WO2022108268A1 - Matériau actif d'anode et batterie secondaire au lithium le comprenant - Google Patents

Matériau actif d'anode et batterie secondaire au lithium le comprenant Download PDF

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WO2022108268A1
WO2022108268A1 PCT/KR2021/016606 KR2021016606W WO2022108268A1 WO 2022108268 A1 WO2022108268 A1 WO 2022108268A1 KR 2021016606 W KR2021016606 W KR 2021016606W WO 2022108268 A1 WO2022108268 A1 WO 2022108268A1
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active material
secondary battery
lithium secondary
negative active
long axis
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PCT/KR2021/016606
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English (en)
Korean (ko)
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원종민
김영욱
김재명
나재호
신창수
염철
이대혁
이중호
추희영
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삼성에스디아이 주식회사
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/364—Composites as mixtures
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/386—Silicon or alloys based on silicon
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • It relates to an anode active material and a lithium secondary battery including the same.
  • Lithium secondary batteries which have recently been spotlighted as power sources for portable and small electronic devices, use an organic electrolyte, and thus exhibit a discharge voltage that is twice or more higher than that of batteries using an aqueous alkali solution, resulting in high energy density.
  • LiCoO 2 , LiMn 2 O 4 , LiNi 1-x Co x O 2 (0 ⁇ x ⁇ 1) Oxides are mainly used.
  • One embodiment is to provide an anode active material for a lithium secondary battery capable of suppressing volume expansion during charging and discharging, thereby improving cycle life characteristics.
  • Another embodiment is to provide a lithium secondary battery including the negative active material.
  • an anode active material for a lithium secondary battery including at least one silicon primary particle assembled secondary particle and amorphous carbon, and having a donut shape with an empty center.
  • the ratio of the long axis length of the central part to the long axis length of the negative active material may be 0.2 or more, and may be 0.2 to 0.9.
  • the amorphous carbon may surround the surface of the primary particle and the surface of the secondary particle.
  • the silicon primary particles may have a particle diameter of 10 nm to 200 nm.
  • the long axis length of the negative active material may be 50 ⁇ m or less, or 4 ⁇ m to 50 ⁇ m.
  • the amorphous carbon may be soft carbon, hard carbon, or a combination thereof.
  • the silicon primary particles may be of a flake type.
  • the silicon primary particles may have an aspect ratio (width/thickness) of 5 to 20.
  • the negative electrode including the negative active material; a positive electrode including a positive electrode active material; and a lithium secondary battery including a non-aqueous electrolyte.
  • the negative active material for a lithium secondary battery according to an exemplary embodiment can reduce stress due to volume expansion generated during charging and discharging, thereby exhibiting excellent cycle life characteristics.
  • FIG. 1 is a view schematically showing an anode active material for a lithium secondary battery according to an embodiment
  • FIG. 2 is a view schematically showing a lithium secondary battery according to another embodiment.
  • FIG. 3A is a SEM photograph of a negative active material for a lithium secondary battery prepared according to Example 1.
  • FIG. 3A is a SEM photograph of a negative active material for a lithium secondary battery prepared according to Example 1.
  • Figure 3b is an SEM photograph showing an enlarged view of Figure 3a.
  • Figure 3c is an SEM photograph of the negative electrode prepared according to Example 1.
  • the negative active material for a lithium secondary battery includes secondary particles and amorphous carbon to which at least one silicon primary particles are assembled, and has a donut shape in which the central portion of the negative active material is empty.
  • 1 schematically shows such a negative active material
  • the negative active material 1 includes secondary particles and amorphous carbon 5 to which silicon primary particles 3 are assembled, and the central portion (a) is empty, so that the entire has the shape of a donut. 1 shows that the silicon primary particles (3) in the center are exposed to show that they are located, but in reality, the silicon primary particles (3) in the center are also covered with amorphous carbon (5), most of which are It is not exposed to the outside.
  • the negative active material according to an exemplary embodiment has an empty center and thus the whole has a donut shape, in which an area with an empty center, that is, a hole, is open to the outside and exposed to the outside.
