WO2024082291A1 - 锂离子电池和用电装置 - Google Patents

锂离子电池和用电装置 Download PDF

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WO2024082291A1
WO2024082291A1 PCT/CN2022/126797 CN2022126797W WO2024082291A1 WO 2024082291 A1 WO2024082291 A1 WO 2024082291A1 CN 2022126797 W CN2022126797 W CN 2022126797W WO 2024082291 A1 WO2024082291 A1 WO 2024082291A1
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negative electrode
active material
lithium
electrode active
battery
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PCT/CN2022/126797
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English (en)
French (fr)
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郭洁
韩昌隆
吴则利
姜彬
张翠平
王冠
蔡林华
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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 PCT/CN2022/126797 priority Critical patent/WO2024082291A1/zh
Publication of WO2024082291A1 publication Critical patent/WO2024082291A1/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

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  • the present application relates to the technical field of lithium batteries, and in particular to a lithium-ion battery and an electrical device.
  • lithium-ion batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • mileage anxiety and long charging time have become the main problems hindering the development of secondary batteries. How to improve the fast charging capability of secondary batteries is one of the focuses of technical personnel in this field.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a lithium-ion battery, which comprises a negative electrode active material with a specific average width-to-length ratio, an electrolyte with a specific ionic conductivity, and has a specific range of the ratio CB of the negative electrode lithium insertion capacity to the positive electrode lithium removal capacity, so that the corresponding battery has a large-rate fast charging capability and good cycle performance.
  • the present application provides a lithium-ion battery and an electrical device.
  • the first aspect of the present application provides a lithium ion battery, which comprises a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a negative electrode active material layer comprising a negative electrode active material attached to at least one surface of the negative electrode current collector, wherein the average width-to-length ratio of the particles of the negative electrode active material is 0.1-1; the ion conductivity of the electrolyte is 7-15mS/cm; and the ratio CB of the negative electrode lithium insertion capacity to the positive electrode lithium removal capacity is 1.05-1.5.
  • the lithium-ion battery of the present application comprises a negative electrode active material with a specific average width-to-length ratio, an electrolyte with a specific ionic conductivity, and has a specific range of the ratio CB of the negative electrode lithium embeddable capacity to the positive electrode lithium removable capacity, thereby effectively reducing the tortuosity inside the negative electrode plate, thereby improving the liquid phase transport conditions of lithium ions and providing more active sites at the negative electrode for lithium ion embedding, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the average current of the battery during charging from 0% state of charge to 80% state of charge at 35° C. is greater than or equal to 4 times the lithium removable capacity of the positive electrode per unit time.
  • the high-rate fast charging capability and cycle performance of the battery are further improved.
  • the porosity of the negative electrode active material layer is 20-60%, thereby further providing more active sites for lithium ion embedding in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the compaction density of the negative electrode active material layer is 1.2-1.9 g/cm 3 and the coating weight is 5-18 mg/cm 2 .
  • the coating weight is 5-18 mg/cm 2 .
  • the negative electrode active material includes natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide or a combination thereof.
  • more active sites are further provided at the negative electrode for lithium ion embedding, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the thickness of the negative electrode active material layer is 30-150 ⁇ m, thereby further improving the liquid phase transport conditions of lithium ions and providing more active sites for lithium ion embedding at the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the active material layer includes a first active material layer including a first negative electrode active material, and a second active material layer including a second negative electrode active material attached to a surface of the first active material layer away from the current collector.
  • the average volume particle size D v50 of the first negative electrode active material is greater than the average volume particle size D v50 of the second negative electrode active material.
  • the compaction density of the first negative electrode active material layer is greater than the compaction density of the second negative electrode active material layer, thereby further providing more active sites for lithium ion embedding in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the electrolyte comprises a lithium salt, a solvent and an additive; wherein the lithium salt comprises a main lithium salt and a secondary lithium salt.
  • the liquid phase transport conditions of lithium ions are further improved, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the main lithium salt is different from the secondary lithium salt, and the main lithium salt or the secondary lithium salt is independently selected from at least one of LiPF 6 , LiN(SO 2 F) 2 , LiBF 4 , LiN(CF 3 SO 2 ) 2 , LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 , LiBF 2 C 2 O 4 , lithium difluorobis(oxalate)phosphate, LiPO 2 F 2 , LiFSO 3 , and LiF.
  • the liquid phase transport conditions of lithium ions are further improved, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the main lithium salt is lithium hexafluorophosphate or LiFSI, and its content is 8-20wt%, based on the total weight of the electrolyte;
  • the secondary lithium salt is at least one of lithium difluorooxalatoborate, LiBF4 , LiB( C2O4 ) 2 , and lithium difluorobisoxalatophosphate , and its content is 0.001wt%-2wt%, based on the total weight of the electrolyte.
  • the solvent comprises a cyclic ester and a linear ester; the content of the cyclic ester accounts for 5-40% of the solvent mass, and the content of the linear ester accounts for 60-95% of the solvent mass.
  • the liquid phase transmission conditions of lithium ions are further improved, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the cyclic ester is ethylene carbonate, propylene carbonate or a combination thereof; the linear ester comprises dimethyl carbonate.
  • the liquid phase transport conditions of lithium ions are further improved, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the linear ester is selected from diethyl carbonate, ethyl methyl carbonate, methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate or a combination thereof.
  • the liquid phase transport conditions of lithium ions are further improved, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the percentage b% of the linear ester in the solvent by mass and the ionic conductivity a (mS/cm) of the electrolyte satisfy the following relationship:
  • liquid phase transport conditions of lithium ions are further improved, and more active sites are provided at the negative electrode for lithium ion embedding, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the positive electrode comprises a current collector and a positive electrode active material layer comprising a positive electrode active material attached to at least one surface of the current collector, wherein the positive electrode active material comprises a ternary material of the formula LiNi x Co y Q z M 1-xyz O 2 , wherein Q is Mn or Al, M comprises at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1.
  • the liquid phase transport conditions of lithium ions are further improved, and more active sites are provided at the negative electrode for lithium ion embedding, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the second aspect of the present application provides an electrical device, characterized by comprising the secondary battery described in the first aspect of the present application.
  • the lithium-ion battery of the present application comprises a negative electrode active material with a specific average width-to-length ratio, an electrolyte with a specific ionic conductivity, and has a specific range of the ratio CB of the negative electrode lithium embedding capacity to the positive electrode lithium deintercalation capacity, so that the liquid phase transport conditions of lithium ions are improved, and more active sites are provided at the negative electrode for lithium ion embedding, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • Secondary battery 51. Casing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device.
  • “Scope” disclosed in the present application is defined in the form of lower limit and upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: 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 lithium-ion battery of the first aspect of the present application comprises a negative electrode active material with a specific average width-to-length ratio, an electrolyte with a specific ionic conductivity, and has a specific range of the ratio CB of the negative electrode lithium embeddable capacity to the positive electrode lithium de-embeddable capacity, wherein adjusting the average width-to-length ratio of the negative electrode active material particles can effectively reduce the tortuosity inside the negative electrode sheet, while improving the conductivity of the electrolyte, greatly improving the liquid phase transport conditions of lithium ions, and a higher CB value also provides more active sites at the negative electrode for lithium ion embedding, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the first aspect of the present application provides a lithium ion battery comprising a positive electrode, a negative electrode and an electrolyte
  • the negative electrode comprises a negative electrode current collector and a negative electrode active material layer comprising a negative electrode active material attached to at least one surface of the negative electrode current collector, wherein the average width-to-length ratio of the particles of the negative electrode active material is 0.1-1, optionally 0.6-1;
  • the ionic conductivity of the electrolyte is 7-15mS/cm, optionally 8-13mS/cm, further optionally 9-11mS/cm, measured according to HG/T4067-2015;
  • the ratio CB of the negative electrode lithium insertion capacity to the positive electrode lithium removal capacity is 1.05-1.5, optionally 1.1-1.3, further optionally 1.1-1.2.
  • the lithium-ion battery of the present application comprises a negative electrode active material with a specific average width-to-length ratio, an electrolyte with a specific ionic conductivity, and has a specific range of the ratio CB of the negative electrode lithium embeddable capacity to the positive electrode lithium deintercalable capacity, thereby effectively reducing the tortuosity inside the negative electrode plate, improving the liquid phase transport conditions of lithium ions, and providing more active sites at the negative electrode for lithium ion embedding, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the "width-to-length ratio" of the negative electrode active material refers to the ratio of the wide diameter to the long diameter of the negative electrode active material particles.
  • the width-to-length ratio of the negative electrode active material can be obtained by dynamic particle image analysis (for example, using a Sympatec QICPIC dynamic particle image analyzer).
  • the "wide diameter" of the negative electrode active material particles refers to the minimum value between parallel lines tangent to the projected image of the particles.
  • the "long diameter” of the negative electrode active material particles refers to the maximum value between parallel lines tangent to the projected image of the particles.
  • the ionic conductivity of the electrolyte refers to the electrical conductivity of the electrolyte.
  • the term "positive electrode removable lithium capacity” refers to the actual removable lithium capacity of the positive electrode material in the battery.
  • the lithium desorption capacity of the positive electrode is 2000-300000 mAh, optionally 3000-150000 mAh, and further optionally 3000-4000 mAh.
