Charging method of rechargeable lithium battery

Abstract

The present disclosure relates to a charging method of a rechargeable lithium battery, the method comprising constant current charging of the rechargeable lithium battery at a current density of 4 C to 10 C and constant voltage charging of the rechargeable lithium battery, where the rechargeable lithium battery comprises a positive electrode active material, the positive electrode active material includes a lithium nickel-based composite oxide having a nickel content of greater than or equal to about 80 mol% based on 100 mol% of a metal other than lithium.

Description

Technical Field

[0001] A method for charging rechargeable lithium batteries has been disclosed. Background Technology

[0002] Recently, with the rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, the demand for rechargeable batteries with high energy density and high capacity has increased rapidly. Accordingly, research and development to improve the performance of rechargeable lithium batteries are actively underway.

[0003] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of intercalating and deintercalating lithium ions, and an electrolyte, and generates electrical energy through oxidation and reduction reactions if (for example, when) lithium ions are intercalated and deintercalated at the positive and negative electrodes.

[0004] Rechargeable lithium-ion batteries can be recharged after discharge and used continuously (e.g., substantially continuously), thus exhibiting performance differences depending on their charge / discharge states. Therefore, efforts are underway to improve the performance of rechargeable lithium-ion batteries by refining charging methods. Summary of the Invention

[0005] Some exemplary embodiments of this disclosure provide a charging method for a rechargeable lithium battery that can shorten charging time and improve the cycle life characteristics of the battery by avoiding or reducing structural degradation reactions of the positive electrode active material.

[0006] Some example embodiments provide a charging method for a rechargeable lithium battery comprising a positive electrode active material comprising a lithium-nickel composite oxide having a nickel content of greater than or equal to about 80 mol% based on 100 mol% of metals other than lithium. The method comprises: charging the rechargeable lithium battery at a constant current density of 4C to 10C; and charging the rechargeable lithium battery at a constant voltage.

[0007] The charging method for rechargeable lithium batteries according to some example embodiments can shorten charging time and improve the cycle life characteristics of the battery by avoiding or reducing structural degradation reactions of the positive electrode active material. Attached Figure Description

[0008] The accompanying drawings, together with the specification, illustrate embodiments of the subject matter of this disclosure and, together with the description, serve to explain the principles of embodiments of the subject matter of this disclosure.

[0009] Figures 1-4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments.

[0010] Figure 5The dQ / dV diagram is shown for the rechargeable lithium battery cell of Example 1 after formation.

[0011] Figure 6 The dQ / dV diagram is shown for the rechargeable lithium battery cell of Example 3 after oxidation.

[0012] Figure 7 Capacity-voltage diagrams for standard charge / discharge cycles performed in Example 1 and Comparative Example 1.

[0013] Figure 8 To show a scanning electron microscope (SEM) image of the cross-section of the positive electrode active material particles after discharge, following 100 cycles of charge / discharge in Example 1.

[0014] Figure 9 To show a cross-sectional SEM image of the positive electrode active material particles after discharge, following 100 cycles of charge / discharge in Comparative Example 1.

[0015] Figure 10 To show a cross-sectional SEM image of the positive electrode active material particles after discharge, following 100 cycles of charge / discharge in Comparative Example 2.

[0016] Figure 11 To show a cross-sectional SEM image of the positive electrode active material particles after discharge, following 100 cycles of charge / discharge in Comparative Example 6.

[0017] Figure 12 To show a cross-sectional SEM image of the positive electrode active material particles after discharge, following 100 cycles of charge / discharge in Comparative Example 7.

[0018] Explanation of reference numerals in the attached figures

[0019] 100: Rechargeable lithium battery; 10: Positive electrode

[0020] 11: Positive electrode lead connector 12: Positive electrode terminal

[0021] 20: Negative electrode 21: Negative electrode lead connector

[0022] 22: Negative electrode terminal; 30: Diaphragm

[0023] 40: Electrode assembly; 50: Housing

[0024] 60: Sealing component; 70: Electrode terminal piece

[0025] 71: Positive electrode connector; 72: Negative electrode connector Detailed Implementation

[0026] Embodiments of this disclosure will be described in more detail below. However, these embodiments are presented by way of example, and this disclosure is not limited thereto, and is defined by the scope of the claims and their equivalents.

[0027] The terminology used herein is for descriptive purposes only and is not intended to limit this disclosure. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0028] As used herein, “combinations thereof” refers to mixtures of components, laminates, complexes, copolymers, alloys, blends, reaction products, etc.

[0029] In implementation, it should be understood that terms such as “comprises,” “includes,” or “have” are intended to indicate the presence of the implemented features, quantities, steps, elements, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or combinations thereof.

[0030] In the accompanying drawings, for clarity, the thickness of layers, films, panels, areas, etc., may be enlarged, and the same reference numerals denote the same elements throughout the specification. It will be understood that if (e.g., when) an element (such as a layer, film, area, or substrate) is referred to as being "on" another element (such as a layer, film, area, or substrate), it may be directly on the other element (such as a layer, film, area, or substrate), or an intermediary element may also be present. In embodiments, if (e.g., when) an element (such as a layer, film, area, or substrate) is referred to as being "directly on" another element (such as a layer, film, area, or substrate), then an intermediary element is not present.

[0031] In this implementation, the term "layer" includes not only shapes formed across the entire surface when viewed from a plan view, but also shapes formed on a portion of the surface.

