Negative active material for lithium secondary battery, method of preparing same, and lithium secondary battery comprising same

Abstract

The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery comprising the same. A negative electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises lithium niobium oxide; and a carbon material, silicon, or both.

Description

Technology Field

[0001] The present invention relates to a negative electrode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery comprising the same. Background Technology

[0003] Lithium secondary batteries, which are currently in the spotlight as power sources for small portable electronic devices, are batteries that exhibit high energy density by using an organic electrolyte and showing a discharge voltage more than twice as high as that of conventional batteries using an alkaline aqueous solution.

[0004] LiCoO2, LiMn2O4, and LiNi are used as positive electrode active materials for lithium secondary batteries. 1-x Co x O2(0 <x<1) 등과 같이, 리튬의 삽입(intercalation)이 가능한 구조를 가진 리튬과 전이 금속으로 이루어진 산화물을 주로 사용하고 있다.

[0005] In addition, various forms of carbon-based materials, including artificial graphite, natural graphite, and hard carbon capable of lithium deintercalation, have been applied as negative electrode active materials. Among the above carbon-based materials, graphite, such as artificial or natural graphite, has a discharge voltage of -0.2 V compared to lithium, whereas batteries using graphite as a negative electrode active material exhibit a high discharge voltage of 3.6 V, providing advantages in terms of energy density of lithium batteries. Furthermore, it is the most widely used because its excellent reversibility ensures a long lifespan for lithium secondary batteries. However, when manufacturing electrode plates using graphite as an active material, the electrode plate density is low, resulting in a problem of low capacity in terms of energy density per unit volume of the electrode plate. Additionally, at high discharge voltages, side reactions between graphite and the organic electrolyte are prone to occur, posing a risk of battery malfunction and ignition or explosion due to overcharging.

[0006] To solve these problems, oxide cathode active materials are being developed recently. For example, the amorphous tin oxide developed by Fujifilm exhibits a high capacity of 800 mAh / g by weight. However, this tin oxide has a critical problem with an initial irreversible capacity of about 50%, and serious side effects also occur, such as some of the tin oxide being reduced from oxide to tin metal during charging and discharging, making it even more difficult to use in batteries.

[0007] In addition, as an oxide cathode, Li in Japanese Patent Publication No. 2002-216753 a Mg b VO c A negative electrode active material with (0.05≤a≤3, 0.12≤b≤2, 2≤2c-a-2b≤5) is described. Additionally, in the Japan Battery Forum 2002 Abstract No. 3B05, Li 1.1 V 0.9 It has been reported on the negative electrode characteristics of O2 in lithium secondary batteries.

[0008] However, oxide cathodes have not yet demonstrated satisfactory battery performance, so continued research on this is necessary.

[0009] The aforementioned background technology is one that the inventor possessed or acquired in the process of deriving the disclosure of the present invention, and it cannot be considered as prior art disclosed to the general public prior to the filing of this application. The problem to be solved

[0011] The present invention aims to solve the aforementioned problems, and the objective of the present invention is to provide a negative electrode active material for a lithium secondary battery having high capacity and excellent lifespan characteristics.

[0012] Another technical problem to be solved by the present invention is to provide a method for manufacturing the negative electrode active material for the lithium secondary battery.

[0013] In addition, another technical problem to be solved by the present invention is to provide a lithium secondary battery comprising the above-mentioned negative electrode active material.

[0014] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0016] A negative electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises lithium niobium oxide; and a carbon material, silicon, or both.

[0017] In one embodiment, the lithium niobium oxide is Li 1.1 Nb 0.9 It could be O2.

[0018] In one embodiment, the weight ratio of the lithium niobium oxide and the carbon material may be 9:1 to 8:2.

[0019] In one embodiment, the carbon material may comprise at least one selected from the group consisting of: graphite-based materials such as natural graphite, artificial graphite, graphene, super P, and super C; active carbon-based materials; carbon black-based materials such as Denka black, Ketjen black, channel black, furnace black, thermal black, contact black, lamp black, and acetylene black; and carbon nanostructures such as carbon fiber, carbon nanotube (CNT), and fullerene.

[0020] In one embodiment, the silicon is metallic silicon (Si) or silicon oxide (SiO₂). x , here 0 <x<2) 실리콘 탄화물(SiC) 및 Si-Y 합금 (상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속 및 희토류 원소로 이루어진 군으로부터 선택되는 적어도 어느 하나를 포함하는 원소이며, Si은 아님)로 이루어진 군으로부터 선택되는 적어도 어느 하나를 포함하는 것일 수 있다.

[0021] In one embodiment, the negative electrode active material for the lithium secondary battery may have a P63 / mmc structure.

[0022] In one embodiment, the cathode active material is a Li in which, during charging and discharging in the in-situ XRD measurement voltage range of 1.0 V to 0.0 V, the 2θ (theta) value changes in the XRD (002) peak at 16° to 17°, the XRD (010) peak at 35° to 36°, the XRD (012) peak at 39° to 41°, and the XRD (013) peak at 44° to 46°. 1.1 Nb 0.9 It may contain O2.

