Negative electrode active material, method for manufacturing same, and lithium secondary battery comprising same

Abstract

The present invention relates to a negative electrode active material comprising at least one metal-containing particle, in which the longest straight line length (r2) connecting the end of the metal-containing particle farthest from the center point of the negative electrode active material to the center point of the negative electrode active material, and the longest straight line length (r3) connecting the end of the metal-containing particle farthest from the center point of the negative electrode active material to the end of the metal-containing particle farthest from the center point of the negative electrode active material to the end of the metal-containing particle farthest from the center point of the negative electrode active material. The ratio (r2 / r1) of the radius (r1) of the negative electrode active material to the radius (r1) of the negative electrode active material is 0.8 or more and 0.95 or less.

Description

Technical Field

[0001] The present invention relates to a negative electrode active material, a method for manufacturing the same, and a lithium secondary battery including the negative electrode active material, and more particularly, to a negative electrode active material, a method for manufacturing the same, and a lithium secondary battery including the negative electrode active material, which improve performance by adjusting the ratio (r2 / r1) of the longest straight-line length (r2) between the end farthest from the center point of the negative electrode active material among the metal-containing particles that are farthest from the center point of the negative electrode active material to the center point of the negative electrode active material to the radius (r1) of the negative electrode active material and / or by adjusting the porosity. Background Art

[0002] Lithium Ion Batteries (LIBs) have a high energy density, are easy to design, and are used as the main power supply for mobile electronic devices. In the future, their application scope will be further expanded to electric vehicles or power storage devices for renewable energy.

[0003] In order to be applicable to new application fields, there is an ongoing demand for research on LIB materials with characteristics such as higher energy density and longer lifespan.

[0004] In particular, for negative electrode materials, various substances such as carbon, silicon, tin, and germanium have been studied.

[0005] Among them, compared with the currently commonly used graphite negative electrode material, silicon-based negative electrode materials have attracted much attention due to their very high energy density.

[0006] However, silicon-based negative electrode materials have fatal disadvantages. For example, side reactions between the silicon surface and the electrolyte form an unstable SEI film, resulting in a decline in electrochemical characteristics or the pulverization of electrode materials due to internal stress caused by the sharp volume expansion during charge and discharge.

[0007] To solve this problem, many studies have been conducted on improving the surface reversibility of silicon-based negative electrode materials through various surface treatments, especially the method of using carbon materials for surface coating or compositeization has been widely studied.

[0008] On the one hand, various surface treatments using carbon materials require complex and costly processes. Although the partial lifespan characteristics of silicon-based negative electrode materials have been improved through surface treatment using carbon materials, due to the reduction in the ionic conductivity of silicon-based negative electrode materials, there are limitations in improving the output characteristics of fast-charging and discharging lithium ion batteries (LIBs) whose demand has recently increased.

[0009] Therefore, there is an urgent need to develop technologies for high-capacity silicon-based negative electrode active materials in order to further improve battery characteristics while suppressing the volume expansion of silicon-based negative electrode materials.

[0010] [Prior Art Documents]

[0011] [Patent Documents]

[0012] (Patent Document 1) Korean Published Patent No. 10-2016-0040125. Summary of the Invention

[0013] Technical Problem to be Solved by the Invention

[0014] In view of this, an object of the present invention is to provide a negative electrode active material having a high capacity and a high energy density, and being used for a secondary battery with high output and long life.

[0015] In addition, an object thereof is to provide a manufacturing method capable of manufacturing the negative electrode active material with high efficiency and low cost.

[0016] Furthermore, an object of the present invention is to provide an electrode and a lithium secondary battery including the negative electrode active material.

[0017] However, the technical problems to be solved herein are not limited to the above-mentioned problems, and those skilled in the art can clearly understand other unmentioned problems from the following description.

[0018] One aspect of the present invention provides a negative electrode active material including at least one metal-containing particle, wherein

[0019] the ratio (r2 / r1) of the longest straight-line length (r2) connecting the end of the metal-containing particle farthest from the center point of the negative electrode active material among the metal-containing particles farthest from the center point of the negative electrode active material to the center point of the negative electrode active material to the radius (r1) of the negative electrode active material is 0.8 or more and 0.95 or less.

[0020] Another aspect of the present invention provides an electrode including:

[0021] the negative electrode active material.

[0022] Still another aspect of the present invention provides a secondary battery including:

[0023] a negative electrode containing the negative electrode active material;

[0024] a positive electrode opposite to the negative electrode; and

[0025] an electrolyte disposed between the negative electrode and the positive electrode.

[0026] Advantages of the Invention

[0027] The negative electrode active material according to the present invention not only has a high capacity and a high energy density, but also can provide a secondary battery with high output and long life.

[0028] In addition, it has the effect of being able to manufacture the negative electrode active material with high efficiency and low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram showing the radius (r1) of the negative electrode active material according to an embodiment of the present invention and the longest straight-line length (r2) between the center point of the negative electrode active material and the end of the metal-containing particle that is farthest from the center point of the negative electrode active material and is connected to the point farthest from the center point of the negative electrode active material.

