Porous alumina with ultralow magnetic impurity content, preparation method, battery component and battery

Abstract

The invention provides porous aluminum oxide with ultralow magnetic impurity content, a preparation method, a battery component and a battery, and relates to the technical field of battery materials, the porous aluminum oxide is an orthorhombic crystal system and / or cubic crystal system aluminum oxide particle with holes formed on the particle surface and / or inside; the aperture of holes formed in the aluminum oxide particles is not higher than 50nm; the content of magnetic impurities in the porous aluminum oxide is not higher than 0.15 ppm; the method for detecting the content of the magnetic impurities in the porous aluminum oxide comprises the following steps: demagnetizing Mkg of prepared porous aluminum oxide by adopting demagnetizing equipment with the magnetic strength of 50000 Gs, weighing the obtained magnetic impurities by m, and calculating the content of the magnetic impurities in the porous aluminum oxide according to a calculation formula of m / M. The invention also provides a preparation method of the porous aluminum oxide, and a battery component and a battery based on the aluminum oxide. The porous aluminum oxide provided by the invention is extremely low in magnetic impurity content, and is beneficial to the safety and the electrical performance of the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of battery materials, in particular to a porous alumina with ultra-low magnetic impurity content, a preparation method thereof, a battery component and a battery. BACKGROUND

[0002] The basic structure of a lithium ion battery includes two electrodes, a separator disposed between the electrodes, and an electrolyte filled between the electrodes, and the charging and discharging of the lithium ion battery is achieved according to the embedding and de-embedding of metal ions in the electrolyte on the negative electrode and the positive electrode. Since the substrate of the existing separator is usually an olefin polymer, in order to improve the thermal stability and strength of the separator, forming a ceramic coating layer on the surface of the separator has become one of the main means to improve the performance of the separator. Alumina has become one of the preferred inorganic ceramic particles in the ceramic coating layer on the separator because of its good thermal stability and high strength. Since metal ions move between the negative electrode and / or the positive electrode to generate current, and the battery is a closed space, the content of other active metals, especially magnetic metals, in the separator and the electrolyte has a huge impact on the stability and safety performance of the lithium ion battery. Therefore, those skilled in the art are committed to providing alumina with higher purity for the separator coating of the lithium ion battery.

[0003] In the prior art, the impurities in the alumina for the separator coating mainly come from two sources: (1) raw materials; (2) equipment impurities in the preparation process. Among them, the impurities brought by the raw materials are mainly in ionic form, which can be reduced by increasing the purity of the raw materials to reduce the impurity content; and the impurities brought by the impurities in the preparation process are removed by the electromagnetic demagnetization method commonly used in the prior art. However, in the prior art, the electromagnetic demagnetization can only remove 3-5 ppm of magnetic impurities in the alumina, and it is difficult to achieve the requirement of 1 ppm or less of the magnetic impurity content of the alumina. SUMMARY

[0004] The present application provides a porous alumina with ultra-low magnetic impurity content, which can reduce the magnetic impurity content in the porous alumina to 0.15 ppm or less, and can meet the ultra-high impurity requirement of 1 ppm or less of the magnetic impurity content in the alumina used in the ion battery.

[0005] The present application also provides a preparation method of the porous alumina with ultra-low magnetic impurity content.

[0006] Another object of the present application is to provide a battery component.

[0007] Still another object of the present application is to provide a battery.

[0008] In a first aspect, the present application provides a porous alumina with an ultra-low content of magnetic impurities, wherein the porous alumina is an alumina particle with pores formed on the surface and / or inside of the particle, and the alumina particle is of an orthorhombic system and / or a cubic system; and the pore diameter of the pores formed on the alumina particle is not higher than 50 nm.

[0009] The content of the magnetic impurities in the porous alumina is not higher than 0.15 ppm.

[0010] The content of the magnetic impurities in the porous alumina is detected by the following method: the porous alumina prepared by M is subjected to demagnetization by a demagnetization device with a magnetic intensity of 50000 Gs, the obtained magnetic impurities are weighed as m, and the content of the magnetic impurities in the porous alumina is calculated according to the calculation formula of m / M.

[0011] Further, in some embodiments of the present application, the content of the metallic iron, cobalt, nickel and zinc in the porous alumina is not higher than 0.15 ppm.

[0012] The content of the metallic iron, cobalt, nickel and zinc in the porous alumina is detected by the following method: the porous alumina prepared by M is subjected to demagnetization by a demagnetization device with a magnetic intensity of 50000 Gs, 250 g of dry powder is subjected to water screening, the magnetic impurities after water screening are collected, dried, and the weight and composition of the magnetic impurities are detected by an ICP tester.

[0013] Further, in some embodiments of the present application, the content of the iron, cobalt, nickel and zinc elements in the porous alumina is not higher than 100 ppm.

[0014] The content of the iron, cobalt, nickel and zinc elements in the porous alumina is detected by the following method: the porous alumina prepared by Ng is subjected to weighing detection to detect the content n of the iron, cobalt, nickel and zinc elements, and the content of the iron, cobalt, nickel and zinc elements in the porous alumina is calculated according to the calculation formula of n / N.

[0015] Further, in some embodiments of the present application, the D50 of the porous alumina is 0.2-5 μm.

[0016] In a second aspect, the present application further provides a preparation method of the porous alumina with an ultra-low content of magnetic impurities, which comprises a first slurry preparation process and a first low-temperature high-magnetic device demagnetization process.

[0017] The first slurry preparation process comprises adjusting the pH value of the slurry formed by completing the hydrothermal reaction to 7-9 and adjusting the solid content to 15-17%.

