Preparation method of ceramic slurry and lithium ion battery

Abstract

The invention provides a preparation method of ceramic slurry and a lithium ion battery. The preparation method comprises the following steps: mixing ceramic particles and a binder, and carrying out first stirring and first dispersion to obtain a first mixture; carrying out second stirring, second dispersion, third stirring and third dispersion on the first mixture and an organic solvent to obtain a third mixture with the solid content of 67-73%; performing fourth stirring, fourth dispersion, fifth stirring and fifth dispersion on the third mixture and an organic solvent to obtain a fourth mixture with the solid content of 62-68%; performing sixth stirring and sixth dispersion on the fourth mixture and an organic solvent to obtain a fifth mixture with the solid content of 50-60%; and carrying out seventh stirring and seventh dispersion on the fifth mixture and the organic solvent to obtain the ceramic slurry with the solid content of 38-40%. The preparation method solves the problems of non-uniform dispersion, overload of homogenizing equipment, slurry climbing, difficulty in wall scraping and the like caused by increase of the solid content of the slurry.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a method for preparing a ceramic slurry and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries, as a new type of rechargeable battery, have advantages such as high energy density and power density, high operating voltage, light weight, small size, long cycle life, and good safety. Therefore, lithium-ion batteries are widely used.

[0003] The positive electrode in a lithium-ion battery comprises two materials: the positive electrode material itself, mainly composed of ternary lithium, lithium iron phosphate, or lithium manganese iron phosphate active substances, whose primary function is to facilitate the insertion and extraction of lithium ions from the negative electrode, thereby maximizing battery energy; and a ceramic coating, which serves three main purposes: 1) Improving battery performance stability: Ceramic coating enhances the structural stability of the positive electrode material, enabling it to withstand higher voltages and currents, thus increasing the battery's cycle life. Furthermore, the ceramic coating reduces the interaction between the positive electrode material and the electrolyte, preventing electrolyte loss and electrode surface damage, further improving battery performance stability. 2) Increasing battery energy density: The ceramic coating increases the charge conductivity of the positive electrode material, reducing electrode internal resistance and thus increasing the battery's energy density. Simultaneously, the ceramic coating increases the specific surface area of ​​the electrode, increasing the contact area for electron and ion reactions, promoting electrochemical reactions, and further enhancing battery energy density. 3) Improving battery safety: The ceramic coating possesses high thermal stability and corrosion resistance, effectively preventing the degradation and dissolution of the battery's positive electrode material, thereby reducing the risk of thermal runaway and combustion. In addition, ceramic edges can reduce the battery's self-discharge rate, extend battery life, and thus improve battery safety.

[0004] Currently, the preparation of ceramic slurries for forming ceramic coatings typically employs a dry process. The main process route includes: stirring and dispersing borosilicate and binder powders, adding solvent for cutting, kneading, and scraping the slurry wall, and finally adding solvent for high-speed dispersion followed by slow stirring and degassing. However, the solid content of the ceramic slurry obtained using this process is relatively low, generally between 30% and 33%, while the solid content of the cathode slurry is generally between 63% and 68%. This leads to the following problems: 1) The large difference in solid content between the ceramic slurry and the cathode slurry results in stricter requirements for baking temperature, air frequency, and process conditions for coating, and a higher solvent addition ratio, increasing the material composition and preparation cost. 2) Simply increasing the solid content of the ceramic slurry can cause overload of the homogenizing equipment and large slurry fineness, leading to problems such as the inability to coat and knead the slurry. Summary of the Invention

[0005] The main objective of this invention is to provide a method for preparing ceramic slurry and a lithium-ion battery, so as to solve the problems of uneven slurry dispersion, overload of homogenizing equipment, slurry climbing and difficulty in scraping the wall caused by increasing the solid content of ceramic slurry in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a ceramic slurry is provided, the method comprising: step S1, mixing raw materials including ceramic particles and a binder and then sequentially performing a first stirring and a first dispersion to obtain a first mixture; wherein the mass ratio of ceramic particles to binder is 85-90:10-15; step S2, dividing an organic solvent into two parts to obtain a first organic solvent and a second organic solvent; sequentially performing a second stirring and a second dispersion on the raw materials including the first mixture and the first organic solvent to obtain a second mixture; sequentially performing a third stirring and a third dispersion on the raw materials including the second mixture and the second organic solvent to obtain a third mixture; wherein the solid content of the third mixture is 67-73%; step S3, mixing the raw materials including the third mixture... The raw materials, including the mixture and the third organic solvent, are sequentially subjected to fourth stirring, fourth dispersion, fifth stirring, and fifth dispersion to obtain a fourth mixture; wherein the solid content of the fourth mixture is 62-68%; the rotation speed of the fifth dispersion is 350-600 rpm higher than that of the fourth dispersion; in step S4, the raw materials including the fourth mixture and the fourth organic solvent are sequentially subjected to sixth stirring and sixth dispersion to obtain a fifth mixture; wherein the solid content of the fifth mixture is 50-60%; and in step S5, the raw materials including the fifth mixture and the fifth organic solvent are sequentially subjected to seventh stirring and seventh dispersion to obtain a ceramic slurry; wherein the solid content of the ceramic slurry is 38-40%; the rotation speeds of the sixth and seventh dispersions are each independently 100-400 rpm higher than that of the fifth dispersion.

[0007] Further, in step S1 above, the first stirring speed is 10~15 rpm, the first stirring time is 10~20 min; and / or, the first dispersion speed is 150~250 rpm, the first dispersion time is 10~20 min.

