Anode active material particles, anode including said anode active material particles, and secondary battery including said anode

Abstract

The present invention relates to anode active material particles, anodes including the anode active material particles, and secondary batteries including the anodes. Specifically, the anode active material particles include a core and a coating layer located on the core, the core including silicon-based particles, and the coating layer including a polymer including an aromatic cyclic monomer unit having an alkyl group and containing a heteroatom. This makes it possible to prevent side reactions such as hydrogen gas generation during aqueous mixing of a slurry without increasing resistance.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0110315, filed on August 31, 2022, and all contents disclosed in the documents of this Korean patent application are incorporated herein by reference.

[0002] The present invention relates to anode active material particles, anodes including the anode active material particles, and secondary batteries including the anodes. Specifically, the anode active material particles include a core and a coating layer located on the core, the core including silicon-based particles, and the coating layer including a polymer having an alkyl group in a side chain and including an aromatic cyclic monomer unit containing a heteroatom. [Background technology]

[0003] With the rapid increase in the use of fossil fuels, there is an increasing need for alternative and clean energy, and as part of this, the most actively researched field is the field of power generation and storage using electrochemical reactions.

[0004] Currently, secondary batteries are a typical example of electrochemical elements that use electrochemical energy, and their range of use is gradually expanding. Recently, with the development of technologies and increasing demand for portable devices such as mobile computers, mobile phones, and cameras, the demand for secondary batteries as energy sources has rapidly increased. Among such secondary batteries, lithium secondary batteries with high energy density, i.e., high capacity, have been the focus of much research and are now widely used commercially.

[0005] Generally, a secondary battery is composed of a positive electrode, a negative electrode, an electrolyte, and a separator. The negative electrode includes a negative electrode active material that inserts and extracts lithium ions released from the positive electrode. The negative electrode active material may be silicon-based particles that have a large discharge capacity.

[0006] Meanwhile, a negative electrode can be manufactured by coating a negative electrode slurry on a negative electrode current collector and drying it. When a negative electrode slurry containing silicon-based particles is mixed with water as a solvent (hereinafter referred to as aqueous mixing), the silicon-based particles react with the water to generate silicon dioxide and hydrogen gas. The hydrogen gas remains in the negative electrode slurry in the form of bubbles, making it difficult to form a uniform negative electrode active material layer. Furthermore, the hydrogen gas remaining in the negative electrode is flammable and explosive, which can pose a significant risk during the battery manufacturing process and battery operation.

[0007] To solve this problem, a technique of forming a carbon coating layer on silicon-based particles has been used. However, as time passes after the negative electrode slurry is prepared, moisture permeates the carbon coating layer or enters through gaps in the carbon coating layer, which results in a problem that moisture is not effectively blocked from contacting the silicon-based particles.

[0008] Therefore, the present invention provides negative electrode active material particles and a method for manufacturing the negative electrode active material particles, which can minimize the generation of hydrogen gas during the mixing process of the negative electrode slurry. Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide negative electrode active material particles that can minimize hydrogen gas generation during mixing of a negative electrode slurry.

[0010] Another object of the present invention is to provide a method for producing the negative electrode active material particles.

[0011] A further object of the present invention is to provide a negative electrode containing the negative electrode active material particles.

[0012] Another problem to be solved by the present invention is to provide a secondary battery including the negative electrode. [Means for solving the problem]

[0013] According to one embodiment of the present invention, there is provided an anode active material particle including a core and a coating layer disposed on the core, wherein the core includes silicon-based particles, and the coating layer includes a polymer including an aromatic cyclic monomer unit having an alkyl group in a side chain and including a heteroatom.

[0014] According to another embodiment of the present invention, there is provided a method for manufacturing anode active material particles, the method including: introducing core particles including silicon-based particles into a coating solution including a solvent and a polymer having an alkyl group in a side chain and including an aromatic cyclic monomer unit containing a heteroatom.

[0015] According to yet another embodiment of the present invention, there is provided a negative electrode including the negative electrode active material particles.

