Lithium-ion battery and electric device

Abstract

A lithium ion battery and an electric device comprising the same, the lithium ion battery comprising 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 aspect ratio of the particles of the negative electrode active material is 0.1-1; the ionic conductivity of the electrolyte is 7-15 mS / cm; and the ratio CB of the lithium insertion capacity of the negative electrode to the lithium extraction capacity of the positive electrode is 1.05-1.5. The lithium ion battery has a large rate capability of fast charging and good cycle performance.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and more particularly to a lithium-ion battery and an electrical device. Background Technology

[0002] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. However, compared to traditional fuel-powered devices, range anxiety and long charging times have become major obstacles to the development of rechargeable batteries. How to improve the fast-charging capability of rechargeable batteries is one of the focuses of attention for those skilled in the art.

[0003] Improving the fast-charging capability of batteries is a complex undertaking that requires changes and upgrades to battery materials. Traditional research has focused primarily on improving negative electrode materials, but this also necessitates the coordination of electrolytes, conductive agents, and other materials. Therefore, existing batteries with fast-charging capabilities still require further improvement. Summary of the Invention

[0004] This application is made in view of the above-mentioned problems, and its purpose is to provide a lithium-ion battery that includes a negative electrode active material with a specific average aspect ratio, an electrolyte with a specific ionic conductivity, and has a specific range of a negative electrode lithium intercalation capacity to positive electrode lithium deintercalation capacity ratio CB, so that the corresponding battery has a high-rate fast charging capability and good cycle performance.

[0005] To achieve the above objectives, this application provides a lithium-ion battery and an electrical device.

[0006] The first aspect of this application provides a lithium-ion battery comprising 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 aspect ratio of the particles of the negative electrode active material is 0.1-1; the electrolyte has an ionic conductivity of 7-15 mS / cm; and the ratio CB of the lithium intercalation capacity of the negative electrode to the lithium deintercalation capacity of the positive electrode is 1.05-1.5.

[0007] The lithium-ion battery of this application effectively reduces the tortuosity inside the negative electrode by including a negative electrode active material with a specific average aspect ratio, an electrolyte with a specific ionic conductivity, and a specific range of the ratio CB of the negative electrode lithium intercalation capacity to the positive electrode lithium deintercalation capacity. This improves the liquid phase transport conditions of lithium ions and provides more active sites for lithium ion intercalation in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0008] In any embodiment, the battery exhibits a current greater than or equal to four times the positive electrode's lithium-depleting capacity per unit time during charging from 0% to 70% state of charge at 35°C. This further improves the battery's high-rate fast-charging capability and cycle performance.

[0009] In any embodiment, the average current of the battery during the charging process from 0% state of charge to 80% state of charge at 35°C is greater than or equal to four times the positive electrode's lithium-depleting capacity per unit time. This further improves the battery's high-rate fast-charging capability and cycle performance.

[0010] In any embodiment, the porosity of the negative electrode active material layer is 20-60%. This provides more active sites for lithium-ion insertion at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0011] In any embodiment, the compaction density of the negative electrode active material layer is 1.2-1.9 g / cm³. 3 The coating weight is 5-18 mg / cm³. 2 This provides more active sites for lithium ion insertion at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0012] In any embodiment, the negative electrode active material includes natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, silicon oxide, or combinations thereof. This further provides more active sites for lithium-ion intercalation in the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0013] In any embodiment, the thickness of the negative electrode active material layer is 30-150 μm. This further improves the liquid-phase transport conditions of lithium ions and provides more active sites for lithium ion insertion at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0014] In any embodiment, the active material layer includes a first active material layer comprising a first negative electrode active material, and a second active material layer comprising a second negative electrode active material attached to the surface of the first active material layer away from the current collector. This further improves the liquid-phase transport conditions of lithium ions and provides more active sites at the negative electrode for lithium ion insertion, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0015] In any embodiment, the average volume particle size D of the first negative electrode active material is... v50 The average volume particle size D of the second negative electrode active material is greater than that of the second negative electrode active material. v50This provides more active sites for lithium ion insertion at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0016] In any embodiment, the compaction density of the first negative electrode active material layer is greater than that of the second negative electrode active material layer. This provides more active sites for lithium-ion intercalation in the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0017] In any embodiment, the electrolyte comprises a lithium salt, a solvent, and additives; wherein the lithium salt comprises a primary lithium salt and a secondary lithium salt. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the battery's high-rate fast-charging capability and cycle performance.

[0018] In any embodiment, the primary lithium salt and the secondary lithium salt are different, and each primary or secondary lithium salt is independently selected from at least one of LiPF6, LiN(SO2F)2, LiBF4, LiN(CF3SO2)2, LiClO4, LiAsF6, LiB(C2O4)2, LiBF2C2O4, lithium difluorodioxalate phosphate, LiPO2F2, LiFSO3, and LiF. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0019] In any embodiment, the primary lithium salt is lithium hexafluorophosphate or LiFSI, with a content of 8-20 wt% based on the total weight of the electrolyte; the secondary lithium salt is at least one selected from lithium difluorooxalatoborate, LiBF4, LiB(C2O4)2, and lithium difluorodiooxalatophosphate, with a content of 0.001 wt%-2 wt% based on the total weight of the electrolyte. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0020] In any embodiment, the solvent comprises cyclic esters and linear esters; the content of the cyclic esters accounts for 5-40% of the solvent mass, and the content of the linear esters accounts for 60-95% of the solvent mass. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0021] In any embodiment, the cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof; the linear ester comprises dimethyl carbonate. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the battery's high-rate fast-charging capability and cycle performance.