[0008] Further, in step S2 above, the second stirring speed is 10~15 rpm, and the second stirring time is 5~20 min; and / or, the second dispersion speed is 100~150 rpm, and the second dispersion time is 5~20 min; and / or, the third stirring speed is 20~30 rpm, and the third stirring time is 10~20 min; and / or, the third dispersion speed is 100~150 rpm, and the third dispersion time is 10~20 min.

[0009] Further, in step S3 above, the fourth stirring speed is 20~30 rpm, and the fourth stirring time is 10~30 min; and / or, the fourth dispersion speed is 100~300 rpm, and the fourth dispersion time is 10~30 min; and / or, the fifth stirring speed is 20~30 rpm, and the fifth stirring time is 45~75 min; and / or, the fifth dispersion speed is 500~700 rpm, and the fifth dispersion time is 45~75 min.

[0010] Furthermore, in step S4 above, the speed of the sixth stirring is 20~30 rpm, and the stirring time is 30~60 min; and / or, the speed of the sixth dispersion is 800~900 rpm, and the dispersion time is 30~60 min.

[0011] Furthermore, in step S5 above, the speed of the seventh stirring is 20~30 rpm, and the stirring time is 45~60 min; and / or, the speed of the seventh dispersion is 800~900 rpm, and the dispersion time is 45~60 min.

[0012] Furthermore, the above preparation method also includes: defoaming the mixture after the seventh dispersion to obtain a ceramic slurry; wherein the defoaming process includes the eighth stirring and the eighth dispersion performed sequentially; the stirring speed of the eighth stirring is 10~20 rpm, and the stirring time of the eighth stirring is ≥30 min; and / or, the stirring speed of the eighth dispersion is 100~200 rpm, and the dispersion time of the eighth dispersion is ≥30 min.

[0013] Furthermore, the ceramic particles are selected from any one or more of boehmite, alumina, and lithium aluminum titanium phosphate; and / or, the binder is selected from any one or more of polyacrylic acid, polyvinylidene fluoride, sodium carboxymethyl cellulose, and styrene-butadiene rubber; and / or, the first organic solvent, the second organic solvent, the third organic solvent, the fourth organic solvent, and the fifth organic solvent are each independently N-methylpyrrolidone.

[0014] Furthermore, the viscosity of the ceramic slurry is 3000~5000 Pa·s; and / or, the fineness of the ceramic slurry is <25 μm.

[0015] According to another aspect of the present invention, a lithium-ion battery is provided, comprising a positive electrode, a negative electrode, and a separator, wherein the positive electrode comprises a positive electrode material and a ceramic coating, the ceramic coating being prepared from a ceramic slurry prepared by the above-described preparation method.

[0016] By applying the technical solution of this invention, this application adjusts the preparation process of the ceramic slurry, changing the single-kneading process to a multi-kneading process, and adjusting the kneading solid content, dispersion speed, and stirring speed of each step. This significantly increases the solid content of the ceramic slurry, reduces its fineness, and improves its dispersion uniformity, thereby improving coating and wall scraping and avoiding the problem of slurry climbing. Simultaneously, ceramic slurries with solid content within the above range reduce the difference between their solid content and that of the cathode slurry, which helps to lower the coating temperature and stabilize the operating current of the homogenizing equipment used for stirring and dispersion, thus reducing energy consumption costs in the processing. Specifically, it is preferable to control the rotation speed of the fifth dispersion stage to be 350-600 rpm higher than that of the fourth dispersion stage. This enhances the dispersion effect, increases the shear force within the slurry, thereby reducing the agglomeration of ceramic particles and binders. Simultaneously, it helps the solvent to more fully wet the ceramic particles and binders in the fifth dispersion stage, thereby improving the stability and uniformity of the slurry, and ultimately improving the density of the ceramic coating. Preferably, the rotation speeds of the sixth and seventh dispersion stages are each independently 100-400 rpm higher than the fifth dispersion stage. This further refines the particles, thereby improving the uniformity and density of the ceramic coating. Simultaneously, increasing the rotation speeds of the sixth and seventh dispersion stages allows for further adjustment of the slurry viscosity, making the slurry more suitable for the coating process. The aforementioned stirring process accelerates the slurry flow, resulting in a more uniform particle distribution in the liquid. The dispersion process further breaks up particle agglomerates through high shear force, resulting in finer and more uniformly distributed particles. The combined use of stirring and dispersion helps to improve the dispersion effect and uniformity of the slurry. Furthermore, the preparation method of this application can reduce the amount of organic solvent added during homogenization, thereby reducing material costs. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the embodiments.

[0018] Mixing: The blades of the mixing equipment revolve around the revolution, and the rotation speed of the mixing equipment is the revolution speed.

[0019] Dispersion: The dispersion disc rotates and shears, and the rotational speed of the dispersion is the rotational speed.

[0020] As analyzed in the background section of this application, existing technologies suffer from problems such as uneven slurry dispersion, overload of homogenizing equipment, slurry climbing, and difficulty in scraping the wall due to increasing the solid content of ceramic slurry. In order to solve the above problems, this application provides a method for preparing ceramic slurry and a lithium-ion battery.

