Positive electrode sheet and manufacturing method therefor, sodium ion battery, and electrical device

Abstract

A positive electrode sheet and a manufacturing method therefor, a sodium ion battery, and an electrical device. The positive electrode sheet comprises a positive electrode active layer containing a manganese-based positive electrode material; the particle size D10 of the manganese-based positive electrode material, the particle size D50 of the manganese-based positive electrode material and the single-sided areal density CW1 of the positive electrode sheet satisfy the following relational expressions: 1.5<CW1 / D10<10, and 0.5<CW1 / D50<4; the particle size D10 of the manganese-based positive electrode material is 1.5-5 μm, and the particle size D50 thereof is 6-15 μm; the single-sided areal density CW1 of the positive electrode sheet is 8-30 mg / cm2. Controlling the particle sizes and the single-sided areal density to satisfy 1.5<CW1 / D10<10 and 0.5<CW1 / D50<4 can prevent the positive electrode sheet from being prone to material shedding during cutting, being prone to fracturing and powder shedding during winding, etc., and improves the rate capability and the cycle performance of sodium ion batteries containing the positive electrode sheet.

Description

Positive electrode sheet and preparation method thereof, sodium ion battery and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application with application number CN202311725749.8 filed with the Patent Office of China on December 15, 2023, entitled “A positive electrode plate and its preparation method, sodium ion battery and electrical equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present disclosure relates to the technical field of sodium ion batteries, and in particular to a positive electrode plate and a preparation method thereof, a sodium ion battery, and an electrical device. Background Art

[0004] Due to the abundant, readily available, and stable, low-cost sodium resources, sodium-ion batteries offer significant cost advantages over lithium-ion batteries. Furthermore, sodium-ion batteries offer superior safety, high energy density, a higher cycle life, and wide temperature tolerance. This has ushered in a new phase in the research and industrialization of sodium-ion batteries.

[0005] In sodium-ion batteries, manganese-based positive electrode materials have excellent electrochemical properties and cost advantages, but they also have their disadvantages. Therefore, in the actual application of sodium-ion batteries, in order to obtain outstanding performance advantages: high cycle life, high rate, and high initial efficiency, the battery needs to be comprehensively designed to obtain a sodium-ion battery with excellent comprehensive performance.

[0006] The particles of manganese-based positive electrode sodium ion material are relatively hard and difficult to deform and extend during the electrode rolling process. They are also relatively brittle. When the electrode is brittle, it is easy to cause problems such as material falling off during cutting and breaking and powdering during winding, resulting in low electrode production quality rate and reduced rate performance and cycle performance of sodium ion batteries.

[0007] In view of this, the present disclosure is proposed.

[0008] Application Contents

[0009] The first object of the present disclosure is to provide a positive electrode sheet by adjusting the particle size D of the manganese-based positive electrode material. 10 and particle size D 50 And the single surface density CW1 of the positive electrode sheet meets 1.5 <CW1 / D 10 <10 and 0.5 <CW1 / D 50<4, which can reduce the risk of material shedding during cutting and breakage and powder loss during winding of the positive electrode sheet, thereby improving the rate performance and cycle performance of the sodium-ion battery containing the positive electrode sheet. This solves the problem in the prior art that positive electrode sheets containing manganese-based positive electrode materials are brittle, prone to material shedding during cutting and breakage and powder loss during winding, resulting in low electrode sheet quality and reduced rate performance and cycle performance of the sodium-ion battery.

[0010] The second object of the present disclosure is to provide a method for preparing a positive electrode sheet, which has the advantages of simple operation, short process flow, and suitability for mass production.

[0011] A third object of the present disclosure is to provide a sodium ion battery having high cycle life, high rate performance, and high initial efficiency.

[0012] A fourth objective of the present disclosure is to provide an electrical device.

[0013] In order to achieve the above-mentioned purpose of the present disclosure, the following technical solutions are adopted:

[0014] The present disclosure first provides a positive electrode sheet, comprising a positive electrode active layer containing a manganese-based positive electrode material;

[0015] The particle size D of the manganese-based positive electrode material 10 , the particle size D of the manganese-based positive electrode material 50 And the single-surface density CW1 of the positive electrode sheet satisfies the following relationship:

[0016] 1.5 <CW1 / D 10 <10, and 0.5 <CW1 / D 50 <4;

[0017] Wherein, the particle size D of the manganese-based positive electrode material 10 And the particle size D of the manganese-based positive electrode material 50 The unit of is μm, and the unit of the single surface density CW1 of the positive electrode sheet is mg / cm 2 ;

[0018] The particle size D of the manganese-based positive electrode material 10 The particle size D of the manganese-based positive electrode material is 1.5 to 5 μm; 50 6~15μm;

[0019] The single surface density CW1 of the positive electrode sheet is 8 to 30 mg / cm 2 .

