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CN108878770B - Battery cell and secondary battery comprising same - Google Patents

Battery cell and secondary battery comprising same Download PDF

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Publication number
CN108878770B
CN108878770B CN201810708805.XA CN201810708805A CN108878770B CN 108878770 B CN108878770 B CN 108878770B CN 201810708805 A CN201810708805 A CN 201810708805A CN 108878770 B CN108878770 B CN 108878770B
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current collector
cell
positive
negative
battery
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CN108878770A (en
Inventor
杜鑫鑫
骆福平
王升威
覃炎运
张漫芳
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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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

The application provides an electric core and secondary battery including this electric core, electric core includes positive pole piece, negative pole piece and barrier film, positive pole piece including the coating have the anodal mass flow body in anodal diaphragm layer area and with the anodal utmost point ear of mass flow body coupling, negative pole piece including the coating have the negative pole mass flow body on negative pole diaphragm layer and with the negative pole mass flow body coupling's negative pole utmost point ear, the barrier film sets up between positive pole piece and negative pole piece. Wherein, the negative pole piece satisfies the relational expression: 0.04 (L) or less1×ρ1)/(N1×N1×W1×H1) Less than or equal to 2.50. The battery charging method and the battery charging device can greatly improve the charging capacity of the battery and reduce the internal resistance of the battery, and meanwhile, the battery is guaranteed to have the characteristics of low heat production, high energy efficiency, good safety and long cycle life.

Description

Battery cell and secondary battery comprising same
Technical Field
The application relates to the field of energy storage, in particular to an electric core and a secondary battery comprising the same.
Background
With the development of portable electronic products and new energy vehicles, people have made higher demands on the charging speed of batteries, which requires further improvement of the charging capability of batteries. In the prior art, a great deal of research is carried out to improve the charging capability of the battery, for example, the conductive capability and the crystal structure stability of the positive and negative active material particles can be improved by reducing the particle size of the positive and negative active material particles and carrying out coating and doping modification on the positive and negative active material particles, and the releasing and embedding speed of ions between the positive and negative electrodes can be improved; the migration speed of ions between the positive and negative pole pieces and the isolating membrane is improved by using low-viscosity electrolyte; the migration resistance of ions at the interface of the separator and the like is reduced by using a separator of high porosity. Although these measures have a certain improvement effect on the improvement of the charging capability of the battery, the improvement degree is small, and it is difficult to meet the actual use requirements of portable electronic products and new energy vehicles.
Disclosure of Invention
In view of the problems existing in the background art, an object of the present application is to provide an electrical core and a secondary battery including the same, which can greatly improve the charging capability of the battery and reduce the internal resistance of the battery, and simultaneously ensure that the battery also has the characteristics of low heat generation, high energy efficiency, good safety and long cycle life.
In order to reach above-mentioned purpose, the first aspect of this application provides an electric core, and it includes positive pole piece, negative pole piece and barrier film, positive pole piece including the coating have the anodal mass flow body in anodal diaphragm layer area and with the anodal utmost point ear of being connected of mass flow body, negative pole piece including the coating have the negative pole mass flow body on negative pole diaphragm layer and with the negative pole utmost point ear of being connected of mass flow body, the barrier film sets up between positive pole piece and negative pole piece. Wherein, the negative pole piece satisfies the relational expression: 0.04 (L) or less1×ρ1)/(N1×N1×W1×H1)≤2.50。L1The total length of a negative current collector in the battery cell is in mm; w1The unit of the width of a negative current collector in the battery cell is mm; h1The thickness of a negative current collector in the battery cell is in mm; n is a radical of1The total number of the negative pole lugs in the battery core is shown; rho1The specific resistance of the negative current collector in the battery cell is represented by mOhm mm.
A second aspect of the present application provides a secondary battery comprising at least one cell as described in the first aspect of the present application.
Compared with the prior art, the application at least comprises the following beneficial effects:
this application can greatly promote the charge capacity of electric core and reduce the battery internal resistance through the relation between the rational design negative pole mass flow body and the negative pole utmost point ear, guarantees simultaneously that electric core still has the characteristics that the heat production is low, energy efficiency is high, the security is good and long cycle life.
