WO2023133833A1 - 一种二次电池、电池模块、电池包和用电装置 - Google Patents

一种二次电池、电池模块、电池包和用电装置 Download PDF

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Publication number
WO2023133833A1
WO2023133833A1 PCT/CN2022/072109 CN2022072109W WO2023133833A1 WO 2023133833 A1 WO2023133833 A1 WO 2023133833A1 CN 2022072109 W CN2022072109 W CN 2022072109W WO 2023133833 A1 WO2023133833 A1 WO 2023133833A1
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Prior art keywords
secondary battery
negative electrode
capacity
positive electrode
lithium
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PCT/CN2022/072109
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English (en)
French (fr)
Inventor
李璇
孙信
吴李力
苏辉森
韦健人
陈兴布
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宁德时代新能源科技股份有限公司
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to EP22919483.2A priority Critical patent/EP4273987A4/en
Priority to CN202280020075.9A priority patent/CN116964804A/zh
Priority to PCT/CN2022/072109 priority patent/WO2023133833A1/zh
Priority to US18/324,992 priority patent/US20230352692A1/en
Publication of WO2023133833A1 publication Critical patent/WO2023133833A1/zh

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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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
    • 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

Definitions

  • the present application relates to the field of electrochemistry, in particular to a secondary battery, a battery module, a battery pack and an electrical device.
  • Secondary batteries have the advantages of high energy storage density, high open circuit voltage, low self-discharge rate, long cycle life, and good safety. They are widely used in various fields such as electric energy storage, mobile electronic equipment, electric vehicles, and aerospace equipment. With the rapid development of mobile electronic devices and electric vehicles, the market has put forward higher and higher requirements for the energy density, cycle performance and safety performance of secondary batteries.
  • the purpose of the present application is to provide a secondary battery, a battery module, a battery pack and an electrical device, so that the secondary battery has good cycle performance and safety performance while improving its energy density.
  • the present application provides a secondary battery, a battery module, a battery pack and an electrical device.
  • the first aspect of the present application provides a secondary battery, which includes a negative pole piece, a positive pole piece, and a separator between the negative pole piece and the positive pole piece; the negative pole piece or the The separator includes a safety coating; the charging negative electrode capacity Nc and the charging positive electrode capacity Pc of the secondary battery meet: 0.45 ⁇ Nc/Pc ⁇ 1, and/or, the discharging negative electrode capacity Nd and the discharging positive electrode capacity of the secondary battery Pd satisfies: 0.45 ⁇ Nd/Pd ⁇ 1. Therefore, by setting the ratio of Nc/Pc and/or Nd/Pd in the secondary battery and the setting of the safety coating, the secondary battery can have good cycle performance and safety performance while increasing its energy density.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the safety coating is disposed on the surface of the negative electrode film layer.
  • the generation of lithium dendrites is effectively reduced, and the possibility of lithium dendrites piercing through the separator and directly contacting the positive electrode sheet can also be reduced. Therefore, the energy density of the secondary battery is improved while having good cycle performance and safety performance.
  • the safety coating is disposed on the first surface of the separator facing the negative electrode sheet. In this way, the formation of lithium dendrites is effectively reduced, and the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet can also be reduced. Therefore, the energy density of the secondary battery is improved while having good cycle performance and safety performance.
  • the capacity Nc of the charged negative electrode and the capacity Pc of the charged positive electrode of the secondary battery satisfy: 0.5 ⁇ Nc/Pc ⁇ 0.85.
  • the energy density of the secondary battery can be effectively improved.
  • the deposition of excess lithium ions on the surface of the negative electrode sheet is effectively reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the discharged negative electrode capacity Nd and the discharged positive electrode capacity Pd of the secondary battery satisfy: 0.5 ⁇ Nd/Pd ⁇ 0.87.
  • the energy density of the secondary battery can be effectively improved.
  • the deposition of excess lithium ions on the surface of the negative electrode sheet is effectively reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the negative electrode film layer includes a negative electrode active material
  • the negative electrode active material includes at least one of graphite, silicon carbon, silicon oxide, tin oxide, iron oxide (Fe 3 O 4 ) and titanium oxide.
  • the deposition of lithium metal on the surface of the negative electrode sheet is reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the lithium metal and the negative electrode active material form a composite lithium metal material, which improves the energy density of the secondary battery.
  • the safety coating includes additives and carbon materials;
  • the additives include metal elements of gold, silver, magnesium, and aluminum, and at least one of oxides, nitrates, and phosphates of silver, magnesium, and aluminum.
  • the carbon material includes at least one of graphite, graphene and carbon nanotubes. Therefore, the energy density of the secondary battery is improved while having good cycle performance and safety performance.
  • the mass ratio of the additive to the carbon material is (0.05-100):100, preferably (10-80):100, more preferably (20-50):100. Regulating the mass ratio of additives and carbon materials within the above range can reduce the generation of lithium dendrites on the surface of the negative electrode sheet without affecting other properties of the secondary battery (such as rate performance), so that the secondary battery has While good cycle performance and safety performance, its energy density is improved.
  • the additive includes at least one of silver, magnesium, aluminum oxide, nitrate and phosphate, and the mass ratio of the additive to the carbon material is (0.05-100):100, Preferably (15-80):100, more preferably (25-60):100.
  • the mass ratio of the additives to the materials is regulated within the above range, which is more conducive to alleviating the formation of lithium dendrites on the surface of the negative electrode sheet, which is more conducive to improving the energy density of the secondary battery and making the secondary battery It has good cycle performance and safety performance.
  • the security coating has a thickness of 0.5 ⁇ m to 15 ⁇ m. Regulating the safety coating within the above thickness range reduces the formation of lithium dendrites on the surface of the negative electrode sheet, and also reduces the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet. Therefore, it is more conducive to improving the energy density of the secondary battery, and also enables the secondary battery to have good cycle performance and safety performance.
  • the negative electrode sheet includes the negative electrode current collector and the negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the safety coating is disposed on the surface of the negative electrode film layer , the security coating has a thickness of 0.5 ⁇ m to 15 ⁇ m, preferably 3 ⁇ m to 10 ⁇ m. Regulating the safety coating within the above thickness range reduces the formation of lithium dendrites on the surface of the negative electrode sheet, and also reduces the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet. Therefore, it is more conducive to improving the energy density of the secondary battery, and also enables the secondary battery to have good cycle performance and safety performance.
  • the safety coating is disposed on the first surface of the separator facing the negative electrode sheet, and the thickness of the safety coating is 0.5 ⁇ m to 15 ⁇ m, preferably 3 ⁇ m to 10 ⁇ m. Regulating the safety coating within the above thickness range reduces the formation of lithium dendrites on the surface of the negative electrode sheet, and also reduces the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet. Therefore, it is more conducive to improving the energy density of the secondary battery, and also enables the secondary battery to have good cycle performance and safety performance.
  • a second aspect of the present application provides a battery module including the secondary battery of the first aspect of the present application.
  • a third aspect of the present application provides a battery pack, including the battery module of the second aspect of the present application.
  • the fourth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. kind.
