KR20230012315A - Anode active material, method for preparing the same, and rechargeable lithium battery comprising the same - Google Patents

Abstract

The present invention relates to a negative electrode active material, a manufacturing method thereof, and a lithium secondary battery including the same, wherein the negative electrode active material includes: a core including metal particles; and a shell surrounding the core, and the pore volume of the core is 0.1 cc/g or less. The present invention allows a negative electrode active material to be manufactured with high efficiency and low costs.

Description

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

The present invention relates to a negative electrode active material, a manufacturing method thereof, and a lithium secondary battery including the same, and specifically, a negative electrode active material capable of stable charge/discharge behavior even under high current density by introducing lithium-containing oxide particles, a manufacturing method thereof, and the same It relates to a lithium secondary battery comprising

Lithium Ion Battery (LIB) has high energy density and is easy to design, so it is adopted and used as a major power supply source for mobile electronic devices. The range is getting wider.

In order to apply to new application fields, research on LIB materials having characteristics such as higher energy density and longer life is continuously required.

In particular, in the case of cathode materials, research has been conducted on various materials such as carbon, silicon, tin, and germanium.

Among them, silicon-based anode materials have received a lot of attention because they have a very high energy density compared to currently commercialized graphite anode materials.

However, the silicon-based negative electrode material has fatal disadvantages such as deterioration of electrochemical properties due to the formation of an unstable SEI layer due to side reactions between the silicon surface and the electrolyte, or crushing of the electrode material due to internal stress due to rapid volume expansion occurring during charging and discharging. has

In order to solve this problem, a lot of research has been conducted on improving reversibility on the surface through various surface treatments of silicon-based negative electrode materials, and in particular, methods of surface coating or compounding carbon materials have been widely studied.

On the other hand, various surface treatments using carbon materials required complex and expensive processes, and although some lifespan characteristics of silicon-based anode materials were improved through surface treatment using carbon materials, the ionic conductivity of silicon-based anode materials was lowered, resulting in recent demand. There was a limit to improving the output characteristics for the implementation of the high-speed charge-discharge LIB, which is increasing.

That is, since the conventional surface treatment using a carbon material proceeds with complexing with carbon without improving the low ionic conductivity of the silicon-based negative electrode material, it is difficult to reach the output characteristics required for a high-speed charge/discharge LIB.

Therefore, there is a demand for developing a technology for surface treatment of a high-capacity silicon-based negative electrode active material that suppresses the volume expansion of the silicon-based negative electrode material and at the same time improves the low ionic conductivity of the silicon-based negative electrode material.

Republic of Korea Patent Publication No. 2016-0104720

Accordingly, an object of the present invention is to provide an anode active material for a high-output secondary battery capable of stable charge/discharge behavior under high current density while having high capacity and high energy density.

In addition, it is an object of the present invention to provide a manufacturing method capable of manufacturing the negative electrode active material at high efficiency and low cost.

In addition, an object of the present invention is to provide an electrode and a lithium secondary battery including the negative electrode active material.

However, the problem to be solved by the present application is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

One aspect of the present disclosure is a core including metal particles (core); and

Includes; a shell surrounding the core,

The metal particles include at least one selected from the group consisting of Mg, Al, Si, Ca, Fe, Mg, Mn, Co, Ni, Zn, and Ge,

The pore (pore) volume of the core is 0.1 cc / g or less,

An anode active material is provided.

Another aspect of the present disclosure is to prepare a precursor powder by spray drying a solution containing metal-containing particles;

preparing a heat-treated powder by mixing the precursor powder and the first amorphous carbon and performing a first heat treatment;

mixing and complexing the heat-treated powder, crystalline carbon, and second amorphous carbon; and

A second heat treatment step; including,

The metal is at least one selected from Si, Al, Ti, Mn, Ni, Cu, V, Zr, Mn, Co, Fe and Nb,

A method for producing a negative electrode active material is provided.

Another aspect of the present application, including the negative electrode active material,

electrodes are provided.

Another aspect of the present application is a negative electrode including the negative electrode active material;

an anode positioned opposite to the cathode; and

It provides a lithium secondary battery comprising an electrolyte disposed between the negative electrode and the positive electrode.

The negative electrode active material according to the present invention has an effect of providing a high-output secondary battery capable of stable charge/discharge behavior under high current density while having high capacity and high energy density.

In addition, there is an effect of producing a negative electrode active material with high efficiency and low cost.

1 is a schematic diagram showing an anode active material having a core-shell structure according to an embodiment of the present invention.
2 is a result of measuring the pore volume of the core part measured by BET of the negative electrode active material according to Example 1 of the present invention.
3 is a scanning electron microscope (SEM) photograph of a cross section of the negative electrode active material according to Example 1 of the present invention.

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

Therefore, since the configuration of the embodiments described in this 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, various equivalents and modifications that can replace them at the time of the present application It should be understood that examples may exist.

