CN118969964B - Positive electrode sheet, secondary battery and power-using device - Google Patents

Positive electrode sheet, secondary battery and power-using device Download PDF

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Publication number
CN118969964B
CN118969964B CN202411449883.4A CN202411449883A CN118969964B CN 118969964 B CN118969964 B CN 118969964B CN 202411449883 A CN202411449883 A CN 202411449883A CN 118969964 B CN118969964 B CN 118969964B
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positive electrode
electrode plate
active material
lithium
electrode sheet
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CN118969964A (en
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单旭意
黎重重
张潇阳
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China Innovation Aviation Technology Group Co ltd
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China Innovation Aviation Technology Group Co ltd
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Priority to CN202411936439.5A priority Critical patent/CN119725391B/en
Priority to CN202411449883.4A priority patent/CN118969964B/en
Publication of CN118969964A publication Critical patent/CN118969964A/en
Priority to PCT/CN2025/089607 priority patent/WO2026081445A1/en
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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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • 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
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M2004/028—Positive 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)
  • Composite Materials (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention relates to the technical field of electrochemistry, and particularly discloses a positive pole piece, a secondary battery and an electric device. The positive electrode active material of the positive electrode plate comprises a manganese-containing phosphate material, wherein the positive electrode plate meets the following relational expression that (A multiplied by H)/I Al is less than or equal to 0.08 and less than or equal to 27, wherein A is manganese content in the positive electrode active material, H is hydrogen ion content increase rate of the positive electrode plate immersed in a mixed solution, and when I Al carries out XPS analysis on the positive electrode plate at different depths, the difference of peak intensities of characteristic peaks of aluminum elements in an XPS graph. According to the invention, the content of manganese element in the positive electrode active material, the hydrogen ion growth characteristic of the positive electrode plate and the Al peak-to-peak intensity of different depths of the plate are comprehensively controlled, so that the gas production problem of the secondary battery containing the positive electrode plate is greatly improved, and the internal resistance growth rate of the battery after circulation is low.

Description

Positive electrode plate, secondary battery and electricity utilization device
Technical Field
The invention relates to the technical field of batteries, in particular to a positive electrode plate, a secondary battery and an electric device.
Background
Lithium iron manganese phosphate (LMFP) cathode materials are receiving widespread attention in the field of electric automobiles and portable electronic devices due to their higher energy density. Compared with lithium iron phosphate (LFP), the LMFP improves the theoretical energy density of the battery by introducing manganese element, so that the battery has longer endurance.
However, an increase in the manganese content causes problems of manganese elution, and particularly, elution of manganese ions may be aggravated under high-temperature environments. Manganese dissolution not only causes gas generation inside the battery and increases the risk of swelling of the battery, but also forms deposits which are formed inside the battery, increases the internal resistance of the battery, and reduces the charge-discharge efficiency and the life of the battery.
Accordingly, there is a need to provide a positive electrode sheet that improves the gassing problem and reduces the internal resistance.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a positive electrode plate, a secondary battery and an electric device, wherein the gas production problem of the secondary battery containing the positive electrode plate is greatly improved by comprehensively controlling the content of manganese element in a positive electrode active material, the hydrogen ion growth characteristics of the positive electrode plate and the Al peak-to-peak intensities of different depths of the positive electrode plate, and the internal resistance growth rate of the battery after circulation is low.
In order to achieve the above object, in a first aspect of the present invention, there is provided a positive electrode tab 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 including a manganese-containing phosphate material;
The positive plate satisfies the following relation:
0.08≤(A×h) /IAl≤27;
wherein A is the molar content of manganese element in the positive electrode active material to the transition metal element, and the unit is mol%;
H is the hydrogen ion content increasing rate of the positive electrode plate immersed in a mixed solution from T 1 H to T 2 H at 60 ℃, and T 2-T1=72,T1 is more than 0, wherein the mixed solution contains an organic solvent and lithium salt, and the unit of H is;
i Al= I2-I1, wherein I 1 is the peak intensity of an aluminum element characteristic peak in an X-ray photoelectron spectroscopy (XPS) analysis on the surface of the positive electrode plate, I 2 is the peak intensity of the aluminum element characteristic peak in the XPS graph after etching treatment is carried out on the positive electrode plate at the etching depth of 50nm, and the units of I 1、I2 and I Al are counts/s.
As a preferred embodiment of the present invention, the positive electrode sheet satisfies the following relation 0.16≤A.times.h/I Al≤4.5.
As a preferred embodiment of the present invention, the range of A is 50 to 95mol%.
As a further preferred embodiment of the present invention, the range of A is 55 to 85mol%.
As a preferred embodiment of the present invention, the range of H is 12-42%.
As a further preferable embodiment of the present invention, the range of H is 15 to 35%.
As a preferred embodiment of the invention, the range of I Al is 100 to 9000 counts/s.
As a further preferred embodiment of the present invention, the range of I Al is 600 to 7000 counts/s.
As a preferred embodiment of the invention, the range of I 1 is 100-12800 counts/s.
As a preferred embodiment of the present invention, the positive electrode active material includes a lithium iron manganese phosphate-based material.
As a preferable embodiment of the invention, the average particle size of the particles of the lithium manganese iron phosphate material is 30-400 nm.
As a preferred embodiment of the invention, the mixed solution comprises ethylene carbonate, methyl ethyl carbonate and lithium perchlorate, wherein the volume ratio of the ethylene carbonate to the methyl ethyl carbonate is 3:7, and the molar concentration of the lithium perchlorate in the mixed solution is 1mol/L.
In a second aspect of the present invention, the present invention provides a secondary battery, including a positive electrode tab, a negative electrode tab, and an electrolyte, wherein the positive electrode tab is the positive electrode tab described above.
In a third aspect of the present invention, the present invention provides an electric device comprising the above secondary battery.
The invention has the beneficial effects that:
The invention develops a positive pole piece, a secondary battery and an electric device. By comprehensively controlling the content of manganese element in the positive electrode active material, the hydrogen ion growth characteristic of the positive electrode plate and the Al peak intensities of different depths of the plate, the gas production problem of the secondary battery containing the positive electrode plate is greatly improved, and the internal resistance growth rate of the battery after circulation is low.
