Cylindrical lithium secondary battery

Abstract

The present invention relates to a cylindrical lithium secondary battery having an X value, as defined by equation 1, of 7 to 16 m2 (X=[AA×LA×(1-P)×{(RAng×BAng)+(RAag×BAag)}] / (STc / ST)×100, wherein, in equation 1, AA (unit: cm2) is an area of an anode active material, LA (unit: g / cm2) is a loading amount of the anode active material formed on an anode current collector, P (no unit) is porosity of the anode active material, RAng is a weight ratio of natural graphite to the total weight of the natural graphite and artificial graphite included in the anode active material layer, BAng (unit: m2 / g) is a BET specific surface area of the natural graphite, RAag is a weight ratio of the artificial graphite to the total weight of the natural graphite and the artificial graphite included in the anode active material layer; BAag (unit: m2 / g) is a BET specific surface area of the artificial graphite, STc (unit: micrometer) is the thickness of a ceramic coating layer within a separator, ST (unit: micrometer) refers to the thickness of the separator). By adjusting a mixing ratio of the artificial graphite and the natural graphite within the negative electrode active material layer, a reaction area of the anode active material layer, and a thickness ratio of the ceramic coating layer within the separator, the cylindrical lithium secondary battery maintains a low ignition potential while having a wide reaction area, thereby exhibiting excellent safety characteristics.

Description

cylindrical lithium secondary battery

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0102781, filed August 1, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a cylindrical lithium secondary battery, and more particularly, to a high-capacity cylindrical lithium secondary battery with excellent thermal safety and economic efficiency.

[0003] With technological advancements in electric vehicles, portable electronic devices, and other devices, the demand for lithium secondary batteries as an energy source is rapidly increasing.

[0004] Lithium secondary batteries can be classified into cylindrical, square, and pouch-type batteries depending on the shape of the battery case. Among these, cylindrical batteries are manufactured by sequentially stacking sheet-shaped positive electrodes, separators, and negative electrodes in a cylindrical battery can, winding them in one direction, and then housing a jelly-roll-type electrode assembly, which is then sealed by covering the top of the battery can with a cap plate.

[0005] In the case of cylindrical batteries, small cylindrical secondary batteries with a form factor of 1865 (a cylindrical secondary battery with a diameter of 18 mm × a height of 65 mm) or 2170 (a cylindrical secondary battery with a diameter of 21 mm × a height of 70 mm) were mainly used in the past, but recently, as electric vehicles require increased driving distances and faster charging speeds, the development and use of large cylindrical secondary batteries with larger form factors, such as 4680 (a cylindrical secondary battery with a diameter of 46 mm × a height of 80 mm), are being considered.

[0006] However, in the case of small cylindrical secondary batteries with form factors such as 18650 (cylindrical secondary batteries with a diameter of 18 mm × height of 65 mm) or 21700 (cylindrical secondary batteries with a diameter of 21 mm × height of 70 mm), which were mainly used in the past, resistance and heat generation were not major issues, but in the case of large cylindrical secondary batteries, the width of the electrodes is wide due to the high-capacity design, and as a result, the amount of active material that reacts with the electrolyte in the electrodes increases, which is a problem in that the amount of heat generated also increases.

[0007] Accordingly, among artificial graphite and natural graphite, which are generally used as negative active materials, natural graphite is known to have excellent price competitiveness and a high capacity due to its high crystallinity compared to other carbon-based active materials such as artificial graphite. However, since it has a large specific surface area compared to artificial graphite, which increases the reaction area, it has been difficult to apply it at a high rate to large cylindrical secondary batteries due to the possibility of ignition.

[0008] Therefore, there is a need for the development of a technology that has a low production cost, high capacity, and excellent safety for large-sized cylindrical secondary batteries applicable to medium- to large-sized devices such as automobiles.

[0009]

[0010] The present invention is intended to solve the above problems, and to provide a cylindrical secondary battery having a wide reaction area and excellent safety due to low possibility of ignition by controlling the thickness ratio of the reaction area of ​​the negative active material layer and the ceramic coating layer in the separator.

[0011] [1] The present invention is a cylindrical lithium secondary battery including an electrode assembly in which a cathode, a cathode, and a separator interposed between the cathode and the cathode are wound in one direction; a battery can in which the electrode assembly and an electrolyte are stored; wherein the cathode includes a cathode active material layer formed on a cathode current collector, and the cathode active material layer includes natural graphite and artificial graphite as the cathode active material, and the separator includes a ceramic coating layer entirely coated on one or both sides of a substrate and the separator substrate, and the value of X defined by the following formula 1 is 7 m 2 16 m inland 2 It provides a lithium secondary battery.

[0012] [Formula 1]

[0013]

[0014] In the above equation 1,

[0015] AA (unit: cm) 2 ) is the area of ​​the negative electrode active material layer, and LA (unit: g / cm 2 ) is the loading amount of the negative electrode active material layer formed on the negative electrode current collector, P (unitless) is the porosity of the negative electrode active material layer, and RA NG is the weight ratio of natural graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer, and BA NG (Unit: m 2 / g) is the BET surface area of ​​natural graphite, and RA AG is the weight ratio of artificial graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer, and BA AG (Unit: m 2 / g) is the BET surface area of ​​artificial graphite, and ST c (Unit: ㎛) is the thickness of the ceramic coating layer within the separator, and ST (Unit: ㎛) is the thickness of the separator.

[0016] [2] In the present invention, in the above [1], the AA is 5500 cm 2 6000 cm inland 2A cylindrical lithium secondary battery is provided.

[0017] [3] The present invention, in the above [1] or [2], the RA NG A cylindrical lithium secondary battery having a capacity of 0.5 or more is provided.

[0018] [4] The present invention, in at least one of the above [1] to [3], the BA NG is 1 m 2 / g to 3 m 2 A cylindrical secondary battery having a mass of / g is provided.

[0019] [5] The present invention, in at least one of the above [1] to [4], the BA AG is 0.5 m 2 / g to 0.9 m 2 A cylindrical secondary battery having a mass of / g is provided.

[0020] [6] The present invention, in at least one of the above [1] to [5], the negative electrode has a total reaction area of ​​artificial graphite and natural graphite of the negative electrode active material layer of 200 m 2 A cylindrical lithium secondary battery having an ideal shape is provided.

[0021] [7] The present invention, in at least one of the above [1] to [6], the LA is 0.025 g / cm 2 0.035 g / cm 2 A cylindrical lithium secondary battery is provided.

[0022] [8] The present invention provides a cylindrical lithium secondary battery in which, in at least one of the above [1] to [7], P is 0.35 or less.

[0023] [9] The present invention provides a cylindrical lithium secondary battery in at least one of the above [1] to [8], wherein the ST is 12 ㎛ to 15 ㎛.

[0024]

[0010] The present invention, in at least one of the above [1] to [9], the ST cA cylindrical lithium secondary battery having a diameter of 5 μm or less is provided.

[0025]

[0011] The present invention, in at least one of the above [1] to

[0010] , the ST c / ST provides a cylindrical lithium secondary battery having a capacity of 0.05 to 0.3.

[0026]

[0012] The present invention provides a cylindrical lithium secondary battery, wherein in at least one of the above [1] to

[0011] , the lithium secondary battery has a ratio (R / H) of the diameter (R) of the lithium secondary battery to the height (H) of the lithium secondary battery of 0.4 or more.

[0027]

[0014] The present invention provides a battery pack including a cylindrical lithium secondary battery according to at least one of the above [1] to

[0013] as a unit cell.

[0028]

[0029] The cylindrical lithium secondary battery according to the present invention can improve the thermal safety of the negative electrode and the thermal / mechanical properties of the separator by controlling the thickness of the ceramic coating layer of the separator so that the ratio of the ceramic coating layer in the separator, the porosity of the negative electrode active material layer, the product of the ratios of artificial graphite and natural graphite, the product of the specific surface areas of artificial graphite and natural graphite, the loading amount of the negative electrode, and the negative electrode area satisfy a specific relationship, thereby improving the capacity and output characteristics of the lithium secondary battery.

[0030]

[0031] Figure 1 is a drawing showing a state of lamination before winding of an electrode assembly according to the present invention.

[0032] Figure 2 is a cross-sectional view showing the structure of an electrode of an electrode assembly according to one embodiment of the present invention.

[0033] FIG. 3 is a drawing for explaining the structure of an electrode assembly according to one embodiment of the present invention.

[0034] Figure 4 is a cross-sectional view showing the structure of a lithium secondary battery according to one embodiment of the present invention.

[0035] FIG. 5 is a cross-sectional view showing the structure of a lithium secondary battery according to another embodiment of the present invention.

[0036] Figure 6 is a drawing for explaining a battery pack according to the present invention.

[0037]

[0038] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0039] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0040] In this specification, it should be understood that terms such as “include,” “have,” or “have” are intended to specify the presence of a feature, number, step, component, or combination thereof implemented, but do not preemptively exclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof. In addition, in this specification, when it is said that a part such as a layer, film, region, or plate is formed on another part, the direction in which it is formed is not limited to the upper direction, and includes those formed in the side or lower direction.

[0041] In this specification, the terms "upper surface" and "lower surface" are used as relative concepts to facilitate easy understanding of the technical ideas of the present invention. Therefore, "upper surface" and "lower surface" do not refer to a specific direction, position, or component and can be used interchangeably. For example, "upper surface" may be interpreted as "lower surface," and "lower surface" may be interpreted as "upper surface." Accordingly, the "upper surface" may be expressed as "first" and the "lower surface" as "second," or the "lower surface" may be expressed as "first" and the "upper surface" as "second." However, within one embodiment, the terms "upper surface" and "lower surface" are not used interchangeably.

[0042] Hereinafter, the present invention will be described in more detail.

