An organic solvent slurry containing nano-titanium aluminum lithium phosphate and a preparation method thereof

Abstract

The application relates to the technical field of lithium electronic batteries, and provides an organic solvent slurry containing nano lithium aluminum titanium phosphate and a preparation method thereof, which comprises the following steps: adding nano lithium aluminum titanium phosphate powder into part of environment-friendly cosolvent, stirring and dispersing to form a suspension, and then adding a composite modification additive; mixing polyethyleneimine grafted polyethylene glycol, polyimide oligomer and polyester type high molecular dispersant; simultaneously, dispersing polyether modified organosilicon defoaming agent and modified fumed silica rheological additive in a small amount of environment-friendly cosolvent in advance; mixing gamma-butyrolactone main solvent, propylene glycol methyl ether acetate, ethanol and butyl acetate in proportion to build environment-friendly cosolvent; sequentially adding the modified powder suspension, the dispersant premix liquid and the functional additive mother liquor into the prepared environment-friendly cosolvent to obtain initial mixed slurry; and performing post-treatment to obtain finished product organic solvent slurry. The application can coat the surface of the LATP in a chemical bonding mode, so that the agglomeration caused by the double-cation charge conflict can be avoided.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to an organic solvent slurry containing nano-lithium titanium aluminum phosphate and its preparation method. Background Technology

[0002] Lithium aluminum titanium phosphate (LATP) is one of the most promising inorganic solid electrolyte materials for industrialization. It possesses high lithium-ion conductivity, excellent mechanical strength, and thermal stability. Dispersing it at the nanoscale in lithium-ion battery cathode slurry can effectively improve battery ion transport efficiency, thermal safety performance, and cycle life. However, nano-LATP has extremely high surface energy and abundant surface defects, making it prone to spontaneous aggregation. When added to the cathode slurry, it adsorbs polyvinylidene fluoride (PVDF) molecular chains, triggering physical crosslinking and chemical elimination reactions of PVDF. This ultimately leads to a sharp increase in the viscosity of the cathode slurry and gel solidification, making continuous coating impossible. This has become the core bottleneck restricting the large-scale application of nano-LATP in the lithium battery field.

[0003] Chinese invention patent application CN202410473416.9 discloses an organic solvent slurry containing nano-lithium titanium aluminum phosphate, its preparation method, and its application. This invention involves adding small molecule compounds containing highly electronegative atoms and / or groups as additives to the organic solvent slurry. These compounds are then adsorbed onto the positively charged metal ion surface exposed on the surface of the lithium titanium aluminum phosphate nanoparticles, effectively suppressing the entanglement of PVDF molecular chains on the surface of the nano-lithium titanium aluminum phosphate in the cathode slurry. This effectively inhibits gelation caused by the physical cross-linking of PVDF molecular chains. However, the modifying additive uses a combination of cationic quaternary ammonium salt and aminosilane. This dual-cationic system easily leads to supersaturation of the LATP surface charge, causing particle bridging and aggregation, indicating room for further optimization. Summary of the Invention

[0004] Therefore, in order to solve the problem of easy agglomeration of existing nano-lithium titanium aluminum phosphate slurries, this invention provides an organic solvent slurry containing nano-lithium titanium aluminum phosphate and its preparation method, the specific technical solution of which is as follows: An organic solvent slurry containing nano-lithium titanium aluminum phosphate is composed of the following raw material components in weight percentage: 12wt% to 18wt% nano-lithium titanium aluminum phosphate powder, 0.2wt% to 0.6wt% composite modifying additive, 0.3wt% to 0.8wt% grafted compound dispersant, 0.1wt% to 0.3wt% rheology modifier, 0.05wt% to 0.15wt% defoamer, and the balance being an environmentally friendly co-solvent; The composite modified additive is a mixture of epoxy silane coupling agent and fatty acid modified polyglycerol ester. The grafted compound dispersant is composed of polyethyleneimine grafted polyethylene glycol, polyimide oligomer and polyester polymeric dispersant. The environmentally friendly cosolvent is composed of main solvent, propylene glycol methyl ether acetate, ethanol and butyl acetate. The main solvent is γ-butyrolactone.

[0005] In the organic solvent slurry containing nano-lithium aluminum titanium phosphate, the composite modified additive is a compound of epoxy silane coupling agent and fatty acid modified polyglycerol ester. It can chemically coat the LATP surface, thereby avoiding agglomeration caused by the charge conflict of the two cations. In addition, the grafted compound dispersant of polyethyleneimine grafted polyethylene glycol and polyimide oligomer provides sufficient steric hindrance and no molecular chain entanglement at a fixed ratio, which can stably control the slurry particle size at D50≤180nm and D100≤900nm, and there is no obvious particle re-agglomeration after long-term standing.

[0006] Preferably, the mass ratio of epoxy silane coupling agent to fatty acid modified polyglycerol is 1:1 to 3, and the mass ratio of polyethyleneimine grafted polyethylene glycol to polyimide oligomer is 2.2:1 to 2.5:1.

[0007] Preferably, the number average molecular weight of polyethyleneimine grafted polyethylene glycol is 1200-1500, and the number average molecular weight of the polyimide oligomer is 8000-12000.

