Negative electrode active material and rechargeable lithium battery including same

Abstract

The present invention relates to a negative electrode active material and a rechargeable lithium battery including same. The negative electrode active material has a span value of 1.1 to 1.6 by equation 1 below, and comprises: secondary particles each composed of assembled primary particles, each of which comprises a silicon nanoparticle and a metal coating layer enclosing the silicon nanoparticle and containing a metal-based material; and an amorphous carbon coating layer enclosing surfaces of the primary and secondary particles. [Equation 1] Span = (D90-D10) / D50 (In equation 1, D10 represents the particle size corresponding to 10% cumulative volume in the particle size distribution, D50 represents the particle size corresponding to 50% cumulative volume in the particle size distribution, and D90 represents the particle size corresponding to 90% cumulative volume in the particle size distribution)

Description

Negative active material and lithium secondary battery containing the same

[0001] The present invention relates to a negative electrode active material and a lithium secondary battery including the same.

[0002] Recently, with the rapid spread of electronic devices that use batteries, such as mobile phones, laptop computers, and electric vehicles, the demand for small, lightweight, and relatively high-capacity lithium secondary batteries is rapidly increasing.

[0003] In addition, the development of high-energy density electricity has recently been demanded, and for this purpose, high-capacity cathode active materials are required.

[0004] Attempts are being made to use Si-based negative electrode active materials as these high-capacity negative electrode active materials.

[0005] One embodiment provides a negative electrode active material exhibiting excellent conductivity.

[0006] Another embodiment provides a lithium secondary battery comprising the negative active material.

[0007] One embodiment provides a negative active material comprising: a secondary particle assembled with primary particles having a span value of 1.1 to 1.6 in Equation 1 below, a silicon nanoparticle and a metal coating layer surrounding the surface of the silicon nanoparticle, the metal coating layer including a metal-based material; and an amorphous carbon coating layer surrounding the surface of the primary particle and the secondary particle.

[0008] [Formula 1]

[0009] Span = (D90-D10) / D50

[0010] (In the above formula 1, D10 means the particle diameter of a particle having a cumulative volume of 10% by volume in the particle size distribution, D50 means the particle diameter of a particle having a cumulative volume of 50% by volume in the particle size distribution, and D90 means the particle diameter of a particle having a cumulative volume of 90% by volume in the particle size distribution)

[0011] According to another embodiment, a lithium secondary battery is provided, which includes a negative electrode including the negative active material; a positive electrode; and an electrolyte.

[0012] The negative active material according to one embodiment can exhibit excellent conductivity.

[0013] Figure 1 is a schematic drawing of a lithium secondary battery according to one embodiment.

[0014] Hereinafter, embodiments of the present invention will be described in detail. However, these are presented as examples and are not intended to limit the present invention. The present invention is defined solely by the scope of the claims set forth below.

[0015] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0016] Here, “combination of these” means a mixture, laminate, composite, copolymer, alloy, blend, reaction product, etc. of the components.

[0017] It should be understood that the terms "include," "comprising," or "having" herein are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0018] To clearly illustrate various layers and regions in the drawings, their thicknesses are enlarged, and similar parts are designated by the same drawing reference numerals throughout the specification. When an element such as a layer, film, region, or plate is said to be "over" or "on" another element, this includes not only the case where it is "directly over" the other element, but also the case where there is another element in between. Conversely, when an element is said to be "directly over" another element, it means that there is no other element in between.

[0019] Also, the term "layer" here includes not only a shape formed on the entire surface when observed in a plan view, but also a shape formed on a portion of the surface.

[0020] Here, "or" is not interpreted in an exclusive sense, for example, "A or B" is interpreted to include A, B, A+B, etc.

[0021] Unless otherwise defined herein, the particle diameter or size may be the average particle diameter. This average particle diameter refers to the average value of the particle diameter according to the cumulative volume in the particle size distribution of particles contained in the negative electrode active material. The particle size distribution can be measured by a method widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope photograph or a scanning electron microscope photograph. Alternatively, the average particle diameter value can be obtained by measuring with a measuring device that utilizes dynamic light-scattering, performing data analysis to count the number of particles for each particle size range, and calculating from this.

[0022] According to one embodiment, a negative active material comprises secondary particles assembled with primary particles having a span value of 1.1 to 1.6 in Equation 1 below, including silicon nanoparticles and a metal coating layer comprising a metal-based material surrounding the surface of the silicon nanoparticles; and an amorphous carbon coating layer surrounding the surface of the primary particles and the secondary particles.

[0023] [Formula 1]

[0024] Span = (D90-D10) / D50

[0025] In the above equation 1, D10 means the particle diameter of a particle having a cumulative volume of 10% by volume in the particle size distribution, D50 means the particle diameter of a particle having a cumulative volume of 50% by volume in the particle size distribution, and D90 means the particle diameter of a particle having a cumulative volume of 90% by volume in the particle size distribution.

[0026] In one embodiment, the span value may be 1.1 to 1.55, or may be 1.1 to 1.5.

[0027] When the span value of the negative active material falls within the above range, this means that the negative active material contains substantially no fine particles. That is, since it contains almost no fine particles having a size of 1 μm or less and which are typically irregular in shape, it can exhibit a low specific surface area, thereby reducing electrolyte side reactions and improving the lifespan.

