Sulfide corrosion resistant current collector coating and use thereof

Abstract

The application discloses a sulfide corrosion-resistant current collector coating and application thereof, and relates to the field of battery materials. The preparation raw materials of the sulfide corrosion-resistant current collector coating include an adhesive and a conductive dispersion liquid. The preparation method of the adhesive comprises the following steps: S1, polyacrylonitrile is added into a strong alkali solution with a mass concentration of 1-2%, and the temperature is increased to 75-85 DEG C for hydrolysis for 20-60 min to obtain a light yellow suspension; S2, the light yellow suspension is cooled to room temperature, centrifugal separation is carried out, and the liquid is boiled and concentrated to a solid content of 20-30% to obtain hydrolyzed polyacrylonitrile; and S3, the hydrolyzed polyacrylonitrile is mixed with sulfonated phthalocyanine cobalt, the pH is adjusted to 3-5, then polyvinyl alcohol is added, continuous stirring is carried out, then standing and defoaming are carried out to obtain the adhesive. The application can effectively improve the cycle performance of a sulfide solid-state battery through the combined action of hydrolyzed polyacrylonitrile, polyvinyl alcohol and sulfonated phthalocyanine cobalt.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery materials, in particular to a sulfide corrosion resistant current collector coating and application thereof. BACKGROUND

[0002] The ionic conductivity of sulfide solid electrolyte can reach 10 -2 S / cm level, so sulfide solid-state battery is currently considered as the most potential solid-state battery route for industrialization. In traditional battery electrode, Cu (copper) foil is often used as negative electrode current collector, and Al (aluminum) foil is used as positive electrode current collector. However, through research, for sulfide solid-state battery, due to the material properties of sulfide itself, the sulfide solid electrolyte will react with trace water in the working environment to generate H2S gas, thereby corroding the Al foil and Cu foil current collector, resulting in reduced cycle performance of the sulfide solid-state battery. At the same time, in the high voltage environment, the interface between the sulfide solid electrolyte and the oxide active material (LiCoO2, LiMn2O4 and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.) will react to generate high impedance substances (Li2S n , S and P2S x ), which is not conducive to the enrichment of Al foil electrons, reducing the cycle performance of the sulfide solid-state battery.

[0003] Therefore, it is necessary to provide a conductive coating which is resistant to sulfide corrosion and can slowly decompose the high impedance substances generated between the Al foil current collector and the positive electrode active material, so as to solve the corrosion of H2S generated by sulfide reaction on the Al foil and Cu foil current collector, improve the electron transfer efficiency between the positive electrode active material and the current collector, and improve the cycle performance of the sulfide solid-state battery. SUMMARY

[0004] In order to effectively improve the cycle performance of the sulfide solid-state battery, the present application provides a sulfide corrosion resistant current collector coating and application thereof.

[0005] In a first aspect, the present application provides a sulfide corrosion resistant current collector coating which adopts the following technical solution:

[0006] A sulfide corrosion resistant current collector coating, the preparation raw materials of the sulfide corrosion resistant current collector coating include adhesive and conductive dispersion liquid, the preparation method of the adhesive includes the following steps:

[0007] S1, polyacrylonitrile is added into a strong alkali solution with a mass concentration of 1-2%, and hydrolysis is carried out at 75-85℃ for 20-60min to obtain a light yellow suspension;

[0008] S2, after the light yellow suspension is cooled to room temperature, centrifugal separation is performed to obtain liquid, and the liquid is boiled and concentrated to a solid content of 20-30% to obtain hydrolyzed polyacrylonitrile;

[0009] S3, the hydrolyzed polyacrylonitrile is mixed with sulfonated cobalt phthalocyanine, the pH is adjusted to 3-5, then polyvinyl alcohol is added, continuous stirring is performed, then standing is performed to remove bubbles, and an adhesive is obtained.

