CN116230857B

CN116230857B - Positive pole piece, battery and electric equipment

Info

Publication number: CN116230857B
Application number: CN202310507530.4A
Authority: CN
Inventors: 吴凯; 魏冠杰; 古力; 孟阵; 宋育倩; 李星; 石鹏; 张宇; 赵延杰
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2023-05-08
Filing date: 2023-05-08
Publication date: 2023-07-18
Anticipated expiration: 2043-05-08
Also published as: CN116230857A

Abstract

The positive electrode plate comprises a positive electrode current collector, a positive electrode lug and a positive electrode active material layer, wherein at least one end of the positive electrode current collector in a first direction is connected with the positive electrode lug, the first direction is perpendicular to the thickness direction of the positive electrode plate, and the positive electrode active material layer is arranged on at least one side of the positive electrode current collector; the positive electrode active material layer comprises an edge part and a middle part, wherein the edge part is distributed at two ends of the middle part in the first direction, and the positive electrode active material materials of the middle part and the edge part comprise nickel-containing lithium-rich manganese-based materials and lithium-containing phosphates; regarding the average molar content of nickel in the nickel-containing lithium-rich manganese-based material, the middle portion is higher than the edge portion. In the positive electrode plate, the nickel-containing lithium-rich manganese-based material and the lithium-containing phosphate are used in a matched mode, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material in the middle portion is regulated and controlled to be relatively high, the phenomenon of lithium precipitation can be reduced, and the cycle performance is improved.

Description

Positive pole piece, battery and electric equipment

Technical Field

The application relates to the technical field of batteries, in particular to a positive pole piece, a battery and electric equipment.

Background

At present, in order to better regulate and control the energy density, structural stability, cycle performance and the like of the positive electrode active material, the positive electrode active material materials of different systems are generally mixed and matched for use. In some embodiments, the lithium-rich manganese-based material is used in combination with a lithium-containing phosphate; however, the battery is susceptible to lithium precipitation during use, resulting in deterioration of the cycle performance of the power battery.

Disclosure of Invention

In view of the above problems, the application provides a positive electrode plate, a battery and electric equipment, which can reduce the phenomenon of lithium precipitation and improve the cycle performance.

Embodiments of the present application are implemented as follows:

in a first aspect, an embodiment of the present application provides a positive electrode sheet, including a positive electrode current collector, a positive electrode tab, and a positive electrode active material layer, where at least one end of the positive electrode current collector in a first direction is connected with the positive electrode tab, the first direction is perpendicular to a thickness direction of the positive electrode sheet, and the positive electrode active material layer is disposed on at least one side of the positive electrode current collector; the positive electrode active material layer comprises an edge part and a middle part, wherein the edge part is distributed at two ends of the middle part in the first direction, and the positive electrode active material materials of the middle part and the edge part comprise nickel-containing lithium-rich manganese-based materials and lithium-containing phosphates; at the middle part, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material is n1; at the edge part, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material is n2; n1 > n2.

According to the technical scheme, the nickel-containing lithium-rich manganese-based material and the lithium-containing phosphate are matched in the positive electrode active material layer, the edge part and the middle part are divided in the positive electrode active material layer along the first direction, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material in the middle part is regulated and controlled to be higher than that of nickel of the nickel-containing lithium-rich manganese-based material in the edge part, the whole nickel-containing lithium-rich manganese-based material in the middle part has larger lattice contraction, the lattice contraction of the middle part is improved, the lattice expansion of the negative electrode can be buffered better, the problem that the expansion force of the middle part of the pole piece is overlarge is solved, and therefore the lithium precipitation phenomenon can be reduced, and the cycle performance is improved.

In some embodiments, at least one of the following conditions (a 1) and (a 2) is satisfied: (a 1) n1/n2 is 1.1.ltoreq.n 1/n 2.ltoreq.2; (a 2) 1.3.ltoreq.n1/n2.ltoreq.1.8. In these embodiments, the average molar content of nickel in the nickel-containing lithium-rich manganese-based material in the middle portion and the edge portion satisfies a specific ratio, so that the middle portion has a suitable lattice contraction enhancement relative to the edge portion, and the lithium precipitation phenomenon can be better improved, so that the cycle performance is better improved.

In some embodiments, the nickel-containing lithium-rich manganese-based material includes nLi ₂ MnO ₃ •(1-n)Li _x1 Ni _x2 Mn _x3 M1 _x4 O _2-x5 Wherein n is more than or equal to 0.1 and less than or equal to 0.3,0.2, x1 is more than or equal to 1.2,0.3 and less than or equal to x2 is less than 1, x3 is more than or equal to 0 and less than or equal to 0.7,0 and less than or equal to x4 is more than or equal to 0.1, x5 is more than or equal to 0 and less than or equal to 0.2, and M1 comprises one or more of Na, mg, al, ca, ba, V, zn, ti, fe, co, cr, nb, W, mo, zr, ta and Hf. In these embodiments, the nickel-containing lithium-rich manganese-based material has a composition of a specific molecular formula that enables a better gram capacity performance of the nickel-containing lithium-rich manganese-based material, and in some cases, at low voltages (e.g., 4.35V) gram capacity performance can be up to 150mAh/g.

In some embodiments, at least one of the following conditions (b 1) - (b 5) is satisfied: (b1) In the nickel-containing lithium-rich manganese-based material at the edge part, x2 is more than or equal to 0.3 and less than or equal to 0.6; (b2) In the nickel-containing lithium-rich manganese-based material at the edge part, x2 is more than or equal to 0.5 and less than or equal to 0.6; (b3) In the nickel-containing lithium-rich manganese-based material at the middle part, x2 is more than or equal to 0.6 and less than 1; (b4) In the nickel-containing lithium-rich manganese-based material in the middle part, x2 is more than or equal to 0.6 and less than or equal to 0.9; (b5) In the nickel-containing lithium-rich manganese-based material at the middle part, x2 is more than or equal to 0.6 and less than or equal to 0.7. In the embodiments, the value of x2 in the middle part is larger than that of x2 in the edge part, so that n1 > n2 > 0 can be conveniently regulated and controlled; meanwhile, x2 is in a specific range, so that the nickel-containing lithium-rich manganese-based material at the edge part and the middle part has higher nickel content, and the nickel-containing lithium-rich manganese-based material is favorable for realizing better gram capacity exertion.

In some embodiments, the mass ratio of lithium-containing phosphate in the middle positive electrode active material is w1; in the positive electrode active material at the edge part, the mass ratio of the lithium-containing phosphate is w2; w1 > w2 > 0. In these embodiments, the increase in the mass ratio of the lithium-containing phosphate can increase the overall lattice contraction, and the mass ratio of the lithium-containing phosphate in the middle part is higher than that in the edge part, which is beneficial to further increasing the size of the lattice contraction of the middle part relative to the edge part, and can better buffer the lattice expansion of the negative electrode, thereby reducing the lithium precipitation phenomenon and improving the cycle performance.

In some embodiments, 58% or less w1 or less than 85%, and/or 30% or less w2 or less than 50%. In these examples, the mass ratio of lithium-containing phosphate is within a specific range, which can provide a larger lattice contraction; meanwhile, the gram capacity of the middle part is favorably adjusted to be similar to or even equal to that of the edge part, so that the middle part can give consideration to higher gram capacity, and the positive electrode plate has higher energy density.

In some embodiments, the lithium-containing phosphate comprises Li _1+y1 Fe _y2 Mn _y3 M2 _y4 P _1-y5 O _4-y6 Wherein, -0.8.ltoreq.y1.ltoreq.0.2, 0.ltoreq.y2.ltoreq.1, 0.ltoreq.y3.ltoreq.1, 0.ltoreq.y4.ltoreq.0.1, 0.ltoreq.y5.ltoreq.0.1, 0.ltoreq.y6.ltoreq.0.4, M2 including one or more of Al, cu, mg, zn, ni, ti, V, zr, co, ga, sn, sb, nb and Ge. In these examples, the lithium-containing phosphate has a composition of a specific molecular formula, so that the lithium-containing phosphate has a larger lattice contraction, and the positive electrode active material layer can better buffer the lattice expansion of the negative electrode, thereby reducing the phenomenon of lithium precipitation and improving the cycle performance.

