Anode active material, method for preparing the same, and rechargeable lithium battery comprising the same

Abstract

The present invention relates to a negative electrode active material, a method for manufacturing the same, and a lithium secondary battery including the same. Specifically, the invention relates to a negative electrode active material having a hard carbon layer formed surrounding all or part of a metal-containing particle having an oxide film layer, a method for manufacturing the same, and a lithium secondary battery including the same, thereby providing a secondary battery with excellent lifespan characteristics of high capacity, high efficiency, and high output.

Description

Technology 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 same. Specifically, the invention relates to a negative electrode active material having a hard carbon layer formed surrounding all or part of a metal-containing particle having an oxide film layer, a method for manufacturing the same, and a lithium secondary battery including the same. Background Technology

[0003] Lithium-ion batteries (LIBs) possess high energy density and are easy to design, so they are widely adopted as the primary power source for mobile electronic devices, and their application range is expanding further in the future to include electric vehicles and power storage devices for new and renewable energy.

[0004] In order to apply them to new fields, continuous research is required on LIB materials with characteristics such as higher energy density and longer lifespan.

[0005] In particular, regarding cathode materials, research has been conducted on various materials including carbon, silicon, tin, and germanium.

[0006] Among these, silicon-based anode materials have attracted significant attention due to their very high energy density compared to currently commercialized graphite anode materials.

[0007] However, silicon-based cathode materials have fatal drawbacks, such as the deterioration of electrochemical properties due to the formation of an unstable SEI layer caused by side reactions between the silicon surface and the electrolyte, or the pulverization of the electrode material due to internal stress resulting from rapid volume expansion during charging and discharging.

[0008] To address this, much research has been conducted to improve surface reversibility through various surface treatments of silicon-based cathode materials, and in particular, methods of surface coating or composite with carbon materials are being studied.

[0009] However, conventional surface treatments failed to sufficiently suppress the volume expansion of the electrodes, leading to problems such as low battery life or reduced output.

[0010] Therefore, there is a need for technological development regarding surface treatment of cathode active materials to suppress volume expansion of silicon-based cathode materials while simultaneously enabling the manufacture of high-capacity, high-efficiency, and high-output batteries. Prior art literature

[0012] Republic of Korea Published Patent Application No. 2016-0104720 The problem to be solved

[0013] Accordingly, the objective of the present invention is to provide a negative electrode active material for a high-output secondary battery that can manufacture a lithium secondary battery with sufficient capacity, high initial efficiency, stable charging and discharging, and a long lifespan due to a low expansion rate.

[0014] In addition, the purpose is to provide a method for manufacturing the above-mentioned cathode active material.

[0015] In addition, the purpose is to provide an electrode and a lithium secondary battery comprising the above-mentioned negative electrode active material.

[0016] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other problems not mentioned but intended to be solved will be clearly understood by those skilled in the art to which the present invention belongs from the content to be described below. means of solving the problem

[0018] One aspect of the present invention comprises metal-containing particles, and

[0019] The above metal-containing particles include a metal-containing core, an oxide film layer, and a hard carbon layer,

[0020] The above oxide film layer is formed on part or all of the surface of the metal-containing core, and

[0021] The above hard carbon layer is formed on part or all of the surface of the oxide film layer, and

[0022] The above metal-containing core comprises one or more selected from the group consisting of Si, Mg, Ge, Sn, Al, Ca, Fe, Mg, Mn, Co, Ni, and Zn,

[0023] Provides a negative electrode active material.

[0024] Another aspect of the present invention is a step of preparing a precursor powder by spray-drying a solution containing metal-containing particles;

[0025] A step of compounding the above precursor powder with amorphous carbon, crystalline carbon, or a combination thereof; and

[0026] Includes a heat treatment step;

[0027] The above metal is one or more selected from Si, Mg, Ge, Sn, Al, Ca, Fe, Mg, Mn, Co, Ni, and Zn,

[0028] A method for manufacturing a cathode active material is provided.

[0029] Another aspect of the present invention is a cathode active material comprising the above-mentioned cathode active material,

[0030] Provides an electrode.

[0031] Another aspect of the present invention is that the electrode comprises,

[0032] Provides a secondary battery. Effects of the invention

[0034] It has the effect of providing a negative electrode active material for a high-output secondary battery that can be manufactured with a large capacity lithium secondary battery, has high initial efficiency, enables stable charging and discharging, and has a long lifespan due to its low expansion rate.

[0035] In addition, there is an effect of being able to manufacture the above-mentioned cathode active material. Brief explanation of the drawing

[0037] Figure 1 shows a schematic diagram of the cathode active material of the present invention. Figure 2 is a transmission electron microscope image of the precursor powder of Example 1 after heat treatment. FIGS. 3(a) to 3(c) show transmission electron microscope images of Example 1 with colors separated by atoms containing the cathode active material, FIG. 3(d) shows the colors separated by atoms simultaneously in a single image, and FIG. 3(e) is the original transmission electron microscope image. Figure 4 shows the negative electrode active material prepared according to Example 1 observed using an ion-milling scanning electron microscope (CP-SEM). Specific details for implementing the invention

[0038] Hereinafter, the operation and effects of the invention will be described in more detail through specific embodiments and drawings. However, these embodiments are merely examples of the invention and do not define the scope of the invention.

