CN118448564A - Negative electrode plate and secondary battery - Google Patents

Negative electrode plate and secondary battery Download PDF

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Publication number
CN118448564A
CN118448564A CN202410616892.1A CN202410616892A CN118448564A CN 118448564 A CN118448564 A CN 118448564A CN 202410616892 A CN202410616892 A CN 202410616892A CN 118448564 A CN118448564 A CN 118448564A
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China
Prior art keywords
infiltration
active material
negative electrode
material layer
current collector
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CN202410616892.1A
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Chinese (zh)
Inventor
胡迪伦
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Dongguan Weike Battery Co ltd
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Dongguan Weike Battery Co ltd
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Priority to CN202410616892.1A priority Critical patent/CN118448564A/en
Publication of CN118448564A publication Critical patent/CN118448564A/en
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/04—Processes of manufacture in general
    • 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
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • 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
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative 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)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a negative electrode plate which comprises a current collector and a negative electrode active material layer coated on the current collector, wherein the negative electrode active material layer forms an infiltration structure through a laser process; the impregnating structure comprises at least one first impregnating groove formed along the length direction X of the current collector and at least two second impregnating grooves formed along the width direction Y of the current collector, the impregnating speed of electrolyte to the pole piece can be improved through the arrangement of the impregnating grooves, lithium precipitation is prevented, and the charging window of the battery can be improved; the depth of the first infiltration groove and the depth of the second infiltration groove are A, the thickness of the anode active material layer is Z, and the A and the Z satisfy the relation: a=0.05 to 0.95Z; the width B of the first infiltration tank and the second infiltration tank is 5-100 mu m, and the electrolyte has good infiltration effect in the horizontal and vertical directions by controlling the depth and the width of the infiltration tanks. In addition, the invention also discloses a secondary battery comprising the negative plate.

Description

Negative electrode plate and secondary battery
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a negative electrode plate and a secondary battery.
Background
Lithium ion batteries are increasingly used in the fields of mobile phones, computers, tablets, bluetooth headsets, electric tools, automobiles, energy storage and the like. The customers put higher demands on the energy density, the multiplying power performance and the cycle life of the lithium ion battery, and the development of batteries with high energy density, quick charge and long cycle life has become industry consensus, so that the thick electrode technology is widely used in the batteries, namely, the number of layers of the pole pieces and the current collector is reduced by increasing the thickness of the active material layer of the pole pieces of the battery under the condition that the total thickness of the battery is unchanged, so that the energy density of the whole battery is improved.
At present, the active material layer is perforated to enable electrolyte to directly enter the active material layer, so that the migration path of lithium ions is shortened, the rate capability and the cycle performance of the battery are improved, and lithium precipitation on the surface of an electrode is reduced. However, although this method increases the infiltration rate of the electrolyte in the vertical direction of the pole piece, it cannot increase the infiltration rate of the electrolyte in the horizontal direction of the pole piece. The lithium separation condition in the middle of the pole piece is improved by punching, but the lithium separation condition of the edge of the pole piece exposed to the electrolyte and supplied by excessive lithium cannot be improved, so that the improvement range of the multiplying power performance and the cycle performance of the battery after punching is smaller.
Based on this, there is a need to invent a negative electrode sheet to solve the foregoing technical problems.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects in the prior art, the negative plate is provided with a wetting structure, so that electrolyte has good wetting property on the negative plate.
In order to solve the technical problems, the application adopts the following technical scheme:
The negative electrode plate comprises a current collector and a negative electrode active material layer coated on the current collector, wherein the negative electrode active material layer is formed with a wetting structure through a laser process; the infiltration structure comprises at least one first infiltration groove formed along the length direction X of the current collector and at least two second infiltration grooves formed along the width direction Y of the current collector; the depth of the first infiltration groove and the depth of the second infiltration groove are A, the thickness of the anode active material layer is Z, and the A and the Z satisfy the relation: a=0.05 to 0.95Z; the width B of the first infiltration tank and the second infiltration tank is 5-100 mu m.
Specifically, a and Z satisfy the relationship: a=0.35 to 0.45Z; the width B of the first infiltration tank and the second infiltration tank is 45-55 mu m.
Specifically, the first infiltration tank and the second infiltration tank are both arranged in a linear structure, and the first infiltration tank is perpendicular to the second infiltration tank;
the distance C between two adjacent second infiltration grooves is 1.9-2.1 mm, the distance D between the second infiltration grooves and the two edges of the negative electrode active material layer in the length direction X of the current collector is 2-6 mm, and the distance F between the second infiltration grooves and the two edges of the negative electrode active material layer in the width direction Y of the current collector is 0.1-0.9 mm.
Specifically, an uncoated empty foil area is reserved on the current collector, and the distance H between the second infiltration groove and the empty foil area in the width direction Y of the current collector is 0.8-1.6 mm; and the distance I between the two second infiltration grooves close to the empty foil area and the empty foil area is less than or equal to 3.5mm in the length direction X of the current collector.
Specifically, the number of the first infiltration grooves is one, the number of the second infiltration grooves is multiple, and the intervals between two adjacent second infiltration grooves are equal.