  • a typical silicon-based negative active material if the center is not empty and is filled, volume expansion occurs due to silicon during charging and discharging. have.
  • the negative active material according to one embodiment has a donut shape exposed to the outside while the center is empty, the stress received during the volume expansion of the negative active material during battery charging and discharging is low, and the shape is maintained between lithium ion insertion/deintercalation It has the advantage of being easy to do.
  • the inside of the negative active material having a donut shape is empty, a binder and a conductive material may be filled into the inside of the negative electrode when the negative electrode is manufactured. Therefore, compared to the case in which the hollow part is not exposed to the outside, the density is excellent, and a battery having a high current density can be provided.
  • the negative electrode since the hole in the center is opened to the outside, the surface area of the active material is increased, so that the number of reaction sites can be increased.
  • the ratio of the long axis length of the central axis to the long axis length of the negative electrode active material may be 0.2 or more, 0.2 to 0.9, or 0.6 to 0.9.
  • the length of the major axis refers to a diameter when the active material and the central portion are substantially spherical, and refers to a length of the long axis when the active material and the central portion are substantially spherical.
  • the conductive material and the binder may be positioned at the center of the active material during the preparation of the negative electrode to facilitate the movement of lithium ions, and the high packing density of the active material layer can enable
  • the long axis length of the negative active material may be 50 ⁇ m or less, or 4 ⁇ m to 50 ⁇ m.
  • the long axis length of the center may be 4 ⁇ m to 49 ⁇ m, may be 6 ⁇ m to 14 ⁇ m.
  • the long axis length of the anode active material is within the above range, lithium ions may easily diffuse into the anode active material, and electrical resistance and rate characteristics may be further improved.
  • the long axis length of the central portion is included in the above range, there may be an advantage in that the negative electrode active material is more uniformly dispersed in the negative electrode to reduce expansion.
  • the particle diameter may be an average particle diameter of the particle diameters.
  • the average particle diameter may mean a particle diameter (D50) measured as a cumulative volume volume.
  • the particle diameter (D50) means the average particle diameter (D50), which means the diameter of particles having a cumulative volume of 50% by volume in the particle size distribution.
  • the average particle diameter (D50) can be measured by a method well known to those skilled in the art, for example, it is measured with a particle size analyzer, or a transmission electron microscope photograph or a scanning electron microscope (Scanning). It can also be measured with an electron microscope. As another method, it is measured using a measuring device using dynamic light-scattering, data analysis is performed, the number of particles is counted for each particle size range, and the average particle diameter ( D50) value can be obtained.
  • the amorphous carbon is positioned while surrounding the secondary particle surface, and as shown in enlarged view in FIG. 1, amorphous carbon is filled between the primary particles 3, while surrounding the primary particle surface can be located
  • amorphous carbon is filled between the primary particles, it is possible to more effectively prevent the silicon primary particles from being directly exposed to the electrolyte, thereby forming a more stable interface.
  • the amorphous carbon is filled between the silicon primary particles and located on the surface of the primary particles, it can serve as a path for electrons to move between the silicon primary particles and the electrolyte to further improve conductivity, thereby further increasing the electrode resistance. can be reduced
  • the amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbide, calcined coke, or a combination thereof.
  • the silicon primary particles are nanoparticles, and may have a particle diameter of 10 nm to 200 nm.
  • the particle diameter may be an average particle diameter of the particle diameters.
  • the average particle diameter may mean a particle diameter (D50) measured as a cumulative volume volume.
  • the particle diameter (D50) means the average particle diameter (D50), which means the diameter of particles having a cumulative volume of 50% by volume in the particle size distribution.
  • the average particle diameter (D50) can be measured by a method well known to those skilled in the art, for example, it is measured with a particle size analyzer, or a transmission electron microscope photograph or a scanning electron microscope (Scanning). It can also be measured with an electron microscope. As another method, it is measured using a measuring device using dynamic light-scattering, data analysis is performed, the number of particles is counted for each particle size range, and the average particle diameter ( D50) value can be obtained.