[0039] Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0040] Therefore, it should be understood that the configuration of the embodiments described in this specification is merely one of the most preferred embodiments of the present invention and does not represent all of the technical ideas of the present invention, and that various equivalents and modifications that can replace them may exist at the time of filing this application.

[0041] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as “comprising,” “comprising,” or “having” are intended to specify the existence of the implemented features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0042] Where various parameters in this specification are given as an enumeration of ranges, preferred ranges, preferred upper limits, and preferred lower limits, it should be understood that any pair of any upper range limit or preferred value and any lower range limit or preferred value specifically discloses all ranges formed by any pair of any upper range limit or preferred value, regardless of whether the range is disclosed separately.

[0043] Where a range of numerical values ​​is mentioned in this specification, unless otherwise described, the range is intended to include its endpoint and all integers and fractions within the range.

[0044] The scope of the present invention is not intended to be limited to specific values ​​mentioned when defining the scope.

[0045] In the present specification, "a to b" and "a~b" indicating numerical ranges are defined as ≥a and ≤b.

[0046] Embodiments of the present invention have been described in detail below, but the present invention is not limited thereto.

[0048] In one aspect of the present invention, the cathode active material may include metal-containing particles, and the metal-containing particles may include a metal-containing core, an oxide film layer, and a hard carbon layer, the oxide film layer may be formed on part or all of the surface of the metal-containing core, and the hard carbon layer may be formed on part or all of the surface of the oxide film layer, and the metal-containing core may include one or more selected from the group consisting of Si, Mg, Ge, Sn, Al, Ca, Fe, Mg, Mn, Co, Ni, and Zn.

[0049] That is, the metal-containing particle may have a structure in which an oxide film layer is formed as a first shell on all or part of the surface of the metal-containing core, and a hard carbon layer is formed as a second shell on all or part of the surface of the first shell, which is the oxide film layer.

[0050] The metal-containing particles may have a core-shell structure with a two-layer shell formed.

[0051] Meanwhile, the above-mentioned cathode active material itself may not have a core-shell structure as a shell is not formed.

[0052] In one embodiment of the present invention, the metal-containing core may be a silicon (Si)-containing particle.

[0053] The above silicon (Si)-containing particles may include one or more selected from the group consisting of silicon particles, silicon oxide particles, silicon carbide particles, and silicon alloy particles.

[0054] In addition, for example, if the metal-containing particles contain germanium (Ge) or tin (Sn), the metal-containing particles may contain oxide particles of germanium or tin.

[0055] In one embodiment of the present invention, the silicon (Si) containing particles may have an average particle size (D50) of 80 nm to 140 nm.

[0056] For example, the average particle size of the silicon-containing particles may be 82 nm to 130 nm, 84 nm to 120 nm, 86 nm to 110 nm, or 88 nm to 100 nm.

[0057] If the average particle size of the silicon-containing particles exceeds 140 nm, a high battery capacity can be obtained, but the battery life may be very short, and if the average particle size of the silicon-containing particles is less than 80 nm, the battery capacity and efficiency may be lower and manufacturing costs may be higher.

[0058] Since the oxide film layer may have a lower volume expansion rate compared to silicon, manufacturing a battery using metal-containing particles with an oxide film layer has the effect of mitigating volume expansion during charging and discharging. Mitigating the volume expansion of the battery can improve its lifespan characteristics.

[0059] In one embodiment of the present invention, the oxide film layer may be represented by the following chemical formula 1.

[0061] [Chemical Formula 1]

[0062] SiO x (0 < x < 2)

[0064] In the above Chemical Formula 1, if x is 2 or greater, there may be adverse effects on battery capacity and efficiency. That is, lithium ions react with oxygen to form Li2O, Li-silicate (Li x Si y O z Irreversible products such as ) are generated. As a result, lithium ions that react with the cathode material cannot return to the electrolyte or anode material and become trapped inside the cathode, failing to develop capacity and reducing efficiency.

[0065] The thickness of the hard carbon layer may be 5 nm or more and 30 nm or less, 6 nm or more and 28 nm or less, 7 nm or more and 26 nm or less, or 8 nm or more and 24 nm or less.

[0066] If the thickness of the hard carbon layer exceeds that of the present invention, the capacity of the battery may be small due to the relatively low silicon content, and the hard carbon layer may not be formed with a uniform thickness, resulting in insufficient coverage of silicon and consequently a reduced effect of suppressing volume expansion.

[0067] If the thickness of the hard carbon layer is lower than that of the present invention, the effect of suppressing volume expansion may be reduced, and as a result, the lifespan of the battery may be reduced.

[0068] The metal-containing particles may include oxygen (O) and carbon (C). In this case, the atomic ratio of the metal to oxygen may be 1:0.3 to 1:1, and the atomic ratio of the metal to carbon may be 1:0.1 to 1:3.

