Lithium secondary battery

Abstract

The present invention relates to a lithium secondary battery and a method for manufacturing same, the lithium secondary battery including: an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; an electrolyte including a lithium salt and an organic solvent; and a battery case accommodating the electrode assembly and the electrolyte, wherein Y defined by equation 1 has a value of 0.15 to 0.30.

Description

Lithium secondary battery The present invention relates to a lithium secondary battery, and more particularly, to a lithium secondary battery designed so that the battery specifications and the gas composition, electrolyte residual amount, solvent composition, and discharge capacity within the secondary battery after activation satisfy specific conditions. With the advancement of technology in electric vehicles, portable electronic devices, etc., the demand for lithium secondary batteries as an energy source is rapidly increasing. Lithium secondary batteries can be classified into cylindrical, square, 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 accommodate 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 electrically connected to an external power source. For reference, the positive electrode terminal is a cap plate, and the negative electrode terminal is a battery case. Previously, small-sized 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. However, recently, in response to the demands for increased driving range and faster charging speeds for electric vehicles, the development and use of large-sized 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. Meanwhile, since large cylindrical secondary batteries have large capacities, there is a problem that when strip-shaped electrode tabs are used, as in 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, a so-called tab-less cylindrical secondary battery has been proposed, which utilizes the current collectors themselves of the non-conductive portions of the positive and negative electrodes as electrode tabs instead of using separate strip-shaped electrode tabs. A cylindrical secondary battery having a tab-less structure can exhibit relatively large capacity characteristics and energy density, and has the advantage of increasing the production efficiency of cylindrical secondary batteries for electric vehicles and reducing their production costs. In addition, by applying the tab-less structure, the number of parts is reduced while increasing the electrical connection (contact) area between the electrode tab and the electrode terminal and shortening the movement distance of electrons, thereby improving the output characteristics and dissipating the heat generated during the charging and discharging processes. However, since large cylindrical secondary batteries using the above tab-less structure, etc. perform a process of compressing a part where the active material layer is not coated in order to provide sufficient weldability with the case and terminal parts, the electrolyte movement passage between the positive electrode, the separator, and the 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, 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 a conventional small cylindrical secondary battery is applied to a large cylindrical secondary battery, it is difficult to implement the desired electrochemical performance. Therefore, there is a need for the development of technology that can realize excellent electrochemical performance in large-sized cylindrical secondary batteries applicable to medium and large-sized devices such as automobiles. The present invention is intended to solve the above problems and to provide a lithium secondary battery capable of implementing excellent electrochemical performance by designing the battery specifications and the gas composition, electrolyte residual amount, solvent composition, and discharge capacity within the secondary battery after activation to satisfy specific conditions. [1] The present invention is a lithium secondary battery including an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; an electrolyte including a lithium salt and an organic solvent; and a battery case accommodating the electrode assembly and the electrolyte. The above organic solvent includes dimethyl carbonate, A lithium secondary battery is provided, wherein the Y value defined by the following equation 1 is 0.15 to 0.30. [Formula 1] In the above equation 1, FF is the ratio of the diameter to the height of the battery case, E is the electrolyte residual amount measured in g, r DMC is the weight ratio of dimethyl carbonate to the total weight of the solvent in the electrolyte, V CH4 is the volume of CH4 gas present in the lithium secondary battery, measured in mL; C is the discharge capacity measured in Ah when the lithium secondary battery is charged and discharged at 0.5C in the range of 2.5 V to 4.2 V. The above Y is a dimensionless number. [2] The present invention provides a lithium secondary battery in which the ratio of the volume of CH4 gas to the total volume of gas present in the lithium secondary battery is 0.40 to 0.80 in the above [1]. [3] The present invention provides a lithium secondary battery having a residual amount of electrolyte of 25 g to 32 g in the above [1] or [2]. [4] The present invention provides a lithium secondary battery having a discharge capacity of 10 Ah to 50 Ah when the lithium secondary battery is charged and discharged in a range of 2.5 V to 4.2 V at 0.5 C in at least one of the above [1] to [3]. [5] The present invention provides a lithium secondary battery in which, in at least one of the above [1] to [4], the weight ratio of dimethyl carbonate to the total weight of the solvent in the electrolyte is 0.60 to 0.90. [6] The present invention provides a lithium secondary battery, wherein in at least one of the above [1] to [5], the electrolyte includes at least one additive selected from the group consisting of vinylene carbonate, 1,3-propane sultone, succinonitrile, and methyl propargyl carbonate. [7] The present invention provides a lithium secondary battery, wherein in at least one of the above [1] to [6], the lithium secondary battery is a cylindrical battery having a form factor ratio of the diameter to the height of the battery case of 0.4 or more. [8] The present invention provides a lithium secondary battery, wherein in at least one of the above [1] to [7], the lithium secondary battery is a 46110 cell, a 48110 cell, a 4880 cell or a 4680 cell. [9] The present invention provides a lithium secondary battery, wherein, in at least one of the above [1] to [8], the lithium secondary battery includes 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 positive electrode non-conductive portion or the negative electrode non-conductive portion is defined as an electrode tab.

[0010] The present invention provides a lithium secondary battery, wherein, in the above [9], the positive electrode non-coated portion and the negative electrode non-coated portion are formed along the direction in which the electrode assembly is wound on one end of the positive and negative electrodes, respectively, and a current collecting plate is coupled to each of the positive electrode non-coated portion and the negative electrode non-coated portion, and the current collecting plate is connected to an electrode terminal.

