High-heat-resistance lithium battery diaphragm as well as preparation method and application thereof

Abstract

The invention discloses a high-heat-resistance lithium battery diaphragm and a preparation method and application thereof.The high-heat-resistance lithium battery diaphragm comprises a base membrane and a coating on the base membrane, and the coating comprises, by mass, 1-5 parts of aluminum oxide, 1-5 parts of an adhesive, 1-5 parts of a dispersing agent, 1-5 parts of silicon dioxide aerogel and 1-5 parts of polyvinylpyrrolidone; the ratio of the aluminum oxide to the adhesive to the dispersing agent to the silicon dioxide aerogel to the polyvinylpyrrolidone is (5-10): (5-8): (0.1-0.5): (1.59-3.18): (0.159-0.318), and the aluminum oxide is a mixture of coralline aluminum oxide and spherical aluminum oxide. The surface of the base membrane is coated with the slurry containing the coralline aluminum oxide, the spherical aluminum oxide and the silicon dioxide aerogel, the formed high-heat-resistance lithium battery diaphragm has macroporous, mesoporous and microporous structures, and the heat resistance, the liquid absorption rate and the liquid retention rate of the diaphragm are improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery separators, and specifically relates to a high-heat-resistant lithium battery separator and a preparation method and application thereof. Background Art

[0002] As environmental issues become increasingly severe, more and more new energy projects are attracting public attention, with electric vehicles being particularly popular. As the power source for electric vehicles, the safety and endurance of lithium-ion batteries are key research priorities. The performance of the diaphragm, a key internal component of lithium-ion batteries, determines the battery's interface structure and internal resistance, directly impacting its capacity, cycle life, and safety. In lithium-ion batteries, the diaphragm absorbs electrolyte to prevent short circuits while allowing lithium ions to conduct. During overcharging or elevated temperatures, the diaphragm blocks current flow through its closed pores, preventing explosion.

[0003] Based on the above, the high temperature resistance of lithium-ion batteries has become a focus of more attention. Conventional lithium battery separators have a high short-circuit rate, low battery heat resistance, and poor separator wettability. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the object of the present invention is to provide a highly heat-resistant lithium battery separator.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned high-heat-resistant lithium battery separator.

[0006] The purpose of the present invention is achieved through the following technical solutions.

[0007] A high-heat-resistant lithium battery separator comprises a base film and a coating on the base film. The coating comprises aluminum oxide, an adhesive, a dispersant, silicon dioxide aerogel and polyvinyl pyrrolidone. The ratio of aluminum oxide, adhesive, dispersant, silicon dioxide aerogel and polyvinyl pyrrolidone is (5-10): (5-8): (0.1-0.5): (1.59-3.18): (0.159-0.318) by mass. The aluminum oxide is a mixture of coral-shaped aluminum oxide and spherical aluminum oxide.

[0008] In the above technical solution, the ratio of coralline alumina to spherical alumina is (0.5-2):(2-3) by mass.

[0009] The method for preparing the high-heat-resistant lithium battery separator comprises: coating the slurry on a base film, drying, and obtaining a coating on the base film to obtain the high-heat-resistant lithium battery separator.

[0010] In the above technical solution, the drying temperature is 50-70° C., and the drying time is 1-3 minutes.

[0011] In the above technical solution, the coating speed is 30 to 50 m / min.

[0012] In the above technical solution, the thickness of the coating is 1 to 3 μm.

[0013] A slurry comprises: alumina, water, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone, wherein the ratio of alumina, water, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone is (5-10): (74.75-91.4): (5-8): (0.1-0.5): (1.59-3.18): (0.159-0.318) by mass, and the alumina is a mixture of coral-shaped alumina and spherical alumina.

[0014] In the above technical solution, the ratio of coralline alumina to spherical alumina is (0.5-2):(2-3) by mass.

[0015] In the above technical solution, the particle size of coral-shaped alumina is: D50=400~800nm, and the particle size of spherical alumina is: D50≤200nm.

[0016] In the above technical solution, the density of silica aerogel is 50-150 mg / cm 3 The porosity is 85-99.8%, and the specific surface area is 800-1200 m2 / g.