[0069] For example, the content ratio of silicon atoms, carbon atoms, and oxygen atoms of the metal-containing particles (silicon atoms:carbon atoms:oxygen atoms) may be 64.9:11.5:23.6 or 49.1:21:29.9 or 27.1:60:12.9.

[0070] In one embodiment of the present invention, the metal core particles may be spherical, flake-like, or a combination thereof, or may include other shapes.

[0071] In one embodiment of the present invention, the hard carbon layer may be formed by carbonizing a polymer.

[0072] The above hard carbon may refer to non-graphitizable carbon and may have the characteristic of not turning into graphite even at a high temperature of 2,500°C. The above hard carbon layer may be formed in a form that surrounds all or part of the metal-containing particles.

[0073] When charging and discharging a battery, volume expansion of the battery may occur, and the hard carbon layer has the effect of suppressing the expansion of the battery, so the lifespan characteristics of the battery can be improved.

[0074] The above polymer may include polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyvinyl acetate (PVA), polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polystyrene (PS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), polyurethane (PU), polyamide (PA), polyimide (PI), polyetherimide (PEI), ethylene carbonate (EC), hydroxypropylmethylcellulose (HPMC), polycarbonate (PC), carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), or a combination thereof.

[0075] For example, when manufacturing a cathode active material, if polyvinylpyrrolidone is added and then subjected to a heat treatment process, the polyvinylpyrrolidone can be carbonized to form a hard carbon layer.

[0076] In one embodiment of the present invention, the negative electrode active material may further comprise amorphous carbon, crystalline carbon, or a combination thereof.

[0077] For example, the cathode active material may additionally include only the amorphous carbon, additionally include only the crystalline carbon, or additionally include both the amorphous carbon and the crystalline carbon.

[0078] The above amorphous carbon, crystalline carbon, or a combination thereof acts as a binder that binds the metal-containing particles together by filling the voids between the primary particles of the secondary particles, which are aggregates of primary metal-containing particles, while simultaneously enabling the negative electrode active material to maintain its shape and the battery's performance despite the expansion behavior of the metal-containing particles during the charging and discharging process of the battery.

[0079] In addition, the amorphous carbon, crystalline carbon, or a combination thereof may serve as a matrix that surrounds the surface of the primary metal-containing particles and binds the metal-containing particles together in the cathode active material, which is a composite containing metal-containing particles.

[0080] Meanwhile, the amorphous carbon, crystalline carbon, or a combination thereof may form a third shell formed on all or part of the surface of the hard carbon layer, which is the second shell of the metal-containing particles.

[0081] When the above-mentioned negative electrode active material and carbon-based material are used together, direct contact between the metal-containing particles formed by the hard carbon layer and the electrolyte is limited. In addition, the oxidation reaction of the silicon-based active material can be suppressed, and a stable film can be formed by effectively forming a Solid Electrolyte Interphase (SEI) film, and the charge / discharge characteristics of lithium can be further improved by bringing about an improvement in electrical conductivity.

[0082] The above amorphous carbon, crystalline carbon, or combinations thereof may be formed by carbonizing one or more selected from the group consisting of coal-based pitch, mesophase pitch, petroleum-based pitch, petroleum-based coke, formalin, 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 vinyl chloride resin, block copolymer, polyol, polyimide resin, graphite, natural graphite, artificial graphite, expanded graphite, graphene, carbon black, and fullerene.

[0083] In one embodiment of the present invention, based on 100 weight% of the total weight of the negative electrode active material, the content of the metal-containing particles may be 30 weight% to 90 weight%, and the weight of the amorphous carbon, crystalline carbon, or a combination thereof may be 10 weight% to 70 weight%.

[0084] Conventional negative electrode active material materials may be mixed and blended with the aforementioned negative electrode active material, coated on the surface of the aforementioned negative electrode active material, or used in any other combined form.

[0085] A method for manufacturing the above-mentioned cathode active material according to another aspect of the present invention may include the step of preparing a precursor powder by spray-drying a solution containing metal-containing particles; the step of compounding the precursor powder with amorphous carbon, crystalline carbon, or a combination thereof; and the step of heat treatment; wherein the metal may be one or more selected from Si, Mg, Ge, Sn, Al, Ca, Fe, Mg, Mn, Co, Ni, and Zn.

[0086] In one embodiment of the present invention, the step of preparing the precursor powder may include the step of introducing a polymer.

[0087] In one embodiment of the present invention, the polymer may comprise polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyvinyl acetate (PVA), polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polystyrene (PS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), polyurethane (PU), polyamide (PA), polyimide (PI), polyetherimide (PEI), ethylene carbonate (EC), hydroxypropylmethylcellulose (HPMC), polycarbonate (PC), carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), or a combination thereof.

[0088] In one embodiment of the present invention, the polymer may be 0.01 weight% or more and 1 weight% or less based on 100 weight% of the total weight of the solution containing the metal-containing particles.

