CN111799470B - Positive pole piece and sodium ion battery - Google Patents

Positive pole piece and sodium ion battery Download PDF

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Publication number
CN111799470B
CN111799470B CN201910275491.3A CN201910275491A CN111799470B CN 111799470 B CN111799470 B CN 111799470B CN 201910275491 A CN201910275491 A CN 201910275491A CN 111799470 B CN111799470 B CN 111799470B
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active material
positive
positive electrode
ion battery
electrode active
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CN111799470A (en
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苏硕剑
郭永胜
王莹
梁成都
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex 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
    • H01M4/64—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
    • 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
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The application discloses a positive pole piece and a sodium ion battery, wherein the positive pole piece comprises a positive current collector and a positive active substance layer arranged on at least one surface of the positive current collector, and the positive active substance layer comprises a positive active substance; wherein the thickness d of the positive electrode active material layer1Thickness d of positive current collector2The ratio of d is more than or equal to 1.61/d2Less than or equal to 24. The application makes the sodium ion battery have higher cycle performance by limiting the ratio of the thickness of the positive active material layer to the thickness of the positive current collector in a specific range.

Description

Positive pole piece and sodium ion battery
Technical Field
The application belongs to the technical field of energy storage devices, and particularly relates to a positive pole piece and a sodium-ion battery.
Background
At present, lithium ion batteries occupy the core position of power batteries, and meanwhile, the lithium ion batteries also face great challenges, such as increasing shortage of lithium resources, rising price of upstream materials, lagging development of recycling technology, low recycling rate of old batteries and the like. The sodium ion battery can realize charge and discharge by utilizing the deintercalation process of sodium ions between a positive electrode and a negative electrode, and the reserve of sodium resources is far more abundant than that of lithium, the distribution is more extensive, and the cost is far lower than that of lithium, so the sodium ion battery becomes a new generation electrochemical system with potential to replace a lithium ion battery.
However, the current research on commercialization of sodium ion batteries is still in a relatively coarse stage, and it can be seen that the reported cycle performance of sodium ion batteries is far lower than that of lithium ion batteries. In order to make sodium ion batteries really become a new generation of electrochemical system for replacing or supplementing lithium ion batteries, the cycle performance of the sodium ion batteries is required to be improved.
Disclosure of Invention
In view of the problems in the background art, the present application provides a positive electrode sheet and a sodium ion battery, aiming to improve the cycle performance of the sodium ion battery.
In order to achieve the above object, a first aspect of the present application provides a positive electrode sheet for a sodium ion battery, including a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material; wherein the thickness d of the positive electrode active material layer1Thickness d of positive current collector2The ratio of d is more than or equal to 1.61/d2≤24。
The second aspect of the application provides a sodium ion battery, and the sodium ion battery comprises a positive pole piece, a negative pole piece, an isolating membrane and electrolyte, wherein the positive pole piece is the positive pole piece according to the first aspect of the application.
Compared with the prior art, the method has the following beneficial effects:
according to the positive pole piece, the ratio of the thickness of the positive active material layer to the thickness of the positive current collector is limited within a specific range, so that the positive pole piece has good mechanical property and electrochemical cycle stability, the damage of stress accumulated by the sodium-ion battery due to the continuous change of the volume to the body structure of the positive pole piece and the porous structure of the positive active material layer is effectively prevented, and the cycle performance of the sodium-ion battery is effectively improved; meanwhile, the positive pole piece is effectively prevented from being broken or cracked in the processing and using processes, the processing performance of the positive pole piece is improved, the preparation excellent rate and the service life of the positive pole piece and the battery cell in the sodium-ion battery are effectively improved, and therefore the cycle performance of the sodium-ion battery is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a positive electrode tab according to an embodiment of the present application.
Fig. 2 is a schematic structural diagram of a positive electrode tab according to another embodiment of the present application.
Detailed Description
In order to make the purpose, technical solution and advantageous technical effects of the present invention clearer, the present invention is described in detail with reference to specific embodiments below. It should be understood that the embodiments described in this specification are only for the purpose of explaining the present application and are not intended to limit the present application.
For the sake of brevity, only some numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Also, although not explicitly recited, each point or individual value between endpoints of a range is encompassed within the range. Thus, each point or individual value can form a range not explicitly recited as its own lower or upper limit in combination with any other point or individual value or in combination with other lower or upper limits.