[0008] Preferably, after pretreatment, dispersion, and sand milling and classification, the particle size of the organic solvent slurry meets the requirements of D50≤180nm and D100≤900nm; the pH value of the slurry system is stably controlled at 6.5~7.5, the water content is ≤500ppm, and there is no gelation or stratification at -5℃.

[0009] Preferably, the mass ratio of propylene glycol methyl ether acetate to ethanol is 3:1 to 4:1.

[0010] Preferably, the epoxy silane coupling agent is γ-glycidyl etheroxypropyltriethoxysilane KH560, and the rheology modifier is a modified fumed silica thixotropic modifier.

[0011] Preferably, the slurry is milled 2-3 times using a horizontal nano-grind mill with 0.1-0.3mm zirconia beads, and then centrifuged and classified to achieve stable particle size control and no obvious particle re-agglomeration within 24 hours of storage.

[0012] A method for preparing an organic solvent slurry containing nano-lithium titanium aluminum phosphate, used to prepare the aforementioned organic solvent slurry containing nano-lithium titanium aluminum phosphate.

[0013] Preferably, the method for preparing the organic solvent slurry includes the following steps: S1. Add nano-lithium aluminum titanium phosphate powder to a portion of environmentally friendly co-solvent, stir and disperse to form a suspension, then add composite modifying additives, and stir at a constant temperature of 45℃~65℃ under inert gas protection for 1.5h~3h to complete the chemical bonding and coating modification of the powder surface, and cool for later use. S2, polyethyleneimine-grafted polyethylene glycol, polyimide oligomer, and polyester-type polymeric dispersant are mixed and stirred at low speed at room temperature for 0.5h to 1h to obtain a grafted compound dispersant premix; simultaneously, polyether-modified organosilicon defoamer and modified fumed silica rheology modifier are pre-dispersed in a small amount of environmentally friendly co-solvent and stirred until completely dissolved and transparent to obtain a functional additive mother liquor; S3, mix γ-butyrolactone as the main solvent, propylene glycol methyl ether acetate, ethanol, and butyl acetate in proportion, stir evenly, and construct a polar gradient environmentally friendly co-solvent system; S4, add the modified powder suspension of S1, the premixed dispersant of S2, and the mother liquor of functional additives to the prepared environmentally friendly co-solvent in sequence, stir at a low speed of 300r / min to 500r / min for 5min to 10min, and then increase the speed to 1500r / min to 2500r / min for high-speed shear dispersion for 20min to 40min to obtain the initial mixed slurry; S5 is processed through nano-grinding, centrifugal classification, slurry pH adjustment, filtration, and sealing to obtain the finished organic solvent slurry.

[0014] Preferably, S5 specifically includes: S51, the initial mixed slurry is fed into a horizontal nano-sand mill, using 0.1mm to 0.3mm zirconia grinding beads, and is circulated and milled 2 to 3 times, controlling the milling temperature to ≤40℃; after milling, the oversized particles are removed by centrifugation. S52 uses an organic weak acid buffer to adjust the pH of the slurry to 6.5-7.5, adds a molecular sieve dehydrating agent and stirs to mix evenly, and controls the overall moisture content of the slurry to ≤500ppm; S53, Filter-sealed encapsulation: Vacuum filtration using a 200-300 mesh precision filter, with full nitrogen atmosphere protection and sealed light-proof encapsulation to produce the finished organic solvent slurry. Attached Figure Description

[0015] The invention will be further understood from the following description taken in conjunction with the accompanying drawings. The components in the drawings are not necessarily drawn to scale, but rather the emphasis is on illustrating the principles of the embodiments. In different views, the same reference numerals designate corresponding parts.

[0016] Figure 1 This is a schematic diagram of the overall process for preparing an organic solvent slurry containing nano-lithium titanium aluminum phosphate in one embodiment of the present invention. Figure 2 This is a flowchart illustrating step S5 in one embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to its embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the scope of protection of the invention.

[0018] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly attached to the other element or there may be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0020] In this invention, "first" and "second" do not represent a specific quantity or order, but are merely used to distinguish names.

[0021] like Figure 1 As shown, one embodiment of the present invention provides an organic solvent slurry containing nano-lithium titanium aluminum phosphate, which is composed of the following raw material components by weight percentage: 12wt%–18wt% nano-lithium titanium aluminum phosphate powder, 0.2wt%–0.6wt% composite modifying additive, 0.3wt%–0.8wt% grafted compound dispersant, 0.1wt%–0.3wt% rheology modifier, 0.05wt%–0.15wt% defoamer, and the balance being an environmentally friendly cosolvent. The composite modifying additive is a mixture of epoxy silane coupling agent and fatty acid modified polyglycerol ester; the grafted compound dispersant is composed of polyethyleneimine grafted polyethylene glycol, polyimide oligomer and polyester-type polymeric dispersant; and the environmentally friendly cosolvent is composed of a main solvent, propylene glycol methyl ether acetate, ethanol and butyl acetate, with γ-butyrolactone selected as the main solvent.

