A composite lithium metal anode material for lithium metal batteries and a preparation method thereof
By forming a hybrid Li3Bi/LiF artificial solid electrolyte interface film on the surface of the metal lithium negative electrode, the problems of lithium dendrites and electrode volume expansion are solved, and the cycle stability and high energy density of the high-performance metal lithium negative electrode are achieved.
Patent Information
- Application Number
- CN202210676756.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-06-15
- Publication Date
- 2025-06-10
- Estimated Expiration
- 2042-06-15
AI Technical Summary
The existing metal lithium anode materials have problems with lithium dendrites and electrode volume expansion, and the artificial solid electrolyte interface film has low lithium ion diffusion ability and low electronic resistivity, making it difficult to achieve a high-performance metal lithium anode.
A hybrid Li3Bi/LiF artificial solid electrolyte interface film is used to spontaneously react the submicron polyhedral BiF3 with the metal lithium negative electrode to form an interface film to form a composite metal lithium negative electrode material. The interface film has high ion diffusion ability, high resistivity and high Young's modulus.
Effectively inhibit the vertical growth of lithium dendrites, promote the uniform deposition of metal lithium at the SEI/Li interface, significantly improve the cycling stability of metal lithium negative electrodes, and achieve stable cycling under high current density and high surface capacity.
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Figure CN115101729B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of anode materials for lithium metal batteries, and specifically provides a composite metal lithium anode material with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film and a preparation method thereof. Background Art
[0002] The metallic lithium anode is regarded as the holy grail of anode materials due to its extremely high theoretical specific capacity (3860 mAh / g) and the lowest redox potential (-3.04 V vs. standard hydrogen electrode). However, its commercial application is severely restricted by the unrestricted growth of lithium dendrites and the unrestricted volume expansion of electrode materials.
[0003] To solve the above key problems, various modification schemes such as optimizing the electrolyte system, modifying the artificial solid electrolyte interface film, alloying lithium metal, and three-dimensional current collectors have been proposed, and the electrochemical performance of the metallic lithium anode has been modified to varying degrees. Among them, the artificial solid electrolyte interface film, as an effective modification strategy, can not only effectively inhibit the vertical growth of lithium dendrites but also alleviate the volume expansion of the lithium anode. However, the currently reported artificial solid electrolyte interface films still face the drawbacks of low lithium ion diffusion ability and low electron resistivity, and it is difficult to solve. Therefore, developing an ideal artificial solid electrolyte interface film with high ion diffusion ability, high resistivity, and high Young's modulus is the key to realizing a high-performance metallic lithium anode and has extremely high commercial application value. Summary of the Invention
[0004] The purpose of the present invention is to provide a composite metal lithium anode material with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film for lithium metal batteries and a preparation method thereof. The composite metal lithium anode material consists of a metallic lithium anode and a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film on its surface. Among them, the hybrid Li 3 Bi / LiF artificial solid electrolyte interface film has the characteristics of high ion diffusion ability, high resistivity, and high Young's modulus, so that the composite metal lithium anode material can effectively solve the key problems such as lithium dendrite growth and electrode volume expansion existing in the existing metallic lithium anode materials, and can induce uniform lithium deposition at the SEI / Li interface of metallic lithium.
[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:
[0006] A composite metal lithium anode material for lithium metal batteries, which consists of a metallic lithium anode and an artificial solid electrolyte interface film on its surface. It is characterized in that the artificial solid electrolyte interface film is a hybrid Li3 Bi / LiF artificial solid electrolyte interface film.
[0007] Further, the hybrid Li 3 The Bi / LiF artificial solid electrolyte interface film is formed by the spontaneous reaction of sub-micron polyhedral BiF 3 with the lithium metal anode.
[0008] Further, the hybrid Li 3 The thickness of the Bi / LiF artificial solid electrolyte interface film is 5 μm to 50 μm.
