CN116435503A - Negative electrode material layer, negative electrode plate, preparation method of negative electrode plate, secondary battery, battery pack and electric equipment - Google Patents

Negative electrode material layer, negative electrode plate, preparation method of negative electrode plate, secondary battery, battery pack and electric equipment Download PDF

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Publication number
CN116435503A
CN116435503A CN202310375802.XA CN202310375802A CN116435503A CN 116435503 A CN116435503 A CN 116435503A CN 202310375802 A CN202310375802 A CN 202310375802A CN 116435503 A CN116435503 A CN 116435503A
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material layer
negative electrode
active material
active
porosity
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林颖鑫
赖少波
沈刘学
文佳琪
张敏
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Xiamen Hithium Energy Storage Technology Co Ltd
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Xiamen Hithium Energy Storage Technology Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

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  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The invention relates to the technical field of batteries, in particular to a negative electrode material layer, a negative electrode plate, a preparation method of the negative electrode plate, a secondary battery, a battery pack and electric equipment. The negative electrode material layer comprises a first active material layer and a second active material layer which are arranged in a stacked mode, wherein the first active material layer comprises first active particles, and the second active material layer comprises second active particles. The thickness D1, the porosity P1 and the median diameter D of the first active material layer 1 50, thickness d2 of the second active material layer, porosity P2, and median of the second active particlesValue particle diameter D 2 50, satisfy d1×P1/D 1 50＜d2×P2/D 2 50. The negative electrode material layer can improve the dynamic performance of the negative electrode, reduce sodium precipitation on the surface of the negative electrode during high-rate charging, reduce side reaction between sodium and electrolyte, reduce irreversible capacity loss of the sodium ion battery, improve the energy density, the circulation rate and the circulation service life of the sodium ion battery, and ensure the use safety of the sodium ion battery.

Description

Negative electrode material layer, negative electrode plate, preparation method of negative electrode plate, secondary battery, battery pack and electric equipment
Technical Field
The invention relates to the technical field of batteries, in particular to a negative electrode material layer, a negative electrode plate, a preparation method of the negative electrode plate, a secondary battery, a battery pack and electric equipment.
Background
The sodium ion battery is used as a secondary battery system for energy storage, and needs to meet the performance requirements of safety, long service life, suitability for high and low temperature conditions and the like, and the long-cycle performance is an important index for evaluating the performance of the sodium ion battery. The existing sodium ion battery has insufficient cathode dynamics, sodium ions are enriched in the cathode and electrons obtained on the surface of the cathode active material layer are separated out on the surface of the cathode in the form of sodium dendrite during high-rate charging, so that side reactions with electrolyte are increased, irreversible capacity is lost, and the cycle life of the sodium ion battery is reduced.
Disclosure of Invention
The embodiment of the invention discloses a negative electrode material layer, a negative electrode plate and a preparation method thereof, a secondary battery, a battery pack and electric equipment, wherein the negative electrode material layer can improve the dynamic performance of a negative electrode, reduce sodium precipitation on the surface of the negative electrode during high-rate charging, reduce side reaction between sodium and electrolyte, reduce irreversible capacity loss of a sodium ion battery, improve the energy density, the circulation rate and the circulation life of the sodium ion battery, and ensure the use safety of the sodium ion battery.
In order to achieve the above object, in a first aspect, the present invention discloses a negative electrode material layer, comprising:
a first active material layer having a thickness D1, a porosity P1, and comprising first active particles having a median particle diameter D 1 50; and
a second active material layer stacked on the surface of the first active material layer, wherein the thickness of the second active material layer is D2, the porosity is P2, the second active material layer comprises second active particles, and the median particle diameter of the second active particles is D 2 50, and d1×P1/D 1 50＜d2×P2/D 2 50。
As an alternative embodiment, in the embodiment of the present invention, d1×p1/D of the first active material layer 1 50 is 0.6 to 3.6, and/or D2 x P2/D of the second active material layer 2 50 is 0.8-4.
As an alternative embodiment, in an embodiment of the present invention, the thickness d1 of the first active material layer is 45 μm to 100 μm, and/or the thickness d2 of the second active material layer is 10 μm to 35 μm.
As an alternative embodiment, in an embodiment of the present invention, the porosity P1 of the first active material layer is 10% to 30%, and/or the porosity P2 of the second active material layer is 20% to 40%.
As an alternative embodiment, in the examples of the invention, the median particle diameter D of the first active particles 1 50 is 7 μm to 14 μm, and/or the median particle diameter D of the second active particles 2 50 is 3-5 μm.
As an alternative embodiment, in an embodiment of the present invention, the first active particles are a mixture of one or more of hard carbon and soft carbon; and/or the number of the groups of groups,
the second active particles are one or more of hard carbon and soft carbon; and/or the number of the groups of groups,
the second active particles are spherical or spheroid.
As an alternative embodiment, in an embodiment of the present invention, the first active material layer further includes a first binder and a first conductive agent, wherein the first binder is a mixture of one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polyacrylate, carboxymethyl cellulose, sodium alginate, etc., and/or the first conductive agent is a mixture of one or more of acetylene black, super-P, carbon nanotubes, carbon fibers, graphene, etc.;
and/or the number of the groups of groups,
the second active material layer further comprises a second binder and a second conductive agent, wherein the second binder is one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polyacrylate, carboxymethyl cellulose, sodium alginate and the like, and/or the second conductive agent is one or more of acetylene black, super-P, carbon nano tubes, carbon fibers, graphene and the like.
In a second aspect, the invention discloses a negative electrode plate, which comprises a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer is the negative electrode material layer according to the first aspect, and the first active material layer is coated on the surface of the negative electrode current collector.
In a third aspect, the invention discloses a method for preparing the negative electrode plate according to the second aspect, which comprises the following steps:
mixing and coating the first active particles, a first conductive agent and a first binder on the surface of the current collector to form a first active material layer and drying the first active material layer;
mixing and coating the second active particles, a second conductive agent and a second binder on the surface of the first active material layer to form the second active material layer and drying;
and (5) post-processing to obtain the negative electrode plate.
In a fourth aspect, the present invention discloses a secondary battery comprising a negative electrode tab according to the second aspect.
In a fifth aspect, the present invention discloses a battery pack comprising a case and the secondary battery according to the fourth aspect disposed in the case.
In a sixth aspect, the invention discloses an electric device, which comprises an electric device body and the secondary battery according to the fourth aspect, wherein the secondary battery is arranged in the electric device body and is used for supplying power to the electric device body.
