Positive electrode plate, method for manufacturing a positive electrode plate, lithium-ion secondary battery and EVTOL

Abstract

To provide a positive electrode plate, a manufacturing method of the positive electrode plate, and a lithium ion battery including the positive electrode plate.SOLUTION: The present invention provides a positive electrode plate. The positive electrode plate includes: a positive electrode current collector; and a coating layer provided on a surface of the positive electrode current collector. The coating layer includes a nickel-containing positive electrode active material and a conductive agent, and the coating layer satisfies a relational expression represented by 3<a×c / 100b<5...(I). In the formula (I), a represents a mole percent of nickel in the nickel-containing positive electrode active material, b represents a mass percent of the conductive agent in the coating layer, and c represents a single-sided surface density of the coating layer, and a unit thereof is mg / cm2. In the present invention, when the positive electrode plate satisfies the formula (I), the lithium ion battery manufactured using the positive electrode plate can ensure an energy density and cycle life of an electrode body and has excellent DCR performance.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention belongs to the technical field of lithium-ion batteries, and more specifically relates to positive electrodes, methods for manufacturing positive electrodes, lithium-ion secondary batteries, and EVTOLs. [Background technology]

[0002] With the development of modern society and the advancement of science and technology, automobiles are gradually becoming the dominant alternative to walking. However, as the number of automobiles increases, traffic congestion is gradually worsening, and vertical take-off and landing (VTOL) facilities are gradually attracting attention. In addition, with crude oil prices rising year after year, electric vertical take-off and landing (EVTOL) facilities have become a goal that science and technology must pursue. Currently, lithium-ion batteries are the optimal choice for EVTOL power supply. Due to the unique nature of EVTOLs, lithium-ion batteries are required to possess high energy density, high power output, and long lifespan. In light of this, lithium-ion batteries that can continuously provide high power output while maintaining energy density and have a long lifespan are essential requirements for promoting the development of the aircraft industry. [Overview of the project] [Problems that the invention aims to solve]

[0003] In view of this, the technical problem that the present invention aims to solve is to provide a positive electrode plate, a method for manufacturing a positive electrode plate, a lithium-ion secondary battery, and an EVTOL. A lithium-ion battery manufactured from the positive electrode plate according to the present invention can guarantee the energy density and cycle life of the electrode body and have excellent DCR performance. [Means for solving the problem]

[0004] The positive electrode plate according to the present invention includes a positive electrode current collector and a coating layer provided on the surface of the positive electrode current collector, wherein the coating layer contains a nickel-containing positive electrode active material and a conductive agent, and the coating layer satisfies the relation shown in the following formula (I). 3 <a×c / 100b<5···(I) (In formula (I), a is the mole percent of nickel in the nickel-containing positive electrode active material, b is the mass percent of the conductive agent in the coating layer, and c is the surface density of the coating layer on one side in mg / cm². 2 (That is the case.)

[0005] The range of the value of a × c / 100b is preferably 3.35 to 4.8.

[0006] It is preferable that a is 63% ≤ a ≤ 92%.

[0007] It is preferable that b is 2.5% ≤ b ≤ 4%.

[0008] It is preferable that c is 12 ≤ c ≤ 18.

[0009] The nickel-containing positive electrode active material is selected from a mixture of one or two of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. The positive electrode current collector is preferably selected from one of aluminum foil and carbon-coated aluminum foil.

[0010] The present invention further discloses a method for manufacturing the positive electrode plate described above, and the manufacturing method is as follows: The process involves mixing a nickel-containing positive electrode active material, a conductive agent, and an auxiliary agent to obtain a slurry, The step includes applying the slurry to the surface of the positive electrode current collector and drying it to obtain a positive electrode plate, The coating layer on the positive electrode plate satisfies the relationship shown by equation (I). 3 <a×c / 100b<5···(I) (In formula (I), a is the mole percent of nickel in the nickel-containing positive electrode active material, b is the mass percent of the conductive agent in the coating layer, and c is the surface density of the coating layer on one side in mg / cm². 2 (That is the case.)

