Polymer-inorganic filler composite electrolyte, lithium battery and preparation method of polymer-inorganic filler composite electrolyte

Abstract

The invention discloses a polymer-inorganic filler composite electrolyte, a lithium battery and a preparation method of the polymer-inorganic filler composite electrolyte, and belongs to the technical field of solid electrolytes. The preparation method comprises the following steps: obtaining a polyoxyethylene-water colloidal solution, adjusting the solution to be alkaline, dropwise adding tetraethoxysilane into the alkaline colloidal solution until the tetraethoxysilane is hydrolyzed to form uniformly-distributed quantum dot-level silicon oxide particles to obtain a polyoxyethylene-silicon oxide mixed solution, adding a lithium salt into the polyoxyethylene-silicon oxide mixed solution to obtain an electrolyte mixed solution, and carrying out vacuum drying on the electrolyte mixed solution to obtain the lithium ion battery. And removing water to obtain the polymer-inorganic filler composite electrolyte. In the preparation method disclosed by the invention, the inorganic filler is synthesized in situ through hydrolysis and can be more uniformly dispersed in the polymer component, so that the solid electrolyte with higher ionic conductivity is obtained. Meanwhile, the preparation method is simple in process and suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to the technical field of solid electrolytes, and particularly to polymer-inorganic composite electrolytes, lithium batteries, and their preparation methods. Background Technology

[0002] Solid electrolytes used in lithium-ion solid-state batteries can be classified into several categories, including oxide-type, sulfide-type, halide-type, and polymer-type. Among them, inorganic solid electrolytes, represented by oxides, sulfides, and halides, have high ionic conductivity and a wide electrochemical window, but their insufficient ductility leads to poor interfacial mechanical stability in solid-state batteries. On the other hand, although polymer electrolytes have good ductility and can construct mechanically stable solid-state interfaces, they suffer from insufficient ionic conductivity.

[0003] To improve the ionic conductivity of polymer electrolytes, inorganic fillers are often added to form polymer-inorganic filler composite electrolytes. This reduces polymer crystallinity, constructs a space charge layer, and enhances local ion transport performance, thereby achieving the goal of improving the overall ionic conductivity of solid electrolytes.

[0004] However, the conventional method for combining polymers and inorganic fillers involves mechanical mixing in a colloidal solution environment, where the polymer is dissolved in a solvent and then the molded inorganic filler is added. Composite solid electrolytes prepared using this method often suffer from high porosity due to uneven distribution of the inorganic filler, leading to reduced ionic conductivity and severely hindering the large-scale application of composite solid electrolytes.

[0005] Furthermore, the space charge layer formed at the interface between the inorganic filler and the polymer is an important channel for ion transport. However, the inorganic fillers in traditional composite electrolytes are mostly in the range of hundreds of nanometers to micrometers in size, resulting in a limited contact area with the polymer and thus a relatively low ionic conductivity. To increase the interfacial contact area and improve ionic conductivity, smaller inorganic fillers can be used, but this approach leads to a deterioration in the processing performance of the composite electrolyte and increased agglomeration of the inorganic fillers. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to propose a novel method for preparing a polymer-inorganic filler composite electrolyte, as well as the resulting composite electrolyte and lithium battery. This preparation method can synthesize uniformly distributed quantum dot-level silica inorganic fillers in situ within the polymer, significantly increasing the interfacial area between the polymer and inorganic components, thereby increasing the space charge layer area. The resulting composite electrolyte exhibits advantages such as good processability and high ionic conductivity.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing a polymer-inorganic filler composite electrolyte, comprising:

[0009] (1) Dissolve polyethylene oxide in water to obtain a colloidal solution;

[0010] (2) Adjust the colloidal solution to be alkaline to obtain an alkaline colloidal solution;

[0011] (3) Tetraethyl orthosilicate is added dropwise to the alkaline colloidal solution until it hydrolyzes to form uniformly distributed quantum dot-level silica particles, thus obtaining a polyethylene oxide-silica mixture;

[0012] (4) Add lithium salt to the polyethylene oxide-silica mixture and mix to obtain an electrolyte mixture;

[0013] (5) Heat the electrolyte mixture to remove water, and obtain a polymer-inorganic filler composite electrolyte.

[0014] According to some preferred embodiments of the present invention, the polyoxyethylene content in the colloidal solution is 3.0-15.0 wt%.

