Lithium ion battery containing thick pole piece and electric device

Abstract

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery containing a thick pole piece and a power utilization device. The lithium ion battery comprises a current collector, and a first coating layer and a second coating layer are sequentially arranged on the two sides of the current collector respectively; the first coating layer comprises first active substance particles, a conductive agent and a binder, and the second coating layer comprises second active substance particles, a conductive agent and a binder; wherein the distribution width Q1 of the first active material particles and the distribution width Q2 of the second active material particles meet the following relational expression: Q1 is greater than or equal to 3.5 and greater than or equal to Q2 and greater than or equal to 0; and the distribution width Qn of the active material particles satisfies the following relational expression: Qn = (D90-D10) / D50, and n = 1 or 2.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a lithium-ion battery and an electrical device containing a thick electrode sheet. Background Art

[0002] In the field of lithium-ion battery manufacturing, improving the energy density and structural stability of electrodes is the core issue that the industry has been continuously working on.

[0003] Increasing the thickness of the battery electrode sheet can improve the overall mass energy density of the battery and can also reduce the number of layers or winding turns of the battery cell, simplify the battery cell assembly process, and improve production efficiency.

[0004] However, the current coating process has bottlenecks such as limited active material loading and insufficient mechanical strength of the electrode sheet. When the electrode sheet thickness exceeds 150 μm, microcracks and interface delamination are likely to occur, resulting in a decrease in the battery cycle life. In addition, after the electrode sheet thickness increases, its electrochemical impedance increases significantly, and the polarization during application is very large, which cannot support high-rate applications.

[0005] Therefore, how to overcome the defect of unstable structural performance of thick electrode sheets with a thickness exceeding 150 μm is a technical problem that urgently needs to be solved in this field.

[0006] It should be noted that the above information disclosed in this background art section is only used to understand the background art of the concept of this application. Therefore, the above description is not considered as information on the prior art. Summary of the Invention

[0007] The embodiments of the present disclosure at least provide a lithium-ion battery and an electrical device containing a thick electrode sheet.

[0008] In a first aspect, the embodiments of the present disclosure provide a lithium-ion battery containing a thick electrode sheet, including: a current collector, with a first coating layer and a second coating layer sequentially arranged on both sides of the current collector; the first coating layer includes first active material particles, a conductive agent, and a binder, and the second coating layer includes second active material particles, a conductive agent, and a binder; wherein, the distribution widths Q1 of the first active material particles and Q2 of the second active material particles satisfy the following relational expression: 3.5 ≥ Q1 ≥ Q2 ≥ 0; and, the distribution width Qn of the active material particles satisfies the following relational expression: Qn = (D90 - D10) / D50, where n = 1 or 2.

[0009] In an optional embodiment, the D50 is the average value of the data obtained by measuring the particles with a line segment parallel to the direction of the current collector and taking the maximum length as the particle size; the D10 and D90 are respectively the average values of the smallest 10% and the largest 10% of the obtained data.

[0010] In an alternative embodiment, the D50 particle size of the first active material particles is 8 - 25 μm, the D50 particle size of the second active material particles is 2 - 12 μm, and the difference in D50 particle size between the first active material particles and the second active material particles is ≥ 3 μm; and the porosity of the first coating layer is 10% - 28%, and the porosity of the second coating layer is 12% - 35%.

[0011] In an alternative embodiment, the content range of the conductive agent in the first coating layer is 1.5 - 4 wt%, and the content range of the conductive agent in the second coating layer is 0.5 - 3 wt%; the conductive agent includes one or more of carbon nanotubes, graphene, acetylene black, Super P, carbon fiber VGCF, conductive graphite KS6, and conductive graphite SFG - 6; and the content of the conductive agent in the first coating layer is greater than the content of the conductive agent in the second coating layer.

[0012] In an alternative embodiment, the first active material particles include one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate; the second active material particles include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate.

[0013] In an alternative embodiment, the binder includes any one or more of styrene - acrylic rubber SA, PTFE, PVDF, and PAN. The content of the binder in the first coating layer is not less than 1.5%, and the content of the binder in the second coating layer is not less than 1.2%; and the difference in the content of the binder between the first coating layer and the second coating layer is not less than 0.3%.

