Negative electrode material for secondary batteries, negative electrode for secondary batteries, and secondary batteries

Abstract

The present invention provides a negative electrode material and a negative electrode for secondary batteries, which provide the secondary battery with good electrical capacity and stability. [Solution] The present invention provides a negative electrode material for a secondary battery, a negative electrode for a secondary battery, and a secondary battery. The negative electrode material for a secondary battery includes a plurality of oxide particles and a protective layer. The protective layer coats the plurality of oxide particles, and the material of the protective layer includes carbon.

Description

[Technical Field]

[0001] The present invention relates to electrode materials, electrodes, and batteries, and more particularly to negative electrode materials for secondary batteries, negative electrodes for secondary batteries, and secondary batteries. [Background technology]

[0002] In recent years, the market demand for secondary lithium batteries, which are capable of repeated charging and discharging and possess features such as light weight, high voltage, and high energy density, has been increasing day by day. Therefore, the demand for performance characteristics such as lightweight durability, high voltage, high energy density, and high safety in secondary lithium batteries is also increasing. Secondary lithium batteries have considerable potential for application and expansion, particularly in lightweight electric vehicles, electric vehicles, and the large-scale energy storage industry. While graphite is generally the most widely used commercially available electrode material, its electrical capacity (theoretical value 372 mAh / g) is low, limiting the performance of batteries produced with it. Therefore, finding electrode materials for secondary batteries that possess high stability and high electrical capacity is currently one of the goals that engineers in this field aim to achieve. [Overview of the Initiative] [Problems that the invention aims to solve]

[0003] In view of this, the present invention provides a negative electrode material and a negative electrode for secondary batteries, which provide the secondary battery with good electrical capacity and stability. [Means for solving the problem]

[0004] An embodiment of the present invention provides a negative electrode material for a secondary battery, comprising a plurality of oxide particles and a protective layer. The protective layer coats the plurality of oxide particles, and the material of the protective layer contains carbon.

[0005] An embodiment of the present invention provides a negative electrode for a secondary battery, comprising a current collector and a negative electrode material layer. The negative electrode material layer is disposed on the current collector and comprises the negative electrode material for the secondary battery.

[0006] A secondary battery provided by one embodiment of the present invention includes a positive electrode, a negative electrode, an electrolyte, and a package structure. The negative electrode is disposed separately from the positive electrode and is a negative electrode for the secondary battery. The electrolyte is placed between the positive electrode and the negative electrode. The package structure covers the positive electrode, the negative electrode, and the electrolyte. [Effects of the Invention]

[0007] Based on the foregoing, the negative electrode material for secondary batteries of the present invention contains multiple oxide particles, and a protective layer containing carbon is coated thereon, which not only makes it applicable to the negative electrode of secondary batteries, but also enables secondary batteries to have good electrical capacity, stability, and charge-discharge cycle life.

[0008] To make the aforementioned features and advantages of the present invention easier to understand, embodiments will be described in detail below, with reference to the accompanying drawings. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of the negative electrode material for one embodiment of the present invention. [Figure 2] This is a schematic diagram of a negative electrode material according to another embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view of a secondary battery according to one embodiment of the present invention. [Figure 4] These are the cyclic life curves for the secondary batteries of Example 1 and Comparative Example 1. [Figure 5] These are the cyclic life curves for the secondary batteries of Example 2 and Comparative Example 2. [Figure 6] This is a diagram of the cyclic life curves of the secondary batteries for Example 3 and Comparative Example 3. [Figure 7] These are the cyclic life curves for the secondary batteries of Example 4 and Comparative Example 4. [Figure 8] This is a diagram of the cyclic life curves of the secondary batteries for Example 5 and Comparative Example 5. [Modes for carrying out the invention]

[0010] In this specification, the range expressed as "from one number to another number" is a general expression intended to avoid listing every single number within that range in the specification. Therefore, the description of a particular numerical range includes any number within that range and any smaller numerical range defined by any number within that range, and is equivalent to explicitly stating that any number and the smaller numerical range in the specification.

[0011] As used herein, “approximately,” “essentially,” or “substantively” include the mean values ​​within an acceptable range of deviations of the stated values ​​and specific values ​​determined by a person skilled in the art, taking into account the measurement and specific quantities of error associated with the measurement (i.e., the limits of the measurement system). For example, “approximately” can represent within one or more standard deviations of the stated values, or within, for example, ±30%, ±20%, ±15%, ±10%, ±5%. Furthermore, as used herein, “approximately,” “essentially,” or “substantively” may be interpreted as allowing for the selection of a more acceptable range of deviations or standard deviations depending on the nature of the measurement or other properties, and it is not necessary to apply one standard deviation to all properties.

[0012] To manufacture a negative electrode applicable to secondary batteries and to produce a negative electrode material that provides secondary batteries with good stability and electrical capacity, the present invention provides a negative electrode material that can achieve the above advantages. Hereinafter, embodiments will be given as examples to illustrate that the present invention can be reliably implemented.

[0013] Figure 1 is a schematic diagram of the negative electrode material of one embodiment of the present invention.

[0014] Referring to Figure 1, the negative electrode material 10 of this embodiment includes a plurality of oxide particles 12 and a protective layer 14 covering the plurality of oxide particles 12. More specifically, the plurality of oxide particles 12 include a plurality of primary oxide particles M and a plurality of secondary oxide particles N. That is, in this embodiment, the plurality of oxide particles 12 can include two different groups of oxides.

