Positive electrode sheet and lithium ion battery comprising the same

Abstract

The application provides a positive electrode sheet for a lithium ion battery and a lithium ion battery comprising the positive electrode sheet, the positive electrode sheet comprising a current collector and specially designed capacity layer and power layer, which can effectively eliminate the negative effects of the lithium supplement material on the battery performance during the lithium supplement material de-lithiation process in an economical and simple manner, thereby significantly improving the first coulomb efficiency, cycle performance and service life of the battery.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically to positive electrode sheets for lithium-ion batteries, as well as batteries, battery modules, battery packs and electrical devices including the positive electrode sheets. Background Technology

[0002] With the development of related fields in recent years, rechargeable batteries (also known as secondary batteries) are increasingly used in daily consumer goods, new energy vehicles, large-scale energy storage, aerospace, ships, heavy machinery, and even as primary power and energy supply equipment in these fields. Among the various secondary batteries developed, lithium-ion secondary batteries have attracted widespread attention due to their excellent performance. However, lithium-ion secondary batteries themselves also face some technical challenges that have remained unresolved to date. One such widely discussed issue is how to improve lithium-ion battery replenishment technology. Existing lithium-ion battery replenishment technology typically involves simply coating an additional lithium replenishment layer containing a lithium replenishing agent onto the positive electrode active material layer. However, these lithium replenishing agents are often highly alkaline and have large particle sizes, while the replenishment layer often needs to be relatively thin. Under these circumstances, it is difficult to form a uniform lithium replenishment layer. The non-uniformity of the lithium replenishment layer significantly increases the risk of lithium plating during the charge-discharge process and the local expansion force, leading to a significant increase in battery life and power degradation and the probability of battery failure. Meanwhile, during the charging and discharging process of the battery, the lithium replenisher delithiates and forms electronically insulating oxides, which affect the conductivity of the positive electrode and lead to a decline in the performance of the lithium-ion battery. Furthermore, it is known in the art that using positive electrode active materials with smaller particle sizes and larger BET specific surface areas often results in increased impurity content and increased side reactions, significantly shortening the effective lifespan of the lithium-ion battery; however, using positive electrode active materials with larger particle sizes and smaller BET specific surface areas leads to a decrease in battery power. This contradiction has remained unresolved to date.

[0003] Therefore, there is an urgent need in the field for an improved technical solution to effectively overcome the above problems in an economical and simple manner, achieve excellent lithium replenishment effect, significantly reduce or even eliminate the impact of lithium removal products of lithium replenishment agents on battery performance, significantly reduce the risk of battery crystallization or expansion, and improve battery power efficiency and cycle performance. Summary of the Invention

[0004] The inventors of this invention have conducted extensive and in-depth research and unexpectedly developed a unique technical solution that solves the aforementioned technical problems that have been urgently needed to be addressed in the prior art by specially designing the specific composition of multiple layers in the positive electrode sheet.

[0005] The first aspect of this application provides a positive electrode sheet for a lithium-ion battery, the positive electrode sheet comprising: i) a current collector; ii) at least one capacity layer comprising a first binder, a first conductive agent, and a first positive electrode active material having a first average particle size; and ii) at least one power layer comprising a second binder, a second conductive agent, a lithium replenishing agent, and a second positive electrode active material having a second average particle size; and the first average particle size is larger than the second average particle size. This application, by employing a capacity layer comprising a first positive electrode active material and a power layer simultaneously comprising a lithium replenishing agent and a second positive electrode active material, and by controlling the average particle size of the positive electrode active materials in these two layers, ensures the uniformity of the power layer in a simple and economical manner, and effectively suppresses the negative impact of electronic insulating oxides generated by the lithium replenishing agent after delithiation on battery performance, thereby significantly reducing the risk of crystallization or expansion of the battery and improving the battery's power efficiency and cycle performance.

[0006] According to one embodiment of the first aspect of this application, the positive electrode includes at least one capacity layer located on at least one surface of the current collector, and at least one power layer located on the surface of the at least one capacity layer opposite to the current collector, i.e., the capacity layer is lower (inner) and the power layer is upper (outer). According to another embodiment of the first aspect of this application, the positive electrode includes a power layer located on at least one surface of the current collector, and at least one capacity layer located on the surface of the at least one power layer opposite to the current collector, i.e., the capacity layer is upper (outer) and the power layer is lower (inner). By selecting any of the above design structures according to the required application and operating environment of the lithium-ion battery, the lithium-ion battery can better meet the performance requirements.

[0007] According to one embodiment of the first aspect of this application, the first average particle size of the first positive electrode active material is 0.8-1.3 micrometers. According to another embodiment of the first aspect of this application, the second average particle size of the second positive electrode active material is 0.1-0.7 micrometers, preferably 0.2-0.45 micrometers. By specifically designing the particle size of the positive electrode active materials in the capacity layer and power layer as described above, the influence of lithium replenishment detachment products on conductivity is reduced while ensuring the energy density of the positive electrode itself.

[0008] According to another embodiment of the first aspect of this application, the first positive electrode active material and the second positive electrode active material are each independently selected from: lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium vanadium oxide, lithium vanadate, lithium manganese oxide, the positive electrode active material shown in Formula I, the positive electrode active material shown in Formula II, and combinations thereof:

[0009] LiNix Co y A z O2 type I

[0010] In formula I, A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1;

[0011] Li Fe 1-m-n Mn m B n PO4 type II

[0012] In Formula II, 0 ≤ m ≤ 1, 0 ≤ n ≤ 0.1, and B is selected from at least one transition metal element other than Fe and Mn, as well as a non-transition metal element. According to another embodiment of the first aspect of this application, the first positive electrode active material is lithium iron phosphate, and the second positive electrode active material is also lithium iron phosphate. All of the above-mentioned positive electrode active materials can be used in the technical solution of this application, making battery manufacturing highly flexible and allowing for the selection of suitable positive electrode active materials based on battery performance and cost requirements. In other words, the technical solution of this application has a wide range of applications.

[0013] According to another embodiment of the first aspect of this application, the lithium supplement is selected from one or more of the following: Li2M1O2, Li2M2O3, Li2M3O4, Li3M4O4, Li5M5O4, Li5M6O6, Li6M7O4, Li a C b O cAccording to another embodiment of the first aspect of this application, the lithium replenishing agent is Li₂M₁O₂, wherein M₁ is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca. According to another embodiment of the first aspect of this application, the lithium replenishing agent is Li₂M₂O₃, wherein M₂ is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo, Zr, Si, Cu, Ru. According to another embodiment of the first aspect of this application, the lithium replenishing agent is Li₂M₃O₄, wherein M₃ is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, V, Nb. According to another embodiment of the first aspect of this application, the lithium replenishing agent is Li₃M₄O₄, wherein M₄ is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca. According to another embodiment of the first aspect of this application, the lithium replenishing agent is Li5M5O4, wherein M5 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo. According to another embodiment of the first aspect of this application, the lithium replenishing agent is Li5M6O6, wherein M6 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca. According to another embodiment of the first aspect of this application, the lithium replenishing agent is Li6M7O4, wherein M7 is selected from one or more of the following: Ni, Co, Mn, Fe, Ru. According to another embodiment of the first aspect of this application, the lithium replenishing agent is Li a C b O c Where a is an integer 1 or 2, b is an integer 0, 1, 2, 3 or 4, and c is an integer 1, 2, 3, 4, 5 or 6. According to another embodiment of the first aspect of this application, the lithium replenishing agent comprises Li₂Cu. 0.5 Ni 0.5 O2, Li5FeO4, and combinations thereof. All of the above-mentioned lithium replenishing agents can be used in the technical solution of this application, making battery manufacturing highly flexible and allowing for the selection of suitable lithium replenishing agent materials based on battery performance and cost requirements. In other words, the technical solution of this application has a wide range of applications.

