Lithium-ion battery having a cathode containing NMC material as the core and carbon black as the 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 electrical 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 a 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 lithium-containing materials such as lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), and lithium iron phosphate (LiFePO4). Lithium cobalt oxide (LiCoO2) was the first positive electrode active material used in the manufacture of lithium-ion batteries, but its safety is low. Lithium manganese oxide (LiMn2O4) has high thermal stability and safety, but its cycle life is short. Lithium iron phosphate (LiFePO4) has high safety, is small, highly stable, and has a high cycle life, but its energy density is lower compared to other types of lithium batteries. Furthermore, there is lithium nickel manganese cobalt oxide (NMC material, or LiNMC or NMC) which contains nickel, manganese, and cobalt in different elemental ratios. For example, NMC111 is a LiNMC containing nickel, manganese, and cobalt in a 1:1:1 ratio, or NMC811 contains nickel, manganese, and cobalt in an 8:1:1 ratio. The above LiNMCs utilize the excellent properties of nickel, manganese, and cobalt. For example, nickel has a 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, making it suitable for applications requiring high battery capacity and low heat generation, such as electric vehicles.

[0005] However, in order to improve the electrical conductivity of the positive electrode, the positive electrode active material consists of an NMC material formed with a metal oxide core, and the shell (core-shell particles) is designed to increase the energy from the electrolyte adsorption surface and promote increased electrical conductivity, which can affect the performance and lifespan of the battery. This type of invention has been disclosed in various patent documents.

[0006] For example, Patent Document 1 discloses an invention relating to a positive electrode having a positive electrode active material in which an NMC material is used as the core and carbon nanotubes are used as the shell, the proportion of the carbon nanotube shell being 0.01 to 5% by weight of the NMC material core, and the particle size of the NMC material core being 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 (milliampere-hours / gram), and a capacity retention rate of 90% after 100 charge cycles.

[0007] Patent Document 2 discloses the manufacture of a cathode containing an NMC material as a core, and a carbon shell containing nano-sized magnesium oxide or aluminum oxide.

[0008] Patent Document 3 discloses an invention for a positive electrode of a lithium-ion battery in a form comprising 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 NMC material core and graphene shell used to the 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 a variety of 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, which is carbon such as graphite or nanocarbon, or a lithium-containing material. In the manufacture of the negative electrode, the negative electrode active material can be combined with conductive materials and binders to improve the performance of the negative electrode.

[0010] The aforementioned electrolyte solution contains lithium salts; typical examples of such lithium salts include lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), and lithium bis(fluorosulfonyl)imide (LiFSI). These lithium salts are dissolved in organic solutions such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and propylene carbonate (PC). In addition, there is a separator that keeps the positive and negative electrodes apart to avoid contact; this separator is typically made of polymers such as polyethylene (PE) or polypropylene (PP). Inventions relating to lithium-ion batteries using positive electrodes, negative electrodes, and electrolyte solutions are disclosed in various patent documents.

[0011] For example, Patent Document 4 discloses a battery having a positive electrode using an NMC111 material as the positive electrode active material, which is a combination of conductive carbon and a polyvinylidene fluoride (PVDF) type binder, and a negative electrode using an artificial graphite material as the negative electrode active material, which is a combination of styrene-butadiene rubber (SBR) and carboxymethylcellulose (CMC). The electrolyte solution is used when the lithium salts are lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium tetrafluoroborate (LiBF4), in a ratio of 1 mole to 0.01 to 1.2 moles to 0.05 to 0.7 moles, respectively. In addition, 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 propanesultone (PS) additives are present in 1 to 10 weight percent of the electrolyte solution.

