Negative current collector, method for manufacturing the same, negative electrode sheet, battery, and electric device

Abstract

The application relates to the field of batteries, in particular to a negative electrode current collector and a preparation method thereof, a negative electrode sheet, a battery and a power utilization device. The application provides a negative electrode current collector, which comprises a base body and a modification layer formed on the surface of the base body; the modification layer comprises a crystal face with an adsorption energy of (-0.1 eV) to (0.1 eV), and the exposure area ratio of the crystal face is not less than 50% of the single-side surface of the base body. The adsorption of lithium by the current collector is moderate, which can ensure the adsorption of lithium and simultaneously prevent the adsorption from being too strong to affect the diffusion of lithium on the surface of the copper foil, thereby being beneficial to the formation of dendrite-free lithium deposition and the improvement of the service life of the battery.

Description

Technical Field

[0001] This application relates to a negative electrode current collector and its preparation method, a negative electrode sheet, a battery, and an electrical device. Background Technology

[0002] In recent years, with the development of lithium-ion rechargeable battery technology, lithium-ion rechargeable batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion rechargeable batteries, higher requirements have been placed on their battery life. Summary of the Invention

[0003] The purpose of this application is to provide a negative electrode current collector and its preparation method, a negative electrode sheet, a battery, and an electrical device.

[0004] The embodiments of this application are implemented as follows:

[0005] In a first aspect, embodiments of this application provide a negative electrode current collector, which includes a substrate and a modification layer formed on the surface of the substrate; the modification layer includes crystal planes with adsorption energies of (-0.1eV) to (0.1eV), and the exposed area of ​​the crystal planes accounts for not less than 50% of the surface of one side of the substrate.

[0006] Currently, the commonly used negative electrode current collector is conventional copper foil (mainly Cu(100) crystal plane). The lithium deposition morphology on the surface of this conventional copper foil is dendritic, which easily leads to short circuit problems, as well as more side reactions and poor battery life. Studies have found that this is because conventional copper foil has a strong adsorption of lithium (adsorption energy is generally -0.23 eV), which is not conducive to the diffusion of lithium on the surface of the copper foil, thus easily leading to lithium dendrites. Therefore, this application provides a negative electrode current collector, which includes a substrate and a modification layer formed on the surface of the substrate; the modification layer includes crystal planes with adsorption energy of (-0.1 eV) to (0.1 eV), and the exposed area of ​​the crystal planes is not less than 50% of the surface of one side of the substrate. This current collector has moderate lithium adsorption, which can ensure lithium adsorption, but at the same time, it is not so strong as to affect the diffusion of lithium on the surface of the copper foil, thus facilitating the formation of dendrite-free lithium deposition; which is beneficial to improving battery life.

[0007] In some alternative implementations, the adsorption energy of the crystal plane is (-0.05 eV) to (-0.08 eV).

[0008] By further limiting the adsorption energy of the crystal plane to between (-0.05eV) and (-0.08eV), the adsorption of lithium can be further improved without the adsorption being too strong and affecting the diffusion of lithium on the copper foil surface, thus facilitating the formation of dendrite-free lithium deposition.

[0009] In some alternative implementations, the exposed area of ​​the crystal facet is greater than or equal to 62% and less than or equal to 100% of the single-sided surface of the substrate.

[0010] The exposed area of ​​the crystal facet is greater than or equal to 62% and less than or equal to 100% of the single-sided surface of the substrate, which can effectively improve the lithium deposition morphology and the battery cycle life.

[0011] In some optional implementations, the exposed area of ​​the crystal facet is not less than 80% of the surface area of ​​a single side of the substrate.

[0012] The exposed area of ​​the crystal facet is greater than or equal to 80% and less than or equal to 100% of the single-sided surface of the substrate, which can greatly improve the lithium deposition morphology and the battery cycle life.

[0013] In some alternative implementations, the substrate includes at least one of copper foil, nickel foil, titanium foil, or stainless steel.

[0014] All of the above materials can be used as substrates for negative electrode current collectors. They are easy to modify to obtain a modified layer with crystal planes having an adsorption energy of (-0.1eV) to (0.1eV) and the exposed area of ​​the crystal planes being no less than 50% of the surface of one side of the substrate.

[0015] In some alternative embodiments, the crystal plane includes at least one of Fe(110) crystal plane or Cu(111) crystal plane.

[0016] The adsorption energy of the Fe(110) crystal plane is -0.08eV, which can ensure the adsorption of lithium without being too strong and affecting the diffusion of lithium on the copper foil surface, thus facilitating the formation of dendrite-free lithium deposition.

[0017] The adsorption energy of the Cu(111) crystal plane is -0.05eV, which can ensure the adsorption of lithium without being too strong and affecting the diffusion of lithium on the copper foil surface, thus facilitating the formation of dendrite-free lithium deposition.

[0018] In some alternative implementations, the substrate is selected as copper foil and the crystal plane is selected as Fe(110) crystal plane.

[0019] Fe(110) crystal planes are easily formed on the substrate surface of copper foil, and both copper foil and Fe(110) crystal planes have excellent properties, which is conducive to the formation of dendrite-free lithium deposition and improves battery cycle life.

[0020] In some alternative implementations, the thickness of the modification layer is less than 1 μm.