In the description herein, it is to be noted that, unless otherwise specified, "above" and "below" are inclusive and "one or more" means "several" are two or more.
The above summary of the present application is not intended to describe each disclosed embodiment or every implementation of the present application. The following description more particularly exemplifies illustrative embodiments. At various points throughout this application, guidance is provided through a list of embodiments that can be used in various combinations. In each instance, the list is merely a representative group and should not be construed as exhaustive.
Positive pole piece
First, a positive electrode sheet according to a first aspect of an embodiment of the present application, which is used for a sodium-ion battery, will be described. Referring to fig. 1 and 2, the positive electrode sheet includes a positive electrode collector 11 and a positive electrode active material layer 12 disposed on at least one surface of the positive electrode collector 11, and the positive electrode active material layer 12 includes a positive electrode active material.
As an example, the positive electrode current collector 11 includes two opposite surfaces in its thickness direction, and the positive electrode active material layer 12 may be provided on either one of the two opposite surfaces of the positive electrode current collector 11, or the positive electrode active material layers 12 may be provided on the two opposite surfaces of the positive electrode current collector 11, respectively.
Further, the thickness d of the positive electrode active material layer 121Thickness d of positive electrode current collector 112Satisfies the following conditions: d is not less than 1.61/d2≤24。
Herein, the thickness d of the positive electrode active material layer 121And the compacted density C, mass, volume mentioned hereinafter are based on the positive electrode active material layer 12 on one side of the positive electrode current collector 11.
The application provides a positive pole piece, through thickness d with positive active material layer 121Thickness d of positive electrode current collector 112The ratio of the positive electrode to the negative electrode is limited in a specific range, so that the positive electrode plate has good mechanical property and electrochemical cycling stability, the damage of the stress accumulated by the sodium-ion battery due to the continuous change of the volume to the body structure of the positive electrode plate and the porous structure of the positive electrode active material layer 12 in the cycling process is effectively prevented, and the cycling performance of the sodium-ion battery is effectively improved.
At the same time, the thickness d of the positive electrode active material layer 12 is set1Thickness d of positive electrode current collector 112The ratio of the positive pole piece to the negative pole piece is limited in a specific range, so that the positive pole piece has good mechanical property, the positive pole piece is effectively prevented from being broken or cracked in the processing and using processes, the processing property of the positive pole piece is improved, the preparation excellent rate and the service life of the positive pole piece and the battery cell in the sodium-ion battery are effectively improved, and the cycle performance of the sodium-ion battery is improved.
In addition, the thickness d of the positive electrode active material layer 121Thickness d of positive electrode current collector 112The ratio of the first to the second is 1.6In addition, the sodium ion battery has higher capacity performance and energy density.
In some alternative embodiments, the thickness d of the positive electrode active material layer 121Thickness d of positive electrode current collector 112The upper limit of the ratio may be 24, 22, 20, 18, 16, 15, 14, 12, 10 and the lower limit may be 9, 8, 7, 6, 5, 4, 3, 2, 1.6. d1/d2May consist of any of the preceding upper limit values and any of the preceding lower limit values.
Preferably, the thickness d of the positive electrode active material layer 121Thickness d of positive electrode current collector 112D is more than or equal to 31/d2Less than or equal to 10, and can better improve the cycle performance and the energy density of the sodium-ion battery.
The thickness d of the positive electrode plate, positive current collector 11 of the embodiment of the present application2Preferably 5 to 25 μm, more preferably 5 to 15 μm.
Thickness d of positive current collector 112The optimal size is more than 5 mu m, so that the positive active material layer 12 can be supported and protected, the positive pole piece has high mechanical property, the stress accumulated by the sodium ion battery due to the continuous change of the volume in the circulating process is effectively prevented from damaging the body structure of the positive pole piece and the porous structure of the positive active material layer, and the circulating performance of the sodium ion battery is effectively improved. Thickness d of positive current collector 112Preferably more than 5 μm, and also ensures that the positive current collector 11 has higher conductivity, which is beneficial to reducing battery polarization and improving the cycle performance of the sodium ion battery.
Thickness d of positive current collector 112Preferably less than 25 μm, and more preferably less than 15 μm, which is advantageous for reducing the volume and weight of the sodium ion battery, thereby improving the energy density of the sodium ion battery.