[0043] Large cylindrical lithium secondary batteries, such as the 4680 cylindrical battery, have excellent energy densities, but their total heat output increases, making it crucial to improve thermal safety. According to the present invention, even if the total heat output of a large cylindrical lithium secondary battery increases due to the inclusion of a high proportion of natural graphite in the negative active material layer, thermal safety can be improved by adjusting the proportion of the ceramic coating layer in the separator.

[0044] Accordingly, the present invention provides an optimal numerical range of the ceramic coating layer ratio in the separator with respect to the ratio of artificial graphite and natural graphite in the negative active material, and it was confirmed that a lithium secondary battery satisfying this range has excellent thermal safety. In particular, in large-sized batteries, even though the total amount of heat generated increases due to the large amount of active material reacting with the electrolyte in the electrode, it is significant that thermal safety can be supplemented by coating the separator with ceramic at an appropriate numerical ratio, and that a numerical range is provided that improves thermal safety without deteriorating output characteristics.

[0045] Specifically, if an excessive ceramic coating layer is formed to improve the thermal / mechanical properties of the separator, the distance between the positive and negative electrodes may increase, resulting in poor output characteristics of the cell and increased occurrence of side reactions due to increased moisture. In addition, if the ceramic coating layer is formed thinly, the effect of improving thermal safety may be minimal. However, the cylindrical lithium secondary battery according to the present invention can improve both output characteristics and thermal safety.

[0046]

[0047] Specifically, the lithium secondary battery of the present invention is a cylindrical lithium secondary battery including an electrode assembly in which a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode are wound in one direction; and a battery can in which the electrode assembly and an electrolyte are stored.

[0048] In addition, the negative electrode included in the lithium secondary battery of the present invention includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, and the negative electrode active material layer includes natural graphite and artificial graphite as the negative electrode active material.

[0049] In addition, the separator included in the lithium secondary battery of the present invention includes a ceramic coating layer that is entirely coated on one or both sides of the substrate and the separator substrate.

[0050]

[0051] Specifically, according to the present invention, the X value defined by the following equation 1 is 7 m 2 16 m inland 2 , specifically 7.1 m 2 16 m inland 2 , 7.1 m 2 15.9 m inland 2 , 7.2 m 2 16 m inland 2 or 7.2 m 2 15.9 m inland 2 , more specifically 7.3 m 2 15.9 m inland 2 , 7.3 m 215.8 m inland 2 or 7.3 m 2 15.7 m inland 2 , more specifically 7.4 m 2 15.6 m inland 2 , 7.4 m 2 15.5 m inland 2 or 7.4 m 2 15.4 m inland 2 , most specifically 7.5 m 2 15.3 m inland 2 A cylindrical lithium secondary battery is provided. The X value is 7 m 2 If it is less than 16 m, the ratio of the ceramic coating layer in the separator is high compared to the reaction area of ​​the negative active material layer, so the thermal / mechanical properties of the separator may be improved, but the distance between the positive and negative electrodes may be far, so the output characteristics of the cell may be deteriorated. 2 If it exceeds , the ratio of the ceramic coating layer in the separator is low compared to the reaction area of ​​the negative active material layer, which may increase the possibility of the battery igniting. If the X value satisfies the above-described range, a cylindrical secondary battery having excellent capacity and productivity while also improving thermal safety can be provided.

[0052] [Formula 1]

[0053]

[0054] In the above equation 1, AA (unit: cm 2 ) means “the area of ​​the negative electrode active material layer in a cylindrical lithium secondary battery.” The area of ​​the negative electrode active material layer refers to the area of ​​the horizontal surface of the negative electrode current collector coated with the negative electrode active material, and can be measured by multiplying the length and width of the negative electrode active material layer. The AA is 5500 cm 2 6000 cm inland 2 , specifically 5550 cm 2 6000 cm inland 2 , 5500 cm 2 5950 cm inland 2 or 5550 cm 2 5950 cm inland2 , more specifically 5560 cm 2 5950 cm inland 2 , 5570 cm 2 5950 cm inland 2 or 5580 cm 2 5900 cm inland 2 , more specifically 5600 cm 2 5900 cm inland 2 , 5620 cm 2 5880 cm inland 2 or 5650 cm 2 5850 cm inland 2 , most specifically 5700 cm 2 5800 cm inland 2 It can be. If AA satisfies the above-described range, it can have higher energy density and better thermal safety.

[0055] Also, in the above formula 1, RA NG means “the weight ratio of natural graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer.” The above RA NG is 0.4 or greater, specifically 0.41 or greater, 0.42 or greater, or 0.43 or greater, more specifically 0.44 or greater, 0.45 or greater, or 0.46 or greater, even more specifically 0.47 or greater, 0.48 or greater, or 0.49 or greater, and most specifically 0.5 or greater. RA NG When the above-described range is satisfied, high-capacity characteristics can be realized and productivity can be excellent because natural graphite with high lithium ion storage capacity is included in a high proportion.

[0056] Also, in the above equation 1, BA NG (Unit: m 2 / g) means “BET specific surface area of ​​natural graphite included in the negative electrode active material layer.” In the present invention, the BET specific surface area is measured by the BET method and means the specific surface area of ​​the measured particle itself. The above BANG is 1 m 2 / g to 3 m 2 / g, specifically 1.2 m 2 / g to 3 m 2 / g, 1.3 m 2 / g to 3 m 2 / g, 1.2 m 2 / g to 2.9 m 2 / g, 1.3 m 2 / g to 2.9 m 2 / g, 1.4 m 2 / g to 2.9 m 2 / g or 1.3 m 2 / g to 2.8 m 2 / g, more specifically 1.4 m 2 / g to 2.8 m 2 / g, 1.4 m 2 / g to 2.7 m 2 / g, 1.5 m 2 / g to 2.7 m 2 / g or 1.6 m 2 / g to 2.7 m 2 / g, more specifically 1.7 m 2 / g to 2.7 m 2 / g, 1.8 m 2 / g to 2.7 m 2 / g, 1.8 m 2 / g to 2.6 m 2 / g, 1.8 m 2 / g to 2.5 m 2 / g, 1.8 m 2 / g to 2.4 m 2 / g, 1.8 m 2 / g to 2.3 m 2 / g or 1.9 m 2 / g to 2.2 m 2 / g, most specifically 2.1 m 2 / g. When the specific surface area of ​​natural graphite satisfies the above-described range, the high-temperature storage characteristics and high-temperature life characteristics can be better.

[0057] Also, in the above formula 1, RA AG means “the weight ratio of artificial graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer.” The above RA AG is 0.6 or less, specifically 0.59 or less, 0.58 or less, or 0.57 or less, more specifically 0.56 or less, or 0.55 or less, even more specifically 0.54 or less, 0.53 or less, or 0.52 or less, and most specifically 0.5 or less. RA AG If the above-described range is satisfied, the capacity characteristics can be better.

[0058] Also, in the above equation 1, BA AG (Unit: m 2 / g) means “BET specific surface area of ​​artificial graphite included in the negative electrode active material layer.” The above BA AG is 0.5 m 2 / g to 0.9 m 2 / g, specifically 0.5 m 2 / g to 0.8 m 2 / g, 0.6 m 2 / g to 0.9 m 2 / g or 0.6 m 2 / g to 0.8 m 2 / g, more specifically 0.7 m 2 / g may be. If the specific surface area of ​​artificial graphite satisfies the above-described range, the structural safety and output characteristics of the secondary battery may be further improved.

[0059] In addition, the cylindrical lithium secondary battery according to one embodiment of the present invention has a “total reaction area of ​​artificial graphite and natural graphite included in the negative electrode active material layer” of 200 m 2 Above, specifically 205 m 2 Above, 210 m 2 or more than 215 m 2 Above, more specifically 218 m 2 Above, 221 m 2 or 224 m2 Above, more specifically 225 m 2 Above, 226 m 2 Above, 227 m 2 or 228 m 2 Above, most specifically 230 m 2 It can be ideal. When the total reaction area of ​​artificial graphite and natural graphite satisfies the above-described range, the capacity is excellent and productivity and thermal safety can be improved together. In the present invention, the total reaction area of ​​artificial graphite and natural graphite means the sum of the reaction areas of each graphite negative electrode active material calculated by the following formula, and in the above formula 1, the molecule AA×LA×{(BA AG ×RA AG ) + (BA NG ×RA NG ) means the value.

[0060]

[0061] Reaction area (m) of each graphite negative electrode active material 2 ) = Area of ​​the negative electrode active material layer (AA, unit: cm 2 ) × negative electrode active material layer loading amount (LA, unit: g / cm 2 ) × Weight ratio of each graphite to the total weight of graphite included in the negative electrode active material layer × BET specific surface area (m) of each graphite included in the negative electrode active material layer 2 / g)

[0062]

[0063] Also, in the above equation 1, LA (unit: g / cm 2 ) means “the loading amount of the negative electrode active material layer”. In the present invention, the loading amount of the negative electrode active material layer is 1 cm 2 It refers to the mass (g) of the negative electrode active material layer included per area, and refers to the mass obtained by excluding the weight of the negative electrode current collector from the weight of the negative electrode per unit area. The above LA is 0.025 g / cm 2 0.035 g / cm 2 , specifically 0.026 g / cm 2 0.034 g / cm2 , more specifically 0.027 g / cm 2 0.033 g / cm 2 or 0.027 g / cm 2 0.032 g / cm 2 , more specifically 0.028 g / cm 2 0.031 g / cm 2 , most specifically 0.029 g / cm 2 0.030 g / cm 2 It can be. When the loading amount of the negative active material layer satisfies the above-described range, the capacity characteristics and life characteristics can be improved.