In this specification, singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as "comprise", "comprise" or "having" are intended to indicate that there is an embodied feature, number, step, component, or combination thereof, but one or more other features or It should be understood that the presence or addition of numbers, steps, components, or combinations thereof is not precluded.

As shown in FIG. 1 , the negative active material according to one aspect of the present disclosure may include a core including metal particles and a shell surrounding the core.

In addition, the metal particles may include at least one selected from the group consisting of Mg, Al, Si, Ca, Fe, Mg, Mn, Co, Ni, Zn, and Ge, and may be spherical or scaly. there is.

Meanwhile, the pore volume of the core may be 0.1 cc/g or less. When the void volume of the core exceeds 0.1 cc/g, AC resistance of the negative active material increases, and thus, output characteristics of a battery including the negative active material may deteriorate.

In addition, the voids may reduce the initial irreversible capacity of the battery and help mitigate the volume expansion of the metal particles. As the distance from the center of the core increases, the specific gravity of the void may decrease.

In one embodiment, the metal particle may be a silicon (Si)-containing particle, and the silicon (Si)-containing particle is at least one selected from the group consisting of a silicon particle, a silicon oxide particle, a silicon carbide particle, and a silicon alloy particle. can include

In addition, the average particle diameter (D50) of the silicon (Si)-containing particles is 50 to 200 nm, and may be represented by Formula 1 below.

[Formula 1]

SiOx (0≤x≤0.5)

In Formula 1, when x exceeds 0.5, there may be adverse effects on battery capacity and efficiency. That is, lithium ions react with oxygen to produce irreversible products such as Li ₂ O and Li-silicate (Li _x Si _y O _z ). Due to this, lithium ions that have reacted with the negative electrode material cannot return to the electrolyte or the positive electrode material and are trapped inside the negative electrode, so that capacity cannot be expressed and efficiency is also reduced.

In addition, for example, the silicon carbide may be SiC, and the silicon alloy may be, for example, a Si—Z alloy (where Z is an alkali metal, an alkaline earth metal, a group 13 element, a group 14 element, a transition metal, or a rare earth element) And one or more elements selected from combinations thereof, but not Si).

The average particle diameter of the silicon-containing particles was measured with a particle size measuring instrument (Mastersizer 3000, Malvern Panalytical) using an organic solution in which the silicon-containing particles were dispersed.

When the average particle diameter of the silicon-containing particles exceeds 200 nm, high battery capacity may be obtained, but battery life may be very short, and when the average particle diameter of the silicon-containing particles is less than 50 nm, battery capacity and efficiency are lowered and manufacturing Expenses may increase.

In one embodiment, the size of the crystal grains of the metal particles may be 5 to 50 nm, preferably 10 to 20 nm.

The grain size of the metal particles was measured by X-ray diffraction analysis (XRD). That is, the crystal grain size of the metal particle was measured by applying the Scherrer equation to a specific peak measured by XRD.

When the grain size of the metal particle exceeds 50 nm, manufacturing cost increases and lifetime stability may deteriorate. When the grain size of the metal particle size is less than 5 nm, battery capacity may decrease.

In one embodiment, the metal particles may be included in 50 to 95% by weight based on the total weight of the core. That is, when the weight of the entire core is 100% by weight, 50 to 95% by weight may correspond to the weight of the metal particles.

In one embodiment, the distance between the metal particles adjacent to each other may be within 200 nm from the center of each particle.

That is, the metal particles included in the core are very close to each other, for example, the distance between the center of one metal particle and the center of another adjacent metal particle is very close to each other within 200 nm.

The center of the metal particle may be, for example, the middle point of the diameter of the metal particle in the case of a spherical metal particle, or the center point of a major axis or a minor axis of the metal particle in the case of a scaly metal particle.

Meanwhile, a part of the surface of one metal particle may come into contact with a part of the surface of another adjacent metal particle.

As the metal particles are closer to each other in the core, the pore volume of the core of the negative electrode active material decreases, which affects the output characteristics of the battery.

In addition, the density of the core may be 0.5 to 2.0 g/cc, and the density of the shell may be 1.0 to 2.3 g/cc.

When the density of the core or the shell is less than the above range, it may be difficult to form an electrode.

In one embodiment, the negative electrode active material may have an average particle size (D50) of 5 μm to 20 μm.

The average particle size of the anode active material was measured using a particle size measuring instrument (Mastersizer 3000, Malvern Panalytical) using an organic solution in which the anode active material was dispersed.

In addition, the ratio of the average particle diameter (D50) of the core and the average particle diameter (D50) of the negative electrode active material (average particle diameter (D50) of the core/average particle diameter (D50) of the negative electrode active material) may be 0.1 to 0.9.

The average particle diameter of the core was measured with a particle size measuring system (Mastersizer 3000, Malvern Panalytical) using an organic solution in which the core was dispersed.

At this time, in the manufacturing method of the negative electrode active material, the heat-treated powder that had undergone the first heat treatment step was regarded as the core.