[0022] Specifically, the mass ratio of epoxy silane coupling agent to fatty acid modified polyglycerol ester is 1:1 to 3, and the mass ratio of polyethyleneimine-grafted polyethylene glycol to polyimide oligomer is 2.2:1 to 2.5:1. The defoamer is a polyether-modified silicone defoamer, and the defoamer does not undergo phase separation or precipitation with the dispersant and modifying additives in the slurry.

[0023] The number average molecular weight of polyethyleneimine-grafted polyethylene glycol is 1200–1500, and the number average molecular weight of the polyimide oligomer is 8000–12000. After pretreatment dispersion and sand milling classification, the particle size of the organic solvent slurry meets the requirements of D50≤180nm and D100≤900nm; the pH value of the slurry system is stably controlled at 6.5–7.5, the water content is ≤500ppm, and there is no gelation or stratification at -5℃.

[0024] The mass ratio of propylene glycol methyl ether acetate to ethanol is 3:1 to 4:1. The epoxy silane coupling agent is γ-glycidyl etheroxypropyltriethoxysilane KH560, and the rheology modifier is a modified fumed silica thixotropic agent.

[0025] The slurry is milled 2-3 times using a horizontal nano-grind mill with 0.1-0.3mm zirconia beads, and then centrifuged and classified to achieve stable particle size control and prevent significant particle re-aggregation within 24 hours of storage.

[0026] The nano-lithium aluminum titanium phosphate powder is pretreated with composite modified additives for liquid-phase surface chemical bonding and coating before being mixed and dispersed with the remaining components. An environmentally friendly co-solvent is used to construct a polar gradient system, with butyl acetate accounting for 2wt% to 5wt% of the environmentally friendly co-solvent.

[0027] Throughout the slurry production and storage process, nitrogen gas is used for sealing and protection. A trace amount of molecular sieve dehydrating agent is added to the system to effectively inhibit the hydrolysis of nano-lithium titanium aluminum phosphate by water absorption. Finally, after the slurry forms a film, the residual amount of organic additives is ≤0.5%, and the system is free of chloride ions and free amino impurities.

[0028] In the organic solvent slurry containing nano-lithium aluminum titanium phosphate, the composite modified additive is a compound of epoxy silane coupling agent and fatty acid modified polyglycerol ester. It can chemically coat the surface of LATP (Lithium Aluminum Titanium Phosphate) to avoid agglomeration caused by the charge conflict of the two cations. In addition, the grafted compound dispersant of polyethyleneimine grafted with polyethylene glycol and polyimide oligomer provides sufficient steric hindrance and no molecular chain entanglement at a fixed ratio. It can stably control the particle size of the slurry at D50≤180nm and D100≤900nm, and there is no obvious particle re-agglomeration after long-term standing.

[0029] An embodiment of the present invention also provides a method for preparing an organic solvent slurry containing nano-lithium titanium aluminum phosphate, for preparing the aforementioned organic solvent slurry containing nano-lithium titanium aluminum phosphate, such as... Figure 1 As shown, it includes the following steps: S1. Add nano-lithium aluminum titanium phosphate powder to a portion of an environmentally friendly co-solvent, stir and disperse to form a suspension, then add composite modifying additives, and stir at a constant temperature of 45℃~65℃ under inert gas protection for 1.5h~3h to ensure that the KH560 epoxy group and the LATP surface hydroxyl group form chemical bonds, thereby completing the chemical bonding and coating modification of the powder surface, and then cool for later use.

[0030] Here, the inert gas is high-purity nitrogen, and the nitrogen flow rate is controlled at 0.2 m3 / h to 0.5 m3 / h. The stirring can be carried out at a speed of 300-500 r / min.

[0031] Coating efficiency Where T represents the isothermal temperature of the coating reaction, which is between 45℃ and 65℃; t represents the isothermal stirring time, which ranges from 1.5 to 3 hours. Too long a time may cause side reactions, while too short a time will result in insufficient coating; H represents the actual ambient humidity. The numbers represent the mass concentrations of the epoxy silane coupling agent (such as γ-glycidyl etheroxypropyltriethoxysilane KH560) and the fatty acid-modified polyglycerol ester, respectively. The two together constitute the compound system, and their ratio affects the coating uniformity. This can be understood as the concentration ratio of KH560 to fatty acid-modified polyglycerol ester, reflecting the effect of the ratio of the two on the coating effect. A value that is too high or too low will reduce the efficiency.

[0032] Specifically, This is a temperature-dependent activity factor used to quantify the contribution of reaction temperature to silane bonding activity. Generally, the lower the temperature, the weaker the activity and the slower the coating process. Within the range of 5–65 °C, temperature and coating activity can be considered to have a linear positive correlation. The synergistic factor is a Gaussian function with the optimal ratio as its peak value, used to precisely lock the ratio. Here, 1.3 represents the optimal mass ratio (1:1.3), and 2 is the Gaussian peak coefficient. When the ratio is 1:1.3, the synergistic factor is 1, indicating the highest coating efficiency. Deviating from 1:1.3 (too high / too low), the synergistic factor drops rapidly, and the coating efficiency decreases sharply. This mechanism helps to avoid charge conflict, uneven coating, and nanoparticle aggregation.

