A stacked sodium ion battery and its production method

Abstract

The present invention discloses a sodium ion battery in a laminated manner and a production method thereof. The sodium ion battery comprises a plurality of electrode plates and a plurality of diaphragms. The plurality of electrode plates comprise a single-sided conventional current collector positive electrode plate, a double-sided composite current collector double electrode plate, a double-sided conventional current collector double electrode plate, and a single-sided conventional current collector negative electrode plate. A plurality of repeating units are arranged between the single-sided conventional current collector positive electrode plate and the single-sided conventional current collector negative electrode plate. Along the direction from the single-sided conventional current collector positive electrode plate to the single-sided conventional current collector negative electrode plate, the repeating unit consists of one double-sided composite current collector double electrode plate and one double-sided conventional current collector double electrode plate. The diaphragm is arranged between two adjacent electrode plates. The sodium ion battery can improve safety performance while taking into account electrical performance.

Description

Technical Field

[0001] The present invention relates to a sodium ion battery, and in particular to a stacked sodium ion battery and a production method thereof. Background Art

[0002] Sodium-ion batteries, as green and environmentally friendly batteries, offer advantages such as abundant resources, high operating voltage, and low cost. Sodium-ion batteries consist of a positive electrode, a negative electrode, a separator, and an electrolyte. During safety testing, such as overcharging, hot box testing, and probing, sodium-ion batteries are prone to short circuits, generating sparks that can ignite the electrolyte and cause explosions, posing a significant safety hazard. Probing presents the greatest safety challenge for battery cells.

[0003] In order to solve this technical problem, composite current collectors are widely used in the electrodes of sodium-ion batteries in the existing technology. However, composite current collectors have some manufacturing difficulties and the side effect of weakening electrical performance. They have the following disadvantages: 1. The surface tension is low. Compared with conventional current collectors, the composite current collector has poor adhesion to the slurry, which will seriously affect the later cycle performance; 2. The plastic elongation in the middle of the composite current collector is too large and is obviously out of sync with the aluminum foil metal on the upper and lower surfaces. This limits the upper limit of the current collector's compaction, which is at least 0.5 points smaller than that of a normal current collector; seriously affecting the improvement of energy density; 3. Due to its composite structure, the actual metal layer thickness is very thin, resulting in the current collector's overcurrent capability being much worse than that of a conventional current collector, resulting in poor rate and low-temperature performance. 4. Due to its composite structure, the actual metal layer thickness is very thin, resulting in the ultrasonic energy not being easily transmitted during ultrasonic welding of the battery cell. Therefore, the number of battery cell layers is limited, and the battery cell cannot be made too large. Summary of the Invention

[0004] The present invention aims to provide a sodium ion battery in a laminated manner and a production method thereof, wherein the sodium ion battery can improve safety performance while taking into account electrical performance.

[0005] In order to achieve the above-mentioned object, the present invention provides a sodium ion battery in a laminated manner, wherein the sodium ion battery comprises a plurality of electrode sheets and a plurality of diaphragms; the plurality of electrode sheets comprise a single-sided conventional current collector positive electrode sheet, a double-sided composite current collector double electrode sheet, a double-sided conventional current collector double electrode sheet, and a single-sided conventional current collector negative electrode sheet; a plurality of repeating units are provided between the conventional current collector positive electrode sheet and the single-sided conventional current collector negative electrode sheet; along the direction from the single-sided conventional current collector positive electrode sheet to the single-sided conventional current collector negative electrode sheet, the repeating unit consists of one double-sided composite current collector double electrode sheet and one double-sided conventional current collector double electrode sheet; the diaphragm is provided between two adjacent electrode sheets;

[0006] Among them, the single-sided conventional current collector positive electrode sheet includes an aluminum foil current collector and a positive electrode material coated on a single side of the aluminum foil current collector; the double-sided composite current collector double electrode sheet includes an aluminum foil-plastic-aluminum foil composite current collector and a positive electrode material and a negative electrode material respectively coated on both sides of the aluminum foil-plastic-aluminum foil composite current collector; the double-sided conventional current collector double electrode sheet includes an aluminum foil current collector and a positive electrode material and a negative electrode material respectively coated on both sides of the aluminum foil current collector; the single-sided conventional current collector negative electrode sheet includes an aluminum foil current collector and a negative electrode material coated on a single side of the aluminum foil current collector.

[0007] The present invention also provides a method for producing a sodium ion battery in the stacking manner as described above, comprising:

[0008] 1) Dispersing the positive electrode material in a solvent to prepare a positive electrode slurry; dispersing the negative electrode material in a solvent to prepare a negative electrode slurry;

[0009] 2) Coating the positive electrode slurry on one side of an aluminum foil current collector and an aluminum foil-plastic-aluminum foil composite current collector; coating the negative electrode slurry on one side of an aluminum foil current collector and an aluminum foil-plastic-aluminum foil composite current collector; wherein, a portion of the aluminum foil current collector is coated with the positive electrode slurry or the negative electrode slurry on one side, and the remaining aluminum foil current collector is coated with the positive electrode slurry and the negative electrode slurry on both sides; and the aluminum foil-plastic-aluminum foil composite current collector is coated with the positive electrode slurry and the negative electrode slurry on both sides.