[0020] Furthermore, the manganese-based positive electrode material includes sodium, manganese and transition metal elements;

[0021] Furthermore, the chemical formula of the manganese-based positive electrode material is Na x A y Mn z O2, wherein 0.4≤x≤1, 0.2≤y≤0.5, 0.5≤z≤0.8, y+z=1, and A includes a transition metal element.

[0022] Furthermore, the positive electrode active layer also contains a sodium supplement.

[0023] Furthermore, the sodium supplement includes at least one of sodium oxalate, sodium azide, sodium phosphide, sodium peroxide, sodium nickelate, sodium chromate and sodium carbonate.

[0024] Furthermore, the mass of the sodium supplement accounts for 0.05% to 10% of the total mass of the positive electrode active layer.

[0025] Furthermore, the positive electrode active layer also contains hydrogenated butyronitrile, and the mass of the hydrogenated butyronitrile accounts for 0.05% to 2% of the total mass of the positive electrode active layer.

[0026] The present disclosure further provides a method for preparing the positive electrode sheet, comprising the following steps:

[0027] A positive electrode slurry containing a manganese-based positive electrode material is coated on a current collector, and dried to obtain the positive electrode sheet.

[0028] Furthermore, the positive electrode slurry also contains a sodium supplement.

[0029] Furthermore, the positive electrode slurry also contains hydrogenated butyronitrile.

[0030] Furthermore, after the drying, the steps of rolling, slitting and cutting are sequentially performed.

[0031] The present disclosure further provides a sodium ion battery, comprising a negative electrode plate and the positive electrode plate.

[0032] Furthermore, the single-surface density CW2 of the negative electrode sheet and the single-surface density CW1 of the positive electrode sheet satisfy the following relationship: 1.5 <CW1 / CW2<4.5。

[0033] Furthermore, the single-surface density CW2 of the negative electrode sheet is 5 to 15 mg / cm 2 .

[0034] Furthermore, the single-surface density CW1 of the positive electrode sheet is 8 to 30 mg / cm 2 .

[0035] Furthermore, the negative electrode active material in the negative electrode plate includes at least one of amorphous carbon, titanium-based materials, metal oxides, metal sulfides and alloys.

[0036] The present disclosure also provides an electrical device comprising the sodium ion battery. DETAILED DESCRIPTION

[0037] In a first aspect, the present disclosure provides a positive electrode sheet for a sodium-ion battery, comprising a positive electrode active layer. The positive electrode active layer comprises a manganese-based positive electrode material. It is understood that the manganese-based positive electrode material comprises sodium and manganese.

[0038] The particle size D of the manganese-based positive electrode material 10 , the particle size D of the manganese-based positive electrode material 50 And the single surface density CW1 of the positive electrode sheet satisfies the following relationship: 1.5 <CW1 / D 10 <10, and 0.5 <CW1 / D 50 <4.

[0039] Among them, CW1 / D 10 The value of includes but is not limited to any one of 1.6, 1.8, 2, 2.5, 3, 4, 5, 6, 7, 8, 9 or any range between two of them; CW1 / D 50 The value of includes but is not limited to any one of 0.6, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 3.8 or a range of values ​​between any two of them.

[0040] Wherein, the particle size D of the manganese-based positive electrode material 10 The unit is μm, and the particle size D of the manganese-based positive electrode material 50 The unit of is μm, and the unit of the single surface density CW1 of the positive electrode sheet is mg / cm 2 .

[0041] In D 50 The following particles belong to the small particle range. Small particles have a filling effect between large particles. When the filling effect is strong, a stable structure is formed, resulting in worse ductility of the electrode. At this time, the positive electrode is more brittle. The smaller the particles, the stronger the filling effect, and the more brittle the electrode. Therefore, the present disclosure regulates the upper limit of the surface density of the positive electrode in combination with the particle size of the small particles, so that the electrode is in a better state and reduces the probability of problems such as material falling off during electrode cutting and breaking and powdering during winding. At the same time, considering the minimum single-sided surface density that the positive electrode can achieve during processing, the present disclosure also regulates CW1 / D 10 and CW1 / D 50 The lower limit value of .

