Secondary batteries and power consumption devices including them

Abstract

This application provides a secondary battery and a power consumption device including the same. [Solution] The secondary battery comprises a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the porosity of the positive electrode plate is A, the porosity of the negative electrode plate is B, the electrolyte contains a first component, the first component contains one or more compounds shown in Formula 1, the weight percentage content of the first component in the electrolyte is D1, and the secondary battery satisfies 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50. The secondary battery of this application can achieve both high energy density and good cycle performance and power performance. JPEG2026086726000015.jpg29170

Description

[Technical Field]

[0001] This application belongs to the field of battery technology, and more specifically relates to secondary batteries and power consumption devices including them. [Background technology]

[0002] In recent years, rechargeable batteries have been widely used in energy storage and power systems such as hydroelectric, thermal, wind, and solar power plants, as well as in various fields including power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. As rechargeable batteries are applied and become more widespread, their overall performance is attracting increasing attention. For example, rechargeable batteries need to simultaneously meet requirements such as high energy density, long cycle life, and excellent power performance. Therefore, how to provide rechargeable batteries with good overall performance is a technological problem that urgently needs to be solved. [Overview of the Initiative]

[0003] The objective of this application is to provide a secondary battery and a power consumption device including the same that can achieve both high energy density and good cycle performance and power performance.

[0004] A first aspect of this application provides a secondary battery comprising a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the porosity of the positive electrode plate is A, the porosity of the negative electrode plate is B, the electrolyte comprises a first component, the first component comprising one or more compounds shown in Formula 1, where R1 and R2 each independently represent a fluorine atom, or represent at least one of the group consisting of partially fluorinated or fully fluorinated C1-C10 alkyl groups, C2-C10 alkenyl groups, C2-C10 alkynyl groups, C6-C8 aryl groups, C1-C10 alkoxy groups, C2-C10 alkenyloxy groups, C2-C10 alkynyloxy groups, and C6-C8 aryloxy groups, Me comprises one or more alkali metals and alkaline earth metals, and the weight percentage content of the first component in the electrolyte is D1. [ka] The secondary battery satisfies the conditions 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50.

[0005] The inventors of this application have discovered the following in their research: When the porosity A of the positive electrode plate, the porosity B of the negative electrode plate, and the content D1 of the first component in the electrolyte are adjusted to satisfy 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50, the desorption / adsorption of ions at the positive electrode and adsorption / desorption at the negative electrode are relatively well matched, thereby ensuring that the compound shown in Equation 1 permeates the positive and negative electrode plates as uniformly as possible, and that the compound shown in Equation 1 effectively participates in film formation on the negative and positive electrode surfaces, forming a low-impedance interfacial film. In this case, both the battery polarization and internal resistance are relatively small, the rate of capacity decay during charging and discharging of the battery decreases, the amount of heat generated decreases, and assuming that the secondary battery has a high energy density, it is possible to further improve power performance and have a long cycle life. In addition, the secondary battery can also have good low-temperature discharge performance.

[0006] In any embodiment of this application, 0.85 ≤ A / B ≤ 1.15, and selectively, 0.90 ≤ A / B ≤ 1.15. This contributes to further improving the matching between the positive and negative electrode plates, to forming a low-impedance interfacial film on both the positive and negative electrode surfaces, and further contributes to reducing battery polarization and internal resistance.

[0007] In any embodiment of this application, 0.16 ≤ 100D1 / B ≤ 1.40, and selectively, 0.20 ≤ 100D1 / B ≤ 1.20. This ensures that the compound shown in Equation 1 effectively participates in film formation on the negative and positive electrode surfaces and forms an interfacial film with lower impedance, thereby enabling the secondary battery to better combine high energy density, good power performance, and low-temperature discharge performance.

[0008] In any embodiment of this application, the secondary battery further satisfies 0.16 ≤ 100D1 / A ≤ 1.20, and selectively 0.20 ≤ 100D1 / A ≤ 1.10. When the secondary battery further satisfies the above parameter ranges, it is possible to better ensure that the compound shown in Equation 1 is effectively involved in film formation on the positive electrode surface, further improving film formation quality and forming an interfacial film with lower impedance, thereby enabling the secondary battery to better combine high energy density and good power performance, and at the same time the secondary battery can have a long cycle life.

[0009] In any embodiment of this application, 18% ≤ A ≤ 32%.

[0010] In any embodiment of this application, 20% ≤ B ≤ 35%.

[0011] If the porosity A of the positive electrode plate and / or the porosity B of the negative electrode plate further satisfy the above-mentioned specific range, it contributes to the positive electrode plate and / or the negative electrode plate having an even more optimal electron transmission network and an optimal ion conduction channel, thereby further improving the electrochemical performance of the secondary battery.

[0012] In any embodiment of this application, 0.05% ≤ D1 ≤ 0.3%. When the content D1 of the first component in the electrolyte is within an appropriate range, it contributes to the formation of a low-impedance interfacial film on both the positive and negative electrode surfaces, and further enables the secondary battery to have good power performance and a long cycle life.

[0013] In any embodiment of this application, the compaction density of the positive electrode plate is P1g / cm³. 3 The compaction density of the negative electrode plate is P2g / cm³. 3Furthermore, the secondary battery satisfies the following relationships: 1.75 ≤ P1 / P2 ≤ 2.50, and selectively, 2.00 ≤ P1 / P2 ≤ 2.40. By adjusting the ratio of the compaction density of the positive electrode plate to the compaction density of the negative electrode plate to be within the above range, it is possible to form a low-impedance interfacial film on both the positive and negative electrode surfaces, and further contribute to the positive and negative electrode plates having an optimal electron transmission network and an optimal ion conduction channel, thereby further improving the electrochemical performance of the secondary battery.

[0014] In any embodiment of this application, the compaction density of the positive electrode plate is P1g / cm³. 3 Furthermore, the secondary battery satisfies 1.43 ≤ 10000D1 / P1 ≤ 9.34, and selectively 2.00 ≤ 10000D1 / P1 ≤ 8.00. In this case, it is possible to ensure that the compound shown in Equation 1 is effectively involved in film formation on the positive electrode surface, further improving the quality of film formation and forming an interfacial film with lower impedance, and also contributing to avoiding deterioration of the power performance of the secondary battery due to the compaction density of the positive electrode plate being too high or too low.

[0015] In any embodiment of this application, the compaction density of the negative electrode plate is P2g / cm³. 3 Furthermore, the secondary battery satisfies 2.78 ≤ 10000D1 / P2 ≤ 21.40, and selectively 5.00 ≤ 10000D1 / P2 ≤ 15.00. In this case, it is ensured that the compound shown in Equation 1 is effectively involved in film formation on the negative electrode surface, further improving film formation quality and forming an interfacial film with lower impedance, and contributing to avoiding deterioration of the power performance and / or low-temperature discharge performance of the secondary battery due to the compaction density of the negative electrode plate being too high or too low.

[0016] In any embodiment of this application, 2.8 ≤ P1 ≤ 3.65, and selectively, 3.2 ≤ P1 ≤ 3.5.

[0017] In any embodiment of this application, 1.2 ≤ P2 ≤ 1.85, and selectively, 1.4 ≤ P2 ≤ 1.8.

[0018] If the compaction density P1 of the positive electrode plate and / or the compaction density P2 of the negative electrode plate further satisfy the above-mentioned specific range, it contributes to the positive electrode plate and / or the negative electrode plate having appropriate porosity, an optimal electron transmission network, and an optimal ion conduction channel, thereby further improving the electrochemical performance of the secondary battery.

[0019] In any embodiment of this application, Me represents Li.

[0020] In any embodiment of this application, the compound shown in Formula 1 is [ka] This includes one or more of the above-mentioned compounds.

[0021] In any embodiment of this application, the aqueous electrolyte further comprises a second component, the second component comprising lithium hexafluorophosphate.

[0022] In any embodiment of this application, the weight percentage content D2 of the second component in the electrolyte is 5% or more, and selectively 8% or more.

[0023] Lithium hexafluorophosphate has the characteristic of high ionic conductivity, and when its content is within an appropriate range, it contributes to improving the overall ionic conductivity of the electrolyte, accelerating ion transmission, and improving the capacity of secondary batteries.

[0024] In any embodiment of this application, the electrolyte further comprises a third component, the third component comprising one or more of lithium tetrafluoroborate, lithium difluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate, and selectively comprising lithium tetrafluoroborate, lithium difluorophosphate, or a combination thereof.

[0025] In any embodiment of this application, the weight percentage content D3 of the third component in the electrolyte is 0.5% or less, and selectively 0.25% or less.

[0026] The third component, acting as an auxiliary lithium salt, can further improve the interfacial properties of the positive and / or negative electrodes, or improve the ionic conductivity or thermal stability of the electrolyte.

[0027] In any embodiment of this application, the weight ratio D3 / D1 of the third component to the first component is 0.5 to 2. This contributes to fully exhibiting the synergistic effect of the third component and the first component, as well as to good low-temperature discharge performance of the secondary battery.

[0028] In any embodiment of this application, the aqueous electrolyte further comprises a fourth component, the fourth component comprising fluoroethylene carbonate.

[0029] In any embodiment of this application, the weight percentage content D4 of the fourth component in the electrolyte is 5% or less, and selectively 2.5% or less.

[0030] When the electrolyte contains fluoroethylene carbonate, the cycle performance of secondary batteries can be effectively improved.

[0031] In any embodiment of this application, the weight ratio D4 / D1 of the fourth component to the first component is 5 to 100. When the weight ratio of the fourth component to the first component is within an appropriate range, the synergistic effect between the fourth component and the first component can be fully realized, which not only prevents a significant increase in the amount of gas generated by the secondary battery but also further improves the cycle performance of the secondary battery.

[0032] In any embodiment of this application, the electrolyte further comprises a fifth component, the fifth component comprising one or more of cyclic carbonate compounds, linear carbonate compounds, carboxylic acid ester compounds, sulfone compounds, and ether compounds, and selectively comprising cyclic carbonate compounds and linear carbonate compounds.

[0033] In any embodiment of this application, the weight percentage content D5 of the fifth component in the electrolyte is 60% or more, and selectively 75% or more.

[0034] In any embodiment of this application, the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector and containing a positive electrode active material, wherein the positive electrode active material optionally includes one or more of layered lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds, optionally includes one or more of layered lithium transition metal oxides and their modified compounds, or includes a mixture of layered lithium transition metal oxides and their modified compounds and lithium-containing phosphates and their modified compounds.

[0035] In any embodiment of this application, the form of the positive electrode active material includes one or more spherical and subspherical shapes.

[0036] In any embodiment of this application, the positive electrode active material comprises primary particles, secondary particles, or a combination thereof, and selectively comprises secondary particles or a combination of primary and secondary particles.