[0021] In some optional embodiments, the thickness of the modified layer is 10 nm to 1 μm; alternatively, the thickness of the modified layer is 100 nm to 300 nm.

[0022] The thickness of the modification layer is 10 nm to 1 μm. Within this thickness range, the morphology of the modification layer formed on the substrate surface is easily controlled, and within this thickness range, the resistance of the entire current collector will not be too high.

[0023] When the thickness of the modification layer is greater than 1 μm, the resistance of the modification layer itself will affect the resistance of the entire current collector, making the resistance of the entire current collector too high, which is detrimental to the cycle performance of the battery.

[0024] The modified layer has a thickness of 100nm to 300nm and exhibits better battery cycle life and lithium deposition morphology.

[0025] In some alternative implementations, the thickness of the modification layer is 0.25 nm to 10 nm; alternatively, the thickness of the modification layer is 1 nm to 5 nm.

[0026] The thickness of the modification layer is set to 0.25nm to 10nm. Within this thickness range, it is easy to control the morphology of the modification layer formed on the substrate surface, and within this thickness range, the resistance of the entire current collector will not be too high.

[0027] When the thickness of the modification layer is less than 0.25 nm (the diameter of both iron and copper atoms is approximately 0.25 nm), which is less than one atomic layer, it is almost impossible to control the morphology of the modification layer, making it difficult to obtain a modification layer with a good morphology. When the morphology of the modification layer is poor, the lithium deposited in these poor areas will still exist in the form of dendrites, which may not only puncture the separator and cause safety risks, but also lead to more side reactions due to the large specific surface area of ​​lithium, resulting in a decrease in the cycle performance of the battery.

[0028] The modified layer has a thickness of 1nm to 5nm and exhibits better battery cycle life and lithium deposition morphology.

[0029] In some alternative implementations, the resistance of the negative current collector is 1.75 nΩ / cm. 2 ~5nΩ / cm 2 .

[0030] By setting the resistance of the negative current collector to 1.75 nΩ / cm 2 ~5nΩ / cm 2 Within this range, it is beneficial to obtain good battery cycle performance.

[0031] Secondly, embodiments of this application provide a method for preparing a current collector, comprising:

[0032] A modification layer with crystal planes having an adsorption energy of (-0.1eV) to (0.1eV) is formed on the surface of a substrate, wherein the exposed area of ​​the crystal planes accounts for not less than 50% of the surface area of ​​a single side of the substrate.

[0033] In the above technical solution, a modification layer with a crystal plane having an adsorption energy of (-0.1eV) to (0.1eV) is formed on the substrate surface. The exposed area of ​​the crystal plane accounts for no less than 50% of the single-sided surface of the substrate, which can ensure the adsorption of lithium, while not being too strong to affect the diffusion of lithium on the copper foil surface, thus facilitating the formation of dendrite-free lithium deposition and improving battery life.

[0034] In some alternative embodiments, forming a modification layer on the substrate surface having crystal planes with adsorption energies of (-0.1 eV) to (0.1 eV) includes:

[0035] A modification layer is atomically deposited on the substrate surface, with a thickness of 0.25 nm to 10 nm.

[0036] Atomic deposition technology makes it easy to obtain a modified layer with a thickness between 0.25 nm and 10 nm and a stable morphology.

[0037] In some alternative embodiments, forming a modification layer on the substrate surface having crystal planes with adsorption energies of (-0.1 eV) to (0.1 eV) includes:

[0038] An electrodeposition modification layer is induced on the substrate surface, with a thickness of 10 nm to 1 μm.

[0039] By employing induced electrodeposition, it is easy to obtain a modified layer with a thickness ranging from 1 atomic layer to 10 nm and a stable morphology.

[0040] In some alternative embodiments, an electrodeposition modification layer is induced on the substrate surface, including:

[0041] An inducing agent is used to induce electrodeposition of a modified layer on the substrate surface.

[0042] Using an inducing agent to induce an electrodeposition modification layer on the substrate surface can easily improve the lithium deposition morphology and battery cycle life.

[0043] In some alternative implementations, the inducing agent includes Zn. 2+ Zn in the inducer 2+ The concentration is 0.2 mol / L to 0.4 mol / L.

[0044] Within the above concentration range, it is easy to obtain a morphologically stable modified layer.

[0045] Thirdly, embodiments of this application provide a negative electrode sheet, which includes: the negative current collector provided in any of the first aspects above.

[0046] The negative electrode in the above scheme includes the aforementioned negative current collector. When this negative electrode is applied in a battery, it can improve the problem that the negative electrode is prone to forming dendritic morphology, short circuits, and numerous side reactions.

[0047] Fourthly, embodiments of this application provide a battery, wherein the battery has a negative electrode sheet provided in any of the third aspects described above.

[0048] The battery in the above technical solution includes the aforementioned negative electrode sheet, which can improve the problems of the negative electrode sheet being prone to dendritic morphology, short circuits, numerous side reactions, and poor lifespan.

[0049] Fifthly, embodiments of this application provide an electrical device, which includes the battery provided in any of the fourth aspects above.