[0023] A method for manufacturing a negative electrode active material for a lithium secondary battery according to another embodiment of the present invention comprises: a step of preparing a first mixture by solid-state mixing a lithium (Li) precursor and a niobium (Nb) precursor; a step of preparing a lithium niobium oxide by drying and heat-treating the first mixture; a step of preparing a second mixture by mixing a carbon material with the lithium niobium oxide; and a step of drying and then calcining the second mixture.

[0024] In one embodiment, the lithium (Li) precursor may comprise at least one selected from the group consisting of Li2CO3, LiNO3, LiOH, Li2O, Li(CO2)2, LiCl, LiCoO2, CH3COOLi, Li2(COO)2, LiOCO2CH3, and LiF.

[0025] In one embodiment, the niobium (Nb) precursor may comprise at least one selected from the group consisting of Nb2O3, Nb2O5, and NbO.

[0026] In one embodiment, the carbon material may comprise at least one selected from the group consisting of: graphite-based materials such as natural graphite, artificial graphite, graphene, super P, and super C; active carbon-based materials; carbon black-based materials such as Denka black, Ketjen black, channel black, furnace black, thermal black, contact black, lamp black, and acetylene black; and carbon nanostructures such as carbon fiber, carbon nanotube (CNT), and fullerene.

[0027] In one embodiment, the step of preparing the first mixture may be to mix the lithium (Li) precursor and the niobium (Nb) precursor in a solid state such that the molar ratio of Li to Nb is 1.1 to 0.9.

[0028] In one embodiment, the step of preparing the first mixture may be to mix 0.55 (Li2CO3) and 0.45 (Nb2O3).

[0029] In one embodiment, the heat treatment may be performed at 400°C to 600°C for 9 to 12 hours.

[0030] In one embodiment, the sintering may be performed at 800°C to 1,200°C for 18 to 72 hours.

[0031] In one embodiment, the heat treatment and calcination are performed under a reducing atmosphere, and the reducing atmosphere may include at least one selected from the group consisting of a hydrogen atmosphere, a nitrogen atmosphere, an argon atmosphere, an N2 / H2 mixed gas atmosphere, a CO / CO2 mixed gas atmosphere, a helium atmosphere, and combinations thereof.

[0032] A lithium secondary battery according to another embodiment of the present invention comprises: a negative electrode comprising a negative electrode active material for a lithium secondary battery according to one embodiment of the present invention or a negative electrode active material for a lithium secondary battery manufactured by a method for manufacturing a negative electrode active material for a lithium secondary battery according to another embodiment of the present invention; a positive electrode comprising a positive electrode active material; and a non-aqueous electrolyte. Effects of the invention

[0034] A negative electrode active material for a lithium secondary battery according to one embodiment of the present invention is characterized by using a lithium-transition metal oxide structure, such as LiCoO2 which was conventionally used as a positive electrode active material, in which Co is substituted with another metal element, Nb.

[0035] In other words, the negative electrode active material for a lithium secondary battery according to the present invention exhibits a higher density compared to conventionally used graphite active materials, thereby increasing the energy density per unit volume, and is also a negative electrode active material that exhibits a smaller volume change due to the insertion and removal of lithium ions compared to conventional metal or alloy-based active materials.

[0036] The negative electrode active material for a lithium secondary battery according to the present invention also has superior safety with organic electrolytes compared to carbon-based negative electrode active materials.

[0037] A method for manufacturing a negative electrode active material for a lithium secondary battery according to another embodiment of the present invention comprises preparing a mixture by solid-state mixing of a lithium precursor and a niobium precursor, and performing a process of drying and heat-treating the mixture to produce a Li with excellent capacity characteristics per unit volume. 1.1 Nb 0.9 It is possible to manufacture a negative electrode active material for a lithium secondary battery containing O2.

[0038] A lithium secondary battery according to one embodiment of the present invention exhibits high capacity and excellent lifespan characteristics, and in particular, can exhibit high capacity during high-rate charging and discharging. Brief explanation of the drawing

[0040] FIG. 1 is a flowchart illustrating a method for manufacturing a negative electrode active material for a lithium secondary battery according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a lithium secondary battery according to one embodiment of the present invention. FIG. 3 is Li according to an embodiment of the present invention 1.1 Nb 0.9 This is a diagram showing the XRD measurement results of O2. FIG. 4 is of Example 1 of the present invention. (Li 1.1 Nb 0 .9 O2) This is a graph showing the charge-discharge efficiency of a secondary battery containing a negative electrode active material. FIG. 5 is according to an embodiment of the present invention (L 1.1 Nb 0.9 This is a diagram showing the XRD measurement results of O2) + CNT. FIG. 6 is of Example 2 (L 1.1 Nb 0.9 This is a graph showing the charge-discharge efficiency of a secondary battery containing O2) + CNT negative electrode active material. FIG. 7 is according to an embodiment of the present invention (L 1.1 Nb 0.9 This is a diagram showing the XRD measurement results of O2) + Si. FIG. 8 is of Example 2 (L1.1 Nb 0.9 This is a graph showing the charge-discharge efficiency of a secondary battery containing O2) + Si negative electrode active material. FIG. 9 is L according to the present invention 1.1 Nb 0.9 This is a graph showing the change in 2θ (theta) values ​​for each XDR peak during charging and discharging in the in-situ XRD measurement region of a secondary battery containing O2 negative electrode active material. Specific details for implementing the invention