[0015] According to some preferred embodiments of the present invention, the polyoxyethylene content in the colloidal solution is 3.0 wt%, 5.5 wt%, 7.0 wt%, 8.0 wt%, 10.5 wt%, 11.0 wt%, 12.5 wt%, 14.0 wt%, or 15.0 wt%.

[0016] According to some preferred embodiments of the present invention, the pH value of the alkaline colloidal solution is 8.5-12.5.

[0017] According to some preferred embodiments of the present invention, the pH value of the alkaline colloidal solution is 8.5, 9.0, 9.3, 9.7, 10.2, 10.5, 10.8, 11.5, 12.0 or 12.5.

[0018] According to some preferred embodiments of the present invention, the mass percentage of tetraethyl orthosilicate added to the polyethylene oxide-silica mixture is 0.5-5.0 wt%.

[0019] According to some preferred embodiments of the present invention, the mass percentage of tetraethyl orthosilicate added to the polyethylene oxide-silica mixture is 0.5wt%, 1.0wt%, 1.8wt%, 2.0wt%, 2.5wt%, 3.0wt%, 3.5wt%, 4.0wt%, and 5.0wt%.

[0020] According to some preferred embodiments of the present invention, the particle size of the quantum dot-level silicon oxide particles is 2-20 nm.

[0021] More preferably, the particle size of the quantum dot-level silicon oxide particles is 5, 10, 15 or 20 nm.

[0022] According to some preferred embodiments of the present invention, the concentration of lithium salt in the electrolyte mixture is 0.1-1.2 mol / L.

[0023] More preferably, the concentration of lithium salt in the electrolyte mixture is 0.5 mol / L.

[0024] According to some preferred embodiments of the present invention, the lithium salt is selected from one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

[0025] According to some preferred embodiments of the present invention, the heating is vacuum heating, with a vacuum degree of 0.01-1 Pa, a heating temperature of 50-80°C, and a heating time of 20-50 h.

[0026] According to some preferred embodiments of the present invention, the vacuum degree is 0.01 Pa, 0.1 Pa, 0.3 Pa, 0.6 Pa or 0.9 Pa.

[0027] According to some preferred embodiments of the present invention, the heating temperature is 50°C, 55°C, 60°C, 70°C or 80°C.

[0028] According to some preferred embodiments of the present invention, the heating time is 20h, 30h, 40h, 45h or 50h.

[0029] According to some preferred embodiments of the present invention, the lithium salt is selected from lithium hexafluorophosphate; the mass percentage of polyethylene oxide in the colloidal solution is 8.5 wt%; the pH value of the alkaline colloidal solution is 10.0; the mass percentage of tetraethyl orthosilicate added to the polyethylene oxide-silica mixture is 3.5 wt%; and the concentration of lithium salt in the electrolyte mixture is 0.5 mol / L.

[0030] The present invention further provides a polymer-inorganic filler composite electrolyte prepared by the above preparation method.

[0031] In this composite electrolyte, the silicon oxide particles are at the quantum dot level, with a particle size of 2-20 nm, and are uniformly distributed.

[0032] The present invention further provides a lithium battery containing the above-mentioned polymer-inorganic filler composite electrolyte, such as a conventional lithium-ion battery, a solid-state lithium-ion battery, a lithium metal battery, or a solid-state lithium metal battery.

[0033] The preparation method of the present invention can obtain a polymer-inorganic filler composite electrolyte with uniform inorganic filler distribution by in-situ synthesis of inorganic filler silica, which can effectively improve the ionic conductivity of the composite solid electrolyte. Attached Figure Description

[0034] Figure 1 This is a transmission electron microscope image of the polymer-inorganic filler composite electrolyte obtained in Example 1.

[0035] Figure 2 The image shows a transmission electron microscope image of the polymer-inorganic filler composite electrolyte obtained in Comparative Example 1.

[0036] Figure 3 The electrochemical impedance spectroscopy of the polymer-inorganic filler composite electrolyte obtained in Example 1 is shown.

[0037] Figure 4 The electrochemical impedance spectroscopy of the polymer-inorganic filler composite electrolyte obtained in Comparative Example 1 is shown. Detailed Implementation

[0038] The technical solutions of the present invention will be further described below with reference to the embodiments and accompanying drawings. The embodiments described below are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0039] Example 1

[0040] The polymer-inorganic filler composite electrolyte was prepared by the following steps:

[0041] (1) Polyethylene oxide (PEO) with a molecular weight of 2-2 million is dissolved in water to obtain a colloidal solution. The mass percentage of PEO in the colloidal solution is 8.5 wt%.

