Lithium ion battery aluminum foil negative material and preparation method thereof

Abstract

This invention provides an aluminum foil anode material for lithium-ion batteries and its preparation method. The method applies metallic aluminum to a monolithic material system. Based on a chemical displacement reaction, a rolling-heat treatment method is used to dope the target metal element into the aluminum foil composite material, achieving alloy composition design of the aluminum foil. Furthermore, carbon elements can be incorporated into the interlayer of the aluminum foil to improve the lithium storage performance of the aluminum foil anode. The preparation method of this invention is simple and feasible, with a simple process flow and low cost. It can modify a large quantity of aluminum foil in a short time, and the reaction raw materials can react completely, with useless reaction products volatilizing spontaneously. In addition, the modified aluminum foil material can be directly used as a lithium-ion battery anode material, effectively improving the lithium storage performance of the aluminum foil anode material.

Description

Technical Field

[0001] This invention relates to the field of lithium battery processing technology, and in particular to an aluminum foil anode material for lithium-ion batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries possess advantages such as high specific energy, high rate performance, long cycle life, no memory effect, high output voltage, low self-discharge, and a wide operating temperature range, making them an important electrochemical energy storage technology. In the process of improving the energy density and power density of lithium-ion batteries, the development of electrode materials has always been a key research focus. Since the energy density of cathode materials has already approached their theoretical specific capacity, it is difficult to achieve a significant increase in battery energy density through modification of cathode materials. Therefore, developing novel anode materials is one of the research hotspots for significantly improving the energy density of lithium-ion batteries.

[0003] Currently, the main commercial anode material is graphite, which has advantages such as long service life, low price, and abundant resources. However, its theoretical specific capacity is relatively low, only 372 mAh / g, which cannot meet market demand. Alloyed anode materials such as silicon, aluminum, and tin typically have higher theoretical specific capacities and are expected to become the next generation of commercial anode materials. Silicon is one of the most researched anode materials, and silicon-carbon anodes have already achieved small-scale commercial applications. The theoretical specific capacity of silicon reaches 4200 mAh / g (Li). 4.4 Silicon (Si) operates at approximately 0.4V, which perfectly meets market demands. However, silicon exhibits significant volume expansion (Li). 4.4 The loss of Si (360%) leads to the detachment of active materials and the continuous formation of the SEI film, ultimately resulting in a sharp decline in lithium storage performance.

