Composition for positive electrode active material layer and lithium secondary battery

Abstract

The present invention relates to a composition for a positive electrode active material layer of a lithium secondary battery, the composition including a positive electrode active material containing nickel, cobalt, and manganese, and containing 80 mol % or more and less than 100 mol % of nickel among metals excluding lithium, and containing a single particulate lithium composite transition metal compound, and an additive represented by chemical formula A; and a positive electrode, a lithium secondary battery, a battery module, and a battery pack each including the composition.

Description

[Technical field]

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2021-0160759 filed with the Korean Intellectual Property Office on November 19, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference.

[0002] The present application relates to a composition for a positive electrode active material layer and a lithium secondary battery. [Background technology]

[0003] In recent years, with the rapid spread of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles as well as power tools and vacuum cleaners, the demand for secondary batteries that are small and lightweight yet have relatively high capacity and / or high output is rapidly increasing. In particular, lithium secondary batteries are lightweight and have high energy density, and are in the spotlight as driving power sources for electronic devices. For this reason, research and development efforts are being actively conducted to improve the performance of lithium secondary batteries.

[0004] In a lithium secondary battery, an organic electrolyte or polymer electrolyte is filled between a positive electrode and a negative electrode, which are made of active materials that allow the intercalation and deintercalation of lithium ions, and electrical energy is produced by oxidation and reduction reactions that occur when lithium ions are inserted and extracted from the positive and negative electrodes.

[0005] Lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMnO2 or LiMn2O4, etc.), lithium iron phosphate compound (LiFePO4), etc. are used as positive electrode active materials for lithium secondary batteries. Among them, lithium cobalt oxide (LiCoO2) is widely used because of its advantages of high operating voltage and excellent capacity characteristics, and is applied as a positive electrode active material for high voltage. However, due to the rising price of cobalt (Co) and unstable supply, there is a limit to its mass use as a power source in fields such as electric vehicles, and the need for the development of an alternative positive electrode active material has emerged.

[0006] As a result, nickel-cobalt-manganese-based lithium transition metal composite oxides (hereinafter simply referred to as "NCM-based lithium transition metal composite oxides") were developed, in which part of the cobalt (Co) was replaced with nickel (Ni) and manganese (Mn). In recent years, research has been conducted to increase the Ni content in NCM-based lithium transition metal composite oxides to increase capacity. However, high-concentration nickel (Ni-rich) positive electrode active materials with a high nickel content have the disadvantages of reduced thermal stability and increased resistance and gas generation due to increased side reactions during electrochemical reactions.

[0007] On the other hand, graphite is mainly used as the negative electrode active material for lithium secondary batteries, but since graphite has a small capacity per unit mass of 372 mAh / g, it is difficult to increase the capacity of lithium secondary batteries. For this reason, in order to increase the capacity of lithium secondary batteries, negative electrode materials such as silicon, tin, and their oxides have been developed as non-carbon-based negative electrode materials with higher energy density than graphite. However, such non-carbon-based negative electrode materials have problems such as low initial efficiency, large lithium consumption during initial charging and discharging, and large irreversible capacity loss, although they have a large capacity. Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present inventors is to provide a composition for a positive electrode active material layer of a lithium secondary battery that can improve battery performance, and a positive electrode, a lithium secondary battery, a battery module, and a battery pack each including the same. [Means for solving the problem]

[0009] One embodiment of the present application is a positive electrode active material including a single particle lithium composite transition metal compound that includes nickel, cobalt, and manganese, and includes 80 mol % or more and less than 100 mol % of nickel among metals other than lithium; and An additive represented by the following chemical formula A: A composition for a positive electrode active material layer of a lithium secondary battery is provided, comprising: [Chemical formula A] Li x Co (1-y-z-m) Zinc y Al z M m O4 In the above formula A, M is Ti, Zr, Mn, or Ni; 5≦x≦7; 0 <y≦0.5、0<z≦0.5、0<y+z+m<1、0≦m≦0.5である。

[0010] A further embodiment of the present application provides a positive electrode for a lithium secondary battery, comprising: a positive electrode current collector; and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer comprising a composition according to the above-described embodiment.

[0011] A further embodiment of the present application is a lithium secondary battery comprising: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, The positive electrode active material layer includes the composition according to the above-described embodiment, and the lithium secondary battery is provided.

[0012] According to a further embodiment of the present application, the negative electrode active material layer of the above-mentioned embodiment includes 15 parts by weight or more of silicon-based oxide per 100 parts by weight of the total negative electrode active material.

[0013] Further embodiments of the present application provide a battery module including the above-described lithium secondary battery, and a battery pack including the battery module. Effect of the Invention

[0014] According to the embodiments described herein, it is possible to increase the energy density of a lithium secondary battery designed in a limited space, improve the high-output performance, and also improve the battery cycle performance. [Brief description of the drawings]

[0015] [Figure 1] 1 shows a graph of 55° C. cycles of the batteries produced in Example 1, Example 3, and Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The present invention will be described in more detail below to help understanding of the present invention. The present invention may be realized in various different forms and is not limited to the embodiments described herein. In this regard, the terms and words used in the present specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as meanings and concepts that are consistent with the technical ideas of the present invention, based on the principle that the inventors can appropriately define the concepts of terms in order to best describe their invention.

[0017] It should be understood that, as used herein, terms such as "comprise," "provide," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the presence or additional possibility of one or more other features, numbers, steps, components, or combinations thereof.

[0018] In addition, when a part such as a layer is said to exist "on" or "above" another part, this includes not only the case where it exists "directly above" the other part, but also the case where there is another part between them. Conversely, when a part is said to exist "directly above" another part, it means that there is no other part between them. In addition, being "on" or "above" a reference part means being located above or below the reference part, and does not necessarily mean being located "on" or "above" the reference part in the opposite direction of gravity.