[0017] In the above technical solution, the adhesive is polyacrylate.

[0018] In the above technical solution, the dispersant is a mixture of ammonium polyacrylate and polyether siloxane, and the ratio of ammonium polyacrylate to polyether siloxane is (2-3): (0.5-1.5) by mass.

[0019] A method for preparing a slurry comprises: mixing alumina, water, an adhesive, a dispersant, a silica aerogel and polyvinyl pyrrolidone until uniformly mixed to obtain a slurry, wherein the ratio of the alumina, water, the adhesive, the dispersant, the silica aerogel and the polyvinyl pyrrolidone is (5-10): (74.75-91.4): (5-8): (0.1-0.5): (1.59-3.18): (0.159-0.318) by mass, and the alumina is a mixture of coral-shaped alumina and spherical alumina.

[0020] In the above technical solution, the ratio of coralline alumina to spherical alumina is (0.5-2):(2-3) by mass.

[0021] In the above technical solution, the particle size of coral-shaped alumina is: D50=400~800nm, and the particle size of spherical alumina is: D50≤200nm.

[0022] In the above technical solution, the density of silica aerogel is 50-150 mg / cm 3 The porosity is 85-99.8%, and the specific surface area is 800-1200 m2 / g.

[0023] In the above technical solution, the adhesive is polyacrylate.

[0024] In the above technical solution, the dispersant is a mixture of ammonium polyacrylate and polyether siloxane, and the ratio of ammonium polyacrylate to polyether siloxane is (2-3): (0.5-1.5) by mass.

[0025] In the above technical solution, the method for preparing the slurry specifically includes the following steps:

[0026] Step 1: mixing a dispersant, a first portion of water, and aluminum oxide until uniformly mixed to obtain a first solution, wherein the ratio of the dispersant, the first portion of water, and aluminum oxide is (0.1-0.5): (71.5-84.9): (5-10) by mass;

[0027] In step 1, the dispersant, the first portion of water, and the aluminum oxide are mixed, stirred, and then ultrasonicated until uniformly mixed to obtain a first solution. The stirring speed is 1500 to 3100 rpm, the orbital speed is 20 to 50 rpm, and the stirring time is 10 to 20 minutes. The ultrasonic frequency is 10 to 50 kHz, and the ultrasonication time is 10 to 20 minutes.

[0028] Step 2: Mix the first solution, adhesive, silica aerogel, polyvinyl pyrrolidone and the second part of water until uniformly distributed to obtain a slurry. The ratio of alumina, adhesive, silica aerogel, polyvinyl pyrrolidone and the second part of water is (5-10): (5-8): (1.59-3.18): (0.159-0.318): (3.25-6.5) by mass.

[0029] In step 2, the first solution, adhesive, silica aerogel, polyvinyl pyrrolidone, and the second portion of water are mixed and simultaneously sonicated and stirred under vacuum conditions for 10 to 20 minutes until uniform. The vacuum degree of the vacuum conditions is 0.06 to 0.08 kPa. The stirring speed is 1000 to 3800 rpm, the revolution speed is 20 to 40 rpm, and the ultrasonic frequency is 5 to 8 kHz.

[0030] Application of coral-like alumina, spherical alumina, silica aerogel and polyvinyl pyrrolidone to synergistically improve the liquid absorption rate and / or liquid retention rate of the diaphragm.