[0014] In an alternative embodiment, the first active material particles satisfy one or more of the following conditions: (1) the tapped density is between 2.0 g / cm 3 and 2.15 g / cm 3 ; (2) the specific surface area is between 0.06 m 2 / g and 0.42 m 2 / g; (3) the water molecule content is less than 410 ppm; (4) D10 ≥ 5.00 μm, D90 ≤ 30.00 μm; (5) the Li element content is 7.0 - 7.40 wt%, the Ni element content is 46% - 48.2 wt%, the Co element content is 6.0 - 7.1 wt%, the Mn element content is 4.9 - 5.5 wt%, the Fe element content is ≤ 45 ppm, the Cu element content is ≤ 46 ppm, the Na element content is ≤ 480 ppm, the Ca element content is ≤ 190 ppm, the Mg element content is ≤ 180 ppm, the pH is 10.2 - 11.80, and the content of magnetic foreign matters is ≤ 45 ppb. The magnetic foreign matters include Fe, Cr, and Zn.

[0015] In an alternative embodiment, it further includes a third coating layer disposed outside the second coating layer. The third coating layer includes third active material particles, and the distribution width Q3 of the third active material particles satisfies the following relational expression: Q3 ≤ (Q1 + Q2) / 2. The third active material particles include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate.

[0016] In an alternative embodiment, the first active material particles include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-carbon materials, and silicon-oxygen materials with large particle sizes. The second active material particles include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-carbon materials, and silicon-oxygen materials with small particle sizes. And the average particle size of the first active material particles is greater than or equal to the average particle size of the second active material particles, the specific capacity per gram of the first active material particles is greater than or equal to the specific capacity per gram of the second active material particles, and the particle strength of the first active material particles is less than or equal to the particle strength of the second active material particles.

[0017] In an alternative embodiment, the binder includes any one or more of styrene-butadiene rubber SBR, PAA, and CMC. The content of the binder in the first coating layer is not less than 2.0%, and the content of the binder in the second coating layer is not less than 1.7%. Moreover, the difference in the content of the binder between the first coating layer and the second coating layer is not less than 0.5%.

[0018] In a second aspect, the embodiments of the present disclosure further provide an electrical device, including the lithium-ion battery as described above.

[0019] The beneficial effects of the present invention are that the lithium-ion battery and the electrical device containing thick electrode sheets set the existing single-layer coating as a multi-layer coating, and use small particle size particles with a more uniform particle size distribution in the outer coating layer, so that the porosity of the outer coating layer is increased to have better lithium-ion conduction ability, ensuring that lithium ions are not blocked by lithium intercalation during the stage of passing through the outer coating layer, improving the conduction efficiency. At the same time, the multi-layer coating layer with a gradient particle distribution also overcomes the defect of unstable overall structure when the overall thickness of the electrode sheet increases.

[0020] Other features and advantages of the present invention will be described in the subsequent specification, and some will become obvious from the specification, or be understood by implementing the present invention. The objectives and other advantages of the present invention are achieved and obtained by the structures specifically pointed out in the specification and the drawings.

[0021] To make the above objects, features, and advantages of the present invention more apparent and understandable, the following provides preferred embodiments in conjunction with the accompanying drawings and describes them in detail as follows. Description of the Drawings

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0023] Figure 1 Structural schematic diagram of a thick electrode provided by an embodiment of the present disclosure;

[0024] Figure 2 Structural schematic diagram of a positive thick electrode provided by an embodiment of the present disclosure;

[0025] Figure 3 Structural schematic diagram of a lithium-ion battery provided by an embodiment of the present disclosure.

[0026] In the figure:

[0027] 1. Current collector; 2. First coating layer; 3. Second coating layer; 4. Third coating layer;

[0028] 10. Housing; 20. Positive electrode; 30. Negative electrode. Detailed Embodiments

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions of the present invention in conjunction with the drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0030] As used herein, phrases such as "in one embodiment", "according to one embodiment", "in some embodiments", etc. generally refer to the fact that the specific feature, structure, or characteristic after such phrase can be included in at least one embodiment of the present disclosure. Thus, a specific feature, structure, or characteristic can be included in more than one embodiment of the present disclosure, such that these phrases do not necessarily refer to the same embodiment. As used herein, the terms "example", "exemplary", etc. are used "as an example, instance, or illustration. Any embodiment, aspect, or design described herein as "example" or "exemplary" is not necessarily to be construed as preferred or superior to other embodiments, aspects, or designs. Instead, the use of the terms "example", "exemplary", etc. is intended to present concepts in a concrete manner.

