Cathode materials and lithium secondary batteries containing them

Abstract

This invention relates to a cathode material comprising: a first cathode active material comprising a lithium manganese oxide having a spinel structure; and a second cathode active material comprising a lithium nickel oxide having a layered structure and comprising nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al), wherein the lithium manganese oxide and the lithium nickel oxide are single-particle particles.

Description

Technical Field

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2023-0190076, filed on December 22, 2023, with the Korean Intellectual Property Office, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to a cathode material and a lithium secondary battery containing the same, and more particularly to a cathode material having excellent thermal stability and capacity characteristics while reducing manganese leaching at high temperatures, and a lithium secondary battery containing the cathode material. Background Technology

[0004] Recently, the development of large-volume, large-can battery packs has been underway to further increase the capacity of batteries used in electric vehicles. With conventionally used small cylindrical batteries (i.e., cylindrical batteries with a form factor of 1865 or 2170), the small capacity means that resistance or heat generation does not significantly affect battery performance. However, applying the specifications of conventional small cylindrical batteries to large batteries could potentially lead to serious battery safety issues.

[0005] As battery size increases, the amount of heat and gas generated inside the battery also increases. This heat and gas can cause the internal temperature and pressure to rise, potentially leading to battery fire or explosion. To prevent this, the heat and gas inside the battery need to be properly vented to the outside. Therefore, the cross-sectional area of ​​the battery, which serves as the channel for heat dissipation, needs to increase proportionally with the volume. However, since increasing the cross-sectional area is often insufficient to increase the volume, the heat generated inside the battery increases as it becomes larger, leading to other problems including increased explosion risk and reduced output. Furthermore, rapid charging at high voltages can cause battery fires due to the large amount of heat generated around the electrode tabs in a short period.

[0006] On the other hand, lithium manganese oxides with a spinel structure, such as LiMn2O4, have the advantages of excellent thermal stability and low cost, but they also have problems such as small capacity and high efficiency during charge and discharge due to the presence of Mn. 3+ The structural deformation (Jahn-Teller distortion) and the dissolution of Mn due to the formation of HF by reacting with the electrolyte at high temperatures will cause the performance of lithium secondary batteries to degrade rapidly.

[0007] Therefore, there is a need to develop a lithium secondary battery with excellent thermal stability and capacity characteristics, low manganese leaching at high temperatures, and excellent lifespan characteristics. Summary of the Invention

[0008] Technical issues

[0009] The present invention aims to solve the aforementioned problems and provide a cathode material comprising a lithium manganese oxide with a spinel structure while reducing manganese leaching at high temperatures. Furthermore, the present invention aims to provide a lithium secondary battery with excellent thermal stability, high-temperature life characteristics, and capacity characteristics by incorporating the cathode material according to the present invention.

[0010] Technical solution

[0011] [1] This invention provides a cathode material, the cathode material comprising: A first positive electrode active material, the first positive electrode active material comprising a lithium manganese oxide having a spinel structure; and The second positive electrode active material comprises a lithium nickel oxide having a layered structure and containing nickel (Ni), cobalt (Co), manganese (Mn) and aluminum (Al). Among them, lithium manganese oxides and lithium nickel oxides are single-particle particles.

[0012] [2] The present invention provides a cathode material according to [1], wherein the lithium nickel oxide contains more than 90 mol% nickel relative to all metals except lithium.

[0013] [3] The present invention provides a positive electrode material according to [1] or [2], wherein the weight ratio of the first positive electrode active material to the second positive electrode active material is 75:25 to 50:50.

[0014] [4] The present invention provides a cathode material according to at least one of [1] to [3], wherein the average particle size (D) of the first cathode active material and the second cathode active material is... 50 The ratio of ) is 5:1 to 1.5:1.

[0015] [5] The present invention provides a cathode material according to at least one of [1] to [4], wherein the average particle size (D) of the first cathode active material is... 50 The thickness ranges from 5 μm to 20 μm.

[0016] [6] The present invention provides a cathode material according to at least one of [1] to [5], wherein the average particle size (D) of the second cathode active material is... 50 The range is from 1 μm to 10 μm.

[0017] [7] The present invention provides a cathode material according to at least one of [1] to [6], wherein the lithium manganese oxide has a composition represented by [Chemical Formula 1].

[0018] [Chemical Formula 1]

[0019] Li 1+a1 Mn 2-x1 M 1 x1 O 4-y1 A y1

[0020] In chemical formula 1, M 1 It is a doping element selected from Al, Li, Mg, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au, and Si. A is one or more elements selected from F, Cl, Br, I, At, and S. 0≤a1≤0.4,0 <x1≤0.5,0≤y1≤0.1。

[0021] [8] The present invention provides a cathode material according to at least one of [1] to [7], wherein the lithium manganese oxide contains 0.5% to 3% M based on the total weight of the lithium manganese oxide. 1 .

[0022] [9] The present invention provides a cathode material according to at least one of [1] to [8], comprising a first coating on the surface of a lithium manganese oxide, and

[0023] The first coating contains one or more elements selected from Al, Ti, W, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, S, and B.

[0024]

[10] The present invention provides a cathode material according to [9], wherein the content of the first coating is from 0.05% by weight to 0.3% by weight based on the total weight of the first cathode active material.

[0025]

[11] The present invention provides a cathode material according to at least one of [1] to

[10] , wherein the lithium nickel oxide has a composition represented by [Chemical Formula 2].

[0026] [Chemical Formula 2]

[0027] Li a2 [Ni x2 Co y2 Mn z2 Al w2 M 2 v2 O2

[0028] In chemical formula 2, M 2 It is a doping element selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. 0.8≤a²≤1.2, 0.9≤x²<1, 0 <y2≤0.2,0<z2≤0.2,0<w2≤0.2,0≤v2≤0.1。

[0029]

[12] The present invention provides a cathode material according to at least one of [1] to

[11] , comprising a second coating on the surface of a lithium nickel oxide, and

[0030] The second coating contains one or more elements selected from Ti, W, B, F, P, Mg, Ni, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, S, Co, and Al.

[0031]

[13] The present invention provides a cathode material according to

[12] , wherein the content of the second coating is from 0.01% by weight to 5% by weight based on the total weight of the second cathode active material.

[0032]

[14] The present invention provides a lithium secondary battery, the lithium secondary battery comprising: An electrode assembly comprising: a positive electrode comprising a positive electrode material comprising any one of [1] to

[13] , a negative electrode, and a separator between the positive electrode and the negative electrode; Electrolytes; and A battery case that houses the electrode assembly and electrolyte.

[0033]

[15] The present invention provides a lithium secondary battery according to

[14] , wherein the battery casing is a cylindrical battery casing.

[0034]

[16] The present invention provides a lithium secondary battery according to

[14] or

[15] , wherein the ratio of the diameter (T) to the height (H) of the lithium secondary battery (shape factor ratio) is 0.4 or more.

[0035]

[17] The present invention provides a lithium secondary battery according to at least one of

[14] to

[16] , wherein the lithium secondary battery includes uncoated portions on at least a portion of the positive and negative electrodes, wherein no active material layer is formed thereon, and

[0036] The uncoated portions of the positive and negative electrodes are defined as electrode tabs.

[0037] Beneficial effects

[0038] According to the present invention, the amount of manganese leaching at high temperatures can be significantly reduced by using a cathode material in which lithium manganese oxide with a spinel structure is mixed with lithium nickel oxide containing nickel, cobalt, manganese and aluminum, and both the lithium manganese oxide and the lithium nickel oxide are single-particle particles. Therefore, compared with conventional materials, the cathode material according to the present invention can have excellent high-temperature storage characteristics and high-temperature cycling characteristics.

[0039] Furthermore, the cathode material according to the present invention can improve the thermal stability of lithium secondary batteries by including lithium manganese oxides with spinel structures, and can achieve high energy density and high capacity characteristics by including lithium nickel oxides with excellent capacity characteristics. Attached Figure Description

[0040] Figure 1 This is a diagram showing the stacked state of the electrode assembly according to the invention before winding.

[0041] Figure 2 This is a cross-sectional view showing the structure of the electrodes of an electrode assembly according to an embodiment of the present invention.

[0042] Figure 3 This is a diagram illustrating the structure of an electrode assembly according to an embodiment of the present invention.

[0043] Figure 4 This is a cross-sectional view showing the structure of a lithium secondary battery according to an embodiment of the present invention.

[0044] Figure 5 This is a cross-sectional view showing the structure of a lithium secondary battery according to another embodiment of the present invention.

[0045] Figure 6 This is a diagram illustrating the battery pack according to the present invention.

[0046] Figure 7 This is a surface image of the lithium manganese oxide prepared in Preparation Example 1 of the present invention at a magnification of 3,000x, obtained using a scanning electron microscope.

[0047] Figure 8 This is a surface image of the lithium nickel oxide prepared in Preparation Example 3 of the present invention at a magnification of 5,000x, obtained using a scanning electron microscope.

[0048] Figure 9 This is a surface image of the lithium nickel oxide prepared in Preparation Example 4 of the present invention, obtained using a scanning electron microscope at a magnification of 5,000x. Detailed Implementation

[0049] The invention will be described in more detail below.

[0050] The words or terms used in this specification and claims should not be construed as having the meanings defined in common dictionaries. The words or terms should be interpreted as having meanings consistent with the technical spirit of the invention, based on the principle that the inventors can appropriately define the meanings of the words or terms to best interpret the invention.

[0051] The terminology used in this specification is for illustrative purposes only and is not intended to limit the invention. Unless otherwise expressly stated, singular expressions include plural expressions.

[0052] In this specification, the terms “comprising,” “including,” or “having” are intended to specify the presence of a feature, number, step, constituent element, or combination thereof, but should be understood to not exclude the possibility of the presence or addition of more than one other feature, number, step, constituent element, or combination thereof.

[0053] In this invention, "single-particle type particle" refers to a particle composed of 30 or fewer nodules, and includes the concepts of single particles and quasi-single particles. "Single particle" refers to a particle composed of a single nodule, while "quasi-single particle" refers to a particle that is a complex formed as 30 or fewer nodules.

[0054] In this invention, a “small piece” is a particle unit that constitutes a single particle and a quasi-single particle, and can be a single crystal without grain boundaries, or a polycrystalline material that does not appear to have grain boundaries when observed with a scanning electron microscope (SEM) at a magnification of 5,000 to 20,000 times.

[0055] In this invention, a "secondary particle" refers to a particle formed by the aggregation of dozens to hundreds of primary particles. More specifically, a secondary particle can be an aggregation of more than 40 primary particles.

[0056] In this invention, the term "particle" includes any one or all of the following: single particle, quasi-single particle, primary particle, small piece, and secondary particle.