[0010] In the present application, the key improvement of the sulfide corrosion resistant current collector coating lies in the adhesive, which is prepared from hydrolyzed polyacrylonitrile obtained by hydrolysis of polyacrylonitrile under specific conditions, sulfonated cobalt phthalocyanine and polyvinyl alcohol, wherein the hydrolyzed polyacrylonitrile obtained by hydrolysis under specific conditions contains specific proportions of -COONa, -CONH and -CN groups, which can make the hydrolyzed polyacrylonitrile uniformly dispersed in the conductive dispersion liquid, and due to the strong polarity of these groups, they can adsorb sulfides and also can assist in inhibiting the shuttling of sulfides, thereby improving the corrosion performance of sulfides on aluminum foil current collectors and copper foil current collectors. In addition, the introduction of sulfonated cobalt phthalocyanine can catalyze the crosslinking reaction between -COONa in hydrolyzed polyacrylonitrile and polyvinyl alcohol, and catalyze the formation of hydrogen bonds between -CN and -CONH and -OH, which can inhibit the shuttling effect of sulfides; on the other hand, sulfonated cobalt phthalocyanine also has a high active Co-N4 center, which can decompose the high impedance substances generated between the positive active material and the current collector through sulfur reduction catalytic decomposition, such as Li2S n and P2S x , which is conducive to the enrichment of Al foil current collector electrons, and also can improve the cycle performance of sulfide solid-state batteries; at the same time, sulfonated cobalt phthalocyanine can also form a thin layer on the surface of the copper foil current collector, which can reduce the influence of space charge effect on lithium deposition, so that lithium is uniformly deposited, and also can improve the cycle performance of sulfide solid-state batteries.

[0011] That is, through the combined action of hydrolyzed polyacrylonitrile, polyvinyl alcohol and sulfonated cobalt phthalocyanine, the present application can not only improve the corrosion problem of H2S generated by sulfide reaction on Al foil current collector and Cu foil current collector, but also further improve the electron transfer efficiency between the positive active material and the current collector, which can effectively improve the cycle performance of sulfide solid-state batteries.

[0012] In some specific S1 steps, the hydrolysis time is controlled to be 30-40 min.

[0013] In the present application, by controlling the hydrolysis time of polyacrylonitrile to be 30-40 min, the proportion of -COONa, -CONH and -CN groups in the hydrolyzed polyacrylonitrile can be controlled in a more suitable range, which can further inhibit the shuttling of sulfides, improve the corrosion problem of H2S generated by sulfide reaction on Al foil current collector and Cu foil current collector, and thus further improve the cycle performance of sulfide solid-state batteries.

[0014] In some specific embodiments, the weight ratio of the hydrolyzed polyacrylonitrile, the sulfonated cobalt phthalocyanine and the polyvinyl alcohol in the S3 step is 300:(2-5):(15-25).

[0015] In some preferred embodiments, the weight ratio of the hydrolyzed polyacrylonitrile, the sulfonated cobalt phthalocyanine and the polyvinyl alcohol in the S3 step is 300:(3-4):(15-25).

[0016] The application further preferably has a weight ratio of the hydrolyzed polyacrylonitrile, the sulfonated cobalt phthalocyanine and the polyvinyl alcohol of 300:(3-4):(15-25), so that the amount of sulfonated cobalt phthalocyanine is within a suitable range, further improving the cycle performance of the sulfide solid-state battery; too much sulfonated cobalt phthalocyanine will reduce the cycle performance, because the pH value of the adhesive will limit the solubility of the sulfonated cobalt phthalocyanine, and too much will easily cause precipitation, affecting the cycle performance of the sulfide solid-state battery.

[0017] In some specific embodiments, the conductive dispersion liquid is uniformly mixed by 5-20wt% of graphite, 5-20wt% of carbon black, 10-15wt% of polyacrylic acid, 20-50wt% of isopropyl alcohol and the balance of deionized water.

[0018] The conductive dispersion liquid in the application is preferably the conductive dispersion liquid with the above composition, which can be uniformly dispersed with the adhesive and is conducive to improving the conductive performance of the sulfide solid-state battery.

