Preparation method for constructing artificial SEI film on surface of lithium negative electrode

Abstract

The invention discloses a preparation method for constructing an artificial SEI film on the surface of a lithium negative electrode. According to the method, a mixture of a hydroxyl rare earth metal compound and a carboxyl compound is added, and the rare earth metal-metal organic framework (MOF) composite material is prepared through the steps of stirring, ultrasonic treatment, drying, high-temperature heating and the like. And then, the material and a high-ionic-conductivity binder are coated on a copper foil, and proper pressure is applied to transfer and press the material on a lithium negative electrode, so that an SEI film with high stability and ionic conductivity is formed, and the performance and the safety of the lithium metal battery are effectively improved.

Description

Technical Field

[0001] The invention discloses a preparation method for constructing an artificial SEI film on the surface of a lithium negative electrode, and relates to the field of chemical power sources. Background Art

[0002] Lithium metal anodes have attracted much attention in the battery field because of their extremely high theoretical specific capacity (3860mAh / g) and lowest electrochemical potential, which makes them have great potential in improving battery energy density. This feature makes lithium metal anodes very suitable for battery technologies with high energy requirements, such as lithium-sulfur and lithium-air batteries. However, the high activity of lithium metal also brings a series of technical challenges, including the formation of lithium dendrites and unstable solid electrolyte interface (SEI) layer. These problems may lead to battery short circuit, capacity decay, and even safety hazards.

[0003] To address these issues, constructing an artificial SEI layer has become an important method. The natural SEI layer is difficult to stabilize during charging and discharging, while the artificial SEI layer can enhance the mechanical strength and ionic conductivity through a variety of materials (such as LiF, Li2O, polymers, etc.), provide higher chemical stability, thereby inhibiting the growth of lithium dendrites and reducing the decomposition of the electrolyte. Therefore, we artificially construct a SEI containing rare earth metal MOF and ionic liquid modified binder to effectively enhance the mechanical strength of the SEI and restrain the lithium ion flow, so that the lithium ions are deposited more evenly on the negative electrode surface. Summary of the invention

[0004] To achieve the above object, the present invention adopts the following technical solution:

[0005] In a first aspect, a method for preparing an artificial SEI film on the surface of a lithium negative electrode is provided, characterized in that the method comprises the following steps:

[0006] S1: adding a hydroxyl-containing rare earth metal compound to a mixture of an appropriate amount of DMF and an appropriate amount of deionized water, stirring for a certain period of time, and then ultrasonically treating, which is recorded as solution A; mixing a carboxyl-containing structure compound, DMF, deionized water and an organic amine, stirring for a certain period of time, and then ultrasonically treating, to obtain solution B;

[0007] S2: gradually introducing solution B into solution A and continuing stirring; collecting the resulting reaction product, drying it, and then transferring it to a ceramic container, and then heating it at a high temperature for a certain period of time to obtain a rare earth metal-containing MOF composite material;

[0008] S3: The rare earth metal-containing MOF composite material and the high ion conductive adhesive prepared in S2 are coated on a copper foil in an appropriate proportion, and then the copper foil is placed in an oven for drying; then the copper foil containing the active material is attached to the lithium metal negative electrode, and after pressing under a certain pressure for a period of time, the copper foil is peeled off to obtain an artificially constructed SEI film on the lithium metal surface.

[0009] Preferably, the rare earth metal compound in S1 is scandium hydroxide (Sc(OH)3), lanthanum hydroxide (La(OH)3), cerium hydroxide (Ce(OH)4), oxyhydroxy yttrium (YOOH), tetrahydroxy yttrium, tetrahydroxy lanthanum, tetrahydroxy cerium, tetrahydroxy neodymium and other rare earth metal polyhydroxy compounds; trimellitic anhydride, phthalic acid, isomellitic anhydride, 1,2,4,5-benzenetetracarboxylic anhydride, maleic anhydride, adipic anhydride; the ratio of DMF and deionized water is 1: (0.1-100), the organic amine is trimethylamine, tri-n-butylamine, triethylamine, N,N-diethylmethylamine, N,N-dimethylethylamine, triisopropylamine, diethylamine and diisopropylethylamine, etc.; the stirring time is 0.2-2000h, and the ultrasonic time is 0.1-1000h.

