Lithium metal negative electrode and preparation method, lithium metal battery, and electric device
By forming a protective layer on the surface of the negative electrode of a lithium metal battery, which is a polymer of compound I and alkene-bonded monomers containing sulfonic acid groups, the problems of lithium dendrites and SEI film rupture are solved, thereby improving the cycle performance and safety of lithium metal batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SVOLT ENERGY TECHNOLOGY CO LTD
- Filing Date
- 2023-12-28
- Publication Date
- 2026-07-24
AI Technical Summary
Lithium metal batteries suffer from lithium dendrite formation and SEI film rupture during charging and discharging, leading to decreased battery performance and safety risks. Existing polymer protective layers cannot effectively regulate lithium-ion transport, resulting in uneven lithium deposition.
A protective layer is formed by polymerizing compound I with alkene monomers containing sulfonic acid groups, providing an ion-conducting elastic protective layer, regulating uniform lithium deposition, suppressing lithium dendrites and SEI film rupture, and promoting lithium-ion conduction by forming a flexible polymer protective layer on the surface of the lithium metal anode sheet.
Improving the cycle performance and safety of lithium metal batteries by suppressing lithium dendrite growth and SEI film rupture enhances battery stability and lifespan.
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Abstract
Description
Technical Field
[0001] This application belongs to the field of battery materials technology, specifically relating to a lithium metal anode and its preparation method, a lithium metal battery, and an electrical device. Background Technology
[0002] Lithium metal possesses a high theoretical specific capacity (3860 mAh / g) and low reduction potential, making it one of the ideal materials for lithium-ion battery anodes. However, due to the extremely high electrochemical activity of lithium metal, severe side reactions occur on the lithium metal surface of the electrolyte, and lithium dendrites are easily generated during deposition, leading to safety issues such as internal short circuits and thermal runaway. The development of lithium metal batteries faces a series of major challenges, including: the significant volume change of the lithium metal anode during charging and discharging, which can easily cause SEI rupture during deposition; the exposed fresh lithium metal continuously reacts with the electrolyte, leading to reduced coulombic efficiency, electrolyte desiccation, and shortened battery life; lithium dendrites generated by uneven deposition / stripping of lithium metal can pierce the separator, causing internal short circuits, leading to battery combustion or even explosion; and lithium dendrites easily detach from their roots, causing some lithium metal to break away from the substrate, forming "dead lithium," which accumulates and leads to a continuous reduction in battery active components and a sharp increase in battery interface impedance.
[0003] To address the aforementioned problems in lithium metal batteries, researchers have used polymers as protective layers to prevent lithium metal from reacting with the electrolyte layer. Polymers such as polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), and polyacrylonitrile (PAN) are used to create polymer films by adding lithium salts. However, these polymers react with lithium... + The affinity of these compounds is weak, and they cannot effectively regulate Li. + Even with proper transmission, uneven lithium deposition is still inevitable, inducing the formation of lithium dendrites, leading to a decline in battery performance and posing safety risks.
[0004] Therefore, how to improve the structure and performance of lithium metal anodes to avoid the rupture and regeneration of lithium dendrites and SEI film during lithium metal battery cycling is a problem that needs to be solved. Summary of the Invention
[0005] This application provides a lithium metal anode and its preparation method, a lithium metal battery, and an electrical device, aiming to overcome the shortcomings of existing lithium metal battery material technology and provide a lithium metal anode with an ion-conducting elastic protective layer to regulate the uniform deposition of lithium, thereby solving the problems of lithium dendrites and SEI film rupture-regeneration during the cycling process of lithium metal batteries, and thus improving the cycle performance of lithium metal batteries.
[0006] On one hand, embodiments of this application provide a lithium metal anode, including an anode body and a protective layer coated on the surface of the anode body. The anode body includes lithium metal, and the protective layer is polymerized from compound I and an olefinic monomer containing sulfonic acid groups.
[0007] The chemical formula of compound I is:
[0008]
[0009] In the formula, R1 is H or CH3, R2 is H, CH3 or CH2CH3, and n = 1 to 4.
[0010] In some embodiments, the alkylene monomer containing a sulfonic acid group includes at least one of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, N,N-dimethyl-N-methacrylamidopropyl-N,N-dimethyl-N-propanesulfonic acid inner salt, sodium styrene sulfonate, sodium 3-prop-2-enoyloxypropane-1-sulfonate, and potassium propyl methacrylate.
