A rare earth oxide-based artificial SEI film, and a preparation method and application thereof

Abstract

This invention provides a rare-earth oxide-based artificial SEI film, its preparation method, and its application, belonging to the field of lithium metal battery technology. First, a dispersant and a binder are mixed to obtain solution A. Rare-earth oxides and solution A are mixed to obtain a precursor slurry. Then, the precursor slurry is coated onto a copper foil and dried to obtain the rare-earth oxide-based artificial SEI film. The rare-earth oxide-based artificial SEI film prepared by this invention helps extend the lifespan of the lithium metal anode. The artificial SEI film has good electrolyte wettability and a uniform and stable structure, promoting lithium-ion nucleation and growth kinetics and ensuring the stability of lithium ions during deposition / stripping. This allows the lithium metal anode to maintain a low and stable electrode / electrolyte interface impedance, helping to reduce overpotential during lithium-ion deposition, thereby improving the long cycle life of the lithium metal anode.

Description

Technical Field

[0001] This invention relates to the field of lithium metal battery technology, and in particular to a rare earth oxide-based artificial SEI film, its preparation method, and its application. Background Technology

[0002] Lithium metal anodes possess extremely high theoretical specific capacity and low electrochemical potential, making them key anode materials for constructing high-energy-density batteries. However, lithium metal anodes are prone to problems during cycling, such as lithium dendrite growth, severe interfacial side reactions, and unstable SEI film that repeatedly breaks down and reconstructs, leading to decreased coulombic efficiency, shortened cycle life, and potential safety hazards such as short circuits and thermal runaway. Constructing artificial SEI films on the electrode surface is an effective way to improve interfacial stability. Rare earth oxides exhibit wide-bandgap electronic insulation properties, high chemical stability, and excellent interfacial compatibility, demonstrating unique advantages in lithium metal anode interface engineering. However, the construction of existing rare earth oxide SEIs mostly relies on vapor phase deposition or complex liquid phase processes, which suffer from high equipment costs, poor process adaptability, and insufficient film uniformity and adhesion, limiting their large-scale application. Therefore, it is urgent to study a rare earth oxide-based artificial SEI film and its preparation method to balance interfacial performance and production feasibility. Summary of the Invention

[0003] The purpose of this invention is to provide a rare earth oxide-based artificial SEI film, its preparation method, and its application, so as to solve the problems of insufficient uniformity and adhesion of rare earth oxide SEI film layers in the prior art.

[0004] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing a rare earth oxide-based artificial SEI film, comprising the following steps: (1) Mix the dispersant and binder to prepare solution A; (2) A precursor slurry is prepared by mixing rare earth oxides and solution A. The precursor slurry is then coated onto copper foil and dried to obtain a rare earth oxide-based artificial SEI film.

[0005] Preferably, in step (1), the dispersant comprises one or more of N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide and γ-butyrolactone.

[0006] Preferably, in step (1), the adhesive comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate and polyacrylic acid.

[0007] Preferably, in step (1), the mass ratio of the dispersant to the binder is 1~3:0.1~0.2.

[0008] Preferably, in step (1), the mixing temperature is 25~60℃, the stirring speed is 200~600rpm, and the time is 8~24h.

[0009] Preferably, in step (2), the rare earth oxide comprises one or more of yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, and scandium oxide; and the particle size of the rare earth oxide is 100 nm to 10 μm.

[0010] Preferably, in step (2), the mass ratio of the rare earth oxide to solution A is 0.3~0.5:1.1~3.2.

[0011] Preferably, in step (2), the mixing temperature is 25~60℃, the stirring speed is 200~600rpm, and the time is 8~24h; the coating thickness is 15~65μm; and the drying temperature is 100~130℃ and the time is 15~30min.

[0012] The present invention also provides a rare earth oxide-based artificial SEI membrane prepared by the above-described method.

[0013] The present invention also provides an application of the above-described rare earth oxide-based artificial SEI film in lithium metal batteries.

