Pouch-type rechargeable lithium battery

Abstract

Disclosed is a pouch-type rechargeable lithium battery. The pouch-type rechargeable lithium battery includes: an electrode assembly including a first electrode plate, a second electrode plate, and a separator interposed between the first electrode plate and the second electrode plate; and an electrolyte into which the electrode assembly is impregnated, in which the separator includes a porous substrate and a coating layer disposed on at least one surface of the porous substrate. The coating comprises a binder and a filler. The binder includes a (meth) acrylic binder including a first structural unit derived from (meth) acrylic acid, a (meth) acrylate, or a salt thereof, a second structural unit derived from a hydroxyalkyl (meth) acrylate, and a third structural unit derived from a (meth) acrylamide sulfonic acid or a salt thereof. The electrolyte has an ethyl propionate content in the non-aqueous organic solvent ranging from about 10% by volume to about 40% by volume.

Description

[0001] This application claims priority to Korean Patent Application No. 10-2024-0163686, filed on November 16, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates to a pouch-type rechargeable lithium battery. Background Technology

[0003] With the increasing prevalence of battery-powered electronic devices (such as mobile phones, laptops, and electric vehicles), the demand for rechargeable lithium-ion batteries with high energy density and high capacity is growing. Therefore, improving the performance of rechargeable lithium-ion batteries can be advantageous.

[0004] A rechargeable lithium battery includes a positive electrode and a negative electrode containing active materials capable of inserting and deintercalating lithium ions, as well as an electrolyte, and generates electrical energy through oxidation and reduction reactions when lithium ions are deintercalated from the positive electrode and inserted into the negative electrode / deintercalated from the negative electrode and inserted into the positive electrode.

[0005] Rechargeable lithium batteries may include a separator positioned between a positive electrode and a negative electrode. The separator is immersed in an electrolyte and bonded to either the positive or negative electrode. Therefore, it may be desirable for the separator to have a low thermal shrinkage rate and low membrane resistance in the electrolyte.

[0006] Pouch-type rechargeable lithium batteries are small, stacked / wound types. Therefore, the separators used in pouch-type rechargeable lithium batteries can have higher adhesion strength to either the positive or negative electrode compared to the separators used in cylindrical, prismatic, or coin-shaped rechargeable lithium batteries. Summary of the Invention

[0007] One example embodiment includes a pouch-type rechargeable lithium battery, the pouch-type rechargeable lithium battery including a separator for the rechargeable lithium battery, the separator for the rechargeable lithium battery having a low thermal shrinkage rate and low membrane resistance in the electrolyte, and high wet adhesion strength to the positive or negative electrode.

[0008] According to aspects of this disclosure, a pouch-type rechargeable lithium battery is provided.

[0009] The pouch-type rechargeable lithium battery includes: an electrode assembly including a first electrode plate, a second electrode plate, and a separator disposed between the first electrode plate and the second electrode plate; and an electrolyte, wherein the electrode assembly is immersed in the electrolyte, the separator includes a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating including an adhesive and a filler, the adhesive including a (meth)acrylic acid adhesive, the (meth)acrylic acid adhesive including a first structural unit derived from (meth)acrylic acid, (meth)acrylate or a salt thereof, a second structural unit derived from (meth)acrylic acid hydroxyalkyl ester or a third structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof, and the electrolyte including ethyl propionate in a non-aqueous organic solvent at about 10% by volume to about 40% by volume. Attached Figure Description

[0010] The following accompanying drawings illustrate exemplary embodiments of the present disclosure and, together with the detailed description thereof, further describe aspects and features of the disclosure. Therefore, the disclosure should not be construed as limited to the drawings, in which: Figure 1 This is a schematic diagram illustrating a pouch-type rechargeable lithium battery according to an example embodiment; and Figure 2 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment. Detailed Implementation

[0011] Hereinafter, exemplary embodiments of the present disclosure are described in detail. However, it should be understood that these embodiments are presented by way of example and are not intended to limit the present disclosure, which is defined only by the scope of the appended claims.

[0012] Unless otherwise specifically stated in this specification, the term "on" another component, such as a layer, film, region, plate, etc., includes not only the case where the component is "directly on" the other component, but also the case where the other component is placed therein.

[0013] Unless otherwise specified in this specification, the singular form may also include the plural form. Furthermore, unless otherwise specified herein, the term "A or B" may mean "including A, including B, or including both A and B".

[0014] In this specification, the term "combination thereof" may refer to mixtures, laminates, complexes, copolymers, alloys, blends, and reaction products of the composition.

[0015] In this specification, the term "particle size (D50)" refers to the average particle size, which represents the size of particles that have a cumulative volume of 50% in the particle size distribution. The particle size distribution can be measured using methods known to those skilled in the art. For example, it can be measured using a particle size analyzer or using transmission electron microscopy or scanning electron microscopy. Alternatively, the particle size can be measured using a dynamic light scattering measuring device, data analysis can be performed to count the number of particles in each particle size range, and the particle size (D50) can be calculated from this. Optionally, the D50 value can be measured using laser diffraction. For example, in the case of measurement by laser diffraction, the particles to be measured are dispersed in a dispersion medium, introduced into a commercially available laser diffraction particle size measuring device (e.g., Microtrac MT 3000), and irradiated with ultrasound at an output of 60W at approximately 28 kHz. The D50 value can then be calculated based on the 50% particle size distribution in the measuring device.

[0016] When the particles are spherical, the size can refer to the diameter.

[0017] In this specification, the term "(meth)acryloyl" refers to acrylamide and / or methacryloyl.

[0018] Unless otherwise defined below, the term "substitution" means that hydrogen in a compound is replaced by a substituent, such as or including C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C6 to C30 aryl, C7 to C30 alkylaryl, C1 to C30 alkoxy, C1 to C30 heteroalkyl, C3 to C30 heteroalkylaryl, C3 to C30 cycloalkyl, C3 to C15 cycloalkenyl, C6 to C30 cycloalkynyl, C2 to C30 heterocycloalkyl, halogen (F, Cl, Br or I), hydroxyl (-OH), nitro (-NO2), cyano (-CN), amino (-NRR') (wherein R and R' are both independently hydrogen or C1 to C6 alkyl), sulfobetaine (-RR'N) + (CH2) n SO3 - Where n is a natural number from 1 to 10), carboxybenzene base (-RR'N) + (CH2) n COO -The following groups are used: (where n is a natural number from 1 to 10) (where R and R' are both independently C1 to C20 alkyl groups), azide (-N3), amidine (-C(=NH)NH2), hydrazine (-NHNH2), hydrazone (=N(NH2)), carbamoyl (-C(=O)NH2), thiol (-SH), acyl (-C(=O)R, where R is hydrogen, C1 to C6 alkyl, C1 to C6 alkoxy or C6 to C12 aryl), carboxyl (-COOH) or a salt thereof (-C(=O)OM, where M is an organic or inorganic cation), sulfonic acid (-SO3H) or a salt thereof (-SO3M, where M is an organic or inorganic cation), phosphate (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, where M is an organic or inorganic cation), and combinations thereof.

[0019] In the following text, C1 to C3 alkyl groups are methyl, ethyl, or propyl. C1 to C10 alkylene groups can be, for example, C1 to C6 alkylene groups, C1 to C5 alkylene groups, or C1 to C3 alkylene groups, and can be, for example, methylene, ethylene, or propylene. C3 to C20 cycloalkylene groups can be, for example, C3 to C10 cycloalkylene groups or C5 to C10 cycloalkylene groups, and can be, for example, cyclohexylene. C6 to C20 arylene groups can be, for example, C6 to C10 arylene groups, and can be, for example, phenylene. C3 to C20 heterocyclic groups can be, for example, C3 to C10 heterocyclic groups, and can be, for example, pyridyl.