Drawings
Fig. 1 is an XPS diagram of the positive electrode sheet of example 6.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is apparent that the described embodiments are 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 invention, the technical characteristics described in an open mode comprise a closed technical scheme composed of the listed characteristics and also comprise an open technical scheme comprising the listed characteristics.
In the present invention, the numerical ranges are referred to as continuous, and include the minimum and maximum values of the ranges, and each value between the minimum and maximum values, unless otherwise specified. Further, when a range refers to an integer, each integer between the minimum and maximum values of the range is included. Further, when multiple range description features or characteristics are provided, the ranges may be combined. In other words, unless otherwise indicated, all ranges disclosed herein are to be understood to include any and all subranges subsumed therein.
In the present invention, the specific dispersing and stirring treatment method is not particularly limited.
The reagents or apparatus used in the present invention are conventional products commercially available without the manufacturer's knowledge.
Positive electrode plate
The embodiment of the invention provides a positive electrode plate, which comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material, and the positive electrode active material comprises a manganese-containing phosphate material;
The positive plate satisfies the following relation:
0.08≤(A×H) /IAl≤27;
wherein A is the molar content of manganese element in the positive electrode active material to the transition metal element, and the unit is mol%;
H is the hydrogen ion content increasing rate of the positive electrode plate immersed in a mixed solution from T 1 H to T 2 H at 60 ℃, and T 2-T1=72,T1 is more than 0, wherein the mixed solution contains an organic solvent and lithium salt, and the unit of H is;
I Al= I2-I1, wherein I 1 is the peak intensity of an aluminum element characteristic peak in an XPS graph when XPS analysis is carried out on the surface of the positive electrode plate, I 2 is the peak intensity of the aluminum element characteristic peak in the XPS graph after etching treatment is carried out on the positive electrode plate at the etching depth of 50nm, and the units of I 1、I2 and I Al are counts/s.
According to the invention, the content of manganese element in the positive electrode active material, the hydrogen ion growth rate of the positive electrode plate and the Al peak intensity of the positive electrode plate at different depths are comprehensively controlled, so that the gas production problem of the secondary battery containing the positive electrode plate is greatly improved, and the internal resistance growth rate of the battery after circulation is low.
According to the research of the invention, the positive electrode plate contains a certain amount of aluminum (Al), which is beneficial to improving the gas production phenomenon in the battery. In the first charging process of the battery, al in the positive electrode piece can participate in chemical reaction earlier than manganese (Mn), and a solid electrolyte interface film (CEI film) is formed on the surface of the positive electrode piece. The CEI film is formed rapidly, so that the positive electrode can be effectively protected before manganese is dissolved out, thereby greatly reducing side reaction between the positive electrode active material and electrolyte and reducing the generation of gas in the battery. However, the Al content in the surface layer (mainly the CEI film) of the positive electrode sheet is not preferably excessively high. Al in the surface layer of the positive electrode plate can dissolve out to the negative electrode plate to participate in the formation of a negative electrode solid electrolyte interface film (SEI film), and when the content of Al is too high, the film resistance of the negative electrode SEI film can be increased, so that the internal resistance of the battery is increased.
In XPS analysis, the characteristic peak position of an element is mainly determined by binding energy, and the characteristic peak position is generally related to the element type, valence state, structure and test environment. For the positive electrode plate, an aluminum element characteristic peak generally appears in an XPS graph with the binding energy of 60-90 eV. The peak intensity of the characteristic peak of the aluminum element in the XPS can represent the relative content of the Al at the position. I Al is the difference of peak intensities of Al peaks of the positive electrode plate under different etching depths, and the invention controls the content distribution of Al at different depth positions of the positive electrode plate by adjusting the size of I Al, so that the battery can keep lower internal resistance under the condition of improving the gas production phenomenon of the battery.
H is the hydrogen ion content increasing rate of the positive electrode plate immersed in the mixed solution containing the lithium perchlorate. The positive electrode plate is immersed in a mixed solution containing lithium salt, and the positive electrode active material and the mixed solution undergo an interface reaction to generate hydrogen ions. The greater the rate of increase of the hydrogen ion content during the impregnation process, the higher the degree of interfacial reaction. The degree of particle passivation of the positive electrode active material is an important factor affecting the above reaction degree, and thus, the hydrogen ion growth rate in the present invention reflects the degree of particle passivation of the positive electrode active material to some extent. The passivation degree is adjusted by controlling the H value, the oxidability of the positive electrode active material is reduced by utilizing the passivation effect, the protection of the positive electrode plate can be realized, the dissolution of manganese is reduced, the gas production condition of the battery is improved, and the internal resistance of the battery is also reduced. However, the H value is not too low, which may mean that passivation is excessive, and electron transfer inside the positive electrode sheet is blocked, and the internal resistance of the battery becomes large.
The magnitude of the H value is related to various factors such as the particle structure of the positive electrode active material, the particle coating condition, the additive composition of the battery electrolyte, and the doping elements and contents of the positive electrode active material. That is, the contents of Al and Mn in the positive electrode sheet both affect the H value. Therefore, the invention comprehensively controls the manganese element content in the positive electrode active material, the hydrogen ion growth rate of the positive electrode plate and the Al peak intensity of the positive electrode plate at different depths, and improves the gas production problem of the secondary battery containing the positive electrode plate by controlling the content of the manganese element in the positive electrode active material to be less than or equal to 0.08 (A multiplied by H)/I Al to be less than or equal to 27, and the internal resistance growth rate of the battery after circulation is low.
When the value of (a×h)/I Al is too small, below 0.08, there may be a case where passivation is excessive or the content of aluminum element in the surface layer of the positive electrode sheet is too high, resulting in an excessively high internal resistance increase rate of the battery, and when the value of (a×h)/I Al is too high, above 27, there may be a case where the gas generation of the battery is serious and the internal resistance increase rate is also high.