Thickness d of positive electrode active material layer 12 of the positive electrode sheet of the embodiment of the present application1Preferably 16 to 240 μm, more preferably 40 to 120 μm.
Thickness d of positive electrode active material layer 12 at a certain compacted density1Preferably 16 μm or more, more preferably 40 μm or moreThe method is favorable for leading the sodium ion battery to have higher specific capacity and energy density; thickness d of positive electrode active material layer 121Preferably below 240 μm, more preferably below 120 μm, sodium ions and electrons are less hindered in the migration process, the resistivity of the positive pole piece is smaller, and the sodium ion battery has higher rate performance and cycle performance.
In the positive electrode sheet of the embodiment of the present application, the ratio C/a of the compacted density C of the positive electrode active material layer 12 to the true density a of the positive electrode active material is preferably 0.3 or more and 0.95 or less, where C is expressed in units of g/cm3The unit of A is g/cm3。
The above-mentioned compacted density C of the positive electrode active material layer 12 is a meaning well known in the art, and refers to a ratio of the mass of the positive electrode active material layer 12 to the volume thereof. The mass of the positive electrode active material layer 12 includes the total mass of the positive electrode active material present in the positive electrode active material layer 12 and the optional conductive agent and binder; the volume of the positive electrode active material layer 12 is the apparent volume of the positive electrode active material layer 12, and includes the volume of the positive electrode active material and optional conductive carbonaceous agent and binder present in the positive electrode active material layer 12 and the volume of the pores inside the particles and between the particles.
The above-mentioned true density a of the positive electrode active material is a well-known meaning in the art, and refers to a ratio of the mass of the positive electrode active material to its true volume, wherein the true volume is an actual volume of the solid material excluding the volume of pores present inside the positive electrode active material particles.
By enabling the surface density C of the positive active material layer 12 and the true density A of the positive active material to satisfy the specific relationship, the positive active material layer 12 is beneficial to keeping proper flexibility, and the problems of breakage and the like caused in the winding process and when the positive active material layer is impacted by external force are effectively prevented, so that the mechanical property of the positive pole piece is further improved, the conductive continuity in the positive active material layer 12 is ensured, the electrochemical cycle stability of the positive pole piece is improved, and the cycle performance of the sodium-ion battery is further improved.
In some alternative embodiments, the upper limit value of the ratio C/a of the areal density C of the positive electrode active material layer 12 to the true density a of the positive electrode active material is 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, and the lower limit value is 0.3, 0.35, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52. The range of C/A may be comprised of any upper value and any lower value described above.
More preferably, the area density C of the positive electrode active material layer 12 and the true density a of the positive electrode active material satisfy: C/A is more than or equal to 0.5 and less than or equal to 0.8.
In the positive electrode sheet of the embodiment of the present application, the compacted density C of the positive electrode active material layer 12 is preferably 0.6g/cm3～4g/cm3More preferably 1.0g/cm3～2.5g/cm3. The compaction density C of the positive active material layer 12 is in the range, which is beneficial to enabling the sodium ion battery to have higher specific capacity and energy density, reducing the resistivity of a positive pole piece, reducing the polarization of the positive pole of the battery and improving the cycle performance of the sodium ion battery.
In the positive electrode sheet of the embodiment of the present application, the true density a of the positive electrode active material in the positive electrode active material layer 12 is preferably 1.5g/cm3～5g/cm3More preferably 1.8g/cm3～4.5g/cm3. The true density A of the positive active material is in the range, which is beneficial to improving the specific capacity and the energy density of the sodium ion battery, and ensures that the positive active material layer has higher structural stability in the electrochemical cycle process, thereby preventing the positive active material layer from cracking and improving the cycle performance of the sodium ion battery.
In the positive electrode sheet of the embodiment of the present application, the average particle diameter D of the positive electrode active materialv50 is preferably 0.3 to 25 μm, more preferably 1 to 15 μm. The average particle diameter D of the positive electrode active materialv50 within the range, the positive pole piece can be ensured to have higher mechanical property and electrochemical cycling stability, and can also be ensured to have lower resistivity, so that the rate capability and the cycling performance of the sodium-ion battery are improved. The average particle diameter D of the positive electrode active materialv50 in the range, the capacity of the positive active material is favorably exerted, and the capacity performance of the sodium-ion battery is improved.