[0010] 3) After the positive electrode slurry or negative electrode slurry is coated, baking, rolling, and cutting are performed to produce a single-sided conventional current collector positive electrode sheet, a double-sided composite current collector double electrode sheet, a double-sided conventional current collector double electrode sheet, and a single-sided conventional current collector negative electrode sheet;

[0011] 4) The single-sided conventional current collector positive electrode sheet, double-sided composite current collector dual electrode sheet, double-sided conventional current collector dual electrode sheet, single-sided conventional current collector negative electrode sheet, separator, and electrolyte are sequentially stacked, assembled, baked, welded and sealed, injected, and formed to produce a hard-shell battery cell.

[0012] The innovation of the above technical solution lies in the stacking method of different pole pieces. The double-sided composite current collector double electrode pole piece B1 and the double-sided conventional current collector double electrode pole piece B2 must be stacked alternately to effectively prevent ultrasonic welding faults. The conventional current collector positive pole piece A and the single-sided conventional current collector negative pole piece C are to prevent electrochemical corrosion. Separator membranes must be added between each pole piece. Because sodium ions do not form an alloy reaction with aluminum foil, aluminum foil can be used for both positive and negative current collectors. In other words, the positive and negative electrode slurries can be coated on both sides of the aluminum foil to improve stacking efficiency. By mixing different current collectors and different coating processes, the battery safety performance is improved while ensuring high-quality electrical performance.

[0013] Among them, the use of aluminum foil-plastic-aluminum foil composite current collector is to improve safety. The sodium ions in the sodium battery cell are more active, and the required negative electrode material is generally amorphous carbon, which has better conductivity than conventional graphite. The risk factor of contact between aluminum foil and the negative electrode membrane is higher, so when the current collector becomes a composite current collector, the chance of contact between aluminum foil and the negative electrode membrane is greatly reduced, and the safety factor of the battery cell is greatly improved.

[0014] The single-sided coating process is used to stack two single-sided coated positive and negative electrode sheets on the outermost side of the battery cell, which has three functions: 1. Prevent electrochemical corrosion during long-term use. Since the outermost layer of the bare battery cell is aluminum packaging, which is the same material as the positive electrode current collector, there is no potential difference, so there is no electrochemical corrosion, which improves the reliability of the battery cell; 2. Save the use of positive electrode slurry and reduce costs; 3. Reduce the overall thickness of the battery cell and improve the volume energy density of the battery cell.

[0015] From the above description, it can be seen that the present invention has the following advantages: 1. This patent can significantly improve the safety performance of the battery cell; 2. It can also increase the capacity; 3. It is simple to operate and improves process efficiency.

[0016] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the following detailed description, they are used to explain the present invention but do not constitute a limitation of the present invention. In the accompanying drawings:

[0018] Figure 1 This is a schematic structural diagram of a preferred embodiment of a stacked sodium ion battery provided by the present invention;

[0019] Figure 2 1 is a capacity box plot of the batteries of Example 1 and Comparative Example 1;

[0020] Figure 3 This is the acupuncture diagram of Example 1. DETAILED DESCRIPTION

[0021] The following is a detailed description of the specific embodiments of the present invention. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0022] The present invention provides a sodium ion battery in a laminated manner, such as Figure 1 As shown, the sodium ion battery includes multiple electrode sheets and multiple diaphragms; the multiple electrode sheets include a single-sided conventional current collector positive electrode sheet A, a double-sided composite current collector double electrode sheet B1, a double-sided conventional current collector double electrode sheet B2, and a single-sided conventional current collector negative electrode sheet C; a plurality of repeating units are provided between the conventional current collector positive electrode sheet A and the single-sided conventional current collector negative electrode sheet C; along the direction from the single-sided conventional current collector positive electrode sheet A to the single-sided conventional current collector negative electrode sheet C, the repeating unit consists of a double-sided composite current collector double electrode sheet B1 and a double-sided conventional current collector double electrode sheet B2; the diaphragm is provided between two adjacent electrode sheets;

[0023] Among them, the single-sided conventional current collector positive electrode sheet A includes an aluminum foil current collector and a positive electrode material coated on a single side of the aluminum foil current collector; the double-sided composite current collector double electrode sheet B1 includes an aluminum foil-plastic-aluminum foil composite current collector and a positive electrode material and a negative electrode material respectively coated on both sides of the aluminum foil-plastic-aluminum foil composite current collector; the double-sided conventional current collector double electrode sheet B2 includes an aluminum foil current collector and a positive electrode material and a negative electrode material respectively coated on both sides of the aluminum foil current collector; the single-sided conventional current collector negative electrode sheet C includes an aluminum foil current collector and a negative electrode material coated on a single side of the aluminum foil current collector.

