Preparation method of NCA coated modified material

Abstract

The embodiment of the invention provides a preparation method of an NCA coated modified material, and belongs to the technical field of preparation of battery materials, the method comprises the following steps: providing nickel-cobalt-containing lithium aluminate NCA particles as a matrix material, and carrying out dispersion treatment on the NCA particles to ensure uniform particle size; the method comprises the following steps: forming a reaction mixing system by using a uniformly dispersed solution and a coating material containing aluminum oxide or magnesium oxide, and heating and stirring under a specific temperature condition so that the coating material can be effectively deposited on the surfaces of NCA particles; stirring is controlled based on preset time and speed parameters, and a coating material is promoted to be uniformly and firmly attached to the surfaces of NCA particles, so that the problem that a coating layer is not uniformly distributed or is poorly combined with a matrix is solved; and carrying out high-temperature heat treatment on the NCA particles with the coating layers under the protection of nitrogen so as to enhance the interface stability. Through the scheme of the embodiment of the invention, the problem of how to solve the problem of uneven distribution of the coating layer or poor combination with the matrix in the preparation process of the NCA coating modified material can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of battery material preparation, and in particular to a method for preparing an NCA-coated modified material. Background Art

[0002] The preparation method of NCA coated modified materials generally refers to a technical process, which involves forming a layer of stable protective material on the surface of NCA (nickel cobalt aluminum oxide) materials by physical or chemical means, so as to improve the electrochemical properties and stability of NCA materials and enhance their application effect in lithium-ion batteries. In the actual preparation process, a major problem may be faced - how to effectively control the good adhesion of the coating layer on the entire substrate surface and ensure its uniformity. Due to the uneven distribution of the coating layer or the inability to firmly adhere to the NCA substrate during the preparation process, it may lead to excessive exposure of battery active materials, increased side reactions, and shortened cycle life. The existence of these problems will not only affect the structural stability and electrochemical properties of the material itself, but will also further hinder the commercialization progress of NCA batteries in a wider range of applications. Therefore, how to overcome these defects of NCA coated modified materials is the key to improving the performance of the final lithium-ion battery. Summary of the invention

[0003] In view of this, the embodiments of the present disclosure provide a method for preparing an NCA-coated modified material, which at least partially solves the problems existing in the prior art.

[0004] A method for preparing an NCA coated modified material, the method comprising the following steps:

[0005] S101, providing nickel-cobalt-aluminate lithium NCA particles as a matrix material, and dispersing the NCA particles to ensure uniform particle size;

[0006] S102, using a uniformly dispersed solution and a coating material containing aluminum oxide or magnesium oxide to form a reaction mixture system, heating and stirring under specific temperature conditions so that the coating material can be effectively deposited on the surface of the NCA particles;

[0007] S103, controlling stirring based on preset time and speed parameters to promote the coating material to adhere evenly and firmly to the surface of the NCA particles, thereby solving the problem of uneven distribution of the coating layer or poor bonding with the substrate;

[0008] S104, subjecting the NCA particles with the coating layer to high temperature heat treatment under nitrogen protection to enhance interface stability.

[0009] Preferably, controlling the stirring based on pre-set time and speed parameters comprises:

[0010] S201. First, preset the time interval ΔT and set the stirring speed to Nrpm according to the experimental objective;

[0011] S202. Then, through the control system, adjust to the speed of Nrpm and start stirring within each ΔT time;

[0012] S203. When the current time reaches the next time point, i.e., the current time + ΔT, the control system reduces or maintains the stirring speed until the entire cycle is completed;

[0013] After the end of the entire cycle, check the coating uniformity to ensure that no abnormalities occur.

[0014] Further, controlling the stirring based on the preset time and speed parameters further includes:

[0015] If the current set speed and time meet the stirring effect, continue to run according to these parameters;

[0016] If N > Nmax or t < tmin, then change the stirring speed or time,

[0017] where _N_ represents the preset speed, Nmax represents the maximum speed, t represents the preset stirring time, and tmin represents the minimum time;

[0018] When it is found that the stirring effect is not good after inspection, reset the stirring speed or time, and return to execute the set stirring operation until the stirring effect meets the requirements;

[0019] On the premise of achieving the specified stirring effect, stop modifying the time or stirring speed.

[0020] The motion system records the final effective speed and time settings to ensure the consistency and reproducibility of future batches.

[0021] Further, the conditions for resetting meet the following conditions:

[0022] S401. Let the new value after the speed change be Nrpm, and judge if |NN| < δN and N >= Nth, where Nth represents the minimum reasonable rotational speed difference;

[0023] S402. If the above conditions are met, and if t + tadd >= ttotal and tadd is the additional stirring time period, where ttotal represents the total required duration to reach the stable state;

[0024] As long as all the foregoing logical tests yield positive results, correct the stirring time and stirring speed;

[0025] After the particle samples are stirred, the surface uniformity and consistency are confirmed by microstructure testing, and the steady-state condition is considered to be reached, and the stirring parameters are optimized accordingly.

[0026] Furthermore, the final stirring is tested to ensure that the stability is achieved under the following conditions:

[0027] S0501, confirm that the coverage ratio of the coating material on the particle surface under the microscopic image is not less than η_{min}, and this threshold is determined according to the needs and should be greater than 70%;

[0028] S0502, verify that the average particle size change D under the scanning electron microscope cannot be greater than the original average size D by more than μ%;

[0029] S0503, if |(DD) / D|*100>μ, repeat stirring, where μ represents the maximum allowable error threshold;

[0030] S0504, when the conditions are met, stop modifying the stirring process parameters to ensure that the thickness of the coating layer after stirring is not much different;

[0031] S0505, by comparing and testing the effects of different process conditions on NCA coating modification and selecting the optimal parameters for large-scale production.