[0015] In this embodiment, the material of the plurality of first oxide particles M is FeO, Fe2O3, Fe3O4, Al y Fe 1-y O, Al y Fe 2-y O3, Al y Fe 3-y O4, Ti y Fe 1-y O, Ti y Fe 2-y O3, Ti y Fe 3-y O4, MnO, Mn2O3, Mn3O4, MnO2, Al y Mn 1-y O, Al y Mn 2-y O3, Al y Mn 1-y O2, Al y Mn 3-y O4, Ti y Mn 1-y O, Ti y Mn 2-y O3, Ti y Mn 1-y O2, Ti y Mn 3-y O4, Ca y Mn 1-y O, Ca y Mn 2-y O3, Ca y Mn 1-y O2, Ca y Mn 3-y O4 and (Al a Zn b Mn c Fe d Cu e )3O4, and includes one or more of them, provided that y ≦ 20 atomic%, and each of a, b, c, d, and e is 10 atomic% or more, and a + b + c + d + e = 1. That is, the material of the plurality of first oxide particles M can include iron-containing oxides, manganese-containing oxides, or high-entropy oxides (HEO).

[0016] More specifically, in this embodiment, the iron-containing oxide may be a multi-component metal oxide containing other metals such as Al and Ti, in addition to those that exist in the usual way (i.e., oxides composed only of iron (Fe) and oxygen (O), such as FeO, Fe2O3, Fe3O4, etc.), and the manganese-containing oxide may be a multi-component metal oxide containing other metals such as Al, Ti, Ca, in addition to those that exist in the usual way (i.e., oxides composed only of manganese (Mn) and oxygen (O), such as MnO, Mn2O3, Mn3O4, MnO2, etc.). Notably, by including a plurality of primary oxide particles M, which are iron-containing oxides and / or manganese-containing oxides as materials, lithium ions can be transferred in and out via different paths in a secondary battery in which the negative electrode is fabricated using the negative electrode material 10, thereby mitigating the polarization effect and improving the charge-discharge cycle life. In this way, the electrical capacity of a secondary battery using a negative electrode material 10 containing a plurality of primary oxide particles M can be significantly increased.

[0017] Furthermore, in this embodiment, (Al a Zn b Mn c Fe d Cu e )3O4 has a spinel structure. Of note is the (Al) in the material of multiple primary oxide particles M. a Zn b Mn c Fe d Cu e The 3O4 having the above structure allows for the presence of more oxygen vacancies, which in a secondary battery using a negative electrode material 10 containing multiple primary oxide particles M allows lithium ions to enter and exit conveniently and quickly, thus effectively improving lithium ion diffusion rate and ionic conductivity.

[0018] In this embodiment, the material of the plurality of secondary oxide particles N includes one or more of SiO2, SnO2, TiO2, CuO2, CuO, CaO, ZnO, and MoO3. More specifically, the plurality of secondary oxide particles N are mainly composed of binary oxides, i.e., oxides mainly composed of metal or metalloid elements and oxygen (O). Notably, by fabricating a negative electrode using a negative electrode material 10 containing the plurality of secondary oxide particles N, lithium ions can be transferred in and out through different pathways, the polarization effect can be mitigated, and the charge-discharge cycle life can be improved. Thus, the electrical capacity of a secondary battery using a negative electrode material 10 containing the plurality of primary oxide particles M can be significantly increased. Also noteworthy is that the plurality of secondary oxide particles N can act as a segregation layer in the negative electrode material 10, preventing decay during the redox reaction period, further improving the structural stability of the negative electrode produced by the negative electrode material 10, and improving the charge-discharge cycle life of the battery.

[0019] In this embodiment, the atomic ratio of multiple primary oxide particles M is 90 atomic% or more, and the atomic ratio of multiple secondary oxide particles N is 10 atomic% or less. That is, in the multiple oxide particles 12, the content of primary oxide particles M is significantly higher than that of secondary oxide particles N.

[0020] In this embodiment, the particle size of the plurality of primary oxide particles M is between 20 nm and 20 μm, and the particle size of the plurality of secondary oxide particles N is between 20 nm and 20 μm. When the particle sizes of the plurality of primary oxide particles M and the plurality of secondary oxide particles N are within the above range, it is advantageous for forming a negative electrode with good properties. In one embodiment, grinding can be performed using a mortar and pestle, a ball mill, a 3D ball mill, a vibrating ball mill, or a planetary ball mill to obtain the plurality of primary oxide particles M and the plurality of secondary oxide particles N having the above specific particle size range, but the present invention is not limited thereto.

[0021] In this embodiment, the material of the protective layer 14 contains carbon. Specifically, the carbon used in the protective layer 14 includes one or more types of defective carbon, conductive carbon, amorphous carbon, nitrogen-doped carbon, and boron-doped carbon. In this embodiment, the thickness of the protective layer 14 is 20 nm or less. When the thickness of the protective layer 14 is within the above range, a carbon-containing protective layer 14 of this thickness acts as a good lithium ion and electron transfer channel, effectively improving the battery's charge-discharge cycle life and fast charge-discharge capability. Of particular note is that the protective layer 14 covering the surface of the multiple oxide particles 12 (i.e., multiple primary oxide particles M and multiple secondary oxide particles N) acts at the solid electrolyte interface (SEI), thereby preventing further reactions between the multiple primary oxide particles M and multiple secondary oxide particles N and the electrolyte solution, and acting as a diffusion channel for the oxidation-reduction reaction of lithium ions within the multiple primary oxide particles M and multiple secondary oxide particles N. In this way, the charge-discharge cycle life of a secondary battery using a negative electrode material 10 that includes the protective layer 14 covering the multiple oxide particles 12 can be improved. Also noteworthy is that the protective layer 14 protects the multiple primary oxide particles M, preventing structural damage due to volume expansion during the oxidation-reduction reaction, thereby improving the structural stability of the negative electrode obtained from the negative electrode material 10 and improving the charge-discharge cycle life of the battery. Furthermore, by including the protective layer 14 made of a carbon-containing material, the negative electrode material 10 is provided with better electron conduction pathways, thereby promoting the effective transfer of electrons generated by the reaction and contributing to the reduction of charge polarization phenomena during the charge-discharge cycle process.

