Cathode active material for lithium secondary battery and manufacturing method therefor

Abstract

Provided is a cathode active material in the form of secondary particles formed by aggregation of primary particles comprising a lithium transition metal composite oxide. The lithium transition metal composite oxide comprises lithium, nickel, and manganese, and additionally comprises boron as a doping element, wherein, in the lithium transition metal composite oxide, a molar content of manganese is greater than a molar content of nickel. The primary particles have an average particle size of 200-800 nm, and the secondary particles have a particle size (D50) of 0.5-3.0 ㎛. As the cathode active material contains a trace amount of boron as a doping element, excellent flowability may be exhibited despite a small particle size.

Description

Cathode active material for lithium secondary batteries and method for producing the same

[0001] The present invention relates to a cathode active material for a lithium secondary battery and a method for producing the same. Specifically, the present invention relates to a lithium manganese-rich cathode active material for a lithium secondary battery, comprising a lithium transition metal composite oxide in the form of secondary particles in which primary particles are aggregated, and a method for producing the same. The lithium transition metal composite oxide comprises lithium, nickel, and manganese, and includes boron as a doping element.

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0096128, filed July 22, 2024, and Korean Patent Application No. 10-2025-0097943, filed July 21, 2025, the entire contents of which are incorporated herein by reference.

[0003] Recent technological advancements in electric vehicles and other fields have led to a growing demand for high-capacity secondary batteries. Consequently, research into cathodes utilizing high-nickel (High Ni) cathode active materials with superior capacity characteristics has been actively underway. However, high-nickel cathode active materials face the challenge of increased manufacturing costs due to the use of cobalt and excessive nickel.

[0004] Accordingly, a layered lithium manganese-rich (LiMn rich) cathode active material with a higher manganese content than nickel content is attracting attention as a next-generation cathode active material. It is not only cheaper than the existing high-nickel cathode active material, but also has the advantage of a high discharge capacity of over 250 mAh / g and operation at high voltage. This lithium manganese-rich cathode active material is composed of manganese and nickel, which are redox active transition metals, and consists of two phases, Li2MnO3 and LiMnO2, and is activated through high-voltage formation operation, and at this time, Li + Ions are extracted, oxygen evolution (O2 evolution) occurs, and LiO2 or Li with excellent electrical conductivity is formed. x As MnO2 is formed, it has a high capacity. In addition, lithium manganese-rich cathode active materials can operate stably at high temperatures and have relatively little decomposition.

[0005] The above-mentioned positive electrode active material can generally be manufactured through a manufacturing method such as a co-precipitation method using a precursor. However, the lithium manganese rich positive electrode active material manufactured in this way has a small primary particle size and low press density (P / D), so when applied to a battery, the energy density per volume is low, and the performance of the battery may be reduced due to problems such as particle breakage.

[0006] Accordingly, the inventors of the present invention studied a method for manufacturing a lithium manganese-rich cathode active material using a precursor-free spray drying method, rather than conventional manufacturing methods such as precursor-based co-precipitation. By adjusting the conditions of the spray drying method, a novel lithium manganese-rich cathode active material was obtained. However, this cathode active material suffered from processability issues, such as poor flowability. After continuous research to improve these issues, the present invention was completed.

[0007] [Prior Art Literature]

[0008] [Patent Document]

[0009] (Patent Document 1) Republic of Korea Patent Publication No. 10-2021-0046575

[0010] The present invention provides a lithium manganese-rich positive electrode active material in the form of secondary particles in which primary particles containing a lithium transition metal composite oxide are aggregated, which has novel characteristics that are distinct from conventional positive electrode active materials, and a positive electrode active material for a lithium secondary battery doped with boron and a method for producing the same.

[0011] According to the first aspect of the present invention,

[0012] The present invention provides a cathode active material in the form of secondary particles in which primary particles including a lithium transition metal composite oxide are aggregated.

[0013] In one specific example of the present invention, the lithium transition metal composite oxide includes lithium, nickel, and manganese, and additionally includes boron as a doping element, and the molar content of manganese in the lithium transition metal composite oxide is greater than the molar content of nickel.

[0014] In one specific example of the present invention, the primary particles have an average particle size of 200 nm to 800 nm, and the secondary particles have a particle size (D) of 0.5 μm to 1.5 μm. 50 ) has.

[0015] In one specific example of the present invention, the content of boron in the lithium transition metal composite oxide is greater than 0.05 mol% and less than 2.5 mol% based on the total mole number of lithium and transition metal.

[0016] In one specific example of the present invention, the lithium transition metal composite oxide is represented by the following chemical formula 1.

[0017] [Chemical Formula 1]

[0018] xLi2MnO3·(1-x)LiTMO2

[0019] In the above chemical formula 1, x is 0 <x<1이고, TM은 망간, 니켈 및 붕소를 포함하는 전이금속이다.

[0020] In one specific example of the present invention, the secondary particle (D 90 -D 10 ) / D 50 is 0.8 to 1.5.

[0021] In one specific example of the present invention, 75 wt% or more of the total weight of the entire phase of boron in the positive electrode active material is BO2. - It's a prize.

[0022] In one specific example of the present invention, the positive electrode active material has a static contact angle with water of 40° or more.

[0023] In one specific example of the present invention, the positive electrode active material has a capillary constant for n-hexane of 2.5×10 -4 mm 5 That's all.

[0024] In one specific example of the present invention, the positive electrode active material has a DBP absorption amount of 5.0 ml / 100 g or less.

[0025] According to the second aspect of the present invention,

[0026] The present invention provides a method for producing the above-described positive electrode active material.

[0027] In one specific example of the present invention, the method for producing the positive electrode active material includes: 1) mixing a lithium raw material, a nickel raw material, a manganese raw material, and a boron doping raw material to produce a mixture; 2) adding a solvent to the mixture and pulverizing a solid content to produce a slurry; 3) spray-drying the slurry to produce a dried product; 4) calcining the dried product to produce a calcined product; and 5) pulverizing the calcined product to obtain a positive electrode active material.

[0028] In one specific example of the present invention, the particle size (D) of the solid content in the slurry prepared in step 2) 50 ) is 0.1㎛ to 0.4㎛.

[0029] In one specific example of the present invention, spray drying in step 3) is performed at a temperature of 100°C to 250°C.

[0030] In one specific example of the present invention, in step 4), the firing is performed at 800°C to 1100°C for 5 to 15 hours.

[0031] In one specific example of the present invention, the sintered product manufactured in step 4) has a particle size (D) of 4 µm to 12 µm. 50 ) has.

[0032] According to the third aspect of the present invention,

[0033] The present invention provides a positive electrode comprising the positive electrode active material described above.

[0034] According to the fourth aspect of the present invention,

[0035] The present invention provides a lithium secondary battery including the above-described positive electrode, negative electrode, a separator interposed between the positive electrode and negative electrode, and an electrolyte.

[0036] According to one specific embodiment of the present invention, a cathode active material is a lithium manganese rich cathode active material in the form of secondary particles in which primary particles including a lithium transition metal composite oxide are aggregated, and has the form of secondary particles but has a relatively small particle size. As the particle size of the cathode active material is smaller, the contact area between the particles increases, which may cause the particles to aggregate with each other, thereby reducing flowability. According to one specific embodiment of the present invention, the cathode active material contains a trace amount of boron as a doping element, thereby exhibiting excellent flowability despite the small particle size. In addition, when the cathode active material is applied to a battery, the performance is maintained or improved compared to the cathode active material before doping by doping a trace amount of boron.

[0037] Figure 1 is a graph showing the XRD results of a positive electrode active material manufactured according to Example 1.

[0038] Figure 2 is a graph showing the XRD results of a positive electrode active material manufactured according to Comparative Example 1.

[0039] Figure 3 is a graph showing the XRD results of a positive electrode active material manufactured according to Comparative Example 2.

[0040] Fig. 4 is an SEM image of a positive electrode active material manufactured according to Example 1. Specifically, Fig. 4a is an SEM image of the positive electrode active material of Example 1 before disintegration, and Fig. 4b is an SEM image of the positive electrode active material of Example 1 after disintegration.