[0031] In this document, example embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. As used herein, expressions such as "at least one of..." modify the entire list of elements when following a list of elements, rather than modifying individual elements in the list. For example, the expression "at least one of a, b, and c" should be understood to include only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c.

[0032] The terms used herein are only for describing specific exemplary configurations and are not intended to be limiting. As used herein, the singular articles "a", "an", and "the" may also be intended to include the plural forms, unless it is clearly stated otherwise herein. The terms "comprising", "including", and "having" are inclusive, and thus specify the presence of the specified features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. The method steps, processes, and operations described herein should not be construed as necessarily requiring them to be performed in the specific order discussed or shown, unless specifically identified as an order of execution. Additional or alternative steps may be employed.

[0033] In actual applications, the kinetics of the first coating layer is worse than that of the second coating layer in actual applications. Lithium ions need to first pass through the second coating layer and then enter the first coating layer. When a single-layer coating design is adopted, when the electrode sheet is too thick, the lithium intercalation in the lower part is often blocked. In addition, during cold pressing, the second coating layer will be under greater pressure from the roller. If the design is not optimized, it is easy to cause the pores to be pressed to death, resulting in the failure of the battery cell.

[0034] Therefore, simply changing the single-layer coating to a double-layer coating can, to a certain extent, solve the problems of microcracks and interface delamination that are likely to occur when the thickness of the electrode sheet exceeds 150 μm, but it will have a negative effect of decreasing rather than increasing the performance of the battery.

[0035] All the defects existing in the above solutions are the results obtained by the inventors through practice and careful research. Therefore, the process of discovering the above problems and the solutions proposed by the present disclosure for the above problems in the following text should both be the contributions made by the inventors to the present disclosure during the process of the present disclosure.

[0036] It should be noted that similar reference numerals and letters denote similar items in the following figures. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0037] The following will describe in detail some embodiments of the present invention with reference to the accompanying drawings. Without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0038] Please refer to Figure 1 , as Figure 1 shown, an embodiment of the present disclosure provides a lithium-ion battery including a thick electrode, which includes: a current collector, with a first coating layer and a second coating layer sequentially arranged on both sides of the current collector; the first coating layer includes first active material particles, a conductive agent, and a binder, and the second coating layer includes second active material particles, a conductive agent, and a binder; wherein, the distribution widths Q1 of the first active material particles and Q2 of the second active material particles satisfy the following relational expression: 3.5≥Q1≥Q2≥0; and, the distribution width Qn of the active material particles satisfies the following relational expression: Qn=(D90-D10) / D50, where n = 1 or 2.

[0039] In some embodiments, specifically, the D50 is the average value of the data obtained by measuring the particles with a line segment parallel to the direction of the current collector and taking the maximum length as the particle size; the D10 and D90 are respectively the average values of the smallest 10% and the largest 10% of the obtained data.

[0040] Specifically, the test method for the particle size is to take 1 battery, fully discharge it at 0.2C at room temperature, disassemble it after standing for 2h to obtain the target electrode, randomly take 3 electrodes at different positions, and process them into cross-sections; within the same coating, from left to right, from top to bottom, measure the particle size of each particle in turn, and require that each sample statistically includes no less than 30 particles; the particles to be statistically are at least not less than 1um (excluding the interference of fine powder), and the rule for measuring the particle size is to measure the particles with a line segment parallel to the direction of the current collector and take the maximum length as the particle size.

[0041] In some embodiments, specifically, the D50 particle size of the first active material particles is 8 - 25 μm, the D50 particle size of the second active material particles is 2 - 12 μm, and the difference in D50 particle size between the first active material particles and the second active material particles is ≥ 3 μm; and the porosity of the first coating layer is 10% - 28%, and the porosity of the second coating layer is 12% - 35%.

[0042] In some embodiments, specifically, the content range of the conductive agent in the first coating layer is 1.5 - 4 wt%, and the content range of the conductive agent in the second coating layer is 0.5 - 3 wt%; the conductive agent includes one or more of carbon nanotubes, graphene, acetylene black, Super P, carbon fiber VGCF, conductive graphite KS6, and conductive graphite SFG - 6; and the content of the conductive agent in the first coating layer is greater than the content of the conductive agent in the second coating layer.

[0043] In some embodiments, specifically, when performing double - layer coating as a positive electrode sheet, the first active material particles include one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate; the second active material particles include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate.