[0019] In some specific embodiments, the graphite includes at least one of flaky graphite, crystalline graphite and aphanitic graphite.

[0020] In some specific embodiments, the carbon black includes at least one of acetylene black, ketjen black and furnace black.

[0021] In some specific embodiments, the weight ratio of the adhesive and the conductive dispersion liquid is (12-18):50.

[0022] In the application, the weight ratio of the adhesive and the conductive dispersion liquid is controlled to be (12-18):50, which can further promote the uniform dispersibility of the two, and is conducive to obtaining a corrosion-resistant current collector coating with good uniformity.

[0023] In a second aspect, the application provides the use of any one of the above-mentioned sulfide corrosion-resistant current collector coatings, which is specifically used as a carbon coating layer for coating a carbon aluminum foil current collector or a carbon copper foil current collector.

[0024] In a third aspect, the application provides a sulfide solid-state battery, wherein the positive electrode current collector of the sulfide solid-state battery adopts the carbon-coated aluminum foil current collector comprising the sulfide corrosion-resistant current collector coating described above, and / or the negative electrode current collector of the sulfide solid-state battery adopts the carbon-coated copper foil current collector comprising the sulfide corrosion-resistant current collector coating described above.

[0025] In summary, the application at least includes the following beneficial technical effects:

[0026] (1) The application can improve the corrosion of Al foil current collector and Cu foil current collector caused by H2S produced by sulfide reaction, further improve the electron transfer efficiency between the positive active material and the current collector, and effectively improve the cycle performance of the sulfide solid-state battery through the combined action of hydrolyzed polyacrylonitrile, polyvinyl alcohol and sulfonated cobalt phthalocyanine.

[0027] (2) In the application, the hydrolysis time of polyacrylonitrile is controlled in the range of 30-40 min, the ratio of -COONa, -CONH and -CN groups in the hydrolyzed polyacrylonitrile can be controlled in a more suitable range, the sulfide shuttle can be further inhibited, the corrosion of Al foil current collector and Cu foil current collector caused by H2S produced by sulfide reaction can be improved, and the cycle performance of the sulfide solid-state battery can be further improved.

[0028] (3) The application further preferably controls the weight ratio of hydrolyzed polyacrylonitrile, sulfonated cobalt phthalocyanine and polyvinyl alcohol to be 300:(3-4):(15-25), so that the amount of sulfonated cobalt phthalocyanine is in a suitable range, and the cycle performance of the sulfide solid-state battery is further improved; too much sulfonated cobalt phthalocyanine will reduce the cycle performance, because the pH value of the adhesive will limit the solubility of the sulfonated cobalt phthalocyanine, and too much will easily cause precipitation, affecting the cycle performance of the sulfide solid-state battery. DETAILED DESCRIPTION

[0029] The application will be further described below in combination with specific experiments.

[0030] Preparation Example

[0031] Preparation Example 1

[0032] A kind of adhesive, preparation method includes the following steps:

[0033] S1, 1000g of polyacrylonitrile (Taicang Kailida Plastic Raw Material Co., Ltd., 150,000 molecular weight) is added to 5L of 1% sodium hydroxide solution, and hydrolysis is carried out at 80℃ for 20min to obtain a light yellow suspension;

[0034] S2, after the light yellow suspension is cooled to room temperature, centrifugal separation is conducted using a high-speed centrifuge at 8000 r / min, liquid is taken and boiled to concentrate to a solid content of 25%, to obtain hydrolyzed polyacrylonitrile;

[0035] S3, 300 g of hydrolyzed polyacrylonitrile is mixed with 2 g of sulfonated cobalt phthalocyanine, the pH is adjusted to 3-5, then 20 g of polyvinyl alcohol (China Taiwan Changchun BP-26) is added, stirring is continued, then standing is performed to remove bubbles, to obtain an adhesive.