[0041] Fig. 5 is an SEM image of a positive electrode active material manufactured according to Comparative Example 1. Specifically, Fig. 5a is an image of the positive electrode active material of Comparative Example 1 before disintegration, and Fig. 5b is an image of the positive electrode active material of Comparative Example 1 after disintegration.

[0042] The specific embodiments provided in accordance with the present invention can all be achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention and that the present invention is not necessarily limited thereto.

[0043] For the properties described in this specification, if the measurement conditions and methods are not specifically described, the properties are measured according to the measurement conditions and methods generally used by those skilled in the art.

[0044]

[0045] <Cathode active material>

[0046]

[0047] The present invention provides a novel lithium manganese-rich cathode active material capable of improving the problems of conventional lithium manganese-rich cathode active materials. According to one specific example of the present invention, the lithium manganese-rich cathode active material has a secondary particle form in which primary particles are aggregated. Although the lithium manganese-rich cathode active material has a secondary particle form, the primary particles are aggregated in a number of only a few dozen at most, which is lower than that of general secondary particles that are aggregated in hundreds or more. Accordingly, the difference in particle size between the primary particles and the secondary particles is not large, and some lithium manganese-rich cathode active materials may exist in the form of primary particles without being aggregated. Therefore, in the present specification, the lithium manganese-rich cathode active material having a secondary particle form refers to the overall particle form, and does not exclude single primary particles that are not aggregated. In other words, the secondary particle form may include both single primary particles and secondary particles in which primary particles are aggregated.

[0048] The above lithium manganese rich positive electrode active material has a secondary particle form and a relatively small particle size. As the particle size becomes smaller, the contact area between particles increases, which may cause the particles to aggregate with each other, thereby reducing flowability. To solve this problem, the positive electrode active material is doped with a small amount of boron. By doping a small amount of boron into the positive electrode active material, the flowability of the positive electrode active material can be significantly improved without deteriorating the excellent properties of the existing positive electrode active material. As the flowability of the positive electrode active material is improved, the processability during manufacturing is significantly improved, and it also helps improve the performance when applied to the positive electrode of a lithium secondary battery.

[0049] The present invention provides a positive electrode active material in the form of secondary particles in which primary particles comprising a lithium-transition metal composite oxide are aggregated. The lithium-transition metal composite oxide comprises lithium, nickel, and manganese, and additionally comprises boron (B) as a doping element, wherein the molar content of manganese in the lithium-transition metal composite oxide is greater than the molar content of nickel. The positive electrode active material comprising such a lithium-transition metal composite oxide is also referred to herein as a lithium-manganese-rich positive electrode active material.

[0050] In one specific embodiment of the present invention, the lithium-transition metal composite oxide has a layered structure. The layered structure can be formed by the lithium-manganese-rich positive electrode active material being divided into two phases. The lithium-transition metal composite oxide includes a “lithium manganese-rich phase” and a “secondary phase.” Simply expressed in terms of the elements of lithium, manganese, and oxygen, excluding additional components such as nickel, the lithium-manganese-rich phase refers to a phase having a layered rock salt structure based on a Li2MnO3 phase, and the secondary phase refers to a phase having a spinel structure based on a LiMnO2 phase. Additional transition metals such as nickel are included, for example, in the secondary phase. This lithium-transition metal composite oxide can be expressed by the following chemical formula 1.

[0051]

[0052] [Chemical Formula 1]

[0053] xLi2MnO3·(1-x)LiTMO2

[0054]

[0055] In the above chemical formula 1, TM refers to a transition metal including manganese, nickel, boron, etc. As boron is doped, some boron may be included in the Mn or TM position in the above chemical formula 1. Specifically, the boron may be included in the TM position.

[0056] According to one specific example of the present invention, in the chemical formula 1, x is 0 <x<1이다. 구체적으로, 상기 x는 0<x<1, 0.1<x<0.9, 0.2<x<0.8, 0.3<x<0.7, 0.4<x<0.6일 수 있다.

[0057] In the above chemical formula 1, TM can be separated according to the transition metal included. For example, when manganese and nickel are included as transition metals, TM is Mn y1 Ni y2(Here, y1+y2=1) can be classified. The above y1 is 0 <y1<1, 0.1<y1<0.9, 0.3<y1<0.8, 0.5<y1<0.7일 수 있고, 상기 y2는 0<y2<1, 0.1<y2<0.9, 0.2<y2<0.7, 0.3<y2<0.5일 수 있다. 붕소가 도핑됨에 따라, 상기 화학식 1에서 TM 자리에 붕소가 일부 포함될 수 있다.

[0058] The above lithium transition metal composite oxide can be represented as Chemical Formula 1 to distinguish between two phases, but can also be represented as a single composition formula as Chemical Formula 2 below.

[0059]

[0060] [Chemical Formula 2]

[0061] Li a TM b O2

[0062]

[0063] In the above chemical formula 2, a+b=2.

[0064] According to one specific example of the present invention, in the chemical formula 2, a is 1.10 <a<1.30이다. 구체적으로, 상기 a은 1.10<a<1.30, 1.10<a<1.25, 1.10<a<1.20일 수 있다.

[0065] In the above chemical formula 2, TM can be separated depending on the transition metal included. For example, when manganese and nickel are included as transition metals, TM b is Mn b1 Ni b2(Here, b1+b2=b) can be classified. In a lithium manganese rich cathode material such as the present invention, b1 has a value greater than b2. According to one specific example of the present invention, b1 is 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, 2.0 times or more than b2. In addition, individually, b1 is 0.10 <b1<0.40, 0.15<b1<0.35, 0.20<b1<0.30일 수 있고, 상기 b2는 0.40<b2<0.80, 0.45<b2<0.75, 0.50<b2<0.70일 수 있다. 붕소가 도핑됨에 따라, 상기 화학식 2에서 TM 자리에 붕소가 일부 포함될 수 있다. 붕소는 TM 자리에 B b3 It can be included in the form of, and the above b3 is 0.0001 <b3<0.05, 0.0005<b3<0.03, 0.001<b3<0.01일 수 있다.

[0066] According to one specific example of the present invention, the content of boron is greater than 0.05 mol% and less than 2.5 mol% based on the total mole number of lithium and transition metal. Specifically, the content of boron is greater than 0.05 mol%, greater than 0.06 mol%, greater than 0.07 mol%, greater than 0.08 mol%, greater than 0.09 mol%, greater than 0.1 mol%, less than 2.5 mol%, less than 2 mol%, less than 1.5 mol%, less than 1 mol%, less than 0.5 mol%, less than 0.4 mol%, less than 0.3 mol%, less than 0.2 mol%, and may be greater than 0.05 mol% and less than 2.5 mol%, greater than 0.07 mol% and less than 1 mol%, and greater than 0.1 mol% and less than 0.5 mol%. In the present invention, the doping of boron is primarily intended to improve problems such as flowability that may arise due to the novel positive electrode active material having secondary particles but relatively small sizes. As described above, significant improvement in performance is possible even by doping a small amount of boron. Conventional positive electrode active materials have relatively large particle sizes, so their actual flowability is not significantly reduced, and thus this issue may not be recognized for conventional positive electrode active materials.

[0067] According to one specific example of the present invention, the primary particles in the positive electrode active material have an average particle size of 200 nm to 800 nm. The method for measuring the primary particle size is not particularly limited as long as it is a method generally used in the relevant technical field, and for example, an SEM image may be obtained using a scanning electron microscope (SEM, manufacturer: FEI, product name: Inspect F), and the primary particle size may be measured using an image processing program (Image J). In the examples and comparative examples, the primary particle size is based on this. In this case, the particle size average is an arithmetic mean of the measured values, and is calculated by utilizing at least 7 SEM images and removing outliers based on the particle size distribution. Specifically, the average particle size of the primary particles may be 200 nm or more, 250 nm or more, 300 nm or more, 800 nm or less, 750 nm or less, 700 nm or less, and may be 200 nm to 800 nm, 250 nm to 750 nm, or 300 nm to 700 nm. The cathode active material according to one specific example of the present invention has advantageous properties for improving battery performance, such as having a form of secondary particles in which primary particles are aggregated, and having relatively large primary particles within the particles so that the secondary particles have a uniform particle distribution.

