Title of invention: negative active material for secondary battery, negative electrode including same, and method
Technical field
[One]
This application claims the benefit of priority based on Korean Patent Application No. 10-2018-0163075 filed on December 17, 2018, and all contents disclosed in the documents of the Korean patent application are included as part of this specification.
[2]
The present invention relates to a negative active material for a secondary battery, a negative electrode including the same, and a method of manufacturing the same. In more detail, the present invention relates to an anode active material having improved cycle swelling and high rate charging characteristics, an anode, and a method of manufacturing the same.
Background
[3]
As the price of energy sources rises due to the depletion of fossil fuels and interest in environmental pollution increases, the demand for eco-friendly alternative energy sources is becoming an indispensable factor for future life. In particular, technology development for mobile devices As the demand and demand increase, the demand for secondary batteries as energy sources is increasing rapidly.
[4]
Typically, in terms of the shape of the battery, there is a high demand for prismatic secondary batteries and pouch-type secondary batteries that can be applied to products such as mobile phones with a thin thickness. There is high demand for lithium secondary batteries such as lithium ion polymer batteries.
[5]
In general, secondary batteries constitute a positive electrode and a negative electrode by coating an electrode mixture containing an electrode active material on the surface of a current collector, and an electrode assembly is formed with a separator interposed therebetween, and then a cylindrical or rectangular metal can or aluminum laminate sheet. It is mounted inside the pouch-shaped case of the electrode assembly, and is manufactured by mainly injecting or impregnating a liquid electrolyte into the electrode assembly or using a solid electrolyte.
[6]
In addition, secondary batteries are classified according to the structure of the electrode assembly of the anode/separator/cathode structure. Typically, long sheet-shaped anodes and cathodes are wound up with a separator interposed between them. Roll (wound type) electrode assembly, stacked (stacked) electrode assembly in which a plurality of anodes and cathodes cut in units of a predetermined size are sequentially stacked with a separator interposed, A stack/folding electrode assembly having a structure in which bi-cells or full cells stacked in a state are wound with a separator sheet may be mentioned.
[7]
Meanwhile, the electrode generates an electric current through the exchange of ions, and the positive electrode and the negative electrode constituting the electrode have a structure in which an electrode active material is coated on an electrode current collector made of metal.
[8]
Among them, in the case of the negative electrode, conventionally, lithium metal was used as the negative electrode in the secondary battery, but the battery short-circuit due to the formation of dendrites and the risk of explosion due thereto are known, while maintaining structural and electrical properties, and reversible Phosphorus lithium ions are being replaced by carbon-based compounds capable of intercalation and removal.
[9]
The carbon-based compound has a very low discharge potential of about -3V with respect to the standard hydrogen electrode potential, and exhibits excellent electrode life characteristics due to very reversible charging and discharging behavior due to the uniaxial orientation of the graphene layer. . In addition, when charging Li ions, since the electrode potential is 0V Li/Li + , which can exhibit a potential similar to that of pure lithium metal, there is an advantage that higher energy can be obtained when configuring a battery with an oxide-based positive electrode.
[10]
The carbon-based compound includes crystalline carbon and amorphous carbon. As for crystalline carbon, graphite carbon such as natural graphite and artificial graphite is representative, and amorphous carbon is heat treated with non-graphitizable carbons (hard carbons) obtained by carbonizing a polymer resin and pitch. And the resulting graphitizable carbons (soft carbons).
[11]
In particular, as a carbon-based material, natural graphite having a high capacity or excellent artificial graphite such as high-temperature properties is used, but artificial graphite exhibits a lower capacity than natural graphite, and the negative electrode slurry is There are problems such as poor processability, such as poor manufacturing and electrode adhesion, and poor electrode rolling characteristics. In addition, natural graphite exhibits a swelling phenomenon according to a high degree of orientation or poor fast charging performance, and has a relatively large number of functional groups on the surface compared to artificial graphite, resulting in poor high-temperature characteristics.
[12]
Korean Patent Laid-Open Publication No. 10-2015-0073107 discloses that natural graphite and artificial graphite are mixed as the carbon-based negative active material, and the artificial graphite is mosaic coke-based artificial graphite. However, when using natural graphite as described above, the mechanical strength of the electrode is weakened, and the cycle swelling and rapid charging performance during charging and discharging are not good. In this case, the electrode may swell during charging and discharging, resulting in a problem such as a reduction in cycle life.
[13]
Therefore, it is necessary to develop a technology for solving the above problems.
[14]
Detailed description of the invention
Technical challenge
[15]
The present invention was invented to solve the above problems, and in a negative electrode active material using a mixture of natural graphite and artificial graphite, natural graphite It is an object of the present invention to provide a negative electrode active material having improved cycle characteristics, swelling characteristics, and rapid charging performance at the level of artificial graphite, a negative electrode including the same, and a method of manufacturing the same.
Means of solving the task
[16]
The negative active material for a secondary battery according to the present invention,
[17]
It is a mixture of artificial graphite and spheroidized natural graphite,
[18]
The spheronized natural graphite may have an average particle diameter (D 50 ) of 12 μm or less, and a D 90 -D 10 value of 5 to 12 μm.
[19]
In addition, in the negative active material for a secondary battery according to the present invention, the artificial graphite is included in an amount of 65 to 85% by weight based on the total weight of the negative active material, and the spheroidized natural graphite is 15 based on the total weight of the negative active material. It may be included in to 35% by weight.
[20]
In addition, in the negative active material for a secondary battery according to the present invention, the average particle diameter (D50) of the natural graphite may be 9 to 11 μm.
[21]
In addition, in the negative active material for a secondary battery according to the present invention, the D 90 -D 10 value of the natural graphite may be 7 to 9 μm.
[22]
In addition, in the negative active material for a secondary battery according to the present invention, the tap density of the negative active material may be 1.10 to 1.25 g/cc.
[23]
In addition, in the negative active material for a secondary battery according to the present invention, the negative active material may have an adhesion to the current collector after rolling is 20 to 35 gf/cm.