[0019] One embodiment of the present application comprises: A positive electrode active material containing nickel, cobalt, and manganese, containing 80 mol % or more and less than 100 mol % of nickel among metals other than lithium, and containing a single-particulate lithium composite transition metal compound; and An additive represented by the following chemical formula A: A composition for a positive electrode active material layer of a lithium secondary battery is provided, comprising: [Chemical formula A] Li x Co (1-y-z-m) Zinc y Al z M m O4 In the above formula A, M is Ti, Zr, Mn, or Ni; 5≦x≦7; 0 <y≦0.5、0<z≦0.5、0<y+z+m<1、0≦m≦0.5である。

[0020] Lithium secondary batteries have a size required depending on the application, and must be designed accordingly within a limited space. Consumer demands for increased energy density and improved high output performance are increasing, but when using a high-capacity positive electrode material, the content of the negative electrode material must be increased to match it, so there is a limit to how much battery efficiency can be increased within a limited space. In addition, depending on the type of negative electrode material, it is necessary to design a positive electrode material with an efficiency that matches the efficiency of the negative electrode material.

[0021] The composition for a positive electrode active material layer according to the above-mentioned embodiment of the present invention is useful when a silicon-based oxide is used as the negative electrode active material. Specifically, when a silicon-based oxide is used as the negative electrode active material, a specific composition is used as the positive electrode material so as to match the efficiency of the negative electrode active material. In particular, a lithium composite transition metal oxide containing nickel, cobalt, and manganese is used as the positive electrode active material, and in this case, the nickel content of the metals other than lithium is 80 mol % or more and less than 100 mol %, and a single particulate material is used together with a specific type of additive.

[0022] Silicon oxides used as negative electrode active materials have an efficiency of, for example, a ratio of charge capacity to discharge capacity in the first cycle (charge 0.1C to 5mV, 0.005C cut-off, discharge 0.1C to 1.5V) of usually 70% to 90%, and a discharge capacity of 1,000 to 1,600mAh / g. Thus, silicon oxides have a high capacity and can be used to increase the energy density of the battery and achieve high output, but their efficiency is lower than that of graphite, and it is necessary to lower the efficiency of the positive electrode to match the efficiency of the negative electrode.

[0023] Therefore, in the above-mentioned embodiment, silicon-based oxide is used as the negative electrode active material, and a high-capacity material with a relatively high nickel content is used as the positive electrode active material. In this case, by using a single particle, the efficiency of the positive electrode can be matched to the efficiency of the negative electrode.

[0024] Specifically, the inventors have confirmed that in the case of a lithium transition metal composite oxide having a high nickel content, the powder resistance of a single particle is slightly higher than that of a secondary particle, and by employing a single particle as a positive electrode active material, the efficiency of the positive electrode can be matched to the efficiency of the negative electrode when a silicon-based oxide is used as the negative electrode active material.

[0025] The battery is also characterized in that the material of formula A is used as an additive. The additive of formula A can provide a lithium ion source or reservoir to compensate for the irreversible capacity loss of silicon-based oxides used as the negative electrode active material, but has a lower efficiency than a general positive electrode active material. In addition, the material of formula A has a higher capacity than LiNiO2 and can be blended in a relatively small amount. LiNiO2 is vulnerable to exposure to moisture in the air, and can cause gas generation in the battery, deterioration of thermal stability, and an increase in by-products in the slurry, which can lead to gelation problems, such as gelation of PVDF. In contrast, the material of formula A can play a role in matching the capacity and efficiency of the positive electrode with the negative electrode even in a relatively small amount, and can ensure moisture stability and slurry stability compared to other materials such as LiNiO2.

[0026] According to a further embodiment of the present application, the lithium composite transition metal compound containing nickel, cobalt, and manganese and containing nickel at 80 mol % or more and less than 100 mol % of the metals excluding lithium may contain one or a mixture of two or more kinds represented by the following chemical formula 1. [Chemical formula 1] Li a Ni 1-b-c-d Co b Mn c Q d O 2+δ In the above formula, Q is at least one element selected from the group consisting of Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, and Zr, and 1≦a≦1.5, 0 <b≦0.5、0<c≦0.5、0≦d≦0.1、0<b+c+d≦0.2、-0.1≦δ≦1.0である。

[0027] In the lithium composite transition metal oxide of Chemical Formula 1, Li may be contained in an amount corresponding to a, that is, 1 ≤ a ≤ 1.5. If a is less than 1, the capacity may decrease. If a exceeds 1.5, the particles may sinter in the firing process, making it difficult to manufacture the positive electrode active material. Considering the significance of the improvement effect of the capacity characteristics of the positive electrode active material by controlling the content of Li and the balance of the sinterability during the production of the active material, the Li may more preferably be contained in an amount of 1.1 ≤ a ≤ 1.2.

[0028] In the lithium composite transition metal oxide of Chemical Formula 1, Ni may be contained in an amount corresponding to 1-(b + c + d), for example, 0.8 ≤ 1-(b + c + d) < 1. If the content of Ni in the lithium composite transition metal oxide of Chemical Formula 1 is 0.8 or more, a sufficient amount of Ni contributing to charge and discharge can be ensured, and high capacity can be achieved. Preferably, 1-(b + c + d), which is the content of Ni, may be 0.8, preferably 0.83 or more, and more preferably 0.85 or more. Preferably, 1-(b + c + d), which is the content of Ni, may be 0.99 or less, 0.96 or less.

[0029] In the lithium composite transition metal oxide of Chemical Formula 1, Co may be contained in an amount corresponding to b, that is, 0 < b ≤ 0.5. If the content of Co in the lithium composite transition metal oxide of Chemical Formula 1 exceeds 0.5, there is a risk of increased cost. Considering the significance of the improvement effect of the capacity characteristics by containing Co, the Co may more specifically be contained in an amount of 0.05 ≤ b ≤ 0.2.

[0030] In the lithium composite transition metal oxide of Chemical Formula 1, Mn may be contained in an amount corresponding to c, that is, 0 < c ≤ 0.5. If c in the lithium composite transition metal oxide of Chemical Formula 1 exceeds 0.5, there is a risk that the output characteristics and capacity characteristics of the battery may instead decrease. The Mn may more specifically be contained in an amount of 0.05 ≤ c ≤ 0.2.

[0031] In the lithium composite transition metal oxide of Chemical Formula 1, Q may be a doping element contained in the crystal structure of the lithium composite transition metal oxide, and Q may be contained in an amount corresponding to d, i.e., 0≦d≦0.1. Q may be one or more selected from Na, K, Mg, Ca, Sr, Ni, Co, Ti, Al, Si, Sn, Mn, Cr, Fe, V, and Zr, and for example, Q may be Al.