  • the application provides a secondary battery, a battery module, a battery pack, and an electrical device, wherein the secondary battery includes a negative pole piece, a positive pole piece, and a separator between the negative pole piece and the positive pole piece;
  • the sheet or separator includes a safety coating; the charging negative electrode capacity Nc and the charging positive electrode capacity Pc of the secondary battery meet: 0.45 ⁇ Nc/Pc ⁇ 1, and/or, the discharging negative electrode capacity Nd and the discharging positive electrode capacity Pd of the secondary battery meet : 0.45 ⁇ Nd/Pd ⁇ 1.
  • FIG. 1 is a schematic diagram of a cross-sectional structure of a negative pole piece in some embodiments of the present application
  • Fig. 2 is a schematic diagram of the location structure of the safety coating in other embodiments of the present application.
  • FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Fig. 4 is an exploded view of the secondary battery according to one embodiment of the present application shown in Fig. 3;
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • Fig. 7 is an exploded view of the battery pack according to an embodiment of the present application shown in Fig. 6;
  • FIG. 8 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • 1 battery pack 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 10 negative current collector; 20 negative film layer; 30 safety coating; 51 shell; 100 isolation film; 200 negative pole piece; 300 positive pole piece.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • the applicant found that the excess lithium ions produced by the negative pole piece during the charge-discharge cycle are deposited on the surface of the negative pole piece, which easily causes the volume expansion of the secondary battery. Moreover, due to the uneven current density and lithium ion concentration in the electrolyte, the deposition rate of certain sites during the lithium ion deposition process is too fast, forming a lithium dendrite structure, which seriously affects the energy density and cycle performance of the secondary battery. Moreover, as the number of charge-discharge cycles increases, the lithium dendrites become sharper, which is likely to pierce the separator and directly contact the positive electrode sheet to form a short circuit, causing serious safety accidents.
  • the present application provides a secondary battery, a battery module, a battery pack and an electrical device.
  • the application proposes a secondary battery, which includes a negative pole piece, a positive pole piece, and a separator between the negative pole piece and the positive pole piece; the negative pole piece or the separator includes a safety Coating; the charging negative electrode capacity Nc and the charging positive electrode capacity Pc of the secondary battery meet: 0.45 ⁇ Nc/Pc ⁇ 1, and/or the discharging negative electrode capacity Nd and the discharging positive electrode capacity Pd of the secondary battery meet: 0.45 ⁇ Nd/Pd ⁇ 1.
  • the negative pole piece can also be a negative pole
  • the positive pole piece can also be a positive pole.
  • the composite lithium metal material is formed with the negative electrode active material in the form of lithium metal, thereby effectively improving the energy density of the secondary battery.
  • the deposition of excess lithium ions on the surface of the negative electrode sheet is effectively reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the negative electrode sheet or the separator includes a safety coating, so that lithium ions are deposited under the safety coating, and the safety coating reduces the generation of lithium dendrites on the surface of the negative electrode sheet through physical barriers; and, the safety coating is in the secondary During the charging and discharging process of the battery, it can form an alloy with lithium ions, further reducing the generation of lithium dendrites on the surface of the negative electrode sheet. Therefore, while the secondary battery has good cycle performance and safety performance, its energy density can be effectively improved.
  • the negative electrode sheet or the separator includes a safety coating; and the charged negative electrode capacity Nc and the charged positive electrode capacity Pc of the secondary battery satisfy: 0.45 ⁇ Nc/Pc ⁇ 1, and/ Or, the discharged negative electrode capacity Nd and the discharged positive electrode capacity Pd of the secondary battery satisfy: 0.45 ⁇ Nd/Pd ⁇ 1.
  • the secondary battery has high energy density while having good cycle performance and safety performance.
  • the above-mentioned Nc/Pc ⁇ 1, and/or, Nd/Pd ⁇ 1 is achieved by reducing the proportion (k 1 ) of the negative electrode active material in the negative electrode film layer or reducing the negative electrode sheet
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the safety coating is disposed on the surface of the negative electrode film layer.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the "surface” here may be the entire area of the negative electrode current collector, or a partial area of the negative electrode current collector.
  • the safety coating being disposed on the surface of the negative electrode film layer means that the safety coating is disposed on the entire surface of the negative electrode film layer. Exemplarily, as shown in FIG.
  • the negative electrode sheet 200 includes a negative electrode current collector 10 and a negative electrode film layer 20 arranged on the opposite surfaces A and B of the negative electrode current collector 10, and the two safety coatings 30 are each independently It is disposed on the surface of the negative electrode film layer 20 away from the negative electrode current collector 10 .
  • the safety coating is arranged on the surface of the negative electrode film layer.
  • lithium ions are deposited under the safety coating layer, that is, the side adjacent to the safety coating layer and the negative electrode film layer.
  • the safety coating layer passes through physical The barrier reduces the generation of lithium dendrites on the surface of the negative electrode sheet, and can also be understood as reducing the generation of lithium dendrites on the surface of the safety coating close to the positive electrode sheet.
  • the safety coating can form an alloy with lithium ions during the charging and discharging process of the secondary battery, further reducing the generation of lithium dendrites on the surface of the negative electrode sheet. In this way, the generation of lithium dendrites is effectively reduced, and the possibility of lithium dendrites piercing through the separator and directly contacting the positive electrode sheet can also be reduced. Therefore, the secondary battery has good cycle performance and safety performance, and has high energy density.
  • the security coating is disposed on the first surface of the separator facing the negative electrode sheet.
  • the separator 100 is located between the positive electrode sheet 300 and the negative electrode sheet 200
  • the safety coating 30 is disposed on the first surface C of the separator 100 facing the negative electrode sheet 200 .
  • the safety coating reduces the formation of lithium dendrites on the surface of the negative electrode sheet through physical barriers , and the safety coating can form an alloy with lithium ions, further reducing the generation of lithium dendrites on the surface of the negative electrode sheet. In this way, the generation of lithium dendrites is effectively reduced, and the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet is also reduced. Therefore, the secondary battery has good cycle performance and safety performance, and has high energy density.
  • the charged negative electrode capacity Nc and the charged positive electrode capacity Pc of the secondary battery satisfy: 0.5 ⁇ Nc/Pc ⁇ 0.85.
  • the reversible capacity of the positive electrode is greater than that of the negative electrode, so that the excess lithium ions in the positive electrode relative to the negative electrode will form a composite lithium metal material with the negative electrode active material in the form of lithium metal during the charging process of the secondary battery. Therefore, the energy density of the secondary battery is effectively improved.
  • the deposition of excess lithium ions on the surface of the negative electrode sheet is effectively reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the discharged negative electrode capacity Nd and the discharged positive electrode capacity Pd of the secondary battery satisfy: 0.5 ⁇ Nd/Pd ⁇ 0.87.
  • the reversible capacity of the positive electrode is greater than that of the negative electrode, so that the excess lithium ions in the positive electrode relative to the negative electrode will form a composite lithium metal material with the negative electrode active material in the form of lithium metal during the charging process of the secondary battery. Therefore, the energy density of the secondary battery is effectively improved.
  • the deposition of excess lithium ions on the surface of the negative electrode sheet is effectively reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the charging negative electrode capacity Nc and the charging positive electrode capacity Pc of the secondary battery meet: 0.5 ⁇ Nc/Pc ⁇ 0.85; and the discharging negative electrode capacity Nd and discharging positive electrode capacity Pd of the secondary battery meet: 0.5 ⁇ Nd/Pd ⁇ 0.87.