[24]
In addition, in the negative active material for a secondary battery according to the present invention, the artificial graphite may be pitch coke manufactured by heat treatment of coal tar, coal tar pitch, petroleum pitch, or heavy oil. .
[25]
In addition, in the negative electrode active material for a secondary battery according to the present invention, spheroidized natural graphite is treated with an acid or a base in the form of scaled natural graphite, and then, in a spheronization device, the rotor speed is 30 m/s to 100 m/s. Can be obtained by spheronizing for 10 to 30 minutes.
[26]
In addition, the present invention provides a negative electrode for a secondary battery, wherein the negative electrode for a secondary battery includes a current collector and a negative electrode mixture layer coated on the current collector,
[27]
The negative electrode mixture layer includes a conductive material, a binder, and the negative electrode active material.
[28]
In addition, the present invention provides a method of manufacturing a negative electrode for a secondary battery. The method of manufacturing a negative electrode for a secondary battery includes preparing a negative electrode mixture and coating the negative electrode mixture on a current collector and then drying the negative electrode. The negative electrode active material included in the negative electrode mixture includes a mixture of artificial graphite and spheroidized natural graphite,
[29]
The negative active material is as described above.
Effects of the Invention
[30]
According to the present invention, the cell performance such as cycle characteristics, swelling characteristics, and rapid charging can be improved by using a negative electrode active material in which artificial graphite and spherical natural graphite having a small particle size and uniform particle size are mixed.
Brief description of the drawing
[31]
1 is a schematic diagram showing the structure of a negative electrode for a secondary battery including a negative active material according to the present invention.
Best mode for carrying out the invention
[32]
Terms used in the present specification and claims should not be construed as being limited to a conventional or dictionary meaning, and that the inventor can appropriately define the concept of terms in order to describe his own invention in the best way. Based on the principle, it should be interpreted as a meaning and concept consistent with the technical idea of ​​the invention. Therefore, the configuration shown in the embodiments described in the present specification is only one of the most preferred embodiments of the present invention and does not represent all of the technical spirit of the present invention, and various equivalents that can replace them at the time of the present application And it should be understood that there may be variations.
[33]
In the entire specification of the present application, when a certain part is said to be ``connected'' with another part, this includes not only ``directly connected'' but also ``electrically connected'' with another element interposed therebetween. .
[34]
Throughout this specification, terms such as "comprise" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other It is to be understood that it does not preclude the presence or addition of features, numbers, steps, actions, components, parts, or combinations thereof. In addition, when a part such as a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where the other part is "directly above" but also the case where there is another part in the middle. Conversely, when a part such as a layer, a film, a region, or a plate is said to be "under" another part, this includes not only the case where the other part is "directly below", but also the case where there is another part in the middle. In addition, in the present application, the term "above" may include a case where it is disposed not only above but also below.
[35]
The terms "about", "substantially" and the like used throughout this specification are used as a meaning at or close to the numerical value when manufacturing and material tolerances specific to the stated meaning are presented, and are accurate to aid the understanding of the present application. Or absolute figures are used to prevent unfair use of the stated disclosure by unconscionable infringers.
[36]
In the entire specification of the present application, the term "combination(s) thereof" included in the expression of the Makushi format refers to one or more mixtures or combinations selected from the group consisting of the constituent elements described in the expression of the Makushi format, It means to include at least one selected from the group consisting of the above components.
[37]
[38]
Hereinafter, the present invention will be described in detail.
[39]
The negative electrode active material for a secondary battery according to the present invention includes a graphite material as a main component.
[40]
Specifically, the negative active material is a mixture of artificial graphite and spheroidized natural graphite. In general, artificial graphite has excellent high-temperature characteristics, but has a problem in that it exhibits low capacity and low fairness, and thus natural graphite having excellent initial discharge capacity can be mixed to improve the capacity of the active material. However, as the charge/discharge cycle of natural graphite is repeated, a swelling phenomenon may occur due to an electrolyte solution decomposition reaction occurring at the edge of the natural graphite, and charge/discharge efficiency and capacity may be deteriorated. In addition, natural graphite has many internal voids, and there is a problem in that the internal voids are clogged during electrode rolling and receive a lot of mechanical stress.
[41]
Therefore, as described later, spheroidized natural graphite with a small particle diameter and uniform particle size is mixed with artificial graphite to retain the advantages of artificial graphite and natural graphite, while low cycle characteristics, swelling characteristics, and rapid charging characteristics, which were disadvantages of conventional natural graphite. Can be improved.
[42]
Specifically, the spheroidized natural graphite may have an average particle diameter (D 50 ) of 12 μm or less, and preferably 11 μm or less, more preferably 9 to 11 μm, in consideration of the initial efficiency of the secondary battery. By using spheroidized natural graphite having an average particle diameter within the above range, it is possible to obtain an advantage of improving the rapid charging capability at high energy density. When the average particle diameter of the spheroidized natural graphite exceeds 12 µm, the tap density of the electrode (cathode) and the adhesive strength characteristics of the active material decrease as described later, thereby reducing the effect of improving the swelling phenomenon of the electrode. The charge/discharge performance of the secondary battery may decrease.
[43]
In addition, according to the present invention, in order to improve the performance degradation that may occur when using natural graphite, the particle size distribution must be uniform. In the particle size distribution of the spheroidized natural graphite, the D 90 -D 10 value may be 5 to 12 μm. , Preferably it may be 7 to 9㎛. Here, D 90 is the particle diameter that accumulates 90% from the smallest particle in the order of particle diameter, D 10 is the particle diameter that accumulates 10% from the smallest particle in the order of particle diameter, and D 50 is the particle diameter from the smallest particle in the order of particle diameter. This means the particle size of 50%. The smaller the D 90 -D 10 value, the sharper the particle size distribution curve appears. If the D 90 -D 10 is less than 5 μm, the rapid charging characteristics may be deteriorated, and if the D 90 -D 10 exceeds 12 μm, it may be difficult to obtain an appropriate density. I.e. D 90 -D 10If it is out of the above range, there is a problem in that the tap density of the active material is too low, the thickness of the electrode active material layer becomes thick and the pressability decreases accordingly, and thus there is a disadvantage in implementing a high energy density.