[0032] Furthermore, the evaluation of the coating effect is further ensured by the following methods:

[0033] S601, determining the initial particle size (D) and coating thickness (L) by SEM microscopic examination of the NCA surface before and after stirring;

[0034] The theoretical prediction of the core / shell model for L_{th}(μm) is as follows for a core particle with R=5μm:

[0035] S602, if LL_{th}≤ε, then the coating is deemed qualified and meets the requirements;

[0036] S603, for unqualified samples, improve the original solution or replace the raw materials according to the size of the error ε and repeat the whole process until all indicators meet expectations;

[0037] By analyzing quality fluctuations between different batches and performing statistical evaluations, the quality management level of the production process can be continuously improved.

[0038] Preferably, controlling the stirring based on pre-set time and speed parameters comprises:

[0039] S701, firstly preset the time interval ΔT and the stirring speed Rpm according to the experimental target;

[0040] S702, secondly, starting the timing and stirring device under the set temperature conditions;

[0041] S703, adjusting the stirring process again according to the stirring time and speed;

[0042] S704, finally check whether the coating is evenly distributed after the stirring is completed.

[0043] Further, controlling the stirring based on pre-set time and speed parameters includes:

[0044] S801, determining a coating uniformity threshold ε and comparing it with a current detection value to verify whether the stirring time is reasonable;

[0045] S802, if ε is less than the set standard value, increase the stirring time ΔT to improve the coating uniformity;

[0046] S803, adjusting the stirring speed based on the actual stirring condition to ensure that the coating layer on the surface of the NCA particles is more evenly distributed;

[0047] S804, monitoring the stirring state through periodic sampling and characterization testing throughout the stirring process.

[0048] Furthermore, the process of adjusting the stirring speed based on the actual change of the stirring condition further includes:

[0049] S901, judging whether the dispersion performance of the NCA particles meets expectations based on the particle viscosity coefficient μ at the initial stage of stirring, where μ = τ / γ. When the coating begins to adsorb on the surface, the particle viscosity coefficient tends to increase with the increase of stirring time;

[0050] S902, based on the change of the viscosity coefficient of the NCA particles, the rotation speed is controlled in real time to make the relative movement between the particles smoother and more uniform;

[0051] S903, the monitoring and adjustment process is repeated multiple times until the coating distribution uniformity reaches the preset standard ε;

[0052] S904, characterize the coating quality, evaluate its uniformity and optimize the next processing parameters.

[0053] Furthermore, real-time speed control includes the following specific steps:

[0054] S1001, define the stirring efficiency η, which represents the ratio between the rotation speed Rpm and the coating adhesion rate under certain conditions: η = kR / δ, where k represents the bonding coefficient between the coating and the NCA particles and δ represents the actual coating weight per unit area;

[0055] S1002, when the measured result of η is less than the theoretical optimal stirring efficiency ηmax, the rotation speed is increased to make η approach the theoretical maximum value while avoiding the risk of damage caused by excessive collision intensity between NCA particles due to excessive acceleration;

[0056] S1003, re-detecting η after completing an adjustment cycle and comparing and judging with ηmax;

[0057] S1004, the speed adjustment process is continuously iterated and the best result is recorded as the standard basis for the next processing to ensure the quality of the final product.

[0058] After completing an adjustment cycle, η is compared with ηmax, which specifically includes the following steps:

[0059] S1101, if η>=ηmax, it is considered that the coating is sufficiently uniform, then the speed increase is stopped and the next processing step is entered;

[0060] S1102, if η<ηmax, then appropriately increase the stirring speed, wait for a period of time, and then test the value of η again to confirm whether the coating becomes more uniform;

[0061] S1103, repeating the above steps, continuously monitoring the stirring effect under the speed adjustment, and performing necessary intervention;

[0062] S1104, complete the final adjustment, confirm that after all steps are completed, the stirring operation can be stopped and the product can be processed to the next step to ensure the overall process efficiency and product quality.

[0063] The disclosed embodiment provides a method for preparing an NCA coated modified material, comprising the following steps: providing nickel cobalt lithium aluminate NCA particles as a matrix material, dispersing the NCA particles to ensure uniform particle size; using a uniformly dispersed solution and a coating material containing aluminum oxide or magnesium oxide to form a reaction mixture system, heating and stirring under specific temperature conditions so that the coating material can be effectively deposited on the surface of the NCA particles; controlling the stirring based on pre-set time and speed parameters to promote the coating material to adhere uniformly and firmly to the surface of the NCA particles, thereby solving the problem of uneven distribution of the coating layer or poor bonding with the matrix; and subjecting the NCA particles with the coating layer to high-temperature heat treatment under nitrogen protection to enhance interface stability. Through the solution of the disclosed embodiment, it is possible to solve the problem of uneven distribution of the coating layer or poor bonding with the matrix during the preparation of the NCA coated modified material. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0065] Figure 1 It is a flow chart of a method for preparing a NCA coated modified material;

[0066] Figure 2 It is a flow chart for controlling stirring based on pre-set time and speed parameters;

[0067] Figure 3 is a further flow chart for controlling stirring based on pre-set time and speed parameters;

[0068] Figure 4 It is a schematic diagram of the conditions that should be met for the reset;

[0069] Figure 5 is a flow chart of the conditions for testing after final mixing is completed to ensure that stability is achieved;

[0070] Figure 6 It is a schematic diagram of the process of evaluating the coating effect;

[0071] Figure 7 It is a process of controlling mixing based on pre-set time and speed parameters. Figure 1 ;

[0072] Figure 8 It is a process of controlling mixing based on pre-set time and speed parameters. Figure 2 ;

[0073] Fig. 9 is a further flow chart of the process of adjusting the stirring speed based on actual changes in stirring conditions;

[0074] Fig.10 It is a flow chart of the specific steps of real-time speed control;

[0075] Fig.11 It is a flowchart of the specific steps of comparing η and ηmax after completing an adjustment cycle. DETAILED DESCRIPTION

[0076] The embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0077] The following describes the embodiments of the present disclosure through specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the contents disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all of the embodiments. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present disclosure.