Compared with the prior art, the invention has the beneficial effects that:
the anode material layer is used for an anode piece, and comprises a first active material layer and a second active material layer, wherein the first active material layer comprises first active particles, and the second active material layer comprises second active particles. The thickness D1, the porosity P1 and the median diameter D of the first active material layer 1 50; and a thickness D2, a porosity P2, a median diameter D of the second active material layer 2 50, the above parameters satisfy the relation d1×P1/D 1 50＜d2×P2/D 2 50. The thickness, the porosity and the median particle diameter can influence the dynamic performance of the cathode and the performance of the interfacial electrochemical reaction. Synergistic control of D1, P1, D 1 50、d2、P2、D 2 50 these parameters are kept in the range of the above-mentioned relation, so that the sodium ion transmission resistance is reduced, the sodium ion transmission rate is raised, the dynamics performance of the negative electrode is raised, and the sodium precipitation on the surface of the negative electrode is reduced. Further, the cooperation of the parameters can also reduce side reaction between the negative electrode plate and the electrolyte, reduce irreversible capacity loss of the sodium ion battery, improve energy density, circulation multiplying power and circulation service life of the sodium ion battery, and ensure use safety of the sodium ion battery.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a negative electrode sheet according to an embodiment of the present invention.
Reference numerals: 100. a negative electrode plate; 1. a negative electrode material layer; 11. a first active material layer; 12. a second active material layer; 2. and a negative electrode current collector.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the present invention, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal" and the like indicate an azimuth or a positional relationship based on that shown in the drawings. These terms are only used to better describe the present invention and its embodiments and are not intended to limit the scope of the indicated devices, elements or components to the particular orientations or to configure and operate in the particular orientations.
Also, some of the terms described above may be used to indicate other meanings in addition to orientation or positional relationships, for example, the term "upper" may also be used to indicate some sort of attachment or connection in some cases. The specific meaning of these terms in the present invention will be understood by those of ordinary skill in the art according to the specific circumstances.
Furthermore, the terms "mounted," "configured," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; may be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements, or components. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
Furthermore, the terms "first," "second," and the like, are used primarily to distinguish between different devices, elements, or components (the particular species and configurations may be the same or different), and are not used to indicate or imply the relative importance and number of devices, elements, or components indicated. Unless otherwise indicated, the meaning of "a plurality" is two or more.
The technical scheme of the invention will be further described with reference to the examples and the accompanying drawings.
In the electrochemical reaction process of the sodium ion battery, the insufficient kinetic performance of the negative electrode can cause uneven deposition of sodium ions on the surface of the negative electrode, and the sodium ions are separated out on the surface of the negative electrode in the form of sodium dendrites to cause more side reactions with electrolyte. In addition, the breakage of the sodium dendrites during the dissolution process also forms dead sodium, which results in an irreversible decrease in the capacity of the sodium ion battery, reducing the cycle life of the sodium ion battery. In order to reduce the sodium precipitation phenomenon, the related art adopts to improve the dynamic performance of the negative electrode of the sodium ion battery by reducing the compacted density or the surface density of the electrode sheet of the sodium ion battery, so as to reduce the sodium precipitation on the surface of the negative electrode, but the reduction of the compacted density or the surface density of the electrode sheet leads to the reduction of the energy density of the sodium ion battery.
Based on the above, in order to improve the dynamic performance of the negative electrode, reduce precipitation of sodium dendrite and side reaction of sodium and electrolyte, thereby reducing the capacity loss of the sodium ion battery and improving the energy density, rate capability and cycle life of the sodium ion battery, the applicant proposes the following technical scheme.
In a first aspect, the present application provides a negative electrode material layer.
The negative electrode material layer is used for a negative electrode plate, and comprises: a first active material layer and a second active material layer stacked on a surface of the first active material layer. The first active material layer has a thickness d1 and a porosity P1, and comprises first active particles with a median particle diameter ofD 1 50. The second active material layer has a thickness D2 and a porosity P2, and comprises second active particles with a median particle diameter D 2 50, and the above parameters satisfy d1×P1/D 1 50＜d2×P2/D 2 50. The thickness, the porosity and the median particle diameter of the first active material layer and the second active material layer can influence the transmission of sodium ions, so that the kinetic performance of the negative electrode and the performance of electrochemical reaction of a negative electrode interface are influenced, and the energy density, the multiplying power performance and the cycle life of the sodium ion battery can be regulated and controlled. Synergistic control of D1, P1, D 1 50、d2、P2、D 2 50 the parameters are kept in the range of the relational expression, the sodium ion transmission resistance is small, the sodium ion transmission rate is improved, and the dynamics performance of the cathode is improved, so that sodium precipitation on the surface of the cathode pole piece is reduced. Further, the synergistic cooperation of the parameters can also reduce the occurrence of side reaction between the negative electrode plate and the electrolyte, reduce the irreversible capacity loss of the sodium ion battery, and improve the energy density, the circulation multiplying power and the circulation service life of the sodium ion battery.
The porosity may be a volume porosity or a cross-sectional porosity.
The volume porosity refers to the ratio of the pore volume to the total volume, wherein for the first active material layer, the volume porosity is the ratio of the pore volume in the first active material layer to the total volume of the first active material layer. For the second active material layer, the volume porosity is the ratio of the pore volume in the second active material layer to the total volume of the second active material layer.
The cross-sectional porosity refers to the porosity of the longitudinal section of the anode material layer, and for the first active material layer, the cross-sectional porosity refers to the porosity of the longitudinal section of the first active material layer; for the second active material layer, the section porosity refers to the porosity of the longitudinal section of the second active material layer.
In some embodiments, the d1×P1/D is satisfied 1 50＜d2×P2/D 2 50D 1 XP 1/D of the first active material layer on the premise of the relation 1 50 is 0.6About 3.6, and/or D2 XP 2/D of the second active material layer 2 50 is 0.8-4.
