How to charge a lithium-ion battery

Abstract

Providing a method for charging lithium-ion batteries. [Solution] The present disclosure relates to a method for charging a lithium secondary battery, which includes a positive electrode active material containing a lithium nickel-based composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the metal excluding lithium, and comprises the steps of: charging the lithium secondary battery with a constant current at a current density of 4C to 10C; and charging the lithium secondary battery with a constant voltage.

Description

[Technical Field]

[0001] This document discusses methods for charging lithium-ion batteries. [Background technology]

[0002] In recent years, with the rapid proliferation of electronic devices that use batteries, such as mobile phones, laptops, and electric vehicles, the demand for high-energy-density, high-capacity rechargeable batteries has been rapidly increasing. Consequently, research and development to improve the performance of lithium-ion rechargeable batteries is being actively pursued.

[0003] A lithium-ion secondary battery is a battery that contains an electrolyte and positive and negative electrodes, which are active materials that allow for the insertion and deintercalation of lithium ions. It produces electrical energy through oxidation and reduction reactions that occur when lithium ions are inserted into and deintercalated at the positive and negative electrodes.

[0004] The aforementioned lithium secondary battery can be recharged and used continuously even after discharge, and its performance varies depending on the charge / discharge state. Therefore, efforts are being made to improve the performance of lithium secondary batteries by improving the charging method. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Korean Patent Publication No. 2017-0105320 [Overview of the project] [Problems that the invention aims to solve]

[0006] One embodiment provides a method for charging a lithium secondary battery that can shorten the charging time, avoid structural degradation reactions of the positive electrode active material, and improve the battery's lifespan characteristics. [Means for solving the problem]

[0007] One embodiment provides a method for charging a lithium secondary battery, which includes a positive electrode active material containing a lithium nickel-based composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the metal excluding lithium, and the method includes the steps of: charging the lithium secondary battery with a constant current at a current density of 4C to 10C; and charging the lithium secondary battery with a constant voltage.

[0008] A charging method for a lithium secondary battery according to one embodiment can shorten the charging time, avoid structural degradation reactions of the positive electrode active material, and improve the battery's lifespan characteristics. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 2] This is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 3] This is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 4] This is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 5] This is a dQ / dV graph of the lithium secondary battery after chemical conversion for manufacturing example 1. [Figure 6] This is a dQ / dV graph of the lithium secondary battery after chemical conversion for manufacturing example 3. [Figure 7] This is a capacity-voltage graph for standard charge-discharge cycles performed in Example 1 and Comparative Example 1. [Figure 8] This is an SEM image showing a cross-section of the discharged positive electrode active material particles after repeating the charge-discharge cycle performed in Example 1 100 times. [Figure 9] This is an SEM image showing a cross-section of the discharged positive electrode active material particles after repeating the charge-discharge cycle performed in Comparative Example 1 100 times. [Figure 10] This is an SEM image showing a cross-section of the discharged positive electrode active material particles after repeating the charge-discharge cycle performed in Comparative Example 2 100 times. [Figure 11] This is an SEM image showing a cross-section of the discharged positive electrode active material particles after repeating the charge-discharge cycle performed in Comparative Example 6 100 times. [Figure 12] This is an SEM image showing a cross-section of the discharged positive electrode active material particles after repeating the charge-discharge cycle performed in Comparative Example 7 100 times. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described in detail below. However, these are presented as examples only and do not limit the present invention, which is defined only by the categories of claims described later.

[0011] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

[0012] Here, "these combinations" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, etc. of the composition.

[0013] Here, terms such as “include,” “equip,” or “possess” are intended to specify the presence of a particular feature, number, stage, component, or combination thereof, and should be understood not to preemptively exclude the possibility of the presence or addition of one or more other features, numbers, stages, components, or combinations thereof.

[0014] To clearly represent multiple layers and regions in the drawings, thicknesses are shown enlarged, and similar parts are given the same drawing reference numerals throughout the specification. When a layer, film, region, plate, or other part is "on top of" or "on" another part, this includes not only when it is "directly on top of" another part, but also when there is another part in between. Conversely, when one part is said to be "directly on top of" another part, it means that there is no other part in the middle.

[0015] Furthermore, the term "layer" here includes not only shapes that are formed across the entire surface when observed in a plan view, but also shapes that are formed on one side.

[0016] In this specification, unless otherwise specified, singular nouns may also include plural nouns. Furthermore, unless otherwise specified, "A or B" may mean "including A, including B, or including both A and B."

[0017] The term "metal" is interpreted as a concept that includes general metals, transition metals, and semimetals (metalloids).

[0018] Unless otherwise defined herein, particle size may refer to average particle size. Furthermore, particle size refers to the average particle size (D50), which is the diameter of the particle whose cumulative volume in the particle size distribution is 50% by volume. Average particle size (D50) can be measured by methods widely known to those skilled in the art, such as using a particle size analyzer, or by using a transmission electron microscope or scanning electron microscope. Alternatively, it can be measured using a dynamic light-scattering device, analyzed, and the average particle size (D50) value calculated from the count of particles within each particle size range. Alternatively, it can be measured using the laser diffraction method. In the case of measurement using laser diffraction, more specifically, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (for example, Microtrac MT 3000), and after irradiating with ultrasound at approximately 28 kHz at an output of 60 W, the average particle size (D50) based on the 50% standard of the particle size distribution in the analyzer can be calculated.