[0014] According to another embodiment of the first aspect of this application, the average particle size of the lithium replenishing agent is 5-15 micrometers, for example, 6-10 micrometers. By adjusting the average particle size of the lithium replenishing agent, it is beneficial to form a uniform and thin power layer to improve the power and life of the battery and further reduce the risk of lithium plating and swelling in the cell.

[0015] According to another embodiment of the first aspect of this application, based on the total weight of the capacity layer, the capacity layer comprises 1-30 wt% of a first binder, 0.1-10 wt% of a first conductive agent, and 60-98.5 wt% of a first positive electrode active material. According to another embodiment of the first aspect of this application, based on the total weight of the power layer, the power layer comprises 1-30 wt% of a second binder, 0.1-10 wt% of a second conductive agent, 0.1-30 wt% of a lithium replenishing agent, and 50-97 wt% of a second positive electrode active material. According to another embodiment of the first aspect of this application, the content of the second conductive agent in the power layer is equal to or greater than the content of the first conductive agent in the capacity layer. According to another embodiment of the first aspect of this application, the weight ratio of the power layer to the capacity layer is 1:9 to 9:1. By selecting the above preferred ratios, a further improved lithium replenishment effect is achieved, specifically manifested in the lithium battery simultaneously exhibiting high initial coulombic efficiency, optimized energy density, and excellent cycle life.

[0016] The second aspect of this application provides a lithium-ion battery comprising a negative electrode, an electrolyte, a separator, and a positive electrode for a lithium-ion battery as described in any one embodiment of the first aspect above. The third aspect of this application provides a battery module comprising the lithium-ion battery described in the second aspect of this application. The fourth aspect of this application provides a battery pack comprising the battery module described in the third aspect of this application. The lithium-ion battery, battery module, and battery pack achieve excellent lithium replenishment effects due to the use of the positive electrode of this invention. Specifically, they significantly reduce the problem of battery power degradation caused by delithiation products of the lithium replenishment material, significantly extend the effective life of the battery, and ensure stable and excellent efficiency, conductivity, power, and energy density during the effective lifespan of the battery.

[0017] A fifth aspect of the present invention provides an electrical device comprising at least one of the lithium-ion battery, battery module, and battery pack described in any of the preceding aspects. The electrical device achieves excellent lithium replenishment performance by employing the positive electrode sheet of the present invention. Specifically, it significantly reduces the problem of battery power degradation caused by delithiation products of the lithium replenishment material, significantly extends the effective lifespan of the battery, and ensures stable and excellent efficiency, conductivity, power, and energy density of the battery during its effective lifespan, thereby ensuring the long-term stable operation of the electrical device. Attached Figure Description

[0018] Figure 1A This is a cross-sectional view of a positive electrode sheet according to an embodiment of the present invention, wherein a capacity layer and a power layer are disposed on one surface of a current collector, with the capacity layer below the power layer; Figure 1BThis is a cross-sectional view of a positive electrode sheet according to another embodiment of the present invention, wherein a capacity layer and a power layer are disposed on one surface of the current collector, and the capacity layer is on (outside) the power layer.

[0019] Figure 2A This is a cross-sectional view of a positive electrode sheet according to another embodiment of the present invention, wherein a capacity layer and a power layer are respectively disposed on two surfaces of the current collector, with the capacity layer below the power layer; Figure 2B This is a cross-sectional view of a positive electrode sheet according to another embodiment of the present invention, wherein a capacity layer and a power layer are respectively disposed on two surfaces of the current collector, and the capacity layer is on (outside) the power layer.

[0020] Figure 3 This is a schematic diagram of one embodiment of the lithium-ion battery of this application.

[0021] Figure 4 yes Figure 3 The diagram shows an exploded view of a lithium-ion battery.

[0022] Figure 5 This is a schematic diagram of one embodiment of the battery module of this application.

[0023] Figure 6 This is a schematic diagram of one embodiment of the battery pack of this application.

[0024] Figure 7 yes Figure 6 An exploded view of the battery pack shown.

[0025] Figure 8 This is a schematic diagram of one embodiment of an electrical device using the lithium-ion battery of this application as a power source.

[0026] In the detailed embodiments section below, the design details of the positive electrode sheet, the lithium-ion battery including the positive electrode sheet, the battery module, the battery pack, and the power supply device designed in this application are described. Detailed Implementation

[0027] The "range" disclosed herein is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this document; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0028] Unless otherwise specified in this application, all embodiments and preferred embodiments mentioned herein can be combined to form new technical solutions.

[0029] Unless otherwise specified, all technical features and preferred features mentioned herein can be combined to form new technical solutions.

[0030] In this application, unless otherwise specified, the terms "comprising" and "including" as used herein are open-ended or closed-ended. For example, "comprising" and "including" may mean that other components not listed may also be included, or that only the listed components may be included.

[0031] In the description of this article, it should be noted that, unless otherwise stated, "above" and "below" include the number itself, and "several" in "one or more" means two or more.

[0032] In this description, unless otherwise stated, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0033] In this application, the terms "lithium-ion battery" and "lithium-ion rechargeable battery" are used interchangeably to refer to a lithium-ion battery capable of repeated charging and discharging. Throughout this application, the terms "negative electrode" and "anode" are used interchangeably to refer to the same electrode in the battery; the terms "positive electrode" and "cathode" are used interchangeably to refer to the same electrode in the battery.

[0034] According to one embodiment of the present invention, a positive electrode sheet for a lithium-ion battery has been developed, the positive electrode sheet comprising a current collector, at least one capacity layer, and at least one power layer.

[0035] According to one embodiment of this application, the current collector is a metal foil, a metal alloy foil, a polymer sheet with a metal coating, or a polymer sheet with a metal alloy coating; wherein the metal in the metal foil and the metal coating is selected from copper, silver, iron, titanium, nickel, and aluminum; the metal alloy in the metal alloy foil and the metal alloy coating is selected from copper alloy, nickel alloy, titanium alloy, silver alloy, iron alloy, and aluminum alloy; and the polymer sheet is selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, and mixtures or copolymers thereof.

[0036] Throughout this application, the "capacity layer" primarily comprises a "high specific capacity / high energy" positive electrode active material, used to provide a layer with high energy density for the battery. According to one embodiment of this application, the capacity layer comprises a first binder, a first conductive agent, and a first positive electrode active material, the first positive electrode active material having a first average particle size. Preferably, based on the total weight of the capacity layer, the capacity layer comprises 1-30% by weight of binder, 0.1-10% by weight of conductive agent, and 60-95% by weight of first positive electrode active material. According to one embodiment of this application, the capacity layer does not contain intentionally added lithium replenishing agents, particularly not the lithium replenishing agents mentioned when describing the composition of the power layer below.

[0037] In this application, when describing various components in the capacity layer and power layer, such as binders, conductive agents and positive electrode active materials, the prefixes "first" and "second" are used to define them, respectively. The purpose is only to distinguish the components in the two layers in terms of description, and it does not mean that the corresponding components in the two layers are necessarily different. The scope of protection of this application includes embodiments in which the same or different kinds of binders, conductive agents and / or positive electrode active materials are used in the capacity layer and power layer, respectively.

[0038] According to one embodiment of this application, the first positive electrode active material used for the capacity layer is selected from one or more of the following: lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium vanadium oxide, lithium manganese oxide, the positive electrode active material shown in Formula I, the positive electrode active material shown in Formula II, and combinations thereof:

[0039] LiNi x Co y A z O2 type I

[0040] Where A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium, and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1. For the positive electrode active material shown in Formula I, the value of x can be within the range of values ​​obtained by using any two of the following values ​​as the upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 1 / 3, 0.35, 0.4, 0 0.45, 0.5, 0.55, 0.6, 0.65, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99; The value of y can be within the range obtained by using any two of the following values ​​as the upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085 The values ​​of z can be obtained within the range of values ​​obtained by using any two of the following values ​​as the upper and lower limits respectively: 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 0.99; The values ​​of x, y, and z are 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 2 / 3, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, and 0.99; and the values ​​of x, y, and z satisfy x + y + z = 1.