[0041] Hereinafter, embodiments are described in detail with reference to the attached drawings. However, various modifications may be made to the embodiments, and thus the scope of the patent application is not limited or restricted by these embodiments. It should be understood that all modifications, equivalents, and substitutions to the embodiments are included within the scope of the rights.

[0042] The terms used in the embodiments are for illustrative purposes only and should not be interpreted as intended to be limiting. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0043] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by those skilled in the art to which the embodiments pertain. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and should not be interpreted in an ideal or overly formal sense unless explicitly defined in this application.

[0045] In addition, when describing with reference to the attached drawings, identical components are assigned the same reference numeral regardless of drawing symbols, and redundant descriptions thereof are omitted. In describing the embodiments, if it is determined that a detailed description of related prior art could unnecessarily obscure the essence of the embodiments, such detailed description is omitted.

[0046] In addition, terms such as first, second, A, B, (a), (b), etc. may be used when describing the components of the embodiments. These terms are used merely to distinguish the components from other components, and the essence, order, or sequence of the components is not limited by the terms.

[0047] Components included in any one embodiment and components having common functions shall be described using the same names in other embodiments. Unless otherwise stated, the description in any one embodiment may also apply to other embodiments, and specific descriptions shall be omitted to the extent of overlap.

[0049] Hereinafter, the negative electrode active material for a lithium secondary battery, the method for manufacturing the same, and the lithium secondary battery including the same according to the present invention will be described in detail with reference to the examples and drawings. However, the present invention is not limited to these examples and drawings.

[0051] A negative electrode active material for a lithium secondary battery according to one embodiment of the present invention comprises lithium niobium oxide; and a carbon material, silicon, or both.

[0052] In one embodiment, the lithium niobium oxide is Li 1.1 Nb 0.9 It could be O2.

[0053] In one embodiment, the carbon material may comprise at least one selected from the group consisting of: graphite-based materials such as natural graphite, artificial graphite, graphene, super P, and super C; active carbon-based materials; carbon black-based materials such as Denka black, Ketjen black, channel black, furnace black, thermal black, contact black, lamp black, and acetylene black; and carbon nanostructures such as carbon fiber, carbon nanotube (CNT), and fullerene.

[0054] Preferably, the carbon material may include carbon nanotubes (CNT).

[0055] In one embodiment, the silicon is metallic silicon (Si) or silicon oxide (SiO₂). x , here 0 <x<2) 실리콘 탄화물(SiC) 및 Si-Y 합금 (상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속 및 희토류 원소로 이루어진 군으로부터 선택되는 적어도 어느 하나를 포함하는 원소이며, Si은 아님)로 이루어진 군으로부터 선택되는 적어도 어느 하나를 포함하는 것일 수 있다.

[0056] The above element Y may include at least one selected from the group consisting of 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, and Po.

[0057] In one embodiment, the negative electrode active material for the lithium secondary battery may have a P63 / mmc structure.

[0058] The (003) plane and the (104) plane of the above cathode active material can be analyzed using in-situ XRD (X-ray Diffraction).

[0059] In one embodiment, the cathode active material is a Li in which, during charging and discharging in the in-situ XRD measurement voltage range of 1.0 V to 0.0 V, the 2θ (theta) value changes in the XRD (002) peak at 16° to 17°, the XRD (010) peak at 35° to 36°, the XRD (012) peak at 39° to 41°, and the XRD (013) peak at 44° to 46°. 1.1 Nb 0.9 It may contain O2.

[0060] Therefore, through XRD analysis, the Li of the above-mentioned cathode active material 1.1 Nb 0.9 The crystal structure of O2 can be determined.

[0061] The present invention is characterized by using a lithium-transition metal oxide structure, such as LiCoO2, which was conventionally used as a positive electrode active material, in which Co is substituted with another metal element, Nb.

[0062] In other words, the negative electrode active material for a lithium secondary battery according to the present invention exhibits a higher density compared to conventionally used graphite active materials, thereby increasing the energy density per unit volume, and is also a negative electrode active material that exhibits a smaller volume change due to the insertion and removal of lithium ions compared to conventional metal or alloy-based active materials.

[0063] The negative electrode active material for a lithium secondary battery according to the present invention also has superior safety with organic electrolytes compared to carbon-based negative electrode active materials.

