Negative current collector, preparation method thereof, negative pole piece with negative current collector, and lithium secondary battery

Abstract

The invention provides a negative current collector, a preparation method thereof, a negative pole piece with the negative current collector, a lithium secondary battery, a battery module, a battery pack and an electric device. The negative electrode current collector sequentially comprises a current collector substrate, a lithium-loving plating layer and a metal organic framework array layer, the lithium-loving plating layer is arranged on the current collector substrate, the metal organic framework array layer grows on the surface of the lithium-loving plating layer in situ, and the metal organic framework array layer is of a nano pore channel structure; the thickness of the lithium-loving plating layer is 50 nm to 100 nm, and the thickness of the metal organic framework array layer is 0.5 [mu] m to 8 [mu] m. Through the negative current collector, uniform deposition of lithium can be induced, growth of lithium dendrites is inhibited, and the electrochemical performance of the lithium secondary battery is improved.

Description

[0001] This application is a divisional application of the invention patent application with the application date of December 30, 2021, application number 202111655217.2, and invention name "Negative electrode current collector and preparation method thereof, negative electrode sheet having the same, and lithium secondary battery". Technical Field

[0002] The present application relates to the field of batteries, and in particular to a negative electrode current collector and a preparation method thereof, a negative electrode sheet having the same, and a lithium secondary battery, a battery module, a battery pack and an electrical device. Background Art

[0003] With the strong demand for renewable energy and the increasing requirements for new energy vehicles, lithium secondary batteries using traditional graphite anodes are no longer sufficient to meet the growing social demands. Therefore, it is particularly important to develop a large-scale energy storage system with high energy density, safety and reliability. Lithium metal has a high theoretical specific capacity (3680mAh g -1 ) and the lowest reduction potential (-3.04 V vs. SHE), and is considered to be an ideal negative electrode material for developing a new generation of high-energy-density batteries.

[0004] However, the problems faced by lithium metal anodes, such as dendrite growth, irreversible lithium loss and volume change, have largely limited the practical application of lithium secondary batteries. Due to its high chemical activity, lithium anodes easily react with electrolytes to spontaneously generate unstable SEI films on the surface. During repeated lithium deposition / precipitation processes, the chemically inhomogeneous and structurally unstable SEI films will be destroyed, resulting in Li on the interface. + The flux distribution is uneven, which triggers the formation of dendrites. In addition, during the lithium precipitation process, the lithium dendrites are easily broken from the root and converted into "dead lithium", resulting in reduced battery coulombic efficiency and serious capacity decay. What's worse, the continuously growing lithium dendrites will pierce the diaphragm, causing battery short circuit and thermal runaway and other safety issues. Therefore, designing a dendrite-free and highly stable lithium negative electrode is of great significance for the development of high-performance lithium secondary batteries.

[0005] The prior art proposes a copper-based current collector modified by a protective coating, which loads an organic-inorganic composite protective coating composed of polyacrylonitrile, polymethyl methacrylate, nano-silicon dioxide and plasticizer on a commercially available copper foil. The protective coating effectively regulates the negative electrode surface Li + distribution, inducing the uniform deposition of lithium metal; at the same time, good flexibility and mechanical strength can adapt to the volume change of lithium metal during the cycle and effectively inhibit the growth of lithium dendrites, realizing long-life and high-safety lithium secondary batteries.

[0006] However, the construction of substrate protective coating is usually mostly achieved through non-in-situ coating methods. The protective layer obtained by non-in-situ coating often leads to local uneven coating due to the randomness of artificial coating. In addition, during the drying process, as the coating solution evaporates, gaps will be generated between the coating and the substrate. Under high current density or high deposition capacity, the coating is easy to fall off or break, and the protective effect fails.

[0007] Although the lithium-philic coating can be used as an inducing seed for the nucleation of lithium metal deposition to a certain extent, it can effectively improve the Li + The distribution of lithium on the surface of the current collector inhibits the growth of dendrites. However, during the repeated lithium deposition / precipitation process, the volume change on the negative electrode side can easily cause the lithium-philic coating structure to collapse and become severely pulverized, making it difficult to provide effective space for lithium deposition. In addition, the coating may also react with the electrolyte to reduce the coulombic efficiency and shorten the cycle life. Summary of the invention

[0008] The present application is made in view of the above-mentioned problems, and its purpose is to provide a negative electrode current collector and its preparation method, a pole piece having the same, as well as a lithium secondary battery, a battery module, a battery pack and an electrical device. The negative electrode current collector can induce uniform deposition of lithium, inhibit the growth of lithium dendrites, and improve the electrochemical performance of the lithium secondary battery.

[0009] In order to achieve the above-mentioned objectives, the first aspect of the present application is to provide a negative electrode current collector, wherein the negative electrode current collector comprises, in sequence: a current collector substrate, a lithium-philic coating layer, and a metal organic framework array layer, wherein the lithium-philic coating layer is arranged on the current collector substrate, and the metal organic framework array layer (hereinafter sometimes referred to as "MOF array layer") is in situ grown on the surface of the lithium-philic coating layer, and the metal organic framework array layer has a nanopore structure.

[0010] The negative electrode current collector of the present application is formed on the lithium-philic coating substrate by simple in-situ growth to form a MOF array layer with a unique nanopore structure. The ordered nanopores inherent in the MOF array layer have a similar "ion sieve" effect, which can effectively and evenly distribute Li + The flux is conducive to the uniform deposition of metallic lithium. At the same time, the "ion sieve" array layer can avoid direct contact between the electrolyte solvent and the highly reducible metallic lithium layer, reduce side reactions, and improve the coulombic efficiency and cycle stability of lithium secondary batteries. In addition, the lithium-philic plating layer provides an effective nucleation site for the deposition of metallic lithium. + It is easy to form an alloy with the lithium-philic coating, which can effectively reduce the deposition interface energy between lithium metal and the current collector, thereby inducing the uniform deposition of metallic lithium, inhibiting the growth of lithium dendrites, and improving the electrochemical performance of lithium secondary batteries.

[0011] In some embodiments, the thickness of the lithium-philic coating is 50 nm to 100 nm.

[0012] In some embodiments, the metal organic framework array layer has a thickness of 0.5 μm to 8 μm.

[0013] In some embodiments, in the negative electrode current collector of the present application, the metal organic framework array layer (MOF array layer) is composed of a metal ion coordination center and an organic ligand, and the metal coordination center is a zinc ion (Zn 2+ ), tin (Sn 2+ ) or magnesium (Mg 2+ )

[0014] In some embodiments, in the negative electrode current collector of the present application, the organic ligand is selected from 2-methylimidazole, nicotinic acid, isonicotinic acid, terephthalic acid, 2,5-dihydroxyterephthalic acid, dimethyl 2,5-dihydroxyterephthalate, 1,2,4-triazole, and oxalate. Since the lithium-philic coating is preferably one of Zn, Sn, and Mg, it is necessary to select an organic ligand that can match the coordination center of the above metal ions to achieve a dual-function negative electrode current collector that induces uniform lithium deposition.

[0015] In some embodiments, the metal ion coordination center in the metal organic framework array layer is a zinc ion Zn 2+ , the organic ligand is 2-methylimidazole. The use of the above metal ion coordination center and organic ligand can make the preparation process of the metal organic framework array layer simpler.

[0016] In some embodiments, in the negative electrode current collector of the present application, the thickness of the metal organic framework array layer (MOF array layer) is 200 nm~8 μm. If the thickness of the MOF array layer exceeds 8 μm, the ion transmission capacity between the electrode and the electrolyte will be reduced, and the battery polarization will increase. If it is less than 200 nm, the mechanical stability of the coating caused by volume change during the cycle will be poor. Therefore, by making the thickness of the MOF array layer within the range of 200 nm~8 μm, a protective layer with high mechanical stability and fast ion transmission performance can be obtained, further inhibiting the growth of lithium dendrites during the cycle.

