CN115842096A - Pre-lithiation pole piece, preparation method thereof, secondary battery and power utilization device - Google Patents

Pre-lithiation pole piece, preparation method thereof, secondary battery and power utilization device Download PDF

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Publication number
CN115842096A
CN115842096A CN202210846555.2A CN202210846555A CN115842096A CN 115842096 A CN115842096 A CN 115842096A CN 202210846555 A CN202210846555 A CN 202210846555A CN 115842096 A CN115842096 A CN 115842096A
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China
Prior art keywords
pole piece
layer
lithium
prelithiation
active material
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Pending
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CN202210846555.2A
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Chinese (zh)
Inventor
王绍杉
何建福
刘倩
叶永煌
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to CN202210846555.2A priority Critical patent/CN115842096A/en
Publication of CN115842096A publication Critical patent/CN115842096A/en
Priority to PCT/CN2023/099576 priority patent/WO2024016891A1/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • 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

Abstract

The application relates to the technical field of secondary batteries, in particular to a prelithiation pole piece, a preparation method thereof, a secondary battery and an electric device. The prelithiation pole piece comprises a current collector and an active material layer arranged on at least one surface of the current collector; a lithium supplement layer is arranged between the current collector and the at least one active material layer; wherein, the surface roughness of the current collector is 2-5 μm, and the active material layer is a porous structure. The current collector with certain surface roughness can bear the lithium supplementing material to form a lithium supplementing layer, the traditional electric core structure is not required to be changed, the active lithium can be released through the pores of the active material layer, and the lithium can be supplemented to the battery. The pre-lithiation pole piece has a simple structure, can be produced by adopting the existing pole piece preparation process, does not need new equipment, and can effectively reduce the production cost.

Description

Pre-lithiation pole piece, preparation method thereof, secondary battery and power utilization device
Technical Field
The application relates to the technical field of secondary batteries, in particular to a prelithiation pole piece, a preparation method thereof, a secondary battery and an electric device.
Background
During the first charge of a lithium ion battery, a large amount of lithium from the positive electrode is permanently consumed due to the formation of a solid electrolyte phase interface (SEI) film, resulting in a low first cycle coulombic efficiency (ICE), which reduces the capacity and energy density of the lithium ion battery. In order to solve the problem and further improve the capacity and energy density of the lithium ion battery, people develop a "prelithiation technology", that is, lithium is added into the battery in advance before the lithium ion battery works to supplement lithium ions, which is also called a "lithium pre-insertion technology" or a "lithium supplement technology", so that lithium loss caused by the formation of an SEI film is offset, and the reduction of the battery performance is avoided. However, because most of lithium supplement agents have poor stability in air, the prelithiation usually requires great changes to the traditional pole piece structure and preparation process to avoid the inactivation of the lithium supplement agents, which greatly increases the production cost.
Disclosure of Invention
Therefore, a pre-lithiated pole piece which is simple in structure and can be produced by adopting the existing pole piece preparation process, a preparation method of the pre-lithiated pole piece, a secondary battery and an electric device are needed to be provided.
In a first aspect of the present application, there is provided a prelithiation pole piece comprising a current collector and an active material layer disposed over at least one surface of the current collector; a lithium supplement layer is arranged between the current collector and at least one active material layer;
wherein, the surface roughness of the current collector is 2-5 μm, and the active material layer is in a porous structure.
The current collector with certain surface roughness can bear the lithium supplementing material to form a lithium supplementing layer, the traditional electric core structure is not required to be changed, the active lithium can be released through the pores of the active material layer, and the lithium can be supplemented to the battery. The pre-lithiation pole piece has a simple structure, can be produced by adopting the existing pole piece preparation process, does not need new equipment, and can effectively reduce the production cost.
In some embodiments, the Dv50 particle size of the lithium supplement agent in the lithium supplement layer is 2 μm or less. The lithium supplement agent can be better embedded into the pits on the rough surface of the current collector by the proper particle size, the formed lithium supplement layer and the current collector have better adhesive force, the surface is smooth, and the coating of a subsequent film layer cannot be influenced by mottle.
In some embodiments, the amount of the lithium supplement agent in the lithium supplement layer is 1% to 5% of the mass of the active material in the active material layer. The dosage of the lithium supplement agent is controlled within a proper range, the basic requirement of the battery for lithium supplement is met, the active material proportion is not excessively reduced, and the reduction of the volume capacity of the battery is avoided.
In some embodiments, the lithium supplement layer has a thickness of 1 μm to 2 μm. The appropriate thickness of the lithium supplement layer can avoid excessive collapse of the pole piece after the lithium supplement is finished while the lithium supplement requirement is met, and the excessive position of the pole piece can not be occupied, so that the volume capacity of the battery is reduced.
In some embodiments, the active material layer has a porosity of 20% to 40%. The porosity of the active material layer is slightly larger than that of the active material layer in the conventional pole piece, so that active lithium can be better transferred, and adverse effects such as lithium precipitation and the like caused by too high lithium supplement speed can be avoided.
In some embodiments, the pre-lithiated pole piece is a positive pole piece, and the active material layer has a porosity of 20% to 30%. Because the oxidation voltage of the positive electrode side is higher, the lithium supplement material is easy to release active lithium, the porosity is set to be smaller, and the lithium supplement speed is favorably controlled.
In some embodiments, the pre-lithiated pole piece is a negative pole piece, and the active material layer has a porosity of 30% to 40%. The reduction voltage of the negative electrode side is low, and the lithium supplement material releases slowly, so that larger porosity is needed to promote the lithium supplement rate to be in a more proper range.
In some embodiments, the prelithiation pole piece is a positive pole piece, and the lithium supplement agent in the lithium supplement layer comprises Li 1+x Ni 0.5 Mn 1.5 O 4 、Li 2 NiO 2 、Li 5 FeO 4 、LiF、Li 2 S、Li 2 C 2 O 4 、LiMn 2 O 4 ；Li 2 O 2 、Li 2 O and Li 3 N, wherein the value of x is selected from any value of 0-1.