[0089] For example, the polymer may be 0.02 wt% or more and 0.8 wt% or less, 0.03 wt% or more and 0.6 wt% or less, 0.04 wt% or more and 0.5 wt% or less, or 0.05 wt% or more and 0.4 wt% or less, based on 100 wt% of the total weight of the solution containing the metal-containing particles.

[0090] In one embodiment of the present invention, the amorphous carbon, crystalline carbon, or a combination thereof may be one or more selected from the group consisting of coal-based pitch, mesophase pitch, petroleum-based pitch, petroleum-based coke, formalin, 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 vinyl chloride resin, block copolymer, polyol, polyimide resin, graphite, natural graphite, artificial graphite, expanded graphite, graphene, carbon black, and fullerene.

[0091] For example, it can be compounded by adding petroleum-based pitch and graphite.

[0092] In one embodiment of the present invention, the weight of the precursor powder may be 30% or more and 90% or less based on 100% by weight of the total weight of the precursor powder and the amorphous carbon, crystalline carbon, or a combination thereof.

[0093] At this time, the weight ratio of the mixture of the amorphous carbon and the crystalline carbon (weight of the amorphous carbon:weight of the crystalline carbon) may be 10:90 to 70:30.

[0094] For example, the weight ratio of the mixture of the amorphous carbon and the crystalline carbon may be 20:80, 40:60, or 60:40.

[0095] For example, the weight ratio of the precursor powder, the petroleum-based pitch, and the graphite (weight of the precursor powder:weight of the petroleum-based pitch:weight of the graphite) may be 50:10:40, 50:20:30, or 50:30:20.

[0096] An electrode according to another aspect of the present invention may include the above-mentioned negative electrode active material.

[0097] In one embodiment of the present invention, the expansion rate of the electrode in the 100th cycle of repeating the charging and discharging of the battery may be 47% or less.

[0098] For example, the size of the electrode at the 100th charge / discharge cycle of the battery may be expanded by more than 15% and less than 47%, more than 17% and less than 46%, or more than 19% and less than 45% compared to the size of the electrode at the 1st cycle.

[0099] If the expansion rate of the electrode exceeds the range of the present invention, the negative electrode active material may detach from the current collector, or the electrolyte may be consumed due to the formation of an SEI layer, thereby shortening the lifespan of the battery.

[0100] The above cathode may optionally further include a conductive agent to provide a conductive path to the cathode active material to further improve electrical conductivity.

[0101] As the conductive agent, any material generally used in lithium batteries may be used, such as carbon-based materials including carbon black, acetylene black, Ketjen black, and carbon fibers (e.g., vapor-grown carbon fibers); metal-based materials including metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; or conductive materials including mixtures thereof. The content of the conductive material may be appropriately adjusted. For example, the weight ratio of the negative electrode active material to the conductive agent may be added in the range of 99:1 to 90:10.

[0102] The above solvent may include N-methylpyrrolidone (NMP), acetone, water, etc. The content of the above solvent is used in an amount of 1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material. When the solvent content is within the above range, the process of forming the active material layer is easy.

[0103] In addition, the current collector is generally made with a thickness of 3 to 500 μm. The current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloy may be used.

[0104] In addition, fine irregularities can be formed on the surface to strengthen the bonding strength of the cathode active material, and it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven materials.

[0105] A negative electrode plate can be manufactured by directly coating the manufactured negative active material composition onto a current collector, or by casting the negative active material film onto a separate support and laminating the film, peeled off from the support, onto a copper foil current collector. The negative electrode is not limited to the forms listed above and may be in a form other than those listed above.

[0106] The above negative electrode active material composition can be used not only for manufacturing electrodes of lithium secondary batteries but also for manufacturing printable batteries by printing on a flexible electrode substrate.

[0107] Separately, in order to fabricate the anode, an anode active material composition is prepared by mixing an anode active material, a conductive agent, a binder, and a solvent.

[0108] As the above-mentioned positive active material, any lithium-containing metal oxide commonly used in the relevant technical field may be used.

[0109] For example, Li a A 1-b B b D2 (wherein 0.90≤a≤1.8, and 0≤b≤0.5); Li a E1-bBb O2-cD c (In the above 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 above formula, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b B c D α (In the above 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 above equation, 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 above equation, 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 above equation, 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 above 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 above equation, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c Gd O2(in the above equation, 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 G e O2(in the above equation, 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 above equation, 0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(in the above equation, 0.90≤a≤1.8, 0.001≤b≤0.1); Li a MnG b O2(in the above equation, 0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4 (wherein the above equation, 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) Compounds represented by any one of the chemical formulas of Fe2(PO4)3(0≤f≤2); LiFePO4 may be used.

[0110] In the above 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; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0111] Of course, a coating layer on the surface of this compound may be used, or a mixture of the compound and a compound having a coating layer may be used. This coating layer may include a coating element compound of an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of a coating element. The compounds forming this coating layer may be amorphous or crystalline. As coating elements included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used. For the coating layer formation process, any coating method may be used as long as the compound can be coated using these elements in a way that does not adversely affect the physical properties of the cathode active material (e.g., spray coating, immersion method, etc.). Since this is a matter that is well understood by those skilled in the art, a detailed explanation will be omitted.

