Lithium silicon oxide, negative electrode comprising same, and lithium secondary battery comprising negative electrode

Abstract

The present invention relates to a lithium silicon oxide in which gas generation is suppressed when an aqueous slurry is applied, a negative electrode comprising same, and a lithium secondary battery comprising the negative electrode. In a 29Si NMR spectrum obtained through 29Si solid state magic angle spinning (MAS) NMR measuring, the lithium silicon oxide has, within a range of -88 to -99 ppm, a first peak having a width of 0.2 to 2.0 ppm and a second peak having a width of 3 to 10 ppm, wherein the ratio of the integral of the first peak to the integral of the second peak (first peak / second peak) is greater than 0.22 and less than or equal to 0.31.

Description

Lithium silicon oxide, a negative electrode comprising the same, and a lithium secondary battery comprising the negative electrode

[0001] [Cross-citation with related applications]

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0075097, filed June 12, 2023, the entire contents of which are incorporated herein by reference.

[0003] [Technical Field]

[0004] The present invention relates to a lithium silicon oxide having suppressed gas generation when applied to an aqueous slurry, a negative electrode comprising the same, and a lithium secondary battery comprising the negative electrode.

[0005]

[0006] Recently, as the application areas of lithium secondary batteries have rapidly expanded to include not only power supply for electronic devices such as electric, electronic, communication, and computer devices, but also power storage for large-area devices such as automobiles and power storage devices, the demand for lithium secondary batteries with high capacity, high output, and high stability is increasing.

[0007] Lithium secondary batteries are generally manufactured by applying a slurry containing a positive electrode material capable of inserting and de-inserting lithium ions or a negative electrode material capable of absorbing and releasing lithium ions, and optionally a binder and a conductive material, to a positive electrode current collector and a negative electrode current collector, respectively, and removing the solvent by heat, etc., and then laminating these on both sides of a separator to form an electrode current collector of a predetermined shape, and then inserting the electrode current collector and a non-aqueous electrolyte into a battery case.

[0008] Graphite-based anode materials, which are representative anode materials, have excellent structural stability even during lithium insertion and de-insertion, and show stable capacity retention characteristics even after long cycles. However, their low theoretical capacity (350 mAh / g for LiC6) makes them unsuitable for the high-capacity, high-output materials currently required. Accordingly, silicon-based anode materials, such as silicon or silicon oxide, are attracting attention as anode materials for next-generation lithium secondary batteries due to their low reduction potential with lithium, abundant reserves, and theoretical capacity (2700~4200 mAh / g for Li4.4Si) that is about 10 times higher than that of graphite. However, despite these advantages, silicon-based anode materials consume about three times more lithium than graphite-based anode materials, and there is a problem that a large amount of lithium inserted into the anode during the initial charge does not return to the anode due to volume expansion and surface side reactions during charge and discharge of lithium secondary batteries using silicon-based anode materials, resulting in a high initial irreversible capacity.

[0009] In addition, in order to solve the initial efficiency problem caused by the irreversible reaction of Li ions, especially in the case of silicon oxide (SiOx) particles, various methods have been attempted to improve the initial efficiency by doping Mg or prelithiating Li into silicon oxide particles. However, when manufacturing a negative electrode material slurry using this method through an aqueous process, the Li2O generated inside the prelithiated silicon oxide particles reacts with H2O to produce a LiOH byproduct, which lowers the viscosity of the slurry and generates hydrogen, deteriorating the coating properties of the slurry, and as a result, there are still problems of reduced adhesion between the negative electrode material layer and the current collector and volume expansion.

[0010] Therefore, there is a need to develop a cathode material that has excellent initial capacity and capacity retention, has minimal viscosity change when manufacturing cathode material slurry through an aqueous process, suppresses hydrogen generation, and suppresses volume expansion during charge / discharge of the cathode using the cathode material.

[0011] [Prior Art Literature]

[0012] [Patent Document]

[0013] (Patent Document 1) KR10-2014-0091388A

[0014]

[0015] The present invention has been devised to solve the problems of the above-mentioned prior art, and aims to provide a lithium silicon oxide useful as an anode material, which has excellent initial capacity and capacity retention rate, has little change in viscosity when producing a slurry through an aqueous process, and suppresses hydrogen generation.

[0016] In addition, the present invention aims to provide a negative electrode including the lithium silicon oxide.

[0017] In addition, the present invention aims to provide a lithium secondary battery including the negative electrode.

[0018]

[0019] To solve the above problem, the present invention provides a lithium silicon oxide, a negative electrode including the same, and a lithium secondary battery.

[0020] (1) The present invention 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 A lithium silicon oxide is provided, which comprises a first peak having a width of 0.2 to 2.0 ppm and a second peak having a width of 3 to 10 ppm within a range of -88 to -99 ppm in a Si NMR spectrum, and a ratio of the integral of the first peak to the integral of the second peak (first peak / second peak) of more than 0.22 and less than or equal to 0.31.