[0011] The present invention provides a lithium secondary battery in which, in the above [9] or

[0010] , the positive electrode non-woven portion and the negative electrode non-woven portion are processed into a plurality of independently foldable segments, and at least some of the plurality of segments are folded toward the winding center of the electrode assembly.

[0012] The present invention provides a lithium secondary battery in which, in the above

[0011] , 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.

[0013] The present invention provides a battery pack including a lithium secondary battery according to at least one of the above [1] to

[0012] as a unit cell. The lithium secondary battery according to the present invention is designed so that the specifications and capacity, the amount of electrolyte solution, the ratio of DMC in the organic solvent, and the volume of CH4 in the cell after activation satisfy specific conditions, which means that a stable film is formed on the electrode by the oxidation / reduction reaction during the charge / discharge process. Therefore, the lithium secondary battery according to the present invention has minimized performance degradation due to decomposition and regeneration of the electrode film and decomposition of the organic solvent in the electrolyte, and can exhibit excellent life characteristics even in a large cylindrical battery or a battery with a tab-less structure with relatively low electrolyte impregnation. Figure 1 is a drawing showing a state of lamination before winding of an electrode assembly according to the present invention. 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. FIG. 3 is a drawing for explaining the structure of an electrode assembly according to one embodiment of the present invention. Figure 4 is a cross-sectional view showing the structure of a lithium secondary battery according to one embodiment of the present invention. FIG. 5 is a cross-sectional view showing the structure of a lithium secondary battery according to another embodiment of the present invention. Figure 6 is a drawing for explaining a battery pack according to the present invention. Hereinafter, the present invention will be described in more detail. In general, lithium secondary batteries form a solid electrolyte interphase (SEI) film and a cathode electrolyte interphase (CEI) film as passive films on the surfaces of the anode and cathode during the activation process when the solvent and additives included in the electrolyte undergo oxidation and reduction reactions on the surfaces of the anode and cathode. Among them, hydrocarbon-based gases are mainly generated when the cathode SEI film is formed, and CH4 gas is mainly generated when the electrolyte additive or the organic solvent dimethyl carbonate is decomposed and the SEI film is formed on the cathode. Specifically, electrolyte additives such as vinylene carbonate (VC) contribute to the formation of the SEI film, but if the amount of additives contributing to the formation of the SEI film is insufficient, DMC is consumed to form the SEI film instead. Therefore, a large content of DMC confirmed after activation can represent that the SEI film has been sufficiently formed by the additive. Therefore, the degree of SEI film formation can be estimated by confirming the ratio of DMC and the volume of CH4 gas present in the battery after activation. On the other hand, if the SEI film is formed too little, the side reactions between the electrolyte and the electrode surface increase, which leads to increased electrode degradation and gas generation, resulting in reduced life characteristics, and if the SEI film is formed too excessively, there is a problem in which the electrode surface resistance increases. Therefore, in order to achieve excellent electrochemical performance of a secondary battery, the SEI film must be formed appropriately. The degree of formation of an appropriate SEI film varies depending on a complex combination of factors, such as the specifications and capacity of the battery, because the electrolyte wettability and reaction surface area vary depending on the battery type. Since the degree of formation of the SEI film varies depending on such complex factors, it has been difficult to determine the correlation between the degree of formation of the SEI film and the performance of the secondary battery. However, as a result of continuous research by the present inventors, it was found that a new parameter Y, which reflects the gas composition, electrolyte residual amount, solvent composition, discharge capacity and battery specifications in a secondary battery after activation, can represent the degree of SEI film formation, and when the Y value satisfies a specific range, the electrochemical performance of a secondary battery, especially a large-sized battery with low electrolyte impregnation or a battery with a tab-less structure, is significantly improved. Specifically, a lithium secondary battery according to the present invention comprises an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; an electrolyte including a lithium salt and an organic solvent; and a battery case accommodating the electrode assembly and the electrolyte, wherein the organic solvent includes dimethyl carbonate, and the Y value defined by the following formula 1 may be 0.15 to 0.30, preferably 0.15 to 0.25, and more preferably 0.15 to 0.23. [Formula 1] In the above equation 1, FF is the ratio of the diameter to the height of the battery case, E is the electrolyte residual amount measured in g, r DMC is the weight ratio of dimethyl carbonate to the total weight of the solvent in the electrolyte, V CH4 is the volume of CH4 gas present in the lithium secondary battery, measured in mL; C is the discharge capacity measured in Ah when the lithium secondary battery is charged and discharged at 0.5C in the range of 2.5 V to 4.2 V. The above Y is a dimensionless number. If the above Y value is less than 0.15, this may mean that the amount of electrolyte injected is not sufficient for the standard required in the present invention, which means that the SEI film cannot be sufficiently formed, which is not desirable. On the contrary, if the Y value is more than 0.30, this may mean that the amount of electrolyte injected is excessive, which may cause an excessive additive decomposition reaction, which may increase the amount of gas generated inside the cell, and thus may deteriorate cell performance, which is not desirable. In the present invention, activation can be performed, for example, by charging to 4.2 V at 0.2 C at 25° C. and discharging to 2.5 V. Specifically, it can be performed by charging to 3.8 V at 0.2 C at 25° C., storing at 60° C. for 12 hours, and then charging again to 4.2 V at 25° C. and discharging to 2.5 V. V of the above formula 1 CH4 The volume of CH4 gas corresponding to the value is a value obtained by measuring the volume of CH4 gas present in the lithium secondary battery after activation, and may be 4.0 mL to 11.0 mL, preferably 4.5 mL to 10.0 mL, and more preferably 4.8 mL to 9.3 mL. In addition, the ratio of the volume of CH4 gas to the total volume of gas present in the lithium secondary battery after activation (V CH4 / V total) may be 0.40 to 0.80, preferably 0.44 to 0.70, and more preferably 0.60 to 0.67. The ratio of CH4 gas satisfying the above range may be an indicator that the SEI film is properly formed on the cathode. The volume of the CH4 gas can be measured by analyzing the gas captured in the cell using a GC-TCD (gas chromatography-thermal conductivity detector). The electrolyte residual amount corresponding to the E value of the above equation 1 is a value measured by the amount of electrolyte present in the lithium secondary battery after activation, and may be 25 g to 32 g. Since some of the electrolyte is consumed during the activation process, the electrolyte residual amount may be about 75 to 85% of the electrolyte injection amount. The electrolyte residual amount can be measured through NMR (Nuclear Magnetic Resonance spectroscopy) analysis. Specifically, the electrolyte is extracted from the lithium secondary battery, diluted in acetone, and then an internal standard is added to confirm the absolute content through NMR analysis. Additionally, qualitative analysis of the composition within the electrolyte is also possible using relative content analysis using NMR and GC / MS (Gas Chromatography / Mass Spectrometry). r in the above equation 1 DMCThe weight ratio of the corresponding dimethyl carbonate (DMC) corresponding to the value is a value representing the weight ratio of DMC with respect to the total weight of the solvent in the electrolyte present in the lithium secondary battery after activation, when it is regarded as 1, and may be 0.60 to 0.90, preferably 0.65 to 0.85, and more preferably 0.70 to 0.80. The weight ratio of the dimethyl carbonate can be measured through relative content analysis using the NMR signal intensity ratio. During activation, a portion of DMC is decomposed into DMDOHC (dimethyl 2,5-dioxahexane dicarboxylate) by the high-temperature process, but as described above, in the lithium secondary battery of the present invention, since DMC is not consumed in the formation of the SEI film, a considerable amount may remain in the form of DMC. The discharge capacity corresponding to the C value of the above equation 1 may be 10 Ah to 50 Ah, preferably 15 Ah to 40 Ah, and more preferably 20 Ah to 30 Ah, as measured when the lithium secondary battery is charged and discharged in the range of 2.5 V to 4.2 V at 0.5 C after activation, specifically, after charging to 4.2 V at 0.5 C under CC-CV conditions at 25° C. and then CP discharged to 2.5 V at 19.1 W. Meanwhile, FF of the above formula 1 is r / h, which is the ratio of the diameter to the height of the battery case when the height is h and the diameter is r, and this is called the form factor ratio. The FF may be 0.4 or more, preferably 0.4 to 0.6. That is, the lithium secondary battery may be a cylindrical battery having a form factor ratio of 0.4 or more, preferably 0.4 to 0.6. 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 representing the form factor, the first two numbers represent the diameter of the cell, and the next two or three numbers represent the height of the cell. Meanwhile, a lithium secondary battery satisfying the Y value of the above formula 1 of 0.15 to 0.30 can be manufactured by appropriately controlling the electrolyte composition according to the battery case shape, electrode assembly shape, and battery capacity. Specifically, a method for manufacturing a lithium secondary battery according to the present invention includes a step of manufacturing an electrode assembly including a positive electrode, an negative electrode, and a separator interposed between the positive electrode and the negative electrode, and a step of inserting the electrode assembly into a battery case and then injecting 30 g to 45 g of an electrolyte. The above electrolyte may include a lithium salt; an organic solvent including dimethyl carbonate (DMC); and one or more additives selected from the group consisting of vinylene carbonate (VC), 1,3-propane sultone (PS), succinonitrile (SN), and methyl propargyl carbonate. The above organic solvent may contain 60 to 90 wt% of dimethyl carbonate based on the total weight of the organic solvent. Next, each component of the lithium secondary battery according to the present invention will be described in more detail. A lithium secondary battery according to the present invention comprises 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. Electrolyte The electrolyte according to the present invention comprises a lithium salt and an organic solvent. The above lithium salt can be used without limitation as a lithium secondary battery electrolyte, and specifically, the above lithium salt is Li as a cation. + , and the anion is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , B 10 Cl 10 - , AlCl4 - , AlO2 - , PF6 - , CF3SO3 - , CH3CO2 - , CF3CO2 - , AsF6 - , SbF6 - , CH3SO3 - , (CF3CF2SO2)2N - , (CF3SO2)2N - , (FSO2)2N - , BF2C2O4 - , BC4O8 - , BF2C2O4CHF-, PF4C2O4 - , PF2C4O8 - , PO2F2 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN - It may include one or more selected from the group consisting of: Specifically, the lithium salt may be at least one selected from the group consisting of LiPF6, LiClO4, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(pentafluoroethanesulfonyl)imide (LiBETI), lithium trifluoromethanesulfonate (LiSO3CF3), lithium difluorophosphate (LiPO2F2), lithium bis(oxalato)borate (LiBOB), lithium difluoro(oxalato)borate (LiFOB), lithium difluoro(bisoxalato)phosphate (LiDFOP), lithium tetrafluoro(oxalato)phosphate (LiTFOP), and lithium fluoromalonato(difluoro)borate (LiFMDFB), and preferably LiPF6. In one embodiment of the present invention, the concentration of the lithium salt in the non-aqueous organic solution containing the lithium salt and the organic solvent may be 0.5 M to 4.0 M, specifically 0.5 M to 3.0 M, and more specifically 1.2 M to 2.0 M. When the concentration of the lithium salt is within the above range, the effects of improving low-temperature output and improving cycle characteristics can be sufficiently secured, while preventing excessive increase in viscosity and surface tension, thereby obtaining appropriate electrolyte impregnation properties. As the organic solvent, various organic solvents commonly used in lithium electrolytes can be used together with dimethyl carbonate (DMC). For example, the organic solvent may further include a cyclic carbonate solvent, a linear carbonate solvent, a linear ester solvent, a cyclic ester solvent, a nitrile solvent, or a mixture thereof, and preferably, it may be a mixture of a linear carbonate solvent including DMC and a cyclic carbonate solvent. A mixture of a linear carbonate solvent and a cyclic carbonate solvent is preferable in terms of increasing the ionic conductivity of the electrolyte. The above linear carbonate solvent is an organic solvent having low viscosity and low dielectric constant, and in addition to dimethyl carbonate (DMC), at least one selected from the group consisting of diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate can be used together. Meanwhile, electrolyte additives, particularly vinylene carbonate (VC), mainly contribute to the formation of the SEI film. If the amount of the additive contributing to the formation of the SEI film is insufficient, DMC is consumed to form the SEI film instead. Therefore, a large content of DMC confirmed after activation can represent that the SEI film has been sufficiently formed by the additive. The above cyclic carbonate solvent is a high-viscosity organic solvent having a high dielectric constant and thus can easily dissociate a lithium salt in the electrolyte, and may be at least one 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, and preferably, may be ethylene carbonate (EC) or propylene carbonate (PC) or a mixture thereof. The linear ester solvent may be at least one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, and preferably methyl propionate, ethyl propionate or propyl propionate. The above cyclic ester solvent may be at least one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone. The above nitrile solvent may be at least one selected from the group consisting of succinonitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, and preferably succinonitrile. Meanwhile, the electrolyte may include at least one additive selected from among a cyclic carbonate compound, a sultone compound, a sulfate compound, a phosphorus compound, a nitrile compound, an amine compound, a silane compound, a benzene compound, and a lithium salt compound, as needed. The above cyclic carbonate compound may be at least one selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoroethylene carbonate (FEC), and methyl propargyl carbonate, and specifically may be vinylene carbonate. The above sultone compound is a substance capable of forming