CN117650244B - Structure, method and application for protecting lithium metal negative electrode material - Google Patents

Abstract

The invention provides a structure, a method and application for protecting a lithium metal anode material. The structure for protecting the lithium metal anode material comprises a multifunctional protection layer, wherein the raw materials of the multifunctional protection layer comprise 3 wt-10 wt% of polyhalogenated alkyl acrylate and 5-15% by weight of lanthanide metal halide. The structure can regulate the uniform deposition growth of lithium, promote the rapid transmission of lithium ions, reduce the side reaction of metal lithium and electrolyte and effectively relieve the formation of lithium dendrites; the method for protecting the lithium metal anode material is simple and easy to operate, high in controllability, low in cost and suitable for large-scale and industrialized operation; the lithium metal battery containing the protective structure has excellent cycle stability and safety.

Description

Structure, method and application for protecting lithium metal negative electrode material

Technical Field

The present invention belongs to the technical field of lithium batteries, and specifically relates to a structure, method and application of protecting lithium metal negative electrode materials, a lithium metal negative electrode material and a lithium metal battery.

Background technique

Modern society is highly dependent on high-performance electrochemical energy storage systems, and batteries that can be used in portable electronic devices, renewable energy, and electrified transportation have received widespread attention. Metallic lithium is considered the most promising battery anode material due to its ultra-high theoretical specific capacity (3860 mAh g ^-1 ), light weight (6.94 g mol ^-1 ), and low redox potential (-3.04 V compared to the standard hydrogen electrode). However, lithium metal anodes have two major problems: safety (dendrite growth) and cycle stability, which are bottlenecks for their application. During the battery cycle, a solid electrolyte (SEI) film will form at the lithium anode interface. The interfacial dendrite growth and side reactions are closely related to the properties of the anode SEI interfacial film. The inhomogeneous SEI film is easy to rupture during the battery cycle, causing direct contact between the electrolyte and the anode, triggering side reactions. In addition, the inhomogeneous structure of the interface will induce local aggregation of surface negative charges, enhance interfacial polarization, form an uneven distribution of interfacial ion concentration, accelerate dendrite growth, and cause battery safety issues.

In order to overcome the chemical and mechanical instabilities of the electrode/electrolyte interface and thus develop stable and high-performance lithium metal anodes (LMAs), the composition and properties of the SEI need to be precisely controlled. Surface and interface engineering plays a key role in improving the interfacial physicochemical properties and electrochemical performance of LMAs because of its strong ability to construct various functional artificial SEIs. Therefore, the development of an artificial interfacial multifunctional protective layer with the ability to inhibit lithium dendrites, uniform lithium deposition, and excellent cycling performance is particularly critical for the development of lithium metal batteries.

Summary of the invention

In order to solve all or part of the above technical problems, the present invention provides the following technical solutions:

One of the purposes of the present invention is to provide a structure for protecting a lithium metal negative electrode material, the structure comprising a multifunctional protective layer, the raw materials of the multifunctional protective layer comprising 3 wt% to 10 wt% of a polyhalogenated alkyl acrylate and 5 to 15 wt% of a lanthanide metal halide.

The lanthanide metal halide in the structure for protecting the lithium metal negative electrode material forms inorganic components such as lanthanide metal, lithium alloy, and lithium halide with lithium, which can induce uniform deposition and growth of lithium, provide higher mechanical strength and lower lithium ion diffusion barrier, and inhibit dendrite growth from both mechanical stress and chemical diffusion. The polyhalogenated alkyl acrylate organic component not only has good flexibility and ion permeability, and can buffer the volume change of lithium metal, but also can promote the dispersibility and film-forming property of lanthanide metal halide, and inhibit the dissolution of lanthanide metal halide and the interfacial side reaction of free solvent. Under the synergistic effect of the interface of the multi-component protective layer, the occurrence of side reactions is effectively reduced, and the lithium insertion/stripping cycle is maintained under a stable interface, which greatly reduces the formation of lithium dendrites and the volume expansion effect.