  • the particle diameter of the secondary particles to which the primary particles are assembled may be 2 ⁇ m to 15 ⁇ m, may be 5 ⁇ m to 10 ⁇ m.
  • the particle size of the secondary particles is included in the above range, lithium ions may more easily diffuse into the negative active material, and electrical resistance and rate characteristics may be further improved.
  • the silicon primary particles may be of a flake type. That is, the silicon primary particle may be flaky having a long axis and a short axis, and in this case, a ratio of the long axis/short axis of the Si particle, for example, a width/thickness may be 5 to 20.
  • a ratio of the long axis/short axis of the Si particles is within the above range, the expansion of the silicon primary particles can be reduced, and thus the initial efficiency and lifespan characteristics of the battery including the active material can be improved.
  • the half-width FWHM (111) of the diffraction peak of the (111) plane by X-ray diffraction using CuK ⁇ of the silicon primary particles may be 0.5 degrees (°) to 7 degrees (°).
  • the half-maximum width FWHM (111) of the silicon primary particle is included in the above range, lifespan characteristics of the battery may be improved.
  • the negative active material according to an embodiment may be manufactured by the following process.
  • a silicone particle solution is prepared by adding the silicone particles and a dispersing agent to a solvent so that the solid content is 6 wt% to 15 wt% based on 100 wt% of the total particle solution.
  • an anode active material having a desired donut shape may be manufactured. If the solid content is out of the above range, the anode active material having a porous spherical shape rather than a donut shape can be prepared because the solid content cannot easily move to the outside when the silicon particle liquid, that is, the droplets are dried in the subsequent drying process. Not appropriate.
  • the silicon particles may be nanometer-sized primary particles or micrometer-sized bulk silicon.
  • alcohols that are easily volatilized without oxidizing the silicon particles may be suitably used, for example, isopropyl alcohol, ethanol, methanol, butanol, N-methyl pyrrolidone, propylene glycol, or a combination thereof.
  • the dispersant includes stearic acid, polyvinylpyrrolidone, polyvinyl alcohol, polyacrylic acid, gallic acid, carboxymethyl cellulose, sucrose, ethylene glycol, citric acid, or these may be a combination of
  • the mixing ratio of the silicon particles and the dispersant may be 100: 40 to 100: 10 by weight.
  • the silicon particles can be effectively dispersed in the solvent, and the amorphous carbon can better surround the surfaces of the primary particles and the secondary particles, which is appropriate.
  • the mixing process may be performed using a bead mill or a ball mill. In this milling process, bulk silicon may be pulverized into nano-sized primary particles, and this mixing process is pulverized It may be carried out so that the silicon particle size is 10 nm to 200 nm.
  • the primary particles may be nanoparticles, which may be nanoparticles having a particle diameter of 10 nm to 200 nm. Silicon primary particles of these nanoparticles can be obtained by performing a process for obtaining conventional nanoparticles, such as a pulverization process.
  • the half-width FWHM(111) of the diffraction peak of the (111) plane by X-ray diffraction using CuK ⁇ ray of the silicon primary particle may be 0.5 degrees (°) to 7 degrees (°).
  • the silicon primary particles may have an aspect ratio (width/thickness) of 5 to 20.
  • a process of uniformly dispersing the obtained mixed solution using a homogenizer may be further performed.
  • the prepared silicone particle solution is spray-dried.
  • the solvent on the surface of the droplet is first dried and when the solvent inside moves to the outside, the solids move together to form a donut shape.
  • the spray drying process can be carried out using a nozzle, and the nozzle is a two fluid nozzle capable of forming fine particles by mixing two fluids of a liquid and a gas, and a disk type.
  • a gas such as a nozzle or an ultrasonic nozzle, may be used, and there is no need to be limited thereto.
  • the spray drying process is performed while flowing the nozzle gas at a pressure (flow rate) of 0.3 Mpa to 0.8 MPa (blowing while blowing), and it is appropriate to carry out while injecting the silicon particle solution at an input amount of 25 g/min to 500 g/min. do.