a stable SEI film by a reduction reaction on the cathode surface, and may be at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, prop-1-ene-1,3-sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone, and specifically, may be 1,3-propane sultone (PS) or prop-1-ene-1,3-sultone (PRS). The above sulfate-based compound is a substance that can form a stable SEI film that is electrically decomposed on the cathode surface and does not crack even when stored at high temperatures, and may be at least one selected from the group consisting of ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS). The above-mentioned phosphorus compound may be a phosphate-based or phosphite-based compound, and specifically, may be at least one selected from the group consisting of tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(trifluoroethyl)phosphite. The above nitrile compound may be at least one selected from the group consisting of succinonitrile (SN), adiponitrile (ADN), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, 4-fluorophenylacetonitrile, ethylene glycol bis(2-cyanoethyl) ether (ASA3), 1,3,6-hexane tricarbonitrile (HTCN), 1,4-dicyano 2-butene (DCB), and 1,2,3-tris(2-cyanoethyl)propane (TCEP). there is. The above amine compound may be at least one selected from the group consisting of triethanolamine and ethylenediamine, and the silane compound may be tetravinylsilane. The above benzene compound may be at least one selected from the group consisting of monofluorobenzene, difluorobenzene, trifluorobenzene, and tetrafluorobenzene. The above lithium salt-based compound is a compound different from the lithium salt included in the non-aqueous electrolyte, and may be at least one compound selected from the group consisting of lithium difluorophosphate (LiDFP; LiPO2F2), lithium bisoxalatoborate (LiBOB; LiB(C2O4)2), lithium tetrafluoroborate (LiBF4), lithium tetraphenylborate, lithium difluoro(oxalato)borate (LiDFOB), and lithium difluoro(bisoxalato)phosphate (LiDFOP). Preferably, the additive may include at least one additive selected from the group consisting of vinylene carbonate (VC), 1,3-propane sultone (PS), succinonitrile (SN), and methyl propargyl carbonate as an additive contributing to SEI film formation. The total weight of the above additive may be 3 wt% to 7 wt%, preferably 4 wt% to 6 wt%, based on the total weight of the electrolyte. If the additive contributing to SEI film formation is not sufficiently included, the amount of electrolyte itself increases to compensate for this, in which case the Y value may exceed 0.30, and the amount of gas generated may increase due to side reactions within the cell, which may lead to a deterioration in cell performance. Meanwhile, the remainder of the electrolyte, excluding the content of the lithium salt and additives, may be an organic solvent unless otherwise specified. Electrode assembly An electrode assembly according to the present invention includes an anode, a cathode, and a separator interposed between the anode and the cathode. 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. 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). 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). As described above, by using a positive electrode (10) and a negative electrode (11) including a non-conductive portion (22), 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 an electrode tab can be implemented without providing a separate electrode tab. Specifically, the non-conductive portion (22) can be formed long along the winding direction (X) at one end of the current collector (20), and a current collecting plate is combined with each of the positive non-conductive portion and the negative non-conductive portion, and the current collecting plate is connected to an electrode terminal, thereby functioning as an electrode tab. 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 folded 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. Meanwhile, the positive electrode uncoated portion and the negative electrode uncoated portion may be processed into a plurality of independently foldable segments, and at least some of the plurality of segments may be folded toward the winding center (C) of the electrode assembly. 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. 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 improving the welding characteristics with the current collecting plate. The collector plate and the plain portion are generally joined by welding. In order to improve the welding characteristics, strong pressure should be applied to the welding area of ​​the plain portion to fold the plain portion as flat as possible. However, during this bending process, the shape of the plain portion may be distorted and deformed irregularly, and the deformed portion may come into contact with an electrode of the opposite polarity, causing an internal short circuit or inducing micro-cracks in the plain portion. However, if the plain portions of the positive and negative electrodes are processed into a plurality of independently bendable segments, the stress applied to the plain portion during bending can be relieved, thereby minimizing deformation and damage to the plain portion. 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 folding, 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 away 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. 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 along a direction parallel to the winding direction of the electrode assembly. In the case of a battery having a tab-less structure in which the non-conductive portion (22c) of the positive electrode (10) and the non-conductive portion (22a) of the negative electrode (11) are used 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. Preferably, the insulating layer (24) may be provided on at least one surface of the positive electrode (10) current collector, and preferably, may be provided on both surfaces of the positive electrode (10). 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, in the case 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 opposite side of the surface that faces the negative electrode (11) after being folded, it is preferable that the insulating layer (24) be formed only in a part of the non-coated portion (22c), for example, up to the point before the bending of the non-coated portion (22c). This is because, if the insulating layer (24) is formed in the entire area of ​​the non-coated portion on the opposite side of the surface that faces the negative electrode (11), electrical contact with the current collecting plate is impossible, and thus, it cannot function as an electrode tab. Meanwhile, the insulating layer (24) can be attached to the anode while securing insulating performance, and its material or component is not particularly limited. For example, the insulating layer can be an insulating coating layer or an insulating tape, and the insulating coating layer can include an organic binder and inorganic particles. At this time, the organic binder can be, for example, styrene-butadiene rubber (SBR), and the inorganic particles can be, but are not limited to, alumina oxide. Next, each component of the electrode assembly of the present invention will be described in more detail. anode The above positive electrode can be manufactured by a method of applying positive electrode slurry to one side 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 portion can be manufactured by a method of not applying the positive electrode slurry to some area of ​​the positive electrode collector, for example, one end of the positive electrode collector, during the application of the positive electrode slurry. Meanwhile, as the positive electrode collector, various positive electrode collectors used in the relevant technical field can be used. For example, as the positive electrode collector, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The positive electrode collector can typically have a thickness of 3 to 500 ㎛, and fine unevenness can be formed on the surface of the positive electrode collector to increase the adhesive strength of the positive electrode active material. The positive electrode collector 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. 