Method for predicting fast charging performance of cylindrical lithium secondary battery, cylindrical lithium secondary battery, and method for manufacturing same

Abstract

An embodiment of the present invention provides a method for predicting fast charging performance of a cylindrical lithium secondary battery comprising a cathode, a separator, an anode, and an electrolyte, wherein the anode comprises an anode current collector and an anode active material layer formed on at least one surface of the anode current collector, the method comprising determining the fast charging performance of the cylindrical lithium secondary battery using the diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, the porosity Panode of the anode active material layer, and the tortuosity Tanode within the pores of the anode active material layer.

Description

Method for predicting rapid charging performance of a cylindrical lithium secondary battery, cylindrical lithium secondary battery and method for manufacturing the same

[0001] This application claims the benefit of the filing date of Korean Patent Application No. 10-2024-0192036 filed with the Korean Intellectual Property Office on December 19, 2024, the entire contents of which are incorporated herein.

[0002] The present invention relates to a method for predicting the rapid charging performance of a cylindrical lithium secondary battery, a cylindrical lithium secondary battery, and a method for manufacturing the same.

[0003] Secondary batteries, which offer high applicability across product categories and possess electrical characteristics such as high energy density, are widely applied not only to portable devices but also to electric vehicles (EVs) and hybrid electric vehicles (HEVs) powered by electric driving sources.

[0004] These secondary batteries are attracting attention as a new energy source for improving eco-friendliness and energy efficiency, as they not only have the primary advantage of being able to drastically reduce the use of fossil fuels but also the advantage of not generating any by-products from the use of energy.

[0005] In particular, lithium-ion batteries are gaining attention as power sources for electronic devices due to their lightweight nature and high energy density. Accordingly, active research and development efforts are underway to improve the performance of lithium-ion batteries.

[0006] In a lithium secondary battery, electrical energy is produced by oxidation and reduction reactions when lithium ions are inserted into or removed from the positive and negative electrodes, which are composed of active materials capable of lithium ion intercalation and deintercalation, with an organic or polymer electrolyte charged between them.

[0007] Lithium-ion batteries can be classified into cylindrical, prismatic, and pouch types depending on the battery can shape. In particular, with the recent advancement of electric vehicle technology and the increasing demand for high-capacity batteries, the development and use of bulky large cylindrical secondary batteries are being considered.

[0008] While conventionally used small cylindrical batteries, such as 1865 or 2170 form factors, did not require high rapid charging performance, large cylindrical secondary batteries are applied to electric vehicles, making rapid charging characteristics critical. However, when performing rapid charging at high voltage and high C-rates, the electrolyte decomposes rapidly, potentially generating large amounts of gases such as CO2 and CH4, which increase the internal pressure of the battery. As the electrolyte is displaced due to this increased internal pressure, it becomes localized. Consequently, lithium ions that have migrated through the localized electrolyte concentrate in specific negative electrode regions, leading to a phenomenon called lithium plating (Li-plating), where lithium ions that could not be inserted into the negative electrode precipitate on the surface of the negative electrode.

[0009] In other words, due to high current density, lithium cannot be inserted into the interior of the anode, leading to lithium plating. This causes lithium to precipitate on the anode surface, and the accumulation of lithium byproduct layers degrades the rapid charge life characteristics. Consequently, lithium plating can cause battery degradation or ignition, posing a risk to the battery's lifespan and safety.

[0010] Therefore, there is an urgent need to develop lithium secondary batteries capable of improving rapid charging performance by effectively controlling the lithium plating phenomenon during rapid charging; to this end, research and development of technologies capable of accurately predicting and optimizing rapid charging performance is required.

[0011] The present invention aims to provide a method for predicting the rapid charging performance of a cylindrical lithium secondary battery having excellent lifespan characteristics and stability by preventing lithium plating during rapid charging, a cylindrical lithium secondary battery, and a method for manufacturing the same.

[0012] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems will be clearly understood by those skilled in the art from the description of the invention below.

[0013] One embodiment of the present invention is a method for predicting the rapid charging performance of a cylindrical lithium secondary battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte, wherein

[0014] The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and

[0015] The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode A method for predicting the rapid charging performance of a cylindrical lithium secondary battery is provided, comprising the step of verifying the rapid charging performance of the cylindrical lithium secondary battery using [the method].

[0016] One embodiment of the present invention is a cylindrical lithium secondary battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte, wherein

[0017] The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and

[0018] The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anodeA cylindrical lithium secondary battery satisfying a P value of 5 or more of the following formula 1 containing , and a method for manufacturing the same are provided.

[0019] [Equation 1]

[0020]

[0021] The inventors have developed a rapid charging performance prediction method that can ensure excellent lifespan characteristics and safety by effectively preventing lithium plating during rapid charging of a cylindrical lithium secondary battery.

[0022] Specifically, the inventors conducted research to suppress the lithium plating phenomenon during rapid charging and to improve lifespan characteristics and safety. As a result, they verified the rapid charging performance of a cylindrical lithium secondary battery using the battery's form factor, the porosity of the negative electrode active material layer, and the tortuosity within the pores of the negative electrode active material layer. For example, when specific conditions are satisfied, they were able to suppress the localization of the electrolyte caused by gas generated during rapid charging, thereby minimizing the lithium plating phenomenon and significantly improving rapid charging lifespan characteristics and safety.

[0023] Accordingly, even before manufacturing or completing a cylindrical lithium secondary battery, the diameter (R) and height (h) of the cylindrical lithium secondary battery, as well as the porosity of the negative electrode active material layer and the curvature within the pores of the negative electrode active material layer, can be measured to predict the rapid charging performance of the secondary battery in advance, thereby reducing costs and time and improving productivity.

[0024] In addition, the cylindrical lithium secondary battery according to the present invention can have excellent lifespan characteristics and stability by preventing lithium plating during rapid charging.

[0025] Specifically, the cylindrical lithium secondary battery can improve lithium deposition and rapid charging life characteristics by defining and controlling parameters that reflect the porosity of the negative electrode active material layer, the curvature inside the pores of the negative electrode active material layer, and the form factor, so that lithium does not degrade battery performance due to lithium deposition on the electrode surface caused by the lithium plating phenomenon.

[0026] Furthermore, the above-mentioned cylindrical lithium secondary battery can be manufactured according to the method for manufacturing a cylindrical lithium secondary battery according to the present invention.

[0027] However, the advantageous effects obtainable through the present invention are not limited to those described above, and other unmentioned effects will be clearly understood by those skilled in the art from the description of the invention below.

[0028] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings.

[0029] Figure 1 is a figure showing the capacity retention rate (%) of a cylindrical lithium secondary battery according to one embodiment and a comparison state of the present invention.

[0030] FIG. 2 is a schematic diagram illustrating the form factor of a cylindrical lithium secondary battery according to one embodiment of the present invention.

[0031] FIG. 3 shows the tortuosity T inside the pores of the cathode active material layer according to one embodiment and a comparative state of the present invention. anode This is a diagram representing .

[0032] FIG. 4 shows R from EIS analysis in Equation 2 according to one embodiment of the present invention. pore This is a diagram showing the method for finding .

[0033] FIG. 5 is a schematic diagram illustrating the tortuosity inside the pores of a cathode active material layer according to one embodiment of the present invention.

[0034] The present invention will be described in more detail below.

