CN115842133A

CN115842133A - Negative current collector, preparation method thereof, negative pole piece with negative current collector and lithium secondary battery

Info

Publication number: CN115842133A
Application number: CN202111655217.2A
Authority: CN
Inventors: 张楠楠; 刘成勇; 薛文文; 何晓宁; 黄显; 胡波兵
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2023-03-24
Also published as: WO2023125023A1

Abstract

The application 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 current collector of the present application possesses in proper order: the lithium ion battery comprises a current collector substrate, a lithium-philic coating and a metal organic frame array layer, wherein the lithium-philic coating is arranged on the current collector substrate, the metal organic frame array layer grows on the surface of the lithium-philic coating in situ, and the metal organic frame array layer has a nanopore structure. The negative current collector can induce the uniform deposition of lithium, inhibit the growth of lithium dendrites and improve the electrochemical performance of the lithium secondary battery.

Description

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

Technical Field

The application relates to the field of batteries, in particular to 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.

Background

With the strong demand of people on renewable energy and the continuous improvement of the demand on new energy automobiles, the lithium secondary battery using the traditional graphite cathode is not enough to meet the increasing social demand, so that the development of a large-scale energy storage system with high energy density, safety and reliability is very important. Lithium metal has high theoretical specific capacity (3680 mAh g) ^-1 ) And the lowest reduction potential (-3.04v vs. she), are considered ideal negative electrode materials for the development of a new generation of high specific energy batteries.

However, the problems of dendrite growth, irreversible lithium loss, and volume change, which are encountered in the lithium metal negative electrode, greatly limit the practical application of the lithium secondary battery. The lithium negative electrode is easy to react with electrolyte to spontaneously generate an unstable SEI film on the surface due to high chemical activity, and the SEI film with uneven chemistry and unstable structure can be damaged in the repeated lithium deposition/precipitation process, so that Li on the interface is generated ⁺ Flux is unevenly distributed, so that generation of dendritic lithium dendrites is triggered, and in addition, in the lithium precipitation process, the lithium dendrites are easily broken from roots and converted into dead lithium, so that the coulomb efficiency of the battery is reduced, the capacity is seriously attenuated, and even more, the continuously-grown lithium dendrites can pierce through a diaphragm to cause short circuit of the battery and cause safety problems such as thermal runaway and the like. Therefore, designing a dendrite-free, highly stable lithium negative electrode is of great significance for developing a high-performance lithium secondary battery.

The prior art provides a copper-based current collector modified based on a protective coating, wherein an organic-inorganic composite protective coating consisting of polyacrylonitrile, polymethyl methacrylate, nano silicon dioxide, a plasticizer and the like is loaded on a commercially available copper foil, and the protective coating effectively adjusts Li on the surface of a negative electrode by virtue of high ionic conductivity and surface polar functional groups of the protective coating ⁺ Distributing and inducing the uniform deposition of lithium metal; at the same time, the user can select the desired position,good flexibility and mechanical strength, can adapt to the volume change of lithium metal in the circulating process, effectively inhibits the growth of lithium dendrites, and realizes a lithium secondary battery with long service life and high safety.

However, the substrate protective coating is usually constructed by an ex-situ coating method, the protective layer obtained by ex-situ coating often causes local unevenness of the coating due to the accidental nature of manual coating, and a gap is generated between the coating and the substrate along with the volatilization of a coating solution in the drying process, so that the coating is easy to fall off or break under the condition of high current density or high deposition capacity, and the protective effect is ineffective.

Although the lithium-philic coating can be used as an induction seed crystal for the deposition and nucleation of the metallic lithium to a certain extent, the Li is effectively improved ⁺ The distribution on the surface of the current collector inhibits the growth of dendrites. However, in the repeated lithium deposition/precipitation process, the volume change at the negative electrode side easily causes collapse of the structure of the lithium-philic plating layer and severe pulverization, and it is difficult to provide an effective space for lithium deposition, and in addition, the plating layer may have a side reaction with the electrolyte solution, resulting in reduced coulombic efficiency and shortened cycle life.

Disclosure of Invention

The present invention has been made in view of the above problems, and an object of the present invention is to provide a negative electrode current collector capable of inducing uniform deposition of lithium, suppressing growth of lithium dendrites, and improving electrochemical performance of a lithium secondary battery, a method for manufacturing the same, a pole piece including the same, and a lithium secondary battery, a battery module, a battery pack, and an electric device.

In order to achieve the above object, a first aspect of the present invention provides a negative electrode current collector, including: the lithium ion battery comprises a current collector substrate, a lithium-philic coating and a metal organic framework array layer, wherein the lithium-philic coating is arranged on the current collector substrate, and the metal organic framework array layer (hereinafter sometimes also referred to as the MOF array layer) is grown in situ on the surface of the lithium-philic coating, and has a nanopore structure.

The negative current collector is prepared on a lithium-philic coating substrate by simple in-situ generationAnd the MOF array layer with a unique nano-pore structure is formed by the growth. Ordered nano-pores inherent in the MOF array layer have the effect similar to that of an ion sieve and can effectively and uniformly Li ⁺ Flux is beneficial to realizing uniform deposition of metal lithium, and meanwhile, the 'ion sieve' array layer can avoid direct contact of an electrolyte solvent and a high-reducibility metal lithium layer, reduce side reaction and improve the coulomb efficiency and the cycle stability of the lithium secondary battery; in addition, the lithium-philic coating provides effective nucleation sites for the deposition of metallic lithium, li during charging ⁺ The lithium ion secondary battery is easy to form alloy with the lithium-philic coating, and can effectively reduce the deposition interface energy between lithium metal and a current collector, thereby inducing the uniform deposition of the lithium metal, inhibiting the growth of lithium dendrites and improving the electrochemical performance of the lithium secondary battery.

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 metal ion coordination centers and organic ligands, and the metal coordination centers are zinc ions (Zn) ²⁺ ) Tin (Sn) ²⁺ ) Or magnesium (Mg) ²⁺ ) More than one of them.

In some embodiments, in the negative electrode current collector of the present application, the organic ligand is one or more selected from the group consisting of 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, an organic ligand capable of matching the coordination center of the metal ion needs to be selected to realize the negative electrode current collector capable of bifunctional induced uniform lithium deposition.

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 200nm to 8 μm. If the thickness of the MOF array layer exceeds 8 μm, the ion transmission capability between an electrode and an electrolyte is reduced, the polarization of a battery is increased, and if the thickness of the MOF array layer is less than 200nm, the mechanical stability of a coating layer caused by volume change in the circulation process is poor, so that a protective layer with high mechanical stability and fast ion transmission performance can be obtained by enabling the thickness of the MOF array layer to be in the range of 200 nm-8 μm, and the growth of lithium dendrite in the circulation process is further inhibited.

In some embodiments, in the negative electrode current collector of the present application, the lithium-philic plating layer has a thickness of 50 to 500nm. If the thickness of the lithium-philic coating exceeds 500nm, the internal resistance of the battery is increased due to the poorer conductivity of the metal zinc than copper, meanwhile, the energy density is reduced due to the corresponding increase of the battery quality, if the thickness of the lithium-philic coating is less than 50nm, the lower coating thickness is difficult to provide enough deposition space for more lithium, excessive lithium is deposited on the surface of the alloy layer, and the growth of lithium dendrite is induced, so that the lithium uniform deposition induced by the optimal lithium-philic coating can be obtained by enabling the thickness of the lithium-philic coating to be in the range of 50-500 nm, and the smooth deposition appearance is obtained.

In some embodiments, in the negative electrode collector of the present application, the collector substrate is 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. 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.

