Current collector, method for manufacturing the same, secondary battery, and electric device

Abstract

The application provides a current collector and a preparation method thereof, a secondary battery and an electric device. The current collector comprises a nickel-based alloy layer, the nickel-based alloy layer comprises a nickel element and a first metal element other than the nickel element, the first metal element comprises one or more of Fe, Zn, Ti, V, Cr, Mn or Co; the mass content of the first metal element in the current collector is 10% to 50%, and the variance of the mass content of the first metal element in the current collector is less than or equal to 1.5. The current collector is applied to a battery and has improved cycle performance.

Description

[0001] Related applications

[0002] This application claims priority to Chinese Patent Application No. 2025101735554, filed on February 17, 2025, entitled "Battery cell, battery device, power supply device and current collector", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to current collectors and their preparation methods, secondary batteries and electrical devices. Background Technology

[0004] In recent years, the application range of secondary batteries has become increasingly wide, and they are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0005] However, in practical applications, it has been found that the cycle performance of solid-state batteries and other secondary batteries is not ideal and further improvements are needed. Summary of the Invention

[0006] In view of the above problems, this application provides a current collector and its preparation method, a secondary battery and an electrical device, aiming to improve the cycle performance of the battery.

[0007] The first aspect of this application provides a current collector including a nickel-based alloy layer, the nickel-based alloy layer including nickel and a first metal element other than nickel, the first metal element including one or more of Fe, Zn, Ti, V, Cr, Mn or Co, the mass content of the first metal element in the current collector being 10% to 50%, and the variance of the mass content of the first metal element in the current collector being ≤1.5.

[0008] The current collector described in this application includes a nickel-based alloy layer, which has better corrosion resistance than copper foil, nickel foil, stainless steel foil, etc. Based on the mass content of the first metal element in the current collector being 10%~50%, the variance of the mass content of the first metal element in the current collector is controlled to be ≤1.5, thereby improving the uniformity of the distribution of the first metal element in the nickel-based alloy layer, making its alloying degree higher, improving its corrosion resistance, and thus improving the cycle performance of the battery in which it is applied.

[0009] In some embodiments, the variance of the mass content of the first metal element in the current collector is 0.08 to 0.8.

[0010] The smaller the variance, the more uniform the distribution of the first metallic element in the nickel-based alloy layer, and the better its corrosion resistance.

[0011] In some embodiments, the variance of the mass content of nickel in the current collector is ≤1.5, and can be selected as 0.1~0.5.

[0012] The variance of the nickel content in the current collector is within this range, indicating that the distribution of nickel in the nickel-based alloy layer is relatively uniform, and the uniformity of distribution between nickel and the first metallic element is even better. The smaller the variance, the more uniform the distribution of nickel in the nickel-based alloy layer, and the better its corrosion resistance.

[0013] In some embodiments, one or more of the following features are satisfied:

[0014] (1) The mass content of the first metal element in the current collector is 20%~40%;

[0015] (2) The mass content of nickel in the current collector is 45%~85%, and can be selected as 55%~80%;

[0016] (3) The mass content of the nickel element and the first metal element in the current collector is ≥95%.

[0017] Nickel-based alloy layers with nickel content within the above range have both high tensile strength and good plasticity, which is beneficial for balancing the strength and elongation at break of the current collector, reducing the risk of cracking of the current collector or electrode during long cycles, and improving the cycle life of the battery cell.

[0018] In some embodiments, the first metallic element includes Fe, and the nickel-based alloy layer includes a γ solid solution phase and an α solid solution phase.

[0019] In the X-ray diffraction spectrum of the nickel-based alloy layer, the γ solid solution phase includes (111) crystal plane and (200) crystal plane, and the α solid solution phase includes (110) crystal plane and (200) crystal plane;

[0020] Based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, the percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase is 60%~80%.

[0021] The percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase can characterize the degree of alloying of nickel and the first metal element in the nickel-based alloy layer to a certain extent. The larger the parameter, the higher the degree of alloying, which means that the content of the first metal element or nickel element in the form of elemental substance in this region is relatively small, which can improve the problem of local easy corrosion of the current collector to a certain extent and improve its corrosion resistance.

[0022] In some embodiments, the mass content of nickel is greater than the mass content of the other metal elements based on the total mass of the nickel-based alloy foil layer. Further, the mass content of nickel in the nickel-based alloy layer is greater than the mass content of the first metal element. In one example, the nickel-based alloy layer is a nickel-iron alloy layer, in which the mass content of nickel is greater than the mass content of iron.

[0023] In some embodiments, the nickel-based alloy layer comprises a crystalline structure; optionally, the average grain size of the nickel-based alloy layer is 15 nm to 100 nm, or optionally 15 nm to 80 nm.

[0024] The average grain size of the nickel-based alloy layer can be adjusted by regulating the electroplating process, such as the proportion of nickel content. Controlling the average grain size within the aforementioned smaller range in the nickel-based alloy layer is because smaller grains are easier to orient, specifically, the orientation distribution of the crystal plane corresponding to the strongest peak of the grain, thus resulting in higher transverse tensile strength and transverse elongation at break of the current collector. Furthermore, the good bending resistance of the nickel-based alloy layer can also be considered, thus ensuring good bending resistance of the current collector. Specifically, when the nickel-based alloy layer is a nickel-iron alloy foil, the crystal plane corresponding to the strongest peak of the grain is the (111) crystal plane.

[0025] In some embodiments, one or more of the following features are satisfied:

[0026] (1) In the X-ray diffraction spectrum of the nickel-based alloy layer, the texture coefficient of the (111) crystal plane accounts for 30%~80%;

[0027] (2) In the X-ray diffraction spectrum of the nickel-based alloy layer, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane is less than 0.5, and can be selected as 0~0.3.

[0028] The fact that the texture coefficient of the (111) crystal plane is within the above range means that the orientation degree of the (111) crystal plane in the grains of the nickel-based alloy layer is high, which is beneficial for the current collector to slide by means of the (111) crystal plane and improve the plasticity of the current collector.

[0029] Based on the X-ray diffraction spectrum of the nickel-based alloy layer, the ratio of the diffraction peak intensity of the (110) crystal plane to that of the (111) crystal plane is less than 0.5, which means that the current collector is mainly composed of face-centered cubic cell structure, which is beneficial to improving the plasticity of the current collector.

[0030] The preferred orientation of the (111) crystal plane in the nickel-based alloy layer makes it easier for the current collector to undergo plastic deformation rather than brittle fracture under stress. This is beneficial for the current collector to further balance tensile strength and plasticity, delays the time when the cell will experience crack failure, and helps to improve the cycle life of the battery cell.

[0031] In some embodiments, the thickness of the nickel-based alloy layer is 3μm to 8μm, and optionally 4μm to 6μm.

[0032] A nickel-based alloy layer thickness of 1 μm or more helps maintain good structural stability of the negative electrode current collector, further improving the battery's cycle performance. A negative electrode current collector thickness of less than 8 μm allows for a smaller current collector thickness, reducing its weight and thus contributing to increased battery energy density.

[0033] In some embodiments, one or more of the following features are satisfied:

[0034] (1) The transverse tensile strength MD of the current collector is 1200MPa~2200MPa, and can be selected as 1400MPa~2200MPa;

[0035] (2) The longitudinal tensile strength TD of the current collector is 1100MPa~2100MPa, and can be selected as 1150MPa~2100MPa;

[0036] (3) The transverse tensile strength MD of the current collector is greater than the longitudinal tensile strength TD of the current collector;

[0037] (4) The lateral elongation of the current collector is 3%~8%, and can be selected as 3%~6%;

[0038] (5) The longitudinal elongation of the current collector is 2%~7%, and can be selected as 3%~5%;

[0039] (6) The transverse fracture elongation of the current collector is greater than the longitudinal fracture elongation of the current collector.

[0040] The aforementioned current collector has high transverse tensile strength, which increases the cumulative strain that the battery cell can withstand along its length, thus improving the cell's resistance to expansion, reducing the risk of electrode breakage, and improving the cycle life of the battery cell.

[0041] The current collector has high longitudinal tensile strength, which increases the cumulative strain that the battery cell can withstand along the width direction, thereby reducing the risk of current collector fracture and improving the overall cumulative strain that the battery cell can withstand, thus improving the cycle life of the battery cell.

[0042] The nickel-based alloy layer in the current collector has high strength, and the tensile strength of the current collector is different from that of the longitudinal tensile strength. By controlling the current collector to have better tensile strength, the risk of breakage of the current collector and the electrode with the current collector is reduced, the ability of the battery cell to resist stress such as expansion is improved, and the cycle life of the battery cell is increased.

[0043] A second aspect of this application provides a method for preparing a current collector, comprising the following steps:

[0044] An insoluble anode, an electroplating solution, and a cathode are provided for electroplating to form a nickel-based alloy layer on the surface of the cathode; after the electroplating process, the nickel-based alloy layer is separated from the surface of the cathode.

[0045] The electroplating solution includes a nickel source, a first metal source, a complexing agent, and a first additive. The first additive contains a benzene ring and a sulfonic acid group connected to the benzene ring. The benzene ring is optionally connected with a carbon chain substituent with a number of carbon atoms less than or equal to 3. The first metal element in the first metal source is a metal element other than nickel. The first metal element includes one or more of Fe, Zn, Ti, V, Cr, Mn, or Co. The mass content of the first metal element in the current collector is 10% to 50%.

[0046] In the above-mentioned method for preparing the current collector, the electroplating solution includes a nickel source and a first metal source, the two of which have different deposition rates. The first additive, which does not contain long carbon chains, contains sulfonic acid groups linked to benzene rings, making it easier for the sulfonic acid groups to be adsorbed on the surface of the cathode roller, forming an electric double layer or a steric hindrance effect. By utilizing the repulsion of like charges or the hindering effect of polymer chains, it prevents the metal ions from excessively agglomerating due to van der Waals forces, resulting in local concentrations that are too high or too low. In this way, the nickel source and the first metal source can be fully dispersed in it. The complexing agent can cooperate with the nickel ions and the first metal ions to allow them to be deposited together on the cathode roller. In this way, the first additive and the complexing agent work together to allow the first metal elements such as nickel and iron to be deposited as simultaneously as possible. This reduces the variance of the mass content of the first metal elements in the resulting alloy layer, improves the uniformity of the mass content distribution of the first metal elements and nickel elements, enhances its corrosion resistance, and improves the cycle performance of the battery in which it is applied.

[0047] The above preparation method can produce the current collector of the first aspect of this application. The current collector produced has the same characteristics as the current collector of the first aspect, which will not be described again here.

[0048] In some embodiments, one or more of the following features are satisfied:

[0049] (1) The concentration of the first additive in the electroplating solution is 0.1 g / L to 0.9 g / L;

[0050] (2) The concentration of the complexing agent in the electroplating solution is 20 g / L to 60 g / L;

[0051] (3) The pH value of the electroplating solution is 2~3;

[0052] (4) The flow rate of the electroplating solution is 50 L / min to 80 L / min;

[0053] (5) The rotational speed of the cathode is 0.2 m / min to 0.8 m / min;

[0054] (6) In the electroplating process, the current density is 2A / dm. 2 ~10A / dm 2 Optional 5A / dm 2 ~10A / dm 2 .

[0055] In some embodiments, one or more of the following features are satisfied:

[0056] (1) The concentration of the nickel source in the electroplating solution is 150 g / L to 250 g / L;

[0057] (2) The nickel source includes one or more of nickel sulfate, nickel chloride, or nickel carbonate;

[0058] (3) The first metal source includes an Fe source, and the concentration of the Fe source in the electroplating solution is 20 g / L to 80 g / L;

[0059] (4) The electroplating solution further includes a second additive; optionally, the second additive includes one or more of saccharin, sodium saccharin, polyethylene glycol, polyethyleneimine, 1,4-butynediol, sodium naphthalene disulfonate or formaldehyde; optionally, the concentration of the second additive in the electroplating solution is 3 g / L to 5 g / L.

[0060] (5) The electroplating solution further includes a third additive, which includes one or more of thiourea and its derivatives, and thiocyanate; optionally, the concentration of the third additive in the electroplating solution is 0.1 g / L to 0.5 g / L.

[0061] (6) The electroplating solution further includes a wetting agent; optionally, the wetting agent includes one or more of sodium dodecyl sulfate or sodium dodecyl sulfonate; optionally, the concentration of the wetting agent in the electroplating solution is 0.1 g / L to 0.5 g / L;

[0062] (7) The electroplating solution further includes a stabilizer; optionally, the stabilizer includes one or more of boric acid, citric acid or fluoroborate; optionally, the concentration of the stabilizer in the electroplating solution is 40 g / L to 80 g / L.

[0063] In a third aspect, this application provides a secondary battery including an electrode assembly, the electrode assembly including a positive electrode and a negative electrode, the negative electrode including a negative current collector, the negative current collector including the current collector provided in the first aspect of this application or the current collector prepared by the preparation method of the current collector provided in the second aspect of this application.

[0064] In some embodiments, the electrode assembly further includes a solid electrolyte layer located between the positive electrode and the negative electrode;

[0065] Optionally, the solid electrolyte layer includes one or more of sulfide electrolytes, halide electrolytes, or oxide electrolytes.

[0066] In solid-state batteries, solid electrolytes such as sulfides can corrode the traditional copper foil negative electrode current collector, leading to damage to the current collector and consequently degrading battery performance. In the aforementioned solid-state batteries, the nickel-based alloy layer exhibits better corrosion resistance, reducing the risk of corrosion loss of the negative electrode current collector and improving battery cycle performance.

[0067] In some embodiments, the negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one surface of the current collector; the negative electrode film layer includes a negative electrode active material, which includes at least one of silicon-based materials, lithium metal, and lithium metal alloys.

