CN116759673A - Positive plate, energy storage device and electric equipment - Google Patents

Positive plate, energy storage device and electric equipment Download PDF

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Publication number
CN116759673A
CN116759673A CN202311051502.2A CN202311051502A CN116759673A CN 116759673 A CN116759673 A CN 116759673A CN 202311051502 A CN202311051502 A CN 202311051502A CN 116759673 A CN116759673 A CN 116759673A
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China
Prior art keywords
lithium
containing compound
particles
equal
area
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CN202311051502.2A
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Chinese (zh)
Inventor
柳文静
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Shenzhen Haichen Energy Storage Control Technology Co ltd
Xiamen Hithium Energy Storage Technology Co Ltd
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Shenzhen Haichen Energy Storage Control Technology Co ltd
Xiamen Hithium Energy Storage Technology Co Ltd
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Priority to CN202311051502.2A priority Critical patent/CN116759673A/en
Publication of CN116759673A publication Critical patent/CN116759673A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The application discloses a positive plate, an energy storage device and electric equipment, and relates to the technical field of energy storage. The positive electrode sheet includes: current collectors and coatings; the coating layer includes a first lithium-containing compound and a second lithium-containing compound, the first lithium-containing compound is a positive electrode active material, the median particle diameter of particles of the second lithium-containing compound is less than or equal to 13 micrometers, the number of particles of the second lithium-containing compound is greater than or equal to 2 and less than or equal to 5 in an observation area of the coating layer, and an average spacing between particles of the second lithium-containing compound is greater than or equal to 10 micrometers and less than or equal to 35 micrometers. In the embodiment of the application, the second lithium-containing compound is added into the coating, and the median particle diameter of the particles of the second lithium-containing compound and the average spacing between the particles of the second lithium-containing compound in the observation area of the coating are defined, so that the uniform replenishment of active lithium in the coating is realized, and the lithium precipitation phenomenon is avoided while the lithium replenishment effect is ensured.

Description

Positive plate, energy storage device and electric equipment
Technical Field
The application relates to the technical field of energy storage, in particular to a positive plate, an energy storage device and electric equipment.
Background
Secondary batteries, also called rechargeable batteries or secondary batteries, are batteries that can be used continuously by activating active materials by charging after the battery is discharged. The recyclable characteristic of the secondary battery gradually becomes a main power source of electric equipment, and as the demand of the secondary battery gradually increases, the performance requirements of people on all aspects of the secondary battery are also higher and higher, and particularly the energy density of the unit volume of the battery is required. The lithium ion battery has been widely used in the fields of new energy and the like in recent years because of the characteristics of high energy density and high multiplying power.
In the first charging process of the lithium ion battery, a solid electrolyte membrane formed on the surface of the negative electrode consumes part of active lithium to cause lithium loss of a positive electrode material, and the common graphite negative electrode consumes about 10% of lithium source in the first charging process; in addition, active lithium is continuously consumed in the continuous operation process of the lithium ion battery except for the first charge and discharge process, so that capacity attenuation after circulation is caused. Therefore, how to supplement the consumption of active lithium is the focus of research on lithium ion battery lithium supplementing technology.
Disclosure of Invention
The application mainly aims to provide a positive plate, an energy storage device and electric equipment which can realize uniform replenishment of active lithium.
In order to achieve the purposes of the application, the application adopts the following technical scheme:
according to an aspect of the present application, there is provided a positive electrode sheet including: a current collector, and a coating on a surface of the current collector;
the coating layer comprises a first lithium-containing compound and a second lithium-containing compound, wherein the first lithium-containing compound is a positive electrode active material, and the second lithium-containing compound (Li 2) is Li x M y N z Q p Wherein x is more than or equal to 1 and less than or equal to 6, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 5, and the uneven values of y, z and p are 0, M and N are one of elements C, ni, co, mn, cu, mo, fe, mnSeed; q is one of the elements O, N, F, P;
the particles of the second lithium-containing compound have a median particle diameter of less than or equal to 13 microns, the number of particles of the second lithium-containing compound is greater than or equal to 2 and less than or equal to 5 within an observation area of the coating, and the average spacing between the particles of the second lithium-containing compound is greater than or equal to 10 microns and less than or equal to 35 microns, the observation area being a visible area of a zeiss sigma300 microscope on the coating at a magnification of 3K.
The inventors have found through a great deal of research that, when the positive electrode sheet includes a first lithium-containing compound as a positive electrode active material and a second lithium-containing compound as a lithium-supplementing material, the median particle diameter of particles of the second lithium-containing compound, and the number of particles of the second lithium-containing compound and the average spacing between particles in the observation area all affect the lithium supplementing effect and the lithium precipitation condition of the energy storage device having the positive electrode sheet.
The inventors found that when the median particle diameter of the particles of the second lithium-containing compound is large (for example, greater than 13 μm), the energy storage device having the positive electrode sheet described above is prone to cause a lithium precipitation phenomenon due to the fact that the particles of the local lithium supplement (second lithium-containing compound) are relatively loose and the content of lithium element is relatively concentrated during use. The inventors have observed through a large amount of experimental data that not only found: when the median particle diameter of the particles of the second lithium-containing compound is smaller (less than or equal to 13 micrometers), and when the particle number of the second lithium-containing compound in the observation area on the coating layer (212) under the magnification of 3K of a zeiss sigma300 microscope is smaller than 2, the energy storage device with the positive plate is easy to influence the lithium supplementing effect due to the fact that the lithium supplementing particles (the second lithium-containing compound) in the observation area are smaller in content of lithium elements in use, and when the particle number of the second lithium-containing compound in the observation area is larger than 5, the energy storage device with the positive plate is easy to cause the phenomenon of lithium precipitation due to the fact that the lithium supplementing particles (the second lithium-containing compound) in the observation area are larger in content in use; it was also found that: when the median particle diameter of the particles of the second lithium-containing compound is smaller (less than or equal to 13 micrometers), and when the average distance between the particles of the second lithium-containing compound in the observation area on the coating layer under the magnification of 3K of the zeiss sigma300 microscope is smaller than 10 micrometers, the energy storage device with the positive plate is easy to cause a lithium separation phenomenon because of more lithium element content caused by more aggregation of the lithium-supplementing particles (the second lithium-containing compound) in the observation area in the use process, and when the average distance between the particles of the second lithium-containing compound in the observation area is larger than 35 micrometers, the energy storage device with the positive plate is easy to influence the lithium supplementing effect because of less lithium element content caused by more looseness of the lithium-supplementing particles (the second lithium-containing compound) in the observation area in the use process.