In some embodiments, the polyhalogenated alkyl acrylate is obtained by polymerization of halogenated alkyl acrylate monomers with methacryloyl fluoride and azobisisobutyronitrile.

Further, the halogenated alkyl acrylate monomer includes one or more combinations of 2-bromomethyl ethyl acrylate, 2-bromoethyl acrylate, 2-chloromethyl ethyl acrylate, 2-chloroethyl methacrylate, 2,3-dibromopropyl acrylate, 2-bromomethyl methyl acrylate, and 2,3-dibromopropyl acrylate.

In some embodiments, the lanthanide metal halide includes one or more of LaF ₃ , CeF ₃ , NdF ₃ , LaCl ₃ , CeCl ₃ , NdCl ₃ , CeI ₃ , LaI ₃ , and NdI ₃ .

In some embodiments, the raw material of the multifunctional protective layer further includes an organic solvent, and the organic solvent includes one or a combination of tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, ethylene glycol dimethyl ether, and 1,3-dioxolane.

In some embodiments, the structure for protecting the lithium metal negative electrode material further includes a substrate, and the multifunctional protective layer is bonded to the surface of the substrate.

Furthermore, the substrate includes copper foil and/or aluminum foil.

In some embodiments, the weight average molecular weight of the polyhalogenated alkyl acrylate is 7000-9000.

In some embodiments, the thickness of the multifunctional protective layer is 2-5 μm. If the protective layer is too thick, the battery capacity will be reduced, the conductivity will be deteriorated, the internal resistance of the battery will increase, and the charging speed will also be slowed down. In addition, excessive film thickness will also increase the internal pressure of the battery, and may even cause the battery to swell and leak, increasing safety risks; if the protective layer is too thin, the battery life will be shortened, and internal short circuits and leakage will easily occur, and the risk of overcharging and over-discharging of the battery will be increased. The inventors found that when the thickness of the multifunctional protective layer is 2-5 μm, the overall performance of the battery is better.

A second object of the present invention is to provide a method for protecting a lithium metal negative electrode material, the method comprising:

Providing a coating solution, the coating solution comprising 3 wt% to 10 wt% of a polyhalogenated alkyl acrylate, 5 to 15 wt% of a lanthanide metal halide, and an organic solvent;

The coating liquid is prepared into a film, and dried to form a multifunctional protective layer;

The multifunctional protective layer is bonded to the surface of metallic lithium.

The addition amount of the polymer and lanthanide metal halide provided by the present invention can effectively alleviate the formation of lithium dendrites, and further improve the safety and cycle performance of lithium ion batteries. It should be noted that if the concentration of polyhalogenated alkyl acrylate and lanthanide metal halide in the coating solution is low or high, the cycle performance of the battery will be significantly reduced, and the polarization voltage and internal resistance will increase.

In some embodiments, the preparation method of the polyhalogenated alkyl acrylate comprises: subjecting a mixed reactant containing a halogenated alkyl acrylate monomer, methacryloyl fluoride, and azobisisobutyronitrile to polymerization reaction under an inert atmosphere to obtain the polyhalogenated alkyl acrylate.

Furthermore, in the mixed reactant, the mass fractions of the halogenated alkyl acrylate monomer, methacryloyl fluoride, and azobisisobutyronitrile are 30 wt % to 60 wt %, 10 wt % to 40 wt %, and 5 wt % to 10 wt %, respectively.

Furthermore, the reaction temperature of the polymerization reaction is 50-80°C, and the reaction time is 8-16 h.

Furthermore, the preparation method further comprises: after the polymerization reaction is completed, drying the reaction product, wherein the drying temperature of the drying treatment is 80-100° C. and the drying time is 3-6 hours to obtain the polyhalogenated alkyl acrylate.

Further, the halogenated alkyl acrylate monomer includes one or more combinations of 2-bromomethyl ethyl acrylate, 2-bromoethyl acrylate, 2-chloromethyl ethyl acrylate, 2-chloroethyl methacrylate, 2,3-dibromopropyl acrylate, 2-bromomethyl methyl acrylate, and 2,3-dibromopropyl acrylate.