[0021] (2) The present invention, in the above (1), 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 A lithium silicon oxide is provided in which no peak exists in the range of -71 to -77 ppm in the Si NMR spectrum.

[0022] (3) The present invention, in the above (1) or (2), Si, SiOx(0 <x≤2) 및 리튬 함유 화합물을 포함하는 것인 리튬실리콘산화물을 제공한다.

[0023] (4) The present invention, in the above (3), the Si and SiOx(0 <x≤2)는 표면에 탄소 코팅층을 포함하는 것인 리튬실리콘산화물을 제공한다.

[0024] (5) The present invention provides a lithium silicon oxide according to (3), wherein the lithium-containing compound includes at least one of lithium disilicate and lithium silicide.

[0025] (6) The present invention provides a negative electrode comprising a conductive metal current collector; and a negative electrode material layer provided on at least one surface of the current collector, wherein the negative electrode material layer comprises a lithium silicon oxide of any one of (1) to (5).

[0026] (7) The present invention provides a lithium secondary battery including a negative electrode according to (6); a positive electrode; and a separator and electrolyte interposed between the positive electrode and the negative electrode.

[0027]

[0028] The lithium silicon oxide negative electrode material according to the present invention has excellent initial capacity and capacity retention rate because hydrogen generation is suppressed even when manufactured as an aqueous negative electrode material slurry, and has less change in viscosity and reduced hydrogen generation compared to an aqueous negative electrode material slurry containing conventional silicon particles or silicon oxide particles, so that slurry coating defects and reduced adhesive strength due to reduced slurry viscosity can be suppressed, and has excellent storage stability.

[0029] In addition, the negative electrode according to the present invention includes a negative electrode material layer including lithium silicon oxide as a negative electrode material, so that the initial efficiency is excellent and the volume expansion of the negative electrode is suppressed, thereby enabling an excellent capacity retention rate.

[0030]

[0031] The following drawings attached to this specification illustrate specific embodiments of the present invention, and serve to further understand the technical idea of ​​the present invention together with the contents of the invention described above, and therefore the present invention should not be interpreted as being limited to matters described in such drawings.

[0032] Figure 1 is a diagram of lithium silicon oxide manufactured in Example 1. 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 This is a Si NMR spectrum.

[0033] Figure 2 is a view of lithium silicon oxide manufactured in Example 2. 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 This is a Si NMR spectrum.

[0034] Figure 3 shows the lithium silicon oxide manufactured in Comparative Example 1. 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 This is a Si NMR spectrum.

[0035] Figure 4 shows the lithium silicon oxide manufactured in Comparative Example 2. 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 This is a Si NMR spectrum.

[0036] Figure 5 shows the lithium silicon oxide manufactured in Comparative Example 3. 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 This is a Si NMR spectrum.

[0037]

[0038] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0039] The terms or words used in the description and claims of the present invention should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0040]

[0041] measurement method

[0042] In this specification 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 Si NMR spectra were measured using a Bruker 400MHz (Bruker) with a probe 4mm MAS rotor, 99 ㎕, sample rotation speed 10 kHz, measurement environment temperature 25℃, and delay time 30 s. The sample was prepared by placing it in a 4 mm diameter zirconia rotor.

[0043]

[0044] lithium silicon oxide

[0045] The present invention provides a lithium silicon oxide useful as an anode material, which has excellent initial capacity and capacity retention rate, has little change in viscosity when producing a slurry through an aqueous process, and suppresses hydrogen generation.

[0046] Lithium silicon oxide according to one embodiment of the present invention 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 It is characterized in that it includes a first peak having a width of 0.2 to 2.0 ppm and a second peak having a width of 3 to 10 ppm within a range of -88 to -99 ppm in a Si NMR spectrum, and a ratio of the integral of the second peak to the integral of the first peak (first peak / second peak) is greater than 0.22 and less than or equal to 0.31.

[0047]

[0048] Graphite-based anode materials are known as anode materials, and graphite-based anode materials have excellent structural stability even during lithium insertion and de-insertion, and show stable capacity retention characteristics even after long-term cycling. However, due to their low theoretical capacity (350 mAh / g for LiC6), they are not suitable as high-capacity, high-output materials currently needed. Therefore, silicon or silicon oxide, which have a theoretical capacity about 10 times higher than graphite (~4200 mAh / g for Li4.4Si), are attracting attention. However, silicon-based anode materials consume about three times more lithium than graphite-based anode materials and have a problem with increased irreversible capacity. In order to solve the initial efficiency problem caused by the irreversible reaction of lithium ions, a method is being attempted to improve the initial efficiency by prelithiating Li. Prelithiated silicon-based anode materials have excellent charge-discharge efficiency, which is advantageous in cycle characteristics, but there are problems with capacity reduction and gas generation during the process. In particular, crystalline lithium silicate and crystalline silica exist in the prelithiated silicon-based negative electrode material, and crystalline lithium silicate is easily dissolved in water. Therefore, when manufacturing an aqueous negative electrode slurry using the prelithiated silicon-based negative electrode material, it dissolves in water, and when the silicon and water inside come into contact, the silicon is oxidized and the water is reduced, generating hydrogen gas, which changes the viscosity of the slurry and deteriorates the slurry coating characteristics, causing serious defects in the slurry coating, and as a result, fatal problems such as a rapid decrease in capacity due to an electrical short circuit with the current collector may occur.

