Positive electrode sheet, preparation method for positive electrode sheet, and lithium-ion battery

Abstract

The present application relates to the technical field of batteries, and in particular to a positive electrode sheet, a preparation method for a positive electrode sheet, and a lithium-ion battery. To address the problem of poor rate capability of existing lithium-ion batteries, the applied improvement is as follows: a positive electrode sheet and a positive electrode material layer satisfy a relational expression 3.0<η*D50<10, where η is the porosity of the positive electrode sheet, and D50 is a corresponding particle size when a cumulative particle size distribution of the positive electrode material layer is 50%. By means of the improvement above, the positive electrode sheet has higher rate capability and a longer cycle life.

Description

Positive electrode sheet, method for preparing positive electrode sheet, and lithium-ion battery Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a positive electrode sheet, a method for preparing a positive electrode sheet, and a lithium-ion battery. Background Art

[0002] With technological advancements, the electrification of tools has become a trend. This includes mobility tools such as electric bicycles, electric cars, and the developing electric aircraft. Battery life, a key performance indicator for mobility tools, determines how long or how far a tool can travel on a single charge. The longer the battery life, the greater the range and convenience of the mobility tool.

[0003] However, achieving longer battery life presents significant challenges in terms of rate performance and cycle performance of lithium-ion batteries. Clearly, the rate performance of existing lithium-ion batteries still needs to be improved.

[0004] Application Contents

[0005] The present application provides a positive electrode sheet, a method for preparing a positive electrode sheet, and a lithium-ion battery to improve the rate performance of the battery.

[0006] To achieve the above-mentioned object, the present application provides a positive electrode sheet in the first aspect, comprising a positive electrode current collector and a positive electrode material layer coated on at least one side of the positive electrode current collector; the positive electrode sheet and the positive electrode material layer satisfy the relationship 3.0<η*D 50 <10, where η is the porosity of the positive electrode sheet, D 50 It is the particle size corresponding to when the cumulative particle size distribution of the positive electrode material layer is 50%.

[0007] In some embodiments, the value of η ranges from 20% to 60%.

[0008] In some embodiments, D 50 The value range is 8μm~20μm.

[0009] In some embodiments, the positive electrode material layer on the positive electrode current collector also meets 2.0 mg / dm 2 ≤ρ≤3.5mg / dm 2 , wherein ρ is the coating weight of the positive electrode material layer per unit area.

[0010] In some embodiments, the positive electrode sheet also meets the requirements of 3.3g / cm 3 ≤PD≤3.5g / cm 3 , wherein PD is the compaction density of the positive electrode sheet.

[0011] In some embodiments, the chemical formula of the positive electrode material layer is Li a Ni x Co y M 1-x-y O2, wherein M includes Mn and / or Al, 0.8<a<1.5, 0<x<1, 0<y<1, 0<x+y<1.

[0012] In some embodiments, the positive electrode material layer includes a positive electrode conductive agent; the positive electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene, and Ketjen black.

[0013] In some embodiments, the positive electrode material layer includes a binder; the binder includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, and polyvinyl alcohol.

[0014] The second aspect of the present application provides a method for preparing a positive electrode sheet, comprising the following steps:

[0015] Mixing the positive electrode active material, auxiliary materials and solvent to obtain a positive electrode slurry;

[0016] coating the positive electrode slurry on at least one side of the positive electrode current collector;

[0017] drying and cold pressing the positive electrode current collector coated with the positive electrode slurry in sequence to transform the positive electrode slurry into a positive electrode material layer;

[0018] The positive electrode current collector coated with the positive electrode material layer is cut into strips to obtain a positive electrode sheet; wherein the positive electrode sheet and the positive electrode material layer satisfy the relationship 3.0<η*D 50 <10, η is the porosity of the positive electrode sheet, D 50 It is the particle size corresponding to when the cumulative particle size distribution of the positive electrode material layer is 50%.

