Solid electrolyte layer-forming composition, solid electrolyte layer, and lithium secondary battery

Abstract

The composition for forming a solid electrolyte layer according to an embodiment of the present invention comprises a ketone solvent, a nitrile rubber binder, and inorganic electrolyte particles, wherein the nitrile rubber contains 25% to 50% by weight of acrylonitrile. The solid electrolyte layer according to an embodiment of the present invention comprises a ketone compound, nitrile rubber, and inorganic electrolyte particles.

Description

Technical Field

[0001] This invention relates to a composition for forming a solid electrolyte layer, a solid electrolyte layer, and a lithium secondary battery. Background Technology

[0002] Rechargeable batteries are batteries that can be recharged and discharged repeatedly. With the development of the information communication and display industries, rechargeable batteries are widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptops. In addition, in recent years, battery packs that include rechargeable batteries have been developed for use as power sources in environmentally friendly vehicles such as hybrid electric vehicles.

[0003] Secondary batteries can be categorized into, for example, lithium secondary batteries, nickel-cadmium batteries, and nickel-metal hydride batteries. Among them, lithium secondary batteries have high operating voltage and energy density per unit weight, and are advantageous for charging speed and lightweight design, so they are actively being researched and developed.

[0004] Currently, commercially available lithium-ion batteries primarily use liquid electrolytes, which pose safety risks such as leakage, fire, and explosion due to rapid environmental changes including temperature fluctuations and external impacts. To address these issues, efforts are underway to solidify the electrolyte to ensure stability and increase energy density.

[0005] All-solid-state batteries can incorporate solid electrolytes such as gel polymers, oxides or sulfides, and composite polymers. Therefore, they can improve stability against fires and explosions caused by external impacts or changes in the external environment. Summary of the Invention

[0006] (a) Technical problems to be solved One technical problem of the present invention is to provide a composition for forming a solid electrolyte layer with improved dispersion stability.

[0007] One technical problem of the present invention is to provide a composition for forming a solid electrolyte layer with improved cohesiveness.

[0008] One technical problem of the present invention is to provide a composition for forming a solid electrolyte layer, which has excellent adhesion to the electrode during slurry casting.

[0009] One technical problem of the present invention is to provide a lithium secondary battery comprising a solid electrolyte layer manufactured from the composition for forming the solid electrolyte layer.

[0010] (II) Technical Solution The composition for forming a solid electrolyte layer according to an exemplary embodiment may comprise: a ketone solvent; a nitrile rubber binder; and inorganic electrolyte particles, wherein the acrylonitrile content in the nitrile rubber may be from 25% to 50% by weight.

[0011] In some embodiments, the acrylonitrile content in the nitrile rubber can be from 28% to 40% by weight.

[0012] In some embodiments, the nitrile rubber may include hydrogenated nitrile rubber.

[0013] In some embodiments, the ketone solvent may include at least one selected from methyl ethyl ketone, methyl propyl ketone, and methyl isobutyl ketone.

[0014] In some embodiments, the inorganic electrolyte particles may include oxide-based inorganic electrolytes.

[0015] In some embodiments, the oxide-based inorganic electrolyte may include garnet compounds, sodium superionic conductor compounds, perovskite compounds, lithium superionic conductor (LISICON)-based compounds, lithium phosphorus oxynitride (LIPON)-based compounds, and Li3BO4. 2.5 N 0.5 Li9SiAlO8 or combinations thereof.

[0016] In some embodiments, the oxide-based inorganic electrolyte may include at least one selected from LLTO-based compounds, LLZO-based compounds, LATP-based compounds, and LAGP-based compounds.

[0017] In some embodiments, the oxide-based inorganic electrolyte may include LLZO.

[0018] In some embodiments, the weight ratio of nano-LLZO to micro-LLZO in the LLZO can be from 1:1 to 1:5.

[0019] In some embodiments, the viscosity of the composition for forming the solid electrolyte layer can be from 300 cp to 5000 cp.

[0020] In some embodiments, the cohesive strength of the composition for forming the solid electrolyte layer can be 0.1 N or more.

[0021] In some embodiments, the composition for forming a solid electrolyte layer may further comprise at least one additive selected from unsaturated cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sulcinolone compounds, cyclic sulfate compounds, fluorinated phosphate compounds, and oxalate phosphate compounds.

[0022] The solid electrolyte layer according to an exemplary embodiment may comprise: a ketone compound; nitrile rubber; and inorganic electrolyte particles.

[0023] In some embodiments, the acrylonitrile content in the nitrile rubber can be from 28% to 40% by weight.

[0024] In some embodiments, the nitrile rubber may include hydrogenated nitrile rubber.

[0025] In some embodiments, the ketone compound may include at least one selected from methyl ethyl ketone, methyl propyl ketone, and methyl isobutyl ketone.

[0026] In some embodiments, the inorganic electrolyte particles may include oxide-based inorganic electrolytes.

[0027] In some embodiments, the oxide-based inorganic electrolyte may include garnet compounds, sodium superionic conductor (NASICON) compounds, perovskite compounds, lithium superionic conductor (LISICON)-based compounds, lithium phosphorus oxynitride (LIPON)-based compounds, and Li3BO4. 2.5 N 0.5 Li9SiAlO8 or combinations thereof.

