Positive electrode and secondary battery including same

Abstract

The present invention relates to a positive electrode and a method for manufacturing same, in which the positive electrode comprises a positive electrode mixture layer including a high-nickel positive electrode active material with a nickel content of 80 mol% or more of the total metals excluding lithium, and has an A of 1 or less as defined by expression (1). Expression (1): A = 0.00076 ln (-2.435 x (a / b) +268.4) x w. In expression (1), a is the length of the positive electrode mixture layer measured in mm units, b is the width of the positive electrode mixture layer measured in mm units, and w is the moisture content value of the positive electrode measured in ppm units.

Description

Anode and secondary battery containing the same

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0190457, filed December 22, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a positive electrode and a secondary battery including the same, and more particularly, to a positive electrode designed so that the dimensions of the positive electrode composite layer and the moisture content within the positive electrode satisfy a specific relationship, and to a lithium secondary battery including the same.

[0003] With the recent technological advancements in electric vehicles, the demand for high-capacity batteries is increasing, and the application of cathode active materials with high nickel content and / or high loading is increasing.

[0004] Cathode materials with high nickel content are vulnerable to moisture intrusion. If moisture infiltrates the cathode, lithium byproducts on the cathode active material surface react with the moisture to form impurities, leading to cathode degradation. Cathode degradation not only degrades battery performance but also increases the defect rate during manufacturing. This problem is particularly acute in large-capacity batteries, such as the 4680 cell, due to their high cathode loading.

[0005] Therefore, there is a need for the development of a cathode that can suppress cathode degradation even when applying a high-nickel cathode active material or when applied to a large-sized battery such as a 4680 cell.

[0006] The present invention is intended to solve the above problems, and to provide an anode having excellent electrochemical performance, particularly energy density, and a method for manufacturing the same, in which the dimensions of the anode composite layer and the moisture content within the anode satisfy specific conditions.

[0007] In addition, the present invention seeks to provide a lithium secondary battery having a high capacity and low energy loss, including the above and the positive electrode.

[0008] According to one embodiment, the present invention provides a positive electrode including a positive electrode composite layer including a high-nickel positive electrode active material having a nickel content of 80 mol% or more among all metals excluding lithium, and wherein A defined by the following formula (1) is 1 or less, preferably 0.7 or less, more preferably 0.5 or less.

[0009] Equation (1): A = 0.00076ln(-2.435×(a / b)+268.4)×w

[0010] In the above equation (1), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

[0011] At this time, the high nickel positive electrode active material may include a lithium transition metal oxide represented by the following [chemical formula 1].

[0012] [Chemical Formula 1]

[0013] Li a Ni x Co y M 1 z M 2 w O2

[0014] In the above chemical formula 1,

[0015] M 1 is at least one of Mn and Al, and M 2 It contains at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 0.9≤a≤1.1, 0.8≤x<1, 0 <y<0.2, 0<z<0.2, 0≤w≤0.1임.

[0016] Meanwhile, a / b, which is the ratio of the length a of the positive electrode composite layer to the width b of the positive electrode composite layer, may be 40 to 70, preferably 45 to 65, and more preferably 50 to 65.

[0017] In addition, the length a of the positive electrode composite layer may be 3000 mm to 5000 mm, preferably 3500 mm to 4500 mm, more preferably 3700 mm to 4200 mm, and the width b of the positive electrode composite layer may be 50 mm to 90 mm, preferably 55 mm to 85 mm, more preferably 65 mm to 65 mm.

[0018] Meanwhile, the above anode may satisfy the following equation (2).

[0019] Equation (2): w ≤ 4(a / b) + 54

[0020] In the above equation (2), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

[0021]

[0022] According to another embodiment, the present invention provides a method for manufacturing a positive electrode, comprising the steps of: preparing a positive electrode including a positive electrode composite layer including a high-nickel positive electrode active material having a nickel content of 80 mol% or more among all metals excluding lithium; and storing the positive electrode in a controlled environment such that A, defined by the following formula (1), is 1 or less, preferably 0.7 or less, more preferably 0.5 or less.

[0023] Equation (1): A = 0.00076ln(-2.435×(a / b)+268.4)×w

[0024] In the above equation (1), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

[0025] Specifically, the step of storing the above positive electrode may be storing it in an environment with a relative humidity of 15% or less for 17 weeks or less.

[0026] According to another embodiment, the present invention provides a lithium secondary battery comprising an electrode assembly in which the positive electrode, the separator, and the negative electrode of the present invention are sequentially laminated and wound in one direction; an electrolyte; and a battery case in which the electrode assembly and the electrolyte are accommodated.

[0027] At this time, the battery case may include 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.

[0028] Preferably, the lithium secondary battery may be a cylindrical battery, and the cylindrical battery may have a ratio of battery diameter to battery height of 0.4 or more. Specifically, the battery diameter may be 40 mm or more, preferably 40 mm to 60 mm, more preferably 45 mm to 60 mm, and the battery height may be 70 mm or more, preferably 70 mm to 120 mm, more preferably 75 mm to 120 mm.

[0029] In addition, the lithium secondary battery may have a structure in which the positive and negative electrodes of the electrode assembly include a non-conductive portion, and the non-conductive portion defines an electrode tab.

[0030] The present invention minimizes moisture-induced side reactions by controlling the storage environment of the anode and adjusting the moisture content according to the dimensions of the anode composite layer. When the dimensions and moisture content of the anode composite layer meet the numerical ranges of the present invention, degradation of the electrochemical performance of high-nickel, high-loading anodes, which are vulnerable to moisture, is suppressed.