[0021] In a typical embodiment of this application, a method for preparing a ceramic slurry is provided. The method includes: step S1, mixing raw materials including ceramic particles and a binder and then sequentially performing a first stirring and a first dispersion to obtain a first mixture; wherein the mass ratio of ceramic particles to binder is 85~90:10~15; step S2, dividing an organic solvent into two parts to obtain a first organic solvent and a second organic solvent; sequentially performing a second stirring and a second dispersion on the raw materials including the first mixture and the first organic solvent to obtain a second mixture; sequentially performing a third stirring and a third dispersion on the raw materials including the second mixture and the second organic solvent to obtain a third mixture; wherein the solid content of the third mixture is 67~73%; step S3, mixing raw materials including the third mixture... The raw materials containing the third organic solvent are sequentially subjected to fourth stirring, fourth dispersion, fifth stirring, and fifth dispersion to obtain a fourth mixture; wherein the solid content of the fourth mixture is 62-68%; the rotation speed of the fifth dispersion is 350-600 rpm higher than that of the fourth dispersion; in step S4, the raw materials including the fourth mixture and the fourth organic solvent are sequentially subjected to sixth stirring and sixth dispersion to obtain a fifth mixture; wherein the solid content of the fifth mixture is 50-60%; and in step S5, the raw materials including the fifth mixture and the fifth organic solvent are sequentially subjected to seventh stirring and seventh dispersion to obtain a ceramic slurry; wherein the solid content of the ceramic slurry is 38-40%; the rotation speeds of the sixth and seventh dispersions are each independently 100-400 rpm higher than that of the fifth dispersion.

[0022] This application, by adjusting the preparation process of the ceramic slurry, transforms the single-kneading process into a multi-kneading process, and adjusts the kneading solid content, dispersion speed, and stirring speed in each step, can significantly increase the solid content of the ceramic slurry, reduce its fineness, and improve its dispersion uniformity. This results in better coating and wall scraping, avoiding slurry creep. Simultaneously, ceramic slurries with solid content within the aforementioned range reduce the difference in solid content between the slurry and the cathode slurry, thereby facilitating lower coating temperatures and stabilizing the operating current of the homogenizing equipment used for stirring and dispersion, thus reducing energy consumption costs in the processing. Specifically, it is preferable to control the rotation speed of the fifth dispersion stage to be 350-600 rpm higher than that of the fourth dispersion stage. This enhances the dispersion effect, increases the shear force within the slurry, thereby reducing the agglomeration of ceramic particles and binders. Simultaneously, it helps the solvent to more fully wet the ceramic particles and binders in the fifth dispersion stage, thus improving the stability and uniformity of the slurry, and consequently, the density of the ceramic coating. Preferably, the rotation speeds of the sixth and seventh dispersion stages are each independently 100-400 rpm higher than the fifth dispersion stage. This further refines the particles, thereby improving the uniformity and density of the ceramic coating. Simultaneously, increasing the rotation speeds of the sixth and seventh dispersion stages allows for further adjustment of the slurry viscosity, making the slurry more suitable for the coating process. The aforementioned stirring process accelerates the slurry flow, resulting in a more uniform particle distribution in the liquid. The dispersion process further breaks up particle agglomerates through high shear force, resulting in finer and more uniformly distributed particles. The combined use of stirring and dispersion helps to improve the dispersion effect and uniformity of the slurry. Furthermore, the preparation method of this application can reduce the amount of organic solvent added during homogenization, thereby reducing material costs.

[0023] Furthermore, the mass ratio of ceramic particles to binder can be 85:15, 86:14, 87:13, 88:12, 89:11, or 90:10. The solid content of the third mixture can be 67%, 68%, 69%, 70%, 71%, 72%, or 73%. The solid content of the fourth mixture can be 62%, 63%, 64%, 65%, 66%, 67%, or 68%. The solid content of the fifth mixture can be 50%, 52%, 64%, 56%, 58%, or 60%. The solid content of the ceramic slurry can be 38%, 39%, or 40%.

[0024] The speed of the fifth dispersion can be 350 rpm, 400 rpm, 450 rpm, 500 rpm, 550 rpm, or 600 rpm higher than the speed of the fourth dispersion. The speeds of the sixth and seventh dispersions can each be independently 100 rpm, 200 rpm, 300 rpm, or 400 rpm higher than the speed of the fifth dispersion.

[0025] In one embodiment of this application, in step S1 above, the first stirring speed is 10~15 rpm and the first stirring time is 10~20 min; and / or, the first dispersion speed is 150~250 rpm and the first dispersion time is 10~20 min.

[0026] Preferably controlling the rotation speed and time of the first stirring within the above-mentioned range helps to ensure uniform mixing of ceramic particles and binder. Preferably controlling the rotation speed and time of the first dispersion within the above-mentioned range helps to further break up agglomerated particles in the raw materials, making the ceramic particles and binder finer, which is beneficial for the subsequent dispersion of ceramic particles in the solvent to form a stable slurry system.

[0027] The initial stirring speed can be 10 rpm, 11 rpm, 12 rpm, 13 rpm, 14 rpm, or 15 rpm. The initial dispersion speed can be 150 rpm, 180 rpm, 200 rpm, 220 rpm, or 250 rpm.

[0028] In one embodiment of this application, in step S2 above, the second stirring speed is 10-15 rpm and the second stirring time is 5-20 min; and / or, the second dispersion speed is 100-150 rpm and the second dispersion time is 5-20 min; and / or, the third stirring speed is 20-30 rpm and the third stirring time is 10-20 min; and / or, the third dispersion speed is 100-150 rpm and the third dispersion time is 10-20 min.

[0029] The preferred volume ratio of the first organic solvent to the second organic solvent is 5~8:2~5. Controlling the speed and time of the second stirring, the speed and time of the second dispersion, the speed and time of the third stirring, and the speed and time of the third dispersion within the above range helps to disperse ceramic particles and binder more evenly in the organic solvent, thereby improving the uniformity of the slurry.

