High energy density electrochemical device

Abstract

The present invention relates to an electrochemical element capable of simultaneously satisfying a high energy density of 400 Wh / kg or more, excellent lifespan characteristics, and stability, the electrochemical element according to the present invention comprising: a positive electrode; a negative electrode including a negative electrode current collector, or a negative electrode current collector and a lithium metal; and an electrolyte; the positive electrode includes: a positive electrode current collector; and a positive electrode active material layer formed on the positive electrode current collector and including a porous binder support and positive electrode active material particles.

Description

Technical Field

[0001] The present invention relates to a high energy density electrochemical element, and more particularly to a lithium metal battery and a negative electrode-free lithium battery with high energy density. Background Art

[0002] With the recent rapid increase in required battery energy density, the development of high-capacity lithium batteries has become increasingly urgent. To this end, some researchers have proposed replacing existing negative electrode materials such as graphite and silicon with lithium metal, or developing anode-free batteries. However, simply changing the negative electrode material is unlikely to meet the increasing performance requirements. In addition to changing the negative electrode material, research is also actively underway on thick-film cathodes, which increase the thickness of the positive electrode active material layer by increasing the density and loading of the positive electrode active material.

[0003] However, the thicker the positive electrode active material layer becomes, the more difficult it is to ensure stable battery performance and service life, so there is actually a limit to its thickness increase. As an example, these thick-film positive electrodes have the fundamental problem of uneven distribution of the positive electrode material. This causes uneven flow characteristics of lithium ions, and uneven charging and discharging characteristics in the thickness direction and polarization phenomena occur. In addition, there is a problem that as the thickness of the positive electrode increases, the distance that lithium ions move also increases, thereby causing a decrease in battery performance.

[0004] In addition, the uneven flow characteristics of lithium ions exacerbate the problem of dendrite formation on the surface of lithium metal, which not only shortens the service life of the battery but also reduces the stability of the battery. Summary of the Invention

[0005] Problem to be solved

[0006] One aspect of the present invention is to provide an electrochemical device that can simultaneously meet high energy density of 400 Wh / kg or more, excellent service life characteristics, and stability.

[0007] Technical solutions to the problem

[0008] According to one aspect of the present invention, the electrochemical element is characterized in that the electrochemical element includes: a positive electrode; a negative electrode including a negative electrode collector, or a negative electrode collector and lithium metal; and an electrolyte, and the electrochemical element is an electrochemical element with an energy density of more than 400Wh / kg, and the positive electrode includes: a positive electrode collector; and a positive electrode active material layer formed on the positive electrode collector and including a porous adhesive support and positive electrode active material particles.

[0009] The energy density of the electrochemical element may be 450 Wh / kg to 650 Wh / kg.

[0010] The electrochemical element may further include a separator.

[0011] The positive electrode active material layer may include 50 wt % or more relative to the total weight of the electrochemical device.

[0012] The positive electrode active material layer may include 60 wt % to 85 wt % relative to the total weight of the electrochemical element.

[0013] The positive electrode active material particles may include 80 wt % to 99 wt % relative to the total weight of the positive electrode active material.

[0014] The positive electrode active material layer may be a thick film type positive electrode having a thickness of 50 μm to 2000 μm.

[0015] The positive electrode may be a positive electrode active material layer formed on one side of a positive electrode current collector with a capacity of 4 mAh / cm 2 Up to 150mAh / cm 2 Thick film positive electrode.

[0016] The positive electrode may be a thick film type positive electrode having a positive electrode active material layer mixture density (g / cc) of 3.3 to 3.8.

[0017] In the positive active material layer, positive active material particles may be uniformly dispersed, and a porous binder scaffold may exist in the empty spaces between the particles.

[0018] The porous binder support may be included in an amount of 0.01 to 40 parts by weight relative to 100 parts by weight of the positive active material particles.

[0019] The porous adhesive support may also include a conductive material.

[0020] The positive electrode active material layer may further include a metal salt.

[0021] The metal salt may be included in an amount of 0.01 to 50 parts by weight relative to 100 parts by weight of the positive active material particles.

[0022] The metal salt may be contained in or surface-adsorbed on at least one of the porous binder support and the positive electrode active material particles.

[0023] The metal salt may be a sulfonyl group-containing metal salt selected from the following Chemical Formula 1 or Chemical Formula 2.

[0024] [Chemical Formula 1]

[0025]

[0026] [Chemical Formula 2]

[0027]

[0028] (In the chemical formulas 1 and 2,

[0029] n is 1 or 2;

[0030] A is an n-valent cation;

[0031] And R1 to R3 are each independently a fluoro(C1-C7)alkyl group or a fluoro group.)

[0032] The A can be lithium, sodium, zinc, copper, aluminum, silver, gold, cesium, indium, magnesium or calcium.

[0033] When the cross-section of the positive electrode active material layer is analyzed by X-ray CT, relative to the average concentration of the conductive material (C0) of the positive electrode active material layer, the deviation between the conductive material concentration (C1) of the first active material layer corresponding to the boundary surface between the positive electrode collector and the positive electrode active material layer to 1 / 3 in the thickness direction of the positive electrode active material layer, the conductive material concentration (C2) of the second active material layer corresponding to 1 / 3 to 2 / 3 in the thickness direction of the positive electrode active material layer, and the conductive material concentration (C3) of the third active material layer from 2 / 3 in the thickness direction of the positive electrode active material layer to the surface can be less than 10%.

[0034] A half cell manufactured using the positive electrode may have a discharge capacity retention rate of 80% or more at 0.3C compared to the discharge capacity at 0.1C.

[0035] The electrolyte may be a liquid electrolyte, a solid electrolyte, or a combination thereof.

[0036] The ratio (g / Ah) of the electrolyte injection amount to the battery capacity ratio of the lithium metal battery in the electrolyte may be lower than 1.2.

[0037] The electrolyte may be included in an amount of 15 to 30 parts by weight relative to 100 parts by weight of the positive electrode.

[0038] The electrochemical element may have a 0.1C discharge capacity realization ratio of 0.9 or greater compared to a designed capacity.

[0039] The electrochemical element may be a lithium metal battery or a negative electrode-free lithium battery.

[0040] The positive electrode's internal electrode curvature (Tortuosity, τ) calculated according to the following relationship may be less than 6.

[0041] [Relational formula]

[0042] τ(bending)=(K 电解质 / K电极 )×(porosity)

[0043] (In the above formula, K 电解质 represents the ionic conductivity of the electrolyte, K 电极 represents the ionic conductivity of the positive electrode, and porosity represents the porosity of the positive electrode.

[0044] Effects of the Invention

[0045] The lithium metal battery according to the present invention can simultaneously meet the high energy density of more than 400Wh / kg, excellent service life characteristics and stability. Specifically, the lithium metal battery according to one aspect can effectively suppress the occurrence of polarization even when using a thick film positive electrode, and can achieve uniform charge and discharge characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 These are the results of SEM analysis of the surface of the positive electrode produced in Comparative Example 1.

[0047] Figure 2 This is the SEM analysis result of the positive electrode surface manufactured in Example 1.

[0048] Figure 3 This is the result of SEM analysis of the cross section of the positive electrode produced in Comparative Example 1.

[0049] Figure 4 This is the SEM analysis result of the cross section of the positive electrode manufactured in Example 1.