Illustratively, in the present invention, the value of (A×H)/I Al may be 0.08、0.10、0.15、0.20、0.50、1.0、2.0、5.0、10.0、15.0、20.0、25.0、25.5、26.0、26.5、26.8、26.85、26.90、26.95、27.0, or a range of intervals formed by any two of the above values.
In one embodiment, the positive electrode sheet satisfies the following relationship 0.16≤A×h)/I Al≤4.5.
Further research of the invention finds that when the positive pole piece is in the preferable range, the gas production condition and the internal resistance growth rate of the battery are better.
In one embodiment, the range of a is 50 to 95mol%, for example, the a may be 50mol%, 55mol%, 60mol%, 70mol%, 80mol%, 90mol%, 95mol%.
In one preferred embodiment, the range of A is 55 to 85mol%.
In the present invention, a positive electrode active material having a higher manganese element content is preferable, contributing to a battery having a more excellent energy density. However, the value A is not too high, and the possibility of manganese dissolution is aggravated due to the too high value A, and the passivation effect of the anode is affected to deteriorate the gas production condition of the battery, so that the internal resistance of the battery is increased.
The method for detecting A is not limited in the invention, and a person skilled in the art can detect the molar content of manganese element in the phosphate material according to conventional technical means, such as ICP test.
Illustratively, a may be detected using the following method:
And disassembling the battery in the empty state to obtain a positive electrode plate, processing to obtain positive electrode active material powder, and performing ICP test to obtain the molar content of manganese element in the positive electrode active material to transition metal element.
In one embodiment, the range of H is 12 to 42%, for example, the H may be 12%, 15%, 18%, 25%, 30%, 35%, 38%, 40%, 42%.
In one preferred embodiment, the range of H is 15-35%.
The H value represents the passivation degree of the positive electrode active material and is influenced by various factors such as the particle structure, particle diameter, coating layer thickness, coating integrity, coating amount and the like of the positive electrode active material, the additive composition of the battery electrolyte, whether the additive contains an additive for promoting film formation passivation, the doping elements and the content in the bulk phase of the positive electrode active material and the like. The H value is in the preferable range, which shows that the passivation effect of the positive electrode active material is proper, so that the gas production condition of the battery can be effectively improved, and the internal resistance of the battery can not be increased too much.
In one embodiment, the mixed solution comprises Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and lithium perchlorate, wherein the volume ratio of the ethylene carbonate to the ethylmethyl carbonate is 3:7, and the molar concentration of the lithium perchlorate in the mixed solution is 1mol/L.
When the mixed solution is adopted, the positive electrode plate is immersed in the mixed solution, lithium salt and solvents (EC and EMC) react to form a solvated structure, interface reaction between the solvents and positive electrode active materials is promoted, the solvents react and are dehydrogenated to generate hydrogen ions, and the content of the hydrogen ions in the mixed solution increases along with the extension of the immersion time. Lithium perchlorate is used as a lithium salt with stable properties, and is helpful for more accurate detection of H value.
Illustratively, H may be detected using the following method:
Disassembling the battery in a full charge state to obtain a positive pole piece in the full charge state, drying at 80 ℃ for 4 hours to obtain the positive pole piece, and cutting the positive pole piece into a pole piece to be detected of 7cm multiplied by 7 cm;
At the test temperature of 60 ℃, dipping the pole piece to be tested into 20ml of mixed solution, wherein the mixed solution consists of ethylene carbonate, ethylmethyl carbonate and lithium perchlorate, the volume ratio of the ethylene carbonate to the ethylmethyl carbonate is 3:7, and the molar concentration of the lithium perchlorate in the mixed solution is 1mol/L;
detecting the content of hydrogen ions in the mixed solution when the pole piece to be detected is immersed in the mixed solution for 48 hours and marking as H 1 ppm;
wherein the hydrogen ion content can be tested by an acid-base titration method;
Calculating the hydrogen ion content increase rate H= (H 2- H1)/ H1 multiplied by 100%) of the positive electrode sheet immersed in the mixed solution containing the high-chloric acid, wherein the hydrogen ion content of the sheet to be detected immersed in the mixed solution for 48 hours is taken as the initial hydrogen ion content, and the process of fully immersing the mixed solution and the positive electrode sheet is considered.
In one embodiment, the I Al is in the range of 100 to 9000counts/s, e.g., the I Al may be 100 counts/s、200counts/s、500 counts/s、1000counts/s、3000counts/s、5000counts/s、8000counts/s、8500counts/s、9000counts/s.
In one preferred embodiment, the I Al is in the range of 600 to 7000 counts/s.
In one embodiment, the I 1 ranges from 100 to 12800counts/s.
A value of I Al greater than 0 indicates that Al is more present in the positive electrode active material layer than in the CEI film layer. When I Al is in the above preferred range, the distribution condition of Al is more suitable, and enough aluminum elements exist in the positive electrode active material layer at the middle position (etching depth of 50 nm) of the positive electrode plate, so that the effective improvement of the gas production condition of the battery is facilitated, and the aluminum element content in the surface layer (etching depth of 0 nm) of the positive electrode plate is low, so that the degradation of the internal resistance of the battery is avoided.
Since no I 1、I2 is likely to be negative, it can be inferred that when the value of I Al is too low, it means that the value of I 2 is small (the value of I 1 is relatively smaller), or that the value of I 1、I2 is very close. The value of I 1、I2 is too small, which indicates that the content of Al in the positive electrode plate is low, the improvement on the gas production problem of the battery is not obvious enough, and the value of I 1、I2 is very close, which indicates that the difference value of the content of Al between the middle position and the surface layer position of the positive electrode plate is too small, and the internal resistance of the battery is possibly high. When the value of I Al is higher than 9000counts/s, the content of Al (i.e. I 2) at the middle position of the positive electrode plate is not lower than 9000counts/s, and the overall content of Al in the positive electrode plate is too high, so that the internal resistance increase rate of the battery in the circulation process is possibly larger.