[44]
The particle size of the spheroidized natural graphite can be measured using, for example, a laser diffraction method. In general, the laser diffraction method can measure a particle diameter of about several mm from a submicron region, and high reproducibility and high resolution results can be obtained. More specifically, the particle size measurement of the spheroidized natural graphite is performed by dispersing spheroidized natural graphite in an ethanol/water solution, and then introducing it into a commercially available laser diffraction particle size measuring device (for example, Microtrac MT 3000), and using ultrasonic waves of about 28 kHz. After irradiating with an output of 60 W, it can calculate based on the particle size distribution in a measuring device.
[45]
In addition, the spheroidized natural graphite can be obtained by applying an external mechanical force to the general natural graphite and subjecting it to granulated spheroidization. For example, spheroidized natural graphite is spheroidized for 10 to 30 minutes at a rotor speed of 30 m/s to 100 m/s in a spheroidizing device after treating the scaled natural graphite with an acid or a base. It can be manufactured by making, but is not limited thereto.
[46]
The tap density of the spheroidized natural graphite may be 1.10 to 1.25 g/cc, more preferably 1.15 to 1.20 g/cc. The tap density of the active material is the apparent density of the powder obtained by vibrating the container under certain conditions when filling the powder. In the present invention, the tap density can be measured after tapping 2000 times using a tap density measuring instrument, TAP-2S manufactured by LOGAN.
[47]
The higher the tap density, the higher the packing density of the electrode. Specifically, for manufacturing an electrode, an active material is mixed with a binder or a conductive material, coated on a current collector in a thin film state, and pressure is applied to make the electrode hard. In this case, if the filling is not done well, the electrode cannot be made thin and occupy a large volume, so that a high capacity cannot be realized under a given volume condition of the battery.
[48]
The tap density of the spheroidized natural graphite is affected by the particle diameter of the natural graphite, the tap density decreases as the particle diameter of natural graphite increases, and the tap density may increase as the particle diameter of natural graphite decreases. In general, in order to improve the adhesion between the active material and the electrode current collector, the greater the contact area between the particles, the greater the adhesion area, and thus the adhesion is improved.
[49]
When the tap density of the spheroidized natural graphite is less than 1.10 g/cc, the contact area between the particles is insufficient, so that adhesion properties may be deteriorated, and the energy density per unit volume may decrease. On the other hand, when the tap density of spheroidized natural graphite exceeds 1.25 g/cc, the tortuosity of the electrode and the wet-ability of the electrolyte decrease, resulting in a decrease in the output characteristics during charging and discharging. There is a problem that it may cause a decrease in efficiency and deterioration of high-temperature characteristics, which is not preferable.
[50]
In addition, in the negative active material according to the present invention, the spheronization degree of the spheroidized natural graphite may be 0.94 to 0.98, and specifically 0.95 to 0.96. The degree of sphericity may mean a short diameter compared to a long diameter of the first particle. The degree of sphericity can be measured through a particle shape analyzer frame. Specifically, after deriving the cumulative distribution of the spheronization degree of the spheroidized natural graphite particles through a particle shape analyzer, the spheronization degree corresponding to 50% of the distribution ratio from the particles having a large sphericity degree is determined Can be judged as.
[51]
When the spheronization degree of the spheroidized natural graphite particles is less than 0.94, a problem of low electrode adhesion may occur due to the excessively curved surface of the first particles. In addition, when the spheronization degree of the spheroidized natural graphite particles is more than 0.98, since a large amount of spheroidized natural graphite particles are required to derive a high sphericity degree, a problem of lowering the manufacturing yield may occur.
[52]
In addition, in the negative active material according to the present invention, the adhesion to the current collector after rolling of the spheroidized natural graphite may be 20 to 35 gf/cm, more preferably 25 to 30 gf/cm. In general, natural graphite exhibits excellent adhesion to the current collector compared to artificial graphite with a low surface defect or functional group content due to the presence of functional groups on the surface. In this case, adhesion of the negative active material mixed with artificial graphite to the current collector may be improved.
[53]
The adhesion of the spheroidized natural graphite to the current collector may be affected by the particle size, and the larger the particle diameter, the smaller the surface area and the smaller the adhesion to the current collector. When the adhesive force of the spheroidized natural graphite to the current collector is less than 20 gf/cm, the negative active material is easily peeled from the current collector, and thus the capacity of the battery may rapidly decrease as the cycle proceeds. On the other hand, when the electrode adhesion exceeds 35 gf/cm, the high-speed charging characteristics may deteriorate due to an increase in electrode resistance.
[54]
Next, the artificial graphite used in the present invention will be described.
[55]
In the negative active material for an interest battery according to the present invention, artificial graphite contained in the negative active material may be prepared from a precursor such as pitch coke, and the pitch coke is coal tar, coal tar pitch, petroleum pitch. It can be prepared using a carbon precursor such as (petroleum pitch) or heavy oil. The coke may be mechanically pulverized and polished, and then heat-treated (graphitized) at a temperature of 2800°C to 3000°C.
[56]
The artificial graphite is not limited and may be powder, flake, block, plate, or rod, but in order to show the best output characteristics, the shorter the movement distance of lithium ions is, the better the movement distance in the electrode direction is. In order to be short, the degree of orientation of the crystal grains of the artificial graphite is preferably isotropic, and therefore, a flake shape or a plate shape, more specifically a flake shape is preferable.
[57]
In addition, the tap density of the artificial graphite may be 0.80 to 1.00 g/cc, more preferably 0.85 to 0.95 g/cc. When the tap density of the artificial graphite particles is less than 0.80 g/cc, the contact area between the particles is insufficient, so that adhesion properties may be deteriorated, and the energy density per unit volume may decrease. On the other hand, if the tap density of artificial graphite exceeds 1.00 g/cc, the electrode's tortuosity and electrolyte solution wet-ability decrease, resulting in a decrease in the output characteristics during charge and discharge, and the initial efficiency decrease There is a problem that it may cause deterioration of the high-temperature characteristics and, it is not preferable.
