Negative electrode active material and electrochemical device comprising same

Abstract

Disclosed is a negative electrode active material for improving the performance of an electrochemical device. According to one aspect, provided is a negative electrode active material comprising particles and a polymer compound on the particles, wherein the polymer compound contains a fluorine atom.

Description

Negative active material and electrochemical device including the same

[0001] The present disclosure relates to a negative electrode active material, and more specifically, to a negative electrode active material, a negative electrode, and an electrochemical device including the same.

[0002] The rapid growth of the secondary battery market is rapidly increasing the demand for high-capacity batteries, which in turn is driving a surge in demand for silicon-based cathode active materials that theoretically enable high capacities.

[0003] However, silicon-based negative electrode materials have the problem of exhibiting low coulombic efficiency and low capacity due to side reactions with the electrolyte compared to existing graphite-based negative electrode materials, and there is a problem of weakening durability due to changes in the volume of silicon particles during the charging / discharging process of the secondary battery.

[0004] According to one aspect of the present invention, a negative electrode active material having enhanced mechanical durability is provided to increase the capacity retention rate of an electrochemical device.

[0005] According to another aspect of the present invention, there is provided a negative electrode active material that forms a stable SEI (Solid electrolyte interphase) and can maintain long-term cycle performance of an electrochemical device.

[0006] According to another aspect of the present invention, a negative electrode including the negative electrode active material is provided.

[0007] According to another aspect of the present invention, an electrochemical device including the cathode is provided.

[0008] The purposes of the present invention are not limited to those mentioned above, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof described in the specification.

[0009] [1] According to one aspect of the present invention, a negative electrode active material is provided, which includes particles and a polymer compound on the particles, wherein the polymer compound includes a fluorine atom.

[0010] [2] In the above [1], the particles may include at least one selected from the group consisting of silicon-based particles, carbon-based particles, and metal-based particles.

[0011] [3] In the above [1] or [2], the polymer compound may include a cationic repeating unit and an anionic functional group.

[0012] [4] In the above [3], the cationic repeating unit may include a structure represented by the following general formula 1.

[0013] [General Formula 1]

[0014]

[0015] In the general formula 1 above, A is a pentagonal ring, a hexagonal ring or a chain-like divalent linking group, and each of the rings and the chain-like divalent linking group independently includes one or more nitrogens; or one or more phosphorus, and * is a point connected to another part in the molecule. For example, the chain-like divalent linking group may be -CH2-CHR`-. Here, R` is a side chain bonded to the polymer main chain, and may include one or more nitrogens or one or more phosphorus, and specifically may include an ammonium ion or a phosphonium ion. For example, the R` is -Ph(phenylene group)-CH2-P +(R``) 3, or -Ph(phenylene group)-CH2-N + (R``)3, and specifically, R`` may each independently be a straight-chain or branched alkyl group having 1 to 5 carbon atoms; or an aryl group having 6 to 20 carbon atoms, and more specifically, a phenyl group.

[0016] [5] In the above [4], A of the general formula 1 may include a nitrogen cation or a phosphorus cation.

[0017] [6] In the above [4] or [5], A of the general formula 1 may include an aromatic ring structure.

[0018] [7] In any one of the above [4] to [6], A of the general formula 1 may include a structure represented by the following general formula 1a.

[0019] [General Formula 1a]

[0020]

[0021] In the general formula 1a above, R1 is each independently nitrogen or phosphorus, and R2 is each independently any one selected from the group consisting of a hydrogen atom; a substituted or unsubstituted alkyl group; a substituted or unsubstituted cycloalkyl group; a substituted or unsubstituted alkoxy group; a substituted or unsubstituted amine group; a substituted or unsubstituted allyl group; a substituted or unsubstituted (meth)acryl group; a substituted or unsubstituted benzyl group; a substituted or unsubstituted styrene group; a substituted or unsubstituted (meth)acrylamide group; a substituted or unsubstituted vinyl ester group; and a substituted or unsubstituted vinylamide group.

[0022] [8] In any one of the above [3] to [7], the fluorine atom of the polymer compound may be included in the anionic functional group.

[0023] [9] In any one of the above [3] to [8], the anionic functional group may include a nitrogen anion, a phosphorus anion, a boron anion or an oxygen anion.

[0024]

[0010] In any one of the above [1] to [9], the fluorine atom of the polymer compound may be included in at least one selected from the group consisting of FSI (Fluorosulfonyl imide), TFSI (Trifluoromethanesulfonyl imide), FSA (Fluorosulfonate), TFMSA (Trifluoromethane sulfonate), hexafluorophosphate, and tetrafluoroborate.

[0025]

[0011] In any one of the above [1] to

[0010] , the polymer compound may further contain a boron atom.

[0026]

[0012] In any one of the above [1] to

[0011] , the content of fluorine atoms based on the total weight of the negative electrode active material may be 0.05 to 10 wt%, and preferably 0.5 to 1 wt%.

[0027]

[0013] In any one of the above [1] to

[0012] , the weight ratio of carbon atoms and fluorine atoms in the negative electrode active material may be 100:0.05 to 100:35.

[0028]

[0014] In any one of the above [1] to

[0013] , the BET specific surface area of ​​the negative electrode active material is 75 m 2 / g can be less.

[0029]

[0015] According to another aspect of the present invention, a negative electrode including a negative electrode active material according to any one of [1] to

[0013] can be provided.

[0030]

[0016] According to another aspect of the present invention, an electrochemical device is provided, comprising: a negative electrode according to

[0015] ; a positive electrode spaced apart from the negative electrode; and an electrolyte. Here, the negative electrode may comprise a negative electrode active material according to any one of [1] to

[0014] .

[0031]

[0017] In the above

[0016] , the electrochemical device may further include SEI (Solid electrolyte interphase) formed on the surface of the cathode.

[0032]

[0018] In the above

[0016] or

[0017] , the electrochemical device may further include a separator interposed between the cathode and the anode.

[0033] The solutions to the above problems are not exhaustive and may be combined with several embodiments of the present disclosure. The various features of the present invention and their corresponding advantages and effects can be understood in more detail by referring to the detailed description below.

[0034] According to one aspect of the present invention, a negative electrode active material having enhanced mechanical durability and increasing the capacity retention rate of an electrochemical device can be implemented.

[0035] According to another aspect of the present invention, a negative electrode active material capable of maintaining long-term cycle performance of an electrochemical device can be implemented by forming a stable SEI (Solid electrolyte interphase).

[0036] According to another aspect of the present invention, an electrochemical device having high capacity retention, excellent cycle performance, and rapid charging performance can be implemented.

[0037] In addition to the aforementioned effects, specific effects of the present invention are described below along with specific details for implementing the invention. Furthermore, the effects of the present invention are not limited to the effects described above and can be readily achieved using the means and combinations thereof described in the specification.

[0038] Figure 1 shows the ionic monomer (DAI-FSI). 1 This is the result of H-NMR analysis.

[0039] Fig. 2a is an SEM photograph of a negative electrode active material according to Comparative Example 1, and Fig. 2b is an SEM photograph of a negative electrode active material according to Example 2.

[0040] Figure 3a is a SEM photograph and EDS (Energy Dispersive Spectroscopy) result of the cathode in the electrochemical device according to Comparative Example 1 after 50 cycles under the measurement conditions of Experimental Example 3, and Figure 3b is a SEM photograph and EDS (Energy Dispersive Spectroscopy) result of the cathode in the electrochemical device according to Example 2 under the measurement conditions of Experimental Example 3.

[0041] Fig. 4a is an SEM photograph of the cathode in the electrochemical device according to Comparative Example 1 after 100 cycles under the measurement conditions of Experimental Example 3, and Fig. 4b is an SEM photograph of the cathode in the electrochemical device according to Example 2 after 100 cycles under the measurement conditions of Experimental Example 3.

[0042] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0043] The terms "comprise" and / or "comprising" in this specification specify the presence of stated features, steps, numbers, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, numbers, operations, elements, elements and / or groups thereof.

[0044] In this specification, “At least one of a, b and c” may include a, b or c alone, or a combination of two or more selected from the group consisting of a, b and c.

[0045] If multiple embodiments are described in this specification, the embodiments may be combined unless specifically stated otherwise. In this case, the effects of the present invention may be defined as including the effects derived from each embodiment and the effects resulting from the organic combination of the embodiments. For example, even if Embodiments 1 and 2 are described independently in this specification, Embodiments 1 and 2 may be organically combined with each other, unless the context clearly indicates otherwise, and the effects of the present invention may include the effects resulting from the combination of Embodiments 1 and 2.

