Preparation method of lithium metal three-dimensional composite pole piece, lithium metal three-dimensional composite pole piece and lithium metal battery

Abstract

The invention discloses a preparation method of a lithium metal three-dimensional composite pole piece, the lithium metal three-dimensional composite pole piece and a lithium metal battery, and relates to the technical field of lithium metal batteries, the preparation method comprises the following steps: uniformly mixing metal powder, lithium salt and solid electrolyte powder according to a mass ratio of 1: (1-5): (1-10), and grinding to obtain a powder composite material; the preparation method comprises the following steps: performing physical tabletting on a powder composite material, placing an obtained mixed tablet between two metal lithium sheets, pressing the mixed tablet into the two metal lithium sheets, and repeatedly folding and rolling to obtain the lithium metal three-dimensional composite pole piece with a 3D ion conductive built-in SE I frame, so that the 3D ion conductive built-in SE I frame is prevented from being in contact with an electrolyte, and the service life of the lithium metal three-dimensional composite pole piece is prolonged. And the diffusion and reduction of L < i + > in a bulk phase are promoted, so that an electro-deposition part and an electrolyte contact interface are isolated, large-grain electro-deposition and generation of thin and inorganic-rich SE I are facilitated, the side reaction of metal lithium and the electrolyte are further prevented, and the cycle performance of the lithium metal battery is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium metal batteries, and in particular to a method for preparing a lithium metal three-dimensional composite pole piece, a lithium metal three-dimensional composite pole piece, and a lithium metal battery. Background Art

[0002] Lithium metal is considered the "holy grail" of all anode materials for next-generation lithium batteries due to its high theoretical specific capacity (3860 mAh / g) and the lowest redox potential (-3.04 V). However, the formation of uncontrolled lithium dendrites and "host-free" deposition have hindered its further development. It is generally believed that constructing three-dimensional (3D) composite lithium metal anodes can partially address these issues by reducing the local current density and maintaining the electrode volume during cycling.

[0003] However, in existing technologies, most strategies for constructing 3D composite lithium metal anodes require electrodeposition or melt infusion processes. Although these strategies are effective, considering cost and safety, these processes involve multiple complex processing steps, such as high temperature and other harsh experimental conditions, which cannot meet actual production needs.

[0004] Therefore, there is an urgent need for a new method to construct three-dimensional composite electrodes without involving harsh conditions, complicated processes or high-end equipment. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a lithium metal three-dimensional composite pole piece, a lithium metal three-dimensional composite pole piece, and a lithium metal battery, to solve the following technical problems:

[0006] How to reduce the construction conditions of three-dimensional composite pole pieces.

[0007] The purpose of the present invention can be achieved through the following technical solutions:

[0008] In a first aspect, the present invention discloses a method for preparing a lithium metal three-dimensional composite electrode, comprising the following steps:

[0009] Step 1: mixing metal powder, lithium salt and solid electrolyte powder in a mass ratio of 1:(1-5):(1-10) and grinding to obtain a powder composite material; placing the powder composite material into a tablet press according to the designed weight ratio for physical tableting to obtain a mixed tablet;

[0010] Step 2: Place the mixed pressed sheet between two metal lithium sheets with a thickness of 60-200um, press the mixed sheet into the two metal lithium sheets by roller pressing, and then fold and roll repeatedly 10-50 times. The thickness of the composite electrode obtained after each rolling is (1 / 2)-(1 / 4) of the thickness before rolling. After rolling, a lithium metal three-dimensional composite electrode is obtained.

[0011] Furthermore, by controlling the distance between the upper and lower rollers, lithium metal three-dimensional composite pole pieces of different thicknesses can be obtained. Preferably, the distance between the upper and lower rollers is 0.1-2 mm.

[0012] More preferably, the distance between the upper and lower rollers is 0.1 mm, that is, the final lithium metal three-dimensional composite electrode is 0.1 mm.

