Electrochemical apparatus and electronic apparatus

Abstract

The electrochemical device (5) and electronic device include a positive electrode piece, the positive electrode piece including a positive electrode current collector and a positive electrode active material layer provided on one or both sides of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material. Here, D v The ratio of 99 is 0.5≦D v 99 / H1≦0.9. A scanning electron microscope is used to observe an agglomerated region on the surface of the positive electrode active material layer, the diameter D0 of the bright spot being 20 μm or larger than 20 μm, and the number density per unit area of ​​the agglomerated region on the surface of the positive electrode active material layer is 5 pieces / cm 2 or 5 pieces / cm 2 The electrochemical device (5) has good high-temperature cycle characteristics.

Description

[Technical Field]

[0001] Cross-reference of related applications This application claims priority to the Chinese patent application filed on November 1, 2022, with application number 202211353337.1, and the title of the invention is "Electrochemical Apparatus and Electronic Apparatus," the entire contents of which are incorporated into this invention by reference.

[0002] Technical field This invention relates to the technical field of electrochemical apparatus, and more specifically to electrochemical apparatus and electronic apparatus. [Background technology]

[0003] Consumer electronic devices, electric transportation vehicles, and other such devices have become an indispensable part of people's lives. These devices require electrochemical equipment to supply electrical energy, and therefore are driving the rapid development of electrochemical equipment, exemplified by lithium-ion secondary batteries.

[0004] However, in related technologies, electrochemical equipment has poor high-temperature cycling characteristics, which limits its application to certain devices. [Overview of the project]

[0005] The present invention provides an electrochemical apparatus and an electronic apparatus, the electrochemical apparatus having good high-temperature cycling characteristics.

[0006] In a first embodiment, an embodiment of the present invention provides an electrochemical apparatus. The electrochemical apparatus includes a positive electrode piece, the positive electrode piece includes a positive electrode current collector and a positive electrode active material layer provided on one or both sides of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material. Here, the D of the positive electrode active material relative to the thickness H1 of the positive electrode active material layer on one side is v The ratio of 99 is 0.5 ≤ D vIt satisfies 99 / H1 ≤ 0.9. By means of a scanning electron microscope, an aggregation region where the diameter D0 of the bright spots on the surface of the positive electrode active material layer is 20 μm or larger than 20 μm is observed, and the number density per unit area of the aggregation region on the surface of the positive electrode active material layer is 5 pieces / cm 2 or less than 5 pieces / cm 2 .

[0007] In the electrochemical device provided by the embodiment of the present invention, the ratio of D v 99 of the positive electrode active material to the thickness H1 of the positive electrode active material layer on one side satisfies 0.5 ≤ D v 99 / H1 ≤ 0.9. Thereby, the positive electrode sheet can be made thinner, the ion transport path can be reduced, further the ion polarization can be reduced, and further the resistance of the electrochemical device can be reduced. Also, the diameter D0 of the bright spots on the surface of the positive electrode active material layer observed by the scanning electron microscope is 20 μm or an aggregation region larger than 20 μm, and the number density per unit area on the surface of the positive electrode active material layer is 5 pieces / cm 2 or less than 5 pieces / cm 2 , which can reduce the number of positive electrode active materials crushed in the roll pressing process of the positive electrode active material layer, and is helpful for improving the high-temperature cycle characteristics of the electrochemical device.

[0008] According to any one of the above embodiments of the first aspect of the present invention, D v 99 of the positive electrode active material satisfies 15 μm ≤ D v 99 ≤ 30 μm, and the thickness H1 of the positive electrode active material layer on one side satisfies 10 μm ≤ H1 ≤ 35 μm.

[0009] According to any one of the above embodiments of the first aspect of the present invention, the ratio of D v 10 of the positive electrode active material to D v 50 of the positive electrode active material satisfies 1.0 ≤ D v 50 / D v ≤ 2.5.

[0010] According to any one of the above embodiments of the first aspect of the present invention, the ratio of D v 10 of the positive electrode active material to D vThe ratio of 50 is 1.0 ≤ D v 50 / D v The condition satisfies 10 ≤ 2.0.

[0011] According to any one of the above embodiments of the first aspect of the present invention, the positive electrode active material includes a nickel-cobalt-manganese ternary material.

[0012] According to any one of the above embodiments of the first aspect of the present invention, the mole fraction of nickel in the nickel-cobalt-manganese ternary material is 60% or greater than 60%.

[0013] According to any one of the above embodiments of the first aspect of the present invention, the thickness H2 of the positive electrode current collector is I) 0.3 ≤ H2 / D v 99 ≤ 1, II) 1 ≤ H1 / H2 ≤ 4, III) 7μm ≤ H2 ≤ 20μm, It satisfies at least one of the following conditions.

[0014] According to any one of the above embodiments of the first aspect of the present invention, the thickness H2 of the positive electrode current collector satisfies 8 μm ≤ H2 ≤ 12 μm.

[0015] According to any one of the above embodiments of the first aspect of the present invention, the surface density of the positive electrode active material layer is 80 mg / 1540.25 mm 2 ~180mg / 1540.25mm 2 That is the case.

[0016] According to any one of the above embodiments of the first aspect of the present invention, the compressed density of the positive electrode active material layer is 3.3 g / cm³. 3 ~3.7g / cm 3 That is the case.

[0017] According to any one of the above embodiments of the first aspect of the present invention, the compressed density of the positive electrode active material layer is 3.5 g / cm³. 3 ~3.65g / cm 3 That is the case.

[0018] According to any one of the above embodiments of the first aspect of the present invention, the positive electrode active material layer further comprises a binder, the binder having a characteristic peak in the corresponding Fourier transform infrared spectrum: 1684 cm⁻¹ -1 It holds.

[0019] According to any one of the above embodiments of the first aspect of the present invention, the binder comprises a polyvinylidene fluoride copolymer.

[0020] According to any one of the above embodiments of the first aspect of the present invention, the binder has the structural formula of formula (A), (VDF)m(TFE)n(HFP)r(PVP)x (A) In equation (A), VDF is Poly TFE is a structural unit of vinylidene fluoride. Poly HFP is a structural unit of tetrafluoroethylene. Poly PVP is the structural unit of hexafluoropropylene, and the structural unit of polyvinylpyrrolidone, where m, n, r, and x satisfy 0.35 ≤ m ≤ 1, 0 ≤ n ≤ 0.4, 0 ≤ r ≤ 0.2, 0 ≤ x ≤ 0.2, and m + n + r + x = 1.

[0021] In a second aspect, an embodiment of the present invention provides an electronic apparatus including an electrochemical apparatus described in any embodiment of the first aspect of the present invention.