[0022] In any embodiment, the linear ester is selected from diethyl carbonate, methyl ethyl carbonate, methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, or combinations thereof. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0023] In any embodiment, the percentage b% of linear ester in the solvent by mass and the ionic conductivity a (mS / cm) of the electrolyte satisfy the following relationship:

[0024] 8 ≤ a + 3b % ≤ 16. This further improves the liquid-phase transport conditions of lithium ions and provides more active sites for lithium ion insertion at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0025] In any embodiment, 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 LiNi x Co y Q z M 1-x-y-z The ternary material O2, wherein Q is Mn or Al, and M includes at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, wherein 0≤x<1, 0≤y≤1, 0≤z≤1, and x+y+z≤1. This further improves the liquid-phase transport conditions of lithium ions and provides more active sites for lithium ion intercalation at the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0026] The second aspect of this application provides an electrical device, characterized in that it includes the secondary battery described in the first aspect of this application.

[0027] The lithium-ion battery of this application improves the liquid phase transport conditions of lithium ions by including a negative electrode active material with a specific average aspect ratio, an electrolyte with a specific ionic conductivity, and having a specific range of a negative electrode lithium intercalation capacity to positive electrode lithium deintercalation capacity ratio CB, and provides more active sites for lithium ion intercalation in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0029] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0030] Figure 3 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to an embodiment of this application.

[0031] Explanation of reference numerals in the attached figures:

[0032] 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. Detailed Implementation

[0033] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the lithium-ion battery and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0034] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0035] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0036] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0037] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0038] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0039] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: 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).

[0040] Currently, compared to traditional fuel-powered devices, range anxiety and long charging times are the main obstacles to the development of rechargeable batteries. Improving the fast-charging capability of rechargeable batteries is one of the focuses of attention for those skilled in the art.

[0041] Improving the fast-charging capability of batteries is a systematic project that requires changes and upgrades to battery materials. Traditional research focuses primarily on improving negative electrode materials, but this also necessitates the coordination of electrolytes, conductive agents, and other materials. Therefore, existing fast-charging batteries still require further improvement. The inventors have discovered that the lithium-ion battery of the first aspect of this application comprises a negative electrode active material with a specific average aspect ratio, an electrolyte with a specific ionic conductivity, and a specific range of the ratio (CB) of lithium intercalation capacity in the negative electrode to lithium deintercalation capacity in the positive electrode. Adjusting the average aspect ratio of the negative electrode active material particles can effectively reduce the tortuosity inside the negative electrode sheet, while simultaneously increasing the conductivity of the electrolyte, greatly improving the liquid-phase transport conditions of lithium ions. Furthermore, a higher CB value provides more active sites for lithium ion intercalation in the negative electrode, thereby improving the high-rate fast-charging capability and cycle performance of the battery.

[0042] Lithium-ion batteries

[0043] In some embodiments, a first aspect of this application provides a lithium-ion battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode current collector and a layer of negative electrode active material comprising a negative electrode active material attached to at least one surface of the negative electrode current collector, wherein the average aspect ratio of the particles of the negative electrode active material is 0.1-1, optionally 0.6-1; the electrolyte has an ionic conductivity of 7-15 mS / cm, optionally 8-13 mS / cm, further optionally 9-11 mS / cm, measured according to HG / T4067-2015; and the ratio CB of the negative electrode's lithium intercalation capacity to the positive electrode's lithium deintercalation capacity is 1.05-1.5, optionally 1.1-1.3, further optionally 1.1-1.2.

[0044] The lithium-ion battery of this application effectively reduces the tortuosity inside the negative electrode by including a negative electrode active material with a specific average aspect ratio, an electrolyte with a specific ionic conductivity, and a specific range of the ratio CB of the negative electrode lithium intercalation capacity to the positive electrode lithium deintercalation capacity. This improves the liquid phase transport conditions of lithium ions and provides more active sites for lithium ion intercalation in the negative electrode, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0045] In this application, the "width-to-length ratio" of the negative electrode active material refers to the ratio of the width diameter to the length diameter of the negative electrode active material particles. The width-to-length ratio of the negative electrode active material can be obtained through dynamic particle image analysis (e.g., using a NewPatek QICPIC dynamic particle image analyzer). The "width diameter" of the negative electrode active material particles refers to the minimum value between parallel lines tangent to the projected image of the particle. The "length diameter" of the negative electrode active material particles refers to the maximum value between parallel lines tangent to the projected image of the particle. When the width-to-length ratio of the negative electrode active material is small, the negative electrode active material particles are elongated; when it is close to 1, the negative electrode active material particles are spherical.

[0046] In this application, the ionic conductivity of the electrolyte refers to the electrolyte's ability to conduct electricity.

[0047] In this application, the term "positive electrode delithiation capacity" refers to the actual delithiation capacity of the positive electrode material in the battery. The testing method is as follows: The battery is disassembled in a Braun glove box (PRS340 / 11-119-11), the positive electrode sheet is removed, and assembled into a CR2430 model semi-button battery with a positive electrode and lithium sheet. The positive electrode sheet area used is a mm². 2The electrolyte used was a 1M LiPF6 solution in EC / EMC / DEC = 3 / 5 / 2. The assembled semi-coin cells were then left to stand for 3 hours. The test was conducted at 25°C. The cells were first charged at 0.1C in the voltage range of 2.5-eV to remove lithium, where e is the upper limit voltage of the cell design. Then, the cells were discharged at 0.05C to insert lithium to 2.5V. The cycle was repeated twice. The discharge capacity of the second cycle was recorded as Y mAh. The actual battery design has a positive electrode film length of b mm and a width of c mm. The number of surfaces of the positive electrode active material coated on the positive electrode current collector is d. Therefore, the positive electrode delithiation capacity is X = Y / a*b*c*d.

[0048] In some embodiments, the lithium-delithiable capacity of the positive electrode is 2000-300000mAh, optionally 3000-150000mAh, and further optionally 3000-4000mAh.