[0014] The beneficial effects of this invention are: The rare earth oxide-based artificial SEI film provided by this invention has a simple and low-cost preparation process. The SEI film is prepared by simply coating a precursor slurry onto a copper foil, and then using this slurry to construct a rare earth oxide interface layer. This process requires no harsh high-temperature conditions, is simple to operate, and uses inexpensive and readily available raw materials, making it suitable for large-scale preparation.

[0015] The rare earth oxide-based artificial SEI film prepared by this invention helps to extend the lifespan of lithium metal anodes. The artificial SEI film has good electrolyte wettability and a uniform and stable structure, which promotes lithium ion nucleation and growth kinetics and ensures the stability of lithium ions during the deposition / stripping process. This allows the lithium metal anode to maintain a low and stable electrode / electrolyte interface impedance, which helps to reduce the overpotential during the lithium ion deposition process, thereby improving the long cycle life of the lithium metal anode.

[0016] The rare earth oxide-based artificial SEI film prepared by this invention can inhibit the growth of lithium dendrites and improve the safety of lithium metal anodes.

[0017] The rare earth oxide-based artificial SEI film prepared by this invention has good mechanical strength and physicochemical stability. It can adapt to the volume change of the lithium metal anode without cracking during the charge-discharge cycle of lithium metal battery, inhibit the growth of lithium dendrites, and reduce the risk of short circuit and thermal runaway of lithium metal battery. Attached Figure Description

[0018] Figure 1 The impedance spectra of the Y2O3@Cu electrode and the pure copper foil electrode in Example 1 are shown, where a represents the impedance of the pure copper foil electrode as a function of cycle number, b represents the impedance of the Y2O3@Cu electrode as a function of cycle number, and c represents the impedance of the pure copper foil electrode and the Y2O3@Cu electrode, respectively. SEI The value changes with the number of cycle cycles; Figure 2 This is a comparison of the coulombic efficiency of the Y2O3@Cu electrode and the pure copper foil electrode in Example 2 under different current densities and discharge capacities, where a represents the efficiency when the discharge capacity is 1 mAh cm⁻¹. -2 The current densities were 1, 2, and 5 mA cm⁻¹, respectively. -2 A comparison of the coulombic efficiencies of the two electrodes is shown in Figure b, where b represents the efficiency when the current density is 1 mA cm⁻¹. -2 The discharge capacities are 2, 5, and 10 mAh cm⁻¹, respectively. -2 A comparison of the coulombic efficiencies of the two electrodes. Detailed Implementation

[0019] This invention provides a method for preparing a rare earth oxide-based artificial SEI film, comprising the following steps: (1) Mix the dispersant and binder to prepare solution A; (2) A precursor slurry is prepared by mixing rare earth oxides and solution A. The precursor slurry is then coated onto copper foil and dried to obtain a rare earth oxide-based artificial SEI film.

[0020] In this invention, in step (1), the dispersant comprises one or more of N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide and γ-butyrolactone.

[0021] In this invention, in step (1), the adhesive comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate and polyacrylic acid.

[0022] In this invention, in step (1), the mass ratio of the dispersant to the binder is 1~3:0.1~0.2, specifically 1.01:0.1, 1.5:0.1, 1.5:0.2, or 2:0.12.

[0023] In this invention, in step (1), the mixing temperature is 25~60℃, specifically 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, the stirring speed is 200~600rpm, specifically 200rpm, 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, 600rpm, and the time is 8~24h, specifically 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h.

[0024] In this invention, the general formula of the rare earth oxide is RE2O3.

[0025] In this invention, in step (2), the rare earth oxide comprises one or more of yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, and scandium oxide; the particle size of the rare earth oxide is 100nm~10μm, specifically 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 800nm, 1μm, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm.