In some embodiments, the gram volume of the middle portion is C1; the gram capacity of the edge part is C2; c1: c2 = (0.98 to 1.02): (0.98-1.02). In these embodiments, the gram capacities of the middle portion and the edge portion are similar or even equal, so that the middle portion can give consideration to a higher gram capacity, and thus the positive electrode sheet has a higher energy density.

In some embodiments, in a cross section of the positive electrode active material layer in a specified direction, the area of the positive electrode active material layer is S, the area of the middle portion is S1, and the cross section in the specified direction is perpendicular to the thickness direction of the positive electrode tab, s1=s× (45% -65%). In the embodiments, the middle part has proper area ratio in the positive electrode active material layer, so that the problem of overlarge expansion force of the middle part of the pole piece can be better solved, the lithium precipitation phenomenon can be better reduced, and the cycle performance can be better improved.

In some embodiments, in a cross section of the positive electrode active material layer in a specified direction, the positive electrode active material layer has a dimension L in the first direction, and the intermediate portion has a maximum dimension L1 in the first direction, L1. Ltoreq.l×65%. In these embodiments, the intermediate portion has a suitable size ratio in the positive electrode active material layer, and is conveniently controlled so that the positive electrode active material layer has a suitable area ratio.

In some embodiments, one side of the positive current collector in the first direction is connected with a positive electrode tab, edge parts at two ends of the middle part in the first direction are a first edge and a second edge respectively, and the first edge is positioned at one end of the middle part close to the positive electrode tab; in the cross section of the positive electrode active material layer in the predetermined direction, the area of the first edge is S2, and the area of the second edge is S3, S2 > S3 > 0. In these embodiments, since the tab has a thinned portion, lithium is more easily separated from the middle of the pole piece at the end close to the tab, and the area of the first edge is larger than that of the second edge, that is, the area of the edge portion close to the positive pole tab is larger, which is favorable for better reducing the lithium separation phenomenon and improving the cycle performance.

In some embodiments, s2=s× (25% -35%), and/or s3=s× (10% -20%). In these embodiments, the first edge and/or the second edge has a suitable size ratio in the positive electrode active material layer, which is convenient to regulate so that the positive electrode active material layer has a suitable area ratio.

In some embodiments, in a cross section of the positive electrode active material layer in a specified direction, the positive electrode active material layer has a dimension L in a first direction, a maximum dimension of the first edge in the first direction is L2, and a maximum dimension of the second edge in the first direction is L3; wherein L2 is less than or equal to L multiplied by 35%, and/or L3 is less than or equal to L multiplied by 20%. In these embodiments, the first edge and/or the second edge have a suitable size ratio in the positive electrode active material layer, which facilitates the regulation such that the positive electrode active material layer has a suitable area ratio size.

In some embodiments, the positive electrode sheet is a wound structure, and the edge portions are distributed at both ends of the middle portion in the first direction. In these embodiments, in the positive electrode sheet of the winding structure, edge portions are distributed at two ends in the first direction, so that the lithium precipitation phenomenon can be reduced better, and the cycle performance is improved effectively.

In some embodiments, the positive electrode sheet is a lamination structure, and edge portions are also distributed at two ends of the middle portion in a second direction, and the second direction is perpendicular to the first direction and the thickness direction of the positive electrode sheet respectively. In the embodiments, the edge portions are evenly distributed at the two ends of the lamination structure in the first direction and the second direction, so that the lithium precipitation phenomenon can be well reduced, and the cycle performance is effectively improved.

In a second aspect, an embodiment of the present application provides a battery, including the positive electrode sheet of the above embodiment.

In a third aspect, an embodiment of the present application provides an electric device, including the battery of the above embodiment.

The foregoing description is only an overview of the technical solutions of the embodiments of the present application, and may be implemented according to the content of the specification in order to make the technical means of the present application more clearly understood, and in order to make the above and other objects, features and advantages of the present application more clearly understood, the following specific embodiments of the present application are specifically described below.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic illustration of a vehicle according to some embodiments of the present application;

FIG. 2 is an exploded view of a battery provided in some embodiments of the present application;

FIG. 3 is an exploded view of a battery cell according to some embodiments of the present application;

fig. 4 is a schematic structural diagram of a first positive electrode sheet at a first view angle according to some embodiments of the present application;

fig. 5 is a cross-sectional view of a first positive electrode tab at a second view angle provided in some embodiments of the present application;

fig. 6 is a cross-sectional view of a first positive electrode tab at a first viewing angle provided in some embodiments of the present application;

fig. 7 is a cross-sectional view of a first positive electrode tab at a first viewing angle provided in some embodiments of the present application;

fig. 8 is a cross-sectional view of a first positive electrode tab at a first viewing angle provided in some embodiments of the present application;

Fig. 9 is a schematic structural diagram of a second positive electrode sheet according to some embodiments of the present application at a first viewing angle.

1000-vehicle;

100-cell; 200-a controller; 300-motor;

10-a box body; 11-a first part; 12-a second part; 13-accommodation space;

20-battery cells; 21-a housing; 22-electrode assembly; 23-electrode terminals; 24-pressure relief structure;

211-a housing; 212-a cover; 213-sealing the space;

221-positive pole piece; 2211—positive current collector; 2212-positive tab; 2213—a positive electrode active material layer; 2213 a-middle part; 2213 b-edge region; 2213b 1-a first edge; 2213b 2-a second edge;

a is the thickness direction of the positive pole piece; b-a first direction; c-second direction.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.

Embodiments of the technical solutions of the present application will be described in detail below with reference to the accompanying drawings. The following examples are only for more clearly illustrating the technical solutions of the present application, and thus are only examples, and are not intended to limit the scope of protection of the present application.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application; the terms "comprising" and "having" and any variations thereof in the description and claims of the present application and in the description of the figures above are intended to cover non-exclusive inclusions.

In the description of the embodiments of the present application, the technical terms "first," "second," etc. are used merely to distinguish between different objects and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated, a particular order or a primary or secondary relationship.

In the description of the embodiments of the present application, the technical terms "and/or" such as "feature 1 and/or feature 2" each refer to "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2" alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship.

In the description of the embodiments of the present application, unless otherwise indicated, the meaning of "plurality of" in "one or more" means two and more than two.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. Those of skill in the art will explicitly and implicitly appreciate that the embodiments described herein may be combined with other embodiments.

In the embodiments of the present application, the same reference numerals denote the same components, and in the interest of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the dimensions of the height, length, width, etc. of the various components in the embodiments of the present application, as well as the overall height, length, width, etc. of the integrated device, are shown by way of example only and should not be construed as limiting the present application in any way.

The more widely the application of power cells is seen from the development of market situation. The power battery is not only applied to energy storage power supply systems such as hydraulic power, firepower, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles, electric automobiles, and the like, and a plurality of fields such as military equipment, aerospace, and the like. With the continuous expansion of the application field of the power battery, the market demand of the power battery is also continuously expanding.

Along with the continuous strong market of new energy automobiles, the demand of power batteries is growing increasingly, and the development of power lithium ion batteries with high energy density, stable structure and high cycle stability is becoming an urgent demand of the current market. At present, in order to better regulate and control the energy density, structural stability, cycle performance and the like of the positive electrode active material, the positive electrode active material materials of different systems are generally mixed and matched for use.

Lithium-containing phosphates such as lithium iron phosphate materials have good thermal stability and cycle performance, but generally suffer from relatively low volumetric and gravimetric energy densities; however, the lithium-rich manganese-based material has the advantages of high energy density, low cost and the like, but is generally relatively poor in structural stability and high-temperature cycle performance, so that in some schemes, the lithium-rich manganese-based material and the lithium-containing phosphate are used in a matched manner.

