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

Abstract

The present invention relates to a negative electrode active material, a method for preparing same, and a lithium secondary battery comprising same, the negative electrode active material comprising at least one metal-containing particle and a conductive polymer, thereby having improved lifespan characteristics and output characteristics according to enhanced binding force.

Description

Negative electrode active material, method of manufacturing the same, and lithium secondary battery including the same

[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 comprising at least one metal-containing particle and a conductive polymer, wherein lifespan characteristics and output characteristics are improved due to enhanced binding strength, a method for manufacturing the same, and a lithium secondary battery including the same.

[0002]

[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 battery characteristics through various surface treatments of silicon-based cathode materials, and in particular, methods of surface coating or composite with carbon materials are being widely studied.

[0009] However, there are still limitations to improving battery lifespan, and there is a need for technological development regarding surface treatment of silicon-based anode active materials that suppresses volume expansion while simultaneously improving battery lifespan.

[0010]

[0011] [Prior Art Literature]

[0012] [Patent Literature]

[0013] (Patent Document 1) Republic of Korea Registered Patent Publication No. 10-1666878

[0014]

[0015] Accordingly, the present invention aims to provide a negative electrode active material for a secondary battery with improved lifespan and output characteristics due to enhanced binding strength, comprising at least one metal-containing particle having its surface, either wholly or partially, coated with a conductive polymer.

[0016] In addition, the present invention aims to provide a negative electrode active material for a long-life secondary battery having high capacity and high energy density.

[0017] In addition, the present invention aims to provide a negative electrode active material for a secondary battery having high power output due to the high electrical conductivity characteristics of the conductive polymer.

[0018] In addition, the purpose is to provide a manufacturing method for a Si / C cathode material containing a conductive polymer among silicon-based cathode materials that dramatically improves the capacity of the cathode active material compared to graphite, which enables the manufacturing of the cathode active material with high efficiency and low cost.

[0019] In addition, the purpose is to provide an electrode and a lithium secondary battery comprising the above-mentioned negative electrode active material.

[0020] However, the problems that this invention seeks to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0021]

[0022] One aspect of the present invention provides a negative electrode active material comprising at least one metal-containing particle and a conductive polymer.

[0023] Another aspect of the present invention is a step of preparing a precursor powder by spray-drying a solution containing metal-containing particles;

[0024] A step of introducing a conductive polymer into the above precursor powder; and

[0025] Includes a heat treatment step;

[0026] The above metal comprises one or more selected from the group consisting of Si, Al, Sn, Ge, Pb, In, As, Sb, P, and Ag.

[0027] A method for manufacturing a cathode active material is provided.

[0028] Another aspect of the present invention is a cathode active material comprising the above-mentioned cathode active material,

[0029] Provides an electrode.

[0030] Another aspect of the present invention is a cathode comprising the above-mentioned cathode active material;

[0031] An anode positioned opposite to the above cathode; and

[0032] A lithium secondary battery is provided, comprising an electrolyte disposed between the above-mentioned cathode and the above-mentioned anode.

[0033]

[0034] The negative electrode active material according to the present invention comprises at least one metal-containing particle and a conductive polymer, and as the conductive polymer coats the surface of the metal-containing particle in whole or in part, the binding strength of the negative electrode active material can be enhanced due to the binding properties of the conductive polymer.

[0035] In particular, by strengthening the binding force of the negative electrode active material with large volume expansion, it has the effect of providing a secondary battery with improved lifespan characteristics.

[0036] In addition, due to the high electrical conductivity of the conductive polymer, it has the effect of providing a secondary battery with improved output characteristics.

[0037] In addition, it has the effect of enabling the manufacture of cathode active materials optimized for high capacity and high efficiency.

[0038]

[0039] FIG. 1 is a schematic diagram showing a negative electrode active material according to one embodiment of the present invention.

[0040]

[0041] 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.

[0042] 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.

[0043] 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.

[0044] In the present specification, "a to b" and "a~b" indicating numerical ranges, "to" and "~" are defined as ≥ a and ≤ b.

[0045]

[0046] A negative electrode active material according to one aspect of the present invention may include at least one metal-containing particle and a conductive polymer, as shown in FIG. 1.

[0047] In one embodiment, the surface of the metal-containing particles may be coated with the conductive polymer, either wholly or partially.

[0048] At this time, as the conductive polymer coats the surface of the metal-containing particles entirely or partially, the binding strength of the negative electrode active material can be enhanced due to the binding properties of the conductive polymer.

[0049] In particular, by selectively strengthening the binding force of the negative electrode active material with large volume expansion, stable expansion and contraction of the electrode plate are enabled even during repeated charging and discharging, thereby improving the battery's lifespan characteristics (capacity retention rate).

[0050] In addition, due to the high electrical conductivity of the conductive polymer, electrical connections between particles are maintained, which can also improve the output characteristics of the battery.

[0051] In one embodiment, as the conductive polymer coats the surface of the metal-containing particles in whole or in part, a conductive polymer coating layer may be formed on the surface of the metal particles in whole or in part.

[0052] At this time, the thickness of the conductive polymer coating layer may be 10 nm to 5 μm.