In view of the above, the inventors believe that it is desirable to define, for the second lithium-containing compound included in the coating layer, particles of the second lithium-containing compound having a median particle diameter of less than or equal to 13 microns and a number of particles of the second lithium-containing compound of greater than or equal to 2 and less than or equal to 5 and an average spacing between the particles of the second lithium-containing compound of greater than or equal to 10 microns and less than or equal to 35 microns in an observation region on the coating layer under a zeiss sigma300 microscope at a magnification of 3K. Thus, replenishment of active lithium is achieved by the addition of a second lithium-containing compound; and the content of lithium elements in the observation area is limited by limiting the median particle diameter of the particles of the second lithium-containing compound and limiting the particle number of the second lithium-containing compound in the observation area and the average interval among the particles, so that the lithium separation phenomenon is avoided while the lithium supplementing effect is ensured.
According to an embodiment of the present application, a ratio of an orthographic projection area of the second lithium-containing compound to an area of the observation area is greater than or equal to 0.008 and less than or equal to 0.02.
In the embodiment of the application, the ratio of the orthographic projection area of the second lithium-containing compound in the observation area to the area of the observation area is limited to represent the uniform distribution of the particles of the second lithium-containing compound in the coating in the observation area, so as to further ensure the uniformity of the distribution of active lithium in the coating.
According to an embodiment of the present application, the element M, N included in the second lithium-containing compound is a marker element, and a ratio of a forward projection area of the marker element to an area of the observation area is less than or equal to 0.002.
In an embodiment of the present application, the marking element included in the second lithium-containing compound facilitates marking the position of the particles of the second lithium-containing compound within the observation area, thereby facilitating confirming the boundary of the orthographic projection of the particles of the second lithium-containing compound.
According to an embodiment of the present application, the orthographic projection area of the second lithium-containing compound in the observation area refers to the sum of areas surrounded by edges of orthographic projection of each particle of the second lithium-containing compound in the observation area.
According to an embodiment of the present application, the orthographic projection area of the second lithium-containing compound in the observation area refers to a sum of circle areas of a minimum circumscribed circle of orthographic projection of each particle of the second lithium-containing compound in the observation area.
According to an embodiment of the present application, the orthographic projection area of the second lithium-containing compound in the observation area refers to a sum of circle areas of maximum inscribed circles of orthographic projections of each particle of the second lithium-containing compound in the observation area.
According to an embodiment of the present application, the orthographic projection area of the second lithium-containing compound in the observation area refers to an area sum of the spliced rectangles included in the orthographic projection of each particle of the second lithium-containing compound in the observation area, and the orthographic projection of each particle is formed by splicing a plurality of rectangles with the same size.
According to an embodiment of the present application, the difference between the maximum and minimum pitches between the particles of the second lithium-containing compound in the observation region is greater than or equal to 20 micrometers and less than or equal to 135 micrometers.
In the embodiment of the application, the difference between the maximum spacing and the minimum spacing among the particles is limited to represent the uniform distribution of the particles of the second lithium-containing compound in the coating in the observation area, so that the uniformity of the distribution of active lithium in the coating is further ensured.
According to an embodiment of the application, the spacing between particles of the second lithium-containing compound in the observation region is greater than or equal to 5 microns and less than or equal to 160 microns.
In the embodiment of the application, the maximum spacing and the minimum spacing between the particles of the second lithium-containing compound in the observation area are limited, so that the situation that the lithium is easy to be separated out due to the fact that the content of active lithium in the area is large because the number of the particles of the second lithium-containing compound in the observation area is large is avoided; and avoiding that the second lithium-containing compound in the observed area has a smaller particle number, so that the active lithium content in the area is smaller, and the effect of lithium supplementation cannot be effectively realized.
According to an embodiment of the present application, the distance between the particles of the second lithium-containing compound refers to the distance between the centers of the smallest circumscribed circles of the orthographic projections of the particles of the second lithium-containing compound.
According to an embodiment of the present application, the distance between the particles of the second lithium-containing compound refers to the distance between the centers of the largest inscribed circles of the orthographic projections of the particles of the second lithium-containing compound.
According to an embodiment of the present application, wherein the second lithium-containing compound is Li 2 CO 3 、Li 2 O 2 、Li 2 Cu 0.5 Ni 0.5 O 2 、Li 3 N、Li 5 FeO 4 、Li 6 CoO 4 、Li 2 NiO 2 、Li 2 MnO 3 、Li 2 MoO 3 At least one of them.
According to an aspect of the present application, there is provided an energy storage device comprising:
a housing including a receiving chamber having an opening;
the electrode assembly is accommodated in the accommodating cavity and comprises a positive plate, a negative plate and a diaphragm which are arranged in a stacked manner, wherein the positive plate is the positive plate in the aspect;
and an end cap unit sealing the opening of the accommodating chamber.
In an embodiment of the present application, for the energy storage device including the positive electrode sheet according to the above aspect, the capacity attenuation of the energy storage device can be reduced under the condition of having enough active lithium, so that the problem of circulating water jump of the energy storage device can be reduced, and the service life of the energy storage device can be prolonged.
According to an aspect of the present application, there is provided an electric device, which includes the energy storage device according to the above aspect, and the energy storage device supplies power to the electric device.
In the embodiment of the application, for the electric equipment comprising the energy storage device, in the use process, the working stability of the electric equipment is conveniently improved, the working time of the electric equipment is prolonged, and the service life is prolonged.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the application as claimed.
Drawings
The above and other features and advantages of the present application will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.
Fig. 1 is a schematic cross-sectional structure of an energy storage device according to an exemplary embodiment.
Fig. 2 is a schematic cross-sectional structure of an electrode assembly according to an exemplary embodiment.
Fig. 3 is a schematic cross-sectional structure of a positive electrode sheet according to an exemplary embodiment.
Fig. 4 is a schematic illustration of a inter-particle distance of a second lithium-containing compound within a viewing area, according to an exemplary embodiment.
Fig. 5 is another schematic illustration of inter-particle distances of a second lithium-containing compound within a viewing area, according to an example embodiment.
