Positive electrode sheet, lithium battery and device

Abstract

A positive electrode sheet, a lithium battery and a device. The positive electrode sheet comprises a positive electrode current collector, and a first positive electrode material layer and a second positive electrode material layer which are sequentially stacked on at least one side of the positive electrode current collector, wherein the first positive electrode material layer comprises a first lithium manganese iron phosphate material, and the second positive electrode material layer comprises a second lithium manganese iron phosphate material.

Description

Positive electrode sheet, lithium battery, and device

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 29, 2023, with application number 202311868802.X and invention name “Positive Electrode Plate, Lithium Battery and Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of lithium-ion batteries, and in particular to a positive electrode sheet, a lithium battery, and a device. Background Art

[0003] Compared to lithium iron phosphate (LFP), lithium manganese phosphate (LMP) has a higher voltage plateau (approximately 4.0V), resulting in a theoretical energy density approximately 20% higher than LFP. However, LMP is nearly an insulator, resulting in an extremely low actual specific capacity and virtually no commercialization potential. Therefore, lithium manganese iron phosphate (LMFP), formed by partially replacing Fe with Mn, is considered a next-generation phosphate-based cathode material for improving battery energy density.

[0004] However, due to the introduction of Mn ions, the intrinsic impedance of the LMFP material is relatively high, resulting in a high positive electrode polarization voltage during high-rate charging, which results in a long battery charging time. To improve the fast-charging performance of the LMFP material, the Mn content in the LMFP material can be reduced. However, this reduction in Mn content will reduce the average discharge voltage, resulting in a decrease in the material's mass energy density. Therefore, a technical solution is needed to provide a battery positive electrode containing LMFP material that can achieve both good fast-charging performance and high energy density.

[0005] Summary of the Invention

[0006] In view of this, the present application provides a double-coated positive electrode plate to solve the problem that existing lithium batteries using LMFP material for the positive electrode cannot achieve both good fast charging performance and high energy density.

[0007] Specifically, the first aspect of the present application provides a positive electrode plate, which includes a positive electrode current collector and a first positive electrode material layer and a second positive electrode material layer stacked on at least one side of the positive electrode current collector, wherein, on the same side of the positive electrode current collector, the second positive electrode material layer is arranged on the side of the first positive electrode material layer away from the positive electrode current collector; the first positive electrode material layer includes a first lithium iron manganese phosphate material, and the second positive electrode material layer includes a second lithium iron manganese phosphate material; the Mn / (Mn+Fe) molar ratio in the first lithium iron manganese phosphate material is x, and the Mn / (Mn+Fe) molar ratio in the second lithium iron manganese phosphate material is y, wherein x<y, 0.4≤x≤0.65, 0.6≤y≤0.8; the D50 particle size of the first lithium iron manganese phosphate material is in the range of 0.8μm-2μm, and the D50 particle size of the second lithium iron manganese phosphate material is in the range of 0.2μm-0.6μm.

[0008] In one embodiment, the single-surface areal density of the first positive electrode material layer is greater than or equal to the single-surface areal density of the second positive electrode material layer.

[0009] In one embodiment, the ratio of the single-surface density of the first positive electrode material layer to the second positive electrode material layer is 1-10.

[0010] In one embodiment, the ratio of the single-surface density of the first positive electrode material layer to the second positive electrode material layer is 1-9.

[0011] In one embodiment, the single surface density of the first positive electrode material layer is 100 g / m 2 -200g / m 2 .

[0012] In one embodiment, the single surface density of the second positive electrode material layer is 20 g / m 2 -100g / m 2 .

[0013] In one embodiment, the compaction density of the first positive electrode material layer is greater than the compaction density of the second positive electrode material layer.

[0014] In one embodiment, the compaction density of the first cathode material layer is 2.3-2.7 g / cm 3 ; and / or the compaction density of the second cathode material layer is 2.0-2.4g / cm 3 .

[0015] In one embodiment, the x and the y satisfy: 0.45≤x≤0.60, 0.65≤y≤0.75.

[0016] In one embodiment, the mass proportion of the first lithium iron manganese phosphate material in the first positive electrode material layer is greater than 85%; the mass proportion of the second lithium iron manganese phosphate material in the second positive electrode material layer is greater than 80%.

[0017] In one embodiment, the mass ratio of the first lithium iron manganese phosphate material to the second lithium iron manganese phosphate material is 1-10.

[0018] In one embodiment, the mass ratio of the first lithium iron manganese phosphate material to the second lithium iron manganese phosphate material is 1-9.

[0019] In one embodiment, the first positive electrode material layer is in direct contact with the positive electrode current collector, and / or the second positive electrode material layer is in direct contact with the first positive electrode material layer.

[0020] In the above-mentioned positive electrode plate of the embodiment of the present application, two lithium manganese iron phosphate materials that meet the above requirements are introduced at the same time, and they are layered as above, so that the lithium battery using the positive electrode plate can have both good fast charging performance and high energy density characteristics, and the overall performance is relatively excellent.

[0021] In a second aspect, the present application provides a lithium battery, comprising the positive electrode sheet according to the first aspect of the present application.

[0022] Due to the use of the above-mentioned positive electrode plate, the lithium battery can better balance good fast charging performance and high energy density.

[0023] In a third aspect, the present application provides a device comprising the lithium battery according to the second aspect of the present application. The device may be an electrical device or an energy storage system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIG1 is a schematic structural diagram of a positive electrode plate provided in this application.

[0025] FIG2 is another structural schematic diagram of the positive electrode sheet provided in this application.

[0026] FIG3 shows the EIS test curves of button cells made using the positive electrode sheets of Examples 1-3 and Comparative Examples 6 and 7.

[0027] Explanation of reference numerals: 100 - positive electrode sheet, 10 - positive electrode current collector, 21 - first positive electrode material layer, 22 - second positive electrode material layer. DETAILED DESCRIPTION

[0028] The technical solutions of the embodiments of the present application will be described below with reference to the accompanying drawings.

