CN114447408B - Battery and electronic equipment - Google Patents

Battery and electronic equipment Download PDF

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Publication number
CN114447408B
CN114447408B CN202210120303.1A CN202210120303A CN114447408B CN 114447408 B CN114447408 B CN 114447408B CN 202210120303 A CN202210120303 A CN 202210120303A CN 114447408 B CN114447408 B CN 114447408B
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Prior art keywords
active material
battery
thickness
material layer
edge region
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CN202210120303.1A
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CN114447408A (en
Inventor
彭冲
李俊义
徐延铭
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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

Abstract

The invention provides a battery and electronic equipment, the battery includes electric core, electrolyte and membrane shell, the electric core and electrolyte are set up in membrane shell, the electric core includes positive pole piece and negative pole piece, the positive pole piece is coiled after laminating with the negative pole piece, the positive pole piece includes current collector, undercoat and active material layer; along the width direction of the positive plate, the positive plate comprises an edge area and a middle area; in the edge region, an active material layer is disposed on the current collector, and a primer layer is disposed between the current collector and the active material layer; the active material layer thickness in the edge region is less than the active material layer thickness in the middle region. Therefore, the ratio of the active material capacity of the negative electrode to the active material capacity of the positive electrode can be increased by increasing the ratio of the bottom coating in the positive electrode plate so as to reduce the swelling caused by lithium precipitation of the battery and improve the safety of the battery.

Description

Battery and electronic equipment
Technical Field
The present invention relates to the field of battery technologies, and in particular, to a battery and an electronic device.
Background
Lithium batteries are rapidly developed and widely applied to portable mobile electronic devices such as notebook computers and smart phones. However, the current density of the existing lithium ion battery is larger near the edge of the battery pole piece due to uneven current density distribution, so that the problem of lithium precipitation at the edge of the battery core is easily caused, and the battery bulges and has potential safety hazards.
It can be seen that the battery in the prior art has a problem of low safety.
Disclosure of Invention
The embodiment of the invention provides a battery and electronic equipment, which are used for solving the problem of lower safety of the battery in the prior art.
The embodiment of the invention provides a battery, which comprises a battery core, electrolyte and a membrane shell, wherein the battery core and the electrolyte are arranged in the membrane shell, the battery core comprises a positive plate and a negative plate, the positive plate and the negative plate are wound after being laminated, and the positive plate comprises a current collector, an undercoat and an active material layer;
the positive plate comprises an edge area and a middle area along the width direction of the positive plate; in the edge region, the active material layer is disposed on the current collector, and the primer layer is disposed between the current collector and the active material layer;
the active material layer thickness of the edge region is less than the active material layer thickness of the intermediate region.
Optionally, the edge region includes a top section and a bottom section of the positive electrode sheet, the middle region is located between the top section and the bottom section, and the primer layer is disposed between the top section and the bottom section.
Optionally, in the edge region, the thickness of the undercoat layer gradually increases along the direction from the intermediate region to the edge region;
alternatively, in the edge region, the undercoat layer includes a plurality of paint regions disposed at intervals, the active material layer being disposed on the current collector through the undercoat layer in the paint regions, the active material layer being embedded in the undercoat layer between adjacent ones of the paint regions.
Optionally, in the edge region, the thickness of the active material layer is a first thickness, and the thickness of the primer layer is a second thickness; in the intermediate region, the thickness of the active material layer is a third thickness; wherein the sum of the first thickness and the second thickness is not greater than the third thickness.
Optionally, the active material layer includes an active material, a conductive agent, and a first binder.
Optionally, the ratio of the ranges of the mass percentages of the active substance, the conductive agent and the first binder is: (85-99.5 wt%): (0.1 to 1 weight percent): (0.5 wt% -15 wt%).
Optionally, the active material includes at least one of lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, and lithium-rich manganese;
the conductive agent comprises at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder and carbon fiber;
the first binder includes at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polyvinylidene fluoride, polytetrafluoroethylene, and lithium polyacrylate.
Optionally, the primer layer includes an inorganic material and a second binder;
the inorganic material is present in the primer layer in an amount ranging from 60wt% to 90wt%, and the second binder is present in the primer layer in an amount ranging from 10wt% to 40wt%.
