Preparation method of biomass modified lithium ion battery current collector and application thereof

Abstract

This invention relates to a method for preparing biomass-modified lithium-ion battery current collectors and their applications, belonging to the field of lithium-ion battery technology. The preparation method of this invention includes the following steps: first, preparing a soybean protein isolate composite polyethyleneimine solution; then, dropping the prepared soybean protein isolate composite polyethyleneimine solution onto the surface of a copper foil; after standing, washing with water and drying, a copper current collector with a highly tough biomass interface film adhering to its surface is obtained. The current collector prepared by the method of this invention can inhibit dendrite growth and improve battery cycle life.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method for preparing a current collector for a biomass-modified lithium-ion battery and its application. Background Technology

[0002] In the field of lithium metal batteries, the current collector, as the negative electrode carrier, has a decisive influence on lithium deposition behavior and battery cycle stability. Currently, constructing a lithiophilic interface film on the surface of copper current collectors using biomolecules or polymers to induce uniform lithium-ion deposition and inhibit lithium dendrite growth has become an important research direction for improving battery performance.

[0003] However, existing modification technologies still have the following limitations: First, in terms of material selection, existing bio-based modified materials are mostly derived from natural product extraction, resulting in limited raw material sources, high costs, and difficulty in meeting the needs of large-scale industrial applications. Second, regarding structural stability, existing linear peptide or polymer coatings are usually simple one-dimensional or two-dimensional structures with insufficient mechanical toughness; during long-term battery cycling, these coatings are prone to structural cracking due to the huge volume expansion effect of lithium metal, leading to protective layer failure and shortening battery life. Furthermore, at the interface design level, existing technologies mostly rely on single polar functional groups to adsorb lithium ions, resulting in a single interfacial reaction site. This fails to fully utilize the complex three-dimensional conformational changes of biomolecules such as proteins to construct an interpenetrating network structure that firmly binds to the current collector surface, limiting the structural control capability and electrochemical stability of the interfacial film.

[0004] Therefore, there is an urgent need to develop a novel interface modification scheme that is low-cost and can combine excellent mechanical toughness and lithium-ion control capability by constructing a three-dimensional network structure. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a low-cost method for preparing and applying biomass-modified lithium-ion battery current collectors.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a biomass-modified lithium-ion battery current collector, comprising the following steps: S1. Prepare a soy protein isolate compound polyethyleneimine solution; S2. Add the soy protein isolate and polyethyleneimine solution to the surface of the copper foil and let it stand. The mass ratio of soy protein isolate to polyethyleneimine in the soy protein isolate composite polyethyleneimine solution is (0.6~1.2):1; the solution temperature during preparation of the soy protein isolate composite polyethyleneimine solution is 50-60℃.

[0007] Because soy protein isolate is rich in aspartic acid and glutamic acid, and has a high carboxyl content, it undergoes denaturation and unfolding under ultrasonic water bath conditions at specific temperatures. These carboxylic acid lithium-philic sites can more effectively homogenize lithium-ion flux and reduce nucleation overpotential. Simultaneously, utilizing the negative charge of soy protein isolate in an alkaline environment and the positive charge of polyethyleneimine, the unfolded long soy protein chains form a complex electrostatic complex network with polyethyleneimine, assembling into a membrane through electrostatic self-assembly. Compared to short-chain peptides, this composite membrane exhibits better tensile strength and can adapt to volume changes during lithium metal charging and discharging.

[0008] This invention utilizes water bath ultrasound at a specific temperature to induce thermal denaturation and expansion of soy protein. This temperature range represents a specific "melting window" that disrupts the hydrogen bonds and hydrophobic interactions within soy globulin, inducing the full expansion of the globulin structure and exposing the internally encapsulated polar groups while preventing peptide chain breakage. When the water bath ultrasound temperature is too low, soy protein isolate maintains its natural dense "spherical" structure, with most lithium-philic functional groups encapsulated within the molecule. This prevents soy protein from forming an effective cross-linking network with polyethyleneimine and results in extremely weak lithium-ion adsorption and homogenization capabilities, leading to no modification effect. When the water bath ultrasound temperature is too high, irreversible excessive thermal denaturation or hydrolytic chain breakage occurs, resulting in the destruction of the long-chain structure and loss of toughness after film formation. Consequently, the coating is prone to powdering and detachment during battery cycling.