[0112] For example, LiNiO2, LiCoO2, LiMn x O 2x (x=1, 2), LiNi 1-x Mn x O2(0 <x<1), LiNi 1-x-y Cox Mn y O2 (0≤x≤0.5, 0≤y≤0.5), LiFeO2, V2O5, TiS, MoS, etc. can be used.

[0113] In the positive electrode active material composition, the conductive agent, binder, and solvent may be the same as those used in the aforementioned negative electrode active material composition. In some cases, it is also possible to form voids within the electrode plate by adding a plasticizer to the positive electrode active material composition and the negative electrode active material composition. The content of the positive electrode active material, conductive agent, binder, and solvent is at a level typically used in lithium batteries.

[0114] The above positive current collector has a thickness of 3 μm to 500 μm and is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. may be used. The current collector may also form fine irregularities on its surface to increase the adhesion of the positive active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.

[0115] The prepared positive active material composition can be directly coated and dried onto a positive current collector to manufacture a positive electrode plate. Alternatively, the positive active material composition can be cast onto a separate support, and then the film obtained by peeling from the support can be laminated onto a positive current collector to manufacture a positive electrode plate.

[0116] The above-mentioned positive and negative electrodes can be separated by a separator, and any separator commonly used in lithium batteries may be used. In particular, it is suitable to have low resistance to ion movement of the electrolyte and excellent electrolyte wetting ability. For example, it may be a material selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, and may be in the form of a non-woven fabric or a woven fabric. The separator used has a pore diameter of 0.01 to 10 μm and a thickness generally of 5 to 300 μm.

[0117] Lithium salt-containing non-aqueous electrolytes consist of a non-aqueous electrolyte and lithium. Non-aqueous electrolyte solutions, solid electrolytes, and inorganic solid electrolytes are used as non-aqueous electrolytes.

[0118] As the above-mentioned non-aqueous electrolyte, for example, non-protic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl lactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, ethyl propionate, etc. may be used.

[0119] The above organic solid electrolyte may be, for example, a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymer containing an ionic dissociator, etc.

[0120] As the above-mentioned 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., may be used.

[0121] Any lithium salt commonly used in lithium batteries may be used, and as a substance that dissolves well in the non-aqueous electrolyte, examples include LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10 One or more substances such as LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (CF3SO2)2NLi, lithium chloroborate, lithium lower aliphatic carboxylate, lithium 4-phenylborate, and imide may be used.

[0122] A secondary battery of another aspect of the present invention may include the electrode and may be a lithium secondary battery.

[0123] Rechargeable batteries are generally evaluated as having higher quality as they possess greater capacity, higher efficiency, and higher output; however, they suffer from the problem of capacity decreasing with repeated charging and discharging cycles. Therefore, a battery is considered to be of superior quality if it has a larger initial discharge capacity and higher initial efficiency. Furthermore, a battery is considered superior if its discharge capacity after repeated charging and discharging cycles is greater relative to its initial discharge capacity.

[0124] In one embodiment of the present invention, the initial discharge capacity of the secondary battery may be 1,300 mAh / g or more.

[0125] For example, the above initial discharge capacity may be 1,300 mAh / g or more and 1,700 mAh / g or less, 1,320 mAh / g or more and 1,670 mAh / g or less, 1,340 mAh / g or more and 1,640 mAh / g or less, 1,360 mAh / g or more and 1,620 mAh / g or less, or 1,380 mAh / g or more and 1,600 mAh / g or less.

[0126] In one embodiment of the present invention, the initial efficiency of the secondary battery may be 80% or more.

[0127] For example, the above initial efficiency may be 81% or more and 99% or less, 82% or more and 98% or less, 83% or more and 97% or less, 84% or more and 96% or less, or 85% or more and 95% or less.

[0128] In one embodiment of the present invention, the lifespan characteristic of the secondary battery may be 70% or more.

[0129] For example, the above life characteristic may mean a value representing the discharge capacity of the 100th cycle as a percentage of the discharge capacity of the 1st cycle, and may be 70% or more and 99% or less, 71% or more and 98.5% or less, 72% or more and 98% or less, 73% or more and 97.5% or less, or 74% or more and 97% or less.

[0130] In one embodiment of the present invention, the output characteristic of the secondary battery may be 70% or more.

[0131] For example, the above output characteristic may mean a value representing the discharge capacity of the 100th cycle as a percentage relative to the discharge capacity of the 1st cycle, and may be 70% or more and 99% or less, 71% or more and 98.5% or less, 72% or more and 98% or less, 73% or more and 97.5% or less, or 74% or more and 97% or less.

[0132] Lithium secondary batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used; they can be classified into cylindrical, prismatic, coin, and pouch types depending on their shape; and they can be divided into bulk and thin-film types depending on their size.