[0031] Application of coral-like alumina, spherical alumina, silica aerogel and polyvinyl pyrrolidone to synergistically improve the heat resistance of separators.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention uses a slurry containing coral-like alumina, spherical alumina and silica aerogel to coat the surface of the base film. The formed high-heat-resistant lithium battery separator has a macroporous, mesoporous and microporous structure (coral-like alumina constructs a 3D network to form macropores, spherical alumina forms mesopores, and silica aerogel forms micropores), which increases the heat resistance, liquid absorption rate and liquid retention rate of the separator. The coral-like structure of coral-like alumina forms a three-dimensional skeleton, with spherical alumina filling the pores within this framework, improving the coating's density and structural stability. Combined with silica aerogel, the coating's thermal shielding effect is enhanced. Specifically, the coral-like alumina's three-dimensional skeleton and the spherical alumina filling its pores inhibit high-temperature deformation, making the separator less susceptible to deformation at high temperatures. This improves electrolyte diffusion efficiency and optimizes the lithium-ion transport pathway. The silica aerogel provides both a liquid storage unit and a thermal insulation barrier, achieving a three-dimensional electrolyte structure characterized by "macropore rapid infiltration, mesopore directional transport, and micropore long-term liquid retention." The open pores of coral-like alumina combined with the nanopores of the silica aerogel prolong electrolyte retention, thereby increasing the separator's liquid absorption and retention rate. PVP improves the dispersion of aerogel particles, reduces agglomeration, and forms a more uniform porous structure, increasing liquid absorption and retention, and improving the separator's wettability to electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a SEM image of the separator prepared from the slurry of Example 1. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further described below with reference to specific embodiments.

[0036] Coralline alumina was purchased from Jiangsu Tianxing New Materials Co., Ltd.

[0037] Spherical alumina was purchased from Jiangsu Tianxing New Materials Co., Ltd.

[0038] Conventional alumina was purchased from Zhengzhou Xide Chemical New Materials Co., Ltd.

[0039] Silica aerogel was purchased from Shanghai Zhenlishi Network Technology Co., Ltd., Cabot P200. The density of silica aerogel is 80 mg / cm 3 The porosity is 91.8% and the specific surface area is 950㎡ / g.

[0040] Double planetary mixer: XFZH-30L.

[0041] The water in the following examples and comparative examples is pure water.

[0042] Examples 1 to 3

[0043] A method for preparing a slurry comprises: mixing alumina, water, an adhesive, a dispersant, silica aerogel, and polyvinyl pyrrolidone until uniformly distributed to obtain a slurry, wherein the ratio of alumina, water, adhesive, dispersant, silica aerogel, and polyvinyl pyrrolidone is X by weight, and the alumina is a mixture of coralline alumina and spherical alumina. Water is added twice. The slurry preparation method specifically comprises the following steps:

[0044] Step 1: Mix the dispersant, the first portion of water, and aluminum oxide in a double planetary mixer, stir and then ultrasonicate until the mixture is uniformly mixed to obtain a first solution, wherein the ratio of the dispersant, the first portion of water, and the aluminum oxide is Y by mass, the rotation speed of the stirring is A1 r / min, the revolution speed is A2 r / min, the stirring time is 15 minutes, the ultrasonic frequency is C1 kHz, and the ultrasonic time is 15 minutes;

[0045] Step 2: Add an adhesive, silica aerogel, polyvinyl pyrrolidone, and a second portion of water to the first solution, and simultaneously ultrasonicate and stir for 15 minutes under vacuum conditions until uniform to obtain a slurry. In parts by mass, the ratio of alumina, adhesive, silica aerogel, polyvinyl pyrrolidone, and the second portion of water (in step 1) is Z, the vacuum degree is 0.07 kPa, the rotation speed of the stirring is A3 r / min, the revolution speed is A4 r / min, and the frequency of the ultrasound is C2 kHz.

[0046] The alumina is a mixture of coralline alumina and spherical alumina. The ratio of coralline alumina to spherical alumina is 1:3 by mass. The particle size of the coralline alumina is D50 = 500 nm, and the particle size of the spherical alumina is D50 = 200 nm. The adhesive is polymethyl acrylate (number average molecular weight of 300,000 g / mol). The dispersant is a mixture of ammonium polyacrylate (number average molecular weight of 20,000 g / mol) and polyether siloxane (Shanghai Sangjing Chemical Co., Ltd.: Digao Wet 270). The ratio of ammonium polyacrylate to polyether siloxane is 2:1 by mass.

[0047] A1, A2, C1, A3, A4, C2, X, Y and Z are shown in Table 1.