[0050] Figure 5 These are graphs showing distribution patterns of conductive materials in the thickness direction of the positive electrodes based on the results of X-ray CT analysis of cross sections of the positive electrodes produced in (a) Comparative Example 1 and (b) Example 1.

[0051] Figure 6 This is a graph showing the distribution of the conductive material content (vol %) in the first active material layer, the second active material layer, and the third active material layer based on X-ray CT imaging results. DETAILED DESCRIPTION

[0052] Unless otherwise defined herein, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The terms used in this specification are only used to describe specific embodiments and are not intended to limit the present invention.

[0053] Unless otherwise indicated in the context, the singular forms used in this specification may also be intended to include the plural forms.

[0054] In this specification and the accompanying patent claims, when it is mentioned that part of a film (layer), region, constituent element, etc. is located on or above other parts, it includes not only the case where it is in contact with other parts and directly located thereon, but also the case where other films (layers), other regions, other constituent elements, etc. are sandwiched therebetween.

[0055] In addition, the numerical ranges used in this specification include the lower limit and the upper limit, as well as all values within the range, increments logically derived from the form and amplitude of the defined range, all values of the double limit, and all possible combinations of the upper and lower limits of the numerical range defined by other forms. Unless otherwise specified in this specification, values outside the numerical range that may appear due to experimental errors or numerical rounding are also included in the defined numerical range.

[0056] The term "comprising" in this specification is an open description with equivalent meanings to expressions such as "having", "containing", "having" or "characterized by", and does not exclude elements, materials or processes that are not additionally listed.

[0057] The term "porous adhesive scaffold" in this specification refers to a network structure formed uniformly in three dimensions by an adhesive, and refers to a structure in which the adhesive forms a skeleton and develops abundant pores within the skeleton. The above-mentioned pores preferably have an open pore structure, and the above-mentioned porous network structure formed by the adhesive can serve as a support body for uniformly distributing the positive electrode active material and the conductive material. The above-mentioned pores may have a diameter of 0.1 μm to 50 μm, specifically a diameter of 0.5 μm to 10 μm. More specifically, the above-mentioned porous adhesive scaffold may include fibers formed by self-assembly of an organic adhesive and a conductive material as a unit structure, and may include a support body of a thin inner wall structure formed by the secondary self-assembly of the above-mentioned fibrous unit structure. In other words, the adhesive scaffold is an open-cell foam structure formed by the above-mentioned inner wall structure, and the internal space can be divided by the inner wall structure. More specifically, the above-mentioned inner wall structure may be a porous inner wall, and the above-mentioned internal space may include a plurality of pores that are larger than the pores formed in the inner wall structure. The positive electrode active material may be located in the aforementioned internal space. More specifically, the positive electrode active material may be located in the aforementioned internal space and may be fixed in contact with the aforementioned porous inner wall structure. Compared to a fiber mesh structure, the aforementioned binder scaffold structure can form a superior conductive network and provide excellent adhesion to the positive electrode active material particles.

[0058] To meet the performance requirements of next-generation lithium batteries, it is necessary to replace existing negative electrode materials with lithium metal or achieve anode-free design. Furthermore, by increasing the density and loading of the positive electrode active material, combined with thick-film positive electrodes with increased thickness of the positive electrode active material layer, capacity can be further increased. However, existing technologies have fundamental technical limitations, such as the uneven distribution of the positive electrode material or the formation of cracks as the positive electrode active material layer thickens. This also reduces the battery's service life and stability. Therefore, research is ongoing to address this issue.

[0059] The present invention aims to address the aforementioned problems of the prior art by providing an electrochemical device that simultaneously achieves a high energy density exceeding 400 Wh / kg, excellent lifespan characteristics, and stability. When calculating energy density, the weight (kg) of the electrochemical device refers to the weight of the final product, including auxiliary materials (bags, tabs, etc.).

[0060] Specifically, according to one aspect, an electrochemical element is characterized in that it includes: a positive electrode; a negative electrode collector, or a negative electrode including a negative electrode collector and lithium metal; and an electrolyte, the above-mentioned positive electrode includes: a positive electrode collector; and a positive electrode active material layer, formed on the above-mentioned positive electrode collector and including a porous adhesive support and positive electrode active material particles.

[0061] The porous binder scaffold is a network structure with abundant pores within a binder-formed skeleton. This porous network structure serves as a support for uniformly distributing positive electrode materials, such as positive electrode active material and conductive material. Specifically, according to one aspect, the positive electrode, by making the binder component microporous, prevents cracking even when the positive electrode is thickened, and allows for highly uniform distribution of the positive electrode material, thereby maintaining excellent battery performance.

[0062] That is, the electrochemical element according to one aspect can satisfy both excellent service life characteristics and stability even if it adopts a thick film positive electrode that can achieve a high energy density of more than 400Wh / kg, or 450Wh / kg to 750Wh / kg, or 450Wh / kg to 650Wh / kg.

[0063] According to one aspect, the above-mentioned electrochemical element may include a positive electrode active material layer of more than 50 weight%, more than 55 weight%, or more than 60 weight%, or less than 95 weight%, or less than 90 weight%, or less than 88 weight%, or 50 weight% to 90 weight%, or 60 weight% to 90 weight%, or 60 weight% to 85 weight%, relative to the total weight.

[0064] In addition, relative to the total weight of the above-mentioned positive electrode active material layer, it can include more than 70 weight%, or more than 80 weight%, or less than 99%, or less than 97%, less than 95%, less than 93%, or less than 90%, or 70 weight% to 99 weight%, or 80 weight% to 99 weight% of positive electrode active material particles.

[0065] In addition, the above-mentioned positive electrode can be a thick film positive electrode in which the thickness of the positive electrode active material layer is 50 μm or more, or 100 μm or more, or 200 μm or more, or a thickness of 2000 μm or less, or 1,500 μm or less, or 1,000 μm or less, or a thickness of 150 μm to 2000 μm, or 100 μm to 2000 μm, or 100 μm to 1,000 μm, or 100 μm to 500 μm, or 200 μm to 500 μm.

[0066] Alternatively, the positive electrode may include a positive electrode active material layer having a capacity of 4 mAh / cm formed on one side of the positive electrode current collector. 2 Up to 150mAh / cm 2 , or 4mAh / cm 2 Up to 100mAh / cm 2 、5mAh / ㎝ 2 Up to 50mAh / cm 2 Thick film positive electrode.

[0067] In addition, the above-mentioned positive electrode can be a positive electrode active material layer mixture density (g / cc) of 2.0 or more, or 2.5 or more, or 3.0 or more, or 3.0 or more, or it can be a thick film positive electrode having a positive electrode active material layer mixture density (g / cc) of 2.0 to 5.0, or 3.0 to 5.0, or 3.3 to 3.8.

[0068] In addition, the electrode inner curvature (Tortuosity, τ) of the above-mentioned positive electrode calculated by the following relationship may be 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less, and, without limitation, may be 1 or more. Specifically, the electrode inner curvature may be 1 to 10, 2 to 9, 3 to 8, 4 to 7, or 5 to 6.

[0069] [Relational formula]

[0070] τ(bending)=(K 电解质 / K 电极 )×(porosity)

[0071] In the above formula, K 电解质 represents the ionic conductivity of the above electrolyte, K 电极 represents the ionic conductivity of the positive electrode, and porosity represents the porosity of the positive electrode.

