Cylindrical lithium-ion rechargeable battery

Abstract

The present invention provides a lithium secondary battery comprising a battery case, an electrode assembly housed inside the battery case, and an electrolyte, wherein the electrode assembly comprises a positive electrode containing a positive electrode active material, a separation membrane, and a negative electrode containing a negative electrode active material, the electrolyte comprises LiPF6 as a lithium salt and ethylene carbonate as an organic solvent, and the lithium secondary battery has a form factor ratio of diameter (r) to height (h) of the battery case of 0.4 or more and satisfies the conditions of the following formula (1). JPEG2026518684000011.jpg28170 (In the above formula (1), h is the height of the battery case (mm), r is the diameter of the battery case (mm), W LiPF6 This indicates the LiPF6 content as a percentage (%) relative to the total weight of the electrolyte, W EC This indicates the ethylene carbonate content as a percentage (%) relative to the total weight of the electrolyte, W EL (This refers to the total weight (g) of the electrolyte contained in the lithium secondary battery.)

Description

[Technical Field]

[0001] The present invention relates to a lithium secondary battery, and more particularly to a cylindrical lithium secondary battery with improved high-temperature durability and long-term life characteristics.

[0002] This application claims priority rights under Korean Patent Application No. 10-2023-0093983 dated July 19, 2023, and Korean Patent Application No. 10-2024-0095334 dated July 18, 2024, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference. [Background technology]

[0003] With the advancement of technologies such as electric vehicles and portable electronic devices, the demand for lithium-ion batteries as an energy source is rapidly increasing.

[0004] Lithium-ion batteries are classified into cylindrical, prismatic, and pouch-type batteries based on the shape of their battery case. Of these, cylindrical batteries have a sheet-like positive electrode and a separator membrane in a cylindrical battery case. 、 The battery case is manufactured by sequentially stacking the positive and negative electrodes and then winding them in one direction to form a jelly roll type electrode assembly, which is then housed inside the battery case, and a cap plate is placed over the top of the battery case to seal it. The positive and negative electrodes are each provided with strip-shaped positive and negative electrode tabs, and these tabs are connected to electrode terminals to electrically connect to an external power source. The positive electrode terminal is the cap plate, and the negative electrode terminal is the battery case. However, in conventional cylindrical batteries with such a structure, the current is concentrated in the strip-shaped electrode tabs, resulting in high resistance, excessive heat generation, and poor current collection efficiency.

[0005] However, small cylindrical rechargeable batteries having the form factor of the conventionally used 18650 (cylindrical rechargeable battery with a diameter of 18 mm and a height of 65 mm) or 21700 (cylindrical rechargeable battery with a diameter of 21 mm and a height of 70 mm) in Resistance and heat generation teethIt did not become a major issue.

[0006] However, recently, as the driving range and fast charging speed of electric vehicles have increased, the development and use of larger cylindrical secondary batteries with a larger form factor, such as 46800 (cylindrical secondary battery with a diameter of 46 mm and a height of 80 mm), have been considered. In addition, in order to improve the rapid charging characteristics of such larger cylindrical secondary batteries, instead of using a separate strip-shaped electrode tab, a so-called tab-less cylindrical secondary battery that utilizes the current collectors of the non-patterned portions of the positive and negative electrodes as electrode tabs has been proposed.

[0007] The larger cylindrical secondary battery having the tab-less structure not only exhibits relatively large capacity characteristics and energy density, but also has the advantages of improving the production efficiency of the cylindrical secondary battery for electric vehicles and reducing its production cost. In addition, by applying the tab-less structure, while reducing the number of parts, the electrical connection (contact) area between the electrode tab and the electrode terminal is increased to shorten the electron movement distance, thereby improving the output characteristics and also dispersing the heat generation during the charging and discharging processes.

[0008] However, in the larger cylindrical secondary battery applying the tab-less structure or the like in In order to provide sufficient weldability with the case and terminal portions, a process of pressing the portion where the active material layer is not coated is performed. Therefore, the positive electrode, separator 、 And there is a problem that the electrolyte movement passage between the negative electrodes is blocked and the movement of the electrolyte is not properly performed, resulting in a decrease in the impregnation property of the electrolyte.

[0009] Therefore, in a larger cylindrical secondary battery applicable to medium and large-sized devices such as automobiles, the development of a technology for improving the impregnation property of the electrolyte and improving various performances is urgently required.

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention aims to solve the above-mentioned problems and relates to a lithium secondary battery that can achieve excellent high-temperature durability and cycle characteristics by adjusting the composition and amount of electrolyte according to the dimensions of a larger lithium secondary battery to which a tablet structure or the like is applied, thereby establishing optimal electrolyte impregnation conditions. [Means for solving the problem]

[0011] According to one embodiment, the present invention relates to a lithium secondary battery comprising a battery case, an electrode assembly housed inside the battery case, and an electrolyte, The electrode assembly includes a positive electrode containing a positive electrode active material, a separation membrane, and a negative electrode containing a negative electrode active material. The electrolyte comprises LiPF6 as a lithium salt and ethylene carbonate as an organic solvent. The lithium secondary battery described above has a form factor ratio (r) of 0.4 or more to the height (h) of the battery case and satisfies the conditions of the following formula (1).

[0012]

number

[0013] (In the above formula (1), h is the height of the battery case (mm), r is the diameter of the battery case (mm), W LiPF6 This indicates the LiPF6 content as a percentage (%) relative to the total weight of the electrolyte. W EC This indicates the ethylene carbonate content as a percentage (%) relative to the total weight of the electrolyte. W EL (This refers to the total weight (g) of the electrolyte contained in the lithium secondary battery.)

[0014] On the other hand, the lithium secondary battery may be a tabletless battery in which at least a portion of the positive electrode and the negative electrode includes blank portions in which no active material layer is formed, and the blank portion of the positive electrode or the blank portion of the negative electrode is defined as an electrode tab.

[0015] On the other hand, the positive electrode active material is a lithium transition metal oxide containing Ni and Co, and the lithium transition metal oxide may satisfy the following formula (2).

[0016] [ Formula (2) ] 18 ≤ X Ni / X Co ≤48 (In the above equation (2), X Ni This is the mole percent of Ni relative to the total metal excluding lithium in the lithium transition metal oxide, and X Co (This is the molar percentage of Co relative to all metals excluding lithium in the lithium transition metal oxide.) [Effects of the Invention]

[0017] As with the lithium secondary battery according to the present invention, when the composition and amount of the electrolyte satisfy specific conditions based on the dimensions of the battery cell, and the composition ratio of Ni and Co contained in the positive electrode active material satisfies specific conditions, optimal electrolyte impregnation conditions can be established, minimizing side reactions at the interface between the positive electrode and the electrolyte, thereby achieving excellent high-temperature durability and cycle characteristics. [Brief explanation of the drawing]

[0018] [Figure 1] This figure shows the stacked state of the electrode assembly according to the present invention before winding. [Figure 2] This is a cross-sectional view showing the structure of the electrode plate of an electrode assembly according to one embodiment of the present invention. [Figure 3] This diagram illustrates the structure of an electrode assembly according to one embodiment of the present invention. [Figure 4]This is a cross-sectional view showing the structure of a cylindrical battery with a tablet structure according to one embodiment of the present invention. [Figure 5] This is a cross-sectional view showing the structure of a cylindrical battery with a tablet structure according to another embodiment of the present invention. [Figure 6] This is a diagram illustrating the battery pack according to the present invention. [Modes for carrying out the invention]

[0019] The terms and words used in this specification and in the claims should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical concept of the present invention, in accordance with the principle that inventors can appropriately define the concepts of terms in order to best describe their invention.

[0020] In larger cylindrical lithium secondary batteries that utilize conventional tabless structures, the electrolyte impregnation is reduced compared to smaller batteries, and the same applies to larger batteries. chemical properties (Chemistry) had the disadvantage of making it difficult to obtain the desired performance. In particular, when manufacturing larger cylindrical secondary batteries, increasing the amount of electrolyte injected into the limited space inside the cylindrical cell reduces the internal space and increases the internal pressure, which in turn increases the gas byproducts generated during activation. but If the electrolyte is not discharged to the outside of the electrode assembly and remains inside, it is pushed out of the electrode assembly, leading to a decrease in wetting. Conversely, if the amount of electrolyte injected decreases, increasing the internal space, the electrolyte does not easily absorb moisture into the electrode assembly, resulting in poor wetting. Thus, the wetting properties of the electrolyte are closely related to cell resistance. In other words, if the electrolyte is insufficient or the wetting properties decrease, the resistance increases (Seong Jin An et al 2017 J. Electrochem. Soc. 2017, 164 A1195).

