CN114242935A - Electrode assembly and application thereof - Google Patents
Electrode assembly and application thereof Download PDFInfo
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- CN114242935A CN114242935A CN202111542947.1A CN202111542947A CN114242935A CN 114242935 A CN114242935 A CN 114242935A CN 202111542947 A CN202111542947 A CN 202111542947A CN 114242935 A CN114242935 A CN 114242935A
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- 239000007774 positive electrode material Substances 0.000 claims abstract description 111
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 70
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 70
- 239000002245 particle Substances 0.000 claims description 48
- 238000004804 winding Methods 0.000 claims description 47
- 238000009826 distribution Methods 0.000 claims description 26
- 239000011230 binding agent Substances 0.000 claims description 11
- 239000006258 conductive agent Substances 0.000 claims description 9
- 238000003475 lamination Methods 0.000 claims description 5
- 230000007423 decrease Effects 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 description 14
- 239000003792 electrolyte Substances 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 9
- 238000007599 discharging Methods 0.000 description 7
- 238000007086 side reaction Methods 0.000 description 6
- 238000007600 charging Methods 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- 239000011149 active material Substances 0.000 description 4
- 238000010280 constant potential charging Methods 0.000 description 4
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- 239000002985 plastic film Substances 0.000 description 4
- 229920006255 plastic film Polymers 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000013543 active substance Substances 0.000 description 3
- 230000003247 decreasing effect Effects 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical group C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 3
- 230000002829 reductive effect Effects 0.000 description 3
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 229920002134 Carboxymethyl cellulose Polymers 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 description 2
- 239000006183 anode active material Substances 0.000 description 2
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- 239000003795 chemical substances by application Substances 0.000 description 2
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- 229910052799 carbon Inorganic materials 0.000 description 1
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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
-
- 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides an electrode assembly and application thereof. The electrode assembly of the present invention comprises positive electrode sheets including an internal positive electrode sheet located inside the electrode assembly, an external positive electrode sheet located outside the electrode assembly, and an intermediate positive electrode sheet located between the internal positive electrode sheet and the external positive electrode sheet, wherein D50 of the positive electrode active material of the internal positive electrode sheetInner partD50 of positive electrode active material of the external positive electrode sheetOuter coverD50 of positive electrode active material of the intermediate positive electrode sheetInThe following relationship is satisfied: d50Inner partGreater than D50Outer cover，D50InNot greater than D50Inner partAnd D50InNot less than D50Outer cover. The electrode assembly provided by the invention can enable the lithium ion battery to have relatively excellent high-temperature high-pressure charge and discharge performance and low-temperature discharge performance, and broadens the application scenes of the lithium ion battery.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to an electrode assembly and application thereof.
Background
At present, the temperature rise inside the battery is easily caused to be large when the battery is charged with a large multiplying power, and the heat inside the battery is difficult to quickly dissipate due to the limit of the fixed size of the battery, so that a continuous high-temperature hot zone is formed inside the battery. It is known that the sustained high temperature and high pressure may aggravate the irreversible phase change of the positive active material, and cause the side reaction of the positive active material and the electrolyte, thereby causing the degradation of the charge and discharge performance of the battery at high temperature.
On the other hand, although the probability of side reactions between the positive electrode active material and the electrolyte decreases in the battery in a low-temperature environment, the influence of the internal resistance of the battery on the cycle performance of the battery increases significantly in the low-temperature environment.
Therefore, it is urgently needed to prepare a lithium ion battery having both excellent high-temperature and high-voltage charge and discharge performance and excellent low-temperature discharge performance.
Disclosure of Invention
The invention provides an electrode assembly which can enable a lithium ion battery to have excellent high-temperature high-pressure charge and discharge performance and low-temperature discharge performance at the same time, and broadens the application scenes of the lithium ion battery.
The invention provides a lithium ion battery, which comprises the electrode assembly, has excellent high-temperature high-pressure charge and discharge performance and low-temperature discharge performance and has a wide application range.
The invention provides an electrode assembly, which comprises a positive plate, wherein the positive plate comprises an internal positive plate positioned in the electrode assembly, an external positive plate positioned outside the electrode assembly and an intermediate positive plate positioned between the internal positive plate and the external positive plate, and D50 of a positive active material of the internal positive plateInner partD50 of positive electrode active material of the external positive electrode sheetOuter coverD50 of positive electrode active material of the intermediate positive electrode sheetInThe following relationship is satisfied: d50Inner partGreater than D50Outer cover，D50InNot greater than D50Inner partAnd D50InNot less than D50Outer cover。
The electrode assembly as set forth above, wherein the electrode assembly is a lamination stack;
the number ratio of the internal positive plate to the intermediate positive plate to the external positive plate is 1: (1-4): 1, and D50Inner part＝D50In(ii) a Or,
the number ratio of the internal positive plate to the intermediate positive plate to the external positive plate is 1: (1-4): 1, and D50Outer cover＝D50In。
The electrode assembly as set forth above, wherein the electrode assembly is a laminate structure, the intermediate positive electrode tab includes a first intermediate positive electrode tab and a second intermediate positive electrode tab, and the first intermediate positive electrode tab is adjacent to the inner positive electrode tab, wherein D50 of the positive active material of the first intermediate positive electrode tabIn the firstD50 of positive electrode active material of the second intermediate positive electrode sheetIn the second placeThe number ratio of the internal positive plate to the first intermediate positive plate to the second intermediate positive plate to the external positive plate satisfies the following relationship;
the number ratio of the internal positive plate to the first intermediate positive plate to the second intermediate positive plate to the external positive plate is 1: (1-4): 1, and D50Inner part＝D50In the first，D50Outer cover＝D50In the second place。
The electrode assembly as described above, wherein the electrode assembly is a laminated structure, the number of the intermediate positive electrode sheets is N, and according to the direction in which the internal positive electrode sheet points to the external positive electrode sheet, D50 of the positive electrode active materials in the internal positive electrode sheet, the N intermediate positive electrode sheets, and the external positive electrode sheet gradually decrease, and N is greater than or equal to 1.