[0072] An electrochemical element including such a positive electrode has excellent ion conductivity due to a short ion transport path within the electrode, and can have excellent battery performance.

[0073] In addition, the discharge capacity retention rate of a half cell manufactured using the above-described positive electrode at 0.3C may be 80% or more, or 85% or more, or 90% or more, or may be 80% to 99%, or 90% to 98%, compared to the discharge capacity at 0.1C. As a non-limiting example, the discharge capacity retention rate at 0.1C and at 0.3C may be measured after one charge, five charges, ten charges, or thirty charges, but is not limited thereto.

[0074] In addition, the 0.1C discharge capacity realization ratio of the electrochemical device according to one aspect may be 0.8 or more, 0.85 or more, 0.9 or more, or 0.95 or more, or 0.8 to 1.0, 0.9 to 1.0, or 0.95 to 1.0, compared to the design capacity. The design capacity refers to a theoretical value calculated from the total weight of the positive electrode active material contained in the battery and the reversible discharge capacity of the positive electrode active material.

[0075] That is, according to one aspect, even if the above-mentioned positive electrode active material layer is high-density / high-loaded, no cracks will be generated at all, and the positive electrode material can be distributed very evenly in the thickness direction, and can effectively maintain the uniform flow characteristics of lithium ions and uniform charging and discharging characteristics in the thickness direction.

[0076] Furthermore, since the binder forms a porous scaffold structure, the positive electrode active material layer according to one aspect can achieve excellent mechanical properties even with a small amount of binder, thereby further increasing the positive electrode active material content and achieving even better energy density.

[0077] As an example, the porous binder scaffold may include 0.01 to 40 parts by weight, or 0.01 to 20 parts by weight, or 0.01 to 10 parts by weight, or 0.01 to 5 parts by weight, or 0.01 to 1 part by weight per 100 parts by weight of the positive active material particles.

[0078] The porous adhesive support can be any polymer adhesive commonly used in the art, and can be either an aqueous polymer adhesive or a non-aqueous polymer adhesive. Specifically, the polymer adhesive can be a fluorine-based resin, a rubber-based material, a polyolefin-based resin, an acrylic resin, an imide-based resin, a cellulose-based resin, or the like. More specifically, the polymer binder can include polyvinylidene fluoride, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene, polyvinyl pyrrolidone, polyacrylonitrile, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride-trifluorochloroethylene, polymethyl methacrylate, polyvinyl acetate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, polyvinyl alcohol, carboxymethyl cellulose, starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, nitrile rubber, fluororubber, or mixtures thereof, but are not limited thereto.

[0079] In addition, the positive electrode active material layer according to one aspect may further include a conductive material. In this case, the conductive material may be contained in or adsorbed on the porous binder support.

[0080] The conductive material is not particularly limited as long as it is a material commonly used in the relevant technical field. As a non-limiting example, it can be a carbon-based conductive material, and the carbon-based conductive material can include a point-shaped carbon-based conductive material, a linear carbon-based conductive material, a plate-shaped carbon-based conductive material, or a mixture thereof. Examples of the point-shaped carbon-based conductive material include acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon black, etc.; examples of the linear carbon-based conductive material include carbon nanotubes, conductive carbon fibers, etc.; and examples of the plate-shaped carbon-based conductive material include graphene (including GRO), etc.

[0081] In addition, according to one aspect, the positive electrode active material layer may further include a metal salt, and the metal salt may be contained in or surface-adsorbed on at least one of the porous binder support and the positive electrode active material particles. Specifically, the metal ions of the metal salt may be metal ions (active ions) participating in the electrochemical reaction, and the salt may induce effective composite formation of the carbon-based conductive material and the binder, and may remain in a state contained in or surface-adsorbed on at least one of the porous binder support structure and the positive electrode active material particles, and may remain in a crystalline phase inherent to the salt.

[0082] The metal salt may be included in an amount of 0.01 to 50 parts by weight, 0.01 to 30 parts by weight, 0.01 to 10 parts by weight, or 0.01 to 1 part by weight relative to 100 parts by weight of the positive active material particles.

[0083] The metal salt may be a sulfonyl group-containing metal salt. In this case, the metal salt may remain in the electrode to further improve the electrochemical performance of the electrode, enhance the flame retardancy of the electrode, and further enhance the wettability of the electrode to the electrolyte.

[0084] The molecular weight (g / mole) of the sulfonyl group-containing metal salt may be 1000 or less, specifically 500 or less, more specifically 400 or less, and may have a molecular weight of 10 or more, 20 or more, or 30 or more. Furthermore, the number of anions per metal salt molecule of the sulfonyl group-containing metal salt may be 1 to 4, specifically 1 to 3, more specifically 1 to 2.

[0085] Specifically, the metal salt may be selected from the following Chemical Formula 1 or Chemical Formula 2, but is not limited thereto.

[0086] [Chemical Formula 1]

[0087]

[0088] [Chemical Formula 2]

[0089]

[0090] (In the above Chemical Formula 1 and Chemical Formula 2,

[0091] n is 1 or 2;

[0092] A is an n-valent cation;

[0093] and R1 to R3 are each independently a fluoro(C1-C7)alkyl group or a fluoro group.

[0094] As an example, R1 to R3 can each independently be F, CFH2, CF2H, CF3, C2F5, C3F7, C4F9 or C5H 11 .

[0095] As an example, A is a monovalent cation or a divalent cation. The monovalent cation may be an alkali metal ion, and the divalent cation may be an alkaline earth metal ion or a post-transition metal ion. Specifically, A may be lithium, sodium, zinc, copper, aluminum, silver, gold, cesium, indium, magnesium, or calcium.

[0096] As an example, the sulfonyl group-containing metal salt can be any one or more selected from lithium trifluoromethanesulfonate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(perfluoroethanesulfonyl)imide, zinc trifluoromethanesulfonate, bis[lithium bis(trifluoromethylsulfonyl)imide]zinc, etc.

[0097] According to one aspect, when the cross-section of the above-mentioned positive electrode active material layer is analyzed by X-ray CT photography, relative to the average conductive material concentration (C0) of the positive electrode active material layer, the deviation between the conductive material concentration (C1) of the first active material layer corresponding to the boundary surface between the positive electrode collector and the positive electrode active material layer to 1 / 3 in the thickness direction of the positive electrode active material layer, the conductive material concentration (C2) of the second active material layer corresponding to 1 / 3 to 2 / 3 in the thickness direction of the positive electrode active material layer, and the conductive material concentration (C3) of the third active material layer from 2 / 3 in the thickness direction of the positive electrode active material layer to the surface can be less than 10%.

[0098] That is, according to one aspect, the positive electrode active material layer is characterized in that as the binder component is made microporous to form a porous binder frame, even if the thickness of the positive electrode active material layer increases, the positive electrode material such as the conductive material and the positive electrode active material particles are distributed very uniformly in the thickness direction.

[0099] A first aspect of an electrochemical element according to one aspect may be a lithium metal battery, comprising: the thick film positive electrode; a negative electrode comprising a negative electrode current collector and lithium metal formed on the negative electrode current collector; and an electrolyte.

[0100] In addition, a second aspect of the electrochemical element according to one aspect may be an anode-free lithium metal battery, comprising: the above-mentioned thick film positive electrode; an anode current collector; and an electrolyte.

