A lithium-ion battery having a positive electrode containing an NMC material as a core and carbon black as a shell

Abstract

A lithium-ion battery using a positive electrode containing a positive electrode active material with an NMC material as the core and carbon black as the shell, a negative electrode containing a negative electrode active material that is graphite-type carbon, an oxide material, or lithium according to the form of the lithium-ion battery of the present invention, a vinylene carbonate (VC)-type additive, and other additives including fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), and methylene methanedisulfonate (MMDS), and an electrolyte solution containing a lithium hexafluorophosphate (LiPF6) salt in a solvent, which minimizes gas generation in the lithium-ion battery during charge / discharge and helps maintain the performance of the battery. The production of the positive electrode consists of mechanofusion, and the negative electrode can be produced by pulverizing the negative electrode active material using high-energy ball milling or lithium can be used as the negative electrode. Next, the lithium-ion battery is formed by combining a positive electrode active material, a negative electrode active material, and an electrolyte solution with a polymer film as a separator.

Description

Technical Field

[0001] The present invention relates to a lithium-ion battery having a positive electrode containing an NMC (nickel manganese cobalt) material as a core and carbon black as a shell, and belongs to the fields of electricity and chemical engineering.

Background Art

[0002] A battery is an energy storage device that can convert chemical energy into electric power. Batteries can be divided into two types, namely, primary batteries that are disposable and secondary batteries that are rechargeable. The currently popular secondary battery is the lithium-ion battery, which uses lithium in the form of an inorganic compound that can generate electric power from the mobility of lithium ions.

[0003] Lithium-ion batteries are very popular not only in the electric vehicle industry but also in electronic and portable electric devices. Lithium-ion batteries can be manufactured in several forms according to their applications, such as button batteries, cylindrical batteries, pouch batteries, and prismatic batteries. There are also battery packs used for large-scale power generation such as electric vehicles.

[0004] A lithium-ion battery cell consists of a positive electrode, a negative electrode, an electrolyte solution, and a separator. The positive electrode contains a positive electrode active material capable of absorbing and releasing lithium ions, which is made of a lithium-containing material such as lithium cobalt oxide (LiCoO₂), lithium manganese oxide (LiMn₂O₄), and lithium iron phosphate (LiFePO₄). The above lithium cobalt oxide (LiCoO₂) is the first positive electrode active material in the manufacture of the positive electrode of a lithium-ion battery, but its safety is low. The above lithium manganese oxide (LiMn₂O₄) has high thermal stability and safety but a short cycle life. The above lithium iron phosphate (LiFePO₄) has high safety, is small in size, has high stability, and a high cycle usage, but has a lower energy density compared to other types of lithium batteries. Furthermore, there is lithium nickel manganese cobalt oxide (NMC material, or LiNMC or NMC) containing nickel, manganese, and cobalt in different element ratios. For example, NMC111 is LiNMC containing nickel, manganese, and cobalt in a ratio of 1:1:1, or NMC811 contains nickel, manganese, and cobalt in a ratio of 8:1:1. The above LiNMC utilizes the good characteristics of nickel, manganese, and cobalt. For example, nickel has high specific energy but low stability, while manganese has low internal resistance. The combination of these elements imparts strength and thermal stability to the lithium material and is suitable for use requiring high battery capacity and low heat generation rate, such as in electric vehicles.

[0005] However, in order to enhance the electrical conductivity of the positive electrode, the positive electrode active material is made of an NMC material formed in a structure with a metal oxide as the core. Regarding the shell (core-shell particles, core@shell), the external shell promotes an increase in the energy from the electrolyte adsorption surface and an increase in the electrical conductivity that can affect the performance and service life of the battery. This type of invention is disclosed in various patent documents.

[0006] For example, Patent Document 1 discloses an invention regarding a positive electrode having a positive electrode active material that includes an NMC material as a core and carbon nanotubes as a shell, where the proportion of the carbon nanotube shell is 0.01 to 5% by weight of the NMC material core, and the particle size of the NMC material core is 5 to 15 microns. The positive electrode of this invention has a charge of 2.5 to 4.5 V, an initial charge / discharge rate exceeding 240 mAh / g (milliamperes per hour / gram), and a capacity retention rate of 90% after 100 charge cycles.

[0007] Patent Document 2 discloses the production of a positive electrode containing an NMC material as a core and a carbon shell containing nanosized magnesium oxide or aluminum oxide.

[0008] Patent Document 3 discloses an invention regarding a positive electrode of a lithium-ion battery in a form that includes an NMC material as a core and a shell. The NMC material core can be selected from NMC111, NMC532, or NMC811, and graphene is used as the shell. Here, the ratio of the NMC material core to the graphene shell is 1:0.005 to 0.1, and the ratio of the used NMC material core, graphene shell, acetylene black type conductive material, and polyvinylidene fluoride (PVDF) type binder is 80:10:10.

[0009] Based on the above information regarding lithium-ion batteries, it has been found that the positive electrode has various compositions and is an important variable that affects the performance and characteristics of the battery. The negative electrode, electrolyte solution, and separator are also important. The negative electrode contains a negative electrode active material that is carbon such as graphite or nanocarbon, or a lithium-containing material. The production of the negative electrode can combine the negative electrode active material with a conductive material and a binder to enhance the performance of the negative electrode.

