Single ion conductor coating, electrode, battery and preparation method

Abstract

According to the single-ion conductor coating, the electrode, the battery and the preparation method, the single-ion conductor coating has a selective repulsive effect on lithium salt and a solvent in electrolyte, the effect of specifically protecting anions is achieved, the interface solvation structure of the electrolyte can be optimized, and the performance of the battery is improved. The interface side reaction between the lithium salt and the solvent and the electrode is effectively relieved, so that the volume expansion of the negative electrode is inhibited, and the method has important significance for improving the long-cycle stability of the silicon-based battery. In addition, the cyano group in the side chain of the single-ion conductor coating can also form hydrogen bond interaction with the hydroxyl group on the surface of the silicon negative electrode, so that the problem of volume expansion of the electrode is effectively relieved. The single-ion conductor coating can be used for preparing lithium batteries, sodium batteries, potassium batteries and the like, and is wide in application range.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of electrochemistry, and relates to a single-ion conductor coating, an electrode, a battery and a preparation method. BACKGROUND

[0002] In recent years, with the rapid development of new energy electric vehicles, people have increasingly high requirements for the energy density and safety performance of lithium secondary batteries. High-nickel ternary positive electrodes matched with lithium metal negative electrodes or high-capacity silicon-carbon negative electrodes can effectively improve the energy density of the battery. However, according to literature reports, lithium hexafluorophosphate in commercial electrolyte can have the following interface side reaction with the silicon negative electrode: Si + LiPF6→ Li2SiF6+ PF3, and the poor conductor of the generated Li2SiF6electrons and ions can cause lithium in the lithium-silicon alloy to be difficult to deintercalate, exacerbating the problem of irreversible volume expansion of the silicon negative electrode.

[0003] In recent years, researchers have found that a coating can effectively improve the interface compatibility between the electrolyte and the electrode. For example: CN117038988A discloses a silicon-based negative electrode polymer buffer layer, which introduces hard carbon and heterocyclic conjugated organic matter with a large π conjugated plane rigid structure in the polymer buffer layer, can increase the lithium ion rapid transmission channel, improve the battery rate performance, improve the electronic conductivity of the silicon negative electrode, and effectively improve the low temperature performance of the battery. CN 117438569A discloses a high-thermal-stability negative electrode silicon-carbon material, which includes a core and a coating layer. The coating layer has oxidizing properties and is processed into a porous structure through acidification, improving its adsorption and reaction with reducing gases and effectively inhibiting the diffusion of reducing gases to the positive electrode. CN 118173789A discloses a polymer interface protection layer for high-voltage lithium batteries, which mixes polysiloxane, glycidyl ether, polyethylene glycol derivative, initiator and soluble lithium salt in an organic solvent to obtain a mixed solution; the mixed solution is heated to perform thermal polymerization of each monomer to obtain a polymer interface protection layer material. The formed solid-state polymer interface protection layer can effectively alleviate the volume change of the positive electrode and the negative electrode generated during charging and discharging, release stress to protect the electrode structure from being damaged, and improve the cycle stability and safety performance of the lithium metal battery.

[0004] However, the above-mentioned coating will swell under the action of the solvent, resulting in a large number of anions still passing through the coating with the solvated structure of lithium ions, and then reacting with the silicon negative electrode. Most of the neutral coatings do not have specific repulsion to anions, and therefore cannot completely inhibit the interface side reaction between the anions and the silicon negative electrode. SUMMARY

[0005] The purpose of this invention is to provide a single-ion conductor coating, electrode, battery, and preparation method to solve the problem of interfacial side reactions between electrolyte anions and silicon electrodes.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this application provides a single-ion conductor coating that provides specific protection against anions. The single-ion conductor coating comprises a polymer, the side chains of which contain β-groups and cyano-groups, wherein the β-groups include boron-based, aluminum-based, niobium-based, gallium-based, indium-based, or phosphorus-based groups.