[0028] According to one embodiment, the negative active material may have a low specific surface area, i.e., a low BET specific surface area, and the specific surface area may be from 0.5 m2 / g to 2 m2 / g, from 0.8 m2 / g to 2 m2 / g, or from 0.8 m2 / g to 1.5 m2 / g. This specific surface area is lower than the specific surface area of ​​the silicon-carbon composite negative active material, which is about 3 m2 / g.

[0029] According to one embodiment, a negative active material includes primary particles and secondary particles assembled with the primary particles, and includes an amorphous carbon coating layer surrounding the surfaces of the primary particles and the secondary particles.

[0030] In one embodiment, the primary particle comprises a silicon nanoparticle and a metal coating layer surrounding the surface of the silicon nanoparticle, wherein the metal coating layer comprises a metal-based material. Additionally, the amorphous carbon coating layer may comprise a metal-based material.

[0031] In one embodiment, the metal included in the metal coating layer and the amorphous carbon coating layer may be the same.

[0032] In one embodiment, the negative active material comprises a primary particle, a silicon nanoparticle surrounded by a metal coating layer, wherein a layered coating layer comprising a metal-based material is formed on the surface of the silicon nanoparticle and is substantially continuously positioned. For example, since the surface of the silicon nanoparticle is entirely covered by the metal coating layer, the surface of the silicon nanoparticle is not exposed. In one embodiment, the metal coating layer being positioned in a layered manner may mean that the metal coating layer is positioned in area contact with the silicon nanoparticles positioned at a certain thickness along the surface of the silicon nanoparticles. This improves the internal conductivity of the negative active material, thereby improving charge-discharge uniformity. In addition, the improved electrical conductivity due to the coating layer may increase silicon utilization and reduce side reactions. If the metal is present in the form of islands discontinuously positioned on the surface of the silicon nanoparticles, the effect of forming the metal coating layer is not sufficient. In one embodiment, the presence of islands means that the metal is positioned in point contact only at specific locations on the surface of the silicon nanoparticles.

[0033] The thickness of the metal coating layer may be 1 nm to 30 nm, 1 nm to 20 nm, or 5 nm to 20 nm. When the thickness of the metal coating layer is within the above range, the effect of improving electrical conductivity due to the metal coating layer can be further enhanced, and the interior of the active material can be more uniformly utilized when the battery is operated.

[0034] In a negative active material according to one embodiment, the amorphous carbon coating layer surrounds the primary particles and the secondary particle surfaces, for example, is filled between the primary particles and is also positioned on the secondary particle surfaces.

[0035] The above amorphous carbon coating layer comprises a metallic material.

[0036] The metal material included in the amorphous carbon coating layer may be present in the amorphous carbon coating layer during the process of forming a metal coating layer on the surface of silicon nanoparticles during the negative active material manufacturing process. Accordingly, the metal included in the amorphous carbon coating layer may be the same as the metal in the metal coating layer.

[0037] In one embodiment, the metal-based material included in the metal coating layer and the amorphous carbon coating layer may be a metal or a metal compound.

[0038] The above metal compound may be a metal oxide, a metal nitride or a combination thereof.

[0039] The metal may be a metal alloyable with lithium, and may be an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or a combination thereof. For example, the metal may be Ag, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. In one embodiment, the metal may be Ag.

[0040] Since the coating layer including the above metal is distributed on the surface of the primary particle and the surface of the secondary particle, that is, inside and outside of the active material, the conductivity of the active material can be improved both inside and outside.

[0041] The content of the metal-based material may be 0.01 wt% to 20 wt%, 0.05 wt% to 15 wt%, or 0.01 wt% to 10 wt% based on 100 wt% of the total negative active material. In one embodiment, the content of the metal-based material is the total content of the metal-based material included in the negative active material, and the respective contents included in the metal coating layer or the amorphous carbon coating layer need not be limited. When the content of the metal-based material is included in the above range, the conductivity of the active material can be further improved, thereby allowing the inside of the active material to be used more uniformly when the battery is operated.

[0042] In the negative active material according to one embodiment, when measuring the X-ray diffraction intensity, the diffraction peak intensity (I) due to Si (111) detected at 2θ = 27.5° to 29.5° Si(111) ) diffraction peak intensity (I) by metal (111) detected at 2θ=37.5° to 40.0°금속(111) ) peak intensity ratio (I 금속(111) / I Si(111) ) can be 0.05 to 0.5. Peak intensity ratio (I 금속(111) / I Si(111) ) may be 0.2 to 0.4, or 0.1 to 0.4. The peak intensity ratio may vary depending on the type of metal, and for example, the peak intensity ratio may be a value that is satisfied when the metal is Ag. For example, the diffraction peak intensity ratio is I Ag(111) / I Si(111) It could be.

[0043] Peak intensity ratio (I Ag(111) / I Si(111) ) is included in the above range, it means that Si and metal (e.g., Ag) exist in a certain ratio within the structure of the negative electrode active material, which means that the conductivity of the negative electrode active material increases. The increase in the conductivity of the active material means that substantially most of the silicon nanoparticles can participate in the charge / discharge reaction, thereby inducing uniform charge / discharge, and thus exhibiting high capacity and long life.

