Negative current collector and preparation method thereof, battery monomer, battery and electric device

Abstract

The invention discloses a negative electrode current collector and a preparation method thereof, a battery monomer, a battery and a power utilization device, and the preparation method of the negative electrode current collector comprises the following steps: providing a metal matrix which is of a two-dimensional metal structure or a three-dimensional porous metal structure; and irradiating at least part of the surface of the metal matrix by adopting laser to melt and recrystallize metal grains in a laser ablation heat affected zone of the metal matrix to form metal grains with smaller sizes, thereby obtaining the negative electrode current collector. The reliability and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] The present application relates to a negative electrode current collector and a preparation method thereof, a battery cell, a battery and an electrical device. Background Art

[0002] Compared to ion-type battery cells, metal-based battery cells can have higher energy density. However, unlike the negative electrodes of ion-based battery cells, metal-based battery cells suffer from a more severe dendrite problem, which has hampered their commercialization. Dendrite growth can cause internal short circuits in the battery cell, affecting its reliability and cycle performance. Summary of the Invention

[0003] The present application provides a negative electrode current collector and a preparation method thereof, a battery cell, a battery and an electrical device, which can improve the reliability and cycle performance of the battery.

[0004] In a first aspect, the present application provides a method for preparing a negative electrode current collector, comprising the following steps: providing a metal substrate, wherein the metal substrate is a two-dimensional metal structure or a three-dimensional porous metal structure; irradiating at least a portion of the surface of the metal substrate with a laser to melt and recrystallize the metal grains in the laser ablation heat-affected zone of the metal substrate to form smaller metal grains, thereby obtaining a negative electrode current collector.

[0005] By adjusting the laser irradiation processing parameters, the present application can melt and recrystallize the metal grains in the laser ablation heat-affected zone of the metal matrix to form smaller metal grains, and the reliability and cycle performance of the battery cell using the negative electrode current collector can be improved.

[0006] In some embodiments, the laser generating the laser is a pulsed laser, the laser wavelength of the pulsed laser is 694 nm to 1070 nm, the average power of the laser is 30 W to 90 W, the pulse repetition frequency of the laser is 30 KHz to 90 KHz, and the pulse width of the laser is 20 ns to 120 ns.

[0007] The present application adjusts the laser irradiation processing parameters to melt and recrystallize the metal grains in the laser ablation heat-affected zone and form smaller metal grains. These smaller metal grains form more grain boundary defects and rapidly increase the surface energy of the metal matrix, thereby improving the wettability of metals such as lithium and sodium on the surface of the metal matrix and the wettability of the electrolyte, thereby reducing the nucleation overpotential of the negative electrode current collector, reducing dendrite formation, and improving the reliability and cycle performance of the battery cell. At the same time, laser irradiation can also activate the surface of the negative electrode current collector, thereby increasing the electrochemical active area of the negative electrode current collector, thereby further improving the cycle performance of the battery cell.

[0008] In some embodiments, the pulse energy of the pulse laser is 1 mJ.

[0009] In some embodiments, the pulsed laser includes one or more of a ruby laser, a fiber laser, a glass laser, and a YAG laser.

[0010] In some embodiments, the pulse laser has a laser wavelength of 1050 nm to 1070 nm.

[0011] In some embodiments, the laser is operated at a speed of 1000 mm / s to 3500 mm / s.

[0012] In some embodiments, the initial size of the metal grains of the metal matrix is greater than 100 nm; and / or the size of the metal grains formed by recrystallization of the laser ablation heat affected zone of the metal matrix is 10 nm-100 nm.

[0013] In some embodiments, the metal substrate is a two-dimensional metal structure, and a thickness H1 of the two-dimensional metal structure is 5 μm to 12 μm.

[0014] In some embodiments, the metal substrate is a two-dimensional metal structure, and the two-dimensional metal structure is a two-dimensional copper foil, a two-dimensional copper alloy foil, a two-dimensional nickel foil, or a two-dimensional nickel alloy foil.

[0015] In some embodiments, the metal substrate is a two-dimensional metal structure, and the average power of the laser is 30W to 80W, optionally 40W to 80W. When the average power of the laser is within this range, a larger laser ablation heat-affected zone (HAZ) can be formed on the surface of the two-dimensional metal structure while avoiding melting of the entire two-dimensional metal structure. Furthermore, the metal grains in the HAZ can be melted and recrystallized to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0016] In some embodiments, the metal substrate is a two-dimensional metal structure, and the laser pulse repetition frequency is 30 kHz to 80 kHz, optionally 40 kHz to 80 kHz. A laser pulse repetition frequency within this range can prevent the entire two-dimensional metal structure from melting while providing a larger laser ablation heat-affected zone on the surface of the two-dimensional metal structure. Furthermore, the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0017] In some embodiments, the metal substrate is a two-dimensional metal structure, and the laser pulse width is 40ns to 120ns, optionally 60ns to 120ns. A laser pulse width within this range can provide a larger laser ablation heat-affected zone (HAZ) on the surface of the two-dimensional metal structure and can also cause the metal grains in the HAZ to melt and recrystallize to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0018] In some embodiments, the metal substrate is a two-dimensional metal structure, and the laser defocus is between -120 μm and 20 μm, optionally between -(H1×70%) μm and 0. When the laser defocus is within this range, the surface of the two-dimensional metal structure can have a larger laser ablation heat-affected zone, and the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0019] In some embodiments, the metal substrate is a three-dimensional porous metal structure, and a thickness H2 of the three-dimensional porous metal structure is 80 μm to 1000 μm.

[0020] In some embodiments, the metal substrate is a three-dimensional porous metal structure, and the three-dimensional porous metal structure is mesh copper, mesh nickel, foam copper, or foam nickel.

[0021] In some embodiments, the metal substrate is a three-dimensional porous metal structure, and the average power of the laser is 40W to 90W, optionally 60W to 90W. When the average power of the laser is within this range, the surface of the three-dimensional porous metal structure can have a larger laser ablation heat-affected zone (HAZ) while preventing the ribs of the three-dimensional porous metal structure from being burned. Furthermore, the metal grains in the HAZ can be melted and recrystallized to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0022] In some embodiments, the metal substrate is a three-dimensional porous metal structure, and the laser pulse repetition frequency is 40 kHz to 90 kHz, optionally 60 kHz to 90 kHz. A laser pulse repetition frequency within this range can prevent the ribs of the three-dimensional porous metal structure from being burned, while providing a larger laser ablation heat-affected zone on the surface of the three-dimensional porous metal structure. Furthermore, the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0023] In some embodiments, the metal substrate is a three-dimensional porous metal structure, and the laser pulse width is 40ns to 120ns, optionally 60ns to 120ns. A laser pulse width within this range can provide a larger laser ablation heat-affected zone (HAZ) on the surface of the three-dimensional porous metal structure and can also cause the metal grains in the HAZ to melt and recrystallize to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0024] In some embodiments, the metal substrate is a three-dimensional porous metal structure, and the laser defocus is between -(H2×100%)μm and 0, and may optionally be between -(H2×70%)μm and -(H2×50%)μm. Within this range, the laser defocus can provide a larger laser ablation heat-affected zone (HAZ) on the surface of the three-dimensional porous metal structure and can also cause the metal grains in the HAZ to melt and recrystallize to form smaller metal grains, thereby further improving the reliability and cycle performance of the battery cell.

[0025] In some embodiments, the microstructure morphology of the surface of the negative electrode current collector includes one or more of surface ablation without pores, pits, bowl holes, through holes, and grooves.

[0026] In some embodiments, before irradiating the surface of the metal substrate with laser, the method further includes the step of cleaning the oil stains, impurities and / or oxide layer on the surface of the metal substrate.