[0024] The main differences between the four types of pole pieces mentioned above are the different current collectors and double-sided coated electrodes: the first is a conventional aluminum foil current collector (directly purchased) with a single-sided coating of positive electrode material, hereinafter referred to as single-sided conventional current collector positive pole piece A; the second is an aluminum foil-plastic-aluminum foil composite current collector (directly purchased) with double-sided coating, one side with positive electrode material and the other side with negative electrode material, hereinafter referred to as double-sided composite current collector double electrode pole piece B1; the third is a conventional aluminum foil current collector (directly purchased) with double-sided coating, one side with positive electrode material and the other side with negative electrode material, hereinafter referred to as double-sided conventional current collector double electrode pole piece B2; the fourth is a conventional aluminum foil current collector (directly purchased) with a single-sided coating of negative electrode material, hereinafter referred to as single-sided conventional current collector negative pole piece C. Pole pieces A and C must be conventional aluminum foil, because single-sided coated pole pieces are prone to curling after cold pressing, and the sandwich aluminum foil is inherently thin and light, and the pole pieces are extremely prone to curling after cold pressing, making them difficult to handle. Electrode pieces A / B1 / B2 / C are cut to the desired dimensions using a punching machine. Then, the separator is assembled into a composite structure consisting of separator + A + (separator + B1 + separator + B2) * n + separator + C + separator, where n is determined by the cell capacity. The outer shell of a hard-shell battery is aluminum, while the outer film of a soft-shell battery is aluminum-plastic film. This approach offers significant advantages in large hard-shell battery cells.

[0025] In the present invention, the arrangement direction of the single-sided conventional current collector positive electrode sheet A and the single-sided conventional current collector negative electrode sheet C can be selected within a wide range, but in order to further improve the safety performance and capacity of the sodium ion battery, preferably, the coating surface of the electrode material of the single-sided conventional current collector positive electrode sheet A and the single-sided conventional current collector negative electrode sheet C faces the interior of the battery cell.

[0026] In the present invention, the number of repetitions of the repeating unit can be selected within a wide range, but in order to further improve the safety performance and capacity of the sodium ion battery, preferably, the number of repetitions of the repeating unit is n, and the range of n is 1-1000, and n is determined according to the capacity of the battery cell; more preferably, n is 30-110.

[0027] In the present invention, the thickness of the single-sided conventional current collector positive electrode sheet A, the double-sided composite current collector double electrode sheet B1, the double-sided conventional current collector double electrode sheet B2, and the single-sided conventional current collector negative electrode sheet C can also be selected within a wide range. However, in order to further improve the safety performance and capacity of the sodium ion battery, preferably, the thickness of the aluminum foil current collector in the single-sided conventional current collector positive electrode sheet A, the double-sided conventional current collector double electrode sheet B2, and the single-sided conventional current collector negative electrode sheet C is each independently 11-13 μm; the thickness of the aluminum foil-plastic-aluminum foil composite current collector in the double-sided composite current collector double electrode sheet B1 is 7-9 μm.

[0028] In the present invention, the coating density of the positive electrode material in the single-sided conventional current collector positive electrode sheet A, the double-sided composite current collector double electrode sheet B1, and the double-sided conventional current collector double electrode sheet B2 can also be selected in a wide range. However, in order to further improve the safety performance and capacity of the sodium ion battery, preferably, in the single-sided conventional current collector positive electrode sheet A, the double-sided composite current collector double electrode sheet B1, and the double-sided conventional current collector double electrode sheet B2, the average single-sided coating area density of the positive electrode material is 0.1-0.25g / 1000mm 2 .

[0029] In the above embodiment, the components of the positive electrode material can be selected within a wide range, but in order to further improve the safety performance and capacity of the sodium ion battery, preferably, in the single-sided conventional current collector positive electrode sheet A, the double-sided composite current collector double electrode sheet B1, and the double-sided conventional current collector double electrode sheet B2, the positive electrode material contains an O3 type sodium ion positive electrode, conductive carbon black and polyvinylidene fluoride; more preferably, in the positive electrode material, the mass percentage of the O3 type sodium ion positive electrode is 92-96%, the mass percentage of the conductive carbon black is 2-5%, and the mass percentage of the polyvinylidene fluoride is 2-5%.

