A Lithium Manganese Iron Phosphate Battery and a Method for Molding Its Shell

Abstract

The present invention discloses a lithium iron manganese phosphate battery and a method for forming its housing, comprising: adding a dual-responsive system containing organic coordination groups and mechanically sensitive particles to a metal matrix in a liquid or semi-cured state; applying cyclic thermal loads and mechanical loads to the modified metal matrix, and simultaneously introducing an electrolyte containing phosphate groups to obtain data on the migration and enrichment of manganese ions; analyzing the manganese ion diffusion parameters and stress distortion parameters based on the obtained data, and performing decoupling analysis to obtain stress corrosion data; finally, through accelerated aging treatment, obtaining spectral response, local stress, and interfacial electrochemical data, and accordingly regulating the forming process parameters. The technical solution of the present invention realizes the early identification of microscopic corrosion caused by the activation of manganese ions through a dual-responsive system during the forming process of the housing of the lithium iron manganese phosphate battery, and accurately evaluates the corrosion risk through multi-physical field coupling analysis, thereby preventing and controlling potential safety hazards caused by manganese corrosion at the source.

Description

Technical Field

[0001] The present invention relates to the field of detection technology in the production and manufacturing of battery shells, and in particular to a lithium manganese iron phosphate battery and a shell molding method thereof. Background Art

[0002] Lithium iron manganese phosphate (LiFeMnPO4) battery is a new type of lithium-ion battery. Its positive electrode material is lithium iron manganese phosphate, which has the advantages of good safety, long cycle life and low cost. This type of battery has broad application prospects in electric vehicles, energy storage systems and other fields.

[0003] During the manufacturing and service of lithium manganese iron phosphate batteries, the battery shell materials face special corrosion challenges. This is mainly due to the unique activation characteristics of manganese under specific temperature, humidity and electrochemical conditions, which makes the shell prone to microscopic side reactions during high-temperature welding, vacuum drying, liquid injection and other stages in the manufacturing process. This reaction can cause imperceptible early corrosion risks on the surface or inner layer of the shell. Unlike conventional metal materials, the shell of lithium manganese iron phosphate batteries is simultaneously subjected to high-temperature stress and mechanical deformation, as well as the migration and precipitation of manganese ions in a complex electrolyte environment. This "electrochemical-mechanical" coupling effect may form an enrichment of manganese corrosion products at local interfaces or gaps, leading to extremely small grain boundary cracks or local passivation layer peeling.

[0004] Traditional appearance inspection, hardness test or simple mechanical fatigue analysis is difficult to capture such hidden defects in the early stage. Once these potential corrosion points are aggravated during the later high-rate discharge and thermal shock process, they may cause serious safety accidents. At present, mass-produced shells may carry these invisible defects after leaving the factory or assembly, and general metal flaw detection technology is difficult to effectively identify them. Conventional surface morphology scanning or mechanical fatigue testing is also unable to accurately characterize the coupling effect of manganese ion migration and stress corrosion. Therefore, how to accurately identify and quantitatively evaluate such potential defects in the multi-stage process before shell molding and packaging has become a core technical problem that needs to be solved urgently. Summary of the invention

[0005] The main purpose of the present invention is to solve the technical problem that in the existing process of forming the shell of lithium manganese iron phosphate battery, the hidden danger of microscopic corrosion caused by the activation of manganese ions cannot be discovered and evaluated in time.

[0006] A first aspect of the present invention provides a shell molding method for a lithium manganese iron phosphate battery, the shell molding method for the lithium manganese iron phosphate battery comprising:

[0007] During the liquid or semi-cured forming stage of the metal matrix, a part of the metal matrix is obtained as a sample to be tested, and a dual-responsive system is added to the sample to be tested. The dual-responsive system includes an organic coordination group with manganese ion coordination function and a mechanically sensitive particle. The dual-responsive system is distributed in the internal and surface regions of the sample to be tested, and the modified sample to be tested is obtained;

[0008] Apply cyclic thermal load and mechanical load to the modified sample to be tested, and at the same time introduce an electrolyte containing phosphate group into the modified sample to be tested. Through the dual-responsive system, obtain the migration and enrichment data of manganese ions in the modified sample to be tested, and obtain the manganese corrosion response data;

[0009] According to the manganese corrosion response data, obtain the diffusion parameter and stress distortion parameter of the manganese ions, and perform decoupling analysis on the manganese corrosion response data to obtain the stress corrosion data induced by manganese ions;

[0010] According to the stress corrosion data, perform accelerated aging treatment on the modified sample to be tested, obtain spectral response data, local stress data and interfacial electrochemical data, and adjust the forming process parameters of the remaining metal matrix according to the obtained data.