[0027] In a second aspect, the present application provides a negative electrode current collector, which includes a laser ablation heat affected zone and a non-laser ablation heat affected zone, wherein the metal grain size of the laser ablation heat affected zone is smaller than the metal grain size of the non-laser ablation heat affected zone.

[0028] In some embodiments, the metal grain size of the laser ablation heat-affected zone is 10 nm-100 nm; and / or the metal grain size of the non-laser ablation heat-affected zone is greater than 100 nm.

[0029] In some embodiments, the microstructure morphology of the surface of the negative electrode current collector includes one or more of surface ablation without pores, pits, bowl holes, through holes, and grooves.

[0030] In some embodiments, the negative electrode current collector is prepared by the preparation method of the first aspect of the present application.

[0031] In a third aspect, the present application provides a battery cell, which includes a negative electrode current collector prepared by the preparation method of the first aspect of the present application or the negative electrode current collector of the second aspect of the present application, and the battery cell includes at least one of a negative electrode-free lithium metal battery cell and a negative electrode-free sodium metal battery cell.

[0032] In a fourth aspect, the present application provides a battery comprising the battery cell according to the third aspect of the present application.

[0033] In a fifth aspect, the present application provides an electrical device comprising the battery according to the fourth aspect of the present application, wherein the battery is used to provide electrical energy.

[0034] The electric device of the present application includes the battery provided by the present application, and thus has at least the same advantages as the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] To more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on the drawings without inventive effort.

[0036] Figure 1 A schematic diagram showing a battery cell provided by some embodiments of the present application.

[0037] Figure 2 A schematic diagram of an exploded view of a battery cell provided by some embodiments of the present application is shown.

[0038] Figure 3 A schematic diagram of a battery module provided in some embodiments of the present application is shown.

[0039] Figure 4 A schematic diagram of a battery pack provided in some embodiments of the present application is shown.

[0040] Figure 5 yes Figure 4 Schematic diagram of the battery pack shown.

[0041] Figure 6 Shown are scanning electron microscope images of the negative electrode current collector provided by some embodiments of the present application.

[0042] Figure 7 Scanning electron microscope images of negative electrode current collectors provided in some other embodiments of the present application are shown.

[0043] Figure 8 Scanning electron microscope images of negative electrode current collectors provided in some other embodiments of the present application are shown.

[0044] Figure 9 Scanning electron microscope images of negative electrode current collectors provided in some other embodiments of the present application are shown.

[0045] Figure 10 Scanning electron microscope images of negative electrode current collectors provided in some other embodiments of the present application are shown.

[0046] Figure 11 A schematic diagram of an electrical device provided in some embodiments of the present application is shown.

[0047] Figure 12 X-ray diffraction images of the negative electrode collectors of Comparative Example 1-1 and Example 1-9 are shown, Curve I represents the X-ray diffraction image of the negative electrode collector of Comparative Example 1-1, and Curve II represents the X-ray diffraction image of the negative electrode collector of Example 1-9.

[0048] Figure 13 The electron backscattered diffraction (EBSD) images of the negative electrode collectors of Comparative Example 1-1 and Example 1-9 are shown. Figure (a) shows the electron backscattered diffraction (EBSD) image of the negative electrode collector of Comparative Example 1-1, and Figure (b) shows the electron backscattered diffraction (EBSD) image of the negative electrode collector of Example 1-9.

[0049] In the accompanying drawings, the drawings are not necessarily drawn to scale.

[0050] The reference numerals are as follows: 1 battery pack, 2 upper case, 3 lower case, 4 battery module, 5 battery cell, 51 shell, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0051] Below, with appropriate reference to the accompanying drawings, the embodiments of the negative electrode current collector and its preparation method, battery cell, battery and electrical device of the present application are described in detail. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0052] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present application.

[0054] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of this application.

[0055] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0056] In this application, the terms "plurality" and "multiple" refer to two or more.

[0057] In the description of the embodiments of the present application, unless otherwise specified, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, a first feature being "above," "above," and "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is at a higher level than the second feature. A first feature being "below," "below," and "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is at a lower level than the second feature.

[0058] Unless otherwise specified, the terms used in this application have the common meanings that are commonly understood by those skilled in the art.

[0059] Unless otherwise stated, the numerical values of the various parameters mentioned in this application can be measured using various test methods commonly used in the art, for example, they can be measured according to the test methods given in the examples of this application. Unless otherwise stated, the test temperature of each parameter is 25°C.

[0060] The battery mentioned in the embodiments of the present application may be a single physical module including one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in the present application may include a battery cell, a battery module, or a battery pack.

[0061] A battery cell is the smallest unit that makes up a battery and can independently realize the function of charging and discharging. A battery cell can be cylindrical, rectangular or other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 As an example, a battery cell 5 having a rectangular parallelepiped structure is shown.

[0062] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed series via a busbar. In some embodiments, the battery may be a battery module; when there are multiple battery cells, the multiple battery cells are arranged and fixed to form a battery module. In some embodiments, the battery may be a battery pack, which includes a housing and battery cells, with the battery cells or battery modules housed in the housing. In some embodiments, the housing may serve as part of the vehicle's chassis structure. For example, a portion of the housing may form at least a portion of the vehicle's floor, or a portion of the housing may form at least a portion of the vehicle's crossbeam or longitudinal beam.

[0063] In some embodiments, the battery may be an energy storage device, including an energy storage container, an energy storage cabinet, and the like.

[0064] The battery cell includes an electrode assembly, which may be a wound structure or a laminated structure, and the present invention is not limited thereto.

[0065] The battery cell may also include an outer packaging that can be used to encapsulate the electrode assembly. The outer packaging can be a hard shell, such as a hard plastic shell, aluminum shell, steel shell, etc. The outer packaging can also be a soft shell, such as a bag-type soft shell. The soft shell material can be a plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0066] In some embodiments, as Figure 2 As shown, the outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a base plate and side plates connected to the base plate, which together form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 is used to cover the opening, thereby sealing the receiving cavity. The electrode assembly 52 is enclosed in the receiving cavity. The number of electrode assemblies 52 contained in a battery cell 5 can be one or more, and can be adjusted according to needs.

[0067] In some embodiments, battery cells may be assembled into a battery module. A battery module may contain multiple battery cells, and the specific number may be adjusted according to the application and capacity of the battery module. Figure 3 FIG. 4 is a schematic diagram of a battery module 4 as an example. Figure 3 As shown, in the battery module 4, the plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0068] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0069] In some embodiments, the battery modules described above may also be assembled into a battery pack, and the number of battery modules contained in the battery pack may be adjusted according to the application and capacity of the battery pack.

[0070] Figure 4 and Figure 5 FIG. 1 is a schematic diagram of a battery pack 1 as an example. Figure 4 and Figure 5 As shown, a battery pack 1 may include a housing and multiple battery modules 4 disposed therein. The housing comprises an upper housing 2 and a lower housing 3. The upper housing 2 covers the lower housing 3 and forms an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 may be arranged in any manner within the housing.

[0071] The battery cells provided in the embodiments of the present application may include negative electrode-free lithium metal battery cells, negative electrode-free sodium metal battery cells, and the like.

[0072] A negative electrode-free battery cell generally refers to a battery cell constructed without the active negative electrode layer being applied during the manufacturing process. For example, a negative electrode active material layer is not applied to the negative electrode through coating or deposition, or a carbonaceous active material layer is used to form the negative electrode active material layer. During initial charging, ions on the negative electrode side gain electrons and deposit on the surface of the negative electrode current collector to form metal. During discharge, the metal can be converted back to ions and returned to the positive electrode, enabling cyclic charge and discharge. Compared to other battery cells, negative electrode-free battery cells can achieve higher energy density due to the lack of a negative electrode active material layer. In some embodiments, to improve battery cell performance, the negative electrode side of the negative electrode-free battery cell may also be provided with some conventional negative electrode active materials, such as carbon materials. Although these materials have a certain capacity, their content is relatively low and they are not used as the primary negative electrode active material in the battery cell. Therefore, the battery cell constructed in this manner can still be considered a negative electrode-free battery cell. The CB (Cell Balance) value of a battery cell without a negative electrode is typically very small. For example, in some embodiments, the CB value of a battery cell without a negative electrode can be less than or equal to 0.1. The CB value is the unit area capacity of the negative electrode in the battery cell divided by the unit area capacity of the positive electrode. Because a battery cell without a negative electrode contains no or only a small amount of negative electrode active material, the unit area capacity of the negative electrode is relatively small, and thus the CB value is very small, for example, typically less than or equal to 0.1.