[0049] However, the lithium silicon oxide according to the present invention 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29Since the first and second peaks exist in a specific range of chemical shift in the Si NMR spectrum and the ratio of the integral values ​​of the first and second peaks satisfies a specific value, even when manufactured as an aqueous negative electrode material slurry, it does not dissolve in water, thereby preventing slurry coating defects and adhesive strength deterioration due to hydrogen generation, and thus the stability (integrity) and capacity retention rate of the negative electrode can be excellent.

[0050]

[0051] Hereinafter, the lithium silicon oxide according to the present invention will be described in detail.

[0052] According to one embodiment of the present invention, the lithium silicon oxide is useful as an anode material, particularly as an anode material for aqueous slurry. 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 A Si NMR spectrum comprising a first peak having a width of 0.2 to 2.0 ppm within a range of -88 to -99 ppm and a second peak having a width of 3 to 10 ppm, wherein a ratio of the integral of the first peak to the integral of the second peak (first peak / second peak) satisfies a value greater than 0.22 and less than or equal to 0.31.

[0053] In addition, the lithium silicon oxide according to one embodiment of the present invention 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 There may be no peak in the chemical shift range of -71 to -77 ppm in the Si NMR spectrum.

[0054]

[0055] In the present invention, the lithium silicon oxide is produced by prelithiating Li into a silicon-based compound, such as silicon and / or silicon oxide.

[0056] Meanwhile, when a silicon-based compound is lithiated, crystalline lithium silicate (Li2SiO3) and lithium disilicate (Li2Si2O5) are generally produced by the lithiation. However, the lithium silicate is easily dissolved in water, and when an aqueous slurry is produced using the lithium silicate, there is a problem of process and efficiency degradation due to hydrogen gas generation.

[0057] However, the lithium silicon oxide according to the present invention is manufactured through the pre-lithiation process described below using a specific concentration of LiBP (lithium biphenyl). 29 It may meet certain peak conditions in the Si NMR spectrum, and additionally may contain no or little crystalline lithium silicate and only crystalline lithium disilicate that is insoluble in water.

[0058] The lithium silicon oxide according to the present invention satisfies the above properties, thereby preventing hydrogen generation during slurry production through an aqueous process, thereby preventing coating defects and reduced adhesive strength, and exhibiting excellent initial capacity characteristics and capacity retention rate.

[0059]

[0060] In addition, the lithium silicon oxide is Si (silicon particles), SiOx (0 <x≤2)(실리콘 산화물 입자) 및 리튬 함유 화합물을 포함하는 것일 수 있다.

[0061] The above Si and SiOx may each have an amorphous structure, and the Si may have an average particle diameter (D) of 1 ㎛ to 20 ㎛. 50 ), the SiOx has an average particle diameter (D) of 5 nm to 1 ㎛ 50 ) may have.

[0062] Additionally, the Si or SiOx may include a carbon coating layer on the surface, and the thickness of the carbon coating layer may be 1 nm to 1 ㎛, or 100 nm to 1 ㎛.

[0063] The carbon coating layer includes a carbon-based material, and the carbon-based material may include at least one of amorphous carbon and crystalline carbon.

[0064] The above crystalline carbon can further improve the conductivity of the negative electrode material, and may be, for example, at least one selected from the group consisting of fluorene, carbon nanotubes, and graphene.

[0065] In addition, the amorphous carbon appropriately maintains the strength of the carbon coating layer, and may be, for example, at least one carbide selected from the group consisting of tar, pitch, and other organic substances, or a carbon-based material formed using a hydrocarbon as a source of chemical vapor deposition, and the carbide of the other organic substance may be a carbide of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or kedohexose, and a combination thereof.

[0066] In addition, the hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, a substituted or unsubstituted aromatic hydrocarbon, and examples thereof include metherine, etherene, isobutane, acetylene, propane, butane, butene, pentane, isobutane, or hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenimethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene.

[0067]

[0068] The above lithium-containing compound may be a compound formed by doping lithium metal into Si and / or SiOx while Si and / or SiOx is prelithiated, and specifically may include at least one of lithium disilicate and lithium silicide.