Optionally, the inorganic material comprises at least one of alumina, zirconia, titania, magnesia, silica;
the second binder comprises at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polyvinylidene fluoride, polytetrafluoroethylene and lithium polyacrylate.
The embodiment of the invention also provides electronic equipment comprising the battery.
In the embodiment of the invention, the bottom coating is arranged at the edge area of the positive plate, so that the active material layer is arranged on the current collector through the bottom coating, and the duty ratio of the active material layer in the positive plate can be reduced by increasing the duty ratio of the bottom coating in the positive plate, thereby improving the ratio of the active material capacity of the negative electrode to the active material capacity of the positive electrode, reducing the swelling caused by lithium precipitation of the battery and improving the safety of the battery.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural view of a positive electrode sheet of a battery according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of an undivided positive plate of a battery according to an embodiment of the present invention;
FIG. 3 is a second schematic diagram of an undivided positive plate of the battery according to the embodiment of the present invention;
FIG. 4 is a second schematic structural view of a positive plate of a battery according to an embodiment of the present invention;
FIG. 5 is a third schematic structural view of a positive plate of a battery according to an embodiment of the present invention;
fig. 6 is a schematic structural view of a negative electrode sheet of a battery according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the structures so used are interchangeable under appropriate circumstances such that embodiments of the invention are capable of operation in sequences other than those illustrated or otherwise described herein, and that the objects identified by "first," "second," etc. are generally of a type and do not limit the number of objects, for example, the first object can be one or more. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.
The embodiment of the invention provides a battery, as shown in fig. 1 to 6, which comprises a battery cell, electrolyte and a membrane shell, wherein the battery cell and the electrolyte are arranged in the membrane shell, the battery cell comprises a positive plate 10 and a negative plate 20, the positive plate 10 and the negative plate 20 are wound after being laminated, and the positive plate 10 comprises a current collector 101, an undercoat 102 and an active material layer 103;
along the width direction of the positive electrode sheet 10, the positive electrode sheet 10 includes an edge region 501 and a middle region 502; in the edge region, an active material layer 103 is disposed on the current collector 101, and an undercoat layer 102 is disposed between the current collector 101 and the active material layer 103;
the thickness of the active material layer 103 in the edge region 501 is less than the thickness of the active material layer 103 in the middle region 502.
In this embodiment, the primer layer 102 is provided in the edge region 501 of the positive electrode sheet 10, so that the active material layer 103 is provided on the current collector 101 through the primer layer 102, and thus, the ratio of the active material layer 103 in the positive electrode sheet 10 can be reduced by increasing the ratio of the primer layer 102 in the positive electrode sheet 10, thereby increasing the CB value (Cell Balance value, i.e., the ratio of the active material capacity of the negative electrode to the active material capacity of the positive electrode), reducing the swelling caused by lithium precipitation of the battery, and improving the safety of the battery.
Wherein the edge region 501 comprises a top segment 5011 and a bottom segment 5012 of the positive electrode sheet 10, the middle region 502 is located between the top segment 5011 and the bottom segment 5012, and the primer coating 102 is disposed between the top segment 5011 and the bottom segment 5012.
In this way, in the non-edge region of the positive electrode sheet 10, that is, in the middle region 502 of the positive electrode sheet 10, the active material layer 103 may be directly disposed on the current collector 101, so as to improve the energy density of the middle region 502 of the positive electrode sheet 10, and consider the safety of the battery, and improve the performance of the battery at the same time; the active material layer 103 can be disposed on the current collector 101 through the undercoat layer 102 in the edge region 501 of the positive electrode sheet 10, that is, in the top segment 5011 and the bottom segment 5012 of the positive electrode sheet 10, so that the thickness of the active material layer 103 in the edge region 501 is smaller than that of the active material layer 103 in the middle region 502, so as to reduce the duty ratio of the active material layer 103 in the edge region 501 in the positive electrode sheet 10, thereby reducing the deintercalation speed of lithium ions in the edge region 501, reducing the aggregation of lithium ions on the negative electrode sheet 20 at the corresponding position of the edge region 501, reducing the occurrence of lithium precipitation on the negative electrode sheet 20 and causing swelling, and improving the safety of the battery.
In some alternative embodiments, the primer layer 102 may be described as follows:
as shown in fig. 1, in the edge region 501, the thickness of the undercoat layer 102 may gradually increase along the direction from the intermediate region 502 to the edge region 501, so that the thickness of the active material layer 103 may gradually decrease along the direction from the intermediate region 502 to the edge region 501.
