Positive electrode plate, lithium ion battery, and electric apparatus

Abstract

To provide a positive electrode plate capable of obtaining excellent DCR performance while ensuring energy density and cycle life of an electrode body in a manufactured lithium ion battery.SOLUTION: A positive electrode plate includes a positive electrode current collector and a coating layer coated on at least one surface of the positive electrode current collector perpendicular to a thickness direction. The coating layer includes a positive electrode active material and a conductive agent. The positive electrode active material includes a single-crystal ternary material and a polycrystalline ternary material. The coating layer satisfies a relation 0.39<106ab2 / c2<2 (I). In Formula (I), a is the mass fraction of the single-crystal ternary material in the positive electrode active material, b is the mass percent of the conductive agent in the coating layer, and c is the areal density of the coating layer, whose unit is mg / cm2.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to the technical field of lithium ion batteries, and more particularly to positive electrode plates, lithium ion batteries, and electrical devices. [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) aircraft 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) aircraft have become a technologically pursued goal. Currently, lithium-ion batteries are the optimal choice for EVTOL power. 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, providing lithium-ion batteries that can sustainably provide high power output while maintaining energy density and cycle life is 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 lithium ion battery, and an electrical device, and a lithium ion battery manufactured using the positive electrode plate according to the present invention can ensure the energy density and cycle life of the electrode body and can also achieve excellent DCR performance. [Means for solving the problem]

[0004] The present invention provides a positive electrode plate, comprising a positive electrode current collector and a coating layer applied to at least one surface of the positive electrode current collector perpendicular to the thickness direction, the coating layer containing a positive electrode active material and a conductive agent, the positive electrode active material containing a single-crystalline ternary material and a polycrystalline ternary material, and the coating layer satisfying the relational expression shown in formula (I) below: 0.39<10 6 ab 2 / c 2 <2 (I) In formula (I), a is the mass fraction of the single-crystal ternary material in the positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density of the coating layer, expressed in mg / cm. 2 is.

[0005] 10 6 ab 2 / c 2 The value of is preferably in the range of 0.59 to 1.41.

[0006] Preferably, a satisfies 10%≦a≦50%, and more preferably 15%≦a≦35%.

[0007] Preferably, b satisfies 2.5%≦b≦4%, and more preferably 2.6%≦b≦3.3%.

[0008] c is 12 mg / cm 2 ≦c≦18mg / cm 2 Preferably, it is 14 mg / cm 2 ≦c≦16mg / cm 2 It is more preferable that:

[0009] the 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 one of aluminum foil and carbon-coated aluminum foil.

[0010] The thickness of the coating layer is preferably 65 to 120 μm.

[0011] The present invention 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.

[0012] 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 1.3 to 1.65 g / cm. 3 and The negative electrode coating layer preferably contains a negative electrode active material selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, and silicon-based materials.

[0013] The present invention provides an electrical device including 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 coated on at least one surface of the positive electrode current collector perpendicular to a thickness direction, the coating layer including a positive electrode active material and a conductive agent, the positive electrode active material including a single-crystal ternary material and a polycrystalline ternary material, and the coating layer satisfies the relationship shown in formula (I): 0.39<10 6 ab 2 / c 2 <2. In formula (I), a is the mass fraction of the single crystal ternary material in the positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density of the coating layer, expressed in mg / cm 2 In the present invention, when the positive electrode plate satisfies the relational expression shown in formula (I), a lithium ion battery manufactured using the positive electrode plate can ensure the energy density and cycle life of the electrode body and can also obtain excellent DCR performance. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention provides a positive electrode plate, which includes a positive electrode current collector and a coating layer coated on at least one surface of the positive electrode current collector perpendicular to a thickness direction, the coating layer including a positive electrode active material and a conductive agent, the positive electrode active material including a single-crystal ternary material and a polycrystalline ternary material, and the coating layer satisfying a relational formula represented by the following formula (I): 0.39<10 6 ab 2 / c 2 <2 (I) In formula (I), a is the mass fraction of the single-crystal ternary material in the positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density of the coating layer, expressed in mg / cm. 2 is.

[0016] Preferably, a is 10%≦a≦50%, b is 2.5%≦b≦4%, and c is 12 mg / cm 2 ≦c≦18mg / cm 2 is.