[0069] The above lithium silicide is Li y Si(2 <y<5)를 포함하는 것일 수 있고, 예시적으로 Li 4.4 Si, Li 3.75Si, Li 3.25 Si and Li 2.33 It may be one or more selected from the group consisting of Si.

[0070]

[0071] Method for producing lithium silicon oxide

[0072] The present invention provides a method for producing the lithium silicon oxide.

[0073]

[0074] The method for producing the lithium silicon oxide according to one embodiment of the present invention comprises adding Si or SiO to a lithium compound-containing solution under an inert atmosphere. x (0 <x≤2) 입자를 첨가하고 교반하는 단계(S1); 및 생성된 입자를 분리시킨 후 건조 및 소성하는 단계(S2)를 포함하고, 상기 리튬 화합물 함유 용액의 농도는 0.5 M 초과 1.0 M 미만인 것일 수 있다.

[0075] A method for producing lithium silicon oxide according to one embodiment of the present invention comprises adding a silicon-based negative electrode material to a lithium compound-containing solution of more than 0.5 M and less than 1.0 M, wherein the lithium compound is dissolved in an organic solvent at a specific concentration, and stirring and heat-treating the solution, thereby causing an appropriate oxidation-reduction process to occur as Li is inserted and diffused into the silicon-based negative electrode, thereby producing lithium silicon oxide having the aforementioned properties.

[0076]

[0077] Hereinafter, a method for manufacturing a lithium silicon oxide composite according to one embodiment of the present invention will be described in more detail step by step.

[0078] (S1) Step

[0079] The above (S1) step is Si or SiO x (0 <x≤2)가 전리튬화되어 리튬실리콘산화물 입자를 생성하는 단계로, 불활성 가스 분위기 하에서, 리튬 화합물 함유 용액에 Si 또는 SiO x(0≤x≤2) It is performed by adding particles and stirring, and the lithium compound-containing solution may be more than 0.5 M and less than 1.0 M.

[0080] Here, the lithium compound-containing solution being more than 0.5 M and less than 1.0 M means that the lithium compound is dissolved in more than 0.5 mol and less than 1.0 mol per 1 L of the solution.

[0081]

[0082] In one embodiment of the present invention, the Si and SiO x (0 <x≤2)는 각각 비정질 구조를 갖는 것일 수 있으며, 상기 실리콘(Si)은 1 ㎛ 내지 20 ㎛의 평균입경(D 50 ), the silicon oxide (SiO x (0 <x≤2))은 5 nm 내지 1 ㎛의 평균입경(D 50 ) may have.

[0083] Additionally, the silicon and silicon oxide may include a carbon coating layer on the surface, and the thickness of the carbon coating layer may be 1 nm to 1 ㎛, or 100 nm to 1 ㎛.

[0084] The carbon coating layer includes a carbon-based material, and the carbon-based material may include at least one of amorphous carbon and crystalline carbon.

[0085] The above crystalline carbon can further improve the conductivity of the negative electrode material, and may be, for example, at least one selected from the group consisting of fluorene, carbon nanotubes, and graphene.

[0086] In addition, the amorphous carbon appropriately maintains the strength of the carbon coating layer, and may be, for example, at least one carbide selected from the group consisting of tar, pitch, and other organic substances, or a carbon-based material formed using a hydrocarbon as a source of chemical vapor deposition, and the carbide of the other organic substance may be a carbide of sucrose, glucose, galactose, fructose, lactose, mannose, ribose, aldohexose, or kedohexose, and a combination thereof.

[0087] In addition, the hydrocarbon may be a substituted or unsubstituted aliphatic or alicyclic hydrocarbon, a substituted or unsubstituted aromatic hydrocarbon, and examples thereof include metherine, etherene, isobutane, acetylene, propane, butane, butene, pentane, isobutane, or hexane, benzene, toluene, xylene, styrene, ethylbenzene, diphenimethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, or phenanthrene.

[0088]

[0089] In one embodiment of the present invention, the silicon or silicon oxide may be added in an amount of more than 0.131 parts by weight and less than 0.142 parts by weight per 100 parts by weight of the lithium compound-containing solution.

[0090] Here, the lithium compound-containing solution may be prepared by adding a polycyclic aromatic compound or a linear polyphenylene compound to an organic solvent and stirring to prepare a polycyclic aromatic compound solution or a linear polyphenylene compound solution, and then adding lithium particles to the polycyclic aromatic compound solution or the linear polyphenylene compound solution and reacting the polycyclic aromatic compound solution or the linear polyphenylene compound solution.

[0091] In addition, the lithium particles react with a polycyclic aromatic compound or a linear polyphenylene compound in a polycyclic aromatic compound solution or a linear polyphenylene compound solution at a 1:1 molar ratio.

