A method for preparing an alumina-lithium porous ceramic diaphragm using secondary aluminum dross as raw material

Abstract

The present application relates to a kind of porous ceramic diaphragm of alumina lithium prepared with secondary aluminum ash as raw material, belong to diaphragm material field.The method with secondary aluminum ash as main raw material, cooperate with lithium hydroxide, pore-forming agent, doping adjuvant, after moulding, high-temperature calcination obtains the porous ceramic with alumina lithium as main phase, again after hydrothermal surface lithiation of lithium hydroxide solution, obtain the porous ceramic diaphragm material used in lithium ion battery.The porous ceramic diaphragm has excellent thermal stability, completely eliminates the security problem that traditional lithium ion battery diaphragm is shrunk and deformed to lead to internal short circuit of battery fire due to heating.The alumina lithium porous ceramic diaphragm has higher porosity, good electrolyte affinity, while alumina lithium has fast ion conduction characteristics, effectively improves the lithium ion transport efficiency of diaphragm, and then improves the capacity retention rate of battery in large current charge and discharge and long time operation.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery separator technology, and relates to a method for preparing a lithium-ion battery separator that is resistant to high temperatures and suitable for high-current charging and discharging. Background Technology

[0002] Lithium-ion batteries are widely used in various fields of production and daily life. The separator, a crucial component of lithium-ion batteries, plays a vital role in battery safety. Currently, commercially available lithium-ion battery separators are mainly porous polyolefin separators. While polyolefin separators offer many advantages for lithium-ion batteries, they shrink and deform at temperatures exceeding 130°C, potentially leading to short circuits and fires. For high-functionality batteries used in large-scale battery storage power stations supporting wind and photovoltaic power generation, the larger charging and discharging currents are more prone to causing temperature fluctuations, resulting in more severe safety issues. To address this problem, researchers have used inorganic particles such as Al2O3, SiO2, and ZrO2 to coat the surface of polyolefin separators to create composite separators, leveraging the high heat resistance of inorganic particles to improve the thermal stability of the composite separators. However, coated separators still contain organic materials (polyolefin matrix or organic binders), which are still susceptible to thermal degradation and shrinkage, leading to serious safety issues in overheated environments. Therefore, some researchers have proposed using nano-Al2O3 and SiO2 through high-temperature calcination to prepare pure inorganic separators. This type of inorganic separator possesses unparalleled thermal stability, but its low porosity, ionic conductivity, and poor electrolyte affinity are detrimental to battery performance improvement. Therefore, while retaining the high heat resistance advantage of inorganic separators, finding new raw materials and methods to prepare inorganic separators with high porosity, ionic conductivity, and electrolyte affinity has become a new research direction.

[0003] Aluminum ash is a solid byproduct of the production of metallic aluminum or aluminum alloys. It consists of metallic aluminum, alumina, and other compounds, and is classified into primary and secondary aluminum ash. Secondary aluminum ash is obtained by extracting metallic aluminum from primary aluminum ash. The use of inorganic salt additives in this process makes the composition of secondary aluminum ash more complex. The metallic aluminum and aluminum nitride in secondary aluminum ash can produce hydrogen and ammonia gases when exposed to water or moisture, making the comprehensive recycling and utilization of aluminum ash an urgent priority. Currently, the utilization of secondary aluminum ash mainly involves recovering alumina, sodium chloride, and potassium chloride from it, as well as using it as a raw material to prepare low-value-added products such as building materials, water purification agents, and refractory materials. Research on the use of secondary aluminum ash in the preparation of high-value-added products such as lithium-ion battery separators has not yet been reported. Summary of the Invention

[0004] The purpose of this invention is to eliminate the battery safety hazards caused by the poor thermal stability of lithium-ion battery separators, improve the battery's capacity retention rate during high-current charging and discharging and long-term operation, and fully utilize the various components in secondary aluminum ash to achieve high-value-added applications of solid waste. To this end, secondary aluminum ash is used as a key raw material, combined with lithium hydroxide, a pore-forming agent, and doping agents, and molded into a porous ceramic with lithium alumina (LiAlO2) as the main component after high-temperature calcination. This porous ceramic, after surface treatment with lithium hydroxide, can be used as a lithium-ion battery separator.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] Secondary aluminum ash, lithium hydroxide, pore-forming agent, and doping additives are mixed evenly in a certain proportion and then dry-formed using a mold. 70 o After vacuum drying at C for 10 hours, it is then placed in a muffle furnace at 5-8 °C. o The heating rate is C / min, from room temperature to 700-1000. o C, keep warm for 2-5 hours; place the calcined product in a 0.5-3 mol / L lithium hydroxide solution at 100-140°C. o The porous material surface lithiation process was completed by holding the sample in a reaction vessel at temperature for 4-12 hours; the resulting sample was then rinsed with distilled water until neutral, and then... o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours; the pore-forming agent is one of starch and glucose; the doping agent is one of vanadium pentoxide and titanium dioxide; the mass ratio of secondary aluminum ash, lithium hydroxide, pore-forming agent and doping agent is 33-50:25-60:10-23:0.5-2; the aluminum oxide content in the secondary aluminum ash is greater than 85%.

