WO2023044934A1 - 二次电池、电池模块、电池包以及用电装置 - Google Patents

二次电池、电池模块、电池包以及用电装置 Download PDF

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WO2023044934A1
WO2023044934A1 PCT/CN2021/121108 CN2021121108W WO2023044934A1 WO 2023044934 A1 WO2023044934 A1 WO 2023044934A1 CN 2021121108 W CN2021121108 W CN 2021121108W WO 2023044934 A1 WO2023044934 A1 WO 2023044934A1
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secondary battery
positive electrode
battery
general formula
electrolyte
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PCT/CN2021/121108
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English (en)
French (fr)
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李丽叶
陈培培
张立美
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宁德时代新能源科技股份有限公司
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Priority to KR1020227030943A priority Critical patent/KR20230046273A/ko
Priority to CN202180087213.0A priority patent/CN116648805A/zh
Priority to JP2022553657A priority patent/JP2024504217A/ja
Priority to PCT/CN2021/121108 priority patent/WO2023044934A1/zh
Priority to EP21925088.3A priority patent/EP4187669A4/en
Priority to US17/943,212 priority patent/US20230104940A1/en
Publication of WO2023044934A1 publication Critical patent/WO2023044934A1/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
    • 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
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • 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
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • 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 technical field of secondary batteries, in particular to a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development and great demand of secondary batteries, higher requirements are put forward for their energy density, cycle performance and safety performance, and there are more expectations for the improvement of their cost performance.
  • the positive electrode in secondary batteries, especially in lithium-ion secondary batteries, during charging and storage, the positive electrode is in a high SOC state, and the interface oxidation activity between the positive electrode and the solvent is very high. After the solvent contacts the positive electrode interface, an oxidative decomposition reaction will occur and It leads to the instability of the structure of the positive electrode material, the reduction of the ability and speed of intercalation and extraction of lithium, and further leads to continuous self-discharge inside the secondary battery cell, which accelerates the life of the secondary battery. In addition, the reaction between the solvent and the positive electrode interface produces gas at the interface It will also lead to an increase in the interface impedance of the positive electrode.
  • the electrolyte and the positive electrode interface are generally physically separated by doping the positive electrode material or various coatings to obtain a stable positive electrode structure.
  • the interface reaction continues to occur, the self-discharge of the battery cell is serious, and the battery life decays rapidly; or due to the small amount of doping or coating material added, the protection is insufficient, resulting in limited improvement in battery performance; or the addition of doping or coating material is sufficient to form Stable interface protective film, but the protective film seriously deteriorates the problem of interface impedance. Therefore, the existing processing technology for cathode materials still needs to be improved.
  • This application is made in view of the above-mentioned technical problems, and its purpose is to provide a battery that reduces the cost of the secondary battery, effectively reduces the self-discharge rate of the battery cell, improves the growth rate of the storage resistance of the battery cell, and has a good discharge rate. capacity-efficient secondary batteries.
  • the inventors of the present application conducted in-depth research and found that the above technical problems can be solved by adjusting the specific metal elements in the positive electrode material of the secondary battery and using specific additives in the electrolyte.
  • the first aspect of the present application provides a secondary battery, including: a positive electrode sheet, a negative electrode sheet and an electrolyte,
  • the positive pole piece comprises a positive active material
  • the content of Co element satisfies: Co ⁇ 0.09
  • the content of Al element satisfies: 500ppm ⁇ Al ⁇ 10000ppm
  • the electrolyte contains a compound represented by the following general formula (I),
  • a 1 to A 4 are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R 1 and R 1 ' are each independently R2 is Wherein R3 is an alkylene or alkyleneoxy group with 1 to 3 carbon atoms.
  • the cost of the positive electrode material can be reduced, and by including Al in the positive electrode active material, and properly adjusting the content of Al, the loss caused by the reduction of the Co content can be reduced.
  • the degree of Li and Ni mixing can improve the structural stability and ion-conducting ability of the positive electrode material.
  • the compound represented by the general formula (I) can be combined with the Al forms a chelate to effectively stabilize the Al element on the surface of the positive electrode material, isolate the interface between the electrolyte and the positive electrode, and reduce interface side reactions, thereby reducing the cost of the secondary battery, effectively reducing the self-discharge rate of the battery cell, and improving the cell. Storage impedance growth rate, and improved rate discharge capacity efficiency of the secondary battery.
  • the mass percentage of the compound of general formula (I) in the electrolyte is 0.01% to 15%, optionally 0.1% to 10%, further optionally 0.5% to 5% %.
  • the reduction of the self-discharge rate of the secondary battery, the reduction of the growth rate of the storage resistance of the battery cell, and the improvement of the rate discharge capacity efficiency can be taken into account in a balanced manner.
  • a 1 to A 4 are each independently a single bond or an alkylene group with 1 to 3 carbon atoms, and may further be a single bond or an alkylene group. methyl.
  • R2 is Wherein R 3 is an alkylene or alkyleneoxy group with 1 or 2 carbon atoms.
  • the formation of chelates between the compound represented by the general formula (I) and Al can effectively stabilize the surface of the positive electrode material, isolate the electrolyte and the positive electrode interface, thereby effectively reducing the self-discharge rate of the battery cell and improving the growth rate of the storage resistance of the battery cell. And improve the rate discharge capacity efficiency of the battery.
  • the compound represented by the general formula (I) is selected from at least one of the following compounds 1-18.
  • the surface of the positive electrode material can be further stabilized, the self-discharge rate of the cell can be reduced, the growth rate of the storage impedance of the cell can be improved, and the rate discharge capacity efficiency can be improved.
  • the Al element content satisfies 1000ppm ⁇ Al ⁇ 10000ppm, and further optionally satisfies 1000ppm ⁇ Al ⁇ 7000ppm.
  • the self-discharge rate of the cell can be further reduced, the growth rate of the storage impedance of the cell can be improved, and the rate discharge capacity efficiency can be improved.
  • the electrolyte also contains at least one element selected from lithium tetrafluoroborate, lithium dioxalate borate, lithium difluorooxalate borate, tris(trimethylsilane) borate other additives.
  • the mass percentage of the total amount of the other additives in the electrolyte is 0.2%-3%.
  • the positive electrode active material has a specific surface area of 0.5-3 m 2 /g, further optionally 0.5-2.5 m 2 /g. In this way, it can balance the needs of rapid transport of lithium ions and control of side reactions on the surface of the positive electrode, and meet the needs of high-rate charge and discharge of the battery.
  • the second aspect of the present application further provides a battery module including the secondary battery according to the first aspect of the present application.
  • the third aspect of the present application also provides a battery pack, which includes the battery module of the second aspect of the present application.
  • a fourth aspect of the present application further provides an electrical device, which includes the secondary battery of the first aspect of the present application, the battery module of the second aspect, or the battery pack of the third aspect.
  • the battery module, battery pack and electric device of the present application include the secondary battery according to the first aspect of the present application, and thus have at least the same or similar technical effects as the above secondary battery.