[0009] The preparation method of the above composite lithium metal anode material for lithium metal batteries is characterized by comprising the following steps:
[0010] S1: Mix a bismuth source, a fluorine source, and a solvent to obtain a mixed solution;
[0011] S2: Subject the mixed solution obtained in S1 to a hydrothermal reaction to obtain sub-micron polyhedral BiF 3 ;
[0012] S3: In a glove box under an inert atmosphere, disperse the sub-micron polyhedral BiF obtained in S2 3 in a solvent to obtain a dispersion;
[0013] S4: In a glove box under an inert atmosphere, drop the dispersion obtained in S3 onto the surface of the lithium metal anode and dry it to obtain a composite lithium metal anode with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film.
[0014] Further, in step S1, the solvent is a mixture of one or more of anhydrous ethanol, ethylene glycol, and diethylene glycol, the bismuth source is a mixture of one or more of bismuth nitrate and bismuth sulfate, and the fluorine source is a mixture of one or more of ammonium fluoride and ammonium tetrafluoroborate.
[0015] Further, in step S1, the preparation process of the mixed solution is as follows: Dissolve 0.5 g to 5 g of the bismuth source and 0.1 g to 3 g of the fluorine source in 50 mL of the solvent, perform ultrasonic dissolution, and then let it stand at room temperature to obtain a mixed liquid.
[0016] Further, in step S2, the temperature of the hydrothermal reaction is 120 °C to 180 °C, and the time is 1 to 5 h.
[0017] Further, in step S3, the solvent is a mixture of one or more of dimethyl carbonate, diethyl carbonate, and tetrahydrofuran, and the concentration of the dispersion is 20 mM to 100 mM (mM is millimole per liter).
[0018] Further, in step S4, the dropping amount is 50 μL to 200 μL, and the drying temperature is 100°C to 200°C. It should be noted that: there is no special limit on the drying time, until the dispersion liquid is completely dried on the surface of the lithium metal anode.
[0019] Based on the above technical solution, the beneficial effects of the present invention are as follows:
[0020] 1. The hybrid Li 3 Bi / LiF artificial solid electrolyte interface film for lithium metal batteries can provide a high lithium ion diffusion ability, a high resistivity, and a high Young's modulus, and effectively induce the uniform deposition of metallic lithium at the SEI / Li interface without the vertical growth of lithium dendrites, significantly promoting the cycle stability of the lithium metal anode. More specifically: LiF in the hybrid Li 3 Bi / LiF artificial solid electrolyte interface film improves the resistivity of the interface film, and can effectively avoid the electronic breakdown of the artificial solid electrolyte film and thus produce uncontrollable deposition; Li 3 in the hybrid Li 3 Bi / LiF artificial solid electrolyte interface film 3 Bi improves the lithium ion diffusion ability of the interface film and stabilizes the interface film, and can effectively induce the uniform deposition of metallic lithium; the hybrid Li 3 Bi / LiF artificial solid electrolyte interface film has a high Young's modulus, enabling it to withstand the huge volume expansion during cycling and inhibiting the vertical growth of lithium dendrites. Finally, the hybrid Li 2 Bi / LiF artificial solid electrolyte interface film in the present invention realizes the stable cycling of metallic lithium at a high current density of 10 mA / cm 2 and a areal capacity of 2 mAh / cm 4 , providing a new perspective in the research on the protection of lithium metal anodes; furthermore, by using LiFePO 3 as the cathode and the composite metallic lithium with the hybrid Li
[0021] 2. The preparation process of the hybrid Li 3 Bi / LiF artificial solid electrolyte interface film for lithium metal batteries in the present invention is simple. BiF with a submicron polyhedral morphology is prepared through a hydrothermal reaction 3 , and it is dispersed and then dropped on the surface of the lithium metal anode, and then the hybrid Li 3 Bi / LiF artificial solid electrolyte interface film is in-situ formed through a spontaneous reaction with the lithium metal anode during the drying process, which is essentially different from the preparation processes of similar interface films in the prior art. Moreover, the present invention has good dispersibility, and the formed hybrid Li 3The Bi / LiF artificial solid electrolyte membrane has the advantages of being stable, simple to prepare, low in cost, and good in synthetic consistency, etc. Description of the Drawings
[0022] Figure 1 SEM image of the submicron polyhedron BiF synthesized in Example 1 of the present invention 3
[0023] Figure 2 Cross-sectional SEM image of the hybrid Li 3 Bi / LiF artificial solid electrolyte interface membrane composite metal lithium anode
[0024] Figure 3 X-ray diffraction pattern of the hybrid Li 3 Bi / LiF artificial solid electrolyte interface membrane composite metal lithium anode synthesized in Example 1 of the present invention
[0025] Figure 4 Cyclic voltammogram of the lithium / lithium symmetric battery assembled in Example 1 of the present invention
[0026] Figure 5 Cycling performance graph of the lithium / lithium symmetric battery assembled in Example 1 of the present invention
[0027] Figure 6 Cycling performance graph of the lithium / lithium symmetric battery assembled in Example 1 of the present invention under high current
[0028] Figure 7 Cycling performance graph of the composite metal lithium anode / lithium iron phosphate cathode battery assembled in Example 2 of the present invention Detailed Description of the Invention
[0029] To make the objectives, technical solutions, and technical effects of the present invention clearer and more complete, the present invention will be further described in detail below with reference to the drawings and embodiments.
