Secondary battery and charging method thereof

Abstract

The present invention may provide a secondary battery and a charging method thereof, wherein the maximum charging rate (C) of the secondary battery, the average particle size (m) of a negative electrode active material, the diffusivity (m2 / s) of the negative electrode active material, and the porosity of the negative electrode active material satisfy specific conditions such that the secondary battery has an excellent capacity retention rate and undergoes minimal battery life degradation during rapid charging, and the charging rate of the secondary battery when charging at a relatively low maximum charging rate is equivalent to the charging rate when charging at a high maximum charging rate.

Description

Secondary battery and charging method thereof

[0001] The present invention relates to a secondary battery and a method for charging the same. The present application claims the benefit of priority based on Korean Patent Application No. 10-2024-0187147 filed on December 16, 2024, and all contents disclosed in the document of said Korean patent application are incorporated herein as part of the specification.

[0002] With the advancement of portable electronic devices such as mobile phones and laptop computers, the demand for secondary batteries as an energy source is rapidly increasing. Recently, the use of secondary batteries as power sources for hybrid electric vehicles (HEVs) and electric vehicles (EVs) has become a reality. Accordingly, extensive research is being conducted on secondary batteries capable of meeting various requirements, and in particular, there is a rising trend in demand for lithium secondary batteries that possess high energy density, high discharge voltage, and high output.

[0003] Since these secondary batteries can be recharged and used continuously even after discharge, and thus exhibit performance differences depending on the charge / discharge state, efforts are underway to improve the performance of secondary batteries by improving charging methods.

[0004] However, when a battery is rapidly charged at a high charging speed of 5C or higher, lifespan characteristics such as capacity retention rate are degraded, so there is a need to develop a secondary battery and a charging method that can maintain lifespan characteristics while keeping the charging time short.

[0005] The present invention aims to solve the above problem by providing a secondary battery having a substantial charging speed and excellent lifespan characteristics, and a charging method thereof.

[0006] The present invention relates to a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode comprises a negative electrode active material layer comprising a negative electrode active material and satisfies the following [Equation 1]:

[0007] [Equation 1]

[0008] C max 3 ·R 2 / (D·(P-0.25)) ≤ 5×10 6 [C 3 · s]

[0009] In Equation 1, C max ε is the maximum charging speed (C) of the secondary battery, R is the average particle size (m) of the negative electrode active material, and D is the diffusivity (m) of the negative electrode active material. 2 / s), P is the porosity of the cathode active material, and P > 0.25.

[0010] In one embodiment, the above C max It can be characterized as being smaller than 5C.

[0011] In one embodiment, the above P may be characterized as being 0.4 or less.

[0012] In one embodiment, R is 1×10 -6 m to 2×10 -5 It can be characterized as being m.

[0013] In one embodiment, D is 1.0×10 -15 m 2 / s to 1.0×10 -13 m 2 It can be characterized as being / s.

[0014] In one embodiment, the cathode active material may be characterized by including a carbonaceous material.

[0015] In one embodiment, the negative electrode active material may further comprise a silicon compound, and the silicon compound may be characterized as being included in an amount of 20 weight% or less relative to the total negative electrode active material.

[0016] In one embodiment, the cathode active material layer further comprises a conductive material, wherein the conductive material comprises one or more selected from the group consisting of graphite such as natural graphite or artificial graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber, and the conductive material may be characterized in that it is included in an amount of 10 weight% or less relative to the entire cathode active material layer.

[0017] In one embodiment, the negative electrode active material layer may further comprise a binder, wherein the binder comprises an aqueous binder, and the binder may be characterized in that it is included in an amount of 10 weight% or less relative to the entire negative electrode active material layer.

[0018] In one embodiment, the positive electrode may be characterized by comprising a positive electrode active material layer comprising a positive electrode active material, and the positive electrode active material may comprise a lithium nickel-based oxide.

[0019] In one embodiment, the anode may be characterized by including an anode active material, and the porosity of the anode active material may be 0.15 to 0.4.

[0020] In one embodiment, the secondary battery further comprises a separator, and the separator may be characterized by comprising one or more selected from the group consisting of ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer.

[0021] The present invention also provides a method for charging a secondary battery satisfying the following [Equation 1], wherein the method includes a fast charging process in at least a part of the total charging process, and the fast charging process in at least a part C max The present invention relates to a method for charging a secondary battery characterized by including a charging section at a charging speed:

[0022] [Equation 1]

[0023] C max 3·R 2 / (D·(P-0.25)) ≤ 5×10 6 [C 3 · s]

[0024] In Equation 1, C max ε is the maximum charging speed (C) of the secondary battery, R is the average particle size (m) of the negative electrode active material, and D is the diffusivity (m) of the negative electrode active material. 2 / s), P is the porosity of the cathode active material, and P > 0.25.

[0025] In one embodiment, the method of charging the secondary battery has a charging speed of C during the entire charging process. max It can be characterized by not exceeding.

[0026] In one embodiment, the method of charging a secondary battery is the above C max After charging at a certain speed, the secondary battery can be charged by reducing the charging speed by a specific amount over time.

[0027] The present invention can provide a secondary battery and a charging method thereof that, even when charging at a relatively low maximum charging speed, has a charging speed equivalent to that of charging at a high maximum charging speed, has an excellent capacity retention rate, and minimizes the degradation of battery life that occurs during rapid charging.

[0028] Figures 1 and 2 are graphs showing the anode voltage according to the state of charge (SoC) when charged to 5C and 3.2C, respectively.