For example, in the case where the thickness of the positive electrode sheet 10 is 70 micrometers, the thickness of the undercoat layer 102 near the intermediate region 502 may be 1 micrometer, the thickness of the undercoat layer 102 far from the intermediate region 502 may be 10 micrometers, and the thickness of the undercoat layer 102 gradually increases from 1 micrometer to 10 micrometers in the direction from the intermediate region 502 to the edge region 501, the thickness of the active material layer 103 near the intermediate region 502 may be 10 micrometers in the edge region 501, the thickness of the active material layer 103 far from the intermediate region 502 may be 1 micrometer, and the thickness of the active material layer 103 gradually decreases from 10 micrometers to 1 micrometer in the direction from the intermediate region 502 to the edge region 501, and the thickness of the active material layer 103 provided on the undercoat layer 102 gradually decreases by gradually increasing the thickness of the undercoat layer 102 in the edge region 501. Therefore, the lithium ion extraction speed in the edge area 501 is reduced, the situation that the negative electrode plate 20 is swelled due to lithium precipitation is reduced, and the safety of the battery is improved.
Wherein, in the edge region 501, the thickness of the active material layer 103 may be a first thickness, and the thickness of the undercoat layer 102 may be a second thickness; in the intermediate region 502, the thickness of the active material layer 103 may be a third thickness; wherein the sum of the first thickness and the second thickness is not greater than the third thickness. So that the thickness ratio of the active material layer 103 in the edge region 501 to the positive electrode sheet 10 is smaller than the thickness ratio of the active material layer 103 in the middle region 502 to the positive electrode sheet 10, the CB value is increased, and the swelling caused by lithium precipitation of the battery is reduced.
It should be noted that, the edge region 501 may include a top section 5011 and a bottom section 5012 of the positive electrode sheet 10, and the thickness of the undercoat 102 may gradually increase along the first direction from the middle region 502 to the top section 5011, so that the thickness of the active material layer 103 disposed on the undercoat 102 along the first direction may gradually decrease, which may also achieve the same technical effects, and will not be described herein again;
the thickness of the primer layer 102 may gradually increase along the second direction from the middle region 502 to the bottom section 5012, so that the thickness of the active material layer 103 disposed on the primer layer 102 along the second direction may gradually decrease, and the same technical effects may be achieved, which will not be described herein;
wherein the first direction and the second direction may be opposite directions.
The width of the current collector 101 may be 300 mm to 900 mm, for example, in the case where the width of the current collector 101 is 400 mm, the width of the positive electrode sheet 10 may be 80 mm; the primer coating 102 in the top segment 5011 can be 75 millimeters to 85 millimeters from the primer coating 102 in the bottom segment 5012; the width of the primer layer 102 in the top segment 5011 or the bottom segment 5012 may be 20 mm or less so that the primer layer 102 is provided at the edge area 501 of the positive electrode sheet 10.
In other alternative embodiments, as shown in fig. 5, primer layer 102 may include a plurality of spaced apart coating regions at edge region 501 where active material layer 103 may be disposed on current collector 101 through primer layer 102, and where active material layer 103 may be embedded in primer layer 102 between adjacent coating regions.
In this embodiment, the undercoat layer 102 may include a plurality of coating regions disposed at intervals in the edge region 501, the active material layer 103 covers the coating regions, and the active material layer 103 embedded between adjacent coating regions may abut against the current collector to optimize the CB value of the edge region 501, improving the performance of the battery, and by increasing the thickness of the coating regions to reduce the thickness of the active material layer 103 covered on the coating regions, the deintercalation speed of lithium ions on the positive electrode sheet 10 is reduced, so that the number of lithium ions collected or received on the negative electrode sheet 20 per unit time is reduced, thereby reducing the occurrence of lithium precipitation, and improving the safety of the battery.
Alternatively, as shown in fig. 5, the thickness of the undercoat 102 gradually increases from a first position B of the current collector 101 to a second position C of the current collector 101, the thickness of the undercoat 102 gradually decreases from the second position C to a third position D of the current collector 101, and the second position C is located between the first position B and the third position D.