  • FIG. 1 is a schematic diagram of a secondary battery according to one embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 1 .
  • Fig. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Fig. 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • Fig. 5 is an exploded view of the battery pack according to one embodiment of the present application shown in Fig. 4 .
  • Fig. 6 is a schematic diagram of an electrical device according to an embodiment of the present application.
  • 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 also contemplated. Furthermore, 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, wherein 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 method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may also 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 present application proposes a secondary battery, and as an example, the present application proposes a lithium ion secondary battery.
  • the secondary battery of the present application comprises: a positive electrode sheet, a negative electrode sheet and an electrolyte solution, wherein the positive electrode sheet contains a positive electrode active material, and in the positive electrode active material, the content of Co element satisfies: Co ⁇ 0.09, and the content of Al element Satisfy: 500ppm ⁇ Al ⁇ 10000ppm, in addition, the compound represented by the following general formula (I) is contained in the electrolytic solution,
  • a 1 to A 4 are each independently a single bond or an alkylene group having 1 to 5 carbon atoms, and R 1 and R 1 ' are each independently R2 is Wherein R3 is an alkylene or alkyleneoxy group with 1 to 3 carbon atoms.
  • the cost of positive electrode materials accounts for the highest proportion.
  • the price of cobalt element in the ternary positive electrode is the most expensive and fluctuates greatly, and resources are scarce. Therefore, reducing the content of cobalt element can Significantly reduce the cost of secondary batteries.
  • the Al element on the surface is easy to participate in the reaction during the charge and discharge process, thus failing to achieve the effect of stabilizing the surface of the material.
  • a compound represented by the above general formula (I) in the electrolyte as an additive, the compound can be oriented connected to the Al on the surface of the positive electrode to form a chelate structure when the first charge is made, and the double-ring open rings are connected to each other to form a three-dimensional network structure Covering the surface of the positive electrode particles can effectively stabilize the Al element on the surface of the positive electrode material and isolate the interface between the electrolyte and the positive electrode. This not only improves the surface structure stability and ion conductivity of the positive electrode, but also reduces interface side reactions, greatly reduces the self-discharge rate of the cell, reduces the growth rate of storage impedance, and stabilizes cycle performance.
  • the coordination relationship between the above-mentioned positive electrode active material and the electrolyte proposed by the present application is not limited to a battery structure. When winding, etc.), the coordination relationship is still applicable.
  • the positive electrode sheet includes a positive electrode collector and a positive electrode material arranged on at least one surface of the positive electrode collector.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode material is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode material of the present application includes a positive electrode active material, and the positive electrode active material is selected from materials capable of extracting and intercalating lithium ions.
  • the positive electrode active material can be selected from lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, other cobalt-containing oxide positive electrodes, and the above compounds with lithium iron phosphate, lithium manganese iron phosphate, lithium cobalt oxide, Composite positive electrodes composed of lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, etc.; and one or more of the compounds obtained by adding other transition metals or non-transition metals to the above compounds, but the present invention is not limited to these materials.
  • the content of Co element satisfies: Co ⁇ 0.09. Therefore, the content of Co, which is the most expensive in the ternary positive electrode material, is reduced, the cost of the secondary battery can be reduced, and the cost performance of the secondary battery can be improved.
  • the reduction of Co element will lead to a decrease in the electron conductivity of the ternary cathode material, and it will also increase the mixing phenomenon of Li and Ni, which will reduce the ion transport performance of the cathode material; it will also lead to an irreversible phase change of the cathode material, which will aggravate the fragmentation of the cathode particles.
  • Al element is contained, and the Al element content satisfies: 500ppm ⁇ Al ⁇ 10000ppm.
  • the uniform distribution of Al elements in the bulk phase and surface of the positive electrode active material it not only effectively reduces the degree of Li and Ni mixing caused by the reduction of Co elements, but also improves the structural stability and ion conductivity of the positive electrode material. It can also promote the spherical shape of the positive electrode material to be more uniform, which is conducive to the stress release of the structural change of the positive electrode material during the process of intercalation and delithiation, and further improves the structural stability of the positive electrode material.
  • the Al element on the surface of the positive electrode active material material will react with the compound represented by the above general formula (I) contained in the electrolyte to form a chelate structure when charging for the first time, so that the Al element on the surface of the positive electrode active material material is stabilized, And the formed chelating substance can isolate the interface between the electrolyte and the positive electrode material, thereby further stabilizing the positive electrode material, reducing interface side reactions, greatly reducing the self-discharge rate of the battery cell, reducing the growth rate of storage impedance, and improving cycle stability and battery life.
  • the content of Al element satisfies 1000ppm ⁇ Al ⁇ 10000ppm, optionally satisfies 1000ppm ⁇ Al ⁇ 7000ppm.
  • the structural stability of the positive electrode material can be further improved, the self-discharge rate of the cell can be reduced, the growth rate of the storage impedance can be reduced, and the cycle stability and battery life can be improved.
  • the specific surface area of the positive electrode active material is 0.5 to 3 m 2 /g, optionally 1 to 2.5 m 2 /g. If the specific surface area of the positive electrode active material is too small, the lack of reactive active sites will lead to interfacial lithium ions The transport is slow, and the specific surface area is too large, which will lead to increased side reactions and increase the transport distance of lithium ions at the interface, which is manifested as a significant increase in the charge transfer resistance (Rct).
  • the specific surface area of the positive electrode active material at 0.5-3m 2 /g, it is possible to control the amount of side reactions on the surface of the positive electrode, reduce the impact on the lithium ion transport path and interface impedance, and ensure sufficient active sites on the surface of the positive electrode. Based on the rapid transport performance of the interface of lithium ions, it meets the high-rate charge and discharge requirements of the battery cell.
  • the positive electrode material also optionally includes a conductive agent.
  • a conductive agent there is no specific limitation on the type of conductive agent, which can be selected by those skilled in the art according to actual needs.
  • the conductive agent used for the positive electrode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a metal foil or a composite current collector can be used as the positive electrode 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 Ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates), but the present application is not limited to these Material.
  • PP polypropylene
  • PET polyethylene terephthalic acid Ethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode sheet can be prepared according to methods known in the art.
  • the positive electrode material, conductive agent and binder of the present application can be dispersed in a solvent (such as N-methylpyrrolidone (NMP)) to form a uniform positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector After drying, cold pressing and other processes, the positive electrode sheet is obtained.
  • NMP N-methylpyrrolidone
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece, and contains organic solvents, lithium salts and additives.
  • the electrolyte solution contains a compound represented by the following general formula (I) as an additive.
  • a 1 to A 4 are each independently a single bond or an alkylene group with 1 to 5 carbon atoms, optionally a single bond or an alkylene group with 1 to 3 carbon atoms, and optionally is a single bond or methylene;
  • R 1 , R 1 ' are independently R2 is
  • R 3 is an alkylene or alkyleneoxy group with 1 to 3 carbon atoms, optionally an alkylene or alkyleneoxy group with 1 or 2 carbon atoms.