[0032] In this specification, the term "single particle" is used to distinguish it from conventional secondary particle-like positive electrode active material particles formed by agglomeration of tens to hundreds of primary particles, and is a concept that includes a single particle consisting of one primary particle and an aggregate particle consisting of 10 or less primary particles.

[0033] In one embodiment of the present application, the average particle size (D 50 ) may be 1 μm to 10 μm, preferably 2 μm to 7 μm, for example, 3 μm to 7 μm.

[0034] The single particles have an average particle size (D 50 For example, the positive electrode active material in the form of a single particle can have a strength of 650 kgf / cm. 2 When rolled with a force of 100 MPa to 300 MPa, the powder may have a particle strength of 100 MPa to 300 MPa.

[0035] As a result, the positive electrode active material in the form of single particles is subjected to a pressure of 650 kgf / cm 2 Even if the electrode is rolled with a strong force, the phenomenon of an increase in fine particles in the electrode due to particle cracking is mitigated, thereby improving the life characteristics of the battery.

[0036] The method for forming the single-particle lithium transition metal composite oxide is not particularly limited, but may generally be formed by over-firing at an elevated firing temperature, using an additive such as a grain growth promoter that is useful for over-firing, or by changing a starting material.

[0037] In one embodiment of the present application, the additive represented by chemical formula A is represented by the following chemical formula A: [Chemical formula A] Li x Co (1-y-z-m) Zinc y Al z M m O4 In the above formula A, M is Ti, Zr, Mn, or Ni; 5≦x≦7; 0 <y≦0.5、0<z≦0.5、0<y+z+m<1、0≦m≦0.5である。

[0038] In the above chemical formula A, when m is 0, it may be represented by the following chemical formula A-1. [Chemical formula A-1] Li x Co (1-y-z) Zinc y Al z O4

[0039] When M is present, M may be Ti, Zr, Mn, or Ni, for example, Zr.

[0040] In the above chemical formulas A and A-1, 5.5≦x≦6.5, 0.2≦y≦0.4, 0 <z≦0.1、0≦m≦0.1であってもよい。

[0041] In one embodiment of the present application, the additive represented by the chemical formula A may be included in an amount of 0.3 parts by weight to 10 parts by weight based on 100 parts by weight of the positive electrode active material.

[0042] The additive represented by Formula A may be included in an amount of 0.3 parts by weight or more, 0.4 parts by weight or more, or 0.5 parts by weight or more, based on 100 parts by weight of the positive electrode active material. The additive represented by Formula A may be included in an amount of 10 parts by weight or less, 8 parts by weight or less, 6 parts by weight or less, 4 parts by weight or less, 2 parts by weight or less, 1 part by weight or less, or 0.8 parts by weight or less, based on 100 parts by weight of the positive electrode active material.

[0043] Using a content within this range is advantageous in matching the efficiency of the positive electrode and the negative electrode by adding the additive represented by the formula A. It is preferable to design the efficiency of the positive electrode by combining the single particle positive electrode active material contained in the positive electrode with the additive represented by the formula A to be lower than the efficiency of the negative electrode by the negative electrode active material containing a silicon-based oxide or a silicon-based oxide and a carbon-based active material. Therefore, the content of the additive represented by the formula A can be determined according to the capacity and efficiency of the positive electrode and the negative electrode active materials, and in particular, according to the content of the silicon-based oxide.

[0044] According to a further embodiment of the present application, in the composition for a positive electrode active material layer according to the above-described embodiment, the single-particulate lithium composite transition metal compound containing nickel, cobalt, and manganese and containing 80 mol % or more and less than 100 mol % of nickel among the metals excluding lithium may be 90 parts by weight to 100 parts by weight, for example 100 parts by weight, relative to 100 parts by weight of the total positive electrode active material.

[0045] In a further embodiment of the present application, the composition for the positive electrode active material layer may further include a secondary particle positive electrode active material, the content of which may be 10 parts by weight or less relative to 100 parts by weight of the positive electrode active material included in the positive electrode active material layer. This can maximize the above-mentioned effect due to the presence of the single particle positive electrode active material. When the composition for the positive electrode active material in the form of secondary particles is included, the components may be the same as those exemplified as the single particle positive electrode active material described above, but may be in the form of an aggregate of single particles.

[0046] According to a further embodiment of the present application, the composition for a positive electrode active material layer according to the above-mentioned embodiment may further include a positive electrode binder and a conductive material.

[0047] The positive electrode binder can improve the adhesion between the positive electrode active material particles and the adhesive strength between the positive electrode active material particles and the positive electrode current collector. Any positive electrode binder known in the art can be used, and non-limiting examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one or more of these may be used alone or in combination.

[0048] The positive electrode binder may be included in an amount of 0.1 parts by weight to 50 parts by weight, for example, preferably 0.3 parts by weight to 35 parts by weight, more preferably 0.5 parts by weight to 20 parts by weight, based on 100 parts by weight of the composition for positive electrode active material layer.

[0049] The conductive material contained in the positive electrode active material layer composition is used to impart electrical conductivity to the electrode, and can be used without any particular limitation as long as it has electronic conductivity without causing chemical changes in the battery.Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and one or more of these may be used alone or in mixture.

[0050] Specifically, in one embodiment, the conductive material may include one or more of single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). The conductive material may be included in an amount of 0.1 to 2 parts by weight based on 100 parts by weight of the composition for positive electrode active material layer, for example, preferably 0.3 to 1.5 parts by weight, more preferably 0.5 to 1.2 parts by weight.

[0051] According to a further embodiment of the present application, the composition for a positive electrode active material layer has a viscosity of 10,000 cps or less when stored for 3 days at 40° C. and 10% RH. The viscosity may be a viscosity of a positive electrode slurry produced using the composition for a positive electrode active material layer and then stored for 3 days at 40° C. and 10% RH.

[0052] The viscosity is a value measured using a Brookfield viscometer with a No. 64 spindle at 12 rpm, and the RH 10% refers to the humidity range.