[0016] According to yet another embodiment of the present invention, there is provided a secondary battery including the negative electrode. [Effects of the Invention]

[0017] In the negative electrode active material particles according to one embodiment of the present invention, a coating layer including a polymer having an alkyl group in a side chain and including a heteroatom-containing aromatic cyclic monomer unit is disposed on the surface of a core including silicon-based particles. This suppresses the reaction between water and the silicon-based particles during aqueous mixing of the negative electrode slurry, thereby minimizing the generation of hydrogen gas. This improves safety during the negative electrode manufacturing process and during battery operation.

[0018] In addition, according to a method for manufacturing anode active material particles according to another embodiment of the present invention, a coating layer is formed on a core using a coating solution including a solvent and a polymer having an alkyl group in a side chain and including an aromatic cyclic monomer unit containing a heteroatom. As a result, the polymer having an alkyl chain in a side chain can be effectively coated on the core including the silicon-based particle. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a schematic diagram showing a negative electrode active material particle according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0020] The present invention will now be described in more detail to aid in understanding the invention.

[0021] The terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted as having meanings and concepts that are consistent with the technical idea of ​​the present invention, based on the principle that inventors can appropriately define the concepts of terms in order to best explain their inventions.

[0022] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0023] It should be understood that in this specification, the terms "comprises," "includes," "has," and the like specify the presence of embodied features, numbers, steps, components, or combinations thereof, but do not preclude the possible presence or addition of one or more different features, numbers, steps, components, or combinations thereof.

[0024] In this specification, the average particle size (D 50 The average particle size (D) can be defined as the particle size corresponding to 50% of the cumulative volume in the particle size distribution curve. 50 ) can be measured using, for example, a laser diffraction method. The laser diffraction method generally enables measurement of particle sizes from the submicron range to several mm, and can provide results with high reproducibility and high resolution.

[0025] In this specification, the term "weight average molecular weight (Mw)" refers to a value measured by gel permeation chromatography (GPC) and converted to a standard polystyrene. Specifically, the weight average molecular weight is a value measured by GPC under the following conditions and converted, and a calibration curve is prepared using standard polystyrene from an Agilent system.

[0026] <Measurement conditions> Measurement equipment: Agilent GPC (Agulent 1200 series, USA) Column: PL Mixed B 2 columns connected Column temperature: 40℃ Eluent: tetrahydrofuran Flow rate: 1.0mL / min Concentration: ~1mg / mL (100μL injection)

[0027] In this specification, the content (wt %) of the "polymer having an alkyl chain in its side chain" in the negative electrode active material particles can be confirmed by TGA, where the measurement conditions are as follows.

[0028] Measuring device: Seiko Exstar 6000 manufactured by Seiko Injected gas (atmospheric gas): Ar Heating rate: 5℃ / min Sample measurement amount: 10 mg

[0029] <Negative electrode active material particles> Referring to FIG. 1, an anode active material particle 10 according to an embodiment of the present invention includes a core 100 and a coating layer 110 disposed on the core. The core 100 may include a silicon-based particle, and the coating layer 110 may include a polymer having an alkyl group in a side chain and including an aromatic cyclic monomer unit containing a heteroatom.

[0030] The core may include a silicon-based particle, and more specifically, the core may be made of a silicon-based particle. When the core is a silicon-based particle, one of the silicon-based particles may correspond to one core.

[0031] The silicon-based particles are SiO x (0≦x<2) x (0≦x<2) may be a form containing Si and SiO2, and the Si may form a phase. That is, the x may be the SiO x The ratio of O to Si is within the range of 0≦x<2. x When (0≦x<2) is included, the discharge capacity of the secondary battery can be improved. Specifically, the silicon-based particles can be particles made of Si.

[0032] The average particle size (D 50 ) can be 0.1 μm to 100 μm, specifically 1 μm to 10 μm, and more specifically 4 μm to 6 μm. When this range is satisfied, reactions inside and outside the silicon-based particles can occur uniformly during battery operation, and a pore structure can be effectively formed in the negative electrode active material layer, allowing reactions inside the negative electrode active material layer to occur uniformly. This can improve the battery life.

[0033] The coating layer may be located on the core, specifically, the coating layer may cover at least a portion of the surface of the core.