[0011] The present invention further discloses a lithium-ion battery, which includes a positive electrode plate selected from the above-described positive electrode plates, a negative electrode plate, a separator, and an electrolyte.

[0012] Preferably, the negative electrode plate includes a negative electrode current collector and a negative electrode coating layer coated on the negative electrode current collector. The negative electrode coating layer contains a negative electrode active material selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, and silicon-based materials. The negative electrode current collector is selected from copper foils.

[0013] The present invention further discloses an eVTOL, which includes the above-described lithium-ion battery.

Effects of the Invention

[0014] Compared with the prior art, the present invention provides a positive electrode plate, which includes a positive electrode current collector and a coating layer provided on the surface of the positive electrode current collector. The coating layer contains a nickel-containing positive electrode active material and a conductive agent, and the coating layer satisfies the relational expression represented by 3 < a × c / 100b < 5 in Formula (I). In Formula (I), a is the mole percentage of nickel in the nickel-containing positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density per side of the coating layer with the unit of mg / cm 2 and is. In the present invention, when the positive electrode plate satisfies the formula represented by Formula (I), the lithium-ion battery composed of the positive electrode plate can guarantee the energy density and cycle life of the electrode body and obtain excellent DCR performance.

Modes for Carrying Out the Invention

[0015] The present invention provides a positive electrode plate, which includes a positive electrode current collector and a coating layer composite on the surface of the positive electrode current collector. The coating layer contains a nickel-containing positive electrode active material and a conductive agent, and the coating layer satisfies the relational expression represented by the following Formula (I). 3 < a × c / 100b < 5 ··· (I) In formula (I), a is the molar percentage of nickel in the nickel-containing positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density per side of the coating layer with the unit of mg / cm 2 is as follows.

[0016] The positive electrode plate according to the present invention includes a positive electrode current collector. The present invention is not particularly limited with respect to the type of the positive electrode current collector, and any type of current collector well-known to those skilled in the art may be used, but it is preferably one of an aluminum foil and a carbon-coated aluminum foil.

[0017] In another embodiment, the positive electrode plate according to the present invention includes a coating layer provided on the surface of the positive electrode current collector, and the coating layer includes a nickel-containing positive electrode active material, a conductive agent, and a binder.

[0018] The coating layer satisfies the relational expression represented by formula (I). 3 < a×c / 100b < 5 ··· (I) In formula (I), a is the molar percentage of nickel in the nickel-containing positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density per side of the coating layer with the unit of mg / cm 2 is as follows.

[0019] In the positive electrode plate according to the present invention, the molar percentage of nickel in the nickel-containing positive electrode active material, the areal density per side of the coating layer, and the ratio of the conductive agent in the positive electrode coating layer all affect the energy density and output performance of the electrode body, but there are certain limits and correlations in the influence. As a result of intensive research by the present inventors, it has been found that by making the positive electrode plate satisfy 3 < a×c / 100b < 5, it has a high energy density and excellent output performance, can avoid a large number of DOE experiments, and can save the research and development time and cost of the battery.

[0020] The range of the value of a×c / 100b is preferably 3.35 to 4.8. In this case, higher energy density, cycle life, and better power performance are obtained. For example, the value of a×c / 100b may be 3.35, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, or any value between 3.35 and 4.8.

[0021] The molar percentage a of nickel in the nickel-containing cathode active material is 63% to 92%, and may be 63%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, or any value between 63% and 92%, but preferably any value between 65% and 91%. In the nickel-containing cathode active material, one Ni can release two lithium ions, and increasing the Ni content can improve the discharge gram capacity of the material, and therefore the capacity of the electrode body can be improved. One Co can release one lithium ion, and increasing the Co content in the electrode body can improve the rate performance of the material. Mn has no change in valence and plays a role in improving structural stability as a supporting element. As the Ni content increases, the gram capacity of the ternary material improves, but the rate performance and cycle performance of the material gradually deteriorate. Therefore, in order to meet the requirements for energy density, cycle performance, and output performance of the EVTOL electrode body, it is necessary to control the Ni content in the cathode ternary material within an appropriate range.