In some embodiments, the lanthanide metal halide includes one or more of LaF ₃ , CeF ₃ , NdF ₃ , LaCl ₃ , CeCl ₃ , NdCl ₃ , CeI ₃ , LaI ₃ , and NdI ₃ .

In some embodiments, the organic solvent includes one or more of tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, ethylene glycol dimethyl ether, and 1,3-dioxolane.

In some embodiments, the method for preparing the coating solution includes: adding polyhalogenated alkyl acrylate and lanthanide metal halide to an organic solvent, and stirring at a rotation speed of 500-800 r/min for 3-6 hours.

In some embodiments, the method specifically includes: coating the coating liquid on the surface of the substrate, and drying the coating liquid to obtain the multifunctional protective layer.

In some embodiments, the drying includes: vacuum drying the coating liquid at a temperature of 60-80° C. for 6-10 h to form the multifunctional protective layer.

In some embodiments, the step of bonding the multifunctional protective layer to the surface of the lithium metal specifically includes: bonding the multifunctional protective layer to the lithium metal and then performing a roll pressing process. The method of bonding the multifunctional protective layer to the surface of the lithium metal by a roll pressing process can make the protective layer more uniform. If the coating liquid is directly coated on the lithium foil, the protective layer will be uneven because the lithium foil is too soft and the process requirements are relatively high.

In some embodiments, the multifunctional protective layer has a thickness of 2-5 μm.

The third object of the present invention is to provide a lithium metal negative electrode material, comprising metallic lithium, and also comprising a structure for protecting the lithium metal negative electrode material as described in any of the above technical solutions and bonded to the surface of the metallic lithium.

A fourth object of the present invention is to provide a structure for protecting a lithium metal negative electrode material in any of the above technical solutions, a method for protecting a lithium metal negative electrode material in any of the above technical solutions, or a use of the lithium metal negative electrode material in any of the above technical solutions in the preparation of a lithium metal battery.

A fifth object of the present invention is to provide a lithium metal battery, comprising a positive electrode, a negative electrode and an electrolyte, wherein the negative electrode comprises the lithium metal negative electrode material described in the above technical solution.

Compared with the prior art, the present invention has at least the following beneficial effects:

(1) In the structure for protecting lithium metal negative electrode materials provided by the present invention, lanthanide metal halides can form inorganic components such as lanthanide metals, lithium alloys, and lithium halides with lithium, thereby inducing uniform deposition and growth of lithium, providing higher mechanical strength and lower lithium ion diffusion barriers, and inhibiting dendrite growth from both mechanical stress and chemical diffusion. The polyhalogenated alkyl acrylate organic component can promote the dispersibility and film-forming properties of lanthanide metal halides and inhibit the dissolution of lanthanide metal halides and the interfacial side reactions of free solvents. On the other hand, the organic component enables the protective structure to have better flexibility and ion permeability, and can buffer the volume change of lithium metal. Under the synergistic effect of the interface of the multi-component protective layer, the occurrence of side reactions is effectively reduced, and the lithium insertion/stripping cycle is kept under a stable interface, which greatly reduces the formation of lithium dendrites and the volume expansion effect.

(2) The method for protecting lithium metal negative electrode materials provided by the present invention is simple and easy to operate, has high controllability, low cost, and is suitable for large-scale and industrial operations;

(3) A secondary battery including the protective structure has excellent cycle stability and safety.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a SEM image of the surface of the protective structure-modified metal lithium negative electrode prepared in Example 1 of the present invention;

FIG. 2 is a SEM image of the protective structure prepared in Example 1 of the present invention after lithium deposition.

Detailed ways

The technical solution of the present invention is described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solution of the present invention. The specific functional details disclosed herein should not be interpreted as limiting, but only as the basis for the claims and as a representative basis for teaching those skilled in the art to adopt the present invention in different ways in any appropriate detailed embodiment.