[0029] Please refer to Figures 1 and 2 together. The embodiment of the present application provides a positive electrode plate 100 for a lithium battery. The positive electrode plate 100 includes a positive electrode current collector 10 and a first positive electrode material layer 21 and a second positive electrode material layer 22 stacked on at least one side of the positive electrode current collector 10. The second positive electrode material layer 22 is arranged on the same side of the positive electrode current collector 10 as the first positive electrode material layer 21 away from the positive electrode current collector 10. The first positive electrode material layer 21 includes a first lithium iron manganese phosphate material, and the second positive electrode material layer 22 includes a first lithium iron manganese phosphate material. The material layer 22 includes a second lithium iron manganese phosphate material; the Mn / (Mn+Fe) molar ratio in the first lithium iron manganese phosphate material is x, and the Mn / (Mn+Fe) molar ratio in the second lithium iron manganese phosphate material is y, wherein x<y, 0.4≤x≤0.65, 0.6≤y≤0.8; the D50 particle size of the first lithium iron manganese phosphate material is in the range of 0.8μm-2μm, and the D50 particle size of the second lithium iron manganese phosphate material is in the range of 0.2μm-0.6μm.

[0030] Two lithium manganese iron phosphate materials are introduced into the above-mentioned positive electrode plate 100 at the same time, and they are arranged in layers. The first lithium manganese iron phosphate material with a large D50 particle size and a small Mn / (Mn+Fe) molar ratio (hereinafter referred to as "LMFP-1") is arranged in the first positive electrode material layer 21 close to the positive electrode current collector 10, and the second lithium manganese iron phosphate material with a small D50 particle size and a large Mn / (Mn+Fe) molar ratio (hereinafter referred to as "LMFP-2") is arranged in the second positive electrode material layer 22 away from the positive electrode current collector 10. This can make the two LMFP materials "play to their strengths and avoid their weaknesses", ensuring that the overall positive electrode plate 100 has both good fast charging performance and high energy density characteristics.

[0031] Specifically, the Mn / (Mn+Fe) molar ratio of the LMFP-1 material is lower than that of the LMFP-2 material, and its intrinsic resistivity is lower. Placing it close to the positive electrode current collector 10 is more conducive to reducing the electrode impedance, improving the electron transmission efficiency on the positive electrode current collector side, and ensuring the fast charging performance of the material in the overall electrode. The present application also controls the D50 particle size of the LMFP-1 material with a low Mn / (Mn+Fe) molar ratio to be larger, which is conducive to ensuring that the compaction density and surface density of the first positive electrode material layer 21 in which it is located are high, which is conducive to improving the energy density of the battery and reducing the impact of the low Mn / (Mn+Fe) molar ratio of the LMFP-1 material on the reduction of energy density.

[0032] The LMFP-2 material has a small D50 particle size, a large specific surface area, and many active sites for lithium intercalation and deintercalation. Positioning it away from the positive electrode current collector 10 (closer to the electrolyte) enriches the porosity of the positive electrode material layer, strengthens the electrolyte retention capacity, and increases the liquid phase transport speed of active ions in the layer. Consequently, when charging at high rates, the charge polarization is low, the charging power is higher, the battery has a strong fast-charging capability, and the fast-charging time is short. This also reduces the adverse effects of the high Mn / (Mn+Fe) molar ratio of LMFP-2 on the battery's fast-charging performance. Furthermore, the high Mn / (Mn+Fe) molar ratio of the LMFP-2 material is beneficial for improving the average discharge voltage and mass energy density, and also reduces the effect of the small D50 particle size of the LMFP-2 material on the reduction of the battery's volume energy density.

[0033] Therefore, the present application controls the D50 particle size and Mn / (Mn+Fe) molar ratio of the two LMFP materials within the above range, so that their performance can be differentiated to a certain extent, and with the help of the two LMFP materials that meet the above requirements, they are layered as above, so that the lithium battery using the above-mentioned positive electrode plate 100 can have both good fast charging performance and high energy density characteristics, and has better overall performance.

[0034] In addition, the active materials in the two positive electrode material layers of the above-mentioned positive electrode plate 100 are both homogeneous lithium manganese iron phosphate materials, and there is no problem of mismatch in the working voltage window between heterogeneous materials, and the degradation effect on the cycle life of the battery cell is relatively low; the two LMFP materials are olivine-type positive electrode materials, the intrinsic thermodynamic properties of the materials are stable, and the safety performance of the battery is guaranteed.

[0035] In this application, the molar ratio of Mn / (Mn+Fe) refers to the molar ratio of Mn in the lithium manganese iron phosphate, based on the sum of the molar ratios of Mn and Fe. Specifically, x refers to the molar ratio of Mn in the first lithium manganese iron phosphate material, based on the sum of the molar ratios of Mn and Fe; y refers to the molar ratio of Mn in the second lithium manganese iron phosphate material, based on the sum of the molar ratios of Mn and Fe.

[0036] In this application, the above LMFP-1 material may include LiMn x Fe 1-x PO4, the above LMFP-2 material may include LiMn y Fe 1-yPO4, wherein x<y, 0.4≤x≤0.65, 0.6≤y≤0.8. Specifically, x can be 0.4, 0.42, 0.45, 0.48, 0.50, 0.52, 0.55, 0.56, 0.58, 0.60, 0.62, 0.63, 0.64, etc. y can be 0.61, 0.62, 0.64, 0.65, 0.66, 0.68, 0.69, 0.70, 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.78, 0.79, etc. In some embodiments of the present application, 0.45≤x≤0.60, 0.65≤y≤0.75. In this case, the performance of LMFP-1 material and LMFP-2 material can be clearly distinguished. LMFP-1 material has a lower impedance, while LMFP-2 material has a higher average discharge voltage and higher energy density. Therefore, when the two are layered as above, the battery can better balance fast charging performance and high energy density.

[0037] In the present application, the D50 particle size of the LMFP-1 material may be specifically 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, or 1.9 μm. The D50 particle size of the LMFP-2 material may be specifically 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, or 0.58 μm. In some embodiments, the D50 particle size of the LMFP-1 material may be in the range of 1.0 μm-1.5 μm, and the D50 particle size of the LMFP-2 material may be in the range of 0.4 μm-0.6 μm.