[0033] This can be understood as a time-kinetic factor, used to simulate the kinetics of surface chemical bonding. 0.8 is the preset coating reaction rate constant. As the stirring time increases, the coating efficiency rises rapidly and tends to saturate. When t=1.5h, the effective coating threshold can be reached, and when t=3h, the coating is almost complete. Further extension yields no gain. This can prevent incomplete coating due to insufficient time and side reactions due to excessive time.

[0034] This is a humidity suppression factor used to implement humidity threshold protection. 40 is the critical humidity upper limit, and 60 is the humidity attenuation coefficient, max(H) 40,0) indicates that attenuation is only triggered when the humidity exceeds 40%. When H≤40%RH, the humidity inhibition factor = 1, and humidity does not affect the coating efficiency; when H>40%RH, the higher the humidity, the smaller the humidity inhibition factor, and the coating efficiency decreases linearly; thus, it can prevent LATP from absorbing water and hydrolyzing, and KH560 from prematurely hydrolyzing and becoming ineffective, ensuring the stability of chemical bonds.

[0035] In summary, the coating efficiency function normalizes and couples the four core process parameters—temperature, ratio, time, and humidity—transforming qualitative processes into predictable models and suppressing agglomeration at its source. Furthermore, based on the coating efficiency function, it can guide parameter optimization such as humidity, time, and ratio, shortening the R&D cycle and reducing the scrap rate.

[0036] S2, polyethyleneimine-grafted polyethylene glycol, polyimide oligomer, and polyester-type polymeric dispersant are mixed and stirred at low speed at room temperature for 0.5h to 1h to obtain a grafted compound dispersant premix; simultaneously, polyether-modified organosilicon defoamer and modified fumed silica rheology modifier are pre-dispersed in a small amount of environmentally friendly co-solvent and stirred until completely dissolved and transparent to obtain a functional additive mother liquor.

[0037] Specifically, the premixing speed of the grafted compound dispersant is 200 r / min to 300 r / min; the preparation of the functional additive mother liquor is carried out by ultrasonic-assisted dispersion with an ultrasonic power of 200 W to 300 W and an ultrasonic time of 10 to 20 min.

[0038] S3, γ-butyrolactone as the main solvent, propylene glycol methyl ether acetate, ethanol, and butyl acetate are mixed in proportion and stirred evenly to construct a polar gradient environmentally friendly co-solvent system.

[0039] The mass ratio of propylene glycol methyl ether acetate (PMA) to ethanol is strictly controlled at 3:1 to 4:1, and butyl acetate accounts for 2 wt% to 5 wt% of the total mass of the environmentally friendly co-solvent.

[0040] S4, add the modified powder suspension of S1, the premixed dispersant of S2, and the mother liquor of functional additives to the prepared environmentally friendly co-solvent in sequence, stir at a low speed of 300r / min to 500r / min for 5min to 10min, and then increase the speed to 1500r / min to 2500r / min for high-speed shear dispersion for 20min to 40min to obtain the initial mixed slurry; S5 is processed through nano-grinding, centrifugal classification, slurry pH adjustment, filtration, and sealing to obtain the finished organic solvent slurry.

[0041] Specifically, such as Figure 2 As shown, S5 specifically includes: S51, the initial mixed slurry is fed into a horizontal nano-sand mill, using 0.1mm to 0.3mm zirconia grinding beads, and is circulated and milled 2 to 3 times, with the milling temperature controlled at ≤40℃; after milling, the oversized particles are removed by centrifugal classification.

[0042] During the sand milling process, the filling rate of the grinding beads is controlled between 70% and 85%, and the slurry circulation flow rate is controlled between 5L / min and 10L / min.

[0043] As a preferred technical solution, the main rotation speed of the sand mill, the number of grinding cycles (i.e., the effective number of times the slurry is processed in the sand mill), the diameter of the zirconia grinding beads, and the LATP solid content can be obtained first, based on (the main rotation speed of the sand mill). 1.2 The core mechanical energy input term is calculated as (× number of grinding cycles × zirconia bead filling rate) / (zirconia bead diameter × LATP solid content). Here, the 1.2 power of the mill rotor speed represents the shear / collision kinetic energy intensity. Generally, the higher the speed, the stronger the particle crushing force. An exponent of 1.2 is the optimal fit value for nano-grinding, balancing efficiency and temperature rise. The zirconia bead filling rate is the proportion of the grinding beads to the effective volume of the mill cavity, typically between 70% and 85%. Within this range, a higher filling rate results in a higher bead collision frequency and higher grinding efficiency. Exceeding the optimal range leads to excessive temperature rise, while insufficient filling rate results in inefficiency. The numerator (mill rotor speed 1.2 × number of grinding cycles × zirconia bead filling rate) represents the effective mechanical energy supply, contributing positively.

[0044] Smaller grinding beads result in a larger specific surface area and higher nano-crushing efficiency. LATP solid content is the mass fraction of nano-lithium aluminum titanium phosphate in the slurry. Higher solid content leads to higher slurry viscosity, poorer flow, greater grinding resistance, and higher energy requirements. The denominator (zirconia grinding bead diameter × LATP solid content) characterizes the energy damping factor, which has a negative contribution.

