Negative active material, method of preparing same, and rechargeable lithium battery including same

Abstract

Disclosed are a negative active material, a method of preparing the same, and a rechargeable lithium battery including the same. The negative electrode active material includes: a core including a carbonaceous material; and a metal-containing nitride on the surface of the core and having a lower lithium adsorption energy and a lower lithium ion diffusion energy than the core.

Description

TECHNICAL FIELD

[0001] Embodiments of the present disclosure relate to a negative active material, a method of preparing the same, and a rechargeable lithium battery including the same. BACKGROUND

[0002] Recently, as electronic devices using batteries (e.g., mobile phones, laptop computers, and electric vehicles) are rapidly popularized, the demand for rechargeable lithium batteries that are smaller, lighter, and relatively high in capacity is rapidly increasing. It has been considered to improve the performance of rechargeable lithium batteries.

[0003] A rechargeable lithium battery includes a positive electrode and a negative electrode including an active material capable of intercalating and deintercalating lithium ions, and an electrolyte, and generates electric energy through oxidation and reduction reactions when lithium ions are intercalated / deintercalated at the positive electrode and the negative electrode. SUMMARY

[0004] One or more embodiments of the present disclosure provide a negative active material exhibiting high initial efficiency, long cycle life characteristics, and excellent rapid charging rate.

[0005] Another embodiment provides a method of preparing the negative active material.

[0006] Still another embodiment provides a rechargeable lithium battery including the negative active material.

[0007] One or more embodiments provide a negative active material including: a core including a carbonaceous material; and a metal-containing nitride on a surface of the core and having a low lithium adsorption energy and a low lithium ion diffusion energy compared to the core.

[0008] Another embodiment provides a method of preparing a negative active material, the method including: coating a crystalline carbon with a metal compound liquid to prepare a primary coated material; performing a primary heat treatment on the primary coated material to prepare a primary heat treatment product; preparing a mixture including the primary heat treatment product and a magnesium powder; performing a secondary heat treatment on the mixture under a nitrogen atmosphere to prepare a secondary heat treatment product; and etching the secondary heat treatment product.

[0009] Still another embodiment provides a rechargeable lithium battery including: a negative electrode including the negative active material; a positive electrode; and a non-aqueous electrolyte.

[0010] The negative active material according to one or more embodiments can exhibit high initial efficiency, long cycle life characteristics, and excellent rapid charging rate. BRIEF DESCRIPTION OF DRAWINGS

[0011] The accompanying drawings, together with the specification, illustrate embodiments of the presently disclosed subject matter and, along with the description of the

[0012] Figures 1 to 4 is a schematic diagram illustrating a rechargeable lithium battery according to some embodiments.

[0013] Figure 5A is a graph showing the results of X-ray diffraction analysis of the negative electrode active material prepared according to Example 1 to Example 6 and Comparative Example 1, and Figure 5B and Figure 5C is Figure 5A is a magnified view of a portion of

[0014] Figure 6A is a transmission electron microscope (TEM) image of the negative electrode active material prepared according to Example 2, and Figure 6B is a set of fast Fourier transform (FFT) images of the negative electrode active material prepared according to Example 2. DETAILED DESCRIPTION

[0015] Hereinafter, embodiments of the present disclosure are described in more detail. However, these embodiments are examples, the present disclosure is not limited thereto, and the present disclosure is defined by the scope of the appended claims and equivalents thereof.

[0016] As used herein, when an element, such as a layer, film, region, or substrate, is referred to as being "on" another element, it can be directly on the other element, or intervening elements can also be present.

[0017] The singular expression includes the plural expression unless otherwise specified in the specification. Unless otherwise stated, "A or B" can mean "including A, including B, or including A and B".

[0018] As used herein, the term "combination thereof" can include a mixture, a laminate, a composite, a copolymer, an alloy, a blend, a reactant, and / or a reaction product of the components.

[0019] As used herein, the particle diameter can be an average particle diameter, when not otherwise provided. Such a particle diameter indicates an average particle diameter (D50) at which the cumulative volume is about 50% by volume in a particle size distribution. The average particle diameter (D50) can be measured by any suitable method generally used in the art (for example, by a particle size analyzer and / or by a transmission electron micrograph image and / or a scanning electron micrograph image). In some embodiments, data analysis is performed using a dynamic light scattering measuring device, and the number of particles for each particle size range is counted, and from this the average particle diameter (D50) value can be easily obtained by calculation. The average particle diameter can be measured by a laser diffraction method. Laser diffraction can be performed by dispersing the particles to be measured in a dispersion solvent and introducing them into a commercially available laser diffraction particle measuring device (for example, an MT 3000 available from Microtrac Corporation), irradiating ultrasonic waves at about 28 kHz at a power of about 60 W, and calculating the average particle diameter (D50) at 50% of the particle distribution in the measuring device.

[0020] In some embodiments, the average particle diameter can be measured by various suitable techniques, and for example, can be measured by a particle analyzer.

[0021] In some embodiments, the thickness can be measured for a cross-section by SEM and / or TEM images, but is not limited thereto, and can be measured by any suitable technique in the art, as long as it can measure a suitable thickness. The thickness can be an average thickness.

[0022] As used herein, soft carbon refers to graphitizable carbon materials that are easily graphitized by heat treatment at high temperatures (for example, about 2800°C), and hard carbon refers to non-graphitizable carbon materials that are substantially not graphitized or slightly graphitized by heat treatment. The terms "soft carbon" and "hard carbon" can be easily understood by a person of ordinary skill in the art upon reading the present disclosure.