[0022] The materials of the multiple oxide particles 12 in the negative electrode material 10 can be selected from two different groups of oxides, but the present invention is not limited thereto. Referring to Figure 2, in another embodiment, the multiple oxide particles 12 in the negative electrode material 20 may consist only of a plurality of primary oxide particles M. That is, the materials of the multiple oxide particles 12 in the negative electrode material 20 may be selected from only a single group of oxides.

[0023] In one embodiment, a method for producing the anode material 10 or anode material 20 may include the following steps: First, particle size adjustment is performed on a plurality of oxide particles 12 to make their particle sizes consistent. More specifically, particle size adjustment is performed on a plurality of primary oxide particles M and a plurality of secondary oxide particles N to bring the particle sizes of the plurality of primary oxide particles M and a plurality of secondary oxide particles N within the aforementioned ranges. In one embodiment, the particle size adjustment can be performed on a plurality of primary oxide particles M or a plurality of secondary oxide particles N by grinding them using a mortar and pestle, a ball mill, a 3D ball mill, a vibrating ball mill, or a planetary ball mill, but the present invention is not limited thereto.

[0024] Next, a plurality of oxide particles 12 with uniform particle size are mixed. This step can be omitted because the negative electrode material 20 contains only a plurality of primary oxide particles M. In one embodiment, the method for mixing the plurality of primary oxide particles M and the plurality of secondary oxide particles N may include a physical dry mixing method or a physical wet mixing method.

[0025] Subsequently, multiple oxide particles 12 are aggregated and formed using a particle aggregation method. In one embodiment, particle aggregation can be performed using a drying method or a granulation method.

[0026] Furthermore, a protective layer 14 is formed on the surface of a plurality of oxide particles 12 to form a negative electrode material 10 or a negative electrode material 20. In one embodiment, the protective layer 14 can be formed by methods such as thermal deposition, chemical vapor deposition (CVD), physical vapor deposition (PVD), atomic layer deposition (ALD), plasma deposition, hydrothermal method, sol-gel method, or spin-coating. In one embodiment, carbon sources that can be used to form the protective layer 14 may include glucose, sucrose, furfuryl alcohol, citric acid, polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinyl chloride (PVC), polyvinylpyrrolidone (PVP), pyromellitic acid, dopamine hydrochloride, etc.

[0027] Another embodiment of the present invention also provides a secondary battery that utilizes either of the negative electrode materials presented in the above-described embodiments (i.e., negative electrode material 10 or negative electrode material 20).

[0028] Figure 3 is a schematic cross-sectional view of a secondary battery according to one embodiment of the present invention. Referring to Figure 3, the secondary battery 100 can include a negative electrode 102, a positive electrode 104, an electrolyte 108, and a package structure 112. In this embodiment, the secondary battery 100 can include a separator 106. Also, in this embodiment, the secondary battery 100 can be a lithium-ion battery.

[0029] In this embodiment, the negative electrode 102 may include a current collector 102a and a negative electrode material layer 102b disposed on the current collector 102a. In this embodiment, the current collector 102a may be a metal foil (e.g., copper foil, aluminum foil, molybdenum foil, nickel foil), copper foil having a molybdenum-containing coating, nickel foil having a molybdenum-containing coating, aluminum foil having a molybdenum-containing coating, copper foil having a carbon nanotube-containing coating, nickel foil having a carbon nanotube-containing coating, or aluminum foil having a carbon nanotube-containing coating. In this embodiment, the thickness of the current collector 102a may be in the range of about 5 μm to about 300 μm.

[0030] In this embodiment, the negative electrode material layer 102b includes one of the negative electrode materials presented in the previous embodiment (i.e., negative electrode material 10 or negative electrode material 20). In this embodiment, the negative electrode material can be disposed on the current collector 102a by, for example, coating, sputtering, hot pressing, sintering, physical vapor deposition, or chemical vapor deposition.

[0031] Furthermore, in this embodiment, the negative electrode material layer 102b may further contain a conductive agent mixed with the negative electrode material. In this embodiment, the conductive agent may be carbon nanotubes, graphene, graphite (e.g., natural graphite, artificial graphite), or conductive carbon (e.g., VGCF, Super P, KS4, KS6, or ECP). Specifically, the conductive agent is used to improve the electrical contact between the negative electrode materials.

[0032] Furthermore, in this embodiment, the negative electrode material layer 102b may further contain a binder. In this embodiment, the binder may be sodium carboxymethylcellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polyamide, melamine resin, or a combination of the above. Specifically, the negative electrode material can be bonded onto the current collector 102a by the binder.

[0033] In this embodiment, the positive electrode 104 and the negative electrode 102 are arranged separately. In this embodiment, the positive electrode 104 includes a current collector 104a and a positive electrode material layer 104b disposed on the current collector 104a. In this embodiment, the current collector 104a can be a metal foil (such as copper foil, nickel foil, molybdenum foil, aluminum foil or high-conductivity stainless steel foil), a copper foil having a molybdenum-containing coating film, a nickel foil having a molybdenum-containing coating film, an aluminum foil having a molybdenum-containing coating film, a copper foil having a carbon nanotube-containing coating film, a nickel foil having a carbon nanotube-containing coating film or an aluminum foil having a carbon nanotube-containing coating film. In this embodiment, the thickness of the current collector 104a can be in the range of about 5 μm to about 300 μm.

[0034] In this embodiment, the positive electrode material layer 104b contains a positive electrode material. In this embodiment, the positive electrode material can include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), lithium nickel oxide (LiNiO2), lithium iron phosphate (LiFePO4), lithium nickel cobalt manganese oxide (for example: NMC811, NMC622 or NMC532), lithium manganese iron phosphate (LiMn x Fe 1-x PO4, 0 < x < 1, LMFP) or a combination thereof. In this embodiment, the positive electrode material can be disposed on the current collector 104a by, for example, coating, sputtering, hot pressing, sintering, physical vapor deposition method or chemical vapor deposition method. Also, in this embodiment, the positive electrode material layer 104b can further contain a binder. In this embodiment, the binder can be polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), polyamide, melamine resin or a combination of the above. Specifically, the positive electrode material can be adhered to the current collector 104a by a binder.