Specifically, the number of the first infiltration tanks is multiple, and the intervals L 1 between two adjacent first infiltration tanks are equal; the number of the second infiltration tanks is multiple, and the interval L 2 between two adjacent second infiltration tanks is equal; the satisfaction of L 1 and L 2: l 1≤L2.
Specifically, the first infiltration grooves and the second infiltration grooves are all arranged to be of a linear structure, the number of the first infiltration grooves is one, the first infiltration grooves are parallel to the length direction X of the current collector, the number of the second infiltration grooves is multiple, and the end parts of two adjacent second infiltration grooves are communicated to form a V-shaped structure.
Specifically, the first infiltration tank and the second infiltration tank are all set up to the straight line structure, the first infiltration tank with the quantity of second infiltration tank is many, two adjacent the tip intercommunication of first infiltration tank, two adjacent the tip intercommunication of second infiltration tank, and they all form continuous "V" shape structure.
Specifically, the first infiltration tank and the second infiltration tank are all set to curve structures, the first infiltration tank and the second infiltration tank are mutually communicated to form various irregular patterns uniformly distributed on the anode active material layer, and the sum of the areas of the first infiltration tank and the second infiltration tank accounts for 10% -30% of the area of the anode active material layer.
Specifically, the sum of the areas of the first infiltration groove and the second infiltration groove accounts for 20% of the area of the anode active material layer, and the first infiltration groove and the second infiltration groove are uniformly distributed in the center of the anode active material layer.
Specifically, the negative electrode active material layer comprises a first active material layer and a second active material layer coated on the first active material layer, wherein the first active material layer is coated on at least one surface of the current collector; the first active material layer is a high-compaction graphite layer, the second active material layer is a fast-charging graphite layer, and the infiltration structure is arranged on the second active material layer through a laser process.
Specifically, the lithium ion battery further comprises a conductive carbon layer, wherein the conductive carbon layer is arranged between the current collector and the negative electrode active material layer.
The invention has the beneficial effects that: the first infiltration tank and the second infiltration tank which are formed in the length direction and the width direction through the laser process provide channels for the electrolyte to circulate, so that the infiltration speed of the electrolyte in the horizontal direction is high, the lithium ion concentration difference of the electrolyte at the edge position and the center position of the negative electrode plate is reduced, the negative electrode plate is not easy to separate lithium, and the lithium ion infiltration channels are formed by controlling the relation between the depth of the first infiltration tank and the second infiltration tank and the thickness of the active material layer and the width of the first infiltration tank and the second infiltration tank, so that lithium ions can directly enter the active material layer, the transmission path of the lithium ions is reduced, and the high-rate charge and discharge performance of the battery is improved.
The second object of the present invention is: the utility model provides a secondary battery, including the positive plate that is convoluteed each other or piles up and above-mentioned negative plate, the negative plate divide into excess region and overlap region, before the laser technology handles, the capacity of negative plate with the capacity of positive plate's ratio is CB 1, after the laser technology handles, forms infiltration structure, the capacity of negative plate with the capacity of positive plate's ratio is CB 2, and they satisfy the relational expression: CB 1-CB2 is more than or equal to 0.005 and less than or equal to 0.03.
Specifically, before the laser process treatment, the ratio of the capacity of the negative plate to the capacity of the positive plate is CB 1, after the laser process treatment, an infiltration structure is formed, the ratio of the capacity of the negative plate to the capacity of the positive plate is CB 2, and they satisfy the relation: CB 1-CB2 is less than or equal to 0.01 and less than or equal to 0.02, so that the battery keeps proper CB value after the infiltration structure is formed, and lithium precipitation caused by too small CB value is prevented.
Specifically, the absolute value of the difference between the thickness of the exceeding area and the thickness of the overlapping area is less than or equal to 8 mu m.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention and do not constitute a limitation on the invention. In the drawings:
FIG. 1 is a schematic diagram of embodiment 1 of the present invention;
FIG. 2 is a second schematic structural diagram of embodiment 1 of the present invention;
FIG. 3 is a schematic structural diagram of embodiment 2 of the present invention;
FIG. 4 is a schematic structural view of embodiment 3 of the present invention;
FIG. 5 is a schematic view of the structure of embodiment 4 of the present invention;
FIG. 6 is a schematic structural diagram of embodiment 5 of the present invention;
FIG. 7 is a schematic view of the structure of embodiment 6 of the present invention;
FIG. 8 is a schematic view of the structure of embodiment 7 of the present invention;
FIG. 9 is a schematic view of the structure of embodiment 8 of the present invention;
FIG. 10 is a schematic view showing the structure of embodiment 9 of the present invention;
FIG. 11 is a schematic view of the structure of embodiment 10 of the present invention;
FIG. 12 is a schematic view showing the structure of embodiment 11 of the present invention;
FIG. 13 is a graph comparing infiltration rates for perforated and unperforated pole pieces according to the present invention;
Wherein: 1-a current collector; 2-a negative electrode active material layer; 21-a first active material layer; 22-a second active material layer; 3-infiltration structure; 31-a first infiltration tank; 32-a second infiltration tank; 4-empty foil areas; a 5-conductive carbon layer; 100-negative electrode sheet; 101-out of area; 102-overlapping region; 200-positive plate.