[0034] The coating layer may include a polymer having an alkyl group in a side chain and including a heteroatom-containing aromatic cyclic monomer unit. The polymer having an alkyl group in a side chain and including a heteroatom-containing aromatic cyclic monomer unit suppresses the reaction between the silicon-based core particles and water when the negative electrode slurry containing the negative electrode active material particles is mixed with an aqueous solution, thereby reducing the amount of hydrogen gas generated. This improves safety during the negative electrode manufacturing process and during battery operation.

[0035] In the polymer, the alkyl group may be an alkyl group having 1 to 50 carbon atoms, preferably an alkyl group having 3 to 40 carbon atoms, an alkyl group having 3 to 30 carbon atoms, more preferably an alkyl group having 3 to 20 carbon atoms, specifically an alkyl group having 5 to 15 carbon atoms, and even more specifically an alkyl group having 7 to 9 carbon atoms. When an alkyl group having a carbon number within the above range is contained as a side chain, the reaction between the silicon-based particles and water during the aqueous mixing of the negative electrode slurry can be more effectively suppressed, and the amount of hydrogen gas generated can be effectively reduced. Furthermore, because the alkyl group is not excessively long, lithium ion insertion and extraction at the negative electrode can be effectively performed, and the loss of capacity of the negative electrode active material particles can be minimized.

[0036] In addition, the polymer may contain one or more atoms selected from the group consisting of nitrogen (N), sulfur (S), and phosphorus (P) as heteroatoms, preferably one or more selected from nitrogen and sulfur. Such heteroatoms may have more remaining electrons than carbon alone, allowing for free electron movement through π-π bonds and improving conductivity. However, because insufficient bonding strength between the silicon-based particle core and the polymer coating layer can lead to detachment of the coating layer, it is preferable to use a polymer containing heteroatoms.

[0037] Furthermore, when the polymer contains an aromatic cyclic monomer unit and is chain-like, even if it is a conductive polymer, it may not achieve a desired level of conductivity unless it is doped with an atom having a high electronegativity. Even if it contains a heteroatom, the flexibility of the main chain is higher than when the basic unit is an aromatic cyclic monomer unit, and the polymers tend to become entangled with each other on the surface of the core when swollen with a solvent during the coating process, which may prevent good adsorption to the core surface and may not be effective in improving conductivity or adhesion to the core. In addition, aliphatic cyclic monomer units may not be suitable because electrons cannot move freely.

[0038] The polymer including an aromatic cyclic monomer unit having an alkyl group in a side chain and containing a heteroatom may include at least one selected from the group consisting of a polymer including a repeating unit of the following Chemical Formula 1, a polymer including a repeating unit of the following Chemical Formula 2, and a polymer including a repeating unit of the following Chemical Formula 3:

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] In the above Chemical Formula 1, R1 and R2 are each either hydrogen or an alkyl group having 5 to 15 carbon atoms, and at least one of R1 and R2 is an alkyl group having 5 to 15 carbon atoms. In the above Chemical Formula 1, the alkyl group having 5 to 15 carbon atoms can specifically be an alkyl group having 7 to 9 carbon atoms, and more specifically, -CH 17The n1 may be an integer of 1 to 10,000, specifically an integer of 10 to 1,000, and more specifically an integer of 100 to 500. The polymer containing the repeating unit of Chemical Formula 1 may be poly(3-octylthiophene) containing the repeating unit of Chemical Formula 1-1 below.

[0043] [ka]

[0044] In the above Chemical Formula 2, R3 to R6 are each either one of hydrogen and an alkyl group having 5 to 15 carbon atoms, and at least one of R3 to R6 is an alkyl group having 5 to 15 carbon atoms. In the above Chemical Formula 2, the alkyl group having 5 to 15 carbon atoms can specifically be an alkyl group having 7 to 9 carbon atoms, and more specifically, -CH 17 The n2 may be an integer of 1 to 10,000, specifically an integer of 10 to 1,000, more specifically an integer of 100 to 500. The polymer containing a repeating unit of Chemical Formula 2 may be a polymer containing a repeating unit of Chemical Formula 2-1 below.