[0038] In the present application, the specific surface area of ​​the LMFP-2 material is greater than that of the LMFP-1 material. In the embodiment of the present application, the specific surface area of ​​the LMFP-2 material is 10-25m 2 / g range. The LMFP-2 material with a small D50 particle size has a suitable specific surface area, which helps to reduce the problems of large interface side reactions with the electrolyte and high manganese dissolution during battery charge and discharge cycles caused by the material's excessive specific surface area. In the embodiment of the present application, the specific surface area of ​​the above-mentioned LMFP-1 material is 2-12m 2 / g range. The specific surface area of ​​the LMFP-1 material with a large D50 particle size is within an appropriate range, which can help ensure that its specific capacity is as high as possible, and avoid its specific surface being too small and not conducive to the specific capacity. Specifically, the specific surface area of ​​the LMFP-2 material can be specifically 12m 2 / g、15m 2 / g、18m 2 / g, 20m 2 / g、22m2 / g, 23m 2 / g、24m 2 / g, etc. The specific surface area of ​​LMFP-1 material can be specifically 3m 2 / g、5m 2 / g、6m 2 / g、8m 2 / g、10m 2 / g、11m 2 / g, 11.5m 2 / g, etc.

[0039] In the present application, the first positive electrode material layer 21 can be in direct contact with the positive electrode current collector 10, that is, the first positive electrode material layer 21 can be directly disposed on at least one side of the positive electrode current collector 10; alternatively, another primer layer can be disposed between the first positive electrode material layer 21 and the positive electrode current collector 10. The second positive electrode material layer 22 can be in direct contact with the first positive electrode material layer 21, that is, the second positive electrode material layer 22 can be directly disposed on the surface of the first positive electrode material layer 21; alternatively, another intermediate layer can be disposed between the second positive electrode material layer 22 and the first positive electrode material layer 21.

[0040] In some embodiments of the present application, the single-surface areal density of the first positive electrode material layer 21 is greater than or equal to the single-surface areal density of the second positive electrode material layer 22. Because the D50 particle size of the LMFP-1 material is larger than the D50 particle size of the LMFP-2 material, its compaction density is greater than that of LMFP-2. However, as a low-compactness material, LMFP-2 has an excessively high mass fraction, which can lead to a decrease in the compaction density of the positive electrode sheet 100. Therefore, controlling the areal density of the second positive electrode material layer 22 where LMFP-2 is located to be no higher than that of the first positive electrode material layer 21 where LMFP-1 is located helps ensure a high energy density of the battery.

[0041] In some embodiments of the present application, the ratio of the single-sided surface density of the first positive electrode material layer 21 to the second positive electrode material layer 22 is 1-10. The surface density of the first positive electrode material layer 21 where the LMFP-1 material with a large D50 particle size is located is controlled at an appropriately high level to ensure that it can effectively improve the volume energy density of the battery, which is more conducive to reducing the impact of the low compaction density of the small-particle LMFP-2 material on the reduction of the volume energy density of the battery, and avoiding the surface density of the second positive electrode material layer 22 being too low to effectively improve the fast charging performance of the battery. Specifically, the ratio of the single-sided surface density can be 1.1, 1.2, 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 9.5, etc. In some embodiments, the ratio of the single-sided surface density is 1-9 times, and can further be 1-8 times or 1.5-9 times, etc.

[0042] In some embodiments of the present application, the single surface density of the second positive electrode material layer 22 is 20 g / m 2-100g / m 2 The single-sided surface density of the positive electrode material layer where the small-particle LMFP-2 material is located is within an appropriate range, which can ensure that its surface density is not too high to reduce the compaction density of the overall positive electrode plate 100 and deteriorate the battery volume energy density, and that the tortuosity of the electrode is not increased due to its high surface density and excessive thickness, thereby ensuring good battery fast charging performance, and avoiding the inability to effectively improve the battery fast charging performance due to its low surface density. In some embodiments of the present application, the single-sided surface density of the first positive electrode material layer 21 is 100g / m 2 -200g / m 2 The single surface density of the positive electrode material layer containing the large-particle LMFP-1 material is within an appropriate range, which can ensure that the compaction density of the overall positive electrode sheet 100 is high, the battery volume energy density is high, and the battery fast charging performance is good. For example, the single surface density of the second positive electrode material layer 22 can be specifically 20g / m 2 , 30g / m 2 , 40g / m 2 , 50g / m 2 , 60g / m 2 , 70g / m 2 , 80g / m 2 , 90g / m 2 , 100g / m 2 The single surface density of the first positive electrode material layer 21 can be specifically 100 g / m 2 , 110g / m 2 , 120g / m 2 , 130g / m 2 , 140g / m 2 , 150g / m 2 , 160g / m 2 , 170g / m 2 , 180g / m 2 , 190g / m 2 , 195g / m 2 wait.

[0043] In some embodiments of the present application, in the positive electrode plate 100, the mass ratio of LMFP-1 material to LMFP-2 material is (1-10):1, optionally (1-9):1. This enables the battery using the positive electrode plate 100 to better improve the fast charging performance while ensuring high energy density. Among them, the mass proportion of large-particle LMFP-1 material is relatively high, and the compaction density of the first positive electrode material layer 21 in which it is located is relatively high, which mainly plays a role in ensuring a high energy density of the battery. The small-particle LMFP-2 material is introduced into the second positive electrode material layer 22 on the surface of the plate to mainly play a role in improving the fast charging performance. Specifically, the mass ratio of LMFP-1 material to LMFP-2 material can be, for example, 1:1, 1.5:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, or 9:1.

[0044] In some embodiments of the present application, the compaction density of the first positive electrode material layer 21 is greater than the compaction density of the second positive electrode material layer 22. This is mainly due to the larger D50 particle size of the LMFP-1 material than that of the LMFP-2 material. The larger compaction density of the first positive electrode material layer 21 is beneficial to reduce the effect of the small Mn / (Mn+Fe) molar ratio of the LMFP-1 material on the reduction of mass energy density. In some embodiments of the present application, the compaction density of the first positive electrode material layer 21 is 2.3-2.7 g / cm 3 The compaction density of the second positive electrode material layer 22 is 2.0-2.4 g / cm 3 . The positive electrode material layer where the LMFP-1 material with a large D50 particle size is located has an appropriate compaction density, which is beneficial to the high compaction density of the overall positive electrode plate 100 and effectively improves the battery volume energy density. At the same time, it also ensures that the compaction density of the first positive electrode material layer 21 is not too high, its porosity is appropriate, and its liquid retention capacity is also enhanced. The positive electrode material layer where the LMFP-2 material with a small D50 particle size is located has an appropriately high compaction density, which can reduce the effect of the small particle size material on the battery volume energy density, and is beneficial to improve the energy density with its high Mn content. Specifically, the compaction density of the first positive electrode material layer 21 can be 2.35, 2.40, 2.45, 2.50, 2.55, 2.60, 2.65 or 2.68 g / cm 3 The compaction density of the second positive electrode material layer 22 may be specifically 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35 or 2.38 g / cm 3 wait.