[0004] As an alloyed anode material, aluminum metal possesses a stable voltage plateau (lithiation plateau ~0.25V and delithiation plateau ~0.48V) and a high theoretical specific capacity (993mAh / g ~LiAl). It also boasts advantages such as high conductivity, low cost, and environmental friendliness. Therefore, aluminum-based anode materials have great development potential. However, aluminum anodes are prone to failure during the lithium insertion / deintercalation process, leading to a sharp deterioration in their electrochemical performance. There is no unified understanding of the failure mechanism of aluminum-based anode materials in academia, but some progress has been made: (1) The large lattice strain energy generated during lithium intercalation hinders the lithium-aluminum alloy phase transformation and the lithium diffusion process in the distorted matrix; (2) The oxide layer on the surface of metallic aluminum hinders the coupling reaction between lithium ions and electrons, and aluminum oxide will irreversibly consume lithium ions to form Li-Al-O glass; (3) Based on the control of the bidirectional diffusion process, some lithium ions are trapped inside the active material and cannot escape; (4) Repeated volume expansion leads to poor electrode structure stability, resulting in continuous reduction and decomposition of the electrolyte and continuous thickening of the SEI film. The aluminum-based material modification strategies formulated for the above failure mechanisms are mainly focused on two directions: one is the construction of nanostructures, and the other is the design of alloy components. The construction of nanostructures can effectively overcome the phenomenon of electrode material crushing and destruction caused by volume expansion, so it is still difficult to obtain nano-aluminum-based materials with excellent electrochemical performance. Top-down synthesis methods (such as mechanical ball milling) are relatively simple and feasible from an industrial production perspective. However, the low Mohs hardness of metallic aluminum makes it difficult to obtain nanoscale aluminum-based materials at the target size. Bottom-up synthesis methods (such as plasma-enhanced chemical vapor deposition and liquid-phase reduction) can achieve in-situ synthesis of nanoscale aluminum-based materials, but require complex and stringent synthesis techniques that are not compatible with current production processes. Furthermore, the strong reducing properties of metallic aluminum place even stricter requirements on oxygen and water conditions during the synthesis process. During nanosizing, metallic aluminum easily forms an oxide layer. The high specific surface area of ​​the oxide layer leads to a sharp decrease in the surface conductivity of nanoscale aluminum, hindering the coupling reaction between lithium ions and electrons, and thus negatively impacting the lithium storage performance of nanoscale aluminum. Alloy composition design aims to introduce active components (such as silicon, tin, and antimony) or inactive components (such as copper, iron, and nickel) into the bulk phase of metallic aluminum, enabling the development of large-size aluminum foil electrode materials with specific alloy phase compositions, thereby improving the energy density of lithium-ion batteries. Introducing active components can disrupt the crystal structure of aluminum-based materials, thereby improving their mechanical stability. Introducing inactive components can effectively enhance the electrical conductivity of aluminum-based materials and alleviate stress changes during charging and discharging. However, the methods for designing alloy compositions are currently limited, primarily relying on magnetron sputtering, which has high preparation costs and is not conducive to commercial applications.

[0005] Currently, commercially available lithium-ion battery anodes contain a large amount of inactive materials, including conductive agents, binders, and current collectors. This electrode design boasts a high specific surface area, fully utilizing active materials and enabling extremely fast lithium-ion transport. However, this traditional electrode design significantly reduces the overall electrode's specific capacity, and its fabrication process is complex, failing to meet market demands for higher energy densities. Therefore, metal foil systems, which can improve electrode performance while reducing design complexity, should be considered. Furthermore, in terms of electrode material recycling, metal foil offers advantages such as ease of recycling and reprocessing compared to the complex traditional electrode design. Aluminum possesses a high theoretical specific capacity and low volume expansion, while also being environmentally friendly, low-cost, and easy to process; therefore, aluminum foil anode materials are currently a key research focus. However, aluminum foil as an electrode also presents some challenges, such as the inability of dense aluminum foil to form efficient lithium-ion transport channels and volume expansion leading to electrode pulverization. These issues have long limited the development of aluminum foil anodes. Significant progress has been made in research on aluminum foil anodes, including lithiation / delithiation models, lithium diffusion at grain boundaries, pre-lithiation techniques for aluminum foil, and "bidirectional diffusion lithium traps" within aluminum foil. However, current mainstream research on aluminum foil anodes focuses on the basic electrochemical properties of aluminum foil, lacking simple and effective modification strategies to improve lithium storage performance and hindering the commercial application of aluminum foil anodes. Summary of the Invention

[0006] This invention provides an aluminum foil anode material for lithium-ion batteries and its preparation method, aiming to solve the aforementioned problems in the development of aluminum-based materials in the background art.

[0007] To achieve the above objectives, embodiments of the present invention provide a lithium-ion battery aluminum foil anode material and its preparation method. This method applies metallic aluminum to a single-sheet material system, achieves micro-region alloy design of aluminum foil based on chemical displacement reaction, and can incorporate carbon elements between aluminum foil layers. The preparation process is simple, feasible, and low-cost, and the obtained material can be used as a lithium-ion battery anode material.