Alternatively, d1×P1/D of the first active material layer 1 50 is 0.6 to 3.6 and d2×P2/D of the second active material layer 2 50 is 0.8-4. Alternatively, only d1×P1/D of the first active material layer 1 50 is 0.6-3.6. Alternatively, only d2×P2/D of the second active material layer 2 50 is 0.8-4. In the above-described aspect, preferably, d1×p1/D of the first active material layer 1 50 is 0.6 to 3.6 and d2×P2/D of the second active material layer 2 50 is 0.8-4. Different parameters have different effects on the performance of the sodium ion battery, and the factors which need to be considered for the cooperative control of the parameters such as porosity, thickness and median particle diameter are more complex. The applicant found in the study that controlling the parameters in the above range can avoid the conditions of too small or too large porosity, too small or too large median particle diameter and too thick or too thin thickness, so that the related parameters can cooperate with each other and the functions are complementary, and the improvement of the dynamic performance and the electrochemical performance of the cathode is finally realized.
Further, d1×P1/D of the first active material layer 1 50 is preferably in the range of 1.0 to 2.4, and/or D2 XP 2/D of the second active material layer 2 50 is preferably in the range of 1.2 to 3. When d1×P1/D 1 50＜d2×P2/D 2 50. And d1×P1/D of the first active material layer 1 50 is 1.0 to 2.4, d2×P2/D of the second active material layer 2 When 50 is 1.2-3, parameters of the first active material layer and the second active material layer are controlled to meet the above range, so that the synergistic effect of porosity, thickness and median particle diameter is better, the dynamic performance of the negative electrode can be remarkably improved, sodium precipitation on the surface of the negative electrode is reduced, and the rate performance, energy density and cycle performance of the sodium ion battery are improved.
Illustratively, d1×P1/D of the first active material layer 1 50 may be any point value within the above range, including, but not limited to: 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, etc. d2×P2/D of second active material layer 2 50 may be the above-mentioned rangeAny point value within the enclosure including, but not limited to: 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, etc.
In some embodiments, the thickness d1 of the first active material layer is 45 μm to 100 μm, and/or the thickness d2 of the second active material layer is 10 μm to 35 μm. The thicknesses d1 and d2 also have a certain influence on the performance of the negative electrode plate. When the thickness d1 and d2 is reduced, the electrolyte is facilitated to infiltrate on the negative electrode plate, so that the liquid phase transmission rate of sodium ions is increased, the sodium ion transmission resistance is small, the sodium precipitation on the surface of the negative electrode plate is avoided, the safety problems of short circuit, fire and the like of the battery caused by sodium dendrites are reduced, but the energy density of the battery is reduced due to the fact that d1 and d2 are too small. When the thickness d1 and d2 is increased, the energy density of the sodium ion battery is correspondingly improved, but too thick d1 and d2 can make electrolyte infiltration difficult, sodium ion transmission resistance is increased, battery polarization is increased, so that the dynamic performance of the negative electrode plate is reduced, and the multiplying power performance of the battery is affected, therefore, d1 and d2 are controlled within the range, the electrolyte infiltration on the negative electrode plate can be ensured, the sodium ion transmission resistance is reduced, the sodium ion liquid phase transmission rate is improved, the negative electrode dynamic performance is improved, sodium precipitation on the surface of the negative electrode plate is reduced, the safety is ensured, and the energy density of the sodium ion battery can be also improved.
Alternatively, the thickness d1 of the first active material layer is 45 μm to 100 μm and the thickness d2 of the second active material layer is 10 μm to 35 μm. Alternatively, only the first active material layer has a thickness d1 of 45 μm to 100 μm. Alternatively, only the second active material layer has a thickness d2 of 10 μm to 35 μm. Preferably, the thickness d1 of the first active material layer is 45 μm to 100 μm and the thickness d2 of the second active material layer is 10 μm to 35 μm.
Further, the thickness d1 of the first active material layer preferably ranges from 50 μm to 70 μm, and/or the thickness d2 of the second active material layer preferably ranges from 15 μm to 30 μm.
Further preferably, the thickness d1 of the first active material layer is 50 μm to 70 μm and the thickness d2 of the second active material layer is 15 μm to 30 μm. Therefore, d1 and d2 are controlled in the preferred range, so that the electrolyte has better infiltration effect, the liquid phase transmission rate of sodium ions is faster, the transmission resistance of sodium ions is smaller, the dynamic performance of the cathode is improved more preferentially, sodium precipitation is obviously reduced during high-rate charging, the energy density and rate performance of the sodium ion battery can be obviously improved, and the safety and stability of the sodium ion battery are further improved.
Illustratively, the thickness d1 of the first active material layer is any point value within the above range, including, but not limited to: 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, etc. The thickness d1 of the second active material layer is any point value within the above range, including but not limited to: 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 22 μm, 25 μm, 27 μm, 30 μm, 32 μm, 35 μm, etc.
In some embodiments, the first active material layer has a porosity P1 of 10% to 30%, and/or the second active material layer has a porosity P2 of 20% to 40%. The porosities P1 and P2 also have a certain influence on the performance of the negative electrode plate. When the porosities P1 and P2 are larger, the electrolyte infiltration effect is better, the electrolyte is more fully contacted with the first active particles and the second active particles, the sodium ion transmission is facilitated, and the side reaction between the first active particles and the second active particles and the electrolyte is increased when the porosities are too large. When the porosity is too small, the electrolyte of the first active material layer and the second active material layer is poor in infiltration, the electrolyte is low in holding quantity, the sodium ion transmission resistance is increased, the dynamic performance of the cathode is reduced, and sodium precipitation is caused. Therefore, the porosities P1 and P2 are controlled within the above range, so that the electrolyte can be fully contacted with the first active particles and the second active particles, the transmission resistance of sodium ions is reduced, the transmission of sodium ions is facilitated, the dynamic performance of the cathode is improved, the sodium precipitation is reduced, and the side reaction with the electrolyte can be reduced.
Alternatively, the first active material layer has a porosity P1 of 10% to 30% and the second active material layer has a porosity P2 of 20% to 40%. Or only the first active material layer has a porosity P1 of 10% to 30%. Alternatively, only the second active material layer has a porosity P2 of 20% to 40%. Preferably, the first active material layer has a porosity P1 of 10% to 30% and the second active material layer has a porosity P2 of 20% to 40%. Meanwhile, P1 and P2 are controlled to be kept in the porosity range, so that the electrolyte infiltration effect of the first active material layer and the second active material layer is better, the transmission resistance of sodium ions in each layer is further reduced, the dynamics performance of the cathode is improved, and the sodium precipitation phenomenon and side reaction are fewer.
Further, the porosity P1 of the first active material layer is preferably in the range of 20% to 30%, and/or the porosity P2 of the second active material layer is preferably in the range of 30% to 40%.