[58]
In addition, the average particle diameter (D 50 ) of the artificial graphite may be 9 to 30 μm, preferably 10 to 20 μm. When the average particle diameter of the artificial graphite is less than 9 μm, the initial efficiency of the secondary battery decreases due to the increase in the specific surface area, and thus the battery performance may decrease. When the average particle diameter of the artificial graphite exceeds 30 μm, the electrode adhesion decreases. The cycle characteristics of the battery may deteriorate.
[59]
In particular, the average particle diameter (D in the artificial graphite 50 ) has an average particle diameter (D in the sphering natural graphite 50 can baeil 1 to 2 times, preferably 1.2 to 1.7 in). When the ratio between the average particle diameter of artificial graphite and the average particle diameter of spheroidized natural graphite is within the above range, the filling density of the active material in the electrode is improved, and the specific surface area of ​​the active material is reduced, thereby preventing side reactions with the electrolyte.
[60]
When the average particle diameter of the artificial graphite is out of the above range, the size of either particle is enlarged, and it is difficult to uniformly distribute the artificial graphite and the spheroidized natural graphite. Characteristics may deteriorate.
[61]
In addition, in the negative active material according to the present invention, the artificial graphite may be included in an amount of 65 to 85% by weight, more preferably 70 to 80%, based on the total weight of the negative active material.
[62]
In addition, the spheroidized natural graphite may be included in an amount of 15 to 35% by weight, preferably 20 to 30% by weight, based on the total weight of the negative active material.
[63]
When the content of the artificial graphite in the negative active material is less than 65% and the content of spheroidized natural graphite exceeds 35%, the content of natural graphite is too large, so a side reaction with the electrolyte may occur at a high temperature and a swelling phenomenon may occur. In addition, the mechanical properties of the electrode are weakened due to the internal voids, and the rapid charging performance is reduced, so that the object of the present invention cannot be achieved. Conversely, when the content of artificial graphite exceeds 85% by weight and the content of spheroidized natural graphite is less than 15%, the amount of artificial graphite is too large, so the capacity of the battery decreases, fairness decreases, and rolling characteristics are poor. Occurs and is not desirable.
[64]
In addition, when one of artificial graphite and spheroidized natural graphite is used too much, voids in the negative electrode active material layer exist excessively due to the morphology of each particle, so that filling between the artificial graphite and natural graphite is not smoothly performed. As a result, adhesion between particles in the negative active material and adhesion between the negative active material and the current collector may be poor. When the amounts of artificial graphite and spheroidized natural graphite are adjusted within the above range, the voids in the negative electrode active material layer are reduced, and since the artificial graphite and spheroidized natural graphite are present in a state in which they are smoothly engaged with each other, electrode adhesion can be improved.
[65]
In addition, the negative electrode active material according to the present invention may further include a pressure-sensitive adhesive component that assists in bonding of artificial graphite and spheroidized natural graphite. The pressure-sensitive adhesive is a component that aids in the bonding of spheroidized natural graphite and artificial graphite, and a hard carbon precursor, a soft carbon precursor, and the like may be used, but is not limited thereto. When the negative electrode active material further includes the pressure-sensitive adhesive component in addition to artificial graphite and natural graphite, the pressure-sensitive adhesive may be included in an amount of 1 to 40% by weight. The hard carbon precursor is sucrose, phenol resin, naphthalene resin, polyvinyl alcohol resin, furfuryl alcohol resin, polyacrylonitrile resin, polyamide resin, furan resin, cellulose resin, styrene resin, polyether resin. Mid resin, epoxy resin, vinyl chloride resin, and the like may be used, and the soft carbon may be coke, needle coke, polyvinyl chloride, mesophase pitch, tar, or heavy oil.
[66]
[67]
The present invention also provides a negative electrode for a secondary battery comprising the negative active material.
[68]
1 is a schematic diagram showing the structure of a negative electrode for a secondary battery including a negative active material according to the present invention.
[69]
Referring to FIG. 1, the negative electrode 10 may be manufactured by applying a negative electrode mixture including a negative electrode active material on the current collector 11 and drying it. The negative electrode mixture includes a binder, a conductive material, and A filler or the like may be optionally further included. In this case, a mixture of the above-described artificial graphite 12 and spheroidized natural graphite 13 may be used as the negative active material.
[70]
In the case of a negative electrode current collector sheet, it is generally made to have a thickness of 3 to 500 µm. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel For example, carbon, nickel, titanium, silver, etc. surface-treated, aluminum-cadmium alloy, and the like may be used. In addition, like the positive electrode current collector, it is possible to strengthen the bonding force of the negative electrode active material by forming fine irregularities on the surface thereof, and it may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.
[71]
The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; Carbon blacks such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.
[72]
The binder is a component that aids in bonding of an active material and a conductive material and bonding to a current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, poly Propylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, and various copolymers.
[73]
The filler is selectively used as a component that suppresses the expansion of the electrode, and is not particularly limited as long as it is a fibrous material without causing chemical changes in the battery, and examples thereof include olefinic polymerizers such as polyethylene and polypropylene; Fibrous materials such as glass fiber and carbon fiber are used.
[74]
Other ingredients, such as viscosity modifiers, adhesion promoters, and the like, may be further included optionally or as a combination of two or more. The viscosity modifier is a component that adjusts the viscosity of the electrode mixture so as to facilitate the mixing process of the electrode mixture and the application process on the current collector thereof, and may be added up to 30% by weight based on the total weight of the negative electrode mixture. Examples of such viscosity modifiers include carboxy methylcellulose, polyvinylidene fluoride, and the like, but are not limited thereto. In some cases, the solvent described above may simultaneously serve as a viscosity modifier.