Example 1

Preparation of polyethyl bromide methylacrylate: under an inert atmosphere, 40 g of ethyl 2-bromomethylacrylate monomer, 25 g of methacryloyl fluoride, and 5 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the polymerization reaction was carried out at 80° C. for 12 h. The obtained product was dried at 80° C. for 6 h to obtain polyethyl bromide methylacrylate;

In a dry environment, 10 g of polybromomethylacrylate and 10 g of LaF ₃ were added to 80 g of tetrahydrofuran, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 6 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 3.5 μm;

The protective structure is attached to the surface of the metal lithium sheet by rolling to obtain a negative electrode of a lithium metal battery, which is photographed by a scanning electron microscope, as shown in FIG1 . FIG1 shows that the protective layer is evenly distributed.

CR2016 button cells were assembled in an argon-filled glove box, with a copper foil containing a protective layer as the cathode, Celgard2400 as the separator, a conventional carbonate electrolyte (1M _LiPF6 , EC/DMC/FEC (v/v/v=3/7/0.5), and lithium foil as the anode. The cells were deposited at 1 mA ^cm2 for 2 h, and then the cells were moved to an argon-filled glove box for disassembly and photographed by a scanning electron microscope. The results are shown in Figure 2. Figure 2 shows that the lithium deposition presents a flat and smooth sheet structure and a dense morphology without dendrite growth.

The negative electrode containing the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M _LiPF6 , EC/DMC/FEC (v/v/v=3/7/0.5), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 2

Preparation of polybromoethyl acrylate: Under an inert atmosphere, 40 g of 2-bromoethyl acrylate monomer, 25 g of methacryloyl fluoride, and 5 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the mixture was polymerized at 80° C. for 12 h. The obtained product was dried at 80° C. for 6 h to obtain polybromoethyl acrylate;

In a dry environment, 5 g of polybromoethyl acrylate and 15 g of CeF ₃ were added to 80 g of tetrahydrofuran, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 6 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 3.7 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode with the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5)), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 3

Preparation of polyethyl chloromethylacrylate: Under an inert atmosphere, 35 g of ethyl 2-chloromethylacrylate monomer, 25 g of methacryloyl fluoride, and 10 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the mixture was polymerized at 70° C. for 10 h. The obtained product was dried at 100° C. for 5 h to obtain polyethyl chloromethylacrylate;

In a dry environment, 8 g of polyethyl chloromethylacrylate and 15 g of LaCl ₃ were added to 77 g of N, N-dimethylformamide, and stirred at 500 r/min for 6 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 60° C. for 10 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 4.2 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode containing the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 4

Preparation of polychloroethyl methacrylate: Under an inert atmosphere, 40 g of 2-chloroethyl methacrylate monomer, 23 g of methacryloyl fluoride, and 7 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the mixture was polymerized at 60° C. for 16 h. The obtained product was dried at 100° C. for 6 h to obtain polychloroethyl methacrylate;

In a dry environment, 6 g of polychloroethyl methacrylate and 14 g of CeCl ₃ were added to 80 g of ethylene glycol dimethyl ether, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 6 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 3.7 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode with the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5)), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 5

Preparation of polydibromopropyl acrylate: Under an inert atmosphere, 40 g of 2,3-dibromopropyl acrylate monomer, 23 g of methacryloyl fluoride, and 7 g of azobisisobutyronitrile were dispersed in water, and polymerized at 60° C. for 16 h. The obtained product was dried at 80° C. for 6 h to obtain polydibromopropyl acrylate;

In a dry environment, 10 g of polydibromopropyl acrylate and 10 g of NdCl ₃ were added to 80 g of dimethyl sulfoxide, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 6 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 3.4 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode with the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5)), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 6

Preparation of polybromomethyl acrylate: under an inert atmosphere, 50 g of 2-bromomethyl acrylate monomer, 15 g of methacryloyl fluoride, and 5 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the mixture was polymerized at 70° C. for 12 h. The obtained product was dried at 80° C. for 6 h to obtain polybromomethyl acrylate;