[0030] In the present invention, the coating density of the negative electrode material in the single-sided conventional current collector positive electrode sheet A, the double-sided composite current collector double electrode sheet B1, and the double-sided conventional current collector double electrode sheet B2 can also be selected in a wide range. However, in order to further improve the safety performance and capacity of the sodium ion battery, preferably, in the double-sided composite current collector double electrode sheet B1, the double-sided conventional current collector double electrode sheet B2, and the single-sided conventional current collector negative electrode sheet C, the average single-sided coating area density of the negative electrode material is 0.04-0.16g / 1000mm 2 .

[0031] In the above embodiment, the components of the negative electrode material can be selected within a wide range, but in order to further improve the safety performance and capacity of the sodium ion battery, preferably, in the double-sided composite current collector double electrode plate B1, the double-sided conventional current collector double electrode plate B2, and the single-sided conventional current collector negative electrode plate C, the negative electrode material comprises amorphous carbon, conductive carbon black, styrene-butadiene rubber and sodium carboxymethyl cellulose; more preferably, in the negative electrode material, the mass percentage of the amorphous carbon is 90-94%, the mass percentage of the conductive carbon black is 2-4%, the mass percentage of the styrene-butadiene rubber is 2-4%, and the mass percentage of the sodium carboxymethyl cellulose is 1-3%.

[0032] In the above embodiment, the type of the separator can be selected from a wide range, but in order to further improve the safety performance and capacity of the sodium ion battery, preferably, the separator is a PE film.

[0033] The present invention also provides a method for producing a sodium ion battery in the stacking manner as described above, comprising:

[0034] 1) Dispersing the positive electrode material in a solvent to prepare a positive electrode slurry; dispersing the negative electrode material in a solvent to prepare a negative electrode slurry;

[0035] 2) Coating the positive electrode slurry on one side of an aluminum foil current collector and an aluminum foil-plastic-aluminum foil composite current collector; coating the negative electrode slurry on one side of an aluminum foil current collector and an aluminum foil-plastic-aluminum foil composite current collector; wherein, a portion of the aluminum foil current collector is coated with the positive electrode slurry or the negative electrode slurry on one side, and the remaining aluminum foil current collector is coated with the positive electrode slurry and the negative electrode slurry on both sides; and the aluminum foil-plastic-aluminum foil composite current collector is coated with the positive electrode slurry and the negative electrode slurry on both sides.

[0036] 3) After the positive electrode slurry or negative electrode slurry is coated, baking, rolling, and cutting are performed to produce a single-sided conventional current collector positive electrode sheet A, a double-sided composite current collector double electrode sheet B1, a double-sided conventional current collector double electrode sheet B2, and a single-sided conventional current collector negative electrode sheet C;

[0037] 4) The single-sided conventional current collector positive electrode sheet A, double-sided composite current collector dual electrode sheet B1, double-sided conventional current collector dual electrode sheet B2, single-sided conventional current collector negative electrode sheet C, separator, and electrolyte are stacked, assembled, baked, welded and sealed, injected, and formed in sequence to produce a hard-shell battery cell.

[0038] In the above step 3), the baking temperature can be selected within a wide range. However, in order to improve the baking effect, preferably, in step 3), the baking temperature is 80-90°C.

[0039] In the above step 4), the baking temperature can be selected within a wide range. However, in order to improve the baking effect, preferably, in step 4), the baking temperature is 105-110°C.

[0040] In the above step 4), the type of the electrolyte can be selected from a wide range, but in order to further improve the safety performance and capacity of the sodium ion battery, preferably, in step 4), the electrolyte is prepared by dissolving sodium hexafluorophosphate in a mixed solvent comprising ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate, wherein the volume ratio of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate solvent is 3:1.8-2.2:4.8-5.2, and the concentration of sodium hexafluorophosphate is 0.5-1.5 mol / L.

[0041] The present invention is described in detail below using examples. In the following examples, the electrolyte was prepared by dissolving sodium hexafluorophosphate in a mixed solvent comprising ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate, wherein the volume ratio of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate was 3:2:5, and the concentration of sodium hexafluorophosphate was 1 mol / L. The composite aluminum foil was 8 μm thick and was commercially available from Soteria Battery Innovation Group, while the conventional aluminum foil was 12 μm thick and was commercially available from Shandong Deli Aluminum Technology Co., Ltd.

[0042] Example 1

[0043] A hard-shell battery with a size of 54173200 (54mm thickness * 173mm length * 200mm height) was prepared, and finally a needle penetration test (representing safety performance) and a capacity test (representing electrical performance) were performed.

[0044] The hard shell production process is as follows:

[0045] 1. Add 94% by mass of O3 type sodium ion positive electrode, 3% conductive carbon black, and 3% polyvinylidene fluoride into a stirring tank, then add N-methylpyrrolidone solvent (solid content of 70%), and then stir to form a positive electrode slurry;

[0046] 2. The positive electrode slurry described in step 1 is coated on a conventional aluminum foil, and then baked at 95°C, rolled, and cut to produce a single-sided conventional aluminum foil positive electrode sheet A. The average density of the single-sided coating is controlled to be 0.2g / 1000mm 2 A portion of the positive electrode slurry was coated on a composite aluminum foil and dried without rolling or cutting, and was set aside, temporarily referred to as A1. A portion of the positive electrode slurry was coated on a conventional aluminum foil and dried without rolling or cutting, and was set aside, temporarily referred to as A2.