[0073] Copper current collector is currently the commonly used current collector for negative electrodes. Metals such as lithium and sodium have poor wettability on conventional copper current collectors, which leads to a large nucleation overpotential. It is easy for them to preferentially nucleate at certain surface defect positions (such as protrusions, impurity positions, etc.) of conventional copper current collectors. The preferential nucleation positions will form advantageous growth points, which in turn will easily lead to dendrite formation and internal short circuit of the battery, affecting the reliability and cycle performance of the battery.

[0074] An embodiment of the present application provides a method for preparing a negative electrode current collector. The negative electrode current collector prepared by the preparation method is used in a negative electrode-free lithium metal battery or a negative electrode-free sodium metal battery, which can make the battery have good cycle performance and high reliability.

[0075] The preparation method of the negative electrode current collector provided in the embodiment of the present application includes the following steps: providing a metal substrate, which is a two-dimensional metal structure or a three-dimensional porous metal structure; using a laser to irradiate at least a portion of the surface of the metal substrate to melt and recrystallize the metal grains in the laser ablation heat-affected zone of the metal substrate to form smaller metal grains, thereby obtaining a negative electrode current collector.

[0076] Lasers have high energy. Irradiating at least part of a metal substrate's surface vaporizes and removes some of the metal atoms at the irradiated location. The remaining metal and the surrounding metal are heated, creating a heat-affected zone (HAZ). Laser ablation of the HAZ is generally considered to affect the properties of the metal substrate.

[0077] By adjusting the laser irradiation processing parameters, the present application can melt and recrystallize the metal grains in the laser ablation heat-affected zone of the metal matrix to form smaller metal grains, and the reliability and cycle performance of the battery cell using the negative electrode current collector can be improved.

[0078] By irradiating at least part of the surface of the metal substrate with a suitable laser, the metal in the laser ablation heat-affected zone can be rapidly heated to above the melting temperature, and then the metal quickly melts and recrystallizes. This melting-recrystallization process can rapidly reduce the size of the metal grains in the laser ablation heat-affected zone. Smaller metal grains form more grain boundary defects and rapidly increase the surface energy of the metal substrate, thereby improving the wettability of metals such as lithium and sodium on the surface of the metal substrate and the wettability of the electrolyte, thereby reducing the nucleation overpotential of the negative electrode current collector, reducing dendrite formation, and further improving the reliability and cycle performance of the battery cell. That is, these smaller metal grains can play the role of affinity treatment. At the same time, these smaller metal grains are formed in situ on the surface of the metal substrate, and have better bonding with the metal substrate, which helps to further improve the cycle performance of the battery cell.

[0079] In addition, laser irradiation can also activate the surface of the negative electrode current collector, thereby increasing the electrochemical active area of the negative electrode current collector, thereby further improving the cycle performance of the battery cell.

[0080] In some embodiments, the laser generating the laser is a pulsed laser, the laser wavelength of the pulsed laser can be 694nm to 1070nm, the average power of the laser can be 30W to 90W, the pulse repetition frequency of the laser can be 30KHz to 90KHz, and the pulse width of the laser can be 20ns to 120ns.

[0081] The average power of the laser is 30W to 90W, which can prevent the entire metal matrix from melting or some of the edges from being burned off, and make the surface of the metal matrix have a larger laser ablation heat-affected zone. It can also make the metal grains in the laser ablation heat-affected zone melt and recrystallize to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0082] The laser pulse repetition frequency is 30KHz to 90KHz, which can prevent the entire metal matrix from melting or some of the ribs from being burned off, and make the metal matrix surface have a larger laser ablation heat-affected zone. It can also make the metal grains in the laser ablation heat-affected zone melt and recrystallize to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0083] The longer the laser pulse width, the wider the laser ablation heat-affected zone (HAZ) on the metal substrate. A laser pulse width of 20ns to 120ns can create a larger HAZ on the metal substrate surface and cause the metal grains in the HAZ to melt and recrystallize into smaller metal grains, thereby improving the reliability and cycle performance of the battery cells.

[0084] The present application adjusts the laser irradiation processing parameters to melt and recrystallize the metal grains in the laser ablation heat-affected zone and form smaller metal grains. These smaller metal grains form more grain boundary defects and rapidly increase the surface energy of the metal matrix, thereby improving the wettability of metals such as lithium and sodium on the surface of the metal matrix and the wettability of the electrolyte, thereby reducing the nucleation overpotential of the negative electrode current collector, reducing dendrite formation, and improving the reliability and cycle performance of the battery cell. At the same time, laser irradiation can also activate the surface of the negative electrode current collector, thereby increasing the electrochemical active area of the negative electrode current collector, thereby further improving the cycle performance of the battery cell.

[0085] It should be noted that the preparation method, which uses a laser with parameters not within the range provided in the embodiments of the present application to irradiate at least part of the surface of a metal substrate, and can melt and recrystallize the metal grains in the laser ablation heat-affected zone of the metal substrate to form smaller metal grains, that is, similar concepts in which the laser irradiation parameters are not within the range provided in the embodiments of the present application, still fall within the scope of protection of the present application.

[0086] Optionally, the laser wavelength of the pulse laser may be 1050 nm to 1070 nm.

[0087] In some embodiments, the pulse energy of the pulsed laser may be 1 mJ.

[0088] In some embodiments, the pulsed laser may include one or more of a ruby laser, a fiber laser, a glass laser, and a YAG laser. Alternatively, the glass laser may be a neodymium glass laser. Alternatively, the YAG laser may be a neodymium:YAG laser.

[0089] In some embodiments, the laser can be run at a speed of 1000 mm / s to 3500 mm / s. Adjusting the laser speed can adjust the microstructural morphology of the negative electrode current collector surface. Slow laser speeds allow for close irradiation, facilitating the formation of continuous lines. Fast laser speeds allow for distant irradiation, facilitating the formation of pores. The appropriate speed can be selected based on the microstructural morphology.

[0090] In some embodiments, before laser irradiation treatment, the initial size of the metal grains of the metal matrix can be greater than 100 nm; after laser irradiation treatment, the size of the metal grains formed by recrystallization of the laser ablation heat affected zone of the metal matrix can be 10 nm-100 nm, optionally 10 nm-50 nm.

[0091] The size of metal grains can be determined using the Electron Backscattered Diffraction (EBSD) scanning method. During testing, the sample is fixed to the sample stage, and parameters such as the angle between the EBSD probe plane and the sample surface to be tested, the acceleration voltage, the magnification, and the step size are adjusted. The number of grains in the observation field is also adjusted, for example, to be greater than or equal to 100. The diffraction pattern in the analysis area is then scanned to determine the size of all grains within the analysis area.

[0092] The metal matrix is a two-dimensional metal structure or a three-dimensional porous metal structure. The metal matrix can be purchased commercially or prepared by a preparation process known in the art.

[0093] In some embodiments, the thickness H1 of the two-dimensional metal structure may be 5 μm to 12 μm, and optionally 5 μm to 9 μm.

[0094] Optionally, the two-dimensional metal structure may be a two-dimensional copper foil, a two-dimensional copper alloy foil, a two-dimensional nickel foil or a two-dimensional nickel alloy foil.