[0044] In addition, when the content of metal-based materials increases, the diffraction peak intensity (I) due to metal, for example, Ag Ag(111) ) increases, the peak intensity ratio (I Ag(111) / I Si(111) ) can increase. Therefore, the peak intensity ratio (I Ag(111) / I Si(111) ) is included in the above range, it may mean that Ag is appropriately included.

[0045] In one embodiment, the peak intensity may be a height value of the peak or an integrated area value of the peak, and may be an integrated area value of the peak.

[0046] The above X-ray diffraction intensity was measured using CuKα rays as a target line, and the measurement conditions at this time are 2θ = 20° to 80°, the scan speed (° / S) may be 0.044 to 0.089, and the step size (° / step) may be 0.013 to 0.039. In addition, the peak intensity ratio (I metal(111) / I Si(111) ), for example, I Ag(111) / I Si(111) Since it represents the ratio of peak intensities, i.e., a relative value, the peak intensity (I) of the metal (111) plane is determined according to the X-ray diffraction analysis measurement conditions. metal(111) )) and peak intensity (I) of the Si(111) plane Si(111) ) may vary, but their peak intensity ratios (I metal(111) / I Si(111) ) is of course practically unchanged.

[0047] In one embodiment, the particle size of the metal-based material included in the amorphous carbon coating layer may be 1 nm to 30 nm, and according to another embodiment, may be 1 nm to 20 nm, or 5 nm to 20 nm. When the particle size of the metal-based material is within the above range, the interior of the active material can be used more uniformly when the battery is operated.

[0048] In one embodiment, the particle size of the silicon nanoparticles may be 10 nm to 1,000 nm, and according to another embodiment, may be 10 nm to 200 nm, or 20 nm to 150 nm. When the particle size of the silicon nanoparticles is within the above range, excessive volume expansion occurring during charge and discharge can be suppressed, and disconnection of the conductive path due to particle fragmentation during charge and discharge can be prevented.

[0049] In the above amorphous carbon coating layer, the amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof. The thickness of the amorphous carbon coating layer may be 1 nm to 2 μm, 1 nm to 500 nm, 10 nm to 300 nm, or 20 nm to 200 nm. When the thickness of the amorphous carbon coating layer is within the above range, silicon volume expansion during charge and discharge can be well suppressed.

[0050] In the above negative active material, the content of the silicon nanoparticles may be 44 wt% to 65 wt%, or 52 wt% to 62 wt%, based on 100 wt% of the total negative active material. In addition, the content of the amorphous carbon coating layer may be 34 wt% to 46 wt%, or 36 wt% to 41 wt%, based on 100 wt% of the total negative active material.

[0051] A negative active material according to one embodiment can be manufactured by the following process.

[0052] Micrometer-sized silicon particles, a metal precursor, and a dispersant are mixed in a solvent. The mixing process can be performed by ball milling using zirconia balls, etc., but is not limited thereto, and can be performed by any process capable of pulverizing silicon particles. By performing pulverization through the mixing process, nano-sized silicon primary particles can be manufactured. The solvent may be an organic solvent such as ethanol, methanol, or propanol. The particle size of the silicon primary particles may be 1 nm to 1000 nm, 10 nm to 100 nm, or 20 nm to 150 nm. The dispersant used at this time may be stearic acid, boron nitride (BN), MgS, polyvinylpyrrolidone (PVP), or a combination thereof.

[0053] The mixing ratio of the silicon particles and the metal precursor can be adjusted so that the mixing ratio of silicon and metal is 100:1 to 100:30 by weight, or 100:1 to 100:25. In the mixing process, the amount of the dispersant used may be an amount appropriate for the silicon particles and the metal precursor to be well dispersed in the solvent, and is not particularly limited, but may be, for example, 100:1 to 100:30 by weight, or 100:10 to 100:30 by weight.

[0054] The metal precursor may be a metal, a metal nitride, a metal carbide, a metal sulfide, a metal halide, or a combination thereof. The halide may be chloride or fluoride. In this case, the metal is a metal alloyable with lithium, as described above. The obtained mixture is dried. This drying process may be performed by a spray drying process. By performing the drying process by a spray drying process, a dried product having particles with a more uniform particle size and a spherical shape can be formed, and secondary particles in which primary particles are assembled can be formed. In addition, a metal or a metal oxide can be positioned on the surface of the silicon primary particles. In addition, the silicon primary particles and the metal precursor can be assembled together to form assembled secondary particles. In addition, some of the metal precursor present between the primary particles can be positioned on the surface of the secondary particles. When the dried product has particles with a uniform particle size and a spherical shape, the amorphous carbon layer formed subsequently can be formed more uniformly over the entire surface.

[0055] During the above process, some of the metallic material may be included in the amorphous carbon formed later.

[0056] An amorphous carbon layer is formed on the dried product. The amorphous carbon layer formation process can be performed by vapor-coating an amorphous carbon precursor gas, or by mixing the dried product with an amorphous carbon precursor and performing a carbonization process.

[0057] As the amorphous carbon precursor gas, methane (CH4) gas, ethylene (C2H4) gas, acetylene (C2H2) gas, propane (C3H8) gas, propylene (C3H6) gas, or a combination thereof can be used, and as the amorphous carbon precursor, petroleum coke, coal coke, petroleum pitch, coal pitch, green coke, or a combination thereof can be used.