[0078] It should be noted that various aspects of the embodiments within the scope of the appended claims are described below. It should be apparent that the aspects described herein may be embodied in a wide variety of forms, and any specific structure and / or function described herein is merely illustrative. Based on the present disclosure, it should be understood by those skilled in the art that an aspect described herein may be implemented independently of any other aspect, and two or more of these aspects may be combined in various ways. For example, any number of aspects described herein may be used to implement the device and / or practice the method. In addition, other structures and / or functionalities other than one or more of the aspects described herein may be used to implement this device and / or practice this method.

[0079] Next, refer to Figure 1 The preparation method of this NCA coated modified material is described as follows:

[0080] S101: The particles containing lithium nickel cobalt aluminum oxide NCA are carefully selected as the basic skeleton, and the dispersion treatment is carried out on the basis of ensuring that the particle morphology and particle size are as consistent as possible. In order to achieve this goal, we usually choose to disperse the matrix particles by ball milling or stirring to make them uniformly dispersed to avoid agglomeration to form large particles and affect the effect of subsequent coating. For example, in an experimental environment, a certain amount of standard NCA particles such as 20g can be prepared, and then these particles can be placed in a stainless steel bottle or glass bottle with sufficient capacity, and an appropriate amount of dispersion medium such as water or isopropanol is added, and then mixed in a magnetic stirrer or planetary ball mill at a speed of about 600-1000 rpm for up to 45 minutes to 1 hour until the NCA particles can swim freely in the solution and are evenly distributed without agglomeration. The key at this stage is to make all particles in a relatively stable and uniform state, providing a good initial state foundation for further operations. In this way, the phenomenon of uneven subsequent coating caused by inconsistent substrates can be effectively prevented.

[0081] S102: Add a solution containing a powder of the selected material such as aluminum oxide or magnesium oxide to the uniformly dispersed matrix particles. This powder must be fully ground in advance to reduce the particle size to ensure smooth deposition. In order to form an ideal coating mixture, stirring the solution within a specific temperature range is one of the most important steps, which not only increases the contact area between the particles but also ensures that the particle surface can evenly adsorb the coating material to achieve good adhesion. In this example, assuming that aluminum oxide is selected for modification, we first prepare a 2% AlNO33·9H2O aqueous solution and add the dispersed NCA suspension. They are maintained in a constant temperature water bath at 85-90°C and stirred continuously for 4-6 hours until the coating process is completed, in order to obtain a uniform and stable deposition effect of the coating material on the particle surface, while ensuring that the contact surface between the particles is large enough for more uniform distribution. When performing this stage, the environmental conditions including temperature must be controlled to remain within the optimal range so that the coating can be effectively adsorbed on the surface of the particles without being affected by the external environment and becoming unstable.

[0082] On this basis, the stirring rate and reaction cycle are precisely adjusted to ensure that the adsorption of the coating material is comprehensive and deep, covering every corner of the particle surface and ensuring that the coating layer will not fall off due to excessive stirring or too short a time. To this end, the speed of the agitator can be controlled by a predefined program. In the above case, the speed is kept at 800RPM for 6 hours to ensure that the coating layer is firmly attached to the surface of the NCA particles and will not fall off. In actual operation, the temperature changes should be closely monitored to ensure that holes are not generated inside the coating layer due to excessive heating, thereby reducing the battery performance.

[0083] Finally, after the preliminary preparation work, heat treatment is performed to further consolidate the adhesion between the coating and the substrate and improve the overall thermal stability and chemical stability of the entire structure to meet the needs of battery application environments. Usually, the coated NCA particles are subjected to low-temperature heat treatment at 720±30℃ for 240-480 minutes in an inert atmosphere, that is, an N2 environment with a purity of more than 99.95%. This allows the formed film layer to be better solidified on the particle surface while eliminating possible residual gas molecules, thereby improving the quality stability and chemical durability of the overall product.

[0084] Through the effective combination of the above preparation processes, a series of challenges faced in the manufacture of NCA modified coating materials can be solved, especially the problem of poor material use due to unbalanced distribution or poor adhesion of the coating layer can be well prevented. In actual production practice and research experiments, the high-efficiency coating prepared in this way not only ensures the good reaction activity and cycle life of the battery components during charging and discharging, but also significantly improves the overall product performance and reduces the probability of adverse effects, creating a solid foundation for the development of high-performance new energy storage systems.

[0085] Next, refer to Figure 2 Describe the specific steps of controlling stirring according to preset time and speed parameters in a method for preparing a NCA coated modified material:

[0086] S201: The entire stirring control phase is started by presetting the key parameters of the experimental process. This step first involves determining a preset time interval ΔT and a specified stirring speed Nrpm required for stirring. These parameters can be set by control system programming or user input during implementation. For example, assuming the set value is ΔT = 5 minutes and Nrpm = 300, it means that the system will adjust to the predetermined speed at 300 revolutions per minute every 5 minutes and perform stirring operation.