[0042] (2) Add ammonia to the colloidal solution to adjust the pH value to 10.0 to obtain an alkaline colloidal solution;

[0043] (3) Tetraethyl orthosilicate is added dropwise to an alkaline colloidal solution until it hydrolyzes naturally to form uniformly distributed quantum dot-level silica particles, thus obtaining a PEO-silica mixture. The mass percentage of tetraethyl orthosilicate added is 3.5 wt% of the total mass of the PEO-silica mixture.

[0044] (4) Add lithium bis(difluorosulfonyl)imide to the PEO-silica mixture to obtain an electrolyte mixture. The concentration of lithium bis(difluorosulfonyl)imide added to the electrolyte mixture is 0.5 mol / L.

[0045] (5) The mixed solution was heated for 40 hours under a pressure of 0.5 Pa and a temperature of 70 °C to remove the water and obtain the polymer-inorganic filler composite electrolyte.

[0046] Example 2

[0047] The polymer-inorganic filler composite electrolyte was prepared using the same steps as in Example 1, except that the mass percentage of PEO in the colloidal solution was 6.5 wt%.

[0048] Example 3

[0049] The polymer-inorganic filler composite electrolyte was prepared using the same steps as in Example 1, except that the pH value was adjusted to 9.5 in step (2).

[0050] Example 4

[0051] The polymer-inorganic filler composite electrolyte was prepared using the same steps as in Example 1, except that the pH value was adjusted to 10.5 in step (2).

[0052] Example 5

[0053] The polymer-inorganic filler composite electrolyte was prepared using the same steps as in Example 1, except that the amount of tetraethyl orthosilicate added to the PEO-silica mixture was 5.0 wt%.

[0054] Example 6

[0055] The polymer-inorganic filler composite electrolyte was prepared using the same steps as in Example 1, except that the lithium salt added was lithium hexafluorophosphate.

[0056] Example 7

[0057] The polymer-inorganic filler composite electrolyte was prepared using the same steps as in Example 1, except that the lithium salt added was lithium bis(oxalatoborate).

[0058] Example 8

[0059] The polymer-inorganic filler composite electrolyte was prepared using the same steps as in Example 1, except that the colloidal solution was heated for 30 hours in step (5).

[0060] Comparative Example 1

[0061] (1) Polyethylene oxide (PEO) with a molecular weight of 2-2 million is dissolved in water to obtain a colloidal solution. The mass percentage of PEO in the colloidal solution is 8.5 wt%.

[0062] (2) Add ammonia to the deionized water solution to adjust the pH value to 10.0 to obtain an alkaline water solution;

[0063] (3) Add tetraethyl orthosilicate dropwise to an alkaline aqueous solution until it hydrolyzes naturally to form uniformly distributed quantum dot-level silica particles, and obtain a silica dispersion. The mass of the added tetraethyl orthosilicate is 3.5% of the total mass of the colloidal solution in step (1).

[0064] (4) The silica dispersion obtained in step (3) is dried under a pressure of 0.5 Pa and a temperature of 50 °C to obtain silica powder;

[0065] (5) Add silica powder and lithium bis(difluorosulfonyl)imide to the colloidal solution obtained in step (1) to obtain an electrolyte mixture. The concentration of lithium bis(difluorosulfonyl)imide added to the electrolyte mixture is 0.5 mol / L.

[0066] (6) The electrolyte mixture was heated for 40 hours under a pressure of 0.5 Pa and a temperature of 70 °C to remove the water and obtain a polymer-inorganic filler composite electrolyte.

[0067] The polymer-inorganic filler composite electrolytes obtained in the examples and comparative examples were characterized by transmission electron microscopy to obtain the particle size distribution (as shown in Table 1) and distribution of the inorganic filler. The transmission electron microscopy images of Example 1 and Comparative Example 1 are attached. Figure 1 , 2 As shown. (Through) Figure 1 It can be seen that in the polymer-inorganic filler composite electrolyte of Example 1, the silica particles synthesized in situ by hydrolysis are uniformly distributed in the electrolyte with a particle size of approximately 20 nm. Figure 2 It can be seen that in the polymer-inorganic filler composite electrolyte of Comparative Example 1, the particle size of the silica particles that were pre-mixed and dispersed by stirring is the same as that of Example 1, but its dispersion uniformity is poor and there is obvious agglomeration.