[0017] The positive electrode plate according to the present invention includes a positive electrode current collector. The type of the positive electrode current collector is not particularly limited in the present invention, and any type of current collector known to those skilled in the art may be used, but the positive electrode current collector is preferably one of aluminum foil and carbon-coated aluminum foil.

[0018] The positive electrode plate according to the present invention further includes a coating layer coated on the surface of the positive electrode current collector, the coating layer including a positive electrode active material and a conductive agent.

[0019] The coating layer satisfies the relational expression shown in formula (I). 0.39<10 6 ab 2 / c 2 <2···Formula (I) The mass ratio of the single crystal ternary material in the positive electrode active material of the positive electrode plate, the surface density of the coating layer, and the ratio of the conductive agent in the coating layer all affect the energy density and output performance of the electrode body, but there are certain limits and correlations to these effects. 6 ab 2 / c 2By satisfying the relationship <2, we found that it is possible to simultaneously achieve high energy density, long cycle life, and excellent power performance, while avoiding the need for a large number of DOE experiments, thereby saving battery development time and costs.

[0020] 10 6 ab 2 / c 2 The value of is preferably taken from the range of 0.59 to 1.41, and may be, for example, 0.59, 0.60, 0.70, 0.80, 0.90, 1.00, 1.10, 1.20, 1.30, 1.40, 1.41, or any value between 0.59 and 1.41.

[0021] The mass proportion (a) of the single-crystal ternary material in the positive electrode active material in the coating layer is 10% to 50%, and may be, for example, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value between 10% and 50%, preferably 15% to 35%. The mass proportion (a) of the single-crystal ternary material is specifically the mass percentage of the single-crystal ternary material in the positive electrode active material relative to the total mass of the positive electrode active material. The positive electrode active material includes a single-crystal ternary material and a polycrystalline ternary material. The single-crystal ternary material is a material formed from a single crystal with a particle diameter of 2 to 6 μm, and the polycrystalline ternary material is a secondary particle formed by aggregation of primary particles with a particle diameter of 100 to 300 nm. Single-crystalline ternary materials have large particle sizes, small contact areas with the electrolyte, and relatively few side reactions between the material and the electrolyte, resulting in good cycle performance. However, the lithium ion migration distance within the single-crystalline ternary material is long and there are few active sites for electrochemical reactions, resulting in poor output performance. Polycrystalline ternary materials have small primary particle sizes, large specific surface areas, many active sites for electrochemical reactions, and short lithium ion migration distance within the material, resulting in good output performance. However, the large number of active sites increases the risk of side reactions, resulting in poor cycle performance. In the present invention, the ratio of single-crystalline ternary material to polycrystalline ternary material in the positive electrode can be controlled within a reasonable range to meet the requirements for output performance and cycle performance of the electrode assembly.

[0022] The mass percentage (b) of the conductive agent in the coating layer is 2.5% to 4%, for example, 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%, 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 power 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. Furthermore, the conductive agent in the positive electrode can improve the deterioration of conductivity caused by the expansion and phase transition of the electrode assembly during cycling, thereby improving the cycle performance of the electrode assembly. If the content of the conductive agent in the positive electrode is too high, electronic impedance is no longer a limiting factor for power. Therefore, even if the conductive agent content of the electrode assembly is further increased, the output performance of the electrode assembly cannot be significantly improved, and instead the energy density of the electrode assembly is reduced. If the content of the conductive agent in the coating layer is too low, this is advantageous for improving the energy density of the electrode assembly, but as the content of the conductive agent decreases, the electronic impedance increases, affecting the output performance of the electrode assembly. In the present invention, by controlling the mass percentage of the conductive agent in the coating layer within an appropriate range, the requirements for output performance, cycle performance, and energy density of the electrode assembly can be met.