[0042] Therefore, the present invention controls the particle size D of the manganese-based positive electrode material. 10 and particle size D 50 And the single surface density CW1 of the positive electrode sheet meets 1.5 <CW1 / D10 <10 and 0.5 <CW1 / D 50 <4, which can prevent the positive electrode sheet from falling off during cutting and breaking and losing powder during winding, thereby improving the rate performance and cycle performance of the sodium ion battery containing the positive electrode sheet.

[0043] The particle size D of the manganese-based positive electrode material 10 1.5 to 5 μm; including but not limited to any one of 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, and 5 μm, or a range between any two of the values.

[0044] The particle size D of the manganese-based positive electrode material 50 6 to 15 μm, including but not limited to any one of 6 μm, 7 μm, 8 μm, 10 μm, 12 μm, 14 μm, and 15 μm, or a range between any two of the values.

[0045] The single surface density CW1 of the positive electrode sheet is 8 to 30 mg / cm 2 ; Including but not limited to 8mg / cm 2 、10mg / cm 2 、13mg / cm 2 、15mg / cm 2 、18mg / cm 2 , 20mg / cm 2 , 23mg / cm 2 , 25mg / cm 2 , 28mg / cm 2 、30mg / cm 2 Any point value in or any range of values ​​between them.

[0046] The particle size D in the above range is used 10 , particle size D 50 and single-sided surface density CW1, can obtain better rate performance and cycle performance.

[0047] In some specific embodiments, the manganese-based positive electrode material includes sodium, manganese and transition metal elements.

[0048] In some specific embodiments, the chemical formula of the manganese-based positive electrode material is Na x A y Mn z O2, wherein 0.4≤x≤1, 0.2≤y≤0.5, 0.5≤z≤0.8, y+z=1, and A includes a transition metal element.

[0049] It can be understood that the values ​​of x, y, and z satisfy the charge balance of the chemical formula.

[0050] Among them, the chemical formula Na x A y Mn z x in O2 includes but is not limited to any one of 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 or a range between any two of them; y includes but is not limited to any one of 0.2, 0.23, 0.25, 0.28, 0.3, 0.32, 0.35, 0.38, 0.4, 0.43, 0.45, 0.48, 0.5 or a range between any two of them; z includes but is not limited to any one of 0.5, 0.53, 0.55, 0.58, 0.6, 0.63, 0.65, 0.68, 0.7, 0.73, 0.75, 0.78, 0.8 or a range between any two of them.

[0051] Doping transition metal elements into manganese-based positive electrode materials can increase the material capacity, improve the material's cycle performance, reduce gas production, or improve the material's safety performance.

[0052] In some specific embodiments, the transition metal element includes but is not limited to at least one of Sc, Ti, V, Cr, Mn, Cu, Fe, Zn, Co, Ni, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0053] In some specific embodiments, the positive electrode active layer further contains a sodium supplement.

[0054] The negative electrode material in a sodium-ion battery consumes a certain amount of active sodium to form an SEI film during the initial charge and discharge process, resulting in a reduction in the active sodium in the battery. The manganese-based positive electrode material in the positive electrode plate of the present disclosure has a relatively low gram capacity. If the negative electrode further consumes more active sodium, the battery capacity will be lowered; or more positive electrode material will be required to compensate for the lost active sodium, which is equivalent to increasing the surface density of the positive electrode, increasing the impedance of the positive electrode plate, and causing the battery performance to decline. Therefore, the present disclosure can compensate for the active sodium consumed by the negative electrode by adding a sodium supplement to the positive electrode plate, thereby increasing the capacity of the sodium-ion battery.

[0055] In some specific embodiments, the sodium supplement includes at least one of sodium oxalate, sodium azide, sodium phosphide, sodium peroxide, sodium nickelate, sodium chromate and sodium carbonate.

[0056] Furthermore, the sodium supplement includes sodium oxalate. Compared with other sodium supplements, sodium oxalate is more stable and can exist stably in the air after being added. It also has a lower cost and a lower decomposition voltage.

[0057] In some specific embodiments, the mass of the sodium supplement accounts for 0.05% to 10% of the total mass of the positive electrode active layer, including but not limited to any one of 0.05%, 0.1%, 0.2%, 0.5%, 1%, 3%, 5%, 7%, 9%, 10% or a range between any two of them; it can further be 1% to 5%.