[0018] The first low-temperature high-magnetic equipment demagnetization process comprises: demagnetizing the slurry adjusted in the first slurry adjusting process under the condition that the magnetic field strength of the excitation magnetic field is at least 9T and the temperature is not higher than 80 DEG C, and the demagnetization time is at least 12h.

[0019] The ratio of the slurry feed flow rate to the magnetic field strength is not higher than 0.60.

[0020] Further, in some embodiments of the present application, the first low-temperature high-magnetic equipment demagnetization process comprises at least three magnetic field temperature zones, i.e., an A zone, a B zone and a C zone.

[0021] During the demagnetization process of the low-temperature high-magnetic equipment, the temperature of the A zone and the B zone is stabilized below 3.5 DEG C.

[0022] During the demagnetization process of the low-temperature high-magnetic equipment, the temperature of the C zone is stabilized below 35 DEG C, and the stable temperature of the C zone during the demagnetization process of the low-temperature high-magnetic equipment is higher than the temperature of the A zone during the demagnetization process of the low-temperature high-magnetic equipment.

[0023] In the first low-temperature high-magnetic equipment demagnetization process, the residence time of the slurry in the A zone, the B zone and the C zone is 2-2.5h, 2-2.5h and 2-2.5h, respectively.

[0024] Further, in some embodiments of the present application, the preparation method further comprises a second slurry adjusting process and a second low-temperature high-magnetic equipment demagnetization process.

[0025] The second slurry adjusting process comprises: adjusting the solid content of the slurry formed by configuring the powder formed after crushing the calcined porous alumina to 15%-17%.

[0026] The second low-temperature high-magnetic equipment demagnetization process comprises: demagnetizing the slurry adjusted in the second slurry adjusting process under the condition that the second magnetic field strength of the excitation magnetic field is at least 5T and the temperature is not higher than 80 DEG C, and the demagnetization time is at least 12h.

[0027] Further, in some embodiments of the present application, the second low-temperature high-magnetic equipment demagnetization process comprises at least three magnetic field temperature zones, i.e., an a zone, a b zone and a c zone.

[0028] During the demagnetization process of the second low-temperature high-magnetic equipment, the temperature of the a zone and the b zone is stabilized below 3.5 DEG C.

[0029] During the demagnetization process of the low-temperature high-magnetic equipment, the temperature of the c zone is stabilized below 35 DEG C, and the stable temperature of the c zone during the demagnetization process of the second low-temperature high-magnetic equipment is higher than the temperature of the a zone during the demagnetization process of the low-temperature high-magnetic equipment.

[0030] In the second low-temperature high-magnetic equipment demagnetization process, the residence time of the slurry in the a zone, the b zone and the c zone is 2-2.5 h, 2-2.5 h and 2-2.5 h, respectively.

[0031] In a third aspect, the application further provides a battery component, which comprises the porous alumina with ultra-low magnetic impurity content prepared by the preparation method of the porous alumina with ultra-low magnetic impurity content according to the first aspect or the second aspect.

[0032] In a fourth aspect, the application further provides a battery comprising the battery component according to the third aspect.

[0033] The porous alumina provided by the application has rhombic or cubic particles with a specific pore size range, and the content of magnetic impurities in the porous alumina is extremely low, which can be less than 0.15 ppm, so that the influence of the introduction of magnetic impurities on the stability and safety of the battery can be better improved.

[0034] The preparation method of the porous alumina with ultra-low magnetic impurity content provided by the application uses a low-temperature high-magnetic equipment process to remove magnetic impurities from slurry with a specific solid content and pH value range, which not only achieves good removal of magnetic impurities, but also has good effect on the removal of metal ions, so that the acid method for removing metal ions in the prior art is not needed, and the gelation of the alumina slurry caused by the addition of strong acid is avoided, so that the defects of the control of the particle morphology, particle size and specific surface area of the porous alumina are avoided. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the embodiments of the application clearer, the technical solutions in the embodiments of the application will be described clearly and completely. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0036] Ion battery is sealed for the purpose of keeping the stable conduction of metal ions, and the chemical reaction and thermal effect inside the battery are limited in the sealed space. Therefore, even the introduction of a small amount of impurities will have a significant impact on the electrical performance and safety of ion battery, especially the introduction of magnetic impurities with strong activity and magnetism. Therefore, the skilled in the art is committed to reducing the content of magnetic impurities in the materials used in ion battery. Alumina has good chemical stability, high strength, and is easy to obtain, and has become a commonly used inorganic material in ion battery components. Alumina is usually applied in the form of powder in battery components, which needs to be ground, crushed and other means, and it is difficult to avoid the introduction of some very fine magnetic particles. These magnetic particles are dispersed in very fine alumina powder, and it is difficult to remove them. Especially when the content of magnetic impurities is removed to about 1 ppm / kg, it is difficult to further remove the content of magnetic impurities by electromagnetic impurity removal and other methods. The possible reason may be that when the content of magnetic impurities is removed to about 1 ppm, the magnetic impurities in the alumina powder are difficult to exhibit magnetic properties, or the magnetic properties are difficult to be captured, so it is difficult to continue to remove, and it is difficult to provide alumina powder with a content of magnetic impurities below 1 ppm or even 0.5 ppm.

[0037] In this case, the applicant proposes a porous alumina with ultra-low content of magnetic impurities in the present application, which is formed with pores on the surface and / or inside of the orthorhombic and / or cubic alumina particles; and the pore size of the pores formed on the alumina particles is not higher than 50 nm.