  • N 2 , Ar, O 2 , CH 4 , or a combination thereof may be used as the nozzle gas.
  • the inlet temperature of the equipment used in the spray drying process for example, the inlet temperature of the nozzle used
  • the type of solvent of the silicon particle solution for example, the boiling point of the solvent used. It can be carried out within the range of +30 °C to the boiling point of the solvent +70 °C.
  • ethanol when used as a solvent, it may be carried out within the range of 108.37° C. to 148.37° C.
  • the speed at which the droplets are dried and the viscosity of the moving solvent can be controlled, so that the silicone primary particles are assembled to form secondary particles, and a donut shape with an empty center can be manufactured. .
  • the obtained secondary particles are mixed with an amorphous carbon precursor.
  • the mixing ratio of the secondary particles and the amorphous carbon precursor may be 80:20 to 60:40 by weight.
  • a polymer resin such as coal-based pitch, mesophase pitch, petroleum-based pitch, mesocarbon pitch, coal-based oil, petroleum-based heavy oil or phenol resin, furan resin, and polyimide resin can be used.
  • the obtained mixture is heat-treated to prepare an anode active material for a lithium secondary battery.
  • the heat treatment process may be performed at 700°C to 1000°C.
  • the heat treatment process may be performed in an N 2 atmosphere or an argon atmosphere.
  • the amorphous carbon precursor may be converted to amorphous carbon and formed to surround the surface of the secondary particles.
  • a lithium secondary battery including a negative electrode, a positive electrode, and an electrolyte.
  • the negative electrode may include a current collector and a negative active material layer formed on the current collector and including the negative active material according to an exemplary embodiment.
  • the anode active material layer may further include a crystalline carbon anode active material.
  • crystalline carbon negative active material include graphite such as natural graphite or artificial graphite in amorphous, plate-like, flake, spherical, or fibrous shape.
  • the mixing ratio of the first negative active material: the second negative active material is 1:99 to It may be a 40:60 weight ratio.
  • the first negative active material and the second negative active material are mixed and used within the above range, the negative electrode current density can be further improved, and a thin film electrode can be manufactured.
  • the first negative active material including silicon in the negative electrode may be more uniformly present, and thus the expansion of the negative electrode may be more effectively suppressed.
  • the content of the negative active material in the negative active material layer may be 95 wt% to 99 wt% based on the total weight of the negative active material layer.
  • the negative active material layer includes a binder, and may optionally further include a conductive material.
  • the content of the binder in the anode active material layer may be 1 wt% to 5 wt% based on the total weight of the anode active material layer.
  • 90 wt% to 98 wt% of the negative active material, 1 wt% to 5 wt% of the binder, and 1 wt% to 5 wt% of the conductive material may be used.
  • the binder serves to well adhere the negative active material particles to each other and also to adhere the negative active material to the current collector.
  • a non-aqueous binder, an aqueous binder, or a combination thereof may be used as the binder.
  • non-aqueous binder examples include ethylene propylene copolymer, polyacrylonitrile, polystyrene, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.
  • aqueous binder examples include styrene-butadiene rubber, acrylated styrene-butadiene rubber (ABR), acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, ethylene oxide-containing polymer, polyvinylpyrrolidone , polyepichlorohydrin, polyphosphazene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or a combination thereof can be
  • a cellulose-based compound capable of imparting viscosity may be further included.
  • the cellulose-based compound one or more of carboxymethyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, or alkali metal salts thereof may be mixed and used.
  • the alkali metal Na, K or Li may be used.
  • the amount of the thickener used may be 0.1 parts by weight to 3 parts by weight based on 100 parts by weight of the negative active material.
  • the conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used without causing a chemical change.
  • the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; Metal-based substances, such as metal powders, such as copper, nickel, aluminum, and silver, or a metal fiber; conductive polymers such as polyphenylene derivatives; or a conductive material containing a mixture thereof.
  • the current collector one selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with conductive metal, and combinations thereof may be used.
