CN114242956B - Polymer negative electrode protective layer and preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of electrochemical energy, and discloses a polymer negative electrode protective layer, a preparation method and application thereof; according to the invention, a lithium source and a polystyrene sulfonic acid solution are mixed and stirred to obtain a gel solution 1; adding N-methyl pyrrolidone into the gel solution 1, and stirring to obtain gel solution 2; adding poly (vinylidene fluoride-co-hexafluoropropylene) and solid thermoplastic polyurethane rubber into the gel solution 2, and uniformly stirring to obtain a gel solution 3; and (3) coating the gel liquid 3 on the pole piece, and drying the pole piece to obtain the polymer negative electrode protective layer. And carrying out lithium precipitation operation on the polymer negative electrode protective layer to obtain the metal lithium electrode. The preparation method of the polymer negative electrode protective layer has the advantages of simplicity, convenience in control, high yield, easiness in industrialization and the like. The prepared metallic lithium negative electrode plate with the high-toughness and fast ion conduction interface transmission layer has good electrochemical performance in the application aspect of lithium metal batteries.

Description

A kind of polymer negative electrode protection layer and its preparation method and application

technical field

The invention belongs to the technical field of electrochemical energy, and in particular relates to a polymer negative electrode protection layer and a preparation method and application thereof.

Background technique

With the continuous development of the energy industry, the human demand for high energy density of energy storage devices is also increasing. Efficient energy storage and conversion is the driving force for the development of science and technology, and the emergence of batteries can help us use energy more efficiently and conveniently. Since the last century, various battery forms have achieved commercial applications, such as: lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, and lithium-ion batteries. The emergence of lithium-ion batteries has changed people's lifestyles and promoted the rapid development of camcorders, mobile phones, notebook computers, and electric vehicles.

However, despite the rapid development of lithium-ion batteries, the energy density of these commercial batteries has been increasing slowly. In the past 150 years, the energy density of batteries has only increased from 40Wh·kg ^-1 of lead-acid batteries in the past to 200Wh·kg ^-1 of lithium-ion batteries at present. This growth rate is far from meeting people's demand for energy. As the actual energy density of graphite anodes in lithium-ion batteries is gradually approaching its theoretical limit, we urgently need more efficient electrode materials to meet the needs of emerging high-end energy storage devices.

Lithium metal anode is widely regarded as the most promising lithium ion anode material due to its extremely high theoretical capacity (3860mAh·g ^-1 ) and lowest (negative) potential (-3.04Vvs standard hydrogen electrode), and has been studied great attention from personnel. At present, lithium metal batteries using metal lithium as the negative electrode mainly include: lithium-sulfur batteries, lithium-air batteries and lithium-oxide batteries, and these new batteries have shown high theoretical energy densities (lithium-air batteries: 3500Wh kg ^-1 , lithium-sulfur battery: 2600Wh kg ^-1 , lithium-oxide battery: 1000-1500Wh kg ^-1 . Therefore, lithium metal batteries with metal lithium as the negative electrode are likely to become the next generation of energy storage batteries However, these metal lithium batteries have serious safety problems (lithium dendrite growth) and are difficult to cycle stably. The growth of lithium dendrites will cause short circuits in the battery, which may cause thermal runaway, triggering the risk of fire or even explosion. This problem directly leads to Lithium metal secondary batteries cannot be used commercially. Since the commercial application of lithium ion batteries, most lithium metal battery products have been abandoned by the market. However, as a negative electrode material with extremely high energy density, researchers have explored lithium metal It has never stopped. In recent years, various emerging strategies have been developed to suppress the lithium dendrite growth of metallic lithium anodes, thereby improving the safety and service life of batteries, in anticipation of their eventual practical applications.

Utilizing the interfacial transport layer as the protective layer of the metal lithium negative electrode is a very effective method, which can reduce the side reaction with the electrolyte during the metal lithium deposition process, and can effectively inhibit the growth of lithium dendrites. (D. Luo, L. Zheng, Z. Zhang, M. Li, Z. Chen, R. Cui, Y. Shen, G. Li, R. Feng, S. Zhang, G. Jiang, L. Chen, A. .Yu,X.Wang,Nat.Commun.2021,12,186.) However, the ion transport speed and uniformity of ion transport during metal lithium deposition are the key to the uniform deposition of metal lithium. Swelling, and easy to have irreversible side reactions with the electrolyte, the current research on the metal lithium interface transport layer is not sufficient. Therefore, the interfacial transport layer materials for lithium metal anode need more in-depth research.

Contents of the invention

In order to overcome the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a method for preparing a high-toughness, fast ion-conducting polymer negative electrode protective layer, which aims to regulate the ion transmission speed on the surface of the current collector and limit the growth range of metal lithium , Inhibit the formation of metallic lithium dendrites.