[0046] The numerical range indicated by the term "to" in this specification refers to a numerical range that includes the values ​​described before and after the term as the lower limit and the upper limit, respectively. When multiple numerical values ​​are disclosed as the upper and lower limits of an arbitrary numerical range, the numerical range disclosed in this specification can be understood as any numerical range that has any one of the multiple lower limit values ​​and any one of the multiple upper limit values ​​as the lower limit and the upper limit, respectively. For example, when a to b, or c to d is described in the specification, it can be understood that a or more and b or less, a or more and d or less, c or more and d or less, or c or more and b or less is described.

[0047] As used herein, terms such as "about" or "substantially" mean a reasonable amount of variation from the term that does not significantly alter the final result. These terms may be interpreted to include a variation of at least ±5% or at least ±10%, provided that such variation does not alter the meaning of the term and render it invalid.

[0048] In this specification, the term "layer" or film may include cases where it is formed not only over the entire area when observing the area where the layer or film exists, but also cases where it is formed over only a portion of the area. For example, the surface of the layer or film may be defined to include a flat shape, a non-flat shape, and a combination thereof; or a continuous shape, a discontinuous shape, and a combination thereof. For example, when another element is formed as a layer or film directly on top of one element, the coverage of the other element on the surface of the one element may be defined as 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 99% or more. For example, even when a plurality of particles form a clustered structure, it may be defined as a "layer" or "film."

[0049] In this specification, the average particle diameter of the particles is the particle diameter (D) when the cumulative percentage in the volume-based particle size distribution curve is 50% when measured by a laser diffraction particle size distribution measuring device. 50 ) can be defined. For example, the average particle diameter of the particles can be calculated by dispersing the target particles in a dispersion medium, introducing them into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and measuring the difference in diffraction pattern according to particle size when the particles pass through a laser beam.

[0050] In this specification, “weight average molecular weight” or “number average molecular weight” refers to the standard polystyrene-converted molecular weight, which can be analyzed using a GPC (Gel permeation chromatography) device. For example, in the case of the GPC analysis method, the developing solvent may be Tetrahydrofuran (THF), the column may be PL Olexis from Polymer Laboratories, the sample concentration may be 5 mg / mL, the sample injection amount may be 100 ㎕, the flow rate may be 1 mL / min, the detector may be Agilent High Temperature RI detector, and the column temperature may be set to 40°C.

[0051] As used herein, "substituted" means a group in which at least one hydrogen atom is substituted with a halogen atom, a hydroxyl group, a carboxyl group, a nitro group, an amine group, a sulfide group, a thiol group, an alkoxy group, an acetoxy group, a nitrile group, an aldehyde group, an ether group, an ester group, an acetal group, a ketone group, a C1 to C 30 Alkyl group of C2 to C 30 Alkenyl group, C2 to C 30 Alkynyl group, C1 to C 40 Alkylsilyl group, C5 to C 40 Arylsilyl group, C3 to C 30 Cycloalkyl group, C3 to C 30 Allyl group, C6 to C 30 Aryl group, heterocyclic group (e.g. C2 to C) 30 Heterocycloalkyl group, C3 to C 30 is defined as being replaced by any one selected from the group consisting of heteroaryl groups, derivatives thereof, and combinations thereof. Here, each of the above substituents may combine with each other when adjacent to each other to form a substituted or unsubstituted fused ring or spiro structure.

[0052] In this specification, “fused ring” means a ring in which two or more rings are joined by sharing two or more atoms, and may include, for example, a fused aliphatic ring, a fused aromatic ring, a fused heteroaliphatic ring, a fused heteroaromatic ring, or a combination thereof.

[0053] For example, the alkyl group may be straight chain or branched, and specifically, methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, cyclopentylmethyl, cyclohexylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl-propyl, It can be 1,1-dimethyl-propyl, isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, etc.

[0054] For example, an ester group may mean -COO-R, or R-COO-, wherein the number of carbon atoms in the R group of the ester group may be 1 to 50.

[0055] For example, the cycloalkyl group can be cyclopropyl, cyclobutyl, cyclopentyl, 3-methylcyclopentyl, 2,3-dimethylcyclopentyl, cyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2,3-dimethylcyclohexyl, 3,4,5-trimethylcyclohexyl, 4-tert-butylcyclohexyl, cycloheptyl, cyclooctyl, and the like.

[0056] For example, the alkenyl group may be straight or branched, and the number of carbon atoms is not particularly limited, but is preferably 2 to 40. Specific examples include vinyl, 1-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 3-methyl-1-butenyl, 1,3-butadienyl, allyl, 1-phenylvinyl-1-yl, 2-phenylvinyl-1-yl, 2,2-diphenylvinyl-1-yl, 2-phenyl-2-(naphthyl-1-yl)vinyl-1-yl, 2,2-bis(diphenyl-1-yl)vinyl-1-yl, stilbenyl, and styrenyl.

[0057] For example, the aryl group may be a monocyclic aryl group or a polycyclic aryl group, and specifically may be a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, anthracenyl group, a phenanthryl group, a pyrenyl group, a perylenyl group, a chrysenyl group, a fluorenyl group, etc.

[0058] For example, a heterocyclic group includes one or more non-carbon atoms, heteroatoms, and the heteroatoms may include one or more atoms selected from the group consisting of O, N, Se, and S. The number of carbon atoms in the heterocyclic group is not particularly limited, but it may be preferable that it has 2 to 60 carbon atoms. Examples of heterocyclic groups include thiophene group, furan group, pyrrole group, imidazole group, thiazole group, oxazole group, oxadiazole group, triazole group, pyridyl group, bipyridyl group, pyrimidyl group, triazine group, triazole group, acridyl group, pyridazine group, pyrazinyl group, quinolinyl group, quinazoline group, quinoxalinyl group, phthalazinyl group, pyrido pyrimidinyl group, pyrido pyrazinyl group, pyrazino pyrazinyl group, isoquinoline group, indole group, carbazole group, benzoxazole group, benzimidazole group, benzothiazole group, benzocarbazole group, benzothiophene group, dibenzothiophene group, benzofuranyl group, phenanthroline group, thiazolyl group, isoxazolyl group, Examples include, but are not limited to, oxadiazolyl group, thiadiazolyl group, benzothiazolyl group, phenothiazinyl group, and dibenzofuranyl group.

[0059] In this specification, “*” may mean a point of connection to another part within the molecule.

[0060] As used herein, "electrochemical device" may refer to a primary battery, a secondary battery, or a supercapacitor, and may specifically be a secondary battery, and more specifically, a lithium-ion secondary battery. In some examples, the electrochemical device may be a lithium-ion battery including a liquid electrolyte, or an all-solid-state battery including a solid electrolyte without a separator.

[0061] The silicon-based negative electrode materials used in the past had problems such as low coulombic efficiency and low capacity due to side reactions with the electrolyte, and decreased durability due to changes in the volume of silicon particles during the charging / discharging process of the secondary battery.

[0062] According to one aspect of the present invention, a negative electrode active material is provided, which includes particles and a polymer compound on the particles, wherein the polymer compound includes a fluorine atom. According to one aspect of the present invention, by including the polymer compound having the fluorine atom in the negative electrode active material, the mechanical durability of the negative electrode active material can be enhanced while effectively controlling the specific surface area of ​​the negative electrode active material. Accordingly, a stable and uniformly thick SEI can be formed at the interface between the negative electrode and the electrolyte in an electrochemical device, thereby increasing the capacity retention rate of the electrochemical device and improving cycle performance.

[0063] Below, the configuration of the present invention is described in more detail.

[0064] 1. Negative active material

[0065] particle

[0066] In this specification, a "particle" may be a core of a negative electrode active material. For example, the shape of the particle is not particularly limited and may be appropriately modified to suit the characteristics of the material.

[0067] The particles according to the present invention can reversibly absorb and release lithium ions released from the positive electrode while allowing current to flow through an external circuit.

[0068] In some embodiments of the present invention, the particles may include at least one selected from the group consisting of silicon-based particles, carbon-based particles, and metal-based particles, and specifically may include silicon-based particles.

[0069] In some examples, the silicon particles are silicon particles that are ground into nano-sizes, such as Si, SiOx(0 <x≤2), Si-C 복합체 및 Si-Y 합금(Y는 알칼리금속, 알칼리토금속, 전이금속, 13족 원소, 14족 원소 및 희토류 원소로 이루어진 군에서 선택된 어느 하나의 원소이다)으로 이루어진 군에서 선택되는 1종 이상을 포함할 수 있고, 구체적으로 실리콘(Si)을 포함할 수 있다.

[0070] In some embodiments of the present invention, the silicon-based particles may be secondary particles formed by agglomerating primary particles. In some embodiments of the present invention, the silicon-based particles include secondary particles formed by agglomerating primary particles, so that the voids between the primary particles can effectively prevent local expansion of the silicon-based particles due to lithium insertion during charging. In addition, the secondary particles can lower the total surface area to form a stable and uniformly thick SEI at the interface between the negative electrode and the electrolyte in the electrochemical device, thereby increasing the capacity retention rate of the electrochemical device and improving cycle performance.