Detailed Description
The battery cell according to the present application and the secondary battery including the same are described in detail below.
A cell according to a first aspect of the present application is first explained.
According to this application first aspect's electric core includes positive pole piece, negative pole piece and barrier film, positive pole piece including the coating have the anodal mass flow body in positive diaphragm layer area and with the anodal utmost point ear of being connected of mass flow body, negative pole piece including the coating have the negative pole mass flow body on negative diaphragm layer and with the negative pole utmost point ear of being connected of mass flow body, the barrier film sets up between positive pole piece and negative pole piece. Wherein, the negative pole piece satisfies the relational expression: 0.04 (L) or less1×ρ1)/(N1×N1×W1×H1)≤2.50。
L1The total length of a negative current collector in the battery cell is in mm; w1The unit of the width of a negative current collector in the battery cell is mm; h1The thickness of a negative current collector in the battery cell is in mm; n is a radical of1The total number of the negative pole lugs in the battery core is shown; rho1The specific resistance of the negative current collector in the battery cell is represented by mOhm mm.
When the battery core is designed, a certain number of negative pole lugs are required to be arranged on the negative pole current collector for conducting the negative pole pieces and an external circuit, so that the performance of the battery core can be influenced by matching between the negative pole lugs and the negative pole current collector. The design of the structural parameters of the negative pole piece is controlled to meet the requirement that L is more than or equal to 0.04 (L) through reasonable matching1×ρ1)/(N1×N1×W1×H1) When the voltage is less than or equal to 2.50, the negative pole piece can have excellent dynamic performance and smaller resistance, so that the charging capacity of the battery cell is greatly improved.
The conduction of the current on the negative pole piece needs to pass through a negative current collector at the bottom of the negative pole piece, the current is conducted along the length direction of the negative current collector, and the conduction of electrons can be blocked by the negative current collector in the length direction. When the length of the negative current collector is longer, the larger the negative resistance is, the larger the internal resistance of the battery cell is, and the larger the internal resistance of the battery cell is, the larger the voltage drop in the charging process is, and further the sum of the voltage drop and the open-circuit voltage of the battery cell in a certain specific charge state may be larger than the maximum charging voltage of the battery cell, so that the battery cell cannot be charged or can be charged only at a lower speed, and the charging capability of the battery cell is obviously deteriorated. Therefore, the structural parameters of the negative pole piece are controlled within a reasonable range, so that the negative pole has smaller resistance, the battery cell has smaller internal resistance, the voltage drop in the battery cell charging process is reduced, and the battery cell has better charging capacity and higher energy efficiency. The structural parameters of the negative pole piece are controlled within a reasonable range, so that the formation of dendritic crystals in the rapid charging process can be reduced, and the safety of the battery cell is improved; in addition, can also reduce the heat production of electric core, reduce electric core temperature rise of charging, effectively prolong the life cycle of electric core.
Structural parameter (L) of the negative electrode sheet1×ρ1)/(N1×N1×W1×H1) When the total length of the negative current collector in the battery cell is larger than 2.50, the total length of the negative current collector in the battery cell is too large, or the width and the thickness of the negative current collector are too small, or the total number of the negative pole lugs in the battery cell is too small, so that the electronic conduction capacity between the negative pole lugs and the negative current collector is poor, the electronic conduction in the negative current collector is also poor due to larger resistance, the charge exchange speed of ions and electrons in the charging process is slower, the negative pole cannot timely accept ions separated from the positive pole, the polarization of the battery cell is increased, the internal resistance is increased, and further the voltage drop in the charging process is increased, the battery cell can be charged at a smaller speed, and the charging capacity of the battery cell is obviously deteriorated. If the cell is still charged at a relatively high charging rate (which exceeds the cell's withstand capacity), the negative electrode has poor electron conductivity and the ions are ionizedThe charge exchange speed with the electron is slower, and then the negative pole will not possess the ability of in time receiving the positive ion of deviating from, and a large amount of dendrites can be formed to the negative pole surface, and at subsequent circulation charge-discharge in-process, dendrites constantly grow, impale the barrier film even and make the interior short circuit of electricity core, seriously influence the security of electricity core, and the cycle life of electricity core will also be very poor.
