sodium ion battery cell.

[0069] Embodiment 2

[0070] The embodiment 2 of the present application provides a sodium ion battery cell with high cycle retention rate, which comprises a positive electrode material, a negative electrode material and an electrolyte.

[0071] The positive electrode material comprises a positive electrode sheet, a positive electrode active material, a conductive material A, a bonding material A and a solvent A.

[0072] The positive electrode sheet is a copper foil, and the thickness of the positive electrode sheet is 6 pm.

[0073] The positive electrode material comprises, by weight, 30 parts of the positive electrode active material, 8 parts of the conductive material A, 10 parts of the bonding material A and 40 parts of the solvent A.

[0074] The positive electrode active material is Na3V2(PO4)3.

[0075] The Na3V2(PO4)3 is of NVP-20 pm and is purchased from Shenzhen Keyi Zhida Technology Co., Ltd.

[0076] The conductive material A is single-walled carbon nanotubes, the tube diameter of the single-walled carbon nanotubes is 1-5 nm, and the length of the single-walled carbon nanotubes is 20-50 pm.

[0077] The single-walled carbon nanotubes have a CAS number of 308068-56-6 and a purity of 99.9%, and are purchased from Zhejiang Yame Nanometer Technology Co., Ltd.

[0078] The adhesive material A is a combination of polyvinyl alcohol and sodium alginate, when the mass ratio of the polyvinyl alcohol and sodium alginate is 1.2:4, the viscosity (25℃) of the polyvinyl alcohol is 54.0-66.0 mPa.s, and the viscosity (25℃) of the sodium alginate is 200±20 mPa.s.

[0079] The solvent A is deionized water.

[0080] The polyvinyl alcohol has a CAS number of 9002-89-5 and a model number of P139535, and is purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.; the sodium alginate has a CAS number of 9005-38-3 and a model number of S817372, and is purchased from Shanghai Macklin Biochemical Technology Co., Ltd.

[0081] The negative material includes a negative pole piece, a negative active material, an adhesive material B, and a solvent B.

[0082] The negative pole piece is a copper foil, and the thickness of the negative pole piece is 6μm.

[0083] The negative material includes, by weight parts, 25 parts of a negative active material, 6 parts of an adhesive material B, and 25 parts of a solvent B.

[0084] The negative active material is MoO3, activated carbon, and expandable graphite, and the mass ratio of the MoO3, activated carbon, and expandable graphite is 2:1:1.

[0085] The MoO3 has a CAS number of 1313-27-5 and a product number of M104354, and is purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.; the activated carbon has a model number of SAC-18 and is purchased from Shenzhen Keyi Zhida Technology Co., Ltd.; and the expandable graphite is purchased from Shenzhen Keyi Zhida Technology Co., Ltd.

[0086] The adhesive material B is polyvinyl alcohol, and the viscosity (25℃) of the polyvinyl alcohol is 80.0-110.0 mPa.s.

[0087] The polyvinyl alcohol has a CAS number of 9002-89-5 and a model number of P139541, and is purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.

[0088] The solvent B is deionized water.

[0089] The electrolyte is an aqueous electrolyte.

[0090] The aqueous electrolyte comprises an electrolyte and a solvent C; the preparation method of the aqueous electrolyte is: dissolving the electrolyte in the solvent C to obtain; the solvent C is deionized water; the electrolyte is sodium nitrate and sodium bis(fluorosulfonyl)imide, the molar concentration of the sodium nitrate is 0.75 mol / L, and the molar concentration of the sodium bis(fluorosulfonyl)imide is 0.25 mol / L.

[0091] The CAS number of the sodium bis(fluorosulfonyl)imide is 100669-96-3, and the sodium bis(fluorosulfonyl)imide is purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0092] Embodiment 2 of the present application provides, in another aspect, a preparation method of a sodium ion battery cell with a high cycle retention rate, which comprises the following preparation steps:

[0093] (1) using a vacuum stirrer to stir the positive active material, the conductive material A, the bonding material A and the solvent A into a slurry to obtain a positive electrode slurry;

[0094] (2) using a vacuum stirrer to stir the negative active material, the bonding material B and the solvent B into a slurry to obtain a negative electrode slurry;

[0095] (3) coating the positive electrode slurry and the negative electrode slurry onto the upper and lower surfaces of the positive electrode sheet and the negative electrode sheet at a speed of 1.2 m / s;

[0096] (4) rolling, slitting and winding the electrode sheet with the positive electrode slurry and the negative electrode slurry attached to obtain a sodium ion bare battery cell;

[0097] (5) dissolving the electrolyte in the solvent C to obtain an electrolyte, and injecting the electrolyte into the sodium ion bare battery cell to obtain the sodium ion battery cell.