[0030] Example 1
[0031] This example provides a composite metal lithium anode material for a lithium metal battery, which consists of a metal lithium anode and a hybrid Li 3 Bi / LiF artificial solid electrolyte interface membrane on its surface. The preparation process is specifically as follows:
[0032] S1: Dissolve 4.85 of bismuth nitrate pentahydrate and 0.786 g of ammonium tetrafluoroborate in a solvent by ultrasonic dissolution, and then let it stand at room temperature to obtain a mixed liquid; wherein, the solvent is a mixture of 25 mL of absolute ethanol and 25 mL of ethylene glycol;
[0033] S2: Hydrothermally react the mixed solution obtained in S1 at 150 °C for 3 h, and wash and dry the product to obtain submicron polyhedral BiF 3 ;
[0034] S3: In a stainless-steel glove box under an inert atmosphere, disperse the submicron polyhedral BiF 3 obtained in S2 in dimethyl carbonate solvent to form a dispersion, and the concentration of the dispersion is 80 mM;
[0035] S4: In a stainless-steel glove box under an inert atmosphere, drop the dispersion obtained in S3 onto the surface of a lithium metal negative electrode and dry it to obtain a composite lithium metal negative electrode with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film; wherein, the dropping amount is 100 uL, and the drying temperature is 100 °C and the time is 3 minutes.
[0036] Based on the above composite lithium metal negative electrode material, this embodiment also provides a high-energy-density lithium metal secondary battery, which uses LiFePO 4 as the positive electrode material, and uses a composite lithium metal negative electrode material with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film, and is prepared by the following steps:
[0037] S5: In a stainless-steel glove box under an inert atmosphere, grind and mix the LiFePO 4 positive electrode material, a conductive agent, and a binder according to a mass ratio of 8-10:1-2:1, and coat it on an aluminum foil current collector to make a positive electrode plate; wherein, the conductive agent is a mixture of one or more of acetylene black, conductive carbon black, and Super P, and the binder is a mixture of one or more of polyacrylic acid, polytetrafluoroethylene, and polyvinylidene fluoride, and the grinding time is 1-5 minutes;
[0038] S6: In a stainless-steel glove box under an inert atmosphere, dry the positive electrode plate obtained in S5 at 80-100 °C and then cut it to obtain an electrode plate, and match and assemble the positive electrode plate with the prepared negative electrode plate into a button-type lithium metal secondary battery; wherein, the electrolyte is prepared by mixing 1M LiTFSI with DOL / DME (v:v = 1:1), and is assembled in an Ar gas atmosphere stainless-steel glove box with a water and oxygen content of less than 1 ppm using a PP separator.
[0039] Meanwhile, this embodiment also provides Comparative Example 1: An unmodified lithium metal negative electrode is used as the negative electrode material, and a lithium-lithium symmetric battery is assembled under the same process as in this embodiment.