In a dry environment, 3 g of polybromomethyl methacrylate and 5 g of NdF ₃ were added to 92 g of 1,3-dioxolane, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 8 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 2 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode with the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5)), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 7

Preparation of polydibromopropyl acrylate: under an inert atmosphere, 40 g of 2,3-dibromopropyl acrylate monomer, 20 g of methacryloyl fluoride, and 5 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the mixture was polymerized at 80° C. for 12 h. The obtained product was dried at 80° C. for 6 h to obtain polydibromopropyl acrylate;

In a dry environment, 8 g of polydibromopropyl acrylate and 8 g of NdF ₃ were added to 84 g of tetrahydrofuran, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 8 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 2.6 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode with the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5)), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 8

Preparation of polyethyl bromide methylacrylate: under an inert atmosphere, 40 g of ethyl 2-bromomethylacrylate monomer, 20 g of methacryloyl fluoride, and 5 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the mixture was polymerized at 80° C. for 12 h. The obtained product was dried at 80° C. for 6 h to obtain polyethyl bromide methylacrylate;

In a dry environment, 5 g of polybromomethylacrylate and 15 g of LaI ₃ were added to 80 g of tetrahydrofuran, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 6 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 3.8 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode with the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5)), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Example 9

Preparation of polyethyl bromide methylacrylate: under an inert atmosphere, 40 g of ethyl 2-bromomethylacrylate monomer, 25 g of methacryloyl fluoride, and 5 g of azobisisobutyronitrile were dispersed in 30 g of deionized water, and the polymerization reaction was carried out at 80° C. for 12 h. The obtained product was dried at 80° C. for 6 h to obtain polyethyl bromide methylacrylate;

In a dry environment, 10 g of polyethyl bromide methylacrylate and 15 g of LaF ₃ were added to 75 g of tetrahydrofuran, and stirred at 600 r/min for 8 h to obtain a uniform dispersion; the prepared dispersion was coated on the surface of the copper foil, and dried at 80° C. for 6 h to obtain a protective layer formed by drying on the surface of the copper foil. The thickness of the protective layer in this embodiment was 5 μm;

The protective structure is attached to the surface of the lithium metal sheet by rolling to obtain a lithium metal negative electrode;

The negative electrode with the protective structure prepared above was assembled into a 3.8 Ah soft pack battery with Celgard2400 separator, NCM811 positive electrode, and conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v=3/7/0.5)), and the electrochemical performance was tested under the conditions of 3-4.3 V, 0.2 C/0.5 C charge and discharge for 100 times. The test data are shown in Table 1.

Comparative Example 1

The difference between Comparative Example 1 and Examples 1 to 8 is that the lithium metal negative electrode does not contain the improved structure described in the present invention, and the lithium metal negative electrode without a protective structure is used to prepare a soft pack battery according to the soft pack battery preparation method of Example 1, that is, an unmodified lithium sheet is used as the negative electrode, the positive electrode is NCM811, and the electrolyte is a conventional carbonate electrolyte (1M LiPF6, EC/DMC/FEC (v/v/v＝3/7/0.5)), assembled into a 3.8 Ah soft pack battery, and the electrochemical performance test is performed on it, and the test conditions are: 3-4.3 V, 0.2 C/0.5 C charge and discharge 100 times. The test data are shown in Table 1.

Comparative Example 2

The only difference from Example 1 is that, in a dry environment, 20 g of polybromomethylacrylate was added to 80 g of tetrahydrofuran, stirred at 600 r/min for 8 h to obtain a uniform dispersion, which was coated on the surface of the copper foil with a protective layer thickness of 3 μm. The rest was implemented in the same manner as Example 1, and the obtained battery performance is shown in Table 1.

Comparative Example 3

The only difference from Example 1 is that, in a dry environment, 20 g of LaF ₃ is added to 80 g of tetrahydrofuran, stirred at 600 r/min for 8 h to obtain a uniform dispersion, which is coated on the surface of the copper foil with a protective layer thickness of 3.7 μm. The rest is the same as in Example 1. The obtained battery performance is shown in Table 1.

