Positive electrode plate and lithium-ion battery

Abstract

To provide a positive electrode polar plate capable of providing a high energy density and an excellent DCR performance to a lithium battery at the same time.SOLUTION: A positive electrode polar plate contains a positive electrode collector; and a positive electrode active material layer provided to the positive electrode collector. In that, a that is a pressure density of the positive electrode active material layer is 2.9≤a≤3.5; a unit is g / cm3; b that is a surface density of the positive electrode active material layer is 0.012≤b≤0.018; a unit is g / cm2; c that is a mass percentage of a conductive agent in the positive electrode active material layer is 2.4%≤c≤4.4%; and the positive electrode active material layer satisfies a formula of 3.3<a2*b / c<5.5. In the case where the positive electrode polar plate satisfies the above condition, a lithium battery manufactured from the positive electrode polar plate can have a DCR performance as well as secures an energy density of a cell, and thus, can avoid many DOE experiments. The research and development time and cost of the lithium battery can be effectively saved.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to the technical field of batteries, and in particular to positive electrode plates and lithium ion batteries. [Background technology]

[0002] With the development of modern society and advances in science and technology, automobiles have gradually become 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 increase year by year, electric-powered 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 EVTOL, lithium-ion batteries are required to combine high energy density, high power output, and long life.

[0003] In light of this, providing lithium-ion batteries that can maintain energy density and provide sustained high output is a requirement for promoting the development of the aircraft industry. Summary of the Invention [Problem to be solved by the invention]

[0004] The technical problem to be solved by the present invention is to provide a positive electrode plate and a lithium ion battery, and to provide a lithium battery including the positive electrode plate with high energy density and excellent DCR performance by controlling the areal density, compaction density, and conductive agent content of the positive electrode active material layer on the surface of the positive electrode plate. [Means for solving the problem]

[0005] In order to solve the above problems, the present invention provides the following technical solutions.

[0006] A first aspect of the present invention is a positive electrode plate, a positive electrode current collector; a positive electrode active material layer provided on the positive electrode current collector, The compaction density a of the positive electrode active material layer is 2.9≦a≦3.5, and the unit is g / cm 3 and b, which is the areal density of the positive electrode active material layer, is 0.012≦b≦0.018, and the unit is g / cm 2 wherein c, which is the mass percentage of the conductive agent in the positive electrode active material layer, is 2.4%≦c≦4.4%; The positive electrode active material layer is 3.3 2 ×b / c<5.5 A positive electrode plate is provided.

[0007] Furthermore, the compaction density of the positive electrode active material layer is more preferably 3.1≦a≦3.3.

[0008] Furthermore, the areal density of the positive electrode active material layer is more preferably 0.014≦b≦0.016.

[0009] Furthermore, the mass percentage of the conductive agent in the positive electrode active material layer is more preferably 3%≦c≦4%.

[0010] Furthermore, the positive electrode active material layer has a thickness of 3.35 2 It is more preferable that the formula ×b / c<5 is satisfied.

[0011] Furthermore, the conductive agent in the positive electrode active material layer is conductive carbon black.

[0012] Furthermore, the positive electrode current collector is preferably an aluminum foil or a carbon-coated aluminum foil.

[0013] Furthermore, the positive electrode active material contained in the positive electrode active material layer may be one or more selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0014] ​​Furthermore, the positive electrode plate can be manufactured by a wet coating method, which specifically includes: uniformly mixing a positive electrode active material, a conductive agent, a binder, and a solvent to obtain a positive electrode slurry; and uniformly applying the prepared positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it to obtain the positive electrode plate.

[0015] A second aspect of the present invention provides a lithium ion battery comprising the positive electrode plate according to the first aspect.

[0016] The lithium ion battery further includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer has a compaction density of 1.35 g / cm. 3 and the areal density of the negative electrode active material layer is preferably 0.0058 g / cm 2 and the mass percentage of the conductive agent in the negative electrode active material layer is preferably 1.6%. [Effects of the Invention]

[0017] Compared with the prior art, the technical advantages of the present invention are as follows: The present invention provides a positive electrode plate, and the values ​​of the compaction density a, areal density b, and mass percentage c of the conductive material layer in the positive electrode plate are reasonably controlled, and the three are within the range of 3.3. 2 By satisfying the specific relational expression of ×b / c<5.5, a lithium ion battery including the positive electrode plate can have both high energy density and high output performance. DETAILED DESCRIPTION OF THE INVENTION

[0018] ​Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms used herein are only for describing specific examples and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the associated items listed. "Comprise" or "contain" as used herein means that other components may be included in addition to the component(s). "Comprise" or "contain" as used herein may be replaced with the closed form "is" or "consisting of."