[75]
The adhesion promoter is an auxiliary component added to improve the adhesion of the active material to the current collector, and may be added in an amount of 10% by weight or less relative to the binder, for example, oxalic acid, adipic acid, Formic acid (formic acid), acrylic acid (acrylic acid) derivatives, itaconic acid (itaconic acid) derivatives, etc. are mentioned.
[76]
The present invention also provides a secondary battery manufactured by the present method. Specifically, the secondary battery includes two or more electrodes for secondary batteries manufactured according to the present invention, and the electrode assembly is embedded in a battery case, wherein the secondary battery is wound with a separator interposed between the electrodes for secondary batteries. And a non-aqueous electrolyte containing a lithium salt is impregnated with the electrode assembly. The secondary battery electrode may be a positive electrode and/or a negative electrode. In this case, the negative electrode may be the same as described above, and the negative electrode may be assembled into an electrode assembly and then sealed in a battery case together with an electrolyte to be manufactured as a lithium secondary battery through an activation process. The secondary battery may be a cylindrical battery, a prismatic battery, a pouch-type battery, or a coin-type battery, and there is no particular limitation on the shape of the battery.
[77]
The electrode assembly is not particularly limited as long as it has a structure consisting of an anode and a cathode, and a separator interposed therebetween, and for example, a folding type structure, a stack type structure, or a stack/folding type (SNF) structure, or a lamination/stack It may be a type (LNS) structure structure.
[78]
The electrode assembly of the folding-type structure includes at least one anode, at least one cathode, and at least one separator interposed between the anode and the cathode, and the anode, the separator, and the cathode do not cross each other at one end and the other end. It may be a structure that does not.
[79]
In addition, the electrode assembly of the stacked structure includes one or more positive electrodes, one or more negative electrodes, and one or more separators interposed between the positive and negative electrodes, and the positive electrode, the separator, and the negative electrode cross each other at one end and the other end. It can be a structure to do.
[80]
The electrode assembly of the stack/folding structure includes at least one anode, at least one cathode, and at least one separator interposed between the anode and the cathode, and the separator includes a first separator and a second separator, One end and the other end of each of the anode, the first separator, and the cathode do not cross each other, and the second separator may have a structure surrounding a side surface of an electrode where no electrode tab is formed.
[81]
The electrode assembly of the lamination/stack type structure may include at least one improved electrode in which a separator is laminated on one or both surfaces. The improved electrode may be implemented in a structure in which, for example, a separator is bonded to one side of an anode or a cathode. In addition, the separator may be implemented in a structure in which both sides of an anode or both sides of a cathode are bonded. In addition, it may be implemented in a structure in which an anode, a separator, and a cathode are bonded to each other while a separator is interposed between the anode and the cathode.
[82]
In the secondary battery according to the present invention, the positive electrode may be prepared by applying an electrode mixture containing a positive electrode active material on a current collector and then drying. The positive electrode mixture may optionally contain a binder, a conductive material, a filler, etc. Can be included more
[83]
In the present invention, the positive electrode current collector is generally made to have a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes to the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. Surface treatment of carbon, nickel, titanium, silver, or the like may be used on the surface of. The current collector may increase the adhesion of the positive electrode active material by forming fine irregularities on its surface, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible.
[84]
In the present invention, the positive electrode active material is a material capable of causing an electrochemical reaction, as a lithium transition metal oxide, containing two or more transition metals, and, for example, lithium cobalt oxide (LiCoO 2) substituted with one or more transition metals. ), layered compounds such as lithium nickel oxide (LiNiO 2 ); Lithium manganese oxide substituted with one or more transition metals; Formula LiNi 1-y M y O 2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, Cr, Zn or Ga, and including one or more of the above elements, 0.01≤y≤0.7) Lithium nickel-based oxide represented by; Li 1+z Ni 1/3 Co 1/3 Mn 1/3 O 2 , Li 1+z Ni 0.4 Mn 0.4 Co 0.2 O 2Li 1+z Ni b Mn c Co 1-(b+c+d) M d O (2-e) A e (where -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤ 0.8, 0≤d≤0.2, 0≤e≤0.2, b+c+d<1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl) Lithium nickel cobalt manganese composite oxide; Formula Li 1 + x M 1-y M ' y PO 4-z X z , and (wherein, M = a transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S, or N, and -0.5≤x≤0.5, 0≤y≤0.5, 0≤z≤0.1, and the like) represented by olivine lithium metal phosphate, but are not limited thereto.
[85]
In the positive electrode, additive materials such as a binder, a conductive material, and a filler are as described above.
[86]
The separator is interposed between the anode and the cathode, and an insulating thin ultrathin having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. Examples of such separation membranes include olefin-based polymers such as polypropylene having chemical resistance and hydrophobicity; Sheets or non-woven fabrics made of glass fiber or polyethylene are used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as a separator.
[87]
The lithium salt-containing non-aqueous electrolyte is composed of an electrolyte and a lithium salt, and as the electrolyte, a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, or the like is used.
[88]
As the non-aqueous organic solvent, for example, N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma -Butyl lactone, 1,2-dimethoxy ethane, tetrahydroxy franc (franc), 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone , Acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid tryster, trimethoxy methane, dioxolone derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbo An aprotic organic solvent such as an acid derivative, a tetrahydrofuran derivative, an ether, a methyl pyropionate, or an ethyl propionate may be used.
[89]
As the organic solid electrolyte, for example, a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, a poly agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymerization agent or the like containing an ionic dissociating group may be used.
[90]
As the inorganic solid electrolyte, for example, Li 3 N, LiI, Li 5 NI 2 , Li 3 N-LiI-LiOH, LiSiO 4 , LiSiO 4 -LiI-LiOH, Li 2 SiS 3 , Li 4 SiO 4 , Nitrides , halides, and sulfates of Li such as Li 4 SiO 4 -LiI-LiOH and Li 3 PO 4 -Li 2 S-SiS 2 may be used.
[91]
The lithium salt is a material that is soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenyl borate and imide.