[0038] The content of magnetic impurities in the porous alumina is not higher than 0.15 ppm.

[0039] The detection method of the content of magnetic impurities in the porous alumina is as follows: the porous alumina prepared by M is subjected to magnetic removal by a magnetic removal device with a magnetic strength of 50000Gs, the obtained magnetic impurities are weighed as m, and the content of magnetic impurities in the porous alumina is calculated according to the calculation formula of m / M.

[0040] The porous alumina provided by the present application is mainly single crystal particles, and the porous structure on the surface is mainly open pores formed on the surface and internal closed pores, and the pore size is not higher than 50 nm. The applicants have unexpectedly found that when the morphology of the porous alumina prepared is controlled within the above range, the content of magnetic impurities can be further removed to below 0.15 ppm. The reason can be that when the pore size of the porous alumina is low and the internal pores are mainly closed pores, the magnetic particles are difficult to enter the internal pores of the porous alumina, and the porous alumina provided by the present application is mainly single crystal particles, so the magnetic particles are not easily fixed in the gap between the crystal particles, which provides the necessary conditions for the removal of magnetic impurities.

[0041] In the present application, the detected pore volume of the porous alumina is usually not higher than 0.1 cm 3 / g, and further not higher than 0.08 cm 3 / g, and the apparent density of the porous alumina is not higher than 3 g / cm 3 , and even not higher than 2.8 g / cm 3 The internal pores of the porous structure in the porous alumina are mainly closed pores, which provide a lower density for the battery components using the porous alumina, and the open pores on the surface and a small amount of internal through pores can provide channels for ion conduction in the battery components, especially the battery separator.

[0042] Further, the pore size of the porous alumina provided by the present application is 10-50 nm.

[0043] In some embodiments, the content of metal iron, cobalt, nickel and zinc in the porous alumina provided by the present application is not higher than 0.15 ppm;

[0044] The detection method of the content of metal iron, cobalt, nickel and zinc in the porous alumina is as follows: the porous alumina prepared by M is subjected to demagnetization by a demagnetization device with a magnetic strength of 50000Gs, 250g of dry powder is subjected to water screening, the magnetic impurities after water screening are collected, dried, and the weight and composition of the magnetic impurities are detected by ICP tester.

[0045] Metal iron, cobalt, nickel and zinc have strong activity and are difficult to form stable oxidation forms or other forms on the surface to limit further reaction, and are easy to form soluble ionic state, which has obvious influence on the safety and electrical performance of the ion battery. The content of iron, cobalt, nickel and zinc in the porous alumina provided by the present application is controlled below a very low range, which is beneficial to the optimization of safety and stability of the battery.

[0046] In addition, the porous alumina provided by the present application also has advantages in the content of iron, cobalt, nickel and zinc elements. The content of iron, cobalt, nickel and zinc elements in the porous alumina provided by the present application is not higher than 100 ppm, and the detection method is as follows:

[0047] The detection method of the content of iron, cobalt, nickel and zinc elements in the porous alumina is as follows: the content n of iron, cobalt, nickel and zinc elements in the porous alumina prepared by Ng is detected by the weighing detection method, and the content of iron, cobalt, nickel and zinc elements in the porous alumina is calculated by the calculation formula of n / N.

[0048] It should be noted that the content of iron, cobalt, nickel and zinc elements in the porous alumina provided by the present application refers to the total content of all valence states of iron, cobalt, nickel and zinc elements in the porous alumina, which includes the total content of elemental iron, cobalt, nickel and zinc elements and non-elemental iron, cobalt, nickel and zinc elements in the porous alumina.

[0049] The elemental iron, cobalt, nickel and zinc and other magnetic impurities have certain differences in the influence on the battery compared with the non-magnetic (ionic state or other state) iron, cobalt, nickel and zinc elements. The non-magnetic iron, cobalt, nickel and zinc elements also have negative effects on the performance of the battery, and are difficult to remove in the conventional demagnetization process. In the prior art, the non-magnetic iron, cobalt, nickel and zinc elements are often removed by means of acid washing and then cleaning. However, for the porous alumina particles, it is difficult to clean the non-magnetic iron, cobalt, nickel and zinc elements in the pores, and the boehmite or other alumina intermediates prepared by the hydrothermal method have high activity. Therefore, if the strong acid cleaning method is used, the particle morphology will be damaged, and it is difficult to maintain the integrity of the alumina morphology.

[0050] The porous alumina provided by the present application has a particle size D50 in the range of 0.3-2 μm, and the morphology is an alumina particle of orthorhombic system and / or cubic system. The apparent morphology of the particle is mainly a cubic structure surrounded by six rectangles or parallelograms (including two end faces and four side faces) (ignoring the surface pore structure). The integrity of the morphology is good, which is beneficial to the dispersion, coating and formation of the required film layer, especially when used for thin (<3 μm) battery separator coating, the integrity of the morphology is more beneficial to the coating and optimization of the coating performance.

[0051] Further, the particle size distribution of the porous alumina provided by the present application is narrow, and the value of (D90-D10) / D50 is not higher than 3, or even not higher than 2. The narrow particle size distribution is more beneficial to the dispersion. When the porous alumina is used for thin battery separator coating, the porous alumina provided by the present application is more inclined to select the porous alumina with D50 of 0.4 μm-1 μm, and more preferably 0.5 μm-0.6 μm.