[0035] Terms and words used in this specification and claims are not limited to their ordinary or dictionary meanings, and must be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0036] In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0037] Furthermore, when it is said that a part, such as a layer, is "above" or "on" another part, this includes not only the case where it is "directly above" the other part, but also the case where there is another part in between. Conversely, when it is said that a part is "directly above" another part, it means that there is no other part in between. Also, saying that a part is "above" or "on" a reference part means that it is located above or below the reference part, and it does not necessarily mean that it is located "above" or "on" facing the opposite direction of gravity.

[0038] In this specification, "Porosity" refers to the ratio of pores present within a material, which serve as a channel for lithium ions to be transported as the electrolyte seeps through the pores. The "Porosity" is expressed as a percentage (%) of the total volume occupied by pores and can be obtained through the BET gas adsorption method or by the following Equation 1-1.

[0039] [Equation 1-1]

[0040] Porosity = 1 - Electrode Density (ED) / Solid Density (SCD)

[0041] The above electrode density (ED) can be calculated as the loading amount per unit area of ​​the electrode (mg / cm²) / electrode thickness (cm), and the electrode thickness is the thickness of the electrode active material layer excluding the thickness of the current collector, which can be measured with a micrometer, etc.

[0042] In this specification, the "Porosity" can be calculated using Equation 1-1.

[0043] In this specification, "tortuosity" indicates how much a path inside a material is curved, and with reference to FIG. 5, it represents the ratio of the actual path to a straight path.

[0044] One embodiment of the present invention is a method for predicting the rapid charging performance of a cylindrical lithium secondary battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte, wherein

[0045] The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and

[0046] The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anodeA method for predicting the rapid charging performance of a cylindrical lithium secondary battery is provided, comprising the step of verifying the rapid charging performance of the cylindrical lithium secondary battery using [the method].

[0047] By including a step of verifying the rapid charging performance of the above-mentioned cylindrical lithium secondary battery, the rapid charging performance can be predicted and designed before the cylindrical lithium secondary battery is completed, thereby reducing costs and time for production and manufacturing and improving productivity.

[0048] In addition, based on the prediction of the rapid charging performance of the above-mentioned cylindrical lithium secondary battery, the cylindrical lithium secondary battery can suppress the lithium plating phenomenon during rapid charging and significantly improve lifespan characteristics and safety.

[0049] In one embodiment of the present invention, the step of confirming the rapid charging performance of the cylindrical lithium secondary battery is T, which is the tortuosity inside the pores of the negative electrode active material layer. anode P, which is the porosity of the above-mentioned cathode active material layer for . anode Uses the ratio of.

[0050] In one embodiment of the present invention, the step of confirming the rapid charging performance of the cylindrical lithium secondary battery comprises the diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and P, which is the porosity of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode It includes a step of checking whether the P value of the following Equation 1 containing is 5 or greater.

[0051] [Equation 1]

[0052]

[0053] The method for predicting the rapid charging performance of the above-mentioned cylindrical lithium secondary battery comprises the diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and P, which is the porosity of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode By including a step of checking whether the P value of the above Equation 1, which includes , satisfies 5 or more, rapid charging performance can be predicted and designed before the cylindrical lithium secondary battery is completed, and thus, costs and time for production and manufacturing can be reduced and productivity can be improved.

[0054] In addition, according to the prediction of the rapid charging performance of the above cylindrical lithium secondary battery, a cylindrical lithium secondary battery satisfying Equation 1 can suppress the lithium plating phenomenon during rapid charging and significantly improve lifespan characteristics and safety.

[0055] Specifically, the cylindrical lithium secondary battery can improve lithium deposition and rapid charging life characteristics by defining and controlling parameters that reflect the porosity of the negative electrode active material layer, the curvature inside the pores of the negative electrode active material layer, and the form factor, so that lithium does not degrade battery performance by being deposited on the electrode surface due to the lithium plating phenomenon.

[0056] The P value according to the above Equation 1 may be 5 or more, 5.3 or more, 5.5 or more, 6 or more, or 6.15 or more.

[0057] If the above range is satisfied, rapid charging performance can be predicted and designed before the cylindrical lithium secondary battery is completed, and lithium plating during rapid charging can be suppressed and lifespan characteristics and safety improved.

[0058] The P value according to the above Equation 1 may be in % units.

[0059] In this specification, "form factor" may refer to the ratio of the diameter (R) of the cylindrical lithium secondary battery to the height (h) of the cylindrical lithium secondary battery, with reference to FIG. 2.

[0060] The ratio of the diameter (R) of the cylindrical lithium secondary battery to the height (h) of the cylindrical lithium secondary battery (R / h, form factor ratio) may be 0.4 or more, preferably 0.4 to 0.6, and more preferably 0.5 to 0.6.

[0061] If the above range of form factor ratio is satisfied, high capacity characteristics can be realized as a large cylindrical lithium secondary battery.

[0062] According to one embodiment of the present invention, in a method for predicting the rapid charging performance of the cylindrical lithium secondary battery, the T anode is calculated by the following Equations 2 and 3, and the above T anode Includes a step of checking whether is 2 or more and 3 or less.

[0063] [Equation 2]

[0064]

[0065] [Equation 3]

[0066]

[0067] In the above Equation 2, the R pore is a value measured from EIS analysis, and the above R th is calculated from Equation 3, and

[0068] In the above Equation 3, d is the thickness of the negative electrode active material layer, A is the surface area of ​​the negative electrode active material layer, and P anode is the porosity of the above-mentioned negative electrode active material layer, and σ is the conductivity of lithium ions in the above-mentioned electrolyte.

[0069] According to one embodiment of the present invention, T, which is the tortuosity inside the pores of the negative electrode active material layer, anode It can be obtained through the above Equations 2 and 3.

[0070] That is, T, which is the tortuosity inside the pores of the above-mentioned cathode active material layer anode It can be obtained through the Impedance analysis in Equations 2 and 3 above, and the thickness, surface area, porosity, and conductivity of lithium ions in the electrolyte of the cathode active material layer.

[0071] The above curvature can be calculated by using the graphs measured by EIS (Electrochemical Impedance Spectroscopy) by manufacturing an electrode assembly by interposing a separator between two electrodes to be measured, inserting it into a battery case, injecting a reference electrolyte (EC:EMC=3:7), and aging it for 12 to 24 hours to manufacture a symmetric coin cell, and then applying a current of 0.1 to 1,000,000 Hz and 10 Mv to the symmetric coin cell.

[0072] Specifically, the above-mentioned EIS analysis (Electrochemical Impedance Spectroscopy) is an electrochemical impedance spectroscopy method that applies an alternating current voltage of small amplitude to a system and measures the resulting current response to measure impedance in various frequency ranges to analyze the electrochemical characteristics of the system, and the measured impedance can be composed of a real part (resistive component) and an imaginary part (capacitive component).

[0073] FIG. 4 shows R from EIS analysis in Equation 2 according to one embodiment of the present invention. pore This is a diagram illustrating the method for calculating . Referring to FIG. 4, the R in Equation 2 above pore In EIS analysis, the real and imaginary parts of the impedance are set as the x and y axes, respectively, and the slope can be measured from Equation 2-1 below by fitting the slope.

[0074] [Equation 2-1]

[0075] R pore = 3×(R high-R low )

[0076] That is, the measured impedance can be composed of a real part (resistive component) and an imaginary part (capacitive component), and for example, by fitting the slope with the x-axis of Fig. 4 as the real part (z') and the y-axis as the imaginary part (-z''), R high and R low R from the difference in values pore It can be calculated, and this can be the difference of the real part of the impedance. The -z'' on the y-axis above is a complex number, and "-" can be seen as indicating the direction.