[0036]

Preparation Example 2

[0037] An adhesive, which is different from

Preparation Example 1

[0038]

Preparation Example 3

[0039] An adhesive, which is different from

Preparation Example 1

[0040]

Preparation Example 4

[0041] An adhesive, which is different from

Preparation Example 1

[0042]

Preparation Example 5

[0043] An adhesive, which is different from

Preparation Example 1

[0044]

Preparation Example 6

[0045] An adhesive, which is different from

Preparation Example 1

[0046] Comparative Preparation Example

[0047]

Comparative Preparation Example 1

[0048] An adhesive, which is different from

Preparation Example 1

[0049]

Comparative Preparation Example 2

[0050] An adhesive, which is different from

Preparation Example 1

[0051]

Comparative Preparation Example 3

[0052] An adhesive, which is different from

Preparation Example 1

[0053] Example

[0054] Example 1

[0055] A sulfide corrosion resistant current collector coating, the raw materials for preparation include 180g of the adhesive and 500g of the conductive dispersion liquid, the adhesive is the adhesive prepared in

Preparation Example 1

[0056] Wherein, when the sulfide corrosion resistant current collector coating is prepared, the adhesive and the conductive dispersion liquid are mixed, and then stirred at a stirring speed of 800r / min for 2h.

[0057] Example 2

[0058] A sulfide corrosion resistant current collector coating, the raw materials for preparation include 120g of the adhesive and 500g of the conductive dispersion liquid, the adhesive is the adhesive prepared in

Preparation Example 1

[0059] Example 3

[0060] A sulfide corrosion resistant current collector coating, which is different from

Example 1

Preparation Example 2

[0061] Example 4

[0062] A sulfide corrosion resistant current collector coating, which is different from

Example 1

Preparation Example 3

[0063] Example 5

[0064] A sulfide corrosion resistant current collector coating, which is different from

Example 1

Preparation Example 4

[0065] Example 6

[0066] A sulfide corrosion resistant current collector coating, which is different from

Example 1

Preparation Example 5

[0067] Example 7

[0068] A sulfide corrosion resistant current collector coating, which differs from that of

Example 1

Preparation Example 6

[0069] Comparative Example

[0070]

Comparative Example 1

[0071] A sulfide corrosion resistant current collector coating, which differs from that of

Example 1

Comparative Preparation Example 1

[0072]

Comparative Example 2

[0073] A sulfide corrosion resistant current collector coating, which differs from that of

Example 1

Comparative Preparation Example 2

[0074]

Comparative Example 3

[0075] A sulfide corrosion resistant current collector coating, which differs from that of

Example 1

Comparative Preparation Example 3

[0076] Application Example

[0077]

Application Example 1

[0078] A carbon-coated aluminum foil current collector, which comprises an aluminum foil and a sulfide corrosion resistant current collector coating coated on the surface of the aluminum foil, wherein the thickness of the aluminum foil is 12 μm, the sulfide corrosion resistant current collector coating is the coating in

Example 1

Example 7

[0079]

Application Example 2

[0080] A carbon-coated copper foil current collector, which comprises a copper foil and a sulfide corrosion resistant current collector coating coated on the surface of the copper foil, wherein the thickness of the copper foil is 8 μm, the sulfide corrosion resistant current collector coating is the coating in

Example 1

Example 7

[0081] Comparative Application Example

[0082]

Comparative Application Example 1

[0083] A carbon-coated aluminum foil current collector includes an aluminum foil and a sulfide corrosion-resistant current collector coating applied to the surface of the aluminum foil, wherein the aluminum foil has a thickness of 12 μm, the sulfide corrosion-resistant current collector coating is applied using the coating of Comparative Example 1-Comparative Example 3, and the coating thickness is 1 μm. After the coating is completed, the sulfide corrosion-resistant current collector coating is baked at 140°C for 1 min.

[0084] Comparative Application Example 1

[0085] A carbon-coated copper foil current collector includes a copper foil and a sulfide corrosion-resistant current collector coating applied to the surface of the copper foil, wherein the copper foil has a thickness of 8 μm, the sulfide corrosion-resistant current collector coating is applied using the coating of Comparative Example 1-Comparative Example 3, and the coating thickness is 1 μm. After the coating is completed, the sulfide corrosion-resistant current collector coating is baked at 140°C for 1 min.

