Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery comprising: a battery case; an electrode assembly accommodated in the battery case; and an electrolyte, wherein the G value defined by formula (1) is 1.8 to 3.5. Formula (1): In Formula (1), VCH is the volume (unit: mL) of a hydrocarbon-based gas present in the lithium secondary battery, VCO is the volume (unit: mL) of a carbon oxide-based gas present in the lithium secondary battery, VTotal is the total volume (unit: mL) of gas present in the lithium secondary battery, and C is the discharge capacity when the lithium secondary battery is charged and discharged at 0.33 C in a voltage range of 2.5 V to 4.2 V.

Description

lithium secondary battery

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0190459, filed December 22, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery designed so that the gas composition within the secondary battery satisfies specific conditions after activation.

[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, prismatic, and pouch-type batteries depending on the shape of the battery case. Among these, a cylindrical battery is manufactured by sequentially stacking a sheet-shaped positive electrode, a separator, and an anode in a cylindrical battery case, and then winding them in one direction to form a jelly-roll-type electrode assembly, and then covering the top of the battery case with a cap plate to seal it. The positive and negative electrodes are each provided with a strip-shaped positive electrode tab and a negative electrode tab, and the positive and negative electrode tabs are connected to electrode terminals and are electrically connected to an external power source. For reference, the positive electrode terminal is the cap plate, and the negative electrode terminal is the battery case.

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

[0006] Meanwhile, large cylindrical secondary batteries have a large capacity, so when using strip-shaped electrode tabs like conventional small cylindrical secondary batteries, the amount of current concentrated on the electrode tabs increases, which increases resistance and heat generation and reduces current collection efficiency. Accordingly, so-called tab-less cylindrical secondary batteries are being proposed, which utilize the current collectors of the non-conductive portions of the positive and negative electrodes themselves as electrode tabs instead of using separate strip-shaped electrode tabs.

[0007] Cylindrical secondary batteries with a tab-less structure not only exhibit relatively high capacity characteristics and energy density, but also have the advantage of increasing the production efficiency and lowering the production cost of cylindrical secondary batteries for electric vehicles. Furthermore, the application of the tab-less structure reduces the number of components, increases the electrical connection (contact) area between the electrode tabs and electrode terminals, and shortens the electron travel distance, thereby improving output characteristics and dissipating heat generated during charging and discharging.

[0008] However, since the large cylindrical secondary battery applying the above tab-less structure, etc. performs a process of compressing the part where the active material layer is not coated in order to provide sufficient weldability with the case and terminal parts, the electrolyte movement path between the positive electrode, separator, and negative electrode inside the rolled electrode current collector is blocked, so that the electrolyte movement does not occur properly, resulting in a decrease in electrolyte impregnation property, which causes a change in the SEI film component formed in the activation process and an increase in the decomposition reaction of the electrolyte solvent when the battery is operated. Therefore, if the same electrolyte system as that of the existing small cylindrical secondary battery is applied to a large cylindrical secondary battery, it is difficult to realize the desired electrochemical performance.

[0009] Therefore, there is a need for the development of technology that can achieve excellent electrochemical performance in large-sized cylindrical secondary batteries applicable to medium- to large-sized devices such as automobiles.

[0010]

[0011] The present invention is intended to solve the above-mentioned problems, and to provide a lithium secondary battery capable of implementing excellent electrochemical performance by designing the gas composition present in the secondary battery after activation to satisfy specific conditions.

[0012]

[0013] According to one embodiment, the present invention provides a lithium secondary battery comprising a battery case, an electrode assembly housed inside the electric case, and an electrolyte, wherein the electrode assembly comprises a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and the electrolyte comprises a lithium salt and an organic solvent, and the lithium secondary battery has a G value defined by the following formula (1) of 1.8 to 3.5, preferably 2.0 to 3.0.

[0014] Equation (1):

[0015]

[0016] In the above equation (1), V CH is the volume (unit: mL) of hydrocarbon gas present in a lithium secondary battery after activation, and V CO is the volume (unit: mL) of carbon oxide gas present in a lithium secondary battery after activation, and V total is the total volume (unit: mL) of gas present in a lithium secondary battery after activation, and C is the discharge capacity when the lithium secondary battery is charged and discharged at 0.33C in a voltage range of 2.5 V to 4.2 V.

[0017] Meanwhile, the difference between the volume of hydrocarbon gas and the volume of carbon oxide gas with respect to the total volume of gas present in the lithium secondary battery after activation, i.e., (V CH - V CO ) / V total may be 0.40 to 0.85, preferably 0.45 to 0.8.