[0026] In this invention, in step (2), the mass ratio of the rare earth oxide to solution A is 0.3~0.5:1.1~3.2, preferably 0.35~0.45:1.11~3.0, and more preferably 0.4:1.5~2.12.

[0027] In this invention, in step (2), the mixing temperature is 25~60℃, specifically 25℃, 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, or 60℃; the stirring speed is 200~600 rpm, specifically 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, or 600 rpm; and the time is 8~24 hours, specifically 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, or 18 hours. The coating process is carried out at temperatures ranging from 100 to 130°C, specifically 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, and 130°C, for 15 to 30 minutes, specifically 15 minutes, 20 minutes, 25 minutes, and 30 minutes.

[0028] The present invention also provides a rare earth oxide-based artificial SEI membrane prepared by the above-described method.

[0029] This invention also provides an application of the above-described rare-earth oxide-based artificial SEI film in lithium metal batteries. The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0030] Example 1 NMP (1.01 g) was added to a weighing bottle containing PVDF (0.1 g), and the mixture was magnetically stirred until the PVDF was completely dissolved. The stirring temperature was 40℃, the stirring speed was 500 rpm, and the stirring time was 10 h to obtain solution A. Yttrium oxide powder (0.4 g) with a particle size of 5 μm and a lamellar morphology was added to the weighing bottle containing solution A, and the mixture was stirred at 25℃ and 300 rpm for 8 h. The slurry was coated onto the surface of a copper foil using a scraper to a thickness of 50 μm. The coated copper foil was then vacuum dried at 120℃ for 20 min to obtain a yttrium oxide-based artificial SEI film. The film was then die-cut to obtain a Y2O3@Cu electrode with a diameter of 12 mm. Assemble a symmetrical battery. The components of the symmetrical battery are: negative electrode shell, Y2O3@Cu electrode, separator, Y2O3@Cu electrode, and positive electrode shell. The electrolyte composition is LiTFSI / DOL+DME, and the separator is Celgard 2400. The test conditions for the symmetrical battery are: current density 1 mA cm⁻¹. -2 Discharge capacity 1 mAh cm -2 (Hereinafter referred to as 1-1), under the above conditions, it can be stably cycled for 500 hours.

[0031] from Figure 1 It can be seen that the impedance changes of both electrodes exhibit the same pattern as cycling progresses: the impedance value decreases with increasing cycle number, and the impedance value of the Y2O3@Cu electrode is consistently lower than that of the Cu electrode. The small and stable impedance value of the Y2O3@Cu electrode is attributed to the uniform and stable structure of the yttrium oxide interface. The electrolyte wettability at the electrode / electrolyte interface affects the nucleation and growth kinetics of lithium metal on the electrode surface. The small and stable impedance value of the Y2O3@Cu electrode ensures the stability of lithium ions during the deposition / stripping process, helps reduce the overpotential during lithium ion deposition, and thus improves the long-cycle performance of the Y2O3@Cu electrode.

[0032] Example 2 2 g of NMP was added to a weighing bottle containing 0.12 g of PVDF. The mixture was magnetically stirred until the PVDF was completely dissolved. The stirring temperature was 50 °C, the stirring speed was 600 rpm, and the stirring time was 10 h to obtain solution A. 0.4 g of yttrium oxide powder with a particle size of 200 nm and a granular morphology was added to the weighing bottle containing solution A. The mixture was stirred at 25 °C and 200 rpm for 24 h. The slurry was then coated onto the surface of a copper foil with a coating thickness of 15 μm using a scraper. The coated copper foil was then vacuum dried at 120 °C for 20 min to obtain a yttrium oxide-based artificial SEI film. A Y2O3@Cu electrode with a diameter of 12 mm was obtained by die-cutting. Assemble a half-cell, which consists of: a positive electrode shell, a Y2O3@Cu electrode, a separator, a lithium metal disc, a gasket, a spring, and a negative electrode shell. The electrolyte composition is LiTFSI / DOL+DME, and the separator is Celgard 2400. It can maintain 500 cycles at 1-1; 175 cycles at 2-1; 120 cycles at 5-1; 140 cycles at 1-2; 71 cycles at 1-5; and 54 cycles at 1-10.