[0101] Non-limiting examples of the negative electrode current collector include foils made of copper, gold, nickel, copper alloys, or combinations thereof. Non-limiting examples of the positive electrode current collector include foils made of aluminum, nickel, or combinations thereof.

[0102] The positive active material according to one aspect may be a nickel-cobalt-manganese-based positive active material, and may be represented by the following Chemical Formula 11.

[0103] [Chemical Formula 11]

[0104] LiNi a Co b Mn c O2

[0105] In the above chemical formula 11, a+b+c=1, and 0.5 <a<1.0,0<b<0.5,0<c<0.5。

[0106] As an example, a+b+c=1, and it can be 0.6≤a≤0.9, 0 <b≤0.2,0<c≤0.2。

[0107] Specifically, the positive electrode active material according to one aspect may be LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.88 Co 0.06 Mn 0.06 O2、LiNi 0.9 Co 0.05 Mn 0.05 O2 or mixtures thereof, but not limited thereto.

[0108] The electrolyte may be a liquid electrolyte, a solid electrolyte, or a combination thereof. Specifically, the electrolyte may be a liquid electrolyte, and the liquid electrolyte may include a non-aqueous organic solvent and a lithium salt.

[0109] The non-aqueous organic solvent can be selected from a cyclic carbonate solvent, a linear carbonate solvent, and a mixed solvent thereof; the cyclic carbonate solvent can be selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, and a mixture thereof; the linear carbonate solvent can be selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and a mixture thereof. Specifically, the non-aqueous organic solvent can be a mixed solvent of a cyclic carbonate solvent and a linear carbonate solvent, and can be mixed and used with a mixed volume ratio of cyclic carbonate solvent: linear carbonate solvent of 1:1 to 1:9, or a volume ratio of 1:1 to 1:4.

[0110] As the lithium salt, one or more of the lithium salts may be selected from the group consisting of LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiC(SO2CF3)3, LiN(SO3CF3)2, LiC4F9SO3, LiAlO4, LiAlCl4, LiCl, and LiI, but are not limited thereto. The concentration of the lithium salt may be 0.6M to 2.0M.

[0111] As an example, for the above-mentioned liquid electrolyte, the ratio of the electrolyte injection amount to the capacity of the electrochemical device according to one aspect (g / Ah) may be less than 2.0, less than 1.5, less than 1.2, or less than 1.1. In addition, the content of the above-mentioned liquid electrolyte relative to 100 parts by weight of the positive electrode may be 10 to 30 parts by weight, or 10 to 25 parts by weight, or 15 to 25 parts by weight.

[0112] That is, the positive electrode of the electrochemical device according to one aspect has excellent wettability with respect to the electrolyte, and thus a higher energy density can be achieved while reducing the amount of electrolyte used.

[0113] In addition, according to one embodiment, the electrochemical element may further include a diaphragm. The above-mentioned diaphragm is not limited as long as it is commonly used in the relevant technical field. However, as a non-limiting example, it can be selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene or a combination thereof, and can be in the shape of a non-woven fabric or a woven fabric, and can selectively adopt a single-layer or multi-layer structure.

[0114] According to another aspect of the present invention, an electrochemical element is provided, comprising: a positive electrode; a negative electrode comprising a negative electrode collector, or a negative electrode collector and lithium metal; and an electrolyte, and as an electrochemical element with an energy density of 400Wh / kg or more, the positive electrode comprises: a positive electrode collector; and a positive electrode active material layer comprising positive electrode active material particles, a binder and a conductive material formed on the positive electrode collector, and when a cross-section of the positive electrode active material layer is analyzed by X-ray CT imaging, relative to the average concentration (C0) of the conductive material of the positive electrode active material layer, the conductive material concentration (C1) of the first active material layer corresponding to the boundary surface between the positive electrode collector and the positive electrode active material layer to 1 / 3 in the thickness direction of the positive electrode active material layer, the conductive material concentration (C2) of the second active material layer corresponding to 1 / 3 to 2 / 3 in the thickness direction of the positive electrode active material layer, and the conductive material concentration (C3) of the third active material layer from 2 / 3 in the thickness direction of the positive electrode active material layer to the surface are deviated by less than 10%.

[0115] A third aspect of the electrochemical element according to one aspect may be a lithium metal battery including: the thick film positive electrode; a negative electrode including a negative electrode current collector and lithium metal formed on the negative electrode current collector; and an electrolyte.

[0116] In addition, a fourth aspect of the electrochemical element according to one aspect may be an anode-free lithium battery, comprising: the above-mentioned positive electrode; a negative electrode current collector; and an electrolyte.

[0117] Since they are the same as those described above, descriptions of the types of the positive electrode active material particles, the binder, the conductive material, the negative electrode current collector, and the electrolyte are omitted below.

[0118] In an electrochemical element according to one aspect, the binder can form a porous binder scaffold structure, which develops a network structure with abundant pores. This porous network structure can serve as a support for uniformly distributing positive electrode materials such as the positive electrode active material and the conductive material. Specifically, the positive electrode according to one aspect achieves highly uniform distribution of the positive electrode materials by making the binder component microporous, thereby maintaining excellent battery performance.

[0119] Specifically, the electrochemical element according to one aspect can satisfy both excellent service life characteristics and stability even if it adopts a thick film positive electrode that can achieve a high energy density of more than 400Wh / kg, or 450Wh / kg to 750Wh / kg, or 450Wh / kg to 650Wh / kg.

[0120] According to one aspect, the electrochemical element may include, relative to the total weight, more than 50 weight %, more than 55 weight %, or more than 60 weight %, or less than 95 weight %, or less than 90 weight %, or less than 88 weight %, or 50 weight % to 90 weight %, or 60 weight % to 90 weight %, or 60 weight % to 85 weight % of the positive electrode active material layer.

[0121] In addition, relative to the total weight of the above-mentioned positive electrode active material layer, the positive electrode active material particles may include 70% by weight or more, or 80% by weight or more, or 99% or less, or 97% or less, 95% or less, 93% or less, or 90% or less, or 70% to 99% by weight, or 80% to 99% by weight.

[0122] In addition, the above-mentioned positive electrode can be a positive electrode active material layer with a thickness of 50 μm or more, or 100 μm or more, or 200 μm or more, or a thickness of 2000 μm or less, or 1,500 μm or less, or 1,000 μm or less, or a thick film positive electrode with a thickness of 150 μm to 2000 μm, or 100 μm to 2000 μm, or 100 μm to 1,000 μm, or 100 μm to 500 μm, or 200 μm to 500 μm.

[0123] Alternatively, the positive electrode may have a positive electrode active material layer formed on one side of the positive electrode current collector with a capacity of 4 mAh / cm. 2 Up to 150mAh / cm 2 , or 4mAh / cm 2 Up to 100mAh / cm 2 、5mAh / ㎝ 2Up to 50mAh / cm 2 Thick film positive electrode.

[0124] In addition, the above-mentioned positive electrode can be a thick film positive electrode in which the positive electrode active material layer mixture density (g / cc) can be greater than 2.0, or greater than 2.5, or greater than 3.0, or greater than 3.0, or can be 2.0 to 5.0, or 3.0 to 5.0, or 3.3 to 3.8.

[0125] In addition, a half cell manufactured using the above-described positive electrode may have a discharge capacity retention rate at 0.3C of 80% or more, 85% or more, or 90% or more, and may be 80% to 99%, or 90% to 98% compared to the discharge capacity at 0.1C. As non-limiting examples, the discharge capacity retention rates at 0.1C and 0.3C may be measured after one charge, five charges, ten charges, or thirty charges, but are not limited thereto.