[0057] In this invention, "average particle size D50" refers to the particle size at 50% of the volumetric cumulative particle size distribution of the positive electrode active material powder, and can be measured using laser diffraction. For example, after dispersing the positive electrode active material powder in a dispersion medium, the dispersion is introduced into a commercially available laser diffraction particle size measurement device (e.g., Microtrac MT 3000) and irradiated with ultrasonic waves outputting 60 W and approximately 28 kHz to obtain a volumetric cumulative particle size distribution map. Then, the particle size corresponding to 50% of the volumetric cumulative amount is obtained, thereby measuring the particle size.

[0058] In order to develop cathode materials with excellent thermal stability and excellent high-temperature storage and cycling characteristics, the inventors of this invention have conducted repeated research and found that if single-particle lithium manganese oxides with spinel structures are used together with single-particle lithium nickel oxides, the amount of manganese leaching at high temperatures is significantly reduced, resulting in excellent high-temperature storage and high-temperature cycling characteristics, while also improving thermal stability and capacity characteristics, thus completing this invention.

[0059] The present invention will be described in detail below.

[0060] The cathode material and / or lithium secondary battery according to the present invention comprises at least one of the disclosed configurations, and may comprise any combination of technically feasible configurations thereof.

[0061] cathode materials

[0062] The cathode material according to the present invention comprises: A first positive electrode active material, the first positive electrode active material comprising a lithium manganese oxide having a spinel structure; and The second positive electrode active material comprises a lithium nickel oxide having a layered structure and containing nickel (Ni), cobalt (Co), manganese (Mn) and aluminum (Al). Among them, lithium manganese oxides and lithium nickel oxides are single-particle particles.

[0063] Generally, if lithium manganese oxides with a spinel structure are used as cathode materials for lithium secondary batteries, the advantages are that lithium secondary batteries using lithium manganese oxides can have excellent thermal stability and can reduce costs. However, if lithium manganese oxides are used alone, the disadvantage is that there are limitations in the capacity characteristics of lithium secondary batteries.

[0064] Furthermore, in the case of lithium manganese oxides with a spinel structure, if the oxidation number of manganese falls below +3.5 during repeated charging and discharging, it is possible that due to the high spin d... 4 electronic configuration of Mn 3+ This leads to structural deformation (Jahn-Teller distortion). Therefore, the structure of lithium manganese oxides with a spinel structure may become unstable, especially at temperatures above 50°C. 3+ Mn can be formed through disproportionation reaction 2+ Ions, and the presence of Mn 2+There is the issue of ions dissolving into the electrolyte. Furthermore, repeated charging and discharging under high voltage conditions causes the LiPF6 additive in the electrolyte to decompose, producing hydrofluoric acid (HF). Since HF accelerates manganese dissolution, it exacerbates the degradation of the cathode material, leading to further deterioration of the lithium-ion battery's performance.

[0065] To address the aforementioned problems, the inventors of this invention conducted repeated research and discovered that by mixing lithium manganese oxides with a spinel structure with lithium nickel cobalt manganese aluminum oxides, and using single-particle forms of both lithium manganese oxides and lithium nickel cobalt manganese aluminum oxides, the amount of manganese leaching at high temperatures was significantly reduced, thereby improving lifetime and capacity characteristics. On the other hand, according to the inventors' research, even when lithium manganese oxides and lithium nickel cobalt manganese aluminum oxides are mixed and used, if one of them has a secondary particle form, or if the lithium nickel oxide is not a quaternary oxide containing nickel, cobalt, manganese, and aluminum, the effect of reducing high-temperature manganese leaching is not significant.

[0066] On the other hand, in this invention, the weight ratio of the first positive electrode active material to the second positive electrode active material can be from 75:25 to 50:50, preferably from 70:30 to 52:48, more preferably from 65:35 to 55:45, and even more preferably from 62:38 to 57:43. If this range is met, thermal stability, high-temperature lifetime characteristics, capacity characteristics, and resistance characteristics can be achieved simultaneously and excellently.

[0067] Cathode materials can include average particle size (D) 50 Different first and second positive electrode active materials. Preferably, the average particle size (D) of the first positive electrode active material is... 50 The particle size can be larger than the average particle size (D) of the second positive electrode active material. 50 In this case, the leaching of manganese from the first positive electrode active material can be more effectively suppressed, resulting in further improvements in the battery's high-temperature storage and high-temperature cycling characteristics. Furthermore, during the electrode rolling process, the smaller particle size of the second positive electrode active material fills the pores of the larger particle size of the first positive electrode active material, thereby increasing the positive electrode density and achieving high energy density, thus enabling excellent capacity characteristics.

[0068] Specifically, the average particle size (D) of the first positive electrode active material and the second positive electrode active material 50 The ratio of the components can be from 5:1 to 1.5:1, preferably from 4.5:1 to 1.7:1, more preferably from 4:1 to 2:1, even more preferably from 3.5:1 to 2:1, and even more preferably from 3:1 to 2:1. If this range is met, the high-temperature life characteristics and capacity characteristics can be further improved.

[0069] Hereinafter, the first positive electrode active material and the second positive electrode active material will be described in detail.

[0070] (1) First positive electrode active material

[0071] The first positive electrode active material contains a lithium manganese-based oxide having a spinel structure.

[0072] If it contains a lithium manganese-based oxide having a spinel structure, there are advantages in terms of low cost, non-toxicity, and it is possible to achieve a positive electrode active material with excellent electrochemical and thermal stability.

[0073] The lithium manganese-based oxide may have a composition represented by the following [Chemical Formula 1].

[0074] [Chemical Formula 1]

[0075] Li 1+a1 Mn 2-x1 M 1 x1 O 4-y1 A y1

[0076] In Chemical Formula 1, M 1 is a doping element that replaces the manganese site in the lithium manganese-based oxide, and can specifically be one or more doping elements selected from Al, Li, Mg, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au, and Si. Preferably, M 1 can be one or more doping elements selected from Al, B, Li, Mg, and Zn.

[0077] A is an element that replaces the oxygen site in the lithium manganese-based oxide, and can be one or more elements selected from F, Cl, Br, I, At, and S.

[0078] On the other hand, 1 + a1 represents the molar ratio of lithium in the lithium manganese-based oxide, and can be 0 ≤ a1 ≤ 0.4, preferably 0.1 ≤ a1 ≤ 0.4, more preferably 0.25 ≤ a1 ≤ 0.35.

[0079] x1 represents the molar ratio of the doping element M 1 in the lithium manganese-based oxide, and can be 0 < x1 ≤ 0.5, preferably 0.03 ≤ x1 ≤ 0.25. If the molar ratio x1 of M 1 satisfies this range, a positive electrode active material with a stable structure can be obtained while minimizing the decrease in the capacity of the lithium secondary battery containing the lithium manganese-based oxide.

[0080] y1 represents the molar ratio of element A in lithium manganese oxides, and can be 0≤y1≤0.1, preferably 0.01≤y1≤0.05.

[0081] The lithium manganese oxides represented by the above chemical formula 1 contain a dopant element M with a low oxidation number. 1 This results in a relatively high average oxidation number of Mn ions, which in turn leads to an increased Mn content during charge and discharge. 3+ Minimize the resulting structural deformation (Jahn-Teller distortion), thereby reducing the occurrence of manganese (Mn) leaching at high temperatures.

[0082] Based on the total weight of lithium manganese oxides, the lithium manganese oxides may contain M in an amount of 0.5 wt% to 3 wt%, preferably 0.8 wt% to 2.5 wt%, more preferably 1.0 wt% to 2.0 wt%, and even more preferably 1.3 wt% to 1.6 wt%. 1 If this range is met, then during charging and discharging, due to Mn 3+ This minimizes the resulting structural deformation, thereby reducing manganese leaching at high temperatures, and excellent thermal stability can be achieved by including Mn in lithium manganese oxides at a sufficient molar ratio.

[0083] The lithium manganese oxide may include a first coating, and the first coating may be located on the surface of the lithium manganese oxide.

[0084] The first coating can block the contact between lithium manganese oxides and the electrolyte, thereby suppressing gas generation during charging and discharging and preventing manganese (Mn) from dissolving at high temperatures.

[0085] The first coating may contain one or more elements selected from Al, Ti, W, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, S, and B (hereinafter referred to as "coating elements"), preferably one or more elements selected from Al, Ti, Zn, W, and B, and more preferably one or more elements selected from B, W, and Al. If the first coating contains coating elements, the dissolution of manganese caused by HF formed through a side reaction with the electrolyte can be more effectively suppressed.

[0086] On the other hand, the first coating can be formed continuously or discontinuously on the surface of the lithium manganese oxide represented by the above [Chemical Formula 1].

[0087] For example, the first coating can be formed in the form of particles containing coating elements discontinuously attached to the surface of lithium manganese oxides. In this case, the particles containing coating elements can be oxide particles such as ZnO, Al2O3, TiO2, WO3, MgO, CaO, B2O3, NbO2, SrO, CrO, Mo2O5, Bi2O3, and SiO. If the oxide particles are present on the surface of the lithium manganese oxide particles, as shown in Reaction 1 below, the dissolution of Mn caused by HF is more effectively suppressed because the oxide particles capture and decompose HF formed by reaction with the electrolyte.

[0088] [Reaction 1]

[0089] B₂O₃ + 6HF → 2BF₃ + 3H₂O

[0090] ZnO + 2HF → ZnF2 + H2O

[0091] Al₂O₃ + 6HF → 2AlF₃ + 3H₂O

[0092] Alternatively, the first coating can be formed on the surface of the lithium manganese oxide as a film containing the coating element. If the first coating is formed in the form of a film, the effect of blocking the contact between the electrolyte and the lithium manganese oxide and the effect of inhibiting manganese dissolution are even better. If the first coating in the form of the above-mentioned film is formed on the surface of the lithium manganese oxide particles, the first coating blocks the contact with the electrolyte, thereby further inhibiting side reactions with the electrolyte and gas generation.

[0093] Based on the total weight of the first positive electrode active material, the first coating may be included in 0.05 wt% to 0.3 wt%, preferably 0.07 wt% to 0.25 wt%, more preferably 0.08 wt% to 0.2 wt%, and even more preferably 0.09 wt% to 0.13 wt%. If this range is met, the increase in resistance of the positive electrode due to the first coating can be minimized, while effectively blocking the contact between the electrolyte and lithium manganese oxides, thereby reducing manganese dissolution at high temperatures.

[0094] On the other hand, the first coating can be formed in an area corresponding to 50% to 100%, preferably 80% to 100%, and more preferably 90% to 100% of the total surface area of ​​the lithium manganese oxide. If the area of ​​the first coating meets this range, the contact between the electrolyte and the lithium manganese oxide can be effectively blocked.

[0095] In addition, lithium manganese oxides are single-particle particles.