[0037] In any embodiment of this application, the quantitative occupancy rate of secondary particles in the positive electrode active material is 50% or more.

[0038] In any embodiment of this application, the volume-average particle size of the positive electrode active material is 2.5 μm ≤ Dv50 ≤ 30 μm, and selectively satisfies the condition 2.5 μm ≤ Dv50 ≤ 25 μm.

[0039] In any embodiment of this application, the volume-average particle size of the positive electrode active material is 1 ≤ (Dv90 - Dv10) / Dv50 ≤ 5, and selectively satisfies 1 ≤ (Dv90 - Dv10) / Dv50 ≤ 2.

[0040] By adjusting one or more of the following parameters of the positive electrode active material—particle morphology, volume-average particle size Dv50, and diameter-to-diameter distance (Dv90-Dv10) / Dv50—to satisfy the above range, it is possible to contribute to the positive electrode plate having an appropriate porosity and / or compaction density, and further contribute to the secondary battery exhibiting a better combination of high energy density, high power density, and high capacity.

[0041] In any embodiment of this application, the negative electrode plate includes a negative electrode current collector and a negative electrode film layer installed on at least one surface of the negative electrode current collector and containing a negative electrode active material, wherein the negative electrode active material optionally includes one or more of carbon-based materials, silicon-based materials, tin-based materials, lithium titanate, and composite materials obtained by coating modification of the above materials, and further optionally includes one or more of carbon-based materials and composite materials obtained by coating modification of the above materials. Selectively, the carbon-based material optionally includes one or more of graphite, soft carbon, hard carbon, and composite materials obtained by coating modification of the above materials.

[0042] In any embodiment of this application, the form of the negative electrode active material includes one or more of the following: spherical, subspherical, block-shaped, and sheet-shaped.

[0043] In any embodiment of this application, the negative electrode active material comprises primary particles, secondary particles, or a combination thereof, and selectively comprises secondary particles or a combination of primary and secondary particles.

[0044] In any embodiment of this application, the quantitative occupancy rate of secondary particles in the negative electrode active material is 50% or more.

[0045] In any embodiment of this application, the volume-average particle size of the negative electrode active material is 8 μm ≤ Dv50 ≤ 22 μm, and selectively satisfies 10 μm ≤ Dv50 ≤ 16 μm.

[0046] In any embodiment of this application, the radial distance of the negative electrode active material is 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 5, and selectively satisfies 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.5.

[0047] By adjusting one or more of the following parameters of the negative electrode active material—particle morphology, volume-average particle size Dv50, and diameter-to-diameter distance (Dv90-Dv10) / Dv50—to satisfy the above range, it is possible to contribute to the negative electrode plate having an appropriate porosity and / or compaction density, and further contribute to the secondary battery exhibiting a better combination of high energy density, high power density, and high capacity.

[0048] A second aspect of this application provides a power consumption device which includes a secondary battery according to the first aspect of this application.

[0049] The inventors of this application have discovered in their research the following: By adjusting the porosity A of the positive electrode plate, the porosity B of the negative electrode plate, and the content D1 of the first component in the electrolyte to satisfy 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50, the secondary battery can be given good power performance and a long cycle life, assuming it has a high energy density, and the secondary battery can also have good low-temperature discharge performance. The power consumption device of this application includes the secondary battery of this application and therefore has at least the same advantages as the said secondary battery. [Brief explanation of the drawing]

[0050] To more clearly illustrate the technical concept of the embodiments of this application, the following is a brief introduction to the drawings that may be used in the embodiments of this application. Obviously, the drawings described below represent only a few embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without expending any creative effort. [Figure 1] This is a schematic diagram of one embodiment of the battery cell of this application. [Figure 2] This is an exploded schematic diagram of one embodiment of the battery cell of the present application. [Figure 3] This is a schematic diagram of one embodiment of the battery module of this application. [Figure 4] This is a schematic diagram of one embodiment of the battery pack of this application. [Figure 5] Figure 4 is an exploded schematic diagram of an embodiment of the battery pack shown. [Figure 6] This is a schematic diagram of one embodiment including a power consumption device that uses a secondary battery of the present application as a power source. [Modes for carrying out the invention]

[0051] Hereinafter, embodiments specifically disclosing the secondary battery and power consumption device including the same of this application will be described in detail with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed explanations of well-known matters and repeated explanations of structures that are actually the same may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to make it easily understandable to those skilled in the art. The drawings and the following explanation are provided to enable those skilled in the art to fully understand this application and are not intended to limit the topics described in the claims.

[0052] The “range” disclosed in this application is limited in the form of a lower limit and an upper limit, and a given range is limited by selecting one lower limit and one upper limit, which define the boundary of a particular range. The range thus limited may or may not include the limit value, and any combination is possible, that is, any lower limit may be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is assumed that this is understood to mean the ranges 60-110 and 80-120. Furthermore, if the minimum range values ​​are listed as 1 and 2, and the maximum range values ​​are listed as 3, 4 and 5, then the ranges 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5 are all conceivable. In this application, unless otherwise specified, the numerical range “ab” represents an abbreviation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have already been listed in this specification, and "0-5" is simply a shortened representation of combinations of these numbers. Similarly, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that this parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and such technical solutions should be considered to be included in the disclosures of this application.

[0054] Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical concepts, and such technical concepts should be considered to be included in the disclosures of this application.

[0055] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, the fact that the method referred to above may further include step (c) means that step (c) may be added to the method in any order, for example the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), and so on.

[0056] Unless otherwise specified, the terms “includes” and “inclusion” as used in this application may represent an open or closed configuration. For example, the terms “includes” and “inclusion” may mean that other components not listed may be included or inclusion, or that only the listed components may be included or inclusion.

[0057] 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, any of the following conditions satisfy "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) but B is true (or exists); and both A and B are true (or exist).

[0058] In various parts of this specification, substituents of compounds are disclosed in groups or ranges. Such descriptions are expressly intended to include each individual subcombination of members of these groups and ranges. For example, the term “C1-C6 alkyl” is expressly intended to disclose the alkyl groups of C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C6, C2-C5, C2-C4, C2-C3, C3-C6, C3-C5, C3-C4, C4-C6, C4-C5 and C5-C6 individually.

[0059] In this application, the terms "multiple" and "multiple types" refer to two or more.

[0060] In this application, the porosity of the electrode plate has the meaning known in the art, meaning the percentage of the total volume of the electrode plate after roll pressing that is occupied by the void volume inside the electrode plate after roll pressing, and can be tested using methods known in the art, for example, by referring to GB / T 24586-2009. The test instrument may be a fully automated true density tester, such as the AccuPyc II 1340 from Micromeritics, Inc., USA. An exemplary test method may include the steps of punching out a small wafer of a certain diameter (e.g., 14 mm) from a well-dried electrode plate using a punching machine, where the small wafer is required to have a perfect edge and no chipping, and accurately measuring the true volume V1 of the electrode plate sample to be measured by using a small molecular diameter inert gas (e.g., helium) substitution method and combining Archimedes' principle and Bore's law. The porosity of the electrode plate = [(V2-V1) / V2] × 100%, where V2 is the apparent volume of the electrode plate, V2 = S × H × A, where S represents the area of ​​the electrode plate sample, H represents the thickness of the electrode plate sample, and A represents the number of electrode plate samples.

[0061] In this application, the compaction density of the electrode plate has a meaning known in the art and can be tested using methods known in the art. Compaction density of the electrode plate = surface density of the electrode plate / thickness of the electrode film layer. The surface density of the electrode plate has a meaning known in the art and can be tested using methods known in the art. For example, an electrode plate coated on one side and cold-pressed (if both sides of the electrode plate are coated, the electrode film layer on one side may be wiped off first) is taken, punched into a small wafer with an area of ​​S0, and its weight is recorded as M1. Next, the electrode film layer of the electrode plate after weighing is wiped off, the weight of the current collector is weighed and recorded as M0, and the surface density of the electrode plate = (M1-M0) / S0. The thickness of the electrode film layer has a meaning known in the art and can be tested using methods known in the art. For example, it can be measured using a spiral micrometer.

[0062] In this application, the volume particle sizes Dv90, Dv50, and Dv10 of the electrode active material have meanings known in the art, and represent the particle sizes corresponding to when the cumulative volume distribution percentage of the material reaches 90%, 50%, and 10%, respectively, and can be measured with instruments and methods known in the art. For example, they may be measured using a laser particle size analyzer with reference to GB / T 19077-2016. The test instrument may be a Mastersizer 2000E laser particle size analyzer from Malvern Panalytical, UK.

[0063] In this application, when testing relevant parameters of electrode plates (e.g., surface density, compaction density, porosity), sampling may be performed during the manufacturing process of the secondary battery, or sampling may be performed from the manufactured secondary battery. An exemplary method of sampling from a manufactured secondary battery may include the steps of letting the secondary battery stand at 25°C for 30 minutes and discharging it at a constant current of 0.33C until it reaches the discharge cutoff voltage, letting it stand again for 30 minutes, then disassembling the secondary battery, removing the electrode plates and immersing them in a solvent for a certain period of time (e.g., dimethyl carbonate, immersion for 20 hours), and then thoroughly drying the electrode plates in a drying chamber (e.g., drying for 2 hours or more) to obtain a test sample.

[0064] The secondary batteries referred to in the embodiments or examples of this application are a single physical module comprising one or more battery cells that provide higher voltage and capacity. For example, the secondary batteries referred to in this application may include battery cells, battery modules, or battery packs. A battery cell is the smallest unit that constitutes a secondary battery and can independently realize the functions of charging and discharging. This application does not particularly limit the shape of the battery cell, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows a rectangular battery cell 5 as an example.

[0065] In some embodiments, the battery cell includes an electrode assembly, and the battery cell may further include an outer casing. The electrode assembly may be manufactured by a winding process and / or a lamination process, consisting of a positive electrode plate, a negative electrode plate, and a separator, and the outer casing may be used to package the electrode assembly. The outer casing may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case. The outer casing may be a pouch, such as a bag-shaped pouch. The material of the pouch may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), or polybutylene succinate (PBS).

[0066] In some embodiments, as shown in Figure 2, the casing may include a case 51 and a cover plate 53. The case 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates enclosing and forming a housing cavity. The case 51 has an opening that communicates with the housing cavity, and the cover plate 53 is used to cover the opening and seal the housing cavity. The electrode assembly 52 is packaged in the housing cavity. The number of electrode assemblies 52 included in the battery cell 5 may be one or more and can be adjusted according to the requirements.

[0067] In some embodiments of this application, battery cells can be assembled into a battery module, and the number of battery cells included in the battery module may be multiple, and the specific number can be adjusted according to the application and capacity of the battery module. Figure 3 is a schematic diagram of an example battery module 4. As shown in Figure 3, in the battery module 4, multiple battery cells 5 may be arranged sequentially along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, these multiple battery cells 5 may be fixed by fasteners.