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. The above cathode active material can be any cathode active material commonly used in the relevant technical field, and its type is not particularly limited. 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]. [Chemical Formula 1] Li a Ni b Co c M 1 d M 2 e O2 In the above chemical formula 1, M 1 is Mn, Al or a combination thereof, M 2 is at least one selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta and Nb, The above a, b, c, d and e are 0.8≤a≤1.2 and 0.50, respectively. <b<1, 0<c<0.50, 0<d<0.50, 0≤e≤0.1를 만족하며, b+c+d+e=1이다. Preferably, the above M 1 can be Mn or Mn and Al. M 2 Elements are not essential, but when included in appropriate amounts, they can promote grain growth during sintering or play a role in improving crystal structure stability. 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. 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. 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. The above d is M of all metals except 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. The above e is M of all metals except lithium in lithium nickel oxide. 2It represents the molar ratio of elements, and can be 0≤e≤0.1, or 0≤e≤0.05. 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 Co 0.10 Mn 0.10 )O 2, Li(Ni) 0.90 Mn 0.05 Co 0.05 )O 2, Li[Ni 0.93 Co 0.05 Mn 0.02 ]O2, 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 thereto. Meanwhile, the positive electrode slurry may optionally further include at least one of a conductive agent and a binder. 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 special restrictions. Specific examples include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; carbon-based structures such as carbon fibers and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and the like, and 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. The above binder serves to improve the adhesion between positive electrode active material particles and the adhesive strength between the positive electrode active material and the positive electrode current collector, and specific examples thereof include a fluorine resin 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. cathode The above negative electrode can be manufactured by a method of applying negative electrode slurry to one side 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 a method of 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. Meanwhile, as the negative electrode collector, negative electrode 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 collector can typically have a thickness of 3 to 500 ㎛, and, like the positive electrode collector, fine unevenness can be formed on the surface of the 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, and a non-woven fabric. 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. As the above negative electrode active material, a carbon-based negative electrode active material used in the relevant industry can be used, and further, a silicon-based negative electrode active material can be mixed with the carbon-based negative electrode active material and used. The above carbon-based active material may be any of various carbon-based materials used in the art, for example, graphite-based materials such as natural graphite, artificial graphite, and Kish graphite; high-temperature calcined carbon such as pyrolytic carbon, mesophase pitch based carbon fiber, carbon microbeads, mesophase pitches, and 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. In addition, the silicon-based negative electrode active material may be, for example, silicon (Si), silicon carbide (SiC), silicon chloride, and silicon oxide (SiO). k , here 0 <k<2), Si-Y1합금(상기 Y1은 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 Y1은 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. Meanwhile, the carbon-based negative electrode active material and the silicon-based negative electrode active material may be included in the negative electrode slurry 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. 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 securing 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 preferable. Meanwhile, the cathode slurry may optionally additionally include at least one of a conductive material and a binder. The conductive material is used to provide conductivity to the negative electrode, and can be used without special restrictions as long as it does not cause a chemical change in the battery to be formed and has electronic conductivity. Specific examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; carbon-based structures such as carbon fibers and carbon nanotubes; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; 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 be typically included in an amount of 1 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, relative to the total weight of the negative electrode active material layer. The above binder serves to improve adhesion between negative active material particles and adhesiveness between the negative active material and the negative current collector. Specific examples thereof include: a fluorine resin 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 wt% to 30 wt%, preferably 1 wt% to 20 wt%, and more preferably 1 wt% to 10 wt%, based on the total weight of the negative electrode active material layer. Membrane The above separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. If it is generally used as a separator in a lithium secondary battery, it can be used without any special 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 general porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may 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. Lithium secondary battery Next, a lithium secondary battery according to the present invention will be described. FIGS. 4 and 5 disclose implementation examples of lithium secondary batteries according to the present invention. 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 only show one embodiment of the present invention, and the structure of the battery of the present invention is not limited to the range disclosed in FIGS. 4 and 5. 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. 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). At this time, the electrode assembly may be a laminate of a positive electrode, a separator, and a negative electrode, which is wound 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 laminated and wound such 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. 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 the inner space through the open end at the top, and also accommodates an electrolyte (not shown). Meanwhile, it is preferable that the lithium secondary battery (140) of the present invention does not include a current interruption device (CID). Meanwhile, as illustrated in FIG. 4, the battery case (142) is electrically connected to the negative electrode 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. 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. 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). Next, the sealing body (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 and insulation between the cap plate (143a) and the battery case (142), and, if necessary, may further include a connecting plate (143c) that is electrically and mechanically coupled to the cap plate (143a). 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). 