[0011] Optionally, before adding the dual-responsive system to the sample to be tested, it includes:

[0012] Perform plasma activation treatment on the sample to be tested to form a nano-scale rough structure on the surface of the sample to be tested, and obtain the surface-pretreated sample to be tested;

[0013] Introduce an inert conductive polymer into the surface-pretreated sample to be tested to form a uniformly distributed conductive layer, and obtain the pretreated sample to be tested.

[0014] Optionally, adding the dual-responsive system to the sample to be tested, the dual-responsive system includes an organic coordination group with manganese ion coordination function and a mechanically sensitive particle. The dual-responsive system is distributed in the internal and surface regions of the sample to be tested, and the modified sample to be tested is obtained, including:

[0015] Inject an organic coordination group containing multiple mercapto groups into the internal region of the pretreated sample to be tested. The organic coordination group containing multiple mercapto groups forms a stable coordination structure with manganese ions to obtain the internally modified sample to be tested;

[0016] Coat the surface region of the internally modified sample to be tested with nano-metal particles with stress-sensitive groups on the surface. The nano-metal particles deform under mechanical stress to obtain the surface-modified sample to be tested;

[0017] The surface-modified sample to be tested is subjected to vacuum impregnation treatment, so that the organic coordination groups containing multiple mercapto groups and the nano metal particles form a synergistic distribution structure, and the modified sample to be tested is obtained.

[0018] Optionally, a cyclic thermal load and a mechanical load are applied to the modified sample to be tested, and at the same time, an electrolyte containing phosphate is introduced into the modified sample to be tested. Migration and enrichment data of manganese ions in the modified sample to be tested are obtained through the dual-response system, and manganese corrosion response data are obtained, including:

[0019] An electrolyte containing phosphate is introduced into the modified sample to be tested, and the initial coordination signal of the organic coordination group is obtained to obtain initial coordination data;

[0020] According to the initial coordination data, a cyclic thermal load and a mechanical load are applied to the modified sample to be tested, and the coordination signal change of the organic coordination group and the deformation signal of the mechanically sensitive particles are obtained to obtain response change data;

[0021] According to the response change data, the manganese ion enrichment region in the modified sample to be tested is determined, and the stress distribution data of the manganese ion enrichment region are obtained to obtain manganese corrosion response data.

[0022] Optionally, the step of, according to the initial coordination data, applying a cyclic thermal load and a mechanical load to the modified sample to be tested, and obtaining the coordination signal change of the organic coordination group and the deformation signal of the mechanically sensitive particles to obtain response change data includes:

[0023] The detection region is determined according to the initial coordination data, and the detection region is subjected to thermal cycling treatment at a heating rate of 2 °C / min in the temperature range of 25 °C to 45 °C, and the change in the coordination signal intensity of the organic coordination group is obtained to obtain thermal response data;

[0024] According to the thermal response data, a high-signal response region is selected, and thermal cycling is performed at a heating rate of 3 °C / min in the temperature range of 45 °C to 65 °C, and at the same time, a periodic compressive stress of 0.5 MPa to 2 MPa is applied, and the coordination signal change curve of the organic coordination group and the stress-strain curve of the mechanically sensitive particles are obtained to obtain load response data;

[0025] According to the load response data, the first ratio of the signal intensity value of each detection point in the coordination signal change curve to the initial coordination data, and the second ratio of the displacement of each detection point in the stress-strain curve to the reference displacement measured at 25 °C are calculated, and the overlapping part of the regions where the first ratio is greater than 1.5 and the second ratio is greater than 1.002 is calibrated to obtain response change data.

[0026] Optionally, based on the manganese corrosion response data, obtaining the diffusion parameter and stress distortion parameter of the manganese ions, and performing decoupling analysis on the manganese corrosion response data to obtain stress corrosion data induced by manganese ions, including:

[0027] Based on the manganese corrosion response data, extracting the change rate of the coordination signal intensity of the organic coordination group in the temperature range of 25°C to 65°C and the deformation response rate of the mechanically sensitive particles in the stress range of 0.5 MPa to 2 MPa to obtain dual-response change data;

[0028] Based on the dual-response change data, determining the target region where the ratio of the change rate of the coordination signal intensity to the deformation response rate is greater than 1.5, and obtaining the diffusion coefficient of manganese ions in the target region;

[0029] Analyzing the change trend of the diffusion coefficient in the temperature range of 45°C to 65°C, and obtaining the acceleration factor of the diffusion coefficient with the increase of temperature;

[0030] Determining the high-risk region where the acceleration factor is greater than 2.0, and obtaining the stress concentration coefficient under the stress of 0.5 MPa to 2 MPa in the high-risk region to obtain stress corrosion data induced by manganese ions.