[0133] The manufacturing methods of these batteries are widely known in this field, so a detailed explanation is omitted.

[0135] Hereinafter, the operation and effects of the invention will be explained in more detail through specific embodiments of the invention. However, these embodiments are merely presented as examples of the invention and do not define the scope of the invention.

[0137] [Example 1]

[0138] 1 wt% of silicon (Metal Grade Silicon) with a purity of 99.5% or higher, ground to an average particle size (D50) of 15 μm, 98.8 wt% of isopropyl alcohol, and 0.2 wt% of polyvinylpyrrolidone were fed into a bread mill (Zeta RS4, Netzsch) and ground to a particle size of 90 nm.

[0139] A precursor powder with an average particle size (D50) of 5㎛ was prepared by spray-drying a ground silicon-containing solution using a spray dryer (Mobile Minor, GEA).

[0140] The above precursor powder, petroleum-based pitch with a softening point of 230°C, and graphite with a purity of 99.9% or higher and a particle size of 200 mesh or larger were fed into a compounder (manufactured by Hansol Chemical) in a weight ratio of 50:30:20 and compounded for 30 minutes.

[0141] A negative electrode active material was prepared by carbonizing with heat treatment at 900℃.

[0142] A schematic diagram of the manufactured cathode active material is shown in Fig. 1.

[0144] [Example 2]

[0145] A negative electrode active material was prepared using the same method as in Example 1, except that 0.1 wt% of polyvinylpyrrolidone was added.

[0147] [Example 3]

[0148] A negative electrode active material was prepared in the same manner as in Example 1, except that 0.05 wt% of the polyvinylpyrrolidone of Example 1 was added.

[0150] [Example 4]

[0151] A negative electrode active material was prepared in the same manner as in Example 1, except that the precursor powder of Example 1, petroleum pitch, and graphite were compounded in a weight ratio of 50:20:30.

[0153] [Example 5]

[0154] A negative electrode active material was prepared in the same manner as in Example 1, except that the precursor powder of Example 1, petroleum pitch, and graphite were compounded in a weight ratio of 50:10:40.

[0156] [Comparative Example 1]

[0157] A negative electrode active material was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone was not added and precursor powder, petroleum pitch, and graphite were composited in a weight ratio of 50:0:50.

[0159] [Comparative Example 2]

[0160] A negative electrode active material was prepared in the same manner as in Example 1, except that polyvinylpyrrolidone was not added.

[0162] [Comparative Example 3]

[0163] A negative electrode active material was prepared in the same manner as in Example 1, except that precursor powder, petroleum pitch, and graphite were compounded in a weight ratio of 50:0:50.

[0165] [Preparation Example]

[0166] Coin Half Cell Production

[0167] A cathode slurry was prepared by uniformly mixing the cathode active material prepared according to Examples 1 to 5 and Comparative Examples 1 to 3, the conductive material (Super P), and the binder (SBR-CMC) in a weight ratio of 93:3:4.

[0168] The prepared cathode slurry was coated onto a copper foil current collector with a thickness of 20 μm, and the coated electrode plate was dried at 120°C for 30 minutes and then pressed to manufacture the cathode.

[0169] A CR2032 type coin half cell was manufactured using metallic lithium as the negative electrode and counter electrode, a PE separator as the separator, and 1.0 M LiPF6 dissolved in a mixed solvent of EC (ethylene carbonate):DEC (diethyl carbonate):DMC (dimethyl carbonate) (3:5:2 volume ratio) as the electrolyte.

[0171] Coin pool cell production

[0172] The cathode used in the above coin half cell was used, and the anode was manufactured as follows. An anode slurry was prepared by mixing LiNi0.6Co0.2Mn0.2O2 as the anode active material and PVA-PAA as the binder in a weight ratio of 1:1, the anode slurry was coated onto an aluminum foil current collector with a thickness of 12 μm, the coated electrode plate was dried at 120°C for 15 minutes, and then pressed to manufacture the anode.

[0173] A CR2032 type coin pool cell was manufactured using the above anode and cathode, a PE separator as the separator, and 1.5M LiPF6 dissolved in a mixed solvent of EC (ethylene carbonate): DEC (diethyl carbonate): DMC (dimethyl carbonate) (2:1:7 volume ratio) + FEC 20% as the electrolyte.

[0175] [Evaluation Example 1] : Transmission Electron Microscopy (TEM) Analysis

[0176] The precursor powder of Example 1 was heat-treated at a temperature of 900°C in a nitrogen (N2) atmosphere furnace without a separate compounding process, and the results were observed using a transmission electron microscope (TEM) and are shown in Figure 2.

[0177] The negative electrode active material prepared according to Example 1 was observed using a transmission electron microscope (TEM) and is shown in Fig. 3.

[0178] It was confirmed that the negative electrode active material prepared according to Example 1 contained metal-containing particles, and that an oxide film and a hard carbon layer were formed.

[0179] FIGS. 3(a) to 3(c) show the colors separated by atoms contained in the negative electrode active material of Example 1, and FIG. 3(d) shows the colors separated by atoms as a single photograph.