[0068] Selectively, the battery module 4 may further include a housing having a housing space, in which a plurality of battery cells 5 are housed.

[0069] In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack. Figures 4 and 5 are schematic diagrams of an example battery pack 1. As shown in Figures 4 and 5, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed inside the battery box. The battery box includes an upper housing 2 and a lower housing 3, the upper housing 2 covering the lower housing 3 and used to form a sealed space for housing the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0070] The secondary battery of this application comprises a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the porosity of the positive electrode plate is A, the porosity of the negative electrode plate is B, and the electrolyte comprises a first component, the first component comprising one or more compounds shown in Formula 1, where R1 and R2 each independently represent a fluorine atom, or partially fluorinated or fully fluorinated C1-C10 alkyl group, C2-C10 alkenyl group, C2-C10 alkynyl group, C6- The first component represents at least one of the group consisting of a C8 aryl group, a C1-C10 alkoxy group, a C2-C10 alkenyloxy group, a C2-C10 alkynyloxy group, and a C6-C8 aryloxy group; Me includes one or more alkali metals and alkaline earth metals; the weight percentage content of the first component in the electrolyte is D1; ​​and the secondary battery satisfies 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50. [ka]

[0071] In the operating process of a secondary battery, the structure and parameter design of the electrode plates are crucial for the performance of the secondary battery, as they relate to a series of mass transfer and reaction processes such as electron conduction, ion conduction, and electrochemical reactions. The two most important indicators for a secondary battery are energy density and power density. Energy density refers to the energy stored per unit volume or weight of the secondary battery, while power density refers to the power that can be output per unit weight or volume of the secondary battery.

[0072] The smaller the porosity of the electrode plates, the more electrode plates can be fitted into a limited battery case, and the higher the weight occupancy rate of the electrode active material. This not only improves the volumetric energy density of the secondary battery, but also improves the gravimetric energy density. However, a smaller porosity of the electrode plates is not always desirable. A smaller porosity of the electrode plates increases the degree of extrusion between the electrode active material particles, making it more difficult for the electrolyte to sufficiently penetrate the electrode plates, and further worsening the capacity of the electrode active material. Moreover, a smaller porosity of the electrode plates worsens the electrolyte absorption and retention capacity of the secondary battery, and the internal resistance and polarization also increase significantly during the secondary battery's cycle process, resulting in a significantly faster capacity decay.

[0073] Furthermore, high energy density and high power density are mutually contradictory in the design and manufacturing processes of secondary batteries. To improve the energy density of a secondary battery, it is necessary to increase the weight occupancy of the electrode active material and decrease the porosity of the electrode plates. For high-power batteries, it is required that the discharge current is relatively large during use and sufficient power output is provided, resulting in relatively high heat generation during discharge. This leads to a relatively large decomposition reaction of the electrolyte at the electrode interface, further increasing the electrode interface impedance and affecting the performance of the secondary battery. Therefore, to improve the power performance of a secondary battery, it is necessary to increase the porosity of the electrode plates, decrease the amount of heat generated during discharge, and decrease the electrode interface impedance.

[0074] Therefore, balancing the energy density and power density of secondary batteries is extremely difficult, and currently, it is difficult to achieve good power performance and a long cycle life while assuming that secondary batteries have high energy density.

[0075] In their research, the inventors of this application discovered that by adjusting the porosity A of the positive electrode plate, the porosity B of the negative electrode plate, and the content D1 of the first component in the electrolyte to satisfy 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50, it is possible to obtain a secondary battery that combines high energy density with good cycle performance and power performance.

[0076] The first component of the electrolyte contains one or more of the compounds shown in Formula 1. The compounds shown in Formula 1 have a fluorine atom in their molecular structure, which is preferentially reduced at the negative electrode over organic solvents, and the reduction product has even lower impedance properties, thus contributing to the formation of a low-impedance negative electrode interface film. The compounds shown in Formula 1 have an oxalate group in their molecular structure, which is preferentially oxidized at the positive electrode over organic solvents, and the oxidation product has even lower impedance properties, thereby contributing to the formation of a low-impedance positive electrode interface film. Furthermore, the B atom in the molecular structure of the compounds shown in Formula 1 readily bonds strongly with inorganic components such as LiF in the positive electrode interface film and / or negative electrode interface film, thereby accelerating ion transfer and significantly reducing battery polarization.

[0077] The compound shown in Equation 1 has relatively high thermal stability, superior to, for example, general LiPF6, thereby contributing to improved heat resistance of the entire electrolyte. At the same time, the compound shown in Equation 1 is not as sensitive to moisture as LiPF6, thus improving the water resistance of the electrolyte, reducing HF formation, and lowering the acidity of the electrolyte. Therefore, when the electrolyte contains the compound shown in Equation 1, the electrolyte can have relatively high thermal and electrochemical stability, which reduces the decomposition reaction of the electrolyte at high temperatures and lowers the internal resistance of the battery. As can be seen from Joule's law, the amount of heat generated by a secondary battery is directly related to its internal resistance. Therefore, after the internal resistance of the battery decreases, the amount of heat generated by the secondary battery also decreases, and the secondary battery can have good power performance while having a high energy density.

[0078] Therefore, the compound shown in Equation 1 forms a low-impedance interfacial film on the surface of the positive and / or negative electrode, contributing to improving the performance of the secondary battery. However, in further research, the inventors of this application discovered that the content of the compound shown in Equation 1 must be rationally combined with the porosity of the positive and negative electrode plates to achieve an ideal match between ion desorption / intersorption at the positive electrode and intersorption / desorption at the negative electrode.

[0079] In this application, the porosity A of the positive electrode plate and the porosity B of the negative electrode plate must satisfy 0.80 ≤ A / B ≤ 1.20. In further research, the inventors of this application discovered the following: In this case, the compatibility between the positive electrode plate and the negative electrode plate is relatively good, and in particular, the compatibility between the desorption / adsorption of ions at the positive electrode and the adsorption / desorption of ions at the negative electrode is relatively good. This ensures that the compound shown in Equation 1 permeates the positive and negative electrode plates as uniformly as possible, which is advantageous for completing the subsequent formation of a chemical film, and contributes to the formation of a low-impedance interfacial film on both the positive and negative electrode surfaces, and further contributes to reducing the polarization and internal resistance of the battery. When A / B is greater than 1.20, the porosity of the positive electrode plate is large and the porosity of the negative electrode plate is small. This results in poor electrolyte penetration into the negative electrode plate, relatively poor film formation quality on the negative electrode, and poor capacity performance. Furthermore, ions that desorb smoothly from the positive electrode and transition to the negative electrode are less likely to be absorbed into the negative electrode active material in a timely manner. In addition, some ions are directly reduced and deposited on the negative electrode surface, forming dendrites. Moreover, the porosity of the negative electrode plate is small, and its electrolyte absorption and retention capacity is relatively poor. As a result, polarization increases significantly during the secondary battery cycle process, and capacity decay becomes significantly faster. When A / B is less than 0.80, the porosity of the positive electrode plate is small and the porosity of the negative electrode plate is large. In this case, the electrolyte penetration into the positive electrode plate is poor, the positive electrode film formation quality is relatively poor, and capacity performance is relatively poor, making it difficult to achieve both high energy density and good power performance in the secondary battery. In some embodiments, A / B may be in the range of any of the following values: 0.80, 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, 1.20, or greater. Selectively, 0.85 ≤ A / B ≤ 1.15 and 0.90 ≤ A / B ≤ 1.15. This contributes to further improving the matching between the positive and negative electrode plates, to forming a low-impedance interfacial film on both the positive and negative electrode surfaces, and further contributes to reducing battery polarization and internal resistance.

[0080] In this application, the porosity B of the negative electrode plate and the content D1 of the first component in the electrolyte must further satisfy 0.14 ≤ 100D1 / B ≤ 1.50. In further research, the inventors of this application discovered the following: At this time, the compound shown in Equation 1 can effectively participate in film formation on the negative electrode surface and the positive electrode surface and ensure the formation of a low-impedance interfacial film, thereby enabling the secondary battery to have both high energy density and good power performance. Furthermore, since the rate of increase in negative electrode impedance at low temperatures is much higher than that of the positive electrode, having a low-impedance interfacial film on the negative electrode surface contributes to the secondary battery having even better low-temperature discharge performance. When 100D1 / B is greater than 1.50, the content of the first component in the electrolyte is high and the porosity of the negative electrode plate is small. As a result, the compound shown in Equation 1 preferentially participates in film formation on the negative electrode surface. This leads to excessively thick film formation on the negative electrode, high negative electrode interface impedance, and difficulty in achieving both high energy density and good power performance in the secondary battery. Simultaneously, the low-temperature discharge performance of the secondary battery also deteriorates. When 100D1 / B is less than 0.14, the content of the first component in the electrolyte is low and the porosity of the negative electrode plate is large. As a result, the compound shown in Equation 1 cannot effectively participate in film formation on the negative electrode surface or the positive electrode surface. Furthermore, both the negative electrode interface impedance and the positive electrode interface impedance are relatively high, and in this case, the power performance and cycle performance of the secondary battery are clearly degraded. In some embodiments, 100D1 / B may be in the range of 0.16, 0.18, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.50 or any of the above values. Selectively, 0.16 ≤ 100D1 / B ≤ 1.40 and 0.20 ≤ 100D1 / B ≤ 1.20. This ensures that the compound shown in Equation 1 effectively participates in film formation on the negative and positive electrode surfaces and forms an interfacial film with lower impedance, thereby enabling the secondary battery to better combine high energy density, good power performance, and low-temperature discharge performance.

[0081] Therefore, when the secondary battery satisfies 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50, the desorption / adsorption of ions at the positive electrode and the adsorption / desorption at the negative electrode are relatively well matched, ensuring that the compound shown in Equation 1 permeates the positive and negative electrode plates as uniformly as possible, and ensuring that the compound shown in Equation 1 effectively participates in film formation on the negative and positive electrode surfaces, forming a low-impedance interfacial film. In this case, both the battery polarization and internal resistance are relatively small, the rate of capacity decay during charging and discharging decreases, the amount of heat generated decreases, and assuming the secondary battery has a high energy density, it can further provide good power performance and a long cycle life. In addition, the secondary battery can also have good low-temperature discharge performance.