[0023] The surface density c of the coating layer is 12 to 18 (unit: mg / cm 2), and may be, for example, 12, 13, 14, 14.5, 15, 15.5, 16, 17, 18, or any value between 12 and 18, with 14 to 16 being more preferred. During discharge of a lithium-ion battery, lithium ions are desorbed from the negative electrode material and inserted into the positive electrode active material, and the distance traveled by the lithium ions is related to the areal density. As the areal density increases, the proportion of auxiliary materials in the electrode body decreases, increasing the energy density of the electrode body. However, the lithium ion migration distance increases, resulting in a decrease in output performance. Furthermore, the electrode plate expands significantly, resulting in poor conductivity and poor cycle performance. If the areal density is too high, the lithium ion migration distance becomes a limiting factor in high-rate discharge of the electrode body, rapidly reducing the output performance of the electrode body. If the areal density is too low, the output performance of the electrode body improves, but the energy density of the electrode body decreases as the proportion of auxiliary materials in the electrode body increases. In the present invention, by controlling the surface density of the coating layer within an appropriate range, it is possible to satisfy the requirements for output performance, cycle performance and energy density of the electrode assembly.

[0024] In other words, the mass proportion of the single-crystalline ternary material in the positive electrode active material of the coating layer of the positive electrode plate, the proportion of the conductive agent, and the areal density all affect the energy density, cycle performance, and power performance of the electrode assembly. Increasing the proportion of the single-crystalline ternary material in the positive electrode active material reduces the number of reactive active sites of the single-crystalline ternary material, lowering the gram capacity and increasing the solid-state diffusion distance of lithium ions in the positive electrode active material, thereby improving the cycle performance of the battery but reducing the power performance and energy density. Increasing the content of the conductive agent within an appropriate range reduces the areal density, improving the electronic conductivity of the electrode plate and shortening the liquid-phase migration distance of lithium ions in the electrolyte, thereby improving the cycle performance and output performance of the electrode assembly. In light of this, the inventors have discovered that by adjusting these three parameters to complement each other and ensuring that the coating layer satisfies the relationship shown in formula (I), a lithium-ion battery can be made to have high energy density, high cycle performance, and excellent output performance.

[0025] In the present invention, the thickness of the coating layer is 65 to 120 μm.

[0026] In the present invention, the positive electrode active material in the positive electrode plate is selected from one or a mixture of two of lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide.

[0027] The present invention further provides a method for producing the above-mentioned positive electrode plate, the method comprising: mixing a positive electrode active material, a conductive agent, and an auxiliary agent 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). 0.39<10 6 ab 2 / c 2 <2···Formula (I) In formula (I), a is the mass fraction of the single-crystal ternary material in the positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density of the coating layer, expressed in mg / cm. 2 is.

[0028] Specifically, in the present invention, a positive electrode active material, a conductive agent, and an auxiliary agent are mixed to obtain a slurry, where the auxiliary agent is selected from a binder.

[0029] In this invention, a positive electrode active material, a conductive agent, and an auxiliary agent are dispersed in a solvent and stirred to form a uniformly mixed, stable positive electrode slurry. To ensure the energy density and cycle life of the electrode body and achieve excellent DCR performance, the mass percentage of the single-crystal ternary material of the positive electrode active material in the coating layer is controlled to satisfy 10%≦a≦50% and the mass percentage of the conductive agent in the coating layer is controlled to satisfy 2.5%≦b≦4%.

[0030] The positive electrode slurry is uniformly applied to a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode plate, where the solvent is preferably NMP.

[0031] In the present invention, when coating, the surface density of the resulting electrode plate is 12 mg / cm 2 ~18mg / cm 2 It is preferable to monitor the surface density of the coating in real time using a balance so that the range of (a) is satisfied.

[0032] The positive electrode plate manufactured by the above method has a resistance of 0.39<10 6 ab 2 / c 2 <2, thereby ensuring that the electrode body has high energy density, long cycle life and excellent power performance.

[0033] 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.

[0034] In the present invention, the method for producing a lithium ion battery includes: A positive electrode plate, a separator, a negative electrode plate, and a separator are stacked and wound or laminated to assemble an electrode body, and an electrolyte is injected into the dried electrode body to obtain a lithium ion secondary battery.

[0035] In the present invention, the manufacturing methods and materials of the separator, electrolyte and negative electrode plate are not particularly limited, 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.

[0036] Here, 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 has a compaction density of 1.3 to 1.65 g / cm. 3 For example, 1.30, 1.35, 1.4, 1.5, 1.6, 1.65, or 1.3 to 1.65 g / cm 3The 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-based materials. The current collector is preferably copper foil. Here, the process for producing a negative electrode plate includes mixing the negative electrode active material, conductive agent, and binder in a predetermined ratio, adding deionized water, and stirring to form a uniformly mixed and stable negative electrode slurry. The negative electrode slurry is then uniformly applied to a positive electrode current collector, and the mixture is dried and cold-pressed to obtain a negative electrode plate.