In some embodiments, the pre-lithiated pole piece is a negative pole piece, and the lithium supplement agent in the lithium supplement layer includes one or more of lithium powder and pre-lithiated graphite.
In some embodiments, a conductive layer is disposed between at least one of the lithium supplement layers and the active material layer, and the conductive layer is a porous structure. The introduction of the conducting layer can better passivate the lithium supplement agent, and the inactivation of the lithium supplement agent due to the contact of water and oxygen is avoided; in addition, after lithium supplement is finished, the conducting layer can play a supporting role, and the pole piece is prevented from collapsing and demoulding; furthermore, the arrangement of the conducting layer can enable the coating of the active material layer to be more uniform, balance the contact resistance among all layers of the pole piece and prevent the active material from being released uniformly.
In some embodiments, the conductive layer has a porosity of 40% to 50%. The proper porosity of the conducting layer can realize the regulation and control of the lithium supplementing rate, the conducting layer has certain rigidity, a supporting effect can be provided, and the pole piece collapse caused after the lithium supplementing is finished is avoided.
In some embodiments, the pre-lithiated pole piece is a positive pole piece, and the porosity of the conductive layer is 40% to 45%. Because the oxidation voltage of the positive electrode side is higher, the lithium supplement material is easy to release active lithium, the porosity is set to be smaller, and the lithium supplement speed is favorably controlled.
In some embodiments, the pre-lithiated pole piece is a negative pole piece, and the porosity of the conductive layer is 45% to 50%. The reduction voltage of the negative electrode side is low, and the lithium supplement material releases slowly, so that larger porosity is needed to promote the lithium supplement rate to be in a more proper range.
In some embodiments, the conductive layer has a thickness of 1 μm to 2 μm. The thickness of the conductive layer also needs to be controlled within a proper range, so that the supporting, the lithium supplementing rate control and the uniform contact resistance can be better realized, and meanwhile, the conductive layer does not occupy too many positions to cause the reduction of the volume capacity of the battery.
In some embodiments, the conductive layer includes a conductive agent and a binder.
In some embodiments, the conductive agent comprises one or more of conductive graphite, conductive carbon black, carbon fibers, carbon nanotubes, and graphene.
In some embodiments, the binder comprises one or more of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene, and polyvinylidene fluoride. The proper binder can provide enough binding force, and simultaneously, the conductive agent can be uniformly dispersed without agglomeration, so that the function of the conductive layer can be better exerted.
In some embodiments, the mass ratio of the conductive agent to the binder is 1 (0.03 to 0.07). The proper dosage ratio of the conductive agent to the binder can ensure that the conductive agent is uniformly dispersed, does not agglomerate, has good caking property and does not fall off a mold, and simultaneously, the pole piece has smaller resistance.
In some embodiments, the conductive layer further comprises inorganic nanoparticles therein.
In some embodiments, the inorganic nanoparticles comprise Au, sn, znO, moS 2 And Al 2 O 3 One or more of (a). The introduction of inorganic nano-particles of proper category can increase the migration rate of active lithium, and the overall balance and regulation of lithium supplement rate can be realized by combining the control of parameters such as porosity and the like.
In some embodiments, the mass ratio of the conductive agent to the inorganic nanoparticles is 1 (0.001 to 0.01). The appropriate dosage ratio of the conductive agent to the inorganic nanoparticles can balance the conductivity and the lithium affinity of the conductive layer, improve the conductivity and avoid influencing the transmission of active lithium.
In a second aspect of the present application, a method for preparing a prelithiation pole piece is provided, which includes the following steps:
providing a current collector with the surface roughness of 2-5 mu m, and preparing a lithium supplement layer on at least one surface of the current collector;
and preparing an active material layer having a porous structure on the lithium supplement layer.
In a third aspect of the present application, a secondary battery is provided that includes a prelithiated pole piece as described in one or more of the foregoing embodiments.
In a fourth aspect of the present application, there is provided a battery module including the aforementioned secondary battery.
In a fifth aspect of the present application, there is provided a battery pack including the aforementioned battery module.
In a sixth aspect of the present application, an electric device is provided, which includes one or more of the foregoing secondary battery, battery module, and battery pack.
Drawings
Fig. 1 is a schematic view of a secondary battery according to an embodiment of the present application.
Fig. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in fig. 1.
Fig. 3 is a schematic view of a battery module according to an embodiment of the present application.
Fig. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
Fig. 5 is an exploded view of the battery pack according to the embodiment of the present application shown in fig. 4.
Fig. 6 is a schematic diagram of an electric device in which a secondary battery according to an embodiment of the present application is used as a power source.
Description of reference numerals:
1: a battery pack; 2: an upper box body; 3: a lower box body; 4: a battery module; 5: a secondary battery; 51: a housing; 52: an electrode assembly; 53: a cover plate; 6: and (4) a power utilization device.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are given in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the invention, "a plurality" means at least two, e.g., two, three, etc., unless explicitly specified otherwise. In the description of the present application, "a number" means at least one, such as one, two, etc., unless specifically limited otherwise.
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 present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the present application, the technical features described in the open form include a closed technical solution including the listed features, and also include an open technical solution including the listed features.
In the present application, reference is made to numerical ranges which are considered to be continuous within the numerical ranges, unless otherwise specified, and which include the minimum and maximum values of the range, as well as each and every value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range-describing features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to encompass any and all subranges subsumed therein.
The percentage contents referred to in the present application mean, unless otherwise specified, mass percentages for solid-liquid mixing and solid-solid phase mixing, and volume percentages for liquid-liquid phase mixing.