[0050] In the above technical solution, the electrical device has a better battery life by incorporating the battery provided by the fourth aspect. Attached Figure Description

[0051] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0052] Figure 1 This application provides structural schematic diagrams of vehicles for some embodiments;

[0053] Figure 2 Exploded views of batteries provided for some embodiments of this application;

[0054] Figure 3 for Figure 2 The exploded view of the battery cell shown;

[0055] Figure 4 A partial structural schematic diagram of an electrode assembly provided in some embodiments of this application;

[0056] Figure 5 SEM test results of current collectors provided in some embodiments of this application;

[0057] Figure 6 SEM test results of current collectors provided in other embodiments of this application;

[0058] Figure 7 SEM test results of current collectors provided for some comparative examples in this application.

[0059] icon:

[0060] 1000 vehicles;

[0061] Battery 100; Controller 200; Motor 300;

[0062] Box body 10; First part 11; Second part 12; Storage space 13;

[0063] Battery cell 20; casing 21; electrode assembly 22; electrode terminals 23; pressure relief structure 24;

[0064] 211 housing; 212 cover; 221 positive electrode plate; 222 negative electrode plate; 223 separator;

[0065] Positive electrode current collector 2211; Positive electrode active material layer 2212;

[0066] Negative electrode current collector 2221; negative electrode active material layer 2222. Detailed Implementation

[0067] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0068] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0069] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0070] In the description of the embodiments of this application, the technical terms "inner" and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0071] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0072] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0073] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the height, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall height, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0074] Currently, the commonly used negative electrode current collector is conventional copper foil (mainly Cu(100) crystal plane). The lithium deposition morphology on the surface of this conventional copper foil is dendritic, which easily leads to short circuit problems, as well as more side reactions and poor battery life. Studies have found that this is because conventional copper foil has a strong adsorption of lithium (adsorption energy is generally -0.23 eV), which is not conducive to the diffusion of lithium on the surface of the copper foil, thus making it easy for lithium dendrites to form.

[0075] This application provides a negative electrode current collector, which includes a substrate and a modification layer formed on the surface of the substrate; the modification layer includes crystal planes with adsorption energies of (-0.1eV) to (0.1eV), and the exposed area of ​​the crystal planes accounts for not less than 50% of the surface of one side of the substrate.

[0076] Theoretical calculations show that the suitable adsorption energy range for lithium is (-0.1 eV) to (0.1 eV). This range provides moderate lithium adsorption, ensuring sufficient adsorption without excessively strong adsorption that could hinder lithium diffusion on the copper foil surface. This facilitates the formation of dendrite-free lithium deposition and improves battery life. Based on the above research, this application provides a current collector comprising a substrate and a modification layer formed on the substrate surface. The modification layer includes crystal planes with adsorption energies of (-0.1 eV) to (0.1 eV), and the exposed area of ​​the crystal planes accounts for no less than 50% of the surface area of ​​a single side of the substrate. By providing a modification layer with crystal planes having adsorption energies of (-0.1 eV) to (0.1 eV) and an exposed area of ​​the crystal planes accounting for no less than 50% of the surface area of ​​a single side of the substrate, the problem of dendrite formation during lithium deposition can be effectively mitigated.

[0077] The negative electrode provided in this application includes the current collector mentioned above. When applied in a battery, the negative electrode can improve the problem that the negative electrode is prone to dendritic morphology, short circuit, and numerous side reactions.

[0078] The battery provided in this application includes the negative electrode sheet mentioned above, thereby improving the problems of the negative electrode sheet being prone to dendritic morphology, short circuits, numerous side reactions, and poor lifespan.

[0079] The electrical device provided in this application includes the battery mentioned above, thereby improving the service life of the electrical device.

[0080] For ease of explanation, the following embodiments use a lithium-ion battery according to an embodiment of this application as an example.

[0081] See Figure 1 , Figure 1 This is a schematic diagram of the structure of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0082] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0083] In this application, battery 100 can refer to a physical module including a single battery cell, or it can be a single physical module including multiple battery cells 20 to provide higher voltage and capacity. Battery 100 can be in the form of a battery module or battery pack, and battery 100 can include a housing 10 for encapsulating one or more battery cells 20. Housing 10 can prevent liquids or other foreign objects from affecting the charging or discharging of battery cells 20.

[0084] See Figure 2 , Figure 2 The exploded view of a battery 100 provided in some embodiments of this application shows that the battery 100 may include a housing 10 and a battery cell 20, with the battery cell 20 housed within the housing 10. The housing 10 is used to house the battery cell 20 and may have various structures. In some embodiments, the housing 10 may include a first portion 11 and a second portion 12, which overlap each other, defining a housing space 13 for accommodating the battery cell 20. The second portion 12 may be a hollow structure with one open end, and the first portion 11 may be a plate-like structure, overlapping the open side of the second portion 12 to form a housing 10 with the housing space 13. Alternatively, both the first portion 11 and the second portion 12 may be hollow structures with one open side, overlapping the open side of the second portion 12 to form a housing 10 with the housing space 13. Of course, the first portion 11 and the second portion 12 may have various shapes, such as cylinders, cuboids, etc.

[0085] In battery 100, there can be one or more battery cells 20. If there are multiple battery cells 20, they can be connected in series, in parallel, or in a mixed configuration. A mixed configuration means that multiple battery cells 20 are connected in both series and parallel. Multiple battery cells 20 can be directly connected in series, in parallel, or in a mixed configuration, and then the whole assembly of multiple battery cells 20 is housed in housing 10. Alternatively, multiple battery cells 20 can first be connected in series, in parallel, or in a mixed configuration to form modules, and then multiple modules can be connected in series, in parallel, or in a mixed configuration to form a whole, which is then housed in housing 10. Battery 100 may also include other structures. For example, multiple battery cells 20 can be electrically connected through a busbar component to achieve parallel, series, or mixed configuration of multiple battery cells 20.