[0045] In some embodiments of the present application, the surface of the first lithium manganese iron phosphate material further comprises a conductive coating layer; and / or the surface of the second lithium manganese iron phosphate material further comprises a conductive coating layer. The presence of the conductive coating layer can improve the conductivity of the LMFP material, thereby enhancing its rate performance. Specifically, the conductive coating layer may include a conductive carbon coating layer, etc. Furthermore, the first and second lithium manganese iron phosphate materials may contain doping elements to enhance their electronic and ionic conductivity.

[0046] In some embodiments of the present application, the first lithium iron manganese phosphate material can account for 85% or more of the first positive electrode material layer 21 by mass; and the second lithium iron manganese phosphate material can account for 80% or more of the second positive electrode material layer 22 by mass. The lithium iron manganese phosphate material, as the positive electrode active material, has a high mass fraction in each positive electrode material layer, which facilitates providing a high reversible capacity for each positive electrode material layer, thereby ensuring a high reversible capacity for the overall positive electrode sheet 100. Specifically, the above mass fractions can independently be greater than 85%, for example, 85% to 95%.

[0047] In the present application, in addition to containing the above-mentioned first manganese iron lithium phosphate material in the first positive electrode material layer 21, and in addition to containing the above-mentioned second manganese iron lithium phosphate material in the second positive electrode material layer 22, the first positive electrode material layer 21 and the second positive electrode material layer 22 may also independently contain a binder and a conductive agent. Among them, each binder and each conductive agent can be a conventional choice in the field of batteries. For example, each conductive agent can be independently selected from one or more of conductive carbon black (such as acetylene black, Ketjen black, Super-P, 350G carbon black, etc.), carbon nanotubes (single-walled carbon nanotubes, or multi-walled carbon nanotubes), graphene, carbon fiber, ordered mesoporous carbon, etc. Each binder can be independently selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyolefins (such as polyethylene (PE), polypropylene (PP)), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyacrylate, polyimide (PI), styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), sodium alginate (SA), gelatin, etc., but is not limited thereto.

[0048] The first positive electrode material layer 21 and the second positive electrode material layer 22 can be formed by coating and drying the corresponding slurries. The solvents contained in each slurry can be the same or different and can be independently selected from one or more of N-methylpyrrolidone (NMP), N-ethylpyrrolidone, dimethylformamide (DMF), diethylformamide (DEF), dimethyl sulfoxide, tetrahydrofuran, and alcohol solvents, but are not limited thereto. The solid content of each slurry is not particularly limited, as long as it can meet the fluidity and uniformity of the slurry coating.

[0049] The positive electrode current collector 10 may include, but is not limited to, aluminum foil, aluminum alloy foil, a polymer film coated with metal aluminum, or the aforementioned materials with carbon coating on the surface. In some embodiments of the present application, the positive electrode current collector 10 is aluminum foil, or carbon-coated aluminum foil. In the present application, a stacked structure of a first positive electrode material layer 21 and a second positive electrode material layer 22 may be formed on both opposite sides of the positive electrode current collector 10 (as shown in FIG1 ), or a stacked structure of a first positive electrode material layer 21 and a second positive electrode material layer 22 may be formed on one side of the positive electrode current collector 10 (as shown in FIG2 ).

[0050] The embodiment of the present application further provides a lithium battery, which includes the positive electrode plate 100 described above in the embodiment of the present application.

[0051] In some embodiments of the present application, the lithium battery further includes a negative electrode plate, an electrolyte, and a separator disposed between the negative electrode plate and the positive electrode plate.

[0052] The negative electrode sheet generally includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector. The negative electrode material layer generally contains a negative electrode active material, a conductive agent, and a binder. In the embodiments of the present application, the negative electrode active material for the lithium battery can be selected from one or more of hard carbon, soft carbon, graphite, mesophase carbon microbeads, silicon-carbon composite materials, and the like.

[0053] The separator is used to separate the positive and negative electrode sheets, maintaining insulation and fluid retention between them. Together, the separator, the positive and negative electrode sheets form the battery cell, which is housed in a battery casing and is soaked in electrolyte. In some embodiments of the present application, the lithium battery can be assembled by the following method: stacking the positive electrode sheet, separator, and negative electrode sheet in sequence to form a cell; placing the cell in a battery casing, injecting electrolyte, and then sealing the battery casing to produce the battery. The cell can be wound or laminated, for example.

[0054] The separator can be any separator material used in batteries. For example, the separator may include, but is not limited to, single-layer PP (polypropylene) film, single-layer PE (polyethylene) film, double-layer PP / PE, double-layer PP / PP, triple-layer PP / PE / PP, and other polymer separators, or non-woven fabrics. The electrolyte includes an electrolyte salt and an organic solvent. The specific types and compositions of the electrolyte salt and organic solvent are conventional in the battery field and can be selected according to actual needs.

[0055] The embodiment of the present application also provides a device, which includes the above-mentioned lithium battery of the embodiment of the present application. Among them, the device can be an electric vehicle (such as a car, motorcycle, bicycle, etc.), an electric toy, a 3C product (such as a mobile phone, a laptop, a tablet computer, a pen-input computer, an e-book player, a wearable device, etc.) and other electrical equipment; it can also be an energy storage system. The energy storage system may include a plurality of the above-mentioned lithium batteries and a battery management system. The energy storage system can also supply power to electrical equipment. Among them, the electrical equipment powered by the above-mentioned lithium battery has a fast charging speed and a long operating time.

[0056] Before introducing the specific embodiments of the present application, the test methods for the various parameters mentioned above in the present application are first introduced.