Further preferably, the porosity P1 of the first active material layer is preferably in the range of 20% to 30%, and the porosity P2 of the second active material layer is preferably in the range of 30% to 40%. Therefore, the P1 and P2 are controlled to be in optimal porosity, so that the electrolyte infiltration effect of the first active material layer and the second active material layer is optimal, the dynamic performance of the negative electrode is improved optimally, and sodium precipitation and side reaction are minimized.
Illustratively, the porosity P1 of the first active material layer may be any point value within the above range, including, but not limited to: 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc. The porosity P2 of the second active material layer may be any point value within the above range, including but not limited to: 20%, 22%, 24%, 26%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, etc.
In some embodiments, the median particle diameter D of the first active particles 1 50 is 7 μm to 14 μm, and/or the median particle diameter D of the second active particles 2 50 is 3-5 μm. It is understood that D50 refers to the particle size corresponding to a cumulative particle size distribution of 50% for a sample, also referred to as the average particle size of the particle population. In some embodiments, the second active particles are spherical or spheroid. The median particle diameter of the first active particles and the second active particles and the particle morphology also have a certain influence on the performance of the negative electrode plate. In the sodium ion battery with the same thickness of the negative electrode material layer, the larger the median particle diameter is, the side reaction with the electrolyte is reduced, and the SEI film (Solid Electrolyte Interphase, solid electrolyte interfacial film) is more stable, which is advantageous for improving the cycle performance of the battery.
When D is 1 50 and D 2 When 50 is too large, the longer the solid-phase diffusion path of sodium ions is, the larger the transmission resistance of sodium ions is, and the dynamics performance of the cathode is reduced. When D is 1 50 and D 2 At 50, the shorter the solid-phase diffusion path of sodium ions, the smaller the transmission resistance, the more favorable the improvement of the kinetic performance of the anode, but D 1 50 and D 2 When 50 is too small, more binder is needed in preparation of the negative electrode plate, and side reaction of sodium and electrolyte is increased due to increase of contact area, so that energy density and primary charge and discharge efficiency of the battery are reduced. Thus, D is 1 50 and D 2 50 control in the above-mentioned scope, not only can improve the dynamic performance of negative pole, reduce the natrium of separating out, can reduce the quantity of other inactive material moreover, reduce with the side reaction of electrolyte for the SEI membrane is more stable, is favorable to promoting cycle performance, energy density and the first charge-discharge efficiency of battery.
Alternatively, the median particle diameter D of the first active particles 1 50 is 7-14 mu m and the median diameter D of the second active particles 2 50 is 3-5 μm. Alternatively, only the median particle diameter D of the first active particles 1 50 is 7-14 μm. Alternatively, only the median particle diameter D of the second active particles 2 50 is 3-5 μm. Preferably, the median particle diameter D of the first active particles 1 50 is 7-14 mu m and the median diameter D of the second active particles 2 50 is 3-5 μm.
Illustratively, the median particle diameter D of the first active particles 1 50 is any point within the above range, including but not limited to: 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, etc. Median particle diameter D of the second active particles 2 50 is any point within the above range, including but not limited to: 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, etc.
In some embodiments, the first active particles are a mixture of one or more of hard carbon, soft carbon; and/or the second active particles are a mixture of one or more of hard carbon, soft carbon. The first active particles can be the same material or different materials, and the quantity of the materials is the same or different, so that when the first active particles and the second active particles are the same material and the quantity of the first active particles and the second active particles are the same, the synergistic improvement effect on the performance of the sodium ion battery is better.
Illustratively, the first and second active particles may be soft carbon, which is low cost, high in carbon yield, good in electron conductivity, and excellent in rate capability. Further exemplary, the first active particle and the second active particle are both hard carbon. The hard carbon is a corresponding hard carbon material obtained by pyrolyzing various carbon-containing precursors, and can be, for example, phenolic resin hard carbon, epoxy resin hard carbon, polyfurfuryl alcohol hard carbon, coal tar pitch hard carbon, petroleum pitch hard carbon, natural pitch hard carbon, cellulose hard carbon, lignin hard carbon, starch hard carbon, and the like. The hard carbon has excellent electrochemical performance, cycle performance and higher reversible specific capacity. Preferably, the first active particles and the second active particles are both hard carbon materials.
Therefore, the above parameters D1, P1, D are cooperatively controlled for the negative electrode tab of the sodium ion battery 1 50、d2、P2、D 2 50 and designing a layered structure of the anode material layer, and has the following comprehensive technical effects: the second active material layer is stacked on the surface of the first active material layer, the first active material particles in the first active material layer have larger particle sizes, and the second active material particles in the second active material layer have smaller particle sizes and are spherical or spheroidic.
When sodium ions migrate to the surface of the negative electrode plate, as the second active particles with small particle size, spherical shape or sphere-like shape have better diffusion kinetics, the second active material layer has better high-rate quick charge performance, and part of sodium ions firstly diffuse into the second active material layer quickly, so that the concentration of sodium ions in the area near the surface of the first active material layer is reduced. Therefore, the concentration difference of sodium ions in the first active material layer and the area near the surface of the first active material layer is reduced, the sodium ion aggregation speed is reduced, the position distribution of the sodium ions in the area near the surface of the first active material layer is more uniform, the concentration distribution is more uniform, and sufficient time can be provided for the sodium ions to enter the first active material layer, so that the precipitation of the sodium ions on the surface of the negative electrode plate can be effectively reduced.
Simultaneously, the thickness and the porosity of the first active material layer are controlled, the infiltration effect of the electrolyte can be improved, the transmission resistance of sodium ions is further reduced, the liquid phase transmission rate of sodium ions is improved, the dynamic performance of the negative electrode is improved, sodium precipitation and side reaction on the surface of the negative electrode plate are further reduced, the SEI layer formed on the surface of the negative electrode plate is more stable, and the energy density, the multiplying power quick charging performance and the circulation performance of the sodium ion battery can be improved while the safety is ensured.
In some embodiments, the first active material layer further includes a first binder and a first conductive agent, the first binder is a mixture of one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polyacrylate, carboxymethyl cellulose, sodium alginate, etc., and/or the first conductive agent is a mixture of one or more of acetylene black, super-P (one of conductive carbon blacks, commercially available), carbon nanotubes, carbon fibers, graphene, etc.;
and/or the number of the groups of groups,
the second active material layer further comprises a second binder and a second conductive agent, wherein the second binder is one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polyacrylate, carboxymethyl cellulose, sodium alginate and the like, and/or the second conductive agent is one or more of acetylene black, super-P, carbon nano tubes, carbon fibers, graphene and the like. Therefore, the first conductive agent and the second conductive agent are selected to enable the conductive performance of the anode material layer to be better, and the first adhesive and the second adhesive are selected to enable the anode material layer to be better in adhesive force and stable in structure.