[0028] In some embodiments, the oxide-based inorganic electrolyte may include at least one selected from LLTO-based compounds, LLZO-based compounds, LATP-based compounds, and LAGP-based compounds.

[0029] In some embodiments, the oxide-based inorganic electrolyte may include LLZO.

[0030] In some embodiments, the weight ratio of nano LLZO to micro LLZO in the LLZO can be from 1:1 to 1:5.

[0031] In some embodiments, the solid electrolyte layer may further comprise at least one additive selected from unsaturated cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sulcinolone compounds, cyclic sulfate compounds, fluorinated phosphate compounds, and oxalate phosphate compounds.

[0032] A lithium secondary battery according to an exemplary embodiment may include: a positive electrode; a negative electrode disposed opposite to the positive electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0033] (III) Beneficial Effects The composition for forming a solid electrolyte layer according to an exemplary embodiment contains a ketone solvent, thereby improving the dispersion stability of the slurry.

[0034] The nitrile rubber adhesive in the solid electrolyte layer forming composition according to the exemplary embodiment contains an amount of acrylonitrile within a certain range, thereby improving the cohesiveness between particles and the adhesion to the electrode. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the cross-section of a secondary battery according to an exemplary embodiment. Detailed Implementation

[0036] The composition for forming a solid electrolyte layer according to an exemplary embodiment of the present invention comprises a ketone solvent, a nitrile rubber binder, and inorganic electrolyte particles.

[0037] The present invention will now be described in detail. However, this is merely an exemplary description, and the present invention is not limited to the specific embodiments described herein.

[0038] In this specification, the term "solid electrolyte" can be used as the opposite of a liquid electrolyte. For example, the solid electrolyte may include quasi-solid electrolytes, gel polymer electrolytes, semi-solid electrolytes, etc.

[0039] In this specification, the term "solid electrolyte layer forming composition" may include quasi-solid electrolyte layer forming composition, gel polymer electrolyte layer forming composition, semi-solid electrolyte layer forming composition, etc.

[0040] In an exemplary embodiment, the composition for forming a solid electrolyte layer comprises a ketone solvent, a nitrile rubber binder, and inorganic electrolyte particles.

[0041] Nitrile ligands in nitrile rubber can enhance coordination bonds, thereby maintaining stronger bonding forces on the metal surface that serves as a current collector.

[0042] In some embodiments, the acrylonitrile content in the nitrile rubber can be from 25% to 50% by weight. Within this range, the cohesive force between particles can be improved, and when the slurry is cast onto the electrode, it can have excellent adhesion to the electrode.

[0043] For example, when the acrylonitrile content in the nitrile rubber is less than 25% by weight, the cohesive force between particles may be weak, and the adhesion of the slurry to the electrode when it is cast onto the electrode may be reduced.

[0044] For example, when the acrylonitrile content in the nitrile rubber exceeds 50% by weight, the adhesive may not be able to mix sufficiently into the composition for forming the solid electrolyte layer, and may result in slurry clumping.

[0045] In some embodiments, the acrylonitrile content in the nitrile rubber can be from 28% to 40% by weight, for example, from 28% to 35% by weight. Within the above range, the cohesive force between particles can be further improved, thereby further improving the adhesion of the slurry to the electrode when it is cast onto the electrode.

[0046] In some embodiments, the nitrile rubber may include hydrogenated nitrile rubber. In this case, the structural stability and electrochemical stability of the composition for forming the solid electrolyte layer can be improved.

[0047] In some embodiments, the content of the nitrile rubber may be 0.1% to 5% by weight, 1% to 4% by weight, or 2% to 3% by weight relative to the total weight of the composition for forming the solid electrolyte layer.

[0048] Within the aforementioned range, the cohesion and stability of the composition for forming a solid electrolyte layer can be improved.

[0049] Ketone solvents can effectively disperse inorganic electrolyte particles. The better the dispersibility of the inorganic electrolyte particles, the lower the viscosity and shear stress of the composition, which facilitates the formation of the electrolyte layer and improves the performance of the manufactured battery.

[0050] In some embodiments, the ketone solvent may include at least one selected from methyl ethyl ketone, methyl propyl ketone, and methyl isobutyl ketone.

[0051] In some embodiments, the ketone solvent has a Hansen solubility parameter. It can be 15MPa 0.5 up to 28MPa 0.5 .

[0052] The Hansen solubility parameter is a parameter for determining the solubility of a specific substance by comprehensively considering its dispersion force, dipole-dipole interaction, and hydrogen bonding force, and can be expressed by the following Equation 1.

[0053] [Formula 1] In Equation 1, Hansen solubility parameter (MPa) 0.5 ), δ d This indicates the solubility parameter (MPa) based on the dispersion force. 0.5 ), δ p This represents the solubility parameter (MPa) based on dipole-dipole interactions. 0.5 ), δ h This indicates the solubility parameter (MPa) based on hydrogen bonding forces. 0.5 ).

[0054] Within the aforementioned range, the interaction forces between the ketone solvent and the nitrile rubber adhesive and inorganic electrolyte particles can be appropriately maintained. Therefore, the nitrile rubber can be readily dissolved in the ketone solvent, and the inorganic electrolyte particles can exhibit excellent dispersibility.

