CN115483365A - Positive plate, roll core and battery - Google Patents

Positive plate, roll core and battery Download PDF

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Publication number
CN115483365A
CN115483365A CN202211167639.XA CN202211167639A CN115483365A CN 115483365 A CN115483365 A CN 115483365A CN 202211167639 A CN202211167639 A CN 202211167639A CN 115483365 A CN115483365 A CN 115483365A
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active material
lithium
positive electrode
lini
positive
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徐寒姣
李瑞年
王烽
李素丽
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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
    • 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
    • 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
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • 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)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention relates to the technical field of lithium ion batteries, and provides a positive plate, a winding core and a battery. The positive plate comprises a positive current collector, wherein the positive current collector is divided into an arc area and a flat area; at least one surface of the arc area is provided with a first active material coating, and at least one surface of the flat area is provided with a second active material coating; wherein the first active material coating comprises a first active material and the second active material coating comprises a second active material; the volume shrinkage rate of the first active material is larger than that of the second active material, and the volume shrinkage rate of the first active material is 0.1-8%. In the positive plate, the active material coating with large volume shrinkage is coated in the arc area, so that the problem that the adhesive layer blocks the hole of the diaphragm in the arc area is avoided in the charging process of the battery containing the positive plate, the lithium ion transmission is not influenced, and the problem of black spot lithium precipitation, and the cycle performance and the safety performance of the high-lithium ion battery are effectively solved.

Description

Positive plate, roll core and battery
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a positive plate, a winding core containing the positive plate and a battery containing the positive plate or the battery core.
Background
Lithium ion batteries are increasingly popular in the fields of intelligent digital products, new energy vehicles and the like due to their small size, light weight and excellent energy storage capacity. The lithium ion battery comprises a winding type battery cell, wherein the winding type battery cell is an electrode assembly formed by winding a positive plate, a negative plate and a diaphragm which are rolled by a winding machine. In a winding type battery cell, the battery cell can be divided into an unbent flat area and a bent arc area.
In the charging process of the winding type battery cell, the pole piece can expand, internal stress is generated in the battery cell due to the limitation of the structure, and the plane area can expand outwards in the thickness direction of the battery cell, so that the internal stress is low; and the circular arc region compares the plane region because circular arc structure's restriction, and the internal stress that leads to by the inflation that charges here is bigger more concentrated, and this phenomenon will lead to rolling up a core inner structure extrusion, and the regional diaphragm of electric core circular arc easily takes place the gum layer stifled hole, leads to lithium ion transmission to be obstructed, and then takes place the black spot and analyse lithium.
Therefore, the development of the battery pole piece capable of solving the problem of black spot lithium deposition is of great significance.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provide a positive plate, a winding core containing the positive plate and a battery containing the positive plate or the battery core. Different functional areas (arc area and flat area) are arranged on the positive plate, and active materials with large volume shrinkage are coated on the arc area, so that the problem that the battery containing the positive plate is blocked by an adhesive layer due to the fact that a diaphragm of the arc area is prevented from occurring in the charging process, the lithium ion transmission is not influenced, the problem that lithium is separated out due to black spots is effectively solved, and the cycle performance and the safety performance of the lithium ion battery are improved.
The inventor of the invention finds that the active material with large volume shrinkage rate is coated on the arc area of the positive current collector, the conventional active material (such as lithium cobaltate active material) is coated on the flat area, the active material in the arc area can shrink in volume when the battery is charged and delithiated, and the volume shrinkage of the arc area can counteract the volume expansion caused by lithium intercalation of a part of negative plates, so that the stress of the arc area in the charging process is reduced, the blocking of holes by a diaphragm in the arc area is prevented, and the risk of lithium precipitation caused by black spots in the arc area is avoided.
In order to achieve the above object, a first aspect of the present invention provides a positive electrode sheet, including a positive electrode current collector, wherein the positive electrode current collector is divided into an arc area and a flat area; at least one surface of the circular arc area is provided with a first active material coating, and at least one surface of the flat area is provided with a second active material coating; wherein the first active material coating comprises a first active material and the second active material coating comprises a second active material; the volume shrinkage rate of the first active material is greater than that of the second active material, and the volume shrinkage rate of the first active material is 0.1-8%.