Detailed Description
The following description of the embodiments of the present application will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
The present invention will be described in further detail below with reference to the drawings, but is not limited thereto.
Example 1
As shown in fig. 1-2, the present inventors have found that the prior art negative electrode sheet 100 mainly reduces lithium precipitation of the negative electrode sheet 100 in the case of high-rate charge and discharge by punching holes in the surface of the negative electrode sheet 100. However, punching the surface of the negative electrode sheet 100 slightly increases the wetting rate of the electrolyte in the horizontal direction of the negative electrode sheet 100, and the edges of the negative electrode sheet 100 are exposed to excessive lithium supply in the electrolyte, resulting in rapid lithiation saturation and even lithium dendrite growth. Meanwhile, the core region of the negative electrode sheet 100 cannot obtain enough lithium from the electrolyte, and a low lithiation level is maintained even after a charging operation, and the manner of punching the negative electrode sheet 100 reduces the negative electrode active material more aggravates the excessive lithium supply of the negative electrode, resulting in easier lithium precipitation. Based on the problem, the inventor can make electrolyte diffuse into the soaking structure 3 of the negative electrode plate 100 rapidly through the first soaking groove 31 and the second soaking groove 32 arranged in the length direction X and the width direction Y of the current collector 1, and diffuse into active substances at each position of the negative electrode plate 100 from the saturated soaking structure 3, and meanwhile, surrounding electrolyte is replenished continuously rapidly, so that the ion transmission efficiency is effectively accelerated, lithium ions with higher concentration at the edge are transmitted to the central area of the negative electrode plate 100 in time, and lithium precipitation at the edge of the negative electrode plate 100 is prevented. In addition, the CB value after the laser process is controlled, so that lithium precipitation of the battery is further prevented.
As shown in fig. 1-2, the application provides a negative electrode sheet 100, which comprises a current collector 1 and a negative electrode active material layer 2 coated on the current collector 1, wherein the negative electrode active material layer 2 is provided with an infiltration structure 3 through a laser process, the infiltration rate of the negative electrode sheet 100 in the horizontal direction is improved through the arrangement of the infiltration structure 3, the transmission of lithium ions is facilitated, the concentration difference of the lithium ions at each position of the negative electrode sheet 100 is reduced, and the lithium precipitation caused by the overhigh concentration of the lithium ions in a part of area is prevented; the impregnating structure 3 comprises at least one first impregnating groove 31 formed along the length direction X of the current collector 1 and at least two second impregnating grooves 32 formed along the width direction Y of the current collector 1, and the lithium ion transmission speed to the position of the edge of the width direction Y of the negative electrode sheet 100 can be improved by arranging more second impregnating grooves 32 than the first impregnating grooves 31; the first and second infiltration grooves 31 and 32 have a depth a, and the negative electrode active material layer 2 has a thickness Z, and a and Z satisfy the relation: a=0.05 to 0.95Z, and when the relation is satisfied, the depth of the infiltration groove can satisfy the infiltration requirement of the negative electrode sheet 100 on the electrolyte, and the energy density of the negative electrode sheet 100 is not excessively reduced too deeply, the value range of the thickness Z is 30 to 70 μm, and the corresponding value of a can be 1.5 μm, 6.5 μm, 11.5 μm, 16.5 μm, 21.5 μm, 26.5 μm, 31.5 μm, 36.5 μm, 41.5 μm, 46.5 μm, 51.5 μm, 56.5 μm, 61.5 μm and 66.5 μm; the width B of the first infiltration tank 31 and the second infiltration tank 32 is 5-100 μm, so that the infiltration effect of the electrolyte on the active substances of the negative electrode sheet 100 is better, the formation of the groove capillary structure is facilitated, and the surrounding electrolyte can be rapidly supplemented into the infiltration structure 3.
Preferably, a and Z satisfy the relation: a=0.35 to 0.45Z; the width B of the first and second infiltration grooves 31 and 32 is 45 to 55 μm, and the infiltration effect and capillary effect of the negative electrode sheet 100 are better in the above-described range.
Example 2
As shown in fig. 1 to 3, unlike example 1, the following are: the first immersion groove 31 and the second immersion groove 32 in this embodiment are both configured as a linear structure, the first immersion groove 31 is perpendicular to the second immersion groove 32, and the center of the area surrounded by the first immersion groove 31 and the second immersion groove 32 is closest to the first immersion groove 31 and the second immersion groove 32 when the areas are the same.
The distance C between two adjacent second infiltration grooves 32 is 1.9 mm-2.1 mm, so that all positions of the negative electrode plate 100 are well infiltrated, the distance D between the second infiltration grooves 32 and two edges of the negative electrode active material layer2 in the length direction X of the current collector 1 is 2-6 mm, the distance F between the second infiltration grooves 32 and two edges of the negative electrode active material layer2 in the width direction Y of the current collector 1 is 0.1-0.9 mm, the electric field at the edge of the negative electrode plate 100 is strong, and lithium is easy to separate out in the concave position of the infiltration structure 3 when the infiltration structure 3 is arranged on the edge. The spacing of the edges of the present application may prevent lithium precipitation from the wetting structure 3 near the edges, and in some embodiments the spacing of the first and second wetting grooves 31 and 32 may be set to be smaller at the edges and larger at the middle portions, in such a way that lithium precipitation at the edges of the negative electrode sheet 100 may be reduced.