[0086] Each battery cell 20 can be a lithium-ion battery, such as a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery or a magnesium-ion battery, but is not limited to these.

[0087] See Figure 3 , Figure 3 for Figure 2The diagram shows an exploded view of a single battery cell 20. A single battery cell 20 refers to the smallest unit that makes up the battery 100. A single battery cell 20 may include a housing 21, an electrode assembly 22, and an electrolyte, with the electrode assembly 22 and electrolyte both housed within the housing 21.

[0088] The outer casing 21 may include a housing 211 and a cover 212. The housing 211 is an assembly that fits with the cover 212 to form an internal sealed space for the battery cell 20, wherein the formed sealed space can accommodate the electrode assembly 22, electrolyte, and other components. The cover 212 is a component that covers the opening of the housing 211 to isolate the internal environment of the battery cell 20 from the external environment. The shape of the cover 212 may be adapted to the shape of the housing 211 to fit the housing 211, and the cover 212 may also be provided with functional components such as electrode terminals 23 and pressure relief structures 24. A sealing ring may be provided between the opening of the housing 211 and the cover 212 to achieve a seal between the housing 211 and the cover 212.

[0089] The housing 211 and cover 212 can be of various shapes and sizes, such as cuboids, cylinders, and hexagonal prisms. Specifically, the shapes of the housing 211 and cover 212 can be determined according to the specific shape and size of the electrode assembly 22. The materials of the housing 211 and cover 212 can be various, such as, but not limited to, metals like copper, iron, aluminum, stainless steel, and aluminum alloys. The materials of the sealing ring can be various, such as, but not limited to, materials resistant to electrolyte corrosion, high toughness, and fatigue resistance, such as PP (polypropylene), PC (polycarbonate), and PET (polyethylene terephthalate). A plating layer can be formed on the outer surface of the housing 211, and the plating layer material can be various, such as, but not limited to, corrosion-resistant materials like Ni and Cr.

[0090] See Figure 4 The electrode assembly 22 may consist of a positive electrode 221, a negative electrode 222, and a separator 223. The separator 223 is located between the positive electrode 221 and the negative electrode 222 and serves as an separator. The electrode assembly 22 may be a wound structure or a stacked structure, and the embodiments of this application are not limited thereto.

[0091] See Figure 4The positive electrode 221 includes a positive current collector 2211 and a positive active material layer 2212. Taking a lithium-ion battery cell 20 as an example, the material of the positive current collector 2211 can be aluminum. The positive active material layer 2212 includes a positive active material. In some embodiments of this application, the positive active material may include: layered structure materials (e.g., LiMO2, where M = Co, Ni, NiCo, NiCoMn, NiCoAl), olivine structure materials (e.g., LiMPO4, where M = Fe, Co, Mn), or spinel structure materials (e.g., LiM2O4, where M = Fe, Co, Mn).

[0092] Please continue reading Figure 4 The negative electrode 222 includes a negative electrode current collector 2221 and a negative electrode active material layer 2222, wherein the negative electrode active material layer 2222 includes a negative electrode active material. The negative electrode active material includes at least one of graphite, silicon, silicon alloy, or tin alloy.

[0093] In other optional embodiments of this application, the negative electrode sheet 222 can be directly formed from the negative electrode current collector 2221, without the negative electrode active material layer 2222.

[0094] In some embodiments of this application, the negative electrode current collector 2221 described above includes a substrate and a modification layer formed on the surface of the substrate; the modification layer includes crystal planes with adsorption energies of (-0.1eV) to (0.1eV), and the exposed area of ​​the crystal planes accounts for not less than 50% of the surface of one side of the substrate.

[0095] Using the above-mentioned current collector can effectively improve the problems of lithium deposition, such as the easy formation of dendritic morphology, short circuits, numerous side reactions, and poor lifespan.

[0096] Furthermore, in some embodiments of this application, the adsorption energy of the crystal plane is (-0.05eV) to (-0.08eV).

[0097] By further limiting the adsorption energy of the crystal plane to (-0.05eV) to (-0.08eV), the adsorption of lithium can be further improved without the adsorption being too strong and affecting the diffusion of lithium on the copper foil surface, thus facilitating the formation of dendrite-free lithium deposition.

[0098] Furthermore, in some embodiments of this application, the adsorption energy of the crystal plane described above is, for example, -0.05 eV, -0.06 eV, -0.07 eV, -0.08 eV or -0.1 eV.

[0099] Furthermore, in some embodiments of this application, the adsorption energy of the crystal plane described above is obtained by density functional theory (DFT) calculation.

[0100] Furthermore, in some embodiments of this application, the exposed area of ​​the crystal plane is greater than or equal to 62% and less than or equal to 100% of the single-sided surface of the substrate.

[0101] If the exposed area of ​​the crystal facet is too low, the lithium deposited in these areas will still exist in dendritic form because a large number of faces are still the substrate (e.g., Fe(100) / (111) crystal facets). This may not only puncture the isolation membrane and cause safety risks, but also lead to more side reactions due to the large specific surface area of ​​lithium, resulting in a decrease in cycle performance.