[0010] The electrolyte solution contains a lithium salt; typical examples of such lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)imide (LiFSI), etc. These lithium salts are dissolved in organic solvents such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and propylene carbonate (PC). In addition, there is a separator that separates the positive electrode and the negative electrode to avoid contact, and polymers such as polyethylene (PE) and polypropylene (PP) are common. Inventions related to lithium-ion batteries using a positive electrode, a negative electrode, and an electrolyte solution are disclosed in various patent documents.

[0011] For example: Patent Document 4 discloses a battery having a positive electrode using a positive electrode active material that is an NMC111 material combined with a conductive carbon and a polyvinylidene fluoride (PVDF) type binder, and a negative electrode using a negative electrode active material that is artificial graphite combined with styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC). When the lithium salts are lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium tetrafluoroborate (LiBF4), and they are in a ratio of 1 mol to 0.01 - 1.2 mol to 0.05 - 0.7 mol respectively, the electrolyte solution is used. Also, a solvent mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) is used. Similarly, vinylene carbonate (VC), fluoroethylene carbonate (FEC), and propane sultone (PS) additives are 1 - 10 weight percent of the electrolyte solution.

[0012] Patent Document 5 discloses the use of a negative electrode active material that is artificial graphite, and Patent Document 6 discloses the use of a negative electrode holding material that is artificial graphite, but also discloses surface improvement by nitrogen atom addition. Patent Document 7 discloses a battery having a positive electrode containing an NMC material; a negative electrode containing graphite coated with amorphous carbon; a lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) electrolyte solution in a solvent mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC); and a lithium difluorophosphate (LiPO2F2) additive.

[0013] Furthermore, there is a research journal on related inventions, namely, the Journal of Energy Storage Materials. In this journal, there is a research article titled "Core-Shell Ni-Rich NMC Nanocarbon Cathodes from Scalable Solvent-Free Mechanofusion for High-Performance 18650 Li-Ion Batteries", which describes the manufacture of a cathode active material having a structure with an NMC material using the NMC811 material as the core and a nanocarbon shell, and the ratio of the NMC material to the nanocarbon is 90:10 weight percent. The nanocarbon used above was of the carbon black type that passed through mechanofusion to form a structure containing the NMC material as the core and the nanocarbon as the shell. Also, carbon black was used as the conductive material, and polyvinylidene fluoride (PVDF) was used as the binder for manufacturing the cathode of the battery. The battery was manufactured using an NMC material as the core containing a nanocarbon shell, carbon black as the conductive material, and polyvinylidene fluoride (PVDF) in a ratio of 946:24:3 parts by weight, respectively, as 18650 cylindrical cells. As the electrolyte solution, a solution containing 10 moles of lithium hexafluorophosphate (LiPF6) in a solvent of ethylene carbonate (EC) combined with dimethyl carbonate (DMC) in a ratio of 1:1 part by volume was used. The negative electrode consisted of a graphite-type negative electrode active material, carbon black as the conductive material, and polyvinylidene fluoride (PVDF) in a ratio of 96.6:1.7:1.7 parts by weight, respectively. Furthermore, lithium was used as the negative electrode, and an invention of a button battery was disclosed in which the positive electrode contains an NMC material as the core, nanocarbon as the shell, carbon black as the conductive material, and polyvinylidene fluoride in a ratio of 80:10:10 parts by weight, respectively.

[0014] Apart from the above foreign patent documents, there is a patent document that discloses an invention related to a lithium-ion battery filed in Thailand.

[0015] For example, Patent Document 8 discloses an invention regarding a positive electrode of a lithium-sulfur battery in the form of a structure including a core and a shell. Sulfur is used as the core and nanocarbon is used as the shell, each at a ratio of 95:5 by weight. Mechanofusion is used to form the materials into a core and shell structure, and it is disclosed that the ratio of the positive electrode containing nanocarbon sulfide as the shell, the nanocarbon-type conductive material, and the polyvinylidene fluoride (PVDF)-type binder is 6:3:1 by weight, respectively.

[0016] Patent Document 9 discloses an invention of an electrode made of an NMC material as a positive electrode active material, showing that the ratio of the positive electrode active material, the nanocarbon-type conductive material, and the polyvinylidene fluoride (PVDF)-type binder is 8:1:1 by weight, respectively. Patent Document 10 discloses an invention of a positive electrode of a lithium-ion battery having a structure with a core and a shell. Polysulfide lithium is used as the core and nanocarbon is used as the shell, each at a ratio of 95:5 by weight, and it is shown that the ratio of the positive electrode containing nanocarbon sulfide as the shell, the nanocarbon-type conductive material, and the polyvinylidene fluoride (PVDF)-type binder is 6:3:1 by weight, respectively.

[0017] Patent Document 11 discloses an invention of a positive electrode of a lithium-ion battery in a form having a positive electrode active material containing lithium nickel aluminate as the core and nanocarbon as the shell, each at a ratio of 70 - 95:5 - 30 by weight.

[0018] Patent Document 12 discloses a method for manufacturing an electrode of a lithium-ion battery, in which the positive electrode contains a lithium metal silicate mixed with a carbon-type conductive material and a binder such as polyvinylidene fluoride (PVDF). The obtained mixture is coated on an aluminum foil, and the obtained lithium-ion battery has an initial discharge of 1,950 mAh / g at a battery discharge rate (C-rate) of 0.05.

[0019] Patent Document 13 discloses a negative electrode in which the negative electrode active material is silicon, graphene is used as the conductive material, and polyacrylic acid is used as the binder, and they are used in proportions of 15 to 85:3 to 75:3 to 60 parts by weight, respectively.