[0032] Unless otherwise indicated in this specification, a singular designation may also include a plural designation. In implementation, unless otherwise indicated, “A or B” may mean “including A, including B, or including both A and B”.

[0033] In the implementation, the term "metal" is interpreted as including the concepts of common metals, transition metals, and / or quasi-metals (semi-metals).

[0034] As used herein, particle size may be the average particle size if (e.g., when) it is not otherwise defined. In embodiments, particle size may refer to the average particle size (D). 50 The average particle size (D) can refer to the diameter of particles that constitute 50% of the total volume in the particle size distribution. 50The average particle size (D) can be measured by any suitable method commonly available in the art, for example, by a particle size analyzer and / or by transmission electron microscopy (TEM) images and / or scanning electron microscopy (SEM) images. In an embodiment, a dynamic light scattering measurement device can be used for data analysis and can count the number of particles for each particle size range. Thus, the average particle size (D) can be readily obtained by calculation. 50 The value can be measured using laser diffraction. In an embodiment, it can be measured using laser diffraction. If, for example, the particle to be measured is dispersed in a dispersion medium, it is then introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT3000), and ultrasonic waves can be irradiated at approximately 28 kHz and 60 W output power to calculate the average particle size (D) based on 50% of the particle size distribution in the measuring device. 50 ).

[0035] Charging methods for rechargeable lithium batteries

[0036] A charging method for a rechargeable lithium battery according to some example embodiments includes (1) charging the rechargeable lithium battery at a current density (C rate) of 4C to 10C under constant current (CC), and (2) charging the rechargeable lithium battery under constant voltage (CV), wherein the rechargeable lithium battery includes a positive electrode active material comprising a lithium-nickel composite oxide having a nickel content of greater than or equal to about 80 mol% based on 100 mol% of metals other than lithium.

[0037] The charging method may include constant voltage charging (2) after constant current charging (1). For example, constant voltage charging (2) may be performed immediately (or substantially immediately) after constant current charging (1), without interruption (or substantially without interruption).

[0038] As the nickel content increases, nickel-based positive electrode active materials exhibit increased reversible capacity, but their structural stability, thermal stability, and cycle life characteristics may deteriorate.

[0039] Some example implementations provide a charging method for a rechargeable lithium battery comprising a nickel-based positive electrode active material with a high nickel content, wherein the charging time is shortened by intentionally increasing the current density during constant current charging of the rechargeable lithium battery, and cycle life characteristics are improved by avoiding or reducing structural degradation reactions of the positive electrode active material while exhibiting similar capacity compared to conventional charging.

[0040] A charging method for a rechargeable lithium battery according to some example embodiments includes (1) charging the rechargeable lithium battery at a constant current density of 4C to 10C. The current density can be expressed as a C-rate, and the unit of the C-rate is C. Constant current charging can be performed at any C-rate selected from the range of 4C to 10C. In embodiments, 1C can be 200 mA / g, but it can be appropriately changed according to the battery material and design, and is not limited thereto.

[0041] During the charging process of a rechargeable lithium battery, the positive electrode active material can undergo continuous (e.g., substantially continuous) phase transitions, such as H1 (hexagonal 1) phase → M (monoclinic) phase → H2 (hexagonal 2) phase → H3 (hexagonal 3) phase. The H1 phase is a crystal structure in which the positive electrode active material has an intrinsic lattice constant in the c-axis direction; the H2 phase is a crystal structure in which the positive electrode active material has a lattice constant in the c-axis direction that is longer than the intrinsic lattice constant; and the H3 phase is a crystal structure in which the positive electrode active material has a lattice constant in the c-axis direction that is shorter than the intrinsic lattice constant.

[0042] If a rechargeable lithium-ion battery comprising a high-nickel positive electrode active material is charged at a conventional current density of 1C, the positive electrode active material may undergo a phase transition (H2→H3) during charging in a high-voltage region (e.g., approximately 4.2V or higher). If this H2→H3 phase transition occurs, the positive electrode active material may shrink rapidly in the c-axis direction and become structurally degraded. If this structural degraded positive electrode active material occurs, there is a problem of increased impedance (e.g., resistance) and reduced cycle life of the rechargeable lithium-ion battery.

[0043] A charging method for a rechargeable lithium battery according to some example embodiments includes charging the rechargeable lithium battery at a high current density of about 4C to about 10C to a charging cutoff voltage, in order to intentionally induce an overpotential caused by polarization and passivate the H2-H3 phase transition, thereby suppressing the lithium concentration on the positive electrode surface from decreasing to a level that would lead to the degradation of the positive electrode active material, resulting in improved cycle life compared to conventional charging methods.

[0044] For example, the current density in constant current charging can be about 5C to about 10C, such as about 5C to about 6C or about 5C to about 7C. In an embodiment, for example, about 1C = about 200mA / g.

[0045] If the current density is within the range described in this paper, the H2-H3 phase transition of the positive electrode active material can be effectively passivated, thereby improving the cycle life characteristics of the rechargeable lithium battery.

[0046] In constant current charging, the rechargeable lithium battery can be charged to a charging cutoff voltage of approximately 4.2V to approximately 5V, for example, to a charging cutoff voltage of approximately 4.3V to approximately 5V or to a charging cutoff voltage of approximately 4.4V to approximately 5V.