  • the term "negative electrode lithium insertion capacity” refers to the actual lithium insertion capacity of the negative electrode material in the battery.
  • the negative electrode can have a lithium embedding capacity of 2100-315000 mAh, optionally 3000-100000 mAh, and further optionally 3500-4500 mAh.
  • the current is an instantaneous current.
  • the lithium-removable capacity of the positive electrode per unit time refers to the amount of lithium removed from the positive electrode per unit time (1 hour); the average current generated during this process is used as the basis for current quantification in this application. In this way, the lithium-removable capacity of the positive electrode can be associated with the current.
  • a constant current direct charging method is generally used in the charging process from 0% state of charge to 70% state of charge at 35°C, for example, charging from 0% state of charge to 70% state of charge with a current of 4 times the positive electrode removable intercalation capacity per unit time; a step-by-step charging method may also be used, for example, 0-10% SOC uses A times the current of the positive electrode removable intercalation capacity per unit time, 10-20% SOC uses B times the current of the positive electrode removable intercalation capacity per unit time, 20-30% SOC uses C times the current of the positive electrode removable intercalation capacity per unit time, 30-40% SOC uses D times the current of the positive electrode removable intercalation capacity per unit time, 40-50% SOC uses E times the current of the positive electrode removable intercalation capacity per unit time, 50-60% SOC uses F times the current of the positive electrode removable intercalation capacity per unit time, 60-70% SOC uses G times the current of the positive electrode removable intercalation capacity per unit time, etc., wherein at least
  • the positive electrode lithium removal capacity detection method is used to test the positive electrode lithium removal capacity X; the battery is charged using the above charging mode, and then the positive electrode plate is disassembled and the positive electrode lithium removal capacity detection method is used to test the positive electrode lithium removal capacity Z at this time. If Z/X ⁇ 40%, it is considered to meet the charging rate of 4 times the positive electrode lithium removal capacity per unit time.
  • the average current of the battery during the charging process from 0% state of charge to 70% state of charge (0-70% SOC) at 35°C is greater than or equal to 4 times the positive electrode lithium desorption capacity per unit time, and optionally greater than or equal to 5 times the positive electrode lithium desorption capacity per unit time.
  • the high-rate fast charging capability and cycle performance of the battery are further improved.
  • the test method for the average current of 0-70% SOC is that if constant current direct charging is adopted, the average current is the charging current; if the step-by-step charging method as described above is adopted, the average current is (A+B+C+D+E+F+G)/7.
  • the porosity of the negative electrode active material layer is 20-60%, optionally 25-40%, and further optionally 25-31%, thereby further providing more active sites for lithium ion embedding in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the compaction density of the negative electrode active material layer is 1.2-1.9 g/cm 3 , and can be 1.5-1.78 g/cm 3 ; the coating weight is 5-18 mg/cm 2 .
  • the compaction density of the negative electrode active material layer is 1.2-1.9 g/cm 3 , and can be 1.5-1.78 g/cm 3 ; the coating weight is 5-18 mg/cm 2 .
  • the active material layer includes a first active material layer including a first negative electrode active material, and a second active material layer including a second negative electrode active material attached to a surface of the first active material layer away from the current collector.
  • the average volume particle size D v50 of the first negative electrode active material is greater than the average volume particle size D v50 of the second negative electrode active material, thereby further providing more active sites for lithium ion embedding in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the average volume particle size D v50 of the first negative electrode active material is 10-20 ⁇ m, optionally 12-16 ⁇ m, and the average volume particle size D v50 of the second negative electrode active material is 9-19 ⁇ m, measured according to the particle size distribution laser diffraction method (refer to GB/T19077.1-2009).
  • the thickness of the first negative electrode active material layer is 10-120 ⁇ m
  • the thickness of the second negative electrode active material layer is 10-120 ⁇ m, measured by ion polishing cross-sectional morphology analysis using scanning electron microscopy (specifically referring to JY/T010-1996) (measure at least 5 locations and take the average value).
  • the negative electrode active material includes natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide or a combination thereof, thereby further providing more active sites for lithium ion embedding in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the thickness of the negative electrode active material layer is 30-150 ⁇ m, thereby further improving the liquid phase transport conditions of lithium ions and providing more active sites for lithium ion embedding at the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the compaction density of the first negative electrode active material layer is greater than the compaction density of the second negative electrode active material layer, thereby further providing more active sites for lithium ion embedding in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the compaction density of the first negative electrode active material layer is 1.3-2g/cm3, and the compaction density of the second negative electrode active material layer is 1.2-1.9g/cm3.
  • the mass per unit area of the negative electrode material layer i.e., the coating surface density CW (mg/ cm2 )
  • CW the coating surface density
  • the thickness of the negative electrode material layer is measured by scanning electron microscopy ion polishing cross-sectional morphology analysis (refer to JY/T010-1996) (at least 5 locations are measured and the average value is taken).
  • the compaction density of the coating negative electrode sheet coating surface density CW (mg/ cm2 )/negative electrode material layer thickness (cm)
  • the compaction density PD of the negative electrode material layer (unit: mg/ cm3 ) is calculated and then converted into g/ cm3 for measurement.
  • the electrolyte comprises a lithium salt, a solvent and an additive, wherein the lithium salt comprises a main lithium salt and a secondary lithium salt, thereby further improving the liquid phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the main lithium salt is different from the secondary lithium salt, and the main lithium salt or the secondary lithium salt is independently selected from at least one of LiPF 6 , LiN(SO 2 F) 2 (LiFSI), LiBF 4 , LiN(CF 3 SO 2 ) 2 (LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFOP), LiPO 2 F 2 , LiFSO 3 , and LiF.
  • LiPF 6 LiN(SO 2 F) 2
  • LiBF 4 LiN(CF 3 SO 2 ) 2
  • LiTFSI LiN(CF 3 SO 2 ) 2
  • LiClO 4 LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), lithium difluorobis(oxalate)phosphate (L
  • the main lithium salt is lithium hexafluorophosphate or LiFSI, and its content is 8-20wt%, based on the total weight of the electrolyte;
  • the secondary lithium salt is at least one of lithium difluorooxalatoborate LiBF2C2O4 (LiDFOB), LiBF4 , LiB ( C2O4 ) 2 (LiBOB), and lithium difluorobisoxalatophosphate (LiDFOP), which can be LiDFOB or LiDFOP, and its content is 0.001wt%-2wt%, based on the total weight of the electrolyte.
  • the molar concentration b of the lithium salt in the electrolyte is 0.6-1.5 mol/L.
  • the solvent comprises a cyclic ester and a linear ester; the cyclic ester accounts for 5-40% of the solvent mass, and the linear ester accounts for 60-95% of the solvent mass.
  • the liquid phase transport conditions of lithium ions are further improved, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC) or a combination thereof; the linear ester comprises dimethyl carbonate (DMC).
  • EC ethylene carbonate
  • PC propylene carbonate
  • DMC dimethyl carbonate
  • the linear ester may include at least one selected from the following components in addition to DMC: diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate (MA), ethyl acetate (EA), butyl acetate, acetonitrile (SN), methyl propionate, ethyl propionate (EP), methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate and combinations thereof; diethyl carbonate DEC, ethyl acetate EA, methyl acetate MA, acetonitrile SN, ethyl propionate EP and combinations thereof may be selected.
  • DEC diethyl carbonate
  • EA ethyl methyl carbonate
  • MA methyl formate
  • EA ethyl acetate
  • EP butyl acetate
  • the cyclic ester is ethylene carbonate (EC), and the linear ester comprises dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • the percentage b% of the linear ester in the solvent by mass and the ionic conductivity a (mS/cm) of the electrolyte satisfy the following relationship:
  • liquid phase transmission conditions of lithium ions are further improved, thereby improving the high-rate fast charging capability and cycle performance of the battery.
  • the positive electrode comprises a current collector and a positive electrode active material layer comprising a positive electrode active material attached to at least one surface of the current collector, wherein the positive electrode active material comprises a ternary material of the formula LiNi x Co y Q z M 1-xyz O 2 , wherein Q is Mn or Al, M comprises at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0 ⁇ x ⁇ 1, optionally 0.5 ⁇ x ⁇ 1; 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1.
  • the high-rate fast charging capability and cycle performance of the battery are further improved.
  • a second aspect of the present application provides an electrical device, characterized in that it includes the secondary battery described in the first aspect of the present application.
  • lithium-ion batteries include a positive electrode, a negative electrode, an electrolyte, and a separator.
  • active ions are embedded and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the separator is set between the positive electrode and the negative electrode, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.
  • the positive electrode active material includes a ternary material of the formula LiNi x Co y Q z M 1-xyz O 2 , wherein Q is Mn or Al, M includes at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0 ⁇ x ⁇ 1, optionally 0.5 ⁇ x ⁇ 1; 0 ⁇ y ⁇ 1, 0 ⁇ z ⁇ 1, x+y+z ⁇ 1.
  • the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • Polymer material substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.
  • the positive electrode active material may be at least one of lithium nickel cobalt oxide, lithium nickel cobalt manganese oxide (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 referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 )), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ), LiNi 1/3 Co 1/3 Al 1/3 O 2 or modified compounds thereof, preferably NCM 622 .
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination of
  • the positive electrode active material may also include other positive electrode active materials for batteries known in the art.