The electrode assembly as described above, wherein the electrode assembly is a wound structure, and the internal positive plate, the intermediate positive plate and the external positive plate are connected end to end in sequence;
the number ratio of the winding sections of the internal positive plate, the intermediate positive plate and the external positive plate is 1: (1-4): 1, and D50Inner part＝D50In(ii) a Or,
the number ratio of the winding sections of the internal positive plate, the intermediate positive plate and the external positive plate is 1: (1-4): 1, and D50Outer cover＝D50In。
The electrode assembly is of a winding structure, the internal positive plate, the intermediate positive plate and the external positive plate are sequentially connected end to end, the intermediate positive plate comprises a first intermediate positive plate and a second intermediate positive plate which are sequentially connected end to end, the first intermediate positive plate is close to the internal positive plate, the first intermediate positive plate comprises M1 winding sections which are sequentially connected end to end, the second intermediate positive plate comprises M2 winding sections which are sequentially connected end to end, M1 is not less than 1, M2 is not less than 1, and D50 of the first intermediate positive plate is 50In the firstD50 of the second intermediate positive plateIn the second placeThe number ratio of the winding sections of the internal positive plate, the first intermediate positive plate, the second intermediate positive plate and the external positive plate satisfies the following relationship;
the number ratio of the winding sections of the internal positive plate, the first intermediate positive plate, the second intermediate positive plate and the external positive plate is 1: (1-4): 1, and D50Inner part＝D50In the first，D50Outer cover＝D50In the second place。
The electrode assembly as described above, wherein D50 of the positive electrode active material of the internal positive electrode tabInner partSatisfies the following conditions: d50 with the particle size of 14 mu m or lessInner part≤20μm 28μm≤D90Inner partLess than or equal to 35 mu m; and/or the presence of a gas in the gas,
d90 of positive electrode active material of the external positive electrode sheetOuter coverSatisfies the following conditions: d50 with the particle size of 8 mu m or lessOuter cover≤14μm。
The electrode assembly as set forth above, wherein the positive electrode of said internal positive electrode tabThe particle size distribution of the active substance is: d10 with the particle size of 7 mu m or lessInner part≤12μm，28μm≤D90Inner partLess than or equal to 35 mu m; and/or the presence of a gas in the gas,
the particle size distribution of the positive active material of the external positive plate is as follows: d10 with the particle size of 2 mu m or lessOuter cover≤7μm，μm≤D90Outer cover≤27μm。
The electrode assembly as described above, wherein the positive electrode active layer of the internal positive electrode tab includes, in mass percent: 90 to 99 percent of positive active material, 0.5 to 5 percent of binder and 0.5 to 5 percent of conductive agent; and/or the presence of a gas in the gas,
the positive active layer of the external positive plate comprises the following components in percentage by mass: 90 to 99 percent of positive active material, 0.5 to 5 percent of binder and 0.5 to 5 percent of conductive agent.
The invention provides a lithium ion battery comprising the electrode assembly as described above.
Electrode assembly, positive electrode active material for external positive electrode sheet D50 of the present inventionOuter coverD50 of positive active material smaller than that of internal positive plateInner partAnd D50 for the intermediate positive plateInNot greater than D50 of internal positive plateInner partD50 for the intermediate positive plateInD50 not smaller than external positive plateOuter cover. According to the invention, by limiting the composition of the positive plate, the lithium ion battery comprising the electrode assembly has excellent high-temperature high-pressure charge-discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened.
The lithium ion battery provided by the invention has excellent high-temperature and high-voltage charge and discharge performance and low-temperature discharge performance due to the electrode assembly, and has a wide application range.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the related art, the drawings used in the description of the embodiments of the present invention or the related art are briefly introduced below. It is obvious that the drawings in the following description are only some embodiments of the invention, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is a schematic view illustrating the structure of an electrode assembly according to a first embodiment of the present invention;
FIG. 2 is a schematic view illustrating the structure of an electrode assembly according to a second embodiment of the present invention;
fig. 3 is a schematic view of the structure of an electrode assembly in a third embodiment of the present invention.
Description of reference numerals:
1: a centerline;
2. 2 ', 4': a positive plate;
3: a middle positive plate;
31: a first intermediate positive plate;
32: and a second intermediate positive plate.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in 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.
Fig. 1 is a schematic view illustrating the structure of an electrode assembly according to a first embodiment of the present invention; FIG. 2 is a schematic view illustrating the structure of an electrode assembly according to a second embodiment of the present invention; fig. 3 is a schematic view of the structure of an electrode assembly in a third embodiment of the present invention. A first aspect of the present invention provides an electrode assembly, as shown in any one of fig. 1 to 3, comprising positive electrode tabs including an inner positive electrode tab located inside the electrode assembly, an outer positive electrode tab located outside the electrode assembly, and an intermediate positive electrode tab located between the inner positive electrode tab and the outer positive electrode tab, wherein D50 of the positive active material of the inner positive electrode tabInner partD50 of Positive electrode active Material for external Positive electrode sheetOuter coverD50 of Positive electrode active Material of intermediate Positive electrode sheetInThe following relationship is satisfied: d50Inner partGreater than D50Outer cover，D50InNot greater than D50Inner partAnd D50InNot less than D50Outer cover。
It is understood that the electrode assembly of the present invention further includes a negative electrode tab and a separator disposed between the negative electrode tab and the positive electrode tab. The positive plate, the diaphragm and the negative plate are stacked to form an electrode assembly with a laminated structure; after the positive electrode sheet, the separator, and the negative electrode sheet are stacked, the positive electrode sheet, the separator, and the negative electrode sheet are wound to obtain an electrode assembly having a wound structure. The negative electrode sheet and the separator are not particularly limited in the present invention and may be selected from negative electrode sheets and separators commonly used in the art.