[0008] Embodiments of the present invention provide a method for preparing aluminum foil anode material for lithium-ion batteries, comprising the following steps:

[0009] S1: Dissolve metal chloride and methylcellulose in ultrapure water, heat and stir until homogeneous to obtain a slurry;

[0010] S2: The slurry is coated on the surface of aluminum foil, folded and rolled to make the slurry spread evenly on the surface of aluminum foil to obtain the precursor of aluminum foil composite material; the rolling can introduce residual stress, which helps to balance the compressive stress generated by the electrochemical lithium insertion and extraction process; the aluminum foil is plastically deformed by repeatedly coating the slurry and folding and rolling the aluminum foil, and the thickness of the single layer of aluminum foil is reduced, which facilitates the diffusion of subsequent transition metal atoms into the aluminum bulk phase, thus obtaining the precursor of aluminum foil composite material;

[0011] S3: The precursor of the aluminum foil composite material is subjected to heat treatment, during which a chemical displacement reaction occurs to obtain an aluminum foil composite material with micro-region alloy design.

[0012] Furthermore, the concentration range of the metal chloride is 0.5 mol / L to 2 mol / L, and the concentration range of methylcellulose is 40 g / L to 70 g / L.

[0013] Furthermore, the heating temperature in step S1 is 60°C to 90°C.

[0014] Furthermore, in step S2, the folding and rolling process along the long side employs a gradually decreasing roller spacing.

[0015] Furthermore, in step S3, the heat treatment calcination atmosphere is 5 sccm of hydrogen and 95 sccm of argon, the calcination rate is 10 °C / min, the calcination temperature is 500 °C to 600 °C, and the holding time is 2 hours. More preferably, the calcination temperature is 500 °C.

[0016] Furthermore, the metal element in the metal chloride has a standard electrode potential higher than that of aluminum, such as cobalt, iron, zinc, etc.

[0017] Furthermore, the thickness of the aluminum foil ranges from 16 μm to 50 μm. The rolling process changes accordingly with the thickness. Increasing the aluminum foil thickness requires increasing the initial spacing during the rolling process, setting more pressure gradients in the real-time rolling mill, and reducing the number of folding rolls. For example, for a 16 μm thick aluminum foil, a folding roll is repeated 4 times with an initial spacing of 100 μm and pressure gradients of 1 ton, 3 tons, 7 tons, and 10 tons; for a 30 μm thick aluminum foil, a folding roll is repeated 3 times with an initial spacing of 150 μm and pressure gradients of 1 ton, 2 tons, 5 tons, 8 tons, and 10 tons.

[0018] Furthermore, the aluminum foil composite material contains 90wt% to 95wt% aluminum, 2wt% to 4wt% doped metal elements, and 3wt% to 6wt% carbon elements, thereby achieving micro-area alloy design.

[0019] Furthermore, the aluminum foil composite material contains 92 wt% aluminum, 3 wt% doped metal elements, and 5 wt% carbon elements, thereby achieving micro-area alloy design.

[0020] Based on a general inventive concept, the present invention also provides a lithium-ion battery aluminum foil anode material obtained by the above preparation method.

[0021] This invention utilizes inexpensive metal chlorides. During heat treatment, the metal chlorides, in close contact with the aluminum foil, etch the oxide layer on the foil surface and react with the aluminum to generate the corresponding zero-valent metal and aluminum chloride. The generated aluminum chloride volatilizes and escapes at high temperatures, eliminating the need for additional steps to remove the product. Simultaneously, the doped metal element and metallic aluminum undergo solid-phase diffusion, with the doped metal atoms diffusing into the aluminum lattice, enabling micro-region alloy composition design.

[0022] Methylcellulose is used to increase the viscosity of the slurry, allowing metal chlorides to be evenly distributed on the aluminum foil surface. Furthermore, the methylcellulose in the slurry carbonizes at high temperatures, and the resulting carbon chains bridge the interlayers of the aluminum foil, improving the overall conductivity of the foil.

[0023] Using thinner aluminum foil facilitates the diffusion of doped metal atoms into the aluminum bulk phase, enabling alloy composition design. The thinner the aluminum foil, the easier it is for doped metal atoms to enter the aluminum lattice; however, if the aluminum foil is too thin, rolling operations become impossible, hindering the implementation of the modification strategy of this invention.