[92]
In addition, for the purpose of improving charge/discharge properties, flame retardancy, etc., the electrolyte solution includes, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, and nitro. Benzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. . In some cases, in order to impart non-flammability, a halogen-containing solvent such as carbon tetrachloride and ethylene trifluoride may be further included, and carbon dioxide gas may be further included in order to improve high-temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate), PRS (Propene sultone), and the like may be further included.
[93]
In one preferred example, lithium salts such as LiPF 6 , LiClO 4 , LiBF 4 , and LiN(SO 2 CF 3 ) 2 are used in the cyclic carbonate of EC or PC as a highly dielectric solvent and DEC, DMC or EMC as a low viscosity solvent. The lithium salt-containing non-aqueous electrolyte can be prepared by adding it to a mixed solvent of linear carbonate.
[94]
[95]
The method of manufacturing a negative electrode of the present invention includes preparing a negative electrode mixture and drying after applying the negative electrode mixture on a current collector.
[96]
In addition, the negative electrode active material included in the negative electrode mixture includes a mixture of artificial graphite and spheroidized natural graphite,
[97]
Specifically, the negative active material may be the same as described above.
[98]
More specifically, in the method of manufacturing the negative electrode, the preparing of the negative electrode mixture may include spheronizing natural graphite; Manufacturing artificial graphite; And mixing the spheroidized natural graphite and artificial graphite.
[99]
Spheronizing the natural graphite; Is a step of applying a mechanical external force to general scale-like natural graphite to spheronize it.After treating the scale-like natural graphite with an acid or a base as described above, 30 m/s to 100 m/s in a spheroidizing device It can be obtained by spheronizing for 10 to 30 minutes at a rotor speed of.
[100]
Preparing the artificial graphite; The steps of producing pitch coke by coking a carbon precursor such as the coal tar, coal tar pitch, petroleum pitch, or heavy oil; And performing heat treatment (graphitization) at a temperature of 2800°C to 3000°C after mechanically grinding and polishing the coke. It may include.
[101]
In addition, spheronizing the natural graphite; And preparing artificial graphite. Classifying so that the particle size distribution of the prepared spheroidized natural graphite and artificial graphite particles is uniform; It may further include.
[102]
Through the classification step, the average particle diameter (D50) of spheroidized natural graphite and artificial graphite can be adjusted to the above-described value, and in particular, the D 90 -D 10 value is 5 to 12 μm, preferably through the classification step. It can be adjusted to be 7 to 9㎛.
[103]
The classification process may be performed by any method, but it is appropriate to perform the classification process by air flow classification process. In the case of performing the air flow classification process, the conditions of the air flow classification process can be appropriately adjusted according to the type of active material or the like.
[104]
When the spheroidized natural graphite and artificial graphite are prepared, the spheroidized natural graphite and the artificial graphite are mixed, and the mixing method is not particularly limited, and for example, one having a high-speed chopper such as a Henschel mixer or a Spartan Ruder, It can be uniformly mixed at high speed using a ribbon mixer or the like.
[105]
The spheroidized natural graphite and artificial graphite are mixed, a binder and a conductive material are added, and a solvent such as water is added thereto to prepare a negative electrode mixture slurry, and a thickener such as carboxymethylcellulose (CMC) is further included if necessary. can do.
[106]
[107]
Hereinafter, examples will be described in detail to aid understanding of the present invention. However, the embodiments according to the present invention may be modified in various forms, and the scope of the present invention should not be construed as being limited by the following examples. The embodiments of the present invention are provided to more completely describe the present invention to those of ordinary skill in the art.
[108]
[109]
[Example 1]
[110]
Preparation of cathode
[111]
A negative electrode was manufactured using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D 50 ) of 11 μm in the particle size distribution , D 90 was 15 μm, D 10 was 6 μm, and D 90 -D 10 was 9 μm. In addition, the tap density of the spheroidized natural graphite was 1.15 g/cc (measured by performing tapping 2000 times using a tap density measuring instrument made by LOGAN, Inc.), and the resulting electrode adhesion was 25 gf/cm after rolling. . As the artificial graphite , flake-like artificial graphite (tap density: 0.90 g/cc) having an average particle diameter (D 50 ) of 15.5 μm was used.
[112]
The natural graphite was used as a negative electrode active material, SuperC65 as a conductive material, styrene butadiene high part (SBR) as a binder, and carboxymethylcellulose (CMC) as a thickener were mixed in a weight ratio of 96.6:1:1.3:1.1, respectively, and water was added. A slurry was prepared.
[113]
The slurry prepared as described above was coated on a copper foil, and vacuum-dried at about 130° C. for 10 hours to prepare a negative electrode having an area of 1.4875 cm 2 . At this time, the loading amount of the negative electrode was prepared to be 3.61mAh/cm 2 .
[114]
[115]
Manufacturing of battery cells
[116]
By applying the negative electrode active material on copper foil, 1.7671 cm 2 load amount to the area of the 3.61mAh / cm 2 working electrode (cathode) LiCoO as a cathode active material in the manufacture, and the aluminum foil so that the second positive electrode material mixture containing (LCO) Was applied to prepare a 1.4875 cm 2 counter electrode (anode). An electrode assembly was manufactured by interposing a polyethylene separator between the working electrode and the counter electrode. And 1M LiPF 6 was added to a solvent in which 0.5% by weight of a nonaqueous electrolyte additive VC was added in a volume ratio of 1:4 to prepare a nonaqueous electrolyte, and then injected into the electrode assembly. I did. The electrode assembly was put into a case to prepare a coin-type full-cell secondary battery.
[117]
In addition, the negative electrode active material is 1.4875 cm was applied to the copper foil 2 area to the loading amount of the 3.61mAh / cm 2 1.7671cm to prepare a working electrode (cathode), so that, as a counter electrode (anode) 2, a lithium metal having an area of Was used. An electrode assembly was manufactured by interposing a polyethylene separator between the working electrode and the counter electrode. And 1M LiPF 6 was added to a solvent in which 0.5% by weight of a nonaqueous electrolyte additive VC was added in a volume ratio of 1:4 to prepare a nonaqueous electrolyte, and then injected into the electrode assembly. I did. The electrode assembly was put into a case to prepare a coin-type half-cell secondary battery.