[0031] Therefore, when the positive electrode according to the present invention is applied, not only is the occurrence of defects due to positive electrode deterioration suppressed, so that the yield is greatly improved, but also the deterioration of the electrochemical properties of the battery and energy loss can be minimized.

[0032] Figure 1 is a drawing showing a state of lamination before winding of an electrode assembly according to the present invention.

[0033] Fig. 2 is a cross-sectional view showing the structure of an electrode plate of an electrode assembly according to one embodiment of the present invention.

[0034] FIG. 3 is a drawing for explaining the structure of an electrode assembly according to one embodiment of the present invention.

[0035] Figure 4 is a cross-sectional view showing the structure of a lithium secondary battery according to one embodiment of the present invention.

[0036] FIG. 5 is a cross-sectional view showing the structure of a lithium secondary battery according to another embodiment of the present invention.

[0037] Figure 6 is a drawing for explaining a battery pack according to the present invention.

[0038] Figure 7 is a graph comparing the resistance characteristics according to SOC of the cells of Example 8 and Comparative Examples 3 and 4.

[0039] Hereinafter, the present invention will be described in more detail.

[0040] In the present invention, “moisture content (unit: ppm)” means 10 6 It refers to the weight of moisture contained per gram and can be measured according to the following method.

[0041] <Moisture content measurement method>

[0042] The anode (electrode semi-finished product) that had completed the rolling process was stamped into a size of 30 mm x 40 mm, and four sheets were overlapped to produce a sample. The sample was placed in a 20 mL vial, and the moisture content in the sample was measured using a Metrohm 851 Titando electrode moisture measuring device. At this time, the measurement was performed in a dry room with a temperature of 23+ / -3℃, a humidity of 1% or less, and a dew point temperature of -35℃ or less, and the measured moisture content was divided by the total weight of the anode composite layer of the sample to evaluate the moisture content.

[0043] In the present invention, “absolute moisture content (unit: mg)” means the weight of moisture contained in the entire anode, and can be calculated by multiplying the moisture content measured above by the weight of the anode.

[0044]

[0045] The inventors of the present invention have conducted repeated research to suppress performance degradation of anodes using high-nickel cathode active materials for high-capacity implementation, and as a result, have found that if the cathode storage environment is controlled to adjust the dimensions of the cathode composite layer and the anode moisture content to satisfy specific conditions, cathode degradation due to side reactions with moisture can be effectively suppressed, thereby completing the present invention.

[0046]

[0047] anode

[0048] First, the anode according to the present invention will be described.

[0049] The positive electrode according to the present invention includes a positive electrode composite layer including a high-nickel positive electrode active material having a nickel content of 80 mol% or more among all metals excluding lithium, and A defined by the following formula (1) may be 1 or less, preferably 0.7 or less, and more preferably 0.5 or less.

[0050] Equation (1): A = 0.00076ln(-2.435×(a / b)+268.4)×w

[0051] In the above equation (1), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

[0052] When the dimensions of the anode composite layer and the moisture content value of the anode satisfy the range of the above equation (1), the deterioration of electrochemical performance due to side reactions with moisture, particularly energy loss, can be minimized.

[0053] In the case of anodes using high-nickel cathode active materials that are vulnerable to moisture, there is a problem that the discharge voltage drops when exposed to moisture and the moisture content within the cathode increases, resulting in a decrease in energy density when applied to cells. This problem can be solved by keeping the moisture content of the cathode very low through methods such as vacuum storage, but this leads to a sharp increase in the cost of manufacturing the battery, which is uncompetitive. Therefore, the inventors of the present invention studied a method for preventing the degradation of high-nickel cathodes without significantly increasing the manufacturing cost. As a result, they found that the degree of degradation according to the moisture content of the cathode varies depending on the dimension of the cathode composite layer. Accordingly, by adjusting the dimension and moisture content of the cathode composite layer so that A in Equation (1) is 1 or less, it is possible to suppress anode degradation due to moisture while minimizing the increase in manufacturing cost. Specifically, when a cathode having A in Equation (1) or less is applied, the loss of energy density due to a decrease in the cathode discharge voltage can be minimized.

[0054]

[0055] In addition, it is more preferable that the above anode satisfies the following equation (2).

[0056] Equation (2): w ≤ 4(a / b) + 54

[0057] In the above equation (2), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

[0058] When the anode moisture content and the dimensions of the anode composite layer satisfy the relationship of Equation (2), the effect of suppressing electrochemical performance degradation due to side reactions with moisture is more excellent.

[0059]

[0060] Meanwhile, the anode moisture content (w) can be controlled by adjusting the storage environment of the anode. In the case of high-nickel anodes, the moisture content increases during the storage process by absorbing moisture present in the atmosphere. Therefore, the moisture content within the anode can be controlled by storing the anode in a low-humidity environment. Furthermore, even in a low-humidity environment, the moisture content may increase if stored for a long period of time. Therefore, it is desirable to control the storage period along with the humidity control. Meanwhile, as described above, the anode degradation due to moisture is also related to the dimensions of the anode composite layer. Therefore, the humidity and storage period can be appropriately controlled depending on the dimensions of the anode composite layer.

[0061]

[0062] Meanwhile, the positive electrode composite layer includes a high-nickel positive electrode active material having a nickel content of at least 80 mol% among all metals excluding lithium. When a positive electrode active material having a nickel content of at least 80 mol% is used, high-capacity characteristics can be achieved.

[0063] For example, the above high nickel positive electrode active material may include a lithium transition metal oxide represented by the following [chemical formula 1].