Fig. 6 is yet another inter-particle distance schematic of a second lithium-containing compound within a viewing area, according to an example embodiment.
Fig. 7 is a schematic view of a projected area of a second lithium-containing compound within a viewing area, according to an example embodiment.
Fig. 8 is another schematic view of a projected area of a second lithium-containing compound within a viewing area, according to an example embodiment.
Fig. 9 is an electron microscope image of a viewing area shown according to an example embodiment.
Fig. 10 is a binary gray scale corresponding to the electron microscope image shown in fig. 9.
Fig. 11 is a graph illustrating capacity retention of an energy storage device according to an example embodiment.
Wherein reference numerals are as follows:
100. an energy storage device;
10. a housing; 20. an electrode assembly; 30. an end cap unit;
11. a receiving chamber;
21. a positive plate; 22. a negative electrode sheet; 23. a diaphragm; 31. a cover plate; 32. an electrode terminal;
211. a current collector; 212. a coating;
li1, a first lithium-containing compound; li2, a second lithium-containing compound.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. However, the exemplary embodiments can be embodied in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus detailed descriptions thereof will be omitted.
Embodiments of the present application provide an energy storage device that may be, but is not limited to, a single battery, a battery module, a battery pack, a battery system, etc. The unit cell may be a lithium ion secondary battery, a lithium sulfur battery, a sodium lithium ion battery, or the like, and the unit cell may be a cylinder, a flat body, a rectangular parallelepiped, or the like, which is not limited in the embodiment of the present application.
Next, the energy storage device is taken as an example of a cylindrical single battery, and the energy storage device will be explained in detail.
Fig. 1 illustrates a schematic structure of an energy storage device 100 according to an embodiment of the present application. As shown in fig. 1, the energy storage device 100 includes a case 10, an electrode assembly 20, and an end cap unit 30, the case 10 including a receiving chamber 11 having an opening; the electrode assembly 20 is accommodated in the accommodating chamber; the end cap unit 30 seals the opening of the accommodation chamber 11.
Wherein the housing 10 may have a cylindrical structure with one end opened, and the energy storage device 100 includes an end cap unit 30 to be capable of sealing one opening of the housing 10; of course, the housing 10 may have a cylindrical structure with two open ends, and the energy storage device 100 may include one end cap unit 30 and one end cap, or include two end cap units 30, so that two openings of the housing 10 can be sealed.
As shown in fig. 1, the end cap unit 30 includes a cover plate 31 and an electrode terminal 32 (including one electrode terminal 32 or two electrode terminals 32 (positive electrode terminal and negative electrode terminal)), the cover plate 31 is provided with an explosion-proof valve and a liquid injection hole, the electrode terminal 32 is arranged on the cover plate 31 in a penetrating manner, one end of the electrode terminal is connected with one tab, and the other end of the electrode terminal is exposed out of the casing 10 to serve as an output end of the energy storage device 100; the explosion-proof valve is used for exhausting the gas in the accommodating cavity 11 to improve the use safety of the energy storage device 100, and the liquid injection hole is used for injecting electrolyte into the accommodating cavity 11 of the energy storage device 100.
As shown in fig. 2, the electrode assembly 20 includes a positive electrode sheet 21, a negative electrode sheet 22 and a separator 23 that are stacked, and the separator 23 is located between the positive electrode sheet 21 and the negative electrode sheet 22, and the ends of the positive electrode sheet 21 and the negative electrode sheet 22 each have a tab to form a positive tab and a negative tab of the electrode assembly 20. The positive electrode tab and the negative electrode tab may be located at the same end of the electrode assembly 20 or may be located at different ends of the electrode assembly 20, and when the positive electrode tab and the negative electrode tab are located at the same end of the electrode assembly 20, the positive electrode tab and the negative electrode tab are respectively connected with the positive electrode terminal and the negative electrode terminal included in the end cover unit 30, so as to realize output of electric energy of the electrode assembly 20 through the positive electrode terminal and the negative electrode terminal; when the positive electrode tab and the negative electrode tab are positioned at both ends of the electrode assembly 20, one of the positive electrode tab and the negative electrode tab is connected with the electrode terminal 32 included in the end cap unit 30, and the other is connected with the bottom of the case 10 or the electrode terminal 32 included in the other end cap unit 30 to achieve the output of the electric power of the electrode assembly 20 through the electrode terminal 32 of the end cap unit 30 and the bottom of the case 10 or through the electrode terminals 32 of the two end cap units 30.
It should be noted that, the energy storage device 100 further includes a connecting member, and the connection between one tab of the electrode assembly 20 and one electrode terminal 32 of the end cap unit 30 can be achieved through the connecting member, so as to ensure the stability of the connection between the electrode assembly 20 and the electrode terminal 32.
During the use of the energy storage device 100, particularly when the energy storage device 100 is used for the first time, a solid electrolyte interface film is formed on the surface of the negative electrode sheet 22 of the electrode assembly 20 to consume active lithium of the energy storage device 100, and when the energy storage device 100 is used subsequently, the active lithium is consumed for various reasons, so that the capacity of the energy storage device 100 is attenuated, and the problem of circulating water jump is caused. The embodiment of the application provides a positive plate 21 for realizing the supplement of active lithium and avoiding the phenomenon of lithium precipitation at the same time, so as to reduce the capacity attenuation of the energy storage device 100, further reduce the problem of circulating water jump of the energy storage device 100, and prolong the service life of the energy storage device 100.
The positive electrode sheet 21 according to the present application will be explained in detail.
Fig. 3 illustrates a schematic cross-sectional structure of a positive electrode sheet 21 according to an embodiment of the present application. As shown in fig. 3, the positive electrode sheet 21 includes: a current collector 211, and a coating 212 on the surface of the current collector 211.
The positive electrode sheet 21 may have a coating 212 on one surface of the current collector 211, or may have a coating 212 on both surfaces of the current collector 211. Compared with the case where the surface of one side of the current collector 211 has the coating 212, the case where the surfaces of both sides of the current collector 211 have the coating 212 can effectively increase the content of active lithium in the unit volume of the positive electrode sheet 21, so that the specific capacity of the energy storage device 100 including the positive electrode sheet 21 can be effectively increased, and meanwhile, the weight of the energy storage device 100 can be reduced because the amount of the current collector 211 is reduced.