[0011] In some embodiments, the thickness of the protective layer is 2–15 μm.
[0012] In some embodiments, the thickness ratio of the protective layer to the negative electrode body is (2-15):
[0013] (20~100).
[0014] On the other hand, embodiments of this application provide a method for preparing a lithium metal anode, used to prepare the lithium metal anode in any of the above embodiments, comprising the following steps:
[0015] Compound I and an olefinic monomer containing a sulfonic acid group were dissolved in an ether solvent, and a lithium salt and a photoinitiator were added. The mixture was then reacted to obtain a precursor solution.
[0016] The precursor solution is coated onto the surface of the negative electrode body and then irradiated to obtain the lithium metal negative electrode.
[0017] In some embodiments, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium difluorooxalate borate.
[0018] In some embodiments, the ether solvent includes at least one selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, and 2-methyltetrahydrofuran.
[0019] In some embodiments, the photoinitiator includes at least one selected from 2-hydroxy-2-methyl-1-phenyl-1-propanone, methyl benzoylcarbamate, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and ethyl 2,4,6-trimethylbenzoylphenylphosphonate.
[0020] In some embodiments, the mass ratio of compound I to the alkene monomer containing sulfonic acid group is (1-5):(1-5).
[0021] In some embodiments, the total mass ratio of the compound I and the alkene monomer containing the sulfonic acid group to the lithium salt is (1-5):1.
[0022] In some embodiments, the mass percentage of the photoinitiator relative to the total mass of Compound I and the alkene monomer containing sulfonic acid groups is 0.5% wt to 2% wt.
[0023] In some embodiments, the amount of the ether solvent added is 5% wt to 30% wt of the total mass of compound I and the alkene monomer containing sulfonic acid groups.
[0024] This application also provides a lithium metal battery, including the lithium metal negative electrode in any of the above embodiments.
[0025] This application also provides an electrical device comprising the aforementioned lithium metal battery.
[0026] This application provides a lithium metal anode, comprising an anode body and a protective layer coated on the surface of the anode body. The anode body comprises lithium metal, and the protective layer is polymerized from compound I and an alkene monomer containing sulfonic acid groups. Compound I provides flexibility to the polymer, while the alkene monomer containing sulfonic acid groups provides lithium-ion conductivity. This allows the protective layer of the lithium metal anode to possess both conductivity and elasticity, reducing lithium dendrite formation and SEI film rupture-regeneration problems during lithium metal battery cycling, while simultaneously improving the cycle performance of the lithium metal battery. The preparation method of the lithium metal anode includes: dissolving compound I and an alkene monomer containing sulfonic acid groups in an ether solvent, adding a lithium salt and a photoinitiator, mixing and reacting to obtain a precursor solution; coating the precursor solution onto the surface of the anode body, and irradiating with light to obtain the lithium metal anode. By mixing two monomers with lithium salt and additives to form a precursor solution, and then polymerizing in situ on the anode body to form the polymer protective layer, the process is simple. Detailed Implementation
[0027] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0028] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, an electrical connection, or a connection that allows for mutual communication; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances. In the description of this application, "multiple" means two or more, unless otherwise expressly and specifically limited. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features.
[0029] The following disclosure provides many different implementations or examples for carrying out different structures of this application. To simplify the disclosure of this application, the components and arrangements of specific examples are described below. Of course, these are merely examples and are not intended to limit this application.
[0030] The first embodiment of this application provides a lithium metal anode, including an anode body and a protective layer coated on the surface of the anode body. The anode body includes lithium metal, and the protective layer is polymerized from monomer A and monomer B.
[0031] Monomer A is compound I, with the chemical formula shown below:
[0032]
[0033] In the formula, R1 is H or CH3, R2 is H, CH3 or CH2CH3, and n = 1 to 4.
[0034] Monomer B is an olefinic monomer containing a sulfonic acid group.