[0047] 3. Add 92% by mass of amorphous carbon, 3% of conductive carbon black, 3% of styrene-butadiene rubber, and 2% of sodium carboxymethyl cellulose into a stirring tank, then add deionized water (solid content of 53%), and stir to form a negative electrode slurry;

[0048] 4. Apply the negative electrode slurry described in step 3 to the empty thin surface of the electrode sheet A1 in step 2, and then bake at 85°C, roll-press, and cut to form a double-sided composite current collector dual-electrode electrode sheet B1 of composite aluminum foil. Bake the empty thin surface of the electrode sheet A2 in step 2 at 85°C, roll-press, and cut to form a double-sided conventional current collector dual-electrode electrode sheet B2 of conventional aluminum foil. Apply a portion of the negative electrode slurry to an empty conventional aluminum foil, and then bake at 85°C, roll-press, and cut to form a single-sided conventional aluminum foil negative electrode sheet C. The average density of the single-sided coating surface is controlled to be 0.126g / 1000mm 2 .

[0049] 5. The single-sided conventional aluminum foil positive electrode sheet, the positive and negative electrode sheet, the single-sided conventional aluminum foil negative electrode sheet, the PE isolation film, and the electrolyte are made into a hard-shell battery cell through the processes of stacking, assembling, baking at 105°C, welding and sealing, liquid injection, and formation.

[0050] Electrode piece B1 and Electrode piece B2 are 62 layers, with the top and bottom layers being single-sided coated, respectively, with the positive and negative electrodes A and C, with the coated side facing the interior of the cell. The other electrodes are double-sided coated. The number of layers is defined as one layer for a single-sided positive and negative electrode, with one layer for each single-sided coated positive and negative electrode. Separator film + electrode piece A + (separator film + electrode piece B1 + separator film + electrode piece B2) * 62 + separator film + electrode piece C + separator film. After completion, the separator film wraps around the cell to enclose the bare cell.

[0051] 6. Randomly select samples for capacity test at 25℃; the average capacity is about 144.51Ah.

[0052] 7. After randomly selecting batteries and fully charging them, conduct a needle penetration test according to GBT 31485-2015 standard. The test results are shown in Figure 3 As can be seen from the figure, the temperature is controlled within 200℃; after the test, the battery cell only smoked but did not catch fire or explode, passing the national safety standards.

[0053] Example 2

[0054] Prepare a hard-shell battery with a size of 48174128 (48mm thickness * 174mm length * 128mm height), and finally perform a needle penetration test (representing safety performance) and a capacity test (representing electrical performance).

[0055] The hard shell production process is as follows:

[0056] 1. Add 92% by mass of O3 type sodium ion positive electrode, 4% conductive carbon black, and 4% polyvinylidene fluoride into a stirring tank, then add N-methylpyrrolidone solvent (solid content 68%), and then stir to form a positive electrode slurry;

[0057] 2. The positive electrode slurry described in step 1 is coated on a conventional aluminum foil, and then baked at 90°C, rolled, and cut to produce a single-sided conventional aluminum foil positive electrode sheet A. The average single-sided coating density is controlled to be 0.22g / 1000mm 2 A portion of the positive electrode slurry was coated on a composite aluminum foil and dried without rolling or cutting, and was set aside, temporarily referred to as A1. A portion of the positive electrode slurry was coated on a conventional aluminum foil and dried without rolling or cutting, and was set aside, temporarily referred to as A2.

[0058] 3. Add 90% by mass of amorphous carbon, 4% of conductive carbon black, 4% of styrene-butadiene rubber, and 2% of sodium carboxymethyl cellulose into a stirring tank, then add deionized water (solid content of 51%), and then stir to form a negative electrode slurry;

[0059] 4. Apply the negative electrode slurry described in step 3 to the empty thin surface of the electrode sheet A1 in step 2, then bake at 80°C, roll-press, and cut to form the positive and negative electrode sheets B1 of the composite aluminum foil. Bake the empty thin surface of the electrode sheet A2 in step 2 at 80°C, roll-press, and cut to form the positive and negative electrode sheets B2 of conventional aluminum foil. Apply a portion of the negative electrode slurry to the empty conventional aluminum foil, then bake at 80°C, roll-press, and cut to form the single-sided conventional aluminum foil negative electrode sheet C. The average density of the single-sided coating is controlled to be 0.14g / 1000mm 2 .