[0020] Although many lithium-ion batteries and their components have been invented, the development of lithium-ion batteries for improving performance (capacity increase, thermal stability, weight, and safety) is still needed in the industry. Therefore, the present inventors have developed a positive electrode having a positive electrode active material containing an NMC material core and a carbon black shell, an improved electrolyte solution for improved performance, the use of additives that help minimize undesirable reactions that can generate gas in the system and affect the useful life, and an optimized negative electrode composition for the battery.

Prior Art Documents

Patent Documents

[0021]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Patent Document 8

Patent Document 9

Patent Document 10

Patent Document 11

Patent Document 12

Patent Document 13

Summary of the Invention

Problems to be Solved by the Invention

[0022] The present invention focuses on the improvement of the positive electrode and aims to manufacture a high-performance lithium-ion battery using a core-shell particle-shaped positive electrode active material. The NMC material (LiNMC or NMC) is used as the core, and carbon black is used as the shell. Here, the positive electrode uses a predetermined ratio of the NMC material as the core to the carbon black as the shell, and the mass ratio is in the range of 95.01:4.99 to 99.5:0.5. In addition, the electrolyte solution is set to have the characteristic of minimizing gas pores by using additives.

[0023] The present invention relates to a method for manufacturing a lithium-ion battery and includes the following steps: Step A. Mixing of materials used for manufacturing a positive electrode including a positive electrode active material, a conductive material, and a binder; here, the positive electrode active material is in the form of core-shell particles, the core is an NMC material, and carbon black is used as the shell. The manufactured positive electrode is coated on an aluminum foil. Step B. Mixing of materials used for manufacturing a negative electrode including a negative electrode active material, a highly conductive material, and a binder; depending on the type of the negative electrode, the manufactured negative electrode is coated on a copper foil. Step C. Preparation of an electrolyte solution composed of a lithium salt, a solvent, and an additive. Step D. Assembly of a lithium-ion battery using the positive electrode manufactured in Step A, the negative electrode manufactured in Step B, a polymer film as a separator, and the electrolyte solution as an ion conductor prepared in Step C.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0025] The present invention discloses a lithium-ion battery having a positive electrode containing an NMC material as a core and carbon black as a shell, and a method for manufacturing the battery as follows.

[0026] The positive electrode contains a positive electrode active material, and this positive electrode active material is formed from a lithium-containing material having a core@shell shape, and can absorb and release lithium ions. Here, the metal oxide core is lithium nickel manganese cobalt oxide (NMC material or LiNMC or NMC), and the shell has a predetermined ratio of the NMC material as the core to carbon black as the shell, and the ratio is in the range of 95.01:4.99 to 99.5:0.5 in terms of mass ratio (parts by weight), respectively. The preferred mass ratio is in the range of 98:2 to 99:1, respectively. The most preferred mass ratio is 99:1, respectively. Further, the positive electrode further contains carbon as a conductive material and contains a binder used for the positive electrode. The positive electrode has a composition ratio of NMC material core, carbon black shell (NMC@C): carbon used as a (counter) conductive material: binder of 80-99:0.5-10:0.5-10 by mass ratio (parts by weight). The best composition ratio of the above-mentioned NMC material core, carbon black shell (NMC@C), carbon used as a conductive material, and binder is 94:4:2 parts by weight respectively.

[0027] The carbon used as the conductive material can be selected from any one of carbon black, nanocarbon, graphite, or a combination thereof, and the best carbon used as the conductive material is carbon black. The binder for the positive electrode can be selected from any one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, butadiene rubber, styrene-butadiene rubber (SBR), poly(vinyl alcohol) (PVA), or polyacrylic acid, or a combination thereof, and the most preferred binder for the positive electrode is polyvinylidene fluoride (PVDF).

[0028] The negative electrode contains, depending on the form of the lithium-ion battery of the present invention, any one of graphite-type carbon, an oxide material, lithium, or a combination thereof to form the negative electrode active material. Here, the preparation of the negative electrode from either or both of graphite-type carbon or an oxide material includes carbon as a conductive material and a binder used for the negative electrode. The most preferred graphite-type carbon is artificial graphite. The carbon used as the conductive material can be selected from any one of carbon black, nanocarbon, graphite, or a combination thereof. Here, the best carbon used as the conductive material is carbon black. The binder for the negative electrode can be selected from any one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, butadiene rubber, styrene-butadiene rubber (SBR), poly(vinyl alcohol) (PVA), or polyacrylic acid, or a combination thereof. Here, the most preferred binder for the negative electrode is either or both of carboxymethyl cellulose (CMC) or styrene-butadiene rubber (SBR).

[0029] The negative electrode has a composition ratio among the compositions of graphite-type carbon or oxide material constituting the negative electrode active material, carbon used as a conductive material, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR). The composition ratios are 80 - 98.5:0.5 - 10:0.5 - 5:0.5 - 5 parts by weight, respectively. The best composition ratio is 94.5:1:2.25:2.25 parts by weight, respectively. The most preferred negative electrode active material is artificial graphite for manufacturing the negative electrode with the above configuration.