In order to better explain the technical scheme of the invention, the attached drawing of the invention is a structural schematic diagram of an electrode assembly without a negative electrode sheet and a diaphragm.
Hereinafter, the types of the positive electrode sheets of the electrode assembly of the present invention will be described according to the positions of the positive electrode sheets, taking the laminate-type electrode assembly shown in fig. 1 and 2 and the wound-type electrode assembly shown in fig. 3 as examples.
The present invention distinguishes between positive electrode tabs located at different positions in an electrode assembly. The electrode assembly has a center line 1, and in the present invention, the positive electrode tabs 2 and 2 'closest to the center line 1 of the electrode assembly are referred to as internal positive electrode tabs, the positive electrode tabs 4 and 4' distant from the center line 1 of the electrode assembly are referred to as external positive electrode tabs, and the other positive electrode tabs than the internal positive electrode tabs and the external positive electrode tabs are referred to as intermediate positive electrode tabs 3. It is understood that the external positive electrode tab, the internal positive electrode tab, and the intermediate positive electrode tab of the present invention all include a positive electrode active layer.
In the electrode assembly having the lamination structure shown in fig. 1, the extending direction of the central line 1 is parallel to the extending direction of the positive electrode tab and is located at the center position of the electrode assembly, wherein the positive electrode tabs 2 and 2 'are closest to the central line 1, so the internal positive electrode tabs of the electrode assembly are the positive electrode tabs 2 and 2', and the positive electrode tabs 4 and 4 'are far from the central line 1, so the external positive electrode tabs of the electrode assembly are the positive electrode tabs 4 and 4', and the other positive electrode tabs are the intermediate positive electrode tabs 3.
In the electrode assembly having the lamination structure shown in fig. 2, the extending direction of the central line 1 is parallel to the extending direction of the positive electrode tab and is located at the center of the electrode assembly, wherein the positive electrode tab 2 is closest to the central line 1, so the inner positive electrode tab of the electrode assembly is the positive electrode tab 2, and the positive electrode tabs 4 and 4 'are far from the central line 1, so the outer positive electrode tabs of the electrode assembly are the positive electrode tabs 4 and 4', and the other positive electrode tabs are the middle positive electrode tab 3.
In the electrode assembly of the winding structure shown in fig. 3, the center line 1 is located at the center of the electrode assembly and the extending direction of the center line 1 is identical to the length direction of the positive electrode tab of the horizontal segment. The positive plate of the winding structure is obtained by winding one end of the positive plate as a starting end and the other end as a tail end, one end close to a central line 1 is called the starting end, and a positive plate 2 corresponding to a winding section obtained by winding 360 degrees in the winding direction by taking the starting end as an end point is called an internal positive plate; the other end is called a tail end, and the positive plate 4 corresponding to a winding section obtained by winding 360 degrees in the reverse winding direction by taking the tail end as an end point is called an external positive plate; and the winding section between the outer positive electrode sheet and the inner positive electrode sheet is the intermediate positive electrode sheet 3. That is, in the electrode assembly of the winding structure, each of the inner positive electrode tab and the outer positive electrode tab is only 1 winding step.
In fig. 3, the positive electrode sheet 2 corresponding to the ab winding section is an internal positive electrode sheet, the positive electrode sheet 4 corresponding to the de winding section is an external positive electrode sheet, the other positive electrode sheets are intermediate positive electrode sheets 3, and the intermediate positive electrode sheets 3 include a winding section bc and a winding section cd.
According to the invention, the composition of different positive plates is limited, so that the lithium ion battery has excellent high-temperature high-voltage charge and discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened.
The positive plate comprises a positive current collector and a positive active layer arranged on at least one functional surface of the positive current collector, wherein the positive active layer comprises a positive active substance, a binder and a conductive agent. Specifically, the invention limits the D50 of the anode active materials of different anode plates, so that the lithium ion battery has excellent high-temperature high-voltage charge and discharge performance and low-temperature discharge performance, and the application scenes of the lithium ion battery are widened. It is understood that the positive electrode active materials of the different positive electrode sheets in the present invention are the same material, but the material has different D50. The above functional surfaces refer to two surfaces of the positive electrode current collector having the largest area and being oppositely disposed. In the present invention, the positive electrode active material D50 of the different positive electrode sheets was measured using a laser particle size analyzer.
D50 of the positive electrode active material in each positive electrode sheet of the present invention satisfies the following relationship: d50Inner partGreater than D50Outer cover，D50InNot greater than D50Inner partAnd D50InNot less than D50Outer cover。
In the present invention, D50 indicates that the volume of the positive electrode active material having a particle diameter within this range accounts for 50% of the total volume of the positive electrode active material. D50Inner partD50, D50 referring to internal positive plateOuter coverD50, D50 referring to external positive plateInReferred to as D50 of the middle positive plate.
The positive electrode active material of the present invention is not particularly limited, and a positive electrode active material commonly used in the art may be selected.