The average particle diameter D of the positive electrode active materialv50 is the bookThe measurement can be carried out by an apparatus and a method known in the art. This may conveniently be done, for example, using a laser particle size analyser, such as the Mastersizer 3000 laser particle size analyser from malvern instruments ltd, uk.
In the positive electrode plate of the embodiment of the application, the positive active material may be one or more of a sodium transition metal oxide, a polyanionic compound and a prussian blue compound.
For example, in the sodium transition metal oxide, the transition metal may be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce. The sodium transition metal oxide is, for example, NaxMO2Wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0<x≤1。
The polyanionic compound may have sodium ion, transition metal ion, and tetrahedral type (YO)4)n-A class of compounds of anionic units. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; y can be one or more of P, S and Si; n represents (YO)4)n-The valence of (c).
The polyanionic compound may have sodium ion, transition metal ion, and tetrahedral (YO)4)n-Anionic units and halogen anions. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; y may be one or more of P, S and Si, and n represents (YO)4)n-The valence of (a); the halogen may be F, Cl or Br.
The polyanionic compound may also be of sodium ion, tetrahedral (YO)4)n-Anion unit, polyhedral unit (ZO)y)m+And optionally a halide anion. Y may be one or more of P, S and Si, and n represents (YO)4)n-The valence of (a); z represents transition metal, and can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents (ZO)y)m+The valence of (a);the halogen may be F, Cl or Br.
The polyanionic compound being, for example, NaFePO4、Na3V2(PO4)3、NaM’PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VOy)2(PO4)2F3-2y(y is more than or equal to 0 and less than or equal to 1).
The Prussian blue compound may be sodium ion, transition metal ion and cyanide ion (CN)-) A class of compounds of (1). The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are for example NaaMebMe’c(CN)6Wherein Me and Me' are respectively and independently one or more of Ni, Cu, Fe, Mn, Co and Zn, 0<a≤2，0<b<1，0<c<1。
Optionally, the positive electrode active material layer 12 may further include a conductive agent to improve the conductive performance of the positive electrode. The type of the conductive agent is not particularly limited, and can be selected according to actual requirements. As an example, the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers.
Optionally, the positive electrode active material layer 12 may further include a binder to firmly bind the positive electrode active material and the optional conductive agent to the positive electrode collector 11. The application does not specifically limit the type of the binder, and the binder can be selected according to actual requirements. As an example, the binder may be one or more of polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyvinyl alcohol (PVA), ethylene-vinyl acetate copolymer (EVA), Styrene Butadiene Rubber (SBR), carboxymethyl cellulose (CMC), Sodium Alginate (SA), polymethacrylic acid (PMA), and carboxymethyl chitosan (CMC).
Further, in the positive electrode active material layer 12, the weight ratio of the positive electrode active material, the conductive agent and the binder is 80-100: 0-20.
The positive current collector 11 may be a conductive carbon sheet, a metal foil, a carbon-coated metal foil, or a porous metal plate, wherein the conductive carbon material of the conductive carbon sheet may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphite, graphene, and carbon nanofibers, and the metal materials of the metal foil, the carbon-coated metal foil, and the porous metal plate may be independently one or more selected from copper, aluminum, nickel, and stainless steel.
The positive electrode current collector 11 is, for example, one or more of a copper foil, an aluminum foil, a nickel foil, a stainless steel mesh, and a carbon-coated aluminum foil, and preferably, an aluminum foil is used.
The positive electrode sheet can be prepared according to a conventional method in the field. The positive electrode active material, and optionally a conductive agent and a binder are generally dispersed in a solvent (e.g., N-methylpyrrolidone, abbreviated as NMP) to form a uniform positive electrode slurry, and the positive electrode slurry is coated on a positive electrode current collector 11, dried and cold-pressed to obtain a positive electrode sheet.
Sodium ion battery
A second aspect of the embodiments of the present application provides a sodium-ion battery including the positive electrode sheet of the first aspect of the embodiments of the present application.
By adopting the positive pole piece of the first aspect of the embodiment of the application, the sodium-ion battery has higher structural stability and working stability, the cycle performance of the sodium-ion battery is effectively improved, and the sodium-ion battery is favorable for having higher safety performance.
The sodium ion battery also comprises a negative pole piece, a separation film and electrolyte.
The negative electrode plate can be a metal sodium plate.
