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 an electric device, and the preparation method of the negative electrode current collector comprises the following steps: providing a substrate which comprises copper; placing the substrate in a vacuum cavity of a vacuum plasma cleaning machine; and vacuumizing the vacuum cavity, introducing O2 into the vacuum cavity, and starting a plasma generator of the vacuum plasma cleaning machine to carry out plasma cleaning treatment so as to form a Cu2O layer on the surface of the substrate in situ, 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 with ion-type batteries, metal batteries can have higher energy density. However, unlike the negative electrode of ion-type batteries, the negative electrode of metal batteries has a more serious dendrite problem, which affects its commercialization. The growth of dendrites will cause internal short circuits in the battery, affecting the reliability of the battery; at the same time, during the metal deposition and stripping process, the unstable solid electrolyte interface (SEI) film is repeatedly torn and rebuilt, which will continuously consume active ions and electrolytes, thereby affecting the battery's cycle performance. The above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art. 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 substrate, wherein the substrate comprises copper; placing the substrate in a vacuum chamber of a vacuum plasma cleaning machine; evacuating the vacuum chamber, then introducing O2 into the vacuum chamber, and starting a plasma generator of the vacuum plasma cleaning machine to perform plasma cleaning to form a Cu2O layer in situ on the surface of the substrate to obtain a negative electrode current collector.

[0005] The preparation method of the negative electrode current collector provided in the embodiment of the present application can quickly form a Cu2O layer on the surface of the substrate. The Cu2O layer can reduce the nucleation overpotential of the negative electrode current collector through a conversion reaction, thereby improving the reliability and cycle performance of the battery.

[0006] Plasma cleaning can remove oil stains, oxide layers, and passivation layers on the substrate surface, and can also improve the roughness of the substrate surface to expose fresh Cu. At the same time, the substrate surface temperature increases during plasma cleaning, so that in a pure oxygen environment, the substrate surface can be rapidly oxidized to form a Cu2O layer.

[0007] Since the plasma cleaning treatment has an indiscriminate cleaning effect on the substrate surface, Cu2O will not be selectively formed on the substrate surface, thereby avoiding the occurrence of dominant growth points, reducing dendrite formation, and further improving the reliability and cycle performance of the battery.

[0008] In some embodiments, the substrate comprises a two-dimensional copper foil or a three-dimensional porous copper. Optionally, the three-dimensional porous copper comprises a mesh copper or a foam copper.

[0009] In some embodiments, the gas flow rate of O2 introduced into the vacuum chamber is 10 mL / min-80 mL / min, and can be optionally 30 mL / min-50 mL / min.

[0010] In some embodiments, the power of the plasma generator is 100W-350W.

[0011] In some embodiments, the plasma cleaning time is 15 seconds / side to 180 seconds / side.

[0012] By adjusting the O2 gas flow rate, the power of the plasma generator, and the plasma cleaning time within the above range, a dense and uniform Cu2O layer can be formed on the substrate surface, thereby reducing the nucleation overpotential of the negative electrode current collector and improving the reliability and cycle performance of the battery.

[0013] In some embodiments, the vacuum chamber is evacuated, and then O2 is introduced into the vacuum chamber, and before the plasma generator of the vacuum plasma cleaning machine is started to perform plasma cleaning, a gas washing step is further included: the vacuum chamber is evacuated, and then O2 is introduced into the vacuum chamber for gas washing. Optionally, the gas washing process is repeated 2-3 times.

[0014] The gas washing process can clean the impurity gases remaining in the vacuum chamber of the vacuum plasma cleaning machine, thereby retaining only O2, thereby ensuring that the subsequent plasma cleaning process is not affected by other gas particles.

[0015] In some embodiments, the vacuum degree of the vacuum chamber is less than or equal to 10 -2 MPa.

[0016] In some embodiments, the preparation method further includes the steps of: after the plasma cleaning treatment is completed, introducing air into the vacuum chamber, and then taking out the sample to obtain the negative electrode current collector after the air pressure of the vacuum chamber is restored to the standard atmospheric pressure.