[0017] Further controlling the thickness of the metal organic framework array layer to 1 μm~8 μm is conducive to better inhibiting the growth of lithium dendrites and at the same time making the lithium secondary battery have better electrochemical performance.

[0018] In some embodiments, in the negative electrode current collector of the present application, the thickness of the metal organic framework array layer is 1 μm to 4 μm. In this way, while effectively inhibiting the growth of lithium dendrites, it is more conducive to improving the first cycle specific capacity and first cycle coulombic efficiency of the lithium secondary battery.

[0019] In some embodiments, in the negative electrode current collector of the present application, the thickness of the lithium-philic coating is 50 nm to 500 nm. If the thickness of the lithium-philic coating exceeds 500 nm, the internal resistance of the battery will increase due to the poorer conductivity of metal zinc than copper, and the battery mass will increase accordingly, resulting in a decrease in energy density. If it is less than 50 nm, the lower coating thickness is difficult to provide sufficient deposition space for more lithium, and excessive lithium is deposited on the surface of the alloy layer, thereby inducing lithium dendrite growth. Therefore, by making the thickness of the lithium-philic coating within the range of 50 nm to 500 nm, it is possible to obtain uniform lithium deposition induced by the optimal lithium-philic coating, and obtain a smooth deposition morphology.

[0020] Furthermore, the thickness of the lithium-philic coating is 50 nm to 100 nm, which is more conducive to inhibiting the growth of lithium dendrites and making the lithium secondary battery have better electrochemical performance.

[0021] In some embodiments, in the negative electrode current collector of the present application, the current collector substrate is metal or non-metal, the metal is one or more selected from Cu, Al, Fe, Ni, Ti and stainless steel, and the non-metal is one or more selected from graphene and carbon fiber. Due to the excellent conductivity of the metal and non-metal materials, the electron migration rate is accelerated and the intrinsic resistance of the battery is reduced.

[0022] The second aspect of the present application is to provide a method for preparing a negative electrode current collector, which includes: depositing a lithium-philic coating on a copper foil substrate by magnetron sputtering, and the target material is one or more selected from Zn, Sn and Mg; and in-situ growth of a metal organic framework array layer (MOF array layer) having a nanopore structure on the surface of the lithium-philic coating by a wet chemical method. The in-situ growth of the MOF array layer on the surface of the lithium-philic coating is achieved by a simple and low-cost wet chemical method (i.e., wet chemical method), firstly, a metal oxide thin layer is formed on the surface of the lithium-philic coating by pre-oxidation treatment, and then the oxide thin layer is etched by an etchant to generate a large amount of metal ions, and the metal oxidant coordinates with the etchant, so that a uniform and dense MOF array layer is formed on the surface of the lithium-philic coating. The preparation method of the negative electrode current collector of the present application can inhibit the growth of lithium dendrites by in-situ growth of uniform lithium metal deposition, so that the lithium secondary battery exhibits high coulombic efficiency and excellent cycle stability. In addition, the preparation method of the present application is low-cost, simple to operate, highly controllable, and can be used for commercial production.

[0023] In some embodiments, in the preparation method of the negative electrode current collector of the present application, the reaction time of the in-situ growth is 5 h to 36 h, and the reaction temperature is 25 ℃ to 120 ℃. If the reaction time of the in-situ growth exceeds 36 h, the thickness of the obtained MOF layer will be too large, which is not conducive to the ion transport between the electrode and the electrolyte. If it is less than 5 h, the MOF layer will grow unevenly on the surface of the substrate, making it difficult to form a dense layer and prone to cracks. Therefore, by making the reaction time of the in-situ growth within the range of 5 h to 36 h, a uniform and thickness-controlled MOF layer can be obtained, which is conducive to the subsequent uniform deposition of lithium. In addition, if the reaction temperature of the in-situ growth exceeds 120 ℃, the preparation process will be complicated and the cost will increase. If it is lower than 25 ℃, the ion migration rate in the reaction solution at low temperature will be reduced, and the reaction will be incomplete. Therefore, by making the reaction temperature of the in-situ growth within the range of 25 ℃ to 120 ℃, a uniform MOF array layer with simple operation and low cost can be obtained.

[0024] The third aspect of the present application is to provide a negative electrode plate, which comprises the negative electrode collector according to the first aspect of the present application.

[0025] In some embodiments, the negative electrode plate further includes pre-deposited lithium supported on the negative electrode current collector, and the capacity of the pre-deposited lithium in the negative electrode plate is 1 mAh cm -2 ~15 mAh cm -2 By providing the above-mentioned pre-deposited lithium on the negative electrode current collector, it is beneficial to construct a lithium-rich negative electrode. Replenishing lithium to the negative electrode material by pre-depositing lithium can offset the irreversible lithium loss caused by the formation of the SEI film and improve the total capacity and energy density of the battery.

[0026] In some embodiments, the capacity of the pre-deposited lithium in the negative electrode sheet is 5 mAh cm -2 ~15 mAh cm -2 . This is conducive to achieving better lithium supplementation effects.

[0027] A fourth aspect of the present application is to provide a lithium secondary battery, which includes the negative electrode sheet according to the third aspect of the present application.

[0028] A fifth aspect of the present application is to provide a battery module, which includes the lithium secondary battery according to the fourth aspect of the present application.

[0029] A sixth aspect of the present application is to provide a battery pack, which includes the battery module according to the fifth aspect of the present application.

[0030] The seventh aspect of the present application is to provide an electrical device, which includes at least one of the lithium secondary battery described in the fourth aspect of the present application, the battery module described in the fifth aspect of the present application, and the battery pack described in the sixth aspect of the present application.

[0031] According to the present application, a MOF array layer with a unique nanopore structure is formed on a negative electrode current collector based on a lithium-philic coating layer by simple in-situ growth, thereby providing Li + It provides a uniform transmission channel and can also serve as a "physical barrier" to avoid direct contact between the lithium negative electrode and the electrolyte, reducing side reactions; and it induces uniform deposition of lithium and effectively inhibits the growth of lithium dendrites. For lithium secondary batteries using this negative electrode current collector, it exhibits high coulombic efficiency and excellent cycle stability, greatly improving the electrochemical performance of lithium secondary batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1a is a schematic diagram of a prior art copper-based current collector for lithium deposition; Figure 1b Schematic diagram of a copper-based current collector with uniform in-situ growth of lithium deposition according to one embodiment of the present application.

[0033] Figure 2 It is a schematic structural diagram of a current collector according to another embodiment of the present application.

[0034] Figure 3 It is a schematic diagram of the crystal structure of ZIF-8 MOF according to another embodiment of the present application.

[0035] Figure 4 is a schematic diagram of a lithium secondary battery according to one embodiment of the present application.

[0036] Figure 5 yes Figure 4 An exploded view of a lithium secondary battery according to one embodiment of the present application is shown.

[0037] Figure 6 is a schematic diagram of a battery module according to an embodiment of the present application.

[0038] Figure 7 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0039] Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of the present application is shown.

[0040] Figure 9 It is a schematic diagram of an electric device using a lithium secondary battery according to one embodiment of the present application as a power source.

[0041] Figure 10a , Figure 10b ,Figure 10c is the surface morphology characterization of the lithium metal negative electrode of the lithium secondary battery in Examples 1 to 17 and Comparative Examples 1 to 5 of the present application, wherein: Figure 10a is the SEM image of no dendrites after cycling; Figure 10b This is the SEM image of slight dendrites after cycling; Figure 10c This is a SEM image showing severe dendrites after cycling.

[0042] Description of reference numerals:

[0043] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 lithium secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0044] Hereinafter, the negative electrode current collector and its manufacturing method, negative electrode plate, lithium secondary battery, battery module, battery pack and electric device of the present application are specifically disclosed in detail with appropriate reference to the drawings. However, there are 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.