[0022] The above description is merely an outline of the technical proposal of the present invention. In order to more clearly understand the technical solution of the present invention and to implement it in accordance with the specification, and in order to more clearly understand the above and other objectives, features, and advantages of the present invention, specific embodiments of the present invention will be described below. [Brief explanation of the drawing]

[0023] Various other advantages and benefits will become apparent to those skilled in the art by reading the detailed description of the embodiments below. The drawings are for illustrative purposes only and should not be considered to limit the invention. Throughout the drawings, identical components are denoted by the same reference numerals. In the drawings, [Figure 1] Figure 1 is a schematic diagram of the structure of an electrochemical apparatus provided in an embodiment of the present invention. [Figure 2] Figure 2 is a schematic diagram of the disassembled structure of the electrochemical apparatus shown in Figure 1. [Figure 3] Figure 3 is an SEM view of the positive electrode piece in the electrochemical apparatus provided in Example 1 of the present invention. [Figure 4] Figure 4 is an SEM view of the positive electrode piece in the electrochemical apparatus provided by Comparative Example 1 of the present invention. [Explanation of symbols]

[0024] 5-Electrochemical apparatus, 51-Case, 52-Electrode assembly, 53-Top cover assembly. [Modes for carrying out the invention]

[0025] The following describes in detail embodiments of the technical solutions of the present invention with reference to the drawings. The following embodiments are used solely to more clearly illustrate the technical concepts of the present invention and are therefore illustrative only, and do not limit the scope of protection of the present invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention pertains. The terms used herein are for illustrative purposes only and are not intended to limit the present invention. The terms “including” and “having,” and any variations thereof, in the description of the present invention, the claims, and the drawings above, are intended to include non-exclusive inclusion.

[0027] In the description of embodiments of the present invention, terms such as “first,” “second,” etc., are used solely to distinguish different subjects and should not be understood as indicating or implying relative importance, or implying the number, specific order, or primary-to-secondary relationship of the technical features shown. In the description of embodiments of the present invention, “multiple” means two or more unless specifically limited.

[0028] In this specification, “Examples” means that certain features, structures, or properties described in relation to the Examples may be included in at least one example of the Invention. The phrase “Examples” appearing in various parts of the Specification does not necessarily refer to the same Example, nor does it refer to separate or alternative Examples that are mutually exclusive with each other. Those skilled in the art will understand, both explicitly and implicitly, that the Examples described herein are combined with other Examples.

[0029] In describing embodiments of the present invention, the term "and / or" simply describes the relationship between related objects, indicating that three relationships are possible. For example, "A and / or B" can represent three situations: A existing alone, A and B existing simultaneously, and B existing alone. In this specification, the letter " / " usually indicates an "or" relationship between the preceding and following related objects.

[0030] In the description of embodiments of the present invention, unless otherwise specified, "greater than or equal to" and "less than or equal to" include a standard quantity, and "multiple types" and "multiple" in "one or more types" and "one or more" mean two or more types (pieces).

[0031] The grouping of alternative elements or embodiments disclosed herein should not be construed as limiting. Each group member may be adopted and claimed independently, or adopted and claimed in any combination with other members of the group or other elements found herein. One or more members of a group may be included in or removed from a group for convenience and / or patentability reasons. In any event of such inclusion or removal, this specification shall be deemed to include the modified group and thus satisfy the written description of all Markush groups used in the claims.

[0032] It will be apparent to those skilled in the art that various modifications and changes can be made to the present invention without departing from the scope of protection. Therefore, the present invention is intended to cover modifications and changes to the present invention that fall within the corresponding claims (the scope of protection claimed) and their equivalent scope. Furthermore, embodiments relating to the examples of the present invention can be combined with each other, insofar as they do not contradict each other.

[0033] Before describing the scope of protection according to embodiments of the present invention, we will first specifically describe the problems that exist in the related technologies of the present invention in order to make the embodiments easier to understand.

[0034] Electrochemical devices, such as lithium-ion rechargeable batteries, are widely used in consumer electronics, electric transportation vehicles, and other devices due to their high energy density, good cycle characteristics, and rechargeability. With the rapid development of rechargeable battery technology, the development of rapid charge and discharge technology has been promoted, and lithium-ion rechargeable batteries that support rapid charge and discharge have become one of the most popular electrochemical devices on the market.

[0035] In related technologies, lithium-ion secondary batteries generate a large amount of heat during high-rate charging and discharging, causing the battery temperature to rise and making polarization more likely. To reduce polarization in lithium-ion secondary batteries, the thickness of the electrode pieces can be reduced to shorten the ion transport path. However, with reduced electrode thickness, when aggregated slurry is applied to the surface, protrusions are formed, and the active material within these protrusions is easily crushed during the roll-pressing process. This causes the temperature of the lithium-ion secondary battery to rise during high-rate charging and discharging processes, degrading the cycle characteristics of the lithium-ion secondary battery.

[0036] In view of this, embodiments of the present invention provide an electrochemical apparatus and an electronic apparatus, the electrochemical apparatus having good high-temperature cycling characteristics.

[0037] In the present invention, the electrochemical apparatus includes any apparatus in which an electrochemical reaction occurs, and specific examples include all types of primary batteries, secondary batteries, fuel cells, solar cells, and capacitors. Exemplarily, the electrochemical apparatus is a lithium secondary battery, which may include lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, and lithium-ion polymer secondary batteries.

[0038] Electrochemical apparatus Embodiments of the present invention provide an electrochemical apparatus including a positive electrode piece, the positive electrode piece comprising a positive electrode current collector and a positive electrode active material layer provided on one or both sides of the positive electrode current collector, the positive electrode active material layer comprising a positive electrode active material. Here, the D of the positive electrode active material relative to the thickness H1 of the positive electrode active material layer on one side is... v The ratio of 99 is 0.5 ≤ D v The condition 99 / H1 ≤ 0.9 is satisfied. Scanning electron microscopy reveals aggregated regions on the surface of the positive electrode active material layer with a bright spot diameter D0 of 20 μm or greater than 20 μm, and the number density of aggregated regions per unit area on the surface of the positive electrode active material layer is 5 particles / cm³. 2 It is either 5 pieces / cm 2 Smaller.

[0039] In this invention, the protrusions on the surface of the pole piece form aggregated regions with a diameter D0 of 20 μm or greater after roll pressing. By reducing the number of protrusions on the surface of the pole piece, the quantity of aggregated regions per unit area is reduced, thereby improving the uniformity of the surface of the pole piece and improving the problem of reduced cycle characteristics due to the crushing of protrusions during the roll pressing process of the pole piece. A smaller aggregated region indicates fewer protrusions on the surface of the pole piece before roll pressing, and therefore, a smaller aggregated region on the pole piece after roll pressing is desirable.

[0040] D v 99 indicates that in a volume-based particle size distribution, volume accumulation is observed from the small particle size side. 99 This represents the particle size at which a percentage is obtained.

[0041] Diameter D0 refers to the maximum measurable distance in a region when it does not form a clearly defined shape.

[0042] The aggregated region refers to an area formed in the positive electrode slurry where aggregated particles, after being coated onto the surface of the positive electrode current collector, protrude from the surface of the formed positive electrode active material layer and are then formed after roll pressing.