[0018] The above lithium secondary battery may have a discharge capacity C of 20 Ah to 50 Ah, preferably 20 Ah to 45 Ah, and more preferably 22 Ah to 40 Ah when charged and discharged at 0.33 C in a voltage range of 2.5 V to 4.2 V.

[0019] Meanwhile, the lithium salt included in the electrolyte may include LiPF6, the organic solvent may include ethylene carbonate, and the electrolyte may have an E value defined by the following formula (2) of 15 to 20, preferably more than 15 and less than 18, and more preferably 15.1 to 17.9.

[0020] Equation (2):

[0021]

[0022] In the above equation (2), M EC is the number of moles of ethylene carbonate in the electrolyte, and M LiPF6 is the number of moles of LiPF6 in the electrolyte, M Solvent is the total moles of organic solvent in the electrolyte, and MW EC is the molecular weight of ethylene carbonate, A is the solubility constant of LiPF6 in the electrolyte, and C is the discharge capacity when the lithium secondary battery is charged and discharged at 0.33C in the voltage range of 2.5 V to 4.2 V.

[0023] At this time, the mole number M of ethylene carbonate in the electrolyte EC The molar number M of LiPF6 in the electrolyte may be 0.070 to 0.090 mol, preferably 0.075 to 0.085 mol, more preferably 0.078 to 0.085 mol. LiPF6 The amount may be 0.3 to 0.5 mol, preferably 0.3 to 0.4 mol, and more preferably 0.32 to 0.35 mol.

[0024]

[0025] In addition, the total mole number M of organic solvent in the electrolyte SolventThe molar mass of LiPF6 may be 0.30 to 0.40 mol, preferably 0.30 to 0.38 mol, more preferably 0.32 to 0.35 mol, and the solubility constant A of LiPF6 in the electrolyte may be 3 to 4, preferably 3.5.

[0026]

[0027] Meanwhile, the lithium secondary battery may be a cylindrical battery having a ratio of the diameter (r) to the height (h) of the battery case (form factor ratio) of 0.4 or more, preferably 0.4 to 0.6, and may be, for example, a 46110 cell, a 48110 cell, a 4880 cell, or a 4680 cell.

[0028]

[0029] The above lithium secondary battery may include a non-conductive portion in which an active material layer is not formed on at least a portion of the positive electrode and the negative electrode, and the non-conductive portion of the positive electrode and the non-conductive portion of the negative electrode may be defined as electrode tabs.

[0030] At this time, the positive electrode uncoated portion and the negative electrode uncoated portion are formed along the direction in which the electrode assembly is wound on one end of the positive electrode and the negative electrode, respectively, and a current collecting plate is coupled to each of the positive electrode uncoated portion and the negative electrode uncoated portion, and the current collecting plate may be connected to an electrode terminal.

[0031] In addition, the positive and negative electrode portions may be processed into a plurality of independently foldable segments, at least some of the plurality of segments may be folded toward the winding center of the electrode assembly, at least some of the folded plurality of segments may be overlapped on the upper and lower ends of the electrode assembly, and the current collecting plate may be bonded to the plurality of overlapped segments.

[0032] According to another embodiment, the present invention provides a battery pack including the lithium secondary battery according to the present invention as a unit cell.

[0033] The lithium secondary battery according to the present invention is designed so that the gas composition within the cell satisfies specific conditions, thereby minimizing the reduction in lifespan due to the decomposition and regeneration of SEI and CEI films and the decomposition of organic solvents within the electrolyte during charge and discharge. Since the gas present within the lithium secondary battery is generated from the interfacial reaction between the electrode and the electrolyte, the process of film formation and change on the electrode surface can be inferred from the gas composition ratio. The fact that the gas composition within the lithium secondary battery satisfies the range of the present invention means that a film is stably formed on the surfaces of the positive and negative electrodes, and when a stable film is formed on the electrode surface, additional interfacial reactions between the electrode and the electrolyte are suppressed during the cycling or storage process, thereby realizing stable cell performance.

[0034] In addition, when the gas composition conditions according to the present invention are satisfied, excellent life characteristics can be realized even in large cylindrical batteries or tab-less batteries with relatively low electrolyte impregnation.

[0035] Figure 1 is a drawing showing a state of lamination before winding of an electrode assembly according to the present invention.

[0036] Figure 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.

[0037] FIG. 3 is a drawing for explaining the structure of an electrode assembly according to one embodiment of the present invention.