[0045] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 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 ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both 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.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0048] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0049] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0050] Negative current collector

[0051] In one embodiment of the present application, a negative electrode current collector is provided, which comprises, in sequence: a current collector substrate, a lithium-philic coating layer, and a metal organic framework array layer, wherein the lithium-philic coating layer is provided on the current collector substrate, and the metal organic framework array layer is in situ grown on the surface of the lithium-philic coating layer, and the metal organic framework array layer has a nanopore structure.

[0052] Furthermore, the metal organic framework array layer is composed of a metal ion coordination center and an organic ligand, wherein the metal coordination center is one or more of zinc, tin or magnesium, and the organic ligand is one or more selected from 2-methylimidazole, nicotinic acid, isonicotinic acid, terephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid dimethyl ester, 1,2,4-triazole, and oxalate. From the perspective of simple preparation process, it is preferred that the metal coordination center is zinc and the organic ligand is 2-methylimidazole.

[0053] refer to Figure 1a It can be seen that in the prior art, depositing lithium on a copper-based current collector easily leads to uneven lithium deposition, resulting in Li + The flux distribution is uneven, thus triggering dendritic lithium dendrites, which leads to reduced battery coulombic efficiency and severe capacity attenuation. Even the continuous growth of lithium dendrites can pierce the separator and cause battery failure.

[0054] refer to Figure 1bIt can be seen that the present invention forms a dense and regular nanopore structure by in-situ growth of lithium deposition on a copper-based current collector. + Provide a uniform transmission channel so that Li + The lithium ions flow evenly, thus suppressing the generation of lithium dendrites and ensuring the electrochemical performance of the battery.

[0055] Regarding the in-situ growth of a metal organic framework array layer with a nanoporous structure on the surface of a lithium-philic coating substrate, reference Figure 2 It can be seen that a MOF array layer is in situ grown on the lithium-philic coating (shown as a zinc-plated copper foil, i.e., a zinc layer is plated on the copper foil), and the MOF array layer has a dense and regular nanopore structure, which can be Li + Provide a uniform transmission channel so that Li + Flow evenly.

[0056] The growth mechanism of the MOF array layer is described in detail below using zinc as the metal coordination center and 2-methylimidazole as the organic ligand as a specific example.

[0057] First, a thin ZnO layer is formed on the surface of the zinc layer by a simple pre-oxidation treatment, and then ZnO is etched by 2-methylimidazole (HMIM) to generate a large amount of Zn 2+ , Zn 2+ A uniform MOF array layer is formed on the surface of the galvanized copper foil by coordination with HMIM. The type of the MOF array layer is ZIF-8, and its structural formula is described below.

[0058] refer to Figure 3 It can be seen that the crystal structure of the MOF array layer of ZIF-8 formed above is a zeolite topological structure, belonging to the face-centered cubic system, I-43m space group, and this structure can be regarded as a Zn metal 2+ ZnN is formed by connecting with the nitrogen atom in methylimidazolate (mIm) 4 It is composed of tetrahedral structural units.

[0059] From the perspective of uniformity of the MOF array layer and the speed of ion transport, the thickness of the metal organic framework array layer is preferably 200 nm to 8 μm.

[0060] In order to better inhibit the growth of lithium dendrites, the thickness of the metal organic framework array layer can be selected to be 1 μm~8 μm. In order to improve the first cycle specific capacity and first cycle coulomb efficiency of lithium secondary batteries, the thickness can be selected to be 1 μm~4 μm.

[0061] From the perspective of providing sufficient deposition space for more lithium and improving energy density, the thickness of the lithium-philic coating is preferably 50 nm to 500 nm, and can further be 50 nm to 100 nm.

[0062] From the viewpoint of the conductivity of the current collector, the current collector substrate is preferably a metal or a non-metal, the metal is one or more selected from Cu, Al, Fe, Ni, Ti and stainless steel, and the non-metal is one or more selected from graphene and carbon fiber. Furthermore, from the viewpoint of the lower potential of the negative electrode to lithium, it is more preferred that the metal is Cu and the non-metal is graphene.

[0063] Preparation method of negative current collector

[0064] In one embodiment of the present application, a method for preparing a negative electrode current collector is provided, which comprises: depositing a lithium-philic coating on a copper foil substrate by magnetron sputtering, and the target material is one or more selected from Zn, Sn and Mg; and in-situ growth of a metal organic framework array layer (MOF array layer) having a nanopore structure on the surface of the lithium-philic coating by a wet chemical method. Among them, the magnetron sputtering method can be carried out by conventional means in the art, as long as the lithium-philic coating of the present application can be prepared. Furthermore, the target material is preferably Zn. The wet chemical method of the present application is to contact the surface of the lithium-philic coating with a compound solution having an etching and coordination effect, and form a coordination layer on the surface of the lithium-philic coating. The etching and coordination effect is called "in-situ growth".

[0065] In addition, the lithium-philic coating may be pre-treated, including oxidation treatment, before forming the MOF array layer.

[0066] From the perspective of the uniformity of the MOF array layer, the speed of ion transport and the simplicity of the preparation process, the preferred in-situ growth reaction time is 5 h~36 h and the reaction temperature is 25 ℃~120 ℃.

[0067] Negative electrode sheet

[0068] In one embodiment of the present application, a negative electrode plate is provided, wherein the negative electrode plate comprises the negative electrode current collector of the present application and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0069] Specifically, the pole piece of the present application is based on the negative electrode current collector of the present application, obtained by pre-depositing lithium. The role of pre-depositing lithium is to construct a lithium-rich negative electrode for a lithium metal secondary battery. The negative electrode material is supplemented with lithium by pre-depositing lithium to offset the irreversible lithium loss caused by the formation of the SEI film, so as to improve the total capacity and energy density of the battery.

[0070] In this application, lithium foil is used as the negative electrode, immersed in an electrolyte, and discharged for a certain period of time using an electrochemical deposition method, so that the pre-deposited lithium of the negative electrode can be controlled in the range of 1~15 mAh cm -2If the pre-deposited lithium capacity of the lithium negative electrode exceeds 15 mAh cm -2 , it will cause an excessive lithium source on the negative electrode side, further leading to a decrease in the battery energy density. If it is lower than 1 mAh cm -2 , due to side reactions occurring on the electrode surface during charge and discharge, it will cause consumption of the electrolyte and the negative electrode, resulting in a serious shortage of the lithium source on the negative electrode side. Therefore, by making the pre-deposited lithium capacity of the lithium negative electrode within the range of 1 - 15 mAh cm -2 , a lithium metal negative electrode that can match positive electrodes of different capacities can be obtained.

[0071] Furthermore, the pre-deposited lithium capacity can be selected to be 5 mAh cm -2 ~15 mAh cm -2 .

[0072] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode film layer is provided on either one or both of the two opposite surfaces of the negative electrode current collector.

[0073] In addition, the lithium secondary battery, battery module, battery pack, and electrical device of the present application will be described below with appropriate reference to the drawings.

[0074] Lithium secondary battery

[0075] In one embodiment of the present application, a lithium secondary battery is provided.

[0076] The lithium secondary battery of the present application includes the negative electrode sheet, positive electrode sheet, electrolyte, and separator of the present application described above. During the charge and discharge process of the battery, active ions are embedded and extracted back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is disposed between the positive electrode sheet and the negative electrode sheet, mainly playing a role in preventing short circuit between the positive and negative electrodes, and at the same time allowing ions to pass through.

[0077] [Negative Electrode Sheet]

[0078] The negative electrode sheet includes the negative electrode current collector of the present application and the negative electrode film layer provided on at least one surface of the negative electrode current collector of the present application.