[0065] A method for manufacturing a negative electrode active material for a lithium secondary battery according to another embodiment of the present invention comprises: a step of preparing a first mixture by solid-state mixing a lithium (Li) precursor and a niobium (Nb) precursor; a step of preparing a lithium niobium oxide by drying and heat-treating the first mixture; a step of preparing a second mixture by mixing a carbon material with the lithium niobium oxide; and a step of drying and then calcining the second mixture.

[0066] FIG. 1 is a flowchart illustrating a method for manufacturing a negative electrode active material for a lithium secondary battery according to one embodiment of the present invention.

[0067] Referring to FIG. 1, a method for manufacturing a negative electrode active material for a lithium secondary battery according to one embodiment of the present invention includes a first mixture preparation step (110), a lithium niobium oxide preparation step (120), a second mixture preparation step (130), and a calcination step (140).

[0068] The first mixture preparation step (110) above is to prepare the first mixture by mixing the lithium (Li) precursor and the niobium (Nb) precursor in a solid state.

[0069] In one embodiment, the lithium (Li) precursor may comprise at least one selected from the group consisting of Li2CO3, LiNO3, LiOH, Li2O, Li(CO2)2, LiCl, LiCoO2, CH3COOLi, Li2(COO)2, LiOCO2CH3, and LiF.

[0070] Preferably, the lithium (Li) precursor may be Li2CO3.

[0071] In one embodiment, the niobium (Nb) precursor may comprise at least one selected from the group consisting of Nb2O3, Nb2O5, and NbO.

[0072] Preferably, the niobium (Nb) precursor may be Nb2O3.

[0073] The above mixing process can be performed using a ball mill at 150 rpm to 250 rpm for 2 to 4 hours.

[0074] In one embodiment, the step of preparing the first mixture may be to mix the lithium (Li) precursor and the niobium (Nb) precursor in a solid state such that the molar ratio of Li to Nb is 1.1 to 0.9.

[0075] In one embodiment, the step of preparing the first mixture may be to mix 0.55 (Li2CO3) and 0.45 (Nb2O3).

[0076] The lithium niobium oxide preparation step (120) above is to prepare lithium niobium oxide by drying and heat-treating the first mixture.

[0077] The above drying may involve drying at a temperature of 60°C to 80°C; 60°C to 70°C; or 70°C to 80°C, followed by a heat treatment process.

[0078] In one embodiment, the heat treatment may be performed at 400°C to 600°C; 400°C to 500°C; or 500°C to 600°C for 9 to 12 hours.

[0079] If the temperature falls outside the range of the above heat treatment temperature, an impurity phase may be formed, which is undesirable as it may lead to a decrease in capacity and lifespan.

[0080] The second mixture preparation step (130) above is to prepare the second mixture by mixing a carbon material with the lithium niobium oxide.

[0081] In one embodiment, the carbon material may comprise at least one selected from the group consisting of: graphite-based materials such as natural graphite, artificial graphite, graphene, super P, and super C; active carbon-based materials; carbon black-based materials such as Denka black, Ketjen black, channel black, furnace black, thermal black, contact black, lamp black, and acetylene black; and carbon nanostructures such as carbon fiber, carbon nanotube (CNT), and fullerene.

[0082] Preferably, the carbon material may include carbon nanotubes (CNT).

[0083] The above mixing process can be performed using a ball mill at 150 rpm to 250 rpm for 2 to 4 hours.

[0084] The above calcination step (140) is to calcinate the second mixture after drying it.

[0085] In one embodiment, the sintering may be performed by performing a heat treatment for 18 to 72 hours at 800 ℃ to 1,200 ℃; 800 ℃ to 1,100 ℃; 800 ℃ to 1,000 ℃; 800 ℃ to 900 ℃; 900 ℃ to 1,200 ℃; 900 ℃ to 1,100 ℃; 900 ℃ to 1,000 ℃; 1,000 ℃ to 1,200 ℃; 1,000 ℃ to 1,100 ℃; or 1,100 ℃ to 1,200 ℃.

[0086] If the firing temperature falls outside the above range, an impurity phase may be formed, which is undesirable as it may lead to a decrease in capacity and lifespan.

[0087] In one embodiment, the heat treatment and sintering may be performed under a reducing atmosphere.

[0088] The above reducing atmosphere may include at least one selected from the group consisting of a hydrogen atmosphere, a nitrogen atmosphere, an argon atmosphere, an N2 / H2 mixed gas atmosphere, a CO / CO2 mixed gas atmosphere, a helium atmosphere, and combinations thereof.

[0089] A method for manufacturing a negative electrode active material for a lithium secondary battery according to another embodiment of the present invention comprises preparing a mixture by solid-state mixing of a lithium precursor and a niobium precursor, and performing a process of drying and heat-treating the mixture to produce a Li with excellent capacity characteristics per unit volume. 1.1 Nb 0.9 It is possible to manufacture a negative electrode active material for a lithium secondary battery containing O2.