[0180] Yellow represents silicon atoms, green represents carbon atoms, and red represents oxygen atoms.

[0182] [Evaluation Example 2] : Ion Miller Scanning Electron Microscope (CP-SEM) Analysis

[0183] The negative electrode active material prepared according to Example 1 was observed using an ion-milling scanning electron microscope (CP-SEM) and is shown in Fig. 4.

[0184] It was confirmed that a negative electrode active material with uniformly distributed silicon-containing particles was manufactured.

[0186] [Evaluation Example 3] : Evaluation of Electrode and Battery Characteristics

[0187] The battery characteristics of coin half cells and coin full cells manufactured using the negative electrode active materials prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 were evaluated as follows.

[0188] Coin pool cells were used to measure lifespan characteristics, while coin half cells were used for evaluating other battery characteristics.

[0189] Coin half cells prepared using the negative active materials prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 were each charged with a constant current at a rate of 0.1C at 25°C until the voltage reached 0.01V (vs. Li), and then charged with a constant voltage while maintaining 0.01V until the current reached 0.05C. After the cells were fully charged, they were rested for 10 minutes, and then discharged with a constant current of 0.1C until the voltage reached 1.5V (vs. Li) during discharge (2 times, initial formation). The above "C" represents the discharge rate of the cell, which is the value obtained by dividing the total capacity of the cell by the total discharge time.

[0190] Coin pool cells prepared using the negative electrode active materials prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 were each charged with a constant current at a rate of 0.1C at 25°C until the voltage reached 4.2V (vs. Li), and then charged with a constant voltage while maintaining 4.2V until the current reached 0.05C. After the charged cells were rested for 10 minutes, they were discharged with a constant current of 0.1C until the voltage reached 2.7V (vs. Li) during discharge (2 times, initial formation).

[0191] Subsequently, the cell was charged with a constant current at a rate of 1.0C at 25℃ until the voltage reached 4.2V (vs. Li), and then charged with a constant voltage while maintaining 4.2V until the current reached 0.05C. After the charged coin cell was rested for 10 minutes, a cycle of discharging with a constant current of 1.0C until the voltage reached 2.7V (vs. Li) was repeated (cycles 1 through 100).

[0193] The volume expansion rates of electrodes prepared using the negative active materials prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 1 below.

[0195] Expansion rate (%) Example 1 28 Example 2 32 Example 3 38 Example 4 31 Example 5 36 Comparative Example 1 48 Comparative Example 2 45 Comparative Example 3 38

[0197] The expansion rate of the electrode was calculated from the following mathematical formula 1.

[0199] <Mathematical Formula 1>

[0200] Expansion rate [%] = [(Size of electrode at the 100th cycle - Size of electrode at the 1st cycle) / Size of electrode at the 1st cycle] * 100

[0202] As shown in Table 1 above, it was confirmed that the electrode expansion rate of the battery prepared using the negative electrode active material of Examples 1 to 5 was at least 10.0% lower than that of the battery prepared using the negative electrode active material of Comparative Example 1, and at least 7% lower than that of the battery of Comparative Example 2.

[0203] In addition, Comparative Example 3 showed a larger expansion rate than the examples excluding Example 3, and overall, it was confirmed that Examples 1 to 5 showed a superior expansion rate compared to the Comparative Example.

[0205] The measured initial discharge capacity, initial efficiency, and lifespan characteristics of cells using the negative electrode active materials prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 2 below.

[0207] Initial discharge capacity (mAh / g) Initial efficiency (%) Lifespan characteristics (%@100th) Example 1 1569 90.1 96.9 Example 2 1552 89.5 94.1 Example 3 1543 89.1 85.5 Example 4 1577 88.9 88.7 Example 5 1506 85.3 83.8 Comparative Example 1 1293 79.2 68.2 Comparative Example 2 1548 88.2 78.3 Comparative Example 3 1398 82.3 80.5

[0209] The initial discharge capacity is the discharge capacity in the first cycle.

[0210] The initial efficiency and life characteristics were calculated using the following Equation 2 and Equation 3, respectively.

[0212] <Mathematical Formula 2>

[0213] Initial efficiency [%] = [Discharge capacity in the 1st cycle / Charge capacity in the 1st cycle] * 100

[0215] <Mathematical Formula 3>

[0216] Lifespan characteristic[%]=[Discharge capacity of the 100th cycle / Discharge capacity of the 1st cycle]*100

[0218] As shown in Table 2 above, it was confirmed that the battery manufactured using the negative electrode active material of Examples 1 to 5 had an initial discharge capacity that was at least 250 mAh / g greater than the battery manufactured using the negative electrode active material of Comparative Examples 1 to 3, an initial efficiency that was at least 6% higher, and a lifespan characteristic that was at least 15.6% better.

[0219] In addition, all examples except Example 3 showed a higher initial discharge capacity compared to Comparative Example 2, all examples except Example 5 showed a higher initial efficiency compared to Comparative Example 2, and it was confirmed that all examples had superior life characteristics compared to Comparative Example 2.