However, in the scheme of using the lithium-rich manganese-based material and the lithium-containing phosphate in a mixed manner, since the lattice contraction of the lithium-rich manganese-based material is small, a small buffer space can be provided for the lithium intercalation expansion of the negative electrode, and in the later cycle period of the battery, the situation that the expansion force of the middle part of the pole piece is too large along the direction in which the pole lug protrudes relative to the current collector can occur, so that lithium is separated from the middle part of the large surface, and the cycle performance of the power battery is damaged.

Based on this, the embodiment of the application proposes a positive electrode sheet, a battery monomer, a battery and electric equipment, in the positive electrode active material of the positive electrode sheet, under the condition that the lithium-rich manganese-based material and the lithium-containing phosphate are matched for use, an edge part and a middle part are divided in the positive electrode active material layer along the setting direction of the positive electrode tab, and the edge part and the middle part of the positive electrode active material layer are configured according to different standards, wherein the lithium-rich manganese-based material adopts the nickel-containing lithium-rich manganese-based material, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material of the middle part is regulated and controlled to be higher than the average molar content of nickel of the nickel-containing lithium-rich manganese-based material of the edge part, and as the average molar content of nickel of the nickel-containing lithium-rich manganese-based material of the middle part is relatively higher, the whole nickel-rich lithium-manganese-based material of the middle part has larger lattice contraction, the lattice contraction of the middle part is improved, the lattice expansion of the negative electrode can be buffered better, and thus the lithium precipitation phenomenon can be reduced, and the cycle performance is improved.

The battery cell applying the positive electrode plate disclosed by the embodiment of the application can be used in electric devices such as vehicles, ships or aircrafts, but is not limited to the electric devices. The embodiment of the application provides an electricity utilization device using a battery as a power supply, wherein the electricity utilization device can be, but is not limited to, a mobile phone, a tablet, a notebook computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft and the like. Among them, the electric toy may include fixed or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric plane toys, and the like, and the spacecraft may include planes, rockets, space planes, and spacecraft, and the like.

For convenience of explanation, the following embodiments take an electric device in the embodiments of the present application as an example of a vehicle.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a vehicle 1000 according to some embodiments of the present application. The vehicle 1000 may be a fuel oil vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle may be a pure electric vehicle, a hybrid vehicle or a range-extended vehicle. The battery 100 is provided in the interior of the vehicle 1000, and the battery 100 may be provided at the bottom or the head or the tail of the vehicle 1000. The battery 100 may be used for power supply of the vehicle 1000, for example, the battery 100 may be used as an operating power source of the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300, the controller 200 being configured to control the battery 100 to power the motor 300, for example, for operating power requirements during start-up, navigation, and travel of the vehicle 1000.

In some embodiments of the present application, battery 100 may not only serve as an operating power source for vehicle 1000, but may also serve as a driving power source for vehicle 1000, instead of or in part instead of fuel oil or natural gas, to provide driving power for vehicle 1000.

In this application, the battery 100 refers to a single physical module including one or more battery cells 20 to provide a certain voltage and capacity, which may be in the form of a battery pack, a battery module, or the like. The battery 100 may include a case 10 for enclosing one or more battery cells 20, and the case 10 may prevent liquid or other foreign matter from affecting the charge or discharge of the battery cells 20.

Referring to fig. 2, fig. 2 is an exploded view of a battery 100 provided in some embodiments of the present application. The battery 100 includes a case 10 and a plurality of battery cells 20, and the plurality of battery cells 20 are accommodated in the case 10. The case 10 is used for accommodating the battery cells 20, and the case 10 may have various structures. In some embodiments, the case 10 may include a first portion 11 and a second portion 12, the first portion 11 and the second portion 12 being overlapped with each other, the first portion 11 and the second portion 12 together defining an accommodating space 13 for accommodating the battery cell 20. The second portion 12 may be a hollow structure having one end opened, the first portion 11 is a plate-shaped structure, and the first portion 11 is covered on an opening side of the second portion 12 to form a case 10 having an accommodating space 13; the first portion 11 and the second portion 12 may also be hollow structures each having an opening at one side, and the opening side of the first portion 11 is engaged with the opening side of the second portion 12 to form the case 10 having the accommodation space 13. Of course, the first portion 11 and the second portion 12 may be of various shapes, such as a cylinder, a rectangular parallelepiped, or the like.

In the battery 100, the plurality of battery cells 20 may be connected in series or parallel or a series-parallel connection, wherein a series-parallel connection refers to that the plurality of battery cells 20 are connected in series or parallel. The plurality of battery cells 20 can be directly connected in series, in parallel or in series-parallel, and then the whole body formed by the plurality of battery cells 20 is accommodated in the box 10. The plurality of battery cells 20 may be connected in series or parallel or series-parallel to form a module, and the plurality of modules may be connected in series or parallel or series-parallel to form a whole and be accommodated in the case 10. The battery 100 may further include other structures, for example, electrical connection between the plurality of battery cells 20 may be achieved through a bus bar member to achieve parallel connection or series-parallel connection of the plurality of battery cells 20.

The battery cell 20 refers to the smallest unit constituting the battery pack. The battery cell 20 may be a lithium ion battery, a lithium sulfur battery, a sodium ion battery, or a magnesium ion battery, but is not limited thereto.

Referring to fig. 3, the battery cell 20 may include a case 21, an electrode assembly 22, and an electrolyte, both of which are contained in the case 21.

The housing 21 may include a case 211 and a cover 212. The case 211 is an assembly for fitting the cover 212 to form an inner sealed space 213 of the battery cell 20, wherein the formed sealed space 213 may be used to accommodate the electrode assembly 22, the electrolyte, and other components. The cover 212 is a member that is covered at the opening of the case 211 to isolate the internal environment of the battery cell 20 from the external environment, the shape of the cover 212 may be adapted to the shape of the case 211 to fit the case 211, and the cover 212 may be further provided with functional members such as the electrode terminal 23, the pressure release structure 24, and the like. A sealing ring may be disposed between the opening of the housing 211 and the cover 212, for sealing between the housing 211 and the cover 212.

The housing 211 and the cover 212 may be of various shapes and various sizes, such as rectangular parallelepiped, cylindrical, hexagonal prism, etc. Specifically, the shapes of the case 211 and the cover 212 may be determined according to the specific shape and size of the electrode assembly 22. The material of the housing 211 and the cover 212 may be various, such as, but not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, and the like. The material of the seal ring may be various, for example, but not limited to, a material resistant to electrolyte corrosion, high toughness and fatigue such as PP (polypropylene), PC (polycarbonate), PET (polyethylene terephthalate), etc. The outer surface of the housing 211 may be formed with a plating layer made of various materials, such as, but not limited to, a corrosion-resistant material such as Ni, cr, etc.

The battery cells 20 may also be in the form of a pouch, such as a pouch-type pouch. The material of the flexible bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

The electrode assembly 22 includes a negative electrode tab, a separator, and a positive electrode tab 221 (see fig. 4 and 5). The battery cell 20 operates primarily by virtue of metal ions moving between the positive electrode tab 221 and the negative electrode tab. During the charge and discharge process, active ions are inserted and extracted back and forth between the positive electrode plate 221 and the negative electrode plate; the isolating film is arranged between the positive pole piece 221 and the negative pole piece, and mainly plays a role in preventing the positive pole piece and the negative pole piece from being short-circuited, and can enable ions to pass through. The electrode assembly 22 may be a roll-to-roll structure or a lamination structure, and the embodiment of the present application is not limited thereto.

The negative electrode plate comprises a negative electrode current collector, a negative electrode tab and a negative electrode active material layer, wherein the negative electrode active material layer is arranged on at least one side of the negative electrode current collector, and a bottom coating and the like can be arranged between the negative electrode current collector and the negative electrode tab; the negative electrode tab protrudes from the negative electrode current collector, and is located at one end or two opposite ends of the negative electrode current collector, for example.

