Positive electrode sheet, method of manufacturing the same, and use

Abstract

This invention relates to a positive electrode sheet, its manufacturing method, and its use, and belongs to the technical field of lithium battery energy storage. In addition to the conventional current collector and active material layer, the positive electrode sheet according to this invention has a lithium replenishment layer and isolation layer introduced between the structures in a specific order. This allows for effective lithium replenishment and the formation of a stable SEI layer after the product is assembled with the electrolyte and negative electrode sheet to manufacture a lithium battery energy storage device. Furthermore, it avoids reactions between the active material and the lithium replenisher or other lithium replenishment products in the lithium replenishment layer, resulting in a product with excellent electrochemical properties. The positive electrode sheet is easy to manufacture and can be produced on an industrial scale.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery energy storage, and specifically relates to a positive electrode sheet, a manufacturing method thereof, and use thereof.

Background Art

[0002] During the first charge-discharge cycle of a lithium battery energy storage device, a solid electrolyte interface (SEI) film is formed on the negative electrode interface, so that some active lithium is deactivated and irreversible capacity loss occurs. Therefore, such a device usually needs to be replenished with lithium. A conventional general lithium replenishment process is to add a certain amount of lithium-containing compound to the active material layer during the manufacture of the positive electrode sheet of the device, thereby replenishing a certain amount of lithium ions during the charge-discharge process of the device.

[0003] However, lithium-containing compounds have low stability in air and are likely to deteriorate when exposed to air by contacting and reacting with moisture and carbon dioxide in the air. Furthermore, they directly affect the active material in the positive electrode sheet. As a result, not only can the expected lithium replenishment effect not be achieved, but it may even lead to a significant decline in the electrochemical properties of the lithium battery energy storage device.

Summary of the Invention

Problems to be Solved by the Invention

[0004] Based on the defects existing in the prior art, the object of the present invention is to provide a positive electrode sheet in which, in addition to a normal current collector and active material layer, a lithium replenishment layer and an isolation layer are introduced in a specific order between the structures. After assembling with an electrolyte and a negative electrode sheet to manufacture a lithium battery energy storage device, it can effectively perform lithium replenishment, not only form a stable SEI layer, but also avoid the reaction between the active material and the lithium replenishing agent or other lithium replenishing products in the lithium replenishment layer, and provide a positive electrode sheet with excellent electrochemical properties.

Means for Solving the Problems

[0005] To achieve the above objectives, the technical solutions employed in this invention are: It includes a current collector, an active material layer, an isolation layer, and a positive electrode lithium replenishment layer, which are stacked in order. The isolation layer comprises at least one of a conductive agent, a solid electrolyte, and a polyanionic phosphate. The aforementioned positive electrode lithium replenishment layer is a positive electrode sheet containing a lithium-containing compound and a reducing agent.