[0009] In this invention, soy protein isolate and polyethyleneimine, at a specific ratio, form a perfect interpenetrating network structure where the long-chain backbone of soy protein isolate and the ion-conducting flexible chains of polyethyleneimine combine high mechanical toughness and low interfacial impedance. When the mass ratio of soy protein isolate to polyethyleneimine is too low, the insufficient content of soy protein as a rigid backbone leads to an excessively low mechanical modulus of the resulting interfacial film. During lithium deposition and volume expansion, the film layer cannot provide sufficient mechanical restraint, easily rupturing and causing dendrite growth. Simultaneously, excessive polyethyleneimine swells in the electrolyte, leading to interfacial instability. When the mass ratio of soy protein isolate to polyethyleneimine is too high, the concentration of denatured protein molecules is too high, easily causing intermolecular self-aggregation, resulting in decreased coating density and unevenness. Furthermore, the lack of a sufficient proportion of polyethyleneimine to assist lithium-ion transport leads to increased interfacial impedance and a higher lithium nucleation overpotential.

[0010] As a preferred embodiment of the preparation method of the biomass modified lithium-ion battery current collector of the present invention, the step of preparing the soybean protein isolate and polyethyleneimine composite solution in step S1 is as follows: soybean protein isolate and polyethyleneimine are added to Tris buffer, ultrasonically treated in a water bath for 20-40 min, preferably 30 min, and then filtered to obtain the filtrate. In a preferred embodiment of the preparation method of the biomass-modified lithium-ion battery current collector of the present invention, the pH of the buffer solution is 8.0~9.0, preferably 8.5. The Tris buffer solution is composed of Tris base and HCl. Controlling the pH of the Tris buffer solution within this range is beneficial for the appropriate denaturation of soybean protein isolate to expose active groups, and promotes its electrostatic recombination with polyethyleneimine to form a film.

[0011] In a preferred embodiment of the preparation method of the biomass-modified lithium-ion battery current collector of the present invention, the total concentration of the soybean protein composite polyethyleneimine solution is 0.005~0.02 g / mL, preferably 0.009 g / mL.

[0012] In a preferred embodiment of the preparation method of the biomass-modified lithium-ion battery current collector of the present invention, the frequency of the ultrasound is 40~80 kHz and the power is 100~300 W, preferably 50 kHz and 200 W.

[0013] In a preferred embodiment of the preparation method of the biomass-modified lithium-ion battery current collector according to the present invention, the standing time in step S2 is t, where t ≥ 30 min. This duration is sufficient to allow protein molecules to fully adsorb and assemble, forming a dense interfacial film.

[0014] In a preferred embodiment of the preparation method of the biomass-modified lithium-ion battery current collector of the present invention, the copper foil in step S2 is pre-treated by ultrasonic cleaning with anhydrous ethanol, washing with water, and drying. This pretreatment can effectively remove surface oil and impurities, providing a clean substrate for the modified layer.

[0015] In a preferred embodiment of the preparation method of the biomass-modified lithium-ion battery current collector of the present invention, in step S2, the copper foil is further rinsed and dried slowly with deionized water after standing; the drying temperature is 20~30℃, and the drying time is a, where a≥24 h. This mild condition can completely remove the solvent without damaging the protein structure.

[0016] Secondly, the present invention provides a lithium-ion battery current collector, which is prepared by the above-described method.