[0017] In some embodiments, the thickness of the Cu2O layer is less than or equal to 10 nm. Thus, on the one hand, the affinity of the negative electrode current collector to metals such as lithium and sodium can be improved, and the nucleation overpotential of the negative electrode current collector can be reduced. On the other hand, the irreversible consumption of active ions can be reduced, so that the battery has good cycle performance.

[0018] In a second aspect, the present application provides a negative electrode current collector prepared by the preparation method of the first aspect of the present application.

[0019] In some embodiments, the negative electrode current collector comprises a substrate and a Cu2O layer formed in situ on at least one surface of the substrate. Optionally, the thickness of the Cu2O layer is less than or equal to 10 nm.

[0020] 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.

[0021] Optionally, 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.

[0022] In a fourth aspect, the present application provides a battery, which includes the battery cell of the third aspect of the present application.

[0023] In a fifth aspect, the present application provides an electrical device, which includes the battery of the fourth aspect of the present application, and the battery is used to provide electrical energy.

[0024] 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

[0025] In order 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 implementation methods of the present application, and for ordinary technicians in this field, other drawings can be obtained based on the drawings without creative work.

[0026] Figure 1 A schematic diagram showing a battery cell provided by some embodiments of the present application.

[0027] Figure 2 A schematic diagram of an exploded view of a battery cell provided by some embodiments of the present application is shown.

[0028] Figure 3 A schematic diagram of a battery module provided in some embodiments of the present application is shown.

[0029] Figure 4 A schematic diagram of a battery pack provided in some embodiments of the present application is shown.

[0030] Figure 5 yes Figure 4 An exploded diagram of the battery pack is shown.

[0031] Figure 6 A schematic diagram of an electrical device provided in some embodiments of the present application is shown.

[0032] Figure 7A scanning electron microscope (SEM) image of the negative electrode current collector prepared in Comparative Example 1-1 is shown.

[0033] Figure 8 The Cu 2p XPS spectrum and Auger spectrum of the negative electrode current collector prepared in Comparative Example 1-1 are shown.

[0034] Fig. 9 A scanning electron microscope (SEM) image of the negative electrode current collector prepared in Example 1-2 is shown.

[0035] Fig.10 The Cu 2p XPS spectrum and Auger spectrum of the negative electrode current collector prepared in Example 1-2 are shown.

[0036] Fig.11 The XPS spectrum at a depth of 10 nm of the negative electrode current collector prepared in Example 1-2 is shown.

[0037] In the drawings, the drawings may not be drawn according to the actual scale. The reference numerals are as follows: 1 battery pack, 2 upper box, 3 lower box, 4 battery module, 5 battery, 51 housing, 52 electrode assembly, 53 cover plate. DETAILED DESCRIPTION

[0038] Hereinafter, the negative electrode current collector and its preparation method, battery cell, battery and electric device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. 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 descriptions 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.

[0039] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a 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 a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present 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 real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it 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.

[0040] If not otherwise specified, all embodiments and optional embodiments of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0041] Unless otherwise specified, all technical features and optional technical features of the present application may be combined with each other to form new technical solutions, and such technical solutions should be deemed to be included in the disclosure of the present application.

[0042] If there is no special explanation, all steps of the present application can 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 also 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.

[0043] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0044] 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”, or “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 higher in level than the second feature. A first feature being “below”, “below”, or “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 lower in level than the second feature.

[0045] Unless otherwise specified, the terms used in this application have the commonly understood meanings that are commonly understood by those skilled in the art.

[0046] Unless otherwise specified, the values ​​of the parameters mentioned in this application can be measured by 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 specified, the test temperature of each parameter is 25°C.

[0047] 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.

[0048] A battery cell is the smallest unit of a battery, which can independently realize the functions of charging and discharging. The battery cell can be cylindrical, rectangular or in other shapes, etc., which is not limited in the embodiments of the present application. Figure 1 The battery cell 5 is a rectangular parallelepiped structure as an example.