  • the compound represented by the above general formula (I) can be orientedly connected to Al on the surface of the positive electrode to form a chelate structure during the first charge, and at the same time, the bicyclic rings of the compound are connected to each other to form a three-dimensional network
  • the carbon-like structure covers the surface of the positive electrode particles, which can effectively stabilize the Al element on the surface of the positive electrode material, and isolate the interface between the electrolyte and the positive electrode, thereby not only improving the stability of the positive electrode surface structure and ion-conducting ability, but also reducing interface side reactions and cell self-discharge
  • the rate is greatly reduced, the growth rate of storage impedance is reduced, the cycle stability of the battery is improved, and the rate discharge capacity efficiency is improved.
  • the compound represented by the general formula (I) is selected from at least one of the following compounds 1-18.
  • the mass percentage of the compound represented by general formula (I) in the electrolyte is 0.01%-15%, preferably 0.1%-10%, more preferably 0.5%-5%.
  • the introduction of the compound represented by the general formula (I) can stabilize the Al on the surface of the positive electrode, ensuring that Al exerts its ability to inhibit the mixing of Li and Ni, and stabilize the Positive electrode material structure and the effect of improving ion conduction ability;
  • the chelation of the compound shown in general formula (I) and Al can also promote the uniform distribution of the compound on the surface of the positive electrode, and the compound itself is ring-opened and cross-linked to form a network structure, Thereby further protecting the positive electrode interface and reducing interface side reactions.
  • the type of lithium salt contained in the electrolyte solution of the present application is not particularly limited, and can be selected according to actual needs.
  • the lithium salt may be selected from LiN(C x F 2x +1SO 2 )(C y F 2y +1SO 2 ), LiPF 6 , LiBF 4 , LiBOB, LiAsF 6 , Li(FSO 2 ) 2 N, LiCF 3 SO 3 and one or more of LiClO 4 , where x and y are natural numbers.
  • the organic solvent contained in the electrolyte solution of the present application can be selected according to actual needs, specifically, it can include one or more of chain carbonates, cyclic carbonates, and carboxylates. Among them, the types of chain carbonates, cyclic carbonates, and carboxylates are not specifically limited, and can be selected according to actual needs.
  • the organic solvent in the electrolyte may include diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, ethylene propyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, One or more of ⁇ -butyrolactone, methyl formate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, methyl propionate, tetrahydrofuran.
  • the electrolytic solution of the present application may further contain as other additives selected from cyclic carbonate compounds containing unsaturated bonds, halogen-substituted cyclic carbonate compounds, sulfite compounds, sulfonic acid internal At least one of ester compound, disulfonic acid compound, nitrile compound, aromatic compound, isocyanate compound, phosphazene compound, cyclic acid anhydride compound, phosphite compound, phosphate compound, borate compound, carboxylate compound. Therefore, the performance of the secondary battery may be further improved, for example, the self-discharge rate of the secondary battery may be further reduced, the growth rate of storage resistance may be reduced, and the like.
  • the negative electrode sheet can include a negative electrode current collector and a negative electrode material layer that is arranged on the negative electrode current collector and contains the negative electrode active material.
  • the negative electrode material layer can be arranged on one of the surfaces of the negative electrode current collector or can be provided on both surfaces of the negative electrode collector.
  • the type of negative electrode active material is not subject to specific restrictions, preferably selected from graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fibers, carbon nanotubes, elemental silicon, silicon oxide compounds, silicon-carbon composites, titanic acid One or more of lithium.
  • the negative electrode material layer in the present application may also include a conductive agent, a binder and other optional additives, wherein the types and contents of the conductive agent and the binder are not specifically limited, and may be selected according to actual needs.
  • the negative electrode material layer is usually formed by coating and drying the negative electrode slurry.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material and optional conductive agent and binder in a solvent and stirring them evenly.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water.
  • the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), One or more of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • Other optional additives are, for example, thickeners (such as sodium carboxymethylcellulose (CMC-Na) and the like.
  • the type of the negative electrode current collector is not specifically limited, and can be selected according to actual needs.
  • the negative electrode current collector can be metal foil or 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, polyethylene terephthalate ester, polybutylene terephthalate, polystyrene, polyethylene, etc.)
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive pole piece and the negative pole piece to play the role of isolation.
  • 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 can be selected from more than one of 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 bag may be plastic, and examples of plastic include polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • FIG. 1 shows a square-shaped secondary battery 5 as an example.
  • the outer package may include a housing 51 and a top cover assembly 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 casing 51 has an opening communicating with the accommodating cavity, and the top cover assembly 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. 3 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 also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack 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 more than one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack provided in the present application can be used as a power source of the device, and can also be used as an energy storage unit of the device.
  • the electrical device of the present application can be, but not limited to, 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, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • secondary batteries, battery modules, or battery packs can be selected according to their usage requirements.
  • Figure 6 is an example device.
  • the device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • battery packs or battery modules can 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.
  • the positive electrode active material Add the positive electrode active material, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) into the solvent N-methylpyrrolidone (NMP) in a weight ratio of 94:3:3, and mix uniformly to obtain the positive electrode slurry.
  • the positive electrode slurry is coated on the positive electrode current collector aluminum foil, and after drying, cold pressing, slitting and other processes, the positive electrode sheet is obtained.
  • the structural formula and element content of the positive electrode active material are shown in Table 1.
  • Negative electrode slurry is obtained after uniform mixing in ionized water, and the negative electrode slurry is coated on the negative electrode current collector copper foil, and the negative electrode sheet is obtained through drying, cold pressing, slitting and other processes.
  • a polypropylene film was used as the separator.
  • Capacity retention (%) of the secondary battery after 1000 cycles at 45°C (discharge capacity of the 1000th cycle/discharge capacity of the first cycle) ⁇ 100%.
  • Comparing Comparative Example 1, Comparative Example 2 and 6, it can be known that only reducing the content of Co element to reduce the cost of the positive electrode material but without Al element in the positive electrode material will increase the self-discharge rate and storage resistance of the secondary battery Even if the additive vinylene carbonate (VC), which inhibits the reduction of the electrolyte solvent, is added to the electrolyte, the performance of the secondary battery cannot be improved very well.
  • VC vinylene carbonate
  • Comparative Example 2 and Comparative Example 3 it can be seen that by including Al element in the positive electrode material with reduced Co element content, the self-discharge rate and storage resistance growth rate can be reduced to a certain extent and the post-storage rate can be improved. discharge capacity efficiency.
  • Al element can reduce the mixing of Li and Ni caused by the reduction of Co content, improve the structural stability of the positive electrode material, and thus improve the performance of the secondary battery to a certain extent.
  • the Al element on the surface is easy to participate in the reaction during the charge and discharge process, so that the effect of completely stabilizing the surface of the material cannot be achieved.