[0019] In a third aspect, the present application proposes a lithium-ion battery comprising a battery cell, an electrolyte, and a shell for accommodating the battery cell and the electrolyte, wherein the battery cell comprises a positive electrode sheet, a negative electrode sheet, and an isolation membrane located between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet is the above-mentioned positive electrode sheet.

[0020] The positive electrode plate provided in the present application needs to satisfy the same relationship between the porosity of the positive electrode plate and the particle size of the positive electrode material layer, and is limited to an appropriate numerical range. The synergistic relationship is strong, and the rate performance and cycle life of the positive electrode plate can be jointly improved, so that the positive electrode plate has higher rate performance and longer cycle life. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] FIG1 is a schematic structural diagram of an embodiment of a positive electrode plate of the present application;

[0022] FIG2 is a schematic structural diagram of an embodiment of a lithium-ion battery of the present application;

[0023] FIG3 is a schematic structural diagram of an embodiment of a battery cell of the present application.

[0024] Specific implementation methods of this application

[0025] The following is a clear and complete description of the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of them. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0026] In addition, the descriptions of "first", "second", etc. in this application are for descriptive purposes only and should not be understood as indicating or implying their relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0027] [Term Explanation]

[0028] Positive electrode sheet: During battery charging and discharging, the positive electrode sheet provides a channel for electron migration and collects and conducts current. The positive electrode sheet mainly includes positive active material, positive conductive agent, positive current collector and binder.

[0029] Positive current collector: The positive current collector is generally made of metal foil, which serves as a conductive skeleton to help collect and transmit current.

[0030] Positive electrode material layer: Transformed from the positive electrode slurry. After the positive electrode slurry is applied to the positive electrode current collector, it needs to be dried and cold pressed in sequence. Drying is to remove the solvent in the positive electrode slurry and improve the conductivity and structural stability of the electrode. Cold pressing is to enhance the density of the electrode, improve the contact between the positive electrode active material and the positive electrode current collector, and further enhance the electrical performance of the electrode.

[0031] Striping: used to cut the coated electrode into electrode pieces of specified length to facilitate subsequent assembly and battery manufacturing.

[0032] Porosity: It is the overall statistics of various pores in the electrode material, including pores, capillary pores, controlled pores, etc.

[0033] Cumulative particle size distribution: also known as cumulative particle size distribution / cumulative distribution, is a statistical method used to describe the distribution of particles according to different particle sizes.

[0034] Compaction density: The density of the active material and adhesive after they are compacted to form the electrode.

[0035] Positive electrode active material: It is the main component of the positive electrode sheet and can provide energy for the battery.

[0036] Positive conductive agent: helps to transfer charge.

[0037] Binder: used to bond the positive electrode active material and the positive electrode conductive agent together, and can also increase the mechanical strength of the electrode.

[0038] Referring to FIG1 , the present embodiment provides a positive electrode sheet 100, comprising a positive electrode current collector 101 and a positive electrode material layer 102 coated on at least one side of the positive electrode current collector 101; the positive electrode sheet 100 and the positive electrode material layer 102 satisfy the relationship 3.0 < η * D 50 <10, where η is the porosity of the positive electrode sheet 100, D 50 is the particle size corresponding to the cumulative particle size distribution of the positive electrode material layer 102 at 50%. In the aforementioned positive electrode sheet 100, the porosity of the positive electrode sheet 100 and the particle size of the positive electrode material layer 102 need to satisfy the same relationship and be limited to an appropriate numerical range. This has a strong synergistic relationship and can jointly improve the rate performance and cycle life of the positive electrode sheet 100, thereby enabling the positive electrode sheet 100 to have higher rate performance and longer cycle life.