[0055] In some embodiments, the content of the ketone solvent may be 20% to 50% by weight, 25% to 40% by weight, or 30% to 35% by weight relative to the total weight of the composition for forming the solid electrolyte layer.

[0056] Within the aforementioned range, the binder and inorganic electrolyte particles can be appropriately dispersed, and the composition for forming the solid electrolyte layer can maintain an appropriate viscosity.

[0057] In some embodiments, the inorganic electrolyte particles may include oxide-based inorganic electrolytes.

[0058] In some embodiments, the oxide-based inorganic electrolyte may include an ionicly conductive compound containing metal and oxygen.

[0059] In some embodiments, the oxide-based inorganic electrolyte may include garnet compounds, sodium superionic conductor (NASICON) compounds, perovskite compounds, lithium superionic conductor (LISICON)-based compounds, lithium phosphorus oxynitride (LIPON)-based compounds, and Li3BO4. 2.5 N 0.5 Li9SiAlO8 or combinations thereof.

[0060] In some embodiments, the oxide-based inorganic electrolyte may include a garnet compound, which is a compound having a garnet crystal structure or a garnet-like crystal structure, for example, it may include LLZO-based compounds, Li6La2CaTa2O 12 Li6La2ANb2O 12 (where A is Ca or Sr) etc.

[0061] For example, the LLZO-based compound can be an oxide containing lithium, lanthanum, and zirconium. The LLZO-based compound can further contain Al, Ga, In, Sc, Ba, Nb, etc. For example, the LLZO-based compound can include not only LLZO compounds (e.g., Li7La3Zr2O) 12 It can also include their doped variants (e.g., Li). 6.4 La3Zr 1.4 Ta 0.6 O 12 )wait.

[0062] In some embodiments, the sodium superionic conductor compound is a compound having a sodium superionic conductor crystal structure or a sodium-like superionic conductor crystal structure, for example, it may include LATP-based compounds, LAGP-based compounds, LiAl... x Zr 2-x (PO4)3 (where 0 ≤ x ≤ 1), LiTi x Zr 2-x (PO4)3(0≤x≤1), Li2Nd3TeSbO 12 wait.

[0063] For example, the LATP-based compound can be a phosphorus oxide containing lithium, aluminum, and titanium. For example, the LATP-based compound can include Li... 1+x Al x Ti 2-x (PO4)3 (where 0 ≤ x ≤ 0.5), specifically, it can include Li 1.3 Al 0.3 Ti 1.7 (PO4)3, etc.

[0064] For example, the LAGP-based compound can be a phosphorus oxide comprising lithium, aluminum, and germanium. For example, the LAGP-based compound can include Li... 1+x Al x Ge 2-x (PO4)3 (where 0 ≤ x ≤ 0.5), specifically, it can include Li 1.5 Al 0.5 Ge 1.5 (PO4)3, etc.

[0065] In some embodiments, the perovskite compound is a compound having a perovskite crystal structure or a perovskite-like crystal structure, and may include LLTO-based compounds having an ABO3 structure.

[0066] For example, the LLTO-based compound can be an oxide comprising lithium, lanthanum, and titanium. For example, the LLTO-based compound can include Li... 0.31 La 0.56 TiO3, Li 0.34 La 0.51 TiO3, etc.

[0067] In some implementations, lithium superionic conductor (LISICON)-based compounds may include a quasi-three-dimensional (3D) framework with an amorphous phase, for example, a Li4SiO4-Li3PO4 composite structure may be used.

[0068] In some implementations, lithium phosphorus oxynitride (LIPON)-based compounds can be represented as Li x PO y N z (Where 2.5 ≤ x ≤ 4.5, 2.5 ≤ y ≤ 4.5, 0.05 ≤ z ≤ 0.6), for example, it can include Li 3.48 PO 3.43 N 0.14 wait.

[0069] For example, the oxide-based inorganic electrolyte may include LLZO-based compounds (e.g., LLZO compounds or their doped variants, more specifically, Li7La3Zr2O). 12 Li 6.4 La3Zr 1.4 Ta 0.6 O 12 Li6La2CaTa2O 12 Li6La2ANb2O 12 (where A is Ca or Sr), LATP-based compounds (e.g., Li) 1.3 Al 0.3 Ti 1.7 (PO4)3), LAGP-based compounds (e.g., Li) 1.5 Al 0.5 Ge 1.5 (PO4)3), LiAl x Zr 2-x (PO4)3 (where 0 ≤ x ≤ 1), LiTi x Zr 2-x (PO4)3 (where 0 ≤ x ≤ 1), Li2Nd3TeSbO 12 LLTO-based compounds (e.g., Li)0.31 La 0.56 TiO3, Li 0.34 La 0.51 TiO3), lithium superionic conductor (LISICON) based compounds (e.g., Li4SiO4-Li3PO4 composite structure), lithium phosphorus oxynitride (LIPON) based compounds (e.g., Li 3.48 PO 3.43 N 0.14 Li3BO 2.5 N 0.5 Li9SiAlO8 or combinations thereof.

[0070] For example, the oxide-based inorganic electrolyte may include at least one selected from LLTO-based compounds, LLZO-based compounds, LATP-based compounds, and LAGP-based compounds.

[0071] In some embodiments, the oxide-based inorganic electrolyte may include LLZO.