In this embodiment, the first position B, the second position C and the third position D may be three adjacent positions on the same side of the current collector, and may be a coating region in the undercoat layer 102 gradually increases in thickness from the first position B to the second position C and gradually decreases in thickness from the second position C to the third position D, so as to further optimize the CB value of the edge region and improve the performance of the battery.
For example, a coating region in the undercoat layer 102 may be provided in an arch, trapezoid, triangle or the like shape, and the thickness of the positive electrode sheet 10 is uniformly set within an error range.
The coating region may be provided as an isosceles trapezoid, the thickness of the active material layer 103 covered in the direction of the height of the isosceles trapezoid has a minimum value, the thickness of the active material layer 103 covered on both sides of the isosceles trapezoid is gradually changed to optimize the CB value of the edge region, improving the performance of the battery, and the thickness of the active material layer 103 covered on the coating region may be adjusted by increasing the thickness of the coating region and changing the shape of the coating region, so that the deintercalation speed of lithium ions on the positive electrode sheet 10 is reduced, so that the number of lithium ions collected or received on the negative electrode sheet 20 per unit time is reduced, thereby reducing the occurrence of lithium precipitation, and improving the safety of the battery.
It should be noted that the shapes of the coating areas include, but are not limited to, the arch, trapezoid, and triangle, and may be other shapes, and the same technical effects may be achieved, which are not described herein.
Referring to fig. 1 to 3, fig. 2 is one of schematic structural diagrams of an undivided positive plate of a battery according to an embodiment of the present invention, and fig. 1 is one of schematic structural diagrams of a positive plate of a battery according to an embodiment of the present invention.
The positive electrode sheet 10 and the negative electrode sheet 20 having the specific widths shown in fig. 1 are obtained by slitting at the target position a of the non-slit positive electrode sheet shown in fig. 2, and the slitting position may be a position at which the positive electrode sheet 10 or the negative electrode sheet 20 is cut off when the slitting operation is performed. For disassembling the battery core after long-term circulation, the lithium is seriously separated from the position corresponding to the upper edge area 501 of the negative electrode plate 20 of the lithium ion battery, especially at the slitting position of the negative electrode plate 20. After the positive electrode sheet 10 and the negative electrode sheet 20 are wound, the slitting position of the positive electrode sheet 10 may be flush with the slitting position of the negative electrode sheet 20. The target position a may be a cutting position of the positive electrode sheet 10, and after the target position a is cut, the cross section of the positive electrode sheet 10 is shown in fig. 4.
By providing the undercoat layer 102 at the target position a to reduce the thickness of the active material layer 103 at the target position a, the occurrence of lithium precipitation at the slit position of the negative electrode sheet 20 is reduced, and the safety of the battery is improved.
The total thickness of the positive electrode sheet 10 may be 60 micrometers to 100 micrometers, for example, the thickness of the positive electrode sheet 10 is 70 micrometers, the thickness of the positive electrode sheet 10 may be 70 micrometers at the edge region 501, and the thickness of the positive electrode sheet 10 may be 70 micrometers at the intermediate region 502. In the case where the thickness of the positive electrode sheet 10 is 70 micrometers, the thickness of the undercoat layer 102 may be 1 to 10 micrometers, for example, the thickness of the undercoat layer 102 is 2 micrometers, and the thickness of the active material layer 103 coated on the undercoat layer 102 may be 68 micrometers. Thus, by adjusting the coating thickness of the undercoat layer 102, the thickness of the active material layer 103 in the edge region 501 of the positive electrode sheet 10 is easily adjusted.
In the actual production process, the thickness of the positive electrode sheet 10 may be kept uniform within a tolerance range, for example, the tolerance is 0.1 μm, and the thickness of the positive electrode sheet 10 is uniform.
Alternatively, the active material layer 103 may include an active material, a conductive agent, and a first binder.
Alternatively, the range ratio of the mass percentages between the active material, the conductive agent and the first binder may be: (85-99.5 wt%): (0.1 to 1 weight percent): (0.5 wt% -15 wt%).
Alternatively, the active material may include at least one of lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, and lithium-rich manganese;
the conductive agent may include at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder, and carbon fiber;
the first binder may include at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polyvinylidene fluoride, polytetrafluoroethylene, and lithium polyacrylate.