[0087] S202: Then, at the beginning of each ΔT time period, the stirring device adjusts the stirring rate to the set target Nrpm through the automatic control system. Under this setting, once the current time point reaches a new stirring cycle start point, for example, after every five minutes, the control system will drive the stirring mechanism to accelerate to a predetermined stirring rate of 300 rpm to ensure the consistency of stirring and the uniformity of material distribution.

[0088] S203: Then, as the time progresses within the cycle, the stirring process continues until the next predetermined time point, that is, the current time plus ΔT, arrives. For example, when the stirring has been running for five minutes and reaches the preset point, the control system intervenes and manages the deceleration or maintenance of the speed according to the set logic to smoothly transition to the next stirring cycle.

[0089] S204: Under this setting, when the current stirring cycle reaches the preset stop time, the stirring device will either slow down to a low stirring level or even stop or continue to maintain the current stirring speed so that the material can be dispersed consistently in the subsequent stirring cycle. In this way, it is ensured that the material will not be damaged or coating uniformity problems will occur under excessive speed change rate.

[0090] S205: After the entire mixing cycle is completed, the technician will evaluate the integrity and uniformity of the material coating and verify that no abnormal conditions have occurred to prove whether the operating mode set in this process has successfully achieved the goal. Generally speaking, this evaluation involves physical inspections such as observing the state of the particle surface and chemical property analysis.

[0091] Through the above steps, the dynamic parameters in the mixing process can be effectively implemented and monitored to improve the product quality and performance characteristics of the manufactured material.

[0092] Next, refer to Figure 3 Describe the specific steps of controlling the stirring process according to the preset time and speed parameters in the preparation method of a NCA coated modified material:

[0093] S301: Monitoring and determination: The control system determines whether the stirring meets the set requirements by real-time monitoring and comparing whether the actual rotation speed _N_ of the stirrer is within the set operating window, that is, not exceeding the maximum rotation speed N_{max} and whether the preset stirring time _t_ exceeds the minimum continuous stirring requirement t_{min}. In this process, if the current actual setting meets the ideal stirring condition _N<=N_{max} and _t>=t_{min}, the stirring device maintains the original stirring parameters; if the actual speed exceeds the maximum allowable speed or the stirring time is lower than the minimum required value, it will enter the parameter adjustment stage.

[0094] S302: Dynamic adjustment and optimization of parameters: If it is found that the actual working parameters fail to achieve the ideal stirring performance conditions - that is, if the current set speed is too fast or the stirring time is too short, the control system will accordingly adjust the speed of the mixer or appropriately extend the duration of the stirring process to optimize the physical and mechanical environment of the entire process, improve material dispersion and coating uniformity, until the stirring state meets the standard; this adjustment process may be repeated until the stirring performance reaches the expected standard or meets the pre-set termination conditions such as the set stirring effect; at the same time, on this basis, it also ensures that the same level of product properties such as coating uniformity and stability can be obtained through the same stirring speed and holding time in future batches of production.

[0095] S303: End of stirring conditions and records: Once the stirring effect meets the predetermined evaluation index, any further adjustment of the stirring rate and time in the stirring operation will be immediately terminated to maintain the existing performance conditions. In order to ensure the accuracy, comparability, consistency and other requirements of future batch production, the control system will automatically save the effective mixer operating parameters after the stirring is completed for reference when the next batch of materials is produced. The purpose of this is to establish a stable standardized production process to avoid problems such as product quality fluctuations caused by operational differences.

[0096] Next, refer to Figure 4 Describe the specific steps of adjusting the stirring parameters under specific conditions involved in the preparation method of NCA coated modified materials:

[0097] S401: Determine the suitability of the newly set conditions by evaluating the speed of the current stirring process and its changes. Assume that the initial stirring speed is Nrpm, and after possible fine-tuning or changes, a new value NNrpm is formed. In order to ensure that this adjustment does not lead to excessive deviations and at least maintain the minimum rationality required for the stirring process, it is necessary to calculate the difference between the absolute values ​​of the two and determine whether this difference is less than the pre-defined threshold δN, which represents the maximum allowable change. At the same time, the new stirring speed value NN must not be less than the minimum feasible stirring speed threshold N_{th}. The purpose of this design is to ensure that the stability of the mixing process and the consistency of the particle surface modification are not significantly disturbed. The next step is considered only when these two logical conditions, namely |\NN-N\|<δN and NN≥\N_{th}\, are met;

[0098] S402: After confirming the above-mentioned new setting of the stirring speed, further verify the time arrangement of the overall stirring process. Specifically, based on the known actual stirring time, add the subsequent operation time \t_{add}\, and check whether this total time t+\t_{add}\ has reached the pre-set total target time, that is, the expected shortest duration for the stirring system to achieve uniform coating of the particulate material \t_{total}\ or has exceeded this value. This check is also to confirm that the system can still ensure sufficient stirring time after a specific speed correction in order to achieve the final uniform dispersion effect. If the judgment at this time is true, it means that the key control parameters in the stirring process can be further optimized;

[0099] S403: After confirming that the speed and the added time can be changed in the previous step, the stirring parameters are updated and executed according to the new situation. After the stirring is completed, a certain number of representative samples are obtained for microstructure testing. This includes the observation of the uniformity of the surface coverage of the material particles, which refers to the consistency of the distribution of the modified coating thickness in various parts, and the evaluation of the integrity of the coating microstructure. These experimental methods are mainly to verify whether the processing results after adjusting the parameters can meet the ideal technical specifications, especially the requirements for surface properties. Once the particle appearance quality and micromorphology are verified to meet the expected qualified standards, then it can be considered that the change plan of the stirring parameters is successful and can be used as a benchmark to further guide subsequent production operations or conduct further product modification tests.