[0006] In conventional processes, lithium replenishers are typically added to the active material layer to replenish lithium in the positive electrode sheet. However, this method has been shown to be less than ideal. The reasons for this include the following: While lithium replenishers can effectively supply additional lithium ions to the active material layer, the lithium ion conduction efficiency of the final lithium battery energy storage device is still limited by the formation of an SEI film, as the active material is still in direct contact with the electrolyte and quickly forms an SEI film. Furthermore, the lithium replenisher itself reacts with the electrolyte and active material, producing products such as oxygen, which can cause oxidation of the active material. As a result, not only is an effective lithium replenishment not achieved, but the capacity and cycle characteristics of the lithium battery energy storage device may even rapidly deteriorate. Therefore, in the technical solution of the present invention, the positive electrode sheet adopts a current collector-active material layer-isolation layer-positive electrode lithium replenishment layer structure distribution. When applied to a lithium battery energy storage device, the active material layer and the positive electrode lithium replenishment layer achieve electron conduction through the action of the current collector. During the charging process, lithium desorption occurs in both the active material of the active material layer and the lithium-containing compound of the positive electrode lithium replenishment layer, thereby achieving lithium replenishment. At this time, a certain amount of residue is generated in the positive electrode lithium replenishment layer, and together with the isolation layer, direct contact between the active material layer and the electrolyte is prevented. This further enhances the stability of the SEI film on the positive electrode surface, improving the cycle stability of the lithium energy storage device. On the other hand, the isolation layer located between the active material layer and the positive electrode lithium replenishment layer contains at least one of a conductive agent, a solid electrolyte, and a polyanionic phosphate, thereby significantly improving the ion / electron conduction efficiency of the positive electrode sheet. Most importantly, this isolation layer effectively prevents direct contact between the active material layer and the positive electrode lithium replenishment layer. This prevents the lithium-containing compounds and reducing agents in the positive electrode lithium replenishment layer from undergoing side reactions with the active material, and also prevents the reaction products generated in the positive electrode lithium replenishment layer from reacting with the active material during lithium replenishment.Furthermore, the reducing agent in the positive electrode lithium replenishing layer can sufficiently lower the potential of the lithium-containing compound in the lithium replenishing process, so that the lithium replenishing performance can be further improved without worrying that the excessive reaction will affect the original lithium desorption / insertion efficiency of the active material.

[0007] Preferably, the active material layer contains a positive electrode active material, and the positive electrode active material is a doped or undoped material and contains at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganate, ternary positive electrode material, lithium nickel manganate, and lithium-rich material.

[0008] The positive electrode sheet according to the present invention is applicable to each conventional general active material positive electrode system. The main reasons are considered as follows. In the technical solution of the present invention, not only the lithium replenishing component and the active material are separated in the form of different layers, but also an isolation layer is provided between the two layers, so that regardless of the lithium desorption / insertion rate of the active material, it will not affect the lithium replenishing efficiency of the positive electrode lithium replenishing layer.

[0009] More preferably, the active material layer further contains a conductive agent and a binder.

[0010] Preferably, the conductive agent is at least one of conductive carbon black, carbon nanotube, graphene, and carbon nanofiber, the solid electrolyte is at least one of oxide solid electrolyte, chloride solid electrolyte, and polymer solid electrolyte, and the polyanionic phosphate is lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium manganese iron phosphate (LiMn x Fe 1-x PO4, where 0 < x < 1), lithium vanadium phosphate (Li3V2(PO4)3), lithium cobalt phosphate (LiCoPO4), and lithium nickel phosphate (LiNiPO4).

[0011] More preferably, the isolation layer comprises a conductive agent and a solid electrolyte. More preferably, the conductive agent is a carbon nanotube, and the solid electrolyte is a LATP (lithium aluminum titanium phosphate with a sodium ion conductor (NaSICON) structure) solid electrolyte. More preferably, the isolation layer comprises carbon nanotubes and LATP solid electrolyte, with a mass ratio of (1:9) to (4:6).

[0012] The inventors have found that when any of the conductive agent, solid electrolyte, or polyanionic phosphate in the isolation layer is used alone during the lithium replenishment and cycling process of the positive electrode sheet, the lithium ion / electron conduction rate of the positive electrode sheet can be effectively improved. Furthermore, the charge / discharge capacity and cycle stability of the product when applied to a lithium battery energy storage device differ depending on the type of conductive agent and solid electrolyte selected. When carbon nanotubes are selected as the conductive agent and LATP solid electrolyte as the solid electrolyte, the electrochemical properties of the positive electrode sheet are superior, and in particular, when these two are combined in the preferred ratio described above, the product exhibits optimal electrochemical activity.

[0013] Preferably, the solid electrolyte includes the solid electrolyte after coating.