[0047] The differential capacity (dQ / dV)-voltage (V) plot of a rechargeable lithium battery evaluated after formation at 1C = 200 mA / g, current density 5C, and 3.6V to 4.3V may include a first peak at a charging voltage between approximately 3.8V and approximately 3.9V; a second peak at a charging voltage between approximately 4.0V and approximately 4.1V; and a third peak at a charging voltage between approximately 4.25V and approximately 4.3V.

[0048] Formation can be considered the first charge / discharge process after battery manufacturing. Following formation, a standard charge / discharge cycle can be performed, such as a second charge / discharge cycle. The differential capacity (dQ / dV)-voltage (V) diagram can be represented as a dQ / dV diagram based on the charge / discharge voltage, and is simply expressed as a dQ / dV diagram.

[0049] In an embodiment, the dQ / dV diagram may be, for example, a diagram obtained by charging / discharging a rechargeable lithium battery, which includes: an electrode assembly having a structure having a positive electrode containing a positive electrode active material, a polyolefin separator, and a lithium metal counter electrode stacked in sequence; and an electrolyte including a carbonate solvent and a lithium salt.

[0050] The dQ / dV plot represents the voltage-dependent capacity characteristics of the working ions of the active material in the positive electrode. The position, intensity difference, and area of ​​the main peak can be appropriately changed according to the type (or category) and physical properties of the active material in the positive electrode.

[0051] The first peak can be H1-M, where the positive electrode active material undergoes a phase transition from H1 (hexagonal 1) to M (monoclinic) during the charging process of the rechargeable lithium battery; the second peak can be M-H2, where the positive electrode active material undergoes a phase transition from M (monoclinic) to H2 (hexagonal 2) during the charging process of the rechargeable lithium battery; and the third peak can be H2-H3, where the positive electrode active material undergoes a phase transition from H2 (hexagonal 2) to H3 (hexagonal 3) during the charging process of the rechargeable lithium battery.

[0052] In the charging method of a rechargeable lithium battery according to some example embodiments, because constant current charging is performed at a high current density, the H2-H3 peak (the third peak) can be shifted to the right of the horizontal axis of the dQ / dV diagram and has a lower intensity, which can passivate the H2-H3 phase transition and thus improve the cycle life of the battery.

[0053] For example, if (for example, when) the intensity of the first peak is I1, the intensity of the second peak is I2 and the intensity of the third peak is I3, then I1>I2>I3 can be satisfied.

[0054] A charging method for a rechargeable lithium battery according to some example embodiments includes (2) constant voltage (CV) charging of the rechargeable lithium battery after constant current charging.

[0055] If only constant current charging is included, then because the charging capacity is limited, the remaining charging capacity can be supplemented by constant voltage charging after charging to the charging cutoff voltage using constant current charging.

[0056] For example, constant voltage charging can charge a rechargeable lithium battery to a charging capacity of approximately 175 mAh / g to approximately 240 mAh / g, wherein the charging capacity can be appropriately varied depending on the type (or kind) of the positive electrode active material.

[0057] Positive electrode active material

[0058] According to some example embodiments, the positive electrode active material comprises a lithium-nickel composite oxide having a nickel content of greater than or equal to about 80 mol% based on 100 mol% of metals other than lithium.

[0059] For example, the positive electrode active material can take the form of secondary particles in which multiple primary particles aggregate, and the average particle size (D) of the secondary particles... 50 The average particle size can range from approximately 10 μm to approximately 18 μm, for example, approximately 10 μm to approximately 16 μm or approximately 12 μm to approximately 15 μm. 50 The particle size distribution can be obtained by randomly measuring the size (diameter or major axis length) of approximately 20 particles in a scanning electron microscope image of the positive electrode active material, and taking the diameter of the particles that constitute 50% of the total volume in the particle size distribution as the average particle size (D). 50 If (for example, when) the average particle size (D) of the positive electrode active material 50 If the above range is met, high capacity and long cycle life can be achieved.

[0060] For example, the positive electrode active material may include a high-nickel positive electrode active material, wherein the nickel content is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 88 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91 mol%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%, based on 100 mol% of metals other than lithium in a lithium-nickel composite oxide. High-nickel positive electrode active materials can achieve high capacity and can be used in high-capacity, high-density rechargeable lithium batteries.

[0061] For example, the positive electrode active material may include a lithium nickel-based composite oxide represented by Chemical Formula 1.

[0062] Chemical Formula 1

[0063] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0064] 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, M 1 and M 2 are each independently one or more elements selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Y and Zr, and X is one or more elements selected from F, P and S. <0​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Co, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr, and X is one or more elements selected from F, P, and S.

[0071] In Chemical Formula 2, 0.9 ≤ x2 < 1, 0 < y2 ≤ 0.1, and 0 ≤ z2 ≤ 0.1; 0.91 ≤ x2 < 1, 0 < y2 ≤ 0.09, and 0 ≤ z2 ≤ 0.08; or 0.94 ≤ x2 < 1, 0 < y2 ≤ 0.06, and 0 ≤ z2 ≤ 0.06.

[0072] Chemical Formula 3

[0073] Li a3 Ni x3 Co y3 M 4 z3 O 2-b3 X b3

[0074] 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, and 0 ≤ b3 ≤ 0.1, M 4 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr, and X is one or more elements selected from F, P, and S.