[0071] In some embodiments of the present invention, the average particle diameter (D) of the primary particles 50) may be 800 nm or less, 700 nm or less, 600 nm or less, 500 nm or less, specifically 50 to 500 nm, 60 to 400 nm, 70 to 300 nm, 80 to 300 nm, 80 to 200 nm, 90 to 150 nm, or 100 to 120 nm. According to some embodiments of the present invention, when the average particle diameter of the primary particles satisfies the numerical range, the lifespan of the electrochemical device can be further extended.

[0072] In some embodiments of the present invention, the average particle diameter (D) of the secondary particles 50 ) may be 1 to 50 μm, 5 to 15 μm, or 9 to 11 μm. In some embodiments of the present invention, by controlling the average particle diameter of the secondary particles to the above numerical range, a stable and uniform thickness SEI is formed at the interface between the negative electrode and the electrolyte in the electrochemical device, thereby increasing the capacity retention rate of the electrochemical device and improving the cycle performance.

[0073] In some embodiments of the present invention, the silicon particles may be pulverized silicon raw material powder. Specifically, the average particle diameter (D) of the silicon raw material powder 50 ) may be 30 to 300 μm, more specifically 100 to 200 μm. According to some embodiments of the present invention, the average particle diameter of the silicon raw material powder satisfies the above numerical range, so that the particle diameter of the silicon particles is controlled, thereby further extending the lifespan of the electrochemical device.

[0074] In some examples, the silicon particles may be pulverized metal silicon (Metallurgical Grade Silicon; MG-Si). Specifically, the purity of the metal silicon may be 97 wt% or greater.

[0075] In some examples, the carbonaceous particles may comprise any one selected from the group consisting of non-graphitizable carbon, graphite, and combinations thereof.

[0076] In some examples, the above metal materials include lithium metal (Li metal), LixFe2O3(0≤x≤1), Li x It may include any one selected from the group consisting of WO2(0≤x≤1), SnO, SnO2, PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, and Bi2O5, and specifically may include lithium metal.

[0077] polymer compounds

[0078] The polymer compound according to the present invention can form a coating layer containing a large amount of LiF on the surface of an anode active material and contribute to the formation of a thin, uniformly thick SEI on the surface of the anode. Accordingly, the lifespan of an electrochemical device using the anode active material can be extended during the charging / discharging process, while also exhibiting excellent rapid charging characteristics.

[0079] The polymer compound according to the present invention contains a fluorine atom. Specifically, the fluorine atom, by being included in the polymer compound, can induce the formation of a coating layer containing a large amount of LiF on the surface of the negative electrode active material during the charging / discharging process of the electrochemical device. In general, if a LiF coating layer is formed without using a polymer compound containing a fluorine atom, there may be a problem in that the stability of the reactants remaining in the LiF coating layer is reduced in moisture and atmospheric environments. According to one aspect of the present invention, by forming a coating layer on the surface of the particle using the polymer compound containing the fluorine atom, a synergistic effect of enhancing the durability of the negative electrode active material can be realized. In addition, when such a negative electrode active material is applied to an electrochemical device, not only can the life performance and output performance of the electrochemical device be excellently expressed, but also the rapid charging effect can be realized better.

[0080] In some embodiments of the present invention, the polymer compound may be included in a polymer coating layer on the particle. In some examples, the polymer coating layer may be coated on a portion or all of the surface of the particle. In some examples, the polymer coating layer may be coated on the surface of at least one of the plurality of particles.

[0081] In some embodiments of the present invention, the thickness of the polymer coating layer may be 1 to 50 nm, 1 to 30 nm, or 5 to 30 nm, and specifically 10 to 20 nm. According to some embodiments of the present invention, when the thickness of the polymer coating layer satisfies the numerical range, the durability of the negative electrode active material can be improved within a limit that does not lower the ionic conductivity of the electrochemical device.

[0082] In some embodiments of the present invention, the polymer compound may be a polymer in which cationic repeating units are polymerized and an anion is ionically bonded. That is, the polymer compound may include cationic repeating units and an anionic functional group. As used herein, "anionic functional group" is defined to mean an atomic group of an anion.

[0083] In some embodiments of the present invention, the polymer compound may include a cationic repeating unit. Specifically, by including the cationic repeating unit, the polymer compound can form an ionic bond with a source anion having a fluorine atom, which will be described later, thereby further enhancing the durability of the negative electrode active material and simultaneously achieving excellent lifespan performance and output performance of the electrochemical device.

[0084] In some embodiments of the present invention, the cationic repeating unit may include a structure represented by the following general formula 1.

[0085] [General Formula 1]

[0086]

[0087] In the general formula 1 above, A is a pentagonal ring, a hexagonal ring, or a chain-like divalent linking group, and each of the rings and the chain-like divalent linking group independently includes one or more nitrogens; or one or more phosphorus, and * represents a point connected to another part in the molecule. Here, by having a repeating structure including nitrogen or phosphorus in A, chemical and thermal stability is improved, so that reduction stability within the operating voltage of the electrochemical device can be guaranteed. According to some embodiments of the present invention, since the cationic repeating unit includes a structure represented by the general formula 1, the durability of the negative active material can be further improved, while at the same time ensuring reduction stability within the operating voltage, and the life performance and output performance of the electrochemical device can be excellently implemented. Specifically, when A in the general formula 1 above is a pentagonal ring or a hexagonal ring structure, the capacity retention rate under normal cycle and rapid charge conditions of the electrochemical device can be further improved compared to the chain-like divalent linking group.

[0088] For example, the chain-like divalent linking group may be -CH2-CHR`-. Here, R` is a side chain bonded to the polymer main chain, which may include one or more nitrogens or one or more phosphorus atoms, and specifically, may include an ammonium ion or a phosphonium ion. For example, the R` may be -Ph(phenylene group)-CH2-P + (R``) 3, or -Ph(phenylene group)-CH2-N + (R``)3, and specifically R`` may be a straight-chain or branched alkyl group having 1 to 5 carbon atoms; or an aryl group having 6 to 20 carbon atoms, and more specifically a phenyl group.

[0089] In some examples, nitrogen or phosphorus in each of the above rings may be an atom within the ring.

[0090] In some examples, each of the above rings may be composed of one or more nitrogen atoms, or may be composed of one or more phosphorus atoms.

[0091] In some non-limiting examples, the five-membered ring may be a heterocycle containing one or more nitrogen atoms within the ring, and specifically may be an imidazole moiety.

[0092] In some non-limiting examples, the hexagonal ring may be a heterocycle containing one or more nitrogen atoms within the ring, and specifically may be a pyridine moiety.

[0093] In some examples, the number of nitrogen atoms in the ring may be two or three, and the number of phosphorus atoms in the ring may be two or three.

[0094] In some embodiments of the present invention, A in the general formula 1 may include a nitrogen cation or a phosphorus cation, and specifically may include a nitrogen cation. According to some embodiments of the present invention, when A includes a nitrogen cation, the effect of further increasing the coulombic efficiency of the electrochemical device may be realized. For example, the nitrogen cation may be a nitrogen cation having an imidazolium or pyridinium structure, and the phosphorus cation may be a phosphorus cation having a phosphonium structure.

[0095] In some embodiments of the present invention, A of the general formula 1 may include an aromatic ring structure. According to some embodiments of the present invention, since A includes an aromatic ring structure, the structural stability of the polymer in which the cationic repeating unit is polymerized is achieved compared to the chain-type divalent linker, thereby effectively preventing unnecessary side reactions within the polymer coating layer. Accordingly, the capacity retention rate under normal cycle and rapid charging conditions of the electrochemical device can be further improved compared to the chain-type divalent linker.

[0096] In some embodiments of the present invention, A of the general formula 1 may include a structure represented by the following general formula 1a.

[0097] [General Formula 1a]

[0098]

[0099] In the general formula 1a above, R1 is each independently nitrogen or phosphorus, and R2 may be any one selected from the group consisting of a hydrogen atom; a substituted or unsubstituted alkyl group; a substituted or unsubstituted cycloalkyl group; a substituted or unsubstituted alkoxy group; a substituted or unsubstituted amine group; a substituted or unsubstituted allyl group; a substituted or unsubstituted (meth)acryl group; a substituted or unsubstituted benzyl group; a substituted or unsubstituted styrene group; a substituted or unsubstituted (meth)acrylamide group; a substituted or unsubstituted vinyl ester group; and a substituted or unsubstituted vinylamide group. Here, in the general formula 1a, * represents a point at which the structure represented by the general formula 1a is connected to another part in the cationic repeating unit, and may be connected to a linking group generated through a polymerization reaction.