[0082] In some embodiments, the secondary battery further satisfies 0.16 ≤ 100D1 / A ≤ 1.20. In further research, the inventors of this application have found the following: When the secondary battery further satisfies the above parameter range, it is better ensured that the compound shown in Equation 1 is effectively involved in film formation on the positive electrode surface, further improving film formation quality and forming an interfacial film with lower impedance, thereby enabling the secondary battery to better combine high energy density and good power performance, while at the same time the secondary battery can have a long cycle life. Furthermore, the following situations can be effectively avoided. If 100D1 / A is greater than 1.20, the compound shown in Equation 1 may form a relatively thick film on the positive electrode, which may result in a relatively high positive electrode interface impedance and further reduce the effectiveness of improving the power performance and cycle performance of the secondary battery. If 100D1 / A is less than 0.16, the compound shown in Equation 1 is more effectively involved in preferential film formation on the negative electrode surface, which may result in relatively little film formation on the positive electrode, a relatively poor effect on reducing the positive electrode interface impedance, and further reduce the effectiveness of improving the power performance of the secondary battery. In some embodiments, 100D1 / A may be in the range of any of the following values: 0.18, 0.20, 0.30, 0.40, 0.50, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, or 1.20 or greater. Selectively, 0.20 ≤ 100D1 / A ≤ 1.10 and 0.30 ≤ 100D1 / A ≤ 1.10.

[0083] In some embodiments, the porosity A of the positive electrode plate satisfies 18% ≤ A ≤ 32%, and for example, A may be in the range of 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, or any of these values. Selectively, 24% ≤ A ≤ 32%.

[0084] In some embodiments, the porosity B of the negative electrode plate satisfies 20% ≤ B ≤ 35%, and for example, B may be in the range of 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or any of these values.

[0085] The principle of the charge-discharge reaction in secondary batteries is the bonding of electrons and ions. To ensure that secondary batteries have good power performance and a long cycle life, it is necessary to match the transfer speeds of ions and electrons, resulting in a secondary battery with an optimal electron transmission network and optimal ion conduction channels. If the porosity A of the positive electrode plate and / or the porosity B of the negative electrode plate further meet the above specific range, it contributes to the positive electrode plate and / or the negative electrode plate having an even more optimal electron transmission network and optimal ion conduction channels, thereby further improving the electrochemical performance of the secondary battery. If the electrode plates have a high porosity, it contributes to having good ion conduction channels, but the electron contact between the electrode active material particles deteriorates. This increases the contact electron impedance between the electrode active material particles and between the electrode active material particles and the current collector, further increasing the internal resistance of the battery, which is detrimental to further improving the electrochemical performance of the secondary battery. While a low porosity in electrode plates contributes to a well-developed electron transmission network, it also makes ion conduction through the electrode plates difficult, increasing ion conduction impedance. Simultaneously, the contact area between the electrode active material particles and the electrolyte increases, increasing charge exchange impedance. Both of these factors lead to an increase in the internal resistance of the battery, which is detrimental to further improving the electrochemical performance of the secondary battery.

[0086] In some embodiments, 0.05% ≤ D1 ≤ 0.3%, and for example, D1 may be in the range of 0.05%, 0.08%, 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, 0.3%, or any of these values. When the content D1 of the first component in the electrolyte is within an appropriate range, it contributes to the formation of a low-impedance interfacial film on both the positive and negative electrode surfaces, and further enables the secondary battery to have good power performance and a long cycle life. Moreover, the following situations can be effectively avoided. If the content D1 of the first component in the electrolyte is greater than 0.3%, it increases the thickness of the film formation on the positive electrode surface and / or negative electrode surface, which can lead to an increase in the internal resistance of the battery, resulting in poor power performance and cycle performance, and simultaneously a decrease in capacity. If the content D1 of the first component in the electrolyte is less than 0.05%, the effect of the first component on reducing the internal resistance of the battery is not significant, and furthermore, the improvement effect on the power performance and cycle performance of the secondary battery may not be significant.

[0087] In some embodiments, the compaction density of the positive electrode plate is P1g / cm³. 3 The compaction density of the negative electrode plate is P2g / cm³. 3 Furthermore, the secondary battery satisfies the relationship 1.75 ≤ P1 / P2 ≤ 2.50. For example, P1 / P2 may be in the range of 1.80, 1.85, 1.90, 1.95, 2.00, 2.05, 2.10, 2.15, 2.20, 2.25, 2.30, 2.35, 2.40, 2.45, 2.50, or any of these values, and selectively, 2.00 ≤ P1 / P2 ≤ 2.40 may also be the case.

[0088] The compaction density of the electrode plates is an important indicator in the manufacturing process of the electrode plates, and adjusting the compaction density of the electrode plates contributes to obtaining electrode plates with an appropriate porosity. Furthermore, by adjusting the ratio of the compaction density of the positive electrode plate to the compaction density of the negative electrode plate within the above range, it contributes to the uniform penetration of the compound shown in Equation 1 into the positive and negative electrode plates, which is advantageous for completing the subsequent formation of a chemical deposition film, and contributes to the formation of a low-impedance interfacial film on both the positive and negative electrode surfaces. In addition, it contributes to the positive and negative electrode plates having an optimal electron transmission network and an optimal ion conduction channel, thereby further improving the electrochemical performance of the secondary battery.

[0089] In some embodiments, the secondary battery further satisfies 1.43 ≤ 10000D1 / P1 ≤ 9.34. For example, 10000D1 / P1 may be in the range of 1.45, 1.50, 2.00, 2.50, 3.00, 3.50, 4.00, 4.50, 5.00, 5.50, 6.00, 6.50, 7.00, 7.50, 8.00, 8.50, 9.00, or any of these values, and selectively, 2.00 ≤ 10000D1 / P1 ≤ 8.00. In further research, the inventors of this application have found the following: At this time, the compound shown in Equation 1 is ensured to effectively participate in film formation on the positive electrode surface, further improving film formation quality and enabling the formation of an interface film with lower impedance. Furthermore, it contributes to avoiding the deterioration of the power performance of the secondary battery due to the compaction density of the positive electrode plate being too high or too low.

[0090] In some embodiments, the secondary battery further satisfies 2.78 ≤ 10000D1 / P2 ≤ 21.40. For example, 10000D1 / P2 may be in the range of 2.80, 3.00, 4.00, 5.00, 6.00, 7.00, 8.00, 9.00, 10.00, 11.00, 12.00, 13.00, 14.00, 15.00, 16.00, 17.00, 18.00, 19.00, 20.00, 21.00 or any of these values, and optionally 5.00 ≤ 10000D1 / P2 ≤ 15.00. In further research, the inventors of this application have found the following: At this time, the compound shown in Equation 1 is ensured to effectively participate in film formation on the negative electrode surface, further improving film formation quality and enabling the formation of an interfacial film with lower impedance. Furthermore, it contributes to avoiding deterioration of the power performance and / or low-temperature discharge performance of the secondary battery due to the compaction density of the negative electrode plate being too high or too low.

[0091] In some embodiments, the secondary battery also satisfies 1.75 ≤ P1 / P2 ≤ 2.50, 1.43 ≤ 10000D1 / P1 ≤ 9.34, and 2.78 ≤ 10000D1 / P2 ≤ 21.40 simultaneously. This contributes to further optimizing the performance of the secondary battery.

[0092] In some embodiments, the compaction density P1 g / cm³ of the positive electrode plate is observed. 3 The condition 2.8 ≤ P1 ≤ 3.65 is satisfied, and for example, P1 may be in the range of 2.8, 2.85, 2.9, 2.95, 3.0, 3.05, 3.1, 3.15, 3.2, 3.25, 3.3, 3.35, 3.4, 3.45, 3.5, 3.55, 3.6, 3.65 or any of these values, and selectively, 3.2 ≤ P1 ≤ 3.5.

[0093] In some embodiments, the compaction density of the negative electrode plate is P2g / cm³. 3P2 satisfies 1.2 ≤ P2 ≤ 1.85, for example, P2 may be in the range of 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8, 1.85, or any of these values, and selectively, 1.4 ≤ P2 ≤ 1.8.

[0094] If the compaction density P1 of the positive electrode plate and / or the compaction density P2 of the negative electrode plate further satisfy the above-mentioned specific range, it contributes to the positive electrode plate and / or the negative electrode plate having appropriate porosity, an optimal electron transmission network, and an optimal ion conduction channel, thereby further improving the electrochemical performance of the secondary battery.

[0095] In this application, the parameters of the cold pressing process of the electrode plate, such as the cold pressing speed, cold pressing temperature, cold pressing pressure, and number of cold pressing cycles, affect the porosity and / or compaction density of the electrode plate. Parameters of the electrode active material itself, such as particle size, particle size distribution, and particle morphology, also affect the porosity and / or compaction density of the electrode plate. Furthermore, the composition of the electrode film layer or electrode slurry, such as the type and content of each component, also affects the porosity and / or compaction density of the electrode plate. Therefore, the magnitude of the porosity and / or compaction density of the electrode plate can be adjusted by adjusting one or more of the parameters of the electrode active material itself, the composition of the electrode film layer or electrode slurry, and the cold pressing process parameters of the electrode plate.

[0096] In some embodiments, the form of the positive electrode active material includes one or more spherical and subspherical shapes.

[0097] In some embodiments, the positive electrode active material comprises primary particles, secondary particles, or a combination thereof, and selectively comprises secondary particles or a combination of primary and secondary particles. Combining a positive electrode active material in the form of primary particles with a positive electrode active material in the form of secondary particles is advantageous in improving the compaction density of the positive electrode plate, thereby improving the energy density of the secondary battery. In some embodiments, selectively, the quantity occupancy of the secondary particles is 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more.

[0098] In some embodiments, the positive electrode plate contains a positive electrode active material whose volume-average particle size is 2.5 μm ≤ Dv50 ≤ 30 μm, and selectively 2.5 μm ≤ Dv50 ≤ 25 μm.

[0099] Selectively, when the positive electrode active material is in primary particle form, the volume-average particle size of the positive electrode active material in primary particle form satisfies 2.5 μm ≤ Dv50 ≤ 7 μm, and more selectively, 2.5 μm ≤ Dv50 ≤ 5.5 μm.

[0100] Selectively, when the positive electrode active material is in the form of secondary particles, the volume-average particle size of the positive electrode active material in the form of secondary particles satisfies 6 μm ≤ Dv50 ≤ 30 μm, and more selectively satisfies 6 μm ≤ Dv50 ≤ 25 μm.

[0101] Different volume-average particle sizes Dv50 of the positive electrode active material particles affect the porosity and / or compaction density of the positive electrode plate due to differences in the particle's compressive strength. When the volume-average particle size Dv50 of the positive electrode active material is within an appropriate range, it contributes to the positive electrode plate having appropriate porosity and / or compaction density, and further contributes to both ions and electrons having relatively high conductivity.

[0102] In some embodiments, the diameter distance of the positive electrode active material satisfies 1 ≤ (Dv90 - Dv10) / Dv50 ≤ 5, and selectively satisfies 1 ≤ (Dv90 - Dv10) / Dv50 ≤ 2. The diameter distance of the positive electrode active material (Dv90 - Dv10) / Dv50 can reflect the degree of discreteness of the particle size distribution of the positive electrode active material, and the degree of discreteness of the particle size distribution affects the porosity and / or compaction density of the positive electrode plate. When the diameter distance of the positive electrode active material (Dv90 - Dv10) / Dv50 is within an appropriate range, it contributes to the positive electrode plate having an appropriate porosity and / or compaction density, and at the same time, the void size distribution of the positive electrode plate can be made more uniform, thereby contributing to the secondary battery better combining high energy density, high power density and high capacity.