[0039] In some embodiments, the value range of η is 20% to 60%. If the porosity is too large, the compaction density will be reduced and the membrane structure will be easily brittle. Although the effective reaction area between the electrolyte and the positive electrode active material increases and the migration efficiency of lithium ions is improved, the contact between the active particles per unit volume is less, and the discharge capacity of the battery will gradually decrease. If the porosity is too small, the diffusion resistance of lithium ions increases, which will lead to a decrease in rate performance. Therefore, the appropriate porosity is the key to the battery cell having high rate performance and long cycle life. That is, in this embodiment, the porosity η of the positive electrode sheet 100 is in the range of 20% to 60%, which can ensure that the battery cell has high rate performance and long cycle life.

[0040] In some embodiments, D 50 The value range of is 8μm to 20μm. Within this value range, the particle size of the positive electrode material layer 102 is kept moderate. On the one hand, it avoids the particle size of the positive electrode material layer 102 being too small, which would make the positive electrode slurry difficult to disperse and coat during homogenization. On the other hand, it avoids the particle size of the positive electrode material layer 102 being too large, which would reduce the rate performance of the battery cell during charge and discharge.

[0041] In some embodiments, the positive electrode material layer 102 on the positive electrode current collector 101 also meets the 2.0 mg / dm 2 ≤ρ≤3.5mg / dm 2 , where ρ is the coating weight of the positive electrode material layer per unit area. If the coating weight is too light, the positive electrode material layer 102 may be too thin and unable to provide sufficient capacity and energy, thereby affecting the performance of the battery. If the coating weight is too heavy, the positive electrode material layer 102 may be too thick, increasing the resistance of the electrode and also affecting the rate performance of the battery. Therefore, in order to obtain good rate performance, it is necessary to select a suitable coating weight, that is, in this embodiment, the coating weight ρ of the positive electrode material layer 102 per unit area satisfies 2.0 mg / dm 2 ≤ρ≤3.5mg / dm 2 , which can make the battery have good rate performance.

[0042] In some embodiments, the positive electrode sheet 100 also meets the requirements of 3.3 g / cm 3 ≤PD≤3.5g / cm 3 , where PD is the compaction density of the positive electrode sheet 100. The compaction density will affect the electrochemical performance of the positive electrode sheet 100. Too high a compaction density will cause the gaps between the electrode materials to become smaller, limiting the transmission path of lithium ions and reducing the ion diffusion efficiency, thereby affecting the rate performance of the battery. Too low a compaction density will cause the gaps between the electrode materials to be too large, making the electrode structure unstable and reducing the capacity utilization of the electrode material, thereby affecting the rate performance of the battery. Therefore, in order to obtain good rate performance, it is necessary to select a suitable compaction density, that is, in this embodiment, the compaction density PD of the positive electrode sheet 100 meets 3.3g / cm 3 ≤PD≤3.5g / cm 3 , which can make the battery have good rate performance.

[0043] In some embodiments, the chemical formula of the positive electrode material layer 102 is Li a Ni x Co y M 1-x-y O2, wherein M includes Mn and / or Al, 0.8<a<1.5, 0<x<1, 0<y<1, and 0<x+y<1. In the chemical formula, Li is lithium, Ni is nickel, Co is cobalt, M represents a single element or a combination of multiple elements, Mn represents manganese, Al represents aluminum, and O represents oxygen.

[0044] In some embodiments, the positive electrode material layer 102 includes a positive electrode conductive agent; the positive electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene, and Ketjen black.

[0045] In some embodiments, the positive electrode material layer 102 includes a binder; the binder includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, and polyvinyl alcohol.

[0046] The present embodiment further provides a method for preparing a positive electrode sheet 100, comprising the following steps:

[0047] Step S1: Mixing the positive electrode active material, auxiliary materials and solvent to obtain positive electrode slurry.

[0048] In this step, the auxiliary materials illustratively include at least a positive electrode conductive agent and a binder. Exemplarily, the positive electrode conductive agent includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotubes, graphene, and Ketjen black. Exemplarily, the binder includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate, and polyvinyl alcohol.

[0049] Step S2: coating the positive electrode slurry on at least one side of the positive electrode current collector 101 .

[0050] Step S3: drying and cold pressing the positive electrode current collector 101 coated with the positive electrode slurry in sequence to transform the positive electrode slurry into the positive electrode material layer 102 .