The second aspect of the invention provides a winding core, wherein the winding core is a winding structure formed by a first diaphragm, a first pole piece, a second diaphragm and a second pole piece which are sequentially stacked, and the first pole piece or the second pole piece is the positive pole piece in the first aspect of the invention; wherein, along the stretching direction of the winding core, the width of the arc area is not more than the bending part of the winding structure, and the width of the flat area is not less than the non-bending part of the winding structure.
In a third aspect, the invention provides a battery comprising at least one of the positive electrode sheet according to the first aspect of the invention and the winding core according to the second aspect of the invention.
The invention adopts the technical scheme and has the following beneficial effects:
(1) According to the positive plate provided by the invention, the volume shrinkage of the arc area of the positive plate can counteract the volume expansion caused by lithium embedding of part of the negative plate, so that the stress of the arc area in the charging process is reduced, the blocking of holes by a diaphragm in the arc area is prevented, and the risk of lithium precipitation caused by black spots in the arc area is avoided;
(2) The battery provided by the invention has higher cycle performance and safety performance.
The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to encompass values close to these ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
Drawings
FIG. 1 is a schematic view of a core structure according to an embodiment of the present invention.
Fig. 2 is a schematic view of a roll core structure according to an embodiment of the present invention.
Fig. 3 is a schematic diagram showing a top view of the positive electrode sheet according to the present invention in the width direction (both ends are not shown).
Fig. 4 is a schematic view showing a cross-sectional structure of the positive electrode sheet of the present invention in the width direction (both ends are not shown).
Description of the reference numerals
101: a positive plate circular arc area; 102: a positive plate flat area; 103: and a negative electrode.
Detailed Description
The following describes in detail specific embodiments of the present invention. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are given by way of illustration and explanation only, not limitation.
Unless defined otherwise, all scientific and technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.
The invention provides a positive plate, which comprises a positive current collector, wherein the positive current collector is divided into an arc area and a flat area; at least one surface of the circular arc area is provided with a first active material coating, and at least one surface of the flat area is provided with a second active material coating;
wherein the first active material coating comprises a first active material and the second active material coating comprises a second active material; the volume shrinkage rate of the first active material is larger than that of the second active material, and the volume shrinkage rate of the first active material is 0.1-8%.
When positive and negative pole piece and diaphragm were convoluteed and are formed the roll core structure, the different regions of positive pole piece can present two kinds of states: the bent state and the unbent state, and correspondingly, the positive electrode collector may have a bent region and an unbent region. In the invention, the "arc area" may be a part of the bent area of the positive current collector, and the part includes an inflection point at the bent position, and the "arc area" may also be the whole bent area of the positive current collector. The "flat region" may be a whole unbent region and a partial bent region of the positive electrode current collector, and the partial bent region does not include a bending point, and the "flat region" may also be a whole unbent region of the positive electrode current collector. And the inflection point of the bending part is the intersection point of the central line of the winding core and the bending area.
The inventor of the present invention finds that, in the battery system conventionally used at present, a conventional binary metal lithium salt is mainly used as a positive electrode active material, for example, lithium cobaltate which is conventionally used, but the volume of the lithium cobaltate expands during charging and lithium removing, and the volume shrinks during discharging lithium intercalation, so that the volumes of the positive and negative electrode plates of the wound battery core expand during charging, and black spot lithium deposition easily occurs in the arc region of the battery. Based on this, the inventor coats the multielement positive electrode material with large volume shrinkage rate in the circular arc area of the positive electrode plate, and when the battery is charged, the volume of the multielement positive electrode material can be shrunk, so that the volume expansion caused by lithium intercalation of a part of negative electrode plates can be counteracted, further, the stress in the charging process of the circular arc area is reduced, the blocking of the diaphragm in the circular arc area is prevented, and the risk of lithium precipitation caused by black spots in the circular arc area is avoided.
In order to better solve the problem of lithium deposition from battery black spots, one or more technical characteristics of the battery black spots can be further optimized.
Illustratively, the positive electrode current collector is a substance having conductivity without causing adverse chemical changes in the secondary battery, including, but not limited to, aluminum alloys, nickel alloys, titanium alloys.
In one example, both opposing surfaces of the circular arc region are coated with a first active material coating and both opposing surfaces of the flat region are coated with a second active material coating.
In one example, the first active material is a multi-element positive electrode material, and the volume shrinkage of the multi-element material is 0.1-8%.
Illustratively, the volume shrinkage of the multielement material may be 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% or a range between any two points.
Preferably, the volume shrinkage of the first active material is 2 to 7%, more preferably 3 to 6%.