[0038] Figure 4 is a cross-sectional view showing the structure of a lithium secondary battery according to one embodiment of the present invention.

[0039] Figure 5 is a cross-sectional view showing the structure of a lithium secondary battery according to another embodiment of the present invention.

[0040] Figure 6 is a drawing for explaining a battery pack according to the present invention.

[0041] Terms or words used in this specification and the scope of the 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.

[0042]

[0043] Hereinafter, the present invention will be described in more detail.

[0044] The inventors of the present invention have conducted repeated research to realize excellent electrochemical performance in large-sized batteries or tab-less batteries with relatively low electrolyte impregnation, and as a result, have discovered that when the gas composition within a secondary battery after activation satisfies certain conditions, the degradation of life characteristics due to SEI film decomposition and regeneration occurring during the charge / discharge process and the decomposition of organic solvents within the electrolyte can be minimized, thereby completing the present invention.

[0045]

[0046] Specifically, a lithium secondary battery according to the present invention includes a battery case, an electrode assembly housed inside the electric case, and an electrolyte, and the G value defined by the following formula (1) may be 1.8 to 3.5, preferably 2.0 to 3.0.

[0047] Equation (1):

[0048]

[0049] In the above equation (1), V CH is the volume (unit: mL) of hydrocarbon gas present in a lithium secondary battery after activation, and the hydrocarbon gas may be, for example, CH4, C2H6, etc.

[0050] V COis the volume (unit: mL) of carbon oxide gas present in a lithium secondary battery after activation, and may be a carbon oxide gas, for example, CO, CO2, etc.

[0051] V total is the total volume (unit: mL) of gas present in a lithium secondary battery after activation.

[0052] Meanwhile, C may be a discharge capacity of 20 Ah to 50 Ah, preferably 20 Ah to 45 Ah, and more preferably 22 Ah to 40 Ah when the lithium secondary battery is charged and discharged at 0.33 C in a voltage range of 2.5 V to 4.2 V.

[0053]

[0054] During the activation process of a lithium secondary battery, the solvents and additives contained in the electrolyte undergo oxidation and reduction reactions on the surfaces of the positive and negative electrodes, forming a SEI (Solid Electrolyte Interphase) film and a CEI (Cathode Electrolyte Interphase) film, which are passive films, on the surfaces of the positive and negative electrodes. During the oxidation and reduction reactions of the components in the electrolyte, gases are generated. When the negative SEI film is formed, mainly hydrocarbon-based gases are generated, and when the positive CEI film is formed, mainly carbon oxide-based gases are generated. Therefore, the degree of formation of passive films on the surfaces of the positive and negative electrodes can be estimated through the gas composition within the battery after activation.

[0055] Meanwhile, if the SEI film and CEI film are formed too little, the side reactions between the electrolyte and the electrode surface increase, which increases electrode degradation and gas generation, resulting in a decrease in the life characteristics. In addition, if the SEI film and CEI film are formed excessively, there is a problem of an increase in the electrode surface resistance. In addition, if only one of the SEI film and CEI film is formed excessively or insufficiently, the balance between the positive and negative electrodes is not right, which accelerates electrode degradation and may result in a decrease in the life characteristics. Therefore, in order to achieve excellent electrochemical performance of a secondary battery, the SEI film and CEI film must be formed appropriately.

[0056] The degree of formation of SEI and CEI films varies depending on a complex combination of factors, such as the electrolyte composition, capacity of the secondary battery, and the shape of the electrode assembly or battery. This is because the degree of oxidation and reduction reactions on the surfaces of the positive and negative electrodes varies depending on the electrolyte composition, and the electrolyte wettability and reaction surface area vary depending on the battery capacity or shape. Because the degree of formation of SEI and CEI films varies depending on such complex factors, it has been difficult to determine the correlation between the degree of formation of SEI and CEI films and the performance of the secondary battery.

[0057] However, as a result of continuous research by the present inventors, it was found that the degree of formation of SEI film and CEI film can be represented through a specific relationship between gas composition and battery capacity in a secondary battery after activation, G, and that when the G value satisfies the range of 1.8 to 3.5, the electrochemical performance of the secondary battery (especially, a large-capacity battery with low electrolyte impregnation) is significantly improved.

[0058] Specifically, when the G value is less than 1.8, it means that the anode side reaction occurs excessively during the activation process, resulting in a large amount of carbon oxide gas. In this case, the anode resistance increases, which may cause an increase in cell resistance and a decrease in energy density. On the other hand, when the G value exceeds 3.5, it means that the cathode side reaction occurs excessively during the activation process, resulting in a large amount of hydrocarbon gas. In this case, the cathode degradation may be accelerated, resulting in a decrease in the life characteristics.