[0103] Therefore, by adjusting one or more of the following parameters of the positive electrode active material—particle morphology, volume-average particle size Dv50, and diameter-to-diameter distance (Dv90-Dv10) / Dv50—to satisfy the above range, it is possible to contribute to the positive electrode plate having an appropriate porosity and / or compaction density, and further contribute to the secondary battery exhibiting a better combination of high energy density, high power density, and high capacity.

[0104] In some embodiments, the form of the negative electrode active material includes one or more of the following: spherical, subglobose, block-shaped, and sheet-shaped.

[0105] In some embodiments, the negative electrode active material comprises primary particles, secondary particles, or a combination thereof, and selectively comprises secondary particles or a combination of primary and secondary particles. Combining a negative electrode active material in the form of primary particles with a negative electrode active material in the form of secondary particles is advantageous in improving the compaction density of the negative electrode plate, thereby improving the energy density of the secondary battery. In some embodiments, selectively, the quantity occupancy of the secondary particles is 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more.

[0106] In some embodiments, the negative electrode plate is fitted with a negative electrode active material having a volume-average particle size of 8 μm ≤ Dv50 ≤ 22 μm, and selectively, 10 μm ≤ Dv50 ≤ 16 μm. Different volume-average particle sizes Dv50 of the negative electrode active material particles affect the porosity and / or compaction density of the negative electrode plate due to differences in the particle's compressive strength. When the volume-average particle size Dv50 of the negative electrode active material is within an appropriate range, it contributes to the negative electrode plate having an appropriate porosity and / or compaction density, and further contributes to both ions and electrons having relatively high conductivity.

[0107] In some embodiments, the diameter distance of the negative electrode active material is 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 5, and selectively satisfies 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 1.5. The diameter distance of the negative electrode active material (Dv90 - Dv10) / Dv50 can reflect the degree of discreteness of the particle size distribution of the negative electrode active material, and the degree of discreteness of the particle size distribution affects the porosity and / or compaction density of the negative electrode plate. When the diameter distance of the negative electrode active material (Dv90 - Dv10) / Dv50 is within an appropriate range, it contributes to the negative electrode plate having an appropriate porosity and / or compaction density, and at the same time, it can make the distribution of void size in the negative electrode plate more uniform, thereby contributing to the secondary battery better combining high energy density, high power density and high capacity.

[0108] Therefore, by adjusting one or more of the following parameters of the negative electrode active material—particle morphology, volume-average particle size Dv50, and diameter-to-diameter distance (Dv90-Dv10) / Dv50—to satisfy the above range, it is possible to contribute to the negative electrode plate having an appropriate porosity and / or compaction density, and further contribute to the secondary battery exhibiting a better combination of high energy density, high power density, and high capacity.

[0109] The quantitative occupancy rate of secondary particles on the electrode plate may be obtained by the following method: Take any of several test regions in the electrode film layer, acquire images of the multiple test regions using a scanning electron microscope, statistically calculate the occupancy rate of the number of secondary particle morphology particles in each image relative to the total number of electrode active material particles, and the average of the statistical results for the multiple test regions is the quantitative occupancy rate of secondary particles.

[0110] [Electrolyte] In this application, R1 and R2 represent fluorine atoms or fluorine-containing groups (e.g., partially fluorinated or fully fluorinated organic groups), and the presence of fluorine atoms contributes to the formation of thinner and denser positive electrode and / or negative electrode interface films, thereby contributing to uniform ion transmission and effectively suppressing dendrite formation.

[0111] In some embodiments, one of R1 and R2 represents a fluorine atom, and the other represents at least one from the group consisting of partially fluorinated or fully fluorinated C1-C10 alkyl groups, C2-C10 alkenyl groups, C2-C10 alkynyl groups, C6-C8 aryl groups, C1-C10 alkoxy groups, C2-C10 alkenyloxy groups, C2-C10 alkynyloxy groups, and C6-C8 aryloxy groups.

[0112] In some embodiments, one of R1 and R2 represents a fluorine atom, and the other represents at least one of the group consisting of a partially fluorinated or fully fluorinated methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, tert-butyl group, vinyl group, propenyl group, allyl group, butadienyl group, ethynyl group, propynyl group, phenyl group, methoxy group, ethoxy group, propoxy group, vinyloxy group, propenyloxy group, acetyleneoxy group, propynyloxy group, and phenoxy group.

[0113] In some embodiments, both R1 and R2 represent fluorine atoms.

[0114] In this application, Me includes one or more alkali metals and alkaline earth metals. Selectively, the alkali metal includes one or more of Li, Na, and K. Selectively, the alkaline earth metal includes Ca, Mg, or a combination thereof.

[0115] In some embodiments, Me represents Li.

[0116] In some embodiments, the compound shown in Formula 1 is [ka] This includes one or more of the above-mentioned compounds.

[0117] In some embodiments, the aqueous electrolyte further comprises a second component, the second component comprising lithium hexafluorophosphate (LiPF6).

[0118] Lithium hexafluorophosphate has the characteristic of high ionic conductivity, and when its content is within an appropriate range, it contributes to improving the overall ionic conductivity of the electrolyte, accelerating ion transport, and improving the capacity of secondary batteries. However, lithium hexafluorophosphate has relatively poor thermal stability in high-temperature environments, and it decomposes at relatively high temperatures to produce PF5. PF5 reacts with water to form HF, which corrodes the positive electrode active material and increases battery expansion. When the electrolyte contains both the compound shown in Formula 1 and lithium hexafluorophosphate, the compound shown in Formula 1 can further react with lithium hexafluorophosphate to form the compound LiPF4C2O4, which can reduce some of the decomposition of lithium hexafluorophosphate and the formation of HF, and furthermore, the secondary battery can have even higher cycle performance.

[0119] In some embodiments, the weight percentage content D2 of the second component in the electrolyte is selectively 5% or more, and more selectively 8% or more, for example, 8% to 30%, 10% to 25%, or 10% to 20%.

[0120] In some embodiments, the electrolyte further comprises a third component, which comprises one or more of lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP). The third component, as an auxiliary lithium salt, can further improve the interfacial properties of the positive and / or negative electrodes, or improve the ionic conductivity or thermal stability of the electrolyte.

[0121] In some embodiments, the third component selectively includes lithium tetrafluoroborate, lithium difluorophosphate, or a combination thereof. Lithium tetrafluoroborate has relatively high thermal stability, thereby improving the high-temperature stability of the secondary battery. Furthermore, lithium tetrafluoroborate has relatively low charge transfer resistance, thereby improving the low-temperature discharge performance of the secondary battery and widening the electrochemical window of the electrolyte. Lithium difluorophosphate has relatively high electrochemical stability, improving the ionic conductivity of the electrolyte and improving the properties of the positive electrode interface film and / or negative electrode interface film. It contributes to constructing a stable, low-impedance positive electrode interface film and / or negative electrode interface film, thereby effectively reducing electrolyte decomposition and further improving the power performance and safety performance of the secondary battery.

[0122] In some embodiments, the weight percentage content D3 of the third component in the electrolyte is selectively 0.5% or less, and more selectively 0.25% or less.

[0123] In some embodiments, the weight ratio D3 / D1 of the third component to the first component is selectively set to 0.5 to 2. This contributes to fully realizing the synergistic effect between the third component and the first component, as well as to good low-temperature discharge performance of the secondary battery.

[0124] In some embodiments, the weight percentage content D3 of the third component in the electrolyte is selectively such that D3 is 0.5% or less and D3 / D1 is 0.5 to 2. This is advantageous for further enhancing the synergistic effect between the third component and the first component.

[0125] In some embodiments, the electrolyte further comprises a fourth component, the fourth component comprising fluoroethylene carbonate (FEC). FEC can induce a reductive decomposition reaction at a relatively high potential and form an interfacial film with certain flexibility on the surface of the negative electrode active material. Furthermore, it can suppress the reductive decomposition of organic solvents at relatively low potentials and prevent the organic solvent from embedding into the negative electrode active material. Therefore, when the electrolyte contains FEC, the cycle performance of the secondary battery can be effectively improved. However, FEC readily decomposes to form HF, which destroys the positive electrode interfacial film and corrodes the positive electrode active material, increasing the heat generation and gas generation of the secondary battery. On the other hand, the compound shown in Formula 1 can be used as a stabilizer for the positive electrode active material. Its B atom interacts with the O atom on the surface of the positive electrode active material, thereby stabilizing the crystal structure of the positive electrode active material and reducing the destruction of the crystal structure of the positive electrode active material by HF. Therefore, using the compound shown in Formula 1 in combination with FEC is advantageous for fully utilizing the further improvement effect of FEC on the cycle performance of the secondary battery. Furthermore, FEC has a relatively high dielectric constant, and the anions of the compound shown in Equation 1 become free ions, contributing to a reduction in the association of anions and cations. This allows the compound to fully exert its effect of improving the power performance and cycle performance of the secondary battery shown in Equation 1.

[0126] In some embodiments, the weight percentage content D4 of the fourth component in the electrolyte is selectively 5% or less, and more selectively 2.5% or less.

[0127] In some embodiments, the weight ratio D4 / D1 of the fourth component to the first component is selectively 5 to 100, and more selectively 5 to 75, 5 to 50, and 5 to 40. The inventors further researched and found that when the weight ratio of the fourth component to the first component is within an appropriate range, the synergistic effect between the fourth component and the first component can be fully realized, and in this case not only does the amount of gas generated in the secondary battery not increase significantly, but also further improves the cycle performance of the secondary battery.

[0128] In some embodiments, the weight percentage content D4 of the fourth component in the electrolyte is selectively such that D4 is 5% or less and D4 / D1 is 5 to 100. This is advantageous for further enhancing the synergistic effect between the fourth component and the first component.

[0129] In some embodiments, the electrolyte further comprises a fifth component, the fifth component comprising one or more of cyclic carbonate compounds, linear carbonate compounds, carboxylic acid ester compounds, sulfone compounds, and ether compounds. In this application, the fifth component is used primarily as an organic solvent to dissolve the other components in the electrolyte.

[0130] For example, the cyclic carbonate compound may include one or more of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). For example, the chain carbonate compound may include one or more of ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), and ethyl propyl carbonate (EPC). For example, the carboxylic acid ester compound may include one or more of methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), and 1,4-butyrolactone (GBL). For example, the sulfone compound may include one or more of sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE). For example, the ether compound may include one or more of tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxolane (DOL), ethylene glycol monomethyl ether, ethylene glycol dimethyl ether (DME), tetraethylene glycol dimethyl ether, dimethoxymethane (DMM), and diethylene glycol dimethyl ether (DG).