[0064] [Chemical Formula 1]

[0065] Li a Ni x Co y M 1 z M 2 w O2

[0066] In the above chemical formula 1, M 1 may be at least one of Mn and Al, and specifically, may be Mn, Al or a combination of Mn and Al.

[0067] M 2 is a doping element including at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo. As the Ni content increases, the structural stability and thermal stability of the positive electrode active material deteriorate, but when the doping element is additionally included, the effect of improving the structural stability and / or thermal stability of the positive electrode active material can be obtained.

[0068] The above a represents the molar fraction of lithium in the lithium transition metal oxide, and may be 0.9≤a≤1.1, 0.95≤a≤1.1, or 1.0≤a≤1.1.

[0069] The above x is the mole fraction of nickel among all metals excluding lithium, and may be 0.8≤x<1, 0.83≤x<1, 0.86≤x<1, or 0.88≤x≤0.95. When the nickel content in the lithium transition metal oxide satisfies the above range, high capacity can be achieved.

[0070] The above y is the mole fraction of cobalt among all metals excluding lithium, 0 <y<0.2, 0<y<0.17, 0<y<0.14, 또는 0.01≤y<0.12일 수 있다.

[0071] The above z is M among all metals except lithium 1 As the mole fraction of an element, 0 <z<0.2, 0<z<0.17, 0<z<0.14, 또는 0.01≤z<0.12일 수 있다.

[0072] The above w is M among all metals except lithium 2 The mole fraction of an element may be 0≤w≤0.1, 0≤w≤0.05, or 0≤w≤0.03.

[0073]

[0074] Meanwhile, the positive electrode active material may further include, if necessary, a coating layer comprising one or more coating elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb. Mo, Sr, Sb, Bi, Si and S on the surface of the lithium transition metal oxide particles. Preferably, the coating element may be Al, B, Co or a combination thereof. When the coating layer exists on the surface of the lithium transition metal oxide particles, contact between the electrolyte and the lithium composite transition metal oxide is suppressed by the coating layer, thereby obtaining the effect of reducing transition metal elution or gas generation due to side reactions with the electrolyte.

[0075] Meanwhile, the form of the positive electrode active material is not particularly limited, and may be in the form of secondary particles in which multiple primary particles are aggregated, in the form of single particles composed of one primary particle, or in the form of a mixture thereof.

[0076] The above positive electrode active material may be included in an amount of 80 to 99 wt%, preferably 85 to 99 wt%, and more preferably 90 to 99 wt%, based on the total weight of the positive electrode composite layer.

[0077]

[0078] Meanwhile, the positive electrode composite layer may further include a positive electrode conductive material and a positive electrode binder in addition to the positive electrode active material.

[0079] The above-described positive electrode conductive material is used to provide conductivity to the positive electrode, and in the battery to be formed, any material that does not cause a chemical change and has electronic conductivity can be used without any particular limitation. Specific examples of the positive electrode conductive material 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 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 composite layer.

[0080] Next, the positive electrode binder plays a role of improving the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples thereof include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, 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 positive 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 positive electrode composite layer.

[0081]

[0082] Meanwhile, the ratio a of the length a of the positive electrode composite layer to the width b of the positive electrode composite layer, a / b, may be 40 to 70, preferably 45 to 65, and more preferably 50 to 65. When a / b satisfies the above range, positive electrode degradation and deformation are effectively prevented, thereby improving productivity and quality, and increasing the electrode storage period, which is economically advantageous. When a / b is less than the above range, additional air conditioning facilities may be required to control the moisture content in the positive electrode, which may cause a problem of increased manufacturing costs, and when it exceeds the above range, the moisture content in the positive electrode may increase, which may cause a problem of decreased energy density and occurrence of side reactions due to moisture.

[0083]

[0084] Specifically, the positive electrode composite layer may have a length a of 3000 mm to 5000 mm, preferably 3500 mm to 4500 mm, more preferably 3700 mm to 4200 mm, and a width b of 50 mm to 90 mm, preferably 55 mm to 85 mm, more preferably 65 mm to 65 mm. When the length and width of the positive electrode composite layer satisfy the above ranges, it is suitable for implementing a large cylindrical battery such as a 4680 cell or a 4695 cell. When the length and width of the positive electrode composite layer are out of the above ranges, problems such as a decrease in energy density and an overhang of the negative electrode face may occur, and when stored in a conventional air-conditioned environment, the absolute moisture content may increase, which may cause positive electrode degradation.

[0085]

[0086] Method for manufacturing anode

[0087] Next, a method for manufacturing a positive electrode according to the present invention will be described.

[0088] The method for manufacturing a positive electrode according to the present invention comprises the steps of (1) preparing a positive electrode including a positive electrode composite layer including a high-nickel positive electrode active material having a nickel content of 80 mol% or more among all metals excluding lithium; and (2) storing the positive electrode in a controlled environment such that A, defined by the following formula (1), is 1 or less, preferably 0.7 or less, and more preferably 0.5 or less.

[0089] Equation (1): A = 0.00076ln(-2.435×(a / b)+268.4)×w

[0090] In the above equation (1), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

[0091]

[0092] The step of preparing the above positive electrode can be performed by a method of manufacturing a positive electrode well known in the art, for example, a method of forming a positive electrode composite layer by applying a positive electrode slurry containing a high-nickel positive electrode active material having a nickel content of 80 mol% or more, a positive electrode conductive material, and a positive electrode dispersant on a positive electrode current collector.

[0093] Specifically, the positive electrode can be manufactured by applying positive electrode slurry to one or both sides of a long sheet-shaped positive electrode collector, removing the solvent of the positive electrode slurry through a drying process, and then rolling and drying. Meanwhile, a positive electrode including a non-coated region can be manufactured by 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.