A second aspect of the present application is to provide a method for preparing a negative electrode current collector, including: depositing a lithium-philic coating on the copper foil substrate by a magnetron sputtering method, wherein the target material is more than one selected from Zn, sn and Mg; and carrying out in-situ growth of a metal organic framework array layer (MOF array layer) with 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 realized by a wet chemical method (namely, a wet chemical method) which is simple to operate and low in cost. According to the preparation method of the negative current collector, the current collector obtained by the in-situ growth lithium metal uniform deposition can inhibit the growth of lithium dendrites, so that the lithium secondary battery shows high coulombic efficiency and excellent cycling stability, and the preparation method is low in cost, simple to operate, high in controllability and capable of being used for commercial production.

In some embodiments, in the method for preparing the negative electrode current collector of the present application, the in-situ growth is performed for a reaction time of 5 to 36 hours and a reaction temperature of 25 to 120 ℃. If the reaction time of in-situ growth exceeds 36h, the thickness of the obtained MOF layer is too large, which is not favorable for ion transmission between an electrode and an electrolyte, and if the reaction time of in-situ growth is less than 5h, the MOF layer is not uniform in growth morphology on the surface of a substrate, a compact layer is difficult to form, and cracks are easy to generate, so that the reaction time of in-situ growth is within the range of 5-36 h, the MOF layer with uniform and controllable thickness can be obtained, and the subsequent uniform deposition of lithium is favorable. Moreover, if the reaction temperature of in-situ growth exceeds 120 ℃, the preparation process is complicated, the cost is increased, and if the reaction temperature is lower than 25 ℃, the ion migration rate in the reaction solution at low temperature is reduced, and the reaction is incomplete, so that the uniform MOF array layer which is simple and convenient to operate and low in cost can be obtained by enabling the reaction temperature of in-situ growth to be in the range of 25-120 ℃.

The third aspect of the present application is to provide a negative electrode tab, which includes the negative electrode current collector according to the first aspect of the present application.

A fourth aspect of the present application is to provide a lithium secondary battery comprising the negative electrode tab according to the third aspect of the present application.

A fifth aspect of the present application is to provide a battery module including the lithium secondary battery according to the fourth aspect of the present application.

A sixth aspect of the present application is to provide a battery pack including the battery module according to the fifth aspect of the present application.

A seventh aspect of the present application is to provide an electric device including at least one of the lithium secondary battery according to the fourth aspect of the present application, the battery module according to the fifth aspect of the present application, and the battery pack according to the sixth aspect of the present application.

According to the application, an MOF array layer with a unique nano-pore channel structure is formed on a negative current collector taking a lithium-philic coating as a substrate through simple in-situ growth, so that the MOF array layer is Li ⁺ A uniform transmission channel is provided, and the lithium anode can be used as a physical barrier to avoid direct contact of the lithium anode and electrolyte, so that side reactions are reduced; and the uniform deposition of lithium is induced, the growth of lithium dendrite is effectively inhibited, and for a lithium secondary battery using the negative electrode current collector, high coulombic efficiency and excellent cycling stability are shown, so that the electrochemical performance of the lithium secondary battery is greatly improved.

Drawings

FIG. 1a is a schematic illustration of a prior art lithium deposited copper-based current collector; fig. 1b is a schematic illustration of an in-situ grown lithium uniformly deposited copper-based current collector according to one embodiment of the present application.

Fig. 2 is a schematic structural view of a current collector according to another embodiment of the present application.

FIG. 3 is a schematic representation of the crystal structure of a ZIF-8 MOF of yet another embodiment of the present application.

Fig. 4 is a schematic view of a lithium secondary battery according to an embodiment of the present application.

Fig. 5 is an exploded view of the lithium secondary battery according to the embodiment of the present application shown in fig. 4.

Fig. 6 is a schematic view of a battery module according to an embodiment of the present application.

Fig. 7 is a schematic view of a battery pack according to an embodiment of the present application.

Fig. 8 is an exploded view of the battery pack of fig. 7 according to one embodiment of the present application.

Fig. 9 is a schematic diagram of an electric device in which a lithium secondary battery according to an embodiment of the present application is used as a power source.

10a, 10b, 10c are surface topography characterizations of lithium metal negative electrodes of the lithium secondary batteries of examples 1-17 and comparative examples 1-5 of the present application, wherein FIG. 10a is an SEM image of no dendrites generated after cycling; FIG. 10b is an SEM image of slight dendrite generation after cycling; fig. 10c is an SEM image of severe dendrite generation after cycling.

Description of reference numerals:

1, a battery pack; 2, putting the box body on the box body; 3, discharging the box body; 4 a battery module; 5 a lithium secondary battery; 51 a housing; 52 an electrode assembly; 53 Top cover Assembly

Detailed Description

Hereinafter, embodiments of the negative electrode current collector and the method for manufacturing the same, the negative electrode sheet, the lithium secondary battery, the battery module, the battery pack, and the electric device according to the present invention are specifically disclosed in detail with reference to the drawings as appropriate. But a detailed description thereof will be omitted. For example, detailed descriptions of already known matters and repetitive descriptions of actually the same configurations may be omitted. This is to avoid unnecessarily obscuring the following description, and to facilitate understanding by those skilled in the art. The drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

The "ranges" disclosed herein are defined in terms of lower limits and upper limits, with a given range being defined by a selection of one lower limit and one upper limit that define the boundaries of the particular range. Ranges defined in this manner may or may not include endpoints and may be arbitrarily combined, i.e., any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, 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 are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In this application, unless otherwise stated, the numerical range "a-b" represents a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 to 5" have been listed herein, and "0 to 5" is only a shorthand representation of the combination of these numbers. In addition, when a parameter is an integer of 2 or more, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3,4, 5, 6, 7, 8, 9, 10, 11, 12, or the like.

All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, if not specifically stated.

All technical and optional features of the present application may be combined with each other to form new solutions, if not otherwise specified.

The terms "comprises" and "comprising" as used herein mean either open or closed unless otherwise specified. For example, the terms "comprising" and "comprises" may mean that other components not listed may also be included or included, or that only listed components may be included or included.

In this application, the term "or" is inclusive, if not otherwise specified. For example, the phrase "a or B" means "a, B, or both a and B. More specifically, either of the following conditions satisfies the condition "a or B": a is true (or present) and B is false (or not present); a is false (or not present) and B is true (or present); or both a and B are true (or present).

Negative current collector

In one embodiment of the present application, there is provided a negative electrode current collector including, in order: the lithium ion battery comprises a current collector substrate, a lithium-philic coating and a metal organic frame array layer, wherein the lithium-philic coating is arranged on the current collector substrate, the metal organic frame array layer grows on the surface of the lithium-philic coating in situ, and the metal organic frame array layer has a nanopore structure. The metal organic framework array layer is composed of a metal ion coordination center and an organic ligand, wherein the metal coordination center is more than one of zinc, tin or magnesium, and the organic ligand is more than one selected from 2-methylimidazole, nicotinic acid, isonicotinic acid, terephthalic acid, 2, 5-dihydroxyterephthalic acid dimethyl ester, 1,2, 4-triazole and oxalate. From the viewpoint of simple production process, it is preferable that the metal coordination center is zinc and the organic ligand is 2-methylimidazole.

Referring to fig. 1a, it can be seen that the prior art, in which lithium is deposited on a copper-based current collector, easily results inUneven lithium deposition with consequent Li ⁺ The flux is unevenly distributed, triggering dendritic lithium dendrites. Resulting in a reduction in the coulombic efficiency of the cell, a severe capacity fade, and even continued growth of lithium dendrites can puncture the separator causing a cell segment.

