A method and apparatus for reducing residual alkali of llzo

Abstract

The application relates to the technical field of battery preparation, and provides a LLZO residual alkali reduction method and equipment, which comprises the following steps: S1, LLZO material is stirred and filtered by adding water, the step is repeated for several times, and then the LLZO material is aged; S2, the liquid after the aging is boiled, naturally cooled to room temperature, filtered, boiled by adding water again, the step is repeated for several times until the pH is reduced to 8, and then the LLZO material is filtered and dried; and S3, the dried material obtained in the step S2 is boiled by adding water, filtered, and then dried. Through the water washing of the LLZO material in multiple steps, lithium and its salt in the interior of the LLZ0 crystal and on the surface of the material can be diffused into water, the original cubic phase garnet structure is retained, Li+ / H+ ion exchange is fully carried out, protonated garnet LLZO is generated, the residual alkali is greatly reduced, the sensitivity of the protonated garnet LLZ0 to air is greatly reduced, the stability of the protonated garnet LLZ0 in air can be improved, and the application and operation difficulty can be reduced.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, and more specifically, to a method and apparatus for reducing residual alkali in LLZO. Background Technology

[0002] LLZO is a ceramic material with a garnet crystal structure, composed of lithium, lanthanum (La), zirconium (Zr), and oxygen atoms, with the chemical formula Li6.4La3Zr1.4Ta0.6O12. LLZO has a cubic garnet structure, consisting of a ZrO6 octahedral network and Li / La ions. The ZrO6 octahedra are arranged in a three-dimensional framework, with Li / La ions occupying interstitial positions between the octahedra. Li+ ions can conduct electric current by moving through these interstitial sites.

[0003] LLZO is considered a promising SSE (Solid-state electrolyte) material because it possesses several complex inherent properties, including a lithium-ion conductivity as high as 10⁻⁶ at room temperature (RT). -3 S·cm -1 The electronic conductivity is as low as about 10. -8 S·cm -1 (RT), with a wide electrochemical stability window (experimentally observed voltage greater than 6V for Li+ / Li), and significant thermal and chemical stability in the presence of metallic lithium.

[0004] Due to its advantageous properties such as ionic conductivity, energy density, chemical stability, electrochemical stability, air stability, thermal stability, and safety, LLZO garnet-based electrolyte is widely considered the most promising and indispensable solid-state electrolyte material. However, LLZO presents some manufacturing challenges, particularly the formation of large amounts of lithium carbonate and lithium hydroxide on its surface due to Li / H exchange, resulting in high residual alkali and a pH of approximately 14. This makes slurry preparation difficult during the mixing with cathode materials and the coating of the separator. Summary of the Invention

[0005] Based on this, in order to reduce the residual alkali content on the surface of LLZO, the present invention provides a method for reducing residual alkali in LLZO, the specific technical solution of which is as follows: A method for reducing residual alkali in LLZO includes the following steps: S1, Add water to the LLZO material, stir, filter, repeat several times, and then age; S2, after aging, the liquid is boiled, naturally cooled to room temperature, filtered, and then boiled again with water. This process is repeated several times until the pH drops to 8, and then filtered and dried. S3, add water to the dried material obtained in step S2, boil, filter, and then dry.

[0006] The method for reducing residual alkali in LLZO involves multiple steps of water washing of the LLZO material. This allows lithium and its salts inside the LLZO crystal and on the surface of the material to diffuse into the water, preserving the original cubic garnet structure while fully exchanging Li+ / H+ ions to generate protonated garnet LLZO. This significantly reduces residual alkali, and the protonated garnet LLZO is much less sensitive to air, improving its stability in air and reducing the difficulty of application and operation.

[0007] Preferably, the method for reducing residual alkali of LLZO further includes the following steps: S4. The dried material obtained in step S3 is subjected to air jet milling to deagglomerate the particles, reducing the particle size to the nanoscale.

[0008] Preferably, in step S3, boiling the dried material with water, filtering it, and then drying it specifically includes: boiling the dried material with water, naturally cooling it to room temperature and then filtering it, boiling the filter cake with water and filtering it, and repeating the above steps until pH=8.

[0009] Preferably, in step S2, the boiling time is 30 min, the drying temperature is 110 °C, and the drying time is 10 h.