The value of I Al can be controlled by adding a doping element during the preparation of the positive electrode active material or adding an aluminum element during the preparation of the positive electrode sheet.
Illustratively, I Al can be tested using the following method:
And respectively carrying out XPS analysis on the surface of the pole piece to be detected and the etching depth of 50nm to obtain the difference of peak intensities of characteristic peaks of aluminum elements.
In one embodiment, the positive electrode active material includes a lithium manganese iron phosphate-based material.
The lithium manganese iron phosphate material comprises at least one of lithium manganese iron phosphate (LMFP), lithium manganese iron phosphate containing doping elements and lithium manganese iron phosphate containing a coating layer.
In one embodiment, the average particle size of the lithium manganese iron phosphate material is 30-400 nm.
The lithium iron manganese phosphate material can be single particles or agglomerates composed of primary particles. When the lithium manganese iron phosphate material is an agglomerate, the average particle size of the lithium manganese iron phosphate material is the average particle size of the primary particles.
The doping element may be an aluminum element.
The coating layer is coated on the surface of the LMFP particles, and the coating layer can be a carbon layer.
In the invention, the preparation method of the LMFP is not limited, and a person skilled in the art can prepare the LMFP according to a conventional technical means.
The preparation method of the LMFP can comprise the following steps:
mixing a manganese source, an iron source, a phosphorus source and a lithium source according to a certain molar ratio, and grinding;
and (3) carrying out spray drying treatment on the ground product, and sintering the product in an atmosphere with the oxygen concentration of less than 150ppm to obtain the LMFP.
The process of milling-spray drying-sintering may be performed multiple times when preparing LMFP, as desired. For example, the method comprises mixing manganese source, iron source, phosphorus source and lithium source, grinding, spray drying, sintering in an atmosphere with oxygen concentration less than 150ppm, and post-treating to obtain LMFP.
The lithium source may include at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium oxalate, lithium dihydrogen phosphate, lithium citrate, or lithium acetate.
The phosphorus source may include at least one of diammonium phosphate, lithium dihydrogen phosphate, ammonium phosphate, or lithium phosphate.
The iron source may include at least one of ferrous oxalate, ferric hydroxide, ferrous hydroxide, ferric phosphate, ferrous phosphate, ferric acetate, ferrous acetate, ferric carbonate, ferrous carbonate, ferric oxide, or ferric oxalate.
The manganese source may include at least one of manganese carbonate, manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, or manganese acetate.
The manganese iron phosphate can be used as a manganese source, an iron source and a phosphorus source at the same time, and the iron phosphate can be used as an iron source and a phosphorus source at the same time.
When the LMFP further contains doping elements, a certain amount of doping element sources can be weighed and mixed with a manganese source, an iron source, a phosphorus source and a lithium source together for ball milling.
When the doping element is aluminum, the doping element source is aluminum. The aluminum source may include at least one of aluminum formate, aluminum acetate, aluminum glycolate, aluminum lactate, aluminum tartrate, aluminum oxalate, aluminum phosphate, aluminum hydrogen phosphate, aluminum dihydrogen phosphate, aluminum carbonate, aluminum oxide, aluminum hydroxide, aluminum fluoride, aluminum chloride, aluminum nitrate, aluminum sulfate, aluminum bromide.
When the LMFP also contains a coating, a certain amount of coating material may be weighed and mixed with a manganese source, an iron source, a phosphorus source, and a lithium source together, and ball milled.
When the coating layer is a carbon layer, the coating layer raw material is a carbon source. The carbon source may include at least one of glucose, sucrose, and polydiethanol.
In one embodiment, the positive electrode active material includes at least one of lithium iron phosphate and lithium nickel cobalt manganate.
When the lithium iron manganese phosphate material is compounded with other types of positive electrode materials (such as lithium iron phosphate or lithium nickel cobalt manganese oxide) to be used as a positive electrode active material, when the positive electrode plate meets 0.08-27 (A multiplied by H)/I Al, the secondary batteries using the positive electrode plate have less gas yield and lower cycle internal resistance increase rate.
The positive electrode active material layer may contain a conductive agent and a binder in addition to the positive electrode active material described above.
The kind of the conductive agent is not particularly limited in the present invention as long as the conductive agent has suitable electron conductivity without causing adverse chemical changes in the battery. Specifically, the conductive agent may employ at least one of carbon nanotubes, carbon black, or graphene.
The binder is used to improve the adhesion between the positive electrode active material particles and the adhesion between the positive electrode active material and the current collector, and in the present invention, the binder may be a conventional choice in the field of batteries. Specifically, the conductive agent may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin, sodium carboxymethyl cellulose (CMC), or sodium alginate.
The present invention is not particularly limited as long as it has conductivity without causing adverse chemical changes in the battery, and may use, for example, stainless steel, aluminum, nickel, titanium, fired carbon, or aluminum or stainless steel surface-treated with one of carbon, nickel, titanium, silver, etc.
The positive electrode sheet can be prepared according to a conventional method in the field. For example, the positive electrode active material, the conductive agent and the binder are dispersed in a solvent to form uniform positive electrode slurry, the positive electrode slurry is coated on a positive electrode current collector, and the positive electrode sheet is obtained after procedures such as drying, rolling and the like.
Secondary battery
An embodiment of the invention provides a secondary battery, which comprises the positive electrode plate.
The electrochemical device includes a negative electrode sheet, a separator, and an electrolyte in addition to the positive electrode sheet.
The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material. As for the anode active material, the kind of the anode active material is not particularly limited in the embodiment of the present invention, and may be selected according to actual demands. As examples, the anode active material may be natural graphite, artificial graphite, intermediate phase micro carbon spheres (MCMB), hard carbon, soft carbon, silicon-carbon composite.
The diaphragm is positioned between the positive pole piece and the negative pole piece and is used for spacing the positive pole piece and the negative pole piece and preventing the positive pole piece and the negative pole piece from being in contact short circuit. The separator may be any of a variety of materials suitable for use in the art as separator membranes for electrochemical energy storage devices. Specifically, the diaphragm comprises at least one of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
The electrolyte of the present invention may be any electrolyte suitable for use in an electrochemical energy storage device in the art. The electrolyte includes an electrolyte, which may generally include a lithium salt, and a solvent.