[0126] In addition, the electrochemical element according to one aspect may have a 0.1C discharge capacity realization ratio compared to the design capacity of 0.8 or more, 0.85 or more, 0.9 or more, or 0.95 or more, and may be between 0.8 and 1.0, between 0.9 and 1.0, or between 0.95 and 1.0. The design capacity refers to a theoretical value calculated from the total weight of the positive electrode active material contained in the battery and the reversible discharge capacity of the positive electrode active material.

[0127] That is, according to one aspect, even if the above-mentioned positive electrode active material layer is high-density / high-loaded, no cracks will be generated, and the positive electrode material can be distributed very evenly in the thickness direction, and can effectively maintain the uniform flow characteristics of lithium ions and the uniform charging and discharging characteristics in the thickness direction.

[0128] In addition, according to one aspect, as the binder forms a porous scaffold structure, the positive electrode active material layer can achieve excellent mechanical properties even with a small amount of binder, thereby further increasing the positive electrode active material content and achieving better energy density.

[0129] As an example, the porous binder scaffold may include 0.01 to 40 parts by weight, or 0.01 to 20 parts by weight, or 0.01 to 10 parts by weight, or 0.01 to 5 parts by weight, or 0.01 to 1 part by weight for every 100 parts by weight of the positive electrode active material particles.

[0130] In addition, the positive electrode active material layer according to one aspect may further include a metal salt, and the metal salt may be contained in or adsorbed on the surface of at least one of the porous binder support and the positive electrode active material particles.

[0131] Relative to 100 parts by weight of the above-mentioned positive electrode active material particles, the metal salt may be included in an amount of 0.01 to 50 parts by weight, or 0.01 to 30 parts by weight, or 0.01 to 10 parts by weight, or 0.01 to 10 parts by weight, or 0.01 to 1 part by weight, and since it is the same as described above, the description of the type of metal salt will be omitted.

[0132] In addition, the ratio of the electrolyte injection amount (g / Ah) compared to the capacity of the electrochemical device according to one aspect may be less than 2.0, less than 1.5, less than 1.2, or less than 1.1. In addition, the liquid electrolyte may be included in an amount of 10 to 30 parts by weight, or 10 to 25 parts by weight, or 15 to 25 parts by weight relative to 100 parts by weight of the positive electrode.

[0133] That is, the positive electrode of the electrochemical device according to one aspect has excellent wettability with respect to the electrolyte, and thus a higher energy density can be achieved while reducing the amount of electrolyte used.

[0134] In one aspect of the present invention, the means for making the above-mentioned binder component microporous to form a porous binder support is not particularly limited, but as an example, a pore former can be used when manufacturing the positive electrode material slurry, and the above-mentioned pore former can be, for example, a mixed solvent of two or more having different solubility parameters, a metal salt, or a combination thereof.

[0135] Since it is the same as described above, the description of the kind of the metal salt will be omitted.

[0136] The mixed solvent may be a mixed solvent of a first solvent and a second solvent having different solubility parameters. Due to the different solubility parameters, the first solvent and the second solvent may have different solubilities for the binder. Due to the different solubilities between the solvents, solidification of the binder may occur when the solvent remains during the drying process of the positive electrode material slurry. During and / or after the curing process of the binder, as the residual solvent evaporates, the binder component may become porous in the positive electrode.

[0137] The difference in solubility parameters between the first solvent and the second solvent can be 0.1 to 20, or 0.1 to 10, or 0.1 to 5, or 1 to 5. Specifically, it can be greater than 0.5, greater than 1, greater than 2, greater than 3, or greater than 4, or less than 15, less than 10, less than 9, less than 8, less than 7, less than 6, or less than 5.

[0138] Here, the solubility parameters (based on 25°C) can be based on the Hansen solubility parameters of each substance type (as an example, Charles Hansen, "Hansen Solubility Parameters: A User's Handbook" CRC Press (2007), "The CRC Handbook and Solubility Parameters and Cohesion Parameters," Allan FM Barton (1999), etc.) or values calculated by commercial software such as Dynacomp Software, and the Hansen solubility parameters of each substance type are values known to or can be easily calculated by those skilled in the art.

[0139] As an example, when a solvent having excellent solubility in the binder is referred to as the first solvent and a solvent having poor solubility in the binder is referred to as the second solvent, the second solvent can function as a pore-forming agent, and the porosity of the binder can be adjusted by adjusting the relative amounts of the first and second solvents. As an example, the weight ratio of the first solvent to the second solvent can be 1:0.1 to 1:10, 1:0.1 to 1:5, 1:0.1 to 1:1, or 1:0.1 to 1:0.5, but is not necessarily limited thereto.

[0140] The method for producing the electrochemical element according to the present invention is not particularly limited as long as a positive electrode, a negative electrode, and an electrolyte are used, and the element can be produced using a known method.

[0141] According to one aspect, the positive electrode manufacturing method includes: applying a positive electrode material slurry containing the positive electrode active material, a conductive material, a binder, and a salt on a current collector; and drying the applied positive electrode material slurry.

[0142] The positive electrode material slurry can be coated by one or more methods selected from spin coating, roll coating, spray coating, dip coating, flow coating, doctor blade, dispensing, inkjet printing, offset printing, template printing, screen printing, pad printing, gravure printing, reverse gravure printing, gravure offset printing, flexography coating, imprinting, xerography, slit extrusion coating, rod coating and roll-to-roll coating, but is not limited thereto.

[0143] After the positive electrode slurry is applied, a step of applying energy to the slurry coating (the applied positive electrode slurry) for drying may also be performed. The energy applied may be heat energy, light energy, or heat and light energy, and the application of heat energy and light energy may include sequential application or simultaneous application. In the case of applying light energy, the light may be near-infrared light, i.e., heat rays.

[0144] The positive electrode material slurry can be manufactured by mixing the above-mentioned positive electrode active material, conductive material, binder and salt into the above-mentioned mixed solvent. When manufacturing the positive electrode material slurry, the order of adding the positive electrode active material, conductive material, binder and salt is not particularly limited. As an example, the positive electrode material slurry can be manufactured by adding the positive electrode active material, conductive material, binder and salt into the solvent at the same time and mixing them. As another example, the positive electrode material slurry can be manufactured by adding the positive electrode active material into a mixture pre-mixed with a conductive material, binder and salt. The positive electrode material slurry manufactured by this method can form a more stable porous binder support structure when it is subsequently dried to form the positive electrode active material layer.

[0145] The above embodiments will be described in more detail below through examples, which are for illustrative purposes only and are not intended to limit the scope of the claims.