[0045] Then, the particle size crushing difficulty term, ln(initial LATP particle size / target particle size D50), is obtained based on the ratio between the initial LATP particle size before grinding and the target particle size D50. This term characterizes the difficulty coefficient of crushing LATP particles from the initial particle size to the target particle size. It can be understood that with a fixed initial particle size, the smaller the target particle size, the larger the logarithm, and the higher the energy required. Simultaneously, a sand milling temperature constraint factor is obtained to forcibly limit energy input through temperature feedback, preventing excessive sand milling temperature rise. This factor is calculated as: sand milling temperature constraint factor = 1 - max(real-time sand milling chamber temperature - 40, 0) / 15. When the real-time sand milling chamber temperature is no greater than 40 degrees Celsius, the sand milling temperature constraint factor = 1, all energy is effective, and normal grinding occurs. When the real-time sand milling chamber temperature is greater than 40 degrees Celsius, the sand milling temperature constraint factor linearly decreases, forcibly reducing effective energy and preventing the re-aggregation of PVDF gel and LATP particles due to high temperatures.

[0046] Finally, the effective grinding specific energy E_grind is obtained based on the characteristic constant of the slurry system, the core term of mechanical energy input, the term of particle size crushing difficulty, and the grinding temperature constraint factor. That is, the effective grinding specific energy is positively correlated with the product of the characteristic constant of the slurry system, the core term of mechanical energy input, the term of particle size crushing difficulty, and the grinding temperature constraint factor.

[0047] The characteristic constant of the slurry system can be understood as an adjustment coefficient, a dimensionless correction coefficient determined by the slurry system itself. It reflects the combined influence of dispersion efficiency, solvent viscosity, and powder surface properties on milling energy. Influencing factors include the grafted compound dispersant (PEI-g-PEG+PI oligomer+polyester), the environmentally friendly co-solvent system, and the LATP surface coating efficiency η. Generally, the better the dispersion system, the smaller the value of this coefficient, and the higher the energy utilization rate. This adjustment coefficient can be determined by experimental back-calculation: fix the milling process parameters and measure the effective milling specific energy, substitute it into the effective milling specific energy function for back-calculation, and take the average value as the final characteristic constant of the slurry system through multiple parallel experiments.

[0048] Effective grinding specific energy is the effective mechanical energy consumed to achieve nano-dispersion of a unit mass of LATP powder. It is used to uniformly quantify grinding intensity and achieve reproducible and benchmarkable particle size effects across different formulations / equipment. Generally, E_grind needs to be minimized while ensuring D50≤180nm to avoid excessive energy leading to temperature rise, gelation, and particle re-aggregation.

[0049] Thus, by calculating the effective grinding specific energy of the grinding process, it is possible to achieve stable particle size control of nano-lithium aluminum titanium phosphate (LATP) slurry with D50≤180nm and D100≤900nm, guide the matching of process parameters, control temperature to prevent gelation, prevent particle re-agglomeration, and avoid particle size exceeding the standard or over-grinding.

[0050] S52 uses an organic weak acid buffer to adjust the pH of the slurry to 6.5-7.5, adds a molecular sieve dehydrating agent and stirs to mix evenly, and controls the overall moisture content of the slurry to ≤500ppm.

[0051] The amount of molecular sieve dewatering agent added is 0.03wt% to 0.1wt% of the total mass of the slurry.

[0052] S53, Filter-sealed encapsulation: Vacuum filtration using a 200-300 mesh precision filter, with full nitrogen atmosphere protection and sealed light-proof encapsulation to produce the finished organic solvent slurry.

[0053] After filtration, the slurry undergoes vacuum degassing treatment, with the vacuum level controlled between -0.08MPa and -0.095MPa, and the degassing time controlled between 15min and 30min, in order to eliminate micro-bubbles inside the slurry.

[0054] The ambient humidity was controlled to ≤40% throughout the preparation process to prevent the slurry from absorbing moisture and hydrolyzing. Ultimately, the finished slurry had a stable particle size that met the requirements of D50≤180nm and D100≤900nm. After standing at -5℃ for 72 hours, there was no gelation or stratification. After being stored at room temperature in a sealed container for 30 days, there was no significant increase in particle size.

[0055] In the method for preparing the organic solvent slurry containing nano-lithium titanium aluminum phosphate, the nano-lithium titanium aluminum phosphate powder is pretreated by adding the powder to a portion of an environmentally friendly co-solvent, stirring and dispersing it to form a suspension, then adding a composite modifier, and stirring at a constant temperature of 45℃~65℃ under inert gas protection for 1.5h~3h to complete the chemical bonding and coating modification of the powder surface. This allows the powder to chemically coat the LATP surface, thereby avoiding agglomeration caused by the charge conflict between the two cations. Furthermore... By mixing polyethyleneimine-grafted polyethylene glycol, polyimide oligomer, and polyester-type polymeric dispersant, and stirring at low speed for 0.5-1 h at room temperature, a grafted compound dispersant premix is ​​prepared. Simultaneously, polyether-modified organosilicon defoamer and modified fumed silica rheology modifier are pre-dispersed in a small amount of environmentally friendly co-solvent and stirred until completely dissolved and transparent to prepare a functional additive mother liquor. This mother liquor can stably control the slurry particle size to D50≤180nm and D100≤900nm, and there is no obvious particle re-agglomeration after long-term standing.