[0098] Embodiment 3

[0099] Embodiment 3 of the present application provides, in another aspect, a sodium ion battery cell with a high cycle retention rate, which comprises a positive electrode material, a negative electrode material and an electrolyte.

[0100] The positive electrode material comprises a positive electrode sheet, a positive active material, a conductive material A, a bonding material A and a solvent A.

[0101] The positive electrode sheet is a copper foil, and the thickness of the positive electrode sheet is 6 μm.

[0102] The positive electrode material comprises, by weight, 25 parts of the positive active material, 5 parts of the conductive material A, 6 parts of the bonding material A and 30 parts of the solvent A.

[0103] The positive active material is Na3V2(PO4)3.

[0104] The Na3V2(PO4)3 type is NVP-20μm, purchased from Shenzhen Kexing Zhida Technology Co., Ltd.

[0105] The conductive material A is single-walled carbon nanotubes, the tube diameter of the single-walled carbon nanotubes is 1-5nm, and the length is 20-50μm.

[0106] The CAS number of the single-walled carbon nanotubes is 308068-56-6, and the purity is 99.9, purchased from Zhejiang Yame Nanometer Technology Co., Ltd.

[0107] The adhesive material A is a combination of polyvinyl alcohol and sodium alginate, when the mass ratio of the polyvinyl alcohol and sodium alginate is 0.8:2, the viscosity of the polyvinyl alcohol (25℃) is 54.0-66.0mPa.s, and the viscosity of the sodium alginate (25℃) is 200±20mpa.s.

[0108] The solvent A is deionized water.

[0109] The CAS number of the polyvinyl alcohol is 9002-89-5, the model is P139535, and it is purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.; the CAS number of the sodium alginate is 9005-38-3, the model is S817372, and it is purchased from Shanghai Maikelin Biochemical Technology Co., Ltd.

[0110] The negative electrode material includes a negative electrode sheet, a negative electrode active material, an adhesive material B, and a solvent B.

[0111] The negative electrode sheet is a copper foil, and the thickness of the negative electrode sheet is 6μm.

[0112] The negative electrode material includes 18 parts of a negative electrode active material, 4 parts of an adhesive material B, and 20 parts of a solvent B by weight.

[0113] The negative electrode active material is MoO3, activated carbon, and expandable graphite, and the mass ratio of the MoO3, activated carbon, and expandable graphite is 4:2:1.

[0114] The CAS number of the MoO3 is 1313-27-5, the product number is M104354, and it is purchased from Shanghai Aldrich Biochemical Technology Co., Ltd.; the model of the activated carbon is SAC-18, and it is purchased from Shenzhen Kexing Zhida Technology Co., Ltd.; and the expandable graphite is purchased from Shenzhen Kexing Zhida Technology Co., Ltd.

[0115] The adhesive material B is polyvinyl alcohol, and the viscosity of the polyvinyl alcohol (25℃) is 80.0-110.0mPa.s.

[0116] The polyvinyl alcohol has a CAS number of 9002-89-5, a model number of P139541, and is purchased from Shanghai Aladdin Biochem Technology Co., Ltd.

[0117] The solvent B is deionized water.

[0118] The electrolyte is a water-based electrolyte.

[0119] The water-based electrolyte comprises an electrolyte and a solvent C; the preparation method of the water-based electrolyte is: dissolving the electrolyte in the solvent C to obtain; the solvent C is deionized water; the electrolyte is sodium nitrate and sodium bis(fluorosulfonyl)imide, the molar concentration of the sodium nitrate is 0.7 mol / L, and the molar concentration of the sodium bis(fluorosulfonyl)imide is 0.3 mol / L.

[0120] The sodium bis(fluorosulfonyl)imide has a CAS number of 100669-96-3 and is purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0121] Embodiment 3 of the application further provides a preparation method of a sodium ion battery cell with a high cycle retention rate, which comprises the following preparation steps:

[0122] (1) using a vacuum stirrer to stir the positive active material, the conductive material A, the bonding material A and the solvent A into a slurry to obtain a positive electrode slurry;

[0123] (2) using a vacuum stirrer to stir the negative active material, the bonding material B and the solvent B into a slurry to obtain a negative electrode slurry;

[0124] (3) coating the positive electrode slurry in step (1) and the negative electrode slurry in step (2) onto the upper and lower surfaces of the positive electrode sheet and the negative electrode sheet at a speed of 1.2 m / s;

[0125] (4) rolling, slitting and winding the electrode sheet with the positive electrode slurry and the negative electrode slurry attached to obtain a sodium ion bare battery cell;

[0126] (5) dissolving the electrolyte in the solvent C to obtain an electrolyte, and injecting the electrolyte into the sodium ion bare battery cell to obtain the sodium ion battery cell.