[0010] Preferably, in step S3, the drying temperature is 110°C and the drying time is 10 hours.

[0011] Preferably, the method for obtaining LLZO material specifically includes: adding LLZO coarse powder to an alcohol solvent and then sand milling it to obtain LLZO material.

[0012] Preferably, in step S1, the process of adding water to the LLZO material, stirring, and filtering is repeated three times.

[0013] Preferably, in step S2, the process of boiling the aged liquid, naturally cooling it to room temperature, filtering it, and then adding water and boiling it again is repeated three times.

[0014] An LLZO residual alkali reduction device, comprising: Controller; Memory, which stores executable instructions; The executable instructions can run on the controller to implement the LLZO residual alkali reduction method. 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 of an LLZO residual alkali reduction method in one embodiment of the present invention; Figure 2 This is a schematic flowchart of a method for reducing residual alkali with LLZO in another embodiment of the present invention; Figure 3 This is a schematic diagram of the storage stability monitoring of LLZO water-washed samples in one embodiment of the present invention. Figure 1 ; Figure 4 This is a schematic diagram of the storage stability monitoring of LLZO water-washed samples in one embodiment of the present invention. Figure 2 ; Figure 5 This is a comparative schematic diagram of the color development reaction after mixing an LLZO water-washed sample with PVDF adhesive 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] Example 1: like Figure 1 As shown, an embodiment of the present invention provides a method for reducing residual alkali in LLZO, comprising the following steps: S1, add water to the LLZO material, stir, filter, repeat several times, and then age.

[0022] Aging means soaking the material in water for a full night, for example, about 8-12 hours. The specific method for obtaining LLZO material includes: adding coarse LLZO powder to an alcohol solvent and then milling it to obtain the LLZO material.

[0023] Preferably, the process of adding water to the LLZO material, stirring, and filtering is repeated three times. Alcohol solvents include, but are not limited to, isopropanol or ethanol.

[0024] S2, after aging, the liquid is boiled, naturally cooled to room temperature, filtered, and then boiled again with water. This process is repeated several times until the pH drops to 8, and then filtered and dried.

[0025] Preferably, the boiling time is 30 minutes, the drying temperature is 110°C, and the drying time is 10 hours. The process of boiling the aged liquid, naturally cooling it to room temperature, filtering it, and then adding water and boiling it again is repeated three times.

[0026] S3, add water to the dried material obtained in step S2, boil, filter, and then dry.

[0027] Specifically, in step S3, boiling the dried material with water, filtering it, and then drying it includes: boiling the dried material with water, naturally cooling it to room temperature, filtering it, boiling the filter cake with water and filtering it, and repeating the above steps until pH=8. Preferably, the drying temperature is 110°C and the drying time is 10 hours.

[0028] Preferably, the method for reducing residual alkali in LLZO further includes the following step: S4, performing air jet milling to deagglomerate the dried material obtained in step S3, reducing the particle size to the nanoscale.

[0029] The final product maintained a stable pH of around 8, with no significant increase in pH after being exposed to air for two days. This demonstrates that the water washing process of this invention effectively reduces the air sensitivity of LLZO materials, achieving the dual goals of residual alkali control and stability improvement.

[0030] Storage stability monitoring was performed on the LLZO product obtained after water washing, such as... Figures 3-5 As shown, the LLZO product obtained after washing was stored in aluminum-plastic bags, glove boxes, and air. After one week, the pH rose to 10, and the phase did not change significantly. After five weeks of storage in air, the pH of the LLZO product obtained after washing stabilized at around 10.

[0031] The results after one month of storage showed that the washed LLZO product had a satisfactory phase composition, and while the pH changed slightly, it remained at a low level. This demonstrates that the LLZO residual alkali reduction method described in this invention can yield a stable and satisfactory LLZO product, which is beneficial for subsequent pulping.

[0032] In summary, the LLZO residual alkali reduction method, through multiple steps of water washing of the LLZO material, allows lithium and its salts inside the LLZO crystal and on the material surface to diffuse into the water. While preserving the original cubic garnet structure, it fully facilitates Li+ / H+ ion exchange, generating protonated garnet LLZO, thereby significantly reducing residual alkali. Furthermore, the protonated garnet LLZO exhibits significantly reduced sensitivity to air, improving its stability in air and reducing the difficulty of application and operation.