[0092] In addition, the polycyclic aromatic compound may be at least one selected from the group consisting of naphthalene, anthracene, phenanthrene, naphthacene, pentacene, pyrene, picene, triphenylene, coronene, chrysene, fluorene, and 9,9-dimethylfluorene, and the linear polyphenylene compound may be at least one selected from the group consisting of biphenyl, terphenyl, and 4,4-dimethylbiphenyl. Specifically, the polycyclic aromatic compound may be any one selected from naphthalene, fluorene, and 9,9-dimethylfluorene, and the linear polyphenylene compound may be biphenyl or 4,4-dimethylbiphenyl.

[0093] In addition, the organic solvent may be an ether solvent, a ketone solvent, an ester solvent, an alcohol solvent, an amine solvent, or a mixed solvent thereof. For example, the ether solvent may be diethyl ether, tert-butyl methyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,2-dimethoxyethane, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, or a mixed solvent thereof. Among these, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, and 1,2-dimethoxyethane may be preferable.

[0094] In addition, acetone, acetophenone, etc. can be used as the ketone solvent, and methyl formate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, or a mixed solvent thereof can be used as the ester solvent.

[0095] Additionally, methanol, ethanol, propanol, isopropyl alcohol or a mixed solvent thereof can be used as an alcohol-based solvent, and methylamine, ethylamine, ethylenediamine or a mixed solvent thereof can be used as an amine-based solvent.

[0096] In addition, the reaction for obtaining the lithium compound-containing solution may be performed while stirring at a temperature range of 20°C to 90°C for 0.5 to 6.0 hours, and by stirring at the temperature for the time, the lithium compound can be formed more effectively.

[0097]

[0098] In the above step (S1), stirring is performed by first stirring for more than 1 hour at a temperature range of 30°C to 90°C, and then second stirring while cooling to room temperature, taking into account the control of lithium ion diffusion rate and appropriate prelithiation. The first stirring and second stirring may be performed for the same amount of time.

[0099]

[0100] (S2) Step

[0101] The above step (S2) is a step for manufacturing lithium silicon oxide by separating, drying, and calcining lithium silicon oxide particles produced in step (S1), and can be performed by separating, drying, and calcining the particles produced in step (S1).

[0102] The particles generated above may be separated from the solution by a means conventional in the art, for example, the solution may be centrifuged to separate the supernatant and the generated particles, which are precipitates.

[0103] The above drying can be performed by means conventional in the art, for example, by leaving it at a temperature range of 70°C to 90°C, or at 75°C to 85°C for 2 hours or more.

[0104] Additionally, the above-mentioned calcination can be performed by heat treatment in an inert gas atmosphere at a temperature range of 850°C to 900°C for 1 to 2 hours.

[0105] Meanwhile, in the method for manufacturing lithium silicon oxide according to one embodiment of the present invention, the inert gas may be argon, nitrogen, or a combination thereof.

[0106]

[0107] cathode

[0108] The present invention provides a negative electrode comprising the lithium silicon oxide.

[0109] According to one embodiment of the present invention, the negative electrode comprises a conductive metal current collector; and a negative electrode material layer provided on at least one surface of the current collector, wherein the negative electrode material layer comprises the lithium silicon oxide.

[0110]

[0111] The negative electrode according to the present invention includes a negative electrode material layer including lithium silicon oxide, so that the initial efficiency is excellent and the volume expansion of the negative electrode is suppressed, so that the capacity retention rate and long-term stability can be excellent.

[0112]

[0113] The conductive metal current collector includes a highly conductive metal, and the conductive metal current collector is not particularly limited as long as it is non-reactive in the voltage range of the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. In addition, the current collector may have a thickness of 3 μm to 500 μm.

[0114]

[0115] Meanwhile, the negative electrode may be manufactured by mixing an aqueous solvent, the lithium silicon oxide, a binder, and a conductive material to prepare a negative electrode material slurry, applying the negative electrode material slurry on at least one surface of a conductive metal current collector, and drying the same. Here, the aqueous solvent may be water.

[0116] In addition, the conductive material may be included without special limitation as long as it does not cause a chemical change and has electronic conductivity, but specifically, the conductive material may include graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive tubes such as carbon nanotubes; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives, and among these, one type alone or a mixture of two or more types may be used.

[0117] In addition, the binder may be typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode material layer, and examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0118]

[0119] lithium secondary battery

[0120] The present invention provides a lithium secondary battery including the above negative electrode.

[0121] According to one embodiment of the present invention, the lithium secondary battery may include the negative electrode; the positive electrode; a separator interposed between the positive electrode and the negative electrode, and an electrolyte. In addition, the lithium secondary battery may optionally further include a battery container that houses the electrode assembly of the negative electrode, the positive electrode, and the separator, and a sealing member that seals the battery container.

[0122] According to one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode material layer positioned on the positive electrode current collector.