[0064] In addition, in the above formula 1, P (unitless) means “porosity of the negative electrode active material layer”. In the present invention, the porosity of the negative electrode active material layer means the ratio of pores (empty spaces) in the negative electrode active material layer, and may have a value of 0 or more and less than 1. The porosity can be controlled by rolling during the manufacture of the negative electrode. The P may be 0.35 or less, specifically 0.1 to 0.35 or 0.2 to 0.35, more specifically 0.22 to 0.3, even more specifically 0.24 to 0.3, and most specifically 0. 25 to 0. 3. When the porosity P of the negative electrode active material layer satisfies the above-described range, the energy density, capacity characteristics, and electrolyte impregnation property can be improved at the same time. In addition, in the present invention, 1-P means the ratio of the actual negative electrode active material occupied by the negative electrode active material layer excluding the ratio of pores occupied by the negative electrode active material layer.

[0065] In addition, in the above formula 1, ST (unit: ㎛) means “thickness of the separator.” In the present invention, the thickness of the separator means the thickness including the ceramic coating layer coated on one or both sides of the separator. The ST may be 12 ㎛ to 15 ㎛, specifically 12 ㎛ to 14.5 ㎛, more specifically 12 ㎛ to 14 ㎛, even more specifically 12.5 ㎛ to 14 ㎛, and most specifically 12.5 ㎛ to 13.5 ㎛. When the ST satisfies the above-described range, the cell resistance value can be minimized while preventing a short circuit between the positive and negative electrodes, thereby improving the life characteristics and output characteristics of the lithium secondary battery.

[0066] Also, in the above equation 1, ST c (Unit: ㎛) means "thickness of the ceramic coating layer within the separator." In the present invention, the thickness of the ceramic coating layer within the separator means the total thickness of the ceramic coating layer coated on one or both sides of the separator substrate. For example, when the ceramic coating layer is coated on both sides of the separator substrate, it means the sum of the thicknesses of the coating layers formed on each side. The ST c The particle size may be 5 ㎛ or less, specifically 0.1 ㎛ to 4.5 ㎛, more specifically 0.5 ㎛ to 4.5 ㎛, even more specifically 0.5 ㎛ to 3.5 ㎛, and most specifically 1 ㎛ to 3 ㎛. ST c If the above range is satisfied, low resistance can be achieved and output characteristics can be improved. ST c If it exceeds 5 ㎛, the distance between the positive and negative electrodes may increase, which may result in poor output characteristics of the battery and increased side reactions due to increased moisture.

[0067] In addition, the ratio of the ceramic coating layer of the separator of the cylindrical lithium secondary battery according to one embodiment of the present invention ST c / ST may be 0.05 to 0.3, specifically 0.06 to 0.3, 0.06 to 0.29, 0.07 to 0.29 or 0.07 to 0.28, more specifically 0.07 to 0.27 or 0.08 to 0.27, even more specifically 0.09 to 0.27, 0.09 to 0.26, 0.09 to 0.25, 0.1 to 0.25 or 0.11 to 0.25, most specifically 0.11 to 0.24. ST c / If ST satisfies the above-described range, capacity characteristics and thermal stability can be improved simultaneously. ST c / If ST is less than 0.05, the possibility of ignition may increase, and if it exceeds 0.3, it may be difficult to reduce resistance and the life performance may deteriorate.

[0068] Therefore, in the present invention, the numerator of Equation 1 means the reaction area of ​​the negative active material layer, and the denominator is a value proportional to the ceramic coating layer ratio of the separator, and by mutually adjusting the reaction area and the ceramic coating layer ratio of the separator, X defined by Equation 1 is 7 m 2 16 m inland 2 By satisfying this, the problem of increased total heat and deteriorated thermal safety was solved when a high proportion of natural graphite was included in the negative active material of a large cylindrical lithium secondary battery.

[0069]

[0070] Next, each component of the cylindrical lithium secondary battery according to the present invention will be described in more detail.

[0071] A cylindrical lithium secondary battery according to the present invention includes an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and a battery can including an electrolyte.

[0072]

[0073] (1) Electrode assembly

[0074] An electrode assembly according to the present invention includes an anode, a cathode, and a separator interposed between the anode and the cathode.

[0075] The above electrode assembly can be formed by sequentially stacking an anode, a separator, and a cathode, and the anode and cathode can be mutually insulated by the separator.

[0076] Specifically, the electrode assembly may be formed by sequentially stacking a positive electrode, a separator, and a negative electrode and winding them in one direction.

[0077]

[0078] FIG. 1 illustrates a pre-wound laminated structure of an electrode assembly according to one embodiment of the present invention, FIG. 2 illustrates a cross-sectional structure of an electrode plate (positive electrode or negative electrode) according to one embodiment of the present invention, and FIG. 3 illustrates a structure of an electrode assembly according to one embodiment of the present invention.

[0079] Referring to FIGS. 1 and 2, the electrode assembly (A) of the present invention can be manufactured by winding a laminate formed by sequentially stacking a separator (12), an anode (10), a separator (12), and a cathode (11) at least once in one direction (X).

[0080] At this time, the positive electrode (10) and negative electrode (11) have a structure in which an active material layer (21) is formed on a sheet-shaped current collector (20), and may include a non-conductive portion (22) in which the active material layer (21) is not formed in some area of ​​the current collector (20).

[0081] By using the positive electrode (10) and negative electrode (11) including the non-conductive portion (22) as described above, a battery having a structure in which at least a portion of the non-conductive portion of the positive electrode (10) and negative electrode (11) defines the electrode tab can be implemented without providing a separate electrode tab.

[0082] Specifically, the above-mentioned non-conductive portion (22) can be formed long along the winding direction (X) at one end of the current collector (20), and a current collector plate is coupled to each of the positive non-conductive portion and the negative non-conductive portion, and the current collector plate is connected to an electrode terminal, thereby functioning as an electrode tab.

[0083] For example, a battery in which the positive electrode non-coated portion and the negative electrode non-coated portion function as electrode tabs can be manufactured by the following method. First, a separator, a positive electrode, a separator, and a negative electrode are sequentially laminated so that the positive electrode non-coated portion and the negative electrode non-coated portion are positioned in opposite directions, and then wound in one direction to manufacture a jelly-roll type electrode assembly. Then, the positive and negative electrode non-coated portions are bent toward the winding center (C), and then current collector plates are welded to the positive electrode non-coated portion and the negative electrode non-coated portion, respectively, to join them, and the current collector plates are connected to electrode terminals to manufacture a battery. The current collector plates have a larger cross-sectional area than the strip-type electrode tabs, and since resistance is inversely proportional to the cross-sectional area of ​​a path through which current flows, when a secondary battery is formed with the above structure, the cell resistance can be significantly reduced.

[0084] Meanwhile, the positive and negative electrode portions may be processed into a plurality of independently bendable segments, and at least some of the plurality of segments may be bent toward the winding center (C) of the electrode assembly.

[0085] The above segments can be formed by processing the positive and negative current collectors through a metal foil cutting process such as laser notching, ultrasonic cutting, or punching.

[0086] When the non-conductive portions of the positive and negative electrodes are processed in the form of multiple segments, the stress applied to the non-conductive portion during bending can be reduced, thereby preventing deformation or damage to the non-conductive portion, and the welding characteristics with the current collector plate can be improved.

[0087] The collector plate and the non-coated portion are typically joined by welding. To improve welding properties, strong pressure must be applied to the welding area of ​​the non-coated portion to fold it as flat as possible. However, during this bending process, the non-coated portion may become irregularly distorted and deformed, and the deformed portion may contact the electrode of the opposite polarity, causing an internal short circuit or causing micro-cracks in the non-coated portion. However, if the non-coated portions of the positive and negative electrodes are processed into multiple independently bendable segments, the stress applied to the non-coated portion during bending can be alleviated, thereby minimizing deformation and damage to the non-coated portion.

[0088] In addition, when the non-conductive portion is processed in the form of segments as described above, overlap occurs between the plurality of segments during bending, which increases the welding strength with the current collector plate, and when using the latest technology such as laser welding, it is possible to prevent the problem of the laser penetrating into the electrode assembly and melting the separator or active material. Preferably, at least some of the plurality of folded segments may overlap on the upper and lower sides of the electrode assembly, and the current collector plate may be bonded on the plurality of overlapped segments.

[0089] Meanwhile, the electrode assembly according to the present invention may be formed with a structure in which an insulating layer (24) is additionally formed on the positive electrode (10), as illustrated in FIG. 3. Specifically, the insulating layer (24) may be formed to cover a portion of the positive electrode active material layer and a portion of the non-conductive portion in a direction parallel to the winding direction of the electrode assembly.

[0090] In the case of a battery having a tab-less structure that uses the non-conductive portion (22c) of the positive electrode (10) and the non-conductive portion (22a) of the negative electrode (11) as electrode tabs, an electrode assembly is formed so 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 folded and then combined with a current collecting plate. However, when the positive electrode (10) or negative electrode (11) is folded as described above, the current collector of the positive electrode (10) or negative electrode (11) is positioned close to an electrode of the opposite polarity beyond the separator, which may cause the positive electrode and negative electrode to come into electrical contact, thereby causing an internal short circuit. However, as shown in Fig. 3, when an insulating layer (24) covering a portion of the positive electrode active material layer and the non-conductive portion is formed, the positive electrode (10) and the negative electrode (11) can be prevented from electrically contacting each other by the insulating layer (24), thereby preventing a short circuit from occurring inside the battery.

[0091] Preferably, the insulating layer (24) may be provided on at least one side of the positive electrode (10) current collector, and preferably, may be provided on both sides of the positive electrode (10).

[0092] In addition, the insulating layer (24) may be formed in an area of ​​the positive electrode (10) that is likely to face the active material layer (21a) of the negative electrode (11). For example, on the surface of the non-coated portion (22c) of the positive electrode (10) that faces the negative electrode (11) after being folded, the insulating layer (24) may be formed to extend to the end of the non-coated portion (22c). However, in the case of the surface opposite to the surface that faces the negative electrode (11) after being folded, it is preferable that the insulating layer (24) be formed only on a part of the non-coated portion (22c), for example, up to the bending point of the non-coated portion (22c). This is because, if the insulating layer (24) is formed on the entire area of ​​the non-coated portion on the surface opposite to the surface that faces the negative electrode (11), electrical contact with the current collecting plate is impossible, making it impossible to function as an electrode tab.