According to the invention, through reasonably setting the D50 of the anode active materials of different anode plates, the lithium ion battery has excellent high-temperature high-voltage charge and discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened. The inventors analyzed this phenomenon, and it is possible that, in one aspect, the present invention was accomplished by disposing D50 inside the electrode assemblyInner partThe large positive active material can reduce the contact area between the electrolyte and the positive active material in the lithium ion battery, further reduce the probability of side reaction between the positive active material and the electrolyte, and improve the charge and discharge performance of the lithium ion battery under high temperature and high pressure; on the other hand, D50 of positive electrode active material provided in the external positive electrode sheet of the electrode assemblyOuter coverThe lithium ion battery has small size, and can effectively reduce the internal resistance of the electrode assembly, thereby improving the low-temperature discharge performance of the lithium ion battery.
As described above, the present invention is directed to D50 of the positive electrode active material of the intermediate positive electrode sheet 3InIs not limited to a specific one, provided that D50 of the positive electrode active material of the internal positive electrode sheet is not excessively containedInner partAnd D50 of positive electrode active material of external positive electrode sheetOuter coverThe above requirements are satisfied, that is, at least part of D50 of the positive electrode active material of the intermediate positive electrode sheet 3InCan be used forD50 of positive electrode active material with internal positive electrode sheetInner partD50 of the positive electrode active material of the intermediate positive electrode sheet 3 being equal to, or at least partiallyInD50 of positive active material capable of being contacted with external positive plateOuter coverEqual to, or, D50 of the positive electrode active material of the intermediate positive electrode sheet 3InD50 of positive electrode active material in internal positive electrode sheetInner partD50 of positive electrode active material with external positive electrode sheetOuter coverIn the meantime. When the electrode assembly is of a laminated structure, the number of the D50 of the positive active material of each positive plate is matched with the number of the internal positive plate, the number of the intermediate positive plate 3 and the number of the external positive plates, so that the lithium ion battery has excellent high-temperature high-voltage charge and discharge performance and excellent low-temperature discharge performance, and the application scene of the lithium ion battery is widened.
For example, when D50Inner part＝D50InAnd the number ratio of the internal positive plate, the middle positive plate 3 and the external positive plate is 1: (1-4): 1, or alternatively,
when D50Outer cover＝D50InAnd the number ratio of the internal positive plate, the middle positive plate 3 and the external positive plate is 1: (1-4): 1.
of course, D50 of the positive electrode active material of each intermediate positive electrode sheet 3 of the electrode assembly of the lamination structureInOr may not be all the same.
In some embodiments of the present invention, part of D50 of the positive active material of the intermediate positive electrode sheet 3InThe same is true. As shown in fig. 1, the intermediate positive electrode sheet 3 includes a first intermediate positive electrode sheet 31 and a second intermediate positive electrode sheet 32, and the first intermediate positive electrode sheet 31 is adjacent to the internal positive electrode sheet, wherein D50 of the positive electrode active material of the first intermediate positive electrode sheet 31In the firstD50 of positive electrode active material of second intermediate positive electrode sheet 32In the second placeThe number ratio of the first intermediate positive plate to the internal positive plate to the second intermediate positive plate to the external positive plate satisfies the following relationship;
the number ratio of the internal positive plate, the first intermediate positive plate 31, the second intermediate positive plate 32 and the external positive plate is (1-2): (1-8): (1-8): (1-2), and D50Inner part＝D50In the first，D50Outer coverD50 thIIIn (1).
As can be seen from fig. 1, the electrode assembly has two internal positive electrode tabs, two external positive electrode tabs, and N intermediate positive electrode tabs 3, wherein at least one intermediate positive electrode tab 3 adjacent to the internal positive electrode tab is referred to as a first intermediate positive electrode tab 31, and the other intermediate positive electrode tabs 3 are second intermediate positive electrode tabs 32, and N is greater than or equal to 1.
When the internal positive plate, the first intermediate positive plate 31, the second intermediate positive plate 32 and the external positive plate have the positive active material D50, and the internal positive plate, the first intermediate positive plate 31, the second intermediate positive plate 32 and the external positive plate have the above relationship, the obtained electrode assembly can enable the lithium ion battery to have relatively excellent high-temperature and high-voltage charge and discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened.
In other embodiments of the present invention, the electrode assembly is a laminated structure, the number of the intermediate positive electrode sheets 3 is N, and according to the direction in which the internal positive electrode sheet points to the external positive electrode sheet, D50 of the positive electrode active materials in the internal positive electrode sheet, the N intermediate positive electrode sheets 3 and the external positive electrode sheet gradually decrease, where N is greater than or equal to 1.
According to the invention, because the temperature of the electrode assembly is gradually decreased from the inside to the outside when the lithium ion battery is charged and discharged rapidly, when the temperature of the D50 of the positive electrode active material in each positive plate is gradually decreased from the inside to the outside, the D50 of the positive electrode active material in each positive plate can be matched with the temperature of each positive plate, the probability of side reaction between the positive electrode active material and electrolyte can be reduced as far as possible, the internal resistance of the electrode assembly is reduced, the lithium ion battery can have excellent high-temperature high-voltage charging and discharging performance and low-temperature discharging performance, and the application scene of the lithium ion battery is widened.
Similarly, when the electrode assembly is of a winding structure, the number of the D50 of the positive active material of each positive plate is matched with the number of the winding sections of each positive plate, so that the lithium ion battery has excellent high-temperature high-voltage charge and discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened.