[0049] When there are multiple battery cells, the multiple battery cells are connected in series, in parallel, or in mixed connection through 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 case and battery cells, and the battery cells or battery modules are accommodated in the case. In some embodiments, the case may serve as part of the chassis structure of the vehicle. For example, part of the case may become at least a part of the floor of the vehicle, or part of the case may become at least a part of the crossbeam and longitudinal beam of the vehicle.

[0050] In some embodiments, the battery may be an energy storage device, which includes an energy storage container, an energy storage cabinet, and the like.

[0051] The battery cell includes an electrode assembly. The electrode assembly may be a winding structure or a laminated structure, which is not limited in the present application.

[0052] The battery cell may also include an outer package, which may be used to encapsulate the electrode assembly. The outer package may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).

[0053] In some embodiments, Figure 2 As shown, the outer package may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 is used to cover the opening to close the receiving cavity. The electrode assembly 52 is encapsulated in the receiving cavity. The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, which can be adjusted according to demand.

[0054] In some embodiments, battery cells may be assembled into a battery module. The 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 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of battery cells 5 may be fixed by fasteners.

[0055] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of battery cells 5 are received in the receiving space.

[0056] 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.

[0057] 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, the battery pack 1 may include a box body and a plurality of battery modules 4 disposed in the box body. The box body includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the box body in any manner.

[0058] 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.

[0059] A battery cell without a negative electrode generally refers to a battery cell that is formed by not actively setting a negative electrode active material layer on the negative electrode side during the manufacturing process of the battery cell, for example, in the manufacturing process of the battery cell, a layer is not set at the negative electrode through processes such as coating or deposition, or a negative electrode active material layer is formed by a carbonaceous active material layer. During the first charge, the ions obtain electrons on the negative electrode side and deposit on the surface of the negative electrode current collector to form a metal. During discharge, the metal can be converted into ions and return to the positive electrode to achieve cyclic charge and discharge. Compared with other battery cells, a battery cell without a negative electrode can obtain a higher energy density because it does not have a negative electrode active material layer. The CB (Cell Balance) value of a battery cell without a negative electrode is usually 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. Since the battery cell without a negative electrode does not contain or only contains a small amount of negative electrode active material, the unit area capacity of the negative electrode is small, and thus the CB value is very small, for example, usually less than or equal to 0.1.

[0060] Metals such as lithium and sodium have poor wettability on conventional copper current collectors, which leads to a large nucleation overpotential. They are prone to preferential nucleation at certain surface defect locations of conventional copper current collectors. The preferential nucleation locations will form advantageous growth points, which in turn can easily lead to dendrite formation and cause internal short circuits in the battery, affecting the reliability and cycle performance of the battery.

[0061] The 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.

[0062] The preparation method of the negative electrode current collector provided in the embodiment of the present application includes the following steps: providing a substrate, the substrate including copper; placing the substrate in a vacuum chamber of a vacuum plasma cleaning machine; evacuating the vacuum chamber, then introducing O2 into the vacuum chamber, and starting the plasma generator of the vacuum plasma cleaning machine to perform plasma cleaning to form a Cu2O layer in situ on the surface of the substrate to obtain a negative electrode current collector.

[0063] The preparation method of the negative electrode current collector provided in the embodiment of the present application can quickly form a Cu2O layer on the surface of the substrate. The Cu2O layer can reduce the nucleation overpotential of the negative electrode current collector through a conversion reaction, thereby improving the reliability and cycle performance of the battery.

[0064] Plasma cleaning can remove oil stains, oxide layers, and passivation layers on the substrate surface, and can also improve the roughness of the substrate surface to expose fresh Cu. At the same time, the substrate surface temperature increases during plasma cleaning, so that in a pure oxygen environment, the substrate surface can be rapidly oxidized to form a Cu2O layer.

[0065] Since the plasma cleaning treatment has an indiscriminate cleaning effect on the substrate surface, Cu2O will not be selectively formed on the substrate surface, thereby avoiding the occurrence of dominant growth points, reducing dendrite formation, and further improving the reliability and cycle performance of the battery.

[0066] In some embodiments, the thickness of the Cu2O layer can be less than or equal to 10 nm. Thus, on the one hand, the affinity of the negative electrode current collector to metals such as lithium and sodium can be improved, and the nucleation overpotential of the negative electrode current collector can be reduced. On the other hand, the irreversible consumption of active ions can be reduced, so that the battery has good cycle performance.