[0010] Preferably, the speed of adding solution B to solution A in S2 is 0.1-300 ml / min; the stirring speed is 0.1-3000 rpm / min; the heating temperature is 200-600°C;

[0011] Preferably, the highly conductive adhesive in S3 is polydiallyldimethylammonium bis(trifluoromethanesulfonyl)imide (PDDATFSI), PVDF-BMIM-TFSI, PAA-EMIM-BF4, CMC-EMIM-TFSI, PAN-Py13-TFSI and PEO-BMIM-Cl; the oven temperature is 30-100°C; the pressure is 20-500mPa; and the pressing time is 0.1-200h.

[0012] In a second aspect, the present invention provides a composition for constructing an artificial SEI on the surface of a lithium negative electrode, which is prepared by the preparation method described in any one of the steps in the first aspect.

[0013] In the third aspect, a composition for constructing an artificial SEI on the surface of a lithium negative electrode as described in the second aspect is characterized in that it is applied to lithium metal batteries, lithium ion batteries, sodium ion batteries, sodium metal batteries, potassium ion batteries, and potassium metal batteries.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] 1. Improve battery safety: By constructing an artificial SEI film on the surface of the lithium negative electrode, the growth of lithium dendrites can be effectively inhibited. Lithium dendrites are the main cause of battery short circuit and thermal runaway. The construction of an artificial SEI layer reduces this risk, thereby greatly improving battery safety.

[0016] 2. Extend cycle life: The high mechanical strength and good ionic conductivity of the artificial SEI layer make it more stable, which can reduce electrolyte decomposition and interfacial reaction, significantly slow down capacity decay, and improve the battery's cycle stability and long-term performance.

[0017] 3. Promote lithium ion desolvation: The MOF layer containing rare earth metals plays an important role in the SEI layer. It can help lithium ions migrate stably during the desolvation process. The pore structure of MOF can accelerate the desolvation process of lithium ions, reduce electrolyte decomposition, improve interface stability, reduce battery internal resistance, and thus improve the electrochemical performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Charge and discharge curves of sulfur-based polymer cathode materials. DETAILED DESCRIPTION

[0019] In order to facilitate the understanding of the present invention, the present invention will be described in more comprehensive and detailed manner below in conjunction with the accompanying drawings and preferred experimental examples, but the protection scope of the present invention is not limited to the following specific embodiments.

[0020] Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0021] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0022] Implementation Case 1

[0023] Lanthanum tetrahydroxy (1.5 g) was added to a mixture of 75 ml of DMF and 15 ml of deionized water, stirred for 2 hours, and then ultrasonically treated for half an hour to obtain solution A. Maleic anhydride (0.5 g), 75 ml of DMF, 15 ml of deionized water and 3 ml of tri-n-butylamine were mixed, stirred for 2 hours and ultrasonically treated for half an hour to obtain solution B. Solution B was gradually added dropwise to solution A and stirred for 2 hours. The product was collected, dried at 60°C overnight, and calcined at 600°C for 3 hours to obtain a La-MOF composite material. The composite material and PVDF-BMIM-TFSI binder were coated on copper foil in a 1:1 ratio, dried, and pressed on a lithium negative electrode at a pressure of 500 mPa to obtain a lithium negative electrode with an artificial SEI layer. The lithium-sulfur battery was assembled, and the reversible discharge specific capacity was 707 mAh / g at a current density of 0.2C, which could maintain a stable cycle for 600 weeks. Figure 1 shown.

[0024] Implementation Case 2

[0025] Tetrahydroxyyttrium (2g) was added to a mixture of 80 ml of DMF and 20 ml of deionized water, stirred for 3 hours and ultrasonically treated for half an hour to obtain solution A. Adipic anhydride (1g), 80 ml of DMF, 20 ml of deionized water and 5 ml of N,N-diethylmethylamine were mixed, stirred for 1 hour, and ultrasonically treated for half an hour to obtain solution B. Solution B was gradually introduced into solution A and stirred for 3 hours. The product was dried and heated at 650°C for 3 hours to obtain a Y-MOF composite material. This composite material was mixed with PDDATFSI binder and coated with copper foil. After drying, it was pressed on the lithium negative electrode with a pressure of 400mPa to obtain a lithium negative electrode with an artificial SEI layer. The lithium-sulfur battery was assembled, and the reversible discharge specific capacity was 730mAh / g at a current density of 0.2C, which could maintain a stable cycle for 500 weeks.