[0072] In some embodiments, the weight ratio of nano-LLZO to micro-LLZO in the LLZO can be from 1:1 to 1:5. Within this range, the stability and ionic conductivity of the composition for forming the solid electrolyte layer can be improved.

[0073] In some embodiments, the average particle size (D50) of the inorganic electrolyte particles can be from about 100 nm to 5 μm. For example, the average particle size (D50) of the inorganic electrolyte particles can be from 150 nm to 3 μm or from 200 nm to 1 μm.

[0074] Within the aforementioned range, the processability of the composition for forming the solid electrolyte layer can be ensured, while allowing lithium ions to migrate smoothly. "Average particle size (D50)" can be defined as the particle size corresponding to a cumulative volume percentage of 50% in the particle size distribution obtained from particle volume.

[0075] In some embodiments, the content of the inorganic electrolyte particles may be from 50% to 80% by weight relative to the total weight of the solid electrolyte layer forming composition. For example, the content of the inorganic electrolyte particles may be from 60% to 70% by weight relative to the total weight of the solid electrolyte layer forming composition. Within the above range, the ionic conductivity of the solid electrolyte layer forming composition can be further improved, and the charge and discharge speed of the lithium secondary battery can be increased.

[0076] In some embodiments, the viscosity of the composition for forming the solid electrolyte layer can be from 300 cp to 5000 cp. For example, the viscosity of the composition for forming the solid electrolyte layer can be from 300 cp to 1500 cp. Within the above range, the dispersion stability of the composition for forming the solid electrolyte layer can be improved, and it can be uniformly cast onto the substrate without agglomeration.

[0077] In some embodiments, the cohesive strength of the composition for forming the solid electrolyte layer can be 0.1 N or more. Within this range, the stability of the composition and its adhesion to the electrode can be improved, and the stability of the lithium secondary battery during charging and discharging can be enhanced.

[0078] In some embodiments, the composition for forming the solid electrolyte layer may further comprise at least one additive selected from unsaturated cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sulcinolone compounds, cyclic sulfate compounds, fluorinated phosphate compounds, and oxalate phosphate compounds.

[0079] The unsaturated cyclic carbonate compounds may include vinyl ethylene carbonate (VEC), vinylene carbonate (VC), etc.

[0080] The fluorine-substituted cyclic carbonate compound may include fluoroethylene carbonate (FEC).

[0081] The sulfonyl compounds may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0082] The cyclic sulfate-based compounds may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0083] The fluorine-substituted phosphate compounds may include lithium difluorophosphate (LiPO2F2), etc.

[0084] The oxalate phosphate-based compound may include lithium difluorobis(oxalate)phosphate, etc.

[0085] These can be used individually or in combination of two or more.

[0086] The content of the additive may be from about 0.01% by weight to 5% by weight of the total weight of the composition for forming the solid electrolyte layer.

[0087] The solid electrolyte layer according to the present invention comprises a ketone compound, nitrile rubber, and inorganic electrolyte particles. The ketone compound may be a compound derived from the aforementioned ketone solvent.

[0088] The nitrile rubber and inorganic electrolyte particles can be the same as those described above.

[0089] The solid electrolyte layer can be formed from a solid electrolyte layer forming composition. The solid electrolyte layer can be formed by thermal polymerization or photopolymerization of the solid electrolyte layer forming composition.

[0090] For example, the solid electrolyte layer forming composition can be coated onto a porous membrane or electrode substrate and then heated (thermal polymerization) or irradiated with light (photopolymerization) to form a solid electrolyte layer. Alternatively, the solid electrolyte layer forming composition can be added to a mold of a predetermined shape and then heated (thermal polymerization) or irradiated with light (photopolymerization) to form a solid electrolyte layer.

[0091] When the composition for forming the solid electrolyte layer is thermally polymerized, the solid electrolyte layer can be formed by placing it at a temperature of about 50°C to 150°C for about 20 to 60 minutes.

[0092] According to an exemplary embodiment, the thickness of the solid electrolyte layer can be from about 10 μm to 200 μm. According to some embodiments, the thickness of the solid electrolyte layer can be from about 15 μm to 150 μm.

[0093] The lithium secondary battery according to the present invention includes: a positive electrode; a negative electrode disposed opposite to the positive electrode; and a solid electrolyte layer disposed between the positive electrode and the negative electrode.

[0094] Figure 1 This is a schematic diagram of the cross-section of a secondary battery according to an exemplary embodiment.

[0095] Reference Figure 1 The secondary battery includes: a positive electrode 300; a negative electrode 200 disposed opposite to the positive electrode 300; and a solid electrolyte layer (electrolyte layer 100) disposed between the positive electrode 300 and the negative electrode 200, and manufactured by a composition for forming the solid electrolyte layer.

[0096] The positive electrode 300 may include a positive electrode current collector 310 and a positive electrode active material layer 320 disposed on at least one side of the positive electrode current collector 310.

[0097] The positive electrode current collector 310 may comprise stainless steel, nickel, aluminum, titanium, or alloys thereof. The positive electrode current collector 310 may also comprise aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The thickness of the positive electrode current collector may be, for example, from 10 μm to 50 μm.

[0098] The positive electrode active material layer 320 may contain a positive electrode active material. The positive electrode active material may contain compounds that enable reversible insertion and extraction of lithium ions.