[0057] In the present application, the test method for the Mn / (Mn+Fe) molar ratio of each of the above-mentioned LMFP materials is as follows: the lithium-ion battery is completely discharged and disassembled to obtain the positive electrode sheet, and the positive electrode sheet is placed in a solvent dimethyl carbonate (DMC) and soaked for 10-20 minutes to clean the residual electrolyte. After the positive electrode sheet is dried, it is soaked in water to inactivate the binder in the positive electrode sheet so that the dressing layer can be peeled off from the positive electrode collector. After drying the dressing layer on the positive electrode collector side and the diaphragm side, the upper and lower layers of the dressing layer are scraped with a ceramic scraper (or polished with sandpaper) to obtain the first positive electrode material layer powder and the second positive electrode material layer powder, respectively. Then, the two positive electrode material layer powders are tested using an inductively coupled plasma spectrometer (ICP) to obtain the Mn content and Fe content in the corresponding positive electrode material layer, and then the Mn / (Mn+Fe) molar ratio of the LMFP material in each positive electrode material layer is obtained.

[0058] The D50 test methods for the above LMFP materials are as follows:

[0059] (1) After the lithium-ion battery is fully discharged, it is disassembled to obtain the positive electrode sheet. The positive electrode sheet is then immersed in a solvent, dimethyl carbonate (DMC), for 10-20 minutes to clean the residual electrolyte. The positive electrode sheet is dried and then immersed in water to inactivate the binder so that the dressing layer can be peeled off from the positive electrode collector. After drying the dressing layer on the positive electrode collector side and the separator side, the upper and lower layers of the dressing layer are scraped with a ceramic scraper (or polished with sandpaper) to obtain the first positive electrode material layer powder and the second positive electrode material layer powder, respectively.

[0060] (2) The first cathode material layer powder and the second cathode material layer powder were then dissolved in a solvent, N-methylpyrrolidone (NMP), and heated at 80°C to accelerate dissolution. The dissolved material was filtered to separate the solid material, and the solid material was washed with NMP. The resulting mixture containing the solid material and NMP was then centrifuged at 5000 rpm, and the upper layer containing the conductive agent was discarded, while the lower layer containing the LMFP was collected. The LMFP-containing material was washed with NMP and centrifuged six times to obtain a purified LMFP solid. The dried LMFP material was then vacuum dried at 105°C for 2 hours.

[0061] (3) Finally, laser particle size testing was performed on each dried LMFP material according to GB / T19077-2016 “Laser Diffraction Method for Particle Size Analysis” to obtain the particle size distribution curve of the material. From the curve, the particle size corresponding to the volume cumulative distribution percentage of the material reaching 50% can be read, that is, the D50 of each LMFP material is obtained.

[0062] The single-surface density of each positive electrode material layer is obtained as follows:

[0063] (1) After the lithium-ion battery is fully discharged, it is disassembled to obtain a positive electrode sheet, and the positive electrode sheet is placed in a solvent dimethyl carbonate (DMC) and soaked for 10 minutes to 20 minutes to clean the residual electrolyte. After the positive electrode sheet is dried, the dressing layer on one side of the positive electrode sheet (i.e., the laminated structure of the first positive electrode material layer and the second positive electrode material layer) is peeled off with water, and after drying, the dressing layer is sampled and weighed using a sampler with a diameter of 0.015m to obtain a mass m. The sum of the single-surface density M of the first positive electrode material layer 21 and the second positive electrode material layer 22 can be calculated using the formula M = m / (0.0075×0.0075×π);

[0064] (2) The dried dressing layer is subjected to an ICP test to obtain a Mn content in the dressing layer of c. Assuming that the ratio of the surface density M1 of the first positive electrode material layer 21 to the surface density M2 of the second positive electrode material layer 22 is X (where M1+M2=M), the measured Mn contents of the LMFP materials in the upper and lower positive electrode material layers are a and b, respectively, according to the following formula:

[0065] The above X=(bc) / (ca) can be calculated, and thus the surface densities M1 and M2 of the upper and lower positive electrode material layers can be obtained according to the above M value.

[0066] The method for obtaining the compacted density of each positive electrode material layer includes the following steps: cutting the positive electrode sheet using CP testing (argon ion thinning), specifically using an argon ion beam to cut the positive electrode sheet at a microscopic scale to obtain a complete electrode sheet interface; photographing the electrode sheet interface using a scanning electron microscope (SEM). Due to the large difference in particle size of the upper and lower LMFP materials, the thicknesses of the upper and lower positive electrode material layers can be measured as h1 and h2, respectively. Based on the measured areal densities M1 and M2 of the upper and lower positive electrode material layers, the compacted density of the first positive electrode material layer can be calculated as M1 / h1, and the compacted density of the second positive electrode material layer can be calculated as M2 / h2.

[0067] The technical solution of the present application is further described below in conjunction with a number of specific embodiments.

[0068] Example 1

[0069] A positive electrode sheet, the preparation method of which comprises:

[0070] The chemical formula is LiMn 0.6 Fe 0.4 PO4 LMFP-1 material (as shown in Table 1, its Mn content is 60%, D50 particle size is 1μm) is mixed with binder PVDF and conductive agent carbon black in NMP solvent at a mass ratio of 92:3:2, and stirred evenly to obtain the first slurry. 0.75 Fe 0.25 The LMFP-2 material of PO4 (its Mn content and D50 particle size are shown in Table 1) is mixed with the binder PVDF and the conductive agent carbon black in an NMP solvent at a mass ratio of 93:3:4 and stirred evenly to obtain a second slurry.

[0071] The first slurry is first coated on the positive electrode current collector - aluminum foil, and after drying, a surface density of 150g / m 2 The first positive electrode material layer (abbreviated as "coating 1" in Table 1) was formed, and the second slurry was then coated on the first positive electrode material layer to form a surface density of 50 g / m 2 The second positive electrode material layer (abbreviated as "coating 2" in Table 1) is then prepared on the reverse side of the aluminum foil. The first positive electrode material layer and the second positive electrode material layer are then prepared, and after rolling, a double-sided positive electrode sheet is obtained.

[0072] According to the parameters summarized in Table 1, positive electrode sheets of other embodiments and comparative examples were prepared.

[0073] The only difference between Example 2 and Example 1 is that the ratio of the surface density of coating 1 to that of coating 2 is 9. That is, in Example 2, the surface density of coating 1 is changed to 180 g / m 2 , the single-sided surface density of coating 2 is changed to 20g / m2 .