The percentage concentrations referred to in this application, unless otherwise indicated, refer to the final concentrations. The final concentration refers to the ratio of the additive component in the system to which the component is added.
The temperature parameter in the present application is not particularly limited, and may be a constant temperature treatment or a treatment within a certain temperature range. The constant temperature process allows the temperature to fluctuate within the accuracy of the instrument control.
Due to the formation of the SEI film, part of lithium ions can be consumed, so that the irreversible capacity of the battery during first charge and discharge is increased, and the charge and discharge efficiency and the cycle performance of the electrode material are reduced. In order to replenish the consumed lithium ions, the pole piece needs to be subjected to lithium replenishing treatment. However, in the conventional technology, in order to supplement lithium, the structure of the pole piece is often redesigned, which is different from the existing pole piece structure, and thus, the existing processing equipment is inconvenient to process, and the production cost is greatly increased. In addition, the traditional technology rarely relates to the regulation and control of lithium supplement rate, cannot realize long-acting lithium supplement, and has limited service life improvement on batteries.
Against the above background, in a first aspect of the present application, there is provided a prelithiation pole piece comprising a current collector and an active material layer disposed over at least one surface of the current collector; a lithium supplement layer is arranged between the current collector and the at least one active material layer;
wherein, the surface roughness of the current collector is 2-5 μm, and the active material layer is a porous structure.
The current collector with certain surface roughness can bear the lithium supplement material to form a lithium supplement layer, the traditional cell structure is not required to be changed, the release of active lithium can be realized through the pores of the active material layer, and the lithium supplement is carried out on the battery. The pre-lithiation pole piece has a simple structure, can be produced by adopting the existing pole piece preparation process, does not need new equipment, and can effectively reduce the production cost.
The surface roughness of the current collector is preferably 2-3.5 μm, and the surface roughness of the current collector can be 2.5 μm, 3 μm, 3.5 μm, 4 μm or 4.5 μm; the proper roughness can ensure that the current collector has enough adhesive force to the lithium supplement agent, and can avoid the influence on the release caused by poor infiltration of the electrolyte of the lithium supplement agent in the deep part of the pit due to overlarge roughness.
In some embodiments, the Dv50 particle size of the lithium supplement agent in the lithium supplement layer is 2 μm or less. Alternatively, the Dv50 particle size of the lithium supplement may be, for example, 300nm to 2 μm, or, for example, 500nm, 750nm, 1 μm, 1.25 μm, 1.5 μm, or 1.75 μm. The lithium supplement agent can be better embedded into the pits on the rough surface of the current collector by the proper particle size, the formed lithium supplement layer and the current collector have better adhesive force, the surface is smooth, and the coating of a subsequent film layer cannot be influenced by mottle.
In the present application, dv50 particle size means: in the volume cumulative distribution curve of the particle size, the physical meaning of the particle size corresponding to the cumulative volume distribution of particles up to 50% is that the volume fraction of particles having a particle size smaller (or larger) than this value is 50% each. By way of example, dv50 may conveniently be determined using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer from Malvern instruments Inc., of England, with reference to the GB/T19077-2016 particle size distribution laser diffraction method.
In some embodiments, the amount of the lithium supplement agent in the lithium supplement layer is 1% to 5% of the mass of the active material in the active material layer, and the amount of the lithium supplement agent may be, for example, 2%, 3%, or 4%. The dosage of the lithium supplement agent is controlled within a proper range, the basic requirement of the battery for lithium supplement is met, the active material proportion is not excessively reduced, and the reduction of the volume capacity of the battery is avoided.
In some embodiments, the lithium supplement layer has a thickness of 1 μm to 2 μm. Alternatively, the thickness of the lithium-supplementing layer may also be 1.25 μm, 1.5 μm, or 1.75 μm, for example. The appropriate thickness of the lithium supplement layer can avoid excessive collapse of the pole piece after the lithium supplement is finished while the lithium supplement requirement is met, and the excessive position of the pole piece can not be occupied, so that the volume capacity of the battery is reduced.
In some embodiments, the active material layer has a porosity of 20% to 40%. Alternatively, the thickness of the active material layer may also be 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, or 38%, for example. The porosity of the active material layer is slightly larger than that of the active material layer in the conventional pole piece, so that the active lithium can be better transferred, and the adverse effects of lithium precipitation and the like caused by the excessively high lithium supplementing speed can be avoided.
In some embodiments, the prelithiated pole piece is a positive pole piece, and the active material layer has a porosity of 20% to 30%. Because the oxidation voltage of the positive electrode side is higher, the lithium supplement material is easy to release active lithium, the porosity is set to be smaller, and the lithium supplement speed is favorably controlled.
In some embodiments, the prelithiated pole piece is a negative pole piece, and the active material layer has a porosity of 30% to 40%. The reduction voltage of the negative electrode side is low, and the lithium supplement material releases slowly, so that larger porosity is needed to promote the lithium supplement rate to be in a more proper range.
In some embodiments, the prelithiation pole piece is a positive pole piece, and the lithium supplement agent in the lithium supplement layer comprises Li 1+ x Ni 0.5 Mn 1.5 O 4 、Li 2 NiO 2 、Li 5 FeO 4 、LiF、Li 2 S、Li 2 C 2 O 4 、LiMn 2 O 4 ；Li 2 O 2 、Li 2 O and Li 3 And N, wherein the value of x is selected from any value of 0-1, and optionally x is 0, 0.5 or 1.
In some embodiments, the pre-lithiated pole piece is a negative pole piece, and the lithium supplement agent in the lithium supplement layer includes one or more of lithium powder and pre-lithiated graphite.