  • other positive electrode active materials may include at least one of the following materials: lithium-containing phosphates with an olivine structure, 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 manganese cobalt oxides, lithium nickel manganese oxides and modified compounds thereof.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate 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 referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80-100 weight %, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • the weight ratio of the binder in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode film layer may further include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, carbon black (e.g., acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.
  • the positive electrode can be prepared by the following method: the components for preparing the positive electrode, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40-80wt%, and the viscosity at room temperature is adjusted to 5000-25000mPa ⁇ s, the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, the positive electrode is formed by cold rolling; the positive electrode powder coating unit area density is 12-26mg/ cm2 , and the positive electrode compaction density is 2.0-3.6g/ cm3 , and can be optionally 2.3-3.5g/ cm3 .
  • the compaction density is calculated by the formula:
  • Compacted density coating surface density/(thickness after extrusion - thickness of current collector).
  • the negative electrode includes a negative electrode current collector and a negative electrode film layer (also referred to as a negative electrode active material layer) disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material.
  • the active material layer includes a first active material layer including a first negative electrode active material, and a second active material layer including a second negative electrode active material attached to a surface of the first active material layer away from the current collector.
  • the negative electrode includes the technical features of the negative electrode as described above in the present application.
  • the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • a metal foil a copper foil may be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate.
  • the composite current collector may be formed by forming a metal material on a polymer material substrate.
  • the metal material includes but is not limited to copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.
  • the polymer material substrate includes but is not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates.
  • the negative electrode active material may adopt the negative electrode active material for batteries known in the art.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used.
  • These negative electrode active materials may be used alone or in combination of two or more.
  • the weight ratio of the negative electrode active material in the negative electrode film layer is 70-100% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode active material includes at least one of natural graphite, artificial graphite, mesophase microcarbon beads, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide, or a combination thereof.
  • the negative electrode active material comprises one or more of natural graphite, artificial graphite, mesophase microcarbon beads (MCMB for short), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , spinel-structured lithiated TiO 2 -Li 4 Ti 5 O 12 , and Li-Al alloy.
  • MCMB mesophase microcarbon beads
  • the first negative electrode active material is at least one of natural graphite, artificial graphite, mesophase microcarbon beads (referred to as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithiated TiO 2 -Li 4 Ti 5 O 12 with a spinel structure, and Li-Al alloy;
  • the second negative electrode active material is at least one of natural graphite, artificial graphite, mesophase microcarbon beads (referred to as MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO 2 , lithiated TiO 2 -Li 4 Ti 5 O 12 with a spinel structure, and Li-Al alloy.
  • the negative electrode active material comprises silicon, wherein the silicon content accounts for 1-10% by weight of the negative electrode active material layer and is distributed in at least one layer of the active material layer.
  • the silicon content (in terms of SiO 2 ) in the first active material layer is 0-25%, based on the weight of the first active material layer; the silicon content (in terms of SiO 2 ) in the second active material layer is 0-25%, based on the weight of the second active material layer.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), 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
  • the negative electrode film layer may further include a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, carbon black (e.g., acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the weight ratio of the conductive agent in the negative electrode film layer is 0-20% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode film layer may further include other additives, such as a thickener (such as sodium carboxymethyl cellulose (CMC-Na)), etc.
  • a thickener such as sodium carboxymethyl cellulose (CMC-Na)
  • the weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.
  • the negative electrode can be prepared by the following method: the components for preparing the negative electrode, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70wt%, and the viscosity at room temperature is adjusted to 2000-10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing such as rolling, the negative electrode is obtained.
  • the negative electrode powder coating unit area density is 6-16mg/ cm2
  • the negative electrode compaction density is 1.2-2.0g/ m3 .
  • the mass M of the negative electrode active material per unit area in the negative electrode active material layer can be obtained by weighing using a standard balance.
  • the thickness T of the negative electrode active material layer can be measured by using a micrometer, for example, a Mitutoyo 293-100 micrometer with an accuracy of 0.1 ⁇ m. It should be noted that the thickness of the negative electrode active material layer described in the present invention refers to the thickness of the negative electrode active material layer in the negative electrode of the assembled battery after cold pressing.
  • the electrolyte conducts ions between the positive and negative electrodes.
  • the electrolyte comprises the technical features of the present application as described above.
  • the electrolyte comprises a lithium salt, a solvent, and an additive; wherein the lithium salt comprises a main lithium salt and a secondary lithium salt.
  • the main lithium salt is different from the secondary lithium salt, and the main lithium salt or the secondary lithium salt is each independently selected from one or more of lithium hexafluorophosphate (LiPF 6 ), lithium bis(SO 2 F) 2 (LiFSI), lithium tetrafluoroborate (LiBF 4 ), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium trifluoromethanesulfonate (LiTFS), lithium bis(oxalatoborate) (LiB(C 2 O 4 ) 2 , LiBOB), lithium difluorooxalatoborate (LiBF 2 C 2 O 4 , LiDFOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobis(oxalatophosphate) (LiDFOP), LiPO
  • the main lithium salt is different from the secondary lithium salt, and the main lithium salt or the secondary lithium salt is independently selected from at least one of LiPF 6 , LiN(SO 2 F) 2 (LiFSI), LiBF 4 , LiN(CF 3 SO 2 ) 2 (LiTFSI), LiClO 4 , LiAsF 6 , LiB(C 2 O 4 ) 2 (LiBOB), LiBF 2 C 2 O 4 (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFOP), LiPO 2 F 2 , LiFSO 3 , and LiF.
  • the main lithium salt is different from the secondary lithium salt in that their contents are different.
  • the main lithium salt is lithium hexafluorophosphate or LiFSI, and its content is 8-20wt%, based on the total weight of the electrolyte;
  • the secondary lithium salt is at least one of lithium difluorooxalatoborate LiBF2C2O4 ( LiDFOB ), LiBF4 , LiB ( C2O4 ) 2 (LiBOB), and lithium difluorobis( oxalate )phosphate (LiDFOP), which can be LiDFOB or LiDFOP, and its content is 0.001wt%-2wt%, based on the total weight of the electrolyte.
  • the molar concentration b of the lithium salt in the electrolyte is 0.8-1.2 mol/L.
  • the solvent comprises a cyclic ester and a linear ester; the cyclic ester accounts for 5-40% by mass of the solvent, and the linear ester accounts for 60-95% by mass of the solvent.
  • the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC), or a combination thereof; and the linear ester comprises dimethyl carbonate (DMC).
  • EC ethylene carbonate
  • PC propylene carbonate
  • DMC dimethyl carbonate
  • the linear ester may include at least one selected from the following components in addition to DMC: diethyl carbonate (DEC), ethyl methyl carbonate (EMC), methyl formate, methyl acetate (MA), ethyl acetate (EA), butyl acetate, acetonitrile (SN), methyl propionate, ethyl propionate (EP), methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate and combinations thereof; diethyl carbonate DEC, ethyl acetate EA, methyl acetate MA, acetonitrile SN, ethyl propionate EP and combinations thereof may be selected.
  • DEC diethyl carbonate
  • EA ethyl methyl carbonate
  • MA methyl formate
  • EA ethyl acetate
  • EP butyl acetate
  • the cyclic ester is ethylene carbonate (EC), and the linear ester comprises dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • the additive comprises a carbonate (e.g., fluoroethylene carbonate FEC), a sulfate (e.g., vinyl sulfate DTD), and a sulfonate (e.g., 1,3-propane sultone PS).
  • a carbonate e.g., fluoroethylene carbonate FEC
  • a sulfate e.g., vinyl sulfate DTD
  • a sulfonate e.g., 1,3-propane sultone PS
  • the carbonate comprises at least one of fluoroethylene carbonate (FEC), vinyl carbonate (VC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate.
  • FEC fluoroethylene carbonate
  • VC vinyl carbonate
  • 1,2-difluoroethylene carbonate 1,1-difluoroethylene carbonate
  • 1,1,2-trifluoroethylene carbonate 1,1,2,2-tetrafluoroethylene carbonate
  • 1-fluoro-2-methylethylene carbonate 1-fluoro-1-methylethylene carbonate
  • 1,2-difluoro-1-methylethylene carbonate 1,1,2-trifluoro-2-methylethylene carbonate
  • the sulfate comprises at least one of vinyl sulfate (DTD), diethyl sulfate (DES), dimethyl sulfate (DMS), and 4,4-bis(1,3,2-dioxathiacyclopentane)-2,2,2,2-tetraoxide.
  • the sulfonate ester includes at least one of 1,3-propane sultone (1,3-PS), propylene sultone (PES), 3-fluoro-1,3-propane sultone (FPS), and vinyl methane disulfonate (MMDS).
  • the additive comprises fluoroethylene carbonate (FEC), diethylene sulfate (DTD) and 1,3-propane sultone (1,3-PS).
  • FEC fluoroethylene carbonate
  • DTD diethylene sulfate
  • 1,3-propane sultone 1,3-PS
  • the content of the additive accounts for 0-7% by mass of the total mass of the electrolyte.
  • the electrolyte may further include other additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the isolation film has a thickness of 6-40 ⁇ m, and optionally 12-20 ⁇ m.
  • the positive electrode, the negative electrode, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package that can be used to encapsulate the electrode assembly and the electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode, the negative electrode and the separator can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the 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.
  • secondary batteries may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack may include a battery box and a plurality of battery modules disposed in the battery box.