[0053] For example, the thickness of the conductive polymer coating layer may be 10 nm to 3 μm, 10 nm to 1 μm, 100 nm to 1 μm, 500 nm to 1 μm, 50 nm to 500 nm, 1 μm to 3 μm, or 3 μm to 5 μm.

[0054] The conductive polymer coating layer can limit direct contact between the negative electrode active material and the electrolyte, and can suppress the excessive formation of the SEI (Solid Electrolyte Interphase) layer generated on the surface of the negative electrode active material.

[0055] In addition, when forming the cathode active material, at least one metal-containing particle (primary particle) may be included, and an aggregate of metal-containing particles (secondary particle) may be formed.

[0056] At this time, the conductive polymer 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.

[0057] In addition, the conductive polymer may serve as a matrix that surrounds the surface of the primary metal-containing particles in the negative electrode active material, which is a composite containing metal-containing particles, and binds the metal-containing particles together. At this time, the metal-containing particles can be connected to each other through the conductive polymer.

[0058] In one embodiment, the negative electrode active material may include the metal-containing particles that are not in direct contact with each other, the metal-containing particles that are in direct contact with each other, or a combination thereof.

[0059] The above-mentioned cathode active material may not have a core-shell structure.

[0060] In one embodiment, the metal-containing particles may include one or more selected from the group consisting of Si, Al, Sn, Ge, Pb, In, As, Sb, P, and Ag.

[0061] In one embodiment, based on 100% by weight of the total weight of the negative electrode active material, the content of the conductive polymer may be 0.1% by weight or more and 6.5% by weight or less.

[0062] For example, based on 100% by weight of the total weight of the cathode active material, the content of the conductive polymer may be 0.5% by weight or more, 6.5% by weight or less, 0.5% by weight or more, 6% by weight or less, 0.5% by weight or more, 5% by weight or less, 1% by weight or more, 6.5% by weight or less, 1% by weight or more, 6% by weight or less, or 1% by weight or more, 5% by weight or less.

[0063] If the content of the conductive polymer exceeds the range of the present invention, the amount of coating of the conductive polymer on the surface of the metal-containing particles becomes too large, so there are no pores for the electrolyte to infiltrate inside the metal-containing particles, and thus the electrode plate resistance value may increase; and if the content of the conductive polymer falls below the range of the present invention, the amount of coating of the conductive polymer becomes too small, so the metal-containing particles are not completely coated, and the electrical connection between the metal-containing particles is not smooth, and thus the electrode plate resistance value may increase.

[0064] In one embodiment, the conductive polymer may be a poly(3,4-ethylenedioxythiophene), PEDOT homopolymer or copolymer, a polyphenylene sulfide (PPS) homopolymer or copolymer, a polyaniline (PANI) homopolymer or copolymer, a polypyrrole (PPY) homopolymer or copolymer, a polyacetone (PAC) homopolymer or copolymer, a polyphenylene vinylene (PPV) homopolymer or copolymer, or a combination thereof.

[0065] In one embodiment, the conductive polymer may be a copolymer of the poly(3,4-ethylenedioxythiophene), PEDOT and the polyphenylene sulfide (PPS).

[0066] For example, when the conductive polymer is a copolymer of the polyethylenedioxythiophene and the polyphenylene sulfide (hereinafter referred to as PEDOT:PPS), the content ratio of PEDOT:PPS is 6:4 to 9:1.

[0067] For example, the content ratio of PEDOT:PPS above is 7:3.

[0068] In addition, the molecular weight of PEDOT:PPS measured by gel permeation chromatography (GPC) may be 35,000 g / mol or more and 75,000 g / mol or less.

[0069] For example, the molecular weight of the above PEDOT:PPS may be 40,000 g / mol or more and 60,000 g / mol or less.

[0070] In one embodiment, the conductive polymer comprises a water-soluble dopant doped therein, and the molecular weight of the water-soluble dopant may be 35,000 g / mol or more and 75,000 g / mol or less.

[0071] For example, the molecular weight of the above water-soluble dopant may be 37,000 g / mol or more and 73,000 g / mol or less, 39,000 g / mol or more and 72,000 g / mol or less, or 40,000 g / mol or more and 70,000 g / mol or less.

[0072] The above dopant may be any commonly used dopant, for example, polyacrylic acid (PAA), carboxymethylcellulose (CMC), or a combination thereof.

[0073] In one embodiment, the conductive polymer may have a pH of 2 or higher and 5 or lower, and a viscosity of 10 cP or higher and 300 cP or lower.

[0074] For example, the pH of the conductive polymer may be 3 or higher and 5 or lower, 3 or higher and 4 or lower, or 3.5 or higher and 5 or lower.

[0075] The pH of the above conductive polymer was measured using a pH meter (Expert Pro-ISM).

[0076] For example, the viscosity of the conductive polymer may be 50 cP or more and 300 cP or less, 50 cP or more and 200 cP or less, or 100 cP or more and 200 cP or less.

[0077] The viscosity of the above conductive polymer was measured at 25°C at a rotational speed of 200 RPM using a Cone & Plate viscometer manufactured by Brookfield. At this time, the viscosity was measured using spindle No. 31.

[0078] In one embodiment, the electrical conductivity of the negative electrode active material may be 3 S / cm or higher.