[0094] 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 μm, 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.

[0095] Additionally, the positive electrode slurry can be manufactured by dispersing the positive electrode active material in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water.

[0096]

[0097] Next, the anode prepared as described above is stored in a controlled environment so as to satisfy the following equation (1). For example, the storage may be performed by controlling the relative humidity and / or the storage period.

[0098] As described above, since the high-nickel anode absorbs moisture present in the atmosphere during storage, thereby increasing its moisture content, the moisture content within the anode can be controlled by adjusting the storage environment of the anode. Specifically, the moisture content within the anode can be controlled by adjusting the relative humidity during storage of the anode and the storage period. More specifically, the relative humidity within the air conditioner in which the anode is stored and the storage period within the air conditioner can be controlled. In this case, the relative humidity within the air conditioner is a value defined by the following equation (3).

[0099] Equation (3): Relative humidity (RH%) inside the air conditioner = (actual vapor density / saturated vapor density) × 100

[0100] In the above equation (3), the actual vapor density is 611e(17.3×dew point temperature inside the air conditioner) / (273+dew point temperature), the saturated vapor density is 611e(17.3×temperature inside the air conditioner) / (273+temperature inside the air conditioner), and the temperature unit is ℃.

[0101] The above relative humidity and storage period may vary depending on the dimensions of the anode composite layer, but preferably, the relative humidity is 15% or less, and the storage period is 17 weeks or less. This is because if the relative humidity exceeds 15% or the storage period exceeds 17 weeks, the moisture content within the anode increases, making it difficult to satisfy the condition of Equation (1).

[0102]

[0103] lithium secondary battery

[0104] Next, a lithium secondary battery according to the present invention will be described.

[0105] A lithium secondary battery according to the present invention comprises an electrode assembly, an electrolyte, and a battery case that accommodates the electrode assembly and the electrolyte. In this case, the electrode assembly is formed by sequentially stacking the positive electrode, separator, and negative electrode of the present invention described above and winding them in one direction.

[0106]

[0107] Below, each component of the lithium secondary battery according to the present invention will be described in more detail.

[0108]

[0109] electrode assembly

[0110] An electrode assembly according to the present invention comprises an anode, a cathode, and a separator interposed between the anode and the cathode. Since the anode has been described above, the remaining components excluding the anode will be described below.

[0111] 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.

[0112] 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).

[0113] 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 long sheet-shaped current collector (20), and may include a non-conductive portion (22) in which an active material layer (21) is not formed in some area of ​​the current collector (20).

[0114] 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.

[0115] 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.

[0116]

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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. 5, when an insulating layer (24) covering the positive electrode active material layer and a portion of 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.

[0125] 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).

[0126] 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.

[0127] 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.

[0128]

[0129] Meanwhile, the negative electrode may be formed in a structure in which a negative electrode composite layer is formed on one or both sides of a sheet-shaped negative electrode collector, and the negative electrode composite layer may include a negative electrode active material, a negative electrode conductive material, and a negative electrode binder.

[0130] Specifically, the negative electrode can be manufactured by applying a negative electrode slurry prepared by dispersing a negative electrode active material, a negative electrode conductive material, and a negative electrode binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc. on 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 a part of the negative electrode collector, for example, one end of the negative electrode collector, when applying the negative electrode slurry.

[0131]

[0132] The above negative active material may be a compound capable of reversible intercalation and deintercalation of lithium. Specific examples of the negative active material include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Si, Si-Me alloy (wherein, Me is at least one selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiOy (wherein, 0 <y<2), Si-C 복합체 등과 같은 실리콘계 물질; 리튬 금속 박막; Sn, Al 등과 같이 리튬과 합금화가 가능한 금속 물질; 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.

[0133] Preferably, the negative electrode according to the present invention may include a silicon-based negative electrode active material. The silicon-based negative electrode active material may be Si, a Si-Me alloy (wherein Me is at least one selected from the group consisting of Al, Sn, Mg, Cu, Fe, Pb, Zn, Mn, Cr, Ti, and Ni), SiOy (wherein 0 <y<2), Si-C 복합체 또는 이들의 조합일 수 있으며, 바람직하게는 SiOy(여기서, 0<y<2)일 수 있다. 실리콘계 음극 활물질은 높은 이론 용량을 가지기 때문에 실리콘계 음극 활물질을 포함할 경우, 용량 특성을 향상시킬 수 있다.

[0134] Meanwhile, the above silicon-based negative electrode active material is M b It may be doped with a metal, in which case, the M b The metal may be a Group 1 metal element or a Group 2 metal element, and specifically, may be Li, Mg, etc. Specifically, the silicon negative electrode active material is M b Metal-doped Si, SiOy (where, 0 <y<2), Si-C 복합체 등일 수 있다. 금속 도핑된 실리콘계 음극 활물질의 경우, 도핑 원소로 인해 활물질 용량은 다소 저하되나 높은 효율을 갖기 때문에, 높은 에너지 밀도를 구현할 수 있다.

[0135] In addition, the silicon-based negative electrode active material may further include a carbon coating layer on the particle surface. In this case, the amount of the carbon coating may be 20 wt% or less, preferably 1 to 20 wt%, based on the total weight of the silicon-based negative electrode active material.

[0136]

[0137] In addition, the negative electrode may further include a carbon-based negative electrode active material as the negative electrode active material, if necessary. The carbon-based negative electrode active material may be, for example, artificial graphite, natural graphite, graphitized carbon fiber, amorphous carbon, soft carbon, hard carbon, etc., but is not limited thereto.