  • the compound shown in the above general formula (I) as an additive in the electrolyte, the compound can be oriented connected to the Al on the surface of the positive electrode to form a chelate structure when the first charge is made, and the double rings of the compound are connected to each other at the same time.
  • a three-dimensional network structure covers the surface of the positive electrode particles, which can effectively stabilize the Al element on the surface of the positive electrode material and isolate the interface between the electrolyte and the positive electrode, thereby not only improving the stability of the positive electrode surface structure and ion-conducting ability, but also reducing interface side reactions.
  • the core self-discharge rate is greatly reduced, the growth rate of storage impedance is reduced, the battery cycle stability is improved, and the rate discharge capacity efficiency is improved.
  • the amount of Al added continues to increase beyond a certain range, many inactive sites are formed in the positive electrode material, thereby limiting the internal conduction and diffusion of lithium ions, which deteriorates the ion-conducting ability of the positive electrode material and leads to the comprehensive degradation of the secondary battery. Performance drops.
  • the amount of Al added is in the preferred range of 1000-7000, the self-discharge rate of the secondary battery is ⁇ 150mV/h, the growth rate of storage impedance is ⁇ 70%, the rate discharge capacity efficiency is >93%, and the overall performance is particularly excellent.
  • Examples 4 and 7-11 illustrates the effect of adjusting the specific surface area of the positive electrode material on the performance of the secondary battery.
  • the specific surface area of the positive electrode material gradually increases, the self-discharge rate also shows a gradually increasing trend. This is because the specific surface area directly affects the degree of interface side reactions. The larger the specific surface area, the more side reactions, and the corresponding increase in the self-discharge rate. After storage, the impedance growth and the rate discharge capacity efficiency show a trend of improvement first and then deterioration.
  • various compounds represented by the general formula (I) can achieve the same degree of performance improvement.
  • the compound represented by the general formula (I) together with lithium difluorooxalate borate (LiODFB) or fluoroethylene carbonate (FEC), three-dimensional ion channels can be formed on the surface of the positive electrode, and side reactions at the negative electrode interface can be reduced. It has better performance improvement effect.
  • LiODFB lithium difluorooxalate borate
  • FEC fluoroethylene carbonate
  • 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 solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects 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

本申请提供了一种降低了电池材料成本，同时有效降低了电芯自放电率，并改善了电芯存储阻抗性能的二次电池，该二次电池包含正极极片、负极极片和电解液，其中，正极极片包含正极活性材料，正极活性材料中，Co元素的含有率满足：Co≤0.09，且Al元素含量满足：500ppm≤Al≤10000ppm；电解液包含下述通式（Ⅰ）所示的化合物。

Description

二次电池、电池模块、电池包以及用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展并且需求极大，因此对其能量密度、循环性能和安全性能等也提出了更高的要求，而且对其性价比的提高也有更多期待。
另外，在二次电池中，尤其是在锂离子二次电池中，在充电保存时，正极处于高SOC状态，正极与溶剂的界面氧化活性很高，溶剂接触正极界面后会发生氧化分解反应并导致正极材料结构不稳定、嵌脱锂的能力和速度降低，并进一步导致二次电池电芯内部持续自放电、加速二次电池寿命衰减，另外，溶剂和正极界面的反应在界面处产生的气体也会导致正极界面阻抗增加等。
现有技术中一般是通过对正极材料进行掺杂或各种包覆将电解液与正极界面进行物理隔离以获得稳定的正极结构，但是这些技术中依然存在由于包覆层容易破碎而一旦破碎会导致界面反应继续发生，电芯自放电严重，电池寿命极速衰减；或者由于掺杂或包覆物质加入量少，保护不足，导致电池性能改善有限；或者掺杂或包覆物质加入量虽足以形成稳定的界面保护膜，但保护膜严重恶化界面阻抗的问题。因此，现有的对正极材料的处理技术仍有待改进。
发明内容