[0068] In some embodiments, lithium metal or lithium metal alloy is deposited on the negative electrode current collector during charging and is consumed during discharging.

[0069] In a fourth aspect, this application provides an electrical device comprising one or more of the current collector provided in the first aspect of this application, a current collector prepared by the method for preparing the current collector provided in the second aspect of this application, or a secondary battery provided in the third aspect of this application.

[0070] The electrical device of this application includes the secondary battery provided in this application, and therefore has at least the same advantages as the secondary battery.

[0071] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0072] To better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more accompanying drawings. Additional details or examples used to describe the drawings should not be considered as limiting the scope of any of the disclosed applications, the currently described embodiments or examples, or the best mode of conduct of these applications as currently understood. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0073] Figure 1 This is a schematic diagram of a single cell of a secondary battery according to one embodiment of this application.

[0074] Figure 2 This is a schematic diagram of a battery module according to one embodiment of this application.

[0075] Figure 3 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0076] Figure 4 yes Figure 3 An exploded view of a battery pack according to one embodiment of this application is shown.

[0077] Figure 5 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0078] Figure 6 This is a nickel-iron element distribution diagram of the current collector cross section obtained in Example 1 of this application.

[0079] Figure 7 This is a schematic diagram of the current collector prepared in Embodiment 1 of this application being scanned along the thickness direction.

[0080] Figure 8 This is a line scan intensity map of elemental distribution obtained by scanning the current collector prepared in Embodiment 1 of this application along the thickness direction.

[0081] Figure 9 This is a schematic diagram of the current collector prepared in Comparative Example 1 of this application being linearly scanned along the thickness direction.

[0082] Figure 10 This is a line scan intensity map of elemental distribution obtained by linearly scanning the current collector prepared in Comparative Example 1 of this application along the thickness direction.

[0083] Figure 11 This is a SEM image of the corrosion resistance test of the current collector in Example 1 of this application.

[0084] Explanation of reference numerals in the attached figures:

[0085] 1. Battery pack; 2. Upper casing; 3. Lower casing; 4. Battery module; 5. Individual battery cell; 6. Electrical device. Detailed Implementation

[0086] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0087] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints. Any endpoint can be independently included or excluded, and they can be combined arbitrarily; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this document; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, stating that a parameter is an integer ≥2 is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, stating that a parameter is an integer selected from "2~10" is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0088] In this application, the terms "multiple" or "various" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "one or more" means one or more types.

[0089] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0090] 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 or implementation 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. The term "implementation" as used herein has a similar understanding.

[0091] Those skilled in the art will understand that the order in which the steps are written in the methods of various embodiments or examples does not imply a strict execution order and does not constitute any limitation on the implementation process. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0092] In this application, unless otherwise specified, A (e.g., B) means that B is a non-limiting example of A, and it is understood that A is not limited to B.

[0093] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0094] In traditional batteries, the copper foil used as the negative electrode current collector is susceptible to corrosion, reducing its lifespan and deteriorating the battery's cycle performance. For example, solid-state batteries often use sulfide solid electrolytes because they possess high ionic conductivity, which facilitates lithium-ion transport and provides crucial support for stable battery cycling. However, sulfide solid electrolytes are sensitive to water and readily react with it to form hydrogen sulfide. Hydrogen sulfide easily corrodes the copper foil of the negative electrode current collector, leading to its damage and further deteriorating the battery's cycle performance. Furthermore, the high ionic conductivity of sulfide electrolytes promotes rapid diffusion of the corrosion reaction, causing damage to the copper foil structure and increasing interfacial impedance, thus reducing the battery's cycle stability and safety.

[0095] New foil materials such as nickel foil and stainless steel foil are also susceptible to corrosion by sulfide electrolytes. Nickel-based alloy layers such as nickel-iron alloy foil have certain corrosion resistance, but in practical applications, it has been found that their corrosion resistance needs further improvement to further enhance the cycle stability of the battery. Taking nickel-iron alloy foil as an example, in practical applications, it is prone to localized pitting corrosion. Research has found that this is closely related to the distribution of iron content. When the iron content is too high in certain areas, it is easy to form elemental iron grains instead of nickel-iron alloy particles. The elemental iron grains react with sulfides such as hydrogen sulfide, thus making it prone to localized corrosion. This situation is even more pronounced in the preparation of current collectors with relatively high iron content. As the electroplating process proceeds, a localized alkalinity develops near the cathode roller. Taking nickel-iron alloy foil as an example, iron elements locally accumulate to form ferric hydroxide colloids. These colloids are difficult to disperse, and the iron enrichment in the electroplating solution leads to the deposition of elemental iron grains, resulting in uneven iron distribution in the current collector. When preparing nickel-based alloy layers with relatively high iron content, the higher the concentration of iron ions in the electroplating solution, the more pronounced the uneven distribution and deposition of iron elements in the current collector, making it even more difficult to achieve a uniform distribution of iron elements. The first metallic elements Zn, Ti, V, Al, Cr, Mn, or Co all exhibit similar technical problems to Fe.

[0096] Therefore, this application improves the process of nickel-based alloy layer current collectors to obtain a nickel-based alloy layer current collector with a more uniform element distribution, a higher degree of alloying, and improved corrosion resistance, thereby improving the cycle performance of the batteries in which it is applied.

[0097] The first aspect of this application provides a current collector including a nickel-based alloy layer, the nickel-based alloy layer including nickel and a first metal element other than nickel, the first metal element including one or more of Fe, Zn, Ti, V, Cr, Mn or Co; the mass content of the first metal element in the current collector is 10% to 50%, and the variance of the mass content of the first metal element in the current collector is ≤1.5.

[0098] Variance measures the degree of deviation of multiple data points from their average. The variance of the mass content of the first metallic element in a nickel-based alloy foil layer measures the degree of deviation of multiple measured values ​​of the first metallic element in the nickel-based alloy foil layer from its average. The core physical meaning of the variance of the mass content of the first metallic element in the nickel-based alloy foil layer is the uniformity of its distribution. The smaller the variance of the mass content of the first metallic element in the nickel-based alloy foil layer, the better the uniformity of its distribution at different locations within the nickel-based alloy foil layer. The variance of the mass content of the first metallic element in the nickel-based alloy foil layer is related to the uniformity of the microstructure distribution of the nickel-based alloy foil layer, such as the uniformity of the nickel-based alloy phase distribution. The variance of the mass content of the first metallic element in the nickel-based alloy foil layer affects the performance inhomogeneity and potential weaknesses of the nickel-based alloy foil layer, thus affecting its performance stability.

[0099] Understandably, the variance of the mass content of the first metallic element in the current collector is dimensionless.

[0100] The current collector described in this application includes a nickel-based alloy layer, which has better corrosion resistance than copper foil, nickel foil, stainless steel foil, etc. Based on the mass content of the first metal element in the current collector being 10%~50%, the variance of the mass content of the first metal element in the current collector is controlled to be ≤1.5, thereby improving the uniformity of the distribution of the first metal element in the nickel-based alloy layer, making its alloying degree higher, improving its corrosion resistance, and thus improving the cycle performance of the battery in which it is applied.

[0101] In this application, nickel-based alloys refer to alloys whose main constituent element is nickel, and the mass content of Ni in nickel-based alloys generally exceeds 40%. Nickel-based alloys combine high tensile strength with good structural stability and material ductility, which is beneficial for balancing the strength and elongation at break of the current collector and improving the cycle life of the battery cell. It is understood that the alloy layer may include any one of solid solution, eutectoid, eutectic, or compound (intermetallic compound), or a combination of these.

[0102] The method for testing the mass content and variance of the first metallic element in the current collector is as follows:

[0103] Cut the current collector into a sample of a certain width (e.g., 5 cm) along the width direction, exposing two cross-sections in the thickness direction of the sample. Take several (e.g., 10) test samples consecutively from the sample, ensuring that the mass of each test sample is ≥1 g (the size can be, for example, 5 cm × 5 cm).

[0104] First, pure first metallic element is used as the standard sample. Multiple standard solutions of the first metallic element with different concentrations are prepared and sequentially analyzed by an ICP instrument. The correspondence between the intensity signal value of the characteristic spectral line of the first metallic element and the concentration of the standard solution is recorded to generate a standard curve. As an example, the specific steps are as follows: Pure first metallic element is digested using a mixture of nitric acid and hydrochloric acid, either by hot plate or microwave, until the solution is clear. After cooling, the solution is diluted to volume with ultrapure water (e.g., 50 mL) and filtered to remove undissolved particles. The solution is serially diluted with 3wt% nitric acid to target concentrations of 0.1 mg / L, 0.5 mg / L, 1.0 mg / L, 5.0 mg / L, and 10.0 mg / L. The intensity signal value of the characteristic spectral line of the first metallic element is obtained by testing each standard solution using an inductively coupled plasma optical generator (ICP). This yields the standard curve relating the concentration of the first metallic element to the intensity signal value of its characteristic spectral line.

[0105] The test solutions were prepared using the same method described above for each sample. The expected concentration range of the test solutions was within the concentration range of the standard solutions. Then, the intensity signal of the characteristic spectral line of the first metal element was measured using an inductively coupled plasma optical emission spectrometer (ICP). Based on the measured intensity signal of the characteristic spectral line of the first metal element and the standard curve of the first metal element, the concentration of the first metal element in the test solution was calculated. As an example, the specific steps are as follows: A mixture of nitric acid and hydrochloric acid was used, and digestion was performed using a hot plate or microwave until the solution became clear. After cooling, the solution was diluted to a final volume with ultrapure water (e.g., 50 mL), and filtered to remove undissolved particles. The solution was then serially diluted with 3 wt% nitric acid to a target concentration of 1.0 mg / L. The intensity signal of the characteristic spectral line of the first metal element was then measured using an inductively coupled plasma optical emission spectrometer (ICP). Based on the measured intensity signal of the characteristic spectral line of the first metal element and the standard curve of the first metal element, the concentration of the first metal element in the test solution was calculated.

[0106] The mass content of the first metallic element in the sample to be tested, calculated based on the concentration of the first metallic element in the sample, is given by the following formula: X (first metallic element) = (C × V × dilution factor) / (m × 1000) × 100%; where:

[0107] X (first metallic element): the mass content of the first metallic element in the current collector;

[0108] C: The concentration (mg / L) of the first metallic element in the test solution as measured by ICP.

[0109] V: Fixed volume (L, e.g., 50mL = 0.05L);

[0110] Dilution factor: If dilution was performed during the digestion process, it needs to be multiplied by this factor (1 if undiluted).

[0111] m: Sample mass (g).

[0112] As an example, 10 samples are taken, and each sample is tested once, resulting in 10 test values ​​of the mass content of the first metal element in the sample to be tested in the current collector. The arithmetic mean of these 10 test values ​​is calculated to obtain the mass content of the first metal element in the current collector. The variance of the mass content of the first metal element in the current collector is calculated based on the 10 test values ​​of the mass content of the first metal element in the current collector.

[0113] The formula for the arithmetic mean is to sum all the test values ​​and then divide by the number of test values. For example, sum 10 test values ​​and then divide by 10.

[0114] The formula for calculating the variance of the mass content of the first metallic element in the above current collector is as follows:

[0115] ;

[0116] in Xi is the arithmetic mean of the sample, Xi is a single test value of the mass content of the first metal element in the current collector, Σ represents summation, and n is 10.

[0117] To ensure the accuracy of the test results, the above test steps can be followed multiple times to obtain samples and test the variance of the iron content. The arithmetic mean of the results of each test is the final result.

[0118] The variance of the mass content of the first metal element in the current collector can illustrate the uniformity of the mass content of the first metal element in the cross-section of the current collector along the width direction.

[0119] Understandably, the method for testing the variance of the nickel content in the current collector is similar to the method for testing the variance of the first metallic element's content in the current collector. Multiple test values ​​of the nickel content in the current collector are thus obtained; for example, 100 test values ​​of the nickel content in the sample to be tested are obtained. The arithmetic mean is calculated based on these 100 test values ​​to obtain the nickel content in the current collector. The variance is then calculated based on these 100 test values ​​to obtain the variance of the nickel content in the current collector. The arithmetic mean and variance are similar.

[0120] Understandably, in one embodiment, the current collector is a nickel-based alloy layer, the mass content of the first metal element in the current collector is the same as the mass content of the first metal element in the nickel-based alloy layer, and the variance of the mass content of the first metal element in the current collector is the same as the variance of the mass content of the first metal element in the nickel-based alloy layer. In some examples, the mass content of the first metal element in the nickel-based alloy layer is 10% to 50%, and the variance of the mass content of the first metal element in the nickel-based alloy layer is ≤1.5.

[0121] As an example, the variance of the mass content of the first metallic element in the current collector or nickel-based alloy layer is within the range of 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.5 or any two of these values.

[0122] In some embodiments, the variance of the mass content of the first metal element in the current collector is ≤0.8.

[0123] In some embodiments, the variance of the mass content of the first metal element in the current collector is 0.08 to 0.8.

[0124] The smaller the variance, the more uniform the distribution of the first metallic element in the nickel-based alloy layer, and the better its corrosion resistance.

[0125] In some embodiments, the variance of the mass content of nickel in the current collector is ≤1.5, and can be selected as 0.1~0.5. As an example, the variance of the mass content of nickel in the current collector is within the range of 0.08, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.2, 1.3, 1.5, or any value between two of these ranges. A variance of the mass content of nickel in the current collector within this range indicates that the distribution of nickel in the nickel-based alloy layer is relatively uniform, and the distribution uniformity between nickel and the first metallic element is better. The smaller the variance, the more uniform the distribution of nickel in the nickel-based alloy layer, and the better its corrosion resistance.