[0013] Furthermore, the metal powder is any one or more of tin powder, aluminum powder, copper powder, antimony powder, magnesium powder, zinc powder, silver powder, and gold powder.

[0014] Furthermore, the lithium salt powder is any one or more of lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorooxalatophosphate, lithium bis(difluorosulfonyl)imide, and lithium bis(oxalatoborate).

[0015] Furthermore, the solid electrolyte powder is any one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, and lithium titanium aluminum phosphate.

[0016] Furthermore, the weight of the metal powder, lithium salt and solid electrolyte powder respectively accounts for 1wt%-15wt% of the total weight of the lithium metal three-dimensional composite pole piece.

[0017] In a second aspect, the present invention further discloses a lithium metal three-dimensional composite pole piece, which is prepared by the above-mentioned method for preparing a lithium metal three-dimensional composite pole piece.

[0018] In a third aspect, the present invention further discloses a lithium metal battery, which contains the lithium metal three-dimensional composite electrode sheet as described above, and also includes an electrolyte and a positive electrode.

[0019] Furthermore, the preparation method of the lithium metal battery is: using a lithium metal three-dimensional composite electrode sheet as the negative electrode of the lithium metal battery, a ternary positive electrode material NCM811 as the positive electrode, and a commercial carbonate electrolyte as the electrolyte; the battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0020] Beneficial effects of the present invention:

[0021] (1) The lithium metal three-dimensional composite electrode prepared by the present invention has a 3D ion conductive built-in SEI framework inside, which avoids contact with the electrolyte and promotes Li + It diffuses and reduces in the bulk phase, thereby isolating the electrodeposition site and the electrolyte contact interface, which is conducive to large-grain electrodeposition and the formation of a thin, inorganic-rich SEI, further preventing the side reactions between metallic lithium and the electrolyte. Its application in lithium metal batteries can significantly improve the cycle performance of lithium metal batteries.

[0022] (2) The preparation method of the three-dimensional composite electrode provided by the present invention has the advantages of convenient operation, simple process, excellent performance, and can be prepared in large quantities. It has excellent application prospects in the industrial production of high-performance lithium metal batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described below with reference to the accompanying drawings.

[0024] Figure 1 This is a surface characterization image of the lithium metal three-dimensional composite electrode prepared in Example 1 of the present invention;

[0025] Figure 2 This is a cross-sectional representation of the lithium metal three-dimensional composite electrode prepared in Example 1 of the present invention;

[0026] Figure 3 The charge-discharge cycle diagrams of Example 1 and Comparative Example 1 of the present invention at different rates;

[0027] Figure 4 The cycle curves of Example 1 and Comparative Example 1 of the present invention at a rate of 0.5C are shown; DETAILED DESCRIPTION

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0029] Example 1

[0030] Step 1. Preparation of lithium metal three-dimensional composite electrode: Take lithium hexafluorophosphate, tin powder and lithium lanthanum zirconium oxide, each accounting for 5wt% of the lithium metal three-dimensional composite electrode, mix and grind them evenly, then put the mixed powder into a tablet press for physical cold pressing to obtain a mixed tablet, and then place it between two metal lithium sheets with a thickness of 80um, push it horizontally into a pair of rollers with a gap of 0.1mm, and roll it to make the mixed tablet enter the lithium metal. After rolling, the area of the composite electrode is 1.6 times the area of the original lithium sheet. Fold the composite electrode in half and roll it again, keeping the thickness of the electrode at 0.1mm. Repeat the folding and rolling steps 20 times to finally obtain a three-dimensional composite electrode with a 3D ion-conductive built-in SE I frame inside.