[0077] The above R high represents the x-axis intercept value of the real part (z') of the impedance in the high-frequency region in EIS analysis, and the above R low can represent the x-axis intercept value of the real part (z') of the impedance in the low-frequency region in EIS analysis.

[0078] According to one embodiment of the present invention, the conductivity of lithium ions in the electrolyte can be measured through EIS analysis. For example, the bulk resistance (Rb) can be identified from a Nyquist plot obtained through EIS measurement, and the ionic conductivity (σ) can be calculated from Equation 3-1 below using the measured resistance value and cell constant.

[0079] [Equation 3-1]

[0080] σ = 2L / (Rb×B×p) (L: electrode thickness, B: electrode area, p: electrode porosity)

[0081] According to one embodiment of the present invention, the surface area of ​​the negative electrode active material layer may refer to the area excluding the surface in contact with the negative electrode current collector, and the area of ​​the pores included therein is not included in the surface area. In Equation 3-1, the electrode thickness (L) refers to the thickness of the unactivated electrode, and the electrode porosity (p) is calculated through the loading and thickness of the electrode.

[0082] According to one embodiment of the present invention, when the calculation based on the curvature includes a decimal point, the T anode It can be written up to the second decimal place by rounding to the third decimal place.

[0083] The above T anode may be 2 or more, 2.10 or more, 2.15 or more, 2.20 or more, or 2.25 or more. The above T anode It may be 3 or less, 2.90 or less, 2.80 or less, 2.70 or less, or 2.60 or less.

[0084] When the above range is satisfied, lithium ions can be inserted into the negative electrode active material layer, thereby improving side reactions such as lithium plating (Li-plating) precipitating on the electrode surface, and thus improving and predicting rapid charging life characteristics.

[0085] T, the tortuosity inside the pores of the above-mentioned cathode active material layer anode This can be controlled by using artificial graphite having a different orientation index (OI) from the negative electrode active material, for example, graphite included in the negative electrode active material, or by controlling the D50 particle size.

[0086] The above orientation index is an indicator representing the degree of crystallographic orientation of graphite particles, indicating how parallel the (002) crystal planes of graphite are aligned with respect to the electrode surface, and is measured through X-ray diffraction (XRD) analysis. For example, the higher the orientation index, the more parallel the (002) crystal planes of graphite are aligned with respect to the electrode surface, which may restrict the ion transport pathway. The orientation index may be 6 to 18, or 7 to 17.

[0087] The above D50 particle size refers to the median particle size in the particle size distribution, represents a particle size corresponding to 50% of the cumulative volume, and is measured through laser diffraction or dynamic light scattering.

[0088] The larger the D50 value, the larger the inter-particle voids and the simpler the structure, allowing for low curvature; conversely, the smaller the D50 value, the smaller the inter-particle voids and the more complex the structure, allowing for high curvature.

[0089] In addition, T, which is the tortuosity inside the pores of the above-mentioned cathode active material layer anode This can be controlled by adjusting the ratio of artificial graphite and natural graphite in the negative electrode active material, for example, the graphite included in the negative electrode active material.

[0090] In other words, natural graphite has a plate-like structure with high orientation, which restricts the lithium ion movement path in the horizontal direction. Due to the complex stacking structure, particles are stacked layer upon layer to form serpentine pores. Since the actual path for ion movement through these narrow and complex pores is longer than the straight-line distance and forms a more restricted ion channel compared to the point contact of artificial graphite, the curvature of the negative electrode active material layer can be increased by increasing the proportion of natural graphite.

[0091] According to one embodiment of the present invention, the method for predicting the rapid charging performance of the cylindrical lithium secondary battery includes the step of checking whether the P value of Equation 1 is 6 or higher and 8 or lower.

[0092] The value of P in Equation 1 above may be 6 or greater, or 6.15 or greater, and may be 8 or less, 7.8 or less, 7.3 or less, 6.9 or less, or 6.6 or less.

[0093] If the above range is satisfied, lithium precipitation and rapid charge life characteristics can be improved.

[0094] According to one embodiment of the present invention, in a method for predicting the rapid charging performance of the cylindrical lithium secondary battery, the P anode (%) is 25% or more and 27% or less.

[0095] The above P anode represents the porosity of the negative electrode active material layer, which indicates the ratio of pores existing within the negative electrode active material layer, and acts as a channel through which the electrolyte seeps in and lithium ions are transported.

[0096] The above P anode The ratio of the voids to the total volume is expressed as a percentage (%) and can be obtained through the BET gas adsorption method or by the following Equation 1-1.

[0097] [Equation 1-1]

[0098] Porosity = 1 - Electrode Density (ED) / Solid Density (SCD)

[0099] The above electrode density (ED) can be calculated as the loading amount per unit area of ​​the electrode (mg / cm²) / electrode thickness (cm), and the electrode thickness is the thickness of the electrode active material layer excluding the thickness of the current collector, which can be measured with a micrometer, etc.

[0100] According to one embodiment of the present invention, when the calculation based on the porosity includes a decimal point, the P anode (%) can be written up to the first decimal place by rounding to the second decimal place.

[0101] The above P anode (%) may be 25.0% or more, 25.3% or more, 25.5% or more, or 25.8% or more. The above P anode (%) may be 27.0% or less, 26.7% or less, 26.4% or less, or 26.1% or less.

[0102] When the above range is satisfied, lithium ions can be inserted into the negative electrode active material layer, thereby improving side reactions such as lithium plating (Li-plating) precipitating on the electrode surface, and thus improving and predicting rapid charging life characteristics.

[0103] According to one embodiment of the present invention, in the method for predicting the rapid charging performance of the cylindrical lithium secondary battery, the cylindrical lithium secondary battery satisfying a P value of 5 or more in Equation 1 has a capacity retention rate (%) of 89% or more after 100 cycles of charging and discharging at 20°C at a 1C-rate.

[0104] According to one embodiment of the present invention, if the calculation based on the capacity retention rate (%) includes a decimal point, it may be written up to the first decimal place by rounding to the second decimal place.

[0105] The above cylindrical lithium secondary battery may have a capacity retention rate (%) of 89% or more, 90% or more, or 91% or more after 100 cycles of charging and discharging at 20°C at a 1C-rate.

[0106] The above cylindrical lithium secondary battery may have a capacity retention rate (%) of 98% or less, 97% or less, 96% or less, 95% or less, or 94% or less after 100 cycles of charging and discharging at 20°C at a 1C-rate. When the above cylindrical lithium secondary battery satisfies the above range, it can be confirmed that lithium deposition and rapid charging life characteristics are improved.

[0107] One embodiment of the present invention is a cylindrical lithium secondary battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte, wherein

[0108] The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and

[0109] The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer.anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode provides a cylindrical lithium secondary battery that satisfies a P value of 5 or more in the following Equation 1.

[0110] [Equation 1]

[0111]

[0112] In the above-mentioned cylindrical lithium secondary battery, the diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode By satisfying the following Equation 1, the lithium plating phenomenon during rapid charging can be suppressed and lifespan characteristics and safety can be significantly improved.

[0113] Specifically, the cylindrical lithium secondary battery can improve lithium deposition and rapid charging life characteristics by defining and controlling parameters that reflect the porosity of the negative electrode active material layer, the curvature inside the pores of the negative electrode active material layer, and the form factor, so that lithium does not degrade battery performance by being deposited on the electrode surface due to the lithium plating phenomenon.