[0058] Additionally, the carbonization process can be performed at a temperature of 600°C to 1,000°C. The dispersant can be removed during the carbonization process. The carbonization process can be performed in an N2 atmosphere, a helium atmosphere, or a combination thereof.

[0059] When the above carbonization process is performed within the above temperature range, the problem of excessive growth of Si particles can be suppressed, and the formation of SiC can be suppressed, while at the same time improving the electrical conductivity of amorphous carbon. Depending on the carbonization process, the amorphous carbon precursor can be converted into amorphous carbon, and can be formed to surround the surface of the secondary particles to form an amorphous carbon layer. In addition, some of the amorphous carbon can be inserted into the pores formed between the primary particles, and can be located on the surface of the primary particles to surround the surface of the primary particles. When the atmosphere of the carbonization process is included in the above conditions, amorphous carbon can be effectively formed while suppressing the oxidation of silicon and the formation of SiC, thereby reducing the resistance of the active material.

[0060] Next, the heat-treated product is subjected to a classification process. This classification process can be performed using a sieve so that the span value (defined by the above formula 1) of the negative active material becomes 1.1 to 1.6. For example, the classification process can be performed so as to obtain an active material having a particle size such that the span value obtained from the D10, D50, and D90 of the active material becomes 1.1 to 1.6.

[0061] Another embodiment provides a lithium secondary battery comprising a cathode, a cathode, and an electrolyte.

[0062] The above negative electrode may include a current collector and a negative electrode active material layer formed on the current collector and including the negative electrode active material according to one embodiment.

[0063] According to one embodiment, the negative electrode active material may be included as the first negative electrode active material, and crystalline carbon may be included as the second negative electrode active material. At this time, the mixing ratio of the first negative electrode active material and the second negative electrode active material may be included in a weight ratio of 80:20 to 90:10. More specifically, the negative electrode active material may include the first negative electrode active material and the second negative electrode active material in a weight ratio of 85:15 to 90:10.

[0064] In the above negative electrode active material layer, the content of the negative electrode active material may be 95 wt% to 98 wt% with respect to 100 wt% of the entire negative electrode active material layer.

[0065] The above negative electrode active material layer may include a binder and may further include a conductive material. The content of the binder may be 1 wt% to 5 wt% with respect to 100 wt% of the entire negative electrode active material layer. The content of the conductive material may be 1 wt% to 5 wt% with respect to 100 wt% of the entire negative electrode active material layer.

[0066] 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. The binder may be a non-aqueous binder, an aqueous binder, or a combination thereof.

[0067] The non-aqueous binder may include ethylene propylene copolymer, polyacrylonitrile, polystyrene, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0068] The above-mentioned aqueous binder may be styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber (ABR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluoroelastomer, polyethylene oxide, polyvinylpyrrolidone, polypropylene, polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, polyvinyl alcohol, or a combination thereof.

[0069] The negative electrode binder may include a cellulose-based compound, and the cellulose-based compound may be used together with the aqueous binder. The cellulose-based compound may be a mixture of one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or an alkali metal salt thereof. The alkali metal may be Na, K, or Li. The cellulose-based compound may function as a thickener and may also function as a binder. Since it may be used by appropriately adjusting it within the binder content range described above, there is no need for a special limitation, but for example, the content of the cellulose-based compound may be 0.1 to 3 parts by weight based on 100 parts by weight of the negative electrode active material.

[0070] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0071] The 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.

[0072] The above positive electrode includes a current collector and a positive electrode active material layer formed on the current collector.

[0073] As the positive electrode active material, a compound capable of reversible intercalation and deintercalation of lithium (lithiated intercalation compound) can be used. Specifically, at least one compound oxide of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof can be used. A more specific example is a compound represented by any one of the following chemical formulas. Li a A 1-b X b D 1 2(0.90 ≤a≤1.8, 0≤b≤0.5); Li a A 1-b X b O 2-c1 D 1 c1 (0.90≤a≤1.8, 0≤b≤0.5, 0≤c1≤0.05); Li a E 1-b X b O 2-c1 D 1 c1(0.90≤a≤1.8, 0≤b≤0.5, 0≤c1≤0.05); Li a HAVE BEEN 2-b X b O 4-c1 D 1 c1 (0.90≤a ≤1.8, 0≤b≤0.5, 0≤c1≤0.05); Li a Ni 1-b-c Co b X c D 1 α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); Li a Ni 1-b-c Co b X c O 2-α T α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Co b X c O 2-α T2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mr b X c D 1 α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α≤2); Li a Ni 1-b-c Mr b X c O 2-α T α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni 1-b-c Mr b X c O 2-α T2(0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0<α<2); Li a Ni b HAVE BEEN c G d O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li aNi b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1) Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); QO2; QS2; LiQS2; V2O5; LiV2O5; LiZO2; LiNiVO4; Li (3-f) J2(PO4)3(0≤f≤2); Li (3-f) Fe2(PO4)3(0≤f≤2); Li a FePO4(0.90≤a≤1.8)

[0074] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D 1 is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; T is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; Z is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof; L 1 is Mn, Al or a combination thereof.