The other structures are the same as those of embodiment 1, and will not be described here again.
Example 3
As shown in fig. 4, unlike example 2, there is: the current collector 1 of the embodiment is provided with an uncoated empty foil region 4 which can be used for arranging a tab, and the distance H between the second infiltration groove 32 and the empty foil region 4 in the width direction Y of the current collector 1 is 0.8-1.6 mm; in the length direction X of the current collector 1, the distance I between the two second infiltration grooves 32 close to the empty foil region 4 and the empty foil region 4 is smaller than or equal to 3.5mm, and lithium precipitation near the electrode lugs can be prevented by controlling.
The other structures are the same as those of embodiment 1, and will not be described here again.
Example 4
As shown in fig. 1 to 5, unlike embodiment 2 or 3, there is: in this embodiment, the number of the first infiltration grooves 31 is one, the number of the second infiltration grooves 32 is plural, and the intervals between two adjacent second infiltration grooves 32 are equal, so that the improvement of the infiltration effect of each region on the vertical direction of the active material layer is the same when the intervals are equal, and the lithium precipitation caused by the long internal resistance of the lithium ion transmission path in the region with larger interval during high-rate charge and discharge can be prevented.
The other structures are the same as those of embodiment 1, and will not be described here again.
Example 5
As shown in fig. 1 to 6, unlike embodiment 2 or 3, there is: the number of the first infiltration slots 31 in the embodiment is multiple, and the spacing L 1 between two adjacent first infiltration slots 31 is equal; the number of the second infiltration grooves 32 is multiple, and the spacing L 2 between two adjacent second infiltration grooves 32 is equal; the satisfaction of L 1 and L 2: l 1≤L2, the L 2 is larger when the negative electrode plate 100 is a coiled electrode plate, so that the processing difficulty of the electrode plate can be reduced.
The other structures are the same as those of embodiment 1, and will not be described here again.
Example 6
As shown in fig. 1, 2 and 7, unlike embodiment 1, there is: the first infiltration grooves 31 and the second infiltration grooves 32 of the embodiment are all arranged to be of a linear structure, the number of the first infiltration grooves 31 is one, the first infiltration grooves 31 are parallel to the length direction X of the current collector 1, the number of the second infiltration grooves 32 is multiple, the end parts of two adjacent second infiltration grooves 32 are communicated, and a V-shaped structure is formed, because the end parts between the second infiltration grooves 32 are communicated with each other, the laser etching of the first infiltration grooves 31 and the second infiltration grooves 32 can be completed at one time without stopping the travel route of the laser, and the processing efficiency is high.
The other structures are the same as those of embodiment 1, and will not be described here again.
Example 7
As shown in fig. 1,2 and 8, unlike embodiment 1, there is: the first infiltration tank 31 and the second infiltration tank 32 of this embodiment are all set up to the straight line structure, and the quantity of first infiltration tank 31 and second infiltration tank 32 is many, and the tip intercommunication of two adjacent first infiltration tanks 31, the tip intercommunication of two adjacent second infiltration tanks 32, and they all form continuous "V" shape structure, all have good effect of improving infiltration rate to the different directions of negative pole piece 100 when machining efficiency is high.
The other structures are the same as those of embodiment 1, and will not be described here again.
Example 8
As shown in fig. 1,2 and 9, unlike embodiment 1, there is: the first infiltration tank 31 and the second infiltration tank 32 of this embodiment are all set to a curve structure, the first infiltration tank 31 and the second infiltration tank 32 are mutually communicated to form various irregular patterns uniformly distributed in the anode active material layer 2, the sum of the areas of the first infiltration tank 31 and the second infiltration tank 32 accounts for 10% -30% of the area of the anode active material layer 2, along with the increase of intelligent electronic equipment in the development of technology, the shape of the battery is diversified, the infiltration structure 3 is set in an irregular form, and the infiltration structure 3 can be made to adapt to anode sheets 100 in different shapes.
Preferably, the sum of the areas of the first and second infiltration grooves 31 and 32 occupies 20% of the area of the anode active material layer 2, and the first and second infiltration grooves 31 and 32 are uniformly distributed at the center of the anode active material layer 2, so that the infiltration effect of the electrolyte is the best.
The other structures are the same as those of embodiment 1, and will not be described here again.
Example 9
As shown in fig. 1, 2 and 10, the difference from any of the embodiments 1 to 8 is that: the anode active material layer 2 of the present embodiment includes a first active material layer 21 and a second active material layer 22 coated on the first active material layer 21, wherein the first active material layer 21 is coated on at least one surface of the current collector 1; the first active material layer 21 is a highly compacted graphite layer, the second active material layer 22 is a fast-charged graphite layer, and the wetting structure 3 is disposed on the second active material layer 22 by a laser process. The energy density of the negative electrode sheet 100 can be improved by the first active material layer 21 being high-compaction graphite, and the second active material layer 22 being rapid-filling graphite, which has relatively large pores, and can have better permeability, so that the electrolyte can permeate through and infiltrate the first active material layer 21. In addition, the arrangement of the wetting structure 3 on the second active material layer 22 can save cost because less active material is lost due to the laser process, and the arrangement of the wetting structure 3 can also improve the wettability of the electrolyte, thereby being beneficial to the wetting of the first active material layer 21.