  • the battery box includes an upper box body and a lower box body, and the upper box body can be covered on the lower box body to form a closed space for accommodating the battery modules.
  • the plurality of battery modules can be arranged in the battery box in any manner.
  • the present application also provides an electrical 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 for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical device may include mobile devices (such as mobile phones, laptops, 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., but are not limited to these.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • FIG3 is an example of an electric 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.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • the device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • the preparation of the electrolyte was carried out in an argon atmosphere glove box with a water content of ⁇ 10ppm.
  • ethylene carbonate (EC), ethyl methyl carbonate (DMC) and diethyl carbonate (EMC) were mixed in a mass ratio of 3:4:3, and then 1 mol/L of the main lithium salt LiPF 6 , 1 wt% of the secondary lithium salt LiDFOB+LiPO 2 F 2 of the whole electrolyte, and 5 wt% of the additive FEC+DTD of the whole electrolyte were added, and mixed evenly to obtain an electrolyte.
  • the concentration of the lithium salt was 1 mol/L.
  • the ionic conductivity of the electrolyte was 10 mS/cm.
  • the positive electrode active material ternary material LiNi 1/3 Co 1/3 Mn 1/3 O 2 , the binder polyvinylidene fluoride, and the conductive agent acetylene black were mixed in a weight ratio of 98:1:1 and dissolved in a solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry, and then the slurry was coated on the current collector aluminum foil, and after drying, cold pressing, trimming, cutting, and striping were performed to prepare a positive electrode sheet with a size of 87*665 mm for use.
  • NMP solvent N-methylpyrrolidone
  • the negative electrode active material graphite, SiO2, binder styrene butadiene rubber and dispersant sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 92.8:5:1.2:1 to form a negative electrode slurry.
  • a 6um copper foil is used as a negative electrode current collector.
  • the first layer of negative electrode slurry is first coated on the negative electrode current collector with a coating weight of 4.25mg/ cm2 to form a first active material layer. After the first active material layer is dried, the second negative electrode slurry is coated.
  • the negative electrode active material graphite, SiO2, binder styrene butadiene rubber and dispersant sodium carboxymethyl cellulose are dissolved in deionized water at a weight ratio of 92.8:5:1.2:1 to form a second negative electrode slurry; the coating weight of the second active material layer is 4.25mg/ cm2 to form a second active material layer.
  • the composite negative electrode sheet is then obtained through drying, cold pressing and cutting. After cold pressing, the thickness of the composite active material layer coated on one surface of the copper foil is 51 um, and the compacted density of the active material layer is 1.65 g/cm 3 .
  • the isolation membrane substrate is 8 ⁇ m thick polyethylene (PE), and a 2 ⁇ m alumina ceramic layer is coated on both sides of the isolation membrane substrate. Finally, 2.5 mg of binder polyvinylidene fluoride (PVDF) is coated on both sides of the ceramic layer and dried.
  • PE polyethylene
  • PVDF binder polyvinylidene fluoride
  • the positive electrode sheet, separator, and negative electrode sheet are wound or stacked in order so that the separator is located between the positive and negative electrode sheets to obtain a bare battery cell.
  • the bare battery cell is placed in an outer package, and 9.5 g of the prepared electrolyte is injected into the dried battery cell. After standing, forming, shaping and other processes, a lithium-ion secondary battery with a capacity of 3100 mAh is obtained.
  • Examples 2-27 and Comparative Examples 1-6 are similar to those of Example 1, but the materials or compositions of the electrolyte or the negative electrode are changed, see Table 1.
  • the aspect ratio of the negative electrode active material can be obtained by dynamic particle image analysis (for example, using a Sympatec QICPIC dynamic particle image analyzer).
  • Rate performance test (test of charging to 80% SOC): adjust the test temperature to 35°C, charge the lithium-ion battery at xC rate (x is 0.5, 0.8, 1, 1.2, 1.5, 2, 2.5, 3), and then discharge it at 1C. The charge rate increases successively, and the anode potential of 0V is used as the charging cutoff condition to obtain the maximum charge rate that can be achieved in the range of 0-10% SOC, 10-20% SOC, 20-30% SOC, 30-40% SOC, 40-50% SOC, 50-60% SOC, and 60-70% SOC, thereby calculating the charging time (min) required for 0-80% SOC.
  • the batteries of the embodiments and comparative examples were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 2 below.
  • the lithium-ion battery of the present application has good fast charging capability and capacity retention rate while satisfying the conditions that the average aspect ratio of the particles of the negative electrode active material is 0.1-1, the electrolyte ion conductivity is in the range of 7-15mS/cm and the CB value is 1.1-1.5.