[0095] Optionally, the metal substrate is a two-dimensional metal structure, and the average power of the laser can be 30W to 80W, for example, 30W, 35W, 40W, 45W, 50W, 55W, 60W, 65W, 70W, 75W, 80W, or a range consisting of any of the above values. More preferably, the average power of the laser can be 40W to 80W.

[0096] When the average power of the laser is within the above range, the surface of the two-dimensional metal structure can have a larger laser ablation heat-affected zone while avoiding the overall melting of the two-dimensional metal structure. The metal grains in the laser ablation heat-affected zone can also be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0097] Optionally, the metal substrate is a two-dimensional metal structure, and the laser pulse repetition frequency can be 30 kHz to 80 kHz, for example, 30 kHz, 35 kHz, 40 kHz, 45 kHz, 50 kHz, 55 kHz, 60 kHz, 65 kHz, 70 kHz, 75 kHz, 80 kHz, or any range thereof. More preferably, the laser pulse repetition frequency can be 40 kHz to 80 kHz.

[0098] When the laser pulse repetition frequency is within the above range, the surface of the two-dimensional metal structure can have a larger laser ablation heat-affected zone while avoiding the overall melting of the two-dimensional metal structure. The metal grains in the laser ablation heat-affected zone can also be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0099] Optionally, the metal substrate is a two-dimensional metal structure, and the laser pulse width can be 40 ns to 120 ns, for example, 40 ns, 45 ns, 50 ns, 55 ns, 60 ns, 65 ns, 70 ns, 75 ns, 80 ns, 90 ns, 100 ns, 110 ns, 120 ns, or a range consisting of any of the above values. More preferably, the laser pulse width can be 60 ns to 120 ns.

[0100] When the laser pulse width is within the above range, the surface of the two-dimensional metal structure can have a larger laser ablation heat-affected zone, and the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0101] Optionally, the metal substrate is a two-dimensional metal structure, and the defocus of the laser can be -120 μm to 20 μm, optionally -(H1×100%) μm to 0, and more optionally -(H1×70%) μm to 0.

[0102] When the laser defocus amount is within the above range, the surface of the two-dimensional metal structure can have a larger laser ablation heat-affected zone, and the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0103] In some embodiments, the thickness H2 of the three-dimensional porous metal structure may be 80 μm to 1000 μm, and optionally 100 μm to 600 μm.

[0104] Optionally, the three-dimensional porous metal structure may be mesh copper, mesh nickel, foam copper or foam nickel.

[0105] Optionally, the metal substrate is a three-dimensional porous metal structure, and the average power of the laser can be 40W to 90W, for example, 40W, 45W, 50W, 55W, 60W, 65W, 70W, 75W, 80W, 85W, 90W, or a range consisting of any of the above values. More preferably, the average power of the laser can be 60W to 90W.

[0106] When the average power of the laser is within the above range, the surface of the three-dimensional porous metal structure can have a larger laser ablation heat-affected zone while avoiding the burning of some ridges of the three-dimensional porous metal structure. The metal grains in the laser ablation heat-affected zone can also be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0107] Optionally, the metal substrate is a three-dimensional porous metal structure, and the pulse repetition frequency of the laser can be 40 kHz to 90 kHz, for example, 40 kHz, 45 kHz, 50 kHz, 55 kHz, 60 kHz, 65 kHz, 70 kHz, 75 kHz, 80 kHz, 85 kHz, 90 kHz, or a range consisting of any of the above values. More preferably, the pulse repetition frequency of the laser can be 60 kHz to 90 kHz.

[0108] When the laser pulse repetition frequency is within the above range, the surface of the three-dimensional porous metal structure can have a larger laser ablation heat-affected zone while avoiding the burning of some ridges of the three-dimensional porous metal structure. The metal grains in the laser ablation heat-affected zone can also be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0109] Optionally, the metal matrix is a three-dimensional porous metal structure, and the laser pulse width can be 40 ns to 120 ns, for example, 40 ns, 45 ns, 50 ns, 55 ns, 60 ns, 65 ns, 70 ns, 75 ns, 80 ns, 90 ns, 100 ns, 110 ns, 120 ns, or a range consisting of any of the above values. More preferably, the laser pulse width can be 60 ns to 120 ns.

[0110] When the laser pulse width is within the above range, the surface of the three-dimensional porous metal structure can have a larger laser ablation heat-affected zone, and the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0111] Optionally, the metal matrix is a three-dimensional porous metal structure, and the defocus amount of the laser can be -(H2×150%)μm to 0, optionally -(H2×100%)μm to 0, and more optionally -(H2×70%)μm to -(H2×50%)μm.

[0112] When the laser defocus amount is within the above range, the surface of the three-dimensional porous metal structure can have a larger laser ablation heat-affected zone, and the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby better improving the reliability and cycle performance of the battery cell.

[0113] In some embodiments, after laser irradiation treatment, the microstructure morphology of the surface of the negative electrode current collector may include one or more of surface ablation without pores, pits, bowl holes, through holes, and grooves.

[0114] Optionally, after the laser irradiation treatment, the microstructure morphology of the surface of the two-dimensional metal structure may include one or more of surface ablation without pores, bowl holes, through holes, and grooves.

[0115] The size of the metal grains at the position where the surface is ablated but no holes are formed and the area nearby becomes smaller, for example, it can be 10nm-100nm, optionally 10nm-50nm.

[0116] The size of the metal grains at the bowl hole position and the vicinity thereof becomes smaller, for example, it may be 10 nm-100 nm, optionally 10 nm-50 nm.

[0117] The size of the metal grains at the edge of the through hole and in the vicinity thereof becomes smaller, for example, it may be 10 nm-100 nm, or optionally 10 nm-50 nm.

[0118] The size of the metal grains at the groove position and the vicinity thereof becomes smaller, for example, it may be 10 nm-100 nm, optionally 10 nm-50 nm.

[0119] Optionally, the bowl hole may be an array of bowl holes.

[0120] Optionally, the diameter of the array bowl holes may be 20 μm-50 μm, the hole spacing may be greater than or equal to 15 μm, and the hole depth may be less than or equal to 2 / 3 of the thickness H1 of the negative electrode current collector. Furthermore, the hole spacing may be less than 100 μm.

[0121] Optionally, the through hole may be an array of through holes.

[0122] Optionally, the diameter of the array through holes may be 20 μm-140 μm, and the hole spacing may be greater than or equal to 15 μm. Furthermore, the hole spacing may be less than 100 μm.

[0123] The hole spacing refers to the shortest distance between the edges of two adjacent holes.

[0124] Optionally, the interval between the grooves may be greater than or equal to 15 μm, and the depth of the grooves may be less than or equal to 2 / 3 of the thickness H1 of the negative electrode current collector.

[0125] like Figure 6 As shown, after laser irradiation treatment, the surface of the two-dimensional metal structure is ablated but no holes are formed.

[0126] Optionally, the area of the region where metal grain melting and recrystallization occurs on the surface of the two-dimensional metal structure after laser irradiation treatment can be 40%-100%, and more optionally 50%-100%, 60%-100%, 70%-100%, 80%-100%.

[0127] like Figure 7 As shown, after laser irradiation treatment, an array of bowl holes is formed on the surface of the two-dimensional metal structure.

[0128] like Figure 8 As shown, after laser irradiation treatment, an array of through holes is formed on the surface of the two-dimensional metal structure.

[0129] like Figure 9 As shown, grooves are formed on the surface of the two-dimensional metal structure after laser irradiation treatment.

[0130] Optionally, after the laser irradiation treatment, the microstructural morphology of the surface of the three-dimensional porous metal structure may include one or more of surface ablation without pores, and pits.

[0131] The size of the metal grains at the position where the surface is ablated but no holes are formed and the area nearby becomes smaller, for example, it can be 10nm-100nm, optionally 10nm-50nm.