[0019] How to charge a lithium-ion battery A charging method for a lithium secondary battery according to one embodiment includes the steps of (1) constantly charging the lithium secondary battery with a constant current (CC) at a current density (C-rate) of 4C to 10C, and (2) constantly charging the lithium secondary battery with a constant voltage (CV), for a lithium secondary battery containing a positive electrode active material containing a lithium nickel-based composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the metal other than lithium.

[0020] The charging method may be to continue with constant current charging (1) followed by constant voltage charging (2), or for example, constant voltage charging (2) may be performed immediately after constant current charging (1) without any rest period.

[0021] Nickel-based cathode active materials exhibit increased reversible capacity as their nickel content increases, but their structural stability, thermal stability, and lifetime characteristics may decrease.

[0022] One embodiment discloses a method for charging a lithium secondary battery containing a nickel-based positive electrode active material with a high nickel content. By intentionally increasing the current density during constant current charging of the lithium secondary battery, the charging time can be shortened, and while achieving a similar charge-to-capacity ratio to that of a typical battery, structural degradation reactions of the positive electrode active material can be avoided, thereby improving the battery's lifespan.

[0023] A charging method for a lithium secondary battery according to one embodiment includes the step of (1) constantly charging the lithium secondary battery at a current density of 4C to 10C. The current density can be expressed in C-rate, and the unit of C-rate is C. This step means constantly charging at any one C-rate in the range of 4C to 10C. Here, 1C may be 200mAh / g, but this can be changed depending on the battery material and design, and is not limited to this.

[0024] During the charging process of a lithium secondary battery, the positive electrode active material can undergo a series of phase transitions, such as H1 (hexagonal 1) phase → M (monoclinic) phase → H2 (hexagonal 2) phase → H3 (hexagonal 3) phase. In this case, the H1 phase is a phase in which the positive electrode active material has a crystal structure with a lattice constant specific to the c-axis direction, the H2 phase is a phase in which the positive electrode active material has a crystal structure with a lattice constant longer than the specific lattice constant specific to the c-axis direction, and the H3 phase is a phase in which the positive electrode active material has a crystal structure with a lattice constant shorter than the specific lattice constant specific to the c-axis direction.

[0025] When charging lithium secondary batteries containing high-nickel positive electrode active materials at a typical current density of 1C, a phase transition from H2 to H3 in the positive electrode active material may occur in the high-voltage region (e.g., above approximately 4.2V). If a phase transition from H2 to H3 occurs, the positive electrode active material may rapidly contract in the c-axis direction, potentially leading to structural degradation of the positive electrode active material. If structural degradation of the positive electrode active material occurs, the resistance of the lithium secondary battery increases, resulting in a decrease in cycle life.

[0026] A charging method for a lithium secondary battery according to one embodiment includes a step of constant current charging of the lithium secondary battery at a high current density of 4C to 10C until the charging termination voltage is reached. By intentionally causing overpotential due to polarization and inactivating the H2-H3 phase transition, the concentration of lithium on the positive electrode surface is prevented from becoming so low as to cause degradation, thereby improving the cycle life compared to general charging.

[0027] For example, the current density in a constant current charging step may be 5C to 10C, or for example, 5C to 6C, or 5C to 7C. In this case, for example, 1C = 200mA / g.

[0028] When the current density within the specified range is met, the H2-H3 phase transition of the positive electrode active material can be effectively inactivated, improving the lifespan characteristics of the lithium secondary battery.

[0029] The constant current charging step can charge a lithium secondary battery to a charging termination voltage of 4.2V to 5V, for example, to 4.3V to 5V or 4.4V to 5V.

[0030] Lithium secondary batteries, evaluated after chemical formation under conditions of 1C=200mAh / g, 5C, and 3.6V~4.3V, may exhibit a differential capacitance (dQ / dV)-voltage (V) graph that includes a first peak appearing at charging voltages between 3.8V and 3.9V; a second peak appearing at charging voltages between 4.0V and 4.1V; and a third peak appearing at charging voltages between 4.25V and 4.3V.

[0031] Formation can be described as the first charge / discharge process after battery manufacturing. The period following formation can be considered the standard charge / discharge cycle performed after the formation process, for example, the second charge / discharge cycle. The differential capacitance (dQ / dV)-voltage (V) graph can be expressed as a dQ / dV graph based on charge / discharge voltage, and can simply be expressed as a dQ / dV graph.

[0032] Furthermore, the dQ / dV graph may be obtained by performing charge and discharge operations on a lithium secondary battery containing, for example, a structure in which a positive electrode containing a positive electrode active material, a polyolefin separator, and a lithium metal counter electrode are sequentially stacked, and an electrolyte containing a carbonate-based solvent and a lithium salt.

[0033] The dQ / dV graph represents the capacitance characteristics of the working ion relative to the positive electrode active material at different voltages. The position, intensity difference, and area relative to the main peak may vary depending on the type and physical properties of the positive electrode active material.