[0100] For example, the alkyl group is C1 to C 30 It can be straight chain or branched chain, specifically methyl, ethyl, propyl, n-propyl, isopropyl, butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, heptyl, n-heptyl, 1-methylhexyl, cyclopentylmethyl, cyclohexylmethyl, octyl, n-octyl, tert-octyl, 1-methylheptyl, 2-ethylhexyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl-propyl, 1,1-dimethyl-propyl, It can be isohexyl, 2-methylpentyl, 4-methylhexyl, 5-methylhexyl, etc.

[0101] For example, the cycloalkyl group is C3 to C 30It may be a cycloalkyl group, and specifically, it may be cyclopropyl, cyclobutyl, cyclopentyl, 3-methylcyclopentyl, 2,3-dimethylcyclopentyl, cyclohexyl, 3-methylcyclohexyl, 4-methylcyclohexyl, 2,3-dimethylcyclohexyl, 3,4,5-trimethylcyclohexyl, 4-tert-butylcyclohexyl, cycloheptyl, cyclooctyl, etc.

[0102] For example, the alkoxy group may be a chain or cyclic alkoxy group, and specifically, the chain alkoxy group may be C1 to C 30 It may have a carbon number of C3 to C, and the cyclic alkoxy group is C3 to C 30 can have a carbon number of .

[0103] For example, the number of carbon atoms in the above allyl group may be 3 to 30.

[0104] For example, the above (meth)acrylic group is -OOC-C(R)=C(R)2, where R is each independently a hydrogen atom or C1 to C 30 It may be a functional group that is an alkyl group.

[0105] For example, the (meth)acrylamide group may be -N(R)CO-C(R)=C(R)2, where R is each independently a hydrogen atom or C1 to C 10 It may be an alkyl group.

[0106] For example, the vinyl ester group may be a compound in which at least one hydrogen atom bonded to the vinyl group is substituted or unsubstituted with another atom. In one example, the vinyl ester may have 3 to 30 carbon atoms.

[0107] For example, the vinylamide group may be a compound in which at least one hydrogen atom bonded to the vinyl group is substituted or unsubstituted with another atom. In one example, the vinylamide group may have 3 to 30 carbon atoms.

[0108] In some embodiments of the present invention, the fluorine atom of the polymer compound may be included in the anionic functional group. In some embodiments of the present invention, by including the fluorine atom of the polymer compound in the anionic functional group, the specific surface area of ​​the negative electrode active material may be controlled, thereby further increasing the capacity retention rate and coulombic efficiency of the electrochemical device.

[0109] In some embodiments of the present invention, the anionic functional group may include a nitrogen anion, a phosphorus anion, a boron anion, or an oxygen anion, and specifically may include a nitrogen anion. In some embodiments of the present invention, by the anionic functional group including a nitrogen anion, a phosphorus anion, a boron anion, or an oxygen anion, the lifespan and rapid charging performance of the electrochemical device may be further improved.

[0110] In some embodiments of the present invention, the anionic functional group including the nitrogen anion may include any one selected from the group consisting of FSI (Fluorosulfonyl imide), TFSI (Trifluorosulfonyl imide) and combinations thereof, and specifically may include a -CF3 group. In some embodiments of the present invention, the anionic functional group including the nitrogen anion includes a -CF3 group, so that the capacity retention rate and initial Coulombic efficiency of the electrochemical device can be further improved.

[0111] In some non-limiting examples, the anionic functional group comprising the above anion may include hexafluorophosphate.

[0112] In some non-limiting examples, the anionic functional group comprising the boron anion may comprise tetrafluoroborate.

[0113] In some non-limiting examples, the anionic functional group comprising the oxygen anion may include any one selected from the group consisting of Fluorosulfonate (FSA), Trifluoromethane sulfonate (TFMSA), and combinations thereof.

[0114] In some examples, the fluorine atom of the polymer compound may be included in or derived from one or more selected from the group consisting of FSI (Fluorosulfonyl imide), TFSI (Trifluorosulfonyl imide), FSA (Fluorosulfonate), TFMSA (Trifluoromethane sulfonate), hexafluorophosphate, and tetrafluoroborate. According to some embodiments of the present invention, the fluorine atom of the polymer compound is included in or derived from at least one selected from the group consisting of FSI (Fluorosulfonyl imide), TFSI (Trifluorosulfonyl imide), FSA (Fluorosulfonate), TFMSA (Trifluoromethane sulfonate), hexafluorophosphate, and tetrafluoroborate, thereby forming a coating layer containing a large amount of LiF on the surface of the negative electrode active material and forming a SEI having a thin and uniform thickness. Accordingly, an electrochemical device to which the negative electrode active material is applied can exhibit excellent lifespan and excellent rapid charging characteristics during the charging / discharging process.

[0115] In some embodiments of the present invention, the polymer compound may further include boron atoms. By further including the boron atoms in the polymer compound, a uniform ionic conductivity can be induced on the surface of the negative electrode active material, thereby alleviating problems such as lithium deposition. In some examples, the boron atoms may be derived from an anionic functional group including the boron anion described above.

[0116] In some embodiments of the present invention, the content of fluorine atoms may be 0.05 to 10 wt%, 0.1 to 5 wt%, 0.5 to 3 wt%, 0.5 to 2 wt%, or 0.5 to 1 wt% based on the total weight of the negative electrode active material. Here, the content of fluorine atoms may be measured using an energy dispersive spectroscopy (EDS) analysis method. According to some embodiments of the present invention, since the content of the fluorine atoms satisfies the numerical range, the specific surface area of ​​the negative electrode active material is effectively controlled, so that the capacity retention rate and coulombic efficiency of the electrochemical device can be further increased.

[0117] In some embodiments of the present invention, the silicon-based particles may include a core including the above-described secondary particles; and a carbon layer on the core. Specifically, the carbon layer may be formed on the surface of the core. In some non-limiting examples, the carbon layer may be coated on a portion or the entire surface of the core. In some embodiments of the present invention, the carbon layer is formed on the surface of the secondary particles, thereby effectively preventing expansion of the silicon-based negative electrode active material during the lithiation process of silicon. Accordingly, a stable and uniformly thick SEI is formed at the interface between the negative electrode and the electrolyte, thereby increasing the capacity retention rate of the electrochemical device and improving cycle performance.

[0118] In some non-limiting examples, the average thickness of the carbon layer may be 1 to 110 nm, 10 to 100 nm, 20 to 80 nm, or 40 to 80 nm. The average thickness of the carbon layer can be measured by observing a TEM (Transmission Electron Microscope) image of the manufactured negative active material. By controlling the thickness of the carbon layer within the above numerical range, the capacity and capacity retention rate of the battery can be further increased.

[0119] In some embodiments of the present invention, the weight ratio of carbon atoms to fluorine atoms (carbon atoms: fluorine atoms) in the negative electrode active material may be 100:0.05 to 100:35, 100:0.15 to 100:20, 100:1.5 to 100:10, or 100:1.5 to 100:5. Here, the weight ratio of the carbon atoms to the fluorine atoms may be measured using an energy dispersive spectroscopy (EDS) analysis method. According to some embodiments of the present invention, when the weight ratio of the carbon atoms to the fluorine atoms satisfies the numerical range, the specific surface area of ​​the negative electrode active material is effectively controlled, so that the capacity retention rate and Coulombic efficiency of the electrochemical device can be further increased. In some non-limiting examples, the carbon atoms in the negative electrode material may be analyzed through a carbon layer formed by spray drying a dispersion comprising milled first silicon particles and a carbon precursor (e.g., pitch powder) and then heat treating.

[0120] In some embodiments of the present invention, the weight ratio of Si and F (Si:F) in the negative electrode active material may be 100:0.015 to 100:16, 100:0.050 to 100:10, or 100:0.7 to 100:1.4. Here, the weight ratio of Si and F may be measured using an energy dispersive spectroscopy (EDS) analysis method. According to some embodiments of the present invention, when the weight ratio of Si and F satisfies the numerical range, the specific surface area of ​​the negative electrode active material is effectively controlled, so that the capacity retention rate and coulombic efficiency of the electrochemical device can be further increased.

[0121] In some embodiments of the present invention, the BET specific surface area of ​​the negative electrode active material is 75 m 2 / g or less, 70 m 2 / g or less 65 m 2 / g or less, 62 m 2 / g or less, 61 m 2 / g or less, 60 m 2 / g or less, 58 m 2 / g or less, 56 m 2 / g or less, 55 m 2 / g or less, 54 m 2 / g or less, 53 m 2 / g or less, or 50 m 2 / g or less. Here, the BET surface area is 22 m 2 / g or more may be a range in which any one of the above-mentioned multiple numerical values ​​is set as an upper limit. According to some embodiments of the present invention, by controlling the BET specific surface area of ​​the negative electrode active material to the above numerical range, the capacity retention rate and coulombic efficiency of the electrochemical device can be further increased.