[0049] In this application, the term "negative electrode lithium intercalation capacity" refers to the actual lithium intercalation capacity of the negative electrode material in the battery. The testing method is as follows: the battery is disassembled in a PRS340 / 11-119-11 Braun glove box, the negative electrode sheet is removed, and assembled into a CR2430 model semi-button battery with a negative electrode-lithium sheet configuration. The negative electrode sheet area used is f mm². 2 The electrolyte used was a 1M LiPF6 solution in EC / EMC / DEC = 3 / 5 / 2. The assembled semi-coin cells were then left to stand for 3 hours. The test was conducted at 25°C. The cells were first discharged at 0.1C in the voltage range of 2V-0V to insert lithium, and then discharged at 0.05C to remove lithium to 2V. The cycle was repeated twice. The discharge capacity of the second cycle was recorded as ZmAh. The actual battery design had a negative electrode film with a length of h mm and a width of i mm. The number of surfaces of the negative electrode active material coated on the negative electrode current collector was d. The delithiation capacity of the negative electrode was W = Z / f*h*i*d.

[0050] In some embodiments, the lithium-intercalable capacity of the negative electrode is 2100-315000mAh, optionally 3000-100000mAh, and further optionally 3500-4500mAh.

[0051] In some embodiments, during the charging process from 0% state of charge (SOC) to 70% SOC at 35°C, the battery exhibits a current greater than or equal to four times the positive electrode's lithium-deintercalation capacity per unit time. Optionally, this current is greater than or equal to five times the positive electrode's lithium-deintercalation capacity per unit time, and more preferably five to six.5 times the positive electrode's lithium-deintercalation capacity per unit time. This further improves the battery's high-rate fast charging capability and cycle performance. In this embodiment, the current is an instantaneous current.

[0052] In this application, "the lithium-depleting capacity of the cathode per unit time" refers to the amount of lithium depleted from the cathode per unit time (1 hour); the average current generated during this process is used as the benchmark for current quantification in this application. Thus, the lithium-depleting capacity of the cathode can be correlated with the current.

[0053] In some implementations, constant current direct charging can typically be used during the charging process from 0% to 70% state of charge at 35°C, for example, charging from 0% to 70% state of charge with a current four times the positive electrode's deintercalation capacity per unit time. Alternatively, a step-by-step charging method can be used, for example, using A times the positive electrode's deintercalation capacity per unit time for 0-10% SOC, B times the positive electrode's deintercalation capacity per unit time for 10-20% SOC, and so on for 20-30%. The SOC is calculated using C times the current that the positive electrode can be de-intercalated per unit time; for 30-40% SOC, D times the current that the positive electrode can be de-intercalated per unit time; for 40-50% SOC, E times the current that the positive electrode can be de-intercalated per unit time; for 50-60% SOC, F times the current that the positive electrode can be de-intercalated per unit time; and for 60-70% SOC, G times the current that the positive electrode can be de-intercalated per unit time, etc., where at least one of A, B, C, D, E, and F is not 4. Those skilled in the art will understand that in step charging, the SOC and current magnitude of each step can be adjusted as needed.

[0054] For a packaged battery, the positive electrode delithiation capacity X is tested using the positive electrode delithiation capacity detection method. The battery is then charged using the above charging mode, and the positive electrode is disassembled and the positive electrode sheet is removed. The positive electrode delithiation capacity Z is then tested using the positive electrode delithiation capacity detection method. If Z / X ≥ 40%, it is considered to meet the charging rate requirement of 4 times the positive electrode deintercalation capacity per unit time.

[0055] In some embodiments, the average current of the battery during charging from 0% to 70% state of charge (0-70% SOC) at 35°C is greater than or equal to 4 times the positive electrode delithiation capacity per unit time, and optionally greater than or equal to 5 times the positive electrode deintercalation capacity per unit time. This further improves the battery's high-rate fast charging capability and cycle performance.

[0056] In one embodiment, the average current of the 0-70% SOC is tested by constant current direct charging, in which case the average current is the charging current; or by step charging as described above, the average current is (A+B+C+D+E+F+G) / 7.

[0057] In some embodiments, the porosity of the negative electrode active material layer is 20-60%, optionally 25-40%, and further optionally 25-31%. This provides more active sites for lithium-ion insertion in the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0058] In some embodiments, the compaction density of the negative electrode active material layer is 1.2-1.9 g / cm³. 3 The selectable value is 1.5-1.78 g / cm³. 3 The coating weight is 5-18 mg / cm³. 2 This provides more active sites for lithium ion insertion at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0059] In some embodiments, the active material layer includes a first active material layer comprising a first negative electrode active material, and a second active material layer comprising a second negative electrode active material attached to the surface of the first active material layer away from the current collector. This further improves the liquid-phase transport conditions of lithium ions and provides more active sites at the negative electrode for lithium ion intercalation, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0060] In some embodiments, the average volumetric particle size D of the first negative electrode active material v50 The average volume particle size D of the second negative electrode active material is greater than that of the second negative electrode active material. v50 This provides more active sites for lithium ion insertion at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0061] In some embodiments, the average volumetric particle size D of the first negative electrode active material v50 The average volumetric particle size D of the second negative electrode active material is 10-20 μm, optionally 12-16 μm. v50 The particle size is 9-19 μm, measured by laser diffraction method according to particle size distribution (refer to GB / T19077.1-2009).

[0062] In some embodiments, the thickness of the first negative electrode active material layer is 10-120 μm, and the thickness of the second negative electrode active material layer is 10-120 μm, measured according to the morphology analysis of the cross-section by ion polishing using scanning electron microscopy (refer to JY / T010-1996 for details) (measured at least 5 locations and the average value is taken).