[0114] The P value according to the above Equation 1 may be 5 or more, 5.3 or more, 5.5 or more, 6 or more, or 6.15 or more.

[0115] If the above range is satisfied, the lithium plating phenomenon during rapid charging can be suppressed and lifespan characteristics and safety can be improved.

[0116] According to one embodiment of the present invention, in the cylindrical lithium secondary battery, the T anode is calculated by the following Equations 2 and 3, and the above T anode is 2 or more and 3 or less.

[0117] [Equation 2]

[0118]

[0119] [Equation 3]

[0120]

[0121] In the above Equation 2, the R pore is a value measured from EIS analysis, and the above R th is calculated from Equation 3, and

[0122] In the above Equation 3, d is the thickness of the negative electrode active material layer, A is the surface area of ​​the negative electrode active material layer, and P anode is the porosity of the above-mentioned negative electrode active material layer, and σ is the conductivity of lithium ions in the above-mentioned electrolyte.

[0123] In this specification, "tortuosity" indicates how much a path inside a material is curved, and with reference to FIG. 5, it represents the ratio of the actual path to a straight path.

[0124] According to one embodiment of the present invention, T, which is the tortuosity inside the pores of the negative electrode active material layer, anode It can be obtained through the above Equations 2 and 3.

[0125] That is, T, which is the tortuosity inside the pores of the above-mentioned cathode active material layer anode The value can be obtained through the Impedance analysis in Equations 2 and 3 above, as well as the thickness, surface area, porosity, and conductivity of lithium ions in the electrolyte. Specifically, the conductivity of lithium ions in the electrolyte can be measured using Electrochemical Impedance Spectroscopy (EIS) analysis.

[0126] According to one embodiment of the present invention, when the calculation based on the curvature includes a decimal point, the T anode It can be written up to the second decimal place by rounding to the third decimal place.

[0127] The above Tanode may be 2 or more, 2.10 or more, 2.15 or more, 2.20 or more, or 2.25 or more. The above T anode It may be 3 or less, 2.90 or less, 2.80 or less, 2.70 or less, or 2.60 or less.

[0128] When the above range is satisfied, lithium ions can be inserted into the negative electrode active material layer, thereby improving side reactions such as lithium plating (Li-plating) precipitating on the electrode surface and enhancing rapid charging life characteristics.

[0129] According to one embodiment of the present invention, in the cylindrical lithium secondary battery, the value of P of Equation 1 is 6 or more and 8 or less.

[0130] The value of P in Equation 1 above may be 6 or greater, or 6.15 or greater, and may be 8 or less, 7.8 or less, 7.3 or less, 6.9 or less, or 6.6 or less.

[0131] If the above range is satisfied, lithium precipitation and rapid charge life characteristics can be improved.

[0132] According to one embodiment of the present invention, in the cylindrical lithium secondary battery, the P anode (%) is 25% or more and 27% or less.

[0133] The above P anode represents the porosity of the negative electrode active material layer, which indicates the ratio of pores existing within the negative electrode active material layer, and acts as a channel through which the electrolyte seeps in and lithium ions are transported.

[0134] The above P anode The ratio of the voids to the total volume is expressed as a percentage (%) and can be obtained through the BET gas adsorption method or by the following Equation 1-1.

[0135] [Equation 1-1]

[0136] Porosity = 1 - Electrode Density (ED) / Solid Density (SCD)

[0137] The above electrode density (ED) can be calculated as the loading amount per unit area of ​​the electrode (mg / cm²) / electrode thickness (cm), and the electrode thickness is the thickness of the electrode active material layer excluding the thickness of the current collector, which can be measured with a micrometer, etc.

[0138] According to one embodiment of the present invention, when the calculation based on the porosity includes a decimal point, the P anode (%) can be written up to the first decimal place by rounding to the second decimal place.

[0139] The above P anode (%) may be 25.0% or more, 25.3% or more, 25.5% or more, or 25.8% or more. The above P anode (%) may be 27.0% or less, 26.7% or less, 26.4% or less, or 26.1% or less.

[0140] When the above range is satisfied, lithium ions can be inserted into the negative electrode active material layer, thereby improving side reactions such as lithium plating (Li-plating) precipitating on the electrode surface and enhancing rapid charging life characteristics.

[0141] According to one embodiment of the present invention, in the cylindrical lithium secondary battery, the energy retention (%) is 89% or more after 100 cycles of charging and discharging at 20°C at a 1C-rate.

[0142] According to one embodiment of the present invention, if the calculation based on the capacity retention rate (%) includes a decimal point, it may be written up to the first decimal place by rounding up from the second decimal place.

[0143] The above cylindrical lithium secondary battery may have a capacity retention rate (%) of 89% or more, 90% or more, or 91% or more after 100 cycles of charging and discharging at 20°C at a 1C-rate.

[0144] The above cylindrical lithium secondary battery may have a capacity retention rate (%) of 98% or less, 97% or less, 96% or less, 95% or less, or 94% or less after 100 cycles of charging and discharging at 20°C at a 1C-rate. When the above cylindrical lithium secondary battery satisfies the above range, it can be confirmed that lithium deposition and rapid charging life characteristics are improved.

[0145] According to one embodiment of the present invention, the initial resistance (DC-IR) of the cylindrical lithium secondary battery at SOC 50% is 4.1 mΩ to 4.5 mΩ.

[0146] The initial resistance (DC-IR) of the above cylindrical lithium secondary battery at SOC 50% may be 4.1 mΩ to 4.3 mΩ or 4.2 mΩ to 4.3 mΩ.

[0147] In the above initial resistance (DC-IR), “initial” refers to the state immediately after manufacturing or immediately after the first charge-discharge process (formation process) performed after battery manufacturing, and “initial resistance” may refer to the internal resistance value measured when the battery is in its most optimal state before actual use.

[0148] The above initial resistance can be calculated by charging each cell to 100% SOC with a constant current of 0.25C at 20℃, discharging it at 50% SOC with a constant current of 0.5C for 10 seconds, and then using the voltage drop that appears.

[0149] According to one embodiment of the present invention, a step of manufacturing a jelly roll wound with an anode, a separator, and a cathode laminated; and

[0150] The method comprises the step of manufacturing a cylindrical lithium secondary battery that includes housing the above-mentioned jelly roll in a battery can, providing an electrolyte, and including a sealing body that seals the above-mentioned battery can.

[0151] The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and

[0152] The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer anode and T, which is the tortuosity inside the pores of the cathode active material layer included in the cathode. anode The present invention provides a method for manufacturing a cylindrical lithium secondary battery as described above, comprising the step of designing such that the P value of the following formula 1, including , satisfies 5 or more.

[0153] [Equation 1]

[0154]

[0155] In the above method for manufacturing a cylindrical lithium secondary battery, the details regarding Formula 1 and the cylindrical lithium secondary battery are the same as those described above, so a detailed explanation is omitted.

[0156] According to one embodiment of the present invention, the anode can be manufactured by applying an anode slurry to one or both sides of a sheet-shaped anode current collector, removing the solvent of the anode slurry through a drying process, and then rolling.

[0157] Meanwhile, an anode including an uncoated portion can be manufactured by not applying the anode slurry to a portion of the anode current collector, for example, one end of the anode current collector, when applying the anode slurry.

[0158] In addition, the anode slurry can be prepared by dispersing the anode material according to the present invention in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water.