[0122] 2. Cathode

[0123] According to another aspect of the present invention, a negative electrode comprising a negative electrode active material of some embodiments may be provided.

[0124] A method for manufacturing a negative electrode according to the present invention may include the steps of preparing a negative electrode slurry including a silicon negative electrode active material, an electrode conductive material, and a negative electrode binder according to some embodiments; coating and drying the negative electrode slurry on at least one surface of a negative electrode current collector to form a negative electrode active material layer; and rolling the current collector on which the negative electrode active material layer is formed.

[0125] In some examples, the negative electrode current collector may serve as a passage to transfer electrons from the outside to cause an electrochemical reaction in the negative electrode active material or to receive electrons from the negative electrode active material and send them to the outside. For example, the negative electrode current collector may be made of copper, stainless steel, nickel, titanium, calcined carbon, or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. Specifically, a transition metal that adsorbs carbon well, such as copper or nickel, may be used as the current collector. For example, the thickness of the negative electrode current collector may be 6 μm to 55 μm, but the thickness of the negative electrode current collector is not limited thereto.

[0126] In some examples, the step of rolling the current collector having the negative electrode active material layer formed thereon may be performed under conditions of a composite density of 1.0 g / cc or more. When using a silicon negative electrode active material according to some embodiments of the present invention, even if the rolling process is performed under the above conditions, the particles are not destroyed, thereby further improving the compression resistance. Here, the composite density refers to the degree to which the composite material is pressed well, and may vary depending on the pressure and thickness of the roll press.

[0127] In some embodiments of the present invention, the negative electrode slurry may further include a graphite-based active material in addition to the silicon negative electrode active material. For example, the graphite-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, graphitized carbon fibers, and graphitized mesocarbon microbeads.

[0128] The above-mentioned negative electrode binder can suppress separation between negative electrode active material (silicon negative electrode active material) particles, or between the negative electrode active material layer and the current collector. A polymer commonly used in electrodes in the relevant technical field can be used as the above-mentioned negative electrode binder. These negative electrode binders include, but are not limited to, poly(vinylidene fluoride co-hexafluoropropylene), poly(vinylidene fluoride-co-trichloroethylene), poly(methylmethacrylate), poly(ethylhexylacrylate), poly(butylacrylate), poly(acrylonitrile), poly(vinylpyrrolidone), poly(vinyl acetate), poly(ethylene-co-vinyl acetate), poly(ethylene oxide), polyacrylate, cellulose acetate, cellulose acetate butyrate. Examples of such polymers include, but are not limited to, cellulose acetate propionate, cyano ethyl pullulan, cyano ethyl poly(vinylalcohol), cyanoethylcellulose, cyano ethylsucrose, pullulan, and carboxyl methyl cellulose.

[0129] The conductive material for an electrode according to the present invention is not particularly limited and may be one selected from the group consisting of graphite, carbon black, carbon fibers or metal fibers, metal powders, conductive whiskers, conductive metal oxides, activated carbon, and polyphenylene derivatives, or a mixture of two or more conductive materials thereof, and more specifically, may be one selected from the group consisting of natural graphite, artificial graphite, super-p, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, Denka black, aluminum powder, nickel powder, zinc oxide, potassium titanate, and titanium oxide, or a mixture of two or more conductive materials thereof.

[0130] 3. Electrochemical devices

[0131] According to another aspect of the present invention, an electrochemical device is provided, comprising: a negative electrode including a negative electrode active material of some embodiments; a positive electrode spaced apart from the negative electrode; and an electrolyte.

[0132] anode

[0133] The positive electrode according to the present invention may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer may include a positive electrode active material, a conductive material, and a positive electrode binder.

[0134] In some examples, the positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Specifically, the positive electrode current collector may be made of copper, stainless steel, aluminum, titanium, calcined carbon, stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. The positive electrode current collector may typically have a thickness of 6 to 20 μm.

[0135] In some examples, the cathode active material may include a lithium transition metal oxide. The lithium transition metal oxide may be, for example, Li x1 CoO2(0.5 <x1<1.3), Li x2 NiO2(0.5 <x2<1.3), Li x3 MnO2(0.5 <x3<1.3), Li x4 Mn2O4(0.5 <x4<1.3), Li x5 (Ni a1 Co b1 Mn c1 )O2(0.5 <x5<1.3, 0<a1<1, 0<b1<1, 0<c1<1, a1+b1+c1=1), Li x6 Ni 1-y1 Co y1 O2(0.5 <x6<1.3, 0<y1<1), Li x7 Co 1-y2 Mn y2 O2(0.5 <x7<1.3, 0≤y2<1), Li x8 Ni 1-y3 Mn y3 O2(0.5 <x8<1.3, 0≤y3<1), Li x9 (Ni a2 Co b2 Mn c2 )O4(0.5 <x9<1.3, 0<a2<2, 0<b2<2, 0<c2<2, a2+b2+c2=2), Li x10 Mn 2-z1 Ni z1 O4(0.5 <x10<1.3, 0<z1<2), Li x11 Mn 2-z2 Co z2 O4(0.5 <x11<1.3, 0<z2<2), Li x12 CoPO4(0.5 <x12<1.3) 및 Li x13 FePO4(0.5 <x13<1.3)로 이루어진 군에서 선택되는 하나 이상일 수 있다.

[0136] In some examples, the conductive material used in the anode may be the same as or different from the conductive material used in the cathode.

[0137] In some examples, the positive electrode binder may be the same as or different from the negative electrode binder.

[0138] membrane

[0139] The separation membrane according to the present invention may be composed of a porous substrate or may include a porous substrate and a coating layer.

[0140] The porous substrate according to the present invention can be a porous structure having high electrolyte resistance and fine pore diameters, capable of providing a path for lithium ions to move while electrically insulating the negative electrode and the positive electrode to prevent short circuits.

[0141] In some examples, any organic or inorganic material having electrical insulation properties may be used as a constituent material of the porous substrate without particular limitation. The porous substrate may include, for example, at least one selected from the group consisting of polyolefin, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulphone, polyphenyleneoxide, polyphenylenesulfide, and polyethylenenaphthalate, and may specifically include polyolefin. Polyolefin not only has excellent coating properties, but also allows for thinning the separator, increasing the ratio of the electrode active material layer in the battery, and thus increasing the capacity per volume.

[0142] In some examples, the weight average molecular weight (Mw) of the polyolefin may be 100,000 to 500,000 g / mol. If the weight average molecular weight of the polyolefin is less than the above numerical range, it may be difficult to secure sufficient mechanical properties, and if it exceeds the above numerical range, the shutdown function may not be implemented or molding may become difficult. The shutdown function refers to the function of blocking the movement of ions and preventing thermal runaway of the battery by melting the thermoplastic resin and closing the pores of the porous substrate when the temperature of the secondary battery increases.

[0143] In some examples, the thickness of the porous substrate may be, for example, 3 to 50 μm or 4 to 30 μm. If the thickness of the porous substrate is less than the numerical range, the function of the conductive barrier may not be sufficient, and if it exceeds the numerical range, the resistance of the separator may increase excessively.

[0144] In some examples, the average diameter of the pores included in the porous substrate may be, for example, 10 to 100 nm. The pores included in the porous substrate have a structure that is interconnected with each other, so that gas or liquid can pass from one side of the porous substrate to the other side.

[0145] A separator according to another embodiment of the present invention may include a coating layer disposed on at least one surface of the porous substrate, which can improve the mechanical strength and heat resistance of a separator for a secondary battery and increase ion conductivity within the secondary battery.

[0146] The coating layer according to the present invention may include a binder polymer and inorganic particles.

[0147] The binder polymer according to the present invention can connect inorganic particles and stably fix them. The binder polymer may be, for example, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, poly(ethylene-co-vinyl acetate), polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, One or more selected from the group consisting of cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene butadiene copolymer, polyimide, and styrene-butadiene rubber may be used in combination.

[0148] According to another embodiment of the present invention, the weight ratio of the inorganic particles and the binder polymer (inorganic particles: binder polymer) may be 50:50 to 99:1, specifically 70:30 to 95:5. If the content ratio of the inorganic particles to the binder polymer is less than the above numerical range, the content of the binder polymer may increase, thereby deteriorating the thermal stability improvement performance of the separator, and the pore size and porosity may decrease due to a decrease in the empty space formed between the inorganic particles, thereby causing a deterioration in the performance of the final battery, and if the content of the binder polymer is exceeded, the content of the binder polymer may be too small, thereby weakening the peeling resistance of the coating layer.