[0019] As described in the background art, in order to promote the development of the aircraft industry, there is a demand for lithium-ion batteries that can maintain energy density and provide sustained high power output.

[0020] In order to solve the above technical problems, an embodiment of the present invention provides a positive electrode plate including a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector.

[0021] Here, the compaction density a of the positive electrode active material layer is 2.9≦a≦3.5, and the unit is g / cm 3 The areal density b of the positive electrode active material layer is 0.012≦b≦0.018, and the unit is g / cm 2 The mass percentage c of the conductive agent in the positive electrode active material layer is 2.4%≦c≦4.4%. 2 ×b / c<5.5.

[0022] Specifically, the inventors discovered that the compaction density, areal density, and mass ratio of the conductive agent of the positive electrode active material layer in the positive electrode plate affect the energy density and output performance of the cell, but that the influence has certain limits and correlations.

[0023] ​During discharge, lithium ions are released from the negative electrode material and inserted into the positive electrode material. The process of lithium ion insertion into the positive electrode is related to the packing density, and a packing density that is too high or too low affects the battery's rate performance. When the packing density is too high, the distance between the raw material particles decreases, resulting in closer contact and correspondingly improved electronic conductivity. However, the liquid absorption capacity of the positive electrode active material layer decreases with increasing packing density, and the ion migration paths are correspondingly reduced or blocked, which is unfavorable for the rapid migration of large amounts of ions. As a result, ion diffusion resistance increases, which limits high-current discharge, reduces discharge voltage, and reduces discharge capacity. When the packing density is too low, the distance between the raw material particles increases, which strengthens the positive electrode active layer's absorption capacity for the electrolyte and correspondingly increases the ion paths, which is favorable for rapid ion migration. However, the contact probability and contact area between particles decrease with decreasing packing density, which is unfavorable for electron conduction. As a result, the electronic resistance increases, which affects the large current discharge and increases the discharge polarization. In view of this, the inventors have determined that the compaction density of the positive electrode active material layer is set within an appropriate range, i.e., 2.9≦a≦3.5, and the unit is g / cm. 3 By controlling the temperature within a certain range, it was discovered that the ion migration paths are not blocked and sufficient contact can be achieved between the raw material particles, ensuring both good conductivity and rapid ion migration capability during large current discharge, thereby reducing discharge polarization.

[0024] In some preferred embodiments, the range of the value of the compaction density of the positive electrode active material layer is more preferably 3.1≦a≦3.3, and for example, a may be 3.1, 3.12, 3.13, 3.14, 3.15, 3.16, 3.17, 3.18, 3.19, 3.2, 3.25, 3.3, etc., including but not limited to the above values.

[0025] Furthermore, in the embodiments of the present invention, when a lithium-ion battery is discharged, lithium ions are desorbed from the negative electrode material and inserted into the positive electrode material, and the distance traveled by the lithium ions is related to the areal density. If the areal density is too high, the distance traveled by the lithium ions increases with an increase in areal density, and the ion diffusion resistance increases accordingly, resulting in a decrease in the output performance of the cell. If the areal density is too low, the output performance of the cell improves, but the energy density of the cell decreases as the proportion of the cell auxiliary material increases. In view of this, the inventors have determined that the areal density of the positive electrode active material layer should be set within an appropriate range, i.e., 0.012≦b≦0.018, and the unit is g / cm. 2 It has been discovered that by controlling the temperature within a certain range, it is possible to ensure that the lithium-ion battery has both good power performance and high energy density.

[0026] In some preferred embodiments, the range of the areal density of the positive electrode active material layer is more preferably 0.014≦b≦0.016, where b is, for example, 0.014, 0.0142, 0.0143, 0.0144, 0.0145, 0.0146, 0.0147, 0.0148, 0.0149, 0.015, 0.155, 0.016, etc., including but not limited to the above values.