The negative electrode plate may also include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. For example, the negative electrode current collector includes two opposite surfaces, and the negative electrode active material layer is stacked on either or both of the two surfaces of the negative electrode current collector.
The negative electrode current collector may be made of metal foil, carbon-coated metal foil, porous metal plate, or the like, and is preferably made of copper foil.
The negative active material layer generally includes a negative active material, which may be one or more of natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, and soft carbon, and optionally a conductive agent, a binder, and a thickener, wherein the conductive agent may be one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, the binder may be one or more of Styrene Butadiene Rubber (SBR), water-based acrylic resin (water-based acrylic resin), and carboxymethyl cellulose (CMC), and the thickener may be carboxymethyl cellulose (CMC). However, the present application is not limited to these materials, and other materials that can be used as the negative electrode active material, the conductive agent, the binder, and the thickener of the sodium ion battery may be used.
In some preferred embodiments, the anode active material of the anode active material layer includes hard carbon. The hard carbon is used as a negative electrode material of the sodium ion battery, has higher specific capacity (more than 300 mAh/g), and is beneficial to improving the specific capacity and the energy density of the sodium ion battery; and the hard carbon material has higher reversible specific capacity, and can improve the cycle performance of the sodium ion battery. In addition, hard carbon has the advantage of wide raw material sources.
Further, the weight percentage content of the negative electrode active material in the negative electrode active material layer is 80 wt% or more, further 90 wt% or more.
Further, the hard carbon content in the negative electrode active material is 30 wt% or more, further 50 wt% or more, further 80 wt% or more, further 90 wt% or more, for example, 100 wt%.
In some embodiments, the thickness d of the positive active material layer in a sodium ion battery1Thickness d of the negative electrode active material layer3The ratio of (d) is preferably 1. ltoreq. d1/d3≤3。
Optionally, the thickness d of the positive electrode active material layer in the sodium ion battery1Thickness d of the negative electrode active material layer3The upper limit of the ratio is 3, 2.8, 2.6, 2.5, 2.4, 2.2, 2.0, 1.8, and the lower limit is 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8.d1/d3May consist of any of the preceding upper limit values and any of the preceding lower limit values.
In these examples, the thickness d of the positive electrode active material layer1Thickness d of the negative electrode active material layer3The ratio of the sodium ion battery and the lithium ion battery is in the range, so that irreversible capacity loss of the battery in the circulating process is reduced, and the circulating performance of the sodium ion battery is improved.
In these examples, the compacted density C of the positive electrode active material layer is preferably 0.6g/cm3～4.0g/cm3(ii) a The compacted density of the anode active material layer is preferably 0.8g/cm3～1.6g/cm3。
The above negative electrode sheet may be prepared according to a conventional method in the art. Generally, a negative electrode active material, an optional conductive agent, a binder and a thickening agent are dispersed in a solvent, wherein the solvent can be deionized water, so as to form uniform negative electrode slurry, the negative electrode slurry is coated on a negative electrode current collector, and the negative electrode pole piece is obtained after the working procedures of drying, cold pressing and the like.
The separator is not particularly limited, and any known separator having a porous structure and electrochemical and chemical stability may be used, and may be, for example, a single-layer or multi-layer film of one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride.
The electrolyte may include an organic solvent and an electrolyte sodium salt. As an example, the organic solvent may be one or more of Ethylene Carbonate (EC), Propylene Carbonate (PC), Ethyl Methyl Carbonate (EMC), and diethyl carbonate (DEC); the sodium salt of the electrolyte may be NaPF6、NaClO4、NaBCl4、NaSO3CF3And Na (CH)3)C6H4SO3One or more of them.
Stacking the positive pole piece, the isolating film and the negative pole piece in sequence, so that the isolating film is positioned between the positive pole piece and the negative pole piece to play an isolating role, and obtaining the battery cell, or obtaining the battery cell after winding; and (4) placing the battery core in a packaging shell, injecting electrolyte and sealing to obtain the sodium ion battery.
Examples
The present disclosure is more particularly described in the following examples that are intended as illustrative only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are on a weight basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further treatment, and the equipment used in the examples is commercially available.