Referring to fig. 1b, the present application can be seen from the fact that a compact and regular nanopore structure, which can be Li, is formed by in-situ growth of lithium deposition on a copper-based current collector ⁺ Provide uniform transmission channel so that Li ⁺ And the flow is uniform, so that the generation of lithium dendrites is inhibited, and the electrochemical performance of the battery is ensured.

Referring to fig. 2, as for the metal organic framework array layer with the nano-porous structure grown in situ on the surface of the lithium-philic plating layer substrate, it can be known that the MOF array layer is formed by in-situ growth on the lithium-philic plating layer (illustrated as a zinc-plated copper foil, i.e., a zinc-plated layer on a copper foil), and the MOF array layer has a compact and regular nano-porous structure, which can be a Li-porous structure ⁺ Provide uniform transmission channel so that Li ⁺ And uniformly flows through the filter.

The following will describe in detail the mechanism of MOF array layer growth, taking a specific example of zinc as a metal coordination center and 2-methylimidazole as an organic ligand.

Firstly, forming a ZnO thin layer on the surface of a zinc layer by simple pre-oxidation treatment, and then etching the ZnO by 2-methylimidazole (HMIM) to generate a large amount of Zn ²⁺ ，Zn ²⁺ The MOF array layer is coordinated with HMIM to form a uniform MOF array layer on the surface of the galvanized copper foil, the type of the MOF array layer is ZIF-8, and the structural formula of the MOF array layer is described later.

Referring to FIG. 3, the crystal structure of the MOF array layer of ZIF-8 formed above is a zeolite topology, belonging to the face-centered cubic system, I-43m space group, which can be regarded as being formed by Zn metal ²⁺ ZnN formed by linking to the N atom of methylimidazolyl ester (mIm) ₄ Tetrahedral structural units.

From the viewpoint of uniformity of the MOF array layer and fast and slow ion transport, the thickness of the metal-organic framework array layer is preferably 200nm to 8 μm.

The thickness of the lithium-philic plating layer is preferably 50 to 500nm from the viewpoint of whether it can provide a sufficient deposition space for more lithium and increase the energy density.

From the viewpoint of current collector conductivity, the current collector substrate is preferably a metal selected from one or more of Cu, al, fe, ni, ti, and stainless steel, or a nonmetal selected from one or more of graphene and carbon fiber, and from the viewpoint of a lower negative electrode lithium potential, the metal is more preferably Cu, and the nonmetal is graphene.

Preparation method of negative current collector

In one embodiment of the present application, there is provided a method of preparing a negative electrode current collector, including: depositing a lithium-philic coating on the copper foil substrate by a magnetron sputtering method, wherein the target is more than one selected from Zn, sn and Mg; and carrying out in-situ growth of a metal organic framework array layer (MOF array layer) with a nanopore structure on the surface of the lithium-philic coating by a wet chemical method. The magnetron sputtering method may be performed by a conventional method in the art, as long as the lithium-philic plating layer of the present application can be prepared. Further, the target is preferably Zn. The wet chemical method of the application is to make the surface of the lithium-philic coating contact with a compound solution with etching and coordination functions to form a coordination layer on the surface of the lithium-philic coating. This etching, coordination, is referred to as "in situ growth".

In addition, the lithium-philic coating may also be pretreated, including being oxidized, prior to forming the MOF array layer.

From the viewpoints of uniformity of the MOF array layer, high and low ion transmission speed and simple preparation process, the reaction time of in-situ growth is preferably 5 to 36 hours, and the reaction temperature is preferably 25 to 120 ℃.

Negative pole piece

In an embodiment of this application, provide a negative pole piece, the negative pole piece possesses the above-mentioned negative current collector of this application and sets up the negative film layer on negative current collector at least one surface.

Specifically, the electrode sheet of the present application is based on the negative electrode current collector of the present application, and is obtained by pre-depositing lithium. The pre-deposited lithium functions to construct a lithium-rich negative electrode for a lithium metal secondary battery. The lithium is supplemented to the cathode material through the pre-deposited lithium, and the irreversible lithium loss caused by the SEI film is offset, so that the total capacity and the energy density of the battery are improved.

In the application, a lithium foil is taken as a negative electrode, is immersed in electrolyte, and is discharged for a certain time by adopting an electrochemical deposition method, so that the pre-deposited lithium of the negative electrode can be controlled within the range of 1-15 mAh cm ^-2 And (4) the following steps. If the pre-deposited lithium capacity of the lithium negative electrode exceeds 15mAh cm ^-2 It will cause an excessive amount of lithium source on the negative electrode side, further resulting in a decrease in the energy density of the battery if it is less than 1mAh cm ^-2 Since the electrolyte and the negative electrode are consumed due to the occurrence of side reactions on the surface of the electrode during the charge and discharge processes, the lithium source on the negative electrode side is seriously insufficient, and therefore, the capacity of the lithium pre-deposited on the lithium negative electrode is 1 to 15mAh cm ^-2 So that a lithium metal negative electrode that can match positive electrodes of different capacities can be obtained.

As an example, the negative electrode current collector has two surfaces opposite in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two surfaces opposite to the negative electrode current collector.

The lithium secondary battery, the battery module, the battery pack, and the electric device according to the present invention will be described below with reference to the drawings as appropriate.

Lithium secondary battery

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

The lithium secondary battery comprises the negative pole piece, the positive pole piece, electrolyte and the isolating membrane. In the process of charging and discharging the battery, active ions are embedded and separated back and forth between the positive pole piece and the negative pole piece. The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The isolating membrane is arranged between the positive pole piece and the negative pole piece, mainly plays a role in preventing the short circuit of the positive pole and the negative pole, and can enable ions to pass through.

[ negative electrode sheet ]

The negative pole piece includes the negative pole mass flow body of above-mentioned this application and sets up the negative pole rete on the negative pole mass flow body at least one surface of this application.

[ Positive electrode sheet ]

The positive pole piece comprises a positive pole current collector and a positive pole film layer arranged on at least one surface of the positive pole current collector. In some embodiments, the positive electrode comprises a material capable of extracting and intercalating lithium ions. The positive electrode material is Li during charging ⁺ The electrolyte is removed from the positive electrode, migrates to the surface of the negative electrode through the electrolyte and is embedded into the negative electrode, and the discharging process is just reverse.

As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two surfaces opposite to the positive electrode current collector.

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

In some embodiments, the positive active material may employ a positive active material for a battery, which is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: olivine structured lithium-containing phosphates, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive electrode active material of a battery may be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of the lithium transition metal oxide may include, but are not limited to, lithium cobalt oxide (e.g., liCoO) ₂ ) Lithium nickel oxides (e.g., liNiO) ₂ ) Lithium manganese oxide (e.g., liMnO) ₂ 、LiMn ₂ O ₄ ) Lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., liNi) ₁ /3Co ₁ /3Mn ₁ /3O ₂ (may be abbreviated as NCM 333) and LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (may also be abbreviated as NCM 523) and LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (may be abbreviated as NCM 211) and LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (may be abbreviated as NCM 622) and LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (also abbreviated as NCM 811), lithium nickel cobalt aluminum oxides (e.g., liNi-Co-Al-O-Si) _0.85 Co _0.15 Al _0.05 O ₂ ) And modified compounds thereof, and the like. Examples of olivine structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (e.g., liFePO) ₄ (also referred to as LFP for short)), a composite material of lithium iron phosphate and carbon, and lithium manganese phosphate (e.g., liMnPO) ₄ ) At least one of a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

In some embodiments, it is preferable that the positive electrode active material is one or more selected from the group consisting of a polyanion oxide, a lithium transition metal composite oxide, and a compound of a lithium transition metal oxide with addition of other transition metals or non-transition metals. And further preferably, the polyanion oxide includes one structure selected from the two structures of olivine and NASICON, and the lithium transition metal complex 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 Li ⁺ Extraction and insertion from the positive electrode.