本申请是鉴于上述技术问题而进行的，其目的在于，提供一种一种兼顾降低二次电池的成本，并且有效降低电芯自放电率，改善电芯存储阻抗增长 率，具有良好的倍率放电容量效率的二次电池。
为了达到上述目的，本申请发明人进行了深入研究，结果发现通过对二次电池的正极材料中特定的金属元素进行调节，并在电解液中配合使用特定的添加剂，可以解决上述技术问题。
本申请的第一方面提供了一种二次电池，其中，包含：正极极片、负极极片和电解液，
所述正极极片包含正极活性材料，
所述正极活性材料中，Co元素的含有率满足：Co≤0.09，且Al元素含量满足：500ppm≤Al≤10000ppm，
所述电解液包含下述通式(Ⅰ)所示的化合物，
Figure PCTCN2021121108-appb-000001
通式(I)中，A 1～A 4分别单独地为单键或碳原子数1～5的亚烷基，R 1、R 1’分别单独地为
Figure PCTCN2021121108-appb-000002
R 2为
Figure PCTCN2021121108-appb-000003
Figure PCTCN2021121108-appb-000004
其中R 3为碳原子数1～3的亚烷基或亚烷氧基。
由此，本申请发明中通过减少正极活性材料中的Co的含量，可以降低正极材料的成本，通过在正极活性材料中包含Al，并且适当调节Al的含量，可以减少由于Co含量的减少导致的Li、Ni混排程度，提高正极材料的结构稳定性和导离子能力，进一步通过在电解液中包含上述通式(Ⅰ)所示的化合物，可以通过该通式(Ⅰ)所示的化合物与Al形成螯合物而有效稳定正极材料表面的Al元素，并隔离电解液和正极界面，减少界面副反应，从而可以得到兼顾降低二次电池的成本，有效降低电芯自放电率，改善电芯存储阻抗增长率，并提高了倍率放电容量效率的二次电池。
在任意实施方式中，所述通式(I)的化合物在所述电解液中的质量百分含量为0.01％～15％，可选为0.1％～10％，进一步可选为0.5％～5％。
由此，可以平衡地兼顾二次电池的自放电率的降低、电芯存储阻抗增长 率的降低以及倍率放电容量效率的提高。
在任意实施方式中，可选地，所述通式(I)中，A 1～A 4分别单独地为单键或碳原子数1～3的亚烷基，进一步可选为单键或亚甲基。可选地，R 2为
Figure PCTCN2021121108-appb-000005
其中R 3为碳原子数为1或2的亚烷基或亚烷氧基。
由此，通过通式(Ⅰ)所示的化合物与Al形成螯合物可以有效稳定正极材料表面，隔离电解液和正极界面，从而有效降低电芯自放电率，改善电芯存储阻抗增长率，并提高电池的倍率放电容量效率。
另外，在任意实施方式中，该通式(I)所示的化合物选自如下化合物1-18中的至少一种。
Figure PCTCN2021121108-appb-000006
Figure PCTCN2021121108-appb-000007
由此，可以进一步稳定正极材料表面，降低电芯自放电率，改善电芯存储阻抗增长率，并提高倍率放电容量效率。
在任意实施方式中，可选地，Al元素含量满足1000ppm≤Al≤10000ppm，进一步可选地满足1000ppm≤Al≤7000ppm。
由此，可以进一步降低电芯自放电率，改善电芯存储阻抗增长率，并提高倍率放电容量效率。
另外，在任意实施方式中，所述正极活性材料的通式为：LiNi zMn yCo xAl aO 2，其中x≤0.09，0.0005≤a≤0.01，0.5＜z＜1，0＜y＜0.4，x+y+z+a＝1。由此，可以得到兼顾降低二次电池的成本和提高正极材料的结构稳定性和导离子能力。
在任意实施方式中，可选的，所述电解液还含有选自四氟硼酸锂、二草酸硼酸锂、二氟草酸硼酸锂、三(三甲基硅烷)硼酸酯中的至少一种的其它添加剂。可选的，所述其它添加剂的总量在所述电解液中的质量百分含量为0.2％～3％。由此，可以进一步降低电芯自放电率，改善电芯存储阻抗增长率，并提高倍率放电容量效率。
在任意实施方式中，可选的，所述正极活性材料的比表面积为0.5～3m 2/g，进一步可选为0.5～2.5m 2/g。由此可以平衡满足锂离子的快速传输和控制正极表面副反应的需求，满足电芯的高倍率充放电需求。
本申请的第二方面还提供一种电池模块，其包括本申请第一方面的二次电池。
本申请的第三方面还提供一种电池包，其包括本申请第二方面的电池模块。
本申请的第四方面还提供一种用电装置，其包括本申请第一方面的二次电池、第二方面的电池模块或者第三方面的电池包。
本申请的电池模块、电池包和用电装置包括本申请第一方面的二次电池，因而至少具有与上述二次电池相同或类似的技术效果。
附图说明
图1是本申请一个实施方式的二次电池的示意图。
图2是图1所示的本申请一个实施方式的二次电池的分解图。
图3是本申请一个实施方式的电池模块的示意图。
图4是本申请一个实施方式的电池包的示意图。
图5是图4所示的本申请一个实施方式的电池包的分解图。
图6是本申请一个实施方式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；51壳体；52电极组件；53顶盖组件
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、电池包和电学装置的实施方式。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，除非有其它说明，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可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可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，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
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它组分，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)。
本申请的一个实施方式中，本申请提出了一种二次电池，作为一例，本申请提出了一种锂离子二次电池。
[二次电池]
本申请的二次电池包含：正极极片、负极极片和电解液，其中，正极极片包含正极活性材料，在正极活性材料中，Co元素的含有率满足：Co≤0.09，且Al元素含量满足：500ppm≤Al≤10000ppm，另外，在电解液中包含下述通式(Ⅰ)所示的化合物，
Figure PCTCN2021121108-appb-000008
通式(I)中，A 1～A 4分别单独地为单键或碳原子数1～5的亚烷基，R 1、 R 1’分别单独地为
Figure PCTCN2021121108-appb-000009
R 2为
Figure PCTCN2021121108-appb-000010
Figure PCTCN2021121108-appb-000011
其中R 3为碳原子数1～3的亚烷基或亚烷氧基。
申请人意外地发现，通过降低二次电池的正极活性材料中Co元素的含量，并且含有适量的Al元素，进一步在电解液中包含通式(I)所示的化合物，从而能够得到兼顾了降低二次电池的成本，并且有效降低电芯自放电率，改善电芯存储阻抗增长率，具有良好的倍率放电容量效率的二次电池。
虽然机理尚不明确，但申请人认为如下。
由于二次电池的组成中，正极材料的成本占比最高，以锂离子二次电池为例，其三元正极中钴元素的价格最贵且波动大，而且资源稀缺，因此降低钴元素含量能够大幅降低二次电池的成本。但另一方面，降低了钴元素含量不仅会降低三元正极材料的导电子能力，还会增加Li、Ni混排现象，制约锂离子的固相迁移和扩散，降低正极材料的离子传输性能；而且Li、Ni混排还会导致正极材料的不可逆相变，加剧正极颗粒破碎并暴露很多新鲜表面，于是正极活性材料与电解液在正极材料与电解液的界面持续发生副反应，导致电芯内部持续自放电，阻抗显著增加。
为此通过在正极活性材料合成中引入Al元素，并实现Al元素在体相和表面的均匀分布，从而不仅有效减少了Li、Ni混排程度，提高了正极材料的结构稳定性和导离子能力，还能促进正极材料的成球形貌更均匀，有利于正极材料在嵌脱锂过程中结构变化的应力释放，进一步提高正极材料的结构稳定性。
但是由于正极材料表面的成键不饱和结构不稳定，表面的Al元素容易在充放电过程中参与反应，从而达不到稳定材料表面的作用。而通过在电解液中配合含有上述通式(I)表示的化合物作为添加剂，从而首次充电时该化合物可与正极表面的Al定向连接形成螯合结构，同时双环开环相互连接成三维网状结构覆盖在正极颗粒表面，可有效稳定正极材料表面的Al元素，并隔离电解液和正极界面。这样不仅提高正极表面结构稳定性和导离子能力，还能减少界面副反应，电芯自放电率大幅降低，存储阻抗增长率减少，循环性能稳定。
