Negative electrode unit, preparation method thereof and secondary battery

Abstract

The invention discloses a negative electrode unit and a preparation method thereof and a secondary battery, the negative electrode unit comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one surface of the negative electrode current collector, an ion channel is arranged in the negative electrode active material layer, the included angle between the ion channel and the negative electrode current collector is beta, beta meets the relational expression that beta is larger than 0 degree and smaller than 180 degrees. Compared with the prior art, the negative electrode unit provided by the invention is provided with the ordered ion channels, and the ordered ion channels provide a rapid transmission path for ions, so that the transmission time of the ions in the material is shortened, the embedding and separating efficiency of the ions is improved, and the charge-discharge performance and the cycle life of the battery are further optimized.

Description

Technical Field

[0001] This invention relates to the field of secondary battery technology, and in particular to a negative electrode unit, its preparation method, and a secondary battery. Background Technology

[0002] With the rapid development of rechargeable battery technology, the negative electrode, as a key component of the battery, directly affects the overall performance of the battery. Negative electrode cells often suffer from problems such as slow ion diffusion rates and low conductivity, which limit the battery's high-rate charge / discharge capability and cycle stability.

[0003] In negative electrode materials, the design and optimization of ion channels are crucial for improving battery performance. This is especially true in the application of one-dimensional and two-dimensional negative electrode active materials, where ion channel design becomes paramount. As the pathway for lithium-ion transport, the design of ion channels directly affects the efficiency of lithium-ion insertion and extraction, thus influencing the battery's charge-discharge performance and cycle life. Optimizing the ion channel structure and reducing ion transport resistance is key to improving battery performance.

[0004] Despite significant progress in ion channel design for two-dimensional anode active materials in existing technologies, several technical challenges remain. These include poor interlayer stability in two-dimensional materials and the inability to precisely control the orientation of ion channels within the anode unit.

[0005] Given the aforementioned defects in the current fabrication of negative electrode units, it is indeed necessary to provide a technical solution to address these problems. Summary of the Invention

[0006] The purpose of this invention is to provide a negative electrode unit that, by setting ordered ion channels, provides a rapid transport path for ions and reduces the transport time of ions within the material.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A negative electrode unit includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer has ion channels, and the angle between the ion channels and the negative electrode current collector is β, where β satisfies the relationship: 0° < β < 180°.

[0009] Preferably, the negative electrode active material layer includes the sheet-like negative electrode active material; the sheet-like negative electrode active material is formed from large-size negative electrode material slices of millimeter size or larger, and the large-size negative electrode material has a chemically continuous size of a in at least one direction in three-dimensional space, where a satisfies the relationship: a≥0.5mm.

[0010] Preferably, the negative electrode active material layer comprises N sheet-like negative electrode active materials, wherein N≥1; the N sheet-like negative electrode active materials are laid flat on the negative electrode current collector.

[0011] Preferably, the angle between the ion channel and the negative electrode current collector is β, and β satisfies the relationship: 70°<β<110°.

[0012] Preferably, the large-size negative electrode material includes negative electrode active material particles, which are negative electrode active materials with one-dimensional ion channel structures, two-dimensional ion channel structures, or anisotropic negative electrode active materials with three-dimensional ion channel structures.

[0013] Preferably, the large-size negative electrode material is produced by chemical synthesis, in-situ growth, or high-temperature sintering.

[0014] Preferably, the negative electrode active material of the one-dimensional ion channel structure is carbon nanotube or single-walled carbon nanotube; the negative electrode active material of the two-dimensional ion channel structure is graphite, hard carbon, soft carbon, graphene, black phosphorus, Na₂Ti₃O₇, Na 0.66 [Li 0.22 Ti 0.78 O2, Na 0.6 [Cr 0.6 Ti 0.4 The anode active material with anisotropic three-dimensional ion channel structure is one of the following: O2, NaTiOPO4, NH4TiOPO4, KTiOPO4, two-dimensional metal-based chalcogenides, and metal-based oxides;

[0015] Preferably, the sheet-like negative electrode active material is connected to the negative electrode current collector by bonding, pressurization, or heating.

[0016] Preferably, the ion channels in the sheet-like negative electrode active material are parallel to each other.

[0017] Preferably, the chemical size is at the atomic or molecular level.