[0093] Meanwhile, the insulating layer (24) can be attached to the anode while ensuring insulating performance, and its material or composition 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 include an organic binder and inorganic particles. In this case, the organic binder may be, for example, styrene-butadiene rubber (SBR), and the inorganic particles may be, but are not limited to, alumina oxide.

[0094]

[0095] Hereinafter, each component of the electrode assembly of the present invention will be described in more detail.

[0096]

[0097] anode

[0098] The above positive electrode can be manufactured by a method of applying positive electrode slurry to one or both sides of a sheet-shaped positive electrode collector, removing the solvent of the positive electrode slurry through a drying process, and then rolling. Meanwhile, a positive electrode including a non-coated region can be manufactured by a method of not applying the positive electrode slurry to some areas of the positive electrode collector, for example, one end of the positive electrode collector, during the application of the positive electrode slurry.

[0099] In addition, the positive electrode slurry can be manufactured by dispersing the positive electrode material according to the present invention in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water.

[0100]

[0101] The positive electrode manufactured thus may include a positive electrode current collector; and a positive electrode active material layer; and the positive electrode active material layer may include a positive electrode active material.

[0102] As the positive electrode current collector, various positive electrode current collectors used in the relevant technical field can be used. For example, the positive electrode current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The positive electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine unevenness may be formed on the surface of the positive electrode current collector to increase the adhesion of the positive electrode active material. The positive electrode current collector may be used in various forms, such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0103] The positive electrode active material layer may be positioned on the positive electrode current collector, and specifically, may be positioned on one or both sides of the positive electrode current collector. The positive electrode active material layer may have a single layer or a multilayer structure of two or more layers.

[0104] The above-mentioned positive electrode active material may be a positive electrode active material generally used in the relevant technical field, and the type thereof is not particularly limited. The above-mentioned positive electrode active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium-transition metal composite oxide containing lithium and at least one transition metal composed of nickel, cobalt, manganese, and aluminum, preferably a lithium-transition metal composite oxide containing lithium and a transition metal containing nickel, cobalt, and manganese. More specifically, the lithium-transition metal composite oxide may include a lithium-manganese-based oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt-based oxide (e.g., LiCoO2, etc.), a lithium-nickel-based oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese-based oxide (e.g., LiNi 1-Y Mn Y O2 (here, 0 <Y<1), LiMn 2-z Ni zO4 (where 0<Z<2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2 (here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2 (here, 0 <Y2<1), LiMn 2-z1 Co z1 O4 (wherein, 0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(wherein, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (wherein, 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2) etc.), or lithium-nickel-cobalt-transition metal(M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 ) O2 (Here, M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r3 and s2 are atomic fractions of independent elements, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+r3+s2=1) etc.), and any one or more compounds of these may be included. Among these, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, lithium nickel cobalt manganese oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15)O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc.), or lithium nickel cobalt aluminum oxides (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 )O2, etc.), and considering the remarkable improvement effect according to the control of the type and content ratio of the constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide may be Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 )O2, etc., and any one of these or a mixture of two or more of them may be used.

[0105] Preferably, the positive electrode active material may include a lithium transition metal composite oxide including nickel, cobalt, manganese, and aluminum.

[0106] In addition, the positive electrode active material may be a single particle, a secondary particle, or a mixture thereof, and among these, it is more preferable to use a mixture of single particle and secondary particles. Single particle positive electrode active materials have an advantage in that they have less side reactions with the electrolyte than secondary particle positive electrode active materials, and thus, when used, gas generation can be minimized. In the case of large-capacity batteries, the amount of gas generated during charge and discharge increases rapidly compared to small batteries, which causes a problem in that the lifespan characteristics are reduced. Therefore, it is preferable to improve the lifespan characteristics by applying a single particle positive electrode active material that can minimize gas generation. However, since single particle positive electrode active materials have high resistance, when used alone, there is a problem in that the output and capacity are reduced. Therefore, when considering the lifespan, output, and capacity characteristics, it is preferable to use a mixture of single particle and secondary particles in an appropriate ratio as a positive electrode active material. For example, the above-described positive electrode active material may be used by mixing single-particle particles and secondary particles in a weight ratio of 50:50 to 90:10, preferably 50:50 to 80:20. When the mixing ratio of single-particle particles and secondary particles satisfies the above range, excellent electrochemical properties can be realized even in large-sized batteries having a diameter exceeding 40 mm. Specifically, when the single-particle particle content is less than 50 wt%, the effects of suppressing gas generation and improving lifespan are minimal, and when it exceeds 90 wt%, the resistance may be too high, resulting in a deterioration in output characteristics.

[0107] The above-mentioned positive electrode active material may be included in an amount of 80 wt% to 99 wt%, preferably 92 wt% to 98.5 wt%, based on the total weight of the positive electrode active material layer, taking into account sufficient capacity of the positive electrode active material, etc.

[0108] Meanwhile, the positive electrode active material layer may optionally further include at least one of a positive electrode conductive material and a positive electrode binder.

[0109] The above-described positive electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The positive electrode conductive material may typically be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the positive electrode active material layer.

[0110] The above positive electrode binder serves to improve adhesion between positive electrode particles and adhesion between the positive electrode and the positive electrode current collector, and specific examples thereof include a fluororesin binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber binder including styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; a cellulose binder including carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol binder including polyvinyl alcohol; a polyolefin binder including polyethylene and polypropylene; a polyimide binder; and a polyester binder. And silane binders, etc. can be mentioned, and one of these can be used alone or a mixture of two or more can be used. The positive electrode binder can be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the positive electrode active material layer.

[0111]

[0112] cathode

[0113] The above negative electrode can be manufactured by applying negative electrode slurry to one or both sides of a sheet-shaped negative electrode collector, removing the solvent of the negative electrode slurry through a drying process, and then rolling. Meanwhile, a negative electrode including a non-coated region can be manufactured by not applying the negative electrode slurry to some areas of the negative electrode collector, for example, one end of the negative electrode collector, during the application of the negative electrode slurry.

[0114] The above negative electrode slurry can be prepared by dispersing the negative electrode active material in a solvent such as distilled water, ethanol, methanol, or isopropyl alcohol.

[0115] Alternatively, the negative electrode may be manufactured by casting the negative electrode slurry onto a separate support, then peeling the film from the support and laminating the resulting film onto a negative electrode current collector.

[0116]

[0117] The negative electrode manufactured thus may include a negative electrode current collector; and a negative electrode active material layer; and the negative electrode active material layer may include a negative electrode active material.

[0118] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. The negative electrode current collector can typically have a thickness of 3 to 500 ㎛.

[0119] In addition, the negative electrode current collector, like the positive electrode current collector, can form fine irregularities on the surface of the negative electrode current collector to strengthen the bonding strength of the negative electrode active material. For example, it can be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0120] The negative electrode active material layer may be positioned on the negative electrode current collector, and specifically, may be positioned on one or both sides of the negative electrode current collector. The negative electrode active material layer may have a single layer or a multilayer structure of two or more layers.

[0121] As the above negative active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. Specific examples may include artificial graphite and natural graphite.

[0122] In addition, one or a mixture of two or more of carbonaceous materials such as graphitized carbon fiber, amorphous carbon, etc.; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metallic oxides capable of doping and dedoping lithium such as SiOβ (0 < β < 2), SnO2, vanadium oxide, or lithium vanadium oxide; or composites including the above metallic compounds and carbonaceous materials such as Si-C composites or Sn-C composites may be additionally included.

[0123] The above negative electrode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the negative electrode active material layer.

[0124] Meanwhile, the negative electrode active material layer may optionally further include a negative electrode conductive material and a negative electrode binder in addition to the negative electrode active material.

[0125] The above-described negative electrode conductive material is used to provide conductivity to the electrode, and in the battery to be formed, as long as it does not cause a chemical change and has electronic conductivity, it can be used without any particular limitation. Specific examples include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, and carbon nanotube; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like. One of these may be used alone or a mixture of two or more may be used. The negative electrode conductive material may typically be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the negative electrode active material layer.

[0126] The above negative electrode binder serves to improve adhesion between negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof. The above negative electrode binder may be included in an amount of 1 to 30 wt%, preferably 1 to 20 wt%, and more preferably 1 to 10 wt%, based on the total weight of the negative electrode active material layer.

[0127]

[0128] membrane

[0129] The above separator means that it is interposed between the positive electrode and the negative electrode to separate the negative electrode and the positive electrode and provide a passage for the movement of lithium ions.

[0130] A separator for a secondary battery according to the present invention includes a separator substrate and a ceramic coating layer formed on the separator substrate.

[0131] The above-mentioned separator substrate is not particularly limited as long as it is used in a known separator, and it is preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity. The above-mentioned separator substrate may include a porous substrate. A specific example may be a microporous membrane or nonwoven fabric made of one or more components selected from the group consisting of polyolefin resins, fluorine resins, polyester resins, polyacrylonitrile resins, and cellulose materials. More specifically, the separator substrate may be a microporous membrane or nonwoven fabric made of one or more components selected from the group consisting of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, polyethylene terephthalate, and polybutylene terephthalate.

[0132] The thickness of the above membrane substrate may be 1 ㎛ to 20 ㎛, specifically 3 ㎛ to 18 ㎛, more specifically 5 ㎛ to 17 ㎛, and even more specifically 7 ㎛ to 13 ㎛.

[0133] The above ceramic coating layer may be formed on one or both sides of the separator substrate to secure heat resistance or mechanical strength of the separator. The ceramic coating layer may include inorganic particles and a ceramic coating layer binder.