[0034] The first peak may be the H1-M peak, which occurs when the positive electrode active material undergoes a phase transition from H1 (hexagonal 1) to M (monoclinic) during the charging process of the lithium secondary battery; the second peak may be the M-H2 peak, which occurs when the positive electrode active material undergoes a phase transition from M (monoclinic) to H2 (hexagonal 2) during the charging process of the lithium secondary battery; and the third peak may be the H2-H3 peak, which occurs when the positive electrode active material undergoes a phase transition from H2 (hexagonal 2) to H3 (hexagonal 3) during the charging process of the lithium secondary battery.

[0035] According to one embodiment of a lithium secondary battery charging method, the constant current charging step proceeds at a high current density, causing the H2-H3 peak (third peak) to shift in the x-axis (+) direction of the dQ / dV graph. This weakens the intensity of the H2-H3 peak (third peak), deactivating the H2-H3 phase transition and improving the battery's cycle life.

[0036] For example, if we denote the intensity of the first peak as I1, the intensity of the second peak as I2, and the intensity of the third peak as I3, then we can satisfy the condition I1 > I2 > I3.

[0037] A method for charging a lithium secondary battery according to one embodiment includes, after a constant current charging step, (2) a step of constant voltage charging (CV) the lithium secondary battery.

[0038] If the charging step consists only of a constant current charging step, the charging capacity will be limited. Therefore, after charging up to the charging termination voltage through the constant current charging step, the remaining charging capacity can be supplemented with constant voltage charging.

[0039] For example, a constant voltage charging step can charge a lithium secondary battery to a charging capacity of 175 mAh / g to 240 mAh / g, and the charging capacity may vary depending on the type of positive electrode active material.

[0040] positive electrode active material The positive electrode active material according to one embodiment includes a lithium nickel-based composite oxide in which the content of nickel with respect to the total metal excluding lithium is 80 mol% or more.

[0041] As an example, the positive electrode active material may be in the form of secondary particles in which a plurality of primary particles are aggregated, and the average particle diameter (D 50 ) may be 10 μm to 18 μm, for example, 10 μm to 16 μm, or 12 μm to 15 μm. The average particle diameter is obtained by randomly measuring the sizes (diameter or major axis length) of 20 particles from a scanning electron microscope image of the positive electrode active material to obtain a particle size distribution, and the diameter (D 50 ) of the particle with a cumulative volume of 50% by volume from the particle size distribution may be taken as the average particle diameter. When the average particle diameter of the positive electrode active material satisfies the above range, high capacity and long life can be realized.

[0042] As an example, the positive electrode active material may be a high-nickel positive electrode active material in which the content of nickel with respect to 100 mol% of the metal excluding lithium from the lithium nickel-based composite oxide is 80 mol% or more, 85 mol% or more, 88 mol% or more, 90 mol% or more, 91 mol% or more, or 94 mol% or more, 99 mol% or less. The high-nickel positive electrode active material can achieve high capacity and can be applied to high-capacity and high-density lithium secondary batteries.

[0043] As an example, the positive electrode active material may include a lithium nickel-based composite oxide represented by the following Chemical Formula 1. [Chemical Formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In Chemical Formula 1, 0.9 ≦ a1 ≦ 1.8, 0.8 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 0.2, 0 ≦ z1 ≦ 0.2, 0.9 ≦ x1 + y1 + z1 ≦ 1.1, and 0 ≦ b1 ≦ 0.1, and M 1 and M 2Each of the following elements is independently selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0044] In chemical formula 1, M 1 and M 2 These elements may be different from each other.

[0045] In chemical formula 1, for example, 0.8 ≤ x 1 < 1, 0 <y1≦0.2、0≦z1≦0.2、または0.9≦x1<1、0<y1≦0.1、0≦z1≦0.1、または0.91≦x1<1、0<y1≦0.09、0≦z1≦0.08、または0.94≦x1<1、0<y1≦0.06、0≦z1≦0.06であってもよい。

[0046] As an example, the positive electrode active material may include a lithium nickel-manganese composite oxide represented by the following chemical formula 2, a lithium nickel-cobalt composite oxide represented by the following chemical formula 3, or a combination thereof. [Chemical formula 2] Li a2 Ni x2 Mn y2 M 3 z2 O 2-b2 X b2 In chemical formula 2, 0.9≦a2≦1.8, 0.8≦x2<1, 0 <y2≦0.2、0≦z2≦0.2、0.9≦x2+y2+z2≦1.1、および0≦b2≦0.1であり、M 3 X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Co, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0047] In chemical formula 2, 0.9 ≤ x² < 1, 0 <y2≦0.1、0≦z2≦0.1、または0.91≦x2<1、0<y2≦0.09、0≦z2≦0.08、または0.94≦x2<1、0<y2≦0.06、0≦z2≦0.06であってもよい。 [Chemical formula 3] Li a3 Ni x3 Co y3 M 4 z3 O 2-b3 X b3 In chemical formula 3, 0.9≦a3≦1.8, 0.8≦x3<1, 0 <y3≦0.2、0≦z3≦0.2、0.9≦x3+y3+z3≦1.1、および0≦b3≦0.1であり、M 4 X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

[0048] In chemical formula 3, 0.9 ≤ x³ < 1, 0 <y3≦0.1、0≦z3≦0.1、または0.91≦x3<1、0<y3≦0.09、0≦z3≦0.08、または0.94≦x3<1、0<y3≦0.06、0≦z3≦0.06であってもよい。

[0049] positive electrode In one embodiment, the present invention includes a current collector and a positive electrode active material layer located on the current collector, wherein the positive electrode active material layer provides a positive electrode containing the aforementioned positive electrode active material.