[0007] When lithium ions pass through the coating, anions in the polymer side chains can replace PF6 in the solvated structure. - , making PF6 - The single-ion conductor coating prevents direct contact between anions and the silicon anode, effectively mitigating interfacial side reactions and avoiding the formation of interfacial side reaction products such as Li2SiF6. Furthermore, the -CN groups in the single-ion conductor coating can form hydrogen bonds with the -OH groups on the silicon anode surface, further alleviating the volume expansion problem of the silicon anode.

[0008] In this application, the polymer in the single-ion conductor coating has the following structural formula: Where x is 1-500, y is 1-200, z is 0-300, and n is 0-4; R1 is , , , , , , , , , , , , , , , , , , or , A is Na + Li + or K + B is boron, aluminum, niobium, gallium, indium, or phosphorus.

[0009] In this application, the single-ion conductor coating further includes inorganic fillers to improve the ionic conductivity of the single-ion conductor coating. The mass fraction of the inorganic filler in the single-ion conductor coating is 0-80%. More preferably, the inorganic filler includes one or more of lithium fluoride, indium fluoride, oxide fast ion conductors, sulfide fast ion conductors, halide fast ion conductors, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, silicon nitride, diatomaceous earth, montmorillonite, and kaolin.

[0010] In a second aspect, this application provides an electrode comprising an electrode sheet or a diaphragm, wherein the surface of the electrode sheet or diaphragm is coated with the single-ion conductor coating described in the first aspect.

[0011] Thirdly, this application provides a method for preparing an electrode, comprising: S01: Under anhydrous and oxygen-free conditions, the single-ion conductor coating is dissolved in a solvent and mixed evenly to form a single-ion conductor solution. The mass ratio of the single-ion conductor coating to the solvent is (1-20):10. The solvent can be DMF (N,N-Dimethylformamide), NMP (N-Methylpyrrolidone), water, or a similar solvent.

[0012] S02: The single-ion conductor solution is coated on the surface of the electrode sheet or diaphragm and vacuum dried at 60°C for 24 hours to obtain an electrode containing a single-ion conductor coating.

[0013] A single-ion conductor solution is uniformly coated onto the surface of an electrode sheet or diaphragm to a thickness of 0.1–5 μm. After coating, the electrode is vacuum-dried at 60 °C for 24 h to obtain an electrode with a single-ion conductor coating.

[0014] Furthermore, the single-ion conductor solution also includes an inorganic filler, the mass ratio of which to the single-ion conductor coating is (1-3):10.

[0015] Furthermore, the single-ion conductor solution also includes an electrolyte, which comprises Li3PS4 and Li7La3Zr2O. 12 wait.

[0016] Fourthly, this application provides a battery, including the electrode of the second aspect or the electrode prepared by the preparation method of the third aspect.

[0017] Furthermore, the battery can be a lithium battery, a sodium battery, or a potassium battery.

[0018] Fifthly, this application provides a method for preparing a battery, comprising: mixing a single-ion conductor coating and an electrode slurry at a mass ratio of (0.005-0.1):1 to obtain a battery containing a single-ion conductor.

[0019] Furthermore, an inorganic filler is added to the electrode slurry, with a mass ratio of the inorganic filler to the electrode slurry of 0.01:1.

[0020] The present invention has the following beneficial effects: (1) The single-ion conductor coating has a selective repulsion effect on lithium salts and solvents in the electrolyte, thus achieving the effect of specific protection of anions.

[0021] (2) The single-ion conductor coating can optimize the interfacial solvation structure of the electrolyte, effectively alleviate the interfacial side reactions between lithium salt and solvent and electrode, and thus suppress the volume expansion of the negative electrode, which is of great significance for improving the long-cycle stability of silicon-based batteries.

[0022] (3) The cyano groups in the side chain of the single-ion conductor coating can also form hydrogen bond interactions with the hydroxyl groups on the surface of the silicon anode, effectively alleviating the problem of electrode volume expansion.

[0023] (4) This single-ion conductor coating can be used in the preparation of lithium batteries, sodium batteries, potassium batteries, etc., and has a wide range of applications. Detailed Implementation

[0024] The technical solution of the present invention will be further explained and described below through specific embodiments.