In some embodiments, a conductive layer is disposed between the at least one lithium supplement layer and the active material layer, and the conductive layer is a porous structure. The introduction of the conducting layer can better passivate the lithium supplement agent, and the inactivation of the lithium supplement agent due to the contact of water and oxygen is avoided; in addition, after the lithium supplement is finished, the conducting layer can play a supporting role, so that the pole piece is prevented from collapsing and demoulding; furthermore, the arrangement of the conducting layer can enable the coating of the active material layer to be more uniform, balance the contact resistance among all layers of the pole piece and prevent the active material from being released uniformly.
It can be understood that the lithium supplement pole piece in the present application may have any one of the following structures:
(1) The active material layer A + lithium supplement layer A + current collector;
(2) The active material layer A + lithium supplement layer A + current collector + active material layer B;
(3) The active material layer A + lithium supplement layer A + current collector + lithium supplement layer B + active material layer B;
(4) The active material layer A + the conductive layer A + the lithium supplement layer A + the current collector;
(5) The active material layer A + the conductive layer A + the lithium supplement layer A + the current collector + the active material layer B;
(6) The active material layer A + the conductive layer A + the lithium supplement layer A + the current collector + the lithium supplement layer B + the conductive layer B + the active material layer B.
In some embodiments, the porosity of the conductive layer is between 40% and 50%. Alternatively, the thickness of the conductive layer can also be 42%, 44%, 46% or 48%, for example. The proper porosity of the conducting layer can realize the regulation and control of the lithium supplementing rate, the conducting layer has certain rigidity, a supporting effect can be provided, and the pole piece collapse caused after the lithium supplementing is finished is avoided.
In some embodiments, the prelithiated pole piece is a positive pole piece, and the porosity of the conductive layer is 40% to 45%. Because the oxidation voltage of the positive electrode side is higher, the lithium supplement material is easy to release active lithium, the porosity is set to be smaller, and the lithium supplement speed is favorably controlled.
In some embodiments, the prelithiated pole piece is a negative pole piece, and the porosity of the conductive layer is 45% to 50%. The reduction voltage of the negative electrode side is low, and the lithium supplement material releases slowly, so that larger porosity is needed to promote the lithium supplement rate to be in a more proper range.
In some embodiments, the conductive layer has a thickness of 1 μm to 2 μm. Alternatively, the thickness of the conductive layer may also be 1.25 μm, 1.5 μm, or 1.75 μm, for example. The thickness of the conductive layer also needs to be controlled within a proper range, so that the supporting, the lithium supplementing rate control and the uniform contact resistance can be better realized, and meanwhile, the conductive layer does not occupy too many positions to cause the reduction of the volume capacity of the battery.
In some embodiments, the conductive layer includes a conductive agent and a binder.
In some embodiments, the conductive agent comprises one or more of conductive graphite, conductive carbon black, carbon fibers, carbon nanotubes, and graphene. Preferably, the carbon fibers are chopped carbon fibers, and the length of the chopped carbon fibers is 2 mm-4 mm.
In some embodiments, the binder comprises one or more of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene, and polyvinylidene fluoride. The proper binder can provide enough binding force, and simultaneously, the conductive agent can be uniformly dispersed without agglomeration, so that the function of the conductive layer can be better exerted.
Preferably, the polyacrylic acid has a weight average molecular weight of 2000Da to 3000Da.
Preferably, the weight average molecular weight of the polytetrafluoroethylene is 3-5 w Da.
Preferably, the weight average molecular weight of the polyvinylidene fluoride is 40-50 w Da.
In some embodiments, the mass ratio of the conductive agent to the binder is 1 (0.03 to 0.07). Alternatively, the mass ratio of the conductive agent to the binder may also be, for example, 1. The proper dosage ratio of the conductive agent to the binder can ensure that the conductive agent is uniformly dispersed, does not agglomerate, has good caking property and does not fall off a mold, and simultaneously, the pole piece has smaller resistance.
In some embodiments, the conductive layer further comprises inorganic nanoparticles.
In some embodiments, the inorganic nanoparticles comprise Au, sn, znO, moS 2 And Al 2 O 3 One or more of (a). The introduction of inorganic nano-particles of proper category can increase the migration rate of active lithium, and the overall balance and regulation of lithium supplement rate can be realized by combining the control of parameters such as porosity and the like.
In some embodiments, the mass ratio of the conductive agent to the inorganic nanoparticles is 1 (0.001 to 0.01). Alternatively, the mass ratio of the conductive agent to the inorganic nanoparticles may also be, for example, 1. The appropriate dosage ratio of the conductive agent to the inorganic nanoparticles can balance the conductivity and the lithium affinity of the conductive layer, improve the conductivity and avoid influencing the transmission of active lithium.
In a second aspect of the present application, a method for preparing a prelithiation pole piece is provided, which includes the following steps:
providing a current collector with the surface roughness of 2-5 mu m, and preparing a lithium supplement layer on at least one surface of the current collector;
and preparing an active material layer having a porous structure on the lithium supplement layer.
It is understood that in the present application, preparing or forming the target layer B on a certain layer a includes preparing or forming the target layer B directly on the layer a, and also includes preparing or forming the layer B on other layers C, D8230, 8230above the layer a. For example, "preparing an active material layer having a porous structure over a lithium supplement layer" means: the active material layer can be directly prepared and formed on the surface of the lithium supplement layer, or other film layers such as a conductive layer can be prepared on the surface of the lithium supplement layer, and then the active material layer is prepared and formed on the surface of the conductive layer.
It is understood that, in the present application, the preparation of the film layers on the two surfaces of the current collector is independent and unaffected. For example, a lithium supplement layer and an active material layer may be sequentially prepared on one surface of a current collector, and only the active material layer may be prepared on the other surface; for another example, a lithium supplement layer, a conductive layer, and an active material layer may be sequentially prepared on one surface of the current collector, and only the active material layer may be prepared on the other surface, or the lithium supplement layer and the active material layer may be sequentially prepared. Of course, the two surfaces may be symmetrically distributed, and the film layers having the same structure may be disposed.