  • the reversible capacity of the positive electrode is much greater than that of the negative electrode. Therefore, the excess lithium ions in the positive electrode relative to the negative electrode will form a composite lithium metal with the negative active material in the form of lithium metal during the charging process of the secondary battery. material, thereby effectively increasing the energy density of the secondary battery.
  • the deposition of excess lithium ions on the surface of the negative electrode sheet is effectively reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the negative electrode film layer includes a negative electrode active material
  • the negative electrode active material includes at least one of graphite, silicon carbon, silicon oxide, tin oxide, iron oxide, and titanium oxide.
  • the selection of the above-mentioned negative electrode active material can provide a certain storage space for lithium extracted from the positive electrode, and the pores between the particles of each negative electrode active material can provide space for lithium deposition. In this way, the deposition of lithium metal on the surface of the negative electrode sheet is reduced, and the lithium dendrites on the surface of the negative electrode sheet are greatly reduced, thereby improving the cycle performance and safety performance of the secondary battery.
  • the lithium metal and the negative electrode active material form a composite lithium metal material, which improves the energy density of the secondary battery.
  • the security coating includes additives and carbon materials;
  • the additives include metal elements of gold, silver, magnesium, and aluminum, and at least one of oxides, nitrates, and phosphates of silver, magnesium, and aluminum; carbon
  • the material includes at least one of graphite, graphene and carbon nanotubes.
  • the selection of carbon materials provides a certain space for lithium deposition.
  • the selection of additives can effectively improve the safety coating and make the current density on the surface of the negative electrode sheet more uniform, so that lithium metal can be deposited evenly on the surface of the negative electrode sheet, and the additive can form an alloy with lithium ions to further relieve the negative electrode surface. formation of lithium dendrites.
  • the mass ratio of the additive to the carbon material is (0.05-100):100, preferably (10-80):100, more preferably (20-50):100.
  • the mass ratio of additives and carbon materials is 0.05:100, 1:100, 5:100, 10:100, 15:100, 20:100, 30:100, 40:100, 50:100, 60:100, 70:100, 80:100, 90:100, 100:100 or any value between any two value ranges above.
  • the content of additives in the security coating affects the conductivity of the security coating and the content of alloys formed by additives and lithium ions.
  • additives in the safety coating improves the conductivity of the safety coating and can also form more alloys with lithium ions to alleviate the formation of lithium dendrites on the surface of the negative electrode sheet.
  • too much content of additives may easily cause the risk of short circuit, or increase the resistance of the negative electrode sheet and increase the polarization, which will affect the rate performance of the secondary battery.
  • Regulating the mass ratio of additives and carbon materials within the above range can reduce the generation of lithium dendrites on the surface of the negative electrode sheet without affecting other properties of the secondary battery (such as rate performance), thereby improving the performance of the secondary battery.
  • the energy density also makes the secondary battery have good cycle performance and safety performance.
  • the additive includes at least one of silver, magnesium, aluminum oxide, nitrate and phosphate
  • the mass ratio of the additive to the carbon material is (0.05-100):100, preferably (15-80 ):100, more preferably (25-60):100.
  • the mass ratio of additives and carbon materials is 0.05:100, 1:100, 5:100, 10:100, 15:100, 20:100, 25:100, 30:100, 40:100, 50:100 , 60:100, 70:100, 80:100, 90:100, 100:100 or any value between any two value ranges above.
  • Oxides, nitrates, and phosphates have different electrical conductivity compared to their metal elements.
  • the mass ratio of the additives to the materials is regulated within the above range, which is more conducive to alleviating the formation of lithium dendrites on the surface of the negative electrode sheet, which is more conducive to improving the energy density of the secondary battery and making the secondary battery It has good cycle performance and safety performance.
  • the security coating has a thickness of 0.5 ⁇ m to 15 ⁇ m.
  • the thickness of the security coating is 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 7 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 13 ⁇ m, 15 ⁇ m or any value between any two of the above ranges. If the thickness of the safety coating is too thin (for example, less than 0.5 ⁇ m), the effect of the safety coating cannot be exerted; if the thickness of the safety coating is too thick (for example, greater than 15 ⁇ m), the energy density of the secondary battery will decrease and the impedance will increase.
  • Regulating the safety coating within the above thickness range reduces the formation of lithium dendrites on the surface of the negative electrode sheet, and also reduces the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet. Therefore, it is more conducive to improving the energy density of the secondary battery, and also enables the secondary battery to have good cycle performance and safety performance.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, the safety coating is disposed on the surface of the negative electrode film layer, and the thickness of the safety coating is 0.5 ⁇ m to 15 ⁇ m, 3 ⁇ m to 10 ⁇ m is preferred.
  • the thickness of the security coating is 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 11 ⁇ m, 13 ⁇ m, 15 ⁇ m or any value between any two of the above ranges.
  • Regulating the safety coating within the above thickness range reduces the formation of lithium dendrites on the surface of the negative electrode sheet, and also reduces the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet. Therefore, it is more conducive to improving the energy density of the secondary battery, and also enables the secondary battery to have good cycle performance and safety performance.
  • the safety coating is disposed on the first surface of the separator facing the negative electrode sheet, and the thickness of the safety coating is 0.5 ⁇ m to 15 ⁇ m, preferably 3 ⁇ m to 10 ⁇ m.
  • the thickness of the security coating is 0.5 ⁇ m, 1 ⁇ m, 3 ⁇ m, 5 ⁇ m, 8 ⁇ m, 10 ⁇ m, 11 ⁇ m, 13 ⁇ m, 15 ⁇ m or any value between any two of the above ranges. Regulating the safety coating within the above thickness range reduces the formation of lithium dendrites on the surface of the negative electrode sheet, and also reduces the possibility of lithium dendrites piercing the separator and directly contacting the positive electrode sheet. Therefore, it is more conducive to improving the energy density of the secondary battery, and also enables the secondary battery to have good cycle performance and safety performance.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays the role of preventing the short circuit between the positive pole and the negative pole, and at the same time allows active ions to pass through.
  • the positive pole piece includes a positive current collector and a positive film layer arranged on at least one surface of the positive current collector.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material known in the art for batteries.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also abbreviated as NCM 622 ), LiNi At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 )), lithium nickel cobalt aluminum oxide (such as LiN
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), phosphoric acid At least one of a composite material of lithium manganese and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate
  • phosphoric acid At least one of a composite material of lithium manganese and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer preferably further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer preferably further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode film layer preferably further includes a binder.
  • the binder is preferably selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polyformaldehyde At least one of polyacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer preferably also includes a conductive agent.
  • the conductive agent is preferably at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer preferably further includes other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt is preferably selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethanesulfonyl lithium difluorooxalate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent is preferably selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, carbonic acid Butylene, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate , 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone at least one.
  • the electrolyte preferably further includes electrolyte additives.
  • electrolyte additives can include negative electrode film-forming additives, positive electrode film-forming additives, and electrolyte additives that can improve certain performances of secondary batteries, such as electrolyte additives that improve the overcharge performance of secondary batteries, and improve the high temperature of secondary batteries. Or electrolyte additives with low temperature performance, etc.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film is preferably at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 3 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 5 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a case having an accommodation space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 8 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • SBR styrene-butadiene rubber
  • the safety coating slurry prepared above was evenly coated on the surface of the double-sided negative electrode film layer to obtain a safety coating with a thickness of 5 ⁇ m. After the coating is completed, a negative electrode sheet of 76 mm ⁇ 851 mm is obtained by drying, cold pressing, and slitting, and the tabs are welded for use.