[0159] The positive electrode manufactured accordingly comprises a positive electrode current collector; and a positive electrode active material layer, wherein the positive electrode active material layer may comprise a positive electrode active material.

[0160] Various positive current collectors used in the relevant technical field may be used as the positive current collector. For example, the positive current collector may be stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. The positive current collector may typically have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase the adhesion of the positive active material. The positive current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0161] The positive active material layer may be located on the positive current collector, and specifically, may be located on one or both sides of the positive current collector. The positive active material layer may be a single layer or a multilayer structure of two or more layers.

[0162] The above-mentioned positive active material may be any positive active material commonly used in the relevant technical field, and its type is not particularly limited. The above-mentioned positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, may include a lithium transition metal composite oxide comprising lithium and at least one transition metal composed of nickel, cobalt, manganese, and aluminum, preferably a lithium transition metal composite oxide comprising lithium and a transition metal comprising nickel, cobalt, and manganese.

[0163] More specifically, the lithium transition metal composite oxide includes a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), and a lithium-nickel-manganese oxide (e.g., LiNi 1-Y MnYO2(here, 0 <Y<1), LiMn 2-z Ni zO4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1CoY1 O2(here, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(here, 0 <Y2<1), LiMn 2-z 1Co z1 O4 (where 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r1 )O2(where, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) or Li(Ni p1 Co q1 Mn r2 )O4 (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel-cobalt-transition metal (M) oxide (e.g., Li(Ni p2 Co q2 Mn r3 M S2 Examples include )O2 (wherein M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r3, and s2 are each atomic fractions of independent elements, such that 0 < p2 < 1, 0 < q2 < 1, 0 < r3 < 1, 0 < s2 < 1, and p2 + q2 + r3 + s2 = 1), etc., and any one or more of these compounds may be included. Among these, the lithium transition metal composite oxide is LiCoO2, LiMnO2, LiNiO2, and lithium nickel-manganese-cobalt oxide (for example, Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn0.1 Co 0.1 )O2, etc.), or lithium nickel-cobalt-aluminum oxide (e.g., Li(Ni 0.8 Co 0.15 Al 0.05 It may be )O2, etc., and considering the significant improvement effect resulting from controlling the type and content ratio of constituent elements forming the lithium transition metal composite oxide, the lithium transition metal composite oxide is Li(Ni 0.6 Mn 0.2 Co 0.2 )O2, Li(Ni 0.5 Mn 0.3 Co 0.2 )O2, Li(Ni 0.7 Mn 0.15 Co 0.15 )O2 or Li(Ni 0.8 Mn 0.1 Co 0.1 It may be O2, etc., and any one of these or a mixture of two or more may be used.

[0164] Meanwhile, the above-mentioned positive active material layer may optionally further include at least one of a positive conductive material and a positive binder.

[0165] The above-mentioned positive electrode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, any material that possesses electronic conductivity without causing chemical changes can be used without any particular limitations. 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, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above-mentioned positive electrode conductive material may typically be included in an amount of 1 to 30 weight%, preferably 1 to 20 weight%, and more preferably 1 to 10 weight% based on the total weight of the positive electrode active material layer.

[0166] The above-mentioned anode binder serves to improve adhesion between anode material particles and adhesion between the anode material and the anode current collector. Specific examples include fluoropolymer-based binders comprising polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); rubber-based binders comprising styrene butadiene rubber (SBR), acrylonitrile-butadiene rubber, or styrene-isoprene rubber; cellulose-based binders comprising carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, or regenerated cellulose; polyalcohol-based binders comprising polyvinyl alcohol; polyolefin-based binders comprising polyethylene or polypropylene; polyimide-based binders; and polyester-based binders. Examples include silane-based binders, and one of these alone or a mixture of two or more may be used. The anode binder may be included in an amount of 1 to 30 weight%, preferably 1 to 20 weight%, and more preferably 1 to 10 weight% based on the total weight of the anode active material layer.

[0167] According to one embodiment of the present invention, the cathode can be manufactured by applying a cathode slurry to one or both sides of a sheet-shaped cathode current collector, removing the solvent of the cathode slurry through a drying process, and then rolling. Meanwhile, a cathode including an uncoated portion can be manufactured by not applying the cathode slurry to a portion of the cathode current collector, for example, one end of the cathode current collector, when applying the cathode slurry.

[0168] The above cathode slurry can be prepared by dispersing a cathode active material in a solvent such as distilled water, ethanol, methanol, or isopropyl alcohol.

[0169] Alternatively, the cathode may be manufactured by casting the cathode slurry onto a separate support and then laminating the film obtained by peeling off from the support onto a cathode current collector.

[0170] The cathode manufactured accordingly comprises a cathode current collector; and a cathode active material layer, wherein the cathode active material layer may comprise a cathode active material.

[0171] The above-mentioned negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. The above-mentioned negative current collector may typically have a thickness of 3 to 500 μm.

[0172] In addition, the above-mentioned negative current collector, like the positive current collector, may form fine irregularities on the surface of the current collector to strengthen the bonding force of the negative active material. For example, it can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0173] The above negative electrode active material layer may be located on the negative electrode current collector, and specifically, may be located on one or both sides of the negative electrode current collector. The above negative electrode active material layer may be a single layer or a multilayer structure of two or more layers.

[0174] The thickness of the above-mentioned cathode active material layer may be 180㎛ to 200㎛, preferably 180㎛ to 190㎛, and more preferably 184㎛ to 190㎛. If the above range is satisfied, the capacity characteristics and lifespan characteristics can be improved.

[0175] The above-mentioned cathode active material may include a carbon-based active material. For example, the carbon-based active material may be one or more selected from the group consisting of amorphous, plate-like, flake-like, spherical, or fibrous natural graphite or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch-derived cokes.

[0176] Preferably, the negative electrode active material may be graphite and may include one or more selected from the group consisting of natural graphite and artificial graphite. When the negative electrode active material is included, capacity characteristics and lifespan characteristics may be improved.

[0177] The above-mentioned cathode active material may include artificial graphite and natural graphite, and in this case, the artificial graphite and natural graphite may be included in a ratio of 1:9 to 9:1, 2:8 to 8:2, 3:7 to 7:3, 4:6 to 6:4, or 5:5.

[0178] The above-mentioned negative electrode active material may be included in an amount of 90% to 99% by weight, preferably 93% to 99% by weight, and more preferably 96% to 99% by weight, based on the total weight of the negative electrode active material layer.

[0179] Meanwhile, the above-mentioned cathode active material layer may optionally further include a cathode conductive material and a cathode binder in addition to the cathode active material.

[0180] The above-mentioned cathode conductive material is used to impart conductivity to the electrode, and in the battery being constructed, it may be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. 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, carbon nanotube; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and one of these alone or a mixture of two or more may be used. The above-mentioned cathode conductive material may typically be included in an amount of 1 to 30 weight%, preferably 1 to 20 weight%, and more preferably 1 to 10 weight% based on the total weight of the cathode active material layer.

[0181] The above-mentioned cathode binder serves to improve adhesion between cathode active material particles and adhesion between the cathode active material and the cathode current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and one of these alone or a mixture of two or more may be used. The above-mentioned cathode binder may be included in an amount of 1 to 30 weight%, preferably 1 to 20 weight%, and more preferably 1 to 10 weight% based on the total weight of the cathode active material layer.

[0182] Since the thickness, porosity, and loading amount of the above-mentioned cathode are the same as those described above, a detailed explanation is omitted.