Structural parameter (L) of the negative electrode sheet1×ρ1)/(N1×N1×W1×H1) When the length-width ratio of the negative pole piece is less than 0.04, the length-width ratio of the negative pole piece is reduced, the conduction resistance of electrons in the width direction of the negative pole current collector is increased, and when current passes through the negative pole current collector, a large potential drop is generated on the negative pole current collector. From this, when electric core charges, because the great potential drop of negative pole mass flow body leads to negative pole piece potential reduction, the ion can form dendrite when contacting the negative pole, causes electric core charging capacity to reduce, can impale the barrier film when serious and make short circuit in the electric core, leads to the security of electric core to reduce, and the cycle life of electric core also can worsen.
Preferably, the negative pole piece satisfies 0.09 ≦ (L)1×ρ1)/(N1×N1×W1×H1) Less than or equal to 1.90; more preferably, the negative electrode sheet satisfies 0.10. ltoreq. L1×ρ1)/(N1×N1×W1×H1)≤1.40。
In the battery cell according to the first aspect of the present application, preferably, the total length L of the negative electrode current collector12000mm to 35000 mm; more preferably, the total length L of the negative electrode current collector1Is 6000 mm-15000 mm.
In the battery cell according to the first aspect of the present application, preferably, the width W of the negative electrode current collector130 mm-400 mm; more preferably, the width W of the negative electrode current collector1Is 50 mm-200 mm.
In the battery cell according to the first aspect of the present application, preferably, the thickness H of the negative electrode current collector1Is 0.006 mm-0032 mm; more preferably, the thickness H of the negative electrode current collector1Is 0.006 mm-0.016 mm.
In the battery cell according to the first aspect of the present application, preferably, the total number N of negative electrode tabs in the battery cell16 to 100; more preferably, the total number N of the negative electrode tabs in the battery cell1Is 10 to 60.
In the battery cell according to the first aspect of the present application, preferably, the resistivity ρ of the negative electrode current collector is1Is 0.005-0.04 mOhm mm; preferably, the resistivity ρ of the negative electrode current collector1Is 0.01-0.03 mOhm.
In the battery cell according to the first aspect of the present application, preferably, the negative electrode current collector is a copper foil, a carbon-coated copper foil, or a polymer conductive film; more preferably, the negative electrode current collector is a copper foil.
In the battery cell according to the first aspect of the present application, preferably, the positive electrode current collector is an aluminum foil, a nickel foil, or a polymer conductive film; more preferably, the positive electrode current collector is an aluminum foil.
In the electric core according to the first aspect of the present application, the negative electrode tab is obtained by die-cutting the negative electrode current collector, and the positive electrode tab is obtained by die-cutting the positive electrode current collector.
In the battery cell according to the first aspect of the present disclosure, the height of the negative electrode tab may be 12mm to 40mm, and the width of the negative electrode tab may be 6mm to 40 mm.
In the battery cell according to the first aspect of the present disclosure, the height of the positive electrode tab may be 12mm to 40mm, and the width of the positive electrode tab may be 6mm to 40 mm.
In the electric core according to the first aspect of the present application, when the structural parameter design of the positive electrode sheet further satisfies the relation: less than or equal to 0.01 (L)2×ρ2)/(N2×N2×W2×H2) Not more than 3.0, and the positive pole piece also has excellent performanceThe different dynamic performance and the smaller resistance, thereby further improving the performance of the battery core. Wherein L is2The total length of the positive current collector in the battery cell is in mm; w2The unit of the width of the positive current collector in the battery cell is mm; h2The thickness of the positive current collector in the battery cell is in mm; n is a radical of2The total number of the positive electrode lugs in the battery cell is shown; ρ 2 is the resistivity of the positive current collector in the battery cell, and the unit is mOhm mm.
Further, the structural parameters of the positive pole piece are controlled within a reasonable range, the embedding capacity of ions in the positive active material when the battery cell discharge is about to end can be effectively improved, the smaller the structural parameters of the positive pole piece are, the easier the ions are embedded into the crystal lattice of the positive active material when the battery cell discharges, and further more ions are embedded back to the positive electrode from the negative electrode when the battery cell discharges, so that more ions shuttle between the positive electrode and the negative electrode in the continuous cyclic charge and discharge process of the battery cell, and the longer cycle life of the battery cell can be ensured.