[0079] For example, the electrical conductivity of the above-mentioned cathode active material may be 4 S / cm or more, 5 S / cm or more, 5.5 S / cm or more, 5.9 S / cm or more, 10 S / cm or less, 8 S / cm or less, 4 S / cm or more and 10 S / cm or less, 5 S / cm or more and 8 S / cm or less.

[0080] The electrical conductivity of the above-mentioned negative electrode active material was measured by pelletizing the powder of the negative electrode active material and using a 4-probe measurement method.

[0081] Specifically, 500 mg of the powder of the above-mentioned cathode active material was placed in a powder resistance measuring container (metal container) with an inner diameter of 2.54 cm, and then pressure was applied to the powder of the cathode active material through a cylindrical conductive jig (fixing device) at the top and bottom of the container.

[0082] At this time, the pressure of the jig was gradually increased from 200 kgf to 2400 kgf to compress the pelletized powder and measure the electrical resistance in real time.

[0083] The thickness (t) and electrical resistance (R) of the pelletized powder were measured when the pressure of the jig was 2400 kgf, and the electrical conductivity was calculated using the following mathematical formula 1.

[0084]

[0085] <Mathematical Formula 1>

[0086] Electrical conductivity = 1 / [R (measured resistance) * t (thickness) * C (correction factor = 4.532)]

[0087]

[0088] In one embodiment, the conductivity of the negative electrode active material is 60 mΩ -1 80 mΩ or more -1 It may be less than.

[0089] For example, the conductivity of the above negative electrode active material is 60 mΩ -1 80 mΩ or more -1 Below, 65 mΩ -1 75 mΩ or higher -1 Below, 70 mΩ -1 80 mΩ or more -1 Less than or equal to 70 mΩ -1 It could be.

[0090] At this time, the conductivity is the reciprocal of the measured resistance value DC-IR (mΩ -1 It was calculated as ).

[0091] In one embodiment, the negative electrode active material may further include amorphous carbon, crystalline carbon, or a combination thereof.

[0092] 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.

[0093] 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.

[0094] The above-mentioned negative electrode active material may additionally include only amorphous carbon. Additionally, when the above-mentioned negative electrode active material further includes amorphous carbon, crystalline carbon, or a combination thereof, the content of amorphous carbon may be greater than the content of crystalline carbon.

[0095] For example, the content of amorphous carbon may be 10 to 60 parts by weight based on 100 parts by weight of the negative electrode active material, and the content of crystalline carbon may be 5 to 40 parts by weight based on 100 parts by weight of the negative electrode active material.

[0096] The above amorphous carbon may be formed from one or more selected from the group consisting of coal-based pitch, mesophase pitch, petroleum-based 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 vinyl chloride resin, block copolymer, polyol, and polyimide resin.

[0097] The crystalline carbon above may be formed from one or more selected from the group consisting of natural graphite, artificial graphite, expanded graphite, graphene, carbon black, and fullerene.

[0098] In one embodiment, the metal-containing particles may be silicon (Si)-containing particles.

[0099] In one embodiment, the 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.

[0100]

[0101] The above silicon-containing particles can be represented by the following chemical formula 1.

[0102]

[0103] [Chemical Formula 1]

[0104] SiOx (0≤x≤0.5)

[0105]

[0106] If x in Chemical Formula 1 above exceeds 0.5, adverse effects may occur in 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.

[0107] In addition, for example, the silicon carbide may be SiC, and the silicon alloy may be, for example, a Si-Z alloy (wherein 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 is not Si).

[0108] In one embodiment, the average particle size (D50) of the metal-containing particles may be 60 nm or more and 160 nm or less.

[0109] For example, the average particle size (D50) of the metal-containing particles may be 60 nm or more, 150 nm or less, 70 nm or more, 150 nm or less, 80 nm or more, 150 nm or less, or 80 nm or more, 140 nm or less.

[0110] At this time, if the average particle size of the metal-containing particles exceeds the range of the present invention, a battery with high initial efficiency can be obtained, but the battery capacity may be significantly reduced, and if the average particle size of the silicon-containing particles falls below the range of the present invention, the battery efficiency may be lowered and the manufacturing cost may be increased.

[0111] The average particle size (D50) of the metal-containing particles was measured using a particle size meter (Mastersizer 3000, Malvern Panalytical) with an organic solution in which the metal-containing particles were dispersed.

[0112]

[0113] A method for manufacturing a cathode active material according to another aspect of the present invention comprises the step of preparing a precursor powder by spray-drying a solution containing metal-containing particles;

[0114] A step of introducing a conductive polymer into the above precursor powder; and

[0115] It may include a heat treatment step; and

[0116] The above metal-containing particles may include one or more selected from the group consisting of Si, Al, Sn, Ge, Pb, In, As, Sb, P, and Ag.

[0117] In one embodiment, in the step of manufacturing the precursor powder, the step of grinding the metal-containing particles may be performed first. At this time, a solution containing the ground metal-containing particles may be formed.

[0118] In one embodiment, in the step of preparing the precursor powder, the solution containing the metal-containing particles may additionally contain 15 to 30 parts by weight of a polymer material based on 100 parts by weight of the total weight of the solution containing the metal-containing particles.