In some embodiments, the lithium supplement layer is prepared using a dry process. When the prelithiation pole piece is a negative pole piece, a lithium supplement layer is prepared preferably by a dry method, and a lithium supplement agent is pressed into a pit on the surface of the current collector by a direct rolling mode.
In some embodiments, the lithium supplement layer is prepared using wet coating. When the prelithiation pole piece is a positive pole piece, a wet coating is preferably adopted to prepare the lithium supplement layer, and the lithium supplement agent and solvents such as N-methylpyrrolidone (NMP), ethanol, propylene glycol, water and the like are prepared into a dispersion liquid, and then coating is carried out to prepare the lithium supplement layer.
In a third aspect of the present application, a secondary battery is provided that includes the prelithiated pole piece of one or more of the foregoing embodiments.
In a fourth aspect of the present application, there is provided a battery module including the aforementioned secondary battery.
In a fifth aspect of the present application, there is provided a battery pack including the aforementioned battery module.
In a sixth aspect of the present application, an electric device is provided, which includes one or more of the foregoing secondary battery, battery module, and battery pack.
The secondary battery, the battery module, the battery pack, and the electric device according to the present invention will be described below with reference to the drawings as appropriate.
In one embodiment of the present application, a secondary battery is provided.
In general, a secondary battery includes a positive electrode tab, a negative electrode tab, an electrolyte, and a separator. In the process of charging and discharging the battery, active ions are embedded and separated back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable ions to pass through.
At least one of the positive pole piece and the negative pole piece of the secondary battery provided by the application is the prelithiation pole piece provided by the first aspect of the application. For example, the pre-lithiation electrode sheet provided by the first aspect of the present application is used as the positive electrode sheet, and the conventional negative electrode sheet is used as the negative electrode sheet, or the pre-lithiation electrode sheet provided by the first aspect of the present application is used as the negative electrode sheet, and the conventional positive electrode sheet is used as the positive electrode sheet. The structure, the material and the like of the conventional positive pole piece or negative pole piece are as follows:
positive pole piece
The positive pole piece includes the anodal mass flow body and sets up the anodal rete on anodal mass flow body at least one surface, anodal rete includes the anodal active material of the first aspect of this application.
As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.
In some embodiments, the positive electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the positive active material may employ a positive active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) 2 ) Lithium nickel oxides (e.g., liNiO) 2 ) Lithium manganese oxide (e.g., liMnO) 2 、LiMn 2 O 4 ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) 1/3 Co 1/3 Mn 1/3 O 2 (may also be abbreviated as NCM) 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (may also be abbreviated as NCM) 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (may also be abbreviated as NCM) 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (may also be abbreviated as NCM) 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (may also be abbreviated as NCM) 811 ) Lithium nickel cobalt aluminum oxides (e.g., liNi) 0.85 Co 0.15 Al 0.05 O 2 ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) 4 (also referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) 4 ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
In some embodiments, the positive electrode film layer further optionally includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin.
In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.
Negative pole piece
The negative pole piece includes the negative pole mass flow body and sets up the negative pole rete on the negative pole mass flow body at least one surface, the negative pole rete includes negative pole active material.
As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel alloy, titanium alloy, silver alloy, etc.) on a base material of a polymer material (e.g., a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
In some embodiments, the negative active material may employ a negative active material for a battery known in the art. As an example, the anode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate and the like. The silicon-based material can be at least one selected from the group consisting of elemental silicon, a silicon oxy compound, a silicon carbon compound, a silicon nitrogen compound and a silicon alloy. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative active material may also be used. These negative electrode active materials may be used alone or in combination of two or more.
In some embodiments, the anode film layer further optionally includes a binder. The binder may be at least one selected from Styrene Butadiene Rubber (SBR), polyacrylic acid (PAA), sodium Polyacrylate (PAAs), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium Alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).
In some embodiments, the negative electrode film layer further optionally includes a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
In some embodiments, the negative electrode film layer may also optionally include other adjuvants, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)), and the like.
In some embodiments, the negative electrode sheet can be prepared by: dispersing the components for preparing the negative electrode plate, such as a negative electrode active material, a conductive agent, a binder and any other components, in a solvent (such as deionized water) to form negative electrode slurry; and coating the negative electrode slurry on a negative electrode current collector, and drying, cold pressing and the like to obtain the negative electrode pole piece.
Electrolyte
The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The kind of the electrolyte is not particularly limited and may be selected as desired. For example, the electrolyte may be liquid, gel, or all solid.
In some embodiments, the electrolyte is an electrolytic solution. The electrolyte includes an electrolyte salt and a solvent.
In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.
In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, propyl methyl carbonate, propyl ethyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1, 4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.
In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery, such as an additive for improving overcharge properties of the battery, an additive for improving high-temperature or low-temperature properties of the battery, and the like.
Isolation film
In some embodiments, a separator is further included in the secondary battery. The type of the separator is not particularly limited, and any known separator having a porous structure and good chemical and mechanical stability may be used.
In some embodiments, the material of the isolation film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.
In some embodiments, the secondary battery may include an exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.
In some embodiments, the outer package of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The outer package of the secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
The shape of the secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other shape. For example, fig. 1 is a secondary battery 5 of a square structure as an example.
In some embodiments, referring to fig. 2, the overwrap may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity. The housing 51 has an opening communicating with the accommodation chamber, and a cover plate 53 can be provided to cover the opening to close the accommodation chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. An electrode assembly 52 is enclosed within the receiving cavity. The electrolyte is impregnated into the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 may be one or more, and those skilled in the art can select them according to the actual needs.
In some embodiments, the secondary batteries may be assembled into a battery module, and the number of the secondary batteries included in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
Fig. 3 is a battery module 4 as an example. Referring to fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in series along the longitudinal direction of the battery module 4. Of course, the arrangement may be in any other manner. The plurality of secondary batteries 5 may be further fixed by a fastener.