[0041] Li Fe 1-m-n Mn m B n PO4 type II

[0042] In Formula II, 0 ≤ m ≤ 1, 0 ≤ n ≤ 0.1, and B is selected from at least one transition metal element other than Fe and Mn, as well as a non-transition metal element. For example, for the positive electrode active material shown in Formula II, the value of m can be within the range of any two of the following values, which are respectively the upper and lower limits: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, 1 / 3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 2 / 3, 0.7, 0. 75, 0.8, 0.85, 0.9, 0.95, 0.99; the value of n can be within the range of values ​​obtained by using any two of the following values ​​as the upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1; B can be selected from the following metallic elements: Cu, Ni, Cr, Mo, Zn, Sn, Mg, Ca, Co, Zr, Si, Ru, V, Nb, and combinations thereof.

[0043] According to another independent embodiment of this application, the capacity layer contains only lithium iron phosphate (LiFePO4) as the first positive electrode active material, that is, it does not contain any other first positive electrode active material besides lithium iron phosphate.

[0044] Based on the total weight of the capacity layer, the content of the first positive electrode active material can be 60-98.5% by weight, for example, 70-98% by weight or 80-97% by weight. For example, the content of the first binder can be within the range of any two of the following values, which are respectively used as upper and lower limits: 60% by weight, 61% by weight, 62% by weight, 63% by weight, 64% by weight, 65% by weight, 66% by weight, 67% by weight, 68% by weight, 69% by weight, 70% by weight, 71% by weight, 72% by weight, 73% by weight, 74% by weight, 75% by weight, 76% by weight, 77% by weight, 78% by weight, 79% by weight, 80% by weight, 81% by weight, 82% by weight, 83% by weight, 84% by weight, 85% by weight, 86% by weight, 87% by weight, 88% by weight, 89% by weight, 90% by weight, and 91% by weight. 92% by weight, 93% by weight, 94% by weight, 95% by weight, 96% by weight, 97% by weight, 98% by weight, 98.5% by weight.

[0045] In this application, the volume average particle size is used to describe the particle size, which is measured using a laser scattering particle size analyzer. The particle size can be characterized by D10, D50, D90, and D99, where "D50 = a specific value" means that in the total volume set of the tested particles, 50% (by volume) of the particles have a particle size greater than this specific value, and 50% of the particles have a particle size smaller than this value; "D10 = a specific value" means that in the total volume set of the tested particles, 10% (by volume) of the particles have a particle size smaller than this specific value, and the remaining particles have a particle size greater than this specific value; "D90 = a specific value" means that in the total volume set of the tested particles, 90% (by volume) of the particles have a particle size smaller than this specific value, and the remaining particles have a particle size greater than this specific value; "D99 = a specific value" means that in the total volume set of the tested particles, 99% (by volume) of the particles have a particle size smaller than this specific value, and the remaining particles have a particle size greater than this specific value. In this application, the average particle size is described by the volume average particle size D50. That is to say, unless otherwise specified, the terms “average particle size”, “volume average particle size” and “volume average particle size” all refer to the D50 of the particle.

[0046] According to one embodiment of this application, the D10 of the first positive electrode active material is greater than 0.3 and less than or equal to 0.6 micrometers. For example, its D10 can be within the range of values ​​obtained by taking any two of the following values ​​as the upper and lower limits respectively: 0.31 micrometers, 0.4 micrometers, 0.5 micrometers and 0.6 micrometers. According to one embodiment of this application, the D90 of the first positive electrode active material is greater than 1.2 micrometers and less than or equal to 4 micrometers. For example, its D90 can be within the range of values ​​obtained by using any two of the following values ​​as the upper and lower limits respectively: 1.21 micrometers, 1.3 micrometers, 1.4 micrometers, 1.5 micrometers, 1.6 micrometers, 1.7 micrometers, 1.8 micrometers, 1.9 micrometers, 2.0 micrometers, 2.1 micrometers, 2.2 micrometers, 2.3 micrometers, 2.4 micrometers, 2.5 micrometers, 2.6 micrometers, 2.7 micrometers, 2.8 micrometers, 2.9 micrometers, 3.0 micrometers, 3.1 micrometers, 3.2 micrometers, 3.3 micrometers, 3.4 micrometers, 3.5 micrometers, 3.6 micrometers, 3.7 micrometers, 3.8 micrometers, and 4.0 micrometers. According to one embodiment of this application, the D99 of the first positive electrode active material is greater than 3.0 micrometers, for example, it can be 3.1-8.0 micrometers. For example, its D99 can be within the range of any two of the following values, which are respectively used as the upper and lower limits: 3.1 micrometers, 3.2 micrometers, 3.3 micrometers, 3.4 micrometers, 3.5 micrometers, 3.6 micrometers, 3.7 micrometers, 3.8 micrometers, 4.0 micrometers, 4.1 micrometers, 4.2 micrometers, 4.3 micrometers, 4.4 micrometers, 4.5 micrometers, 4.6 micrometers, 4.7 micrometers, 4.8 micrometers, 4... 0.9 micrometers, 5.0 micrometers, 5.1 micrometers, 5.2 micrometers, 5.3 micrometers, 5.4 micrometers, 5.5 micrometers, 5.6 micrometers, 5.7 micrometers, 5.8 micrometers, 5.9 micrometers, 6.0 micrometers, 6.1 micrometers, 6.2 micrometers, 6.3 micrometers, 6.4 micrometers, 6.5 micrometers, 6.6 micrometers, 6.7 micrometers, 6.8 micrometers, 6.9 micrometers, 7.0 micrometers, 7.1 micrometers, 7.2 micrometers, 7.3 micrometers, 7.4 micrometers, 7.5 micrometers, 7.6 micrometers, 7.7 micrometers, 7.8 micrometers, 7.9 micrometers, 8.0 micrometers.

[0047] According to another independent embodiment of this application, the volume average particle size (also called bulk average particle size) D50 of the first positive electrode active material is 0.8-1.3 micrometers. For example, its volume average particle size D50 can be within a range of values ​​obtained by using any two of the following values ​​as upper and lower limits respectively: 0.8 micrometers, 0.9 micrometers, 1.0 micrometers, 1.1 micrometers, 1.2 micrometers, and 1.3 micrometers. Preferably, the D50 of the first positive electrode active material used in the capacity layer is greater than the D50 of the second positive electrode active material used in the power layer. More preferably, the following relationships are simultaneously satisfied: the D50 of the first positive electrode active material used in the capacity layer is greater than the D50 of the second positive electrode active material used in the power layer, the D10 of the first positive electrode active material is greater than the D10 of the second positive electrode active material, the D90 of the first positive electrode active material is greater than the D90 of the second positive electrode active material, and the D99 of the first positive electrode active material is greater than the D99 of the second positive electrode active material.

[0048] According to one embodiment of this application, the first adhesive used for the capacity layer may comprise one or more of the following: polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, polystyrene-butadiene rubber (SBR), fluorinated rubber, polychlorotrifluoroethylene, water-soluble unsaturated resin SR-1B, sodium alginate, polyurethane, sodium polyacrylate, sodium polymethacrylate, acrylamide, carboxymethyl chitosan, and any mixtures or copolymers thereof. Depending on the total weight of the capacity layer, the content of the first adhesive can be 1-30% by weight, for example, 1-10% by weight or 2-5% by weight. For example, the content of the first adhesive can be within the range of any two of the following values, which are respectively the upper and lower limits: 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight, and 30% by weight.