[0126] The aforementioned first metallic element possesses both high strength and ductility. The nickel-based alloy layer improves the fracture elongation and bendability of the current collector by alloying nickel with the first metallic element. This allows the current collector to expand and contract during cycling, thereby reducing the risk of electrode breakage. This is beneficial for improving the current collector's resistance to expansion during long cycles and increasing the cycle life of the battery cell.

[0127] As an example, the mass content of the first metal element in the current collector or nickel-based alloy layer can be 10%, 15%, 20%, 25%, 30%, 32%, 35%, 36%, 37%, 40%, 45%, 50%, or any value between two of these. In some embodiments, the mass content of the first metal element in the current collector is 20% to 40%.

[0128] In some embodiments, the mass content of nickel in the current collector is 45% to 85%, optionally 55% to 80%; as an example, the mass content of nickel in the nickel-based alloy layer can be 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, or any value range between the two.

[0129] Nickel-based alloy layers with nickel content within the above range have both high tensile strength and good plasticity, which is beneficial for balancing the strength and elongation at break of the current collector, reducing the risk of cracking of the current collector or electrode during long cycles, and improving the cycle life of the battery cell.

[0130] In some embodiments, the total mass content of nickel and the first metal element in the nickel-based alloy layer is ≥95%, which may be 95%, 98%, 99%, 100%, or any value range between the two.

[0131] Furthermore, the nickel-based alloy layer also contains iron. Optionally, the nickel-based alloy layer comprises a nickel-iron-based alloy. Nickel-iron-based alloys exhibit high stability in electrochemical environments, are not prone to corrosion, and simultaneously possess high tensile strength and deformability. This allows the electrode to maintain high resistance to external shell pressure during cycling, while also retaining high residual elongation at break after stretching.

[0132] Optionally, the iron content in the nickel-based alloy layer is 10% to 50% by mass, and for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any value between two of these, with a possible value of 20% to 40%. Optionally, the total mass content of iron and nickel in the nickel-based alloy layer is ≥95%, and can be 95%, 98%, 100%, or any value between two of these.

[0133] In some implementations, the mass content of nickel in the current collector is greater than the mass content of the other metal elements.

[0134] In some embodiments, the first metallic element includes Fe, and the nickel-based alloy layer includes a γ solid solution phase and an α solid solution phase. In the X-ray diffraction pattern of the nickel-based alloy layer, the γ solid solution phase includes (111) and (200) crystal planes, and the α solid solution phase includes (110) and (200) crystal planes. Based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, the percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase is 60%–80%.

[0135] The percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase can, to a certain extent, characterize the degree of alloying between nickel and the first metallic element in the nickel-based alloy layer. The larger this parameter, the higher the degree of alloying, indicating that the content of the first metallic element or nickel in elemental form in that region is relatively low. This can, to a certain extent, improve the problem of localized corrosion of the current collector and enhance its corrosion resistance. In this way, the current collector can achieve good corrosion resistance while also maintaining good bending resistance.

[0136] It is understood that the γ solid solution phase includes the (111) and (200) crystal planes. Based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, the percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase can represent the relative volume percentage of the γ solid solution phase in the alloy layer. The relative volume percentage of the γ solid solution phase represents the percentage of the volume of the γ solid solution phase relative to the sum of the volumes of the γ solid solution phase and the α solid solution phase.

[0137] It is understandable that the α solid solution phase includes the (110) and (200) crystal planes. Based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, the percentage of the sum of the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase can represent the relative volume percentage of the α solid solution phase in the alloy layer. The relative volume percentage of the α solid solution phase represents the percentage of the volume of the α solid solution phase relative to the sum of the volumes of the γ solid solution phase and the α solid solution phase.

[0138] Optionally, in the nickel-based alloy layer, the relative volume percentage of the γ solid solution phase in the nickel-based alloy layer can be 60%, 61%, 62%, 65%, 68%, 70%, 71%, 72%, 75%, 78%, 80%, or any value within the range of any two of the above values, further being 60%~75%, and optionally 65%~75% or 65%~72%.

[0139] However, the higher the relative volume percentage of the γ solid solution phase in the nickel-based alloy layer, the more prone it is to brittle fracture during the application of the current collector, thereby reducing the service life of the current collector and affecting the cycle performance of the battery. Therefore, by controlling the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, and keeping the percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase between 65% and 75%, the current collector can achieve both good corrosion resistance and better bending resistance, thereby enabling the battery to obtain better cycle performance.

[0140] In alloys containing nickel and iron, the γ solid solution phase, or face-centered cubic (FCC) solid solution, is the main stable phase of the alloy, in which iron atoms form a face-centered cubic lattice and nickel atoms dissolve within it.

[0141] In this application, the test method for the relative volume percentage of γ-solution phase and α-solution phase in the nickel-based alloy layer is as follows: 1. Obtain the target area sample by cutting the alloy layer along the thickness direction using wire cutting or abrasive wheel, and grind it with sandpaper up to 2000# to ensure a smooth surface. 2. Electrolyze the sample with an electrolyte of 10wt% perchloric acid and 90wt% ethanol at a voltage of 20-30V for 10-15 seconds to eliminate the mechanical damage layer and avoid pseudo-phase interference. 3. Place the sample in the center of the stage, clean it with alcohol, and compact it to ensure no residual impurities. 4. Perform X-ray diffraction (XRD) on the alloy layer using CuKα rays as the X-ray source. As an example, at 25℃, use CuKα rays as the X-ray source, scan at a scanning speed of 2º / min, and scan the range of 10º-100º; obtain the X-ray diffraction spectrum, and calculate the relative volume percentage of γ-solution phase and α-solution phase in the nickel-based alloy layer by calculating the diffraction peak area ratio.

[0142] X-ray diffraction (XRD) technology utilizes the interaction between incident X-ray photons and electrons in atoms of a sample to create a diffraction phenomenon. This diffraction phenomenon is used to obtain the characteristics of the diffracted X-ray signals, which are then processed to obtain an X-ray diffraction pattern (XRD pattern). The diffraction peaks in an XRD pattern are produced by the constructive interference of monochromatic X-ray beams diffracted at specific angles from each set of lattice planes (crystal planes) in the sample. Therefore, the diffraction peaks in an XRD pattern correspond to the crystal planes of the sample. Furthermore, each diffraction peak in an XRD pattern satisfies Bragg's equation: 2dsinθ=nλ, where θ is the incident angle, d is the interplanar spacing, n is the diffraction order, λ is the incident wavelength, and 2θ is the diffraction angle. The peak area of ​​a diffraction peak in an XRD pattern refers to the total area of ​​the peak above the background line, representing the integrated intensity. The integrated intensity of a diffraction peak of a certain phase is directly proportional to the volume percentage of that phase in the sample; therefore, the integrated intensity of a diffraction peak directly reflects the volume percentage of the phase in the compound. In practice, the peak area of ​​diffraction peaks is usually calculated directly by XRD analysis software, such as the "Calculate Peak Area" function in MDI JADE software.

[0143] For example, based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the (110) and (200) crystal planes of the α solid solution phase, the percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase can represent the relative volume percentage of the γ solid solution phase in the alloy layer.

[0144] In the X-ray diffraction spectrum of the nickel-based alloy layer, the peak position of the (111) crystal plane of the γ solid solution phase is 43.2±0.2°, the peak position of the (200) crystal plane of the γ solid solution phase is 51.7±0.3°, the peak position of the (110) crystal plane of the α solid solution phase is 44.7±0.2°, and the peak position of the (200) crystal plane of the α solid solution phase is 52.3±0.3°.

[0145] In some embodiments, the sum of the volume percentages of the γ-solution phase and the α-solution phase in the nickel-based alloy layer is greater than or equal to 98%. In this case, the γ-solution phase and the α-solution phase constitute the majority of the alloy layer, while impurity phases, such as hard and brittle phases like carbides, are present in small quantities. This reduces the risk of these harmful phases becoming stress concentration sources, thereby reducing the risk of brittle fracture of the alloy layer under stress. Optionally, the sum of the volume percentages of the γ-solution phase and the α-solution phase in the nickel-based alloy layer can be 98%, 98.2%, 98.5%, 98.8%, 99%, 99.2%, 99.5%, 99.8%, 99.9%, 100%, or any value within the range of any two of the above values. In a nickel-based alloy layer, the sum of the volume percentages of the γ solid solution phase and the α solid solution phase refers to the ratio of the total area of ​​the diffraction peaks of the γ solid solution phase (111) and (200) crystal planes, and the sum of the areas of the diffraction peaks of the α solid solution phase (110) and (200) crystal planes, based on the total area of ​​the diffraction peaks of the X-ray diffraction spectrum of the nickel-based alloy layer.

[0146] In some embodiments, the ratio of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase to the sum of the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase is greater than or equal to 1.2. By controlling the volume ratio of the γ solid solution phase to the α solid solution phase, a better balance between tensile strength and toughness can be achieved, further reducing the risk of damage to the alloy layer under stress, and thus further improving the cycle performance of the battery.

[0147] In some embodiments, the ratio of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase to the sum of the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase is 1.2 to 4. As an example, the ratio of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase to the sum of the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase can be 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.2, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, and any value within the range of any two of the above values, and can be selected as 1.5 to 3.5. In some embodiments, the percentage of the diffraction peak area of ​​the (111) crystal plane of the γ solid solution phase is 30% to 50% based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the (110) and (200) crystal planes of the α solid solution phase. For example, the percentage of the diffraction peak area of ​​the (111) crystal plane of the γ solid solution phase can be 30%, 32%, 35%, 38%, 40%, 42%, 45%, 48%, 50%, or any value within the range of any two of the above values.

[0148] In some embodiments, the percentage of the diffraction peak area of ​​the (200) crystal plane of the γ solid solution phase is 20% to 40% based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the (110) and (200) crystal planes of the α solid solution phase. Optionally, based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the (110) and (200) crystal planes of the α solid solution phase, the percentage of the diffraction peak area of ​​the (200) crystal plane of the γ solid solution phase can be 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, or any value within the range of any two of the above values.

[0149] In some embodiments, the nickel-based alloy layer comprises a crystalline structure. In other words, the alloy particles in the nickel-based alloy layer have a crystalline structure.

[0150] Optionally, the average grain size of the nickel-based alloy layer is 15 nm to 100 nm, and optionally 15 nm to 80 nm. As an example, the average grain size of the nickel-based alloy layer can be 15 nm, 15.8 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value range between the two.

[0151] The average grain size of the nickel-based alloy layer can be adjusted by regulating the electroplating process, such as the proportion of nickel content. Controlling the average grain size within the aforementioned smaller range in the nickel-based alloy layer is because smaller grains are easier to orient, specifically, the orientation distribution of the crystal plane corresponding to the strongest peak of the grain, thus resulting in higher transverse tensile strength and transverse elongation at break of the current collector. Furthermore, the good bending resistance of the nickel-based alloy layer can also be considered, thus ensuring good bending resistance of the current collector. Specifically, when the nickel-based alloy layer is a nickel-iron alloy foil, the crystal plane corresponding to the strongest peak of the grain is the (111) crystal plane.

[0152] In this application, the average grain size of the nickel-based alloy layer can be tested as follows: X-ray diffraction (XRD) is performed on the nickel-based alloy layer in the current collector to analyze the average grain size. As an example, at 25°C, using CuKα rays as the X-ray source, a scanning speed of 2° / min is used, with a scanning range of 10°-100°. X-ray diffraction patterns are measured using an X-ray diffractometer. The peak with the highest diffraction intensity in the X-ray diffraction pattern is used as a reference, and the average grain size is calculated using the Scherrer formula D=Kλ / (βcosθ), where D is the average grain size, K is the Scherrer constant (0.89), λ is the X-ray wavelength (selectable wavelength in the test is 0.154 nm), β is the full width at half maximum (FWHM) of the diffraction peak, and θ is the diffraction angle.

[0153] The nickel-based alloy layer improves the tensile strength and elongation at break of the current collector through grain refinement, reducing the risk of battery failure due to current collector fracture.

[0154] In some embodiments, the thickness of the nickel-based alloy layer is 3 μm to 8 μm, optionally 4 μm to 6 μm. As an example, the thickness of the nickel-based alloy layer can be selected from 3 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 8 μm or any value range between the two.

[0155] A nickel-based alloy layer thickness of 3 μm or more helps maintain good structural stability of the negative electrode current collector, further improving the battery's cycle performance. A negative electrode current collector thickness of less than 8 μm allows for a smaller current collector thickness, reducing its weight and thus contributing to increased battery energy density.

[0156] The thickness of the current collector can be measured directly using a micrometer.

[0157] In some embodiments, the texture coefficient of the (111) crystal plane accounts for 30% to 80% in the X-ray diffraction spectrum of the nickel-based alloy layer.

[0158] The fact that the texture coefficient of the (111) crystal plane is within the above range means that the orientation degree of the (111) crystal plane in the grains of the nickel-based alloy layer is high, which is beneficial for the current collector to slide by means of the (111) crystal plane and improve the plasticity of the current collector.

[0159] (111) The proportion of texture coefficient of crystal plane can be obtained by X-ray diffraction test of nickel-based alloy layer.

[0160] The X-ray diffraction pattern of the nickel-based alloy layer was compared with the standard pattern. The phase and crystal plane corresponding to the diffraction peak of the nickel-based alloy layer were analyzed. The texture coefficient M of the (111) crystal plane was calculated with reference to Equation I.

[0161] M(111)=I(111) / IR(111) (Formula I);

[0162] Where I(111) is the diffraction peak intensity of the (111) crystal plane in the X-ray diffraction spectrum obtained by actual testing, and IR(111) is the standard intensity of the (111) crystal plane in the standard XRD spectrum of the main phase.

[0163] (111) The proportion of the texture coefficient P(111) of the crystal plane is calculated by Equation II.