[0075] Of course, a compound having a coating layer on the surface of the compound can be used, or a compound having the compound and a coating layer can be mixed and used. The coating layer can include at least one coating element compound among an oxide of the coating element, a hydroxide of the coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, and a hydroxycarbonate of the coating element. The compounds forming these coating layers can be amorphous or crystalline. The coating elements included in the coating layer can be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer forming process can use any coating method as long as it can coat the compound with these elements by a method (for example, spray coating, dipping, etc.) that does not adversely affect the properties of the positive electrode active material, and since this is well understood by those working in the relevant field, a detailed description thereof will be omitted.

[0076] In the above positive electrode, the content of the positive electrode active material may be 90 wt% to 98 wt% with respect to the total weight of the positive electrode active material layer.

[0077] In one embodiment, the positive electrode active material layer may further include a binder and a conductive material. In this case, the content of the binder and the conductive material may be 1 wt% to 5 wt%, respectively, based on the total weight of the positive electrode active material layer.

[0078] The above binder serves to adhere the positive electrode active material particles well to each other and also to adhere the positive electrode active material well to the current collector. Representative examples of the binder include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc.

[0079] The conductive material is used to provide conductivity to the electrode, and any material that does not cause chemical changes and is electronically conductive can be used in the battery. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal-based materials such as metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials containing mixtures thereof.

[0080] Al may be used as the above current collector, but is not limited thereto.

[0081] The above electrolyte comprises a non-aqueous organic solvent and a lithium salt.

[0082] The above non-aqueous organic solvent acts as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0083] As the above non-aqueous organic solvent, a carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent can be used.

[0084] Examples of the carbonate solvent that can be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and the like. Examples of the ester solvent that can be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methylpropionate, ethylpropionate, propyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, and the like. Examples of the ether solvent that can be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc., and examples of the ketone solvent that can be used include cyclohexanone, etc. In addition, examples of the alcohol solvent that can be used include ethyl alcohol, isopropyl alcohol, etc., and examples of the aprotic solvent that can be used include nitriles such as R-CN (where R is a hydrocarbon group having a linear, branched, or cyclic structure 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, 1,4-dioxolane, etc.

[0085] The above organic solvents can be used alone or in combination of one or more, and when using one or more in combination, the mixing ratio can be appropriately adjusted depending on the desired battery performance, which is widely understood by those working in the relevant field.

[0086] When the above non-aqueous organic solvents are used in combination, a mixed solvent of a cyclic carbonate and a chain carbonate, a mixed solvent of a cyclic carbonate and a propionate solvent, or a mixed solvent of a cyclic carbonate, a chain carbonate, and a propionate solvent can be used. As the propionate solvent, methyl propionate, ethyl propionate, propyl propionate, or a combination thereof can be used.

[0087] At this time, when using a mixture of cyclic carbonate and chain carbonate or cyclic carbonate and propionate solvent, it may be appropriate in terms of electrolyte performance to use them in a volume ratio of 1:1 to 1:9. In addition, when using a mixture of cyclic carbonate, chain carbonate, and propionate solvent, they may be mixed and used in a volume ratio of 1:1:1 to 3:3:4. Of course, the mixing ratio of the above solvents may be appropriately adjusted depending on the desired properties.

[0088] The above organic solvent may further include an aromatic hydrocarbon-based organic solvent in addition to the above carbonate-based solvent. In this case, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0089] As the above aromatic hydrocarbon organic solvent, an aromatic hydrocarbon compound of the following chemical formula 1 can be used.

[0090] [Chemical Formula 1]

[0091]

[0092] (In the above chemical formula 1, R1 to R6 are the same or different and are selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and combinations thereof.)

[0093] Specific examples of the above aromatic hydrocarbon organic solvents include 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, 2,3-difluorotoluene, 2,4-difluorotoluene, 2,5-difluorotoluene, 2,3,4-trifluorotoluene, 2,3,5-trifluorotoluene, chlorotoluene, 2,3-dichlorotoluene, 2,4-dichlorotoluene, 2,5-dichlorotoluene, 2,3,4-trichlorotoluene, 2,3,5-trichlorotoluene, iodotoluene, 2,3-diiodotoluene, 2,4-diiodotoluene, 2,5-diiodotoluene, 2,3,4-triiodotoluene, 2,3,5-triiodotoluene, xylene, and combinations thereof.

[0094] The above electrolyte may further include vinylethyl carbonate, vinylene carbonate or an ethylene carbonate compound of the following chemical formula 2 as a life-span improving additive to improve battery life.

[0095] [Chemical Formula 2]

[0096]

[0097] (In the above chemical formula 2, R7 and R8 are the same or different from each other and are selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO2) and a fluorinated alkyl group having 1 to 5 carbon atoms, and at least one of R7 and R8 is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO2) and a fluorinated alkyl group having 1 to 5 carbon atoms, provided that both R7 and R8 are not hydrogen.)

[0098] Representative examples of the above ethylene carbonate compounds include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, and fluoroethylene carbonate. When such life-prolonging additives are further used, the amount used can be appropriately adjusted.

[0099] The above lithium salt is a substance that is dissolved in an organic solvent and acts as a source of lithium ions in the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes. Representative examples of such lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide: LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1SO2) (wherein, x and y are natural numbers, for example, integers from 1 to 20), lithium difluoro(bisoxolato) phosphate, LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalato) borate: LiBOB) and lithium difluoro(oxalato)borate (LiDFOB) are included as a supporting electrolyte salt. 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.