[0023] In some embodiments, crystalline carbon and amorphous carbon can be distinguished by X-ray diffraction (XRD) measurement. Crystalline carbon includes natural graphite and artificial graphite. Natural graphite can mean graphite that can be naturally produced by separating it from a mineral, and if measured by XRD, the interplanar spacing (d002) of the (002) plane can be about 3.350 Å to about 3.360 Å. Artificial graphite can mean graphite manufactured by graphitization, and if (for example, when) measured by XRD, the interplanar spacing (d002) of the (002) plane can be about 3.355 Å to about 3.365 Å. In embodiments, if measured by XRD, the interplanar spacing (d002) of the (002) plane of amorphous carbon can be about 3.34 Å or less. XRD can be measured using CuKα rays as a target ray, with an X-ray diffractometer (for example, product name: X'Pert, manufacturer: Malvern Panalytical) and by removing a monochromator to improve peak density resolution. The measurement conditions can be 2θ = 10° to 80°, the scan speed (° / s) is 0.044 to 0.089, and the step (° / step) is 0.013 to 0.039.

[0024] The negative electrode active material according to one or more embodiments includes: a core including a carbonaceous material; and a metal-containing nitride on a surface of the core and having a low lithium adsorption energy and a low lithium ion diffusion energy compared to the core.

[0025] In one or more embodiments, the lithium adsorption energy of the metal-containing nitride can be about -5.0 eV or more and less than about -1.0 eV, about -4.0 eV or more and less than about -1.0 eV, or about -3.0 eV to about -1.5 eV.

[0026] In one or more embodiments, the lithium adsorption energy refers to an adsorption energy for lithium, and can be theoretically obtained by density functional theory (DFT) calculation.

[0027] The lithium ion diffusion energy of the metal-containing nitride can be about 0 eV to about 0.20 eV, about 0 eV to about 0.10 eV, or about 0 eV to about 0.05 eV.

[0028] In one or more embodiments, the lithium adsorption energy of the carbonaceous material core can be about -1.0 eV to about 1.0 eV, about -1.0 eV to about 0 eV, about -0.5 eV to about 0 eV, or about -0.2 eV to about 0 eV. The lithium ion diffusion energy of the carbonaceous material core can be about 0.01 eV to about 1.0 eV, about 0.01 eV to about 0.7 eV, or about 0.05 eV to about 0.5 eV.

[0029] The lithium adsorption energy and lithium ion diffusion energy of the metal nitride-containing substance are lower than the lithium adsorption energy and lithium ion diffusion energy of the carbonaceous material core, and in one or more embodiments, a metal nitride-containing substance having a lithium adsorption energy of about -5.0 eV or more and less than about -1.0 eV and a lithium ion diffusion energy of about 0 eV to about 0.20 eV can facilitate lithium ion intercalation and can adsorb and effectively transfer lithium ions on the surface of the carbonaceous material core, thereby serving as a path for transporting lithium ions.

[0030] If the metal nitride-containing substance is located on the surface of the carbonaceous material core, a lithium ion transport path that facilitates lithium ion intercalation during charging and discharging is formed, and thus, lithium ions can be rapidly intercalated into the interior of the carbonaceous material.

[0031] The metal nitride-containing substance can reduce the interfacial resistance generated on the surface of the carbonaceous material core. The interfacial resistance generated on the surface of the carbonaceous material increases, causing slow intercalation of lithium ions, thereby causing formation of lithium metal dendrites. In one or more embodiments, the metal nitride-containing substance reduces the interfacial resistance, thereby overcoming or reducing the disadvantages associated with the formation of lithium metal dendrites. Thus, deterioration of rapid charging rate and cycle life characteristics due to dendrites can be effectively prevented or reduced. As a result, the negative active material according to one or more embodiments can exhibit improved rapid charging rate and cycle life characteristics.

[0032] A metal nitride whose lithium adsorption energy or lithium ion diffusion energy is higher than the lithium adsorption energy or lithium ion diffusion energy of the carbonaceous material core can not be able to facilitate lithium ion intercalation, or can not be able to adsorb lithium ions and can hinder dispersion of lithium ions on the surface, and thus, lithium ions can not be transferred. If the metal nitride includes at least one metal, it is appropriate or desirable that all the metals included have a lithium adsorption energy or lithium ion diffusion energy lower than the lithium adsorption energy or lithium ion diffusion energy of the carbonaceous material core.

[0033] For example, aluminum nitride or silicon nitride having a lithium adsorption energy out of the range can not achieve the desired effect. ScN2 has a lithium adsorption energy of about -5.0 eV to about -4.0 eV, which is lower than graphite (about -1.0 eV to about 0 eV) as the carbonaceous material, but has a lithium ion diffusion energy of about 0.20 eV to about 0.25 eV, which is higher than graphite (about 0.01 eV to about 0.10 eV), and thus, it cannot serve as or include a path for transferring lithium ions.

[0034] The metal nitride-containing substance can be represented by Chemical Formula 1.

[0035] Chemical Formula 1 Me x N y wherein Me is Ti, Zr, Hf, Cr, Mo, Nb, Ta, W, V, or a combination thereof, 1≤x≤2 and 1≤y≤3.

[0036] The metal-containing nitride is TiN, ZrN, HfN, VN, NbN, TaN, CrN, or a combination thereof.

[0037] In one or more embodiments, the amount of the metal-containing nitride can be about 0.5 wt% to about 20 wt%, or about 0.5 wt% to about 10 wt% based on 100 wt% of the negative active material. If the amount of the metal-containing nitride is within the foregoing range, more excellent rapid charge and discharge characteristics and cycle life characteristics can be exhibited.

[0038] In some embodiments, it is not necessary to limit the morphology of the metal-containing nitride on the surface of the core. For example, the metal-containing nitride can be provided in a layer form such that the metal-containing nitride can be continuously present, or can be provided in an island form such that the metal-containing nitride can be discontinuously present.

[0039] The metal-containing nitride can be located on the surface of the core in a thickness of about 5 nm to about 300 nm, or can be provided in a thickness of about 5 nm to about 200 nm, in a thickness of about 5 nm to about 100 nm, or in a thickness of about 10 nm to about 50 nm. If the metal-containing nitride is located on the surface of the core in the foregoing thickness range, the metal-containing nitride can be more uniformly present on the surface of the core.