[0014] Furthermore, when a conductive agent and a solid electrolyte are used in a mixture in the isolation layer according to the present invention, both may be in a structure where they are mixed as powders, or they may exist in the form of a bonding layer. That is, in the isolation layer, the conductive agent may exist in a layered or powdered form, while the solid electrolyte may be bonded to the surface of the conductive agent in a layered form, or bonded to the surface of the conductive agent in a powdered form, and the same applies when the positions of the two are reversed. As those skilled in the art will see, the above bonding forms are actually related to the normal inherent forms of both, and the above differences in bonding forms do not affect the final performance of the product.

[0015] Preferably, the isolation layer further comprises a binder.

[0016] Preferably, the lithium-containing compound is Li a M b O c (Here, a = 1 to 12, M is at least one of Ni, Cu, Mo, V, Ru, Mn, Si, Nb, Ti, Fe, Ta, Re, Co, W, Zr, Bi, Sn, Ce, b = 0 to 2, and c = 0 to 11) More preferably, the lithium-containing compound is LiO2, Li2O, Li2O2, Li2NiO2, Li2CuO2, Li2MoO3, Li2VO3, Li2RuO3, Li2MnO3, Li2SiO3, Li2Si2O5, Li3VO4, Li3NbO4, Li3RuO4, Li3PO4, Li4SiO4, Li4TiO4, Li5FeO4, Li5NbO5, Li5TaO5, Li5ReO6, Li6CoO4, Li6MnO4, Li6NiO4, Li6WO6, Li6Zr2O7, Li7NbO6, Li7VO6, Li7BiO6, Li7TaO6, Li8ZrO6, Li8SnO6, Li8SiO6, Li8CeO6, Li8MoO6, Li8MnO6, Li8Nb2O9, Li 12 Nb2O 11 It is at least one of the following.

[0017] Preferably, the reducing agent is at least one of boride, sulfide, phosphide, and reducing elemental compounds. More preferably, the boride is at least one of cobalt boride, molybdenum boride, calcium boride, aluminum boride, magnesium boride, titanium boride, zirconium boride, silicon boride, and lanthanum boride; the sulfide is at least one of sodium sulfide, iron sulfide, cobalt sulfide, molybdenum sulfide, tungsten sulfide, titanium sulfide, magnesium sulfide, calcium sulfide, copper sulfide, lanthanum sulfide, zinc sulfide, tin sulfide, nickel sulfide, and silicon sulfide; the phosphide is at least one of iron phosphide, boron phosphide, nickel phosphide, sodium phosphide, and zinc phosphide; and the reducing element is at least one of elemental sulfur, elemental phosphorus, elemental boron, elemental silicon, elemental aluminum, elemental germanium, elemental arsenic, elemental iodine, elemental vanadium, elemental manganese, elemental iron, elemental cobalt, elemental nickel, and elemental tin.

[0018] Preferably, the positive electrode lithium replenishment layer further contains a conductive agent and a binder.

[0019] Preferably, the positive electrode active material is a ternary positive electrode material and / or a lithium nickel manganese oxide positive electrode material, and the positive electrode lithium replenishment layer contains Li4SiO4 and elemental sulfur.

[0020] Preferably, a phosphate cathode material or electrolyte may be further added to the lithium replenishment layer of the cathode. More preferably, the positive electrode lithium replenishment layer contains, as components, a lithium-containing compound, 80 to 96 parts by weight of a conductive agent, 2 to 10 parts by weight of a conductive agent, and 2 to 10 parts by weight of a binder.

[0021] Except for the isolation layer limited in the present invention, there are no special restrictions on the conductive agents contained in other layers, and those skilled in the art can select self-made or commercially available conductive agents according to the actual situation. The conductive agents here include, but are not limited to, acetylene black, carbon black, carbon fiber, carbon nanotube, ketjen black, etc. The binders used in each of the above layers can also be selected as self-made or commercially available according to the actual situation. The binders here include, but are not limited to, polyvinyl pyrrolidone, polyvinylidene fluoride, polyethylene oxide, polytetrafluoroethylene, carboxymethyl cellulose, copolymer of styrene and butadiene, etc.