[0030] The electrolyte solution contains a lithium salt and a solvent, where: A. The lithium salt is lithium hexafluorophosphate (LiPF6) in a molar concentration range of 1.0 - 1.5; the most preferred concentration is 1.2 mol. B. The solvent can be selected from any one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), or a combination thereof. Here, the solvent ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) is 5-30:5-40:30-90 parts by weight, and the best solvent ratio is 25:5:70 parts by weight respectively. C. The additive can be selected from any one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), methylene methane disulfonate (MMDS), or a combination thereof in an amount of 0.1-12% by weight of the electrolyte solution. Here, the preferred additive is a combination of any one of fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), or methylene methane disulfonate (MMDS) additive or a combination thereof in an amount of 0.1-10% by weight of the electrolyte solution and vinylene carbonate (VC) in an amount of 2% by weight of the electrolyte solution. The most preferred additive amount is 2% vinylene carbonate (VC) combined with fluoroethylene carbonate (FEC) in an electrolyte solution of 0.1 weight percent.

[0031] As described above, the most preferred electrolyte solution consists of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), and contains 1.2 moles of lithium hexafluorophosphate in a solvent having a ratio of 25:5:70 parts by weight respectively, and contains vinylene carbonate (VC) and fluoroethylene carbonate (FEC) additives in amounts of 2 and 0.1 weight percent of the electrolyte solution respectively.

[0032] The manufacture of a lithium-ion battery having a positive electrode containing an NMC material as a core and carbon black as a shell includes the following steps.

[0033] Step A. The positive electrode is manufactured by producing a positive electrode active material using mechanofusion, with lithium manganese cobalt oxide (NMC) as the core and carbon black as the shell. In this method, the introduced energy compresses the fine particles, which adhere to each other, and then the produced positive electrode active material is mixed with carbon used as a conductive material and a binder, and the produced positive electrode is coated on an aluminum foil and dried. Step B. Depending on the negative electrode active material, the negative electrode is manufactured by two possible methods: The first method involves using a negative electrode active material that is either graphite-type carbon or an oxide material or both, and pulverizing the graphite-type carbon or oxide material using a high-energy ball mill. Then, carbon used as a conductive material, a binder, and an organic solvent are added, and the organic solvent can be selected from any of N-methyl-2-pyrrolidone, ethanol, water, or a combination thereof. Next, the produced negative electrode is coated on a copper foil and dried. The second method uses a negative electrode containing a negative electrode active material that is lithium metal in the form of a lithium metal sheet. Step C. Prepare an electrolyte solution containing lithium hexafluorophosphate (LiPF6) salts, a solvent, and additives. Step D. Assemble a lithium-ion battery using the positive electrode produced from Step A, the negative electrode produced from Step B, a polymer film as a separator, and the electrolyte solution as ion transport prepared from Step C.

[0034] From Steps A and B, the positive electrode manufactured and coated on the aluminum foil has a weight range of 17 - 23 milligrams per square centimeter (mg / cm 2 ) and a thickness range of 110 - 250 micrometers (μm). The negative electrode with the graphite-type carbon or oxide produced and coated on the copper foil as the negative electrode active material has a weight range of 10 - 15 milligrams per square centimeter and a thickness range of 100 - 250 micrometers.

[0035] In the process of manufacturing the positive electrode active material from Project A, the positive electrode contains the positive electrode active material in the form of core-shell particles (core@shell) with an NMC material (LiNMC or NMC) as the metal oxide core, together with a carbon black shell (NMC@C). Here, the ratio of the NMC material as the core to the carbon black as the shell in the material is 95.01:4.99 to 99.5:0.5 parts by weight, respectively, and the preferred ratio is 98:2 to 99:1 parts by weight, respectively. The most preferred ratio is 99:1 parts by weight, respectively. Also, the positive electrode has a ratio of the NMC material core, the carbon black shell, the carbon used as the conductive material, and the binder of 80-99:0.5-10:0.5-10 parts by weight, respectively. The best ratio of the positive electrode is 94:4:2 parts by weight, respectively. The carbon used as the conductive material can be selected from any one of carbon black, nanocarbon, or graphite, or a combination thereof. Here, the best carbon used as the conductive material is carbon black. The binder for the positive electrode can be selected from polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, butadiene rubber, styrene-butadiene rubber, poly(vinyl alcohol) (PVA), or polyacrylic acid, or a combination thereof. Here, the most preferred binder for the positive electrode is polyvinylidene fluoride (PVDF).

[0036] From Project B, the negative electrode manufacturing process of the first process using a negative electrode active material that is either graphite-type carbon or an oxide material, or both, includes carbon used as a conductive material and a binder used for the negative electrode. The most preferred negative electrode active material for graphite-type carbon is artificial graphite; the carbon used as a conductive material can be selected from any of carbon black, nanocarbon, graphite, or a combination thereof, where the best carbon used as a conductive material is carbon black; the binder for the negative electrode can be selected from any one of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, butadiene rubber, styrene-butadiene rubber (SBR), poly(vinyl alcohol) (PVA), or polyacrylic acid, or a combination thereof, where the most preferred binder for the negative electrode is either carboxymethyl cellulose (CMC) or styrene-butadiene rubber (SBR), or both. The negative electrode has a preferred composition ratio including a negative electrode active material of graphite-type carbon or an oxide material, carbon used as a conductive material, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR), and the composition ratio is 80 - 98.5:0.5 - 10:0.5 - 5:0.5 - 5 parts by weight, respectively. The best composition ratio of the negative electrode is 94.5:1:2.25:2.25 parts by weight, respectively. The most preferred negative electrode active material is artificial graphite for manufacturing the negative electrode with the above composition.