[0012] Patent Document 5 discloses the use of artificial graphite as a negative electrode active material, and Patent Document 6 discloses the use of artificial graphite as a negative electrode holding material, but also discloses surface improvement by nitrogen atom addition. Patent Document 7 discloses the manufacture of a battery having a positive electrode containing NMC material; a negative electrode containing graphite coated with amorphous carbon; an electrolyte solution of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium hexafluorophosphate (LiPF6) 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, which contains a study titled "Scalable Core-Shell Ni-Rich NMC Nanocarbon Cathode from Solvent-Free Mechanofusion for High-Performance 18650 Li-Ion Batteries." This study describes the production of a cathode active material having a structure with an NMC material using NMC811 material as the core and a nanocarbon shell, with the ratio of NMC material to nanocarbon being 90:10 by weight percent. The nanocarbon used was of the carbon black type that passed through mechanofusion to form a structure containing NMC material as the core and nanocarbon as the shell. In addition, carbon black was used as the conductive material, and polyvinylidene fluoride (PVDF) was used as the binder for manufacturing the battery cathode. The aforementioned battery was manufactured as 18,650 cylindrical cells using NMC material as a core containing a nanocarbon shell, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) in a ratio of 946:24:3 parts by weight, respectively. The electrolyte solution used consisted of 10 moles of lithium hexafluorophosphate (LiPF6) in a solvent of ethylene carbonate (EC) combined with dimethyl carbonate (DMC) in a ratio of 1:1 parts by volume, respectively. The negative electrode consisted of a graphite-type negative electrode active material, carbon black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder, in a ratio of 96.6:1.7:1.7 parts by weight, respectively. Furthermore, an invention of a button cell has been disclosed in which lithium is used as the negative electrode, and the positive electrode contains NMC material as the core, nanocarbon as the shell, carbon black as the conductive material, and polyvinylidene fluoride, each in a ratio of 80:10:10 parts by weight.

[0014] In addition to the foreign patent documents mentioned above, there is a patent document filed in Thailand disclosing an invention related to lithium-ion batteries.

[0015] For example, Patent Document 8 discloses an invention relating to a positive electrode for a lithium-sulfur battery in the form of a core and shell structure, using sulfur as the core and nanocarbon as the shell in a ratio of 95:5 parts by weight, using mechanofusion to form the materials into a core and shell structure, and disclosing 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 parts by weight, respectively.

[0016] Patent Document 9 discloses an electrode made of NMC material as the positive electrode active material, and shows 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 parts by weight, respectively. Patent Document 10 discloses a positive electrode for a lithium-ion battery having a core and shell structure, using lithium polysulfide as the core and nanocarbon as the shell in a ratio of 95:5 parts by weight, and showing 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 parts by weight, respectively.

[0017] Patent Document 11 discloses a positive electrode for a lithium-ion battery having a positive electrode active material in which lithium nickel aluminum oxide is used as the core and nanocarbon is used as the shell, in a ratio of 70-95:5-30 parts by weight, respectively.

[0018] Patent document 12 discloses a method for manufacturing an electrode for a lithium-ion battery in which the positive electrode contains a lithium metal silicate mixed with a carbon-type conductive material such as polyvinylidene fluoride (PVDF) and a binder. The resulting mixture is coated onto aluminum foil, and the resulting 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 (increasing capacity, thermal stability, weight, and safety) is still needed in the industry. Therefore, the inventor has 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 property 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]This graph shows the capacity of button batteries at various battery charge / discharge rates (C-rates). [Figure 2] This graph shows the capacity retention rate (percentage) when using pouch batteries with an electrolyte solution additive consisting of 2% by weight of vinylene carbonate (VC) and 0-10% by weight of fluoroethylene carbonate (FEC). [Figure 3] This graph shows the capacity retention rate (percentage) at battery charge / discharge rates (C-rates) of 0.5C and 1.0C when using pouch batteries with an electrolyte solution additive of 2% by weight of vinylene carbonate (VC) and 0.1% by weight of fluoroethylene carbonate (FEC). [Modes for carrying out the invention]