[0031] Optionally, based on the dual-response change data, determining the target region where the ratio of the change rate of the coordination signal intensity to the deformation response rate is greater than 1.5, and obtaining the diffusion coefficient of manganese ions in the target region, including:

[0032] Calculating the ratio of the change rate of the coordination signal intensity to the deformation response rate at each detection point in the dual-response change data, and screening out the set of detection points with a ratio greater than 1.5;

[0033] Performing adjacent point connection analysis on the set of detection points, and dividing adjacent detection points with a spacing less than 100 microns into the same target region;

[0034] Respectively obtaining the manganese ion concentration gradient data at 25°C and 45°C in the target region, and calculating the diffusion coefficient of manganese ions in the target region according to the change rate of the concentration gradient with time.

[0035] Optionally, based on the stress corrosion data, performing accelerated aging treatment on the modified sample to be tested, obtaining spectral response data, local stress data and interfacial electrochemical data, and regulating the forming process parameters of the remaining metal matrix according to the obtained data, including:

[0036] According to the distribution of the high-risk regions induced by manganese ions in the stress corrosion data, performing cyclic temperature rise treatment on the modified sample to be tested at 65°C to 85°C to obtain the spectral response data of the organic coordination group;

[0037] During the cyclic temperature increase treatment, a cyclic stress load of 2 MPa to 5 MPa is applied to the high-risk area to obtain local stress data of the mechanically sensitive particles;

[0038] Injecting an electrolyte with a pH value of 3 to 4 into the sample to be tested, applying a potential scan from -0.5 V to 1.0 V to the high-risk area, and acquiring interface electrochemical data;

[0039] Determine the accelerated corrosion rate of the high-risk area according to the spectral response data, local stress data and interface electrochemical data, and establish a corresponding relationship between manganese corrosion risk and molding process parameters;

[0040] According to the corresponding relationship, the forming temperature, stress distribution and surface treatment process parameters of the remaining metal matrix are adjusted to achieve process control of manganese corrosion risk.

[0041] A second aspect of the present invention provides a lithium manganese iron phosphate battery, the lithium manganese iron phosphate battery comprising a shell, and the shell is prepared by the shell molding method of the lithium manganese iron phosphate battery described in the above embodiment.

[0042] The technical solution provided in the embodiment of the present application is to extract part of the material as the sample to be tested when the metal matrix is ​​still in a liquid state or semi-solidified, and add a combination structure containing an organic coordination group and mechanically sensitive particles thereto so that it is evenly distributed on the surface and inside of the sample. The original intention of doing so is that a probe that can respond to the coordination behavior of manganese ions and stress changes has been buried at the key node before the material is fully finalized. Subsequently, a cyclic heat load and a mechanical load are applied to the modified sample, and a phosphate-containing electrolyte is introduced at the same time. Since the organic coordination group will produce a characteristic coordination signal with the migrated or enriched manganese ions, and the mechanically sensitive particles will respond to the local stress distortion, these two types of signals together constitute a set of monitoring systems that can reflect the process of "diffusion and stress state evolution of manganese in the metal matrix" in real time. On this basis, by decoupling the manganese corrosion response data, the degree and distribution of manganese ion-induced stress corrosion can be analyzed, providing direction for subsequent accelerated aging treatment. Finally, the corrosion risk is comprehensively evaluated through various data such as spectral response, local stress, and interface electrochemistry, and targeted adjustments are made to the forming process of the remaining metal matrix (such as parameters such as temperature gradient, surface treatment, or stress distribution).

[0043] This idea of detecting and grading manganese-induced corrosion at an early stage of self-forming significantly improves the ability to capture microscopic hidden defects. Compared with only conducting finished product inspections at a later stage, here the potential activation tendency of manganese ions and local stress concentration areas can be sensed before the macroscopic shaping of the material. Once extremely small cracks or local corrosion begin to occur, the above dual-response system will show corresponding perturbations in chemical coordination signals and mechanical deformation signals, and can quantitatively output key parameters such as the diffusion coefficient of manganese ions and the degree of stress concentration. Accelerated aging further magnifies these early signs, making potential hazards that may only erupt during high-rate discharge or thermal shock at a later stage appear in advance, and the process control link can accordingly correct the temperature curve, pressure application method, surface passivation treatment, or nanostructure modification during shaping, thereby reducing the probability of large-area diffusion or local concentration of stress corrosion at the source. Through this series of detection and control means throughout the entire forming process, the problem of difficult to accurately identify and quantitatively evaluate microscopic corrosion hazards at an early stage can be effectively solved, realizing rapid early warning and prevention and control of corrosion risks caused by the activation characteristics of manganese. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0045] Figure 1 It is a schematic diagram of an embodiment of the method for forming the housing of a lithium iron manganese phosphate battery in an embodiment of the present invention.