[0040] Perform SEM testing on the submicron polyhedral BiF 3 in this embodiment, and the results are as Figure 1 shown. As can be seen from the figure, the prepared BiF3 shows a polyhedral morphology with a size of 200 - 500 nm, providing more active sites and better dispersibility for the lithium metal anode.
[0041] For Li in this example 3 Bi / LiF artificial solid electrolyte interface film was tested by SEM, and the results are as Figure 2 shown. As can be seen from the figure, the prepared Li 3 Bi / LiF artificial solid electrolyte interface film is dense and uniform.
[0042] For Li 3 Bi / LiF artificial solid electrolyte interface film in this example was analyzed by XRD, and the results are as Figure 3 shown. As can be seen from the figure, the XRD diffraction curve shows that the prepared BiF 3 modified lithium metal anode contains the characteristic peaks of Bi, Li 3 Bi and LiF, indicating that after treatment with BiF 3 the lithium metal anode undergoes two-step spontaneous reactions (3Li + BiF 3 → Bi + 3LiF, Li + Bi → Li 3 Bi) to form Bi, Li 3 Bi and LiF; the presence of Li 3 Bi improves the lithium ion diffusion ability of the interface film and stabilizes the interface film, and can effectively induce the uniform deposition of lithium metal; LiF increases the resistivity of the interface film and can effectively avoid the electron breakdown of the artificial solid electrolyte film to produce uncontrollable deposition; at the same time, Li 3 Bi and LiF together enhance the mechanical strength of the artificial solid electrolyte interface film.
[0043] The lithium / lithium symmetric battery assembled in this example was tested by cyclic voltammetry, and its cyclic voltammogram is as Figure 4 shown. As can be seen from the figure, the composite lithium metal anode with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film shows broad peaks at 0.7 V and -0.7 V, corresponding to the reversible reaction: 3Li + Bi → Li 3 Bi, which obviously proves that electrochemically active Bi can reversibly store Li through an alloy reaction and form a Li 3 Bi alloy.
[0044] The lithium / lithium symmetric batteries assembled in this example and Comparative Example 1 were tested for cyclic performance, and the results are as Figure 5 shown. As can be seen from the figure, at a current density of 1 mA / cm 2 and an areal capacity of 1 mAh / cm 2 , with a hybrid Li3 The composite lithium metal anode with Bi / LiF artificial solid electrolyte interface film can cycle stably with a relatively low overpotential. As the cycling depth increases, the overpotential shows no obvious increasing trend. At the same time, the overpotential of the unmodified lithium metal electrode is significantly higher than that of the former and the polarization gradually increases significantly.
[0045] The cycling performance tests of the lithium / lithium symmetric batteries assembled in this example and Comparative Example 1 were carried out at high current, and the results are as Figure 6 shown. As can be seen from the figure, at a current density of 10 mA / cm 2 and an areal capacity of 2 mAh / cm 2 , the composite lithium metal anode with hybrid Li 3 Bi / LiF artificial solid electrolyte interface film can cycle stably for more than 2000 cycles. As the cycling depth increases, the overpotential shows no obvious increasing trend. At the same time, for the unmodified lithium metal electrode, as the cycling depth increases, the overpotential gradually increases.
[0046] In summary, the composite lithium metal anode with hybrid Li 3 Bi / LiF artificial solid electrolyte interface film provided by the present invention shows more excellent interfacial stability performance compared with the unmodified lithium metal anode. Li 3 Bi, as a lithiophilic alloy, can accelerate the transport of lithium ions at the interface, and LiF can improve the electronic insulation performance of the interface.
[0047] Example 2
[0048] This example provides a high-energy-density lithium metal secondary battery, which uses LiFePO 4 as the cathode material and uses the composite lithium metal anode material with hybrid Li 3 Bi / LiF artificial solid electrolyte interface film in Example 1. The only difference from Example 1 is that both electrodes in Example 1 are composite lithium metal anode materials, while in this example, one side uses LiFePO 4 as the cathode material and the anode material is the composite lithium metal anode material. Among them, the electrolyte is prepared by mixing 1 M LiPF 6 with EC / DMC (v:v = 1:1). At the same time, the present invention also provides a Comparative Example 2, and the only difference from this example is that the anode material in Comparative Example 2 is an unmodified lithium metal anode.