[0033] The present invention also provides an LLZO residual alkali reduction device, which includes: a controller; a memory storing executable instructions; wherein the executable instructions can run on the controller to implement the LLZO residual alkali reduction method.

[0034] Example 2: like Figure 1 As shown, an embodiment of the present invention provides a method for reducing residual alkali in LLZO, comprising the following steps: S1, add water to the LLZO material, stir, filter, repeat several times, and then age.

[0035] Aging means soaking the material in water for a full night, for example, about 8-12 hours. The specific method for obtaining LLZO material includes: adding coarse LLZO powder to an alcohol solvent and then milling it to obtain the LLZO material.

[0036] Preferably, the process of adding water to the LLZO material, stirring, and filtering is repeated three times. Alcohol solvents include, but are not limited to, isopropanol or ethanol.

[0037] S2, after aging, the liquid is boiled, naturally cooled to room temperature, filtered, and then boiled again with water. This process is repeated several times until the pH drops to 8, and then filtered and dried.

[0038] Preferably, the boiling time is 30 minutes, the drying temperature is 110°C, and the drying time is 10 hours. The process of boiling the aged liquid, naturally cooling it to room temperature, filtering it, and then adding water and boiling it again is repeated three times.

[0039] S3, add water to the dried material obtained in step S2, boil, filter, and then dry.

[0040] Specifically, in step S3, boiling the dried material with water, filtering it, and then drying it includes: boiling the dried material with water, naturally cooling it to room temperature, filtering it, boiling the filter cake with water and filtering it, and repeating the above steps until pH=8. Preferably, the drying temperature is 110°C and the drying time is 10 hours.

[0041] Preferably, the method for reducing residual alkali in LLZO further includes the following step: S4, performing air jet milling to deagglomerate the dried material obtained in step S3, reducing the particle size to the nanoscale.

[0042] The final product maintained a stable pH of around 8, with no significant increase in pH after being exposed to air for two days. This demonstrates that the water washing process of this invention effectively reduces the air sensitivity of LLZO materials, achieving the dual goals of residual alkali control and stability improvement.

[0043] Storage stability monitoring was performed on the LLZO product obtained after water washing, such as... Figures 3-5 As shown, the LLZO product obtained after washing was stored in aluminum-plastic bags, glove boxes, and air. After one week, the pH rose to 10, and the phase did not change significantly. After five weeks of storage in air, the pH of the LLZO product obtained after washing stabilized at around 10.

[0044] The table below shows the particle size comparison of samples with different particle sizes before and after water washing and deagglomeration. Among them, D10 / D50 / D90 are the particle size of the material, and the corresponding parameters before and after water washing represent the particle volume at 10%, 50%, and 90% of the material according to the volume distribution.

[0045]

[0046] Analysis of the table above shows that the washing process has a significant impact on the particle size distribution of the LLZO samples. The proportion of coarse particles (D99) has increased significantly, and the particle size distribution range has been broadened, which is beneficial to improving the energy density.

[0047] After one month of storage, the average Li₂CO₃ (%) of the washed LLZO product was 0.52, and the average LiOH (%) was 0, indicating that its phase composition was acceptable. The pH showed a slight change but remained at a low level. Therefore, the LLZO residual alkali reduction method described in this invention can yield a stable and acceptable LLZO product, which is beneficial for subsequent pulping.

[0048] In summary, the LLZO residual alkali reduction method, through multiple steps of water washing of the LLZO material, allows lithium and its salts inside the LLZO crystal and on the material surface to diffuse into the water. While preserving the original cubic garnet structure, it fully facilitates Li+ / H+ ion exchange, generating protonated garnet LLZO, thereby significantly reducing residual alkali. Furthermore, the protonated garnet LLZO exhibits significantly reduced sensitivity to air, improving its stability in air and reducing the difficulty of application and operation.

[0049] The present invention also provides an LLZO residual alkali reduction device, which includes: a controller; a memory storing executable instructions; wherein the executable instructions can run on the controller to implement the LLZO residual alkali reduction method.