[0100] Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators may include polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films comprising two or more layers thereof. Furthermore, mixed multilayer films 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.

[0101] Fig. 1 illustrates an exploded perspective view of a lithium secondary battery according to one embodiment of the present invention. While the lithium secondary battery according to one embodiment is described as having a square shape, the present invention is not limited thereto and can be applied to various types of batteries, such as cylindrical and pouch-shaped.

[0102] Referring to FIG. 1, a lithium secondary battery (100) according to one embodiment may include an electrode assembly (40) wound with a separator (30) interposed between a positive electrode (10) and a negative electrode (20), and a case (50) in which the electrode assembly (40) is housed. The positive electrode (10), the negative electrode (20), and the separator (30) may be impregnated with an electrolyte (not shown).

[0103] Hereinafter, examples and comparative examples of the present invention will be described. The following examples are merely exemplary of the present invention, and the present invention is not limited to the following examples.

[0104] (Example 1)

[0105] In an ethanol solvent, a mixing process was performed in which silicon particles with an average particle size of 8 μm, nano-sized Ag, and a stearic acid dispersant were ball milled using zirconia balls for 8 hours. In this process, silicon primary particles with an average particle size (D50) of 100 nm were formed. At this time, the mixing ratio of silicon particles and stearic acid dispersant was 100:25 by weight (silicon particles:stearic acid dispersant), and the amount of Ag used was such that the mixing ratio of silicon and Ag was 100:20 by weight.

[0106] The above mixture was spray-dried to produce secondary particles having an average particle diameter (D50) of 7 μm and containing pores.

[0107] The generated secondary particles and petroleum pitch were mixed in a weight ratio of 60:40, and the mixture was carbonized at a temperature of 1,000°C under N2 atmosphere conditions.

[0108] Next, a classification process was performed on the carbonized product so that the span value was obtained as shown in Table 1, thereby manufacturing a negative electrode active material.

[0109] The manufactured negative active material has a surface, a surface surrounded by Ag with a thickness of 20 nm (Ag coating layer thickness: 20 nm), a secondary particle with an average particle diameter (D50) of 7 μm assembled from silicon primary particles with an average particle diameter (D50) of 100 nm, and a soft carbon coating layer that coats the primary particles and the secondary particles and includes Ag.

[0110] At this time, with respect to the total weight of the negative active material, the content of Ag was 10 wt%, the content of silicon nanoparticles was 50 wt%, and the content of the soft carbon was 40 wt%.

[0111] A slurry for a negative electrode active material layer was prepared by mixing 97.5 wt% of the manufactured negative electrode active material, 1.5 wt% of carboxymethyl cellulose, and 1 wt% of styrene butadiene rubber in a water solvent.

[0112] The negative electrode was manufactured by coating, drying, and rolling the negative electrode active material layer slurry on a Cu foil current collector to form a negative electrode active material layer.

[0113] A half-cell was manufactured using the above-mentioned negative electrode, lithium metal counter electrode, and electrolyte by a conventional method. The electrolyte used was a mixed solvent (volume ratio 3:7) of ethylene carbonate and dimethyl carbonate in which 1M LiPF6 was dissolved.

[0114] In addition, a coin-type full cell was manufactured using the above-mentioned negative electrode, LiCoO2 positive electrode, and electrolyte in a conventional manner. The electrolyte used was a mixed solvent (volume ratio 3:7) of ethylene carbonate and dimethyl carbonate in which 1M LiPF6 was dissolved.

[0115] (Example 2)

[0116] A negative electrode, a half cell, and a coin-type on-cell were manufactured in the same manner as in Example 1, except that a classification process was performed so that the span value was 1.5 to manufacture the negative electrode active material.

[0117] (Example 3)

[0118] A negative electrode, a half cell, and a coin-type on-cell were manufactured in the same manner as in Example 1, except that Zn was used instead of Ag, and a negative electrode active material having a span value of 1.1 and a Zn content of 10 wt% with respect to the total weight of the negative electrode active material was manufactured.

[0119] (Example 4)

[0120] An anode, a half cell, and a coin-type on-cell were manufactured in the same manner as in Example 1, except that Ag was used in a weight ratio of 100:6 for silicon and Ag, a span value of 1.1, an Ag content of 3 wt% with respect to the total weight of the anode active material, and secondary particles having an average particle diameter (D50) of 7 μm were assembled by surrounding Ag with a thickness of 5 nm (Ag coating layer thickness: 5 nm) with Ag, and the primary particles and the secondary particles were coated, and a anode active material having a soft carbon coating layer including Ag was manufactured. In the manufactured anode active material, the content of Ag was 3 wt%, the content of the silicon nanoparticles was 57 wt%, and the content of the soft carbon was 40 wt%.

[0121] (Comparative Example 1)

[0122] A negative electrode active material having a span value of 1.1 was manufactured in the same manner as in Example 1 except that Ag was not used, and a negative electrode, a half-cell, and a coin-type on-cell were manufactured using this negative electrode active material in the same manner as in Example 1.

[0123] (Comparative Example 2)

[0124] In an ethanol solvent, silicon particles with an average particle size of 8 μm and a stearic acid dispersant were mixed, and the mixture was ball milled using zirconia balls for 8 hours. Through this process, Si primary particles with an average particle size (D50) of 100 nm were produced. At this time, the mixing ratio of silicon particles and stearic acid dispersant was 100:25 by weight.