[0044] In some embodiments, specifically, the binder includes any one or more of styrene - acrylonitrile rubber SA, PTFE, PVDF, and PAN. The content of the binder in the first coating layer is not less than 1.5%, and the content of the binder in the second coating layer is not less than 1.2%; and the difference in the content of the binder between the first coating layer and the second coating layer is not less than 0.3%.

[0045] Specifically, by adding a fluorine - containing binder and regulating its proportion, the fluorine content of the first coating layer is higher and more electrolyte - philic, which helps the electrolyte to penetrate and infiltrate better. Additionally, more conductive agent will be added to the first coating layer to ensure its more excellent conductivity and help electrons in the thick electrode sheet transfer faster between the first coating layer and the current collector.

[0046] In some embodiments, specifically, the first active material particles satisfy one or more of the following conditions: (1) the tap density is between 2.0 g / cm 3 and 2.15 g / cm 3 ; (2) the specific surface area is between 0.06 m 2 / g and 0.42 m 2 / g; (3) the water molecule content is lower than 410 ppm; (4) D10 ≥ 5.00 μm, D90 ≤ 30.00 μm; (5) the Li element content is 7.0 - 7.40 wt%, the Ni element content is 46% - 48.2 wt%, the Co element content is 6.0 - 7.1 wt%, the Mn element content is 4.9 - 5.5 wt%, the Fe element content ≤ 45 ppm, the Cu element content ≤ 46 ppm, the Na element content ≤ 480 ppm, the Ca element content ≤ 190 ppm, the Mg element content ≤ 180 ppm, the pH is 10.2 - 11.80, and the content of magnetic foreign matters ≤ 45 ppb, and the magnetic foreign matters include Fe, Cr, and Zn.

[0047] Specifically, in combination with the formulation optimization of the double-layer electrode sheet, the difference in the double-layer conductivity is controlled to make the inner layer have better conductivity, so as to ensure the overall conductivity of the electrode sheet to be balanced.

[0048] Please refer to Figure 2 , such as Figure 2 shown, when performing double-layer coating as the positive electrode sheet, it further includes a third coating layer disposed outside the second coating layer. The third coating layer includes third active material particles, and the distribution width Q3 of the third active material particles satisfies the following relational expression: Q3 ≤ (Q1 + Q2) / 2; the third active material particles include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate.

[0049] In some embodiments, specifically, when performing double-layer coating as the negative electrode sheet, the first active material particles include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-carbon materials, and silicon-oxygen materials with large particle sizes; the second active material particles include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-carbon materials, and silicon-oxygen materials with small particle sizes; and the average particle size of the first active material particles is greater than or equal to the average particle size of the second active material particles, the specific capacity per gram of the first active material particles is greater than or equal to the specific capacity per gram of the second active material particles, and the particle strength of the first active material particles is less than or equal to the particle strength of the second active material particles.

[0050] In some embodiments, specifically, the binder includes any one or more of styrene-butadiene rubber SBR, PAA, and CMC. The content of the binder in the first coating layer is not less than 2.0%, and the content of the binder in the second coating layer is not less than 1.7%; and the difference in the content of the binder between the first coating layer and the second coating layer is not less than 0.5%.

[0051] Specifically, in the case of the positive electrode sheet as an example, there is a third coating layer, i.e., the edge coating. Since the edge coating is carried out synchronously with the coating during the processing, its particle size distribution is regulated to be at or below the average level of the upper and lower double layers to ensure that the processing characteristics after particle stacking are close to it. If its particle size distribution is too wide, the coating uniformity after coating is low, and the rolling pressure of the thick electrode sheet is large. It is easy to form uneven defects during the rolling process under too high pressure, and even cause material loss in some areas. In addition, more solvents will volatilize during the drying process of the thick electrode sheet. If the solvent loss rate of the edge coating is too fast, it will also cause material loss, etc.

[0052] In a second aspect, an electrical device provided by an embodiment of the present disclosure includes the lithium-ion battery as described above.

[0053] Example 1. This example shows a negative electrode sheet as shown according to the following process parameters. Figure 1 as shown.

[0054] For the first coating solution, the first active material particles, graphite, are selected. The D90 of the particles is 24 μm, the D50 is 16.4 μm, the D10 is 3.9 μm, and Q1 is 1.23.