[0045] [ka]

[0046] In the chemical formula 3, the R to R 10 are each either one of hydrogen and an alkyl group having 5 to 15 carbon atoms, and the R 10 At least one of the above is an alkyl group having 5 to 15 carbon atoms. In Chemical Formula 3, the alkyl group having 5 to 15 carbon atoms may specifically be an alkyl group having 7 to 9 carbon atoms, and more specifically, -CH 17The n3 may be an integer of 1 to 10,000, specifically an integer of 10 to 1,000, more specifically an integer of 100 to 500. The polymer including the repeating unit of Chemical Formula 3 may be a polymer including a repeating unit of Chemical Formula 3-1 below.

[0047] [ka]

[0048] That is, the polymer having an alkyl group in its side chain and including an aromatic cyclic monomer unit containing a heteroatom may include poly(3-octylthiophene) or poly(3-octylpyrroles), and preferably, the polymer having an alkyl group in its side chain and including an aromatic cyclic monomer unit containing a heteroatom may be poly(3-octylthiophene). When the polymer having an alkyl group in its side chain and including an aromatic cyclic monomer unit containing a heteroatom includes a polymer having a repeating unit selected from Formulas 1-1 to 1-3, the reaction between silicon-based particles and water during aqueous mixing of the negative electrode slurry is more effectively suppressed, thereby further significantly reducing the amount of hydrogen gas generated. Furthermore, since the polymer has high conductivity, the conductivity within the negative electrode is improved, thereby improving the battery life and fast charging performance.

[0049] The weight-average molecular weight of the polymer having an alkyl group in a side chain and including a heteroatom-containing aromatic cyclic monomer unit may be 200 g / mol to 2,000,000 g / mol, specifically 2,000 g / mol to 200,000 g / mol, more specifically 10,000 g / mol or more, 15,000 g / mol or more, 20,000 g / mol or more, or 25,000 g / mol or more, and 150,000 g / mol or less, 130,000 g / mol or less, 100,000 g / mol or less, or 90,000 g / mol or less. When the weight-average molecular weight is within this range, the polymer having an alkyl group in a side chain and including a heteroatom-containing aromatic cyclic monomer unit can uniformly coat the entire surface of the silicon-based particles, thereby preventing aggregation of the polymer and the silicon-based particles during the preparation of a negative electrode active material.

[0050] The polymer containing an alkyl chain in its side chain may be included in the negative electrode active material particles in an amount of 0.1 wt% to 50 wt%, specifically, 1.0 wt% or more, 3.0 wt% or more, 4.0 wt% or more, 5.0 wt% or more, 6.0 wt% or more, or 7.0 wt% or more, or 30 wt% or less, 25 wt% or less, 20 wt% or less, 18 wt% or less, 15 wt% or less, or 12 wt% or less. When this range is satisfied, the capacity per weight of the negative electrode active material particles is maintained at an appropriate level, and lithium ions can easily diffuse to the core, improving the life of the negative electrode and the battery.

[0051] The average particle size (D 50 ) may be 0.1 μm to 150 μm, specifically 1 μm to 20 μm, more specifically 3 μm to 10 μm, for example, 5 μm to 7 μm. When this range is satisfied, gas generation during preparation of the negative electrode slurry can be more effectively suppressed, and the battery life and fast charging performance can be further improved.

[0052] <Method of manufacturing negative electrode active material particles> A method for manufacturing anode active material particles according to another embodiment of the present invention may include introducing core particles including silicon-based particles into a coating solution including a solvent and a polymer having an alkyl chain in a side chain.

[0053] Here, the negative electrode active material particles are the same as the negative electrode active material particles of the above-described embodiment. The core particles correspond to the cores included in the negative electrode active material particles of the above-described embodiment. The polymer having an alkyl chain in its side chain is the same as the polymer having an alkyl chain in its side chain of the above-described embodiment. Therefore, a description thereof will be omitted. The polymer having an alkyl chain in its side chain is disposed on the core particles, and the coating layer described in the above-described embodiment can be formed.

[0054] The coating solution may include a solvent and a polymer containing alkyl chains on its side chains.

[0055] The solvent may include at least one selected from the group consisting of chloroform, toluene, hexane, benzene, and tetrahydrofuran. Polymers having alkyl chains in their side chains exhibit hydrophobicity. Therefore, when the solvent includes at least one selected from the group consisting of chloroform, toluene, hexane, benzene, and tetrahydrofuran, the polymers having alkyl chains in their side chains can be effectively dispersed in the solvent. This allows the coating layer to be stably formed with a uniform thickness.