[0138] Meanwhile, when a mixture of a silicon-based negative electrode active material and a carbon-based negative electrode active material is used as the negative electrode active material, the mixing ratio of the silicon-based negative electrode active material and the carbon-based negative electrode active material may be 1:99 to 20:80 by weight, preferably 1:99 to 15:85, and more preferably 1:99 to 10:90.

[0139]

[0140] The above negative electrode active material may be included in an amount of 80 to 99 wt%, preferably 85 to 99 wt%, and more preferably 90 to 99 wt%, based on the total weight of the negative electrode composite layer.

[0141]

[0142] Meanwhile, as the negative electrode current collector, negative electrode current collectors generally used in the relevant technical field can be used, 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 ㎛, and like the positive electrode current collector, fine unevenness can be formed on the surface of the 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, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0143] The above-described negative electrode conductive material is used to provide conductivity to the negative electrode, and in the battery to be formed, any material that does not cause a chemical change and has electronic conductivity 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 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 composite layer.

[0144] 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 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 composite layer.

[0145]

[0146] Next, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions, and can be used without any special restrictions as long as it is commonly used as a separator in lithium secondary batteries. Specifically, the separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof. In addition, a conventional porous non-woven fabric, for example, a non-woven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength.

[0147]

[0148] electrolyte

[0149] The electrolyte according to the present invention comprises a lithium salt and an organic solvent.

[0150] 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 be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2. LiCl, LiI, or LiB(C2O4)2. The concentration of the lithium salt is preferably within the range of 0.1 to 5.0 M, and preferably 0.1 to 3.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0151]

[0152] The above organic solvent may include at least one of a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, a linear ester-based organic solvent, and a cyclic ester-based organic solvent.

[0153] The above cyclic carbonate-based organic solvent is a high-viscosity organic solvent, and may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0154] In addition, the linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and representative examples thereof include at least one organic solvent selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and specifically, may include ethylmethyl carbonate (EMC).

[0155] Specific examples of the linear ester organic solvent include at least one organic solvent selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate.

[0156] The above cyclic ester organic solvent may include at least one organic solvent selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone.

[0157] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0158]

[0159] Meanwhile, in addition to the electrolyte components, the electrolyte may additionally include other additives for the purpose of improving the life characteristics of the battery, suppressing battery capacity reduction, and improving the discharge capacity of the battery.

[0160] These other additives may include, as representative examples, at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sultone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt included in the electrolyte.

[0161] Specifically, the other 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, One or more compounds 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) may be mentioned.

[0162] The above-mentioned other additives may be included in an amount of 0.01 to 20 wt% based on the total weight of the electrolyte, and preferably 0.05 to 5.0 wt%. If the content of the above-mentioned other additives is less than 0.01 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 above-mentioned other additives exceeds 20 wt%, there is a possibility that excessive side reactions occur in the electrolyte during charge and discharge of the battery. In particular, when the above-mentioned SEI film forming additives are added in excessive amounts, they may not be sufficiently decomposed at high temperatures and may exist as unreacted substances or precipitated substances in the electrolyte at room temperature. Accordingly, side reactions that reduce the life or resistance characteristics of the secondary battery may occur.

[0163]

[0164] battery case

[0165] The above battery case is for accommodating the electrode assembly and the electrolyte, and various battery cases known in the art, such as a cylindrical battery case, a square battery case, a pouch-type battery case, etc., can be used.

[0166] Preferably, the battery case may be a can-shaped battery case including a battery can in which the electrode assembly and the electrolyte are stored; and a sealing body for sealing an open end of the battery can.

[0167]

[0168] More preferably, the lithium secondary battery according to the present invention may be a cylindrical battery having a cylindrical battery case, and may be a large cylindrical battery, preferably having a form factor ratio (defined as the ratio of the diameter (T) to the height (H) of the cylindrical battery divided by the height) of 0.4 or more, preferably 0.4 to 0.6. Here, the form factor means a value indicating the diameter and height of the cylindrical battery. At this time, the battery diameter may be 40 mm or more, preferably 40 mm to 60 mm, more preferably 45 mm to 60 mm, and the battery height may be 70 mm or more, preferably 70 mm to 120 mm, more preferably 75 mm to 120 mm.

[0169] The cylindrical battery according to the present invention may be, for example, a 46110 cell (diameter 46 mm, height 110 mm, form factor ratio 0.418), a 48110 cell (diameter 48 mm, height 110 mm, form factor ratio 0.436), a 4880 cell (diameter 48 mm, height 80 mm, form factor ratio 0.600), or a 4680 cell (diameter 46 mm, height 80 mm, form factor ratio 0.575). In the numerical value indicating the form factor, the first two numbers indicate the diameter of the cell, and the next two or three numbers indicate the height of the cell.

[0170]

[0171] 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 .

[0172]

[0173] FIG. 4 shows a cross-sectional view of a lithium secondary battery according to one embodiment of the present invention.

[0174] Referring to FIG. 4, a lithium secondary battery (140) according to the present invention includes an electrode assembly (141), a battery case (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 case (142).

[0175] At this time, the electrode assembly may be a laminate of a positive electrode, a separator, and a negative electrode, rolled in one direction. In addition, the positive electrode and the negative electrode of the electrode assembly may each include a non-coated portion on which an active material layer is not formed, and may be rolled and laminated 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.

[0176] Meanwhile, the battery case (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 case accommodates an electrode assembly (141) in an inner space through the open end at the top, and also accommodates an electrolyte (not shown).

[0177] Meanwhile, it is preferable that the lithium secondary battery (140) of the present invention does not include a current interruption device (CID).