[0030] Figure 2 It is a graph showing the battery capacity / efficiency characteristics of the negative electrode active material manufactured using Examples 1 to 3 and Comparative Examples 1 to 6.

[0031] Figure 3 It is a graph showing the battery life characteristics of the negative electrode active material manufactured using Examples 1 to 3 and Comparative Examples 1 to 6.

[0032] Figure 4 It is a graph showing the battery output characteristics of the negative electrode active material manufactured using Examples 1 to 3 and Comparative Examples 1 to 6. DETAILED DESCRIPTION

[0033] The terms or words used in this specification and the claims of the invention should not be construed as limited to their general meanings or dictionary meanings. Instead, based on the principle that the inventor can appropriately define concepts such as terms in order to best explain his invention, they should be construed as meanings and concepts that conform to the technical spirit of the present invention.

[0034] Therefore, it should be understood that the structures of the embodiments described in this specification are only one of the preferred embodiments of the present invention and do not represent all the technical spirits of the present invention. Therefore, various equivalent substitutions and modifications can be made for this application.

[0035] Unless the context clearly indicates otherwise, the singular forms used in this specification include the plural forms. It should be understood that in this text, terms such as "comprising", "having" or "including" are intended to specify the presence of implemented features, numbers, steps, structural elements or combinations thereof, and do not exclude the presence or addition of one or more other features, numbers, steps, structural elements or combinations thereof.

[0036] In this specification, the "to" and "~" in the numerical range "a to b" and "a~b" are defined as ≥a and ≤b.

[0037] Regarding the negative electrode active material according to one aspect of the present invention, the ratio (r2 / r1) of the longest straight-line length (r2) connecting the end of the metal-containing particle that is farthest from the center point of the negative electrode active material to the center point of the negative electrode active material, to the radius (r1) of the negative electrode active material can be 0.8 or more and 0.95 or less.

[0038] The r1 and r2 of the negative electrode active material are as Figure 1 shown. For example, when the metal-containing ions of the negative electrode active material are in the form of flakes as Figure 1 shown, r2 is the distance (the longest straight-line distance) between the center point of the negative electrode active material and the end of the metal-containing ions that is farthest from the center point of the negative electrode active material among the two ends of the metal-containing ions.

[0039] When the r2 / r1 of the negative electrode active material exceeds or is lower than the scope of the present application, the life characteristics and output characteristics of the secondary battery may deteriorate.

[0040] This is because if r2 / r1 exceeds the scope of the present application, the carbon-based material may be damaged due to the volume expansion of the metal-containing ions (for example, silicon particles), and when r2 / r1 is lower than the scope of the present application, the movement of lithium ions to the metal-containing ions (for example, silicon particles) will be interfered with.

[0041] In addition, the negative electrode active material includes a core and a shell surrounding the core, the metal-containing particle includes any one or more selected from the group consisting of Mg, Al, Si, Ca, Fe, Mg, Mn, Co, Ni, Zn, and Ge, and the metal-containing particle may be included in the core.

[0042] In one implementation example, the metal-containing particle may be a silicon (Si)-containing particle, and the silicon (Si)-containing particle may include any one or more selected from the group consisting of silicon particles, silicon oxide particles, silicon carbide particles, and silicon alloy particles.

[0043] In addition, the average particle diameter (D 50 ) of the silicon (Si)-containing particle is 80 nm or more and 200 nm or less, and can be represented by the following Chemical Formula 1.

[0044] [Chemical Formula 1]

[0045] SiO x (0 ≤ x ≤ 0.5)

[0046] In the Chemical Formula 1, when x exceeds 0.5, adverse effects may occur on the battery capacity and efficiency. That is, lithium ions react with oxygen to generate Li2O, Li-silicate (Li xSi y O z ) and other irreversible products. Therefore, the lithium ions reacting with the negative electrode material are trapped inside the negative electrode and cannot return to the electrolyte or the positive electrode material, resulting in the inability to express the capacity and a reduction in efficiency.

[0047] In addition, for example, the silicon carbide may be SiC, and the silicon alloy may be, for example, a Si-Z alloy (where Z is one or more elements selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and Si is not an element selected from the above combinations).

[0048] The average particle size of the silicon-containing particles is measured using an organic solution in which the silicon-containing particles are dispersed and a particle size analyzer (Mastersizer 3000, Malvern Panalytical).

[0049] When the average particle size of the silicon-containing particles exceeds 200 nm, a high battery capacity can be obtained, but the battery life may be very short; when the average particle size of the silicon-containing particles is less than 80 nm, the battery capacity and efficiency will decrease, and the manufacturing cost will increase.

[0050] In one implementation example, the negative electrode active material may contain 30% by weight or more and 80% by weight or less of a carbon-based material.

[0051] For example, the carbon content of the negative electrode active material is 50% or more and 55% or less, and the oxygen content may be 5.5% or more and 6.5% or less.

[0052] The carbon-based material may be any one or more of amorphous carbon and crystalline carbon.