[0068] According to one specific example of the present invention, the secondary particles in the positive electrode active material have a particle size (D) of 0.5 μm to 3.0 μm. 50 ) has. In this specification, the size of the secondary particles refers to the overall positive electrode active material particles, and the inclusion of some single primary particles does not exclude them. The secondary particle size (D 50 ) is not particularly limited as long as it is a method commonly used in the relevant technical field, and for example, it can be measured by the method described in Experimental Example 3. In this specification, the particle size (D 50) is the particle size corresponding to 50% of the volume accumulation amount in the particle size measuring device, which can also be interpreted as the average value of the particle size. Specifically, the particle size (D) of the secondary particle 50 ) is 0.5㎛ or more, 0.6㎛ or more, 0.7㎛ or more, 3.0㎛ or less, 2.5㎛ or less, 2.0㎛ or less, 1.5㎛ or less, and may be 0.5㎛ to 3.0㎛, 0.6㎛ to 2.5㎛, or 0.7㎛ to 2.0㎛. The positive electrode active material according to one specific example of the present invention has advantageous properties for improving battery performance, such as primary particles being densely aggregated within small secondary particles.

[0069] The above positive electrode active material has a relatively wide particle size distribution compared to the non-doped boron. Nevertheless, the positive electrode active material according to one specific example of the present invention has a narrow particle size distribution before doping with boron, and thus the particle size distribution is not wide compared to a general positive electrode active material. According to one specific example of the present invention, the secondary particles of the positive electrode active material (D 90 -D 10 ) / D 50 is 0.8 to 1.5. Here, the particle size (D 10 ) means the particle size corresponding to 10% of the volume accumulation in the particle size measuring device, and the particle size (D 90 ) means the particle size corresponding to 90% of the volume accumulation amount in the particle size measuring device. Specifically, (D of the secondary particle 90 -D 10 ) / D 50 is 0.8 or more, 0.9 or more, 1.0 or more, 1.5 or less, 1.4 or less, 1.3 or less, and may be 0.8 to 1.5, 0.9 to 1.4, 1.0 to 1.3. The above range is a relatively large value compared to a positive electrode active material manufactured by the same manufacturing method and not doped with boron, but it is a range in which the uniformity of the particles is not significantly reduced.

[0070] Boron doped in the cathode active material can exist in various phases. The phases are composed of boron, oxygen, and lithium, for example, BO2. - LiBO3 - LiB2O3 - LiB2O4 - Top, B3O5 - Li2B3O6 - The phases may be phases, etc. The phases may have oxidation numbers less than 0, and such substances may exist in a state of being combined with substances having oxidation numbers greater than 0. The distribution of the phases may indicate characteristics of the internal structure, which is derived from the manufacturing method of the positive electrode active material and may be related to the performance of the positive electrode active material. According to one specific example of the present invention, in the positive electrode active material, boron is BO2. - The most abundant boron is BO2, and more than 75 wt% of the total weight of the entire boron phase in the positive electrode active material is BO2. - It is a prize. Specifically, the above BO2 - The content of the composition may be 75 wt% or more, 75.5 wt% or more, 76 wt% or more, 76.5 wt% or more, 77 wt% or more, 77.5 wt% or more, 78 wt% or more, 90 wt% or less, 89% wt% or less, 88% wt% or less, 87% wt% or less, 86% wt% or less, 85% wt% or less, and may be 75 wt% or more, 75 wt% to 90 wt%, 76 wt% to 87 wt%, 77 wt% to 85 wt%.

[0071] According to one specific example of the present invention, in the positive electrode active material, boron is BO2 - Next is LiB2O4 - The most abundant phase is LiB2O4, and more than 10 wt% of the total weight of the entire phase of boron in the positive electrode active material is - It is a prize. The above LiB2O4 -The content of the top is 10 wt% or more, 11 wt% or more, 12 wt% or more, 13 wt% or more, 14 wt% or more, 15 wt% or more, 19% wt% or less, 18.5% wt% or less, 18% wt% or less, 17.5% wt% or less, 17% wt% or less, and may be 10 wt% or more, 10 wt% to 19 wt%, 11 wt% to 18.5 wt%, 12 wt% to 18 wt%.

[0072] According to one specific example of the present invention, BO2 in the boron in the positive electrode active material - LiB2O4 - The content ratio of the top is 4 or more. Specifically, the content ratio is 4 or more, 4.1 or more, 4.2 or more, 4.3 or more, 4.4 or more, 4.5 or more, 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, and may be 4 or more, 4 to 10, 4.3 to 8, 4.5 to 6.

[0073] BO2 in boron in the above positive electrode active material - and LiB2O4 - Other than the above, there may be relatively small amounts of other prizes. BO2 - and LiB2O4 - For example, LiBO3 is a non-monotonous substance. - LiB2O3 - Top, B3O5 - Li2B3O6 - There may be a prize, etc. According to one specific example of the present invention, in the boron in the positive electrode active material, BO2 - and LiB2O4 -Phases other than the phase may be present in an amount of 5 wt% or less based on the total weight of the entire phase of boron. Specifically, the contents of the phases may be 5 wt% or less, 4.5 wt% or less, 4 wt% or less, 3.5 wt% or less, 3 wt% or less, and 2.5 wt% or less, respectively. According to one specific example of the present invention, in the boron in the positive electrode active material, LiBO3 - LiB2O3 - Top, B3O5 - Li2B3O6 - The awards may be present in the positive electrode active material in an amount of 0.1 wt% or more based on the total weight of the entire boron phase.

[0074] According to one specific example of the present invention, the cathode active material is manufactured to have the following physical properties while possessing relatively small particles with a large contact area between particles. This prevents the formation of additional aggregates between particles during the manufacturing process and ensures excellent flowability. Furthermore, a certain level of internal voids can be secured, thereby providing additional functionality.

[0075] According to one specific embodiment of the present invention, the positive electrode active material has a static contact angle with respect to water of 40° or more. The higher the static contact angle with respect to water, the lower the affinity with respect to water. This may also affect the cohesion between positive electrode active materials. Specifically, the static contact angle with respect to water may be 40° or more, 41° or more, 42° or more, 70° or less, 60° or less, 50° or less, and may be 40° or more, 40° to 70°, 41° to 60°, or 42° to 50°. The positive electrode active material according to one specific embodiment of the present invention does not have a high affinity with a solvent such as water, and thus cohesion between particles mediated by such substances may not easily occur.

[0076] According to one specific example of the present invention, the positive electrode active material has a capillary constant for n-hexane of 2.5×10 -4 mm 5As the capillary constant increases, the pore size and ratio inside the positive electrode active material increase. Specifically, the capillary constant is 2.5×10 -4 mm 5 Above, 2.6×10 -4 mm 5 Above, 2.7×10 -4 mm 5 Above, 6.0×10 -4 mm 5 Below, 5.5×10 -4 mm 5 Below, 5.0×10 -4 mm 5 Below, 4.5×10 -4 mm 5 Below is 2.5×10 -4 mm 5 6.0×10 -4 mm 5 , 2.6×10 -4 mm 5 5.5×10 -4 mm 5 , 2.7×10 -4 mm 5 5.0×10 -4 mm 5 It may be. The positive electrode active material according to one specific example of the present invention can secure a certain level of pores inside by doping with boron.

[0077] According to one specific example of the present invention, the positive electrode active material has a DBP absorption of 5.0 ml / 100 g or less. The DBP absorption is the amount of dibutyl phthalate (DBP) oil absorbed, and as the value increases, the size and irregularity of the aggregates increase. Specifically, the DBP absorption may be 5.0ml / 100g or less, 4.5ml / 100g or less, 4.0ml / 100g or less, 3.5ml / 100g or less, 1.0ml / 100g or more, 1.5ml / 100g or more, 2.0ml / 100g or more, 2.5ml / 100g or more, 3.0ml / 100g or more, 5.0ml / 100g or less, 1.0ml / 100g to 5.0ml / 100g, 1.5ml / 100g to 4.5ml / 100g, 2.0ml / 100g to 4.0ml / 100g. The positive electrode active material according to one embodiment of the present invention may have a DBP absorption low enough that aggregation between particles does not easily occur.