[0060] 5. The single-sided conventional aluminum foil positive electrode sheet, the positive and negative electrode sheet, the single-sided conventional aluminum foil negative electrode sheet, the PE isolation film, and the electrolyte are made into a hard-shell battery cell through the processes of lamination, assembly, baking at 100°C, welding and sealing, liquid injection, and formation.

[0061] Electrode sheets B1 and B2 each have 30 layers. The top and bottom layers are single-sided coated positive and negative electrodes A and C, respectively, with the coated side facing the interior of the cell. The other electrodes are double-sided coated. One layer represents a single electrode sheet with both positive and negative electrodes, with one layer each for the two single-sided coated positive and negative electrodes. Separator + electrode sheet A + (separator + electrode sheet B1 + separator + electrode sheet B2) * 30 + separator + electrode sheet C + separator. After completion, the separator wraps around the cell to enclose the bare cell.

[0062] 6. Randomly select samples for capacity test at 25℃; the average capacity is about 71.2Ah.

[0063] 7. After randomly selecting battery cells and fully charging them, a needle penetration test was performed according to the GBT 31485-2015 standard. After the test, the battery cells only smoked but did not catch fire or explode, passing the national safety standard.

[0064] Example 3

[0065] A hard-shell battery with a size of 72173200 (72mm thickness * 173mm length * 200mm height) was prepared, and finally a needle penetration test (representing safety performance) and a capacity test (representing electrical performance) were performed.

[0066] The hard shell production process is as follows: 1. Add 96% by mass of O3 type sodium ion positive electrode, 2% conductive carbon black, and 2% polyvinylidene fluoride into a stirring tank, then add N-methylpyrrolidone solvent (solid content of 73%), and then stir to form positive electrode slurry;

[0067] 2. The positive electrode slurry described in step 1 is coated on a conventional aluminum foil, and then baked at 100°C, rolled, and cut to produce a single-sided conventional aluminum foil positive electrode sheet A. The average single-sided coating density is controlled to be 0.12g / 1000mm 2 A portion of the positive electrode slurry was coated on a composite aluminum foil and dried without rolling or cutting, and was set aside, temporarily referred to as A1. A portion of the positive electrode slurry was coated on a conventional aluminum foil and dried without rolling or cutting, and was set aside, temporarily referred to as A2.

[0068] 3. Add 94% by mass of amorphous carbon, 2% of conductive carbon black, 4% of styrene-butadiene rubber, and 1% of sodium carboxymethyl cellulose into a stirring tank, then add deionized water (solid content of 49%), and stir to form a negative electrode slurry;

[0069] 4. Apply the negative electrode slurry described in step 3 to the empty thin surface of the electrode sheet A1 in step 2, then bake at 90°C, roll-press, and cut to form the positive and negative electrode sheets B1 of the composite aluminum foil. Bake the empty thin surface of the electrode sheet A2 in step 2 at 90°C, roll-press, and cut to form the positive and negative electrode sheets B2 of conventional aluminum foil. Apply a portion of the negative electrode slurry to the empty conventional aluminum foil, then bake at 90°C, roll-press, and cut to form the single-sided conventional aluminum foil negative electrode sheet C. The average density of the single-sided coating surface is controlled to be 0.07g / 1000mm 2 .

[0070] 5. The single-sided conventional aluminum foil positive electrode sheet, the positive and negative electrode sheet, the single-sided conventional aluminum foil negative electrode sheet, the PE isolation film, and the electrolyte are made into a hard-shell battery cell through the processes of lamination, assembly, baking at 110°C, welding and sealing, liquid injection, and formation.

[0071] Electrode piece B1 and Electrode piece B2 are 102 layers, with the top and bottom layers being single-sided coated, respectively, with the positive and negative electrodes A and C, with the coated side facing the interior of the cell. The other electrodes are double-sided coated. The number of layers is defined as one layer for a single-sided positive and negative electrode, with one layer for each single-sided coated positive and negative electrode. Separator film + Electrode piece A + (Separator film + Electrode piece B1 + Separator film + Electrode piece B2) * 102 + Separator film + Electrode piece C + Separator film. After completion, the separator film wraps around the cell to enclose the bare cell.

[0072] 6. Randomly select samples for capacity test at 25℃; the average capacity is about 196.3Ah.

[0073] 7. After randomly selecting battery cells and fully charging them, a needle penetration test was performed according to the GBT 31485-2015 standard. After the test, the battery cells only smoked but did not catch fire or explode, passing the national safety standard.

[0074] Comparative Example 1

[0075] A hard-shell battery with a size of 54173200 (54mm thickness * 173mm length * 200mm height) was produced, and finally a needle penetration test (representing safety performance) and a capacity test (representing electrical performance) were performed.