[0030] The second stirring speed can be 10 rpm, 11 rpm, 12 rpm, 13 rpm, 14 rpm, or 15 rpm. The second dispersing speed can be 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, or 150 rpm. The third stirring speed can be 20 rpm, 22 rpm, 25 rpm, 27 rpm, or 30 rpm. The third dispersing speed can be 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, or 150 rpm.

[0031] In one embodiment of this application, in step S3 above, the fourth stirring speed is 20-30 rpm and the fourth stirring time is 10-30 min; and / or, the fourth dispersion speed is 100-300 rpm and the fourth dispersion time is 10-30 min; and / or, the fifth stirring speed is 20-30 rpm and the fifth stirring time is 45-75 min; and / or, the fifth dispersion speed is 500-700 rpm and the fifth dispersion time is 45-75 min.

[0032] Preferably controlling the speed and time of the fourth stirring, the speed and time of the fourth dispersion, the speed and time of the fifth stirring, and the speed and time of the fifth dispersion within the above range helps to further reduce the agglomeration of ceramic particles and binder, thereby improving the stability and uniformity of the slurry, and thus improving the density of the ceramic coating.

[0033] The fourth stirring speed can be 20 rpm, 22 rpm, 25 rpm, 27 rpm, or 30 rpm. The fourth dispersion speed can be 100 rpm, 150 rpm, 200 rpm, 250 rpm, or 300 rpm. The fifth stirring speed can be 20 rpm, 22 rpm, 25 rpm, 27 rpm, or 30 rpm. The fifth dispersion speed can be 500 rpm, 550 rpm, 600 rpm, 650 rpm, or 700 rpm.

[0034] In one embodiment of this application, in step S4 above, the speed of the sixth stirring is 20~30 rpm, and the stirring time is 30~60 min; and / or, the speed of the sixth dispersion is 800~900 rpm, and the dispersion time is 30~60 min.

[0035] Preferably controlling the speed and time of the sixth stirring and the speed and time of the sixth dispersion within the above range helps to further refine the particles, thereby further improving the uniformity and density of the ceramic coating. At the same time, increasing the speed in the sixth dispersion stage helps to further adjust the viscosity of the slurry, which is beneficial to the slurry coating.

[0036] The sixth stirring speed can be 20 rpm, 22 rpm, 25 rpm, 27 rpm, or 30 rpm. The sixth dispersing speed can be 800 rpm, 820 rpm, 850 rpm, 870 rpm, or 900 rpm.

[0037] In one embodiment of this application, in step S5 above, the speed of the seventh stirring is 20~30 rpm, and the time of the seventh stirring is 45~60 min; and / or, the speed of the seventh dispersion is 800~900 rpm, and the time of the seventh dispersion is 45~60 min.

[0038] Preferably controlling the speed and time of the seventh stirring and the speed and time of the seventh dispersion within the above range helps to further refine the particles, thereby further improving the uniformity and density of the ceramic coating. At the same time, increasing the speed in the seventh dispersion stage helps to further adjust the viscosity of the slurry, which is beneficial to the slurry coating.

[0039] The seventh stirring speed can be 20 rpm, 22 rpm, 25 rpm, 27 rpm, or 30 rpm. The seventh dispersing speed can be 800 rpm, 820 rpm, 850 rpm, 870 rpm, or 900 rpm.

[0040] In one embodiment of this application, the preparation method further includes: defoaming the mixture after the seventh dispersion to obtain a ceramic slurry; wherein the defoaming process includes an eighth stirring and an eighth dispersion performed sequentially; the stirring speed of the eighth stirring is 10~20 rpm, and the stirring time of the eighth stirring is ≥30 min, preferably 30~60 min; and / or, the stirring speed of the eighth dispersion is 100~200 rpm, and the dispersion time of the eighth dispersion is ≥30 min, preferably 30~60 min.

[0041] Preferably controlling the speed and time of the eighth stirring and the speed and time of the eighth dispersion within the above range helps to better remove air bubbles, thereby enabling the ceramic slurry to form a more uniform and dense coating during coating, which in turn helps to improve the performance stability, energy density and safety of the battery.

[0042] The stirring speed for the eighth step can be 10 rpm, 12 rpm, 15 rpm, 17 rpm, or 20 rpm. The dispersion speed for the eighth step can be 100 rpm, 120 rpm, 140 rpm, 160 rpm, 180 rpm, or 200 rpm.

[0043] In order to better and more uniformly disperse the ceramic particles and binder in the solvent, in one embodiment of this application, the ceramic particles are selected from any one or more of boehmite, alumina (high-purity alumina), and lithium aluminum titanium phosphate (LATP); and / or, the binder is selected from any one or more of polyacrylic acid, polyvinylidene fluoride, sodium carboxymethyl cellulose, and styrene-butadiene rubber; and / or, the first organic solvent, the second organic solvent, the third organic solvent, the fourth organic solvent, and the fifth organic solvent are each independently N-methylpyrrolidone.

[0044] In one embodiment of this application, the viscosity of the ceramic slurry is 3000~5000 mPa·s; and / or, the fineness of the ceramic slurry is <25 μm.

[0045] The preferred viscosity of the ceramic slurry is within the above-mentioned range, which helps the ceramic slurry maintain good fluidity while ensuring good uniformity and suitable thickness of the coating. The preferred fineness of the ceramic slurry is within the above-mentioned range, which helps improve the uniformity and density of the coating, thereby enhancing the electrochemical performance of the battery.