[0058] Sodium oxalate has strong water absorption and is easy to cause the positive electrode slurry to gel during processing. In addition, sodium oxalate increases the risk of gas production in the battery. Therefore, the present invention controls the mass of the sodium supplement to be between 0.5% and 10% of the total mass of the positive electrode active layer to ensure the electrochemical performance of the sodium ion battery.

[0059] In some specific embodiments, the positive electrode active layer further contains hydrogenated butyronitrile.

[0060] Manganese-based cathode materials are highly alkaline, and in the presence of moisture, this can cause the binder PVDF to gel. However, hydrogenated nitrile, because it contains no fluorine, can mitigate this gelation. Furthermore, due to the high manganese content in manganese-based cathode materials, manganese ions will be leached during long cycles due to reactions. Hydrogenated nitrile contains cyano groups, which complex with manganese ions, thus limiting their leaching and improving cycling performance.

[0061] In some specific embodiments, in order to avoid excessive addition of hydrogenated butyronitrile, which increases the electrode sheet resistance and thus increases the battery resistance and affects the battery performance, the present disclosure optimizes the amount of hydrogenated butyronitrile. The mass of the hydrogenated butyronitrile accounts for 0.05% to 2% of the total mass of the positive electrode active layer, including but not limited to any one of 0.05%, 0.08%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, and 2%, or a range between any two of the values; further, it can be 0.1% to 0.8%.

[0062] In some specific embodiments, the positive electrode active layer is mainly composed of a manganese-based positive electrode material, a sodium supplement, hydrogenated butyronitrile, a binder and a conductive agent.

[0063] In a second aspect, the present disclosure provides a method for preparing the positive electrode sheet, comprising the following steps:

[0064] A positive electrode slurry containing a manganese-based positive electrode material is coated on a current collector, and dried to obtain the positive electrode sheet.

[0065] The preparation method has the advantages of simple operation, short process flow and suitability for batch production.

[0066] In some specific embodiments, in order to compensate for the active sodium consumed by the negative electrode and improve the capacity of the sodium ion battery, the positive electrode slurry further contains a sodium supplement.

[0067] In some specific embodiments, the sodium supplement includes at least one of sodium oxalate, sodium azide, sodium phosphide, sodium peroxide, sodium nickelate, sodium chromate and sodium carbonate.

[0068] In some specific embodiments, in order to further improve the cycle performance of the sodium ion battery, the positive electrode slurry further contains hydrogenated butyronitrile.

[0069] In some specific embodiments, after the drying, the steps of rolling, slitting and cutting are further performed in sequence.

[0070] In some specific embodiments, the preparation method of the positive electrode plate includes the following steps: mixing and stirring the manganese-based positive electrode material, PVDF (polyvinylidene fluoride), cyanide butyronitrile, conductive agent, sodium oxalate and NMP (N-methylpyrrolidone) evenly, and then uniformly coating the surface of the current collector according to the required surface density. After drying, the positive electrode plate is rolled according to the required thickness to the required thickness, and after slitting and cutting processes, a positive electrode plate of a specific size that meets the requirements is obtained.

[0071] In some specific embodiments, the current collector may be made of aluminum foil, but is not limited thereto.

[0072] In a third aspect, the present disclosure provides a sodium ion battery comprising a negative electrode plate and the above-mentioned positive electrode plate.

[0073] The sodium ion battery provided by the present disclosure has high first coulombic efficiency, high rate performance and excellent cycle retention rate.

[0074] In some specific embodiments, the sodium ion battery further includes a separator and an electrolyte.

[0075] The negative electrode plate includes any negative electrode plate commonly used in the art.

[0076] As an example, the negative electrode plate includes a current collector and a negative electrode material coated on the current collector. The current collector includes but is not limited to copper foil. In addition to the negative electrode active material, the negative electrode material also includes at least one of a binder and a conductive agent. The binder can be a binder material commonly used in the art, such as at least one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polytetrafluoroethylene, carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), and aqueous glue, but is not limited thereto. The conductive agent can be a conductive material commonly used in the art, such as at least one of conductive graphite, acetylene black, carbon nanotubes, nanopowder, and graphene, but is not limited thereto.

[0077] In some specific embodiments, the single-sided areal density CW2 of the negative electrode sheet and the single-sided areal density CW1 of the positive electrode sheet satisfy the following relational expression: 1.5 < CW1 / CW2 < 4.5.

[0078] Among them, the value of CW1 / CW2 includes, but is not limited to, any point value or range value between any two of 1.6, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.4.