[0063] In some embodiments, the negative electrode active material includes natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composites, silicon oxide, or combinations thereof. This further provides more active sites for lithium-ion intercalation at the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0064] In some embodiments, the thickness of the negative electrode active material layer is 30-150 μm. This further improves the liquid-phase transport conditions of lithium ions and provides more active sites for lithium ion intercalation in the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0065] In some embodiments, the compaction density of the first negative electrode active material layer is greater than that of the second negative electrode active material layer. This provides more active sites for lithium-ion intercalation in the negative electrode, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0066] In some embodiments, the compaction density of the first negative electrode active material layer is 1.3-2 g / cm³, and the compaction density of the second negative electrode active material layer is 1.2-1.9 g / cm³. The mass per unit area of ​​the negative electrode material layer, i.e., the coating surface density CW (mg / cm³), can be calculated by weighing the negative electrode material layer using a standard balance and measuring the coating area of ​​the negative electrode sheet using a ruler. 2 Then, the thickness of the negative electrode material layer was measured by scanning electron microscopy (SEM) and ion polishing cross-sectional morphology analysis (refer to JY / T010-1996) (measurements were taken at least 5 times, and the average value was taken). The coating compaction density was calculated as follows: CW (mg / cm³) = negative electrode coating surface density. 2 The compaction density PD (unit: mg / cm³) of the negative electrode material layer is calculated by dividing the negative electrode material layer thickness (cm). 3 ), then convert to g / cm³ 3 Measurement.

[0067] In some embodiments, the electrolyte comprises a lithium salt, a solvent, and additives; wherein the lithium salt comprises a primary lithium salt and a secondary lithium salt. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the battery's high-rate fast-charging capability and cycle performance.

[0068] In some embodiments, the primary lithium salt and the secondary lithium salt are different, and each primary or secondary lithium salt is independently selected from at least one of LiPF6, LiN(SO2F)2 (LiFSI), LiBF4, LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB), LiBF2C2O4 (LiDFOB), lithium difluorodioxalate phosphate (LiDFOP), LiPO2F2, LiFSO3, and LiF. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery. The primary and secondary lithium salts differ only in their content.

[0069] In some embodiments, the primary lithium salt is lithium hexafluorophosphate or LiFSI, with a content of 8-20 wt% 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 difluorodioxalatophosphate (LiDFOP), optionally LiDFOB or LiDFOP, with a content of 0.001 wt%-2 wt% based on the total weight of the electrolyte. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0070] In some preferred embodiments, the molar concentration b of the lithium salt in the electrolyte is 0.6-1.5 mol / L.

[0071] In some embodiments, the solvent comprises cyclic esters and linear esters; the cyclic esters account for 5-40% of the solvent mass, and the linear esters account for 60-95% of the solvent mass. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0072] In some embodiments, the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC), or a combination thereof; the linear ester comprises dimethyl carbonate (DMC). This further improves the liquid-phase transport conditions of lithium ions, thereby improving the battery's high-rate fast-charging capability and cycle performance.

[0073] In some embodiments, the linear ester, in addition to DMC, may also contain at least one component selected from: 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; optionally, it may be diethyl carbonate (DEC), ethyl acetate (EA), methyl acetate (MA), acetonitrile (SN), ethyl propionate (EP), and combinations thereof. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the high-rate fast charging capability and cycle performance of the battery.

[0074] In a preferred embodiment, the cyclic ester is ethylene carbonate (EC), and the linear ester comprises dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0075] In some embodiments, the percentage b% of linear ester by mass in the solvent and the ionic conductivity a (mS / cm) of the electrolyte satisfy the following relationship:

[0076] 8≤a+3b%≤16, or optionally 9≤a+3b%≤15. This further improves the liquid-phase transport conditions of lithium ions, thereby improving the battery's high-rate fast charging capability and cycle performance.

[0077] In some embodiments, the positive electrode includes a current collector and a layer of positive electrode active material comprising a positive electrode active material attached to at least one surface of the current collector, wherein the positive electrode active material includes LiNi. x Co y Q z M 1-x-y-z The ternary material O2, wherein Q is Mn or Al, and M includes at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V, and Ti, wherein 0 ≤ x < 1, and may be selected as 0.5 ≤ x < 1; 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, and x + y + z ≤ 1. This further improves the high-rate fast charging capability and cycle performance of the battery.

[0078] A second aspect of this application provides an electrical device, characterized in that it includes the secondary battery described in the first aspect of this application.

[0079] The lithium-ion battery and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0080] Typically, a lithium-ion battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0081] positive electrode

[0082] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, wherein the positive electrode film layer includes a positive electrode active material. The positive electrode active material includes the formula LiNi. x Co y Q z M 1-x-y-z O2 is a ternary material, wherein Q is Mn or Al, and M includes at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, 0≤x<1, which can be selected as 0.5≤x<1; 0≤y≤1, 0≤z≤1, x+y+z≤1.

[0083] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0084] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material substrate 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 the polymer material substrate. The metal material includes, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. The polymer material substrate may be (e.g., polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0085] In some embodiments, the positive electrode active material may be lithium nickel cobalt oxide or lithium nickel cobalt manganese oxide (LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 O2), LiNi 1 / 3 Co 1 / 3 Al 1 / 3 At least one of O2 or its modified compounds, preferably NCM 622 However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0086] In some embodiments, the positive electrode active material may further comprise other positive electrode active materials known in the art for use in batteries. As examples, other positive electrode active materials may include at least one of the following: lithium phosphates with an olivine structure, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium manganese cobalt oxides, lithium nickel manganese oxides, and their modified compounds. Examples of lithium phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also abbreviated as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites.

[0087] In some embodiments, the positive electrode active material accounts for 80-100% by weight in the positive electrode film, based on the total weight of the positive electrode film.