[0018] Preferably, the negative electrode current collector includes one of copper foil, aluminum foil, composite copper foil, and composite aluminum foil.

[0019] This invention also provides a method for preparing a negative electrode unit, comprising the following steps:

[0020] Step 1: The negative electrode active material particles are made into large-size negative electrode materials of millimeter size and above, and the internal structure of the large-size negative electrode materials is obtained by scanning the large-size negative electrode materials with an electron microscope;

[0021] Step 2: The angle between the cutting direction and the ion channel of the large-size negative electrode material is α, where α satisfies the relationship: 0° < α < 180°, thus obtaining a sheet-like negative electrode active material;

[0022] Step 3: Install the sheet-like negative electrode active material onto at least one surface of the negative electrode current collector to obtain a negative electrode unit.

[0023] The present invention also provides a secondary battery, including the above-described negative electrode unit.

[0024] Compared to existing technologies, the advantages of this invention are as follows: This invention provides a negative electrode unit, including a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer contains ion channels, and the angle between the ion channels and the negative electrode current collector is β, where β satisfies the relationship: 0° < β < 180°. This unit, by setting ordered ion channels, provides a rapid transport path for ions, reduces the ion transport time within the material, improves the efficiency of lithium ion insertion and extraction, and thus optimizes the charge-discharge performance and cycle life of the battery. Attached Figure Description

[0025] Figure 1 This is one of the cross-sectional views of the negative electrode unit according to an embodiment of the present invention;

[0026] Figure 2 This is a second cross-sectional view of the negative electrode unit according to an embodiment of the present invention;

[0027] Figure 3 This is a third cross-sectional view of the negative electrode unit according to an embodiment of the present invention;

[0028] Figure 4 This is a top view of the negative electrode unit according to an embodiment of the present invention.

[0029] Among them, 1-negative electrode current collector; 2-negative electrode active material layer; 3-ion channel. Detailed Implementation

[0030] To make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0032] Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in this invention can be purchased commercially or prepared by existing methods.

[0033] According to a first aspect of the present invention, a negative electrode unit includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer contains ion channels, and the angle between the ion channels and the negative electrode current collector is β, where β satisfies the relationship: 0° < β < 180°. The ion channels in the negative electrode active material layer of the present invention are ordered, which can significantly improve the lithium-ion transport efficiency and the overall performance of the battery.

[0034] In one embodiment of the present invention, the negative electrode active material layer includes a sheet-like negative electrode active material, which is formed by large-size negative electrode material slices of millimeter size or larger. The large-size negative electrode material has a chemically continuous size of a in at least one direction in three-dimensional space, and a satisfies the relationship: a≥0.5mm.

[0035] The negative electrode active material layer comprises N sheet-like negative electrode active materials, where N ≥ 1; these N sheet-like negative electrode active materials are laid flat on the negative electrode current collector. The negative electrode active material layer can consist of a single sheet-like negative electrode active material or two or more sheet-like negative electrode active materials. Each sheet-like active material is cut according to a specific direction of its internal structure, resulting in multiple sheet-like negative electrode active materials with parallel internal ion channels. There can be gaps between adjacent sheet-like negative electrode active materials, or adjacent sheet-like negative electrode active materials can be mounted tightly against the negative electrode current collector. In summary, these ordered ion channels in the negative electrode active unit provide a rapid transport path for lithium ions or sodium ions, reducing the ion transport time within the material.

[0036] In one embodiment of the present invention, the large-size negative electrode material includes negative electrode active material particles, which are negative electrode active materials with one-dimensional ion channel structures, two-dimensional ion channel structures, or anisotropic negative electrode active materials with three-dimensional ion channel structures. When these three materials are used as negative electrode active materials to prepare negative electrode sheets, if the direction of the ion channels is parallel to the negative electrode current collector or if the numerous ion channels are randomly arranged, the ion transport rate will be severely reduced, affecting the electrochemical performance of the battery.

[0037] According to one embodiment of the present invention, large-size negative electrode materials are produced by chemical synthesis, in-situ growth, or high-temperature sintering. Chemical synthesis and high-temperature sintering methods are simple and easy to operate.