[0059] Preferably, in the above equation (1), (V CH - V CO ) / V total may be 0.40 to 0.85, specifically, 0.45 to 0.8. When the gas composition in the electrolyte satisfies the above range, the passive film of the anode and cathode is appropriately formed, resulting in excellent resistance characteristics and life characteristics.

[0060]

[0061] Meanwhile, a lithium secondary battery satisfying the G value of the above formula (1) of 1.8 to 3.5 can be manufactured by appropriately adjusting the electrolyte composition according to the battery case shape, electrode assembly shape, and battery capacity.

[0062] For example, a lithium secondary battery satisfying the G value according to the present invention can be manufactured by controlling the electrolyte composition per unit capacity so that the E value defined by the following equation (2) is 15 to 20, preferably more than 15 and less than 18, more preferably 15.1 to 17.9.

[0063] Equation (2):

[0064]

[0065] In the above equation (2), the M EC is the number of moles of ethylene carbonate in the electrolyte, including but not limited to the above M ECThe molar number of ethylene carbonate in the electrolyte may be 0.070 to 0.090 mol, preferably 0.075 to 0.085 mol, and more preferably 0.078 to 0.085 mol. When the molar number of ethylene carbonate in the electrolyte satisfies the above range, a stable film reaction can be induced during the activation process.

[0066] Above M LiPF6 is the number of moles of LiPF6 in the electrolyte, but is not limited thereto. LiPF6 may be 0.3 to 0.5 mol, preferably 0.3 to 0.4 mol, and more preferably 0.32 to 0.35 mol. When the molar number of LiPF6 in the electrolyte satisfies the above range, a passive film is stably formed during the activation process, and a battery with excellent long-term durability and impregnation properties can be manufactured. If the molar number of LiPF6 is too large, a Lewis acid component such as HF may be generated, which may increase gas generation and electrode degradation, and the viscosity of the electrolyte may increase, thereby reducing the impregnation properties. On the other hand, if the molar number of LiPF6 is too small, the proportion of Free-EC that is not combined with lithium in the electrolyte may increase, which may increase side reactions. Ethylene carbonate with a high dielectric constant combines with Li ions while dissociating LiPF6. Ethylene carbonate combined with lithium in this way is called Solvated EC, and ethylene carbonate that is not combined with Li ions is called Free-EC. Because Free-EC has poor electrochemical stability, increasing the proportion of Free-EC in the electrolyte increases side reactions. However, if the Free-EC proportion is too low, it can negatively affect film formation. Therefore, to stably form a passive film while improving electrolyte impregnation and long-term battery durability, it is desirable to include LiPF6 in a molar number that satisfies the scope of the present invention.

[0067] M Solvent is the total mole number of organic solvent in the electrolyte, and is not limited thereto, but is SolventThe total mole number of organic solvents in the electrolyte may be 0.30 to 0.40 mol, preferably 0.30 to 0.38 mol, and more preferably 0.32 to 0.35 mol. When the total mole number of organic solvents in the electrolyte satisfies the above range, the electrolyte viscosity and conductivity are excellent.

[0068] The above MW EC is the molecular weight of ethylene carbonate, which is 88.06 g / mol.

[0069] The above A is the solubility constant of LiPF6 in the electrolyte, and the solubility constant may vary depending on the composition of the organic solvent in the electrolyte and the type and content of the additive. In the present invention, the above A may be 3 to 4, preferably 3.5.

[0070] When the E value defined by the above formula (2) satisfies 15.0 to 20, the SEI film and the CEI film are appropriately formed during the activation process, and the gas composition within the secondary battery can be formed with a G value in the range of 1.8 to 3.5.

[0071]

[0072] Next, each component of the lithium secondary battery according to the present invention will be described in more detail.

[0073] A lithium secondary battery according to the present invention includes an electrolyte; an electrode assembly including a positive electrode, a negative electrode, and a separator; and a battery case accommodating the electrode assembly and the electrolyte.

[0074]

[0075] electrolyte

[0076] The electrolyte according to the present invention comprises a lithium salt containing LiPF6 and an organic solvent containing ethylene carbonate.

[0077] It is preferable that the electrolyte according to the present invention be manufactured by controlling the mole number of LiPF6, ethylene carbonate, and organic solvent and the type and content of additives so that the E value of the above-described formula (2) satisfies 15.0 to 20.