Structural parameter (L) of the Positive electrode sheet2×ρ2)/(N2×N2×W2×H2) Greater than 3.0, probably because the total length of the positive current collector in the electric core is designed too big, or the width and the thickness of the positive current collector are designed too little, or the total number of the positive pole lugs of the electric core is designed too little, the electronic conductivity between the positive current collector and the positive pole lug and between a plurality of positive pole lugs is poor, the electronic conduction in the positive current collector is also greatly hindered, the charge exchange speed of ions and electrons becomes slow, a large amount of ions cannot be smoothly embedded back to the positive pole when the electric core discharges, the energy loss of the battery is large, and the cycle life of the electric core can be influenced.
Structural parameter (L) of the Positive electrode sheet2×ρ2)/(N2×N2×W2×H2) Less than 0.01, the length-width ratio of the positive pole piece is reduced, the conduction resistance of electrons in the width direction of the positive current collector is increased, and when current passes through the positive current collector, a larger potential drop is generated on the positive current collector. Thus, when the battery cellWhen the battery is discharged, the potential of the positive pole piece is reduced due to the larger potential drop of the positive current collector, the dynamics of ions embedded into the crystal lattice of the positive active material is reduced, ions stored in the negative active material at the last stage of discharge cannot be embedded into the positive active material, the battery cell cannot be completely discharged, and the energy density loss of the battery cell is serious.
Preferably, the positive electrode plate satisfies the relation: 0.1 is less than or equal to (L)2×ρ2)/(N2×N2×W2×H2) Less than or equal to 1.7; more preferably, the positive electrode sheet satisfies the relation: less than or equal to 0.2 (L)2×ρ2)/(N2×N2×W2×H2)≤1.0。
In the battery cell according to the first aspect of the present application, preferably, the total length L of the positive electrode current collector22000mm to 35000 mm; more preferably, the total length L of the positive electrode current collector25000 mm-15000 mm.
In the battery cell according to the first aspect of the present application, preferably, the width W of the positive electrode current collector230 mm-400 mm; more preferably, the width W of the positive electrode current collector2Is 50 mm-200 mm.
In the battery cell according to the first aspect of the present application, preferably, the thickness H of the positive electrode current collector20.012 mm-0.048 mm; more preferably, the thickness H of the positive electrode current collector2Is 0.012 mm-0.036 mm.
In the battery cell according to the first aspect of the present application, preferably, the total number N of positive electrode tabs in the battery cell25 to 100; more preferably, the total number N of positive electrode tabs in the battery cell2Is 10 to 60.
In the battery cell according to the first aspect of the present application, preferably, the resistivity ρ of the positive electrode current collector is2Is 0.005-0.04 mOhm mm; more preferably, the resistivity ρ of the positive electrode current collector2Is 0.01-0.03 mOhm.
In the cell according to the first aspect of the present application, when the cell further satisfies the relationship: 0.2 ≤ [ (L)2×ρ2)/(N2×N2×W2×H2)]/[(L1×ρ1)/(N1×N1×W1×H1)]When the ratio is less than or equal to 5.0, the matching degree of the structural parameters of the positive pole piece and the negative pole piece is higher, and the performance of the battery cell is better.
Preferably, the battery cell further satisfies the relation: 0.6 ≤ [ (L)2×ρ2)/(N2×N2×W2×H2)]/[(L1×ρ1)/(N1×N1×W1×H1)]≤4.6。
In the battery cell according to the first aspect of the present disclosure, the positive electrode film layer includes a positive electrode active material, a conductive agent, and a binder, and the types and contents of the positive electrode active material, the conductive agent, and the binder are not particularly limited and can be selected according to actual requirements. The negative electrode diaphragm layer comprises a negative electrode active material, a conductive agent and a binder, the types and the contents of the negative electrode active material, the conductive agent and the binder are not particularly limited, and the negative electrode diaphragm layer can be selected according to actual requirements. The kind of the separator is also not particularly limited, and may be any separator material used in the prior art, such as polyethylene, polypropylene, polyvinylidene fluoride, and multi-layer composite films thereof, but not limited thereto.