[0035] Monomer A contains flexible segments, which, after polymerization, act as soft segments to enhance the interaction with the lithium substrate. This allows the polymer protective layer to not only be uniformly and smoothly coated on the lithium anode, but also to buffer the large volume changes during cycling, effectively preventing side reactions between the electrolyte and the lithium anode caused by SEI film rupture. Monomer B contains sulfonic acid groups, which can provide more Li-containing polymer segments. + Adsorption sites, capable of dispersing Li + And through cation-dipole interactions along -SO 3- Interchain migration, entering the current collector, thereby accelerating Li + The high transfer rate promotes uniform lithium nucleation and growth, preventing the growth of lithium dendrites. When the polymer-protected lithium metal anode sheet provided by this invention is used in lithium metal secondary batteries, it can effectively improve the cycle stability and safety of the lithium metal secondary batteries.
[0036] In some embodiments, the alkylene monomer containing a sulfonic acid group includes at least one of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, N,N-dimethyl-N-methacrylamidopropyl-N,N-dimethyl-N-propanesulfonic acid inner salt, sodium styrene sulfonate, sodium 3-prop-2-enoyloxypropane-1-sulfonate, and potassium propyl methacrylate.
[0037] In some embodiments, the lithium salt includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium difluorooxalate borate.
[0038] In some embodiments, the thickness of the protective layer is 2 to 15 μm. It is understood that the thickness of the protective layer (unit: μm) can be any value of 2, 4, 6, 8, 10, 12, 15 or a range between any two values.
[0039] Furthermore, the thickness of the protective layer is preferably 3–5 μm. It can be understood that the thickness of the protective layer (unit: μm) can be any value among 3, 4, and 5, or a range between any two values. When the thickness of the protective layer meets the above-mentioned range, it can effectively suppress side reactions between lithium metal and the electrolyte and resist lithium dendrite penetration, while also not affecting the effective transport of lithium ions, thus ensuring the normal operation of the battery.
[0040] In some embodiments, the thickness ratio of the protective layer to the negative electrode body is (2-15):(20-100). When the thickness ratio of the protective layer to the negative electrode body meets the above range, the side reactions between lithium metal and electrolyte can be further effectively suppressed, while the interface impedance is kept at a low level, without affecting the normal operation of the battery.
[0041] The second embodiment of this application provides a method for preparing a lithium metal anode, used to prepare the lithium metal anode in any of the above embodiments, comprising the following steps:
[0042] Compound I and an olefinic monomer containing a sulfonic acid group were dissolved in an ether solvent, and a lithium salt and a photoinitiator were added. The mixture was then reacted to obtain a precursor solution.
[0043] The precursor solution is coated onto the surface of the negative electrode body and then irradiated to obtain a lithium metal negative electrode.
[0044] In some embodiments, the ether solvent includes at least one selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxane, 1,4-dioxane, tetrahydrofuran, and 2-methyltetrahydrofuran.
[0045] In some embodiments, the photoinitiator includes at least one selected from 2-hydroxy-2-methyl-1-phenyl-1-propanone, methyl benzoylcarbamate, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and ethyl 2,4,6-trimethylbenzoylphenylphosphine ester.
[0046] In some embodiments, the mass ratio of compound I to the alkene monomer containing a sulfonic acid group is (1-5):(1-5), more preferably (1-4):(1-2).
[0047] In some embodiments, the total mass ratio of compound I and the alkene monomer containing sulfonic acid groups to the lithium salt is (1-5):1, more preferably (2-4):1.
[0048] In some embodiments, the mass percentage of the photoinitiator relative to the total mass of Compound I and the alkene monomer containing sulfonic acid groups is 0.5% wt to 2% wt. It is understood that the mass percentage of the photoinitiator relative to the total mass of Compound I and the alkene monomer containing sulfonic acid groups can be any value from 0.5% wt, 1% wt, 1.5% wt, 2% wt, or a range between any two values.
[0049] In some embodiments, the amount of ether solvent added is 5% wt to 30% wt of the total mass of Compound I and the alkene monomer containing sulfonic acid groups. It is understood that the percentage of ether solvent added to the total mass of Compound I and the alkene monomer containing sulfonic acid groups can be any value or a range between any two of 5% wt, 10% wt, 15% wt, 20% wt, 25% wt, and 30% wt. When the amount of ether solvent added meets the above range, it can promote the dissolution of the alkene monomer, improve the ionic conductivity of the protective layer, and ensure that the protective layer has ideal mechanical strength.
