Positive electrode plate, manufacturing method of the 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] The present invention relates to the technical field of lithium ion batteries, and more particularly to a positive electrode plate, a method for manufacturing a positive electrode plate, a lithium ion secondary battery, and an EVTOL. [Background technology]

[0002] With the development of modern society and advances in science and technology, automobiles are gradually becoming a mainstream alternative to walking. However, as the number of automobiles increases, traffic congestion gradually increases, and vertical take-off and landing (VTOL) systems are gradually attracting people's attention. In addition, as crude oil prices continue to rise year by year, electric vertical take-off and landing (EVTOL) systems have become a technologically pursued goal. Currently, lithium-ion batteries are the optimal choice for EVTOL powertrains. Due to the unique characteristics of EVTOLs, lithium-ion batteries must combine high energy density, high power output, and long life. In light of this, lithium-ion batteries that can continuously provide high power output while maintaining energy density and have a long life are a requirement for promoting the development of the aviation industry. Summary of the Invention [Problem to be solved by the invention]

[0003] In view of this, the technical problem to be solved by the present invention is to provide a positive electrode plate, a method for manufacturing the positive electrode plate, a lithium ion secondary battery, and an EVTOL. The lithium ion battery manufactured from the positive electrode plate according to the present invention can ensure the energy density and cycle life of the electrode assembly 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 a surface of the positive electrode current collector, the coating layer including a nickel-containing positive electrode active material and a conductive agent, and the coating layer satisfies the relational expression shown in the following formula (I): 3 <a×c / 100b<5···(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 single-side areal density of the coating layer, expressed in mg / cm 2 )

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

[0006] It is preferable that a satisfies the condition 63%≦a≦92%.

[0007] It is preferable that b satisfies the condition 2.5%≦b≦4%.

[0008] It is preferable that c satisfies the condition 12≦c≦18.

[0009] the nickel-containing positive electrode active material is selected from one or a mixture of 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 above-mentioned positive electrode plate, the method comprising: Mixing a nickel-containing positive electrode active material, a conductive agent, and an auxiliary to obtain a slurry; applying the slurry to a surface of a positive electrode current collector and drying the slurry to obtain a positive electrode plate; The coating layer of the positive electrode plate satisfies the relational expression shown in formula (I). 3 <a×c / 100b<5···(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 single-side areal density of the coating layer, expressed in mg / cm 2 )

[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 applied to the negative electrode current collector. The negative electrode coating layer includes 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 includes 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 of formula (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 single-sided surface density of the coating layer with the unit of mg / cm 2 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 compounded on the 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 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 single-sided surface density 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 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 aluminum foil and 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 single-sided surface density 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 single-sided surface density 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 inventor, 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 value of a×c / 100b is preferably in the range of 3.35 to 4.8. In this case, higher energy density, cycle life, and superior output performance are achieved. 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 mole percentage (a) of nickel in the nickel-containing positive electrode 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 is preferably any value between 65% and 91%. In nickel-containing positive electrode active materials, one Ni atom 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 assembly. One Co atom can release one lithium ion, and increasing the Co content in the electrode assembly can improve the rate performance of the material. Mn, without changing its valence, serves as a supporting element to improve structural stability. 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, to meet the energy density, cycle performance, and output performance requirements of EVTOL electrode assembly, the Ni content in the positive electrode ternary material must be controlled 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 is preferably 2.6% to 3.3%. 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 content of the 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 assembly. However, as the content of the conductive agent increases, the proportion of the positive electrode active material in the coating layer decreases, which affects the energy density of the electrode assembly. If the content of the positive electrode conductive agent is too high, electronic impedance will no longer be a limiting factor for output, and further increasing the content of the conductive agent in the electrode assembly will not significantly improve the output performance of the electrode assembly, and will instead reduce the energy density of the electrode assembly. If the content of the conductive agent in the coating layer is too low, this will be advantageous for improving the energy density of the electrode assembly, but the electronic impedance will increase as the content of the conductive agent decreases, affecting the output performance of the electrode assembly. Therefore, it is necessary to control the mass percentage of the conductive agent in the coating layer within an appropriate range.

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

[0024] In a positive electrode plate, the Ni content in the ternary material active material, the conductive agent content in the plate, and the areal density of the plate all affect the cycle performance, power performance, and energy density of the electrode assembly. In an embodiment of the present invention, the three factors complement each other to simultaneously improve the energy density, cycle performance, and power performance of the electrode assembly. Specifically, increasing the molar ratio of Ni in the ternary material enhances the gram capacity of the positive electrode active material, thereby improving the energy density of the electrode assembly. However, if the molar ratio of Ni is too high, the structure of the positive electrode active material deteriorates, changing from a layered structure to a spinel structure and then to a non-conductive NiO-like phase, thereby reducing the battery's power and cycle performance. Controlling the conductive agent content can improve the conductivity reduction caused by the surface phase transition of the ternary material, thereby improving power performance. Controlling the areal density can reduce the material's expansion thickness, thereby suppressing the increase in impedance during cycling and improving the battery's cycle and power performance. Based on the above, the inventors have conducted extensive research and found that by optimizing the molar ratio of Ni, the ratio of conductive agent, and the areal density in the ternary material and by making the coating layer satisfy the relationship shown in formula (I), the energy density, output performance, and cycle performance of the electrode body can all be improved.