In some embodiments, the positive electrode film layer further optionally includes 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 fluoroacrylate resin.

In some embodiments, the positive electrode film layer further optionally includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

In some embodiments, the positive electrode sheet may be prepared by: dispersing the above components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; and coating the positive electrode slurry on a positive electrode current collector, and drying, cold pressing and the like to obtain the positive electrode piece.

[ electrolyte ]

The electrolyte plays a role in conducting ions between the positive pole piece and the negative pole piece. The kind of the electrolyte is not particularly limited and may be selected as desired. For example, the electrolyte may be a liquid electrolyte, a gel electrolyte, or a solid electrolyte. Each of which is described in detail below.

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

The lithium salt is selected from LiPF ₆ 、LiBF ₄ 、LiTFSI、LiClO ₄ 、LiAsF ₆ 、LiBOB、LiDFOB、LiTFOP、LiN(SO2RF) ₂ 、LiN(SO ₂ F)(SO ₂ RF), wherein the substituent RF = C _n F _2n+1 And n is an integer of 1 to 10.

The organic solvent is more than one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl formate, ethyl propionate, propyl propionate, methyl butyrate, ethyl acetate, acid anhydride, N-methyl pyrrolidone, N-methyl formamide, N-methyl acetamide, 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 ester and sulfur-containing cyclic organic ester.

Preferably, the concentration of the lithium salt in the electrolyte is 0.5 to 10mol/L, and the content of the organic solvent in the electrolyte is 60 to 90 mass%.

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

The polyether polymer is more than one selected from polyethylene oxide (PEO), polypropylene oxide (PPO), polyethylene glycol (PEG), polyethylene glycol dimethyl ether (EPGDME) and polysiloxane; the polyolefin polymer is selected from more than one of Polyethylene (PE), polypropylene (PP), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE) and polyvinyl chloride (PVC); the polynitrile polymer is Polyacrylonitrile (PAN) and/or polytrimeric nitrile amine; the polycarboxylate polymer is polymethyl methacrylate (PMMA) and/or polymethyl acrylate (PMA); the polycarbonate polymer is Polypropylene Carbonate (PC) and/or polyethylene carbonate (PEC).

The content of the polymer phase in the gel electrolyte is 0.1 to 99.9 mass%, and the content of the electrolyte phase in the gel electrolyte is 0.1 to 99.9 mass%.

The solid electrolyte is a polymer electrolyte, an inorganic solid electrolyte or a composite of the polymer electrolyte and the inorganic solid electrolyte, the polymer electrolyte consists of a polymer body and a lithium salt, and the polymer body is one selected from polyether polymers, polyolefin polymers, polynitrile polymers and polycarboxylate polymersThe above; 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 of 1 to 10; the inorganic solid electrolyte is one selected from oxide fast ion conductor, sulfide fast ion conductor and halide fast ion conductor.

The polyether polymer is more than one selected from polyethylene oxide, polypropylene oxide, polyethylene glycol dimethyl ether and polysiloxane; the polyolefin polymer is more than one selected from polyethylene, polypropylene, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene and polyvinyl chloride; the polynitrile polymer is polyacrylonitrile and/or polymacronitrile amine; the polycarboxylate polymer is polymethyl methacrylate and/or polymethyl acrylate; the polycarbonate polymer is polypropylene carbonate and/or polyethylene carbonate.

The oxide fast lithium ion conductor is selected from NASICON (Na) ⁺ superior conductor) structure, LISICON (Li) ⁺ superior conductor), garnet (Garnet), perovskite (Pervoskite); the sulfide fast lithium ion conductor is yLi ₂ S-(100-y)P ₂ S ₅ And MS ₂ Or LiqQ, wherein y is more than 1 and less than 100, M is selected from Si, ge and Sn, Q is selected from F, cl, br, I, O, N and PO ₄ ^3- 、SO ₄ ^2- 、BO ₃ ^3- 、SiO ₄ ^4- Q is a natural number of 1 to 4; the halide fast lithium ion conductor is Li _a CX _b Wherein C is one or more of Ga, in, sc, Y and La, X is one or more of F, cl and Br, a is more than 0 and less than or equal to 10, b is more than or equal to 1 and less than or equal to 13.

In some embodiments, the electrolyte is an electrolytic solution. The electrolyte includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis-fluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalato borate, lithium dioxaoxalato borate, lithium difluorodioxaoxalato phosphate, and lithium tetrafluorooxalato phosphate.

In some embodiments, the solvent may 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, dimethylsulfone, methylethylsulfone, and diethylsulfone.

In some embodiments, the electrolyte further optionally includes an additive. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives capable of improving certain properties of the battery, such as an additive for improving overcharge properties of the battery, an additive for improving high-temperature or low-temperature properties of the battery, and the like.

[ isolation film ]

In some embodiments, a separator is further included in the lithium secondary battery. The type of the separator is not particularly limited, and any known separator having a porous structure and good chemical and mechanical stability may be used.

In some embodiments, the material of the isolation film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

In some embodiments, the release film is preferably a polypropylene release film. The polypropylene separator is a conventional separator and has good chemical and mechanical stability, and a porous structure is preferred.

The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.

In some embodiments, the positive electrode tab, the negative electrode tab, and the separator may be manufactured into an electrode assembly through a winding process or a lamination process.

In some embodiments, the lithium secondary battery may include an exterior package. The exterior package may be used to enclose the electrode assembly and electrolyte.

In some embodiments, the outer package of the lithium secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, or the like. The exterior package of the lithium secondary battery may also be a pouch, such as a pouch-type pouch. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

The shape of the lithium secondary battery is not particularly limited, and may be a cylindrical shape, a square shape, or any other shape. For example, fig. 4 is a lithium secondary battery 5 of a square structure as an example.

In some embodiments, referring to fig. 5, the overwrap may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose to form an accommodating cavity. The housing 51 has an opening communicating with the accommodating chamber, and a cover plate 53 can be provided to cover the opening to close the accommodating chamber. The positive electrode tab, the negative electrode tab, and the separator may be formed into the electrode assembly 52 through a winding process or a lamination process. An electrode assembly 52 is enclosed within the receiving cavity. The electrolyte is impregnated into the electrode assembly 52. The number of the electrode assemblies 52 included in the lithium secondary battery 5 may be one or more, and those skilled in the art can select them according to the actual needs.

Battery module

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

Fig. 6 is a battery module 4 as an example. Referring to fig. 6, in the battery module 4, a plurality of lithium secondary batteries 5 may be arranged in series along the longitudinal direction of the battery module 4. Of course, the arrangement may be in any other manner. The plurality of lithium secondary batteries 5 may be further fixed by a fastener.

Alternatively, the battery module 4 may further include a case having a receiving space in which the plurality of lithium secondary batteries 5 are received.

Battery pack

In some embodiments, the battery modules may be assembled into a battery pack, and the number of the battery modules contained in the battery pack may be one or more, and the specific number may be selected by one skilled in the art according to the application and the capacity of the battery pack.

Fig. 7 and 8 are a battery pack 1 as an example. Referring to fig. 7 and 8, a battery pack 1 may include a battery case and a plurality of battery modules 4 disposed in the battery case. The battery box comprises an upper box body 2 and a lower box body 3, wherein the upper box body 2 can be covered on the lower box body 3 and forms a closed space for accommodating the battery module 4. A plurality of battery modules 4 may be arranged in any manner in the battery box.