[0051] In this step, optionally, the chemical formula of the positive electrode material layer 102 is Li a Ni x Co y M 1-x-y O2, wherein M includes Mn and / or Al, 0.8<a<1.5, 0<x<1, 0<y<1, 0<x+y<1.

[0052] Step S4: Slice the positive electrode current collector 101 coated with the positive electrode material layer 102 to obtain the positive electrode sheet 100; wherein the positive electrode sheet 100 and the positive electrode material layer 102 satisfy the relationship 3.0<η*D 50 <10, η is the porosity of the positive electrode sheet 100, D 50 It is the particle size corresponding to when the cumulative particle size distribution of the positive electrode material layer 102 is 50%.

[0053] In this step, optionally, the value range of η is 20% to 60%. 50 The value range of is 8 μm to 20 μm. Optionally, the positive electrode material layer 102 on the positive electrode current collector 101 also meets 2.0 mg / dm 2 ≤ρ≤3.5mg / dm 2 , wherein ρ is the coating weight of the positive electrode material layer 102 per unit area. Optionally, the positive electrode plate 100 also meets 3.3 g / cm 3 ≤PD≤3.5g / cm 3, wherein PD is the compaction density of the positive electrode sheet 100.

[0054] The preparation method provided above is limited to an appropriate numerical range because the porosity of the positive electrode plate 100 and the particle size of the positive electrode material layer 102 need to satisfy the same relationship. They have a strong synergistic relationship and can jointly improve the rate performance and cycle life of the positive electrode plate 100, so that the prepared positive electrode plate 100 has higher rate performance and longer cycle life.

[0055] 2 and 3 , an example of preparing a lithium-ion battery 200 is provided here for explaining the method of preparing the lithium-ion battery 200 . The method of preparing the lithium-ion battery 200 includes:

[0056] Preparation of the positive electrode sheet 100: The preparation method is the same as the above-mentioned positive electrode sheet 100;

[0057] Preparation of negative electrode sheet 203: Artificial graphite, acetylene black, styrene-butadiene rubber, and sodium carboxymethyl cellulose are thoroughly stirred and mixed in a deionized water solvent system at a mass ratio of 96:1:1.5:1.5 to obtain a negative electrode slurry; the negative electrode slurry is coated on a Cu foil, dried, cold pressed, and slit to obtain a negative electrode sheet 203;

[0058] Preparation of isolation film 204: using porous polyethylene material to prepare isolation film 204;

[0059] Preparation of electrolyte: A solution of lithium salt LiPF6 and a non-aqueous organic solvent in a mass ratio of 8:92 is prepared as the electrolyte of the lithium-ion battery 200; wherein the non-aqueous organic solvent is composed of ethylene carbonate, diethyl carbonate, propylene carbonate, propyl propionate, and vinylene carbonate in a mass ratio of 20:30:20:28:2;

[0060] Winding: stack the positive electrode sheet 100, the separator 204, and the negative electrode sheet 203 in order, with the separator 204 located between the positive electrode sheet 100 and the negative electrode sheet 203; wind the positive electrode sheet 100, the separator 204, and the negative electrode sheet 203 to obtain an electrode assembly;

[0061] Packaging: The electrode assembly is placed in the housing 202 , and the electrolyte is injected and packaged to obtain the lithium-ion battery 200 .

[0062] The preparation method provided above has the following beneficial effects:

[0063] (1) In the step of preparing the negative electrode plate 203, a negative electrode slurry with uniform composition and stable performance can be obtained through reasonable proportions and sufficient stirring and mixing, which provides a good foundation for subsequent coating and plate preparation.

[0064] (2) In the step of preparing the electrolyte, an electrolyte with uniform composition and stable performance can be obtained through reasonable proportioning, which provides good protection for the performance and stability of the lithium-ion battery 200; and the non-aqueous organic solvent can provide good solubility and chemical stability, and can ensure high conductivity and high ion mobility of the electrolyte.