The other structures are the same as those of any of embodiments 1 to 8, and will not be described here again.
Example 10
As shown in fig. 1,2 and 11, the difference from any of the embodiments 1 to 9 is that: the negative electrode sheet of this embodiment further includes a conductive carbon layer 5, the conductive carbon layer 5 is disposed between the current collector 1 and the negative electrode active material layer 2, and the arrangement of the conductive carbon layer 5 can reduce the resistance, thereby facilitating the transmission of current, enabling the deintercalation of lithium ions to be faster, and improving the high-rate discharge performance of the battery. In addition, the conductive carbon layer 5 can increase the binding force between the anode active material and the current collector, and prevent the battery from being invalid due to the occurrence of pole piece demoulding in the use process.
Other structures are the same as those of any of embodiments 1 to 9, and will not be described here again.
Example 11
As shown in fig. 12, the present application provides a secondary battery, including a positive electrode sheet 200 and any one of the above-mentioned negative electrode sheets 100 wound or stacked on each other, the negative electrode sheet 100 is divided into an excess region 101 and an overlap region 102, the ratio of the capacity of the negative electrode sheet to the capacity of the positive electrode sheet before laser processing is CB 1, after laser processing, a wet structure is formed, the ratio of the capacity of the negative electrode sheet to the capacity of the positive electrode sheet is CB 2, and they satisfy the relation: CB 1-CB2 is more than or equal to 0.005 and less than or equal to 0.03, and can prevent lithium from being separated due to too small CB value of the battery caused by laser process treatment. In addition, the arrangement of the infiltration structure 3 can be matched with the exceeding area 101, so that the lithium ion transmission speed of the exceeding area is improved, and the series lithium precipitation caused by the arrangement of the exceeding area 101 is prevented.
Preferably, before the laser process treatment, the ratio of the capacity of the negative plate to the capacity of the positive plate is CB 1, after the laser process treatment, an infiltration structure is formed, the ratio of the capacity of the negative plate to the capacity of the positive plate is CB 2, and they satisfy the relation: CB 1-CB2 is 0.01 to 0.02, and lithium is not easy to separate out from the battery in the range.
Preferably, the absolute value of the thickness difference between the excess region 101 and the overlap region 102 is 8 μm or less, preventing the thickness difference from being excessively large. During the charge and discharge of the battery, the active material expands and contracts when lithium ions are extracted, and when the thickness difference is too large, lithium is extracted due to the difference in the lithium extraction sequence between the exceeding region 101 and the overlapping region 102 and the difference in expansion and contraction.
In some embodiments, the excess region 101 is disposed in the length direction of the anode sheet 100, and the first infiltration groove 31 penetrates the anode active material layer 2; in other embodiments, the excess region 101 is disposed in the width direction of the electrode sheet, and the second infiltration groove 32 penetrates the anode active material layer 2.
When the lithium ion battery is charged, lithium ions flow from the positive electrode overlapping region 102 to the exceeding region 101, and in the subsequent discharging process, particularly when the current density is high, the negative electrode can preferentially delithiate in the overlapping region 102, so that the lithium ion deintercalation speeds of the overlapping region 102 and the exceeding region 101 in the negative electrode sheet 100 are different, namely the exceeding region 101 is lower, the overlapping region 102 is higher, and lithium ions in the exceeding region 101 are blocked by dynamics, so that the lithium ions need to migrate from the exceeding region 101 to the overlapping region 102 for a long time, and finally incomplete discharging is caused when the discharging cut-off condition is reached, so that reversible capacity loss is caused. After multiple charge and discharge cycles, the lithium precipitation phenomenon is further caused in the negative electrode region corresponding to the edge of the positive electrode and the vicinity thereof, and the infiltration groove is extended to the exceeding region 101, so that the infiltration of electrolyte in the exceeding region 101 is promoted, the transmission channel of lithium ions is increased, the transmission speed of the lithium ions in the exceeding region 101 is improved, and the reversible capacity loss caused by incomplete discharge is avoided.
The preparation process of the secondary battery comprises the following steps:
1. respectively preparing positive electrode slurry and negative electrode slurry;
2. Coating the positive electrode slurry on the surface of a positive electrode current collector, and then sequentially drying, rolling and cutting to obtain a positive electrode plate;
3. Coating the anode slurry on the surface of an anode current collector, sequentially drying, rolling and cutting, setting an exceeding area by prolonging the cutting distance in the cutting process, calculating CB 1, carrying out laser processing on the anode active material layer, wherein the thickness of the anode active material layer is 50 mu m, the parameters are 50 mu m in width and 20 mu m in depth, a first infiltration groove and a second infiltration groove formed by the laser processing are mutually perpendicular, measuring the value of CB 2, and judging whether the value of CB 1-CB2 is in the range of 0.005-or-not CB 1-CB2 -or-not 0.03, if the value of CB 1-CB2 is not in the range of 0.005-or-not, adjusting the area of the exceeding area by not conforming to the cutting equipment parameters until CB 1 and CB 2 meet the relation of 0.005-or-not CB 1-CB2 -not more than 0.03, and obtaining the anode sheet as in example 1, wherein CB 1 is 1.055, and CB 2 is 1.040, and CB 1-CB2 =0.015;
4. Preparation of a battery: and winding or laminating the positive plate, the isolating film and the negative plate to manufacture a bare cell, and then packaging and injecting electrolyte to manufacture the finished lithium ion battery.