[0075] In Chemical Formula 3, 0.9 ≤ x3 < 1, 0 < y3 ≤ 0.1, and 0 ≤ z3 ≤ 0.1; 0.91 ≤ x3 < 1, 0 < y3 ≤ 0.09, and 0 ≤ z3 ≤ 0.08; or 0.94 ≤ x3 < 1, 0 < y3 ≤ 0.06, and 0 ≤ z3 ≤ 0.06.

[0076] Positive electrode

[0077] In some exemplary embodiments, the positive electrode includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector, wherein the positive electrode active material layer includes the aforementioned positive electrode active material.

[0078] In addition to the aforementioned positive electrode active material, the positive electrode active material layer may further include other types (or kinds) of positive electrode active materials.

[0079] For example, the positive electrode active material layer may further include a compound capable of intercalating and deintercalating lithium (lithiation intercalation compound), and may further include at least one selected from lithium and composite oxides of metals selected from cobalt, manganese, nickel, and combinations thereof.

[0080] As an example, the positive electrode active material layer may further include a compound represented by any one of the following chemical formulas.

[0081] 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, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1- g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f)Fe2(PO4)3 (0≤f≤2); and Li a FePO4 (0.90≤a≤1.8).

[0082] 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; and L 1 It is Mn, Al, or a combination thereof.

[0083] In an embodiment, the positive electrode active material layer may optionally further include a binder, a conductive material (e.g., an electrically conductive material), or a combination thereof.

[0084] The binder is used to securely bond the positive electrode active material particles to each other and also to the positive electrode current collector. Examples of binders may include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon.

[0085] Conductive materials are used to impart conductivity (e.g., electrical conductivity) to electrodes, and any suitable material that does not cause chemical changes (e.g., does not cause undesirable chemical changes in a rechargeable lithium battery) and conducts electrons can be used in a battery. Examples of conductive materials may include: carbon-based materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials in the form of metal powders and / or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0086] For example, the positive electrode may further include components that can be used as a sacrificial positive electrode.

[0087] Based on a 100wt% positive electrode active material layer, the amount of positive electrode active material can be from about 90wt% to about 99wt%, and based on a 100wt% positive electrode active material layer, the amounts of binder and conductive material can be from about 0.5wt% to about 5wt%, respectively.

[0088] The positive electrode current collector may include, but is not limited to, Al foil.

[0089] In some example embodiments, the loading level of the positive electrode active material layer may be about 10 mg / cm². 2 ~ Approximately 40 mg / cm 2 For example, about 10 mg / cm 2 ~ Approximately 30 mg / cm 2 or about 10mg / cm 2 ~ Approximately 20 mg / cm 2 .

[0090] In this embodiment, the density of the positive electrode active material layer in the final pressed positive electrode can be approximately 3.0 g / cc to approximately 3.7 g / cc, for example, approximately 3.1 g / cc to approximately 3.7 g / cc, approximately 3.3 g / cc to approximately 3.6 g / cc, or approximately 3.4 g / cc to approximately 3.58 g / cc. Positive electrodes meeting the loading level and density of the positive electrode active material layer within the above range are suitable for realizing high-capacity, high-energy-density rechargeable lithium batteries.

[0091] Rechargeable lithium batteries

[0092] A rechargeable lithium battery includes the aforementioned positive electrode, negative electrode, and electrolyte. As an example, a rechargeable lithium battery may include a positive electrode, a negative electrode, a separator between the positive and negative electrodes, and an electrolyte.

[0093] Rechargeable lithium batteries can be classified according to their shape as cylindrical batteries, prismatic batteries, pouch batteries, coin-shaped batteries, etc. Figures 1-4 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 1 A cylindrical battery is shown. Figure 2 A prismatic battery is shown, and Figure 3 and Figure 4 A pouch-type battery is shown.

[0094] refer to Figures 1-4 The rechargeable lithium battery 100 includes: an electrode assembly 40 including a separator 30 between a positive electrode 10 and a negative electrode 20; and a housing containing the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte.

[0095] like Figure 1 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. In an embodiment, in Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 3 and Figure 4As shown, the rechargeable lithium battery 100 includes electrode terminals 70 that serve as electrical paths to guide current formed in the electrode assembly 40 to the outside. Figure 4 For example, positive electrode terminal 71 and negative electrode terminal 72. Figure 3 ).

[0096] Rechargeable lithium batteries can be used in automobiles, mobile phones and / or various suitable types (or kinds) of electronic devices, and this disclosure is not limited thereto.

[0097] negative electrode

[0098] The negative electrode may include a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material and may further include a binder, a conductive material (e.g., an electrically conductive material) or a combination thereof.

[0099] Negative electrode active material

[0100] The negative electrode active material may include materials that can reversibly insert / deintercalate lithium ions, lithium metal, lithium metal alloys, materials that can be doped / dedoped with lithium, and / or transition metal oxides.

[0101] Materials that can reversibly insert / deintercalate lithium ions may include carbon-based negative electrode active materials, such as crystalline carbon, amorphous carbon, or combinations thereof. Crystalline carbon may be graphite, such as amorphous, sheet-like, flake-like, spherical, and / or fibrous natural graphite and / or artificial graphite, and amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0102] Lithium metal alloys include alloys of lithium and metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0103] Materials capable of doping / dedoping lithium can be Si-based and / or Sn-based negative electrode active materials. Si-based negative electrode active materials may include silicon, silicon-carbon composites, and SiO₂. x(0 < x ≤ 2), Si-Q alloy (where Q is 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, such as 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 combinations thereof. The Sn-based negative electrode active material may include Sn, SnO x (0 < x ≤ 2) (e.g., SnO2), Sn alloy, or combinations thereof.