  • NCM 811 lithium nickel cobalt manganese oxide
  • conductive agent carbon black conductive agent carbon black
  • binder PVDF solvent N-methylpyrrolidone
  • the positive electrode slurry was uniformly coated on one surface of a positive electrode current collector aluminum foil with a thickness of 10 ⁇ m, dried at 130° C., and cold pressed to obtain a positive electrode sheet with a single positive active material layer thickness of 110 ⁇ m.
  • a positive electrode sheet provided with double-sided positive electrode active material layers.
  • a positive electrode sheet of 74mm ⁇ 867mm is obtained by drying, cold pressing, and cutting, and the tabs are welded for use.
  • ethylene carbonate, ethyl methyl carbonate and diethyl carbonate were mixed at a volume ratio of 1:1:1 to obtain an organic solvent, and then Add lithium salt LiPF 6 into the organic solvent to dissolve and mix evenly to obtain an electrolyte solution with a concentration of 1 mol/L.
  • a polypropylene (PP) film (provided by Celgard) with a thickness of 14 ⁇ m was used.
  • the positive pole piece, separator, and negative pole piece prepared above are stacked in order, so that the separator is placed between the positive pole piece and the negative pole piece, so as to play the role of isolation, and the electrode assembly is obtained by winding. Put the electrode assembly into the aluminum-plastic film casing, remove the water at 80°C, inject the aforementioned electrolyte, and go through the processes of vacuum packaging, standing, chemical formation, and shaping to obtain a secondary battery.
  • Example 7 Except adjusting the kind of additive according to Table 3, all the other are the same as Example 7.
  • Example 12 Except for adjusting the mass ratio of additives and carbon materials according to Table 3, the rest is the same as that of Example 12.
  • a metal lithium sheet was used as a counter electrode, a PP film with a thickness of 14 ⁇ m was selected as a separator, and the electrolyte solution in each embodiment or comparative example was added to assemble a button battery.
  • the actual discharge capacity of the coin cell is C 10 (mAh).
  • the discharge gram capacity C 1 (mAh/g) of the button battery C 0 /W 1
  • the charge gram capacity C 3 (mAh/g) of the button battery 375mAh/g.
  • W 1 is the mass (g) of the negative electrode active material.
  • the mass of the current collector it is obtained by weighing the area of the film layer;
  • Mass energy density (Wh/kg) energy (Wh)/mass (kg).
  • the test temperature is 25°C, charge to 4.4V at 0.7C constant current, charge to 0.025C at constant voltage, and discharge to 3.0V at 0.5C after standing for 5 minutes.
  • the capacity obtained in this step is taken as the initial capacity, and a 0.7C charge/0.5C discharge cycle test is performed, and the capacity at each step is compared with the initial capacity to obtain a capacity decay curve.
  • the room temperature cycle life of the secondary battery is recorded as the number of cycles until the capacity retention rate reaches 90% at 25°C.
  • the secondary batteries of Examples 1-27 when provided with a safety coating, and when the values of Nc/Pc and/or Nd/Pd are within the scope of the application, have achieved good cycle performance, It shows that the lithium dendrites generated during the cycle of the secondary battery did not puncture the secondary battery, thus indicating that the secondary battery has good safety performance. At the same time, the secondary battery also maintains a high energy density.
  • Example 2 and Example 6 when the value of the secondary battery Nc/Pc and Nd/Pd is the same, the safety coating is arranged at the position within the scope of the application, and the secondary battery has good cycle performance and While maintaining safety performance, it can maintain high energy density.
  • the secondary battery is not provided with a safety coating, and the values of Nc/Pc and Nd/Pd are outside the scope of this application, and the energy density, cycle performance and safety performance of the secondary battery are not At the same time, effective improvement was achieved.