[0025] This invention discloses a lithium-ion battery having a positive electrode containing 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, which is formed from a lithium-containing material in the shape of core-shell particles and is capable of absorbing and releasing lithium ions, where the metal oxide core is lithium nickel manganese cobalt oxide (NMC material or LiNMC or NMC), and the shell has a predetermined ratio of NMC material as the core to carbon black as the shell, with the ratios being in the range of 95.01:4.99 to 99.5:0.5 by mass (parts by weight). Preferred mass ratios are in the range of 98:2 to 99:1, respectively. The most preferred mass ratio is 99:1. Furthermore, the positive electrode further contains carbon as a conductive material and includes a binder used in the positive electrode, and the composition ratio of the NMC material core and carbon black shell (NMC@C) to the carbon used as a conductive material and the binder is 80-99:0.5-10:0.5-10 in mass ratio (parts by weight). The best composition ratio of the NMC material core and carbon black shell (NMC@C) to the carbon used as a conductive material and the binder is 94:4:2 parts by weight, respectively.

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

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

[0029] The anode has a composition ratio among the following materials that constitute the anode active material: graphite-type carbon or oxide material, carbon used as a conductive material, carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR), with the composition ratio being 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 anode active material is artificial graphite for manufacturing the anode having the above configuration.

[0030] The electrolyte solution comprises a lithium salt and a solvent, where: A. The lithium salt is lithium hexafluorophosphate (LiPF6) in a concentration range of 1.0 to 1.5 molars; the most preferred concentration is 1.2 molars. B. The solvent can be selected from one of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), or a combination thereof, where 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 disulfate (MMDS), or a combination thereof, in an amount of 0.1 to 12% by weight of the electrolyte solution, where the preferred additive is vinylene carbonate (VC) in an amount of 2% by weight of the electrolyte solution, combined with any one of the following additives: fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), or methylene methane disulfate (MMDS), or a combination thereof, in an amount of 0.1 to 10% by weight of the electrolyte solution. The most preferred amount of additive is 2% vinylene carbonate (VC) in combination with fluoroethylene carbonate (FEC) in a 0.1% by weight electrolyte solution.

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

[0032] The manufacturing of a lithium-ion battery having a cathode containing NMC material as the core and carbon black as the shell includes the following steps:

[0033] Step A. The positive electrode is manufactured by using lithium manganese cobalt oxide (NMC) as the core and carbon black as the shell, and producing the positive electrode active material using mechanofusion. In this method, the introduced energy compresses the fine particles, causing them to adhere to each other. After the positive electrode active material is mixed with carbon and a binder used as a conductive material, the manufactured positive electrode is coated onto aluminum foil and dried. Step B. Depending on the negative electrode active material, the negative electrode is manufactured using two feasible methods: The first method involves using a negative electrode active material which is either graphite-type carbon or an oxide material, or both, and grinding the graphite-type carbon or oxide material using a high-energy ball mill. Subsequently, carbon to be used as a conductive material, a binder, and an organic solvent are added, the organic solvent can be selected from N-methyl-2-pyrrolidone, ethanol, water, or a combination thereof, and then the manufactured negative electrode is coated onto copper foil and dried. The second method uses a negative electrode containing a negative electrode active material which 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 an additive. Step D: The lithium-ion battery is assembled 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 transporter prepared in Step C.

[0034] From processes A and B, the positive electrode manufactured and coated on aluminum foil has a viscosity of 17-23 milligrams / square centimeter (mg / cm²). 2 The negative electrode has a weight range of 10 to 15 milligrams / cm² and a thickness range of 110 to 250 micrometers (μm). The negative electrode, which is a graphite-type carbon or oxide manufactured and coated on the copper foil, has a weight range of 10 to 15 milligrams / cm² and a thickness range of 100 to 250 micrometers.

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

[0036] From step B, the negative electrode manufacturing step of the first process using a negative electrode active material which 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 of graphite-type carbon is artificial graphite; the carbon used as a conductive material can be selected from 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 polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), sodium carboxymethylcellulose, 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 carboxymethylcellulose (CMC) or styrene-butadiene rubber (SBR), or both. The anode has a preferred composition ratio comprising a graphite-type carbon or oxide material anode active material, carbon used as a conductive material, carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR), with the respective composition ratios being 80-98.5:0.5-10:0.5-5:0.5-5 parts by weight. The best anode composition ratio is 94.5:1:2.25:2.25 parts by weight. The most preferred anode active material is artificial graphite for manufacturing the anode of the above composition.