[0053] In one implementation example, the amorphous carbon may be selected from coal tar pitch, meso phase pitch, petroleum pitch, tar, coal-based oil, petroleum-based heavy oil, organic synthetic pitch, sucrose, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, polyacrylonitrile resin, polyamide resin, phenolic resin, furan resin, cellulose resin, styrene resin, epoxy resin, or any one or more selected from the group consisting of polyvinyl chloride-based resins, block copolymers, polyols, and polyimide resins.

[0054] In addition, the crystalline carbon may be any one or more selected from the group consisting of natural graphite, artificial graphite, expanded graphite, graphene, carbon black, and fullerenes.

[0055] Natural graphite is graphite occurring in nature, which includes flake graphite, high-crystalline graphite, microcrystalline or cryptocrystalline; amorphous graphite, etc. Artificial graphite is synthetic graphite, which is formed by heating amorphous carbon at high temperature, and includes primary or electrographite, secondary graphite, graphite fiber, etc.

[0056] Expanded graphite is formed by heating after inserting chemical substances such as acids or alkalis between the layers of graphite and expanding the vertical layers of the molecular structure. Graphene contains a single layer or multiple single layers of graphite.

[0057] Carbon black is a crystalline substance with less regularity than graphite. Carbon black can be turned into graphite by heating for a long time at about 3,000 °C. Fullerene is a carbon mixture containing at least 3% by weight of a polyhedral bundle compound fullerene composed of 60 or more carbon atoms. The first carbon-based material can use one of these crystalline carbons alone or use two or more in combination. For example, natural graphite or artificial graphite can be used. The crystalline carbon can have a spherical, plate-like, fibrous, tubular or powdery shape.

[0058] Preferably, pitch can be used as the amorphous carbon. The pitch can be pitch with a softening point of 100 to 250 °C, especially pitch with a QI (Quinolone Insoluble) component of 5% by weight or less, and more preferably petroleum-based or coal-based pitch with 1% by weight or less.

[0059] On the one hand, natural graphite can preferably be used as the crystalline carbon. The purity of the graphite can be a grade with a fixed carbon content of 99% by weight or more, and more preferably, a high-purity grade of 99.95% by weight or more can be used.

[0060] In addition, flake graphite is suitable for improving conductivity by contacting with metal ions.

[0061] On the one hand, the weight ratio of the amorphous carbon to the crystalline carbon (weight of amorphous carbon / weight of crystalline carbon) of the negative electrode active material can be 0.6 or more and 1 or less.

[0062] For example, it can be 0.7 or more and 0.99 or less.

[0063] When the weight ratio of amorphous carbon to crystalline carbon (weight of amorphous carbon / weight of crystalline carbon) of the negative electrode active material exceeds or is lower than the scope of the present application, the value of r2 / r1 of the negative electrode active material will exceed the scope of the present application, and the characteristics of the secondary battery may be degraded.

[0064] In one implementation example, the core and the battery may include one or more selected from the group consisting of amorphous carbon and crystalline carbon.

[0065] For example, the core may include both the amorphous carbon and the crystalline carbon, and the housing may include both the amorphous carbon and the crystalline carbon.

[0066] The additional carbon components of the core and the housing can play a role in alleviating the volume expansion of metal ions during charge and discharge.

[0067] In one implementation example, the average particle size (D 50 ) of the negative electrode active material may be 3 μm or more and 20 μm or less.

[0068] On the one hand, the negative electrode active material may include pores. In particular, pores may be mainly formed on the core of the negative electrode active material. The pores can reduce the initial irreversible capacity of the secondary battery and contribute to alleviating the volume expansion of metal ions.

[0069] In one implementation example, the porosity of the negative electrode active material may be 10% or less. When the porosity of the negative electrode active material exceeds the scope of the present application, the life and output characteristics of the secondary battery may be degraded.

[0070] This is because when the porosity exceeds 10%, the electrolyte solvent will penetrate into the pore part due to the destruction of the carbon-based material, becoming a factor that damages metal ions (for example, silicon particles), thereby degrading its life characteristics. In addition, due to the reduction of the electron transfer path density, the smooth electrochemical reaction may be disturbed, thereby degrading the output characteristics.

[0071] According to another aspect of the present application, a method for manufacturing a negative electrode active material may include the following steps: spray-drying a solution containing metal ions to prepare a precursor powder; mixing the precursor powder, amorphous carbon, and crystalline carbon and performing compounding; and performing heat treatment.

[0072] The metal ions provided in the preparation of the precursor powder may be pulverized to a required average particle size through a pulverization process.

[0073] The metal may be one or more selected from Si, Al, Ti, Mn, Ni, Cu, V, Zr, Mn, Co, Fe, and Nb.

[0074] In one implementation example, the compounding can be performed by a physical method.

[0075] The physical method may include any one or more selected from the group consisting of high-energy processes such as grinding, stirring, mixing, and compression.

[0076] For example, the compounding can be performed by ball milling. In particular, a planetary ball mill can effectively mix and crush a mixture by a mixing method of rotating and revolving in a non-contact manner with the composition.

[0077] The balls that can be used for ball milling can be, for example, zirconia balls, etc. The type of the balls is not limited. The size of the balls can be, for example, about 0.3 to 10 mm, but is not limited thereto.