The negative electrode current collector may be a metal foil or a composite current collector, for example, the materials of the negative electrode current collector and the negative electrode tab may be copper, the composite current collector may include a polymer material base layer and a metal layer formed on at least one side of the polymer material base material, and the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

The negative electrode active material in the negative electrode active material layer may be a negative electrode active material such as carbon or silicon. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like. The silicon-based material may be at least one selected from elemental silicon, silicon oxygen compounds, silicon carbon composites, silicon nitrogen composites, and silicon alloys. The tin-based material may be at least one selected from elemental tin, tin oxide, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the anode active material may be used.

In some embodiments, the anode active material layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the anode active material layer further optionally includes a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the anode active material layer may optionally further include other adjuvants, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.

The isolating film is positioned between the positive pole piece 221 and the negative pole piece to play a role of isolation; the type of the separator is not particularly limited in the embodiment of the present application, and any known porous separator having good chemical stability and mechanical stability may be used.

In some embodiments, the material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

Referring to fig. 4 and 5, the positive electrode tab 221 includes a positive electrode current collector 2211, a positive electrode tab 2212, and a positive electrode active material layer 2213, the positive electrode active material layer 2213 is disposed on at least one side of the positive electrode current collector 2211, and an undercoat layer or the like may be further disposed between the positive electrode active material layer 2213 and the positive electrode current collector 2211; the positive electrode tab 2212 protrudes from the positive electrode current collector 2211, and the positive electrode tab 2212 is located at one end or opposite ends of the positive electrode current collector 2211, for example.

The positive electrode current collector 2211 may be a metal foil or a composite current collector, and for example, the materials of the positive electrode current collector 2211 and the positive electrode tab 2212 may be aluminum. The composite current collector may include a polymer material base layer and a metal layer formed on at least one side of the polymer material base layer, and may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a polymer material base material such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

The distribution form of the positive electrode active material in the positive electrode active material layer 2213 may be designed according to the technical scheme provided in the embodiment of the application.

In some embodiments, the positive electrode active material layer 2213 may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluoroacrylate resin.

In some embodiments, the positive electrode active material layer 2213 may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

The positive electrode tab 221 according to the embodiment of the present application will be described in detail.

Referring to fig. 4 and 5, in a first aspect, an embodiment of the present application provides a positive electrode tab 221, which includes a positive electrode current collector 2211, a positive electrode tab 2212, and a positive electrode active material layer 2213, wherein at least one end of the positive electrode current collector 2211 in a first direction B is connected with the positive electrode tab 2212, the first direction B is perpendicular to a thickness direction a of the positive electrode tab, and the positive electrode active material layer 2213 is disposed on at least one side of the positive electrode current collector 2211; the positive electrode active material layer 2213 includes an edge portion 2213B and a middle portion 2213a, the middle portion 2213a has edge portions 2213B distributed at both ends in the first direction B, and the positive electrode active material of the middle portion 2213a and the edge portion 2213B includes nickel-containing lithium-rich manganese-based material and lithium-containing phosphate; at the intermediate site 2213a, the average molar content of nickel comprising the nickel-lithium-rich manganese-based material is n1; at edge portion 2213b, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material is n2; n1 > n2.

The positive current collector 2211 may be connected to the positive tab 2212 at one or both ends in the first direction B, and the positive tab 2212 protrudes from the positive current collector 2211 along the first direction B, and may be integrally formed.

The positive electrode active material layer 2213 may be disposed on one side of the positive electrode current collector 2211 or on opposite sides of the positive electrode current collector 2211 in the thickness direction a of the positive electrode sheet.

In the positive electrode active material layer 2213, the intermediate portion 2213a has edge portions 2213B distributed at both ends thereof in the first direction B, that is, the positive electrode active material layer 2213 includes edge portions 2213B distributed at both ends of the intermediate portion 2213a in the first direction B, and the positive electrode active material layer 2213 may further include edge portions 2213B distributed at both ends of the intermediate portion 2213a in the second direction C, which is perpendicular to the first direction B and the thickness direction a of the positive electrode tab, respectively.

In the positive electrode active material layer 2213, other kinds of positive electrode active material such as, but not limited to, lithium cobaltate, lithium sulfur, and the like may be included in addition to the nickel-containing lithium-rich manganese-based material and the lithium-containing phosphate.

The average molar content of nickel in the nickel-containing lithium-rich manganese-based material is achieved by controlling the molar content of nickel in the nickel-containing lithium-rich manganese-based material. The higher average molar content of nickel in the nickel-containing lithium-rich manganese-based material of the intermediate portion 2213a means that the intermediate portion 2213a contains more nickel-containing lithium-rich manganese-based material having a relatively higher nickel content. Wherein, at the middle portion 2213a and the edge portion 2213b, the chemical formula types of the nickel-containing lithium-rich manganese-based material may be the same or different; in the case of different chemical formulas, the intermediate portion 2213a uses a nickel-containing lithium-rich manganese-based material having a relatively high nickel content, and the edge portion 2213b uses a nickel-containing lithium-rich manganese-based material having a relatively low nickel content. Under the condition of the same chemical formula, the middle part 2213a and the edge part 2213b adopt various nickel-containing lithium-rich manganese-based materials with different chemical formulas, the nickel content of the nickel-containing lithium-rich manganese-based materials with different types is different, and the ratio of the nickel-containing lithium-rich manganese-based materials with relatively higher nickel content in the middle part 2213a is higher; for example, the middle portion 2213a and the edge portion 2213b each contain a high nickel lithium-rich manganese-based material and a low nickel lithium-rich manganese-based material, wherein the high nickel lithium-rich manganese-based material is present in the middle portion 2213a at a higher ratio.

The average molar content of nickel of the nickel-containing lithium-rich manganese-based material refers to an average value of the molar content of nickel of the nickel-containing lithium-rich manganese-based material in the corresponding region. In the examples of the present application, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material may be determined by a conventional method test, for example, the elemental composition of the nickel-containing lithium-rich manganese-based material may be measured by ICP (inductively coupled plasma emission spectroscopy), and then the molar content of nickel may be calculated from the elemental composition test result; the average molar content of nickel in the nickel-containing lithium-rich manganese-based material can be obtained by multi-point detection and average value taking.

It is understood that in the examples of the present application, nickel-containing lithium-rich manganese-based material refers to a lithium-rich manganese-based material containing nickel, and thus both n1 and n2 are greater than 0.

In the embodiment of the present application, since the intermediate portion 2213a and the edge portion 2213b are different in composition, the intermediate portion 2213a and the edge portion 2213b can be distinguished by, for example, observing an electron microscope image of the positive electrode active material layer 2213 and a characteristic element distribution (e.g., fe element in LFP) in the positive electrode active material.

In the technical solution of the embodiment of the present application, the nickel-containing lithium-manganese-rich material and the lithium-containing phosphate are used in the positive electrode active material layer 2213 in a matching manner, the edge portion 2213B and the middle portion 2213a are divided in the positive electrode active material layer 2213 along the first direction B, the average molar content of nickel of the nickel-containing lithium-manganese-rich material of the middle portion 2213a is regulated and controlled to be higher than that of nickel of the nickel-containing lithium-manganese-rich material of the edge portion 2213B, so that the whole nickel-containing lithium-manganese-rich material of the middle portion 2213a has larger lattice contraction, the lattice contraction of the middle portion 2213a is improved, the lattice expansion of the negative electrode can be buffered better, the problem that the expansion force of the middle portion of the electrode sheet is overlarge is improved, and therefore the lithium precipitation phenomenon can be reduced, and the cycle performance is improved.

In some embodiments, at least one of the following conditions (a 1) and (a 2) is satisfied: (a 1) n1/n2 is 1.1.ltoreq.n 1/n 2.ltoreq.2; (a 2) 1.3.ltoreq.n1/n2.ltoreq.1.8.

By way of example, n1/n2 may take on values such as, but not limited to, any one point value or range value between any two of 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, and 2.

In these embodiments, the average molar content of nickel in the nickel-containing lithium-rich manganese-based material of the intermediate portion 2213a and the edge portion 2213b satisfies a specific ratio, so that the intermediate portion 2213a has a suitable lattice contraction enhancement with respect to the edge portion 2213b, and the lithium precipitation phenomenon can be better improved, so that the cycle performance is better improved.