[0043] In the electrochemical apparatus provided in the embodiment of the present invention, the D of the positive electrode active material relative to the thickness H1 of the positive electrode active material layer on one side. v The ratio of 99 is 0.5 ≤ D v The condition 99 / H1 ≤ 0.9 is satisfied, and in this way the positive electrode piece can be thinned, reducing the ion transport pathway, further decreasing ionic polarization, and further reducing the resistance of the electrochemical apparatus. In addition, aggregated regions on the surface of the positive electrode active material layer observed by scanning electron microscopy, where the diameter D0 of the bright spots is 20 μm or greater than 20 μm, indicate that the number density per unit area on the surface of the positive electrode active material layer is 5 particles / cm². 2 It is either 5 pieces / cm 2 Being smaller reduces the number of positive electrode active materials crushed during the roll-pressing process of the positive electrode active material layer, which helps improve the high-temperature cycle characteristics of the electrochemical apparatus.

[0044] In the embodiments of the present invention, the D of the positive electrode active material v By rationally combining 99 and the thickness H1 of the positive electrode active material layer on one side, it is possible to make the positive electrode piece thinner and reduce defects that occur during the processing process, as well as reduce the occurrence of fracture of the positive electrode active material.

[0045] In some embodiments of the present invention, the D of the positive electrode active material v 99 is 15μm≦D v The thickness of the positive electrode active material layer on one side satisfies the condition 99 ≤ 30 μm, and the thickness H1 of the positive electrode active material layer on one side satisfies the condition 10 μm ≤ H1 ≤ 35 μm.

[0046] In the above embodiment, the D of the positive electrode active material v By rationally combining 99 and the thickness H1 of the positive electrode active material layer on one side, defects such as scratches during processing of the positive electrode active material layer can be reduced, and the number of positive electrode active materials crushed during the roll press process can be reduced, which helps to improve the high-temperature cycle characteristics of the electrochemical apparatus.

[0047] In some examples, the D of the positive electrode active material v 99 may be, but is not limited to, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, or 30 μm. Furthermore, the thickness H1 of the positive electrode active material layer on one side may be 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, or 35 μm, but is not limited to these.

[0048] Furthermore, by adjusting the other volume particle size distributions of the positive electrode active material to an appropriate range, the occurrence of fragmentation of the positive electrode active material can be reduced, thereby reducing electrochemistry and improving the energy density of the electrochemical apparatus.

[0049] In some embodiments of the present invention, the D of the positive electrode active material v D of the positive electrode active material relative to 10 v The ratio of 50 is 1.0 ≤ D v 50 / D v The condition satisfies 10 ≤ 2.5.

[0050] D v 50 represents the particle size at which the volume accumulation from the smallest particle size side reaches 50% in a volume-based particle size distribution.

[0051] D v 10 represents the particle size at which the volume accumulation from the smallest particle size side reaches 10% in a volume-based particle size distribution.

[0052] In the above embodiment, the D of the positive electrode active material v D for 10 v By satisfying the above relationship with a ratio of 50, the fragmentation of the positive electrode active material can be reduced, the resistance of the positive electrode pieces and the expansion rate of the electrochemical apparatus can be reduced, and the high-temperature cycle characteristics of the electrochemical apparatus can be further improved.

[0053] In some embodiments of the present invention, the D of the positive electrode active material v D of the positive electrode active material relative to 10 v The ratio of 50 is 1.0 ≤ D v 50 / D v The condition satisfies 10 ≤ 2.0.

[0054] In the above embodiment, the D of the positive electrode active material v D for 10 v By satisfying the above relationship with a ratio of 50, the fragmentation of the positive electrode active material can be further reduced, and the high-temperature cycle characteristics of the electrochemical apparatus can be improved.

[0055] In some cases, the D of the positive electrode active material v Diameter D of the positive electrode active material relative to 10 vThe ratio of 50 may be, but is not limited to, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, or 2.5.

[0056] In embodiments of the present invention, the thickness of the positive electrode current collector also affects the compression density and processing of the positive electrode active material layer. In some embodiments of the present invention, the thickness H2 of the positive electrode current collector is I) 0.3 ≤ H2 / D v The condition that 99 ≤ 1, II) The conditions that 1 ≤ H1 / H2 ≤ 4 are met, III) The conditions must be met that 7 μm ≤ H2 ≤ 20 μm, It satisfies at least one of the following conditions.

[0057] In the above embodiment, the thickness of the positive electrode current collector is H2, H2 / D v By ensuring that 99 and H1 / H2 are within appropriate ranges, the compressive density of the positive electrode active material layer can be further improved, reducing the occurrence of fracture of the positive electrode piece due to roll pressing and overpressure damage of the positive electrode active material, thereby reducing the resistance of the positive electrode piece and the expansion rate of the electrochemical apparatus, and improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0058] In some embodiments of the present invention, the thickness H2 of the positive electrode current collector may be in the range of 8 μm to 12 μm. When the thickness H2 of the positive electrode current collector is within this range, the compressive density of the positive electrode active material can be further improved, the resistance of the positive electrode piece can be reduced, and thereby the high-temperature cycle characteristics of the electrochemical apparatus can be improved.

[0059] In some examples, the D of the positive electrode active material vThe ratio of the thickness H2 of the positive electrode current collector to 99 may be, but is not limited to, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, or 1. The ratio of the thickness H1 of the positive electrode active material layer to the thickness H2 of the positive electrode current collector may be, but is not limited to, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4.0. The thickness H2 of the positive electrode current collector may be, but is not limited to, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, or 20 μm.

[0060] The embodiments of the present invention do not particularly limit the material of the positive electrode current collector. The positive electrode current collector may be a metal foil or a porous metal plate, for example, a foil or porous plate of a metal or alloy thereof, such as aluminum, copper, nickel, titanium, or iron. In some embodiments of the present invention, the positive electrode current collector is aluminum foil.

[0061] In some embodiments of the present invention, the compressed density of the positive electrode active material layer is 3.3 g / cm³. 3 ~3.7g / cm 3 That is the case.

[0062] In the above embodiment, by setting the compressed density of the positive electrode active material layer within the above range, it is possible to improve the high-temperature cycle characteristics of the electrochemical apparatus.

[0063] In another embodiment of the present invention, the compressed density of the positive electrode active material layer is 3.5 g / cm³. 3 ~3.65g / cm 3 That is the case.

[0064] In some examples, the compressed density of the positive electrode active material layer is 3.3 g / cm³. 3 3.31 g / cm³ 3 3.32 g / cm³ 3 3.33 g / cm³ 3, 3.34 g / cm 3 , 3.35 g / cm 3 , 3.36 g / cm 3 , 3.36 g / cm 3 , 3.38 g / cm 3 , 3.39 g / cm 3 , 3.40 g / cm 3 , 3.41 g / cm 3 , 3.42 g / cm 3 , 3.43 g / cm 3 , 3.44 g / cm 3 , 3.45 g / cm 3 , 3.46 g / cm 3 , 3.47 g / cm 3 , 3.48 g / cm 3 , 3.49 g / cm 3 , 3.50 g / cm 3 , 3.51 g / cm 3 , 3.52 g / cm 3 , 3.53 g / cm 3 , 3.54 g / cm 3 , 3.55 g / cm 3 , 3.56 g / cm 3 , 3.57 g / cm 3 , 3.58 g / cm 3 , 3.59 g / cm 3 , or 3.6 g / cm 3 and may be, but are not limited to, these values.