[0078] On the one hand, the compounding can be performed at a reaction time of 1 minute to 24 hours, a reaction temperature of 40 to 250 °C, and a reaction atmosphere of air or an inert atmosphere.

[0079] In one implementation example, the heat treatment may include a first heat treatment and a second heat treatment.

[0080] The heat treatment temperature of the first heat treatment is 100 to 500 °C, the heat treatment time can be 10 hours to 48 hours, and it can be performed in a vacuum atmosphere.

[0081] The heat treatment temperature of the second heat treatment is 600 to 1,000 °C, the heat treatment time can be 1 hour to 48 hours, and it can be performed in an atmosphere of an inert gas (for example, nitrogen, argon, etc.).

[0082] The weight ratio (weight of amorphous carbon / weight of crystalline carbon) of the amorphous carbon and the crystalline carbon mixed in the compounding can be 0.6 or more and 1 or less.

[0083] On the other hand, an electrode in this article may include the negative electrode active material. A lithium secondary battery uses the electrode containing the negative electrode active material as the negative electrode, and may include a positive electrode opposite to the negative electrode; and an electrolyte disposed between the negative electrode and the positive electrode.

[0084] The negative electrode contains the negative electrode active material. For example, after mixing the negative electrode active material, a binder, and an optional conductive agent in a solvent to prepare a negative electrode active material composition, it can be formed into a certain shape or coated on a current collector such as a copper foil to be manufactured.

[0085] In addition to the above-mentioned negative electrode active material, the negative electrode may further contain a negative electrode active material material that is commonly used as a negative electrode active material for lithium batteries in this technical field. The commonly used negative electrode active material materials may include any one or more selected from the group consisting of, for example, lithium metal, lithium alloy, transition metal oxide, non-transition metal oxide, and carbon-based material.

[0086] For example, the metal that can be alloyed with the lithium may be Si, Sn, Al, Ge, Pb, Bi, SbSi-Y alloy (where Y is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, transition metal, rare earth element, or a combination thereof, and Si is not the above elements), Sn-Y alloy (where Y is an alkali metal, alkaline earth metal, Group 13 and Group 16 elements, transition metal, rare earth element, or a combination thereof, and Sn is not the above elements), etc. The element Y may be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0087] For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, etc.

[0088] For example, the non-transition metal oxide may be SnO2, SiO x (0 < x ≤ 2), etc. The carbon-based material may be crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be graphite such as amorphous, plate-like, flaky, spherical, or fibrous natural graphite or artificial graphite, and the amorphous carbon may be soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0089] When the negative electrode active material and the carbon-based material are used together, the oxidation reaction of the silicon-based active material can be inhibited, and an SEI film can be effectively formed, thereby forming a stable film, improving the conductivity, and further improving the charge and discharge characteristics of lithium.

[0090] Conventional negative electrode active material materials can be mixed and fused with the above-mentioned negative electrode active material, or coated on the surface of the above-mentioned negative electrode active material, or used in any other combined form.

[0091] The binder used in the negative electrode active material composition is a component that helps bind the negative electrode active material, conductive agent, etc. and the current collector. Based on 100 parts by weight of the negative electrode active material, 1 to 50 parts by weight is added. For example, based on 100 parts by weight of the negative electrode active material, the binder can be added in the range of 1 to 30 parts by weight, 1 to 20 parts by weight, or 1 to 15 parts by weight.

[0092] Such binders include, for example, polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile-butadiene-styrene, phenolic resin, epoxy resin, polyethylene terephthalate, polytetrafluoroethylene, polyphenylene sulfide, polyamideimide, polyetherimide, polyvinyl sulfone, polyamide, polyacetal, polyphenylene ether, polybutylene terephthalate, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluororubber, and various copolymers, etc.

[0093] The negative electrode may also selectively contain a conductive agent to provide a conductive path for the negative electrode active material and further improve conductivity.

[0094] Any substance commonly used in lithium batteries can be used as the conductive agent, such as carbon-based substances like carbon black, acetylene black, Ketjen black, carbon fiber (e.g., vapor-grown carbon fiber), etc.; metal-based materials such as metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives, or conductive materials containing a mixture thereof. The content of the conductive material can be appropriately adjusted as needed. For example, the negative electrode active material and the conductive agent can be added in a weight ratio range of 99:1 to 90:10.

[0095] Solvents such as N-methylpyrrolidone (NMP), acetone, water, etc. can be used. Based on 100 parts by weight of the negative electrode active material, 1 to 10 parts by weight of the solvent is used. When the content of the solvent is within the above range, it is convenient to form the active material layer.

[0096] In addition, the current collector is usually made to have a thickness of 3 to 500 μm. As the current collector, as long as it has conductivity and does not cause chemical changes in the battery, there are no particular restrictions. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, materials with surface treatments such as carbon, nickel, titanium, silver, etc. on the surface of copper or stainless steel, aluminum-cadmium alloy, etc. can be used.

[0097] In addition, fine irregularities can be formed on the surface to enhance the binding force of the negative electrode active material, and it can be used in various forms such as thin films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0098] The manufactured negative electrode active material composition is directly coated on the current collector to manufacture a negative electrode plate, or a negative electrode active material thin film cast on a separate support and peeled off from the support is pressed onto a copper foil current collector to obtain a negative electrode plate. The negative electrode is not limited to the form of the distance, and can also be in a form other than the form.