[0220] In addition, it was confirmed that Examples 1 to 5 were superior to Comparative Example 3 in terms of initial discharge capacity, initial efficiency, and lifespan characteristics.

[0222] The measured output characteristics of coin half cells manufactured using the negative electrode active materials prepared according to Examples 1 to 5 and Comparative Examples 1 to 3 are shown in Table 3 below.

[0224] Output characteristics (%@2.0 C) Example 1 88.5 Example 2 87.2 Example 3 85.3 Example 4 87.4 Example 5 85.9 Comparative Example 1 77.6 Comparative Example 2 83.1 Comparative Example 3 84.2

[0226] The output characteristics were calculated using the following mathematical formula 4.

[0228] <Mathematical Formula 4>

[0229] Output Characteristics [%] = [Discharge capacity at a rate of 2.0 C / Discharge capacity at a rate of 0.1 C] * 100

[0231] As shown in Table 3 above, it was confirmed that the battery manufactured using the negative electrode active material of Examples 1 to 5 had higher output characteristics compared to the battery manufactured using the negative electrode active material of Comparative Examples 1 to 3.

[0233] Therefore, it was confirmed that when an electrode and a secondary battery are manufactured using the embodiments of the present invention, they are superior compared to cases where the embodiments of the present invention are not used in terms of initial discharge capacity, initial efficiency, lifespan characteristics, output characteristics, and expansion rate.

[0235] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

[0236] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention.

Claims

Claim 1 A negative electrode active material comprising metal-containing particles, wherein the metal-containing particles comprise a metal-containing core, an oxide film layer, and a hard carbon layer, wherein the oxide film layer is formed on part or all of the surface of the metal-containing core, and the hard carbon layer is formed on part or all of the surface of the oxide film layer, wherein the metal-containing core comprises one or more selected from the group consisting of Si, Mg, Ge, Sn, Al, Ca, Fe, Mg, Mn, Co, Ni, and Zn, and wherein the thickness of the hard carbon layer is 5 nm or more and 30 nm or less. Claim 2 In claim 1, the metal-containing core is a negative electrode active material that is a silicon (Si)-containing particle. Claim 3 In claim 1, the oxide film layer is a negative electrode active material represented by the following chemical formula 1. [Chemical Formula 1]SiO x (0 < x < 2) Claim 4 delete Claim 5 A negative electrode active material according to claim 1, wherein the metal-containing particles comprise oxygen (O) and carbon (C), the atomic ratio of the metal to oxygen is 1:0.3 to 1:1, and the atomic ratio of the metal to carbon is 1:0.1 to 1:

3. Claim 6 In claim 1, the hard carbon layer is a negative electrode active material formed by carbonizing a polymer. Claim 7 In claim 6, the polymer comprises polyvinylidene fluoride (PVDF), polyvinylpyrrolidone (PVP), polyvinyl chloride (PVC), polyvinyl acetate (PVA), polyethylene (PE), polypropylene (PP), polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), polystyrene (PS), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polylactic acid (PLA), polyurethane (PU), polyamide (PA), polyimide (PI), polyetherimide (PEI), ethylene carbonate (EC), hydroxypropylmethylcellulose (HPMC), polycarbonate (PC), carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), or a combination thereof, forming a negative electrode active material. Claim 8 A negative electrode active material according to claim 1, further comprising amorphous carbon, crystalline carbon, or a combination thereof. Claim 9 A cathode active material according to claim 8, wherein, based on 100 weight% of the total weight of the cathode active material, the content of the metal-containing particles is 30 weight% to 90 weight%, and the content of the amorphous carbon, crystalline carbon, or a combination thereof is 10 weight% to 70 weight%. Claim 10 A method for manufacturing a negative electrode active material according to any one of claims 1 to 3 and claims 5 to 9, comprising: a step of preparing a precursor powder by spray-drying a solution containing metal-containing particles; a step of compounding the precursor powder with amorphous carbon, crystalline carbon, or a combination thereof; and a step of heat treatment; wherein the metal is one or more selected from Si, Mg, Ge, Sn, Al, Ca, Fe, Mg, Mn, Co, Ni, and Zn. Claim 11 A method for manufacturing a negative electrode active material, wherein the step of manufacturing the precursor powder according to claim 10 includes the step of introducing a polymer. Claim 12 A method for manufacturing a negative electrode active material according to claim 10, wherein the content of the polymer is 0.01% by weight or more and 1% by weight or less based on 100% by weight of the total weight of the solution containing the metal-containing particles. Claim 13 A method for manufacturing a negative electrode active material according to claim 10, wherein, based on 100% by weight of the total weight of the precursor powder and the amorphous carbon, crystalline carbon, or a combination thereof, the content of the precursor powder is 30% by weight or more and 90% by weight or less. Claim 14 An electrode comprising a negative active material according to any one of claims 1 to 3 and claims 5 to 9. Claim 15 A secondary battery comprising the electrode of claim 14.

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