[0022] Preferably, in the positive electrode sheet, the thickness of the active material layer is 20 - 300 μm, the thickness of the isolation layer is 0.5 - 20 μm, and the thickness of the positive electrode lithium replenishing layer is 1 - 50 μm.

[0023] Those skilled in the art can install structural layers with different thicknesses on the positive electrode sheet so as to apply it to lithium battery energy storage devices having different positive electrode active materials and electrolyte systems according to actual needs.

[0024] Preferably, the current collector is aluminum foil.

[0025] Another object of the present invention is the step of fabricating an active material layer on a current collector, the step of fabricating an isolation layer on the active material layer, the step of fabricating a positive electrode lithium replenishing layer on the isolation layer, and to provide the manufacturing method of the positive electrode sheet including these steps.

[0026] Preferably, the active material layer is fabricated on the current collector by means of coating, dipping, spraying, roll pressing, pressing and / or adhesion by composite film and / or dry electrode method.

[0027] [[ID=]29] Preferably, the isolation layer is formed on the active material layer by coating, dipping, spraying, composite film and / or roll pressing, pressing and / or adhesion using a dry electrode method.

[0028] Preferably, the positive electrode lithium replenishment layer is fabricated on the isolation layer by coating, dipping, spraying, composite film and / or roll pressing, pressing and / or adhesive methods using a dry electrode method.

[0029] Another object of the present invention is to provide a secondary battery comprising a positive electrode sheet, a separator, and a negative electrode sheet according to the present invention.

[0030] When the positive electrode sheet according to the present invention is applied to a secondary battery, the active lithium in the product is effectively replenished, the active material within the positive electrode sheet is not affected by the lithium replenishment material, a stable SEI film is formed after the initial charge and discharge, and the energy density of the secondary battery is effectively improved by the lithium replenishment action. This secondary battery has the characteristics of high specific capacity, high rate characteristics, and high cycle stability.

[0031] Furthermore, the negative electrode sheet and separator of the secondary battery can both be made from materials commonly used in that field, and the manufacturing method of the secondary battery may be a standard manufacturing method in that field.

[0032] A further object of the present invention is to provide a power consumption device, the power consumption device comprising a secondary battery according to the present invention, the secondary battery functioning as a power supply for the power consumption device. [Effects of the Invention]

[0033] The beneficial effects of the present invention are as follows: The present invention provides a positive electrode sheet in which, in addition to the usual current collector and active material layer, a lithium replenishment layer and isolation layer are introduced between the structure in a specific order. This allows for effective lithium replenishment and the formation of a stable SEI layer after the product is assembled with the electrolyte and negative electrode sheet to manufacture a lithium battery energy storage device. Furthermore, it avoids reactions between the active material and the lithium replenisher or other lithium replenishment products in the lithium replenishment layer, resulting in a product with excellent electrochemical properties. The positive electrode sheet is easy to manufacture and can be produced on an industrial scale. [Modes for carrying out the invention]

[0034] To better illustrate the object, technical solutions, and advantages of the present invention, the present invention will be further described below with reference to specific examples and comparative examples, but this is for the purpose of understanding the content of the present invention in detail and is not intended to limit the present invention. All other examples that can be obtained without creative work by those skilled in the art are within the scope of the protection of the present invention. The experimental reagents and equipment used in carrying out the present invention are commonly used reagents and equipment unless otherwise specified.

[0035] In each example and comparative example, the carbon nanotube mentioned is LB120-50 manufactured by Tiannai Technology Co., Ltd. The graphene mentioned is a product of Senhono Rice Co., Ltd. The carbon fiber mentioned is a product of Kelude Co., Ltd. The solid electrolyte LLZO mentioned is a product of Ganfeng Lithium. The solid electrolyte LATP mentioned is a product of Ganfeng Lithium. The solid electrolyte PEO mentioned is a product of InnoChem. All other raw materials and auxiliaries not mentioned are commercially available products, and the same raw materials and auxiliaries are used in the parallel experiments in each example and comparative example.