[0027] In the present invention, the content of the conductive agent in the positive electrode active material layer directly affects the electronic impedance of the positive electrode plate and the energy density of the battery. If the content of the conductive agent in the positive electrode active material layer is too high, the electronic impedance of the positive electrode plate decreases, which is beneficial for improving the cell's output performance. However, as the content of the conductive agent increases, the proportion of the positive electrode active material in the positive electrode active material layer decreases accordingly, which affects the cell's energy density. If the content of the conductive agent in the positive electrode active material layer is too low, which is beneficial for improving the cell's energy density, the electronic impedance increases as the content of the conductive agent decreases, which affects the cell's output performance. In light of this, the inventors discovered that by controlling the mass percentage of the conductive agent in the positive electrode active material layer within an appropriate range, i.e., 2.4%≦c≦4.4%, a lithium-ion battery can have high energy density and excellent output performance.

[0028] In some preferred embodiments, the range of the mass percentage of the conductive agent in the positive electrode active material layer is more preferably 3%≦c≦4%, where c is, for example, 3.1%, 3.13%, 3.16%, 3.18%, 3.2%, 3.22%, 3.24%, 3.26%, 3.28%, 3.3%, 3.4%, 3.5%, 3.6%, 3.7%, 3.8%, 3.9%, etc., including but not limited to the above values.

[0029] By optimizing the compaction density, areal density, or mass ratio of the conductive agent in the positive electrode active material layer, the energy density or output performance of the lithium ion battery can be improved to some extent, but each factor has a significant limit in terms of improving both the energy density and output performance. The inventors have found that the above parameters are within appropriate value ranges and 3.3 2 It was found that unless the formula b / c<5.5 is satisfied, a lithium-ion battery including the positive electrode plate can not achieve both high energy density and high output performance. 2 The formula ×b / c<5.5 was obtained as follows: (1) The logical positive / negative correlation between the magnitude of each factor and the cell energy density and power performance was examined. For example, within the preferred ranges of a and b, as the values ​​increase, the corresponding cell's energy density increases and power performance decreases (the DCR value increases). Meanwhile, as the value of c increases (within the preferred range), the cell's energy density decreases and power performance improves (the DCR value decreases). (2) Given that the logical positive / negative correlation between the magnitude of each factor and the cell's energy density and power performance is known, the formula was constructed by determining the power (e.g., squared or cubed) of each factor based on the importance of the impact of the value of each factor on cell performance. (3) The formula was adjusted based on experimental data obtained through a 100% survey to obtain the preferred range of the formula.

[0030] In some preferred embodiments, the positive electrode active material layer has a thickness of 3.35 2 It is more preferable that the formula b / c<5 is satisfied. For example, 2 ​​​The value of ×b / c may be in the range of 3.5 to 4.0, 4.0 to 4.3, 4.3 to 4.5, or 4.5 to 5.0.

[0031] In some preferred embodiments, the conductive agent in the positive electrode active material layer is conductive carbon black (SP).

[0032] In some preferred embodiments, the positive electrode current collector is preferably aluminum foil or carbon-coated aluminum foil.

[0033] In some preferred embodiments, the positive electrode active material contained in the positive electrode active material layer is preferably one or more selected from lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide, and is more preferably an NCM-based or NCA6-based positive electrode active material, for example, an NCM8-based positive electrode active material LiNi 0.83 Co 0.12 Mn 0.05 O2 is more preferred.

[0034] An embodiment of the present invention further provides a method for manufacturing the above-mentioned positive electrode plate, the method comprising: uniformly mixing a positive electrode active material, a conductive agent, a binder, and a solvent to obtain a positive electrode slurry; and uniformly applying the prepared positive electrode slurry onto a positive electrode current collector, drying it, and cold pressing it to obtain the positive electrode plate.

[0035] In some preferred embodiments, the binder may be one or more of polyacrylic acid, polyvinylidene fluoride, polyvinylidene difluoride, carboxymethyl cellulose, and styrene butadiene latex, and the solvent may be N-methylpyrrolidone (NMP).

[0036] An embodiment of the present invention further provides a lithium ion battery including the positive electrode plate.

[0037] Specifically, a lithium-ion battery includes a case, a positive electrode plate, a separator, a negative electrode plate, and an electrolyte. The positive electrode plate, the separator, and the negative electrode plate are stacked and laminated or wound to form a bare cell, and the tabs are ultrasonically welded. The bare cell is placed in a case, dried to remove moisture, and then the electrolyte is injected and sealed to obtain a battery.

[0038] In some preferred embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, where the negative electrode current collector may be a copper foil.

[0039] In some preferred embodiments, the negative electrode active material layer has a compacted density of 1.35 g / cm 3 The surface density of the negative electrode active material layer is preferably 0.0058 g / cm 2 The mass percentage of the conductive agent in the negative electrode active material layer is preferably 1.6%.