[0037] From Process C, the prepared electrolyte solution contains 1.0 to 1.5 moles of lithium hexafluorophosphate (LiPF6); a solvent that can be selected from any one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) or a combination thereof; and an additive that can be selected from any one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), and methylene methane disulfonate (MMDS) or a combination thereof, in an amount of 0.1 to 12% by weight based on the total amount of the electrolyte solution. The most preferred concentration of lithium hexafluorophosphate (LiPF6) is 1.2 moles in a mixed solvent consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a composition ratio of 5 to 30 parts by weight to 5 to 40 parts by weight to 30 to 90 parts by weight, where the best solvent ratio is 25:5:70 parts by weight. The vinylene carbonate (VC) additive is used in an amount of 2% by weight of the electrolyte solution and, when combined with other above-mentioned additives, is used in an amount of 0.1 to 10% by weight of the electrolyte solution, where the most preferred additive consists of 2% by weight of vinylene carbonate (VC) combined with 0.1% by weight of fluoroethylene carbonate (FEC) of the electrolyte solution.

Example

[0038] Examples of the manufacture of a lithium-ion battery using a positive electrode with an NMC material as the core and carbon black as the shell, and performance tests of the manufactured battery are shown below. However, the present invention is not limited to these examples.

[0039] <Example A: Invention of a Lithium-Ion Button Battery> A lithium-ion button battery was manufactured using a positive electrode active material in the form of an NMC material as the core and carbon black as the shell (LiNMC@C or NMC@C). The manufacturing process is as follows: 1) A positive electrode for a lithium-ion button battery was manufactured. A material containing an NMC material was mixed using mechanofusion for 1 to 10 minutes, then carbon black was added and stirred, and further mixed for 1 to 60 minutes. The weight ratios of the NMC material and carbon black were 98:2 and 99:1 respectively, and a positive electrode active material having an NMC material core and a carbon black shell was obtained. The obtained positive electrode active material was mixed with carbon black, which is a conductive carbon, and a polyvinylidene fluoride (PVDF) binder at a ratio of 94:4:2 parts by weight. The NMC material used was NMC622 with an organic solvent, which is an N-methyl-2-pyrrolidone solution, added thereto. 2) Using 1.2 mol of lithium hexafluorophosphate (LiPF6), in a solvent mixture containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) at a ratio of 25:5:70 parts by weight of the electrolyte solution respectively, two additives, namely vinylene carbonate (VC) and fluoroethylene carbonate (FEC), were used at 2% by weight and 0.5% by weight of the electrolyte solution respectively to prepare an electrolyte solution. 3) A lithium-ion button battery was assembled using the positive electrode manufactured as above and the prepared electrolyte solution. For the negative electrode, a polymer film separator made of lithium and polyethylene was used. A CR2032 button battery was manufactured.

[0040] The capacity of the manufactured lithium-ion button battery was tested. Here, at 3.0 to 4.2 V and 25 °C for 5 cycles each, the charge / discharge rate (C-rate) of the battery was adjusted to 0.1C to 5.0C. According to Figure 1, it was found that the battery capacity when the positive electrode active material is an NMC material without a shell is lower than that when the electrode active material is an NMC material core and a carbon black shell. Also, carbon black used in an amount of 1% as the shell, or when the weight ratio of the NMC material and carbon black is 99:1 at a C-rate of 0.1C, was found to have a higher capacity retention rate compared to when carbon black used in an amount of 2% as the shell, or when the weight ratio of the NMC material and carbon black is 99:2 at the charge / discharge rate of the battery.

[0041] When the amount of carbon black used as the shell is increased up to 2% or the weight ratio of the NMC material per carbon black is increased up to 98:2, the charge capacity decreases less from 3C or more at the C rate than when the amount of carbon black used as the shell is 1%, or when the weight ratio of the NMC material per carbon black is 99:1.

[0042] Therefore, according to the tests of this example, the NMC material core and the carbon black shell used as the positive electrode active material of the lithium-ion battery can improve the battery performance when using a positive electrode active material with a ratio of NMC material to carbon black shell of 99:1 by weight, especially at the charge / discharge rate of the battery from 0.1 to 2.0C.

[0043] <Example B: Invention of Lithium-Ion Pouch Battery> 1. The positive electrode for the lithium-ion pouch battery was manufactured using the same composition and method as in Step 1 of Example A. For the positive electrode active material having an NMC material core and a carbon black shell, a selected weight ratio of 99 parts by weight of the NMC material to 1 part by weight of carbon black was used, coated on an aluminum foil, and then dried.

[0044] 2. The negative electrode for the lithium-ion pouch battery used artificial graphite as the negative electrode active material. After pulverizing the artificial graphite using a high-energy ball mill, it was mixed with carbon black, which is conductive carbon, and two binders, styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC). The manufactured negative electrode had a ratio of artificial graphite, carbon black as conductive carbon, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) of 94.5:1:2.25:2.25, respectively. Furthermore, an organic solvent selectable from either or both of ethanol and water was added. Here, in this Example B, ethanol mixed with water at a ratio of 30:70 parts by volume was used. This was coated on a copper foil and then dried.

[0045] 3. Using 1.2 moles of lithium hexafluorophosphate (LiPF6) in a solvent mixture in which the ratios of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) are 25:5:70 parts by weight of the electrolyte solution respectively; and a first additive which is 2% by weight of vinylene carbonate (VC) of the electrolyte solution, and a second additive selected from any one of fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), methylene methane disulfonate (MMDS), or a combination thereof, an electrolyte solution was prepared.