本申请提出的上述正极活性材料与电解液的配合关系并不仅限于适用于一种电池结构，当因为其它需求改变电池外包装、电池的形状、改变电剂组件的组装方式(如叠片、卷绕等)等时，该配合关系仍适用。
[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材料。
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，正极材料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。
本申请的正极材料包含正极活性材料，正极活性材料选自能够脱出和嵌入锂离子的材料。具体地，所述正极活性材料可选自锂镍钴锰氧化物、锂镍钴铝氧化物、其它含钴氧化物正极，以及上述化合物与磷酸铁锂、磷酸锰铁锂、锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍锰氧化物等组成的复合正极；以及上述化合物添加其它过渡金属或非过渡金属得到的化合物中的一种或几种，但本发明并不限定于这些材料。
在本申请的正极活性材料中，Co元素的含有率满足：Co≤0.09。由此，降低了三元正极材料中价格最为昂贵的Co的含量，能够降低二次电池的成本，提高二次电池的性价比。但是Co元素的减少会导致三元正极材料的导电子能力降低，还会增加Li、Ni混排现象，降低正极材料的离子传输性能；而且还会导致正极材料的不可逆相变，加剧正极颗粒破碎并暴露很多新鲜表面，使正极活性材料与电解液在正极材料与电解液的界面持续发生副反应，导致电芯内部持续自放电，阻抗显著增加。
为此，在本申请的正极活性材料中，含有Al元素，并且Al元素含量满足：500ppm≤Al≤10000ppm。通过控制实现Al元素在正极活性材料的体相和表面的均匀分布，不仅有效减少上述由于Co元素的减少所带来的Li、Ni混排程度，提高正极材料的结构稳定性和导离子能力，还能促进正极材料的成球形貌更均匀，有利于正极材料在嵌脱锂过程中结构变化的应力释放，进一步提高正极材料的结构稳定性。
进一步，正极活性物质材料表面的Al元素会在首次充电时与电解液中所含的上述通式(I)所表示的化合物反应形成螯合结构，从而正极活性物质材料表面的Al元素被稳定，并且所形成的螯合物质能够隔离电解液和正极材料 界面，从而进一步稳定正极材料，减少界面副反应，电芯自放电率大幅降低，存储阻抗增长率减少，可提高循环稳定性和电池寿命。
在一些实施方式中，正极活性物质中，Al元素含量满足1000ppm≤Al≤10000ppm，可选地满足1000ppm≤Al≤7000ppm。由此，可进一步提高正极材料的结构稳定性，降低电芯自放电率，减少存储阻抗增长率，提高循环稳定性和电池寿命。
在一些实施方式中，正极活性材料的通式为：LiNi zMn yCo xAl aO 2，其中x≤0.09，0.0005≤a≤0.01，0.5＜z＜1，0＜y＜0.4，x+y+z+a＝1。由此，能够得到结构稳定的正极活性材料，降低电芯自放电率，减少存储阻抗增长率，提高循环稳定性和电池寿命。
在一些实施方式中，正极活性材料的比表面积为0.5～3m 2/g，可选为1～2.5m 2/g，正极活性材料的比表面积过小，反应活性位点不足会导致界面锂离子传输缓慢，比表面积过大又会导致副反应增加，增加锂离子在界面传输距离，表现为电荷传递电阻(Rct)显著增大。通过将正极活性材料的比表面积控制在0.5～3m 2/g，既可以控制正极表面副反应的量，减少对锂离子传输路径和界面阻抗的影响，又能保证正极表面足够的活性位点用于锂离子的界面快速传输性能，满足电芯的高倍率充放电需求。
在一些实施方式中，正极材料还可选地包括导电剂。但对导电剂的种类不做具体限制，本领域技术人员可以根据实际需求进行选择。作为示例，用于正极材料的导电剂可以选自超导碳、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一种以上。
本申请的二次电池中，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，但本申请并不限定于这些材料。
本申请中可按照本领域已知的方法制备正极极片。作为示例，可以将本申请的正极材料、导电剂和粘结剂分散于溶剂(例如N-甲基吡咯烷酮(NMP)) 中，形成均匀的正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，得到正极极片。
[电解液]
电解液在正极极片和负极极片之间起到传导离子的作用，包含有机溶剂、锂盐和添加剂。
本申请中，电解液中作为添加剂包含下述通式(I)所示的化合物。
Figure PCTCN2021121108-appb-000012
通式(I)中，A 1～A 4分别单独地为单键或碳原子数1～5的亚烷基，可选地为单键或碳原子数1～3的亚烷基，可选地为单键或亚甲基；R 1、R 1’分别单独地为
Figure PCTCN2021121108-appb-000013
R 2为
Figure PCTCN2021121108-appb-000014
Figure PCTCN2021121108-appb-000015
其中R 3为碳原子数1～3的亚烷基或亚烷氧基，可选地为碳原子数为1或2的亚烷基或亚烷氧基。
通过在电解液中配合使用上述通式(I)所示的化合物作为添加剂，首次充电时该化合物可与正极表面的Al定向连接形成螯合结构，同时该化合物的双环开环相互连接成三维网状结构覆盖在正极颗粒表面，可有效稳定正极材料表面的Al元素，并隔离电解液和正极界面，从而不仅提高正极表面结构稳定性和导离子能力，还能减少界面副反应，电芯自放电率大幅降低，存储阻抗增长率减少，电池循环稳定性提高，倍率放电容量效率提高。
在一些实施方式中，该通式(I)所示的化合物选自如下化合物1～18中的至少一种。
Figure PCTCN2021121108-appb-000016
Figure PCTCN2021121108-appb-000017
由此能够更好地提高正极表面结构稳定性，降低电芯自放电率，减少存储阻抗增长率，并提高倍率放电容量效率。
在任意实施方式中，通式(I)所示的化合物在电解液中的质量百分数为0.01％～15％，优选为0.1％～10％，进一步优选为0.5％～5％。通过将通式(I)所示的化合物的含量范围控制在上述范围内，能够通过通式(I)所示的化合物的引入稳定正极表面的Al，保证Al发挥抑制Li、Ni混排、稳定正极材料结构及改善导离子能力的作用；另外通式(I)所示的化合物与Al的螯合还能促进该化合物在正极表面均匀分布，并且该化合物自身开环交联形成网状结构，从而进一步保护正极界面，减少界面副反应。
本申请的电解液中包含的锂盐的种类没有特别的限制，可根据实际需求 进行选择。具体地，锂盐可选自LiN(C xF 2x+1SO 2)(C yF 2y+1SO 2)、LiPF 6、LiBF 4、LiBOB、LiAsF 6、Li(FSO 2) 2N、LiCF 3SO 3以及LiClO 4中的一种或几种，其中，x、y为自然数。
本申请的电解液中包含的有机溶剂可根据实际需求进行选择，具体地，可包括链状碳酸酯、环状碳酸酯、羧酸酯中的一种或几种。其中，链状碳酸酯、环状碳酸酯、羧酸酯的种类没有具体的限制，可根据实际需求进行选择。可选地，电解液中的有机溶剂可包括碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、γ-丁内酯、甲酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸甲酯、四氢呋喃中的一种或几种。
在一些实施方式中，本申请的电解液中还可进一步包含作为其它添加剂的选自含有不饱和键的环状碳酸酯化合物、卤素取代的环状碳酸酯化合物、亚硫酸酯化合物、磺酸内酯化合物、二磺酸化合物、腈化合物、芳香化合物、异氰酸酯化合物、磷腈化合物、环状酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、硼酸酯化合物、羧酸酯化合物中的至少一种。由此可能进一步提高二次电池的性能，例如进一步降低二次电池的自放电率、减小存储阻抗增长率等。
[负极极片]