[0119] At this time, a precursor powder can be prepared by spray-drying the solution containing the metal-containing particles after adding 15 to 30 parts by weight of a polymer material based on 100 parts by weight of the total weight of the solution containing the metal-containing particles.

[0120] For example, the content of the polymer material may be 10 to 20 parts by weight based on 100 parts by weight of the total weight of the solution containing the metal-containing particles.

[0121] For example, the above polymeric material is polyvinylpyrrolidone (PVP), polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile butadiene styrene, phenolic resin, epoxy resin, polyethylene terephthalate, polytetrafluoroethylene, polyphenyl sulfide, polyamideimide, polyetherimide, polyethylenesulfone, polyamide, polyacetal, polyphenylene oxide, polybutylene terephthalate, ethylene-propylene-dienterate polymer (EPDM), sulfonated EPDM, styrene butadiene Examples include rubber, fluororubber, and various copolymers.

[0122] For example, the polymer material may be polyvinylpyrrolidone (PVP).

[0123] In one embodiment, the content of the conductive polymer introduced in the step of introducing the conductive polymer into the precursor powder may be 0.1% or more and 6.5% or less based on 100% by weight of the total weight of the negative electrode active material.

[0124] For example, the content of the conductive polymer introduced above may be 0.5 wt% or more, 6.5 wt% or less, 0.5 wt% or more, 6 wt% or less, 0.5 wt% or more, 5 wt% or less, 1 wt% or more, 6.5 wt% or less, 1 wt% or more, 6 wt% or less, or 1 wt% or more, 5 wt% or less, based on 100 wt% of the total weight of the negative electrode active material.

[0125] At this time, the metal-containing particles may be connected to each other through the conductive polymer.

[0126] In one embodiment, in the step of introducing a conductive polymer into the precursor powder, amorphous carbon, crystalline carbon, or a combination thereof is additionally included,

[0127] The above amorphous carbon is formed from one or more selected from the group consisting of coal-based pitch, mesophase pitch, petroleum-based 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 vinyl chloride resin, block copolymer, polyol, and polyimide resin.

[0128] The crystalline carbon above may be formed from one or more selected from the group consisting of natural graphite, artificial graphite, expanded graphite, graphene, carbon black, and fullerene.

[0129] Natural graphite is graphite that occurs naturally and includes flake graphite, high crystalline graphite, and amorphous (microcrystalline or cryptocrystalline; amorphous) graphite. Artificial graphite is graphite that is artificially synthesized and is produced by heating amorphous carbon to high temperatures; it includes primary or electrographite, secondary graphite, and graphite fiber.

[0130] Expanded graphite is produced by intercalating chemicals, such as acids or alkalis, between layers of graphite and heating them to expand the vertical layers of the molecular structure. Graphene comprises a single layer or multiple single layers of graphite.

[0131] Carbon black is a crystalline material with less regularity than graphite, and carbon black can be transformed into graphite when heated at approximately 3,000°C for a long time. Fullerene is a carbon mixture containing at least 3% by weight of fullerene, which is a polyhedral bundle-shaped compound composed of 60 or more carbon atoms. The first carbon-based material may use such crystalline carbon as a single type or in combination of two or more types. For example, natural graphite or artificial graphite may be used. The crystalline carbon may have a spherical, plate-like, fibrous, tubular, or powder form.

[0132] Preferably, pitch can be used as the amorphous carbon. Pitch with a softening point of 100 to 250°C can be used, and in particular, petroleum-based or coal-based pitch with a QI (Quinolone Insoluble) content of 5% by weight or less, more preferably 1% by weight or less can be used.

[0133] Meanwhile, natural graphite can preferably be used as the crystalline carbon. The graphite can be of high purity with a fixed carbon content of 99 weight% or more, more preferably 99.95 weight% or more.

[0134] In addition, flake graphite may be suitable for increasing conductivity through contact with metal-containing particles.

[0135] In one embodiment, the method for manufacturing the cathode active material may include a compounding step.

[0136] The above compounding step can be performed by a physical method.

[0137] The above physical method may include one or more selected from the group consisting of high-energy processes such as milling, stirring, mixing, and compression.

[0138] For example, the compounding step can be performed by ball milling. In particular, a planetary ball mill can efficiently mix and grind the mixture by a mixing method in which the mixture rotates and revolves in a non-contact manner with the composition.

[0139] The balls that can be used for ball milling may be, for example, zirconia balls, and there are no restrictions on the type of ball. The size of the ball may be, for example, about 0.3 to 10 mm, but is not limited thereto.

[0140] Meanwhile, the reaction time of the compounding step can be 1 minute to 24 hours, the reaction temperature can be 40 to 1000℃, and the reaction atmosphere can be carried out under the conditions of air or an inert atmosphere.

[0141] In addition, the processing temperature of the heat treatment step may be 100°C or higher, and preferably 200°C or lower.

[0142] For example, it can be dried in an oven at a temperature of 100°C or higher and 150°C or lower.

[0143] The heat treatment time is not specifically limited, but can be performed, for example, in the range of 12 to 30 hours.

[0144] For example, it can be dried in an oven at a temperature of 100°C or higher and 150°C or lower for 22 to 26 hours.