In one embodiment, the electrical conductivity of the negative electrode active material may be 50 S/cm or less, preferably 30 to 50 S/cm.

In one embodiment, the anode active material may have a height ratio (I _d /I _g ) of a peak corresponding to amorphous carbon (I _d ) and a corresponding peak (I _g ) of crystalline carbon through Raman analysis of 0.5 to 2.0.

In addition, the negative electrode active material may have a full width at half maximum of a D band peak corresponding to amorphous carbon through Raman analysis of 50 to 150, and a full width at half maximum of a G band peak corresponding to crystalline carbon through Raman analysis of 30 to 80.

In one embodiment, the core may further include amorphous carbon, and the shell may include crystalline carbon.

In particular, the shell may be mostly composed of crystalline carbon, and the additional carbon component of the core may be mostly amorphous carbon.

In addition, the shell may include a small amount of amorphous carbon, and the core may include a small amount of crystalline carbon.

When a small amount of crystalline carbon is included in the core, the specific gravity of graphite may increase as the distance from the center of the core increases.

The amorphous carbon of the core may surround the metal particles while being located between the metal particles. That is, the amorphous carbon may serve as a matrix and become a core in which metal particles are dispersed.

The added carbon component of the shell and core may play a role of mitigating the volume expansion of silicon-containing particles coated with lithium-containing oxide particles on their surfaces during charging and discharging.

A method for producing an anode active material according to another aspect of the present disclosure includes preparing a precursor powder by spray-drying a solution containing metal-containing particles; preparing a heat-treated powder by mixing the precursor powder and the first amorphous carbon and performing a first heat treatment; mixing and complexing the heat-treated powder, crystalline carbon, and second amorphous carbon; and performing a second heat treatment.

The metal may be at least one selected from Si, Al, Ti, Mn, Ni, Cu, V, Zr, Mn, Co, Fe, and Nb.

The metal-containing particles provided in the step of preparing the precursor powder may be prepared by being pulverized to have a desired average particle diameter through a pulverization process.

In one embodiment, the first and second amorphous carbons are respectively coal-based pitch, mesophase pitch, petroleum-based pitch, tar, coal-based oil, petroleum-based heavy oil, organic synthetic pitch, sucrose, naphthalene Resins, polyvinyl alcohol resins, furfuryl alcohol resins, polyacrylonitrile resins, polyamide resins, phenolic resins, furan resins, cellulose resins, styrene resins, epoxy resins or vinyl chloride resins, block copolymers, polyols And it may be any one or more selected from the group consisting of polyimide resin.

In addition, the crystalline carbon may be at least one selected from the group consisting of natural graphite, artificial graphite, expanded graphite, graphene, carbon black, and fullerene.

Natural graphite is naturally occurring graphite, and includes flake graphite, high crystalline graphite, and microcrystalline or cryptocrystalline (amorphous) graphite. Artificial graphite is artificially synthesized graphite, which is made by heating amorphous carbon to a high temperature, and includes primary or electrographite, secondary graphite, graphite fiber, and the like.

Expanded graphite Inflates vertical layers of molecular structure by intercalating chemicals such as acids or alkalis between graphite layers and heating them. Graphene includes a single layer or multiple monolayers of graphite.

Carbon black is a crystalline material with a smaller regularity than graphite, and when carbon black is heated at about 3,000° C. for a long time, it can be changed into graphite. Fullerene is a carbon mixture containing at least 3% by weight of fullerene, which is a polyhedral bundle-shaped compound of 60 or more carbon atoms. As the first carbon-based material, one kind or a combination of two or more kinds of these crystalline carbons may be used. For example, natural graphite or artificial graphite may be used. The crystalline carbon may have a spherical, plate-like, fibrous, tubular or powdery form.

Preferably, pitch may be used as the amorphous carbon. The pitch may use a pitch having a softening point of 100 to 250 ° C, and in particular, a petroleum or coal-based pitch having a QI (quinolone insoluble) component of 5% by weight or less, more preferably 1% by weight or less may be used.

Meanwhile, as the crystalline carbon, natural graphite may be preferably used. As for the purity of the graphite, a high purity grade having a fixed carbon content of 99% by weight or more, more preferably 99.95% by weight or more can be used.

In addition, flaky graphite may be suitable for enhancing conductivity through contact with silicon.

In one embodiment, the conjugation step may be performed by a physical method.

The physical method may include at least one selected from the group consisting of high-energy processes such as milling, stirring, mixing, and compression.

For example, the compounding step may be performed by ball milling. In particular, the planetary ball mill can efficiently mix and pulverize the mixture in a non-contact manner with the composition in a rotating and revolving mixing manner.

A ball that can be used for ball milling may be, for example, a zirconia ball, and the type of ball is not limited, and the size of the ball may be, for example, about 0.3 to 10 mm, but is not limited thereto.