[0021] Therefore, as a result of repeated research for improving the performance of a large-sized cylindrical lithium secondary battery, the inventors have found that when an appropriate electrolyte injection amount is injected, appropriate impregnation properties can be ensured, an increase in the initial resistance of the cell can be suppressed, and rapid charge cycle characteristics can be improved. Further, the inventors have found a method for calculating an appropriate electrolyte injection amount, and thus completed the present invention.

[0022] Hereinafter, the lithium secondary battery according to the present invention will be specifically described.

[0023] Specifically, the present invention provides a lithium secondary battery including a battery case, an electrode assembly housed inside the battery case, and an electrolyte, wherein the electrode assembly includes a positive electrode containing a positive electrode active material, a separator, and a negative electrode containing a negative electrode active material, the electrolyte contains LiPF6 as a lithium salt and ethylene carbonate as an organic solvent, and the lithium secondary battery has a ratio (form factor ratio) of the diameter (r) to the height (h) of the battery case of 0.4 or more and satisfies the conditions of the following formula (1).

[0024]

Equation

[0025] (In the above formula (1), h is the height (mm) of the battery case, r is the diameter (mm) of the battery case, W LiPF6 represents the content of LiPF6 in the total weight of the electrolyte in percentage (%), W EC represents the content of ethylene carbonate in the total weight of the electrolyte in percentage (%), W EL means the weight (g) of all the electrolyte contained in the lithium secondary battery)

[0026] In the above formula (1),

[0027]

number

[0028] Preferably, it may be 5.65 to 8.6, and more preferably 6.5 to 8.6.

[0029]

number

[0030] If the value of satisfies the above range, the optimal electrolyte impregnation conditions can be established by the dimensions of the battery cell, and the performance of the secondary battery can be effectively improved.

[0031] On the other hand, the lithium secondary battery according to the present invention may be a cylindrical lithium secondary battery having a form factor ratio of 0.4 or more, preferably 0.4 to 0.6.

[0032] On the other hand, in equation (1) above, W EL This is the actual amount (g) of total electrolyte injected into the battery case, which varies depending on the dimensions and size of the battery cell, but specifically, in the case of a cylindrical lithium secondary battery with a form factor ratio of 0.4 to 0.6, it is preferably about 30g to 50g.

[0033] In the case of a cylindrical battery with a form factor ratio of 0.4 or more and 0.5 or less, the W EL It is preferable that the amount is approximately 35g to 50g. Also, if the form factor ratio is greater than 0.5 and 0.6 or less, the above W EL The amount may be approximately 30g to 40g. On the other hand, the amount of electrolyte injected into the battery case (g) (W) EL If the amount of electrolyte injected into the battery case is slightly less, the impregnation of the electrolyte will decrease, making it difficult to achieve the desired battery performance. EL If the amount is slightly high, gas generation will become more intense, which could lead to explosions or electrolyte leaks.

[0034] In the above equation (1), W LiPF6 This represents the percentage (%) of LiPF6 content relative to the total weight of the electrolyte during its manufacture, and the viscosity of the electrolyte can be adjusted by controlling the LiPF6 content.

[0035] Specifically, when manufacturing an electrolyte applicable to cylindrical lithium secondary batteries with a form factor ratio of 0.4 to 0.6, the W LiPF6 For example, this may be about 12% to 16% by weight, preferably 13% to 16% by weight. LiPF6 If the value of is somewhat low, the viscosity of the electrolyte is low and its fluidity is high, making it easy to inject the electrolyte into a large-capacity battery. On the other hand, this can reduce the conductivity of lithium ions and lead to deterioration of cycle characteristics, etc. In contrast, the aforementioned W LiPF6 If the value is slightly high, the viscosity of the electrolyte increases and its fluidity decreases, so the electrolyte's wetting ability is decline This can lead to a decrease in initial performance, resulting in reduced high-temperature durability and cycle characteristics.

[0036] In the above equation (1), W EC This represents the percentage (%) of ethylene carbonate content relative to the total weight of the electrolyte during its manufacture, and the viscosity of the electrolyte can be adjusted by controlling the ethylene carbonate content.

[0037] The aforementioned ethylene carbonate is an organic solvent with excellent affinity for carbon materials and has been mainly used as an electrolyte solvent for lithium secondary batteries. However, if the electrolyte contains a slightly high amount of ethylene carbonate, a large amount of CO2 gas (gas) may be generated by the decomposition of ethylene carbonate during charging and discharging, which can adversely affect the performance of the secondary battery. Furthermore, ethylene carbonate is a high-melting-point solvent, and if it is present in a slightly high amount, the low-temperature characteristics will decrease, the conductivity will be low and the high-power characteristics will decrease, and the viscosity of the electrolyte will increase. On the other hand, if the electrolyte contains a slightly low amount of ethylene carbonate, the electrical conductivity will decrease, and the thermal stability and lifespan performance may decrease.

[0038] When the form factor ratio of the lithium secondary battery of the present invention is 0.4 to 0.6, the ethylene carbonate content in the electrolyte (W EC The amount of W is approximately 13% to 25% by weight, preferably 15% to 20% by weight. EC If the value satisfies the above range, optimal electrolyte impregnation conditions for high-capacity cylindrical secondary batteries can be established.

[0039] On the other hand, the high-temperature durability and cycle characteristics of lithium secondary batteries are closely related to the viscosity of the electrolyte. That is, as mentioned above, when a high-viscosity electrolyte is injected into a large-capacity cylindrical lithium secondary battery with a form factor ratio of 0.4 or higher, preferably 0.4 to 0.6, the impregnation (wetting) of the electrode assembly decreases, resulting in a problem where the charge and discharge performance of the lithium secondary battery is greatly reduced or even impossible. Conversely, when a low-viscosity electrolyte is injected into a large-capacity battery, the impregnation (wetting) of the electrode assembly improves, but the charge and discharge performance of the lithium secondary battery is greatly reduced due to the low concentration of lithium salt in the electrolyte, etc.

[0040] In this invention, by ensuring that the composition and amount of the electrolyte satisfy specific conditions as shown in formula (1) above, depending on the dimensions of the battery cell, it is possible to establish optimal electrolyte impregnation conditions suitable for large-capacity cylindrical lithium secondary batteries, thereby enabling the manufacture of lithium secondary batteries that exhibit excellent high-temperature durability and cycle characteristics. Specifically, by injecting an appropriate amount of electrolyte containing the optimal lithium salt (LiPF6) and EC into the limited space inside the cylindrical cell, it is possible to control the internal pressure of the cell while improving the wetting of the electrode assembly into the electrolyte, suppressing the increase in resistance, and significantly improving high-temperature cycle characteristics.

[0041] On the other hand, Figure 1 shows the laminated structure of the electrode assembly according to the present invention before winding, Figure 2 shows the cross-sectional structure of the electrode plate (positive electrode or negative electrode) according to the present invention, and Figure 3 shows the structure of the electrode assembly according to one embodiment of the present invention. Furthermore, Figures 4 and 5 show cross-sectional views of a cylindrical battery with a tablet structure according to one embodiment of the present invention. Hereinafter, each component of the cylindrical battery with a tablet structure according to the present invention will be described in more detail with reference to the drawings.

[0042] [Electrode assembly] Referring to Figures 1 and 2, the electrode assembly A of the present invention can be manufactured by winding a laminate formed by sequentially stacking a separation membrane 12, a positive electrode 10, another separation membrane 12, and a negative electrode 11 at least once in one direction (X).

[0043] Here, 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-like current collector 20, and the current collector 20 may include a plain portion 22 in which the active material layer 21 is not formed in a part of the region.

[0044] As described above, by using a positive electrode 10 and a negative electrode 11 that include a blank portion 22, it is possible to realize a battery with a tabless structure in which at least a portion of the blank portions of the positive electrode 10 and the negative electrode 11 defines an electrode tab, without providing a separate electrode tab.

[0045] Specifically, the blank portion 22 may be formed along the winding direction (X) at the end of one side of the current collector 20, and a current collector plate can be attached to the blank portion of the positive electrode and the blank portion of the negative electrode, and the current collector plate can be connected to the electrode terminals to realize a tabless battery structure.

[0046] For example, a tabless battery can be manufactured by the following method. First, a jelly roll type electrode assembly is manufactured by sequentially stacking a separator film, a positive electrode, a separator film, and a negative electrode so that the blank portions 22 of the positive electrode 10 and the negative electrode 11 are positioned in opposite directions, and then winding them in one direction. Next, the blank portions 22 of the positive electrode and the negative electrode are bent towards the winding center (C), and then current collector plates are welded to the blank portions of the positive electrode and the negative electrode, respectively, and the current collector plates are connected to the electrode terminals to manufacture a tabless battery. On the other hand, the current collector plate has a larger cross-sectional area than a strip-type electrode tab, and resistance is inversely proportional to the cross-sectional area of ​​the current passage, so when a secondary battery is formed with the above structure, the cell resistance can be significantly reduced.