  • the negative electrode is formed by preparing an active material composition by mixing an anode active material, a binder, and optionally a conductive material in a solvent, and applying the active material composition to a current collector. Water may be used as the solvent.
  • the positive electrode includes a current collector and a positive electrode active material layer formed on the current collector and including a positive electrode material.
  • a compound capable of reversible intercalation and deintercalation of lithium (a lithiated intercalation compound) may be used, and specifically, selected from cobalt, manganese, nickel, and combinations thereof. At least one of a complex oxide of a metal and lithium may be used. As a more specific example, a compound represented by any one of the following formulas may be used.
  • Li a A 1-b X b D 2 (0.90 ⁇ a ⁇ 1.8, 0 ⁇ b ⁇ 0.5); Li a A 1-b X b O 2-c D c (0.90 ⁇ a ⁇ 1.8, 0 ⁇ b ⁇ 0.5, 0 ⁇ c ⁇ 0.05); Li a E 1-b X b O 2-c D c (0.90 ⁇ a ⁇ 1.8, 0 ⁇ b ⁇ 0.5, 0 ⁇ c ⁇ 0.05); Li a E 2-b X b O 4-c D c (0.90 ⁇ a ⁇ 1.8, 0 ⁇ b ⁇ 0.5, 0 ⁇ c ⁇ 0.05); Li a Ni 1-bc Co b X c D ⁇ (0.90 ⁇ a ⁇ 1.8, 0 ⁇ b ⁇ 0.5, 0 ⁇ c ⁇ 0.5, 0 ⁇ ⁇ ⁇ 2); Li a Ni 1-bc Co
  • A is selected from the group consisting of Ni, Co, Mn, and combinations thereof;
  • X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof;
  • D is selected from the group consisting of O, F, S, P, and combinations thereof;
  • E is selected from the group consisting of Co, Mn, and combinations thereof;
  • T is selected from the group consisting of F, S, P, and combinations thereof;
  • G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof;
  • Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof;
  • Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof;
  • J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.
  • a compound having a coating layer on the surface of the compound may be used, or a mixture of the compound and a compound having a coating layer may be used.
  • the coating layer may include at least one coating element compound selected from the group consisting of an oxide of a coating element, a hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, and a hydroxycarbonate of a coating element.
  • the compound constituting these coating layers may be amorphous or crystalline.
  • the coating element 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.
  • any coating method may be used as long as it can be coated by a method that does not adversely affect the physical properties of the positive electrode active material by using these elements in the compound (eg, spray coating, immersion method, etc.). Since the content can be well understood by those engaged in the field, a detailed description thereof will be omitted.
  • the content of the positive active material may be 90 wt% to 98 wt% based on the total weight of the positive active material layer.
  • the positive active material layer may further include a binder and a conductive material.
  • the content of the binder and the conductive material may be 1 wt% to 5 wt%, respectively, based on the total weight of the positive electrode active material layer.
  • the binder serves to adhere the positive active material particles well to each other and also to the positive active material to the current collector, and representative examples thereof include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl. Chloride, carboxylated polyvinylchloride, polyvinylfluoride, polymers including ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. may be used, but the present invention is not limited thereto.
  • the conductive material is used to impart conductivity to the electrode, and in the configured battery, any electronically conductive material may be used without causing a chemical change.
  • the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber; Metal-based substances, such as metal powders, such as copper, nickel, aluminum, and silver, or a metal fiber; conductive polymers such as polyphenylene derivatives; or a conductive material containing a mixture thereof.
  • the current collector may be an aluminum foil, a nickel foil, or a combination thereof, but is not limited thereto.
  • the positive active material layer and the negative active material layer are formed by mixing an active material, a binder, and optionally a conductive material in a solvent to prepare an active material composition, and applying the active material composition to a current collector. Since such a method for forming an active material layer is widely known in the art, a detailed description thereof will be omitted herein.
  • the solvent may include, but is not limited to, N-methylpyrrolidone.
  • water may be used as a solvent used in preparing the anode active material composition.