In some embodiments, the nickel-containing lithium-rich manganese-based material includes nLi ₂ MnO ₃ •(1-n)Li _x1 Ni _x2 Mn _x3 M1 _x4 O _2-x5 Wherein n is more than or equal to 0.1 and less than or equal to 0.3,0.2, x1 is more than or equal to 1.2,0.3 and less than or equal to x2 is less than 1, x3 is more than or equal to 0 and less than or equal to 0.7,0 and less than or equal to x4 is more than or equal to 0.1, x5 is more than or equal to 0 and less than or equal to 0.2, and M1 comprises one or more of Na, mg, al, ca, ba, V, zn, ti, fe, co, cr, nb, W, mo, zr, ta and Hf.

The value of n is, for example but not limited to, 0.1, 0.2, 0.3, etc.

In the positive electrode tab 221, the battery cell 20, and the electric device, lithium ions are consumed by the processes such as formation and circulation, and thus the content of lithium element in the positive electrode active material is measured to be reduced. Meanwhile, if the positive electrode tab 221 and the negative electrode tab are subjected to lithium supplementation, the content of lithium element in the positive electrode active material is increased after the processes such as formation and circulation.

The value of x1 is, for example, but not limited to, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, etc.

The value of x2 is, for example, but not limited to, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc.

The value of x3 is, for example, but not limited to, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, etc.

The value of x4 is, for example, but not limited to, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, etc.

In the positive electrode tab 221, the battery cell 20, and the electric device, the oxygen element in the positive electrode active material is lost through the cycle or the like, and thus the measured oxygen element content in the positive electrode active material may be reduced.

The value of x5 is, for example, but not limited to, 0, 0.1, 0.2, etc.

nLi ₂ MnO ₃ •(1-n)Li _x1 Ni _x2 Mn _x3 M1 _x4 O _2-x5 Can be determined by testing by conventional methods. As an example, elemental composition is measured by ICP (inductively coupled plasma emission spectrometer); determination of Li by XRD decomposition of characteristic peaks ₂ MnO ₃ Phase and Li _x1 Ni _x2 Mn _x3 M1 _x4 O _2-x5 Is a ratio of (2).

In these embodiments, the nickel-containing lithium-rich manganese-based material has a composition of a specific molecular formula that enables a better gram capacity performance of the nickel-containing lithium-rich manganese-based material, and in some cases, at low voltages (e.g., 4.35V) gram capacity performance can be up to 150mAh/g.

In some embodiments, at least one of the following conditions (b 1) - (b 5) is satisfied: (b1) In the nickel-containing lithium-rich manganese-based material of the edge part 2213b, x2 is more than or equal to 0.3 and less than or equal to 0.6; (b2) In the nickel-containing lithium-rich manganese-based material of the edge part 2213b, x2 is more than or equal to 0.5 and less than or equal to 0.6; (b3) In the nickel-containing lithium-rich manganese-based material of the middle part 2213a, x2 is more than or equal to 0.6 and less than 1; (b4) In the nickel-containing lithium-rich manganese-based material of the middle part 2213a, x2 is more than or equal to 0.6 and less than or equal to 0.9; (b5) In the nickel-containing lithium-rich manganese-based material of the intermediate portion 2213a, x2 is more than or equal to 0.6 and less than or equal to 0.7.

In the nickel-containing lithium-rich manganese-based material of the edge portion 2213b, the value of x2 is, for example, but not limited to, any one point value or a range value between any two points of 0.3, 0.35, 0.4, 0.45, 0.5, 0.55 and 0.6.

In the nickel-containing lithium-rich manganese-based material of the intermediate portion 2213a, the value of x2 is, for example, but not limited to, any one point value or a range value between any two of 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 and 0.95.

As an example, x2 of the nickel-containing lithium-rich manganese-based material of the edge portion 2213b < x2 of the nickel-containing lithium-rich manganese-based material of the intermediate portion 2213 a; that is, when the value of x2 of the nickel-containing lithium-rich manganese-based material of the edge portion 2213b is 0.6, the value of x2 of the nickel-containing lithium-rich manganese-based material of the intermediate portion 2213a needs to be greater than 0.6; when the x2 value of the nickel-containing lithium-rich manganese-based material of the middle portion 2213a is 0.6, the x2 value of the nickel-containing lithium-rich manganese-based material of the edge portion 2213b needs to be less than 0.6.

In these embodiments, the value of x2 of the middle portion 2213a is greater than the value of x2 of the edge portion 2213b, so that n1 > n2 > 0 can be conveniently adjusted and controlled; meanwhile, x2 is in a specific range, so that the nickel-containing lithium-rich manganese-based materials of the edge part 2213b and the middle part 2213a have higher nickel content, and the nickel-containing lithium-rich manganese-based materials are favorable for realizing better gram capacity exertion.

In some embodiments, in the positive electrode active material of the intermediate portion 2213a, the mass ratio of the lithium-containing phosphate is w1; in the positive electrode active material of the edge portion 2213b, the mass ratio of the lithium-containing phosphate is w2; w1 > w2 > 0.

The mass ratio of the lithium-containing phosphate can be determined by testing by conventional methods. As an example, the middle part 2213a and the edge part 2213b are scraped off from the positive electrode current collector 2211 to obtain positive electrode powder, and an adhesive, a conductive agent, other additives and the like in the positive electrode powder are removed by high-temperature calcination and the like, so that a positive electrode active material is left, and the total quality of the positive electrode active material is tested; digesting the left positive electrode active material by a mixed solution of concentrated nitric acid and concentrated hydrochloric acid, introducing the solution into an inductively coupled plasma emission spectrometer, measuring the content of characteristic elements, and determining the type and mass ratio of the corresponding positive electrode active material according to the content of the characteristic elements; for example, when the lithium-containing phosphate is LFP, the Fe element content is measured, the mass ratio of LFP in the positive electrode active material is calculated from the Fe element content and the chemical formula of LFP, and the mass ratio of LFP is subtracted by 100% to obtain the mass ratio of the nickel-containing lithium-rich manganese-based material.

In these embodiments, the increase in the mass ratio of the lithium-containing phosphate increases the overall lattice contraction, and the mass ratio of the lithium-containing phosphate in the intermediate portion 2213a is higher than that in the edge portion 2213b, which is advantageous for further increasing the size of the lattice contraction of the intermediate portion 2213a with respect to the edge portion 2213b, and for better buffering the lattice expansion of the negative electrode, so that the lithium precipitation phenomenon can be reduced, and the cycle performance can be improved.

In some embodiments, 58% or less w1 or less than 85%, and/or 30% or less w2 or less than 50%.

By way of example, w1 may take on values such as, but not limited to, any one point value or range value between any two of 58%, 60%, 65%, 70%, 75%, 80% and 85%.

As an example, w2 may take on values such as, but not limited to, any one point value or range value between any two of 30%, 35%, 40%, 45%, and 50%.

In these examples, the mass ratio of lithium-containing phosphate is within a specific range, which can provide a larger lattice contraction; meanwhile, the gram capacity of the middle portion 2213a is favorably adjusted to be similar to or even equal to that of the edge portion 2213b, so that the middle portion 2213a can give consideration to higher gram capacity, and the positive electrode sheet 221 has higher energy density.

In some embodiments, the lithium-containing phosphate comprises Li _1+y1 Fe _y2 Mn _y3 M2 _y4 P _1-y5 O _4-y6 Wherein, -0.8.ltoreq.y1.ltoreq.0.2, 0.ltoreq.y2.ltoreq.1, 0.ltoreq.y3.ltoreq.1, 0.ltoreq.y4.ltoreq.0.1, 0.ltoreq.y5.ltoreq.0.1, 0.ltoreq.y6.ltoreq.0.4, M2 including one or more of Al, cu, mg, zn, ni, ti, V, zr, co, ga, sn, sb, nb and Ge.

The value of y1 is, for example, but not limited to, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1, 0, 0.1, 0.2, etc.