[0036] Examples 1-24 In one embodiment of the positive electrode sheet and its manufacturing method according to the present invention, the method for manufacturing the positive electrode sheet according to this embodiment includes the following steps. (1) An active material layer was prepared on a 12 μm aluminum foil. The method for producing the active material layer was as follows: A commercially available positive electrode active material, conductive carbon black super P as a conductive agent, and PVDF as a binder were weighed in a mass ratio of 95:2:3, and then NMP was added to prepare a slurry, which was applied to the aluminum foil and dried to obtain the active material layer. (2) An isolation layer was prepared on the surface of the active material layer. The method for producing the isolation layer was as follows: A conductive agent or solid electrolyte and a binder, PVDF, were weighed in a mass ratio of 85:15, then NMP, a solvent, was added to prepare a slurry, which was then applied to the active material layer and dried to obtain the isolation layer. Alternatively, a conductive agent and a solid electrolyte and a binder, PVDF, were weighed in a mass ratio of 90:10, then NMP, a solvent, was added to prepare a slurry, which was then applied to the active material layer and dried to obtain the isolation layer. (3) A positive electrode lithium replenishment layer was prepared on the surface of the isolation layer. The method for producing the positive electrode lithium replenishment layer was as follows: A reducing agent and a lithium-containing compound, a conductive agent SP, and a binder PVDF were weighed in a mass ratio of 80:15:15, and then NMP was added to prepare a slurry, which was applied to the isolation layer and dried to obtain the positive electrode lithium replenishment layer. The mixing ratios and composition of each raw material are shown in Table 1.

[0037] [Table 1] JPEG2026524716000002.jpg243168JPEG2026524716000003.jpg243168 Comparative example 1

[0038] A positive electrode sheet and a method for manufacturing the same, the method for manufacturing a positive electrode sheet according to this embodiment includes the following steps. (1) A lithium replenishment layer for the positive electrode was prepared on a 12 μm aluminum foil. The manufacturing method for the lithium replenishment layer for the positive electrode was as follows: A reducing agent and a lithium-containing compound, a conductive agent SP, and a binder PVDF were weighed in a mass ratio of 80:15:15. Then, a solvent NMP was added to prepare a slurry, which was applied to the aluminum foil and dried to obtain the lithium replenishment layer for the positive electrode. (2) An isolation layer was prepared on the surface of the positive electrode lithium replenishment layer. The method for manufacturing the isolation layer was as follows: A conductive agent and a binder, PVDF, were weighed in a mass ratio of 85:15, and then NMP, a solvent, was added to prepare a slurry. This slurry was then applied to the positive electrode lithium replenishment layer and dried to obtain the isolation layer. (3) An active material layer was prepared on the surface of the isolation layer. The method for producing the active material layer was as follows: A commercially available positive electrode active material, conductive carbon black super P as a conductive agent, and PVDF as a binder were weighed in a mass ratio of 95:2:3, and then NMP as a solvent was added to prepare a slurry, which was applied to the isolation layer and dried to obtain the active material layer. The thickness of each layer is the same as the thickness of the corresponding layer in Example 1, but the only difference from Example 1 is that the order in which the structural layers of the positive electrode sheet are fabricated is different. Comparative Example 2