[0040] In one or more embodiments, the carbonaceous material included in the core can be crystalline carbon. The crystalline carbon can be natural graphite and / or artificial graphite of unspecified shape, flaky, flake-like, spherical, and / or fibrous, or a combination thereof.

[0041] In one or more embodiments, the amount of the core can be about 80 wt% to about 99.5 wt% or about 90 wt% to about 99.5 wt% based on total 100 wt% of the negative active material. In one or more embodiments, the core consists of the carbonaceous material, and thus, the amount of the core represents the amount of the carbonaceous material.

[0042] In one or more embodiments, the carbonaceous material can have a particle diameter, for example, an average particle diameter D50 of about 3 μm to about 20 μm or about 5 μm to about 15 μm. Maintaining the particle diameter of the carbonaceous material within the foregoing range can help to ensure the advantage or benefit of shortening the path of transporting lithium ions inside and between the carbonaceous materials. In one or more embodiments, if the core includes the carbonaceous material having a particle diameter within the foregoing range, the core can also have a particle diameter within the foregoing range.

[0043] In one or more embodiments, the metal-containing nitride can be on the surface of the carbonaceous material, for example, coated on the surface of the carbonaceous material, which can be confirmed by X-ray photoelectron spectroscopy (XPS) analysis. In one or more embodiments, if the negative active material according to one or more embodiments is subjected to XPS analysis, a peak related to the metal-containing nitride can be seen. For example, if a peak appears at about 36° to about 37°, about 42° to about 43°, about 61° to about 62°, it can be seen that TiN exists on the surface.

[0044] The metal-containing nitride on the surface of the carbonaceous material can be detected by a transmission electron microscope (TEM) image, for example, a fast Fourier transform (FFT) result of a high-resolution transmission electron microscope (HRTEM). In one or more embodiments, in the FFT result, if a crystal plane spacing is shown as about 0.20 nm to about 0.21 nm or about 0.23 nm to about 0.24 nm, the crystal plane spacing can correspond to TiC (200) and TiC (111), which can confirm that TiN exists on the surface. In one or more embodiments, the metal-containing nitride on the surface of the carbonaceous material can be detected by a SEM image and / or an EDS (energy dispersive spectroscopy) result.

[0045] The negative active material according to one or more embodiments can be used as a negative active material for a rechargeable lithium battery.

[0046] Method of manufacturing a negative active material The negative active material according to one or more embodiments can be manufactured by coating a crystalline carbon with a metal compound liquid to manufacture a primary coated material, subjecting the primary coated material to a primary heat treatment to manufacture a primary heat treatment product, preparing a mixture including the primary heat treatment product and a magnesium powder, subjecting the mixture to a secondary heat treatment under a nitrogen atmosphere to manufacture a secondary heat treatment product, and etching the secondary heat treatment product. Hereinafter, each process will be explained in more detail.

[0047] Coating a crystalline carbon with a metal compound liquid to manufacture a primary coated material.

[0048] The metal compound liquid can be prepared by adding a metal compound to a solvent, and the solvent can be methanol, ethanol, propanol, butanol, or a combination thereof, or can be anhydrous type (or kind), for example, anhydrous ethanol.

[0049] The metal compound can be a metal alkoxide, for example, a metal methoxide, a metal ethoxide, a metal butoxide, a metal propanoxide, or a combination thereof.

[0050] The metal can be Ti, Zr, Hf, Cr, Mo, Nb, Ta, W, V, or a combination thereof.

[0051] The metal compound can be added to the solvent to have about 0.5 wt% to about 20 wt%, about 0.5 wt% to about 10 wt%, or about 2 wt% to about 10 wt% of the metal compound based on 100 wt% of the crystalline carbon.

[0052] The coating can be performed by adding the crystalline carbon to the metal compound liquid, mixing, and removing the solvent therefrom. The removal of the solvent can be performed by drying.

[0053] The mixing can be performed at a speed (or rate) of about 50 rpm to about 500 rpm or at a speed of about 100 rpm to about 300 rpm. If the mixing is performed at the above speed, the crystalline carbon can be uniformly (e.g., substantially uniformly) dispersed in the metal compound liquid.

[0054] In the coating, a molten salt can be further added to the crystalline carbon. The molten salt can be NaCl, MgCl2, NaF, or a combination thereof, and in one or more embodiments, the molten salt can be a mixture of NaCl and MgCl2 and / or a mixture of NaCl and NaF. In the mixture, the mixing ratio of NaCl and MgCl2 or the mixing ratio of NaCl and NaF can be about 1:1 to about 8:1 by weight, about 2:1 to about 6:1 by weight, or about 3:1 to about 5:1 by weight.

[0055] In the coating, if the molten salt is further added, the metal compound liquid can be more uniformly coated on the carbonaceous material, and the metal compound can be converted into a metal oxide at a lower temperature in a subsequent process. In one or more embodiments, the use of the mixture having the mixing ratio as the molten salt can allow the melting temperature to be further reduced, thereby converting the mixture into a metal oxide at a significantly lower temperature.

[0056] In one or more embodiments, the amount of the molten salt can be about 50 parts by weight to about 200 parts by weight, about 100 parts by weight to about 200 parts by weight, or about 100 parts by weight to about 150 parts by weight based on 100 parts by weight of the crystalline carbon. If the amount of the molten salt is added within the above range, the effect of more uniform coating due to the use of the molten salt can be more sufficiently obtained.

[0057] The primary coating material can be subjected to a primary heat treatment to produce a primary heat treatment product. The primary heat treatment can be performed by increasing the temperature to about 600°C to about 1200°C at a temperature increase rate of about 0.5°C / min to about 7°C / min and maintaining for about 2 hours to about 8 hours. In one or more embodiments, the temperature increase rate can be about 1°C / min to about 7°C / min or about 1°C / min to about 5°C / min, the increased temperature can be about 600°C to about 1000°C, or about 800°C to about 1000°C, and the maintaining time can be about 2 hours to about 6 hours or about 2 hours to about 4 hours.

