Composite diaphragm as well as preparation method and application thereof

Abstract

The invention relates to the technical field of diaphragms, in particular to a composite diaphragm as well as a preparation method and application thereof. According to the preparation method of the composite diaphragm, a glass fiber diaphragm is coated with a layer of aluminum through magnetron sputtering, then treatment is carried out in plasma through fluorine-containing gas, an aluminum-aluminum oxide-aluminum fluoride composite coating layer is formed on the glass fiber diaphragm, and the composite diaphragm is obtained. The AlF3 component is additionally introduced to the glass fiber diaphragm, so that the components of a potassium metal negative electrode interface SEI layer are improved, the ion transmission rate is increased, the ion concentration distribution is improved, dendritic crystal growth is inhibited, and long-acting stable circulation of the battery is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of diaphragms, and in particular to a composite diaphragm and a preparation method and application thereof. Background Art

[0002] Potassium-ion batteries are seen as a storage method that can replace lithium-ion batteries in the future because of their similar electrode potential to lithium-ion batteries, wide availability, low cost, and high ionic conductivity. Therefore, potassium metal anodes are also seen as anode materials with significant application prospects. However, the non-uniform deposition of potassium ions during the electrochemical process and the resulting uncontrollable growth of potassium dendrites seriously affect the cycle stability of the battery, thus restricting the application of potassium metal anodes. Existing research has achieved remarkable results in improving the interface of potassium metal anode materials. Methods such as improving the electrolyte and potassium metal interface modification have been used to improve the concentration distribution and deposition behavior of potassium ions at the electrode interface, thereby inhibiting the formation of dendrites.

[0003] In addition to electrolyte and electrode materials, the separator also plays an important role in the composition of the battery. It not only prevents the positive and negative electrodes from short-circuiting, but also plays a key role in promoting ion transmission and improving ion concentration distribution. Therefore, separator modification is also favored by researchers as a method to inhibit dendrite growth and improve battery performance. Summary of the invention

[0004] The purpose of the present invention is to address the above-mentioned deficiencies of the prior art and to provide a composite diaphragm and its preparation method and application, so as to improve the heterogeneity of ion transport in the electrochemical process, thereby inhibiting the growth of dendrites and improving the cycle stability of the battery.

[0005] The invention discloses a method for preparing a composite diaphragm, which comprises coating a layer of aluminum on a glass fiber diaphragm by magnetron sputtering, and then treating the glass fiber diaphragm with a fluorine-containing gas in plasma to form a composite coating layer of aluminum-aluminum oxide-aluminum fluoride on the glass fiber diaphragm to obtain a composite diaphragm.

[0006] Furthermore, the thickness of the aluminum coated by magnetron sputtering is 100-300 nm.

[0007] Furthermore, the thickness of the aluminum coated by magnetron sputtering is 100-200 nm.

[0008] Furthermore, the sputtering time is controlled to obtain aluminum with different thicknesses.

[0009] Furthermore, the plasma treatment power is 60 W and the treatment time is 5 min.

[0010] Furthermore, the fluorine-containing gas is CF4 gas.

[0011] A composite diaphragm prepared by the above-mentioned preparation method.

[0012] An application of the composite diaphragm as described above in a potassium ion battery.

[0013] The method for modifying the glass fiber diaphragm provided by the present invention is a method of combining magnetron sputtering and plasma multi-physical fields. The method is gentle and non-destructive, and does not cause structural damage to the glass fiber diaphragm. The magnetron sputtering and plasma treatment are performed gradually, and both are surface treatment processes. The resulting composite coating layer is composed of aluminum, aluminum oxide and aluminum fluoride from the inside to the outside. This composite coating layer can not only assist in the generation of an SEI layer rich in Al2O3, KF, and AlF3 during the electrochemical process, thereby improving the interface composition, uniform cation flux, achieving uniform metal deposition, and inhibiting dendrite growth, but also Al2O3 can remove acidic byproducts (HF, etc.) in the electrolyte to achieve a long-term stable cycle of the battery.

[0014] The coating layer obtained by the diaphragm of the present invention has uniform thickness and uniform composition, and is superior to the coating layers obtained by other coating methods.

[0015] In summary, the present invention improves the composition of the SEI layer at the interface of the potassium metal negative electrode by introducing AlF3 components onto the glass fiber diaphragm, accelerates the ion transfer rate, improves the ion concentration distribution, thereby inhibiting dendrite growth and achieving long-term stable cycle of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a photo of the composite diaphragm prepared in Example 1;

[0017] Figure 2 This is a SEM image of the composite diaphragm prepared in Example 1 of the present invention; the image shows the coating morphology of the coating layer on the diaphragm glass fiber;

[0018] Figure 3 The XPS test results of the composite diaphragm prepared in Example 1 of the present invention; the test results show the composition of the coating layer;

[0019] Figure 4 The XRD test results of the composite membrane prepared in Example 1 of the present invention;

[0020] Figure 5 This is the XPS test result of the composite membrane prepared in Example 1 of the present invention;

[0021] Figure 6 The composite diaphragm prepared in Example 1 of the present invention and the ordinary glass fiber diaphragm are -2 , 0.5mAh cm -2 Performance of potassium metal symmetric batteries under conditions of . DETAILED DESCRIPTION

[0022] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0023] Example 1

[0024] 1) Cut the glass fiber diaphragm to a suitable size and then place it in the inner chamber of a magnetron sputtering machine. By controlling different sputtering times and calibrating the film thickness meter, a glass fiber diaphragm with an aluminum coating layer of 100 nm thickness is obtained.