In the battery cell according to the first aspect of the present application, a preparation method of the battery cell is not limited, and the battery cell may be a winding battery cell or a laminated battery cell.
When the cell is a laminated cell, the cell may include a plurality of stacked negative electrode plates and a plurality of stacked positive electrode plates, the plurality of negative electrode plates are the same in composition and size (length × width × thickness), and the plurality of positive electrode plates are also the same in composition and size (length × width × thickness). Thus, the negative electrode described in the present applicationTotal length L of current collector1The total length L of the positive current collector is the sum of the lengths of the negative current collectors in the negative pole pieces (namely the product of the length of the negative current collector in a certain negative pole piece and the number of the negative pole pieces), and the total length L of the positive current collector is defined in the application2The sum of the lengths of the positive current collectors in the positive pole pieces (namely the product of the length of the positive current collector in one positive pole piece and the number of the positive pole pieces). Since several negative pole pieces have the same size (length x width x thickness), the width W of the negative current collector described in this application1And a thickness H1The width and the thickness of the negative current collector in one negative pole piece are kept consistent. Also, since several positive electrode plates all have the same size (length × width × thickness), the width W of the positive current collector described in this application2And a thickness H2The width and the thickness of the positive current collector in one positive pole piece are kept consistent.
When the battery cell is a winding battery cell, the negative pole tabs can be uniformly distributed on the negative pole pieces, and the positive pole tabs can be uniformly distributed on the positive pole pieces.
Next, a secondary battery according to a second aspect of the present application will be described.
A secondary battery according to a second aspect of the present application includes at least one cell as described in the first aspect of the present application.
The secondary battery according to the second aspect of the present application further includes an electrolyte, and the kind and composition of the electrolyte are not limited and can be selected according to actual needs.
The specific type of the secondary battery of the present application is not particularly limited, and may preferably be a lithium ion battery or a sodium ion battery.
In the secondary battery of the second aspect of the present application, the specific kind of the positive electrode active material is not particularly limited and may be selected according to actual needs.
When the battery is a lithium ion battery, the positive active material maySelected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt aluminum oxide, olivine-structured lithium-containing phosphate, etc., but the present application is not limited to these materials, and other conventionally known materials that can be used as a positive electrode active material for a lithium ion battery may also be used. These positive electrode active materials may be used alone or in combination of two or more. Preferably, the positive active material may be selected from LiCoO2、LiNiO2、LiMnO2、LiMn2O4、LiNi1/3Co1/3Mn1/3O2(NCM333)、LiNi0.5Co0.2Mn0.3O2(NCM523)、LiNi0.6Co0.2Mn0.2O2(NCM622)、LiNi0.8Co0.1Mn0.1O2(NCM811)、LiNi0.8Co0.1Al0.1O2、LiNi0.85Co0.15Al0.05O2、LiFePO4、LiMnPO4One or more of them.
When the battery is a sodium ion battery, the positive active material may be selected from transition metal oxides NaxMO2(M is a transition metal, preferably one or more selected from Mn, Fe, Ni, Co, V, Cu and Cr, 0<x is less than or equal to 1), polyanionic materials (phosphate, fluorophosphate, pyrophosphate, sulfate), Prussian blue materials and the like, but the application is not limited to the materials, and other conventionally known materials which can be used as the positive active material of the sodium-ion battery can be used. These positive electrode active materials may be used alone or in combination of two or more. Preferably, the positive active material may be selected from NaFeO2、NaCoO2、NaCrO2、NaMnO2、NaNiO2、NaNi1/2Ti1/2O2、NaNi1/2Mn1/2O2、Na2/3Fe1/3Mn2/3O2、NaNi1/3Co1/3Mn1/3O2、NaFePO4、NaMnPO4、NaCoPO4Prussian blue material with the general formula AaMb(PO4)cOxY3-xWherein A is selected from H+、Li+、Na+、K+、NH4+M is transition metal cation, preferably one or more selected from V, Ti, Mn, Fe, Co, Ni, Cu and Zn, Y is halogen anion, preferably one or more selected from F, Cl and Br, 0<a≤4，0<b is less than or equal to 2, c is less than or equal to 1 and less than or equal to 3, and x is more than or equal to 0 and less than or equal to 2).