[0029] Figure 3 is a graph showing the results of measuring the state of charge (SoC) at which the cathode potential reaches 0V while varying the charging speed (decreasing from 5C to 0.8C in increments of 0.2C).

[0030] Figures 4 to 6 are graphs showing the capacity retention rate according to the cycle for the examples and comparative examples.

[0031] Terms and words used in this specification and claims shall not be interpreted as being limited to their ordinary or dictionary meanings, but shall 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.

[0032] Therefore, the configurations of the embodiments described in this specification are merely one of the most preferred embodiments of the present invention and do not represent all of the technical ideas of the present invention; thus, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application. In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0033] In this specification, when a part is described as “comprising” a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Thus, for example, a composition comprising compound A may include compounds other than A. However, the term “comprising” also encompasses, in a more restrictive sense as a specific embodiment thereof, “essentially / essentially composed of” and “composed of,” so, for example, a “composition comprising compound A” may also be (essentially / essentially) composed of compound A.

[0034] In connection with this, terms such as “comprising” or “having,” as described in this specification, are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should not be understood as precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0035] In this specification, when any member is described as being located “on” another arbitrary member, this includes not only cases where such member is in contact with another member, but also cases where another member or material exists between the two members.

[0036] Where in this specification a quantity, concentration, or other value or parameter is given as an enumeration of a range, a preferred range, a preferred upper limit, and a preferred lower limit, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether the range is disclosed separately, specifically discloses all ranges that may be formed. Where a range of numerical values ​​is mentioned in this specification, unless otherwise stated, for example, without limiting terms such as greater than or less than, the range is intended to include its endpoint value and all integers and fractions within that range. The scope of the invention is not intended to be limited to the specific value mentioned when defining the range.

[0037] Among the physical properties mentioned in this specification, if the measured temperature affects the property, the property is measured at room temperature unless specifically otherwise specified. The term "room temperature" refers to a natural temperature that has not been heated or cooled, and may mean, for example, any temperature within the range of about 10°C to 30°C, about 23°C, or about 25°C. Furthermore, unless specifically otherwise specified, the unit of temperature in this specification is °C.

[0038] In addition, among the physical properties mentioned in this specification, if the measured pressure affects the physical property, unless otherwise specifically defined, the physical property is measured at atmospheric pressure, that is, at about 1 atmosphere.

[0039] The first aspect of the present invention relates to a secondary battery.

[0040] The present invention is a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode may comprise a negative electrode active material layer comprising a negative electrode active material and may be characterized by satisfying the following [Equation 1]:

[0041] [Equation 1]

[0042] C max 3 ·R 2 / (D·(P-0.25)) ≤ 5×10 6 [C 3 · s]

[0043] In Equation 1, C max ε is the maximum charging speed (C) of the secondary battery, R is the average particle size (m) of the negative electrode active material, and D is the diffusivity (m) of the negative electrode active material. 2 / s) and P is the porosity of the cathode active material, and P > 0.25.

[0044] Equation 1 above, for example, is based on the trend according to the charging speed of the State of Charge (SoC) where the negative potential drops below 0V during charging, and represents the maximum charging speed (C max After confirming that it is possible to determine the charge state, it was derived by focusing on the fact that the tendency of this charge state is related to the characteristics of the cathode active material, specifically porosity (P), diffusivity (D), and average particle size (R).

[0045] Specifically, when charging a secondary battery, the slower the charging speed, the more the negative electrode potential drops below 0V after being charged (at a higher charge state). In this regard, a three-electrode assembly manufactured by the same method as Example 1 described below was charged while maintaining speeds of 3.2C and 5C, and the negative electrode potential (Anode Voltage, V) according to the charge state (SoC, %) was measured, and the results are shown in FIGS. 1 and 2. Referring to FIGS. 1 and 2, it was confirmed that when charged at 5C, the negative electrode potential reached 0V at approximately 19% of the charge state (SoC) (see FIG. 1), whereas when charged at 3.2C, the negative electrode potential reached 0V at approximately 56% of the charge state (SoC) (see FIG. 2).

[0046] As such, the state of charge where the cathode potential drops below 0V appears at a higher position as the charging speed decreases, and this state of charge increases particularly rapidly in specific charging speed ranges. In this regard, for a three-electrode assembly manufactured by the same method as Example 1 described below, the state of charge (SoC) at which the cathode potential reaches 0V was measured while varying the charging speed (decreasing from 5C to 0.8C in increments of 0.2C), and the results are shown in FIG. 3. Referring to FIG. 3, it can be confirmed that a significant gap occurred between 3.2C and 3.4C. That is, when charged at 3.2C, the lithium plating phenomenon begins to occur at a significantly higher state of charge (SoC) compared to when charged at a speed of 3.4C. As a result, when charging at a maximum charging speed of 3.4C or higher, the process of lowering the charging speed to prevent lithium plating occurs is carried out starting from a relatively low charge state, so as a result, the time required to fully charge the secondary battery does not differ significantly from charging at a maximum charging speed of 3.2C.

[0047] Meanwhile, based on the trend of charging speed in a charging state where the negative electrode potential drops below 0V, it was confirmed that by setting the maximum charging speed based on the interval where a deviation in charging speed occurs, a secondary battery with excellent capacity retention rate while minimizing charging time can be obtained, and thus the present invention was completed. This will be described in the examples below.