[0088] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder constitutes 0-20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0089] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, carbon black (e.g., acetylene black, Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0090] In some embodiments, the positive electrode can be prepared by dispersing the components used to prepare the positive electrode, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, wherein the solid content of the positive electrode slurry is 40-80 wt%, the viscosity at room temperature is adjusted to 5000-25000 mPa·s, the positive electrode slurry is coated on the surface of the positive electrode current collector, dried, and then cold-pressed in a cold rolling mill to form the positive electrode; the areal density of the positive electrode powder coating is 12-26 mg / cm². 2 The positive electrode compaction density is 2.0-3.6 g / cm³. 3 The concentration can be selected as 2.3-3.5 g / cm³. 3 The formula for calculating the compaction density is as follows:

[0091] Compacted density = Coating surface density / (Thickness after extrusion - Current collector thickness).

[0092] negative electrode

[0093] 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, the negative electrode active material layer including a negative electrode active material. The active material layer includes a first active material layer comprising a first negative electrode active material, and a second active material layer comprising a second negative electrode active material attached to the surface of the first active material layer away from the current collector. The negative electrode includes the technical features of the negative electrode described above in this application.

[0094] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0095] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate 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 the polymer material substrate. The metal material includes, but is not limited to, copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc., and the polymer material substrate includes, but is not limited to, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0096] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, 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, and 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. However, this application is not limited to these materials, and other conventional 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 percentage 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.

[0097] In some embodiments, the negative electrode active material includes at least one of natural graphite, artificial graphite, mesophase microcarbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide, or combinations thereof.

[0098] In some embodiments, the negative electrode active material comprises natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, silicon-oxygen composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 One or more of Li-Al alloys.

[0099] In some embodiments, the first negative electrode active material is natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, or spinel-structured lithiated TiO2-Li4Ti5O. 12At least one of the following: Li-Al alloy; the second negative electrode active material is natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, silicon-oxygen composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, or spinel-structured lithiated TiO2-Li4Ti5O 12 At least one of Li-Al alloys.

[0100] In some embodiments, the negative electrode active material comprises silicon. The silicon content accounts for 1-10% of the weight of the negative electrode active material layer and is distributed in at least one layer of the active material layer.

[0101] In some embodiments, the silicon content (as SiO2) in the first active material layer is 0-25% based on the weight of the first active material layer; and the silicon content (as SiO2) in the second active material layer is 0-25% based on the weight of the second active material layer.

[0102] In some embodiments, the negative electrode film layer may optionally 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). The binder accounts for 0-30% by weight of the negative electrode film layer, based on the total weight of the negative electrode film layer.

[0103] In some embodiments, the negative electrode film may optionally 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 conductive agent accounts for 0-20% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0104] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). The other additives constitute 0-15% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0105] In some embodiments, the negative electrode can be prepared by dispersing the components used to prepare the negative electrode, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70 wt%, and the viscosity at room temperature is adjusted to 2000-10000 mPa·s; the obtained negative electrode slurry is coated onto a negative electrode current collector, and after a drying process, cold-pressed, for example, by rollers, to obtain the negative electrode. The areal density of the negative electrode powder coating is 6-16 mg / cm².2 The compaction density of the negative electrode is 1.2-2.0 g / m³. 3 .

[0106] The porosity P of the negative electrode active material layer can be obtained by gas displacement method. Porosity P = (V1-V2) / V1×100%, where V1 represents the apparent volume of the negative electrode active material layer and V2 represents the actual volume of the negative electrode active material layer.

[0107] The mass M of the negative electrode active material in a unit area negative electrode active material layer can be obtained by weighing using a standard balance.

[0108] The thickness T of the negative electrode active material layer can be measured using a micrometer, such as a Mitutoyo 293-100 micrometer with an accuracy of 0.1 μm. It should be noted that the thickness of the negative electrode active material layer mentioned in this invention refers to the thickness of the negative electrode active material layer in the negative electrode used for battery assembly after cold pressing and compaction.

[0109] electrolytes

[0110] Electrolytes act as conductors for ions between the positive and negative electrodes.

[0111] The electrolyte contains the technical features described above in this application.

[0112] In some embodiments, the electrolyte comprises a lithium salt, a solvent, and an additive; wherein the lithium salt comprises a primary lithium salt and a secondary lithium salt.

[0113] In some embodiments, the primary lithium salt is different from the secondary lithium salt, and each primary lithium salt or secondary lithium salt is independently selected from one or more of lithium hexafluorophosphate (LiPF6), lithium bis(SO2F)2 (LiFSI), lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium trifluoromethanesulfonate (LiTFS), lithium dioxolaneborate (LiB(C2O4)2 (LiBOB), lithium difluorooxolaneborate (LiBF2C2O4 (LiDFOB)), lithium difluorophosphate (LiPO2F2), lithium difluorodioxolane phosphate (LiDFOP), LiPO2F2, LiFSO3, LiF, and lithium tetrafluorooxolane phosphate (LiTFOP).

[0114] In some embodiments, the primary lithium salt and the secondary lithium salt are different, and each primary lithium salt or secondary lithium salt is independently selected from at least one of LiPF6, LiN(SO2F)2 (LiFSI), LiBF4, LiN(CF3SO2)2 (LiTFSI), LiClO4, LiAsF6, LiB(C2O4)2 (LiBOB), LiBF2C2O4 (LiDFOB), lithium difluorodioxalate phosphate (LiDFOP), LiPO2F2, LiFSO3, and LiF. The primary lithium salt and the secondary lithium salt are distinguished by their different contents.

[0115] In some preferred embodiments, the primary lithium salt is lithium hexafluorophosphate or LiFSI, with a content of 8-20 wt% 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 difluorodioxalatophosphate (LiDFOP), optionally LiDFOB or LiDFOP, with a content of 0.001 wt%-2 wt% based on the total weight of the electrolyte.

