CN115249785A - Battery positive plate and preparation method and application thereof - Google Patents

Battery positive plate and preparation method and application thereof Download PDF

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Publication number
CN115249785A
CN115249785A CN202110463078.7A CN202110463078A CN115249785A CN 115249785 A CN115249785 A CN 115249785A CN 202110463078 A CN202110463078 A CN 202110463078A CN 115249785 A CN115249785 A CN 115249785A
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battery
region
active material
active
passivated
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牛富军
焦晓朋
魏彦宽
江正福
李娜
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BYD Co Ltd
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BYD Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • 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
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 application provides a battery positive plate, which comprises a current collector and an active material layer arranged on the surface of the current collector; the active material layer includes an active region and passivation regions on opposite sides of the active region in a first direction; the active region and the passive region include an active material; compacted density p of passivated regions 2 Greater than the compacted density p of the active area 1 . The positive plate of the battery has good structural stability, is not easy to fall off, and can effectively inhibit the lithium precipitation of the batteryWhen the lithium ion battery is applied to the battery, the cycle performance and the safety performance of the battery can be effectively improved, and the energy density of the battery cannot be influenced, so that the battery is ensured to have excellent electrochemical performance. The application also provides a preparation method and application of the battery positive plate.

Description

Battery positive plate and preparation method and application thereof
Technical Field
The application relates to the technical field of batteries, in particular to a battery positive plate and a preparation method and application thereof.
Background
In the preparation process of the battery pole piece, because a blank current collector is reserved to weld a tab, the battery pole piece is usually prepared by adopting an intermittent coating method. However, the thickness of the edge of the active material layer formed by the intermittent coating method is not uniform, and the active material layer with non-uniform thickness can cause lithium precipitation and material dropping of the electrode plate, which is not favorable for long-term use of the battery.
In order to reduce the influence of the thickness unevenness of the active material layer on the battery, a method of attaching an adhesive tape to the edge position of the active material layer to suppress the lithium precipitation and the material falling of the battery is currently adopted. However, the adhesive in the tape easily diffuses into the electrolyte, reducing the performance of the battery; and after the battery with the positive electrode rubberized is subjected to multiple charge-discharge cycles, more lithium dendrites can still be precipitated on the surface of the negative electrode corresponding to the rubberized position, and the formed lithium dendrites can reduce the safety performance of the battery on one hand, and can cause the reduction of the battery capacity and the attenuation of the battery cycle performance on the other hand, so that the use of the battery is not facilitated.
Disclosure of Invention
In view of this, the present application provides a positive plate of a battery, which has good structural stability, is not prone to material dropping, and can effectively inhibit lithium precipitation of a negative electrode of the battery, and when the positive plate is applied to the battery, the cycle performance and the safety performance of the battery can be effectively improved, and the energy density of the battery is not affected, so that the battery has excellent electrochemical performance.
The application provides a battery positive plate in a first aspect, which comprises a current collector and an active material layer arranged on the surface of the current collector; the active material layer includes an active region and passivation regions on opposite sides of the active region in the first direction; the active region and the passive region comprise an active material; compacted density p of the passivated region 2 Greater than the compacted density p of the active area 1 。
At present, when an intermittent coating method is adopted to coat an active material layer on the surface of a current collector, because a machine adopts segmented coating, the thicknesses of the active material layers formed at the positions of starting coating and finishing coating by the machine are not uniform, so that the active material layer is unstable in structure, easy to drop materials and easy to generate lithium dendrites on a negative electrode, and the region with the non-uniform thickness is a defective region. According to the battery positive plate, the poor area is passivated, so that the compaction density of the passivated area is greater than that of the active area, and the higher compaction density can improve the structural stability of the positive electrode and reduce the phenomenon of material falling; on the other hand, the density of the passivation region is higher, the electrolyte is difficult to infiltrate, and the lithium ions of the active material in the passivation region are difficult to be extracted, so that the concentration of the lithium ions in the passivation region is reduced, and the phenomenon that lithium is separated out from the negative electrode opposite to the passivation region to form lithium dendrites is improved.
Optionally, the compacted density ρ of the passivated region 2 Compacted density p with the active area 1 Is greater than or equal to 1.1.
Optionally, the density of compaction of the passivated region ρ 2 A ratio to the true density of the active material is greater than or equal to 0.8.
Optionally, in the active material layer, an absolute value of a difference between the thickness of the passivation region and the thickness of the active region is less than or equal to 5 μm.
Optionally, the width of the passivation region along the first direction is 3mm-2cm.
Optionally, the active material comprises a material capable of reversibly intercalating and deintercalating lithium ions.