[0183] According to one embodiment of the present invention, the separator is interposed between the positive electrode and the negative electrode to separate the negative electrode and the positive electrode and to provide a pathway for the movement of lithium ions, and can be used without special limitations as long as it is used as a separator in a lithium secondary battery. Specifically, the separator may be a porous polymer film, for example, a porous polymer film made of a polyolefin-based 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 fibers, polyethylene terephthalate fibers, etc., may be used. Furthermore, a coated separator containing a ceramic component or a polymer material may be used to ensure heat resistance or mechanical strength.

[0184] Meanwhile, the above anode and cathode have a structure in which an active material layer is formed on a sheet-shaped current collector, and may include an unactive portion in which an active material layer is not formed in a part of the current collector.

[0185] As described above, by using an anode and a cathode that include a non-electrode portion, a battery structure can be implemented in which at least a portion of the non-electrode portions of the anode and cathode defines an electrode tab without having to provide a separate electrode tab.

[0186] Specifically, the above-mentioned non-current portion can be formed lengthwise along the winding direction (X) at one end of the current collector, and a current collecting plate is attached to each of the positive non-current portion and the negative non-current portion, and by connecting the current collecting plate to an electrode terminal, it can function as an electrode tab.

[0187] According to one embodiment of the present invention, the battery can may be a cylindrical battery can for accommodating the electrode assembly and the electrolyte.

[0188] The above electrode assembly may be a jelly roll wound with an anode, a separator, and a cathode laminated together.

[0189] The form factor ratio of the cylindrical lithium secondary battery according to the present invention (defined as the value obtained by dividing the diameter of the cylindrical battery by the height, i.e., the ratio of the diameter (R) to the height (H)) is the same as described above, so a detailed explanation is omitted.

[0190] The cylindrical lithium secondary battery according to the present invention may be, for example, a 46110 cell (diameter 46 mm, height 110 mm, form factor ratio 0.418), a 4875 cell (diameter 48 mm, height 75 mm, form factor ratio 0.640), a 48110 cell (diameter 48 mm, height 110 mm, form factor ratio 0.436), a 4880 cell (diameter 48 mm, height 80 mm, form factor ratio 0.600), a 4680 cell (diameter 46 mm, height 80 mm, form factor ratio 0.575), or a 4695 cell (diameter 46 mm, height 95 mm, form factor ratio 0.484). In the figures representing the form factor, the first two digits represent the diameter (R) of the lithium secondary battery, and the next two or three digits represent the height (H) of the lithium secondary battery.

[0191] According to one embodiment of the present invention, the electrolyte comprises a lithium salt and an organic solvent.

[0192] The above lithium salt can be used without special limitations as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the above lithium salt may include one or more selected from the group consisting of LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2, preferably one or more selected from the group consisting of LiPF6. The concentration of the above lithium salt may be 1.0 to 1.5 M, preferably 1.0 to 1.4 M, more preferably 1.0 to 1.3 M, and even more preferably 1.15 to 1.3 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0193] The above organic solvent may include one or more selected from the group consisting of cyclic carbonate-based organic solvents, linear carbonate-based organic solvents, linear ester-based organic solvents, and cyclic ester-based organic solvents.

[0194] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent and may include at least one organic solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate, and vinylene carbonate.

[0195] In addition, the above-mentioned linear carbonate-based organic solvent is an organic solvent having low viscosity and low dielectric constant, and as a representative example, 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 may be used, and specifically, it may include ethylmethyl carbonate (EMC).

[0196] Specific examples of the above linear ester-based organic solvent may 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.

[0197] The above-mentioned cyclic ester-based 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.

[0198] Preferably, the electrolyte according to the present invention may include ethylene carbonate and dimethyl carbonate as organic solvents.

[0199] Meanwhile, in addition to the electrolyte components, the above electrolyte may additionally include other additives for the purpose of improving the lifespan characteristics of the battery, suppressing the reduction of battery capacity, and improving the discharge capacity of the battery.

[0200] These other additives may include at least one other additive selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds different from the lithium salt contained in the electrolyte, as representative examples.

[0201] Specifically, the above other additives are vinylene carbonate (VC), vinylethylene carbonate, fluoroethylene carbonate (FEC), 1,3-propane sulfone (PS), 1,4-butane sulfone, ethene sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, 1-methyl-1,3-propene sulfone, ethylene sulfate (ESA), trimethylene sulfate (TMS), methyl trimethylene sulfate (MTMS), tetraphenyl borate, lithium oxalyl difluoroborate, succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, Examples include 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 bis-oxalate toborate (LiB(C2O4)2)) and LiBF4.

[0202] The above other additives may be included in an amount of 0.01 to 20 weight% based on the total weight of the electrolyte, and preferably in an amount of 0.05 to 5.0 weight%. If the content of the above other additives is less than 0.01 weight%, the effect of improving low-temperature output, high-temperature storage characteristics, and high-temperature life characteristics of the battery is negligible, and if the content of the above other additives exceeds 20 weight%, there is a possibility that excessive side reactions may occur within the electrolyte during charging and discharging of the battery. In particular, when the above SEI film-forming additives are added in excess, they may not decompose sufficiently at high temperatures and may remain as unreacted substances or precipitated within the electrolyte at room temperature. Accordingly, side reactions that degrade the lifespan or resistance characteristics of the secondary battery may occur.

[0203] The present invention provides a battery module including a cylindrical lithium secondary battery and a battery pack including the same according to one embodiment of the present invention.

[0204] A battery pack comprising a cylindrical lithium secondary battery according to one embodiment of the present invention is provided.

[0205] The cylindrical lithium secondary battery according to the present invention as described above can be used to manufacture a battery pack. The battery pack comprises an assembly of lithium secondary batteries electrically connected according to the present invention and a pack housing that accommodates the same, wherein the pack housing may include a busbar for electrically connecting the lithium secondary batteries, a cooling unit, an external terminal, etc. The battery pack may be mounted in 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. In particular, the lithium secondary battery according to the present invention has high energy density and excellent rapid charging performance, so it can be usefully used as a battery for an electric vehicle.

[0206] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

[0207]

[0208] Example 1

[0209] A cathode slurry was prepared by adding a cathode active material, a conductive material, and a binder to distilled water in a weight ratio of 98:0.2:1.8. In this case, graphite (synthetic graphite:natural graphite = 5:5) was used as the cathode active material, carbon nanotubes were used as the conductive material, and a cellulose-based binder was used as the binder. The cathode slurry was applied onto a copper current collector with a thickness of 8 μm, dried, and then subjected to roll pressing to manufacture a cathode containing a cathode active material layer. At this time, the thickness of the cathode was 190 μm, and the loading amount was 0.35 g / 25 cm 2 The porosity was 26.1% and the curvature was 2.44. The porosity and curvature of the above-mentioned cathode active material layer are listed in Table 1.

[0210] A positive electrode slurry was prepared by adding a positive electrode active material, a conductive material, and a binder to N-methylpyrrolidone in a weight ratio of 98:0.5:1.5. At this time, lithium nickel-cobalt-manganese oxide was used as the positive electrode active material, carbon nanotubes were used as the conductive material, and PVDF was used as the binder. The positive electrode slurry was coated onto an aluminum current collector, dried, and then roll-pressed to produce a positive electrode.

[0211] A jellyroll-type electrode assembly was manufactured by stacking the anode and cathode prepared as described above in the order of separator / anode / separator / cathode and then winding them.