[0132] The size of the metal grains at the pit position and the vicinity thereof becomes smaller, for example, it may be 10 nm-100 nm, optionally 10 nm-50 nm.

[0133] like Figure 10 As shown in FIG, after laser irradiation treatment, the surface of the foam metal structure is ablated but no pores are formed.

[0134] In some embodiments, before laser irradiation of the metal substrate surface, a step may be included: cleaning the metal substrate surface of oil, impurities, and / or oxide layers. Optionally, cleaning may include ultrasonic cleaning, chemical cleaning, water washing, weak acid washing, or alcohol washing.

[0135] The present application also provides a negative electrode current collector including a laser ablation heat-affected zone and a non-laser ablation heat-affected zone, wherein the metal grain size of the laser ablation heat-affected zone is smaller than that of the non-laser ablation heat-affected zone.

[0136] The metal grains in the heat-affected zone of laser ablation are smaller. These smaller metal grains form more grain boundary defects and rapidly increase the surface energy of the negative electrode current collector. This improves the wettability of metals such as lithium and sodium on the surface of the negative electrode current collector, as well as the wettability of the electrolyte. This reduces the nucleation overpotential of the negative electrode current collector, reduces dendrite formation, and improves the reliability and cycle performance of the battery cell. At the same time, the electrochemically active area of the negative electrode current collector increases, which can further improve the cycle performance of the battery cell.

[0137] The laser ablation heat-affected zone may be a continuous zone or a plurality of discontinuous zones arranged at intervals.

[0138] In some embodiments, the non-laser ablation heat-affected zone may include at least a portion of the surface area, that is, at least a portion of the surface of the negative electrode current collector may be the non-laser ablation heat-affected zone.

[0139] In some embodiments, the metal grain size of the laser ablation heat-affected zone may be 10 nm-100 nm, and optionally 10 nm-50 nm.

[0140] In some embodiments, the metal grain size of the non-laser ablation heat-affected zone may be greater than 100 nm.

[0141] In some embodiments, the microstructure morphology of the surface of the negative electrode current collector includes one or more of surface ablation without pores, pits, bowl holes, through holes, and grooves.

[0142] The negative electrode current collector is a two-dimensional metal structure or a three-dimensional porous metal structure.

[0143] Optionally, the microstructure morphology of the surface of the two-dimensional metal structure may include one or more of surface ablation without pores, bowl holes, through holes, and grooves.

[0144] The size of the metal grains at the position where the surface is ablated but no holes are formed and the area nearby is smaller. Optionally, the size of the metal grains at the position where the surface is ablated but no holes are formed and the area nearby can be 10nm-100nm, optionally 10nm-50nm.

[0145] The size of the metal grains at the bowl hole position and its vicinity is smaller. Optionally, the size of the metal grains at the bowl hole position and its vicinity can be 10nm-100nm, or optionally 10nm-50nm.

[0146] The size of the metal grains at the edge of the through hole and its vicinity is smaller. Optionally, the size of the metal grains at the edge of the through hole and its vicinity can be 10nm-100nm, or optionally 10nm-50nm.

[0147] The size of the metal grains at the groove position and its vicinity is smaller. Optionally, the size of the metal grains at the groove position and its vicinity can be 10nm-100nm, or optionally 10nm-50nm.

[0148] Optionally, the bowl hole may be an array of bowl holes.

[0149] Optionally, the diameter of the array bowl holes may be 20 μm-50 μm, the hole spacing may be greater than or equal to 15 μm, and the hole depth may be less than or equal to 2 / 3 of the thickness H1 of the negative electrode current collector. Furthermore, the hole spacing may be less than 100 μm.

[0150] Optionally, the through hole may be an array of through holes.

[0151] Optionally, the diameter of the array through holes may be 20 μm-140 μm, and the hole spacing may be greater than or equal to 15 μm. Furthermore, the hole spacing may be less than 100 μm.

[0152] Optionally, the interval between the grooves may be greater than or equal to 15 μm, and the depth of the grooves may be less than or equal to 2 / 3 of the thickness H1 of the negative electrode current collector.

[0153] Optionally, the area ratio of the laser ablation heat-affected zone on the surface of the two-dimensional metal structure can be 40%-100%, and more optionally 50%-100%, 60%-100%, 70%-100%, or 80%-100%.

[0154] Optionally, the microstructure morphology of the surface of the three-dimensional porous metal structure may include one or more of surface ablation without pores, and pits.

[0155] The size of the metal grains at the position where the surface is ablated but no holes are formed and the area nearby becomes smaller, for example, it can be 10nm-100nm, optionally 10nm-50nm.

[0156] The size of the metal grains at the pit position and the vicinity thereof becomes smaller, for example, it may be 10 nm-100 nm, optionally 10 nm-50 nm.

[0157] In some embodiments, the negative electrode current collector can be prepared by the above preparation method.

[0158] Other characteristics of the negative electrode current collector can refer to the above preparation method and will not be repeated here.

[0159] The negative electrode current collector provided in the embodiments of the present application is used in a negative electrode-free lithium metal battery or a negative electrode-free sodium metal battery, which can make the battery have good cycle performance and high reliability.

[0160] [Positive electrode]

[0161] The battery cell includes a positive electrode plate.

[0162] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and comprising a positive electrode active material. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposing surfaces of the positive electrode current collector.

[0163] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0164] As an example, the positive electrode active material may include, but is not limited to, one or more of lithium transition metal oxides, metal chalcogenides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium titanium oxide, and their respective modified compounds. Lithium transition metal oxides may include, but are not limited to, layered structures and spinel structures. Examples of lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, a composite material of lithium iron manganese phosphate and carbon, and their respective modified compounds.

[0165] In some embodiments, in order to further improve the energy density of the battery cell, the positive electrode active material may include a general formula of Li a Ni b Co c M d O e D f One or more lithium transition metal oxides and modified compounds thereof. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M may include but is not limited to one or more of Ge, Mo, Sn, Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and D may include but is not limited to one or more of N, F, S and Cl.

[0166] In some embodiments, the positive electrode active material may include both a lithium transition metal oxide and a lithium-containing phosphate, thereby facilitating the production of a battery with both high capacity and high reliability.

[0167] As an example, the positive electrode active material may include but is not limited to LiCoO2, LiNiO2, LiMnO2, LiNi 1 / 2 Mn 1 / 2O2、LiMn2O4、Li 4 / 3 Ti5 / 3 O4、LiNi 1 / 2 Mn 1 / 2 O2、LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333),LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523),LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.80 Co 0.15 Al 0.05 O2, LiFePO4, LiMnPO4, Li 1.13 Ti 0.57 Fe 0.3 One or more of S2.

[0168] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting sodium. For example, the positive electrode active material may include, but is not limited to, one or more of layered transition metal oxides (including but not limited to P2 type, O3 type, etc.), polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian materials.

[0169] In some embodiments, as examples, the positive electrode active material may include but is not limited to NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, Na 0.67 MO2 (M includes at least two of Fe, Co, Cr, Mn, Ni, V, Ti, Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, Mo), NaFePO4, NaMnPO4, NaCoPO4, Na4Fe3(PO4)2O7, Na3V2(PO4)2F3, Na3V2(PO4)3, Prussian blue, Prussian white, and one or more of their respective modified compounds.

[0170] The modified compounds of the above-mentioned positive electrode active materials may be used to perform doping modification and / or surface coating modification on the positive electrode active materials.

[0171] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0172] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polyethylene oxide, fluorinated acrylic resin, styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and one or more of carboxymethyl chitosan (CMCS).