As shown in fig. 3, in some embodiments of the present invention, the internal positive electrode tab, the intermediate positive electrode tab 3, and the external positive electrode tab are connected end to end in sequence;
the number ratio of the winding sections of the internal positive plate, the middle positive plate 3 and the external positive plate is 1: (1-4): 1, and D50Inner part＝D50In(ii) a Or,
the number ratio of the respective winding sections of the internal positive plate, the intermediate positive plate and the external positive plate is 1: (1-4): 1, and D50Outer cover＝D50In。
In other embodiments of the present invention, the internal positive plate, the intermediate positive plate 3 and the external positive plate are sequentially connected end to form an electrode assembly of a winding structure, the intermediate positive plate 3 includes a first intermediate positive plate 31 and a second intermediate positive plate 32, which are sequentially connected end to end, the first intermediate positive plate 31 is close to the internal positive plate, the first intermediate positive plate 31 includes M1 winding sections, which are sequentially connected end to end, the second intermediate positive plate 32 includes M2 winding sections, which are sequentially connected end to end, wherein M1 is greater than or equal to 1, M2 is greater than or equal to 1, and D50 of the positive active material of the first intermediate positive plate 31 is D50In the firstD50 of positive electrode active material of second intermediate positive electrode sheet 32In the second placeWhen the number ratio of the winding sections of the internal positive plate, the first intermediate positive plate 31, the second intermediate positive plate 32 and the external positive plate satisfies the following relationship, the lithium ion battery has excellent high-temperature high-voltage charge and discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened.
The number ratio of the winding sections of the internal positive electrode sheet, the first intermediate positive electrode sheet 31, the second intermediate positive electrode sheet 32, and the external positive electrode sheet is 1 to 2): (1-8): (1-8): (1-2), and D50Inner part＝DIn the first，D50Outer cover＝D50In the second placeThen (c) is performed.
In some embodiments of the present invention, in order to make the lithium ion battery have both more excellent high-temperature and high-voltage charge and discharge performance and low-temperature discharge performance, and further widen the application range of the lithium ion battery, D50 of the positive electrode active material of the internal positive electrode sheetInner partSatisfies the following conditions: d50 with the particle size of 14 mu m or lessInner partLess than or equal to 20 mu m; and/or the presence of a gas in the gas,
d50 of positive electrode active material of external positive electrode sheetOuter coverSatisfies the following conditions: d50 with the particle size of 8 mu m or lessOuter cover≤14μm。
In some embodiments of the present invention, the particle size distribution of the positive electrode active material of the internal positive electrode sheet is: d10 with the particle size of 7 mu m or lessInner part≤12μm，28μm≤D90Inner part≤35μm。
In the present invention, D10 represents that the volume of the positive electrode active material having a particle diameter within this range accounts for 10% of the total volume of the positive electrode active material. D90 indicates that the volume of the positive electrode active material having a particle diameter within this range accounts for 90% of the total volume of the positive electrode active material. D10Inner partD10, D90 designating positive electrode active material of internal positive electrode sheetInner partD90, which is the positive electrode active material of the internal positive electrode sheet.
According to the invention, the particle size distribution of the positive active material of the internal positive plate is in the range, so that the particle size of the positive active material of the internal positive plate can be more matched with the temperature in the electrode assembly, the probability of side reaction between the positive active material and the electrolyte is reduced, the lithium ion battery has excellent high-temperature and high-voltage charge and discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened.
Further, in some embodiments, the particle size distribution of the positive electrode active material of the internal positive electrode sheet is: d10 with the particle size of 7 mu m or lessInner part≤9μm，17μm≤D50Inner part≤19μm，30μm≤D90Inner part≤32μm。
In some embodiments of the present invention, in order to reduce the internal resistance of the electrode assembly while reducing the probability of side reactions between the positive active material and the electrolyte as much as possible, so that the lithium ion battery has both more excellent high-temperature and high-voltage charge and discharge performance and lower-temperature discharge performance, and broadens the application scenarios of the lithium ion battery, in the positive active layer of the external positive plate, the particle size distribution of the positive active material of the external positive plate is as follows: d10 with the particle size of 2 mu m or lessOuter cover≤7μm，18μm≤D90Outer cover≤27μm。
Further, in some embodiments, the particle size distribution of the positive electrode active material of the external positive electrode sheet is: d10 with the particle size of 3 mu m or lessOuter cover≤5μm，10μm≤D50Outer cover≤12μm，20μm≤D90Outer cover≤24μm。
In the present invention, D10Outer coverD10, D90 designating positive electrode active material of external positive electrode sheetOuter coverD90 indicating the positive electrode active material of the external positive electrode sheet.
According to the invention, the composition of the positive active layer of the internal positive plate is specifically matched with the particle size distribution of the positive active material, and/or the composition of the positive active layer of the external positive plate is specifically matched with the particle size distribution of the positive active material, so that the lithium ion battery has excellent high-temperature and high-voltage charge and discharge performance and low-temperature discharge performance, and the application scene of the lithium ion battery is widened. In some embodiments of the present invention, the positive active layer of the internal positive electrode sheet includes, by mass: 90 to 99 percent of positive active material, 0.5 to 5 percent of binder and 0.5 to 5 percent of conductive agent; and/or the presence of a gas in the gas,
the positive active layer of the external positive plate comprises the following components in percentage by mass: 90 to 99 percent of positive active material, 0.5 to 5 percent of binder and 0.5 to 5 percent of conductive agent.
A second aspect of the invention provides a lithium ion battery comprising the electrode assembly described above.
In the invention, the electrode assembly is placed in an aluminum-plastic film, and electrolyte is injected into the aluminum-plastic film, so that the lithium ion battery can be obtained. The lithium ion battery provided by the invention has excellent high-temperature and high-voltage charge and discharge performance and low-temperature discharge performance due to the electrode assembly, and is wide in application range.
Hereinafter, the technical solution of the present invention will be described with reference to specific examples.
Example 1
The lithium ion battery of the present example was prepared by the following steps:
1. preparation of positive plate
A. Preparation of internal positive plate
Mixing a positive electrode active material, a binder PVDF and a conductive agent according to a weight ratio of 97.8: 1.1: 1.1, adding N-methyl pyrrolidone into the mixed substance, stirring and dispersing to prepare positive active slurry, coating the positive active slurry on two functional surfaces of a copper foil, and then drying, rolling, slitting and flaking to obtain an internal positive plate comprising a positive active layer;
wherein, positive pole active material is nickel cobalt lithium, and the conducting agent is conductive carbon black, and positive pole active material's particle size distribution is: d10Inner part8 μm, D50Inner part18 μm, D90Inner partAnd 30 μm.