Comparative Example 4

The only difference from Example 1 is that, in a dry environment, 2 g of polybromomethylacrylate and 3 g of LaF ₃ are added to 95 g of tetrahydrofuran, and stirred at 600 r/min for 8 h to obtain a uniform dispersion, which is then coated on the surface of the copper foil with a protective layer thickness of 1.5 μm. The rest is the same as in Example 1, and the obtained battery performance is shown in Table 1.

Comparative Example 5

The only difference from Example 1 is that, in a dry environment, 12 g of polybromomethylacrylate and 18 g of LaF ₃ are added to 70 g of tetrahydrofuran, and stirred at 600 r/min for 8 h to obtain a uniform dispersion. The thickness of the protective layer is 5.5 μm. The rest is the same as in Example 1. The obtained battery performance is shown in Table 1.

Comparative Example 6

The only difference from Example 1 is that polybromomethylacrylate and _LaF3 are directly added to the electrolyte, the amount of polybromomethylacrylate added is 1wt% of the electrolyte, the amount of _LaF3 added is 1wt% of the electrolyte, the negative electrode is not modified, and the lithium metal negative electrode without a protective structure is prepared according to the soft pack battery preparation method of Example 1. The soft pack battery is assembled into a 3.8 Ah soft pack battery, and the electrochemical performance test is performed on _it . The test conditions are: 3-4.3 V, 0.2 C/0.5 C charge and discharge 100 times. The test data are shown in Table 1.

It can be seen that compared with the method of directly adding it to the electrolyte, the protective layer based on fluoroalkyl ethyl methacrylate polymer and lanthanide metal halide can more effectively improve the battery performance. This may be because the protective layer formed in situ in the electrolyte has poor mechanical stability and does not have a high modulus, making it difficult to mechanically inhibit dendrite growth.

Table 1 Battery voltage, internal resistance and cycle performance measurement results of the embodiments and comparative examples

By comparing the test results of Examples 1 to 8 with Comparative Examples 1 to 6, it can be seen that the battery composed of a metal lithium negative electrode having a multifunctional protection structure with 3 wt% to 10 wt% of polyhalogenated alkyl acrylate and 5 to 15 wt% of lanthanide metal halides can significantly improve the polarization voltage and cycle stability of the lithium metal battery. This is mainly because the protection structure provided by the present invention can make lithium deposit and grow uniformly, promote rapid transmission of lithium ions, and reduce side reactions between metal lithium and the electrolyte. At the same time, the structure has good flexibility, can inhibit dendrite growth and alleviate volume changes during cycling, so the lithium metal battery containing the negative electrode exhibits more excellent performance.

The various aspects, embodiments, features and examples of the present invention should be considered as illustrative in all aspects and are not intended to limit the present invention, the scope of the present invention is defined only by the claims. Other embodiments, modifications and uses will be apparent to those skilled in the art without departing from the spirit and scope of the claimed invention.

In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

Although the present invention has been described with reference to illustrative embodiments, it will be appreciated by those skilled in the art that various other changes, omissions and/or additions may be made without departing from the spirit and scope of the present invention and that the elements of the embodiments may be replaced by substantial equivalents. In addition, many modifications may be made without departing from the scope of the present invention to adapt specific circumstances or materials to the teachings of the present invention. Therefore, it is not intended herein to limit the present invention to the disclosed specific embodiments for performing the present invention, but it is intended that the present invention will include all embodiments within the scope of the appended claims. In addition, unless specifically stated, any use of the terms first, second, etc. does not indicate any order or importance, but rather uses the terms first, second, etc. to distinguish one element from another element.