Electric device

In addition, the present application also provides an electric device including at least one of the lithium secondary battery, the battery module, or the battery pack provided in the present application. The lithium secondary battery, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The powered device may include a mobile device (e.g., a mobile phone, a laptop computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc., but is not limited thereto.

As the electricity-using device, a lithium secondary battery, a battery module, or a battery pack may be selected according to the use requirements thereof.

Fig. 9 is 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 and the like. In order to meet the demand of the electric device for high power and high energy density of the lithium secondary battery, a battery pack or a battery module may be used.

As another example, the device may be a cell phone, a tablet, a laptop, etc. The device is generally required to be thin and light, and a lithium secondary battery may be used as a power source.

Examples

Hereinafter, examples of the present application will be described. The following description of the embodiments is merely exemplary in nature and is in no way intended to limit the present disclosure. The examples do not specify particular techniques or conditions, and are performed according to techniques or conditions described in literature in the art or according to the product specification. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available.

Example 1

Preparing a negative current collector:

preparing a ZIF-8 (MOF)/Zn @ Cu negative electrode current collector:

step 1 (S1) preparation of a zinc-plated copper foil: the zinc-plated copper foil is prepared by a magnetron sputtering method, and sputtering/electron beam/ICP-CVD (base pressure is less than 1 x 10) ^-6 Torr, ICP-CVD chamber). Based on the deposition conditions that the flow of plasma gas is 100sccm, the plasma power is 200W and the sputtering time is 60s, a 100nm galvanized layer is deposited on the copper foil substrate.

Step 2 (S2) pretreatment of the galvanized copper foil: soaking the prepared galvanized copper foil in a 1M Ammonium Persulfate (APS) solution for 10min for oxidation treatment, washing with deionized water and absolute ethyl alcohol for multiple times, and drying in a 60 ℃ forced air drying oven for later use.

Procedure 3 (S3) construction of MOF array layer: preparing an MOF array layer by adopting a wet chemical method, putting the galvanized copper foil treated by S1 into a prepared 0.5M 2-methylimidazole (HMIM) aqueous solution for reaction for 12 hours at room temperature, wherein the thickness of the obtained MOF array layer is 1 mu m, then washing surface impurities with deionized water, and performing vacuum drying at 60 ℃ to obtain a ZIF-8 (MOF)/Zn @ Cu negative current collector, wherein the type of the MOF array layer is ZIF-8, the structural formula of the MOF array layer is shown in the specification, the type of the lithium-philic coating layer is Zn, and the substrate is copper.

Preparing a negative pole piece:

the pre-deposition of lithium metal is performed by assembling the half-cell. In a half cell, a current collector is used as a positive electrode, a commercial lithium foil is used as a negative electrode, 1M lithium bistrifluoromethanesulfonylimide (LiTFSI)/1, 3 Dioxolane (DOL) + ethylene glycol dimethyl ether (DME) (volume ratio of 1: 1) is used as an electrolyte, PE is used as a separator, and the thickness of the separator is 1mA cm ^-2 Discharging for 10h under current density by electrochemical deposition method to obtain a pre-deposition capacity of 10mAh cm ^-2 The electrode of (1).

Preparing a positive pole piece:

the anode active material LiFePO is added ₄ Mixing acetylene black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder according to the mass ratio of 7: 2: 1, adding a proper amount of N-methylpyrrolidone (NMP) and grinding into uniform slurry, then uniformly coating the positive slurry on an aluminum foil with the thickness of 12 mu m, drying in vacuum at the temperature of 80 ℃ for 12 hours, and punching into 4 x 5cm ² The electrode sheet (a) is ready for use. LiFePO for selected commercial lithium secondary batteries ₄ The surface capacity of the positive electrode is 144mAh cm ^-2 。

And (3) isolation film:

the isolating membrane is a conventional Polypropylene (PE) isolating membrane.

Assembling the battery:

copper-based current collector pre-deposited lithium with in-situ grown lithium uniform deposition based on the prepared in example 1 negative electrode was used as a negative electrode to commercialize LiFePO for lithium secondary battery ₄ The laminated battery is formed by placing a positive pole piece, an isolating membrane and a negative pole piece in sequence, wherein the positive pole piece, the isolating membrane and the negative pole piece are positioned between the positive pole piece and the negative pole piece to play an isolating role, and then injecting electrolyte to assemble the laminated battery.

Example 2

The preparation method is basically the same as that of the example 1, except that:

in the preparation process of MOF/Zn @ Cu, the reaction time of the galvanized copper foil and 0.5M HMIM aqueous solution is 5h, and the thickness of the corresponding obtained MOF array layer is 200nm.

Example 3

in the preparation process of MOF/Zn @ Cu, the reaction time of the galvanized copper foil and 0.5M HMIM aqueous solution is 8h, and the thickness of the corresponding obtained MOF array layer is 500nm.

Example 4

in the preparation process of MOF/Zn @ Cu, the reaction time of the galvanized copper foil and 0.5M HMIM aqueous solution is 24h, and the thickness of the corresponding obtained MOF array layer is 4 μ M.

Example 5

in the preparation process of MOF/Zn @ Cu, the reaction time of the galvanized copper foil and 0.5M HMIM aqueous solution is 36h, and the thickness of the corresponding obtained MOF array layer is 8 μ M.

Example 6

and analyzing the compactness of the MOF array layer by utilizing the corrosion effect of dilute hydrochloric acid on the lithium-philic zinc layer. First, 0.5M diluted hydrochloric acid (diluted HCl) was prepared, and then the copper-based current collector with in-situ grown lithium uniform deposition obtained in example 1 was placed in the diluted HCl, and whether bubbles were generated on the surface of the MOF array layer was observed. The zinc layer reacts in the presence of dilute HCl, and the corrosion degree of the zinc layer can be judged according to the generation rate of bubbles on the surface of the functionalized copper-based current collector, so that the compactness of the MOF array layer can be judged.

Example 7

The preparation method is basically the same as that of the example 2, and the difference is that:

and analyzing the compactness of the MOF array layer by utilizing the corrosion effect of dilute hydrochloric acid on the lithium-philic zinc layer. First, 0.5M diluted HCl was prepared, and then the copper-based current collector with in-situ grown lithium uniform deposition obtained in example 2 was placed in diluted 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, and the corrosion degree of the zinc layer can be judged according to the generation rate of bubbles on the surface of the functionalized copper-based current collector, so that the compactness of the MOF array layer can be judged.

Example 8

in the preparation process of MOF/Zn @ Cu, the galvanized copper foil is prepared by adopting a magnetron sputtering method, and sputtering/electron beam/ICP-CVD (base pressure is less than 1 multiplied by 10) ^-6 Torr, ICP-CVD chamber). And depositing a 50nm zinc coating on the copper foil substrate based on the deposition conditions that the flow rate of the plasma gas is 100sccm, the plasma power is 200W and the sputtering time is 30 s.

Example 9

The preparation method is basically the same as that of example 1, except that:

in the preparation process of MOF/Zn @ Cu, the galvanized copper foil is prepared by adopting a magnetron sputtering method, and sputtering/electron beam/ICP-CVD (base pressure is less than 1 multiplied by 10) ^-6 Torr, ICP-CVD chamber). And depositing a 500nm zinc coating on the copper foil substrate based on the deposition conditions that the flow rate of the plasma gas is 100sccm, the plasma power is 200W and the sputtering time is 240 s.