[0102] The exposed area of ​​the crystal facet is greater than or equal to 62% and less than or equal to 100% of the single-sided surface of the substrate, which can effectively improve the lithium deposition morphology and the battery cycle life.

[0103] Furthermore, in some embodiments of this application, the exposed area of ​​the crystal plane is greater than or equal to 80% and less than or equal to 100% of the single-sided surface of the substrate.

[0104] By further limiting the exposed area of ​​the crystal facets to the aforementioned range, the lithium deposition morphology can be greatly improved, and the battery cycle life can be greatly improved.

[0105] Furthermore, in some embodiments of this application, the aforementioned exposure area percentage is calculated according to the following formula:

[0106]

[0107] In the formula, TC represents the percentage of exposed area, and I... (hkl) I represents the diffraction intensity of the crystal plane of the modified layer material powder (hkl); 0(hkl) The diffraction intensity of the modified layer material corresponding to the standard powder (hkl) crystal plane.

[0108] For example, for the Fe(110) crystal plane, the above (hkl) is (110).

[0109] Furthermore, in some embodiments of this application, for example, the exposed area percentage of the crystal plane is 65%, 70%, 75%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 95%, or 100% of the single-sided surface of the substrate.

[0110] Furthermore, in some embodiments of this application, the substrate mentioned above includes at least one of copper foil, nickel foil, titanium foil, or stainless steel.

[0111] The aforementioned copper foil, nickel foil, titanium foil, or stainless steel can all be used as negative electrode current collectors, and the aforementioned modification layer can be easily formed on their surface.

[0112] Furthermore, in some embodiments of this application, the crystal plane includes at least one of the Fe(110) crystal plane or the Cu(111) crystal plane.

[0113] The adsorption energy of the Fe(110) or Cu(111) crystal planes mentioned above is between (-0.05eV) and (-0.08eV). They have strong adsorption of lithium, but the adsorption is not so strong that it would affect the diffusion of lithium on the copper foil surface, thus facilitating the formation of dendrite-free lithium deposition.

[0114] Furthermore, in some embodiments of this application, the substrate is selected as copper foil, and the crystal plane is selected as Fe(110) crystal plane.

[0115] Copper foil, as the substrate material for negative electrode current collectors, has superior performance compared to nickel foil, titanium foil, or stainless steel. The adsorption energy of lithium on the Fe(110) crystal surface is about -0.08eV, and the adsorption strength of lithium is moderate. It can adsorb lithium without being too strong and affecting the diffusion of lithium on the copper foil surface. When combined with copper foil, they can interact to achieve better results and are more conducive to the formation of dendrite-free lithium deposition.

[0116] Furthermore, in some embodiments of this application, the thickness of the modification layer is less than 1 μm.

[0117] By setting the thickness of the modification layer to less than 1 μm, it is beneficial to keep the resistance of the entire current collector within an optimal range.

[0118] Furthermore, in some embodiments of this application, the thickness of the modification layer is 10 nm to 1 μm.

[0119] The thickness of the modification layer is set to 10 nm to 1 μm. Within this thickness range, it is easy to control the morphology of the modification layer formed on the substrate surface, and within this thickness range, the resistance of the entire current collector will not be too high.

[0120] When the thickness of the modification layer is greater than 1 μm, the resistance of the modification layer itself will affect the resistance of the entire current collector, making the resistance of the entire current collector too high, which is detrimental to the cycle performance of the battery.

[0121] Furthermore, the thickness of the aforementioned modification layer is 10 nm to 1 μm, which is easy to form in terms of process. For example, an electrodeposition process can be used to form a modification layer with a thickness of 10 nm to 1 μm on the substrate surface.

[0122] Furthermore, in some embodiments of this application, the thickness of the above-mentioned modification layer is, for example, 20nm, 50nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm or 800nm.

[0123] Furthermore, in some embodiments of this application, the thickness of the modification layer is 100 nm to 300 nm.

[0124] The modified layer has a thickness of 100nm to 300nm and exhibits better battery cycle life and lithium deposition morphology.

[0125] Furthermore, in some embodiments of this application, the thickness of the modification layer is 0.25 nm to 10 nm.

[0126] The thickness of the modification layer is set to 0.25nm to 10nm. Within this thickness range, it is easy to control the morphology of the modification layer formed on the substrate surface, and within this thickness range, the resistance of the entire current collector will not be too high.

[0127] When the thickness of the modification layer is less than 0.25 nm (the diameter of both iron and copper atoms is approximately 0.25 nm), which is less than one atomic layer, it becomes extremely difficult to control the morphology of the modification layer, making it challenging to obtain a modification layer with a good morphology. When the morphology of the modification layer is poor, the lithium deposited in these poorly shaped areas will still exist in dendrite form. This not only risks puncturing the separator and causing safety hazards, but also leads to more side reactions due to the large specific surface area of ​​lithium, resulting in decreased battery cycle performance.

[0128] Furthermore, in some embodiments of this application, the thickness of the modification layer is set to 0.25 nm to 10 nm, which is also easy to form in terms of process. For example, the thickness of the modification layer can be formed by atomic layer deposition.

[0129] Furthermore, in some embodiments of this application, the thickness of the above-mentioned modification layer is, for example, 0.3nm, 0.4nm, 0.6nm, 0.8nm, 1nm, 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm or 9nm.