[0007] Beneficial Effects: This invention uses secondary aluminum ash as the main raw material to prepare a lithium-ion battery ceramic separator. It fully utilizes the aluminum-containing components in the secondary aluminum ash, such as elemental aluminum, alumina, aluminum nitride, aluminum carbide, and magnesium aluminum spinel, which are converted into lithium alumina under the action of lithium hydroxide. Aluminum nitride and aluminum carbide release gases during high-temperature calcination, acting as pore-forming agents. Simultaneously, the addition of pore-forming agents achieves ceramic porosity with lithium alumina as the main matrix. Lithium alumina is a fast ion conductor, capable of conducting lithium-ion solid electrolytes. Therefore, this porous ceramic with lithium alumina as the main matrix, when used as a lithium-ion battery separator after absorbing electrolyte, can achieve a dual-channel effect for lithium-ion conduction; that is, lithium ions can be conducted both in the electrolyte and in the lithium alumina ceramic matrix, thereby greatly improving the ionic conductivity of this inorganic separator and increasing the charge-discharge capacity of the battery under high current conditions. Using vanadium pentoxide or titanium dioxide as doping agents enables lattice doping of lithium alumina by pentavalent vanadium ions or tetravalent titanium ions, providing more lattice vacancies and improving the ionic conductivity of lithium alumina as a solid electrolyte. The trace amounts of heavy metal ions in secondary aluminum ash can also serve as doping ions. Furthermore, the calcined lithium alumina product undergoes hydrothermal treatment with lithium hydroxide solution to ensure complete formation of the lithium alumina phase on the inner surface of the porous ceramic channels. Since lithium alumina has excellent affinity for the organic electrolytes used in lithium-ion batteries, complete lithiation of the pores on the inner surface of the porous ceramic will facilitate sufficient wetting of the ceramic separator by the electrolyte. Attached Figure Description

[0008] Figure 1 Optical photographs of lithium alumina porous ceramic membranes

[0009] Figure 2 Scanning electron microscope images of lithium alumina porous ceramic membranes

[0010] Figure 3 XRD patterns of lithium alumina porous ceramic membranes

[0011] Figure 4 Rate performance curves of lithium / lithium iron phosphate batteries using lithium alumina porous ceramic separators Detailed Implementation

[0012] The present invention will be further described in detail with reference to the embodiments:

[0013] Secondary aluminum ash, lithium hydroxide, starch (or glucose), and vanadium pentoxide (or titanium dioxide) are mixed evenly in a mass ratio of 33-50:25-60:10-23:0.5-2, and then dry-formed using a mold. (The final step is missing from the original text.) o After vacuum drying at C for 10 hours, it is then placed in a muffle furnace at 5-8 °C. oThe heating rate is C / min, from room temperature to 700-1000. o C, keep warm for 2-5 hours; place the calcined product in a 0.5-3 mol / L lithium hydroxide solution at 100-140°C. o The porous material surface lithiation process was completed by holding the sample in a reaction vessel at temperature for 4-12 hours; the resulting sample was then rinsed with distilled water until neutral, and then... o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours.

[0014] Example 1

[0015] Secondary aluminum ash, lithium hydroxide, starch, and vanadium pentoxide are mixed evenly in a mass ratio of 33:30:20:2, and then dry-formed using a mold. 70 o After vacuum drying at 5°C for 10 hours, it is then placed in a muffle furnace at 5°C. o The heating rate is C / min, from room temperature to 900°C. o C, keep warm for 3 hours; place the calcined product in a 0.5 mol / L lithium hydroxide solution at 100 o The porous material surface lithiation process was completed by holding the sample at a temperature of 8 hours in reactor C; the resulting sample was then rinsed with distilled water until neutral, and then subjected to 100... o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours.

[0016] The porous ceramic membrane made of lithium alumina has a porosity of 56.8%, a liquid absorption rate of 212%, and an ionic conductivity of 3.7 mS / cm. -1 .

[0017] Example 2

[0018] Secondary aluminum ash, lithium hydroxide, glucose, and titanium dioxide are mixed evenly in a mass ratio of 40:50:23:1, and then dry-formed using a mold. 70 o After vacuum drying at 7°C for 10 hours, it is then placed in a muffle furnace at 7°C. o The heating rate is C / min, from room temperature to 1000 o C, keep warm for 4 hours; place the calcined product in a 1.5 mol / L lithium hydroxide solution at 140°C. o The porous material surface lithiation process was completed by holding the sample at a temperature of 6 hours in reactor C; the resulting sample was then rinsed with distilled water until neutral, and then subjected to 100... o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours.