[0020] In the following text, the term "heterogeneous" means that a compound includes one or more heteroatoms such as or containing at least one of N, O, S, Si and P.

[0021] In chemical formulas, the symbol "*" indicates a portion attached to the same or different atoms, groups, or structural units. Unless otherwise specified in the chemical formulas described herein, it can be assumed that hydrogen is bonded to the structure of the chemical formula.

[0022] In the following text, the term "alkali metal" refers to elements belonging to Group 1 of the periodic table that can exist in either a cation or a neutral state (such as lithium, sodium, potassium, rubidium, cesium, or francium).

[0023] When describing numerical ranges in this specification, the term "X to Y" means X or greater and Y or less (≥X and ≤Y).

[0024] When the terms “about” or “substantially” are used in conjunction with numerical values ​​in this specification, it is intended that the relevant numerical value includes a tolerance of ±10% around the stated value. When a range is specified, the range includes all values ​​within that range, such as increments of 0.1%.

[0025] A pouch-type rechargeable lithium battery according to an example embodiment includes: an electrode assembly including a negative electrode plate, a positive electrode plate, and a separator disposed between the negative electrode plate and the positive electrode plate; and an electrolyte in which the electrode assembly is immersed, wherein the separator includes a porous substrate and a coating disposed on at least one surface of the porous substrate, the coating including an adhesive and a filler. The adhesive includes a (meth)acrylic acid adhesive, said (meth)acrylic acid adhesive comprising a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from (meth)acrylate hydroxyalkyl ester, and a third structural unit derived from (meth)acrylamide sulfonic acid, or a salt thereof. The volume range of ethyl propionate (EP) is based on 100% of the volume of the non-aqueous organic solvent of the electrolyte. When EP is present in the non-aqueous organic solvent of the electrolyte in an amount ranging from about 10% by volume to about 40% by volume, the adhesive strength of the separator / electrode plate can be improved. Furthermore, an amount of EP in the non-aqueous organic solvent of the electrolyte ranging from about 10% by volume to about 30% by volume is considered an improved or optimal condition.

[0026] According to one example embodiment, the component of the non-aqueous organic solvent in the electrolyte consists of or includes at least one of ethylene carbonate (EC), propylene carbonate (PC), ethyl propionate (EP), and propyl propionate (PP).

[0027] According to one example embodiment, the electrolyte composition may consist of or include lithium salt (1.3M LiPF6), non-aqueous organic solvent EC / PC / EP / PP (10% / 15% / 30% / 45% volume), and additives (e.g., 7% volume of fluoroethylene carbonate (FEC), 1% volume of vinyl ethylene carbonate (VEC), and 3% volume of propylene sulfone (PS)). The amount of additives may be based on 100% volume of the non-aqueous organic solvent.

[0028] The separator can have low membrane resistance, thereby improving the capacity of rechargeable lithium batteries.

[0029] According to one example embodiment, the diaphragm may have a membrane resistance of about 1.2 Ω or less.

[0030] The separator exhibits significantly high wet adhesion strength to the positive or negative electrode in the electrolyte and significantly low thermal shrinkage rate in the electrolyte, thereby enhancing the reliability of rechargeable lithium batteries.

[0031] Pouch cells that include a separator but have an electrolyte other than those described above may face challenges due to the separator not exhibiting sufficient wet bond strength. Pouch cells that include an electrolyte but have a separator that does not meet the same requirements as the separators described above may face challenges to separator life and safety due to high membrane resistance or high thermal shrinkage in the electrolyte.

[0032] According to one example embodiment, the separator in the electrolyte may have a thermal shrinkage rate of about 25% or less in the longitudinal direction (MD) and about 25% or less in the transverse direction (TD). The aforementioned "MD" and "TD" refer to the same directions as the MD and TD of the porous substrate, respectively.

[0033] The diaphragm can have a wet bond strength of about 0.5 gf / mm or greater.

[0034] Membranes having coatings formed from compositions for coating that do not contain (meth)acrylic binders or contain binders other than (meth)acrylic binders, or including compositions for coating that do not contain (meth)acrylic binders or contain binders other than (meth)acrylic binders, may present challenges in having electrolyte shrinkage rates or membrane resistance characteristics suitable for battery manufacturing.

[0035] According to one example embodiment, the (meth)acrylic adhesive may be included in an amount of about 95% by weight or more (e.g., in the range of about 98% by weight to about 100% by weight, or 100% by weight) of the total adhesive (e.g., non-adhesive adhesive) in the composition.

[0036] Figure 1 This is a schematic diagram illustrating a pouch-type rechargeable lithium battery according to an example embodiment.

[0037] Reference Figure 1 The pouch-type rechargeable lithium battery 100 may include an electrode assembly 110 and a pouch 130 configured to house the electrode assembly 110.

[0038] The electrode assembly 110 can be formed by a stack of a first electrode plate 112, a diaphragm 116, and a second electrode plate 114, which are formed into a sheet or film shape by winding or stacking.

[0039] When the electrode assembly 110 is a wound laminate, the winding axis can be parallel to the longitudinal direction of the sealing portion 132. Furthermore, the electrode assembly can be stacked rather than wound, and the shape of the electrode assembly is not limited in this disclosure.

[0040] In addition, the electrode assembly 110 may be a Z-stacked electrode assembly, wherein the positive electrode plate and the negative electrode plate are inserted on both sides of a diaphragm that is Z-stacked and folded.

[0041] Additionally, electrode assembly 110 can be accommodated in sealing portion 132 by stacking one or more electrode assemblies such that their long sides are adjacent to each other, and the number of electrode assemblies is not limited in this disclosure.

[0042] The electrode assembly 110 is immersed in the electrolyte 120 contained in the bag 130.

[0043] Because pouch-type rechargeable lithium batteries have low membrane resistance provided by the separator and electrolyte, low thermal shrinkage in the electrolyte, and high wet bond strength, the separator and electrolyte are described in detail first.

[0044] Diaphragm: The diaphragm includes the coating described above.

[0045] The adhesive includes a (meth)acrylic adhesive, which comprises a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from a hydroxyalkyl methacrylate, and a third structural unit derived from (meth)acrylamide sulfonic acid, or a salt thereof.

[0046] According to one example embodiment, the (meth)acrylic adhesive can be a non-adhesive adhesive.

[0047] (Meth)acrylic binders can fix fillers onto porous substrates and enable coatings to adhere to both the porous substrate and electrode plates, thus improving the heat resistance, permeability, and oxidation resistance of the separator. Furthermore, (meth)acrylic binders can promote lithium-ion movement to reduce membrane resistance and improve ionic conductivity, increase the adhesion strength of the coating to the porous substrate and electrode plates, and enhance the dispersion of fillers within the coating. Additionally, (meth)acrylic binders can provide separators with low membrane resistance in coatings including fillers described below.

[0048] The first, second, and third structural units can be included in a total of about 95 mol% or more (e.g., from about 95 mol% to about 100 mol%, for example, 100 mol%) relative to 100 mol% of the (meth)acrylic binder. Within the above range, the aforementioned effects of the diaphragm can be readily achieved.