[118]
[119]
[Example 2]
[120]
Preparation of cathode
[121]
A negative electrode was manufactured using a negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D 50 ) of 9 μm in a particle size distribution , D 90 was 13 μm, D 10 was 6 μm, and D 90 -D 10 was 7 μm. In addition, the tap density of the spheroidized natural graphite was 1.20 g/cc, and the corresponding electrode adhesion was 30 gf/cm after rolling. As the artificial graphite , flake-like artificial graphite (tap density: 0.93 g/cc) having an average particle diameter (D 50 ) of 14.5 μm was used.
[122]
The natural graphite was used as a negative electrode active material, SuperC65 as a conductive material, styrene butadiene high part (SBR) as a binder, and carboxymethylcellulose (CMC) as a thickener were mixed in a weight ratio of 96.6:1:1.3:1.1, respectively, and water was added. A slurry was prepared.
[123]
The slurry prepared as described above was coated on a copper foil, and vacuum-dried at about 130° C. for 10 hours to prepare a negative electrode having an area of 1.4875 cm 2 . At this time, the loading amount of the negative electrode was prepared to be 3.61mAh/cm 2 .
[124]
[125]
Manufacturing of battery cells
[126]
A battery (coin-type full-cell and half-cell battery) was manufactured in the same manner as in Example 1 using the negative active material of Example 2.
[127]
[128]
[Example 3]
[129]
A negative electrode and a battery (coin-type Of full-cell and half-cell batteries) were prepared.
[130]
[131]
[Example 4]
[132]
The negative electrode and battery (coin type Of full-cell and half-cell batteries) were prepared.
[133]
[134]
[Example 5]
[135]
A negative electrode and a battery (coin type) in the same manner as in Example 1, except that the negative electrode active material contains 65% by weight of the artificial graphite of Example 1 and 35% by weight of the spheroidized natural graphite of Example 1. Of full-cell and half-cell batteries) were prepared.
[136]
[137]
[Comparative Example 1]
[138]
A negative electrode and a battery (coin type) in the same manner as in Example 1, except that 90% by weight of the artificial graphite of Example 1 and 10% by weight of the spheroidized natural graphite of Example 1 were used in the negative active material. Of full-cell and half-cell batteries) were prepared.
[139]
[140]
[Comparative Example 2]
[141]
A negative electrode and a battery (coin type) in the same manner as in Example 1, except that the negative active material contains 60% by weight of the artificial graphite of Example 1 and 40% by weight of the spheroidized natural graphite of Example 1. Of full-cell and half-cell batteries) were prepared.
[142]
[143]
[Comparative Example 3]
[144]
A negative electrode was manufactured using the negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. Specifically, natural graphite with a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D 50 ) of 15 μm in the particle size distribution , D 90 was 21 μm, D 10 was 7 μm, and D 90- D 10 was 14 μm. In addition, the tap density of the spheroidized natural graphite was 1.15 g/cc, and the corresponding electrode adhesion was 15 gf/cm after rolling.
[145]
A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a half cell including the negative electrode were prepared using the negative active material.
[146]
[147]
[Comparative Example 4]
[148]
A negative electrode was manufactured using the negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D 50 ) of 17 μm in a particle size distribution , D 90 of 28 μm , D 10 of 10 μm, and D 90 -D 10 was 18 μm. In addition, the tap density of the spheroidized natural graphite was 1.10 g/cc, and the corresponding electrode adhesion was 14 gf/cm after rolling.
[149]
A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a half cell including the negative electrode were prepared using the negative active material.
[150]
[151]
[Comparative Example 5]
[152]
A negative electrode was manufactured using the negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. Specifically, natural graphite having a small particle diameter and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D 50 ) of 11 μm in the particle size distribution , D 90 was 21 μm , D 10 was 6 μm, and D 90 -D 10 was 15 μm. In addition, the tap density of the spheroidized natural graphite was 1.05 g/cc, and the corresponding electrode adhesion was 11 gf/cm after rolling.
[153]
A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a half cell including the negative electrode were prepared using the negative active material.
[154]
[155]
[Comparative Example 6]
[156]
A negative electrode was manufactured using the negative electrode active material containing 80% by weight of artificial graphite and 20% by weight of spheroidized natural graphite of Example 1. At this time, the spheroidized natural graphite was made to act as an adhesive between the flakes by adding a binder in the step of granulating and spheronizing the flaky graphite. Specifically, natural graphite having a small particle size and uniform particle size was used for the negative electrode active material, and the natural graphite had an average particle diameter (D 50 ) of 14 μm in particle size distribution , D 90 of 27 μm , D 10 of 8 μm, 90 -D 10 was 19 μm. In addition, the tap density of the spheroidized natural graphite was 1.00 g/cc, and the corresponding electrode adhesion was 8 gf/cm after rolling.
[157]
A battery was manufactured in the same manner as in Example 1, except that a negative electrode and a coin-type full cell and a half cell including the negative electrode were prepared using the negative active material.
[158]
[159]
The contents of artificial graphite and spheroidized natural graphite used in the above Examples and Comparative Examples are shown in Table 1, and the physical properties of natural graphite used in each Example and Comparative Example are shown in Table 2.