[0086] Performance test

[0087] First, a sulfide solid-state battery to be tested is prepared according to the following method, and the preparation method of the sulfide solid-state battery includes the following steps:

[0088] Step 1, preparation of a negative electrode sheet:

[0089] Micron silicon material, conductive carbon black, and CMC binder are weighed according to a mass ratio of 95:3:2, wet-mixed to prepare a negative electrode slurry. The negative electrode slurry is coated on the copper foil current collector for the negative electrode prepared in each of the application examples and the comparative application examples to form a negative electrode layer, and the areal density of the active material in the negative electrode layer is 0.4 mg / cm 2 ;

[0090] Step 2, preparation of a positive electrode sheet:

[0091] NCM811, LPSCl, conductive carbon black, and PTFE binder are weighed according to a mass ratio of 70:26:2:2, dry-mixed at 80°C for 2 h, and the positive electrode material is coated on the aluminum foil current collector for the positive electrode prepared in each of the application examples and the comparative application examples by hot pressing to form a positive electrode layer, and the areal density of the positive electrode active material in the positive electrode layer is 10 mg / cm 2 ;

[0092] Step 3, preparation of a sulfide solid-state electrolyte layer:

[0093] The electrolyte Li6PS5Cl and the PTFE binder are weighed according to a mass ratio of 99:1, dry-mixed at 80°C for 2 h, the press roller is heated to 80°C, and the electrolyte slurry is coated on a PET film using hot pressing to form an electrolyte film, and the thickness of the electrolyte film is 50 μm.

[0094] Step 4, preparation of the sulfide solid-state battery:

[0095] The above positive electrode sheet, sulfide solid electrolyte layer, and negative electrode sheet are sequentially stacked to assemble a soft package battery.

[0096] The above prepared sulfide solid-state battery is subjected to the following performance tests, and the test results are recorded in Table 1 and Table 3 below:

[0097] 1. Cycle performance of the solid-state battery, the test method is:

[0098] A new battery test cabinet is used to perform room temperature cycle test under the 0.2C / 0.2C charge-discharge protocol, and the cycle number when the battery capacity decays to 80% of the initial capacity is recorded

[0099] 2. Surface resistance of the current collector, the test method is:

[0100] A direct current low resistance tester is used for testing, the coated aluminum foil is placed on a copper base, and a 1cm 2 copper block is placed above the aluminum foil, two probes are used to contact the copper base and the copper block respectively, and the reading is recorded.

[0101] 3. Peeling force of the current collector, the test method is:

[0102] A tensile material testing machine is used for testing, double-sided tape is pasted on a metal plate, carbon-coated aluminum foil and carbon-coated copper foil are pasted on the double-sided tape, and a 19mm wide 3M tape is pasted on the double-sided tape, a part of the 3M tape is pulled out, the metal plate and the end of the 3M tape pulled out are fixed, and the tape is pulled at a speed of 200mm / min, the force obtained by peeling the tape is measured, and the reading is recorded.

[0103] Table 1

[0104]

[0105] Table 2

[0106]

[0107] Table 3

[0108]

[0109] According to the detection data of the sulfide solid-state battery 1, the sulfide solid-state battery 3-4, the sulfide solid-state battery 8-9, and Table 1-Table 3, it is known that the hydrolysis time of polyacrylonitrile affects the inhibition of the adhesive to the sulfide shuttle performance, and the hydrolysis time of polyacrylonitrile should be controlled within 20-60min, and too long or too short is not conducive to improving the cycle performance of the sulfide solid-state battery.

[0110] In combination with the detection data of sulfide solid-state battery 1, sulfide solid-state battery 10 and Tables 1-3, it can be seen that when preparing the adhesive, the sulfonated cobalt phthalocyanine adopts equal mass of zinc carbide-based porous carbon, the cycle performance of the sulfide solid-state battery is reduced, and the reason may be that the zinc carbide-based porous carbon is poor in the ability to promote the uniform deposition of lithium or the ability to promote the hydrogen bonding or cross-linking reaction between the hydrolyzed polyacrylonitrile and polyvinyl alcohol.