[0173] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include but is not limited to one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include but is not limited to one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0174] The positive electrode film layer is typically formed by coating a positive electrode slurry onto a positive electrode current collector, drying, and cold pressing. The positive electrode slurry is typically formed by dispersing the positive electrode active material, optional positive electrode conductive agent, optional positive electrode binder, and any other components in a solvent and stirring them uniformly. The solvent may be, but is not limited to, N-methylpyrrolidone (NMP).

[0175] [Electrolytes]

[0176] The battery cells include an electrolyte.

[0177] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and an organic solvent.

[0178] In some embodiments, the electrolyte includes anions, which may include bis(fluorosulfonyl)imide anions (FSI - ), bis(trifluoromethanesulfonyl)imide anion (TFSI - ), dioxalatoborate anion (BOB - ), difluorooxalatoborate anion (DFOB - ), difluorobis(oxaloyl)phosphate anion (DFOP - ), tetrafluorooxalophosphate anion (TFOP -), difluorophosphate anion (PO2F2 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), hexafluoroarsenate anion (AsF6 - ), trifluoromethanesulfonate anion (CF3SO3 - )

[0179] In some embodiments, the electrolyte includes cations, which may include one or more of lithium ions and sodium ions.

[0180] In some embodiments, the concentration of the electrolyte salt may be greater than 0.3 mol / L, and may be greater than 0.7 mol / L. The concentration of the electrolyte salt may further be less than 4 mol / L, and may be less than 2.5 mol / L or less than 1.7 mol / L. When the concentration of the electrolyte salt is within the above range, the electrolyte solution can have suitable ionic conductivity.

[0181] Organic solvent can include but not limited to one or more in esters, ethers, sulfones, nitrile etc.Ester can include but not limited to one or more in carbonate, phosphate, carboxylate, sulfate, sulfonate etc.Carbonate can comprise cyclic carbonate and / or chain carbonate, alternatively, carbonate can comprise cyclic carbonate and chain carbonate simultaneously.Chain carbonate can comprise low-viscosity polar chain carbonate, aliphatic branched-chain carbonate etc.

[0182] As an example, the organic solvent may include, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), tetraethylene glycol dimethyl ether (TEGDME), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), trimethyl phosphate, 3-methoxypropionitrile, H(CF2)2OCH3, C4F9O CH3, H(CF2)2OCH2CH3, H(CF2)2OCH2CF3, H(CF2)2CH2O(CF2)2H, CF3CHFCF2OCH3, CF3CHFCF2OCH2CH3, 2-trifluoromethylhexafluoropropyl methyl ether, 2-trifluoromethylhexafluoropropyl ethyl ether, 2-trifluoromethylhexafluoropropyl propyl ether, 3-trifluoromethyloctafluorobutyl methyl ether, 3-trifluoromethyloctafluorobutyl ethyl ether, 3-trifluoromethyloctafluorobutyl propyl ether, 4-trifluoromethyl One or more of trifluoromethyl decafluoropentyl methyl ether, 4-trifluoromethyl decafluoropentyl ethyl ether, 4-trifluoromethyl decafluoropentyl propyl ether, 5-trifluoromethyl dodecafluorohexyl methyl ether, 5-trifluoromethyl dodecafluorohexyl ethyl ether, 5-trifluoromethyl dodecafluorohexyl propyl ether, 6-trifluoromethyl tetradecafluoroheptyl methyl ether, 6-trifluoromethyl tetradecafluoroheptyl ethyl ether, 6-trifluoromethyl tetradecafluoroheptyl propyl ether, 7-trifluoromethyl hexafluorooctyl methyl ether, 7-trifluoromethyl hexafluorooctyl ethyl ether, and 7-trifluoromethyl hexafluorooctyl propyl ether.

[0183] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, or additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature power performance.

[0184] [Isolation film]

[0185] A battery cell may also include a separator, which is located between the positive electrode and the negative electrode and mainly serves to prevent internal short circuits.

[0186] The present application has no particular limitation on the type of isolation membrane, and any known porous metal structure isolation membrane with good chemical stability and mechanical stability can be selected.

[0187] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of fiberglass, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The isolation membrane may be a single-layer film or a multi-layer composite film. When the isolation membrane is a multi-layer composite film, the materials of each layer may be the same or different.

[0188] The preparation method of battery cells is well known. In some embodiments, the positive electrode sheet, separator, negative electrode current collector and electrolyte can be assembled to form a battery cell. As an example, the positive electrode sheet, separator, negative electrode current collector can be formed into an electrode assembly through a winding process and / or a lamination process, and the electrode assembly is placed in an outer package, dried and injected with the above-mentioned electrolyte, and then vacuum packaged, allowed to stand, formed and other processes to obtain a battery cell. Multiple battery cells can also be further connected in series, in parallel or in a mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in a mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0189] The present application also provides an electrical device, which includes a battery provided in the present application. The battery can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device can be, but is not limited to, a mobile device (such as a mobile phone, a tablet computer, a laptop computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.

[0190] The electrical device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0191] Figure 11 The diagram is a schematic diagram of an exemplary electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of this device, a battery pack or battery module can be used.

[0192] As another example, an electric device may be a mobile phone, a tablet computer, a laptop computer, etc. Such an electric device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0193] Example

[0194] The following examples describe the present disclosure in more detail and are intended to be illustrative only, as various modifications and variations within the scope of the present disclosure will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages, and ratios reported in the following examples are by weight, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further processing, and all instruments used in the examples are commercially available.

[0195] Comparative Example 1-1

[0196] Commercially available double-sided, two-dimensional copper foil with a thickness of 8 μm was used as the negative electrode current collector. The surface of the copper foil was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum-dried at 80°C. The initial size of the metal grains in the copper foil was greater than 100 nm.

[0197] Examples 1-1 to 1-7 and Comparative Examples 1-2 to 1-5

[0198] Commercially available double-sided two-dimensional copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum-dried at 80°C.

[0199] The dried copper foil is placed on the workpiece table and fixed, the laser irradiation processing parameters are set, and the laser beam path is set; the laser is started, the voltage is loaded, and the copper foil is laser irradiated; after the laser irradiation treatment is completed, when the sample temperature drops below 30°C, the sample is taken out and used as the negative electrode current collector.

[0200] The laser used was an IPG YLPN-1-20X120-100 laser. The laser had a wavelength of 1064 nm, a pulse energy of 1 mJ, an adjustable pulse width from 20 ns to 120 ns, and an adjustable pulse repetition frequency. The laser irradiation treatment parameters are shown in Table 1.

[0201] Before laser irradiation, the initial size of the copper foil metal grains is greater than 100nm. After laser irradiation, the size of the metal grains formed by recrystallization in the laser ablation heat-affected zone is 10nm-100nm.

[0202] Table 1

[0203]

[0204] Performance Testing

[0205] (1) Test of copper foil improvement effect after laser irradiation treatment

[0206] After laser irradiation treatment, the metal grain size in the area where metal grain melting and recrystallization occurs on the copper foil surface is smaller, and the color of this position will be different from the color before laser irradiation treatment. By observing the color change of the copper foil surface after laser irradiation treatment through a light microscope, the area ratio of the area where metal grain melting and recrystallization occurs on the copper foil surface after laser irradiation treatment can be determined.

[0207] After laser irradiation treatment, the color distinction of the copper foil surface is not obvious. It can be considered that the area of the copper foil surface where metal grains melt and recrystallize after laser irradiation treatment accounts for more than or equal to 80%. At this time, the improvement effect of the copper foil after laser irradiation treatment is excellent.

[0208] After laser irradiation treatment, the area of the color change region on the surface of the copper foil accounts for greater than or equal to 60% and less than 80%, and it is believed that the improvement effect of the copper foil after laser irradiation treatment is better.

[0209] After the laser irradiation treatment, the area of the color change region on the surface of the copper foil accounts for greater than or equal to 40% and less than 60%, and it is considered that the improvement effect of the copper foil after the laser irradiation treatment is moderate.