Specifically, the lithium salt includes at least one of lithium hexafluorophosphate (LiPF 6), lithium tetrafluoroborate (LiBF 4), lithium perchlorate (LiClO 4), lithium hexafluoroarsenate (LiAsF 6), lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethanesulfonyl) imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (lidaob), lithium difluoroborate (LiBOB), lithium difluorophosphate (LiPO 2F2), lithium difluorodioxaato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP). The concentration of the electrolyte in the electrolyte may be 0.5 to 5mol/L.
Specifically, the solvent includes at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene Carbonate (BC), fluoroethylene carbonate (FEC), methyl Formate (MF), methyl Acetate (MA), ethyl Acetate (EA), propyl Acetate (PA), methyl Propionate (MP), ethyl Propionate (EP), propyl Propionate (PP), methyl Butyrate (MB), ethyl Butyrate (EB), 1, 4-butyrolactone (GBL), sulfolane (SF), dimethylsulfone (MSM), methylsulfone (EMS) and diethylsulfone (ESE).
Power utilization device
An embodiment of the present invention provides an electric device including the above-described secondary battery.
The power utilization device is used as a power supply of the power utilization device.
The electric device refers to any other device or devices which can utilize electric energy and convert the electric energy into mechanical energy, thermal energy, optical energy and the like to form energy, such as an electric motor, an electric heat engine, an electric light source and the like. Specifically, the system can comprise, but is not limited to, mobile equipment, electric vehicles, electric trains, ships, satellites, energy storage systems and the like, wherein the mobile equipment can be mobile phones, notebook computers, unmanned aerial vehicles, sweeping robots, electronic cigarettes and the like, and the electric vehicles can be pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks and the like.
The invention is further illustrated by the following specific examples:
Example 1
The embodiment provides a lithium ion battery, which is specifically prepared by the following steps:
(1) Preparation of positive electrode plate
S1, accurately weighing Mn 3O4、FePO4、LiH2PO4 according to a molar ratio n (Li) n (Mn+Fe) n (P) =1:1:1 and n (Mn) n (Fe) =75:25, and mixing to obtain a mixture;
Weighing a carbon source (75 wt.% glucose and 25wt.% polyethylene glycol) and an aluminum source (Al 2O3), adding into the mixture, and performing ball milling, spraying and sintering for the first time to obtain a first-time sintered precursor;
Wherein, the aluminum source is weighed according to the mol ratio of n (Al)/n (Mn) =6000 ppm;
wherein the carbon source is weighed according to 5wt.% of the weight of the mixture;
The condition of the first ball milling is 500rpm,25 ℃ and 22 hours;
the first spraying condition is that the spraying pressure is 0.65MPa;
The condition of the first sintering is 500 ℃ and 10 hours;
s2, weighing a certain amount of carbon source (75 wt.% glucose and 25wt.% polyethylene glycol), mixing with a burning precursor, performing secondary ball milling, secondary spraying and secondary sintering, and crushing, sieving and removing impurities to obtain a lithium iron manganese phosphate material (lithium iron manganese phosphate with a carbon material layer coated on the surface) with an average particle size of 85.2nm, wherein the lithium iron manganese phosphate material is the positive electrode active material;
wherein, the amount of the carbon source is regulated, and the carbon coating amount of the lithium iron manganese phosphate (the mass ratio of the carbon material to the lithium iron manganese phosphate material) is controlled to be 2.8 wt%;
The condition of the second ball milling is 500 rpm,25 ℃ and 22 hours;
the condition of the second spraying is that the spraying pressure is 0.65MPa;
the condition of the second sintering is 600 ℃ and 10h.
S3, mixing the positive electrode active material with a binder (PVDF) and a conductive agent (SP) according to the mass ratio of 96:3:1, dispersing in NMP to obtain positive electrode slurry, uniformly coating the mixed positive electrode slurry on an aluminum foil, drying in a 100 ℃ vacuum furnace, rolling, cutting and baking to obtain the positive electrode plate.
(2) Preparation of negative electrode plate
Mixing a negative electrode active material (artificial graphite), a conductive agent (SP) and a binder (carboxymethyl cellulose, CMC) according to a mass ratio of 92:4:4, dispersing in deionized water to obtain a negative electrode slurry, uniformly coating the negative electrode slurry on a negative electrode current collector (copper foil), transferring the negative electrode current collector coated with the negative electrode slurry into a vacuum environment in an oven, drying at 100 ℃, rolling, cutting and baking to obtain a negative electrode plate.
(3) Preparation of electrolyte
Mixing Ethylene Carbonate (EC), ethylmethyl carbonate (EMC) and diethyl carbonate (DEC) according to the volume ratio of 1:1:1 to obtain an organic solvent, and then dissolving fully dried lithium salt LiPF 6 in the mixed organic solvent to prepare the electrolyte with the concentration of 1 mol/L.
(4) Preparation of separator
Polyethylene (PE) separators are used.
(5) Preparation of a Battery
And (3) winding the prepared positive electrode plate, the diaphragm and the negative electrode plate to obtain a bare cell without filling liquid, placing the bare cell in an outer packaging foil, filling the prepared electrolyte into the dried bare cell, and performing the procedures of vacuum packaging, standing, formation, shaping, sorting and the like to obtain the lithium ion battery.