[0048] Table 1

[0049]

[0050] Comparative Example 1

[0051] A method for preparing a slurry comprises the following steps:

[0052] Step 1: conventional alumina (irregular shape), water and dispersant are mixed in a double planetary mixer, stirred and then ultrasonicated until the mixture is uniform, to obtain solution A, wherein the stirring rotation speed is 3100 r / min, the revolution speed is 20 r / min, the stirring time is 15 min, the ultrasonic frequency is 50 kHz, and the ultrasonic time is 15 min;

[0053] Step 2: Add adhesive to solution A, ultrasonicate and stir for 15 minutes under vacuum until uniform, to obtain slurry. The vacuum degree is 0.07KPA, the stirring speed is 1000r / min, the revolution speed is 40r / min, and the ultrasonic frequency is 5kHz.

[0054] Calculated by mass, the ratio of conventional alumina, water, dispersant and adhesive is 5:89.8:0.2:5, the dispersant is ammonium polyacrylate (the same as in Example 1), the adhesive is polymethyl acrylate (the same as in Example 1), and the particle size of conventional alumina (particles) is: D50 = 0.821 microns, D90 = 1.681 microns.

[0055] Comparative Example 2

[0056] A method for preparing a slurry is basically the same as that of Comparative Example 1, except that "conventional alumina (irregular shape)" is replaced by "spherical alumina".

[0057] Comparative Example 3

[0058] A method for preparing a slurry is basically the same as that of Comparative Example 1, except that "conventional alumina (irregular shape)" is replaced by "coral-like alumina".

[0059] Comparative Example 4

[0060] A method for preparing a slurry is substantially the same as that of Example 1, except that the phrase "alumina is a mixture of coralline alumina and spherical alumina" is replaced with "alumina is a mixture of coralline alumina and regular alumina (irregularly shaped)." The ratio of coralline alumina to regular alumina is 1:3 by mass.

[0061] Comparative Example 5

[0062] A method for preparing a slurry is substantially the same as that of Example 1, except that polyvinyl pyrrolidone (PVP) is not added in Comparative Example 5.

[0063] Examples 4 to 6 and Comparative Examples 6 to 10

[0064] A method for preparing a diaphragm comprises placing a base film (9 μm PE film) on a coating machine loaded with a slurry, coating the slurry on one side of the base film at a coating speed of D m / min, drawing the slurry through a traction roller into a drying apparatus and drying the slurry at E°C for T min to form a coating on the base film, thereby producing a diaphragm. The slurry is one of the slurries prepared in Examples 1-3 and Comparative Examples 1-5. The values ​​of D, E, and T are shown in Table 2.

[0065] Table 2

[0066] diaphragm Slurry used to prepare diaphragms D(m / min) E(℃) T(min) Example 4 Example 1 30 50 3 Example 5 Example 2 40 60 2 Example 6 Example 3 50 70 1 Comparative Example 6 Comparative Example 1 30 50 3 Comparative Example 7 Comparative Example 2 30 50 3 Comparative Example 8 Comparative Example 3 30 50 3 Comparative Example 9 Comparative Example 4 30 50 3 Comparative Example 10 Comparative Example 5 30 50 3

[0067] The test results of the diaphragm (Example 4) prepared from the slurry of Example 1 are as follows:

[0068]

[0069] The test results of the diaphragm (Example 5) prepared from the slurry of Example 2 are as follows:

[0070]

[0071] The test results of the diaphragm (Example 6) prepared from the slurry of Example 3 are as follows:

[0072]

[0073]

[0074] The test results of the diaphragm (Comparative Example 6) prepared from the slurry of Comparative Example 1 are as follows:

[0075]

[0076] The test results of the diaphragm (Comparative Example 7) prepared from the slurry of Comparative Example 2 are as follows:

[0077]

[0078] The test results of the diaphragm (Comparative Example 8) prepared from the slurry of Comparative Example 3 are as follows:

[0079]

[0080] The test results of the diaphragm (Comparative Example 9) prepared from the slurry of Comparative Example 4 are as follows:

[0081]

[0082] The test results of the diaphragm (Comparative Example 10) prepared from the slurry of Comparative Example 5 are as follows:

[0083]

[0084]

[0085] By combining coral-like alumina and spherical alumina, the diaphragm formed after coating is more uniform and dense, and the silica aerogel forms a heat shielding layer on the surface of the coating, which can block heat conduction and synergistically inhibit high-temperature deformation, making the diaphragm less likely to deform at high temperatures; at the same time, the open pores of the coral-like alumina are combined with the nanopores of the silica aerogel to extend the electrolyte retention time, thereby increasing the liquid absorption rate and liquid retention rate of the diaphragm; the distribution between conventional alumina particles is relatively loose, and the thermal performance and liquid retention performance of the diaphragm prepared in Comparative Example 6 are very poor.