[0046] The viscosity of the ceramic slurry can be 3000 mPa·s, 3200 mPa·s, 3500 mPa·s, 3800 mPa·s, 4000 mPa·s, 4300 mPa·s, 4500 mPa·s, 4700 mPa·s, or 5000 mPa·s. The fineness of the ceramic slurry can be 3 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, or 24 μm.

[0047] The preferred rheological properties of ceramic slurry are η1, which is 2000~7000 mPa·s; and η1000, which is 20~100 mPa·s.

[0048] The rheological η1 of the ceramic slurry can be 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, 3500 mPa·s, 4000 mPa·s, 4500 mPa·s, 5500 mPa·s, 6000 mPa·s, 6500 mPa·s, or 7000 mPa·s. The rheological η1000 of the ceramic slurry can be 20 mPa·s, 30 mPa·s, 40 mPa·s, 50 mPa·s, 60 mPa·s, 70 mPa·s, 80 mPa·s, 90 mPa·s, or 100 mPa·s.

[0049] η1 represents the rate at which the shear rate is low (1 s). -1 The viscosity measured at a high shear rate (1000 s⁻¹) reflects the viscosity of the slurry under slow flow or static conditions. η1000 represents the viscosity at a high shear rate (1000 s⁻¹). -1 The viscosity measured under these conditions reflects the viscosity of the slurry under high-speed stirring.

[0050] In another typical embodiment of this application, a lithium-ion battery is provided, including a positive electrode, a negative electrode, and a separator. The positive electrode includes a positive electrode material and a ceramic coating. The ceramic coating is prepared by a ceramic slurry prepared by the preparation method described above.

[0051] Lithium-ion batteries with the aforementioned ceramic coating exhibit good cycle life, performance stability, safety performance, and high energy density.

[0052] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0053] Example 1 Step S1: Ceramic boehmite particles and binder polyacrylic acid are mixed at a mass ratio of 88:12, and then subjected to a first stirring and a first dispersion to obtain a first mixture. The first stirring speed is 12 rpm, and the first stirring time is 15 min; the first dispersion speed is 200 rpm, and the first dispersion time is 15 min.

[0054] Step S2: The organic solvent N-methylpyrrolidone (NMP) is divided into two parts to obtain a first organic solvent NMP solvent and a second organic solvent NMP solvent (volume ratio 1:1). The first mixture and the first organic solvent NMP solvent are sequentially subjected to a second stirring and a second dispersion to obtain a second mixture. The second mixture and the second organic solvent NMP solvent are sequentially subjected to a third stirring and a third dispersion to obtain a third mixture with a solid content of 70%. Specifically, the second stirring speed is 12 rpm and the second stirring time is 12 min; the second dispersion speed is 125 rpm and the second dispersion time is 12 min; the third stirring speed is 25 rpm and the third stirring time is 15 min; and the third dispersion speed is 125 rpm and the third dispersion time is 15 min.

[0055] Step S3: The third mixture and the third organic solvent NMP are sequentially subjected to fourth stirring, fourth dispersion, fifth stirring, and fifth dispersion to obtain a fourth mixture with a solid content of 65%. Specifically, the fourth stirring speed is 25 rpm, and the fourth stirring time is 20 min; the fourth dispersion speed is 200 rpm, and the fourth dispersion time is 20 min; the fifth stirring speed is 25 rpm, and the fifth stirring time is 60 min; the fifth dispersion speed is 600 rpm, and the fifth dispersion time is 60 min.

[0056] In step S4, the fourth mixture and the fourth organic solvent NMP are sequentially subjected to a sixth stirring and a sixth dispersion to obtain a fifth mixture with a solid content of 55%. The sixth stirring speed is 25 rpm, and the stirring time is 45 min; the sixth dispersion speed is 850 rpm, and the dispersion time is 45 min.

[0057] Step S5: The fifth mixture and the fifth organic solvent NMP are sequentially subjected to seventh stirring and seventh dispersion to obtain a mixture after seventh dispersion. The mixture after seventh dispersion is then subjected to eighth stirring and eighth dispersion to remove bubbles, resulting in a ceramic slurry with a solid content of 39%. Specifically, the seventh stirring speed is 25 rpm, and the seventh stirring time is 50 min; the seventh dispersion speed is 850 rpm, and the seventh dispersion time is 50 min; the eighth stirring speed is 15 rpm, and the eighth stirring time is 30 min; the eighth dispersion speed is 150 rpm, and the eighth dispersion time is 30 min.

[0058] Example 2 Step S1: Ceramic particles (boehmite) and binder (polyvinylidene fluoride) are mixed at a mass ratio of 85:15, and then subjected to a first stirring and a first dispersion to obtain a first mixture. The first stirring speed is 12 rpm, and the first stirring time is 15 min; the first dispersion speed is 200 rpm, and the first dispersion time is 15 min.

[0059] Step S2: The organic solvent N-methylpyrrolidone (NMP) is divided into two parts to obtain a first organic solvent NMP solvent and a second organic solvent NMP solvent (volume ratio 1:1). The first mixture and the first organic solvent NMP solvent are sequentially subjected to a second stirring and a second dispersion to obtain a second mixture. The second mixture and the second organic solvent NMP solvent are sequentially subjected to a third stirring and a third dispersion to obtain a third mixture with a solid content of 67%. Specifically, the second stirring speed is 12 rpm and the second stirring time is 12 min; the second dispersion speed is 125 rpm and the second dispersion time is 12 min; the third stirring speed is 25 rpm and the third stirring time is 15 min; and the third dispersion speed is 125 rpm and the third dispersion time is 15 min.