Examples 2 to 9, examples 11 to 18 and comparative examples 1 and 2
Examples 2 to 9, examples 11 to 18 and comparative examples 1 and 2 provide lithium ion batteries, respectively, and the specific preparation method is similar to example 1, except that in the preparation of the positive electrode sheet:
in S1, values of n (Mn), n (Fe), n (Al)/n (Mn) are shown in Table 1;
the time of the first ball milling is shown in table 1;
S2, crushing and sieving, and adjusting the average particle size of particles of the lithium iron manganese phosphate material to meet the requirements shown in table 1, adjusting the amount of a carbon source, and controlling the carbon coating amount of the lithium iron manganese phosphate material to meet the requirements shown in table 1, wherein the time of the second ball milling is shown in table 1;
For example 3, step S2 is also different in that after the lithium iron manganese phosphate material is obtained, the lithium iron manganese phosphate material and lithium iron phosphate are mixed according to a mass ratio of 8:2, and the positive electrode active material is obtained;
for example 15, step S2 is also different in that after the lithium iron manganese phosphate material is obtained, the lithium iron manganese phosphate material and the ternary material (LiNi 0.6Co0.2Mn0.2O2) are mixed according to the mass ratio of 2:8, namely the positive electrode active material;
For example 16, step S2 is also different in that after the lithium iron manganese phosphate material is obtained, the lithium iron manganese phosphate material and the ternary material (LiNi 0.8Co0.1Mn0.1O2) are mixed according to the mass ratio of 2:8, namely the positive electrode active material.
Example 10
Example 10 provides a lithium ion battery, the specific preparation method is similar to example 1, except that in the preparation of the positive electrode sheet, the following method is adopted:
Accurately weighing Mn 3O4、FePO4、LiH2PO4 according to the molar ratio n (Li): n (Mn+Fe): n (P) =1:1:1 and n (Mn): n (Fe) =56:44, and mixing to obtain a mixture;
Weighing a carbon source (75 wt.% glucose and 25wt.% polyethylene glycol) and an aluminum source (Al 2O3), adding into a mixture, and performing first ball milling, first spraying and first sintering to obtain a lithium iron manganese phosphate material (lithium iron manganese phosphate with a carbon material layer coated on the surface) with the average particle size of 210 nm;
wherein, the aluminum source is weighed according to the mol ratio of n (Al)/n (Mn) =7600 ppm;
Adjusting the amount of a carbon source, and controlling the carbon coating amount of the lithium iron manganese phosphate (the mass ratio of the carbon material to the lithium iron manganese phosphate material) to be 2.0 wt percent;
The condition of the first ball milling is 500rpm,25 ℃ and 24 hours;
the first spraying condition is that the spraying pressure is 0.65MPa;
the condition of the first sintering is 600 ℃ for 10 hours;
And then mixing the positive electrode active material with a binder (PVDF) and a conductive agent (SP) according to the mass ratio of 96:3:1, dispersing in NMP to obtain positive electrode slurry, uniformly coating the mixed positive electrode slurry on an aluminum foil, drying in a 100 ℃ vacuum furnace, rolling, cutting and baking to obtain the positive electrode plate.
Comparative example 3
Comparative example 3 provides a lithium ion battery, the specific preparation method is similar to example 1, except that in the preparation of the positive electrode sheet:
in S1, no aluminum source is added, and the value of n (Mn): n (Fe) is shown in table 1, wherein the time of the first ball milling is shown in table 1;
S2, crushing and sieving, and adjusting the average particle size of particles of the lithium iron manganese phosphate material to meet the requirements shown in table 1, adjusting the amount of a carbon source, and controlling the carbon coating amount of the positive electrode active material to meet the requirements shown in table 1, wherein the time of the second ball milling is shown in table 1;
S3 is as follows:
S3, mixing an anode active material, a binder (PVDF) and a conductive agent (SP) according to a mass ratio of 96:3:1, dispersing in NMP to obtain first anode slurry, and adding 1.2 wt percent of Al 2O3 into the first anode slurry to obtain second anode slurry;
and uniformly coating the second positive electrode slurry on an aluminum foil, drying in a 100 ℃ vacuum furnace, rolling, cutting and baking to obtain the positive electrode plate.
The carbon coating amount of the lithium iron manganese phosphate material is determined by the following method:
The sample is weighed by an electronic balance and then enters a combustion reaction tank, the sample is heated and burned at high temperature by a high-frequency furnace under the condition of sufficient oxygen, carbon is oxidized into carbon dioxide, the carbon dioxide is filtered and dried, and then enters a corresponding absorption tank to absorb the corresponding infrared radiation spectrum (4200 nm of carbon dioxide), and then the carbon dioxide is converted into the corresponding electric signal by a detector. The signal is collected by a computer, converted into a numerical value proportional to carbon dioxide after linear correction, then the numerical value of the whole analysis process is accumulated, after the analysis is finished, the accumulated value is divided by the weighing value in the computer, and then the correction coefficient is multiplied, so that the mass fraction of carbon in the sample, namely the carbon coating quantity (unit wt.%) can be obtained.
TABLE 1
The cathode sheets A, h and I Al of the lithium ion batteries prepared in the above examples and comparative examples were tested as follows, and the test results are shown in table 2.
The detection method comprises the following steps:
disassembling the lithium ion battery in the empty state to obtain a positive electrode plate, drying the positive electrode plate for 4 hours at 80 ℃, placing the positive electrode plate in a 400 ℃ sintering furnace for sintering for 4 hours, and scraping positive electrode active material powder by using a ceramic knife;
Accurately weighing 0.5g of positive electrode active material powder, dispersing in 20mL of water, adding 10mL of nitric acid, uniformly mixing, heating, dissolving the positive electrode active material powder, and metering the volume of the material to 100mL by using water to obtain a solution to be measured;
ICP testing is carried out on the solution to be tested, wherein ICP testing conditions are that the detection spectral wavelength (Mn wavelength 257.61 nm) of elements is selected, proper ICP instrument working conditions are set according to the characteristics of samples and elements to be detected, the gas flow is 0.5L/min, the power is 1150W, and Mn content of the elements in the ICP testing is carried out, so that the molar content of manganese element in the positive electrode active material, namely the value of A, is obtained, and the unit is mol%.