[0049] According to one embodiment of this application, the first conductive agent used for the capacity layer may comprise one or more of the following: superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene graphite, mesophase carbon microspheres, soft carbon, hard carbon, carbon fiber, graphene, Super P, furnace black, vapor-grown carbon fiber (VGCF), and carbon nanofibers. Based on the total weight of the capacitance layer, the content of the first conductive agent can be 0.1-10% by weight, for example, 0.5-5% by weight or 1-2% by weight. For example, the content of the first conductive agent can be within a range of values ​​obtained by using any two of the following values ​​as upper and lower limits: 0.1% by weight, 0.2% by weight, 0.3% by weight, 0.4% by weight, 0.5% by weight, 0.6% by weight, 0.7% by weight, 0.8% by weight, 0.9% by weight, 1% by weight, 1.2% by weight, 1.5% by weight, 1.8% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, and 10% by weight. According to the most preferred embodiment, the first conductive agent included in the capacitance layer is a carbon-based conductive agent, such as one or more of the carbon-based conductive agents described above. Based on the total weight of the capacitance layer, the content of the first conductive agent is ≤1.3% by weight, for example, 1.2% by weight. Preferably, the content of the first conductive agent in the capacity layer is less than the content of the second conductive agent in the power layer.

[0050] According to another independent embodiment of this application, the compaction density of the capacity layer is greater than that of the power layer, and the BET specific surface area of ​​the capacity layer is smaller than that of the power layer. According to one embodiment of this application, the capacity layer may have a density ≥2.4 g / cm³. 3 Its compaction density, for example, can be 2.4-3.0 g / cm³. 3 For example, its compacted density can be obtained within a range of values ​​where any two of the following values ​​are used as the upper and lower limits respectively: 2.4 g / cm³ 3 2.5 g / cm 3 2.6 g / cm 3 2.7 g / cm 3 2.8 g / cm 3 2.9 g / cm 3 and 3.0 g / cm 3 According to another embodiment of this application, the BET specific surface area of ​​the capacity layer is ≤13 m². 2 / gram, or 5-13 meters 2 / gram, for example, its BET specific surface area can be obtained within a range of values ​​where any two of the following values ​​are used as upper and lower limits respectively: 5 meters 2 / gram, 6 meters 2 / gram, 7 meters2 / gram, 8 meters 2 / gram, 9 meters 2 / gram, 10 meters 2 / gram, 11 meters 2 / gram, 12 meters 2 / gram, 13 meters 2 / gram.

[0051] Throughout this application, the "power layer" primarily comprises a "high-power" positive electrode active material, used to provide high power to the battery. The power layer of this application also includes a second positive electrode active material and a lithium replenishing agent. Through specialized design of the particle size of the second positive electrode active material, an excellent electronic conductivity network is provided for the lithium replenishing agent, thereby effectively suppressing or significantly eliminating the impact of the lithium replenishing agent's delithiation products on the overall conductivity of the positive electrode sheet. According to one embodiment of this application, the power layer comprises a second binder, a second conductive agent, a lithium replenishing agent, and a second positive electrode active material, the second positive electrode active material having a second average particle size. As described above, the second average diameter of the second positive electrode active material is significantly smaller than the first average diameter of the first positive electrode active material.

[0052] According to one embodiment of this application, the second adhesive for the power layer may include one or more of the first adhesives listed above that can be used in the capacity layer. Preferably, for the purpose of simplifying the manufacturing process, the same type of adhesive is used in both the power layer and the capacity layer. Depending on the total weight of the power layer, the content of the second adhesive may be 1-30% by weight, for example, 1-10% by weight or 2-5% by weight. For example, the content of the second adhesive may be within the range of any two of the following values, which are respectively the upper and lower limits: 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight, and 30% by weight.

[0053] According to one embodiment of this application, the second conductive agent used in the power layer may include one or more of the first conductive agents listed above that can be used in the capacity layer. Preferably, for the purpose of simplifying the manufacturing process, the same type of conductive agent is used in both the power layer and the capacity layer. Depending on the total weight of the power layer, the content of the second conductive agent may be 0.1-10% by weight, for example, 0.5-5% by weight or 1-2% by weight. For example, the content of the second conductive agent may be within the range of any two of the following values, which are respectively used as upper and lower limits: 0.1% by weight, 0.2% by weight, 0.3% by weight, 0.4% by weight, 0.5% by weight, 0.6% by weight, 0.7% by weight, 0.8% by weight, 0.9% by weight, 1% by weight, 1.2% by weight, 1.5% by weight, 1.8% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, and 10% by weight. According to the most preferred embodiment, the second conductive agent included in the power layer is a carbon-based conductive agent, such as one or more of the carbon-based conductive agents listed above. Preferably, based on the total weight of the power layer, the content of the second conductive agent is ≥1.4% by weight, for example, 1.45% by weight.

[0054] According to one embodiment of this application, the second positive electrode active material for the power layer may include one or more of the first positive electrode active materials listed above that can be used in the capacity layer. Preferably, for the purpose of simplifying the manufacturing process, the same type of positive electrode active material is used in both the power layer and the capacity layer. More preferably, lithium iron phosphate is used as the positive electrode active material in both the power layer and the capacity layer.

[0055] According to one embodiment of this application, based on the total weight of the power layer, the content of the second positive electrode active material can be 50-97% by weight, for example, 70-94% by weight or 80-90% by weight. For example, the content of the second binder can be within the range of any two of the following values, which are respectively used as upper and lower limits: 60% by weight, 61% by weight, 62% by weight, 63% by weight, 64% by weight, 65% by weight, 66% by weight, 67% by weight, 68% by weight, 69% by weight. 70% by weight, 71% by weight, 72% by weight, 73% by weight, 74% by weight, 75% by weight, 76% by weight, 77% by weight, 78% by weight, 79% by weight, 80% by weight, 81% by weight, 82% by weight, 83% by weight, 84% by weight, 85% by weight, 86% by weight, 87% by weight, 88% by weight, 89% by weight, 90% by weight, 91% by weight, 92% by weight, 93% by weight, 94% by weight, 95% by weight, 96% by weight, 97% by weight.

[0056] According to one embodiment of this application, the D10 of the second positive electrode active material is ≤0.3 micrometers, for example <0.3 micrometers, or 0.1-0.25 micrometers. For example, its D10 can be within the range of any two of the following values ​​as the upper and lower limits respectively: 0.1 micrometers, 0.15 micrometers, 0.20 micrometers, 0.25 micrometers, 0.28 micrometers, 0.29 micrometers, 0.30 micrometers, and the D10 of the second positive electrode active material is less than the D10 of the first positive electrode active material. According to one embodiment of this application, the D90 of the second positive electrode active material is ≤1.2 micrometers, for example <1.2 micrometers, or 0.5-1.1 micrometers. For example, its D90 can be within the range of values ​​obtained by using any two of the following values ​​as the upper and lower limits respectively: 0.5 micrometers, 0.6 micrometers, 0.7 micrometers, 0.8 micrometers, 0.9 micrometers, 1.0 micrometers, 1.1 micrometers, 1.15 micrometers, and 1.20 micrometers, and the D90 of the second positive electrode active material is less than the D90 of the first positive electrode active material. According to one embodiment of this application, the D99 of the second positive electrode active material is ≤3.0 micrometers, for example, it can be 1.0-3.0 micrometers. For example, its D99 can be within the range of any two of the following values ​​as the upper and lower limits respectively: 1.1 micrometers, 1.2 micrometers, 1.3 micrometers, 1.4 micrometers, 1.5 micrometers, 1.6 micrometers, 1.7 micrometers, 1.8 micrometers, 1.9 micrometers, 2.0 micrometers, 2.1 micrometers, 2.2 micrometers, 2.3 micrometers, 2.4 micrometers, 2.5 micrometers, 2.6 micrometers, 2.7 micrometers, 2.8 micrometers, 2.9 micrometers, and 3.0 micrometers, and the D99 of the second positive electrode active material is less than the D99 of the first positive electrode active material. According to another independent embodiment of this application, the volume average particle size (also called bulk average particle size) D50 of the second positive electrode active material is ≤0.45 micrometers, or 0.2-0.45 micrometers, for example, within the range of values ​​obtained by using any two of the following values ​​as the upper and lower limits respectively: 0.20 micrometers, 0.21 micrometers, 0.22 micrometers, 0.23 micrometers, 0.24 micrometers, 0.25 micrometers, 0.26 micrometers, 0.27 micrometers, 0.28 micrometers, 0.29 micrometers, 0.30 micrometers, 0.31 micrometers, 0.32 micrometers, 0.33 micrometers, 0.34 micrometers, 0.35 micrometers, 0.36 micrometers, 0.37 micrometers, 0.38 micrometers, 0.39 micrometers, 0.40 micrometers, 0.41 micrometers, 0.42 micrometers, 0.43 micrometers, 0.44 micrometers, and 0.45 micrometers, and the D50 of the second positive electrode active material is smaller than the D50 of the first positive electrode active material.