In the secondary battery of the second aspect of the present application, the specific kind of the negative electrode active material is also not particularly limited and may be selected according to actual needs. For example, the material can be one or more selected from graphite, soft carbon, hard carbon, carbon fiber, mesocarbon microbeads, silicon-based materials and tin-based materials. The graphite can be selected from artificial graphite and natural graphite, the silicon-based material can be selected from elemental silicon, silicon-oxygen compound, silicon-carbon compound and silicon alloy, and the tin-based material can be selected from elemental tin, tin-oxygen compound and tin alloy.
The present application is further illustrated below by taking a lithium ion battery as an example and combining specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present application.
The lithium ion batteries of examples 1 to 13 and comparative examples 1 to 3 were each prepared as follows.
(1) Preparation of negative pole piece
Mixing a negative electrode active material graphite, a conductive agent acetylene black, a thickening agent CMC and a binder SBR according to a mass ratio of 96.4:1:1.2:1.4, adding a solvent deionized water, and stirring under the action of a vacuum stirrer until a system is uniform to obtain a negative electrode slurry; and uniformly coating the negative electrode slurry on a negative electrode current collector copper foil (with the resistivity of 0.0172mOhm & ltmm & gt), airing at room temperature, transferring to an oven for continuous drying, and then performing cold pressing, slitting and die cutting on a tab (with the height multiplied by the width of 22mm multiplied by 40mm) to form a negative electrode pole piece. The length, width, thickness, resistivity, and total number of the negative electrode tab designs of the negative electrode current collector can be referred to table 1.
(2) Preparation of positive pole piece
Mixing a positive electrode active material NCM523, a conductive agent acetylene black and a binder PVDF according to a mass ratio of 96:2:2, adding a solvent NMP, and stirring under the action of a vacuum stirrer until the system is uniform to obtain positive electrode slurry; and uniformly coating the positive electrode slurry on a positive electrode current collector aluminum foil (with the resistivity of 0.0283mOhm & ltmm & gt), airing at room temperature, transferring to an oven for continuous drying, and then performing cold pressing, slitting and die cutting on a tab (with the height multiplied by the width of 21mm multiplied by 40mm) to form the positive electrode piece. The length, width, thickness, resistivity and total number of positive electrode tab designs of the positive electrode current collector can be referred to table 2.
(3) Preparation of the electrolyte
Mixing Ethylene Carbonate (EC), Ethyl Methyl Carbonate (EMC) and diethyl carbonate (DEC) according to a volume ratio of 1:1:1 to obtain an organic solvent, and then fully drying lithium salt LiPF6Dissolving the mixture in the mixed organic solvent to prepare electrolyte with the concentration of 1 mol/L.
(4) Preparation of the separator
Selected from polyethylene films as barrier films.
(5) Preparation of lithium ion battery
Stacking the positive pole piece, the isolating film and the negative pole piece in sequence to enable the isolating film to be positioned between the positive pole piece and the negative pole piece to play an isolating role, and then winding to obtain a battery cell; and (3) placing the battery core in an outer packaging shell, drying, injecting electrolyte, and performing vacuum packaging, standing, formation, shaping and other processes to obtain the lithium ion battery.
TABLE 1 parameters of negative electrode Pole pieces of examples 1-13 and comparative examples 1-3
TABLE 2 parameters of positive electrode sheets of examples 1-13 and comparative examples 1-3
Next, performance tests of the lithium ion battery are explained.
(1) Testing internal resistance IMP of the battery: the lithium ion batteries prepared in examples and comparative examples were charged to 70% SOC at 25 ℃, and then placed on an ac impedance tester to test internal resistance at a frequency of 1000 Hz.
(2) And (3) testing the dynamic performance: at 25 ℃, the lithium ion batteries prepared in the examples and the comparative examples are fully charged with x C and fully discharged with 1C for 10 times, then the lithium ion batteries are fully charged with x C, then the negative pole piece is disassembled, and the lithium separation condition on the surface of the negative pole piece is observed. And if no lithium is separated from the surface of the negative electrode, gradually increasing the charging multiplying power x C by taking 0.1C as a gradient, and testing again until lithium is separated from the surface of the negative electrode, and stopping testing, wherein the charging multiplying power (x-0.1) C at the moment is the maximum charging multiplying power of the lithium ion battery.