[0104] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size (D 50 ) may be, for example, about 0.5 μm to about 20 μm. According to some example embodiments, 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 (cores) in which primary silicon particles are assembled and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be between the primary silicon particles and, for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in the amorphous carbon matrix.

[0105] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or combinations thereof. The amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, calcined coke, etc.

[0106] If (e.g., when) the silicon-carbon composite includes silicon and amorphous carbon, then based on 100 wt% of the silicon-carbon composite, the amount of silicon may be about 10 wt% to about 50 wt%, and the amount of amorphous carbon may be about 50 wt% to about 90 wt%. In an embodiment, if (e.g., when) the silicon-carbon composite includes silicon, amorphous carbon, and crystalline carbon, then based on 100 wt% of the silicon-carbon composite, the amount of silicon may be about 10 wt% to about 50 wt%, the amount of crystalline carbon may be about 10 wt% to about 70 wt%, and the amount of amorphous carbon may be about 20 wt% to about 40 wt%.

[0107] In an embodiment, the thickness of the amorphous carbon coating may be about 5 nm to about 100 nm. The average particle size (D 50) can be from about 10 nm to about 1 μm or from about 10 nm to about 200 nm. The silicon particles can exist as elemental silicon (e.g., pure silicon), in the form of a silicon alloy, and / or in an oxidized form of silicon. The oxidized form of silicon can be represented as SiO x (0 < x ≤ 2). In an embodiment, the atomic content ratio of Si:O indicating the degree of oxidation can be from about 99:1 to about 33:67. In this specification, as used herein, if (e.g., when) no other limitation is provided otherwise, the average particle size (D 50 ) indicates the diameter of the particles in which the cumulative volume in the particle distribution is about 50% by volume.

[0108] Si-based negative electrode active materials and / or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials. If (e.g., when) a mixture of Si-based negative electrode active materials and / or Sn-based negative electrode active materials and carbon-based negative electrode active materials is used, the weight mixing ratio can be from about 1:99 to about 90:10.

[0109] A binder is used to attach the negative electrode active material particles to each other well and also to attach the negative electrode active material well to the negative electrode current collector. The binder can include a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0110] The non-aqueous binder can include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0111] The aqueous binder can be selected from styrene-butadiene rubber, (meth)acrylated 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 a combination thereof.

[0112] If (e.g., when) an aqueous binder is used as the binder in the negative electrode active material layer, a cellulose-based compound capable of imparting or increasing viscosity can be further included. The cellulose-based compound can include at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and its alkali metal salts. The alkali metal can include Na, K, and / or Li.

[0113] Dry adhesives can be polymeric materials that are capable of being fibrous (e.g., capable of being fibrous), and can be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0114] This includes conductive materials to provide electrode conductivity (e.g., electrical conductivity), and any suitable conductive material may be used as a conductive material (e.g., electrical conductivity material) unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Examples of conductive materials include carbon-based materials such as natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials such as metal powders and / or metal fibers, including copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0115] Based on a 100wt% negative electrode active material layer, the amount of negative electrode active material can be from about 95wt% to about 99.5wt%, and based on the 100wt% negative electrode active material layer, the amount of binder can be from about 0.5wt% to about 5wt%. For example, the negative electrode active material layer may include about 90wt% to about 99wt% of negative electrode active material, 0.5wt% to about 5wt% of binder, and 0.5wt% to about 5wt% of conductive material.

[0116] 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), and / or alloys thereof, and may be in the form of foil, sheet, and / or foam. The thickness of the negative electrode current collector may be, for example, about 1 μm to about 20 μm, about 5 μm to about 15 μm, or about 7 μm to about 10 μm.

[0117] electrolyte

[0118] For example, the electrolyte used in rechargeable lithium batteries may be an electrolyte that may include non-aqueous organic solvents and lithium salts.

[0119] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of a battery. Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0120] Carbonate solvents may 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), butyl carbonate (BC), etc. Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. In embodiments, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include: nitriles, such as R-CN (where R is a C2-C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0121] Non-aqueous organic solvents may be used alone or in mixtures of two or more types (or kinds), and if (for example, when) a mixture of two or more types (or kinds) is used, the mixing ratio may be appropriately or suitably adjusted according to suitable or desired battery performance, as will be readily apparent to a person skilled in the art upon reading this disclosure.

[0122] In an embodiment, if (for example, when) a carbonate solvent is used, cyclic carbonates and chain carbonates can be mixed and used, and the cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0123] 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 about 1:1 to about 30:1.

[0124] The electrolyte may further include ethylene carbonate, vinylene carbonate and / or ethylene carbonate compounds to improve battery cycle life.

[0125] Examples of ethylene carbonate compounds may include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, etc.

[0126] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in the battery, ensuring the basic operation of the rechargeable lithium battery and improving lithium ion transport between the positive and negative electrodes. For example, lithium salts may include those selected from 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 SO2 (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0127] The concentration of lithium salt can be in the range of about 0.1 M to about 2.0 M. If the concentration of lithium salt is within this range, the electrolyte has appropriate or suitable ionic conductivity and viscosity, thus achieving excellent performance and allowing lithium ions to move efficiently.