[0099] The negative electrode active material composition can be not only used for manufacturing the electrodes of lithium secondary batteries, but also printed on a flexible electrode substrate and used for manufacturing printable batteries.

[0100] In addition, to manufacture a positive electrode, a positive electrode active material composition mixed with a positive electrode active material, a conductive agent, a binder, and a solvent is prepared.

[0101] As the positive electrode active material, any lithium-containing metal oxide commonly used in the technical field can be used.

[0102] For example, Li a A 1-b B b D2 (in the formula, 0.90 ≤ a ≤ 1.8 and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (in the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (in the formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (in the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α F α (in the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li aNi 1-b-c Co b B c O 2-α F α (In the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c O 2-α F α (In the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2 (In the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2 (In the formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (In the formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (In the formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (In the formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G bO4 (in the formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3 (0 ≤ f ≤ 2); Li (3-f) Any compound represented by Fe2(PO4)3 (0 ≤ f ≤ 2) or the chemical formula of LiFePO4.

[0103] In the chemical formula, A is Ni, Co, Mn or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; F 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; I is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0104] Of course, substances having a coating layer on the surface of the compound can also be used, or the compound and the compound having a coating layer can be used in combination. The coating layer can include an oxide of the coating element, a hydroxide, a hydroxyoxide of the coating element, a carbonate-oxide of the coating element, or a coating element compound of a hydroxycarbonate of the coating element. The compounds constituting 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 a mixture thereof. Those skilled in the art can understand that in the coating layer formation process, as long as the method of coating these elements on the compound does not have an adverse effect on the physical properties of the positive electrode active material (for example, spray coating, impregnation method, etc.), any coating method can be used. Therefore, the detailed description of this process will be omitted.

[0105] For example, LiNiO2, LiCoO2, LiMn x O 2x (x = 1, 2), LiNi 1-x Mn x O2 (0 < x < 1), LiNi 1-x- y Co x Mn y O2 (0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.5), LiFeO2, V2O5, TiS, MoS, etc.

[0106] In the positive electrode active material composition, the conductive agent, binder, and solvent can be the same substances as those in the above-mentioned negative electrode active material composition. In some cases, a plasticizer can be further added to the positive electrode active material composition and the negative electrode active material composition to form pores inside the electrode plate. The contents of the positive electrode active material, conductive agent, binder, and solvent are at levels commonly used in lithium batteries.

[0107] The thickness of the positive electrode current collector is 3 to 500 μm. As long as it has high electrical conductivity and does not cause chemical changes in the battery, it is not particularly limited. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or materials with surface treatments such as carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel can be used. The current collector can form fine irregularities on its surface to improve the adhesion of the positive electrode active material, and can be in various forms such as thin films, sheets, foils, meshes, porous bodies, foams, non-woven fabrics, etc.

[0108] The prepared positive electrode active material composition can be directly coated and dried on the positive electrode current collector to manufacture the positive electrode plate. Alternatively, the positive electrode active material composition can be cast on a separate support, and then the film obtained by peeling the support is laminated on the positive electrode current collector to manufacture the positive electrode plate.

[0109] The positive electrode and the negative electrode can be separated by a separator, and the separator can be any separator commonly used in lithium batteries. In particular, for the ion movement of the electrolyte, those with low resistance and excellent electrolyte moisture content capacity are suitable. For example, materials such as glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE) and compositions selected from them can also be in the form of non-woven fabrics or woven fabrics. The separator uses a separator with a pore diameter of 0.01 to 10 μm and a thickness usually of 5 to 300 μm.

[0110] The non-aqueous electrolyte containing a lithium salt consists of a non-aqueous electrolyte and lithium. The non-aqueous electrolyte uses non-aqueous electrolytes, solid electrolytes, inorganic solid electrolytes, etc.

[0111] For the non-aqueous electrolyte, for example, aprotic organic solvents such as N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate can be used.

[0112] For the organic solid electrolyte, for example, polyethylene derivatives, poly(ethylene oxide) derivatives, poly(propylene oxide) derivatives, phosphate esters, poly(agitation lysine), polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymers containing ionic dissociative groups, etc. can be used.

[0113] For the inorganic solid electrolyte, for example, nitrides, halides, sulfates of Li such as Li3N, LiI, Li5NI2, Li3N - LiI - LiOH, LiSiO4, LiSiO4 - LiI - LiOH, Li2SiS3, Li4SiO4, Li4SiO4 - LiI - LiOH, Li3PO4 - Li2S - SiS2, etc. can be used.

[0114] Any material that is commonly used in lithium batteries can be used as the lithium salt, and the lithium salt is a material that is easily soluble in non-aqueous electrolytes. For example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB 10 Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborate, lithium salts of lower aliphatic carboxylic acids, lithium tetraphenylborate, imides, etc., one or more of these substances can be used.

[0115] Lithium secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries according to the types of separators and electrolytes used, and can be classified into cylindrical, square, coin-shaped, pouch-shaped, etc. according to the form, and can be classified into bulk and thin film types according to the size.