[0210] After laser irradiation treatment, the area of the color change region on the surface of the copper foil accounts for greater than or equal to 20% and less than 40%, and it is considered that the improvement effect of the copper foil after laser irradiation treatment is poor.

[0211] After laser irradiation treatment, the area of the color change region on the copper foil surface accounts for less than 20%, and it is believed that the improvement effect of the copper foil after laser irradiation treatment is very poor.

[0212] (2) Nucleation overpotential test

[0213] In an argon-protected glove box, a button-type battery was assembled using a lithium metal sheet as the counter electrode and the anode current collector prepared above. The electrolyte salt was LiFSI at a concentration of 1 mol / L, and the solvent was ethylene glycol dimethyl ether (DME). A 12 μm thick PE film was used as the separator.

[0214] At 25°C, the assembled button cell was left to stand for 12 hours and the current was measured at 1 mA / cm 2 The current density is constant current discharge to 1 mAh / cm 2 At the beginning of the lithium metal deposition process, there will be a significant voltage drop, followed by a flat voltage platform. The difference (absolute value) between the voltage at the lowest point of the discharge curve and the flat part of the voltage platform is used as the nucleation overpotential of the negative electrode current collector.

[0215] (3) Cyclic performance test

[0216] Lithium iron phosphate, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were mixed uniformly in an appropriate amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1 to obtain a positive electrode slurry. The positive electrode slurry was coated on the positive electrode current collector aluminum foil and dried to obtain a positive electrode plate. In an argon-protected glove box, the positive electrode plate and the above-prepared negative electrode current collector were assembled into a button cell. The electrolyte salt of the electrolyte was LiFSI with a concentration of 1 mol / L, and the solvent of the electrolyte was ethylene glycol dimethyl ether (DME). The separator was a 12μm thick PE film.

[0217] After the assembled button cell was allowed to rest for 12 hours at 25°C, it was charged at a constant current of 0.2C to 3.65V. Then, it was charged at a constant voltage of 3.65V to 0.05C. After the button cell was allowed to rest for 10 minutes, it was discharged at a constant current of 0.5C to 2V. The button cell was cycled according to the above method, and the number of cycles corresponding to the discharge capacity reaching 50% of the initial discharge capacity was recorded. The number of button cell samples can be more than 6 during testing, and the test results are averaged.

[0218] Table 2

[0219]

[0220]

[0221] It can be seen from the test results in Table 2 that by selecting appropriate laser irradiation processing parameters, the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains without melting the entire copper foil, which can also better improve the cycle performance of the battery.

[0222] In Comparative Example 1-2, the average power of the laser is small, and no obvious traces are left on the surface of the copper foil after laser irradiation treatment, which results in an insignificant improvement in the battery cycle performance.

[0223] In comparative examples 1-3, the average power of the laser is large, and the copper foil has been melted after the laser irradiation treatment.

[0224] In comparative examples 1-4, the pulse repetition frequency of the laser is low, and no obvious traces are left on the surface of the copper foil after laser irradiation treatment, which results in an insignificant improvement in the battery cycle performance.

[0225] In comparative examples 1-5, the pulse repetition frequency of the laser is large, and the copper foil has been melted after the laser irradiation treatment.

[0226] It can be seen from the test results of Example 1-1 and Example 1-2 that by further selecting a suitable average laser power, the surface of the metal substrate can have a larger laser ablation heat-affected zone while avoiding the overall melting of the metal substrate. The metal grains in the laser ablation heat-affected zone can also be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0227] It can be seen from the test results of Example 1-1 and Example 1-3 that by further selecting a suitable laser pulse repetition frequency, the surface of the metal substrate can have a larger laser ablation heat-affected zone while avoiding the overall melting of the metal substrate. The metal grains in the laser ablation heat-affected zone can also be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0228] It can be seen from the test results of Example 1-1, Example 1-4 and Example 1-5 that by further selecting a suitable laser pulse width, the surface of the metal substrate can have a larger laser ablation heat-affected zone, and the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0229] It can be seen from the test results of Example 1-1, Example 1-6 and Example 1-7 that by further selecting a suitable laser defocus amount, the surface of the metal substrate can have a larger laser ablation heat-affected zone, and the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0230] Examples 1-8 to 1-10

[0231] Commercially available double-sided two-dimensional copper foil with a thickness of 8 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum-dried at 80°C.

[0232] The dried copper foil is placed on the workpiece table and fixed, the laser irradiation processing parameters are set, and different laser beam paths are set; the laser is started, the voltage is loaded, and the copper foil is laser irradiated; after the laser irradiation treatment is completed, the sample temperature is lowered to below 30°C, and the sample is taken out as the negative electrode current collector.

[0233] The laser used was an IPG YLPN-1-20X120-100 laser. The laser wavelength was 1064 nm, the pulse energy was 1 mJ, the pulse width was adjustable from 20 ns to 120 ns, and the pulse repetition frequency was adjustable. The laser irradiation parameters are shown in Table 3. The test results are shown in Table 4.

[0234] Before laser irradiation, the initial size of the copper foil metal grains is greater than 100nm. After laser irradiation, the size of the metal grains formed by recrystallization in the laser ablation heat-affected zone is 10nm-100nm.

[0235] Table 3

[0236]

[0237] Table 4

[0238]

[0239] Figure 12 X-ray diffraction images of the negative electrode collectors of Comparative Example 1-1 and Example 1-9 are shown, Curve I represents the X-ray diffraction image of the negative electrode collector of Comparative Example 1-1, and Curve II represents the X-ray diffraction image of the negative electrode collector of Example 1-9. Figure 13 The electron backscatter diffraction (EBSD) images of the negative electrode current collectors of Comparative Example 1-1 and Example 1-9 are shown. FIG. (a) shows the electron backscatter diffraction (EBSD) image of the negative electrode current collector of Comparative Example 1-1, and FIG. (b) shows the electron backscatter diffraction (EBSD) image of the negative electrode current collector of Example 1-9. Figure 12 It can be seen that after laser irradiation treatment, the half-height width of the copper diffraction peak becomes larger, which indicates that the copper grain size becomes smaller. Figure 13 It can be seen that after laser irradiation treatment, smaller metal grains are formed in the laser ablation heat affected zone, and the laser ablation heat affected zone is located at the edge of the through hole and its vicinity.

[0240] The test results of Examples 1-1, 1-8, and 1-10 show that when the copper foil surface microstructure is bowl-shaped or through-hole, the battery can have better cycling performance. This is because bowl-shaped or through-hole copper foil surface microstructures have a larger specific surface area and a larger electrochemically active area.

[0241] Comparative Example 2-1

[0242] Commercially available 3D copper foam with a thickness of 120 μm was used as the negative electrode current collector. The copper foil surface was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then vacuum-dried at 80°C. The initial size of the copper foam metal grains was greater than 100 nm.

[0243] Examples 2-1 to 2-8 and Comparative Examples 2-2 to 2-5

[0244] Commercially available three-dimensional foam copper with a thickness of 120 μm was first wiped with a 1 mol / L acetic acid solution, then ultrasonically cleaned with ethanol and deionized water, and then dried in a vacuum oven at 80°C.

[0245] The dried copper foam is placed on a workpiece table and fixed, and the laser irradiation processing parameters and the laser beam path are set. The laser is started, the voltage is loaded, and the copper foam is subjected to laser irradiation processing. After the laser irradiation processing is completed, the sample temperature is lowered to below 30°C, and the sample is taken out as a negative electrode current collector.

[0246] The laser used was an IPG YLPN-1-20X120-100 laser. The laser wavelength was 1064 nm, the pulse energy was 1 mJ, the pulse width was adjustable from 20 ns to 120 ns, and the pulse repetition frequency was adjustable. The laser irradiation parameters are shown in Table 5. The test results are shown in Table 6.