Example 10

preparation of MOF-74 (MOF)/zn @ cu negative electrode current collector:

step 1 (S1) preparation of a magnesium-plated copper foil: the magnesium-plated copper foil is prepared by a magnetron sputtering method, and sputtering/electron beam/ICP-CVD (base pressure is less than 1 x 10) ^-6 Torr, ICP-CVD chamber). Based on the deposition conditions that the flow rate of the plasma gas is 100sccm, the plasma power is 200W and the sputtering time is 60s, a 100nm magnesium-plated layer is deposited on the copper foil substrate.

Step 2 (S2) pretreatment of the magnesium-plated copper foil: soaking the prepared galvanized copper foil in a 1M Ammonium Persulfate (APS) solution for 10min for oxidation treatment, washing with deionized water and absolute ethyl alcohol for multiple times, and drying in a 60 ℃ forced air drying oven for later use.

Procedure 3 (S3) construction of MOF array layer: preparing an MOF array layer by adopting a wet chemical method, firstly preparing 0.1M 2, 5-dihydroxyterephthalic acid solution by taking tetrahydrofuran as a solvent, then putting the magnesium-plated copper foil treated by S1 into the prepared solution for reaction at room temperature for 12h, then washing surface impurities with deionized water, and performing vacuum drying at 60 ℃ to obtain an MOF-74 (MOF)/Zn @ Cu negative current collector, wherein the MOF array layer is MOF-74, the structural formula of the MOF array layer is shown as follows, the lithium-philic plating layer is Zn, the substrate is copper, and the thickness of the corresponding obtained MOF array layer is 4.6 mu m.

Example 11

preparation of (Sn (II) -BDC) MOF/Sn @ Cu negative electrode current collector:

step 1 (S1) preparation of a tin-plated copper foil: the tin-plated copper foil is prepared by a magnetron sputtering method, and sputtering/electron beam/ICP-CVD (base pressure is less than 1 x 10) ^-6 Torr, ICP-CVD chamber). Based on the deposition conditions that the flow rate of the plasma gas is 100sccm, the plasma power is 200W and the sputtering time is 60s, a tin-plated layer with the thickness of 100nm is deposited on the copper foil substrate.

Step 2 (S2) pretreatment of tin-plated copper foil: the prepared tin-plated copper foil is soaked in 1M Ammonium Persulfate (APS) solution for 10min for oxidation treatment, then washed with deionized water and absolute ethyl alcohol for multiple times, and dried in a 60 ℃ forced air drying oven for later use.

Procedure 3 (S3) construction of MOF array layer: firstly, dissolving 1mmol of terephthalic acid (BDC) and 2mmol of NaOH in 10mL of deionized water, performing ultrasonic treatment for 10min to form a uniform solution, then putting the tinned copper foil treated by S2 into the prepared solution, transferring the solution into a 25mL reaction kettle, performing hydrothermal reaction at 120 ℃ for 24h, cooling to room temperature after the reaction is finished, then washing surface impurities with deionized water, and performing vacuum drying at 60 ℃ to obtain a (Sn (II) -BDC) MOF/Sn @ Cu negative electrode current collector, wherein the type of MOF is Sn (II) -BDC, the structural formula of the MOF is shown in the specification, the type of a lithium-philic plating layer is Sn, the substrate is copper, and the thickness of the corresponding MOF array layer is 7.8 mu m.

Example 12

preparation of lithium metal negative electrode: the pre-deposition of lithium metal is performed by assembling the half-cell. In a half cell, a current collector is used as a positive electrode, commercial lithium foil is used as a negative electrode, 1M LiTFSI/DOL + DME (volume ratio is 1: 1) is used as an electrolyte, PE is used as a separator, and the thickness of the separator is 1mA cm ^-2 Discharging for 1h under current density by electrochemical deposition method to obtain a pre-deposition capacity of 1mAh cm ^-2 The electrode of (1).

Example 13

preparation of lithium metal negative electrode: the pre-deposition of lithium metal is performed by assembling the half-cell. In a half cell, a current collector is used as a positive electrode, commercial lithium foil is used as a negative electrode, 1M LiTFSI/DOL + DME (volume ratio is 1: 1) is used as an electrolyte, PE is used as a separator, and the thickness of the separator is 1mA cm ^-2 Discharging for 5h under current density by electrochemical deposition method to obtain a pre-deposition capacity of 5mAh cm ^-2 The electrode of (1).

Example 14

The preparation method is basically the same as that of example 1, except that:

preparation of lithium metal negative electrode: the pre-deposition of lithium metal is performed by assembling the half-cell. In a half cell, a current collector is used as a positive electrode, commercial lithium foil is used as a negative electrode, 1M LiTFSI/DOL + DME (volume ratio is 1: 1) is used as an electrolyte, PE is used as a separator, and the thickness of the separator is 1mA cm ^-2 Discharging for 15h under current density by electrochemical deposition method to obtain a pre-deposition capacity of 15mAh cm ^-2 The electrode of (1).

Example 15

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

Preparation of gel electrolyte: firstly, PVDF-HFP is dissolved in acetone (PVDF-HFP: acetone = 1: 8), the mixture is stirred for 2 hours at 50 ℃ to obtain uniform transparent slurry, the uniform transparent slurry is quickly coated on an aluminum foil and is dried for 24 hours under vacuum at 100 ℃ to obtain a polymer film with the thickness of 22 mu M, and then the polymer film is soaked in 1M LiTFSI/DOL + DME (volume ratio of 1: 1) electrolyte for 24 hours and then taken out, and the redundant electrolyte on the surface is removed. The liquid holdup of the obtained gel polymer electrolyte is controlled at 300wt%.

Assembling the battery: copper-based current collector pre-deposited lithium with in-situ grown lithium uniform deposition based on the prepared in example 1 negative electrode was used as a negative electrode to commercialize LiFePO for lithium secondary battery ₄ The laminated battery is formed by taking PVDF-HFP +1M LiTFSI/DOL + DME (volume ratio is 1: 1) as an electrolyte membrane, sequentially placing a positive pole piece, a gel electrolyte membrane and a lithium metal negative pole, and enabling the electrolyte membrane to be positioned between the positive pole piece and the negative pole piece to play a role in isolation, and assembling the laminated battery.

Example 16

The preparation method is basically the same as that of the example 11, except that:

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

Preparation of gel electrolyte: 5g of the polymer matrix CA, 5g of the crosslinker PEGDA (Mn = 400) and 0.05g of the initiator Azobisisobutyronitrile (AIBN) are added to 50g1M LiPF ₆ In a/EC + DEC liquid electrolyte, stirring at room temperature for 12h to obtain an electrolyte precursor solution, and then maintaining the precursor solution at 70 ℃ for 1h to obtain a CA/PEGDA gel electrolyte.

Assembling the battery: copper-based current collector pre-deposited lithium with in-situ grown lithium uniform deposition based on the prepared in example 1 negative electrode was used as a negative electrode to commercialize LiFePO for lithium secondary battery ₄ Placing an anode plate, a barrier film and a lithium metal cathode in sequence to enable an electrolyte membrane to be positioned between the anode plate and the cathode plate to play a role of isolation, then injecting an electrolyte precursor solution into the battery to stand for 6 hours to ensure that the electrode and the barrier film are completely soaked, and finally heating the battery at 70 ℃ for 1 hour to enable the electrolyte precursor solution to be polymerized and crosslinked in situ in the battery to obtain a polymerA lithium compound secondary battery.

Example 17

Li/LiFePO ₄ the electrolyte in the battery is a solid electrolyte with a composition of 60wt% polyethylene oxide PEO +13wt% lithium bistrifluoromethylenesulphonate (LiTFSI) +27wt% plastic Succinonitrile (SN).