[0046] 4. A lithium-ion pouch battery was assembled using the fabricated positive electrode in an amount of 4.17 to 23 milligrams per square centimeter, the fabricated negative electrode in an amount of 10 to 15 milligrams per square centimeter, the prepared electrolyte solution in an amount of 18 to 20% of the battery weight, and a polymer film separator made of polyethylene. Here, the capacity of the fabricated lithium-ion pouch battery was 200 milliamperes per hour (mAh).

[0047] From a lithium-ion pouch cell manufactured using a combination of two additives (the first additive was vinylene carbonate (VC)); the use of a second additive that helps minimize gas formation in the electrolyte solution during charge / discharge and contributes to minimizing potential reactions in the system was tested and examined at 2.7 to 4.2 volts and 25 °C; and using 1 wt% of the second additive in the electrolyte solution combined with 2 wt% of the first additive in the electrolyte solution, the charge / discharge rate (C-rate) of the battery was controlled at 1.0C as shown in Table 1, and it was found that the use of propane sultone (PS) as the second additive combined with vinylene carbonate (VC) as the first additive was most useful for minimizing the gas formed. In addition, comparing the amounts of the second additive, fluoroethylene carbonate (FEC), used at 0.1, 1.0, and 10 weight percent in the electrolyte solution, as shown in Table 1, it was found that the greater the amount of fluoroethylene carbonate (FEC), the less gas was formed in the electrolyte solution.

[0048] Table 1 shows the types and amounts of the second additive used in a 1.2 molar lithium hexafluorophosphate (LiPF6) electrolyte solution in a solvent mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (EC:EMC:DMC) in a ratio of 25:5:70 parts by weight, respectively, in the presence of 2 wt% of the first additive, vinylene carbonate (VC), in the electrolyte solution.

[0049]

Table 1

[0050] However, when a second additive, ethylene carbonate fluoride (FEC), was used in amounts of 0.1, 1.0, and 10 wt% of the electrolyte solution, and a first additive, vinylene carbonate (VC), was used in an amount of 2 wt% of the electrolyte solution, and the charge / discharge rate (C-rate) of the battery was controlled at 0.5C, the battery capacity performance was tested as shown in FIG. 2. It was found that when the number of cycles was large, when ethylene carbonate fluoride (FEC) was used at 1.0 and 10 wt% of the electrolyte solution, the battery capacity decreased rapidly compared to the case where ethylene carbonate fluoride (FEC) was not used. However, when ethylene carbonate fluoride (FEC) was used in a 0.1 wt% electrolyte solution, the battery capacity decreased the least compared to the cases where ethylene carbonate fluoride (FEC) was used in 1.0 wt% and 10 wt% electrolyte solutions, and was found to be better than using vinylene carbonate (VC) alone. In addition, FIG. 3 shows the results of testing the charge / discharge rate (C-rate) using an additive that combines 2% vinylene carbonate (VC) and ethylene carbonate fluoride (FEC) at 0.1 wt% of the electrolyte solution at 0.5C and 1.0C. It was found that after 400 charge / discharge cycles, the battery still had a capacity exceeding 90% of its original capacity.

[0051] Based on the above-prepared tests, it was found that each additive not only helps to minimize gas formation in the electrolyte solution but also affects other performance aspects of the battery, such as charge / discharge, conductivity, and stability during use. Therefore, the optimal type and amount of additive resulted in optimized battery performance. A lithium-ion pouch battery using the positive and negative electrode compositions provided above, and an electrolyte solution combining vinylene carbonate (VC) and ethylene carbonate fluoride (FEC) as additives at 2 and 0.1 wt% of the electrolyte solution, respectively, was found to be the lithium-ion battery with the best performance.

[0052] Best Mode for Carrying Out the Invention As described in the detailed description of the invention.

Claims

1. A lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell, the lithium-ion battery includes a positive electrode, a negative electrode, a polymer film separator, and an electrolyte solution, the positive electrode contains LiNMC or NMC that forms a metal oxide core having a carbon black shell (NMC@C), that is, a metal oxide core with a carbon black shell (NMC@C), the most preferable mass ratio of the LiNMC or NMC core to the carbon black shell in the positive electrode active material ranges from 98:2 to 99:1, and preferably is 99:1, the positive electrode further contains a binder and carbon as a conductive material, a lithium-ion battery.

2. the mass ratio of the LiNMC or NMC core having a carbon black shell (NMC@C), a carbon conductive material, and a binder in the positive electrode is 80-99:0.5-10:0.5-10 respectively, A lithium-ion battery according to Claim 1, having a positive electrode with an NMC material as the core and carbon black as the shell.

3. the most preferable mass ratio of the NMC material core having a carbon black shell (NMC@C), a carbon conductive material, and a binder in the positive electrode is 94:4:2 respectively, A lithium-ion battery according to Claim 1 or 2, having a positive electrode with an NMC material as the core and carbon black as the shell.

4. the most preferable binder for the negative electrode is carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), or a combination thereof, A lithium-ion battery according to Claim 1, having a positive electrode with an NMC material as the core and carbon black as the shell.

5. the negative electrode contains a negative electrode active material, and the negative electrode active material is selected from any one of graphite-type carbon, oxide, lithium, or a combination thereof, the negative electrode, which is any one of graphite-type carbon, oxide, or a combination thereof and most preferably artificial graphite, contains a carbon conductive material, and the carbon conductive material is selected from any one or more of carbon black, nanocarbon, graphite, or a combination thereof. The binders for the positive and negative electrodes are selected from any one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, butadiene rubber, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyacrylic acid, or combinations thereof. Preferably, for the negative electrode, the mass ratio of graphite-type carbon or oxide, carbon conductive material, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) is 94.5 to 98.5: 0.5 to 10: 0.5 to 5: 0.5 to 5, respectively. The lithium-ion battery according to claim 1, comprising a positive electrode having an NMC material as a core and carbon black as a shell.