[0035] In this embodiment, the electrolyte 108 is installed between the negative electrode 102 and the positive electrode 104. The electrolyte 108 can include a liquid electrolyte, a gel electrolyte, a molten salt electrolyte or a solid electrolyte.

[0036] In this embodiment, the separator 106 is placed between the negative electrode 102 and the positive electrode 104, and the separator 106, the negative electrode 102, and the positive electrode 104 define a containment region 110, and the electrolyte 108 is placed in the containment region 110. In this embodiment, the material of the separator 106 can be an insulating material, for example polyethylene (PE), polypropylene (PP), or a composite structure made of the above materials (e.g., PE / PP / PE). In this embodiment, the secondary battery 100 includes the separator 106, which insulates the negative electrode 102 and the positive electrode 104 and allows ion permeation, but the present invention is not limited thereto. In other embodiments, if the electrolyte 108 is a solid electrolyte, the secondary battery 100 does not include a separator.

[0037] In this embodiment, the package structure 112 covers the negative electrode 102, the positive electrode 104, and the electrolyte 108. In this embodiment, the material of the package structure 112 is, for example, aluminum foil, aluminum plastic film, or stainless steel.

[0038] In this embodiment, the structure of the secondary battery 100 is not limited to that shown in Figure 1. In other embodiments, the secondary battery 100 may have a wound structure manufactured by winding a negative electrode, a positive electrode, and a separator installed as needed, or a laminated structure manufactured by stacking flat plates. In this embodiment, the secondary battery 100 may be, for example, a paper battery, a button battery, a coin battery, a laminated battery, a cylindrical battery, or a prismatic battery.

[0039] Of particular note is that since the negative electrode 102 of the secondary battery 100 uses one of the negative electrode materials presented in the above-described embodiment, as stated in the preceding paragraph, the secondary battery 100 can have good electrical capacity, stability, and charge-discharge cycle life.

[0040] The features of the present invention will be described in more detail below with reference to Examples 1 to 5 and Comparative Examples 1 to 5. While Examples 1 to 5 are described below, the materials used, their quantities and ratios, processing details, and processing flow can be appropriately modified without departing from the scope of the present invention. Therefore, the present invention should not be interpreted as being limited by the examples described below.

[0041] Example 1 Manufacturing of negative electrode materials At room temperature, Fe2O3 powder (primary oxide particles M) and SnO2 powder (secondary oxide particles N) were pulverized and physically wet-mixed using a ball mill with added water to form a slurry. The mixture was then dried using a drying method to obtain a powder in which the particles aggregated, forming the multiple oxide particles of Example 1. Here, the particle size of both the primary oxide particles M and the secondary oxide particles N was 10 μm. In a high-temperature furnace, the temperature was first raised to 100°C and held for 2 hours to evaporate the water vapor. Next, the temperature was raised to 600°C and held for 5 hours or more. The purpose of this step is to form amorphous carbon (protective layer) on the surface of the multiple oxide particles of Example 1 by thermal deposition using glucose as the gas source, and the heating rate in all heating processes was 5°C / min. Next, the temperature was lowered to room temperature to obtain the negative electrode material of Example 1. Here, the thickness of the protective layer was 5 nm, the atomic ratio of primary oxide particles M was 95%, and the atomic ratio of secondary oxide particles N was 5%.

[0042] Manufacturing of rechargeable batteries The negative electrode material from Example 1, Super P conductive carbon, and binder (carboxymethylcellulose sodium (CMC) and styrene-butadiene rubber (SBR)) were dissolved in water in a weight ratio of 7:2:1 to form a slurry. Next, a high-speed slurry mixer (manufactured by Gelon Co., Ltd.; model number: GN-VM-7P) was used to create a slurry at a rotation speed of 2000 rpm for approximately 30 minutes to form the negative electrode slurry. Subsequently, the slurry was applied to the copper foil (current collector of the negative electrode) using a scraper (100 μm), and after being uniformly flattened, the copper foil coated with the slurry was placed in a vacuum oven and dried at approximately 100°C for approximately 12 hours. After that, the dried copper foil was cut to a diameter of approximately 14 mm using a cutting machine to obtain the negative electrode of Example 1.

[0043] Using the negative electrode from Example 1 as the negative electrode and NMC622 (diameter 14 mm) as the positive electrode, lithium salt LiPF6 was dissolved in a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio EC:DEC = 1:1) to prepare a 1 M electrolyte. A button cell (model number: CR2032) was assembled using a polypropylene membrane (product name: Celgard #2400, manufactured by Celgard) as the separator and a stainless steel 304 or 316 cover as the package structure. This produced the secondary battery of Example 1. The amount of electrolyte added to each battery was 35 μL.

[0044] Example 2 Manufacturing of negative electrode materials At room temperature, Fe2O3 powder (primary oxide particles M) and CaO powder (secondary oxide particles N) were pulverized and physically wet-mixed using a ball mill with added water to form a slurry. The slurry was then dried using a drying method to obtain a powder in which the particles aggregated, forming the multiple oxide particles of Example 2. Here, the particle size of both the primary oxide particles M and the secondary oxide particles N was 10 μm. In a high-temperature furnace, the temperature was first raised to 100°C and held for 2 hours to evaporate the water vapor. Next, the temperature was raised to 600°C and held for 5 hours or more. The purpose of this step is to form amorphous carbon (protective layer) on the surface of the multiple oxide particles of Example 2 by thermal deposition using glucose as the gas source, and the heating rate in all heating processes was 5°C / min. After that, the temperature was lowered to room temperature to obtain the negative electrode material of Example 2. Here, the thickness of the protective layer was 5 nm, the atomic ratio of primary oxide particles M was 95%, and the atomic ratio of secondary oxide particles N was 5%.