[0024] The above-described solution of the present invention has the following beneficial effects:

[0025] (1) This invention employs a roll pressing-heat treatment method to dope the target metal element into the aluminum foil composite material, thereby achieving the alloy composition design of the aluminum foil and improving the lithium storage performance of the aluminum foil anode. This method is based on chemical substitution reaction to achieve micro-region alloy design of the aluminum foil, reducing the cost required for traditional alloy composition design and providing a novel modification strategy for aluminum foil.

[0026] (2) The preparation method of the present invention is simple and feasible, with a simple process flow and low cost. It can modify a large amount of aluminum foil in a short time, and the reaction raw materials can react completely, while the useless reaction products can volatilize on their own. In addition, the modified aluminum foil material can be directly used as a negative electrode material for lithium-ion batteries, which can effectively improve the lithium storage performance of aluminum foil negative electrode materials.

[0027] (3) The preparation method of the present invention is scalable and can be extended to the alloy composition design of other metal elements and other metal foils. Attached Figure Description

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 These are X-ray diffraction patterns of the aluminum foil composite materials prepared in Example 1 and Comparative Example 1 of this invention;

[0030] Figure 2 These are scanning electron microscope images and elemental analysis diagrams of the interlayer of the aluminum foil composite material prepared in Example 1 of this invention;

[0031] Figure 3 Cyclic voltammetry tests were performed on the aluminum foil negative electrodes prepared in Example 1 and Comparative Example 1 of this invention.

[0032] Figure 4 The cycling performance of the aluminum foil negative electrode prepared in Example 1 and Comparative Example 1 of this invention is shown.

[0033] Figure 5 These are the charge-discharge voltage variation curves of the aluminum foil negative electrodes prepared in Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0034] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] This invention addresses existing problems by providing an aluminum foil anode material for lithium-ion batteries and its preparation method.

[0038] Example 1

[0039] A method for preparing aluminum foil anode material for lithium-ion batteries, comprising the following specific steps:

[0040] S1: Using cobalt chloride as a metal chloride, take 2g of CoCl2·6H2O, add 5mL of ultrapure water, heat to 80℃, stir to dissolve, and obtain an aqueous solution of CoCl2. Take 0.35g of methylcellulose, add it to the aqueous solution of CoCl2, stir for 20min, and wait for it to be evenly distributed to obtain a slurry containing CoCl2.

[0041] S2: Take a 12cm*28cm piece of aluminum foil with a thickness of 16μm, coat the aluminum foil with a slurry containing CoCl2, and fold it along the long side and roll it; use a gradually decreasing rolling gap, roll it 4 times in sequence. Before rolling, set the initial gap of the rolling press to 100μm, and the real-time pressure of the rolling press to 1 ton, 3 tons, 7 tons, and 10 tons to obtain a gradually decreasing rolling gap; the above steps are recorded as one rolling and folding operation. Repeat the coating of slurry and folding and rolling 4 times to obtain the precursor of aluminum foil composite material;

[0042] S3: The precursor of the aluminum foil composite material is loaded into a 10cm quartz tube and placed in a tube furnace for calcination. The calcination atmosphere is 10sccm H2 and 90sccm Ar. The calcination temperature is increased to 500℃ at a rate of 10℃ / min and held for 2 hours. After natural cooling, it is taken out to obtain aluminum foil composite material A.