  • the electrolyte includes a non-aqueous organic solvent and a lithium salt.
  • the non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.
  • non-aqueous organic solvent carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvents may be used.
  • Examples of the carbonate-based solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC), etc.
  • Examples of the ester solvent include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, propyl propionate, decanolide, mevalonolactone, Caprolactone and the like may be used.
  • ether-based solvent dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc.
  • cyclohexanone and the like may be used as the ketone-based solvent.
  • alcohol-based solvent ethyl alcohol, isopropyl alcohol, etc.
  • the aprotic solvent is R-CN (R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms.
  • nitriles such as nitriles (which may contain double bonds, aromatic rings or ether bonds), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, sulfolanes, etc. may be used .
  • the non-aqueous organic solvent may be used alone or in combination of one or more.
  • the mixing ratio can be appropriately adjusted according to the desired battery performance, which can be widely understood by those skilled in the art.
  • the carbonate-based solvent it is preferable to use a mixture of a cyclic carbonate and a chain carbonate.
  • the cyclic carbonate and the chain carbonate are mixed in a volume ratio of 1:1 to 1:9, the performance of the electrolyte may be excellent.
  • a mixed solvent of a cyclic carbonate and a chain carbonate a mixed solvent of a cyclic carbonate and a propionate-based solvent, or a cyclic carbonate, a chain carbonate, and a propionate-based solvent
  • a mixed solvent of solvents may be used.
  • the propionate-based solvent methyl propionate, ethyl propionate, propyl propionate, or a combination thereof may be used.
  • the performance of the electrolyte may be excellent when mixed in a volume ratio of 1:1 to 1:9.
  • a cyclic carbonate, a chain carbonate, and a propionate-based solvent when mixed and used, they may be mixed and used in a volume ratio of 1:1:1 to 3:3:4.
  • the mixing ratio of the solvents may be appropriately adjusted according to desired physical properties.
  • the non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent in the carbonate-based solvent.
  • the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1:1 to 30:1.
  • aromatic hydrocarbon-based organic solvent an aromatic hydrocarbon-based compound represented by the following Chemical Formula 1 may be used.
  • R 1 to R 6 are the same as or different from each other and are selected from the group consisting of hydrogen, halogen, an alkyl group having 1 to 10 carbon atoms, a haloalkyl group, and combinations thereof.
  • aromatic hydrocarbon-based organic solvent examples include benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-tri Fluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1 ,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1, 2,4-triiodobenzene, toluene, fluorotoluene, 2,3-difluorotoluene, 2,4-difluoro
  • the electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound of Formula 2 as a lifespan improving additive to improve battery life.
  • R 7 and R 8 are the same as or different from each other, and are selected from the group consisting of hydrogen, a halogen group, a cyano group (CN), a nitro group (NO 2 ), and a fluorinated C1 to C5 alkyl group, , wherein R 7 and R 8 At least one of them is selected from the group consisting of a halogen group, a cyano group (CN), a nitro group (NO 2 ) and a fluorinated alkyl group having 1 to 5 carbon atoms, provided that R 7 and R 8 are not both hydrogen.
  • ethylene carbonate-based compound examples include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate or fluoroethylene carbonate.
  • a life-enhancing additive is further used, its amount can be appropriately adjusted.
  • the electrolyte may further include vinylethylene carbonate, propane sultone, succinonitrile, or a combination thereof, and the amount of the electrolyte may be appropriately adjusted.
  • the lithium salt is dissolved in an organic solvent, acts as a source of lithium ions in the battery, enables basic lithium secondary battery operation, and serves to promote movement of lithium ions between the positive electrode and the negative electrode.
  • Representative examples of such lithium salts include LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 C 2 F 5 ) 2 , Li(CF 3 SO 2 ) 2 N, LiN(SO 3 C 2 F 5 ) 2 , LiC 4 F 9 SO 3 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiPO 2 F 2 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ), where x and y are natural numbers and, for example, an integer from 1 to 20), lithium difluoro (bisoxolato) phosphate, LiCl, LiI, LiB (C 2 O 4 ) 2 (lithium bisoxalate borate (lith
  • the concentration of lithium salt is 0.1M to It is recommended to use within the range of 2.0 M.