[0033] from Figure 2 It can be seen that the Y2O3@Cu electrode exhibits superior rate performance at current densities of 1 and 2 mA cm⁻¹. -2 At that time, the Y2O3@Cu electrode maintained a coulombic efficiency of 98% and remained stable for 300 and 175 cycles, while the Cu electrode could only remain stable for 143 and 119 cycles, and even at 5 mA cm⁻¹, it failed to achieve the same efficiency. -2 Under high current density conditions, the Y2O3@Cu electrode still maintains a coulombic efficiency of 96% after 120 cycles, which is twice that of the Cu electrode (63 cycles). Meanwhile, the Y2O3@Cu electrode also exhibits high efficiency at discharge capacities of 2, 5, and 10 mAh cm⁻¹. -2 The stable cycle counts under the given conditions are 140, 71, and 54 cycles, far exceeding the 118, 34, and 17 cycles of the pure Cu electrode. The superior rate performance of the Y2O3@Cu electrode is attributed to the excellent stability of the yttrium oxide artificial SEI film. The ability of the electrode interface to remain stable and undamaged under high current density and large deposition capacity is key to the electrode's high cycle life.

[0034] Example 3 NMP (1.5 g) was added to a weighing bottle containing PVDF (0.1 g), and the mixture was magnetically stirred until the PVDF was completely dissolved. The stirring temperature was 60°C, the stirring speed was 600 rpm, and the stirring time was 8 h to obtain solution A. Ytterbium oxide powder (0.4 g) with a particle size of 3 μm was added to the weighing bottle containing solution A, and the mixture was stirred at 25°C and 300 rpm for 8 h. The slurry was then coated onto the surface of a copper foil using a scraper to a thickness of 35 μm. The coated copper foil was then vacuum dried at 120°C for 20 min to obtain a ytterbium oxide-based artificial SEI film. A Yb2O3@Cu electrode with a diameter of 12 mm was obtained by die-cutting. A half-cell was assembled with the same composition as in Example 2, and the test was conducted under the 1-1 conditions. Under these conditions, the initial deposition overpotential of the modified electrode in the first pass was 130 mV, which was lower than the 160 mV of the unmodified electrode.

[0035] Example 4 NMP (1.5 g) was added to a weighing bottle containing PVDF (0.2 g), and the mixture was magnetically stirred until the PVDF was completely dissolved. The stirring temperature was 45℃, the stirring speed was 450 rpm, and the stirring time was 24 h to obtain solution A. 0.2 g of tungsten oxide powder and 0.2 g of yttrium oxide powder were added to the weighing bottle containing solution A. Both powders had a lamellar morphology and a particle size of 500 nm. The mixture was stirred at 25℃ and 300 rpm for 24 h. The slurry was then coated onto the surface of a copper foil using a scraper to a thickness of 20 μm. The coated copper foil was then vacuum dried at 120℃ for 20 min to obtain a tungsten oxide / yttrium oxide-based artificial SEI film. A 12 mm diameter Sm₂O₃ / Y₂O₃@Cu electrode was obtained by die-cutting. Assemble a half-cell with the same composition as in Example 2 and test it under 1-1 conditions. Under these conditions, the initial deposition overpotential of the modified electrode in the first cycle is 88 mV, which is lower than the 160 mV of the unmodified electrode, and it maintains a stable coulombic efficiency of 98% for 300 cycles.