[0067] In some embodiments, the vacuum chamber is evacuated, and then O2 is introduced into the vacuum chamber. Before starting the plasma generator of the vacuum plasma cleaning machine for plasma cleaning, a gas washing step is also included: the vacuum chamber is evacuated, and then O2 is introduced into the vacuum chamber for gas washing.

[0068] Optionally, the scrubbing process can be repeated 2-3 times.

[0069] The gas washing process can clean the impurity gases remaining in the vacuum chamber of the vacuum plasma cleaning machine, thereby retaining only O2, thereby ensuring that the subsequent plasma cleaning process is not affected by other gas particles.

[0070] In some embodiments, the preparation method may further include the steps of: after the plasma cleaning treatment is completed, introducing air into the vacuum chamber, and then after the air pressure of the vacuum chamber is restored to the standard atmospheric pressure, taking out the sample to obtain the negative electrode current collector.

[0071] In some embodiments, the vacuum degree of the vacuum chamber can be less than or equal to 10 -2 MPa.

[0072] In some embodiments, the substrate may include a two-dimensional copper foil or a three-dimensional porous copper. Alternatively, the three-dimensional porous copper may include a mesh copper or a foam copper.

[0073] In some embodiments, the gas flow rate of O2 introduced into the vacuum chamber may be 10 mL / min-80 mL / min, and may be optionally 30 mL / min-50 mL / min.

[0074] In some embodiments, the power of the plasma generator may be 100W-350W.

[0075] In some embodiments, the frequency of the plasma generator may be 13.56 MHz.

[0076] In some embodiments, the plasma cleaning time may be 15 seconds per surface to 180 seconds per surface, that is, the cleaning time of each surface of the substrate is 15 seconds to 180 seconds.

[0077] By adjusting the O2 gas flow rate, the power of the plasma generator, and the plasma cleaning time within the above range, a dense and uniform Cu2O layer can be formed on the substrate surface, thereby reducing the nucleation overpotential of the negative electrode current collector and improving the reliability and cycle performance of the battery.

[0078] When the O2 gas flow rate is small and the cleaning time is short, the O2 content introduced into the vacuum chamber is small, which makes the oxidation effect on the substrate surface poor, and the formed Cu2O layer is not dense and uniform enough, which leads to the poor affinity of the negative electrode collector to metals such as lithium and sodium, and the high nucleation overpotential of the negative electrode collector, which in turn makes the battery reliability and cycle performance poor.

[0079] When the O2 gas flow rate is large and the cleaning time is long, the O2 content introduced into the vacuum chamber increases and the degree of oxidation on the substrate surface increases. At this time, in addition to the formation of Cu2O on the substrate surface, a small amount of CuO may also be formed, which will reduce the affinity of the negative electrode collector to metals such as lithium and sodium, increase the nucleation overpotential of the negative electrode collector, and thus deteriorate the reliability and cycle performance of the battery.

[0080] When the power of the plasma generator is low, the plasma cleaning treatment has a poor effect on raising the temperature of the substrate itself, which results in poor oxidation effect on the substrate surface, and the formed Cu2O layer is not dense and uniform enough, which leads to poor affinity of the negative electrode collector for metals such as lithium and sodium, and a high nucleation overpotential of the negative electrode collector, which in turn leads to poor reliability and cycle performance of the battery.

[0081] When the power of the plasma generator is relatively high, overoxidation problems may occur on the substrate surface, such as yellow or purple overoxidation spots.

[0082] The embodiment of the present application also provides a negative electrode current collector prepared by the above preparation method. The negative electrode current collector includes a substrate and a Cu2O layer formed in situ on at least one surface of the substrate.

[0083] Optionally, the thickness of the Cu2O layer is less than or equal to 10 nm.

[0084] [Positive electrode]

[0085] The battery cell includes a positive electrode plate.

[0086] 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 including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0087] In some embodiments, the positive electrode active material includes a material capable of extracting and inserting lithium.