  • the type of negative electrode active material usually also affects the performance of the secondary battery. From Example 2 and Examples 7 to 9, it can be seen that the secondary battery whose negative electrode active material is within the scope of the application has good cycle performance and safety performance, and has high energy density.
  • the type of additive also generally affects the performance of the secondary battery. It can be seen from Example 7 and Examples 10 to 14 that the secondary battery with additives within the scope of the present application has high energy density while having good cycle performance and safety performance.
  • the mass ratio of additives and carbon materials also generally affects the performance of secondary batteries. It can be seen from Example 12 and Examples 15-23 that the secondary battery with the mass ratio of additives and carbon materials within the scope of the present application has high energy density while having good cycle performance and safety performance.
  • the thickness of the safety coating usually also affects the performance of the secondary battery. From Example 7 and Examples 24 to 27, it can be seen that the secondary battery with the thickness of the safety coating within the scope of the application has good cycle performance and safety performance, as well as high energy density.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same function and effect are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供了一种二次电池、电池模块、电池包和用电装置，其中，二次电池包括负极极片、正极极片及位于负极极片和正极极片之间的隔离膜；负极极片或隔离膜包括安全涂层；二次电池的充电负极容量Nc与充电正极容量Pc满足：0.45≤Nc/Pc＜1，和/或，二次电池的放电负极容量Nd与放电正极容量Pd满足：0.45≤Nd/Pd＜1。通过对二次电池中Nc/Pc和/或Nd/Pd的大小、以及安全涂层的设置，使二次电池在保持高能量密度的同时，具有良好的循环性能和安全性能。

Description

一种二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电化学领域，具体涉及一种二次电池、电池模块、电池包和用电装置。
背景技术
二次电池，具有储能密度大、开路电压高、自放电率低、循环寿命长、安全性好等优点，广泛应用于电能储存、移动电子设备、电动汽车和航天航空设备等各个领域。随着移动电子设备和电动汽车进入高速发展阶段，市场对二次电池的能量密度、循环性能和安全性能等都提出了越来越高的要求。
但是，二次电池在充放电循环过程中形成的锂枝晶结构，严重影响了二次电池的能量密度、循环性能和安全性能。因此，如何抑制锂枝晶的生长，进而改善二次电池的能量密度、循环性能和安全性能，已成为二次电池在广泛应用的过程中一项亟需解决的重要课题。
发明内容
本申请的目的在于提供一种二次电池、电池模块、电池包和用电装置，以使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
为了达到上述目的，本申请提供了一种二次电池、电池模块、电池包和用电装置。
本申请的第一方面提供了一种二次电池，其包括负极极片、正极极片及位于所述负极极片和所述正极极片之间的隔离膜；所述负极极片或所述隔离膜包括安全涂层；所述二次电池的充电负极容量Nc与充电正极容量Pc满足：0.45≤Nc/Pc＜1，和/或，所述二次电池的放电负极容量Nd与放电正极容量Pd满足：0.45≤Nd/Pd＜1。由此，通过对二次电池中Nc/Pc和/或Nd/Pd的比值的设置、以及安全涂层的设置，使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
在任意实施方式中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层，所述安全涂层设置于所述负极膜层的表面。这样，有效减少了锂枝晶的生成，也能降低锂枝晶刺破隔离膜与正极极片直接接触的可能性。由此，使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
在任意实施方式中，所述安全涂层设置于所述隔离膜朝向所述负极极片的第一表面。这样，有效减少了锂枝晶的生成，也能减少锂枝晶刺破隔离膜与正极极片直接接触的可能性。由此，使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
在任意实施方式中，所述二次电池的充电负极容量Nc与充电正极容量Pc满足：0.5≤Nc/Pc≤0.85。这样，能够有效提高二次电池的能量密度。并且，有效减少了过量锂离子在负极极片表面的沉积，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。
在任意实施方式中，所述二次电池的放电负极容量Nd与放电正极容量Pd满足：0.5≤Nd/Pd≤0.87。这样，能够有效提高二次电池的能量密度。并且，有效减少了过量锂离子在负极极片表面的沉积，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。
在任意实施方式中，所述负极膜层包括负极活性材料，所述负极活性材料包括石墨、硅碳、氧化硅、氧化锡、氧化铁(Fe 3O 4)和氧化钛中的至少一种。这样，锂金属在负极极片表面的沉积减少，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。锂金属与负极活性材料形成复合锂金属材料，提高了二次电池的能量密度。
在任意实施方式中，所述安全涂层包括添加剂和碳材料；所述添加剂包括金、银、镁、铝的金属单质，及银、镁、铝的氧化物、硝酸盐和磷酸盐中的至少一种；所述碳材料包括石墨、石墨烯和碳纳米管中的至少一种。由此，使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
在任意实施方式中，所述添加剂和所述碳材料的质量比为(0.05-100):100，优选为(10-80):100，更优选为(20-50):100。将添加剂和碳材料的质量比调控在上述范围内，能够在不影响二次电池的其他性能(如倍率性能)的同时，减少锂枝晶在负极极片表面的生成，从而使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
在任意实施方式中，所述添加剂包括银、镁、铝的氧化物、硝酸盐和磷酸盐中的至少一种，所述添加剂和所述碳材料的质量比为(0.05-100):100，优选为(15-80):100，更优选为(25-60):100。当添加剂选用上述材料时，将添加剂和材料的质量比调控在上述范围内，更利于缓解负极极片表明的锂枝晶的生成，从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
在任意实施方式中，所述安全涂层的厚度为0.5μm至15μm。将安全涂层调控在上述厚度范围内，锂枝晶在负极极片表面的生成减少，也减少了锂枝晶刺破隔离膜与正极极片直接接触的可能性。从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
在任意实施方式中，所述负极极片包括所述负极集流体以及设置在所述负极集流体至少一个表面上的所述负极膜层，所述安全涂层设置于所述负极膜层的表面，所述安全涂层的厚度为0.5μm至15μm，优选3μm至10μm。将安全涂层调控在上述厚度范围内，锂枝晶在负极极片表面的生成减少，也减少了锂枝晶刺破隔离膜与正极极片直接接触的可能性。从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