[0131] In some embodiments, the weight percentage content D5 of the fifth component in the electrolyte is selectively 60% or more, selectively 65% ​​or more, 70% or more, 75% or more, or 80% or more.

[0132] In some embodiments, the fifth component selectively comprises at least a cyclic carbonate compound and a linear carbonate compound. When the content of lithium salts, such as lithium hexafluorophosphate, is relatively high, the viscosity of the electrolyte increases, the ionic conductivity decreases, and ion transport becomes unfavorable. Cyclic carbonate compounds have a relatively high dielectric constant, which can increase the ionic conductivity of the electrolyte, and linear carbonate compounds have a relatively low viscosity, which can reduce the viscosity of the electrolyte. Therefore, when the fifth component comprises both a cyclic carbonate compound and a linear carbonate compound, it contributes to the electrolyte having appropriate viscosity and ionic conductivity, and is further advantageous for ion transport.

[0133] Cyclic carbonate compounds have relatively high dielectric constants and contribute to increasing the ionic conductivity of the electrolyte. However, they are prone to decomposition reactions, which affect the storage performance of secondary batteries. Therefore, their content needs to be controlled within an appropriate range.

[0134] In some embodiments, the weight percentage content of the cyclic carbonate compound in the electrolyte is greater than 0 and 40% or less, and may be selectively 5% to 40%, 8% to 35%, or 10% to 30%.

[0135] In some embodiments, the weight percentage content of the linear carbonate compound in the electrolyte is 40% to 85%, and may be selectively 50% to 80%, 55% to 80%, or 60% to 80%.

[0136] In some embodiments, the electrolyte may further contain other components besides those described above, such as one or more of halogen-substituted cyclic carbonate compounds, nitrile compounds, phosphazene compounds, aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds, isocyanate compounds, acid anhydride compounds, sulfate ester compounds, sulfite ester compounds, sulfonic acid ester compounds and disulfonic acid ester compounds. The present application does not particularly limit the types of other components in the electrolyte, and may contain, for example, one or more of 1,3-propanesultone (PS), vinylene carbonate (VC), and vinyl sulfate (DTD), as long as they do not impair the spirit of the present application.

[0137] In some embodiments, the total weight percentage content of these other components is selectively 5% or less, and more selectively 2.5% or less based on the total weight of the electrolyte.

[0138] In this application, each component in the electrolyte and its content can be measured according to methods known in the art. For example, they can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and inductively coupled plasma emission spectroscopy (ICP-OES).

[0139] It should be noted that when testing the electrolyte of this application, a freshly manufactured electrolyte may be taken directly, or the electrolyte may be obtained from a secondary battery. One exemplary method for obtaining the electrolyte from a secondary battery includes the step of discharging the secondary battery to its discharge cutoff voltage (generally fully discharging the battery for safety), then centrifuging it, and then taking an appropriate amount of the liquid obtained by centrifugation, i.e., the electrolyte. The electrolyte may also be obtained directly from the filling port of the secondary battery.

[0140] [Positive electrode plate] The positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector and containing a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0141] The positive electrode active material may be a positive electrode active material known in the art for use in secondary batteries. For example, the positive electrode active material includes one or more of layered lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds, selectively includes one or more of layered lithium transition metal oxides and their modified compounds, or includes a mixture of layered lithium transition metal oxides and their modified compounds and lithium-containing phosphates and their modified compounds. Optionally, the layered lithium transition metal oxide may include one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their respective modified compounds. Optionally, the lithium-containing phosphate includes one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite material of lithium manganese iron phosphate and carbon, and their respective modified compounds. In this application, the modified compound of each of the above positive electrode active material may perform doping modification and / or surface coating modification on the positive electrode active material.

[0142] In some embodiments, in order to further improve the energy density of the secondary battery, the positive electrode active material has a molecular formula of Li a Ni b Co c Mn d Al e M f O g A hIt contains a layered lithium transition metal oxide, where M represents a transition metal site-doped cation and A represents an oxygen site-doped anion, with 0.8 ≤ a ≤ 1.2, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ d ≤ 1, 0 ≤ e ≤ 1, 0 ≤ f ≤ 0.2, 0 ≤ g ≤ 2, 0 ≤ h ≤ 2, b + c + d + e + f = 1, g + h = 2.

[0143] The molecular formula is Li a Ni b Co c Mn d Al e M f O g A h The layered lithium transition metal oxide can be modified by selectively doping with M cations, by doping with A anions, or by simultaneously doping with M cations and A anions. The crystal structure of the layered lithium transition metal oxide obtained after doping is even more stable, and the electrochemical performance of the secondary battery, such as cycle performance and power performance, can be further improved.

[0144] In some embodiments, M includes one or more of Si, Ti, Mo, V, Ge, Se, Zr, Nb, Ru, Pd, Sb, Ce, Te, and W.

[0145] In some embodiments, A includes one or more of F, N, P, and S. Selectively, A is F. After F doping modification, Li a Ni b Co c Mn d Al e M f O g A h Its crystal structure is even more stable, which allows secondary batteries to have better cycle performance and power performance.

[0146] The values ​​of a, b, c, d, e, f, g, h are Li a Ni b Co c Mn d Al e M f Og A h satisfies the condition of being electrically neutral.

[0147] In some embodiments, 0 < b < 0.98. Optionally, 0.50 ≤ b < 0.98, 0.55 ≤ b < 0.98, 0.60 ≤ b < 0.98, 0.65 ≤ b < 0.98, 0.70 ≤ b < 0.98, 0.75 ≤ b < 0.98 or 0.80 ≤ b < 0.98.

[0148] In some embodiments, c = 0.

[0149] In some embodiments, 0 < c ≤ 0.20. Optionally, 0 < c ≤ 0.15, 0 < c ≤ 0.10, 0 < c ≤ 0.09, 0 < c ≤ 0.08, 0 < c ≤ 0.07, 0 < c ≤ 0.06, 0 < c ≤ 0.05, 0 < c ≤ 0.04, 0 < c ≤ 0.03, 0 < c ≤ 0.02 or 0 < c ≤ 0.01. Since cobalt has a relatively low content in the earth's crust, is difficult to mine and has a very high price, low cobalt or cobalt-free has become an inevitable development trend of the positive electrode active material. However, the contribution of cobalt to the diffusion rate of positive electrode active material ions is huge, and low cobalt or cobalt-free reduces the ion diffusion rate of the positive electrode active material and affects the cycle performance of the secondary battery. Researchers have been focusing on enhancing the ion diffusion rate of low cobalt or cobalt-free positive electrode active materials all the time, but no good solution has been proposed yet.

[0150] During the research, the inventor of the present application unexpectedly discovered the following. The compound shown in Formula 1 in the electrolyte can form a protective film with low impedance on the surface of the positive electrode active material, and the B atom in its molecular structure is likely to bond with the O atom in the positive electrode active material, thereby reducing the diffusion resistance of ions in the bulk phase of the positive electrode active material. Therefore, when the electrolyte contains an appropriate content of the compound shown in Formula 1, the low-cobalt or cobalt-free positive electrode active material can have a significantly improved ion diffusion rate, and the ions in the bulk phase of the low-cobalt or cobalt-free positive electrode active material can be replenished to the surface in a timely manner, stabilizing the crystal structure of the low-cobalt or cobalt-free positive electrode active material. Since the crystal structure of the low-cobalt or cobalt-free positive electrode active material is more stable, the probability of problems such as instability of the crystal structure characteristics, chemical characteristics or electrochemical characteristics of the positive electrode active material can be significantly reduced. For example, the probability of irreversible strain and lattice defects of the positive electrode active material can be reduced.

[0151] In some embodiments, d = 0 and 0 < e < 0.50. Optionally, d = 0 and 0 < e ≤ 0.45, d = 0 and 0 < e ≤ 0.40, d = 0 and 0 < e ≤ 0.35, d = 0 and 0 < e ≤ 0.30, d = 0 and 0 < e ≤ 0.25, d = 0 and 0 < e ≤ 0.20, d = 0 and 0 < e ≤ 0.15 or d = 0 and 0 < e ≤ 0.10.

[0152] In some embodiments, e = 0 and 0 < d < 0.50. Optionally, e = 0 and 0 < d ≤ 0.45, e = 0 and 0 < d ≤ 0.40, e = 0 and 0 < d ≤ 0.35, e = 0 and 0 < d ≤ 0.30, e = 0 and 0 < d ≤ 0.25, e = 0 and 0 < d ≤ 0.20, e = 0 and 0 < d ≤ 0.15 or e = 0 and 0 < d ≤ 0.10.

[0153] In some embodiments, 0 < d < 0.50 and 0 < e < 0.50. Optionally, 0 < d ≤ 0.30 and 0 < e ≤ 0.10.

[0154] In some embodiments, g = 2 and h = 0.

[0155] In some embodiments, g = 0 and h = 2.

[0156] In some embodiments, 0 < g < 2, 0 < h < 2, and g + h = 2.

[0157] As an example, a layered lithium transition metal oxide having the molecular formula Li a Ni b Co c Mn d Al e M f O g A h includes, but is not limited to, one or more of LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.8 Co 0.05 Mn 0.15 O2, LiNi 0.7 Mn 0.3 O2, LiNi 0.69 Co 0.01 Mn 0.3 O2, LiNi 0.68 Co 0.02 Mn 0.3 O2, LiNi 0.65 Co 0.05 Mn 0.3 O2, LiNi 0.63 Co 0.07 Mn 0.3 O2, and LiNi 0.61 Co 0.09 Mn 0.3 O2.

[0158] Li a Ni b Co c Mn d Al e M f O g A hIt can be manufactured according to conventional methods in the art. An exemplary manufacturing method involves mixing a lithium source, a nickel source, a cobalt source, a manganese source, an aluminum source, an M element precursor, and an A element precursor, and then sintering them. The sintering atmosphere may be an oxygen-containing atmosphere, such as a gas atmosphere or an oxygen atmosphere. The O2 concentration of the sintering atmosphere is, for example, 70% to 100%. The sintering temperature and sintering time can be adjusted according to the actual conditions.