[0130] Furthermore, in some embodiments of this application, the thickness of the modification layer is 1 nm to 5 nm.

[0131] The modified layer has a thickness of 1nm to 5nm and exhibits better battery cycle life and lithium deposition morphology.

[0132] Furthermore, in some embodiments of this application, the thickness of the above-mentioned modification layer can be tested by cross-sectional SEM or TEM.

[0133] Furthermore, in some embodiments of this application, the resistance of the current collector is 1.75 nΩ / cm. 2 ~5nΩ / cm 2 .

[0134] By setting the resistance of the current collector to 1.75 nΩ / cm 2 ~5nΩ / cm 2 Within this range, it is beneficial to obtain good battery cycle performance.

[0135] Alternatively, the current collector resistance is 1.75 nΩ / cm. 2 ~4.31nΩ / cm 2 .

[0136] By setting the resistance of the current collector to 1.75 nΩ / cm 2 ~4.31nΩ / cm 2 Within this range, it is beneficial to improve battery cycle performance.

[0137] Further, optionally, in some embodiments of this application, the resistance of the current collector is 1.75 nΩ / cm. 2 ~3.43nΩ / cm 2 .

[0138] The resistivity of the current collector is further reduced to 1.75 nΩ / cm. 2 ~3.43nΩ / cm 2 This is beneficial for obtaining better battery cycle performance.

[0139] Furthermore, in some embodiments of this application, the resistance of the current collector is, by way of example, 1.75 nΩ / cm. 2 1.76 nΩ / cm 2 1.80 nΩ / cm 2 1.82nΩ / cm 2 1.95nΩ / cm 2 2.00 nΩ / cm 2 2.14 nΩ / cm 2 2.15 nΩ / cm 2 2.16 nΩ / cm 2 2.50 nΩ / cm 2 Or 3.00 nΩ / cm 2 .

[0140] In some embodiments of this application, the above-described method for preparing the current collector includes:

[0141] A modification layer with crystal planes having an adsorption energy of (-0.1eV) to (0.1eV) is formed on the surface of a substrate, wherein the exposed area of ​​the crystal planes accounts for not less than 50% of the surface area of ​​a single side of the substrate.

[0142] A modification layer with crystal planes having an adsorption energy of (-0.1eV) to (0.1eV) is formed on the substrate surface. The exposed area of ​​the crystal planes accounts for no less than 50% of the surface of a single side of the substrate. This ensures the adsorption of lithium without being too strong and affecting the diffusion of lithium on the copper foil surface, thus facilitating the formation of dendrite-free lithium deposition and improving battery life.

[0143] Furthermore, in some embodiments of this application, forming a modification layer on the substrate surface having crystal planes with adsorption energies of (-0.1 eV) to (0.1 eV) includes:

[0144] A modification layer is atomically deposited on the substrate surface, with a thickness of 0.25 nm to 10 nm.

[0145] Atomic deposition technology makes it easy to obtain a modified layer with a thickness of 0.25 nm to 10 nm and a stable morphology.

[0146] Furthermore, in some embodiments of this application, forming a modification layer on the substrate surface having crystal planes with adsorption energies of (-0.1 eV) to (0.1 eV) includes:

[0147] An electrodeposition modification layer is induced on the substrate surface, with a thickness of 10 nm to 1 μm.

[0148] By employing induced electrodeposition, it is easy to obtain a modified layer with a thickness of 10 nm to 1 μm and a stable morphology.

[0149] Furthermore, in some embodiments of this application, an electrodeposition modification layer is induced on the substrate surface, including:

[0150] An inducing agent is used to induce electrodeposition of a modified layer on the substrate surface.

[0151] Under the same conditions, compared with the absence of an inducing agent, the use of an inducing agent to induce an electrodeposition modification layer on the substrate surface is more likely to improve the lithium deposition morphology and battery cycle life.

[0152] Furthermore, in some embodiments of this application, the inducing agent includes Zn. 2+ Zn in the inducer 2+ The concentration is 0.2 mol / L to 0.4 mol / L.

[0153] Further, optionally, in some embodiments of this application, the inducing agent includes Zn. 2+ Zn in the inducer 2+ The concentration ranges from 0.21 mol / L to 0.39 mol / L.

[0154] For example, Zn in the inducer 2+The concentrations are 0.22 mol / L, 0.24 mol / L, 0.26 mol / L, 0.28 mol / L, 0.30 mol / L, 0.32 mol / L, 0.34 mol / L, 0.36 mol / L, or 0.38 mol / L.

[0155] Within the above concentration range, it is easy to obtain a morphologically stable modified layer.

[0156] The following specific embodiments are provided to better illustrate this application.

[0157] [Preparation of negative electrode current collector]:

[0158] Using iron or copper as raw materials, a modification layer (iron layer or copper layer) is deposited on two surfaces of a substrate (copper foil) with a thickness of 10 μm through deposition technology. The modification layer includes crystal planes with specific orientations.

[0159] The iron-modified layer includes Fe(110) crystal planes; the copper-modified layer includes Cu(111) crystal planes.

[0160] Deposition technology:

[0161] For current collectors that form modified layers thicker than one atomic layer, electron deposition is used for deposition; for iron-modified layers, a certain concentration of Zn is used. 2+ Induced electron deposition; electron deposition (without inducer) is used for copper-modified layers.