[0091] A lithium secondary battery according to another embodiment of the present invention comprises: a negative electrode comprising a negative electrode active material for a lithium secondary battery according to one embodiment of the present invention or a negative electrode active material for a lithium secondary battery manufactured by a method for manufacturing a negative electrode active material for a lithium secondary battery according to another embodiment of the present invention; a positive electrode comprising a positive electrode active material; and a non-aqueous electrolyte.

[0092] Lithium-ion batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium-polymer batteries depending on the type of separator and electrolyte used; they can be classified by shape into cylindrical, prismatic, coin, and pouch types; and they can be divided into bulk and thin-film types based on size. As the structures and manufacturing methods of these batteries are widely known in this field, a detailed description is omitted.

[0093] FIG. 2 is a schematic cross-sectional view of a lithium secondary battery according to one embodiment of the present invention.

[0094] Referring to FIG. 2, the manufacturing process of the lithium secondary battery of the present invention is described as follows.

[0095] The above lithium secondary battery (200) can be manufactured by placing an electrode assembly (240), which includes a positive electrode (210), a negative electrode (220), and a separator (230) existing between the positive electrode (210) and the negative electrode (220), into a case (250), injecting an electrolyte into the top of the case (250), and sealing it with a cap plate (260) and a gasket (270).

[0096] The cathode of the present invention comprises a current collector and a cathode active material layer formed on the current collector, and the cathode active material layer comprises a cathode active material.

[0097] The negative electrode active material for a lithium secondary battery according to the present invention is a Li-120 electrode in which, during charging and discharging in the in-situ XRD measurement voltage range of 1 V to 0 V, the 2θ (theta) value changes in the XRD (002) peak at 16° to 17°, the XRD (010) peak at 35° to 36°, the XRD (012) peak at 39° to 41°, and the XRD (013) peak at 44° to 46°. 1.1 Nb 0.9 Includes O2.

[0098] The above-described negative electrode active material is the same as previously described, and it is preferable to include it in an amount of 1% to 99% by weight relative to the total weight of the negative electrode active material layer, and more preferably in an amount of 10% to 98% by weight. If the content falls outside the above range, it is undesirable as there is a risk of reduced bonding strength with the current collector due to a decrease in capacity or a decrease in the relative amount of binder.

[0099] The above-mentioned cathode may be manufactured by mixing the cathode active material, a binder, and optionally a conductive material in a solvent to prepare a composition for forming a cathode active material layer, and then applying this composition to a cathode current collector such as copper. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted in this specification.

[0100] The above binder serves to adhere the negative electrode active material particles well to each other and also to adhere the negative electrode active material well to the current collector. For example, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylene cellulose, diacetylene cellulose, polyvinyl chloride, polyvinylpyrrolidone, carboxylated polyvinyl chloride, polyvinyl difluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. may be used, but are not limited thereto.

[0101] The above conductive material is used to impart conductivity to the electrode, and any electronically conductive material that does not cause chemical changes in the battery being constructed can be used. For example, natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, metal powder such as copper, nickel, aluminum, silver, or metal fiber can be used, and conductive materials such as polyphenylene derivatives can also be mixed and used.

[0102] The above solvent may include N-methylpyrrolidone, but is not limited thereto.

[0103] The above current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

[0104] The above-mentioned positive electrode comprises a current collector and a positive electrode active material layer formed on the current collector, and the positive electrode active material layer comprises a positive electrode active material.

[0105] The above-mentioned positive electrode active material may use a lithiated intercalation compound capable of reversible insertion and extraction of lithium. Specifically, at least one of a composite oxide of lithium and a metal selected from cobalt, manganese, nickel, molybdenum, titanium, and combinations thereof may be used.

[0106] In addition, the above compound may have a coating layer on its surface, or the above compound and the compound having the coating layer may be mixed and used. This coating layer may include at least one coating element compound selected from the group consisting of oxides, hydroxides, oxyhydroxides, oxycarbonates, and hydroxycarbonates of the coating element. The compounds forming these coating layers may be amorphous or crystalline. As coating elements included in the coating layer, Mg, Co, K, Na, Ca, Si, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof may be used. The coating layer formation process may be any coating method that allows coating without adversely affecting the physical properties of the cathode active material by using these elements on the above compound (e.g., spray coating, immersion method, etc.), and since this is a matter that is well understood by those skilled in the art, a detailed explanation will be omitted.

[0107] The above anode can also be manufactured in the same way as the cathode by mixing the above anode active material, a binder, and optionally a conductive material to prepare a composition for forming an anode active material layer, and then applying the composition for forming an anode active material layer to an anode current collector such as aluminum.

[0108] As the electrolyte charged into the above lithium secondary battery, a non-aqueous electrolyte or a known solid electrolyte may be used.

[0109] As the above-mentioned non-aqueous electrolyte, a lithium salt dissolved in a non-aqueous organic solvent may be used. The above-mentioned lithium salt acts as a source of lithium ions within the battery, enabling the operation of a basic lithium secondary battery. Examples of the above-mentioned lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiN(C2F5SO2)2, LiAlO4, LiAlCl4, and LiN(Cp F 2p+1 SO2)(C q F 2q+1 SO2) (where p and q are natural numbers), LiSO3CF3, LiCl, LiI, and combinations thereof can be used, selected from the group consisting of these.