[0078]

[0079] The positive electrode active material having the above-described particulate characteristics can be manufactured, for example, using the following manufacturing method. Hereinafter, a method for manufacturing a positive electrode active material according to one embodiment of the present invention will be described in detail.

[0080]

[0081] <Method for manufacturing positive electrode active material>

[0082]

[0083] The present invention provides a method for producing the positive electrode active material described above. The positive electrode active material can be produced from a solution in which raw materials are mixed at once, for example, by the Pezzini method. However, the synthetic solution synthesized by the Pezzini method has a problem in that the volume of the dried product expands as the solvent such as water evaporates during drying, resulting in a sharp decrease in the yield per volume during mass production through scale-up. The drying problem that occurs during drying of the synthetic solution can be solved through spray drying, which evaporates the solvent such as water simultaneously with spraying. The method for producing a positive electrode active material according to one specific example of the present invention basically produces the positive electrode active material by spray-drying a solution in which raw materials and doping raw materials are mixed at once, and then calcining the solution, while appropriately controlling conditions at each step.

[0084] A method for producing a positive electrode active material according to one specific example of the present invention comprises the steps of: 1) mixing a lithium raw material, a nickel raw material, a manganese raw material, and a boron doping raw material to produce a mixture; 2) adding a solvent to the mixture and pulverizing a solid content to produce a slurry; 3) spray-drying the slurry to produce a dried product; 4) calcining the dried product to produce a calcined product; and 5) pulverizing the calcined product to obtain a positive electrode active material.

[0085] In the above step 1), the lithium raw material, nickel raw material, and manganese raw material may be materials in the form generally used in the relevant technical field. Specifically, the lithium raw material may be a lithium-containing sulfate, nitrate, acetate, carbonate, oxalate, citrate, halide, hydroxide, or oxyhydroxide, and for example, Li2CO3, LiNO3, LiNO2, LiOH, LiOH H2O, LiH, LiF, LiCl, LiBr, LiI, CH3COOLi, Li2O, Li2SO4, CH3COOLi, Li3C6H5O7, or a mixture thereof.

[0086] The above nickel raw material and manganese raw material may include acetate, nitrate, sulfate, carbonate, halide, sulfide, hydroxide, oxide or oxyhydroxide of each transition metal. As a specific example, the nickel raw material may be Ni(OH)2, NiO, NiOOH, NiCO3·2Ni(OH)2·4H2O, NiC2O2·2H2O, Ni(NO3)2·6H2O, NiSO4, NiSO4·6H2O, fatty acid nickel salt or nickel halide, and any one or a mixture of two or more thereof may be used. In addition, the manganese raw material may be manganese oxides such as Mn2O3, MnO2 and Mn3O4; manganese salts such as MnCO3, Mn(NO3)2, MnSO4, manganese acetate, manganese dicarboxylic acid salt, manganese citrate and fatty acid manganese salt; It may be manganese oxyhydroxide or manganese chloride, and any one of these or a mixture of two or more of them may be used.

[0087] The above lithium raw material, nickel raw material, and manganese raw material can be more specifically selected and used to manufacture a positive electrode active material having the above-described characteristics, and according to one specific example of the present invention, the lithium raw material, nickel raw material, and manganese raw material are oxides, hydroxides, or carbonates. Specifically, lithium carbonate can be used as the lithium raw material, nickel hydroxide can be used as the nickel raw material, and manganese carbonate can be used as the manganese raw material.

[0088] The above boron doping raw material is not particularly limited as long as it contains boron, and for example, one or more selected from among H3BO3, H4BO4, B2O3, LiBO2, Li2B4O7, B4C, AlBO2, and AlB2O4 may be used. Specifically, H3BO3 and B2O3 may be used as the boron doping raw material, and more specifically, H3BO3 may be used.

[0089] The mixing of the above-described raw materials and doping raw materials is not particularly limited as long as it is a method commonly used in the relevant technical field. The purpose of the mixing is to uniformly disperse various raw materials, and a milling device (e.g., a ball mill) can be utilized. The present invention is characterized by introducing the doping raw materials together with the raw materials without separate separation, and the doping raw materials have distinct functionality from the raw materials due to differences in content and reaction energy.

[0090] After mixing the raw materials in step 1), in step 2), a solvent (e.g., water) is added to the mixture, and the solids are ground to an appropriate size to prepare a slurry. The content of the solids in the slurry may be 10 wt% to 30 wt%, 15 wt% to 30 wt%, or 15 wt% to 25 wt%. A milling device (e.g., a bead mill) may be utilized to evenly ground the solids in the slurry. According to one specific example of the present invention, the particle size (D) of the solids in the slurry 50 ) is 0.1㎛ to 0.4㎛. Specifically, the particle size (D) of the solid 50 ) is 0.1㎛ or more, 0.15㎛ or more, 0.2㎛ or more, 0.25㎛ or more, 0.4㎛ or less, 0.35㎛ or less, 0.3㎛ or less, and may be 0.1㎛ to 0.4㎛, 0.15㎛ to 0.35㎛, 0.25㎛ to 0.3㎛. The particle size of the solid content in the slurry may affect the particle size of the final product as well as the intermediate product in the manufacturing step.

[0091] In the above step 3), the slurry is spray-dried. According to one specific example of the present invention, the spray-drying is performed at a temperature of 150°C to 250°C, 150°C to 230°C, or 150°C to 200°C. In the spray-drying, the input hot air temperature is set higher than the exhaust hot air temperature. The dried product through spray-drying is dispersed with sufficient pores inside, which may be an advantageous form for controlling the particle size by crushing after calcination.

[0092] In the above step 4), the dried product by spray drying is fired. According to one specific example of the present invention, the firing is performed at 800°C to 1100°C for 5 to 15 hours. Specifically, the firing temperature is 800°C or higher, 850°C or higher, 900°C or higher, 1100°C or lower, 1050°C or lower, 1000°C or lower, and may be 800°C to 1100°C, 850°C to 1050°C, or 900°C to 1000°C. In addition, the firing time may be 5 hours or higher, 6 hours or higher, 7 hours or higher, 15 hours or lower, 14 hours or lower, 13 hours or lower, and 5 to 15 hours, 6 to 14 hours, or 7 to 13 hours. According to one specific example of the present invention, the fired product after spray drying has a particle size (D) of 4 ㎛ to 12 ㎛ 50 ) has. Specifically, the particle size (D) of the sintered product 50 ) is 4㎛ or more, 4.5㎛ or more, 5㎛ or more, 5.5㎛ or more, 6㎛ or more, 12㎛ or less, 11.5㎛ or less, 11㎛ or less, 10.5㎛ or less, 10㎛ or less, 9.5㎛ or less, 9㎛ or less, and may be 4㎛ to 12㎛, 5㎛ to 10.5㎛, or 6㎛ to 9㎛. The fired product after spray drying has the characteristics of large particle size and porosity.

[0093] In step 5), the sintered product is disintegrated to obtain a positive electrode active material. Here, disintegration refers to the process of separating the porous, agglomerated particles obtained after spray drying and sintering to obtain the final positive electrode active material with the particle size targeted by the present invention. The disintegration can utilize a milling device (e.g., a jet mill). The final product, the positive electrode active material, is in the form of secondary particles formed by agglomeration of primary particles, and its specific physical properties are as described above.

[0094]

[0095] Bipolar

[0096]

[0097] The present invention provides a positive electrode comprising the positive electrode active material described above.

[0098] According to one specific example of the present invention, the positive electrode includes a positive electrode current collector, a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer includes the positive electrode active material described above.