[0038] In one embodiment of the present invention, the negative electrode active material of the one-dimensional ion channel structure is carbon nanotube or single-walled carbon nanotube; the negative electrode active material of the two-dimensional ion channel structure is graphite, hard carbon, soft carbon, graphene, black phosphorus, Na2Ti3O7, Na 0.66 [Li 0.22 Ti 0.78 O2, Na 0.6 [Cr 0.6 Ti 0.4 The materials selected include O2, NaTiOPO4, NH4TiOPO4, KTiOPO4, two-dimensional metal-based chalcogenides, and metal-based oxides; materials with anisotropic three-dimensional ion channel structures include silicon-carbon anode materials, lithium-carbon anode materials, lithium polymer anode materials, carbon nanotube sphere anode materials, silicon nanowire sphere anode materials, germanium nanowire sphere anode materials, tin nanowire sphere anode materials, and graphene sphere anode materials. Specifically, this invention has found that the orientation of ion channels within the anode active material layer can be controlled by directional cutting and molding to improve the ion transport rate of the anode sheet and further optimize the electrochemical performance of the battery; however, it is not limited to these materials, and other materials whose ion channel orientation within the anode active material layer can be artificially controlled should be included.

[0039] In one embodiment of the present invention, the angle between the ion channel and the negative electrode current collector is β, and β satisfies the relationship: 70°<β<110°, for example, it can be 70°, 71°, 72°, 73°, 74°, 75°, 76°, 77°, 78°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°, 89°, 90°, 91°, 92°, 93°, 94°, 95°, 96°, 97°, 98°, 99°, 100°, 101°, 102°, 103°, 104°, 105°, 106°, 107°, 108°, 109°, 110°. By controlling the angle between the ion channel and the negative electrode current collector within this range, the lithium-ion transport efficiency can be significantly improved. Furthermore, when all ion channels are controlled within this range, even if the ion channels are not parallel to each other, there is still a good ion transport efficiency.

[0040] According to one embodiment of the present invention, the sheet-like negative electrode active material and the negative electrode current collector are connected by bonding, pressurization or heating.

[0041] In one embodiment of the invention, the ion channels in the sheet-like negative electrode active material are parallel. The parallel arrangement of the ion channels in the sheet-like negative electrode active material on one surface of the negative electrode current collector represents a significant advancement in ion channel design, as these ordered ion channels provide a rapid transport path for ions, reducing ion transport time within the material, improving the efficiency of lithium ion insertion and extraction, and thus optimizing the battery's charge-discharge performance and cycle life.

[0042] In the optimal case, the ion channels in the sheet-like anode active material are parallel. However, the ion channels in the entire anode active material layer are not necessarily parallel. This invention has found that due to lattice defects or other factors, it is difficult to obtain a material in which all ion channels are parallel. Therefore, it is only required that the ion channels in the sheet-like anode active material are parallel.

[0043] In one embodiment of the invention, the chemical size is either atomic or molecular.

[0044] In one embodiment of the present invention, the thickness of the sheet-like negative electrode active material is 10–5000 μm, for example, 10 μm, 50 μm, 100 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm, 900 μm, or 1000 μm; the width is 1–1000 mm, for example, 1 mm, 5 mm, 10 mm, 50 mm, or 100 mm. 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, 800mm, 900mm, 1000mm; lengths from 1 to 1000mm, for example, 1mm, 5mm, 10mm, 50mm, 100mm, 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, 800mm, 900mm, 1000mm. The specific size of the sheet-like negative electrode active material is related to the size of the large-size negative electrode material. If the large-size negative electrode material is large, a larger sheet-like negative electrode active material can be cut out. If the large-size negative electrode material is small, only a smaller sheet-like negative electrode active material can be cut out. The specific size of the sheet-like negative electrode active material is also related to the internal structure of the large-size negative electrode material. If the internal structure of the large-size negative electrode material is relatively regular, a larger sheet-like negative electrode active material can be cut out. Conversely, only a smaller sheet-like negative electrode active material can be cut out. The thickness of the sheet-like negative electrode active material depends on the requirements of the specific negative electrode sheet being prepared.

[0045] In one embodiment of the present invention, the negative electrode current collector includes one of copper foil, aluminum foil, composite copper foil, and composite aluminum foil. The negative electrode current collector of the present invention can be one of copper foil, aluminum foil, composite copper foil, and composite aluminum foil, or any material in the art that can be used as a negative electrode current collector.