The values of y4 and y5 are, for example and without limitation, 0, 0.05, 0.1, etc.

The values of y2 and y3 are, for example and without limitation, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, etc.

The value of y6 is, for example but not limited to, 0, 0.1, 0.2, 0.3, 0.4, etc.

In the examples of the present application, the chemical formula of the lithium-containing phosphate is the chemical formula of the material used in the preparation process. In the positive electrode tab 221, the battery cell 20, and the electrical device, elements in the chemical formula of the lithium-containing phosphate may be lost due to processes such as formation and circulation, as will be understood by those skilled in the art. For example, the P element and the O element are consumed, and thus, the content of the P element in the lithium-containing phosphate is reduced and/or the content of the oxygen element is reduced.

Li _1+y1 Fe _y2 Mn _y3 M2 _y4 P _1-y5 O _4-y6 Can be determined by testing by conventional methods. As an example, elemental composition was measured by ICP (inductively coupled plasma emission spectrometer).

As an example, the lithium-containing phosphate includes doped or undoped LiFePO ₄ 、LiMnPO ₄ And LiMn _1-z Fe _z PO ₄ Wherein 0 < z < 1.

In these embodiments, the lithium-containing phosphate has a composition of a specific molecular formula, so that the lithium-containing phosphate has a larger lattice contraction, and the positive electrode active material layer 2213 can better buffer the lattice expansion of the negative electrode, thereby reducing the lithium precipitation phenomenon and improving the cycle performance.

In some embodiments, the gram capacity of intermediate portion 2213a is C1; the gram capacity of edge portion 2213b is C2; c1: c2 = (0.98 to 1.02): (0.98-1.02).

By way of example, the ratio of C1 to C2 is, for example, but not limited to, any one point value or a range value between any two of (0.98:1), (0.99:1), (1:1), (1.01:1), (1.02:1), (1:0.98), (1:0.99), (1:1.01), and (1:1.02).

Gram capacity refers to the ratio of the amount of electricity that an active material can release to the mass of the active material. Gram volume can be measured by the following method: and performing a charge-discharge test, and obtaining a discharge capacity according to the charge-discharge test, wherein the gram capacity is the ratio of the discharge capacity to the mass of the active material.

As an example, the boundary of the intermediate portion 2213a and the edge portion 2213b may be determined first, the positive electrode tab 221 may be cut along the boundary to separate the intermediate portion 2213a and the edge portion 2213b, and then the gram capacities of the intermediate portion 2213a and the edge portion 2213b may be tested, respectively.

In these embodiments, the gram capacities of the intermediate portion 2213a and the edge portion 2213b are similar or even equal, so that the intermediate portion 2213a can give consideration to a higher gram capacity, thereby enabling the positive electrode tab 221 to have a higher energy density.

Referring to fig. 6, in some embodiments, in a cross section of the positive electrode active material layer 2213 in a specified direction, the area of the positive electrode active material layer 2213 is S, the area of the intermediate portion 2213a is S1, and the cross section in the specified direction is perpendicular to the thickness direction a of the positive electrode tab (refer to fig. 5), s1=s× (45% -65%).

As an example, the value of S1/S is, for example, but not limited to, any one point value or range value between any two of 45%, 50%, 55%, 60% and 65%.

In these embodiments, the intermediate portion 2213a has a suitable area ratio in the positive electrode active material layer 2213, so that the problem of overlarge expansion force in the middle of the pole piece can be better improved, and the lithium precipitation phenomenon can be better reduced, so that the cycle performance is better improved.

Referring to fig. 7, in some embodiments, in a cross section of the positive electrode active material layer 2213 in a specified direction, the dimension of the positive electrode active material layer 2213 in the first direction B is L, and the largest dimension of the intermediate portion 2213a in the first direction B is L1, L1 +.l×65%.

In a cross section of the positive electrode active material layer 2213 in a designated direction, boundary lines of both sides of the intermediate portion 2213a in the first preset direction may be in a straight line form, a curved line form, and a broken line form, and may be parallel or non-parallel to the boundary line of the positive electrode active material layer 2213 in the straight line form. Accordingly, the L1 corresponding to each of the intermediate portions 2213a in the first direction B may be the same or different; in the embodiment of the present application, L1 corresponding to each of the intermediate portions 2213a in the first direction B satisfies L1 ∈lχ65%.

In addition, since the value of L1 needs to satisfy s1=s× (45% to 65%), the minimum value of L1 is determined according to the requirement of s1=s× (45% to 65%).

In these embodiments, the intermediate portion 2213a has a suitable size ratio in the positive electrode active material layer 2213, and is conveniently controlled so that the positive electrode active material layer 2213 has a suitable area ratio.

Referring to fig. 8, in some embodiments, a positive electrode tab 2212 is connected to one side of the positive electrode current collector 2211 in the first direction B, edge portions 2213B at two ends of the intermediate portion 2213a in the first direction B are a first edge 2213B1 and a second edge 2213B2, respectively, and the first edge 2213B1 is located at one end of the intermediate portion 2213a close to the positive electrode tab 2212; in a cross section of the positive electrode active material layer 2213 in the predetermined direction, the area of the first edge 2213b1 is S2, and the area of the second edge 2213b2 is S3, S2 > S3 > 0.

In these embodiments, since the tab has a thinned portion, lithium is more easily separated from the middle of the pole piece at the end close to the tab, and the area of the first edge 2213b1 is larger than that of the second edge 2213b2, that is, the area of the edge portion 2213b close to the positive electrode tab 2212 is larger, which is favorable for better reducing the lithium separation phenomenon and improving the cycle performance.

In some embodiments, s2=s× (25% -35%), and/or s3=s× (10% -20%).

As an example, the value of S2/S is, for example and without limitation, any one point value or range value between any two of 25%, 30% and 35%.

As an example, the value of S3/S is, for example and without limitation, any one point value or range value between any two of 10%, 15% and 20%.

In these embodiments, the first edge 2213b1 and/or the second edge 2213b2 have a suitable size ratio in the positive electrode active material layer 2213, and are conveniently controlled so that the positive electrode active material layer 2213 has a suitable area ratio.

Referring to fig. 7, in some embodiments, in a cross section of the positive electrode active material layer 2213 in a designated direction, the dimension of the positive electrode active material layer 2213 in the first direction B is L, the largest dimension of the first edge 2213B1 in the first direction B is L2, and the largest dimension of the second edge 2213B2 in the first direction B is L3; wherein L2 is less than or equal to L multiplied by 35%, and/or L3 is less than or equal to L multiplied by 20%.

In a cross section of the positive electrode active material layer 2213 in a given direction, a boundary line of one side of the first and second edges 2213b1 and 2213b2 near the intermediate portion 2213a may be in a straight line form, a curved line form, and a broken line form, and may be parallel or non-parallel with an edge of the positive electrode active material layer 2213 in the straight line form. Accordingly, L2 corresponding to each of the first edges 2213B1 along the first direction B may be the same or different, and L3 corresponding to each of the second edges 2213B2 along the first direction B may be the same or different; in the embodiment of the present application, L2 corresponding to each of the first edges 2213B1 along the first direction B satisfies L2 l×35%, and L3 corresponding to each of the second edges 2213B2 along the first direction B satisfies L3 l×20%.

In addition, since the value of L2 needs to satisfy s2=s× (25% to 35%), the minimum value of L2 is determined according to the requirement of s2=s× (25% to 35%). In order to take the value of L2, s3=s× (10% to 20%) needs to be satisfied, and therefore, the minimum value of L3 is determined according to the s3=s× (10% to 20%) requirement.

In these embodiments, the first edge 2213b1 and/or the second edge 2213b2 have a suitable size ratio in the positive electrode active material layer 2213, so that the first edge 2213b1 and/or the second edge 2213b2 have a suitable size ratio in the positive electrode active material layer 2213 is convenient to regulate, so that the positive electrode active material layer 2213 has a suitable area ratio size.

Referring to fig. 4, in some embodiments, the positive electrode tab 221 is a wound structure, and the edge portions 2213B are distributed at both ends of the intermediate portion 2213a in the first direction B.