[0037] From step C, the prepared electrolyte solution contains 1.0 to 1.5 moles of lithium hexafluorophosphate (LiPF6); a solvent which may be selected from one or a combination thereof of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC); and an additive which may be selected from one or a combination thereof of vinylene carbonate (VC), fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), and methylene methane disulfonate (MMDS), in an amount of 0.1 to 12% by weight relative to the total amount of the electrolyte solution. The most preferred lithium hexafluorophosphate (LiPF6) concentration 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 5-30 parts by weight, 5-40 parts by weight, and 30-90 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, or in an amount of 0.1-10% by weight of the electrolyte solution when combined with the other additives mentioned above, where the most preferred additive is 2% by weight of vinylene carbonate (VC) combined with 0.1% by weight of fluoroethylene carbonate (FEC) in the electrolyte solution. [Examples]

[0038] The following describes manufacturing examples of lithium-ion batteries using NMC material as the core and carbon black as the shell for the cathode, and performance tests of the manufactured batteries. However, the present invention is not limited to these examples.

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

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

[0041] It was found that increasing the amount of carbon black used as the shell to 2%, or increasing the weight ratio of NMC material to carbon black to 98:2, resulted in a decrease in the charging capacity from 3C or higher in C-rate compared to when the amount of carbon black used as the shell was 1%, or when the weight ratio of NMC material to carbon black was 99:1.

[0042] Therefore, according to the tests of this embodiment, it has been shown that NMC material cores and carbon black shells used as positive electrode active materials for lithium-ion batteries improve battery performance, especially at battery charge / discharge rates of 0.1 to 2.0 C, when using a positive electrode active material with a ratio of NMC material to carbon black shell of 99:1 parts by weight.

[0043] <Example B: Invention of a 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, with a positive electrode active material having an NMC material core and a carbon black shell, using a selected weight ratio of NMC material to carbon black, namely 99 parts by weight to 1 part by weight, coated onto aluminum foil, and then dried.

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

[0045] 3. An electrolyte solution was prepared using 1.2 moles of lithium hexafluorophosphate (LiPF6) in a solvent mixture in which ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were each in a ratio of 25:5:70 parts by weight of the electrolyte solution; and a combination of a first additive, vinylene carbonate (VC) in a ratio of 2% by weight of the electrolyte solution, and a second additive, which could be selected from fluoroethylene carbonate (FEC), propane sultone (PS), lithium difluorophosphate (LiPO2F2), methylene methane disulfate (MMDS), or a combination thereof.

[0046] Lithium-ion pouch batteries were assembled using a manufactured positive electrode in an amount of 4.17–23 milligrams / cm², a manufactured negative electrode in an amount of 10–15 milligrams / cm², a prepared electrolyte solution in an amount of 18–20% of the battery weight, and a polyethylene polymer film separator. The capacity of the manufactured lithium-ion pouch batteries was 200 milliampere-hours (mAh).

[0047] From lithium-ion pouch batteries manufactured using a combination of two additives (the first additive being vinylene carbonate (VC)); the use of a second additive was tested and investigated at 2.7–4.2 volts and 25°C to help minimize gas formation in the electrolyte solution during charging / discharging and to contribute to minimizing potential reactions in the system; and it was found that the use of a second additive, propanesultone (PS), combined with a first additive, was most effective in minimizing formed gases, when the battery's charge / discharge rate (C-rate) was controlled to 1.0C using a second additive, 1% by weight of the second additive, combined with a first additive, vinylene carbonate (VC). In addition, when comparing the amounts of the second additive, fluoroethylene carbonate (FEC), used in 0.1, 1.0, and 10 weight percent of the electrolyte solution, it was found that the more fluoroethylene carbonate (FEC) used, the less gas was formed in the electrolyte solution, as shown in Table 1.

[0048] Table 1 shows the type and amount of the second additive used in 1.2 moles of 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 a first additive, vinylene carbonate (VC), which is 2% by weight of the electrolyte solution.