The coating layer 212 includes a first lithium-containing compound Li1 and a second lithium-containing compound Li2, wherein the first lithium-containing compound Li1 is a positive electrode active material, and the second lithium-containing compound Li2 is a lithium supplementing material, so that the active lithium is supplemented by the added second lithium-containing compound Li 2.
The coating layer 212 includes at least a conductive agent, a binder, and a solvent in addition to the first lithium-containing compound Li1 and the second lithium-containing compound Li2, and the components (conductive agent, binder, solvent, first lithium-containing compound Li1, second lithium-containing compound Li 2) included in the coating layer 212 may be stirred at high speed to form a positive electrode slurry, and the positive electrode slurry is further coated on the surface of the current collector 211 to form the coating layer 212 on the surface of the current collector 211 after drying. In this way, by stirring the components at a high speed, the first lithium-containing compound Li1 and the second lithium-containing compound Li2 in the coating layer 212 are uniformly distributed, and the phenomenon of lithium precipitation caused by larger active lithium content in a local area on the coating layer 212 is avoided.
The conductive agent may be at least one of conductive carbon black, conductive graphite, graphene, carbon nanotubes, carbon fibers and the like, the binder may be at least one of styrene-butadiene rubber, polyvinylidene fluoride, polyvinyl alcohol, polyvinyl acrylic acid, polystyrene acid ester, polytetrafluoroethylene and the like, and the solvent may be at least one of deionized water, N-methylpyrrolidone and the like. In high speed agitation of the components of coating 212, the agitation speed may be greater than or equal to 800 rpm, such as 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm.
Wherein the first lithium-containing compound Li1 may be a positive electrode active material such as LiFePO 4 、LiCoO 2 、LiMn 2 O 4 At least one of NCM, the selection criteria of the first lithium-containing compound Li1 can be reduced, the manufacturing cost of the coating layer 212 can be reduced, and meanwhile, the electrical performance of the positive electrode sheet 21 can be improved by forming the first lithium-containing compound Li1 from multiple types of positive electrode active materials.
Wherein the second lithium-containing compound Li2 is Li x M y N z Q p X is more than or equal to 1 and less than or equal to 6, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 5, and the uneven values of y, z and p are 0, M and N are one of C, ni, co, mn, cu, mo, fe, mnThe method comprises the steps of carrying out a first treatment on the surface of the Q is one of O, N, F, P. In this way, it is ensured that the active lithium content of the second lithium-containing compound Li2 is greater than the active lithium content of the first lithium-containing compound Li 1.
The second lithium-containing compound Li2 may be, for example, li 2 CO 3 、Li 2 O 2 、Li 2 Cu 0.5 Ni 0.5 O 2 、Li 3 N、Li 5 FeO 4 、Li 6 CoO 4 、Li 2 NiO 2 、Li 2 MnO 3 Or Li (lithium) 2 MoO 3 Of course, it may be Li 2 CO 3 、Li 2 O 2 、Li 2 Cu 0.5 Ni 0.5 O 2 、Li 3 N、Li 5 FeO 4 、Li 6 CoO 4 、Li 2 NiO 2 、Li 2 MnO 3 、Li 2 MoO 3 A combination of the above.
The D50 of the particles of the second lithium-containing compound Li2 is less than or equal to 13 micrometers, that is, the median particle diameter of the particles of the second lithium-containing compound Li2 is less than or equal to 13 micrometers, so that after the second lithium-containing compound Li2 is uniformly distributed in the coating 212, the uniformity of the distribution of active lithium in the coating 212 is ensured, the situation that the spacing between the particles of the second lithium-containing compound Li2 is larger and the content of lithium element is more concentrated due to the larger particles of the quantitative second lithium-containing compound Li2 is avoided, and therefore, in the use process of the energy storage device 100 with the positive plate 21, the phenomenon of lithium precipitation caused by the larger content of lithium element is avoided while lithium supplementation is realized.
Wherein the element M, N in the second lithium-containing compound Li2 is used to mark the particle position of the second lithium-containing compound Li2, that is, one or two of the elements C, ni, co, mn, cu, mo, fe, mn included in the second lithium-containing compound Li2 can be used to mark the particle position of the second lithium-containing compound Li2 when the coating layer 212 of the positive electrode sheet 21 is observed under a microscope, thereby facilitating determination of parameters such as the particle size, the inter-particle distance, and the like of the second lithium-containing compound Li2 included in the coating layer 212.
Of course, it is also possible to provide the particles of the second lithium-containing compound Li2 with a larger particle diameter so as to distinguish the particles of the second lithium-containing compound Li2 in the coating layer 212 by the size of the particle diameter when viewed under a microscope. Illustratively, the particles of the second lithium-containing compound Li2 have a median particle diameter of greater than or equal to 10 microns. Thus, for the particles of the second lithium-containing compound Li2 having a median particle diameter of 10 micrometers or more and 13 micrometers or less, the particles of the second lithium-containing compound Li2 in the coating layer 212 can be clearly distinguished from each other according to the particle diameter when the coating layer 212 is observed under a microscope. In addition, for the particles of the second lithium-containing compound Li2 having a median particle diameter of greater than or equal to 10 micrometers and less than or equal to 13 micrometers, when the components of the coating layer 212 are stirred at a high speed, the particles of the second lithium-containing compound Li2 are conveniently uniformly distributed in the positive electrode slurry, so that the uniformity of the active lithium content in each region of the coating layer 212 is ensured, and in the use process of the energy storage device 100 with the positive electrode sheet 21, the situation that the lithium precipitation phenomenon is easily caused due to the fact that the local region lithium element content of the positive electrode sheet 21 is large and the lithium supplementing effect is poor due to the fact that the local region lithium element content is small is avoided.
In the present application, the content of active lithium of the first lithium-containing compound Li1 may be greater than or equal to the content of active lithium of the second lithium-containing compound Li2, and of course, may be smaller than the content of active lithium of the second lithium-containing compound Li2, which is not limited in the embodiment of the present application.
When the content of active lithium of the first lithium-containing compound Li1 is greater than or equal to the content of active lithium of the second lithium-containing compound Li2, it is necessary at this time to additionally add the second lithium-containing compound Li2 while ensuring that the component content of the first lithium-containing compound Li1 of the coating layer 212 is unchanged, so as to achieve a lithium supplementing effect by the second lithium-containing compound Li 2.