[0058] The primary heat treatment can be performed under an inert atmosphere, and the inert atmosphere can be nitrogen (N2), argon (Ar), or a combination thereof.

[0059] The primary heat treatment can decompose the metal compound and convert the metal compound into a metal oxide.

[0060] The mixture can be prepared by mixing the primary heat treatment product with magnesium powder. The magnesium powder can be a catalyst or a reducing agent, and the magnesium powder can generate a nitride in the secondary heat treatment.

[0061] In one or more embodiments, the mixing ratio of the primary heat treatment product and the magnesium powder can be adjusted to have a weight ratio of about 1:0.08 to about 1:0.3, a weight ratio of about 1:0.08 to about 1:0.2, or a weight ratio of about 1:0.1 to about 1:0.2. If the mixing ratio of the primary heat treatment product and the magnesium powder is within the foregoing range, the primary heat treatment product and the magnesium powder can be more uniformly dispersed, and safety can be further ensured or provided in the preparation.

[0062] The mixture is subjected to a secondary heat treatment under a nitrogen atmosphere to produce a secondary heat treatment product.

[0063] The secondary heat treatment can be performed by increasing the temperature to about 600°C to about 1200°C at a temperature increase rate of about 0.5°C / min to about 7°C / min and maintaining at the increased temperature for about 2 hours to about 8 hours. In one or more embodiments, the temperature increase rate can be about 1°C / min to about 7°C / min or about 1°C / min to about 5°C / min, and the maintaining time can be about 2 hours to about 6 hours or about 2 hours to about 4 hours.

[0064] The secondary heat treatment can convert the primary heat treatment product (e.g., the metal oxide) into a metal-containing nitride.

[0065] Thereafter, the secondary heat treatment product is subjected to etching to produce a negative active material.

[0066] Before the etching, cooling to room temperature and pulverization can be further performed.

[0067] The etching can be chemical etching, such as chemical etching using an acid, and in one or more embodiments, the etching can include adding a secondary heat treatment product to the acid and mixing. The acid can be hydrochloric acid, nitric acid, sulfuric acid, or a combination thereof. The acid can have a concentration of about 0.1M to about 5M, about 0.5M to about 3M, or about 1M to about 3M.

[0068] The mixing can be carried out at a speed of about 100 rpm to about 1000 rpm, about 200 rpm to about 800 rpm, or about 200 rpm to about 600 rpm.

[0069] The etching can effectively remove by-products that may be generated in the secondary heat treatment.

[0070] After the etching, separation of the resulting product can be further carried out, such as centrifugation and drying.

[0071] Rechargeable lithium battery Another embodiment provides a rechargeable lithium battery including a negative electrode containing the negative electrode active material, a positive electrode, and an electrolyte.

[0072] Negative electrode The negative electrode includes a current collector and a negative electrode active material layer on the current collector.

[0073] The negative electrode active material layer includes a negative electrode active material according to one or more embodiments. In one or more embodiments, the negative electrode active material according to one or more embodiments can include a first active material and a silicon-based negative electrode active material can include a second active material. The mixing ratio of the first negative electrode active material and the second negative electrode active material can be about 99:1 to about 50:50 by weight ratio, or about 95:5 to about 80:20 by weight ratio.

[0074] The silicon-based negative electrode active material can be Si, Si-C composite, SiO x (0 < x ≤ 2), Si-Q alloy (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, but not Si), etc., or can be a mixture of at least one of them and SiO2. The element Q can be 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, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or combinations thereof.

[0075] In one or more embodiments, the Si-C composite may include silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the Si-C composite may include secondary particles in which primary silicon particles are aggregated and an amorphous carbon coating on the surface of the secondary particles. The amorphous carbon may be between the primary silicon particles, for example, to be coated on the primary silicon particles. The Si-C composite may also include a core in which silicon particles are distributed in an amorphous carbon matrix and an amorphous carbon coating coated on the surface of the core.

[0076] Secondary particles can be located at the center of the Si-C composite, and thus can be referred to as the core or central portion. The amorphous carbon coating can be referred to as the outer portion or shell.

[0077] The silicon particles can be nano-sized silicon particles. The particle diameter of the nano-sized silicon particles can be from about 10 nm to about 1,000 nm, and according to one or more embodiments, it can be from about 20 nm to about 900 nm, from about 20 nm to about 800 nm, from about 20 nm to about 500 nm, from about 20 nm to about 300 nm, or from about 20 nm to about 150 nm. If the average particle size of the silicon particles is within the aforementioned range, excessive volume expansion during charging and discharging can be suppressed or reduced, and the breakage of conductive paths due to particle fragmentation can be prevented or reduced.

[0078] The mixing ratio of nano-silicon and amorphous carbon can be from about 20:80 to about 70:30 by weight.

[0079] In one or more embodiments, the secondary particles or core may further comprise crystalline carbon. If the Si-C composite also comprises crystalline carbon, the Si-C composite may comprise secondary particles in which the primary silicon particles and crystalline carbon aggregate, and an amorphous carbon coating on the surface of the secondary particles.

[0080] If the Si-C composite comprises silicon particles, crystalline carbon, and amorphous carbon, then based on a total of 100 wt% of the Si-C composite, the amount of amorphous carbon can be from about 30 wt% to about 70 wt%, and based on a total of 100 wt% of the Si-C composite, the amount of crystalline carbon can be from about 1 wt% to about 20 wt%. Based on a total of 100 wt% of the Si-C composite, the amount of silicon particles can be from about 20 wt% to about 69 wt%, and according to one or more embodiments, it can be from about 30 wt% to about 69 wt%.

[0081] The particle size of the Si-C composite can be adjusted appropriately or suitably, and there are no specific limitations.

[0082] If amorphous carbon is present around the surface of the secondary particles, its thickness can be suitably or appropriately adjusted, but it can be provided, for example, at a thickness of about 5 nm to about 100 nm.

[0083] The negative electrode active material layer may include a binder and may also include a conductive material (e.g., an electrically conductive material).