  • the charging time required for 0-70% SOC can be shortened to 7-8 minutes, and the capacity retention rate is still maintained above 95% after 600 cycles.

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Abstract

一种锂离子电池及包含其的用电装置，锂离子电池包含正极、负极和电解液，其中，负极包含负极集流体及附着在负极集流体至少一个表面上的包含负极活性材料的负极活性材料层，其中负极活性材料的颗粒的平均宽长比为0.1-1；电解液的离子电导率为7-15mS/cm；并且负极可嵌锂容量与正极可脱锂容量的比值CB为1.05-1.5。锂离子电池具有大倍率的快充能力以及良好的循环性能。

Description

锂离子电池和用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种锂离子电池和用电装置。
背景技术
近年来，随着锂离子电池的应用范围越来越广泛，锂离子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。但是相比于传统的燃油驱动设备，里程焦虑、充电时间长等问题成为阻碍二次电池发展的主要问题，如何提高二次电池的快充能力是本领域技术人员的关注的焦点之一。
提高电池的快充能力是一个系统工程，其需要对电池的材料作出改变和升级。传统技术研究最多的是负极材料的改进，但同时还需要电解液、导电剂等材料的配合。因此，现有的具有快充能力的电池仍需要进一步改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种锂离子电池，其包含特定平均宽长比的负极活性材料、特定离子电导率的电解液并具有特定范围的负极可嵌锂容量与正极可脱锂容量的比值CB，使得相应的电池具有大倍率的快充能力以及良好的循环性能。
为了达到上述目的，本申请提供了一种锂离子电池和用电装置。
本申请的第一方面提供一种锂离子电池，其包含正极、负极和电解液，其中，所述负极包含负极集流体及附着在负极集流体至少一个表面上的包含负极活性材料的负极活性材料层，其中所述负极活性材料的颗粒平均宽长比为0.1-1；所述电解液的离子电导率为7-15mS/cm；并且负极可嵌锂容量与正极可脱锂容量的比值CB为1.05-1.5。
本申请的锂离子电池通过包含特定平均宽长比的负极活性材料、特定离子电导率的电解液并具有特定范围的负极可嵌锂容量与正极可脱锂容量的比值CB，有效降低负极极片内部的曲折度，使得锂离子的液相传输条件得到改善，并在负极提供更多的活 性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述电池在35℃下自0％荷电状态到70％荷电状态的充电过程中存在大于等于4倍的单位时间内正极可脱锂容量的电流。由此，进一步改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述电池在35℃下自0％荷电状态到80％荷电状态的充电过程中的平均电流大于等于4倍的单位时间内正极可脱锂容量。由此，进一步改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述负极活性材料层的孔隙率为20-60％。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述负极活性材料层的压实密度为1.2-1.9g/cm 3，涂布重量为5-18mg/cm 2。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述负极活性材料包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、氧化硅或其组合物。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述负极活性材料层的厚度为30-150μm。由此，进一步改善锂离子的液相传输条件，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述活性材料层包括包含第一负极活性材料的第一活性材料层，以及附着在所述第一活性材料层远离所述集流体的表面上的包含第二负极活性材料的第二活性材料层。由此，进一步改善锂离子的液相传输条件，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述第一负极活性材料的平均体积粒径D v50大于第二负极活性材料的平均体积粒径D v50。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述第一负极活性材料层的压实密度大于第二负极活性材料层的压实密度。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述电解液包含锂盐、溶剂和添加剂；其中所述锂盐包含主锂盐和副锂盐。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述主锂盐与副锂盐不同，并且所述主锂盐或副锂盐各自独立地选自LiPF 6、LiN(SO 2F) 2、LiBF 4、LiN(CF 3SO 2) 2、LiClO 4、LiAsF 6、LiB(C 2O 4) 2、LiBF 2C 2O 4、二氟二草酸磷酸锂、LiPO 2F 2、LiFSO 3、LiF中的至少一种。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述主锂盐为六氟磷酸锂或LiFSI，其含量为8-20wt％，基于所述电解液的总重量计；所述副锂盐为二氟草酸硼酸锂、LiBF 4、LiB(C 2O 4) 2、二氟二草酸磷酸锂中的至少一种，其含量为0.001wt％-2wt％，基于所述电解液的总重量计。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述溶剂包含环状酯和线性酯；所述环状酯的含量占溶剂质量的5-40％，所述线性酯的含量占溶剂质量的60-95％。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述环状酯为碳酸亚乙酯、碳酸亚丙基酯或其组合；所述线性酯包含碳酸二甲酯。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述线性酯选自碳酸二乙酯、碳酸甲乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丁酯、丙酸甲酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、丁酸丁酯、乙酸异丙酯、乙酸异戊酯或其组合。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，溶剂中线性酯占溶剂质量的百分比b％与电解液的离子电导率a(mS/cm)之间满足以下关系式：
8≤a+3b％≤16。由此，进一步改善锂离子的液相传输条件，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在任意实施方式中，所述正极包含集流体及附着在集流体至少一个表面上的包含正极活性材料的正极活性材料层，所述正极活性材料包含式LiNi xCo yQ zM 1-x-y-zO 2的三元材料，其中Q为Mn或Al，M包含Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、 Cr、Sr、V和Ti中至少一种，0≤x＜1，0≤y≤1，0≤z≤1，x+y+z≤1。由此，进一步改善锂离子的液相传输条件，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
本申请的第二方面提供一种用电装置，其特征在于，包括本身请的第一方面所述的二次电池。
本申请的锂离子电池通过包含特定平均宽长比的负极活性材料、特定离子电导率的电解液并具有特定范围的负极可嵌锂容量与正极可脱锂容量的比值CB，使得锂离子的液相传输条件得到改善，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
附图说明
图1是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是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：
5、二次电池；51、壳体；52、电极组件；53、盖板；6、用电装置。
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锂离子电池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)。
目前，相比于传统的燃油驱动设备，里程焦虑、充电时间长等问题成为阻碍二次电池发展的主要问题，如何提高二次电池的快充能力是本领域技术人员的关注的焦点之一。
提高电池的快充能力是一个系统工程，其需要对电池的材料作出改变和升级。传统技术研究最多的是负极材料的改进，但同时还需要电解液、导电剂等材料的配合。因此，现有的具有快充能力的电池仍需要进一步改进。发明人研究发现本申请第一方面的锂离子电池包含特定平均宽长比的负极活性材料、特定离子电导率的电解液并具有特定范围的负极可嵌锂容量与正极可脱锂容量的比值CB，其中调整负极活性材料颗粒的平均宽长比可有效降低负极极片内部的曲折度，同时提升电解液的电导率，极大 地改善了锂离子的液相传输条件，并且较高的CB值也使得在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
锂离子电池
在一些实施方式中，本申请的第一方面提供一种锂离子电池，其包含正极、负极和电解液，其中，所述负极包含负极集流体及附着在负极集流体至少一个表面上的包含负极活性材料的负极活性材料层，其中所述负极活性材料的颗粒平均宽长比为0.1-1，可选为0.6-1；所述电解液的离子电导率为7-15mS/cm，可选为8-13mS/cm，进一步可选为9-11mS/cm，根据HG/T4067-2015测量；并且负极可嵌锂容量与正极可脱锂容量的比值CB为1.05-1.5，可选为1.1-1.3，进一步可选为1.1-1.2。
本申请的锂离子电池通过包含特定平均宽长比的负极活性材料、特定离子电导率的电解液并具有特定范围的负极可嵌锂容量与正极可脱锂容量的比值CB，有效降低负极极片内部的曲折度，使得锂离子的液相传输条件得到改善，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在本申请中，所述负极活性材料的“宽长比”指的是负极活性材料颗粒的宽径与长径的比值。负极活性材料的宽长比可通过动态颗粒图像分析(例如，使用新帕泰克QICPIC动态颗粒图像分析仪)获得。负极活性材料颗粒的“宽径”指的是与颗粒的投影图像相切的平行线之间的最小数值。负极活性材料颗粒的“长径”指的是与颗粒的投影图像相切的平行线之间的最大数值。负极活性材料的宽长比较小时，负极活性材料颗粒呈细长形状，接近于1时，负极活性材料颗粒呈球形。
在本申请中，所述电解液的离子电导率意指电解液的导电能力。
在本申请中，所述术语“正极可脱锂容量”意指在电池中，正极材料实际的可脱锂容量。其测试方法如下：在PRS340/11-119-11布劳恩手套箱中拆解电池，取正极极片，组装成正极-锂片的CR2430型号半扣式电池，采用的正极极片面积为a mm 2，其中电解液采用1M LiPF6于EC/EMC/DEC＝3/5/2中的溶液；然后将组装好的半扣式电池静置3h，测试在25℃下进行，采用0.1C先在电压区间2.5-eV下进行充电(Charge)脱锂，其中e为电芯设计的使用上限电压，再采用0.05C放电(Discharge)嵌锂至2.5V，循环2次，取第二次循环的放电扣电容量记为Y mAh，实际电池设计的正极膜片长为b mm，宽为c mm，正极活性材料涂覆于正极集流体的面数d，则正极脱锂容量为X＝Y/a*b*c*d。
在一些实施方式中，所述正极可脱锂容量为2000-300000mAh，可选为3000-150000mAh，进一步可选为3000-4000mAh。