[0100] Next, refer to Figure 5Describe the specific steps of the final stability condition test in the preparation method of NCA coated modified materials:

[0101] S501: First, confirm that the material surface is observed through appropriate analytical means such as an optical microscope, and ensure that the coated material has at least a specified minimum coverage, such as η_min greater than 70%, as a quality control standard; if it is not met, consider adjusting the previous process parameters such as temperature, mixing degree or additive concentration, and re-execute the stirring process to ensure that the quality of the final product meets the requirements.

[0102] S502: Next, the particle size of the NCA material particles after the coating process is measured using a scanning electron microscope (SEM). Compared with the average particle size of the initial uncoated material particles, the change shall not exceed a preset ratio μ%, where μ can be regarded as a control parameter to ensure the stability and size uniformity of the final product. The formula used to calculate the percentage change in particle diameter is: |D'-D / D|*100%, where D is the original particle size, and D' is the particle size obtained after the coating process. If the deviation exceeds the predetermined acceptable value, the process parameters need to be adjusted accordingly and the stirring process needs to be performed again until a qualified product is obtained before entering the next stage of the process steps;

[0103] S503: Monitor the performance characteristics of NCA materials under various processing conditions through continuous testing, especially whether the coating effect remains stable and consistent and whether the coating thickness after stirring changes, that is, the coating weight gain change rate. If the coating thickness has a large variation, it means that the process needs to be fine-tuned to achieve a consistent effect;

[0104] S504: Finally, based on the result data obtained from the laboratory test, the effects of various stirring parameters on the entire coating process are comprehensively evaluated to screen out the optimal combination of conditions and apply it to large-scale production practice. This can achieve scale while ensuring that each particle of material can be effectively and evenly coated.

[0105] Next, refer to Figure 6 Describe the specific steps for evaluating and ensuring the coating effect in a preparation method of NCA coated modified materials:

[0106] S601: Determining coating properties through microstructural analysis

[0107] After implementing the method described in claim 5, in order to further confirm the actual effect of the coating modification, the surface of NCA nickel cobalt aluminum lithium is subjected to SEM scanning electron microscopy before and after the mixing process. SEM inspection is used to accurately measure the particle size D in the original state and the layer thickness L after coating. This comparative microscopic inspection can not only provide intuitive information about the distribution and uniformity of the coating, but also obtain specific measurement data through direct images to assist in the determination of the quality of the coating layer and the subsequent adjustment of process parameters.

[0108] S602: Verification using theoretical values

[0109] According to the obtained coating material layer thickness L, it is compared with the theoretical coating thickness L_{th} calculated in advance based on the core / shell model. Here, the core particle with radius R = 5 microns is used as the model basis to theoretically predict the optimal thickness of the coating layer. If the actual measured thickness L obtained by experiment meets the following conditions: L≤L_{th} plus or minus error ε, ε is a threshold used to reflect the closeness between the actual value and the theoretical value, it is considered that the coating layer has reached the ideal state and can be regarded as a qualified product that meets expectations. The core here is to quantitatively compare the actual layer thickness data with the preset standard to determine whether the product meets the regulations.

[0110] S603: Continuous improvement and iteration based on feedback

[0111] If the sample is determined to be unqualified after the above evaluation steps, it is necessary to make appropriate adjustments to the production process or materials used according to the size of the error. This includes but is not limited to changing the coating precursor ratio, improving the operating parameters of the equipment during the coating process, or replacing different brands of basic particle raw materials. Then the full set of coating processes needs to be performed again, and the entire step needs to be reviewed to evaluate the modification results. This stage may need to be repeated many times until all relevant technical indicators fully meet the established goals.

[0112] S604: Quality Monitoring and Statistical Analysis

[0113] In addition, in order to improve the quality stability of the entire preparation process, samples of multiple batches of products are regularly taken for comparison and analysis, and the trend of quality fluctuations of finished products after each adjustment is closely monitored. Based on statistical data and trend evaluation, the effect of improvement measures in the production process can be more accurately evaluated, and the corresponding operating procedures or control parameters can be optimized and improved accordingly.

[0114] Next, refer to Figure 7 Describe the specific steps of controlling stirring according to preset time and speed parameters in a method for preparing a NCA coated modified material:

[0115] S701: Initialize the stirring process by setting the time interval ΔT and stirring speed Rpm under the preset experimental conditions. Before the actual preparation, the operation time and mixing rate of the stirring equipment must be clearly set according to the specific characteristics of the target coating material and the experimental requirements to ensure the consistency of subsequent process parameters. For example, in the preparation process of a certain NCA positive electrode material coating, the time interval that may need to be set is 20 minutes, and the stirring equipment runs at a speed of 600rpm.

[0116] S702: By setting the temperature environment required for the experiment, start the device for timing and material stirring. When the equipment is at the desired working temperature, which usually corresponds to the uniform dispersion of the NCA precursor within a specific temperature range, start the stirring timer and activate the stirring mechanism to achieve the preset stirring rate.

[0117] S703: Monitor and adjust the stirring process in real time according to the defined stirring time and speed. During this period, the technicians will pay close attention to the changes in the material state and the actual operation of the process equipment to ensure that the actual value remains close to the expected value. Assuming that the viscosity of the liquid decreases due to heating, the original stirring rate may need to be increased by 5% to adapt to the changes in the current fluid dynamics environment to ensure the uniformity of the coating layer distribution.