[0022] The mass percentage b of the conductive agent in the coating layer is 2.5% to 4%, and may be 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%, 4.0%, or any value between 2.5% and 4%, but preferably 2.6% to 3.3%. Here, the content of the conductive agent in the coating layer directly affects the electronic impedance of the positive electrode plate and the energy density of the battery. As the proportion of conductive agent in the coating layer increases, the electronic impedance of the positive electrode plate decreases, which is advantageous for improving the output performance of the electrode body. However, as the proportion of conductive agent decreases, the proportion of positive electrode active material in the coating layer decreases, which affects the energy density of the electrode body. If the content of the positive electrode conductive agent is too high, the electronic impedance is no longer a limiting factor for output. Therefore, even if the content of the conductive agent in the electrode body is further increased, the output performance of the electrode body cannot be significantly improved, and on the contrary, the energy density of the electrode body decreases. If the content of the conductive agent in the coating layer is too low, it is advantageous for improving the energy density of the electrode body, but the electronic impedance increases as the content of the conductive agent decreases, affecting the output performance of the electrode body. For this reason, it is necessary to control the mass percentage of the conductive agent in the coating layer within an appropriate range.

[0023] The range of the surface density c value for the single-sided coating layer is 12 to 18, and the unit is mg / cm³. 2The value may be 12, 13, 14, 14.5, 15, 15.5, 16, 17, 18, or any value between 12 and 18, but 14 to 16 is more preferred. During discharge of a lithium-ion battery, lithium ions are detached from the negative electrode active material and inserted into the positive electrode active material, and the distance traveled by lithium ions is related to the surface density. As the surface density increases, the proportion of auxiliary material in the electrode body decreases, increasing the energy density of the electrode body, but at the same time, the distance traveled by lithium ions increases, and the output performance decreases. If the surface density is too high, the distance traveled by lithium ions becomes a limiting factor for high-rate discharge of the electrode body, and the output performance of the electrode body rapidly decreases. If the surface density is too low, the output performance of the electrode body improves, but as the proportion of auxiliary material in the electrode body increases, the energy density of the electrode body decreases. Therefore, it is necessary to control the surface density of the coating layer within an appropriate range.

[0024] In a positive electrode plate, the proportion of Ni in the ternary material (active material), the content of the conductive agent in the electrode plate, and the surface density of the electrode plate all affect the cycle performance, output performance, and energy density of the electrode body. In the embodiment of the present invention, the energy density, cycle performance, and output performance of the electrode body are simultaneously improved by the mutual complementarity of these three factors. Specifically, increasing the molar proportion of Ni in the ternary material further enhances the gram capacity of the positive electrode active material, thereby improving the energy density of the electrode body. However, if the molar proportion of Ni is increased too much, the structure of the positive electrode active material deteriorates, changing from a layered structure to a spinel structure, and further converting to a non-conductive NiO-like phase, thus reducing the output performance and cycle performance of the battery. By controlling the content of the conductive agent, the decrease in conductivity due to the surface phase transition of the ternary material can be improved, and therefore the output performance can be improved. By controlling the surface density, the expansion thickness of the material can be reduced, thereby suppressing the increase in impedance during cycling and improving the cycle performance and output performance of the battery. Based on the above, the inventors have diligently conducted research and have found that by optimizing the molar ratio of Ni, the ratio of conductive agent, and the surface density values ​​in the ternary material, and by ensuring that the coating layer satisfies the relation shown in equation (I), the energy density, output performance, and cycle performance of the electrode body are all excellent.

[0025] Based on the above, if the nickel content ratio, conductive agent ratio, and single-sided density in the ternary material of the coating layer satisfy the above requirements, the lithium-ion battery can achieve both high energy density and excellent output performance.