[0043] Comparative Example 1

[0044] The aluminum foil, which has not been coated with slurry but has undergone rolling and heat treatment, is prepared using the same steps as in Example 1, as follows:

[0045] S1: Take a 12cm*28cm aluminum foil with a thickness of 16μm, fold it in half along the long side and roll it; use a gradually decreasing rolling gap, roll it 4 times in sequence. Before rolling, set the initial gap of the rolling press to 100μm, and the real-time pressure of the rolling press to 1 ton, 3 tons, 7 tons, and 10 tons to obtain a gradually decreasing rolling gap; the above steps are recorded as one rolling and folding operation. Repeat the coating of slurry and folding and rolling 4 times to obtain the precursor of aluminum foil composite material;

[0046] S2: The precursor of the aluminum foil composite material is loaded into a 10cm quartz tube and placed in a tube furnace for calcination. The calcination atmosphere is 10sccm H2 and 90sccm Ar. The calcination temperature is increased to 500℃ at a rate of 10℃ / min and held for 2 hours. After natural cooling, it is taken out to obtain aluminum foil composite material B.

[0047] Furthermore, composite materials that haven't undergone heat treatment cannot form micro-alloys because they lack this process. The slurry remains in precursor form (containing water and metal chlorides), directly causing battery failure during charge-discharge processes, resulting in extremely poor electrochemical performance. Composite materials that haven't undergone rolling also lack the ability to achieve uniform micro-alloy design. After precursor heat treatment, the target product is directly exposed on the material surface. Due to the uneven electrode surface, it easily leads to battery failure during the early stages of charge-discharge processes, resulting in poor electrochemical performance. Therefore, without these two processes, aluminum foil composite materials will directly cause battery failure during charge-discharge processes, offering no electrochemical performance.

[0048] In summary, rolling and heat treatment are essential means to realize the micro-area alloy design of this invention. Comparative Example 1 uses aluminum foil composite material B prepared without coating paste but after rolling and heat treatment. Compared with Example 1, the influence of the rolling and heat treatment process on the aluminum foil itself can be eliminated, enabling a single-factor (coating paste) comparison of the influence before and after the micro-area alloy design.

[0049] Application Example 1

[0050] The aluminum foil composite materials obtained in Example 1 and Comparative Example 1 were characterized by X-ray diffraction (XRD), while the aluminum foil composite material obtained in Example 1 was characterized by scanning electron microscopy (SEM) and elemental analysis (EDS).

[0051] Specific equipment and parameters: XRD was performed using a TD-3500X X-ray diffractometer manufactured by Dandong Tongda Technology Co., Ltd., with a copper target as the K. α The radiation source was set at 35 kV, with a current of 30 mA, a step size of 0.02, and a scanning range of 3–80°. The SEM was performed using a MIRA3 scanning electron microscope manufactured by TESCAN (Czech Republic) at 15 kV. The EDS was performed using an Element SDD manufactured by AMETEK (USA) at 15 kV.

[0052] Characterization results: such as Figure 1 As shown, the relative diffraction intensity of the (111)(200) crystal planes of the aluminum foil composite material in Example 1 is higher than that in Comparative Example 1. This is because the coating of the paste makes the precursor thicker, and the plastic deformation of the aluminum metal is more severe, resulting in more crystal planes being exposed on the aluminum foil. Figure 2 As shown, metal particles smaller than 1 μm can be observed in the interlayer of the aluminum foil in Example 1. At the same time, carbon elements were successfully introduced into the interlayer of the aluminum foil. Quantitative analysis results show that the proportions of each component are 92 wt% aluminum, 3 wt% cobalt and 5 wt% carbon, proving that the modification strategy of the present invention can realize micro-area alloy design.

[0053] Application Example 2

[0054] The aluminum foil composite materials obtained in Example 1 and Comparative Example 1 were used to assemble CR2032 batteries for electrochemical performance testing. The specific procedures are as follows:

[0055] The heat-treated multilayer aluminum foil was compacted using a tablet press at a pressure of 15 tons to achieve densification. Then, it was cut into 12mm diameter circular electrode sheets using a slicing machine. The electrode sheets were then compacted again using a tablet press at a pressure of 15 tons to obtain dense electrode sheets. In a glove box, the CR2032 coin cell was assembled from bottom to top in the following order: negative electrode shell, spring, gasket, lithium sheet, electrolyte, separator, electrolyte, aluminum foil electrode sheet, and positive electrode shell. After assembly, the coin cell was sealed using a sealing machine at a pressure of 500 psi. LiPF6 was used as the electrolyte, and Celgard 2500 series separators were used.