[0049] The first structural unit is derived from (meth)acrylic acid, (meth)acrylate, or their salts, thus enabling the filler to be fixed onto the porous substrate while providing adhesive strength, allowing the coating to adhere to both the porous substrate and the electrode plate, and contributing to improved heat resistance and permeability of the diaphragm. Furthermore, the first structural unit can improve the dispersibility of the coating slurry by having a carboxyl functional group (-C(=O)O-) within the structural unit.

[0050] The first structural unit can be represented by any one of the following chemical formulas 1 to 3: Chemical Formula 1: .

[0051] Chemical formula 2: .

[0052] Chemical formula 3: .

[0053] Based on a 100 mol% binder for rechargeable lithium batteries, the first structural unit can be in the form of about 20 mol% to about 75 mol% (e.g., 20 mol%, 21 mol%, 22 mol%, 23 mol%, 24 mol%, 25 mol%, 26 mol%, 27 mol%, 28 mol%, 29 mol%, 30 mol%, 31 mol%, 32 mol%, 33 mol%, 34 mol%, 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%). The amounts included are within the range of 49 mol%, 50 mol%, 51 mol%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, from 25 mol% to 70 mol%, from 30 mol% to 65 mol%, from 30 mol% to 60 mol%, or from 40 mol% to 65 mol%. When the first structural unit is included within the above range, the diaphragm can exhibit low membrane resistance, desired or improved adhesion strength to the porous substrate and electrode plates, heat resistance, air permeability, and oxidation resistance.

[0054] According to one example embodiment, the first structural unit may include structural units represented by chemical formula 2 and structural units represented by chemical formula 3. In this case, the structural units represented by chemical formula 2 and structural units represented by chemical formula 3 may be included in a molar ratio ranging from about 10:1 to about 1:2, or from about 10:1 to about 1:1, or from about 5:1 to about 1:1.

[0055] According to another example embodiment, the first structural unit may consist only of structural units represented by chemical formula 2.

[0056] The second structural unit is derived from (meth)acrylate hydroxyalkyl ester, thus enabling the filler to be fixed onto the porous substrate while providing adhesive strength, allowing the coating to adhere to both the porous substrate and the electrode plate. Furthermore, the second structural unit can improve the dispersibility of the coating slurry by having carboxyl functional groups (-C(=O)O-) within the structural unit.

[0057] The second structural unit can be represented by the following chemical formula 4: Chemical formula 4: .

[0058] Based on 100 mol% of the binder for rechargeable lithium batteries, the second structural unit can be included in an amount ranging from about 1 mol% to about 20 mol% (e.g., 1 mol%, 2 mol%, 3 mol%, 4 mol%, 5 mol%, 6 mol%, 7 mol%, 8 mol%, 9 mol%, 10 mol%, 11 mol%, 12 mol%, 13 mol%, 14 mol%, 15 mol%, 16 mol%, 17 mol%, 18 mol%, 19 mol%, 20 mol%, 2 mol% to 15 mol%, or 5 mol% to 15 mol%). Within the above range, the second structural unit can readily increase the adhesion strength of the coating to the porous substrate and the electrode plate.

[0059] The second structural unit can be, for example, a structural unit derived from (meth)acrylate hydroxyalkyl esters. Here, alkyl can be or include C1 to C20 alkyl, C1 to C10 alkyl, or C1 to C6 alkyl.

[0060] Hydroxyalkyl methacrylates may include at least one of, for example, methyl methacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, and 6-hydroxyhexyl methacrylate.

[0061] The third structural unit derived from (meth)acrylamide sulfonic acid or its salt can reduce the membrane resistance of the separator by increasing the lithium ion mobility in the presence of the first and second structural units.

[0062] The third structural unit enhances the membrane's heat resistance by increasing the glass transition temperature through the inclusion of bulk functional groups derived from (meth)acrylamide sulfonic acid or its salts. Furthermore, when the third structural unit includes functional groups derived from salts of (meth)acrylamide sulfonic acid, the metal (M) can move through the third structural unit via the metal (M)-substituted sulfonic acid functional groups, thereby exhibiting a reduction in membrane resistance.

[0063] The third structural unit can be represented by at least one of the following chemical formulas 5, 6, and 7, and combinations thereof: Chemical formula 5: .

[0064] Chemical formula 6: .

[0065] Chemical Formula 7: .

[0066] The third structural unit may include only one or more of the structural units represented by chemical formula 5, chemical formula 6, and chemical formula 7. As an example, the third structural unit may include a structural unit represented by chemical formula 6. As another example, the third structural unit may include structural units represented by chemical formula 6 and structural units represented by chemical formula 7.

[0067] The third structural unit may be or includes, for example, a structural unit derived from (meth)acrylamide alkyl sulfonic acid or a salt thereof. Here, the alkane may be or includes C1 to C20 alkanes, C1 to C10 alkanes, or C1 to C6 alkanes, and the alkyl group may be or includes C1 to C20 alkyl groups, C1 to C10 alkyl groups, or C1 to C6 alkyl groups. The salt consists of or includes the aforementioned sulfonic acid and suitable ions. The ions may be or include, for example, alkali metal ions. In this case, the salt may be or includes an alkali metal sulfonic acid salt.

[0068] For example, (meth)acrylamidine sulfonic acid can be 2-(meth)acrylamido-2-methylpropane sulfonic acid.

[0069] The third structural unit can be in the range of about 20 mol% to about 75 mol% (e.g., 20 mol%, 21 mol%, 22 mol%, 23 mol%, 24 mol%, 25 mol%, 26 mol%, 27 mol%, 28 mol%, 29 mol%, 30 mol%, 31 mol%, 32 mol%, 33 mol%, 34 mol%, 35 mol%, 36 mol%, 37 mol%, 38 mol%, 39 mol%, 40 mol%, 41 mol%, 42 mol%, 43 mol%, 44 mol%, 45 mol%, 46 mol%, 47 mol%, 48 mol%, 49 mol%, 50 mol%, 51 mol%). The amounts of (meth)acrylic acid binders within the range of 1%, 52 mol%, 53 mol%, 54 mol%, 55 mol%, 56 mol%, 57 mol%, 58 mol%, 59 mol%, 60 mol%, 61 mol%, 62 mol%, 63 mol%, 64 mol%, 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, 73 mol%, 74 mol%, 75 mol%, 25 mol% to 70 mol%, 20 mol% to 65 mol%, 30 mol% to 65 mol%, or 30 mol% to 60 mol% are included in the (meth)acrylic acid binder. When the third structural unit is included within the above range, the (meth)acrylic acid binder and the diaphragm including it can exhibit significantly low membrane resistance.

[0070] Now, let's describe chemical formulas 1 through 7.

[0071] R 1 To R 14 They can all be or include hydrogen or C1 to C10 alkyl groups independently. For example, R 1 To R 7 and R 9 To R 14 It may consist entirely of or include hydrogen or methyl; R 8 It can be or include methyl.

[0072] L 1 To L 4 Each of these groups may independently be or include substituted or unsubstituted C1 to C10 alkylene groups, substituted or unsubstituted C3 to C20 cycloalkylene groups, substituted or unsubstituted C6 to C20 arylene groups, or substituted or unsubstituted C3 to C20 heterocyclic groups. For example, L 1 It may include or contain methylene or ethylene; L 2 To L 4 They can all be or include *-C(CH3)2-CH2-* independently.

[0073] a, b, c, and d can each be an integer in the range of 0 to 2. For example, a, b, c, and d can all be equal to 1.

[0074] M may be or include an alkali metal, and the alkali metal may be or include at least one of lithium, sodium, potassium, rubidium, and cesium. For example, M may be lithium or sodium.

[0075] A representative example of a binder for a rechargeable lithium battery according to an example embodiment is represented by the following chemical formula 8: Chemical formula 8: .