[0060] Step S3: The third mixture and the third organic solvent NMP are sequentially subjected to fourth stirring, fourth dispersion, fifth stirring, and fifth dispersion to obtain a fourth mixture with a solid content of 62%. Specifically, the fourth stirring speed is 25 rpm, and the fourth stirring time is 20 min; the fourth dispersion speed is 200 rpm, and the fourth dispersion time is 20 min; the fifth stirring speed is 25 rpm, and the fifth stirring time is 60 min; the fifth dispersion speed is 600 rpm, and the fifth dispersion time is 60 min.

[0061] In step S4, the fourth mixture and the fourth organic solvent NMP are sequentially subjected to a sixth stirring and a sixth dispersion to obtain a fifth mixture with a solid content of 50%. The sixth stirring speed is 25 rpm, and the sixth stirring time is 45 min; the sixth dispersion speed is 850 rpm, and the sixth dispersion time is 45 min.

[0062] Step S5: The fifth mixture and the fifth organic solvent NMP are sequentially subjected to seventh stirring and seventh dispersion to obtain a mixture after seventh dispersion. The mixture after seventh dispersion is then subjected to eighth stirring and eighth dispersion to remove bubbles, resulting in a ceramic slurry with a solid content of 38%. Specifically, the seventh stirring speed is 25 rpm, and the seventh stirring time is 50 min; the seventh dispersion speed is 850 rpm, and the seventh dispersion time is 50 min; the eighth stirring speed is 15 rpm, and the eighth stirring time is 30 min; the eighth dispersion speed is 150 rpm, and the eighth dispersion time is 30 min.

[0063] Example 3 Step S1: The ceramic particles (boehmite) and binder are mixed at a mass ratio of 90:10, and then subjected to a first stirring and a first dispersion to obtain a first mixture. The first stirring speed is 12 rpm, and the first stirring time is 15 min; the first dispersion speed is 200 rpm, and the first dispersion time is 15 min.

[0064] Step S2: The organic solvent N-methylpyrrolidone (NMP) is divided into two parts to obtain a first organic solvent NMP solvent and a second organic solvent NMP solvent (volume ratio 1:1). The first mixture and the first organic solvent NMP solvent are sequentially subjected to a second stirring and a second dispersion to obtain a second mixture. The second mixture and the second organic solvent NMP solvent are sequentially subjected to a third stirring and a third dispersion to obtain a third mixture with a solid content of 73%. Specifically, the second stirring speed is 12 rpm and the second stirring time is 12 min; the second dispersion speed is 125 rpm and the second dispersion time is 12 min; the third stirring speed is 25 rpm and the third stirring time is 15 min; and the third dispersion speed is 125 rpm and the third dispersion time is 15 min.

[0065] Step S3: The third mixture and the third organic solvent NMP are sequentially subjected to fourth stirring, fourth dispersion, fifth stirring, and fifth dispersion to obtain a fourth mixture with a solid content of 68%. Specifically, the fourth stirring speed is 25 rpm, and the fourth stirring time is 20 min; the fourth dispersion speed is 200 rpm, and the fourth dispersion time is 20 min; the fifth stirring speed is 25 rpm, and the fifth stirring time is 60 min; the fifth dispersion speed is 600 rpm, and the fifth dispersion time is 60 min.

[0066] In step S4, the fourth mixture and the fourth organic solvent NMP are sequentially subjected to a sixth stirring and a sixth dispersion to obtain a fifth mixture with a solid content of 60%. The sixth stirring speed is 25 rpm, and the sixth stirring time is 45 min; the sixth dispersion speed is 850 rpm, and the sixth dispersion time is 45 min.

[0067] Step S5: The fifth mixture and the fifth organic solvent NMP are sequentially subjected to seventh stirring and seventh dispersion to obtain a mixture after seventh dispersion. The mixture after seventh dispersion is then subjected to eighth stirring and eighth dispersion to remove bubbles, resulting in a ceramic slurry with a solid content of 40%. Specifically, the seventh stirring speed is 25 rpm, and the seventh stirring time is 50 min; the seventh dispersion speed is 850 rpm, and the seventh dispersion time is 50 min; the eighth stirring speed is 15 rpm, and the eighth stirring time is 30 min; the eighth dispersion speed is 150 rpm, and the eighth dispersion time is 30 min.

[0068] Example 4 The difference from Example 1 is that the rotation speed of the fourth dispersion is 150 rpm and the rotation speed of the fifth dispersion is 500 rpm, ultimately yielding a ceramic slurry.

[0069] Example 5 The difference from Example 1 is that the rotation speed of the fourth dispersion is 100 rpm and the rotation speed of the fifth dispersion is 700 rpm, and a ceramic slurry is finally obtained.

[0070] Example 6 The difference from Example 1 is that the rotation speed of the fourth dispersion is 300 rpm and the rotation speed of the fifth dispersion is 650 rpm, and a ceramic slurry is finally obtained.

[0071] Example 7 The difference from Example 1 is that the rotation speed of the fourth dispersion is 150 rpm, the rotation speed of the fifth dispersion is 500 rpm, and the rotation speed of the sixth dispersion is 600 rpm, finally obtaining a ceramic slurry.