[0079] The capacity of the manganese-based positive electrode material is relatively low. Therefore, when matching the negative electrode material, it is easy to form a situation where the areal density of the positive electrode sheet is relatively large. It is necessary to comprehensively consider the areal density of the electrode sheet to obtain better rate performance and cycling performance. Specifically, the manganese-based positive electrode material itself has low conductivity, so it accounts for a relatively large proportion in the battery impedance and has a significant impact on the rate and cycling performance. If the areal density deviation between the positive electrode sheet and the negative electrode sheet is large, it will lead to a relatively high areal density of the positive electrode sheet, and the overall performance of the battery will be greatly damaged. Moreover, it is difficult to dry when the areal density of the positive electrode sheet is on the high side, increasing the processing energy consumption.

[0080] Therefore, by controlling the single-sided areal density CW2 of the negative electrode sheet and the single-sided areal density CW1 of the positive electrode sheet to satisfy the relational expression 1.5 < CW1 / CW2 < 4.5, the present disclosure can further improve the rate and cycling performance of the sodium-ion battery.

[0081] In some specific embodiments, the single-sided areal density CW2 of the negative electrode sheet is 5 - 15 mg / cm 2 ; including, but not limited to, any point value or range value between any two of 5 mg / cm 2 , 7 mg / cm 2 , 9 mg / cm 2 , 10 mg / cm 2 , 13 mg / cm 2 , 15 mg / cm 2 .

[0082] In some specific embodiments, the single-sided areal density CW1 of the positive electrode sheet is 8 - 30 mg / cm 2 ; including, but not limited to, any point value or range value between any two of 8 mg / cm 2 , 10 mg / cm 2 , 15 mg / cm 2 , 20 mg / cm 2 , 25 mg / cm 2 , 30 mg / cm 2 .

[0083] The positive electrode and the negative electrode adopt the above-mentioned single-sided surface density, which can further improve the rate and cycle performance of the sodium ion battery.

[0084] In some specific embodiments, the negative electrode active material in the negative electrode plate includes at least one of amorphous carbon, titanium-based materials, metal oxides, metal sulfides, and alloys.

[0085] In a fourth aspect, the present disclosure provides an electrical device comprising the above-mentioned sodium ion battery.

[0086] Among them, electrical equipment includes any equipment or device containing the above-mentioned sodium ion batteries, including but not limited to electric vehicles, electric motorcycles, electric bicycles, power tools, energy storage systems, electronic products and office equipment.

[0087] The embodiments of the present disclosure will be described in detail below with reference to the examples. However, those skilled in the art will appreciate that the following examples are intended only to illustrate the present disclosure and should not be construed as limiting the scope of the present disclosure. Where specific conditions are not specified in the examples, the experiments were performed under conventional conditions or the conditions recommended by the manufacturer. Where the manufacturer of the reagents or instruments is not specified, all are commercially available conventional products.

[0088] Example 1

[0089] The method for preparing the positive electrode sheet provided in this embodiment includes the following steps:

[0090] Manganese-based cathode material Na 0.47 Cu 0.33 Mn 0.67 O2(D 10 =3.2μm, D 50 =9μm), PVDF, cyanide butyronitrile, conductive agent and sodium oxalate were mixed in a mass ratio of 96:1.5:0.3:2:0.2 (i.e., the mass of the sodium supplement agent accounted for 0.2% of the total mass of the positive electrode active layer, and the mass of the cyanide butyronitrile accounted for 0.3% of the total mass of the positive electrode active layer), and NMP solvent was added thereto and stirred evenly to obtain a positive electrode slurry. According to the single surface density of 15.5mg / cm 2 The positive electrode slurry is evenly coated on the surface of the aluminum foil. After being dried in an oven, the positive electrode sheet is rolled according to the designed thickness until it reaches the designed thickness, and then cut and trimmed to obtain the positive electrode sheet.

[0091] Example 2

[0092] The preparation method of the positive electrode sheet provided in this embodiment is basically the same as that in embodiment 1, except that the single-surface density is 22.1 mg / cm 2 The positive electrode slurry is evenly coated on the surface of the aluminum foil.

[0093] Example 3

[0094] The preparation method of the positive electrode plate provided in this embodiment is basically the same as that in Example 1, except that the mass ratio of the manganese-based positive electrode material, PVDF, cyanide butyronitrile, conductive agent and sodium oxalate is replaced with 95.3:1.5:1:2:0.2 (that is, the mass of cyanide butyronitrile accounts for 1% of the total mass of the positive electrode active layer).