[0026] The present invention further provides a method for manufacturing a positive electrode plate, and the manufacturing method is as follows: The process involves mixing a nickel-containing positive electrode active material, a conductive agent, and an auxiliary agent to obtain a slurry, The step includes applying the slurry to the surface of the current collector and drying it to obtain a positive electrode plate, The coating layer on the positive electrode plate satisfies the relationship shown by equation (I). 3 <a×c / 100b<5···(I) In formula (I), a is the molar percentage of nickel in the nickel-containing positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, c is the single-sided surface density of the coating layer, and the unit is mg / cm 2 is as follows.

[0027] Furthermore, the present invention mixes a positive electrode active material, a conductive agent, and an auxiliary agent to obtain a slurry. Here, the auxiliary agent is selected from binders.

[0028] In the present invention, the nickel-containing positive electrode active material, the conductive agent, and the auxiliary agent are dispersed in a solvent and stirred to form a stable positive electrode slurry that is uniformly mixed. Here, the solvent is preferably NMP. In order to ensure the energy density and cycle life of the electrode body and obtain excellent DCR performance, it is controlled such that the molar percentage of nickel in the nickel-containing positive electrode active material satisfies 63% ≤ a ≤ 92%, and the mass percentage of the conductive agent in the coating layer satisfies 2.5% ≤ b ≤ 4%.

[0029] The positive electrode slurry is uniformly coated on the positive electrode current collector, dried, and cold-pressed to obtain a positive electrode plate.

[0030] In the present invention, during coating, it is preferable to use a scale to monitor the surface density of the coating in real time so that the single-sided surface density of the obtained coating layer satisfies the range of 12 to 18 mg / cm 2 .

[0031] The positive electrode plate manufactured by the above method satisfies 3 < a×c / 100b < 5, thereby ensuring that the electrode body obtains high energy density, cycle life, and excellent output performance.

[0032] The present invention further provides a lithium-ion battery, which includes a positive electrode plate selected from the above-mentioned positive electrode plates, a negative electrode plate, a separator, and an electrolyte.

[0033] In the present invention, the manufacturing method of the lithium-ion battery is It includes laminating a positive electrode plate, a separator, and a negative electrode plate, assembling them by winding or laminating to form a bare cell, and injecting an electrolytic solution into the dried bare cell to obtain a lithium-ion secondary battery.

[0034] In the present invention, there is no particular limitation on the manufacturing methods of the separator, the electrolytic solution, and the negative electrode plate, and any separator, electrolytic solution, and negative electrode plate for lithium-ion batteries well-known to those skilled in the art may be used.

[0035] Here, the negative electrode plate includes a negative electrode current collector and a negative electrode coating layer coated on the negative electrode current collector, and the compaction density of the negative electrode coating layer is 1.35 g / cm 3 . The negative electrode coating layer includes a negative electrode active material, a conductive agent, a binder, and a dispersant. The present invention does not particularly limit the types of the negative electrode active material, the conductive agent, the binder, and the dispersant, but the negative electrode active material is preferably selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, and silicon materials, and the current collector is preferably a copper foil. Here, the manufacturing process of the negative electrode plate includes mixing the negative electrode active material, the conductive agent, and the binder at a predetermined ratio, adding deionized water, stirring to form a stable negative electrode slurry uniformly mixed, uniformly coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing to obtain the negative electrode plate.

[0036] The separator is preferably made of materials such as a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, and a non-woven fabric.

[0037] The electrolytic solution includes a lithium salt and a solvent. Here, the present invention does not particularly limit the types of the lithium salt and the solvent, and they can be selected according to actual needs. Among them, the lithium salt is preferably LiPF6, LiTFSI, or LiBF4.

[0038] The EVTOL according to the present invention includes the above lithium-ion battery.

[0039] The positive electrode plate according to the present invention satisfies the formula shown in formula (I), and a lithium-ion battery manufactured using the positive electrode plate can guarantee the energy density and cycle life of the electrode body and have excellent DCR performance.

[0040] To further understand the present invention, the positive electrode plate, method for manufacturing the positive electrode plate, lithium-ion battery, and EVTOL according to the present invention will be described below with reference to examples, but the scope of protection of the present invention is not limited to the following examples.