[0053] The positive electrode active material layer composition may have a viscosity of 1,000 cps or more, 2,000 cps or more, 3,000 cps or more, or 4,000 cps or more when stored for 3 days at 40° C. and RH 10%. The positive electrode active material layer composition may have a viscosity of 10,000 cps or less, 9,000 cps or less, 8,000 cps or less, or 7,000 cps or less when stored for 3 days at 40° C. and RH 10%.

[0054] The composition for the positive electrode active material layer can satisfy the above range by including the additive represented by the formula A, which is advantageous in ensuring moisture stability and slurry stability. Specifically, LiNiO2 is vulnerable to exposure to moisture in the atmosphere, and the amount of by-products in the slurry increases, which can cause gelation problems, such as gelation of PVDF, but the additive represented by the formula A can play a role in matching the capacity and efficiency of the positive electrode with the negative electrode even in a relatively small amount, and can ensure moisture stability and slurry stability by preventing gelation in the slurry compared to other materials such as LiNiO2.

[0055] A further embodiment of the present application is a positive electrode current collector; and a positive electrode active material layer provided on the positive electrode current collector and including a composition for a positive electrode active material layer according to the above-described embodiment; The present invention provides a positive electrode for a lithium secondary battery, comprising:

[0056] A further embodiment of the present application is a lithium secondary battery comprising: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, The positive electrode active material layer includes the composition for a positive electrode active material layer according to the above-described embodiment, to provide a lithium secondary battery.

[0057] According to a further embodiment of the present application, in the lithium secondary battery according to the above-described embodiment, the negative electrode active material layer contains 15 parts by weight or more of the silicon-based oxide per 100 parts by weight of the negative electrode active material.

[0058] The silicon-based oxide may be included in an amount of 15 to 70 parts by weight, preferably 15 to 60 parts by weight, based on 100 parts by weight of the negative active material included in the negative active material layer.

[0059] The silicon-based oxide may be contained in an amount of 15 parts by weight or more, 15.5 parts by weight or more, 16 parts by weight or more, 16.5 parts by weight or more, or 17 parts by weight or more, based on 100 parts by weight of the negative electrode active material contained in the negative electrode active material layer. The silicon-based oxide may be contained in an amount of 70 parts by weight or less, 60 parts by weight or less, 30 parts by weight or less, 20 parts by weight or less, or less than 20 parts by weight, based on 100 parts by weight of the negative electrode active material contained in the negative electrode active material layer.

[0060] Using the silicon-based oxide within the above range is advantageous for realizing high capacity and high output performance. For example, the higher the content of the silicon oxide, the more advantageous it is for realizing high output. However, since the thickness of the negative electrode can become thinner, it is necessary to design an appropriate thickness range for realizing processability in a mass production line. By using the silicon-based oxide within the above range, it is possible to achieve high output performance and processability.

[0061] The silicon-based oxide contained in the negative electrode active material layer may be present in a particulate state and may contain SiO x (0 < x < 2). The SiO x (0 < x < 2) may correspond to a matrix within the silicon-based oxide particles. The SiO x (0 < x < 2) may be in a form containing Si and SiO2, and the Si may form a phase. That is, the x corresponds to the number ratio of O to Si contained in the SiO x (0 < x < 2). When the silicon-based oxide particles contain the SiO x (0 < x < 2), the discharge capacity of the secondary battery can be improved.

[0062] In a further embodiment of the present application, the silicon-based oxide may further contain a metal or a metal oxide. For example, the silicon-based oxide may further contain at least one of Li and Mg or a compound phase thereof.

[0063] When the silicon-based oxide contains Mg, the Mg may exist as an Mg compound phase. The Mg compound phase may include at least any one selected from the group consisting of, for example, Mg silicate, Mg silicide, and Mg oxide. The Mg silicate may include at least any one of Mg2SiO4 and MgSiO3. The Mg silicide may include Mg2Si. The Mg oxide may include MgO.

[0064] When the silicon-based oxide contains Li, the Li may exist as an Li compound phase. The Li compound phase may exist in at least one form of lithium silicate, lithium silicide, and lithium oxide. The Li compound phase may be lithium silicate, for example, Li a Si b O c (2 ≤ a ≤ 4, 0 < b ≤ 2, 2 ≤ c ≤ 5), and more specifically, it may include one or more selected from the group consisting of Li2SiO3, Li2Si2O5, Li3SiO3, and Li4SiO4.

[0065] The Mg compound and / or Li compound may be distributed on the surface and / or inside of the silicon-based compound particles in a form doped into the particles of the silicon-based oxide. The Mg compound and / or Li compound is distributed on the surface and / or inside of the silicon-based oxide particles, and can control the expansion / contraction of the volume of the silicon-based oxide particles to an appropriate level, and can play a role in preventing damage to the active material. Also, the Mg compound and / or the Li compound may be included in terms of reducing the proportion of the irreversible phase (for example, SiO2) of the silicon-based oxide particles and increasing the efficiency of the active material.

[0066] The content of the Mg element or Li element can be confirmed by ICP analysis. For the ICP analysis, a certain amount (about 0.01 g) of the negative electrode active material is accurately taken and then transferred to a platinum crucible, and nitric acid, hydrofluoric acid, and sulfuric acid are added to completely decompose it on a hot plate. Then, using an inductively coupled plasma optical emission spectrometer (ICPAES, Perkin-Elmer 7300), the intensity of a standard solution prepared using a standard solution (5 mg / kg) is measured at a wavelength specific to the Mg element or Li element to create a reference calibration curve. Then, the pretreated sample solution and a blank sample are introduced into the instrument, and the respective intensities are measured to calculate the actual intensity. The concentration of each component is calculated based on the created calibration curve, and the total sum is converted to a theoretical value, so that the Mg element content of the manufactured negative electrode active material can be analyzed.

[0067] When Mg and / or Li are contained in the silicon-based oxide particles, the content of each of them may be 0.1 atm % to 20 atm % relative to 100 atm % of Si element.

[0068] According to one embodiment, the silicon-based oxide particles may further include a carbon layer provided on at least a portion of the surface.

[0069] The carbon layer may cover the entire surface of the silicon-based oxide particle, or may cover only a part of the surface. The carbon layer imparts electrical conductivity to the silicon-based oxide particle, effectively suppresses volumetric changes in the negative electrode active material containing the silicon-based oxide particle, and improves the life characteristics of the battery.