B. Preparation of external positive plate
Mixing a positive electrode active material, a binder PVDF and a conductive agent according to a weight ratio of 97.8: 1.1: 1.1, adding N-methyl pyrrolidone into the mixed substance, stirring and dispersing to prepare positive active slurry, coating the positive active slurry on two functional surfaces of a copper foil, and then drying, rolling, slitting and flaking to obtain an external positive plate comprising a positive active layer;
wherein, positive pole active material is nickel cobalt lithium, and the conducting agent is conductive carbon black, and positive pole active material's particle size distribution is: d10Outer coverIs 4 μm, D50Outer cover11 μm, D90Outer coverAnd 22 μm.
2. Preparation of negative plate
Adding conductive carbon, binder styrene-butadiene rubber, carboxymethyl cellulose and water into the negative active substance to prepare negative active slurry, and then drying, rolling, slitting and tabletting to obtain a negative plate comprising a negative active layer;
wherein the mass ratio of the negative active material graphite to the conductive carbon black to the binder styrene butadiene rubber to the carboxymethyl cellulose is 96.9: 0.5: 1.3: 1.3.
3. preparation of lithium ion battery
Stacking the positive plate and the diaphragm in the step 1 and the negative plate in the step 2 to obtain an electrode assembly with a laminated structure;
the structure of the electrode assembly of this embodiment is shown in fig. 1, wherein the number of the internal positive electrode tabs is 2, the number of the external positive electrode tabs is 2, four intermediate positive electrode tabs 3 are respectively arranged on two sides of a central line 1 (i.e. the number of the intermediate positive electrode tabs is 8), and the composition of the intermediate positive electrode tabs 3 is the same as that of the external positive electrode tabs;
placing the electrode assembly in an aluminum-plastic film, sealing, injecting electrolyte into the aluminum-plastic film, and then carrying out formation, secondary packaging, sorting and aging processes to obtain the lithium ion battery;
wherein the electrolyte consists of EC, DEC and EMC with equal volume, wherein LiPF6The content of (b) is 1 mol/L.
Example 2
The preparation method of the lithium ion battery of this embodiment is substantially the same as that of embodiment 1, except that, in step 3, there are one first intermediate positive electrode plate 31 and one second intermediate positive electrode plate 32 on both sides of the center line 1 (i.e., there are two first intermediate positive electrode plates 31 and two second intermediate positive electrode plates 32 in total), the composition of the first intermediate positive electrode plate 31 is the same as that of the internal positive electrode plate, and the composition of the second intermediate positive electrode plate 32 is the same as that of the external positive electrode plate.
Example 3
The preparation method of the lithium ion battery of this example is basically the same as that of example 1, except that in step 3, the composition of the intermediate positive electrode sheet 3 is the same as that of the internal positive electrode sheet.
Example 4
The lithium ion battery of this example was prepared in substantially the same manner as in example 1, except that, in step 3,
after the positive plate, the diaphragm and the negative plate are arranged in a laminated mode, winding is carried out, and an electrode assembly with a winding structure is obtained;
the structure of the electrode assembly of this embodiment refers to fig. 3, wherein the positive plate is obtained by sequentially connecting an internal positive plate, an intermediate positive plate and an external positive plate end to end, the intermediate positive plate 3 has 4 winding sections sequentially connected end to end, and the composition of the intermediate positive plate 3 is the same as that of the external positive plate.
Example 5
The lithium ion battery of this example was prepared in substantially the same manner as in example 4, except that, in step 3,
the middle positive plate 3 close to the internal positive plate is a first middle positive plate 31, the first middle positive plate 31 is provided with two winding sections, the middle positive plate 3 close to the external positive plate is a second middle positive plate 32, the second middle positive plate 32 is provided with two winding sections, the composition of the first middle positive plate 31 is the same as that of the internal positive plate, and the composition of the second middle positive plate 32 is the same as that of the external positive plate.
Example 6
The preparation method of the lithium ion battery of this example is basically the same as that of example 4, except that in step 3, the composition of the intermediate positive electrode sheet 3 is the same as that of the internal positive electrode sheet.
Example 7
The preparation method of the lithium ion battery of the embodiment is basically the same as that of the embodiment 1, and the only difference is that two sides of the central line 1 are respectively provided with a first middle positive plate, a second middle positive plate and a third middle positive plate, the middle positive plate close to the internal positive plate is the first middle positive plate, the middle positive plate close to the external positive plate is the second middle positive plate, and the positive plate between the first middle positive plate and the second middle positive plate is the third middle positive plate;
wherein, in the first intermediate positive plate, the particle size distribution of the positive active material is as follows: d10In the firstIs 7 μm, D50In the first16 μm, D90In the firstIs 28 μm; in the third intermediate positive electrode sheet, the particle size distribution of the positive electrode active material is: d10In the third place6 μm, D50In the third place14 μm, D90In the third place26 μm; in the second intermediate positive electrode sheet, the particle size distribution of the positive electrode active material is: d10In the second placeIs 4 μm, D50In the second place11 μm, D90In the second placeAnd 22 μm.
Example 8
The preparation method of the lithium ion battery of the present example is substantially the same as that of example 1, except that the particle size distribution of the positive electrode active material of the internal positive electrode sheet is as follows: d10Inner partIs 7 μm, D50Inner part14 μm, D90Inner partIs 28 μm; the particle size distribution of the positive active material of the external positive plate is as follows: d10Outer coverIs 2 μm, D50Outer coverThe particle size of the nano-particles is 8 mu m,D90outer coverAnd 18 μm.