In a second aspect, embodiments of the present application further provide a negative electrode tab. The negative electrode plate comprises a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer is the negative electrode material layer according to the first aspect, and the first active material layer is stacked on the surface of the negative electrode current collector.
Referring to fig. 1, fig. 1 shows a negative electrode tab 100, which includes a negative electrode material layer 1 and a negative electrode current collector 2, wherein the two negative electrode material layers 1 are respectively disposed on the upper surface and the lower surface of one negative electrode current collector 2 at the same time. Therefore, the arrangement area of the anode material layer is further increased, the arrangement areas of the first active material layer and the second active material layer are further increased, sodium ions in almost all nearby areas of the anode pole piece can be regulated and controlled, the distribution positions and the distribution concentration of the sodium ions in more areas are more uniform, and the formation of sodium dendrites is greatly reduced.
Alternatively, the negative electrode current collector may be any one of copper foil, stainless steel foil, copper alloy foil, carbon coated copper foil, aluminum foil, carbon coated aluminum foil.
In a third aspect, an embodiment of the present application further provides a method for preparing the negative electrode sheet according to the second aspect, where the method includes:
mixing and coating first active particles, a first conductive agent and a first binder on the surface of a negative electrode current collector to form a first active material layer and drying;
Coating the second active particles, a second conductive agent and a second binder on the surface of the first active material layer in a mixing way to form a second active material layer and drying;
and (5) post-processing to obtain the negative electrode plate.
Specifically, the first active particles, the first conductive agent and the first binder (carboxymethyl cellulose and styrene-butadiene rubber) are placed in a vacuum stirrer according to the mass ratio of 95.5:1 (1.5:2), deionized water is added, and the mixture is stirred and mixed, so that the first negative electrode slurry is obtained. And uniformly coating the first negative electrode slurry on the surfaces of two opposite sides of the negative electrode current collector to form a first active material layer, and transferring the negative electrode current collector coated with the first negative electrode slurry into an oven for drying. Placing the second active particles, the second conductive agent and the second binder (carboxymethyl cellulose and styrene-butadiene rubber) in a vacuum mixer according to a mass ratio of 95.5:1 (1.5:2), adding deionized water, stirring and mixing to obtain second negative electrode slurry, uniformly coating the second negative electrode slurry on the surface of the first active material layer, and transferring the second negative electrode slurry into an oven for drying. And finally, rolling and slitting the dried negative electrode material layer to obtain the negative electrode plate.
In a fourth aspect, embodiments of the present application also provide a secondary battery. The secondary battery comprises a positive electrode plate, a negative electrode plate, electrolyte and a diaphragm, wherein the diaphragm is arranged between the positive electrode plate and the negative electrode plate. The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, a third binder, and a third conductive agent. Alternatively, for sodium ion batteries, the positive electrode active material includes a transition metal oxide, a polyanionic compound (which may be, for example, sodium vanadium phosphate Na 3 V 2 (PO 4 ) 3 ) One or more of organic polymer and Prussian blue material. The separator may be any separator material in existing batteries. The third conductive agent may be a material of the first conductive agent or the second conductive agent in the negative electrode sheet, and the third adhesive may be a material of the first adhesive or the second adhesive in the negative electrode sheet. Optionally, the separator comprises one or more of polypropylene, polyethylene, and ceramic separator. The electrolyte comprises electrolyte salt and organic solvent, wherein the specific types and compositions of the electrolyte salt and the organic solvent are conventional choices in the field of batteries, and the electrolyte salt and the organic solvent can be selected according to actual requirements.
On the basis of the preparation of the negative electrode plate, the embodiment of the application also provides a preparation method of the secondary battery, which comprises the following steps:
preparing a negative electrode sheet by the preparation method of the third aspect;
preparing a positive electrode plate: placing the positive electrode active material, the third conductive agent and the third binder in a vacuum stirrer according to the mass ratio of 95:2.5:2.5, adding N-methyl pyrrolidone, and uniformly stirring and mixing to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on the surfaces of two opposite sides of the aluminum foil of the positive electrode current collector, transferring the positive electrode current collector coated with the positive electrode slurry into an oven for drying, and rolling and cutting to obtain the positive electrode plate.
Preparing an electrolyte: mixing ethylene carbonate, methyl ethyl carbonate and diethyl carbonate according to the volume ratio of 1:1:1 to obtain a mixed solvent, adding dried sodium salt sodium hexafluorophosphate into the mixed solvent, and adding a fluoroethylene carbonate additive with the mass fraction of 2% to prepare the electrolyte with the sodium salt concentration of 1 mol/L.
Post-treatment preparation of secondary battery: and sequentially stacking the prepared positive electrode plate, negative electrode plate and polypropylene diaphragm, enabling the polypropylene diaphragm to be positioned between the positive electrode plate and the negative electrode plate, then winding to obtain a bare cell, loading the bare cell into an aluminum plastic film soft package, drying, injecting electrolyte, and carrying out the procedures of vacuum packaging, standing, formation, shaping and the like to obtain the secondary battery.
In a fifth aspect, embodiments of the present application also provide a battery pack. The battery pack includes a case and the secondary battery according to the third aspect disposed in the case. The plurality of secondary batteries are accommodated in the case, and the connection method of the plurality of secondary batteries includes at least one of series connection and parallel connection. The battery pack has fixing and protecting functions for the secondary battery.
In a sixth aspect, an embodiment of the present application further provides an electric apparatus, where the electric apparatus may be an energy storage base station, an electric vehicle, a ship, a passenger car, or the like. The electric equipment comprises an electric equipment body and the secondary battery as in the third aspect, wherein the secondary battery is arranged in the electric equipment body and is used for supplying power to the electric equipment body. The electric equipment body comprises an equipment anode and an equipment cathode, wherein an anode plate of the secondary battery is electrically connected with the equipment anode, and a cathode plate is electrically connected with the equipment cathode.
The present application will be further illustrated with reference to specific examples and experimental data:
example 1
The application provides a secondary battery, this secondary battery is sodium ion battery, and this secondary battery can establish ties and obtain the battery package, can be for the consumer power supply.