  • the electrolyte has appropriate conductivity and viscosity, so that excellent electrolyte performance can be exhibited, and lithium ions can move effectively.
  • a separator may exist between the positive electrode and the negative electrode depending on the type of the lithium secondary battery.
  • a separator polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof may be used.
  • a polyethylene/polypropylene two-layer separator, a polyethylene/polypropylene/polyethylene three-layer separator, and polypropylene/polyethylene/poly It goes without saying that a mixed multilayer film such as a propylene three-layer separator or the like can be used.
  • FIG. 2 is an exploded perspective view of a lithium secondary battery according to an embodiment of the present invention.
  • the lithium secondary battery according to an embodiment is described as an example of a prismatic shape, the present invention is not limited thereto, and may be applied to various types of batteries, such as a cylindrical shape and a pouch type.
  • a lithium secondary battery 100 includes an electrode assembly 40 wound with a separator 30 interposed between the positive electrode 10 and the negative electrode 20 , and the electrode assembly 40 ) may include a built-in case 50.
  • the positive electrode 10 , the negative electrode 20 , and the separator 30 may be impregnated with an electrolyte (not shown).
  • a mixing process was performed in which bulk silicone having an average particle diameter (D50) of 8 ⁇ m and a stearic acid dispersant were mixed in an ethanol solvent, and dispersed for 6 hours using a bead mill.
  • the mixing ratio of the bulk silicone and the stearic acid dispersant was 8:2 by weight
  • the ethanol solvent had the bulk silicone and the stearic acid dispersant content and the ethanol solvent content in the 8:100 weight ratio, that is, 100% by weight of the total mixture obtained with the solid content. , was used so as to be about 7% by weight.
  • Si primary particles having an average particle diameter (D50) of 8 nm and flaky were obtained.
  • the half width FWHM (111) of the diffraction peak of the (111) plane by X-ray diffraction using CuK ⁇ ray of the obtained Si primary particles was 0.5 degrees (°).
  • the scan speed (°/S) was 0.054
  • the step size (°/step) was 0.01313
  • the time/step (Time per step) was It was measured under the measurement condition of 62.475s.
  • the aspect ratio (width/thickness) of the Si primary particles was about 7.
  • the obtained mixture was subjected to a homogenizer and homogeneously dispersed for 30 minutes to prepare a homogeneous dispersion.
  • the obtained homogeneous dispersion was spray dried using a two-fluid nozzle, and at this time, the spray drying was carried out under the conditions of a homogeneous dispersion input amount of 30 g / min and N 2 nozzle gas pressure (flow rate) 0.4 Mpa, and the nozzle was This was carried out by adjusting the inlet temperature to 135 °C. Primary particles were assembled by this spray drying, and secondary particles in the form of donuts with an empty center were formed.
  • the formed secondary particles and mesocarbon pitch were mixed in a weight ratio of 80:20, and the obtained mixture was heat-treated under 800 and N 2 atmospheres to prepare an anode active material.
  • the prepared negative active material includes secondary particles to which silicon primary particles are assembled, and soft carbon positioned on the surface of the primary and secondary particles, has a donut shape with an empty center, and has a particle diameter (D50, major axis length) of 12 It was an anode active material of ⁇ m.
  • the central particle diameter (D50, long axis length, diameter) was 4 ⁇ m, and the ratio of the central diameter (major axis length) to the diameter (particle diameter, D50, long axis length) of the negative active material was 0.33.
  • a mixed negative active material in which the first and second negative active materials are mixed in a 95: 5 weight ratio and styrene-butadiene rubber ( Styrene Butadiene Rubber) 1.2 wt% and carboxymethyl cellulose (Carboxymethyl cellulose) 1.0 wt% were mixed to prepare a negative electrode active material slurry, and the slurry was coated on a Cu foil current collector, dried and rolled to prepare a negative electrode.