[0164] P(111)=M(111) / ∑M(hkl) (Equation II);

[0165] Where M(hkl) is the texture coefficient of each crystal plane of the main phase in the X-ray diffraction spectrum obtained by actual testing.

[0166] In some embodiments, the texture coefficient of the (111) crystal plane in the X-ray diffraction spectrum of the nickel-based alloy layer can be selected as 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, or any value between the two.

[0167] In some embodiments, the ratio of the diffraction peak intensity of the (110) crystal plane to that of the (111) crystal plane in the X-ray diffraction spectrum of the nickel-based alloy layer is less than 0.5, and can be selected as 0 to 0.3.

[0168] Based on the X-ray diffraction spectrum of the nickel-based alloy layer, the ratio of the diffraction peak intensity of the (110) crystal plane to that of the (111) crystal plane is less than 0.5, which means that the current collector is mainly composed of face-centered cubic cell structure, which is beneficial to improving the plasticity of the current collector.

[0169] The preferred orientation of the (111) crystal plane in the nickel-based alloy layer makes it easier for the current collector to undergo plastic deformation rather than brittle fracture under stress. This is beneficial for the current collector to further balance tensile strength and plasticity, delays the time when the cell will experience crack failure, and helps to improve the cycle life of the battery cell.

[0170] The diffraction peak intensities of the (110) and (111) crystal planes can be obtained through X-ray diffraction testing of the nickel-based alloy layer. The X-ray diffraction spectrum of the nickel-based alloy layer is compared with the standard XRD pattern of the standard sample specified by the Joint Committee on Powder Diffraction Standards (JCPDS) to analyze the phase and crystal planes corresponding to the diffraction peaks of the nickel-based alloy layer. The diffraction peak intensity of the (110) crystal plane in the X-ray diffraction pattern of the nickel-based alloy layer is calculated and divided by the diffraction peak intensity of the (111) crystal plane.

[0171] As an example, in the X-ray diffraction pattern of the nickel-based alloy layer, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane can be selected as 0, 0.1, 0.2, 0.3, 0.4, 0.49, 0.5, or any value range between the two. Optionally, in the X-ray diffraction pattern of the nickel-based alloy layer, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane can be selected as 0.1~0.2, 0.1~0.3, 0.1~0.4, 0.1~0.49, 0.2~0.3, 0.2~0.4, 0.2~0.49, 0.3~0.4, 0.3~0.49, 0.4~0.49, etc.

[0172] In some embodiments, the ratio of the diffraction peak intensity of the (110) crystal plane to that of the (111) crystal plane in the X-ray diffraction spectrum of the nickel-based alloy layer is 0 to 0.3.

[0173] In the X-ray diffraction spectrum of the nickel-based alloy layer, the ratio of the diffraction peak intensity of the (110) crystal plane to that of the (111) crystal plane is within the above range, which means that the nickel-based alloy layer has the (111) crystal plane as the preferred orientation plane, which is beneficial to improve the grain slip characteristics, improve the plasticity of the current collector, improve the current collector's ability to withstand repeated expansion and contraction during cycling, and delay the timing of the cell crack failure.

[0174] In some embodiments, the transverse tensile strength MD of the current collector is 1200MPa~2200MPa, optionally 1400MPa~2200MPa or 1500MPa~2200MPa, and in some examples 1750MPa~2200MPa. As an example, the transverse tensile strength of the current collector can be selected from 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1600MPa, 1700MPa, 1750MPa, 1800MPa, 1900MPa, 2000MPa, 2100MPa, 2200MPa, or any value between two of these ranges.

[0175] The aforementioned current collector has high transverse tensile strength, which increases the cumulative strain that the battery cell can withstand along its length, thus improving the cell's resistance to expansion, reducing the risk of electrode breakage, and improving the cycle life of the battery cell.

[0176] In some embodiments, the longitudinal tensile strength TD of the current collector is 1100MPa~2100MPa, optionally 1150MPa~2100MPa or 1200MPa~2100MPa, and in some examples 1400MPa~2100MPa. As an example, the tensile strength of the current collector in the width direction can be selected from 1100MPa, 1150MPa, 1180MPa, 1200MPa, 1250MPa, 1300MPa, 1350MPa, 1400MPa, 1450MPa, 1500MPa, 1600MPa, 1700MPa, 1800MPa, 1900MPa, 2000MPa, 2100MPa or any value between two of these.

[0177] The current collector has high longitudinal tensile strength, which increases the cumulative strain that the battery cell can withstand along the width direction, thereby reducing the risk of current collector fracture and improving the overall cumulative strain that the battery cell can withstand, thus improving the cycle life of the battery cell.

[0178] In some embodiments, the transverse tensile strength MD of the current collector is greater than the longitudinal tensile strength TD of the current collector. The nickel-based alloy layer in the current collector itself has high strength, and the transverse and longitudinal tensile strengths of the current collector are different. By controlling the current collector to have a better transverse tensile strength, the risk of breakage of the current collector and the electrode sheet on which the current collector is provided is reduced, the ability of the battery cell to resist stress such as expansion is improved, and the cycle life of the battery cell is increased.

[0179] In some embodiments, the difference between the transverse tensile strength MD and the longitudinal tensile strength TD of the current collector is 50 MPa to 500 MPa, and can be selected as 100 MPa to 300 MPa. As an example, the difference between the transverse tensile strength MD and the longitudinal tensile strength TD of the current collector can be 50 MPa, 80 MPa, 100 MPa, 150 MPa, 200 MPa, 250 MPa, 300 MPa, 350 MPa, 400 MPa, 450 MPa, 500 MPa, or any value between the two.

[0180] In some embodiments, the ratio of the transverse tensile strength MD of the current collector to the longitudinal tensile strength TD of the current collector is 1.01 to 1.3, and can be selected as 1.05 to 1.3; as examples, it can be 1.01, 1.02, 1.03, 1.05, 1.1, 1.15, 1.17, 1.2, 1.25, 1.3 or any value between the two.

[0181] The tensile strength of the current collector differs in the transverse and longitudinal directions, with the transverse tensile strength being greater. This increases the cumulative strain that the battery cell can withstand along the length direction. At the same time, the difference is controlled within an appropriate range, taking into account the cumulative strain that can be withstood in the width direction. This reduces the risk of breakage of the current collector and the electrode sheet on which the current collector is located, thereby improving the overall cumulative strain that the battery cell can withstand and enhancing the cycle life of the battery cell.

[0182] In this application, the transverse tensile strength MD and longitudinal tensile strength TD of the current collector at 25℃ can be obtained by testing the tensile fracture curve of the current collector. The specific test method can be referred to GB / T5230-1995 "Electrolytic Copper Foil" standard.

[0183] As an example, the test procedure for the transverse tensile strength MD of the current collector at 25°C in this application is as follows: The current collector is cut along its length to obtain at least four specimens with a length of 150±0.5 mm (the extension direction of this length is the same as the length direction of the current collector), a width of 15±0.25 mm, and a gauge length of 50±0.5 mm. If it is a wound electrode assembly, the length direction of the current collector refers to the winding direction of the current collector. The maximum tensile stress of the specimen during tensile fracture is taken as the tensile strength of the specimen, in MPa. The maximum tensile stress of the specimen is calculated by dividing the maximum load borne by the specimen during tensile fracture by the cross-sectional area of ​​the specimen. The cross-sectional area of ​​the specimen is calculated by multiplying the specimen width by the thickness, and the thickness of the specimen is measured using a micrometer. At least four specimens are tested, and the average value is taken as the transverse tensile strength MD of the current collector.

[0184] As an example, the test procedure for the longitudinal tensile strength TD of the current collector at 25°C in this application is as follows: The current collector is cut along its width to obtain at least four specimens with a length of 150±0.5 mm (the extension direction of this length is the same as the width direction of the current collector), a width of 15±0.25 mm, and a gauge length of 50±0.5 mm. The maximum tensile stress of the specimen during tensile fracture is taken as the tensile strength of the specimen, in MPa. The maximum tensile stress of the specimen is calculated by dividing the maximum load borne by the specimen during tensile fracture by the cross-sectional area of ​​the specimen. The cross-sectional area of ​​the specimen is calculated by multiplying the specimen width by its thickness, and the specimen thickness is measured using a micrometer. At least four specimens are tested, and the average value is taken as the longitudinal tensile strength TD of the current collector.

[0185] It is understood that the current collector can be obtained from a freshly prepared negative electrode sheet or from a negative electrode sheet disassembled from a battery. Note: The maximum tensile stress of the specimen during tensile fracture is the tensile force applied along the length of the specimen, reflecting the material's performance under stress in that direction; the same applies below. It is understood that the transverse tensile strength MD and longitudinal tensile strength TD of the electrode sheet containing the aforementioned current collector in this application can also be tested using the aforementioned method.

[0186] The transverse tensile strength MD and longitudinal tensile strength TD of the current collector in this application were both tested under the conditions of 25℃ and tensile speed of 50±0.5mm / min.

[0187] In some embodiments, the transverse elongation at break of the current collector is greater than the longitudinal elongation at break of the current collector.

[0188] In some embodiments, the lateral elongation at break δ of the current collector is 3% to 8%, optionally 3% to 6%. As an example, the lateral elongation at break δ of the current collector can be 3%, 4%, 5%, 6%, 6.5%, 7%, 8%, or any value range between the two.

[0189] By controlling the lateral fracture elongation δ of the current collector within the above range, the possibility of stress concentration causing the current collector to fracture in the length direction is reduced, thereby reducing the fracture risk of the current collector and the electrode with the current collector, improving the overall tolerable cumulative strain of the battery cell, and improving the cycle life of the battery cell.

[0190] In some embodiments, the longitudinal elongation at break δ' of the current collector is 2% to 7%, optionally 3% to 5%. As an example, the longitudinal elongation at break δ' of the current collector can be 2%, 3%, 4%, 5%, 6%, 7%, or any value range between two of these.

[0191] By controlling the longitudinal fracture elongation δ' of the current collector within the above range, the possibility of stress concentration causing the current collector to fracture in the width direction is reduced, thereby reducing the fracture risk of the current collector and the electrode with the current collector, improving the overall tolerable cumulative strain of the battery cell, and improving the cycle life of the battery cell.

[0192] In some embodiments, the difference δ-δ' between the transverse elongation at break and the longitudinal elongation at break of the current collector is 0.5% to 5%, optionally 1% to 3%. As an example, the difference can be 0.5%, 1%, 1.5%, 2%, 3%, 4%, 5%, or any value range between the two.

[0193] In some embodiments, the ratio of the transverse elongation at break to the longitudinal elongation at break of the current collector is 1.01 to 1.7, and can be selected as 1.1 to 1.7; as examples, it can be 1.01, 1.02, 1.03, 1.05, 1.1, 1.15, 1.17, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or any value between the two.

[0194] The current collector has a difference in transverse and longitudinal elongation at break. By controlling the difference within an appropriate range, the cumulative strain that can be tolerated in both length and width directions is taken into account. This reduces the risk of breakage of the current collector and the electrode with the current collector, thereby improving the overall tolerable cumulative strain of the battery cell and enhancing the cycle life of the battery cell.

[0195] In this application, the transverse elongation at break and the longitudinal elongation at 25°C of the current collector can be obtained by testing the tensile fracture curve of the current collector. The specific test method can be carried out in accordance with the GB / T5230-1995 standard "Electrolytic Copper Foil".

[0196] As an example, in this application, the test procedure for the transverse elongation at break of the current collector at 25°C is as follows: The current collector is cut along its length to obtain at least four specimens with a length of 150±0.5 mm (the extension direction of this length is the same as the length direction of the current collector), a width of 15±0.25 mm, and a gauge length of 50±0.5 mm. If it is a wound electrode assembly, the length direction of the current collector refers to the winding direction of the current collector. The elongation at break is the ratio of the displacement at tensile fracture (i.e., the length of the specimen elongation) to the gauge length of the specimen. At least four specimens are tested, and the average value is taken as the transverse elongation at break of the current collector.

[0197] As an example, in this application, the test procedure for the longitudinal elongation at break of the current collector at 25°C is as follows: The current collector is cut along its width to obtain at least four specimens with a length of 150±0.5 mm (the extension direction of this length is the same as the width direction of the current collector), a width of 15±0.25 mm, and a gauge length of 50±0.5 mm. The elongation at break is the ratio of the displacement at tensile fracture (i.e., the length of the specimen elongation) to the gauge length of the specimen. At least four specimens are tested, and the average value is taken as the longitudinal elongation at break of the current collector.

[0198] It is understood that the current collector can be obtained from a freshly prepared negative electrode sheet or from a negative electrode sheet disassembled from a battery. It is also understood that the elongation at break of the electrode sheet containing the aforementioned current collector in this application can be tested using the aforementioned method.

[0199] The transverse and longitudinal elongation at break of the current collector in this application were obtained under test conditions of 25℃ and tensile speed of 50±0.5mm / min.

[0200] In a second aspect, one embodiment of this application provides a method for preparing a current collector, comprising the following steps:

[0201] An insoluble anode, an electroplating solution, and a cathode are provided for electroplating to form a nickel-based alloy layer on the surface of the cathode; after electroplating, the nickel-based alloy layer is separated from the surface of the cathode.

[0202] The electroplating solution includes a nickel source, a first metal source, a complexing agent, and a first additive. The first additive contains a benzene ring and a sulfonic acid group connected to the benzene ring. The benzene ring may optionally be connected to a carbon chain substituent with a number of carbon atoms less than or equal to 3. The first metal element in the first metal source is a metal element other than nickel, and the first metal element includes one or more of Fe, Zn, Ti, V, Cr, Mn, or Co.

[0203] Understandably, during the electroplating process, the cathode rotates relative to the anode located in the electroplating solution, thereby forming a continuous nickel-based alloy layer on the cathode. Furthermore, the cathode is a cathode roller.