[0078] Meanwhile, the electrolyte of the present invention may additionally include at least one organic solvent among 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, excluding ethylene carbonate (EC), as needed.

[0079] 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 propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0080] 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).

[0081] 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.

[0082] 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.

[0083] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0084]

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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 side reactions may occur excessively 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 remain unreacted or precipitated in the electrolyte at room temperature. Accordingly, side reactions that reduce the life or resistance characteristics of the secondary battery may occur.

[0089]

[0090] electrode assembly

[0091] An electrode assembly according to the present invention includes an anode, a cathode, and a separator interposed between the anode and the cathode.

[0092] 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.

[0093] 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).

[0094] 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).

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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).

[0106] 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.

[0107] 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.

[0108]

[0109] Next, each component of the electrode assembly of the present invention will be described in more detail.

[0110] anode

[0111] The above 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. 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.

[0112] Meanwhile, 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 made of 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.

[0113] 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.

[0114] The above positive electrode active material may be any positive electrode active material commonly used in the relevant technical field, and the type thereof is not particularly limited.

[0115] Preferably, the positive electrode active material may include a lithium transition metal oxide containing Ni and Co, and more preferably, may include a lithium nickel-based oxide represented by the following [chemical formula 1].

[0116] [Chemical Formula 1]

[0117] Li a Ni b Co c M 1 d M 2 e O2

[0118] In the above chemical formula 1, M 1 It may be Mn, Al or a combination thereof, preferably Mn or Mn and Al.

[0119] Above M 2 M may be at least one selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb. 2 Although elements are not essential, when included in appropriate amounts, they can promote grain growth during firing or play a role in improving crystal structure stability.

[0120] The above a represents the molar ratio of lithium in the lithium nickel-based oxide, and may be 0.8≤a≤1.2, 0.85≤a≤1.15, or 0.9≤a≤1.2. When the molar ratio of lithium satisfies the above range, the crystal structure of the lithium nickel-based oxide can be stably formed.

[0121] The above b represents the molar ratio of nickel among all metals excluding lithium in the lithium nickel oxide, and is 0.50. <b<1, 0.60≤b<1, 0.80≤b<1, 0.85≤b<1, 또는 0.90≤b<1일 수 있다.

[0122] The above c represents the molar ratio of cobalt among all metals excluding lithium in the lithium nickel oxide, and is 0. <c<0.50, 0<c<0.40, 0<c<0.20, 0<c<0.15, 또는 0<c<0.10일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0123] The above d is M of all metals excluding lithium in lithium nickel oxide. 1 It represents the molar ratio of elements, 0 <d<0.50, 0<d<0.40, 0<d<0.20, 0<d<0.15, 또는 0<d<0.10일 수 있다. M 1 When the molar ratio of the elements satisfies the above range, the structural stability of the positive electrode active material is excellent.

[0124] The above e is M of all metals except lithium in lithium nickel oxide. 2 It represents the molar ratio of elements, and can be 0≤e≤0.1 or 0≤e≤0.05.

[0125] Specifically, the lithium nickel oxide is Li(Ni 0.60 Co 0.10 Mn 0.30 )O 2, Li(Ni) 0.60 Co 0.20 Mn 0.20 )O 2, Li(Ni) 0.80 Co0.10 Mn 0.10 )O 2, Li(Ni) 0.90 Mn 0.05 Co 0.05 )O 2, Li(Ni) 0.94 Co 0.04 Mn 0.02 )O 2, Li(Ni) 0.87 Mn 0.07 Co 0.04 Al 0.02 )O2 or Li(Ni) 0.90 Mn 0.03 Co 0.05 Al 0.02 )O2, but is not limited to these.

[0126] Meanwhile, the positive electrode slurry may optionally further include at least one of a conductive material and a binder.

[0127] The 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 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.

[0128] The above binder serves to improve adhesion between positive electrode active material particles and adhesion between the positive electrode active material 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 carboxyl methyl cellulose (CMC), starch, hydroxy propyl 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 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.

[0129]

[0130] cathode

[0131] The above negative electrode can be manufactured by applying negative electrode slurry to one or both sides of a long 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.

[0132] 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.

[0133] Additionally, the negative electrode slurry can be manufactured by dispersing the negative electrode active material in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, water, etc.

[0134] As the above negative electrode active material, a carbon-based negative electrode active material used in the relevant industry can be used, and in addition, a silicon-based negative electrode active material can be mixed with the carbon-based negative electrode active material and used.