[0149] The inorganic particles according to the present invention can contribute to improving the mechanical strength and heat resistance of a separator for a secondary battery. Specifically, the inorganic particles are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles that can be used in the present invention can be used within the operating voltage range of the secondary battery to which they are applied (e.g., Li / Li). + There are no particular restrictions as long as no oxidation and / or reduction reaction occurs at a voltage of 0 to 5 V as a standard. For example, when using inorganic particles with a high dielectric constant as inorganic particles, it can contribute to increasing the degree of dissociation of electrolyte salts, such as lithium salts, in a liquid electrolyte, thereby improving the ionic conductivity of the electrolyte.

[0150] For the reasons described above, the inorganic particles may be inorganic particles having a dielectric constant of 5 or more, inorganic particles having lithium ion transport capability, or a mixture thereof. In some examples, the inorganic particles having a dielectric constant of 5 or more may be Al2O3, SiO2, ZrO2, AlO(OH), Al(OH)3, Mg(OH)2, BaSO4, TiO2, BaTiO3, Pb(Zr x Ti 1-x )O3(PZT, where 0 <x<1), Pb 1-x La x Zr 1-y Ti yO3(PLZT, where 0 < x < 1, 0 < y < 1), (1-x)Pb(Mg 1 / 3 Nb 2 / 3 )O 3-x The inorganic particles having lithium ion transport capability may be one or a mixture of two or more selected from the group consisting of PbTiO3 (PMN-PT, where 0 < x < 1), HfO2, SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, and SiC. In some examples, the inorganic particles having lithium ion transport capability may be lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3, 0< x < 2, 0 < y < 3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y Series glass (0 < x < 4, 0 < y < 13), lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3), lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride (Li x N y , 0 < x <4, 0 < y < 2), SiS2 series glass(Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4) and P2S5 series glass(Li x P y S z, 0 < x < 3, 0 < y < 3, 0 < z < 7) may be one or a mixture of two or more selected from the group consisting of. In some examples, the average particle diameter (D) of the inorganic particles 50 ) may be 1 nm to 10 μm, specifically 10 nm to 2 μm, and more specifically 50 nm to 1 μm, for forming a coating layer of uniform thickness and having an appropriate porosity. The "average particle diameter (D 50 )" means the particle diameter at the 50% point of the cumulative distribution of the number of particles according to particle diameter. The above average particle diameter can be measured using the laser diffraction method. Specifically, after dispersing the powder to be measured in a dispersion medium, it is introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500) and measuring the difference in diffraction pattern according to particle size when the particles pass through the laser beam, thereby calculating the particle size distribution.

[0151] In some examples, the thickness of the coating layer may be 0.1 to 10 μm, specifically 1 to 3 μm, and more specifically 1.4 to 1.6 μm. When the thickness of the coating layer satisfies the above numerical range, the insulation and thermal stability of the separator can be increased, while the energy density of the battery can be improved.

[0152] electrolyte

[0153] As used herein, the term "electrolyte" is defined as a medium that facilitates the smooth movement of ions between the anode and cathode within an electrochemical device. In some non-limiting examples, the electrolyte may be a liquid electrolyte or a solid electrolyte.

[0154] The electrolyte according to the present invention is A + B - It may contain a lithium salt having the same structure as A. Here, A + is Li + , Na + , K +Contains ions composed of alkali metal cations or combinations thereof, such as B - is PF6 - , BF4 - , Cl - , Br - , I - , ClO4 - , AsF6 - , CH3CO2 - , CF3SO3 - , N(CF3SO2)2 - , C(CF2SO2)3 - It may be any one selected from the group consisting of anions such as or a combination thereof.

[0155] The electrolyte according to the present invention may further include a solvent that dissolves the lithium salt. For example, the solvent may be dissolved or dissociated in an organic solvent composed of propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone (γ-butyrolactone), or a mixture thereof, but is not limited thereto.

[0156] The electrolyte according to the present invention may further include an additive for forming a stable SEI. For example, the additive may include at least one selected from the group consisting of lithium tribis(fluorosulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(oxalate)borate (LiBOB), lithium hexafluorophosphate (LiPF6), and lithium fluoride (LiF). In this case, the interaction between the negative electrode active material of some embodiments and the electrolyte including the additive may form an SEI having a stable and uniform thickness at the interface where the electrolyte and the negative electrode come into contact. Accordingly, the life performance and rapid charging performance of the electrochemical device may be further improved.

[0157] In some non-limiting examples, when the electrochemical device is an all-solid-state battery, the electrolyte may include at least one selected from the group consisting of a sulfide-based solid electrolyte, an oxide-based solid electrolyte, and a polymer-based solid electrolyte.

[0158] In some embodiments of the present invention, the electrochemical device may further include a solid electrolyte interphase (SEI) formed on the surface of the negative electrode. Specifically, by including a stable and uniformly thick solid electrolyte interphase (SEI) on the surface of the negative electrode, the life performance and rapid charging performance of the electrochemical device can be further improved.

[0159] In some examples, the SEI may comprise LiF, wherein the LiF may be derived from the negative active material of some embodiments and / or the additives.

[0160] In some examples, the thickness of the SEI may be 1 to 150 nm.

[0161] In some examples, the thickness deviation of the SEI may be less than 10% of the thickness average.

[0162] In some preferred embodiments of the present invention, the electrochemical device may be a lithium secondary battery. The battery may be used as a unit cell, and may be used as a battery module including the unit cell, a battery pack including the battery module, or a device including the battery pack as a power source. The devices may include, but are not limited to, small devices such as computers, mobile phones, and power tools, and medium to large devices such as electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs) that are powered by an electric motor and move, electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters), electric golf carts, and power storage systems.

[0163] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following contents.

[0164] [Manufacturing Example 1: Manufacturing of Negative Electrode Material]

[0165] <Examples 1 to 14: Preparation of negative electrode active material complexed with silicon particles and fluorine-containing polymer compound>

[0166] Synthesis of ionic monomers:

[0167] To a solution of imidazole, a cationic compound structure, and allyl bromide, which has a polymerization site structure, dissolved in ACN (Acetonitrile) at an equivalent ratio of 1:2.4, 1.1 equivalents of sodium bicarbonate (based on 1 equivalent of the imidazole) was added, and the mixture was stirred at room temperature for 3 days. Thereafter, the stirred resultant was filtered and vacuum-dried at room temperature for 12 hours to obtain an intermediate (Diallyl imidazoliium bromide, DAI-Br) in the form of an orange liquid.

[0168] The intermediate (DAI-Br) and a fluorine-containing anionic structure such as lithium fluorosulfonyl imide (LiFSI), lithium fluorosulfonate (anhydrous, LiFSA), lithium trifluoromethanesulfonate (LiTFMSA), lithium hexafluorophosphate (LiPF6), or lithium tetrafluoroborate (LiBF4) were dissolved in distilled water and stirred at room temperature for 1 day. Thereafter, the ionic monomer (DAI-FSI, DAI-FSA, DAI-TFMSA, DAI-PF6, or DAI-BF4) was finally synthesized through purification and solvent drying processes.

[0169] Meanwhile, Figure 1 shows the ionic monomer (DAI-FSI) 1 This is the result of H-NMR analysis. Referring to Figure 1, it can be confirmed that an ionic monomer (DAI-FSI) was synthesized.

[0170] Manufacturing of negative electrode active materials:

[0171] 1.1 Preparation of secondary particles

[0172] Milled first silicon particles (D 50: 120 nm) and pitch powder were dispersed in ethanol, and the dispersion was sprayed through a spray dryer to produce second silicon particles (secondary particles). The content of the milled first silicon particles was adjusted to 3 wt% based on the total weight of the dispersion, and the content of the pitch powder was adjusted to the content (parts by weight) based on 100 parts by weight of the first silicon particles. Using the nozzle-type spray dryer, pressure (100 torr) was applied through an inert gas (Ar) to an extent that droplets could be sprayed evenly, and the outlet temperature of the spray dryer was set to 85°C to obtain an average size (D 50 ) were manufactured as second silicon particles (secondary particles) having a size of 9 μm.

[0173] 1.2 Heat treatment process

[0174] The above second silicon particles (secondary particles) were put into a sintering furnace and subjected to a heat treatment process at 800°C to manufacture a silicon-based negative electrode active material precursor coated with a carbon layer (average thickness: 60 nm).