[0017] Thirdly, the present invention provides a lithium-ion battery, including the above-mentioned lithium-ion battery current collector.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes soybean protein isolate, a widely available and extremely low-cost agricultural byproduct, and electrostatically assembles it with polyethyleneimine to form a highly tough interpenetrating network interface film capable of regulating ion deposition, thereby achieving low-cost, high-performance lithium dendrite suppression. Attached Figure Description

[0019] Figure 1 The surface morphology of copper foil coated with a soy protein isolate composite polyethyleneimine interface film, i.e., Cu@soy protein@PEI in the figure; Figure 2 The image shows the surface morphology of the uncoated copper foil, represented by Cu. Detailed Implementation

[0020] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0021] In the following embodiments, the battery cycle life was tested as follows: A Li | 1.0 M LiPF6 in DME / DOL (1:1 vol%) + 2.0 wt% LiNO3 | Celgard 2500 | 1.0 M LiPF6 in DME / DOL (1:1 vol%) + 2.0 wt% LiNO3 | Cu battery was assembled, and the CR2032 coin cell was cycle-tested using the Blue Battery Testing System. After assembly, the battery was left to stand for 12 hours, and then tested in a constant current charge-discharge mode at 25°C: 1 mAh / cm² of lithium was deposited on copper foil at a current density of 0.5 mA / cm², and then stripped to 1.0 V (vsLi / Li⁺) at the same current density, with a 10-minute rest period between each step. The cycle test continued until the coulombic efficiency was below 80% or a voltage short-circuit characteristic appeared. The number of cycles at this point was recorded as the battery's cycle life.

[0022] In the following examples, the soy protein isolate was sourced from Sigma-Aldrich, catalog number S9668.

[0023] In the following examples, the beef serum albumin was sourced from Sigma-Aldrich, catalog number A7906.

[0024] Unless otherwise specified, all other materials and reagents used in the examples are commercially available.

[0025] Examples 1-9 and Comparative Examples 1-9 The preparation methods of lithium-ion negative electrode current collectors in Examples 1-9 and Comparative Examples 1-9 are as follows: S1. Cut copper foil to 10 cm × 10 cm, ultrasonically clean it with anhydrous ethanol, then rinse it with deionized water and dry it for later use. S2. Prepare a protein-composite polyethyleneimine solution; S3. Use a dropper to add the above protein-polyethyleneimine solution to one side of the copper foil and let it stand for 30 minutes. S4. Pour off the excess solution from the surface of the copper foil and rinse slowly with deionized water; S5. Place the rinsed copper foil into a vacuum drying oven and dry it at 25°C for 24 hours to obtain a modified composite current collector. The modified current collector includes a copper foil and a modified layer of approximately 500 nm thickness containing composite particles on the copper foil.

[0026] The preparation method of the protein-polyethyleneimine complex solution in step S2 is as follows: S21. Weigh the protein and polyethyleneimine and add them to 10 mL of Tris buffer to obtain a mixed solution with a concentration of cg / mL.

[0027] S22. Place the above mixed solution in a T℃ water bath and sonicate for 30 min.

[0028] S23. After ultrasonic water bath, filter the solution using a 0.45μm needle filter and take the supernatant, which is the protein complex polyethyleneimine solution.

[0029] The composition and amount of current collector, ultrasonic water bath temperature T, solution concentration c, ultrasonic frequency and power, and buffer pH value of the lithium-ion batteries in Examples 1-9 and Comparative Examples 1-9 are shown in Table 1.

[0030] The current collector stripping strength, lithium deposition overpotential, and cycle life of the batteries assembled in Examples 1-9 and Comparative Examples 1-9 were tested respectively, and the test results are shown in Table 2.

[0031] Table 1 Table 2 As can be seen from Tables 1 and 2, the lithium-ion batteries prepared in Examples 1-9 have high current collector stripping strength, low lithium deposition overpotential, and long cycle life. Figure 1 The image shows the SEM morphology of the current collector prepared in Example 1. Figure 2 This is a SEM image of the uncoated copper foil.

[0032] Comparing Examples 1-3 with Comparative Examples 1-2 and 9, it was found that the change in the component ratio in the interface film affects the material properties. The experimental results show that when the ratio of soy protein isolate to polyethyleneimine is 0.6:1 to 1.2:1, the current collector has a higher interface film peel strength, a lower lithium deposition overpotential, and a longer cycle life of the resulting battery.