On the other hand, the reaction time of the complexation step is 1 minute to 24 hours, the reaction temperature is 40 ~ 250 ℃, the reaction atmosphere can be carried out under the conditions of the atmosphere or inert atmosphere.

In one embodiment, the first heat treatment step may be performed under vacuum, and the heat treatment temperature may be 100 to 500 °C.

In addition, the first heat treatment time is not particularly limited, but may be performed in the range of 10 minutes to 48 hours, for example.

Through the first heat treatment step, the first amorphous carbon is incorporated into the precursor powder and fills the pores of the precursor powder. That is, the pore volume of the negative electrode active material may be adjusted through the first heat treatment step.

In one embodiment, the treatment temperature of the second heat treatment step may be 700 ~ 1,100 ℃.

The second heat treatment time is not particularly limited, but may be performed in the range of 10 minutes to 24 hours, for example.

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

The negative electrode includes the negative electrode active material. For example, after preparing a negative active material composition by mixing the negative electrode active material, a binder, and optionally a conductive agent in a solvent, the negative electrode active material composition is molded into a predetermined shape, or copper foil, etc. It can be manufactured by a method of applying to the current collector of.

The anode may further include an anode active material commonly used as an anode active material of a lithium battery in the art in addition to the anode active material described above. Commonly used anode active materials may include, for example, at least one selected from the group consisting of lithium metal, metals alloyable with lithium, transition metal oxides, non-transition metal oxides, and carbon-based materials.

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

For example, the transition metal oxide may be lithium titanium oxide, vanadium oxide, or lithium vanadium oxide.

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

When the anode active material and the carbon-based material are used together, the oxidation reaction of the silicon-based active material is suppressed, an SEI film is effectively formed to form a stable film, and electrical conductivity is improved, thereby further improving the charge and discharge characteristics of lithium. there is.

Conventional anode active materials may be mixed and blended with the anode active material described above, coated on the surface of the anode active material, or used in any other combination.

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

Examples of such binders include polyvinylidene fluoride, polyvinylidene chloride, polybenzimidazole, polyimide, polyvinyl acetate, polyacrylonitrile, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropyl Cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polystyrene, polymethyl methacrylate, polyaniline, acrylonitrile butadiene styrene, phenol resin, epoxy resin, polyethylene terephthalate, polytetrafluoro Roethylene, polyphenylsulfide, polyamideimide, polyetherimide, polyethylenesulfone, polyamide, polyacetal, polyphenylene oxide, polybutyleneterephthalate, ethylene-propylene-dienter polymer (EPDM), sulfonated EPDM , styrene butadiene rubber, fluororubber, various copolymers, and the like.

The negative electrode may optionally further include a conductive agent in order to further improve electrical conductivity by providing a conductive passage to the negative electrode active material.

As the conductive agent, anything generally used in a lithium battery may be used, and examples thereof include carbon-based materials such as carbon black, acetylene black, ketjen black, and carbon fiber (eg vapor grown carbon fiber); metal-based materials such as metal powders or metal fibers, such as copper, nickel, aluminum, and silver; A conductive material comprising a conductive polymer such as a polyphenylene derivative or a mixture thereof can be used. The content of the conductive material can be appropriately adjusted and used. For example, the weight ratio of the negative electrode active material and the conductive agent may be added in a range of 99:1 to 90:10.

N-methylpyrrolidone (NMP), acetone, water, etc. may be used as the solvent. The amount of the solvent is 1 to 10 parts by weight based on 100 parts by weight of the negative electrode active material. When the content of the solvent is in the above range, the operation for forming the active material layer is easy.

In addition, the current collector is generally made to have a thickness of 3 to 500 μm. The current collector is not particularly limited as long as it does not cause chemical change in the battery and has conductivity. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, fired carbon, copper or stainless steel A surface treated with carbon, nickel, titanium, silver, or the like, an aluminum-cadmium alloy, or the like may be used.

In addition, fine irregularities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous materials, foams, and nonwoven fabrics.

A negative electrode plate may be obtained by directly coating the prepared negative active material composition on a current collector to prepare a negative electrode plate, or by casting on a separate support and laminating a negative active material film peeled from the support to a copper foil current collector. The negative electrode is not limited to the forms listed above and may have forms other than the above forms.

The negative active material composition may be used not only for manufacturing an electrode of a lithium secondary battery, but also for manufacturing a printable battery by being printed on a flexible electrode substrate.

Separately, a cathode active material composition in which a cathode active material, a conductive agent, a binder, and a solvent are mixed is prepared to manufacture a cathode.

As the cathode active material, any lithium-containing metal oxide commonly used in the art may be used.