Optionally, the active material comprises LiFePO 4 、Li 3 V 2 (PO 4 ) 3 、LiMn 2 O 4 、LiMnO 2 、LiNiO 2 、LiCoO 2 、LiVPO 4 F、LiFeO 2 Or Li 1+x L 1－y－z M y N z O 2 Of the composition, wherein, x is more than or equal to 0.1 and less than or equal to 0.2, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, y + z is more than or equal to 0 and less than or equal to 1.0, L, M and N are respectively selected from Sc, ti, N, Y, Z, L, M, N, and N are respectively selected from the group consisting of,V, cr, mn, fe, co, ni, cu, zn, al, mg and Ga.
Optionally, the active region and the passivation region further comprise a conductive agent and a binder.
Optionally, the binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, styrene butadiene rubber, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polyamide, polyacrylonitrile, and polyacrylate.
Optionally, the conductive agent includes one or more of acetylene black, carbon nanotubes, carbon nanofibers, activated carbon, and graphene.
Optionally, the active material is 65% to 99.8% by mass in the passivation region.
Optionally, the mass percentage content of the binder in the passivation region is 0.1% -15%. Further, the mass percentage of the binder in the passivation area is 1% -7%.
Optionally, the conductive agent is contained in the passivation region by 0.1-20% by mass. Further, the mass percentage content of the conductive agent in the passivation region is 1% -5%.
Optionally, the current collector has a thickness of 5 μm to 100 μm. Further, the thickness of the current collector is 8-20 μm.
Optionally, the active material layer has a thickness of 10 μm to 200 μm.
The battery positive plate that this application first aspect provided forms the passivation zone through carrying out passivation treatment to bad region, and the passivation zone has higher compaction density, and passivation zone is difficult to be infiltrated to electrolyte to reduce deviating from and migration rate of lithium ion in the passivation zone, reduce lithium ion concentration, and then improve the problem that lithium was analysed to the negative pole position that passivation zone corresponds, improve the cyclicity ability and the security performance of battery.
In a second aspect, the present application provides a method for preparing the above battery positive plate, comprising the following steps:
providing a current collector, coating an active material on the surface of the current collector, and rolling the active material for the first time to form an active material layer to be passivated; the active material layer to be passivated comprises an active region and regions to be passivated, wherein the regions to be passivated are positioned on two opposite sides of the active region along a first direction;
rolling the region to be passivated for n times to form a passivated region to obtain a battery positive plate, wherein n is more than or equal to 1, and the compaction density rho of the passivated region is 2 Greater than the compacted density of the active region, p 1 。
Optionally, the pressure of the first rolling is 1Mpa to 10Mpa.
Optionally, the pressure of the n rolling is 1Mpa to 3Mpa.
The preparation method of the battery positive plate is simple and controllable in process, easy to operate and beneficial to achieving automatic production, the obtained battery positive plate has good electrochemical performance and structural stability, and the battery can have good cycle performance and safety performance when the preparation method is applied to the battery.
In a third aspect, the present application provides a battery, including a positive electrode, a negative electrode, an electrolyte, and a separator located between the positive electrode and the negative electrode, where the positive electrode includes the positive electrode sheet of the battery according to the first aspect of the present application or the positive electrode sheet of the battery obtained by the preparation method according to the second aspect of the present application.
In a fourth aspect, the present application provides a powered vehicle including the battery of the third aspect of the present application.
Drawings
FIG. 1 is a schematic diagram of a battery;
FIG. 2 is a top view of a coated pole piece made by the batch coating process;
FIG. 3 is a front view of a coated pole piece made by the batch coating process;
FIG. 4 is a schematic view of a defective area of an electrode in a battery;
fig. 5 is a plan view of a positive electrode plate of a battery according to an embodiment of the present disclosure;
fig. 6 is a front view of a positive plate of a battery according to an embodiment of the present disclosure;
fig. 7 is a schematic structural view of an active material layer of a positive electrode sheet of a battery according to an embodiment of the present disclosure.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, 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 application.
Referring to fig. 1, fig. 1 is a schematic structural diagram of a battery. The core components of the battery comprise a positive battery plate 10, a negative battery plate 20, a diaphragm 30, an electrolyte 40 and corresponding communication accessories and circuits. In the related art, because a tab is welded in a blank area of a reserved part of a current collector, an intermittent coating method is usually adopted to coat an active material layer to obtain a coated pole piece, and then the coated pole piece is cut and rolled to obtain a battery pole piece. The intermittent coating method is to coat a section of slurry on the surface of the current collector, leave a blank and coat the next section of slurry, please refer to fig. 2, and fig. 2 is a top view of the coated pole piece prepared by the intermittent coating method. Wherein, the active material layers 102 are arranged on the surface of the current collector 101 at intervals, and the current collector 101 has empty areas at intervals. In the case of the batch coating method, the thickness of the active material layer formed by the machine at the positions where the coating is started and ended is not uniform, and the thickness of the edge position of the active material layer is larger. Referring to fig. 3, fig. 3 is a front view of a coated electrode sheet prepared by a batch coating method, in fig. 3, the thickness of the active material layer 102 in the coating direction in the edge region is greater than that in the middle region, and the region with the greater thickness is a defective region of the positive electrode sheet of the battery.