[0212] The electrolyte was prepared by adding LiPF6 at a molar concentration of 1.25 M to an organic solvent mixed with ethylene carbonate (EC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC) in a weight ratio of 2:7:1.

[0213] After inserting the above electrode assembly into a cylindrical battery can, 25.7 mL of the above electrolyte was injected to manufacture 4680 cells as a cylindrical lithium secondary battery.

[0214] In the above Equation 1, the diameter (R) and the height (h) of the cylindrical lithium secondary battery are measured through the external appearance of the cell, the porosity is calculated by Equation 1-1 through the thickness and loading amount of the electrode, and the curvature is calculated by Equations 2 and 3.

[0215]

[0216] Example 2

[0217] A cathode and a cylindrical lithium secondary battery were manufactured in the same manner as in Example 1 above, except that the porosity of the cathode was 25.8% and the curvature was 2.27.

[0218]

[0219] Comparative Example 1

[0220] A negative electrode and a lithium secondary battery were manufactured in the same manner as in 1 above, except that the porosity of the negative electrode active material layer was 25.1% and the curvature was 3.42.

[0221] In particular, artificial graphite with a higher degree of orientation compared to Example 1 was used, or the D50 particle size was adjusted to increase the tortuosity inside the pores of the cathode active material layer.

[0222]

[0223] Comparative Example 2

[0224] A negative electrode and a lithium secondary battery were manufactured in the same manner as in Example 1 above, except that the porosity of the negative electrode active material layer was 24.8% and the curvature was 3.22.

[0225] In particular, artificial graphite with a higher degree of orientation compared to Example 1 was used, or the D50 particle size was adjusted to increase the tortuosity inside the pores of the cathode active material layer.

[0226]

[0227] Comparative Example 3

[0228] A negative electrode and a lithium secondary battery were manufactured in the same manner as in Example 1 above, except that graphite (artificial graphite: natural graphite = 4:6) was used as the negative electrode active material, the porosity of the negative electrode active material layer was 25.6%, and the curvature was 3.85.

[0229] In particular, the tortuosity inside the pores of the negative electrode active material layer was controlled to be high by adjusting the ratio of natural graphite to be higher compared to Example 1 above.

[0230]

[0231] Comparative Example 4

[0232] A negative electrode and a lithium secondary battery were manufactured in the same manner as in Example 1 above, except that graphite (synthetic graphite: natural graphite = 3:7) was used as the negative electrode active material, the porosity of the negative electrode active material layer was 24.7%, and the curvature was 4.3.

[0233] In particular, the tortuosity inside the pores of the negative electrode active material layer was controlled to be high by adjusting the ratio of natural graphite to be higher compared to Example 1 above.

[0234]

[0235] Comparative Example 5

[0236] A negative electrode and a lithium secondary battery were manufactured in the same manner as in Example 1 above, except that the porosity of the negative electrode active material layer was 25.9% and the curvature was 4.27.

[0237]

[0238] Comparative Example 6

[0239] A cathode and a lithium secondary battery were manufactured in the same manner as in Example 1 above, except that the porosity of the cathode was 26.1% and the curvature was 4.3.

[0240]

[0241] The characteristics of the cylindrical lithium secondary batteries prepared in Examples 1 to 2 and Comparative Examples 1 to 6, the P value represented by Formula 1 below, and the energy retention rate are shown in Table 1 and Figure 1 below.

[0242]

[0243] The composition of the cathode and the porosity of the cathode active material layer prepared in Examples 1 to 2 and Comparative Examples 1 to 6 above and the tortuosity inside the pores of the negative electrode active material layer are listed in Table 2. In addition, Figure 3 shows T, which is the tortuosity inside the pores of the negative electrode active material layer according to one embodiment and a comparative state of the present invention. anode This is a diagram representing .

[0244]

[0245] R (mm)h (mm)P anode (%)T anode PEnergy retention (%) Example 1: 468026.12.446.1592.8 Example 2: 468025.82.276.5491.6 Comparative Example 1: 1468025.13.424.2284.5 Comparative Example 2: 2468024.83.224.4284.6 Comparative Example 3: 3468025.63.853.8274.7 Comparative Example 4: 468024.74.33.3050.5 Comparative Example 5: 468025.94.273.4974.3 Comparative Example 6: 468026.14.33.4974.0

[0246] Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Porosity (%) 26.1 25.8 25.1 24.8 25.6 24.7 25.9 26.1R pore 18.917.926.7525.830.434.734.934.3R th7.757.887.8287.898.078.178Tortuosity2.442.273.423.223.854.304.274.30

[0247]

[0248] Experimental Example 1: Evaluation of whether lithium plating occurs during rapid charging

[0249] Each cell prepared in the above examples and comparative examples was charged in CC / CV mode at 40°C with a constant current (CC) of 1.0C until it reached 4.2V (cut-off current 0.05C), and then discharged in CC mode with a constant current (CC) of 1.0C until it reached 2.5V. The above charging and discharging process was defined as one cycle, and after repeating the charging and discharging up to 100 cycles, the 4680 cells were disassembled and the electrode assembly separated to visually check for the occurrence of lithium plating on the surface of the negative electrode. The results are shown in Table 3 below.

[0250] - O: Lithium plating occurred.

[0251] - X: No lithium plating occurs.

[0252]

[0253] Whether lithium plating occurs Example 1X Example 2X Comparative Example 10 Comparative Example 20 Comparative Example 30 Comparative Example 40 Comparative Example 50 Comparative Example 60

[0254]

[0255] Experimental Example 2: Rapid Charge Life Characteristics

[0256] Each cell manufactured in the above examples and comparative examples was charged in CC / CV mode at 20°C with a constant current (CC) of 1.0C until it reached 4.2V (cut-off current 0.05C), and then discharged in CC mode with a constant current (CC) of 1.0C until it reached 2.5V. The above charging and discharging process was defined as one cycle, and after repeating the charging and discharging up to 100 cycles, the capacity retention rate was measured and recorded in Table 1 above.

[0257] According to Table 1 above, the characteristics of the cylindrical lithium secondary battery manufactured according to Examples 1 and 2, such as the diameter (R) and height (h) of the cylindrical lithium secondary battery, and the porosity of the negative electrode active material layer And the tortuosity inside the pores satisfies the P value of Equation 1 above being 5 or higher, so it was possible to predict that the rapid charging performance of the cylindrical lithium secondary battery is excellent.

[0258] In addition, the cylindrical lithium secondary battery showed a capacity retention rate (%) of 89% or higher after 100 cycles of charging and discharging at 20°C at a 1C-rate, confirming that the rapid charging performance of the cylindrical lithium secondary battery is excellent.

[0259] In the above example, even if the movement of lithium ions is restricted due to an overvoltage applied to the negative electrode during rapid charging caused by a high current density, the porosity of the negative electrode active material layer is larger and the curvature is lower compared to the comparative example, allowing lithium ions to be inserted into the interior of the negative electrode active material layer, thereby improving side reactions such as lithium deposition on the electrode surface according to Table 3 and improving rapid charging life characteristics.

[0260] On the other hand, characteristics of the cylindrical lithium secondary battery manufactured according to Comparative Examples 1 to 6, e.g., the diameter (R) and height (h) of the cylindrical lithium secondary battery, and the porosity of the negative electrode active material layer And since the tortuosity inside the pores does not satisfy the P value of Equation 1 above of 5 or more, it was predicted that the rapid charging performance of the cylindrical lithium secondary battery would not be improved.