Discharging the lithium ion battery at 0.33C rate, charging the lithium ion battery to 4.25V cut-off voltage at 0.33C rate, cutting off current at 0.05C, enabling the battery to reach 100% SOC (state of charge), disassembling the battery in the state of charge to obtain a positive pole piece in the state of charge, drying at 80 ℃ for 4 hours to obtain the positive pole piece, and cutting the positive pole piece into a pole piece to be measured of 7cm multiplied by 7 cm;
dipping a pole piece to be detected in 20ml of mixed solution at the temperature of 60 ℃, wherein the mixed solution consists of ethylene carbonate, ethylmethyl carbonate and high-chloric acid, the volume ratio of the ethylene carbonate to the ethylmethyl carbonate is 3:7, and the molar concentration of lithium perchlorate in the mixed solution is 1mol/L;
Detecting the content of hydrogen ions in the mixed solution when the pole piece to be detected is immersed in the mixed solution for 48 hours and marking as H 1 ppm;
The hydrogen ion content (H 1、H2) in the mixed solution was measured by the following method:
Preparing triethylamine and methyl ethyl carbonate (EMC) into a triethylamine titration solution with the concentration of 0.05mol/L, taking a mixed solution of an impregnated positive electrode plate as a solution to be detected, adding 10-30 drops of methyl red into the mixed solution as an indicator, dripping the triethylamine titration solution into the solution to be detected containing the methyl red, recording the consumption of the triethylamine titration solution when the solution to be detected turns orange, and then obtaining the hydrogen ion content according to a formula:
Hydrogen ion content = M x V x 20010/M, hydrogen ion content in ppm;
wherein M is the concentration of triethylamine titration solution, the unit mol/L,
V is the volume of titration solution consumed by triethylamine, unit mL,
M is the mass of the solution to be measured, the unit is g,
20010 The positive electrode sheet filled with the electrolyte component LiPF 6, which is =20.01x10 3, 20.01 is molecular mass of HF, the positive electrode active material reacts with EC and EMC to dehydrogenate, HF is generated in the presence of LiPF 6, and the amount of HF represents hydrogen ions.
And calculating the increase rate H= (H 2- H1)/ H1 multiplied by 100%) of the hydrogen ion content of the positive electrode plate immersed in the mixed solution containing the high-chloric acid.
I Al, disassembling the battery to obtain a positive electrode plate, and drying the positive electrode plate at 80 ℃ for 4 hours to obtain a to-be-detected electrode plate;
XPS analysis is carried out on the surface of the pole piece to be detected, and the peak intensity of the characteristic peak of the aluminum element in the obtained XPS graph is I 1 counts/s;
Etching the pole piece to be detected at the etching depth of 50nm, and then performing XPS analysis to obtain the peak intensity of the characteristic peak of the aluminum element in the XPS graph as I 2 counts/s;
The XPS analysis condition is that a 120W monochromized Al K alpha X ray source is adopted, the energy resolution is less than or equal to 0.48 eV, the test beam light spot is 400 microns, the instrument automatically supplements the test energy range according to the element to be tested, the etching treatment condition is that Ar ions are adopted for etching, and the etching depth is controlled to be 50nm by adjusting the etching rate or the etching time and the like;
After the XPS analysis is finished, the instrument automatically gives out a test result, namely I 1 and I 2 can be read out;
The units of I Al= I2-I1,I1、I2 and I Al are calculated to be counts/s.
Fig. 1 is an XPS diagram of a positive electrode sheet of example 6, wherein the lower line is an XPS spectrum obtained by performing XPS analysis on the surface of the sheet to be measured, and the upper line is an XPS spectrum obtained by performing XPS analysis after performing etching treatment on the sheet to be measured at an etching depth of 50 nm. In FIG. 1, the position of the characteristic peak of aluminum element is at the binding energy of 84.+ -.1 eV.
TABLE 2
The gas generating properties of the positive electrode sheets prepared in the above examples and comparative examples, and the internal resistance (DCR) increase rates of the lithium ion batteries prepared in the examples and comparative examples were tested, and the specific test methods are as follows, and the test results are shown in table 3.
(1) Gas production performance:
The positive electrode plate, the diaphragm and the negative electrode plate of each example and the comparative example are subjected to roll cutting, assembly, drying and liquid injection procedures to prepare a soft package battery;
installing a special container, an electronic scale, one soft package battery, a lead, a bracket and a formation device, injecting water into the special container until water overflows from an opening of the special container, and completely immersing the soft package battery in the water;
the method comprises the steps of (1) carrying out formation (the formation process comprises the steps of charging 0.02C to 2.4V, standing for 10min, discharging 0.02C to 2V, standing for 10min, repeating the steps for three times, charging 0.02C to 3.5V, standing for 10min, charging 0.1C to 4.25V), and continuously expanding the volume of the battery by gas generation in the soft package battery in the formation process to continuously overflow the liquid in the special container, so that the indication of the electronic scale is changed at the same time, and the volume of water overflow is the volume of generated gas;
After the formation is finished, the liquid loss mass is obtained according to the reading of the electronic scale, and the density of water is known, wherein the unit of gas production = liquid loss mass/density of water is milliliter (ml);
The soft package battery is subjected to constant volume test (constant current charging is carried out to 4.25V at a rate of 1/3C, constant voltage charging is carried out to a current of less than 0.05C, more than 3 times of processing steps are carried out, and the capacity of the battery is recorded to obtain the actual capacity (the unit is Ah) of the soft package battery;
The gas production performance of the positive electrode sheet was evaluated by the gas production per unit capacity of the battery, gas production per unit capacity=gas production/actual capacity (unit: ml/Ah).
(2) DCR growth rate:
Constant volume is carried out on the lithium ion battery, the lithium ion battery is fully charged to 4.25V at 0.33 ℃, constant voltage cut-off current is 0.05C, discharge is carried out at 0.33C, 50% SOC is regulated, the lithium ion battery is kept stand for 2 hours, then 1C discharge is carried out at 50% SOC, initial battery internal resistance is measured, and DCR 1 is obtained;
Placing the lithium ion battery in a 55 ℃ incubator, emptying the lithium ion battery at a constant current of 0.33 ℃, and then circulating in the incubator for 300 circles under the conditions of a charge-discharge test multiplying power of 1C/1C and a circulating voltage range of 2.5-4.25V;
after 300 circles of circulation, discharging and charging by 0.33C to adjust 50% of SOC, standing for 2 hours, discharging by 1C under 50% of SOC, and testing the internal resistance of the circulated battery to obtain DCR 2;
taking the voltage of the last second of standing as V0, the voltage of the 18s after discharging as V1, and the current in the discharging process as I, wherein DCR= (V0-V1)/I;
DCR increase rate= (DCR 2-DCR1)/DCR1 ×100% was calculated.