[0025] In the single-ion conductor coatings provided in the embodiments of this application, due to the wide variety of options for B groups and cationic A in the polymer, many single-ion conductor coatings with different structures can be generated. Only some are listed in the following description, but this does not limit the scope of protection of this application.

[0026] Example 1 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=50, y=30) and N,N-dimethylformamide are mixed and dissolved at a mass ratio of 1:10 to form a single-ion conductor solution. The single-ion conductor solution is uniformly coated on the surface of SiC650 negative electrode and dried under vacuum at 60℃ for 24h to obtain a negative electrode containing a single-ion conductor coating.

[0027] A battery containing a single-ion conductor coating is assembled with an NCM811 to obtain a battery containing a single-ion conductor coating.

[0028] Example 2 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=40, y=20), Li3PS4 and N,N-dimethylformamide were mixed and dissolved in a mass ratio of 2:2:10 to form a single-ion conductor solution. The single-ion conductor solution was uniformly coated on the surface of SiC1000 negative electrode and dried under vacuum at 60℃ for 24h to obtain a negative electrode containing a single-ion conductor coating.

[0029] A battery containing a single-ion conductor coating is assembled with an NCM9055 to obtain a battery containing a single-ion conductor coating.

[0030] Example 3 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=50, y=50), Li7La3Zr2O 12 A single-ion conductor solution was formed by mixing and dissolving N,N-dimethylformamide at a mass ratio of 3:2:10. The single-ion conductor solution was uniformly coated onto the surface of the SiOx anode and dried under vacuum at 60°C for 24 hours to obtain an anode containing a single-ion conductor coating.

[0031] A battery containing a single-ion conductor coating is assembled with an NCM811 to obtain a battery containing a single-ion conductor coating.

[0032] Example 4 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=50, y=50), Li3PS4 and N,N-dimethylformamide were mixed and dissolved in a mass ratio of 3:3:10 to form a single-ion conductor solution. The single-ion conductor solution was uniformly coated on the surface of SiC450 negative electrode and dried under vacuum at 60℃ for 24h to obtain a negative electrode with a single-ion conductor coating.

[0033] A battery containing a single-ion conductor coating is assembled with an NCM9055 to obtain a battery containing a single-ion conductor coating.

[0034] Example 5 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=50, y=30) and N,N-dimethylformamide were mixed and dissolved at a mass ratio of 1:10 to form a single-ion conductor solution. The single-ion conductor solution was uniformly coated on the surface of the NCM811 positive electrode and dried under vacuum at 60°C for 24 hours to obtain a positive electrode with a single-ion conductor coating.

[0035] A battery containing a single-ion conductor coating is assembled with SiC650 to obtain a battery containing a single-ion conductor coating.

[0036] Example 6 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=40, y=20, z=15), Li3PS4 and N,N-dimethylformamide were mixed and dissolved in a mass ratio of 2:2:10 to form a single-ion conductor solution. The single-ion conductor solution was uniformly coated on the surface of the NCM9055 positive electrode and dried under vacuum at 60°C for 24 h to obtain a positive electrode with a single-ion conductor coating.

[0037] A battery is obtained by assembling a positive electrode with a single-ion conductor coating with SiC1000.

[0038] Example 7 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=50, y=50), Li7La3Zr2O 12 The solution was mixed and dissolved with N,N-dimethylformamide at a mass ratio of 3:2:10 to form a single-ion conductor solution. The single-ion conductor solution was uniformly coated onto the surface of the NCM533 positive electrode and vacuum dried at 60°C for 24 hours to obtain a positive electrode with a single-ion conductor coating.

[0039] A battery is obtained by assembling a positive electrode with a single-ion conductor coating with SiC1000.

[0040] Example 8 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. (x=50, y=50) Li3PS4 and N,N-dimethylformamide were mixed and dissolved in a mass ratio of 3:3:10 to form a single-ion conductor solution. The single-ion conductor solution was uniformly coated on the surface of the LiCoO2 cathode and dried under vacuum at 60°C for 24 h to obtain a cathode containing a single-ion conductor coating.