[0052] It should be noted that the D50 particle size in the present application refers to the particle size corresponding to the cumulative particle size distribution percentage of 50%, D90 refers to the particle size corresponding to the cumulative particle size distribution percentage of 90%, and D10 refers to the particle size corresponding to the cumulative particle size distribution percentage of 10%.

[0053] The porous alumina powder provided in the present application has particles in at least one of theta phase, delta phase, gamma phase, alpha phase, or at least one of eta phase, kappa phase, chi phase, and rho phase.

[0054] Respectively, the content of iron element in the porous alumina is not higher than 50 ppm; the content of zinc element is not higher than 20 ppm; the content of nickel element is not higher than 20 ppm; and the content of cobalt element is not higher than 20 ppm. More preferably, the sum of the contents of iron element, cobalt element, zinc element, and nickel element in the porous alumina is not higher than 50 ppm; avoiding the side reactions of impurity elements with electrolyte and positive and negative electrodes in the charging and discharging process of the battery, increasing the consumption of electrolyte, producing gas and the decrease of ion conductivity, which is conducive to reducing the damage of these impurities to the battery.

[0055] In order for those skilled in the art to better understand and implement the present application, the following also provides a method for preparing the above-mentioned porous alumina with ultra-low magnetic impurity content.

[0056] The method comprises a first slurry adjusting process and a first low-temperature high-magnetic device magnetic removal process.

[0057] The first slurry adjusting process comprises adjusting the pH value of the slurry formed after the hydrothermal reaction to 7-9 and adjusting the solid content to 15-17%.

[0058] The first low-temperature high-magnetic device magnetic removal process comprises removing the magnetic field of the slurry adjusted in the first slurry adjusting process under the condition of a magnetic field strength of at least 9T and a temperature of not higher than 35℃, and the magnetic removal time is at least 12h.

[0059] The ratio of the slurry feed flow rate to the magnetic field strength is not higher than 0.60.

[0060] In the present application, the slurry for slurry adjustment in the first slurry adjusting process is derived from the reaction system formed after the hydrothermal reaction in the process of preparing alumina particles. The preparation of alumina by hydrothermal reaction is the existing technology in the art, and the raw materials can be appropriately adjusted by those skilled in the art as needed, so it is not described in detail in the present application.

[0061] The first sizing process includes pH adjustment and solid content adjustment, and the acid or base used in the pH adjustment is a weak acid or a weak base. The weak acid can be an organic weak acid such as oxalic acid, acetic acid, citric acid, etc., and the weak base can be an inorganic weak base such as ammonia water. To avoid introducing other impurities, pure water is used for solid content adjustment.

[0062] During the pH adjustment and solid content adjustment, the temperature of the slurry is simultaneously reduced to room temperature or below. Then it enters the first low-temperature high-magnetic equipment magnetic removal process. In the first low-temperature high-magnetic equipment magnetic removal process, the magnetic and weakly magnetic substances in the slurry are separated out under high excitation magnetic field strength and low temperature using a superconducting wet magnetic separator, realizing low-temperature high-magnetic equipment. The superconducting wet magnetic separator is a prior art and is not the improvement point of the present application, so its structure will not be described in detail in the present application, and it does not affect the understanding and implementation of the present application by those skilled in the art.

[0063] When the magnetic particles are extremely fine or the magnetic properties of the ionic state magnetic impurities are very weak, it is difficult for conventional magnetic removal processes to separate them out, especially in the wet magnetic removal process, the magnetic particles move rapidly and randomly, and it is difficult for conventional magnetic conductors to effectively capture them. Therefore, the low-temperature high-magnetic equipment technology used in the present application can improve the magnetism of weakly magnetic or effectively captured magnetic particles, so that they can be captured by superconductors, achieving better magnetic removal effect.

[0064] In the magnetic removal process, the applicant found that not only the magnetic field strength and temperature affect the magnetic removal effect, but also the pH value and solid content of the slurry, and the ratio of the slurry flow rate to the magnetic field strength affect the magnetic removal effect. The reason can be that in the case of acidic / strongly alkaline slurry and high solid content, the interaction force between solid particles and the distribution density of solid particles affect the magnetic removal effect. Within the pH value range and solid content range provided in the present application, the magnetic removal effect is optimal, and the amount of pure water required is less. In addition, the ratio of the slurry flow rate to the magnetic field strength is controlled to be less than 0.60, which can achieve better magnetic removal effect. Preferably, the ratio of the slurry flow rate to the magnetic field strength is controlled to be less than 0.58, which can achieve better magnetic removal effect.

[0065] In addition, the applicant also found that the magnetic removal effect of alumina particles mainly in single crystal form is better, and the possible reason is that the agglomerated particles in polycrystalline or other forms tend to wrap magnetic impurities in the agglomerated structure, making it difficult to express magnetism, and thus difficult to achieve good magnetic removal effect.

[0066] In the first low-temperature high-magnetic equipment magnetic removal process, at least three temperature zones A, B and C are included.

[0067] The temperature in the A and B zones is stabilized at 3.5°C or below during the magnetic removal process in the low-temperature high-magnetic equipment.

[0068] During the demagnetization process of the low-temperature high-magnetic equipment, the temperature of region C is stabilized below 35°C; and the stable temperature of region C during the demagnetization process is higher than that of region A during the demagnetization process.

[0069] In the demagnetization process of the first low-temperature high-magnetic equipment, the residence time of the slurry in zone A, zone B and zone C is 2-2.5h, 2-2.5h and 2-2.5h respectively.

[0070] Preferably, the temperatures of zones A, B, and C are controlled within the ranges of 2.5℃~3℃, 3℃~3.5℃, and 25℃~35℃, respectively.