[0057] According to one embodiment of this application, the lithium replenishing agent used for the capacity layer is selected from one or more of the following: Li₂M₁O₂, wherein M₁ is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca; Li₂M₂O₃, wherein M₂ is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo, Zr, Si, Cu, Ru; Li₂M₃O₄, wherein M₃ is selected from one or more of the following: Ni, Cu, Co, Fe, Mn, Sn, Cr, V, Nb; Li₃M 4O4, wherein M4 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca; Li5M5O4, wherein M5 is selected from one or more of the following: Ni, Cu, Co, Fe, Mn, Sn, Cr, Mo, Al; Li5M6O6, wherein M6 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca; Li6M7O4, wherein M5 is selected from one or more of the following: Ni, Cu, Co, Mn, Fe, Ru; Li a C b O c , where a is an integer 1 or 2, b is an integer 0, 1, 2, 3 or 4, and c is an integer 1, 2, 3, 4, 5 or 6.

[0058] According to one embodiment of this application, the lithium supplement is selected from one or more of the following: Li2NiO2, Li2Cu 0.5 Ni 0.5 O2, Li2MoO3, Li5FeO4, Li5Fe 0.9 Al 0.1 O4, Li6MnO4, Li6Mn 0.5 Ru 0.5 O4, Li2O, Li2O2, Li2C2O4, Li2C4O4, LiC2O2, Li2C3O5, and Li2C4O6. According to a preferred embodiment of this application, the lithium supplement includes Li2Cu. 0.5 Ni 0.5 O2, Li5FeO4, and their combinations.

[0059] According to one embodiment of this application, the volume average particle size D50 of the lithium replenishing agent is 5-15 micrometers, preferably 6-10 micrometers, and can be within a numerical range obtained by using any two of the following values ​​as upper and lower limits respectively: 5 micrometers, 6 micrometers, 7 micrometers, 8 micrometers, 9 micrometers, 10 micrometers, 11 micrometers, 12 micrometers, 13 micrometers, 14 micrometers, and 15 micrometers. According to one embodiment of this application, based on the total weight of the power layer, the content of the lithium replenishing agent can be 0.1-30% by weight, for example, 0.5-20% by weight or 1-10% by weight. For example, the content of the lithium replenishing agent can be within a numerical range obtained by using any two of the following values ​​as upper and lower limits respectively: 0.1% by weight, 0.2% by weight, 0.5% by weight, 0.8% by weight, 1.0% by weight, 1.2% by weight, 1.5% by weight, 1.8% by weight, 2.0% by weight, 2.2% by weight, 2.5% by weight, 2.8% by weight, 3.0% by weight, and 3.2% by weight. 3.5 wt%, 3.8 wt%, 4.0 wt%, 4.2 wt%, 4.5 wt%, 4.8 wt%, 5.0 wt%, 5.2 wt%, 5.5 wt%, 5.8 wt%, 6.0 wt%, 6.2 wt%, 6.5 wt%, 6.8 wt%, 7.0 wt%, 7.2 wt%, 7.5 wt%, 7.8 wt%, 8.0 wt%, 8.2 wt%, 8.5 wt%, 8.8 wt%, 9 0.0 wt%, 9.2 wt%, 9.5 wt%, 9.8 wt%, 10.0 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%.

[0060] According to another independent embodiment of this application, the compaction density of the power layer is less than that of the capacity layer, and the BET specific surface area of ​​the power layer is greater than that of the capacity layer. According to one embodiment of this application, the capacity layer may have a density of ≤2.3 g / cm³. 3 Its compaction density, for example, can be 1.8-2.3 g / cm³. 3 For example, its compacted density can be obtained within a range of values ​​where any two of the following values ​​are used as the upper and lower limits respectively: 1.8 g / cm³ 3 1.9 g / cm 3 2.0 g / cm 3 2.1 g / cm 3 2.2 g / cm 3 2.3 g / cm 3According to another embodiment of this application, the BET specific surface area of ​​the capacity layer is ≥14 m². 2 / gram, or 14-25 meters 2 / gram, for example, its BET specific surface area can be obtained within a range of values ​​obtained by using any two of the following values ​​as upper and lower limits respectively: 14 meters 2 / gram, 15 meters 2 / gram, 16 meters 2 / gram, 17 meters 2 / gram, 18 meters 2 / gram, 19 meters 2 / gram, 20 meters 2 / gram, 21 meters 2 / gram, 22 meters 2 / gram, 23 meters 2 / gram, 24 meters 2 / gram, 25 meters 2 / gram.

[0061] According to one embodiment of this application, the total coating weight of the power layer and the capacity layer (the sum of the coating weights of the power layer and the capacity layer per unit area) can be 5-26 g / cm³. 2 For example, 5 g / cm 2 6 g / cm 2 7 g / cm 2 8 g / cm 2 9 g / cm 2 10 g / cm 2 11 g / cm 2 12 g / cm 2 13 g / cm 2 14 g / cm 2 15 g / cm 2 16 g / cm 2 17 g / cm 2 18 g / cm 2 19 g / cm 2 20 g / cm 2 21 g / cm 2 22 g / cm 2 23 g / cm 2 24 g / cm 2 25 g / cm 2 26 g / cm 2According to another embodiment of this application, the solid weight ratio of the power layer to the high-capacity layer is 1:9 to 9:1, preferably 2:8 (i.e., 1:4) to 1:1, and more preferably 2:8 (i.e., 1:4) to 1:2. For example, the solid weight ratio of the power layer to the high-capacity layer can be within the range obtained by taking any two of the following ratios as the upper and lower limits respectively: 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1.

[0062] In various embodiments of this application, the capacity layer and power layer on the current collector can be manufactured by mixing the respective components of each layer, along with other optional additives, with a solvent or dispersant—such as N-methylpyrrolidone (NMP) or deionized water—to form a slurry, sequentially applying the slurry, followed by drying and cold pressing, thereby forming a positive electrode comprising a current collector, a capacity layer, and a power layer. Examples of other additives optionally included in the capacity layer and power layer are thickeners, PTC thermistor materials, etc. The slurry can be applied using conventional coating techniques, such as screen coating, blade coating, cast coating, gravure roller coating, etc.

[0063] Figure 1A and 1B This invention illustrates a positive electrode sheet formed according to an embodiment of the present invention, wherein a capacity layer and a power layer are formed on one surface of the current collector. In this invention, the positions of the capacity layer and the power layer can be selected according to the specific application and required performance of the lithium-ion battery; for example, the capacity layer can be located below (inside) the power layer. Figure 1A The situation shown; or the capacity layer can be located above (outside) the power layer, for example Figure 1B The situation is shown. Figure 2A and 2B A positive electrode sheet formed according to another embodiment of the present invention is shown, wherein a capacity layer and a power layer are formed on the two surfaces of the central current collector, respectively. It should be particularly noted here that... Figure 1A-1B and Figure 2A-2B In the illustrated embodiments, the dimensions (e.g., thickness) of the current collector, capacity layer, and power layer are not drawn to scale, but are merely for the purpose of clearly showing the positive electrode structure. According to one embodiment of the invention, for Figure 1A and 2A As shown, the power layer completely covers the entire outer surface of the capacity layer (the surface of the capacity layer opposite to the current collector). According to another embodiment of the invention, for... Figure 1B and 2BAs shown, the capacity layer completely covers the entire outer surface of the power layer (the surface of the power layer opposite to the current collector). According to a preferred embodiment of this application, the capacity layer is located below (inside) the power layer.