[0110] The concentration of the lithium salt can be used within a range of 0.6 M to 2.0 M, and a range of 0.7 to 1.6 M is more preferable. If the concentration of the lithium salt is less than 0.6 M, the conductivity of the electrolyte is lowered, resulting in reduced electrolyte performance, and if it exceeds 2.0 M, the viscosity of the electrolyte increases, leading to a problem where the mobility of lithium ions decreases.

[0111] The above-mentioned non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. Carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvents may be used as non-aqueous organic solvents.

[0112] The above carbonate-based solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc.

[0113] The above ester-based solvents may include n-methyl acetate, n-ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, etc.

[0114] The above ether-based solvents may include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc.

[0115] Cyclohexanone, etc., may be used as the above-mentioned ketone-based solvent.

[0116] Ethyl alcohol, isopropyl alcohol, etc. can be used as the above alcohol-based solvent.

[0117] The above-mentioned aprotic solvents may include nitriles such as X-CN (where X is a straight-chain, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double bond-directing ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; sulfolanes, etc.

[0118] The above-mentioned non-aqueous organic solvents may be used alone or in a mixture of one or more. When used in a mixture of one or more, the mixing ratio can be appropriately adjusted according to the desired battery performance, which is widely understood by those working in the field.

[0119] In addition, for the above carbonate-based solvent, it is preferable to use a mixture of cyclic carbonates and chain carbonates. In this case, using a mixture of cyclic carbonates and chain carbonates in a volume ratio of 1:1 to 1:9 can result in excellent performance of the electrolyte.

[0120] The non-aqueous organic solvent of the present invention may further include an aromatic hydrocarbon organic solvent in the carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon organic solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0121] Preferably, the aromatic hydrocarbon-based organic solvent is benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, It may include at least one selected from the group consisting of 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4-trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotoluene, 1,2,3-triiodotoluene, 1,2,4-triiodotoluene, and xylene.

[0122] The above-mentioned non-aqueous electrolyte may further include vinylene carbonate or ethylene carbonate-based compounds to improve battery life.

[0123] Representative examples of the above ethylene carbonate-based compounds may include at least one selected from the group consisting of difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, and fluoroethylene carbonate. When further using such life-prolonging additives, the amount used can be appropriately controlled.

[0124] The above-mentioned non-aqueous electrolyte may further include additives such as anti-overchargers like ethylene carbonate and pyrocarbonate.

[0125] In addition, the above-mentioned solid electrolyte may preferably be a polyethylene oxide polymer electrolyte or a polymer electrolyte containing one or more polyorganosiloxane side chains or polyoxyalkylene side chains, a sulfide electrolyte such as Li2S-SiS2, Li2S-GeS2, Li2S-P2S5, or Li2S-B2S3, or an inorganic electrolyte such as Li2S-SiS2-Li3PO4 or Li2S-SiS2-Li3SO4.

[0126] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. As such a separator, polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used, and a mixed multilayer film such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator may also be used.

[0128] The present invention will be described in detail below with reference to the following examples and comparative examples. However, the technical scope of the present invention is not limited or restricted by such examples.

[0130] [Example]

[0131] Comparative Example 1: LiNbO 2 manufacturing

[0132] Li2CO3 and Nb2O3 were solid-state mixed so that the molar ratio of Li to Nb was 1:0.9. The mixing process was performed using a ball mill at 200 rpm for 3 hours. Subsequently, the mixture was recovered, dried at 60 to 80 ℃, heat-treated at 500 ℃ for 24 hours, calcined at 900 ℃ for 20 hours, and then cooled to room temperature to obtain Li1.1 Nb 0.9 A negative electrode active material for a lithium secondary battery using O2 was manufactured.

[0134] Example 1: Li 1.1 Nb 0.9 O 2 manufacturing

[0135] 0.55 (Li2CO3) and 0.45 (Nb2O3) were mixed in a solid state so that the molar ratio of Li to Nb was 1.1 to 0.9. The mixing process requires two heat treatment steps.

[0136] 1.1(Li2CO3)+ 0.3(Nb2O5) → 2(Li 1.1 Nb 0.3 O 1.3 )+1.1(CO2) (I)

[0137] At this time, product 2 (Li 1.1 Nb 0.3 O 1.3 ) must have an oxidation number of +3.

[0138] 2(Li 1.1 Nb 0.3 O 1.3 )+1.1(NbO)→ 3(Li 1.1 Nb 0.0 O2) (II)

[0139] It was performed using a ball mill at 200 rpm for 3 hours. Subsequently, the mixture was recovered and dried at 60 to 80 ℃, then heat-treated at 500 ℃ for 10 hours, followed by calcination at 1200 ℃ for 72 hours, and then cooled to room temperature to L 1.1 Nb 0.9 A negative electrode active material for a lithium secondary battery using O2 was manufactured.