[0084] For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material and about 1 wt% to about 10 wt% of binder, and in another embodiment, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder and about 0.5 wt% to about 5 wt% of conductive material.

[0085] Binders improve the adhesion between negative electrode active material particles and between negative electrode active material particles and current collector. Binders can be non-aqueous binders, aqueous binders, dry binders, or combinations thereof.

[0086] Non-aqueous adhesives may be polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0087] Waterborne adhesives may be styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or combinations thereof.

[0088] Aqueous binders can be cellulose compounds, or cellulose compounds combined with aqueous binders. Cellulose compounds can be called thickeners because they impart or increase viscosity, or they can be used as binders and therefore can be called binders. Cellulose compounds can be used in appropriate or suitable amounts within the scope of binders, and are not limited thereto. Cellulose compounds include one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or their alkali metal salts. The alkali metal can be Na, K, or Li.

[0089] Dry binders can be polymeric materials that are fibrous (e.g., capable of being fiberized). For example, dry binders can be polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0090] Conductive materials are included to provide electrode conductivity (e.g., electrical conductivity). Any suitable conductive material can be used as a conductive material unless it causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Examples of conductive materials can be: carbonaceous materials, such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials, including metal powders and / or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0091] The negative electrode current collector may include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.

[0092] positive electrode The positive electrode may include a current collector and a layer of positive electrode active material on the current collector. The layer of positive electrode active material includes a positive electrode active material and may also include a binder and / or a conductive material (e.g., an electrically conductive material).

[0093] For example, the positive electrode may further include additives that can be used as a sacrificial positive electrode.

[0094] Based on a 100wt% positive electrode active material layer, the amount of positive electrode active material can be from about 90wt% to about 99.5wt%, and based on a 100wt% positive electrode active material layer, the amounts of binder and conductive material can be from 0.5wt% to 5wt%, respectively.

[0095] The positive electrode active material may include compounds capable of intercalating and deintercalating lithium (lithiation intercalation compounds). In some embodiments, at least one of a composite oxide of lithium with a metal selected from cobalt, manganese, nickel, or combinations thereof may be used.

[0096] The composite oxide can be a lithium transition metal composite oxide, and examples of it can include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof.

[0097] For example, the following compounds, represented by any one of the following chemical formulas, can be used. 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).

[0098] In the above chemical formulas, 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.

[0099] For example, the positive electrode active material can be a high-nickel positive electrode active material, which is based on a lithium transition metal composite oxide in which 100 mol% of the metals other than lithium have a nickel content of greater than or equal to about 80 mol%, greater than or equal to about 85 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%. High-nickel positive electrode active materials can achieve high capacity and can be applied to high-capacity, high-density rechargeable lithium batteries.

[0100] Binders improve the adhesion between positive electrode active material particles and between the positive electrode active material and the current collector. Examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, nylon, etc.

[0101] The conductive material includes materials that provide electrode conductivity (e.g., electrical conductivity), and any suitable conductive material can be used as a conductive material unless the conductive material causes a chemical change (e.g., an undesirable chemical change in a rechargeable lithium battery). Examples of conductive materials may include: carbonaceous materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials, including metal powders and / or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (e.g., electrically conductive polymers), such as polyphenylene derivatives; or mixtures thereof.

[0102] The current collector may include, but is not limited to, Al.

[0103] electrolyte The electrolyte includes non-aqueous organic solvents and lithium salts.

[0104] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of the battery.

[0105] Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents and / or aprotic solvents.

[0106] Carbonate solvents can 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.

[0107] Ester solvents can include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanoic acid lactone, mevalonate lactone, valonate lactone, γ-butyrolactone, caprolactone, etc.

[0108] Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. 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 to 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.

[0109] Organic solvents can be used alone or in mixtures of two or more.

[0110] If carbonate solvents are used, cyclic carbonates and chain carbonates can be used together, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0111] The electrolyte may also include vinyl ethylene carbonate, vinylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, dichloroethylene carbonate, dibromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, fluoroethylene carbonate, or combinations thereof as additives.

[0112] Lithium salts dissolved in organic solvents supply lithium ions to the battery, enabling basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts 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 F 2x+1 SO2)(C y F 2y+2 One or at least two of the following supporting electrolyte salts: (SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOP), and lithium bis(oxalate)borate (LiBOB).

[0113] diaphragm Depending on the type (or category) of the rechargeable lithium battery, the separator can be located between the positive and negative electrodes. The separator can be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayers of other materials with two or more layers, and can be a hybrid multilayer, such as a polyethylene / polypropylene double-layer separator, a polyethylene / polypropylene / polypropylene triple-layer separator, a polypropylene / polypropylene / polypropylene triple-layer separator, etc.

[0114] The membrane may include a porous substrate and a coating on one or both surfaces (e.g., two opposing surfaces) of the porous substrate, comprising organic materials, inorganic materials, or combinations thereof.

[0115] The porous substrate can be a polymer film formed from any of the following: 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, Teflon (polytetrafluoroethylene), or copolymers or mixtures of two or more thereof.

[0116] Organic materials may include polyvinylidene fluoride polymers and / or (meth)acrylic acid polymers.

[0117] Inorganic materials can be inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite or combinations thereof, but are not limited thereto.

[0118] Organic and inorganic materials can be mixed in a coating, or coatings containing organic materials and coatings containing inorganic materials can be stacked.

[0119] Rechargeable lithium batteries can be classified according to their shape as cylindrical batteries, prismatic batteries, pouch batteries, or coin-shaped batteries, etc. Figures 1 to 4 This is a schematic diagram illustrating a rechargeable lithium battery according to an embodiment, and 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. (See reference) Figures 1 to 4 The rechargeable lithium battery 100 may include an electrode assembly 40 comprising a separator 30 between a positive electrode 10 and a negative electrode 20, and a housing 50 therein housing the electrode assembly 40. The positive electrode 10, negative electrode 20, and separator 30 may be impregnated with an electrolyte. Figure 1As shown, the rechargeable lithium battery 100 may include a sealing member 60 of the sealed housing 50. Figure 2 In this context, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive terminal 12, a negative electrode lead connector 21, and a negative terminal 22. For example... Figure 3 and Figure 4 As shown, the rechargeable lithium battery 100 may include electrode terminals 70 (e.g., positive electrode terminal 71 and negative electrode terminal 72) that can be used as electrical paths to induce current formed in the electrode assembly 40 to the outside.