[0134] When the above-mentioned inorganic particles are included, the thermal stability of the separator can be increased, shrinkage of the separator can be suppressed under a high-temperature environment, and ignition of the secondary battery cell caused thereby can be prevented. The above-mentioned inorganic particles may include at least one inorganic particle selected from the group consisting of cerium oxide (CeO2), aluminum oxide (Al2O3), boehmite, calcium carbonate hydroxide (CaCO3), barium carbonate (BaCO3), magnesium oxide (MgO), magnesium (Mg(OH)2), aluminum hydroxide (Al(OH)3), clay, silica (SiO2), zirconia (ZrO2), titanium dioxide (TiO2), and zinc oxide (ZnO), and specifically, at least one of cerium oxide (CeO2) and aluminum oxide (Al2O3) can be included.

[0135] The above ceramic coating layer binder is included to improve the adhesive properties and heat resistance of the ceramic coating layer, and is not particularly limited as long as it has excellent bonding strength with the electrode laminated on the separator and bonding strength with the ceramic powder, and is not easily dissolved by the electrolyte. Specifically, the ceramic coating layer binder may include at least one polymer selected from the group consisting of polyacrylic acid, polymethacrylic acid, ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, butadiene-acrylic acid copolymer, butadiene-methacrylic acid copolymer, polyvinyl sulfonate, chlorosulfonated polyethylene, perfluorosulfonated ionomer, sulfonated polystyrene, styrene-acrylic acid copolymer, and sulfonated butyl rubber, or a copolymer including two or more of these components.

[0136]

[0137] (2) Electrolyte

[0138] The electrolyte according to the present invention comprises a lithium salt and an organic solvent.

[0139] The lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt may include at least one selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, LiFSI or LiB(C2O4)2, preferably at least one selected from the group consisting of LiPF6, LiClO4, LiBF4 and LiFSI. The concentration of the lithium salt may be 1.0 to 1.5 M, preferably 1.0 to 1.4 M, more preferably 1.1 to 1.4 M. When the concentration of the lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so that it can exhibit excellent electrolyte performance and lithium ions can move effectively.

[0140]

[0141] The organic solvent includes ethylene carbonate. In this case, the lithium salt can be smoothly dissociated, and when the battery is operated, it can be decomposed to stably form an SEI film on the surface of the negative electrode.

[0142] The organic solvent may contain ethylene carbonate in an amount of 5 to 35% by volume, preferably 10 to 80% by volume, and more preferably 15 to 25% by volume. When the above range is satisfied, an SEI film can be formed sufficiently and firmly on the cathode surface.

[0143] The activated lithium secondary battery may include ethylene carbonate and decomposition products of ethylene carbonate.

[0144] At this time, the decomposition product of the ethylene carbonate may refer to a decomposition product of ethylene carbonate remaining in the electrolyte among the products of ethylene carbonate decomposed during the process of activating a lithium secondary battery.

[0145] Specifically, the decomposition product of the ethylene carbonate may be at least one selected from the group consisting of diethyl carbonate (DEC), dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC), ethylmethyl-2,5-dioxahexane dicarboxylate (EMDOHC), and diethyl-2,5-dioxahexane dicarboxylate (DEDOHC).

[0146]

[0147] The organic solvent may further include dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC).

[0148] When the organic solvent further comprises dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC), the organic solvent may comprise dimethyl-2,5-dioxahexane dicarboxylate (DMDOHC) in an amount of 0.5 to 3.0 vol%, preferably 1.0 to 2.0 vol%, and more preferably 1.3 to 1.5 vol%.

[0149]

[0150] Meanwhile, in addition to the electrolyte components, the electrolyte may additionally include additives for the purposes of improving the ion conductivity of the battery, improving the cation transport rate, improving the life characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery.

[0151] For example, the additive may include at least one additive selected from the group consisting of a cyclic carbonate compound, a halogen-substituted carbonate compound, a sultone compound, a sulfate compound, a borate compound, a nitrile compound, a benzene compound, an amine compound, a silane compound, and a lithium salt compound different from the lithium salt included in the electrolyte.

[0152] More specifically, the additives include vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, 1-methyl-1,3-propene sultone, ethylene sulfate (Esa), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), tetraphenylborate, lithium oxalyldifluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, It may be at least one selected from the group consisting of 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 bisoxalatoborate (LiB(C2O4)2) and LiBF4), and preferably vinylene carbonate (VC).

[0153] The electrolyte may contain the additive in an amount of 2 wt% to 5.5 wt%, preferably 2 wt% to 5 wt% or less, and more preferably 2 wt% to 4 wt%. If the content of the additive is less than 2 wt%, the effects of improving the low-temperature output of the battery and the high-temperature storage characteristics and high-temperature life characteristics are minimal, and if the content of the additive exceeds 5.5 wt%, there is a possibility that excessive side reactions occur within the electrolyte during charge and discharge of the battery. In particular, when the additives for forming the SEI film are added in excessive amounts, they may not be sufficiently decomposed at high temperatures and may remain unreacted or precipitated within the electrolyte at room temperature. Accordingly, side reactions that reduce the life or resistance characteristics of the secondary battery may occur.

[0154] When the content of the above additive satisfies the above range, the low-temperature output characteristics, high-temperature storage characteristics, and high-temperature life characteristics of the battery can be improved, side reactions within the electrolyte can be suppressed during battery charging and discharging, and the cation transport rate and ion conductivity within the electrolyte can be further improved, thereby improving the life characteristics and high-temperature life characteristics of the battery.

[0155]

[0156] (3) Battery can

[0157] Meanwhile, the battery can may be a square can, a cylindrical battery can, a pouch-type battery can, etc. used in the relevant technical field, and preferably may be a cylindrical battery can. Specifically, the battery can may be a can-type battery can including a battery can in which the electrode assembly and the electrolyte are stored, and a sealing body that seals the open end of the battery can.

[0158] Preferably, the lithium secondary battery according to the present invention may be a cylindrical lithium secondary battery including a cylindrical battery can, and more preferably, may be a large cylindrical battery having a form factor ratio (R / H, defined as the ratio of the diameter (R) of the lithium secondary battery to the height (H) of the lithium secondary battery) of 0.4 or more. Here, the form factor means a value representing the diameter and height of the cylindrical lithium secondary battery.

[0159] Specifically, the ratio of the diameter (R) of the lithium secondary battery to the height (H) of the lithium secondary battery may be 0.4 or more, preferably 0.4 to 0.8, and more preferably 0.5 to 0.8. When the above range is satisfied, a large-capacity cylindrical lithium secondary battery can be realized.

[0160] The lithium secondary 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 4875 cell (diameter 48 mm, height 75 mm, form factor ratio 0.640), 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 numbers indicate the diameter of the lithium secondary battery, and the next two or three numbers indicate the height of the lithium secondary battery.

[0161]

[0162]

[0163] Next, a lithium secondary battery according to the present invention will be described.

[0164] Examples of lithium secondary batteries according to the present invention are disclosed in FIGS. 4 and 5 . Hereinafter, a lithium secondary battery according to the present invention will be described with reference to FIGS. 4 and 5 . However, FIGS. 4 and 5 merely illustrate one embodiment of the present invention, and the structure of the battery according to the present invention is not limited to the scope disclosed in FIGS. 4 and 5 .

[0165]

[0166] FIG. 4 shows a cross-sectional view of a lithium secondary battery according to one embodiment of the present invention.

[0167] Referring to FIG. 4, a lithium secondary battery (140) according to the present invention may include an electrode assembly (141), a battery can (142) in which the electrode assembly (141) and an electrolyte (not shown) are stored, and a sealing body (143) that seals an open end of the battery can (142).

[0168] At this time, the electrode assembly is formed by sequentially stacking a positive electrode, a separator, and a negative electrode, and winding them in one direction. In addition, the positive electrode and the negative electrode of the electrode assembly each include a non-coated portion on which an active material layer is not formed, and can be stacked and wound so that the positive electrode non-coated portion and the negative electrode non-coated portion are positioned at the top and bottom of the electrode assembly, respectively. Since the electrode assembly has been described above, only the remaining components excluding the electrode assembly will be described below.

[0169] Meanwhile, the battery can (142) is a can-shaped container with an open end formed at the top and is made of a conductive metal material such as aluminum or steel. The battery can accommodates an electrode assembly (141) in an inner space through the open end at the top, and also accommodates an electrolyte (not shown).

[0170] Meanwhile, it is preferable that the lithium secondary battery (140) of the present invention does not include a current interruption device (CID).

[0171] Meanwhile, as illustrated in FIG. 4, the battery can (142) is electrically connected to the negative electrode's non-conductive portion (146b) and can function as a negative terminal that contacts an external power source and transmits current applied from the external power source to the negative electrode.

[0172] If necessary, a beading portion (147) and a crimping portion (148) may be provided on the upper end of the battery can (142). The beading portion (147) may be formed by pressing the outer circumference of the battery can (142) to a distance of D1. The beading portion (147) may prevent the electrode assembly (141) accommodated inside the battery can (142) from coming out through the upper opening of the battery can (142), and may function as a support portion on which the sealing body (143) is secured.

[0173] The above crimping portion (148) can be formed on the upper portion of the beading portion (147), and has an extended and bent shape to surround the outer surface of the cap plate (143a) placed on the beading portion (147) and a portion of the upper surface of the cap plate (143a).

[0174]

[0175] Next, the sealing member (143) is for sealing the open end of the battery can (142), and includes a cap plate (143a), a first gasket (143b) that provides airtightness between the cap plate (143a) and the battery can (142) and has insulation, and may further include a connecting plate (143c) that is electrically and mechanically coupled to the cap plate (143a), if necessary. The cap plate (143a) is pressed onto a beading portion (147) formed on the battery can (142), and may be fixed by a crimping portion (148).