[0055] For the second coating solution, the second active material particles, silicon carbide, are selected. The D90 of the particles is 11.4 μm, the D50 is 8.2 μm, the D10 is 5.5 μm, and Q2 is 0.72.

[0056] And the difference in D50 between the first active material particles and the second active material particles is 8.2 μm.

[0057] For the first coating, the binder SBR + PAA 1:1 is selected, with a content of 1.74%, the coating porosity is 21.20%, the conductive agent SP content is 2.00%, and the SWCNT content is 0.05%.

[0058] For the second coating, the binder SBR + PAA 1:1 is selected, with a content of 1.35%, the coating porosity is 26.40%, the conductive agent SP content is 1.30%, and the SWCNT content is 0.05%.

[0059] The first coating and the second coating were successively coated on the surface of the negative current collector according to the above parameters to obtain a negative electrode sheet. After the positive electrode sheet and the negative electrode sheet obtained in Example 1 were respectively roll-pressed, slit, and die-cut, they were wound together with the separator at the same time. The positive electrode sheet, the negative electrode sheet, and the separator were wound by a winding machine to form a core. The core was subjected to cutting and stacking of the positive electrode tab and the negative electrode tab, and then the positive current collector and the negative current collector were respectively welded to the core. Then, the negative current collector was welded to the steel shell, an insulating sheet was placed above the positive current collector, and the positive current collector was welded to the cap to obtain an experimental battery core body, which was installed in a battery case. After the processes of injecting electrolyte, sealing, and formation were completed, the experimental battery as shown in Figure 3 was obtained.

[0060] Example 2. This example demonstrates a positive electrode sheet as shown in Figure 2 according to the following process parameters.

[0061] For the first coating solution, the first active material particles, high-nickel NCMA90 polycrystal, were selected. The D90 of the particles was 18.5 μm, the D50 was 10.5 μm, the D10 was 2.2 μm, and Q1 was 1.55;

[0062] For the second coating solution, the second active material particles, high-nickel NCMA92 polycrystal, were selected. The D90 of the particles was 8.2 μm, the D50 was 5.3 μm, the D10 was 3.2 μm, and Q2 was 0.94;

[0063] For the third coating solution, the third active material particles, high-nickel NCMA92 single crystal, were selected. The D90 of the particles was 4.5 μm, the D50 was 2.3 μm, the D10 was 0.9 μm, and Q3 was 1.07;

[0064] Moreover, the difference in D50 between the first active material particles and the second active material particles was 5.2 μm,

[0065] (Q1 + Q2) / 2 = 1.25, satisfying (Q1 + Q2) / 2 ≥ Q3;

[0066] For the first coating, the binder PVDF was selected, with a content of 2.60%, the coating porosity was 15.60%, and the conductive agent SP with a content of 2.50% was selected;

[0067] For the second coating, the binder PVDF was selected, with a content of 2.40%, the coating porosity was 19.80%, and the conductive agent SP with a content of 2.00% was selected;

[0068] For the third coating, the binder PVDF was selected, with a content of 2.2%, the coating porosity was 19.5%, and the conductive agent SP with a content of 2.0% was selected;

[0069] Coat the first coating, the second coating, and the third coating on the surface of the positive current collector in sequence according to the above parameters to obtain a positive electrode sheet. After the positive electrode sheet obtained in Example 2 and the negative electrode sheet are respectively roll-pressed, slit, and die-cut, they are wound simultaneously with the separator. The positive electrode sheet, the negative electrode sheet, and the separator are wound by a winding machine to form a core. The core is subjected to cutting and stacking of the positive electrode tab and the negative electrode tab, and then the positive current collector and the negative current collector are respectively welded to the core. Then, the negative current collector is welded to the steel shell, an insulating sheet is placed above the positive current collector, and the positive current collector is welded to the cap to obtain an experimental battery core body, which is installed in a battery case. After completing the processes of liquid injection, sealing, and formation, the experimental battery as shown in Figure 3 is obtained.

[0070] Specifically, Examples 3-6 and Comparative Examples 1-2 are implemented according to the processes of the negative electrode sheets and positive electrode sheets prepared in Example 1 and Example 2, and the difference parameters are shown in Tables 1 and 2 below:

[0071] Table 1 Difference parameters of coating liquids

[0072]

[0073] Table 2 Difference parameters of coatings

[0074]

[0075]

[0076] Specifically, the experimental batteries are respectively subjected to a hot box test and a cycle retention rate test, and the data results are shown in Table 3 below.