[0047] On the other hand, the plain portions of the positive and negative electrodes may be processed into a plurality of independently bendable segments, and at least a portion of the plurality of segments may be bent toward the winding center (C) of the electrode assembly.

[0048] The segments may be formed by processing the positive and negative electrode current collectors using metal foil cutting processes such as laser notching, ultrasonic cutting, or punching.

[0049] When the plain portions of the positive and negative electrodes are processed into multiple segments, the stress applied to the plain portions during bending can be reduced, preventing deformation and damage to the plain portions and improving welding characteristics with the current collector plate.

[0050] The current collector plate and the blank section are generally joined by welding. However, to improve welding characteristics, strong pressure must be applied to the welding area of ​​the blank section to bend it as flat as possible. However, during such bending, the shape of the blank section may become irregularly distorted and deformed, and the deformed parts may come into contact with electrodes of opposite polarity, causing an internal short circuit, or inducing micro-cracks in the blank section. However, if the blank sections of the positive and negative electrodes are processed into multiple segments that can be bent independently, the stress applied to the blank section during bending can be reduced, minimizing deformation and damage to the blank section.

[0051] Furthermore, if the plain portion is processed into a segmented shape as described above, overlapping occurs between multiple segments during bending, thereby increasing the welding strength with the current collector plate. When using advanced technologies such as laser welding, it is possible to prevent the problem of the laser penetrating into the electrode assembly and melting the separation film or active material. Preferably, at least a portion of the bent multiple segments overlap on the upper and lower ends of the electrode assembly, and the current collector plate is bonded to the overlapping multiple segments.

[0052] On the other hand, the electrode assembly according to the present invention may be formed in a structure in which an insulating layer 24 is further formed on the positive electrode 10, as shown in Figure 3. Specifically, the insulating layer 24 may be formed in a direction parallel to the winding direction of the electrode assembly, covering a part of the positive electrode active material layer and a part of the plain portion.

[0053] In a tabletless battery using the blank portion 22c of the positive electrode 10 and the blank portion 22a of the negative electrode 11 as electrode tabs, the electrode assembly is formed such that the positive electrode 10 protrudes above the separator membrane 12 and the negative electrode 11 protrudes below the separator membrane 12, and the protruding positive electrode 10 and / or negative electrode 11 are bent and then coupled to the current collector plate. However, when 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 will be positioned close to the electrode of the opposite polarity beyond the separator membrane, which may cause the positive electrode and negative electrode to come into electrical contact and induce an internal short circuit. However, Figure 3 As shown, when an insulating layer 24 is formed that covers the positive electrode active material layer and a portion of the blank area, the insulating layer 24 can prevent the positive electrode 10 and the negative electrode 11 from making electrical contact, thereby preventing a short circuit from occurring inside the battery.

[0054] Preferably, the insulating layer 24 may be provided on at least one surface of the current collector of the positive electrode 10, and preferably on both sides of the positive electrode 10.

[0055] Furthermore, the insulating layer 24 may be formed in the region of the positive electrode 10 that may face the active material layer 21a of the negative electrode 11. For example, in the plain portion 22c of the positive electrode 10, the insulating layer 24 may extend to the end of the plain portion 22c on the side that faces the negative electrode 11 after being folded. However, on the opposite side of the side that faces the negative electrode 11 after being folded, it is preferable that the insulating layer 24 is formed only on a part of the plain portion 22c, for example, up to the point before the folding point of the plain portion 22c. This is because if the insulating layer 24 is formed over the entire plain portion on the opposite side of the side that faces the negative electrode 11, electrical contact with the current collector plate becomes impossible, and therefore it cannot function as an electrode tab.

[0056] On the other hand, the insulating layer 24 only needs to be able to be attached to the positive electrode while ensuring insulating performance, and its material and components are not important. teethThe invention is not particularly limited. For example, the insulating layer may be an insulating coating layer or an insulating tape, and the insulating coating layer may contain an organic binder and inorganic particles. Here, the organic binder may be, for example, styrene-butadiene rubber (SBR), and the inorganic particles may be alumina oxide, but are not limited thereto.

[0057] On the other hand, the diameter of the core portion of the electrode assembly of the present invention may be 5 mm or more, specifically 5 mm to 8 mm. When the diameter of the core portion of the electrode assembly is within the above range, the defect rate can be suppressed during the winding process for manufacturing the jelly roll type electrode assembly, and sufficient space can be secured for injecting the electrolyte into the inside of the cylindrical secondary battery. On the other hand, if the diameter of the core portion of the electrode assembly is less than 5 mm, the internal pressure of the cell increases, and issues such as venting may occur. Conversely, if the diameter of the core portion of the electrode assembly exceeds 8 mm, the energy density per unit volume of the cell decreases, the wettability to the electrolyte decreases, and the performance of the cell may deteriorate. In particular, in large cylindrical batteries with a form factor of 0.4 or more, improving the impregnation of the electrolyte into the electrode assembly by injecting an electrolyte with an appropriate level of viscosity can lead to improved cell performance.

[0058] On the other hand, the overall diameter of the electrode assembly may have a normal diameter that corresponds to a large cylindrical battery with a form factor of 0.4 or more.

[0059] Next, each component of the electrode assembly of the present invention will be described in more detail.

[0060] positive electrode The positive electrode can be manufactured by applying a positive electrode slurry to one or both sides of a long, sheet-like positive electrode current collector, removing the solvent from the positive electrode slurry in a drying process, and then rolling it. Alternatively, a positive electrode including a plain area can be manufactured by not applying the positive electrode slurry to a part of the positive electrode current collector, for example, one end of the positive electrode current collector.

[0061] On the other hand, various positive electrode current collectors used in the art can be used as the positive electrode current collector. For example, the positive electrode current collector can be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel whose surfaces have been surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector usually has a thickness of 3 to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to increase the adhesion strength of the positive electrode active material. The positive electrode current collector can be used in various forms, such as film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0062] Furthermore, the positive electrode slurry can be manufactured by dispersing the positive electrode active material in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water.

[0063] As the positive electrode active material, a positive electrode active material commonly used in the art can be used, but preferably a lithium transition metal oxide containing Ni and Co can be used, and more specifically, it may contain a lithium transition metal oxide that satisfies the following formula (2).

[0064] [ Formula (2) ] 18 ≤ X Ni / X Co ≤48

[0065] In equation (2) above, X NiThis is the mole percent of Ni relative to the total metal excluding lithium in the lithium transition metal oxide, and X Co This is the molar percentage of Co relative to the total metal excluding lithium in the lithium transition metal oxide.

[0066] When the composition ratio of Ni and Co in the lithium transition metal oxide represented by formula (2) above is less than 18, side reactions with the electrolyte increase, causing an increase in interfacial resistance. On the other hand, when the composition ratio of Ni and Co satisfies 18 to 48, the structural stability of the positive electrode active material is improved, and oxidation reactions are suppressed, thereby effectively preventing side reactions with the electrolyte. Specifically, the composition ratio of Ni and Co in the lithium transition metal oxide is more preferably 40 or less, or 35 or less.

[0067] The lithium transition metal oxide is preferably represented by the following [Chemical Formula 1].

[0068] [Chemical formula 1] Li a Ni b Co c M 1 d M 2 e O2

[0069] In the above chemical formula (1), M 1 This may be Mn, Al, or a combination thereof, but Mn, or Mn and Al, is preferred.

[0070] Said M 2 This is one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, preferably one or more selected from the group consisting of Zr, Y, Mg, and Ti, and more preferably Zr, Y, or a combination thereof. 2 While elements are not essential, when present in appropriate amounts, they play a role in promoting grain growth during firing or improving the stability of the crystal structure.

[0071] The aforesaid a represents the molar ratio of lithium in the lithium nickel-based oxide, and it may be 0.8 ≦ a ≦ 1.2, 0.85 ≦ a ≦ 1.15, or 0.9 ≦ a ≦ 1.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-based oxide is stably formed.

[0072] The aforesaid b represents the molar ratio of nickel to all metals excluding lithium in the lithium nickel-based oxide, and it may be 0.85 < b < 1, 0.87 ≦ b < 1, or 0.9 ≦ b < 1. When the molar ratio of nickel satisfies the above range, it shows a high energy density and can achieve a high capacity.