[0070] In one embodiment of the present specification, the carbon layer may include at least one of amorphous carbon and crystalline carbon.

[0071] The crystalline carbon may further improve the electrical conductivity of the silicon-based oxide particles. The crystalline carbon may include at least one selected from the group consisting of fullerene, carbon nanotube, and graphene.

[0072] The amorphous carbon can appropriately maintain the strength of the carbon layer and suppress the expansion of the silicon-based oxide particles. The amorphous carbon may be a carbon-based material formed by using at least one carbide or hydrocarbon selected from the group consisting of tar, pitch, and other organic substances as a source of a chemical vapor deposition process.

[0073] The other carbonized organic matter may be a carbonized organic matter selected from carbonized sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or ketohexose, and combinations thereof.

[0074] The hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, or a substituted or unsubstituted aromatic hydrocarbon. The aliphatic or alicyclic hydrocarbon may be methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, or hexane. The substituted or unsubstituted aromatic hydrocarbon may be benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene.

[0075] In one embodiment, the carbon layer may be included in an amount of 1 wt% to 50 wt% based on 100 wt% of the silicon-based oxide particles, specifically 5 wt% to 45 wt%, more specifically 8 wt% to 40 wt%. When the above range is satisfied, the conductivity of the negative electrode active material is improved, and the volume change of the negative electrode active material during charging and discharging of the battery is easily suppressed, thereby improving the life characteristics of the battery.

[0076] In one embodiment, the thickness of the carbon layer may be 1 nm to 500 nm, specifically, 5 nm to 300 nm. When the thickness satisfies the above range, the volume change of the negative electrode active material is easily suppressed, and the side reaction between the electrolyte and the negative electrode active material is suppressed, thereby improving the life characteristics of the battery.

[0077] When the silicon-based oxide particles contain Mg and / or Li, they may be produced by a method including the step of doping the silicon-based oxide particles with Mg and / or Li.

[0078] For example, silicon-based oxide particles containing Mg can be produced by an in-situ doping method. As an example, the step of producing silicon-based oxide particles containing Mg may be formed by a step of mixing a powder of Si powder and SiO2 powder with Mg after vaporizing each of them to form a mixed gas, and a step of heat-treating the mixed gas at 800°C to 950°C in a vacuum state. As another example, the step of producing silicon-based oxide particles containing Mg may be formed by a step of mixing a powder of Si powder and SiO2 powder with Mg, and then vaporizing all of them to form a mixed gas; and a step of heat-treating the mixed gas at 800°C to 950°C in a vacuum state.

[0079] The mixed powder of the Si powder and the SiO2 powder may be heat-treated at 1,000°C to 1,800°C or 1,200°C to 1,500°C to be vaporized, and the Mg powder may be heat-treated at 500°C to 1,200°C or 600°C to 800°C to be vaporized. By reacting the materials in a gaseous state in this way, Mg can be uniformly distributed in the silicon-based oxide particles. In the silicon-based oxide particles, the Mg compound phase may include the above-mentioned Mg silicate, Mg silicide, Mg oxide, etc. The particle size of the silicon-based oxide particles containing Mg produced by the above-mentioned method may be adjusted by a pulverizing method such as a mechanical milling method, if necessary.

[0080] As a further example, the silicon-based oxide particles containing Li may be prepared by an ex-situ doping method. For example, distributing Li in the silicon-based oxide particles may include forming a carbon layer on the surface of the silicon-based oxide particles, and distributing Li in the silicon-based oxide particles on which the carbon layer is formed.

[0081] The step of forming a carbon layer on the surface of the silicon-based oxide particles may be performed by injecting a carbon-based raw material gas such as methane gas and performing heat treatment in a rotary tubular furnace. Specifically, the silicon-based oxide particles may be placed in a rotary tubular furnace, heated to 800°C to 1,150°C, 900°C to 1,050°C, or 950°C to 1,000°C at a rate of 3 to 10°C / min or about 5°C / min, and argon gas and a carbon-based raw material gas may be introduced while rotating the rotary tubular furnace, and heat treatment may be performed for 30 minutes to 8 hours to form a carbon layer.

[0082] The step of distributing Li in the silicon-based oxide particles having the carbon layer formed thereon may be performed by mixing the silicon-based oxide particles having the carbon layer formed thereon with lithium metal powder or a lithium precursor, for example, LiOH, Li2O, and, if necessary, heat treating the mixture at 400° C. to 1200° C. Alternatively, the step may be performed using an electrochemical method.

[0083] If necessary, both the in-situ doping of Mg and the ex-situ doping of Li described above may be carried out to produce silicon-based oxide particles containing both Mg and Li.

[0084] As an example, the method may include forming a carbon layer on at least a portion of a surface of a silicon oxide particle, and doping the silicon oxide particle having the carbon layer formed thereon with Mg and Li.

[0085] Before or after forming the carbon layer, the silicon-based oxide particles may be subjected to a pulverization method such as mechanical milling to adjust the particle size, if necessary.

[0086] The step of forming a carbon layer on the surface of the silicon-based oxide particles may be performed by, for example, injecting a carbon-based raw material gas such as methane gas and performing heat treatment in a rotary tubular furnace. Specifically, the silicon-based oxide particles may be placed in a rotary tubular furnace, heated to 800°C to 1,150°C, 900°C to 1,050°C, or 950°C to 1,000°C at a rate of 3 to 10°C / min or about 5°C / min, and while rotating the rotary tubular furnace, argon gas and a carbon-based raw material gas may be introduced to perform heat treatment for 30 minutes to 8 hours to form a carbon layer.

[0087] The step of doping the silicon-based oxide particles having the carbon layer formed thereon with Li and Mg may be performed by mixing the silicon-based oxide particles having the carbon layer formed thereon with a doping material, for example, magnesium metal powder or a magnesium precursor, for example, MgO; lithium metal powder or a lithium precursor, for example, LiOH, Li2O, and, if necessary, heat treating the mixture at 400° C. to 1200° C. Alternatively, the step may be performed using an electrochemical method.