6. Most preferably, for the negative electrode, the mass ratio of graphite-type carbon or oxide, carbon conductive material, carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) is 94.5: 1: 2.25: 2.25, respectively. The lithium-ion battery according to claim 1 or 5, comprising a positive electrode having an NMC material as a core and carbon black as a shell.

7. The electrolyte solution contains a lithium salt, a solvent, and an additive. Here, A. The lithium salt is lithium hexafluorophosphate (LiPF ６ ) having a concentration in the range of 1.0 to 1.5 moles, B. The solvent is selected from any one or more of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or combinations thereof. C. The additive is in an amount of 0.1 to 12% by mass of the electrolyte solution and is selected from any one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO ２ F ２ ), methylene methanedisulfonate (MMDS), or a combination thereof. The lithium-ion battery according to claim 1, comprising a positive electrode having an NMC material as a core and carbon black as a shell.

8. The mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in the solvent is 5 to 30: 5 to 40: 30 to 90, respectively. The lithium-ion battery according to claim 7, comprising a positive electrode having an NMC material as a core and carbon black as a shell.

9. Most preferably, the mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in the solvent is 25: 5: 70, respectively. The lithium-ion battery according to claim 7 or 8, comprising a positive electrode having an NMC material as a core and carbon black as a shell.

10. The additive preferably includes vinylene carbonate (VC) in an amount of 2% by mass of the electrolyte solution, and any one or more of fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO ２ F ２ ), methylene methanedisulfonate (MMDS), or a combination thereof, in an amount of 0.1 to 10% by mass of the electrolyte solution, The lithium-ion battery according to claim 7, comprising a positive electrode having an NMC material as a core and carbon black as a shell.

11. The most preferred additives are vinylene carbonate (VC) and fluoroethylene carbonate (FEC), each containing 2% by mass and 0.1% by mass of the electrolyte solution, respectively. The lithium-ion battery according to claim 7 or 10, having a positive electrode with an NMC material as the core and carbon black as the shell.

12. The most preferred electrolyte solution has a mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of 25:5:70, respectively, contains 1.2 molar concentration of lithium hexafluorophosphate, and contains vinylene carbonate (VC) and fluoroethylene carbonate (FEC) at 2% by mass and 0.1% by mass of the electrolyte solution, respectively. The lithium-ion battery according to claim 1 or 7, having a positive electrode with an NMC material as the core and carbon black as the shell.

13. A method for manufacturing a lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell, Step A. Using the mechanofusion method, a positive electrode active material is produced from a mixture of an NMC material core and a carbon black shell to manufacture a positive electrode. A carbon conductive material and a binder are mixed with the positive electrode active material, and the manufactured positive electrode is coated on an aluminum plate and fired and dried. Step B. Manufacturing a negative electrode; Step C. Prepare an electrolyte solution containing a lithium salt, namely, lithium hexafluorophosphate (LiPF ６ ), a solvent, and an additive; Step D. Assembling a lithium-ion battery using the positive electrode manufactured in Step A and the negative electrode manufactured in Step B, using a polymer film as the electrode separator and the electrolyte solution prepared in Step C as the ion conductor; including Step B. can be performed by either of two processes, the first and the second, depending on the type of the negative electrode active material. The first process is the case where the negative electrode uses any one of graphite-type carbon, an oxide, or a combination thereof as the negative electrode active material. A step of pulverizing graphite-type carbon or an oxide with a high-energy ball mill; A step of adding a carbon conductive material, a binder, and an organic solvent, where the organic solvent is selected from any one or more of N-methyl-2-pyrrolidone, ethanol, water, or a combination thereof; A step of coating the manufactured negative electrode on a copper plate and firing and drying it for drying; including The second process is a method using a negative electrode in which the negative electrode active material is lithium metal in the form of a lithium metal sheet.

14. The method for manufacturing a lithium-ion battery according to claim 13, wherein the negative electrode active material is preferably graphite-type carbon, and the positive electrode has an NMC material as a core and carbon black as a shell.

15. The method for manufacturing a lithium-ion battery according to claim 13 or 14, wherein the most preferred graphite-type carbon of the negative electrode active material is artificial graphite, and the positive electrode has an NMC material as a core and carbon black as a shell.

16. The positive electrode contains an NMC material (LiNMC or NMC) that forms a positive electrode active material in the form of a metal oxide core having a shell (core@shell), that is, a metal oxide core having a carbon black shell (NMC@C). The mass ratio of the NMC material core to the carbon black shell is in the range of 95.01:4.99 to 99.5:0.

5. The positive electrode further contains a carbon conductive material and a binder. The method for manufacturing a lithium-ion battery according to claim 13, wherein the positive electrode has an NMC material as a core and carbon black as a shell.

17. The method for manufacturing a lithium-ion battery according to claim 13 or 17, wherein the carbon conductive material is selected from any one or more of carbon black, nanocarbon, graphite, or a combination thereof, and the positive electrode has an NMC material as a core and carbon black as a shell.

18. The method for manufacturing a lithium-ion battery according to any one of claims 13, 16, and 17, wherein the most preferred carbon conductive material is carbon black, and the positive electrode has an NMC material as a core and carbon black as a shell.