[0162] For current collectors with a modification layer thickness ranging from 1 atomic layer to 10 nm, atomic layer deposition is used for deposition.

[0163] Iron or copper source:

[0164] Iron source selection: ferrocene; copper source selection: copper hexafluoroacetylacetonate.

[0165] Performance parameter testing of the deposited modified layer and current collector:

[0166] 1. Exposed area of ​​crystal facets:

[0167] (1) For current collectors that form modified layers with a thickness greater than one atomic layer:

[0168] The obtained negative electrode current collector was subjected to XRD testing, and the exposed area of ​​the crystal plane (i.e., TC value) was calculated using the following formula:

[0169]

[0170] In the formula, TC represents the percentage of exposed area, and I... (hkl) I represents the diffraction intensity of the crystal plane of the modified layer material powder (hkl);0(hkl) The diffraction intensity of the modified layer material corresponding to the standard powder (hkl) crystal plane.

[0171] (2) For current collectors that form a modified layer with a thickness of 1 atomic layer:

[0172] Since a single atomic layer cannot characterize its crystal orientation, the same method is used to deposit a sufficient thickness multiple times before characterization is performed to confirm the exposed area.

[0173] The characterization method is the same as that described in (1) above.

[0174] 2. Thickness of the finishing layer:

[0175] The deposition thickness of the modification layer was confirmed by cross-sectional SEM or TEM testing.

[0176] The thickness of the modified layer prepared by atomic layer deposition (ALD) is measured using TEM. When using TEM, a fragment of the current collector is taken for testing, and the thickness of the modified layer can be measured at the edge of the fragment.

[0177] The thickness of the modified layer prepared by the electron deposition process is measured by SEM. When using SEM, the current collector is directly measured to obtain the thickness of the modified layer.

[0178] 3. Resistance of the negative current collector:

[0179] Take an area of ​​1 cm² 2 The resistance of the negative current collector was tested using a diaphragm resistor.

[0180] Examples 1-15

[0181] A negative electrode current collector is provided, which is prepared using the aforementioned method for preparing negative electrode current collectors. The preparation parameters and performance parameters of each embodiment and comparative example are shown in Table 1.

[0182] [Preparation of Lithium-ion Batteries]:

[0183] Lithium-ion batteries were prepared using the negative electrode current collectors provided in the foregoing embodiments and comparative examples; and the performance of the lithium-ion batteries was tested.

[0184] (1) Preparation of lithium-ion batteries:

[0185] Using the negative current collector provided in Examples 1-15 or the comparative examples as the negative electrode and lithium iron phosphate as the positive electrode, an electrolyte (1 mol / L lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dissolved in a volume ratio (1:1) solution of 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME)) was added, and 2 wt% lithium nitrate (LiNO3) was added as an additive to assemble a battery.

[0186] (2) Test the battery performance:

[0187] 1. Battery life test:

[0188] The battery prepared in (1) above was first charged at 25°C with a constant current of 1C to 4.3V, then charged at 4.3V with a constant voltage until the current was less than 0.05C, and then left to stand for 10 minutes. After that, it was discharged at a constant current of 1C to 2.8V, left to stand for 10 minutes, and then charged again. This cycle was repeated until the discharge capacity was 80% of the initial discharge capacity, and the number of cycles was recorded.

[0189] 2. Lithium deposition morphology test:

[0190] Test method:

[0191] The morphology of lithium deposition on the negative electrode current collector was examined by disassembling the batteries of each embodiment and the comparative embodiment with decay to 80% SOH.

[0192] SEM was used to test the negative electrode current collectors of each embodiment and comparative example to observe the lithium deposition morphology.

[0193] When all observed lithium deposition surfaces are lithium dendrites, the lithium deposition morphology is determined to be lithium dendrites.

[0194] When lithium dendrites account for less than 20% of the observed lithium deposition area, the lithium deposition morphology is determined to be a small amount of lithium dendrites.

[0195] When no lithium dendrites are observed on the lithium deposition surface, the lithium deposition morphology is determined to be dense and uniform.

[0196] The test results are shown in Table 2.

[0197] Table 1

[0198]

[0199]

[0200] Table 2

[0201]

[0202]

[0203] As can be seen from the results in Table 2 above:

[0204] In the schemes of Examples 1-15 of this application, the lithium deposition morphology is dense and uniform or has a small amount of lithium dendrites; while in the schemes of Comparative Examples 1-5, the lithium deposition morphology is dense and uniform or has a small amount of lithium dendrites. This shows that the schemes of the embodiments of this application can effectively improve the lithium deposition morphology.

[0205] Furthermore, in the solutions of Examples 1-15 of this application, the battery life (80% SOH) is 460cls to 800cls; while in the solutions of Comparative Examples 1-5, the battery life (80% SOH) is 50cls to 330cls; thus it can be shown that the solutions of the embodiments of this application can effectively improve battery life.

[0206] As can be seen from Examples 6, 11, 13, and 14, when the exposed surface area of ​​the crystal face is greater than or equal to 62% but less than 80%, a small amount of lithium dendrites appear; however, the battery cycle life is improved, with (80% SOH) in the range of 460cls to 650cls. As can be seen from other examples, when the exposed surface area of ​​the crystal face is greater than or equal to 80%, the lithium deposition morphology is greatly improved, and its morphology is dense and uniform; and the battery cycle life is greatly improved, with (80% SOH) in the range of 620cls to 800cls.