[0076] Now, let's describe chemical formula 8.

[0077] R 15 To R 20 They can all be or include hydrogen or C1 to C10 alkyl groups independently. For example, R 15 To R 17 R 19 and R 20 It can be all or include hydrogen or methyl, and R 18 It can be or include methyl.

[0078] L 5 and L 6 Each of these groups may independently be or include substituted or unsubstituted C1 to C10 alkylene groups, substituted or unsubstituted C3 to C20 cycloalkylene groups, substituted or unsubstituted C6 to C20 arylene groups, or substituted or unsubstituted C3 to C20 heterocyclic groups. For example, L 5 It may include or contain methylene or ethylene; and L 6 It can be or include *-C(CH3)2-CH2-*.

[0079] M may be or include an alkali metal, and the alkali metal may be or include at least one of lithium, sodium, potassium, rubidium, and cesium. For example, M may be lithium or sodium.

[0080] l, m, and n are the molar ratios of corresponding units, satisfying that the sum of l, m, and n is 1. For example, it can satisfy 0.20≤l≤0.75, 0.01≤m≤0.2, and 0.2≤n≤0.75 (e.g., 0.25≤l≤0.70, 0.01≤m≤0.15, and 0.25≤n≤0.75 or 0.3≤l≤0.65, 0.05≤m≤0.15, and 0.3≤n≤0.65).

[0081] Both e and f can be independent integers in the range of 0 to 2. For example, both e and f can be equal to 1.

[0082] (Meth)acrylic binders may include alkali metals. Alkali metals may exist in cationic form and may be, for example, lithium, sodium, potassium, rubidium, or cesium. For example, alkali metals may exist as salts bound to the (meth)acrylic binder. Alkali metals can facilitate the synthesis of (meth)acrylic binders in aqueous solvents, enhance the adhesive strength of coatings, and improve the heat resistance, permeability, and oxidation resistance of the membrane.

[0083] Alkali metals may be included in an amount ranging from about 1% by weight to about 40% by weight (e.g., 1% by weight to 30% by weight, 1% by weight to 20% by weight, or 10% by weight to 20% by weight) of the alkali metal and the (meth)acrylic binder. For example, the (meth)acrylic binder and the alkali metal may be included in a weight ratio ranging from about 99:1 to about 60:40 or a weight ratio ranging from about 99:1 to about 70:30 (e.g., a weight ratio ranging from about 99:1 to about 80:20, or, for example, a weight ratio ranging from about 90:10 to about 80:20).

[0084] Based on the total content of alkali metal and (meth)acrylic binder, the alkali metal content can be included in an amount ranging from about 0.1 mol% to about 1.0 mol%. When the alkali metal is included in the above range, the coating can have desired or improved adhesive strength, and the diaphragm including the coating can exhibit desired or improved heat resistance, air permeability, and oxidation resistance.

[0085] (Meth)acrylic adhesives can take various forms, such as alternating polymers in which structural units are distributed alternately, random polymers in which structural units are distributed randomly, and grafted polymers in which some of the structural units are grafted.

[0086] (Meth)acrylic acid adhesives can have a weight-average molecular weight in the range of about 100,000 g / mol to about 1,000,000 g / mol, 100,000 g / mol to 500,000 g / mol, 100,000 g / mol to 150,000 g / mol, 130,000 g / mol to 200,000 g / mol, or 300,000 g / mol to 900,000 g / mol. When the weight-average molecular weight of the (meth)acrylic acid adhesive meets the above ranges, it can exhibit desired or improved adhesive strength and low electrical resistance. The weight-average molecular weight can be the converted average molecular weight of polystyrene measured using gel permeation chromatography.

[0087] (Meth)acrylic acid adhesives can be manufactured by solution polymerization.

[0088] According to one example embodiment, the (meth)acrylic adhesive may be included in the coating of the diaphragm in the form of a film.

[0089] The filler can have a particle size (D50) in the range of about 0.4 μm or smaller. Within this range, when the filler is combined with a (meth)acrylic binder and a crosslinking agent, a low thermal shrinkage rate in the electrolyte can be achieved. For example, the filler can have a particle size (D50) in the range of about 0.35 μm or smaller, about 0.3 μm or smaller, or about 0.1 μm to 0.3 μm. Within this range, improved heat resistance properties can be achieved.

[0090] According to one example embodiment, based on the total amount of filler in the coating, filler having a particle size of about 0.4 μm or smaller (D50) can be included in an amount of about 95% by weight or greater (e.g., in the range of about 95% by weight to about 100% by weight, 98% by weight to 100% by weight, or 100% by weight). Within the above range, the diaphragm effect of this disclosure can be readily achieved.

[0091] According to one example embodiment, the filler may or may not be surface modified.

[0092] The filler may be or includes, for example, inorganic fillers, organic fillers, organic-inorganic composite fillers, or combinations thereof. Inorganic fillers may be or include ceramic materials capable of improving heat resistance. Inorganic fillers may include, for example, at least one of metal oxides, quasi-metal oxides, metal fluorides, metal hydroxides, and combinations thereof. Inorganic fillers may include, for example, at least one of Al₂O₃, SiO₂, TiO₂, SnO₂, CeO₂, MgO, NiO, CaO, GaO, ZnO, ZrO₂, Y₂O₃, SrTiO₃, BaTiO₃, Mg(OH)₂, boehmite, and combinations thereof, but this disclosure is not limited thereto. Organic fillers may include at least one of acrylic compounds, imide compounds, amide compounds, and combinations thereof, but this disclosure is not limited thereto. Organic fillers may have a core-shell structure, but this disclosure is not limited thereto. For example, the filler may be boehmite.

[0093] The filler can be spherical, plate-shaped, cubic, or without a fixed shape. Preferably, the filler can be cubic in shape, and the cubic shape can significantly reduce the shrinkage rate as described above.

[0094] The filler should be included in a desired amount relative to the binder (e.g., (meth)acrylic binder). According to an example embodiment, the (meth)acrylic binder and filler may be included in a mass ratio ranging from about 1:10 to about 1:50 (e.g., 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, 1:50, about 1:10 to about 1:40, or about 1:20 to about 1:30). Within these ranges, improved heat resistance properties in the electrolyte can be achieved.

[0095] Based on the total amount of the coating, the filler can be included in an amount ranging from about 50% by weight to about 99% by weight (e.g., 70% by weight to 99% by weight, 75% by weight to 99% by weight, 80% by weight to 99% by weight, 85% by weight to 99% by weight, 90% by weight to 99% by weight, 95% by weight to 99% by weight). When the filler is included in the above range, desired or improved heat resistance, durability, oxidation resistance, and stability can be exhibited.

[0096] Each of the coatings may have a thickness ranging from about 0.01 μm to about 20 μm. Within the above range, the coating may have a thickness of 0.01 μm to 7 μm, 0.1 μm to 5 μm, or 1 μm to 3 μm.

[0097] The ratio of the overall coating thickness to the thickness of the porous substrate can be in the range of about 0.01 to about 0.7 (e.g., in the range of 0.01 to 0.5, 0.01 to 0.4, or 0.01 to 0.3). Within the above range, the diaphragm can exhibit desired or improved permeability, heat resistance, adhesive strength, etc.

[0098] Porous substrate: Porous substrates can be or include substrates with multiple pores commonly used in electrochemical devices. Non-limiting examples of porous substrates can be or include polymer films formed from or comprising any polymer or copolymers or mixtures of two or more of the above polymers, said polymers being such as or including at least one of polyolefins (such as polyethylene, polypropylene, etc.), polyesters (such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, etc.), polyacetal, polyamide, polyimide, polycarbonate, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, glass fiber, and polytetrafluoroethylene (e.g., Teflon).