[0175] 1.3 Polymer coating process

[0176] 20 g of the carbon-coated silicon-based negative electrode active material precursor prepared according to 1.1 to 1.2 was added to a solution in which 0.01 to 2.2 g of the synthesized ionic monomer and 1 wt% of the initiator (Benzoyl peroxide) based on the weight of the ionic monomer were dissolved in 10 g of tetrahydrofuran (THF), and the mixture was stirred at 1,500 rpm for 10 minutes. At this time, by adjusting the content of the ionic monomer within the above range, the fluorine content in the negative electrode active material was changed. The stirred resultant was vacuum-dried at room temperature for 3 hours in a vacuum dryer to remove tetrahydrofuran. The dried resultant was subjected to a polymerization reaction at 120°C for 12 hours for a heat treatment process (oven device) higher than the polymerization initiation temperature, thereby preparing a negative electrode active material in which the silicon particles and the polymer compound are complexed.

[0177] <Comparative Example 1: Negative active material without a fluorine-containing polymer coating layer>

[0178] Silicon particles (D) as the negative electrode active material of comparative example 1 50 =9 μm) was used.

[0179] <Comparative Example 2: Negative active material synthesized using an ionic monomer that does not contain fluorine>

[0180] A negative electrode active material was manufactured in the same manner as in Example 1, but an intermediate (DAI-Br) was used instead of the DAI-FSI.

[0181] [Experimental Example 1: Measurement of Fluorine Content and BET Specific Surface Area of ​​Negative Electrode Materials]

[0182] Method for measuring the content of fluorine atoms, the weight ratio of C and F, and the weight ratio of Si and F:

[0183] The content of fluorine atoms, the weight ratio of C and F, and the weight ratio of Si and F contained in the negative electrode active material were measured using EDS (Energy dispersive spectroscopy) analysis. At this time, the content of fluorine atoms, the weight ratio of C and F, and the weight ratio of Si and F were measured under an acceleration voltage condition of 15 kV.

[0184] BET surface area measurement method:

[0185] Nitrogen gas was adsorbed onto the negative electrode active material, and the amount of adsorbed nitrogen gas was measured to analyze the BET specific surface area of ​​the silicon negative electrode active material. Specifically, the BET specific surface area was measured at a temperature of 77 K using the static volumetric method.

[0186] Distinctive particle ionic monomer fluorine atom content (wt%) C:F weight ratio Si:F weight ratio BET specific surface area (m 2 / g) Comparative Example 1Si---100:075 Comparative Example 2SiDAI-Br--100:062 Embodiment 1SiDAI-FSI0.1100:0.33100:0.1565 Embodiment 2Si0.5100:1.7100:0.761 Embodiment 3Si1100:3.3100:1.458 Embodiment 4Si2100:6.6100:2.955 Embodiment 5Si3100:10100:4.348 Embodiment 6Si0.01100:0.03100:0.01573 Embodiment 7Si0.05100:0.17100:0.0769 Embodiment 8Si5100:17100:737 Embodiment 9Si10100:33100:1425Example 10Si11100:37100:1622Example 11SiDAI-FSA0.5100:1.7100:0.762Example 12SiDAI-TFMSA0.5100:1.7100:0.760Example 13SiDAI-PF60.5100:1.7100:0.761Example 14SiDAI-BF40.5100:1.7100:0.760

[0187] [Experimental Example 2: Observation of Surface Morphology Changes in Negative Electrode Materials]

[0188] Figure 2 is an SEM photograph of the negative electrode active material according to Comparative Example 1 and Example 2.

[0189] Referring to Fig. 2, it was confirmed that the surface roughness of the negative electrode material according to Example 2 was lower than that of Comparative Example 1.

[0190] [Manufacturing Example 2: Manufacturing of a negative electrode active material using a different type of ionic monomer than Manufacturing Example 1]

[0191] <Examples 15 to 19: When the ionic monomer is DAI-TFSI>

[0192] A negative electrode active material was prepared in the same manner as in Example 1, except that LiTFSI (Lithium bis(trifluoromethanesulfonyl)imide), a fluorine-containing anionic structure, was used. In Examples 15 to 19, the content of fluorine atoms was changed by adjusting the content of the ionic monomer to 0.01 to 2.2 g.

[0193] <Examples 20 to 29>

[0194] (i) Instead of adding imidazole, which is a cationic compound structure, and allyl bromide, which has a polymerization site structure, in an equivalent ratio of 1:2.4, 4-vinylpyridine and allyl bromide, which has a polymerization site structure, were added in an equivalent ratio of 1:1.2 (Examples 20 to 24), or a solution of triphenylphosphine and 4-vinylbenzyl chloride, which has a polymerization site structure, was dissolved in toluene and stirred at room temperature for 40 hours to carry out an ion exchange reaction with a fluorine-containing anionic compound (Examples 25 to 29), and (ii) a negative electrode active material was manufactured in the same manner as in Example 1, except that the content of fluorine atoms relative to the negative electrode active material was adjusted to the values ​​shown in Table 2 below. At this time, the content of fluorine atoms was changed by adjusting the content of the ionic monomer to 0.01 to 2.2 g.

[0195] Distinctive particle ionic monomer fluorine atom content (wt%) C:F weight ratio Si:F weight ratio BET specific surface area (m 2 / g) Example 15 SiDAI-TFSI 0.1100:0.33 100:0.1560 Example 16 Si 0.5 100:1.7 100:0.756 Example 17 Si 1 100:3.3 100:1.450 Example 18 Si 2 100:6.6 100:2.940 Example 19 Si 3 100:10 100:4.332 Example 20 Si Pyridinium-FSI 0.1100:0.33 100:0.1568 Example 21 Si 0.5 100:1.7 100:0.760 Example 22 Si 1 100:3.3 100:1.453 Example 23 Si 2 100: 6.6 100: 2.944 Example 24 Si 3 100: 10 100: 4.340 Example 25 Si Phosphonium-FSI 0.1 100: 0.3 3 100: 0.1569 Example 26 Si 0.5 100: 1.7 100: 0.762 Example 27 Si 1 100: 3.3 100: 1.455 Example 28 Si 2 100: 6.6 100: 2.947 Example 29 Si 3 100: 10 100: 4.342

[0196] [Manufacturing Example 3: Manufacturing of a negative electrode active material with a different type of particle than Manufacturing Example 1]

[0197] <Comparative Examples 3 and 4>

[0198] Silicon-based negative electrode active material precursor coated with the above carbon layer (D) 50 =9 ㎛), the Li thin film (thickness 300 ㎛) or graphite (BET surface area: 1 m 2 A negative electrode active material was prepared in the same manner as in Example 1, except that / g) was used.

[0199] <Examples 30 to 32: When Li was used>

[0200] The content of the ionic monomer was adjusted to 0.01 to 2.2 g, the content of the fluorine atom was controlled to the values ​​shown in Table 3 below, and a negative electrode active material was manufactured in the same manner as in Example 1, except that Li was used instead of the silicon-based negative electrode active material precursor coated with the carbon layer.

[0201] <Examples 33 to 41: When graphite is used>

[0202] A negative electrode active material was manufactured in the same manner as in Example 1, except that the content of the ionic monomer was adjusted to 0.01 to 2.2 g, the content of fluorine atoms was controlled to the values ​​shown in Table 3 below, and graphite was used instead of the silicon-based negative electrode active material precursor coated with the carbon layer.

[0203] Content of fluorine atoms in the particle-ionic monomer (wt%) C:F weight ratio comparison Example 3Li--- Example 30LiDAI-FSI0.5- Example 31LiDAI-FSI1- Example 32LiDAI-FSI2- Comparative Example 4 Graphite --- Example 33 Graphite DAI-FSI 0.1 100: 0.33 Example 34 Graphite DAI-FSI 0.5 100: 1.7 Example 35 Graphite DAI-FSI 1 100: 3.3 Example 36 Graphite DAI-FSI 0.01 100: 0.03 Example 37 Graphite DAI-FSI 0.05 100: 0.17 Example 38 Graphite DAI-FSI 2 100: 6.6 Example 39 Graphite DAI-FSI 5 100: 17 Example 40 Graphite DAI-FSI 10 100: 33 Example 41 Graphite DAI-FSI 15 100: 50

[0204] [Manufacturing Example 4: Manufacturing of the Cathode]

[0205] Each of the negative electrode active materials, conductive materials, CMC (carboxy methyl cellulose) and SBR (styrene-butadiene rubber) manufactured by the methods according to Manufacturing Examples 1 to 3 above was mixed in a weight ratio of 80:0.5:7.5:12, and a solvent (H2O) was added to adjust the viscosity to manufacture a negative electrode slurry having a total solid content of 50 wt%. The manufactured negative electrode slurry was coated on a current collector (copper foil) having a thickness of 18 μm, dried at 90 ° C. for 60 minutes, and then the mixture density was adjusted to 1.6 g / cc using a roll press, and then dried in a vacuum oven at 90 ° C. for 24 hours to manufacture a negative electrode (thickness: 50 μm).