[0064] According to one embodiment of the present invention, the capacity layer and the power layer are in direct contact, and no other layer is disposed between them. According to another embodiment of the present application, one or more additional intermediate layers are optionally disposed between the capacity layer and the power layer. For example, the intermediate layer may be a conductive undercoat (which may consist of a binder and a conductive agent, such as the binder and conductive agent listed above when describing the capacity layer), or it may contain other auxiliary agents known in the art, or optionally contain the same or different positive electrode active materials.

[0065] The positive electrode sheet described in the above embodiments of this application can be used in lithium-ion batteries. In one embodiment of this application, the lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode sheets. The electrolyte acts as a conductor of ions between the positive and negative electrode sheets.

[0066] The lithium-ion battery of this application includes a negative electrode sheet, which comprises a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector. The negative electrode film layer comprises a negative electrode active material, a binder, a conductive agent, and other optional additives. In one embodiment of this application, examples of the negative electrode active material include one or more of the following: natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide, and silicon-carbon composites. The tin-based material may be selected from one or more of elemental tin, tin oxides, and tin alloys. As an example, the conductive agent may include one or more of superconducting carbon, carbon black (e.g., acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers; the binder may include one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, polyacrylic acid (PAA), polymethacrylic acid (PMAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). Other optional additives include thickeners (such as carboxymethyl cellulose CMC, sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, etc.

[0067] According to one embodiment of the present invention, the negative electrode sheet can be manufactured by dispersing the aforementioned negative electrode active material with a binder, a conductive agent and other optional additives in a solvent and stirring until homogeneous to form a slurry with a certain solid content. The solvent can be N-methylpyrrolidone (NMP) or deionized water. In addition, based on the total weight of the prepared slurry, the solid content of the slurry can be 30-80% by weight, for example 50-70% by weight or 55-65% by weight. The slurry is then coated onto a negative electrode current collector, and after drying and optionally cold pressing, a negative electrode sheet is formed. The negative electrode current collector can be a metal foil or a composite current collector. For example, the metal foil can be a copper foil, silver foil, iron foil, or an alloy of the above metals. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. It can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base layer (such as a base layer made of polypropylene PP, polyethylene terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE and its copolymers, etc.).

[0068] Furthermore, in the battery of this application, the negative electrode sheet does not exclude other additional functional layers besides the negative electrode active material layer. For example, in some embodiments, the negative electrode sheet of this application may also include a conductive undercoat layer (e.g., composed of the conductive agent and binder described above that can be used for the negative electrode active material layer) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In other embodiments, the negative electrode sheet of this application may also include a protective covering layer covering the surface of the negative electrode active material layer.

[0069] The electrolyte acts as a conductor of ions between the positive and negative electrodes. The electrolyte can be selected from at least one of solid electrolytes and liquid electrolytes (i.e., electrolyte solutions). In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution comprises an electrolyte salt and a solvent. In some embodiments, the electrolyte salt can be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroarsenate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluorooxalate borate), LiBOB (lithium dioxalate borate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorodioxalate phosphate), and LiTFOP (lithium tetrafluorooxalate phosphate). In one embodiment of this application, the solvent may be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butyl carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), etc. The solvents used are methyl ester (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), and diethyl sulfone (ESE), preferably a mixture of two or more of the above solvents, such as a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), more preferably a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1. In one embodiment of this application, the solvent content, based on the total weight of the electrolyte, is 60-99% by weight, for example 65-95% by weight, or 70-90% by weight, or 75-89% by weight, or 80-85% by weight, or within a numerical range obtained by combining any of the above upper and lower limits. In one embodiment of this application, the electrolyte content is 1-40% by weight, for example 5-35% by weight, or 10-30% by weight, or 11-25% by weight, or 15-20% by weight, or within a numerical range obtained by combining any of the above upper and lower limits.

[0070] In one embodiment of this application, the electrolyte may optionally contain additives. For example, the additives may include one or more of the following: negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, additives that improve battery low-temperature performance, etc.

[0071] In one embodiment of this application, the battery further includes a separator membrane that separates the positive and negative electrode sides of the battery. The separator membrane selectively allows or blocks substances of different types, sizes, and charges within the system. For example, the separator membrane can insulate against electrons, physically isolate the positive and negative electrode active materials of the battery, prevent internal short circuits, and create an electric field in a certain direction. Simultaneously, it allows ions in the battery to pass through the separator membrane and move between the positive and negative electrodes. In one embodiment of this application, the material used to prepare the separator membrane may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. It can be a porous membrane or a non-porous membrane, preferably a polyethylene-polypropylene porous film. The separator membrane can be a single-layer film or a multi-layer composite film. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different.

[0072] In one embodiment of this application, the above-mentioned positive electrode sheet, negative electrode sheet and separator can be manufactured into electrode assembly / bare cell by winding process or stacking process.

[0073] In one embodiment of this application, the lithium-ion battery may include an outer packaging, also referred to as a casing, which can be used to encapsulate the aforementioned electrode components and electrolyte. In some embodiments, the battery's outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. In other embodiments, the battery's outer packaging may be a soft pack, such as a pouch-type soft pack. The material of the soft pack may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0074] The battery in this application can be cylindrical, square, or any other arbitrary shape. Figure 3 The battery 5 is a square structure, which serves as an example. Figure 4 Showing Figure 3An exploded view of battery 5 shows that the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly is encapsulated in the receiving cavity, and the electrolyte is immersed in the electrode assembly 52. ​​The battery 5 may contain one or more electrode assemblies 52.

[0075] According to one embodiment of the present invention, after the battery is assembled and an electrolyte is injected therein, it is subjected to a conventional formation operation to form a solid electrolyte interface layer (SEI film) on the negative electrode surface, thereby obtaining a battery that meets product requirements.

[0076] In one embodiment of this application, several batteries can be assembled together to form a battery module, which contains two or more batteries, the specific number depending on the application of the battery module and the parameters of the individual battery module.

[0077] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 In the battery module 4, multiple batteries 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other manner. Furthermore, the multiple batteries 5 can be fixed in place using fasteners. Optionally, the battery module 4 may also include a housing with a receiving space in which the multiple batteries 5 are housed.

[0078] In one embodiment of this application, two or more of the above-described battery modules can be assembled into a battery pack. The number of battery modules contained in the battery pack depends on the application of the battery pack and the parameters of individual battery modules. The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper box and a lower box, the upper box being able to cover and fit snugly onto the lower box to form a closed space for accommodating the battery modules. Two or more battery modules can be arranged in the battery box in a desired manner.

[0079] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3. The upper body 2 covers the lower body 3, forming a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0080] Electrical appliances

[0081] In one embodiment of this application, the electrical device includes at least one of the battery, battery module, or battery pack described in this application. The battery, battery module, or battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device includes, but is not limited to, mobile digital devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0082] Figure 8 This is an example device. The device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the device's requirements for high power and high energy density, a battery pack or battery module can be used.

[0083] Another example device could be a mobile phone, tablet, laptop, etc. These devices typically require a slim and lightweight design and may use a battery as their power source.

[0084] In the following text, the effect of the positive electrode sheet manufactured according to the embodiments of this application on the performance of the electrical device is characterized based on specific embodiments. However, it should be noted that the scope of protection of this application is defined by the claims and is not limited to the specific embodiments described above.

[0085] Example

[0086] The various raw materials described in Table 1 below are used in the embodiments. Unless otherwise specified, the raw materials used in the embodiments of this application are all commercially available products.

[0087]

[0088] The particle size described in this invention was measured using a laser scattering particle size analyzer.

[0089] In Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4 below, Li5FeO4 was used as a lithium replenishing agent to prepare lithium-ion batteries and their performance was characterized.

[0090] Example 1-1

[0091] In this Example 1-1, a lithium-ion battery was synthesized using the following steps.

[0092] Step 1: Fabrication of the capacity layer.