[0128] diaphragm

[0129] Depending on the type (or category) of the rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include polyethylene separators, polypropylene separators, polyvinylidene fluoride separators, or multilayer films of two or more layers thereof (such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, polypropylene / polyethylene / polypropylene three-layer separators, etc.).

[0130] The diaphragm may include a porous substrate and a coating on one or both surfaces of the porous substrate (e.g., two opposite surfaces), the coating comprising an organic material, an inorganic material, or a combination thereof.

[0131] The porous substrate may be a polymer membrane formed from any one or more copolymers or mixtures of the following polymers: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., ).

[0132] The porous substrate may have a thickness of about 1 μm to about 40 μm (e.g., about 1 μm to about 30 μm, about 1 μm to about 20 μm, about 5 μm to about 15 μm or about 10 μm to about 15 μm).

[0133] Organic materials may include (meth)acrylic acid copolymers, the (meth)acrylic acid copolymers comprising: a first structural unit derived from (meth)acrylamide; and a second structural unit comprising at least one structural unit selected from structural units derived from (meth)acrylic acid or (meth)acrylates and structural units derived from (meth)acrylamidosulfonic acid or salts thereof.

[0134] 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... 50 The range can be approximately 1 nm to approximately 2000 nm, for example, approximately 100 nm to approximately 1000 nm or approximately 100 nm to approximately 700 nm.

[0135] Organic and inorganic materials can be mixed in a single coating, or they can exist in the form of a stacked coating comprising organic materials and a coating comprising inorganic materials.

[0136] The thickness of the coating can be from about 0.5 μm to about 20 μm, for example, from about 1 μm to about 10 μm or from about 1 μm to about 5 μm.

[0137] Embodiments and comparative examples of this disclosure are described below. However, the following embodiments are merely examples of this disclosure, and this disclosure is not limited to the following embodiments.

[0138] Preparation example: Manufacturing of rechargeable lithium battery cells

[0139] Preparation Example 1

[0140] 98.5 wt% of LiNi was used as the positive electrode active material. 0.9 Mn 0.1 O2(D 50 A slurry for the positive electrode active material layer was prepared by mixing 1.0 wt% polyvinylidene fluoride binder (12 μm) and 0.5 wt% carbon nanotube conductive material. This slurry was then coated onto an aluminum foil current collector, dried, and pressed to fabricate the positive electrode. In this paper, the positive electrode active material layer has a concentration of 20 mg / cm³. 2 The loading level, and the final pressed positive electrode has a density of about 3.4 g / cc.

[0141] A negative electrode active material layer slurry was prepared by mixing 97.5 wt% graphite, 1.5 wt% carboxymethyl cellulose, and 1 wt% styrene-butadiene rubber as the negative electrode active material in an aqueous solvent. The negative electrode active material layer slurry was coated onto a copper foil current collector, then dried and pressed to manufacture the negative electrode.

[0142] A polytetrafluoroethylene (PTFE) membrane is provided between the positive and negative electrodes, which is then inserted into a housing, and an electrolyte (prepared by mixing ethylene carbonate and dimethyl carbonate in a 3:7 volume ratio and dissolving 1 M LiPF6 therein) is injected therein to manufacture a rechargeable lithium battery cell.

[0143] Preparation Example 2

[0144] The rechargeable lithium battery cell of Preparation Example 2 was manufactured in essentially the same manner as in Preparation Example 1, except that LiNi was used. 0.88 Co 0.10 Al 0.02 O2(D 50 =12μm) as the active material for the positive electrode.

[0145] Preparation Example 3

[0146] The rechargeable lithium battery cell of Preparation Example 3 was manufactured in essentially the same manner as in Preparation Example 1, except that LiNi was used. 0.66 Mn 0.34 O2(D 50 =12μm) as the active material for the positive electrode.

[0147] Preparation Example 4

[0148] The rechargeable lithium battery cell of Preparation Example 4 was manufactured in essentially the same manner as in Preparation Example 1, except that LiCoO2 (D) was used. 50 =15μm) as the active material for the positive electrode.

[0149] Evaluation Example 1: dQ / dV Evaluation

[0150] The rechargeable lithium battery cell according to Preparation Example 1 was charged at a constant current of 0.2C to the upper limit voltage of 4.3V and charged at a constant voltage to 0.05C, and then discharged at 0.2C to the cutoff voltage of 3.0V for formation process (first charge / discharge).

[0151] Subsequently, the rechargeable lithium-ion battery cells were charged at constant current densities of 0.2C, 0.5C, 1C, 2C, and 5C to the charging cutoff voltage of 4.3V, and then charged at constant voltage until the capacity reached 200mAh / g. They were then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge cycle (second charge / discharge). The dQ / dV of the rechargeable lithium-ion battery cells were evaluated under the conditions of 1C = 200mA / g and 3.6V–4.3V.

[0152] In addition, the rechargeable lithium battery cell of Preparation Example 3 was charged at a constant current of 0.2C to the upper limit voltage of 4.3V and charged at a constant voltage to 0.05C, and then discharged at 0.2C to the cutoff voltage of 3.0V for formation process (first charge / discharge).

[0153] Subsequently, the rechargeable lithium-ion battery cells were charged at constant current densities of 0.2C, 0.5C, 1C, 2C, and 5C to a charging cutoff voltage of 4.3V, and then charged at constant voltage until the capacity reached 180mAh / g. They were then discharged at 0.33C to a cutoff voltage of 3.6V for a standard charge / discharge cycle (second charge / discharge). The dQ / dV of the rechargeable lithium-ion battery cells were evaluated under conditions of 1C = 200mA / g and 3.6V–4.3V.

