CN114156434A - Pole piece and lithium ion battery - Google Patents

Pole piece and lithium ion battery Download PDF

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Publication number
CN114156434A
CN114156434A CN202111446122.XA CN202111446122A CN114156434A CN 114156434 A CN114156434 A CN 114156434A CN 202111446122 A CN202111446122 A CN 202111446122A CN 114156434 A CN114156434 A CN 114156434A
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China
Prior art keywords
protective layer
pole piece
carbide
current collector
layer
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CN202111446122.XA
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Chinese (zh)
Inventor
张健
彭冲
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Zhuhai Cosmx Battery Co Ltd
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Zhuhai Cosmx Battery Co Ltd
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Priority to CN202111446122.XA priority Critical patent/CN114156434A/en
Publication of CN114156434A publication Critical patent/CN114156434A/en
Priority to PCT/CN2022/132059 priority patent/WO2023093576A1/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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • 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
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2200/00—Safety devices for primary or secondary batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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)
  • Materials Engineering (AREA)
  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention provides a pole piece and a lithium ion battery. The invention provides a pole piece, which comprises a substrate, wherein the substrate comprises a current collector and a protective layer arranged on the surface of the current collector, and an active substance layer is also arranged on the protective layer; the protective layer comprises 62-96% of inactive materials, 0.1-8% of conductive agents and 3-30% of binders in percentage by mass; the thickness H1 of the protective layer and the D50 of the inactive material satisfy the relation H1 is more than or equal to 2X D50; the thickness H1 of the protective layer and the D90 of the inactive material satisfy the relation that H1 is more than or equal to D90; the thickness H1 of the protective layer and the thickness H2 of the active material layer satisfy the relation H1/H2 ≤ 1/5. The pole piece provided by the invention can solve the problem that the safety and the electrical property of the lithium ion battery cannot be considered at the same time.

Description

Pole piece and lithium ion battery
Technical Field
The invention relates to a pole piece and a lithium ion battery, and relates to the technical field of electrochemistry.
Background
The lithium ion battery has the advantages of high platform voltage, high energy density, no memory effect, long service life and the like, and is widely applied to the fields of smart phones, notebook computers, Bluetooth, wearable equipment and the like. However, in some extreme cases, for example, when the lithium ion battery is subjected to mechanical damage, such as needle stick, heavy impact, etc., an internal short circuit occurs, and a large amount of heat is released in a short time, so that the lithium ion battery is subjected to fire and failure, and has a great safety hazard.
Researches show that when the lithium ion battery is subjected to internal short circuit, a plurality of short circuit modes exist, at present, the safety of the lithium ion battery is improved by arranging the protective layer on the surface of the current collector, but the electrical property of the lithium ion battery is reduced, so that more and more attention is paid to the safety and the electrical property of the lithium ion battery.
Disclosure of Invention
The invention provides a pole piece which is used for solving the problem that the safety and the electrical property of a lithium ion battery cannot be considered at the same time.
The invention also provides a lithium ion battery which has better safety and electrical property.
The invention provides a pole piece, which comprises a substrate, wherein the substrate comprises a current collector and a protective layer arranged on the surface of the current collector, and an active substance layer is also arranged on the protective layer;
the protective layer comprises 62-96% of inactive materials, 0.1-8% of conductive agents and 3-30% of binding agents in percentage by mass;
the thickness H1 of the protective layer and the D50 of the inactive material satisfy the relation H1 is more than or equal to 2X D50;
the thickness H1 of the protective layer and the D90 of the inactive material satisfy the relation that H1 is more than or equal to D90;
the thickness H1 of the protective layer and the thickness H2 of the active material layer satisfy the relation H1/H2 ≤ 1/5.
According to an embodiment of the invention, the inactive material comprises inorganic particles and/or organic particles, wherein:
the inorganic particles comprise one or more of oxides, carbides, nitrides, inorganic salts and first carbon coating materials, the first carbon coating materials comprise first base particles and first carbon layers coated on at least partial surfaces of the first base particles, and the first base particles are selected from one or more of oxides, carbides, nitrides and inorganic salts;
the organic particles comprise one or more of polystyrene, polymethyl methacrylate, polytetrafluoroethylene and a second carbon coating material, the second carbon coating material comprises second matrix particles and a second carbon layer coated on at least part of the surfaces of the second matrix particles, and the second matrix particles are selected from one or more of polystyrene, polymethyl methacrylate and polytetrafluoroethylene.