Here, the edge portions 2213B are distributed at both ends of the intermediate portion 2213a in the first direction B, which means that the edge portions 2213B are distributed only at both ends of the intermediate portion 2213a in the first direction B.

As an example, each edge portion 2213b extends from one end of the positive electrode active material layer 2213 in the second direction C to the opposite other end.

In these embodiments, in the positive electrode tab 221 of the winding structure, the edge portions 2213B are distributed at both ends in the first direction B, so that the lithium precipitation phenomenon can be reduced better, and the cycle performance can be improved effectively.

Referring to fig. 9, in some embodiments, the positive electrode tab 221 is a laminated structure, and edge portions 2213B are also distributed at two ends of the middle portion 2213a in a second direction C, which is perpendicular to the first direction B and the thickness direction a of the positive electrode tab, respectively.

As an example, edge portions 2213B located at both ends of the intermediate portion 2213a in the first direction B extend from one end of the positive electrode active material layer 2213 in the second direction C to the opposite end; edge portions 2213B located at both ends of the intermediate portion 2213a in the second direction C extend from one end of the positive electrode active material layer 2213 in the first direction B to the opposite end. The edge portion 2213b extends one turn along the edge of the positive electrode active material layer 2213 and encloses a ring corresponding to the edge shape of the positive electrode active material layer 2213 in the whole positive electrode active material layer 2213.

In these embodiments, edge portions 2213B are distributed at both ends of the lamination structure in the first direction B and the second direction C, so that the lithium precipitation phenomenon can be reduced better, and the cycle performance can be improved effectively.

In a second aspect, embodiments of the present application provide a battery 100 including the positive electrode tab 221 of the above-described embodiments.

In a third aspect, an embodiment of the present application provides a powered device, including the battery 100 of the above embodiment.

The following examples are set forth to better illustrate the present application.

1. Preparation of Battery cell

(1) Preparation of positive electrode sheet

The structure of the positive electrode tab is shown in fig. 4 and 5.

The nickel-containing lithium-rich manganese-based material and the lithium-containing phosphate are mixed to form a mixed positive electrode active material. The middle part and the edge part adopt different mixed positive electrode active material materials, wherein the mass ratio and chemical composition of the nickel-containing lithium-rich manganese-based material and the lithium-containing phosphate are shown in tables 1 and 2.

Mixing the mixed anode active material, the conductive agent acetylene black and the binder PVDF (polyvinylidene fluoride) according to the weight ratio of 94:4:2, adding the solvent N-methyl pyrrolidone, and fully stirring and uniformly mixing to obtain the anode slurry at the middle part and the anode slurry at the edge part respectively. And respectively coating the middle part positive electrode slurry and the edge part positive electrode slurry on the middle part and the edge of the two surfaces of the positive electrode current collector aluminum foil, and drying and cold pressing to 2.7g/cc to obtain the positive electrode plate.

(2) Preparation of negative electrode sheet

Mixing artificial graphite, a conductive agent acetylene black, a binder SBR (styrene butadiene rubber) and a thickener CMC-Na (sodium carboxymethylcellulose) according to a weight ratio of 95:1.5:3.1:0.4, adding a solvent deionized water, and fully stirring and uniformly mixing to obtain the negative electrode slurry. And (3) coating the negative electrode slurry on two surfaces of a negative electrode current collector copper foil, drying, and cold pressing to 1.65g/cc to obtain a negative electrode plate.

(3) Preparation of electrolyte

At the water content<10 In a ppm argon atmosphere glove box, EC (ethylene carbonate), PC (polycarbonate), DMC (dimethyl carbonate)Mixing EC: PC: dmc=3:3:3 by weight, then adding LiPF ₆ VC (vinylene carbonate), DTD (vinyl sulfate) and PS (propane sultone), and after uniform stirring, an electrolyte is obtained. Wherein, liPF ₆ The concentration of the catalyst in the electrolyte is 1mol/L, and the mass percentage of the catalyst in VC, DTD, PS is 3%, 1% and 1% in turn.

(4) Providing a barrier film

A polyethylene porous film was used as a separator.

(5) Assembled battery

And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, enabling the isolating film to be positioned between the positive electrode plate and the negative electrode plate to play a role of isolation, winding and then placing the isolating film in an outer package, injecting prepared electrolyte, packaging, injecting the electrolyte, forming, exhausting and the like, thus obtaining the lithium ion battery.

It will be appreciated by those skilled in the art that in the above methods of the specific examples and comparative examples, the order of composition of the steps is not meant to imply a strict order of execution but rather should be construed in view of their function and possible inherent logic.

2. Test method

(1) Test gram Capacity

And determining the boundary of the middle part and the edge part, cutting the positive electrode plate along the boundary to divide the middle part and the edge part, punching small discs with the same size in the corresponding areas of the middle part and the edge part respectively, and then assembling the small discs punched in the middle part and the edge part into a battery respectively. Discharging to 2.5V at 1/3C under the constant temperature environment of 25 ℃; standing for 5min, charging to 4.35V according to 1/3C, and then charging at constant voltage under 4.35V until the current is less than or equal to 0.05C; standing for 5min, discharging to 2.5V at 1/3C, wherein the electric quantity in the discharging process is the discharging capacity, and dividing the discharging capacity by the mass of the corresponding area to obtain gram capacity.

(2) Testing cycle performance

Charging to 4.35V at constant current of 1C under constant temperature of 25deg.C, then charging to 0.05C at constant voltage of 4.35V, Then discharging to 2.5V with 1C constant current to obtain the first week discharge specific capacity (C ₀ ) The method comprises the steps of carrying out a first treatment on the surface of the Repeating the charge and discharge for 1000 weeks to obtain discharge specific capacity after 1000 weeks, and recording as C _n 。

Capacity retention = specific discharge capacity after 1000 weeks of cycling (C _n ) Specific discharge capacity per first week (C) ₀ ）

(3) Testing lithium evolution conditions

Charging to 4.35V at constant current of 1C under constant temperature environment of 25 ℃, then charging to 0.05C at constant voltage of 4.35V, discharging to 2.5V at constant current of 1C, and repeating charging and discharging until 1000 weeks. And fully charging the battery with the temperature of 25 ℃ for 1000 weeks, disassembling the battery monomer after the charging is finished, and observing the lithium precipitation state of the negative electrode interface.

The region corresponding to the middle portion 2213a of the positive electrode tab 221 in the negative electrode interface is a middle region, and the grading standard of the lithium precipitation condition is as follows:

no lithium precipitation: the interface is golden.

Slightly separating out lithium 1: the lithium precipitation area is more than 0 and less than or equal to 1/32 of the area of the middle area.

Slightly separating out lithium 2: the lithium precipitation area is more than 1/32 and less than or equal to 1/16 of the area of the middle area.

Moderately lithium analysis 1: the lithium precipitation area is more than 1/16 and less than or equal to 1/8 of the area of the middle area.

Intermediate lithium separation 2: the lithium precipitation area is more than 1/8 and less than or equal to 1/4 of the area of the middle area.

And (3) severely separating out lithium: the lithium precipitation area is 1/4 < and occupies the area of the middle area.

3. Experimental conditions and test results

The main experimental conditions in each experimental group are shown in table 1 and table 2, table 1 is the experimental condition of the middle part of the positive electrode active material layer, table 2 is the experimental condition of the edge part of the positive electrode active material layer, and specific reference is made to the above-mentioned experimental conditions for the non-described experimental conditions, and the description is omitted herein; the results of the performance test are shown in Table 3.

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In tables 1 and 2, LFP is of the formula LiFePO ₄ Is abbreviated as (1).

In Table 3, n1/n2 is the result of rounding off the reserved two-bit fraction.