Calculation formulas of CB 1 and CB 2:
CB 1 = (anode weight anode area anode active material ratio anode active material gram capacity)/(cathode weight cathode area cathode active material ratio cathode active material gram capacity)
CB 2 = ((anode weight-weight lost by laser process) anode area) anode active material ratio (anode active material gram capacity)/(cathode weight) cathode area (cathode active material ratio) cathode active material gram capacity).
Example 12
Unlike example 11, the following is: the laser process parameters had a width of 50 μm and a depth of 20. Mu.m, the spacing at the edges of the electrode sheets was 1.9mm, and the spacing in the middle was 2.0mm, to obtain a negative electrode sheet as in example 2.
The other components are the same as those in embodiment 11, and will not be described again here.
Example 13
Unlike example 11, the following is: the laser process parameters width 50 μm and depth 20 μm, the spacing H between the second wetting groove 32 and the empty foil region 4 was 1.2mm, and the spacing I between the second wetting groove 32 and the empty foil region 4 was 3.0mm, to obtain a negative electrode sheet as in example 3.
The other components are the same as those in embodiment 11, and will not be described again here.
Example 14
Unlike example 11, the following is: when the CB 1 is 1.055, the CB 2 is 1.050, and the CB 1-CB2 =0.005, the spacing between two adjacent second infiltration grooves 32 is equal during the laser processing, so as to obtain the negative electrode sheet as in example 4.
The other components are the same as those in embodiment 11, and will not be described again here.
Example 15
Unlike example 11, the following is: CB 1 is 1.055, CB 2 is 1.025, CB 1-CB2 =0.03.
The other components are the same as those in embodiment 11, and will not be described again here.
Example 16
Unlike example 11, the following is: the depth of the laser scribe was 15 μm and the width of the laser scribe was 35 μm.
The other components are the same as those in embodiment 11, and will not be described again here.
Example 17
Unlike example 11, the following is: the depth of the laser scribe was 25 μm and the width of the laser scribe was 65 μm.
The other components are the same as those in embodiment 11, and will not be described again here.
Example 18
Unlike example 11, the following is: the ends of the two adjacent second wetting grooves 32 are connected at the time of laser scribing, and a V-shaped structure is formed, resulting in a negative electrode sheet as in example 6.
The other components are the same as those in embodiment 11, and will not be described again here.
Comparative example 1
1. Respectively preparing positive electrode slurry and negative electrode slurry;
2. Coating the positive electrode slurry on the surface of a positive electrode current collector, and then sequentially drying, rolling and cutting to obtain a positive electrode plate;
3. coating the negative electrode slurry on the surface of a negative electrode current collector, and then sequentially drying, rolling and cutting to obtain a negative electrode plate, wherein the thickness of a negative electrode active material layer is 50 mu m;
4. Preparation of a battery: and winding or laminating the positive plate, the isolating film and the negative plate to manufacture a bare cell, and then packaging and injecting electrolyte to manufacture the finished lithium ion battery.
Comparative example 2
The difference from comparative example 1 is that: and coating the negative electrode slurry on the surface of a negative electrode current collector, sequentially drying, rolling and cutting, and then carrying out laser drilling treatment on the negative electrode active material layer, wherein the laser drilling parameter is 20 mu m in depth, so as to obtain a negative electrode plate, and the thickness of the negative electrode active material layer is 50 mu m.
The other components are the same as those of comparative example 1, and will not be described again here.
Comparative example 3
The difference from comparative example 1 is that: the negative electrode slurry is coated on the surface of a negative electrode current collector, then drying, rolling and cutting are sequentially carried out, an exceeding area is set by prolonging the cutting distance in the cutting process, CB 1 is calculated, the thickness of a negative electrode active material layer is 50 mu m, then laser processing is carried out on the negative electrode active material layer, the parameters are that the width is 50 mu m and the depth is 20 mu m, the value of CB 2 is calculated, and the negative electrode sheet CB 1 is 1.055, CB 2 is 1.020, and CB 1-CB2 =0.035.
The other components are the same as those of comparative example 1, and will not be described again here.
Comparative example 4
Unlike comparative example 3, the following are: CB 1 is 1.055, CB 2 is 1.053, CB 1-CB2 =0.002.
The other components are the same as those of comparative example 3, and will not be described again here.
Comparative example 5
Unlike comparative example 3, the following are: the laser scribing parameters were 15 μm width and 5 μm depth, CB 1 was 1.055, CB 2 was 1.040, CB 1-CB2 =0.015.
The other components are the same as those of comparative example 3, and will not be described again here.
Comparative example 6
Unlike comparative example 3, the following are: the laser scribing parameters were 70 μm width and 40 μm depth, CB 1 was 1.055, CB 2 was 1.040, CB 1-CB2 =0.015.
The other components are the same as those of comparative example 3, and will not be described again here.