According to an embodiment of the present invention, the oxide is at least one selected from the group consisting of alumina, titania, magnesia, zirconia, antimony oxysulfide, barium oxide, manganese oxide, silica, iron oxide, and ferroferric oxide; the carbide comprises a metal carbide and/or a non-metal carbide, the metal carbide comprises at least one of titanium carbide, calcium carbide, chromium carbide, tantalum carbide, vanadium carbide, zirconium carbide and tungsten carbide, and the non-metal carbide comprises boron carbide and/or silicon carbide; the nitride comprises a metal nitride and/or a non-metal nitride, the metal nitride comprises at least one of lithium nitride, magnesium nitride, aluminum nitride, titanium nitride and tantalum nitride, and the non-metal nitride comprises at least one of boron nitride, phosphorus pentanitride and silicon tetranitride; the inorganic salt comprises a carbonate and/or a sulfate.
According to an embodiment of the present invention, the thickness H1 of the protective layer and the D10 of the inactive material satisfy the relationship H1 ≧ 8 XD 10.
According to one embodiment of the invention, the inactive material has a D10 ≦ 0.5 μm, a D50 ≦ 2 μm, and a D90 ≦ 5 μm.
According to an embodiment of the invention, the inactive material has a D10 of 0.01-0.2 μm, a D50 of 0.05-0.5 μm, and a D90 of 1-3 μm.
According to an embodiment of the invention, the thickness of the protective layer is 0.1 μm to 10 μm.
According to an embodiment of the present invention, the pole piece is a positive pole piece.
According to an embodiment of the present invention, at least one of the first end and the second end of the pole piece, a vertical distance from the protective layer to an outer edge of the current collector is smaller than a vertical distance from the active material layer to the outer edge of the current collector, and the first end and the second end are opposite; or,
and a hollow foil area is arranged between the protective layer and the outer edge of the current collector at least one of the first end and the second end of the pole piece, the active substance layer comprises a first part and a second part connected with the first part, the first part is arranged on the surface of the protective layer, and the second part is arranged on the surface of the current collector in the hollow foil area.
In a second aspect, the invention provides a lithium ion battery, which includes any of the above pole pieces.
The implementation of the invention has at least the following advantages:
1. the pole piece provided by the invention comprises the protective layer, and the relationship among the mass fraction of each component in the protective layer, the thickness of the protective layer, the particle size of the non-active material and the thickness of the active material layer is controlled, so that the problems of ignition aging and the like of the lithium ion battery under the conditions of mechanical abuse and the like are effectively solved, the electrical property of the lithium ion battery is basically not influenced, and the problem that the safety and the electrical property of the lithium ion battery cannot be considered at the same time is solved.
2. The lithium ion battery provided by the invention has better safety and electrical property.
Drawings
Fig. 1 is a schematic structural diagram of a pole piece according to an embodiment of the present invention;
fig. 2 is a schematic structural diagram of a pole piece according to another embodiment of the present invention.
Description of reference numerals:
100-a current collector;
200-a protective layer;
300-active substance layer.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides a pole piece, which comprises a substrate, wherein the substrate comprises a current collector and a protective layer arranged on the surface of the current collector, and an active substance layer is also arranged on the protective layer;
the protective layer comprises 62-96% of inactive materials, 0.1-8% of conductive agents and 3-30% of binding agents in percentage by mass;
the thickness H1 of the protective layer and the D50 of the inactive material satisfy the relation H1 is more than or equal to 2X D50;
the thickness H1 of the protective layer and the D90 of the inactive material satisfy the relation that H1 is more than or equal to D90;
the thickness H1 of the protective layer and the thickness H2 of the active material layer satisfy the relation H1/H2 ≤ 1/5.