[0099] The porous substrate can be or includes, for example, a polyolefin substrate comprising polyolefins, and the polyolefin substrate can have desired or improved closed-cell functionality, thus contributing to improved battery safety. The polyolefin substrate can be or includes at least one of, for example, polyethylene monolayer films, polypropylene monolayer films, polyethylene / polypropylene bilayer films, polypropylene / polyethylene / polypropylene trilayer films, and polyethylene / polypropylene / polyethylene trilayer films. Furthermore, in addition to olefin resins, polyolefin resins can also include non-olefin resins, or can include copolymers of olefin and non-olefin monomers.

[0100] The porous substrate can have a thickness in the range of about 1 μm to about 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm or 5 μm to 15 μm.

[0101] A separator for a rechargeable lithium battery according to an example embodiment can be manufactured by applying a composition for forming a coating onto one or both sides of a porous substrate and then drying the composition. Drying can be performed using conventional methods known to those skilled in the art.

[0102] Figure 2 This is a cross-sectional view showing a separator for a rechargeable lithium battery according to an example embodiment.

[0103] Reference Figure 2 The separator for a rechargeable lithium battery includes a porous substrate 1 and a coating 2 disposed on both sides of the porous substrate 1. The coating 2 may include a filler 3 and a (meth)acrylic binder 4.

[0104] electrolytes According to one example embodiment, the electrolyte composition may consist of or include lithium salt (1.3M LiPF6), non-aqueous organic solvent EC / PC / EP / PP (10% / 15% / 30% / 45% volume), and additives (e.g., about 7% volume of fluoroethylene carbonate (FEC), about 1% volume of vinyl ethylene carbonate (VEC), and about 3% volume of propylene sulfone (PS)).

[0105] Electrolytes include lithium salts and non-aqueous organic solvents.

[0106] Electrolytes may also include additives.

[0107] The ethyl propionate (EP) content in the non-aqueous organic solvent ranges from about 10% to about 40% by volume. When the EP content is less than about 10% by volume, the wet bond strength to the positive or negative electrode may be poor, the thermal shrinkage rate may be high, and the film resistance may be high. When the EP content is greater than about 40% by volume, the wet bond strength to the positive or negative electrode may be poor, and the thermal shrinkage rate may be high. For example, the EP content in the non-aqueous organic solvent can range from about 10% by volume to about 30% by volume, for example, about 30% by volume.

[0108] In addition to EP, non-aqueous organic solvents may also include at least one of ethylene carbonate (EC), propylene carbonate (PC), and propyl propionate (PP). EC, PC, and PP can also enhance the performance of the separator in pouch cells.

[0109] According to one example embodiment, the non-aqueous organic solvent may be an EC:PC:EP:PP ratio in the range of approximately 5% to 30% volume: 5% to 30% volume: 10% to 30% volume: 45% to 65% volume. According to one example embodiment, the volume ratio may be based on 100% of the total volume.

[0110] According to one example embodiment, the non-aqueous organic solvent can be EC:PC:EP:PP in a ratio ranging from about 10% volume:15% volume:10% volume to 30% volume:45% volume to 65% volume (e.g., 10% volume:15% volume:30% volume:45% volume). According to one example embodiment, the volume ratio can be based on 100% of the total volume.

[0111] According to one example embodiment, the total content of EP, EC, PC and PP in the non-aqueous organic solvent can be about 60% by volume or more (e.g., in the range of about 60% by volume to about 90% by volume, 70% by volume to 90% by volume, 70% by volume, 95% by volume or more (e.g., 95% by volume to 100% by volume or 100% by volume)).

[0112] Lithium salts dissolve in organic solvents and constitute the lithium-ion source within the battery, enabling the basic operation of rechargeable lithium batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide (LiFSI)), LiC4F9SO3, and LiN(C x F 2x+1 SO2)(C yF 2y+1 One or more of the following: (SO2) (where x and y are integers in the range of 1 to 20), lithium trifluoromethane sulfonate, lithium tetrafluoroethane sulfonate, lithium difluoro(oxalate)borate (LiDFOB), lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0113] Lithium salts may be included in the electrolyte in amounts ranging from about 0.1 M to about 2.0 M (e.g., 0.5 M to 1.5 M, e.g., 1.0 M to 1.7 M).

[0114] The additive may include at least one of fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), and propylene sulfone (PS).

[0115] In one example embodiment, based on 100% by volume of non-aqueous organic solvent, FEC may be included in an amount ranging from about 5% by volume to about 10% by volume (e.g., 7% by volume), VEC may be included in an amount ranging from about 0.1% by volume to about 5% by volume (e.g., 1% by volume), and PS may be included in an amount ranging from about 1% by volume to about 5% by volume (e.g., 3% by volume).

[0116] Refer again Figure 1 The first electrode plate 112 may include a first electrode active material portion to which a first electrode active material is applied and a first electrode tab 112a electrically connected to a first uncoated portion, the first uncoated portion being the area in which no first electrode active material is applied. The first electrode tab 112a may be or include a channel for current flow between the first electrode plate 112 and a first current collector (not shown). In some examples, the first electrode tab 112a may be formed by pre-cutting the first electrode plate to protrude to one side during the manufacture of the first electrode plate, and may protrude further to one side than the diaphragm without separate cutting.

[0117] The second electrode plate 114 may include a second electrode active material portion to which a second electrode active material is applied and a second electrode tab 114a electrically connected to a second uncoated portion, the second uncoated portion being the area in which no second electrode active material is applied. The second electrode tab 114a may be, or include, a channel for current flow between the second electrode plate 114 and a second current collector (not shown). In some examples, the second electrode tab 114a may be formed by pre-cutting the second electrode plate to protrude toward the other side during the manufacture of the second electrode plate, and may protrude further toward the other side than the diaphragm without separate cutting.

[0118] In some examples, the first electrode contact 112a may be disposed on the left end side of the electrode assembly, and the second electrode contact 114a may be disposed on the right end side of the electrode assembly, or they may be disposed on one side in the same direction. Here, the terms "left" and "right" are used for convenience based on Figure 1 The rechargeable lithium batteries shown are described, and their positions can change when the rechargeable lithium batteries are rotated to the left, right, up, or down.

[0119] The first electrode terminal 112a and the second electrode terminal 114a are electrically connected to the outside via negative electrode lead 152 and positive electrode lead 154, respectively soldered to external terminals. A terminal film 156 for insulation from the bag 130 is attached to the negative electrode lead 152 and the positive electrode lead 154. The negative electrode lead 152, the positive electrode lead 154, and the terminal film 156 form an integrated terminal film 150.

[0120] The sealing portion 132 of the bag 130 is made of or includes a thermal adhesive material and has a structure that achieves a seal by bonding the thermal adhesive layers together. Since thermal adhesive materials typically have weak adhesion to metals, a thin-film form of a connector film 156 is attached to the connector, such that the connector film 156 is bonded to the bag 130.

[0121] The first electrode plate 112 of the electrode assembly 110 can form a negative electrode, and the second electrode plate 114 can form a positive electrode, and vice versa.

[0122] positive electrode The positive electrode for a rechargeable lithium-ion battery may include a current collector and a layer of positive electrode active material formed on the current collector. The positive electrode active material layer includes positive electrode active material and may also include a binder and / or a conductive material. As an example, the positive electrode may also include additives that can constitute a sacrificial positive electrode.