[0073] The aforesaid c represents the molar ratio of cobalt to all metals excluding lithium in the lithium nickel-based oxide, and it may be 0 < c < 0.06, or 0.01 ≦ c ≦ 0.05. When the molar ratio of cobalt satisfies the above range, good resistance characteristics and output characteristics can be realized.

[0074] The aforesaid d represents the molar ratio of element M to all metals excluding lithium in the lithium nickel-based oxide 1 and it may be 0 < d < 0.15, 0 < d < 0.14, or 0.01 ≦ d ≦ 0.12. When the molar ratio of element M 1 satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0075] The aforesaid e represents the molar ratio of element M to all metals excluding lithium in the lithium nickel-based oxide 2 and it may be 0 ≦ e ≦ 0.1, or 0 ≦ e ≦ 0.05.

[0076] Specifically, the positive electrode active material of the present invention is Li(Ni 0.90 Mn 0.05 Co 0.05 )O2, Li(Ni 0.94 Co 0.04 Mn 0.02 )O2, Li(Ni 0.87 Mn 0.07 Co 0.04 Al0.02 )O2, or Li(Ni 0.90 Mn 0.03 Co 0.05 Al 0.02 )O2 is also acceptable.

[0077] On the other hand, the positive electrode slurry may optionally further include at least one of a conductive material and a binder.

[0078] The conductive material is used to impart conductivity to the electrodes and can be used without particular limitations as long as it does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material is usually used in an amount equal to 1% of the total weight of the positive electrode active material layer. weight% ~30% by weight, preferably 1 weight% ~20% by weight, comfort 1 weight% ~10% by weight in It may be included.

[0079] The binder plays a role in improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples include fluororesin binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose binders containing carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol binders containing polyvinyl alcohol; polyolefin binders containing polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders. One of these can be used alone or in mixtures of two or more. The binder is used in an amount equal to 1% of the total weight of the positive electrode active material layer. weight% ~30% by weight, preferably 1 weight% ~20% by weight, comfort 1 weight% ~10% by weight in It may be included.

[0080] negative electrode The negative electrode can be manufactured by applying a negative electrode slurry to one or both sides of a long, sheet-like negative electrode current collector, removing the solvent from the negative electrode slurry in a drying process, and then rolling it. Alternatively, a negative electrode including a plain area can be manufactured by not applying the negative electrode slurry to a part of the negative electrode current collector, for example, one end of the negative electrode current collector.

[0081] On the other hand, as the negative electrode current collector, a negative electrode current collector commonly used in the art can be used, such as copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel with surface treatment using carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. The negative electrode current collector usually has a thickness of 3 to 500 μm, and similar to the positive electrode current collector, fine irregularities can be formed on the surface of the current collector to strengthen the bonding force of the negative electrode active material. For example, it can be used in various forms such as film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0082] Furthermore, the negative electrode slurry can be manufactured by dispersing the negative electrode active material in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water.

[0083] As the anode active material, a carbon-based anode active material used in this industry can be used, and furthermore, a silicon-based anode active material can be mixed with the carbon-based anode active material.

[0084] As the carbonaceous active material, various carbonaceous materials used in the art can be used, for example, graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; high-temperature calcined carbons such as pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch-derived cokes, soft carbon, hard carbon, etc. The shape of the carbonaceous material is not particularly limited, and substances with various shapes such as amorphous, plate-like, scaly, spherical, fibrous, etc. can be used.

[0085] Also, the silicon-based negative electrode active material may include, for example, silicon (Si), silicon carbide (SiC), silicon chloride, silicon oxide (SiO x , where 0 < x < 2), and Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), and may contain one or more selected from the group consisting of. As the element Y, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db( Dubnium dubnium ) ), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof can be selected from the group consisting of.

[0086] On the other hand, the carbonaceous negative electrode active material and the silicon-based negative electrode active material may be contained in a weight ratio of 95:5 to 99:1, and more specifically, may be contained in a weight ratio of 95:5 to 97:3.

[0087] When the mixing ratio of the carbon-based anode active material and the silicon-based anode active material satisfies the above range, it is possible to improve capacity characteristics while suppressing the volume expansion of the silicon-based compound and ensuring excellent cycle performance. If the amount of silicon (Si)-based compound is too small, it is difficult to increase the energy density, making it difficult to increase the capacity of the battery. If the amount is too large, the degree of volume expansion of the anode becomes large, which is undesirable.

[0088] On the other hand, the negative electrode slurry may optionally further include at least one of a conductive material and a binder.

[0089] The conductive material is used to impart conductivity to the negative electrode and can be used without particular limitations as long as it does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. One of these alone or a mixture of two or more can be used. The conductive material is usually used in an amount equal to 1% of the total weight of the negative electrode active material layer. weight% ~30% by weight, preferably 1 weight% ~20% by weight, comfort 1 weight% ~10% by weight in It may be included.

[0090] The binder plays a role in improving the adhesion between negative electrode active material particles and the adhesion between the negative electrode active material and the negative electrode current collector. Specific examples include fluororesin binders containing polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber binders containing styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; cellulose binders containing carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; polyalcohol binders containing polyvinyl alcohol; polyolefin binders containing polyethylene and polypropylene; polyimide binders; polyester binders; and silane binders. One of these can be used alone or in mixtures of two or more. The binder is used in an amount equal to 1% of the total weight of the negative electrode active material layer. weight% ~30% by weight, preferably 1 weight% ~20% by weight, comfort 1 weight% ~10% by weight in It may be included.

[0091] Separation membrane The aforementioned separation membrane separates the negative electrode and the positive electrode and provides a pathway for lithium ions to move, and is typically used in lithium secondary batteries. Separation membraneAny material used for this purpose can be used without particular limitations. Specifically, the separation membrane can be a porous polymer film, such as a porous polymer film made from polyolefin polymers such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, or ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. Alternatively, a regular porous nonwoven fabric, such as a nonwoven fabric made of high-melting-point glass fiber or polyethylene terephthalate fiber, can also be used. Furthermore, a coated separation membrane containing ceramic components or polymeric substances can be used to ensure heat resistance or mechanical strength.

[0092] [Cylindrical lithium-ion rechargeable battery] Next, the cylindrical lithium secondary battery according to the present invention will be described.

[0093] The cylindrical lithium secondary battery according to the present invention includes an electrode assembly formed by winding a positive electrode and a negative electrode, including a plain portion; an electrolyte; a battery case in which the electrode assembly and the electrolyte are housed; and a seal that seals the open end of the battery case. Furthermore, at least a portion of the plain portion of the positive electrode or the plain portion of the negative electrode can realize a tabless structure defined as an electrode tab.

[0094] Preferably, the cylindrical lithium secondary battery according to the present invention may be a large cylindrical battery having a form factor ratio (defined as the ratio of diameter (T) to height (H) of the cylindrical battery, i.e., the ratio of diameter (T) to height (H)) of 0.4 or more, preferably 0.4 to 0.6. Here, form factor refers to the values ​​indicating the diameter and height of the cylindrical battery.

[0095] The cylindrical battery according to the present invention may be, for example, a 46110 cell (diameter 46 mm, height 110 mm, form factor ratio 0.418), a 48110 cell (diameter 48 mm, height 110 mm, form factor ratio 0.436), a 4880 cell (diameter 48 mm, height 80 mm, form factor ratio 0.600), or a 4680 cell (diameter 46 mm, height 80 mm, form factor ratio 0.575). In the numerical value indicating the form factor, the first two digits indicate the diameter of the cell, and the next two or three digits indicate the height of the cell.

[0096] On the other hand, while the cylindrical battery according to the present invention is preferably a tabless battery that does not include electrode tabs, it is not limited thereto.

[0097] The aforementioned tablet-like battery may have, for example, a structure in which the positive electrode and negative electrode each include blank areas where no active material layer is formed, the blank areas of the positive electrode and negative electrode are located at the upper and lower ends of the electrode assembly, a current collector plate is coupled to the blank areas of the positive electrode and negative electrode, and the current collector plate is connected to the electrode terminals.

[0098] Figures 4 and 5 show cross-sectional views of a cylindrical battery with a tablet structure according to one embodiment of the present invention. Hereinafter, the cylindrical battery according to one embodiment of the present invention will be described with reference to Figures 4 and 5. However, Figures 4 and 5 merely illustrate one embodiment of the present invention, and the structure of the cylindrical battery of the present invention is not limited to the scope shown in Figures 4 and 5.

[0099] A cylindrical battery 140 according to one embodiment of the present invention includes the jelly roll type electrode assembly 141 described above, a battery case 142 in which the electrode assembly 141 and an electrolyte (not shown) are housed, and a seal 143 that seals the open end of the battery case 142.