The invention provides a pole piece, which comprises a substrate, wherein the substrate comprises a current collector and a protective layer arranged on the surface of the current collector, an active substance layer is also arranged on the protective layer, the current collector is a base metal used for attaching other materials such as a protective layer material and an active substance in the pole piece, the current collector comprises two surfaces used for attaching other materials such as a protective layer material and an active substance, the protective layer is arranged on the surface of the current collector, the current collector and the protective layer form the substrate of the pole piece, and the protective layer is also provided with an active substance layer. In order to ensure that the electrical property of the lithium ion battery is not affected basically, the invention selects the non-active material as the main component of the protective layer, the non-active material refers to the material which does not participate in the electrochemical reaction (the function of the active material layer of the pole piece is opposite), the use of the lithium ion battery is not affected by continuous deterioration in the charging and discharging process of the lithium ion battery, the influence of the protective layer on the cycle stability of the lithium ion battery is reduced, and the electrical property of the lithium ion battery is considered; the inactive material is used as a main component of the protective layer 200 and mainly plays a role of supporting the protective layer, when the content of the inactive material is too low, the structural stability of the protective layer is poor, and the inactive material is damaged by the action of the active material layer in the subsequent active material layer coating process or is pressed and dispersed by pressure in the pole piece rolling process, so that the mass percentage of the inactive material is not lower than 62%; it can be understood that the protective layer 200 includes a binder and a conductive agent in addition to the inactive material, the binder is used for binding the inactive material, the conductive agent and other components together to form a coating, and binding the protective layer and the current collector together, so as to improve the stability of the protective layer and the binding force between the protective layer and the current collector, thereby improving the stability and safety of the pole piece, when the content of the binder is too low, the binder cannot perform a binding function, and is not favorable for the protective layer to be well adhered to the current collector, and when the content of the binder is too high, the pole piece is easily embrittled, the compaction density is reduced, and the energy density of the lithium ion battery is affected; the conductive agent can construct an electronic conductive network, particularly when the protective layer is positioned between the current collector and the active substance layer, the conductive agent can be used as an electronic path for connecting the current collector and the active substance layer, the function of the current collector is favorably exerted, the performance of the pole piece such as the multiplying power is improved, if the content of the conductive agent is too low, the conductive performance of the protective layer is insufficient, the electrical performance of the pole piece is influenced, if the content of the conductive agent is too high, the protective function of the protective layer on the pole piece is also influenced to a certain extent, when an internal short circuit occurs, the protective layer has higher conductivity, and the contact with the pole piece with the other polarity can cause severe heat generation at a short circuit point and thermal runaway, so that in order to consider the safety and the electrical performance of the lithium ion battery, the protective layer comprises 62-96% of a non-active material, 0.1-8% of the conductive agent and 3-30% of a binder by mass percentage, namely, the total mass of the protective layer is 100%, the mass of the non-active material is 62-96% of the total mass of the protective layer, the mass of the conductive agent is 0.1-8% of the total mass of the protective layer, and the mass of the binder is 3-30% of the total mass of the protective layer.
Meanwhile, the inventor finds that the relation between the thickness of the protective layer and the particle size of the inactive layer has an important influence on the protective effect of the protective layer, specifically, the inactive material is a key factor for protecting and supporting, and when the inactive material in the protective layer has at least two layers on a plane perpendicular to the current collector, the protective layer can achieve a good protective effect, so that the thickness H1 of the protective layer and the average particle size D50 of the inactive material need to satisfy H1 is not less than 2 × D50. Under the condition, the protective layer is favorably and evenly distributed with at least two inactive material particles in the thickness direction (the direction vertical to the surface of the current collector), which is equivalent to form at least two single-layer protective layers (the average number of the inactive material particles of each single-layer protective layer in the thickness direction is one), is more favorable for the functional exertion of the protective layer and improves the safety of the pole piece; the thickness H1 of the protective layer and the D90 of the inactive material meet the condition that H1 is larger than or equal to D90, so that the particle size of more than 90% of particles in the protective layer is lower than the thickness of the protective layer, the occurrence of coating and scraping is effectively avoided, the foil leakage phenomenon is avoided, and the processing performance of the protective layer is improved; d50 is a particle diameter at which the volume accumulation of the inactive material reaches 50% from the small particle diameter side in the volume-based particle diameter distribution; d90 is a particle size at which the volume of the inactive material reaches 90% cumulatively with the volume from the small particle size side in the volume-based particle size distribution.
In order to further avoid the influence of the protective layer on the energy density of the lithium ion battery, the relation between the thickness H1 of the protective layer and the thickness H2 of the active material layer satisfies H1/H2 ≤ 1/5.
The pole piece provided by the invention comprises the protective layer, and the relationship among the mass fraction of each component in the protective layer, the thickness of the protective layer, the particle size of an inactive material and the thickness of an active material layer is controlled, so that the safety of the lithium ion battery can be effectively improved, the probability of ignition and invalidation of the lithium ion battery is reduced particularly when mechanical abuse occurs, the through-nail test passing rate of the lithium ion battery is improved, the electrical property of the lithium ion battery is basically not influenced, and the problem that the safety and the electrical property of the lithium ion battery cannot be considered simultaneously is solved.