When the active lithium content of the first lithium-containing compound Li1 is smaller than the active lithium content of the second lithium-containing compound Li2, for each component included in the coating layer 212, the same amount of the first lithium-containing compound Li1 can be replaced by a certain amount of the second lithium-containing compound Li2 to achieve the lithium supplementing effect of the positive electrode sheet 21 by more active lithium than the first lithium-containing compound Li1 in the second lithium-containing compound Li2, thereby avoiding adjustment of the content of other components and facilitating simplification of the configuration process of the positive electrode slurry.
The content of active lithium according to the present application is the content of active lithium per unit mass or the volume content of active lithium per unit volume. The unit mass may be the mass of the substance or the amount of the substance (i.e., molar mass).
In an embodiment of the present application, the second lithium-containing compound Li2 is uniformly distributed in the coating layer 212, i.e., particles of the second lithium-containing compound Li2 are uniformly distributed in the coating layer 212.
Wherein the number of particles of the second lithium-containing compound Li2 in the plurality of observation regions of the coating layer 212 is equal, and the number of particles of the second lithium-containing compound Li2 in the observation region is greater than or equal to 2 and less than or equal to 5. Illustratively, as shown in fig. 4, the coating 212 has 4 particles (particles A1, A2, A3, A4, respectively) of the second lithium-containing compound Li2 within the observation region.
The observation area of the coating 212 is a visual area of a microscope when the surface or the section of the coating 212 is observed, specifically, a visual area of a zeiss sigma300 microscope when the working distance is greater than or equal to 4.0 mm and less than or equal to 5.0 mm under a magnification of 3K when the surface or the section of the coating 212 is observed.
Illustratively, the working distances are 4.0 millimeters, 4.2 millimeters, 4.4 millimeters, 4.6 millimeters, 4.8 millimeters, 5.0 millimeters. The area of the observation area is larger than or equal to 15 square millimeters and smaller than or equal to 35 square millimeters, and the observation area can be square, rectangular or circular, and is mainly dependent on a microscope; taking the observation area as a square example, the observation area is a visual area of 3.9 mm×3.9 mm, a visual area of 4.2 mm×4.2 mm, a visual area of 4.7 mm×4.7 mm, a visual area of 5.1 mm×5.1 mm, a visual area of 5.5 mm×5.5 mm, or a visual area of 5.9 mm×5.9 mm.
As shown in fig. 4, the distance s between the particles of the second lithium-containing compound Li2 in the observation region (for example) Greater than or equal to5 microns and less than or equal to 160 microns. Illustratively, the spacing between particles of the second lithium-containing compound Li2 within the observation region is 10 microns, 40 microns, 80 microns, 120 microns, 160 microns, etc. Therefore, the maximum spacing and the minimum spacing among the particles are limited, so that the situation that lithium is easily separated out due to the fact that the content of active lithium in an observation area is large because the number of particles of the second lithium-containing compound Li2 is large in the area is avoided; and avoiding that the second lithium-containing compound Li2 in an observation area has a smaller particle number, so that the active lithium content in the area is smaller, and the effect of lithium supplementation cannot be effectively realized.
Wherein, as shown in fig. 4, the distance between the centers of the minimum circumscribed circles of the orthographic projection of the particles of the second lithium-containing compound Li2 may be referred to as the distance between the centers of the minimum circumscribed circles of the particles of the second lithium-containing compound Li2 in the observation area; alternatively, as shown in fig. 5, it may refer to the distance between the centers of the largest inscribed circles of the orthographic projections of the particles of the second lithium-containing compound Li 2.
The above-mentioned orthographic projections are projections in the thickness direction of the positive electrode sheet 21, but since the particles of the second lithium-containing compound Li2 are small, orthographic projections in the thickness direction of the positive electrode sheet 21 cannot be confirmed, and therefore it can be confirmed that the region surrounded by the edges of the particles of the second lithium-containing compound Li2 on the electron microscope image is orthographic projection of the particles of the second lithium-containing compound Li 2.
And the second lithium-containing compound Li2 may be uniformly distributed in the coating layer 212 in combination with at least one of the following ways, on the basis that the number of particles of the second lithium-containing compound Li2 is equal and the number of particles is greater than or equal to 2 and less than or equal to 5 in a plurality of observation regions of the coating layer 212.
In some embodiments, at least one of the average spacing and the spacing difference between particles of the second lithium-containing compound Li2, and the maximum minimum spacing, may be combined to characterize a uniform distribution of the second lithium-containing compound Li2 in the coating 212.
For the average spacing between particles of the second lithium-containing compound Li 2: the average spacing between particles of the second lithium-containing compound Li2 in the observation region is greater than or equal to 10 micrometers and less than or equal to 35 micrometers. Illustratively, the average spacing between particles of the second lithium-containing compound Li2 within the observation region is 10 microns, 14 microns, 18 microns, 22 microns, 26 microns, 30 microns, 35 microns. In this way, by defining the average spacing between the particles, a uniform distribution of particles of the second lithium-containing compound Li2 in the coating 212 within the observation region is characterized, thereby ensuring uniformity of the distribution of active lithium in the coating 212.
Assuming that the particles A1, A2, A3, A4 of the second lithium-containing compound Li2 are present in the observation area, the average spacing between the particles of the second lithium-containing compound Li2 in the observation area can be determined according to the following formula:
In the above-mentioned formula(s),mean distance between particles of the second lithium-containing compound Li2 in the observation region, +.>Refers to the spacing between particles A1 and A2 of the second lithium-containing compound Li2,/and->Refers to the spacing between particles A1 and A3 of the second lithium-containing compound Li2,/I>Refers to the spacing between particles A1 and A4 of the second lithium-containing compound Li2,refers to the spacing between particles A2 and A3 of the second lithium-containing compound Li2,/I>Refers to the spacing between particles A2 and A4 of the second lithium-containing compound Li2,/I>Refers to the spacing between particles A3 and A4 of the second lithium-containing compound Li 2.
Difference in spacing between particles for the second lithium-containing compound Li 2: the difference between the maximum spacing and the minimum spacing between the particles of the second lithium-containing compound Li2 in the observation region is greater than or equal to 20 micrometers and less than or equal to 135 micrometers. Illustratively, the difference between the maximum and minimum pitches between the particles of the second lithium-containing compound Li2 within the observation region is 20 microns, 50 microns, 80 microns, 110 microns, 135 microns. In this way, the difference between the maximum spacing and the minimum spacing between the particles is defined to characterize the uniform distribution of the particles of the second lithium-containing compound Li2 in the coating 212 in the observation region, thereby ensuring the uniformity of the distribution of active lithium in the coating 212.