[0025] 2) Then the aluminum-coated glass fiber diaphragm is placed in a plasma chamber, CF4 gas is introduced, the power is 150 W, the treatment time is 15 minutes, and the outer side of the coated pure aluminum layer is converted into an AlF3 coating layer, thereby forming an aluminum-aluminum oxide-aluminum fluoride composite coating layer to obtain a composite diaphragm.

[0026] Example 2

[0027] 1) Cut the glass fiber diaphragm to a suitable size and then place it in the inner chamber of a magnetron sputtering machine. By controlling different sputtering times and calibrating the film thickness meter, a glass fiber diaphragm with an aluminum coating layer of 200 nm thickness is obtained.

[0028] 2) Then the aluminum-coated glass fiber diaphragm is placed in a plasma chamber, CF4 gas is introduced, the power is 150 W, the treatment time is 15 minutes, and the outer side of the coated pure aluminum layer is converted into an AlF3 coating layer, thereby forming an aluminum-aluminum oxide-aluminum fluoride composite coating layer to obtain a composite diaphragm.

[0029] Example 3

[0030] 1) Cut the glass fiber diaphragm to a suitable size and then place it in the inner chamber of a magnetron sputtering machine. By controlling different sputtering times and calibrating the film thickness meter, a glass fiber diaphragm with an aluminum coating layer of 300 nm thickness is obtained.

[0031] 2) Then the aluminum-coated glass fiber diaphragm is placed in a plasma chamber, CF4 gas is introduced, the power is 150 W, the treatment time is 15 minutes, and the outer side of the coated pure aluminum layer is converted into an AlF3 coating layer, thereby forming an aluminum-aluminum oxide-aluminum fluoride composite coating layer to obtain a composite diaphragm.

[0032] Performance Testing

[0033] Using metallic potassium as positive and negative electrodes, the composite diaphragm prepared in Example 1 as a diaphragm, and 1M KFSI EC / DEC as an electrolyte, a CR2032 symmetrical battery was assembled in a glove box filled with argon.

[0034] At 0.5mAcm -2 , 0.5mAh cm -2 The performance of the CR2032 symmetrical battery in the ordinary glass fiber separator and the composite separator prepared in Example 1 was tested under the conditions of Figure 6 As shown, from Figure 6 It can be seen that the polarization of the CR2032 symmetrical battery composed of the composite separator has been significantly reduced from 400mv to 200mv, and the cycle stability has been improved.

[0035] Figure 1 This is a photo of the composite diaphragm prepared in Example 1; it can be seen from the figure that the thickness of the composite coating layer is uniform.

[0036] Figure 2 This is a SEM image of the composite diaphragm prepared in Example 1 of the present invention; the image shows the coating morphology of the coating layer on the diaphragm glass fiber, and the coating layer is uniformly coated on the diaphragm glass fiber.

[0037] Figure 3 This is the XPS test result of the composite membrane prepared in Example 1 of the present invention; the test result shows the composition of the coating layer, and the coating layer contains aluminum fluoride.

[0038] Figure 4 This is the XRD test result of the composite diaphragm prepared in Example 1 of the present invention; the test result shows the composition of the coating layer, and the coating layer contains aluminum.

[0039] Figure 5 This is the XPS test result of the composite diaphragm prepared in Example 1 of the present invention; the test result shows the composition of the coating layer, which contains aluminum oxide.

[0040] For matters not mentioned above, the prior art applies.

[0041] Although some specific embodiments of the present invention have been described in detail through examples, those skilled in the art should understand that the above examples are for illustration only and are not intended to limit the scope of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or supplements to the specific embodiments described or replace them in a similar manner, but they will not deviate from the direction of the present invention or exceed the scope defined by the attached claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a composite diaphragm, characterized in that: A layer of aluminum is coated on a glass fiber diaphragm by magnetron sputtering, and then a composite coating layer of aluminum-aluminum oxide-aluminum fluoride is formed on the glass fiber diaphragm by treating the fluorine-containing gas in plasma to obtain a composite diaphragm.

2. The preparation method according to claim 1, characterized in that: The thickness of the magnetron sputtered aluminum coating is 100-300 nm.

3. The preparation method according to claim 2, characterized in that: The thickness of the magnetron sputtered aluminum coating is 100-200 nm.

4. The preparation method according to claim 2, characterized in that: The sputtering time is controlled to obtain different thicknesses of aluminum.

5. The preparation method according to claim 1, characterized in that: The plasma treatment power is 60W to 150W, and the treatment time is 5min to 15min.

6. The preparation method according to claim 1, characterized in that: The fluorine-containing gas is CF4 gas.

7. A composite diaphragm prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the composite diaphragm as claimed in claim 7 in a potassium ion battery.

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