Example 1
Preparation of positive pole piece
Adding Prussian blue type positive electrode active substance Na2MnFe(CN)6The conductive carbon black Super P and the binder PVDF are fully stirred and mixed in a proper amount of NMP according to the weight ratio of 90:5:5 to form uniform anode slurry; and coating the positive electrode slurry on a positive electrode current collector aluminum foil, drying and cold pressing to obtain the positive electrode piece. Wherein the thickness of the positive electrode current collector is 10 μm, the thickness of the positive electrode active material layer is 16 μm, and the compaction density of the positive electrode active material layer is 1.3g/cm3The positive electrode active material has a true density of 2.0g/cm3。
Preparation of negative pole piece
Uniformly mixing hard carbon serving as a negative active material, Styrene Butadiene Rubber (SBR) serving as a binder and conductive carbon black in a proper amount of deionized water according to a weight ratio of 90:5:5 to prepare negative slurry; and then coating the negative electrode slurry on a copper foil of a negative current collector, and drying and cold pressing to obtain a negative electrode pole piece. Wherein the positive electrode active material layer has a compacted density of 0.95g/cm3。
Preparation of the electrolyte
Uniformly mixing Ethylene Carbonate (EC) and Propylene Carbonate (PC) with equal volume to obtain an organic solvent, and then adding NaPF6Uniformly dissolving in the organic solvent to obtain an electrolyte solution, wherein the NaPF6The concentration of (2) is 1 mol/L.
Preparation of sodium ion battery
And (3) stacking the positive pole piece, the isolating membrane (glass fiber film) and the negative pole piece in sequence, winding to obtain a battery cell, putting the battery cell into a packaging shell, adding the electrolyte, sealing, and carrying out processes such as formation, standing and the like to obtain the sodium-ion battery.
Examples 2 to 14 and comparative examples 1 to 6
Different from the embodiment 1, relevant parameters of the positive pole piece are adjusted, and the details are shown in the following table 1.
Test section
(1) And (3) testing the mechanical property of the positive pole piece:
the mechanical property of the positive pole piece is judged by the winding breakage rate of the positive pole piece, and the process is as follows: preparing 100 positive pole pieces, stacking the positive pole pieces, the isolating membrane and the negative pole pieces in sequence, winding to obtain a battery cell, and counting the fracture number of the positive pole pieces.
The winding breakage (%) of the positive electrode sheet was equal to the number of positive electrode sheet breaks/100X 100%
(2) Cycle performance testing of sodium ion batteries:
at 25 ℃, charging the sodium ion battery to the upper limit of a charge-discharge cut-off voltage at a constant current of 1C multiplying power, then charging to a current of 0.2C at a constant voltage, then standing for 5min, then discharging to the lower limit of the charge-discharge cut-off voltage at a constant current of 1C multiplying power, and standing for 5min, wherein the process is a cyclic charge-discharge process, and the discharge capacity of the time is recorded as the discharge capacity of the 1 st cycle of the sodium ion battery, namely the initial capacity of the sodium ion battery. And (3) carrying out 100-cycle charge and discharge tests on the sodium-ion battery according to the method, and detecting to obtain the discharge capacity of the 100 th cycle.
Wherein, the charge-discharge cut-off voltage of the sodium ion batteries of the examples 1 to 12, 14, 1 to 2 and 5 to 6 is 1.9V to 4.0V; the charge/discharge cutoff voltage of the sodium ion battery of example 13 and comparative examples 3 to 4 was 1.9V to 4.2V.
The capacity retention (%) of the sodium-ion battery after 100 cycles at 25 ℃ was equal to the discharge capacity at 100 cycles/discharge capacity at 1 cycle × 100%.
The test results of examples 1 to 14 and comparative examples 1 to 6 are shown in Table 2 below.
TABLE 1
Figure BDA0002019845340000121
In Table 1, d1Thickness of the positive electrode active material layer; d2Is the thickness of the positive current collector; d3Is the thickness of the anode active material layer; c is the compaction density of the positive active material layer; a is the true density of the positive electrode active material.