[0123] As the positive electrode active material, compounds capable of reversibly inserting and deintercalating lithium (lithiation intercalation compounds) can be used. For example, at least one of lithium and a composite oxide of a metal such as or including at least one of cobalt, manganese, nickel and combinations thereof can be used.

[0124] The composite oxide can be or includes lithium transition metal composite oxides, and examples include at least one of lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, and combinations thereof.

[0125] As an example, a compound represented by any of the following chemical formulas can be used: Li a A 1-b X b O2-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Mn 2-b X b About 4-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);Li a Ni 1-b-c Co b X c About 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α<2);Li a Ni 1-b- c Mn b X c About 2-α D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α<2);Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0≤d≤0.5,0≤e≤0.1);Li a NiG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a CoG b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-b G b O2(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn2G b O4(0.90≤a≤1.8,0.001≤b≤0.1);Li a Mn 1-g G g PO4 (0.90≤a≤1.8, 0≤g≤0.5);Li (3-f) Fe2(PO4)3(0≤f≤2);Li a FePO4 (0.90≤a≤1.8).

[0126] In the above chemical formulas, A is or includes at least one of Ni, Co, Mn, and combinations thereof; X is or includes at least one of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is or includes at least one of O, F, S, P, and combinations thereof; G is or includes at least one of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; and L 1 It is or includes at least one of Mn, Al and combinations thereof.

[0127] As an example, the positive electrode active material can be or includes a high-nickel positive electrode active material, in which the nickel content is about 80 mol% or more, about 85 mol% or more, about 90 mol% or more, about 91 mol% or more, or about 94 mol% or more and about 99 mol% or less, based on about 100 mol% of metals other than lithium in the lithium transition metal complex oxide. High-nickel positive electrode active materials can exhibit high capacity and therefore can be used in high-capacity, high-density rechargeable lithium batteries.

[0128] Based on a 100% by weight positive electrode active material layer, the content of the positive electrode active material can be in the range of about 90% by weight to about 99.5% by weight, and based on a 100% by weight positive electrode active material layer, the content of each of the binder and conductive material can be in the range of about 0.5% by weight to about 5% by weight.

[0129] The binder binds the positive electrode active material particles together and binds the positive electrode active material to the current collector. Representative examples of binders include at least one of polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resin, (meth)acrylate resin, polyester resin, and nylon, but this disclosure is not limited thereto.

[0130] Conductive materials can impart conductivity to electrodes, and any material can be used as long as it is electronically conductive without causing adverse chemical changes in the battery to be constructed. Examples of conductive materials include: carbon-based materials, such as at least one of natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials, including at least one of copper, nickel, aluminum, and silver, in the form of metal powder or metal fibers; conductive polymers, such as polyphenylene derivatives; or mixtures thereof.

[0131] Al can be used as a current collector, but this disclosure is not limited thereto.

[0132] negative electrode The negative electrode for a rechargeable lithium battery includes a current collector and a negative electrode active material layer provided on the current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material.

[0133] For example, the negative electrode active material layer may include from about 90% to about 99% by weight of the negative electrode active material, from about 0.5% to about 5% by weight of the binder, and from 0% to about 5% by weight of the conductive material.

[0134] The negative electrode active material includes at least one of a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, an alloy of lithium and a metal, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0135] The material capable of reversibly intercalating / deintercalating lithium ions may include a carbon-based negative electrode active material, for example, crystalline carbon, amorphous carbon, or a combination thereof. Examples of crystalline carbon include graphite (such as natural graphite or artificial graphite in the form of non-fixed shape, plate-like, flake-like, spherical, or fibrous), and examples of amorphous carbon include at least one of soft carbon and hard carbon, mesophase pitch carbide, calcined coke, etc.

[0136] As the alloy of lithium and a metal, an alloy of lithium and at least one metal such as or including Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn may be used.

[0137] As the material capable of doping and dedoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material may be used. The Si-based negative electrode active material may be or include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy (where Q is or includes at least one of an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element (excluding Si), a Group 15 element, a Group 16 element, a transition metal, a rare earth element, and a combination thereof), and a combination thereof. The Sn-based negative electrode active material may be or include at least one of Sn, SnO2, a Sn-based alloy, and a combination thereof.

[0138] Silicon-carbon composites can be or include composites of silicon and amorphous carbon. According to one example embodiment, the silicon-carbon composite can be in the form of silicon particles surface-coated with amorphous carbon. For example, the composite may include secondary particles (cores) in which primary silicon particles are assembled and an amorphous carbon coating (shell) disposed on the surface of the secondary particles. The amorphous carbon may also be disposed between the secondary silicon particles, for example, such that the primary silicon particles can be coated with amorphous carbon. The secondary particles may exist in a state where the secondary particles are dispersed within an amorphous carbon matrix.

[0139] Furthermore, silicon-carbon composites may also include crystalline carbon. For example, a silicon-carbon composite may include a core comprising crystalline carbon and silicon particles, and an amorphous carbon coating disposed on the surface of the core.

[0140] Si-based or Sn-based negative electrode active materials can be used in combination with carbon-based negative electrode active materials.

[0141] The binder binds the negative electrode active material particles together and also binds the negative electrode active material to the current collector. Non-aqueous binders, aqueous binders, dry binders, or combinations thereof can be used as binders.

[0142] Non-aqueous adhesives may include at least one of polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, and combinations thereof.

[0143] The waterborne adhesive may be or include at least one of the following: styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluorinated rubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0144] When using an aqueous binder as the negative electrode binder, it may further include a cellulose-based compound capable of imparting viscosity. As a cellulose-based compound, at least one or more types selected from carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed and used. As an alkali metal, at least one of Na, K, and Li may be used.

[0145] Dry adhesives are or include fibrous polymeric materials and may be or include at least one of, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, and combinations thereof.

[0146] Conductive materials can impart conductivity to electrodes, and any material can be used as long as it is electronically conductive without causing adverse chemical changes in the battery to be constructed. Examples of conductive materials include: carbon-based materials, such as at least one of natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials, including at least one of copper, nickel, aluminum, and silver, in the form of metal powder or metal fibers; conductive polymers, such as polyphenylene derivatives; and mixtures thereof.

[0147] As the negative electrode current collector, any one or more of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof can be used.

[0148] In some examples, the first electrode contact 112a may be disposed on the left end side of the electrode assembly, and the second electrode contact 114a may be disposed on the right end side of the electrode assembly, or they may be disposed on one side in the same direction. Here, the terms "left" and "right" are used for convenience based on Figure 2 The rechargeable lithium batteries shown are described, and their positions can change when the rechargeable lithium batteries are rotated to the left, right, up, or down.

[0149] The first electrode contact 112a and the second electrode contact 114a are electrically connected to the outside via negative electrode lead 152 and positive electrode lead 154, respectively, which are soldered to external terminals. A contact film 156 for insulation from the bag 130 is attached to the negative electrode lead 152 and the positive electrode lead 154. The negative electrode lead 152, the positive electrode lead 154, and the contact film 156 form an integrated contact film 150.

[0150] The sealing portion 132 of the bag 130 is made of or includes a thermal adhesive material and has a structure that achieves a seal by bonding the thermal adhesive layers together. Since thermal adhesive materials typically have weak adhesion to metals, a thin-film form of a connector film 156 is attached to the connector, such that the connector film 156 is bonded to the bag 130.

[0151] Examples and comparative examples of this disclosure are described below. However, it should be understood that the following examples are merely illustrative of this disclosure and are not intended to limit it.