[0206] [Manufacturing Example 5: Manufacturing of an Electrochemical Device]

[0207] Manufacturing of half-cells:

[0208] After arranging the negative electrode of the above Manufacturing Example 4, the polypropylene separator (thickness: 80 μm), and the counter electrode (lithium metal with a thickness of 1,000 μm) in that order, a membrane-electrode assembly was manufactured under an inert gas atmosphere. After placing the membrane-electrode assembly in a battery case, an electrolyte was injected in which 1.0 M LiPF6 was dissolved in a mixed solvent of 1:1 volume ratio of EC (Ethylene carbonate) and DEC (Diethyl carbonate) and 10% by weight of FEC (Fluoroethylene carbonate) was added, thereby manufacturing a half-cell.

[0209] [Experimental Example 3: Performance Evaluation of Half-Cells]

[0210] How to measure capacity retention in a normal cycle:

[0211] The half-cell of the above Manufacturing Example 5 was CC and CV charged at room temperature (25°C) under the conditions of 0.5 C-rate, voltage range 0.01 to 1.5 V, reference capacity 1C = 2,000 mAh / g, and 0.005 C cutoff, and CC discharge at 1 C-rate was performed for a total of 100 cycles, with 1 cycle being considered as one cycle. The capacity retention rate was measured by calculating the discharge capacity in the 100th cycle compared to the discharge capacity in the first cycle, and the results are shown in Tables 4 and 5 below.

[0212] How to measure capacity retention during rapid charging:

[0213] The capacity retention rate of the half-cell according to the above Manufacturing Example 5 was evaluated using a WBCS-3000LE battery tester. First, formation was repeated for 3 cycles by applying a current density of 0.1 C in the voltage range of 0.01 V-1.5 V, and then charging and discharging were performed at high output by applying a current density of 3 C for charging / 1 C for discharging in the same voltage range. At this time, the capacity retention rate (%) was calculated as [(first cycle discharge capacity / 100 cycle discharge capacity) X 100].

[0214] Initial Coulombic efficiency measurement method:

[0215] The half-cell of the above manufacturing example 5 was charged by CC and CV at room temperature (25°C) at 0.1 C-rate, voltage range 0.01 to 1.5 V, reference capacity 1C = 2,000 mAh / g, and 0.005 C cutoff conditions, and discharged by CC at 0.1 C-rate as one cycle, and the initial coulombic efficiency was calculated according to the following mathematical equation 1.

[0216] [Mathematical Formula 1]

[0217] Initial Coulombic Efficiency (ICE, %) = (Q d / Q c ) X 100

[0218] In the above mathematical expression 1, Q c is the charge capacity of the half-cell in the first cycle, and Q d is the discharge capacity of the half-cell in the first cycle.

[0219] Capacity retention rate (%) Rapid charge capacity retention rate (%) Initial coulombic efficiency (%) Comparative example 182.47 1.67 8.2 Comparative example 282.97 2.77 9.1 Example 184.17 3.28 2.6 Example 288 83.38 5.5 Example 387.58 38 5.3 Example 485.17 9.78 4 Example 584.47 5.28 3.1 Example 683.17 2.17 8.5 Example 783.37 2.98 0.7 Example 883.57 4.48 1.5 Example 983 73.57 9.8 Example 1083 737 9.3 Example 1183.88 1.68 4.2 Example 1288.183.986 Example 1389.585.185.9 Example 1490.386.386.5

[0220] Capacity retention rate (%) Rapid charge capacity retention rate (%) Initial coulombic efficiency (%) Example 1583.97 4.28 4.1 Example 1689.68 5.58 6.1 Example 1788.18 3.58 5.6 Example 1886.58 1.78 4.7 Example 198579.78 4 Example 2081.57 1.68 3.5 Example 2186.38 1.38 4.8 Example 2286.18 0.98 4.2 Example 2385.67 8.88 3.5 Example 248577.38 2.9 Example 2580.67 0.18 3.4 Example 2685.97 9.98 4.3 Example 2785.580.283.9 Example 2883.375.483.1 Example 2982.674.482.5 Comparative Example 390.985.590Example 3095.292.190.9Example 3193.890.390.7Example 3291.986.890.3Comparative Example 495.267.494Example 3395.569.394.3Example 3498.677.694.9Example 3598.475.394.4Example 3695.26894Example 3795.968.594.1Example 3897.972.194.2Example 3996.271.794.1Example 409669.594Example 4195.568.194

[0221] [Experimental Example 4: Image of the electrode after cycle evaluation]

[0222] Figure 3a is a SEM photograph and EDS (Energy Dispersive Spectroscopy) result of the cathode in the electrochemical device according to Comparative Example 1 after 50 cycles under the measurement conditions of Experimental Example 3, and Figure 3b is a SEM photograph and EDS (Energy Dispersive Spectroscopy) result of the cathode in the electrochemical device according to Example 2 under the measurement conditions of Experimental Example 3.

[0223] Fig. 4a is an SEM photograph of the cathode in the electrochemical device according to Comparative Example 1 after 100 cycles under the measurement conditions of Experimental Example 3, and Fig. 4b is an SEM photograph of the cathode in the electrochemical device according to Example 2 after 100 cycles under the measurement conditions of Experimental Example 3.

[0224] Referring to Figures 3a, 3b, 4a, and 4b, it was confirmed that since a polymer compound having fluorine atoms is coated on the particle, it is easy to control the interface of the negative electrode active material particle surface even after a long-term cycle evaluation, and the interface between the negative electrode active materials is clearly observed.

[0225] The features described in the above-described embodiment may be combined with other embodiments unless explicitly stated otherwise. Furthermore, while the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art utilizing the basic concepts of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. Particles; and A polymer compound on the above particles; including; The above polymer compound contains a fluorine atom, Negative active material.

2. In paragraph 1, The above particles are, Containing at least one selected from the group consisting of silicon particles, carbon particles, and metal particles. Negative active material.

3. In paragraph 1, The polymer compound comprises a cationic repeating unit and an anionic functional group. Negative active material.

4. In paragraph 3, The above cationic repeating unit is, Containing a structure represented by the following general formula 1, Negative active material: [General Formula 1] In the above general formula 1, A is a pentagonal ring, a hexagonal ring or a chain-like divalent linker, Each of the above rings and the above chain-type divalent linkers are each independently containing one or more nitrogens; or one or more phosphorus, * indicates a point where it connects to another part within the molecule.

5. In paragraph 4, A in the above general formula 1 contains a nitrogen cation or a phosphorus cation, Negative active material.

6. In paragraph 4, A in the above general formula 1 contains an aromatic ring structure, Negative active material.

7. In paragraph 4, A in the above general formula 1 is Containing a structure represented by the following general formula 1a, Negative active material: [General Formula 1a] In the above general formula 1a, R1 is each independently nitrogen or phosphorus, R2 is independently any one selected from the group consisting of a hydrogen atom; a substituted or unsubstituted alkyl group; a substituted or unsubstituted cycloalkyl group; a substituted or unsubstituted alkoxy group; a substituted or unsubstituted amine group; a substituted or unsubstituted allyl group; a substituted or unsubstituted (meth)acryl group; a substituted or unsubstituted benzyl group; a substituted or unsubstituted styrene group; a substituted or unsubstituted (meth)acrylamide group; a substituted or unsubstituted vinyl ester group; and a substituted or unsubstituted vinylamide group.

8. In paragraph 3, The fluorine atoms of the above polymer compound are Included in the above anionic functional group, Negative active material.

9. In paragraph 3, The above anionic functional group is, Containing a nitrogen anion, a phosphorus anion, a boron anion or an oxygen anion, Negative active material.

10. In paragraph 1, The fluorine atoms of the above polymer compound are Contains at least one selected from the group consisting of FSI (Fluorosulfonyl imide), TFSI (Trifluoromethanesulfonyl imide), FSA (Fluorosulfonate), TFMSA (Trifluoromethane sulfonate), hexafluorophosphate, and tetrafluoroborate. Negative active material.

11. In paragraph 1, The above polymer compound further contains boron atoms, Negative active material.

12. In paragraph 1, The content of the fluorine atoms is 0.05 to 10 wt% based on the total weight of the negative electrode active material. Negative active material.

13. In paragraph 1, The content of the fluorine atom is 0.5 to 1 wt% based on the total weight of the negative electrode active material. Negative active material.

14. In paragraph 1, In the above negative electrode active material, the weight ratio of carbon atoms and fluorine atoms is 100:0.05 to 100:

35. Negative active material.

15. In paragraph 1, The BET specific surface area of ​​the above negative electrode active material is 75 m 2 / g or less, Negative active material.

16. A negative electrode comprising a negative electrode active material according to any one of claims 1 to 15; an anode spaced apart from the cathode; and Containing electrolytes, Electrochemical devices.

17. In paragraph 16, Further comprising SEI (Solid electrolyte interphase) formed on the surface of the cathode; Electrochemical devices.

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