[0074] The only difference between Example 3 and Example 1 is that the ratio of the surface density of coating 1 to coating 2 is 1.5. That is, the surface density of coating 1 is changed to 120 g / m 2 , the single-sided surface density of coating 2 is changed to 80g / m 2 .

[0075] The only difference between Example 4 and Example 1 is that the D50 particle size of the LMFP-2 material is changed to 0.6 μm.

[0076] The only difference between Example 5 and Example 1 is that the D50 particle size of the LMFP-1 material is changed to 1.5 μm.

[0077] The only difference between Example 6 and Example 1 is that the Mn content (i.e., Mn / (Mn+Fe)) in the LMFP-1 material is 50%, that is, the chemical formula of the LMFP-1 material in Example 6 includes LiMn 0.5 Fe 0.5 PO4.

[0078] The only difference between Example 7 and Example 1 is that the Mn content in the LMFP-2 material is 65%, that is, the chemical formula of the LMFP-2 material in Example 7 includes LiMn 0.65 Fe 0.35 PO4.

[0079] The only difference between Example 8 and Example 1 is that the Mn content in the LMFP-1 material is changed to 65%, and the Mn content in the LMFP-2 material is changed to 80%. That is, the chemical formula of the LMFP-1 material in Example 8 includes LiMn 0.65 Fe 0.35 The chemical formula of PO4, LMFP-2 materials includes LiMn 0.8 Fe 0.2 PO4.

[0080] The only difference between Example 9 and Example 1 is that the Mn content in the LMFP-1 material is changed to 40%, and the Mn content in the LMFP-2 material is changed to 60%. That is, the chemical formula of the LMFP-1 material in Example 9 includes LiMn 0.4 Fe 0.6 The chemical formula of PO4, LMFP-2 materials includes LiMn 0.6 Fe 0.4 PO4.

[0081] The only difference between Example 10 and Example 1 is that the D50 particle size of the LMFP-1 material is changed to 2 μm, and the D50 particle size of the LMFP-2 material is changed to 0.6 μm.

[0082] The only difference between Example 11 and Example 1 is that the D50 particle size of the LMFP-1 material is changed to 0.8 μm, and the D50 particle size of the LMFP-2 material is changed to 0.2 μm.

[0083] The only difference between Example 12 and Example 1 is that the ratio of the surface density of coating 1 to coating 2 is changed to 10. That is, in Example 12, the surface density of coating 1 is 181.8 g / m 2 The single-sided density of coating 2 is 18.2 g / m 2 .

[0084] The only difference between Example 13 and Example 1 is that the ratio of the surface density of coating 1 to coating 2 is changed to 1. That is, in Example 13, the surface density of coating 1 and coating 2 are both 100g / m 2 .

[0085] The only difference between Example 14 and Example 1 is that the ratio of the surface density of coating 1 to coating 2 is changed to 0.5. That is, in Example 14, the surface density of coating 1 is 66.67 g / m 2 The single-sided density of coating 2 is 133.33 g / m 2 .

[0086] The only difference between Comparative Example 1 and Example 1 is that the Mn contents of LMFP-1 and LMFP-2 materials are 75% and 85%, respectively.

[0087] The only difference between Comparative Example 2 and Example 1 is that the Mn contents of LMFP-1 and LMFP-2 materials are 30% and 50%, respectively.

[0088] The only difference between Comparative Example 3 and Example 1 is that the D50 particle sizes of LMFP-1 and LMFP-2 materials are 3 μm and 1 μm, respectively.

[0089] The only difference between Comparative Example 4 and Example 1 is that the D50 particle sizes of LMFP-1 and LMFP-2 materials are 0.5 μm and 0.1 μm, respectively.

[0090] The only difference between Comparative Example 5 and Example 1 is that the Mn content of the LMFP-1 and LMFP-2 materials is 70%.

[0091] In Comparative Example 6, the positive electrode coating on the aluminum foil is a single layer with a single surface density of 200 g / m 2 Specifically, it is made by containing LiMn with a D50 particle size of 1μm 0.6 Fe 0.4 The slurry obtained by mixing PO4 material with binder PVDF and conductive agent is coated and dried.

[0092] In Comparative Example 7, the positive electrode coating on the aluminum foil is a single layer with a single surface density of 200 g / m 2 Specifically, it is made by LiMn containing D50 particle size of 1.5μm 0.5 Fe 0.5 The slurry obtained by mixing PO4 material with binder PVDF and conductive agent is coated and dried.

[0093] Table 1. Design parameters of positive electrode sheets of various embodiments and comparative examples Note: In Table 1, the Mn content specifically refers to the ratio of the molar amount of the Mn element in the LMFP material to the sum of the molar amounts of the Mn and Fe elements.

[0094] The thickness h1 of the first positive electrode material layer on a single side, the thickness h2 of the second positive electrode material layer on a single side, and the total thickness h2 of the positive electrode coating composed of coating 1 + coating 2 in each positive electrode sheet of each embodiment and comparative examples 1-4 of the present application are summarized in Table 2 below. Based on the formula coating thickness = coating area density / coating compaction density, the compaction density of coating 1, the compaction density of coating 2, and the mixed compaction density of the positive electrode coating can be calculated, and the relevant results are summarized in Table 2. In addition, Table 2 also summarizes the thickness and compaction density values ​​of the positive electrode coating in the single-layer coated positive electrode sheets of comparative examples 5-6.

[0095] Table 2 Summary of relevant test parameters of the positive electrode sheets of various embodiments and comparative examples

[0096] The lithium metal sheets were used as counter electrodes for the positive electrodes provided in the aforementioned embodiments or comparative examples, and assembled into CR2016 button-type lithium batteries. Electrochemical impedance spectroscopy (EIS) testing was performed on each button-type lithium battery to evaluate the positive electrode impedance.