[0135] The above carbon-based active material may be a variety of carbon-based materials used in the art, for example, graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes, soft carbon, hard carbon, etc. The shape of the carbon-based material is not particularly limited, and materials of various shapes such as amorphous, plate-like, flaky, spherical, or fibrous may be used.

[0136] In addition, the silicon-based negative electrode active material may be, for example, silicon (Si), silicon carbide (SiC), silicon chloride, and silicon oxide (SiO). x , here 0 <x<2), Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님)로 이루어진 군으로부터 선택된 1종 이상을 포함할 수 있다. 상기 원소 Y로는 Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db (dubnium), Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0137] Meanwhile, the carbon-based negative electrode active material and the silicon-based negative electrode active material may be included in a weight ratio of 99:1 to 95:10, preferably in a weight ratio of 99:1 to 95:5, and more preferably in a weight ratio of 97:3 to 95:5.

[0138] When the mixing ratio of the above carbon-based negative electrode active material and the silicon-based negative electrode active material satisfies the above range, the capacity characteristics can be improved while the volume expansion of the silicon-based compound is suppressed, thereby ensuring excellent cycle performance. When the silicon (Si)-based compound is too small, it is difficult to increase the energy density, making it difficult to increase the capacity of the battery, and when it is too large, the degree of volume expansion of the negative electrode can be large, which is not desirable.

[0139] Meanwhile, the cathode slurry may optionally additionally include at least one of a conductive material and a binder.

[0140] The conductive material is used to provide conductivity to the negative 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 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.

[0141] The above binder serves to improve adhesion between negative electrode active material particles and adhesiveness between the negative electrode active material and the negative electrode current collector. Specific examples 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 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 negative electrode active material layer.

[0142]

[0143] membrane

[0144] The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without any particular restrictions. 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 nonwoven fabric, for example, a nonwoven 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.

[0145]

[0146] lithium secondary battery

[0147] Next, a lithium secondary battery according to the present invention will be described.

[0148] 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 .

[0149]

[0150] FIG. 4 illustrates a cross-sectional view of a lithium secondary battery having a tab-less structure according to one embodiment of the present invention.

[0151] 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).

[0152] 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.

[0153] 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).

[0154] Meanwhile, it is preferable that the lithium secondary battery (140) of the present invention does not include a current interruption device (CID).

[0155] 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.

[0156] 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.

[0157] 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).

[0158]

[0159] 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).

[0160] 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.

[0161] 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).

[0162] 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).

[0163] 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).

[0164] It may further include a first collector plate (144) and / or a second collector plate (145).

[0165] 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).

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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).

[0170] The insulator (146) may be made of a polymer resin material having insulating properties, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0171] 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.

[0172]

[0173] FIG. 5 shows a cross-sectional view of a lithium secondary battery having a tab-less structure according to another embodiment of the present invention.

[0174] 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.

[0175] 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.

[0176] 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).

[0177] 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).

[0178] 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).

[0179] 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.

[0180] 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.

[0181] 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.

[0182] 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).

[0183] 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.

[0184] 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).

[0185] 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).

[0186] Preferably, the ends of the second collector plate (176) and the non-conductive portion (146b) can be joined by welding, for example, laser welding.

[0187] 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191]

[0192] Meanwhile, the lithium secondary battery according to the present invention may be a cylindrical battery. Preferably, the cylindrical lithium secondary battery according to the present invention may be a large cylindrical battery having a form factor ratio (defined as the ratio of 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 refers to a value indicating the diameter and height of the cylindrical battery.

[0193] 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.

[0194]

[0195] 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.

[0196] 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.

[0197]

[0198] The present invention will be described in more detail below through specific examples.

[0199]

[0200] Examples 1 to 2 and Comparative Examples 1 to 4

[0201] Electrolyte manufacturing

[0202] The number of moles of ethylene carbonate in the electrolyte (MEC ) , Moles of LiPF6 (M LiPF6 ) and an electrolyte was prepared by mixing LiPF6 into an organic solvent containing ethylene carbonate in an amount such that the mole number of the organic solvent (Msolvent) satisfies the mole number described in [Table 1] below.

[0203]

[0204] <Electrode assembly manufacturing>

[0205] A cathode slurry was prepared by adding a cathode active material, a conductive agent, and a binder to N-methylpyrrolidone at a weight ratio of 97.5: 1.0: 1.5. At this time, the cathode active material was Li[Ni 0.93 Co 0.05 Mn 0.02 ]O2 was used, carbon nanotubes were used as a conductive material, and PVDF was used as a binder.