[0111] In combination with the detection data of sulfide solid-state battery 1, sulfide solid-state battery 5-7 and Tables 1-3, it can be seen that when preparing the adhesive, the amount of sulfonated cobalt phthalocyanine affects the inhibition of the shuttle performance of the sulfide by the adhesive, wherein when the adhesive does not add sulfonated cobalt phthalocyanine, the cycle performance of the sulfide solid-state battery is significantly reduced, and in addition, when the amount of sulfonated cobalt phthalocyanine in the S3 step of preparing the adhesive is increased from 2 g to 5 g, the cycle performance of the sulfide solid-state battery is first increased and then decreased, and therefore, the weight ratio of hydrolyzed polyacrylonitrile, sulfonated cobalt phthalocyanine and polyvinyl alcohol is preferably 300:(3-4):(15-25).

[0112] The specific embodiment is only an explanation of the present application, and is not a limitation of the present application, and those skilled in the art can make modifications to the specific embodiment without creative contribution after reading the present specification, but as long as the present application is within the scope of the claims, it is protected by the patent law.

Claims

1. A current collector coating resistant to sulfide corrosion, characterized in that: The raw materials for preparing the sulfide-resistant current collector coating include an adhesive and a conductive dispersion. The adhesive is prepared using the following steps: S1. Polyacrylonitrile is added to a 1-2% (w / w) strong alkaline solution and heated to 75-85°C for 20-60 minutes to hydrolyze, yielding a pale yellow suspension; S2. The pale yellow suspension is cooled to room temperature, centrifuged, and the liquid is boiled and concentrated to a solid content of 20-30% to obtain hydrolyzed polyacrylonitrile; S3. The hydrolyzed polyacrylonitrile is mixed with sulfonated cobalt phthalocyanine, the pH is adjusted to 3-5, polyvinyl alcohol is added, and the mixture is stirred continuously. The mixture is then allowed to stand to remove bubbles, yielding the adhesive. In step S3, the weight ratio of hydrolyzed polyacrylonitrile, sulfonated cobalt phthalocyanine, and polyvinyl alcohol is 300:(2-5):(15-25).

2. The current collector coating resistant to sulfide corrosion according to claim 1, characterized in that: In step S1, the hydrolysis time is controlled at 30-40 minutes.

3. The current collector coating resistant to sulfide corrosion according to claim 1, characterized in that: In step S3, the weight ratio of hydrolyzed polyacrylonitrile, sulfonated cobalt phthalocyanine, and polyvinyl alcohol is 300:(3-4):(15-25).

4. A sulfide-resistant current collector coating according to any one of claims 1-3, characterized in that: The conductive dispersion is obtained by uniformly mixing 5-20 wt% graphite, 5-20 wt% carbon black, 10-15 wt% polyacrylic acid, 20-50 wt% isopropanol and the balance deionized water.

5. A sulfide-resistant current collector coating according to claim 4, characterized in that: The weight ratio of the adhesive to the conductive dispersion is (12-18):

50.

6. The current collector coating resistant to sulfide corrosion according to claim 4, characterized in that: The graphite includes at least one of flake graphite, crystalline graphite, and cryptocrystalline graphite.

7. A current collector coating resistant to sulfide corrosion according to claim 4, characterized in that: The carbon black includes at least one of acetylene black, Ketjen black, and furnace black.

8. The application of a sulfide corrosion resistant current collector coating as described in any one of claims 1-7, characterized in that: A carbon coating layer used as a carbon-coated aluminum foil current collector or a carbon-coated copper foil current collector.

9. A sulfide solid-state battery, characterized in that: The positive electrode current collector of the sulfide solid-state battery adopts the carbon-coated aluminum foil current collector as described in claim 8, and / or the negative electrode current collector of the sulfide solid-state battery adopts the carbon-coated copper foil current collector as described in claim 8.

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