[0097] Figure 3 shows the EIS test curves of button cells made using the positive electrode sheets of Examples 1-3 and Comparative Examples 6 and 7. The larger the arc radius of the EIS curve in Figure 3, the greater the positive electrode impedance. It can be seen from Figure 3 that the positive electrodes of Comparative Examples 6 and 7 are single-layer coated with large-particle LMFP-1 materials, and the positive electrode impedance is relatively large. However, after the positive electrode sheets of the embodiments of the present application are double-layer coated with different types of LMFP materials, the positive electrode impedance can be significantly reduced, which can be beneficial to the improvement of the positive electrode kinetic performance of the battery. Among them, when the sum of the single-sided surface densities of the two positive electrode material layers is equal (such as in Examples 1-3), the higher the surface density of the coating 2 where the LMFP-2 material is located, the lower the positive electrode impedance.

[0098] The positive electrode sheets provided in the above embodiments and comparative examples are respectively assembled with the separator and the negative electrode sheet to form a soft-pack lithium battery. The specific preparation process of the soft-pack lithium battery is as follows: (1) Preparation of double-sided negative electrode sheet: Graphite negative electrode material is mixed with SBR binder and CMC thickener, conductive agent carbon black powder and water in a mass ratio of 100:1:0.5:1:80 to obtain negative electrode slurry; the negative electrode slurry is coated on the opposite sides of the negative electrode current collector, and the negative electrode material layer is formed by drying, and finally the double-sided negative electrode sheet is obtained by rolling, wherein the sum of the double-sided surface density of the negative electrode material layer is 180g / m 2 (2) stacking the above-mentioned negative electrode sheets, PP separators, and positive electrode sheets in order to prepare a bare cell (including 7 positive electrode sheets and 8 negative electrode sheets), and placing the bare cell into a battery casing for welding; using a mixed organic solvent containing 1.0 mol / L LiPF6 and 2 wt% vinylene carbonate (VC) (specifically, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7) as an electrolyte, injecting the electrolyte into the above-mentioned battery casing to assemble a soft-pack lithium battery.

[0099] The soft-pack lithium battery was formed, wherein the specific formation process was as follows: after the battery was filled with electrolyte, it was aged at 45°C for 24 hours to allow the electrolyte to fully infiltrate, then charged at 0.05C to 15% SOC, then charged at 0.1C constant current to a cut-off voltage of 4.3V, and then charged at 4.3V constant voltage to a cut-off current of 0.05C; and then placed in a 45°C oven for aging for 24 hours.

[0100] The capacity of each soft-pack battery after formation is calibrated at room temperature, specifically including: at room temperature (25°C), charging each soft-pack full battery at a constant current and constant voltage of 0.33C to an upper limit voltage of 4.3V, then charging at a constant voltage of 4.3V to a cutoff current of 0.05C, and leaving it for 30 minutes; then discharging at a constant current of 0.33C to a lower limit voltage of 2V, and leaving it for 30 minutes; repeating the above charge and discharge steps 3 times, and recording the capacity discharged for the third time as C0, in Ah; and recording the average discharge voltage during the third discharge. Among them, C0 is the room temperature calibration capacity of the full battery. In addition, the positive electrode gram capacity, positive electrode mass energy density, and positive electrode volume energy density of each soft-pack battery are also calculated. Among them, positive electrode gram capacity = C0 / total mass of positive electrode active materials in a single cell; positive electrode mass energy density = positive electrode gram capacity × average discharge voltage; positive electrode volume energy density = positive electrode mass energy density × compaction density of positive electrode coating in the positive electrode sheet (see Table 2 above). The relevant results are summarized in Table 3 below.

[0101] The positive and negative electrode sheets were assembled into a soft-pack three-electrode battery. This differs from the two-electrode soft-pack battery described above in that a 2μm-diameter copper wire and a separator were placed between a separator in the middle of the bare cell and a negative electrode sheet, separating the copper wire from the negative electrode sheet through the separator. After the soft-pack battery was formed using the aforementioned process, the copper wire was plated with lithium (charging at 50μA for 4 hours). The potential of the copper wire after lithium plating was 0mV vs. Li. Therefore, the lithium-plated copper wire can be used as a reference electrode to calibrate the negative electrode charging potential.

[0102] A fast charge test was performed on each of the above-mentioned soft-pack three-electrode batteries: the test current was gradually changed from 3C to 2.5C to 2C to 1.5C to 1C (specifically, the test current was first charged at a constant current at 3C, and when the battery reached the lithium deposition boundary, the current was reduced to 2C and the test current was charged at a constant current, when the battery reached the lithium deposition boundary, the current was reduced to 2C and the test current was charged at a constant current, when the battery reached the lithium deposition boundary, the current was reduced to 1.5C and the test current was charged at a constant current, when the battery reached the lithium deposition boundary, the current was reduced to 1C and the test current was charged at a constant current). The total fast charge time is the total charging time for the battery's state of charge (SOC) to change from 10% SOC to 80% SOC. In the above-mentioned fast charge test, whether the battery has reached the lithium deposition boundary is determined by the change in the negative electrode potential during the charging process, wherein when the negative electrode potential is reduced to 0mV, it is considered that the lithium deposition boundary has been reached. The fast charge test results are also summarized in Table 3 below.

[0103] Table 3 Electrochemical performance test results of each soft pack battery

[0104] From Table 3 we can see that:

[0105] The positive electrodes in Comparative Examples 6 and 7 are coated with a single layer of large-particle LMFP-1 material. Although the volumetric energy density of the battery positive electrodes is relatively high, the fast-charging performance of the batteries is poor. In contrast, the positive electrode sheets of Examples 1-3, 4, 7, and 12-14 of the present application are coated with a layered coating of large-particle, low-Mn-content LMFP-1 material and small-particle, high-Mn-content LMFP-2 material compared to Comparative Example 6. The fast-charging performance of the batteries in these examples is significantly improved compared to Comparative Example 6.