[0031] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0032] Example 2

[0033] Step 1. Preparation of lithium metal three-dimensional composite electrode: lithium tetrafluoroborate, copper powder and lithium lanthanum zirconium tantalum oxide, each accounting for 10wt% of the lithium metal three-dimensional composite electrode, are uniformly mixed and ground, and the mixed powder is placed in a tablet press for physical cold pressing to obtain a mixed tablet, which is then placed between two metal lithium sheets with a thickness of 100um, and pushed horizontally into a pair of rollers with a gap of 0.1mm. The mixed tablet is rolled to allow the mixed tablet to enter the lithium metal. After rolling, the area of the composite electrode is twice the area of the original lithium sheet. The composite electrode is folded in half and rolled again to keep the thickness of the electrode at 0.1mm. The folding and rolling steps are repeated 30 times to finally obtain a three-dimensional composite electrode with a 3D ion-conductive built-in SE I frame.

[0034] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0035] Example 3

[0036] Step 1. Preparation of lithium metal three-dimensional composite electrode: Take lithium bis(difluoromethanesulfonyl)imide, magnesium powder and lithium aluminum titanium phosphate, each accounting for 15wt% of the lithium metal three-dimensional composite electrode, mix and grind them evenly, then put the mixed powder into a tablet press for physical cold pressing to obtain a mixed tablet, and then place it between two metal lithium sheets with a thickness of 200um, push it horizontally into a pair of rollers with a gap of 0.1mm, and roll it to make the mixed tablet enter the lithium metal. After rolling, the area of the composite electrode is 4 times the area of the original lithium sheet. Fold the composite electrode in half and roll it again to keep the thickness of the electrode at 0.1mm. Repeat the folding and rolling steps 50 times to finally obtain a three-dimensional composite electrode with a 3D ion-conductive built-in SE I frame inside.

[0037] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0038] Example 4

[0039] Step 1. Preparation of lithium metal three-dimensional composite pole piece: take lithium salt powder (a mixture of equal amounts of lithium tetrafluoroborate and lithium hexafluorophosphate), metal powder (a mixture of equal amounts of tin powder, aluminum powder and copper powder) and solid electrolyte powder (a mixture of equal amounts of lithium lanthanum zirconium oxide and lithium lanthanum zirconium oxide tantalum) accounting for 5wt% of the lithium metal three-dimensional composite pole piece, mix and grind them evenly, and then put the mixed powder into a tablet press for physical cold pressing to obtain a mixed tablet, which is then placed between two metal lithium sheets with a thickness of 60um, and pushed horizontally into a pair of rollers with a gap of 0.1mm. Rolling is performed to allow the mixed tablet to enter the lithium metal. After rolling, the area of the composite pole piece is 1.2 times the area of the original lithium sheet. The composite pole piece is folded in half and rolled again to keep the thickness of the pole piece at 0.1mm. Repeat the folding and rolling steps 10 times to finally obtain a three-dimensional composite pole piece with a 3D ion-conductive built-in SE I frame inside.

[0040] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0041] Example 5

[0042] Step 1. Preparation of lithium metal three-dimensional composite pole piece: take lithium salt powder (a mixture of equal amounts of lithium difluorooxalatophosphate, lithium bis(difluorosulfonylimide) and lithium bis(oxalatoborate)) accounting for 15wt% of the lithium metal three-dimensional composite pole piece, metal powder (a mixture of equal amounts of antimony powder, magnesium powder, zinc powder, silver powder and gold powder) and solid electrolyte powder (a mixture of equal amounts of lithium lanthanum zirconium oxide and lithium aluminum titanium phosphate) and mix and grind them evenly, then put the mixed powder into a tablet press for physical cold pressing to obtain a mixed tablet, which is then placed between two metal lithium sheets with a thickness of 100um, and pushed horizontally into a pair of rollers with a gap of 0.1mm. Rolling is performed to allow the mixed tablet to enter the lithium metal. After rolling, the area of the composite pole piece is twice the area of the original lithium sheet. The composite pole piece is folded in half and rolled again to keep the thickness of the pole piece at 0.1mm. The folding and rolling steps are repeated 20 times to finally obtain a three-dimensional composite pole piece with a 3D ion-conductive built-in SEI frame inside.