Example 9
The preparation method of the lithium ion battery of the present example is substantially the same as that of example 1, except that the particle size distribution of the positive electrode active material of the internal positive electrode sheet is as follows: d10Inner part12 μm, D50Inner part20 μm, D90Inner partIs 35 μm; the particle size distribution of the positive active material of the external positive plate is as follows: d10Outer coverIs 7 μm, D50Outer cover14 μm, D90Outer coverIt was 27 μm.
Example 10
The preparation method of the lithium ion battery of the present example is substantially the same as that of example 1, except that the particle size distribution of the positive electrode active material of the internal positive electrode sheet is as follows: d10Inner partIs 7 μm, D50Inner part17 μm, D90Inner partIs 30 μm; the particle size distribution of the positive active material of the external positive plate is as follows: d10Outer coverIs 3 μm, D50Outer cover10 μm, D90Outer coverAnd 20 μm.
Example 11
The preparation method of the lithium ion battery of the present example is substantially the same as that of example 1, except that the particle size distribution of the positive electrode active material of the internal positive electrode sheet is as follows: d10Inner part9 μm, D50Inner part19 μm, D90Inner partIs 32 μm; the particle size distribution of the positive active material of the external positive plate is as follows: d10Outer coverIs 7 μm, D50Outer cover14 μm, D90Outer coverIt was 27 μm.
Example 12
The preparation method of the lithium ion battery of the present example is substantially the same as that of example 1, except that the particle size distribution of the positive electrode active material of the internal positive electrode sheet is as follows: d10Inner partIs 4 μm, D50Inner part11 μm, D90Inner partIs 22 μm; the particle size distribution of the positive active material of the external positive plate is as follows: d10Outer cover8 μm, D50Outer cover18 μm, D90Outer coverAnd 30 μm.
Comparative example 1
The lithium ion battery of this comparative example was prepared in substantially the same manner as in example 1, except that, in step 3, the composition of each positive electrode sheet of the electrode assembly was all the same as that of the internal positive electrode sheet in example 1.
Comparative example 2
The lithium ion battery of this comparative example was prepared in substantially the same manner as in example 1, except that, in step 3, the composition of each positive electrode sheet of the electrode assembly was all the same as that of the external positive electrode sheet in example 1.
Comparative example 3
The lithium ion battery of this comparative example was prepared in substantially the same manner as in example 4, except that in step 3, the composition of each positive electrode sheet of the electrode assembly was all the same as that of the internal positive electrode sheet in example 1.
Comparative example 4
The lithium ion battery of this comparative example was prepared in substantially the same manner as in example 4, except that in step 3, the composition of each positive electrode sheet of the electrode assembly was all the same as that of the external positive electrode sheet in example 1.
Performance testing
The lithium ion batteries of examples and comparative examples were subjected to performance tests, the test results are shown in tables 1 and 2,
1) high temperature charge and discharge test
After the lithium ion battery is placed for 2 hours at the ambient temperature of 45 +/-2 ℃, the lithium ion battery is charged and discharged, and each charging and discharging is carried out in the environment of 45 +/-2 ℃: constant current charging to 4.25V at 3C rate, then constant voltage charging to 2.5C at 4.25V voltage, constant current charging to 4.35V at 2.5C rate, constant voltage charging to 2C at 4.35V voltage, constant current charging to 4.4V at 2C rate, constant voltage charging to 1.5C at 4.4V voltage, constant current charging to 4.5V at 1.5C rate, constant voltage charging to 0.025C at 4.5V voltage, then standing for 5min, discharging at 0.7C, cutting off voltage 3.0V, and standing for 5 min. The step is circulated to monitor the capacity retention rate of the battery in the charging and discharging process.
2) Low temperature charge and discharge test
After the lithium ion battery is placed for 2 hours at the ambient temperature of 25 +/-2 ℃, the lithium ion battery is charged and discharged: charging to 4.5V at constant current under 0.7C multiplying power, charging to 0.025C at constant current under 4.5V voltage, standing for 5min, placing the lithium ion battery in a 0 +/-2 ℃ constant temperature box, standing for 4h, discharging to 3.4V at 0.2C, standing for 5min, and monitoring the capacity retention rate in the 0 ℃ discharging process.
TABLE 1
In Table 1, SInner part：SIn：SOuter coverRefers to the ratio of the number of the internal positive plates, the number of the intermediate positive plates and the number of the external positive plates, SIn the first：SIn the third place：SIn the second placeRefers to the ratio of the number of the first intermediate positive plate, the third intermediate positive plate and the second intermediate positive plate.
TABLE 2
In Table 2, SInner part：SIn：SOuter coverRefers to the ratio of the number of the winding sections of the internal positive plate, the middle positive plate and the external positive plate, SIn the first：SIn the second placeRefers to the ratio of the number of the first intermediate positive electrode sheet winding section and the second intermediate positive electrode sheet winding section.
As can be seen from tables 1 and 2, the lithium ion battery in the embodiment of the present invention has both excellent high-temperature high-voltage charge/discharge performance and low-temperature discharge performance, and a wide application range, which indicates that the specific selection of D50 of the positive electrode active material of different positive electrode sheets can improve the high-temperature high-voltage charge/discharge performance and the low-temperature discharge performance of the battery, and broaden the application range of the lithium ion battery.
Further, when D50 of the positive electrode active material of the internal positive electrode sheet satisfies: d50 with the particle size of 14 mu m or lessInner partLess than or equal to 20 mu m; and/or D50 of positive active material of external positive plateOuter coverSatisfies the following conditions: d50 with the particle size of 8 mu m or lessOuter coverAt less than 14 μm, the electrode assembly enables the batteryHas more excellent high-temperature and high-voltage charge and discharge performance and low-temperature discharge performance.