[0100] Here, the positive and negative electrodes of the electrode assembly may each include plain areas where no active material layer is formed, and the electrode assembly may be laminated and wound up such that the plain areas of the positive and negative electrodes are located at the upper and lower ends, respectively. Since the electrode assembly has been described above, only the other components excluding the electrode assembly will be described below.

[0101] The battery case 142 is a cylindrical container with an opening formed at the top, and is made of a conductive metal material such as aluminum or steel. The battery case houses the electrode assembly 141 in the inner space through the upper opening, and also houses the electrolyte (not shown) together with it.

[0102] On the other hand, it is preferable that the cylindrical battery 140 of the present invention does not include a current interruption device (CID).

[0103] electrolyte On the other hand, the electrolyte used in the cylindrical lithium secondary battery of the present invention may include a lithium salt containing LiPF6 and an organic solvent containing ethylene carbonate.

[0104] Furthermore, the electrolyte of the present invention may optionally further contain at least one organic solvent selected from cyclic carbonate organic solvents, linear carbonate organic solvents, linear ester organic solvents, and cyclic ester organic solvents.

[0105] The cyclic carbonate-based organic solvent is a highly viscous organic solvent, and may typically include at least one organic solvent selected from the group consisting of propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0106] Furthermore, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant. Typical examples include at least one organic solvent selected from the group consisting of ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl propyl carbonate, and ethyl propyl carbonate. Specifically, it may include at least one of ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC).

[0107] Specific examples of the linear ester-based organic solvent include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0108] The cyclic ester organic solvents include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0109] On the other hand, the electrolyte may also contain other additives in addition to the components of the electrolyte, for the purpose of improving the battery's lifespan characteristics, suppressing the decrease in battery capacity, and improving the battery's discharge capacity.

[0110] The aforementioned other additives may include, as typical examples, at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt contained in the electrolyte.

[0111] Specifically, the other additives mentioned above include vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propanesultone (PS), 1,4-butanesultone, ethensultone, 1,3-propensultone (PRS), 1,4-butensultone, 1-methyl-1,3-propensultone, ethylene sulfate (Esa), trimethylene sulfate (TMS), and methyl trimethylene sulfate. Examples include one or more compounds selected from the group consisting of MTMS, tetraphenyl borate, lithium oxalyl difluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonile, cyclohexanecarbonile, 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(trifluoromethane sulfonyl)imide, LiTFSI), LiPO2F2, LiODFB, LiBOB (lithium bisoxalate borate (LiB(C2O4)2) and LiBF4).

[0112] The aforementioned other additives are present in an amount of 0.01 relative to the total weight of the electrolyte. weight% ~20% by weight in It may be included, 0.05 weight% ~5.0wt% inIt is preferable that the other additives be included. If the content of the other additives is less than 0.01% by weight, the improvement in the low-temperature output of the battery, as well as the improvement in high-temperature storage characteristics and high-temperature life characteristics, will be weak. If the content of the other additives exceeds 20% by weight, excessive side reactions may occur in the electrolyte during charging and discharging of the battery. In particular, if an excessive amount of SEI film-forming additive is added, it may not decompose sufficiently at high temperatures and may remain unreacted or precipitated in the electrolyte at room temperature. This may cause side reactions that reduce the life or resistance characteristics of the secondary battery.

[0113] On the other hand, in Figure 4, the battery case 142 is electrically connected to the blank portion 146b of the negative electrode and functions as a negative electrode terminal that contacts an external power source and transmits the current applied from the external power source to the negative electrode.

[0114] Here, the battery case 142 is a cylindrical container with an opening formed at the top, and is made of a conductive metal material such as aluminum or steel. The battery case houses the electrode assembly 141 in the inner space through the upper opening, and also houses the electrolyte (not shown) together with it.

[0115] If necessary, a beading portion 147 and a crimping portion 148 may be provided at the upper end of the battery case 142. The beading portion 147 may be formed by press-fitting the outer circumferential surface of the battery case 142 to a distance D1. The beading portion 147 prevents the electrode assembly 141 housed inside the battery case 142 from coming out of the upper end opening of the battery case 142 and can function as a support portion to which the seal 143 is attached.

[0116] The crimping portion 148 may be formed on the upper part of the beading portion 147 and has a shape that extends and bends to surround the outer circumferential surface and a part of the upper surface of the cap plate 143a which is placed on the beading portion 147.

[0117] Next, the sealing body 143 is for sealing the open end of the battery case 142 and includes a cap plate 143a and a first gasket 143b that provides airtightness and insulation between the cap plate 143a and the battery case 142, and may further include a connecting plate 143c electrically and mechanically coupled to the cap plate 143a as needed. The cap plate 143a may be crimped onto a beading portion 147 formed on the battery case 142 and secured by a crimping portion 148.

[0118] The cap plate 143a is a component made of a conductive metal material and covers the upper opening of the battery case 142. The cap plate 143a is electrically connected to the positive electrode of the electrode assembly 141 and is electrically insulated from the battery case 142 by the first gasket 143b. Therefore, the cap plate 143a can function as the positive electrode terminal of a cylindrical secondary battery. The cap plate 143a may have a projection 143d that protrudes upward from its center C, and the projection 143d may be in contact with an external power source so that current is applied from the external power source.

[0119] A first gasket 143b may be interposed between the cap plate 143a and the crimping portion 148 to ensure the airtightness of the battery case 142 and to electrically insulate the battery case 142 from the cap plate 143a.

[0120] On the other hand, the cylindrical battery 140 according to the present invention may further include current collector plates 144 and 145 as needed. The current collector plates are coupled to the blank portion 146a of the positive electrode and the blank portion 146b of the negative electrode and connected to the electrode terminals (i.e., the positive electrode terminal and the negative electrode terminal).

[0121] Specifically, the cylindrical battery 140 according to the present invention may include a first current collector plate 144 coupled to the upper part of the electrode assembly 141 and a second current collector plate 145 coupled to the lower part of the electrode assembly 141.

[0122] The system may further include a first current collector plate 144 and / or a second current collector plate 145.

[0123] The first current collector plate 144 is coupled to the upper part of the electrode assembly 141. The first current collector plate 144 is made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the blank portion 146a of the positive electrode. A lead 149 may be connected to the first current collector plate 144. The lead 149 may extend above the electrode assembly 141 and be coupled to the connecting plate 143c, or it may be directly coupled to the lower surface of the cap plate 143a. The lead 149 may be coupled to other components by welding. It is preferable that the first current collector plate 144 is formed integrally with the lead 149. In that case, the lead 149 may have a long plate shape extending outward from the center of the first current collector plate 144.

[0124] On the other hand, the first current collector plate 144 is coupled to the end of the blank portion 146a of the positive electrode, and this coupling may be performed by methods such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0125] The second current collector plate 145 is coupled to the lower part of the electrode assembly 141. The second current collector plate 145 is made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the blank portion 146b of the negative electrode. One side of the second current collector plate 145 may be coupled to the blank portion 146b of the negative electrode, and the opposite side may be coupled to the inner bottom surface of the battery case 142. Here, the coupling may be performed by methods such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0126] On the other hand, the cylindrical battery 140 according to the present invention may further include an insulator 146 as needed. The insulator 146 may be positioned to cover the upper surface of the first current collector plate 144. By covering the first current collector plate 144 with the insulator 146, it is possible to prevent the first current collector plate 144 from coming into direct contact with the inner circumferential surface of the battery case 142.

[0127] The insulator 146 is provided with a lead hole 151 to allow a lead 149 extending upward from the first current collector plate 144 to be drawn out. The lead 149 is drawn out upward from the lead hole 151 and coupled to the lower surface of the connecting plate 143c or the lower surface of the cap plate 143a.

[0128] The insulator 146 may be made of an insulating polymer resin, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0129] On the other hand, the cylindrical battery 140 according to the present invention is formed on the lower surface of the battery case 142 as needed. Vent Part 152 may be further provided. Vent Section 152 is a region on the lower surface of the battery case 142 that has a thinner thickness compared to the surrounding area. Vent Because part 152 is thin, it is structurally weaker compared to the surrounding area. Therefore, when the internal pressure of the cylindrical battery 140 increases above a predetermined level, Vent When part 152 ruptures, the battery case 1 4 2. Allow internal gases to be released to the outside, preventing the battery from exploding.

[0130] Figure 5 shows a cross-sectional view of a cylindrical battery with a tablet structure according to another embodiment of the present invention. The cylindrical battery according to another embodiment of the present invention will be described below with reference to Figure 5. However, Figure 5 is merely an illustration of one embodiment of the present invention, and the structure of the cylindrical battery of the present invention is not limited to the scope shown in Figure 5.