在任意实施方式中，所述安全涂层设置于所述隔离膜朝向所述负极极片的第一表面，所述安全涂层的厚度为0.5μm至15μm，优选3μm至10μm。将安全涂层调控在上述厚度范围内，锂枝晶在负极极片表面的生成减少，也减少了锂枝晶刺破隔离膜与正极极片直接接触的可能性。从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
本申请的第二方面提供一种电池模块，包括本申请的第一方面的二次电池。
本申请的第三方面提供一种电池包，包括本申请的第二方面的电池模块。
本申请的第四方面提供一种用电装置，包括选自本申请的第一方面的二次电池、本申请的第二方面的电池模块或本申请的第三方面的电池包中的至少一种。
本申请的有益效果：
本申请提供了一种二次电池、电池模块、电池包和用电装置，其中，二次电池包括负极极片、正极极片及位于负极极片和正极极片之间的隔离膜；负极极片或隔离膜包括安全涂层；二次电池的充电负极容量Nc与充电正极容量Pc满足：0.45≤Nc/Pc＜1，和/或，二次电池的放电负极容量Nd与放电正极容量Pd满足：0.45≤Nd/Pd＜1。通过对二次电池中Nc/Pc和/或Nd/Pd的大小、以及安全涂层的设置，使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
附图说明
图1为本申请一些实施方式的负极极片剖面结构示意图；
图2为本申请另一些实施方式的安全涂层设置位置结构示意图；
图3是本申请一实施方式的二次电池的示意图；
图4是图3所示的本申请一实施方式的二次电池的分解图；
图5是本申请一实施方式的电池模块的示意图；
图6是本申请一实施方式的电池包的示意图；
图7是图6所示的本申请一实施方式的电池包的分解图；
图8是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；10负极集流体；20负极膜层；30安全涂层；51壳体；52电极组件；53盖板；100隔离膜；200负极极片；300正极极片。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及优选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及优选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或 B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
本申请人在研究二次电池的过程中发现，充放电循环过程中负极极片产生的过量锂离子在负极极片表面沉积，易造成二次电池的体积膨胀。并且由于电流密度以及电解液中锂离子浓度的不均匀，使锂离子沉积过程中的某些位点沉积速度过快，形成锂枝晶结构，严重影响二次电池的能量密度和循环性能。而且，随着充放电循环次数的增加，锂枝晶愈发尖锐，极大可能会刺穿隔离膜直接与正极极片接触形成短路，引发严重的安全事故。由此，通过减少锂枝晶在负极极片表面的生成，来改善二次电池的循环性能和安全性能，同时提高二次电池的能量密度，成为本申请人的重点研究方向，以使二次电池应用于用电装置时具有更好的性能，例如更长的续航里程、更久的使用寿命。基于此，本申请提供了一种二次电池、电池模块、电池包和用电装置。
本申请的一个实施方式中，本申请提出了一种二次电池，其包括负极极片、正极极片及位于负极极片和正极极片之间的隔离膜；负极极片或隔离膜包括安全涂层；二次电池的充电负极容量Nc与充电正极容量Pc满足：0.45≤Nc/Pc＜1，和/或，二次电池的放电负极容量Nd与放电正极容量Pd满足：0.45≤Nd/Pd＜1。在本申请中，负极极片也可以为负极，正极极片也可以为正极。
虽然机理尚不明确，但本申请人意外地发现：本申请通过使二次电池的充电负极容量Nc与充电正极容量Pc满足：0.45≤Nc/Pc＜1，和/或，二次电池的放电负极容量Nd与放电正极容量Pd满足：0.45≤Nd/Pd＜1，使正极的可逆容量大于负极的可逆容量，这样，正极相对于负极过量的锂离子，在二次电池充电的过程中，会以锂金属的形式与负极活性材料形成复合锂金属材料，从而有效提高二次电池的能量密度。并且，有效减少了过量锂离子在负极极片表面的沉积，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。同时，负极极片或隔离膜包括安全涂层，使锂离子沉积于安全涂层的下方，安全涂层通过物理阻隔减少锂枝晶在负极极片表面的生成；并且，安全涂层在二次电池充放电过程中能够和锂离子形成合金，进一步减少锂枝晶在负极极片表面的生成。由此，二次电池在具有良好的循环性能和安全性能的同时，能够有效提高其能量密度。
整体而言，本申请提供的二次电池中，负极极片或隔离膜包括安全涂层；以及二次电池的充电负极容量Nc与充电正极容量Pc满足：0.45≤Nc/Pc＜1，和/或，二次电池的放电 负极容量Nd与放电正极容量Pd满足：0.45≤Nd/Pd＜1。使二次电池具有良好的循环性能和安全性能的同时，具有高能量密度。
在本申请中，上述Nc/Pc＜1，和/或，Nd/Pd＜1，是通过以下方式来实现：减少负极活性材料在负极膜层中的占比(k 1)或减少负极极片表面的单位面积的负极膜层的涂布质量(cw 1)；或者增加正极活性材料在正极膜层中的占比(k 2)或增加正极极片表面的单位面积的正极膜层的涂布质量(cw 2)。
在一些实施方式中，负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，安全涂层设置于负极膜层的表面。作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。这里的“表面”可以是负极集流体的全部区域，也可以是负极集流体的部分区域。安全涂层设置于负极膜层的表面是指，安全涂层设置于负极膜层的全部表面。示例性地，如图1所示，负极极片200包括负极集流体10以及设置在负极集流体10相对的两个表面A、B上的负极膜层20，两个安全涂层30各自独立地设置于负极膜层20远离负极集流体10的表面上。安全涂层设置于负极膜层的表面，二次电池在充放电循环过程中，锂离子沉积于安全涂层的下方，即安全涂层与负极膜层相邻的一侧，安全涂层通过物理阻隔减少锂枝晶在负极极片表面的生成，也可以理解为减少锂枝晶在安全涂层靠近正极极片的表面的生成。并且，安全涂层在二次电池充放电过程中能够和锂离子形成合金，进一步减少锂枝晶在负极极片表面的生成。这样，有效减少了锂枝晶的生成，也能降低锂枝晶刺破隔离膜与正极极片直接接触的可能性。由此，二次电池具有良好的循环性能和安全性能的同时，具有高能量密度。
在一些实施方式中，安全涂层设置于隔离膜朝向负极极片的第一表面。示例性地，如图2所示，隔离膜100位于正极极片300和负极极片200之间，安全涂层30设置于隔离膜100朝向负极极片200的第一表面C。二次电池充放电循环过程中，锂离子沉积于安全涂层的下方，即安全涂层与负极极片相邻的一侧，安全涂层通过物理阻隔减少锂枝晶在负极极片表面的生成，并且，安全涂层能够和锂离子形成合金，进一步减少锂枝晶在负极极片表面的生成。这样，有效减少了锂枝晶的生成，也减少了锂枝晶刺破隔离膜与正极极片直接接触的可能性。由此，二次电池具有良好的循环性能和安全性能的同时，具有高能量密度。
在一些实施方式中，二次电池的充电负极容量Nc与充电正极容量Pc满足：0.5≤Nc/Pc ≤0.85。这样，使正极的可逆容量大于负极的可逆容量，由此，正极相对于负极过量的锂离子，在二次电池充电的过程中，会以锂金属的形式与负极活性材料形成复合锂金属材料，从而有效提高二次电池的能量密度。并且，有效减少了过量锂离子在负极极片表面的沉积，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。
在一些实施方式中，二次电池的放电负极容量Nd与放电正极容量Pd满足：0.5≤Nd/Pd≤0.87。这样，使正极的可逆容量大于负极的可逆容量，由此，正极相对于负极过量的锂离子，在二次电池充电的过程中，会以锂金属的形式与负极活性材料形成复合锂金属材料，从而有效提高二次电池的能量密度。并且，有效减少了过量锂离子在负极极片表面的沉积，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。
在一些实施方式中，二次电池的充电负极容量Nc与充电正极容量Pc满足：0.5≤Nc/Pc≤0.85；且二次电池的放电负极容量Nd与放电正极容量Pd满足：0.5≤Nd/Pd≤0.87。这样，使正极的可逆容量远远大于负极的可逆容量，由此，正极相对于负极过量的锂离子，在二次电池充电的过程中，会以锂金属的形式与负极活性材料形成复合锂金属材料，从而有效提高二次电池的能量密度。并且，有效减少了过量锂离子在负极极片表面的沉积，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。
在一些实施方式中，负极膜层包括负极活性材料，负极活性材料包括石墨、硅碳、氧化硅、氧化锡、氧化铁和氧化钛中的至少一种。上述负极活性材料的选用，能够提供给正极脱出的锂一定的储存空间，各负极活性材料颗粒之间的孔隙能够为锂沉积提供空间。这样，锂金属在负极极片表面的沉积减少，使负极极片表面的锂枝晶大大减少，进而也改善了二次电池的循环性能和安全性能。锂金属与负极活性材料形成复合锂金属材料，提高了二次电池的能量密度。
在一些实施方式中，安全涂层包括添加剂和碳材料；添加剂包括金、银、镁、铝的金属单质，及银、镁、铝的氧化物、硝酸盐和磷酸盐中的至少一种；碳材料包括石墨、石墨烯和碳纳米管中的至少一种。碳材料的选用，为锂沉积提供了一定的空间。添加剂的选用，能够有效提高安全涂层，使负极极片表面的电流密度更加均匀，从而使得锂金属能够在负极极片表面均匀沉积，且添加剂能够与锂离子形成合金，进一步缓解负极极片表面的锂枝晶的形成。这样，有效减少了锂枝晶的生成，也能减少锂枝晶刺破隔离膜与正极极片直接接触的可能性。由此，使二次电池具有良好的循环性能和安全性能的同时，提高其能量密度。