During the use of the battery, because the active material in the poor region of the positive plate of the battery is more, the lithium ion concentration in the poor region of the positive plate is higher, and the lithium ion concentration in the corresponding negative electrode region is also higher during the charging process of the battery, so that lithium dendrites are easily generated in the negative electrode in the region. Referring to fig. 4, fig. 4 is a schematic diagram of a defective area of an electrode in a battery. In fig. 4, a region a represents a poor region with a high lithium ion concentration in the positive electrode plate of the battery, that is, the region a is a poor region with a thick positive electrode active material layer, and the region b is a region corresponding to the region a of the negative electrode plate of the battery, after the battery is used for a long time, a large amount of lithium dendrites are easily generated in the region b, and the damage of the lithium dendrites mainly has three aspects: firstly, the puncture penetrates through the diaphragm to cause short circuit, which causes serious safety accidents; secondly, the lithium dendrite can generate in-situ chemical reaction with electrolyte to form an electronic insulation film on the surface, the film can cause mutual electronic insulation between the lithium dendrite, once the root system is broken, the whole lithium dendrite loses electrochemical activity, and the capacity of the battery is rapidly reduced; and the space volume of the lithium dendrite is large, so that the volume expansion of the battery is easy to cause, and the cycle performance of the battery is attenuated. In addition, the poor area of the active material layer of the positive plate is easy to drop, and the cycle performance and the safety performance of the battery are not facilitated.
In order to solve the above problems, in the related art, an adhesive tape is applied to an edge of an active material layer, however, the adhesive tape contains a polyurethane adhesive, and the main components are polyisocyanonate, polyether, alcohol, and the like, and the above components are easily diffused into an electrolyte, which is not favorable for the electrochemical performance and safety performance of a battery, and after a battery using the positive electrode adhesive tape is subjected to multiple charge and discharge cycles, a negative electrode position corresponding to the adhesive tape still has relatively serious lithium dendrite precipitation, and the problem cannot be solved well.
For improving the electrochemical performance and the safety performance of the battery, the application provides the battery positive plate, the battery positive plate passivates a bad area with higher lithium ion concentration, so that the passivated area has higher compaction density, the infiltration of electrolyte into the passivated area is inhibited, the extraction speed of lithium ions is slowed down, and the concentration of lithium ions in the passivated area is reduced, thereby effectively inhibiting the generation of lithium dendrites, simultaneously improving the structural stability of the battery positive plate, and effectively enhancing the cycle performance and the safety performance of the battery by applying the battery positive plate in the battery.
Referring to fig. 5, fig. 5 is a top view of a positive plate of a battery according to an embodiment of the present disclosure. In fig. 5, the battery positive electrode sheet 10 includes a current collector 101 and an active material layer 102 disposed on a surface of the current collector 101; the active material layer 102 includes an active region c and a passivation region d; the passivation regions d are located at opposite sides of the active region c in the first direction. To further illustrate the location of the passivation region of the present application, referring to fig. 6, fig. 6 is a front view of a positive plate of a battery provided in an embodiment of the present application, and in fig. 6, an active material layer 102 includes an active region c and passivation regions d located at two opposite sides of the active region c along a first direction. In the application, the first direction refers to a direction parallel to the coating direction of the battery pole piece, and as the battery pole piece is coated in a segmented manner, the area with thicker thickness at the edge part of the active material layer along the coating direction is a bad area; on the other hand, the active material layer with higher compaction density is not beneficial to the infiltration of electrolyte, thereby inhibiting the lithium ion in the passivation region from being removed, reducing the concentration of the lithium ion in the passivation region and improving the phenomenon that lithium dendrite appears on the negative electrode. It is to be understood that, in the present application, the shape of the active material layer is rectangular, the shape of the active region is rectangular, and two opposite sides of the active region are parallel to the first direction, and the other two opposite sides of the active region are perpendicular to the first direction; the passivation region is rectangular, two opposite sides of the passivation region are parallel to the first direction, and the other two opposite sides of the passivation region are perpendicular to the first direction.