[0096] Typically, in the case of lithium manganese oxides containing secondary particles of tens to hundreds of primary particles aggregated within them, the primary particles are prone to breakage during the rolling process in cathode manufacturing, and internal cracks may form within the particles during charge-discharge processes. Therefore, due to the increased contact area with the electrolyte, the amount of gas generated by side reactions with the electrolyte may increase, and more manganese dissolution occurs due to the HF formed at high temperatures through reactions with the electrolyte. This further increases the degradation of the active material, resulting in a decrease in high-temperature lifetime characteristics.

[0097] Therefore, the positive electrode active material according to the present invention comprises a first positive electrode active material containing single-particle lithium manganese oxide particles, resulting in higher particle strength than conventional secondary-particle lithium manganese oxides. Consequently, less particle breakage occurs during calendering, and due to the smaller number of sub-particle units constituting the particles, the changes caused by the volume expansion and contraction of sub-particle units during charge and discharge are smaller, significantly reducing the occurrence of internal particle cracks. Because of the reduced particle breakage and internal cracking, the contact area between the lithium manganese oxide and the electrolyte becomes smaller, suppressing manganese dissolution caused by reaction with the electrolyte at high temperatures. This improves high-temperature storage characteristics and high-temperature lifetime characteristics, and reduces gas generation due to electrolyte side reactions.

[0098] On the other hand, the average particle size (D) of the first positive electrode active material 50 The average particle size (D) of the first positive electrode active material can range from 5 μm to 20 μm. Specifically, the average particle size (D) of the first positive electrode active material can range from 5 μm to 20 μm. 50 The particle size can be 5 μm or larger, 6 μm or larger, 7 μm or larger, 8 μm or larger, 9 μm or larger, 10 μm or larger, or 11 μm or larger, and can also be less than 20 μm, less than 19 μm, less than 18 μm, less than 17 μm, less than 16 μm, less than 15 μm, less than 14 μm, or less than 13 μm. For example, the average particle size (D) of the first positive electrode active material... 50 The average particle size can be from 5 μm to 20 μm, preferably from 7 μm to 18 μm, more preferably from 10 μm to 15 μm, and even more preferably from 11 μm to 14 μm. If this average particle size range is met, the structural stability of the first positive electrode active material can be excellent, the side reactions with the electrolyte can be few, and the amount of manganese dissolved at high temperatures can be low.

[0099] (2) Second positive electrode active material

[0100] The second positive electrode active material has a layered structure and contains lithium nickel oxides containing nickel (Ni), cobalt (Co), manganese (Mn), and aluminum (Al). The inclusion of lithium nickel oxides allows for high capacity through high energy density. The inclusion of aluminum, which has a strong affinity for oxygen atoms, stabilizes the structure of the second positive electrode active material and suppresses cation mixing during charge and discharge, resulting in electrochemical stability at high potentials. Consequently, compared to ternary lithium nickel oxides containing nickel, cobalt, and manganese, thermal stability and capacity characteristics are further improved.

[0101] First, lithium nickel oxides have a layered structure. Therefore, it is possible to achieve positive electrode active materials with excellent capacity characteristics and structural stability.

[0102] On the other hand, relative to all metals except lithium, lithium nickel oxides can contain 90 mol% or more of nickel, preferably 91 mol% or more, more preferably 92 mol% or more, and even more preferably 93 mol% or more. If this range is met, high capacity characteristics can be achieved through lithium nickel oxides, thus solving the capacity problem of lithium manganese oxides with spinel structures.

[0103] Specifically, lithium nickel oxides can have a composition represented by the following [Chemical Formula 2].

[0104] [Chemical Formula 2]

[0105] Li a2 [Ni x2 Co y2 Mn z2 Al w2 M 2 v2 O2

[0106] In chemical formula 2, M 2 The doping element may be one or more selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, preferably one or more selected from W, Y, Ba, Ca, Ti, Mg, Ta and Nb.

[0107] Additionally, in chemical formula 2, 0.8 ≤ a² ≤ 1.2, 0.9 ≤ x² < 1, 0 <y2≤0.2,0<z2≤0.2,0<w2≤0.2,0≤v2≤0.1。

[0108] Specifically, a2 can refer to the molar ratio of lithium (Li) in the lithium nickel-based oxide, and 0.8 ≤ a2 ≤ 1.2, preferably 0.9 ≤ a2 ≤ 1.15, more preferably 1.0 ≤ a2 ≤ 1.1. If a2 is less than 0.8, there is a concern that the capacity may decrease. If a2 exceeds 1.2, the particles may sinter during the calcination process, making it difficult to manufacture the second positive electrode active material. Therefore, if this range is satisfied, a balance can be achieved between the significant effect of improving the capacity characteristics of the second positive electrode active material according to the Li content control and the sinterability during the manufacture of the second positive electrode active material.

[0109] x2 can refer to the molar ratio of nickel in all metals other than lithium in the lithium nickel-based oxide, and 0.9 ≤ x2 < 1, preferably 0.91 ≤ x2 < 1, more preferably 0.92 ≤ x2 < 1, even more preferably 0.93 ≤ x2 < 1. If this range is satisfied, a sufficient nickel content in the lithium nickel-based oxide to contribute to charge and discharge is ensured, which is beneficial for high capacity.

[0110] y2 can refer to the molar ratio of cobalt in all metals other than lithium in the lithium nickel-based oxide, and 0 < y2 ≤ 0.2, preferably 0 < y2 ≤ 0.18, more preferably 0.01 ≤ y2 ≤ 0.15, even more preferably 0.03 ≤ y2 ≤ 0.12, even more preferably 0.05 ≤ y2 ≤ 0.10. If this range is satisfied, good resistance characteristics and output characteristics can be achieved by including a small amount of cobalt, while having a cost advantage.

[0111] z2 can refer to the molar ratio of Mn in all metals other than lithium in the lithium nickel-based oxide, and 0 < z2 ≤ 0.2, preferably 0 < z2 ≤ 0.18, more preferably 0.01 ≤ z2 ≤ 0.15, even more preferably 0.03 ≤ z2 ≤ 0.10. If this range is satisfied, the structural stability of the lithium nickel-based oxide can be improved.

[0112] w2 can refer to the molar ratio of Al in all metals other than lithium in the lithium nickel-based oxide, and 0 < w2 ≤ 0.2, preferably 0 < w2 ≤ 0.18, more preferably 0.01 ≤ w2 ≤ 0.15, even more preferably 0.03 ≤ w2 ≤ 0.10. If this range is satisfied, the structural stability of the lithium nickel-based oxide can be further improved.

[0113] v2 can refer to the molar ratio of M in all metals other than lithium in the lithium nickel-based oxide 2 and 0 ≤ v2 ≤ 0.1, preferably 0 ≤ v2 ≤ 0.08, more preferably 0 ≤ v2 ≤ 0.05.

[0114] The lithium nickel oxide may include a second coating, and the second coating may be located on the surface of the lithium nickel oxide.

[0115] The second coating can block the contact between lithium nickel oxides and the electrolyte, thereby suppressing the occurrence of electrolyte side reactions. When applied to batteries, it improves lifespan characteristics and increases the filling density of the cathode material.

[0116] The second coating may contain one or more elements selected from Ti, W, B, F, P, Mg, Ni, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, S, Co, and Al (hereinafter referred to as "coating elements"), preferably one or more elements selected from Co and Al.

[0117] Based on the total weight of the second positive electrode active material, the second coating can be included in amounts of 0.01 wt% to 5 wt%, preferably 0.03 wt% to 4 wt%, more preferably 0.04 wt% to 3 wt%, and even more preferably 0.05 wt% to 2 wt%. If this range is met, the occurrence of side reactions between lithium nickel oxides and the electrolyte can be more effectively suppressed, and if applied to a battery, lifespan characteristics can be further improved.

[0118] According to one embodiment, if the second coating contains Co, the second coating may be included in 0.5% to 5% by weight, preferably 1% to 4% by weight, and more preferably 2% to 3% by weight, based on the total weight of the second positive electrode active material.

[0119] According to another embodiment, if the second coating contains Al, the second coating may be included in 0.01% to 0.1% by weight, preferably 0.02% to 0.08% by weight, more preferably 0.03% to 0.07% by weight, based on the total weight of the second positive electrode active material.

[0120] The second coating can be formed on the entire surface of the second positive electrode active material, or it can be formed partially. Specifically, if the second coating is formed partially on the surface of the second positive electrode active material, it can be formed on an area of ​​5% or more but less than 100%, preferably 20% or more but less than 100% of the total surface area of ​​the second positive electrode active material.

[0121] In addition, lithium nickel oxides are single-particle particles.

[0122] If lithium nickel oxides (which are single-particle types) are included together with lithium manganese oxides having a spinel structure, the amount of manganese leaching at high temperatures can be significantly reduced compared to the case where lithium nickel oxides are in the form of secondary particles. Therefore, lithium secondary batteries using the cathode material according to the present invention can have excellent high-temperature storage characteristics and high-temperature cycling characteristics. In addition, the initial resistance can be excellent, and the initial discharge capacity can be improved.

[0123] On the other hand, the average particle size (D) of the second positive electrode active material 50 The average particle size (D) of the second positive electrode active material can range from 1 μm to 10 μm. Specifically, the average particle size (D) of the second positive electrode active material... 50 The particle size can be greater than 1 μm, greater than 1.5 μm, greater than 2 μm, greater than 2.5 μm, greater than 3 μm, greater than 3.5 μm, or greater than 4 μm, and can also be less than 10 μm, less than 9.5 μm, less than 9 μm, less than 8.5 μm, less than 8 μm, less than 7.5 μm, less than 7 μm, less than 6.5 μm, less than 6 μm, less than 5.5 μm, less than 5 μm, less than 4.5 μm, or less than 4 μm. For example, the average particle size (D) of the second positive electrode active material... 50 The micrometer diameter (μm) can range from 1 μm to 10 μm, preferably from 2 μm to 8 μm, more preferably from 2.5 μm to 6.5 μm, and even more preferably from 3 μm to 5 μm. Meeting this range minimizes side reactions with the electrolyte while preventing increases in resistance and decreases in output characteristics.

[0124] Lithium secondary batteries

[0125] Next, the lithium secondary battery according to the present invention will be described.

[0126] The lithium secondary battery according to the present invention comprises: an electrode assembly; an electrolyte; and a battery case housing the electrode assembly and the electrolyte. In this case, the electrode assembly includes a positive electrode comprising the positive electrode material described above according to the present invention, a negative electrode, and a separator between the positive and negative electrodes.

[0127] The constituent elements of the lithium secondary battery according to the present invention will be described in more detail below.

[0128] (1) Electrode assembly

[0129] The electrode assembly according to the present invention includes a positive electrode, a negative electrode, and a separator between the positive electrode and the negative electrode.