[0118] S704: The effect of stirring is finally confirmed by testing and analyzing the surface quality and performance indicators of the finished product, such as surface gloss. Once the stirring process is completed, appropriate evaluation methods, such as microscopic structure observation, need to be used to confirm that the material coating on the particles is evenly distributed. Assuming that the microscopic observation shows that the coating is evenly distributed, it indicates that the stirring parameters are appropriately selected; otherwise, the specific settings of time and speed need to be further optimized for the regulation of different stages.

[0119] Next, refer to Figure 8 Describe the specific steps of controlling stirring according to preset time and speed parameters in a method for preparing a NCA coated modified material:

[0120] S801: The whole process is started by establishing the preset stirring control parameters, and firstly, the coating uniformity threshold ε is defined, such as measured by the particle distribution or the uniformity of the coating material. This threshold is used to evaluate the quality of the NCA coating obtained under the current conditions and compare it with the preset standard value; if the actual measurement ε obtained is less than the standard threshold, it indicates that the current stirring may be insufficient, resulting in uneven distribution of the coating layer of the NCA particles, so it is necessary to improve the coating uniformity by extending the stirring time ΔT as a corrective measure.

[0121] S802: During the entire coating process, it is necessary to regularly fine-tune the stirring speed to ensure that the thickness and uniformity of the final coating layer meet the requirements; this means that after determining the initial stirring conditions, it is necessary to further consider how to dynamically fine-tune the stirring rate appropriately based on the current coating status of the NCA particles. For example, when the distance between the particles is large and the fluidity is good at the beginning, a slightly higher stirring rate can be selected to promote the coating liquid to penetrate into the gaps between the particles; and as the coating time progresses, the stirring speed should be slowed down to avoid damage or destruction of the already coated and relatively thin parts, so that the entire stirring operation can be more efficient and uniform.

[0122] S803: In order to monitor the effect of the above steps, periodic random sampling and performance measurement should be continuously carried out during the entire operation. These measurements may include but are not limited to the measurement of the average, thickest and thinnest thickness of the coating layer, the uniformity of the coating material on the particle surface distribution, etc., and the appearance of a single particle or its aggregate after coating can also be observed using equipment such as an electron microscope. In this way, sufficiently detailed and effective stirring process data can be obtained in real time to facilitate guidance for the next step of operation.

[0123] Next, refer to Fig. 9 Specific steps describing a method for adjusting stirring speed based on particle viscosity to improve coating uniformity:

[0124] S901: This step first evaluates the dispersion of NCA nickel-cobalt-aluminum particles in the liquid system based on the particle viscosity coefficient μ at the beginning of stirring. This evaluation defines the particle viscosity coefficient based on the ratio of τ / γ shear force to shear rate and monitors its change over time. Usually, when the coating begins to be adsorbed on the carrier surface, the viscosity coefficient shows a trend of gradually increasing over time. This step ensures that the initial distribution state of the NCA particles meets specific requirements so that the subsequent process can continue.

[0125] S902: Once the initial dispersion is understood, the stirring speed needs to be adjusted in real time according to the change in the particle viscosity coefficient μ to achieve uniform dispersion between particles. This is done by setting up a suitable stirring mechanism, which can make the suspended particles move in a smoother and more uniform state under the drive of this machine, preventing agglomeration or sedimentation.

[0126] S903: In the following process, the stirring rate will be continuously monitored and appropriately adjusted until the distribution of the coating on the solid carrier reaches the desired uniformity standard ε. The key here is to continuously monitor and adjust the speed in a timely manner to achieve the uniformity requirement of the coating distribution during the entire stirring process. When the monitoring meets the expected standard, it indicates that this round of coating treatment process has achieved the predetermined goal.

[0127] S904: Finally, various physical and chemical methods are used to characterize the quality of the coating to confirm that the final coating film has reached the predetermined target standard and has sufficient uniformity. Based on this test data feedback, various details of the stirring, such as the rotation speed, can be adjusted again for future production batches in order to further improve the efficiency and results of the coating.

[0128] Specifically, to actually apply this step:

[0129] If thin areas of coating are found during the experimental operation, the local rotation speed can be reduced to increase the time the NCA particles stay in these areas to enhance their deposition on the surface of this part of the substrate. At the same time, for areas where the coating is too thick, the rotation speed may be increased to promote the particles in these locations to diffuse more effectively to the surrounding thinner areas, achieving a more reasonable coating thickness and uniform coverage.

[0130] This approach can better control and adjust the quality and uniformity of the coating, and ensure that each NCA particle can fully contact the surface of the carrier substrate at an ideal speed and under ideal conditions to achieve the best adsorption effect. This adjustment can greatly improve the performance consistency and overall yield of the final product.

[0131] Next, refer to Fig.10 Describe the specific steps of real-time speed control:

[0132] S1001: Define stirring efficiency η and related control standards

[0133] First, the stirring efficiency η is defined and set as an indicator between the rotation speed Rpm and the adhesion rate of a coating, such as an aluminum coating, under certain conditions: that is, η = kR / δ. Here k represents the bonding coefficient between the coating and the NCA nickel-cobalt-aluminum composite particles, and δ refers to the actual coating weight per unit area.

[0134] In order to ensure the optimal adhesion performance of the coating, it is also necessary to establish a theoretical optimal stirring efficiency ηmax as an important parameter benchmark for adjusting the rotation speed.