[0065] The positive electrode active material can directly affect the energy density and cycle characteristics of the electrochemical device. Therefore, in some embodiments of the present invention, the positive electrode active material includes a nickel cobalt manganese ternary system material. The nickel cobalt manganese ternary system material can contribute to the improvement of the energy density and cycle characteristics of the electrochemical device.

[0066] The nickel cobalt manganese ternary system material may be a ternary system structural material such as NCM811, NCM622, NCM613, NCM523, NCM111, etc.

[0067] In NCM811, N represents nickel, C represents cobalt, and M represents manganese. 811 indicates the ratio of moles of nickel, cobalt, and manganese in a ternary material. Specifically, the ratio of moles of nickel, cobalt, and manganese is 8:1:1, and in this case, the moles of nickel in the nickel-cobalt-manganese ternary material account for 80% of the total moles of nickel, cobalt, and manganese. In NCM523, the ratio of moles of nickel, cobalt, and manganese is 5:2:3, and the moles of nickel in the nickel-cobalt-manganese ternary material account for 50% of the total moles of nickel, cobalt, and manganese.

[0068] In some embodiments of the present invention, the proportion of the number of moles of nickel in the nickel-cobalt-manganese ternary material to the total number of moles of nickel, cobalt, and manganese is 60% or greater than 60%.

[0069] In other embodiments of the present invention, the positive electrode active material may further include at least one of olivine structural materials such as lithium iron manganese phosphate, lithium iron phosphate, and lithium manganese phosphate, and lithium cobalt oxide materials, lithium manganese oxide materials, and other metal oxides that can release lithium.

[0070] The positive electrode active material layer is formed by coating the positive electrode slurry onto the surface of the positive electrode current collector, and the surface density of the positive electrode active material layer has some influence on the energy density and cycle characteristics of the electrochemical apparatus.

[0071] In this invention, surface density refers to the mass of the positive electrode active material per unit area.

[0072] In some embodiments of the present invention, the surface density of the positive electrode active material layer is 80 mg / 1540.25 mm 2 ~180mg / 1540.25mm 2 That is the case.

[0073] In the above embodiments, setting the surface density of the positive electrode active material layer within the appropriate range contributes to uniformly dispersing each component in the positive electrode active material layer on the surface of the positive electrode current collector, reducing the formation of gels, and is advantageous for improving the high-temperature cycle characteristics of the electrochemical device.

[0074] In some examples, the surface density of the positive electrode active material layer is 80 mg / 1540.25 mm 2 ~90 mg / 1540.25 mm 2 91 mg / 1540.25 mm 2 ~100 mg / 1540.25 mm 2 101 mg / 1540.25 mm 2 ~110 mg / 1540.25 mm 2 111 mg / 1540.25 mm 2 ~120 mg / 1540.25 mm 2 121 mg / 1540.25 mm 2 ~130 mg / 1540.25 mm 2 131 mg / 1540.25 mm 2 ~140 mg / 1540.25 mm 2 141 mg / 1540.25 mm 2 ~150 mg / 1540.25 mm 2 151 mg / 1540.25 mm 2 ~160 mg / 1540.25 mm 2 161 mg / 1540.25 mm 2 ~170 mg / 1540.25 mm 2 or 171 mg / 1540.25 mm 2 ~180 mg / 1540.25 mm 2 although it is not limited thereto.

[0075] In some embodiments of the present invention, the positive electrode active material layer further includes a binder, and the binder has a characteristic peak in the Fourier transform infrared spectrum: 1684 cm -1 having.

[0076] In the above embodiment, the binder can improve the stability of the slurry viscosity, and in particular, it can further reduce gel formation in the positive electrode active material layer of the high-nickel positive electrode active material, thereby contributing to the formation of a uniform and thin positive electrode active material layer.

[0077] In some embodiments of the present invention, the binder comprises a polyvinylidene fluoride copolymer.

[0078] In some embodiments of the present invention, the binder has the structural formula of formula (A), (VDF)m(TFE)n(HFP)r(PVP)x (A) In equation (A), VDF is Poly TFE is a structural unit of vinylidene fluoride. Poly HFP is a structural unit of tetrafluoroethylene. Poly PVP is the structural unit of hexafluoropropylene, and the structural unit of polyvinylpyrrolidone, where m, n, r, and x satisfy 0.35 ≤ m ≤ 1, 0 ≤ n ≤ 0.4, 0 ≤ r ≤ 0.2, 0 ≤ x ≤ 0.2, and m + n + r + x = 1.

[0079] In the above embodiment, the binder has the structural formula of formula (A) and can contribute to the dispersion of slurry components such as conductive agents and positive electrode active materials, suppressing gel formation, further reducing the occurrence of abnormal aggregation between components, reducing the number of protrusions on the surface of the electrode pieces, and also reducing the number of aggregated regions formed by the roll press. In particular, in high-nickel positive electrode active material systems, gel formation in the slurry can be further suppressed, thereby further improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0080] In embodiments of the present invention, having formula (A) binder It can be prepared by the following preparation method.

[0081] A 25L reaction vessel is evacuated, nitrogen gas is added to replace the oxygen gas, and then 18 kg of deionized water, 200 g of a 5% sodium perfluorooctanoate solution, and 80 g of paraffin (melting point 60°C) are added to the reaction vessel. The stirring speed is adjusted to 130 rpm / min, and the temperature of the reaction vessel is raised to 85°C.

[0082] vinylidene fluoride monomer, tetrafluoroethylene monomer, hexafluoropropylene monomer , Nylpyrrolidone monomers are added in proportion to a reaction vessel under a pressure of 5.0 MPa, and then 1.15 g of dioctyl peroxydicarbonate, which is the initiator, is added to carry out the polymerization reaction.

[0083] Next, vinylidene fluoride monomers are replenished to maintain the pressure in the vessel at 5.0 MPa, and 0.01 g of initiator is replenished at 10 min batch intervals. Chain transfer agent HFC-4310 is then replenished in four batches with conversion rates of 20%, 40%, 60%, and 80%, with 5 g added each time, to add a total of 5 kg of vinylidene fluoride monomers to the reaction.

[0084] The reaction is carried out until the internal pressure of the reaction vessel drops to 4.0 MPa, and after the reaction time reaches 140 min, the vessel is evacuated and the material is collected. After centrifugation, washing, and drying, the material has formula (A). binder To obtain.

[0085] In some embodiments of the present invention, the binder is (I) The weight-average molecular weight Mw of the binder satisfies 900,000 ≤ Mw ≤ 1,200,000, (II) The weight-average molecular weight Mw and number-average molecular weight Mn of the binder satisfy 1.8 ≤ Mw / Mn ≤ 2.4, It satisfies at least one of the following characteristics.