The invention prepares the lithium metal composite negative electrode through the method of designing and constructing the fast ion transport layer.

According to the properties and characteristics of the ion interface transport layer, the present invention for the first time prepares a polymer negative electrode protection with high toughness and fast ion conduction characteristics by using polystyrene sulfonic acid, vinylidene fluoride-co-hexafluoropropylene, and thermoplastic polyurethane materials. layer, and prepared a composite metal lithium negative electrode.

The object of the present invention is achieved at least by one of the following technical solutions.

A preparation method with high toughness and fast ion-conducting polymer negative electrode protective layer, comprising the steps of:

(1) mix lithium source and polystyrene sulfonic acid solution, stir and process, obtain gel liquid 1 gel-like liquid);

(2) Add N-methylpyrrolidone (NMP) into the gel solution 1 described in step (1), and stir to obtain the gel solution 2;

(3) Add poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) and solid thermoplastic polyurethane rubber (TPU) into the gel solution 2 described in step (2), and stir evenly to obtain the gel solution 3;

(4) Coating the gel solution 3 described in step (3) on the pole piece, and drying the obtained pole piece to obtain a polymer negative electrode protective layer.

Preferably, the mass percent concentration of the polystyrene sulfonic acid solution in step (1) is 5%-40%; the polystyrene sulfonic acid solution is a solution obtained by uniformly mixing polystyrene sulfonic acid and water.

Further preferably, the mass percent concentration of the polystyrene sulfonic acid solution is 30%;

Preferably, the mol ratio of lithium source and polystyrenesulfonic acid described in step (1) is (1:1)-(3:1);

Further preferably, the molar ratio of the lithium source to polystyrene sulfonic acid is 1:1;

Preferably, the lithium source in step (1) is more than one of LiCl, LiOH, Li ₂ CO ₃ , LiF, LiNO ₃ , LiTFSI and LiFSI;

Further preferably, the lithium source is LiOH·H ₂ O.

Preferably, the time for the stirring treatment in step (1) is 30-90 min, and the temperature is normal temperature.

Further preferably, the time for the stirring treatment is 60 minutes.

Preferably, the volume ratio of N-methylpyrrolidone in step (2) to gel solution 1 in step (1) is (5:1)-(20:1);

Further preferably, the volume ratio of the N-methylpyrrolidone to the gel solution 1 in step (1) is 10:1;

Preferably, the stirring treatment time in step (2) is 30-90min.

Further preferably, the time for the stirring treatment is 60 minutes.

Preferably, the mass ratio of poly(vinylidene fluoride-co-hexafluoropropylene) to solid thermoplastic polyurethane rubber in step (3) is (1:10)-(10:1);

Further preferably, the mass ratio of poly(vinylidene fluoride-co-hexafluoropropylene) to solid thermoplastic polyurethane rubber is 2:1;

Preferably, the mass ratio of the total mass of poly(vinylidene fluoride-co-hexafluoropropylene) and solid thermoplastic polyurethane rubber to the gel solution 1 described in step (1) in step (3) is (1:1 )-(10:1).

Further preferably, the mass ratio of the total mass of poly(vinylidene fluoride-co-hexafluoropropylene) and solid thermoplastic polyurethane rubber to the gel solution 1 described in step (1) is 9:1.

Preferably, the stirring in step (3) is carried out at room temperature, and the stirring time is 6-20 hours.

Further preferably, the stirring time is 12 hours.

Preferably, the coating treatment described in step (4) utilizes a 5-30 μm coater for coating;

Further preferably, the coating process is performed using a 25 μm coater;

Preferably, the temperature of the drying treatment in step (4) is 30-90° C., and the drying time is 3-12 hours.

Further preferably, the temperature of the drying treatment is 50° C., and the drying time is 6 hours.

The polymer negative electrode protective layer prepared by the above preparation method.

Application of the above-mentioned polymer negative electrode protective layer in the preparation of metal lithium electrodes.

Preferably, the polymer negative electrode protective layer is deposited into lithium to obtain a metal lithium electrode.

Further preferably, the lithium sinking operation is a lithium sinking operation performed by assembling a polymer negative electrode protective layer in a button battery.

The lithium metal negative electrode with high toughness and fast ion-conducting polymer negative electrode protective layer provided by the present invention can be directly used as the lithium metal negative electrode.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The high-toughness, fast ion-conducting polymer negative electrode protective layer and metal lithium negative electrode prepared by the invention can effectively inhibit the formation of metal dendrites and greatly reduce the side reaction between metal lithium and electrolyte. This method is easy to synthesize and has good repeatability, and the obtained electrode material can be directly used as a metal lithium battery with no dendrites and high Coulombic efficiency.