[0093] In this step, lithium iron phosphate (D50 of 1.2 μm), the first positive electrode active material, acetylene black, the conductive agent, and polyvinylidene fluoride, were weighed according to a solid weight ratio of 97:1:2. These raw materials were then mixed uniformly in N-methylpyrrolidone to form a slurry with a solid content of 62% by weight. This slurry was coated onto a 60 μm thick aluminum foil current collector in a coating chamber. After drying and cold pressing, a capacity layer was formed with a coating weight of 15.6 g / cm³. 2 The compacted density is 2.5 g / cm³. 3 .

[0094] Step 2: Fabrication of the power layer.

[0095] In this step, the second positive electrode active material lithium iron phosphate (D50 of 0.4 μm), lithium supplementer Li5FeO4 (D50 of 5 μm), conductive agent acetylene black, and binder polyvinylidene fluoride are weighed according to a solid weight ratio of 94.5:2.5:1:2. These raw materials are mixed evenly in N-methylpyrrolidone to form a slurry with a solid content of 60% by weight. This slurry is then coated onto the capacity layer obtained in step 1 in a coating chamber. After drying and cold pressing, a power layer is formed, with a coating weight of 4 g / cm³. 2 The compacted density is 2.3 g / cm³. 3 This resulted in a positive electrode comprising a current collector, a capacity layer, and a power layer. The weight ratio of lithium iron phosphate in the power layer to that in the capacity layer was 2:8.

[0096] Step 3: Manufacturing the negative electrode sheet

[0097] In this step, artificial graphite (negative electrode active material), acetylene black (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were weighed according to a solid weight ratio of 96.5:0.7:1.8:1. These raw materials were mixed evenly in deionized water to form a slurry with a solid content of 56% by weight. This slurry was then coated onto a 60-micron-thick copper foil current collector in a coating chamber. After drying and cold pressing, the negative electrode sheet was formed. The coating weight on the current collector was 10.1 g / cm³. 2 .

[0098] Step 4: Battery Manufacturing

[0099] In this step, the positive electrode, separator, and negative electrode are stacked in that order to form a laminated structure. This laminated structure is placed in an aluminum battery casing, and an electrolyte is injected into it before encapsulation. The electrolyte is a 1.1M solution of lithium hexafluorophosphate electrolyte in an EC:DEC = 1:1 (V:V) solvent mixture. The lithium-ion battery of Example 1 is thus obtained. In this example and in each of the following examples and comparative examples, five batteries were prepared in parallel for parallel testing of high-temperature storage performance.

[0100] Examples 1-2

[0101] In Examples 1-2, lithium-ion batteries were synthesized using the same steps as in Example 1-1. The only difference was that, in the step of manufacturing the power layer of the positive electrode, the solid weight ratio of the second positive electrode active material lithium iron phosphate, the lithium supplementer Li5FeO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride was 96:1:1:2. Simultaneously, the coating weight of the capacity layer was adjusted accordingly to maintain the weight ratio of lithium iron phosphate in the power layer to that in the capacity layer at 2:8.

[0102] Examples 1-3

[0103] In Examples 1-3, lithium-ion batteries were synthesized using the same steps as in Examples 1-1. The only difference was that, in the step of manufacturing the power layer of the positive electrode, the solid weight ratio of the second positive electrode active material lithium iron phosphate, the lithium supplementer Li5FeO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride was 87:10:1:2. Simultaneously, the coating weight of the capacity layer was adjusted accordingly to maintain the weight ratio of lithium iron phosphate in the power layer to that in the capacity layer at 2:8.

[0104] Examples 1-4

[0105] In Examples 1-4, lithium-ion batteries were synthesized using the same steps as in Examples 1-1, except that in the step of manufacturing the power layer of the positive electrode, the solid weight ratio of the second positive electrode active material lithium iron phosphate, the lithium supplementer Li5FeO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride was 77:20:1:2. Simultaneously, the coating weight of the capacity layer was adjusted accordingly to maintain the weight ratio of lithium iron phosphate in the power layer to that in the capacity layer at 2:8.

[0106] Examples 1-5

[0107] In Examples 1-5, lithium-ion batteries were synthesized using the same steps as in Examples 1-1. The only difference was that the coating weights of the power layer and the capacity layer were adjusted so that, with the total coating weights of both remaining constant, the weight ratio of lithium iron phosphate in the power layer to that in the capacity layer was 5:5.

[0108] Examples 1-6

[0109] In Examples 1-6, lithium-ion batteries were synthesized using the same steps as in Examples 1-1. The only difference was that the coating weights of the power layer and the capacity layer were adjusted so that, with the total coating weights of both remaining constant, the weight ratio of lithium iron phosphate in the power layer to that in the capacity layer was 8:2.

[0110] Comparative Example 1-1

[0111] In Comparative Example 1-1, a lithium-ion battery was synthesized using the same steps as in Example 1-1, except that a capacity layer was formed only on the current collector and no power layer was formed in the positive electrode, and the coating weight of the capacity layer in Comparative Example 1-1 was equal to the sum of the coating weights of the capacity layer and the power layer in Example 1-1.

[0112] Comparative Examples 1-2

[0113] In Comparative Examples 1-2, lithium-ion batteries were synthesized using the same steps as in Comparative Example 1-1, except that all lithium iron phosphate with a D50 of 1.2 micrometers used in Comparative Example 1-1 was replaced with the same weight of lithium iron phosphate with a D50 of 0.4 micrometers.

[0114] Comparative Examples 1-3

[0115] In Comparative Examples 1-3, lithium-ion batteries were synthesized using the same steps as in Examples 1-1. The only difference was that, when preparing the power layer, the solid raw materials used were lithium iron phosphate (D50 of 0.4 micrometers), a second positive electrode active material with a solid weight ratio of 97:1:2, conductive agent acetylene black, and binder polyvinylidene fluoride, without using a lithium replenishing agent.

[0116] Comparative Examples 1-4

[0117] In Comparative Examples 1-4, lithium-ion batteries were synthesized using the same steps as in Examples 1-1, except that lithium iron phosphate with a D50 of 1.2 micrometers was used as the second positive electrode active material when preparing the power layer. That is, in Comparative Examples 1-4, the same lithium iron phosphate with a D50 of 1.2 micrometers was used in both the capacity layer and the power layer.

[0118] Battery performance characterization

[0119] The performance of the batteries prepared in Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4 was tested using the following techniques.

[0120] Charge / discharge specific capacity :

[0121] At room temperature (25℃), the battery is charged at a constant current rate of 0.33C to the charging termination voltage, and then charged at a constant voltage to 0.05C. The charging capacity Ec0 is measured. The specific charging capacity is obtained by dividing Ec0 by the mass of the positive electrode active material. That is, the specific charging capacity (mAh / g) = first charge capacity / mass of positive electrode active material.

[0122] Take the battery that has been fully charged and discharge it at a constant current rate of 0.33C until the discharge termination voltage is reached. Measure the discharge capacity as Ed0. Divide Ed0 by the mass of the positive electrode active material to obtain the discharge specific capacity. That is, discharge specific capacity (mAh / g) = first discharge capacity / mass of positive electrode active material.

[0123] The above tests for charging specific capacity and discharging specific capacity were repeated 5 times each, and the average value is the charging specific capacity and discharging specific capacity listed in Table 1 below.

[0124] Battery volumetric energy density calculation

[0125] Measure the internal dimensions of the battery casing: length a, width b, and height c. Measure the discharge energy S0 of each battery after charging it at 1C rate to 3.65V at room temperature and then discharging it at 1C rate to 2.5V.

[0126] Battery volumetric energy density = S0 / (a×b×c)

[0127] Battery high-temperature storage performance test :

[0128] Five batteries were used for parallel tests for each embodiment. Each battery was charged at room temperature at a 1C rate to a voltage of 3.65V, and then discharged at a 1C rate to a voltage of 2.5V. The reversible capacity was measured as E0. The fully charged batteries were then placed in a 60°C oven for 100 days. After that, the batteries were removed, and their reversible capacity was immediately tested and recorded as En. The capacity retention rate ε of the batteries after 100 days of storage at 60°C was calculated using the following formula. The results are summarized in Table 1 below:

[0129] ε=(En-E0) / E0×100%

[0130] DC resistance test

[0131] The secondary battery under test was charged at 1C rate to 3.65V at room temperature, and then discharged at 1C rate to 2.5V. The reversible capacity E0 was then measured.