[0204] Understandably, the benzene ring may optionally be connected to carbon chain substituents with a number of carbon atoms less than or equal to 3, i.e. it does not contain long carbon chains greater than 3, and its adsorption cathode roller has less steric hindrance.

[0205] In the electroplating process, as the electroplating process proceeds, the area near the cathode roller becomes locally alkaline. Taking nickel-iron alloy foil as an example, iron elements are locally enriched to form ferric hydroxide colloids. These ferric hydroxide colloids are difficult to disperse, and the enrichment of iron in the electroplating solution leads to the deposition of elemental iron grains, thus causing uneven distribution of iron elements in the current collector. The higher the concentration of iron ions in the electroplating solution, the more pronounced the uneven distribution and deposition of iron elements in the current collector.

[0206] In the above-mentioned method for preparing the current collector, the electroplating solution includes a nickel source and a first metal source, the two of which have different deposition rates. The first additive, which does not contain long carbon chains, contains sulfonic acid groups linked to benzene rings, making it easier for the sulfonic acid groups to be adsorbed on the surface of the cathode roller, forming an electric double layer or a steric hindrance effect. By utilizing the repulsion of like charges or the hindering effect of polymer chains, it prevents the metal ions from excessively agglomerating due to van der Waals forces, resulting in local concentrations that are too high or too low. In this way, the nickel source and the first metal source can be fully dispersed in it. The complexing agent can cooperate with the nickel ions and the first metal ions to allow them to be deposited together on the cathode roller. In this way, the first additive and the complexing agent work together to allow the first metal elements such as nickel and iron to be deposited as simultaneously as possible. This reduces the variance of the mass content of the first metal elements in the resulting alloy layer, improves the uniformity of the mass content distribution of the first metal elements and nickel elements, enhances its corrosion resistance, and improves the cycle performance of the battery in which it is applied.

[0207] The above preparation method can produce the current collector of the first aspect of this application. The current collector produced has the same characteristics as the current collector of the first aspect, which will not be described again here.

[0208] In some embodiments, the complexing agent includes one or more of sodium citrate, tartaric acid, lactic acid, or sodium gluconate.

[0209] In some embodiments, the first additive includes one or more of p-toluenesulfonic acid, methyl p-toluenesulfonate, or ethyl p-toluenesulfonate.

[0210] In some embodiments, the concentration of the first additive in the electroplating solution is 0.1 g / L to 0.9 g / L; examples include 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, 0.6 g / L, 0.7 g / L, 0.8 g / L, 0.9 g / L, or any value between the two.

[0211] In some embodiments, the concentration of the complexing agent in the electroplating solution is 20 g / L to 60 g / L; as examples, it can be 20 g / L, 25 g / L, 30 g / L, 40 g / L, 45 g / L, 50 g / L, 60 g / L, or any value between two of these. The complexing agent can cooperate with nickel ions and the first metal ions to allow both to be deposited together on the cathode roller. Controlling the concentration of the complexing agent within this range can make the concentration of free nickel ions and the first metal ions in the electroplating solution more uniform, thereby improving the variance of the mass content of the first metal element in the nickel-based alloy layer. Optionally, the concentration of the complexing agent in the electroplating solution is 25 g / L to 45 g / L.

[0212] In some embodiments, the electroplating temperature is 50°C to 60°C. Temperature control within this range helps to increase ion transport speed and improve deposition efficiency.

[0213] In some embodiments, the pH value of the electroplating solution is 2 to 3; controlling the pH value of the electroplating solution within this range can reduce the formation of local precipitation in the electroplating solution and improve the uniformity of metal element distribution in the nickel-based alloy layer formed by electroplating.

[0214] In some embodiments, the flow rate of the electroplating solution is 50 L / min to 80 L / min; as an example, it can be within the range of 50 L / min, 60 L / min, 70 L / min, 80 L / min, or any combination thereof. Controlling the flow rate of the electroplating solution within this range provides a sufficient supply of fresh electroplating solution, improving the uniformity of metal element distribution in the nickel-based alloy layer formed by electroplating.

[0215] In some embodiments, the cathode rotation speed is 0.2 m / min to 0.8 m / min; as examples, it can be 0.2 m / min, 0.3 m / min, 0.4 m / min, 0.5 m / min, 0.6 m / min, 0.7 m / min, 0.8 m / min, or any value between two of these. A slower cathode rotation speed is more conducive to better adsorption of the first additive on the cathode surface and improves the uniformity of the distribution of the first metallic elements such as nickel and iron.

[0216] In some embodiments, the current density during the electroplating process is 2 A / dm². 2 ~10A / dm 2 Optional 5A / dm 2 ~10A / dm 2 As an example, this current density could be 2 A / dm³. 2 3A / dm 2 5A / dm 2 8A / dm 2 10A / dm2 The current density can be any value within a range defined by any two of the above points as endpoints. Adjusting the current density within this range is beneficial for improving deposition efficiency.

[0217] In some of these embodiments, the nickel source includes one or more of nickel sulfate, nickel chloride, or nickel carbonate.

[0218] In some embodiments, the concentration of the nickel source in the electroplating solution is 150 g / L to 250 g / L; as examples, it can be 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, or any value within the range formed by any two of the above points as endpoints, and can be selected as 200 g / L to 250 g / L.

[0219] In some embodiments, the first metal source includes one or more of Fe, Zn, Ti, Cr, Mn, or Co sources. Further, the electroplating solution includes an Fe source. Optionally, the concentration of the Fe source in the electroplating solution is 20 g / L to 80 g / L. As an example, the concentration of the iron source can be 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, or any value within the range of any two of the above values, and can be selected as 40 g / L to 60 g / L.

[0220] In some embodiments, the Fe source includes one or more of ferrous sulfate, ferrous chloride, or iron powder. Ferrous sulfate, for example, is FeSO4·7H2O.

[0221] In some of these embodiments, the Cr source includes, but is not limited to, chromium sulfate.

[0222] In some of these embodiments, the Mn source includes, but is not limited to, manganese sulfate.

[0223] In some embodiments, the first metal source includes one or more ions selected from Fe, Zn, Ti, V, Cr, Mn, or Co.

[0224] In some embodiments, the electroplating solution includes nickel sulfate and ferrous sulfate.

[0225] In some embodiments, the electroplating solution further includes a second additive; optionally, the second additive includes one or more of saccharin, sodium saccharin, polyethylene glycol, polyethyleneimine, 1,4-butynediol, sodium naphthalene disulfonate, or formaldehyde.

[0226] The second additive can refine the average grain size of the nickel-based alloy layer, making the interatomic arrangement more compact, increasing the volume ratio of the γ solid solution phase in the nickel-based alloy layer, and improving its strength.

[0227] In some embodiments, the concentration of the second additive in the electroplating solution is 3 g / L to 5 g / L. As an example, the concentration of the second additive may be 3 g / L, 3.2 g / L, 3.5 g / L, 3.8 g / L, 4 g / L, 4.2 g / L, 4.5 g / L, 4.8 g / L, 5 g / L, or any value within the range formed by any two of the above points as endpoints.

[0228] In some embodiments, the electroplating solution also includes a third additive, which includes one or more of thiourea and its derivatives, and thiocyanates.

[0229] In some embodiments, the concentration of the third additive in the electroplating solution is 0.1 g / L to 0.5 g / L; for example, it is any value within the range of 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, or any two of the above points as endpoints.

[0230] In the above preparation method, the relative volume percentage of the γ solid solution phase obtained by adding a complexing agent and a first additive is relatively high. This parameter can, to some extent, characterize the degree of alloying between nickel and the first metallic element in the nickel-based alloy layer. A larger parameter indicates a higher degree of alloying, representing a lower content of the first metallic element or nickel in elemental form in that region. This can, to some extent, improve the problem of localized corrosion of the current collector and enhance its corrosion resistance. However, a larger parameter has been found to cause brittle fracture during the application of the current collector, thus reducing its service life and affecting the cycle performance of the battery. Therefore, by further adding a third additive, which can be adsorbed on the active sites of nickel-iron alloy crystal growth, the NH2 or SCN structure in the third additive can combine with metal ions to form an adsorption layer. This adsorption layer interferes with the uniform deposition of metal ions, resulting in a loose microstructure of the coating, reduced grain boundary tortuosity, and reduced γ phase. This ensures that the volume percentage of the γ solid solution phase in the resulting alloy layer is not too large, thereby reducing the internal stress of the alloy layer and the risk of brittle fracture. Therefore, in the above-described method for preparing the current collector, the use of a complexing agent, a first additive, and a specific third additive can effectively control the relative volume percentage of the γ-solution phase to be between 65% and 75%, allowing the current collector to exhibit both good corrosion resistance and bending resistance. In some embodiments, the electroplating solution also includes a wetting agent; optionally, the wetting agent includes one or more of sodium dodecyl sulfate or sodium dodecyl sulfonate; optionally, the concentration of the wetting agent in the electroplating solution is 0.1 g / L to 0.5 g / L, and as examples, it can be 0.1 g / L, 0.2 g / L, 0.3 g / L, 0.4 g / L, 0.5 g / L, or any value within the range defined by any two of the above points as endpoints.

[0231] In some embodiments, the electroplating solution further includes a stabilizer; optionally, the stabilizer includes one or more of boric acid, citric acid, or fluoroborate; optionally, the concentration of the stabilizer in the electroplating solution is 40 g / L to 80 g / L. As an example, the concentration of the stabilizer is 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, or any value within the range defined by any two of the above points. The main function of the stabilizer is to maintain pH stability and prevent excessive pH shift due to the hydrogen evolution reaction, which would increase the degree of reaction polarization and thus affect the foil forming efficiency of the nickel-based alloy layer.

[0232] In some embodiments, the electroplating solution may further include a conductive agent; optionally, the conductive agent includes one or more of sodium chloride and ammonium chloride. Optionally, the concentration of the conductive agent in the electroplating solution is 10 g / L to 50 g / L, for example, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, or any value within the range defined by any two of the above points. The conductive agent can enhance ion transport capability and improve deposition efficiency.

[0233] In some embodiments, the electroplating solution comprises: nickel sulfate 150 g / L to 250 g / L, ferrous sulfate 40 g / L to 60 g / L, second additive sodium saccharin 1 g / L to 10 g / L, complexing agent sodium citrate 20 g / L to 60 g / L, wetting agent sodium dodecyl sulfate 0.1 g / L to 0.5 g / L, stabilizer boric acid 40 g / L to 80 g / L, and first additive p-toluenesulfonic acid 0.1 g / L to 0.9 g / L.

[0234] In a third aspect, this application provides a secondary battery including an electrode assembly, which includes a positive electrode and a negative electrode. The negative electrode includes a negative current collector, which includes the current collector provided in the first aspect of this application or the current collector prepared by the preparation method of the current collector provided in the second aspect of this application.

[0235] In a fourth aspect, this application provides an electrical device comprising one or more of the current collector provided in the first aspect of this application, a current collector prepared by the method for preparing the current collector provided in the second aspect of this application, or a secondary battery provided in the third aspect of this application.

[0236] A secondary battery consists of one or more individual battery cells.

[0237] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0238] The positive electrode, negative electrode, and separator are fabricated into an electrode assembly using a winding or stacking process. This electrode assembly is immersed in an electrolyte. Understandably, a single battery cell may include one or more electrode assemblies.

[0239] In some embodiments, the secondary battery includes a battery cell, the battery cell includes an electrode assembly, the electrode assembly includes a positive electrode and a negative electrode, the negative electrode includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector, the negative active layer includes a negative active material, and the negative current collector includes the current collector described above in this application.

[0240] In some embodiments, the secondary battery includes a negative electrode sheet, which includes a negative current collector and a negative active layer disposed on at least one side of the negative current collector. The negative active layer includes a negative active material, and the negative current collector includes the current collector described above in this application.

[0241] As a non-limiting example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode active layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0242] In some embodiments, the negative electrode sheet further includes a negative electrode active layer disposed on at least one side of the negative electrode current collector. The negative electrode active layer includes a negative electrode active material, which includes at least one of silicon-based materials, lithium metal, and lithium metal alloys.

[0243] Furthermore, silicon-based materials include one or more of elemental silicon, silicon-carbon materials, silicon-oxygen materials, silicon-nitrogen materials, and silicon alloys. Furthermore, elemental silicon includes, but is not limited to, silicon nanoparticles.

[0244] Furthermore, the negative electrode active material includes silicon-based materials. Silicon-based materials have high capacity, and using them as negative electrode active materials in secondary batteries is beneficial for improving the battery's energy density. However, silicon-based materials undergo significant volume changes during battery cycling, compressing the negative electrode current collector. If the current collector strength is low, it can easily lead to damage to the negative electrode current collector, thereby deteriorating the battery's cycle performance. In the current collector described in this application, the nickel-based alloy layer has high strength, which can give the negative electrode current collector high tensile strength, reducing the risk of damage to the negative electrode current collector during battery cycling, and thus enabling the battery to maintain good cycle performance.

[0245] Furthermore, the mass content of silicon-based material in the negative electrode active material is ≥20%, and can be selected from 20% to 60%. As an example, based on the total mass of the negative electrode active layer, the mass content of silicon-based material can be selected as 20%, 25%, 30%, 40%, 50%, 60%, or any value range between the two.

[0246] Furthermore, the negative electrode active material includes a silicon-based material, and the mass content of silicon element is ≥10% based on the total mass of the negative electrode active layer, optionally 10%~20%. As an example, the mass content of silicon element based on the total mass of the negative electrode active layer can be 10%, 15%, 20%, or any value range between the two. Furthermore, the mass content of the silicon-based material in the negative electrode active material is 10%~20%, optionally 15%~20%.