In the present application, the compacted density ρ of the passivated region 2 The higher the pores in the passivation area, the more difficult the electrolyte is to infiltrate, the more difficult the lithium ions are to come out, and the better the passivation effect is. To ensure that the lithium ion concentration in the passive region is lower than the lithium ion concentration in the active region, in the embodiments of the present application, the compacted density ρ of the passive region is 2 Compacted density p with active area 1 Is greater than or equal to 1.1. Compacted density of passivated region ρ 2 Compacted density p with active area 1 The ratio of (A) to (B) may specifically but not exclusively be 1.1,1.2, 1.3, 1.4 or 1.5.
In the battery pole piece, the compaction density of the active material layer is related to the components and the preparation process of the active material layer, and taking the active material layer only containing the active material as an example, the compaction density of the active material layer can theoretically reach the true density of the active material to the maximum. In the present application, the compacted density ρ of the passivated region 2 The closer to the true density of the active material, the better the passivation effect. The research of the application finds that the compacted density rho of the passivated area 2 When the ratio to the true density of the active material is 0.8 or more, lithium ions of the active material in the passivation region are substantially difficult to deintercalate, the transmission rate of lithium ions is low, and the risk of lithium dendrite formation at the corresponding negative electrode position is also greatly reduced. In the embodiments of the present application, the compacted density ρ of the passivated region 2 The ratio to the true density of the active material may specifically be, but is not limited to, 0.8, 0.83, 0.85, 0.87, 0.89, 0.9, 0.93, 0.95, 0.98, or 0.99. In some embodiments of the present disclosure, the active material in the positive electrode sheet of the battery is lithium cobaltate, and the compacted density of the active region of the active material layer in the positive electrode sheet of the battery is 3.8g/cm 3 -4.1g/cm 3 The density of the passivation region is 4.1g/cm 3 -5.0g/cm 3 Wherein the active material lithium cobalt oxide has a true density of 5.1g/cm 3 . In some embodiments of the present application, the active material in the positive electrode sheet of the battery is an active material layer in the positive electrode sheet of a lithium iron phosphate battery, and the compacted density of the active area is 2.1g/cm 3 -2.4g/cm 3 The density of the passivation region is 2.9g/cm 3 Wherein the true density of the active material lithium cobalt oxide is 3.6g/cm 3 。
In the embodiment of the application, the compaction density of the passivation region is improved by further compacting on the basis of conventional tabletting preparation of the battery pole piece, and the thickness of the active material layer of the poor region of the battery positive pole piece active material layer can be reduced after compacting. In the present embodiment, the absolute value of the difference between the thickness of the passivation region and the thickness of the active region in the active material layer is less than or equal to 5 μm. The absolute value of the difference in thickness between the passivation region and the active region may specifically be, but not limited to, 5 μm, 3 μm, 1 μm, 0.5 μm, 0.1 μm, 0.05 μm, 0.01 μm, or 0 μm. The smaller the difference between the thicknesses of the passive region and the active region in the active material layer is, the higher the stability of the positive plate of the battery is. In this application, the difference in thickness between the passivation region and the active region refers to the maximum difference in thickness. Referring to fig. 7, fig. 7 is a schematic structural diagram of an active material layer of a positive plate of a battery according to an embodiment of the present disclosure, in fig. 7, a thickness of a passivation region d is greater than a thickness of an active region c, and a thickness difference X between the passivation region and the active region is a difference between a maximum thickness of the passivation region and a minimum thickness of the active region.
In the present application, the passivation regions d are located at both sides of the active region c, and the width of the passivation region in the first direction refers to the width of the one-sided passivation region in the first direction. In the embodiment of the application, the width of the passivation region along the first direction is 1mm-2cm. In some embodiments of the present application, the passivation region has a width along the first direction of 3mm to 1.2cm. The width of the passivation region in the first direction may specifically, but not exclusively, be 1mm, 3mm, 5mm, 7mm, 1cm, 1.2cm or 2cm. Within the above width range, the passivation region can effectively cover the defective region of the electrode, thereby alleviating the problem of lithium deposition from the negative electrode.
In the present application, the active region and the passive region have the same composition and the same percentage of each component in the active region and the passive region, and the active region and the passive region differ in their compaction density. In the present embodiment, the active region and the passivation region include active materials, which refer to materials capable of reversibly extracting and inserting lithium ions. In the present application, the active material is not particularly limited, and any active material known in the art may be used as the active material. In some embodiments of the present application, the active material comprises LiFePO 4 、Li 3 V 2 (PO 4 ) 3 、LiMn 2 O 4 、LiMnO 2 、LiNiO 2 、LiCoO 2 、LiVPO 4 F、LiFeO 2 Or Li 1+x L 1－y－z M y N z O 2 Wherein-0.1-x 0.2, 0-y 1, 0-z 1, 0-y + z 1.0, L, M, N are selected from Sc, ti, V, cr, mn, fe, co, ni, cuZn, al, mg and Ga.