[0206] The above positive electrode slurry was applied onto an aluminum current collector, dried, and then roll pressed to manufacture a positive electrode.

[0207] A negative electrode slurry was prepared by adding a negative electrode active material, a conductive agent, and a binder to distilled water at a weight ratio of 95.0:3.5:1.5. At this time, graphite was used as the negative electrode active material, acetylene black was used as the conductive agent, and a mixture of styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) was used as the binder.

[0208] The above negative electrode slurry was applied onto a copper current collector, dried, and then roll pressed to manufacture a negative electrode.

[0209] 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.

[0210]

[0211] <Lithium secondary battery manufacturing>

[0212] The electrode assembly was inserted into a cylindrical battery can having a diameter of 46 mm and a height of 80 mm, and the electrolyte prepared above was injected in the amount described in [Table 1] below to manufacture a 4680 cell, which was then activated to manufacture a lithium secondary battery.

[0213] The mole number (M) of ethylene carbonate in the electrolyte in each example and comparative example is shown in [Table 1] below. EC ) , Moles of LiPF6 (M LiPF6 ), moles of organic solvent (M solvent ) and the E value of equation (2) are described.

[0214] M EC M LiPF6 M solvent ALiquid amount (g)EExample 10.0830.0340.3413.53817.4Example 20.0780.0330.3223.53615.6Comparative example 10.0920.0380.3793.54020.1Comparative example 20.0690.0290.2843.54015.1Comparative example 30.0800.0270.3323.53618.0Comparative example 40.0770.0360.3173.53615.0

[0215]

[0216] Experimental Example 1: Gas Composition

[0217] Each of the lithium secondary batteries of the examples and comparative examples manufactured as described above was charged and discharged at 0.33C in a voltage range of 2.5 V to 4.2 V to measure the discharge capacity C.

[0218] In addition, after the activation process is completed, the battery case is perforated in a vacuum atmosphere chamber to discharge the gas inside the battery and capture it inside the vacuum chamber, and the composition of the captured gas is analyzed using a gas chromatography-flame ionization detector (GC-FID) (V CH - V co ) / V total The value was measured.

[0219] Then, the measured discharge capacities C and (V CH - V co ) / V total The G value was obtained by substituting it into Equation (1). The measurement results are shown in Table 2 below.

[0220] (V CH - V CO ) / V total CG Example 10.78263.0 Example 20.56262.2 Comparative Example 10.20260.8 Comparative Example 20.94263.6 Comparative Example 30.41261.6 Comparative Example 40.35261.4

[0221]

[0222] Experimental Example 2: Cell Performance Evaluation

[0223] The initial resistance, initial energy, and capacity retention rate after 100 cycles of each lithium secondary battery manufactured by the examples and comparative examples were evaluated as follows. The evaluation results are shown in [Table 3] below.

[0224] (1) Initial resistance (Initial DCIR): A lithium secondary battery was charged to SOC 50 at 0.33C, then discharged at 0.5C at room temperature for 10 seconds to measure the voltage change (ΔV), and the measured voltage change ΔV was divided by the current I to calculate the initial resistance (R = ΔV / I). In [Table 3] below, the relative values ​​of the initial resistance values ​​of each example and comparative example are shown when the initial resistance value of the lithium secondary battery of Comparative Example 1 is taken as the standard (100%).

[0225] (2) Initial Energy: The amount of energy obtained by charging a lithium secondary battery to 4.2 V at 40°C and then discharging it to 2.5 V at 19.1 W was measured. [Table 3] below shows the relative values ​​of the initial energy of each example and comparative example, with the initial energy of the lithium secondary battery of Comparative Example 1 as the standard (100%).

[0226] (3) Cycle characteristics: After charging a lithium secondary battery to 4.2 V in 0.5 C, constant current-constant voltage mode, and then discharging to 2.4 V in 0.5 C, constant current mode, 100 cycles of charge-discharge were performed, and the capacity retention rate (capacity after 100 cycles relative to capacity after 1 cycle) was measured. In [Table 3] below, the relative values ​​of the capacity retention rates of each example and comparative example after 100 cycles are shown, when the capacity retention rate of the lithium secondary battery of Comparative Example 1 after 100 cycles is taken as the standard (100%).