[0125] Nano-sized Ag was added to the obtained product so that the weight ratio of silicon and Ag was 100:20, and then spray-dried to produce secondary particles having an average particle diameter (D50) of 7 μm and containing pores.

[0126] The generated secondary particles were subjected to a primary heat treatment at 350°C in an air atmosphere for 1 hour.

[0127] The generated secondary particles and petroleum pitch were mixed in a weight ratio of 60:40, and the mixture was carbonized at a temperature of 1,000°C under N2 atmosphere conditions to manufacture a negative electrode active material.

[0128] The manufactured negative active material has secondary particles having an average particle diameter (D50) of 7 μm, which are assembled from silicon primary particles having an average particle diameter (D50) of 100 nm, Ag positioned in point contact with the surface of the primary particles, and a soft carbon coating layer that coats the primary particles and the secondary particles and includes Ag.

[0129] At this time, with respect to the total weight of the negative active material, the content of Ag was 10 wt%, the content of silicon nanoparticles was 50 wt%, and the content of the soft carbon was 40 wt%.

[0130] A negative electrode, a half cell, and a coin-type on-cell were manufactured in the same manner as in Example 1, except that the negative electrode active material was used.

[0131] (Comparative Example 3)

[0132] In an ethanol solvent, silicon particles with an average particle size of 8 μm and a stearic acid dispersant were mixed, and the mixture was ball milled using zirconia balls for 8 hours. Through this process, Si primary particles with an average particle size (D50) of 100 nm were produced. At this time, the mixing ratio of silicon particles and stearic acid dispersant was 100:25 by weight.

[0133] The obtained product was spray-dried to produce secondary particles having an average particle diameter (D50) of 7 μm and containing pores.

[0134] The generated secondary particles and petroleum pitch were mixed in a weight ratio of 60:40, and the mixture was subjected to a carbonization process at a temperature of 1,000°C in an N2 atmosphere to produce a Si-carbon composite having secondary particles with an average particle diameter (D50) of 7 μm, in which silicon primary particles with an average particle diameter (D50) of 100 nm were assembled, and a soft carbon coating layer coating the primary particles and the secondary particles.

[0135] The above Si-carbon composite and Ag were mixed in a weight ratio of 100:10 to manufacture a negative electrode active material.

[0136] Using this negative active material, a negative electrode, a half cell, and a coin-type on-cell were manufactured in the same manner as in Example 1.

[0137] (Comparative Example 4)

[0138] Silicon particles with an average particle size of 8 ㎛ and a stearic acid dispersant were pulverized by ball milling using zirconia balls for 8 hours to form silicon primary particles with an average particle size (D50) of 100 nm.

[0139] The above silicon primary particles and Ag2Si were mixed and spray dried to produce secondary particles having an average particle diameter (D50) of 7 μm and containing pores.

[0140] The content of Ag2Si was used so that the Ag content was 10 wt% with respect to 100 wt% of the total final negative electrode active material.

[0141] The generated secondary particles and petroleum pitch were mixed in a weight ratio of 60:40, and the mixture was subjected to a carbonization process at a temperature of 1,000°C under N2 atmosphere conditions to manufacture a negative electrode active material.

[0142] The manufactured negative active material has silicon primary particles having an average particle diameter (D50) of 100 nm, secondary particles having an average particle diameter (D50) of 7 μm in which Ag2Si is assembled with each other, and a soft carbon coating layer coating the primary particles and the secondary particles.

[0143] Using this negative active material, a negative electrode, a half cell, and a coin-type on-cell were manufactured in the same manner as in Example 1.

[0144] Experimental Example 1: Span Value Evaluation

[0145] The D10, D50, and D90 of the negative active materials of Examples 1 to 4 and Comparative Examples 1 to 4 were measured using a particle analyzer (trade name: LS 13 320, manufacturer: Beckman Coulter), and the results are shown in Table 1 below. From these values, the span value of Equation 1 below was obtained, and the results are shown in Table 1 below.

[0146] Experimental Example 2: XRD Characterization of Negative Active Materials

[0147] For the negative active materials of Examples 1 to 4 and Comparative Examples 1 to 4, X-ray diffraction analysis (XRD) was performed using CuKα rays, and the peak intensity (I) of the Si(111) plane was measured. Si(111) ) Peak intensity (I) of Ag(111) surface Ag(111) ) peak intensity ratio (I Ag(111) / I Si(111)) was obtained. At this time, the peak intensity ratio was obtained as the height ratio of the peak. Among the results, the results of Examples 1 to 4 and Comparative Examples 2 and 4 are shown in Table 1 below.

[0148] Experimental Example 3: Charge-Discharge Efficiency Evaluation

[0149] The half-cells manufactured according to Examples 1 to 4 and Comparative Examples 1 to 4 were charged and discharged once at 0.1 C, and the ratio of the discharge capacity to the measured charge capacity was obtained. The results are shown in Table 1 below in terms of efficiency.

[0150] Experimental Example 4: Rate Characteristic Evaluation

[0151] The half-cells manufactured according to Examples 1 to 4 and Comparative Examples 1 to 4 were charged and discharged once at 0.2C and once at 2C. The ratio of the 2C charge capacity to the 0.2C charge capacity was obtained, and the results are shown in Table 1 below as a charge rate.