[0154] Figure 5 The diagram shows the dQ / dV of the rechargeable lithium battery cell of Preparation Example 1 after formation, based on voltage. Figure 5 Five curves are shown after formation at different current densities, with each curve showing the H1-M peak, M-H2 peak, and H2-H3 peak.

[0155] refer to Figure 5 In the case of rechargeable lithium-ion battery cells comprising high-nickel positive electrode active materials, as the current density increases from 0.2C to 5C, the H1-M peak, M-H2 peak, and H2-H3 peak shift to the right of the horizontal axis in the figure. Furthermore, the lower the intensity of the H2-H3 peak, the higher the current density, confirming that the H2-H3 phase transition of the positive electrode active material can be passivated if (e.g., when) charged at a high current density.

[0156] in addition, Figure 6 The graph shows the dQ / dV of the rechargeable lithium battery cell of Preparation Example 3 after formation, based on voltage. Figure 6 Five curves are shown after formation at different current densities, with each curve showing the H1-H2 peaks.

[0157] refer to Figure 6 In rechargeable lithium batteries that include nickel-based positive electrode active materials, with Figure 5Unlike other conditions, even when the charging voltage is increased to 4.3V, there is no H2-H3 phase transition.

[0158] Example: Charging method for a single rechargeable lithium battery cell

[0159] Example 1

[0160] The rechargeable lithium battery cell of Preparation Example 1 was charged at a constant current of 0.2C to the upper limit voltage of 4.3V and then charged at a constant voltage to 0.05C, and then discharged at 0.2C to the cutoff voltage of 3.0V for formation process (first charge / discharge).

[0161] Subsequently, the rechargeable lithium battery cells were charged at a constant current density of 5C to the charging cutoff voltage of 4.3V and then charged at a constant voltage until the capacity reached 200mAh / g. They were then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge cycle (second charge / discharge). The discharge capacity during the standard charge / discharge cycle is shown as the initial discharge capacity in Table 1.

[0162] Subsequently, the rechargeable lithium battery cells were repeatedly charged and discharged 100 times under the same conditions as standard charging / discharging to calculate the ratio of the discharge capacity of the 100th cycle to the initial discharge capacity. This is shown in Table 1 as the 100th cycle life retention rate.

[0163] Comparative Example 1

[0164] First, the rechargeable lithium battery cell of Preparation Example 1 was charged and discharged under the same conditions as the formation process (first charge / discharge) in Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 1C to the charging cutoff voltage of 4.3V, and then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0165] Comparative Example 2

[0166] First, the rechargeable lithium battery cell of Preparation Example 1 was charged and discharged under the same conditions as the formation process (first charge / discharge) in Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 5C to the charging cutoff voltage of 4.3V, and then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0167] Comparative Example 3

[0168] First, the rechargeable lithium battery cell of Preparation Example 1 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current to a charging cutoff voltage of 4.3V by sequentially decreasing the current density at 5C, 3C, and 2C, and then discharged at 0.33C to a cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0169] Example 2

[0170] First, the rechargeable lithium battery cell of Preparation Example 2 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 5C to the charging cutoff voltage of 4.3V, and then charged at a constant voltage until the capacity reached 200mAh / g. Finally, it was discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0171] Comparative Example 2-1

[0172] First, the rechargeable lithium battery cell of Preparation Example 2 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 1C to the charging cutoff voltage of 4.3V, and then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0173] Comparative Example 4

[0174] First, the rechargeable lithium battery cell of Preparation Example 4 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 5C to the charging cutoff voltage of 4.3V, and then charged at a constant voltage until the capacity reached 174mAh / g. Finally, it was discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0175] Comparative Example 4-1

[0176] First, the rechargeable lithium battery cell of Preparation Example 4 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 1C to the charging cutoff voltage of 4.3V, and then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0177] Comparative Example 5

[0178] First, the rechargeable lithium battery cell of Preparation Example 3 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 5C to the charging cutoff voltage of 4.3V, and then charged at a constant voltage until the capacity reached 180mAh / g. Finally, it was discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0179] Comparative Example 6

[0180] First, the rechargeable lithium battery cell of Preparation Example 3 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 1C to the charging cutoff voltage of 4.3V, and then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0181] Comparative Example 7

[0182] First, the rechargeable lithium battery cell of Preparation Example 3 was charged and discharged under the same conditions as the formation process (first charge / discharge) of Example 1. Then, the rechargeable lithium battery cell was charged at a constant current density of 5C to the charging cutoff voltage of 4.3V, and then discharged at 0.33C to the cutoff voltage of 3.6V for a standard charge / discharge (second charge / discharge).

[0183] Evaluation Example 2: SEM Image Analysis

[0184] In Example 1 and Comparative Examples 1, 2, 6, and 7, after 100 cycles were independently repeated under the same conditions as standard charge / discharge, images of the cross-sections of the positive electrode active material particles after discharge were captured using a scanning electron microscope (SEM), and then shown. Figures 8-12 middle.

[0185] refer to Figure 8 and Figure 9 In Comparative Example 1, constant current charging was performed at a current density of 1C, which was lower than that in Example 1. Because the high-nickel positive electrode active material undergoes an H2-H3 phase transition during the charging process, the particles were severely broken.