Alternatively, the primer layer 102 may include an inorganic material and a second binder;
the inorganic material may be present in the primer layer 102 in an amount ranging from 60wt% to 90wt% and the second binder may be present in the primer layer 102 in an amount ranging from 10wt% to 40wt%.
Alternatively, the inorganic material may include at least one of alumina, zirconia, titania, magnesia, silica;
the second binder may include at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polyvinylidene fluoride, polytetrafluoroethylene, and lithium polyacrylate.
In some alternative embodiments, the process of preparing the edge region 501 of the positive electrode sheet 10, i.e., the edge region 501 of the positive electrode sheet 10, can be described as follows:
in the primer layer 102, the inorganic material may be alumina, the second binder may be polyvinylidene fluoride, and the alumina and polyvinylidene fluoride are added into a stirring tank according to a mass ratio of 88:12 to be stirred, and N-methyl pyrrolidone (NMP) is added to prepare a first slurry. Primer coating 102 may be disposed on the surface of current collector 101 in top segment 5011 and bottom segment 5012, respectively. The first paste is applied to the undercoat layer 102 using a coater, and the thickness and width of the undercoat layer 102 may be set as desired, without limitation. The undercoat layer 102 coated on the current collector 101 is dried as shown in fig. 3;
in the active material layer 103, the active material may be lithium cobaltate, the conductive agent may be conductive carbon black, and the first binder may be polyvinylidene fluoride. Adding lithium cobaltate, conductive carbon black and polyvinylidene fluoride into a stirring tank according to the mass ratio of 98.4:0.6:1.0, stirring, adding NMP to prepare a second slurry, wherein the solid content of the second slurry can be 75-80 wt%. Using a coater, coating the second slurry on the first slurry, and on the current collector 101 of the intermediate region 502; and the overall thickness of the coated second paste in the width direction of the positive electrode sheet 10 is controlled to be uniform. The active material layer 103 coated on the undercoat layer 102 is baked as shown in fig. 2; the positive electrode sheet 10 of a certain desired width is then obtained by slitting, as shown in fig. 1. The dicing position is provided with the undercoat layer 102 at a position where the undercoat layer 102 is provided, that is, at the target position a of the edge region 501.
The process of preparing the negative electrode sheet 20 may be described as follows:
the negative electrode active material can be graphite, the dispersing agent can be sodium carboxymethyl cellulose, and the binder can be styrene-butadiene rubber; graphite, conductive carbon black, sodium carboxymethyl cellulose and styrene-butadiene rubber can be added into a stirring tank according to the mass ratio of 96.9:0.5:1.3:1.3, deionized water is added for full stirring to prepare negative electrode slurry, the solid content of the negative electrode slurry can be 45-50wt%, a coating machine is used for coating the negative electrode slurry on a negative electrode current collector, drying is carried out, and a negative electrode sheet 20 with a specific required width is obtained through slitting, as shown in fig. 6.
The positive electrode sheet 10 prepared as described above is wound together with the negative electrode sheet 20 to form a winding core.
It should be noted that, the active material may also be selected from at least one of other materials, such as lithium nickel cobalt manganese oxide, lithium nickel cobalt manganese oxide, lithium iron phosphate and lithium-rich manganese, so as to achieve the same technical effects, and in order to avoid repetition, no description is given here.
It should be noted that, the conductive agent may also be selected from at least one of acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, metal powder and carbon fiber, so as to achieve the same technical effect, and for avoiding repetition, no description is given here.
It should be noted that, the first adhesive may also be made of other materials, such as at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polytetrafluoroethylene and lithium polyacrylate, so as to achieve the same technical effects, and for avoiding repetition, no description is given here.
It should be noted that, the inorganic material may be at least one of zirconium dioxide, titanium dioxide, magnesium oxide, and silicon dioxide, so as to achieve the same technical effect, and the description thereof is omitted herein for avoiding repetition.
It should be noted that, the second binder may also be made of other materials, such as at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polytetrafluoroethylene and lithium polyacrylate, so as to achieve the same technical effects, and for avoiding repetition, no description is given here.
Example 1:
in the first step, a first slurry is prepared, alumina and polyvinylidene fluoride are added into a stirring tank according to the mass ratio of 88:12 for stirring, and N-methyl pyrrolidone (NMP) is added to prepare the first slurry.