[0176] The cap plate (143a) is a component made of a conductive metal material and covers the upper opening of the battery can (142). The cap plate (143a) is electrically connected to the positive electrode of the electrode assembly (141) and is electrically insulated from the battery can (142) via a first gasket (143b). Therefore, the cap plate (143a) can function as a positive electrode terminal of a lithium secondary battery. The cap plate (143a) can have a protrusion (143d) formed to protrude upward from its center portion C, and the protrusion (143d) can come into contact with an external power source to allow current to be applied from the external power source.

[0177] A first gasket (143b) may be interposed between the cap plate (143a) and the crimping portion (148) to ensure the airtightness of the battery can (142) and to provide electrical insulation between the battery can (142) and the cap plate (143a).

[0178] Meanwhile, the lithium secondary battery (140) according to the present invention may further include a current collecting plate (144, 145), if necessary. The current collecting plate is coupled to the positive electrode non-conducting portion (146a) and the negative electrode non-conducting portion (146b), and is connected to the electrode terminals (i.e., the positive electrode terminal and the negative electrode terminal).

[0179] Specifically, a lithium secondary battery (140) according to the present invention may include a first current collecting plate (144) coupled to the upper portion of an electrode assembly (141) and a second current collecting plate (145) coupled to the lower portion of the electrode assembly (141).

[0180] It may further include a first collector plate (144) and / or a second collector plate (145).

[0181] The first current collecting plate (144) is coupled to the upper portion of the electrode assembly (141). The first current collecting plate (144) is made of a conductive metal material such as aluminum, copper, nickel, etc., and is electrically connected to the non-conductive portion (146a) of the positive electrode. A lead (149) may be coupled to the first current collecting plate (144). The lead (149) may extend upward from the electrode assembly (141) and be coupled to the connection plate (143c) or may be directly coupled to the lower surface of the cap plate (143a). The coupling of the lead (149) to other components may be achieved through welding. Preferably, the first current collecting plate (144) may be formed integrally with the lead (149). In this case, the lead (149) may have a plate shape extending outward from the center of the first current collecting plate (144).

[0182] Meanwhile, the first collector plate (144) is coupled to the end of the non-conductive portion (146a) of the anode, and the coupling can be achieved by, for example, laser welding, resistance welding, ultrasonic welding, soldering, or the like.

[0183] The second current collecting plate (145) is coupled to the lower portion of the electrode assembly (141). The second current collecting plate (145) is made of a conductive metal material such as aluminum, copper, nickel, etc., and is electrically connected to the non-conductive portion (146b) of the negative electrode. One side of the second current collecting plate (145) can be coupled to the non-conductive portion (146b) of the negative electrode, and the opposite side can be coupled to the inner bottom surface of the battery can (142). At this time, the coupling can be performed by a method such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0184] Meanwhile, the lithium secondary battery (140) according to the present invention may further include an insulator (146), if necessary. The insulator (146) may be arranged to cover the upper surface of the first current collecting plate (144). By covering the first current collecting plate (144) with the insulator (146), direct contact between the first current collecting plate (144) and the inner surface of the battery can (142) can be prevented.

[0185] The insulator (146) has a lead hole (151) through which a lead (149) extending upward from the first collector plate (144) can be drawn out. The lead (149) is drawn upward through the lead hole (151) and is coupled to the lower surface of the connecting plate (143c) or the lower surface of the cap plate (143a).

[0186] The insulator (146) may be made of a polymer resin material having insulating properties, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0187] Meanwhile, the lithium secondary battery (140) according to the present invention may further include a venting portion (152) formed on the lower surface of the battery can (142), if necessary. The venting portion (152) corresponds to a region of the lower surface of the battery can (142) that has a thinner thickness than the surrounding region. Since the venting portion (152) is thin, it is structurally weaker than the surrounding region. Therefore, when the pressure inside the lithium secondary battery (140) increases above a certain level, the venting portion (152) ruptures, allowing the gas inside the battery can (152) to be discharged to the outside, thereby preventing the battery from exploding.

[0188]

[0189] FIG. 5 shows a cross-sectional view of a lithium secondary battery according to another embodiment of the present invention.

[0190] Referring to FIG. 5, a lithium secondary battery (170) according to another embodiment of the present invention has a different structure of a battery can and a sealing body compared to the lithium secondary battery (140) illustrated in FIG. 4, and the configuration of the electrode assembly and electrolyte is substantially the same.

[0191] Specifically, a lithium secondary battery (170) according to another embodiment of the present invention includes a battery can (171) having a rivet terminal (172) installed therethrough. The rivet terminal (172) is installed in a partially closed closed surface (upper surface in the drawing) of one end of the battery can (171). The rivet terminal (172) is riveted to a through hole (first opening of the first end) of the battery can (171) while an insulating second gasket (173) is interposed therebetween. The rivet terminal (172) is exposed to the outside in a direction opposite to the direction of gravity.

[0192] 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 can (171). The terminal exposure portion (172a) may be located approximately at the center of the partially closed surface of the battery can (171). The maximum diameter of the terminal exposure portion (172a) may be formed to be larger than the maximum diameter of the through hole formed in the battery can (171). The terminal insertion portion (172b) may penetrate approximately at the center of the closed surface of the battery can (171) and be electrically connected to the non-coated portion (146a) of the positive electrode. The terminal insertion portion (172b) may be riveted onto the inner surface of the battery can (171). That is, the end of the terminal insertion portion (172b) may have a shape that is bent toward the inner surface of the battery can (171). The maximum diameter of the end of the terminal insertion portion (172b) may be larger than the maximum diameter of the through hole of the battery can (171).

[0193] The lower surface of the terminal insertion portion (172b) can be welded to the first current collecting plate (144) connected to the non-polarized portion (146a) of the positive electrode. An insulating cap (174) made of an insulating material can be interposed between the first current collecting plate (144) and the inner surface of the battery can (171). The insulating cap (174) covers the upper portion of the first current collecting plate (144) and the upper edge portion of the electrode assembly (141). This can prevent the outer non-polarized portion (B3) of the electrode assembly (141) from coming into contact with the inner surface of the battery can (171) having a different polarity, thereby causing a short circuit. The terminal insertion portion (172b) of the rivet terminal (172) can be welded to the first current collecting plate (144) by penetrating the insulating cap (174).

[0194] The second gasket (173) is interposed between the battery can (171) and the rivet terminal (172) to prevent the battery can (171) and the rivet terminal (172) having opposite polarities from making electrical contact. This allows the upper surface of the battery can (171) having a roughly flat shape to function as the positive terminal of the lithium secondary battery (170).

[0195] The second gasket (173) includes a gasket exposure portion (173a) and a gasket insertion portion (173b). The gasket exposure portion (173a) is interposed between the terminal exposure portion (172a) of the rivet terminal (172) and the battery can (171). The gasket insertion portion (173b) is interposed between the terminal insertion portion (172b) of the rivet terminal (172) and the battery can (171). The gasket insertion portion (173b) can be deformed together with the terminal insertion portion (172b) when riveting so as to be in close contact with the inner surface of the battery can (171). The second gasket (173) can be made of, for example, an insulating polymer resin.

[0196] The gasket exposure portion (173a) of the second gasket (173) may have an extended shape so as to cover the outer surface of the terminal exposure portion (172a) of the rivet terminal (172). When the second gasket (173) covers the outer surface of the rivet terminal (172), a short circuit can be prevented from occurring during the process of connecting an electrical connection component such as a bus bar to the upper surface of the battery can (171) and / or the rivet terminal (172). Although not shown in the drawing, the gasket exposure portion (173a) may have an extended shape so as to cover not only the outer surface of the terminal exposure portion (172a) but also a portion of the upper surface.

[0197] In the case where the second gasket (173) is made of a polymer resin, the second gasket (173) can be joined to the battery can (171) and the rivet terminal (172) by heat fusion. In this case, the sealing properties at the joining interface between the second gasket (173) and the rivet terminal (172) and at the joining interface between the second gasket (173) and the battery can (171) can be strengthened. Meanwhile, in the case where the gasket exposure portion (173a) of the second gasket (173) has a form that extends to the upper surface of the terminal exposure portion (172a), the rivet terminal (172) can be integrally joined to the second gasket (173) by insert injection.

[0198] The remaining area (175) of the upper surface of the battery can (171), excluding the area occupied by the rivet terminal (172) and the second gasket (173), corresponds to a negative terminal having a polarity opposite to that of the rivet terminal (172).

[0199] The second collector plate (176) is coupled to the lower portion of the electrode assembly (141). The second collector plate (176) is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the non-conductive portion (146b) of the negative electrode.

[0200] Preferably, the second current collecting plate (176) is electrically connected to the battery can (171). To this end, at least a portion of the edge portion of the second current collecting plate (176) may be interposed and fixed between the inner surface of the battery can (171) and the first gasket (178b). In one example, at least a portion of the edge portion of the second current collecting plate (176) may be fixed to the bead portion (180) formed at the bottom of the battery can (171) by welding while being supported by the lower surface of the bead portion (180). In a variation, at least a portion of the edge portion of the second current collecting plate (176) may be directly welded to the inner wall surface of the battery can (171).

[0201] The second collector plate (176) may have a plurality of protrusions (not shown) radially formed on a surface facing the non-conductive portion (146b). When the protrusions are formed, the second collector plate (176) can be pressed to press the protrusions into the non-conductive portion (146b).

[0202] Preferably, the ends of the second collector plate (176) and the non-conductive portion (146b) can be joined by welding, for example, laser welding.

[0203] A sealing member (178) for sealing the lower open end of the battery can (171) includes a cap plate (178a) and a first gasket (178b). The first gasket (178b) electrically separates the cap plate (178a) and the battery can (171). A crimping member (181) secures the edge of the cap plate (178a) and the first gasket (178b) together. The cap plate (178a) is provided with a vent member (179). The configuration of the vent member (179) is substantially the same as that of the above-described embodiment.

[0204] Preferably, the cap plate (178a) is made of a conductive metal material. However, since a first gasket (178b) is interposed between the cap plate (178a) and the battery can (171), the cap plate (178a) does not have electrical polarity. The sealing body (178) seals the open end of the lower portion of the battery can (171) and discharges gas when the internal pressure of the battery cell (170) increases above a critical value.