[0099] According to an exemplary embodiment, the positive electrode active material may comprise a lithium-nickel metal oxide. The lithium-nickel metal oxide may further comprise at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0100] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 1.

[0101] [Chemical Formula 1] Li x Ni a M b O 2+z In chemical formula 1, the values ​​can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b≤0.4, and -0.5≤z≤0.1. As mentioned above, M can contain Co, Mn, and / or Al.

[0102] The chemical structure represented by Formula 1 indicates the bonding relationships contained in the layered or crystalline structure of the positive electrode active material, and does not exclude other additional elements. For example, M may contain Co and / or Mn, and Co and / or Mn may be provided together with Ni as the main active element of the positive electrode active material. Formula 1 is provided to represent the bonding relationships of the main active elements and should be understood as including the introduction and substitution of additional elements.

[0103] In one embodiment, in addition to the primary active element, auxiliary elements may be further included to enhance the chemical stability of the positive electrode active material or the layered / crystal structure. These auxiliary elements may be incorporated into the layered / crystal structure and form bonds; this should be understood to also include the chemical structures represented by Formula 1.

[0104] The auxiliary element may include at least one of, for example, Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may function as an auxiliary active element, together with Co or Mn, to contribute to the capacity / power activity of the positive electrode active material; for example, Al.

[0105] For example, the positive electrode active material or the lithium-nickel metal oxide may include a layered structure or a crystal structure represented by the following chemical formula 1-1.

[0106] [Chemical Formula 1-1] Li x Ni a M1 b M2 c O 2+z In chemical formula 1-1, M1 may contain Co, Mn, and / or Al. M2 may contain the aforementioned auxiliary elements. In chemical formula 1-1, the elements can be 0.9≤x≤1.2, 0.6≤a≤0.99, 0.01≤b+c≤0.4, and -0.5≤z≤0.1.

[0107] The positive electrode active material may further include coating elements or doping elements. For example, elements that are substantially the same as or similar to the auxiliary elements described above can be used as coating elements or doping elements. For example, one or more combinations of the elements described above can be used as coating elements or doping elements.

[0108] The coating element or doping element may exist on the surface of the lithium-nickel metal oxide particles, or may penetrate through the surface of the lithium-nickel metal oxide particles and be contained in the bonding structure represented by chemical formula 1 or chemical formula 1-1.

[0109] The positive electrode active material may contain nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, NCM-based lithium oxide with increased nickel content can be used.

[0110] Ni can be provided as a transition metal related to the power and capacity of lithium secondary batteries. Therefore, as described above, by using a high-content (High-Ni) composition for the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0111] However, as the Ni content increases, the long-term storage stability and life stability of the positive electrode or secondary battery may decrease relatively, and the side reactions with the electrolyte may also increase. However, according to exemplary embodiments, the conductivity can be maintained by including Co, and the life stability and capacity retention characteristics can be improved by Mn.

[0112] In the NCM-based lithium oxide, the content of Ni (e.g., the mole fraction of Ni in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, or 0.8 or more. In some embodiments, the content of Ni can be 0.8 to 0.95, 0.82 to 0.95, 0.83 to 0.95, 0.84 to 0.95, 0.85 to 0.95, or 0.88 to 0.95.

[0113] In some embodiments, the positive electrode active material may also include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (e.g., LiFePO4).

[0114] In some embodiments, the positive electrode active material may include, for example, a manganese-rich (Mn-rich)-based active material having a chemical structure or crystal structure represented by Chemical Formula 2, a lithium-rich layered oxide (LLO) / over-lithiated oxide (OLO)-based active material, and a cobalt-less (Co-less)-based active material.

[0115] [Chemical Formula 2] p[Li2MnO3]·(1-p)[Li q JO2] In Chemical Formula 2, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J may include at least one element selected from Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0116] For example, a solvent may be mixed with the positive electrode active material to prepare a positive electrode slurry. The positive electrode slurry may be coated on the positive electrode current collector 310 and then dried and calendered to manufacture the positive electrode active material layer 320. The coating process may be performed by methods such as gravure coating, slot die coating, multi-layer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., and is not limited thereto. The positive electrode active material layer may further include a binder and may further include a conductive material, a thickening agent, etc.

[0117] Non-limiting examples of solvents used in preparing the positive electrode slurry include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0118] The adhesive may include polyvinylidene fluoride (PVDF), vinylidene fluoride-co-hexafluoropropylene copolymer (poly(vinylidene fluoride-co-hexafluoropropylene)), polyacrylonitrile, polymethyl methacrylate, nitrile rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, the PVDF-based adhesive can be used as a positive electrode adhesive.

[0119] The conductive material can be added to enhance the conductivity of the positive electrode active material layer and / or the mobility of lithium ions or electrons. For example, the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), and carbon fiber, and / or metal-based conductive materials including perovskite minerals such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3, but is not limited thereto.

[0120] As needed, the positive electrode slurry may further contain thickeners and / or dispersants. In one embodiment, the positive electrode slurry may contain thickeners such as carboxymethyl cellulose (CMC).

[0121] Depending on the requirements, the positive electrode active material layer may further comprise the aforementioned inorganic electrolyte particles. For example, the positive electrode active material layer may further comprise the aforementioned oxide-based inorganic electrolyte. In this case, the inorganic electrolyte particles contained in the solid electrolyte layer may be the same as or different from the inorganic electrolyte particles contained in the positive electrode active material layer.