Claims (13)

1. The structure for protecting the lithium metal anode material is characterized by comprising a multifunctional protection layer, wherein the raw material of the multifunctional protection layer consists of 3 wt-10% wt% of polyhalogenated alkyl acrylate, 5-15% by weight of lanthanide metal halide and the balance of organic solvent, and the thickness of the multifunctional protection layer is 2-5 mu m;

the poly-halogenated alkyl acrylate is obtained by the polymerization reaction of halogenated alkyl acrylate monomer and methacryloyl fluoride and azodiisobutyronitrile; wherein the halogenated alkyl acrylate monomer comprises one or more of ethyl 2-bromomethacrylate, ethyl 2-chloromethacrylate, 2-chloroethyl methacrylate, 2, 3-dibromopropyl acrylate, methyl 2-bromomethacrylate, and 2, 3-dibromopropyl acrylate.

2. The structure for protecting a lithium metal anode material according to claim 1, wherein: the lanthanide metal halide includes a combination of one or more of LaF₃、CeF₃、NdF₃、LaCl₃、CeCl₃、 NdCl₃、CeI₃、LaI₃、NdI₃.

3. The structure for protecting a lithium metal anode material according to claim 1, wherein: the organic solvent comprises one or more of tetrahydrofuran, N-dimethylformamide, dimethyl sulfoxide, ethylene glycol dimethyl ether and 1, 3-dioxolane.

4. The structure for protecting a lithium metal anode material according to claim 1, wherein: the structure for protecting the lithium metal anode material further comprises a substrate, and the multifunctional protection layer is combined on the surface of the substrate.

5. A method of protecting a lithium metal anode material, comprising:

Providing a coating liquid, wherein the coating liquid consists of 3 wt-10 wt% of polyhalogenated alkyl acrylate, 5-15% by weight of lanthanide metal halide and the balance of organic solvent;

preparing the coating liquid into a film, and drying to form a multifunctional protective layer, wherein the thickness of the multifunctional protective layer is 2-5 mu m;

bonding the multifunctional protective layer on the surface of the metal lithium;

The preparation method of the poly halogenated alkyl acrylate comprises the following steps: under the inert atmosphere condition, carrying out polymerization reaction on a mixed reactant containing halogenated alkyl acrylate monomer, methacryloyl fluoride and azodiisobutyronitrile to obtain the poly halogenated alkyl acrylate; the halogenated alkyl acrylate monomer comprises one or more of ethyl 2-bromomethacrylate, ethyl 2-chloromethacrylate, 2-chloroethyl methacrylate, 2, 3-dibromopropyl acrylate, methyl 2-bromomethacrylate and 2, 3-dibromopropyl acrylate.

6. The method according to claim 5, wherein: the lanthanide metal halide includes a combination of one or more of LaF₃、CeF₃、NdF₃、LaCl₃、CeCl₃、 NdCl₃、CeI₃、LaI₃、NdI₃.

7. The method according to claim 5, wherein: the organic solvent comprises one or more of tetrahydrofuran, N-dimethylformamide, dimethyl sulfoxide, ethylene glycol dimethyl ether and 1, 3-dioxolane.

8. The method according to claim 5, wherein: in the mixed reactant, the mass fractions of the halogenated alkyl acrylate monomer, the methacryloyl fluoride and the azodiisobutyronitrile are 30-wt-60-wt%, 10-wt-40-wt% and 5-wt-10-wt% respectively.

9. The method according to claim 5, wherein: the reaction temperature of the polymerization reaction is 50-80 ℃ and the reaction time is 8-16 h.

10. The method of claim 5, wherein the method of preparing the polyalkyl halide acrylate further comprises: and after the polymerization reaction is finished, drying the reaction product, wherein the drying temperature of the drying treatment is 80-100 ℃ and the drying time is 3-6 hours, and the polyhalogenated alkyl acrylate is obtained.

11. A lithium metal negative electrode material comprising lithium metal, further comprising the structure of any one of claims 1-4 bonded to a surface of the lithium metal to protect the lithium metal negative electrode material.

12. The structure for protecting a lithium metal anode material according to any one of claims 1 to 4, the method for protecting a lithium metal anode material according to any one of claims 5 to 10, or the use of a lithium metal anode material according to any one of claims 11 in the preparation of a lithium metal battery.

13. A lithium metal battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: the negative electrode comprises the lithium metal negative electrode material of any one of claim 11.