TABLE 3 Table 3
According to the test results of Table 3, the lithium ion batteries using the positive electrode plates prepared in each example of the invention have excellent gas production performance (gas production per unit capacity is less than or equal to 24.1 ml/Ah), and the internal resistance increase rate of the lithium ion batteries after circulation is low (DCR increase rate is less than or equal to 65%)
According to examples 1 to 6 and examples 10 to 11, it can be seen that when the positive electrode sheet further satisfies 0.16≤A.times.H)/I Al≤4.5, the overall performance of the battery is better, the production phase is relatively lower, and the internal resistance growth is relatively less.
As can be seen from comparative examples 1-3, when the positive electrode sheet exceeds the technical scheme of the invention, and the ratio of (A multiplied by H)/I Al is not more than 0.08 and not more than 27, the lithium ion battery using the positive electrode sheet has difficulty in achieving both good gas production performance and lower internal resistance growth rate.
Finally, it should be noted that the above embodiments are only for illustrating the technical solution of the present invention and not for limiting the scope of the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made to the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention.

Claims (9)

1.一种正极极片，包括正极集流体和设置于所述正极集流体至少一个表面的正极活性材料层，所述正极活性材料层包括正极活性材料，其特征在于，所述正极活性材料包括磷酸锰铁锂类材料，磷酸锰铁锂类材料为单颗粒，磷酸锰铁锂类材料的颗粒平均粒径为30～400nm；1. A positive electrode sheet, comprising a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector, wherein the positive active material layer comprises a positive active material, wherein the positive active material comprises a lithium iron manganese phosphate material, the lithium iron manganese phosphate material is a single particle, and the average particle size of the lithium iron manganese phosphate material is 30 to 400 nm; 所述正极极片满足如下关系式：The positive electrode sheet satisfies the following relationship: 0.08≤(A×H)/IAl≤27；0.08≤(A×H)/I Al ≤27; 其中，A为正极活性材料中锰元素占过渡金属元素的摩尔含量，单位为mol％，所述A的范围是50～95mol％；Wherein, A is the molar content of manganese element in the positive electrode active material to the transition metal element, in mol%, and the range of A is 50 to 95 mol%; H为正极极片在60℃条件下于混合溶液中浸渍T1 h到T2 h的氢离子含量增长率，T2-T1＝72，T1＞0；所述混合溶液含有有机溶剂和锂盐，H的单位为％，所述H的范围是12～42％；H is the growth rate of hydrogen ion content of the positive electrode sheet from T 1 h to T 2 h when immersed in the mixed solution at 60° C., T 2 -T 1 =72, T 1 >0; the mixed solution contains an organic solvent and a lithium salt, the unit of H is %, and the range of H is 12-42%; IAl＝I2-I1，所述I1为对正极极片的表面进行XPS分析时，XPS图中铝元素特征峰的峰强度；所述I2为以刻蚀深度50nm对正极极片进行刻蚀处理后再进行XPS分析，XPS图中铝元素特征峰的峰强度；I1、I2以及IAl的单位均为counts/s；所述I1的范围为1302～12202counts/s。I Al =I 2 -I 1 , wherein I 1 is the peak intensity of the characteristic peak of aluminum element in the XPS diagram when XPS analysis is performed on the surface of the positive electrode plate; I 2 is the peak intensity of the characteristic peak of aluminum element in the XPS diagram after the positive electrode plate is etched at an etching depth of 50 nm and then subjected to XPS analysis; the units of I 1 , I 2 and I Al are all counts/s; the range of I 1 is 1302 to 12202 counts/s. 2.根据权利要求1所述正极极片，其特征在于，所述正极极片满足如下关系式：0.16≤(A×H)/IAl≤4.5。2. The positive electrode sheet according to claim 1, characterized in that the positive electrode sheet satisfies the following relationship: 0.16≤(A×H)/I Al ≤4.5. 3.根据权利要求1或2所述正极极片，其特征在于，所述A的范围是55～85mol％。3. The positive electrode sheet according to claim 1 or 2, characterized in that the range of A is 55 to 85 mol%. 4.根据权利要求1或2所述正极极片，其特征在于，所述H的范围是15～35％。4. The positive electrode plate according to claim 1 or 2, characterized in that the range of H is 15-35%. 5.根据权利要求1或2所述正极极片，其特征在于，所述IAl的范围是100～9000counts/s。5. The positive electrode plate according to claim 1 or 2, characterized in that the range of I Al is 100 to 9000 counts/s. 6.根据权利要求5所述正极极片，其特征在于，所述IAl的范围是600～7000counts/s。6. The positive electrode plate according to claim 5, characterized in that the range of I Al is 600 to 7000 counts/s. 7.根据权利要求1所述正极极片，其特征在于，所述混合溶液包括碳酸乙烯酯、碳酸甲乙酯和髙氯酸锂，其中碳酸乙烯酯、碳酸甲乙酯的体积比为3:7，高氯酸锂在混合溶液中的摩尔浓度为1mol/L。7. The positive electrode plate according to claim 1 is characterized in that the mixed solution comprises ethylene carbonate, ethyl methyl carbonate and lithium perchlorate, wherein the volume ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, and the molar concentration of lithium perchlorate in the mixed solution is 1 mol/L. 8.一种二次电池，包括正极极片、负极极片和电解液，其特征在于，所述正极极片为权利要求1～7任一项所述正极极片。8. A secondary battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the positive electrode sheet is the positive electrode sheet according to any one of claims 1 to 7. 9.一种用电装置，其特征在于，包括如权利要求8所述二次电池。9. An electrical device, comprising the secondary battery as claimed in claim 8.
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