[0049] The cycling performance tests of the lithium metal secondary batteries assembled in this example and Comparative Example 2 were carried out, and the results are as Figure 7 shown. As can be seen from the figure, at a current density of 1 C, Li 3The full cell corresponding to the composite lithium metal anode modified with Bi / LiF artificial solid electrolyte interphase film can still release a specific capacity of 143.0 mAh / g after 500 cycles, and its capacity retention rate is 93.0%; it should be noted that this slight capacity decay is mainly due to the structural degradation of the cathode material during cycling; therefore, Li 3 The composite lithium metal anode modified with Bi / LiF artificial solid electrolyte interphase film has good cycling stability. In contrast, the full cell corresponding to unmodified lithium metal shows a sharp decline in its discharge capacity after 500 cycles, and its capacity retention rate is only 50.0%; it should be noted that this sharp capacity decay is mainly caused by continuous side reactions and lithium dendrite growth on the anode side during cycling, which is completely irreversible.
[0050] As described above, the above are only specific embodiments of the present invention. Any feature disclosed in this specification, unless specifically stated, can be replaced by other equivalent or alternative features with similar purposes; all the features disclosed, or all the steps in any method or process, except for mutually exclusive features and / or steps, can be combined in any way.
Claims
1. A composite lithium metal anode material for a lithium metal battery, which is composed of a lithium metal anode and an artificial solid electrolyte interface film on its surface. Characterized in that, The artificial solid electrolyte interface film is a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film; The composite metal lithium negative electrode material is prepared by the following steps: S1: Dissolve 4.85 of bismuth nitrate pentahydrate and 0.786 g of ammonium tetrafluoroborate in a solvent by ultrasonic dissolution, and then let it stand at room temperature to obtain a mixed liquid; wherein, the solvent is a mixed solution of 25 mL of absolute ethanol and 25 mL of ethylene glycol. S2: Hydrothermally react the mixed solution obtained in S1 at 150 °C for 3 h, and wash and dry the product to obtain submicron polyhedral BiF 3 ; S3: In a stainless-steel glove box under an inert atmosphere, disperse the sub-micron polyhedral BiF obtained in S2 3 in a dimethyl carbonate solvent to form a dispersion, and the concentration of the dispersion is 80 mM; S4: In a stainless-steel glove box under an inert atmosphere, the dispersion obtained in S3 was dropped onto the surface of a lithium metal anode and dried to obtain a composite lithium metal anode with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film; wherein, the dropping amount was 100 μL, the drying temperature was 100 °C, and the time was 3 minutes; The composite lithium metal anode material has a stable cycle of more than 2000 cycles at a current density of 10 mA / cm 2 and a areal capacity of 2 mAh / cm 2 .
2. The composite lithium metal anode material for a lithium metal battery according to claim 1, Characterized in that, The hybrid Li 3 Bi / LiF artificial solid electrolyte interface film is formed by the spontaneous reaction of sub-micron polyhedral BiF 3 with the lithium metal anode.
3. The composite lithium metal anode material for a lithium metal battery according to claim 1, Characterized in that, The hybrid Li 3 The thickness of the Bi / LiF artificial solid electrolyte interface film is 5 μm to 50 μm.
4. The preparation method of the composite lithium metal anode material for a lithium metal battery according to claim 1, Characterized in that, Comprises the following steps: S1: Mix a bismuth source, a fluorine source and a solvent to obtain a mixed solution. S2: Subject the mixed solution obtained in S1 to a hydrothermal reaction to obtain submicron polyhedral BiF 3 ; S3: In a glove box under an inert atmosphere, disperse the submicron polyhedral BiF obtained in S2 3 in a solvent to obtain a dispersion; S4: In a glove box under an inert atmosphere, the dispersion obtained in S3 is dropped onto the surface of a lithium metal anode and dried to obtain a composite lithium metal anode with a hybrid Li 3 Bi / LiF artificial solid electrolyte interface film.