[0071] After the first low-temperature high-magnetic equipment demagnetization process, the content of magnetic impurities in the resulting slurry is not higher than 0.15 ppm, and the conductivity is not higher than 60 μs / cm.

[0072] Following the demagnetization process in this low-temperature, high-magnetic-energy equipment, the resulting slurry is dried and sintered to obtain dry porous alumina. To further remove magnetic impurities introduced during these processes, as well as magnetic impurities encapsulated in agglomerates, the preparation method provided in this application further includes:

[0073] The second slurry preparation process and the second low-temperature high-magnetic equipment demagnetization process;

[0074] The second slurry preparation process includes: adjusting the solid content of the slurry prepared from the powder formed by crushing the porous alumina formed by calcination to 15% to 17%;

[0075] The second low-temperature high magnetic equipment demagnetization process includes: demagnetizing the slurry adjusted in the second slurry preparation process under the conditions of a second magnetic field strength of at least 5T and a temperature not higher than 80°C, for a demagnetization time of at least 12 hours.

[0076] The second low-temperature high-magnetic equipment demagnetization process includes at least three temperature zones: zone a, zone b, and zone c.

[0077] During the demagnetization process of the second low-temperature high-magnetic equipment, the temperature of regions a and b is stabilized below 3.5℃.

[0078] During the demagnetization process of the low-temperature high-magnetic equipment, the temperature of region c is stabilized below 35°C; and the stable temperature of region c during the demagnetization process of the second low-temperature high-magnetic equipment is higher than the temperature of region a during the demagnetization process of the low-temperature high-magnetic equipment.

[0079] In the demagnetization process of the second low-temperature high-magnetic equipment, the residence time of the slurry in zone a, zone b and zone c is 2-2.5h, 2-2.5h and 2-2.5h respectively.

[0080] In the second low-temperature high-magnetic equipment demagnetization process, the solid content of the slurry is also controlled in the range of 15% to 17%, and the applicant finds that when the solid content of the slurry in the second low-temperature high-magnetic equipment demagnetization process is controlled in the range of 15% to 17%, the content of magnetic impurities in the porous alumina formed after demagnetization is easily controlled below 0.15 ppm, and can even be controlled below 0.1 ppm.

[0081] In the first low-temperature high-magnetic equipment demagnetization process, a small amount of magnetic impurities in the agglomerates may be revealed in the subsequent crushing and calcination processes, resulting in an increase in the content of magnetic impurities in the obtained alumina, especially in the slurry with obvious agglomeration. Therefore, in the present application, a second low-temperature high-magnetic equipment demagnetization process is added after the calcination process after the first low-temperature high-magnetic equipment demagnetization process, which not only removes the magnetic impurities introduced during the calcination process, but also further removes the magnetic impurities revealed due to the calcination process.

[0082] In order to achieve better demagnetization effect, the slurry in the first low-temperature high-magnetic equipment demagnetization process and the slurry in the second low-temperature high-magnetic equipment demagnetization process can be recycled for at least two times.

[0083] In addition, in the demagnetization process, especially before the first low-temperature high-magnetic equipment demagnetization process, the slurry can be filtered through a 400-600 mesh filter before entering the demagnetization equipment, to ensure that the magnetic substances are not wrapped by large slurry agglomerates, and to reduce the demagnetization effect.

[0084] It is further pointed out that the drying means of the slurry provided in the present application can be spray drying or infrared microwave drying. Infrared microwave drying is preferred. After the first low-temperature high-magnetic equipment demagnetization process, the powder dried by infrared microwave drying does not need to be broken up or crushed, and can be directly introduced into the calcination process, saving cost and improving the morphology integrity of the product. In addition, in order to achieve good dispersion effect, when infrared microwave drying is used, the slurry after demagnetization is first pressure-filtered into a filter cake with a water content of free water of not less than 60%, and then broken into small pieces, and then heated to a temperature of not less than 150°C by infrared light irradiation, treated for 8-15 min, then cooled to 80-100°C, treated by microwave heating for 3-10 min, then heated to above 150°C by microwave heating, until the small filter cake automatically explodes into powder.

[0085] The intermediate powder formed by the infrared microwave drying process has low water content, which can be less than or equal to 0.2%, and the appearance of the particles is not damaged by grinding or ball milling, and the integrity is better. Moreover, the crystal particles in the obtained powder are less aggregated, and the single crystal dispersion of the product is better.

[0086] In addition, the calcination process provided by the present application can be the calcination process in the conventional preparation process of alumina, the calcination temperature of which is controlled below 1200°C, preferably 700-1200°C, and the calcination process is controlled in an air environment. During the calcination process, 0.01-0.1% of a barrier agent such as ammonium carbonate or ammonium bicarbonate can be added to the intermediate powder formed by drying the slurry, so that the content of single crystal particles in the porous alumina particles formed is higher, and the particle size distribution is narrower. The sintering temperature should not be too high or too low, and the holding calcination time is preferably 1-5h. Longer calcination time is easy to damage the morphology of alumina, increase the pore size of large pores, and disappear small pores, which is not conducive to the subsequent magnetic removal of alumina particles.

[0087] In a third aspect, the present application also provides a battery component, characterized in that the battery component comprises the porous alumina of the first aspect.

[0088] The battery component can be a battery separator, which comprises a substrate and a coating layer formed on at least one side of the substrate, and the porous alumina is distributed in the coating layer.