[0036] Example 5 2 g of NMP was added to a weighing bottle containing 0.12 g of PVDF. The mixture was magnetically stirred until the PVDF was completely dissolved. The stirring temperature was 50 °C, the stirring speed was 600 rpm, and the stirring time was 10 h to obtain solution A. The above steps were repeated to obtain 3 portions of solution A. 0.4 g of spherical yttrium oxide powder with particle sizes of 500 nm (a), 2 μm (b), and 5 μm (c) were added to each portion, respectively. The mixture was stirred at 25 °C and 200 rpm for 24 h. The slurry was then coated onto the surface of a copper foil with a coating thickness of 15 μm using a scraper. The coated copper foil was then vacuum dried at 120 °C for 20 min to obtain a yttrium oxide-based artificial SEI film. A Y2O3@Cu electrode with a diameter of 12 mm was obtained by die-cutting. A half-cell was assembled, consisting of a positive electrode shell, a Y₂O₃@Cu electrode, a separator, lithium metal discs, a gasket, a spring, and a negative electrode shell. The electrolyte composition was LiTFSI / DOL+DME, and the separator was Celgard 2400. Under 1-1 conditions, the initial lithium nucleation overpotential of group a electrode was 63 mV, group b electrode was 89 mV, and the initial lithium nucleation overpotential of group c electrode was 92 mV. The three groups of electrodes underwent 200 cycles of charge-discharge testing under 1-1 conditions. Group a electrode maintained its original interface morphology without obvious lithium dendrites; group b electrode showed obvious moss-like dendrites in some areas; and group c electrode was completely covered by moss-like dendrites with obvious rod-shaped dendrites. The artificial SEI film composed of yttrium oxide with different particle sizes had varying degrees of suppression of lithium dendrites. Smaller particle sizes helped improve the uniformity and stability of the interface, which was beneficial for the uniform and stable transport of lithium ions.

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a rare earth oxide-based artificial SEI film, characterized in that, Includes the following steps: (1) Mix the dispersant and binder to prepare solution A; (2) A precursor slurry is prepared by mixing rare earth oxides and solution A, and then the precursor slurry is coated on copper foil and dried to obtain a rare earth oxide-based artificial SEI film.

2. The method for preparing a rare earth oxide-based artificial SEI film according to claim 1, characterized in that, In step (1), the dispersant comprises one or more of N-methylpyrrolidone, N-ethylpyrrolidone, dimethylformamide, dimethylacetamide and γ-butyrolactone.

3. The method for preparing a rare earth oxide-based artificial SEI film according to claim 2, characterized in that, In step (1), the adhesive comprises one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium alginate and polyacrylic acid.

4. The method for preparing a rare earth oxide-based artificial SEI film according to any one of claims 1 to 3, characterized in that, In step (1), the mass ratio of the dispersant to the binder is 1~3:0.1~0.

2.

5. The method for preparing a rare earth oxide-based artificial SEI film according to claim 4, characterized in that, In step (1), the mixing temperature is 25~60℃, the stirring speed is 200~600rpm, and the time is 8~24h.

6. The method for preparing a rare earth oxide-based artificial SEI film according to claim 3 or 5, characterized in that, In step (2), the rare earth oxide comprises one or more of yttrium oxide, lanthanum oxide, cerium oxide, praseodymium oxide, neodymium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, erbium oxide, thulium oxide, ytterbium oxide, lutetium oxide, and scandium oxide; the particle size of the rare earth oxide is 100 nm to 10 μm.

7. The method for preparing a rare earth oxide-based artificial SEI film according to claim 6, characterized in that, In step (2), the mass ratio of the rare earth oxide to solution A is 0.3~0.5:1.1~3.

2.

8. The method for preparing a rare earth oxide-based artificial SEI film according to claim 5 or 7, characterized in that, In step (2), the mixing temperature is 25~60℃, the stirring speed is 200~600rpm, and the time is 8~24h; the coating thickness is 15~65μm; and the drying temperature is 100~130℃ and the time is 15~30min.

9. The rare earth oxide-based artificial SEI membrane prepared by the method of any one of claims 1 to 8.

10. The application of the rare earth oxide-based artificial SEI film according to claim 9 in lithium metal batteries.

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