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) through the first gasket (143b). Therefore, the cap plate (143a) can function as a positive electrode terminal of a lithium secondary battery. The cap plate (143a) can have a protrusion (143d) formed to protrude upward from its center portion C, and the protrusion (143d) can come into contact with an external power source to allow current to be applied from the external power source. A first gasket (143b) may be interposed between the cap plate (143a) and the crimping portion (148) to ensure airtightness of the battery case (142) and to provide electrical insulation between the battery case (142) and the cap plate (143a). Meanwhile, the lithium secondary battery (140) according to the present invention may further include a current collecting plate (144, 145), if necessary. The current collecting plate is coupled to the positive electrode non-conducting portion (146a) and the negative electrode non-conducting portion (146b), and is connected to the electrode terminals (i.e., the positive electrode terminal and the negative electrode terminal). Specifically, a cylindrical battery (140) according to the present invention may include a first current collecting plate (144) coupled to an upper portion of an electrode assembly (141) and a second current collecting plate (145) coupled to a lower portion of the electrode assembly (141). It may further include a first collector plate (144) and / or a second collector plate (145). The first collector plate (144) is coupled to the upper portion of the electrode assembly (141). The first collector 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 connected to the first collector 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) and other components may be accomplished by welding. Preferably, the first collector plate (144) may be formed integrally with the lead (149). In this case, the lead (149) may have a plate shape that extends outward from the center of the first collector plate (144). Meanwhile, the first collector plate (144) is joined to an end of the non-conductive portion (146a) of the anode, and the joining can be accomplished by, for example, laser welding, resistance welding, ultrasonic welding, soldering, or the like. The second collector plate (145) is coupled to the lower portion of the electrode assembly (141). The second collector 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 collector 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. 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). Since the insulator (146) covers the first current collecting plate (144), direct contact between the first current collecting plate (144) and the inner surface of the battery case (142) can be prevented. The insulator (146) is provided with 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 coupled to the lower surface of the connecting plate (143c) or the lower surface of the cap plate (143a). The insulator (146) may be made of a polymer resin material having insulating properties, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate. 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, thereby allowing gas inside the battery case (152) to be discharged to the outside, thereby preventing the battery from exploding. FIG. 5 illustrates a cross-sectional view of a lithium secondary battery having a tab-less structure according to another embodiment of the present invention. 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 sealant compared to the lithium secondary battery (140) illustrated in FIG. 4, and the configuration of the electrode assembly and the electrolyte are substantially the same. 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. 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 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-conductive 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, an 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). The lower surface of the terminal insertion portion (172b) can be welded with the first current collecting plate (144) connected to the non-polar 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 prevents the outer non-polar 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). 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 electrically contacting each other. As a result, the upper surface of the battery case (171) having a substantially flat shape can function as a positive terminal of the lithium secondary battery (170). 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) during riveting so as to be in 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. The gasket exposure portion (173a) of the second gasket (173) may have an extended shape so as to cover the outer surface of the terminal exposure portion (172a) of the rivet terminal (172). When the second gasket (173) covers the outer surface of the rivet terminal (172), a short circuit can be prevented from occurring during the process of connecting an electrical connection component such as a bus bar to the upper surface of the battery case (171) and / or the rivet terminal (172). Although not shown in the drawing, the gasket exposure portion (173a) may have an extended shape so as to cover not only the outer surface of the terminal exposure portion (172a) but also a part of the upper surface. 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 at the joining interface between the second gasket (173) and the rivet terminal (172) and 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 joined integrally with the second gasket (173) by insert injection. The remaining area (175) of the upper surface of the battery case (171), excluding the area occupied by the rivet terminal (172) and the second gasket (173), corresponds to a negative terminal having the opposite polarity to the rivet terminal (172). 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 unconducted portion (146b) of the cathode. Preferably, the second collector plate (176) is electrically connected to the battery case (171). To this end, at least a portion of an edge portion of the second collector 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 an edge portion of the second collector plate (176) may be fixed to the beading portion (180) formed at the lower end of the battery case (171) by welding while being supported by the lower surface of the beading portion (180). In a variation, at least a portion of an edge portion of the second collector plate (176) may be directly welded to the inner wall surface of the battery case (171). The second collector plate (176) may have a plurality of protrusions (not shown) formed radially on a surface facing the non-conductive portion (146b). When the protrusions are formed, the second collector plate (176) may be pressed to press the protrusions into the non-conductive portion (146b). Preferably, the ends of the second collector plate (176) and the non-conductive portion (146b) can be joined by welding, for example, laser welding. 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. 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 of the lower portion of the battery case (171) and discharges gas when the internal pressure of the battery cell (170) increases above a critical value. 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, a 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 connection area can be secured when connecting electrical connection components such as bus bars. Accordingly, the lithium secondary battery (170) can lower the resistance at the connection portion of the electrical connection components to a desirable level. 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 the heat generation inside the battery can be effectively reduced, and thus the thermal safety of the battery can be improved. 