[0086] Figure 1 This is a SEM image of the separator prepared from the slurry of Example 1.

[0087] The pore structure of the diaphragm prepared from the slurry of Example 1 is as follows:

[0088] Pore ​​structure type Pore ​​structure size <![CDATA[Pore volume (cm 3 / g)]]> Pore ​​structure ratio micropores <2.0nm 0.0023 85-99％ Mesoporous 2.0-50nm 0.0084 ＜15％ Large hole 50-200nm 0.0119 ＜1％

[0089] The above is an exemplary description of the present invention. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by other skilled in the art without expending creative labor falls within the scope of protection of the present invention.

Claims

1. A high heat-resistant lithium battery separator, characterized in that: include: The base film and the coating on the base film include: aluminum oxide, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone. The ratio of aluminum oxide, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone is (5-10): (5-8): (0.1-0.5): (1.59-3.18): (0.159-0.318) by mass. The aluminum oxide is a mixture of coral-shaped aluminum oxide and spherical aluminum oxide.

2. The high heat-resistant lithium battery separator according to claim 1, characterized in that Calculated by mass, the ratio of coral-like alumina to spherical alumina is (0.5-2): (2-3).

3. A slurry, characterized in that: include: Alumina, water, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone, calculated by mass, the ratio of alumina, water, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone is (5-10): (74.75-91.4): (5-8): (0.1-0.5): (1.59-3.18): (0.159-0.318), and the alumina is a mixture of coral-like alumina and spherical alumina.

4. The slurry according to claim 3, characterized in that The particle size of coralline alumina is: D50=400~800nm, the particle size of spherical alumina is: D50≤200nm.

5. The slurry according to claim 3, characterized in that The density of silica aerogel is 50~150mg / cm 3 The porosity is 85-99.8%, and the specific surface area is 800-1200 m2 / g.

6. A method for preparing a slurry, characterized in that: include: Alumina, water, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone are mixed until uniform to obtain a slurry. The ratio of alumina, water, adhesive, dispersant, silica aerogel and polyvinyl pyrrolidone is (5-10): (74.75-91.4): (5-8): (0.1-0.5): (1.59-3.18): (0.159-0.318) by mass. The alumina is a mixture of coral-like alumina and spherical alumina.

7. The method according to claim 6, characterized in that The following steps are involved: Step 1: mixing a dispersant, a first portion of water, and aluminum oxide until uniformly mixed to obtain a first solution, wherein the ratio of the dispersant, the first portion of water, and aluminum oxide is (0.1-0.5): (71.5-84.9): (5-10) by mass; Step 2: Mix the first solution, adhesive, silica aerogel, polyvinyl pyrrolidone and the second part of water until uniformly distributed to obtain a slurry. The ratio of alumina, adhesive, silica aerogel, polyvinyl pyrrolidone and the second part of water is (5-10): (5-8): (1.59-3.18): (0.159-0.318): (3.25-6.5) by mass.

8. The method for preparing the high heat-resistant lithium battery separator according to claim 1, comprising: The slurry according to claim 3 is coated on a base film and dried to obtain a coating on the base film to obtain a high heat-resistant lithium battery separator.

9. Application of coral-like alumina, spherical alumina, silica aerogel and polyvinyl pyrrolidone to synergistically improve the liquid absorption rate and / or liquid retention rate of the diaphragm.

10. Application of coral-like alumina, spherical alumina, silica aerogel and polyvinyl pyrrolidone to synergistically improve the heat resistance of diaphragms.

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