[0152] Preparation Example 1 1249.72 g of distilled water, 203.69 g of 20% lithium hydroxide aqueous solution, acrylic acid (AA, 0.3 mol), 2-hydroxyethyl methacrylate (HEMA, 0.10 mol), 2-acrylamido-2-methylpropanesulfonic acid (AMPS, 0.6 mol), and ammonium persulfate (0.001 mol) were added to a 3 L four-necked separable flask equipped with a stirrer, thermometer, and condenser. The internal pressure was reduced to 10 mmHg using a diaphragm pump, and then restored to atmospheric pressure using nitrogen. This operation was repeated three times. A methacrylic acid binder was prepared by reacting the reaction solution for 12 hours while maintaining a stable temperature between 65°C and 70°C under controlled heating. After cooling to room temperature, approximately 10 mL of the reaction solution was taken to measure the non-volatile component (NV). The results showed that the non-volatile component (NV) accounted for 9.8 wt% (theoretical value: 10 wt%). Furthermore, in the methacrylic binder poly(lithium acrylate-co-2-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate lithium salt) obtained here, the molar ratio of the first structural unit derived from lithium acrylate, the second structural unit derived from 2-hydroxyethyl methacrylate, and the third structural unit derived from 2-acrylamido-2-methylpropanesulfonate lithium salt is 30:10:60.

[0153] Preparation Example 2 Poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate lithium salt) was prepared by varying the content of the corresponding monomers used in Preparation Example 1. The molar ratio of the structural units derived from lithium acrylate, hydroxyethyl methacrylate, and lithium 2-acrylamido-2-methylpropanesulfonate was 40:10:50. Approximately 10 mL of the reaction solution (reaction product) was taken to measure the non-volatile components. The results showed that the non-volatile components accounted for 9.0 wt% (theoretical value: 10 wt%).

[0154] Preparation Example 3 Poly(lithium acrylate-co-hydroxyethyl methacrylate-co-2-acrylamido-2-methylpropanesulfonate lithium salt) was prepared by varying the content of the corresponding monomers used in Preparation Example 1. The molar ratio of the structural units derived from lithium acrylate, hydroxyethyl methacrylate, and lithium 2-acrylamido-2-methylpropanesulfonate was 65:5:30. Approximately 10 mL of the reaction solution (reaction product) was taken to measure the nonvolatile components. The results showed that the nonvolatile component (NV) accounted for 9.0 wt% (theoretical value: 10 wt%).

[0155] Preparation Example 4 The acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that hydroxyethyl methacrylate and 2-acrylamido-2-methylpropanesulfonic acid were used and acrylic acid was not used. The molar ratio of structural units derived from hydroxyethyl methacrylate to structural units derived from lithium 2-acrylamido-2-methylpropanesulfonic acid was 74:26. ​​The non-volatile components of the reaction solution accounted for 9.0 wt% (theoretical value: 10 wt%).

[0156] Preparation Example 5 The acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that acrylic acid and 2-acrylamido-2-methylpropanesulfonic acid were used, and hydroxyethyl 2-methacrylate was not used. The molar ratio of structural units derived from acrylic acid to structural units derived from lithium 2-acrylamido-2-methylpropanesulfonic acid was 74:26. ​​The non-volatile components of the reaction solution accounted for 9.0 wt% (theoretical value: 10 wt%).

[0157] Preparation Example 6 The acrylic copolymer was prepared in the same manner as in Preparation Example 1, except that acrylic acid and hydroxyethyl 2-methacrylate were used and 2-acrylamido-2-methylpropanesulfonic acid was not used. The molar ratio of the structural units derived from lithium acrylate to those derived from hydroxyethyl 2-methacrylate was 42:58. The non-volatile components of the reaction solution accounted for 9.0 wt% (theoretical value: 10 wt%).

[0158] Example 1 Diaphragm manufacturing: The methacrylic binder (10% by weight in distilled water) prepared in Preparation Example 1 and boehmite (particle size (D50): 150 nm, cubic) as filler were mixed at a methacrylic binder:filler mass ratio of 1:30 based on solids content and added to an aqueous solvent. The resulting mixture was then milled and dispersed for 30 minutes at 25°C using a bead mill to prepare a dispersion.

[0159] A composition for forming a coating was prepared by adding water to a dispersion to achieve a total solids content of 20% by weight.

[0160] The composition used to form the coating was applied to a thickness of 3 μm only on one side of a polyethylene membrane (thickness: 8 μm, SK Corporation, air permeability: 120 sec / 100 cc, puncture strength: 480 kgf) serving as a porous substrate using a molding method, and then dried and cured in an oven at 70°C for 10 minutes to produce a diaphragm.

[0161] Manufacturing of the negative electrode: 97% by weight of graphite particles with an average particle size of 25 μm (used as the negative electrode active material), 1.5% by weight of styrene-butadiene rubber (SBR) binder, and 1.5% by weight of carboxymethyl cellulose (CMC) were mixed, and the resulting mixture was added to distilled water and stirred using a mechanical stirrer for 60 minutes to prepare a slurry of the negative electrode active material. The slurry was coated onto a 10 μm thick copper current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hours, and then dried again at 120°C under vacuum for 4 hours. Finally, it was rolled to fabricate the negative electrode.

[0162] Manufacturing of the positive electrode: 97% by weight of LiCoO2 as the positive electrode active material, 1.5% by weight of carbon black powder as the conductive material, and 1.5% by weight of polyvinylidene fluoride (PVdF) were mixed, and the resulting mixture was added to N-methyl-2-pyrrolidone solvent. The mixture was then stirred using a mechanical stirrer for 30 minutes to prepare a slurry of the positive electrode active material. The slurry was coated onto a 20 μm thick aluminum current collector using a doctor blade, dried in a hot air dryer at 100°C for 0.5 hours, and then dried again at 120°C under vacuum for 4 hours. Finally, the mixture was rolled to fabricate the positive electrode.

[0163] A separator is placed between the positive and negative electrodes to create three positive electrode-separator-negative electrode stacks, which are then placed in a bag. An electrolyte composition (consisting of 1.3M LiPF6 as a lithium salt, ethylene carbonate (EC) / propylene carbonate (PC) / ethyl propionate (EP) / propyl propionate (PP) as a non-aqueous organic solvent (10% / 15% / 10% / 65% by volume), and as additives based on a total of 100% by volume of non-aqueous organic solvent, 7% by volume of fluoroethylene carbonate (FEC), 1% by volume of vinyl ethylene carbonate (VEC), and 3% by volume of propylene sulfone (PS)) is injected, such that the stack is completely immersed in the electrolyte to create a pouch battery.

[0164] Examples 2 to 4 Except for the changes to the composition of the pouch-type rechargeable lithium battery as shown in Table 1 below, the pouch-type battery is manufactured in the same manner as in Example 1.

[0165] Comparison Example 1 to Comparison Example 3 Except for the changes to the composition of the pouch-type rechargeable lithium battery as shown in Table 1 below, the pouch-type battery is manufactured in the same manner as in Example 1.

[0166] Compare Example 4 Except for changing the non-aqueous organic solvent in the electrolyte used in Example 2 as shown in Table 1 below, the pouch cell is manufactured in the same manner as in Example 2.

[0167] Compare Example 5 Except for changing the non-aqueous organic solvent in the electrolyte used in Example 2 as shown in Table 1 below, the pouch cell is manufactured in the same manner as in Example 2.