[0040] In some preferred embodiments, the negative electrode active material contained in the negative electrode active material layer may be one or more selected from graphite, soft carbon, hard carbon, mesocarbon microbeads, and silicon materials. However, the present invention is not limited to these materials, and other well-known negative electrode active materials for lithium ion batteries may also be used.

[0041] In some preferred embodiments, the separator may be a polypropylene film, or other separator materials available for lithium-ion batteries. The electrolyte includes a lithium salt and a solvent. The lithium salt may be LiPF6, LiBF4, LiTFSI, or the like. The solvent may be a mixed solvent of several selected from ethylene carbonate, propylene carbonate, butylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate, for example, a mixed solvent in which ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate are mixed in a volume ratio of 1:1:1.

[0042] The present invention will be further described below with reference to examples so that those skilled in the art can better understand and practice the present invention, but the listed examples are not intended to limit the present invention.

[0043] Example 1 This embodiment relates to the manufacture of a lithium ion battery, and specifically includes the following steps: (1) Manufacturing of positive electrode plate: Positive electrode active material LiNi 0.83 Co 0.12 Mn 0.05 O2, conductive agent SP, and binder PVDF are mixed in a mass ratio of 95.5:3.5:1, and NMP is added and stirred to obtain a homogeneously mixed positive electrode slurry. The positive electrode slurry is uniformly applied to a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode plate. The positive electrode active material layer formed by the positive electrode slurry on the surface of the positive electrode plate has a compaction density of 3.2 g / cm. 3 and the surface density is 0.015 g / cm 2 is. (2) Manufacturing of negative electrode plate: Graphite and silicon oxide (SiO x A negative electrode active material in which SP and CNT are mixed in a mass ratio of 81:19, a conductive agent in which SP and CNT are mixed in a mass ratio of 82:3, and a binder in which PAA and SBR are mixed in a mass ratio of 2:1 are mixed in a mass ratio of 95.1:1.6:3.3, and deionized water is added and stirred to obtain a homogeneously mixed negative electrode slurry. The negative electrode slurry is applied to a negative electrode current collector, dried, and cold-pressed to obtain a negative electrode plate. The negative electrode active material layer formed by the negative electrode slurry on the surface of the negative electrode plate has a compaction density of 1.35 g / cm. 3 and the surface density is 0.0058 g / cm 2 is. (3) Separator: A polyethylene film with a porosity of 45% is used. (4) Electrolyte: Ethylene carbonate, methyl ethyl carbonate, and diethyl carbonate are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and lithium salt LiPF6 is added to obtain an electrolyte with a LiPF6 concentration of 1.2 mol / L. (5) Assembly of lithium-ion battery: Positive electrode plate, separator, and negative electrode plate are stacked and wound to form a bare cell. The bare cell is placed in an outer case, dried, and then an electrolyte is injected. After vacuum sealing, standing, formation, shaping, and other processes, a lithium-ion battery is obtained.

[0044] <Example 2> This embodiment differs from Example 1 in the manufacture of the lithium ion battery only in the manufacture of the positive electrode plate, and everything else is the same. The manufacture of the positive electrode plate is specifically as follows. Cathode active material LiNi 0.83 Co 0.12 Mn 0.05 O2, conductive agent SP, and binder PVDF were mixed in a mass ratio of 95.6:3.4:1, and NMP was added and stirred to obtain a uniformly mixed positive electrode slurry. The positive electrode slurry was uniformly applied to a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode plate. The positive electrode active material layer formed by the positive electrode slurry on the surface of the positive electrode plate had a compaction density of 3.3 g / cm. 3 and the surface density is 0.014 g / cm 2 is.

[0045] Example 3 This embodiment differs from Example 1 in the manufacture of the lithium ion battery only in the manufacture of the positive electrode plate, and everything else is the same. The manufacture of the positive electrode plate is specifically as follows. Cathode active material LiNi 0.83 Co 0.12 Mn 0.05 O2, conductive agent SP, and binder PVDF were mixed in a mass ratio of 95.4:3.6:1, and NMP was added and stirred to obtain a uniformly mixed positive electrode slurry. The positive electrode slurry was uniformly applied to a positive electrode current collector, dried, and cold-pressed to obtain a positive electrode plate. The positive electrode active material layer formed by the positive electrode slurry on the surface of the positive electrode plate had a compaction density of 3.1 g / cm. 3 and the surface density is 0.016 g / cm 2 is.