[0159] For example, the lithium source includes, but is not limited to, one or more of lithium oxide (Li2O), lithium phosphate (Li3PO4), lithium dihydrogen phosphate (LiH2PO4), lithium acetate (CH3COOLi), lithium hydroxide (LiOH), lithium carbonate (Li2CO3), and lithium nitrate (LiNO3). For example, the nickel source includes, but is not limited to, one or more of nickel sulfate, nickel nitrate, nickel chloride, nickel oxalate, and nickel acetate. For example, the cobalt source includes, but is not limited to, at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt oxalate, and cobalt acetate. For example, the manganese source includes, but is not limited to, one or more of manganese sulfate, manganese nitrate, manganese chloride, manganese oxalate, and manganese acetate. For example, the aluminum source includes, but is not limited to, one or more of aluminum sulfate, aluminum nitrate, aluminum chloride, aluminum oxalate, and aluminum acetate. For example, the M element precursor includes, but is not limited to, one or more of the oxides, nitrate compounds, carbonate compounds, hydroacid compounds, and acetate compounds of the M element. For example, the A element precursor includes, but is not limited to, one or more of the ammonium fluoride, lithium fluoride, hydrogen fluoride, ammonium chloride, lithium chloride, hydrogen chloride, ammonium nitrate, ammonium nitrite, ammonium carbonate, ammonium bicarbonate, ammonium phosphate, phosphoric acid, ammonium sulfate, ammonium bisulfite, ammonium sulfite, ammonium hydrogen sulfide, hydrogen sulfide, lithium sulfide, ammonium sulfide, and elemental sulfur.

[0160] In some embodiments, based on the total weight of the positive electrode film layer, the weight percentage content of the layered lithium transition metal oxide with the chemical formula Li a Ni b Co c Mn d Al e M f O g A h is 80% or more, and optionally 85% or more, 90% or more.

[0161] In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. This application is not particularly limited with respect to the type of the positive electrode conductive agent. For example, the positive electrode conductive agent may include one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, based on the total weight of the positive electrode film layer, the weight percentage content of the positive electrode conductive agent is 15% or less, and optionally 10% or less, 5% or less.

[0162] In some embodiments, the positive electrode film layer further optionally includes a positive electrode adhesive. This application is not particularly limited with respect to the type of the positive electrode adhesive. For example, the positive electrode adhesive may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. In some embodiments, based on the total weight of the positive electrode film layer, the weight percentage content of the positive electrode adhesive is 5% or less, and optionally 3% or less, 2% or less.

[0163] In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. Aluminum foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0164] The positive electrode film layer is generally obtained by coating a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, a selective conductive agent, a selective adhesive, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0165] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode film layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0166] The anode active material can be anode active material for secondary batteries known in the art. For example, the anode active material includes one or more of the following: carbon-based materials, silicon-based materials, tin-based materials, lithium titanate, and composite materials obtained by coating modification of the above materials.

[0167] In some embodiments, the negative electrode active material includes one or more carbon-based materials and composite materials obtained by coating modification of the above materials. Selectively, the carbon-based material includes one or more graphite (e.g., natural graphite, artificial graphite, or a combination thereof), soft carbon, hard carbon, and composite materials obtained by coating modification of the above materials.

[0168] In some embodiments, the weight percentage content of the negative electrode active material is 80% or more, and selectively 85% or more, and 90% or more, based on the total weight of the negative electrode film layer.

[0169] In some embodiments, the negative electrode film layer further selectively comprises a negative electrode conductive agent. This application is not particularly limited to the type of negative electrode conductive agent, and for example, the negative electrode conductive agent may comprise one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the weight percentage content of the negative electrode conductive agent, based on the total weight of the negative electrode film layer, is 15% or less, selectively 10% or less, and 5% or less.

[0170] In some embodiments, the negative electrode film layer further selectively includes a negative electrode adhesive. This application is not particularly limited to the type of negative electrode adhesive, and for example, the negative electrode adhesive may include one or more of the following: styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic acid resin (e.g., polyacrylate PAA, polymethacrylate PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). In some embodiments, the weight percentage content of the negative electrode adhesive is 5% or less based on the total weight of the negative electrode film layer.

[0171] In some embodiments, the negative electrode film layer may further selectively contain other additives. For example, the other additives may include thickeners such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, etc. In some embodiments, the weight percentage content of the other additives is 2% or less based on the total weight of the negative electrode film layer.

[0172] In some embodiments, the negative electrode current collector can be a metal foil sheet or a composite current collector. Copper foil can be used as an example of a metal foil sheet. The composite current collector may include a polymer material substrate and a metal material layer formed on at least one surface of the polymer material substrate. For example, the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. For example, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0173] The negative electrode film layer is generally obtained by coating a negative electrode slurry onto a negative electrode current collector, drying, and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, a selective conductive agent, a selective adhesive, and other selective auxiliary agents in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP) or deionized water.

[0174] [Separator] In some embodiments, the secondary battery further includes a separator. The separator is placed between the positive electrode plate and the negative electrode plate and primarily serves to prevent short circuits between the positive and negative electrodes, while also allowing ions to pass through. This application is not particularly limited to the type of separator, and any known porous separator having good chemical and mechanical stability can be selected.

[0175] In some embodiments, the material of the separator may include one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different.

[0176] [Manufacturing method] The method for manufacturing a secondary battery described in this application is known. In some embodiments, a secondary battery can be formed by assembling a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. For example, the positive electrode plate, separator, and negative electrode plate can be formed into an electrode assembly through a winding process and / or a lamination process, the electrode assembly is placed in an outer casing, dried, and then the electrolyte is injected. A battery cell is obtained by going through processes such as vacuum packaging, settling, chemical formation, and shaping. Multiple battery cells may further constitute a battery module via series connection, parallel connection, or series-parallel connection. Multiple battery modules may further constitute a battery pack via series connection, parallel connection, or series-parallel connection. In some embodiments, multiple battery cells may directly constitute a battery pack.

[0177] This application also provides a power consumption device including a secondary battery of this application. The secondary battery can serve as the power source for the power consumption device, or it can serve as the energy storage unit for the power consumption device. The power consumption device may be, but is not limited to, mobile devices (e.g., mobile phones, tablet computers, laptop computers, 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.

[0178] The aforementioned power consumption device can select a specific type of secondary battery, such as a battery cell, battery module, or battery pack, according to its usage needs.

[0179] Figure 6 is a schematic diagram of an example power consumption device. This power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high output and high energy density of this power consumption device, a battery pack or battery module may be used as the power source.

[0180] Other examples of power-consuming devices may include mobile phones, tablet computers, and laptop computers. These power-consuming devices are generally required to be thin, and may use battery cells as their power source.

[0181] Examples The following examples provide a more detailed description of the contents disclosed in this application, and these examples are for illustrative purposes only, as it will be obvious to those skilled in the art that various modifications and changes can be made within the scope of the contents disclosed in this application. Unless otherwise stated, all occupancy rates, percentages, and ratios mentioned in the following examples are calculated on a weight basis, and all reagents used in the examples are commercially available or can be synthesized according to conventional methods and are ready for direct use without further processing, and all instruments used in the examples are commercially available.

[0182] Example 1 Manufacturing of positive electrode plates LiNi 0.6 Co 0.2 Mn 0.2O2 (spherical-like morphology, secondary particle number is 60% or more, Dv50 is 20 μm), carbon black as a conductive agent, and polyvinylidene fluoride (PVDF) as an adhesive were sufficiently stirred and mixed in an appropriate amount of solvent NMP according to a weight ratio of 97.5:1.4:1.1 to form a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on the surface of a positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode plate was obtained. By adjusting one or more of the cold pressing process parameters, such as the cold pressing speed, cold pressing temperature, cold pressing pressure, and cold pressing number of times, the consolidation density of the positive electrode plate was made 3.4 g / cm 3 to 25% porosity.

[0183] Manufacturing of negative electrode plates Graphite as the negative electrode active material (morphology close to spherical, occupancy of secondary particle quantity is 80% or more, Dv50 is 11 μm), styrene-butadiene rubber (SBR) as an adhesive, sodium carboxymethyl cellulose (CMC-Na) as a thickener, and carbon black (Super P) as a conductive agent were sufficiently stirred and mixed in an appropriate amount of solvent deionized water according to a weight ratio of 96.2:1.8:1.2:0.8 to form a uniform negative electrode slurry. The negative electrode slurry was uniformly coated on the surface of a negative electrode current collector copper foil, and after drying and cold pressing, a negative electrode plate was obtained. By adjusting one or more of the cold pressing process parameters, such as the cold pressing speed, cold pressing temperature, cold pressing pressure, and cold pressing number of times, the consolidation density of the negative electrode plate was made 1.6 g / cm 3 to 27% porosity.

[0184] Separator A porous polyethylene (PE) membrane was adopted as the separator.

[0185] Manufacturing of electrolyte Each component was uniformly mixed according to the composition shown in Table 1 to obtain an electrolyte. In Table 1, the addition amount of each component was calculated based on the total weight of the electrolyte.

[0186] The first component is [ka] That is the case.

[0187] The second component is lithium hexafluorophosphate.

[0188] The third component is lithium tetrafluoroborate.

[0189] The fourth component is fluoroethylene carbonate.

[0190] The fifth component is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a weight ratio of 1:1:1.

[0191] Manufacturing of rechargeable batteries A positive electrode plate, a separator, and a negative electrode plate were stacked and wound in sequence to obtain an electrode assembly. The electrode assembly was placed inside an outer casing, the electrolyte was added, and after going through processes such as packaging, standing, chemical conversion, and aging, a secondary battery was obtained.

[0192] Examples 2-7 and Comparative Examples 1-3 The method for manufacturing the secondary battery is similar to that of Example 1, with the only difference being the adjustment of the electrolyte manufacturing parameters, which are shown in detail in Table 1.

[0193] Examples 8-10 and Comparative Examples 4-5 The method for manufacturing the secondary battery is similar to that of Example 1, the difference being that the cold pressing process parameters of the negative electrode plate can be adjusted, for example, one or more of the cold pressing speed, cold pressing temperature, cold pressing pressure, and number of cold pressing cycles can be adjusted, and at the same time the parameters of the negative electrode active material itself can be adjusted to give the negative electrode plates of each example and comparative example different porosity. The Dv50 of the negative electrode active material used in Comparative Example 4 was 12 μm, the Dv50 of the negative electrode active material used in Comparative Example 5 was 10 μm, the Dv50 of the negative electrode active material used in Example 8 was 11.7 μm, the Dv50 of the negative electrode active material used in Example 9 was 11.4 μm, and the Dv50 of the negative electrode active material used in Example 10 was 10.5 μm.

[0194] Examples 11-13 and Comparative Examples 6-7 The method for manufacturing the secondary battery is similar to that of Example 1, the difference being that the cold pressing process parameters of the positive electrode plate can be adjusted, for example, one or more of the cold pressing speed, cold pressing temperature, cold pressing pressure, and number of cold pressing cycles can be adjusted, and at the same time the parameters of the positive electrode active material itself can also be adjusted, so that the positive electrode plates of each example and comparative example have different porosities. The quantity occupancy rate of secondary particles in the positive electrode active material used in Comparative Example 6 was 80%, the quantity occupancy rate of secondary particles in the positive electrode active material used in Comparative Example 7 was 50%, the quantity occupancy rate of secondary particles in the positive electrode active material used in Example 11 was 75%, the quantity occupancy rate of secondary particles in the positive electrode active material used in Example 12 was 70%, and the quantity occupancy rate of secondary particles in the positive electrode active material used in Example 13 was 55%.