Comparative example 7
Unlike comparative example 3, the following are: the negative plate is provided with an empty foil area 4, the laser scribing parameter is that the distance H between the second infiltration groove 32 and the empty foil area 4 is 2.5mm, the distance I between the second infiltration groove 32 and the empty foil area 4 is 6mm, CB 1 is 1.055, CB 2 is 1.040, and CB 1-CB2 =0.015.
The other components are the same as those of comparative example 3, and will not be described again here.
The lithium separation window is the maximum multiplying power corresponding to the fact that the battery cell is directly punched to the cut-off voltage under the conditions of 3.5C,3.4C,3.3C,3.2C,3.1C, 3.0C,2.9C and 2.8C, and lithium is not separated from the battery cell after the battery cell interface is disassembled.
And (3) testing the charge and discharge cycles of the lithium ion battery: the normal temperature capacity retention rate is that the battery after formation is charged to 3.0V (cut-off current is 0.05C) by using a 3C constant current at 23 ℃, then is discharged to 3.0V by using a 1C constant current, thus, the cyclic charge and discharge test is carried out, each discharge capacity is recorded, and the 500 th cycle capacity retention rate is calculated. The steps of the lithium ion battery N cycle capacity retention (%) =n cycle discharge capacity/first cycle discharge capacity are the same, the 45 ℃ capacity retention and the normal temperature capacity retention are the same, only the test temperature is different, and the details are not repeated here, and the results are shown in table 1.
TABLE 1
As is clear from the comparison of example 11 and comparative examples 3 to 6, when CB 1 and CB 2 do not satisfy the relation 0.005.ltoreq.CB 1-CB2.ltoreq.0.03, the CB value is too small, resulting in lithium precipitation; the CB value is too large, so that the capacity loss of the battery is caused, and the initial effect is reduced.
As can be seen from a comparison of example 11 and example 12, the capacity retention rate can be improved when the distance between the wetting structures at the edges is set smaller, since lithium precipitation is easier to form in the excess region when the excess region is set, and the lithium ion transmission in the excess region can be improved by reducing the distance between the wetting structures at the edges, thereby reducing lithium precipitation and improving the capacity retention rate.
As is clear from the comparison of examples 11, 14 and comparative example 4, as the value of CB 1-CB2 decreases, the lithium precipitation window and capacity retention rate of the battery decrease, because as the value of CB 1-CB2 decreases, the active material treated by the laser process becomes less, resulting in insufficient wettability of the electrolyte, and lithium precipitation tends to occur.
As is clear from the comparison between example 11 and comparative example 3, when the value of CB 1-CB2 is too large, the value of CB of the battery after laser processing is too small, and lithium precipitation easily occurs.
As is clear from comparison of examples 11, 16, 17 and comparative examples 5 and 6, when the depth of the laser process and the width of the laser process are too large, lithium is separated out from the battery due to serious structural damage, and when the depth of the laser process and the width of the laser process are too small, the improvement of shortening the lithium ion transmission path of the battery is not obvious, the effect of improving the infiltration speed of the electrolyte to the polar plate cannot be achieved, and lithium ions are easily separated out when the lithium ion battery is charged and discharged at a high rate.
As is clear from comparison between example 13 and comparative example 7, since the empty foil region cannot desorb lithium ions, when the distance between the wetting structure 3 and the empty foil region 4 is too large, too many lithium ions cannot be timely transmitted to other positions of the negative electrode sheet, which easily results in lithium precipitation near the empty foil region, and both the lithium precipitation window and the capacity retention rate of the battery are reduced.
As is clear from comparison of example 11 and example 18, the capacity retention rate of the battery slightly decreased when the negative electrode sheet of example 6 was selected, but the negative electrode sheet of example 6 was selectively produced in order to increase the speed of the laser process.
Comparison of infiltration rates for example 11 and comparative examples 1-2:
the negative electrode sheet to be tested is cut into a preset shape to obtain a coating sample, the coating sample is horizontally placed in a closed diffusion device, electrolyte is vertically dripped into the coating sample from the upper end of the diffusion device, the dripping amount of the test solvent is recorded, the dripping amount of the electrolyte is 2mg, the time of completely infiltrating the coating sample by the electrolyte is measured, the detection of the coating infiltration rate of the battery is completed, and the measurement result is shown in figure 13.
It can be seen that the negative electrode sheet of example 11 of the present application has a faster wetting rate than the perforated negative electrode sheet of comparative example 2 and the negative electrode sheet of comparative example 1, which is not treated.
While the foregoing description illustrates and describes the preferred embodiments of the present invention, it is to be understood that the invention is not limited to the forms disclosed herein, but is not to be construed as limited to other embodiments, and is capable of numerous other combinations, modifications and environments and is capable of changes or modifications within the scope of the inventive concept, either as a result of the foregoing teachings or as a result of the knowledge or skills of the relevant art. And that modifications and variations which do not depart from the spirit and scope of the invention are intended to be within the scope of the appended claims.