[0127] Comparative Example 1

[0128] Comparative Example 1 of the application provides a sodium ion battery cell with a high cycle retention rate, and the specific embodiment is the same as that of Embodiment 1, except that the conductive material A is a multi-walled carbon nanotube, which has a CAS number of 308068-56-6, a product number of C916307, and is purchased from Shanghai Mclinn Biochemical Technology Co., Ltd.

[0129] Comparative Example 2

[0130] The comparative example 2 of the present application provides a sodium-ion battery cell with high cycle retention rate, which has the same embodiment as the example 1 except that the binding material A is sodium alginate.

[0131] Comparative example 3

[0132] The comparative example 3 of the present application provides a sodium-ion battery cell with high cycle retention rate, which has the same embodiment as the example 1 except that the negative active material is activated carbon.

[0133] Comparative example 4

[0134] The comparative example 4 of the present application provides a sodium-ion battery cell with high cycle retention rate, which has the same embodiment as the example 1 except that the electrolyte is sodium sulfate, and the molar concentration of the sodium sulfate is 1 mol / L.

[0135] Performance test method

[0136] (1) Cycle retention rate: the initial discharge capacity of the sodium-ion battery cell obtained by the example and the comparative example and the remaining capacity after 10,000-20,000 cycles of the sodium-ion battery cell are determined, and the cycle retention rate of the sodium-ion battery cell is calculated.

[0137] Cycle retention rate = remaining capacity / initial discharge capacity*100%

[0138] (2) Rate performance: the rate performance of the sodium-ion battery cell obtained by the example and the comparative example is determined, which is represented by the time for completing one charge / discharge cycle of the sodium-ion battery cell obtained by the example and the comparative example, and the unit is hour.

[0139] Test item Cycling retention rate (%) Rate performance (hour) Example 1 92 0.5 Example 2 91 0.52 Example 3 90.5 0.55 Comparative Example 1 87 0.6 Comparative Example 2 85 0.75 Comparative Example 3 83 0.8 Comparative Example 4 84 0.7

Claims

1. A sodium ion battery cell, characterized in that The invention comprises a positive electrode material, a negative electrode material and an electrolyte; the positive electrode material is prepared from a positive electrode sheet and a positive electrode slurry, and the negative electrode material is prepared from a negative electrode sheet and a negative electrode slurry; the positive electrode slurry comprises 25-33 parts of a positive electrode active material, 5-8 parts of a conductive material A, 6-10 parts of a binder material A and 30-40 parts of a solvent A, wherein the positive electrode active material is Na3V2(PO4)3; the conductive material A is a single-walled carbon nanotube, and the diameter of the single-walled carbon nanotube is 1-5 nm and the length is 20-50 μm; the binder material A is a combination of polyvinyl alcohol and sodium alginate, and the mass ratio of polyvinyl alcohol to sodium alginate is (0.5-1.2):(2-4), the viscosity of the polyvinyl alcohol at 25°C is 54.0-66.0 mPa.s, and the viscosity of the sodium alginate at 25°C is 200±20 mPa.s; The negative electrode slurry comprises, by weight, 18-25 parts of a negative electrode active material, 4-6 parts of a binder material B, and 20-30 parts of a solvent B; the negative electrode active materials are MoO3, activated carbon, and expandable graphite, and the mass ratio of MoO3, activated carbon, and expandable graphite is (4-6): (2-3): (1-3); The electrolyte is an aqueous electrolyte.

2. A sodium ion battery cell according to claim 1, characterized in that The positive electrode sheet is selected from any one of aluminum foil and copper foil; the thickness of the positive electrode sheet is 5-8 μm.

3. A method for preparing a sodium ion battery cell according to any one of claims 1 to 2, characterized in that: The method comprises at least the following preparation steps: (1) Using a vacuum mixer, the positive electrode active material, the conductive material A, the binder material A, and the solvent A are stirred into a slurry to obtain a positive electrode slurry; (2) Using a vacuum mixer, the negative electrode active material, the binder material B, and the solvent B are stirred into a slurry to obtain a negative electrode slurry; (3) Apply the positive electrode slurry in step (1) and the negative electrode slurry in step (2) to the upper and lower surfaces of the positive electrode sheet and the negative electrode sheet at a speed of 1.2 m / s; (4) Rolling, cutting, and winding the electrode sheets with positive electrode slurry and negative electrode slurry attached to them by rollers to obtain sodium ion bare cells; (5) Injecting the electrolyte into the sodium ion bare cell to obtain the sodium ion cell.