Alternatively, the battery module 4 may further include a case having an accommodation space in which the plurality of secondary batteries 5 are accommodated.
In some embodiments, the battery modules may be assembled into a battery pack, and the number of the battery modules contained in the battery pack may be one or more, and the specific number may be selected by one skilled in the art according to the application and the capacity of the battery pack.
Fig. 4 and 5 are a battery pack 1 as an example. Referring to fig. 4 and 5, a battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery box comprises an upper box body 2 and a lower box body 3, wherein the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. A plurality of battery modules 4 may be arranged in any manner in the battery box.
In addition, this application still provides a power consumption device, power consumption device includes at least one in secondary battery, battery module or the battery package that this application provided. The secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The electric device may include, but is not limited to, a mobile device, an electric vehicle, an electric train, a ship and a satellite, an energy storage system, and the like. The mobile device may be, for example, a mobile phone, a notebook computer, or the like; the electric vehicle may be, for example, a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, or the like, but is not limited thereto.
As the electricity-using device, a secondary battery, a battery module, or a battery pack may be selected according to the use requirement thereof.
Fig. 6 is an electric device 6 as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle or a plug-in hybrid electric vehicle and the like. In order to meet the demand of the electric device for high power and high energy density of the secondary battery, a battery pack or a battery module may be used.
As another example, the device may be a cell phone, a tablet, a laptop, etc. The device is generally required to be thin and light, and a secondary battery may be used as a power source.
The present application will be described in further detail with reference to specific examples and comparative examples. The experimental parameters not described in the following specific examples, preferably with reference to the directions given in the present application, may also be referred to the experimental manual in the art or other experimental methods known in the art, or to the experimental conditions recommended by the manufacturer. It is understood that the following examples are specific to the particular apparatus and materials used, and in other embodiments, are not limited thereto; the weight of the related components mentioned in the embodiments of the present specification may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the embodiments of the present specification as long as it is scaled up or down according to the embodiments of the present specification. Specifically, the weight described in the specification of the examples of the present application may be in units of mass known in the chemical and chemical fields, such as μ g, mg, g, and kg.
Example 1
(1) Preparation of positive pole piece
a. Selecting Li 5 FeO 4 (Dv 50 grain diameter is 1.5 μm, dosage is 5% of positive active material) as lithium supplement agent, equally dividing the lithium supplement agent into two parts, pressing on two sides of aluminum current collector with roughness of 3 μm to obtainTo a lithium-replenishing current collector comprising two lithium-replenishing layers with a thickness of 1 μm;
b. mixing and dispersing conductive carbon, methyl acrylate and nano Sn particles in a mass ratio of 1.05 to 0.005 in N-methyl pyrrolidone (NMP), and coating the conductive carbon, the methyl acrylate and the nano Sn particles on two sides of the lithium supplement current collector prepared in the step a to obtain a conductive lithium supplement current collector comprising two conductive layers with the thickness of 1 mu m;
c. mixing NCM622, PVDF (polyvinylidene fluoride) and SP (conductive carbon) according to a mass ratio of 80; dissolving a positive electrode active material in NMP (N-methyl pyrrolidone) to prepare positive electrode slurry, coating the positive electrode slurry on two sides of the conductive lithium supplement current collector prepared in the step b, drying, and then carrying out cold pressing to obtain a positive electrode piece;
in the obtained positive pole piece, the porosity of the conductive layer is 40%, and the porosity of the positive active material layer is 25%;
(2) Preparing a negative pole piece:
mix graphite, SBR (styrene butadiene rubber), SP (conductive carbon) according to 90.
(3) Winding, hot pressing, injecting and packaging the positive pole piece, the isolating membrane and the negative pole piece to obtain the lithium ion battery, and carrying out formation (the multiplying power constant current charging of 0.1C is carried out to 3.0V, the multiplying power constant current charging of 0.2C is carried out to 3.75V) and first circle lithium source activation (the multiplying power constant current charging of 0.33C is carried out to 4.50V, the constant voltage charging is carried out to 0.05C, and the multiplying power constant current discharging of 0.33C is carried out to 2.5V).
Example 2
In substantial agreement with example 1, except that, in step (1) a, the aluminum current collector had a roughness of 2 μm, and the one-sided lithium supplement layer was formed to a thickness of 1.1 μm.
Example 3
In substantial agreement with example 1, except that, in step (1) a, the aluminum current collector had a roughness of 5 μm, and the one-sided lithium supplement layer was formed to a thickness of 0.8 μm.
Example 4
In substantial agreement with example 1, with the difference that in step (1) a，Li 5 FeO 4 The Dv50 particle diameter of (2) was 3.5. Mu.m, and the thickness of the one-side lithium-supplement layer was 3.5. Mu.m.
Example 5
Substantially in accordance with example 1, except that in step (1) a, li 5 FeO 4 The Dv50 particle diameter of (2) was 0.5. Mu.m, and the thickness of the one-side lithium-supplement layer was 0.5. Mu.m.
Example 6
Substantially in accordance with example 1, except that, in step (1) a, the thickness of the one-side conductive layer was 3 μm.
Example 7
Substantially in accordance with example 1, except that the porosity of the conductive layer of the positive electrode sheet obtained in step (1) was 35%.
Example 8
Substantially in accordance with example 1, except that the porosity of the conductive layer of the positive electrode sheet obtained in step (1) was 55%.
Example 9
Substantially in accordance with example 1, except that the porosity of the active material layer of the positive electrode sheet obtained in step (1) was 15%.
Example 10
Substantially in accordance with example 1, except that the porosity of the active material layer of the positive electrode sheet obtained in step (1) was 45%.
Example 11
In substantial agreement with example 1, except for the absence of step (1) b, the resulting positive electrode sheet contained no conductive layer.