The secondary battery comprises a positive pole piece, a negative pole piece, electrolyte and a diaphragm, wherein the diaphragm is arranged between the positive pole piece and the negative pole piece.
The negative electrode plate comprises a current collector and a negative electrode material layer, wherein the negative electrode material layer comprises a first active material layer and a second active material layer, the second active material layer is stacked on the surface of the first active material layer, the first active material layer comprises first active particles, a first binder and a first conductive agent, and the second active material layer comprises second active particles, a second binder and a second conductive agent.
The first active material layer has a thickness D1 of 60 μm and a volume porosity P1 of 25%, and the first active particles are hard carbon particles having a large particle diameter, wherein the particle diameter D 1 50 is 9 μm. The second active material layer has a thickness D2 of 25 μm and a volume porosity P2 of 30%, and the second active particles are small-sized, round hard carbon particles having a value of D 2 50 is 4 μm and d1×P1/D 1 50 is 1.67, d2×P2/D 2 50 is 1.88, d1×P1/D 1 50＜d2×P2/D 2 50. The first binder and the second binder are sodium hydroxymethyl cellulose and benzene rubber, and the first conductive agent and the second conductive agent are conductive carbon black.
The present embodiment also provides a method for producing the above secondary battery (sodium ion battery), comprising the steps of:
(1) Preparing the negative electrode plate
Median particle diameter D 1 Placing hard carbon particles with the mass ratio of 50 of 9 mu m, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber in a vacuum stirrer according to the mass ratio of 95.5:1:1.5:2, adding deionized water, stirring and mixing to obtain first negative electrode slurry; uniformly coating the first negative electrode slurry on the surfaces of two opposite sides of a negative electrode current collector to form a first active material layer, and transferring the negative electrode current collector coated with the first negative electrode slurry into an oven for drying; median particle diameter of D 2 Placing spherical hard carbon particles with the mass ratio of 50 mu m, conductive carbon black, carboxymethyl cellulose and styrene-butadiene rubber in a vacuum stirrer according to the mass ratio of 95.5:1:1.5:2, adding deionized water, stirring and mixing to obtain second negative electrode slurry, uniformly coating the second negative electrode slurry on the surface of the first active material layer, transferring the second negative electrode slurry into an oven for drying, and then rolling and slitting to obtain the negative electrode plate.
(2) Preparation of positive electrode sheet
Sodium vanadium phosphate Na 3 V 2 (PO 4 ) 3 Placing conductive carbon black Super-P and polyvinylidene fluoride in a vacuum stirrer according to the mass ratio of 95:2.5:2.5, adding N-methylpyrrolidone, and uniformly stirring and mixing to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on the surfaces of two opposite sides of the aluminum foil of the positive electrode current collector, transferring the positive electrode current collector coated with the positive electrode slurry into an oven for drying, and rolling and cutting to obtain the positive electrode plate.
(3) Preparation of electrolyte
Mixing ethylene carbonate, methyl ethyl carbonate and diethyl carbonate according to the volume ratio of 1:1:1 to obtain a mixed solvent, and adding dried sodium salt sodium hexafluorophosphate NaPF into the mixed solvent 6 2% fluoroethylene carbonate additive is added to prepare the electrolyte with the sodium salt concentration of 1 mol/L.
(4) Post-treatment
And sequentially stacking the prepared positive electrode plate, negative electrode plate and polypropylene diaphragm, enabling the polypropylene diaphragm to be positioned between the positive electrode plate and the negative electrode plate, winding to obtain a bare cell, filling the bare cell into an aluminum plastic film soft package, drying, injecting electrolyte, and carrying out the procedures of vacuum packaging, standing, formation, shaping and the like to obtain the secondary battery.
Example two
The difference from embodiment one is that the thickness D1 of the first active material layer is 65 μm, the volume porosity P1 is 28%, the first active particles are hard carbon particles having a large particle diameter, and the median particle diameter D 1 50 is 12 μm. The second active material layer had a thickness D2 of 20 μm and a volume porosity P2 of 27%, and the second active particles were small-sized, round hard carbon particles having a value of D 2 50 is 3 μm and d1×P1/D 1 50 is 1.52, d2×P2/D 2 50 is 1.80, and the parameters of the method for preparing the secondary battery are correspondingly adjusted, and the rest is kept unchanged.
Example III
The difference from the first embodiment is that the thickness d1 of the first active material layer is 70 μm, the volume porosity P1 is 27%, and the first active particles are hard with large particle sizeCarbon particles, median particle diameter D 1 50 is 10 μm. The second active material layer has a thickness D2 of 30 μm and a volume porosity P2 of 35%, and the second active particles are small-sized, round hard carbon particles having a value of D 2 50 is 5 μm and d1×P1/D 1 50 is 1.89, d2×P2/D 2 50 is 2.10, and the parameters of the method for preparing the secondary battery are correspondingly adjusted, and the rest is kept unchanged.
Example IV
The difference from embodiment one is that the thickness D1 of the first active material layer is 50 μm, the volume porosity P1 is 22%, the first active particles are hard carbon particles having a large particle diameter, and the median particle diameter D 1 50 is 7 μm. The second active material layer had a thickness D2 of 15 μm and a volume porosity P2 of 33%, and the second active particles were small-sized, round hard carbon particles having a value of D 2 50 is 3 μm and d1×P1/D 1 50 is 1.57, d2×P2/D 2 50 is 1.65, and the parameters of the method for preparing the secondary battery are correspondingly adjusted, and the rest is kept unchanged.
Example five
The difference from embodiment one is that the thickness D1 of the first active material layer is 50 μm, the volume porosity P1 is 20%, the first active particles are hard carbon particles having a large particle diameter, and the median particle diameter D 1 50 is 12 μm. The second active material layer has a thickness D2 of 35 μm and a volume porosity P2 of 28%, and the second active particles are small-sized, round hard carbon particles having a value of D 2 50 is 3 μm and d1×P1/D 1 50 is 0.83, d2×P2/D 2 50 is 3.27, and the parameters of the method for preparing the secondary battery are correspondingly adjusted, and the rest is kept unchanged.
Example six
The difference from embodiment one is that the thickness D1 of the first active material layer is 45 μm, the volume porosity P1 is 20%, the first active particles are hard carbon particles having a large particle diameter, and the median particle diameter D 1 50 is 17 μm. The second active material layer has a thickness D2 of 40 μm and a volume porosity P2 of 25%, and the second active particles are small-sized, round hard carbon particles having a value of D 2 50 is 2 μm and d1×P1/D 1 50 is 0.53, d2×P2/D 2 50 is 5.00, and the parameters of the method for preparing the secondary battery are correspondingly adjusted, and the rest is kept unchanged.