Under the condition of satisfying the shrinkage rate range, the specific selection of the multi-element cathode material is not limited, and can be selected in the field according to the needs.
In one example, the multi-component positive electrode material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel cobalt manganese aluminate, and lithium nickel titanium magnesium oxide. Wherein the chemical formula of the nickel cobalt lithium manganate is Li z Ni x Co y Mn 1-x-y O 2 Wherein z is more than or equal to 0.95 and less than or equal to 1.05>0，y>0，0<x+y<1; the chemical formula of the nickel cobalt lithium aluminate is Li z Ni x Co y Al 1-x-y O 2 Wherein z is more than or equal to 0.95 and less than or equal to 1.05>0，y>0，0.8≤x+y<1; the chemical formula of the nickel-cobalt-manganese lithium aluminate is Li z Ni x Co y Mn w Al 1-x-y-w O 2 Wherein z is more than or equal to 0.95 and less than or equal to 1.05>0，y>0，w>0，0.8≤x+y+w<1; the chemical formula of the lithium nickel titanium magnesium oxide is LiNi x Ti y Mg z O 2 Wherein x is>0，y>0，z>0，x+y+z＝1。
In one example, the lithium nickel cobalt manganese oxide has the formula LiNi x Co y Mn 1-x-y O 2 Wherein 0.4<x≤0.8，y>0，0<x+y<1。
In one example, the lithium nickel cobalt aluminate has the formula LiNi x Co y Al 1-x-y O 2 Wherein 0.4<x≤0.8，y>0，0.8≤x+y<1。
In one example, the lithium nickel cobalt manganese aluminate has the formula LiNi x Co y Mn w Al 1-x-y-w O 2 Wherein 0.4<x≤0.8，y>0，w>0，0.8≤x+y+w<1。
In one example, the lithium nickel titanium magnesium oxide has the formula LiNi x Ti y Mg z O 2 Wherein, 0.4<x≤0.8，y>0，z>0，x+y+z＝1。
In one example, the multi-element cathode material is selected from LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.7 Co 0.2 Mn 0.1 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.6 Co 0.2 Al 0.2 O 2 、LiNi 0.5 Co 0.2 Al 0.3 O 2 、LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O 2 And LiNi 0.6 Ti 0.2 Mg 0.2 O 2 At least one of (a).
The inventors of the present invention have made extensive studies and found that LiNi is a large number of positive electrode materials 0.8 Co 0.1 Mn 0.1 O 2 And LiNi 0.8 Co 0.15 Al 0.05 O 2 When the two materials are used together, the mass ratio of the two materials meets 1 (0.2-0.6), the volume shrinkage rate can reach 7-8%, the capacity retention rate of the battery is improved, and the cyclic expansion rate of a battery core is reduced.
The first active material has a greater volumetric shrinkage than the second active material. It is understood that this condition can be satisfied when the volume shrinkage rate of the second active material is negative (i.e., when it exhibits volume expansion characteristics). The invention thus includes the case where the first active material exhibits volume shrinkage characteristics and the second active material exhibits volume expansion characteristics.
In one example, the second active material is a lithium-containing inorganic salt.
Illustratively, the lithium-containing inorganic salt may be selected from at least one of lithium cobaltate, lithium manganate, lithium nickelate, lithium iron phosphate, lithium tantalate, lithium zirconate, lithium titanium phosphate, lithium lanthanum titanate, and lithium aluminum titanium phosphate.
In one example, the lithium-containing inorganic salt is lithium cobaltate.
In the invention, when lithium cobaltate is used as the positive electrode material, the inventor finds that the problem of black spot lithium precipitation of the lithium cobaltate system battery can be effectively solved by coating the circular arc area with the multielement positive electrode material with large volume shrinkage and coating the flat area with the lithium cobaltate. However, if the arc area and the flat area are not distinguished, a certain amount of multi-element anode material is mixed in a lithium cobaltate system, the delithiation volume of the lithium cobaltate expands during charging, the delithiation volume of the ternary anode material contracts, the contraction of the ternary anode material can only counteract the volume expansion generated by the lithium cobaltate but cannot counteract the volume expansion brought by the negative electrode, the problem of large internal stress at the arc position still exists, and the problem of black spot lithium precipitation at the arc area still occurs.
In one example, the first active material is present in an amount of 90-98% based on the total mass of the first active material coating.
Illustratively, the first active material may be present in an amount of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%.