[0049] [Table 1]

[0050] However, when the second additive, fluoroethylene carbonate (FEC), was used in amounts of 0.1, 1.0, and 10% by weight of the electrolyte solution, and the first additive, vinylene carbonate (VC), was used in amounts of 2% by weight of the electrolyte solution, and the battery capacity performance was tested when the battery charge / discharge rate (C-rate) was controlled at 0.5C, as shown in Figure 2, it was found that, when the number of cycles was high, the battery capacity decreased rapidly when fluoroethylene carbonate (FEC) was used in amounts of 1.0 and 10% by weight of the electrolyte solution compared to when fluoroethylene carbonate (FEC) was not used. However, the battery capacity decreased least when fluoroethylene carbonate (FEC) was used in a 0.1% by weight electrolyte solution compared to when fluoroethylene carbonate (FEC) was used in 1.0% and 10% by weight electrolyte solutions, and was found to be better than when vinylene carbonate (VC) was used alone. In addition, Figure 3 shows the results of testing the charge / discharge rate (C-rate) at 0.5C and 1.0C using an additive combining 2% vinylene carbonate (VC) and 0.1% by weight of fluoroethylene carbonate (FEC) in the electrolyte solution. After 400 charge / discharge cycles, the battery was found to still have more than 90% of its original capacity.

[0051] Based on the tests prepared above, it was found that each additive not only helps minimize gas formation in the electrolyte solution but also affects other aspects of the battery's performance, such as charge / discharge, conductivity, and stability for use. Therefore, the optimal type and amount of additive resulted in optimized battery performance. It was found that lithium-ion pouch batteries using the positive and negative electrode compositions provided above, as well as electrolyte solutions combining vinylene carbonate (VC) and fluoroethylene carbonate (FEC) as additives in amounts of 2% and 0.1% by weight, respectively, were lithium-ion batteries with the best performance.

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

Claims

1. A lithium-ion battery having a core made of NMC material and a positive electrode having a carbon black shell, The lithium-ion battery comprises a positive electrode, a negative electrode, a polymer film separator, and an electrolyte solution. The positive electrode includes a positive electrode active material in the form of a core-shell metal oxide, i.e., LiNMC or NMC that forms a metal oxide core having a carbon black shell. The mass ratio of LiNMC or NMC core to carbon black shell in the positive electrode active material is in the range of 98:2 to 99:

1. The positive electrode further comprises carbon as a binder and conductive material. Lithium-ion battery.

2. The positive electrode has a mass ratio of 80-99:0.5-10:0.5-10 between a LiNMC or NMC core having a carbon black shell, a carbon conductive material, and a binder. 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 positive electrode comprises an NMC material core having a carbon black shell, a carbon conductive material, and a binder, with the most preferred mass ratio of each being 94:4:

2. 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 preferred binder for the negative electrode is carboxymethylcellulose (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 includes a negative electrode active material, which is selected from graphite-type carbon, oxide, lithium, or a combination thereof. The negative electrode, which is one of graphite-type carbon, an oxide, or a combination thereof, comprises a carbon conductive material, which is selected from one or more of carbon black, nanocarbon, graphite, or a combination thereof. The binders for the positive and negative electrodes are selected from one or more of the following: polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), sodium carboxymethylcellulose, butadiene rubber, styrene-butadiene rubber (SBR), polyvinyl alcohol (PVA), polyacrylic acid, or a combination thereof. The negative electrode has a mass ratio of graphite-type carbon or oxide, carbon conductive material, carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR) of 94.5 to 98.5:0.5 to 10:0.5 to 5:0.5 to 5, 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.

6. The most preferred mass ratio of the negative electrode to graphite-type carbon or oxide, carbon conductive material, carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR) is 94.5:1:2.25:2.25, respectively. A lithium-ion battery according to claim 1 or 5, having a positive electrode with an NMC material core and a carbon black shell.