[0247] Furthermore, the negative electrode active material also includes carbon-based materials. Carbon-based materials include, but are not limited to, graphite, and graphite includes, but is not limited to, one or more of artificial graphite and natural graphite. Furthermore, the negative electrode active material includes both carbon-based and silicon-based materials. Furthermore, the silicon-based material has a mass content of 25% to 60% in the negative electrode active material, and examples include 25%, 30%, 35%, 40%, 50%, 55%, 60%, or any value range between the two. Furthermore, the carbon-based material or graphite has a mass content of 40% to 75% in the negative electrode active material, and examples include 40%, 50%, 55%, 60%, 65%, 70%, 75%, or any value range between the two.

[0248] Based on the total mass of the negative electrode active layer, the silicon content can be tested using the following method: A cross-section of the negative electrode sheet is sliced, and the silicon content in the cross-section of the negative electrode active layer is determined using a combination of scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS).

[0249] The aforementioned negative electrode current collector enhances the overall tolerance of cumulative strain of the battery cell, thereby reducing the risk of electrode breakage and improving the cycle life of the battery cell. Therefore, the battery cell of this application embodiment can be applied to high-silicon systems, which helps to further improve the energy density per unit mass of the battery cell.

[0250] Without limitation, the mass content of the negative electrode active material in the negative electrode active layer can be ≥80%, and more specifically 80%~99%. As an example, the weight content of the negative electrode active material in the negative electrode active layer can be 80%, 85%, 90%, 95%, 99%, or within the range formed by any two of the above points as endpoints.

[0251] In some embodiments, the negative electrode active layer may optionally include a binder. The binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0252] Non-limitingly, the mass content of the binder in the negative electrode active layer can be 0 to 10%, more specifically 0.1% to 10%, and optionally 1% to 3%. As an example, the mass content of the conductive agent in the negative electrode active layer can be 0.1%, 0.2%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within the range defined by any two of the above values ​​as endpoints.

[0253] In some embodiments, the negative electrode active layer may optionally include a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The carbon fiber includes, but is not limited to, vapor-grown carbon fiber. Further, the carbon fiber may be carbon nanofibers. Non-limitingly, the mass content of the conductive agent in the negative electrode active layer may be 0-15%, more preferably 0-10%, and even more preferably 0-5%.

[0254] In some embodiments, the negative electrode active layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0255] In some embodiments, the negative electrode is a non-negative electrode, meaning it does not have a pre-installed negative electrode active material layer. In other words, the aforementioned secondary battery is a non-negative electrode battery, where lithium metal or lithium metal alloy is deposited on the negative electrode current collector during charging and consumed during discharging. The negative electrode current collector adopts the current collector of the first aspect of this application, and the current collector is in direct contact with the electrolyte or solid electrolyte layer. Furthermore, the aforementioned current collector has good corrosion resistance, thereby improving the cycle performance of the battery in which it is used.

[0256] In some embodiments, when the battery is a negative electrode-free lithium battery, a functional layer is typically provided on at least one surface of the negative electrode current collector, the functional layer comprising amorphous carbon material, metal or quasi-metallic material.

[0257] Optionally, the metallic or near-metallic material includes at least one of gold, platinum, palladium, silicon, silver, aluminum, bismuth, tin, or zinc.

[0258] The functional layer can reduce the nucleation energy of alkali metals, induce alkali metals to deposit on the current collector surface and form alloys with amorphous carbon materials, metals or quasi-metals in the functional layer, so that more alkali metals or alkali metal alloys are deposited on the current collector surface, increasing the amount of active material on the current collector surface and further improving the first coulombic efficiency of the battery.

[0259] Optionally, the functional layer is a porous functional layer. This can promote the deposition of active ions across the functional layer onto the surface of the current collector.

[0260] Alternatively, amorphous carbon may be, for example, carbon black (CB), acetylene black (AB), furnace black (FB), Ketjen black (KB), graphene, etc., but is not limited thereto, and any suitable amorphous carbon classified in the art is possible. Amorphous carbon is carbon with no crystallinity or very low crystallinity, which is distinct from crystalline carbon or graphitic carbon.

[0261] Metallic or quasi-metallic anode active materials may include, but are not limited to, one or more of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn), and any suitable metallic or quasi-metallic material in the art that forms an alloy or compound with lithium is possible.

[0262] In some embodiments, the functional layer comprises one or a mixture of amorphous carbon materials, metals, or metalloids. For example, the functional layer may comprise only amorphous carbon, or may comprise at least one of gold (Au), platinum (Pt), palladium (Pd), silicon (Si), silver (Ag), aluminum (Al), bismuth (Bi), tin (Sn), and zinc (Zn).

[0263] In some embodiments, the functional layer includes an adhesive. Optionally, the adhesive includes, but is not limited to, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, vinylidene fluoride / hexafluoropropylene copolymer, polyacrylonitrile, polymethyl methacrylate, etc., and any suitable adhesive used in the art is possible. The adhesive may be configured as a single adhesive or a variety of different adhesives.

[0264] Non-limitingly, when the secondary battery is a solid-state battery, the negative electrode active layer may include a solid electrolyte. The solid electrolyte in the negative electrode active layer can enhance the ion conductivity of the negative electrode layer, reduce interfacial impedance, and promote the charge transfer efficiency between the negative electrode active material and the external environment, as well as the full release of its capacity.

[0265] Non-limitingly, the mass content of the solid electrolyte in the negative electrode active layer can be 0% to 30%, preferably 0.1% to 30%, and further preferably 5% to 20%. The type of solid electrolyte in the negative electrode active layer can be the same as the selection range of solid electrolyte in the solid electrolyte layer described below.

[0266] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto at least one surface of the negative electrode current collector, and then obtaining the negative electrode sheet after processes such as drying and cold pressing. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or both surfaces of the negative electrode current collector.

[0267] The positive electrode includes a positive current collector and a positive active layer disposed on at least one surface of the positive current collector, the positive active layer including a positive active material.

[0268] As a non-limiting example, the positive current collector has two surfaces that are opposite to each other in its own thickness direction, and the positive active layer is disposed on either or both of the two opposing surfaces of the positive current collector.

[0269] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector known in the art. For example, aluminum foil may be used as a metal foil known in the art. In the positive electrode current collector, a composite current collector known in the art may include a polymeric material substrate and a metal conductive layer formed on at least one surface of the polymeric material substrate. In the positive electrode current collector, the composite current collector can be obtained by forming a metal material on a polymeric material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. Non-limiting examples of the polymeric material substrate in the positive electrode current collector may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0270] In some embodiments, the positive electrode active layer includes a positive electrode active material, which includes lithium ions.

[0271] In some embodiments, the positive electrode active material may be a known positive electrode active material for batteries. As a non-limiting example, the positive electrode active material may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.

[0272] Non-limiting examples of lithium phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Further, the aforementioned carbon composites may be carbon-coated composites.

[0273] Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds.

[0274] Non-limiting examples of lithium cobalt oxides may include LiCoO2; non-limiting examples of lithium nickel oxides may include LiNiO2; non-limiting examples of lithium manganese oxides may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxides may include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 Examples of lithium nickel cobalt aluminum oxides include LiNi, etc. 0.85 Co 0.10 Al 0.05 O2.

[0275] In some embodiments, the positive electrode active layer may optionally include a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0276] In some embodiments, the positive electrode active layer may optionally include a conductive agent. As a non-limiting example, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0277] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent to form a positive electrode slurry; coating the positive electrode slurry onto at least one surface of the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing, and other processes. The solvent can be selected from, but is not limited to, any of the solvents in the foregoing embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or both surfaces of the positive electrode current collector.

[0278] In some embodiments, when the secondary battery is a solid-state battery, the positive electrode active layer may optionally include a positive electrode solid electrolyte. The positive electrode solid electrolyte can improve the conductivity of the positive electrode active layer, which is beneficial for improving the battery's rate performance.

[0279] Optionally, the positive electrode solid electrolyte may include one or more of halide solid electrolytes, sulfide solid electrolytes, and oxide solid electrolytes. The type of solid electrolyte in the positive electrode active layer may be the same as the range of solid electrolytes selected for the solid electrolyte layer described below.

[0280] Optionally, the solid electrolyte in the positive electrode accounts for 0.5% to 10% of the mass percentage of the positive electrode active layer. For example, the mass percentage of the solid electrolyte in the positive electrode can be 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or any value within the range of any two of the above values.

[0281] In some embodiments, the positive electrode active layer includes a positive electrode active material and a positive electrode solid electrolyte.

[0282] In some embodiments, the positive electrode active layer includes a conductive agent. The conductive agent in the positive electrode active layer may be referred to as a positive electrode conductive agent. As a non-limiting example, the positive electrode conductive agent may be a carbon conductive agent. Non-limitingly, the carbon conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0283] In some embodiments, the positive electrode conductive agent may be one or more of the following, including but not limited to SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes (CNTs) and graphene.

[0284] Non-limitingly, the mass percentage of the positive electrode conductive agent in the positive electrode active layer can be 0-20%, more preferably 0-15%, more preferably 0-10%, more preferably 0-5%, and more preferably 2%-20%.

[0285] In some embodiments, the positive electrode active layer may optionally include a binder. The binder in the positive electrode active layer may be referred to as a positive electrode binder. As a non-limiting example, the positive electrode binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins. The aforementioned non-limiting examples of positive electrode binders are all organic binders and are all organic components. Typically, the mass percentage of the positive electrode binder in the positive electrode active layer may be 0-10%, more preferably 0-8%, more preferably 0.1%-5%, and more preferably 1%-5%.

[0286] In some embodiments, the positive electrode sheet can be prepared by: dry mixing the components used to prepare the positive electrode sheet, such as the positive electrode active material, the positive electrode solid electrolyte, the positive electrode conductive agent, the positive electrode binder, and any other components; then heating and pressurizing the mixed material to knead it into a clump; hot rolling is then performed to form a self-supporting positive electrode active layer; the self-supporting positive electrode active layer is then hot-rolled and bonded to the positive electrode current collector. The self-supporting positive electrode active layer can be bonded to one or both sides of the positive electrode current collector to obtain the positive electrode sheet. Non-limitingly, a dual planetary mixer can be used for dry mixing. Non-limitingly, a kneading and heating process can be used. Non-limitingly, the temperature for hot rolling can be 75°C to 85°C, and further, such as 78°C, 80°C, 82°C, etc. The method for assembling solid-state secondary batteries using the positive electrode sheet is suitable for industrial mass production.

[0287] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, the positive solid electrolyte, the positive conductive agent, the positive binder, and any other components, in an organic solvent to form a positive electrode slurry. Further, the positive electrode slurry is coated onto at least one surface of the positive current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained. Cold pressing can be performed using a cold rolling mill. The surface of the positive current collector coated with the positive electrode slurry can be a single surface of the positive current collector or both surfaces of the positive current collector. The solid content of the positive electrode slurry can be 40% to 80%. The viscosity of the positive electrode slurry at room temperature can be adjusted to 5000 mPa·s to 25000 mPa·s.

[0288] In some embodiments, the secondary battery is a solid-state battery. The solid-state battery includes a positive electrode, a solid electrolyte layer, and a negative electrode, with the solid electrolyte layer located between the positive and negative electrode.

[0289] In solid-state batteries, solid electrolytes such as sulfides can corrode the traditional copper foil negative electrode current collector, leading to damage to the current collector and consequently degrading battery performance. In the aforementioned solid-state batteries, the nickel-based alloy layer exhibits better corrosion resistance, reducing the risk of corrosion damage to the negative electrode current collector and improving battery cycle performance.

[0290] The electrolyte exists in the form of a solid electrolyte layer. Specifically, in a solid-state battery, the solid electrolyte layer is located between the negative electrode layer and the positive electrode layer. The solid electrolyte layer serves to conduct ions between the positive and negative electrode layers and also isolates the positive and negative electrode layers, thereby preventing short circuits between the positive and negative electrodes.

[0291] A solid electrolyte layer can be introduced by forming electrode layers on both sides of the solid electrolyte membrane, or it can be introduced on the electrode layer.

[0292] It is understood that the solid electrolyte layer includes a solid electrolyte. The solid electrolyte in the solid electrolyte layer can be a solid electrolyte known in the art that can be used in solid-state batteries.

[0293] Furthermore, solid electrolytes include one or more of the following: sulfide solid electrolytes, halide solid electrolytes, and oxide solid electrolytes.

[0294] Optionally, the solid electrolyte includes sulfide solid electrolytes.

[0295] In some embodiments, the sulfide electrolyte includes one or more of the following: silver sulfide-germanium sulfide electrolyte, LGPS-type sulfide electrolyte, and lithium sulfide-phosphorus pentasulfide complex-type sulfide electrolyte.

[0296] Among them, sulfide electrolytes of the silver-germanium sulfide type include those with the chemical formula Li 6±s P 1-j A j S 5±s-t B t X 1±s Sulfide electrolytes, wherein 0≤s<1, 0≤j<1, 0≤t<1, A includes one or more elements selected from Ge, Si, Sn, and Sb, B includes one or more elements selected from O, Se, and Te, and X includes one or more elements selected from Cl, Br, I, and F. Among them, LGPS type sulfide electrolytes include those with the chemical formula Li 10±δ5 Ge 1-g G g P 2-q Q q S 12-w W wA sulfide electrolyte, where 0 ≤ δ5 < 1, 0 ≤ g ≤ 1, 0 ≤ q ≤ 2, 0 ≤ w < 1, G includes one or both elements of Si and Sn, Q includes Sb, and W includes one or more elements of O, Se, Te, Cl, Br, I, and F.

[0297] Among them, the sulfide electrolyte of the lithium sulfide - phosphorus pentasulfide complex type includes a chemical formula of (100 - u - v)Li2S·uP2S5·vM m N n A sulfide electrolyte, where 0 < u < 100, 0 ≤ v < 100, 0 ≤ u + v < 100, 0 ≤ m < 4, 0 ≤ n < 6, M includes one or more elements of Li, B, Ge, Si, Sn, and Sb, and N includes one or more elements of S, Se, Te, O, Cl, Br, I, and F.