  • a half-cell having a theoretical capacity of 530 mAh/g was prepared using the negative electrode, the lithium counter electrode, and the electrolyte.
  • the electrolyte ethylene carbonate, ethylmethyl carbonate, and dimethyl carbonate (20:10:70 volume ratio) in which 1.5M LiPF 6 was dissolved were used.
  • the mixing ratio of the bulk silicone and the stearic acid dispersant is changed to 9:1 by weight, and the ethanol solvent is such that the content of the bulk silicone and the stearic acid dispersant and the content of the ethanol solvent are 12:100 by weight, that is, 100% by weight of the total mixture obtained with the solid content
  • a negative active material for a lithium secondary battery was prepared in the same manner as in Example 1, except that it was prepared to be about 0.09% by weight, and the inlet temperature of the nozzle was changed to 150° C. during spray drying.
  • the prepared negative electrode active material includes secondary particles to which silicon primary particles are assembled, and soft carbon positioned on the surface of primary and secondary particles. was the active material.
  • a half battery was manufactured in the same manner as in Example 1, except that the prepared negative active material was used as the first negative active material.
  • a negative active material for a lithium secondary battery was prepared in the same manner as in Example 1, except that a disk nozzle was used instead of a two-fluid nozzle as a nozzle type.
  • the prepared negative active material includes secondary particles to which silicon primary particles are assembled, and soft carbon positioned on the surfaces of primary and secondary particles, has a donut shape with an empty center, and has a particle diameter (D50, major axis length) of 75 It was an anode active material of ⁇ m.
  • the central particle diameter (D50, long axis length, diameter) was 25 ⁇ m, and the ratio of the central diameter (major axis length) to the diameter (particle diameter, D50, long axis length) of the negative active material was about 0.33.
  • a half battery was manufactured in the same manner as in Example 1, except that the prepared negative active material was used as the first negative active material.
  • the prepared negative active material includes secondary particles to which silicon primary particles are assembled, and soft carbon positioned on the surfaces of primary and secondary particles, has a donut shape with an empty center, and has a particle diameter (D50, major axis length) of 20 It was an anode active material of ⁇ m.
  • the central particle diameter (D50, long axis length, diameter) was 2 ⁇ m, and the ratio of the central diameter (major axis length) to the diameter (particle diameter, D50, long axis length) of the negative active material was 0.1.
  • a half battery was manufactured in the same manner as in Example 1, except that the prepared negative active material was used as the first negative active material.
  • FIG. 3A A 1000X SEM photograph of the negative active material prepared according to Example 1 is shown in FIG. 3A, and a 15000X SEM photograph of a part thereof is shown in FIG. 3B .
  • FIG. 3C a 15000 times SEM photograph of the negative electrode prepared according to Example 1 is shown in FIG. 3C .
  • the active material prepared according to Example 1 has an empty donut shape with an empty center, an open center, and exposed to the outside. Able to know.
  • the conductive material and the binder are agglomerated in the center of the negative electrode active material.
  • Example 1 The half-cells according to Example 1, Comparative Examples 1 and 2, and Reference Example 1 were charged and discharged 41 times at 0.5C for 20000 minutes.
  • the thickness of the battery was measured before and after charging and discharging, and the ratio of the thickness of the battery after charging and discharging to the thickness of the battery before charging and discharging was calculated. .
  • FIG. 4 it can be seen that the expansion rate of Example 1 is much lower than those of Comparative Examples 1 and 2 and Reference Example 1.

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Abstract

L'invention concerne un matériau actif d'anode pour une batterie secondaire au lithium et une batterie secondaire au lithium le comprenant, le matériau actif d'anode pour une batterie secondaire au lithium comprenant : une particule secondaire dans laquelle au moins une particule primaire de silicium est assemblée ; et du carbone amorphe, la particule secondaire se présentant sous la forme d'un beignet vide en son centre.
PCT/KR2021/016606 2020-11-17 2021-11-15 Matériau actif d'anode et batterie secondaire au lithium le comprenant WO2022108268A1 (fr)

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