For example, Li _a A _1-b B _b D ₂ (wherein 0.90≤a≤1.8 and 0≤b≤0.5); Li _a E _1-b B _b O _2-c D _c (wherein 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiE _2-b B _b O _4-c D _c (wherein 0≤b≤0.5 and 0≤c≤0.05); Li _a Ni _1-bc Co _b B _c D _α (wherein 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li _a Ni _1-bc Co _b B _c O _2-α F _α (wherein 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li _a Ni _1-bc Mn _b B _c D _α (wherein 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li _a Ni _1-bc Mn _b B _c O _2-α F _α (wherein 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li _a Ni _b E _c G _d O ₂ (wherein 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li _a Ni _b Co _c Mn _d GeO ₂ (wherein 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li _a NiG _b O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a MnG _b O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a Mn ₂ G _b O ₄ (wherein, 0.90≤a≤1.8, 0.001≤b≤0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O ₅ ; LiV ₂ O ₅ ; LiIO ₂ ; LiNiVO ₄ ; Li _(3-f) J ₂ (PO ₄ ) ₃ (0≤f≤2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≤f≤2); A compound represented by any one of the chemical formulas of LiFePO ₄ may be used.

In the above formula, A is Ni, Co, Mn, or a combination thereof; B is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or combinations thereof; Q is Ti, Mo, Mn, or a combination thereof; I is Cr, V, Fe, Sc, Y, or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu, or combinations thereof.

Of course, one having a coating layer on the surface of this compound may be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may include a coating element compound of an oxide, a hydroxide, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. Compounds constituting these coating layers may be amorphous or crystalline. As the coating element included in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof may be used. In the process of forming the coating layer, any coating method may be used as long as the compound can be coated in a method (eg, spray coating, dipping method, etc.) that does not adversely affect the physical properties of the positive electrode active material by using these elements. Since it is a content that can be well understood by those skilled in the art, a detailed description thereof will be omitted.

For example, LiNiO ₂ , LiCoO ₂ , LiMn _x O _2x (x=1, 2), LiNi _1-x Mn _x O ₂ (0<x<1), LiNi _1-xy Co _x Mn _y O ₂ (0 ≤x≤0.5, 0≤y≤0.5), LiFeO ₂ , V ₂ O ₅ , TiS, MoS, and the like may be used.

In the cathode active material composition, the conductive agent, binder, and solvent may be the same as those of the anode active material composition described above. In some cases, it is also possible to form voids in the electrode plate by further adding a plasticizer to the positive active material composition and the negative active material composition. The content of the cathode active material, conductive agent, binder, and solvent is at a level commonly used in a lithium battery.

The cathode current collector has a thickness of 3 to 500 μm, and is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, stainless steel, aluminum, nickel, titanium, fired carbon, Alternatively, aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, or the like may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics are possible.

The prepared cathode active material composition may be directly coated on a cathode current collector and dried to prepare a cathode electrode plate. Alternatively, a positive electrode plate may be manufactured by casting the positive active material composition on a separate support and then laminating a film obtained by peeling from the support on a positive current collector.

The positive electrode and the negative electrode may be separated by a separator, and any separator commonly used in a lithium battery may be used. In particular, those having low resistance to ion migration of the electrolyte and excellent ability to absorb the electrolyte are suitable. For example, it is a material selected from glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), and combinations thereof, and may be in the form of non-woven fabric or woven fabric. The separator has a pore diameter of 0.01 to 10 μm and a thickness of generally 5 to 300 μm.

The lithium salt-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and lithium. A non-aqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used as the non-aqueous electrolyte.

Examples of the non-aqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma-butyl Rolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, acetonitrile, nitromethane, methyl formate, Methyl acetate, phosphoric acid triesters, trimethoxy methane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, An aprotic organic solvent such as methyl propionate or ethyl propionate may be used.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, A polymer containing an ionic dissociation group or the like can be used.

Examples of the inorganic solid electrolyte include 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 , Nitride, halide, sulfate, and the like of Li such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , etc. may be used.

The lithium salt can be used as long as it is commonly used in lithium batteries, and is a material that is good for dissolving 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 ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, lithium chloroborate, lower aliphatic carbolic acid One or more materials such as lithium carbonate, lithium 4 phenyl borate, imide, etc. may be used.

Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries according to the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin, pouch, etc. depending on the shape, Depending on the size, it can be divided into a bulk type and a thin film type.

Methods for manufacturing these batteries are well known in the art, so detailed descriptions are omitted.

Hereinafter, the present application will be described in more detail using Examples and Comparative Examples, but the present application is not limited thereto.

[Example 1]

5 parts by weight of silicon powder (average particle diameter (D ₅₀ ): 15 um), 20 parts by weight of isopropyl alcohol (IPA), 1 part by weight of stearic acid, and 0.1 part by weight of LiOH were mixed and put into a bead mill to obtain an average particle size (D ₅₀ ) was ground to 110 nm (grinding step).

The pulverized silicon-containing solution was spray-dried to prepare a precursor powder having an average particle diameter (D ₅₀ ) of 5 μm (precursor powder preparation step). The precursor powder was mixed with petroleum-based pitch at a weight ratio of 65:35 and heat-treated at 180° C. for 6 hours under vacuum (first heat treatment step).