[0145] An electrode according to another aspect of the present invention may include the negative electrode active material, and a lithium secondary battery may include the electrode including the negative electrode active material as the negative electrode, a positive electrode positioned opposite to the negative electrode, and an electrolyte disposed between the negative electrode and the positive electrode.

[0146] In one embodiment, the initial discharge capacity of a secondary battery comprising an electrode containing the negative electrode active material of the present invention as a negative electrode, a positive electrode positioned opposite to the negative electrode, and an electrolyte disposed between the negative electrode and the positive electrode may be 1,700 mAh / g to 2,000.1 mAh / g, an initial efficiency of 85% to 95%, a capacity retention rate of 85% to 95%, and an output characteristic of 85% to 95%.

[0147] For example, the initial discharge capacity may be 1750 mAh / g to 1900.1 mAh / g, 1800 mAh / g to 1900.1 mAh / g, or 1830 mAh / g to 1870 mAh / g.

[0148] For example, the initial efficiency may be 85% to 92%, 87% to 92%, or 88% to 90%.

[0149] For example, the dosage retention rate may be 85% to 92%, 87% to 92%, or 87% to 90%.

[0150] For example, the output characteristics may be 85% to 92%, 85% to 92%, or 87% to 90%.

[0151] In one embodiment, the electrode plate expansion rate of the secondary battery containing the negative electrode active material of the present invention may be 25% to 35%.

[0152] For example, the electrode expansion rate may be 25% to 34%, 27% to 34%, or 29% to 34%.

[0153] In one embodiment, the resistance value DC-IR of the secondary battery containing the negative electrode active material of the present invention may be 630 to 780 mΩ.

[0154] For example, the above resistance value DC-IR may be 630 to 770 mΩ, 630 to 760 mΩ, or 650 to 760 mΩ.

[0155] The above cathode includes the above cathode active material and can be manufactured by, for example, by mixing the above cathode active material, a binder, and optionally a conductive agent in a solvent to prepare a cathode active material composition, and then molding it into a certain shape or applying it to a current collector such as copper foil.

[0156]

[0157] In addition to the aforementioned cathode active material, the above-described cathode may additionally include a cathode active material material that is conventionally used as a cathode active material for lithium batteries in the relevant technical field. Commonly used cathode active material materials may include, for example, one or more selected from the group consisting of lithium metal, metals alloyable with lithium, transition metal oxides, non-transition metal oxides, and carbon-based materials.

[0158] For example, the metals that can be alloyed with the lithium may be Si, Sn, Al, Ge, Pb, Bi, Sb Si-Y alloys (wherein Y is an alkali metal, alkaline earth metal, group 13 element, group 14 element, transition metal, rare earth element, or a combination thereof, and is not Si), Sn-Y alloys (wherein Y is an alkali metal, alkaline earth metal, group 13 to 16 element, transition metal, rare earth element, or a combination thereof, and is not Sn), etc. The above 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.

[0159] For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, lithium vanadium oxide, etc.

[0160] For example, the above non-transfer metal oxides are SnO2, SiOx(0 <x≤2) 등일 수 있다. 상기 탄소계 재료로는 결정질 탄소, 비정질 탄소 또는 이들의 혼합물일 수 있다. 상기 결정질 탄소는 무정형, 판상, 린편상(flake), 구형 또는 섬유형의 천연 흑연 또는 인조 흑연과 같은 흑연일 수 있으며, 상기 비정질 탄 소는 소프트 카본(soft carbon: 저온 소성 탄소) 또는 하드 카본(hard carbon), 메조페이스 피치(mesophase pitch) 탄화물, 소성된 코크스 등일 수 있다.

[0161] When the above-mentioned negative electrode active material and carbon-based material are used together, the oxidation reaction of the silicon-based active material is suppressed, and an SEI film is effectively formed to form a stable film and improve electrical conductivity, thereby further enhancing the charge and discharge characteristics of lithium.

[0162] 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.

[0163] The binder used in the above-mentioned cathode active material composition is a component that assists in the bonding of the cathode active material and the conductive agent, and in the bonding to the current collector, and is added in an amount of 1 to 50 parts by weight based on 100 parts by weight of the cathode active material. For example, the binder may be added in a range of 1 to 30 parts by weight, 1 to 20 parts by weight, or 1 to 15 parts by weight based on 100 parts by weight of the cathode active material.

[0164] Examples of such binders include polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile butadiene styrene, phenolic resin, epoxy resin, polyethylene terephthalate, polytetrafluoroethylene, polyphenyl sulfide, polyamideimide, polyetherimide, polyethylenesulfone, polyamide, polyacetal, polyphenylene oxide, polybutylene terephthalate, ethylene-propylene-dienterate polymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers. there is.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] As the above-mentioned positive active material, any lithium-containing metal oxide commonly used in the relevant technical field may be used.

[0174] For example, Li a A 1-b B b D2 (wherein 0.90≤a≤1.8, and 0≤b≤0.5); Li a E 1-b B b O 2-c D 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-αF 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 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 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 G d 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 GeO2(wherein the above 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 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 aMnG 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.

[0175] 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.

[0176] 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.

[0177] 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. can be used.

[0178] 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 pores inside 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.

[0179] The above positive current collector has a thickness of 3 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.