[0056] Electrochemical performance was tested using the Chenhua electrochemical workstation and the Blue Battery testing system.

[0057] Specific parameters: Cyclic voltammetry test, test range selected as 0.01-1.5V, scan speed 0.1mV / s. Charge-discharge cycle test, discharge cutoff condition is capacity cutoff, i.e., 3mAh / cm³. 2 The charging cutoff condition is a voltage cutoff of 1.5V and a current setting of 0.2C. The voltage change curves during charging and discharging are retrieved from the charge-discharge cycle test using the Blue Electric testing system.

[0058] Test results: such as Figure 3 As shown, the aluminum foil anode of Example 1 exhibits lithium insertion peaks, and the lithium insertion / extraction peaks are both higher than those of Comparative Example 1, indicating that the modification strategy of the present invention can not only effectively reduce the lithium insertion energy barrier of the aluminum foil anode, but also impart faster lithium insertion / extraction kinetics to the aluminum foil anode. Figure 4 As shown, after adopting the modification strategy of the present invention, the cycling performance of the aluminum foil negative electrode in Example 1 is significantly improved. After 160 cycles, the capacity still reaches 2.776 mAh / cm³. 2 The capacity retention rate was 92.53%. In contrast, the aluminum foil negative electrode in Comparative Example 1 only had a cycle life of 90 cycles. Figure 5 As shown, by further comparing the voltage change trends during charging and discharging in the cycle process, the modified strategy of the present invention can reduce the lithium insertion / extraction barrier of the aluminum foil anode, improve its cycle stability, reduce the increase in polarization, and extend the battery cycle life.

[0059] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing aluminum foil anode material for lithium-ion batteries, characterized in that, Includes the following steps: S1: Dissolve metal chloride and methylcellulose in ultrapure water, heat and stir until homogeneous to obtain a slurry; S2: The slurry is coated onto the surface of aluminum foil, folded and rolled to spread the slurry evenly on the surface of aluminum foil, and the process of coating the slurry, folding and rolling is repeated to obtain the precursor of aluminum foil composite material. S3: Heat-treat the precursor of the aluminum foil composite material to obtain the aluminum foil composite material; The standard electrode potential of the metal element in the metal chloride is higher than that of aluminum; The aluminum foil composite material contains 90 wt% to 95 wt% aluminum, 2 wt% to 4 wt% doped metal elements, and 3 wt% to 6 wt% carbon elements, thereby achieving micro-area alloy design.

2. The preparation method according to claim 1, characterized in that, The concentration range of the metal chloride is 0.5 mol / L to 2 mol / L, and the concentration of methylcellulose is 40 g / L to 70 g / L.

3. The preparation method according to claim 2, characterized in that, In step S1, the heating temperature is 60 ℃ to 90 ℃.

4. The preparation method according to claim 3, characterized in that, In step S2, the rollers are folded along the long side and the roller spacing is gradually reduced.

5. The preparation method according to claim 4, characterized in that, In step S3, the heat treatment calcination atmosphere is 5 sccm of hydrogen and 95 sccm of argon, the calcination rate is 10 ℃ / min, the calcination temperature is 500 ℃ to 600 ℃, and the holding time is 2 h.

6. The preparation method according to claim 5, characterized in that, The aluminum foil has a thickness of 16 μm to 50 μm.

7. The preparation method according to claim 6, characterized in that, The aluminum foil composite material contains 92 wt% aluminum, 3 wt% doped metal elements, and 5 wt% carbon elements, thereby achieving micro-area alloy design.

8. A lithium-ion battery aluminum foil anode material obtained by the preparation method according to any one of claims 1 to 7.

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