TABLE 2
Percentage of winding breakage of positive electrode sheet% Capacity retention after 100 cycles%
Example 1 0 96
Example 2 0 93
Example 3 0 92
Practice ofExample 4 0 92
Example 5 2 90
Example 6 0 92
Example 7 0 90
Example 8 5 86
Example 9 10 81
Example 10 0 88
Example 11 0 89
Example 12 20 79
Example 13 0 93
Example 14 0 97
Comparative example 1 50 68
Comparative example 2 80 56
Comparative example 3 48 72
Comparative example 4 70 70
Comparative example 5 45 76
Comparative example 6 68 71
It can be seen from the comparative analysis of examples 1 to 14 and comparative examples 1 to 6 that when the ratio of the thickness of the positive active material layer to the thickness of the positive current collector is within a specific range, the positive electrode sheet has good mechanical properties, and no significant fracture occurs after winding, and when the ratio of the thickness of the positive active material layer to the thickness of the positive current collector is outside the specific range, the winding performance of the positive electrode sheet is deteriorated, and the positive electrode sheet is very likely to fracture and fail. And when the ratio of the thickness of the positive active material layer to the thickness of the positive current collector is outside the specific range, the damage of the stress generated by the volume change of the pole piece caused by the ion intercalation and deintercalation to the body structure of the positive pole piece and the porous structure of the positive active material layer is small in the circulation process of the sodium ion battery, the circulation performance of the sodium ion battery is good, and when the ratio of the thickness of the positive active material layer to the thickness of the positive current collector is outside the specific range, the damage of the stress generated by the volume change of the pole piece caused by the ion intercalation and deintercalation to the body structure of the positive pole piece and the porous structure of the positive active material layer in the circulation process of the sodium ion battery is large, and the circulation performance of the sodium ion battery is poor.
Further, it can be seen from examples 1 to 12 that, when the ratio of the thickness of the positive electrode active material layer to the thickness of the positive electrode current collector is within a specific range and the ratio of the compacted density of the positive electrode active material layer to the true density of the positive electrode active material is within a specific range, both the mechanical properties and the cycle properties of the positive electrode sheet are further improved.
While the invention has been described with reference to specific embodiments, the scope of the invention is not limited thereto, and those skilled in the art can easily conceive various equivalent modifications or substitutions within the technical scope of the invention. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (14)

1. A sodium ion battery comprises a positive pole piece, and is characterized in that the positive pole piece comprises a positive current collector and a positive active substance layer arranged on at least one surface of the positive current collector, the positive active substance layer comprises a positive active substance, and the positive active substance is one or more of sodium transition metal oxide, polyanion type compound and Prussian blue type compound;
wherein the thickness d of the positive electrode active material layer1And the thickness d of the positive current collector2The ratio of d is more than or equal to 1.61/d2≤24；
The compacted density C of the positive electrode active material layer and the true density A of the positive electrode active material layer satisfy: C/A is more than or equal to 0.3 and less than or equal to 0.95, wherein the units of C and A are g/cm3。
2. The sodium-ion battery according to claim 1, wherein the thickness d of the positive electrode active material layer1And the thickness d of the positive current collector2D is more than or equal to 31/d2≤10。
3. The sodium ion battery of claim 1, wherein the thickness d of the positive current collector25-25 μm.
4. The sodium ion battery of claim 1, wherein the thickness d of the positive current collector25-15 μm.
5. The sodium-ion battery according to claim 1, wherein the positive electrode active material layer d1The thickness of (A) is 40 to 120 μm.
6. The sodium-ion battery according to claim 1, wherein the positive electrode active material layer d1The thickness of (A) is 16 to 240 μm.
7. The sodium ion battery of claim 1, wherein 0.5 ≦ C/A ≦ 0.8.
8. The sodium-ion battery according to claim 1 or 7, wherein the positive electrode active material layer has a compacted density C of 0.6g/cm3～4.0g/cm3；
The positive electrode active material has a true density A of 1.5g/cm3～5g/cm3。
9. According to claimThe sodium ion battery according to claim 8, wherein the positive electrode active material layer has a compacted density C of 1.0g/cm3～2.5g/cm3。
10. The sodium-ion battery according to claim 8, wherein the positive electrode active material has a true density A of 1.8g/cm3～4.5g/cm3。
11. The sodium-ion battery according to claim 1, wherein the positive electrode active material has an average particle diameter Dv50 is 0.3-25 μm.
12. The sodium-ion battery according to claim 1, wherein the positive electrode active material has an average particle diameter Dv50 is 1-15 μm.
13. The sodium ion battery of claim 1, further comprising a negative electrode tab comprising a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material comprising hard carbon.
14. The sodium-ion battery of claim 13, wherein the thickness d of the positive electrode active material layer1And the thickness d of the anode active material layer3The ratio of d is more than or equal to 11/d3≤3。
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