[0180] 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.

[0181] 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.

[0182] 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.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] Any lithium salt commonly used in lithium batteries may be used, and as a substance that dissolves well in the above-mentioned non-aqueous electrolyte, examples include LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB 10 Cl 10One 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.

[0187] 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.

[0188] The manufacturing methods of these batteries are widely known in this field, so a detailed explanation is omitted.

[0189]

[0190] The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited thereto.

[0191]

[0192] [Example 1]

[0193] 1 wt% of silicon particles (Metal Grade Silicon, MGS) and 10 wt% of isopropyl alcohol (IPA) were mixed and fed into a bead mill, and the mixture was ground until the average particle size (D50) of the silicon particles became 109 nm to prepare a ground silicon solution.

[0194] Polyvinylpyrrolidone (PVP) was added to the prepared ground silicon solution in a weight ratio of 10 to 20 relative to the weight of the silicon.

[0195] Subsequently, a silicon precursor with an average particle size (D50) of 7.5 μm was prepared by spray drying.

[0196] 1% by weight of the prepared silicon precursor and 10% by weight of water were added to a beaker and dispersed by stirring.

[0197] Subsequently, PEDOT:PSS, a copolymer of poly(3,4-ethylenedioxythiophene), PEDOT, and polyphenylene sulfide (PPS), was added as a conductive polymer at 3% by weight based on the total weight of the negative electrode active material.

[0198] Subsequently, the composite material was prepared by drying it in a 120°C oven for 24 hours under an inert atmosphere.

[0199] The above composite material was classified into 400 mesh to obtain a negative active material.

[0200] At this time, the average particle size (D50) of the silicon particles and the silicon precursor was measured using a particle size meter (Mastersizer 3000, Malvern Panalytical) with an organic solution in which the silicon particles and the silicon precursor were dispersed.

[0201]

[0202] [Example 2]

[0203] A negative electrode active material was prepared in the same manner as in Example 1, except that the content of the added conductive polymer was 1% by weight based on the total weight of the negative electrode active material.

[0204]

[0205] [Example 3]

[0206] A negative electrode active material was prepared in the same manner as in Example 1, except that the content of the added conductive polymer was 5% by weight based on the total weight of the negative electrode active material.

[0207]

[0208] [Example 4]

[0209] A negative electrode active material was prepared in the same manner as in Example 1, except that the content of the added conductive polymer was 7% by weight based on the total weight of the negative electrode active material.

[0210]

[0211] [Comparative Example 1]

[0212] Pitch and graphite were introduced into a compositer (manufactured by Hansol Chemical) to the silicon precursor prepared in Example 1 above so that the weight ratio of silicon precursor:pitch:graphite was 60:20:20, and composited for 20 minutes to perform mixing and coating processes.

[0213] Subsequently, a composite material was manufactured by heat treating at 930°C for 6 hours under an argon (Ar) gas atmosphere.

[0214] The above composite material was ground using a jet mill and then classified into 400 mesh to obtain a cathode active material.

[0215] At this time, the conductive polymer of Example 1 above was not added.

[0216]

[0217] [Comparative Example 2]

[0218] A negative electrode active material was prepared in the same manner as in Example 1, except that the above-mentioned conductive polymer was not added.

[0219]

[0220] [Preparation Example]

[0221] Coin Half Cell Production

[0222] Based on the total weight of the cathode active material, a cathode slurry was prepared by uniformly mixing 9 wt% of the cathode active material prepared according to Examples 1 to 4 and Comparative Examples 1 and 2, 84 wt% of natural graphite, 3 wt% of carbon fiber conductive material, 2 wt% of carboxymethylcellulose, and 2 wt% of styrene-butadiene rubber binder in a pure solvent.

[0223] 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.

[0224] 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.

[0225]

[0226] Coin pool cell production

[0227] The cathode used in the above coin half cell was used, and the anode was manufactured as follows. Based on the total weight of the anode active material, 96 wt% of LiNi0.6Co0.2Mn0.2O2 as the anode active material and 2 wt% of polyvinylidene fluoride (PVDF) as the binder were mixed in an N-methylpyrrolidone solvent to prepare an anode slurry, 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.

[0228] A CR2032 type coin pool cell was manufactured using the above anode and cathode, a PE separator as the separator, and 1.0M LiPF6 dissolved in a mixed solvent of EC (ethylene carbonate): DEC (diethyl carbonate) (3:7 volume ratio) + FEC 5% as the electrolyte.

[0229]

[0230] Evaluation Example 1: Component analysis of cathode active material

[0231] The weight percentage of PEDOT:PSS introduced as a conductive polymer in Examples 1 to 4 and Comparative Examples 1 and 2, whether pitch and graphite were used, and the weight ratio of each component (silicon precursor: pitch: graphite) when pitch and graphite were used are shown in Table 1 below.

[0232] PEDOT:PSS copolymer (weight%) Use of pitch and graphite Silicone precursor: Pitch: Graphite (weight parts) Example 13 Not used Example 21 Not used Example 35 Not used Example 47 Not used Comparative Example 10 Used 60:20:20 Comparative Example 20 Not used

[0233] According to Table 1 above, the weight percentage of PEDOT:PSS introduced as a conductive polymer in Examples 1 to 4 and Comparative Examples 1 and 2 was 0% to 7%, and when pitch and graphite were used, the weight ratio of each component (silicon precursor: pitch: graphite) was 60:20:20.