[0076] The hard shell production process is as follows:

[0077] 1. Add 94% by mass of O3 type sodium ion positive electrode, 3% conductive carbon black, 3% polyvinylidene fluoride, etc. into a stirring tank, then add N-methylpyrrolidone solvent, and then stir at high speed to make positive electrode slurry;

[0078] 2. The positive electrode slurry described in step 1 is coated on a conventional aluminum foil, and then baked at 95°C, rolled, and cut to produce a single-sided conventional aluminum foil positive electrode sheet. The average single-sided coating density is controlled to be 0.2g / 1000mm 2 After coating and drying, some of the electrodes are not rolled or cut into pieces and are ready to be coated with negative electrode slurry.

[0079] 3. Add 92% by mass of amorphous carbon, 3% of conductive carbon black, 3% of styrene-butadiene rubber, and 2% of sodium carboxymethyl cellulose into a stirring tank, then add deionized water, and then stir at high speed to prepare a negative electrode slurry;

[0080] 4. Apply the negative electrode slurry described in step 3 to the empty thin surface of the negative electrode slurry to be applied in step 2, then bake at 85°C, roll-press, and cut to form a single-sided positive and negative electrode sheet. At the same time, apply a portion of the slurry to a blank aluminum foil, then bake at 85°C, roll-press, and cut to form a single-sided conventional aluminum foil negative electrode sheet. The average density of the single-sided coating is controlled to be 0.126g / 1000mm 2 .

[0081] 5. Single-sided conventional aluminum foil positive electrode sheets, positive and negative electrode sheets of the same body, single-sided conventional aluminum foil negative electrode sheets, PE separators, and electrolytes are stacked, assembled, baked at 105°C, welded and sealed, injected, and formed into hard-shell battery cells. The details of the stacking are as follows: the number of layers of positive and negative electrode sheets of the same body is 120, the top and bottom layers are positive and negative electrode sheets coated on one side respectively, and the coated side faces the inside of the battery cell, and the other electrodes are coated on both sides. The number of layers is defined as one layer, representing one positive and negative electrode sheet of the same body, and two single-sided coated positive and negative electrode sheets each with one layer. Separator + single-sided composite current collector positive electrode sheet + (separator + positive and negative electrode sheets of the same body) * 120 + separator + single-sided composite current collector negative electrode sheet + separator. After finishing, the separator will wrap around the battery cell to wrap the bare battery cell.

[0082] 6. Randomly select samples for capacity test at 25℃. The average capacity is about 140.25Ah.

[0083] 7. After randomly selecting battery cells and fully charging them, a needle penetration test was performed according to the GBT 31485-2015 standard. The test found that the battery cell temperature exceeded 1000°C. After the test, the battery cell caught fire and exploded, and the reaction was violent, failing to meet the national safety standard.

[0084] Figure 2 1 is a capacity box plot of the batteries of Example 1 and Comparative Example 1. By comparing Example 1 with Comparative Example 1, it can be seen that the use of the composite current collector can significantly improve the electrical performance of the battery cell.

[0085] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0086] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0087] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A stacked sodium ion battery, characterized in that: The sodium ion battery comprises a plurality of electrode plates and a plurality of diaphragms; the plurality of electrode plates comprise a single-sided conventional current collector positive electrode plate (A), a plurality of double-sided composite current collector double electrode plates (B1), a plurality of double-sided conventional current collector double electrode plates (B2), and a single-sided conventional current collector negative electrode plate (C); a plurality of repeating units are arranged between the single-sided conventional current collector positive electrode plate (A) and the single-sided conventional current collector negative electrode plate (C); along the direction from the single-sided conventional current collector positive electrode plate (A) to the single-sided conventional current collector negative electrode plate (C), the repeating unit consists of one double-sided composite current collector double electrode plate (B1) and one double-sided conventional current collector double electrode plate (B2); the diaphragm is arranged between two adjacent electrode plates; Among them, the single-sided conventional current collector positive electrode sheet (A) includes an aluminum foil current collector and a positive electrode material coated on a single side of the aluminum foil current collector; the double-sided composite current collector double electrode sheet (B1) includes an aluminum foil-plastic-aluminum foil composite current collector and a positive electrode material and a negative electrode material coated on both sides of the aluminum foil-plastic-aluminum foil composite current collector respectively; the double-sided conventional current collector double electrode sheet (B2) includes an aluminum foil current collector and a positive electrode material and a negative electrode material coated on both sides of the aluminum foil current collector respectively; the single-sided conventional current collector negative electrode sheet (C) includes an aluminum foil current collector and a negative electrode material coated on a single side of the aluminum foil current collector.

2. The stacked sodium ion battery according to claim 1, characterized in that: The coating surface of the electrode material of the single-sided conventional current collector positive electrode sheet (A) and the single-sided conventional current collector negative electrode sheet (C) faces the interior of the battery cell.