[0065] Here are some examples of preparing lithium ion batteries 200 to illustrate D 50 , and various options of η, these examples all use reasonable combinations that are consistent with this application.

[0066] Example 1

[0067] The lithium-ion battery 200 was prepared according to the above scheme. In this example, the method for preparing the positive electrode sheet 100 is as follows: the positive electrode active material (NCM), the conductive agent (acetylene black), and the binder (polyvinylidene fluoride (PVDF)) are thoroughly stirred and mixed in an N-methylpyrrolidone solvent system at a mass ratio of 95:3:2, and then coated on the positive electrode current collector 101 Al foil. After drying, cold pressing, and slitting, the positive electrode sheet 100 is obtained. The compacted density PD of the positive electrode sheet 100 in this example is 3.5g / cm 3 , D 50 15um, ρ is 2.5mg / dm 2 ,η is 40%,η*D 50 =6.

[0068] Example 2

[0069] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that D 50 8um, η*D 50 =3.2.

[0070] Example 3

[0071] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that D 50 is 20um, η is 50%, η*D 50 =10.

[0072] Example 4

[0073] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that η is 20%, η*D 50 =3.

[0074] Example 5

[0075] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that η is 60%, η*D 50 =9.

[0076] Some examples of preparing lithium-ion batteries 200 are also provided here, which use unreasonable combinations that are opposite to those of the present application, for comparison with Examples 1-5.

[0077] Comparative Example 1

[0078] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that D 50 6um, η*D 50 =2.4.

[0079] Comparative Example 2

[0080] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that D 50 30um, η*D 50 =12.

[0081] Comparative Example 3

[0082] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that D 50 6um, η is 15%, η*D 50 =0.9.

[0083] Comparative Example 4

[0084] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that η is 70%, η*D 50 =10.5.

[0085] Comparative Example 5

[0086] Compared with the lithium ion battery 200 preparation example proposed in Example 1 above, the only difference is that η is 15%, η*D 50 =2.25.

[0087] ρ, PD, and D corresponding to Examples 1-5 and Comparative Examples 1-5 50 ,η,η*D 50 As shown in Table 1 below.

[0088] Table 1

[0089] In order to understand the performance of the lithium-ion batteries 200 prepared in Examples 1-5 and Comparative Examples 1-5, the following tests were performed:

[0090] (1) Rate performance test

[0091] The lithium-ion batteries 200 prepared in Examples 1-5 and Comparative Examples 1-5 were fully charged at xC and fully discharged at 1C. After repeating this cycle 10 times, the lithium-ion batteries 200 were fully charged at xC again, and the negative electrode 203 was disassembled to observe lithium deposition on the surface of the negative electrode 203. If lithium deposition did not occur on the negative electrode surface, the test was repeated again at a charge rate of xC, increasing in increments of 0.1C until lithium deposition occurred on the surface of the negative electrode 203. The test was then terminated. The charge rate at this point, (x-0.1)C, was the maximum charge rate of the battery. The test results are shown in Table 2 below.

[0092] (2) Cyclic performance test

[0093] Five lithium-ion batteries 200 prepared in Examples 1-5 and Comparative Examples 1-5 were taken, and the lithium-ion batteries 200 were repeatedly charged and discharged through the following steps, and the cycle capacity retention rate of the lithium-ion batteries 200 was calculated.

[0094] First, in an environment of 25°C, perform the first charge and discharge, and perform constant current and constant voltage charging at a charging current of 0.1C (i.e., the current value that completely discharges the theoretical capacity within 10 hours) until the upper limit voltage reaches 4.3V;

[0095] Then, constant current discharge was performed at a discharge current of 1C until the final voltage reached 3V, and the discharge capacity of the first cycle was recorded;

[0096] Then, 100 charge and discharge cycles were performed, and the discharge capacity at the 100th cycle was recorded.