[0041] <Examples> 1. In the manufacturing process of the positive electrode plate, lithium nickel cobalt manganese oxide (NCM) ternary positive electrode active material, conductive agent SP, and binder PVDF are mixed in predetermined proportions. Then, NMP is added and the mixture is stirred to create a uniformly stable positive electrode slurry. The positive electrode slurry is then uniformly applied to the positive electrode current collector, dried, and cold-pressed to obtain the positive electrode plate. Here, the proportion of the binder is 1.1%, the proportion of the conductive agent is shown in Table 1, and the remainder is the ternary positive electrode active material. 2. In the manufacturing process of the negative electrode plate, the negative electrode active material, conductive agent SP+CNTs, and binder PAA+SBR are mixed in predetermined proportions, then deionized water is added and stirred until a uniformly stable negative electrode slurry is formed. The negative electrode slurry is then uniformly applied to the negative electrode current collector, dried, and cold-pressed to obtain the negative electrode piece. The main component of the negative electrode active material is a composite material consisting of graphite and silica, with a compaction density of 1.35 g / cm³. 3 Here, the mass ratio of the negative electrode active material, SP, CNTs, PAA, and SBR is 95.4%:1.5%:0.1%:2%:1%. 3. Polypropylene film will be used as the separator. 4. In the electrode assembly process, the positive electrode plate, separator, and negative electrode plate are arranged in sequence and assembled by winding or laminating. 5. The electrolyte is a mixed solvent prepared by dissolving LiPF6 in ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1, with a concentration of 1.2 mol / L. 6. The electrolyte is injected into the dried electrode body, and then the body is formed and aged to obtain a lithium-ion battery.

[0042] Performance testing was performed on the manufactured batteries, and the results are shown in Table 1.

[0043] [Table 1]

[0044] In Examples 1 to 20, the energy density of the electrode body in each example was obtained based on a model of the 2614897 aluminum case. The charge-discharge cycle method involves charging at a constant current and voltage of 1C up to the upper limit voltage (for material systems with a Ni content of 70% or more, the upper limit voltage is 4.25V, and for materials with a Ni content of 70% or less, the upper limit voltage is 4.4V).

[0045] Energy density tests and DCR tests were performed on the lithium-ion secondary batteries manufactured in Examples 1 to 20. The energy density is the energy density detected at 25°C and 1C. The DCR test conditions were 25°C, 50% SOC, and a discharge of 30s at 2C.

[0046] As can be seen from Table 1, all parameters related to Example 1 are within the range of values defined in the present invention, and the energy density, cycle life, and DCR of the obtained battery are all at a relatively high level. Examples 1 to 8 compared the molar ratios of Ni content in the ternary system materials. Examples 1 to 8 show that the nickel content increases sequentially. As the Ni content increases, the energy density of the electrode body continuously increases. However, when the molar ratio of the Ni content is higher than 92%, the cycle performance of the electrode body continuously deteriorates, the DCR also becomes larger and larger, that is, the output performance becomes worse and worse. In Example 2, 3 < a×c / 100b < 5 is not satisfied, and the ratio of Ni content in the ternary system material is less than 63%. The obtained battery has excellent cycle performance and output performance, but the energy density is low. In Example 8, the ratio of Ni content in the ternary system material does not satisfy 63% ≤ a ≤ 92%. The obtained battery has a high energy density, but the cycle performance and output performance are clearly deteriorated. In Examples 1, 3 to 7, 3 < a×c / 100b < 5 is satisfied, and the ratio of nickel content, the ratio of conductive agent, and the single-sided surface density in the ternary system material of the coating layer all satisfy the above range, and the electrode body of the battery shows excellent comprehensive performance.