[0205] Preferably, the rivet terminal (172) electrically connected to the non-conductive portion (146a) of the positive electrode is used as the positive terminal. In addition, the portion (175) of the upper surface of the battery can (171) electrically connected to the non-conductive portion (146b) of the negative electrode through the second current collecting plate (176), excluding the rivet terminal (172), is used as the negative terminal. In this way, when the two electrode terminals are positioned on the upper portion of the lithium secondary battery, it is possible to place electrical connection components such as bus bars on only one side of the lithium secondary battery (170). This can lead to simplification of the battery pack structure and improvement of energy density. In addition, since the portion (175) used as the negative terminal has a substantially flat shape, a sufficient bonding area can be secured when bonding electrical connection components such as bus bars. Accordingly, the lithium secondary battery (170) can lower the resistance at the bonding portion of the electrical connection components to a desirable level.

[0206] When a lithium secondary battery is formed with a tab-less structure as described above, the current concentration is less than that of a conventional battery having electrode tabs, so heat generation inside the battery can be effectively reduced, and thus the thermal safety of the battery can be improved.

[0207]

[0208]

[0209] Next, a battery pack including a lithium secondary battery according to the present invention as a unit cell is described.

[0210] The lithium secondary battery of the present invention as described above can be used as a unit cell in manufacturing a battery pack. FIG. 6 schematically illustrates the configuration of a battery pack according to an embodiment of the present invention. Referring to FIG. 6, a battery pack (3) according to an embodiment of the present invention includes an assembly of lithium secondary batteries (1) electrically connected thereto and a pack housing (2) accommodating the assembly. The lithium secondary battery (1) is a lithium secondary battery according to the embodiment described above. In the drawing, for the convenience of illustration, components such as a bus bar, a cooling unit, and an external terminal for electrical connection of the lithium secondary batteries (1) are omitted.

[0211] The above battery pack (3) can be mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle includes a four-wheel vehicle or a two-wheel vehicle.

[0212]

[0213] The present invention will be described in more detail below through specific examples.

[0214]

[0215] Manufacturing examples. Manufacturing of Examples 1 to 7 and Comparative Examples 1 to 5.

[0216] Example 1.

[0217] <Manufacturing of negative active materials>

[0218] Artificial graphite (BET: 0.7 m) as the first negative electrode active material 2 / g) as the second negative electrode active material, natural graphite (BET: 2.1 m 2 / g) was used, and artificial graphite and natural graphite were mixed at a weight ratio of 0.5:0.5 to manufacture a negative electrode active material.

[0219]

[0220] <Manufacturing of the cathode>

[0221] The negative electrode active material manufactured above, SW-CNT as a conductive agent, and CMC as a binder were mixed in a weight ratio of 98.95:0.05:1, and water was added to prepare a negative electrode slurry. Then, the negative electrode slurry was applied on a copper current collector, dried, and rolled so that the porosity became 0.259, thereby preparing a negative electrode including a negative electrode active material layer. At this time, the loading amount of the negative electrode active material layer formed on the negative electrode collector was 0.02936 g / cm 2 (LA) was manufactured, and the area of ​​the manufactured negative electrode active material layer was 5724.60 cm 2 (AA) is.

[0222]

[0223] <Manufacturing of membranes>

[0224] After preparing a composition for forming a ceramic coating layer by adding Al2O3 as an inorganic particle and PDVF as a binder to a solvent, the composition for forming a ceramic coating layer was applied to both sides of a polyethylene porous substrate and dried to obtain a thickness of 3 ㎛ (ST C ) was formed, a separator with a total thickness of 13 ㎛ (ST) was manufactured. At this time, the ceramic coating layer ratio of the manufactured separator was (ST c / ST) is 0.2308.

[0225]

[0226] <Manufacturing of Cylindrical Secondary Batteries>

[0227] Lithium nickel cobalt manganese oxide as a cathode active material, Bundle-CNT as a conductive agent, and PVDF as a binder were mixed in a weight ratio of 98:0.6:1.4, and water was added to prepare a cathode slurry, which was then applied onto an aluminum current collector, dried, and rolled to prepare a cathode.

[0228] A separator was interposed between the positive and negative electrodes manufactured as described above, and the electrodes were laminated in the order of separator / positive electrode / separator / negative electrode, and then wound to manufacture a jelly-roll type electrode assembly with a radius of 3 mm at the center of the winding.

[0229] The electrode assembly was inserted into a cylindrical battery can having a height of 80 mm and a diameter of 46 mm, and then an electrolyte was injected to manufacture a 4680 cell.

[0230]

[0231] Example 2.

[0232] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the ceramic coating layer was formed with a thickness of 2 μm in the separator of Example 1. At this time, the ratio of the ceramic coating layer of the manufactured separator was (ST c / ST) is 0.1538.

[0233]

[0234] Example 3.

[0235] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the ceramic coating layer was formed with a thickness of 1.5 μm in the separator of Example 1. At this time, the ratio of the ceramic coating layer of the manufactured separator was (ST c / ST) is 0.1154.

[0236]

[0237] Example 4.

[0238] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the artificial graphite and natural graphite of Example 1 were mixed in a weight ratio of 0.4:0.6.

[0239]

[0240] Example 5.

[0241] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 2, except that the artificial graphite and natural graphite of Example 2 were mixed in a weight ratio of 0.4:0.6.

[0242]

[0243] Example 6.

[0244] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the artificial graphite and natural graphite of Example 1 were mixed in a weight ratio of 0.3:0.7.

[0245]

[0246] Example 7.

[0247] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the artificial graphite and natural graphite of Example 2 were mixed in a weight ratio of 0.3:0.7.

[0248]

[0249] Comparative Example 1.

[0250] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the ceramic coating layer was formed with a thickness of 1 μm in the separator of Example 1. At this time, the ratio of the ceramic coating layer of the manufactured separator was (ST c / ST) is 0.0769.

[0251]

[0252] Comparative Example 2.

[0253] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the ceramic coating layer was formed with a thickness of 1.5 μm in the separator of Example 4. At this time, the ratio of the ceramic coating layer of the manufactured separator was (ST c / ST) is 0.1154.

[0254]

[0255] Comparative Example 3.

[0256] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the ceramic coating layer was formed with a thickness of 1 μm in the separator of Example 4. At this time, the ratio of the ceramic coating layer of the manufactured separator was (ST c / ST) is 0.0769.

[0257]

[0258] Comparative Example 4.

[0259] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the ceramic coating layer was formed with a thickness of 1.5 μm in the separator of Example 6. At this time, the ratio of the ceramic coating layer of the manufactured separator was (ST c / ST) is 0.1154.

[0260]

[0261] Comparative Example 5.

[0262] A cylindrical lithium secondary battery was manufactured in the same manner as in Example 1, except that the ceramic coating layer was formed with a thickness of 1 μm in the separator of Example 6. At this time, the ratio of the ceramic coating layer of the manufactured separator was (ST c / ST) is 0.0769.

[0263]

[0264] In the cylindrical lithium secondary batteries manufactured in the above examples and comparative examples, the ratio of the thickness of the ceramic coating layer to the total thickness including the ceramic coating layer of the separator in the battery (ST c The values ​​calculated for / ST) are shown in Table 1 below.

[0265]

[0266] STc / ST Example 10.2308 Example 20.1538 Example 30.1154 Example 40.2308 Example 50.1538 Example 60.2308 Example 70.1538 Comparative Example 10.0769 Comparative Example 20.1154 Comparative Example 30.0769 Comparative Example 40.1154 Comparative Example 50.0769

[0267]

[0268] Experimental Example 1. Measurement of the reaction area of ​​artificial graphite and natural graphite.

[0269] The BET surface area of ​​artificial graphite and natural graphite used as negative electrode active materials in the lithium secondary batteries manufactured in the above examples and comparative examples was measured, and through this, each reaction area (m) of the graphite negative electrode active material was determined. 2) were calculated and shown in Table 2 below. At this time, the BET specific surface area was measured by nitrogen adsorption using a BET specific surface area analysis device (equipment name: BELSORP-mino II) from BEL Japan, and the reaction area of ​​each graphite negative electrode active material was calculated by multiplying the area (AA) of the negative electrode active material layer and the loading amount (LA) of the negative electrode active material layer by the weight ratio of each graphite to the total graphite weight included in the negative electrode active material layer and the BET specific surface area value of each graphite.

[0270]

[0271] Reaction area (m) of each graphite negative electrode active material 2 ) = Area of ​​the negative electrode active material layer (AA, unit: cm 2 ) × negative electrode active material layer loading amount (LA, unit: g / cm 2 ) × Weight ratio of each graphite to the total weight of graphite included in the negative electrode active material layer × BET specific surface area (m) of each graphite included in the negative electrode active material layer 2 / g)

[0272]

[0273] Cathode active material BET (g / m) 2 )Cathode active material weight ratioCathode active material reaction area (m 2 ) Artificial graphite (BA) AG ) Natural graphite (BA) NG ) Artificial graphite (RA) AG ) Natural graphite (RA NG ) Artificial graphite (AA×LA×BA AG × RA AG ) Natural graphite (AA×LA×BA NG ×RA NG) Example 10.72.10.50.558.826176.478 Example 20.50.558.826176.478 Example 30.50.558.826176.478 Example 40.40.647.061211.774 Example 50.40.647.061211.774 Example 60.30.735.296247.069 Example 70.30.735.296247.069 Comparative Example 10.50.558.826176.478 Comparative Example 20.40.647.061211.774 Comparative Example 30.40.647.061211.774Comparative example 40.30.735.296247.069Comparative example 50.30.735.296247.069

[0274] In addition, the sum of the reaction areas of the measured artificial graphite negative electrode active material and natural graphite negative electrode active material (AA × LA × {(BA AG ×RA AG ) + (BA NG ×RA NG )}) is shown in Table 3 below.