[0041] A battery containing a single-ion conductor coating is assembled with SiC450 to obtain a battery containing a single-ion conductor coating.

[0042] Example 9 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, 0.3g of single-ion conductor coating was applied. (x=50, y=50, z=20) was mixed evenly with 10g of positive electrode slurry and then coated. The positive electrode slurry contained 50wt% NMP solvent, and the solid components and their mass ratio were NCM811:PVDF:conductive carbon black = 8:1:1. After vacuum drying at 60℃ for 24h, the positive electrode sheet was obtained.

[0043] A positive electrode with a single-ion conductor coating is assembled with SiC650 to form a battery, thus obtaining a battery with a single-ion conductor coating.

[0044] Example 10 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, 0.3g of single-ion conductor coating was applied. (x=50, y=50) was mixed evenly with 10g of negative electrode slurry and then coated. The negative electrode slurry contained 50wt% solvent NMP, and the solid components and their mass ratio were silicon-carbon 450:PVDF:conductive carbon black = 8:1:1. After vacuum drying at 60℃ for 24h, the negative electrode sheet was obtained.

[0045] A negative electrode with a single-ion conductor coating is assembled with NCM811 to form a battery, thus obtaining a battery with a single-ion conductor coating.

[0046] Example 11 This application provides an electrode and a battery, wherein the electrode is prepared by means of: Under anhydrous and oxygen-free conditions, a single-ion conductor coating is applied. Lithium fluoride (x=40, y=20) and N,N-dimethylformamide were mixed and dissolved in a mass ratio of 2:2:10 to form a single-ion conductor solution. The single-ion conductor solution was uniformly coated on the surface of a SiC1000 anode and dried under vacuum at 60°C for 24 hours to obtain an anode containing a single-ion conductor coating.

[0047] A battery containing a single-ion conductor coating is assembled with an NCM9055 to obtain a battery containing a single-ion conductor coating.

[0048] Comparative Example 1 Under anhydrous and oxygen-free conditions, PEO (polyethylene oxide) with a molecular weight of 300,000 was dissolved in N,N-dimethylformamide at a mass ratio of 1:10 and stirred to form a homogeneous solution. The solution was then uniformly poured onto the surface of a SiC650 negative electrode and dried in a vacuum oven at 60°C for 24 hours to obtain a polymer coating. The negative electrode containing the polymer coating was then assembled with NCM811 to form a battery.

[0049] Comparative Example 2 Under anhydrous and oxygen-free conditions, PEO, Li3PS4, and N,N-dimethylformamide with a molecular weight of 300,000 were mixed and dissolved in a mass ratio of 2:2:10 and stirred to form a homogeneous solution. The solution was uniformly poured onto the surface of a SiC1000 anode and dried in a vacuum oven at 60°C for 24 hours to obtain a polymer coating. The anode containing the polymer coating was then assembled with an NCM9055 electrode to form a battery.

[0050] To test long-cycle stability, the batteries prepared in Examples 1-11 and Comparative Examples 1 and 2 were subjected to charge-discharge tests at charge-discharge cutoff voltages of 2.8-4.3V in this application embodiment. The test steps were 0.1C for two cycles followed by 0.2C cycling. The test results are shown in Table 1.

[0051] Table 1: Charge-discharge test results of batteries prepared in Examples 1-11 and Comparative Examples 1 and 2 As shown in Table 1: (1) Comparing Example 1 and Comparative Example 1, it can be seen that the batteries of Example 1 and Comparative Example 1 differ only in the single-ion conductor coating in terms of composition, but their first-cycle discharge capacity is not much different. However, the battery prepared in Example 1 has a capacity retention rate of 80% for 452 cycles, which means that the battery prepared in Example 1 has a lifespan of 452 cycles, which is much higher than the lifespan of 130 cycles in Comparative Example 1.