Preparing a positive pole piece: the anode active material LiFePO is added ₄ Mixing acetylene black as a conductive agent, PVDF as a binder and components of a polymer electrolyte according to the mass ratio of 6: 1.5: 1, adding a proper amount of NMP, grinding into uniform slurry, then uniformly coating the positive slurry on an aluminum foil with the thickness of 12 mu m, drying in vacuum at the temperature of 80 ℃ for 12h, and punching into 4 x 5cm ² The electrode sheet (a) is ready for use. LiFePO ₄ The surface capacity of the positive electrode is 123mAh cm ^-2 。

Preparation of solid electrolyte: first PEO and LiTFSI (Li) ⁺ PEO = 1: 32) was dissolved in acetonitrile, stirred at room temperature for 24 hours, then SN was added to the above solution, stirred for 12 hours to prepare a polymer electrolyte slurry, knife-coated on a teflon plate and dried at 40 ℃ under vacuum for 24 hours to remove the acetonitrile solvent, to obtain a solid electrolyte membrane having a thickness of 25 μm.

Assembling the battery: copper-based current collector pre-deposited lithium with in-situ grown lithium uniform deposition based on the prepared in example 1 negative electrode was used as a negative electrode to commercialize LiFePO for lithium secondary battery ₄ And the positive pole piece, the solid electrolyte membrane and the lithium metal negative pole are sequentially placed to enable the electrolyte membrane to be positioned between the positive pole piece and the negative pole piece to play a role in isolation, a laminated battery is assembled, and then the laminated battery is hot-pressed for 2min at 100 ℃ and 250MPa to obtain the all-solid-state lithium secondary battery.

Comparative example 1

A negative current collector: the commercial copper foil is used as a negative current collector, and the negative current collector is free of an MOF array layer and a lithium-philic coating.

Preparing a negative pole piece: the same as in example 1.

Preparing a positive pole piece: the same as in example 1.

And (3) isolation film: the same as in example 1.

Assembling the battery: the same as in example 1.

Comparative example 2

Preparation of the MOF @ Cu negative current collector, mixing pre-synthesized MOF and binder PVDF in a mass ratio of 9: 1, adding a proper amount of NMP, grinding into uniform slurry, blade-coating on a commercial copper foil by using a preparation device, and vacuum-drying at 80 ℃ for 12h to obtain the MOF @ Cu negative current collector without a lithium-philic coating.

Preparing a negative pole piece: the same as in example 1.

Preparing a positive pole piece: the same as in example 1.

And (3) isolation film: the same as in example 1.

Assembling the battery: the same as in example 1.

Comparative example 3

Preparing a Zn @ Cu negative current collector: the galvanized copper foil current collector is prepared by a magnetron sputtering method, a commercial copper foil is used as a substrate, and a galvanized layer with the thickness of 100nm is deposited on the surface of the copper foil, so that a Zn @ Cu negative current collector is obtained, and the negative current collector is free of an MOF array layer.

Preparing a negative pole piece: the same as in example 1.

Preparing a positive pole piece: the same as in example 1.

And (3) isolation film: the same as in example 1.

Assembling the battery: the same as in example 1.

Comparative example 4

Preparation of Mg @ Cu current collector: the magnesium-plated copper foil current collector is prepared by a magnetron sputtering method, a commercial copper foil is used as a substrate, a magnesium-plated layer with the thickness of 100nm is deposited on the surface of the copper foil, and the MOF array layer is not arranged in the negative current collector.

Preparing a negative pole piece: the same as in example 1.

Preparing a positive pole piece: the same as in example 1.

And (3) isolation film: the same as in example 1.

Assembling the battery: the same as in example 1.

Comparative example 5

Preparation of Sn @ Cu negative current collector: the tin-plated copper foil current collector is prepared by a magnetron sputtering method, a commercial copper foil is used as a substrate, a tin-plated layer with the thickness of 100nm is deposited on the surface of the copper foil, and the MOF array layer is not arranged in the negative current collector.

Preparing a negative pole piece: the same as in example 1.

Preparing a positive pole piece: the same as in example 1.

And (3) isolation film: the same as in example 1.

Assembling the battery: the same as in example 1.

The specific parameter settings of examples 1 to 17 and comparative examples 1 to 5 are shown in table 1.

TABLE 1

In Table 1, the MOF species include three of ZIF-8, MOF-74 (Mg), and Sn (II) -BDC MOF, which have the following structural formulas:

the procedure for testing the charge and discharge performance of the lithium secondary batteries of examples 1 to 16 and comparative examples 1 to 5 was as follows: the working voltage range is set to be 2.5-3.7V, and the circulation test is carried out by adopting a constant current charging and discharging mode, wherein the test current is 0.33C (the current density is about 48mA cm/cm) ^-2 ) The test temperature was 25 ℃.

The procedure for testing the charge/discharge characteristics of the all-solid-state lithium secondary battery in example 17 was as follows: the working voltage range is set to be 2.5-3.7V, and the circulation test is carried out by adopting a constant current charging and discharging mode, wherein the test current is 0.1C (the current density is about 10 mA-cm) ^-2 ) The test temperature was 70 ℃.

The surface appearance of the lithium metal negative electrode in the examples 1 to 17 and the comparative examples 1 to 5 is characterized: and (3) disassembling the lithium secondary battery after n cycles, representing the surface appearance of the metal lithium negative pole piece through a field emission Scanning Electron Microscope (SEM), and observing whether lithium dendrite is generated.

The lithium secondary batteries of examples 1 to 17 and comparative examples 1 to 5 were each tested for the first-cycle specific discharge capacity, the first-cycle coulombic efficiency, the number of cycles, and the capacity retention rate after cycles, and 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.

TABLE 2

From examples 1 to 5, it is clear that the thickness of the MOF array layer increases with the reaction time. When the thickness of the MOF array layer is smaller (examples 2 to 3), the MOF array layer has non-uniform morphology on the surface of the galvanized copper foil, a dense layer is difficult to form and cracks are easy to generate, and the mechanical stability of the array layer is deteriorated due to volume change in the circulation process, so that the cycle life of the battery is shortened and the capacity attenuation is accelerated. As the thickness of the MOF array layer increases (examples 4-5), the MOF array layer is tightly packed between the particles, but the increase of the thickness of the array layer leads to the reduction of the ion transport capability between the negative electrode and the electrolyte, and simultaneously leads to the reduction of Li ⁺ The transmission and diffusion paths of (a) are further extended, and finally the polarization of the battery is increased, the first-cycle coulomb efficiency is reduced, and the cycle stability is deteriorated. Compared to the current collector described above, the MOF array layer with a thickness of 1 μm (example 1) exhibited the optimal cycle performance and high coulombic efficiency, therefore the MOF-zn @ cu negative electrode current collector prepared under this condition was preferred.

From examples 6 to 7, it is clear that the denseness of the MOF array layer in the current collector is important for the cycle life of the lithium secondary battery. If the MOF array layer is less dense (example 7), surface defects can lead to Li ⁺ Flux is uneven, thereby promoting the growth of lithium dendrites and reducing the cycle life of the battery; good densification of the MOF array layer (example 6), on the one hand, enables Li ⁺ The lithium ion battery pole piece is uniformly distributed on the surface of the pole piece, so that the uniform deposition of lithium is induced, on the other hand, the direct contact between the electrolyte and the high-reducibility lithium can be avoided, the occurrence of side reactions is effectively reduced, and the coulomb efficiency and the cycling stability of the battery are improved.