[0050] The positive electrode active material layer may also contain other types of positive electrode active materials in addition to the positive electrode active material mentioned above.

[0051] As an example, the positive electrode active material layer may further contain a lithium-induced insertion compound (lithiated insertion compound) that allows for reversible insertion and removal of lithium, and may further contain one or more composite oxides of lithium and a metal selected from, for example, cobalt, manganese, nickel, and combinations thereof.

[0052] As a specific example, the positive electrode active material layer may further contain a compound represented by one of the following chemical formulas.

[0053] Li a A 1-b X b O 2-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);Li a Mn 2-b X b O 4-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);Li a Ni 1-b-c Co b X c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.5, 0<α<2);Li a Ni b Co c L 1 d G e O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0≦e≦0.1);Li a NiG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a CoG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-b G b O2(0.90≦a≦1.8, 0.001b≦0.1);Li a Mn2G b O4(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn 1-g G gPO4(0.90≦a≦1.8, 0≦g≦0.5);Li (3-f) Fe2(PO4)3(0≦f≦2);Li a FePO4 (0.90 ≤ a ≤ 1.8). In the chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, or a combination thereof; D is O, F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; L1 is Mn, Al, or a combination thereof.

[0054] Furthermore, the positive electrode active material layer may selectively further include a binder, a conductive material, or a combination thereof.

[0055] The binder plays a role in ensuring that the positive electrode active material particles adhere well to each other and that the positive electrode active material adheres well to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylic styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0056] Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes can be used in the battery that is constructed from them. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0057] As an example, the positive electrode may further contain an additive that acts as a sacrificial positive electrode.

[0058] The content of the positive electrode active material can be 90% to 99.5% by weight relative to 100% by weight of the positive electrode active material layer, and the content of the binder and conductive material can be 0.5% to 5% by weight, respectively, relative to 100% by weight of the positive electrode active material layer.

[0059] Al can be used as the current collector, but is not limited to it.

[0060] According to one embodiment, the loading level of the positive electrode active material layer is 10 mg / cm³. 2 ~40 mg / cm³ 2 It may be 10 mg / cm³, for example. 2 ~30 mg / cm³ 2 or 10 mg / cm³ 2 ~20 mg / cm³ 2 That's fine.

[0061] Furthermore, the density of the positive electrode active material layer in the rolled final positive electrode may be 3.0 g / cc to 3.7 g / cc, for example, 3.1 g / cc to 3.7 g / cc to 3.7 g / cc, or for example, 3.1 g / cc to 3.7 g / cc, 3.3 g / cc to 3.6 g / cc, or 3.4 g / cc to 3.58 g / cc. A positive electrode that satisfies the above range of loading level and positive electrode density is suitable for realizing a high-capacity, high-energy-density lithium secondary battery.

[0062] Lithium-ion rechargeable battery A lithium secondary battery includes the positive electrode, negative electrode, and electrolyte as described above. For example, a lithium secondary battery may include a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte.

[0063] Lithium-ion batteries can be classified into cylindrical, prismatic, pouch-type, coin-type, and other types depending on their form. Figures 1 to 4 are schematic diagrams showing a lithium-ion battery according to one embodiment; Figure 1 can be a cylindrical type, Figure 2 a prismatic type, and Figures 3 and 4 pouch-type batteries.

[0064] Referring to Figures 1-4, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown).

[0065] The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in Figure 1. Also, in Figure 2, the lithium secondary battery 100 may include a positive lead tab 11 and a positive terminal 12, and a negative lead tab 21 and a negative terminal 22. As shown in Figures 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, namely a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical pathways for guiding the current formed in the electrode assembly 40 to the outside.

[0066] Lithium-ion batteries can be applied to automobiles, mobile phones, and / or various forms of electronic devices, and the present invention is not limited thereto.

[0067] negative electrode The negative electrode may include a current collector and a negative electrode active material layer located on the current collector, the negative electrode active material layer including a negative electrode active material and may further include a binder, a conductive material, or a combination thereof.

[0068] negative electrode active material The negative electrode active material includes a material capable of reversibly inserting / desorbing lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0069] As the material capable of reversibly inserting / desorbing lithium ions, a carbon-based negative electrode active material can be included, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, and the like.

[0070] As the alloy of lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn can be used.

[0071] As the material capable of doping and undoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. The Si-based negative electrode active material may be silicon, a silicon-carbon composite, SiOx (0 < x ≦ 2), a Si-Q alloy (Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material may be Sn, SnO2, a Sn alloy, or a combination thereof.

[0072] The silicon-carbon composite may also be a composite of silicon and amorphous carbon. The average particle size (D) of the silicon-carbon composite particles. 50 The thickness of the silicon-carbon composite may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (core) assembled from primary silicon particles and an amorphous carbon coating layer (shell) located on the surface of these secondary particles. The amorphous carbon may also be located between the primary silicon particles, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0073] Silicon-carbon composites may also further contain crystalline carbon. For example, a silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the surface of this core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, and the like.