[0088] According to another embodiment of the present invention, the average particle size (D 50 The average particle diameter (D) of the silicon oxide particles may be 1 μm to 30 μm. 50 Specifically, the average particle size (D) may be 3 μm to 20 μm, and more specifically, 5 μm to 10 μm. When the above range is satisfied, the side reaction between the negative electrode active material and the electrolyte is controlled, and the discharge capacity and initial efficiency of the battery can be effectively achieved. In the present specification, the average particle size (D 50 The average particle size (D) can be defined as the particle size that corresponds to 50% of the cumulative volume in the particle size distribution curve. 50 ) can be measured, for example, by using a laser diffraction method. The laser diffraction method generally allows measurement of particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0089] According to another embodiment of the present invention, the BET specific surface area of ​​the silicon-based oxide particles is 0.01 m 2 / g~150m 2 The BET specific surface area of ​​the silicon-based oxide particles is preferably 0.1 to 100.0 m 2 / g, particularly preferably 0.2m 2 / g~80.0m 2 / g, specifically 0.6m 2 / g~20m 2 / g, more specifically 0.8m 2 / g~15m 2 / g. When the above range is satisfied, the side reaction between the electrolyte and the negative electrode active material during charging and discharging of the battery can be reduced, and the life characteristics of the battery can be improved. The BET specific surface area can be measured by the BET (Brunauer-Emmett-Teller; BET) method. For example, it can be measured by the BET 6-point method using a porosimetry analyzer (Belsorp-II mini, Bell Japan Inc.) by nitrogen gas adsorption and flow method.

[0090] According to another embodiment of the present invention, the silicon-based oxide particles may further include Si crystal grains, and the Si crystal grains may have a grain size of 1 nm to 15 nm.

[0091] According to a further embodiment of the present application, in the lithium secondary battery according to the above-described embodiment, the negative electrode active material may further include a carbon-based active material.

[0092] In one embodiment of the present application, the negative electrode active material may include a carbon-based active material, and specifically, the carbon-based active material may be graphite. The graphite may be natural graphite, graphite graphite, or a mixture thereof. The carbon-based active material may be included in an amount of more than 0 parts by weight and not more than 85 parts by weight based on 100 parts by weight of the total negative electrode active material included in the negative electrode active material layer.

[0093] According to a further embodiment of the present application, in the lithium secondary battery according to the above-described embodiment, the negative electrode active material layer may further include a negative electrode binder in addition to the silicon-based oxide and the carbon-based active material.

[0094] The negative electrode binder may improve adhesion between negative electrode active material particles and between the negative electrode active material particles and a negative electrode current collector. The negative electrode binder may be any material known in the art. Non-limiting examples of the negative electrode binder include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, and may also include various copolymers thereof.

[0095] The negative electrode binder may be included in an amount of 0.1 parts by weight to 50 parts by weight, for example, preferably 0.3 parts by weight to 35 parts by weight, more preferably 0.5 parts by weight to 20 parts by weight, based on 100 parts by weight of the negative electrode active material layer.

[0096] The negative electrode active material layer may further include a conductive material. The conductive material contained in the negative electrode active material layer is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and may be, for example, graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fibers or metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive materials such as polyphenylene derivatives. The content of the conductive material in the negative electrode active material layer may be 0.01 to 30 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the negative electrode active material layer.

[0097] In one embodiment of the present application, the positive electrode includes a positive electrode current collector, and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0098] The positive electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity, and may be, for example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector may generally have a thickness of 1 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesive strength of the positive electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0099] In one embodiment of the present application, the negative electrode current collector is not particularly limited as long as it does not cause a chemical change in the battery and has electrical conductivity. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface is treated with carbon, nickel, titanium, silver, or the like. Specifically, a transition metal that easily adsorbs carbon, such as copper or nickel, may be used as the current collector. The thickness of the current collector may be 1 μm to 500 μm, but the thickness of the current collector is not limited thereto.

[0100] In one embodiment of the present application, the thickness of the positive electrode and negative electrode active material layers may be 20 μm or more and 500 μm or less, preferably 50 μm or more and 200 μm or less. The thickness of the positive electrode active material layer may be 90% to 110%, for example 95% to 105%, of the thickness of the negative electrode active material layer, or these thicknesses may be the same.

[0101] In one embodiment of the present application, the ratio (C / A) of the efficiency of the positive electrode (C) to the efficiency of the negative electrode (A) may be 1 or less, preferably less than 1. The ratio (C / A) may be 0.8 or more, preferably 0.9 or more, more preferably 0.95 or more, for example 0.96 or more, or 0.97 or more. In one embodiment of the present application, the difference between the efficiency of the positive electrode (C) and the efficiency of the negative electrode (A) may be 10% or less, for example 5% or less, or 3% or less. In one embodiment of the present application, the efficiency of the positive electrode (C) and the efficiency of the negative electrode (A) are preferably 80% or more, more preferably 83% or more, and even more preferably 85% or more. When the positive electrode and the negative electrode have the above-mentioned efficiencies, the irreversible capacity of the positive electrode is even larger, and the target high capacity can be expressed from the beginning.

[0102] In one embodiment of the present application, the ratio (AA / BB) of the content of the additive represented by chemical formula A relative to 100 parts by weight of the positive electrode active material (AA) to the content of the silicon-based oxide relative to 100 parts by weight of the negative electrode active material (BB) may be 0.01 to 0.1, more preferably 0.015 to 0.06, and further preferably 0.02 to 0.04.

[0103] The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator that is generally used as a separator in a secondary battery can be used without any particular limitation. In particular, it is preferable that the separator has low resistance to ion movement of the electrolyte and has excellent electrolyte humidification ability. 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 normal porous nonwoven fabric, for example, a nonwoven fabric made of high-melting glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric substance may be used, and may be selectively used as a single layer or multilayer structure.

[0104] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in the manufacture of lithium secondary batteries.

[0105] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0106] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0107] In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates among the carbonate-based organic solvents, can be preferably used as high-viscosity organic solvents, because they have a high dielectric constant and dissociate lithium salts well. When such cyclic carbonates are mixed in an appropriate ratio with linear carbonates having low viscosity and low dielectric constant, such as dimethyl carbonate and diethyl carbonate, an electrolyte having high electrical conductivity can be prepared, and therefore such a mixture can be used even more preferably.