[0261] In addition, the capacity retention rate (%) of the cylindrical lithium secondary battery was less than 89% after 100 cycles of charging and discharging at 20°C at a 1C-rate, confirming that the rapid charging performance of the cylindrical lithium secondary battery was inferior to that of the example, and it was confirmed that side reactions such as lithium precipitation occurred on the electrode surface according to Table 3.

[0262] In addition, in the case of Comparative Examples 1 to 6, it was confirmed that even if they had similar internal pore curvature, the rapid charging performance was much inferior when the porosity of the cathode was small.

[0263] Furthermore, when comparing Comparative Examples 4 and 6 above, it can be confirmed that even if the curvature of the negative electrode active material layer is similar, the rapid charging performance is inferior when the porosity is small, and when comparing Example 1 and Comparative Example 1 above, it can be confirmed that even if the porosity of the negative electrode active material layer is similar, the rapid charging performance is improved when the curvature is small.

[0264] Comparative Examples 1 and 2 increased the orientation index (OI) or decreased the D50 particle size compared to the artificial graphite of Example 1, thereby controlling the tortuosity inside the pores of the cathode active material layer to be higher than that of Example 1. The orientation index is an indicator representing the degree of crystallographic orientation of graphite particles; the higher the orientation index, the more the (002) crystal planes of the graphite are arranged parallel to the electrode surface, thereby restricting the ion transport pathway. The D50 particle size is the median particle size corresponding to 50% of the cumulative volume in the particle size distribution, and the smaller the D50 particle size, the more complex the inter-particle pore structure becomes, thereby increasing the tortuosity.

[0265] Comparative Examples 3 and 4 controlled the tortuosity inside the pores of the cathode active material layer to be higher by adjusting the ratio of natural graphite to be higher compared to Example 1.

[0266] That is, natural graphite has a plate-like structure with high orientation, so the lithium ion movement path is restricted in the horizontal direction, and due to the complex stacking structure, particles are stacked layer upon layer to form serpentine pores, and the actual path for ion movement through the narrow and complex pores is longer than the straight distance, and surface contact forms a more restricted ion channel compared to the point contact of artificial graphite, so the curvature of the negative electrode active material layer is increased by increasing the ratio of natural graphite compared to Example 1.

[0267] Therefore, it was found that when the porosity of the negative electrode active material layer is large and the curvature is low, lithium ions can be inserted into the interior of the negative electrode active material layer, thereby improving side reactions such as lithium precipitation on the electrode surface and improving rapid charging life characteristics, and it was confirmed that by controlling P in Equation 1 above, lithium precipitation and rapid charging life characteristics can be predicted and improved.

Claims

1. A method for predicting the rapid charging performance of a cylindrical lithium secondary battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte, wherein The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode A method for predicting the rapid charging performance of a cylindrical lithium secondary battery, comprising the step of verifying the rapid charging performance of the cylindrical lithium secondary battery using 2. In Claim 1, The step of verifying the rapid charging performance of the above-mentioned cylindrical lithium secondary battery is T, which is the tortuosity inside the pores of the above-mentioned negative electrode active material layer. anode P, which is the porosity of the above-mentioned cathode active material layer for . anode A method for predicting the rapid charging performance of a cylindrical lithium secondary battery using the ratio of 3. In Claim 1, The step of verifying the rapid charging performance of the above-mentioned cylindrical lithium secondary battery involves the diameter (R) of the above-mentioned cylindrical lithium secondary battery, the height (h) of the above-mentioned cylindrical lithium secondary battery, and P, which is the porosity of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode A method for predicting the rapid charging performance of a cylindrical lithium secondary battery, comprising the step of checking whether the P value of the following Equation 1, which includes , satisfies 5 or more. [Equation 1] 4. In Claim 1, The above T anode is calculated using the following Equations 2 and 3, and The above T anode A method for predicting the rapid charging performance of a cylindrical lithium secondary battery, comprising the step of checking whether is 2 or more and 3 or less: [Equation 2] [Equation 3] In the above Equation 2, the R pore is a value measured from EIS analysis, and the above R th is calculated from Equation 3, and In the above Equation 3, d is the thickness of the negative electrode active material layer, A is the surface area of ​​the negative electrode active material layer, and P anode is the porosity of the above-mentioned negative electrode active material layer, and σ is the conductivity of lithium ions in the above-mentioned electrolyte.

5. In Claim 3, A method for predicting the rapid charging performance of a cylindrical lithium secondary battery, comprising the step of checking whether the P value of the above Equation 1 is 6 or higher and 8 or lower.

6. In Claim 1, The above P anode A method for predicting the rapid charging performance of a cylindrical lithium secondary battery, wherein (%) is 25% or more and 27% or less.

7. In Claim 3, A method for predicting the rapid charging performance of a cylindrical lithium secondary battery, wherein the cylindrical lithium secondary battery satisfying the P value of Equation 1 above of 5 or more has a capacity retention rate (%) of 89% or more after 100 cycles of charging and discharging at 20°C at a 1C-rate.

8. A cylindrical lithium secondary battery comprising a positive electrode, a separator, a negative electrode, and an electrolyte, The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer. anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode A cylindrical lithium secondary battery satisfying a P value of 5 or more in the following Formula 1 containing [Equation 1] 9. In Claim 8, The above T anode is calculated using the following Equations 2 and 3, and The above T anode Cylindrical lithium secondary battery with a value of 2 or more and 3 or less: [Equation 2] [Equation 3] In the above Equation 2, the R pore is a value measured from EIS analysis, and the above R th is calculated from Equation 3, and In the above Equation 3, d is the thickness of the negative electrode active material layer, A is the surface area of ​​the negative electrode active material layer, and P anode is the porosity of the above-mentioned negative electrode active material layer, and σ is the conductivity of lithium ions in the above-mentioned electrolyte.

10. In Claim 8, A cylindrical lithium secondary battery in which the P value of the above Equation 1 is 6 or more and 8 or less.

11. In Claim 8, The above P anode A cylindrical lithium secondary battery in which (%) is 25% or more and 27% or less.

12. In claim 8, The above cylindrical lithium secondary battery is a cylindrical lithium secondary battery having a capacity retention rate (%) of 89% or more after 100 cycles of charging and discharging at 20°C at a 1C-rate.

13. In claim 8, A cylindrical lithium secondary battery having an initial resistance (DC-IR) of 4.1 mΩ to 4.5 mΩ at SOC 50%.

14. A battery module comprising a cylindrical lithium secondary battery according to any one of claims 8 to 13.

15. A battery pack comprising a cylindrical lithium secondary battery according to any one of claims 8 to 13.

16. A battery pack comprising a battery module according to claim 14.

17. A step of manufacturing a jelly roll wound with an anode, a separator, and a cathode laminated; and The method comprises the step of manufacturing a cylindrical lithium secondary battery that includes housing the above-mentioned jelly roll in a battery can, providing an electrolyte, and including a sealing body that seals the above-mentioned battery can. The above cathode comprises a cathode current collector; and a cathode active material layer provided on at least one surface of the cathode current collector, and The diameter (R) of the cylindrical lithium secondary battery, the height (h) of the cylindrical lithium secondary battery, and the porosity P of the negative electrode active material layer anode and T, which is the tortuosity inside the pores of the cathode active material layer. anode A method for manufacturing a cylindrical lithium secondary battery according to any one of claims 8 to 13, comprising the step of designing such that the P value of the following formula 1, including , satisfies 5 or more. [Equation 1]

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