In one embodiment, the inactive material comprises inorganic particles and/or organic particles, wherein:
the inorganic particles comprise one or more of oxides, carbides, nitrides, inorganic salts and first carbon coating materials, the first carbon coating materials comprise first base particles and first carbon layers coated on at least partial surfaces of the first base particles, and the first base particles are selected from one or more of oxides, carbides, nitrides and inorganic salts;
further, the oxide is selected from at least one of alumina, titanium oxide, magnesium oxide, zirconia, antimony oxysulfide, barium oxide, manganese oxide, silicon oxide, iron oxide and ferroferric oxide; the carbide comprises a metal carbide and/or a non-metal carbide, the metal carbide comprises at least one of titanium carbide, calcium carbide, chromium carbide, tantalum carbide, vanadium carbide, zirconium carbide and tungsten carbide, and the non-metal carbide comprises boron carbide and/or silicon carbide; the nitride comprises a metal nitride and/or a non-metal nitride, the metal nitride comprises at least one of lithium nitride, magnesium nitride, aluminum nitride, titanium nitride and tantalum nitride, and the non-metal nitride comprises at least one of boron nitride, phosphorus pentanitride and silicon tetranitride; the inorganic salt comprises a carbonate and/or a sulfate. The carbon coating process is a conventional process in the art and is not described in detail.
The organic particles are micro-particles composed of a high polymer material, such as one or more of polystyrene, polymethyl methacrylate, polytetrafluoroethylene and a second carbon coating material, the second carbon coating material comprises a second matrix particle and a second carbon layer coated on at least part of the surface of the second matrix particle, and the second matrix particle is selected from one or more of polystyrene, polymethyl methacrylate and polytetrafluoroethylene.
In order to further improve the protection effect of the protective layer, the thickness H1 of the protective layer and the D10 of the inactive material meet the condition that H1 is more than or equal to 8 multiplied by D10, the inactive material in the particle size range is selected to be beneficial to ensuring that enough small particle materials are filled in the protective layer, the compactness of the protective layer is improved, and D10 is the particle size of 10% of the volume accumulation of the inactive material from the small particle size side in the particle size distribution of the volume standard.
In combination with the thickness range of the active material layer of the lithium ion battery at present, the thickness of the protective layer is 0.1-10 μm, the D10 of the inactive material is less than or equal to 0.5 μm, the D50 of the inactive material is less than or equal to 2 μm, and the D90 of the inactive material is less than or equal to 5 μm, further, the D10 of the inactive material is 0.01-0.2 μm, the D50 is 0.05-0.5 μm, and the D90 is 1-3 μm.
The binder and the conductive agent in the protective layer may be conventional materials in the art, for example, the binder includes one or more of polyvinylidene fluoride (PVDF), carboxylic acid modified polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), Polyacrylonitrile (PAN), polyacrylates, Polyimide (PI), wherein the carboxylic acid modified PVDF includes acrylic acid modified PVDF; the conductive agent comprises one or more of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes and carbon nanofibers, and a person skilled in the art can select a suitable material, mix the material with a non-active material to obtain a protective layer slurry, coat the protective layer slurry on the surface of the current collector, and obtain a protective layer after drying.
For the coating length of the protective layer and the active material layer on the surface of the current collector, the invention is not further limited, the active material layer may be entirely located on the surface of the protective layer away from the current collector, or partially located on the surface of the protective layer away from the current collector, specifically, at least one of the first end and the second end of the pole piece, the vertical distance from the protective layer to the outer edge of the current collector is smaller than the vertical distance from the active material layer to the outer edge of the current collector, and the first end and the second end are opposite; or,
and a hollow foil area is arranged between the protective layer and the outer edge of the current collector at least one of the first end and the second end of the pole piece, the active substance layer comprises a first part and a second part connected with the first part, the first part is arranged on the surface of the protective layer, and the second part is arranged on the surface of the current collector in the hollow foil area.
For example, fig. 1 is a schematic structural diagram of a pole piece according to an embodiment of the present invention, as shown in fig. 1, the pole piece includes a current collector 100, a protection layer 200 located on an upper surface of the current collector, and an active material layer 300 located on the protection layer 200 and away from the surface of the current collector 100, that is, a vertical distance from the protection layer 200 to an outer edge of the current collector 100 is smaller than a vertical distance from the active material layer 300 to an outer edge of the current collector 100; fig. 2 is a schematic structural diagram of a pole piece according to still another embodiment of the present invention, as shown in fig. 2, the pole piece includes a current collector 100, a protection layer 200, and an active material layer 300, the protection layer 200 is located on an upper surface of the current collector 100, the active material layer 300 includes two parts, a first part of the active material layer 300 is located on the upper surface of the protection layer 200 away from the current collector, and a second part of the active material layer 300 is located on a portion of the upper surface of the current collector where the protection layer is not located, fig. 1-2 show how to locate the protection layer and the active material layer on the upper surface of the current collector, the location of the other surface of the current collector 100 may be the same as or different from the upper surface, for example, the protection layer 200 and the active material layer 300 may be located on the lower surface of the current collector 100, or only the active material layer 300 may be located on the two surfaces of the current collector 100, but at least one surface should be located with the protection layer 200, those skilled in the art can set the actual requirements, and the present invention is not further limited thereto.