[0108] The metal salt may be a lithium salt, which is a substance that is easily dissolved in the non-aqueous electrolyte. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3- , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - One or more selected from the group consisting of may be used.

[0109] In addition to the constituent components of the electrolyte, the electrolyte may further include one or more additives such as a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine 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 a decrease in battery capacity, and improving the discharge capacity of the battery.

[0110] The lithium secondary battery according to an embodiment of the present invention may be a cylindrical battery. The cylindrical battery may mean that the shape of the battery itself including an assembly including a positive electrode, a negative electrode, a separator, and an electrolyte is cylindrical, and specifically, may be composed of a cylindrical can, a battery assembly installed inside the cylindrical can, and a top cap. It is preferable to use a cylindrical battery that is more flexible in terms of gas amount compared to a pouch, but is not limited thereto.

[0111] A further embodiment of the present invention provides a battery module including the cylindrical battery as a unit cell, and a battery pack including the battery module. The battery module and the battery pack include the secondary battery having high capacity, high rate characteristics, and high cycle characteristics, and can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0112] The lithium secondary battery according to the embodiment of the present invention stably exhibits excellent discharge capacity, output characteristics, and cycle performance, and can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems, as well as portable devices such as mobile phones, notebook computers, and digital cameras. For example, the battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, including power tools, electric vehicles (EVs), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEVs), or power storage systems.

[0113] Below, preferred examples are presented to aid in understanding the present invention. However, the following examples are merely for the purpose of illustrating the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and technical spirit of the present description, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0114] <Example 1> Based on 100 parts by weight of the positive electrode active material layer, the positive electrode active material contains 93.3 mol% Ni, 4.9 mol% Co, and 1.8 mol% Mn, among metals other than lithium, and is composed of a single-particle lithium composite transition metal compound and Li6Co 0.7 Zinc 0.25 Al 0.05A positive electrode active material layer forming composition including 98.04 parts by weight of O4 additive (0.5 parts by weight based on 100 parts by weight of positive electrode active material), 1 part by weight of PVDF as a binder, and a CNT pre-dispersion liquid including 0.8 parts by weight of CNT and 0.16 parts by weight of a dispersant as a conductive material was coated on an aluminum foil having a thickness of 30 μm to a dry thickness of 103 μm, and then dried to prepare a positive electrode.

[0115] Based on 100 parts by weight of the negative electrode active material layer, the negative electrode active materials included artificial graphite and natural graphite (weight ratio of 7:3, 85 parts by weight based on 100 parts by weight of the negative electrode active material), 97.7 parts by weight of SiO (15 parts by weight based on 100 parts by weight of the negative electrode active material), which is a silicon-based oxide, and 1.15 parts by weight of SBR (styrene-butadiene rubber) and 1 part by weight of CMC (carboxymethyl cellulose) as binders, and in addition, a CNT pre-dispersion liquid containing 0.09 parts by weight of a dispersant and 0.06 parts by weight of single-walled CNTs was coated on a copper foil having a thickness of 15 μm to a dry thickness of 86 μm, and then dried to manufacture a negative electrode.

[0116] The positive electrode and the negative electrode were laminated with a separator interposed between them, and an electrolyte (1.4M LiPF6, EC (ethylene carbonate) / EMC (ethylmethyl carbonate) / DMC (dimethyl carbonate) = 20 / 5 / 75 (Vol%), SN (succinonitrile) 1%, FEC (fluoroethylene carbonate) 10%) was injected to prepare a battery.

[0117] The content of the additive was set to 0.5 parts by weight based on 100 parts by weight of the positive electrode active material so that the efficiency of the positive electrode was about 86%. A positive electrode slurry was prepared using the composition for forming a positive electrode active material layer containing the additive, and the slurry was stored in an environment of 40° C. and RH 10% to measure the viscosity of the slurry. The results are shown in Table 1.

[0118] <Example 2> A negative electrode was prepared in the same manner as in Example 1, except that 10 parts by weight of SiO, a silicon-based oxide, was added based on 100 parts by weight of the negative electrode active material.

[0119] <Example 3> A negative electrode was prepared in the same manner as in Example 1, except that 20 parts by weight of SiO, which is a silicon-based oxide, was added based on 100 parts by weight of the negative electrode active material.

[0120] <Comparative Example 1> A positive electrode was manufactured in the same manner as in Example 1, except that the additive contained in the positive electrode active material layer was LiNiO2 (2 parts by weight based on 100 parts by weight of the positive electrode active material).

[0121] The content of LiNiO2 was set to 2 parts by weight based on 100 parts by weight of the positive electrode active material so that the efficiency of the positive electrode was about 86%, and the viscosity of the slurry was measured in the same manner as in Example 1. The results are shown in Table 1.

[0122] [Table 1]

[0123] Referring to Table 1, Example 1 contains an additive represented by Chemical Formula A according to the present invention. After preparing a positive electrode slurry using the composition for forming a positive electrode active material layer, the viscosity did not exceed 10,000 cps or gel, and the viscosity was maintained in the range of 10,000 cps or less until the third day of storage in an environment of 40° C. and RH 10%, which is advantageous for the stability of the slurry.

[0124] In contrast, Comparative Example 1 contains LiNiO2, which is not an additive represented by formula A according to the present invention, and after preparing a positive electrode slurry using the composition for forming a positive electrode active material layer, it was confirmed that the viscosity exceeded 10,000 cps on the second day of storage in an environment of 40°C and 10% RH, and gelation occurred on the third day of storage. In the case of LiNiO2, it was confirmed that the viscosity exceeded 10,000 cps due to a sudden increase in viscosity, causing gelation, which may affect the processability during electrode manufacturing and may cause problems with the stability of the slurry.

[0125] <Comparative Example 2> A positive electrode was prepared in the same manner as in Example 1, except that the positive electrode active material contained 93.3 mol% Ni, 4.9 mol% Co, and 1.8 mol% Mn among metals other than lithium, and contained a secondary particle-shaped lithium transition metal composite compound.

[0126] <Comparative Example 3> A positive electrode was prepared in the same manner as in Example 1, except that the positive electrode active material contained 60 mol % Ni, 20 mol % Co, and 20 mol % Mn among the metals other than lithium.