[0099] According to one specific example of the present invention, the positive electrode current collector may include a highly conductive metal, and is not particularly limited as long as it is a metal to which the positive electrode active material layer can be easily adhered and is not reactive in the voltage range of the battery. The positive electrode current collector may be, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum, and a stainless steel surface treated with carbon, nickel, titanium, silver, or the like may be used. In addition, the positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine unevenness may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. The positive electrode current collector may be used in various forms, for example, a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0100] According to one specific example of the present invention, the positive electrode active material layer may optionally include a conductive material and a binder, together with the positive electrode active material, as needed. In this case, the positive electrode active material may be included in the positive electrode active material layer in an amount of 80 wt% to 99 wt%, more specifically 85 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, and excellent capacity characteristics may be exhibited within this range.

[0101] According to one specific example of the present invention, the conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one of these may be used alone or a mixture of two or more may be used. The conductive material may be included in the positive electrode active material layer in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0102] According to one specific embodiment of the present invention, the binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material and the current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens thereof are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above binder may be included in the positive electrode active material layer in an amount of 0.1 wt% to 15 wt% based on the total weight of the positive electrode active material layer.

[0103] According to one specific example of the present invention, the positive electrode can be manufactured according to a conventional positive electrode manufacturing method, except that the positive electrode active material described above is used. Specifically, the positive electrode can be manufactured by applying a composition for forming a positive electrode active material layer, which is manufactured by dissolving or dispersing the positive electrode active material described above and optionally a binder, a conductive material, and a dispersant in a solvent as needed, onto a positive electrode current collector, followed by drying and rolling, or by casting the composition for forming a positive electrode active material layer onto a separate support, and then laminating the film obtained by peeling it from the support onto a positive electrode current collector.

[0104] According to one specific example of the present invention, the solvent may be a solvent generally used in the relevant technical field, such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), dimethylformamide (DMF), acetone, or water, and one of these may be used alone or as a mixture of two or more. The amount of the solvent used is sufficient to dissolve or disperse the positive electrode active material, conductive material, binder, and dispersant in consideration of the coating thickness and manufacturing yield of the slurry, and to have a viscosity that can exhibit excellent thickness uniformity when applied thereafter for manufacturing the positive electrode.

[0105]

[0106] Lithium secondary battery

[0107]

[0108] The present invention provides a lithium secondary battery including the above-described positive electrode.

[0109] According to one specific example of the present invention, the lithium secondary battery includes the above-described positive electrode; the negative electrode; a separator interposed between the positive electrode and the negative electrode; and an electrolyte. In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container.

[0110] According to one specific example of the present invention, the negative electrode may include a negative electrode current collector and a negative electrode active material layer positioned on the negative electrode current collector.

[0111] According to one specific example of the present invention, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. The negative electrode current collector may be, for example, copper, stainless steel, aluminum, nickel, titanium, or calcined carbon, and may be surface-treated copper or stainless steel with carbon, nickel, titanium, silver, or the like, or an aluminum-cadmium alloy or the like. In addition, the negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and, like the positive electrode current collector, fine unevenness may be formed on the surface of the current collector to increase the adhesion of the negative electrode active material. The negative electrode current collector may be used in various forms, for example, a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0112] According to one specific example of the present invention, the negative electrode active material layer may optionally include a binder and a conductive material together with the negative electrode active material.

[0113] According to one specific example of the present invention, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO β (0<β<2), SnO2, vanadium oxide, lithium vanadium oxide, and other metal oxides capable of doping and dedoping lithium; or composites containing the above metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbon material. Representative examples of the low-crystalline carbon include soft carbon and hard carbon, and representative examples of the high-crystalline carbon include amorphous, plate-like, flaky, spherical or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes. The negative electrode active material may be included in the negative electrode active material layer in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0114] According to one specific example of the present invention, the binder of the negative electrode active material layer is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added to the negative electrode active material layer in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, various copolymers thereof, and the like.

[0115] According to one specific example of the present invention, the conductive material of the negative electrode active material layer is a component for further improving the conductivity of the negative electrode active material, and may be added to the negative electrode active material layer in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the negative electrode active material layer. The conductive material is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery. Examples of the conductive material that may be used include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0116] According to one specific example of the present invention, the negative electrode can be manufactured by applying and drying a composition for forming a negative electrode active material layer, which is prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the composition for forming a negative electrode active material layer on a separate support, and then laminating the film obtained by peeling it off from the support on a negative electrode current collector.

[0117] According to one specific example of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitation, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0118] According to one specific example of the present invention, the electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0119] According to one specific example of the present invention, the organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0120] According to one specific example of the present invention, the lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The lithium salt may be at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable that the concentration of the lithium salt be used within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0121] According to one specific example of the present invention, in addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in the electrolyte in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0122] A lithium secondary battery including a cathode active material according to one specific example of the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0123] There is no particular limitation on the external shape of the above lithium secondary battery, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0124] A lithium secondary battery according to one specific example of the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0125] Accordingly, according to one specific example of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0126] According to one specific example of the present invention, the battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0127] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are provided only to make it easier to understand the present invention and the present invention is not limited thereto.

[0128]

[0129] Example (manufacturing of positive electrode active material)

[0130]

[0131] Example 1

[0132] Li2CO3 as a lithium raw material, Ni(OH)2 as a nickel raw material, MnCO3 as a manganese raw material, and H3BO3 as a boron doping raw material were prepared so that the molar ratio of Li:Ni:Mn:B was 1.145:0.256:0.596:0.003. The prepared raw materials were thoroughly mixed. Pure water was added to the mixture, and the mixture was ground at 2500 rpm for 90 minutes using a wet grinding device (manufacturer: NETZSCH, product name: MiniCer) using zirconia beads having a diameter of 0.3 mm to prepare a slurry with dispersed solids. The slurry contained 20 wt% of solids, and the particle size (D) of the solids was 50 / D max) was less than 0.2~0.3㎛ / 1㎛. The slurry was spray-dried using a spray drying device (manufacturer: Buchi, product name: B 290) with the input hot air temperature set to 200℃ and the exhaust hot air temperature set to over 100℃. The dried product was fired at 1000℃ for 9 hours in an air atmosphere. At this time, the particle size (D) of the fired product 50 ) was 6.36㎛, and the sintered product was crushed with a jet milling device (manufacturer: Isaac ENC, product name: Customizing) to obtain a lithium nickel manganese composite oxide. The lithium nickel manganese composite oxide has a layered structure and is composed entirely of Li 1.145 Ni 0.256 Mn 0.596 B 0.003 It had a composition formula of O2(0.435Li2MnO3·0.565LiTMO2, TM is composed of Ni, Mn and B, Ni:Mn=30:70, Li / Me=1.34, Me is Ni and Mn). In addition, the lithium nickel manganese composite oxide was in the form of secondary particles in which primary particles were aggregated, and the average size of the primary particles was 300 to 400 nm, and the size of the secondary particles (D 50 ) was 1.01㎛.

[0133]

[0134] Comparative Example 1

[0135] Li2CO3 as a lithium raw material, Ni(OH)2 as a nickel raw material, and MnCO3 as a manganese raw material were prepared so that the molar ratio of Li:Ni:Mn was 1.148:0.256:0.596, and the prepared raw materials were sufficiently mixed. Pure water was added to the mixture, and zirconia beads with a diameter of 0.3 mm were used for pulverization in a wet pulverization device (manufacturer: NETZSCH, product name: MiniCer) for 90 minutes to prepare a slurry in which the solids were dispersed. The slurry contained 20 wt% of solids, and the particle size (D) of the solids was 50 / D max) was less than 0.2~0.3㎛ / 1㎛. The slurry was spray-dried using a spray drying device (manufacturer: Buchi, product name: B 290) with the input hot air temperature set to 200℃ and the exhaust hot air temperature set to over 100℃. The dried product was fired at 1000℃ for 9 hours in an air atmosphere. At this time, the particle size (D) of the fired product 50 ) was 5.71㎛, and the sintered product was crushed with a jet milling device (manufacturer: Isaac ENC, product name: Customizing) to obtain a lithium nickel manganese composite oxide. The lithium nickel manganese composite oxide has a layered structure and is composed entirely of Li 1.148 Ni 0.256 Mn 0.596 It had a composition formula of O2(0.444Li2MnO3·0.556LiTMO2, TM is composed of Ni and Mn, Ni:Mn=30:70, Li / Me=1.35, Me is Ni and Mn). In addition, the lithium nickel manganese composite oxide was in the form of secondary particles in which primary particles were aggregated, and the average size of the primary particles was 300 to 400 nm, and the size of the secondary particles (D 50 ) was 0.94㎛.