[0046] According to a second aspect of the present invention, a method for preparing a negative electrode unit is also provided, comprising the following steps:

[0047] Step 1: The negative electrode active material particles are made into large-size negative electrode materials of millimeter size and above, and the large-size negative electrode materials are scanned with an electron microscope to obtain the internal structure of the large-size negative electrode materials;

[0048] Step 2: The angle between the cutting direction and the ion channel of the large-size negative electrode material is α, and α satisfies the relationship: 0°<α<180°, thus obtaining a sheet-like negative electrode active material;

[0049] Step 3: Install the sheet-like negative electrode active material onto at least one surface of the negative electrode current collector to obtain a negative electrode unit.

[0050] The internal structure of large-size anode materials can be obtained by scanning with an electron microscope, or by other testing instruments and methods that can obtain the internal structure of large-size anode active materials.

[0051] According to a third aspect of the invention, a secondary battery is also provided, comprising the aforementioned negative electrode unit. The secondary battery can be a liquid battery, a semi-solid battery, or a solid battery. When applied to a solid-state battery, the solid-solid interface contact problem is solved without applying pressure between the cells, thus solving the ionic conductivity problem and the kinetics problem to a certain extent.

[0052] Solid-state batteries offer better safety performance. On the one hand, the electrolyte is solid, resulting in less reactivity and side reactions across the entire temperature range, thus improving safety. On the other hand, like solar cells, even when using up to 70-80% of the capacity, there are still no safety issues such as lithium plating.

[0053] According to a fourth aspect of the present invention, an electrical device is also provided, comprising the aforementioned secondary battery. This electrical device can be a vehicle, mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, or power tool, etc. Vehicles can be gasoline-powered vehicles, natural gas-powered vehicles, or new energy vehicles; new energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc.; spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. The embodiments of this application do not impose special limitations on the aforementioned electrical device.

[0054] The present invention will be further described below through specific embodiments.

[0055] Example 1

[0056] Fabrication of the negative electrode unit:

[0057] Step 1: Fabricate graphite particles into large-size anode materials at the millimeter level or above, and use a scanning electron microscope to scan the large-size anode materials to obtain their internal structure;

[0058] Step 2: The angle between the cutting direction and the ion channel of the large-size negative electrode material is 90° to obtain a sheet-like negative electrode active material;

[0059] Step 3: Spread multiple sheet-like negative electrode active materials on the two surfaces of the negative electrode current collector to obtain a negative electrode unit; wherein the angle between the ion channel and the negative electrode current collector is 90°.

[0060] Solid-state battery fabrication:

[0061] A solid-state battery is obtained by stacking a "sandwich" structure consisting of a positive electrode, a solid electrolyte membrane, and a negative electrode, and then encapsulating it, with LiCoO2 as the positive electrode active material.

[0062] Table 1 shows the experimental parameters of Examples 1-15 and Comparative Example 1. The rest are the same as those of Example 1, and will not be repeated here.

[0063] Table 1

[0064]

[0065]

[0066] Comparative Example 1

[0067] Graphite, conductive carbon nanotubes, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose were mixed evenly in deionized water at a mass ratio of 97.2:1.2:0.8:0.8. After uniform mixing, the negative electrode slurry was coated onto copper foil, baked, rolled, and slit to obtain the negative electrode sheet.

[0068] Preparation of positive electrode

[0069] The experimentally obtained positive electrode material LiCoO2, conductive agent acetylene black, and binder vinylidene fluoride (PVDF) were thoroughly stirred in an N-methylmethylpyrrolidone solvent system at a mass ratio of 95.5:2.5:2. After uniform stirring, a positive electrode slurry was obtained. The slurry was coated onto Al foil, baked, rolled, and slit to obtain the positive electrode sheet.

[0070] Preparation of diaphragm

[0071] Polyethylene (PE) polymer film is used as the separator.

[0072] Preparation of electrolyte

[0073] An organic solution was obtained by mixing the following components and in the following mass ratio: ethylene carbonate (EC): propyl propionate (PP): vinylene carbonate (VC): diethyl carbonate (DEC): propylene carbonate (PC) = 22:25:3:28:22; lithium salt LiPF6 was added to the organic solution at a mass ratio of 9.5:90.5; after mixing thoroughly, an electrolyte was obtained.

[0074] Battery manufacturing

[0075] The positive electrode, separator, and negative electrode are stacked in sequence and wound to obtain an electrode assembly. The electrode assembly is then placed in a packaging shell, electrolyte is injected into the packaging shell, and the shell is sealed to obtain a lithium-ion battery.