[0089] In a fourth aspect, the present application also provides a battery comprising the battery component of the second aspect. The battery can be an ionic battery used in any electrical device such as an electric vehicle, an aircraft, a ship, a mobile phone, a tablet computer, a portable digital device (such as a digital camera), a smart home, a smart wearable (such as a smart bracelet, a smart watch, and smart glasses), etc.

[0090] In order to facilitate those skilled in the art to understand the innovations of the present application, some preferred embodiments are provided below to illustrate the above technical solutions.

[0091] Embodiment 1

[0092] The present embodiment provides a preparation method of porous alumina with ultra-low magnetic impurity content, comprising the following steps:

[0093] Aluminum hydroxide, n-butanol, nitric acid, pure water were put into the reaction container according to the mass ratio of 1:1:0.2:2, the temperature was controlled at 70℃, and the stirring reaction was carried out for 30 min. Aluminum nitrate, citric acid, and pure water were put into the reaction container according to the mass ratio of aluminum hydroxide of 0.2:0.6:1. The kettle temperature was controlled at 70℃, and the stirring reaction was carried out for 2 h. The temperature was raised to 150℃, and the temperature was kept for 8 h. A slurry was obtained;

[0094] The slurry was washed with pure water and filtered to obtain an intermediate. The intermediate was dispersed with pure water, the pH value of the slurry was adjusted to 7.5 with 99% acetic acid, and the solid content of the slurry was adjusted to 15%-17% with pure water.

[0095] The conductor temperatures of A zone, B zone and C zone of the superconducting wet magnetic separation instrument were preset to 3k, 3k and 35k respectively, the excitation magnetic field was 9T, the target current was set to 144A-150A, and after reaching the set value, stable operation was required for 12h-24h. Then, the slurry with adjusted pH value and solid content was injected into the superconducting wet magnetic separation instrument at a flow rate of 2.5T / h, and the slurry was demagnetized in the superconducting wet magnetic separation instrument for 6h to obtain a first slurry after demagnetization.

[0096] Example 2

[0097] The first slurry after demagnetization obtained in Example 1 was spray dried at 200℃ to obtain spray particles. After the spray particles were subjected to air jet milling, intermediate particles with a particle size mainly distributed in the range of 0.2-5μm were obtained. In the intermediate particles, 1333g of ammonium carbonate was added in mass fraction, and after uniform mixing, the temperature was raised to 220℃ at the heating rate of the heat conducting oil, and the temperature was kept for 40h to obtain porous aluminum oxide.

[0098] The obtained porous aluminum oxide was wet ground with pure water to prepare a second slurry with a solid content of 15%-17%. The slurry was injected into the superconducting wet magnetic separation instrument at a flow rate of 2.5T / h, the conductor temperatures of A zone, B zone and C zone were 3k, 3k and 35k respectively, the excitation magnetic field was 9T, and the target current was set to 144A-150A. After reaching the set value, stable operation was required for 12h-24h. After demagnetization for 6h, a second slurry after demagnetization was obtained.

[0099] Example 3

[0100] The present embodiment also provides a method for preparing porous aluminum oxide with ultra-low magnetic impurity content. Compared with Example 1, in the present embodiment, the intermediate is dispersed with pure water, the pH value of the slurry is adjusted to 9 with 8% acetic acid, and the solid content of the slurry is adjusted to 17% with pure water. The remaining steps are the same as those of Example 1 to obtain a first slurry.

[0101] Example 4

[0102] On the basis of example 3, the first slurry is subjected to the same drying and calcining process as in example 2 to form a porous alumina powder, and the obtained porous alumina is wet ground with pure water to prepare a second slurry with a solid content of 17%. The slurry is injected into a superconducting wet magnetic separator at a flow rate of 2.5T / h, with a magnetic field temperature of 3k, 3k, and 35k in the a, b, and c zones, an excitation magnetic field of 9T, and a target current setting of 144A-150A. After reaching the set value, the system is stabilized for 12-24h. After 6h of demagnetization, the second slurry after demagnetization is obtained.

[0103] Example 5

[0104] In this example, the conductor temperatures in the A, B, and C zones of the superconducting wet magnetic separator are set to 3k, 3k, and 35k, the excitation magnetic field is 4.25T, and the target current setting is 144-150A. After reaching the set value, the system is stabilized for 24h. Then, the slurry with adjusted pH and solid content is injected into the superconducting wet magnetic separator at a flow rate of 2T / h, and the slurry is demagnetized in the superconducting wet magnetic separator for 6h. The remaining steps are the same as in example 1, and the first slurry is obtained.

[0105] Example 6

[0106] On the basis of example 5, the first slurry is subjected to the same drying and calcining process as in example 2 to form a porous alumina powder, and the obtained porous alumina is wet ground with pure water to prepare a second slurry with a solid content of 17%. The slurry is injected into a superconducting wet magnetic separator at a flow rate of 2.5T / h, with a magnetic field temperature of 3k, 3k, and 35k in the a, b, and c zones, an excitation magnetic field of 9T, and a target current setting of 144A-150A. After reaching the set value, the system is stabilized for 12-24h. After 6h of demagnetization, the second slurry after demagnetization is obtained.

[0107] Example 7

[0108] In this example, the drying process is different from that in example 2:

[0109] After demagnetization, the slurry is filtered to form a filter cake with a solid content of not less than 65%. The filter cake is broken into small pieces with a diameter of not more than 3cm, and then the temperature of the small pieces is raised to 80℃ using infrared light. The infrared light is turned on throughout the drying process, with an infrared temperature of about 150℃. After drying for 10min, the temperature of the small pieces is further raised to 100℃ using infrared light, causing the internal moisture of the filter cake to gradually evaporate. After drying for 7min, the temperature of the small pieces is raised to 150℃ using microwave, causing the internal and external moisture of the material to evaporate to ≤0.2% and automatically burst into a powder state. The resulting intermediate particles have a particle size mainly distributed in the range of 0.2-5μm. The remaining preparation steps are the same as in example 2, and a porous alumina powder is obtained.