[0088] 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.

[0089] In some embodiments, in order to further improve the energy density of the battery, 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 of 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.

[0090] In some embodiments, the positive electrode active material may include both lithium transition metal oxide and lithium-containing phosphate, thereby facilitating obtaining a battery having both large capacity and high reliability.

[0091] 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 Ti 5 / 3 O4、LiNi 1 / 2 Mn1 / 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.

[0092] In some embodiments, the positive electrode active material includes a material capable of extracting and embedding 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.

[0093] 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, and Mo), NaMO2 (M includes at least two of Fe, Co, Ni, V, Ti, and 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.

[0094] The modified compounds of the above-mentioned positive electrode active materials may be the ones that undergo doping modification and / or surface coating modification on the positive electrode active materials.

[0095] In some embodiments, the positive electrode film layer may also 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.

[0096] In some embodiments, the positive electrode film layer may also 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), carboxymethyl chitosan (CMCS) One or more.

[0097] 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).

[0098] The positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing. The positive electrode slurry is usually formed by dispersing the positive electrode active material, the optional positive electrode conductive agent, the optional positive electrode binder and any other components in a solvent and stirring them uniformly. The solvent can be N-methylpyrrolidone (NMP), but is not limited thereto.

[0099] [Electrolytes]

[0100] The battery cells include an electrolyte.

[0101] In some embodiments, the electrolyte is an electrolyte solution including an electrolyte salt and an organic solvent.

[0102] In some embodiments, the electrolyte includes anions, which may include bis(fluorosulfonyl)imide anions (FSI - ), bis(trifluoromethanesulfonyl)imide anion (TFSI - ), borate oxalate anion (BOB - ), difluorooxalatoborate anion (DFOB - ), difluorobis(oxalate)phosphate anion (DFOP - ), tetrafluorooxalophosphate anion (TFOP -), difluorophosphate anion (PO2F2 - ), hexafluorophosphate anion (PF6 - ), tetrafluoroborate anion (BF4 - ), hexafluoroarsenate anion (AsF6 - ), trifluoromethanesulfonate anion (CF3SO3 - )

[0103] In some embodiments, the electrolyte includes cations, and the cations may include one or more of lithium ions and sodium ions.

[0104] In some embodiments, the concentration of the electrolyte salt may be 0.3 mol / L or more, and may be 0.7 mol / L or more, and the concentration of the electrolyte salt may be 4 mol / L or less, and may be 2.5 mol / L or less, or 1.7 mol / L or less. When the concentration of the electrolyte salt is within the above range, the electrolyte solution may have a suitable ionic conductivity.

[0105] Organic solvents may include, but are not limited to, one or more of esters, ethers, sulfones, nitriles, etc. Esters may include, but are not limited to, one or more of carbonates, phosphates, carboxylates, sulfates, sulfonates, etc. Carbonates may include cyclic carbonates and / or linear carbonates, and optionally, carbonates may include cyclic carbonates and linear carbonates simultaneously. Linear carbonates may include low-viscosity polar linear carbonates, aliphatic branched-chain carbonates, etc.

[0106] 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-trifluoromethylhexafluoropropylmethyl ether, 2-trifluoromethylhexafluoropropylethyl ether, 2-trifluoromethylhexafluoropropylpropyl ether, 3-trifluoromethyloctafluorobutylmethyl ether, 3-trifluoromethyloctafluorobutylethyl ether, 4-trifluoromethyl The invention further comprises 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 hexadecafluorooctyl methyl ether, 7-trifluoromethyl hexadecafluorooctyl ethyl ether, and 7-trifluoromethyl hexadecafluorooctyl propyl ether.

[0107] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and 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.

[0108] [Isolation film]

[0109] The battery cell may also include a separator, which is located between the positive electrode and the negative electrode and mainly plays a role in preventing internal short circuits.

[0110] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0111] In some embodiments, the material of the isolation membrane may include, but is not limited to, one or more of glass fiber, 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 are the same or different.