[0048] The secondary battery of the present invention is, for example, the above C max The secondary battery may be characterized in that the negative electrode potential does not drop below 0 V while charging at a charging rate below. Since lithium plating begins when the negative electrode potential of the secondary battery drops below 0 V, it is necessary to reduce the charging rate continuously or discontinuously during the charging process to prevent this. Therefore, the secondary battery of the present invention, for example, C max Even if charging is started at a charging speed, it is necessary to lower the charging speed to prevent the negative potential of the secondary battery from dropping below 0V, which may lead to an increase in charging time.

[0049] The above C max It may be characterized as being smaller than, for example, 5C. In this specification, the term "maximum charging speed (C)" max )」 refers to the maximum value of the charging speed (C) during the process of charging the secondary battery to a fully charged state. The above C max It can be designed differently depending on the characteristics (R, D, and / or P) of the negative electrode active material included in the manufactured secondary battery. The present invention is particularly the above C max Under conditions where rapid charging is possible with α being 1C or higher, the characteristics of the negative electrode active material and C max It is significant that it was confirmed that by controlling the relationship between them as shown in Equation 1 above, a secondary battery with excellent capacity retention rate and reduced charging time can be provided.

[0050] The above P (porosity) may be, for example, 0.4 or less. In other examples, the above P may be 0.4 or less, 0.39 or less, 0.38 or less, 0.37 or less, 0.36 or less, or 0.35 or less, or greater than 0.25. The secondary battery of the present invention can sufficiently secure the energy density of the secondary battery by maintaining the porosity of the negative electrode active material included in the negative electrode within the above range. The term "porosity (P) of the negative electrode active material" as used in this specification refers to the ratio of the volume of pores to the total volume of the negative electrode active material. The above P may be measured, for example, by measuring the volume V and weight W of the negative electrode active material and substituting them into the formula porosity = W / (d×V) together with the density value d, but is not limited thereto.

[0051] The above R (average particle size) is, for example, 1×10 -6 m to 2×10 -5 It can be characterized as being m. In other examples, the above R is 1.5×10 -6 m or more, 2×10 -6 m or more, 2.5×10 -6 m or more, 3×10 -6 m or more, 4×10 -6 m or more, 5×10 -6 m or more, 6×10 -6 m or more or 7×10 -6 m or more, or 1.9×10 -5 m or less, 1.8×10 -5 m or less, 1.7×10 -5 m or less, 1.6×10 -5 m or less or 1.5×10 -5It may be less than or equal to m. The secondary battery of the present invention can prevent side reactions during charging and discharging while maintaining kinetic properties by maintaining the average particle size of the negative electrode active material contained in the negative electrode within the above-mentioned range, thereby allowing the particles to have an appropriate specific surface area. As used herein, the term "average particle size" refers to the particle size at the 50% reference of the volume-cumulative particle size distribution of the particles constituting the negative electrode active material. The above R may be measured, for example, by photographing a cross- section of the negative electrode active material using a scanning electron microscope (SEM) or by a method such as laser diffraction, but is not limited thereto.

[0052] The above D (diffusivity of the negative electrode active material) is, for example, 1.0 × 10⁻⁶ -15 m 2 / s to 1.0×10 -13 m 2 It may be characterized as being / s. As used herein, the term "porosity" refers to the diffusion coefficient according to Fick's law of diffusion. In other examples, D is 1.1 × 10⁻⁶. -15 m 2 / s or more, 1.2 ×10 -15 m 2 / s or more, 1.3 ×10 -15 m 2 / s or more, 1.4 ×10 -15 m 2 / s or more or 1.5 ×10 -15 m 2 / s or more or 9.5 ×10 -14 m 2 / s or less, 9 ×10 -14 m 2 / s or less, 8.5 ×10 -14 m 2 / s or less, 8×10 -14 m 2 / s or less, 7.5×10 -14 m 2 / s or less, 7×10 -14 m 2 / s or less, 6.5×10 -14 m2 / s or less, 6×10 -14 m 2 / s or less, 5.5×10 -14 m 2 / s or less, 5×10 -14 m 2 / s or less, 4.5×10 -14 m 2 / s or less, 4×10 -14 m 2 / s or less, 3.5×10 -14 m 2 / s or less, 3×10 -14 m 2 / s or less, 2.5×10 -14 m 2 / s or less or 2×10 -14 m 2 It may be less than / s. By maintaining the diffusivity of the negative electrode active material included in the negative electrode within the above range, the secondary battery of the present invention can prevent the phenomenon in which charging and discharging end prematurely due to the restriction of diffusion, and can control the charging and discharging time of the secondary battery within a certain range. The above D may be measured, for example, by the pulsed differential rotational reflection ("PGSE") lithium NMR method, but is not limited thereto.

[0053] As the above-mentioned negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. The above-mentioned negative electrode active material may include, for example, a carbonaceous material. The above-mentioned carbonaceous material may be, for example, artificial graphite, natural graphite, graphitized carbon fiber, or amorphous carbon. As for the carbonaceous material, for example, both low-crystallinity carbon and high-crystallinity carbon may be used. Representative examples of low-crystallinity carbon include soft carbon and hard carbon, while representative examples of high-crystallinity carbon include amorphous, plate-like, flake-like, spherical, or fibrous natural or artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch-derived cokes. The above-described negative electrode active material may also be characterized by including, for example, amorphous carbon. The negative electrode active material of the present invention may include at least one of the aforementioned examples.