[0122] The negative electrode 200 may include a negative electrode current collector 210 and a negative electrode active material layer 220 disposed on at least one side of the negative electrode current collector 210.

[0123] The negative electrode current collector 210 may include, for example, copper foil, nickel foil, stainless steel foil, titanium foil, foam nickel, foam copper, polymer substrate coated with conductive metal, etc. The thickness of the negative electrode current collector 210 may be, for example, from 10 μm to 50 μm, but is not limited thereto.

[0124] The negative electrode current collector 210 is not an essential component, and the negative electrode 200 may not include the negative electrode current collector 210 and may only include the negative electrode active material layer 220.

[0125] The negative electrode active material layer 220 may contain a negative electrode active material. The negative electrode active material may use a material that can adsorb and desorb lithium ions. For example, the negative electrode active material may use carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers; lithium metal; lithium alloys; silicon (Si)-containing substances or tin (Sn)-containing substances, etc.

[0126] Examples of the amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0127] Examples of the crystalline carbon may include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized mesocarbon microbead (MCMB), graphitized mesophase pitch-based carbon fiber (MPCF), etc.

[0128] The lithium metal may include pure lithium metal or lithium metal formed with a protective layer for inhibiting dendrite growth, etc. In one embodiment, a lithium metal-containing layer deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, a lithium thin film layer may also be used as the negative electrode active material layer.

[0129] Elements included in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc.

[0130] The silicon-containing substance may provide further increased capacity characteristics. The silicon-containing substance may include Si, SiO x (0 < x < 2), SiO doped with metal x (0 < x < 2), silicon-carbon composites, etc. The metal may include lithium and / or magnesium, and SiO doped with metal x (0 < x < 2) may include metal silicate.

[0131] As needed, the negative electrode active material layer may further contain the above-mentioned inorganic electrolyte particles. For example, the negative electrode active material layer may further contain the above-mentioned oxide-based inorganic electrolyte. At this time, the inorganic electrolyte particles contained in the solid electrolyte layer and the inorganic electrolyte particles contained in the negative electrode active material layer may be the same or different.

[0132] For example, the negative electrode active material can be mixed in a solvent to prepare a negative electrode slurry. The negative electrode slurry can be coated / deposited onto a negative electrode current collector and then dried and calendered to produce a negative electrode active material layer 220. The coating process can be performed using a method substantially the same as that used to manufacture the positive electrode active material layer 320. The negative electrode active material layer 220 may further include a binder and optionally further include an electrolyte, conductive material, thickener, etc.

[0133] In some implementations, the negative electrode 200 may also include a layer of negative electrode active material in the form of lithium metal formed by a deposition / coating process.

[0134] Examples of solvents used for the negative electrode active material layer include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, tert-butanol, etc.

[0135] The adhesive, conductive material, and thickener may be any of the aforementioned substances that can be used in the manufacture of the positive electrode.

[0136] In some implementations, the negative electrode adhesive may be a styrene-butadiene rubber-based adhesive, carboxymethyl cellulose, polyacrylic acid-based adhesive, or poly(3,4-ethylenedioxythiophene) (PEDOT)-based adhesive.

[0137] In some embodiments, an electrolyte layer 100 may be disposed between the positive electrode 300 and the negative electrode 200 within the electrode assembly. For example, a battery cell may be defined by the positive electrode 300, the negative electrode 200, and the electrolyte layer 100, and the electrode assembly may be formed by stacking multiple said battery cells. For example, the electrode assembly may be formed by winding, stacking, folding, etc.

[0138] For example, tabs (positive and negative tabs) may protrude from the positive and negative current collectors and extend to one side of the housing, respectively. The tabs may be fused to said one side of the housing and connected to electrode leads (positive and negative leads) extending to or exposed outside the housing.

[0139] In an exemplary embodiment, the battery cell can be formed by providing a solid electrolyte layer made of the solid electrolyte layer forming composition between the positive electrode 300 and the negative electrode 200.

[0140] For example, pouch-shaped shells, prismatic shells, cylindrical shells, coin-shaped shells, etc. can be used.

[0141] The embodiments of the present invention will be further described below with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are only for illustrating the present invention and are not intended to limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope of the present invention and its technical concept, which is obvious to those skilled in the art, and such variations and modifications naturally fall within the scope of the claims.

[0142] Example 1 (1) Fabrication of solid electrolyte layer At room temperature, 0.96 g of nitrile butadiene rubber (NBR) adhesive (acrylonitrile (AN) 34 wt%) and 8.64 g of methyl propyl ketone (MPK) were uniformly mixed for 48 hours using a magnetic bar to prepare an adhesive solution containing 10 wt% NBR. 5 mm and 3 mm Zr balls were added in a 3:1 ratio to a bottle used for ball milling, followed by the sequential addition of 8 g of nano-LLZO (~300 nm), 24 g of micron-sized LLZO (~1 μm), the adhesive solution, and 7.36 g of MPK solvent. Ball milling was then performed for approximately 24 hours to prepare a composition for forming a solid electrolyte layer.