[0019] The porous ceramic membrane made of lithium alumina has a porosity of 58.2%, a liquid absorption rate of 237%, and an ionic conductivity of 4.2 mS / cm. -1 .

[0020] Example 3

[0021] Secondary aluminum ash, lithium hydroxide, starch, and titanium dioxide are mixed evenly in a mass ratio of 45:25:10:0.5, and then dry-formed using a mold. (70) o After vacuum drying at 6°C for 10 hours, it is then placed in a muffle furnace at 6°C. o The heating rate is C / min, from room temperature to 800 o C, keep warm for 2 hours; place the calcined product in a 2.5 mol / L lithium hydroxide solution at 130°C. o The porous material was kept at a constant temperature in reactor C for 5 hours to complete the lithiation process on the surface; the resulting sample was rinsed with distilled water until neutral, and then... o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours.

[0022] The porous ceramic membrane made of lithium alumina has a porosity of 49.3%, a liquid absorption rate of 184%, and an ionic conductivity of 3.3 mS / cm. -1 .

[0023] Example 4

[0024] Secondary aluminum ash, lithium hydroxide, glucose, and vanadium pentoxide are mixed evenly in a mass ratio of 50:60:15:1.5, and then dry-formed using a mold. 70 o After vacuum drying at C for 10 hours, it is then placed in a muffle furnace at 8°C. o The heating rate is C / min, from room temperature to 700 o C, keep warm for 5 hours; place the calcined product in a 3 mol / L lithium hydroxide solution at 120°C. o The porous material surface was lithiation was completed by holding the sample in a reactor at temperature for 4 hours; the resulting sample was then rinsed with distilled water until neutral. o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours.

[0025] The porous ceramic membrane made of lithium alumina has a porosity of 48.1%, a liquid absorption rate of 191%, and an ionic conductivity of 3.5 mS / cm. -1 .

[0026] Example 5

[0027] Secondary aluminum ash, lithium hydroxide, starch, and vanadium pentoxide are mixed evenly in a mass ratio of 42:45:17:2, and then dry-formed using a mold. (70) o After vacuum drying at 5°C for 10 hours, it is then placed in a muffle furnace at 5°C. o The heating rate is C / min, from room temperature to 800 o C, keep warm for 2 hours; place the calcined product in a 0.5 mol / L lithium hydroxide solution at 120°C.o The porous material surface lithiation process was completed by holding the sample at a temperature of 12 hours in reactor C; the resulting sample was then rinsed with distilled water until neutral, and then subjected to 100... o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours.

[0028] The porous ceramic membrane made of lithium alumina has a porosity of 51.9%, a liquid absorption rate of 201%, and an ionic conductivity of 4.5 mS / cm. -1 .

[0029] Example 6

[0030] Secondary aluminum ash, lithium hydroxide, glucose, and vanadium pentoxide are mixed evenly in a mass ratio of 35:30:20:1, and then dry-formed using a mold. 70 o After vacuum drying at C for 10 hours, it is then placed in a muffle furnace at 8°C. o The heating rate is C / min, from room temperature to 1000 o C, keep warm for 4 hours; place the calcined product in a 2 mol / L lithium hydroxide solution at 100 o The porous material surface was lithiation was completed by holding the sample in a reactor at temperature for 10 hours; the resulting sample was then rinsed with distilled water until neutral. o The porous lithium-ion battery separator prepared from secondary aluminum ash was obtained by drying at C for 12 hours.

[0031] The porous ceramic membrane made of lithium alumina has a porosity of 60.3%, a liquid absorption rate of 254%, and an ionic conductivity of 5.9 mS / cm. -1 .

Claims

1. A method for preparing a porous ceramic membrane of lithium alumina using secondary aluminum ash as raw material, characterized in that, Includes the following steps: Secondary aluminum ash, lithium hydroxide, pore-forming agent, and doping agent are mixed evenly in a certain proportion, and dry-formed using a mold. After vacuum drying at 70℃ for 10 hours, the mixture is heated from room temperature to 700-1000℃ in a muffle furnace at a heating rate of 5-8℃ / min and held at that temperature for 2-5 hours. The calcined product is placed in a 0.5-3 mol / L lithium hydroxide solution and held in a reaction vessel at 100-140℃ for 4-12 hours to complete the lithiation process on the porous material surface. The resulting sample is rinsed with distilled water until neutral and then dried at 100℃ for 12 hours to obtain an alumina lithium porous ceramic membrane prepared from secondary aluminum ash. The pore-forming agent is one of starch and glucose; the doping agent is one of vanadium pentoxide and titanium dioxide; the mass ratio of secondary aluminum ash, lithium hydroxide, pore-forming agent, and doping agent is 33-50:25-60:10-23:0.5-2; the alumina content in the secondary aluminum ash is greater than 85%.

2. A porous ceramic membrane for preparing lithium alumina using secondary aluminum ash as raw material, characterized in that: Prepared according to the method of claim 1.

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