In one example, the second active material is present in an amount of 90-98% based on the total mass of the second active material coating.
Illustratively, the content of the second active material may be 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, and 98%.
In an example, the first active material coating and the second active material coating each further independently include a positive electrode conductive agent and a positive electrode binder.
The positive electrode conductive agent and the positive electrode binder may be selected as needed in the art, and are not particularly limited.
Illustratively, the positive electrode conductive agent is selected from at least one of conductive graphite, ultrafine graphite, acetylene black, conductive carbon black SP, superconducting carbon black, carbon nanotubes, and conductive carbon fibers.
Illustratively, the positive electrode binder is selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, polyurethane, polyvinyl alcohol, polyvinylidene fluoride, and a copolymer of vinylidene fluoride-fluorinated olefin.
The second aspect of the invention provides a winding core, wherein the winding core is a winding structure formed by a first diaphragm, a first pole piece, a second diaphragm and a second pole piece which are sequentially stacked, and the first pole piece or the second pole piece is the positive pole piece in the first aspect of the invention; and along the stretching direction of the winding core, the width of the arc area is not more than the bending part of the winding structure, and the width of the flat area is not less than the non-bending part of the winding structure.
As shown in fig. 1, 3, and 4, the winding core has a winding structure formed by stacking a first separator, a negative electrode sheet 102, a second separator, and a positive electrode sheet 103 in this order. Along the stretching direction of the winding core, the width of the arc area 101 of the positive plate is the bending part of the winding structure, and the width of the flat area of the positive plate is the non-bending part of the winding structure.
In the present invention, the width direction of the separator is the same as the direction in which the core is stretched.
The inventors of the present invention have found that, in the winding structure of the winding core, the inflection point of the bend region is a portion where the internal stress is the largest, and the black spot deposition of lithium is more likely to occur, and therefore, the effect of suppressing the black spot deposition of lithium can be achieved by applying a plurality of positive electrode materials to the inflection point of the bend region. In order to achieve an effect of more effectively suppressing the black spot lithium deposition, the plurality of positive electrode materials may be coated on the curved region including the inflection point portion of the curve, or the plurality of positive electrode materials may be coated on the entire curved region.
In one example, as shown in fig. 2, the positive electrode tab arc region 101 is a portion of a bent region of the separator and includes a bending inflection point (e.g., a bent portion within a black dotted line frame), and the flat region is a full non-bent region and a partial bent region of the separator and does not include a bending inflection point.
In the invention, the inflection point of the bending part is the intersection point of the central line of the winding core and the bending area.
In one example, as shown in fig. 1, the circular arc region 101 of the positive electrode tab is the whole bent region of the positive electrode tab, and the flat region is the whole unbent region of the positive electrode tab.
In one example, the width L of the arc region is
Figure BDA0003862039720000101
Wherein d is the thickness of the winding core.
In the present invention, the winding core bending region is formed in a semicircular structure having a diameter corresponding to the thickness d of the winding core, and the arc length of the semicircle is the maximum width of the arc region. For example, the structure of the winding core is actually similar to the curvature formed by winding the multilayer cloth, which is not a standard semicircle.
In an example, the minimum width of the circular arc region of 0.01mm refers to the minimum width of the inflection point of the bend that includes the bending region of the diaphragm.
In one example, the maximum width of the arc region
Figure BDA0003862039720000102
Which is the arc length of a semicircle with the core thickness d as the diameter.
Illustratively, the width of the arc region may be 0.1 π d, 0.2 π d, 0.3 π d, 0.4 π d, 0.5 π d.
The structure of the battery except the winding core can be carried out according to the mode in the field, and the effect of inhibiting the lithium deposition of black spots can be realized.
In a third aspect, the invention provides a battery comprising at least one of the positive electrode sheet of the first aspect and the roll core of the second aspect.
In one example, the battery comprises the positive electrode sheet of the first aspect of the present invention, a negative electrode sheet, a nonaqueous electrolytic solution, and a separator.
In one example, the battery includes the winding core according to the second aspect of the present invention.
In one example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector.
The negative electrode current collector is a substance having conductivity without causing adverse chemical changes in the secondary battery, and may be selected from copper, stainless steel, aluminum, nickel, titanium, carbon cloth, or a composite of the materials.
The negative electrode active material layer includes a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder. The anode active material is not particularly limited, and any commonly used anode active material in the art may be used, and for example, may be at least one of graphite, natural graphite, soft carbon, hard carbon, pure silicon, silica, and silicon carbon.