[0123] According to one embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used. In addition, the positive electrode current collector can typically have a thickness of 3 ㎛ to 500 ㎛, and fine unevenness can be formed on the surface to strengthen the bonding strength of the positive electrode material. For example, it can be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric, etc.

[0124] According to one embodiment of the present invention, the cathode material layer may optionally include a binder and a conductive material together with the cathode material.

[0125] According to one embodiment of the present invention, the cathode material may be LiCoO2, LiCoPO4, LiNiO2, Li x Ni a Co b M 1 c M 2 d O2(M 1 and M 2 is independently one kind selected from the group consisting of Al, Mn, Cu, Fe, V, Cr, Mo, Ga, B, W, Mo, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, F, P, S and Y, and 0.9≤x≤1.1, 0 <a<1.0, 0<b<1.0, 0≤c<0.5, 0≤d<0.5, a+b+c+d=1이다.), LiMnO2, LiMnO3, LiMn2O3, LiMn2O4, LiMn 2-e M 3 eO2(M 3 is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, and 0.01≤e≤0.1), Li2Mn3M 4 O8(M 4 is at least one selected from the group consisting of Ci, Ni, Fe, Cu and Zn), and may be one selected from the group consisting of LiFePO4, Li2CuO2, LiV3O8, V2O5, Cu2V2O7 and lithium metal.

[0126] According to one embodiment of the present invention, the binder is a component that assists in bonding between the conductive material, the positive electrode material, and the current collector, and is typically added in an amount of 0.1 wt% to 10 wt% based on the total weight of the positive electrode material layer. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber, nitrile-butadiene rubber, fluororubber, and various copolymers thereof.

[0127] According to one embodiment of the present invention, the conductive material of the positive electrode layer is a component for further improving the conductivity of the positive electrode material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, based on the total weight of the positive electrode material layer. The conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0128] According to one embodiment of the present invention, the positive electrode can be manufactured by applying and drying a slurry for forming a positive electrode material layer prepared by dissolving or dispersing a positive electrode material, and optionally a binder and a conductive material in a solvent, on a positive electrode current collector, or by casting the slurry for forming a positive electrode material layer on a separate support, and then laminating the obtained film by peeling it off from the support on a positive electrode current collector.

[0129] According to one embodiment of the present invention, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in lithium secondary batteries can be used without particular limitation, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may also be used. In addition, a coated separator containing a ceramic component or a polymer material to secure heat resistance or mechanical strength may be used, and may optionally be used in a single-layer or multi-layer structure.

[0130] According to one embodiment of the present invention, the electrolyte may include, but is not limited to, an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, etc. that can be used in the manufacture of a lithium secondary battery. As a specific example, the electrolyte may include an organic solvent and a lithium salt.

[0131] According to one embodiment of the present invention, the organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylenecarbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0132] According to one embodiment of the present invention, the lithium salt may be used without any particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the anion of the lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - At least one selected from the group consisting of may be used, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0133] According to one embodiment of the present invention, in addition to the electrolyte components, the electrolyte may further include, for example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), fluoro ethylene carbonate (FEC), propane sultone (PS), 1,3-propane sultone (PRS), ethylene sulfate (ESA), succinonitrile (SN), adiponitrile (AN), hexane tricarbonitrile (HTCN), γ-butyrolactone, biphenyl (BP), cyclohexyl benzene (CHB), for the purpose of improving the life characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery. One or more additives selected from the group consisting of tert-amyl benzene (TAB), haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride may be further included. At this time, the additives may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

[0134]

[0135] A lithium secondary battery including a negative electrode according to the present invention stably exhibits excellent capacity characteristics, output characteristics, and life characteristics, and is therefore useful in portable devices such as mobile phones, laptop computers, and digital cameras, and in electric vehicles such as hybrid electric vehicles (HEVs) and electric vehicles (EVs).

[0136] There is no particular limitation on the external shape of the lithium secondary battery of the present invention, but it may be a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

[0137] The lithium secondary battery according to the present invention can be used not only as a battery cell used as a power source for a small device, but can also be preferably used as a unit battery in a medium- to large-sized battery module including a plurality of battery cells.

[0138] Accordingly, according to one embodiment of the present invention, a battery module including the lithium secondary battery as a unit cell and a battery pack including the same are provided.

[0139] According to one embodiment of the present invention, the battery module or battery pack can be used as a power source for one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and a plug-in hybrid electric vehicle (PHEV); or a power storage system.

[0140]

[0141] Example

[0142] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0143] Example 1

[0144] 2.78 g of biphenyl was added to 30 ml of 2-methyltetrahydrofuran and stirred for 10 minutes. When the solution turned transparent, 0.125 g of Li powder was added and stirred for 6 hours to prepare a dark green 0.6 M LiBP solution.