[0112] The preparation method of battery cells is well known. In some embodiments, the positive electrode, separator, negative electrode and electrolyte can be assembled to form a battery cell. As an example, the positive electrode, separator, and negative electrode 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, and the above-mentioned electrolyte is injected after drying. After vacuum packaging, standing, formation and other processes, a battery cell is obtained. Multiple battery cells can also be further connected in series, in parallel or in mixed connection to form a battery module. Multiple battery modules can also be connected in series, in parallel or in mixed connection to form a battery pack. In some embodiments, multiple battery cells can also directly form a battery pack.

[0113] 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 and a satellite, an energy storage system, etc.

[0114] The electric device can select the type of battery according to its usage requirements, such as a battery cell, a battery module or a battery pack.

[0115] Figure 6 Schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the requirements of the electric device for high power and high energy density, a battery pack or a battery module may be used.

[0116] As another example, the electric device may be a mobile phone, a tablet computer, a notebook computer, etc. The electric device is usually required to be light and thin, and a battery cell may be used as a power source.

[0117] Example

[0118] The following examples describe the disclosure of the present application in more detail, and these examples are intended for illustrative purposes only, as various modifications and variations within the scope of the disclosure of the present application are apparent to those skilled in the art. Unless otherwise stated, 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 can be used directly without further processing, and the instruments used in the examples are commercially available.

[0119] Example 1-1

[0120] Commercially available double-sided two-dimensional copper foil with a thickness of 8 μm is cut into samples of 10 cm×10 cm and placed in the vacuum chamber of a vacuum plasma cleaning machine. The vacuum plasma cleaning machine may be a TS-PH 10MA radio frequency plasma cleaning machine.

[0121] First, evacuate the vacuum chamber to 10 -2 MPa, and then pure O2 is introduced until the vacuum chamber pressure returns to standard atmospheric pressure; vacuum is evacuated again and pure O2 is introduced for gas washing.

[0122] Then evacuate the vacuum chamber to 10 -2 MPa, pure O2 was introduced to adjust the gas flow rate of O2 to 30mL / min, and the plasma generator of the vacuum plasma cleaning machine was started for plasma cleaning, wherein the power of the plasma generator was 200W and the cleaning time was 30 seconds. After the cleaning was completed, air was filled into the vacuum chamber, and after the air pressure of the vacuum chamber was restored to the standard atmospheric pressure, the hatch was opened to take out the sample to obtain the negative electrode current collector.

[0123] Example 1-2 to Example 1-8

[0124] The preparation method of the negative electrode current collector is similar to that of Example 1-1, except that the parameters of the plasma cleaning treatment are different. The specific parameters are shown in Table 1.

[0125] Comparative Example 1-1

[0126] Commercially available double-sided two-dimensional copper foil with a thickness of 8 μm was directly used as the negative electrode current collector.

[0127] Comparative Example 1-2

[0128] Commercially available double-sided two-dimensional copper foil with a thickness of 8 μm was used as the negative electrode current collector after first wiping the surface of the copper foil with 1 mol / L acetic acid solution, then ultrasonically cleaning it with ethanol and deionized water, and then vacuum drying it at 80°C.

[0129] Performance Testing

[0130] (1) Nucleation overpotential test

[0131] In an argon-protected glove box, a metal lithium sheet was used as the counter electrode and assembled into a button cell with the negative electrode current collector prepared above. 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 isolation membrane was a PE film with a thickness of 12 μm.

[0132] At 25°C, the assembled button cell was left to stand for 12 hours and then charged 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 an obvious voltage drop, followed by a flat voltage platform. The difference between the voltage at the lowest point and the flat part of the voltage platform is used as the nucleation overpotential of the negative electrode current collector.

[0133] (2) Cyclic performance test

[0134] Lithium iron phosphate, conductive agent carbon black (Super P), and binder polyvinylidene fluoride (PVDF) are mixed evenly in a proper amount of solvent N-methylpyrrolidone (NMP) at a weight ratio of 8:1:1 to obtain a positive electrode slurry; the positive electrode slurry is coated on a positive electrode current collector aluminum foil, and after drying, a positive electrode sheet is obtained.