[0086] In the above embodiment, the binder satisfies at least one of (I) and (II), thereby contributing to the dispersion of slurry components such as conductive agents and positive electrode active materials, suppressing gel formation, and further reducing the occurrence of abnormal aggregation between components. In particular, in high-nickel positive electrode active material systems, gel formation in the slurry can be further suppressed, thereby further improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0087] In some embodiments of the present invention, the weight percentage X of the binder relative to the weight of the positive electrode active material layer satisfies 0.5% ≤ X ≤ 3%.

[0088] In the above embodiment, when the weight percentage X of the binder is within the above appropriate range, the bonding force between the positive electrode active material layer and the positive electrode current collector increases, and the stability of the positive electrode active material layer is improved.

[0089] In another embodiment of the present invention, the weight percentage X of the binder satisfies 0.7% ≤ X ≤ 1.5%.

[0090] In some examples, the weight percentage X of the binder may be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, or 3%.

[0091] In some embodiments of the present invention, the positive electrode active material layer further comprises a conductive agent which can contribute to improving the electron conductivity of the positive electrode piece. Exemplarily, the conductive agent is at least one selected from carbon-based materials, metallic materials, conductive polymers, and mixtures thereof. Exemplarily, carbon-based materials are selected from carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanotubes, and any combination thereof. Metallic materials are selected from metal powders, metal fibers, copper, nickel, aluminum, and silver. Conductive polymers are polyphenylene derivatives.

[0092] In some embodiments of the present invention, the binding force F of the positive electrode active material layer satisfies 10 N / m ≤ F ≤ 40 N / m.

[0093] In the above embodiment, the binder can contribute to the bonding force F of the positive electrode active material layer satisfying the above relationship, which is advantageous in satisfying the adhesive force requirements when the positive electrode piece is processed, and at the same time slows down the rate of increase in the expansion rate of the positive electrode piece during the cycle process, allowing the electrochemical apparatus to have better high-temperature cycle characteristics.

[0094] The bonding force in these embodiments described above can be measured by the following measurement method. (1) Remove the dried pole and cut out a sample with a width of 30 mm and a length of 100 mm to 160 mm using a blade. (2) The special double-sided tape is attached to the steel plate, and the double-sided tape is 20 mm wide and 90 mm to 150 mm long. (3) Attach the sample to the double-sided tape, and stick the measurement surface to the double-sided tape with the measurement surface facing downwards. (4) A paper tape whose width is the same as the width of the sample and whose length is 80 mm longer than the length of the sample is inserted below the sample and secured with crepe masking tape to obtain the measurement sample. (5) Turn on the power to the tensile machine (brand: Sansi, model number: Instron 3365), illuminate the indicator lights, and adjust the limit blocks to the appropriate positions. (6) Secure the sample to the measuring stand, fold the paper tape upwards, secure it with a jig, pull the paper tape at a speed of 10 mm / min, the measurement range is 0 mm to 40 mm, pull the paper tape from 90° to separate the positive electrode active material layer attached to the surface of the double-sided tape from the positive electrode current collector, and continue until the measurement is complete. (7) Follow the software's instructions to save the test data, i.e., obtain the bonding force data between the positive electrode active material layer and the positive electrode current collector. After the measurement is complete, remove the sample and close the device.

[0095] The positive electrode piece in this invention can be prepared according to common methods in the art. For example, the active material, conductive material and binder The material is dispersed in N-methylpyrrolidone (NMP) and mixed to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto a positive electrode current collector, and after drying, cold pressing, cutting, slitting, and re-drying, a positive electrode piece is obtained.

[0096] In some embodiments of the present invention, the electrochemical apparatus further comprises a negative electrode piece, a separator, and an electrolyte.

[0097] The negative electrode piece includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. As can be understood, the negative electrode piece may have the negative electrode active material layer provided on one surface of the negative electrode current collector, or on both surfaces of the negative electrode current collector, and the embodiments of the present invention are not particularly limited thereto.

[0098] The negative electrode current collector may be a metal foil or a porous metal plate, for example, a foil or porous plate of a metal such as copper, nickel, titanium, or iron, or an alloy thereof. In some embodiments of the present invention, the negative electrode current collector is a copper foil.

[0099] In the present invention, the type of negative electrode active material in the negative electrode active material layer is not particularly limited and can be selected as needed. Examples of other negative electrode active materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, and spinel-structured Li4Ti5O 12 This includes, but is not limited to, at least one selected from Li-Al alloys.

[0100] In some embodiments of the present invention, the negative electrode active material layer further comprises a binder, which may be at least one selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0101] In some embodiments of the present invention, the negative electrode active material layer further comprises a conductive agent, which may be at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0102] In some embodiments of the present invention, the negative electrode active material layer may further contain other auxiliary agents, such as thickeners (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0103] However, the present invention is not limited to the materials described above, and the negative electrode piece of the present invention may use other known materials used as negative electrode active material, conductive agent, binder, and thickener.

[0104] The negative electrode pieces in this invention can be prepared according to common methods in the industry. For example, a negative electrode active material, a conductive agent, a binder, and a thickener are dispersed in a solvent, the solvent may be N-methylpyrrolidone (NMP) or deionized water, a uniform negative electrode slurry is formed, the negative electrode slurry is coated onto a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode active material layer and thus a negative electrode piece.

[0105] The separator is placed between the positive electrode and the negative electrode and primarily serves to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through. The present invention does not particularly limit the type of separator, and any known porous structure separator having good chemical and mechanical stability can be selected.

[0106] In some embodiments of the present invention, the material of the separator may be one or more selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited thereto. Optionally, the material of the separator may include polyethylene and / or polypropylene. The separator may be a single-layer film or a multilayer composite film. If the separator is a multilayer composite film, the materials of each layer may be the same or different. In other embodiments of the present invention, the separator may be further provided with a ceramic coating layer or a metal oxide coating layer.

[0107] In electrochemical apparatuses, the electrolyte acts as a carrier for ion transport, playing a role in conducting ions between the positive and negative electrodes, thus ensuring advantages such as good cycle characteristics of the electrochemical apparatus.

[0108] In some embodiments of the present invention, the electrolyte comprises an organic solvent, a lithium salt, and a selectable additive, the type of organic solvent, lithium salt, and additive is not specifically limited and can be selected as needed.

[0109] In some embodiments of the present invention, the lithium salt comprises at least one selected from lithium hexafluoride phosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalate)borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalato)phosphate (LiDFOP), and lithium tetrafluoro(oxalato)phosphate (LiTFOP). The above lithium salts may be used individually or in combination of two or more.

[0110] In some examples of the present invention, the organic solvent comprises at least one selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), 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), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE). The above organic solvents may be used individually or in combination of two or more.

[0111] In some embodiments of the present invention, the additives may include a negative electrode film-forming additive and a positive electrode film-forming additive, and may further include additives that can improve specific performance of the battery, such as an additive that improves the overcharge characteristics of the battery and an additive that improves the high-temperature or low-temperature characteristics of the battery.