[0110] Example 8

[0111] Compared with Example 1, the steps for obtaining the slurry are as follows:

[0112] Aluminum hydroxide, dispersant and pure water were put into a reaction container in a mass ratio of 30:0.5:69.5, stirred and ground for 4-7 h, and then seed crystals with an average particle size of 80 nm were immediately added in an amount of 0.1% of the system in mass fraction; the loading capacity of the reaction container was kept within the range of 50-80% of the volume; the temperature was raised to 180°C and kept for 50 h; the slurry was obtained; the remaining steps were the same as those in Example 1 to obtain the first slurry.

[0113] Comparative Example 1

[0114] Compared with Example 1, the electric demagnetization was used in this comparative example, and the demagnetization process of the electric demagnetization was as follows: after adjusting the solid content of the slurry to 15%-17% with pure water, the slurry was subjected to wet electric demagnetization, and the remaining steps were the same as those in Example 1 to obtain the first comparative slurry, which was then filtered and washed in a vacuum filter to obtain a filter cake for subsequent sintering preparation.

[0115] Comparative Example 2

[0116] Compared with Example 1, the pH value of the slurry in this comparative example was adjusted to 5 with 99% acetic acid, and the solid content was adjusted to 30% with pure water.

[0117] The remaining steps were the same as those in Example 1 to obtain the first comparative slurry.

[0118] Comparative Example 3

[0119] Compared with Example 2, the electric demagnetization was used in this comparative example, and the demagnetization process of the electric demagnetization was as follows: the second slurry with a solid content of 15%-17% obtained by wet grinding with pure water was subjected to wet electric demagnetization, and the remaining steps were the same as those in Example 2 to obtain the second comparative slurry, which was then spray dried to obtain the comparative aluminum oxide.

[0120] Comparative Example 4

[0121] Compared with Example 2, the solid content of the slurry in this comparative example was adjusted to 30% with pure water.

[0122] The remaining steps were the same as those in Example 2 to obtain the second comparative slurry.

[0123] Comparative Example 5

[0124] Compared with Example 1, the slurry in the present comparative example does not go through the first low-temperature high-magnetic device demagnetization process, and goes into the drying and calcination processes, and does not go through the second low-temperature high-magnetic device demagnetization process, to obtain the porous alumina. That is, the porous alumina in the present comparative example is obtained without the demagnetization process.

[0125] Test

[0126] 1. Magnetic impurity detection

[0127] 1 kg of the alumina powder is subjected to demagnetization using a demagnetization device with a magnetic strength of 50,000 Gs, the obtained magnetic impurities are weighed as m, and the content of the magnetic impurities in the porous alumina is calculated according to the calculation formula of m / M.

[0128] 2. Sum of the contents of metallic iron, cobalt, nickel and zinc detection

[0129] 250 g (N) of the dry powder is subjected to water screening, the magnetic impurities after water screening are collected, dried, and the weight nμg and the composition of the magnetic impurities are detected using an ICP tester, and the sum of the contents of iron, cobalt, nickel and zinc is calculated according to the proportion of iron, cobalt, nickel and zinc elements (iron%, cobalt%, nickel% and zinc%) in the magnetic impurities, and the calculation formula is as follows:

[0130] W = (n x iron% + n x cobalt% + n x nickel% + n x zinc%) / N.

[0131] 3. Sum of the contents of iron, cobalt, nickel and zinc elements detection

[0132] 0.1 g of the dry powder is weighed, dissolved in 3 ml of hydrochloric acid, and diluted to 100 ml of the clear solution, the prepared porous alumina is detected by an ICP element detector to detect the contents n of iron, cobalt, nickel and zinc elements, and the contents of iron, cobalt, nickel and zinc elements in the porous alumina are calculated according to the calculation formula of n / N.

[0133] The slurry, the slurry / porous alumina obtained by the above Examples 1-8 and Comparative Examples 1-5 are detected for impurity content, particle size, pore volume and pore size, and the test results are shown in Table 1.

[0134] Table 1

[0135]

[0136]

[0137] As can be seen from Table 1, the ordinary electric demagnetization process is used in Comparative Example 1, and the ICP metal content of the porous alumina obtained after demagnetization is higher than that of the low-temperature high-magnetic equipment, so it can be seen that the demagnetization process of the low-temperature high-magnetic equipment is not only beneficial to the removal of magnetic particle impurities, but also beneficial to the removal of other metal impurities in ionic state. As can be seen from Comparative Example 1 and Comparative Example 4 compared with Example 1, if the solid content of the slurry is too high, it will lead to worse demagnetization effect, which is not conducive to the demagnetization effect of the low-temperature high-magnetic equipment. In Comparative Example 5, the porous alumina does not go through any demagnetization process, so the content of magnetic particle impurities in the obtained alumina increases sharply, which is not conducive to the application of the porous alumina in the battery. Therefore, compared with the conventional electric demagnetization process, the low-temperature high-magnetic equipment used in the present application can not only reduce the content of particle-shaped magnetic impurities, but also has a certain removal effect on the impurities in ionic state in the slurry, which can better reduce the content of metal elements such as Fe, Co, Zn and Ni in the porous alumina, and is conducive to the safety of the battery using the porous alumina.