[0116] In some preferred embodiments, the molar concentration b of the lithium salt in the electrolyte is 0.8-1.2 mol / L.

[0117] In some embodiments, the solvent comprises cyclic esters and linear esters; the cyclic esters account for 5-40% of the solvent mass, and the linear esters account for 60-95% of the solvent mass.

[0118] In some embodiments, the cyclic ester is ethylene carbonate (EC), propylene carbonate (PC), or a combination thereof; the linear ester comprises dimethyl carbonate (DMC).

[0119] In some embodiments, the linear ester may, in addition to DMC, comprise at least one component selected from the following: 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; optionally, it may be diethyl carbonate (DEC), ethyl acetate (EA), methyl acetate (MA), acetonitrile (SN), ethyl propionate (EP), and combinations thereof.

[0120] In a preferred embodiment, the cyclic ester is ethylene carbonate (EC), and the linear ester comprises dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC).

[0121] In some embodiments, the additive comprises a carbonate (e.g., fluoroethylene carbonate, FEC), a sulfate (e.g., vinyl sulfate, DTD), and a sulfonate (e.g., 1,3-propanesulfonyl lactone, PS). The carbonate includes at least one of fluoroethylene carbonate (FEC), vinylene 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. The sulfate esters include at least one selected from vinyl sulfate (DTD), diethyl sulfate (DES), dimethyl sulfate (DMS), and 4,4-bis(1,3,2-dioxathiacyclopentane)-2,2,2,2-tetraoxide. The sulfonates include at least one selected from 1,3-propanesulfonate lactone (1,3-PS), propenesulfonate lactone (PES), 3-fluoro-1,3-propanesulfonate lactone (FPS), and vinyl methane disulfonate (MMDS).

[0122] In some preferred embodiments, the additive comprises fluoroethylene carbonate (FEC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (1,3-PS).

[0123] In some preferred embodiments, the additive content accounts for 0-7% of the total mass of the electrolyte.

[0124] In some embodiments, the electrolyte may optionally include other additives. For example, other additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0125] Separating membrane

[0126] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0127] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0128] In some embodiments, the thickness of the isolation membrane is 6-40 μm, optionally 12-20 μm.

[0129] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0130] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the aforementioned electrode assembly and electrolyte.

[0131] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0132] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0133] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0134] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0135] In the battery module, multiple secondary batteries 5 can be arranged sequentially along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be secured with fasteners.

[0136] Optionally, the battery module may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0137] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0138] The battery pack may include a battery box and multiple battery modules disposed within the battery box. The battery box includes an upper body and a lower body, with the upper body covering the lower body to form a closed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0139] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., 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.

[0140] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0141] Figure 3 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0142] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0143] Example

[0144] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0145] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0146] I. Implementation Examples

[0147] Example 1

[0148] 1. Preparation of electrolyte:

[0149] The electrolyte was prepared in an argon-atmospheric glove box with a water content of <10 ppm. First, ethylene carbonate (EC), ethyl methyl carbonate (DMC), and diethyl carbonate (EMC) were mixed in a 3:4:3 mass ratio. Then, 1 mol / L of the main lithium salt LiPF6, 1 wt% of the secondary lithium salt LiDFOB + LiPO2F2, and 5 wt% of the additive FEC + DTD were added. The mixture was thoroughly mixed to obtain the electrolyte. The lithium salt concentration was 1 mol / L. The ionic conductivity of the electrolyte was 10 mS / cm.

[0150] 2. Preparation of the positive electrode sheet:

[0151] The positive electrode active material is ternary material LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, binder polyvinylidene fluoride, and conductive agent acetylene black are mixed in a weight ratio of 98:1:1 and dissolved in the solvent N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The slurry is then coated onto a current collector aluminum foil, dried, and cold-pressed, trimmed, cut, and slit to produce a positive electrode sheet with a size of 87*665mm for later use.

[0152] 3. Preparation of the negative electrode sheet:

[0153] A negative electrode slurry was formed by dissolving graphite (anode active material), SiO2, styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (dispersant) in deionized water at a weight ratio of 92.8:5:1.2:1. A 6µm copper foil was used as the negative electrode current collector. The first layer of negative electrode slurry was coated onto the current collector at a coating weight of 4.25 mg / cm³. 2 A first active material layer is formed. After the first active material layer dries, a second negative electrode slurry is coated on top. The negative electrode active materials 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 the second negative electrode slurry. The weight of the second active material layer coating is 4.25 mg / cm³. 2 This forms a second active material layer.

[0154] After drying, cold pressing, and cutting, a composite negative electrode sheet is obtained. After cold pressing, the thickness of the composite active material layer coated on one surface of the copper foil is 51 μm, and the compaction density of the active material layer is 1.65 g / cm³. 3 .

[0155] 4. Separating membrane

[0156] The separator substrate is 8μm thick polyethylene (PE). A 2μm alumina ceramic layer is coated on each side of the separator substrate. Finally, 2.5mg of polyvinylidene fluoride (PVDF) adhesive is coated on each side of the ceramic layer and then dried.

[0157] 5. Assemble into a battery:

[0158] The above-mentioned positive electrode, separator, and negative electrode are wound or stacked in sequence, with the separator positioned between the positive and negative electrodes, to obtain a bare cell. The bare cell is placed in an outer packaging, and 9.5g of the electrolyte prepared above is injected into the dried cell. After standing, formation, and shaping processes, a lithium-ion secondary battery with a capacity of 3100mAh is obtained.

[0159] The preparation steps of Examples 2-27 and Comparative Examples 1-6 are similar to those of Example 1, but the electrolyte or negative electrode material or composition is changed, see Table 1.