[0186] Evaluation Example 3: Analysis of the characteristics of a rechargeable lithium battery cell

[0187] The initial discharge capacity and charging time required for constant current charging to the charging cutoff voltage of 4.3V were measured in individual rechargeable lithium-ion battery cells of Examples 1 and 2, and Comparative Examples 1 to 7, during each independent standard charge / discharge cycle (second charge / discharge). The results are shown in Table 1. Additionally, the standard charge / discharge cycles of Examples 1 and Comparative Example 1 are shown in the form of capacity-voltage graphs. Figure 7 middle.

[0188] In addition, in Examples 1 and 2 and Comparative Examples 1 to 7, after 100 cycles were independently repeated under the same conditions as standard charging / discharging, the ratio of the discharge capacity of the 100th cycle to the initial discharge capacity was calculated, and then shown in Table 1 as the lifetime retention rate of the 100th cycle.

[0189] Table 1

[0190]

[0191] Referring to Table 1, Example 1 exhibits a short charging time, which is about two-thirds of the charging time of Comparative Example 1, but shows a higher cycle life retention rate than Comparative Examples 1 to 3.

[0192] Example 2 exhibits a larger initial discharge capacity, shorter charging time, and higher cycle life retention compared to Comparative Example 2-1.

[0193] Furthermore, Comparative Examples 4 and 4-1 show that even when using the 5C / CV charging method, the cycle life retention rate is lower than when using the 1C charging method.

[0194] Furthermore, for rechargeable lithium batteries containing nickel-based positive electrode active materials, it was confirmed that the charging methods of Comparative Examples 5 to 7 showed that even when using the 5C / CV charging method, the cycle life retention rate was worse than when using the 1C charging method.

[0195] While the subject matter of this disclosure has been described in conjunction with exemplary embodiments currently considered practical, it should be understood that this disclosure is not limited to the disclosed embodiments. Rather, it is intended to cover various suitable modifications and equivalent arrangements included within the spirit and scope of the claims and their equivalents.

Claims

1. A charging method for a rechargeable lithium battery, the method comprising: The rechargeable lithium battery is charged at a constant current density of 4C to 10C; and the rechargeable lithium battery is charged at a constant voltage. The rechargeable lithium battery includes a positive electrode active material, which comprises a lithium-nickel composite oxide having a nickel content of greater than or equal to 80 mol% based on 100 mol% of metals other than lithium.

2. The method of claim 1, wherein: The current density in the constant current charging is 5C to 10C.

3. The method of claim 1, wherein: In the constant current charging, the rechargeable lithium battery is charged to a charging cutoff voltage of 4.2V to 5V.

4. The method of claim 1, wherein: The differential capacity-voltage diagram was evaluated after formation at 1C = 200 mA / g, a current density of 5C, and a voltage range of 3.6V to 4.3V. The rechargeable lithium battery exhibits a first peak at a charging voltage between 3.8V and 3.9V; a second peak at a charging voltage between 4.0V and 4.1V; and a third peak at a charging voltage between 4.25V and 4.3V.

5. The method of claim 4, wherein: The third peak is the peak at which the positive electrode active material undergoes a phase transition from H2 to H3 during the charging process.

6. The method of claim 4, wherein: If the intensity of the first peak is I1, the intensity of the second peak is I2, and the intensity of the third peak is I3, then I1>I2>I3 is satisfied.

7. The method of claim 1, wherein: In the constant voltage charging process, the rechargeable lithium battery is charged to a charging capacity of 175 mAh / g to 240 mAh / g.

8. The method of claim 1, wherein: The positive electrode active material is in the form of secondary particles formed by the aggregation of multiple primary particles.

9. The method of claim 1, wherein: The average particle size D of the positive electrode active material 50 The size ranges from 10μm to 18μm.

10. The method of claim 1, wherein: The positive electrode active material includes a high-nickel positive electrode active material in which the nickel content of metals other than lithium in the lithium-nickel composite oxide is greater than or equal to 90 mol%.

11. The method of claim 1, wherein: The positive electrode active material includes a lithium-nickel composite oxide represented by 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, M 1 and M 2 Each element is independently selected from one or more elements chosen from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr, and X is selected from one or more elements chosen from F, P, and S.

12. The method of claim 1, wherein: The positive electrode active material includes a lithium-nickel-manganese composite oxide represented by chemical formula 2: Chemical formula 2 Li a2 Ni x2 Mr y2 M 3 z2 O 2-b2 X b2 Among them, 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 and 0 ≤ b2 ≤ 0.1, M 3 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Co, Mo, Nb, Si, Sr, Ti, V, W, Y, and Zr, and X is one or more elements selected from F, P, and S.

13. The method of claim 1, wherein: The positive electrode active material includes a lithium-nickel-cobalt composite oxide represented by chemical formula 3: Chemical formula 3 Li a3 Ni x3 Co y3 M 4 z3 O 2-b3 X b3 Among them, 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 and 0 ≤ b3 ≤ 0.1, M 4 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Y and Zr, and X is one or more elements selected from F, P and S.

14. The method of claim 1, wherein: The rechargeable lithium battery includes a positive electrode active material layer containing the positive electrode active material, and The loading level of the positive electrode active material layer is 10 mg / cm³. 2 ~40mg / cm 2 .

15. The method of claim 14, wherein: The density of the positive electrode active material layer is 3.0 g / cc to 3.7 g / cc.

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