[0039] A positive electrode sheet and a method for manufacturing the same, the method for manufacturing a positive electrode sheet according to this embodiment includes the following steps. (1) An active material layer was prepared on a 12 μm aluminum foil. The method for producing the active material layer was as follows: A commercially available positive electrode active material, conductive carbon black super P as a conductive agent, and PVDF as a binder were weighed in a mass ratio of 95:2:3. Then, NMP as a solvent was added to prepare a slurry, which was applied to the aluminum foil and dried to obtain the active material layer. (2) A positive electrode lithium replenishment layer was prepared on the surface of the active material layer. The method for producing the positive electrode lithium replenishment layer was as follows: A reducing agent and a lithium-containing compound, a conductive agent SP, and a binder PVDF were weighed in a mass ratio of 80:15:15, and then NMP, a solvent, was added to prepare a slurry, which was applied to the active material layer and dried to obtain the positive electrode lithium replenishment layer. (3) An isolation layer was prepared on the surface of the positive electrode lithium replenishment layer. The method for manufacturing the isolation layer was as follows: A conductive agent and a binder, PVDF, were weighed in a mass ratio of 85:15, and then NMP, a solvent, was added to prepare a slurry. This slurry was then applied to the positive electrode lithium replenishment layer and dried to obtain the isolation layer. The thickness of each layer is the same as the thickness of the corresponding layer in Example 1, but the only difference from Example 1 is that the order in which the structural layers of the positive electrode sheet are fabricated is different. Example of effect 1

[0040] To verify the effectiveness of using the positive electrode sheet according to the present invention, the positive electrode sheets manufactured in each example and comparative example were applied to the manufacture of lithium-ion batteries, and the specific method was as follows. A slurry was prepared by mixing commercially available graphite, conductive carbon black, and PVDF (a binder) in a ratio of 93:2:5, and then applied to manufacture a negative electrode sheet. Button batteries were assembled in a glove box using this negative electrode sheet, the positive electrode sheets of each example and comparative example, and an electrolyte (purchased from BASF Electrolytes GmbH in Germany) prepared by dissolving 1 M of LiPF6 in EC / DMC (1:1, volume ratio). After each button battery was left to stand for 24 hours, the LNMO-based, ternary-based, lithium cobalt oxide-based, and lithium nickel oxide-based positive electrode materials were evaluated according to the type of positive electrode material of each battery using the following test methods. For the LNMO, the theoretical relative capacity was set to 146.7 mAh / g and the operating voltage to 3.0~4.85 V. An initial charge-discharge cycle was performed at a rate of 0.05 C, and then the rate was increased to 0.2 C for 100 cycles. The charge and discharge capacities for the initial charge-discharge cycle were statistically recorded, as well as the discharge capacity after 100 cycles. For the ternary system, the theoretical relative capacity was set to 210 mAh / g and the operating voltage to 2.75~4.3 V. An initial charge-discharge cycle was performed at a rate of 0.05 C, and then the rate was increased to 0.2 C for 100 cycles. The charge and discharge capacities for the initial charge-discharge cycle were statistically recorded, as well as the discharge capacity after 100 cycles. For lithium cobalt oxide, the theoretical specific capacity was set to 200 mAh / g and the operating voltage to 3-4.45 V. An initial charge-discharge cycle was performed at a rate of 0.05 C, and then the rate was increased to 0.2 C for 100 cycles. The charge and discharge capacities for the initial charge-discharge cycle were statistically recorded, as well as the discharge capacity after 100 cycles. For lithium nickel oxide, the theoretical specific capacity was set to 220 mAh / g and the operating voltage to 2.75-4.3 V. An initial charge-discharge cycle was performed at a rate of 0.05 C, and then the rate was increased to 0.2 C for 100 cycles. The charge and discharge capacities for the initial charge-discharge cycle were statistically recorded, as well as the discharge capacity after 100 cycles. Furthermore, to facilitate the comparison of the effects of each structural layer of the product, the semi-finished products manufactured in steps (1) and / or (2) of each of Examples 1 to 8 and Comparative Examples 1 and 2 were also tested as positive electrode sheets and named in steps (1) and (2), respectively (for example, in step (1) of Example 1, only a positive electrode sheet containing the current collector and active material layer was obtained, and this semi-finished product was applied to the same test and named Example 1-(1)). The results are shown in Table 2.