7. The electrolyte solution comprises a lithium salt, a solvent, and an additive. Here, A. The lithium salt is lithium hexafluorophosphate (LiPF) having a concentration in the range of 1.0 to 1.5 moles. ６ ) and B. The solvent is selected from one or more of the following: ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), or a combination thereof. C. The additive is present in an amount of 0.1 to 12% by mass of the electrolyte solution and contains vinylene carbonate (VC), fluoroethylene carbonate (FEC), propanesultone (PS), and lithium difluorophosphate (LiPO). ２ F ２ ), methylene methane disulfonate (MMDS), or one or more combinations 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.

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

9. The solvent is characterized by a most preferred mass ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of 25:5:70, respectively. A lithium-ion battery according to claim 7 or 8, having a positive electrode with an NMC material core and a carbon black shell.

10. The aforementioned additives consist of vinylene carbonate (VC) in an amount of 2% by mass of the electrolyte solution, and fluoroethylene carbonate (FEC), propane sultone (PS), and lithium difluorophosphate (LiPO) in an amount of 0.1 to 10% by mass of the electrolyte solution. ２ F ２ ), methylene methane disulfonate (MMDS), or one or more combinations thereof, A lithium-ion battery according to claim 7, having a positive electrode with an NMC material as the core and carbon black as the shell.

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

12. The most preferred electrolyte solution contains lithium hexafluorophosphate at a mass concentration of 1.2 molars, with ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a mass ratio of 25:5:70, respectively, and also contains vinylene carbonate (VC) and fluoroethylene carbonate (FEC) at 2% by mass and 0.1% by mass, respectively, of the electrolyte solution. A lithium-ion battery according to claim 1 or 7, having a positive electrode with an NMC material core and a carbon black 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 a mechanofusion method, a positive electrode active material is prepared 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. The manufactured positive electrode is then coated onto an aluminum plate and fired to dry it. Process B. Manufacturing the negative electrode; Step C. Lithium salt, i.e., lithium hexafluorophosphate (LiPF) ６ Prepare an electrolyte solution containing a solvent and additives; Step D. A lithium-ion battery is assembled using the positive electrode manufactured in Step A and the negative electrode manufactured in Step B, with a polymer film used as the electrode separator and the electrolyte solution prepared in Step C as the ion conductor; Includes, Step B can be carried out by either a first or second process, depending on the type of negative electrode active material. The first process described above is the case in which the negative electrode uses either graphite-type carbon, an oxide, or a combination thereof as the negative electrode active material. A process of grinding graphite-type carbon or oxides using a high-energy ball mill; A step of adding a carbon conductive material, a binder, and an organic solvent, wherein the organic solvent is selected from one or more of N-methyl-2-pyrrolidone, ethanol, water, or a combination thereof; The process involves applying the manufactured negative electrode to a copper plate and then firing it to dry it; Includes, The second process is a method that uses a negative electrode in which the negative electrode active material is lithium metal in the form of a lithium metal sheet.

14. A 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. 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, according to claim 13 or 14, wherein the most preferred negative electrode active material, graphite-type carbon, is artificial graphite.

16. The positive electrode comprises a positive electrode active material in the form of a metal oxide core having a shell, i.e., an NMC material (LiNMC or NMC) that forms a metal oxide core having a carbon black shell. 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 comprises a carbon conductive material and a binder. A method for manufacturing a lithium-ion battery according to claim 13, having a positive electrode with an NMC material as the core and carbon black as the shell.

17. A method for manufacturing a lithium-ion battery having an NMC material as a core and a carbon black as a shell as a positive electrode, according to claim 13 or 16, wherein the carbon conductive material is selected from one or more of the following: carbon black, nanocarbon, graphite, or a combination thereof.

18. 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, according to any one of claims 13, 16, and 17, wherein the most preferred carbon conductive material is carbon black.

19. The binders for the positive and negative electrodes are polyvinylidene fluoride (PVDF), carboxymethylcellulose (CMC), sodium carboxymethylcellulose, butadiene rubber, A method for manufacturing a lithium-ion battery having a positive electrode having an NMC material as the core and a carbon black as the shell, selected from one or more of the following: styrene-butadiene rubber (SBR), poly(vinyl alcohol) (PVA), polyacrylic acid, or a combination thereof.