After carbonization, silicon, petroleum pitch, and graphite were put into a compounding machine at a ratio of 60: 20: 20 by weight, and compounding was performed for 30 minutes (composite step), and then heat treatment was performed at 900 ° C. in an inert atmosphere to prepare a negative electrode active material. (Second heat treatment step).

[Example 2]

An anode active material was prepared in the same manner as in Example 1, except that the average particle diameter (D ₅₀ ) of the silicon particles was 800 nm.

[Example 3]

An anode active material was prepared in the same manner as in Example 1, except that the average particle diameter (D ₅₀ ) of the silicon particles was 45 nm.

[Example 4]

An anode active material was prepared in the same manner as in Example 1, except that 1 part by weight of the silicon powder was added in the grinding step.

[Comparative Example 1]

An anode active material was prepared in the same manner as in Example 1, except that the first heat treatment step was not performed.

[Comparative Example 2]

An anode active material was prepared in the same manner as in Example 1, except that petroleum pitch was not mixed in the first heat treatment step.

[Production Example]

Coin Half Cell Fabrication

An anode slurry was prepared by uniformly mixing the anode active material, conductive material (Super P), and binder (SBR-CMC) prepared in Examples 1 to 4 and Comparative Examples 1 and 2 in a weight ratio of 93:3:4.

The prepared negative electrode slurry was coated on a copper foil current collector having a thickness of 20 μm, and the coated electrode plate was dried at 120° C. for 30 minutes, and then pressed to prepare a negative electrode.

Metal lithium is used as the anode and counter electrode, a PE separator is used as the separator, and EC (ethylene carbonate): DEC (diethyl carbonate): DMC (dimethyl carbonate) (3 :5:2 volume ratio) A CR2032 type coin half cell was prepared by using 1.0M LiPF6 dissolved in a mixed solvent.

coin full cell fabrication

Using the negative electrode used in the coin half cell, the positive electrode was prepared as follows. A positive electrode slurry was prepared by mixing LiNi _0.6 Co _0.2 Mn _0.2 O ₂ as a positive electrode active material and PVA-PAA as a binder in a weight ratio of 1: 1, and the positive electrode slurry was coated on an aluminum foil current collector having a thickness of 12 μm, and the coating The completed electrode plate was dried at 120° C. for 15 minutes, and then pressed to prepare a positive electrode.

The anode and cathode are used, a PE separator is used as the separator, and the electrolyte is EC (ethylene carbonate): DEC (diethyl carbonate): DMC (dimethyl carbonate) (2: 1: 7 volume ratio) + FEC A CR2032 type coin full cell was prepared by dissolving 1.5M LiPF6 in a 20% mixed solvent.

Evaluation Example 1: Raman, BET, density and conductivity analysis

Raman analysis

The negative active materials prepared in Examples 1 to 4 were analyzed using a LabRam HR Evolution Raman spectrometer (Horiba Jobin-Yvon, France).

The Raman system used an Ar+ ion laser operating at a power of 10 mW with an excitation wavelength of 514 nm.

As a result of the analysis, peaks corresponding to the peak corresponding to silicon (near 500 cm ^-1 ), the D band of amorphous carbon (near 1320 cm ^-1 ) and the G band of crystalline carbon (near 1600 cm ^-1 ) were identified, respectively. .

In addition, the height ratio (I _d /I _g ) of the amorphous carbon corresponding peak (I _d ) and the crystalline carbon corresponding peak (I _g ) is 0.5 to 2.0, the full width at half maximum of the D band peak is 50 to 150, and the G band peak It was confirmed that the full width at half maximum of was 30 to 80.

BET Analysis

The surface area and pore volume of the negative electrode active materials of Examples 1 to 4 and Comparative Examples 1 and 2 were measured using a Micromeritics TriStar II 3020 instrument, and are shown in Table 1 below.

In addition, the absorption / desorption characteristics of Example 1 and Comparative Example 2 through BET measurement are shown in FIG. 2.

The surface area and pore volume were measured through the adsorption amount of nitrogen gas according to the relative pressure change at liquid nitrogen temperature (77K).

It was confirmed that the pore volume of Examples 1 to 4 was very small compared to Comparative Example 1 in which the first heat treatment step was not performed or Comparative Example 2 in which the petroleum pitch was not mixed in the first heat treatment step.

That is, it was confirmed that the pore volume of the negative electrode active material could be adjusted through the first heat treatment step.

Conductivity analysis

The electrical conductivity of the anode active materials of Examples 1 to 4 and Comparative Examples 1 and 2 was measured by a 4-needle method connected to a variable potential and current generator, and is shown in Table 1 below.

Specifically, electrical conductivity was measured by a 4-needle method while applying a load of 800-2,400 kgf to the pelletized powder of the negative electrode active material.

density analysis

After loading 2g of anode active material into a rolling mill with a diameter of 18mm, measure the thickness of the pellet while applying a load, and measure the density through this.