在本申请中，所述术语“负极可嵌锂容量”意指在电池中，负极材料实际的可嵌锂容量。其测试方法为：在PRS340/11-119-11布劳恩手套箱中拆解电池，取负极极片，组装成负极-锂片的CR2430型号半扣式电池，采用的负极极片面积为f mm 2，其中电解液采用1M LiPF6于EC/EMC/DEC＝3/5/2中的溶液；然后将组装好的半扣式电池静置3h，测试在25℃下进行，采用0.1C先在电压区间2V-0V下进行放电(Discharge)嵌锂，再采用0.05C充电(Discharge)脱锂至2V，循环2次，取第二次循环的放电扣电容量记为ZmAh，实际电池设计的负极膜片长为h mm，宽为i mm，负极活性材料涂覆于负极集流体的面数d，则负极可脱锂容量为W＝Z/f*h*i*d。
在一些实施方式中，所述负极可嵌锂容量为2100-315000mAh，可选为3000-100000mAh，进一步可选为3500-4500mAh。
在一些实施方式中，所述电池在35℃下自0％荷电状态(SOC)到70％荷电状态的充电过程中(0-70％SOC)存在大于等于4倍的单位时间内正极可脱锂容量的电流，可选地所述电流大于等于5倍的单位时间内正极可脱嵌容量，进一步可选地为5倍至6.5倍的单位时间内正极可脱嵌容量。。由此，进一步改善所述电池的大倍率快充能力和循环性能。在该实施方式中，所述电流为瞬时电流。
在本申请中，“单位时间内正极可脱锂容量”是指正极在单位时间(1h)内的脱锂量；在此过程中产生的平均电流作为本申请中电流量化的基准。由此，可将正极可脱锂容量与电流关联起来。
在一些实施方式中，在35℃下自0％荷电状态到70％荷电状态的充电过程中通常可采用恒流直充的方式，例如以4倍的单位时间内正极可脱嵌容量的电流从0％荷电状态充电至70％荷电状态；也可以采用分步充电方式，例如0-10％SOC采用A倍的单位时间内正极可脱嵌容量的电流，10-20％SOC采用B倍的单位时间内正极可脱嵌容量的电流,20-30％SOC采用C倍的单位时间内正极可脱嵌容量的电流,30-40％SOC采用D倍的单位时间内正极可脱嵌容量的电流,40-50％SOC采用E倍的单位时间内正极可脱嵌容量的电流,50-60％SOC采用F倍的单位时间内正极可脱嵌容量的电流,60-70％SOC采用G倍的单位时间内正极可脱嵌容量的电流等，其中A、B、C、D、E、F至少一个不为4。本领域技术人员可以理解，在分步充电方式中，分步的SOC以及电流大小可根据需要 进行调整。
对于已经封装的电池，采用正极脱锂容量检测方法测试得出正极可脱锂容量X；采用如上测充电模式对电池进行充电，然后拆解取正极极片，采用正极可脱锂容量检测方法测试得出此时正极的脱锂容量Z，如果Z/X≥40％，则认为符合满足4倍的单位时间内正极可脱嵌容量的充电倍率。
在一些实施方式中，所述电池在35℃下自0％荷电状态到70％荷电状态的充电过程中(0-70％SOC)的平均电流大于等于4倍的正极可脱锂容量/单位时间，可选地大于等于5倍的单位时间内正极可脱嵌容量。由此，进一步改善所述电池的大倍率快充能力和循环性能。
在一个实施方式中，所述0-70％SOC的平均电流的测试方法为采用恒流直充的方式的话，平均电流即为充电电流；采用如上所述的分步充电方式的话，平均电流为(A+B+C+D+E+F+G)/7。
在一些实施方式中，所述负极活性材料层的孔隙率为20-60％，可选为25-40％，进一步可选为25-31％。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述负极活性材料层的压实密度为1.2-1.9g/cm 3，可选为1.5-1.78g/cm 3；涂布重量为5-18mg/cm 2。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述活性材料层包括包含第一负极活性材料的第一活性材料层，以及附着在所述第一活性材料层远离所述集流体的表面上的包含第二负极活性材料的第二活性材料层。由此，进一步改善锂离子的液相传输条件，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述第一负极活性材料的平均体积粒径D v50大于第二负极活性材料的平均体积粒径D v50。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述第一负极活性材料的平均体积粒径D v50为10-20μm，可选为12-16μm，第二负极活性材料的平均体积粒径D v50为9-19μm，根据粒度分布激光衍射法(参照GB/T19077.1-2009)测量。
在一些实施方式中，所述第一负极活性材料层的厚度为10-120μm，第二负极活性 材料层的厚度为10-120μm，根据扫描电镜法离子抛光断面形貌分析(具体参照JY/T010-1996)(至少测量5处，取平均值)测量。
在一些实施方式中，所述负极活性材料包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、氧化硅或其组合物。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述负极活性材料层的厚度为30-150μm。由此，进一步改善锂离子的液相传输条件，并在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述第一负极活性材料层的压实密度大于第二负极活性材料层的压实密度。由此，进一步在负极提供更多的活性位点供锂离子嵌入，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述第一负极活性材料层的压实密度为1.3-2g/cm3，第二负极活性材料层的压实密度为1.2-1.9g/cm3，根据分别通过标准天平称量负极材料层质量、通过直尺测量负极极片涂布面积，然后可计算负极材料层单位面积质量，即涂布面密度CW(mg/cm 2)。然后通过扫描电镜法离子抛光断面形貌分析(参照JY/T010-1996)测量负极材料层厚度(至少测量5处，取平均值)，根据涂膜的压实密度＝负极极片涂布面密度CW(mg/cm 2)/负极材料层厚度(cm)，计算得出负极材料层压实密度PD(单位mg/cm 3)，再换算成g/cm 3测量。
在一些实施方式中，所述电解液包含锂盐、溶剂和添加剂；其中所述锂盐包含主锂盐和副锂盐。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述主锂盐与副锂盐不同，并且所述主锂盐或副锂盐各自独立地选自LiPF 6、LiN(SO 2F) 2(LiFSI)、LiBF 4、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)、二氟二草酸磷酸锂(LiDFOP)、LiPO 2F 2、LiFSO 3、LiF中的至少一种。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。所述主锂盐与副锂盐区别在于其含量不同。
在一些实施方式中，所述主锂盐为六氟磷酸锂或LiFSI，其含量为8-20wt％，基于所述电解液的总重量计；所述副锂盐为二氟草酸硼酸锂LiBF 2C 2O 4(LiDFOB)、LiBF 4、LiB(C 2O 4) 2(LiBOB)、二氟二草酸磷酸锂(LiDFOP)中的至少一种，可选为LiDFOB或 LiDFOP，其含量为0.001wt％-2wt％，基于所述电解液的总重量计。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在一些优选的实施方式中，电解液中锂盐的摩尔浓度b为0.6-1.5mol/L。
在一些实施方式中，所述溶剂包含环状酯和线性酯；所述环状酯的含量占溶剂质量的5-40％，所述线性酯的含量占溶剂质量的60-95％。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述环状酯为碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)或其组合；所述线性酯包含碳酸二甲酯(DMC)。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述线性酯除了DMC，还可包含选自以下组分的至少一种：碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、甲酸甲酯、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丁酯、乙腈(SN)、丙酸甲酯、丙酸乙酯(EP)、丁酸甲酯、丁酸乙酯、丁酸丙酯、丁酸丁酯、乙酸异丙酯、乙酸异戊酯和其组合；可选为碳酸二乙酯DEC、乙酸乙酯EA、乙酸甲酯MA、乙腈SN、丙酸乙酯EP和组合。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在一个优选的实施方式中，所述环状酯为碳酸亚乙酯(EC)，所述线性酯包含碳酸二甲酯(DMC)和碳酸甲乙酯(EMC)。
在一些实施方式中，溶剂中线性酯占溶剂质量的百分比b％与电解液的离子电导率a(mS/cm)之间满足以下关系式：
8≤a+3b％≤16，可选为9≤a+3b％≤15。由此，进一步改善锂离子的液相传输条件，从而改善所述电池的大倍率快充能力和循环性能。
在一些实施方式中，所述正极包含集流体及附着在集流体至少一个表面上的包含正极活性材料的正极活性材料层，所述正极活性材料包含式LiNi xCo yQ zM 1-x-y-zO 2的三元材料，其中Q为Mn或Al，M包含Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V和Ti中至少一种，0≤x＜1，可选为0.5≤x＜1；0≤y≤1，0≤z≤1，x+y+z≤1。由此，进一步改善所述电池的大倍率快充能力和循环性能。
本申请的第二方面提供一种用电装置，其特征在于，包括本申请的第一方面所述的二次电池。
以下适当参照附图对本申请的锂离子电池和用电装置进行说明。
通常情况下，锂离子电池包括正极、负极、电解质和隔离膜。在电池充放电过程中，活性离子在正极和负极之间往返嵌入和脱出。电解质在正极和负极之间起到传导离子的作用。隔离膜设置在正极和负极之间，主要起到防止正负极短路的作用，同时可以使离子通过。
正极
正极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，所述正极膜层包括正极活性材料。所述正极活性材料包含式LiNi xCo yQ zM 1-x-y-zO 2的三元材料，其中Q为Mn或Al，M包含Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V和Ti中至少一种，0≤x＜1，可选为0.5≤x＜1；0≤y≤1，0≤z≤1，x+y+z≤1。
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形成在高分子材料基材上而形成。其中，金属材料包括但不限于铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等。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)
在一些实施方式中，所述正极活性材料可为锂镍钴氧化物、锂镍钴锰氧化物(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)、LiNi 1/3Co 1/3Al 1/3O 2或其改性化合物中的至少一种，优选为NCM 622。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。
在一些实施方式中，所述正极活性材料还可包含本领域公知的用于电池的其他正极活性材料。作为示例，其他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)、锂锰钴氧化物、锂镍锰氧化物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，所述正极活性材料在正极膜层中的重量比为80-100重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括粘结剂。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。所述粘结剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、炭黑(例如乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在正极膜层中的重量比为0-20重量％，基于正极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备正极：将上述用于制备正极的组分，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，其中所述正极浆料固含量为40-80wt％，室温下的粘度调整到5000-25000mPa·s，将正极浆料涂覆在正极集流体的表面，烘干后经过冷轧机冷压后形成正极；正极粉末涂布单位面密度为12-26mg/cm 2，正极压实密度为2.0-3.6g/cm 3，可选为2.3-3.5g/cm 3。所述压实密度的计算公式为