20. 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, according to any one of claims 13, 16, and 19, wherein the most preferred binder for the positive electrode is polyvinylidene fluoride (PVDF).

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

1.

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

1.

23. A method for manufacturing a lithium-ion battery having a positive electrode with an NMC material core and a carbon black shell, according to any one of claims 13, 16, 21, and 22, wherein the positive electrode has a mass ratio of 80 to 99:0.5 to 10:0.5 to 10 between an NMC material core having a carbon black shell, a carbon conductive material, and a binder.

24. A method for manufacturing a lithium-ion battery having a positive electrode with an NMC material core and a carbon black shell, according to any one of claims 13, 16, 21 to 23, wherein the most preferred mass ratio of the positive electrode to the NMC material core and carbon black shell, the carbon conductive material and the binder is 94:4:2, respectively.

25. 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, according to any one of claims 13, 16, 19-20, 23, and 24, wherein the most preferred binder for the negative electrode is carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), or a combination thereof.

26. 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, according to any one of claims 13 to 15 and 25, wherein the negative electrode has a negative electrode active material composition of graphite-type carbon or oxide, a carbon conductive material, carboxymethylcellulose (CMC), and styrene-butadiene rubber (SBR), the mass ratio of these is 80 to 98.5:0.5 to 10:0.5 to 5:0.5 to 5, respectively.

27. 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, according to any one of claims 13 to 15 and 26, wherein the most preferred mass ratio of the negative electrode to the negative electrode active material which is graphite-type carbon or oxide, the carbon conductive material, the carboxymethylcellulose (CMC), and the styrene-butadiene rubber (SBR) is 94.5:1:2.25:2.25, respectively.

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

29. 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, according to claim 13 or 28, wherein the solvent has a composition ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of 5 to 30:5 to 40:30 to 90 parts with respect to the mass of the electrolyte solution.

30. 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, according to any one of claims 13, 28, and 29, wherein the solvent has a composition ratio of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) of 25:5:70 parts with respect to the mass of the electrolyte solution.

31. The aforementioned additives consist of vinylene carbonate (VC) in an amount of 2% by mass of the electrolyte solution, and fluoroethylene carbonate (FEC), propane sultone (PS), and lithium difluorophosphate (LiPO) in an amount of 0.1 to 10% by mass of the electrolyte solution. ２ F ２ A method for producing a lithium-ion battery having an NMC material as a core and a carbon black as a shell, comprising one or more of the following: ), methylene methane disulfonate (MMDS), or a combination thereof, according to claim 13 or 28.

32. A method for producing a lithium-ion battery having an NMC material as the core and a carbon black as the shell as described in any one of claims 13, 28, and 31, wherein the most preferred additive is vinylene carbonate (VC) and fluoroethylene carbonate (FEC) in amounts of 2% by mass and 0.1% by mass, respectively, of the electrolyte solution.

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, with a lithium hexafluorophosphate concentration of 1.2 molars, and vinylene carbonate (VC) and fluoroethylene carbonate (FEC) in amounts of 2% by mass and 0.1% by mass, respectively, of the electrolyte solution. A method for manufacturing a lithium-ion battery according to claim 13 or 28, having a positive electrode with an NMC material as the core and carbon black as the shell.

34. The positive electrode, manufactured and coated on an aluminum plate, has a mass of 17 to 23 mg / cm³. ２ A method for manufacturing a lithium-ion battery according to claim 13, having a positive electrode with an NMC material as the core and carbon black as the shell, wherein the thickness is in the range of 110 to 250 μm.

35. The negative electrode is manufactured and coated on a copper plate and has a negative electrode active material which is graphite-type carbon or oxide, and the mass of the negative electrode is 10 to 15 mg / cm³. ２ A method for manufacturing a lithium-ion battery according to claim 13, having a positive electrode with an NMC material as the core and carbon black as the shell, wherein the thickness is in the range of 100 to 250 μm.

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