[0275] AA×LA×{(BA AG ×RA AG ) + (BA NG ×RA NG )}(m 2 ) Example 1235.3040 Example 2235.3040 Example 3235.3040 Example 4258.8344 Example 5258.8344 Example 6282.3648 Example 7282.3648 Comparative Example 1235.3040 Comparative Example 2258.8344 Comparative Example 3258.8344 Comparative Example 4282.3648 Comparative Example 5282.3648

[0276] Experimental Example 2. Calculation of the reaction area of ​​the negative electrode active material layer

[0277] In order to derive a reaction area where a chemical reaction can actually occur, reflecting the ratio of pores in the negative electrode active material layer manufactured in Examples 1 to 7 and Comparative Examples 1 to 5, the ratio of pores in the negative electrode active material layer was calculated by excluding the ratio of pores (empty space) from the porosity (P), which is the ratio of pores in the negative electrode active material layer, and calculating (1-P).

[0278] The porosity of the negative electrode active material layer manufactured in the above examples and comparative examples is 0.259, so the ratio of the cross-sectional area where the actual chemical reaction occurs in the negative electrode active material layer is 0.741, and the reaction area of ​​the negative electrode active material layer was calculated by multiplying the reaction area of ​​the graphite negative electrode active material shown in Table 3 by (1-P), and the results are shown in Table 4 below.

[0279]

[0280] Porosity P1-P Reaction area of ​​the negative electrode active material layer (m 2 )Example 10.2590.741174.3603Example 2174.3603Example 3174.3603Example 4191.7963Example 5191.7963Example 6209.2323Example 7209.2323Comparative Example 1174.3603Comparative Example 2191.7963Comparative Example 3191.7963Comparative Example 4209.2323Comparative Example 5209.2323

[0281] Referring to Tables 2 and 4, RA is the weight ratio of natural graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer. NG The reaction area of ​​the negative electrode active material layer of Examples 6 and 7 and Comparative Examples 4 to 5, which had the largest value of 0.7, was 209.2323 m 2 The largest, RA NG The reaction area of ​​the negative active material layer of Examples 1 to 3 and Comparative Example 1, which had the smallest value of 0.5, was 174.3603 m 2It can be confirmed that the smallest one is , and through this, it can be confirmed that as the ratio of natural graphite, which has a larger BET surface area than artificial graphite, increases, the reaction area of ​​the negative electrode active material layer increases.

[0282] Experimental Example 3. Calculating X Value

[0283] For each of the 4680 cells manufactured in Examples 1 to 7 and Comparative Examples 1 to 5, the X value defined by Equation 1 below was calculated and shown in Table 5 below.

[0284] [Formula 1]

[0285]

[0286] In the above equation 1, AA (unit: cm 2 ) is the area of ​​the negative electrode active material layer, and LA (unit: g / cm 2 ) is the loading amount of the negative electrode active material layer formed on the negative electrode current collector, P (unitless) is the porosity of the negative electrode active material layer, and RA NG is the weight ratio of natural graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer, and BA NG (Unit: m 2 / g) is the BET surface area of ​​natural graphite, and RA AG is the weight ratio of artificial graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer, and BA AG (Unit: m 2 / g) is the BET surface area of ​​artificial graphite, and ST c (Unit: ㎛) is the thickness of the ceramic coating layer within the separator, and ST (Unit: ㎛) is the thickness of the separator.

[0287]

[0288] X Example 17.556 Example 211.333 Example 315.111 Example 48.311 Example 512.467 Example 69.067 Example 713.600 Comparative Example 122.667 Comparative Example 216.622 Comparative Example 324.934 Comparative Example 418.133 Comparative Example 527.200

[0289]

[0290] Referring to Table 5, the X value of Examples 1 to 7 is 7 m 2 16 m inland 2 However, it can be confirmed that the X values ​​of Comparative Examples 1 to 5 fall outside the numerical range.

[0291] Experimental Example 4. Evaluation of High-Temperature Storage Characteristics

[0292] In order to compare the high-temperature storage characteristics of the cylindrical secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 5, a hot box experiment was conducted.

[0293] Specifically, the cylindrical secondary batteries manufactured in Examples 1 to 7 and Comparative Examples 1 to 5 were each placed in a hot box capable of controlling the internal temperature, and the temperature was increased from room temperature to 130°C at a rate of 5°C / min, and then ignition was checked. The results are shown in Table 6 below.

[0294]

[0295] HOTBOX test Ignition Exemplary Example 1 x Exemplary Example 2 x Exemplary Example 3 x Exemplary Example 4 x Exemplary Example 5 x Exemplary Example 6 x Exemplary Example 7 x Comparative Example 1 ○ Comparative Example 2 ○ Comparative Example 3 ○ Comparative Example 4 ○ Comparative Example 5 ○

[0296] Referring to Table 6 above, the ratio of the ceramic coating layer within the separator (ST c / ST) is within the range of 0.13 to 0.25, and the X value is 7 m 2 16 m inland 2 It can be confirmed that the lithium secondary batteries manufactured in Examples 1 to 7 have excellent thermal performance even when the ratio of natural graphite in the negative electrode active material is 0.5 or more.

[0297]

[0298] [Explanation of symbols]

[0299] 1: Lithium secondary battery

[0300] 2: Pack housing

[0301] 3: Battery pack

[0302] 10: Bipolar

[0303] 11: Cathode

[0304] 12: Membrane

[0305] 20: Whole house

[0306] 21: Active material layer

[0307] 21a: Negative active material layer

[0308] 22: Ministry of Immigration

[0309] 22a: Cathode ignorance

[0310] 22c: The polar ignorance

[0311] 24: Insulating layer

[0312] C: Center of winding

[0313] 140: Lithium secondary battery

[0314] 141: Electrode assembly

[0315] 142: Battery can

[0316] 143: Seal

[0317] 143a: Cap plate

[0318] 143b: First gasket

[0319] 143c: Connecting plate

[0320] 143d: protrusion

[0321] 144: First collection plate

[0322] 145: Second collection plate

[0323] 146: Insulator

[0324] 146a: Bipolar ignorance

[0325] 146b: Negative electrode

[0326] 147: Bidding Department

[0327] 148: Crimping section

[0328] 149: Lead

[0329] 151: Lead Hall

[0330] 152: Benting Department

[0331] 170: Lithium secondary battery

[0332] 171: Battery can

[0333] 172: Rivet terminal

[0334] 172a: Terminal exposed part

[0335] 172b: Terminal insertion part

[0336] 173: Second gasket

[0337] 173a: Gasket exposure

[0338] 173b: Gasket insert

[0339] 174: Insulating cap

[0340] 176: Second collector plate

[0341] 178: Seal

[0342] 178a: Cap plate

[0343] 178b: First gasket

[0344] 179: Vent

[0345] 180: Bidding Department

[0346] 181: Crimping section

Claims

1. A cylindrical lithium secondary battery comprising: an electrode assembly in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are wound in one direction; a battery can in which the electrode assembly and an electrolyte are stored; The above negative electrode includes a negative electrode active material layer formed on a negative electrode current collector, The above negative electrode active material layer includes natural graphite and artificial graphite as negative electrode active materials, The above separator comprises a substrate and a ceramic coating layer that is entirely coated on one or both sides of the separator substrate, The value of X defined by the following equation 1 is 7 m 2 16 m inland 2 A cylindrical lithium secondary battery. [Formula 1] In the above equation 1, AA (unit: cm) 2 ) is the area of ​​the negative electrode active material layer, LA (unit: g / cm) 2 ) is the loading amount of the negative electrode active material layer formed on the negative electrode current collector, P (unitless) is the porosity of the negative electrode active material layer, RA NG is the weight ratio of natural graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer, BA NG (Unit: m 2 / g) is the BET surface area of ​​natural graphite, RA AG is the weight ratio of artificial graphite to the total weight of natural graphite and artificial graphite included in the negative electrode active material layer, BA AG (Unit: m 2 / g) is the BET surface area of ​​artificial graphite, ST c (Unit: ㎛) is the thickness of the ceramic coating layer within the separator, ST (unit: ㎛) represents the thickness of the membrane.

2. In paragraph 1, The above AA is 5500 cm 2 6000 cm inland 2 A cylindrical lithium secondary battery.

3. In paragraph 1, The above RA NG A cylindrical lithium secondary battery having a capacity of 0.5 or more.

4. In paragraph 1, The above BA NG is 1 m 2 / g to 3 m 2 / g, cylindrical lithium secondary battery.

5. In paragraph 1, The above BA AG is 0.5 m 2 / g to 0.9 m 2 / g, cylindrical lithium secondary battery.

6. In paragraph 1, The above negative electrode has a total reaction area of ​​artificial graphite and natural graphite in the negative electrode active material layer of 200 m 2 Ideal, cylindrical lithium secondary battery.

7. In paragraph 1, The above LA is 0.025 g / cm 2 0.035 g / cm 2 A cylindrical lithium secondary battery.

8. In paragraph 1, A cylindrical lithium secondary battery, wherein the above P is 0.35 or less.

9. In paragraph 1, The above ST is a cylindrical lithium secondary battery having a diameter of 12 μm to 15 μm.

10. In paragraph 1, The above ST c A cylindrical lithium secondary battery having a size of 5 μm or less.

11. In paragraph 1, The above ST c / ST is 0.05 to 0.3, cylindrical lithium secondary battery.

12. In paragraph 1, The above lithium secondary battery is a cylindrical lithium secondary battery, wherein the ratio (R / H) of the diameter (R) of the lithium secondary battery to the height (H) of the lithium secondary battery is 0.4 or more.

13. In paragraph 1, A cylindrical lithium secondary battery in which the negative active material is made of natural graphite or artificial graphite.

14. A battery pack including the cylindrical lithium secondary battery of claim 1 as a unit cell.

Images