[0045] Manufacturing of rechargeable batteries The negative electrode material of Example 2, Super P conductive carbon, and binders (CMC and SBR) were dissolved in water in a weight ratio of 7:2:1 to form a slurry. Next, a high-speed slurry mixer (manufactured by Gelon Co., Ltd.; model number: GN-VM-7P) was used to form a negative electrode slurry at a rotation speed of 2000 rpm for approximately 30 minutes. Subsequently, the slurry was applied to the copper foil (current collector of the negative electrode) using a scraper (100 μm), and after being uniformly flattened, the copper foil coated with slurry was placed in a vacuum oven and dried at approximately 100°C for approximately 12 hours. After that, the dried copper foil was cut to a diameter of approximately 14 mm using a cutting machine to form the negative electrode of Example 2.

[0046] Using the negative electrode from Example 2 as the working electrode, and lithium metal as the counter electrode (0.2 mm thick), a 1 M electrolyte solution was prepared by dissolving lithium salt LiPF6 in a mixture of EC and DEC (volume ratio EC:DEC = 1:1). A button cell (model number: CR2032) was assembled using a polypropylene membrane (product name: Celgard #2400, manufactured by Celgard) as the separator and a stainless steel 304 or 316 cover as the package structure. This produced the secondary battery of Example 2. The electrolyte amount added to each battery was 35 μL.

[0047] Example 3 Manufacturing of negative electrode materials At room temperature, MnO powder (first oxide particles M) was pulverized and physically wet-mixed using a ball mill by adding water to form a slurry. Then, the mixed slurry was dried using a drying method to obtain a powder in which the particles aggregated, forming the multiple oxide particles of Example 3. Here, the particle size of the first oxide particles M is 10 μm. In a high-temperature furnace, the temperature was first raised to 100°C and held for 2 hours to evaporate the water vapor. Next, the temperature was raised to 600°C and held for 5 hours or more. The purpose of this step is to form amorphous carbon (protective layer) on the surface of the multiple oxide particles of Example 3 by thermal deposition using glucose as the gas source, and the heating rate in all heating processes was 5°C / min. After that, the temperature was lowered to room temperature to obtain the negative electrode material of Example 3. The thickness of the protective layer is 5 nm.

[0048] Manufacturing of rechargeable batteries The negative electrode material from Example 3, Super P conductive carbon, and binders (CMC and SBR) were dissolved in water in a weight ratio of 7:2:1 to form a slurry. Next, a high-speed slurry mixer (manufactured by Gelon Co., Ltd.; model number: GN-VM-7P) was used to create a slurry at a rotation speed of 2000 rpm for approximately 30 minutes to form the negative electrode slurry. Subsequently, the slurry was applied to the copper foil (current collector of the negative electrode) using a scraper (100 μm), and after being uniformly flattened, the copper foil coated with the slurry was placed in a vacuum oven and dried at approximately 100°C for approximately 12 hours. After that, the dried copper foil was cut to a diameter of approximately 14 mm using a cutting machine to form the negative electrode of Example 3.

[0049] Using the negative electrode from Example 3 as the working electrode, and lithium metal as the counter electrode (thickness 0.2 mm), a 1 M electrolyte solution was prepared by dissolving lithium salt LiPF6 in a mixture of EC and DEC (volume ratio EC:DEC = 1:1). A button cell (model number: CR2032) was assembled using a polypropylene membrane (product name: Celgard #2400, manufactured by Celgard) as the separator and a stainless steel 304 or 316 cover as the package structure. This produced the secondary battery of Example 3. The amount of electrolyte added to each battery was 35 μL.

[0050] Example 4 Manufacturing of negative electrode materials At room temperature, MnO powder (first oxide particles M) and CuO powder (second oxide particles N) were pulverized and physically wet-mixed using a ball mill with added water to form a slurry. The slurry was then dried using a drying method to obtain a powder in which the particles aggregated, forming the multiple oxide particles of Example 4. Here, the particle size of both the first oxide particles M and the second oxide particles N was 10 μm. In a high-temperature furnace, the temperature was first raised to 100°C and held for 2 hours to evaporate the water vapor. Next, the temperature was raised to 600°C and held for 5 hours or more. The purpose of this step is to form amorphous carbon (protective layer) on the surface of the multiple oxide particles of Example 4 by thermal deposition using glucose as the gas source, and the heating rate in all heating processes was 5°C / min. After that, the temperature was lowered to room temperature to obtain the negative electrode material of Example 4. The thickness of the protective layer was 5 nm, the atomic ratio of the first oxide particles M was 90%, and the atomic ratio of the second oxide particles N was 10%.

[0051] Manufacturing of rechargeable batteries The negative electrode material of Example 4, Super P conductive carbon, and binders (CMC and SBR) were dissolved in water in a weight ratio of 7:2:1 to form a slurry. Next, a high-speed slurry mixer (manufactured by Gelon Co., Ltd.; model number: GN-VM-7P) was used to form a negative electrode slurry at a rotation speed of 2000 rpm for approximately 30 minutes. Subsequently, the slurry was applied to the copper foil (current collector of the negative electrode) using a scraper (100 μm), and after being uniformly flattened, the copper foil coated with slurry was placed in a vacuum oven and dried at approximately 100°C for approximately 12 hours. After that, the dried copper foil was cut to a diameter of approximately 14 mm using a cutting machine to obtain the negative electrode of Example 4.

[0052] Using the negative electrode from Example 4 as the working electrode, lithium metal as the counter electrode (0.2 mm thick), and dissolving lithium salt LiPF6 in a mixture of EC and DEC (volume ratio EC:DEC = 1:1) to prepare a 1 M electrolyte, a polypropylene membrane (product name: Celgard #2400, manufactured by Celgard) as the separator, and a stainless steel 304 or 316 cover as the package structure were used to assemble a button cell (model number: CR2032). This produced the secondary battery of Example 4. The amount of electrolyte added to each battery was 35 μL.