在一些实施方式中，添加剂和碳材料的质量比为(0.05-100):100，优选为(10-80):100，更优选为(20-50):100。例如，添加剂和碳材料的质量比为0.05:100、1:100、5:100、10:100、15:100、20:100、30:100、40:100、50:100、60:100、70:100、80:100、90:100、100:100或上述任两个数值范围间的任一数值。添加剂在安全涂层中的含量影响了安全涂层的导电性和添加剂与锂离子形成合金的含量。添加剂在安全涂层中的加入，使安全涂层的导电性提高，也可以与锂离子形成更多的合金，以缓解负极极片表面的锂枝晶的形成。但添加剂的含量过多(例如，添加剂和碳材料的质量比大于100:100)，容易引起短路风险，或者引起负极极片电阻增加，极化增大，将影响二次电池的倍率性能。将添加剂和碳材料的质量比调控在上述范围内，能够在不影响二次电池的其他性能(如倍率性能)的同时，减少锂枝晶在负极极片表面的生成，从而提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
在一些实施方式中，添加剂包括银、镁、铝的氧化物、硝酸盐和磷酸盐中的至少一种，添加剂和碳材料的质量比为(0.05-100):100，优选为(15-80):100，更优选为(25-60):100。例如，添加剂和碳材料的质量比为为0.05:100、1:100、5:100、10:100、15:100、20:100、25:100、30:100、40:100、50:100、60:100、70:100、80:100、90:100、100:100或上述任两个数值范围间的任一数值。氧化物、硝酸盐和磷酸盐相对其金属单质而言，导电性有所差异。当添加剂选用上述材料时，将添加剂和材料的质量比调控在上述范围内，更利于缓解负极极片表明的锂枝晶的生成，从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
在一些实施方式中，安全涂层的厚度为0.5μm至15μm。例如，安全涂层的厚度为0.5μm、1μm、3μm、5μm、7μm、9μm、10μm、11μm、13μm、15μm或上述任两个数值范围间的任一数值。安全涂层的厚度过薄(例如小于0.5μm)，无法发挥出安全涂层的效果；安全涂层的厚度过厚(例如大于15μm)，会使二次电池的能量密度降低、阻抗增加。将安全涂层调控在上述厚度范围内，锂枝晶在负极极片表面的生成减少，也减少了锂枝晶刺破隔离膜与正极极片直接接触的可能性。从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
在一些实施方式中，负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，安全涂层设置于负极膜层的表面，安全涂层的厚度为0.5μm至15μm，优选3μm至10μm。例如，安全涂层的厚度为0.5μm、1μm、3μm、5μm、8μm、10μm、11μm、13μm、 15μm或上述任两个数值范围间的任一数值。将安全涂层调控在上述厚度范围内，锂枝晶在负极极片表面的生成减少，也减少了锂枝晶刺破隔离膜与正极极片直接接触的可能性。从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
在一些实施方式中，安全涂层设置于隔离膜朝向负极极片的第一表面，安全涂层的厚度为0.5μm至15μm，优选3μm至10μm。例如，安全涂层的厚度为0.5μm、1μm、3μm、5μm、8μm、10μm、11μm、13μm、15μm或上述任两个数值范围间的任一数值。将安全涂层调控在上述厚度范围内，锂枝晶在负极极片表面的生成减少，也减少了锂枝晶刺破隔离膜与正极极片直接接触的可能性。从而更利于提高二次电池的能量密度，也使二次电池具有良好的循环性能和安全性能。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正极和负极短路的作用，同时可以使活性离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM 333)、 LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811))、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2))及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还优选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还优选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极膜层还优选地包括粘结剂。所述粘结剂优选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还优选地包括导电剂。导电剂优选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还优选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐优选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂优选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还优选地包括电解液添加剂。例如电解液添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善二次电池某些性能的电解液添加剂，例如改善二次电池过充性能的电解液添加剂、改善二次电池高温或低温性能的电解液添加剂等。
[隔离膜]
本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质优选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图3是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图4，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图5是作为一个示例的电池模块4。参照图5，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
优选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图6和图7是作为一个示例的电池包1。参照图6和图7，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例 如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图8是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
<安全涂层浆料的制备>
将添加剂Ag、碳材料石墨、导电剂碳黑和粘结剂丁苯橡胶(SBR)按照质量比1:96:0.5:2.5分散在去离子水中，在25℃下以800rpm的转速搅拌均匀，即得到安全涂层的浆料。
<负极极片的制备>
将负极活性材料石墨、导电剂碳黑、粘结剂SBR、增稠剂CMC-Na按照质量比97:0.5:1.25:1.25进行混合，加入去离子水作为溶剂，充分搅拌混合均匀后调配成为固含量为60wt％的负极浆料。将负极浆料均匀涂覆在在厚度为8μm的负极集流体铜箔上，110℃条件下烘干，冷压后得到单面负极膜层厚度为100μm的负极极片。之后，在该负极极极片的另一个表面上重复以上步骤，即得到设置有双面负极膜层的负极极片。将上述制备得到的安全涂层浆料分别均匀涂布在双面负极膜层的表面，得到厚度为5μm的安全涂层。涂布完成后，经烘干、冷压、分切得到76mm×851mm的负极极片，并焊接极耳待用。
<正极极片的制备>
将正极活性材料锂镍钴锰氧化物(NCM 811)三元材料、导电剂碳黑、粘结剂PVDF按 照质量比95:2:3进行混合，溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后调配成为固含量为75wt％的正极浆料。将正极浆料均匀涂覆在厚度为10μm的正极集流体铝箔的一个表面上，130℃条件下烘干，冷压后得到单面正极活性材料层厚度为110μm的正极极片。之后，在该正极极片的另一个表面上重复以上步骤，即得到设置有双面正极活性材料层的正极极片。涂布完成后，经烘干、冷压、分切得到74mm×867mm的正极极片，并焊接极耳待用。
<电解液的制备>
在氩气气氛手套箱(H 2O＜0.1ppm，O 2＜0.1ppm)中，将碳酸乙烯酯、碳酸甲乙酯和碳酸二乙酯以体积比1:1:1混合得到有机溶剂，然后向有机溶剂中加入锂盐LiPF 6溶解并混合均匀得到浓度为1mol/L的电解液。
<隔离膜的制备>
采用厚度为14μm的聚丙烯(PP)薄膜(Celgard公司提供)。
<二次电池的制备>
将上述制备得到的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片中间，以起到隔离的作用，卷绕得到电极组件。将电极组件装入铝塑膜壳体中，并在80℃下脱去水分，注入前述电解液，经过真空封装、静置、化成、整形等工序得到二次电池。