[0195] Examples 14-22 The method for manufacturing the secondary battery is similar to that of Example 1, with the only difference being the adjustment of the electrolyte manufacturing parameters, which are shown in detail in Table 1.

[0196] Test section (1) Secondary battery room temperature cycle performance test At 25°C, the secondary battery was charged with a constant current of 1C to 4.3V, followed by charging with a constant voltage and current of 0.05C. At this point, the secondary battery was fully charged, and the charge capacity at this time was recorded, which is the charge capacity of the first cycle. After the secondary battery was left to stand for 5 minutes, it was discharged with a constant current of 1C to 2.8V. This constitutes one cycle charge-discharge process, and the discharge capacity at this time was recorded, which is the discharge capacity of the first cycle. A cycle charge-discharge test was performed on the secondary battery according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 600 cycles at 25°C is calculated as: discharge capacity after 600 cycles / discharge capacity of the first cycle × 100%.

[0197] (2) High-temperature cycle performance test of secondary batteries At 45°C, the secondary battery was charged with a constant current of 1C to 4.3V, followed by charging with a constant voltage and current of 0.05C. At this point, the secondary battery was fully charged, and the charge capacity at this time was recorded, which is the charge capacity of the first cycle. After the secondary battery was left to stand for 5 minutes, it was discharged with a constant current of 1C to 2.8V. This constitutes one cycle charge-discharge process, and the discharge capacity at this time was recorded, which is the discharge capacity of the first cycle. A cycle charge-discharge test was performed on the secondary battery according to 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°C is calculated as: discharge capacity after 600 cycles / discharge capacity of the first cycle × 100%.

[0198] (3) Initial DC internal resistance test of secondary battery At 25°C, the secondary battery is charged with a constant current of 1C to 4.3V, and then charged with a constant voltage and current of 0.05C. At this point, the secondary battery is fully charged. The secondary battery is then discharged with a constant current of 0.5C and adjusted to 50% SOC. The voltage of the secondary battery at this point is denoted as U1. The secondary battery is then discharged with a constant current of 4C and current I1 for 30 seconds, and a sample is taken at 0.1 seconds. The final discharge voltage is denoted as U2. The initial DC internal resistance of the secondary battery is expressed using the DC internal resistance of the secondary battery at 50% SOC, and the initial DC internal resistance of the secondary battery (mΩ) = (U1 - U2) / I1.

[0199] (4) Low-temperature performance test of secondary batteries At -10°C, the secondary battery was charged with a constant current of 0.2C to 4.3V, followed by charging with a constant voltage and current of 0.05C. At this point, the secondary battery was fully charged, and the charge capacity at this time was recorded, which is the charge capacity of the first cycle. After the secondary battery was left to stand for 30 minutes, it was discharged with a constant current of 0.2C to 2.8V. This constitutes one cycle charge-discharge process, and the discharge capacity at this time was recorded, which is the discharge capacity of the first cycle. A cycle charge-discharge test was performed on the secondary battery according to the above method, and the discharge capacity after each cycle was recorded. The capacity retention rate (%) of the secondary battery after 200 cycles at -10°C is calculated as: discharge capacity after 200 cycles / discharge capacity of the first cycle × 100%.

[0200] [Table 1-1] [Table 1-2] [Table 1-3]

[0201] [Table 2-1] [Table 2-2] [Table 2-3]

[0202] In summary, the test results in Table 2 indicate that when a secondary battery satisfies both 0.80 ≤ A / B ≤ 1.20 and 0.14 ≤ 100D1 / B ≤ 1.50, it can have relatively low internal resistance and a relatively high capacity retention rate. Assuming high energy density, this allows for good power performance and a long cycle life, and it can also have good low-temperature discharge performance.

[0203] The secondary batteries of Comparative Examples 2 and 3 did not satisfy 0.14 ≤ 100D1 / B ≤ 1.50, and the secondary batteries of Comparative Examples 4 to 7 did not satisfy 0.80 ≤ A / B ≤ 1.20. As a result, assuming that the secondary batteries have high energy density, they cannot further provide good power performance, good low-temperature discharge performance, and long cycle life.

[0204] In summary, the test results from Examples 1 to 13 show that if the secondary battery also satisfies 0.85 ≤ A / B ≤ 1.15 and / or 0.16 ≤ 100D1 / B ≤ 1.40, it contributes to further improving the overall performance of the secondary battery.

[0205] In summary, the test results from Examples 1-6 and Example 7 show that if a secondary battery satisfies at least one of the following conditions: 0.16 ≤ 100D1 / A ≤ 1.20, 1.43 ≤ 10000D1 / P1 ≤ 9.34, and 2.78 ≤ 10000D1 / P2 ≤ 21.40, it contributes to further improving the overall performance of the secondary battery, especially if the secondary battery satisfies 0.16 ≤ 100D1 / A ≤ 1.20, 1.43 ≤ 10000D1 / P1 ≤ 9.34, and 2.78 ≤ 10000D1 / P2 ≤ 21.40 simultaneously.

[0206] The combined test results of Examples 1 and 14-22 show that when the electrolyte further contains a third and / or fourth component in an appropriate amount, it contributes to further improving at least one of the cycle performance, power performance, and low-temperature discharge performance of the secondary battery.

[0207] It should be noted that this application is not limited to the embodiments described above. The embodiments described above are illustrative, and any embodiments that have substantially the same configuration as the technical idea and produce the same effects within the scope of the technical proposal of this application are included within the scope of the technical proposal of this application. Furthermore, other methods constructed by combining some of the components of the embodiments, with various modifications that a person skilled in the art could conceive of, are also included within the scope of this application, as long as they do not depart from the spirit of this application. [Explanation of Symbols]

[0208] In drawings, the drawings are not drawn to the actual scale. 1 Battery pack, 2 Upper housing, 3 Lower housing, 4 Battery module, 5 Battery cell, 51 Case, 52 Electrode assembly, 53 Cover plate.

Claims

1. A secondary battery comprising a positive electrode plate, a negative electrode plate, and an electrolyte, wherein the porosity of the positive electrode plate is A, the porosity of the negative electrode plate is B, the electrolyte comprises a first component, the first component comprises one or more of the compounds shown in Formula 1, and R １ , R ２ Each represents independently a fluorine atom, or at least one of the group consisting of a C1-C10 alkyl group, a C2-C10 alkenyl group, a C2-C10 alkynyl group, a C6-C8 aryl group, a C1-C10 alkoxy group, a C2-C10 alkenyloxy group, a C2-C10 alkynyloxy group, or a C6-C8 aryloxy group, which are partially or completely fluorinated, and Me comprises one or more alkali metals and alkaline earth metals, and the weight percentage content of the first component in the electrolyte is D1. 【Chemistry 1】 The aforementioned secondary battery satisfies the following conditions: 22% ≤ A ≤ 32%, 22% ≤ B ≤ 30%, and 0.04% ≤ D1 ≤ 0.4%.

2. 0.80 ≤ A / B ≤ 1.20, and / or, The secondary battery according to claim 1, wherein 0.14 ≤ 100D1 / B ≤ 1.

50.

3. The secondary battery according to claim 1, further satisfying the condition 0.16 ≤ 100D1 / A ≤ 1.

20.

4. The secondary battery according to claim 1, wherein 0.05% ≤ D1 ≤ 0.3%.

5. The compaction density of the positive electrode plate is P １ g / cm ３ The compaction density of the negative electrode plate is P ２ g / cm ３ Furthermore, the secondary battery also has a limit of 1.75 ≤ P １ / P ２ A secondary battery according to claim 1, satisfying the relation ≤ 2.

50.

6. The consolidation density of the positive electrode plate is P １ g / cm ３ and the secondary battery further satisfies 1.43 ≦ 10000D1 / P １ ≦ 9.

34. The secondary battery according to claim 1

7. The compaction density of the negative electrode plate is P ２ g / cm ３ Furthermore, the secondary battery has a life cycle of 2.78 ≤ 10000 D1 / P ２ A secondary battery according to claim 1, satisfying the condition ≤ 21.

40.

8. 2.8 ≤ P １ ≤ 3.65 and / or, 1.2 ≤ P ２ The secondary battery according to claim 5, wherein the ratio is ≤ 1.

85.

9. Me represents Li and / or The compound shown in formula 1 above is 【Chemistry 2】 The secondary battery according to claim 1, comprising one or more of the above-mentioned compounds.

10. The secondary battery according to claim 1, wherein the electrolyte further comprises a second component, the second component comprising lithium hexafluorophosphate.

11. The secondary battery according to claim 1, wherein the electrolyte further comprises a third component, the third component comprising one or more of lithium tetrafluoroborate, lithium difluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

12. The secondary battery according to claim 1, wherein the electrolyte further comprises a fourth component, the fourth component comprising fluoroethylene carbonate.

13. The secondary battery according to claim 1, wherein the electrolyte further comprises a fifth component, the fifth component comprising one or more of a cyclic carbonate compound, a chain carbonate compound, a carboxylic acid ester compound, a sulfone compound, and an ether compound.

14. The secondary battery according to claim 1, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector and containing a positive electrode active material.

15. The positive electrode active material is (1) The form of the positive electrode active material includes one or more of the following: spherical, subspherical, (2) The positive electrode active material includes primary particles, secondary particles, or a combination thereof, (3) The quantity occupancy rate of secondary particles in the positive electrode active material is 50% or more, (4) The volume-average particle size of the positive electrode active material satisfies the condition that 2.5 μm ≤ Dv50 ≤ 30 μm, (5) The diameter of the positive electrode active material satisfies the condition that 1 ≤ (Dv90 - Dv10) / Dv50 ≤ 5, A secondary battery according to claim 14, satisfying at least one of the following conditions.

16. The secondary battery according to claim 1, wherein the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector and containing a negative electrode active material.

17. The aforementioned negative electrode active material is (1) The form of the negative electrode active material includes one or more of the following: spherical, subspherical, block-shaped, and sheet-shaped. (2) The negative electrode active material includes primary particles, secondary particles, or a combination thereof, (3) The quantity occupancy rate of secondary particles in the negative electrode active material is 50% or more, (4) The volume-average particle size of the negative electrode active material satisfies the condition that 8 μm ≤ Dv 50 ≤ 22 μm, (5) The diameter of the negative electrode active material satisfies the condition 0.5 ≤ (Dv90 - Dv10) / Dv50 ≤ 5, A secondary battery according to claim 16, satisfying at least one of the following conditions.

18. A power consumption device comprising a secondary battery as described in any one of claims 1 to 17.

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