[0056] After the adding step, the coating solution containing the silicon-based particles may be stirred to arrange the polymer having an alkyl chain in its side chain on the silicon-based particles.

[0057] <Negative electrode> A negative electrode according to another embodiment of the present invention may include negative electrode active material particles, where the negative electrode active material particles are the same as the negative electrode active material particles of the above-described embodiment. Specifically, the negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector. The negative electrode active material layer may include the negative electrode active material particles. Furthermore, the negative electrode active material layer may further include a negative electrode binder and / or a negative electrode conductive material.

[0058] The negative electrode current collector is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, the current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. Specifically, transition metals that adsorb carbon well, such as copper and nickel, can be used as the current collector. The thickness of the current collector may be 6 μm to 20 μm, but is not limited thereto.

[0059] The negative electrode binder may include at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, or may include various copolymers thereof.

[0060] The negative electrode conductive material is not particularly limited as long as it does not cause a chemical change in the battery and has conductivity. For example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives may be used.

[0061] <Secondary battery> A secondary battery according to another embodiment of the present invention may include the negative electrode of the above-described embodiment. Specifically, the secondary battery may include a negative electrode, a positive electrode, a separator interposed between the positive electrode and the negative electrode, and an electrolyte, and the negative electrode is the same as the negative electrode described above. Since the negative electrode has been described in detail, detailed description thereof will be omitted.

[0062] The positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector and including the positive electrode active material.

[0063] The positive electrode current collector in the positive electrode is not particularly limited as long as it does not cause chemical changes in the battery and is conductive. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. can be used. The positive electrode current collector typically has a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the current collector to enhance the adhesive strength of the positive electrode active material. It can be used in various forms, such as a film, sheet, foil, mesh, porous material, foam, or nonwoven fabric.

[0064] The positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2) or lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4; or a lithium ion battery having the chemical formula Li 1+c1 Mn 2-c1 O4 (0≦c1≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, and Cu2V2O7; chemical formula LiNi 1-c2 Ni-site type lithium nickel oxide represented by the chemical formula LiMn 2-c3 Examples include, but are not limited to, lithium manganese composite oxides represented by Mc3O2 (where M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦c3≦0.1) or Li2Mn3MO8 (where M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion. The positive electrode may be metallic lithium (Li-metal).

[0065] The positive electrode active material layer may contain a positive electrode conductive material and a positive electrode binder in addition to the above-mentioned positive electrode active material.

[0066] The positive electrode conductive material is used to impart conductivity to the electrode and can be any material that does not cause chemical changes in the battery and has electronic conductivity. Specific examples include graphite such as natural graphite and artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjenburk, channel black, furnace black, lamp black, thermal black, and carbon fiber; metal powder or metal fiber such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These materials may be used alone or in combination.

[0067] The positive electrode binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the positive electrode current collector. Specific examples of the positive electrode binder include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These binders may be used singly or in combination.

[0068] The separator separates the negative electrode and positive electrode and provides a path for lithium ions to move. Any separator typically used in secondary batteries can be used without particular limitations. In particular, separators with low resistance to electrolyte ion movement and excellent electrolyte humidification capacity are preferred. Specifically, porous polymer films, such as those made of polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminate structures of two or more layers thereof can be used. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Separators coated with ceramic components or polymeric materials to ensure heat resistance or mechanical strength can also be used, and they can be selectively used in single-layer or multi-layer structures.

[0069] Examples of the electrolyte include, but are not limited to, organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes that can be used in manufacturing lithium secondary batteries.

[0070] Specifically, the electrolyte may include a non-aqueous organic solvent and a metal salt.

[0071] Examples of the non-aqueous organic solvent that can be used include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0072] In particular, among the carbonate organic solvents, ethylene carbonate and propylene carbonate, which are cyclic carbonates, are preferred because they are high-viscosity organic solvents with high dielectric constants and can dissociate lithium salts well. When such cyclic carbonates are mixed with linear carbonates having low viscosity and low dielectric constants, such as dimethyl carbonate and diethyl carbonate, in an appropriate ratio, an electrolyte having high electrical conductivity can be produced, and these cyclic carbonates are more preferred.