[0054] The above-mentioned negative electrode active material may be characterized by not including, for example, a silicon compound. The above-mentioned negative electrode active material may be composed solely of a carbonaceous material, for example. The meaning of the above-mentioned negative electrode active material being composed solely of a carbonaceous material may mean that the negative electrode active material is substantially composed solely of a carbonaceous material. The fact that the negative electrode active material is substantially composed solely of a carbonaceous material may mean, for example, that the content of the carbonaceous material in the negative electrode active material is 99 weight percent or more. By using a negative electrode active material composed solely of a carbonaceous material, it is possible to prevent the degradation of the secondary battery due to silicon degradation and to provide a negative electrode with low thickness expansion.

[0055] In other examples, the above-mentioned negative electrode active material may be characterized by further including a silicon compound. The silicon compound may include, for example, one or more of a Si-C composite or a Si-O composite. The silicon compound may be included, for example, in an amount of 20 weight% or less relative to the total negative electrode active material. By further including a silicon compound in the negative electrode active material and / or maintaining the content of the silicon compound within the above range, a secondary battery with further improved energy density and enhanced metal charging characteristics can be provided.

[0056] The above-mentioned negative electrode active material may be included in an amount of 80 to 99 weight%, 85 to 99 weight%, or 90 to 99 weight% based on the total weight of the negative electrode active material layer.

[0057] The above-mentioned negative electrode active material layer may additionally include, for example, a conductive material and / or a binder. The conductive material is used to impart conductivity to the electrode and, in the battery being constructed, can be used without special limitations as long as it possesses electronic conductivity without causing chemical changes. The conductive material may include one or more selected from the group consisting of, for example, 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, and carbon fibers; metal powder or metal fibers such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. Preferably, for the sake of ensuring excellent conductivity, the conductive material is, for example, graphite such as natural graphite or artificial graphite; It may include one or more selected from the group consisting of carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber. The conductive material may be included, for example, in an amount of 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, or 5 wt% or less with respect to the entire cathode active material layer.

[0058] The above binder serves to improve adhesion between the negative electrode active material particles and adhesion between the negative electrode active material and the negative electrode current collector. The above binder may be, for example, a water-based binder. Specific examples of the above water-based binder include an acrylic binder comprising poly(meth)acrylic acid, poly(meth)acrylamide, acrylamide-acrylic acid copolymer, and polyacrylonitrile; a cellulose binder comprising carboxymethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose, hydroxypropylmethyl cellulose, nitrocellulose, and diethylaminoethyl cellulose; a rubber binder comprising styrene-butadiene rubber, acrylonitrile-butadiene, acrylonitrile-butadiene-styrene rubber, butyl rubber, fluororubber, and acrylic rubber; or a mixture thereof, and one of these alone or a mixture of two or more may be used. The above binder may be included, for example, in an amount of 10 weight% or less, 9 weight% or less, 8 weight% or less, 7 weight% or less, 6 weight% or less, or 5 weight% or less with respect to the entire negative electrode active material layer.

[0059] The above cathode may additionally include, for example, a dispersant. The dispersant may be an aqueous dispersant such as carboxymethylcellulose (CMC), polyacrylic acid (PAA), polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), or polyoxyethylene (POE), or an organic dispersant such as N-methyl-2-pyrrolidone or polyvinylpyrrolidone (PVP).

[0060] The above-mentioned cathode may additionally include, for example, other additives. As for the additives, known additives that can be introduced into a secondary battery may be used without limitation, provided that they do not impede the purpose of the present invention.

[0061] The above cathode may further include, for example, a cathode current collector. The above cathode may include, for example, a cathode current collector; and a cathode active material layer comprising the aforementioned cathode active material, binder, conductive material, dispersant and / or additive, etc., on at least one surface of the cathode current collector.

[0062] The above-mentioned negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used. In addition, the above-mentioned negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to strengthen the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0063] The cathode of the present invention may include a cathode active material layer comprising a cathode active material. The cathode active material may be characterized by including a lithium transition metal oxide. As the cathode active material, cathode active materials generally used in the relevant technical field may be used. The cathode active material may be, for example, lithium transition metal oxides such as lithium cobalt oxide (LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese oxide (NCM), lithium manganate, and lithium iron phosphate, nickel sulfide, copper sulfide, lithium sulfide, iron oxide, or vanadium oxide, but is not limited thereto; any material used as a cathode active material in the relevant technical field may be used. The cathode active material may be used individually or in a mixture of two or more types.

[0064] The above-mentioned positive electrode active material may include a lithium nickel-based oxide represented by the following [Chemical Formula 1].

[0065] [Chemical Formula 1]

[0066] Li a Ni b Co c M 1 d M 2 e O2

[0067] In the above chemical formula 1, M 1 can be Mn, Al, or a combination thereof. The above M 1 It can be Mn or Mn and Al.

[0068] The above M 2 may be one or more selected from the group consisting of Zr, W, Y, Ba, Ca, Ti, Mg, Ta, and Nb. The above M 2 may be one or more selected from the group consisting of Zr, Y, Mg, and Ti. The above M 2 can be Zr, Y, or a combination thereof. M 2　 Although the element is not necessarily included, if included in an appropriate amount, it can play a role in promoting grain growth during sintering or improving crystal structure stability.

[0069] 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.

[0070] The above b represents the molar ratio of nickel among the total metals excluding lithium in the lithium nickel-based oxide, and may be 0.5≤b<1 or 0.6≤b<1. When the molar ratio of nickel satisfies the above range, it exhibits high energy density, making it possible to realize high capacity.