[0120] As a non-limiting example, the rechargeable lithium battery according to the embodiments can be used in automobiles, mobile phones and / or various suitable types (or kinds) of electronic devices.

[0121] Examples and comparative examples of this disclosure are described below. However, these examples are not to be construed in any way as limiting the scope of this disclosure.

[0122] Comparison Example 1 Artificial graphite with an average particle size of 12 μm was used as the negative electrode active material.

[0123] A negative electrode active material, styrene-butadiene rubber, and carboxymethyl cellulose were mixed in an aqueous solvent at a weight ratio of 97.5:1:1.5 to prepare a negative electrode active material slurry. The negative electrode active material slurry was coated onto a 75 μm thick copper current collector, dried at 80 °C, and then rolled. The product was dried at 80 °C for 12 hours to prepare the negative electrode. The prepared negative electrode had a strength of 6.5 mg / cm³. 2 The loading level is 1.5 g / cc, and the active mass density is 1.5 g / cc.

[0124] A coin-shaped half-cell was fabricated using a negative electrode, a lithium metal counter electrode, and an electrolyte. 1.15 M LiPF6 was used as the electrolyte, dissolved in ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio 3:5:2).

[0125] Example 1 Ti(OC4H9)4 was added to anhydrous ethanol and shaken to prepare a Ti(OC4H9)4 liquid. Artificial graphite was added to the Ti(OC4H9)4 liquid, shaken at 300 rpm, and dried to prepare a primary coating material. Based on 100 wt% artificial graphite (lithium adsorption energy: -0.09 eV, lithium ion diffusion energy: 0.3 eV), the amount of Ti(OC4H9)4 was set to 4 wt%.

[0126] In a sintering furnace, the primary coating material is subjected to primary heat treatment by raising the temperature to 800°C at a heating rate of 5°C / min under an argon atmosphere and holding it at 800°C for 4 hours.

[0127] The primary heat-treated product and magnesium powder were mixed at a weight ratio of 1:10 to prepare a mixture.

[0128] In a sintering furnace, the mixture is subjected to secondary heat treatment by raising the temperature to 900°C at a heating rate of 5°C / min under a nitrogen atmosphere and holding it at 900°C for 6 hours.

[0129] Chemical etching was performed by cooling the secondary heat-treated product to room temperature, pulverizing it, adding 100 mL of 2M HCl to the resulting product, and mixing at 400 rpm.

[0130] The etched product was collected by centrifugation and dried to prepare the negative electrode active material. The prepared negative electrode active material consisted of an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN was 1 wt%, and the TiN was disposed on the surface of the artificial graphite core with a thickness of 10 nm.

[0131] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0132] Example 2 The negative electrode active material was prepared using a process substantially identical to that in Example 1, except that it was based on 100 wt% artificial graphite and used Ti(OC4H9)4 in an amount of 8 wt%. The prepared negative electrode active material consisted of an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN was 2 wt%, and the TiN was disposed on the surface of the artificial graphite core with a thickness of 50 nm.

[0133] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0134] Example 3 The negative electrode active material was prepared using a process substantially identical to that in Example 1, except that it was based on 100 wt% artificial graphite and used 20 wt% Ti(OC4H9)4. The prepared negative electrode active material comprised an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN was 5 wt%, and the TiN was disposed on the surface of the artificial graphite core with a thickness of 100 nm.

[0135] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0136] Example 4 Artificial graphite and a molten salt of a mixture of NaCl and MgCl2 (NaCl to MgCl2 in a weight ratio of 4:1) were added to liquid Ti(OC4H9)4, and the result was subjected to primary heat treatment to prepare a primary heat-treated product. The primary heat-treated product was then mixed with magnesium powder to prepare a mixture. The weight ratio of the primary heat-treated product, molten salt, and magnesium powder was set to 12.5:15:1.

[0137] The negative electrode active material was prepared by secondary heat treatment of the mixture through a process substantially identical to that in Example 1. The prepared negative electrode active material comprised an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN was 1 wt%, and the TiN was disposed on the surface of the artificial graphite core with a thickness of 10 nm.

[0138] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0139] Example 5 Except for using Ti(OC4H9)4 in an amount of 8 wt% based on 100 wt% artificial graphite, the negative electrode active material was prepared through a process substantially identical to that in Example 4. The prepared negative electrode active material comprises an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN is 2 wt%, and the TiN is disposed on the surface of the artificial graphite core with a thickness of 50 nm.

[0140] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0141] Example 6 Except for using Ti(OC4H9)4 in an amount of 20 wt% based on 100 wt% artificial graphite, the negative electrode active material was prepared through a process substantially identical to that in Example 4. The prepared negative electrode active material comprises an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN is 5 wt%, and the TiN is disposed on the surface of the artificial graphite core with a thickness of 100 nm.

[0142] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0143] Example 7 The negative electrode active material was prepared using essentially the same process as in Example 1, except that it was based on 100 wt% artificial graphite and used 2 wt% Ti(OC4H9)4. The prepared negative electrode active material comprised an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN was 0.5 wt%, and the TiN was disposed on the surface of the artificial graphite core with a thickness of 5 nm.

[0144] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0145] Example 8 The negative electrode active material was prepared using a process substantially identical to that in Example 1, except that it was based on 100 wt% artificial graphite and used Ti(OC4H9)4 in an amount of 80 wt%. The prepared negative electrode active material consisted of an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN was 20 wt%, and the TiN was disposed on the surface of the artificial graphite core with a thickness of 300 nm.