[0178] Meanwhile, as illustrated in FIG. 4, the battery case (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.

[0179] If necessary, a beading portion (147) and a crimping portion (148) may be provided on the upper end of the battery case (142). The beading portion (147) may be formed by pressing the outer circumference of the battery case (142) to a distance of D1. The beading portion (147) may prevent the electrode assembly (141) accommodated inside the battery case (142) from coming out through the upper opening of the battery case (142), and may function as a support portion on which the sealing body (143) is secured.

[0180] 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).

[0181]

[0182] Next, the sealing member (143) is for sealing the open end of the battery case (142), and includes a cap plate (143a), a first gasket (143b) that provides airtightness between the cap plate (143a) and the battery case (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 case (142), and may be fixed by a crimping portion (148).

[0183] The cap plate (143a) is a component made of a conductive metal material and covers the upper opening of the battery case (142). The cap plate (143a) is electrically connected to the positive electrode of the electrode assembly (141) and is electrically insulated from the battery case (142) 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) may have a protrusion (143d) formed to protrude upward from its center portion C, and the protrusion (143d) may come into contact with an external power source to allow current to be applied from the external power source.

[0184] A first gasket (143b) may be interposed between the cap plate (143a) and the crimping portion (148) to ensure the airtightness of the battery case (142) and to provide electrical insulation between the battery case (142) and the cap plate (143a).

[0185] 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 electrode terminals (i.e., the positive electrode terminal and the negative electrode terminal).

[0186] Specifically, a cylindrical 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).

[0187] It may further include a first collector plate (144) and / or a second collector plate (145).

[0188] 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).

[0189] 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.

[0190] 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 case (142). At this time, the coupling can be performed by a method such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0191] 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 case (142) can be prevented.

[0192] 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).

[0193] The insulator (146) may be made of a polymer resin material having insulating properties, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0194] 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 case (142), if necessary. The venting portion (152) corresponds to a region of the lower surface of the battery case (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 case (152) to be discharged to the outside, thereby preventing the battery from exploding.

[0195]

[0196] FIG. 5 shows a cross-sectional view of a lithium secondary battery according to another embodiment of the present invention.

[0197] Referring to FIG. 5, a lithium secondary battery (170) according to another embodiment of the present invention has a different structure of a battery case 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.

[0198] Specifically, a lithium secondary battery (170) according to another embodiment of the present invention includes a battery case (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 case (171). The rivet terminal (172) is riveted to a through hole (first opening of the first end) of the battery case (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 gravity direction.

[0199] The rivet terminal (172) includes a terminal exposure portion (172a) and a terminal insertion portion (172b). The terminal exposure portion (172a) is exposed to the outside of the closed surface of the battery case (171). The terminal exposure portion (172a) may be located approximately at the center of the partially closed surface of the battery case (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 case (171). The terminal insertion portion (172b) may penetrate approximately at the center of the closed surface of the battery case (171) and be electrically connected to the non-coated portion (146a) of the positive electrode. The terminal insertion portion (172b) may be riveted onto the inner surface of the battery case (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 case (171). The maximum diameter of the end of the terminal insertion portion (172b) may be larger than the maximum diameter of the through hole of the battery case (171).

[0200] 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 case (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 case (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).

[0201] The second gasket (173) is interposed between the battery case (171) and the rivet terminal (172) to prevent the battery case (171) and the rivet terminal (172) having opposite polarities from making electrical contact. This allows the upper surface of the battery case (171) having a roughly flat shape to function as the positive terminal of the lithium secondary battery (170).

[0202] 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 case (171). The gasket insertion portion (173b) is interposed between the terminal insertion portion (172b) of the rivet terminal (172) and the battery case (171). The gasket insertion portion (173b) can be deformed together with the terminal insertion portion (172b) when riveting and can be brought into close contact with the inner surface of the battery case (171). The second gasket (173) can be made of, for example, an insulating polymer resin.

[0203] The gasket exposure portion (173a) of the second gasket (173) may have an extended shape 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 case (171) and / or the rivet terminal (172). Although not shown in the drawing, the gasket exposure portion (173a) may have an extended shape to cover not only the outer surface of the terminal exposure portion (172a) but also a portion of the upper surface.

[0204] In the case where the second gasket (173) is made of a polymer resin, the second gasket (173) can be joined to the battery case (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 case (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.

[0205] Among the upper surfaces of the battery case (171), the remaining area (175) 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).

[0206] 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.

[0207] Preferably, the second current collecting plate (176) is electrically connected to the battery case (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 case (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 beading portion (180) formed at the bottom of the battery case (171) by welding while being supported by the lower surface of the beading 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 case (171).

[0208] 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).

[0209] Preferably, the ends of the second collector plate (176) and the non-conductive portion (146b) can be joined by welding, for example, laser welding.

[0210] A sealing member (178) for sealing the lower open end of the battery case (171) includes a cap plate (178a) and a first gasket (178b). The first gasket (178b) electrically separates the cap plate (178a) and the battery case (171). A crimping member (181) secures the edge of the cap plate (178a) and the first gasket (178b) together. A vent member (179) is provided in the cap plate (178a). The configuration of the vent member (179) is substantially the same as in the above-described embodiment.

[0211] 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 case (171), the cap plate (178a) does not have electrical polarity. The sealing body (178) seals the open end at the bottom of the battery case (171) and functions to discharge gas when the internal pressure of the battery cell (170) increases above a critical value.

[0212] 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 case (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.

[0213] When a lithium secondary battery is formed with the above structure, the current concentration is less than that of a conventional battery having electrode tabs, so the heat generation inside the battery can be effectively reduced, and thus the thermal safety of the battery can be improved.