Continuing with the above example, the spacing between particles A1 and A2 of the second lithium-containing compound Li2 in the observation regionFor maximum distance, the distance between particles A3 and A4 is>At the minimum spacing, the difference between the maximum spacing and the minimum spacing between the particles of the second lithium-containing compound Li2 in the observation region is +.>And->Difference between them.
In other embodiments, the ratio of the orthographic projected area of the second lithium-containing compound Li2 to the area of the observation region is greater than or equal to 0.008 and less than or equal to 0.02. Illustratively, the ratio of the orthographic projected area of the second lithium-containing compound Li2 to the area of the observation region is 0.008, 0.012, 0.014, 0.016, 0.02. In this way, the ratio of the orthographic projection area of the second lithium-containing compound Li2 in the observation area to the area of the observation area is defined to characterize the uniform distribution of the particles of the second lithium-containing compound Li2 in the coating 212 in the observation area, thereby ensuring the uniformity of the distribution of active lithium in the coating 212. In addition, by limiting the ratio of the orthographic projection area of the second lithium-containing compound Li2 to the area of the observation area, the problem that the lithium-precipitation phenomenon is caused by a relatively large proportion of the second lithium-containing compound Li2 and the lithium-supplementing effect is poor due to a relatively small proportion of the second lithium-containing compound Li2 in the unit area of the positive electrode sheet 21 is avoided in the use process of the energy storage device 100 with the positive electrode sheet 21.
Optionally, the second lithium-containing compound Li2 includes a marker element, that is, the M element and the N element in the second lithium-containing compound Li2 described above, and the marker element includes one or two of C, ni, co, mn, cu, mo, fe, mn; in this way, the marking of the particle positions of the second lithium-containing compound Li2 within the observation region is facilitated by the marking element included in the second lithium-containing compound Li2, and further, the boundary of the orthographic projection of the particles of the second lithium-containing compound Li2 is facilitated to be confirmed.
Wherein, in the observation area, the ratio of the orthographic projection area of the marking element to the area of the observation area is less than or equal to 0.002. Therefore, the ratio of the orthographic projection of the marking element in the observation area to the area of the observation area is limited, so that the position of the particles of the second lithium-containing compound Li2 can be determined, and meanwhile, the content of less marking element is set, so that the content of active lithium in the second lithium-containing compound Li2 can be effectively ensured, and the lithium supplementing effect is improved.
In the present application, the orthographic projection area of the second lithium-containing compound Li2 in the observation area may refer to the sum of areas surrounded by the edges of orthographic projection of each particle of the second lithium-containing compound Li2 in the observation area; or as shown in fig. 7, may refer to the sum of the circle areas of the smallest circumscribed circles of orthographic projections of each particle of the second lithium-containing compound Li2 within the observation area; or as shown in fig. 8, may refer to the sum of the circular areas of the largest inscribed circles of orthographic projection of each particle of the second lithium-containing compound Li2 within the observation region; or may be the sum of the areas of the stitching rectangles comprised by the orthographic projection of each particle of the second lithium-containing compound Li2 in the observation area, the orthographic projection of each particle being composed of a plurality of rectangles of identical size.
Wherein, for the sum of the areas surrounded by the edges of the orthographic projection of each particle of the second lithium-containing compound Li2 in the observation area, optionally, the relational expression of the edges of each particle is determined according to a pre-established rectangular coordinate system, the area of the area surrounded by the edges of each particle is determined by a fixed integral method (refer to the related art specifically), and then the sum of the areas surrounded by the edges of each particle is summed to obtain the total area. Optionally, dividing the orthographic projection of each particle into a plurality of rectangles with the same size according to a pre-established rectangular coordinate system and a plurality of straight lines parallel to a horizontal axis and a vertical axis, determining the orthographic projection area of each particle according to the number of the rectangles and the size of the rectangles, and summing the orthographic projection areas of each particle to obtain the total area.
Continuing with the above example, for particles A1, A2 of the second lithium-containing compound Li2 in the observation region, as shown in fig. 7, the radius of the minimum circumcircle of the orthographic projection of the particles A1 is 1.81 micrometers, the radius of the minimum circumcircle of the orthographic projection of the particles A2 is 1.34 cm, and at this time, the orthographic projection area of the second lithium-containing compound Li2 in the observation region is: the sum of the circular area with a radius of 1.81 cm and the circular area with a radius of 1.34 cm.
The electron micrograph of the observation area shown in fig. 7 was obtained at a working distance of 4.4 mm, a magnification of 3K and an aperture size of 30 μm. In determining the orthographic projection area of the second lithium-containing compound Li2 within the observation area, the observation area is observed by a microscope while performing micro-area analysis (the voltage at which the micro-area analysis is performed may be 5 Kv) on the observation area by using X-rays to identify the marker element included in the second lithium-containing compound Li2, thereby obtaining an electron microscopic image of the observation area (the position in which the particles of the second lithium-containing compound Li2 are marked in the electron microscopic image) as shown in fig. 9, and then performing binarization processing (for example, gray-scale value may be set to 170) on the obtained electron microscopic image to obtain a binarized electron microscopic image (the electron microscopic image in which the black area surrounded by the edges of the particles of the second lithium-containing compound Li2 are highlighted, and which is embodied as orthographic projection of the particles of the second lithium-containing compound Li 2) as shown in fig. 10. Then, in combination with the above-described method of determining the area of the orthographic projection of the particles, the sum of the areas of the orthographic projections of the particles as shown in fig. 10 is determined as the orthographic projection area of the second lithium-containing compound Li2 in the observation area.
In the embodiment of the application, the related electron microscope images are all obtained by a Zeiss sigma300 microscope under the condition of 3K magnification.
Example 1: the energy storage device 100 is manufactured by high-speed stirring of 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), and 3% of a binder (polyvinylidene fluoride, solvent (N-methylpyrrolidone)) in a stirring tank under a humidity of 2% RH or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, and having a single-sided coating density of 0.15mg/mm2 and a compaction density of 2.3g/cm3, and then performing the processes of die cutting, slitting, lamination, winding, shell-in, baking, liquid injection, standing, formation, capacity separation, testing, and the like.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 10 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 2, the average spacing between the particles of the second lithium-containing compound Li2 is 10 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.008.