[0146] <Manufacturing of lithium metal batteries>

[0147] (Example 1)

[0148] Manufacturing the positive electrode

[0149] 95 parts by weight of lithium-nickel-manganese-cobalt composite oxide (LiNi 0.6 Co 0.2 Mn 0.2 O2) as the positive electrode active material, 2 parts by weight of a conductive agent (Super-P) with an average particle size of 40 nm as a conductive material, 3 parts by weight of polyvinylidene fluoride as a binder, and 1.5 parts by weight of lithium trifluoromethanesulfonate as a salt to manufacture the positive electrode material. A mixed solvent obtained by mixing 37.5 parts by weight of N-methyl-2-pyrrolidone with 7.5 parts by weight of propylene carbonate is used, and the positive electrode material is added to the mixed solvent so that the content of the above-mentioned positive electrode material reaches 55% by weight, thereby manufacturing a positive electrode material slurry. The above-mentioned positive electrode material slurry is coated on an aluminum foil with a thickness of 20 μm using a scraper, and after hot air drying at 100°C, it is vacuum dried at 130°C for 24 hours, and rolled by a roller press to form a positive electrode active material layer with a thickness of 200 μm, thereby manufacturing the positive electrode of Example 1 in which the positive electrode active material particles are uniformly distributed in the porous binder support structure.

[0150] Making lithium metal batteries

[0151] The positive electrode and 50 μm thick lithium metal were rolled onto an 8 μm thick copper foil collector as the negative electrode, and a separator (13 μm thick, SC13-D4-BP, Gellec) was laminated to produce a battery assembly. An aluminum battery tab (0.1T x 7mm) was ultrasonically welded to the uncoated portion of the positive electrode, and a nickel battery tab (0.1T x 7mm) was ultrasonically welded to the uncoated portion of the negative electrode. After that, a battery pouch film (153 μm, DNP) custom-formed for the battery assembly was placed and sealed. Subsequently, a liquid electrolyte containing 1 mole of LiPF6 at 1.04 g / Ah was injected into a 1:1 volume ratio mixture of ethylene carbonate and dimethyl carbonate to produce the lithium metal battery of Example 1.

[0152] (Example 2)

[0153] In the above Example 1, when manufacturing the lithium metal battery, the same method was followed to manufacture the negative electrode-free lithium metal battery of Example 2, except that only a copper foil collector with a thickness of 8 μm was used instead of the negative electrode to manufacture the negative electrode-free lithium metal battery.

[0154] (Example 3)

[0155] In the above-mentioned Example 1, when manufacturing the positive electrode, in addition to using lithium-nickel-manganese-cobalt composite oxide (LiNi 0.9 Co 0.05 Mn 0.05 The lithium metal battery of Example 3 was manufactured in the same manner except that O2) was used as the positive electrode active material.

[0156] (Example 4)

[0157] In Example 3, when manufacturing a lithium metal battery, the same method is followed to manufacture the lithium metal battery of Example 4, except that a 0.7 g / Ah liquid electrolyte containing 1 mol of LiPF6 is injected into a solvent of ethylene carbonate and dimethyl carbonate mixed in a volume ratio of 1:1.

[0158] (Example 5)

[0159] In Example 3, a lithium metal battery of Example 5 was manufactured in the same manner as in Example 3 except that the thickness of the positive electrode active material layer was changed to 300 μm.

[0160] (Example 6)

[0161] In Example 3, when manufacturing the positive electrode material slurry, the same method is followed to manufacture the lithium metal battery of Example 6, except that the conductive material, the binder and the salt are first mixed, and the positive electrode active material is added to the mixture of the conductive material, the binder and the salt and then mixed to manufacture the positive electrode material slurry and the electrode.

[0162] (Example 7)

[0163] In Example 6, the lithium metal battery of Example 7 was manufactured in the same manner except that the content of the salt was mixed to 1.0 part by weight.

[0164] (Example 8)

[0165] In Example 6, the lithium metal battery of Example 8 was manufactured in the same manner except that the content of the salt was mixed to 0.5 parts by weight.

[0166] (Example 9)

[0167] The lithium metal battery of Example 9 was manufactured in the same manner as in Example 3, except that the manufactured electrode was rinsed three times with dimethyl carbonate solvent and then dried before use.

[0168] (Comparative Example 1)

[0169] In the above-mentioned Example 1, when manufacturing the positive electrode, except using 94 parts by weight of lithium-nickel-manganese-cobalt composite oxide as the positive electrode active material, 3 parts by weight of a conductive agent (Super-P) as the conductive material and 3 parts by weight of polyvinylidene fluoride as the binder, and mixing the positive electrode material in a single solvent of N-methyl-2-pyrrolidone to manufacture the positive electrode material slurry, the same steps are implemented to manufacture the lithium metal battery of Comparative Example 1.

[0170] (Comparative Example 2)

[0171] A lithium metal battery of Example 2 was manufactured in the same manner as in Example 1 except that the thickness of the positive electrode active material layer was changed to 70 μm.

[0172] (Comparative Example 3)

[0173] A lithium ion battery of Comparative Example 3 was produced in the same manner as in Comparative Example 2 except that the negative electrode produced by the following method was used.

[0174] Making the negative electrode

[0175] A negative electrode slurry was prepared using 96 parts by weight of natural graphite powder as the negative electrode active material, 1 part by weight of a conductive agent (Super-P) with an average particle size of 40 nm as the conductive material, 1.5% by weight of styrene-butadiene rubber as the binder, 1.5 parts by weight of carboxymethyl cellulose as the electrode material, and 100 parts by weight of distilled water. This slurry was applied to 8 μm-thick copper foil using a doctor blade, dried at 120°C, and rolled using a roller press to produce a negative electrode with an active material layer thickness of 110 μm.

[0176] <Evaluation 1. Lithium Metal Battery Performance Evaluation>

[0177] 1-1. Energy density (Wh / kg)

[0178] The energy density was calculated by dividing the unit cell energy (Wh) of the lithium metal batteries of the examples and comparative examples by the total weight (kg) of the lithium metal batteries. The total weight of the lithium metal battery refers to the weight of the final lithium metal battery product including all bags and auxiliary materials such as tabs, and the 0.05C discharge diagram was integrated to measure the unit cell energy.

[0179] 1-2. Capacity realization rate (%)

[0180] The lithium metal batteries of the embodiments and comparative examples were charged to 4.5V at a charge rate (C-rate) of 0.1 under constant current / constant voltage (CC / CV) conditions at 25°C and then cut-off. Subsequently, they were discharged to 3.0V at a charge rate (C-rate) of 0.1 (CC conditions). The capacity realization rate was evaluated by dividing the above discharge capacity by the percentage of the design capacity. The design capacity refers to a value calculated based on the total weight of the positive active material contained in the battery and the reversible discharge capacity of its positive active material.

[0181] The energy density and capacity realization rate of the lithium metal batteries manufactured in the above-mentioned examples and comparative examples were evaluated and recorded in the following Table 1. In Table 1 below, the weight (kg) of the lithium metal battery used to calculate the energy density refers to the weight of the final lithium metal battery product including auxiliary materials such as bags and tabs.

[0182]

Table 1

[0183]

[0184]

[0185] As shown in Table 1 above, the lithium metal batteries according to Examples 1 to 9 can achieve excellent energy density and capacity retention at the same time. That is, even if the lithium metal battery according to the present invention uses a thickened positive electrode, it can still achieve high energy density while maintaining excellent service life characteristics. On the contrary, according to the positive electrode of Comparative Example 1, as the film is thickened, a large number of cracks are generated in the positive electrode active material layer, which makes it impossible to manufacture a lithium metal battery. Moreover, the lithium metal batteries and lithium ion batteries of Comparative Examples 2 and 3, which can manufacture positive electrode levels, cannot achieve the energy density expected by the present invention.