[0298] As a non - restrictive example, the sulfide - based solid electrolyte can include, but is not limited to, Li 10 GeP2S 12 、Li2S - P2S5、Li6PS5Cl、Li 5.5 PS 5.5 Cl 1.5 and so on, one or more of them.

[0299] Non - restrictive examples of oxide - based solid electrolytes can include LISICON - type oxide electrolytes (such as γ - Li3PO4, etc.), NASICON - type oxide electrolytes (such as Li 1+x Al x Ge 2-x (PO4)3, Li 1+x Al x Ti 2-x (PO4)3, etc., 0 ≤ x ≤ 1), Garnet - type (such as Li7La3Zr2O12, etc.), perovskite - type oxide electrolytes (such as Li 3x La 2 / 3-x TiO3, etc., 0 ≤ x ≤ 0.5), and so on, one or more of them.

[0300] As a non - restrictive example, the halide - based solid electrolyte can include one or more of Li3InCl6, Li3YCl6, Li3ScCl6, Li3ErCl6, Li2ZrCl6, etc.

[0301] The solid electrolyte layer can be prepared using a dry method. In some embodiments, the solid electrolyte layer can be formed by pressing a solid electrolyte material into a solid electrolyte membrane. In other embodiments, the solid electrolyte layer is formed by pressing the constituent raw materials of the solid electrolyte layer onto an electrode layer. In still other embodiments, the solid electrolyte membrane can also be prepared using methods such as fibrosis combined with calendering, melt extrusion, or spraying.

[0302] In this application, the sheet-like solid electrolyte membrane may also be referred to as a solid electrolyte membrane sheet.

[0303] Solid electrolyte layers can also be prepared by wet methods, and the electrolyte slurry used includes at least a solid electrolyte and an organic solvent, and usually also includes one or more of a binder and a first additive.

[0304] In some embodiments, the thickness of the solid electrolyte layer can be 3 μm to 50 μm, and can be selected as 10 μm to 100 μm, 100 μm to 800 μm, 500 μm to 800 μm, etc.

[0305] In some implementations, the solid-state battery is an all-solid-state battery.

[0306] In this application, unless otherwise specified, "all-solid-state battery" refers to a solid-state battery in which all electrolytes are solid electrolytes. In this case, the positive electrode layer, negative electrode layer and electrolyte part are all made of solid materials, and no liquid electrolyte is provided in the battery, so it can be called "all-solid-state battery".

[0307] In some embodiments, the thickness of the solid electrolyte layer is 3 μm to 50 μm. This allows the solid electrolyte to have a smaller mass, which is beneficial for further improving the energy density of the solid-state secondary battery. Optionally, the thickness of the solid electrolyte can be 3 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, or any value within the range of any two of the above values. More preferably, the thickness of the solid electrolyte is 5 μm to 20 μm.

[0308] In some embodiments, the conductivity of the solid electrolyte layer is ≥0.1 mS / cm, optionally ranging from 1 mS / cm to 20 mS / cm. The higher conductivity of the solid electrolyte can reduce the internal resistance of the battery and improve its rate performance. Optionally, the conductivity of the solid electrolyte is greater than or equal to 1 mS / cm.

[0309] In some embodiments of this application, the solid electrolyte layer includes one or more of halide solid electrolytes, sulfide solid electrolytes, and oxide solid electrolytes.

[0310] It is understandable that the solid electrolyte in the solid electrolyte layer can be selected from the solid electrolytes listed in the positive electrode solid electrolyte above.

[0311] Optionally, the solid electrolyte in the solid electrolyte layer includes a sulfide solid electrolyte. Sulfides themselves have high conductivity, which helps to reduce the internal resistance of the battery and further improve the rate performance of the battery. More optionally, the solid electrolyte includes Li3PS4 and Li7P3S. 11 Li6PS5Cl and Li 10 GeP2S 12 One or more of them.

[0312] The secondary battery and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0313] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 The image shows a single battery cell, which serves as an example of a square-structured battery cell.

[0314] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above. In some embodiments, the outer packaging of the battery cell may be a rigid shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell may also be a flexible package, such as a pouch. The material of the flexible package may be plastic; further, non-limiting examples of plastic may include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0315] In some embodiments, the outer packaging may include a shell and a cover. The shell may include a base plate and side plates connected to the base plate, the base plate and side plates enclosing a receiving cavity. The shell has an opening communicating with the receiving cavity, and the cover can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly using a winding or stacking process. The electrode assembly is encapsulated within the receiving cavity. The electrode assembly is immersed in an electrolyte. The number of electrode assemblies contained in a single battery cell may be one or more, which can be selected by those skilled in the art according to actual needs.

[0316] In some embodiments, the secondary battery is a battery device. In some embodiments, the secondary battery includes one or more of a battery module and a battery pack. A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number according to the application and capacity of the battery module.

[0317] Figure 3 This is battery module 4 as an example. (See reference...) Figure 3In the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0318] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0319] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select an appropriate number according to the application and capacity of the battery pack.

[0320] Figure 3 and Figure 4 This is battery pack 1 as an example. (See reference...) Figure 3 and Figure 4 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0321] In some embodiments, multiple battery cells 5 can also be arranged in any way in the battery box to directly obtain the battery pack 1.

[0322] In addition, one embodiment of this application also provides an electrical device, which includes the secondary battery provided in this application. The secondary battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc., but are not limited to.

[0323] As an electrical device, a rechargeable battery can be selected based on its usage requirements.

[0324] Figure 5 Here is an example of an electrical device 6. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of this electrical device for its secondary battery, the aforementioned battery pack or battery module can be used as the power source.

[0325] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can utilize the aforementioned battery cells as their power source.

[0326] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0327] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0328] Example 1

[0329] (1) Preparation of negative electrode current collector

[0330] 1.1 The nickel-iron alloy foil layer was prepared using an electroplating apparatus.

[0331] An electroplating apparatus is provided, comprising an insoluble anode, an electroplating solution, and a cathode; the anode is a titanium mesh with a ruthenium-iridium alloy coating on its surface, and the cathode is a titanium roller. The cathode roller is installed in the electroplating apparatus, and the electrolyte is injected into the electrolytic tank, circulated and stirred, with the temperature controlled at 60°C.

[0332] Electroplating is performed to form a nickel-iron alloy foil layer on the surface of the cathode; after electroplating, the nickel-iron alloy foil layer is separated from the surface of the cathode.

[0333] The electroplating solution consists of: nickel sulfate 200 g / L, ferrous sulfate 60 g / L, second additive sodium saccharin 5 g / L, complexing agent sodium citrate 40 g / L, wetting agent sodium dodecyl sulfate 0.5 g / L, stabilizer boric acid 60 g / L, and first additive p-toluenesulfonic acid 0.1 g / L.

[0334] The electroplating parameters are: current density 5.5 A / dm³ 2 The pH value of the electroplating solution is 2.5, the flow rate of the electroplating solution is 50 L / min, and the rotation speed of the cathode roller is 0.5 m / min.

[0335] A nickel-iron alloy foil layer is electroplated on a titanium roller, peeled off, and the thickness is 6μm. The peeled foil is then wound up.

[0336] Based on the total mass of the nickel-iron alloy foil layer, Ni accounts for 68% of the mass, Fe accounts for 30% of the mass, and the remainder is unavoidable impurities, with an average grain size of 42 nm.

[0337] (2) Preparation of negative electrode sheet

[0338] A 10 μm lithium metal layer is set on the nickel-iron alloy foil layer prepared above as the negative electrode active material layer.

[0339] (3) Solid electrolyte Li6PS5Cl and lithium-containing transition metal oxide LiNi 0.9 Co 0.05 Mn 0.05 O2, conductive agent SP, and binder PVDF are mixed evenly in N-methylpyrrolidone in a ratio of 5:91.5:2:1.5 to prepare a positive electrode slurry. The positive electrode slurry is coated on the surface of aluminum foil and dried, and then cold-pressed to prepare a positive electrode sheet.

[0340] (4) Solid electrolyte layer.

[0341] The first solid electrolyte layer is formed by mixing solid electrolyte Li6PS5Cl and binder PTFE at a mass ratio of 97:3 and then cold pressing.

[0342] (5) Battery assembly.

[0343] A solid-state secondary battery is assembled by stacking the positive electrode, solid electrolyte layer, and negative electrode in sequence.

[0344] Examples 2-6

[0345] The process is basically the same as in Example 1, except that the preparation of the negative electrode current collector is different. Specifically, the concentrations of the complexing agent sodium citrate and the first additive p-toluenesulfonic acid in the electroplating solution are different, which in turn causes the variance of the iron content in the nickel-iron alloy foil layer to be different, as shown in Table 1.

[0346] Example 7

[0347] The process is basically the same as in Example 1, except that the preparation of the negative electrode current collector is different. Specifically, the type of complexing agent in the electroplating solution is different, which in turn causes the variance of the iron content in the nickel-iron alloy foil layer to be different, as shown in Table 1.

[0348] Example 8

[0349] The process is basically the same as in Example 1, except that the preparation of the negative electrode current collector is different. Specifically, the type of the first additive in the electroplating solution is different, which in turn causes the variance of the iron content in the nickel-iron alloy foil layer to be different, as shown in Table 1.

[0350] Comparative Example 1

[0351] The process is basically the same as in Example 1, except that the preparation of the negative electrode current collector is different. Specifically, the first additive in Example 1 is omitted from the electroplating solution formula, which results in a different variance in the mass content of iron in the nickel-iron alloy foil layer, as shown in Table 1.

[0352] Comparative Example 2

[0353] The process is basically the same as in Example 1, except that the preparation of the negative electrode current collector is different. Specifically, the type of the first additive in the electroplating solution is different, which in turn causes the variance of the iron content in the nickel-iron alloy foil layer to be different, as shown in Table 1.

[0354] Examples 9-11

[0355] The process is basically the same as in Example 4, except that the preparation of the negative electrode current collector is different. Specifically, the concentration of sodium saccharin in the electroplating solution is different, and a third additive, thiourea, is added. The specific concentrations are shown in Table 2.

[0356] The following are performance tests.

[0357] (1) Test of the mass content of iron element and the variance of its content in the nickel-iron alloy foil layer of the negative electrode current collector.

[0358] Cut the current collector to be tested into a sample of a certain width (e.g., 5 cm) along the width direction of the cutting line, exposing two cross-sections in the thickness direction of the sample. Take several (e.g., 50) test samples consecutively from the sample, ensuring that the mass of each test sample is ≥1g (the size can be, for example, 5cm × 5cm).

[0359] First, pure iron metal is used as the standard sample. Multiple iron standard solutions of different concentrations are prepared and sequentially analyzed by an ICP instrument. The correlation between the intensity signal value of the characteristic spectral line of iron and the concentration of the standard solution is recorded to generate a standard curve. As an example, the specific steps are as follows: Pure iron metal is digested using a mixture of nitric acid and hydrochloric acid, either by hot plate or microwave, until the solution is clear. After cooling, the solution is diluted to volume with ultrapure water (e.g., 50 mL) and filtered to remove undissolved particles. The solution is then serially diluted with 3wt% nitric acid to target concentrations of 0.1 mg / L, 0.5 mg / L, 1.0 mg / L, 5.0 mg / L, and 10.0 mg / L. The intensity signal value of the characteristic spectral line of iron is obtained by testing each standard solution using an inductively coupled plasma optically spectrometer (ICP). This yields the standard curve relating the concentration of iron to the intensity signal value of the characteristic spectral line of iron.

[0360] The test solutions were prepared using the same method described above for each sample. The expected concentration range of the test solutions was within the concentration range of the standard solutions. Then, the intensity signals of the characteristic spectral lines of iron were measured using an inductively coupled plasma optical emission spectrometer (ICP). Based on the measured intensity signals of the characteristic spectral lines of iron and the standard curve of iron, the concentration of iron in the test solution was calculated. As an example, the specific steps are as follows: A mixture of nitric acid and hydrochloric acid was used, and digestion was performed using a hot plate or microwave until the solution became clear. After cooling, the solution was diluted to a final volume with ultrapure water (e.g., 50 mL), and filtered to remove undissolved particles. The solution was then serially diluted with 3 wt% nitric acid to the target concentration of 1.0 mg / L. The intensity signals of the characteristic spectral lines of iron were then measured using an inductively coupled plasma optical emission spectrometer (ICP). Based on the measured intensity signals of the characteristic spectral lines of iron and the standard curve of iron, the concentration of iron in the test solution was calculated.

[0361] The formula for calculating the mass content of iron in the sample to be tested using a current collector is as follows:

[0362] X (iron) = (C × V × dilution factor) / (m × 1000) × 100%; where:

[0363] X (iron): The mass content of iron in the current collector;

[0364] C: The concentration of iron in the test solution as measured by ICP (mg / L);

[0365] V: Fixed volume (L, e.g., 50mL = 0.05L);

[0366] Dilution factor: If dilution was performed during the digestion process, it needs to be multiplied by this factor (1 if undiluted).

[0367] m: Sample mass (g).

[0368] As an example, if 50 samples are taken, and each sample is tested once, a total of 50 test values ​​for the iron content in the current collector are obtained. The arithmetic mean of these 50 test values ​​is then calculated to obtain the iron content in the current collector. The formula for the arithmetic mean is the sum of all test values ​​divided by the number of test values ​​(e.g., the sum of the iron content test values ​​for 50 samples divided by 50).

[0369] The formula for calculating the variance of iron content in the sample tested by the current collector is as follows:

[0370] ;

[0371] Where: Xi is the measured value of the mass content of iron in each test sample. Σ represents the arithmetic mean of the mass content of iron in multiple test samples, where Σ denotes summation and n is the number of test samples (e.g., 50).