Comparative example one
The difference from embodiment one is that the thickness D1 of the first active material layer is 75 μm, the volume porosity P1 is 28%, the first active particles are hard carbon particles having a large particle diameter, and the median particle diameter D 1 50 is 5 μm. The second active material layer has a thickness D2 of 10 μm and a volume porosity P2 of 25%, and the second active particles are small-sized, round hard carbon particles having a value of D 2 50 is 4 μm and d1×P1/D 1 50 is 4.20, d2×P2/D 2 50 is 0.63, and the parameters of the method for preparing the secondary battery are correspondingly adjusted, and the rest is kept unchanged.
Comparative example two
The present comparative example differs from example five in that the anode material layer in the anode tab has only the first active material layer, and the thickness of the first active material layer is 85 μm.
Comparative example three
The present comparative example differs from example five in that the anode material layer in the anode tab has only the second active material layer, and the thickness of the second active material layer is 85 μm.
The porosity of the negative electrode plate provided by the examples and the comparative examples of the application is volume porosity, and is obtained by testing the following testing method: the surface of the negative electrode plate is polished by adopting an argon ion polisher, argon is ionized by utilizing a high-voltage electric field to generate argon ions, and the generated argon ions can degrade the negative electrode plate layer by layer under the action of accelerating voltage so as to achieve the polishing effect. The porosity of the negative electrode sheet was tested using mercury intrusion method (also called "mercury intrusion method"), and specific reference standards are: the GB/T21650.1-2008 mercury intrusion method and gas adsorption method are used for measuring the pore size distribution and the porosity of the solid material. First, the porosity P of the first active material layer and the second active material layer as a whole was measured by mercury intrusion. And then polishing and removing the copper foil of the negative electrode plate and the second active material layer by adopting an argon ion polisher, and testing the polished electrode plate by using a mercury intrusion method to obtain the porosity P1 of the first active material layer. And finally, obtaining the porosity P2 of the second active material layer by using P-P1=P2 by adopting a difference method. The comparative summary of the parameters of the examples and comparative examples is shown in Table one:
Table negative electrode sheet structure parameter tables of examples one to six, comparative examples one to three
Figure BDA0004170498750000171
Performance testing
(1) Energy density testing: the sodium ion batteries provided in each example and comparative example were weighed using an electronic balance at 25 ℃; charging and discharging each prepared sodium ion battery at the rate of 1C at the temperature of 25 ℃, and recording the actual discharge energy at the moment; the ratio of the actual discharge energy of the sodium ion battery to the weight of the sodium ion battery is the actual energy density of the sodium ion battery.
(2) And (3) testing the cycle performance: each sodium ion battery provided in each example and comparative example was charged at a rate of 2C and discharged at a rate of 1C, and a full charge discharge cycle test was performed to record the capacity retention after 1000 cycles.
(3) Kinetic performance test: at 25 ℃, each sodium ion battery is fully charged at n C (n C is charged at a charging rate of current which can be n times of battery capacity per hour, n can be 1, 2, 3, 4 and the like), the battery is fully discharged at 1C, after repeated charge and discharge cycles for 10 times, the battery is charged to a full-charge state at nC multiplying power, then the negative electrode plate is disassembled, and sodium precipitation condition on the surface of the negative electrode plate is observed. Wherein, the area of the sodium precipitation area on the surface of the negative electrode plate is smaller than 2 percent, which is regarded as non-sodium precipitation. The sodium precipitation rate refers to that if sodium is not precipitated on the surface of the negative electrode plate, the charging rate is gradually increased from nC by a gradient of 0.1C, and the test is performed again until sodium is precipitated on the surface of the negative electrode, and the charging rate nC minus 0.1C at this time is the maximum charging rate of the battery under the condition of no sodium precipitation.
The energy density test, cycle performance test and kinetic performance test results of the secondary batteries of examples and comparative examples are shown in table two:
table two secondary battery electrochemical performance summary tables of examples one to six, comparative examples one to three
Group of Energy Density (Wh/kg) Capacity retention rate of 1000 cycles First week charge and discharge efficiency Sodium precipitation rate
Example 1 106 93.1％ 92.2％ 3.0
Example two 108 93.6％ 91.4％ 3.1
Example III 104 91.2％ 90.4％ 2.8
Example IV 102 92.1％ 92.7％ 3.3
Example five 101 88.7％ 88.7％ 2.4
Example six 94 83.8％ 87.6％ 1.5
Comparative example one 90 82.1％ 86.8％ 1.4
Comparative example two 86 77.8％ 85.8％ 1.3
Comparative example three 91 80.1％ 86.5％ 1.4
As can be seen from table one, examples one to six satisfy the relation d as compared with comparative example one1×P1/D 1 50＜d2×P2/D 2 50, and comparative example d1.times.P1/D 1 50 is 4.20 > d2×P2/D 2 50 is 0.63, and does not satisfy the above-described relational expression. The data in Table two show that: the energy density, capacity retention, first week charge and discharge efficiency and sodium precipitation rate of examples one to six were all higher than those of comparative example one, indicating that d1×P1/D will be 1 50、d2×P2/D 2 50 satisfies the relationship d1×P1/D 1 50＜d2×P2/D 2 50, can promote the negative pole dynamics of negative pole, reduce the production of natrium precipitation phenomenon to improve the rate capability and the cycle performance of secondary cell.
d1×P1/D of example six 1 50 is 0.53, not at d1×P1/D 1 50 is in the range of 0.6 to 3.6, d2×P2/D of example six 2 50 is 5.00, not at d2×P2/D 2 50 is in the range of 0.8 to 4, and d1×P1/D of examples one to five 1 50 and d2×P2/D 2 50 satisfy the above parameter ranges. As can be seen from the data in Table II, the electrochemical properties of examples one to five are all better than those of example six, indicating that d1×P1/D will be 1 50 is controlled in the range of 0.6 to 3.6 and d2×P2/D 2 50 is controlled to be in the range of 0.8 to 4, and the energy density, capacity retention, first-week charge/discharge efficiency and sodium precipitation rate of the secondary battery can be improved.