[0135] S1002: Implement automatic speed control scheme

[0136] Once the stirring efficiency η is determined and monitored during the processing, if the measured η value is less than the expected theoretical optimal stirring efficiency ηmax, the rotation speed is automatically increased until η approaches ηmax. During this process, it is necessary to avoid excessively high rotation speeds to reduce the possibility of damage caused by violent impact between NCA particles.

[0137] When the speed reaches a certain level after one adjustment, the stirring efficiency η value under the new state should be measured again immediately and compared with its theoretical target value ηmax to evaluate whether it is close enough to the optimal value.

[0138] S1003: Iterative optimization of mixing control process

[0139] The above speed control and efficiency adjustment process needs to be executed continuously in a loop. After each iteration, the most ideal speed setting scheme and the obtained optimal stirring efficiency value are recorded as the basic reference for future processing operations of the same type of products, so as to ensure the consistency and controllability of product quality. This mechanism enables standardized management of the process.

[0140] Next, refer to Fig.11 Describe the steps of adjusting the η value in a method for preparing an NCA coated modified material:

[0141] S1101: First, after completing a preset time interval as a cycle of stirring and coating formation, the system performance parameter η representing a measure of coating uniformity is compared with a set standard value ηmax. If the observed η value is equal to or exceeds ηmax, that is, η≥ηmax, this indicates that the predetermined maximum stirring effect or sufficient coating uniformity standard has been achieved, so further acceleration of the stirring device is suspended and the next operation process is entered to ensure that the material structure or properties will not be damaged due to excessive processing.

[0142] S1102: When the η value is less than ηmax, that is, η<ηmax, it means that the existing stirring conditions have not made the coating reach the required uniformity level. At this time, it is necessary to appropriately increase the working speed of the stirring device to promote the mixing effect. After a certain residence time, repeat the test of the new coating distribution. Repeat this cycle until the coating distribution tends to the expected uniform state.

[0143] S1103: During the entire adjustment process, the influence of speed parameters in the mixing system on material distribution must be continuously monitored, and necessary speed control measures must be taken based on the test data; this continuous monitoring process can detect deviations in a timely manner and respond to them to avoid unnecessary waste or product quality fluctuations.

[0144] S1104: After the final η value reaches or stabilizes at the ηmax level, confirm that the stirring operation has achieved the optimal effect and terminate the corresponding speed change. At this time, it can be considered that the entire dynamic tuning process has come to an end and the modified material can be transferred to the next processing link, such as drying and other subsequent steps. This not only ensures that the product has excellent and stable performance but also ensures that the entire process has a high economic value.

[0145] In actual operation, when this device is used, a batch of NCA particles containing nickel cobalt aluminum oxide lithium must first be provided as the matrix material, and it is ensured that these NCA particles are dispersed by appropriate means so that their particle size reaches the uniformity requirement, which is a crucial basic condition for subsequent processing. After the dispersion treatment is completed, the uniform solution prepared by a special process is precisely mixed with a substance containing a coating material such as aluminum oxide or magnesium oxide to construct a reaction mixture system. In order to ensure that the coating layer can effectively and stably cover the surface of the NCA particles under predetermined conditions, it is necessary to strictly follow the temperature control standards under the guidance of the process, and to finely control the heating and stirring processes. Under the accurately calculated time and speed, through continuous mixing and stirring, the coating material gradually reacts chemically under the action of heating and is deposited on the surface of the NCA particles, and finally forms a coating layer evenly and firmly, solving the problems that may have occurred before, such as uneven coating or low adhesion between the coating and the substrate. Next, the NCA particles with the above-mentioned treatment and preliminary coating layer are placed in a high-temperature environment under nitrogen protection. By implementing high-temperature heat treatment under preset temperature and time conditions, the structural integrity between the coating layers and the interface bonding strength with the substrate are further strengthened, ensuring the final output of high-quality NCA coated modified materials with better performance. In the entire workflow, each step needs to be carefully coordinated to ensure that the finished product meets the predetermined standards and technical requirements.

[0146] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing an NCA coated modified material, characterized in that: The method includes the following steps: S101, providing lithium nickel cobalt aluminate (NCA) particles as the matrix material, and dispersing the NCA particles to ensure uniform particle size; S102, forming a reaction mixture system by using a uniformly dispersed solution and a coating material containing alumina or magnesia, and heating and stirring under specific temperature conditions so that the coating material can be effectively deposited on the surface of the NCA particles; S103, controlling the stirring based on preset time and speed parameters to promote the uniform and firm attachment of the coating material to the surface of the NCA particles, thereby solving the problems of uneven distribution of the coating layer or poor bonding with the matrix; S104, performing high-temperature heat treatment on the NCA particles with the coating layer under nitrogen protection to enhance the interface stability.

2. The method for preparing a NCA coated modified material according to claim 1, characterized in that: Controlling the stirring based on preset time and speed parameters includes: S201, first presetting a time interval ΔT and a stirring speed set to Nrpm according to the experimental target; S202, then adjusting to a rotation speed of Nrpm through the control system to start stirring within each ΔT time; S203, when the current time reaches the next time point, i.e., the current time + ΔT, the control system reduces or maintains the stirring speed until the end of the entire cycle; After the end of the entire cycle, check the coating uniformity to ensure that no abnormalities occur.

3. The method for preparing a NCA coated modified material according to claim 2, characterized in that: Controlling the stirring based on preset time and speed parameters further includes: If the currently set speed and time meet the stirring effect, continue to run according to these parameters; If N > N_max or t < t_min, then change the stirring speed or time, where N represents the preset speed, N_max represents the maximum speed, t represents the preset stirring time, and t_min represents the minimum time; When it is found that the stirring effect is不佳 after inspection, reset the stirring speed or time, and return to execute the set stirring operation until the stirring effect meets the requirements; On the premise of achieving the specified stirring effect, stop modifying the time or the stirring speed. The motion system records the final effective speed and time settings to ensure the consistency and reproducibility of future batches.