[0234]

[0235] Evaluation Example 2: Battery Characteristics Evaluation

[0236] The battery characteristics of coin half cells and coin full cells manufactured using the negative electrode active materials prepared according to Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated as follows.

[0237] Coin pool cells were used to evaluate lifespan characteristics and electrode expansion rates, while coin half cells were used for evaluating other battery characteristics.

[0238] Coin half cells prepared using the negative active materials prepared according to Examples 1 to 4 and Comparative Examples 1 and 2 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 cells were fully charged, they were rested for 10 minutes, and then discharged with a constant current of 0.1C until the voltage reached 2.7V (vs. Li) (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.

[0239] 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).

[0240]

[0241] The measured initial discharge capacity, initial efficiency, lifespan characteristics (capacity retention rate), output characteristics, electrode plate expansion rate, and resistance value DC-IR of cells using the negative electrode active materials prepared according to Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 2 below.

[0242]

[0243] The initial discharge capacity is the discharge capacity in the first cycle.

[0244] The initial efficiency, lifespan characteristics, output characteristics, and electrode plate expansion rate were each calculated from the following mathematical formulas 2 to 5.

[0245]

[0246] <Mathematical Formula 2>

[0247] Initial efficiency [%] = [Discharge capacity in the 1st cycle / Charge capacity in the 1st cycle] × 100

[0248]

[0249] <Mathematical Formula 3>

[0250] Lifespan Characteristic (Capacity Retention Rate) [%] = [Discharge Capacity of the 100th Cycle / Discharge Capacity of the 1st Cycle] × 100

[0251]

[0252] <Mathematical Formula 4>

[0253] Output Characteristics[%] = (Discharge Capacity at 1.0C / Discharge Capacity at 0.1C) x 100

[0254]

[0255] <Mathematical Formula 5>

[0256] Expansion Rate = [(Thickness of negative electrode plate after 100 charge / discharge cycles - Thickness of current collector) / (Thickness of negative electrode plate before charge / discharge - Thickness of current collector)] × 100%

[0257]

[0258] The resistance value DC-IR was determined by using the negative active materials prepared according to Examples 1 to 4 and Comparative Examples 1 and 2 to charge a coin half cell at 25°C at a constant current rate of 0.1C until the voltage reached 0.01V (vs. Li), and then charging it at a constant voltage while maintaining 0.01V until the current reached 0.05C. After the charging was completed, the cell was rested for 10 minutes, and then discharged at a constant current of 0.1C until the voltage reached 1.5V (vs. Li) (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.

[0259] At this time, the discharge capacity in the first cycle was calculated. In the same way, based on the discharge capacity calculated in the 50th cycle, the DC-IR value was measured by measuring the change in current twice under SOC50 conditions of 0.3C for 300 seconds and 3C for 30 seconds.

[0260] Initial Discharge Capacity (mAh / g) Initial Efficiency (%) Capacity Retention Rate (%) Output (%) Plate Expansion Rate (%) DC-IR (mΩ) Example 1 184 389.289.188.529687.8 Example 2 186 489.188.588.231705.8 Example 3 185 588.887.987.232719.2 Example 4 183 388.687.085.334754.9 Comparative Example 1 175 689.086.287.033793.1 Comparative Example 2 188 689.083.486.936804.9

[0261] According to Table 2 above, it was confirmed that the initial efficiency of the secondary battery using the negative electrode active material prepared according to Examples 1 to 4 was 88.6% or higher, which is equivalent to the initial efficiency of Comparative Examples 1 and 2. In particular, it was confirmed that the initial efficiency of the secondary battery using the negative electrode active material prepared according to Example 1 was the highest at 89.2% or higher.

[0262] In addition, it was confirmed that the output characteristics of the secondary battery using the negative electrode active material prepared according to Examples 1 to 3 were 87.2% or higher, which is an improvement compared to the secondary battery using the negative electrode active material of Comparative Examples 1 and 2.

[0263] Specifically, the initial discharge capacity of the secondary battery using the negative electrode active material of Examples 1 to 4 was 1833~1864 mAh / g, the initial efficiency was 88.6~89.2%, the capacity retention rate was 87.0~89.1%, the output characteristics were 85.3~88.5%, the electrode plate expansion rate was 29~34%, and the resistance value DC-IR was 687.8~754.9 mΩ.

[0264] In the case of a secondary battery using the negative active material of Comparative Example 2, in which no conductive polymer, pitch, or graphite was added, it was confirmed that the capacity retention rate of the secondary battery was reduced and the electrode expansion rate and resistance value DC-IR were significantly increased compared to the secondary battery using the negative active materials of Examples 1 to 4.

[0265] In addition, in the case of a secondary battery using the negative electrode active material of Comparative Example 1, which contains pitch and graphite without the addition of a conductive polymer, it was confirmed that compared to a secondary battery using the negative electrode active material of Examples 1 to 4, the initial discharge capacity and capacity retention rate were reduced, the electrode plate expansion rate was slightly increased, and the resistance value DC-IR was increased.