[0143] The solid electrolyte layer forming composition is thinly coated onto a negative electrode substrate made of Si-C with a silicon content of 11% by weight (specific capacity: 4 mAh cm⁻¹). -2 The upper part of the electrolyte layer is then heat-treated at 90°C for 30 minutes to form a solid electrolyte layer.

[0144] Next, 5% by weight of ethoxylated trimethylolpropane triacrylate (TMPETA), 1% by weight of tert-butyl peroxypentanoate (t-BPP), 16.9% by weight of LiTFSI, 2.1% by weight of LiDFOB and 0.6% by weight of LiPF6 were added to a solvent containing 50.7% by weight of ethyl methyl carbonate (EMC) and 23.7% by weight of fluoroethylene carbonate (FEC) to prepare a polymer electrolyte composition.

[0145] The polymer electrolyte composition prepared above is impregnated on the upper part of the solid electrolyte layer.

[0146] (2) Manufacturing of lithium secondary batteries LiNi will be used as the positive electrode active material 0.88 Co 0.06 Mn 0.06O2, polyvinylidene fluoride (PVDF, Kynar Flex® 2851, Arkema) as a binder, and Ketjenblack as a conductive material are added to a thinky mixer in a weight ratio of 96.5:1.5:2.0 with N-methylpyrrolidone as a solvent. The mixture is stirred for 30 minutes using a rotational and revolution-based mixing method to prepare the positive electrode slurry. The positive electrode slurry is then uniformly coated onto aluminum foil, vacuum dried at approximately 120°C, and calendered to produce the positive electrode (with a loading of approximately 15 mg / cm³). 2 The density of the mixture is approximately 2.5 g / cm³. 3 The specific capacity of the positive electrode is 4 mAh cm⁻¹. -2 .

[0147] The positive electrode is stacked on the solid electrolyte layer to assemble the battery cell. The assembled battery cell is then heat-cured in an oven at approximately 60°C for about 1 hour to manufacture the battery.

[0148] Examples and Comparative Examples The solid electrolyte layer and battery are manufactured using the same method as in Example 1, except that the composition of the composition for forming the solid electrolyte layer is adjusted as shown in Table 1 below.

[0149] [Table 1] The components listed in Table 1 are as follows.

[0150] NBR: Nitrile Butadiene Rubber AN: Acrylonitrile MPK: Methyl Propyl Ketone MEK: Methyl Ethyl Ketone MIBK: Methyl Isobutyl Ketone DIBK: Diisobutyl Ketone IPA: Isopropyl alcohol nBB: Butyl butyrate Ortho-xylene (O-xylene) Experimental Example 1: Evaluation of Cohesion Between Particles Using the SAICAS instrument, the horizontal force (horizontal force) was measured when the upper end of the electrolyte layer coated on the substrate was scraped horizontally to a depth of 10 μm, and the measured horizontal force was interpreted as the cohesive force between particles.

[0151] The evaluation results are shown in Table 2 below.

[0152] Experimental Example 2: Evaluation of the solubility of NBR adhesives At room temperature, the adhesive solutions of the examples and comparative examples were uniformly mixed for 48 hours by stirring with a magnetic rod, and the solubility was compared.

[0153] The evaluation results are shown in Table 2 below. When the adhesive is completely dissolved, it is marked with ◎; when the adhesive is dissolved but slightly opaque, it is marked with ○; when the adhesive is dissolved but opaque, it is marked with △; and when the solubility cannot be evaluated or the adhesive is not dissolved, it is marked with ×.

[0154] Experimental Example 3: Evaluation of the Dispersion Stability of Oxides Oxides (35% by weight of the composition for forming a solid electrolyte layer, using 8g of nano-LLZO (~300nm) and 24g of micron-LLZO (~1μm) from Example 1) were added to the binder solutions of the examples and comparative examples, and the mixture was ball-milled. The dispersion stability of the oxides was then evaluated.

[0155] The evaluation results are shown in Table 2 below. When the oxide powder is well dispersed and no visible sedimentation or emulsification occurs even after 12 hours, it is marked with ◎. When the color changes slightly over time, it is marked with ○. When sedimentation or emulsification occurs over time, it is marked with △. When the dispersion stability cannot be evaluated or stratification occurs, it is marked with ×.

[0156] [Table 2] Referring to Table 2, in the case where the AN content in the NBR adhesive corresponds to 25% to 50% by weight in the examples, it can be confirmed that the cohesive force between particles is greater than 0.09 N.

[0157] On the other hand, in Comparative Example 1, where the AN content in the NBR adhesive was 18% by weight, the cohesive force between particles was 0.018 N, which was about 1 / 8 of that in Example 1. In Comparative Example 2, where the AN content in the NBR adhesive exceeded 50% by weight, the adhesive could not be fully dissolved in the solvent, resulting in slurry clumping.

[0158] Furthermore, in Examples 1 to 5, which contained MPK, MEK, and MIBK solvents, the NBR adhesive exhibited the best solubility. On the other hand, it was confirmed that the NBR adhesive in Example 6, which contained DIBK solvent, had reduced solubility.

[0159] In Comparative Examples 3 to 5, which contained alcohol-based solvents, ester-based solvents, and aromatic solvents, it was confirmed that the solubility of the NBR adhesive was significantly reduced.