[0071] The above c represents the molar ratio of cobalt among the total metals excluding lithium in the lithium nickel-based oxide, where 0 <c<0.3, 0<c<0.25 또는 0.01≤c≤0.2일 수 있다. 코발트의 몰비가 상기 범위를 만족할 때, 양호한 저항 특성 및 출력 특성을 구현할 수 있다.

[0072] The above d is M among the total metals excluding lithium in the lithium nickel-based oxide. 1 Representing the molar ratio of elements, 0 <d<0.3, 0<d<0.25 또는 0.01≤d≤0.2일 수 있다. M 1 When the molar ratio of the elements satisfies the above range, the structural stability of the cathode active material is excellent.

[0073] The above e is M among the total metals excluding lithium in the lithium nickel-based oxide. 2 It represents the molar ratio of the elements, which can be 0≤e≤0.1 or 0≤e≤0.05.

[0074] The above-described cathode active material may further include a coating layer on the surface of the above-described lithium nickel-based oxide particles comprising one or more coating elements selected from the group consisting of Al, Ti, W, B, F, P, Mg, Ni, Co, Fe, Cr, V, Cu, Ca, Zn, Zr, Nb, Mo, Sr, Sb, Bi, Si, and S. The coating element may be Al, B, Co, or a combination thereof. The coating element may be B.

[0075] When a coating layer is present on the surface of lithium nickel-based oxide particles, contact between the electrolyte and the lithium complex transition metal oxide is inhibited by the coating layer, thereby reducing the leaching of transition metals or gas generation caused by side reactions with the electrolyte.

[0076] The above-mentioned positive active material may be included in an amount of 80 to 99 weight%, 85 to 99 weight%, or 90 to 99 weight% based on the total weight of the positive active material layer.

[0077] The above-mentioned positive electrode active material is not particularly limited in its shape and may be in the form of secondary particles formed by the aggregation of multiple primary particles, in the form of a single particle consisting of one primary particle, or in a combined form thereof.

[0078] In the case of the above secondary particles, the formation of pores within the electrode is advantageous, which can improve the electrolyte wettability effect. When using a mixture of the above secondary particles and single particles, the secondary particles and single particles can be mixed in a ratio of 80:20, specifically 50:50.

[0079] The porosity of the above-mentioned positive electrode active material may be, for example, 0.15 to 0.40, 0.16 to 0.39, 0.17 to 0.38, 0.18 to 0.37, 0.19 to 0.36, or 0.20 to 0.35, but is not limited thereto. The porosity of the above-mentioned positive electrode active material may be measured in the same way as the porosity of the negative electrode active material.

[0080] The above-mentioned cathode active material may include a cathode active material composed of a single particle consisting of one primary particle and / or a pseudo-single particle aggregate consisting of 10 or fewer primary particles. By using a cathode active material composed of a single particle consisting of one primary particle and / or a pseudo-single particle aggregate consisting of 10 or fewer primary particles as the cathode active material, a secondary battery with high capacity and excellent safety can be obtained.

[0081] The cathode active material composed of the above single particles and / or similar-single particles may be included in an amount of 95% to 100% by weight, 98% to 100% by weight, 99% to 100% by weight, or 100% by weight, based on the weight of the total cathode active material included in the cathode active material layer. When the content of single particles and / or similar-single particles satisfies the above range, sufficient safety can be obtained when applied to a secondary battery.

[0082] The cathode active material in the form of single particles and / or quasi-single particles has an average particle size D 50This may be 5㎛ or less, 4㎛ or less, 3㎛ or less, or 2㎛ or less. The average particle size D of the above-mentioned cathode active material. 50 The size may be 0.5㎛ to 5㎛, preferably 1㎛ to 5㎛, and more preferably 2㎛ to 5㎛. Average particle size D of the cathode active material 50 When the above range is satisfied, the increase in resistance can be minimized.

[0083] The above-mentioned single-particle and / or pseudo-single-particle type cathode active material may have an average particle size of primary particles of 5 μm or less, 4 μm or less, 3 μm or less, or 2 μm or less, for example, 0.5 μm to 5 μm, 1 μm to 5 μm, or 2 μm to 5 μm. When the average particle size of the primary particles satisfies the above range, a single-particle and / or pseudo-single-particle type cathode active material with excellent electrochemical properties can be formed. If the average particle size of the primary particles is too small, the number of aggregated primary particles forming the cathode active material increases, and the effect of suppressing particle breakage during rolling decreases; if the average particle size of the primary particles is too large, the lithium diffusion path inside the primary particles becomes longer, increasing resistance and potentially degrading output characteristics.

[0084] The above-mentioned cathode active material in the form of a single particle and / or a similar-single particle may have a unimodal particle size distribution. Conventionally, bimodal cathode active materials, which are a mixture of a large-particle cathode active material with a large average particle size and a small-particle cathode active material with a small average particle size, have been widely used to improve the electrode density of the cathode active material layer. However, in the case of cathode active materials in the form of a single particle or a similar-single particle, as the particle size increases, the lithium migration path lengthens, causing a significant increase in resistance; therefore, when large-particle particles are mixed and used, problems such as deterioration of capacity and output characteristics may occur. Accordingly, the present invention enables the minimization of the increase in resistance by using a cathode active material having a unimodal distribution.

[0085] The above-mentioned positive electrode active material may additionally include a conductive material and / or a binder. The conductive material may include, but is not limited to, at least one selected from the group consisting of, 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; metal powder or metal fiber such as copper, nickel, aluminum, or silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. The binder may comprise, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and polymers in which the hydrogens thereof are substituted with Li, Na, or Ca, but is not limited thereto.