When measuring the density, the first heat treatment powder was used for the core, and the second heat treatment powder after mixing graphite and amorphous carbon was used for the shell.

Oxygen content (%) core specific surface area
(m ² /g) core
void volume
(cc/g) conductivity
(S/cm) negative active material density
(g/cc) Example 1 5.8 19.2 0.03 37.9 1.46 Example 2 4.6 6.7 0.02 41.3 1.50 Example 3 6.6 28.7 0.03 31.8 1.29 Example 4 4.9 2.1 0.01 11.3 1.07 Comparative Example 1 5.9 24.5 0.25 12.6 1.19 Comparative Example 2 8.1 97.2 0.68 42.7 1.53

Evaluation Example 2: SEM analysis

The results of scanning electron microscope (SEM) analysis on the cross section of the negative electrode active material prepared in Example 1 are shown in FIG. 3A.

A core containing silicon particles and a carbon-based shell surrounding the core were identified.

In addition, in order to confirm the shape of the silicon particles of the core, the results of scanning electron microscopy (SEM) analysis are shown in FIG. 3B.

Spherical and scaly silicon particles were confirmed, and it was confirmed that the silicon particles are adjacent to each other, and the distance from the center of one silicon particle to the center of another adjacent silicon particle may be 200 nm or less.

That is, through SEM analysis, it was confirmed that the anode active material of the present disclosure has a core-shell structure, and includes silicon particles located adjacent to each other in the core.

Evaluation Example 3: Battery Characteristics Evaluation

The battery characteristics of the coin half cell and the coin full cell manufactured using the anode active material prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated as follows.

A coin full cell was used to measure lifespan characteristics, and a coin half cell was used to evaluate other battery characteristics.

The coin half-cells manufactured using the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to constant current until the voltage reached 0.01V (vs. Li) at a current of 0.1C rate at 25 ° C, respectively. After charging, constant voltage charging was performed until the current reached 0.05C while maintaining 0.01V. After resting the charged cell for 10 minutes, it was discharged with a constant current of 0.1C until the voltage reached 1.5V (vs. Li) during discharge (2 times, initial formation). The "C" is the discharge rate of the cell, which means a value obtained by dividing the total capacity of the cell by the total discharge time.

The coin full cells manufactured using the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were subjected to constant current until the voltage reached 4.2V (vs. Li) at a current of 0.1C rate at 25 ° C, respectively. After charging, constant voltage charging was performed until the current reached 0.05C while maintaining 4.2V. After resting the charged cell for 10 minutes, it was discharged with a constant current of 0.1 C until the voltage reached 2.7V (vs. Li) during discharge (2 times, initial formation).

Thereafter, the cell was charged with a constant current at 25 ° C. at a current of 1.0C rate until the voltage reached 4.2V (vs. Li), and was charged with a constant voltage until the current reached 0.05C while maintaining 4.2V. After resting the charged coin cell for 10 minutes, a cycle of discharging at a constant current of 1.0 C was repeated until the voltage reached 2.7V (vs. Li) during discharge (cycles 1 to 100).

Table 2 below shows the measured initial discharge capacity, initial efficiency, and lifespan characteristics of cells using negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2.

The initial discharge capacity is the discharge capacity in the first cycle.

Initial efficiency and lifetime characteristics were calculated from Equations 1 and 2, respectively.

<Equation 1>

Initial efficiency [%]=[Discharge capacity in the 1st cycle / Charge capacity in the 1st cycle]Х100

<Equation 2>

Life characteristics [%]=[Discharge capacity at the 100th cycle / Discharge capacity at the 1st cycle]Х100

initial discharge capacity
(mAh/g) initial efficiency
(%) life characteristics
(%@100th) Example 1 1374.3 84.2 88.4 Example 2 1489.2 88.9 72.4 Example 3 1318.6 81.7 88.1 Example 4 1174.3 85.8 87.9 Comparative Example 1 1329.6 86.2 85.9 Comparative Example 2 1299.4 77.9 86.4

Compared to Comparative Example 1 in which the first heat treatment step was not performed or Comparative Example 2 in which the petroleum pitch was not mixed in the first heat treatment step, Example 1 was found to have a high initial discharge capacity and excellent life characteristics.

Meanwhile, the measured output characteristics and internal resistance characteristics of the coin half cells manufactured using the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 are shown in Table 3 below.

The output characteristics were calculated from Equation 3 below.