In the invention, the pole piece can be a positive pole piece or a negative pole piece, when the pole piece is the positive pole piece, the pole piece comprises a positive pole current collector, a protective layer and a positive pole active substance layer, and when the pole piece is the negative pole piece, the pole piece comprises a negative pole current collector, a protective layer and a negative pole active substance layer, wherein the positive pole current collector can be an aluminum foil formed by taking aluminum as a main component, or a composite current collector formed by laminating the aluminum foil and other materials (such as polymer materials and the like), or a composite current collector comprising the aluminum foil and a conductive carbon layer coated on the surface of the aluminum foil and the like, wherein the mass content of aluminum in the aluminum foil is generally not lower than 95%; the negative electrode current collector may be a copper foil.
The active material layer comprises active material, binder and conductive agent, the active material is material participating electrochemical reaction in the charge and discharge process of the pole piece/electrochemical device, when the pole piece is a positive pole piece, the active material is positive pole active material, such as positive pole active material providing lithium ion, specifically comprises lithium positive pole composite metal oxide (i.e. lithium-containing inorganic material), such as lithium cobaltate (LiCoO)2) Lithium nickelate (LiNiO)2) Lithium manganate (LiMn)2O4) Lithium iron phosphate (LiFePO)4) At least one of ternary materials, conversion of ternary materialsThe chemical formula can be LiNixCoyMnzO2And x + y + z is 1. When the electrode plate is a negative electrode plate, the active material is a negative electrode active material, and the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, mesocarbon microbeads (MCMB), silicon-carbon composites, silicon oxide, lithium titanate, and lithium metal.
The binder and the conductive agent in the active material layer have the same functions as those of the binder and the conductive agent in the protective layer, and the binder and the conductive agent are selected as described above, and the conductive agent and the binder in the protective layer and the active material layer may be the same or different.
In addition, when the electrode sheet is a negative electrode sheet, the negative active material layer may further include a dispersant including sodium carboxymethylcellulose or the like.
Research shows that when the lithium ion battery is in internal short circuit, various short circuit modes exist, and the internal short circuit caused by the contact of the positive electrode current collector and the negative electrode sheet is the most dangerous mode, so that the electrode sheet can be a positive electrode sheet, namely, the protective layer is arranged on the surface of the positive electrode current collector, and the negative electrode sheet is not provided with the protective layer.
The pole piece provided by the invention further comprises a pole lug, and the arrangement position of the pole lug can be the arrangement position of the pole lug which is conventional in the field, for example, the pole lug can be arranged at the end part or the middle part of the pole piece. When the pole piece is a positive pole piece, the positive pole tab can be an aluminum foil; when the pole piece is a negative pole piece, the negative pole tab can be a copper foil.
The pole piece provided by the invention can be prepared by a coating method and other conventional methods in the field, and in specific implementation, the raw materials of the protective layer can be dispersed in a solvent, uniformly stirred to prepare protective layer slurry, then the protective layer slurry is coated on the surface of a current collector, and a protective layer is formed after drying; dispersing the raw materials of the active substance layer in a solvent, uniformly stirring to prepare active substance layer slurry, coating the active substance layer slurry on the surface of the protective layer far away from the current collector or the region of the surface of the current collector without the protective layer, drying, rolling and other processes to form the active substance layer, and then putting the tab on the surface of the current collector to obtain the pole piece.
In conclusion, the pole piece provided by the invention comprises the protective layer, and the relationship among the mass fraction of each component in the protective layer, the thickness of the protective layer, the particle size of the non-active material and the thickness of the active material layer is controlled, so that the problems of ignition aging and the like of the lithium ion battery under the conditions of mechanical abuse and the like are effectively solved, the electrical property of the lithium ion battery is basically not influenced, and the problem that the safety and the electrical property of the lithium ion battery cannot be considered at the same time is solved.
In a second aspect, the invention provides a lithium ion battery, which includes any of the above pole pieces.