And secondly, preparing a second slurry, namely adding lithium cobaltate, conductive carbon black and polyvinylidene fluoride into a stirring tank according to the mass ratio of 98.4:0.6:1.0, stirring, and adding NMP to prepare the second slurry, wherein the solid content of the second slurry can be 75-80 wt%.
In a third step, the first paste is applied to the primer layer 102 using a coater, and the primer layer 102 may have a thickness of 1 μm and a width of 5 mm. The undercoat layer 102 coated on the current collector 101 is dried.
Fourth, coating the second paste on the first paste and the current collector 101 of the middle region 502 using a coater; and the overall thickness of the coated second paste in the width direction of the positive electrode sheet 10 is controlled to be uniform. The overall thickness of the positive electrode sheet 10 may be set to 82 micrometers. The active material layer 103 coated on the undercoat layer 102 is baked.
Fifth, the positive electrode sheet 10 of a certain desired width is obtained by slitting, wherein the slitting position is provided with the undercoat layer 102 at the position where the undercoat layer 102 is provided, that is, at the target position a of the edge region 501.
Sixth, the negative electrode sheet 20 is prepared. Graphite, conductive carbon black, sodium carboxymethylcellulose and styrene-butadiene rubber in the negative plate 20 can be added into a stirring tank according to the mass ratio of 96.9:0.5:1.3:1.3, deionized water is added for full stirring to prepare negative electrode slurry, the solid content of the negative electrode slurry can be 45-50wt%, a coating machine is used for coating the negative electrode slurry on a negative electrode current collector, drying is carried out, and the negative plate 20 with a specific required width is obtained through slitting.
Seventh, the battery cell is assembled, and the positive electrode sheet 10, the negative electrode sheet 20 and the separator are wound together to form a winding core. And packaging the coiled core by using an aluminum plastic film, baking to remove water, injecting electrolyte, and performing thermocompression forming process to obtain the battery core.
Example 2, example 3, example 4 and example 5 can also be performed according to the above steps. Wherein example 2 differs from example 1 in that: in the third step of example 2, the thickness of the primer layer 102 may be 3 micrometers and the width may be 5 millimeters.
Example 3 differs from example 1 in that: in the third step of example 3, the thickness of the primer layer 102 may be 5 micrometers and the width may be 5 millimeters.
Example 4 differs from example 1 in that: in the third step of example 4, the thickness of the primer layer 102 may be 5 micrometers and the width may be 10 millimeters.
Example 5 differs from example 1 in that: in the third step of example 5, the thickness of the primer layer 102 may be 10 micrometers and the width may be 5 millimeters.
Also, comparative example 1 and comparative example 2 were provided. The positive electrode sheets 10 of comparative examples 1 and 2 were not provided with the undercoat layer 102, i.e., the third step was not performed, but the active material layer 103 was directly provided on the current collector 101.
Comparative example 2 differs from comparative example 1 in that: comparative example 2 increases the ratio of the active material capacity of the negative electrode to the active material capacity of the positive electrode, resulting in a decrease in the thickness of the active material layer 103 in comparative example 2, i.e., the overall thickness of the positive electrode sheet 10 of comparative example 1 was 82 micrometers, and the overall thickness of the positive electrode sheet 10 of comparative example 2 was 80 micrometers.
The structural parameters of the positive electrode sheet 10 in examples 1 to 5, and comparative examples 1 to 2 are specifically shown in table 1 below:
table 1: structural parameters of the positive electrode sheet 10 of examples 1 to 5 and comparative examples 1 to 2
In the above examples 1 to 5 and comparative examples 1 to 2, the positive electrode sheets 10 were prepared in the same compaction and assembled into a soft pack cell of model 386283, wherein the thickness of the cell was 3.8 mm, the width of the cell was 62 mm, and the length of the cell was 83 mm. A 0.2C charge/0.2C discharge test was performed at 25 ℃ to measure the energy density of the cells.
Each of the soft battery cells prepared in examples 1 to 5 and comparative examples 1 to 3 above was subjected to 1.5C charge/0.7C discharge test at 25C, and the battery cells were disassembled at different cycle times to confirm the lithium precipitation at the corresponding edge regions and surfaces of the negative electrode sheet, and the recorded test results are shown in table 2 below:
table 2: results of the relevant test data for examples 1-5 and comparative examples 1-2
Wherein, the edge area slightly separates lithium: represents that the lithium precipitation area accounts for less than 5% of the whole surface area of the cathode; edge area lithium precipitation: representing that the lithium precipitation area accounts for 5% -30% of the whole surface area of the cathode; edge area severely precipitates lithium: the lithium deposition area is 30% or more of the entire negative electrode surface area.