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, parts such as a bus bar, a cooling unit, and an external terminal for electrically connecting the lithium secondary batteries (1) are omitted. The above battery pack (3) can be mounted on a vehicle. The vehicle may be, for example, an electric vehicle, a hybrid vehicle, or a plug-in hybrid vehicle. The vehicle includes a four-wheel vehicle or a two-wheel vehicle. The present invention will be described more specifically through specific examples below. <Example: Manufacturing of lithium secondary battery> Example 1. i) Preparation of electrolyte A non-aqueous organic solution was prepared by dissolving LiPF6 in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) to make 1.25 M. An electrolyte was prepared by mixing 3 wt% of vinylene carbonate (VC), 1 wt% of 1,3-propane sultone (PS), 1 wt% of succinonitrile (SN), 0.5 wt% of methyl propargyl carbonate, and the remainder of the non-aqueous organic solution based on the total weight of the electrolyte. ii) Manufacturing of electrode assembly 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 as an oxide composition, carbon nanotubes were used as a conductive material, and PVDF was used as a binder. The above positive electrode slurry was applied onto an aluminum current collector, dried, and then roll pressed to manufacture a positive electrode. 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 styrene-butadiene rubber (SBR) was used as the binder. The above negative electrode slurry was applied onto a copper current collector, dried, and then roll pressed to manufacture a negative electrode. A polyethylene separator was interposed between the positive and negative electrodes manufactured as described above, and the separator, positive electrode, separator, and negative electrode were laminated in that order, and then wound to manufacture a jelly-roll type electrode assembly. iii) Manufacturing of lithium secondary batteries The electrode assembly manufactured as described above was inserted into a cylindrical battery can having a diameter of 46 mm and a height of 80 mm, and the electrolyte manufactured as described above was injected to manufacture a 4680 cell. At this time, the electrolyte was E / V of Equation 1 CH4 The amount of the solution was injected in an amount satisfying the values ​​listed in Table 1 below. Example 2. E / V CH4 A 4680 cell was manufactured in the same manner as in Example 1, except that the amount of electrolyte solution was increased so that the values ​​were adjusted as shown in Table 1 below. Example 3. E / V CH4 A 4680 cell was manufactured in the same manner as in Example 1, except that the amount of electrolyte solution was increased so that the values ​​were adjusted as shown in Table 1 below. Example 4. E / V CH4A 4680 cell was manufactured in the same manner as in Example 1, except that the amount of electrolyte solution was increased so that the values ​​were adjusted as shown in Table 1 below. Example 5. E / V CH4 A 4680 cell was manufactured in the same manner as in Example 1, except that the amount of electrolyte solution was increased so that the values ​​were adjusted as shown in Table 1 below. Comparative example 1. When manufacturing the electrolyte, the content of vinylene carbonate (VC) was changed to 2 wt%, and E / V CH4 A 4680 cell was manufactured in the same manner as in Example 1, except that the amount of electrolyte solution was reduced so that the values ​​were adjusted as shown in Table 1 below. Comparative example 2. E / V CH4 A 4680 cell was manufactured in the same manner as in Example 1, except that the amount of electrolyte solution was increased excessively so that the values ​​were adjusted as shown in Table 1 below. Comparative example 3. A 2170 cell was manufactured in the same manner as in Example 1, except that a cylindrical battery can having a diameter of 21 mm and a height of 70 mm was used. Comparative example 4. E / V CH4 A 2170 cell was manufactured in the same manner as in Comparative Example 3, except that the amount of electrolyte solution was increased so that the values ​​were adjusted as shown in Table 1 below. <Experimental example> Experimental Example 1.E, r DMC, V CH4 and measurement of C Each cell manufactured in the above examples and comparative examples was charged to 3.8 V at 0.2 C at 25 °C, stored at 60 °C for 12 hours, and then charged again to 4.2 V at 25 °C and discharged to 2.5 V to perform an activation process. Then, the gas captured in the cell was analyzed using a gas chromatography-thermal conductivity detector (GC-TCD), and the volume (V) of CH4 gas was measured. CH4 ) and the total volume of gas produced (V total ) was measured. In addition, the electrolyte was extracted from each cell that went through the activation process, and the ratio of DMC to the total weight of solvent remaining after activation and the remaining amount of the electrolyte were confirmed. Specifically, the extracted electrolyte was diluted in acetone, an internal standard was added, and the remaining electrolyte amount was measured through NMR analysis. In addition, the ratio of the remaining DMC was calculated through relative content analysis using the NMR signal intensity ratio. In addition, the activated cell was charged under CC-CV conditions at 25°C and 0.5C to 4.2 V, and then CP discharged to 2.5 V at 19.1 W to measure the discharge capacity C. Then, the measured V CH4 , E, r DMC By substituting C into Equation 1, the value of Y is obtained and recorded in Table 1. FFE / V CH4 r DMCC[Ah] Formula 1 Y Example 10.5752.8764040.75250.150 Example 20.5753.1807230.75250.166 Example 30.5753.1264370.75250.163 Example 40.5754.3076920.75250.225 Example 50.5753.9452050.75250.206 Comparative Example 10.5752.7526880.75250.144 Comparative Example 20.5756.6666670.75250.348 Comparative Example 30.33.9420290.7551.971 Comparative Example 40.34.0283690.7552.014 Through the above Table 1, it can be confirmed that Comparative Example 3, which is a 2170 cell, has a Y value according to Equation 1 that greatly deviates from the range of 0.15 to 0.30 even though it uses an electrolyte having the same composition as Example 1. Experimental Example 2. Cell Performance Verification (1) Measurement of initial resistance (DCIR) Each cell manufactured in the above Examples and Comparative Examples was charged to 3.8 V at 0.2 C at 25 ° C, stored at 60 ° C for 12 hours, then charged again to 4.2 V at 25 ° C and then discharged to 2.5 V to perform an activation process. Then, the cells were charged (0.05 C cut off) to 4.2 V at 0.5 C (reference capacity 1 C = 25,000 mAh / g) at 25 ° C under CC-CV conditions to fully charge to 100% SOC. The voltage drop that occurs when the fully charged battery is discharged for 10 seconds at a current of 12.5 A at 25 ° C was measured, and the DC resistance was calculated using Ohm's law based on the measured value. When the value measured in Example 1 was set to 100%, the relative values ​​of Examples 2 to 5 and Comparative Examples 1 to 4 were calculated and shown in Table 2 below. (2) Measurement of initial discharge energy and energy retention rate Each cell manufactured in the above examples and comparative examples was charged to 3.8 V at 0.2 C at 25 °C, stored at 60 °C for 12 hours, and then charged again to 4.2 V at 25 °C and discharged to 2.5 V to perform an activation process. Then, the cells were CP (Constant Power) charged to 4.1 V at 48.5 W at 20 °C using a charger / discharger, and CP discharged to 3.0 V at 48.5 W. Such charge / discharge was defined as one cycle, and the initial discharge energy was measured after one cycle. Then, the energy retention rate compared to the initial discharge energy was calculated while repeating the same charge / discharge 200 times. The results are shown in Table 2 below. Meanwhile, for Comparative Examples 3 and 4, the battery specifications were different from those of Examples 1 to 5, so it was not appropriate to apply the same evaluation criteria, and therefore performance evaluation was not conducted. Initial Resistance (%) Initial Discharge Energy (%) Energy Retention Rate (%) Example 1100100100 Example 297.31199.918101.743 Example 395.1199.765100.053 Example 493.39999.582100.317 Example 594.86699.653101.743 Comparative Example 189.97699.37898.225 Comparative Example 288.0299.37898.31 Through the results in Table 2 above, it can be confirmed that in the cells of Examples 1 to 5 and Comparative Examples 1 to 2 of the same 4680 standard, when the Y value according to Equation 1 satisfies 0.15 to 0.30, excellent performance is exhibited in terms of resistance and energy.