[0033] Comparing Examples 1, 4-5 and Comparative Examples 3-4, it was found that the temperature change of the water bath during the preparation of the soybean protein isolate composite polyethyleneimine solution affected the material properties. The experimental results showed that when the water bath temperature was 50-60℃, the interfacial film peeling strength of the current collector was higher, the lithium deposition overpotential was lower, and the cycle life of the battery was longer.

[0034] Comparing Example 1 and Comparative Example 5, the influence of soy protein isolate on material properties was observed. Experimental results showed that the current collector interface film composed of soy protein isolate exhibited higher peel strength, lower lithium deposition overpotential, and a longer battery cycle life. This is because, although bovine serum albumin also contains disulfide bonds, the soy protein isolate used in this application is rich in aspartic acid and glutamic acid, and under the same modification conditions, its effect on reducing the nucleation barrier is significantly better than that of bovine serum albumin.

[0035] Comparing Examples 1, 5-6 and Comparative Example 7, it was found that the change in solution concentration during the preparation of the soybean protein isolate composite polyethyleneimine solution affected the material properties. The experimental results showed that when the concentration was between 0.005 and 0.02 g / mL, the current collector had a higher interfacial film peel strength, a lower lithium deposition overpotential, and a longer cycle life of the resulting battery.

[0036] Comparing Examples 1, 7-8 and Comparative Example 6, it was found that the pH change of the solution during the preparation of the soybean protein isolate composite polyethyleneimine solution affected the material properties. The experimental results showed that when the pH of the solution was weakly alkaline (pH=8.0~9.0), the interfacial film peeling strength of the current collector was higher, the lithium deposition overpotential was lower, and the cycle life of the battery was longer.

[0037] Comparing Example 1 and Comparative Example 7, it was found that the change in ultrasonic power during the preparation of the soybean protein isolate composite polyethyleneimine solution affected the material properties. The experimental results showed that when the ultrasonic power was insufficient, the interfacial film peel strength of the current collector was low, the lithium deposition overpotential was high, and the cycle life of the battery was short.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a biomass-modified lithium-ion battery current collector, characterized in that, Includes the following steps: S1. Prepare a soy protein isolate compound polyethyleneimine solution; S2. Add the soy protein isolate compound polyethyleneimine solution to the surface of copper foil, let it stand, and then slowly rinse and dry it with deionized water. In step S1, soy protein isolate and polyethyleneimine are added to Tris buffer, subjected to ultrasonic water bath treatment, filtered, and the filtrate is collected to obtain a soy protein isolate and polyethyleneimine composite solution. The mass ratio of soy protein isolate to polyethyleneimine in the soy protein isolate and polyethyleneimine composite solution is (0.6~1.2):

1. The total concentration of soy protein isolate and polyethyleneimine in the soy protein isolate and polyethyleneimine composite solution is 0.005~0.02 g / mL. The temperature of the soy protein isolate and polyethyleneimine composite solution during ultrasonic water bath is 50-60℃, and the ultrasonic power is 100~300 W. The pH of the Tris buffer is 8.0~9.

0.

2. The method of claim 1, wherein the biomass-modified lithium-ion battery current collector is prepared by the steps of: In step S1, the ultrasonic water bath time is 20-40 minutes.

3. The method for preparing a biomass-modified lithium-ion battery current collector as described in claim 1, characterized in that, The frequency of the ultrasound is 40~80 kHz.

4. The method for preparing a biomass-modified lithium-ion battery current collector as described in claim 1, characterized in that, The settling time in step S2 is t, where t ≥ 30 min.

5. The method for preparing a biomass-modified lithium-ion battery current collector as described in claim 1, characterized in that, In step S2, the copper foil is first subjected to ultrasonic cleaning with anhydrous ethanol, washing with water, and drying.

6. The method of claim 1, wherein the biomass-modified lithium-ion battery current collector is prepared by the steps of: In step S2, the drying temperature is 20~30℃, and the drying time is a, where a≥24 h.

7. The lithium-ion battery current collector prepared by the method for preparing biomass-modified lithium-ion battery current collectors according to any one of claims 1 to 6.

8. A lithium-ion battery, characterized by, Includes the lithium-ion battery current collector as described in claim 7.

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