When the D50 of the positive active materials of the inner positive plate, the middle positive plate and the outer positive plate is gradually decreased, the electrode assembly can enable the lithium ion battery to have more excellent high-temperature high-voltage charge and discharge performance and low-temperature discharge performance.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. An electrode assembly comprising a positive electrode tab including an internal positive electrode tab located inside the electrode assembly, an external positive electrode tab located outside the electrode assembly, and an intermediate positive electrode tab located between the internal positive electrode tab and the external positive electrode tab, wherein D50 of a positive electrode active material of the internal positive electrode tabInner partD50 of positive electrode active material of the external positive electrode sheetOuter coverD50 of positive electrode active material of the intermediate positive electrode sheetInThe following relationship is satisfied: d50Inner partGreater than D50Outer cover，D50InNot greater than D50Inner partAnd D50InNot less than D50Outer cover。
2. The electrode assembly of claim 1, wherein the electrode assembly is a lamination stack;
the number ratio of the internal positive plate to the intermediate positive plate to the external positive plate is 1: (1-4): 1, and D50Inner part＝D50In(ii) a Or,
the number ratio of the internal positive plate to the intermediate positive plate to the external positive plate is 1: (1-4): 1, and D50Outer cover＝D50In。
3. The electrode assembly according to claim 1, wherein the electrode assembly is a laminate structure, the intermediate positive electrode tab includes a first intermediate positive electrode tab and a second intermediate positive electrode tab, and the first intermediate positive electrode tab is adjacent to the inner positive electrode tab, wherein D50 of the positive electrode active material of the first intermediate positive electrode tabIn the firstD50 of positive electrode active material of the second intermediate positive electrode sheetIn the second placeThe number ratio of the internal positive plate to the first intermediate positive plate to the second intermediate positive plate to the external positive plate satisfies the following relationship;
the number ratio of the internal positive plate, the first intermediate positive plate, the second intermediate positive plate and the external positive plate is (1-2): (1-8): (1-8): (1-2), and D50Inner part＝D50In the first，D50Outer cover＝D50In the second place。
4. The electrode assembly according to claim 1, wherein the electrode assembly has a laminated structure, the number of the intermediate positive electrode tabs is N, and the D50 of the positive electrode active materials in the internal positive electrode tabs, the N intermediate positive electrode tabs and the external positive electrode tabs gradually decreases in a direction in which the internal positive electrode tabs point to the external positive electrode tabs, and N is greater than or equal to 1.
5. The electrode assembly according to claim 1, wherein the electrode assembly is a wound structure, and the inner positive electrode tab, the middle positive electrode tab and the outer positive electrode tab are connected end to end in sequence;
the number ratio of the winding sections of the internal positive plate, the intermediate positive plate and the external positive plate is 1: (1-4): 1, and D50Inner part＝D50In(ii) a Or,
the number ratio of the winding sections of the internal positive plate, the intermediate positive plate and the external positive plate is 1: (1-4): 1, and D50Outer cover＝D50In。
6. The electrode assembly of claim 1, wherein the electrode assembly is a winding structure, the internal positive plate, the intermediate positive plate and the external positive plate are sequentially connected end to end, the intermediate positive plate comprises a first intermediate positive plate and a second intermediate positive plate, the first intermediate positive plate is close to the internal positive plate, the first intermediate positive plate comprises M1 winding sections sequentially connected end to end, the second intermediate positive plate comprises M2 winding sections sequentially connected end to end, M1 is not less than 1, M2 is not less than 1, and D50 of the positive active material of the first intermediate positive plate is D50In the firstD50 of positive electrode active material of the second intermediate positive electrode sheetIn the second placeThe number ratio of the winding sections of the internal positive plate, the first intermediate positive plate, the second intermediate positive plate and the external positive plate satisfies the following relationship;
the number ratio of the winding sections of the internal positive plate, the first intermediate positive plate, the second intermediate positive plate and the external positive plate is (1-2): (1-8): (1-8): (1-2), and D50Inner part＝D50In the first，D50Outer cover＝D50In the second place。
7. The electrode assembly according to any one of claims 1 to 6, wherein D50 of the positive electrode active material of the internal positive electrode tabInner partSatisfies the following conditions: d50 with the particle size of 14 mu m or lessInner partLess than or equal to 20 mu m; and/or the presence of a gas in the gas,
d50 of positive electrode active material of the external positive electrode sheetOuter coverSatisfies the following conditions: d50 with the particle size of 8 mu m or lessOuter cover≤14μm。
8. The electrode assembly according to claim 7, wherein the particle size distribution of the positive electrode active material of the internal positive electrode tab is: d10 with the particle size of 7 mu m or lessInner part≤12μm，28μm≤D90Inner partLess than or equal to 35 mu m; and/or the presence of a gas in the gas,
the particle size distribution of the positive active material of the external positive plate is as follows: d10 with the particle size of 2 mu m or lessOuter cover≤7μm，18μm≤D90Outer cover≤27μm。
9. The electrode assembly according to claim 7 or 8, wherein the positive electrode active layer of the internal positive electrode tab comprises, in mass percent: 90 to 99 percent of positive active material, 0.5 to 5 percent of binder and 0.5 to 5 percent of conductive agent; and/or the presence of a gas in the gas,
the positive active layer of the external positive plate comprises the following components in percentage by mass: 90 to 99 percent of positive active material, 0.5 to 5 percent of binder and 0.5 to 5 percent of conductive agent.
10. A lithium ion battery comprising the electrode assembly of any one of claims 1-9.
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