The invention provides a lithium ion battery, which comprises the pole piece provided by the first aspect of the invention, when the pole piece is a positive pole piece, the lithium ion battery can be prepared by adopting a conventional technical means together with a conventional negative pole piece, a diaphragm and electrolyte, wherein the diaphragm comprises one or more of Polyethylene (PE), polypropylene (PP) and polyimide, the electrolyte comprises carbonates, carboxylic ester solvents, lithium salts and proper additives, in the preparation process, the positive pole piece, the negative pole piece and an isolating membrane are sequentially wound or stacked into a battery cell, then the battery cell is packaged by using a packaging material such as an aluminum plastic membrane and injected with the electrolyte, and the lithium ion battery is prepared through charging and discharging. The lithium ion battery provided by the invention has better safety and electrical property.
The invention is further illustrated below with reference to specific examples:
example 1
The pole piece that this embodiment provided is positive plate, including the mass flow body aluminium foil, be located the protective layer on the mass flow body surface, be located the positive pole active material layer that the protective layer kept away from the mass flow body surface, wherein:
the protective layer comprises 62 parts by mass of alumina, 30 parts by mass of acrylic modified PVDF and 8 parts by mass of carbon black;
the thickness of the protective layer is 2 μm;
the D10 of the alumina is 0.2 μm, the D50 is 0.5 μm, and the D90 is 2 μm;
the positive electrode active material layer comprises 96 parts by mass of a positive electrode active material LCO, 2 parts by mass of a binder PVDF and 2 parts by mass of a conductive agent carbon black;
the thickness of the positive electrode active material layer was 40 μm.
The preparation method of the pole piece provided by the embodiment comprises the following steps: mixing the alumina, the acrylic acid modified PVDF and the carbon black according to the mass fraction, dispersing the mixture in a solvent NMP, uniformly stirring to prepare a protective layer slurry, coating the protective layer slurry on the surface of the aluminum foil, and drying to obtain a protective layer; mixing LCO, PVDF and carbon black according to the mass fraction, dispersing the mixture in NMP solvent, uniformly stirring to prepare positive active material layer slurry, coating the positive active material layer slurry on the surface of the protective layer far away from the current collector, and drying to obtain a positive active material layer; welding a tab on the surface of the current collector to obtain a positive plate;
example 2
The electrode sheet provided in this example can be referred to example 1 except that the protective layer includes 70 parts by mass of alumina, 25 parts by mass of acrylic-modified PVDF, and 5 parts by mass of carbon black.
Example 3
The electrode sheet provided in this example can be referred to example 1 except that the protective layer includes 80 parts by mass of alumina, 15 parts by mass of acrylic-modified PVDF, and 5 parts by mass of carbon black.
Example 4
The electrode sheet provided in this example can be referred to example 1 except that the protective layer includes 90 parts by mass of alumina, 8 parts by mass of acrylic-modified PVDF, and 2 parts by mass of carbon black.
Example 5
The electrode sheet provided in this example can be referred to example 1 except that the protective layer includes 96 parts by mass of alumina, 3.9 parts by mass of acrylic-modified PVDF, and 0.1 parts by mass of carbon black.
Example 6
The pole piece provided by the embodiment can refer to embodiment 1, and the difference is that:
the D10 of the alumina is 0.1 μm, the D50 is 0.5 μm, and the D90 is 2.3 μm;
the thickness of the protective layer was 4 μm.
Example 7
The pole piece provided by the present embodiment can refer to embodiment 6, and the difference is that:
the alumina had a D10 of 0.2 μm, a D50 of 1 μm and a D90 of 3 μm.
Example 8
The pole piece provided by the present embodiment can refer to embodiment 6, and the difference is that:
the alumina had a D10 of 0.5 μm, a D50 of 2 μm and a D90 of 4 μm.
Example 9
The pole piece provided by the embodiment can refer to embodiment 1, and the difference is that:
the thickness of the protective layer is 4 μm.
Example 10
The pole piece provided by the embodiment can refer to embodiment 1, and the difference is that:
the thickness of the protective layer is 8 μm.
Comparative example 1
The electrode sheet provided in this comparative example can be referred to example 1 except that the protective layer includes 50 parts by mass of alumina, 45 parts by mass of acrylic-modified PVDF, and 5 parts by mass of carbon black.
Comparative example 2
The electrode sheet provided in this comparative example can be referred to example 1 except that the protective layer includes 62 parts by mass of alumina, 20 parts by mass of acrylic-modified PVDF, and 18 parts by mass of carbon black.