[0131] Referring to Figure 5, a cylindrical battery 170 according to another embodiment of the present invention is shown in Figure 4 Compared to the cylindrical battery 140 shown, the structure of the battery case and sealing body is different, but the configuration of the electrode assembly and electrolyte is substantially the same.

[0132] Specifically, the cylindrical battery 170 includes a battery case 171 through which a rivet terminal 172 is driven. The rivet terminal 172 is installed on a partially closed closed surface (the top surface in the drawing) at one end of the battery case 171. The rivet terminal 172 is riveted into a through hole (the first opening at the first end) of the battery case 171 with an insulating second gasket 173 interposed between them. The rivet terminal 172 is exposed to the outside in the direction opposite to the direction of gravity.

[0133] The rivet terminal 172 includes a terminal exposure portion 172a and a terminal insertion portion 172b. The terminal exposure portion 172a is exposed to the outside of the closed surface of the battery case 171. The terminal exposure portion 172a may be located approximately in the center of the partially closed surface of the battery case 171. The maximum diameter of the terminal exposure portion 172a may be even larger than the maximum diameter of the through hole formed in the battery case 171. The terminal insertion portion 172b may penetrate approximately in the center of the closed surface of the battery case 171 and be electrically connected to the blank portion 146a of the positive electrode. The terminal insertion portion 172b may be rivet-bonded to the inner surface of the battery case 171. That is, the end of the terminal insertion portion 172b may have a curved shape toward the inner surface of the battery case 171. The maximum diameter of the end of the terminal insertion portion 172b may be even larger than the maximum diameter of the through hole in the battery case 171.

[0134] The lower end surface of the terminal insertion portion 172b may be welded to the first current collector plate 144 connected to the blank portion 146a of the positive electrode. An insulating cap 174 made of an insulating material may be interposed between the first current collector plate 144 and the inner surface of the battery case 171. The insulating cap 174 covers the upper part of the first current collector plate 144 and the upper end edge of the electrode assembly 141. This prevents the blank portion B3 on the outer circumference of the electrode assembly 141 from coming into contact with the inner surface of the battery case 171 which has a different polarity and causing a short circuit. The terminal insertion portion 172b of the rivet terminal 172 may be welded to the first current collector plate 144 through the insulating cap 174.

[0135] The second gasket 173 is interposed between the battery case 171 and the rivet terminal 172, preventing the battery case 171 and the rivet terminal 172, which have opposite polarities, from making electrical contact. As a result, the top surface of the battery case 171, which has a nearly flat shape, can function as the positive terminal of the cylindrical battery 170.

[0136] The second gasket 173 includes a gasket exposed portion 173a and a gasket inserted portion 173b. The gasket exposed portion 173a is interposed between the terminal exposed portion 172a of the rivet terminal 172 and the battery case 171. The gasket inserted portion 173b is interposed between the terminal inserted portion 172b of the rivet terminal 172 and the battery case 171. The gasket inserted portion 173b may deform together with the terminal inserted portion 172b during reveting and adhere tightly to the inner surface of the battery case 171. The second gasket 173 may be made of, for example, an insulating polymer resin.

[0137] The gasket exposed portion 173a of the second gasket 173 may have a shape that extends to cover the outer circumferential surface of the terminal exposed portion 172a of the rivet terminal 172. When the second gasket 173 covers the outer circumferential surface of the rivet terminal 172, it is possible to prevent short circuits from occurring during the process of connecting electrical connection components such as busbars to the upper surface of the battery case 171 and / or the rivet terminal 172. Although not shown, the gasket exposed portion 173a may have a shape that extends to cover not only the outer circumferential surface of the terminal exposed portion 172a but also a part of the upper surface.

[0138] When the second gasket 173 is made of a polymer resin, the second gasket 173 may be bonded to the battery case 171 and the rivet terminal 172 by heat fusion. In this case, the airtightness at 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 case 171 is enhanced. On the other hand, when the gasket exposed portion 173a of the second gasket 173 extends to the upper surface of the terminal exposed portion 172a, the rivet terminal 172 may be integrally bonded to the second gasket 173 by insert injection.

[0139] Of the upper surface of the battery case 171, the area 175 excluding the area occupied by the rivet terminal 172 and the second gasket 173 corresponds to the negative terminal having the opposite polarity to the rivet terminal 172.

[0140] The second current collector plate 176 is coupled to the lower part of the electrode assembly 141. The second current collector plate 176 is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the blank portion 146b of the negative electrode.

[0141] The second current collector plate 176 is preferably electrically connected to the battery case 171. For this purpose, the second current collector plate 176 may be fixed with at least a portion of its edge interposed between the inner surface of the battery case 171 and the first gasket 178b. In one example, at least a portion of the edge of the second current collector plate 176 may be fixed to the beading portion 180 formed at the lower end of the battery case 171 by welding, while being supported by the lower end surface of the beading portion 180. In a modified example, 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.

[0142] The second current collector plate 176 may have a plurality of radially formed bumps (not shown) on the surface facing the plain portion 146b. If bumps are formed, the second current collector plate 176 can be pressed to press the bumps into the plain portion 146b.

[0143] The second current collector plate 176 and the end of the blank portion 146b are preferably joined by welding, for example, laser welding.

[0144] The sealing body 178 that seals the lower open end of the battery case 171 includes a cap plate 178a and a first gasket 178b. The first gasket 178b electrically isolates the cap plate 178a from the battery case 171. The crimping portion 181 secures both the end of the cap plate 178a and the first gasket 178b. The cap plate 178a is provided with a vent portion 179. The configuration of the vent portion 179 is substantially the same as that of the embodiment described above.

[0145] The cap plate 178a is preferably made of a conductive metal material. However, since the first gasket 178b is interposed between the cap plate 178a and the battery case 171, the cap plate 178a does not have electrical polarity. The seal 178 seals the lower open end of the battery case 171. Cylindrical battery When the internal pressure of the 170 unit exceeds a threshold, it performs a function to release gas.

[0146] Preferably, the rivet terminal 172 electrically connected to the blank portion 146a of the positive electrode is used as the positive electrode terminal. Also, the portion 175 of the upper surface of the battery case 171, excluding the rivet terminal 172, electrically connected to the blank portion 146b of the negative electrode via the second current collector plate 176, is used as the negative electrode terminal. In this way, when the two electrode terminals are located at the top of the cylindrical battery, electrical connection components such as busbars can be placed on only one side of the cylindrical battery 170. battery This can lead to a simplification of the pack structure and an improvement in energy density. Furthermore, since the portion 175 used as the negative terminal has a nearly flat shape, sufficient contact area can be secured when joining electrical connection components such as busbars. As a result, the cylindrical battery 170 can reduce the resistance at the connection points of electrical connection components to a desirable level.

[0147] When a cylindrical lithium secondary battery is formed with a tabless structure as described above, the concentration of current is reduced compared to conventional batteries with electrode tabs. This effectively reduces heat generation inside the battery, thereby improving the thermal safety of the battery.

[0148] The cylindrical lithium secondary battery of the present invention described above is battery It can be used in the manufacture of packs. Figure 6 shows an embodiment of the present invention. battery The configuration of the pack is schematically shown. Referring to Figure 6, an embodiment of the present invention battery Pack 3 includes an assembly of cylindrical secondary batteries 1 that are electrically connected, and a pack housing 2 that houses them. The cylindrical secondary batteries 1 are as described in the embodiment above. battery This is a cell. In the drawing, for the sake of illustration convenience, the busbars for electrical connection of the cylindrical secondary battery 1, the cooling unit, external terminals, and other components are omitted from the illustration.

[0149] The aforementioned battery Pack 3 can be installed in a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle may include four-wheeled vehicles or two-wheeled vehicles. [Examples]

[0150] The present invention will be described in more detail below with reference to specific examples.

[0151] Example 1. (Electrolyte manufacturing) LiPF6 is added to a non-aqueous organic solvent mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75. of To achieve a concentration of 1.3M Add, An electrolyte was produced (ethylene carbonate content: 19.17% by weight / LiPF6 content: 15.41% by weight) (see Table 1 below).

[0152] (Manufacturing of secondary batteries) Average particle size D 50 The positive electrode active material (Li(Ni)) has a unimodal particle size distribution of 3 μm and is in single-particle form. 0.90 Mn 0.03 Co 0.05 Al 0.02 A positive electrode slurry was prepared by adding carbon nanotubes and a PVDF binder to N-methylpyrrolidone in a weight ratio of 97.8:0.6:1.6 and mixing. The positive electrode slurry was applied to one surface of an aluminum current collector sheet, dried at 120°C, and then rolled to produce a positive electrode plate.