[0053] Example 5 Manufacturing of negative electrode materials At room temperature, Al2O3 powder (aluminum-containing precursor), ZnO powder (zinc-containing precursor), MnO powder (manganese-containing precursor), Fe2O3 powder (iron-containing precursor), and CuO powder (copper-containing precursor) were each ground using a ball mill. These powders were then mixed and pressurized to form green pellets with a diameter of approximately 1 cm. The green pellets were placed in a high-temperature furnace (temperature 900°C) and (Al a Zn b Mn c Fe d Cu e )3O4 powder (first oxide particles M) was obtained. Here, a is 15 atomic%, b is 15 atomic%, c is 27.5 atomic%, d is 27.5 atomic%, and e is 15 atomic%. Next, using a ball mill, (Al a Znb Mn c Fe d Cu e )3O4 powder (first oxide particles M) was mixed with water, pulverized, and physically wet-mixed to form a slurry. Then, the mixed slurry was dried using a drying method to obtain a powder in which the particles aggregated, forming the multiple oxide particles of Example 5. Here, the particle size of the first oxide particles M is 10 μm. Next, in a high-temperature furnace, the temperature was first raised to 100°C and held for 2 hours to evaporate the water vapor. Next, the temperature was raised to 600°C and held for 5 hours or more. The purpose of this step is to form amorphous carbon (protective layer) on the surface of the multiple oxide particles of Example 5 by thermal deposition using glucose as the gas source. The heating rate for all heating processes was 5°C / min. After that, the temperature was lowered to room temperature to obtain the negative electrode material of Example 5. The thickness of the protective layer is 5 nm.

[0054] Manufacturing of rechargeable batteries The negative electrode material of Example 5, Super P conductive carbon, and binders (CMC and SBR) were dissolved in water in a weight ratio of 7:2:1 to form a slurry. Next, a high-speed slurry mixer (manufactured by Gelon; model number: GN-VM-7P) was used to slurry the mixture at a rotation speed of 2000 rpm for approximately 30 minutes to form a negative electrode slurry. Subsequently, the slurry was applied to the copper foil (current collector of the negative electrode) using a scraper (100 μm), and after being uniformly flattened, the slurry-coated copper foil was dried in a vacuum oven at approximately 100°C for approximately 12 hours. After that, the dried copper foil was cut to a diameter of approximately 14 mm using a cutting machine to obtain the negative electrode of Example 5.

[0055] Using the negative electrode from Example 5 as the working electrode, lithium metal as the counter electrode (0.2 mm thick), and dissolving lithium salt LiPF6 in a mixture of EC and DEC (volume ratio EC:DEC = 1:1) to prepare a 1 M electrolyte, a polypropylene membrane (product name: Celgard #2400, manufactured by Celgard) as the separator, and a stainless steel 304 or 316 cover as the package structure were used to assemble a button cell (model number: CR2032). This obtained the secondary battery of Example 5. The amount of electrolyte added to each battery was 35 μL.

[0056] Comparative Example 1 Manufacturing of negative electrode materials The negative electrode material of Comparative Example 1 was manufactured according to the same method as in Example 1. The main difference between the two is that no protective layer is formed in the negative electrode material of Comparative Example 1. That is, the negative electrode material of Comparative Example 1 contains only multiple oxide particles, with the atomic ratio of primary oxide particles M (Fe2O3) being 95% and the atomic ratio of secondary oxide particles N (SnO2) being 5%.

[0057] Manufacturing of rechargeable batteries A secondary battery of Comparative Example 1 was manufactured following the same manufacturing procedure as in Example 1. The main difference is that while the secondary battery of Example 1 used the negative electrode of Example 1, the secondary battery of Comparative Example 1 used the negative electrode of Comparative Example 1, which was made using the negative electrode material of Comparative Example 1.

[0058] Comparative Example 2 Manufacturing of negative electrode materials The negative electrode material of Comparative Example 2 was manufactured according to the same method as in Example 2. The main difference between the two is that no protective layer is formed in the negative electrode material of Comparative Example 2. That is, the negative electrode material of Comparative Example 2 contains only multiple oxide particles, with the atomic ratio of primary oxide particles M (Fe2O3) being 95% and the atomic ratio of secondary oxide particles N (CaO) being 5%.

[0059] Manufacturing of rechargeable batteries A secondary battery of Comparative Example 2 was manufactured following the same manufacturing procedure as in Example 2. The main difference is that while the secondary battery of Example 2 used the negative electrode of Example 2 as the working electrode, the secondary battery of Comparative Example 2 used the negative electrode of Comparative Example 2, which was manufactured using the negative electrode material of Comparative Example 2, as the working electrode.

[0060] Comparative Example 3 Manufacturing of negative electrode materials The negative electrode material of Comparative Example 3 was manufactured according to the same method as in Example 3. The main difference between the two is that no protective layer is formed in the negative electrode material of Comparative Example 3. That is, the negative electrode material of Comparative Example 3 contains only multiple oxide particles (i.e., primary oxide particles M(MnO)).

[0061] Manufacturing of rechargeable batteries A secondary battery of Comparative Example 3 was manufactured following the same manufacturing procedure as in Example 3. The main difference is that while the secondary battery of Example 3 used the negative electrode of Example 3 as the working electrode, the secondary battery of Comparative Example 3 used the negative electrode of Comparative Example 3, which was manufactured using the negative electrode material of Comparative Example 3, as the working electrode.