3. The stacked sodium ion battery according to claim 1, characterized in that: The number of repetitions of the repeating unit is n, and the range of n is 1-1000.

4. The stacked sodium ion battery according to any one of claims 1 to 3, characterized in that: The thickness of the aluminum foil current collector in the single-sided conventional current collector positive electrode sheet (A), the double-sided conventional current collector dual electrode sheet (B2), and the single-sided conventional current collector negative electrode sheet (C) is independently 11-13 μm; the thickness of the aluminum foil-plastic-aluminum foil composite current collector in the double-sided composite current collector dual electrode sheet (B1) is 7-9 μm.

5. The stacked sodium ion battery according to any one of claims 1 to 3, characterized in that: In the single-sided conventional current collector positive electrode sheet (A), the double-sided composite current collector double electrode sheet (B1), and the double-sided conventional current collector double electrode sheet (B2), the average single-sided coating area density of the positive electrode material is 0.10-0.25g / 1000mm 2 .

6. The stacked sodium ion battery according to any one of claims 1 to 3, characterized in that: In the single-sided conventional current collector positive electrode sheet (A), the double-sided composite current collector double electrode sheet (B1), and the double-sided conventional current collector double electrode sheet (B2), the positive electrode material contains an O3 type sodium ion positive electrode, conductive carbon black, and polyvinylidene fluoride.

7. The stacked sodium ion battery according to claim 6, characterized in that: In the positive electrode material, the mass percentage of the O3 type sodium ion positive electrode is 92-96%, the mass percentage of the conductive carbon black is 2-5%, and the mass percentage of the polyvinylidene fluoride is 2-5%.

8. The stacked sodium ion battery according to any one of claims 1 to 3, characterized in that: In the double-sided composite current collector double electrode sheet (B1), the double-sided conventional current collector double electrode sheet (B2), and the single-sided conventional current collector negative electrode sheet (C), the average single-sided coating area density of the negative electrode material is 0.04-0.16g / 1000mm 2 .

9. The stacked sodium ion battery according to any one of claims 1 to 3, characterized in that: In the double-sided composite current collector double electrode sheet (B1), the double-sided conventional current collector double electrode sheet (B2), and the single-sided conventional current collector negative electrode sheet (C), the negative electrode materials include amorphous carbon, conductive carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose.

10. The stacked sodium ion battery according to claim 9, characterized in that: In the negative electrode material, the mass percentage of the amorphous carbon is 90-94%, the mass percentage of the conductive carbon black is 2-4%, the mass percentage of the styrene-butadiene rubber is 2-4%, and the mass percentage of the sodium carboxymethyl cellulose is 1-3%.

11. The stacked sodium ion battery according to any one of claims 1 to 3, characterized in that: The separator is a PE film.

12. A method for producing a stacked sodium ion battery according to any one of claims 1 to 11, characterized in that: include: 1) Dispersing the positive electrode material in a solvent to prepare a positive electrode slurry; dispersing the negative electrode material in a solvent to prepare a negative electrode slurry; 2) Coating the positive electrode slurry on one side of an aluminum foil current collector and an aluminum foil-plastic-aluminum foil composite current collector; coating the negative electrode slurry on one side of an aluminum foil current collector and an aluminum foil-plastic-aluminum foil composite current collector; wherein, a portion of the aluminum foil current collector is coated with the positive electrode slurry or the negative electrode slurry on one side, and the remaining aluminum foil current collector is coated with the positive electrode slurry and the negative electrode slurry on both sides; and the aluminum foil-plastic-aluminum foil composite current collector is coated with the positive electrode slurry and the negative electrode slurry on both sides. 3) After the positive electrode slurry or negative electrode slurry is coated, baking, rolling, and cutting are performed to produce a single-sided conventional current collector positive electrode sheet (A), a double-sided composite current collector double electrode sheet (B1), a double-sided conventional current collector double electrode sheet (B2), and a single-sided conventional current collector negative electrode sheet (C); 4) The single-sided conventional current collector positive electrode sheet (A), the double-sided composite current collector dual electrode sheet (B1), the double-sided conventional current collector dual electrode sheet (B2), the single-sided conventional current collector negative electrode sheet (C), the separator, and the electrolyte are sequentially stacked, assembled, baked, welded and sealed, injected with liquid, and formed to obtain a hard-shell battery cell.

13. The stacked sodium ion battery according to claim 12, characterized in that: In step 3), the baking temperature is 80-90°C; In step 4), the baking temperature is 105-110°C; In step 4), the electrolyte is prepared by dissolving sodium hexafluorophosphate in a mixed solvent comprising ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate, wherein the volume ratio of ethylene carbonate / dimethyl carbonate / ethyl methyl carbonate solvent is 3:1.8-2.2:4.8-5.2, and the concentration of sodium hexafluorophosphate is 0.5-1.5 mol / L.

Images