[0135] In an argon-protected glove box, the positive electrode sheet and the negative electrode current collector prepared above 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 isolation membrane was a PE film with a thickness of 12 μm.

[0136] At 25°C, after the assembled button cell was left to stand for 12 hours, it was charged to 3.65V at a constant current of 0.2C, and then charged to 0.05C at a constant voltage of 3.65V; after the button cell was left to stand for 10 minutes, it was discharged to 2V at a constant current of 0.5C. The button cell was cycled 200 times according to the above method, and the number of cycles corresponding to the discharge capacity being 50% of the first cycle discharge capacity was recorded.

[0137] During the test, the number of button cell samples may be more than 6, and the test results shall be averaged.

[0138] Table 1

[0139]

[0140] Figure 7 A scanning electron microscope (SEM) image of the negative electrode current collector prepared in Comparative Example 1-1 is shown. Figure 8 The Cu 2p XPS spectrum and Auger spectrum of the negative electrode current collector prepared in Comparative Example 1-1 are shown.

[0141] Comparative Example 1-1 did not perform plasma cleaning on the copper foil. Figure 8 It can be seen that there are Cu and Cu on the surface of copper foil. + and Cu 2+ .

[0142] Fig. 9 A scanning electron microscope (SEM) image of the negative electrode current collector prepared in Example 1-2 is shown. Fig.10 The Cu 2p XPS spectrum and Auger spectrum of the negative electrode current collector prepared in Example 1-2 are shown.

[0143] Depend on Figure 7 and Fig. 9 It can be seen that the cleaning effect of plasma cleaning on the copper foil surface is indiscriminate, and after plasma cleaning, the copper foil surface becomes rough. Fig.10 It can be seen that after plasma cleaning, only Cu and Cu + .

[0144] Fig.11 The 10nm depth XPS spectrum of the negative electrode current collector prepared in Example 1-2 is shown. Fig.11 It can be seen that after plasma cleaning, there is no Cu at a depth of 10nm from the surface of the copper foil. + The satellite peak (abscissa is about 940 eV) indicates that the thickness of the Cu2O layer formed on the surface of the copper foil after plasma cleaning is less than 10 nm.

[0145] It can be seen from the test results in Table 1 that after plasma cleaning, the nucleation overpotential of the copper foil decreases and the cycle performance of the battery is improved.

[0146] It can be seen from the test results of Examples 1-1 to 1-3 that when the power and cleaning time of the plasma generator remain unchanged and the O2 gas flow rate increases, the nucleation overpotential of the copper foil first decreases and then increases, and the number of battery cycles first increases and then decreases.

[0147] From the test results of Example 1-1 and Examples 1-4 to 1-5, it can be seen that when the O2 gas flow rate and cleaning time remain unchanged and the power of the plasma generator increases, the nucleation overpotential of the copper foil first decreases and then increases, and the number of battery cycles first increases and then decreases.

[0148] From the test results of Example 1-1 and Examples 1-6 to 1-8, it can be seen that when the O2 gas flow rate and the power of the plasma generator remain unchanged and the cleaning time increases, the nucleation overpotential of the copper foil first decreases and then increases, and the number of battery cycles first increases and then decreases.

[0149] Example 2-1

[0150] Commercially available three-dimensional copper foam with a thickness of 120 μm was cut into samples of 10 cm×10 cm and placed in the vacuum chamber of a vacuum plasma cleaning machine.

[0151] First, evacuate the vacuum chamber to 10 -2 MPa, and then pure O2 is introduced until the vacuum chamber pressure returns to standard atmospheric pressure; vacuum is evacuated again and pure O2 is introduced for gas washing.

[0152] Then evacuate the vacuum chamber to 10 -2 MPa, pure O2 was introduced to adjust the gas flow rate of O2 to 30mL / min, and the plasma generator of the vacuum plasma cleaning machine was started for plasma cleaning, wherein the power of the plasma generator was 250W and the cleaning time was 60 seconds. After the cleaning was completed, air was filled into the vacuum chamber, and after the air pressure of the vacuum chamber was restored to the standard atmospheric pressure, the hatch was opened to take out the sample to obtain the negative electrode current collector.