Claims

1. A lithium secondary battery comprising an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; an electrolyte including a lithium salt and an organic solvent; and a battery case accommodating the electrode assembly and the electrolyte. The above organic solvent includes dimethyl carbonate, A lithium secondary battery having a Y value of 0.15 to 0.30, as defined by the following equation 1: [Formula 1] In the above equation 1, FF is the ratio of the diameter to the height of the battery case, E is the electrolyte residual amount measured in g, r DMC is the weight ratio of dimethyl carbonate to the total weight of the solvent in the electrolyte, V CH4 is the volume of CH4 gas present in the lithium secondary battery, measured in mL; C is the discharge capacity measured in Ah when the lithium secondary battery is charged and discharged at 0.5C in the range of 2.5 V to 4.2 V. The above Y is a dimensionless number.

2. In claim 1, A lithium secondary battery, wherein the ratio of the volume of CH4 gas to the total volume of gas present in the lithium secondary battery is 0.40 to 0.

80.

3. In claim 1, A lithium secondary battery having a residual amount of electrolyte of 25 g to 32 g.

4. In claim 1, A lithium secondary battery having a discharge capacity of 10 Ah to 50 Ah when the lithium secondary battery is charged and discharged at 0.5 C in a range of 2.5 V to 4.2 V.

5. In claim 1, A lithium secondary battery having a weight ratio of dimethyl carbonate to the total weight of the solvent in the electrolyte of 0.60 to 0.

90.

6. In claim 1, A lithium secondary battery, wherein the electrolyte comprises at least one additive selected from the group consisting of vinylene carbonate, 1,3-propane sultone, succinonitrile, and methyl propargyl carbonate.

7. In claim 1, The lithium secondary battery is a cylindrical battery having a form factor ratio of the diameter to the height of the battery case of 0.4 or more.

8. In claim 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.

9. In claim 1, The above lithium secondary battery includes a non-conductive portion in which an active material layer is not formed on at least a portion of the positive and negative electrodes, A lithium secondary battery, wherein the positive electrode uncharged portion or the negative electrode uncharged portion is defined as an electrode tab.

10. In claim 9, 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.

11. In claim 9, The above positive electrode and negative electrode portions 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.

12. In claim 11, 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.

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

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