[0056] In the following embodiments of the present invention, the low temperature stability was tested under the condition of standing at -5°C for 72 hours, the viscosity of the positive electrode slurry was measured by rotational viscometer at 25°C, the gel state was determined by observation after stirring for 1 hour, and the 120°C thermal shock was measured by button cell.

[0057] Basic information about raw materials includes the following: 1. Nano-sized lithium aluminum titanium phosphate (LATP) powder: D50=3μm, D100<20μm, purity≥99.5%, trigonal crystal form, specific surface area 8-12m²2 / g.

[0058] 2. Composite Modifying Additive: KH560 (γ-glycidyl etheroxypropyltriethoxysilane): Fatty acid modified polyglycerol ester = 1:1.3. The fatty acid modified polyglycerol ester can be C16-C18 fatty acid modified polyglycerol ester, with a degree of esterification of 3-5 and a number average molecular weight of 800-1200.

[0059] 2. Grafted compound dispersant: PEI (Polyethyleneimine) grafted with PEG (Mn=1300):PI oligomer (Mn=10000) = 2.3:1, compounded with polyester-type polymeric dispersant. The polyester-type polymeric dispersant can be anionic polyester dispersant, with an acid value of 20-30 mgKOH / g and a number-average molecular weight of 5000-8000.

[0060] PEG stands for Polyethylene glycol. PI oligomers are composed of polyimide (PI).

[0061] 3. Rheology modifier: Modified fumed silica 4. Defoamer: Polyether-modified silicone defoamer 5. Environmentally friendly co-solvent: γ-butyrolactone (main solvent) + PMA:ethanol = 3.5:1 + butyl acetate (3wt%) 6. Comparison of raw materials: Additives (hexadecyltrimethylammonium chloride / trifluoropropyltrimethoxysilane), dispersant (PEI + polyether), solvent (NMP / DMAC + ethanol) Example 1 (Baseline Formulation) The raw material ratio (total mass 1000g) is as follows: Nano LATP powder: 150g (15wt%); Composite modified additive: 4g (0.4wt%); Grafted compound dispersant: 5g (0.5wt%); Rheology modifier: 2g (0.2wt%); Defoamer: 1g (0.1wt%); Cosolvent: 838g (83.8wt%) The preparation process is as follows: 1. LATP powder was vacuum dried at 150℃ for 18 hours at -0.095MPa to -0.1MPa, with a moisture content ≤200ppm; 2. Add 50% environmentally friendly co-solvent to LATP, add composite modifier under nitrogen protection at 45℃, and stir for 2 hours to complete surface coating; 3. Premix and dissolve the grafted compound dispersant, stirring at 200-300 r / min. Disperse the rheology modifier and defoamer into a mother liquor by ultrasonication at a frequency of 20 kHz for 10-20 min.

[0062] 4. Mix all components and shear at 2000 r / min for 30 min to obtain the initial slurry; 5. Horizontal nano-grinding mill (0.1mm zirconia beads, 75% filling), 3 cycles of cyclic grinding, temperature ≤40℃, mill rotor speed 2000r / min-3000r / min; 6. Adjust pH to 7.0, add molecular sieve (4A spherical molecular sieve, particle size 2-3mm) to remove water, 250 mesh vacuum filtration + vacuum degassing (-0.09MPa, 20min).

[0063] The performance results are as follows: Particle size: D50=162nm, D100=800nm; Moisture content: 420ppm, pH=7.0; Low temperature stability: no gelation or stratification after standing at -5℃ for 72h; Positive electrode slurry (added 2wt%): viscosity=6240cps, no gelation after stirring for 1h; 120℃ thermal shock: voltage drop=0.052V after 2h.

[0064] Example 2 (Low Solids Formulation) The raw material ratio (total mass 1000g) is as follows: Nano LATP powder: 120g (12wt%); Composite modified additive: 3g (0.3wt%); Grafted compound dispersant: 4g (0.4wt%); Rheology modifier: 1.5g (0.15wt%); Defoamer: 0.8g (0.08wt%); Environmentally friendly cosolvent: 870.7g (87.07wt%) The preparation process is the same as in Example 1, but the grinding time is shortened to 2.5 hours. The performance results are as follows: Particle size: D50=151nm, D100=765nm; Moisture content: 390ppm, pH=6.8; Low temperature stability: no gelation or stratification after standing at -5℃ for 72h; Positive electrode slurry (added 2wt%): viscosity=5870cps, no gelation after stirring for 1h; Thermal shock at 120℃: voltage drop=0.048V after 2h.

[0065] Example 3 (High Solids Content Formulation) The raw material ratio (total mass 1000g) is as follows: Nano LATP powder: 180g (18wt%); Composite modified additive: 5g (0.5wt%); Grafted compound dispersant: 6g (0.6wt%); Rheology modifier: 2.5g (0.25wt%); Defoamer: 1.2g (0.12wt%); Environmentally friendly cosolvent: 805.3g (80.53wt%) The preparation process is the same as in Example 1, with sand milling repeated 4 times. The performance results are as follows: Particle size: D50=178nm, D100=890nm; Moisture content: 460ppm, pH=7.2; Low temperature stability: no gelation or stratification after standing at -5℃ for 72h; Positive electrode slurry (added 2wt%): viscosity=6910cps, no gelation after stirring for 1h; 120℃ thermal shock: voltage drop=0.057V after 2h.