[0266] In other words, it was confirmed that when the content of the added conductive polymer falls within the range of the present invention, the binding strength of the negative electrode active material is strengthened due to the binding properties of the conductive polymer, enabling stable expansion and contraction, thereby improving the lifespan characteristics (capacity retention rate) of the battery.

[0267] In addition, when the content of the conductive polymer introduced into the negative electrode active material falls within the scope of the present invention, forming a conductive polymer coating layer on the surface of the metal-containing particles facilitates the electrical connection between the metal-containing particles, thereby improving the output characteristics of the battery and reducing the resistance value DC-IR.

[0268] Meanwhile, in the case of a secondary battery using the negative electrode active material of Example 4, in which PEDOT:PSS was added at 7 wt% based on the total weight of the negative electrode active material, the output characteristics were actually lowered compared to the secondary battery using the negative electrode active material prepared according to Examples 1 to 3 and Comparative Examples 1 and 2, and it was confirmed that the resistance value DC-IR increased compared to the secondary battery using the negative electrode active material prepared according to Examples 1 to 3.

[0269] This is interpreted as the electrode plate resistance value increasing when the content of the conductive polymer exceeds the range of the present invention, because the amount of conductive polymer coating on the surface of the metal-containing particles becomes too large, leaving no voids for the electrolyte to infiltrate inside the metal-containing particles.

[0270] As a result, it was confirmed that a secondary battery having improved discharge capacity, lifespan characteristics (capacity retention rate), initial efficiency, output characteristics, electrode plate expansion rate, and DC-IR resistance value can be manufactured by appropriately adjusting the content of the conductive polymer introduced into the negative electrode active material to the range of the present invention.

[0271]

[0272] 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.

[0273]

[0274] The negative electrode active material according to the present invention comprises at least one metal-containing particle and a conductive polymer, and as the conductive polymer coats the surface of the metal-containing particle in whole or in part, the binding strength of the negative electrode active material can be enhanced due to the binding properties of the conductive polymer.

[0275] In particular, by strengthening the binding force of the negative electrode active material with large volume expansion, it has the effect of providing a secondary battery with improved lifespan characteristics.

[0276] In addition, due to the high electrical conductivity of the conductive polymer, it has the effect of providing a secondary battery with improved output characteristics.

[0277] In addition, it has the effect of enabling the manufacture of cathode active materials optimized for high capacity and high efficiency.

Claims

Comprising at least one metal-containing particle and a conductive polymer, Cathode active material. In paragraph 1, The metal-containing particles are coated with the conductive polymer, either wholly or partially on the surface. Cathode active material. In paragraph 1, The above metal-containing particles comprise one or more selected from the group consisting of Si, Al, Sn, Ge, Pb, In, As, Sb, P, and Ag. Cathode active material. In paragraph 1, Based on 100% by weight of the total weight of the negative electrode active material, The content of the conductive polymer is 0.1 wt% or more and 6.5 wt% or less, Cathode active material. In paragraph 1, The conductive polymer is a poly(3,4-ethylenedioxythiophene) (PEDOT) homopolymer or copolymer, a polyphenylene sulfide (PPS) homopolymer or copolymer, a polyaniline (PANI) homopolymer or copolymer, a polypyrrole (PPY) homopolymer or copolymer, a polyacetone (PAC) homopolymer or copolymer, a polyphenylene vinylene (PPV) homopolymer or copolymer, or a combination thereof. Cathode active material. In paragraph 1, The conductive polymer is a copolymer of the polyethylenedioxythiophene (Poly(3,4-ethylenedioxythiophene), PEDOT) and the polyphenylene sulfide (PPS), Cathode active material. In paragraph 1, The pH of the above conductive polymer is 2 or higher and 5 or lower, and Viscosity of 10 cP or more and 300 cP or less, Cathode active material. In paragraph 1, electrical conductivity of 3 S / cm or higher, Cathode active material. In paragraph 1, Amorphous carbon, crystalline carbon, or a combination thereof additionally comprising, Cathode active material. In paragraph 1, The above metal-containing particles are silicon (Si)-containing particles, Cathode active material. In paragraph 1, The average particle size (D50) of the metal-containing particles is 60 nm or more and 160 nm or less, Cathode active material. A method for manufacturing a negative electrode active material according to any one of claims 1 to 11, A step of preparing a precursor powder by spray-drying a solution containing metal-containing particles; A step of introducing a conductive polymer into the above precursor powder; and Includes a heat treatment step; The above metal comprises one or more selected from the group consisting of Si, Al, Sn, Ge, Pb, In, As, Sb, P, and Ag. Method for manufacturing a negative electrode active material. In Paragraph 12, In the step of adding the conductive polymer to the above precursor powder, the content of the conductive polymer added is 0.1% by weight or more and 6.5% by weight or less, based on 100% by weight of the total weight of the negative electrode active material. Method for manufacturing a negative electrode active material. A cathode active material comprising any one of claims 1 to 11, electrode. A cathode comprising a cathode active material according to any one of claims 1 to 11; An anode positioned opposite to the above cathode; and an electrolyte disposed between the above-mentioned cathode and the above-mentioned anode; comprising Lithium secondary battery.

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