[0097] Finally, the cycle capacity retention rate was calculated according to the formula: cycle capacity retention rate = (discharge capacity of the 100th cycle / discharge capacity of the first cycle) × 100%.

[0098] The cycle performance test data is shown in Table 2 below.

[0099] Table 2

[0100] Among them, the cycle capacity retention rate is the average value. By comparing the test data of Examples 1-5 and Comparative Examples 1-5, it can be seen that when the porosity of the positive electrode sheet 100 is equal to the particle size D of the positive electrode material layer 102, 50 Satisfying the relationship 3.0<η*D 50 <10, the battery cell 201 has a higher rate performance and a longer cycle life, which shows that a reasonable combination of porosity and particle size can allow the two to work together to improve the rate performance and cycle performance of the positive electrode sheet 100.

[0101] Those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples without mutual contradiction.

[0102] The above description is only part or preferred embodiments of the present application. Any equivalent structural transformation made using the contents of the present application specification under the overall concept of the present application, or direct / indirect application in other related technical fields are included in the scope of protection of the present application.

Claims

1. A positive electrode sheet, comprising a positive electrode current collector and a positive electrode material layer coated on at least one side of the positive electrode current collector; characterized in that: The positive electrode sheet and the positive electrode material layer satisfy the relationship 3.0<η*D 50 <10, where η is the porosity of the positive electrode sheet, D 50 It is the particle size corresponding to when the cumulative particle size distribution of the positive electrode material layer is 50%.

2. The positive electrode sheet according to claim 1, characterized in that: The value range of η is 20% to 60%.

3. The positive electrode sheet according to claim 1, characterized in that: D 50 The value range is 8μm~20μm.

4. The positive electrode sheet according to claim 1, characterized in that: The positive electrode material layer on the positive electrode current collector also meets 2.0 mg / dm 2 ≤ρ≤3.5mg / dm 2 , wherein ρ is the coating weight of the positive electrode material layer per unit area.

5. The positive electrode sheet according to claim 1, characterized in that: The positive electrode sheet also meets 3.3g / cm 3 ≤PD≤3.5g / cm 3 , wherein PD is the compaction density of the positive electrode sheet.

6. The positive electrode sheet according to claim 1, characterized in that: The chemical formula of the positive electrode material layer is Li a Ni x Co y M 1-x-y O2, wherein M includes Mn and / or Al, 0.8 <a<1.5,0<x<1,0<y<1,0<x+y<1。 7. The positive electrode sheet according to claim 1, characterized in that: The positive electrode material layer includes a positive electrode conductor; the positive electrode conductor includes at least one of carbon black, conductive graphite, carbon fiber, carbon nanotube, graphene and Ketjen black.

8. The positive electrode sheet according to claim 1, characterized in that: The positive electrode material layer includes an adhesive; the adhesive includes at least one of polyvinylidene fluoride, styrene-butadiene rubber, sodium alginate and polyvinyl alcohol.

9. A method for preparing a positive electrode sheet, characterized in that: The steps include: Mixing positive electrode active materials, auxiliary materials and solvent to obtain positive electrode slurry; Coating the positive electrode slurry on at least one side of the positive electrode current collector; The positive electrode current collector coated with the positive electrode slurry is sequentially dried and cold pressed to transform the positive electrode slurry into a positive electrode material layer; The positive electrode current collector coated with the positive electrode material layer is divided into strips to obtain a positive electrode sheet; wherein the positive electrode sheet and the positive electrode material layer satisfy the relationship 3.0<η*D 50 <10, η is the porosity of the positive electrode sheet, D 50 It is the particle size corresponding to when the cumulative particle size distribution of the positive electrode material layer is 50%.

10. A lithium-ion battery, comprising a battery cell, an electrolyte, and a shell for accommodating the battery cell and the electrolyte, wherein the battery cell comprises a positive electrode sheet, a negative electrode sheet, and a separator between the positive electrode sheet and the negative electrode sheet; characterized in that: The positive electrode plate is the positive electrode plate described in any one of claims 1-8.

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