[0160] Parameter testing

[0161] 1. Porosity (P%) test of the negative electrode active material layer

[0162] The porosity P% of the negative electrode active material layer can be measured as follows: Using an inert gas with a small molecule diameter, such as helium or nitrogen, the actual volume of the sample is accurately measured via a displacement method. The porosity is then calculated using Bohr's law (PV = nRT). Porosity P = (V11 - V12) / V11 × 100%, where V11 represents the apparent volume of the negative electrode active material layer, and V12 represents the actual volume of the negative electrode active material layer.

[0163] 2. Test method for the average aspect ratio distribution of negative electrode active material particles

[0164] The aspect ratio of the negative electrode active material can be obtained through dynamic particle image analysis (e.g., using the New Patek QICPIC dynamic particle image analyzer).

[0165] Table 1. Relevant parameters for each embodiment and comparative example.

[0166]

[0167]

[0168]

[0169] II. Battery Performance Testing

[0170] 1. Lithium-ion battery CB value test

[0171] The test method for the positive electrode lithium intercalation capacity is as follows: The battery is disassembled in a Braun glove box (PRS340 / 11-119-11), the positive electrode sheet is removed, and assembled into a CR2430 model semi-button battery with a positive electrode and lithium sheet. The positive electrode sheet area used is a mm². 2 The electrolyte used was a 1M LiPF6 solution in EC / EMC / DEC = 3 / 5 / 2. The assembled semi-coin cells were then left to stand for 3 hours. The test was conducted at 25°C. The cells were first charged at 0.1C in the voltage range of 2.5-eV to remove lithium, where e is the upper limit voltage of the cell design. Then, the cells were discharged at 0.05C to insert lithium to 2.5V. The cycle was repeated twice. The discharge capacity of the second cycle was recorded as Y mAh. The actual battery design has a positive electrode film length of b mm and a width of c mm. The number of surfaces of the positive electrode active material coated on the positive electrode current collector is d. Therefore, the positive electrode delithiation capacity is X = Y / a*b*c*d.

[0172] The test method for negative electrode delithiation capacity is as follows: The battery is disassembled in a Braun glove box (PRS340 / 11-119-11), the negative electrode sheet is removed, and it is assembled into a CR2430 model semi-button battery with a negative electrode and lithium sheet. The area of ​​the negative electrode sheet used is fmm². 2 The electrolyte used was a 1M LiPF6 solution in EC / EMC / DEC = 3 / 5 / 2. The assembled half-coin cell was then left to stand for 3 hours. The test was conducted at 25°C. Lithium was first inserted by discharging at 0.1C in the voltage range of 2V-0V, and then lithium was removed by charging at 0.05C to 2V. The cycle was repeated twice. The discharge capacity of the second cycle was recorded as ZmAh. The actual battery design had a negative electrode film with a length of h mm and a width of i mm. The number of surfaces of the negative electrode active material coated on the negative electrode current collector was d. The negative electrode delithiation capacity was W = Z / f*h*i*d.

[0173] Then CB = W / X.

[0174] 2. Charging Capacity Test

[0175] Rate performance test (charge to 80% SOC test): Adjust the test temperature to 35℃ and 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 at 1C. The charging rate increases sequentially. With the anode potential of 0V as the charging cutoff condition, obtain the maximum achievable charging rate in the ranges of 0-10% SOC, 10-20% SOC, 20-30% SOC, 30-40% SOC, 40-50% SOC, 50-60% SOC, and 60-70% SOC, and then calculate the charging time (min) required from 0 to 80% SOC.

[0176] 3. Cyclic performance test

[0177] At 25℃, the secondary battery was charged at a constant current of 1C to 4.3V, and then charged at a constant voltage until the current reached 0.05C. At this point, the secondary battery was fully charged, and the charging capacity was recorded, which is the first charge capacity. After the secondary battery was left to stand for 5 minutes, it was discharged at a constant current of 1C to 2.8V. This completes one charge-discharge cycle, and the discharge capacity was recorded, which is the first discharge capacity. The secondary battery was subjected to cyclic charge-discharge tests using the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 45℃ = discharge capacity after 600 cycles / discharge capacity of the first cycle × 100%.

[0178] III. Test Results of Each Embodiment and Comparative Example

[0179] Batteries for each embodiment and comparative example were prepared according to the above method, and various performance parameters were measured. The results are shown in Table 2 below.

[0180] Table 2 shows the battery performance of each embodiment and comparative example.

[0181]

[0182]

[0183]

[0184] As can be seen from the above embodiments and comparative examples, the lithium-ion battery of this application has good fast charging capability and capacity retention rate when it simultaneously meets the requirements of an average aspect ratio of negative electrode active material particles of 0.1-1, electrolyte ionic conductivity in the range of 7-15 mS / cm and CB value of 1.1-1.5. For example, the charging time required for 0-70% SOC can be shortened to 7-8 minutes, and the capacity retention rate is still above 95% after 600 cycles.

[0185] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium-ion battery comprising 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 containing negative electrode active material attached to at least one surface of the negative electrode current collector, wherein the average aspect ratio of the negative electrode active material particles is 0.1-1; the ionic conductivity of the electrolyte is 10-15 mS / cm; and the ratio (CB) of the negative electrode lithium intercalation capacity to the positive electrode lithium deintercalation capacity is 1.05-1.5; the porosity of the negative electrode active material layer is 28%-60%; the electrolyte comprises a lithium salt and additives, wherein the lithium salt comprises a main lithium salt and a secondary lithium salt, the main lithium salt and the secondary lithium salt being different, the main lithium salt or The secondary lithium salts are each independently selected from at least one of LiPF6, LiN(SO2F)2, LiBF4, LiN(CF3SO2)2, LiClO4, LiAsF6, LiB(C2O4)2, LiBF2C2O4, lithium difluorodioxanol phosphate, LiPO2F2, LiFSO3, and LiF; the additives comprise carbonates and sulfates or carbonates and sulfonates, and the additives account for 5%-7% of the total mass of the electrolyte; the compaction density of the negative electrode active material layer is 1.2-1.78 g / cm³. 3 .