[0074] When the silicon-carbon composite contains silicon and amorphous carbon, the silicon content may be 10% to 50% by weight per 100% by weight of the silicon-carbon composite, and the amorphous carbon content may be 50% to 90% by weight. Furthermore, when the composite contains silicon, amorphous carbon, and crystalline carbon, the silicon content may be 10% to 50% by weight per 100% by weight of the silicon-carbon composite, the crystalline carbon content may be 10% to 70% by weight, and the amorphous carbon content may be 20% to 40% by weight.

[0075] Furthermore, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D) of the silicon particles (primary particles) 50) may be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles can exist alone as silicon, in the form of a silicon alloy, or in an oxidized form. The oxidized form of silicon can be represented by SiOx (0 < x ≤ 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be 99:1 to 33:67. In this specification, unless otherwise defined, the average particle size (D 50 ) means the diameter of the particle with a cumulative volume of 50% by volume in the particle size distribution.

[0076] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with the carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 by weight ratio.

[0077] The binder serves to make the negative electrode active material particles adhere well to each other and also make the negative electrode active material adhere well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0078] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0079] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylicated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0080] When using an aqueous binder as the negative electrode binder, it may further contain a cellulosic compound that can impart viscosity. This cellulosic compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. As the alkali metal, Na, K, or Li can be used.

[0081] The dry binder is a polymeric substance that can be formed into fibers, and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0082] Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not undergo chemical changes can be used in the battery that is constructed from them. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0083] The content of the negative electrode active material may be 95% to 99.5% by weight relative to 100% by weight of the negative electrode active material layer, and the content of the binder may be 0.5% to 5% by weight relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive material.

[0084] The negative electrode current collector may include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or alloys thereof, and may be in the form of foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0085] electrolyte An electrolyte for a lithium secondary battery is, for example, a electrolyte solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0086] Non-aqueous organic solvents serve as a medium through which ions involved in the electrochemical reactions of the battery can move. Non-aqueous organic solvents may be carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvents, aprotic solvents, or combinations thereof.

[0087] Suitable carbonate solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC). Suitable ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, and caprolactone. Suitable ether solvents include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Furthermore, ketone solvents such as cyclohexanone can be used. Alcohol solvents such as ethyl alcohol and isopropyl alcohol can be used, and aprotic solvents such as nitriles (R-CN, where R is a linear, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms, and can include double bonds, aromatic rings, or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes can be used. Non-aqueous organic solvents can be used alone or in mixtures of two or more, and the mixing ratio when using a mixture of two or more can be appropriately adjusted according to the desired battery performance, which is widely understood by those working in this field.

[0088] Furthermore, when using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and these can be mixed in a volume ratio of 1:1 to 1:9.

[0089] Non-aqueous organic solvents may further include aromatic hydrocarbon organic solvents. For example, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed and used in a volume ratio of 1:1 to 30:1.

[0090] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0091] Typical examples of ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0092] Lithium salts dissolve in organic solvents and act as a source of lithium ions in batteries, enabling the basic operation of lithium secondary batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Typical examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N(lithium bis(fluorosulfonyl)imide (LiFSI), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C y F 2y+1 It may contain one or more selected from SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0093] It is preferable to use lithium salts within a concentration range of 0.1 M to 2.0 M. When the lithium salt concentration falls within this range, the electrolyte has appropriate ionic conductivity and viscosity, resulting in excellent performance and effective lithium ion movement.

[0094] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, and polypropylene / polyethylene / polypropylene three-layer separators can also be used.

[0095] The separator may include a porous substrate and a coating layer containing organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0096] The porous substrate may be a polymer film formed from one polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyallyl etherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naptalate, glass fiber, Teflon®, and polytetrafluoroethylene, or from copolymers or mixtures of two or more of these polymers.

[0097] The porous substrate can have a thickness of approximately 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0098] The organic material may include a (meth)acrylic copolymer comprising a first structural unit derived from (meth)acrylamide, and a second structural unit comprising at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0099] Inorganic materials may include, but are not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D) of the inorganic particles is... 50 The wavelength range may be 1 nm to 2000 nm, for example, 100 nm to 1000 nm or 100 nm to 700 nm.

[0100] Organic and inorganic materials can exist mixed together in a single coating layer, or they can exist in a layered configuration where one coating layer contains organic materials and the other contains inorganic materials.

[0101] The thickness of the coating layer may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0102] Examples and comparative examples of the present invention are described below. However, the following examples are just one embodiment of the present invention, and the present invention is not limited to these examples.

[0103] (Example of manufacturing: Manufacturing of lithium-ion batteries) Manufacturing Example 1 As the positive electrode active material, LiNi 0.9 Mn 0.1 O2(D 50= 12 μm) 98.5 wt%, polyvinylidene fluoride binder 1.0 wt%, and carbon nanotube conductive material 0.5 wt% were mixed to produce a positive electrode active material layer slurry, which was coated on an aluminum foil current collector, dried, and rolled to produce a positive electrode. At this time, the loading level of the positive electrode active material layer was 20 mg / cm 2 and the density of the final rolled positive electrode was about 3.4 g / cc.