[0116] The manufacturing methods of these batteries are well-known in the art, so detailed descriptions are omitted.

[0117] Next, the present text will be described more specifically using examples and comparative examples, but the present text is not limited thereto.

[0118] [Example 1]

[0119] Mix 5 parts by weight of flaky silicon particles (average particle size (D 50 )): 5 μm), 94 parts by weight of isopropyl alcohol (IPA), and 1 part by weight of stearic acid, and put them into a bead mill for grinding until the average particle size (D 50 )) reaches 110 nm to prepare a ground silicon solution.

[0120] The ground silicon prepared by spray drying was used to manufacture a silicon precursor with an average particle size (D 50 )) of 6 μm.

[0121] The manufactured silicon precursor, petroleum-based pitch, and graphite were put into a compounder (manufactured by Hansol Chemicals) at a weight ratio of 45:25:30, followed by 10 minutes of compounding, and then a primary heat treatment was carried out in a vacuum atmosphere at 180 °C for 24 hours.

[0122] After that, a secondary heat treatment was carried out for 3 hours up to 900 °C in an inert atmosphere to manufacture a composite material.

[0123] The composite material was sieved to 325 mesh to obtain the negative electrode active material.

[0124] [Example 2]

[0125] The negative electrode active material was manufactured in the same manner as in Example 1, except that the weight ratios of the pitch and graphite to the silicon precursor were 45:23:32 parts by weight, respectively.

[0126] [Example 3]

[0127] The negative electrode active material was manufactured in the same manner as in Example 1, except that the weight ratios of the pitch and graphite to the silicon precursor were 45:27:28 parts by weight, respectively.

[0128] [Comparative Example 1]

[0129] The negative electrode active material was manufactured in the same manner as in Example 1, except that the weight ratios of the pitch and graphite to the silicon precursor were 45:30:25 parts by weight, respectively.

[0130] [Comparative Example 2]

[0131] The negative electrode active material was manufactured in the same manner as in Example 1, except that the weight ratios of the pitch and graphite to the silicon precursor were 45:33:22 parts by weight, respectively.

[0132] [Comparative Example 3]

[0133] The negative electrode active material was manufactured in the same manner as in Example 1, except that the weight ratios of the pitch and graphite to the silicon precursor were 45:20:35 parts by weight, respectively.

[0134] [Comparative Example 4]

[0135] The negative electrode active material was manufactured in the same manner as in Example 1, except that the weight ratios of the pitch and graphite to the silicon precursor were 45:18:37 parts by weight, respectively.

[0136] [Comparative Example 5]

[0137] After the composite treatment, the negative electrode active material was produced in the same manner as in Example 1, except that the first heat treatment was carried out at 180 °C for 24 hours in a nitrogen atmosphere instead of a vacuum atmosphere.

[0138] [Comparative Example 6]

[0139] After the composite treatment, the negative electrode active material was produced in the same manner as in Example 1, except that the primary and secondary heat treatments were not carried out.

[0140] [Production Example]

[0141] Fabrication of coin-type half cell

[0142] The negative electrode active materials produced in Examples 1 to 3 and Comparative Examples 1 to 6, a conductive agent (Super P), and a binder (SBR-CMC) were uniformly mixed at a weight ratio of 94:2:4 to prepare a negative electrode paste.

[0143] The prepared negative electrode paste was coated on a copper thin film current collector with a thickness of 10 μm, and the coated electrode plate was dried at 120 °C for 20 minutes and then pressed to produce a negative electrode.

[0144] A CR2032 type coin-shaped half cell was fabricated using metallic lithium as the negative electrode and the counter electrode, a PE separator as the separator, and a mixed solvent of EC (ethylene carbonate):DEC (diethyl carbonate):DMC (dimethyl carbonate) (3:5:2 by volume) dissolved with 1.0 M LiPF6 as the electrolyte.

[0145] Fabrication of coin-type full cell

[0146] Using the negative electrode used in the coin-shaped half cell, the positive electrode was fabricated as follows. As the positive electrode active material, LiNi was mixed at a weight ratio of 95:2:3. 0.6 Co 0.2 Mn 0.2 O2, a conductive agent (Super P), and a binder (PVDF) were used to prepare a positive electrode paste. The positive electrode paste was coated on an aluminum foil current collector with a thickness of 12 μm, and the coated electrode plate was dried at 120 °C for 15 minutes and then pressed to produce a positive electrode.

[0147] Using the positive electrode and the negative electrode, a CR2032 type coin-shaped all-solid-state battery was fabricated with a PE separator as the separator and a mixed solvent of EC (ethylene carbonate): DEC (diethyl carbonate): DMC (dimethyl carbonate) (2:1:7 by volume) dissolved with 1.5 M LiPF6 + 5% FEC as the electrolyte.

[0148] Evaluation Example 1: Analysis of negative electrode active material

[0149] The characteristics of the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 3 were analyzed as shown in Table 1 below.