[0062] Comparative Example 4 Manufacturing of negative electrode materials The negative electrode material of Comparative Example 4 was manufactured according to the same method as in Example 4. The main difference between the two is that no protective layer is formed in the negative electrode material of Comparative Example 4. That is, the negative electrode material of Comparative Example 4 contains only multiple oxide particles, with the atomic ratio of primary oxide particles M (MnO) being 90% and the atomic ratio of secondary oxide particles N (CuO) being 10%.

[0063] Manufacturing of rechargeable batteries A secondary battery of Comparative Example 4 was manufactured following the same manufacturing procedure as in Example 4. The main difference is that while the secondary battery of Example 4 used the negative electrode of Example 4 as the working electrode, the secondary battery of Comparative Example 4 used the negative electrode of Comparative Example 4, which was manufactured using the negative electrode material of Comparative Example 4, as the working electrode.

[0064] Comparative Example 5 Manufacturing of negative electrode materials The negative electrode material of Comparative Example 5 was manufactured according to the same method as in Example 5. The main difference between the two is that no protective layer is formed in the negative electrode material of Comparative Example 5. That is, the negative electrode material of Comparative Example 5 consists of multiple oxide particles (i.e., primary oxide particles M((Al a Zn b Mn c Fe d Cu e Contains only 3O4).

[0065] Manufacturing of rechargeable batteries A secondary battery of Comparative Example 5 was manufactured following the same manufacturing procedure as in Example 5. The main difference is that while the secondary battery of Example 5 used the negative electrode of Example 5 as the working electrode, the secondary battery of Comparative Example 5 used the negative electrode of Comparative Example 5, which was manufactured using the negative electrode material of Comparative Example 5, as the working electrode.

[0066] After manufacturing and obtaining the secondary batteries of Examples 1-5 and Comparative Examples 1-5, charge-discharge cycle measurements were performed on each of the secondary batteries of Examples 1-5 and Comparative Examples 1-5.

[0067] Charge / discharge cycle measurement The electrical capacity of the secondary battery of Example 1 and the secondary battery of Comparative Example 1 were measured at a voltage of 1.1V to 3.9V in an environment of approximately 15°C to approximately 30°C, and the measurement results are shown in Figure 4. The electrical capacity of the secondary batteries of Examples 2 to 5 and the secondary batteries of Comparative Examples 2 to 5 were measured at a voltage of 0.01V to 3V in an environment of approximately 15°C to approximately 30°C, and the measurement results are shown in Figures 5 to 8.

[0068] Figure 4 shows that, after undergoing a high number of cycles (approximately 120 times), the secondary battery of Example 1 has better electrical capacity and electrical capacity retention rate compared to the secondary battery of Comparative Example 1.

[0069] Figure 5 shows that, after undergoing a high number of cycles (more than 100), the secondary battery of Example 2 has better electrical capacity and electrical capacity retention rate compared to the secondary battery of Comparative Example 2.

[0070] Figure 6 shows that, after undergoing a high number of cycles (over 400), the secondary battery of Example 3 has better electrical capacity and electrical capacity retention rate compared to the secondary battery of Comparative Example 3.

[0071] Figure 7 shows that, after undergoing a high number of cycles (over 250), the secondary battery of Example 4 has better electrical capacity and electrical capacity retention rate compared to the secondary battery of Comparative Example 4.

[0072] As can be seen from FIG. 8, after undergoing a high number of charge-discharge cycles (about 120 cycles), it can be seen that the secondary battery of Example 5 has better capacitance and capacitance retention rate compared to the secondary battery of Comparative Example 5.

[0073] Although the above measurements have not been performed on a secondary battery in which the negative electrode includes a protective layer containing defective carbon, conductive carbon, nitrogen-doped carbon, and boron-doped carbon, based on the description of the protective layer in the foregoing text and the measurement results of Examples 1 to 5, those skilled in the art can understand that when the negative electrode includes a protective layer containing defective carbon, conductive carbon, nitrogen-doped carbon, and boron-doped carbon, the manufactured secondary battery also has good capacitance and capacitance retention rate.

[0074] The negative electrode contains first oxide particles M having, as a material, FeO, Fe2O3, or an iron-containing polyvalent metal oxide (e.g., Al y Fe 1-y O, Al y Fe 2-y O3, Al y Fe 3-y O4, Ti y Fe 1-y O, Ti y Fe 2-y O3, Ti y Fe 3-y O4). Although the above measurements have not been performed on a secondary battery containing first oxide particles M having, as a material, FeO, Fe2O3, or an iron-containing polyvalent metal oxide in the negative electrode, based on the description of the first oxide particles M in the foregoing text and the measurement results of Examples 1 and 2, those skilled in the art can understand that when the negative electrode contains first oxide particles M having, as a material, FeO, Fe2O3, or an iron-containing polyvalent metal oxide, the manufactured secondary battery also has good capacitance and capacitance retention rate.

[0075] [[ID=3,6]]The negative electrode contains, as a material, Mn2O3, Mn3O4, MnO2, or a manganese-containing polyvalent metal oxide (e.g., Al y Mn 1-y O, Al y Mn 2-y O3, Al y Mn 1-y O2, Al y Mn 3-y O4, Ti y Mn 1-y O, Tiy Mn 2-y O3, Ti y Mn 1-y O2, Ti y Mn 3-y O4, Ca y Mn 1-y O, Ca y Mn 2-y O3, Ca y Mn 1-y O2, Ca y Mn 3-y Although the above measurements have not been performed on the secondary battery containing the first oxide particles M having (O4), based on the description of the first oxide particles M in the previous text and the measurement results of Examples 3 and 4, those skilled in the art can understand that when the negative electrode contains the first oxide particles M having Mn2O3, Mn3O4, MnO2 or manganese-containing multi-metal oxide as a material, the manufactured secondary battery also has good capacitance and capacitance retention rate.