As can be seen from comparison of example 1 with examples 8 to 9, the batteries exhibited different first cycle discharge specific capacities and different cycle stabilities, depending on the thickness of the lithium-philic coating in the copper-based current collector. Among them, when the thickness of the lithium-philic zinc layer is 100nm (example 1), the battery shows good specific discharge capacity at first cycle and capacity retention rate after cycle. When the thickness of the lithium-philic zinc layer is smaller (example 8), it is difficult to provide enough deposition space for more lithium during charging, and excessive metal lithium will deposit on the surface of the alloy layer, possibly inducing the growth of lithium dendrite, and affecting the battery performance; when the thickness is high (example 9), the conductivity of metal zinc is inferior to that of metal copper, which tends to increase the internal resistance of the battery, cause large polarization of the battery, reduce the specific capacity of the battery, and further reduce the energy density of the battery.

As can be seen from examples 1, 10 to 11 and comparative examples 1 to 5, based on the copper-based current collector with in-situ grown lithium uniform deposition prepared in example 1, the lithium secondary battery exhibited excellent cycle stability and higher first-week coulombic efficiency due to the uniform and dense MOF array layer being Li due to its inherent nanopores like "ionic sieve" action ⁺ The uniform transmission channel is provided, the buffer layer can also be used as a buffer layer to effectively reduce the volume change of the negative electrode side, meanwhile, the lithium-philic coating (the zinc layer, the magnesium layer and the tin layer) provides effective nucleation sites for the deposition of lithium, and the Li and the lithium-philic coating form an alloy in the charging process, so that the uniform deposition of the lithium is induced, and the growth of lithium dendrites is effectively inhibited. Generally, a general copper current collector (comparative example 1) easily causes non-uniform lithium deposition and uncontrolled growth of lithium dendrites during a cycle due to inherent surface roughness, reducing the electrochemical performance of a battery; an MOF array layer is constructed on the surface of a copper foil by adopting a non-in-situ coating method (comparative example 2), and because the accidental nature of manual coating easily causes coating defects, the coating is damaged in the repeated lithium deposition/dissolution process, and the protection effect is invalid; the lithium-philic cladding base copper foil current collectors (comparative examples 3-5) provide lithium-philic nucleation sites, but volume change of the negative electrode side in the circulation process easily causes collapse and severe pulverization of the lithium-philic cladding structure, and is difficult to provide effective space for deposition of lithium, so that the coulombic efficiency of the battery is reduced.

From example 1 and examples 12 to 14, it is clear that the amount of the capacity of the negative electrode pre-deposited lithium has a certain influence on the battery performance. When the capacity of the pre-deposited lithium on the negative electrode side is small (examples 15 to 16), the consumption of the electrolyte and the negative electrode due to the side reaction on the surface of the electrode during the charging and discharging process results in a serious shortage of the lithium source on the negative electrode side, which leads to a reduction in the capacity retention rate of the lithium secondary battery after 200 cycles. When the capacity of the negative electrode pre-deposited lithium is large and the lithium source is sufficient (examples 1 and 17), the battery still shows excellent cycling stability and high coulombic efficiency after 200 weeks of cycling.

As can be seen from example 1 and examples 15 to 17, different electrolyte systems also affected the battery performance based on the bifunctional copper-based current collector prepared in example 1. Among them, the use of the in-situ heat-cured gel electrolyte (example 16) contributes to the improvement of the cycle performance and safety of the battery due to the fact that the good mechanical properties of the gel electrolyte can effectively limit the volume change of the lithium negative electrode during the cycle, and the small amount of the liquid electrolyte can significantly improve the Li content ⁺ The transport speed, which enables sufficient wetting of the electrodes by in situ thermal curing, reduced cell polarization and increased coulombic efficiency in the first run compared to the gel electrolyte obtained by dissolution of the high molecular polymer (example 15). However, the all solid-state lithium secondary battery (example 17) tends to have problems of electrode/electrolyte interface contact and low ion conductivity, and thus, tends to cause an increase in polarization of the battery and a deterioration in electrochemical performance.

Further, with respect to the surface topography characterization of the lithium metal negative electrodes of the lithium secondary batteries in examples 1 to 17 and comparative examples 1 to 5 of the present application, it can be seen with reference to the SEM picture of fig. 10a that dendrites are not generated after cycling; referring to the SEM image of FIG. 10b, slight dendrites were generated after cycling; referring to the SEM image of FIG. 10c, severe dendrites were generated after cycling.

It can be seen from the above test results of examples 1 to 17 and comparative examples 1 to 5 that the copper-based current collector having in-situ grown lithium uniform deposition, the method of preparing the same, and the lithium secondary battery using the same improve the cycle stability and safety performance of the lithium secondary battery, relative to the prior art.

The present application is not limited to the above embodiments. The above embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exhibiting the same operation and effect within the technical scope of the present application are all included in the technical scope of the present application. In addition, various modifications that can be conceived by those skilled in the art are applied to the embodiments and other embodiments are also included in the scope of the present application, in which some of the constituent elements in the embodiments are combined and constructed, without departing from the scope of the present application.

Claims

1. A negative electrode current collector characterized in that,

the negative current collector is provided with: a current collector substrate, a lithium-philic coating, and a metal-organic framework array layer,

wherein the lithium-philic coating is arranged on the current collector substrate, and the metal organic frame array layer is grown in situ on the surface of the lithium-philic coating,

the metal organic framework array layer has a nano-pore structure.

2. The negative electrode current collector of claim 1,

the metal organic framework array layer consists of a metal ion coordination center and an organic ligand,

the coordination center of the metal ions is zinc ions Zn ²⁺ Sn ion Sn ²⁺ Or magnesium ion Mg ²⁺ One or more of the above-mentioned (B) compounds,

the organic ligand is more than one selected from 2-methylimidazole, nicotinic acid, isonicotinic acid, terephthalic acid, 2, 5-dihydroxy dimethyl terephthalate, 1,2, 4-triazole and oxalate.

3. The negative electrode current collector of claim 1 or 2,

the thickness of the metal organic framework array layer is 200 nm-8 μm.

4. The negative electrode current collector of claim 1 or 2,

the thickness of the lithium-philic coating is 50-500 nm.

5. The negative electrode current collector of claim 1 or 2,

the current collector substrate is metallic or non-metallic,

the metal is more than one selected from Cu, al, fe, ni, ti and stainless steel,

the nonmetal is more than one selected from graphene and carbon fiber.

6. A method of preparing the negative electrode current collector as claimed in any one of claims 1 to 5,

the method comprises the following steps:

depositing a lithium-philic coating on the copper foil substrate by a magnetron sputtering method, wherein the target material is more than one selected from a Zn simple substance, a Sn simple substance and a Mg simple substance; and the number of the first and second groups,

and carrying out in-situ growth of the metal organic framework array layer with the nanometer pore structure on the surface of the lithium-philic coating by a wet chemical method.

7. The method of preparing an anode current collector according to claim 6,

the reaction time for in-situ growth is 5-36 h, and the reaction temperature is 25-120 ℃.

8. A negative electrode plate is characterized in that,

the negative electrode tab includes the negative electrode current collector according to any one of claims 1 to 5.

9. A lithium secondary battery is characterized in that,

the lithium secondary battery includes the negative electrode tab of claim 8.

10. A battery module, characterized in that,

the battery module includes the lithium secondary battery according to claim 9.

11. A battery pack is characterized in that a battery pack,

the battery pack includes the battery module of claim 10.

12. An electric device is characterized in that the electric device is provided with a power supply,

the electricity-using device includes at least one selected from the group consisting of the lithium secondary battery according to claim 9, the battery module according to claim 10, and the battery pack according to claim 11.