[0079] [Positive Electrode Sheet]

[0080] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer provided on at least one surface of the positive electrode current collector. In some embodiments, the positive electrode contains a material capable of extracting and embedding lithium ions. As long as the positive electrode material can make Li + extract from the positive electrode during charging, migrate through the electrolyte to the surface of the negative electrode, and embed into the interior of the negative electrode, and the process during discharge is just the opposite.

[0081] As an 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.

[0082] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0083] In some embodiments, the positive electrode active material may be a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds, etc. Examples of lithium-containing phosphates with olivine structure may include but are not limited to lithium iron phosphate (such as LiFePO 4 (also referred to as LFP), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), at least one of a composite material of lithium manganese phosphate and carbon, a composite material of lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0084] In some embodiments, the positive electrode active material is preferably selected from one or more of polyanion oxides, lithium transition metal composite oxides, and compounds obtained by adding other transition metals or non-transition metals to lithium transition metal oxides. And further preferably, the polyanion oxide contains a structure selected from olivine and NASICON, and the lithium transition metal composite oxide is one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, and lithium nickel cobalt aluminum oxide. These structures can effectively ensure that Li + Extraction and embedding from the positive electrode.

[0085] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0086] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0087] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0088] [Electrolytes]

[0089] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be a liquid electrolyte, a gel electrolyte or a solid electrolyte. The following is a detailed description of each.

[0090] The liquid electrolyte is composed of a lithium salt, an organic solvent, and / or an additive, wherein the lithium salt is one or more selected from organic lithium salts and inorganic lithium salts, and the organic solvent is one or more selected from carbonates, carboxylates, sulfates, phosphates, amides, nitriles, and ethers.

[0091] The lithium salt is selected from LiPF 6 , LiBF 4 、LiTFSI、LiClO 4 、LiAsF 6 , LiBOB, LiDFOB, LiTFOP, LiN(SO 2 RF) 2 、LiN(SO 2 F)(SO 2 RF), wherein the substituent RF=C n F 2n+1 , n is an integer ranging from 1 to 10.

[0092] The organic solvent is one or more selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methylpyrrolidone, N-methylformamide, N-methylacetamide, acetonitrile, sulfolane, dimethyl sulfoxide, ethylene sulfite, propylene sulfite, triethyl phosphate, methyl ethyl phosphite, methyl sulfide, diethyl sulfite, dimethyl sulfite, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, fluorine-containing cyclic organic esters, and sulfur-containing cyclic organic esters.

[0093] Furthermore, preferably, the concentration of the lithium salt in the electrolyte is 0.5 to 10 mol / L, and the content of the organic solvent in the electrolyte is 60 to 90% by mass.

[0094] The gel electrolyte is composed of a polymer phase and an electrolyte phase. The polymer phase is obtained by dissolving a high molecular polymer or by in-situ curing polymerization. The main body of the high molecular polymer is one or more selected from polyether polymers, polyolefin polymers, polynitrile polymers, and polycarboxylate polymers.

[0095] The polyether polymers are one or more selected from polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyethylene glycol dimethyl ether (EPGDME), and polysiloxane; the polyolefin polymers are one or more selected from polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - HFP), polytetrafluoroethylene (PTFE), and polyvinyl chloride (PVC); the polynitrile polymers are polyacrylonitrile (PAN) and / or polymelamine; the polycarboxylate polymers are polymethyl methacrylate (PMMA) and / or polyacrylate (PMA); the polycarbonate polymers are polypropylene carbonate (PC) and / or polyethylenecarbonate (PEC).

[0096] Moreover, the content of the polymer phase in the gel electrolyte is 0.1 - 99.9% by mass, and the content of the electrolyte phase in the gel electrolyte is 0.1 - 99.9% by mass.

[0097] As the solid electrolyte, it is a polymer electrolyte, an inorganic solid electrolyte, or a composite of a polymer electrolyte and an inorganic solid electrolyte. The polymer electrolyte consists of a polymer matrix and a lithium salt. The polymer matrix is one or more selected from polyether polymers, polyolefin polymers, polynitrile polymers, and polycarboxylate polymers; the lithium salt is one or more selected from LiPF 6 、LiBF 4 、LiTFSI、LiClO 4 、LiAsF 6 、LiBOB、LiDFOB、LiTFOP、LiN(SO 2 RF) 2 、LiN(SO 2 F)(SO 2 RF), where the substituent RF = C n F 2n+1 , n is an integer from 1 to 10; the inorganic solid electrolyte is one selected from oxide fast ion conductors, sulfide fast ion conductors, and halide fast ion conductors.

[0098] The polyether polymers are one or more selected from polyethylene oxide, polypropylene oxide, polyethylene glycol, polyethylene glycol dimethyl ether, and polysiloxane; the polyolefin polymers are one or more selected from polyethylene, polypropylene, polyvinylidene fluoride, polyvinylidene fluoride - hexafluoropropylene copolymer, polytetrafluoroethylene, and polyvinyl chloride; the polynitrile polymers are polyacrylonitrile and / or polymelamine; the polycarboxylate polymers are polymethyl methacrylate and / or polyacrylate; the polycarbonate polymers are polypropylene carbonate and / or polyethylenecarbonate.

[0099] The oxide fast lithium ion conductor is selected from one or more of NASICON (Na + super ionic conductor) structure, LISICON (Li + super ionic conductor) structure, Garnet structure, and Pervoskite; the sulfide fast lithium ion conductor is yLi 2 S-(100-y)P 2 S 5 mixed with MS 2 or LiqQ, where 1 < y < 100, M is selected from Si, Ge, Sn, and Q is selected from F, Cl, Br, I, O, N, PO 4 3- 、SO 4 2- 、BO 3 3- 、SiO 4 4- , and q is a natural number from 1 to 4; the halide fast lithium ion conductor is Li a CX b , where C is one or more of Ga, In, Sc, Y, La, and X is one or more of F, Cl, Br, 0 < a ≤ 10, 1 ≤ b ≤ 13.

[0100] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0101] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro(bis(oxalato))phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0102] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0103] In some embodiments, the electrolyte may further include additives, such as 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 or low temperature performance, etc.

[0104] [Isolation film]

[0105] In some embodiments, the lithium secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0106] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0107] In some embodiments, the separator is preferably a polypropylene separator, which is a conventional separator and has good chemical stability and mechanical stability, and is preferably a polypropylene separator with a porous structure.

[0108] The isolation film can be a single-layer film or a multi-layer composite film, without any particular limitation. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, without any particular limitation.

[0109] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0110] In some embodiments, the lithium secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0111] In some embodiments, the outer packaging of the lithium secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the lithium secondary battery can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as the plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed.

[0112] The present application has no particular limitation on the shape of the lithium secondary battery, which may be cylindrical, square or any other shape. Figure 4 The lithium secondary battery 5 is a square structure as an example.

[0113] In some embodiments, reference Figure 5, the outer packaging may include a shell 51 and a cover plate 53. Among them, 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 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0114] Battery module

[0115] In some embodiments, lithium secondary batteries can be assembled into a battery module. The number of lithium secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0116] Figure 6 4 is an example of a battery module. Figure 6 In the battery module 4, the plurality of lithium secondary batteries 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 lithium secondary batteries 5 may be fixed by fasteners.

[0117] Optionally, the battery module 4 may further include a housing having a housing space, and the plurality of lithium secondary batteries 5 are housed in the housing space.

[0118] Battery pack

[0119] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0120] Figure 7 and Figure 8 1 is a battery pack 1 as an example. Figure 7 and Figure 8 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0121] Electrical device

[0122] In addition, the present application also provides an electrical device, which includes at least one of the lithium secondary battery, battery module, or battery pack provided in the present application. The lithium secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0123] As the electrical device, a lithium secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0124] Figure 9 The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of lithium secondary batteries, a battery pack or a battery module can be used.

[0125] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a lithium secondary battery may be used as a power source.