Description of drawings

Fig. 1 is the polarization curve of the metal lithium electrode prepared in embodiment 1;

Fig. 2 is the impedance test curve before and after the polarization of the metal lithium electrode prepared in embodiment 1;

Fig. 3 is the lithium symmetric cell cycle diagram of the metal lithium electrode prepared in embodiment 1;

Fig. 4 is the electrode surface SEM test figure of the metal lithium electrode prepared in embodiment 1;

Fig. 5 is the polarization curve of the metal lithium electrode prepared in embodiment 2;

Fig. 6 is the impedance test curve before and after the polarization of the metal lithium electrode prepared in embodiment 2;

Fig. 7 is the lithium symmetric cell cycle diagram of the metal lithium electrode prepared in embodiment 2;

Fig. 8 is the electrode surface SEM test figure of the metal lithium electrode prepared in embodiment 2;

Fig. 9 is the polarization curve of the metal lithium electrode prepared in embodiment 3;

Fig. 10 is the impedance test curve before and after polarization of the metal lithium electrode prepared in embodiment 3;

Fig. 11 is the lithium symmetric battery cycle diagram of the metal lithium electrode prepared in embodiment 3;

Fig. 12 is the electrode surface SEM test figure of the metal lithium electrode prepared in embodiment 3;

Fig. 13 is the polarization curve of the metal lithium electrode prepared in embodiment 4;

Fig. 14 is the impedance test curve before and after the polarization of the metal lithium electrode prepared in embodiment 4;

Figure 15 is a lithium symmetric battery cycle diagram of the metal lithium electrode prepared in Example 4;

16 is an SEM test image of the electrode surface of the metal lithium electrode prepared in Example 4.

Detailed ways

The specific implementation of the present invention will be further described below in conjunction with examples, but the implementation and protection of the present invention are not limited thereto. It should be pointed out that, if there are any processes in the following that are not specifically described in detail, those skilled in the art can realize or understand with reference to the prior art. The reagents or instruments used were not indicated by the manufacturer, and they were regarded as conventional products that can be purchased from the market.

Example 1

A preparation method with high toughness, fast ion-conducting polymer negative electrode protective layer and metal lithium electrode, comprising the steps of:

Weigh 1 mol of 30wt.% polystyrene sulfonic acid solution and 1 mol of LiOH, stir at room temperature for 1 h, add 3.5 mL of NMP after the reaction is complete, and continue stirring at room temperature for 30 min until complete reaction and formation of Hydrogel solution. Then add 6 mol of PVDF-HFP into the above solution and continue to stir for 12 hours. After stirring evenly, continue to add 3 mol of TPU and stir for 6 hours. After the treatment is completed, the obtained slurry is then coated on the copper foil. The thickness of the coater is set to 30 μm, and then the coated pole piece is placed in an oven for drying treatment. The drying condition is 60 ℃, 6h. Then, the obtained pole piece was assembled in an R2032 type button battery for lithium sinking operation, and finally, the metal lithium electrode with high toughness and fast ion conduction artificial SEI (negative electrode protective layer) was obtained. As shown in Figure 1, Figure 2 and Figure 3, the metal lithium anode material obtained according to the electrochemical test has a lower resistance and a higher ion migration number, and shows excellent reversible use of metal lithium in metered lithium symmetric batteries ; The SEM image shows that the ion-conducting layer on the edge surface of the pole piece is very smooth and uniform (as shown in Figure 4).

Example 2

A preparation method with high toughness, fast ion-conducting polymer negative electrode protective layer and metal lithium electrode, comprising the steps of:

Weigh 1 mol of 30wt.% polystyrene sulfonic acid solution and 1 mol of LiOH, stir at room temperature for 1 h, add 3.5 mL of NMP after the reaction is complete, and continue stirring at room temperature for 30 min until complete reaction and formation of Hydrogel solution. Then add 4.5mol of PVDF-HFP into the above solution and continue to stir for 6h, after stirring evenly, continue to add 4.5mol of TPU and stir for 6h. After the treatment is completed, the obtained slurry is then coated. The thickness of the coater is set to 30 μm, and then the coated pole piece is placed in an oven for drying treatment. The drying condition is 60° C. for 6 hours. Then, the obtained pole piece was assembled in an R2032 type button battery for lithium sinking operation, and finally, the metal lithium electrode with high toughness and fast ion-conducting interfacial transport layer was obtained. As shown in Figure 5, Figure 6 and Figure 7, the metal lithium anode material obtained according to the electrochemical test has a lower resistance and a higher ion migration number, and shows excellent reversible use of metal lithium in metered lithium symmetric batteries ; The SEM image shows that the ion-conducting layer on the edge surface of the pole piece is very smooth and uniform (as shown in Figure 8).