[0086] The above-mentioned cathode active material may further include additives, etc. As long as the above-mentioned additives do not impede the purpose of the present invention, known additives may be used without limitation.

[0087] The positive electrode of the present invention may include, for example, a positive current collector; and a positive active material layer comprising the aforementioned positive active material, conductive material and / or binder, etc., on at least one surface of the positive current collector. The positive current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the positive current collector may typically have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the current collector to increase the adhesion of the positive active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0088] The secondary battery of the present invention may additionally include a separator. In the secondary battery, the separator separates the negative electrode and the positive electrode and provides a pathway for the movement of lithium ions. Any separator commonly used in lithium secondary batteries may be used without special limitations, and it is particularly desirable that it has low resistance to the movement of electrolyte ions and excellent electrolyte moisture retention capacity. Specifically, the separator may include one or more selected from the group consisting of polyolefin-based polymers such as, for example, ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer. As the separator, a porous polymer film manufactured through the examples described above or a laminated structure of two or more layers thereof may be used. Alternatively, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc., may be used. In addition, a coated separator containing ceramic components or polymer materials may be used to ensure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0089] The secondary battery of the present invention may include an electrolyte. The electrolyte may include a lithium salt, an organic solvent, and an additive.

[0090] The above lithium salt is used as an electrolyte salt in a secondary battery and serves as a medium for transferring ions. Typically, the lithium salt is, for example, Li as a cation + It includes, and as anion, 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 - , PF4C2O4 - , PF2C4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , C4F9SO3 - , CF3CF2SO3 - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , CF3(CF2)7SO3 - and SCN- At least one selected from the group consisting of can be cited.

[0091] Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 It may include a single substance or a mixture of two or more selected from the group consisting of LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiN(SO2F)2 (lithium bis(fluorosulfonyl)imide; LiFSI), LiN(SO2CF2CF3)2 (lithium bis(perfluoroethanesulfonyl)imide; LiBETI), and LiN(SO2CF3)2 (lithium bis(trifluoromethanesulfonyl)imide; LiTFSI). In addition to these, lithium salts commonly used in the electrolytes of lithium secondary batteries may be used without limitation.

[0092] The above lithium salt may be included in the electrolyte at a concentration of 1.0 M to 1.5 M, preferably 1.1 M to 1.3 M, in order to achieve optimal electrolyte impregnation for the secondary battery. When the concentration of the lithium salt satisfies the above range, the effect of improving cycle characteristics during high-temperature storage of the lithium secondary battery is sufficient, and the viscosity of the non-aqueous electrolyte is appropriate, so electrolyte impregnation can be improved.

[0093] The above organic solvent may include at least one organic solvent 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.

[0094] Specifically, the organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixture thereof.

[0095] The above-mentioned cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can effectively dissociate lithium salts in the electrolyte. Specific examples 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, and among these, it may include ethylene carbonate.

[0096] The above 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).

[0097] In order to produce an electrolyte having high ionic conductivity, the above organic solvent may additionally include at least one ester-based organic solvent selected from the group consisting of a linear ester-based organic solvent and a cyclic ester-based organic solvent in addition to at least one carbonate-based organic solvent selected from the group consisting of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent.

[0098] Specific examples of the above linear ester-based organic solvents 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.

[0099] 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.

[0100] The above organic solvent may be used without limitation by adding organic solvents commonly used in non-aqueous electrolytes as needed. For example, it may additionally include at least one organic solvent among ether-based organic solvents, glyme-based solvents, and nitrile-based organic solvents.

[0101] As the above ether-based solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methylpropyl ether, ethyl propyl ether, 1,3-dioxolane (DOL), and 2,2-bis(trifluoromethyl)-1,3-dioxolane (TFDOL), or a mixture of two or more of these may be used, but is not limited thereto.

[0102] The above-mentioned glyme-based solvent has a high dielectric constant and low surface tension compared to linear carbonate-based organic solvents and is a solvent with low reactivity with metals. It may include at least one selected from the group consisting of dimethoxyethane (glyme, DME), diethoxyethane, diglyme, tri-glyme, and tetra-glyme (TEGDME), but is not limited thereto.

[0103] The above nitrile-based solvent may be one or more selected from the group consisting of acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile, but is not limited thereto.

[0104] The above-mentioned non-aqueous electrolyte may include an electrolyte additive to prevent the non-aqueous electrolyte from decomposing and causing cathode collapse in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, prevention of overcharging, and suppression of battery expansion at high temperatures.

[0105] The above electrolyte additive may include at least one additive for forming an SEI film selected from the group consisting of cyclic carbonate compounds, halogen-substituted carbonate compounds, sulfone compounds, sulfate compounds, phosphate compounds, borate compounds, nitrile compounds, benzene compounds, amine compounds, silane compounds, and lithium salt compounds as representative examples.

[0106] Examples of the above-mentioned cyclic carbonate compounds include vinylene carbonate (VC) or vinylethylene carbonate.

[0107] Examples of the above halogen-substituted carbonate compounds include fluoroethylene carbonate (FEC).

[0108] The above sulfone-based compounds may include at least one compound selected from the group consisting of 1,3-propane sulfone (PS), 1,4-butane sulfone, ethen sulfone, 1,3-propene sulfone (PRS), 1,4-butene sulfone, and 1-methyl-1,3-propene sulfone.

[0109] Examples of the above sulfate compounds include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS).

[0110] The above phosphate-based compounds may include one or more compounds selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)phosphite, tris(2,2,2-trifluoroethyl)phosphate, and tris(2,2,2-trifluoroethyl)phosphite.