[0126] Example

[0127] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0128] Example 1

[0129] Preparation of negative current collector:

[0130] Preparation of ZIF-8(MOF) / Zn@Cu negative electrode current collector:

[0131] Step 1 (S1) Preparation of galvanized copper foil: The galvanized copper foil was prepared by magnetron sputtering, and the sputtering / electron beam / ICP-CVD (base pressure <1×10 -6 Torr, ICP-CVD chamber). Based on the deposition conditions of plasma gas flow rate of 100 sccm, plasma power of 200 W, and sputtering time of 60 s, a 100 nm zinc coating was deposited on the copper foil substrate.

[0132] Step 2 (S2) pretreatment of galvanized copper foil: the pre-prepared galvanized copper foil was immersed in a 1 M ammonium persulfate (APS) solution for 10 min for oxidation treatment, then washed with deionized water and anhydrous ethanol for multiple times, and dried in a 60° C. forced air drying oven for later use.

[0133] Step 3 (S3) Construction of MOF array layer: The MOF array layer was prepared by a wet chemical method. The galvanized copper foil treated by S1 was placed in a prepared 0.5 M 2-methylimidazole (HMIM) aqueous solution and reacted at room temperature for 12 h. The thickness of the obtained MOF array layer was 1 μm. The surface impurities were then rinsed clean with deionized water and dried in vacuo at 60°C to obtain the ZIF-8 (MOF) / Zn@Cu negative electrode current collector, wherein the type of MOF array layer was ZIF-8, whose structural formula is described below, the type of lithium-philic coating was Zn, and the substrate was copper.

[0134] Preparation of negative electrode sheet:

[0135] The pre-deposition of lithium metal was performed by assembling a half-cell. In the half-cell, the current collector was used as the positive electrode, commercial lithium foil was used as the negative electrode, 1 M lithium bistrifluoromethanesulfonyl imide (LiTFSI) / 1,3-dioxolane (DOL) + ethylene glycol dimethyl ether (DME) (volume ratio of 1:1) was used as the electrolyte, and PE was used as the separator. -2 The electrochemical deposition method was used to discharge for 10 h at a current density of 10 mAh cm -2 of electrodes.

[0136] Preparation of positive electrode sheet:

[0137] The positive electrode active material LiFePO 4 The conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 7:2:1, and an appropriate amount of N-methylpyrrolidone (NMP) was added to grind into a uniform slurry. Then, the positive electrode slurry was evenly coated on a 12 μm aluminum foil, vacuum dried at 80 ° C for 12 h, and punched into 4*5 cm 2 The selected commercial lithium secondary battery uses LiFePO 4 The surface capacity of the positive electrode is 144 mAh cm -2 .

[0138] Separator:

[0139] The isolation membrane is made of conventional polypropylene (PE) membrane.

[0140] Assembly of battery:

[0141] Based on the copper-based current collector with in-situ growth of lithium anode uniformly deposited as prepared in Example 1, lithium was pre-deposited as the anode to commercialize lithium secondary batteries with LiFePO 4 As the positive electrode, PE as the separator, 1 M LiTFSI / DOL+DME (volume ratio of 1:1) as the electrolyte, the positive electrode sheet, the separator and the negative electrode sheet are placed in order, so that the separator is in the middle of the positive electrode sheet and the negative electrode sheet to play an isolating role, and then the electrolyte is injected to assemble into a stacked battery.

[0142] Example 2

[0143] The preparation method is basically the same as that of Example 1, except that:

[0144] During the preparation of MOF / Zn@Cu, the reaction time of galvanized copper foil and 0.5 M HMIM aqueous solution was 5 h, corresponding to a MOF array layer thickness of 200 nm.

[0145] Example 3

[0146] The preparation method is basically the same as that of Example 1, except that:

[0147] During the preparation of MOF / Zn@Cu, the reaction time of galvanized copper foil and 0.5 M HMIM aqueous solution was 8 h, corresponding to a MOF array layer thickness of 500 nm.

[0148] Example 4

[0149] The preparation method is basically the same as that of Example 1, except that:

[0150] During the preparation of MOF / Zn@Cu, the reaction time of galvanized copper foil and 0.5 M HMIM aqueous solution was 24 h, corresponding to a MOF array layer thickness of 4 μm.

[0151] Example 5

[0152] The preparation method is basically the same as that of Example 1, except that:

[0153] During the preparation of MOF / Zn@Cu, the reaction time of galvanized copper foil and 0.5 M HMIM aqueous solution was 36 h, corresponding to a MOF array layer thickness of 8 μm.

[0154] Example 6

[0155] The preparation method is basically the same as that of Example 1, except that:

[0156] The compactness of the MOF array layer was analyzed by using the corrosion effect of dilute hydrochloric acid on the lithium-philic zinc layer. First, 0.5 M dilute hydrochloric acid (dilute HCl) was prepared, and then the copper-based current collector with uniform in-situ growth of lithium deposited in Example 1 was placed in dilute HCl to observe whether bubbles were generated on the surface of the MOF array layer. The zinc layer reacts in the presence of dilute HCl. The degree of corrosion of the zinc layer can be judged based on the rate of bubble generation on the surface of the functionalized copper-based current collector, and the compactness of the MOF array layer can be determined.

[0157] Example 7

[0158] The preparation method is basically the same as that of Example 2, except that:

[0159] The compactness of the MOF array layer was analyzed by using the corrosion effect of dilute hydrochloric acid on the lithium-philic zinc layer. First, 0.5 M dilute HCl was prepared, and then the copper-based current collector with uniform in-situ growth of lithium deposited in Example 2 was placed in the dilute HCl to observe whether bubbles were generated on the surface of the MOF array layer. The zinc layer reacted in the presence of dilute HCl. The rate of bubble generation on the surface of the functionalized copper-based current collector was used to determine the degree of corrosion of the zinc layer, and thus the compactness of the MOF array layer.

[0160] Example 8

[0161] The preparation method is basically the same as that of Example 1, except that:

[0162] In the preparation process of MOF / Zn@Cu, the galvanized copper foil was prepared by magnetron sputtering, and the sputtering / electron beam / ICP-CVD (base pressure <1×10 -6 Torr, ICP-CVD chamber). Based on the deposition conditions of plasma gas flow rate of 100 sccm, plasma power of 200 W, and sputtering time of 30 s, a 50 nm zinc coating was deposited on the copper foil substrate.

[0163] Example 9

[0164] The preparation method is basically the same as that of Example 1, except that:

[0165] In the preparation process of MOF / Zn@Cu, the galvanized copper foil was prepared by magnetron sputtering, and the sputtering / electron beam / ICP-CVD (base pressure <1×10 -6 Tor, ICP-CVD chamber). Based on the deposition conditions of plasma gas flow rate of 100 sccm, plasma power of 200 W, and sputtering time of 240 s, a 500 nm zinc coating was deposited on the copper foil substrate.

[0166] Example 10

[0167] The preparation method is basically the same as that in Example 1, except that:

[0168] Preparation of MOF-74(MOF) / Zn@Cu negative electrode current collector:

[0169] Step 1 (S1) Preparation of magnesium-coated copper foil: Magnetron sputtering method was used to prepare magnesium-coated copper foil, and sputtering / electron beam / ICP-CVD (basic pressure <1×10 -6 Torr, ICP-CVD chamber). Based on the deposition conditions of plasma gas flow rate of 100 sccm, plasma power of 200 W, and sputtering time of 60 s, a 100 nm magnesium layer was deposited on the copper foil substrate.

[0170] Step 2 (S2) pretreatment of magnesium-plated copper foil: the pre-prepared galvanized copper foil was immersed in a 1 M ammonium persulfate (APS) solution for 10 min for oxidation treatment, then washed with deionized water and anhydrous ethanol for multiple times, and dried in a 60° C. forced air drying oven for use.