[0037] The separator is preferably made of a material such as a polyethylene film, a polypropylene film, a polyvinylidene fluoride film, or a nonwoven fabric.

[0038] 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. The lithium salt is preferably LiPF, LiTFSI, or LiBF.

[0039] The present invention further provides an electrical device comprising the lithium ion battery described above, which may be, for example, an EVTOL.

[0040] The positive electrode plate according to the present invention satisfies the relationship shown in 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 can also obtain excellent DCR performance.

[0041] In order to further understand the present invention, the positive electrode plate and lithium ion battery 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.

[0042] [Example 1] 1. In the manufacturing process of the positive electrode plate, the ternary positive electrode active material nickel cobalt manganese oxide (NCM), conductive agent SP, and binder PVDF are mixed in a predetermined ratio (1.1% binder, 3% conductive agent, and the remainder is the ternary positive electrode active material, with the mass ratio of the single crystal ternary material in the ternary positive electrode active material being 25%), and then NMP is added and stirred to form a uniformly mixed and stable positive electrode slurry. The positive electrode slurry is then uniformly coated on the positive electrode current collector, dried, and cold-pressed to obtain a positive electrode plate. The areal density of the positive electrode plate is 15 g / cm. 2 is. 2. In the process of manufacturing the negative electrode plate, the negative electrode active material, conductive agent, and binder are mixed in a predetermined ratio (the mass ratio of the negative electrode active material, SP, CNT, PAA, and SBR is 95.4%:1.5%:0.1%:2%:1%), and then deionized water is added and stirred to form a uniformly mixed, 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 plate. The negative electrode active material is a composite material made of graphite and silicon oxide, with a compaction density of 1.35 g / cm. 3 is. 3. Polypropylene film is used as the separator. 4. In the process of assembling the electrode body, the positive electrode plate, separator, negative electrode plate, and separator are arranged in order, and then wound to assemble the electrode body. 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 poured into the dried electrode body, and the resulting lithium-ion battery is formed and aged.

[0043] [Example 2] The lithium ion battery of Example 2 is manufactured according to the manufacturing method of Example 1, except that the mass ratio of the single crystal ternary material in the ternary positive electrode active material is 10% during the manufacturing process of the positive electrode plate.

[0044] [Example 3] The lithium ion battery of Example 3 is manufactured according to the manufacturing method of Example 1, except that the mass ratio of the single crystal ternary material in the ternary positive electrode active material is 15% during the manufacturing process of the positive electrode plate.

[0045] [Example 4] The lithium ion battery of Example 4 is manufactured according to the manufacturing method of Example 1, except that the mass ratio of the single crystal ternary material in the ternary positive electrode active material is 35% during the manufacturing process of the positive electrode plate.

[0046] [Example 5] The lithium ion battery of Example 5 is manufactured according to the manufacturing method of Example 1, except that the proportion of the conductive agent is 2.50% in the manufacturing process of the positive electrode plate.

[0047] [Example 6] The lithium ion battery of Example 6 is manufactured according to the manufacturing method of Example 1, except that the proportion of the conductive agent is 2.60% in the manufacturing process of the positive electrode plate.

[0048] [Example 7] The lithium ion battery of Example 7 is manufactured according to the manufacturing method of Example 1, except that the proportion of the conductive agent is 3.30% in the manufacturing process of the positive electrode plate.

[0049] [Example 8] The lithium ion battery of Example 8 was manufactured according to the manufacturing method of Example 1, except that the proportion of the conductive agent was 4.00% in the manufacturing process of the positive electrode plate.

[0050] [Example 9] The lithium ion battery of Example 9 was manufactured according to the manufacturing method of Example 1, except that the surface density of the positive electrode plate was increased to 12 g / cm. 2 is.

[0051] [Example 10] The lithium ion battery of Example 10 was manufactured according to the manufacturing method of Example 1, except that the surface density of the positive electrode plate was increased to 14 g / cm. 2 is.