[0130] Figure 1 This illustrates the stacked structure of an electrode assembly before winding, according to one embodiment of the present invention. Figure 2This shows the cross-sectional structure of an electrode (positive or negative) according to one embodiment of the present invention. Figure 3 The structure of an electrode assembly according to one embodiment of the present invention is shown.

[0131] refer to Figure 1 and 2 The electrode assembly (A) of the present invention can be manufactured by winding a laminate formed by sequentially stacking a diaphragm (12), a positive electrode (10), a diaphragm (12) and a negative electrode (11) at least once in one direction (X).

[0132] In this case, the positive electrode (10) and the negative electrode (11) have a structure in which an active material layer (21) is formed on a long sheet current collector (20), and may include an uncoated portion (22) in which the active material layer (21) is not formed in a certain region of the current collector (20).

[0133] By using a positive electrode (10) and a negative electrode (11) that include the uncoated portion (22) as described above, a battery having a structure in which at least a portion of the uncoated portion of the positive electrode (10) and the negative electrode (11) is defined as an electrode tab can be realized without providing separate electrode tabs.

[0134] Specifically, the uncoated portion (22) can be formed longitudinally along the winding direction (X) at one end of the current collector (20), and by combining the current collector plate with the positive uncoated portion and the negative uncoated portion respectively, and by connecting the current collector plate to the electrode terminal, the uncoated portion can function as an electrode tab.

[0135] For example, a battery in which the uncoated positive and negative electrodes function as electrode tabs can be manufactured as follows: First, a separator, a positive electrode, another separator, and a negative electrode are stacked sequentially such that the uncoated positive and negative electrodes are in opposite directions, and then wound in one direction to create a jelly-roll type electrode assembly. Next, the uncoated portions of the positive and negative electrodes are bent towards the winding center (C), and a current collector is welded to the uncoated positive and negative electrodes respectively, and then connected to the electrode terminals to manufacture the battery. Compared to strip-type electrode tabs, the current collector has a larger cross-sectional area, and since resistance is inversely proportional to the cross-sectional area of ​​the channel through which current flows, the battery resistance can be significantly reduced if the secondary battery adopts the above structure.

[0136] On the other hand, the uncoated positive electrode portion and the uncoated negative electrode portion can be processed into multiple independently bendable segments, and at least some of the multiple segments can be bent toward the winding center (C) of the electrode assembly.

[0137] This segment can be formed by processing the current collectors for the positive and negative electrodes through metal foil cutting processes (such as laser cutting, ultrasonic cutting, and punching).

[0138] If the uncoated portions of the positive and negative electrodes are processed into multiple segments, the stress applied to the uncoated portions during bending can be reduced, thereby preventing deformation or damage to the uncoated portions and improving the welding characteristics with the current collector plate.

[0139] The current collector plate and the uncoated portion are typically joined by welding. To improve welding characteristics, increased pressure is applied to the welded area of ​​the uncoated portion to bend it as smoothly as possible. However, during the bending process, the shape of the uncoated portion may twist and deform unevenly, and the deformed portion may come into contact with electrodes of opposite polarity, leading to internal short circuits or microcracks in the uncoated portion. However, if the uncoated portions of the positive and negative electrodes are machined into multiple independently bendable segments, the stress applied to the uncoated portion during bending can be alleviated, thereby minimizing deformation and damage to the uncoated portion.

[0140] Furthermore, if the uncoated portion is processed into segments as described above, overlap occurs between the segments during bending, which increases the welding strength to the current collector plate. If modern techniques such as laser welding are used, this prevents the laser from penetrating into the electrode assembly and melting the diaphragm or active material. Preferably, at least some of the bent segments can overlap at the upper and lower ends of the electrode assembly, and the current collector plate can be bonded to the overlapping segments.

[0141] On the other hand, the electrode assembly according to the invention can be configured such that an insulating layer (24) is further formed on the positive electrode (10), as shown in the figure. Figure 3 As shown in the figure. Specifically, the insulating layer (24) can be formed to cover a portion of the positive electrode active material layer and a portion of the uncoated portion along a direction parallel to the winding direction of the electrode assembly.

[0142] In the case of a tabless structure in which the uncoated portion (22c) of the positive electrode (10) and the uncoated portion (22a) of the negative electrode (11) serve as electrode tabs, the electrode assembly is formed such that the positive electrode (10) protrudes above the separator (12) and the negative electrode (11) protrudes below the separator (12), and the protruding positive electrode (10) and / or negative electrode (11) are bent and then combined with the current collector plate. However, if the positive electrode (10) or negative electrode (11) is bent as described above, the current collector of the positive electrode (10) or negative electrode (11) is located outside the separator near the electrode of opposite polarity, which may cause electrical contact between the positive and negative electrodes, resulting in an internal short circuit. However, as Figure 3As shown, if an insulating layer (24) is formed covering part of the positive electrode active material layer and the uncoated part, the positive electrode (10) and the negative electrode (11) can be prevented from making electrical contact with each other through the insulating layer (24), thereby preventing a short circuit inside the battery.

[0143] Preferably, the insulating layer (24) can be disposed on at least one surface of the current collector of the positive electrode (10), and preferably, it can be disposed on both surfaces of the positive electrode (10).

[0144] Alternatively, the insulating layer (24) can be formed in a region of the positive electrode (10) (which may face the active material layer (21a) of the negative electrode (11). For example, the insulating layer (24) can be formed on the surface of the uncoated portion (22c) of the positive electrode (10) facing the negative electrode (11) after bending, thus extending to the end of the uncoated portion (22c). However, in the case of a surface opposite to the surface facing the negative electrode (11) after bending, it is preferable to form the insulating layer (24) only on a portion of the uncoated portion (22c), for example, up to the point where the uncoated portion (22c) bends. This is because if the insulating layer (24) is formed over the entire region of the uncoated portion on the surface opposite to the surface facing the negative electrode (11), it cannot make electrical contact with the current collector plate, and thus the uncoated portion may not be able to function as an electrode tab.

[0145] On the other hand, there are no particular restrictions on the material or composition of the insulating layer (24), as long as it can adhere to the positive electrode while ensuring insulation performance. For example, the insulating layer can be an insulating coating or an insulating tape, and the insulating coating can contain organic adhesives and inorganic particles. In this case, the organic adhesive can be, for example, styrene-butadiene rubber (SBR), and the inorganic particles can be, but are not limited to, aluminum oxide.

[0146] The positive electrode, negative electrode, and diaphragm that make up the electrode assembly will be described in detail below.

[0147] 1) Positive electrode

[0148] The positive electrode can be manufactured by coating a positive electrode slurry onto one or both sides of a long sheet-shaped positive electrode current collector, removing the solvent from the positive electrode slurry through a drying process, and then calendering. On the other hand, when coating the positive electrode slurry, a positive electrode containing an uncoated portion can be manufactured by leaving a portion of the positive electrode current collector (e.g., one end of the positive electrode current collector) uncoated.

[0149] Alternatively, the positive electrode slurry can be prepared by dispersing the positive electrode material according to the invention in a solvent (e.g., dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, and water).

[0150] The positive electrode thus manufactured contains a positive electrode material. Specifically, the positive electrode includes a positive electrode current collector and a positive electrode active material layer, and the positive electrode active material layer may contain the positive electrode material.

[0151] On the other hand, various positive electrode current collectors used in related technical fields can be used as the positive electrode current collector. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., can be used as the positive electrode current collector. The thickness of the positive electrode current collector can typically be 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector, thereby improving the adhesion strength of the positive electrode active material. The positive electrode current collector can be used in various forms such as films, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0152] The positive electrode active material layer can be located on the positive electrode current collector, specifically on one or both sides of the positive electrode current collector. The positive electrode active material layer can have a single layer or a multilayer structure with two or more layers.

[0153] Since the cathode material is the same as described above, its detailed description will be omitted.

[0154] On the other hand, the positive electrode active material layer may optionally also include at least one of a positive electrode conductive material and a positive electrode binder.

[0155] The positive electrode conductive material is used to provide conductivity to the electrode and can be used without particular limitation in the battery to be formed, provided that it does not cause chemical changes and has electronic conductivity. Specific examples include: graphite, such as natural or artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, carbon fibers, and carbon nanotubes; metal powders or fibers of copper, nickel, aluminum, and silver; conductive whiskers of zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and one of them can be used alone or in mixtures of two or more. Based on the total weight of the positive electrode active material layer, the content of the positive electrode conductive material is typically 1 to 30% by weight, preferably 1 to 20% by weight, and more preferably 1 to 10% by weight.

[0156] The positive electrode binder improves the adhesion between positive electrode particles and the bonding strength between the positive electrode material and the positive electrode current collector. Specific examples include: fluoropolymer binders, including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders, including styrene-butadiene rubber (SBR), nitrile rubber, and styrene-isoprene rubber; cellulose binders, including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyol binders, including polyvinyl alcohol; polyolefin binders, including polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders. One of these binders can be used alone, or a mixture of two or more can be used. Based on the total weight of the positive electrode active material layer, the content of the positive electrode binder can be 1 to 30% by weight, preferably 1 to 20% by weight, more preferably 1 to 10% by weight.

[0157] 2) Negative electrode

[0158] The negative electrode can be manufactured by coating a negative electrode slurry onto one or both sides of a long sheet-shaped negative electrode current collector, removing the solvent from the negative electrode slurry through a drying process, and then calendering. On the other hand, when coating the negative electrode slurry, a negative electrode containing an uncoated portion can be manufactured by leaving a portion of the negative electrode current collector (e.g., one end of the negative electrode current collector) uncoated.

[0159] The negative electrode slurry can be prepared by dispersing the negative electrode active material in a solvent (e.g., distilled water, ethanol, methanol, and isopropanol).

[0160] Alternatively, the negative electrode can be manufactured by casting the negative electrode slurry onto a separate support and then stacking the resulting film layer, obtained by peeling it off from the support, onto the negative electrode current collector.

[0161] The resulting negative electrode contains a negative electrode active material. Specifically, the negative electrode includes a negative electrode current collector and a negative electrode active material layer, and the negative electrode active material layer may contain the negative electrode active material.

[0162] There are no particular restrictions on the negative electrode current collector, as long as it has high conductivity and does not cause chemical changes in the battery. For example, materials such as copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys can be used. The thickness of the negative electrode current collector can typically range from 3 to 500 μm.

[0163] In addition, like the positive electrode current collector, the negative electrode current collector can have fine irregularities formed on its surface, thereby enhancing the adhesion of the negative electrode active material. For example, it can be used in various forms such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven fabrics.

[0164] The negative electrode active material layer can be located on the negative electrode current collector, specifically on one or both sides of the negative electrode current collector. The negative electrode active material layer can have a single layer or a multilayer structure with two or more layers.