[0073] The metal salt may be a lithium salt, and the lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte solution. For example, the anion of the lithium salt may be F - , Cl - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 -, CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - , and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0074] In addition to the electrolyte components, the electrolyte may further contain one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethyl alcohol amine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethyl alcohol, or aluminum trichloride, for the purposes of improving the battery's life characteristics, suppressing a decrease in battery capacity, and improving the battery's discharge capacity.

[0075] According to yet another embodiment of the present invention, there is provided a battery module including the secondary battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having high capacity, excellent rate-limiting characteristics, and excellent cycle characteristics, and can be used as a power source for medium- to large-sized devices selected from the group consisting of electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, and power storage systems.

[0076] In the following, preferred embodiments will be presented to facilitate understanding of the present invention. However, the above embodiments are merely illustrative of the present description, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope of the scope and technical ideas of the present description. It goes without saying that such changes and modifications fall within the scope of the appended claims.

[0077] Examples and Comparative Examples Example 1: Production of negative electrode active material particles A coating solution was prepared by dispersing 10 g of poly(3-octylthiophene) containing the repeating unit of the following chemical formula 1-1 in 50 g of chloroform. 50 Silicon particles with a particle size of 5 μm were prepared.

[0078] [ka]

[0079] The core particles were added to the coating solution and stirred for 2 hours using a magnetic bar and a magnetic stirrer to prepare negative electrode active material particles.

[0080] The average particle size (D 50 The particle diameter of the poly(3-octylthiophene) was 6 μm, and the weight average molecular weight of the poly(3-octylthiophene) was 30,000. The poly(3-octylthiophene) was contained in the negative electrode active material particles in an amount of 6 wt %.

[0081] Example 2: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that the content of the poly(3-octylthiophene) in the negative electrode active material particles was 12 wt %.

[0082] Example 3: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that a polymer having a weight-average molecular weight of 30,000 and including a repeating unit of the following Chemical Formula 2-1 was used instead of poly(3-octylthiophene).

[0083] [ka]

[0084] Example 4: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 3, except that the polymer containing the repeating unit of Formula 2-1 was contained in the negative electrode active material particles in an amount of 7 wt %.

[0085] Example 5: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that a polymer having a weight-average molecular weight of 30,000 and including a repeating unit of the following Formula 3-1 was used instead of poly(3-octylthiophene).

[0086] [ka]

[0087] Example 6: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 3, except that the polymer containing the repeating unit of Formula 3-1 was contained in the negative electrode active material particles in an amount of 7 wt %.

[0088] Example 7: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that the content of poly(3-octylthiophene) in the negative electrode active material particles was adjusted to 5 wt %.

[0089] Example 8: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that the content of poly(3-octylthiophene) in the negative electrode active material particles was adjusted to 7 wt %.

[0090] Example 9: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that the content of poly(3-octylthiophene) in the negative electrode active material particles was adjusted to 9 wt %.

[0091] Example 10: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that poly(3-octylthiophene) having a weight average molecular weight of 20,000 was used.

[0092] Example 11: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that poly(3-octylthiophene) having a weight-average molecular weight of 100,000 was used.

[0093] Comparative Example 1: Preparation of negative electrode active material particles Average particle size (D 50 Silicon particles having a particle size of 5 μm were prepared as negative electrode active material particles.

[0094] Comparative Example 2: Production of negative electrode active material A coating solution was prepared by dispersing 10 g of polythiophene without alkyl chains in the side chains in 50 g of chloroform. 50 Silicon particles with a particle size of 5 μm were prepared.

[0095] The core particles were added to the coating solution and stirred for 2 hours using a magnetic bar and a magnetic stirrer to prepare negative electrode active material particles.

[0096] The average particle size (D 50 ) was 6 μm, and the weight average molecular weight of the polythiophene was 20,000. The polythiophene was contained in the negative electrode active material particles in an amount of 5 wt %.

[0097] Comparative Example 3: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that a polymer in which an octyl group was included as a side chain in polyethyleneimine was used instead of poly(3-octylthiophene).

[0098] Comparative Example 4: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that a polymer in which polyacethylene contained an octyl group as a side chain was used instead of poly(3-octylthiophene).