[0046] Example 4 This example relates to the manufacture of a lithium ion battery, and the compaction density of the positive electrode active material layer is 2.9 g / cm 3 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0047] <Example 5> This example relates to the manufacture of a lithium ion battery, and the compaction density of the positive electrode active material layer is 3.5 g / cm 3 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0048] Example 6 This example relates to the manufacture of a lithium ion battery, and is performed in a manner that the areal density of the positive electrode active material layer is 0.012 g / cm 2 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0049] Example 7 This example relates to the manufacture of a lithium ion battery, and is based on a positive electrode active material layer having an areal density of 0.018 g / cm. 2 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0050] Example 8 This example differs from Example 1 in that the mass ratio of the conductive agent in the positive electrode active material layer is 4% in the production of the lithium ion battery, and all other procedures are the same.

[0051] Example 9 This example differs from Example 1 in that the mass ratio of the conductive agent in the positive electrode active material layer is 4.4% in the production of the lithium ion battery, and all other procedures are the same.

[0052] <Comparative Example 1> This comparative example relates to the manufacture of a lithium ion battery, and is based on a positive electrode active material layer having a compaction density of 2.4 g / cm 3 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0053] <Comparative Example 2> This comparative example relates to the manufacture of a lithium ion battery, and the compaction density of the positive electrode active material layer is 3.6 g / cm 3 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0054] <Comparative Example 3> This comparative example relates to the manufacture of a lithium ion battery, and is based on a positive electrode active material layer having an areal density of 0.01 g / cm 2 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0055] <Comparative Example 4> This comparative example relates to the manufacture of a lithium ion battery, and is based on a positive electrode active material layer having an areal density of 0.02 g / cm 2 This embodiment differs from the first embodiment only in that point, and everything else is the same.

[0056] <Comparative Example 5> This comparative example differs from Example 1 in that the mass ratio of the conductive agent in the positive electrode active material layer is 2% in the production of the lithium ion battery, and all other procedures are the same.

[0057] <Comparative Example 6> This comparative example differs from Example 1 in that the mass ratio of the conductive agent in the positive electrode active material layer is 5.5% with respect to the production of the lithium ion battery, and all other procedures are the same.

[0058] <Comparative Example 7> This comparative example differs from Example 1 in that the mass ratio of the conductive agent in the positive electrode active material layer is 2.4% in the production of the lithium ion battery, and all other procedures are the same.

[0059] <Performance test> The energy density and DCR performance of the lithium ion batteries prepared in the above examples and comparative examples were tested, and the specific procedures are as follows:

[0060] Energy density test: At 25°C, the lithium ion batteries prepared in the examples and comparative examples are fully charged at a rate of 1C, and then fully discharged at a rate of 1C, and the actual discharge energy is recorded. The ratio of the actual discharge energy to the weight of the lithium ion battery (weighed at 25°C) is the actual energy density of the lithium ion battery.

[0061] DCR performance test: At 25°C, the lithium-ion batteries manufactured in the examples and comparative examples were fully charged at a constant current and voltage of 1C, left for 5 minutes, then discharged at a constant current of 1C for 30 minutes, left to stand for 5 minutes, and the voltage value V1 at the end of the standing period was recorded. A 30-second pulse discharge was performed at 2C, and the voltage value V2 at the end of the pulse discharge was recorded. The ratio of the voltage difference between V1 and V2 to the 2C current value was the DCR of the battery at 50% SOC discharge.

[0062] The results of the above performance tests are shown in Table 1 below.

[0063] [Table 1]

[0064] As can be seen from the comparison of the data of Examples 1 to 9 and Comparative Examples 1 to 7 in the above table, the compaction density of the positive electrode active material layer in the positive electrode plate is controlled between 2.9 and 3.5, the areal density is controlled between 0.012 and 0.018, the mass ratio of the conductive agent is controlled between 2.4% and 4.4%, and the above parameters are controlled between 3.3 and 4.4%. 2 When the relationship ×b / c<5.5 is satisfied, a lithium ion battery manufactured from the positive electrode plate has both high energy density and excellent DCR performance (i.e., excellent power performance).

[0065] As can be seen from Example 1 and Comparative Examples 1 and 2, either a too low (Comparative Example 1) or too high (Comparative Example 2) compaction density affects the DCR performance of the lithium ion battery, and the formula a 2 The value calculated by ×b / c is not within the range of 3.3 to 5.5, and the overall performance of the battery is inferior.