[0041] [Table 2] JPEG2026524716000005.jpg240165JPEG2026524716000006.jpg118165

[0042] As is clear from the performance of each positive electrode sheet in Table 2, when the thickness, active material layer, isolation layer, and positive electrode lithium replenishment layer composition differ, the positive electrode sheets in each embodiment of the present invention all show significantly improved initial Coulomb efficiency and cycle stability compared to positive electrode sheets containing only a current collector-active material layer or positive electrode sheets containing only a current collector-active material layer-isolation layer. This indicates that in the above positive electrode sheets, the positive electrode lithium replenishment layer can effectively replenish lithium, and that the combined action of the isolation layer and the positive electrode lithium replenishment layer results in a high content of lithium ions that can be reversibly detached and inserted into the product, enabling long-term conduction between the positive and negative electrodes. Here, when a combination of a conductive agent and a solid electrolyte is used as the component of the isolation layer, the performance improvement effect is even more pronounced compared to products containing only a conductive agent or a solid electrolyte. On the other hand, differences in the types of conductive agent and solid electrolyte result in differences in the electrochemical properties of the positive electrode sheet. As can be seen from the performance of the products in Examples 8-19, when the conductive agent is carbon nanotubes, the discharge capacity after 100 cycles of the product using the conductive agent alone still reaches 195.6 mAh / g. However, when the conductive agent is combined with a solid electrolyte, the electrochemical properties of the product are further improved. In particular, when combined with LATP solid electrolyte, the discharge capacity after 100 cycles is as high as 205.2 mAh / g, which is far higher than the effect when carbon nanotubes are combined with other solid electrolytes as the isolation layer. However, in this case, if the mass ratio of the conductive agent to the solid electrolyte falls outside the range of (1:9) to (4:6), optimal performance improvement may not be achieved. For example, the products in Examples 23 and 24 did not show a significant difference in performance compared to Examples 9 and 15, which used the conductive agent or solid electrolyte alone. Furthermore, from Examples 25-30, it was found that similar effects can be obtained when polyanionic phosphates such as lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium cobalt phosphate, and lithium nickel phosphate are used as the isolation layer.

[0043] In contrast, the product of Comparative Example 1 was manufactured with a structure such as current collector-positive electrode lithium replenishment layer-barrier layer-active material layer when the structural layers were fabricated. Although it has a lithium replenishment layer and a barrier layer, the electrochemical properties of the product are inferior, indicating that these two-layer structures cannot effectively suppress direct contact between the active material layer and the electrolyte. The performance of this product is equivalent to the positive electrode sheet obtained in step (1) of Example 1, which contains only a current collector and an active material layer. Similarly, the positive electrode sheet obtained in Comparative Example 2, which employs an inappropriate configuration, also does not possess ideal lithium replenishment performance.

[0044] Furthermore, in order to independently examine the function of the isolation layer in the positive electrode sheet according to the present invention, control samples 1 to 7 were manufactured by the same method as in Examples 1 to 7. These control samples differed from the products of Examples 1 to 7 only in that, in the manufacturing method, instead of manufacturing an isolation layer on the active material layer after manufacturing the active material layer on the current collector, the positive electrode lithium replenishment layer was directly manufactured on the active material layer. Other parameters, processes, and methods were the same as in the corresponding examples. Similarly, control sample 8 was manufactured by the same method as in Comparative Example 1. This control sample differed from the product of Comparative Example 1 only in that, in the manufacturing method, the positive electrode lithium replenishment layer was manufactured on the current collector first, and then the active material layer was directly manufactured. Other parameters, processes, and methods were the same as in the corresponding Comparative Example 1. Control sample 26 was manufactured according to Example 26 by directly adding lithium iron phosphate in the isolation layer to the ternary active material and manufacturing a positive electrode lithium replenishment layer on the surface of the active material without providing an isolation layer.

[0045] The same tests described above were performed on control samples 1-8, and the results are shown in Table 3.