在本申请的二次电池中，负极极片可包括负极集流体以及设置于负极集流体上且包含负极活性材料的负极材料层，负极材料层可设置在负极集流体的其中一个表面上也可以设置在负极集流体的两个表面上。负极活性材料的种类并不受到具体的限制，优选可选自石墨、软碳、硬碳、中间相碳微球、碳纤维、碳纳米管、单质硅、硅氧化合物、硅碳复合物、钛酸锂中的一种或几种。
本申请中的负极材料层还可包括导电剂、粘结剂以及其它可选助剂，其中，导电剂以及粘结剂的种类和含量不受具体的限制，可根据实际需求进行选择。负极材料层通常是由负极浆料涂布干燥而成的。负极浆料涂通常是将负极活性材料以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤 维中的一种以上。作为示例，粘结剂可选自丁苯橡胶(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)中的一种以上。其它可选助剂例如是增稠剂(如羧甲基纤维素钠(CMC-Na)等。
负极集流体的种类也不受具体的限制，可根据实际需求进行选择。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、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等的基材)上而形成。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。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，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种以上。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液。
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(PP)、聚对苯二甲酸丁二醇酯(PBT)以及聚丁二酸丁二醇酯(PBS)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、方形或其它任意的形状。例如，图1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2，外包装可包括壳体51和顶盖组件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，顶盖组件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。
另外，以下适当参照附图对本申请的二次电池、电池模块和电池包进行说明。
[电池模块]
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3是作为一个示例的电池模块4。参照图3，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，也可以按照其它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。
可选地，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。
[电池包]
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本领域技术人员可以根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图4和图5，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。
[用电装置]
另外，本申请还提供一种用电装置，该用电装置包括本申请提供的二次电池、电池模块、或电池包中的一种以上。本申请提供的二次电池、电池模块、或电池包可以用作所述装置的电源，也可以用作所述装置的能量存储单元。本申请的用电装置可以但不限于是移动设备(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。
作为用电装置，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6是作为一个示例的装置。该装置为纯电动车、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，结合实施例，进一步阐述本发明。应理解，这些实施例仅用于说明本发明而不用于限制本发明的范围。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1～24和比较例1～6
按照下述方法制备实施例1～24和比较例1～6的二次电池。
(1)正极极片的制备
将正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比94:3:3加入溶剂N-甲基吡咯烷酮(NMP)中，混合均匀后得到正极浆料，将正极浆料涂覆在正极集流体铝箔上，经过烘干、冷压、分切等工序，得到正极极片。其中，正极活性材料结构式和元素含量如表1所示。
(2)负极片的制备
将作为负极活性物质的人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比95:2:2:1加入到溶剂去离子水中，混合均匀后得到负极浆料，将负极浆料涂覆在负极集流体铜箔上，经过烘干、冷压、分切等工序得到负极极片。
(3)电解液的制备
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂EC/EMC按照体积比3/7混合均匀，加入1mol/L LiPF 6锂盐溶解于有机溶剂中，加入表 1中所示种类和数量的通式(I)所示的化合物或其它添加剂，搅拌均匀得到电解液。
(4)隔离膜的制备
使用聚丙烯膜作为隔离膜。
(5)二次电池的制备
将正极极片、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之间，然后卷绕得到电极组件；将电极组件置于电池壳体中，干燥后注入电解液，再经过化成、静置等工艺制得二次电池。
【正极材料相关参数测试】
1)Al元素含量测试
从正极极片上取2g干燥后的正极材料粉体，用王水(H 2SO 4：HNO 3＝1：1)完全溶解之后，参照标准EPA 6010D-2018进行测试，具体数值参照表1。
2)比表面积S的测试
用刮刀从正极极片上刮取正极材料，参照标准GB/T 19587-2004进行测试，具体数值参照表1。
【电池性能测试】
1、二次电池自放电率测试
在25℃下，将二次电池以0.33C恒流充电至4.35V，然后以4.35V恒压充电至电流小于0.05C，再0.33C恒流放电至2.8V。进行一次充放电后，将二次电池再用0.33C恒流充电至4.35V，并以4.35V恒压充电至电流小于0.05C。静置5min后测量初始电压V1(mV)，将二次电池放置于60℃烘箱中48h，取回恢复至常温后测量二次电池电压V2(mV)。二次电池自放电率K采用公式K＝(V2-V1)/48进行计算(单位mV/h)。
2、存储阻抗增长率测试
将二次电池按0.33C恒流充电至4.35V并恒压充电至电流小于0.05C，静置5min后测量初始电压V1，用4C电流对二次电池进行放电15s，测得放电后电压V3，二次电池初始阻抗R1采用公式R1＝(V3-V1)/4C进行计算(单位Ω)。将二次电池放置于60℃烘箱中1个月，取出恢复至常温后按R1的测试方法测得存储后二次电池阻抗R2，存储阻抗增长率ΔR＝R2/R1×100％。
3、存储后倍率放电容量效率测试
将测试2中存储后的二次电池按1C恒流充电至4.35V并恒压充电至电流小于0.05C，然后将二次电池以1C恒流放电至2.8V，得到1C放电容量Q1；将二次电池再按1C恒流充电至4.35V并恒压充电至电流小于0.05C，然后将二次电池以3C恒流放电至2.8V，得到3C放电容量Q3，按照式子Q3/Q1×100％计算倍率放电容量效率。
4、45℃循环性能测试
在45℃下，将二次电池以1C恒流充电至4.35V，然后以4.35V恒压充电至电流小于0.05C，然后将二次电池以1C恒流放电至2.8V，此为一个循环的充放电过程。如此反复进行充电和放电，计算二次电池循环1000次后的容量保持率。
二次电池45℃循环1000次后的容量保持率(％)＝(第1000次循环的放电容量/首次循环的放电容量)×100％。
【表1】
Figure PCTCN2021121108-appb-000018
【表2】
Figure PCTCN2021121108-appb-000019
对表1的参数和表2的结果进行分析可知如下。