[0111] Examples of the above borate compounds include tetraphenylborate, lithium oxalyl difluoroborate (LiODFB), and lithium bisoxalate toborate (LiB(C2O4)2, LiBOB).

[0112] The above nitrile-based compounds may include at least one compound selected from the group consisting of succinonitrile, adiponitrile, acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanitrile, cyclopentane carbonitrile, cyclohexane carbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0113] Examples of the above benzene-based compounds include fluorobenzene, examples of the above amine-based compounds include triethanolamine or ethylenediamine, and examples of the above silane-based compounds include tetravinylsilane.

[0114] The above lithium salt-based compound is a compound different from the lithium salt included in the above non-aqueous electrolyte, and examples include lithium difluorophosphate (LiDFP), LiPO2F2, or LiBF4.

[0115] A second aspect of the present invention relates to a method for charging a secondary battery.

[0116] The details regarding the first aspect of the present invention may be applied in the same way to the details regarding the second aspect unless specifically described otherwise.

[0117] The secondary battery of the present invention may be characterized by satisfying the following [Equation 1]:

[0118] [Equation 1]

[0119] C max 3 ·R 2 / (D·(P-0.25)) ≤ 5×10 6 [C 3 · s]

[0120] In Equation 1, C max ε₀ may be the maximum charging speed (C) of the secondary battery, R may be the average particle size (m) of the negative electrode active material, and D is the diffusivity (m) of the negative electrode active material. 2 / s) can be, P can be the porosity of the cathode active material, and P > 0.25.

[0121] The charging method of the secondary battery described above includes, for example, a fast charging process in at least part of the total charging process, and the fast charging process includes C in at least part max It can be characterized by including a charging section at a charging speed.

[0122] The charging method of the above secondary battery, for example, has a charging speed of C during the entire charging process. max It can be characterized by not exceeding.

[0123] The charging method of the above secondary battery is, for example, the above C max After charging at a certain speed, the secondary battery may be charged while reducing the charging speed by a specific amount over time. The reduction of the charging speed may be, for example, reduced stepwise or linearly over time, but is not limited thereto. The specific amount may be, for example, 0.1C to 0.5C, but is not limited thereto and can be appropriately adjusted as needed.

[0124] In the following, the present invention is described in detail with reference to examples to specifically explain the disclosure of the present invention as described above and the intended functions and effects of the present invention. However, the examples may be modified in various different forms, and the scope of this specification is not to be interpreted as being limited only to these examples. It is emphasized that the examples are provided to represent the present invention and to explain it more specifically to those skilled in the art.

[0125] Example 1.

[0126] (cathode)

[0127] A negative active material layer is formed on one side of a negative current collector, wherein a copper current collector was used as the negative current collector, and the negative active material layer was formed by preparing a negative slurry by adding a negative active material, a binder, a conductive material, and a dispersant to a solvent, applying the slurry onto the current collector, and then drying and rolling. Graphite (synthetic graphite:natural graphite = 5:5) was used as the negative active material, styrene-butadiene rubber, which is a water-based binder, carbon black, which is a carbon-based material, was used as the conductive material, and CMC (Sodium Carboxymethyl Cellulose) was used as the dispersant, and these were added to water, which is the solvent, in a weight ratio of 97.7:1.35:0.005:0.9 to prepare the negative slurry.

[0128] (anode)

[0129] A positive active material layer is formed on one side of a positive current collector, wherein an aluminum current collector was used as the positive current collector, and the positive active material layer was formed by preparing a positive slurry by adding a positive active material, a binder, and a conductive material to a solvent, applying the slurry onto the current collector, and then drying and rolling. As the positive active material, Li[Ni 0.6 Co 0.2 Mn 0.2O2, PVDF as a binder, and carbon nanotubes (CNT) as a conductive material were used, and an anode slurry was prepared by introducing them into N-methylpyrrolidone (NMP), a solvent, in a weight ratio of 97.37:2.0:0.63.

[0130] (3-electrode assembly)

[0131] A three-electrode assembly was manufactured using the above-manufactured cathode as the working electrode (WE), a saturated calomel electrode (SCE) as the reference electrode (RE), and a platinum (Pt) electrode as the counter electrode (CE).

[0132] Examples 2 to 6 and Comparative Examples 1 to 4.

[0133] C max , C max 3 ·R 2 A secondary battery was manufactured in the same manner as in Example 1, except that / (D·(P-0.25)), R, D, and P were as shown in Table 1 below.

[0134]

[0135] Evaluation Example 1. Charging Time

[0136] For the 3-electrode assemblies of the examples and comparative examples, the time taken to charge at different maximum charging speeds from 10% to 80% charge state was calculated and is shown in Table 2.

[0137] Charging conditions:

[0138] - C max Start charging at the speed

[0139] - SoC 0% to 80%: Decrease by 0.2C each time lithium plating occurs

[0140]

[0141] Example 1, Comparative Example 1, and Comparative Example 2 are three-electrode assemblies incorporating a positive active material having the same characteristics (R, D, P), C max It was confirmed that the charging time (total time required to full charge) was equivalent even though was varied to 3.2C, 3.4C, and 5C, respectively. Example 2 and Comparative Example 3 are also three electrode assemblies incorporating a positive electrode active material having the same characteristics, C max Even though was varied to 3.6C and 5C, respectively, the charging time (total time required to fully charge) was at an equivalent level. Example 4 and Comparative Example 4 are also three-electrode assemblies incorporating a positive electrode active material having the same characteristics, C max Even though the C was varied to 4.6C and 5C, respectively, the charging time (total time required to fully charge) was equivalent. Through this, C max 3 ·R 2 / (D·(P-0.25)) is 5×10 6 [C 3 · When controlled to be less than s], the relatively low maximum charging speed (C max It was confirmed that even when charging with ), the charging time could be equivalent to charging at a high maximum charging speed.