[0136]

[0137] Comparative Example 2

[0138] Li2CO3 as a lithium raw material, Ni(OH)2 as a nickel raw material, and MnCO3 as a manganese raw material were prepared so that the molar ratio of Li:Ni:Mn was 1.145:0.256:0.598. The prepared raw materials were added to pure water, and mixed and ground for 6 hours at 120 rpm using a ball milling device (manufacturer: Daehwa Tech, product name: BTM-series) with a 5 mm diameter ball to prepare a slurry with dispersed solids. The slurry contained 20 wt% of solids, and the particle size of the solids (D 50) was 0.9~1.1㎛. The slurry was dried at a temperature of 100℃ using a centrifugal separator (manufacturer: ThermoFisher, product name: Sorvall ST4F Plus). The dried product was fired at 1000℃ for 9 hours in an air atmosphere. The fired product was crushed using a jet milling device (manufacturer: Isaac ENC, product name: Customizing) to obtain a lithium nickel manganese composite oxide. The lithium nickel manganese composite oxide has a layered structure and is composed entirely of Li 1.145 Ni 0.256 Mn 0.598 It had a composition formula of O2(0.435Li2MnO3·0.565LiTMO2, TM is composed of Ni and Mn, Ni:Mn=30:70, Li / Me=1.34, Me is Ni and Mn). In addition, the lithium nickel manganese composite oxide was in the form of secondary particles in which primary particles were aggregated, and the average size of the primary particles was 1.6㎛, and the size of the secondary particles (D 50 ) was 4.9㎛.

[0139]

[0140] Comparative Example 3

[0141] After adding 4 L of distilled water to a 20 L co-precipitation reactor and maintaining the temperature at 50°C, an ammonia aqueous solution with a concentration of 28 wt% and a transition metal (NiSO4, MnSO4) solution with a concentration of 3.2 mol / L were added. The molar ratio of Ni:Mn in the NiSO4 and MnSO4 of the transition metal solution was 0.35:0.65. In a specific method of introduction, 100 mL of an ammonia aqueous solution was first introduced, and then the transition metal solution and the ammonia aqueous solution were continuously introduced into the co-precipitation reactor at 300 mL / hr and 42 mL / hr, respectively. In the co-precipitation reactor, the mixed solution was stirred at an impeller speed of 400 rpm, and a 40 wt% sodium hydroxide solution was introduced to maintain the pH at 10.0. The co-precipitation reaction was performed for 24 hours to form precursor particles. The precursor particles were separated, washed, and dried in an oven at 130°C to prepare a precursor. Ni synthesized by co-precipitation reaction 0.35 Mn 0.65 (OH)2 precursor was mixed with Li2OH so that the Li / Me(Ni, Mn) molar ratio was 1.32, and the precursor was fired at 500°C for 5 hours in an air atmosphere. The fired product was sieved through a 45 μm sieve and then fired at 910°C for 9 hours in an air atmosphere to obtain a lithium nickel manganese composite oxide. The lithium nickel manganese composite oxide has a layered structure and is composed entirely of Li 1.138 Ni 0.302 Mn 0.560 02 (0.414Li2MnO3·0.586LiTMO2, TM is composed of Ni and Mn, Ni:Mn=35:65, Li / Me=1.32, Me is Ni and Mn) had a composition formula. In addition, the lithium nickel manganese composite oxide was in the form of secondary particles in which primary particles were aggregated, and the average size of the primary particles was 100 nm, and the size of the secondary particles (D 50 ) was 9.74㎛.

[0142]

[0143] Comparative Example 4

[0144] After adding 4 L of distilled water to a 20 L co-precipitation reactor and maintaining the temperature at 50°C, an ammonia aqueous solution with a concentration of 28 wt% and a transition metal (NiSO4, MnSO4) solution with a concentration of 3.2 mol / L were added. The molar ratio of Ni:Mn in the NiSO4 and MnSO4 of the transition metal solution was 0.35:0.65. In a specific method of introduction, 100 mL of an ammonia aqueous solution was first introduced, and then the transition metal solution and the ammonia aqueous solution were continuously introduced into the co-precipitation reactor at 300 mL / hr and 42 mL / hr, respectively. In the co-precipitation reactor, the mixed solution was stirred at an impeller speed of 400 rpm, and a 40 wt% sodium hydroxide solution was introduced to maintain the pH at 10.0. The co-precipitation reaction was performed for 24 hours to form precursor particles. The precursor particles were separated, washed, and dried in an oven at 130°C to prepare a precursor. Ni synthesized by co-precipitation reaction 0.35 Mn 0.65 (OH)2 precursor was mixed with Li2OH so that the molar ratio of Li / Me(Ni, Mn) was 1.32, and H3BO3 as a boron doping raw material was mixed so that the molar ratio of Li:Ni:Mn:B was 1.134:0.301:0.558:0.008. The precursor was fired at 500°C for 5 hours in an air atmosphere. The fired product was sieved through a 45 μm sieve and then fired at 910°C for 9 hours in an air atmosphere to obtain a lithium nickel manganese composite oxide. The lithium nickel manganese composite oxide has a layered structure and is composed entirely of Li 1.134 Ni 0.301 Mn 0.558 B 0.008It had a composition formula of O2(0.414Li2MnO3·0.586LiTMO2, TM is composed of Ni, Mn and B, Ni:Mn=35:65, Li / Me=1.32, Me is Ni and Mn). In addition, the lithium nickel manganese composite oxide was in the form of secondary particles in which primary particles were aggregated, and the average size of the primary particles was 100 nm, and the size of the secondary particles (D 50 ) was 9.50㎛.

[0145]

[0146] Comparative Example 5

[0147] After adding 4 L of distilled water to a 20 L co-precipitation reactor and maintaining the temperature at 50°C, an ammonia aqueous solution with a concentration of 28 wt% and a transition metal (NiSO4, MnSO4) solution with a concentration of 3.2 mol / L were added. The molar ratio of Ni:Mn in the NiSO4 and MnSO4 of the transition metal solution was 0.35:0.65. In a specific method of introduction, 100 mL of an ammonia aqueous solution was first introduced, and then the transition metal solution and the ammonia aqueous solution were continuously introduced into the co-precipitation reactor at 300 mL / hr and 42 mL / hr, respectively. In the co-precipitation reactor, the mixed solution was stirred at an impeller speed of 400 rpm, and a 40 wt% sodium hydroxide solution was introduced to maintain the pH at 10.0. The co-precipitation reaction was performed for 24 hours to form precursor particles. The precursor particles were separated, washed, and dried in an oven at 130°C to prepare a precursor. Ni synthesized by co-precipitation reaction 0.35 Mn 0.65(OH)2 precursor was mixed with Li2OH so that the molar ratio of Li / Me(Ni, Mn) was 1.32. The precursor was fired at 500°C for 5 hours in an air atmosphere. The fired product was sieved through a 45 μm sieve and fired at 910°C for 9 hours in an air atmosphere to obtain a lithium nickel manganese composite oxide. The lithium nickel manganese composite oxide was mixed with H3BO3 as a boron coating raw material so that the molar ratio of Li:Ni:Mn:B was 1.126:0.298:0.554:0.023. The oxide was fired at 850°C for 5 hours in an air atmosphere. The lithium nickel manganese composite oxide had a layered structure and was composed entirely of Li 1.126 Ni 0.298 Mn 0.554 B 0.023 It had a composition formula of O2(0.414Li2MnO3·0.586LiTMO2, TM is composed of Ni, Mn and B, Ni:Mn=35:65, Li / Me=1.32, Me is Ni and Mn). In addition, the lithium nickel manganese composite oxide was in the form of secondary particles in which primary particles were aggregated, and the average size of the primary particles was 100 nm, and the size of the secondary particles (D 50 ) was 9.81㎛.