[0165] As a negative electrode active material, compounds capable of reversibly inserting and de-intercalating lithium can be used, and there are no particular limitations on their types. Specific examples include: carbonaceous materials, such as artificial graphite, natural graphite, graphitized carbon fibers, and amorphous carbon; (semi-)metallic materials that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and (semi-)metal oxides capable of doping and de-doping lithium, such as SiO2. β (0<β<2), SnO2, vanadium oxide and lithium vanadium oxide; or composite materials containing (semi)metallic materials and carbonaceous materials, such as Si-C composite materials or Sn-C composite materials, and one or more of them may be used.

[0166] Additionally, lithium metal thin films can be used as anode active materials. Both low-crystallinity carbon and high-crystallinity carbon can be used as carbon materials. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include: irregular, planar, sheet-like, spherical, or fibrous natural or artificial graphite, condensed graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microspheres, mesophase pitch, and high-temperature calcined carbon such as coke derived from petroleum or coal tar pitch.

[0167] The content of negative electrode active material in the negative electrode active material layer can be from 60% to 99% by weight, preferably from 75% to 95% by weight.

[0168] On the other hand, in addition to the negative electrode active material, the negative electrode active material layer may optionally include a negative electrode conductive material and a negative electrode binder.

[0169] The negative electrode conductive material is used to provide conductivity to the electrode and can be used without particular limitation in the battery to be formed, provided that it does not cause chemical changes and has electronic conductivity. Specific examples include: graphite, such as natural graphite and artificial graphite; carbon materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal cracking black, carbon fiber, carbon nanotubes, etc.; metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive whiskers of zinc oxide, potassium titanate, etc.; conductive metal oxides, such as titanium oxide; or conductive polymers, such as polyphenylene derivatives, and one of them can be used alone or a mixture of two or more can be used. Based on the total weight of the negative electrode active material layer, the content of the negative electrode conductive material is typically 1 to 30% by weight, preferably 1 to 20% by weight, more preferably 1 to 10% by weight.

[0170] The negative electrode binder improves the adhesion between negative electrode active material particles and the bonding strength between the negative electrode active material and the negative electrode current collector. Specific examples include: polyvinylidene fluoride (PVDF), PVDF-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of them can be used alone, or a mixture of two or more of them can be used. Based on the total weight of the negative electrode active material layer, the content of the negative electrode binder can be 1 to 30% by weight, preferably 1 to 20% by weight, more preferably 1 to 10% by weight.

[0171] 3) Diaphragm

[0172] Next, the separator is used to separate the negative and positive electrodes and provide a channel for lithium ions. If it is a separator commonly used in lithium-ion secondary batteries, it can be used without particular limitation. Specifically, the separator can be a porous polymer membrane, such as a porous polymer membrane made of polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. Alternatively, conventional porous nonwoven fabrics can be used, such as nonwoven fabrics made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. Additionally, separators coated with ceramic components or polymer materials can be used to ensure heat resistance or mechanical strength.

[0173] (2) Electrolytes

[0174] The electrolyte according to the present invention comprises a lithium salt and an organic solvent.

[0175] If the lithium salt is a compound capable of providing lithium ions for use in lithium secondary batteries, it can be used without particular limitation. Specifically, the lithium salt can be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt can be in the range of 0.1 to 5.0 M, preferably 0.1 to 3.0 M. If the concentration of the lithium salt is within this range, the electrolyte can have suitable conductivity and viscosity, thus exhibiting excellent electrolyte performance, and lithium ions can move efficiently.

[0176] Organic solvents may include at least one of cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0177] Cyclic carbonate organic solvents are high-viscosity organic solvents and typically contain at least one organic solvent selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, and vinylene carbonate.

[0178] In addition, linear carbonate organic solvents are organic solvents with low viscosity and low dielectric constant, and may typically contain at least one organic solvent selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, specifically ethyl methyl carbonate (EMC).

[0179] As a specific example, linear ester organic solvents can be at least one organic solvent selected from methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0180] As a specific example, cyclic ester organic solvents can be at least one organic solvent selected from γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0181] Preferably, the electrolyte according to the invention may contain ethylene carbonate and dimethyl carbonate as organic solvents.

[0182] On the other hand, in order to improve battery life characteristics, suppress battery capacity decline, and improve battery discharge capacity, in addition to electrolyte components, other additives may also be included in the electrolyte.

[0183] As a representative example, other additives may include at least one other additive selected from the following substances: cyclic carbonates, halogen-substituted carbonates, sulfonyl lactones, sulfates / salts, borates / salts, nitriles, benzenes, amines, silanes, and lithium salts that are different from the lithium salts contained in the electrolyte.

[0184] Specifically, other additives include one or more compounds selected from the following substances: vinylene carbonate (VC), vinyl ethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sulpholactone (PS), 1,4-butane sulpholactone, vinyl sulpholactone, 1,3-propene sulpholactone (PRS), 1,4-butene sulpholactone, 1-methyl-1,3-propene sulpholactone, ethylene sulfate (ESA), trimethylene sulfate (TMS), methyltrimethylamine sulfate (MTMS), tetraphenylborate, lithium difluoroborate oxalate, succinic anionyl nitrile, adiponitrile Acetonitrile, propionitrile, butyronitrile, valerate, octanoic acid, heptacyanide, cyclopentanoic acid, cyclohexanoic acid, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, fluorobenzene, triethanolamine, ethylenediamine, tetravinylsilane, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide, LiFSI), LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bis(oxalatoborate, LiB(C2O4)2)) and LiBF4.

[0185] Based on the total weight of the electrolyte, the content of other additives can be from 0.01 to 20% by weight, preferably from 0.05 to 5.0% by weight. If the content of the aforementioned other additives is less than 0.01% by weight, the improvement effect on the battery's low-temperature output, high-temperature storage characteristics, and high-temperature lifespan characteristics may not be significant. If the content of other additives exceeds 20% by weight, there is a possibility that excessive side reactions may occur in the electrolyte during battery charging and discharging. In particular, if excessive additives for forming the SEI film are added, the additives may not decompose sufficiently at high temperatures and may exist in the electrolyte as unreacted substances or precipitates at room temperature. Therefore, side reactions that reduce the lifespan or resistivity characteristics of the secondary battery may occur.

[0186] (3) Battery casing

[0187] The battery case is used to house the electrode assembly and electrolyte, and various battery cases known in the art can be used, such as cylindrical battery cases, prismatic battery cases, pouch battery cases, etc.

[0188] Preferably, the lithium secondary battery according to the present invention can be a cylindrical battery having a cylindrical battery casing, and is preferably a large cylindrical battery with a shape factor ratio (defined as the value obtained by dividing the diameter of the cylindrical battery by its height, i.e., the ratio of diameter (T) to height (H)) of 0.4 or more, preferably 0.4 to 0.6. Here, the shape factor refers to the value representing the diameter and height of the cylindrical battery.

[0189] The lithium secondary battery according to the present invention can be, for example, a 46110 battery (diameter 46 mm, height 110 mm, shape factor ratio 0.418), a 48110 battery (diameter 48 mm, height 110 mm, shape factor ratio 0.436), a 4880 battery (diameter 48 mm, height 80 mm, shape factor ratio 0.600), or a 4680 battery (diameter 46 mm, height 80 mm, shape factor ratio 0.575). In the numerical representation of the shape factor, the first two digits represent the diameter of the battery, and the next two or three digits represent the height of the battery.

[0190] Figure 4 and Figure 5 Examples of embodiments of the lithium secondary battery according to the present invention are disclosed. In the following, reference will be made to... Figure 4 and Figure 5 A lithium secondary battery according to the present invention is described. However, Figure 4 and Figure 5 Only embodiments of the present invention have been shown; the structure of the battery of the present invention is not limited to these embodiments. Figure 4 and Figure 5 The scope of public disclosure.

[0191] Figure 4 A cross-sectional view of a lithium secondary battery according to one embodiment of the present invention is shown.

[0192] refer to Figure 4 The lithium secondary battery (140) according to the present invention comprises: Electrode assembly (141); A battery case (142) housing the electrode assembly (141) and the electrolyte (not shown); and A sealing body (143) at the open end of a sealed battery case (142).

[0193] In this configuration, the electrode assembly can be a stack of a positive electrode, a separator, and a negative electrode wound in one direction. Furthermore, the positive and negative electrodes of the electrode assembly can each include uncoated portions where no active material layer is formed, and they can be stacked and wound such that the uncoated portions of the positive and negative electrodes are located at the upper and lower ends of the electrode assembly, respectively. Since the electrode assembly has already been described above, only the remaining components will be described below.

[0194] On the other hand, the battery case (142) is a can-shaped container with an open end at the top, and is formed using a conductive metallic material such as aluminum and steel. The battery case houses the electrode assembly (141) in the internal space through the open end at the top, and also houses the electrolyte (not shown).

[0195] On the other hand, the lithium secondary battery (140) of the present invention preferably does not include a current interruption device (CID).

[0196] On the other hand, such as Figure 4 As shown, the battery case (142) is electrically connected to the uncoated portion (146b) of the negative electrode and can function as a contact with an external power source and transmit the current applied from the external power source to the negative terminal of the negative electrode.

[0197] As needed, a beading part (147) and a crimping part (148) can be provided at the upper end of the battery case (142). The beading part (147) can be formed by pressing the outer periphery of the battery case (142) into the battery case (142) to a distance of D1. The beading part (147) prevents the electrode assembly (141) housed inside the battery case (142) from detaching through the upper opening of the battery case (142) and can also function as a support for the seal (143) thereon.

[0198] The crimping portion (148) may be formed on the upper part of the rolled edge portion (147) and has an extended and curved shape to surround the outer periphery of the cover plate (143a) placed on the rolled edge portion (147) and a portion of the upper surface of the cover plate (143a).

[0199] Next, the sealing body (143) is used to seal the open end of the battery case (142) and includes a cover plate (143a), a first gasket (143b) that provides airtightness and insulation between the cover plate (143a) and the battery case (142), and, if necessary, a connecting plate (143c) electrically and mechanically connected to the cover plate (143a). The cover plate (143a) is pressed onto the rolled edge (147) formed on the battery case (142) and can be fixed by a crimping part (148).

[0200] The cover plate (143a) is a component formed using a conductive metal material and covers the upper opening of the battery case (142). The cover plate (143a) is electrically connected to the positive terminal of the electrode assembly (141) and is electrically insulated from the battery case (142) by a first gasket (143b). Therefore, the cover plate (143a) can function as the positive terminal of the lithium secondary battery. The cover plate (143a) may have a protrusion (143d) projecting upward from the center C, and the protrusion (143d) can contact an external power source, thereby allowing current to be applied from an external power source.