[0142] Evaluation Example 2. Dose Retention Rate

[0143] For the examples and comparative examples, the capacity retention rate for a cycle was evaluated by defining one cycle as charging and discharging under the following conditions, and the results are shown in FIGS. 4 to 6.

[0144] Charging conditions:

[0145] - C max Start charging at the speed

[0146] - SoC 0% to 80%: Decrease by 0.2C each time lithium plating occurs

[0147] - SoC 80% to 100%: 1 / 3C

[0148] Discharge conditions: 1 / 3C, 3V

[0149] Although Example 1, Comparative Example 1, and Comparative Example 2 are three-electrode assemblies incorporating a negative electrode active material having the same characteristics (R, D, P), C max As the method was varied, Example 1 satisfied Equation 1, while Comparative Examples 1 and 2 did not satisfy Equation 1. As a result, as shown in FIG. 4, it was confirmed that Example 1 exhibited excellent capacity retention, whereas Comparative Examples 1 and 2 exhibited inferior characteristics.

[0150] Likewise, although Example 2 and Comparative Example 3 are three-electrode assemblies in which a negative active material having the same characteristics (R, D, P) is introduced, C max As the method was varied, Example 2 satisfied Equation 1, while Comparative Example 3 did not satisfy Equation 1. As a result, as shown in FIG. 5, it was confirmed that the capacity retention rate of Example 2 was superior to that of Comparative Example 3.

[0151] Likewise, although Example 4 and Comparative Example 4 are three-electrode assemblies in which a negative active material having the same characteristics (R, D, P) is introduced, C max As the method was varied, Example 4 satisfied Equation 1, while Comparative Example 4 did not satisfy Equation 1. As a result, as shown in FIG. 6, it was confirmed that the capacity retention rate of Example 4 was superior to that of Comparative Example 4.

[0152] Through this, it was confirmed that if Equation 1 is satisfied, a secondary battery with excellent capacity retention rate can be provided while reducing the charging time (total time required to fully charge).

Claims

As a secondary battery comprising a positive electrode, a negative electrode, and an electrolyte, The above cathode includes a cathode active material layer comprising a cathode active material, and A secondary battery characterized by satisfying the following [Equation 1]: [Equation 1] C max 3 ·R 2 / (D·(P-0.25)) ≤ 5×10 6 [C 3 · s] In Equation 1, C max ε is the maximum charging speed (C) of the secondary battery, R is the average particle size (m) of the negative electrode active material, and D is the diffusivity (m) of the negative electrode active material. 2 / s), P is the porosity of the cathode active material, and P > 0.

25. In Article 1, The above C max A secondary battery characterized by being smaller than 5C. In Article 1, A secondary battery characterized in that the above P is 0.4 or less. In Article 1, The above R is 1×10 -6 m to 2×10 -5 A secondary battery characterized by being m. In Article 1, The above D is 1.0×10 -15 m 2 / s to 1.0×10 -13 m 2 A secondary battery characterized by being / s. In Article 1, A secondary battery characterized in that the above-mentioned negative electrode active material comprises a carbonaceous material. In Article 6, A secondary battery characterized in that the above-mentioned negative electrode active material further comprises a silicon compound, and the silicon compound is included in an amount of 20 weight% or less relative to the total negative electrode active material. In Article 1, The above-mentioned negative electrode active material layer further comprises a conductive material, and The above conductive material comprises one or more selected from the group consisting of graphite, such as natural graphite or artificial graphite, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber. A secondary battery characterized in that the above conductive material is included in an amount of 10 weight% or less with respect to the entire negative electrode active material layer. In Article 1, The above negative electrode active material layer further comprises a binder, and The above binder includes a water-based binder, and A secondary battery characterized in that the above binder is included in an amount of 10 weight percent or less relative to the entire negative electrode active material layer. In Article 1, The above-mentioned anode comprises an anode active material layer containing an anode active material, and A secondary battery characterized in that the above-mentioned positive active material comprises a lithium nickel-based oxide. In Article 1, The above-mentioned anode includes an anode active material, and A secondary battery characterized in that the porosity of the positive electrode active material is 0.15 to 0.

4. In Article 1, The above secondary battery additionally includes a separator, and A secondary battery characterized in that the separator comprises one or more selected from the group consisting of ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer. A method for charging a secondary battery satisfying the following [Equation 1], At least part of the entire charging process includes a high-speed charging process, and the high-speed charging process includes C in at least part max A method for charging a secondary battery characterized by including a charging section at a charging speed: [Equation 1] C max 3 ·R 2 / (D·(P-0.25)) ≤ 5×10 6 [C 3 · s] In Equation 1, C max ε is the maximum charging speed (C) of the secondary battery, R is the average particle size (m) of the negative electrode active material, and D is the diffusivity (m) of the negative electrode active material. 2 / s), P is the porosity of the cathode active material, and P > 0.

25. In Article 13, During the entire charging process, the charging speed is C max A method for charging a secondary battery characterized by not exceeding In Article 13, The above C max A method for charging a secondary battery, characterized by charging the secondary battery at a specific rate and then reducing the charging rate over time.

Images