[0095] Example 4

[0096] The preparation method of the positive electrode sheet provided in this embodiment is basically the same as that in embodiment 1, except that the particle size D of the manganese-based positive electrode material is 10 Replaced with 4μm, and the particle size D 50 Replaced with 14μm.

[0097] Example 5

[0098] The preparation method of the positive electrode plate provided in this embodiment is basically the same as that in Example 1, except that the mass ratio of the manganese-based positive electrode material, PVDF, cyanide butyronitrile, conductive agent and sodium oxalate is replaced with 93.2:1.5:0.3:2:3 (that is, the mass of sodium oxalate accounts for 3% of the total mass of the positive electrode active layer).

[0099] Example 6

[0100] The method for preparing a sodium ion battery provided in this embodiment comprises the following steps:

[0101] (1) Preparation of negative electrode sheet: amorphous carbon material (Kuraray, type 2), CMC, SBR and conductive agent were mixed in a mass ratio of 93:2:3:2, and water was added thereto and stirred evenly to obtain negative electrode slurry. The single surface density was 6.1 mg / cm 2 The negative electrode slurry is evenly coated on the surface of the aluminum foil. After being dried in an oven, the negative electrode sheet is rolled according to the designed thickness, pressed to the designed thickness, and then cut and cut to obtain the negative electrode sheet.

[0102] (2) Assembling a battery: Using the negative electrode sheet prepared in step (1) and the positive electrode sheet prepared in Example 1, the positive and negative electrode sheets are subjected to a tab welding process. The positive electrode sheet, separator, and negative electrode sheet are wound together, baked to remove moisture, and then encapsulated with aluminum plastic film. The electrolyte is then injected and sealed. The battery is then activated by dissolving the electrolyte into the electrolyte to obtain an electrochemically active sodium ion battery.

[0103] Example 7

[0104] The positive electrode sheet obtained in Example 2 was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0105] Example 8

[0106] The positive electrode sheet obtained in Example 3 was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0107] Example 9

[0108] The positive electrode sheet obtained in Example 4 was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0109] Example 10

[0110] The positive electrode sheet obtained in Example 5 was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0111] Example 11

[0112] The preparation method of the sodium ion battery provided in this embodiment is basically the same as that in Example 6, except that the single surface density is 10 mg / cm 2 The negative electrode slurry is evenly coated on the surface of the aluminum foil.

[0113] Example 12

[0114] The preparation method of the positive electrode plate provided in this embodiment is basically the same as that in Example 1, except that sodium oxalate is not added, and the mass ratio of the manganese-based positive electrode material, PVDF, cyanide butyronitrile and conductive agent is replaced with 96.2:1.5:0.3:2.

[0115] The positive electrode sheet prepared in this embodiment is used to make a sodium ion battery, and the preparation method and parameters are the same as those in Example 6.

[0116] Example 13

[0117] The preparation method of the positive electrode plate provided in this embodiment is basically the same as that in Example 1, except that cyanide nitrile is not added, and the mass ratio of manganese-based positive electrode material, PVDF, conductive agent and sodium oxalate is replaced with 96.3:1.5:2:0.2.

[0118] The positive electrode sheet prepared in this embodiment is used to make a sodium ion battery, and the preparation method and parameters are the same as those in Example 6.

[0119] Example 14

[0120] The preparation method of the positive electrode provided in this embodiment is basically the same as that in embodiment 1, except that Na 0.47 Cu 0.33 Mn 0.67 O2 is replaced by Na 0.67 Fe 0.08 Cu 0.25 Mn 0.67 O2.

[0121] The positive electrode sheet obtained in this example was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0122] Example 15

[0123] The preparation method of the positive electrode provided in this embodiment is basically the same as that in embodiment 1, except that Na 0.47 Cu 0.33 Mn 0.67 O2 is replaced by Na 0.67 Ni 1 / 6 Co 1 / 3 Mn 1 / 2 .

[0124] The positive electrode sheet obtained in this example was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0125] Example 16

[0126] The preparation method of the positive electrode provided in this embodiment is basically the same as that in embodiment 1, except that Na 0.47 Cu 0.33 Mn 0.67 O2 is replaced by Na 0.67 Fe 0.5 Mn 0.5 .

[0127] The positive electrode sheet obtained in this example was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0128] Comparative Example 1

[0129] The preparation method of the positive electrode sheet provided in this comparative example is basically the same as that of Example 1, except that the particle size D of the manganese-based positive electrode material is 10 Replaced with 1.5 μm, and the particle size D 50 Replaced with 6μm.