Example 2: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) at a high speed in a stirring tank under a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after the high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 4.25V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 11 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 3, the average spacing between the particles of the second lithium-containing compound Li2 is 18 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.012.
Example 3: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) at a high speed in a stirring tank under a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after the high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 4.25V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 12 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 4, the average spacing between the particles of the second lithium-containing compound Li2 is 26 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.016.
Example 4: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 13 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 5, the average spacing between the particles of the second lithium-containing compound Li2 is 35 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.002.
Comparative example 1: the energy storage device 100 was manufactured by stirring 94% of a first lithium-containing compound Li1 (lithium iron phosphate), 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after stirring, having a single-sided coating density of 0.15mg/mm2, and a compacted density of 2.2g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Comparative example 2: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 14 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 4, the average spacing between the particles of the second lithium-containing compound Li2 is 26 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.012.
Comparative example 3: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 14 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 5, the average spacing between the particles of the second lithium-containing compound Li2 is 35 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.016.
Comparative example 4: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 11 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 1, the average spacing between the particles of the second lithium-containing compound Li2 is 18 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.008.
Comparative example 5: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 11 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 6, the average spacing between the particles of the second lithium-containing compound Li2 is 18 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.016.
Comparative example 6: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 12 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 3, the average spacing between the particles of the second lithium-containing compound Li2 is 9 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.012.
Comparative example 7: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 13 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 4, the average spacing between the particles of the second lithium-containing compound Li2 is 36 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.016.
Comparative example 8: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 13 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 5, the average spacing between the particles of the second lithium-containing compound Li2 is 37 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.02.
Comparative example 9: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 12 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 4, the average spacing between the particles of the second lithium-containing compound Li2 is 26 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.007.
Comparative example 10: the energy storage device 100 was manufactured by stirring 92% of a first lithium-containing compound Li1 (lithium iron phosphate), 2% of a second lithium-containing compound Li2, 3% of a conductive agent (conductive carbon black), 3% of a binder (polyvinylidene fluoride), and a solvent (N-methylpyrrolidone) in a stirring tank at a humidity of 2% rh or less, coating the surface of the current collector 211 with the positive electrode slurry after high-speed stirring, having a single-sided coating density of 0.15mg/mm2 and a compact density of 2.3g/cm3, and then performing the steps of die cutting or slitting, lamination or winding, housing, baking, liquid injection, standing, formation, capacity division, testing, and the like. The maximum voltage of the energy storage device 100 is 3.65V.
Wherein the particles of the second lithium-containing compound Li2 have a median particle diameter of 13 micrometers, the number of particles of the second lithium-containing compound Li2 in the observation area of the coating layer 212 is 5, the average spacing between the particles of the second lithium-containing compound Li2 is 35 micrometers, and the area ratio of the projected area of the second lithium-containing compound Li2 in the observation area is 0.022.
For the energy storage device 100 including the positive electrode sheets 21 produced in examples 1 to 4 and comparative examples 1 to 10, respectively, the specific charge capacity, specific discharge capacity and lithium evolution of the energy storage device 100 when the energy storage device 100 was used are shown in the following table.
Confirmation of whether or not each energy storage device 100 is precipitating lithium: charging the energy storage device 100 from an initial temperature T0 (e.g., -20 degrees celsius) to a temperature increase Δt (greater than or equal to 5 degrees celsius) at a charging rate of 0.3-5C to bring the temperature to a target temperature T1; continuing to charge the energy storage device 100 from the target temperature T1 to 80% soc at a charging rate of 0.5C-5C, and then disassembling each energy storage device charged to 80% soc to observe whether lithium is extracted from the anode electrode tab interface, including: 1. no lithium precipitation: the whole negative pole piece has no lithium precipitation area; 2. slightly separating out lithium: the maximum area of a single lithium separation area of the whole negative electrode plate is less than or equal to 5 multiplied by 5mm < 2 >, and the number of the lithium separation areas of the whole negative electrode plate is less than or equal to 1; 3. moderately precipitating lithium: the maximum area of a single lithium separation area of the whole negative electrode plate is less than or equal to 10 multiplied by 10mm < 2 >, and the number of the lithium separation areas of the whole negative electrode plate is less than or equal to 1; 4. and (3) severely separating out lithium: there is lithium precipitation and the judgment conditions for slight lithium precipitation and moderate lithium precipitation are not satisfied.
As shown in fig. 11, a capacity retention rate curve L2 of the energy storage device 100 corresponding to the positive electrode sheet 21 of comparative example 1 and a capacity retention rate curve L1 of the energy storage device 100 corresponding to the positive electrode sheet 21 of example 1 are shown.
As can be seen from the above table and fig. 11, adding the second lithium-containing compound Li2 to the positive electrode sheet 21 of the energy storage device 100, and performing high-speed stirring when the positive electrode slurry is configured, simultaneously controlling the particle size of the second lithium-containing compound Li2, controlling the number of particles of the second lithium-containing compound Li2 in the observation region, and controlling at least one of the average spacing between the particles of the second lithium-containing compound Li2 in the observation region, the spacing difference between the particles of the second lithium-containing compound Li2 in the observation region, and the area ratio of the area of the second lithium-containing compound Li2 to the observation region in the observation region, can effectively realize lithium supplementation of the positive electrode sheet 21, while ensuring the lithium supplementation effect.
The embodiment of the application also provides electric equipment which can be energy storage equipment, vehicles, energy storage containers and the like. The electric equipment comprises the energy storage device in the embodiment, and the energy storage device supplies power for the electric equipment. Therefore, in combination with the above, the electric equipment comprising the energy storage device is convenient to improve the working stability of the electric equipment in the use process, prolongs the working time of the electric equipment and prolongs the service life.
In the examples of the application, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance; the term "plurality" means two or more, unless expressly defined otherwise. The terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; "coupled" may be directly coupled or indirectly coupled through intermediaries. The specific meaning of the terms in the examples of application will be understood by those of ordinary skill in the art as the case may be.
In the description of the application embodiments, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," and the like indicate an orientation or a positional relationship based on that shown in the drawings, and are merely for convenience in describing the application embodiments and simplifying the description, and do not indicate or imply that the devices or units to be referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the application embodiments.