[0148]

[0149] Experimental example (evaluation of positive electrode active material)

[0150]

[0151] Experimental Example 1: X-ray diffraction (XRD) data of positive electrode active material

[0152] XRD data analysis was performed on the positive electrode active materials manufactured in Example 1 and Comparative Examples 1 and 2. The XRD data were measured using an Empyrean XRD device from Panalytical (Cu-target, voltage: 45 kV, current: 40 mA, 2θ: 10˚~90˚). The results are shown in Figs. 1 to 3.

[0153] According to Figures 1 to 3, the positive electrode active material of Example 1, which was doped with a small amount of B, hardly showed glassy boron oxide as an XRD crystal phase, so there was no significant difference in the XRD data of the positive electrode active material of Comparative Example 1. However, the positive electrode active material of Comparative Example 2 had a large particle size before drying with a ball mill and was dried in a poorly dispersed state, so a secondary phase was confirmed in the positive electrode active material manufactured after firing.

[0154]

[0155] Experimental Example 2: Scanning electron microscope (SEM) image of the positive electrode active material.

[0156] SEM image analysis (Manufacturer: JEOL, Product Name: JSM7610F) was performed on the positive electrode active materials manufactured in Example 1 and Comparative Example 1. The results are shown in Figures 4 and 5 below. Specifically, Figure 4a is an image of the positive electrode active material of Example 1 before disintegration, and Figure 4b is an image of the positive electrode active material of Example 1 after disintegration. In addition, Figure 5a is an image of the positive electrode active material of Comparative Example 1 before disintegration, and Figure 5b is an image of the positive electrode active material of Comparative Example 1 after disintegration.

[0157] According to FIGS. 4 and 5, the positive electrode active material of Example 1, which was doped with a small amount of B, had a larger primary particle size than the positive electrode active material of Comparative Example 1 due to the doping of B. As the primary particle size increases, the pores of the sintered product before disintegration may decrease, but the positive electrode active material of Example 1 also formed small positive electrode active material particles through disintegration, just like the positive electrode active material of Comparative Example 1.

[0158]

[0159] Experimental Example 3: Particle size analysis (PSA) data of positive electrode active material

[0160] PSA data analysis (Manufacturer: Microtrac, Product Name: S3500) was performed on the positive electrode active materials manufactured in Example 1 and Comparative Example 1. The results are shown in Table 1 below.

[0161]

[0162] D 10 [㎛]D 50 [㎛]D 90 [㎛](D 90 -D 10 ) / D 50 Example 10.671.011.801.19 Comparative Example 10.740.941.260.55

[0163]

[0164] According to Table 1 above, the positive electrode active material of Example 1 with trace amount of B doped has a larger average particle diameter (D) than the positive electrode active material of Comparative Example 1. 50 ) was confirmed to have slightly increased. However, the positive electrode active material of Example 1 was (D) compared to the positive electrode active material of Comparative Example 1. 90 -D 10 ) / D 50 It was confirmed that the particle size distribution confirmed through was widened by nearly two times.

[0165]

[0166] Experimental Example 4: Mass Spectrometry (MS) Data of the Positive Electrode Active Material

[0167] MS data analysis for boron among the components of the positive electrode active materials manufactured in Example 1 and Comparative Examples 4 and 5 (Manufacturer: ION-TOF, Product name: TOF.SIMS) 5 ) was conducted. The results are shown in Table 2 below.

[0168]

[0169] ionBO2 - LiBO3 - LiB2O3 - LiB2O4 - B3O5 - Li2B3O6 - m / z4366779311314343 / 93 Example 179.0%2.1%1.0%16.6%0.9%0.5%4.76 Comparative Example 471.9%2.4%1.5%21.5%1.3%1.3%3.34 Comparative Example 573.5%1.6%1.5%19.1%2.7%1.6%3.84

[0170]

[0171] According to Table 2 above, boron in the positive electrode active materials of Example 1 and Comparative Examples 4 and 5 is BO2. - It was confirmed that the most abundant one was present, and the positive electrode active material of Example 1 was BO2 - The highest score was 74% or more. BO2 - Next is LiB2O4 - It was confirmed that the most abundant positive electrode active material was LiB2O4 in Example 1. - The lowest score was 19% or less. Furthermore, BO2 - LiB2O4 for the award - The ratio of the top was found to be high, at 4 or more.

[0172]

[0173] Experimental Example 5: Flow parameters of positive electrode active material

[0174] The static contact angle, surface free energy, pore size, and oil absorption-related parameters of the positive electrode active materials manufactured in Example 1 and Comparative Examples 1, 3, and 4 were measured and shown in Table 3 below. The static contact angle was measured using the Drop-Shape-Analysis (DSA) technique using a contact angle analyzer (Manufacturer: Kruss, Product Name: DSA 100) for H2O and methylene iodide (MI) contact angles on the positive electrode active materials. Based on the measured H2O and methylene iodide contact angle results, the surface free energy was calculated by solving the Owens-Wendt theory simultaneous equations. The Owens-Wendt theory simultaneous equations are composed of the following two equations.

[0175]

[0176] [Mathematical Formula 1]

[0177]

[0178]

[0179] γS : Surface energy of solids

[0180] γ SL : Interfacial energy between solid and liquid

[0181] γ L : Surface energy of liquid

[0182] θ: contact angle

[0183]

[0184] [Equation 2]

[0185]

[0186]

[0187] γ d : Dispersive part of surface energy

[0188] γ p : polar part of surface energy

[0189]

[0190] The above gap and oil absorption related parameters are derived by the Washburn method. The Washburn method uses the following two equations.

[0191]

[0192] [Equation 3]

[0193]

[0194]

[0195] r e : effective pore radius

[0196] γ L : Surface energy of liquid

[0197] θ: contact angle

[0198] η: viscosity

[0199]

[0200] [Equation 4]

[0201]

[0202]

[0203] η: viscosity

[0204] ρ: liquid density

[0205] γ L : Surface energy of liquid

[0206] A: Sample contact area

[0207] φ: porosity

[0208] r e : Effective gap radius

[0209] θ: contact angle

[0210] C: capillary constant

[0211]

[0212] The above capillary constant is m when absorbing a complete wetting liquid (e.g., n-hexane) after powder packing. 2 It was calculated based on the slope of the linear section of the graph of t. The capillary constant is a representative factor indicating pore information and can be affected by the porosity and pore size of the sample. According to the mathematical expression 4, the capillary constant (C) is r e φ 2 A 2 can be expressed as. In relation to the above oil absorption parameter, DBP absorption is measured. The DBP absorption is the amount of dibutyl phthalate (DBP) oil absorbed per 100 g of sample, and is related to the size and complexity of particle aggregates such as carbon black structures. The DBP absorption can be measured according to the ASTM D2414 standard.

[0213]

[0214] Example 1 (B doping) Comparative Example 1 (B undoped) Comparative Example 4 (B doping) Comparative Example 3 (B undoped) Static contact angle H2O(θ w )[°]44.2±1.834.1±1.659.3±2.273.7±1.8MI 1) (θ w)[°]46.4±1.234.1±1.666.3±1.692.9±0.7Surface free energy 2) γ S tot 3) [mN / m]59.467.844.630.1γ S d [mN / m]36.342.525.011.5γ S p [mN / m]23.225.319.718.6Polarity 4) [%]39.037.444.161.9 Pore capillary constant 5) [×10 -4 mm 5 ]4.0±1.21.8±0.4UnconfirmedUnconfirmedOil absorption k DBP [mg / s 1 / 2 ]0.8±0.11.7±0.023.1±2.017.5±0.8DBP Absorption [ml / 100g]3.3±0.45.7±0.033.8±2.629.8±1.11) CH2I22) The value obtained through the Owens-Wendt theory simultaneous equations using water and MI as standard solutions.3) γ S tot = γ S d + γ S p 4) Polarity = γ S p / γ S tot ×1005) The capillary constant is for n-hexane.