[0145] The average particle diameter (D) in the above LiBP solution 50 ) SiOx / C(0) having a carbon coating layer on the surface with a thickness of 5 ㎛ <x≤2) 분말 4 g을 투입하고 80℃에서 1시간 동안 교반하였다. 휘발된 용매는 환류냉각기를 통해 포집하여 농도를 일정하게 유지하였다. 이후 상온(25℃)까지 냉각시키면서 1시간 동안 추가적으로 교반하였다. 이때 모든 과정은 아르곤 분위기 하에서 수행하였다.

[0146] Afterwards, the solution was centrifuged to separate only the powder particles, and the separated particles were dried at 80°C for 6 hours and heat-treated at an elevated temperature of 900°C for 2 hours under an argon atmosphere to produce lithium silicon oxide.

[0147]

[0148] Example 2

[0149] In the above Example 1, a 0.8 M LiBP solution was prepared using 3.7 g of biphenyl and 0.166 g of Li powder, and lithium silicon oxide was prepared in the same manner as in Example 1 except that this was used.

[0150]

[0151] Comparative Example 1

[0152] In the above Example 1, a 0.5 M LiBP solution was prepared using 2.31 g of biphenyl and 0.104 g of Li powder, and lithium silicon oxide was prepared in the same manner as in Example 1 except that this was used.

[0153]

[0154] Comparative Example 2

[0155] In the above Example 1, a 1.0 M LiBP solution was prepared using 4.62 g of biphenyl and 0.21 g of Li powder, and lithium silicon oxide was prepared in the same manner as in Example 1 except that this was used.

[0156]

[0157] Comparative Example 3

[0158] SiOx / C(0) containing a carbon coating layer <x≤2)와 금속 리튬을 1:1의 몰비로 혼합기기에서 균일하에 혼합하여 리튬 실리콘산화물 혼합물을 얻고, 이를 500 g 도가니에 넣어 아르곤 분위기 하 600℃에서 6시간 동안 열처리하여 사전 리튬화실리콘 산화물을 제조하였다.

[0159]

[0160] Experimental Example 1

[0161] Each lithium silicon oxide manufactured in the examples and comparative examples 29 The characteristics were compared and analyzed by performing Si solid state MAS (magic angle spinning) NMR analysis, and the results are shown in Figures 1 to 5 and Table 1.

[0162] 29 Si NMR spectra were measured using a Bruker 400MHz (Bruker) with a probe 4mm MAS rotor, 99 ㎕, sample rotation speed 10 kHz, measurement environment temperature 25℃, and delay time 30 s. The sample was prepared by placing it in a 4 mm diameter zirconia rotor.

[0163] measured 29 In the Si NMR spectrum, peaks were observed within the range of -88 to -99 ppm.

[0164] In addition, by fitting the peaks within the above range, the integrals of the first peak with a width of 0.2 to 2.0 ppm and the second peak with a width of 3 to 10 ppm were evaluated, and the ratio of the integral of the first peak to the integral of the second peak (first peak / second peak) was evaluated to confirm whether the following mathematical expression 1 was satisfied. The peak fitting was performed using the "Gaus / Lor" model of "DMFIT PROGRAM", and five peaks (six peaks in the case of Comparative Examples 2 and 3) were assigned to four ranges and then fitted. At this time, the assigned peaks are one peak within the range of -75 to -88 ppm, two peaks within the range of -88 to -99 ppm, one peak within the range of -103 to -124 ppm, and one peak within -124 to -145 ppm. For Comparative Examples 2 and 3, one additional peak within the range of -71 to -77 ppm was assigned. Fit parameters used were nParVar: 6, step: 1, and Thresh: 0.001.

[0165] [Mathematical Formula 1]

[0166] 0.22<(1st peak / 2nd peak)≤0.31

[0167]

[0168] As confirmed through the above Table 1 and Figures 1 to 5, the lithium silicon oxide of Examples 1 and 2 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 In the Si NMR spectrum, a first peak having a width of 0.2 to 2.0 ppm and a second peak having a width of 3 to 10 ppm within a range of -88 to -99 ppm, and a ratio of the integral of the second peak to the integral of the first peak (first peak / second peak) satisfies mathematical expression 1. On the other hand, the lithium silicon oxides of Comparative Examples 1 and 2 29Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 In the Si NMR spectrum, a first peak with a width of 0.2 to 2.0 ppm and a second peak with a width of 3 to 10 ppm within the range of -88 to -99 ppm were included, but the ratio of the integral values ​​of the first and second peaks, mathematical expression 1, was not satisfied.

[0169] In addition, the lithium silicon oxide of Comparative Example 3 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 In the Si NMR spectrum, only a second peak with a width of 3 to 10 ppm was observed within the range of -88 to -99 ppm, and it was confirmed that the ratio of the integral values ​​of the first and second peaks could not be fundamentally characteristic.