[0106] The difference between the positive electrode sheets of Examples 1-3 and Examples 12-14 lies in the different areal density ratios of Coating 1 and Coating 2. A comparison between them reveals that when the areal density ratio of Coating 1 to Coating 2 is less than 1 (as in Example 14), the mass proportion of Coating 2, where the small particles of LFMP-2 are located, is too high, significantly reducing the mixed compaction density of the positive electrode coating and, in turn, the battery volumetric energy density. When the ratio of the surface density of coating 1 to coating 2 is in the range of 1-10, the battery can better balance the volume energy density and the shorter fast charging time, and when the ratio of the surface density of coating 1 to coating 2 is high (such as the ratio is 10 in Example 12), it reflects that the mass proportion of coating 2 where the small particles are located is low, and the battery fast charging performance is not as high as that of the single-layer coated comparative example 5. The improvement is not as high as that of other examples 1-3 and 13, which also reflects that the mass proportion of coating 1 where the large particles are located is high. The gram capacity of the battery is closer to that of comparative example 5 in which the positive electrode adopts large-particle LFP material, which is lower than the positive electrode gram capacity of examples 1-3 and 13, and the mass energy density of the battery is also low. Therefore, the ratio of the surface density of coating 1 to coating 2 is optionally in the range of 1-9, and further optionally in the range of 1-3.

[0107] In Examples 4-11 of this application, compared to Example 1, the D50 particle size of the upper and lower LMFP materials or the Mn content of the upper and lower LMFP materials were modified. This resulted in changes in the fast-charge time and energy density of the all-in-one batteries. However, overall, the batteries still achieved a good balance between these two performance characteristics, resulting in superior overall performance. Furthermore, a comparison between Examples 1 and 6-9 reveals that the Mn content of LMFP-1 is optimal within the range of 0.5-0.6, while that of LMFP-2 is optimal within the range of 0.65-0.75.

[0108] In addition, the Mn content of the two LMFP materials in Comparative Examples 1-2 is not within our required range. If the Mn content of the LMFP material is too high, the intrinsic impedance of the material will be too large, which will significantly affect the capacity, energy density and fast charging performance of the material; if the Mn content is too low, the average discharge voltage will be significantly reduced, which will in turn lead to a decrease in the battery volume energy density.

[0109] The D50 particle sizes of the two LMFP materials in Comparative Examples 3-4 are not within our required range. Among them, the D50 particle size of the material is too small, which is beneficial to the fast charging performance, but will lead to a significant reduction in the compaction of the positive electrode sheet, thereby affecting the volume energy density of the positive electrode; and the D50 particle size of the material is too large, which will deteriorate the fast charging performance of the battery.

[0110] In Comparative Example 5, the Mn content x of the lower layer LMFP material is the same as the Mn content y of the upper layer LMFP material, which does not satisfy x<y. The excessively high Mn content of the lower layer LMFP material will result in a larger intrinsic impedance of the material. When these two LMFP materials are double-coated, the positive electrode capacity of the battery is low, the energy density is low, and the improvement in the battery fast charging performance is not significant.

[0111] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A positive electrode sheet (100), characterized in that, The positive electrode plate (100) includes: A positive current collector (10); and A first positive electrode material layer (21) and a second positive electrode material layer (22) stacked on at least one side of the positive current collector (10), wherein, on the same side of the positive current collector (10), the second positive electrode material layer (22) is disposed on the side of the first positive electrode material layer (21) away from the positive current collector (10); the first positive electrode material layer (21) includes a first lithium iron manganese phosphate material, and the second positive electrode material layer (22) includes a second lithium iron manganese phosphate material; the molar ratio of Mn / (Mn + Fe) in the first lithium iron manganese phosphate material is x, and the molar ratio of Mn / (Mn + Fe) in the second lithium iron manganese phosphate material is y, where x < y, 0.4 ≤ x ≤ 0.65, and 0.6 ≤ y ≤ 0.8; the D50 particle size of the first lithium iron manganese phosphate material is in the range of 0.8 μm - 2 μm, and the D50 particle size of the second lithium iron manganese phosphate material is in the range of 0.2 μm - 0.6 μm.

2. The positive electrode plate (100) according to claim 1, characterized in that, The single-sided areal density of the first positive electrode material layer (21) is greater than or equal to the single-sided areal density of the second positive electrode material layer (22).

3. The positive electrode sheet (100) according to claim 2, characterized in that, The ratio of the single-sided areal density of the first positive electrode material layer (21) to the single-sided areal density of the second positive electrode material layer (22) is 1 - 10.

4. The positive electrode sheet (100) according to claim 3, characterized in that, The ratio of the single-sided areal density of the first positive electrode material layer (21) to the single-sided areal density of the second positive electrode material layer (22) is 1 - 9.

5. The positive electrode plate (100) according to any one of claims 1-4, characterized in that, The single-sided areal density of the first positive electrode material layer (21) is 100 g / m 2 -200 g / m 2 .

6. The positive electrode plate (100) according to any one of claims 1-5, characterized in that, The single-sided areal density of the second positive electrode material layer (22) is 20 g / m 2 - 100 g / m 2 .

7. The positive electrode sheet (100) according to any one of claims 1-6, characterized in that, The tap density of the first positive electrode material layer (21) is greater than the tap density of the second positive electrode material layer (22).

8. The positive electrode plate (100) according to any one of claims 1-7, characterized in that, The tap density of the first positive electrode material layer (21) is 2.3-2.7 g / cm 3 ; and / or the tap density of the second positive electrode material layer (22) is 2.0-2.4 g / cm 3 .

9. The positive electrode plate (100) according to any one of claims 1-8, characterized in that, The x and the y satisfy: 0.45 ≤ x ≤ 0.60, 0.65 ≤ y ≤ 0.

75.

10. The positive electrode sheet (100) according to any one of claims 1-9, characterized in that, The mass proportion of the first lithium iron manganese phosphate material in the first positive electrode material layer (21) is more than 85%; the mass proportion of the second lithium iron manganese phosphate material in the second positive electrode material layer (22) is more than 80%.

11. The positive electrode plate (100) according to any one of claims 1-10, characterized in that, The mass ratio of the first lithium iron manganese phosphate material to the second lithium iron manganese phosphate material is 1 - 10.

12. The positive electrode plate (100) according to claim 11, characterized in that, The mass ratio of the first lithium iron manganese phosphate material to the second lithium iron manganese phosphate material is 1 - 9.

13. The positive electrode plate (100) according to any one of claims 1 - 12, wherein the first positive electrode material layer (21) is in direct contact with the positive current collector (10), and / or the second positive electrode material layer (22) is in direct contact with the first positive electrode material layer (21).

14. A lithium battery, characterized in that, Including the positive electrode plate (100) according to any one of claims 1 - 13.

15. A device, including the lithium battery according to claim 14, wherein the device is an electrical equipment or an energy storage system.

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