[0153] A negative electrode slurry was prepared by adding a negative electrode active material (graphite and SiO=95:5 by weight), a conductive material (super C), styrene-butadiene rubber (SBR), and carboxymethylcellulose (CMC) to water in a weight ratio of 96:2:1.5:0.5 and mixing. The negative electrode slurry was applied to one surface of a copper current collector sheet, dried at 150°C, and then rolled to produce a negative electrode plate.

[0154] A separation membrane is interposed between the positive electrode plate and the negative electrode plate manufactured as described above. Let An electrode assembly (core diameter: 7 mm) was manufactured by stacking a separator membrane / positive electrode plate / separator membrane / negative electrode plate in that order and then winding it up. The electrode assembly manufactured as described above was inserted into a cylindrical battery can (diameter: 46 mm / height: 80 mm), and then 38 g of the electrolyte was injected to manufacture a 4680 cell (form factor ratio: 0.575).

[0155] Example 2. (Manufacturing of secondary batteries) Except for injecting 31 g of the electrolyte from Example 1, an electrolyte and 4680 cells containing it (form factor ratio: 0.575) were manufactured in the same manner as in Example 1.

[0156] Example 3. (Electrolyte manufacturing) LiPF6 is added to a non-aqueous organic solvent mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75. of To achieve a concentration of 1.2M Add, An electrolyte was produced (ethylene carbonate content: 19.40% by weight / LiPF6 content: 14.43% by weight) (see Table 1 below).

[0157] (Manufacturing of secondary batteries) The electrolyte and 4680 cells containing it were manufactured in the same manner as in Example 1, except that 38 g of the manufactured electrolyte was injected.

[0158] Example 4. (Manufacturing of secondary batteries) Except for injecting 31 g of the electrolyte as in Example 3, an electrolyte and 4680 cells containing it (form factor ratio: 0.58) were manufactured in the same manner as in Example 3.

[0159] Example 5. (Electrolyte manufacturing) LiPF6 is added to a non-aqueous organic solvent mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75. of To achieve a concentration of 1.05M Add, An electrolyte was produced (ethylene carbonate content: 19.76% by weight / LiPF6 content: 14.40% by weight) (see Table 1 below).

[0160] (Manufacturing of secondary batteries) The electrolyte and 4680 cells containing it were manufactured in the same manner as in Example 1, except that 31 g of the manufactured electrolyte was injected.

[0161] Example 6. (Electrolyte manufacturing) A non-aqueous organic solvent is prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75. 、The electrolyte was prepared by adding LiPF6 to a concentration of 1.2 M, followed by the addition of 3 wt% vinylene carbonate (VC) and 0.5 wt% 1,3-propanesultone (1,3-PS) (ethylene carbonate content: 19.40 wt% / LiPF6 content: 14.43 wt%) (see Table 1 below).

[0162] (Manufacturing of secondary batteries) The electrolyte and 4680 cells containing it were manufactured in the same manner as in Example 1, except that 38 g of the manufactured electrolyte was injected.

[0163] Example 7. (Electrolyte manufacturing) An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to a concentration of 1.2 M. Subsequently, 3 wt% vinylene carbonate (VC), 0.5 wt% 1,3-propanesultone (1,3-PS), and 1 wt% fluoroethylene carbonate (FEC) were added to produce the electrolyte (ethylene carbonate content: 19.17 wt% / LiPF6 content: 14.40 wt%) (see Table 1 below).

[0164] (Manufacturing of secondary batteries) The electrolyte and 4680 cells containing it were manufactured in the same manner as in Example 1, except that 38 g of the manufactured electrolyte was injected.

[0165] Example 8. (Electrolyte manufacturing) An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to a concentration of 1.2 M, and then adding 3 wt% vinylene carbonate (VC) and 0.5 wt% ethylene sulfate (Esa) (ethylene carbonate content: 19.40 wt% / LiPF6 content: 14.43 wt%) (see Table 1 below).

[0166] (Manufacturing of secondary batteries) The electrolyte and 4680 cells containing it were manufactured in the same manner as in Example 1, except that 38 g of the manufactured electrolyte was injected.

[0167] Comparative Example 1. (Manufacturing of secondary batteries) Except for injecting 43g of the electrolyte as in Example 3, the electrolyte and 4680 cells (form factor ratio: 0.5) containing it were prepared in the same manner as in Example 3. 75 They manufactured ).

[0168] Comparative Example 2. (Manufacturing of secondary batteries) Except for injecting 25g of the electrolyte as in Example 3, the electrolyte and 4680 cells (form factor ratio: 0.5) containing it were prepared in the same manner as in Example 3. 75 They manufactured ).

[0169] Comparative Example 3. (Electrolyte manufacturing) An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent, which was a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75, to a concentration of 0.95 M (ethylene carbonate content: 20.00 wt% / LiPF6 content: 11.89 wt%) (see Table 1 below).

[0170] (Manufacturing of secondary batteries) The electrolyte and 4680 cells containing it were manufactured in the same manner as in Example 1, except that 31 g of the manufactured electrolyte was injected.

[0171] Comparative Example 4. (Electrolyte manufacturing) An electrolyte was prepared by adding LiPF6 to a non-aqueous organic solvent prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 to a concentration of 1.6 M (ethylene carbonate content: 18.50% by weight / LiPF6 content: 17.73% by weight) (see Table 1 below).

[0172] (Manufacturing of secondary batteries) The electrolyte and 4680 cells containing it were manufactured in the same manner as in Example 1, except that 38 g of the manufactured electrolyte was injected.

[0173] Comparative Example 5. (Electrolyte manufacturing) An electrolyte was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 20:5:75 in a non-aqueous organic solvent, to which the LiPF6 concentration was 1.3 M (ethylene carbonate content: 19.17 wt% / LiPF6 content: 15.41 wt%) (see Table 1 below).

[0174] (Manufacturing of secondary batteries) Average particle size D 50 The positive electrode active material (Li(Ni)) has a unimodal particle size distribution of 3 μm and is in single-particle form. 0.90 Mn 0.03 Co 0.05 Al 0.02 A positive electrode slurry was prepared by adding carbon nanotubes and a PVDF binder to N-methylpyrrolidone in a weight ratio of 97.8:0.6:1.6 and mixing. The positive electrode slurry was applied to one surface of an aluminum current collector sheet, dried at 120°C, and then rolled to produce a positive electrode plate.

[0175] A negative electrode slurry was prepared by adding a negative electrode active material (graphite and SiO=95:5 by weight), a conductive material (super C), styrene-butadiene rubber (SBR), and carboxymethylcellulose (CMC) to water in a weight ratio of 96:2:1.5:0.5 and mixing. The negative electrode slurry was applied to one surface of a copper current collector sheet, dried at 150°C, and then rolled to produce a negative electrode plate.

[0176] A separation membrane is interposed between the positive electrode plate and the negative electrode plate manufactured as described above. Let Separation membrane / Positive electrode plate / Separation membrane / Negative electrode plate of An electrode assembly (core diameter: 7 mm) was manufactured by sequentially stacking and then winding the materials. The electrode assembly manufactured as described above was inserted into a cylindrical battery can (diameter: 46 mm, height: 70 mm), and then 38 g of the electrolyte was injected to produce a 4670 cell (form factor ratio: 0.657).

[0177] Comparative Example 6. (Manufacturing of secondary batteries) A 46120 cell (form factor ratio: 0.383) was manufactured in the same manner as in Comparative Example 5, except that the manufactured electrode assembly (core diameter: 7 mm) was inserted into a cylindrical battery can (diameter: 46 mm, height: 120 mm), and then 38 g of electrolyte was injected.

[0178] [Table 1]

[0179] In Table 1 above, equation (1)* is,

[0180]

number

[0181] The values ​​calculated from are shown.

[0182] Experimental example Experimental Example 1. AC Resistance Evaluation The secondary batteries manufactured in Examples 1, 3, 5, 6, and 8, and the secondary batteries manufactured in Comparative Examples 1-4 and 6, were subjected to formation by repeating two cycles (charging: 4.2V CC, discharging: 2.5V CC) at 25°C with a current of 25A (0.1C). Subsequently, CC / CV charging under the conditions of 4.2V, 8.33A (0.3C, 0.05C cut-off) and CC discharging under the conditions of 2.5V, 8.33A (0.3C) were repeated three times. After that, the AC resistance was measured in the 1kHz range using a multi-impedance analyzer (Biologic, model: VMP3) at a temperature of 25°C and a State of Charge (SOC) of 30%, and the results are shown in Table 2 below.