[0132] The secondary battery under test was charged at room temperature at a rate of 0.33C to a voltage of 3.65V, then discharged at a rate of 0.33C for 90 minutes, and then discharged at a rate of 4C for 30 seconds. The resistance at the 30th second was calculated using the following formula.

[0133] DCR=(U 初始 -U 结束 ) / I

[0134] Table 1: Characterization results of charge-discharge specific capacity, energy density, and capacity retention after 100 days of high-temperature storage for the batteries of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4 of this application.

[0135]

[0136] As can be seen from the characterization results in Table 1 above, compared with the comparative examples, all the invention embodiments showed better capacity retention after being stored at 60°C for 100 days. All the invention embodiments also achieved good charge-discharge specific capacity and energy density, which can well meet the market requirements for lithium-ion batteries in this regard.

[0137] Table 2: DC resistance characterization results of batteries in Examples 1-1 to 1-6 and Comparative Examples 1-4 of this application at 30 seconds

[0138]

[0139] As can be seen from the characterization results in Table 2 above, compared with the comparative example, the battery prepared by the embodiment of the present invention has a much lower resistance at 30 seconds. This indicates that by specially designing the particle size of the anode active material in the capacity layer and power layer, the present invention can also effectively suppress the phenomenon of increased battery resistance caused by delithiation, which is common in the prior art, and significantly improve battery performance.

[0140] Examples 2-1 to 2-6

[0141] In Examples 2-1 to 2-6, lithium-ion batteries were synthesized using the same steps as in Examples 1-1 to 1-6, with the only difference being that the same weight of Li₂Ni was used in the fabrication of the power layer. 0.5 Cu 0.5 O2 replaces Li5FeO4 as a lithium supplement.

[0142] Comparative Example 2-1

[0143] In Comparative Example 2-1, a lithium-ion battery was synthesized using the same steps as in Comparative Examples 1-4, the only difference being that the same weight of Li₂Ni was used when fabricating the power layer. 0.5 Cu 0.5O2 replaces Li5FeO4 as a lithium supplement.

[0144] The specific charge capacity, specific discharge capacity, volumetric energy density, capacity retention, and DC resistance of the lithium-ion batteries prepared in Examples 2-1 to 2-6 and Comparative Example 2-1 were characterized according to the steps described above, and are summarized in Table 2 below. To more intuitively compare battery performance, the characterization results of Comparative Examples 1-1 to 1-3, which did not use lithium replenishment agents, are also listed again in Table 3 below.

[0145] Table 3: Characterization results of charge-discharge specific capacity, energy density, and capacity retention after 100 days of high-temperature storage for batteries of Examples 2-1 to 2-6, Comparative Examples 1-1 to 1-3, and Comparative Example 2-1 of this application.

[0146]

[0147] As can be seen from the characterization results in Table 3 above, when the lithium replenishment agent was changed, all the embodiments of the invention also showed significantly better capacity retention than the comparative example, while also having good charge-discharge specific capacity and energy density, which can well meet the market requirements for lithium-ion batteries in this regard.

[0148] Table 4: DC resistance characterization results of batteries in Examples 2-1 to 2-6 and Comparative Example 2-1 of this application at 30 seconds

[0149]

[0150] As can be seen from the characterization results in Table 4 above, even with the replacement of the lithium replenishing agent, the battery prepared in the embodiment of the present invention also achieved a much lower DC resistance at 30 seconds compared to the comparative example. This indicates that by specially designing the particle size of the anode active material in the capacity layer and power layer, the present invention can effectively suppress the phenomenon of increased battery resistance caused by delithiation, which is common in the prior art, and significantly improve battery performance.

Claims

1. A positive electrode for a lithium-ion battery, the positive electrode comprising: i) Current collector; ii) at least one capacity layer comprising a first binder, a first conductive agent, and a first positive electrode active material having a first average particle size D50; and iii) at least one power layer, the power layer comprising a second binder, a second conductive agent, a lithium supplement agent, and a second positive electrode active material, the second positive electrode active material having a second average particle size D50; The first average particle size D50 is greater than the second average particle size D50; the first average particle size D50 of the first positive electrode active material is 0.8-1.3 micrometers; the second average particle size D50 of the second positive electrode active material is 0.1-0.7 micrometers; The average particle size D50 of the lithium supplement is 5-15 micrometers.

2. The positive electrode sheet as described in claim 1, characterized in that, The positive electrode includes at least one capacity layer on at least one surface of the current collector, and at least one power layer on the surface of the at least one capacity layer opposite to the current collector; or The positive electrode includes a power layer on at least one surface of the current collector and at least one capacity layer on the opposite surface of the at least one power layer to the current collector.

3. The positive electrode sheet for lithium-ion batteries as described in claim 1, characterized in that, The second average particle size of the second positive electrode active material is 0.2-0.45 micrometers.

4. The positive electrode sheet for a lithium-ion battery as described in claim 1, characterized in that, The first and second positive electrode active materials are each independently selected from: lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium vanadium oxide, lithium vanadium oxide, the positive electrode active material shown in Formula I, the positive electrode active material shown in Formula II, and combinations thereof. LiNi x Co y A z O2 formula I In formula I, A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1; Li Fe 1-m-n Mn m B n Formula II of PO4 In Formula II, 0≤m≤1, 0≤n≤0.1, and B is selected from at least one of the transition metal elements other than Fe and Mn, as well as non-transition metal elements.

5. The positive electrode sheet for a lithium-ion battery as described in claim 4, characterized in that, Both the first positive electrode active material and the second positive electrode active material are lithium iron phosphate.

6. The positive electrode sheet for a lithium-ion battery as described in claim 1, characterized in that, The lithium supplement is selected from one or more of the following: Li₂M₁O₂, Li₂M₂O₃, Li₂M₃O₄, Li₃M₄O₄, Li₅M₅O₄, Li₅M₆O₆, Li₆M₇O₄, Li₂M₁O₂, Li₂M₁O� a C b O c , M1 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca; M2 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo, Zr, Si, Cu, Ru; M3 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, V, Nb; M4 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca; M5 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo, Al; M6 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, Ca; M7 is selected from one or more of the following: Ni, Co, Mn, Fe, Ru; Where a is an integer 1 or 2, b is an integer 0, 1, 2, 3 or 4, and c is an integer 1, 2, 3, 4, 5 or 6.

7. The positive electrode sheet for a lithium-ion battery as described in claim 6, characterized in that, The lithium supplement includes Li2Cu 0.5 Ni 0.5 At least one of O2 and Li5FeO4.

8. The positive electrode sheet for a lithium-ion battery as described in claim 1, characterized in that, Based on the total weight of the capacity layer, the capacity layer comprises 1-30% by weight of a first binder, 0.1-10% by weight of a first conductive agent, and 60-98.5% by weight of a first positive electrode active material; Based on the total weight of the power layer, the power layer comprises 1-30% by weight of a second binder, 0.1-10% by weight of a second conductive agent, 0.1-30% by weight of a lithium supplement agent, and 50-97% by weight of a second positive electrode active material; and The content of the second conductive agent in the power layer is equal to or greater than the content of the first conductive agent in the capacity layer.

9. The positive electrode sheet for a lithium-ion battery as described in claim 1, characterized in that, The weight ratio of the power layer to the capacity layer is 1:9 to 9:

1.

10. A lithium-ion battery comprising a negative electrode, an electrolyte, a separator, and a positive electrode for a lithium-ion battery according to any one of claims 1-9.

11. A battery module comprising the lithium-ion battery according to claim 10.

12. A battery pack comprising the battery module according to claim 11.

13. An electrical device comprising a lithium-ion battery according to claim 10, a battery module according to claim 11, or a battery pack according to claim 12.

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