In the embodiment of the present application, the active region further includes a conductive agent and a binder, and the passivation region further includes a conductive agent and a binder. In the present application, the binder and the conductive agent are not particularly limited, and may be any known in the art. In some embodiments of the present disclosure, the binder comprises one or more of polyvinylidene fluoride, polytetrafluoroethylene, polyhexafluoropropylene, styrene butadiene rubber, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polyamide, polyacrylonitrile, and polyacrylate. In some embodiments of the present application, the conductive agent includes one or more of acetylene black, carbon nanotubes, carbon nanofibers, activated carbon, and graphene.
In the embodiment of the application, the mass percentage of the active material in the passivation region is 65-99.8%. The mass percentage content of the active material in the passivation region may particularly but not exclusively be 65%, 70%, 75%, 79.9%, 80%, 85%, 90%, 95% or 99.8%. In the embodiment of the application, the mass percentage of the binder in the passivation area is 0.1-15%. The mass percentage content of the binder in the passivation region may specifically be, but is not limited to, 0.1%, 0.5%, 1%, 2%, 5%, 7%, 10%, or 15%. In the embodiment of the application, the mass percentage content of the conductive agent in the passivation region is 0.1-20%. The mass percentage content of the conductive agent in the passivation region may specifically be, but is not limited to, 0.1%, 0.5%, 1%, 2%, 5%, 10%, 15%, or 20%.
In the present embodiment, the thickness of the active material layer is 10 μm to 200 μm. The thickness of the active material layer may specifically be, but not limited to, 10 μm, 20 μm, 50 μm, 100 μm, 150 μm, or 200 μm. In the embodiment of the present application, the thickness of the current collector is 5 μm to 100 μm. In some embodiments of the present application, the current collector has a thickness of 8 μm to 20 μm. The thickness of the current collector may be specifically, but not limited to, 5 μm, 10 μm, 20 μm, 50 μm, 70 μm, 90 μm, or 100 μm.
The application provides a battery positive plate prevents effectively soaking and lithium ion transmission of electrolyte in the battery positive plate passivation region through carrying out passivation treatment to the positive pole to realize hindering the purpose that the lithium ion in this region deviates from, alleviate the problem that the lithium was analysed to the negative pole, and improved battery positive plate's structural stability effectively.
The application also provides a preparation method of the battery positive plate, which comprises the following steps:
step 100: providing a current collector, coating an active material on the surface of the current collector, and rolling the active material for the first time to form an active material layer to be passivated; the active material layer to be passivated comprises an active region and regions to be passivated, wherein the regions to be passivated are positioned on two opposite sides of the active region along a first direction;
step 200: rolling the region to be passivated n times to form a passivated region to obtain a battery positive plate, wherein n is more than or equal to 1, and the compaction density rho of the passivated region 2 Greater than the compacted density p of the active area 1 。
In step 100, an active material is coated on the surface of the current collector by an intermittent coating method, and then dried. And performing first rolling on the active material to mold the active material and form an active material layer to be passivated, wherein the active material layer to be passivated comprises an active region and regions to be passivated, which are positioned on two opposite sides of the active region along a first direction, the first direction is parallel to the coating direction, and the width of the regions to be passivated along the first direction is 1mm-2cm. In the present embodiment, the pressure at which the active material is primarily rolled is 1Mpa to 10Mpa. The pressure of rolling may be specifically, but not limited to, 1MPa, 3MPa, 5MPa or 10MPa.
In the step 200, rolling the region to be passivated n times to form a passivated region and obtain a positive plate of the battery, wherein the compacted density rho of the passivated region in the active material layer after the rolling n times is finished 2 Greater than the compacted density of the active area ρ 1 Wherein the value of n.gtoreq.1,n may specifically but not exclusively be 1,2, 3, 4 or 5. In the embodiment of the application, the pressure of the n-time rolling is 1MPa-3MPa.
According to the preparation method of the battery positive plate, passivation can be achieved by rolling the defective area in the plate for multiple times, so that the battery positive plate has good electrochemical performance and structural stability. The method has simple and controllable process, is easy to operate and is beneficial to realizing automatic production.
The application also provides a lithium ion battery, and this lithium ion battery includes anodal, negative pole, electrolyte and is located the diaphragm between anodal and the negative pole, and wherein, anodal battery positive plate that this application provided including.