[0171] Step 3 (S3) Construction of MOF array layer: The MOF array layer was prepared by a wet chemical method. First, tetrahydrofuran was used as a solvent to prepare a 0.1 M 2,5-dihydroxyterephthalic acid solution. The magnesium-plated copper foil treated with S1 was then placed in the prepared solution to react at room temperature for 12 h. The surface impurities were then rinsed clean with deionized water and dried at 60°C in a vacuum to obtain a MOF-74 (MOF) / Zn @Cu negative electrode current collector, wherein the type of MOF array layer was MOF-74, whose structural formula is described below, the type of lithium-philic plating layer was Zn, and the substrate was copper. The corresponding MOF array layer thickness was 4.6 μm.

[0172] Embodiment 11

[0173] The preparation method is basically the same as that in Example 1, except that:

[0174] (Sn( Preparation of )-BDC)MOF / Sn@Cu negative electrode current collector:

[0175] Step 1 (S1) Preparation of tinned copper foil: The tinned copper foil was prepared by magnetron sputtering, and the sputtering / electron beam / ICP-CVD (base pressure <1×10 -6 Based on the deposition conditions of plasma gas flow rate of 100 sccm, plasma power of 200 W, and sputtering time of 60 s, a 100 nm tin layer was deposited on the copper foil substrate.

[0176] Step 2 (S2) pretreatment of tinned copper foil: the pre-prepared tinned copper foil was immersed in a 1 M ammonium persulfate (APS) solution for 10 min for oxidation treatment, then washed with deionized water and anhydrous ethanol for multiple times, and dried in a 60° C. forced air drying oven for later use.

[0177] Step 3 (S3) Construction of MOF array layer: First, 1 mmol of terephthalic acid (BDC) and 2 mmol of NaOH were dissolved in 10 mL of deionized water and ultrasonicated for 10 min to form a uniform solution. Then, the tinned copper foil treated with S2 was placed in the above-prepared solution and transferred to a 25 mL reactor for hydrothermal reaction at 120 °C for 24 h. After the reaction, it was cooled to room temperature, and then the surface impurities were rinsed with deionized water and dried in vacuum at 60 °C to obtain (Sn( )-BDC)MOF / Sn@Cu negative electrode current collector, wherein the type of MOF is Sn( )-BDC, whose structural formula is described below, the type of lithium-philic coating is Sn, the substrate is copper, and the corresponding MOF array layer thickness is 7.8 μm.

[0178] Example 12

[0179] The preparation method is basically the same as that of Example 1, except that:

[0180] Preparation of lithium metal anode: Pre-deposition of lithium metal was performed by assembling a half-cell. In the half-cell, the current collector was used as the positive electrode, commercial lithium foil was used as the negative electrode, 1 M LiTFSI / DOL+DME (volume ratio of 1:1) was used as the electrolyte, and PE was used as the separator. -2 The pre-deposition capacity was 1 mAh cm-2 at a current density of 1. -2 of electrodes.

[0181] Example 13

[0182] The preparation method is basically the same as that of Example 1, except that:

[0183] Preparation of lithium metal anode: Pre-deposition of lithium metal was performed by assembling a half-cell. In the half-cell, the current collector was used as the positive electrode, commercial lithium foil was used as the negative electrode, 1 M LiTFSI / DOL+DME (volume ratio of 1:1) was used as the electrolyte, and PE was used as the separator. -2 The electrochemical deposition method was used to discharge for 5 h at a current density of 5 mAh cm -2 of electrodes.

[0184] Embodiment 14

[0185] The preparation method is basically the same as that of Example 1, except that:

[0186] Preparation of lithium metal anode: Pre-deposition of lithium metal was performed by assembling a half-cell. In the half-cell, the current collector was used as the positive electrode, commercial lithium foil was used as the negative electrode, 1 M LiTFSI / DOL+DME (volume ratio of 1:1) was used as the electrolyte, and PE was used as the separator. -2 The electrochemical deposition method was used to discharge for 15 h at a current density of 15 mAh cm -2 of electrodes.

[0187] Embodiment 15

[0188] The preparation method is basically the same as that of Example 1, except that:

[0189] Li / LiFePO 4 The electrolyte system in the battery is a gel electrolyte obtained by dissolving a high molecular polymer, and its components are polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) + 1 M LiTFSI / DOL + DME (volume ratio is 1:1).

[0190] Preparation of gel electrolyte: First, PVDF-HFP was dissolved in acetone (PVDF-HFP: acetone = 1:8), stirred at 50 °C for 2 h to obtain a uniform transparent slurry, quickly scraped on aluminum foil and vacuum dried at 100 °C for 24 h to obtain a polymer film with a thickness of 22 μm, then the polymer film was immersed in 1 M LiTFSI / DOL+DME (volume ratio of 1:1) electrolyte for 24 h and then taken out to remove excess electrolyte on the surface. The liquid retention of the obtained gel polymer electrolyte was controlled at 300wt%.

[0191] Battery assembly: Based on the copper-based current collector with in-situ growth of lithium anode uniformly deposited as prepared in Example 1, lithium was pre-deposited as the anode to commercialize lithium secondary batteries with LiFePO 4 As the positive electrode, PVDF-HFP+1 M LiTFSI / DOL+DME (volume ratio of 1:1) is used as the electrolyte membrane. The positive electrode sheet, gel electrolyte membrane and lithium metal negative electrode are placed in sequence, so that the electrolyte membrane is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role, and the battery is assembled into a stacked battery.

[0192] Example 16

[0193] The preparation method is basically the same as that of Example 11, except that:

[0194] Li / LiFePO 4The electrolyte system in the battery is a gel electrolyte obtained by in-situ thermal curing polymerization, and its components are cellulose acetate / polyethylene glycol diacrylate (CA / PEGDA) + 1 M LiPF6 / ethylene carbonate (EC) + diethyl carbonate (DEC) (volume ratio of 1:1).

[0195] Preparation of gel electrolyte: 5 g polymer matrix CA, 5 g crosslinker PEGDA (Mn=400) and 0.05 g initiator azobisisobutyronitrile (AIBN) were added to 50 g 1 M LiPF 6 / EC+DEC liquid electrolyte was stirred at room temperature for 12 h to obtain an electrolyte precursor solution, and then the above precursor solution was kept at 70 °C for 1 h to obtain a CA / PEGDA gel electrolyte.

[0196] Battery assembly: Based on the copper-based current collector with in-situ growth of lithium anode uniformly deposited as prepared in Example 1, lithium was pre-deposited as the anode to commercialize lithium secondary batteries with LiFePO 4 As the positive electrode, PE is the separator. The positive electrode sheet, the separator and the lithium metal negative electrode are placed in order so that the electrolyte membrane is between the positive electrode sheet and the negative electrode sheet to play an isolating role. Then the electrolyte precursor solution is injected into the battery and left to stand for 6 h to ensure that the electrode and the separator are completely infiltrated. Finally, the battery is heated at 70 ° C for 1 h to allow the electrolyte precursor solution to be polymerized and cross-linked in situ in the battery to obtain a polymer lithium secondary battery.

[0197] Embodiment 17

[0198] The preparation method is basically the same as that of Example 1, except that:

[0199] Li / LiFePO 4 The electrolyte component in the battery is a solid electrolyte, which is composed of 60wt% polyethylene oxide PEO+13wt% lithium bis(trifluoromethanesulfonic acid) imide (LiTFSI)+27wt% plastic succinonitrile (SN).

[0200] Preparation of positive electrode sheet: LiFePO 4 The conductive agent acetylene black, the binder PVDF and the polymer electrolyte components were mixed in a mass ratio of 6:1.5:1.5:1, and an appropriate amount of NMP was added to grind into a uniform slurry. Then, the positive electrode slurry was evenly coated on a 12 μm aluminum foil, vacuum dried at 80 °C for 12 h, and punched into 4*5 cm 2 The electrode sheet is reserved. 4 The surface capacity of the positive electrode is 123 mAh . cm -2 .