[0104] 97.5 wt% of graphite negative electrode active material, 1.5 wt% of carboxymethyl cellulose, and 1 wt% of styrene-butadiene rubber were mixed in an aqueous solvent to produce a negative electrode active material layer slurry. The negative electrode active material layer slurry was coated on a copper foil current collector, dried, and rolled to produce a negative electrode.

[0105] A polytetrafluoroethylene separator was interposed between the positive electrode and the negative electrode and inserted into a case, and an electrolytic solution in which 1 M LiPF6 was dissolved in a solvent in which ethylene carbonate and dimethyl carbonate were mixed at a volume ratio of 3:7 was injected, and a lithium secondary battery was manufactured by a normal method.

[0106] Manufacturing Example 2 As the positive electrode active material, LiNi 0.88 Co 0.10 Al 0.02 O2 (D 50 = 12 μm) was used, and a lithium secondary battery according to Production Example 2 was manufactured in the same manner as in Production Example 1, except for this.

[0107] Manufacturing Example 3 As the positive electrode active material, LiNi 0.66 Mn 0.34 O2 (D 50 = 12 μm) was used, and a lithium secondary battery according to Production Example 3 was manufactured in the same manner as in Production Example 1, except for this.

[0108] Manufacturing Example 4 As the positive electrode active material, LiCoO2 (D 50A lithium secondary battery according to Manufacturing Example 4 is manufactured in the same manner as in Manufacturing Example 1, except that a 15μm (=15μm) particle was used.

[0109] Evaluation Example 1: dQ / dV Evaluation The lithium secondary battery manufactured in Manufacturing Example 1 was charged to an upper voltage limit of 4.3V with a constant current of 0.2C, then to 0.05C with a constant voltage, and finally discharged to a termination voltage of 3.0V with 0.2C to perform the chemical conversion process (first charge / discharge).

[0110] Next, the batteries were charged with constant current at current densities of 0.2C, 0.5C, 1C, 2C, and 5C up to a charging termination voltage of 4.3V. Then, they were charged with constant voltage until the capacity reached 200mAh / g, and discharged at 0.33C up to a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge). 1C = 200mAh / g, and the evaluation was performed under conditions of 3.6V to 4.3V.

[0111] Furthermore, the lithium secondary battery manufactured in Manufacturing Example 3 was charged to an upper voltage limit of 4.3V with a constant current of 0.2C, then to 0.05C with a constant voltage, and finally discharged to a termination voltage of 3.0V with 0.2C to perform the chemical conversion process (first charge / discharge).

[0112] Next, the batteries were charged with constant current at current densities of 0.2C, 0.5C, 1C, 2C, and 5C up to a charging termination voltage of 4.3V. After that, they were charged with constant voltage until the capacity reached 180mAh / g, and then discharged at 0.33C up to a termination voltage of 3.6V, performing a standard charge / discharge cycle (second charge / discharge).

[0113] Figure 5 shows the dQ / dV graph for the lithium secondary battery of Manufacturing Example 1, based on the voltage after chemical formation. Figure 5 shows five graphs with different current densities after chemical formation, and the H1-M peak, M-H2 peak, and H2-H3 peak for each are shown.

[0114] Referring to Figure 5, in the case of lithium secondary batteries containing high-nickel (High-Ni) positive electrode active material, it can be seen that as the current density increases from 0.2C to 5C, the H1-M peak, M-H2 peak, and H2-H3 peak shift in the x-axis (+) direction of the graph. Furthermore, since the intensity of the H2-H3 peak decreases as the current density increases, it can be seen that the H2-H3 phase transition of the positive electrode active material may be inactivated during charging at high current densities.

[0115] Furthermore, Figure 6 shows the dQ / dV graph for the lithium secondary battery of manufacturing example 3, based on the voltage after chemical conversion. Figure 6 shows five graphs with different current densities after chemical conversion, and the H1-H2 peaks for each are shown.

[0116] Referring to Figure 6, it can be confirmed that, unlike in Figure 5, in the case of lithium secondary batteries containing a mid-nickel (Mid-Ni) cathode active material, the H2-H3 phase transition does not occur even when the charging voltage is increased to 4.3V.

[0117] (Example: Charging method for lithium secondary batteries) Example 1 For the lithium secondary battery of Manufacturing Example 1, the conversion process (first charge / discharge) was performed by charging it to an upper voltage limit of 4.3V with a constant current of 0.2C, then to 0.05C with a constant voltage, and finally discharging it to a termination voltage of 3.0V with 0.2C.

[0118] Next, the battery was charged with a constant current at a current density of 5C until it reached a charging termination voltage of 4.3V. Then, it was charged with a constant voltage until the capacity reached 200mAh / g, and then discharged at 0.33C until it reached a termination voltage of 3.6V, performing a standard charge-discharge (second charge-discharge). The discharge capacity during the standard charge-discharge is shown in Table 1 below as the initial discharge capacity.

[0119] Next, the cycle was repeated 100 times under the same conditions as standard charge and discharge, and the ratio of the discharge capacity after 100 cycles to the initial discharge capacity was calculated and is shown in Table 1 below as the 100-cycle life retention rate.