[0099] Comparative Example 5: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that poly(p-phenylenevinylene-2,5-dioctyl-p-phenylenevinylene) was used instead of poly(3-octylthiophene).

[0100] Comparative Example 6: Production of negative electrode active material particles Negative electrode active material particles were prepared in the same manner as in Example 1, except that poly(1,4-piperazinediyl-1-oxo-trimethylene) was used instead of poly(3-octylthiophene).

[0101] Experimental Example 1: Evaluation of the compression conductivity of negative electrode active material particles The compression conductivity of the negative electrode active material particles was evaluated by the following method.

[0102] A plurality of the powdered negative electrode active material particles were compressed into a cylindrical shape, and a current was applied through the top and bottom of the compressed negative electrode active material particle sample to measure the electrical conductivity of the compressed negative electrode active material particles, as shown in Table 1.

[0103] Measurement equipment: Powder resistance characteristic measurement equipment (HANTECH HPRM-FA2) Sample loading: 3g Sample loader diameter: 20mm Pressurization pressure: 2,000 kgf / cm 2 Sample applied voltage: 10V

[0104] Experimental Example 2: Evaluation of hydrogen gas generation rate from negative electrode slurry Anode slurries were prepared using the anode active material particles of the examples and comparative examples. Specifically, the anode active material particles, CMC (a binder), Super 65 (a conductive material), and single-walled carbon nanotubes were mixed in water in a ratio of 80:9:10:1 to prepare a mixture, and then the mixture was dispersed in a homomixer at 2,500 rpm for 60 minutes to prepare anode slurries (solid content 30%).

[0105] 4 g of the negative electrode slurry was poured into a 5 ml measuring vessel in a thermostatic chamber at 40° C., and the amount of hydrogen gas generated was evaluated using a device for measuring gas pressure. The results are shown in Table 1.

[0106] Experimental example 3: Evaluation of life (capacity retention rate) Negative electrodes and batteries were manufactured using the negative electrode active materials of the examples and comparative examples, respectively.

[0107] Anode slurries were prepared using the anode active material particles of the examples and comparative examples. Specifically, the anode active material particles, CMC (a binder), Super 65 (a conductive material), and single-walled carbon nanotubes were mixed in water in a ratio of 80:9:10:1 to prepare a mixture, and then the mixture was dispersed in a homomixer at 2,500 rpm for 60 minutes to prepare anode slurries (solid content 30%).

[0108] The negative electrode slurry was applied to a 20 μm-thick copper (Cu) metal thin film as a negative electrode current collector and dried under circulating air at 60° C. The slurry was then rolled and dried in a vacuum oven at 130° C. for 12 hours to prepare a negative electrode.

[0109] The manufactured negative electrode was placed in a 1.7671 cm 2The lithium (Li) metal thin film cut into a circular shape was used as the positive electrode. A porous polyethylene separator was placed between the positive electrode and the negative electrode, and an electrolyte solution of 1M LiPF6 dissolved in a 7:3 volumetric ratio mixture of ethyl methyl carbonate (EMC) and ethylene carbonate (EC) with 0.5 wt% vinylene carbonate dissolved in it was poured into the cell to fabricate a lithium coin half-cell.

[0110] The produced batteries were charged and discharged, and the discharge capacity, initial efficiency, and capacity retention rate were evaluated. The results are shown in Table 1 below.

[0111] The first and second cycles were charged and discharged at 0.1 C, and from the third to the 49th cycles, they were charged and discharged at 0.5 C. The 300th cycle ended in a charged state (with lithium in the negative electrode), and the battery was disassembled to measure the thickness, after which the rate of change in electrode thickness was calculated.

[0112] Charging conditions: CC (constant current) / CV (constant voltage) (5mV / 0.005C current cut-off) Discharge condition: CC (constant current) condition 1.5V The capacity retention rate was calculated as follows: Capacity retention rate (%) = (50th discharge capacity / 1st discharge capacity) x 100

[0113] [Table 1]

[0114] Referring to Table 1, it can be seen that Examples 1 to 11, which used the anode active material particles according to the present invention, were evaluated as excellent in compression conductivity, hydrogen gas generation rate, and capacity retention rate. On the other hand, Comparative Example 1, which did not have a coating layer, showed low conductivity and a large amount of hydrogen gas generation side reaction, resulting in poor life characteristics. Comparative Example 2, which used a polymer without alkyl groups in its side chain, showed improved conductivity but was unable to resolve the problem of hydrogen gas generation, resulting in poor life characteristics.