[0050] The third embodiment of this application provides a lithium metal battery, including the lithium metal negative electrode in any of the above embodiments.
[0051] The fourth embodiment of this application provides an electrical device comprising the above-described lithium metal battery.
[0052] The following description, in conjunction with specific embodiments, illustrates the lithium metal anode, its preparation method, and the lithium metal battery provided in this application:
[0053] Example 1
[0054] This embodiment provides a lithium metal anode, which is prepared through the following steps:
[0055] S1. Weigh 50g of monomer A and 25g of monomer B and dissolve them in 15g of DME solvent. Then add 25g of LiTFSI and 0.75g of photoinitiator HMPP, stir and dissolve evenly to obtain precursor solution I.
[0056] S2. The precursor solution I is applied to the surface of the lithium metal anode sheet by spraying.
[0057] S3. Place the negative electrode coated with the precursor solution under ultraviolet light with a wavelength of 365nm for 5 minutes to obtain a lithium metal negative electrode with a polymer protective layer.
[0058] Battery fabrication:
[0059] This embodiment provides a lithium metal battery, including a positive electrode, a negative electrode, a separator between the positive electrode and the negative electrode, and an electrolyte, wherein the negative electrode is the lithium metal negative electrode prepared by the above steps.
[0060] In this embodiment, the positive electrode, electrolyte, and separator in the lithium metal battery can be conventional positive electrode, electrolyte, and separator in the art.
[0061] Battery assembly:
[0062] A lithium-ion battery positive electrode slurry was prepared by uniformly mixing lithium nickel cobalt manganese oxide ternary material LiNi8Co1Mn1O2 (NCM811), conductive agent conductive carbon black (SuperP), binder polyvinylidene fluoride (PVDF), and carbon nanotubes (CNT) at a mass ratio of 97:1.2:0.8:1.0. This slurry was coated onto aluminum foil for current collectors, dried at 85°C, and then cold-pressed. After edge trimming, cutting, and slitting, the slurry was dried at 85°C under vacuum for 8 hours to produce a lithium metal battery positive electrode sheet. The lithium metal battery positive electrode sheet prepared according to the above process, the lithium metal battery negative electrode sheet from the examples and comparative examples, and the separator were then stacked to form a three-positive, four-negative lithium metal battery. An electrolyte (containing 1M...) was then injected. LiFSI (60 vol% DME (ethylene glycol dimethyl ether) + 40 vol% TTE (1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether) as electrolyte), the mass of electrolyte injected into a single cell is 3.6 g, and the cells are left to stand for 12 h to complete the battery fabrication.
[0063] Examples 2-8 and Comparative Examples 1-3
[0064] The preparation methods for Examples 2-8 and Comparative Examples 1-3 are the same as those for Example 1, except that the relevant parameters in the preparation steps are adjusted to obtain different lithium metal anodes. The relevant preparation parameters are detailed in Table 1.
[0065] Table 1
[0066]
[0067]
[0068] The electrical performance of the batteries prepared in Examples 2-8 and Comparative Examples 1-3 was tested, and the steps are as follows:
[0069] The lithium metal battery was charged to 4.2V at a constant current of 0.3C, then charged at a constant voltage of 4.2V until the current dropped to 0.05C, and finally discharged to 2.8V at a constant current of 1C. The first-cycle discharge specific capacity (C) was obtained. d1 Repeat this charging and discharging process until the nth cycle, and then denote the discharge specific capacity of the lithium secondary battery after n cycles as C. dn Capacity retention rate = discharge specific capacity after n cycles (C dn ) / First-cycle discharge specific capacity (C d1 The battery cycle life is considered to have ended when the capacity retention rate drops to 80% (100%). The test results are shown in Table 2.
[0070] Table 2
[0071]
[0072]
[0073] Comparing Examples 1-14 with Comparative Example 1, it is evident that this application, by providing a polymer protective layer on the lithium metal surface, achieves superior performance. This polymer protective layer exhibits excellent ductility, is less prone to breakage during lithium deposition / stripping, effectively preventing direct contact between the electrolyte and lithium metal, and minimizing side reaction consumption between the electrolyte and lithium metal. The polymer protective layer also contains groups that promote lithium-ion conduction, which facilitates uniform lithium deposition and inhibits / delays lithium dendrite growth. The performance of the polymer protective layer can be adjusted by modifying the type and mass ratio of monomers, the amount and proportion of solvent added, and the amount and proportion of lithium salt added. Compared to lithium metal batteries without a polymer protective layer, the cycle performance of all examples of lithium metal batteries is significantly improved.