[0077] For the hot box test, take one test battery, place it in a constant temperature box at 25 °C for more than 4 h, and conduct the test according to the following steps:

[0078] (1) Discharge the battery at a constant current of 0.1C until it is cut off at 2.5V, and let it stand for 5 min;

[0079] (2) Charge the battery at a constant current of 0.2C until it is cut off at 4.2V, and then charge it at a constant voltage until it is cut off at 0.05C, and let it stand for 5 min;

[0080] (3) Place the battery into a temperature box, set the heating rate to 5 K / min, heat it to 130 °C, and keep it for 1 h, then stop heating and let it cool naturally to below 30 °C;

[0081] (4) If the battery does not catch fire or emit smoke, it is considered to pass, otherwise it fails. At least 6 batteries are tested, and the passing rate is recorded;

[0082] (5) After the test is completed, if the battery does not leak, catch fire, or explode, it is considered to pass, that is, the passing rate of the hot box.

[0083] Cyclic retention rate test, 25°C, 1C / 1C 500cls. Take a test battery, place it in an incubator at 25°C for more than 4 hours, and conduct the test according to the following steps:

[0084] (1) Constant current discharge the battery to cut-off at 2.5V under the condition of 0.1C, and let it stand for 5 minutes;

[0085] (2) Constant current charge the battery to cut-off at 4.2V under the condition of 0.2C, and then constant voltage charge it to cut-off at 0.05C, and let it stand for 5 minutes;

[0086] (3) Constant current discharge the battery to cut-off at 2.5V under the condition of 0.2C, and let it stand for 5 minutes, and read the capacity value C0 at this time;

[0087] (4) Constant current charge the battery to 4.2V under the condition of 1.0C, and then constant voltage charge it to cut-off at 0.05C, and let it stand for 5 minutes;

[0088] (5) Constant current discharge the battery to cut-off at 2.5V under the condition of 2.0C, and let it stand for 5 minutes;

[0089] (6) Repeat steps (4) and (5) 500 times;

[0090] (7) Obtain the cycling performance of a single battery, that is, the cyclic retention rate, through the ratio of the 500th discharge capacity to the 1st discharge capacity in steps (4) and (5).

[0091] Table 3 Performance data

[0092] Hot box passing rate Circulation retention rate Example 1 6 / 6 95.90％ Example 2 6 / 6 90.10％ Example 3 5 / 6 83.30％ Example 4 6 / 6 86.30％ Example 5 3 / 6 73.20％ Example 6 3 / 6 70.50％ Comparative example 1 0 / 6 45.60％ Comparative example 2 1 / 6 50.40％

[0093] Specifically, it can be seen from the data of the examples that when the particle size of the active material particles used in the coating liquid does not meet the range limitation, resulting in an inability to achieve a uniform gradient distribution of the particle size distribution, it will seriously affect the lithium ion conduction ability. In the case of an increase in the thickness of the electrode sheet, it will further lead to a decrease in thermal stability and a decline in the overall stability of the battery.

[0094] In summary, the lithium ion battery and the electrical device with thick electrode sheets set the existing single-layer coating as a multi-layer coating, and use small particle size particles with a more uniform particle size distribution in the outer coating layer, so that the porosity of the outer coating layer is increased, with more excellent lithium ion conduction ability, ensuring that lithium ions will not be blocked by lithium intercalation during the stage of passing through the outer coating layer, improving the conduction efficiency. At the same time, the multi-layer coating layer with a gradient particle distribution also overcomes the defect of unstable overall structure in the case of an increase in the overall thickness of the electrode sheet.

[0095] Inspired by the above-described ideal embodiments of the present invention, through the above description, relevant staff can completely make various changes and modifications without departing from the technical idea of this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A lithium-ion battery with a thick electrode, characterized in that, Comprising: A current collector, with a first coating layer and a second coating layer sequentially arranged on both sides of the current collector; The first coating layer includes first active material particles, a conductive agent, and a binder, and the second coating layer includes second active material particles, a conductive agent, and a binder; Wherein, the distribution widths Q1 of the first active material particles and Q2 of the second active material particles satisfy the following relational expression: 3.5 ≥ Q1 ≥ Q2 ≥ 0; And, the distribution width Qn of the active material particles satisfies the following relational expression: Qn = (D90 - D10) / D50, n = 1 or 2.