[0066] Comparative Example 1 (lacking composite modified additives) Comparison: No KH560+ fatty acid modified polyglycerol ester was added; otherwise, it was the same as in Example 1.

[0067] The performance results are as follows: Particle size: D50=320nm, D100=1500nm (severe agglomeration); Moisture content: 430ppm, pH=6.9; Low temperature stability: stratification and sedimentation after standing at -5℃ for 24h; Positive electrode slurry (added 2wt%): viscosity=31400cps, gelation after stirring for 1h; Thermal shock at 120℃: voltage drop=0.088V after 2h.

[0068] Comparative Example 2 (lacking grafted compound dispersant) Comparison: No PEI-g-PEG+PI oligomer+polyester dispersant added; otherwise, the same as in Example 1.

[0069] Performance results: Particle size: D50=280nm, D100=1300nm (secondary repolymerization); Moisture content: 410ppm, pH=7.0; Low temperature stability: slight gelation after standing at -5℃ for 24h; Positive electrode slurry (added 2wt%): viscosity=29700cps, gelation after stirring for 1h; Thermal shock at 120℃: voltage drop=0.085V after 2h.

[0070] Comparative Example 3 (using the original toxic solvent NMP, without environmentally friendly co-solvents) Comparison points: NMP was used as the main solvent, and the PMA / ethanol / butyl acetate ratio was not used; otherwise, it was the same as in Example 1.

[0071] The performance results are as follows: Particle size: D50=170nm, D100=850nm; Moisture content: 1100ppm, pH=8.2; Low temperature stability: gelation after standing at -5℃ for 48h; Positive electrode slurry (added 2wt%): viscosity=12600cps, gelation after stirring for 1h; Thermal shock at 120℃: voltage drop=0.079V after 2h.

[0072] Comparative Example 4 (dispersant molecular weight exceeds standard) Comparison points: PEI-g-PEG (Mn=900, lower than 1200), PI oligomer (Mn=18000, higher than 12000), the rest are the same as in Example 1.

[0073] Performance results: Particle size: D50=240nm, D100=1200nm; Moisture content: 440ppm, pH=7.1; Low temperature stability: slight gelation after standing at -5℃ for 36h; Positive electrode slurry (added 2wt%): viscosity=15800cps, gelation after stirring for 1h; Thermal shock at 120℃: voltage drop = 0.076V after 2h. The following table compares the core performance of the examples and comparative examples:

[0074] As can be seen from the table above, the embodiments of the present invention are superior to the comparative examples in terms of particle size control, moisture content, low temperature stability, anti-gelling, and thermal stability, which helps to solve the defects of nano-lithium titanium aluminum phosphate slurry such as agglomeration, gelation, poor environmental performance, and unstable storage.

[0075] In summary, the present invention has the following advantages: 1. Nano-dispersion ensures greater stability and completely eliminates agglomeration and re-agglomeration. An epoxy-silane coupling agent and fatty acid-modified polyglycerol ester are compounded at a ratio of 1:1.2–1.5 to chemically coat the LATP surface, avoiding agglomeration caused by dual-cation charge conflict. A grafted dispersant consisting of polyethyleneimine-grafted polyethylene glycol (1200–1500) and polyimide oligomers (8000–12000) provides sufficient steric hindrance and eliminates molecular chain entanglement, allowing for stable control of slurry particle size at D50≤180nm and D100≤900nm, with no significant particle re-agglomeration even after long-term standing.

[0076] 2. Inhibits PVDF gelation at its source, adapting to cathode slurry processing. The non-ionic modification system with no chloride ion residue works synergistically with the optimized dispersant to block the physical cross-linking between the LATP surface and the PVDF molecular chains, while reducing the viscosity of the cathode slurry and preventing the chemical elimination reaction of PVDF. This completely solves the cathode slurry gelation problem caused by nano-LATP, ensuring stability throughout the entire process of stirring, pumping, and coating.

[0077] 3. Environmental upgrades and significantly improved process adaptability. The use of low-toxicity γ-butyrolactone to replace highly toxic main solvents such as NMP (N-Methyl-2-Pyrrolidone) and DMAC (N,N-Dimethylacetamide) ensures VOC (Volatile Organic Compounds) emissions comply with environmental regulations, and drying energy consumption is reduced by more than 30%. A fixed ratio of propylene glycol methyl ether acetate to ethanol of 3:1 to 4:1, combined with butyl acetate, constructs a polar gradient solvent system that matches the evaporation rate, effectively eliminating defects such as coating pinholes, craters, and orange peel.

[0078] 4. Storage and processing performance fully meet standards. The addition of rheology modifiers and defoamers imparts excellent thixotropic properties and foam suppression and defoaming capabilities to the slurry, making it suitable for high-speed coating; stabilizing the system pH at 6.5–7.5 and the water content at ≤500ppm avoids LATP water absorption and hydrolysis, while achieving no gelation or stratification at -5℃ and no performance degradation during long-term sealed storage at room temperature.