In the present application, the negative electrode of the lithium ion battery may be any negative electrode known in the art. In an embodiment of the present application, the negative electrode may include one or more of a carbon-based negative electrode, a silicon-based negative electrode, a tin-based negative electrode, a lithium negative electrode, a sodium negative electrode, a potassium negative electrode, a magnesium negative electrode, a zinc negative electrode, and an aluminum negative electrode. Wherein the carbon-based negative electrode may include graphite, hard carbon, soft carbon, graphene, and the like; the silicon-based negative electrode may include silicon, silicon carbon, silicon oxygen, silicon metal compounds, and the like; the tin-based negative electrode may include tin, tin carbon, tin oxide, tin metal compounds; the lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy. In some embodiments of the present application, the current collector of the negative electrode is a copper foil, the copper foil may be a porous structure or a common copper foil, the copper foil has a thickness of 5 μm to 100 μm, and further, the copper foil has a thickness of 10 μm to 20 μm; the negative active material comprises one or more of natural graphite, artificial graphite, hard carbon, soft carbon, lithium titanate, iron oxide, lithium titanium phosphate, titanium dioxide, silicon monoxide, aluminum, tin and antimony; the binder comprises one or more of polyacrylic acid (PAA), polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), and styrene butadiene latex (SBR); the conductive agent comprises one or more of acetylene black, keqin carbon black, super-P, carbon nano tubes, carbon nano fibers, activated carbon and graphene. In the present application, any method known in the art may be used for the preparation of the negative electrode.
In the present application, the separator of the lithium ion battery may be any separator known to those skilled in the art, for example, the separator may be one or more of a polyolefin microporous membrane, polyethylene terephthalate, polyethylene felt, glass fiber felt, or ultrafine glass fiber paper.
In the present application, the electrolyte of a lithium ion battery includes a solution of an electrolytic lithium salt in a nonaqueous solvent. In the embodiments of the present application, the electrolyte lithium salt includes lithium hexafluorophosphate (LiPF) 6 ) Lithium perchlorate (LiClO) 4 ) Lithium tetrafluoroborate (LiBF) 4 ) Lithium hexafluoroarsenate (LiAsF) 6 ) Lithium hexafluorosilicate (LiSiF) 6 ) Lithium tetraphenylborate (LiB (C) 6 H5) 4 ) Lithium chloride (LiCl), lithium bromide (LiBr), lithium chloroaluminate (LiAlCl) 4 ) Fluorine fluorosulfonic acid lithium (LiC (SO) 2 CF 3 ) 3 )、LiCH 3 SO 3 、LiN(SO 2 CF 3 ) 2 And LiN (SO) 2 C 2 F 5 ) 2 One or more of (a). In some embodiments of the present application, the non-aqueous solvent comprises one or more of a chain acid ester and a cyclic acid ester. In some embodiments of the present application, the chain acid ester comprises one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl Methyl Carbonate (EMC), methyl Propyl Carbonate (MPC), and dipropyl carbonate (DPC). In some embodiments of the present application, the chain acid ester includes a chain organic ester containing a fluorine, sulfur, or unsaturated bond. In some embodiments of the present application, the cyclic acid ester includes one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), vinylene Carbonate (VC), gamma-butyrolactone (gamma-BL), and sultones. In some embodiments of the present application, the cyclic acid ester includes a cyclic organic ester containing fluorine, sulfur, or an unsaturated bond. In some embodiments of the present application, the non-aqueous solvent comprises one or more of a solution of a chain ether and a cyclic ether.
In some embodiments of the present application, the cyclic ether comprises one or more of Tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), 1, 3-Dioxolane (DOL), and 4-methyl-1, 3-dioxolane (4-MeDOL).
In some embodiments of the present application, the cyclic ether includes a cyclic organic ether containing fluorine, sulfur, or an unsaturated bond. In some embodiments of the present application, the chain ether comprises one or more of Dimethoxymethane (DMM), 1, 2-Dimethoxyethane (DME), 1, 2-Dimethoxypropane (DMP), and Diglyme (DG).
In some embodiments of the present application, the chain ether includes a fluorine-, sulfur-or unsaturated-bond-containing chain organic ether. In the embodiment of the present application, the concentration of the electrolytic lithium salt in the electrolytic solution is 0.1mol/L to 15mol/L. In some embodiments of the present application, the concentration of the electrolytic lithium salt is 1mol/L to 10mol/L.
In the embodiment of the present application, the battery may be prepared by any one of a lamination process and a winding process. In some embodiments of the present application, a battery is prepared using a lamination process.
The lithium ion battery provided by the application has good cycle performance and safety performance due to the adoption of the battery positive plate.
The application also provides a power vehicle which comprises the lithium ion battery.
The technical solution of the present application is further illustrated by a plurality of examples.