2. The lithium-ion battery according to claim 1, characterized in that, The battery has a current that is greater than or equal to four times the lithium-depleting capacity of the positive electrode per unit time during the charging process from 0% state of charge to 70% state of charge.

3. The lithium-ion battery according to claim 1 or 2, characterized in that, The average current of the battery during the charging process from 0% state of charge to 80% state of charge is greater than or equal to 4 times the lithium-depleting capacity of the positive electrode per unit time.

4. The lithium-ion battery according to claim 1 or 2, characterized in that, The coating weight of the negative electrode active material layer is 5-18 mg / cm³. 2 .

5. The lithium-ion battery according to claim 1 or 2, characterized in that, The negative electrode active material includes natural graphite, artificial graphite, mesophase micro carbon spheres, hard carbon, soft carbon, silicon, silicon-carbon composite, silicon oxide, or combinations thereof.

6. The lithium-ion battery according to claim 1 or 2, characterized in that, The thickness of the negative electrode active material layer is 30-150 μm.

7. The lithium-ion battery according to claim 1 or 2, characterized in that, The negative electrode active material layer includes a first negative electrode active material layer containing a first negative electrode active material, and a second negative electrode active material layer containing a second negative electrode active material attached to the surface of the first negative electrode active material layer away from the current collector.

8. The lithium-ion battery according to claim 7, characterized in that, The average volume particle size D of the first negative electrode active material v50 The average volume particle size D of the second negative electrode active material is greater than that of the second negative electrode active material. v50 .

9. The lithium-ion battery according to claim 8, characterized in that, The average volume particle size D of the first negative electrode active material v50 The average volumetric particle size D of the second negative electrode active material is 10-20 μm. v50 It is 9-19 μm.

10. The lithium-ion battery according to claim 7, characterized in that, The thickness of the first negative electrode active material layer and the second negative electrode active material layer are each independently 10-120 μm.

11. The lithium-ion battery according to claim 7, characterized in that, The compaction density of the first negative electrode active material layer is greater than that of the second negative electrode active material layer.

12. The lithium-ion battery according to claim 11, characterized in that, The compaction density of the first negative electrode active material layer is 1.3-2 g / cm³. 3 The compaction density of the second negative electrode active material layer is 1.2-1.9 g / cm³. 3 .

13. The lithium-ion battery according to any one of claims 1-2 and 8-12, characterized in that, The electrolyte also contains a solvent.

14. The lithium-ion battery according to any one of claims 1-2 and 8-12, characterized in that, The primary lithium salt is lithium hexafluorophosphate or LiFSI, with a content of 8-20 wt% based on the total weight of the electrolyte; the secondary lithium salt is at least one of lithium difluorooxalate borate, LiBF4, LiB(C2O4)2, and lithium difluorodioxalate phosphate, with a content of 0.001 wt%-2 wt% based on the total weight of the electrolyte.

15. The lithium-ion battery according to any one of claims 1-2 and 8-12, characterized in that, The molar concentration b of the lithium salt in the electrolyte is 0.6-1.5 mol / L.

16. The lithium-ion battery according to claim 13, characterized in that, The solvent comprises cyclic esters and linear esters; the content of the cyclic esters accounts for 5-40% of the solvent mass, and the content of the linear esters accounts for 60-95% of the solvent mass.

17. The lithium-ion battery according to claim 16, characterized in that, The cyclic ester is ethylene carbonate, propylene carbonate, or a combination thereof; the linear ester comprises dimethyl carbonate.

18. The lithium-ion battery according to claim 16, characterized in that, The linear ester is selected from diethyl carbonate, methyl ethyl carbonate, methyl formate, methyl acetate, ethyl acetate, butyl acetate, methyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, butyl butyrate, isopropyl acetate, isoamyl acetate, or combinations thereof.

19. The lithium-ion battery according to claim 16, characterized in that, The following relationship exists between the percentage of linear ester in the solvent (b%) and the ionic conductivity of the electrolyte (a, mS / cm): 8≤a+3b%≤16.

20. The lithium-ion battery according to any one of claims 1-2, 8-12, and 16-19, characterized in that, The carbonate includes at least one of fluoroethylene carbonate, vinylene 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, and trifluoromethylethylene carbonate.

21. The lithium-ion battery according to any one of claims 1-2, 8-12, and 16-19, characterized in that, The sulfate esters include at least one of vinyl sulfate, diethyl sulfate, dimethyl sulfate, and 4,4-bis(1,3,2-dioxathiacyclopentane)-2,2,2,2-tetraoxide.

22. The lithium-ion battery according to any one of claims 1-2, 8-12, and 16-19, characterized in that, The sulfonate esters include at least one of 1,3-propanesulfonate lactone, propenesulfonate lactone, 3-fluoro-1,3-propanesulfonate lactone, and vinyl methane disulfonate.

23. The lithium-ion battery according to any one of claims 1-2, 8-12, and 16-19, characterized in that, The positive electrode comprises a current collector and a positive electrode active material layer containing a positive electrode active material attached to at least one surface of the current collector. The positive electrode active material comprises LiNi x Co y Q z M 1-x-y-z O2 is a ternary material in which Q is Mn or Al, and M includes at least one of Co, Ni, Mn, Mg, Cu, Zn, Al, Sn, B, Ga, Cr, Sr, V and Ti, where 0≤x<1, 0≤y≤1, 0≤z≤1, and x+y+z≤1.

24. An electrical appliance, characterized in that, Includes lithium-ion batteries selected from any one of claims 1-23.

Images