[0130] The positive electrode sheet obtained in this comparative example was used to make a sodium ion battery, and the preparation method and parameters were the same as those in Example 6.

[0131] Comparative Example 2

[0132] The preparation method of the positive electrode sheet provided in this comparative example is basically the same as that in Example 1, except that the single-surface density is 31 mg / cm 2 The positive electrode slurry was evenly coated on the surface of the aluminum foil. A sodium ion battery was made using the positive electrode sheet obtained in this comparative example, and the preparation method and parameters were the same as those in Example 6.

[0133] That is, in this comparative example, the single-surface density of the positive electrode sheet is CW1 = 31 mg / cm 2 , the single surface density of the negative electrode sheet CW2=6.1mg / cm2 , CW1 / CW2=5.08.

[0134] The CW1 / D in the above embodiments and comparative examples 10 and CW1 / D 50 The values ​​of CW1 / CW2 in the above embodiments and comparative examples are shown in Table 2.

[0135] Table 1 CW1 / D in each embodiment and each comparative example 10 and CW1 / D 50

[0136] Table 2 CW1 / CW2 in each embodiment and each comparative example

[0137] Experimental Example 1

[0138] The positive electrode slurries prepared in each embodiment and each comparative example were subjected to static viscosity tests, the degree of material loss and the quality rate of the positive electrode sheets prepared in each embodiment and each comparative example were tested and counted, and the electrochemical performance of the sodium ion batteries prepared in each embodiment and each comparative example was tested. The results are shown in Table 3.

[0139] The viscosity test of the positive electrode slurry was conducted for 8 hours at a dew point of -30°C. When the viscosity of the positive electrode slurry exceeds 10,000 mPa.s, it will have a serious impact on the coating of the slurry onto the aluminum foil.

[0140] Battery first efficiency = 0.2C first discharge capacity / 0.2C first charge capacity × 100%.

[0141] Battery 3C discharge capacity retention rate = 3C discharge capacity / 0.5C discharge capacity × 100%.

[0142] The battery capacity retention rate of 200cl (cl ring) cycle at room temperature 1C / 1C = 200cl discharge capacity / 3cl discharge capacity × 100%.

[0143] Table 3 Results of various performance tests

[0144] By comparing Example 6 with Comparative Example 1, it can be seen that in Comparative Example 1, due to the particle size D 10 Smaller, CW1 / D 10 The higher the value, the greater the degree of material loss during cutting of the positive electrode sheet, the lower the quality rate of the sheet, and the brittleness of the positive electrode sheet, which leads to partial breakage of the sheet, affecting the rate performance and cycle performance of the assembled sodium-ion battery.

[0145] By comparing Example 6 and Comparative Example 2, it can be seen that in Comparative Example 2, due to the relatively large single-sided surface density of the positive electrode sheet, the CW1 / CW2 value is relatively high. Since the impedance value of the positive electrode sheet is relatively large, under the condition dominated by the positive electrode impedance value, the resistance of the assembled battery is relatively high, resulting in serious attenuation of the rate performance and cycle performance of the sodium-ion battery.

[0146] By comparing Example 6 and Example 12, it can be seen that in Example 6, due to the addition of sodium oxalate, the initial efficiency of the battery is significantly improved.

[0147] By comparing Example 6 and Example 13, it can be seen that in Example 6, due to the addition of acrylonitrile butadiene rubber, the gel phenomenon is effectively alleviated. And due to the coordination effect of the cyano group on manganese ions, the dissolution of manganese ions is restricted, thereby significantly improving its cycle performance.

[0148] Compared with the prior art, the beneficial effects of the present disclosure are as follows:

[0149] (1) By controlling the particle size D 10 and particle size D 50 of the manganese-based positive electrode material and the single-sided surface density CW1 of the positive electrode sheet satisfying 1.5 < CW1 / D 10 < 10 and 0.5 < CW1 / D 50 < 4, issues such as material loss during cutting and powder falling during winding and breaking of the positive electrode sheet can be avoided, improving the rate performance and cycle performance of the sodium-ion battery containing the positive electrode sheet.

[0150] (2) By adding a sodium supplement agent to the positive electrode sheet, the active sodium consumed by the negative electrode can be compensated, thereby improving the capacity of the sodium-ion battery.

[0151] (3) By adding acrylonitrile butadiene rubber to the positive electrode sheet, the gel phenomenon can be alleviated and the dissolution of manganese ions can be restricted, thereby improving its cycle performance.