[0043] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0044] Example 6

[0045] Step 1. Preparation of lithium metal three-dimensional composite pole piece: take 1wt% of metal powder (a mixture of equal amounts of antimony powder, magnesium powder, zinc powder, silver powder and gold powder), 3wt% of lithium salt powder (a mixture of equal amounts of lithium difluorooxalate phosphate, lithium bis(difluorosulfonyl imide) and lithium bis(oxalatoborate) and 5wt% of solid electrolyte powder (a mixture of equal amounts of lithium lanthanum zirconium oxide and lithium aluminum titanium phosphate) respectively, mix and grind them evenly, and then put the mixed powder into a tablet press for physical cold pressing to obtain a mixed tablet, which is then placed between two metal lithium sheets with a thickness of 100um, and pushed horizontally into a pair of rollers with a gap of 0.1mm. Rolling is performed to allow the mixed tablet to enter the lithium metal. After rolling, the area of the composite pole piece is twice the area of the original lithium sheet. The composite pole piece is folded in half and rolled again to keep the thickness of the pole piece at 0.1mm. The folding and rolling steps are repeated 20 times to finally obtain a three-dimensional composite pole piece with a 3D ion conductive built-in SEI frame inside.

[0046] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0047] Example 7

[0048] Step 1. Preparation of lithium metal three-dimensional composite pole piece: take 1wt% of metal powder (a mixture of equal amounts of antimony powder, magnesium powder, zinc powder, silver powder and gold powder), 5wt% of lithium salt powder (a mixture of equal amounts of lithium difluorooxalate phosphate, lithium bis(difluorosulfonylimide) and lithium bis(oxalatoborate) and 10wt% of solid electrolyte powder (a mixture of equal amounts of lithium lanthanum zirconium oxide and lithium aluminum titanium phosphate) and mix and grind them evenly. The mixed powder is then placed in a tablet press for physical cold pressing to obtain a mixed tablet, which is then placed between two metal lithium sheets with a thickness of 60um and pushed horizontally into a pair of rollers with a gap of 0.1mm. The mixed tablet is rolled to allow the mixed tablet to enter the lithium metal. The area of the composite pole piece after rolling is 1.2 times the area of the original lithium sheet. The composite pole piece is folded in half and rolled again to keep the thickness of the pole piece at 0.1mm. The folding and rolling steps are repeated 30 times to finally obtain a three-dimensional composite pole piece with a 3D ion-conductive built-in SEI frame.

[0049] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0050] Example 8

[0051] Step 1. Preparation of lithium metal three-dimensional composite electrode: Take 1wt% of lithium difluorooxalate phosphate, 1wt% of gold powder and 1wt% of lithium lanthanum zirconium tantalum oxide, respectively, and mix and grind them evenly. Then put the mixed powder into a tablet press for physical cold pressing to obtain a mixed tablet. Then place it between two metal lithium sheets with a thickness of 80um, push it horizontally into a pair of rollers with a gap of 0.1mm, and roll it to make the mixed tablet enter the lithium metal. After rolling, the area of the composite electrode is twice the area of the original lithium sheet. Fold the composite electrode in half and roll it again to keep the thickness of the electrode at 0.1mm. Repeat the folding and rolling steps 40 times to finally obtain a three-dimensional composite electrode with a 3D ion-conductive built-in SE I frame inside.

[0052] Step 2: Lithium metal battery assembly: The folded and rolled three-dimensional composite electrode is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0053] Comparative Example 1

[0054] Lithium metal battery assembly: 0.1mm thick single-element lithium is used as the negative electrode, NCM811 is used as the positive electrode, the separator is Celgard2400, and the electrolyte is a commercial carbonate electrolyte; the soft pack battery assembly is carried out in a glove box under argon protection, and the oxygen and moisture content in the glove box are both less than 0.1ppm.