压实密度＝涂布面密度/(挤压后厚度-集流体厚度)。
负极
所述负极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(也称为负极活性材料层)，所述负极活性材料层包括负极活性材料。所述活性材料层包括包含第一负极活性材料的第一活性材料层，以及附着在所述第一活性材料层远离所述集流体的表面上的包含第二负极活性材料的第二活性材料层。所述负极包含本申请如上所述的关于负极的技术特征。
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。
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形成在高分子材料基材上而形成。其中，金属材料包括但不限于铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等，高分子材料基材包括但不限于聚丙烯(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)等基材。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。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负极活性材料的传统材料。这些负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。所述负极活性材料在负极膜层中的重量比为70-100重量％，基于负极膜层的总重量计。
在一些实施方式中，所述负极活性材料包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、氧化硅或其组合物中的至少一种。
在一些实施方式中，所述负极活性材料包含天然石墨、人造石墨、中间相微碳球(简称为MCMB)、硬碳、软碳、硅、硅-碳复合物、硅氧复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12、Li-Al合金中的一种或几种。
在一些实施方式中，所述第一负极活性材料为天然石墨、人造石墨、中间相微碳球(简称为MCMB)、硬碳、软碳、硅、硅-碳复合物、硅氧复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12、Li-Al合金中的至少一种；所述第二负极活性材料为天然石墨、人造石墨、中间相微碳球(简称为MCMB)、硬碳、软碳、硅、硅-碳复合物、硅氧复合物、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的锂化TiO 2-Li 4Ti 5O 12、Li-Al合金中的至少一种。
在一些实施方式中，负极活性材料包含硅。所述硅含量占负极活性材料层重量的1-10％，分布于活性材料层的至少一层中。
在一些实施方式中，在所述第一活性材料层中硅含量(以SiO 2计)为0-25％，基于所述第一活性材料层的重量计；在所述第二活性材料层中硅含量(以SiO 2计)为0-25％，基于第二活性材料层的重量计。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述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)中的至少一种。所述粘结剂在负极膜层中的重量比为0-30重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、炭黑(例如乙炔黑、科琴黑)、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。所述导电剂在负极膜层中的重量比为0-20重量％，基于负极膜层的总重量计。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。所述其他助剂在负极膜层中的重量比为0-15重量％，基于负极膜层的总重量计。
在一些实施方式中，可以通过以下方式制备负极：将上述用于制备负极的组分，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，其中所述负极浆料固含量为30-70wt％，室温下的粘度调整到2000-10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极。负极粉末涂布单位面密度为6-16mg/cm 2，负极压实密度1.2-2.0g/m 3。
负极活性材料层的孔隙率P可通过气体置换法得到，孔隙率P＝(V1-V2)/V1×100％，V1表示负极活性材料层的表观体积，V2表示负极活性材料层的真实体积。
单位面积负极活性材料层中负极活性物质的质量M的可使用标准天平称量得到。
负极活性材料层的厚度T可采用万分尺测量得到，例如可使用型号为Mitutoyo293-100、精度为0.1μm的万分尺测量得到。需要说明的是，本发明所述的负极活性材料层厚度是指经冷压压实后并用于组装电池的负极中的负极活性材料层的厚度。
电解质
电解质在正极和负极之间起到传导离子的作用。
所述电解液包含本申请如上所述的技术特征。
在一些实施方式中，所述电解液包含锂盐、溶剂和添加剂；其中所述锂盐包含主锂盐和副锂盐。
在一些实施方式中，所述主锂盐与副锂盐不同，并且所述主锂盐或副锂盐各自独立地选自六氟磷酸锂(LiPF 6)、双氟磺酰亚胺锂(LiN(SO 2F) 2，LiFSI)、四氟硼酸锂 (LiBF 4)、双三氟甲磺酰亚胺锂(LiTFSI)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、三氟甲磺酸锂(LiTFS)、二草酸硼酸锂(LiB(C 2O 4) 2，LiBOB)、二氟草酸硼酸锂(LiBF 2C 2O 4，LiDFOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)、LiPO 2F 2、LiFSO 3、LiF及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
在一些实施方式中，所述主锂盐与副锂盐不同，并且所述主锂盐或副锂盐各自独立地选自LiPF 6、LiN(SO 2F) 2(LiFSI)、LiBF 4、LiN(CF 3SO 2) 2(LiTFSI)、LiClO 4、LiAsF 6、LiB(C 2O 4) 2(LiBOB)、LiBF 2C 2O 4(LiDFOB)、二氟二草酸磷酸锂(LiDFOP)、LiPO 2F 2、LiFSO3、LiF中的至少一种。所述主锂盐与副锂盐区别在于其含量不同。
在一些优选的实施方式中，所述主锂盐为六氟磷酸锂或LiFSI，其含量为8-20wt％，基于所述电解液的总重量计；所述副锂盐为二氟草酸硼酸锂LiBF 2C 2O 4(LiDFOB)、LiBF 4、LiB(C 2O 4) 2(LiBOB)、二氟二草酸磷酸锂(LiDFOP)中的至少一种，可选为LiDFOB或LiDFOP，其含量为0.001wt％-2wt％，基于所述电解液的总重量计。
在一些优选的实施方式中，电解液中锂盐的摩尔浓度b为0.8-1.2mol/L。
在一些实施方式中，所述溶剂包含环状酯和线性酯；所述环状酯的含量占溶剂质量的5-40％，所述线性酯的含量占溶剂质量的60-95％。
在一些实施方式中，所述环状酯为碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)或其组合；所述线性酯包含碳酸二甲酯(DMC)。
在一些实施方式中，所述线性酯除了DMC，还可包含选自以下组分的至少一种：碳酸二乙酯(DEC)、碳酸甲乙酯(EMC)、甲酸甲酯、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丁酯、乙腈(SN)、丙酸甲酯、丙酸乙酯(EP)、丁酸甲酯、丁酸乙酯、丁酸丙酯、丁酸丁酯、乙酸异丙酯、乙酸异戊酯和其组合；可选为碳酸二乙酯DEC、乙酸乙酯EA、乙酸甲酯MA、乙腈SN、丙酸乙酯EP和组合。
在一个优选的实施方式中，所述环状酯为碳酸亚乙酯(EC)，所述线性酯包含碳酸二甲酯(DMC)和碳酸甲乙酯(EMC)。
在一些实施方式中，所述添加剂包含碳酸酯(例如碳酸氟代亚乙酯FEC)、硫酸酯(例如硫酸乙烯酯DTD)和磺酸酯(例如1,3-丙烷磺酸内酯PS)。所述碳酸酯包括碳酸氟代亚乙酯(FEC)、碳酸亚乙烯酯(VC)、碳酸1,2-二氟亚乙酯、碳酸1,1-二氟亚乙酯、碳酸1,1,2-三氟亚乙酯、碳酸1,1,2,2-四氟亚乙酯、碳酸1-氟-2-甲基亚乙酯、碳酸1-氟-1-甲基亚乙酯、碳酸1,2-二氟-1-甲基亚乙酯、碳酸1,1,2-三氟-2-甲基亚乙酯或碳酸三氟 甲基亚乙酯中的至少一种。所述硫酸酯包括硫酸乙烯酯(DTD)、硫酸二乙酯(DES)、硫酸二甲酯(DMS)和4,4-双(1,3,2-二氧杂硫杂环戊烷)-2,2,2,2-四氧化物中的至少一种。所述磺酸酯包括1,3-丙烷磺酸内酯(1,3-PS)、丙烯磺酸内酯(PES)、3-氟-1,3-丙磺酸内酯(FPS)、甲烷二磺酸乙烯酯(MMDS)中的至少一种。
在一些优选的实施方式中，所述添加剂包含碳酸氟代亚乙酯(FEC)、硫酸乙烯酯(DTD)和1,3-丙烷磺酸内酯(1,3-PS)。
在一些优选的实施方式中，所述添加剂含量占电解液总质量的质量百分含量为0-7％。
在一些实施方式中，所述电解液还可选地包括其他添加剂。例如其他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电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
隔离膜
在一些实施方式中，二次电池中还包括隔离膜。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，所述隔离膜的厚度为6-40μm，可选为12-20μm。
在一些实施方式中，正极、负极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、负极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。
在电池模块中，多个二次电池5可以是沿电池模块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。
可选地，电池模块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。
在电池包中可以包括电池箱和设置于电池箱中的多个电池模块。电池箱包括上箱体和下箱体，上箱体能够盖设于下箱体，并形成用于容纳电池模块的封闭空间。多个电池模块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3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
为了使本申请所解决的技术问题、技术方案及有益效果更加清楚，以下将结合实施例和附图对本申请进行进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。以下对至少一个示例性实施例的描述实际上仅仅是说明性的，决不作为对本申请及其应用的任何限制。基于本申请中的实施例，本领域普通技术人员在没有付出创造性劳动前提下所获得的所有其他实施例都属于本申请保护的范围。
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。
一、实施例
实施例1
1、电解液的制备：
电解液的制备在含水量<10ppm的氩气气氛手套箱中进行，首先将碳酸亚乙酯(EC)、碳酸甲乙酯(DMC)和碳酸二乙酯(EMC)按照3:4:3的质量比例进行混合，然后加入1mol/L的主锂盐LiPF 6，占电解液整体的1wt％的副锂盐LiDFOB+LiPO 2F 2，占电解液整体的5wt％的添加剂FEC+DTD，混合均匀，获得电解液。其中，锂盐的浓度为1mol/L。电解液的离子电导率为10mS/cm。
2、正极极片的制备：
将正极活性材料三元材料LiNi 1/3Co 1/3Mn 1/3O 2、粘结剂聚偏氟乙烯、导电剂乙炔黑按照重量比98:1:1的比例进行混合溶于溶剂N-甲基吡咯烷酮(NMP)中制成正极浆料，然后将浆料涂布在集流体铝箔上，干燥后进行冷压、切边、裁片、分条等，制成尺寸为87*665mm的正极极片，备用。