[0168] Thermal shrinkage rate in electrolytes (unit: %) The manufactured pouch cells were sealed and placed at 25°C for 12 hours. Afterward, the pouch cells were placed in an oven at 150°C for 1 hour. After the samples were removed and cooled, the dimensions of the sample sides were measured to calculate the shrinkage rate. The shrinkage rate can be calculated using the following mathematical formula 1.

[0169] Mathematical Formula 1: Shrinkage rate = (L0-L1) / L0×100.

[0170] L0 represents the initial length of the diaphragm, and L1 represents the length of the diaphragm after being placed at 150°C for 1 hour.

[0171] Bond strength of the positive electrode (unit: gf / mm, wet bond strength) The separator is attached to the positive electrode (manufactured in the same manner as for batteries) and inserted into the bag. Subsequently, the electrolyte (prepared in the same manner as for batteries) is injected and left to stand for 12 hours at 10 kgf / cm³. 2 Up to 20 kgf / cm 2 The electrode was pressed under pressure, at a temperature of 70°C to 90°C, and for a duration of 5 to 20 seconds, and then released. After removing the diaphragm and positive electrode from the bag, the positive electrode and diaphragm were unfolded 180°, and the force required to separate the positive electrode from the diaphragm was measured using a tensile testing machine (HT400, Tinius Olsen).

[0172] Membrane resistance (unit: Ω) Membrane resistance was evaluated using electrochemical impedance spectroscopy (EIS). Each of the membranes fabricated in the example and comparative examples was impregnated with electrolyte (in the same manner as those used for batteries), mounted onto lead-line laminated aluminum foil electrodes, and sealed in an aluminum cask to fabricate a test cell. The resistance (Ω) of the test cell was then measured at 20°C using AC impedance spectroscopy (measurement frequency: 100 kHz).

[0173] Table 1:

[0174] As shown in Table 1 above, the example pouch cell has low thermal shrinkage and film resistance in the electrolyte and high wet adhesion strength to either the positive or negative electrode, thereby improving the reliability of the cell.

[0175] On the other hand, as shown in Table 1 above, the batteries of Comparative Examples 1 to 3, which have separators without (meth)acrylic acid binders, exhibit high membrane resistance, low wet bond strength, and high thermal shrinkage. Comparative Examples 4 and 5, whose EP content is outside the range of EP content in the non-aqueous organic solvent in the electrolyte of this application, exhibit high thermal shrinkage and low wet bond strength.

[0176] According to one example embodiment, the pouch-type rechargeable lithium battery exhibits high reliability due to its high wet bond strength to the positive or negative electrode and its low thermal shrinkage and film resistance in the electrolyte.

[0177] Although the present disclosure has been described above with reference to exemplary embodiments thereof, the present disclosure is not limited thereto. Therefore, it should be understood that various changes and modifications can be made within the scope of the claims, the detailed description of the present disclosure, and the drawings, and such changes and modifications also fall within the scope of the present disclosure.

Claims

1. A pouch-type rechargeable lithium battery, the pouch-type rechargeable lithium battery comprising: An electrode assembly includes a first electrode plate, a second electrode plate, and a diaphragm disposed between the first electrode plate and the second electrode plate; as well as An electrolyte, wherein the electrode assembly is immersed in the electrolyte. The diaphragm includes a porous substrate and a coating disposed on at least one surface of the porous substrate. The coating comprises an adhesive and a filler, wherein the adhesive comprises a (meth)acrylic adhesive, the (meth)acrylic adhesive comprising a first structural unit derived from (meth)acrylic acid, (meth)acrylate, or a salt thereof, a second structural unit derived from a hydroxyalkyl methacrylate, and a third structural unit derived from (meth)acrylamide sulfonic acid, or a salt thereof, and The electrolyte has an ethyl propionate content in the range of 10% to 40% by volume in a non-aqueous organic solvent.

2. The pouch-type rechargeable lithium battery according to claim 1, wherein, The first structural unit is represented by at least one of chemical formula 1, chemical formula 2, and chemical formula 3, and combinations thereof: Chemical Formula 1: ； Chemical formula 2: ； Chemical formula 3: ； The second structural unit is represented by chemical formula 4: Chemical formula 4: ;and The third structural unit is represented by at least one of chemical formulas 5, 6, and 7, and combinations thereof: Chemical formula 5: ； Chemical formula 6: ； Chemical Formula 7: ； Among them, R 1 To R 14 Each independently includes hydrogen or C1 to C10 alkyl groups. L 1 To L 4 Each independently comprises a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group. a, b, c, and d are all independent integers in the range of 0 to 2, and M includes alkali metals.

3. The pouch-type rechargeable lithium battery according to claim 1, wherein, The (meth)acrylic adhesive is represented by chemical formula 8: Chemical formula 8: ； in: R 15 To R 20 Each independently includes hydrogen or C1 to C10 alkyl groups. L 5 and L 6 Each independently comprises a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group. M includes alkali metals, and l, m, and n are the molar ratios of the individual units, provided that the sum of l, m, and n is 1. Both e and f are independent integers in the range of 0 to 2.

4. The pouch-type rechargeable lithium battery according to claim 1, wherein: Based on 100 mol% of the (meth)acrylic acid binder, The first structural unit is included in an amount ranging from 20 mol% to 75 mol%. The second structural unit is included in an amount ranging from 1 mol% to 20 mol%; and The third structural unit is included in an amount ranging from 20 mol% to 75 mol%.

5. The pouch-type rechargeable lithium battery according to claim 1, wherein, Based on 100 mol% of the (meth)acrylic adhesive, the total amount of the first structural unit, the second structural unit, and the third structural unit is 95 mol% or greater.

6. The pouch-type rechargeable lithium battery according to claim 1, wherein, The packing material includes packing material with a particle size D50 of 0.4 μm or smaller.

7. The pouch-type rechargeable lithium battery according to claim 1, wherein, The filler is cubic and is boehmite.

8. The pouch-type rechargeable lithium battery according to claim 1, wherein, The (meth)acrylic adhesive and the filler are included in a mass ratio ranging from 1:10 to 1:

50.

9. The pouch-type rechargeable lithium battery according to claim 1, wherein, The non-aqueous organic solvents also include ethylene carbonate, propylene carbonate, and propyl propionate.

10. The pouch-type rechargeable lithium battery according to claim 9, wherein, The non-aqueous organic solvent is ethylene carbonate: propylene carbonate: ethyl propionate: propyl propionate in a ratio ranging from 5% to 30% by volume: 5% to 30% by volume: 10% to 30% by volume: 45% to 65% by volume.

11. The pouch-type rechargeable lithium battery according to claim 9, wherein, The non-aqueous organic solvent is ethylene carbonate: propylene carbonate: ethyl propionate: propyl propionate in a ratio ranging from 10% volume: 15% volume: 10% volume to 30% volume: 45% volume to 65% volume.

12. The pouch-type rechargeable lithium battery according to claim 9, wherein, The electrolyte includes lithium salt and additives.

13. The pouch-type rechargeable lithium battery according to claim 12, wherein, Based on 100% by volume of the non-aqueous organic solvent, the additives include 5% to 10% by volume of fluoroethylene carbonate, 0.1% to 5% by volume of vinyl ethylene carbonate, and 1% to 5% by volume of propylene sulfone.

14. The pouch-type rechargeable lithium battery according to claim 1, wherein, The first electrode plate is a negative electrode plate, and The negative electrode plate includes a carbon-based negative electrode active material.

15. The pouch-type rechargeable lithium battery according to claim 1, wherein, The second electrode plate is a positive electrode plate, and The positive electrode plate includes a positive electrode active material comprising at least one of lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxide, and combinations thereof.

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