[0207] Furthermore, as can be seen from Examples 1, 2, and 7, when using atomic layer deposition technology, the modified layer thickness is ~1nm, resulting in optimal battery life.

[0208] Furthermore, as can be seen from Examples 3, 8, and 9, when using the induced electrodeposition process, the battery life is optimal when the thickness of the modified layer is 100 nm.

[0209] Furthermore, as can be seen from Examples 3, 10, and 11, when using the induced electrodeposition process, the larger the exposed area of ​​the crystal surface, the better the battery life; when the exposed area of ​​the crystal surface decreases, it is not conducive to the lithium deposition morphology, and a small number of lithium dendrites appear.

[0210] Furthermore, as can be seen from Examples 2, 12, and 13, when using atomic layer deposition, the larger the exposed area of ​​the crystal surface, the better the battery life; when the exposed area of ​​the crystal surface decreases, it is not conducive to the lithium deposition morphology, and a small number of lithium dendrites appear.

[0211] Furthermore, comparing Comparative Examples 3-4 with Example 1, it can be seen that when using the atomic layer deposition process, lithium dendrites appear when the exposed area of ​​the crystal surface is less than 50%, and the battery life is severely reduced to 270cls to 330cls.

[0212] Furthermore, comparing Comparative Examples 5-6 with Example 3, it can be seen that during the induced electrodeposition process, when the exposed area of ​​the crystal face is less than 50%, lithium dendrites appear, and the battery life is severely reduced to 190cls-240cls.

[0213] Further, refer to the appendix to the instruction manual. Figure 5 , Figure 5The SEM test results of the current collectors prepared in Examples 1-5, Examples 7-10, Example 12 and Example 15 are shown. The lithium deposition surface was found to be dense and uniform without the presence of lithium dendrites.

[0214] Further, refer to the appendix to the instruction manual. Figure 6 , Figure 6 The SEM test results of the current collectors prepared in Examples 6, 11 and Examples 13, 14 are shown. If the lithium dendrites account for less than 20% of the observed lithium deposition area, the lithium deposition morphology is determined to be a small amount of lithium dendrites.

[0215] Further, refer to the appendix to the instruction manual. Figure 7 , Figure 7 The SEM test results of the current collectors prepared in Comparative Examples 1 to 6 are shown. When all the observed lithium deposit surfaces are lithium dendrites, the lithium deposition morphology is determined to be lithium dendrites.

[0216] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A negative electrode current collector, characterized by, The negative electrode current collector comprises a substrate and a modification layer formed on the surface of the substrate; the modification layer comprises a crystal face with an adsorption energy of (-0.1 eV) to (0.1 eV); the exposed area ratio of the crystal face is greater than or equal to 80% of the single-side surface of the substrate and less than or equal to 100% of the single-side surface of the substrate; the crystal face is a Fe (110) crystal face; the thickness of the modification layer is 0.25 nm to 300 nm; the substrate is a copper foil; and the resistance of the negative electrode current collector is 1.75 nΩ / cm 2 to 2.34 nΩ / cm 2 . 2.The negative electrode current collector according to claim 1, wherein the adsorption energy of the crystal plane is (-0.05 eV) to (-0.08 eV). 3.The negative electrode current collector according to claim 1, wherein the thickness of the modification layer is 100 nm to 300 nm. 4.The negative electrode current collector according to claim 1, wherein the thickness of the modification layer is 0.25 nm to 10 nm. 5.The negative electrode current collector according to claim 1, wherein the thickness of the modification layer is 1 nm to 5 nm. comprising: forming a modification layer with a crystal plane having an adsorption energy of (-0.1 eV) to (0.1 eV) on the surface of the substrate. the modification layer with a crystal plane having an adsorption energy of (-0.1 eV) to (0.1 eV) on the surface of the substrate comprises: depositing the modification layer on the surface of the substrate, so that the thickness of the modification layer is 0.25 nm to 10 nm.

6. The method of producing a negative electrode current collector according to any one of claims 1 to 5, characterized by, the modification layer with a crystal plane having an adsorption energy of (-0.1 eV) to (0.1 eV) on the surface of the substrate comprises: inducing electro-deposition of the modification layer on the surface of the substrate, so that the thickness of the modification layer is 10 nm to 300 nm.

7. The method of producing a negative electrode current collector according to claim 6, wherein 9.The method for preparing the negative electrode current collector according to claim 8, wherein the inducing electro-deposition of the modification layer on the surface of the substrate comprises: using an inducing agent to induce electro-deposition of the modification layer on the surface of the substrate.

8. The method of producing a negative electrode current collector according to claim 6, wherein comprising: the negative electrode tab comprises the negative electrode current collector according to any one of claims 1 to 5, or the negative electrode tab comprises the negative electrode current collector prepared by the method according to any one of claims 6 to 10. the battery comprises the negative electrode tab according to claim 11. the electric device comprises the battery according to claim 12. ​ 10. The method of producing a negative electrode current collector according to claim 9, wherein ​ The inducing agent includes Zn 2+ The concentration of Zn 2+ in the inducing agent is 0.2 mol / L-0.4 mol / L.

11. A negative electrode sheet characterized by comprising: ​ 12. A battery, characterized by ​ 13. An electrical device, characterized by ​

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