[0146] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0147] Example 9 Except for a 12-hour secondary heat treatment, the negative electrode active material was prepared using essentially the same procedures as in Example 1. The prepared negative electrode active material comprised an artificial graphite core and TiN (lithium adsorption energy: -2.0 eV, lithium-ion diffusion energy: 0.01 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of TiN was 1 wt%, and the TiN was disposed on the surface of the artificial graphite core with a thickness of 20 nm.

[0148] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0149] Comparison Example 2 Except for using aluminum isopropoxide instead of Ti(OC4H9)4, the negative electrode active material was prepared through a process substantially identical to that in Example 1. The prepared negative electrode active material comprised an artificial graphite core and AlN (lithium adsorption energy: -1.0 eV, lithium ion diffusion energy: 0.4 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of AlN was 2 wt%, and the AlN was disposed on the surface of the artificial graphite core with a thickness of 50 nm.

[0150] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0151] Comparison Example 3 The negative electrode active material was prepared using essentially the same process as in Example 1, except that Si(OCH3)4 was used instead of Ti(OC4H9)4. The prepared negative electrode active material consisted of an artificial graphite core and Si3N4 (lithium adsorption energy: -1.0 eV, lithium ion diffusion energy: 0.25 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of Si3N4 was 2 wt%, and the Si3N4 was disposed on the surface of the artificial graphite core with a thickness of 50 nm.

[0152] Except for the use of a negative electrode active material, the negative electrode and half cell were prepared by a process that was essentially the same as that in Comparative Example 1.

[0153] Compare Example 4 The negative electrode active material was prepared using a Co3O4 liquid prepared by adding Co3O4 to HNO3 and shaking, instead of the Ti(OC4H9)4 liquid prepared by adding Ti(OC4H9)4 to anhydrous ethanol, through a process substantially identical to that in Example 1. The prepared negative electrode active material comprised an artificial graphite core and CoN (lithium adsorption energy: -1.0 eV, lithium ion diffusion energy: 0.4 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of CoN was 2 wt%, and the CoN was disposed on the surface of the artificial graphite core with a thickness of 50 nm.

[0154] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0155] Compare Example 5 The negative electrode active material was prepared using a mixture of Si(OCH3)4 and Ti(OC4H9)4, prepared by adding Si(OCH3)4 and Ti(OC4H9)4 to anhydrous ethanol and shaking, instead of Ti(OC4H9)4, through a process substantially identical to that in Example 1. The prepared negative electrode active material comprised an artificial graphite core and Si-TiN disposed on the surface of the artificial graphite (lithium adsorption energy of Si: -1.0 eV, lithium ion diffusion energy of Si: 0.25 eV, lithium adsorption energy of Ti: -2.0 eV, lithium ion diffusion energy of Ti: 0.01 eV). Based on 100 wt% of the negative electrode active material, the amount of Si-TiN was 2 wt%, and the Si-TiN was disposed on the surface of the artificial graphite core with a thickness of 50 nm.

[0156] Aside from using the negative electrode active material, the negative electrode and half cell were prepared using a process that was essentially the same as that in Comparative Example 1.

[0157] Comparison Example 6 Except for using ferric ethoxide instead of Ti(OC4H9)4, the negative electrode active material was prepared through a process substantially identical to that in Example 1. The prepared negative electrode active material comprised an artificial graphite core and Fe2N (lithium adsorption energy: -1.9 eV, lithium ion diffusion energy: 0.6 eV) disposed on the surface of the artificial graphite. Based on 100 wt% of the negative electrode active material, the amount of Fe2N was 2 wt%, and the Fe2N was disposed on the surface of the artificial graphite core with a thickness of 50 nm.

[0158] Except for the use of a negative electrode active material, the negative electrode and half cell were prepared by a process that was essentially the same as that in Comparative Example 1.

[0159] The amount of artificial graphite, the amount of nitride, and the thickness of nitride according to Examples 1 to 9 and Comparative Examples 1 to 6 are shown in Table 1.

[0160] Table 1

[0161] Experimental Example 1) Evaluation of X-ray Diffraction X-ray diffraction measurements were performed on the negative electrode active materials of Examples 1 to 9 and Comparative Examples 1 to 6. XRD was performed using CuKα rays as the target line, with an X-ray diffractometer (e.g., product name: X'Pert, manufacturer: Malvern Panalytical), and by removing the monochromator to improve peak density resolution. Measurement conditions could be 2θ = 10° to 80°, a scan rate (° / s) of 0.06436, and a step size (° / step) of 0.026° / step.

[0162] The results are presented in the examples 1 to 6 and the comparison example 1. Figure 5A In the middle. For example Figure 5B and Figure 5C As shown, unlike Comparative Example 1 which only exhibits a graphite structure, Examples 1 to 6 show peaks corresponding to the TiN crystalline phase at 36.4°, 42.3°, and 61.4°. Based on these results, it can be clearly shown that TiN is present on the surface in Examples 1 to 6.

[0163] Experimental Example 2) TEM and FFT Analysis The cross-section of the negative electrode active material prepared in Example 2 was measured by TEM (transmission electron microscopy), and then transformed by FFT (fast Fourier transform) to measure the interplanar spacing. The results are as follows... Figure 6A and Figure 6B As shown ( Figure 6A TEM Figure 6B (FFT). According to Figure 6B The results shown confirm that the interplanar spacing corresponding to TiN (200) is 0.21 nm and the interplanar spacing corresponding to TiN (111) is 0.24 nm.

[0164] Experimental Example 3) Evaluation of Initial Charging Efficiency The half-cells based on Examples 1 to 9 and Comparative Examples 1 to 6 will be tested at 0.01V to 1.5V (vs. Li / Li). + The device was charged and discharged at 0.05C within a voltage range of [voltage range missing]. The measured charge and discharge capacities, and the initial charging efficiency as the ratio of charge capacity to discharge capacity, are shown in Table 2.