[0072] Example 8 The difference from Example 1 is that the rotation speed of the fourth dispersion is 150 rpm, the rotation speed of the fifth dispersion is 500 rpm, and the rotation speed of the sixth dispersion is 900 rpm, finally obtaining a ceramic slurry.

[0073] Example 9 The difference from Example 1 is that the rotation speed of the fourth dispersion is 100 rpm, the rotation speed of the fifth dispersion is 700 rpm, and the rotation speed of the sixth dispersion is 800 rpm, finally obtaining a ceramic slurry.

[0074] Example 10 The difference from Example 1 is that the rotation speed of the fourth dispersion is 150 rpm, the rotation speed of the fifth dispersion is 500 rpm, the rotation speed of the sixth dispersion is 800 rpm, and the rotation speed of the seventh dispersion is 800 rpm, finally obtaining a ceramic slurry.

[0075] Example 11 The difference from Example 1 is that the rotation speed of the fourth dispersion is 150 rpm, the rotation speed of the fifth dispersion is 500 rpm, the rotation speed of the sixth dispersion is 600 rpm, and the rotation speed of the seventh dispersion is 900 rpm, finally obtaining a ceramic slurry.

[0076] Example 12 The difference from Example 1 is that the rotation speed of the fourth dispersion is 100 rpm, the rotation speed of the fifth dispersion is 700 rpm, the rotation speed of the sixth dispersion is 800 rpm, and the rotation speed of the seventh dispersion is 800 rpm, finally obtaining a ceramic slurry.

[0077] Example 13 The difference from Example 1 is that the rotation speed of the fourth dispersion is 100 rpm, the rotation speed of the fifth dispersion is 700 rpm, the rotation speed of the sixth dispersion is 800 rpm, and the rotation speed of the seventh dispersion is 900 rpm, finally obtaining a ceramic slurry.

[0078] Example 14 The difference from Example 1 is that the second stirring speed is 10 rpm, the second dispersion speed is 100 rpm, the third stirring speed is 20 rpm, and the third dispersion speed is 100 rpm, finally obtaining a ceramic slurry.

[0079] Example 15 The difference from Example 1 is that the second stirring speed is 15 rpm, the second dispersion speed is 150 rpm, the third stirring speed is 30 rpm, and the third dispersion speed is 150 rpm, finally obtaining a ceramic slurry.

[0080] Example 16 The difference from Example 1 is that the second stirring speed is 10 rpm, the second dispersion speed is 100 rpm, the third stirring speed is 20 rpm, the third dispersion speed is 100 rpm, the fourth stirring speed is 10 rpm, and the fourth dispersion speed is 100 rpm, finally obtaining a ceramic slurry.

[0081] Example 17 The difference from Example 1 is that the second stirring speed is 10 rpm, the second dispersion speed is 100 rpm, the third stirring speed is 20 rpm, the third dispersion speed is 100 rpm, the fourth stirring speed is 30 rpm, and the fourth dispersion speed is 300 rpm, finally obtaining a ceramic slurry.

[0082] Comparative Example 1 The difference from Example 1 is that the mass ratio of ceramic particles to binder is 80:20, resulting in a ceramic slurry.

[0083] Comparative Example 2 The difference from Example 1 is that the rotation speed of the fourth dispersion is 100 rpm and the rotation speed of the fifth dispersion is 250 rpm, and a ceramic slurry is finally obtained.

[0084] Comparative Example 3 The difference from Example 1 is that the rotation speed of the fifth dispersion is 500 rpm, the rotation speed of the sixth dispersion is 500 rpm, and the final ceramic slurry is obtained.

[0085] Comparative Example 4 The difference from Example 1 is that the rotation speed of the fifth dispersion is 500 rpm, the rotation speed of the seventh dispersion is 500 rpm, and the final ceramic slurry is obtained.

[0086] Test method: Slurry viscosity testing: A rotational viscometer was used for testing.

[0087] Slurry fineness testing: The fineness of the slurry is tested using a scraper fineness meter or a laser particle size analyzer.

[0088] Testing of slurry solid content: The solid content was tested using a solid content analyzer.

[0089] The test results are shown in Table 1.

[0090] Table 1

[0091] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: This application, by adjusting the preparation process of the ceramic slurry, transforms the single-kneading process into a multi-kneading process, and adjusts the kneading solid content, dispersion speed, and stirring speed in each step, can significantly increase the solid content of the ceramic slurry, reduce its fineness, and improve its dispersion uniformity. This results in better coating and wall scraping, avoiding slurry creep. Simultaneously, ceramic slurries with solid content within the aforementioned range reduce the difference in solid content between the slurry and the cathode slurry, thereby facilitating lower coating temperatures and stabilizing the operating current of the homogenizing equipment used for stirring and dispersion, thus reducing energy consumption costs in the processing. Specifically, it is preferable to control the rotation speed of the fifth dispersion stage to be 350-600 rpm higher than that of the fourth dispersion stage. This enhances the dispersion effect, increases the shear force within the slurry, thereby reducing the agglomeration of ceramic particles and binders. Simultaneously, it helps the solvent to more fully wet the ceramic particles and binders in the fifth dispersion stage, thus improving the stability and uniformity of the slurry, and consequently, the density of the ceramic coating. Preferably, the rotation speeds of the sixth and seventh dispersion stages are each independently 100-400 rpm higher than the fifth dispersion stage. This further refines the particles, thereby improving the uniformity and density of the ceramic coating. Simultaneously, increasing the rotation speeds of the sixth and seventh dispersion stages allows for further adjustment of the slurry viscosity, making the slurry more suitable for the coating process. The above stirring process accelerates the slurry flow, resulting in a more uniform particle distribution in the liquid. The above dispersion process further breaks up particle agglomerates through high shear force, making the particles smaller and more evenly distributed. The combined use of stirring and dispersion helps to improve the dispersion effect and uniformity of the slurry. Furthermore, the preparation method of this application can reduce the amount of organic solvent added during homogenization, thereby reducing material costs.