在对比较例1、比较例2及6进行比较可知，仅减少Co元素的含量以降低正极材料成本但在正极材料中不含Al元素的情况下，二次电池的自放电率和存储阻抗增长率显著增加，而且即使在电解液中添加抑制电解液溶剂还原的添加剂碳酸亚乙烯酯(VC)，也不能很好地改善二次电池的性能。另外，通过对比较例2和比较例3的比较可知，通过在减少了Co元素含量的正极材料中含有Al元素，从而能够在一定程度上降低自放电率和存储阻抗增长率并提高存储后倍率放电容量效率。这是由于Al元素的加入能够减少因Co含量的减少所导致的Li、Ni混排，提高正极材料的结构稳定性，从而在一定程度上提高二次电池的性能。但是由于正极材料表面的成键不饱和结构不稳定，表面的Al元素容易在充放电过程中参与反应，从而达不到完全稳定材料表面的作用。
而由实施例1、实施例4和比较例1的比较(参照表3)可知，通过减少Co元素的同时配合适量的Al元素并在电解液中含有通式(I)表示的化合物，从而不仅可以因高价的Co含量的减少而降低二次电池的成本，而且还可以降低二次电池的自放电率、减小存储阻抗增长率，并且提高存储后倍率放电容量效率。这是由于通过在电解液中配合使用上述通式(I)所示的化合物作为添加剂，首次充电时该化合物可与正极表面的Al定向连接形成螯合结构，同时该化合物的双环开环相互连接成三维网状结构覆盖在正极颗粒表面，可有效稳定正极材料表面的Al元素，并隔离电解液和正极界面，从而不仅提高正极表面结构稳定性和导离子能力，还能减少界面副反应，电芯自放电率大幅降低，存储阻抗增长率减少，电池循环稳定性提高，倍率放电容量效率提高。
另外，比较实施例2～6和比较例4和5可知，如果在正极中所含的Al元素过少，则其不足以补偿因Co含量的减少所导致的二次电池的性能恶化。当Al元素的加入量逐渐增加时，足够的Al元素可有效减少因Co含量的减少所导致的Li、Ni混排，稳定正极材料的体相和表面结构稳定性，并且通过结合电解液中所含的通式(I)所表示的化合物添加剂对Al元素的稳定作用和交联网状保护效果，从而二次电池的各方面性能大幅改善并优于高Co含量正极体系的二次电池性能。随着Al加入量持续增加至超过一定范围，在正极材料中形成很多非活性位点，从而限制锂离子的内部传导和扩散，反而恶化了正极材料的导离子能力，并导致二次电池的综合性能下降。当Al元素加入量在 1000～7000的优选范围时，二次电池自放电率＜150mV/h，存储阻抗增长率＜70％，倍率放电容量效率＞93％，综合性能特别优异。
实施例4，7～11的对比说明了调整正极材料的比表面积对二次电池性能的影响。随着正极材料的比表面积逐渐增加，自放电率也呈现逐渐增加的趋势，这是因为比表面积直接影响界面副反应的程度，比表面积越大，副反应越多，自放电率相应增大。存储后阻抗增长和倍率放电容量效率呈现先改善后恶化的趋势，这是因为一定程度的副反应可以起到隔离正极界面与电解液的作用，抑制副反应的进一步发生，从而降低阻抗增长，改善倍率性能；但比表面积过大时，过多的副反应则带来整体性能的显著恶化。当正极材料的比表面积在0.5～2.5的优选范围时，二次电池自放电率＜100mV/h，存储阻抗增长率＜65％，倍率放电容量效率＞92％。
从实施例4，12～24中显示通式(I)所表示的化合物的不同添加量或不同种类或者与其它添加剂一同添加对二次电池性能的影响。从实施例结果来看，随着通式(I)所表示的化合物的加入量逐渐增加，二次电池自放电率呈现逐渐降低的趋势，这是因为足够多的通式(I)的化合物可通过与Al元素反应在正极表面形成致密的网络结构，从而将正极界面和电解液完全隔离开，因此副反应减少，自放电率也相应显著降低。但存储后阻抗增长和倍率放电容量效率却呈现先改善后恶化的趋势，这是因为随着通式(I)的化合物在一定范围内逐渐增加，可参与稳定正极表面的Al元素的通式(I)的化合物量逐渐增加，再结合通式(I)的化合物自身的开环交联成网的保护作用，界面相变和副反应逐渐减少，存储后阻抗增长和倍率放电性能有效提升；但当通式(I)的化合物加入量过多时，不仅影响其与Al的螯合稳定效果，还由于过量的界面保护导致阻抗显著增加，加长锂离子的传输路径、增加锂离子传输难度，所以恶化阻抗增长和倍率放电容量。当通式(I)的化合物的加入量在0.1～10％的优选范围时，二次电池自放电率＜120mV/h，存储阻抗增长率＜75％，倍率放电容量效率＞92％，表现出整体的性能大幅改善。
另外，通式(I)所表示的多种化合物都能达到同等程度的性能改善效果。此外，通过通式(I)所表示的化合物与二氟草酸硼酸锂(LiODFB)或氟代碳酸乙烯酯(FEC)一起使用，还能分别在正极表面形成三维离子通道、减少负极界面副反应，具有更好的性能改善效果。
Figure PCTCN2021121108-appb-000020
另外，参照表4可知，在实施例4、14、19、20中，加入合适含量的通式(I)的化合物还能改善二次电池的高温循环容量保持率，这主要是因为正极表面副反应相比减少后，有利于提高正极材料界面的长程稳定性，从而也能改善循环性能。在此基础上进一步添加LiODFB和FEC，可进一步提高正极材料的导离子能力，兼顾负极界面的稳定性，从而更进一步改善二次电池的高温循环性能。
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，其特征在于，
    包含：正极极片、负极极片和电解液，
    所述正极极片包含正极活性材料，
    所述正极活性材料中，Co元素的含有率满足：Co≤0.09，且Al元素含量满足：500ppm≤Al≤10000ppm，
    所述电解液包含下述通式(Ⅰ)所示的化合物，
    Figure PCTCN2021121108-appb-100001
    通式(I)中，A 1～A 4分别单独地为单键或碳原子数1～5的亚烷基，R 1、R 1’分别单独地为
    Figure PCTCN2021121108-appb-100002
    为
    Figure PCTCN2021121108-appb-100003
    Figure PCTCN2021121108-appb-100004
    其中R 3为碳原子数1～3的亚烷基或亚烷氧基。
  2. 根据权利要求1所述的二次电池，其特征在于，
    所述通式(I)的化合物在所述电解液中的质量百分含量为0.01％～15％，可选为0.1％～10％，进一步可选为0.5％～5％。
  3. 根据权利要求1或2所述的二次电池，其特征在于，
    所述通式(I)中，A 1～A 4分别单独地为单键或碳原子数1～3的亚烷基，可选为单键或亚甲基。
  4. 根据权利要求1～3中任一项所述的二次电池，其特征在于，
    通式(I)中，R 2为
    Figure PCTCN2021121108-appb-100005
    其中R 3为碳原子数为1或2的亚烷基或亚烷氧基。
  5. 根据权利要求1～4中任一项所述的二次电池，其特征在于，
    所述通式(I)的化合物为选自以下化合物1～18中的至少一种，
    Figure PCTCN2021121108-appb-100006
  6. 根据权利要求1～5中任一项所述的二次电池，其特征在于，
    所述Al元素含量满足1000ppm≤Al≤10000ppm，可选地满足1000ppm≤Al≤7000ppm。
  7. 根据权利要求1～6中任一项所述的二次电池，其特征在于，
    所述正极活性材料的通式为：LiNi zMn yCo xAl aO 2，其中x≤0.09，0.0005≤a≤0.01，0.5＜z＜1，0＜y＜0.4，x+y+z+a＝1。
  8. 根据权利要求1～7中任一项所述的二次电池，其特征在于，
    所述电解液还含有选自四氟硼酸锂、二草酸硼酸锂、二氟草酸硼酸锂、三(三甲基硅烷)硼酸酯中的至少一种的其它添加剂。
  9. 根据权利要求8所述的二次电池，其特征在于，
    所述其它添加剂的总量在所述电解液中的质量百分含量为0.2％～3％。
  10. 根据权利要求1～9中任一项所述的二次电池，其特征在于，
    所述正极活性材料的比表面积为0.5～3m 2/g，可选为0.5～2.5m 2/g。
  11. 一种电池模块，其特征在于，包括权利要求1～10中任一项所述的二次电池。
  12. 一种电池包，其特征在于，包括权利要求11所述的电池模块。
  13. 一种用电装置，其特征在于，包括选自权利要求1～10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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