Further, in embodiments one to four, compared with embodiment five, embodiments one to four satisfy not only that d1×p1/D150 is in the range of 0.6 to 3.6, but also that d2×p2/D250 is in the range of 0.8 to 4. And d1×P1/D of examples one to four 1 50、d2×P2/D 2 50 are within the preferred parameters of the present application scheme, i.e., d1×P1/D 1 50 is 1.0-2.4, d2×P2/D 2 50 is 1.2-3. And d1×P1/D of embodiment five 1 50 is 0.83, not in the preferred range of 1.0 to 2.4, d2×P2/D 2 50 is 3.27, which is not in the preferred range of 1.2-3, and experimental result data show that: the energy density, capacity retention rate of 1000 cycles, first week charge and discharge efficiency and maximum charge rate when sodium precipitation occurs in the examples one to four are all obviously higher than those in the fifth example. Therefore, when the relation d1×P1/D is satisfied 1 50＜d2×P2/D 2 50, and such that d1×P1/D 1 50、d2×P2/D 2 The 50 parameters are in the preferred parameter ranges of the scheme, so that the dynamic performance of the cathode can be improved to the greatest extent, the generation of sodium dendrite is reduced, and the cycle performance, the multiplying power performance and the energy density of the secondary battery are improved to the greatest extent.
In the fifth embodiment, compared with the second embodiment, the second active material layer is not provided and only the first active material layer is provided. In the fifth embodiment, compared with the third embodiment, the third embodiment is provided with no first active material layer and only the second active material layer. As can be seen from the experimental data of table two, each electrochemical performance of comparative examples two and three is inferior to that of example five, indicating that the double-layer structure provided with the first active material layer and the second active material layer can improve the cycle performance and the rate performance of the secondary battery compared to the single-layer structure.
Thus, the above parameters D1, P1, D are cooperatively controlled 1 50、d2、P2、D 2 50 and designing a double-layer structure of a negative electrode material layer, the dynamic performance of the negative electrode can be obviously improved, the generation of sodium precipitation phenomenon can be reduced, the occurrence of side reaction can be reduced, and the energy density (battery capacity), the rate capability (quick charge capability) and the cycle performance (cycle life) of the secondary battery are obviously improved.
The above details of the negative electrode material layer, the negative electrode sheet and the preparation method thereof, the secondary battery, the battery pack and the electric equipment disclosed in the embodiments of the present invention, and specific examples are applied to illustrate the principles and the implementation of the present invention, and the above description of the embodiments is only used to help understand the negative electrode material layer, the negative electrode sheet and the preparation method thereof, the secondary battery, the battery pack, the electric equipment and the core ideas thereof: meanwhile, as those skilled in the art will vary in the specific embodiments and application scope according to the idea of the present invention, the present disclosure should not be construed as limiting the present invention in summary.

Claims (12)

1. A negative electrode material layer, comprising:
a first active material layer having a thickness D1, a porosity P1, and comprising first active particles having a median particle diameter D 1 50; and
a second active material layer stacked on the surface of the first active material layer, wherein the thickness of the second active material layer is D2, the porosity is P2, the second active material layer comprises second active particles, and the median particle diameter of the second active particles is D 2 50, and d1×P1/D 1 50＜d2×P2/D 2 50。
2. The anode material layer according to claim 1, wherein d1×p1/D of the first active material layer 1 50 is 0.6 to 3.6, and/or D2 x P2/D of the second active material layer 2 50 is 0.8-4.
3. The anode material layer according to claim 1, wherein the thickness d1 of the first active material layer is 45 μm to 100 μm and/or the thickness d2 of the second active material layer is 10 μm to 35 μm.
4. The anode material layer according to claim 1, wherein the first active material layer has a porosity P1 of 10% to 30%, and/or the second active material layer has a porosity P2 of 20% to 40%.
5. The anode material layer according to claim 1, wherein the first active particles have a median particle diameter D 1 50 is 7 μm to 14 μm, and/or the median particle diameter D of the second active particles 2 50 is 3-5 μm.
6. The anode material layer according to any one of claims 1 to 5, wherein the first active particles are a mixture of one or more of hard carbon and soft carbon; and/or the number of the groups of groups,
the second active particles are one or more of hard carbon and soft carbon; and/or the number of the groups of groups,
The second active particles are spherical or spheroid.
7. The anode material layer according to any one of claims 1 to 5, wherein the first active material layer further comprises a first binder and a first conductive agent, the first binder is a mixture of one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polyacrylate, carboxymethyl cellulose, sodium alginate, and the like, and/or the first conductive agent is a mixture of one or more of acetylene black, super-P, carbon nanotubes, carbon fibers, graphene, and the like;
and/or the number of the groups of groups,
the second active material layer further comprises a second binder and a second conductive agent, wherein the second binder is one or more of styrene-butadiene rubber, polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylonitrile, polyacrylic acid, polyacrylate, carboxymethyl cellulose, sodium alginate and the like, and/or the second conductive agent is one or more of acetylene black, super-P, carbon nano tubes, carbon fibers, graphene and the like.
8. A negative electrode tab, comprising a negative electrode current collector and a negative electrode material layer, wherein the negative electrode material layer is a negative electrode material layer according to any one of claims 1 to 7, and the first active material layer is coated on the surface of the negative electrode current collector.
9. A method of producing the negative electrode sheet according to claim 8, comprising the steps of:
mixing and coating the first active particles, a first conductive agent and a first binder on the surface of the current collector to form a first active material layer and drying the first active material layer;
mixing and coating the second active particles, a second conductive agent and a second binder on the surface of the first active material layer to form the second active material layer and drying;
and (5) post-processing to obtain the negative electrode plate.
10. A secondary battery comprising the negative electrode tab of claim 8.
11. A battery pack, characterized in that the battery pack comprises a case and the secondary battery according to claim 10 provided in the case.
12. An electric device, characterized in that the electric device comprises an electric device body and the secondary battery as claimed in claim 10 arranged in the electric device body, wherein the secondary battery is used for supplying power to the electric device body.
CN202310375802.XA 2023-04-10 2023-04-10 Negative electrode material layer, negative electrode plate, preparation method of negative electrode plate, secondary battery, battery pack and electric equipment Pending CN116435503A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117976818A (en) * 2024-03-28 2024-05-03 宁德时代新能源科技股份有限公司 Battery cell, battery and electricity utilization device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117976818A (en) * 2024-03-28 2024-05-03 宁德时代新能源科技股份有限公司 Battery cell, battery and electricity utilization device

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