[0372] To ensure the accuracy of the test results, the above test steps can be followed multiple times to obtain samples and test the variance of the iron content. The arithmetic mean of the results of each test is the final result.

[0373] (2) Nickel-iron element distribution test of current collector cross section

[0374] A 1cm x 1cm foil sample was selected, placed on the test stage, and the sample surface was precisely polished using argon ion polishing technology to obtain a flat foil cross-section. Then, the elemental distribution spectrum of the cross-section could be obtained by X-ray energy dispersive spectroscopy analysis.

[0375] The nickel-iron element distribution diagrams of the current collector cross section obtained in Example 1 are shown below. Figure 6 As shown.

[0376] (3) Intensity test of element distribution line scanning along the thickness direction of the current collector.

[0377] Test Method: Linear scanning was performed on the sample cross-section. The specific steps are as follows: 1. A thin cross-section with a thickness ≤100 nm was prepared using methods such as ion thinning, FIB (Focused Ion Beam), or embedded slicing to ensure electron beam penetration. 2. Linear scanning was performed in STEM (Scanning Transmission) mode to obtain elemental distribution data with higher spatial resolution. 3. The start and end points and scanning direction on the cross-section were defined using software, and the electron beam collected characteristic X-ray signals point by point along this path. 4. The energy spectrum signal at each point was recorded, generating elemental content variation curves (such as atomic percentage or intensity). Figure 7 This is a schematic diagram of the current collector prepared in Embodiment 1 of this application being scanned along the thickness direction. Figure 8 This is a line scan intensity map of elemental distribution obtained by linearly scanning the current collector prepared in Embodiment 1 of this application along the thickness direction. Figure 8 As can be seen, the iron and nickel elements are evenly distributed at the yellow line position, with good consistency. The line scan intensity of Fe element is 1500~3000, and the line scan intensity of Ni element is 4000~6000.

[0378] Figure 9 This is a schematic diagram of the current collector prepared in Comparative Example 1 of this application being linearly scanned along the thickness direction. Figure 10 This is a line scan intensity map of elemental distribution obtained by linearly scanning the current collector prepared in Comparative Example 1 of this application along the thickness direction. From Figure 10 It can be seen that the uniformity of iron and nickel elements at the yellow line position is poor, which is inferior to Example 1.

[0379] (4) Corrosion test

[0380] At 8% humidity, the current collector substrates prepared in each embodiment and comparative example were directly bonded to the sulfide electrolyte, allowed to absorb moisture for 7 days, and then subjected to isostatic pressing to simulate the electrolyte corrosion of the current collector substrate.

[0381] Example 1: SEM images of corrosion after 1 day, 2 days, and 7 days of moisture absorption are shown below. Figure 11 As shown in (a), (b), and (c), it can be seen that the current collector prepared in Example 1 did not show obvious corrosion within 7 days.

[0382] (5) Test the cycle performance of the battery.

[0383] The test method is as follows: The battery is charged at room temperature at a rate of 0.33C until the voltage equals 4.2V, then charged at a constant voltage to 0.05C, left to stand for 5 minutes, and then discharged at a rate of 0.33C until the voltage equals 2.8V. The reversible capacity is measured as C0. This charging and discharging process is repeated until the discharge capacity C of a certain cycle is reached. n Record the total number of cycles when C0 reaches 80%. This total number of cycles indicates the battery's cycle life; a higher total number of cycles indicates a better cycle life. Where C... n This is the reversible capacity at the nth cycle, and the corresponding cycle number n is recorded as the cycle number. The results are shown in Table 1.

[0384] (6) Bending resistance of the negative electrode current collector

[0385] At 25°C, the current collector sample is folded 180° and then rolled back and forth at the fold with a 1.5Kg roller. After unfolding, observe whether cracking and light transmission occur at the fold. Record the number of times the current collector cracks and transmits light. Test at least ten samples and take the average value as the bending resistance of the current collector.

[0386] Table 1

[0387]

[0388] The current collectors prepared in Examples 1 to 8 all have a transverse tensile strength MD in the range of 1450MPa to 2200MPa and a longitudinal tensile strength TD in the range of 1150MPa to 2100MPa.

[0389] As shown in Table 1, the current collector in Comparative Example 1 did not contain the first additive during preparation. Comparative Example 2 used sodium dodecylbenzenesulfonate as the first additive. Due to its long carbon chain, sodium dodecylbenzenesulfonate's adhesion to the cathode roller was limited, resulting in a poor dispersion effect. The current collectors prepared in Comparative Examples 1 and 2 exhibited a large variance in iron distribution, indicating poor uniformity and the presence of nickel or iron particles in some areas, leading to corrosion and poor cycle performance of the resulting batteries. In contrast, the current collectors prepared in the various examples showed a smaller variance in iron distribution, indicating improved uniformity and reduced corrosion, thus improving the cycle performance of the resulting batteries. Furthermore, the nickel-iron content in the current collectors varied slightly depending on the concentration and type of the complexing agent and the first additive in the electroplating solution.

[0390] Table 2

[0391]

[0392] In Table 2, the relative volume percentage of the γ solid solution phase refers to the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the sum of the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, and the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase.

[0393] The relative volume percentage of the α solid solution phase refers to the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase, and the sum of the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, and the sum of the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase.

[0394] Understandably, the relative volume percentage of the γ solid solution phase + the relative volume percentage of the α solid solution phase = 1.

[0395] γ / α represents the ratio of the relative volume percentage of the γ solid solution phase to the relative volume percentage of the α solid solution phase.

[0396] The percentage of the (111) crystal plane of the γ solid solution phase represents the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, and the percentage of the diffraction peak area of ​​the (111) crystal plane of the γ solid solution phase.

[0397] The percentage of the (200) crystal plane of the γ solid solution phase represents the percentage of the diffraction peak area of ​​the (200) crystal plane of the γ solid solution phase, based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase.

[0398] As shown in Table 2, in Examples 4 and 9-11, the relative volume percentage of the γ solid solution phase was controlled at 60%-80%, resulting in a current collector that exhibits both good corrosion resistance and bending resistance. Furthermore, in the above-mentioned current collector preparation methods, the use of a complexing agent, a first additive, a second additive, and a specific third additive can effectively control the relative volume percentage of the γ solid solution phase to 65%-75%, enabling the current collector to achieve both good corrosion resistance and superior bending resistance, thereby improving the battery's cycle performance.

[0399] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0400] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the scope of the claims.

Claims

1. A current collector, characterized in that, The device includes a nickel-based alloy layer, which comprises nickel and a first metal element other than nickel. The first metal element includes one or more of Fe, Zn, Ti, V, Cr, Mn, or Co. The mass content of the first metal element in the current collector is 10% to 50%, and the variance of the mass content of the first metal element in the current collector is ≤1.

5.

2. The current collector according to claim 1, characterized in that, The variance of the mass content of the first metal element in the current collector is 0.08~0.

8.

3. The current collector according to claim 1 or 2, characterized in that, The variance of the mass content of nickel in the current collector is ≤1.5, and can be selected as 0.1~0.

5.

4. The current collector according to any one of claims 1 to 3, characterized in that, It meets one or more of the following characteristics: (1) The mass content of the first metal element in the current collector is 20%~40%; (2) The mass content of nickel in the current collector is 45%~85%, and can be selected as 55%~80%; (3) The mass content of the nickel element and the first metal element in the current collector is ≥95%.

5. The current collector according to any one of claims 1 to 4, characterized in that, The first metallic element includes Fe, and the nickel-based alloy layer includes a γ solid solution phase and an α solid solution phase. In the X-ray diffraction spectrum of the nickel-based alloy layer, the γ solid solution phase includes (111) crystal plane and (200) crystal plane, and the α solid solution phase includes (110) crystal plane and (200) crystal plane; Based on the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase and the diffraction peak areas of the (110) and (200) crystal planes of the α solid solution phase, the percentage of the sum of the diffraction peak areas of the (111) and (200) crystal planes of the γ solid solution phase is 60%~80%.

6. The current collector according to any one of claims 1 to 5, characterized in that, The nickel-based alloy layer has a crystalline structure; optionally, the average grain size of the nickel-based alloy layer is 15nm~100nm, or optionally 15nm~80nm.

7. The current collector according to any one of claims 1 to 6, characterized in that, It meets one or more of the following characteristics: (1) In the X-ray diffraction spectrum of the nickel-based alloy layer, the texture coefficient of the (111) crystal plane accounts for 30%~80%; (2) In the X-ray diffraction spectrum of the nickel-based alloy layer, the ratio of the diffraction peak intensity of the (110) crystal plane to the diffraction peak intensity of the (111) crystal plane is less than 0.5, and can be selected as 0~0.3; (3) The thickness of the nickel-based alloy layer is 3μm~8μm, and can be selected as 4μm~6μm.

8. The current collector according to any one of claims 1 to 7, characterized in that, It meets one or more of the following characteristics: (1) The transverse tensile strength MD of the current collector is 1200MPa~2200MPa, and can be selected as 1400MPa~2200MPa; (2) The longitudinal tensile strength TD of the current collector is 1100MPa~2100MPa, and can be selected as 1150MPa~2100MPa; (3) The transverse tensile strength MD of the current collector is greater than the longitudinal tensile strength TD of the current collector; (4) The lateral elongation of the current collector is 3%~8%, and can be selected as 3%~6%; (5) The longitudinal elongation of the current collector is 2%~7%, and can be selected as 3%~5%; (6) The transverse fracture elongation of the current collector is greater than the longitudinal fracture elongation of the current collector.

9. A method for preparing a current collector, characterized in that, Includes the following steps: An insoluble anode, an electroplating solution, and a cathode are provided for electroplating to form a nickel-based alloy layer on the surface of the cathode; after the electroplating process, the nickel-based alloy layer is separated from the surface of the cathode. The electroplating solution includes a nickel source, a first metal source, a complexing agent, and a first additive. The first additive contains a benzene ring and a sulfonic acid group connected to the benzene ring. The benzene ring is optionally connected with a carbon chain substituent with a number of carbon atoms less than or equal to 3. The first metal element in the first metal source is a metal element other than nickel. The first metal element includes one or more of Fe, Zn, Ti, V, Cr, Mn, or Co. The mass content of the first metal element in the current collector is 10% to 50%.

10. The method for preparing a current collector according to claim 9, characterized in that, It meets one or more of the following characteristics: (1) The complexing agent includes one or more of sodium citrate, tartaric acid, lactic acid or sodium gluconate; (2) The first additive includes one or more of p-toluenesulfonic acid, methyl p-toluenesulfonate or ethyl p-toluenesulfonate; (3) The concentration of the first additive in the electroplating solution is 0.1 g / L to 0.9 g / L; (4) The concentration of the complexing agent in the electroplating solution is 20 g / L to 60 g / L; (5) The pH value of the electroplating solution is 2~3; (6) The flow rate of the electroplating solution is 50 L / min to 80 L / min; (7) The rotational speed of the cathode is 0.2 m / min to 0.8 m / min; (8) In the electroplating process, the current density is 2A / dm 2 ~10A / dm 2 Optional 5A / dm 2 ~10A / dm 2 .

11. The method for preparing a current collector according to any one of claims 9 to 10, characterized in that, It meets one or more of the following characteristics: (1) The concentration of the nickel source in the electroplating solution is 150 g / L to 250 g / L; (2) The nickel source includes one or more of nickel sulfate, nickel chloride, or nickel carbonate; (3) The first metal source includes an Fe source, and the concentration of the Fe source in the electroplating solution is 20 g / L to 80 g / L; (4) The electroplating solution further includes a second additive; optionally, the second additive includes one or more of saccharin, sodium saccharin, polyethylene glycol, polyethyleneimine, 1,4-butynediol, sodium naphthalene disulfonate or formaldehyde; optionally, the concentration of the second additive in the electroplating solution is 3 g / L to 5 g / L. (5) The electroplating solution further includes a third additive, which includes one or more of thiourea and its derivatives, and thiocyanate; optionally, the concentration of the third additive in the electroplating solution is 0.1 g / L to 0.5 g / L. (6) The electroplating solution further includes a wetting agent; optionally, the wetting agent includes one or more of sodium dodecyl sulfate or sodium dodecyl sulfonate; optionally, the concentration of the wetting agent in the electroplating solution is 0.1 g / L to 0.5 g / L; (7) The electroplating solution further includes a stabilizer; optionally, the stabilizer includes one or more of boric acid, citric acid or fluoroborate; optionally, the concentration of the stabilizer in the electroplating solution is 40 g / L to 80 g / L.

12. A secondary battery, characterized in that, The device includes an electrode assembly comprising a positive electrode and a negative electrode, wherein the negative electrode comprises a negative current collector, and the negative current collector comprises a current collector prepared by any one of claims 1 to 8 or any one of claims 9 to 11.

13. The secondary battery according to claim 12, characterized in that, The electrode assembly further includes a solid electrolyte layer, which is located between the positive electrode and the negative electrode. Optionally, the solid electrolyte layer includes one or more of sulfide electrolytes, halide electrolytes, or oxide electrolytes.

14. The secondary battery according to claim 12 or 13, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer located on at least one surface of the current collector; the negative electrode film layer includes a negative electrode active material, which includes at least one of silicon-based materials, lithium metal, and lithium metal alloys.

15. The secondary battery according to claim 12 or 13, characterized in that, During charging, lithium metal or lithium metal alloy is deposited on the negative electrode current collector, and during discharging, the lithium metal or lithium metal alloy is consumed.

16. An electrical appliance, characterized in that, It includes one or more of the current collectors according to any one of claims 1 to 8, the current collectors prepared by the method of preparing the current collectors according to any one of claims 9 to 11, or the secondary batteries according to any one of claims 12 to 15.

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