In one example, the negative electrode conductive agent is independently selected from at least one of conductive graphite, ultrafine graphite, acetylene black, conductive carbon black SP, superconducting carbon black, carbon nanotubes, and conductive carbon fibers.
In one example, the negative electrode binder is independently selected from at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethylcellulose, styrene butadiene rubber, polyurethane, polyvinyl alcohol, polyvinylidene fluoride, and copolymers of vinylidene fluoride-fluorinated olefins.
The nonaqueous electrolytic solution may use any electrolyte commonly used in the art, and is not particularly limited herein.
In the present invention, when terms such as "first active material", "second active material", and the like are distinguished by numbers, the numbers in such expressions are merely used for distinguishing purposes and do not indicate a sequential order, and the numerical sizes of the numbers do not have any limiting effect on the technical solution unless otherwise specified.
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.
The invention is described in detail below with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.
The volume shrinkage of the active materials in the following examples and comparative examples was obtained by XRD test as follows:
XRD (X-ray diffraction) of the positive plate before and after charging is tested by adopting XRD, rietveld refinement is further carried out on XRD data to obtain lattice parameters of the positive active material, and then the unit cell volume of the positive active material before and after charging is calculated, and the corresponding volume shrinkage rate = (V (before charging) -V (after charging))/(V before charging) × 100%.
Example 1
1. Preparation of positive plate
(1) Preparing a first active material coating slurry
LiNi lithium nickel cobalt manganese oxide 0.6 Co 0.2 Mn 0.2 O 2 As a first active material, a positive electrode slurry was prepared in a formulation of 96% of the first active material, 2.5% of conductive carbon black, and 1.5% of polyvinylidene fluoride, and the first active material coating slurry had a viscosity of about 5000mpa.s and a solid content of about 75%.
Wherein, the nickel cobalt lithium manganate LiNi 0.8 Co 0.1 Mn 0.1 O 2 Shrinkage of about 6%;
(2) Preparing a second active material coating slurry
Lithium cobaltate is used as a second active material, anode slurry is prepared according to the mixture ratio of 96% of the second active material, 2.5% of conductive carbon black and 1.5% of polyvinylidene fluoride, the viscosity of the slurry is about 5000mPa.s, and the solid content is about 75%;
(3) The two slurries are respectively sprayed on two surfaces of the positive current collector through different nozzles of a coater to form a first active material coating in an arc area and a second active material coating in a planar area (as shown in fig. 3 and 4, the thicknesses of the two coatings are the same), wherein the length L of the first active material coating coated on the positive arc area is 5.966mm.
2. Preparation of negative plate
Graphite is used as a negative active substance, negative slurry is prepared according to the mixture ratio of 96.8% of the negative active substance, 1.2% of conductive carbon black and 2% of polyvinylidene fluoride, the viscosity of the slurry is about 4000mPa.s, and the solid content of the slurry is 45%. And (3) coating the slurry on a negative current collector after passing through a screen mesh.
3. Preparation of the Battery
And rolling, die-cutting and slitting the obtained positive and negative plates, winding and assembling into a winding core (as shown in figure 1), packaging with an aluminum-plastic film after a short circuit test is qualified, baking in an oven to remove moisture until the moisture reaches a moisture standard required by liquid injection, injecting electrolyte, aging for 24-48h, and completing primary charging by a hot pressing forming process to obtain an activated battery cell.
Example 2
The process is carried out according to example 1, with the difference from example 1 that:
1. preparation of positive plate
(1) Preparing a first active material coating slurry
LiNi lithium nickel cobalt manganese oxide 0.8 Co 0.15 Al 0.05 O 2 The positive electrode slurry is prepared from the first active material, conductive carbon black and polyvinylidene fluoride according to the proportion of 98% of the first active material, 1% of the conductive carbon black and 1% of the polyvinylidene fluoride, the viscosity of the first active material coating slurry is about 6000mPa.s, and the solid content of the first active material coating slurry is about 70%.
Wherein, the nickel cobalt lithium manganate LiNi 0.5 Co 0.2 Mn 0.3 O 2 Shrinkage of about 5%;
(2) Preparing a second active material coating slurry
Lithium cobaltate is used as a second active material, and anode slurry is prepared according to the mixture ratio of 98% of the second active material, 1% of conductive carbon black and 1% of polyvinylidene fluoride according to a certain mixing process, wherein the viscosity of the slurry is about 3000mPa.s, and the solid content of the slurry is about 70%.