[0112] In some examples, the additive includes at least one selected from fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinylethylene carbonate (VEC), ethylene sulfate (DTD), 1,3-propylene sulfate, ethylene sulfite (ES), 1,3-propanesultone (PS), 1-propene-1,3-sultone (PST), sulfonate cyclic quaternary ammonium salts, succinic anhydride, succinonitrile (SN), adiponitrile (AND), tris(trimethylsilyl) phosphate (TMSP), and tris(trimethylsilyl) borate (TMSB).

[0113] The electrolyte can be prepared according to common methods in the industry. For example, an electrolyte can be obtained by uniformly mixing an organic solvent, a lithium salt, and any additives. The order in which the materials are added is not particularly limited; for example, the lithium salt and any additive can be added to the organic solvent and uniformly mixed to obtain the electrolyte. Alternatively, the lithium salt can be added to the organic solvent first, and then the additive can be added to the organic solvent and uniformly mixed to obtain the electrolyte.

[0114] In some embodiments of the present invention, the positive electrode piece, the negative electrode piece, and the separator can form an electrode assembly by a winding process or a lamination process.

[0115] The electrochemical apparatus of the embodiment of the present invention further includes an outer casing for sealing the electrode assembly and electrolyte. In some embodiments of the present invention, the outer casing may be a rigid case, such as a rigid plastic case, an aluminum case, a steel case, etc., or a soft pack, such as a pouch-type soft pack. The material of the soft pack may be plastic, such as at least one selected from polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0116] The embodiments of the present invention are not particularly limited in terms of the shape of the electrochemical apparatus, and may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows an example of a rectangular electrochemical apparatus.

[0117] In some embodiments of the present invention, referring to Figure 2, the exterior may include a case 51 and a top cover assembly 53. Here, the case 51 includes a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a surrounding housing cavity. The case 51 has an opening communicating with the housing cavity, and the top cover assembly 53 is provided to cover the opening to close the housing cavity. The positive electrode piece, negative electrode piece and separator can be formed by a winding process or a lamination process to form an electrode assembly 52. ​​The electrode assembly 52 is sealed in the housing cavity. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the electrochemical apparatus 5 may be one or more, and those skilled in the art can select them according to their specific practical needs.

[0118] After the electrolyte permeates the electrode assembly, the electrochemical apparatus is obtained after processes such as vacuum sealing, standing, formation, and exhaust molding.

[0119] electronic equipment A second aspect of the present invention provides an electronic device, which includes an electrochemical device provided in the first aspect of the present invention. The electrochemical device provided by the present invention has good high-temperature cycling characteristics and high energy density, and therefore the electronic device provided by the present invention has good high-temperature cycling characteristics.

[0120] Embodiments of the present invention are not particularly limited to electronic devices and can be applied to any electronic device known in the prior art. In some embodiments of the present invention, electronic devices include, but are not limited to, notebook computers, pen-input computers, mobile computers, e-book players, mobile phones, portable facsimile machines, portable copiers, portable printers, stereo headsets, video recorders, LCD televisions, portable cleaners, portable CD players, MiniDiscs, transceivers, electronic notebooks, calculators, memory cards, portable tape recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric assist bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household storage batteries, and lithium-ion capacitors.

[0121] The following examples illustrate the contents disclosed in the present invention in more detail, and 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 present invention. Unless otherwise specified, all parts, percentages, and ratios described in the following examples are by weight, all reagents used in the examples are commercially available or synthesized according to conventional methods and can be used directly without further processing, and the apparatus used in the examples is commercially available.

[0122] In the following embodiments, for the sake of explanation, we will use the case where the electrochemical apparatus is a lithium-ion secondary battery as an example and describe the electrochemical apparatus and its manufacturing method in detail.

[0123] Example 1-1 Preparation of positive electrode pieces Conductive carbon black and a binder were mixed in a fixed ratio, and NMP was added and stirred to produce a conductive adhesive liquid (solid content 7%). Lithium nickel-cobalt manganese oxide (NCM), the positive electrode active material, was added to a conductive adhesive liquid, and the system was continuously stirred under the action of a vacuum stirrer until homogeneous, yielding a positive electrode slurry with a solid content of approximately 75%. Here, the mass ratio of NCM, conductive carbon tube, and binder was 97:1:2. This positive electrode slurry was applied to a 10 μm thick aluminum foil, and after drying, cold pressing, cutting, and tab welding, a positive electrode piece was obtained.

[0124] Preparation of negative electrode piece Artificial graphite, styrene-butadiene rubber, and sodium carboxymethylcellulose were mixed with deionized water and an auxiliary agent in a mass ratio of 96:2:2, and uniformly stirred to obtain a negative electrode slurry. This negative electrode slurry was applied to a 12 μm copper foil, and after drying, cold pressing, cutting, and tab welding, a negative electrode piece was obtained.

[0125] Preparation of electrolyte In a dry argon gas atmosphere, EC, PC, and DEC (weight ratio 1:1:1) were mixed, LiPF6 was added, and the mixture was homogenized to form the base electrolyte. The concentration of LiPF6 at this stage was 1.15 mol / L.

[0126] Preparation of separators A porous polyethylene (PE) polymer film was used as the separator.

[0127] Preparation of lithium-ion secondary batteries A positive electrode piece, a separator, and a negative electrode piece were wound in sequence to form an electrode assembly. The electrode assembly was then placed on an outer foil, and an electrolyte solution was injected into the outer foil to permeate the electrode assembly. A lithium-ion secondary battery was then obtained through processes such as sealing, formation, and shaping.

[0128] Examples 1-2 to 1-6 The preparation method was similar to that of Example 1-1, except for some differences in the parameters of the positive electrode piece. See Table 1 for details.

[0129] Comparative Examples 1-1 to 1-4 The preparation method was similar to that of Example 1-1, except for some differences in the parameters of the positive electrode piece. See Table 1 for details.

[0130] Examples 2-1 to 2-7 The preparation method was similar to that of Example 1-1, except for some differences in the parameters of the positive electrode piece. See Table 2 for details.

[0131] Examples 3-1 to 3-9 The preparation method was similar to that of Example 1-1, except for some differences in the parameters of the positive electrode piece. See Table 3 for details.

[0132] Examples 4-1 to 4-8 The preparation method was similar to that of Example 1-1, except for some differences in the parameters of the positive electrode piece. See Table 4 for details.

[0133] Examples 5-1 to 5-5 The preparation method was similar to that of Example 1-1, except for some differences in the parameters of the positive electrode piece. See Table 5 for details.

[0134] Measuring part 1) Measurement of surface density of the positive electrode active material layer A positive electrode piece coated with a positive electrode active material layer is punched out into 10 small circular pieces, with a surface area of ​​1540.25 mm² for each piece. 2 Next, the positive electrode pieces after punching are weighed, the average value is taken, and the mass m1 is obtained. Then, the positive electrode current collector is taken and similarly punched into 10 small circular pieces, weighed on a balance and the average value is taken, and the mass m2 is obtained. Surface density = (m1-m2) / 1540.25 mm 2 That was the case.