[0050] like Figure 2As shown, in step S1, after soaking the LLZO material in water overnight with stirring, the sample pH reached 14. In step S2, the filter cake was boiled with water while stirring, and the pH reached 13. After filtration and boiling with water again, the pH reached 12. As the number of repetitions of adding water, stirring, boiling, and filtration increased, the pH gradually decreased. When the pH dropped to 8, it was dried at a drying temperature of 110°C for 10 hours. Then, in step S3, the dried material was boiled with water while stirring, filtered, and the above steps were repeated until the pH dropped to 8. It was then dried again at a drying temperature of 110°C for 10 hours to obtain the washed LLZO product, which was finally subjected to depolymerization treatment.

[0051] Specifically, step S1 aims to ensure sufficient contact between the material and water, allowing the surface lithium to dissolve more uniformly into the water, thus initially reducing the surface lithium concentration and residual alkali. In steps S2 and S3, the simultaneous stirring and boiling serves to accelerate molecular motion through heating, thereby increasing the diffusion rate of lithium compounds (residual alkali, such as LiOH) from the material surface into the water.

[0052] The purpose of filtration is to remove the filtrate containing lithium residual alkali. After replacing the water with fresh water, the new water continues to dissolve the residual alkali remaining on the material surface. By repeating filtration multiple times, the residual alkali on the material surface can be significantly reduced, allowing the pH to initially meet the standard. The purpose of drying is to remove most of the moisture from the material, making it dry. During the drying process, a small amount of residual unstable lithium compounds may decompose / restructure, preparing for a secondary fine-tuning process to remove residual alkali. Through the drying treatment in step S3, the moisture is finally removed, resulting in a dry LLZO material with low residual alkali content. The material structure is more stable after drying, facilitating subsequent air stability testing.

[0053] In summary, the method for reducing residual alkali in LLZO is simplified and has a short cycle, which can save the washing time of LLZO materials and improve the washing efficiency.

[0054] For steps S1 and S2, considering the pH decay pattern after filtration and the adsorption-desorption equilibrium of residual alkali, in one embodiment, to stabilize the pH to 8 with the fewest filtrations and avoid excessive filtration increasing time costs, the number of filtrations is... Through formula Obtain; among which, Initial pH value after stirring, where D is the fractal dimension. This is an adjustment coefficient for the number of filtration cycles, set empirically. Specifically, the fractal dimension describes the roughness / porosity of the material surface (obtained through SEM scanning electron microscopy, BET gas adsorption, etc.), reflecting the diffusion resistance of lithium from the surface to water. The more complex the material surface, the higher the fractal dimension, and the more tortuous the diffusion path. Generally, the higher the fractal dimension (more porous the surface), the more difficult it is to completely remove residual alkali; therefore, it is used... Adjust the decay rate (a larger D results in slower decay, requiring more iterations). When... Optimal number of filtrations when ≤8.2 .

[0055] To reduce the initial pH to 8 in the shortest possible time to lay the foundation for subsequent filtration, and to balance mass transfer efficiency with time cost, in one embodiment, according to the formula... The temperature and time of LLZO material being stirred with water were obtained. The formula takes into account the synergistic effect between heating to accelerate diffusion and the liquid-to-solid ratio increasing the contact area. This indicates the amount of pH decrease, i.e. =initial pH - 10. Wherein, Indicates the heating temperature. The liquid-to-solid ratio is calculated as (water added / weight of LLZO material). This is an empirically set adjustment coefficient for heating time, where t represents the heating time (in hours), T / 100 represents temperature normalization, and 0.6 is an empirically set nonlinear influence factor. This indicates the nonlinear effect of the liquid-solid ratio (diminishing marginal benefits). The logarithm of time indicates rapid initial results; 0.3 is a fractal dimension correction factor that can be adjusted empirically. Generally, a more complex material surface is more conducive to mass transfer. When determining the heating temperature and... Then, it can be done according to the formula. Calculate the heating time by reverse calculation.