[0068] Furthermore, the polymer-inorganic filler composite electrolytes obtained in the examples and comparative examples were subjected to electrochemical impedance spectroscopy to test their electrochemical impedance and ionic conductivity. The test frequency range was 7MHz–1Hz, and the perturbation voltage was 50mV. The results are shown in Table 1 below:

[0069] Table 1. Test results of the examples and comparative examples

[0070] Example Inorganic filler particle size (nm) Ionic conductivity (S / cm) Example 1 20 <![CDATA[1.93×10 -5 ]]> Example 2 15 <![CDATA[2.07×10 -5 ]]> Example 3 10 <![CDATA[5.32×10 -5 ]]> Example 4 20 <![CDATA[1.95×10 -5 ]]> Example 5 15 <![CDATA[4.63×10 -5 ]]> Example 6 5 <![CDATA[1.08×10 -4 ]]> Example 7 15 <![CDATA[3.89×10 -5 ]]> Example 8 20 <![CDATA[1.88×10 -5 ]]> Comparative Example 1 20 <![CDATA[1.08×10 -5 ]]>

[0071] The electrochemical impedance spectra of the polymer-inorganic filler composite electrolytes of Example 1 and Comparative Example 1 are shown in the attached figures. Figure 3 , 4 As shown.

[0072] It can be seen that the ionic conductivity of Comparative Example 1 is significantly lower than that of Examples 1-8. Among Examples 1-8, Example 6 has the highest ionic conductivity, and the ionic conductivity increases with decreasing silicon oxide particle size.

[0073] It should be noted that the above descriptions are merely preferred embodiments of the present invention and should not limit the scope of protection of the technical solutions of the present invention. Any modifications made to the technical solutions described in the foregoing embodiments, or equivalent substitutions of technical features, by those skilled in the art within the spirit and principles of the present invention, should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a polymer-inorganic filler composite electrolyte, characterized in that, It includes: (1) Dissolve polyethylene oxide in water to obtain a colloidal solution; (2) Adjust the colloidal solution to be alkaline to obtain an alkaline colloidal solution; (3) Tetraethyl orthosilicate is added dropwise to the alkaline colloidal solution until it hydrolyzes to form uniformly distributed quantum dot-level silica particles, thus obtaining a polyethylene oxide-silica mixture; (4) Add lithium salt to the polyethylene oxide-silica mixture and mix to obtain an electrolyte mixture; (5) Heat the electrolyte mixture to remove water, and obtain a polymer-inorganic filler composite electrolyte.

2. The preparation method according to claim 1, characterized in that, in, In the colloidal solution, the mass percentage of polyethylene oxide is 3.0-15.0 wt%; and / or, the mass percentage of tetraethyl orthosilicate added to the polyethylene oxide-silica mixture is 0.5-5.0 wt%.

3. The preparation method according to claim 1, characterized in that, The pH value of the alkaline colloidal solution is 8.5-12.

5.

4. The preparation method according to claim 1, characterized in that, The particle size of the quantum dot-level silicon oxide particles is 2-20 nm.

5. The preparation method according to claim 1, characterized in that, The concentration of lithium salt in the electrolyte mixture is 0.1-1.2 mol / L.

6. The preparation method according to claim 1, characterized in that, The lithium salt is selected from one or more of lithium perchlorate, lithium tetrafluoroborate, lithium hexafluorophosphate, lithium bis(oxalate)borate, lithium difluorooxalateborate, lithium bis(difluorosulfonyl)imide, and lithium bis(trifluoromethylsulfonyl)imide.

7. The preparation method according to claim 1, characterized in that, The heating is vacuum heating, with a vacuum degree of 0.01-1 Pa, a heating temperature of 50-80℃, and a heating time of 20-50 h.

8. The preparation method according to claim 1, characterized in that, The lithium salt is selected from lithium hexafluorophosphate; the polyoxyethylene content in the colloidal solution is 8.5 wt%; the pH value of the alkaline colloidal solution is 10.0; the tetraethyl orthosilicate added to the polyoxyethylene-silica mixture is 3.5 wt%; and the concentration of lithium salt in the electrolyte mixture is 0.5 mol / L.

9. The polymer-inorganic filler composite electrolyte prepared by the preparation method according to any one of claims 1-8.

10. A lithium battery containing the polymer-inorganic filler composite electrolyte of claim 9.

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