[0215]

[0216] According to Table 3 above, the positive electrode active material (B doped) of Example 1 has a larger static contact angle for H2O or MI than the positive electrode active material (B undoped) of Comparative Example 1, thereby reducing affinity with the solvent (hygroscopicity, etc.). The positive electrode active material of Example 1 has a smaller surface free energy than the positive electrode active material of Comparative Example 1, thereby reducing particle agglomeration. The positive electrode active material of Example 1 has a smaller oil absorption than the positive electrode active material of Comparative Example 1, thereby reducing the size and irregularity of the aggregates. The positive electrode active material of Example 1 has a larger capillary constant than the positive electrode active material of Comparative Example 1, thereby increasing the pore size and ratio.

[0217] In contrast, the positive electrode active materials of Comparative Examples 3 and 4 show opposite tendencies. The positive electrode active material of Comparative Example 4 (B doped) has a smaller static contact angle for H2O or MI than the positive electrode active material of Comparative Example 3 (B undoped), thereby increasing affinity with the solvent (hygroscopicity, etc.). The positive electrode active material of Comparative Example 4 has a larger surface free energy than the positive electrode active material of Comparative Example 3, thereby relatively increasing particle agglomeration. The positive electrode active material of Comparative Example 4 has a larger oil absorption than the positive electrode active material of Comparative Example 3, thereby increasing the size and irregularity of the aggregates.

[0218] As a result, the positive electrode active material (B doping) of Example 1 can improve particle flowability or fairness by reducing cohesion between particles compared to the positive electrode active material (B undoped) of Comparative Example 1. In addition, the positive electrode active material of Example 1 can secure a certain level of internal pores, thereby achieving separate functionality. On the other hand, the positive electrode active material (B undoped) of Comparative Example 3 has good original flowability and does not require any special improvement in flowability, and the positive electrode active material (B doping) of Comparative Example 4 showed reduced particle flowability compared to the positive electrode active material (B undoped) of Comparative Example 3.

[0219]

[0220] Experimental Example 6: Battery Performance Evaluation

[0221] A positive electrode slurry was prepared by mixing 92.5 wt% of the positive electrode active material manufactured in Example 1 and Comparative Example 1, 3.0 wt% of Super P as a conductive agent, and 4.5 wt% of polyvinylidene fluoride (PVDF) as a binder in an N-methylpyrrolidone (NMP) solvent. The prepared positive electrode slurry was applied to one surface of an aluminum current collector, dried at 130°C, and then rolled to prepare a positive electrode.

[0222] An electrode assembly was manufactured using a lithium metal electrode as the negative electrode and a porous polyethylene separator interposed between the positive and negative electrodes. This was placed inside a battery case, and a coin-type half-cell was manufactured by injecting an electrolyte solution containing 1 M LiPF6 dissolved in an organic solvent containing ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) in a volume ratio of 3:4:3.

[0223] Using each manufactured coin-type half-cell, the activation process (formation) was performed by charging to 4.65 V at 0.1 C constant current at 45 °C and then discharging to 2.0 V at 0.1 C. Subsequently, the cells were charged to 4.4 V at 0.33 C constant current at 25 °C and then discharged to 2.5 V at 0.33 C, and the initial average voltage, initial discharge capacity, and initial internal resistance (DCIR) were measured. The results are shown in Table 4 below. In addition, the life characteristics were confirmed by measuring the average voltage, discharge capacity, and internal resistance after 30 charge / discharge cycles under the conditions described above. The results are shown in Table 5 below.

[0224]

[0225] Average voltage [V] Initial discharge capacity [mAh / g] Initial internal resistance [Ω] Example 13.7 14 19 1.1 3 5.7 Comparative example 13.7 0 9 19 1.3 3 2.0

[0226]

[0227] Average voltage discharge capacity Internal resistance voltage [V] change rate *[%]Capacity [mAh / g]Change rate [%]Resistance [Ω]Change rate [%]Example 13.67999.06185.597.0647.1132Comparative example 13.66398.77184.096.1752.2162*Change rate = (Result value after 30 cycles) / (Initial result value)×100

[0228]

[0229] According to Tables 4 and 5 above, the positive electrode active material of Example 1 doped with boron showed no significant difference in initial battery performance compared to the positive electrode active material of Comparative Example 1 not doped with boron when applied to a battery. In addition, the positive electrode active material of Example 1 doped with boron showed a low rate of change over the cycle when applied to a battery, and was confirmed to have superior stability compared to the positive electrode active material of Comparative Example 1 not doped with boron. In particular, the positive electrode active material of Example 1 had a higher initial internal resistance than the positive electrode active material of Comparative Example 1 when applied to a battery, but after 30 cycles, the internal resistance was lower than that of the positive electrode active material of Comparative Example 1.

[0230]

[0231] All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Claims

1. A cathode active material in the form of secondary particles in which primary particles containing a lithium transition metal composite oxide are aggregated, The above lithium transition metal composite oxide contains lithium, nickel and manganese, and additionally contains boron as a doping element, In the above lithium transition metal composite oxide, the molar content of manganese is greater than the molar content of nickel, The above primary particles have an average particle size of 200 nm to 800 nm, The above secondary particles have a particle size (D) of 0.5 μm to 3.0 μm 50 ) is a positive electrode active material.

2. In claim 1, A cathode active material characterized in that the content of boron in the lithium transition metal composite oxide is greater than 0.05 mol% and less than 2.5 mol% based on the total molar number of lithium and transition metal.

3. In claim 1, The above lithium transition metal composite oxide is a cathode active material characterized by being represented by the following chemical formula 1: [Chemical Formula 1] xLi2MnO3·(1-x)LiTMO2 In the above chemical formula 1, x is 0 <x<1이고, TM은 망간, 니켈 및 붕소를 포함하는 전이금속이다.

4. In claim 1, The above secondary particle (D 90 -D 10 ) / D 50 A cathode active material characterized by having a value of 0.8 to 1.

5.

5. In claim 1, In the above positive electrode active material, 75 wt% or more of the total weight of the entire boron phase is BO2. - A cathode active material characterized by a merchant.

6. In claim 1, The above positive electrode active material is a positive electrode active material characterized in that the static contact angle with water is 40° or more.

7. In claim 1, The above positive electrode active material has a capillary constant for n-hexane of 2.5×10 -4 mm 5 A cathode active material characterized by the above.

8. In claim 1, The above positive electrode active material is characterized in that the DBP absorption amount is 5.0 ml / 100 g or less.

9. A method for manufacturing a cathode active material in the form of secondary particles in which primary particles containing a lithium transition metal composite oxide are aggregated, 1) A step of preparing a mixture by mixing lithium raw material, nickel raw material, manganese raw material and boron doping raw material; 2) A step of adding a solvent to the above mixture and grinding the solid content to prepare a slurry; 3) A step of spray drying the above slurry to produce a dried product; 4) A step of firing the above-mentioned dry material to produce a fired product; and 5) A step of crushing the above-mentioned product to obtain a positive electrode active material is included. A method for producing a positive electrode active material in which the molar content of manganese in the above lithium transition metal composite oxide is greater than the molar content of nickel.

10. In claim 9, The particle size (D) of the solid content in the slurry prepared in step 2 above 50 ) is characterized by a method for manufacturing a positive electrode active material having a particle size of 0.1㎛ to 0.4㎛.

11. In claim 9, A method for producing a positive electrode active material, characterized in that spray drying in the above step 3) is performed at a temperature of 100°C to 250°C.

12. In claim 9, A method for manufacturing a positive electrode active material, characterized in that in the above step 4), the calcination is performed at 800°C to 1100°C for 5 to 15 hours.

13. In claim 9, The sintered product manufactured in the above step 4) has a particle size (D) of 4 ㎛ to 12 ㎛ 50 ) is characterized by having a method for manufacturing a positive electrode active material.

14. A positive electrode comprising a positive electrode active material according to claim 1.

15. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte according to claim 14.

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