[0115] Furthermore, in Comparative Examples 3 and 4, in which a chain monomer unit was used as the coating layer polymer, Comparative Example 4, which did not contain any heteroatoms, had very poor conductivity, and even if heteroatoms were included, the conductivity did not deviate from the poor level, indicating that the chain structure limitation could not be overcome. Furthermore, compared to the examples in which an aromatic cyclic monomer was used, it was confirmed that the adhesion strength between the coating layer and the core was low, which caused detachment of the coating layer and resulted in a large amount of gas generation.

[0116] Furthermore, in the case of Comparative Example 5, which differs from the Examples only in that it does not contain heteroatoms, it appears to have poor conductivity due to a lack of free electrons moving due to the π-π bond in the main chain. In contrast, Comparative Example 6, which contains heteroatoms but uses an aliphatic ring monomer unit, can be seen to have significantly poorer conductivity due to the lack of π-π bonds in the main chain.

[0117] Therefore, when silicon-based particles are used as a negative electrode active material, it is understood that it is preferable to use the polymer according to the present invention as a coating layer of the silicon-based particles in order to prevent side reactions such as hydrogen gas generation during preparation of an aqueous slurry and to improve conductivity and thereby improve lifespan.

Claims

1. a core and a coating layer disposed on the core; the core comprises a silicon-based particle; The coating layer includes negative electrode active material particles, the negative electrode active material particles including a polymer having an alkyl group in a side chain and including an aromatic cyclic monomer unit containing a heteroatom.

2. 2. The negative electrode active material particles according to claim 1, wherein the alkyl group has 1 to 50 carbon atoms.

3. The negative electrode active material particles according to claim 1 , wherein the heteroatom is at least one selected from the group consisting of nitrogen (N), sulfur (S), and phosphorus (P).

4. the heteroatom is at least one selected from the group consisting of nitrogen (N) and sulfur (S); 2. The negative electrode active material particles according to claim 1, wherein the alkyl group has 3 to 20 carbon atoms.

5. 2. The negative electrode active material particle according to claim 1, wherein the polymer comprises at least one selected from the group consisting of a polymer including a repeating unit represented by the following Chemical Formula 1, a polymer including a repeating unit represented by the following Chemical Formula 2, and a polymer including a repeating unit represented by the following Chemical Formula 3: 【Chemistry 1】 【Chemistry 2】 【Transformation 3】 In the above Chemical Formula 1, the R １ ~ The above R ２ are each independently either hydrogen or an alkyl group having 5 to 15 carbon atoms, and １ ~ The above R ２ At least one of the n is an alkyl group having 5 to 15 carbon atoms, １ is an integer from 1 to 10,000, In the above Chemical Formula 2, the R ３ ~ The above R ６ are each independently either hydrogen or an alkyl group having 5 to 15 carbon atoms, and ３ ~ The above R ６ At least one of the n is an alkyl group having 5 to 15 carbon atoms, ２ is an integer from 1 to 10,000, In the above Chemical Formula 3, the R ７ ~ The above R １０ are each independently either hydrogen or an alkyl group having 5 to 15 carbon atoms, and ７ ~ The above R １０ At least one of the n is an alkyl group having 5 to 15 carbon atoms, ３ is an integer from 1 to 10,000.

6. 6. The negative electrode active material particles according to claim 1, wherein the polymer has a weight average molecular weight of 200 g / mol to 2,000,000 g / mol.

7. 6. The negative electrode active material particles according to claim 1, wherein the polymer is contained in the negative electrode active material particles in an amount of 0.1% by weight to 50% by weight.

8. The average particle size (D ５０ 6. The negative electrode active material particles according to claim 1, wherein the particle diameter is 0.1 μm to 100 μm.

9. A negative electrode comprising the negative electrode active material particles according to claim 1 .

10. A secondary battery comprising the negative electrode according to claim 9.

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