[0046] [Table 3]

[0047] A comparison of Table 3 and Table 2 reveals that the isolation layer according to the present invention does not merely function as a conventional conductive agent in the positive electrode sheet. For example, as can be seen from the test results of Example 1 and Control Product 1, in the absence of the isolation layer, the lithium replenishment effect of the positive electrode lithium replenishment layer on the entire button battery was very limited, and both the initial capacity and the retained capacity after 100 cycles were close to those of a positive electrode sheet containing only the current collector and active material layer. On the other hand, when the isolation layer was included, the performance of the product improved significantly, and Control Product 8 also showed a decrease in performance compared to the product of Comparative Example 1. This indicates that the isolation layer according to the present invention further effectively suppresses contact between the positive electrode lithium replenishment layer and its reactants and the active material layer, thus avoiding the occurrence of side reactions between these two structural layers. A comparison of Control Product 26 and Example 26 shows that when the lithium iron phosphate isolation layer was included, the performance of the product also improved significantly, indicating that lithium iron phosphate as an isolation layer is not used solely as an active material.

[0048] The above embodiments are used solely to illustrate the technical solutions of the present invention and do not limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the substance and scope of the technical solutions of the present invention.

Claims

1. It is a positive electrode sheet, It includes a current collector, an active material layer, an isolation layer, and a positive electrode lithium replenishment layer, which are stacked in order. The isolation layer comprises at least one of a conductive agent, a solid electrolyte, and a polyanionic phosphate. A positive electrode sheet characterized in that the positive electrode lithium replenishment layer contains a lithium-containing compound and a reducing agent.

2. The positive electrode sheet according to claim 1, characterized in that the active material layer includes a positive electrode active material, the positive electrode active material is a doped or undoped material and includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, ternary positive electrode material, lithium nickel manganese oxide, and lithium-rich material.

3. The positive electrode sheet according to claim 2, characterized in that the conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and carbon nanofibers; the solid electrolyte is at least one of oxide solid electrolytes, chloride solid electrolytes, and polymer solid electrolytes; and the polyanionic phosphate is at least one of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium cobalt phosphate, and lithium nickel phosphate.

4. The positive electrode sheet according to claim 3, characterized in that the isolation layer includes a conductive agent and a solid electrolyte.

5. The positive electrode sheet according to claim 3, characterized in that the solid electrolyte includes a solid electrolyte after coating.

6. The positive electrode sheet according to claim 4, characterized in that the isolation layer contains carbon nanotubes and LATP solid electrolyte, and the mass ratio of the two is (1:9) to (4:6).

7. The isolation layer comprises carbon nanotubes and LATP solid electrolyte, with a mass ratio of 2:8 between the two, the positive electrode active material is a ternary positive electrode material and / or a lithium nickel manganese oxide positive electrode material, and the positive electrode lithium replenishment layer is Li ４ SiO ４ The positive electrode sheet according to claim 6, characterized in that it contains elemental sulfur.

8. The lithium-containing compound is Li ａ M ｂ O ｃ (where a = 1 to 12, M is at least one of Ni, Cu, Mo, V, Ru, Mn, Si, Nb, Ti, Fe, Ta, Re, Co, W, Zr, Bi, Sn, Ce, b = 0 to 2, and c = 0 to 11.) The positive electrode sheet according to claim 1, characterized in that the reducing agent is at least one of boride, sulfide, phosphide, and reducing element.

9. The positive electrode sheet according to claim 1, characterized in that the thickness of the active material layer is 20 to 300 μm, the thickness of the isolation layer is 0.5 to 20 μm, and the thickness of the positive electrode lithium replenishment layer is 1 to 50 μm.

10. A method for manufacturing a positive electrode sheet according to any one of claims 1 to 9, The steps include creating an active material layer on the current collector, The steps include creating an isolation layer on the active material layer, A manufacturing method characterized by comprising the step of creating a positive electrode lithium replenishment layer on an isolation layer.

11. A secondary battery comprising a positive electrode sheet, a separator, and a negative electrode sheet as described in any one of claims 1 to 9.

12. A power consumption device, A power consumption device comprising the secondary battery described in claim 11, wherein the secondary battery functions as a power supply for the power consumption device.

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