2. The lithium-ion battery with a thick electrode plate according to claim 1, characterized in that The D50 is the average value of the data obtained by measuring the particles with a line segment parallel to the direction of the current collector and taking the maximum length as the particle size; The D10 and D90 are respectively the average values of the smallest 10% and the largest 10% of the obtained data.

3. The lithium-ion battery with a thick electrode plate according to claim 2, characterized in that The D50 particle size of the first active material particles is 8 - 25 μm, the D50 particle size of the second active material particles is 2 - 12 μm, and the difference in D50 particle size between the first active material particles and the second active material particles ≥ 3 μm; And, the porosity of the first coating layer is 10% - 28%, and the porosity of the second coating layer is 12% - 35%.

4. The lithium-ion battery with a thick electrode plate according to claim 1, characterized in that The content range of the conductive agent in the first coating layer is 1.5 - 4 wt%, and the content range of the conductive agent in the second coating layer is 0.5 - 3 wt%; The conductive agent includes one or more of carbon nanotubes, graphene, acetylene black, Super P, carbon fiber VGCF, conductive graphite KS6, and conductive graphite SFG-6; And the content of the conductive agent in the first coating layer is greater than the content of the conductive agent in the second coating layer.

5. The lithium-ion battery with a thick electrode plate according to claim 1, characterized in that The first active material particles include one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate; The second active material particles include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate, and lithium nickel cobalt manganese aluminate.

6. The lithium-ion battery with a thick electrode plate according to claim 5, characterized in that The binder includes any one or more of styrene-acrylic rubber SA, PTFE, PVDF, and PAN. The content of the binder in the first coating layer is not less than 1.5%, and the content of the binder in the second coating layer is not less than 1.2%; And, the difference in the content of the binder between the first coating layer and the second coating layer is not less than 0.3%.

7. The lithium-ion battery with a thick electrode plate according to claim 5, characterized in that The first active material particles satisfy one or more of the following conditions: (1) The tapped density is between 2.0 g / cm 3 and 2.15 g / cm 3 ; (2) The specific surface area is between 0.06 m 2 / g and 0.42 m 2 / g; (3) The water molecule content is lower than 410 ppm; (4) D10 ≥ 5.00 μm, D90 ≤ 30.00 μm; (5) The Li element content is 7.0 - 7.40 wt%, and the Ni element content is 46% - 48.2 wt%, The content of Co element is 6.0 - 7.1 wt%, and the content of Mn element is 4.9 - 5.5 wt%. The content of Fe element is ≤ 45 ppm, and the content of Cu element is ≤ 46 ppm. The content of Na element is ≤ 480 ppm, and the content of Ca element is ≤ 190 ppm. The content of Mg element is ≤ 180 ppm, and the pH is 10.2 - 11.

80. The content of magnetic foreign matters is ≤ 45 ppb, and the magnetic foreign matters include Fe, Cr, and Zn.

8. The lithium-ion battery with a thick electrode plate according to claim 1, characterized in that it further includes a third coating layer disposed outside the second coating layer. The third coating layer includes third active material particles, and the distribution width Q3 of the third active material particles satisfies the following relational expression: Q3 ≤ (Q1 + Q2) / 2; The third active material particles include one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and lithium nickel cobalt manganese aluminum oxide.

9. The lithium-ion battery with a thick electrode plate according to claim 1, characterized in that the first active material particles include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-carbon material, and silicon-oxygen material with large particle sizes; the second active material particles include one or more of natural graphite, artificial graphite, hard carbon, soft carbon, mesocarbon microbeads, silicon-carbon material, and silicon-oxygen material with small particle sizes; and the average particle size of the first active material particles is greater than or equal to the average particle size of the second active material particles, the specific capacity per gram of the first active material particles is greater than or equal to the specific capacity per gram of the second active material particles, and the particle strength of the first active material particles is less than or equal to the particle strength of the second active material particles.

10. The lithium-ion battery with a thick electrode plate according to claim 9, characterized in that the binder includes any one or more of styrene-butadiene rubber SBR, PAA, and CMC. The content of the binder in the first coating layer is not less than 2.0%, and the content of the binder in the second coating layer is not less than 1.7%; and the difference in the content of the binder between the first coating layer and the second coating layer is not less than 0.5%.

11. An electrical device, including the lithium-ion battery according to any one of claims 1 - 10.

Images