[0186] <Evaluation 2. Cathode Physical Property Analysis>

[0187] 2-1. Electrode physical property analysis

[0188] The surfaces of the positive electrode active material layers of the positive electrodes manufactured in the examples and comparative examples (5 mm × 5 mm) were observed by scanning electron microscope (SEM) to determine whether cracks were formed on the surfaces of the positive electrode active material layers. The SEM images of the surfaces of the positive electrode active material layers manufactured in the comparative example 1 and the example 1 are shown in FIG. Figure 1 and Figure 2 The results of analysis of whether cracks were formed in each of the Examples and Comparative Examples are shown in Table 2 below. "O" indicates if cracks were formed, and "X" indicates if cracks were not formed.

[0189]

Table 2

[0190]

[0191]

[0192] Figure 1 This is a SEM photograph of the surface of the positive electrode active material layer according to Comparative Example 1. Figure 2 This is a SEM photograph of the surface of the positive electrode active material layer according to Example 1.

[0193] Reference Figures 1 to 2 As shown in Table 1, the positive electrode active material layer of the example has a uniform surface free of cracks (defects). In contrast, the comparative example has a plurality of cracks.

[0194] 2-2. Cross-sectional analysis

[0195] The cross sections of the positive electrodes prepared in Comparative Example 1 and Example 1 were observed by scanning electron microscope (SEM), as shown in FIG. Figure 3 and Figure 4 middle.

[0196] Reference Figure 3 It can be seen that in the case of the positive electrode manufactured in Comparative Example 1, the binder aggregates and has an uneven microstructure and pore distribution.

[0197] On the contrary, refer to Figure 4 In the case of the positive electrode manufactured in Example 1, it was confirmed that the positive electrode active material particles were uniformly distributed throughout, and the binder formed a uniform scaffold structure in the empty pores between the particles. It was also confirmed that the positive electrodes manufactured in Examples 2 to 9 also had a porous scaffold structure similar to that of the positive electrode manufactured in Example 1.

[0198] 2-3. X-ray CT analysis

[0199] The cross sections of the positive electrodes produced in Example 1 and Comparative Example 1 were photographed and analyzed by X-ray CT to analyze the distribution of carbon black as a conductive material. The results are shown in FIG. Figure 5 and Figure 6 middle.

[0200] It can be seen that the positive electrode of Comparative Example 1 ( Figure 5 a) As the positive electrode active material layer becomes thicker, the conductive material moves upwards and exhibits uneven distribution of the conductive material in the thickness direction.

[0201] On the contrary, it can be seen that the positive electrode of Example 1 ( Figure 5 b) The conductive materials in the first active material layer corresponding to the boundary between the positive electrode collector and the positive electrode active material layer to 1 / 3 of the thickness direction of the positive electrode material layer, the second active material layer corresponding to 1 / 3 to 2 / 3 of the thickness direction, and the third active material layer from 2 / 3 of the thickness direction to the surface are all uniformly distributed.

[0202] Figure 6 The distribution of the conductive material content (vol%) in the first active material layer, the second active material layer, and the third active material layer based on the X-ray CT imaging results is shown in a graph. Figure 6 As shown, the deviations in the conductive material concentrations based on the following formula 1 for the positive electrode of Example 1 were all approximately 9% or less. In contrast, the deviations in the conductive material concentrations based on the following formula 1 for the positive electrode of Comparative Example 1 were 45% for the first active material layer and 69% for the third active material layer, demonstrating significant variation. In other words, the conductive material distribution in the positive electrode active material layer of Example 1 was very uniform, while the distribution of the conductive material in the positive electrode active material layer of Comparative Example 1 was very non-uniform.

[0203] [Formula 1]

[0204] (|C0-C n | / C0)×100

[0205] In the above formula 1,

[0206] C0 is the average concentration of conductive material in the positive electrode active material layer (vol%);

[0207] C n is the conductive material concentration (vol %) of the nth active material layer.

[0208] 2-4. Evaluation of ionic conductivity within the electrode

[0209] Two electrodes made from the positive active material composites of the examples and comparative examples were stacked to create a symmetrical cell. Finally, a liquid electrolyte was injected into the cell to fabricate an ionic conductivity measurement cell. The ionic resistance of the cell was measured using impedance analysis to calculate the ionic conductivity within the electrodes.

[0210] 2-5. Electrode Tortuosity Evaluation

[0211] The measured ionic conductivity value in the electrode is used to calculate the tortuosity in the electrode using the MacMullin number (Nm) formula. Nm can be defined as follows.

[0212] Nm=K 电解质 / K 电极 = tortuosity / porosity

[0213] K 电解质 represents the ionic conductivity of the liquid electrolyte, K 电极 This refers to the ionic conductivity of the electrodes according to the Examples and Comparative Examples. The liquid electrolyte was prepared using a 1M LiPF6 solution in a 1:1 volume ratio co-solvent mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). The ionic conductivity of the electrodes was calculated by measuring the ionic conductivity across the thickness of the electrodes after charging them with a 1M LiPF6 solution in EC / DEC.

[0214] Porosity is a measure of pore volume based on the adsorption of nitrogen as measured by changes in nitrogen partial pressure at 77 K. The tortuosity is ultimately calculated from the measured porosity and the McMullin number.

[0215]

Table 3

[0216] distinguish Curvature within the electrode Ionic conductivity (mS / ㎝) Example 1 7.8 0.34 Example 3 7.2 0.37 Example 5 8.1 0.31 Example 6 5.9 0.38 Example 7 5.5 0.39 Example 8 5.6 0.41 Example 9 6.0 0.40 Comparative Example 1 13.2 0.15 Comparative Example 2 10.2 0.25

[0217] As shown in Table 3 above, the electrodes according to Examples 3 to 8 are compared with the electrodes according to the comparative example and it is determined that the curvature and ion conductivity in the electrode are improved. The curvature of the electrode is affected by the pore structure formed in the electrode. When the conductive material and the binder are unevenly distributed, a high curvature value is measured, from which it can be expected that the ion transport path in the electrode becomes longer, resulting in a decrease in battery performance. In the case of Comparative Example 1, due to the high electrode load, the uneven distribution of the conductive material and the binder becomes more serious, so that it can be determined that the curvature of the electrode is greatly increased. On the contrary, the electrodes manufactured according to Examples 1 to 9 form a network by inducing the interaction between the conductive material, the binder and the metal salt, thereby suppressing the uneven movement of the conductive material and the binder that occurs when the electrode is dried, so that the positive active material is evenly distributed in the uniformly formed porous binder support structure, and it can be determined that even under high electrode loads, the curvature in the electrode will not increase significantly. Furthermore, in the case of the electrodes of Examples 6 to 8, by adjusting the timing of metal salt addition during slurry production to more easily induce interaction between the conductive material, binder, and metal salt, it was determined that the structural properties of the porous binder scaffold could be further improved. Furthermore, in the case of Example 9, it was determined that by subjecting the manufactured electrode to solvent treatment to leaching the metal salt, a porous binder scaffold structure with improved ion conductivity could be produced.

[0218] 2-6. Half-cell performance evaluation

[0219] Half cells were prepared using the positive electrodes prepared in Example 3 and Comparative Example 1 to measure the capacities under 0.1C / 0.1C charge / discharge conditions and 0.1C / 0.3C charge / discharge conditions, respectively, and the discharge capacity retention according to the rate (C-rate) was evaluated and reported in Table 2 below.

[0220] Specifically, a half-cell was manufactured in the same manner as in Example 1 except that a lithium metal having a thickness of 200 μm was used as the negative electrode.