[0201] The first gasket (143b) can be located between the cover plate (143a) and the crimping part (148) to ensure the airtightness of the battery case (142) and to provide electrical insulation between the battery case (142) and the cover plate (143a).

[0202] On the other hand, depending on the need, the lithium secondary battery (140) according to the present invention may also include a current collector plate (144, 145). The current collector plate is combined with the uncoated positive electrode portion (146a) and the uncoated negative electrode portion (146b) and connected to the electrode terminals (e.g., the positive terminal and the negative terminal).

[0203] Specifically, the lithium secondary battery (140) according to the present invention may include a first current collector plate (144) attached to the upper part of the electrode assembly (141) and a second current collector plate (145) attached to the lower part of the electrode assembly (141).

[0204] It may also include a first current collector (144) and / or a second current collector (145).

[0205] A first current collector plate (144) is attached to the upper part of the electrode assembly (141). The first current collector plate (144) is formed using a conductive metal material such as aluminum, copper, and nickel, and is electrically connected to the uncoated portion (146a) of the positive electrode. A lead (149) can be connected to the first current collector plate (144). The lead (149) can extend upward from the electrode assembly (141) and connect to the connecting plate (143c) or can be directly connected to the lower surface of the cover plate (143a). The connection of the lead (149) to other components can be achieved by welding. Preferably, the first current collector plate (144) can be integrally formed with the lead (149). In this case, the lead (149) can have a plate shape extending outward from the center of the first current collector plate (144).

[0206] On the other hand, the first current collector plate (144) is bonded to the end of the uncoated positive electrode portion (146a), and this bonding can be achieved by, for example, laser welding, resistance welding, ultrasonic welding, soldering, etc.

[0207] The second current collector plate (145) is attached to the lower part of the electrode assembly (141). The second current collector plate (145) is formed using a conductive metal material such as aluminum, copper, and nickel, and is electrically connected to the uncoated negative electrode portion (146b). One side of the second current collector plate (145) can be attached to the uncoated negative electrode portion (146b), and the opposite side can be attached to the inner bottom surface of the battery case (142). In this case, the attachment can be achieved by, for example, laser welding, resistance welding, ultrasonic welding, brazing, etc.

[0208] On the other hand, the lithium secondary battery (140) according to the present invention may also include an insulator (146) as needed. The insulator (146) may be configured to cover the upper surface of the first current collector plate (144). Since the insulator (146) covers the first current collector plate (144), direct contact between the first current collector plate (144) and the inner surface of the battery case (142) can be prevented.

[0209] The insulator (146) has a lead hole (151) through which a lead (149) extending upward from the first current collector plate (144) can be led out. The lead (149) is led out upward through the lead hole (151) and connected to the lower surface of the connecting plate (143c) or the lower surface of the cover plate (143a).

[0210] The insulator (146) can be formed using a polymer resin with insulating properties, such as polymer resin materials like polyethylene, polypropylene, polyimide and polybutylene terephthalate.

[0211] On the other hand, as needed, the lithium secondary battery (140) according to the invention may also include an vent (152) formed on the lower surface of the battery casing (142). The vent (152) corresponds to a region on the lower surface of the battery casing (142) that is thinner than the surrounding region. Because the vent (152) is thin, it is structurally weaker than the surrounding region. Therefore, if the pressure inside the lithium secondary battery (140) rises above a certain level, the vent (152) may rupture, thereby allowing the gas inside the battery casing (142) to be discharged to the outside, thus preventing the battery from exploding.

[0212] Figure 5 This shows a cross-sectional view of a lithium secondary battery according to another embodiment of the present invention.

[0213] refer to Figure 5 ,and Figure 4 Compared to the lithium secondary battery (140) shown, the lithium secondary battery (170) according to another embodiment of the present invention has a different structure of battery case and sealing body, while the electrode assembly and electrolyte are substantially the same.

[0214] Specifically, a lithium secondary battery (170) according to another embodiment of the present invention comprises a battery case (171) through which a rivet terminal (172) is mounted. The rivet terminal (172) is mounted in a partially closed closed surface (upper surface in the figure) at one end of the battery case (171). The rivet terminal (172) is riveted to a through hole (first opening at the first end) in the battery case (171) while an insulating second washer (173) is interposed therebetween. The rivet terminal (172) is exposed to the outside in a direction opposite to the direction of gravity.

[0215] The rivet terminal (172) includes a terminal protrusion (172a) and a terminal insertion portion (172b). The terminal protrusion (172a) is exposed outside the closed surface of the battery case (171). The terminal protrusion (172a) may be located approximately at the center of the partially closed surface of the battery case (171). The maximum diameter of the terminal protrusion (172a) may be larger than the maximum diameter of the through hole formed in the battery case (171). The terminal insertion portion (172b) may penetrate approximately at the center of the closed surface of the battery case (171) and be electrically connected to the uncoated positive electrode portion (146a). The terminal insertion portion (172b) may be riveted to the inner surface of the battery case (171). That is, the end of the terminal insertion portion (172b) may have a shape that bends toward the inner surface of the battery case (171). The maximum diameter of the end of the terminal insertion portion (172b) may be larger than the maximum diameter of the through hole in the battery case (171).

[0216] The lower surface of the terminal insertion portion (172b) can be welded to the first current collector plate (144) connected to the uncoated positive electrode portion (146a). An insulating cover (174) formed of insulating material can be positioned between the first current collector plate (144) and the inner surface of the battery case (171). The insulating cover (174) covers the upper part of the first current collector plate (144) and the upper edge portion of the electrode assembly (141). As a result, it is possible to prevent the outer uncoated portion of the electrode assembly (141) from contacting the inner surface of the battery case (171) with a different polarity, thereby preventing a short circuit. The terminal insertion portion (172b) of the rivet terminal (172) can be welded to the first current collector plate (144) by penetrating the insulating cover (174).

[0217] The second gasket (173) is positioned between the battery case (171) and the rivet terminal (172), thereby preventing the battery case (171) and the rivet terminal (172) with opposite polarities from making electrical contact with each other. As a result, the upper surface of the battery case (171), which has a substantially flat shape, can function as the positive terminal of the lithium secondary battery (170).

[0218] The second washer (173) includes a washer protrusion (173a) and a washer insertion portion (173b). The washer protrusion (173a) is located between the terminal protrusion (172a) of the rivet terminal (172) and the battery case (171). The washer insertion portion (173b) is located between the terminal insertion portion (172b) of the rivet terminal (172) and the battery case (171). During riveting, the washer insertion portion (173b) can deform together with the terminal insertion portion (172b) and can be tightly attached to the inner surface of the battery case (171). The second washer (173) can be formed using, for example, an insulating polymer resin.

[0219] The washer protrusion (173a) of the second washer (173) may have an extended shape, thereby covering the outer surface of the terminal protrusion (172a) of the rivet terminal (172). If the second washer (173) covers the outer surface of the rivet terminal (172), short circuits can be prevented during the process of attaching electrical connection components such as busbars to the upper surface of the battery case (171) and / or the rivet terminal (172). Although not shown in the figures, the washer protrusion (173a) may have an extended form, thereby covering not only the outer surface of the terminal protrusion (172a) but also a portion of the upper surface.

[0220] When a polymer resin is used to form the second gasket (173), the second gasket (173) can be thermally bonded to the battery casing (171) and the rivet terminal (172). In this case, the sealing performance of the bonding interface between the second gasket (173) and the rivet terminal (172) and the bonding interface between the second gasket (173) and the battery casing (171) can be enhanced. On the other hand, when the gasket protrusion (173a) of the second gasket (173) has the form of extending to the upper surface of the terminal protrusion (172a), the rivet terminal (172) can be integrally bonded to the second gasket (173) by injection molding.

[0221] The remaining area (175) on the upper surface of the battery case (171), excluding the area occupied by the rivet terminal (172) and the second washer (173), corresponds to the negative terminal with the opposite polarity to the rivet terminal (172).

[0222] The second current collector plate (176) is attached to the lower part of the electrode assembly (141). The second current collector plate (176) is formed using conductive metal materials such as aluminum, steel, copper and nickel, and is electrically connected to the uncoated negative electrode portion (146b).

[0223] Preferably, the second current collector plate (176) is electrically connected to the battery case (171). For this purpose, at least a portion of the edge of the second current collector plate (176) may be located between and fixed to the inner surface of the battery case (171) and the first washer (178b). In one embodiment, at least a portion of the edge of the second current collector plate (176) may be supported by the lower surface of a rolled edge (180) formed at the lower end of the battery case (171) and fixed to the rolled edge (180) by welding. In a modified embodiment, at least a portion of the edge of the second current collector plate (176) may be directly welded to the inner wall surface of the battery case (171).

[0224] The second current collector plate (176) may have a plurality of protrusions (not shown) radially formed on the surface facing the uncoated negative electrode portion (146b). If the protrusions are formed, the second current collector plate (176) can be pressed to press the protrusions into the uncoated negative electrode portion (146b).

[0225] Preferably, the end of the second current collector plate (176) and the end of the uncoated negative electrode portion (146b) can be joined by welding (e.g., laser welding).

[0226] The sealing body (178) at the lower open end of the sealed battery case (171) includes a cover plate (178a) and a first gasket (178b). The first gasket (178b) electrically isolates the cover plate (178a) from the battery case (171). A crimping portion (181) secures the edge of the cover plate (178a) to the first gasket (178b). The cover plate (178a) is provided with a vent (179). The configuration of the vent (179) is substantially the same as in the embodiment described above.

[0227] Preferably, the cover plate (178a) is formed of a conductive metal material. However, since the first gasket (178b) is located between the cover plate (178a) and the battery case (171), the cover plate (178a) is not polarized. The seal (178) seals the open end of the lower part of the battery case (171) and releases gas when the internal pressure of the lithium secondary battery (170) rises above a critical value.

[0228] Preferably, the rivet terminal (172) electrically connected to the uncoated positive electrode portion (146a) serves as the positive terminal. Additionally, the portion (175) of the upper surface of the battery casing (171), excluding the rivet terminal (172), electrically connected to the uncoated negative electrode portion (146b) via the second current collector plate (176), serves as the negative terminal. In this way, if the two electrode terminals are located at the top of the lithium secondary battery, electrical connection components such as busbars can be placed only on one side of the lithium secondary battery (170). This can lead to a simplification of the battery pack structure and an improvement in energy density. Furthermore, since the portion (175) used as the negative terminal has a substantially flat shape, sufficient contact area can be ensured when joining electrical connection components such as busbars. Therefore, the lithium secondary battery (170) can reduce the resistance of the contact portion of the electrical connection components to a desired level.

[0229] If a lithium secondary battery with the above structure is formed, the current concentration is smaller than that of a conventional battery with electrode tabs, thus effectively reducing the heat generation inside the battery and thereby improving the thermal safety of the battery.