[0074] Comparing Example 1 and Comparative Examples 2-3, it can be seen that since acrylic acid and acrylamide monomers do not contain functional groups that conduct lithium ions, they cannot induce uniform lithium deposition and cannot effectively inhibit or delay the growth of lithium dendrites, resulting in poor improvement in the cycle performance of their lithium metal batteries.
[0075] Comparing Example 1 and Comparative Example 4, it can be seen that the protective layer formed by polymerization using monomers other than Compound I does not have good flexibility and cannot effectively adapt to the volume expansion during lithium deposition, resulting in an unsatisfactory improvement in the cycle performance of the lithium metal battery.
[0076] The foregoing has provided a detailed description of a lithium metal anode and its preparation method, a lithium metal battery, and an electrical device provided in the embodiments of this application. Specific examples have been used in this application to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.
Claims
1. A lithium metal anode, characterized in that, The device includes a negative electrode body and a protective layer coated on the surface of the negative electrode body. The negative electrode body comprises lithium metal. The protective layer is polymerized from compound I and an olefinic monomer containing sulfonic acid groups. The olefinic monomer containing sulfonic acid groups includes at least one of 3-[N,N-dimethyl-[2-(2-methylprop-2-enoyloxy)ethyl]ammonium]propane-1-sulfonic acid inner salt, N,N-dimethyl-N-methacrylamidopropyl-N,N-dimethyl-N-propanesulfonic acid inner salt, sodium styrene sulfonate, sodium 3-propane-2-enoyloxypropane-1-sulfonate, and potassium propyl methacrylate 3-sulfonate. The protective layer also includes a lithium salt, which includes at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluoromethanesulfonyl)imide, lithium tetrafluoroborate, lithium hexafluorophosphate, and lithium difluorooxalate borate. The chemical formula of compound I is: In the formula, R1 is H or CH3, R2 is H, CH3 or CH2CH3, and n = 1~4.
2. The lithium metal anode according to claim 1, characterized in that, The thickness of the protective layer is 2~15μm.
3. A lithium metal anode according to claim 1, characterized in that, The thickness ratio of the protective layer to the negative electrode body is (1~15):(20~100).
4. A method for preparing a lithium metal anode as described in any one of claims 1 to 3, characterized in that, Includes the following steps: Compound I and an olefinic monomer containing a sulfonic acid group were dissolved in an ether solvent, and a lithium salt and a photoinitiator were added. The mixture was then reacted to obtain a precursor solution. The precursor solution is coated onto the surface of the negative electrode body and then irradiated to obtain the lithium metal negative electrode.
5. The method for preparing a lithium metal anode according to claim 4, characterized in that, The ether solvents include at least one selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, 1,3-dioxopentane, 1,4-dioxane, tetrahydrofuran, and 2-methyltetrahydrofuran; and / or, The photoinitiator includes at least one selected from 2-hydroxy-2-methyl-1-phenyl-1-propanone, methyl benzoylcarbamate, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and ethyl 2,4,6-trimethylbenzoylphenylphosphonate.
6. The method for preparing a lithium metal anode according to claim 4, characterized in that, The mass ratio of compound I to the alkene monomer containing the sulfonic acid group is (1~5):(1~5); and / or, The total mass ratio of compound I and the alkene monomer containing the sulfonic acid group to the lithium salt is (1~5):1; and / or, The photoinitiator accounts for 0.5% wt to 2% wt% of the total mass of compound I and the alkene monomer containing the sulfonic acid group; and / or, The amount of the ether solvent added is 5%wt to 30%wt of the total mass of compound I and the alkene monomer containing sulfonic acid groups.
7. A lithium metal battery, characterized in that, It includes the lithium metal anode as described in any one of claims 1 to 3, or the lithium metal anode prepared by the preparation method as described in any one of claims 4 to 6.
8. An electrical device, characterized in that, It includes the lithium metal battery as described in claim 7.