(3) And (3) testing the cycle performance: the lithium ion batteries prepared in examples and comparative examples were charged at 1C rate, discharged at 1C rate, and subjected to full charge discharge cycle test at 25C until the capacity of the lithium ion battery had decayed to 80% of the initial capacity, and the number of cycles was recorded.
(4) And (3) charging temperature rise test: at 25 ℃, the lithium ion batteries prepared in the examples and the comparative examples are charged at a rate of 1C, discharged at a rate of 1C, and subjected to a full charge and discharge test, and the maximum temperature difference in the charge and discharge processes of the battery core is recorded.
TABLE 3 results of Performance test of examples 1 to 13 and comparative examples 1 to 3
In the embodiment of the application, the structural parameter design of the negative pole piece meets the requirement that L is more than or equal to 0.04 (L) by reasonably designing the relation between the negative pole current collector and the negative pole lug1×ρ1)/(N1×N1×W1×H1) Less than or equal to 2.50, can greatly reduce the internal resistance of the battery and improve the charging capacity of the lithium ion battery, and simultaneously ensures that the lithium ion battery also has the characteristics of low heat production and long cycle life.
By further controlling the relationship between the positive current collector and the positive electrode lug within a reasonable range, the intercalation capacity of lithium ions in the positive active material when the battery discharge is about to end can be further improved, more lithium ions are intercalated into the positive electrode from the negative electrode when the battery discharges, and the lithium ion battery has longer cycle life.
In comparative example 1, the design of the negative pole piece is unreasonable, the structural parameters of the negative pole piece are too small, the length-width ratio of the negative pole piece is small, the conduction resistance of electrons in the width direction of the negative pole current collector is large, and when current passes through the negative pole current collector in the charging process, large potential drop is generated on the negative pole current collector, so that the potential of the negative pole piece is reduced, lithium ions easily form lithium dendrites when contacting the negative pole, the charging capacity of the lithium ion battery is poor, and the cycle life is short.
In comparative examples 2 and 3, the design of the negative pole piece is unreasonable, the structural parameters of the negative pole piece are too large, so that the electronic conduction capacities between the negative pole lug and the negative pole current collector and inside the negative pole current collector are poor, the whole electronic conduction capacity of the negative pole piece is poor, the charge exchange speed of lithium ions and electrons is slow in the charging process, the negative pole cannot timely accept the lithium ions removed from the positive pole, the negative pole can immediately analyze lithium after being charged at a small multiplying power, the charging capacity of the lithium ion battery is poor, and the cycle life is short. In addition, the whole electron conductivity of the negative pole piece is poor, the charge exchange speed of ions and electrons is low, the polarization and the internal resistance of the battery are increased continuously, and the heat production of the battery in the charging and discharging process is high.
Variations and modifications to the above-described embodiments may occur to those skilled in the art based upon the disclosure and teachings of the above specification. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and some modifications and variations of the present invention should fall within the scope of the claims of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims (26)

1. A battery core comprises a positive pole piece, a negative pole piece and an isolating membrane, wherein the positive pole piece comprises a positive current collector coated with a positive membrane layer area and a positive pole lug connected with the positive current collector;
it is characterized in that the preparation method is characterized in that,
the negative pole piece satisfies the relation: 0.04 (L) or less1×ρ1)/(N1×N1×W1×H1)≤2.50；
Wherein,
L1the total length of a negative current collector in the battery cell is in mm;
W1the unit of the width of a negative current collector in the battery cell is mm;
H1the thickness of a negative current collector in the battery cell is in mm;
N1the total number of the negative pole lugs in the battery core is shown;
ρ1the specific resistance of the negative current collector in the battery cell is represented by mOhm mm.