Example 3
The process is carried out according to example 1, with the difference from example 1 that:
1. preparation of positive plate
(1) Preparing a first active material coating slurry
With nickel cobaltLiNi lithium manganate 0.6 Co 0.2 Al 0.2 O 2 As a first active material, a positive electrode slurry was prepared in a ratio of 95% of the first active material, 2.5% of conductive carbon black, and 2.5% of polyvinylidene fluoride, and the first active material coating slurry had a viscosity of about 7000mpa.s and a solid content of about 80%.
Wherein, the nickel cobalt lithium manganate LiNi 0.6 Co 0.2 Al 0.2 O 2 The shrinkage of (a) was 4%;
(2) Preparing a second active material coating slurry
Lithium cobaltate is used as a second active material, anode slurry is prepared according to the mixture ratio of 95% of the second active material, 3% of conductive carbon black and 3% of polyvinylidene fluoride according to a certain mixing process, the viscosity of the slurry is about 5000mPa.s, and the solid content of the slurry is about 80%.
Example 4
The process is carried out according to example 1, with the difference from example 1 that: with LiNi 0.33 Co 0.33 Mn 0.33 O 2 The first active material had a shrinkage of 1.2%.
Example 5
The process is carried out according to example 1, with the difference from example 1 that: with LiNi 0.8 Co 0.1 Mn 0.1 O 2 And LiNi 0.8 Co 0.15 Al 0.05 O 2 Is the first active material, the mass ratio of the two materials satisfies 1.
Example 6
The process is carried out according to example 1, with the difference from example 1 that: the width L of the arc zone is 2.983mm and includes the inflection point of the curvature of the curved region of the diaphragm.
Example 7
The process is carried out according to example 1, with the difference from example 1 that: the width L of the arc zone is 1.4915mm and includes the inflection point of the bend of the bending area of the diaphragm.
Example 8
The process is carried out according to example 1, with the difference from example 1 that: the width L of the arc area is 0.01mm, and the inflection point of the bending part of the diaphragm bending area is included.
Comparative example 1
The process is carried out according to example 1, with the difference from example 1 that: the arc area and the flat area are not distinguished, and lithium cobaltate is used as an active material of the positive plate.
Comparative example 2
The process is carried out according to example 1, with the difference from example 1 that:
(1) Preparation of coating slurry for positive electrode active material
LiNi lithium nickel cobalt manganese oxide 0.6 Co 0.2 Mn 0.2 O 2 And lithium cobaltate is used as a first active material, the positive electrode slurry is prepared according to the mixture ratio of 2 percent of nickel cobalt lithium manganate, 94 percent of lithium cobaltate, 2.5 percent of conductive carbon black and 1.5 percent of polyvinylidene fluoride according to a certain compounding process, the viscosity of the first active material coating slurry is about 5000mPa.s, and the solid content is 75 percent;
(2) The positive current collector does not distinguish the arc area and the flat area, and the slurry is respectively sprayed on two surfaces of the positive current collector through different nozzles of the coating machine.
Examples of the experiments
(1) Normal temperature cycle test
Placing the battery in an environment with the temperature of 25 ℃, charging the battery with 3C constant current and constant voltage to 4.45V and charging the battery with 4.45V and constant voltage to the cutoff current of 0.05C; then standing for 15min; discharge to 3V with 1C current. Recording the initial capacity as Q1, recording the capacity as Q2 after the cycle to 600 weeks, and calculating the capacity retention rate after the normal temperature cycle of the battery by the following formula: capacity retention ratio (%) = (Q2/Q1) 100%.
(2) Battery expansion test
Measuring the initial thickness M1 of the electrode plate, measuring the thickness M2 after the electrode plate is cycled to 600 weeks, and calculating the expansion rate of the battery after normal-temperature cycle according to the following formula: battery swelling rate (%) = [ (M2-M1)/M1 ]100%.
(3) Battery lithium assay
And (4) disassembling the battery which is circulated for 600 weeks to observe whether a lithium precipitation phenomenon occurs.
TABLE 1
Figure BDA0003862039720000181
Note: in comparative example 1-3% means that the lithium cobaltate material expands by about 3% in volume after delithiation.