4. The method for preparing a NCA coated modified material according to claim 3, characterized in that: The conditions for resetting meet the following conditions: S401, setting the new value after the speed change to Nrpm, and judging if |N - N| < δN and N >= N_th, where N_th represents the minimum reasonable rotational speed difference; S402, if the above conditions are met, and if t + t_add >= t_total and t_add is the additional stirring time period, where t_total represents the total required duration to reach the stable state; As long as all the foregoing logical tests yield positive results, correct the stirring time and the stirring speed; After the particle sample after stirring is subjected to microstructure detection to confirm its surface uniformity and consistency, it is considered to reach the steady-state condition and the stirring parameters are optimized accordingly.

5. The method for preparing a NCA coated modified material according to claim 4, characterized in that: The conditions for ensuring stability after the final stirring are: S0501, confirming that the coverage ratio of the coating material on the particle surface under the microscopic image is not less than η_min, and this threshold is determined according to requirements and should be greater than 70%; S0502, verify that the average particle size change D under the scanning electron microscope cannot be greater than the original average size D by more than μ%; S0503, if |(DD) / D|*100>μ, repeat stirring, where μ represents the maximum allowable error threshold; S0504, when the conditions are met, stop modifying the stirring process parameters to ensure that the thickness of the coating layer after stirring is not much different; S0505, by comparing and testing the effects of different process conditions on NCA coating modification and selecting the optimal parameters for large-scale production.

6. The method for preparing a NCA coated modified material according to claim 5, characterized in that: The evaluation of the coating effect is further ensured by the following methods: S601, determining the initial particle size (D) and coating thickness (L) by SEM microscopic examination of the NCA surface before and after stirring; The theoretical prediction of the core / shell model for L_{th}(μm) is as follows for a core particle with R=5μm: S602, if LL_{th}≤ε, then the coating is deemed qualified and meets the requirements; S603, for unqualified samples, improve the original solution or replace the raw materials according to the size of the error ε and repeat the whole process until all indicators meet expectations; By analyzing quality fluctuations between different batches and performing statistical evaluations, the quality management level of the production process can be continuously improved.

7. The method for preparing a NCA coated modified material according to claim 1, characterized in that: Controlling agitation based on pre-set time and speed parameters includes: S701, firstly preset the time interval ΔT and the stirring speed Rpm according to the experimental target; S702, secondly, starting the timing and stirring device under the set temperature conditions; S703, adjusting the stirring process again according to the stirring time and speed; S704, finally check whether the coating is evenly distributed after the stirring is completed.

8. The method for preparing a NCA coated modified material according to claim 7, characterized in that: Controlling agitation based on pre-set time and speed parameters also includes: S801, determining a coating uniformity threshold ε and comparing it with a current detection value to verify whether the stirring time is reasonable; S802, if ε is less than the set standard value, increase the stirring time ΔT to improve the coating uniformity; S803, adjusting the stirring speed based on the actual stirring condition to ensure that the coating layer on the surface of the NCA particles is more evenly distributed; S804, monitoring the stirring state through periodic sampling and characterization testing throughout the stirring process.

9. The method for preparing a NCA coated modified material according to claim 8, characterized in that: The process of adjusting the stirring speed based on the actual change of the stirring condition further includes: S901, judging whether the dispersion performance of the NCA particles meets expectations based on the particle viscosity coefficient μ at the initial stage of stirring, where μ = τ / γ. When the coating begins to adsorb on the surface, the particle viscosity coefficient tends to increase with the increase of stirring time; S902, based on the change of the viscosity coefficient of the NCA particles, the rotation speed is controlled in real time to make the relative movement between the particles smoother and more uniform; S903, the monitoring and adjustment process is repeated multiple times until the coating distribution uniformity reaches the preset standard ε; S904, characterize the coating quality, evaluate its uniformity and optimize the next processing parameters.

10. The method for preparing a NCA coated modified material according to claim 9, characterized in that: Real-time speed control includes the following specific steps: S1001, define the stirring efficiency η, which represents the ratio between the rotation speed Rpm and the coating adhesion rate under certain conditions: η = kR / δ, where k represents the bonding coefficient between the coating and the NCA particles and δ represents the actual coating weight per unit area; S1002, when the measured result of η is less than the theoretical optimal stirring efficiency ηmax, the rotation speed is increased to make η approach the theoretical maximum value while avoiding the risk of damage caused by excessive collision intensity between NCA particles due to excessive acceleration; S1003, re-detecting η after completing an adjustment cycle and comparing and judging with ηmax; S1004, the speed adjustment process is continuously iterated and the best result is recorded as the standard basis for the next processing to ensure the quality of the final product. After completing an adjustment cycle, η is compared with ηmax, which specifically includes the following steps: S1101, if η>=ηmax, it is considered that the coating is sufficiently uniform, then the speed increase is stopped and the next processing step is entered; S1102, if η<ηmax, then appropriately increase the stirring speed, wait for a period of time, and then test the value of η again to confirm whether the coating becomes more uniform; S1103, repeating the above steps, continuously monitoring the stirring effect under the speed adjustment, and performing necessary intervention; S1104, complete the final adjustment, confirm that after all steps are completed, the stirring operation can be stopped and the product can be processed to the next step to ensure the overall process efficiency and product quality.

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