Example 12
Substantially the same as in example 1 except that, in step (1) a, the amount of the lithium replenishing agent was 10% of the positive electrode active material.
Example 13
Substantially the same as example 1, except that in step (1) b, the mass ratio of the conductive carbon, the methyl acrylate, and the nano Sn particles in the raw material of the conductive layer is 1.
Example 14
Substantially the same as example 1, except that in step (1) b, the mass ratio of the conductive carbon, the methyl acrylate and the nano Sn particles in the raw materials of the conductive layer is 1.
Example 15
Basically the same as example 1, except that in step (1) b, the mass ratio of the conductive carbon, the methyl acrylate and the nano Sn particles in the raw materials of the conductive layer is 1.
Example 16
Substantially in accordance with example 1, except that, in step (1) a, the roughness of the aluminum current collector was 2 μm and the amount of the lithium supplement agent was 3% of the positive electrode active material.
Example 17
In substantial agreement with example 1, except that in step (1) a, the lithium replenishing agent was replaced with Li of equal mass 2 O。
Example 18
In substantial agreement with example 1, with the difference that in step (1) a, the roughness of the aluminum current collector was 3.5 μm, and the lithium supplement agent was replaced with Li of equal mass 2 NiO 2 。
Example 19
(1) Preparation of positive pole piece
Mixing NCM622, PVDF (polyvinylidene fluoride) and SP (conductive carbon) according to a mass ratio of 80; dissolving a positive electrode active material in NMP (N-methylpyrrolidone) to prepare positive electrode slurry, coating the positive electrode slurry on two sides of an aluminum current collector, drying, and then carrying out cold pressing to obtain a positive electrode piece;
(2) Preparing a negative pole piece:
a. selecting lithium powder (the Dv50 particle size is 1.5 mu m, and the using amount is 1 percent of that of the negative active material) as a lithium supplement agent, equally dividing the lithium supplement agent into two parts, and pressing the two parts on the two sides of a copper current collector with the roughness of 3 mu m to obtain a lithium supplement current collector comprising two lithium supplement layers with the thickness of 1 mu m;
b. mixing and dispersing conductive carbon, polytetrafluoroethylene (weight average molecular weight 40000 Da) and nano ZnO particles in N-methyl pyrrolidone (NMP) according to the mass ratio of 1;
c. mixing graphite, SBR (styrene butadiene rubber) and SP (conductive carbon) according to a mass ratio of 90;
in the obtained negative pole piece, the porosity of the conductive layer is 45%, and the porosity of the positive active material layer is 35%;
(3) Winding, hot pressing, injecting and packaging the positive pole piece, the isolating membrane and the negative pole piece to obtain the lithium ion battery, and carrying out formation (the multiplying power constant current charging of 0.1C is carried out to 3.0V, the multiplying power constant current charging of 0.2C is carried out to 3.75V) and first circle lithium source activation (the multiplying power constant current charging of 0.33C is carried out to 4.50V, the constant voltage charging is carried out to 0.05C, and the multiplying power constant current discharging of 0.33C is carried out to 2.5V).
Comparative example 1
Substantially in accordance with example 11, except that step (1) a was not included, the resulting positive electrode sheet did not include the lithium supplement layer and the conductive layer.
Comparative example 2
Substantially in accordance with example 1, except that in step (1) a, li 5 FeO 4 The Dv50 particle size of (2) is 2 μm, the roughness of the aluminum current collector is 1 μm, and the thickness of the formed one-side lithium supplement layer is 1.3 μm.
Comparative example 3
Substantially in accordance with example 1, except that in step (1) a, li 5 FeO 4 The Dv50 particle size of (2) is 2 μm, the roughness of the aluminum current collector is 6 μm, and the thickness of the formed one-side lithium supplement layer is 0.7 μm.
Characterization test:
the batteries prepared in the above examples and comparative examples were subjected to the following performance tests:
(1) Testing the first circle capacity of the battery:
the lithium ion secondary battery was placed in a 25 ℃ incubator, charged at a constant current of 0.5C rate to a voltage higher than 4.35V at normal temperature, further charged at a constant voltage of 4.35V to a current lower than 0.05C to be in a fully charged state of 4.35V, and then discharged at a constant current of 0.33C rate to a voltage of 2.5V (cut-off voltage), which was 1 cycle. Recording the discharge capacity D; the first-round capacity boost of each example relative to comparative example 1 was calculated based on the first-round discharge capacity D0 of comparative example 1 without lithium supplementation: (D-D0)/D0.
(2) And (3) testing the cycle life:
the lithium ion secondary battery was placed in a 25 ℃ incubator, charged at a constant current of 0.5C rate to a voltage higher than 4.35V at normal temperature, further charged at a constant voltage of 4.35V to a current lower than 0.05C to be in a fully charged state of 4.35V, and then discharged at a constant current of 0.33C rate to a voltage of 2.5V (cut-off voltage), which was 1 cycle. The cycle was repeated and the discharge capacity D2 was recorded for each cycle, stopping the test when D2/D1=80% and recording the number of cycles.