[0183] Experimental Example 2. Evaluation of DC Resistance (Direct Current Internal Resistance) The secondary batteries manufactured in Examples 1, 3, 5, 6, and 8, and the secondary batteries manufactured in Comparative Examples 1-4 and 6, were subjected to the same formation and three cycles as in Experimental Example 1. They were then fully charged under the conditions of 4.2V and 8.33A (0.3C, 0.05C cut-off), discharged to 50% SOC at room temperature, and the voltage drop generated during discharge at a current of 0.5C for 10 seconds was recorded. The DC resistance (DC-IR) value was measured using Ohm's law (R=V / I), and the results are shown in Table 2 below.

[0184] [Table 2]

[0185] Referring to Table 2 above, it can be seen that the secondary batteries manufactured in Examples 1, 3, 5, 6, and 8 showed suppressed resistance increases and improved cell performance compared to the secondary batteries manufactured in Comparative Examples 1-4 and 6.

[0186] In other words, when comparing the cells of Examples 3, 6, and 8 with the cells of Comparative Examples 1 and 2, it can be seen that even when the cell dimensions and electrolyte composition are the same, the cells of Comparative Examples 1 and 2, where the value calculated from formula (1) considering the amount of electrolyte injected deviates from the conditions of the present invention, show increased resistance and inferior cell performance compared to the cells of Examples 3, 6, and 8.

[0187] Furthermore, comparing the secondary battery manufactured in Example 1 with the secondary battery manufactured in Comparative Example 4, it can be seen that even when the cell dimensions and the amount of electrolyte injected are the same, the cell of Comparative Example 4, in which the value calculated from formula (1) considering the content of lithium salt and ethylene carbonate contained in the electrolyte deviates from the conditions of the present invention, has increased resistance and inferior cell performance compared to the cell of Example 1.

[0188] Furthermore, comparing the secondary battery manufactured in Example 5 with the secondary battery manufactured in Comparative Example 3, it can be seen that even when the cell dimensions and the amount of electrolyte injected are the same, the cell of Comparative Example 3, in which the value calculated from formula (1), which takes into account the content of lithium salt and ethylene carbonate contained in the electrolyte, deviates from the conditions of the present invention, has increased resistance and inferior cell performance compared to the cell of Example 5.

[0189] On the other hand, in the secondary battery of Comparative Example 6, even if the electrolyte composition and the amount of electrolyte injected are the same as in Example 1, it can be confirmed that the wetting properties decrease due to insufficient electrolyte injection volume, resulting in increased resistance compared to the secondary battery of the example, because the form factor ratio falls outside the range of the present invention.

[0190] Experimental Example 3. For each cell manufactured in Examples 1-8 and Comparative Examples 1-6, constant current-constant voltage charging was performed at room temperature (25°C) at a rate of 1.0C up to 4.2V, followed by a 0.5C cutoff discharge, and the initial capacity was measured.

[0191] Next, constant current-constant voltage charging was performed at a high temperature (40°C) at a 1.0C-rate up to 4.2V, followed by discharging at a 0.2C-rate down to 2.5V. This constituted one cycle, and 100 charge-discharge cycles were performed. The capacity retention rate after 100 cycles at 40°C was measured relative to the initial capacity after one cycle, and the results are shown in Table 3 below.

[0192] [Table 3]

[0193] Referring to Table 3 above, it can be seen that the lithium secondary batteries of Examples 1 to 8 of the present invention showed a significantly improved capacity retention rate after 100 cycles compared to the lithium secondary batteries of Comparative Examples 1 to 6. [Explanation of symbols]

[0194] 10 positive electrode 11 Negative electrode 12 Separation membrane 20 Current collector 21, 21a Active material layer 22, 22a, 22c Plain area 24 Insulating layer 140, 170 cylindrical batteries 141 Jelly roll type electrode assembly 142, 171 Battery Case 143, 178 Sealed body 143b, 178b First gasket 144 First current collection plate 145, 176 Second current collection plate 146a Plain area of ​​the positive electrode plate 146b Plain area of ​​the negative electrode plate 146 Insulators 152 、179 Vent Department 172 Rivet terminals 173 Second Gasket to 1 73a Exposed gasket portion 173b Gasket insertion section 147, 180 Beading section 148 、181 Crimping section 149 Reed 172a Exposed terminal part 17 2 b. Terminal insertion section 174 Insulating cap

Claims

1. A lithium secondary battery comprising a battery case, an electrode assembly housed inside the battery case, and an electrolyte, The electrode assembly includes a positive electrode containing a positive electrode active material, a separation membrane, and a negative electrode containing a negative electrode active material. The electrolyte is a lithium salt, LiPF ６ It contains, and contains ethylene carbonate as an organic solvent. The lithium secondary battery is a lithium secondary battery in which the ratio of the diameter (r) to the height (h) of the battery case (form factor ratio) is 0.4 or more, and satisfies the conditions of the following formula (1). [Math 1] (In the above formula (1), h is the height of the battery case (mm), r is the diameter of the battery case (mm), W ＬｉＰＦ６ LiPFF as a percentage of the total weight of electrolytes ６ This indicates the content as a percentage (%). W ＥＣ This indicates the ethylene carbonate content as a percentage (%) relative to the total weight of the electrolyte. W ＥＬ (This refers to the total weight (g) of the electrolyte contained in the lithium secondary battery.)

2. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a cylindrical battery having a form factor ratio of 0.4 to 0.6 for the ratio of the diameter (r) to the height (h) of the battery case.

3. The lithium secondary battery according to claim 1, wherein the lithium secondary battery is a 46110 cell, a 48110 cell, a 4880 cell, or a 4680 cell.

4. The lithium secondary battery according to claim 1, wherein the lithium secondary battery includes blank portions on at least a portion of the positive electrode and the negative electrode where no active material layer is formed, and the blank portion of the positive electrode or the blank portion of the negative electrode is defined as an electrode tab, and is a tabletless battery.

5. The lithium secondary battery according to claim 4, wherein the blank portion of the positive electrode and the blank portion of the negative electrode are each formed at the end of one side of the positive electrode and the negative electrode in the direction in which the electrode assembly is wound, a current collector plate is bonded to each of the blank portions of the positive electrode and the negative electrode, and the current collector plate is connected to the electrode terminals.

6. The plain portion of the positive electrode and the plain portion of the negative electrode are processed into a plurality of segments that can be independently folded. The lithium secondary battery according to claim 5, wherein at least a portion of the plurality of segments is bent toward the winding center of the electrode assembly.

7. The lithium secondary battery according to claim 6, wherein at least a portion of the bent plurality of segments overlap on the upper and lower ends of the electrode assembly, and the current collector plate is bonded to the overlapping plurality of segments.

8. The positive electrode active material is a lithium transition metal oxide containing Ni and Co. The lithium secondary battery according to claim 1, wherein the lithium transition metal oxide satisfies the following formula (2). Formula (2) 18≦X Ｎｉ / X Ｃｏ ≦48 (In the above formula (2), X Ｎｉ is the mole percentage of Ni with respect to all metals excluding lithium in the lithium transition metal oxide, and X Ｃｏ is the mole percentage of Co with respect to all metals excluding lithium in the lithium transition metal oxide)

9. The lithium secondary battery according to claim 8, wherein the lithium transition metal oxide is represented by the following [Chemical Formula 1]. [Chemical formula 1] Li ａ Ni ｂ Co ｃ M １ ｄ M ２ ｅ O ２ In the above chemical formula (1), M １ M is Mn, Al, or a combination thereof. ２ is one or more elements selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb, and satisfies the following conditions: 0.8 ≤ a ≤ 1.2, 0.85 < b < 1, 0 < c < 0.06, 0 < d < 0.15, and 0 ≤ e ≤ 0.

1.

10. The lithium transition metal oxide is Li(Ni ０．９０ Mn ０．０５ Co ０．０５ ) O ２ , Li(Ni ０．９４ Co ０．０４ Mn ０．０２ ) O ２ , Li(Ni ０．８７ Mn ０．０７ Co ０．０４ Al ０．０２ ) O ２ , or Li(Ni ０．９０ Mn ０．０３ Co ０．０５ Al ０．０２ ) O ２ The lithium secondary battery according to claim 9.

11. The aforementioned anode active material is a mixture of a carbon-based anode active material and a silicon-based anode active material. The lithium secondary battery according to claim 1, wherein the carbon-based anode active material and the silicon-based anode active material are contained in a weight ratio of 95:5 to 99:

1.

12. A battery pack comprising a lithium secondary battery according to any one of claims 1 to 11.

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