实施例2～5
除了按照表1的参数将Nc/Pc和Nd/Pd的数值调整为如表2所示以外，其余与实施例1相同。
实施例6
除了在<负极极片的制备>中不设置安全涂层、在<隔离膜的制备>中，在隔离膜的第一表面均匀涂布安全涂层浆料以外，其余与实施例2相同。
实施例7～9
除了按照表3调整负极活性材料的种类以外，其余与实施例2相同。
实施例10～14
除了按照表3调整添加剂的种类以外，其余与实施例7相同。
实施例15～23
除了按照表3调整添加剂和碳材料的质量比以外，其余与实施例12相同。
实施例24～27
除了按照表3调整安全涂层的厚度以外，其余与实施例7相同。
对比例1～2
除了按照表1的参数将Nc/Pc和Nd/Pd的数值调整为如表2所示且不设置安全涂层以外，其余与实施例2相同。
对比例3
除了按照表1的参数将Nc/Pc和Nd/Pd的数值调整为如表2所示以外，其余与实施例1相同。
另外，将上述实施例1～27和对比例1～3制得的二次电池，进行性能测试。
(1)负极活性材料的充电克容量和放电克容量测试
<扣式电池的制备>
将待测试负极活性材料石墨、导电剂碳黑、粘结剂SBR、增稠剂CMC-Na按照质量比97:0.5:1.25:1.25进行混合，加入去离子水作为溶剂，经过搅拌调配成为固含量为40wt％的浆料，利用刮刀在集流体铝箔上涂覆100μm厚度的涂层，130℃下经过12h真空干燥箱烘干后，利用冲压机在干燥环境中切成直径为1cm的圆片，在手套箱中以金属锂片作为对电极，隔离膜选择厚度为14μm的PP薄膜，加入各实施例或对比例中的电解液组装得到扣式电池。
<充电克容量和放电克容量的测试>
在25℃下，将上述制备得到的扣式电池以0.33C恒流充电至2V，然后以2V恒压充电至电流≤0.05C，然后将扣式电池以0.33C恒流放电至0.05V，记录扣式电池的实际放电容量为C 10(mAh)。扣式电池的放电克容量C 1(mAh/g)＝C 0/W 1，扣式电池的充电克容量C 3(mAh/g)＝375mAh/g。其中，W 1为负极活性材料的质量(g)。
(2)正极活性材料的充电克容量和放电克容量测试
<扣式电池的制备>
将待测试正极活性材料NCM 811三元材料、导电剂碳黑、粘结剂PVDF按照质量比80:10:10进行混合，加入NMP作为溶剂，经过搅拌调配成为固含量为40wt％的浆料，利用刮刀在集流体铝箔上涂覆100μm厚度的涂层，130℃下经过12h真空干燥箱烘干后，利用冲压机在干燥环境中切成直径为1cm的圆片，在手套箱中以金属锂片作为对电极，隔离膜选择厚度为14μm的PP薄膜，加入各实施例或对比例中的电解液组装得到扣式电池。
<充电克容量和放电克容量的测试>
在25℃下，将上述制备得到的扣式电池以0.33C恒流充电至4.25V，然后以3.65V恒压充电至电流≤0.05C，然后将扣式电池以0.33C恒流放电至2.5V，记录扣式电池的实际放电容量为C 20(mAh)。扣式电池的放电克容量C 2(mAh/g)＝C 0/W 2，扣式电池的充电克容量C 4(mAh/g)＝235mAh/g。其中，W 2为正极活性材料的质量(g)。
(3)涂布质量的测试
取单面涂布膜层(正极膜层或负极膜层)的极片(正极极片或负极极片)制成面积为1cm 2的小圆片，取20片小圆片进行称重，涂布质量＝(小圆片的质量－集流体的质量)，取测试平均值即为实施例或对比例中的膜层的涂布质量。
集流体的质量：取膜层区域进行称重得到；
小圆片的质量和集流体的质量：单位(g)。
(4)Nc、Pc、Nd、Pd的计算
Nc＝C 3×k 1×cw 1；Pc＝C 4×k 2×cw 2；Nd＝C 1×k 1×cw 1；Pd＝C 2×k 2×cw 2。
(5)能量密度的测试
在各实施例和对比例的<二次电池的制备>中，除了按照上述<扣式电池的制备>中的浆料配比制备负极浆料和正极浆料以外，其余步骤的制备方法与各实施例和对比例相同，制备得到电量为5Ah的二次电池，电压范围2.5V至4.25V，充放电电流0.33C。
能量(Wh)＝电量(Ah)×平台电压(V)。
质量能量密度(Wh/kg)＝能量(Wh)/质量(kg)。
(6)循环性能的测试
测试温度为25℃，以0.7C恒流充电到4.4V，恒压充电到0.025C，静置5min后以0.5C放电到3.0V。以此步得到的容量为初始容量，进行0.7C充电/0.5C放电进行循环测试，以每一步的容量与初始容量做比值，得到容量衰减曲线。以25℃循环截至到容量保持率为90％的圈数记为二次电池的室温循环寿命。
实施例1～6、对比例1～3的制备参数和性能参数如表1和表2所示，实施例7～27的制备参数和性能参数如表3所示：
表1
Figure PCTCN2022072109-appb-000001
表2
Figure PCTCN2022072109-appb-000002
注：表2中的“\”表示无对应参数。
表3
Figure PCTCN2022072109-appb-000003
根据上述结果可知，实施例1～27的二次电池，当设置有安全涂层，且Nc/Pc和/或Nd/Pd的值在本申请范围之内时，均取得了良好的循环性能，表明二次电池循环过程中生成的锂枝晶没有刺破二次电池，从而说明二次电池具有良好的安全性能。同时，二次电池还保持了高能量密度。
从实施例1～5可以看出，二次电池中选用相同的安全涂层时，将Nc/Pc和Nd/Pd的值 调控于本申请范围内，二次电池在具有良好的循环性能和安全性能的同时，能够保持高能量密度。
从实施例2和实施例6可以看出，二次电池Nc/Pc和Nd/Pd的值相同时，将安全涂层设置于本申请范围内的位置，二次电池在具有良好的循环性能和安全性能的同时，能够保持高能量密度。
而相对于此，对比例1中，二次电池未设置有安全涂层，且Nc/Pc和Nd/Pd的值在本申请范围之外，二次电池的能量密度、循环性能和安全性能未同时取得有效改善。
对比例2中，二次电池的Nc/Pc和Nd/Pd的值在本申请范围内，但其未设置有安全涂层，二次电池的循环性能和安全性能下降，其能量密度、循环性能和安全性能未同时取得有效改善。
对比例3中，二次电池的Nc/Pc和Nd/Pd的值在本申请范围之外，二次电池的能量密度、循环性能和安全性能未同时取得有效改善。
负极活性材料的种类通常也会影响二次电池的性能。从实施例2、实施例7～9可以看出，负极活性材料的种类在本申请范围内的二次电池，在具有良好的循环性能和安全性能的同时，具有高能量密度。
添加剂的种类通常也会影响二次电池的性能。从实施例7、实施例10～14可以看出，添加剂的种类在本申请范围内的二次电池，在具有良好的循环性能和安全性能的同时，具有高能量密度。
添加剂和碳材料的质量比通常也会影响二次电池的性能。从实施例12、实施例15～23可以看出，添加剂和碳材料的质量比在本申请范围内的二次电池，在具有良好的循环性能和安全性能的同时，具有高能量密度。
安全涂层的厚度通常也会影响二次电池的性能。从实施例7、实施例24～27可以看出，安全涂层的厚度在本申请范围内的二次电池，在具有良好的循环性能和安全性能的同时，具有高能量密度。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (13)

  1. 一种二次电池，其包括负极极片、正极极片及位于所述负极极片和所述正极极片之间的隔离膜；所述负极极片或所述隔离膜包括安全涂层；
    所述二次电池的充电负极容量Nc与充电正极容量Pc满足：0.45≤Nc/Pc＜1，和/或，所述二次电池的放电负极容量Nd与放电正极容量Pd满足：0.45≤Nd/Pd＜1。
  2. 根据权利要求1所述的二次电池，其中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面上的负极膜层，所述安全涂层设置于所述负极膜层的表面。
  3. 根据权利要求1所述的二次电池，其中，所述安全涂层设置于所述隔离膜朝向所述负极极片的第一表面。
  4. 根据权利要求1至3中任一项所述的二次电池，其中，所述安全涂层的厚度为0.5μm至15μm，优选3μm至10μm。
  5. 根据权利要求1所述的二次电池，其中，所述二次电池的充电负极容量Nc与充电正极容量Pc满足：0.5≤Nc/Pc≤0.85。
  6. 根据权利要求1或5所述的二次电池，其中，所述二次电池的放电负极容量Nd与放电正极容量Pd满足：0.5≤Nd/Pd≤0.87。
  7. 根据权利要求1所述的二次电池，其中，所述负极膜层包括负极活性材料，所述负极活性材料包括石墨、硅碳、氧化硅、氧化锡、氧化铁和氧化钛中的至少一种。
  8. 根据权利要求1所述的二次电池，其中，所述安全涂层包括添加剂和碳材料；所述添加剂包括金、银、镁、铝的金属单质，及银、镁、铝的氧化物、硝酸盐和磷酸盐中的至少一种；所述碳材料包括石墨、石墨烯和碳纳米管中的至少一种。
  9. 根据权利要求8所述的二次电池，其中，所述添加剂和所述碳材料的质量比为(0.05-100):100，优选为(10-80):100，更优选为(20-50):100。
  10. 根据权利要求8所述的二次电池，其中，所述添加剂包括银、镁、铝的氧化物、硝酸盐和磷酸盐中的至少一种，所述添加剂和所述碳材料的质量比为(0.05-100):100，优选为(15-80):100，更优选为(25-60):100。
  11. 一种电池模块，其包括权利要求1至10中任一项所述的二次电池。
  12. 一种电池包，其包括权利要求11所述的电池模块。
  13. 一种用电装置，其包括选自权利要求1至10中任一项所述的二次电池、权利要求11所述的电池模块或权利要求12所述的电池包中的至少一种。
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