[0152] (4) By controlling the single-sided surface density CW2 of the negative electrode sheet and the single-sided surface density CW1 of the positive electrode sheet to satisfy 1.5 < CW1 / CW2 < 4.5, the rate performance and cycle performance of the sodium-ion battery can be further improved.

[0153] (5) The sodium-ion battery provided by the present disclosure has a high initial Coulomb efficiency, high rate performance, and excellent cycle retention rate. Industrial Applicability

[0154] The present disclosure controls the particle size D 10 and particle size D 50 of the manganese-based positive electrode material and the single-sided surface density CW1 of the positive electrode sheet satisfying 1.5 < CW1 / D 10 < 10 and 0.5 < CW1 / D 50<4, which can reduce the risk of material shedding during cutting and breakage and powder loss during winding of the positive electrode sheet, thereby improving the rate performance and cycle performance of the sodium-ion battery containing the positive electrode sheet. The positive electrode sheet and sodium-ion battery can be widely used in various electrical devices.

Claims

1. A positive electrode sheet, characterized in that: including a positive electrode active layer containing a manganese-based positive electrode material; The particle size D of the manganese-based positive electrode material 10 , the particle size D of the manganese-based positive electrode material 50 And the single-sided surface density CW1 of the positive electrode sheet satisfies the following relationship: 1.5 <CW1 / D 10 <10, and 0.5 <CW1 / D 50 <4; Wherein, the particle size D of the manganese-based positive electrode material 10 And the particle size D of the manganese-based positive electrode material 50 The unit of is μm, and the unit of the single-surface density CW1 of the positive electrode sheet is mg / cm 2 ; The particle size D of the manganese-based positive electrode material 10 The particle size D of the manganese-based positive electrode material is 1.5 to 5 μm. 50 6~15μm; The single surface density CW1 of the positive electrode sheet is 8 to 30 mg / cm 2 .

2. The positive electrode sheet according to claim 1, characterized in that: Contains at least one of the following features (1) to (2): (1) The manganese-based positive electrode material includes sodium, manganese and transition metal elements; (2) The chemical formula of the manganese-based positive electrode material is Na x A y Mn z O2, wherein 0.4≤x≤1, 0.2≤y≤0.5, 0.5≤z≤0.8, y+z=1, and A includes transition metal elements.

3. The positive electrode sheet according to claim 1, characterized in that: The positive electrode active layer further contains a sodium supplement, and the sodium supplement comprises at least one of the following features (1) to (2): (1) The sodium supplement comprises at least one of sodium oxalate, sodium azide, sodium phosphide, sodium peroxide, sodium nickelate, sodium chromate and sodium carbonate; (2) The mass of the sodium supplement accounts for 0.05% to 10% of the total mass of the positive electrode active layer.

4. The positive electrode sheet according to claim 1, characterized in that: The positive electrode active layer also contains hydrogenated butyronitrile, and the mass of the hydrogenated butyronitrile accounts for 0.05% to 2% of the total mass of the positive electrode active layer.

5. The method for preparing a positive electrode sheet according to any one of claims 1 to 4, characterized in that: The steps include: The positive electrode slurry containing the manganese-based positive electrode material is coated on the current collector, and the positive electrode sheet is obtained after drying.

6. The method for preparing the positive electrode sheet according to claim 5, characterized in that: Contains at least one of the following features (1) to (3): (1) The positive electrode slurry also contains a sodium supplement; (2) The positive electrode slurry further contains hydrogenated butyronitrile; (3) After the drying, the steps of rolling, slitting and cutting are also included in sequence.

7. A sodium ion battery, characterized in that: It comprises a negative electrode sheet and a positive electrode sheet as claimed in any one of claims 1 to 4.

8. The sodium ion battery according to claim 7, characterized in that: The single-surface density CW2 of the negative electrode sheet and the single-surface density CW1 of the positive electrode sheet satisfy the following relationship: 1.5 <CW1 / CW2<4.5。 9. The sodium ion battery according to claim 8, characterized in that: Contains at least one of the following features (1) to (3): (1) The single-surface density CW2 of the negative electrode sheet is 5 to 15 mg / cm 2 ; (2) The single-surface density CW1 of the positive electrode sheet is 8 to 30 mg / cm 2 ; (3) The negative electrode active material in the negative electrode plate includes at least one of amorphous carbon, titanium-based materials, metal oxides, metal sulfides and alloys.

10. An electrical device, characterized in that: Comprising the sodium ion battery as claimed in any one of claims 7 to 9.

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