[0047] Examples 1, Examples 9 to 14 compared the influence of the content of the conductive agent in the electrode plate on the performance of the electrode body. In Examples 9 to 14, when the ratio of the conductive agent content gradually increased, the cycle performance of the battery gradually increased, and the DCR continuously decreased. However, after the amount of the conductive agent reached a certain level, it was found that when the amount of the conductive agent was further increased, on the contrary, the energy density performance of the electrode body deteriorated. Therefore, in Examples 1, 10 to 13, when 3 < a×c / 100b < 5 and the ratio of nickel content, the ratio of conductive agent, and the single-sided surface density in the ternary system material of the coating layer all satisfy the above range, the electrode body shows excellent comprehensive performance.

[0048] In Examples 15 to 20, the influence of the single-sided surface density of the electrode plate on the performance of the electrode body was compared. In Examples 15 to 20, although the single-sided surface density gradually increased and the energy density gradually improved, it was shown that the output performance and cycle performance continuously decreased. In Example 15, the single-sided surface density was less than 12 mg / cm 2 and the obtained electrode body had excellent cycle performance and output performance, but the energy density was too low. In Example 20, the single-sided surface density was higher than 18 mg / cm 2 and the obtained battery electrode body had significantly inferior cycle performance. In Examples 16 to 19, 3 < a×c / 100b < 5 was satisfied, and the proportion of nickel content, the proportion of conductive agent, and the single-sided surface density in the ternary system material of the coating layer all satisfied the above ranges, and the electrode body showed excellent comprehensive performance.

[0049] From the analysis of the examples, when the molar ratio of Ni, the content of the conductive agent, and the single-sided surface density satisfy 3 < a×c / 100b < 5, and a≧63%, 2.5%≦b≦4%, 12≦c≦18 respectively, the electrode body has excellent comprehensive performance.

[0050] Note that the above content is only a preferred embodiment of the present invention. Those skilled in the art can make some improvements and adjustments without departing from the principle of the present invention, and these improvements and adjustments should also be regarded as within the protection scope of the present invention.

Claims

1. It is a positive electrode plate, It includes a positive electrode current collector and a coating layer provided on the surface of the positive electrode current collector, The coating layer comprises a nickel-containing positive electrode active material and a conductive agent. The aforementioned coating layer satisfies the relationship shown in the following formula (I): A positive electrode plate characterized by the following features. 3.15≦a×c / 100b≦3.40...(I) (In formula (I), a is the mole percent of nickel in the nickel-containing positive electrode active material, where 63% ≤ a ≤ 68%, b is the mass percent of the conductive agent in the coating layer, where b = 3%, and c is the surface density of one side of the coating layer, with units of mg / cm²) ２ Therefore, c = 15.

2. The nickel-containing positive electrode active material is selected from a mixture of one or two of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide. The positive electrode current collector is selected from one of aluminum foil and carbon-coated aluminum foil. The positive electrode plate according to claim 1.

3. A method for manufacturing a positive electrode plate according to claim 1 or 2, The process involves mixing a nickel-containing positive electrode active material, a conductive agent, and an auxiliary agent to obtain a slurry, The step includes applying the slurry to the surface of the positive electrode current collector and drying it to obtain a positive electrode plate, The coating layer of the positive electrode plate satisfies the relation shown in equation (I), A method for manufacturing a positive electrode plate, characterized by the above. 3.15≦a×c / 100b≦3.40...(I) (In formula (I), a is the mole percent of nickel in the nickel-containing positive electrode active material, where 63% ≤ a ≤ 68%, b is the mass percent of the conductive agent in the coating layer, where b = 3%, and c is the surface density of one side of the coating layer, with units of mg / cm²) ２ (And c = 15.)

4. Lithium-ion battery, A positive electrode plate selected from the positive electrode plates described in claim 1 or 2, a negative electrode plate, a separator, and an electrolyte are included. A lithium-ion battery characterized by the following features.

5. The negative electrode plate includes a negative electrode current collector and a negative electrode coating layer applied to the negative electrode current collector. The anode coating layer contains an anode active material, which is selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, and silicon-based materials. The negative electrode current collector is selected from copper foil. The lithium-ion battery according to feature 4.

6. An EVTOL characterized by comprising the lithium-ion battery described in claim 5.

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