2. The electrical core of claim 1, wherein the negative electrode sheet satisfies 0.09 ≦ (L)1×ρ1)/(N1×N1×W1×H1)≤1.90。
3. The electrical core of claim 2, wherein the negative electrode sheet satisfies 0.10 ≦ (L)1×ρ1)/(N1×N1×W1×H1)≤1.40。
4. The cell of claim 1, wherein,
the total length L of the negative current collector12000mm to 35000 mm;
width W of the negative current collector130 mm-400 mm;
the thickness H of the negative current collector10.006 mm-0.032 mm;
the total number N of the negative electrode lugs in the battery core16 to 100;
the resistivity rho of the negative current collector1Is 0.005-0.04 mOhm mm.
5. The cell of claim 4, wherein the total length L of the negative current collector is1Is 6000 mm-15000 mm.
6. The cell of claim 4, wherein the width W of the negative current collector1Is 50 mm-200 mm.
7. The cell of claim 4, wherein the thickness H of the negative current collector1Is 0.006 mm-0.016 mm.
8. The cell of claim 4, wherein the total number N of negative electrode tabs in the cell1Is 10 to 60.
9. The cell of claim 4, wherein the negative current collector has a resistivity p1Is 0.01-0.03 mOhm.
10. The cell of claim 1, wherein,
the negative current collector is a copper foil, a carbon-coated copper foil or a polymer conductive film;
the positive current collector is an aluminum foil, a nickel foil or a polymer conductive film.
11. The cell of claim 10,
the negative current collector is a copper foil.
12. The cell of claim 10,
the positive current collector is aluminum foil.
13. The cell of claim 1, wherein,
the height of the negative pole tab is 12 mm-40 mm, and the width of the negative pole tab is 6 mm-40 mm;
the height of the positive pole lug is 12 mm-40 mm, and the width of the positive pole lug is 6 mm-40 mm.
14. The cell of claim 1, wherein,
the positive pole piece satisfies the relation: less than or equal to 0.01 (L)2×ρ2)/(N2×N2×W2×H2)≤3.0；
Wherein,
L2the total length of the positive current collector in the battery cell is in mm;
W2the unit of the width of the positive current collector in the battery cell is mm;
H2the thickness of the positive current collector in the battery cell is in mm;
N2the total number of the positive electrode lugs in the battery cell is shown;
ρ2the specific resistance of the positive current collector in the battery cell is represented by mOhm mm.
15. The electrical core of claim 14, wherein 0.1 ≦ (L)2×ρ2)/(N2×N2×W2×H2)≤1.7。
16. The electrical core of claim 15, wherein 0.2 ≦ (L)2×ρ2)/(N2×N2×W2×H2)≤1.0。
17. The electrical core of any of claims 14-16,
the total length L of the positive current collector22000mm to 35000mm
The width W of the positive current collector230 mm-400 mm;
the thickness H of the positive current collector20.012 mm-0.048 mm;
the battery cellThe total number N of the middle anode tabs25 to 100;
the resistivity rho of the positive current collector2Is 0.005-0.04 mOhm mm.
18. The cell of claim 17, wherein,
the total length L of the positive current collector25000 mm-15000 mm.
19. The cell of claim 17, wherein the width W of the positive current collector2Is 50 mm-200 mm.
20. The cell of claim 17, wherein the thickness H of the positive current collector2Is 0.012 mm-0.036 mm.
21. The cell of claim 17, wherein the total number N of positive tabs in the cell2Is 10 to 60.
22. The cell of claim 17, wherein the positive current collector has a resistivity p2Is 0.01-0.03 mOhm.
23. The electrical core of any of claims 1, 14-16,
the battery cell satisfies the relational expression:
0.2≤[(L2×ρ2)/(N2×N2×W2×H2)]/[(L1×ρ1)/(N1×N1×W1×H1)]≤5.0。
24. the cell of claim 23, wherein the cell satisfies the relationship:
0.6≤[(L2×ρ2)/(N2×N2×W2×H2)]/[(L1×ρ1)/(N1×N1×W1×H1)]≤4.6。
25. the cell of claim 1, wherein the cell is a wound cell or a laminated cell.
26. A secondary battery, characterized in that it comprises at least one cell according to any of claims 1 to 25.
CN201810708805.XA 2018-07-02 2018-07-02 Battery cell and secondary battery comprising same Active CN108878770B (en)

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