As can be seen from table 2 above, the battery provided by the invention can effectively improve the problem of lithium precipitation in the corresponding edge region of the negative electrode plate 20 of the lithium battery under the condition of not significantly reducing the energy density of the battery core, thereby prolonging the cycle life of the lithium ion battery and improving the cycle expansion. The swelling caused by lithium precipitation of the battery is reduced, and the safety of the battery is improved.
The embodiment of the invention also provides electronic equipment comprising the battery.
Note that the electronic device may be a device such as a notebook computer or a smart phone, and is not limited herein. The implementation manner of the embodiment of the battery is also suitable for the embodiment of the electronic device, and the same technical effects can be achieved, which is not described herein.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element. Furthermore, it should be noted that the scope of the methods and apparatus in the embodiments of the present invention is not limited to performing the functions in the order discussed, but may also include performing the functions in a substantially simultaneous manner or in an opposite order depending on the functions involved, e.g., the described methods may be performed in an order different from that described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.
The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.

Claims (9)

1. The battery is characterized by comprising a battery core, electrolyte and a membrane shell, wherein the battery core and the electrolyte are arranged in the membrane shell, the battery core comprises a positive plate and a negative plate, the positive plate and the negative plate are stacked and then wound, and the positive plate comprises a current collector, an undercoat and an active material layer;
the positive plate comprises an edge area and a middle area along the width direction of the positive plate; in the edge region, the active material layer is disposed on the current collector, and the primer layer is disposed between the current collector and the active material layer;
the active material layer thickness of the edge region is less than the active material layer thickness of the intermediate region;
the edge region comprises a top section and a bottom section of the positive electrode sheet, the middle region is positioned between the top section and the bottom section, and the bottom coating is arranged on the top section and the bottom section;
the primer layer is composed of an inorganic material and a second binder.
2. The battery according to claim 1, wherein the thickness of the undercoat layer gradually increases in the edge region, along the direction from the intermediate region to the edge region;
alternatively, in the edge region, the undercoat layer includes a plurality of paint regions disposed at intervals, the active material layer being disposed on the current collector through the undercoat layer in the paint regions, the active material layer being embedded in the undercoat layer between adjacent ones of the paint regions.
3. The battery according to any one of claims 1 to 2, wherein the thickness of the active material layer is a first thickness and the thickness of the undercoat layer is a second thickness in the edge region; in the intermediate region, the thickness of the active material layer is a third thickness; wherein the sum of the first thickness and the second thickness is not greater than the third thickness.
4. The battery of claim 1, wherein the active material layer comprises an active material, a conductive agent, and a first binder.
5. The battery of claim 4, wherein the ratio of the ranges of the mass percentages of the active material, the conductive agent, and the first binder is: (85 wt% -99.5 wt%): (0.1 wt% -1 wt%): (0.5 wt% -15 wt%).
6. The battery of claim 4, wherein the active material comprises at least one of lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium iron phosphate, and lithium-rich manganese;
the conductive agent comprises at least one of conductive carbon black, conductive graphite, carbon nano tubes, metal powder and carbon fibers;
the first binder includes at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polyvinylidene fluoride, polytetrafluoroethylene, and lithium polyacrylate.
7. The battery of claim 1, wherein the battery is configured to provide the battery with a plurality of cells,
the mass percentage of the inorganic material in the bottom coating is 60-90 wt%, and the mass percentage of the second binder in the bottom coating is 10-40 wt%.
8. The battery of claim 7, wherein the inorganic material comprises at least one of alumina, zirconia, titania, magnesia, silica;
the second binder comprises at least one of styrene-butadiene rubber, polyacrylic acid, polyacrylate, sodium polyacrylate, polyvinylidene fluoride, polytetrafluoroethylene and lithium polyacrylate.
9. An electronic device comprising a battery as claimed in any one of claims 1 to 8.
CN202210120303.1A 2022-02-07 2022-02-07 Battery and electronic equipment Active CN114447408B (en)

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