[0160] Furthermore, in Examples 1 to 5, which contained MPK, MEK, and MIBK solvents, the LLZO oxide particles exhibited excellent dispersion stability, while in Example 6, which contained DIBK solvent, the dispersion stability of the oxides decreased.

[0161] In Comparative Examples 3 to 5, which contained alcohol-based solvents, ester-based solvents, and aromatic solvents, it was confirmed that the dispersion stability of the oxides was reduced and phase separation occurred.

[0162] In Example 7, where the AN content in the NBR adhesive exceeded 40% by weight, excellent cohesion between particles was confirmed, but the solubility of the NBR adhesive and the dispersion stability of the oxides were reduced compared to Examples 1 to 5.

[0163] The above description is merely an example of applying the principles of this invention, and other configurations may be further included without departing from the scope of this invention.

Claims

1. A composition for forming a solid electrolyte layer, comprising: Ketone solvents; Nitrile rubber adhesives; and Inorganic electrolyte particles, in, The acrylonitrile content in the nitrile rubber is from 25% to 50% by weight.

2. The composition for forming a solid electrolyte layer according to claim 1, wherein, The acrylonitrile content in the nitrile rubber is from 28% to 40% by weight.

3. The composition for forming a solid electrolyte layer according to claim 1, wherein, The nitrile rubber includes hydrogenated nitrile rubber.

4. The composition for forming a solid electrolyte layer according to claim 1, wherein, The ketone solvent includes at least one selected from methyl ethyl ketone, methyl propyl ketone, and methyl isobutyl ketone.

5. The composition for forming a solid electrolyte layer according to claim 1, wherein, The inorganic electrolyte particles include oxide-based inorganic electrolytes.

6. The composition for forming a solid electrolyte layer according to claim 5, wherein, The oxide-based inorganic electrolyte includes garnet compounds, sodium superionic conductor compounds, perovskite compounds, lithium superionic conductor-based compounds, lithium phosphorus oxynitride-based compounds, and Li3BO4. 2.5 N 0.5 Li9SiAlO8 or combinations thereof.

7. The composition for forming a solid electrolyte layer according to claim 5, wherein, The oxide-based inorganic electrolyte includes at least one selected from LLTO-based compounds, LLZO-based compounds, LATP-based compounds, and LAGP-based compounds.

8. The composition for forming a solid electrolyte layer according to claim 5, wherein, The oxide-based inorganic electrolyte includes LLZO.

9. The composition for forming a solid electrolyte layer according to claim 8, wherein, The weight ratio of nano LLZO to micro LLZO in the LLZO is 1:1 to 1:

5.

10. The composition for forming a solid electrolyte layer according to claim 1, wherein, The viscosity of the composition for forming the solid electrolyte layer is from 300 cp to 5000 cp.

11. The composition for forming a solid electrolyte layer according to claim 1, wherein, The cohesive strength of the composition for forming the solid electrolyte layer is 0.1 N or more.

12. The composition for forming a solid electrolyte layer according to claim 1, wherein, The composition for forming the solid electrolyte layer further comprises at least one additive selected from unsaturated cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sulcinolone compounds, cyclic sulfate compounds, fluorinated phosphate compounds, and oxalate phosphate compounds.

13. A solid electrolyte layer comprising: ketone compounds; Nitrile rubber; and Inorganic electrolyte particles.

14. The solid electrolyte layer according to claim 13, wherein, The acrylonitrile content in the nitrile rubber is from 28% to 40% by weight.

15. The solid electrolyte layer according to claim 13, wherein, The nitrile rubber includes hydrogenated nitrile rubber.

16. The solid electrolyte layer according to claim 13, wherein, The ketone compound includes at least one selected from methyl ethyl ketone, methyl propyl ketone, and methyl isobutyl ketone.

17. The solid electrolyte layer according to claim 13, wherein, The inorganic electrolyte particles include oxide-based inorganic electrolytes.

18. The solid electrolyte layer according to claim 17, wherein, The oxide-based inorganic electrolyte includes garnet compounds, sodium superionic conductor compounds, perovskite compounds, lithium superionic conductor-based compounds, lithium phosphorus oxynitride-based compounds, and Li3BO4. 2.5 N 0.5 Li9SiAlO8 or combinations thereof.

19. The solid electrolyte layer according to claim 17, wherein, The oxide-based inorganic electrolyte includes at least one selected from LLTO-based compounds, LLZO-based compounds, LATP-based compounds, and LAGP-based compounds.

20. The solid electrolyte layer according to claim 17, wherein, The oxide-based inorganic electrolyte includes LLZO.

21. The solid electrolyte layer according to claim 20, wherein, The weight ratio of nano LLZO to micro LLZO in the LLZO is 1:1 to 1:

5.

22. The solid electrolyte layer according to claim 13, wherein, The solid electrolyte layer further comprises at least one additive selected from unsaturated cyclic carbonate compounds, fluorinated cyclic carbonate compounds, sulcinolone compounds, cyclic sulfate compounds, fluorinated phosphate compounds, and oxalate phosphate compounds.

23. A lithium secondary battery, comprising: positive electrode; The negative electrode is disposed opposite to the positive electrode; and The solid electrolyte layer according to any one of claims 13 to 22, wherein the solid electrolyte layer is disposed between the positive electrode and the negative electrode.

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