[0153] Example 2-2 to Example 2-8

[0154] The preparation method of the negative electrode current collector is similar to that of Example 2-1, except that the parameters of the plasma cleaning treatment are different. The specific parameters are shown in Table 2.

[0155] Comparative Example 2-1

[0156] Commercially available three-dimensional copper foam with a thickness of 120 μm was directly used as the negative electrode current collector.

[0157] Comparative Example 2-2

[0158] Commercially available three-dimensional copper foam with a thickness of 120 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.

[0159] The testing methods of Examples 2-1 to 2-8 and Comparative Examples 2-1 to 2-2 are the same as that of Example 1-1.

[0160] Table 2

[0161]

[0162] It can be seen from the test results in Table 2 that after plasma cleaning, the nucleation overpotential of the copper foam decreases and the cycle performance of the battery is improved.

[0163] It can be seen from the test results of Examples 2-1 to 2-3 that when the power and cleaning time of the plasma generator remain unchanged and the O2 gas flow rate increases, the nucleation overpotential of the foam copper first decreases and then increases, and the number of battery cycles first increases and then decreases.

[0164] From the test results of Example 2-1 and Examples 2-4 to 2-5, it can be seen that when the O2 gas flow rate and cleaning time remain unchanged and the power of the plasma generator increases, the nucleation overpotential of the foam copper first decreases and then increases, and the number of battery cycles first increases and then decreases.

[0165] From the test results of Example 2-1 and Examples 2-6 to 2-8, it can be seen that when the O2 gas flow rate and the power of the plasma generator remain unchanged and the cleaning time increases, the nucleation overpotential of the foam copper first decreases and then increases, and the number of battery cycles first increases and then decreases.

[0166] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining 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 substrate, the substrate comprising copper; Placing the substrate in a vacuum chamber of a vacuum plasma cleaning machine; The vacuum chamber is evacuated, and then O2 is introduced into the vacuum chamber, and a plasma generator of the vacuum plasma cleaning machine is started to perform plasma cleaning to form a Cu2O layer in situ on the surface of the substrate to obtain a negative electrode current collector.

2. The preparation method according to claim 1, characterized in that: The substrate includes two-dimensional copper foil or three-dimensional porous copper, Optionally, the three-dimensional porous copper includes mesh copper and foam copper.

3. The preparation method according to any one of claims 1 to 2, characterized in that: The gas flow rate of O2 introduced into the vacuum chamber is 10mL / min-80mL / min, and can be optionally 30mL / min-50mL / min.

4. The preparation method according to any one of claims 1 to 3, characterized in that The power of the plasma generator is 100W-350W.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The plasma cleaning time is 15 seconds / side to 180 seconds / side.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The vacuum chamber is evacuated, and then O2 is introduced into the vacuum chamber. Before the plasma generator of the vacuum plasma cleaning machine is started to perform plasma cleaning, a gas washing step is also included: The vacuum chamber is evacuated, and then O2 is introduced into the vacuum chamber for scrubbing; Optionally, the scrubbing treatment is repeated 2-3 times.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The vacuum degree of the vacuum chamber is less than or equal to 10 -2 MPa.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The method further comprises the following steps: after the plasma cleaning treatment is completed, air is introduced into the vacuum chamber, and after the air pressure of the vacuum chamber is restored to the standard atmospheric pressure, the sample is taken out to obtain the negative electrode current collector.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The thickness of the Cu2O layer is less than or equal to 10 nm.

10. A negative electrode current collector, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 9.

11. The negative electrode current collector according to claim 10, characterized in that: The negative electrode current collector includes a substrate and a Cu2O layer formed in situ on at least one surface of the substrate. Optionally, the thickness of the Cu2O layer is less than or equal to 10 nm.

12. A battery cell, characterized in that: It comprises a negative electrode current collector prepared by the preparation method according to any one of claims 1 to 9 or a negative electrode current collector according to any one of claims 10 to 11. Optionally, 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.

13. A battery, characterized in that: Comprising the battery cell according to claim 12.

14. An electrical device, characterized in that: The battery according to claim 13 is used to provide electrical energy.

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