<Equation 3>

Output characteristics [%] = [discharge capacity of when discharged at a rate of 2.0C/discharge capacity when heat is generated at a rate of 0.1C] Х100

In addition, the coin half-cells prepared using the negative electrode active materials prepared in Examples 1 to 4 and Comparative Examples 1 and 2 were charged at room temperature (25 ° C. at 4.1 mA and 0.01V and cut-off at 0.01V, so that 5 AC resistance values were measured under the conditions of a very small excitation amplitude of 1 to 10 mV and a frequency of 1 MHz to 1 mHz.

output characteristics
(%@2.0 C) AC Resistance (Ω) Example 1 82.8 48.3 Example 2 78.3 49.1 Example 3 75.1 63.1 Example 4 69.1 46.2 Comparative Example 1 79.1 59.1 Comparative Example 2 72.1 55.7

As shown in Table 3, comparing the characteristics of the batteries manufactured using the negative electrode active materials prepared in Example 1 and Non-Table Examples 1 and 2, in which only the first heat treatment step is different, Comparative Example not subjected to the first heat treatment step Compared to Comparative Example 2 in which petroleum pitch was not mixed in the first heat treatment step or the first heat treatment step, Example 1 had a low AC resistance measurement value and excellent output characteristics.

That is, it was found that the output characteristics and AC resistance characteristics of the battery were affected by the presence or absence of the first heat treatment step and the change in process conditions of the first heat treatment step during the manufacture of the negative electrode active material.

The scope of the present invention is indicated by the claims to be described later rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and equivalent concepts thereof are interpreted as being included in the scope of the present invention. It should be.

Claims (18)

A core containing metal particles; and
Including; a shell surrounding the core;
The metal particles include at least one selected from the group consisting of Mg, Al, Si, Ca, Fe, Mg, Mn, Co, Ni, Zn, and Ge,
The void volume of the core is 0.1 cc / g or less,
cathode active material. According to claim 1,
The metal particle is a particle containing silicon (Si),
cathode active material. According to claim 2,
The silicon (Si)-containing particles include at least one selected from the group consisting of silicon particles, silicon oxide particles, silicon carbide particles, and silicon alloy particles,
cathode active material. According to claim 2,
The average particle diameter (D50) of the silicon (Si)-containing particles is 50 to 200 nm,
Represented by Formula 1 below,
cathode active material.

[Formula 1]
SiOx (0≤x≤0.5) According to claim 1,
The size of the crystal grains of the metal particles is 5 to 50 nm,
cathode active material. According to claim 1,
The metal particles are contained in 50 to 95% by weight based on the total weight of the core,
cathode active material. According to claim 1,
The distance between the metal particles adjacent to each other is within 200 nm from the center of each particle,
cathode active material. According to claim 1,
The average particle size (D50) is 5 to 20 μm,
cathode active material. According to claim 1,
The ratio of the average particle diameter (D50) of the core and the average particle diameter (D50) of the negative active material (average particle diameter (D50) of the core/average particle diameter (D50) of the negative electrode active material) is 0.1 to 0.9,
cathode active material. According to claim 1
electrical conductivity of 50 S/cm or less;
cathode active material. According to claim 1,
The height ratio (I _d /I _g ) of the amorphous carbon corresponding peak (I _d ) and the crystalline carbon corresponding peak (I _g ) through Raman analysis is 0.5 to 2.0,
cathode active material. According to claim 1,
The full width at half maximum of the D band peak of amorphous carbon through Raman analysis is 50 to 150,
The full width at half maximum of the G band peak of crystalline carbon through Raman analysis is 30 to 80,
cathode active material. preparing a precursor powder by spray drying a solution containing metal-containing particles;
preparing a heat-treated powder by mixing the precursor powder and the first amorphous carbon and performing a first heat treatment;
mixing and complexing the heat-treated powder, crystalline carbon, and second amorphous carbon; and
A second heat treatment step; including,
The metal is at least one selected from Si, Al, Ti, Mn, Ni, Cu, V, Zr, Mn, Co, Fe and Nb,
A method for producing an anode active material. According to claim 13,
The first and second amorphous carbons are respectively coal-based pitch, mesophase pitch, petroleum-based pitch, tar, coal-based oil, petroleum-based heavy oil, organic synthetic pitch, sucrose, naphthalene resin, polyvinyl alcohol resin , furfuryl alcohol resin, polyacrylonitrile resin, polyamide resin, phenol resin, furan resin, cellulose resin, styrene resin, epoxy resin or vinyl chloride resin, block copolymer, polyol and polyimide resin At least one selected from the group
The crystalline carbon is at least one selected from the group consisting of natural graphite, artificial graphite, expanded graphite, graphene, carbon black and fullerene,
A method for producing an anode active material. According to claim 13,
The compounding step is performed by any one or more selected from the group consisting of milling, stirring, mixing, and compression.
A method for producing an anode active material. According to claim 13,
The first heat treatment step is treated at 100 to 500 ° C. under vacuum,
The treatment temperature of the second heat treatment step is 700 ~ 1,100 ℃,
A method for producing an anode active material. Comprising the negative electrode active material of any one of claims 1 to 12,
electrode. A negative electrode comprising the negative electrode active material of any one of claims 1 to 12;
an anode positioned opposite to the cathode; and
Including, an electrolyte disposed between the cathode and the anode;
lithium secondary battery.

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