[0120] Comparative Example 1 First, the lithium secondary battery of Manufacturing Example 1 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Subsequently, the lithium secondary battery was charged with a constant current at a current density of 1C up to a charge termination voltage of 4.3V, and then discharged at 0.33C up to a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0121] Comparative Example 2 First, the lithium secondary battery of Manufacturing Example 1 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Subsequently, the lithium secondary battery was charged with a constant current at a current density of 5C to a charge termination voltage of 4.3V, and then discharged at 0.33C to a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0122] Comparative Example 3 First, the lithium secondary battery of Manufacturing Example 1 was subjected to a chemical conversion process (first charge / discharge) under the same conditions as the chemical conversion process (first charge / discharge) performed in Example 1. Subsequently, the lithium secondary battery was charged with a constant current by sequentially decreasing the current density in the order of 5C, 3C, and 2C until it reached a charge termination voltage of 4.3V, and then discharged at 0.33C until it reached a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0123] Example 2 First, the lithium secondary battery of Manufacturing Example 2 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Next, the lithium secondary battery was charged with a constant current at a current density of 5C until it reached a charge termination voltage of 4.3V, then charged with a constant voltage until its capacity reached 200mAh / g, and then discharged at 0.33C until it reached a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0124] Comparative Example 2-1 First, the lithium secondary battery of Manufacturing Example 2 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Subsequently, the lithium secondary battery was charged with a constant current at a current density of 1C up to a charge termination voltage of 4.3V, and then discharged at 0.33C up to a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0125] Comparative Example 4 First, the lithium secondary battery of Manufacturing Example 4 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Next, the lithium secondary battery was charged with a constant current at a current density of 5C until it reached a charge termination voltage of 4.3V, then charged with a constant voltage until it reached 174mAh / g, and then discharged at 0.33C until it reached a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0126] Comparative Example 4-1 First, the lithium secondary battery of Manufacturing Example 4 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Subsequently, the lithium secondary battery was charged with a constant current at a current density of 1C up to a charge termination voltage of 4.3V, and then discharged at 0.33C up to a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0127] Comparative Example 5 First, the lithium secondary battery of Manufacturing Example 3 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Next, the lithium secondary battery was charged with a constant current at a current density of 5C until it reached a charge termination voltage of 4.3V, then charged with a constant voltage until its capacity reached 180mAh / g, and then discharged at 0.33C until it reached a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0128] Comparative Example 6 First, the lithium secondary battery of Manufacturing Example 3 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Subsequently, the lithium secondary battery was charged with a constant current at a current density of 1C up to a charge termination voltage of 4.3V, and then discharged at 0.33C up to a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0129] Comparative Example 7 First, the lithium secondary battery of Manufacturing Example 3 was subjected to the same chemical conversion process (first charge / discharge) as in Example 1. Subsequently, the lithium secondary battery was charged with a constant current at a current density of 5C to a charge termination voltage of 4.3V, and then discharged at 0.33C to a termination voltage of 3.6V to perform a standard charge / discharge (second charge / discharge).

[0130] Evaluation Example 2: SEM Image Analysis After repeating the standard charge-discharge cycle 100 times under the same conditions as those independently performed in Example 1, Comparative Examples 1, 2, 6, and 7, the cross-sections of the discharged positive electrode active material particles are shown as scanning electron microscope (SEM) images in Figures 8 to 12.

[0131] Referring to Figures 8 to 12, it can be seen that in Comparative Example 1, where constant current charging was performed at a lower current density of 1C compared to Example 1, an H2-H3 phase transition occurred in the high-nickel positive electrode active material during the charging process, resulting in severe cracking of the particles.

[0132] Evaluation Example 3: Battery Characteristic Analysis The initial discharge capacity and charging time for each standard charge-discharge cycle (two charge-discharge cycles) performed independently in Examples 1-2 and Comparative Examples 1-7 are shown in Table 1 below. Furthermore, the standard charge-discharge cycles performed in Example 1 and Comparative Example 1 are shown in the capacity-voltage graph in Figure 7.

[0133] Furthermore, after repeating each standard charge-discharge cycle independently performed in Examples 1-2 and Comparative Examples 1-7 100 times, the ratio of the discharge capacity after 100 cycles to the initial discharge capacity was calculated and is shown in Table 1 below as the 100-cycle life retention rate.

[0134] [Table 1]

[0135] Referring to Table 1, it can be seen that in Example 1, the lifespan retention rate is higher than in Comparative Examples 1 to 3, even though the charging time is about half that of Comparative Example 1.

[0136] In Example 2, it can be confirmed that the initial discharge capacity is larger, the charging time is shorter, and the lifespan retention rate is higher than in Comparative Example 2-1.

[0137] Furthermore, in Comparative Examples 4 and 4-1, which use nickel-free positive electrode active materials (cobalt-based positive electrode active materials), it can be confirmed that the life retention rate is lower when using the 5C / CV charging method compared to the 1C charging method.

[0138] Furthermore, in the case of the charging methods of Comparative Examples 5 to 7, which use lithium secondary batteries containing mid-nickel cathode active material, it can be confirmed that the life retention rate is lower even when using the 5C / CV charging method compared to the 1C charging method.