[0201] Preparation of solid electrolyte: PEO and LiTFSI (Li + :PEO=1:32) was dissolved in acetonitrile and stirred at room temperature for 24 h. Subsequently, SN was added to the above solution and stirred for 12 h to prepare a polymer electrolyte slurry, which was then coated on a polytetrafluoroethylene plate and dried at 40 °C in vacuum for 24 h to remove the acetonitrile solvent, thereby obtaining a solid electrolyte membrane with a thickness of 25 μm.

[0202] Battery assembly: Based on the copper-based current collector with in-situ growth of lithium anode uniformly deposited as prepared in Example 1, lithium was pre-deposited as the anode to commercialize lithium secondary batteries with LiFePO 4 As the positive electrode, PEO / LiTFSI / SN is used as the electrolyte membrane. The positive electrode sheet, solid electrolyte membrane and lithium metal negative electrode are placed in order so that the electrolyte membrane is placed between the positive electrode sheet and the negative electrode sheet to play an isolating role. The stacked cells are then assembled at 100°C and 250 MPa for 2 min to obtain an all-solid-state lithium secondary battery.

[0203] Comparative Example 1

[0204] Negative electrode current collector: Commercial copper foil is used as the negative electrode current collector, and the negative electrode current collector does not contain a MOF array layer or a lithium-philic coating layer.

[0205] Preparation of negative electrode sheet: same as in Example 1.

[0206] Preparation of positive electrode sheet: same as in Example 1.

[0207] Isolation film: same as in Example 1.

[0208] Battery assembly: Same as in Example 1.

[0209] Comparative Example 2

[0210] Preparation of MOF@Cu negative electrode current collector: The pre-synthesized MOF and binder PVDF were mixed in a mass ratio of 9:1, and an appropriate amount of NMP was added to grind into a uniform slurry. The slurry was coated on a commercial copper foil with a preparation device, and vacuum dried at 80°C for 12 h to obtain a MOF@Cu negative electrode current collector, which did not contain a lithium-philic coating.

[0211] Preparation of negative electrode sheet: same as in Example 1.

[0212] Preparation of positive electrode sheet: same as in Example 1.

[0213] Isolation film: same as in Example 1.

[0214] Battery assembly: Same as in Example 1.

[0215] Comparative Example 3

[0216] Preparation of Zn@Cu negative electrode current collector: The zinc-coated copper foil current collector was prepared by magnetron sputtering. A zinc coating with a thickness of 100 nm was deposited on the surface of the commercial copper foil as the substrate, thereby obtaining the Zn@Cu negative electrode current collector, which did not contain a MOF array layer.

[0217] Preparation of negative electrode sheet: same as in Example 1.

[0218] Preparation of positive electrode sheet: same as in Example 1.

[0219] Isolation film: same as in Example 1.

[0220] Battery assembly: Same as in Example 1.

[0221] Comparative Example 4

[0222] Preparation of Mg@Cu current collector: The magnesium-coated copper foil current collector was prepared by magnetron sputtering. A commercial copper foil was used as the substrate, and a magnesium-coated layer with a thickness of 100 nm was deposited on the surface of the copper foil. There was no MOF array layer in the negative electrode current collector.

[0223] Preparation of negative electrode sheet: same as in Example 1.

[0224] Preparation of positive electrode sheet: same as in Example 1.

[0225] Isolation film: same as in Example 1.

[0226] Battery assembly: Same as in Example 1.

[0227] Comparative Example 5

[0228] Preparation of Sn@Cu negative electrode current collector: The tin-plated copper foil current collector was prepared by magnetron sputtering. A commercial copper foil was used as the substrate, and a 100 nm thick tin layer was deposited on the surface of the copper foil. There was no MOF array layer in the negative electrode current collector.

[0229] Preparation of negative electrode sheet: same as in Example 1.

[0230] Preparation of positive electrode sheet: same as in Example 1.

[0231] Isolation film: same as in Example 1.

[0232] Battery assembly: Same as in Example 1.

[0233] The specific parameter settings of Examples 1 to 17 and Comparative Examples 1 to 5 are shown in Table 1.

[0234] Table 1

[0235]

[0236] In Table 1, MOF types include ZIF-8, MOF-74(Mg), Sn( )-BDC MOF, their structural formulas are as follows:

[0237]

[0238] The charging and discharging performance test process of the lithium secondary batteries in the above-mentioned embodiments 1 to 16 and comparative examples 1 to 5 is set as follows: the operating voltage range is set to 2.5 to 3.7 V, and the cycle test is performed by constant current charging and discharging, wherein the test current is 0.33 C (current density is about 48 mA cm -2 ), the test temperature is 25℃.

[0239] In Example 17, the charging and discharging performance test process of the all-solid-state lithium secondary battery is set as follows: the operating voltage range is set to 2.5~3.7 V, and the cycle test is performed by constant current charging and discharging, wherein the test current is 0.1 C (current density is about 10 mA . cm -2 ), the test temperature is 70℃.

[0240] Characterization of the surface morphology of the lithium metal negative electrode in Examples 1 to 17 and Comparative Examples 1 to 5: The lithium secondary batteries after the above-mentioned cycles for n weeks were disassembled, and the surface morphology of the metal lithium negative electrode plates was characterized by field emission scanning electron microscopy (SEM) to observe whether lithium dendrites were generated.

[0241] The lithium secondary batteries of Examples 1 to 17 and Comparative Examples 1 to 5 were tested for the first-week discharge specific capacity, first-week coulombic efficiency, number of cycles, and capacity retention rate after cycles. The experimental results are shown in Table 2, which shows the performance test results of the lithium secondary batteries of Examples 1 to 17 and Comparative Examples 1 to 5.

[0242] Table 2

[0243]

[0244] It can be seen from Examples 1 to 5 that as the reaction time increases, the thickness of the MOF array layer also increases. When the thickness of the MOF array layer is small (Examples 2 to 3), the morphology of the MOF array layer on the surface of the galvanized copper foil is uneven, it is difficult to form a dense layer and it is easy to crack. The volume change during the cycle causes the mechanical stability of the array layer to deteriorate, resulting in a shortened cycle life of the battery and accelerated capacity decay. As the thickness of the MOF array layer increases (Examples 4 to 5), the MOF array layer particles are closely stacked, but the increase in the thickness of the array layer will reduce the ion transmission capacity between the negative electrode and the electrolyte, and at the same time make the Li +The transmission and diffusion paths are further extended, and the battery polarization increases, the first cycle coulombic efficiency decreases, and the cycle stability deteriorates. Compared with the above current collector, the MOF array layer with a thickness of 1 μm (Example 1) exhibits the best cycle performance and high coulombic efficiency. Therefore, the MOF-Zn@Cu negative electrode current collector prepared under this condition is preferred.

[0245] It can be seen from Examples 6 and 7 that the compactness of the MOF array layer in the current collector is crucial to the cycle life of the lithium secondary battery. If the MOF array layer has poor compactness (Example 7), surface defects will lead to Li + The flux is uneven, which promotes the growth of lithium dendrites and reduces the battery cycle life; good MOF array layer density (Example 6) can make Li + It is evenly distributed on the surface of the electrode, thereby inducing uniform deposition of lithium. On the other hand, it can avoid direct contact between the electrolyte and highly reducing lithium, effectively reduce the occurrence of side reactions, and improve the coulombic efficiency and cycle stability of the battery.