[0230] The lithium secondary battery of the present invention, as described above, can be used as a unit cell in battery pack manufacturing. Figure 6 The diagram schematically illustrates the configuration of a battery pack according to one embodiment of the present invention. (Reference) Figure 6 According to one embodiment of the present invention, a battery pack (3) includes an assembly of an electrically connected lithium secondary battery (1) and a battery pack housing (2) housing the assembly. The lithium secondary battery (1) is the lithium secondary battery according to the above embodiment. In the drawings, for ease of drawing, components such as busbars, cooling units, and external terminals for the electrical connection of the lithium secondary battery (1) are omitted.

[0231] The battery pack (3) can be installed on the vehicle. The vehicle can be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle can be a four-wheeled vehicle or a two-wheeled vehicle.

[0232] The invention will be described in more detail below through specific embodiments.

[0233] Preparation Example 1

[0234] MnSO4, Al2(SO4)3, and MgO were mixed in a weight ratio of 92.98:4.65:2.37, and then MnSO4·7H2O containing Al2(SO4)3 and MgO was prepared using distilled water purged with N2. The prepared MnSO4·7H2O was added to a continuous stirred tank reactor (CSTR, manufacturer: EMS Tech, product name: CSTR-L0) at a rate of 10 mL / h. As an alkalizing agent, 40% sodium hydroxide aqueous solution was added at a rate of 10 mL / h through the reactor's sodium hydroxide aqueous solution supply section, and 25% ammonia was added at a rate of 30 mL / h through the reactor's ammonia supply section, while the pH was maintained at 10.5 using a pH meter and controller. The reactor temperature was set to 40°C, the residence time (RT) was adjusted to 10 hours, and the mixture was stirred at 1200 rpm to precipitate the Al-containing Mn3O4. The obtained reaction solution was filtered, purified with distilled water, and dried to produce an Al-doped manganese precursor. The Al-doped manganese precursor prepared as described above was mixed with lithium feedstock Li₂CO₃ at a molar ratio of 1.3:2, and then calcined at 900°C for 6 hours to obtain lithium manganese oxide Li. 1.3 Mn 1.9 Al 0.1 O4. Figure 7 The image shows the surface of the lithium manganese oxide produced in Preparation Example 1, obtained by scanning electron microscopy at a magnification of 3,000x, confirming that the lithium manganese oxide particles produced as described above are single-particle particles.

[0235] Lithium manganese oxide and boric acid (H3BO3) as a coating material were mixed in an amount such that the content of B was 1,000 ppm. Subsequently, the mixture was heat-treated at 600°C for 8 hours to prepare a first positive electrode active material A with a coating formed thereon.

[0236] Preparation Example 2

[0237] Lithium manganese oxides (Li) were obtained in the same manner as in Preparation Example 1. 1.3 Mn 1.9 Al 0.1 The difference with O4 is that, except for calcining the Al-doped manganese precursor and the lithium feedstock Li2CO3 at 750°C for 6 hours, the prepared lithium manganese oxide was confirmed to have a secondary particle form.

[0238] Lithium manganese oxide and boric acid (H3BO3) as a coating material were mixed in an amount such that the content of B was 1,200 ppm. Then, the mixture was heat-treated at 600°C for 8 hours to prepare the first positive electrode active material B with a coating formed thereon.

[0239] Preparation Example 3

[0240] A 1.0 M aqueous solution of transition metals was prepared by mixing NiSO4, CoSO4 and MnSO4 in distilled water such that the molar ratio of nickel:cobalt:manganese was 94:5:1.

[0241] Next, deionized water was added to the reactor, and nitrogen gas was introduced into the reactor to remove dissolved oxygen and create a non-oxidizing atmosphere inside the reactor. Then, 2.0 M NaOH was added to maintain the pH inside the reactor at 10.5.

[0242] Subsequently, an aqueous solution of transition metal was added to the reactor at a rate of 10 mL / h, and aqueous solutions of NaOH and NH4OH were added at rates of 10 mL / h and 5 mL / h, respectively. A co-precipitation reaction was carried out for 2 hours at a reaction temperature of 60 °C, a pH of 10, and a stirring speed of 1,000 rpm, thereby preparing an average particle size (D... 50 ) is 4 μm, made of Ni 0.93 Co 0.05 Mn 0.01 (OH)2 represents the precursor.

[0243] The precursor, LiOH, and dopant element Al were mixed in an amount such that the molar ratio of Ni:Co:Mn:Al was 93:5:1:1, and then calcined at 600°C for 13 hours to prepare Li[Ni] 0.93 Co 0.05 Mn 0.01 Al 0.01O2. Figure 8 The image shows the surface of the lithium nickel oxide prepared in Example 3, obtained by scanning electron microscopy at a magnification of 5,000x, confirming that the prepared lithium nickel oxide particles are single-particle particles.

[0244] Then, wash Li[Ni] with water. 0.93 Co 0.05 Mn 0.01 Al 0.01 O2 was dried, and then Co(OH)2 was mixed in an amount such that the Co content was 39,000 ppm, and Al2O3 was mixed in an amount such that the Al content was 500 ppm. Subsequently, a second positive electrode active material A coated with Co and Al was prepared by heat treatment at 500°C for 8 hours.

[0245] Preparation Example 4

[0246] A 1.0 M aqueous solution of transition metals was prepared by mixing NiSO4, CoSO4 and MnSO4 in distilled water such that the molar ratio of nickel:cobalt:manganese was 90:6:4.

[0247] Next, deionized water was added to the reactor, and nitrogen gas was introduced into the reactor to remove dissolved oxygen and create a non-oxidizing atmosphere inside the reactor. Then, 2.0 M NaOH was added to maintain the pH inside the reactor at 11.0.

[0248] Subsequently, an aqueous solution of transition metal was injected into the reactor at a rate of 10 mL / h, and aqueous solutions of NaOH and NH4OH were injected at rates of 10 mL / h and 5 mL / h, respectively. Simultaneously, a co-precipitation reaction was carried out for 4 hours at a reaction temperature of 60℃, a pH of 11, and a stirring speed of 500 rpm, thereby producing an average particle size (D... 50 ) is 9 μm, made of Ni 0.9 Co 0.06 Mn 0.04 (OH)2 represents the precursor.

[0249] The precursor, LiOH, and dopant element Al were mixed in an amount such that the molar ratio of Ni:Co:Mn:Al was 90:6:3:1, and then calcined at 800°C for 13 hours to produce Li[Ni] 0.90 Co 0.06 Mn 0.03 Al 0.01 O2. Figure 9 The image shows the surface of the lithium nickel oxide prepared in Example 4, obtained by scanning electron microscopy at a magnification of 5,000x, confirming that the lithium nickel oxide particles prepared above are secondary particles.

[0250] Then, wash Li[Ni] with water. 0.90 Co 0.06 Mn 0.03 Al 0.01 O2 was dried, and then Al2O3 was mixed in an amount that resulted in an Al content of 500 ppm. Subsequently, heat treatment was carried out at 600°C for 8 hours to prepare the Al-coated second positive electrode active material B.

[0251] The first and second positive electrode active materials prepared in Examples 1 to 4 have the properties shown in Table 1 below.

[0252] [Table 1]

[0253] Example 1

[0254] A positive electrode material was prepared by mixing the first positive electrode active material A prepared in Preparation Example 1 with the second positive electrode active material A prepared in Preparation Example 3 at a weight ratio of 60:40. A positive electrode slurry was prepared by mixing this positive electrode material, carbon nanotubes as a conductive material, PVDF as a binder, and hydrogenated nitrile butadiene copolymer as a dispersant in an N-methylpyrrolidone solvent at a weight ratio of 97.31:0.8:1.65:0.24. This positive electrode slurry was coated onto one surface of an aluminum current collector with a thickness of 15 μm, dried at 130°C, and then calendered to manufacture the positive electrode.

[0255] A negative electrode slurry was prepared by mixing natural graphite (as the negative electrode active material), SBR (as a binder), and CMC (as a dispersant) in distilled water at a weight ratio of 98.1:1.0:0.9. This negative electrode slurry was coated onto a copper current collector with a thickness of 10 μm, dried at 80°C, and calendered to manufacture the negative electrode.

[0256] A polyethylene separator with a 3 μm CCS coating on both sides is inserted between the positive and negative electrodes manufactured as described above, and stacked in the order of separator / positive electrode / separator / negative electrode, and then wound to manufacture an electrode assembly. The electrode assembly manufactured as described above is inserted into a cylindrical battery can, then electrolyte is injected and sealed to manufacture a cylindrical lithium secondary battery.

[0257] In this case, the electrolyte was prepared by adding LiPF6 to a mixed solvent with an EC:DMC:EMC ratio of 20:75:5 at a concentration of 1.3 M.

[0258] Comparative Example 1

[0259] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the second positive electrode active material B prepared in Preparation Example 4 was used instead of the second positive electrode active material A.

[0260] Comparative Example 2

[0261] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the first positive electrode active material B prepared in Preparation Example 2 was used instead of the first positive electrode active material A.

[0262] Comparative Example 3

[0263] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the first positive electrode active material B prepared in Preparation Example 2 was used instead of the first positive electrode active material A, and the second positive electrode active material B prepared in Preparation Example 4 was used instead of the second positive electrode active material A.

[0264] Experimental Example 1: Evaluation of Manganese Leaching at High Temperature

[0265] Using the cylindrical lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3, the amount of manganese leaching after activation and the amount of manganese leaching after storage at high temperature were measured.

[0266] (1) Evaluation of manganese leaching after activation

[0267] The cylindrical lithium-ion batteries of Example 1 and Comparative Examples 1 to 3 were charged at 25°C with a constant current of 0.2C to 4.2 V and 0.1C, respectively, and then activated by discharging at a constant current of 0.2C to 2.5 V, and then completely discharged to 2.5 V. The cylindrical lithium-ion batteries were disassembled, and 1 g of each negative electrode was collected. The content of dissolved manganese on the surface of the negative electrode was measured by ICP analysis. The results are shown in Table 2 below.

[0268] (2) Evaluation of manganese leaching after storage at high temperature

[0269] The cylindrical lithium-ion batteries manufactured in Examples 1 and Comparative Examples 1 to 3 were charged at 25°C with a constant current of 0.2C to 4.2 V and 0.1C, respectively, and then activated by discharging at a constant current of 0.2C to 2.5 V. Subsequently, the cylindrical lithium-ion batteries were charged at 25°C with a constant current of 0.5C to 4.2 V and 0.1C, stored at 55°C for 2 weeks, and then completely discharged to 2.5 V. The cylindrical lithium-ion batteries were disassembled, and 1 g of each negative electrode was collected. The Mn content dissolved on the surface of the negative electrode was measured by ICP analysis. The results are shown in Table 2 below.