[0139] Although preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and can be implemented in various ways within the scope of the claims, the detailed description of the invention, and the attached drawings, and these also naturally fall within the scope of the present invention. [Explanation of symbols]

[0140] 100 Lithium-ion rechargeable batteries 10 positive electrode 11 Positive lead tab 12 Positive terminal 20 negative electrode 21 Negative lead tab 22 Negative terminal 30 Separators 40 Electrode Assembly 50 cases 60 Sealing member 70 Electrode Tabs 71 Positive Tab 72 Negative Electrode Tabs

Claims

1. A charging method for a lithium secondary battery containing a positive electrode active material that includes a lithium nickel-based composite oxide in which the nickel content is 80 mol% or more relative to 100 mol% of the metal excluding lithium, A method for charging a lithium secondary battery, comprising the steps of: charging the lithium secondary battery with a constant current at a current density of 4C to 10C; and charging the lithium secondary battery with a constant voltage.

2. The method for charging a lithium secondary battery according to claim 1, wherein the current density in the constant current charging step is 5C to 10C.

3. The method for charging a lithium secondary battery according to claim 1, wherein the constant current charging step is to charge the lithium secondary battery to a charging termination voltage of 4.2V to 5V.

4. The lithium secondary battery was evaluated using a differential capacitance (dQ / dV)-voltage (V) graph under the conditions of 1C = 200mAh / g, 5C, and 3.6V to 4.3V after chemical formation. A method for charging a lithium secondary battery according to claim 1, comprising a first peak appearing at a charging voltage between 3.8V and 3.9V; a second peak appearing at a charging voltage between 4.0V and 4.1V; and a third peak appearing at a charging voltage between 4.25V and 4.3V.

5. The charging method for a lithium secondary battery according to claim 4, wherein the third peak is the peak in which the positive electrode active material undergoes a phase transition from H2 (hexagonal 2) to H3 (hexagonal 3) during the charging process.

6. The intensity of the first peak is I 1 , the intensity of the second peak is I 2 , the intensity of the third peak is I 3 Therefore, I 1 > I 2 > I 3 A method for charging a lithium secondary battery according to claim 4, which satisfies the condition.

7. The method for charging a lithium secondary battery according to claim 1, wherein the constant voltage charging step is to charge the lithium secondary battery to a charging capacity of 175 mAh / g to 240 mAh / g.

8. The charging method for a lithium secondary battery according to claim 1, wherein the positive electrode active material is in the form of secondary particles formed by the aggregation of a plurality of primary particles.

9. The average particle size (D) of the positive electrode active material 50 The charging method for a lithium secondary battery according to claim 1, wherein the diameter of the wire is 10 μm to 18 μm.

10. The charging method for a lithium secondary battery according to claim 1, wherein the positive electrode active material contains a lithium nickel-based composite oxide in which the nickel content is 90 mol% or more relative to 100 mol% of the metal excluding lithium.

11. The charging method for a lithium secondary battery according to claim 1, wherein the positive electrode active material includes a lithium nickel-based composite oxide represented by the following chemical formula 1: [Chemical formula 1] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1 In the above chemical formula 1, 0.9 ≤ a1 ≤ 1.8, 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, 0 ≤ z1 ≤ 0.2, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 and M 2 Each of these elements is independently selected from the group consisting of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

12. The charging method for a lithium secondary battery according to claim 1, wherein the positive electrode active material includes a lithium nickel-manganese composite oxide represented by the following chemical formula 2: [Chemical formula 2] Li a2 Ni x2 Mn y2 M 3 z2 O 2-b2 X b2 In the above chemical formula 2, 0.9 ≤ a² ≤ 1.8, 0.8 ≤ x² < 1, 0 < y² ≤ 0.2, 0 ≤ z² ≤ 0.2, 0.9 ≤ x² + y² + z² ≤ 1.1, and 0 ≤ b² ≤ 0.1, M 3 X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Co, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

13. The charging method for a lithium secondary battery according to claim 1, wherein the positive electrode active material includes a lithium nickel-cobalt composite oxide represented by the following chemical formula 3: [Chemical formula 3] Li a3 Ni x3 Co y3 M 4 z3 O 2-b3 X b3 In the above chemical formula 3, 0.9 ≤ a³ ≤ 1.8, 0.8 ≤ x³ < 1, 0 < y³ ≤ 0.2, 0 ≤ z³ ≤ 0.2, 0.9 ≤ x³ + y³ + z³ ≤ 1.1, and 0 ≤ b³ ≤ 0.1, M 4 X is one or more elements selected from the group consisting of Al, B, Ba, Ca, Ce, Cr, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, and Zr, and X is one or more elements selected from the group consisting of F, P, and S.

14. The lithium secondary battery includes a positive electrode active material layer containing the positive electrode active material, The loading level of the positive electrode active material layer is 10 mg / cm². 2 ~40 mg / cm³ 2 The method for charging a lithium secondary battery according to claim 1.

15. The charging method for a lithium secondary battery according to claim 14, wherein the density of the positive electrode active material layer is 3.0 g / cc to 3.7 g / cc.

Images