In the description of the present specification, the terms "one embodiment," "some embodiments," "particular embodiments," and the like, mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of an application embodiment. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The above is only a preferred embodiment of the application embodiment, and is not intended to limit the application embodiment, and various modifications and changes may be made to the application embodiment by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the embodiments of the application should be included in the protection scope of the embodiments of the application.

Claims (14)

1. A positive electrode sheet, comprising: a current collector (211), and a coating (212) on the surface of the current collector (211);
the coating (212) includes a first lithium-containing compound (Li 1) and a second lithium-containing compound(Li 2) the first lithium-containing compound (Li 1) is a positive electrode active material, and the second lithium-containing compound (Li 2) is Li x M y N z Q p Wherein x is more than or equal to 1 and less than or equal to 6, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 5, y, z and p are not equal to 0, M and N are one of elements C, ni, co, mn, cu, mo, fe, mn; q is one of the elements O, N, F, P;
the particles of the second lithium-containing compound (Li 2) have a median particle diameter of less than or equal to 13 microns, the number of particles of the second lithium-containing compound (Li 2) is greater than or equal to 2 and less than or equal to 5, and the average spacing between the particles of the second lithium-containing compound (Li 2) is greater than or equal to 10 microns and less than or equal to 35 microns within an observation region of the coating (212) that is a visible region of a zeiss sigma300 microscope at 3K magnification.
2. The positive electrode sheet according to claim 1, wherein a ratio of an orthographic projection area of the second lithium-containing compound (Li 2) to an area of the observation area is greater than or equal to 0.008 and less than or equal to 0.02 in the observation area.
3. The positive electrode sheet according to claim 2, wherein the second lithium-containing compound (Li 2) includes an element M, N as a marker element, and a ratio of a forward projection area of the marker element to an area of the observation area is less than or equal to 0.002 in the observation area.
4. A positive electrode sheet according to claim 2 or 3, wherein the orthographic projection area of the second lithium-containing compound (Li 2) in the observation area means the sum of areas surrounded by the edges of orthographic projection of each particle of the second lithium-containing compound (Li 2) in the observation area.
5. A positive electrode sheet according to claim 2 or 3, wherein the orthographic projection area of the second lithium-containing compound (Li 2) in the observation area means a sum of circle areas of minimum circumscribed circles of orthographic projections of each particle of the second lithium-containing compound (Li 2) in the observation area.
6. A positive electrode sheet according to claim 2 or 3, wherein the orthographic projection area of the second lithium-containing compound (Li 2) in the observation area means a sum of circle areas of maximum inscribed circles of orthographic projections of each particle of the second lithium-containing compound (Li 2) in the observation area.
7. A positive electrode sheet according to claim 2 or 3, wherein the orthographic projection area of the second lithium-containing compound (Li 2) in the observation area means an area sum of the splice rectangles included in the orthographic projection of each particle of the second lithium-containing compound (Li 2) in the observation area, the orthographic projection of each particle being composed of a plurality of rectangular splices of the same size.
8. The positive electrode sheet according to claim 1, wherein a difference between a maximum pitch and a minimum pitch between particles of the second lithium-containing compound (Li 2) in the observation region is greater than or equal to 20 micrometers and less than or equal to 135 micrometers.
9. The positive electrode sheet according to claim 1, wherein a spacing between particles of the second lithium-containing compound (Li 2) in the observation region is greater than or equal to 5 micrometers and less than or equal to 160 micrometers.
10. The positive electrode sheet according to any one of claims 1 to 3, 8, 9, wherein the spacing between the particles of the second lithium-containing compound (Li 2) refers to the distance between the centers of the smallest circumscribed circles of orthographic projections of the particles of the second lithium-containing compound (Li 2).
11. The positive electrode sheet according to any one of claims 1 to 3, 8, 9, wherein the spacing between the particles of the second lithium-containing compound (Li 2) refers to the distance between the centers of the largest inscribed circles of orthographic projections of the particles of the second lithium-containing compound (Li 2).
12. The positive electrode sheet according to claim 1, wherein the second lithium-containing compound (Li 2) is Li 2 CO 3 、Li 2 O 2 、Li 2 Cu 0.5 Ni 0.5 O 2 、Li 3 N、Li 5 FeO 4 、Li 6 CoO 4 、Li 2 NiO 2 、Li 2 MnO 3 、Li 2 MoO 3 At least one of them.
13. An energy storage device, comprising:
A housing (10) comprising a receiving chamber (11) having an opening;
an electrode assembly (20) accommodated in the accommodating cavity (11) and comprising a positive plate (21), a negative plate (22) and a diaphragm (23) which are stacked, wherein the positive plate (21) is the positive plate according to any one of claims 1 to 12;
an end cap unit (30) seals the opening of the accommodation chamber (11).
14. A powered device comprising the energy storage device of claim 13, the energy storage device supplying power to the powered device.
CN202311051502.2A 2023-08-21 2023-08-21 Positive plate, energy storage device and electric equipment Pending CN116759673A (en)

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101207197A (en) * 2006-12-22 2008-06-25 比亚迪股份有限公司 Lithium ion battery anode material and lithium ion battery and anode containing the material
CN113809281A (en) * 2021-09-14 2021-12-17 远景动力技术(江苏)有限公司 Composite positive plate, preparation method thereof and lithium ion battery
CN114094040A (en) * 2021-11-09 2022-02-25 远景动力技术(江苏)有限公司 Positive plate and preparation method and application thereof
CN115911257A (en) * 2022-11-10 2023-04-04 厦门海辰储能科技股份有限公司 Positive electrode plate, electrochemical device and lithium supplementing method

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101207197A (en) * 2006-12-22 2008-06-25 比亚迪股份有限公司 Lithium ion battery anode material and lithium ion battery and anode containing the material
CN113809281A (en) * 2021-09-14 2021-12-17 远景动力技术(江苏)有限公司 Composite positive plate, preparation method thereof and lithium ion battery
CN114094040A (en) * 2021-11-09 2022-02-25 远景动力技术(江苏)有限公司 Positive plate and preparation method and application thereof
CN115911257A (en) * 2022-11-10 2023-04-04 厦门海辰储能科技股份有限公司 Positive electrode plate, electrochemical device and lithium supplementing method

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