[0135] 2) Measurement of the compression density of the positive electrode active material layer The lithium-ion secondary battery to be measured after discharge was disassembled, the positive electrode piece was removed, the positive electrode piece was immersed in DMO (dimethyl oxalate) for 30 minutes to remove the electrolyte and by-products from the surface of the positive electrode piece, then dried in a fume hood for 4 hours, the dried positive electrode piece was removed, the thickness H1 of the positive electrode active material layer on the positive electrode piece was measured with a micrometer with an accuracy of 0.1 μm, then the positive electrode active material layer per unit area was scraped off from the positive electrode piece with a doctor blade, the mass m3 of the positive electrode active material layer per unit area on the positive electrode piece was weighed with a balance, and then the compression density of the positive electrode active material layer was calculated based on = m3 / H1.

[0136] 3) D of the positive electrode active material v 50, D v 10, D v 99 measurements (1) Starting up the instrument: First, the sample injection system of the laser diffraction / scattering particle size analyzer (Master Sizer 3000) was started, then the optical path system and computer were started, and the instrument was preheated for 30 minutes. (2) Cleaning of the sample injection system: Fill the sample injector with water, adjust the rotation speed to maximum, wash for 5 seconds, then adjust the rotation speed to 0. Repeat the washing process three times to ensure that the sample injector is clean. (3) Enter the "Manual Measurement" interface and sequentially set the material name, refractive index, material type, measurement time, and number of measurements. (4) Click "start" to measure light collimation and background light. (5) Disperse the positive electrode active material in an aqueous solution (10 mL) to prepare the sample. Add the sample to the sample pool. The degree of light shielding will increase with the amount of sample added. When the degree of light shielding increases to 8% to 12%, stop the sample injection and wait until the degree of light shielding stabilizes (generally does not fluctuate for 30 seconds). Then click "start" to begin the particle size measurement. After the measurement is complete, D v 50, D v 10, D v I got a score of 99. (6) Measure three parallel samples, D v 50, D v 10, D v I calculated the average of 99.

[0137] 4) Measurement of the thickness H2 of the positive electrode current collector The thickness H2 of the positive electrode current collector was measured using a micrometer with an accuracy of 0.1 μm.

[0138] 5) Measurement of the weight-average molecular weight Mw and number-average molecular weight Mn of the binder Molecular weight and molecular weight distribution were measured using GB / T 21863-2008 gel permeation chromatography, with ultrafast polymer chromatography (ACQUITY APC) and an ACQUITY differential refractive index detector. The measurement procedure was as follows: (1) Startup preheating: Install the chromatography column and pipeline, then turn on the console, measurement power supply, etc. in order, and open the measurement software Empower. (2) Parameters were set. Sample injection volume: 0 μL to 50 μL (determined according to sample concentration); pump flow rate: 0.2 mL / min; mobile phase: 30 mol / L LiBr NMP solution; seal washing solution: isopropanol; pre-column: PL gel 10 μm MiniMIX-B Guard (dimensions: 50 mm × 4.6 mm × 2); analytical phase: PL gel 10 μm MiniMIX-B (dimensions: 250 mm × 4.6 mm); standard: polystyrene set; run time: 30 min; detector: ACQUITY differential refraction (RI) detector; column oven temperature: 90°C; detector temperature: 55°C. (3) Sample Measurement: a. Preparation of Standard and Measurement Samples: Weigh 0.002g to 0.004g of each standard / measurement sample and add it to 2mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard solution, which was left in the refrigerator for >8 hours. b. Measurement of Standard Solution / Sample: Edit the sample group to be measured, select the established sample group method, and after the baseline has stabilized, click the run queue to start the measurement sample. (4) Data processing: Based on the relationship between retention time and molecular weight, a calibration curve was established using a chemical workstation, and integral quantification was performed on the sample spectrum. The chemical workstation automatically generated the molecular weight and molecular weight distribution results.

[0139] 6) Measurement of the diameter D0 and number density per unit area of ​​the aggregated region (1) After drying, the polarity was removed, and a sample measuring 5 cm in width and 5 cm in length was cut out with a blade and fixed to the microscope stand. (2) The microscope measuring device was started, the magnification was adjusted to X100, and the adjustment was made until the interface was clearly visible. (3) Measurement was started, a 1.0 cm × 1.0 cm observation area was selected as the observation area, the number of white aggregated areas in the observation area was statistically recorded, and the maximum diameter of the aggregated area was measured and recorded as D0.

[0140] Figures 3 and 4 show SEM images of the positive electrode pieces of Example 1 and Comparative Example 1, respectively.

[0141] 7) Measurement of the resistance of the positive electrode piece The resistance was measured using a resistance meter, and the specific procedure was as follows: The device's power supply was maintained at 220V, and the atmospheric pressure was increased to more than 0.7MPa. With the battery fully discharged, the positive electrode piece was removed, and the cut positive electrode piece (60 x 80 mm) was placed horizontally on the sample stand. Next, the sample stand was placed in the device's measurement cavity, and the measurement was started. Throughout the entire measurement process, the measurement pressure was set to "0".

[0142] 8) Measurement of volume retention rate The measurement environment temperature was 45°C. For the lithium-ion battery after formation, a constant current charging stage was performed with a current of 1.3C until the cutoff voltage reached 4.5V. Then, constant voltage charging was performed, and charging was stopped until the cutoff current reached 0.05C. After the battery was fully charged, it was left to stand for 5 minutes, and then discharged with a current of 1.0C until it reached 3.0V. This constituted one charge-discharge cycle. After repeating this charge-discharge cycle 500 times, the cycle capacity retention rate was calculated by dividing the discharge capacity after 500 cycles by the discharge capacity of the first cycle.

[0143] 9) Measurement of thickness expansion of lithium-ion secondary batteries: The thickness of the lithium-ion secondary battery was measured using a PPG plate thickness gauge. The thickness expansion rate of the lithium-ion secondary battery was calculated as follows: (thickness after cycle full charge - thickness at initial full charge) / thickness at initial full charge × 100%.

[0144] Table 1 shows the relevant parameters (D) of the positive electrode active material layer in Examples 1-1 to 1-4 and Comparative Examples 1-1 to 1-2. v The 99 / H1, D0, number density) and their measurement results are shown.

[0145] [Table 1]

[0146] As can be seen from Table 1, comparing the measurement results of Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4, in the electrochemical apparatus provided by the examples of the present invention, the D of the positive electrode active material relative to the thickness H1 of the positive electrode active material layer on one side v The ratio of 99 is 0.5 ≤ D v The condition 99 / H1 ≤ 0.9 is satisfied, and the diameter D0 of the bright spots on the surface of the positive electrode active material layer observed by scanning electron microscopy is 20 μm, or the number density per unit area of ​​aggregated regions greater than 20 μm is 5 particles / cm³. 2 It is either 5 pieces / cm 2 Being smaller contributes to achieving a balance between the rate characteristics and high-temperature cycling characteristics of electrochemical equipment.

[0147] Table 2 shows the relevant parameters (D) of the positive electrode active material layer in Examples 2-1 to 2-7. v 50, D v 10, D v 50 / D v 10) and the measurement results are shown.