19. The binder for the positive electrode and the negative electrode is selected from any one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, butadiene rubber, styrene-butadiene rubber (SBR), poly(vinyl alcohol) (PVA), polyacrylic acid, or a combination thereof. The method for manufacturing a lithium-ion battery according to claim 13 or 16, wherein the positive electrode has an NMC material as a core and carbon black as a shell.

20. The method for manufacturing a lithium-ion battery according to any one of claims 13, 16, and 19, wherein the most preferred binder for the positive electrode is polyvinylidene fluoride (PVDF), and the positive electrode has an NMC material as a core and carbon black as a shell.

21. The manufacturing method of a lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell according to claim 13 or 16, wherein the most preferable mass ratio of the NMC material core to the carbon black shell is in the range of 98:2 to 99:

1.

22. The manufacturing method of a lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell according to any one of claims 13, 16, and 21, wherein the most preferable mass ratio of the NMC material core to the carbon black shell is 99:

1.

23. The manufacturing method of a lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell according to any one of claims 13, 16, 21, and 22, wherein the mass ratio of the NMC material core having a carbon black shell (NMC@C), a carbon conductive material, and a binder is 80 to 99:0.5 to 10:0.5 to 10, respectively.

24. The manufacturing method of a lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell according to any one of claims 13, 16, 21 to 33, wherein the most preferable mass ratio of the NMC material core and carbon black shell (NMC@C), a carbon conductive material, and a binder is 94:4:2, respectively.

25. The manufacturing method of a lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell according to any one of claims 13, 16, 19 to 20, 23, and 24, wherein the most preferable binder for the negative electrode is any one of carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), or a combination thereof.

26. The manufacturing method of a lithium-ion battery having a positive electrode with an NMC material as the core and carbon black as the shell according to any one of claims 13 to 15 and 25, wherein the mass ratio of the negative electrode active material composition which is graphite-type carbon or an oxide, a carbon conductive material, carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR) is 80 to 98.5:0.5 to 10:0.5 to 5:0.5 to 5, respectively.

27. The negative electrode is a negative electrode active material that is graphite-type carbon or an oxide, a carbon conductive material, carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR), and the most preferable mass ratio thereof is 94.5:1:2.25:2.25, respectively. The method for manufacturing a lithium-ion battery according to any one of claims 13 to 15 and 26, having a positive electrode with an NMC material as a core and carbon black as a shell.

28. The electrolyte solution contains a lithium salt, a solvent, and an additive. Here, A. The lithium salt is lithium hexafluorophosphate (LiPF ６ ) having a lithium molar concentration of 1.0 to 1.5; B. The solvent is selected from any one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or a combination thereof; C. The additive is in an amount of 0.1 to 12% by mass of the electrolyte solution and is selected from any one of vinylene carbonate (VC), fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO ２ F ２ ), methylene methanedisulfonate (MMDS), or a combination thereof, The method for manufacturing a lithium-ion battery according to claim 13, having a positive electrode with an NMC material as a core and carbon black as a shell.

29. The composition ratio of the ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in the solvent is 5 to 30:5 to 40:30 to 90 parts with respect to the mass of the electrolyte solution. The method for manufacturing a lithium-ion battery according to claim 13 or 28, having a positive electrode with an NMC material as a core and carbon black as a shell.

30. The composition ratio of the ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in the solvent is 25:5:70 parts with respect to the mass of the electrolyte solution. The method for manufacturing a lithium-ion battery according to any one of claims 13, 28, and 29, having a positive electrode with an NMC material as a core and carbon black as a shell.

31. The additive preferably includes vinylene carbonate (VC) in an amount of 2% by mass of the electrolyte solution, and at least one of fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO ２ F ２ ), methylene methanedisulfonate (MMDS), or a combination thereof, and relates to a method for manufacturing a lithium-ion battery having a positive electrode with an NMC material as a core and carbon black as a shell according to claim 13 or 28.

32. The most preferable additives are vinylene carbonate (VC) and fluoroethylene carbonate (FEC), each contained in an amount of 2% by mass and 0.1% by mass of the electrolyte solution, respectively. The method for manufacturing a lithium-ion battery according to any one of claims 13, 28, and 31, having a positive electrode with an NMC material as a core and carbon black as a shell.

33. The most preferred electrolyte solution contains ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a mass ratio of 25:5:70, 1.2 molar concentration of lithium hexafluorophosphate, and vinylene carbonate (VC) and fluoroethylene carbonate (FEC) in amounts of 2% by mass and 0.1% by mass of the electrolyte solution, respectively. A method for manufacturing a lithium-ion battery having a positive electrode with an NMC material as a core and carbon black as a shell according to claim 13 or 28.

34. The positive electrode manufactured and coated on the aluminum plate has a positive electrode mass in the range of 17 to 23 mg / cm ２ The method for manufacturing a lithium-ion battery according to claim 13, having a positive electrode with an NMC material as a core and carbon black as a shell, wherein the range is from 110 to 250 μm in thickness.

35. The negative electrode is manufactured and coated on a copper plate and has a negative electrode active material that is graphite-type carbon or an oxide, and the mass of the negative electrode is in the range of 10 to 15 mg / cm ２ The method for manufacturing a lithium-ion battery according to claim 13, which has a positive electrode with an NMC material as a core and carbon black as a shell, wherein the negative electrode is in the range of 100 to 250 μm in thickness.

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