Example 1
1) Preparation of the battery anode:
the positive electrode active material (LiCoO) was weighed 2 ) 1kg of N-methylpyrrolidone, 20g of a conductive agent (carbon nano tube) and 20g of a binder (vinylidene fluoride, PVDF) are added into 1kg of N-methylpyrrolidone and stirred in a stirrer for 30min to form stable and uniform slurry; uniformly coating the slurry on the surface of a current collector aluminum foil, drying at 80 ℃, and performing wondering on the dried slurry under the pressure of 2MPa to form the slurry and form an active material layer to be passivated; and (3) carrying out secondary rolling on a bad area of 1cm at the edge position of the active material layer to be passivated to realize passivation, wherein the pressure of the secondary rolling is 2Mpa, obtaining a battery positive plate after rolling, and spot-welding a lug to obtain a battery positive electrode.
2) Preparation of a battery cathode:
1kg of a negative electrode active substance (a composite negative electrode material of natural graphite and artificial graphite with the particle size of 15 microns, the mass ratio of the natural graphite to the artificial graphite is 1.
3) Preparing a battery:
the battery positive electrode, the battery negative electrode and the polyolefin microporous membrane separator prepared above were wound to prepare a cell, and after packaging, 1mol/L of lithium hexafluorophosphate electrolyte (EC: DMC: DPC in a solvent of 1.
Example 2
The difference from example 1 is that the pressure of the second roll pressing of the defective region in example 2 was 3MPa. The cell of example 2 was designated DS-2.
Example 3
The difference from example 1 is that the pressure for the second rolling of the defective region in example 3 was 5MPa. The cell of example 3 was designated DS-3.
Example 4
The difference from example 1 is that in example 4, the defective region was further subjected to the third rolling at a pressure of 1Mpa. The cell of example 4 was designated DS-4.
Comparative example 1
Compared with the embodiment 1, the difference is that the battery positive plate is obtained by rolling the dried slurry in the comparative example 1, and then the battery positive electrode is obtained by spot welding the tab, and the battery positive plate in the comparative example 1 is not rolled secondarily. The cell of comparative example 1 was named DS-5.
Comparative example 2
The difference from comparative example 1 is that comparative example 2 rolls the dried slurry to obtain an active material layer, and then attaches an adhesive tape to an area of 1mm at the edge position of the active material layer, the adhesive tape is a commercial BOPP film substrate adhesive tape, and the battery of comparative example 2 is named as DS-6.
Effects of the embodiment
In order to verify the performance of the battery positive plate prepared by the application, the application also provides an effect embodiment.
1) The active material layer passive region and the active region in the positive electrodes of the batteries of examples 1 to 4 and comparative examples 1 to 2 were measured for their compacted densities, where the compacted density of the active region was ρ 1 The compacted density of the passivated region is ρ 2 Please refer to the test resultsSee table 1.
TABLE 1 structural parameters of positive electrodes of batteries of examples 1-4 and comparative examples 1-2
Figure BDA0003042275280000121
2) The batteries of examples 1 to 4 and comparative examples 1 to 2 were subjected to charge and discharge tests under specific test conditions: and connecting the anode and the cathode by using a blue test system, and carrying out two-stage charge and discharge test on the battery. The first stage of charge-discharge system is as follows: standing for 1 min, constant current charging to 4.45V at 8mA current, constant voltage charging at 4.45V with cutoff current of 2mA, standing for 10 min, constant current discharging at 8mA with cutoff voltage of 2V, and standing for 50 hr. The first stage tests were used for cell formation to form SEI films and to mitigate polarization of the cell. The second stage of charge-discharge system is as follows: charging at a constant current of 60mA, wherein the cut-off voltage is 4.45V;4.45V constant voltage charging, and the cut-off current is 2mA; and after standing for 10 minutes, discharging at a constant current of 60mA, stopping the voltage of 2V, and stopping the discharging after 800 circles of second-stage charging and discharging circulation. The second test was used to test the cycling performance of the cell. The first-circle charging means that after the battery is subjected to a first-section test, the battery is charged to 4.45V by a constant current of 60mA, and then charged to a cut-off current of 2mA by a constant voltage of 4.45V; the first-turn discharge capacity refers to the capacity discharged by the battery when the battery is discharged to the voltage of 2V at a constant current of 60 mA. And the discharge capacities after 800 cycles of the subsequent cycle were calculated, respectively, with the discharge capacity of the first cycle as a reference of 100%. Referring to table 2, table 2 shows the variation of the discharge capacity retention rate during 800 cycles of charge and discharge of the batteries of examples 1 to 4 and comparative examples 1 to 2.