[0138] Test 2:

[0139] In order to further study the relationship between the injection flow rate of the first slurry and the excitation magnetic field strength in the demagnetization process of the low-temperature high-magnetic equipment, the applicant also applied different excitation magnetic fields to the slurry obtained in Example 1 under different slurry injection flow rates to study the demagnetization effect, and the demagnetization effect is shown in Table 2.

[0140] Table 2

[0141]

[0142]

[0143] As can be seen from Table 2, when the ratio of the flow rate of the slurry to the excitation magnetic field strength is controlled within the range of 0.6, the demagnetization effect is relatively good, and when the ratio exceeds this value, the content of magnetic impurities is difficult to be controlled below 0.15 ppm.

[0144] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements that can be easily thought of by those skilled in the art within the technical range disclosed in the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A porous alumina having an ultra-low magnetic impurity content, characterized in that, The porous alumina is orthorhombic and / or cubic alumina particles with pores formed on the surface and / or inside of the particles; and the pore diameter of the pores formed on the alumina particles is not higher than 50 nm; The content of magnetic impurities in the porous alumina is not higher than 0.15 ppm; The detection method of the content of magnetic impurities in the porous alumina is as follows: the prepared Mkg porous alumina is subjected to demagnetization by a demagnetization equipment with a magnetic intensity of 50000Gs, the obtained magnetic impurities are weighed as m, and the content of magnetic impurities in the porous alumina is calculated according to the calculation formula of m / M.

2. The porous alumina of claim 1, wherein, The sum of the contents of iron, cobalt, nickel and zinc elements in the porous alumina is not higher than 100 ppm; The detection method of the content of iron, cobalt, nickel and zinc elements in the porous alumina is as follows: the prepared porous alumina Ng is subjected to detection of the contents of iron, cobalt, nickel and zinc elements therein by an ICP element detector, and the content of iron, cobalt, nickel and zinc elements in the porous alumina is calculated according to the calculation formula of n / N.

3. The porous alumina of claim 1, wherein, The D50 of the porous alumina is 0.2-5 μm.

4. The porous alumina of claim 1, wherein, The porous alumina has a pore volume of generally not more than 0.08 cm 3 / g, and an apparent density of not more than 2.8 g / cm 3 .

5. A method of producing porous alumina having an ultra-low magnetic impurity content, characterized by, The method comprises a first slurry adjusting process and a first low-temperature high-magnetic equipment demagnetization process. The first slurry adjusting process comprises adjusting the pH value of the slurry formed by the hydrothermal reaction to 7-9 and adjusting the solid content to 15-17%. The first low-temperature high-magnetic equipment demagnetization process comprises demagnetizing the slurry adjusted in the first slurry adjusting process under the conditions of a magnetic field intensity of at least 9T of the excitation magnetic field and a temperature of not higher than 35℃, and the demagnetization time is at least 12h. The ratio of the slurry feeding flow rate to the magnetic field intensity is not higher than 0.

60.

6. The method of claim 5, wherein the porous alumina has an ultra-low magnetic impurity content. The first low-temperature high-magnetic equipment demagnetization process comprises at least three temperature zones of A zone, B zone and C zone. The temperature of the A zone and the B zone is stabilized at below 3.5℃ during the demagnetization process of the low-temperature high-magnetic equipment. The temperature of the C zone is stabilized at below 35℃ during the demagnetization process of the low-temperature high-magnetic equipment, and the stabilized temperature of the C zone during the demagnetization process of the low-temperature high-magnetic equipment is higher than the temperature of the A zone during the demagnetization process of the low-temperature high-magnetic equipment. In the first low-temperature high-magnetic equipment demagnetization process, the residence time of the slurry in the A zone, the B zone and the C zone is 2-2.5h, 2-2.5h and 2-2.5h, respectively.

7. The method of claim 5, wherein the porous alumina has an ultra-low magnetic impurity content. The method further comprises a second slurry adjusting process and a second low-temperature high-magnetic equipment demagnetization process. The second slurry adjusting process comprises adjusting the solid content of the slurry formed by the powder of the broken calcined porous alumina to 15-17%. The second low-temperature high-magnetic equipment demagnetization process comprises demagnetizing the slurry adjusted in the second slurry adjusting process under the conditions of a second magnetic field intensity of at least 5T of the excitation magnetic field and a temperature of not higher than 35℃, and the demagnetization time is at least 12h.

8. The method of claim 7, wherein the method is characterized by: The second low-temperature high-magnetic equipment demagnetization process comprises at least three temperature zones of a zone, b zone and c zone. The temperature of the a zone and the b zone is stabilized at below 3.5℃ during the demagnetization process of the second low-temperature high-magnetic equipment. The temperature of the c zone is stabilized below 35℃ during the demagnetization process of the low-temperature high-magnetic equipment; and the stabilized temperature of the c zone during the demagnetization process of the second low-temperature high-magnetic equipment is higher than the temperature of the a zone during the demagnetization process of the low-temperature high-magnetic equipment; In the demagnetization process of the second low-temperature high-magnetic equipment, the residence time of the slurry in the a zone, the b zone and the c zone is 2-2.5h, 2-2.5h and 2-2.5h respectively.

9. A battery member characterized by The battery component comprises the porous alumina with ultra-low magnetic impurity content as claimed in any one of claims 1-4 or the porous alumina with ultra-low magnetic impurity content prepared by the method as claimed in any one of claims 5-8.

10. A battery, characterized by The battery component as claimed in claim 11.

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