[0026] Implementation Case 3

[0027] Tetrahydroxyneodymium (1 g) was added to a mixture of 70 ml of DMF and 10 ml of deionized water, stirred for 1 hour and ultrasonically treated for half an hour to obtain solution A. Trimellitic anhydride (0.6 g), 70 ml of DMF, 10 ml of deionized water and 2 ml of triethylamine were mixed, stirred for 1 hour and ultrasonically treated for half an hour to obtain solution B. Solution B was slowly added to solution A and stirred for 2 hours. After drying, it was heated at 550°C for 3 hours to obtain a Nd-MOF composite material. The material was coated on copper foil with CMC-EMIM-TFSI binder, dried and pressed on the surface of the lithium negative electrode at a pressure of 300 mPa to obtain a lithium negative electrode with an artificial SEI layer. The lithium-sulfur battery was assembled, and the reversible discharge specific capacity was 690 mAh / g at a current density of 0.2C, which could maintain a stable cycle for 800 weeks.

Claims

1. A method for preparing an artificial SEI film on the surface of a lithium negative electrode, characterized in that: The following steps are involved: S1: adding a hydroxyl-containing rare earth metal compound to a mixture of an appropriate amount of DMF and an appropriate amount of deionized water, stirring for a certain period of time, and then ultrasonically treating, which is recorded as solution A; mixing a carboxyl-containing structure compound, DMF, deionized water and an organic amine, stirring for a certain period of time, and then ultrasonically treating, to obtain solution B; S2: gradually introducing solution B into solution A and continuing stirring; collecting the resulting reaction product, drying it, and then transferring it to a ceramic container, and then heating it at a high temperature for a certain period of time to obtain a rare earth metal-containing MOF composite material; S3: The rare earth metal-containing MOF composite material and the high ion conductive adhesive prepared in S2 are coated on a copper foil in an appropriate proportion, and then the copper foil is placed in an oven for drying; then the copper foil containing the active material is attached to the lithium metal negative electrode, and after pressing under a certain pressure for a period of time, the copper foil is peeled off to obtain an artificially constructed SEI film on the lithium metal surface.

2. The method for preparing an artificial SEI film on the surface of a lithium negative electrode according to claim 1, characterized in that: The rare earth metal compounds in S1 are scandium hydroxide (Sc(OH)3), lanthanum hydroxide (La(OH)3), cerium hydroxide (Ce(OH)4), oxyhydroxy yttrium (YOOH), tetrahydroxy yttrium, tetrahydroxy lanthanum, tetrahydroxy cerium, tetrahydroxy neodymium rare earth metal polyhydroxy compounds; trimellitic anhydride, phthalic acid, pyromellitic anhydride, 1,2,4,5-benzenetetracarboxylic anhydride, maleic anhydride, adipic anhydride, etc.; the ratio of DMF to deionized water is 1: (0.1-100), and the organic amines are trimethylamine, tri-n-butylamine, triethylamine, N,N-diethylmethylamine, N,N-dimethylethylamine, triisopropylamine, diethylamine and diisopropylethylamine, etc.; the stirring time is 0.2-2000h, and the ultrasonic time is 0.1-1000h.

3. The method for preparing an artificial SEI film on the surface of a lithium negative electrode according to claim 1, characterized in that: The speed of dripping solution B in S2 into solution A is 0.1-300 ml / min; the stirring speed is 0.1-3000 rpm / min; and the heating temperature is 200-600°C.

4. The method for preparing an artificial SEI film on the surface of a lithium negative electrode according to claim 1, characterized in that: The highly conductive adhesives in S3 are polydiallyldimethylammonium bis(trifluoromethanesulfonyl)imide (PDDATFSI), PVDF-BMIM-TFSI, PAA-EMIM-BF4, CMC-EMIM-TFSI, PAN-Py13-TFSI and PEO-BMIM-Cl; the oven temperature is 30-100°C; the pressure is 20-500mPa; and the pressing time is 0.1-200h.

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