[0066] ​As can be seen from Example 1 and Comparative Examples 3 and 4, an areal density that is too low (Comparative Example 3) or too high (Comparative Example 4) affects the energy density and DCR performance of a lithium-ion battery. If the areal density is too low, the DCR value is small, i.e., the battery has good output performance, but the battery's energy density is low, down to 239 Wh / Kg. If the areal density is too high, the battery's energy density is significantly improved, but the DCR value is too high, resulting in poor output performance. In addition, if the battery's energy density is too low or the DCR value is too high, the battery's overall performance is poor. In this case, the formula a 2 The value calculated by ×b / c does not fall within the range of 3.3 to 5.5.

[0067] As can be seen from Example 1 and Comparative Examples 5 and 6, a too low (Comparative Example 5) or too high (Comparative Example 6) mass fraction of the conductive agent in the positive electrode active material layer affects the energy density and DCR performance of the lithium-ion battery. If the mass fraction of the conductive agent in the positive electrode active material layer is too low, the battery has a high energy density, but the DCR value is large and the output performance is correspondingly poor. If the mass fraction of the conductive agent in the positive electrode active material layer is too high, the DCR value is significantly reduced, which is advantageous for improving the output performance of the battery, but the energy density is low.

[0068] As can be seen from Comparative Example 7, the compaction density, areal density and conductive agent content of the positive electrode plate are all within the preferred ranges, but 2 The calculated value of ×b / c was 6.40, which is not within the preferred range. Although the battery manufactured from this positive electrode plate has a high energy density, the DCR value of the battery is too high, resulting in relatively poor overall performance. Meanwhile, it is difficult in the battery field to further reduce the DCR value while maintaining the same energy density.

[0069] The compaction density of the positive electrode active material layer in the positive electrode plate is controlled to be between 3.1 and 3.3, the areal density is controlled to be between 0.014 and 0.016, the mass ratio of the conductive agent is controlled to be between 3% and 4%, and the above parameters are controlled to be between 3.35 and 3.35. 2 ​When the relational expression ×b / c<5 is satisfied, for example, Examples 1, 2, 3, and 8 can achieve both a relatively high energy density and a low DCR value, and have better overall performance.

[0070] As can be seen from the above, the compaction density, areal density, and mass ratio of the conductive agent of the positive electrode active material layer in the positive electrode plate are all optimized, and the above parameters are 3.3 2 By satisfying the formula ×b / c<5.5, a lithium ion battery including the positive electrode plate has both high energy density and high output performance.

[0071] The above embodiments are merely preferred embodiments enumerated to fully explain the present invention, and the scope of protection of the present invention is not limited thereto. Those skilled in the art will recognize that any equivalent substitution or conversion made based on the present invention falls within the scope of protection of the present invention. The scope of protection of the present invention is governed by the claims.​

Claims

1. A positive electrode plate, a positive electrode current collector; a positive electrode active material layer provided on the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, the positive electrode active material being LiNi ０．８３ Co ０．１２ Mn ０．０５ O ２ and The compaction density a of the positive electrode active material layer is 2.9≦a≦3.5, and the unit is g / cm ３ and The area density b of the positive electrode active material layer is 0.012≦b≦0.018, and the unit is g / cm ２ and the mass percentage c of the conductive agent in the positive electrode active material layer is 2.4%≦c≦4.4%, The positive electrode active material layer has a ２ × b / c < 5.5, A positive electrode plate characterized by:

2. The compaction density of the positive electrode active material layer is 3.1≦a≦3.

3. The positive electrode plate according to claim 1 .

3. the areal density of the positive electrode active material layer is 0.014≦b≦0.016; The positive electrode plate according to claim 1 .

4. the mass percentage of the conductive agent in the positive electrode active material layer is 3%≦c≦4%; The positive electrode plate according to claim 1 .

5. The positive electrode active material layer has a ２ × b / c < 5 The positive electrode plate according to claim 1 .

6. the conductive agent in the positive electrode active material layer is conductive carbon black; The positive electrode plate according to claim 1 .

7. The positive electrode current collector is an aluminum foil or a carbon-coated aluminum foil. The positive electrode plate according to claim 1 .

8. The positive electrode plate according to any one of claims 1 to 7, A lithium-ion battery characterized by:

9. The lithium ion battery further includes a negative electrode plate, the negative electrode plate including a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, The compaction density of the negative electrode active material layer is 1.35 g / cm ３ and The surface density of the negative electrode active material layer is 0.0058 g / cm ２ and The mass percentage of the conductive agent in the negative electrode active material layer is 1.6%.

9. The lithium ion battery according to claim 8.

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