Example 3

A preparation method with high toughness, fast ion-conducting polymer negative electrode protective layer and metal lithium electrode, comprising the steps of:

Weigh 1 mol of 30wt.% polystyrene sulfonic acid solution and 1 mol of LiOH, stir at room temperature for 1 h, add 3.5 mL of NMP after the reaction is complete, and continue stirring at room temperature for 30 min until complete reaction and formation of Hydrogel solution. Then add 3 mol of PVDF-HFP into the above solution and continue to stir for 6 hours. After stirring evenly, continue to add 6 mol of TPU and stir for 6 hours. After the treatment is completed, the obtained slurry is then coated. The thickness of the coater is set to 30 μm, and then the coated pole piece is placed in an oven for drying treatment. The drying condition is 60° C. for 6 hours. Then, the obtained pole piece was assembled in an R2032 type button battery for lithium sinking operation, and finally, the metal lithium electrode with high toughness and fast ion-conducting interfacial transport layer was obtained. As shown in Figure 9, Figure 10 and Figure 11, the metal lithium anode material obtained according to the electrochemical test has a lower resistance and a higher ion migration number, and exhibits excellent reversible use of metal lithium in metered lithium symmetric batteries ; The SEM image shows that the ion-conducting layer on the edge surface of the pole piece is very smooth and uniform (as shown in Figure 12).

Example 4

A preparation method of a polymer negative electrode protective layer and a lithium metal electrode, comprising the steps of:

Add 4.5 mol of PVDF-HFP to 3.5 mL of NMP, and continue to stir at room temperature for 30 min until the reaction is complete and a hydrogel solution is formed. Then, after stirring evenly, continue to add 4.5mol of TPU and stir for 6h. After the treatment is completed, the obtained slurry is then coated. The thickness of the coater is set to 30 μm, and then the coated pole piece is placed in an oven for drying treatment. The drying condition is 60° C. for 6 hours. Then, the obtained pole piece was assembled in an R2032 type button battery for lithium sinking operation, and finally, the metal lithium electrode with high toughness and fast ion-conducting interfacial transport layer was obtained. As shown in Fig. 13, Fig. 14 and Fig. 15, the metal lithium anode material obtained according to the electrochemical test has higher resistance and lower ion migration number, and shows poor metal lithium reversibility in metered lithium symmetric batteries. Use; The SEM image shows that the ion-conducting layer on the edge surface of the pole piece is uneven (as shown in Figure 16).

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (9)

1. The preparation method of the polymer negative electrode protective layer is characterized by comprising the following steps of:

(1) Mixing a lithium source with a polystyrene sulfonic acid solution, and stirring to obtain a gel solution 1; the mass percentage concentration of the polystyrene sulfonic acid solution is 5% -40%;

(2) Adding N-methyl pyrrolidone into the gel liquid 1 in the step (1), and stirring to obtain gel liquid 2;

(3) Adding poly (vinylidene fluoride-co-hexafluoropropylene) and solid thermoplastic polyurethane rubber into the gel liquid 2 obtained in the step (2), and uniformly stirring to obtain gel liquid 3; the mass ratio of the poly (vinylidene fluoride-co-hexafluoropropylene) to the solid thermoplastic polyurethane rubber is (1:10) - (10:1); the mass ratio of the total mass of the poly (vinylidene fluoride-co-hexafluoropropylene) to the solid thermoplastic polyurethane rubber to the gel solution 1 in the step (1) is (1:1) - (10:1);

(4) And (3) coating the gel liquid 3 in the step (3) on a pole piece, and drying the pole piece to obtain the polymer negative electrode protective layer.

2. The method of claim 1, wherein the molar ratio of lithium source to polystyrene sulfonic acid in step (1) is (1:1) - (3:1);

the lithium source is LiCl, liOH, li ₂ CO ₃ 、LiF、LiNO ₃ More than one of LiTFSI and LiFSI;

the stirring treatment time in the step (1) is 30-90min, and the temperature is normal temperature.

3. The method according to claim 1, wherein the volume ratio of the N-methylpyrrolidone in step (2) to the gel liquid 1 in step (1) is (5:1) - (20:1);

the stirring treatment time in the step (2) is 30-90min.

4. The method according to claim 1, wherein the stirring in the step (3) is performed at room temperature for 6 to 20 hours.

5. The method according to claim 1, wherein the coating treatment in the step (4) is coating with a coater of 5 to 30 μm;

the temperature of the drying treatment in the step (4) is 30-90 ℃, and the drying time is 3-12h.

6. The polymer negative electrode protective layer prepared by the preparation method of any one of claims 1 to 5.

7. Use of the polymer negative electrode protection layer of claim 6 for the preparation of a metallic lithium electrode.

8. The use according to claim 7, wherein the polymer negative electrode protection layer is subjected to a lithium precipitation operation to obtain a metallic lithium electrode.

9. The use according to claim 8, wherein the lithium sinking operation is a lithium sinking operation performed by assembling a polymer negative electrode protection layer in a button cell.

Images