Comparative example 3
The electrode sheet provided in this comparative example can be referred to example 1 except that the protective layer includes 92 parts by mass of alumina, 2 parts by mass of acrylic-modified PVDF, and 6 parts by mass of carbon black.
Comparative example 4
The electrode sheet provided by this comparative example can be referred to example 1 except that the protective layer includes 92 parts by mass of alumina and 8 parts by mass of acrylic modified PVDF.
Comparative example 5
The pole piece provided by this comparative example does not include a protective layer.
Comparative example 6
The electrode sheet provided by the present comparative example can be referred to example 6, with the difference that:
the alumina had a D10 of 0.8 μm, a D50 of 3 μm and a D90 of 5 μm.
Comparative example 7
The electrode sheet provided by the present comparative example can be referred to example 6, with the difference that:
the alumina had a D10 of 0.4 μm, a D50 of 2 μm and a D90 of 6 μm.
Comparative example 8
The electrode sheet provided by the comparative example can be referred to as example 1, and the difference is that:
the thickness of the protective layer is 10 μm.
Comparative example 9
The electrode sheet provided by the comparative example can be referred to as example 1, and the difference is that:
the alumina had a D10 of 0.5 μm, a D50 of 2 μm and a D90 of 7 μm.
The positive electrode sheets provided in examples 1 to 10 and comparative examples 1 to 9 were combined with a negative electrode sheet and a separator to prepare a bare cell, the bare cell was encapsulated with an aluminum plastic film, a certain amount of electrolyte was injected, and the bare cell was sealed, and a lithium ion battery was prepared by formation, wherein the negative electrode sheet included 96 parts by mass of artificial graphite, 1.5 parts by mass of styrene butadiene rubber, 1.5 parts by mass of sodium carboxymethylcellulose, and 1 part by mass of carbon black.
The lithium ion batteries provided in examples 1-10 and comparative examples 1-9 were then tested for safety and electrical performance, the results of which are shown in table 1, and the test methods were as follows:
(1) nail penetration test
Taking 10 lithium ion batteries of each example (comparative example), placing the fully charged batteries on a through-nail testing device, starting the device, enabling a nail (with the diameter of 3mm) to penetrate into the center position of the batteries at a speed of 130mm/s, perpendicular to the plane of the batteries, stopping for 10min, withdrawing, regarding the batteries as passing batteries without fire, and counting the number of the passing lithium ion batteries.
(2) Rate capability test
Discharging the battery to 3.0V at a rate of 0.5C, standing for 5min, charging the battery to an upper limit voltage at a rate of 0.5C, then charging at constant voltage, and cutting off the current to 0.02C. After standing for 5min, the battery is discharged to 3.0V at a rate of 0.2C, and the capacity is C0. After standing for 5min, the battery was charged to the upper limit voltage at a rate of 0.5C, and then charged at constant voltage with a current cutoff of 0.02C. After standing for 5min, the battery is discharged to 3.0V at a rate of 0.5C, and the capacity is C1. The C1/C0 is the discharge capacity ratio of 0.5C/0.2C, and is used for evaluating the rate discharge capacity.
(3) Lithium ion battery energy density testing
The energy density ED of the lithium ion battery is equal to E/V, wherein E is the discharge energy of the battery, and the test method is to fully charge the battery, then discharge the battery at 0.2C to 3.0V, and the discharge energy is E. V is a system of the battery and is obtained by measuring the length, the width and the height.
The energy density loss rate Δ ED was the energy density ED of the lithium ion battery of comparative example 55Energy density ED of lithium ion battery of corresponding example (comparative example)nDifference of (1)/energy density ED of lithium ion battery of comparative example 55I.e. Δ ED ═ (ED)5-EDn)/ED5。
(4) Test of processability of protective layer
After the protective layer is coated, whether the problem of foil leakage occurs or not is observed, the coating effect of the protective layer is good if no abnormality occurs, and slight scraping and serious scraping indicate that the problem of foil leakage exists, but the foil leakage degree is different.