TABLE 1
Figure BDA0003753082960000161
Figure BDA0003753082960000171
Analyzing data in the table 1, compared with the example 1, the surface roughness of the current collector in the example 2 is smaller, the thickness of the lithium supplement layer formed by the lithium supplement agent with the same amount is slightly increased, the adhesion to the lithium supplement layer is slightly weak, and the cycle performance is influenced to a certain extent; the surface roughness of the current collector in example 3 is large, and although the lithium supplement layer is better attached, the lithium supplement agent in the deep part of the pit on the surface of the current collector can not be released, so the cycle performance is slightly reduced; in example 4, the lithium supplement agent has too large particle size and is poorly matched with the roughness of the current collector, so the adhesion is also poor, and the cycle performance is affected; in example 5, the particle size of the lithium supplement agent is too small, and the formed lithium supplement layer is too thin, and because the particle size is too small, part of the lithium supplement agent is buried in the deep part of the current collector pit and cannot be released, which also affects the battery performance; in embodiment 6, the conducting layer is too thick, occupying more positions of the pole piece, and affecting the cycle performance of the pole piece; in example 7, the porosity of the conductive layer was low, and part of the lithium supplement agent was not released well, thereby affecting the cycle performance to some extent; in example 8, the porosity of the conductive layer was high, and lithium release was too fast, which was not favorable for long-term lithium supplementation, and therefore the cycle performance was reduced; examples 9 and 10 have a similar trend to examples 7 and 8, and the cycle performance is also reduced; in example 11, the conductive layer was not contained, and problems of mold release and excessive release of lithium were liable to occur; in example 12, the lithium supplement agent is used in an excessive amount, which causes lithium precipitation and affects the active material ratio, thereby affecting the cycle performance; in example 13, the binder amount of the conductive layer was small, and there was a risk of mold release; in example 14, the use of excessive binder in the conductive layer increased the impedance of the electrode sheet; in example 15, the lithium-philic inorganic nanoparticles were used in higher amounts, resulting in a too fast release of lithium.
In comparative example 1, the lithium supplement layer and the conductive layer were not included, and the cycle performance was greatly reduced; in comparative examples 2 and 3, the surface roughness was not within the predetermined range, which seriously affected the adhesion of the current collector surface to the lithium supplement layer and the release of the lithium supplement agent, and the cycle performance was also significantly reduced compared to the respective examples.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the patent is subject to the appended claims, and the description and the drawings can be used for explaining the contents of the claims.

Claims (21)

1. A pre-lithiated pole piece is characterized by comprising a current collector and an active material layer arranged on at least one surface of the current collector; a lithium supplement layer is arranged between the current collector and at least one active material layer;
wherein, the surface roughness of the current collector is 2-5 μm, and the active material layer is in a porous structure.
2. The prelithiation pole piece of claim 1, wherein the Dv50 particle size of the lithium supplement agent in the lithium supplement layer is 2 μm or less.
3. The prelithiation pole piece of claim 1, wherein the amount of lithium supplement agent in the lithium supplement layer is 1-5% of the mass of active material in the active material layer.
4. The prelithiation pole piece of claim 1, wherein the lithium supplement layer has a thickness of 1 μm to 2 μm.
5. The prelithiated pole piece of claim 1, wherein the active material layer has a porosity of 20% to 40%.
6. The prelithiation pole piece of any of claims 1 to 5, wherein the prelithiation pole piece is a positive pole piece and the porosity of the active material layer is 20% to 30%.
7. The prelithiation pole piece of any of claims 1 to 5, wherein the prelithiation pole piece is a negative pole piece and the active material layer has a porosity of 30% to 40%.
8. The prelithiation pole piece according to any of claims 1 to 5, wherein the prelithiation pole piece is a positive pole piece, and the lithium supplement agent in the lithium supplement layer comprises Li 1+x Ni 0.5 Mn 1.5 O 4 、Li 2 NiO 2 、Li 5 FeO 4 、LiF、Li 2 S、Li 2 C 2 O 4 、LiMn 2 O 4 ；Li 2 O 2 、Li 2 O and Li 3 N, wherein the value of x is selected from any value of 0-1.
9. The prelithiation pole piece of any of claims 1 to 5, wherein the prelithiation pole piece is a negative pole piece, and the lithium supplement agent in the lithium supplement layer comprises one or more of lithium powder and prelithiation graphite.
10. The prelithiation pole piece of any of claims 1 to 5, wherein a conductive layer is disposed between at least one of the lithium supplement layers and the active material layer, the conductive layer being porous.
11. The prelithiated pole piece of claim 10, wherein the porosity of the conductive layer is between 40% and 50%.
12. The prelithiation pole piece of claim 10, wherein the prelithiation pole piece is a positive pole piece and the porosity of the conductive layer is between 40% and 45%.
13. The prelithiation pole piece of claim 10, wherein the prelithiation pole piece is a negative pole piece and the porosity of the conductive layer is 45% to 50%.
14. The prelithiation pole piece of claim 10, wherein the thickness of the conductive layer is between 1 μ ι η and 2 μ ι η.
15. The prelithiated pole piece of claim 10, wherein the conductive layer comprises a conductive agent and a binder;
optionally, the conductive agent comprises one or more of conductive graphite, conductive carbon black, carbon fibers, carbon nanotubes, and graphene;
optionally, the binder comprises one or more of acrylic acid, methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, methyl methacrylate, ethyl methacrylate, polyacrylic acid, polytetrafluoroethylene, and polyvinylidene fluoride.
16. The prelithiation pole piece of claim 15, wherein the mass ratio of the conductive agent to the binder is 1 (0.03-0.07).
17. The prelithiated pole piece of claim 16, wherein the conductive layer further comprises inorganic nanoparticles;
optionally, the inorganic nanoparticles comprise Au, sn, znO, moS 2 And Al 2 O 3 One or more of (a).
18. The prelithiation pole piece of claim 17, wherein the mass ratio of the conductive agent to the inorganic nanoparticles is 1 (0.001-0.01).
19. A preparation method of a pre-lithiation pole piece is characterized by comprising the following steps:
providing a current collector with the surface roughness of 2-5 mu m, and preparing a lithium supplement layer on at least one surface of the current collector;
and preparing an active material layer having a porous structure on the lithium supplement layer.
20. A secondary battery comprising the prelithiated pole piece of any one of claims 1 to 18.
21. An electric device comprising the secondary battery according to claim 20.
CN202210846555.2A 2022-07-19 2022-07-19 Pre-lithiation pole piece, preparation method thereof, secondary battery and power utilization device Pending CN115842096A (en)

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