[0246] Comparing Example 1 with Examples 8 to 9, it can be seen that the thickness of the lithium-philic plating layer in the copper-based current collector is different, and the battery exhibits different first-week discharge specific capacity and cycle stability. Among them, when the thickness of the lithium-philic zinc layer is 100 nm (Example 1), the battery exhibits good first-week discharge specific capacity and capacity retention rate after cycling. When the thickness of the lithium-philic zinc layer is small (Example 8), it is difficult to provide sufficient deposition space for more lithium during the charging process, and excessive metallic lithium will be deposited on the surface of the alloy layer, which may induce lithium dendrite growth and affect battery performance; when the thickness is high (Example 9), since the conductivity of metallic zinc is worse than that of metallic copper, it is easy to increase the internal resistance of the battery, causing greater polarization of the battery, reducing the specific capacity of the battery, and further reducing the energy density of the battery.

[0247] It can be seen from Example 1, Examples 10-11 and Comparative Examples 1-5 that the copper-based current collector with in-situ growth and uniform lithium deposition prepared in Example 1 exhibits excellent cycle stability and high first-cycle coulomb efficiency, which is attributed to the uniform and dense MOF array layer, due to its inherent nanopores similar to the "ion sieve" effect, which is Li +It provides a uniform transmission channel and can also be used as a buffer layer to effectively reduce the volume change on the negative electrode side. At the same time, the lithium-philic coating (zinc layer, magnesium layer and tin layer) provides an effective nucleation site for the deposition of lithium. During the charging process, Li and the lithium-philic coating form an alloy, thereby inducing the uniform deposition of lithium and effectively inhibiting the growth of lithium dendrites. Generally, the ordinary copper current collector (Comparative Example 1) is prone to uneven lithium deposition and uncontrollable growth of lithium dendrites during the cycle due to its inherent surface roughness, which reduces the electrochemical performance of the battery; the MOF array layer is constructed on the copper foil surface by a non-in-situ coating method (Comparative Example 2), which is prone to coating defects due to the accidental nature of artificial coating, and the coating is damaged during repeated lithium deposition / dissolution, and the protective effect fails; the lithium-philic coating-based copper foil current collector (Comparative Examples 3~5) provides a lithium-philic nucleation site, but the volume change on the negative electrode side during the cycle easily causes the lithium-philic coating structure to collapse and pulverize severely, making it difficult to provide an effective space for lithium deposition, thereby reducing the battery coulomb efficiency.

[0248] It can be seen from Examples 1 and 12 to 14 that the size of the negative electrode pre-deposited lithium capacity has a certain influence on the battery performance. When the pre-deposited lithium capacity on the negative electrode side is small (Examples 15 to 16), the consumption of electrolyte and negative electrode due to the side reactions on the electrode surface during the charge and discharge process causes a serious shortage of lithium source on the negative electrode side, resulting in a decrease in the capacity retention rate of the lithium secondary battery after 200 cycles. When the pre-deposited lithium capacity on the negative electrode is large and the lithium source is sufficient (Examples 1 and 17), the battery still exhibits excellent cycle stability and high coulombic efficiency after 200 cycles.

[0249] It can be seen from Examples 1 and 15 to 17 that different electrolyte systems will also affect the battery performance based on the bifunctional copper-based current collector prepared in Example 1. Among them, the use of in-situ thermally cured gel electrolyte (Example 16) helps to improve the cycle performance and safety of the battery. This is attributed to the good mechanical properties of the gel electrolyte, which can effectively limit the volume change of the lithium negative electrode during the cycle, and the small amount of liquid electrolyte contained can significantly improve the Li + The transmission speed can be fully infiltrated into the electrode through in-situ thermal curing. Compared with the gel electrolyte obtained by dissolving the polymer (Example 15), the battery polarization is reduced and the first-cycle coulomb efficiency is increased. However, all-solid-state lithium secondary batteries (Example 17) often have electrode / electrolyte interface contact problems and low ionic conductivity, which easily cause the battery polarization to increase and the electrochemical performance to decay.

[0250] Further, regarding the surface morphology characterization of the lithium metal negative electrode of the lithium secondary battery in Examples 1 to 17 and Comparative Examples 1 to 5 of the present application, refer to Figure 10a From the SEM image, it can be seen that no dendrites were generated after cycling; Figure 10b From the SEM image, it can be seen that slight dendrites are generated after cycling;Figure 10c From the SEM image, it can be seen that severe dendrites are generated after cycling.

[0251] Combining the test results of the above Examples 1 to 17 and Comparative Examples 1 to 5, it can be seen that, compared with the prior art, the copper-based current collector with in-situ growth of uniform lithium deposition and its preparation method, as well as the lithium secondary battery using the current collector of the present application improve the cycle stability and safety performance of the lithium secondary battery.

[0252] 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 negative electrode current collector, It is characterized in that The negative electrode current collector comprises: a current collector substrate, a lithium-philic coating layer and a metal organic framework array layer in sequence; The lithium-philic coating is arranged on the current collector substrate, and the metal organic framework array layer is in-situ grown on the surface of the lithium-philic coating, and the metal organic framework array layer has a nanopore structure; the thickness of the lithium-philic coating is 50nm~100 nm, and the thickness of the metal organic framework array layer is 0.5 μm~8 μm.

2. The negative electrode current collector according to claim 1, It is characterized in that The metal organic framework array layer is composed of metal ion coordination centers and organic ligands. The metal ion coordination center is zinc ion Zn 2+ 、Sn 2+ or magnesium ion Mg 2+ One or more of the following; The organic ligand is one or more selected from 2-methylimidazole, nicotinic acid, isonicotinic acid, terephthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxyterephthalic acid dimethyl ester, 1,2,4-triazole, and oxalate.

3. The negative electrode current collector according to claim 2, It is characterized in that The metal ion coordination center is zinc ion Zn 2 + , the organic ligand is 2-methylimidazole.

4. The negative electrode current collector according to any one of claims 1 to 3, It is characterized in that The thickness of the metal organic framework array layer is 1 μm to 8 μm.

5. The negative electrode current collector according to claim 4, It is characterized in that The thickness of the metal organic framework array layer is 1 μm to 4 μm.

6. The negative electrode current collector according to any one of claims 1 to 3 and 5, It is characterized in that The current collector substrate is metal or non-metal; The metal is one or more selected from Cu, Al, Fe, Ni, Ti and stainless steel; The non-metal is one or more selected from graphene and carbon fiber.

7. A method for preparing the negative electrode current collector according to any one of claims 1 to 6, It is characterized in that include: A lithium-philic coating with a thickness of 50 nm to 100 nm was deposited on the current collector substrate by magnetron sputtering; In-situ growth of a metal organic framework array layer with a nanopore structure and a thickness of 0.5 μm to 8 μm is performed on the surface of the lithium-philic coating by a wet chemical method.

8. The method for preparing the negative electrode current collector according to claim 7, It is characterized in that The reaction time for in-situ growth is 5 h~36 h, and the reaction temperature is 25 ℃~120 ℃.

9. A negative electrode sheet, It is characterized in that The negative electrode sheet comprises the negative electrode current collector according to any one of claims 1 to 6.

10. The negative electrode sheet according to claim 9, It is characterized in that The negative electrode plate further includes pre-deposited lithium loaded on the negative electrode current collector, and the capacity of the pre-deposited lithium in the negative electrode plate is 1 mAh cm -2 ~15 mAh cm -2 .

11. The negative electrode sheet according to claim 10, It is characterized in that The capacity of the pre-deposited lithium in the negative electrode plate is 5 mAh cm -2 ~15 mAh cm -2 .

12. A lithium secondary battery, It is characterized in that The lithium secondary battery comprises the negative electrode sheet according to claim 10 or 11.

13. A battery module, It is characterized in that The battery module includes the lithium secondary battery according to claim 12.

14. A battery pack, It is characterized in that The battery pack includes the battery module according to claim 13.

15. An electrical device, It is characterized in that The electrical device comprises at least one of the lithium secondary battery of claim 12 , the battery module of claim 13 , and the battery pack of claim 14 .

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