[0127] Table 2 shows the morphology of the lithium transition metal composite compound and the content of SiO, which is a silicon-based oxide, for Examples 1 to 3 and Comparative Examples 2 and 3 (based on 100 parts by weight of the negative electrode active material).

[0128] [Table 2]

[0129] Referring to Table 2, Example 1 according to the present invention contains 15 parts by weight of silicon-based oxide SiO and 85 parts by weight of graphite based on 100 parts by weight of the negative electrode active material, and Example 2 contains 10 parts by weight of silicon-based oxide SiO and 90 parts by weight of graphite. It can be seen that Example 1 has a 5% increase in design capacity compared to Example 2, and that when the content of silicon-based oxide SiO in the negative electrode active material is less than 15 parts by weight, the design capacity of the lithium secondary battery is reduced.

[0130] Meanwhile, it can be seen that the design capacity of Comparative Example 3 is reduced by 14% compared to Example 1. This shows that when the nickel content in the positive electrode active material is 60 mol %, the design capacity of the lithium secondary battery is reduced by 14% compared to when the nickel content is 93.3 mol %.

[0131] In addition, the batteries produced in Example 1, Example 3, and Comparative Example 2 were charged and discharged at 55° C. to evaluate the capacity retention rate, and a graph of the 55° C. cycle of the batteries produced above is shown in FIG. Charging conditions: 0.25C 4.2V, 250mA cut-off at 55℃ Discharge conditions: 1 / 3C 2.5V, cut-off at 55℃ The capacity retention rates were calculated as follows. Capacity retention rate (%) = (Nth discharge capacity / 1st discharge capacity) x 100

[0132] FIG. 1 is a graph showing a cycle number (N) vs. capacity retention rate (%) curve for a 55° C. cycle in which charging and discharging were performed at 55° C. A capacity retention rate of 80% must be met during the 55° C. cycle.

[0133] Example 1, which contains a lithium composite transition metal compound in the form of a single particle and has a content of 93.3 mol % Ni, 4.9 mol % Co, and 1.8 mol % Mn among metals other than lithium as the positive electrode active material according to the present invention, was confirmed to have an excellent result of maintaining a high capacity retention rate during cycles at 55° C. compared to Comparative Example 2, which contains a lithium composite transition metal compound in the form of a secondary particle and has a content of 93.3 mol % Ni, 4.9 mol % Co, and 1.8 mol % Mn among metals other than lithium as the positive electrode active material according to the present invention. On the other hand, in the case of Comparative Example 2, it can be interpreted that the balance between the efficiency of the positive electrode and the efficiency of the negative electrode is lost as the cycle progresses, and as the amount of use of the negative electrode increases, the capacity retention rate drops sharply and the cycle performance drops.

[0134] It can be seen that Example 1 does not fade when cycling at 55° C., compared to Example 3, which contains 20 parts by weight of SiO, a silicon-based oxide, and 80 parts by weight of graphite, based on 100 parts by weight of the negative electrode active material. This can be interpreted as the fact that when the SiO content is relatively high, the efficiency of the negative electrode decreases due to the influence of the material caused by the increased SiO content in the negative electrode, and as the cycle progresses, the negative electrode is used relatively more, resulting in a decrease in cycle performance.

Claims

1. A positive electrode active material including a single particle lithium composite transition metal compound containing nickel, cobalt, and manganese, and containing nickel in an amount of 80 mol % or more and less than 100 mol % of metals other than lithium; and An additive represented by the following chemical formula A: A composition for a positive electrode active material layer of a lithium secondary battery, comprising: [Chemical formula A] Li ｘ Co （１－ｙ－ｚ－ｍ） Zn ｙ Al ｚ M ｍ O ４ In the above chemical formula A, M is Ti, Zr, Mn, or Ni, and 5≦x≦7, 0<y≦0.5, 0<z≦0.5, 0<y+z+m<1, and 0≦m≦0.

5.

2. The composition for a positive electrode active material layer of a lithium secondary battery according to claim 1, wherein the additive is included in an amount of 0.3 to 10 parts by weight based on 100 parts by weight of the positive electrode active material.

3. 2. The composition for a positive electrode active material layer of a lithium secondary battery according to claim 1, wherein the composition contains the nickel, cobalt, and manganese, and contains 80 mol % or more and less than 100 mol % of the nickel among the metals excluding lithium, and the single-particulate lithium composite transition metal compound is contained in an amount of 90 parts by weight to 100 parts by weight per 100 parts by weight of the total positive electrode active material.

4. The composition for a positive electrode active material layer of a lithium secondary battery according to claim 1 , further comprising a positive electrode binder and a conductive material.

5. The composition for a positive electrode active material layer of a lithium secondary battery according to claim 1, wherein the composition for a positive electrode active material layer has a viscosity of 10,000 cps or less when stored at 40° C. and 10% RH for 3 days.

6. A positive electrode current collector; and A positive electrode active material layer provided on the positive electrode current collector, the positive electrode active material layer comprising the composition for a positive electrode active material layer according to any one of claims 1 to 5; A positive electrode for a lithium secondary battery comprising:

7. A lithium secondary battery comprising: a positive electrode; a negative electrode; a separator disposed between the positive electrode and the negative electrode; and an electrolyte, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on the negative electrode current collector, The positive electrode active material layer comprises the composition for a positive electrode active material layer according to any one of claims 1 to 5. A lithium secondary battery.

8. 8. The lithium secondary battery according to claim 7, wherein the negative electrode active material layer contains 15 parts by weight or more of silicon-based oxide with respect to 100 parts by weight of the total negative electrode active material.

9. The lithium secondary battery according to claim 8 , wherein the negative electrode active material layer further comprises a carbon-based active material.

10. The lithium secondary battery according to claim 8 , wherein the silicon-based oxide contains at least one of Mg and Li.

11. The lithium secondary battery according to claim 9 , wherein the negative electrode active material layer further comprises a negative electrode binder and a conductive material.

12. The lithium secondary battery according to claim 7 , wherein the lithium secondary battery is a cylindrical battery.

13. A battery module comprising the lithium secondary battery according to claim 7.

14. A battery pack comprising the battery module according to claim 13.

Images