TABLE 2 CYCLIC PERFORMANCE TEST TABLE FOR BATTERIES OF EXAMPLES 1-4 AND COMPARATIVE EXAMPLES 1-2
Battery number Capacity retention after 800 cycles
DS-1 93％
DS-2 96％
DS-3 98％
DS-4 99％
DS-5 83％
DS-6 87％
As can be seen from the test results in Table 2, the discharge capacity retention rate of the battery DS-5 of comparative example 1 after 800 cycles was maintained at 83%; the battery DS-6 of comparative example 2 covered the defective region of the positive electrode sheet with an adhesive tape, and the discharge capacity retention rate was maintained at 87% after 800 cycles. After the battery pole piece of the embodiment is subjected to local passivation, the discharge capacity retention rate of the battery is obviously improved, the capacity retention rate of the battery is gradually increased along with the increase of the passivation degree, and when the compaction density of a passivation area reaches 4.9g/cm 3 In the process, the capacity retention rate of the DS-4 battery is up to 99%, and the application of the battery positive plate is proved to be capable of well improving the cycle performance of the battery.
In the application, the disassembly observation is carried out on the batteries after the circulation of the examples 1-4 and the comparative examples 1-2, and the disassembly finds that the negative electrode of the battery of the comparative example 1 has obvious lithium precipitation phenomenon, the negative electrode of the battery of the comparative example 2 has the lithium precipitation phenomenon in the negative electrode area corresponding to the edge of the adhesive tape, and the negative electrode of the battery of the example has no lithium precipitation condition. It can be seen that the passivation treatment of the poor region in the electrode plate can effectively inhibit the lithium ions in the poor region of the positive electrode from being separated out, and reduce the risk of lithium enrichment in the corresponding negative electrode region, thereby improving the phenomenon that the negative electrode generates lithium dendrites and improving the cycle performance and safety performance of the battery.
The foregoing is illustrative of the preferred embodiments of the present application and is not to be construed as limiting the scope of the application. It should be noted that, for those skilled in the art, without departing from the principle of the present application, several improvements and modifications can be made, and these improvements and modifications are also considered to be within the scope of the present application.

Claims (10)

1. The positive plate of the battery is characterized by comprising a current collector and an active material layer arranged on the surface of the current collector; the active material layer includes an active region and passivation regions on opposite sides of the active region in the first direction; the active region and the passive region comprise an active material; compacted density p of the passivated region 2 Greater than the compacted density of the active region, p 1 。
2. The positive electrode sheet according to claim 1, wherein the passivation region has a compacted density p 2 Compacted density p with the active area 1 Is greater than or equal to 1.1.
3. The positive electrode sheet for a battery according to claim 1 or 2, wherein the compacted density p of the passivated region is 2 The ratio to the true density of the active material is greater than or equal to 0.8.
4. A positive electrode sheet for a battery according to any one of claims 1 to 3, wherein the thickness of the passivation region and the thickness of the active region in the active material layer are different from each other by an absolute value of 5 μm or less.
5. The positive electrode sheet according to any one of claims 1 to 4, wherein the active material comprises a material capable of reversibly deintercalating and intercalating lithium ions.
6. The positive electrode sheet according to any one of claims 1 to 5, wherein the width of the passivated region in the first direction is 3mm to 2cm.
7. The preparation method of the battery positive plate is characterized by comprising the following steps:
providing a current collector, coating an active material on the surface of the current collector, and rolling the active material for the first time to form an active material layer to be passivated; the active material layer to be passivated comprises an active region and regions to be passivated positioned on two opposite sides of the active region along a first direction;
rolling the region to be passivated n times to form a passivated region to obtain a battery positive plate, wherein n is more than or equal to 1, and the compaction density rho of the passivated region 2 Greater than the compacted density p of the active area 1 。
8. The method of claim 7, wherein the pressure of the n rolling is 1Mpa to 3Mpa.
9. A battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator between the positive electrode and the negative electrode, wherein the positive electrode comprises the positive electrode sheet according to any one of claims 1 to 6 or the positive electrode sheet obtained by the production method according to claim 7 or 8.
10. A powered vehicle, characterized by comprising the battery of claim 9.
CN202110463078.7A 2021-04-27 2021-04-27 Battery positive plate and preparation method and application thereof Pending CN115249785A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116375943A (en) * 2023-06-05 2023-07-04 宁德时代新能源科技股份有限公司 Passivation solution for positive electrode plate, preparation method of positive electrode plate, battery cell, battery and power utilization device

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116375943A (en) * 2023-06-05 2023-07-04 宁德时代新能源科技股份有限公司 Passivation solution for positive electrode plate, preparation method of positive electrode plate, battery cell, battery and power utilization device
CN116375943B (en) * 2023-06-05 2023-10-27 宁德时代新能源科技股份有限公司 Passivation solution for positive electrode plate, preparation method of positive electrode plate, battery cell, battery and power utilization device

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