[0141] Example 2: Li 1.1 Nb 0.9 O 2 + CNT manufacturing

[0142] L prepared in Example 1 above 1.1 Nb 0.9 Except for adding CNTs to O2 in a weight ratio of 9:1, L in the same manner as in Example 1 above 1.1 Nb 0.9 An O2+ CNT negative electrode active material for a lithium secondary battery was prepared.

[0144] Example 3: Li 1.1 Nb 0.9 O 2 + Si manufacturing

[0145] L prepared in Example 1 above 1.1 Nb 0.9 Except for adding CNTs to O2 in a weight ratio of 9:1, L in the same manner as in Example 1 above 1.1 Nb 0.9 An O2+Si negative electrode active material for a lithium secondary battery was prepared.

[0147] Test Example 1: Structural analysis of cathode active material

[0148] X-ray diffraction patterns (Philips X'pert MPD) were measured to analyze the structure of the negative electrode active material prepared in Example 1 above.

[0149] FIG. 3 is the (L prepared in Example 1 of the present invention 1.1 Nb 0.9 This is a diagram showing the XRD measurement results of O2.

[0150] As shown in FIG. 3, (L of Example 1 prepared according to an embodiment of the present invention 1.1 Nb 0.9 The XRD pattern of O2) is a typical cathode active material (L 1.1 Nb 0.9 It was confirmed that it was similar to the XRD pattern of O2), and accordingly, according to the embodiment of the present invention (L 1.1 Nb 0.9 O2) It was found that the negative electrode active material can be usefully utilized as a secondary battery.

[0152] Test Example 2: Li 1.1 Nb 0.9 O 2 Evaluation of the electrochemical characteristics of a battery

[0153] To evaluate the electrochemical characteristics (charge / discharge capacity) of a cathode containing the cathode active material of the present invention, the following experiment was performed.

[0154] The test electrode was prepared by coating a mixture of powders and poly(vinylidene difluoride) binder (10 wt.%) onto a copper foil.

[0155] Charge-discharge tests were performed using a three-electrode cell with a constant current of 18.1 mA / g. A 1 mol dm⁻³(M)LiClO₄ electrolyte was used, consisting of a 1:1 mixture of ethylene carbonate (EC) and diethylcarbonate (DEC) (EC + DEC) (Kishida Chemical Co., Lithium Battery Grade). Lithium foil was used for the counter and reference electrodes. CV measurements were performed between 3.0 and 0.0 V with a sweep rate of 0.5 mV / S. All electrochemical measurements were taken at <-60°C in an argon-filled glove box (Miwa, MDB-1B+MM3-P60S). All potentials were measured in volts vs. Li / Li⁻¹. + It was performed by referring to .

[0156] FIG. 4 is of Example 1 of the present invention (Li 1.1 Nb 0.9 O2) is a graph showing the charge-discharge efficiency of a secondary battery containing a negative electrode active material, and FIG. 5 is a (L 1.1 Nb 0.9 This is a diagram showing the XRD measurement results of O2)+CNT.

[0157] FIG. 6 is of Example 2 (L 1.1 Nb 0.9This is a graph showing the charge-discharge efficiency of a secondary battery containing O2) + CNT negative electrode active material.

[0158] As shown in FIGS. 4 and FIGS. 6, (L 1.1 Nb 0.9 The initial charge / discharge capacity of O2) was found to be 130 mAh / g, and pure (L 1.1 Nb 0.9 When CNTs were coated on O2, the first charge / discharge capacity was found to be 250 mAh / g.

[0159] FIG. 7 is of Example 2 (L 1.1 Nb 0.9 This is a graph showing the charge-discharge efficiency of a secondary battery containing O2) + Si negative electrode active material.

[0160] As shown in Fig. 8, pure (L 1.1 Nb 0.9 When Si was coated on O2, the first charge / discharge capacity was found to be 330 mAh / g.

[0161] From this, L according to the present invention 1.1 Nb 0.9 O2, L 1.1 Nb 0.9 It was found that the O2+ CNT cathode active material has superior charge / discharge efficiency compared to the Li NbO2 cathode active material of Comparative Example 1.

[0163] Test Example 3: Li 1.1 Nb 0.9 O 2 In-situ XDR analysis of the battery

[0164] The Li prepared in Example 1 above 1.1 Nb 0.9 O2 (LTO powder) and a secondary battery (in situ cell) manufactured using it were analyzed using in-situ XRD.

[0165] The above measurement was taken by changing the voltage from 3.0 V to 0.0 V and then changing the voltage back to 3.0 V.

[0166] FIG. 9 is L according to the present invention 1.1 Nb 0.9 This is a graph showing the in-situ XDR measurement results of O2 negative electrode active material powder and a secondary battery containing it.