[0247] Before laser irradiation treatment, the initial size of the foamed copper metal grains is greater than 100nm. After laser irradiation treatment, the size of the metal grains formed by recrystallization of the laser ablation heat-affected zone is 10nm-100nm.

[0248] Table 5

[0249]

[0250] Table 6

[0251]

[0252]

[0253] It can be seen from the test results in Table 6 that by selecting appropriate laser irradiation processing parameters, the metal grains in the laser ablation heat-affected zone can be melted and recrystallized to form smaller metal grains without burning the foam copper ribs, thereby better improving the cycle performance of the battery.

[0254] In comparative example 2-2, the average power of the laser is small, and after laser irradiation treatment, there is no obvious trace on the surface of the foam copper, which leads to an insignificant improvement in the battery cycle performance.

[0255] In Comparative Example 2-3, the average power of the laser is large, and after laser irradiation treatment, some ribs of the foam copper are burned off.

[0256] In comparative examples 2-4, the pulse repetition frequency of the laser is low, and after laser irradiation treatment, there is no obvious trace on the surface of the foam copper, which leads to an insignificant improvement in the battery cycle performance.

[0257] In comparative example 2-5, the pulse repetition frequency of the laser is large, and after laser irradiation treatment, some ribs of the foam copper are burned off.

[0258] It can be seen from the test results of Example 2-1 and Example 2-3 that by further selecting a suitable average laser power, more rib surfaces can be provided with laser ablation heat-affected zones while avoiding the burning of the foam copper ribs. The metal grains in the laser ablation heat-affected zones can also be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0259] It can be seen from the test results of Example 2-1 and Example 2-4 that by further selecting a suitable laser pulse repetition frequency, more rib surfaces can be provided with laser ablation heat-affected zones while avoiding the burning of the foam copper ribs. The metal grains in the laser ablation heat-affected zones can also be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0260] It can be seen from the test results of Example 2-1, Example 2-5 and Example 2-6 that by further selecting a suitable laser pulse width, more rib surfaces can have laser ablation heat-affected zones, and the metal grains in the laser ablation heat-affected zones can be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0261] It can be seen from the test results of Example 2-1, Example 2-7 and Example 2-8 that by further selecting a suitable laser defocus amount, more ribbed surfaces can have laser ablation heat-affected zones, and the metal grains in the laser ablation heat-affected zones can be melted and recrystallized to form smaller metal grains, thereby better improving the cycle performance of the battery.

[0262] The test results of Examples 2-1 and 2-2 show that the formation of pits on the copper foam surface can improve the battery's cycling performance. This is because the formation of pits on the copper foam surface increases the specific surface area and electrochemically active area.

[0263] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a negative electrode current collector, characterized in that: The steps include: Providing a metal substrate, wherein the metal substrate is a two-dimensional metal structure or a three-dimensional porous metal structure; Laser is used to irradiate at least a portion of the surface of the metal substrate, so that metal grains in the laser ablation heat-affected zone of the metal substrate are melted and recrystallized to form metal grains of smaller size, thereby obtaining a negative electrode current collector.

2. The preparation method according to claim 1, characterized in that The laser generating the laser is a pulsed laser, the laser wavelength of the pulsed laser is 694nm to 1070nm, the average power of the laser is 30W to 90W, the pulse repetition frequency of the laser is 30KHz to 90KHz, and the pulse width of the laser is 20ns to 120ns.

3. The preparation method according to claim 2, characterized in that The pulse energy of the pulse laser is 1 mJ.

4. The preparation method according to any one of claims 2 to 3, characterized in that The pulse laser includes one or more of a ruby laser, a fiber laser, a glass laser, and a YAG laser.

5. The preparation method according to any one of claims 2 to 4, characterized in that The laser wavelength of the pulse laser is 1050nm to 1070nm.

6. The preparation method according to any one of claims 2 to 5, characterized in that The laser has an execution speed of 1000 mm / s to 3500 mm / s.

7. The preparation method according to any one of claims 2 to 6, characterized in that The initial size of the metal grains of the metal matrix is greater than 100 nm; and / or, The size of the metal grains formed by recrystallization of the laser ablation heat-affected zone of the metal matrix is 10nm-100nm.

8. The preparation method according to any one of claims 2 to 7, characterized in that The metal substrate is a two-dimensional metal structure, and a thickness H1 of the two-dimensional metal structure is 5 μm to 12 μm.

9. The preparation method according to claim 8, characterized in that The two-dimensional metal structure is a two-dimensional copper foil, a two-dimensional copper alloy foil, a two-dimensional nickel foil or a two-dimensional nickel alloy foil.

10. The preparation method according to any one of claims 8 to 9, characterized in that: The average power of the laser is 30W to 80W; and / or, The laser has a pulse repetition frequency of 30 kHz to 80 kHz; and / or The laser pulse width is 40ns to 120ns; and / or, The defocus amount of the laser is from -120 μm to 20 μm.

11. The preparation method according to claim 10, characterized in that: The average power of the laser is 40W to 80W; and / or, The laser has a pulse repetition frequency of 40 kHz to 80 kHz; and / or The laser pulse width is 60ns to 120ns; and / or, The defocus amount of the laser is -(H1×70%) μm to 0.

12. The preparation method according to any one of claims 2 to 7, characterized in that: The metal matrix is a three-dimensional porous metal structure, and a thickness H2 of the three-dimensional porous metal structure is 80 μm to 1000 μm.

13. The preparation method according to claim 12, characterized in that The three-dimensional porous metal structure is mesh copper, mesh nickel, foam copper or foam nickel.

14. The preparation method according to any one of claims 12 to 13, characterized in that: The average power of the laser is 40W to 90W; and / or, The laser has a pulse repetition frequency of 40 kHz to 90 kHz; and / or The laser pulse width is 40ns to 120ns; and / or, The defocus amount of the laser is -(H2×100%)μm to 0.

15. The preparation method according to claim 14, characterized in that The average power of the laser is 60W to 90W; and / or, The laser has a pulse repetition frequency of 60 kHz to 90 kHz; and / or The laser pulse width is 60ns to 120ns; and / or, The defocus amount of the laser is -(H2×70%) μm to -(H2×50%) μm.

16. The preparation method according to any one of claims 1 to 15, characterized in that: The microstructure morphology of the surface of the negative electrode current collector includes one or more of surface ablation without pores, pits, bowl holes, through holes, and grooves.

17. The preparation method according to any one of claims 1 to 16, characterized in that: Before irradiating the surface of the metal substrate with laser, the method further comprises the step of cleaning the oil stains, impurities and / or oxide layer on the surface of the metal substrate.

18. A negative electrode current collector, characterized in that: The negative electrode current collector includes a laser ablation heat-affected zone and a non-laser ablation heat-affected zone, and the metal grain size of the laser ablation heat-affected zone is smaller than the metal grain size of the non-laser ablation heat-affected zone.

19. The negative electrode current collector according to claim 18, characterized in that: The metal grain size of the laser ablation heat-affected zone is 10 nm-100 nm; and / or the metal grain size of the non-laser ablation heat-affected zone is greater than 100 nm.

20. The negative electrode current collector according to any one of claims 18 to 19, characterized in that: The microstructure morphology of the surface of the negative electrode current collector includes one or more of surface ablation without pores, pits, bowl holes, through holes, and grooves.

21. The negative electrode current collector according to claim 18, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 17.

22. A battery cell, characterized in that: The negative electrode current collector comprises the negative electrode current collector prepared by the preparation method according to any one of claims 1 to 17 or the negative electrode current collector according to any one of claims 18 to 21, and the battery cell comprises at least one of a negative electrode-free lithium metal battery cell and a negative electrode-free sodium metal battery cell.

23. A battery, characterized in that: Comprising the battery cell according to claim 22.

24. An electrical device, characterized in that: The battery according to claim 23 is used to provide electrical energy.

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