[0052] [Example 11] The lithium ion battery of Example 11 was manufactured according to the manufacturing method of Example 1, except that the surface density of the positive electrode plate was increased to 16 g / cm. 2 is.

[0053] [Example 12] The lithium ion battery of Example 12 was manufactured according to the manufacturing method of Example 1, except that the surface density of the positive electrode plate was increased to 18 g / cm. 2 is.

[0054] [Comparative Example 1] The lithium ion battery of Comparative Example 1 was manufactured according to the manufacturing method of Example 1, except that the mass proportion of the single crystal ternary material in the ternary positive electrode active material was 5% during the manufacturing process of the positive electrode plate.

[0055] Comparative Example 2 The lithium ion battery of Comparative Example 2 is manufactured according to the manufacturing method of Example 1, except that the mass ratio of the single crystal ternary material in the ternary positive electrode active material is 50% during the manufacturing process of the positive electrode plate.

[0056] Comparative Example 3 The lithium ion battery of Comparative Example 3 was manufactured according to the manufacturing method of Example 1, except that the mass ratio of the single crystal ternary material in the ternary positive electrode active material was 75% during the manufacturing process of the positive electrode plate.

[0057] Comparative Example 4 The lithium ion battery of Comparative Example 4 was manufactured according to the manufacturing method of Example 1, except that the proportion of the conductive agent was 1.50% in the manufacturing process of the positive electrode plate.

[0058] Comparative Example 5 The lithium ion battery of Comparative Example 5 was manufactured according to the manufacturing method of Example 1, except that the proportion of the conductive agent was 4.50% in the manufacturing process of the positive electrode plate.

[0059] Comparative Example 6 The lithium ion battery of Comparative Example 6 was manufactured according to the manufacturing method of Example 1, except that the surface density of the positive electrode plate was 10 g / cm 2 is.

[0060] Comparative Example 7 The lithium ion battery of Comparative Example 7 was manufactured according to the manufacturing method of Example 1, except that the surface density of the positive electrode plate was increased to 20 g / cm. 2 is.

[0061] The manufactured batteries were subjected to performance tests, and the results are shown in Table 1.

[0062] [Table 1]

[0063] In the cycle life test, the battery was first charged at a constant current of 1 C to 4.25 V at 25°C, then further charged at a constant voltage of 4.25 V until the current I≦0.05 C, allowed to stand for 30 min, and then discharged at a constant current of 1 C to 2.5 V, allowed to stand for 30 min. The initial 1C discharge capacity of the battery was determined and recorded as C0. The above process was repeated until the discharge capacity decayed to 80% of the initial discharge capacity C0, and the number of repeated cycles was recorded.

[0064] The lithium ion secondary batteries manufactured in Examples 1 to 12 and Comparative Examples 1 to 7 were subjected to an energy density test and a DCR test. The energy density test process involved charging at a constant current and voltage of 1C at 25°C until the battery voltage reached 4.25V, then discharging at 1C until the battery voltage reached 2.5V at a final current of 0.05C. Energy density = discharge energy / electrode mass. In the DCR test process, the electrode body was adjusted to 50% SOC at 25°C, left to stand for 1 hour, and then discharged at a constant current of 2 C for 30 seconds. DCR = voltage difference before and after discharge / discharge current.

[0065] As can be seen from Table 1, in Example 1, the mass ratio of the single crystal ternary material in the active material, the ratio of the conductive agent, the areal density and 10 6 ab 2 / c 2 are all within the ranges specified in the present invention, and the resulting batteries have excellent energy density, cycle life, and DCR. Examples 1 to 4 and Comparative Examples 1 and 2 compare the effect of the mass proportion of the single-crystal ternary material in the ternary material on the performance of the electrode assembly. In Examples 1 to 4 and Comparative Examples 1 and 2, the mass proportion of the single-crystal ternary material in the positive electrode active material is successively increased, and as the proportion of the single crystal in the ternary material increases, the energy density of the electrode assembly gradually decreases and the DCR of the electrode assembly gradually increases, but the cycle performance of the electrode assembly gradually improves. In Comparative Example 1, 0.39<10 6 ab 2 / c 2 <2) and the mass ratio of the single crystal ternary material in the active material is low, the resulting battery is excellent in both energy density and power performance, but is poor in cycle life performance. 6 ab 2 / c 2 <2, and the obtained battery had good cycle performance, but the energy density was low and, in particular, the output performance was significantly deteriorated. 6 ab 2 / c 2 <2 and the mass ratio of the single crystal ternary material in the active material was high, and the obtained battery had good cycle characteristics, but the energy density was low and the power performance was significantly deteriorated. 6 ab 2 / c 2 <2, indicating relatively good overall performance.