[0214]

[0215] 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.

[0216] 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-wheeled vehicle or a two-wheeled vehicle.

[0217]

[0218] Hereinafter, the present invention will be described in more detail through specific examples.

[0219]

[0220] Manufacturing Example 1 - Anode A

[0221] Cathode active material (LiNi) 95.9 Co 1.55 Mn 2.55 O2), anode conductive material (CNT), and cathode binder (PVdF) were mixed in a weight ratio of 97.55:0.6:1.85 in N-methyl pyrrolidone to prepare a cathode slurry.

[0222] After the above positive electrode slurry was coated on an aluminum current collector, it was dried, rolled, and slit to form a positive electrode composite layer having a length a of 4132 mm and a width b of 80.5 mm.

[0223]

[0224] Manufacturing Example 2 - Anode B

[0225] Cathode active material (LiNi) 95.9 Co 1.55Mn 2.55 O2), anode conductive material (CNT), and cathode binder (PVdF) were mixed in a weight ratio of 97.55:0.6:1.85 in N-methyl pyrrolidone to prepare a cathode slurry.

[0226] After the above positive electrode slurry was coated on an aluminum current collector, it was dried, rolled, and slit to form a positive electrode composite layer having a length a of 3984 mm and a width b of 65 mm.

[0227]

[0228] Manufacturing Example 3 - Anode C

[0229] Cathode active material (LiNi) 0.971 Co 0.008 Mn 0.021 O2), anode conductive material (CNT), and cathode binder (PVdF) were mixed in a weight ratio of 97.55:0.6:1.85 in N-methyl pyrrolidone to prepare a cathode slurry.

[0230] After the above positive electrode slurry was coated on an aluminum current collector, it was dried, rolled, and slit to form a positive electrode composite layer having a length a of 4520 mm and a width b of 64 mm.

[0231] Eight each of the positive electrodes A and B manufactured by Manufacturing Examples 1 and 2 were stored under different storage conditions (humidity and period) as shown in [Table 1] below, and then the positive electrode moisture content (w) (ppm) and absolute moisture content (g) were measured using the following method. In addition, the positive electrode C manufactured by Manufacturing Example 3 was stored under the storage conditions shown in [Table 1] below, and then the positive electrode moisture content (ppm) and absolute moisture content (g) were measured. At this time, the moisture content was 10 6 It refers to the weight of moisture contained per gram, and absolute moisture content refers to the weight of moisture contained in the entire anode.

[0232] (1) Anode moisture content (unit: ppm): Each of the above anodes was punched out to a size of 30 mm × 40 mm, and 4 sheets were overlapped to produce a sample. The sample was placed in a 20 mL vial, and the moisture content contained in the sample was measured using a Metrohm 851 Titando electrode moisture measuring device. At this time, the measurement was performed in a dry room with a temperature of 23+ / -3℃, a humidity of 1% or less, and a dew point temperature of -35℃ or less, and the measured moisture content was divided by the total weight of the anode composite layer of the sample to evaluate the moisture content.

[0233] (2) Absolute moisture content (unit: mg): The weight of the anode was measured, and the absolute moisture content was measured by substituting the anode weight and the anode moisture content measured above into the following formula.

[0234] Absolute moisture content (mg) = moisture content (ppm) × anode weight (g) × 10 -3

[0235]

[0236] The measured anode moisture content (w) and a / b values ​​were substituted into equation (1) to calculate the A value, and the calculation results are shown in [Table 1] below.

[0237] Sample #Anode typeRelative humidity(%)Storage period(week)Absolute moisture content(mg)Moisture rate(ppm)AA-1Anode A (a / b=51.3)RH 1%215.299.30.3747912A-2RH 1%415.51010.3812076A-3RH 1%814.192.20.3479935A-4RH 1%1015.6101.80.3842271A-5RH 1%1616.8109.80.4144217A-6RH 1%1717.1111.50.4208381A-7RH 15%1846.33021.1398484A-8Outside air Exposure 18107.4699.62.640523B-1 Anode B(a / b=63.1) RH 1% 211.899.30.3579273B-2 RH 1% 412.01010.3640549B-3 RH 1% 811.092.20.3323353B-4 RH 1% 1012.1101.80.3669385B-5 RH 1% 1613.1109.80.3957746B-6 RH 1% 1713.3111.50.4019022B-7 RH 15% 1836.03021.0885603B-8 Outdoor exposure 1883.4699.62.5217113C Anode C(a / b=70.6)RH 10%1741.53101.0764088

[0238] Examples and Comparative Examples

[0239] <Cathode Manufacturing>

[0240] A graphite-based negative electrode active material, a conductive material (carbon black), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 98.45:0.05:0.6:0.9 to prepare a negative electrode slurry. The negative electrode slurry was applied to both sides of a copper current collector sheet, dried at 150°C, and then rolled to prepare a negative electrode.

[0241]

[0242] <Lithium secondary battery manufacturing>

[0243] As described in [Table 2] below, a positive electrode was selected, a separator was interposed between the selected positive electrode and the negative electrode manufactured above, and then the assembly was wound to manufacture a jelly-roll electrode assembly. Then, the jelly-roll electrode assembly was inserted into a cylindrical battery case with a diameter of 46 mm and a height of 80 mm, and an electrolyte was injected to manufacture a 4680 cell.

[0244]

[0245] Experimental Example 1

[0246] Each of the 4680 cells manufactured as described above was charged to 4.25 V in 0.2 C, constant current-constant voltage mode (0.005 C cut-off), and then discharged in 1 C, constant current mode to measure the average discharge voltage, discharge capacity, and energy density. The energy density reduction rate of each cell was calculated based on the energy density of the cell of Example 1 (100%). The measurement results are shown in [Table 2] below.