[0052] (2) Comparing Example 2 and Comparative Example 2, it can be seen that the batteries of Example 2 and Comparative Example 2 differ only in composition in the single-ion conductor coating, and both sets of batteries contain the same amount of Li3PS4 as an inorganic filler. However, the battery prepared in Example 2 has a lifespan of 420 cycles, which is much higher than the 124 cycles of the battery in Comparative Example 2.

[0053] The above content shows that the addition of a B-based single-ion conductor coating to the battery provided in this application embodiment can further improve the compatibility between the electrolyte and the silicon anode, and more effectively improve the long-cycle stability of the battery.

[0054] In addition, the embodiments of this application also perform NMR (Nuclear Magnetic Resonance Spectroscopy) detection on the electrolytes inside the batteries prepared in Examples 1-11 and Comparative Examples 1 and 2 to detect the PF on the negative electrode surface. ­6 - Relative to the content of trifluorotoluene.

[0055] Specifically, the batteries of Examples 1-11 and Comparative Examples 1 and 2 were disassembled after 10 cycles, and the electrolyte on the negative electrode surface was analyzed by NMR. The results are shown in Table 2. 5 mg of trifluorotoluene was added to the NMR deuterated reagent as an internal standard.

[0056] Table 2: PF value of negative electrode surface after 10 battery cycles ­6 - relative to the molar ratio of trifluorotoluene As shown in Table 2, after 10 battery cycles, the PF value on the negative electrode surface of the batteries in Examples 1-11... ­6 - The content of PF on the negative electrode surface of the batteries in both examples is much lower than that in comparative examples 1 and 2. ­6 - Content. This indicates that the single-ion conductor coating in the embodiments of this application can effectively reduce PF6 content on the negative electrode surface. - The content of [specific ingredient] effectively suppressed the interfacial side reactions between the anions on the negative electrode surface and the silicon negative electrode, and the effect was far superior to that of conventional polymer coatings.

[0057] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A single-ion conductor coating, characterized in that, Including polymers having the following structural formula: ， Where x is 1-500, y is 1-200, z is 0-300, and n is 0-4; R1 is , , , , , , , , , , , , , , , , , , or Where A is Na + Li + or K + B is boron, aluminum, niobium, gallium, indium, or phosphorus.

2. The single-ion conductor coating according to claim 1, characterized in that, The single-ion conductor coating further includes inorganic fillers, which include one or more of lithium fluoride, indium fluoride, oxide fast ion conductors, sulfide fast ion conductors, halide fast ion conductors, silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, silicon nitride, diatomaceous earth, montmorillonite, and kaolin.

3. An electrode, characterized in that, It includes an electrode sheet or a diaphragm, the surface of which is coated with the single-ion conductor coating of claim 1 or 2.

4. A method for preparing an electrode, characterized in that, include: The single-ion conductor coating is dissolved in a solvent and mixed evenly to form a single-ion conductor solution; The single-ion conductor solution is coated onto the surface of an electrode sheet or diaphragm and then vacuum dried at 60°C for 24 hours to obtain an electrode containing a single-ion conductor coating.

5. The method for preparing the electrode according to claim 4, characterized in that, The mass ratio of the single-ion conductor coating to the solvent is (1-20):10, and the solvent includes DMF, NMP or water.

6. The method for preparing the electrode according to claim 4, characterized in that, The single-ion conductor solution also includes inorganic filler, and the mass ratio of the inorganic filler to the single-ion conductor coating is (1-3):

10.

7. A battery, characterized in that, This includes the electrode as described in claim 3 or the electrode prepared by any one of the methods in claims 4-6.

8. The battery according to claim 7, characterized in that, The battery is a lithium battery, sodium battery, or potassium battery.

9. A method for preparing a battery, characterized in that, include: The single-ion conductor coating described in claim 1 or 2 is mixed with the electrode slurry at a mass ratio of (0.005-0.1):1 to obtain a battery containing a single-ion conductor.

10. The method for preparing a battery according to claim 9, characterized in that, Inorganic filler is added to the electrode slurry, and the mass ratio of the inorganic filler to the electrode slurry is 0.01:1.

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