[0165] Experiment Example 4) Evaluation of Fast Charging The half-cells according to Examples 1 to 9 and Comparative Examples 1 to 6 are in operation at 0.01V to 1.5V (vs. Li / Li) under the following conditions. + It can be charged and discharged within the voltage range of ).

[0166] One 0.2C charge / 0.5C discharge cycle One 1C charge / 0.5C discharge cycle 2C charge / 0.5C discharge once 3C charging / 0.5C discharging once 4C charge / 0.5C discharge once 5C charge / 0.5C discharge once 6C charge / 0.5C discharge cycle 2C charge / 0.2C discharge once The ratio of charging capacity at 0.2C to charging capacity at 2C was calculated. The results are shown in Table 2 as the fast charging rate (high-rate charging speed).

[0167] Table 2

[0168] As shown in Table 2, Examples 1 to 9 exhibit better initial charging efficiency than Comparative Examples 1 to 6.

[0169] Examples 1 through 9 exhibit better fast charging rates than Comparative Example 1, which does not contain metal nitrides. Comparative Examples 2 through 6, which contain metal nitrides and have lithium adsorption energies or lithium-ion diffusion energies higher than the lithium adsorption energy or lithium-ion diffusion energy of the nucleus, exhibit degraded fast charging rates.

[0170] Experimental Example 5) Impedance Evaluation The half-cells from Examples 1 to 9 and Comparative Examples 1 to 6 were measured at 0.01V to 1.5V (vs. Li / Li). + The battery was charged and discharged once at 0.05C within the voltage range of 50°C, and then discharged at 0.05C at SOC 50 (charging refers to charging to 50% of the total battery capacity based on 100% total charge capacity, and discharging refers to discharging to 50% of the total battery capacity based on 100% total discharge capacity). The impedance of the rechargeable battery was measured by EIS (electrochemical impedance spectroscopy). The impedance measurement range was set from 0.5MHz to 1MHz. The results (i.e., the internal resistance of the electrolyte (bulk resistance, R)) were obtained. b ), the resistance (R) of the SEI layer formed on the negative electrode SEI ) and charge transfer resistance (R ct The results are shown in Table 3.

[0171] Table 3

[0172] As shown in Table 3, the half-cells of Examples 1 to 9 all exhibited lower R values ​​than those of Comparative Examples 1 to 6. b R SEI and R ct .

[0173] While the subject matter of this disclosure has been described in conjunction with what is now considered to be actual exemplary embodiments, it will be understood that this disclosure is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims and their equivalents.

Claims

1. A negative electrode active material, said negative electrode active material comprising: The core includes carbonaceous materials; as well as It contains metal nitrides on the surface of the core and has lower lithium adsorption energy and lower lithium ion diffusion energy compared to the core.

2. The negative electrode active material according to claim 1, wherein, The lithium adsorption energy of the metal nitride is -5.0 eV or greater and less than -1.0 eV.

3. The negative electrode active material according to claim 1, wherein, The lithium-ion diffusion energy of the metal nitride is from 0 eV to 0.20 eV.

4. The negative electrode active material according to claim 1, wherein, The lithium adsorption energy of the carbonaceous material is from -1.0 eV to 1.0 eV.

5. The negative electrode active material according to claim 1, wherein, The lithium-ion diffusion energy of the carbonaceous material is from 0.01 eV to 1.0 eV.

6. The negative electrode active material according to claim 1, wherein, The carbonaceous material is crystalline carbon.

7. The negative electrode active material according to claim 6, wherein, The crystalline carbon is natural graphite, artificial graphite, or a combination thereof.

8. The negative electrode active material according to claim 1, wherein, The metal nitride is represented by chemical formula 1: [Chemical Formula 1] Me x N y Where Me is Ti, Zr, Hf, Cr, Mo, Nb, Ta, W, V or a combination thereof, 1≤x≤2 and 1≤y≤3.

9. The negative electrode active material according to claim 1, wherein, The metal nitride is TiN, ZrN, HfN, VN, NbN, TaN, CrN, or a combination thereof.

10. The negative electrode active material according to claim 1, wherein, Based on 100 wt% of the negative electrode active material, the amount of the metal nitride is from 0.5 wt% to 20 wt%.

11. The negative electrode active material according to claim 1, wherein, The thickness of the metal nitride on the surface of the core is from 5 nm to 300 nm.

12. The negative electrode active material according to claim 1, wherein, Based on 100 wt% of the negative electrode active material, the amount of the core is 80 wt% to 99.5 wt%.

13. A method for preparing a negative electrode active material, the method comprising the following steps: A primary coating material is prepared by coating crystalline carbon with a liquid metal compound. The primary coating material is subjected to primary heat treatment to prepare a primary heat treatment product; Prepare a mixture comprising the primary heat treatment product and magnesium powder; The mixture was subjected to secondary heat treatment under a nitrogen atmosphere to prepare a secondary heat-treated product; as well as The secondary heat treatment product is etched.

14. The method for preparing a negative electrode active material according to claim 13, the method further comprising: Molten salt is added to the crystalline carbon.

15. The method for preparing the negative electrode active material according to claim 14, wherein, The molten salt is NaCl, MgCl2, NaF, or a combination thereof.

16. The method for preparing the negative electrode active material according to claim 14, wherein, Based on 100 parts by weight of the crystalline carbon, the amount of molten salt added is from 50 parts by weight to 200 parts by weight.

17. The method for preparing the negative electrode active material according to claim 13, wherein, The metal compound is a metal alkoxide.

18. The method for preparing the negative electrode active material according to claim 13, wherein, The mixing ratio of the primary heat-treated product and the magnesium powder is from 1:0.08 to 1:0.3 by weight.

19. The method for preparing the negative electrode active material according to claim 13, wherein, The etching step is performed by chemical etching.

20. A rechargeable lithium battery, said rechargeable lithium battery comprising: The negative electrode comprises the negative electrode active material according to any one of claims 1 to 12; Positive electrode; as well as Electrolyte.

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