[0170]

[0171] Experimental Example 2

[0172] A negative electrode aqueous slurry was prepared using the lithium silicon oxide manufactured in the examples and comparative examples, and the amount of gas generated was measured, and the results are shown in Table 2 below.

[0173] Each lithium silicon oxide, graphite, Super-C65 as a conductive material, carboxymethyl cellulose (CMC) as a binder, and styrene-butadiene rubber (SBR) were mixed in a weight ratio of 77:19.2:1:1.1:1.6 in water to prepare an aqueous negative electrode slurry. 5 g of the aqueous negative electrode slurry was placed in an aluminum pouch, sealed, and stored in an oven at 60°C, and the amount of gas evolution was measured using a specific gravity balance.

[0174]

[0175] As confirmed through Table 2 above, it was confirmed that the negative electrode slurry including lithium silicon oxide of Examples 1 and 2 showed a reduced gas generation amount compared to Comparative Examples 1 to 3, and specifically, the gas generation amount was reduced to 1 / 2 compared to Comparative Example 1, the gas generation amount was significantly reduced to 1 / 8 compared to Comparative Example 2 after long-term storage, and the gas generation amount was significantly reduced to 1 / 20 compared to Comparative Example 3 after long-term storage. Meanwhile, in the results of Comparative Example 3, after long-term storage of 136 hours and 160 hours, the slurry gas generation amount greatly increased, making it impossible to measure with a specific gravity balance.

[0176]

[0177] Experimental Example 3

[0178] Half cells were manufactured using the lithium silicon oxide of the examples and comparative examples, and the battery characteristics were measured. The results are shown in Table 3 below.

[0179] Each lithium silicon oxide was mixed with the conductive agent Super-C65 and the binder li-PAA in a weight ratio of 70:15:15 to prepare a negative electrode slurry, which was then applied to copper foil and dried, rolled, and punched to produce a negative electrode.

[0180] Lithium metal was used as a counter electrode, and a porous polyethylene separator was placed between the negative electrode and the lithium metal, and an electrolyte solution containing 1 M LiPF6, 1.5 wt% VC, and 0.5 wt% PS dissolved in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 30:70 was injected to manufacture a coin half-cell.

[0181] After leaving the above coin half-cell for 24 hours, it was charged to 0.005 V with a constant current (CC) of 0.1 C in the range of 0.005-1.5 V vs. Li / Li+, and then charged with a constant voltage (CV) until the charging current became 0.02 C, and discharged with a constant current (CC) of 0.1 C to measure the charge / discharge capacity and initial efficiency of the first cycle.

[0182]

[0183] As confirmed through Table 3 above, it can be confirmed that Examples 1 and 2 have superior initial efficiency compared to Comparative Examples 1 to 3.

[0184]

[0185] From the results in Tables 1 to 3 above, the lithium silicon oxide according to the present invention 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 It was confirmed that the slurry of an aqueous negative electrode material has a first peak with a width of 0.2 to 2.0 ppm and a second peak with a width of 3 to 10 ppm within a range of -88 to -99 ppm in a Si NMR spectrum, and that the ratio of the integral values ​​of the first and second peaks satisfies a specific numerical range, so that even if it is manufactured as an aqueous negative electrode material slurry, it does not dissolve in water and gas generation can be significantly reduced, and thus the stability (integrity) of the negative electrode is excellent, so that the storage stability can be excellent, and the initial capacity and capacity retention rate can be excellent.

Claims

1. 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 In the Si NMR spectrum, it comprises a first peak with a width of 0.2 to 2.0 ppm and a second peak with a width of 3 to 10 ppm within the range of -88 to -99 ppm, Lithium silicon oxide, wherein the ratio of the integral of the first peak to the integral of the second peak (first peak / second peak) is greater than 0.22 and less than or equal to 0.

31.

2. In paragraph 1, 29 Obtained by Si solid state MAS (magic angle spinning) NMR measurement 29 Lithium silicon oxide having no peak in the range of -71 to -77 ppm in the Si NMR spectrum.

3. In paragraph 1, Si, SiOx(0 <x≤2) 및 리튬 함유 화합물을 포함하는 것인 리튬실리콘산화물.

4. In paragraph 3, The above Si and SiOx(0 <x≤2)는 표면에 탄소 코팅층을 포함하는 것인 리튬실리콘산화물.

5. In paragraph 3, Lithium silicon oxide, wherein the lithium-containing compound comprises at least one of lithium disilicate and lithium silicide.

6. Conductive metal current collector; and The above-mentioned collector comprises a negative electrode material layer provided on at least one surface thereof, A cathode, wherein the cathode layer comprises the lithium silicon oxide of claim 1.

7. A lithium secondary battery comprising a negative electrode according to Article 6; a positive electrode; and a separator and electrolyte interposed between the positive electrode and the negative electrode.

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