[0167] As shown in FIG. 9, the Li prepared in Example 1 1.1 Nb 0.9 It was confirmed that four major peaks appeared in the secondary battery (in situ cell) manufactured using O2 at 2θ (theta) values ​​of 16° to 17°, 34 to 37°, 43 to 44°, and 44° to 46°.

[0169] Although the embodiments have been described above with reference to limited examples and drawings, those skilled in the art can make various modifications and variations from the description above. For example, suitable results may be achieved even if the described techniques are performed in a different order than described, and / or the described components are combined or assembled in a form different from described, or replaced or substituted by other components or equivalents. Therefore, other implementations, other embodiments, and equivalents to the claims are also included within the scope of the claims set forth below. Explanation of the symbols

[0171] 200: Lithium secondary battery 210: Anode 220: Cathode 230: Separator 240: Electrode assembly 250: Case 260: Cap Plate 270: Gasket

Claims

Claim 1 A negative electrode active material for a lithium secondary battery comprising: lithium niobium oxide; and a carbon material, silicon, or both; wherein the carbon material comprises at least one selected from the group consisting of carbon fiber, carbon nanotube (CNT), and fullerene. Claim 2 In claim 1, the lithium niobium oxide is Li 1.1 Nb 0.9 A negative electrode active material for a lithium secondary battery that is O2. Claim 3 delete Claim 4 In claim 1, the silicon is metallic silicon (Si) and silicon oxide (SiO₂). x , here 0 <x<2) 실리콘 탄화물(SiC) 및 Si-Y 합금 (상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속 및 희토류 원소로 이루어진 군으로부터 선택되는 적어도 어느 하나를 포함하는 원소이며, Si은 아님)로 이루어진 군으로부터 선택되는 적어도 어느 하나를 포함하는 것인,리튬 이차전지용 음극 활물질. Claim 5 In claim 1, the negative electrode active material for a lithium secondary battery is a negative electrode active material having a P63 / mmc structure. Claim 6 In claim 1, the cathode active material is a Li in which, during charging and discharging in the in-situ XRD measurement voltage range of 1.0 V to 0.0 V, the 2θ (theta) value changes in the XRD (002) peak at 16° to 17°, the XRD (010) peak at 35° to 36°, the XRD (012) peak at 39° to 41°, and the XRD (013) peak at 44° to 46°. 1.1 Nb 0.9 A negative electrode active material for a lithium secondary battery that contains O2. Claim 7 A method for manufacturing a negative electrode active material for a lithium secondary battery according to claim 1, comprising: a step of preparing a first mixture by solid-state mixing a lithium (Li) precursor and a niobium (Nb) precursor; a step of preparing a lithium niobium oxide by drying and heat-treating the first mixture; a step of preparing a second mixture by mixing a carbon material with the lithium niobium oxide; and a step of drying and calcining the second mixture. Claim 8 A method for manufacturing a negative electrode active material for a lithium secondary battery according to claim 7, wherein the lithium (Li) precursor comprises at least one selected from the group consisting of Li2CO3, LiNO3, LiOH, Li2O, Li(CO2)2, LiCl, LiCoO2, CH3COOLi, Li2(COO)2, LiOCO2CH3, and LiF. Claim 9 A method for manufacturing a negative electrode active material for a lithium secondary battery, wherein, in claim 7, the niobium (Nb) precursor comprises at least one selected from the group consisting of Nb2O3, Nb2O5, and NbO. Claim 10 A method for manufacturing a negative electrode active material for a lithium secondary battery, wherein, in claim 7, the step of preparing the first mixture is to mix a lithium (Li) precursor and a niobium (Nb) precursor in a solid state such that the molar ratio of Li to Nb is 1.1 to 0.

9. Claim 11 A method for manufacturing a negative electrode active material for a lithium secondary battery, wherein, in claim 7, the step of preparing the first mixture is to mix 0.55 (Li2CO3) and 0.45 (Nb2O3). Claim 12 A method for manufacturing a negative electrode active material for a lithium secondary battery, wherein, in claim 7, the heat treatment is performed at 400 ℃ to 600 ℃ for 9 to 12 hours. Claim 13 A method for manufacturing a negative electrode active material for a lithium secondary battery, wherein, in claim 7, the calcination is performed at 800 ℃ to 1,200 ℃ for 18 hours to 72 hours. Claim 14 A method for manufacturing a negative electrode active material for a lithium secondary battery, wherein, in claim 7, the heat treatment and calcination are performed under a reducing atmosphere, and the reducing atmosphere comprises at least one selected from the group consisting of a hydrogen atmosphere, a nitrogen atmosphere, an argon atmosphere, an N2 / H2 mixed gas atmosphere, a CO / CO2 mixed gas atmosphere, a helium atmosphere, and combinations thereof. Claim 15 A lithium secondary battery comprising: a negative electrode comprising a negative electrode active material for a lithium secondary battery manufactured by the method for manufacturing a negative electrode active material for a lithium secondary battery according to claim 1 or claim 7; a positive electrode comprising a positive electrode active material; and a non-aqueous electrolyte.

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