[0152] Experimental Example 5: Accelerated Life Evaluation

[0153] Coin-type on-cell batteries manufactured according to Examples 1 to 3 and Comparative Examples 1 to 5 were subjected to 500 cycles of 1C charging and 1C discharging. The ratio of the discharge capacity at 500 cycles to the discharge capacity at 1 cycle was obtained. The results are shown in Table 1.

[0154] D90(㎛)D50(㎛)D10(㎛)Span peak intensity ratio (IAg(111) / Si(111))Efficiency(%)Charge rate(%)Accelerated life(%)Example 113.78.24.71.10.389145.591.5Example 216.98.53.91.50.3890.443.391.3Example 313.78.24.71.10.4090.643.591.2Example 413.78.24.71.10.0790.642.591.0Comparative example 113.78.24.71.1-90.64290.5Comparative example 213.78.24.71.10.3889.842.690.7Comparative Example 313.78.24.71.1-84.142.36.1Comparative Example 413.78.24.71.10.3582.537.284.4

[0155] As shown in Table 1 above, the batteries containing the negative active materials of Examples 1 to 4 exhibited high efficiency and charge rates, and excellent accelerated lifespans. On the other hand, Comparative Example 1, which did not contain Ag, exhibited reduced charge rates and accelerated lifespans.

[0156] In addition, in Comparative Example 2, where Ag was positioned in the form of point contact on the surface of the silicon primary particles, low charge / discharge efficiency was observed. In Comparative Example 3, which used a negative active material simply mixed with a Si-carbon composite and Ag, very low charge / discharge efficiency and a low charge rate were observed, and it can be seen that the accelerated life was significantly reduced to 6.1%.

[0157] In addition, in the case of Comparative Example 4, which used a negative active material mixed with a Si-carbon composite and a Si-Ag compound, very deteriorated charge / discharge efficiency, charge rate, and accelerated life were exhibited.

[0158] Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the patent claims, the detailed description of the invention, and the attached drawings, and it is obvious that this also falls within the scope of the present invention.

Claims

1. The span value of Equation 1 below is 1.1 to 1.6, Secondary particles assembled from primary particles comprising silicon nanoparticles and a metal coating layer comprising a metal material surrounding the surface of the silicon nanoparticles; and An amorphous carbon coating layer surrounding the surfaces of the primary particles and the secondary particles A negative active material comprising: [Formula 1] Span = (D90-D10) / D50 (In the above formula 1, D10 means the particle diameter of a particle having a cumulative volume of 10% by volume in the particle size distribution, D50 means the particle diameter of a particle having a cumulative volume of 50% by volume in the particle size distribution, and D90 means the particle diameter of a particle having a cumulative volume of 90% by volume in the particle size distribution) 2. In paragraph 1, The above metal-based material is a negative electrode active material that is a metal or a metal compound.

3. In paragraph 2, The above metal compound is a negative electrode active material that is a metal oxide, a metal nitride or a combination thereof.

4. In paragraph 1, In the above metal-based material, the metal is a negative electrode active material that is a metal alloyable with lithium.

5. In paragraph 4, The above metal is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a group 15 element, a group 16 element, a transition metal, a rare earth element, or a combination thereof, which is a negative electrode active material.

6. In paragraph 5, The above metal is Ag, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a negative electrode active material having a combination thereof.

7. In paragraph 6, The above metal is Ag, which is a negative electrode active material.

8. In paragraph 1, A negative electrode active material in which the content of the above metal material is 0.01 wt% to 20 wt% based on 100 wt% of the total negative electrode active material.

9. In paragraph 1, A negative electrode active material in which the content of the metal material is 0.05 wt% to 15 wt% based on 100 wt% of the total negative electrode active material.

10. In paragraph 1, A negative electrode active material wherein the amorphous carbon coating layer further comprises a metallic material.

11. In paragraph 7, The above negative active material has a diffraction peak intensity (I) due to Si(111) detected at 2θ=27.5° to 29.5° when measuring X-ray diffraction intensity. Si(111) ) diffraction peak intensity (I) by Ag(111) detected at 2θ=37.5° to 40.0° Ag111) ) peak intensity ratio (I Ag(111) / I Si(111) ) is a negative active material having a value of 0.05 to 0.

5.

12. In paragraph 1, A negative active material in which the metal coating layer is continuously positioned on the surface of the silicon nanoparticles.

13. In paragraph 1, A negative electrode active material having a thickness of the metal coating layer of 1 nm to 30 nm.

14. In paragraph 1, The above silicon nanoparticles have a particle size of 1 nm to 1,000 nm, and are a negative active material.

15. In paragraph 1, A negative electrode active material having a thickness of the amorphous carbon coating layer of 1 nm to 2 μm.

16. In paragraph 1, A negative electrode active material having a content of the above silicon nanoparticles of 44 wt% to 65 wt% based on 100 wt% of the total negative electrode active material.

17. In paragraph 1, A negative electrode active material having a content of the amorphous carbon coating layer of 34 wt% to 46 wt% based on 100 wt% of the total negative electrode active material.

18. A negative electrode comprising the negative active material of any one of claims 1 to 17; Bipolar; and Containing electrolytes Lithium secondary battery.

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