As can be seen from table 1, the experimental data of the embodiment shows that the case of lithium separation in the arc region can be effectively improved by providing the first active material coating in the arc region, and the larger the volume shrinkage of the first active material in the arc region, the less lithium separation in the arc region is, so that the expansion volume generated by lithium intercalation of a part of the negative electrode can be offset by coating the first active material coating, the internal stress of the arc region during charging overcharge is reduced, and the risk of lithium separation caused by hole blockage of the diaphragm in the arc region due to the large internal stress is avoided.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and the like that are within the spirit and principle of the present invention are included in the present invention.

Claims (10)

1. The positive plate is characterized by comprising a positive current collector, wherein the positive current collector is divided into an arc area and a flat area; at least one surface of the circular arc area is provided with a first active material coating, and at least one surface of the flat area is provided with a second active material coating;
wherein the first active material coating comprises a first active material and the second active material coating comprises a second active material;
the volume shrinkage rate of the first active material is greater than that of the second active material, and the volume shrinkage rate of the first active material is 0.1-8%.
2. The positive electrode sheet according to claim 1, wherein the volume shrinkage of the first active material is 5 to 8%.
3. The positive electrode sheet according to claim 1, wherein the first active material is a multi-element positive electrode material; and/or the presence of a gas in the atmosphere,
the multi-element positive electrode material is selected from at least one of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, lithium nickel cobalt manganese aluminate and lithium nickel titanium magnesium oxide.
4. The positive electrode sheet according to claim 3, wherein the lithium nickel cobalt manganese oxide has the chemical formula LiNi x Co y Mn 1-x-y O 2 Wherein 0.4<x≤0.8，y>0，0<x+y<1; and/or the presence of a gas in the atmosphere,
the chemical formula of the nickel cobalt lithium aluminate is LiNi x Co y Al 1-x-y O 2 Wherein 0.4<x≤0.8，y>0，0.8≤x+y<1; and/or the presence of a gas in the atmosphere,
the chemical formula of the nickel-cobalt-manganese lithium aluminate is LiNi x Co y Mn w Al 1-x-y-w O 2 Wherein 0.4<x≤0.8，y>0，w>0，0.8≤x+y+w<1; and/or the presence of a gas in the atmosphere,
the chemical formula of the lithium nickel titanium magnesium oxide is LiNi x Ti y Mg z O 2 Wherein, 0.4<x≤0.8，y>0，z>0，x+y+z＝1。
5. The positive electrode sheet according to claim 3, wherein the plurality of positive electrode materials are selected from LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.6 Co 0.2 Al 0.2 O 2 、LiNi 0.5 Co 0.2 Al 0.3 O 2 、LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O 2 And LiNi 0.6 Ti 0.2 Mg 0.2 O 2 At least one of (1).
6. The positive electrode sheet according to claim 1, wherein the second active material is a lithium-containing inorganic salt;
and/or, the lithium-containing inorganic salt is lithium cobaltate.
7. The positive electrode sheet according to claim 1, wherein the content of the first active material is 90 to 98% based on the total mass of the first active material coating layer; and/or the presence of a gas in the gas,
the content of the second active material is 90-98% based on the total mass of the second active material coating.
8. A winding core, characterized in that the winding core is a winding structure formed by a first diaphragm, a first pole piece, a second diaphragm and a second pole piece which are sequentially stacked, and the first pole piece or the second pole piece is a positive pole piece according to any one of claims 1 to 7;
wherein, along the stretching direction of the winding core, the width of the arc area is not more than the bending part of the winding structure, and the width of the flat area is not less than the non-bending part of the winding structure.
9. The winding core of claim 8, wherein the width L of the circular arc zone is
Figure FDA0003862039710000031
Figure FDA0003862039710000032
Wherein d is the thickness of the winding core.
10. A battery comprising at least one of the positive electrode sheet according to any one of claims 1 to 7 and the jelly roll according to claim 8 or 9.
CN202211167639.XA 2022-09-23 2022-09-23 Positive plate, roll core and battery Pending CN115483365A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117117086A (en) * 2023-10-24 2023-11-24 宁德时代新能源科技股份有限公司 Positive plate, battery monomer, battery and power utilization device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117117086A (en) * 2023-10-24 2023-11-24 宁德时代新能源科技股份有限公司 Positive plate, battery monomer, battery and power utilization device
CN117117086B (en) * 2023-10-24 2024-03-29 宁德时代新能源科技股份有限公司 Positive plate, battery monomer, battery and power utilization device

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