[0079] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0080] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An organic solvent slurry containing nano-lithium titanium aluminum phosphate, characterized in that, It is composed of the following raw material components by weight percentage: 12wt%~18wt% nano-lithium aluminum titanium phosphate powder, 0.2wt%~0.6wt% composite modified additive, 0.3wt%~0.8wt% grafted compound dispersant, 0.1wt%~0.3wt% rheology modifier, 0.05wt%~0.15wt% defoamer, and the balance is an environmentally friendly co-solvent; The composite modified additive is a mixture of epoxy silane coupling agent and fatty acid modified polyglycerol ester. The grafted compound dispersant is composed of polyethyleneimine grafted polyethylene glycol, polyimide oligomer and polyester polymeric dispersant. The environmentally friendly cosolvent is composed of main solvent, propylene glycol methyl ether acetate, ethanol and butyl acetate. The main solvent is γ-butyrolactone.

2. The organic solvent slurry containing nano-lithium titanium aluminum phosphate as described in claim 1, characterized in that, The mass ratio of epoxy silane coupling agent to fatty acid modified polyglycerol is 1:1 to 3, and the mass ratio of polyethyleneimine grafted polyethylene glycol to polyimide oligomer is 2.2:1 to 2.5:

1.

3. The organic solvent slurry containing nano-lithium titanium aluminum phosphate as described in claim 1, characterized in that, The number average molecular weight of the polyethyleneimine-grafted polyethylene glycol is 1200-1500, and the number average molecular weight of the polyimide oligomer is 8000-12000.

4. The organic solvent slurry containing nano-lithium titanium aluminum phosphate as described in claim 1, characterized in that, After pretreatment, dispersion, and sand milling, the organic solvent slurry has a particle size that meets the requirements of D50≤180nm and D100≤900nm. The pH value of the slurry system is stably controlled at 6.5~7.5, the water content is ≤500ppm, and there is no gelation or stratification at -5℃.

5. The organic solvent slurry containing nano-lithium titanium aluminum phosphate as described in claim 1, characterized in that, The mass ratio of propylene glycol methyl ether acetate to ethanol is 3:1 to 4:

1.

6. The organic solvent slurry containing nano-lithium titanium aluminum phosphate as described in claim 1, characterized in that, The epoxy silane coupling agent is γ-glycidyl etheroxypropyltriethoxysilane KH560, and the rheology modifier is a modified fumed silica thixotropic modifier.

7. The organic solvent slurry containing nano-lithium titanium aluminum phosphate as described in claim 1, characterized in that, The slurry is milled 2-3 times using a horizontal nano-grind mill and 0.1-0.3mm zirconia beads, and then centrifuged and classified to achieve stable particle size control and no obvious particle re-aggregation within 24 hours of storage.

8. A method for preparing an organic solvent slurry containing nano-lithium titanium aluminum phosphate, characterized in that, Used to prepare the organic solvent slurry containing nano-lithium titanium aluminum phosphate as described in any one of claims 1-7.

9. The method for preparing organic solvent slurry as described in claim 8, characterized in that, Includes the following steps: S1. Add nano-lithium aluminum titanium phosphate powder to a portion of environmentally friendly co-solvent, stir and disperse to form a suspension, then add composite modifying additives, and stir at a constant temperature of 45℃~65℃ under inert gas protection for 1.5h~3h to complete the chemical bonding and coating modification of the powder surface, and cool for later use. S2, polyethyleneimine-grafted polyethylene glycol, polyimide oligomer, and polyester-type polymeric dispersant are mixed and stirred at low speed at room temperature for 0.5h to 1h to obtain a grafted compound dispersant premix; simultaneously, polyether-modified organosilicon defoamer and modified fumed silica rheology modifier are pre-dispersed in a small amount of environmentally friendly co-solvent and stirred until completely dissolved and transparent to obtain a functional additive mother liquor; S3, mix γ-butyrolactone as the main solvent, propylene glycol methyl ether acetate, ethanol, and butyl acetate in proportion, stir evenly, and construct a polar gradient environmentally friendly co-solvent system; S4, add the modified powder suspension of S1, the premixed dispersant of S2, and the mother liquor of functional additives to the prepared environmentally friendly co-solvent in sequence, stir at a low speed of 300r / min to 500r / min for 5min to 10min, and then increase the speed to 1500r / min to 2500r / min for high-speed shear dispersion for 20min to 40min to obtain the initial mixed slurry; S5 is processed through nano-grinding, centrifugal classification, slurry pH adjustment, filtration, and sealing to obtain the finished organic solvent slurry.

10. The method for preparing organic solvent slurry according to claim 9, characterized in that, S5 specifically includes: S51, the initial mixed slurry is fed into a horizontal nano-sand mill, using 0.1mm to 0.3mm zirconia grinding beads, and is circulated and milled 2 to 3 times, controlling the milling temperature to ≤40℃; after milling, the oversized particles are removed by centrifugation. S52 uses an organic weak acid buffer to adjust the pH of the slurry to 6.5-7.5, adds a molecular sieve dehydrating agent and stirs to mix evenly, and controls the overall moisture content of the slurry to ≤500ppm; S53 uses a 200-300 mesh precision filter for vacuum filtration, is protected by a nitrogen atmosphere throughout the process, and is sealed and light-proof to produce the finished organic solvent slurry.

Images