[0148] [Table 2]

[0149] As can be seen from Table 2, when comparing the measurement results of Examples 2-1 to 2-5, 2-7 and Example 2-6, the particle size distribution of the positive electrode active material is 1.0 ≤ D v 50 / D v If 10 ≤ 2.5 is satisfied, the fragmentation of the positive electrode active material can be reduced, further reducing the resistance of the positive electrode pieces and the expansion rate of the electrochemical apparatus, thereby further improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0150] Table 3 shows the relevant parameters (D) of the positive electrode active material layer in Examples 3-1 to 3-9. v 99, H1), related parameters of the positive electrode current collector (H2, H2 / D v The following shows the results of measurements for 99, H1 / H2, and their respective values.

[0151] [Table 3]

[0152] As can be seen from Table 3, when comparing the measurement results of Examples 3-2, 3-3, 3-5 and 3-8, the particle size distribution D of the positive electrode active material v 99 and H2 / D v When 99 is within an appropriate range, it can contribute to reducing the resistance of the positive electrode piece and the expansion rate of the electrochemical apparatus, thereby improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0153] As can be seen by comparing the measurement results of Examples 3-3 and 3-4, having the thickness H1 and H1 / H2 of the positive electrode active material layer within an appropriate range contributes to reducing the resistance of the positive electrode piece and the expansion rate of the electrochemical apparatus, thereby improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0154] As can be seen by comparing the measurement results of Examples 3-2, 3-6 and 3-7, having the positive electrode current collector thickness H2 and H1 / H2 within an appropriate range contributes to reducing the resistance of the positive electrode piece and the expansion rate of the electrochemical apparatus, thereby improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0155] Table 4 lists the measurement results for different surface densities and compressed densities of the positive electrode active material in Examples 4-1 to 4-8.

[0156] [Table 4]

[0157] Note: The unit of surface density is mg / 1540.25 mm 2 And, The unit of compressed density is g / cm³. 3 That is the case.

[0158] As can be seen from Table 4, comparing the measurement results of Examples 4-1 to 4-4, the compressed density of the positive electrode active material layer is 3.3 g / cm³. 3 ~3.7g / cm 3 When within this range, the resistance of the positive electrode becomes lower, the expansion coefficient of the electrochemical apparatus decreases, and this can further improve the high-temperature cycling characteristics of the electrochemical apparatus.

[0159] As can be seen by comparing the measurement results of Examples 4-5 to 4-7, the surface density of the positive electrode active material layer is 80 mg / 1540.25 mm². 2 ~180mg / 1540.25mm 2When within this range, the resistance of the positive electrode becomes lower, the expansion coefficient of the electrochemical apparatus decreases, and this can further improve the high-temperature cycling characteristics of the electrochemical apparatus.

[0160] [Table 5]

[0161] As can be seen from Table 5, in the electrochemical apparatus provided by the embodiments of the present invention, the binder contained in the positive electrode active material layer can effectively suppress gel formation, which is advantageous for improving the high-temperature cycle characteristics of the electrochemical apparatus.

[0162] Finally, it should be noted that the above embodiments are used to illustrate the technical concepts of the present invention, but are not limiting. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the technical concepts described in the above embodiments or make equivalent substitutions to some or all of their technical features, provided that such modifications or substitutions do not cause the essence of the corresponding technical concepts to deviate from the scope of the technical concepts of the embodiments of the present invention, and that they are all included within the scope of the claims and specification of the present invention. In particular, the technical features described in each embodiment can be combined in any way, provided that there is no structural inconsistency. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical concepts included in the claims.

Claims

1. An electrochemical apparatus, The positive electrode piece includes a positive electrode current collector and a positive electrode active material layer provided on one or both sides of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, Thickness H of the positive electrode active material layer on one side １ D of the positive electrode active material ｖ The ratio of 99 is 0.5 ≤ D ｖ 99 / H １ Satisfying ≤ 0.9, A scanning electron microscope was used to determine the diameter D of the bright spot on the surface of the positive electrode active material layer. ０ The aggregated region is 20 μm or larger than 20 μm, and the number density of the aggregated region per unit area on the surface of the positive electrode active material layer is 5 particles / cm². ２ It is either 5 pieces / cm ２ Smaller, The surface density of the positive electrode active material layer is 130 mg / 1540.25 mm² to 180 mg / 1540.25 mm². Electrochemical apparatus.

2. D of the positive electrode active material ｖ 99 satisfies 15 μm ≤ D ｖ 99 ≤ 30 μm, and the thickness H of the positive electrode active material layer on one side １ satisfies 10 μm ≤ H １ ≤ 35 μm. The electrochemical device according to claim 1

3. D of the positive electrode active material ｖ D of the positive electrode active material relative to 10 ｖ The ratio of 50 is 1.0 < D ｖ 50 / D ｖ The electrochemical apparatus according to claim 1, satisfying 10 ≤ 2.

5.

4. D of the positive electrode active material ｖ D of the positive electrode active material relative to 10 ｖ The ratio of 50 is 1.0 < D ｖ 50 / D ｖ The electrochemical apparatus according to claim 1, satisfying 10 ≤ 2.

0.

5. The electrochemical apparatus according to claim 1, characterized in that the positive electrode active material includes a nickel-cobalt-manganese ternary material.

6. The electrochemical apparatus according to claim 5, wherein the number of moles of nickel in the nickel-cobalt-manganese ternary material is 60% or greater than 60% of the total number of moles of nickel, cobalt, and manganese.

7. The thickness H of the aforementioned positive electrode current collector ２ teeth, I)0.3≦H ２ / D ｖ 99≦1、 I))≦H １ / ２ ≦.、 III)7μm≦H ２ ≦20μm、 An electrochemical apparatus according to claim 1, satisfying at least one of the following:

8. The thickness H of the aforementioned positive electrode current collector ２ 8 μm ≤ H ２ The electrochemical apparatus according to claim 1, satisfying ≤12 μm.

9. The compressed density of the positive electrode active material layer is 3.3 g / cm³. ３ ~3.7 g / cm ３ The electrochemical apparatus according to claim 1.

10. The compressed density of the positive electrode active material layer is 3.5 g / cm³. ３ ~3.65 g / cm ３ The electrochemical apparatus according to claim 1.

11. The positive electrode active material layer further comprises a binder, The aforementioned binder has the structural formula shown in the following formula (A): (VDF)m(TFE)n(HFP)r(PVP)x (A) The electrochemical apparatus according to claim 1, wherein in formula (A), VDF is a structural unit of polyvinylidene fluoride, TFE is a structural unit of polytetrafluoroethylene, HFP is a structural unit of polyhexafluoropropylene, PVP is a structural unit of polyvinylpyrrolidone, and m, n, r, and x satisfy 0.35 ≤ m ≤ 1, 0 ≤ n ≤ 0.4, 0 ≤ r ≤ 0.2, 0 ≤ x ≤ 0.2, and m + n + r + x = 1.

12. An electronic apparatus comprising an electrochemical apparatus as described in any one of claims 1 to 11.

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