A brief analysis in combination with tables 1 to 3 above is as follows:

in examples 1 to 15, different nickel-containing lithium-manganese-rich base materials are adopted in the middle part and the edge part, and the molar content of nickel in the nickel-containing lithium-manganese-rich base material adopted in the middle part is higher, so that the average molar content of nickel in the nickel-containing lithium-manganese-rich base material in the middle part is greater than the average molar content of nickel in the nickel-containing lithium-manganese-rich base material in the edge part, namely n1 is greater than n2 is greater than 0 in examples 1 to 15. In comparative example 1, the same nickel-containing lithium-rich manganese-based material was used for the middle and edge portions, i.e., n1=n2 > 0. Compared with comparative example 1, examples 1 to 15 improved the lithium precipitation to different degrees, and improved the cycle performance to different degrees.

In examples 1 to 9, the division modes of the middle part and the edge part are the same, the types and/or the mass ratio of the nickel-containing lithium-rich manganese-based materials are slightly different, the values of n1/n2 in the examples are distributed between 1.1 and 2, and when the values of n1/n2 are distributed between 1.3 and 1.8, the lithium separation condition is better improved, and the cycle performance is also better.

The lithium-containing phosphate in the middle part of example 1 was higher in mass than in example 4, and the lithium-containing phosphate in the middle part of example 2 was higher in mass than in example 4, and the improvement in lithium evolution condition and cycle performance improvement were better in examples 2 and 4.

In examples 4 to 6, the nickel-containing lithium-rich manganese-based material had a more suitable nickel content in the middle portion of example 4, although the mass ratio of the lithium-containing phosphate was lower than in examples 5 and 6, example 4 also showed a better improvement in the lithium evolution condition and a higher improvement in the cycle performance.

In examples 4 and 10 to 13, examples 4 and 11 to 12 satisfy s1=s× (45% to 65%), examples 10 and 13 do not satisfy s1=s× (45% to 65%), and examples 4 and 11 to 12 show better improvement in lithium precipitation and higher improvement in cycle performance.

In examples 4 and 14, S2 > S3 > 0 was satisfied in example 4, S3 > S2 > 0 in example 14, and example 4 showed better improvement of lithium precipitation and higher improvement of cycle performance.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the embodiments, and are intended to be included within the scope of the claims and description. In particular, the technical features mentioned in the respective embodiments may be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but encompasses all technical solutions falling within the scope of the claims.

Claims

1. The positive electrode plate is characterized by comprising a positive electrode current collector, a positive electrode lug and a positive electrode active material layer, wherein at least one end of the positive electrode current collector in a first direction is connected with the positive electrode lug, the first direction is perpendicular to the thickness direction of the positive electrode plate, and the positive electrode active material layer is arranged on at least one side of the positive electrode current collector;

The positive electrode active material layer comprises an edge part and a middle part, the edge part is distributed at two ends of the middle part in the first direction, and the positive electrode active material materials of the middle part and the edge part comprise nickel-containing lithium-rich manganese-based materials and lithium-containing phosphates;

the nickel-containing lithium-rich manganese-based material comprises nLi ₂ MnO ₃ •(1-n)Li _x1 Ni _x2 Mn _x3 M1 _x4 O _2-x5 Wherein n is more than or equal to 0.1 and less than or equal to 0.3,0.2, x1 is more than or equal to 1.2,0.3 and less than or equal to x2 is less than 1, x3 is more than or equal to 0 and less than or equal to 0.7,0 and less than or equal to x4 is more than or equal to 0.1, x5 is more than or equal to 0 and less than or equal to 0.2, and M1 comprises one or more of Na, mg, al, ca, ba, V, zn, ti, fe, co, cr, nb, W, mo, zr, ta and Hf;

the lithium-containing phosphate comprises Li _1+y1 Fe _y2 Mn _y3 M2 _y4 P _1-y5 O _4-y6 Wherein, -0.8.ltoreq.y1.ltoreq.0.2, 0.ltoreq.y2.ltoreq.1, 0.ltoreq.y3.ltoreq.1, 0.ltoreq.y4.ltoreq.0.1, 0.ltoreq.y5.ltoreq.0.1, 0.ltoreq.y6.ltoreq.0.4, M2 including one or more of Al, cu, mg, zn, ni, ti, V, zr, co, ga, sn, sb, nb and Ge;

at the middle part, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material is n1; at the edge part, the average molar content of nickel of the nickel-containing lithium-rich manganese-based material is n2; n1 > n2.

2. The positive electrode sheet according to claim 1, wherein 1.1.ltoreq.n1/n2.ltoreq.2.

3. The positive electrode sheet according to claim 1, wherein 1.3.ltoreq.n1/n2.ltoreq.1.8.

4. The positive electrode sheet according to claim 1, wherein 0.3.ltoreq.x2.ltoreq.0.6 in the nickel-containing lithium-rich manganese-based material at the edge portion.

5. The positive electrode sheet according to claim 1, wherein 0.5.ltoreq.x2.ltoreq.0.6 in the nickel-containing lithium-rich manganese-based material at the edge portion.

6. The positive electrode sheet according to claim 1, wherein 0.6.ltoreq.x2 < 1 in the nickel-containing lithium-rich manganese-based material in the intermediate portion.

7. The positive electrode sheet according to claim 1, wherein 0.6.ltoreq.x2.ltoreq.0.9 in the nickel-containing lithium-rich manganese-based material in the intermediate portion.

8. The positive electrode sheet according to claim 1, wherein 0.6.ltoreq.x2.ltoreq.0.7 in the nickel-containing lithium-rich manganese-based material in the intermediate portion.

9. The positive electrode sheet according to any one of claims 1 to 3, wherein in the positive electrode active material in the intermediate portion, the mass ratio of the lithium-containing phosphate is w1; in the positive electrode active material at the edge portion, the mass ratio of the lithium-containing phosphate is w2; w1 > w2 > 0.

10. The positive electrode sheet according to claim 9, wherein 58% to 85% w1 and/or 30% to 50% w 2.

11. The positive electrode sheet according to any one of claims 1 to 3, wherein the gram capacity of the intermediate portion is C1; the gram capacity of the edge part is C2; c1: c2 = (0.98 to 1.02): (0.98-1.02).

12. The positive electrode sheet according to any one of claims 1 to 3, wherein in a cross section of the positive electrode active material layer in a predetermined direction, an area of the positive electrode active material layer is S, an area of the intermediate portion is S1, and the cross section in the predetermined direction is perpendicular to a thickness direction of the positive electrode sheet, s1=s× (45% to 65%).

13. The positive electrode sheet according to claim 12, wherein in a cross section of the positive electrode active material layer in the specified direction, a dimension of the positive electrode active material layer in the first direction is L, and a maximum dimension of the intermediate portion in the first direction is L1, L1 is L x 65%.

14. The positive electrode tab according to claim 12, wherein one side of the positive electrode current collector in a first direction is connected with the positive electrode tab, the edge portions of the middle portion at both ends in the first direction are a first edge and a second edge, respectively, and the first edge is located at one end of the middle portion close to the positive electrode tab;

In the cross section of the positive electrode active material layer in the predetermined direction, the area of the first edge is S2, and the area of the second edge is S3, S2 > S3 > 0.

15. The positive electrode sheet according to claim 14, wherein s2=sx (25% -35%), and/or s3=sx (10% -20%).

16. The positive electrode sheet according to claim 15, wherein in a cross section of the positive electrode active material layer in the specified direction, a dimension of the positive electrode active material layer in the first direction is L, a maximum dimension of the first edge in the first direction is L2, and a maximum dimension of the second edge in the first direction is L3;

wherein L2 is less than or equal to L multiplied by 35%, and/or L3 is less than or equal to L multiplied by 20%.

17. The positive electrode sheet according to any one of claims 1 to 3, wherein the positive electrode sheet is of a wound structure, and the edge portions are distributed at both ends of the intermediate portion in the first direction.

18. The positive electrode sheet according to any one of claims 1 to 3, wherein the positive electrode sheet is a laminated structure, the edge portions are also distributed at both ends of the middle portion in a second direction, and the second direction is perpendicular to the first direction and a thickness direction of the positive electrode sheet, respectively.

19. A battery comprising the positive electrode sheet according to any one of claims 1 to 18.

20. A powered device comprising the battery of claim 19.