[0056] To address the pH rebound (from 8 to 14) of the dried material after boiling in step 2, a second washing step (boiling and filtration) is performed in step S3 to stabilize the final pH at 8-8.5. A rebound coefficient β is introduced, and the pH after the second washing is constructed based on this coefficient. ) and number of washes Relationship functions The rebound coefficient characterizes the residual alkali regeneration capacity after air exposure (which can be understood as the pH value after rebound). This refers to the solid-to-recycle ratio. The higher the solid-to-recycle ratio and the more times the solution is rinsed, the faster the pH decreases. This is an adjustment coefficient for the number of washes, set based on experience. These values ​​are set based on experience, and are generally determined according to the final pH stability value of the LLZO material, such as 8.0.

[0057] Observation Formula It can be seen that as the number of washes increases, the exponential term decreases, and the pH gradually approaches a certain value. For example, the number of washes is set to 5, and the wash solution-to-solid ratio is set to 5. The value is set to 8.1 (with an allowable error of 0.1), and the rebound coefficient β is set to 14. Substituting these values ​​into the formula yields the specific value of the rewash frequency adjustment coefficient. Here, the relationship function adopts an exponential decay model, which conforms to the mass transfer law, meaning that the dissolution and removal process of residual alkali on the material surface is a nonlinear process that is initially fast and slows down later. The higher the residual alkali concentration, the greater the amount removed in a single rewash. As the concentration decreases, the removal efficiency decreases, which is consistent with the decay rate of the exponential function decreasing with time / number of washes.

[0058] Introducing the square root of the rewash liquid-to-solid ratio reflects the characteristic that increasing water addition can improve mass transfer efficiency, but with diminishing marginal returns (e.g., increasing the rewash liquid-to-solid ratio from 5:1 to 10:1 often does not improve the alkali removal effect by more than 2 times), which is consistent with reality (excessive water addition increases filtration costs and is not a linear optimization). The relationship function quantitatively links the number of rewashes to the pH rebound repair effect, avoiding the trial-and-error approach of traditional processes. Furthermore, the introduction of the rewash liquid-to-solid ratio and the rebound coefficient can accommodate the residual alkali characteristics of different materials (e.g., materials with different fractal dimensions). The differences between them make relational functions universal.

[0059] 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.

[0060] 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. A method of LLZO residual alkali reduction, characterized by, Includes the following steps: S1, Add water to the LLZO material, stir, filter, repeat several times, and then age; S2, after aging, the liquid is boiled, naturally cooled to room temperature, filtered, and then boiled again with water. This process is repeated several times until the pH drops to 8, and then filtered and dried. S3, add water to the dried material obtained in step S2, boil, filter, and then dry.

2. The method for reducing residual alkali in LLZO as described in claim 1, characterized in that, It also includes the following steps: S4. The dried material obtained in step S3 is subjected to air jet milling to deagglomerate the particles, reducing the particle size to the nanoscale.

3. The method for reducing residual alkali in LLZO as described in claim 2, characterized in that, In step S3, the process of adding water to the dried material, boiling it, filtering it, and then drying it specifically includes: adding water to the dried material, boiling it, naturally cooling it to room temperature, filtering it, adding water to the filter cake, boiling it, filtering it, and repeating the above steps until pH=8.

4. The method for reducing residual alkali in LLZO as described in claim 3, characterized in that, In step S2, the boiling time is 30 minutes, the drying temperature is 110°C, and the drying time is 10 hours.

5. The method for reducing residual alkali in LLZO as described in claim 4, characterized in that, In step S3, the drying temperature is 110°C and the drying time is 10 hours.

6. The method for reducing residual alkali in LLZO as described in claim 5, characterized in that, The specific method for obtaining LLZO material includes: adding LLZO coarse powder to an alcohol solvent and then grinding it to obtain LLZO material.

7. The method for reducing residual alkali in LLZO as described in claim 6, characterized in that, In step S1, the process of adding water to the LLZO material, stirring, and filtering is repeated three times.

8. The method for reducing residual alkali in LLZO as described in claim 7, characterized in that, In step S2, the process of boiling the aged liquid, naturally cooling it to room temperature, filtering it, and then adding water and boiling it again is repeated three times.

9. An LLZO residual alkali reduction device, characterized in that, The LLZO residual alkali reduction equipment includes: Controller; Memory, which stores executable instructions; The executable instructions can run on the controller and implement the LLZO residual alkali reduction method as described in any one of claims 1 to 8.

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