[0227] Initial Resistance Initial Energy 100 Cycle Capacity Retention Rate Example 198104115 Example 299103112 Comparative Example 1 (Ref.) 100100100 Comparative Example 21109495 Comparative Example 31059590 Comparative Example 41089897

[0228] Through the above [Table 3], it can be confirmed that the lithium secondary batteries of Examples 1 and 2 designed to satisfy the G value of 1.8 to 3.5 have superior initial resistance, initial energy, and cycle characteristics compared to the lithium secondary batteries of Comparative Examples 1, 3, and 4 having a G value of less than 1.8 and Comparative Example 2 having a G value of more than 3.5.

Claims

1. A lithium secondary battery including a battery case and an electrode assembly and electrolyte housed inside the electric case, The above electrode assembly includes an anode, a cathode, and a separator interposed between the anode and the cathode, The above electrolyte comprises a lithium salt and an organic solvent, A lithium secondary battery having a G value of 1.8 to 3.5, as defined by the following equation (1). Equation (1): In the above equation (1), V CH is the volume (unit: mL) of hydrocarbon gas present in a lithium secondary battery after activation, and V CO is the volume (unit: mL) of carbon oxide gas present in a lithium secondary battery after activation, and V total is the total volume (unit: mL) of gas present in a lithium secondary battery after activation, and C is the discharge capacity when the lithium secondary battery is charged and discharged at 0.33C in a voltage range of 2.5 V to 4.2 V.

2. In paragraph 1, In the above equation (1), (V CH - V CO ) / V total A lithium secondary battery having an electric field strength of 0.40 to 0.

85.

3. In paragraph 1, A lithium secondary battery having a discharge capacity C of 20 Ah to 50 Ah.

4. In paragraph 1, The above lithium salt contains LiPF6, A lithium secondary battery wherein the organic solvent comprises ethylene carbonate.

5. In paragraph 4, The above lithium secondary battery is a lithium secondary battery having an E value of 14.0 to 17.5 as defined by the following equation (2). Equation (2): In the above equation (2), M EC is the number of moles of ethylene carbonate in the electrolyte, and M LiPF6 is the number of moles of LiPF6 in the electrolyte, M Solvent is the total moles of organic solvent in the electrolyte, and MW EC is the molecular weight of ethylene carbonate, A is the solubility constant of LiPF6 in the electrolyte, and C is the discharge capacity when the lithium secondary battery is charged and discharged at 0.33C in the voltage range of 2.5 V to 4.2 V.

6. In paragraph 5, The mole number M of ethylene carbonate in the above electrolyte EC A lithium secondary battery having a molar mass of 0.070 to 0.090 mol.

7. In paragraph 5, The mole number M of LiPF6 in the above electrolyte LiPF6 A lithium secondary battery having a molar mass of 0.3 to 0.5 mol.

8. In paragraph 5, Total moles M of organic solvent in the above electrolyte Solvent A lithium secondary battery having a molar mass of 0.3 to 0.4 mol.

9. In paragraph 5, A lithium secondary battery having a solubility constant A of LiPF6 in the electrolyte of 3 to 4.

10. In paragraph 1, The above lithium secondary battery is a cylindrical lithium secondary battery having a ratio of the diameter (r) to the height (h) of the battery case (form factor ratio) of 0.4 or more.

11. In paragraph 1, The above lithium secondary battery is a lithium secondary battery which is a 46110 cell, a 48110 cell, a 4880 cell or a 4680 cell.

12. In paragraph 1, A lithium secondary battery, wherein the lithium secondary battery includes a non-conductive portion on which an active material layer is not formed on at least a portion of the positive electrode and the negative electrode, and the non-conductive portion of the positive electrode and the non-conductive portion of the negative electrode are defined as electrode tabs.

13. In paragraph 12, A lithium secondary battery, wherein the positive electrode uncoated portion and the negative electrode uncoated portion are formed along the direction in which the electrode assembly is wound on one end of each of the positive and negative electrodes, and a current collecting plate is coupled to each of the positive electrode uncoated portion and the negative electrode uncoated portion, and the current collecting plate is connected to an electrode terminal.

14. In paragraph 12, The above positive and negative electrode parts are processed into a plurality of independently foldable segments, A lithium secondary battery, wherein at least some of the plurality of segments are bent toward the winding center of the electrode assembly.

15. In paragraph 14, A lithium secondary battery, wherein at least some of the plurality of folded segments overlap on the upper and lower sides of the electrode assembly, and the current collecting plate is bonded to the plurality of overlapped segments.

16. A battery pack comprising a lithium secondary battery according to any one of claims 1 to 15 as a unit cell.

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