[0221] The half-cell was charged to 4.5 V at a charge rate (C-rate) of 0.1 at 25° C. under constant current / constant voltage (CC / CV) conditions and then cut off. Subsequently, it was discharged (CC condition) to 3.0 V at a discharge rate (C-rate) of 0.1 to measure the capacity under 0.1C / 0.1C charge / discharge conditions. The charge / discharge rate (C-rate) was changed to 0.3C to measure the capacity under 0.1C / 0.3C charge / discharge conditions.

[0222] The relative discharge capacity refers to the value obtained by dividing the discharge capacity at 0.3C by the discharge capacity at 0.1C, and the discharge capacity retention rate refers to the value obtained by multiplying the relative discharge capacity at 0.3C by 100.

[0223]

Table 4

[0224]

[0225] As shown in Table 4, the half-cell of the positive electrode according to Example 3 can effectively maintain discharge capacity even at an increased rate. Specifically, the positive electrode according to one aspect has uniform lithium ion flow characteristics and excellent output characteristics even when the thickness is increased.

[0226] In summary, the lithium battery of the present invention can simultaneously meet the requirements of a high energy density of more than 400Wh / kg and excellent service life characteristics and stability through the combination of a thick-film positive electrode in which the positive electrode material is very evenly distributed in the thickness direction and a specific negative electrode.

[0227] As described above, although the present invention has been described through limited embodiments, this is only provided to help a more comprehensive understanding of the present invention. The present invention is not limited to the above embodiments, and ordinary technicians in this field can make various modifications and variations based on this description.

[0228] Therefore, the spirit of the present invention should not be limited to the described embodiments, but include all contents of the following claims and their equivalents or equivalent modifications, which should be considered to belong to the scope of the spirit of the present invention.

Claims

1. An electrochemical element, characterized in that The electrochemical element comprises: positive electrode; a negative electrode comprising a negative electrode current collector, or a negative electrode current collector and lithium metal; and electrolytes, The electrochemical element is an electrochemical element having an energy density of 400Wh / kg or more. The positive electrode comprises: a positive electrode current collector; and The positive electrode active material layer is formed on the positive electrode current collector and includes a porous binder support and positive electrode active material particles.

2. The electrochemical element according to claim 1, wherein The energy density of the electrochemical element is 450Wh / kg to 650Wh / kg. The electrochemical element according to claim 1 , further comprising a separation membrane.

4. The electrochemical element according to claim 3, wherein The positive electrode active material layer comprises 50 wt % or more of the total weight of the electrochemical device.

5. The electrochemical element according to claim 4, wherein The positive electrode active material layer comprises 60 wt % to 85 wt % relative to the total weight of the electrochemical device. The electrochemical element according to claim 1 , wherein: The positive electrode active material particles include 80 wt % to 99 wt % relative to the total weight of the positive electrode active material.

7. The electrochemical element according to claim 1, wherein The positive electrode is a thick-film positive electrode having a positive electrode active material layer with a thickness of 50 μm to 2000 μm.

8. The electrochemical element according to claim 1, wherein The positive electrode is a positive electrode active material layer formed on one side of the positive electrode collector with a capacity of 4 mAh / cm 2 Up to 150mAh / cm 2 Thick film positive electrode.

9. The electrochemical element according to claim 1, wherein The positive electrode is a thick film type positive electrode having a positive electrode active material layer mixture density (g / cc) of 3.3 to 3.

8.

10. The electrochemical element according to claim 1, wherein In the positive electrode active material layer, positive electrode active material particles are uniformly dispersed, and a porous binder scaffold exists in the empty spaces between the particles.

11. The electrochemical element according to claim 10, wherein The porous binder support includes 0.01 parts by weight to 40 parts by weight relative to 100 parts by weight of the positive active material particles.

12. The electrochemical element according to claim 10, wherein The porous adhesive support also includes a conductive material.

13. The electrochemical element according to claim 10, wherein The positive electrode active material layer further includes a metal salt.

14. The electrochemical element according to claim 13, wherein The metal salt is included in an amount of 0.01 to 50 parts by weight relative to 100 parts by weight of the positive electrode active material particles.

15. The electrochemical element according to claim 13, wherein The metal salt is contained in or surface-adsorbed on at least one of the porous binder support and the positive electrode active material particles.

16. The electrochemical element according to claim 13, wherein The metal salt is a sulfonyl group-containing metal salt selected from the following Chemical Formula 1 or Chemical Formula 2: [Chemical Formula 1] [Chemical Formula 2] In the Chemical Formula 1 and the Chemical Formula 2, n is 1 or 2; A is an n-valent cation; And R1 to R3 are each independently a fluoro(C1-C7)alkyl group or a fluoro group.

17. The electrochemical element according to claim 16, wherein A is lithium, sodium, zinc, copper, aluminum, silver, gold, cesium, indium, magnesium or calcium.

18. An electrochemical element, comprising: positive electrode; A negative electrode, comprising a negative electrode current collector, or a negative electrode current collector and lithium metal; as well as electrolytes, The electrochemical element is an electrochemical element having an energy density of 400Wh / kg or more. The positive electrode comprises: a positive electrode current collector; and a positive electrode active material layer formed on the positive electrode current collector and comprising positive electrode active material particles, a binder and a conductive material; When the cross-section of the positive electrode active material layer is analyzed by X-ray CT, relative to the average concentration (C0) of the conductive material of the positive electrode active material layer, the deviation between the conductive material concentration (C1) of the first active material layer corresponding to the boundary surface between the positive electrode collector and the positive electrode active material layer to 1 / 3 in the thickness direction of the positive electrode active material layer, the conductive material concentration (C2) of the second active material layer corresponding to 1 / 3 to 2 / 3 in the thickness direction of the positive electrode active material layer, and the conductive material concentration (C3) of the third active material layer from 2 / 3 in the thickness direction of the positive electrode active material layer to the surface is less than 10%.

19. The electrochemical element according to claim 1 or claim 18, wherein: The half-cell manufactured from the positive electrode has a discharge capacity retention rate of 80% or more at 0.3C compared to the discharge capacity at 0.1C.

20. The electrochemical element according to claim 1 or claim 18, wherein The electrolyte is a liquid electrolyte, a solid electrolyte or a combination thereof.

21. The electrochemical element according to claim 1 or claim 18, wherein: The ratio (g / Ah) of the electrolyte injection amount in the electrolyte to the capacity of the electrochemical device is less than 1.

2.

22. The electrochemical element according to claim 1 or 18, wherein The electrolyte is included in an amount of 15 to 30 parts by weight relative to 100 parts by weight of the positive electrode.

23. The electrochemical element according to claim 21, wherein The electrochemical element has a 0.1C discharge capacity realization ratio of 0.9 or greater compared to the designed capacity.

24. The electrochemical element according to claim 1 or 18, wherein The electrochemical element is a lithium metal battery or a negative electrode-free lithium battery.

25. The electrochemical element according to claim 1 or 18, wherein The inner curvature τ of the positive electrode calculated according to the following relationship is less than 6: [Relational formula] τ(bending)=(K 电解质 / K 电极 )×(porosity) (In the above formula, K 电解质 represents the ionic conductivity of the electrolyte, K 电极 represents the ionic conductivity of the positive electrode, and porosity represents the porosity of the positive electrode).

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