[0270] [Table 2]

[0271] Referring to Table 2 above, it can be confirmed that the amount of manganese leached from the battery manufactured in Example 1 after activation and storage at high temperature is significantly less than that of the batteries manufactured in Comparative Examples 1 to 3. Therefore, it can be understood that the battery manufactured in Example 1 exhibits excellent high-temperature life characteristics.

[0272] Experiment Example 2: Evaluation of Initial Battery Characteristics

[0273] (1) Evaluation of initial discharge capacity

[0274] The initial discharge capacity of the cylindrical lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3 was measured.

[0275] Specifically, each battery was charged at 40°C with a constant current of 0.25C to 4.2 V and 0.1C, and then discharged with a constant current of 1 / 3C to 3.0 V to evaluate the initial discharge capacity. The measurement results are shown in Table 3 below. The discharge capacity of the 4680 battery manufactured in Example 1 was set to 100% and used as a reference value to obtain the relative discharge capacity of the cylindrical lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3.

[0276] (2) Evaluation of initial resistance

[0277] The initial resistance of the cylindrical lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3 was measured.

[0278] Specifically, each battery was charged to 50% SOC at a constant current of 0.5C at 40°C, and then discharged at a constant current of 0.5C for 10 seconds. The initial resistance (DCIR) was then calculated based on the voltage drop that occurred during this time. The measurement results are shown in Table 3 below, where the initial resistance of the cylindrical lithium secondary battery manufactured in Example 1 was set to 100% and used as a reference value to obtain the relative initial resistances of the cylindrical lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3.

[0279] [Table 3]

[0280] Referring to Table 3 above, it can be confirmed that the battery manufactured in Example 1 has a higher initial discharge capacity and a lower initial resistance than the batteries manufactured in Comparative Examples 1 to 3.

[0281] Experimental Example 3: Evaluation of High-Temperature Lifetime Characteristics

[0282] The lifetime characteristics of the cylindrical lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3 were measured at 40°C.

[0283] Specifically, the cylindrical lithium secondary batteries manufactured in Example 1 and Comparative Examples 1 to 3 were charged at 40°C with a constant current of 0.25C until they reached 4.2 V, and then discharged at 0.1C. The batteries were then discharged with a constant current of 1 / 3C until they reached 3.0 V.

[0284] The charging and discharging behavior is considered as one cycle, and this cycle is repeated 400 times. After 400 cycles, the high-temperature lifetime characteristics are evaluated by measuring the capacity retention rate. The measurement results are shown in Table 4 below.

[0285] In this case, the capacity retention rate is calculated using the following mathematical formula.

[0286] Capacity retention rate (%) = {(Discharge capacity after 400 cycles / Discharge capacity after 1 cycle)} × 100.

[0287] [Table 4]

[0288] Referring to Table 4 above, it can be confirmed that the battery manufactured in Example 1 exhibits a higher capacity retention rate during repeated charge-discharge cycles at high temperatures compared to the batteries manufactured in Comparative Examples 1 to 3. Therefore, it can be understood that the battery manufactured in Example 1 possesses excellent high-temperature life characteristics.

[0289] Experiment Example 4: Evaluation of High-Temperature Storage Characteristics

[0290] The cylindrical lithium secondary batteries manufactured in Examples 1 and Comparative Examples 1 to 3 were initially charged and discharged to 4.2 V and 0.05 C at 25°C under CC / CV and 0.5C conditions, and then discharged to 3.0 V under CC and 0.5C conditions. They were then charged to 4.2 V and 0.05 C at 55°C under CC / CV and 0.5C conditions, and then stored at 55°C for 16 weeks.

[0291] (1) Capacity retention

[0292] After 16 weeks of storage, the lithium secondary batteries were charged to 4.2 V and 0.05 C at 25°C under CC / CV and 0.5 C conditions, and then discharged to 3.0 V under CC and 0.5 C conditions to measure the discharge capacity. The capacity retention rate was evaluated according to the following mathematical formula, and the results are shown in Table 5 below.

[0293] Capacity retention (%) = (Discharge capacity after 16 weeks of storage / Initial discharge capacity) × 100

[0294] (2) Rate of increase in resistance

[0295] After the initial charge and discharge, the capacity was checked at room temperature. Based on the discharge capacity, the battery was charged to 50% SOC and discharged at a current of 0.5C for 10 seconds. The resistance was measured based on the voltage drop difference during this time and used as the initial resistance. After storage at 55°C for 16 weeks, the resistance was measured using the same method and used as the final resistance. The rate of increase in resistance was calculated using the following mathematical formula. The results are shown in Table 5 below.

[0296] Resistance increase rate (%) = (final resistance - initial resistance) / (initial resistance) × 100.

[0297] [Table 5]

[0298] Referring to Table 5 above, it can be confirmed that the battery manufactured in Example 1 exhibits a higher capacity retention rate and a lower resistance increase rate during high-temperature storage compared to the batteries manufactured in Comparative Examples 1 to 3. Therefore, it can be understood that the battery manufactured in Example 1 possesses excellent high-temperature storage characteristics.

[0299] [Explanation of reference numerals in the attached figures]

[0300] 1: Lithium secondary battery

[0301] 2: Battery pack casing

[0302] 3: Battery pack

[0303] 10: Positive electrode

[0304] 11: Negative electrode

[0305] 12: Diaphragm

[0306] 20: Current collector

[0307] 21: Active material layer

[0308] 21a: Negative electrode active material layer

[0309] 22: Uncoated area

[0310] 22a: Uncoated portion of the negative electrode

[0311] 22c: Uncoated portion of the positive electrode

[0312] 24: Insulation layer

[0313] C: Winding center

[0314] 140: Lithium secondary battery

[0315] 141: Electrode assembly

[0316] 142: Battery casing

[0317] 143: Sealing body

[0318] 143a: Cover plate

[0319] 143b: First washer

[0320] 143c: Connector

[0321] 143d: Protrusion

[0322] 144: First collector board

[0323] 145: Second collector panel

[0324] 146: Insulator

[0325] 146a: Uncoated portion of the positive electrode

[0326] 146b: Uncoated portion of the negative electrode

[0327] 147: Rolled edge

[0328] 148: Crimping section

[0329] 149: Lead wire

[0330] 151: Lead hole

[0331] 152: Exhaust section

[0332] 170: Lithium secondary battery

[0333] 171: Battery casing

[0334] 172: Rivet Terminal

[0335] 172a: Exposed terminal portion

[0336] 172b: Terminal insertion part

[0337] 173: Second washer

[0338] 173a: Exposed portion of the washer

[0339] 173b: Washer insertion part

[0340] 174: Insulating cover

[0341] 176: Second collector panel

[0342] 178: Sealing body

[0343] 178a: Cover plate

[0344] 178b: First washer

[0345] 179: Exhaust section

[0346] 180: Rolled edge

[0347] 181: Crimping section

Claims

1. A positive electrode material, said positive electrode material comprising: A first positive electrode active material, the first positive electrode active material comprising a lithium manganese oxide having a spinel structure; and The second positive electrode active material comprises a lithium nickel oxide having a layered structure and containing nickel (Ni), cobalt (Co), manganese (Mn) and aluminum (Al). The lithium manganese oxide and the lithium nickel oxide are single-particle particles.

2. The cathode material according to claim 1, wherein the lithium nickel oxide comprises more than 90 mol% nickel relative to all metals other than lithium.

3. The positive electrode material according to claim 1, wherein the weight ratio of the first positive electrode active material to the second positive electrode active material is 75:25 to 50:

50.

4. The positive electrode material according to claim 1, wherein the average particle size (D) of the first positive electrode active material and the second positive electrode active material is... 50 The ratio of ) is 5:1 to 1.5:

1.

5. The positive electrode material according to claim 1, wherein the average particle size (D) of the first positive electrode active material is... 50 The thickness ranges from 5 μm to 20 μm.

6. The positive electrode material according to claim 1, wherein the average particle size (D) of the second positive electrode active material is... 50 The range is from 1 μm to 10 μm.

7. The cathode material according to claim 1, wherein the lithium manganese oxide has a composition represented by the following [Chemical Formula 1]: [Chemical Formula 1] Li 1+a1 Mr 2-x1 M 1 x1 O 4-y1 A y1 In chemical formula 1, M 1 It is a doping element selected from Al, Li, Mg, Zn, B, W, Ni, Co, Fe, Cr, V, Ru, Cu, Cd, Ag, Y, Sc, Ga, In, As, Sb, Pt, Au, and Si. A is one or more elements selected from F, Cl, Br, I, At, and S. 0≤a1≤0.4,0 <x1≤0.5,0≤y1≤0.1。 8. The cathode material according to claim 1, wherein, based on the total weight of the lithium manganese oxide, the lithium manganese oxide contains 0.5% to 3% by weight of M. 1 .

9. The cathode material according to claim 1, comprising a first coating on the surface of the lithium manganese oxide, and The first coating contains one or more elements selected from Al, Ti, W, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, S, and B.

10. The cathode material according to claim 9, wherein the content of the first coating is from 0.05% by weight to 0.3% by weight based on the total weight of the first cathode active material.

11. The cathode material according to claim 1, wherein the lithium nickel oxide has a composition represented by the following [Chemical Formula 2]: [Chemical Formula 2] Li a2 [Ni x2 Co y2 Mr z2 Al w2 M 2 v2 ]O2 In chemical formula 2, M 2 It is a doping element selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. 0.8≤a²≤1.2, 0.9≤x²<1, 0 <y2≤0.2,0<z2≤0.2,0<w2≤0.2,0≤v2≤0.1。 12. The cathode material according to claim 1, comprising a second coating on the surface of the lithium nickel oxide, and The second coating contains one or more elements selected from Ti, W, B, F, P, Mg, Ni, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, S, Co, and Al.

13. The cathode material according to claim 12, wherein the content of the second coating is from 0.01% to 5% by weight based on the total weight of the second cathode active material.

14. A lithium secondary battery, the lithium secondary battery comprising: An electrode assembly comprising: a positive electrode comprising a positive electrode material according to any one of claims 1 to 13, a negative electrode, and a separator between the positive electrode and the negative electrode; Electrolytes; and A battery case that houses the electrode assembly and the electrolyte.

15. The lithium secondary battery according to claim 14, wherein the battery casing is a cylindrical battery casing.

16. The lithium secondary battery according to claim 14, wherein the ratio of the diameter (T) to the height (H) of the lithium secondary battery (shape factor ratio) is 0.4 or more.

17. The lithium secondary battery of claim 14, wherein the lithium secondary battery includes uncoated portions on at least a portion of the positive electrode and the negative electrode, wherein no active material layer is formed thereon, and The uncoated portions of the positive electrode and the uncoated portions of the negative electrode are defined as electrode tabs.

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