[0076] Performance testing:

[0077] The secondary batteries of Examples 1-15 and Comparative Example 1 were subjected to DC internal resistance tests and charge-discharge tests, and the results are shown in Table 2.

[0078] Table 2

[0079]

[0080] As shown in Table 2, comparing the experimental data of Examples 1-15 with those of Comparative Example 1, the time data for charging to 80% capacity at 5C and the discharge rate data of the battery at 1.0C@0.2C in Examples 1-15 are both better than those in Comparative Example 1. This indicates that the ordered ion channels set in this invention can provide a fast transport path for ions, reduce the transport time of ions inside the material, improve the efficiency of lithium ion insertion and extraction, and thus optimize the charge and discharge performance and cycle life of the battery.

[0081] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A negative electrode unit, characterized by comprising: The negative electrode active material layer comprises sheet-shaped negative electrode active material; the sheet-shaped negative electrode active material is formed by slicing a large-size negative electrode material with a millimeter level or above, and a chemical continuous size of the large-size negative electrode material in at least one direction in three-dimensional space is a, which satisfies the relationship: a≥0.5 mm.

2. The negative cell of claim 1, wherein The angle between the ion channel and the negative electrode current collector is β, and β satisfies the relationship: 70°<β<110°.

3. The negative cell of claim 1, wherein The negative electrode active material layer comprises N sheet-shaped negative electrode active materials, wherein N≥1; the N sheet-shaped negative electrode active materials are tiled on the negative electrode current collector.

4. The negative cell of claim 2, wherein The large-size negative electrode material comprises negative electrode active material particles, which are one-dimensional ion channel structure negative electrode active material, two-dimensional ion channel structure negative electrode active material, or three-dimensional ion channel structure anisotropic negative electrode active material.

5. The negative cell of claim 2, wherein The ion channels in the sheet-shaped negative electrode active material are parallel.

6. The negative cell of claim 5, wherein, The negative active material of the one-dimensional ion channel structure is carbon nanotube or single-walled carbon nanotube; the negative active material of the two-dimensional ion channel structure is one of graphite, hard carbon, soft carbon, graphene, black phosphorus, Na2Ti3O7, Na2Ti2O7, Na2TiO2, NaTiOPO4, NH4TiOPO4, KTiOPO4, two-dimensional metal-based chalcogenides and metal-based oxides; and the anisotropic negative active material of the three-dimensional ion channel structure is one of silicon-carbon negative electrode material, lithium-carbon negative electrode material, lithium-polymer negative electrode material, carbon nanotube wire sphere negative electrode material, silicon nanowire sphere negative electrode material, germanium nanowire sphere negative electrode material, tin nanowire sphere negative electrode material and graphene sphere negative electrode material. 0.66 [Li 0.22 Ti 0.78 ]O2, Na 0.6 [Cr 0.6 Ti 0.4 ]O2, NaTiOPO4, NH4TiOPO4, KTiOPO4, two-dimensional metal-based chalcogenides and metal-based oxides; and the anisotropic negative active material of the three-dimensional ion channel structure is one of silicon-carbon negative electrode material, lithium-carbon negative electrode material, lithium-polymer negative electrode material, carbon nanotube wire sphere negative electrode material, silicon nanowire sphere negative electrode material, germanium nanowire sphere negative electrode material, tin nanowire sphere negative electrode material and graphene sphere negative electrode material.

7. The negative cell of claim 2, wherein The chemical size is an atomic level size or a molecular level size.

8. The negative cell of claim 2, wherein, The method comprises the following steps:

9. A method for producing a negative electrode unit, characterized by Step one: negative electrode active material particles are made into large-size negative electrode material with a millimeter level or above, and an electron microscope is used to scan the large-size negative electrode material to obtain the internal structure of the large-size negative electrode material; Step two: the angle between the cutting direction and the ion channel of the large-size negative electrode material is a, which satisfies the relationship: 0°<a<180°, to obtain sheet-shaped negative electrode active material; Step three: the sheet-shaped negative electrode active material layer is installed on at least one surface of the negative electrode current collector to obtain a negative electrode unit. The negative electrode unit comprises any one of claims 1-8.

10. A secondary battery characterized by comprising: ​

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