[0150] [Table 1]

[0151]

[0152] In Table 1 above, the particle size (D 50 ) of the negative electrode active material (composite) was measured using an organic solution in which the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 6 were dispersed, by a particle size analyzer (Mastersizer 3000, Malvern Panalytical).

[0153] In addition, the particle size (D 50 ) of the silicon particles of the negative electrode active materials used in Examples 1 to 3 and Comparative Examples 1 to 6 was measured by the same method as the particle size measurement method of the negative electrode active material.

[0154] On the other hand, the carbon content was determined by quantifying carbon gases such as carbon dioxide and carbon monoxide generated by burning the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 6 at high temperature, using an ELE MENTRAC CS-i (ELTRA), and the oxygen content was determined by quantifying the oxygen generated by burning the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 6 at high temperature, using an 836 Series (LECO).

[0155] In addition, in order to calculate r2 / r1, the cross-sections of the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 6 were processed by Focused-ion beam (FIB), and r1 and r2 were measured by observing the cross-sections with FE-SEM.

[0156] On the one hand, the porosity of the negative electrode active material is calculated by the following formula 1. In the following mathematical formula 1, the true density is 2.33 g / cc. The total pore volume of the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 6 was measured by a TriStar II 3020 device from Micromeritics. The total pore volume was measured by the adsorption amount of nitrogen according to the change in relative pressure at liquid nitrogen temperature (77K).

[0157] [Mathematical formula 1]

[0158]

[0159] As shown in Table 1 above, the particle size of the negative electrode active materials of Examples 1 to 3 was 5.87 to 6.11 μm, the carbon content was 50.7 to 51.7%, the oxygen content was 5.8 to 6.3%, the value of r2 / r1 was 0.82 to 0.89, and the porosity was 5.8 to 6.9%.

[0160] In addition, when manufacturing the negative electrode active material, as the content of petroleum-based pitch increases and the content of graphite decreases, the value of r2 / r1 shows a downward trend.

[0161] That is, it can be confirmed that when manufacturing the negative electrode active material, the value of r2 / r1 of the negative electrode active material can be adjusted by adjusting the content of petroleum-based pitch and graphite.

[0162] In addition, it can be confirmed that by comparing Comparative Examples 5 and 6 which are only different from Example 1 in heat treatment conditions, when changing the primary heat treatment or not performing the primary and secondary heat treatments, the porosity especially increases.

[0163] That is, it can be confirmed that when manufacturing the negative electrode active material, the porosity of the negative electrode active material can be adjusted by changing the heat treatment conditions.

[0164] Evaluation Example 2: Analysis of battery characteristics

[0165] The battery characteristics of the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 6 were analyzed as shown in Table 2 below.

[0166] [Table 2]

[0167]

[0168]

[0169] The evaluation of the battery characteristics of the coin-type half-cells and coin-type full-cells manufactured using the negative electrode active materials of Examples 1 to 3 and Comparative Examples 1 to 6 is as follows.

[0170] To evaluate the lifespan and output characteristics, coin-type full cells were used, and coin-type half cells were used for the evaluation of initial capacity, discharge capacity, and initial efficiency characteristics.

[0171] The coin-type half cells fabricated using the negative electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were each subjected to constant current charging at a current of 0.1 C rate at 25 °C until the voltage reached 0.0

[0172] 1 V (vs. Li), and then constant voltage charging was carried out while maintaining 0.01 V until the current reached 0.05 C. The charged cells were allowed to stand for 10 minutes, and then discharged at a constant current of 0.1 C until the voltage during discharge reached 1.5 V (vs. Li) (performed twice, initial formation). The "C" is the discharge rate of the battery, which represents the value obtained by dividing the total capacity of the battery by the total discharge time.

[0173] The coin-type full cells fabricated using the negative electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were each subjected to constant current charging at a current of 0.1 C rate at 25 °C until the voltage reached 4.2 V (vs. Li), and then constant voltage charging was carried out while maintaining 4.2 V until the current reached 0.05 C. The charged cells were allowed to stand for 10 minutes, and then discharged at a constant current of 0.1 C until the voltage during discharge reached 2.7 V (vs. Li) (performed twice, initial formation).

[0174] After that, constant current charging was carried out at a current of 1.0 C rate at 25 °C until the voltage reached 4.2 V (vs. Li), and then constant voltage charging was carried out while maintaining 4.2 V until the current reached 0.05 C. The charged coin-type cells were allowed to stand for 10 minutes, and then cycled with constant current discharge at 0.1 C until the voltage during discharge reached 2.7 V (vs. Li) (cycles 1 to 200).

[0175] For example, the graphs for measuring the battery capacity / efficiency, lifespan, and output characteristics of the cells fabricated using the negative electrode active materials prepared in Examples 1 to 3 and Comparative Examples 1 to 6 are respectively as Figures 2 to 4 shown.

[0176] On the one hand, the initial charge capacity and the initial discharge capacity in Table 2 are the charge and discharge capacities in the first cycle, respectively.

[0177] The initial efficiency, lifespan, and output characteristics were calculated respectively by the following Mathematical Formulas 2 to 4.