[0092] The above are merely embodiments of the present invention and are not intended to limit the invention. Those skilled in the art will recognize that the present invention can have various modifications and variations. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of preparing a ceramic slurry, characterized by, The preparation method comprises: Step S1, mixing raw materials comprising ceramic particles and a binder, and then sequentially performing first stirring and first dispersion to obtain a first mixture; wherein the mass ratio of the ceramic particles to the binder is 85-90:10-15; Step S2, dividing an organic solvent into two parts to obtain a first organic solvent and a second organic solvent; sequentially performing second stirring and second dispersion on raw materials comprising the first mixture and the first organic solvent to obtain a second mixture; sequentially performing third stirring and third dispersion on raw materials comprising the second mixture and the second organic solvent to obtain a third mixture; wherein the solid content of the third mixture is 67-73%; Step S3, sequentially performing fourth stirring, fourth dispersion, fifth stirring and fifth dispersion on raw materials comprising the third mixture and a third organic solvent to obtain a fourth mixture; wherein the solid content of the fourth mixture is 62-68%; the rotation speed of the fifth dispersion is 350-600 rpm higher than that of the fourth dispersion; Step S4, sequentially performing sixth stirring and sixth dispersion on raw materials comprising the fourth mixture and a fourth organic solvent to obtain a fifth mixture; wherein the solid content of the fifth mixture is 50-60%; and Step S5, sequentially performing seventh stirring and seventh dispersion on raw materials comprising the fifth mixture and a fifth organic solvent to obtain a ceramic slurry; wherein the solid content of the ceramic slurry is 38-40%; The rotation speeds of the sixth dispersion and the seventh dispersion are each independently 100-400 rpm higher than that of the fifth dispersion.

2. The production method according to claim 1, characterized by, In the step S1, the rotation speed of the first stirring is 10-15 rpm, and the time of the first stirring is 10-20 min; and / or, the rotation speed of the first dispersion is 150-250 rpm, and the time of the first dispersion is 10-20 min.

3. The production method according to claim 1 or 2, characterized by, In the step S2, the rotation speed of the second stirring is 10-15 rpm, and the time of the second stirring is 5-20 min; and / or, the rotation speed of the second dispersion is 100-150 rpm, and the time of the second dispersion is 5-20 min; and / or, the rotation speed of the third stirring is 20-30 rpm, and the time of the third stirring is 10-20 min; and / or, the rotation speed of the third dispersion is 100-150 rpm, and the time of the third dispersion is 10-20 min.

4. The production method according to any one of claims 1 to 3, characterized by, In the step S3, the rotation speed of the fourth stirring is 20-30 rpm, and the time of the fourth stirring is 10-30 min; and / or, the rotation speed of the fourth dispersion is 100-300 rpm, and the time of the fourth dispersion is 10-30 min; and / or, the rotation speed of the fifth stirring is 20-30 rpm, and the time of the fifth stirring is 45-75 min; and / or, the rotation speed of the fifth dispersion is 500-700 rpm, and the time of the fifth dispersion is 45-75 min.

5. The production method according to any one of claims 1 to 4, characterized by, In the step S4, the sixth stirring speed is 20-30 rpm, and the sixth stirring time is 30-60 min; and / or, the sixth dispersing speed is 800-900 rpm, and the sixth dispersing time is 30-60 min.

6. The production method according to any one of claims 1 to 5, characterized by, In the step S5, the seventh stirring speed is 20-30 rpm, and the seventh stirring time is 45-60 min; and / or, the seventh dispersing speed is 800-900 rpm, and the seventh dispersing time is 45-60 min.

7. The production method according to any one of claims 1 to 6, characterized by, The preparation method further comprises: defoaming the mixture after the seventh dispersing to obtain the ceramic slurry; wherein, the defoaming process comprises eighth stirring and eighth dispersing performed in sequence; the eighth stirring speed is 10-20 rpm, and the eighth stirring time is ≥ 30 min; and / or, the eighth dispersing speed is 100-200 rpm, and the eighth dispersing time is ≥ 30 min.

8. The production method according to any one of claims 1 to 7, characterized by, The ceramic particles are selected from any one or more of boehmite, alumina, lithium aluminum titanium phosphate; and / or, the binder is selected from any one or more of polyacrylic acid, polyvinylidene fluoride, sodium carboxymethyl cellulose and styrene butadiene rubber; and / or, the first organic solvent, the second organic solvent, the third organic solvent, the fourth organic solvent and the fifth organic solvent are each independently N-methyl pyrrolidone.

9. The production method according to any one of claims 1 to 8, characterized by, The viscosity of the ceramic slurry is 3000-5000 Pa·s; and / or, the fineness of the ceramic slurry is < 25 μm.

10. A lithium-ion battery comprising a positive electrode sheet, a negative electrode sheet, and a separator, the positive electrode sheet comprising a positive electrode material and a ceramic coating layer, the ceramic coating layer being prepared from a ceramic slurry, characterized in that, The ceramic slurry is prepared by the preparation method of any one of claims 1-9. The ceramic slurry is prepared by the preparation method of any one of claims 1-9.

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