[0055] Test Case

[0056] 1. Scan the obtained three-dimensional composite electrode to obtain Figure 1-Figure 2 The morphology representation diagram of Figure 1 It can be observed that after folding and rolling, the specific surface area of the composite electrode increases, which is beneficial to the improvement of rate performance; Figure 2 From the cross-sectional image of the composite electrode, it can be observed that the mixed powder is successfully distributed inside the metallic lithium and forms a 3D layered structure.

[0057] 2. The rate performance of the lithium metal batteries prepared in Example 1 and Comparative Example 1 was tested, and the following results were obtained: Figure 3 The cycle curves at different rates are shown. Figure 3 It can be seen that the lithium metal battery assembled in Example 1 has better rate performance than the lithium metal battery assembled in Comparative Example 1.

[0058] 3. The lithium metal batteries prepared in Example 1 and Comparative Example 1 were subjected to cycle performance tests at a rate of 0.5C, and the following results were obtained: Figure 4 The cycle curve diagram shown is from Figure 4 It can be seen that the lithium metal battery assembled in Example 1 has better cycle performance than the lithium metal battery assembled in Comparative Example 1.

[0059] The above rate performance and cycle performance tests were performed on Examples 2-8. The results showed that the rate performance and cycle performance of the lithium metal batteries prepared in Examples 2-8 were at a comparable level to those of the lithium metal battery prepared in Example 1, and were also significantly better than those in Control Example 1.

[0060] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments using other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0061] The above is a detailed description of an embodiment of the present invention. However, the content described is only a preferred embodiment of the present invention and should not be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for preparing a lithium metal three-dimensional composite electrode, characterized in that: The steps include: Step 1: uniformly mixing metal powder, lithium salt and solid electrolyte powder and grinding the mixture to obtain a powder composite material, and placing the powder composite material into a tablet press for physical tableting to obtain a mixed tablet; Step 2: Place the mixed sheet between two lithium metal sheets, press the mixed sheet into the two lithium metal sheets using a roller pressing method, and then repeatedly fold and roll to obtain a lithium metal three-dimensional composite electrode.

2. The method for preparing a lithium metal three-dimensional composite electrode according to claim 1, characterized in that: In step 1, the mass ratio of the metal powder, lithium salt and solid electrolyte powder is 1:(1-5):(1-10).

3. The method for preparing a lithium metal three-dimensional composite electrode according to claim 2, characterized in that: The metal powder is any one or more of tin powder, aluminum powder, copper powder, antimony powder, magnesium powder, zinc powder, silver powder, and gold powder.

4. The method for preparing a lithium metal three-dimensional composite electrode according to claim 2, characterized in that: The lithium salt powder is any one or more of lithium tetrafluoroborate, lithium hexafluorophosphate, lithium difluorooxalatophosphate, lithium bis(difluorosulfonyl)imide, and lithium bis(oxalatoborate).

5. The method for preparing a lithium metal three-dimensional composite electrode according to claim 2, characterized in that: The solid electrolyte powder is any one or more of lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, and lithium titanium aluminum phosphate.

6. The method for preparing a lithium metal three-dimensional composite electrode according to claim 1, characterized in that: The weight of the metal powder, lithium salt and solid electrolyte powder respectively accounts for 1wt%-15wt% of the total weight of the lithium metal three-dimensional composite pole piece.

7. The method for preparing a lithium metal three-dimensional composite electrode according to claim 1, characterized in that: The thickness of the metal lithium sheet is 60-200 μm.

8. The method for preparing a lithium metal three-dimensional composite electrode according to claim 1, characterized in that: In step 2, the folding and rolling are repeated 10-50 times.

9. A lithium metal three-dimensional composite pole piece, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

10. A lithium metal battery, characterized in that: A three-dimensional lithium metal composite electrode according to claim 9.

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