[160]
[161]
[Table 1]
division Artificial graphite content (% by weight) Spheroidized natural graphite content (% by weight)
Example 1 80 20
Example 2 80 20
Example 3 85 15
Example 4 70 30
Example 5 65 35
Comparative Example 1 90 10
Comparative Example 2 60 40
Comparative Example 3 80 20
Comparative Example 4 80 20
Comparative Example 5 80 20
Comparative Example 6 80 20
[162]
[Table 2]
division D 50 (㎛) D 90 (㎛) D 10 (㎛) D 90 -D 10 (㎛) Tap density (g/cc) Adhesion (gf/cm)
Example 1 11 15 6 9 1.15 25
Example 2 9 13 6 7 1.20 30
Example 3 11 15 6 9 1.15 25
Example 4 11 15 6 9 1.15 25
Example 5 11 15 6 9 1.15 25
Comparative Example 1 11 15 6 9 1.15 25
Comparative Example 2 11 15 6 9 1.15 25
Comparative Example 3 15 21 7 14 1.15 15
Comparative Example 4 17 28 10 18 1.10 14
Comparative Example 5 11 21 6 15 1.05 11
Comparative Example 6 14 27 8 19 1.00 8
[163]
[Experimental Example 1]
[164]
In-situ SAC Swelling Test
[165]
Using the above manufactured coin-type full cell, the charging range is set so that the SOC is from 0 to 95%, the first cycle is 0.1C, the second cycle is 0.2C, and the third cycle is charged at 0.5C from the 30th cycle. Meanwhile, the change in the thickness of the cathode electrode during charging and discharging was expressed as a swelling ratio (%). The results are shown in Table 3 below.
[166]
[167]
[Experimental Example 2]
[168]
Li-Plating Test
[169]
Using the coin-type half cell prepared above, the half cell was charged and discharged at 1C for 3 cycles, and then charged at 3C for 15 minutes, and the profile was first differentiated. At this time, the inflection points appearing in dQ/dV were checked to quantify lithium plating SOC (Li-Plating SOC, %), which is the SOC at the time when lithium precipitation occurs on the surface of the negative electrode. The results are shown in Table 3 below.
[170]
[171]
[Experimental Example 3]
[172]
Adhesion evaluation of cathode electrode (Peel Strength Test)
[173]
The cathode electrode was rolled with a porosity of 28% to perform a Peel Strength Test. At this time, the electrode was directed at a right angle of 90 degrees using a slide glass and the current collector was peeled off to measure the electrode adhesion (peeling strength), and the results are shown in Table 3 below.
[174]
[Table 3]
division Swelling Ratio (%) Li-Plating SOC (%) Electrode adhesion (gf/cm)
Example 1 20.1 41 25
Example 2 21.2 38 30
Example 3 22.3 40 20
Example 4 24.8 38 17
Example 5 25.2 37 22
Comparative Example 1 27.4 32 18
Comparative Example 2 27.9 28 23
Comparative Example 3 28.3 32 15
Comparative Example 4 29.5 31 14
Comparative Example 5 26.8 34 11
Comparative Example 6 30.6 30 8
[175]
As can be seen in Table 3 above, Examples 1 and 2 using the negative electrode active material according to the present invention used spheroidized natural graphite having a small particle diameter and a uniform particle size distribution, and as a result, the particle size was large and the particle size distribution was Compared to the non-uniform Comparative Examples 3 to 6, the electrode adhesion between the active material and the current collector was improved, thereby reducing the swelling ratio and improving the cycle characteristics.
[176]
And comparing Examples 1, 3 to 5, and Comparative Examples 1 and 2 in which the ratio of spheroidized natural graphite contained in the negative electrode active material was different, the swelling ratio of the negative electrode and the battery used in the above Example and It can be seen that the cycle characteristics are improved compared to the comparative example.
[177]
In addition, it can be seen that when the tap density and electrode adhesion of the spheroidized natural graphite of the present invention are out of the range, the electrode adhesion of the negative active material to the current collector is improved, and accordingly, the swelling ratio decreases and the cycle characteristics are improved.
[178]
[179]
The above description is merely illustrative of the technical spirit of the present invention, and those of ordinary skill in the art to which the present invention pertains will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments disclosed in the present invention are not intended to limit the technical spirit of the present invention, but to explain, and the protection scope of the present invention should be interpreted by the following claims, and all technologies within the scope equivalent thereto. The idea should be construed as being included in the scope of the present invention.
[180]
[Explanation of code]
[181]
10: cathode
[182]
11: whole house
[183]
12: artificial graphite
[184]
13: spheroidized natural graphite
Claims
[Claim 1]
As a negative active material for a secondary battery, the negative active material is a mixture of artificial graphite and spheroidized natural graphite, the average particle diameter (D 50 ) of the spheroidized natural graphite is 12 μm or less, and the D 90 -D 10 value is 5 to 12 A negative active material for a secondary battery, characterized in that ㎛.
[Claim 2]
The method of claim 1, wherein the artificial graphite is included in an amount of 65 to 85% by weight based on the total weight of the negative active material, and the spheroidized natural graphite is included in an amount of 15 to 35% by weight based on the total weight of the negative active material. A negative active material for a secondary battery, characterized in that.
[Claim 3]
The negative active material of claim 1, wherein the natural graphite has an average particle diameter (D 50 ) of 9 to 11 μm .
[Claim 4]
The negative active material of claim 1, wherein the natural graphite has a D 90 -D 10 value of 7 to 9 μm.
[Claim 5]
The negative active material of claim 1, wherein the tap density of the natural graphite is 1.10 to 1.25 g/cc.
[Claim 6]
The negative active material of claim 1, wherein the natural graphite has an adhesive strength of 20 to 35 gf/cm to the current collector after rolling.
[Claim 7]
The anode for secondary battery according to claim 1, wherein the artificial graphite is pitch coke manufactured by heat treatment of coal tar, coal tar pitch, petroleum pitch, or heavy oil. Active material.
[Claim 8]
The method of claim 1, wherein the spheroidized natural graphite is treated with an acid or a base in a scale-like natural graphite, and then, in a spheroidizing apparatus, at a rotor speed of 30 m/s to 100 m/s for 10 minutes to 30 minutes. A negative active material for a secondary battery, characterized in that obtained by spheronizing for minutes.
[Claim 9]
A secondary comprising a current collector and a negative electrode mixture layer coated on the current collector, wherein the negative electrode mixture layer comprises a conductive material, a binder, and the negative active material according to any one of claims 1 to 8. Negative electrode for battery.
[Claim 10]
A secondary battery comprising a negative electrode, a positive electrode, a separator interposed between the negative electrode and the positive electrode, and an electrolyte, wherein the negative electrode is the negative electrode of claim 9.