[0247]

[0248] Positive electrode type Average voltage [V] 1C Average discharge capacity [mAh / g] Energy density reduction rate [%] Example 1A-13.8111197.40 Example 2A-23.8083198.90.7 Example 3A-33.8047197.70 Example 4A-43.8015197.30.3 Example 5A-53.8048197.90.1 Example 6A-63.7988197.80.1 Example 7B-13.8111197.40 Example 8B-23.8083198.90.7 Example 9B-33.8047197.70 Example 10B-43.8015197.30.3 Example 11B-53.8048197.90.1 Example 12B-63.7988197.80.1 Comparative Example 1A-73.7909196.51.0 Comparative Example 2A-83.7807195.51.8 Fertilizer Example 3B-73.7909196.51.0 Comparative Example 4B-83.7807195.51.8 Comparative Example 5C3.7897196.51.2

[0249] Through the above [Table 2], it can be confirmed that in the case of lithium secondary batteries of Examples 1 to 12 that applied a positive electrode satisfying Equation (1), the discharge voltage decrease is less and the energy density decrease rate is also lower at less than 1% compared to the lithium secondary batteries of Comparative Examples 1 to 4 that applied a positive electrode that does not satisfy Equation (1).

[0250]

[0251] Experimental Example 2

[0252] The resistance (end-of-discharge resistance) at SOC 0 of the 4680 cells of the above examples and comparative examples was measured. The measurement results are shown in Table 3 below. In addition, the resistance values ​​according to SOC of Example 7 and Comparative Examples 3 and 4 are shown in Fig. 7.

[0253] Through Table 3 and Figure 7 below, it can be confirmed that the cells of the examples applying the positive electrode satisfying Equation (1) have superior discharge terminal resistance characteristics compared to the comparative example cells applying the positive electrode not satisfying Equation (1).

[0254] Positive electrode type Discharge terminal resistance [mΩ] Example 1A-143.7 Example 2A-243.6 Example 3A-343.9 Example 4A-444.0 Example 5A-544.2 Example 6A-644.1 Example 7B-145 Example 8B-245.7 Example 9B-346.5 Example 10B-445.9 Example 11B-546.2 Example 12B-647.0 Comparative Example 1A-760 Comparative Example 2A-861.1 Fertilizer Example 3B-763 Comparative Example 4B-860 Comparative Example 5C57.9

Claims

1. A cathode composite layer comprising a high-nickel cathode active material having a nickel content of 80 mol% or more among all metals excluding lithium, An anode in which A is 1 or less, as defined by the following equation (1). Equation (1): A = 0.00076ln(-2.435×(a / b)+268.4)×w In the above equation (1), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

2. In paragraph 1, The above high nickel positive electrode active material is a positive electrode including a lithium transition metal oxide represented by the following [chemical formula 1]. [Chemical Formula 1] Li a Ni x Co y M 1 z M 2 w O2 In the above chemical formula 1, M 1 is at least one of Mn and Al, and M 2 It contains at least one selected from the group consisting of Ti, Mg, Al, Zr, Y, Ba, Ca, Sr, W, Ta, Nb, and Mo, and 0.9≤a≤1.1, 0.8≤x<1, 0 <y<0.2, 0<z<0.2, 0≤w≤0.1임.

3. In paragraph 1, An anode wherein the ratio a / b, which is the length a of the anode composite layer to the width b of the anode composite layer, is 40 to 70.

4. In paragraph 1, The length a of the above anode composite layer is 3000 mm to 5000 mm, An anode having a width b of the above-mentioned anode composite layer of 50 mm to 90 mm.

5. In paragraph 1, A positive electrode satisfying the following equation (2). Equation (2): w ≤ 4(a / b) + 54 In the above equation (2), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

6. A step for preparing a cathode including a cathode composite layer including a high-nickel cathode active material having a nickel content of 80 mol% or more among all metals excluding lithium; and A method for manufacturing an anode, comprising the step of storing the anode in a controlled environment so that A, defined by the following formula (1), is 1 or less. Equation (1): A = 0.00076ln(-2.435×(a / b)+268.4)×w In the above equation (1), a is the length of the positive electrode composite layer measured in mm, b is the width of the positive electrode composite layer measured in mm, and w is the moisture content value of the positive electrode measured in ppm.

7. In paragraph 6, A method for manufacturing an anode, wherein the step of storing the anode is to store the anode in an environment having a relative humidity of 15% or less.

8. In paragraph 6, A method for manufacturing an anode, wherein the storage period of the anode in the step of storing the anode is 17 weeks or less.

9. An electrode assembly in which the positive electrode of claim 1; a separator; and a negative electrode are sequentially laminated and wound in one direction; electrolyte; and A lithium secondary battery comprising a battery case in which the electrode assembly and electrolyte are stored.

10. In paragraph 9, The above battery case is a battery can in which the electrode assembly and electrolyte are stored; and A lithium secondary battery comprising a sealing body that seals the open end of the battery can.

11. In paragraph 10, The above lithium secondary battery is a cylindrical lithium secondary battery.

12. In paragraph 11, The above cylindrical battery is a lithium secondary battery having a ratio of battery diameter to battery height of 0.4 or more.

13. In paragraph 12, A lithium secondary battery having a battery diameter of 40 mm or more and a battery height of 70 mm or more.

14. In paragraph 10, The positive and negative electrodes of the above electrode assembly include a non-conductive part, A lithium secondary battery having a structure in which the above-mentioned portion defines an electrode tab.

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