3、负极极片的制备：
将负极活性材料石墨、SiO2、粘结剂丁苯橡胶和分散剂羧甲基纤维素钠按重量比92.8：5：1.2：1的比例溶于去离子水中，形成负极浆料。采用6um铜箔作为负极集流体，先将第一层负极浆料涂覆于负极集流体上，涂布重量为4.25mg/cm 2，形成第一活性材料层。待第一活性材料层干燥后再涂覆第二负极浆料，将负极活性材料石墨、 SiO2、粘结剂丁苯橡胶和分散剂羧甲基纤维素钠按重量比92.8：5：1.2：1的比例溶于去离子水中，形成第二负极浆料；第二活性材料层涂覆重量为4.25mg/cm 2，形成第二活性材料层。
再先后经过干燥、冷压、裁切得到复合负极极片，冷压后，涂覆于铜箔一个表面上的复合活性材料层厚度为51um，活性材料层压实密度为1.65g/cm 3。
4、隔离膜
隔离膜基材为8μm厚的聚乙烯(PE)，在隔离膜基材的两侧各涂覆2μm氧化铝陶瓷层，最后在涂布了陶瓷层的两侧各涂覆2.5mg的粘结剂聚偏二氟乙烯(PVDF)，烘干。
5、组装成电池：
将上述的正极极片、隔离膜、负极极片按顺序卷绕或叠好，使隔离膜处于正负极极片中间，得到裸电芯，将裸电芯置于外包装中，将9.5g的上述制备的电解液注入到干燥后的电芯中，经过静置、化成、整形等工序，获得容量为3100mAh的锂离子二次电池。
实施例2-27和对比例1-6的制备步骤与实施例1类似，但是改变电解液或负极的材料或组成，参见表1。
参数测试
1.负极活性材料层的孔隙率P％测试
负极活性材料层的孔隙率P％可以如下进行测量：利用小分子直径的惰性气体如氦气或氮气，通过置换法精确测量得到待测样品的真实体积，并且结合玻尔定律(PV＝nRT)得到待测样品的孔隙率。孔隙率P＝(V11-V12)/V11×100％，其中V11表示负极活性材料层的表观体积，V12表示负极活性材料层的真实体积。
2.负极活性材料颗粒的平均宽长比分布的测试方法
负极活性材料的宽长比可通过动态颗粒图像分析(例如，使用新帕泰克QICPIC动态颗粒图像分析仪)获得。
表1各实施例和对比例的相关参数
Figure PCTCN2022126797-appb-000001
Figure PCTCN2022126797-appb-000002
Figure PCTCN2022126797-appb-000003
二、电池性能测试
1、锂离子电池CB值测试
正极嵌锂容量其测试方法如下：在PRS340/11-119-11布劳恩手套箱中拆解电池，取正极极片，组装成正极-锂片的CR2430型号半扣式电池，采用的正极极片面积为a mm 2，其中电解液采用1M LiPF6于EC/EMC/DEC＝3/5/2中的溶液；然后将组装好的半扣式电池静置3h，测试在25℃下进行，采用0.1C先在电压区间2.5-eV下进行充电(Charge)脱锂，其中e为电芯设计的使用上限电压，再采用0.05C放电(Discharge)嵌锂至2.5V，循环2次，取第二次循环的放电扣电容量记为Y mAh，实际电池设计的正极膜片长为b mm，宽为c mm，正极活性材料涂覆于正极集流体的面数d，则正极脱锂容量为X＝Y/a*b*c*d。
负极脱锂容量其测试方法为：在PRS340/11-119-11布劳恩手套箱中拆解电池，取负极极片，组装成负极-锂片的CR2430型号半扣式电池，采用的负极极片面积为f mm 2，其中电解液采用1M LiPF6于EC/EMC/DEC＝3/5/2中的溶液；然后将组装好的半扣式电池静置3h，测试在25℃下进行，采用0.1C先在电压区间2V-0V下进行放电(Discharge)嵌锂，再采用0.05C充电(Discharge)脱锂至2V，循环2次，取第二次循环的放电扣电容量记为ZmAh，实际电池设计的负极膜片长为h mm，宽为i mm，负极活性材料涂覆于负极集流体的面数d，则负极脱锂容量为W＝Z/f*h*i*d。
则CB＝W/X。
2、充电能力测试
倍率性能测试(充电至80％SOC的测试)：调节测试温度至35℃，对锂离子电池进行xC倍率(x为0.5、0.8、1、1.2、1.5、2、2.5、3)下的充电，然后在1C下放电，充 电倍率依次增高，以阳极电位0V为充电截止条件，获得0-10％SOC、10-20％SOC、20-30％SOC、30-40％SOC、40-50％SOC、50-60％SOC、60-70％SOC区间内能够实现的最大充电倍率，从而计算出0～80％SOC所需的充电时间(min)。
3、循环性能测试
在25℃下，将二次电池以1C恒流充电至4.3V，继续恒压充电至电流为0.05C，此时二次电池为满充状态，记录此时的充电容量，即为第1圈充电容量；将二次电池静置5min后，以1C恒流放电至2.8V，此为一个循环充放电过程，记录此时的放电容量，即为第1圈放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量。二次电池45℃循环600圈容量保持率(％)＝600圈循环后的放电容量/第1圈放电容量×100％。
三、各实施例、对比例测试结果
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表2。
表2各实施例和对比例的电池的性能
Figure PCTCN2022126797-appb-000004
Figure PCTCN2022126797-appb-000005
Figure PCTCN2022126797-appb-000006
通过上述实施例和对比例可得知，本申请的锂离子电池在同时满足负极活性材料的颗粒平均宽长比为0.1-1、电解液离子电导率在7-15mS/cm范围内和CB值为1.1-1.5的情况下，具有良好的快充能力以及容量保持率，例如0-70％SOC所需的充电时间可缩短至7-8分钟，循环600圈后容量保持率仍保持在95％以上。
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 (19)

  1. 一种锂离子电池，其包含正极、负极和电解液，其中，所述负极包含负极集流体及附着在负极集流体至少一个表面上的包含负极活性材料的负极活性材料层，其中所述负极活性材料的颗粒平均宽长比为0.1-1；所述电解液的离子电导率为7-15mS/cm；并且负极可嵌锂容量与正极可脱锂容量的比值CB为1.05-1.5。
  2. 根据权利要求1所述的电池，其特征在于，所述电池在自0％荷电状态到70％荷电状态的充电过程中存在大于等于4倍的单位时间内正极可脱锂容量的电流。
  3. 根据权利要求1或2所述的电池，其特征在于，所述电池在自0％荷电状态到80％荷电状态的充电过程中的平均电流大于等于4倍的单位时间内正可极脱锂容量。
  4. 根据权利要求1-3中任一项所述的电池，其特征在于，所述负极活性材料层的孔隙率为20-60％。
  5. 根据权利要求1-4中任一项所述的电池，其特征在于，所述负极活性材料层的压实密度为1.2-1.9g/cm 3，涂布重量为5-18mg/cm 2。
  6. 根据权利要求1-5中任一项所述的电池，其特征在于，所述负极活性材料包括天然石墨、人造石墨、中间相微碳球、硬碳、软碳、硅、硅-碳复合物、氧化硅或其组合物。
  7. 根据权利要求1-6中任一项所述的电池，其特征在于，所述负极活性材料层的厚度为30-150μm。
  8. 根据权利要求1-7中任一项所述的电池，其特征在于，所述负极活性材料层包括包含第一负极活性材料的第一活性材料层，以及附着在所述第一活性材料层远离所述集流体的表面上的包含第二负极活性材料的第二活性材料层。
  9. 根据权利要求8所述的电池，其特征在于，所述第一负极活性材料的平均体积粒径D v50大于第二负极活性材料的平均体积粒径D v50。
  10. 根据权利要求8或9所述的电池，其特征在于，所述第一负极活性材料层的压实密度大于第二负极活性材料层的压实密度。
  11. 根据权利要求1-10中任一项所述的电池，其特征在于，所述电解液包含锂盐、溶剂和添加剂；其中所述锂盐包含主锂盐和副锂盐。
  12. 根据权利要求11所述的电池，其特征在于，所述主锂盐与副锂盐不同，并且所述主锂盐或副锂盐各自独立地选自LiPF 6、LiN(SO 2F) 2、LiBF 4、LiN(CF 3SO 2) 2、LiClO 4、 LiAsF 6、LiB(C 2O 4) 2、LiBF 2C 2O 4、二氟二草酸磷酸锂、LiPO 2F 2、LiFSO 3、LiF中的至少一种。
  13. 根据权利要求11或12所述的电池，其特征在于，所述主锂盐为六氟磷酸锂或LiFSI，其含量为8-20wt％，基于所述电解液的总重量计；所述副锂盐为二氟草酸硼酸锂、LiBF 4、LiB(C 2O 4) 2、二氟二草酸磷酸锂中的至少一种，其含量为0.001wt％-2wt％，基于所述电解液的总重量计。
  14. 根据权利要求11-13中任一项所述的电池，其特征在于，所述溶剂包含环状酯和线性酯；所述环状酯的含量占溶剂质量的5-40％，所述线性酯的含量占溶剂质量的60-95％。
  15. 根据权利要求14所述的电池，其特征在于，所述环状酯为碳酸亚乙酯、碳酸亚丙基酯或其组合；所述线性酯包含碳酸二甲酯。
  16. 根据权利要求15所述的电池，其特征在于，所述线性酯选自碳酸二乙酯、碳酸甲乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丁酯、丙酸甲酯、丁酸甲酯、丁酸乙酯、丁酸丙酯、丁酸丁酯、乙酸异丙酯、乙酸异戊酯或其组合。
  17. 根据权利要求11-16中任一项所述的电池，其特征在于，溶剂中线性酯占溶剂质量的百分比b％与电解液的离子电导率a(mS/cm)之间满足以下关系式：
    8≤a+3b％≤16。
  18. 根据权利要求1-17中任一项所述的电池，其特征在于，所述正极包含集流体及附着在集流体至少一个表面上的包含正极活性材料的正极活性材料层，所述正极活性材料包含式LiNi xCo yQ zM 1-x-y-zO 2的三元材料，其中Q为Mn或Al，M包含Co、Ni、Mn、Mg、Cu、Zn、Al、Sn、B、Ga、Cr、Sr、V和Ti中至少一种，0≤x＜1，0≤y≤1，0≤z≤1，x+y+z≤1。
  19. 一种用电装置，其特征在于，包括选自权利要求1-18中任一项所述的二次电池。
PCT/CN2022/126797 2022-10-21 2022-10-21 锂离子电池和用电装置 WO2024082291A1 (zh)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013232326A (ja) * 2012-04-27 2013-11-14 Asahi Kasei Corp 非水系二次電池
CN103441305A (zh) * 2013-08-27 2013-12-11 深圳市贝特瑞新能源材料股份有限公司 一种动力与储能锂离子电池及其制备方法
CN105514350A (zh) * 2014-09-25 2016-04-20 东莞新能源科技有限公司 锂离子电池
CN105580184A (zh) * 2013-09-25 2016-05-11 国立大学法人东京大学 非水电解质二次电池
CN113036298A (zh) * 2019-12-06 2021-06-25 宁德时代新能源科技股份有限公司 负极极片及含有它的二次电池、装置
CN115101803A (zh) * 2022-07-14 2022-09-23 江苏正力新能电池技术有限公司 一种二次电池

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013232326A (ja) * 2012-04-27 2013-11-14 Asahi Kasei Corp 非水系二次電池
CN103441305A (zh) * 2013-08-27 2013-12-11 深圳市贝特瑞新能源材料股份有限公司 一种动力与储能锂离子电池及其制备方法
CN105580184A (zh) * 2013-09-25 2016-05-11 国立大学法人东京大学 非水电解质二次电池
CN105514350A (zh) * 2014-09-25 2016-04-20 东莞新能源科技有限公司 锂离子电池
CN113036298A (zh) * 2019-12-06 2021-06-25 宁德时代新能源科技股份有限公司 负极极片及含有它的二次电池、装置
CN115101803A (zh) * 2022-07-14 2022-09-23 江苏正力新能电池技术有限公司 一种二次电池

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