As can be seen from comparison with the data provided in comparative example 5, the provision of the protective layer contributes to improving the safety of the lithium ion battery (nail penetration test), but the energy density is lost to various degrees; according to the data provided by examples 1-5 and comparative examples 1-4, controlling the mass fraction of each component in the protective layer within the range provided by the invention is helpful for balancing the safety and electrical properties of the lithium ion battery; according to the data provided by examples 6 to 8 and comparative examples 6 to 7 and 9, when D50 of the inactive material exceeds 1/2 of the thickness of the protective layer and D90 is greater than the thickness of the protective layer, the protective effect of the protective layer is reduced, the safety performance of the lithium ion battery is deteriorated, and the problem of scraping is easily caused, which affects the processability of the protective layer; according to the data provided in examples 9-10 and comparative example 8, it can be seen that when the protective layer thickness H1 and the active material layer thickness H2 satisfy H1/H2 ≤ 1/5, the energy density loss of the lithium ion battery can be controlled within 6%, and when H1/H2 exceeds 1/5, the energy density loss of the lithium ion battery is large, which affects the endurance of the battery.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Figure BDA0003381800190000141

Claims (10)

1. The pole piece is characterized by comprising a substrate, wherein the substrate comprises a current collector and a protective layer arranged on the surface of the current collector, and an active substance layer is also arranged on the protective layer;
the protective layer comprises 62-96% of inactive materials, 0.1-8% of conductive agents and 3-30% of binders in percentage by mass;
the thickness H1 of the protective layer and the D50 of the inactive material satisfy the relation H1 is more than or equal to 2X D50;
the thickness H1 of the protective layer and the D90 of the inactive material satisfy the relation that H1 is more than or equal to D90;
the thickness H1 of the protective layer and the thickness H2 of the active material layer satisfy the relation H1/H2 ≤ 1/5.
2. The pole piece of claim 1, wherein the inactive material comprises inorganic particles and/or organic particles, wherein:
the inorganic particles comprise one or more of oxides, carbides, nitrides, inorganic salts and first carbon coating materials, the first carbon coating materials comprise first base particles and first carbon layers coated on at least partial surfaces of the first base particles, and the first base particles are selected from one or more of oxides, carbides, nitrides and inorganic salts;
the organic particles comprise one or more of polystyrene, polymethyl methacrylate, polytetrafluoroethylene and a second carbon coating material, the second carbon coating material comprises second matrix particles and a second carbon layer coated on at least part of the surfaces of the second matrix particles, and the second matrix particles are selected from one or more of polystyrene, polymethyl methacrylate and polytetrafluoroethylene.
3. The pole piece of claim 2, wherein the oxide is at least one selected from the group consisting of alumina, titania, magnesia, zirconia, antimony oxysulfide, barium oxide, manganese oxide, silica, iron oxide, and ferroferric oxide; the carbide comprises a metal carbide and/or a non-metal carbide, the metal carbide comprises at least one of titanium carbide, calcium carbide, chromium carbide, tantalum carbide, vanadium carbide, zirconium carbide and tungsten carbide, and the non-metal carbide comprises boron carbide and/or silicon carbide; the nitride comprises a metal nitride and/or a non-metal nitride, the metal nitride comprises at least one of lithium nitride, magnesium nitride, aluminum nitride, titanium nitride and tantalum nitride, and the non-metal nitride comprises at least one of boron nitride, phosphorus pentanitride and silicon tetranitride; the inorganic salt comprises a carbonate and/or a sulfate.
4. The pole piece of any one of claims 1 to 3, wherein the thickness H1 of the protective layer and the D10 of the inactive material satisfy the relationship H1 ≧ 8 XD 10.
5. The pole piece according to any one of claims 1 to 3, characterized in that the inactive material has D10 ≤ 0.5 μm, D50 ≤ 2 μm, and D90 ≤ 5 μm.
6. The pole piece of claim 5, wherein the inactive material has a D10 of 0.01-0.2 μm, a D50 of 0.05-0.5 μm, and a D90 of 1-3 μm.
7. The pole piece of claim 1, wherein the protective layer has a thickness of 0.1 μm to 10 μm.
8. The pole piece of claim 1, wherein the pole piece is a positive pole piece.
9. The pole piece of claim 1, wherein at least one of a first end and a second end of the pole piece, the vertical distance from the protective layer to the outer edge of the current collector is smaller than the vertical distance from the active material layer to the outer edge of the current collector, the first end and the second end being opposite; or,
and a hollow foil area is arranged between the protective layer and the outer edge of the current collector at least one of the first end and the second end of the pole piece, the active substance layer comprises a first part and a second part connected with the first part, the first part is arranged on the surface of the protective layer, and the second part is arranged on the surface of the current collector in the hollow foil area.
10. A lithium ion battery comprising a pole piece according to any one of claims 1 to 9.
CN202111446122.XA 2021-11-29 2021-11-29 Pole piece and lithium ion battery Pending CN114156434A (en)

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