[0066] Examples 5 to 8 and Comparative Examples 4 to 5 compare the effect of the content of the conductive agent in the electrode plate on the performance of the electrode assembly. In Examples 5 to 8 and Comparative Examples 4 to 5, the content of the conductive agent gradually increases, the cycle performance gradually improves, and the DCR gradually decreases. However, once the amount of conductive agent reaches a certain level, it was discovered that further increasing the amount of conductive agent does not contribute to further improvement of the cycle performance of the electrode assembly or further decrease of the DCR. Here, in Examples 5 to 8, 0.39<10 6 ab 2 / c 2 <2, and the mass proportion of the single crystal ternary material in the active material, the proportion of the conductive agent, and the areal density all met the required ranges, so the electrode exhibited excellent overall performance.

[0067] Examples 9 to 12 and Comparative Examples 6 to 7 compare the effect of the surface density of the electrode plate on the performance of the electrode assembly. In Examples 9 to 12 and Comparative Examples 6 to 7, the surface density gradually increases, and the energy density gradually improves, but the output performance and cycle performance gradually decrease. In Comparative Example 6, the surface density is too low, and the cycle performance and output performance are excellent, but the energy density is too low. In Comparative Example 7, the surface density is too high, and the cycle performance is poor. Here, in Examples 9 to 12, 0.39<10 6 ab 2 / c 2 <2, and the mass proportion of the single crystal ternary material in the active material, the proportion of the conductive agent, and the areal density all meet the required ranges, so the electrode body has excellent comprehensive performance.

[0068] From the analysis of the above example, it was found that the mass ratio of the single crystal ternary material in the positive electrode active material, the content of the conductive agent, and the areal density were 0.39<10 6 ab 2 / c 2 <2, a satisfies 10%≦a≦50%, b satisfies 2.5%≦b≦4%, and c satisfies 12 mg / cm 2 ≦c≦18mg / cm 2 When the above condition is satisfied, the electrode assembly has excellent overall performance.

[0069] It should be noted that the above content is merely a preferred embodiment of the present invention, and those skilled in the art may make some improvements and adjustments without departing from the principles of the present invention, and these improvements and adjustments should also be considered as within the protection scope of the present invention.

Claims

1. A positive electrode plate, a positive electrode current collector; and a coating layer applied to at least one surface of the positive electrode current collector perpendicular to a thickness direction, the coating layer contains a positive electrode active material and a conductive agent, the positive electrode active material contains a single-crystal ternary material and a polycrystalline ternary material, and the coating layer satisfies a relational formula represented by the following formula (I): A positive electrode plate characterized by: 0.39<10 ６ ab ２ / c ２ <2・・・(I) (In formula (I), a is the mass proportion of the single-crystal ternary material in the positive electrode active material, b is the mass percentage of the conductive agent in the coating layer, and c is the areal density of the coating layer, expressed in mg / cm ２ It is.)

2. 10 ６ ab ２ / c ２ The range of values ​​is 0.59 to 1.

41. The positive electrode plate according to claim 1 .

3. a is 10%≦a≦50%, preferably 15%≦a≦35%; The positive electrode plate according to claim 1 .

4. b is 2.5%≦b≦4%, preferably 2.6%≦b≦3.3%; The positive electrode plate according to claim 1 .

5. c is 12 mg / cm ２ ≦c≦18mg / cm ２ and preferably 14 mg / cm ２ ≦c≦16mg / cm ２ That is, The positive electrode plate according to claim 1 .

6. the 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 one of aluminum foil and carbon-coated aluminum foil. The positive electrode plate according to claim 1 .

7. The thickness of the coating layer is 65 to 120 μm. The positive electrode plate according to claim 1 .

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 7, 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, and the negative electrode coating layer has a compaction density of 1.3 to 1.65 g / cm ３ and 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; 9. The lithium ion battery according to claim 8.

10. An electrical device comprising the lithium ion battery according to claim 8.

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