[0025] From the above, when the nickel content ratio, conductive agent ratio, and single-sided areal 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, the method comprising: Mixing a nickel-containing positive electrode active material, a conductive agent, and an auxiliary to obtain a slurry; and applying the slurry to a surface of a current collector and drying the slurry to obtain a positive electrode plate. The coating layer of the positive electrode plate satisfies the relational expression shown in 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, c is the single-sided surface density of the coating layer, and the unit is mg / cm 2 is as follows.

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

[0028] In the present invention, a nickel-containing positive electrode active material, a conductive agent, and an 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 a 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 balance 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 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 The method includes stacking a positive electrode plate, a separator, and a negative electrode plate, assembling them by winding or laminating them to form a bare cell, and injecting an electrolyte 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 electrolyte, and the negative electrode plate, and any separator, electrolyte, and negative electrode plate for lithium ion batteries that are 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 negative electrode coating layer has a compaction density of 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 limit the types of the negative electrode active material, conductive agent, binder, and dispersant. However, 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 copper foil. The negative electrode plate manufacturing process includes the steps of: mixing the negative electrode active material, conductive agent, and binder in a predetermined ratio; adding deionized water and stirring to form a uniformly mixed, stable negative electrode slurry; uniformly coating the negative electrode slurry on a negative electrode current collector; drying; and cold-pressing to obtain a negative electrode plate.

[0036] The separator is preferably made of a material such as a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, or a nonwoven fabric.

[0037] The electrolyte solution includes a lithium salt and a solvent. The present invention does not 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 lithium ion battery.

[0039] The positive electrode plate according to the present invention satisfies the formula (I), and a lithium ion battery manufactured using the positive electrode plate can ensure 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, the manufacturing method of the positive electrode plate, the lithium ion battery, and the EVTOL according to the present invention will be described below with reference to the following examples. However, the scope of protection of the present invention is not limited to the following examples.

[0041] <Example> 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 a predetermined ratio, and then NMP is added and stirred to form a uniform and stable positive electrode slurry. The positive electrode slurry is evenly coated on a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode plate. Here, the binder ratio is 1.1%, the conductive agent ratio 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, the conductive agent SP+CNTs, and the binder PAA+SBR are mixed in a predetermined ratio, and then deionized water is added and stirred to form a uniform and stable negative electrode slurry. The negative electrode slurry is then evenly coated on the negative electrode current collector, dried, and cold-pressed to obtain the negative electrode pieces. The main material of the negative electrode active material is a composite material made of graphite and silica, with a compaction density of 1.35 g / cm. 3 Here, the mass ratio of the negative electrode active material, SP, CNTs, PAA, and SBR was 95.4%:1.5%:0.1%:2%:1%. 3. Polypropylene film is used as the separator. 4. In the process of assembling the electrode body, the positive electrode plate, separator, and negative electrode plate are arranged in order and assembled by winding or laminating. 5. The electrolyte used was a mixture of ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate in a volume ratio of 1:1:1, with LiPF6 dissolved in it, and the concentration was 1.2 mol / L. 6. The electrolyte is injected into the dried electrode body, and the formation and aging are carried out to obtain a lithium-ion battery.

[0042] The manufactured batteries were subjected to performance testing, and the results are shown in Table 1.

[0043] [Table 1]

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

[0045] An energy density test and a DCR test were conducted on the lithium ion secondary batteries manufactured in Examples 1 to 20. The energy density was measured at 25°C and 1C. The DCR test conditions were 25°C, 50% SOC, and 30s discharge 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 relatively high levels. 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. With the increase in Ni content, the energy density of the electrode body continuously increases. However, when the molar ratio of 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 increasingly inferior. 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 its 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 its cycle performance and output performance have 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 ranges, 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 ranges, 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 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 satisfied the above ranges, and the electrode body showed excellent comprehensive performance.

[0049] Through 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. A positive electrode plate, a positive electrode current collector; and a coating layer provided on a surface of the positive electrode current collector, the coating layer contains a nickel-containing positive electrode active material and a conductive agent, The coating layer satisfies the relational expression shown in the following formula (I): A positive electrode substrate characterized by: 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 single-side areal density of the coating layer, expressed in mg / cm ２ It is.)

2. The range of the value of a×c / 100b is 3.35 to 4.

8. The positive electrode plate according to claim 1 .

3. a is 63%≦a≦92%; The positive electrode plate according to claim 1 .

4. b is 2.5%≦b≦4%; The positive electrode plate according to claim 1 .

5. c is 12≦c≦18; The positive electrode plate according to claim 1 .

6. the nickel-containing positive electrode active material is selected from one or a mixture of 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 .

7. The method for producing a positive electrode plate according to any one of claims 1 to 6, Mixing a nickel-containing positive electrode active material, a conductive agent, and an auxiliary to obtain a slurry; applying the slurry to a surface of a positive electrode current collector and drying the slurry to obtain a positive electrode plate; The coating layer of the positive electrode plate satisfies the relationship shown in formula (I), A method for manufacturing a positive electrode plate. 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 single-side areal density of the coating layer, expressed in mg / cm ２ It is.)

8. A lithium-ion battery, A battery comprising a positive electrode plate selected from the positive electrode plates according to any one of claims 1 to 6, a negative electrode plate, a separator, and an electrolyte solution. A lithium-ion battery characterized by:

9. 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 includes a negative electrode active material, the negative electrode active material being 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.

9. The lithium ion battery according to claim 8.

10. An EVTOL comprising the lithium ion battery of claim 9.

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