Claims (10)

1. A negative electrode sheet, characterized in that: the cathode active material layer (2) is formed with a wetting structure (3) through a laser process;
the infiltration structure (3) comprises at least one first infiltration groove (31) formed along the length direction X of the current collector (1) and at least two second infiltration grooves (32) formed along the width direction Y of the current collector (1);
The depth of the first infiltration groove (31) and the depth of the second infiltration groove (32) are A, the thickness of the anode active material layer (2) is Z, and the A and Z satisfy the relation: a=0.05 to 0.95Z; the width B of the first infiltration tank (31) and the second infiltration tank (32) is 5-100 mu m.
2. The negative electrode sheet according to claim 1, characterized in that: the first infiltration tank (31) and the second infiltration tank (32) are both arranged in a linear structure, and the first infiltration tank (31) is perpendicular to the second infiltration tank (32);
The distance C between two adjacent second infiltration grooves (32) is 1.9-2.1 mm, the distance D between the second infiltration grooves (32) and two edges of the negative electrode active material layer (2) in the length direction X of the current collector (1) is 2-6 mm, and the distance F between the second infiltration grooves (32) and two edges of the negative electrode active material layer (2) in the width direction Y of the current collector (1) is 0.1-0.9 mm.
3. The negative electrode sheet according to claim 2, characterized in that: the current collector (1) is reserved with an uncoated empty foil area (4), and the distance H between the second infiltration groove (32) and the empty foil area (4) in the width direction Y of the current collector (1) is 0.8-1.6 mm; in the length direction X of the current collector (1), the distance I between the two second infiltration grooves (32) close to the empty foil area (4) and the empty foil area (4) is less than or equal to 3.5mm.
4. A negative electrode sheet according to claim 2 or 3, characterized in that: the number of the first infiltration grooves (31) is one or more, the number of the second infiltration grooves (32) is more than one, the distances L 1 between two adjacent first infiltration grooves (31) are equal, and the distances L 2 between two adjacent second infiltration grooves (32) are equal; the satisfaction of L 1 and L 2: l 1≤L2.
5. The negative electrode sheet according to claim 1, characterized in that: the utility model discloses a solar cell module, including first infiltration groove (31) and second infiltration groove (32), first infiltration groove (31) with the quantity of second infiltration groove (32) all sets up to the straight line structure, the quantity of first infiltration groove (31) is one or more, works as when the quantity of first infiltration groove (31) is one, first infiltration groove (31) with collector (1) length direction X is parallel, the quantity of first infiltration groove (31) with the quantity of second infiltration groove (32) is many, adjacent two the tip intercommunication of first infiltration groove (31), adjacent two the tip intercommunication of second infiltration groove (32), and they all form continuous "V" shape structure.
6. The negative electrode sheet according to claim 1, characterized in that: the first infiltration tank (31) and the second infiltration tank (32) are all arranged to be of curve structures, the first infiltration tank (31) and the second infiltration tank (32) are mutually communicated to form various irregular patterns which are uniformly distributed in the anode active material layer (2), and the sum of the areas of the first infiltration tank (31) and the second infiltration tank (32) accounts for 10% -30% of the area of the anode active material layer (2).
7. The negative electrode sheet according to claim 1, characterized in that: the negative electrode active material layer (2) comprises a first active material layer (21) and a second active material layer (22) coated on the first active material layer (21), and the first active material layer (21) is coated on at least one surface of the current collector (1); the first active material layer (21) is a high-compaction graphite layer, the second active material layer (22) is a fast-charging graphite layer, and the infiltration structure (3) is arranged on the second active material layer (22) through a laser process.
8. The negative electrode sheet according to claim 1, characterized in that: the cathode active material further comprises a conductive carbon layer (5), wherein the conductive carbon layer (5) is arranged between the current collector (1) and the cathode active material layer (2).
9. A secondary battery characterized in that: the cathode sheet (100) according to any one of claims 1 to 8, wherein the cathode sheet (100) is divided into an exceeding area (101) and an overlapping area (102), the ratio of the capacity of the cathode sheet (100) to the capacity of the cathode sheet (200) is CB 1 before the laser processing, a wetting structure (3) is formed after the laser processing, the ratio of the capacity of the cathode sheet (100) to the capacity of the cathode sheet (200) is CB 2, and the following relations are satisfied: CB 1-CB2 is more than or equal to 0.005 and less than or equal to 0.03.
10. The secondary battery according to claim 9, wherein: the thickness of the excess region (101) differs from the thickness of the overlap region (102) by an absolute value of 8 [ mu ] m or less.
CN202410616892.1A 2024-05-17 2024-05-17 Negative electrode plate and secondary battery Pending CN118448564A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118659052A (en) * 2024-08-16 2024-09-17 宁德时代新能源科技股份有限公司 Battery monomer and preparation method thereof, battery device and power-using device
WO2026065478A1 (en) * 2024-09-30 2026-04-02 宁德新能源科技有限公司 Secondary battery and electronic device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN118659052A (en) * 2024-08-16 2024-09-17 宁德时代新能源科技股份有限公司 Battery monomer and preparation method thereof, battery device and power-using device
CN118659052B (en) * 2024-08-16 2024-12-24 宁德时代新能源科技股份有限公司 Battery cell and preparation method thereof, battery device and power-using device
WO2026065478A1 (en) * 2024-09-30 2026-04-02 宁德新能源科技有限公司 Secondary battery and electronic device

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