[0178] [Mathematical Formula 2]

[0179] Initial efficiency [%] = [Discharge capacity in the first cycle / Charge capacity in the first cycle] * 100

[0180] [Mathematical formula 3]

[0181] Life characteristic [%] = [Discharge capacity in the 200th cycle / Charge capacity in the first cycle] * 100

[0182] [Mathematical formula 4]

[0183] Output characteristic [%] = [Discharge capacity at 5.0C / Discharge capacity at 0.1C] * 100

[0184] As shown in Table 2, the initial efficiency of the secondary battery using the negative electrode active materials of Examples 1 to 3 is 87% or more and 90% or less. After 200 cycles of charge and discharge, the life characteristic is 60% or more, and the output characteristic (C5.0 / C0.1) can be 70% or more.

[0185] Specifically, the initial charge capacity of the secondary battery using the negative electrode active materials of Examples 1 to 3 is 1606.9 to 1669.2 mAh / g, the initial discharge capacity is 1410.9 to 1467.2 mAh / g, the initial efficiency is 87.8 to 88.1%, the life characteristic is 62.5 to 63.6%, and the output characteristic is 70.9 to 72.3%.

[0186] In addition, it can be confirmed that the value of r2 / r1 and the porosity of the negative electrode active material significantly affect the life characteristic and output characteristic of the secondary battery.

[0187] It can be confirmed that the life characteristic and output characteristic of the secondary battery using the negative electrode active materials of Comparative Examples 1 to 4 with a value of r2 / r1 greater than 0.8 and less than 0.95 are lower than those of the secondary battery using the negative electrode active materials of Examples 1 to 3.

[0188] That is, when the value of r2 / r1 exceeds or is lower than the range of the present application, a secondary battery having excellent life and output characteristics cannot be obtained.

[0189] On the other hand, it can be confirmed that for the secondary battery using the negative electrode active materials of Comparative Examples 5 and 6 with a porosity exceeding 10%, even if the value of r2 / r1 is within the range of the present application, the life characteristic and output characteristic of the secondary battery are lower than those of the secondary battery using the negative electrode active materials of Examples 1 to 3.

[0190] That is, even if the value of r2 / r1 is within the range of the present application, when the porosity exceeds the range of the present application, a secondary battery having excellent life and output characteristics cannot be obtained.

[0191] The scope of the present invention is defined by the following claims, not by the foregoing detailed description. All changes or modifications derived from the meaning and scope of the claims and their equivalent concepts shall be construed as being included within the scope of the present invention.

[0192] Industrial Applicability

[0193] The negative electrode active material according to the present invention not only has a high capacity and a high energy density, but also can provide a secondary battery with a high output and a long life.

[0194] In addition, there is an effect of manufacturing the negative electrode active material with high efficiency and at low cost.

Claims

1. A negative electrode active material containing at least one metal-containing particle, characterized in that the longest straight-line length (r2) from the end of the metal-containing particle that is farthest from the center point of the negative electrode active material among the metal-containing particles that are farthest from the center point of the negative electrode active material to the center point of the negative electrode active material, and the ratio (r2 / r1) of this length to the radius (r1) of the negative electrode active material is 0.8 or more and 0.95 or less.

2. The negative electrode active material according to claim 1, characterized in that the negative electrode active material comprises: a core; and a shell surrounding the core, wherein the metal-containing particle comprises any one or more selected from the group consisting of Mg, Al, Si, Ca, Fe, Mg, Mn, Co, Ni, Zn, and Ge, and the metal-containing particle is contained in the core.

3. The negative electrode active material according to claim 1, characterized in that the metal-containing particle includes any one or more selected from the group consisting of silicon particles, silicon oxide particles, silicon carbide particles, and silicon alloy particles.

4. The negative electrode active material according to claim 1, characterized in that it contains 30% by weight or more and 80% by weight or less of a carbon-based material.

5. The negative electrode active material according to claim 1, characterized in that the weight ratio of amorphous carbon to crystalline carbon (weight of amorphous carbon / weight of crystalline carbon) is 0.6 or more and 1 or less.

6. The negative electrode active material according to claim 2, characterized in that the core and the shell contain one or more selected from the group consisting of amorphous carbon and crystalline carbon.

7. The negative electrode active material according to claim 1, characterized in that Average particle diameter (D 50 ) is 3 μm or more and 20 μm or less.

8. The negative electrode active material according to claim 1, characterized in that the porosity of the negative electrode active material is 10% or less.

9. A method for manufacturing a negative electrode active material according to any one of claims 1 to 8, characterized in that, comprising the following steps: spray-drying a solution containing metal-containing particles to produce a precursor powder; mixing the precursor powder, amorphous carbon, and crystalline carbon and performing compounding; and performing heat treatment, wherein the metal is selected from one or more of Si, Al, Ti, Mn, Ni, Cu, V, Zr, Mn, Co, Fe, and Nb, and the performing of heat treatment includes a first heat treatment and a second heat treatment.

10. An electrode, comprising: the negative electrode active material according to any one of claims 1 to 8.

11. A lithium secondary battery, comprising: a negative electrode containing the negative electrode active material according to any one of claims 1 to 8; a positive electrode opposite to the negative electrode; and an electrolyte disposed between the negative electrode and the positive electrode.

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