[0076] Although the above measurements have not been performed on the secondary battery containing the second oxide particles N having SiO2, TiO2, CuO2, ZnO and MoO3 as a material, based on the description of the second oxide particles N in the previous text and the measurement results of Examples 1, 2 and 4, those skilled in the art can understand that when the negative electrode contains the second oxide particles N having SiO2, TiO2, CuO2, ZnO and MoO3 as a material, the manufactured secondary battery also has good capacitance and capacitance retention rate.

[0077] Based on the above measurement results, it has been demonstrated that by manufacturing a negative electrode using the negative electrode material for a secondary battery of the present invention, the secondary battery applied with the negative electrode can have good capacitance, stability and charge-discharge cycle life.

[0078] Also, compared with commercially available graphite (theoretical capacitance value: 372 mAh / g), the secondary battery having a negative electrode manufactured using the negative electrode material for a secondary battery of the present invention has a higher capacitance, indicating that the negative electrode material for a secondary battery of the present invention can effectively improve the battery performance.

[0079] ​Although the present invention is disclosed by the embodiments described above, these do not limit the invention, and those skilled in the art can make some changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be based on the appended claims. [Industrial applicability]

[0080] The negative electrode material and negative electrode of the present invention can be used in secondary batteries. [Explanation of Symbols]

[0081] 10, 20 Negative electrode materials 12 Oxide particles 14 Protective layer M primary oxide particles N Secondary oxide particles 100 Secondary battery 102 Negative electrode 102a, 104a current collectors 102b Negative electrode material layer 104 Positive electrode 104b Positive electrode material layer 106 Separator 108 Electrolytes 110 Containment Area 112 Package Structure

Claims

1. Multiple oxide particles, A negative electrode material for a secondary battery comprising a protective layer containing carbon, which coats the plurality of oxide particles.

2. The negative electrode material for a secondary battery according to claim 1, wherein the thickness of the protective layer is 20 nm or less.

3. The negative electrode material for a secondary battery according to claim 1, wherein the carbon comprises one or more of the following: defective carbon, conductive carbon, amorphous carbon, nitrogen-doped carbon, and boron-doped carbon.

4. The plurality of oxide particles include a plurality of first oxide particles M, and the material of the plurality of first oxide particles M is FeO, Fe ４ O ３ 、Fe ３ O ４ 、Al ｙ Fe １－ｙ O、Al ｙ Fe ２－ｙ O ３ 、Al ｙ Fe ３－ｙ O ４ 、Ti ｙ Fe １－ｙ O、Ti ｙ Fe ２－ｙ O ３ 、Ti ｙ Fe ３－ｙ O ４ 、MnO、Mn ２ O ３ 、Mn ３ O ４ 、MnO ２ 、Al ｙ Mn １－ｙ O、Al ｙ Mn ２－ｙ O ３ 、Al ｙ Mn １－ｙ O ２ 、Al ｙ Mn ３－ｙ O ４ 、Ti ｙ Mn １－ｙ O、Ti ｙ Mn ２－ｙ O ３ 、Ti ｙ Mn １－ｙ O ２ 、Ti ｙ Mn ３－ｙ O ４ 、Ca ｙ Mn １－ｙ O、Ca ｙ Mn ２－ｙ O ３ 、Ca ｙ Mn １－ｙ O ２ 、Ca ｙ Mn ３－ｙ O ４ and (Al ａ Zn ｂ Mn ｃ Fe ｄ Cu ｅ ) ３ O ４ The negative electrode material for a secondary battery according to claim 1, comprising one or more of the following, wherein y ≤ 20 atomic%, each of a, b, c, d, and e is 10 atomic%, and a + b + c + d + e = 1.

5. (Al ａ Zn ｂ Mn ｃ Fe ｄ Cu ｅ ) ３ O ４ The negative electrode material for a secondary battery according to claim 4, wherein the material has a spinel structure.

6. The plurality of oxide particles include a plurality of secondary oxide particles N, and the material of the plurality of secondary oxide particles N is SiO ２ , SnO ２ , TiO ２ CuO ２ CuO, CaO, ZnO, and MoO ３ The negative electrode material for a secondary battery according to claim 4, comprising one or more of the above.

7. The negative electrode material for a secondary battery according to claim 6, wherein the atomic number ratio of the plurality of primary oxide particles M is 90 atomic% or more, and the atomic number ratio of the plurality of secondary oxide particles N is 10 atomic% or less.

8. The negative electrode material for a secondary battery according to claim 6, wherein the particle size of the plurality of primary oxide particles M is between 20 nm and 20 μm, and the particle size of the plurality of secondary oxide particles N is between 20 nm and 20 μm.

9. Current collector and, A negative electrode for a secondary battery comprising a negative electrode material layer disposed on the current collector and containing the negative electrode material for a secondary battery described in any one of claims 1 to 8.

10. The negative electrode for a secondary battery according to claim 9, wherein the negative electrode material layer further comprises a conductive agent mixed with the negative electrode material for the secondary battery.

11. The negative electrode for a secondary battery according to claim 10, wherein the conductive agent comprises carbon nanotubes, graphene, graphite, or conductive carbon.

12. The negative electrode for a secondary battery according to claim 9, wherein the current collector includes copper foil, aluminum foil, molybdenum foil, nickel foil, copper foil having a molybdenum-containing coating, nickel foil having a molybdenum-containing coating, aluminum foil having a molybdenum-containing coating, copper foil having a carbon nanotube-containing coating, nickel foil having a carbon nanotube-containing coating, or aluminum foil having a carbon nanotube-containing coating.

13. Positive electrode and, A negative electrode arranged separately from the positive electrode, wherein the negative electrode is the negative electrode for a secondary battery described in claim 9, An electrolyte placed between the positive electrode and the negative electrode, A secondary battery comprising a package structure that covers the positive electrode, the negative electrode, and the electrolyte.

14. The secondary battery according to claim 13, further comprising a separator installed between the positive electrode and the negative electrode, wherein the separator, the positive electrode and the negative electrode define a housing region, and the electrolyte is installed within the housing region.

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