[0046] The realization of the purpose, functional characteristics, and advantages of the present invention will be further described in conjunction with the embodiments with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0048] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0049] In addition, the descriptions involving "first", "second", etc. in the present invention are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, "and / or" throughout the text includes three scenarios. Taking A and / or B as an example, it includes the technical solution of A, the technical solution of B, and the technical solution where both A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, which must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0050] An embodiment of the present application provides a method for forming a housing of a lithium iron manganese phosphate battery. Figure 1 FIG. is a flowchart of a method for forming a housing of a lithium iron manganese phosphate battery provided by an embodiment of the present application. In this embodiment, the method includes:

[0051] Please refer to Figure 1 , in the liquid or semi-cured molding stage of the metal matrix, obtain a part of the metal matrix as a test sample, add a dual-responsive system to the test sample, the dual-responsive system includes an organic coordination group with manganese ion coordination function and mechanical sensitive particles, and the dual-responsive system is distributed in the internal and surface regions of the test sample to obtain a modified test sample;

[0052] In an embodiment of the present invention, before adding the dual-responsive system to the test sample, it includes:

[0053] Perform plasma activation treatment on the test sample to form a nano-scale rough structure on the surface of the test sample to obtain a surface-pretreated test sample;

[0054] Introduce an inert conductive polymer into the surface-pretreated test sample to form a uniformly distributed conductive layer to obtain a pre-treated test sample.

[0055] The following specifically describes the steps involved in the above embodiments:

[0056] When performing plasma activation treatment on a sample to be tested, the sample to be tested needs to be placed in a vacuum environment. By introducing inert gases such as argon or nitrogen and maintaining a stable radio frequency or direct current power, ions can form a high-speed bombardment effect on the surface of the sample to be tested. Commonly used instruments include radio frequency plasma systems or direct current glow discharge devices. The specific values of gas flow and plasma power are controlled according to the material tolerance and nanostructure requirements. Ion bombardment will remove the relatively flat oxide layer or other attachments on the surface of the sample to be tested and produce uneven textures on the microscopic scale, causing nanoscale protrusions or pores to be distributed on the surface. By adjusting the treatment time and gas type, different degrees of roughness can be obtained, enabling the substances introduced subsequently to be more easily dispersed in the nanopores. The result achieved by this process is the formation of a three-dimensional structure in the surface area, which is conducive to the tight binding of the substances introduced subsequently to the metal matrix and increases the overall stability.

[0057] After completing the above surface activation, an inert conductive polymer needs to be evenly coated or infiltrated into the pretreated surface area. Optional inert conductive polymers include polyaniline, polypyrrole, or poly(3,4-ethylenedioxythiophene), etc., which have good conductivity and strong chemical inertness. Generally, solution coating or electrochemical deposition methods are used to introduce such polymers. A spin coater or an electrochemical workstation can be used on the instrument to ensure a continuous distribution without obvious faults in the surface microstructure. If further improvement in dispersion is required, appropriate temperature control or slight vacuum assistance can be supplemented to allow the polymer to fully diffuse in the nanopores. Through this process, a uniform and continuous conductive polymer network is finally formed on the rough surface. Such a design not only improves the overall conductivity but also enables a more uniform stress transfer and electrochemical environment distribution when subsequent electrochemical or mechanical loads are encountered.

[0058] In an embodiment of the present invention, adding a dual-responsive system to the sample to be tested, the dual-responsive system includes an organic coordination group with manganese ion coordination function and mechanical stress-sensitive particles, and the dual-responsive system is distributed in the internal and surface regions of the sample to be tested to obtain a modified sample to be tested, including:

[0059] Injecting an organic coordination group containing multiple mercapto groups into the internal region of the pretreated sample to be tested, and the organic coordination group containing multiple mercapto groups forms a stable coordination structure with manganese ions to obtain an internally modified sample to be tested;

[0060] Coating the surface region of the internally modified sample to be tested with nano-metal particles surface-modified with stress-sensitive groups, and the nano-metal particles deform under mechanical stress to obtain a surface-modified sample to be tested;

[0061] The surface-modified sample to be tested is subjected to vacuum impregnation treatment, so that the organic coordination groups containing multiple mercapto groups form a synergistic distribution structure with the nano metal particles, and the modified sample to be tested is obtained.

[0062] The following specifically describes the steps involved in the above embodiments:

[0063] In the first step, the pretreated sample to be tested is placed in a dedicated impregnation or injection device, and an organic solution or precursor containing multiple mercapto functional groups is introduced, so that the solution gradually penetrates into the internal region of the sample to be tested. To ensure that the solution fully penetrates at the pore and microcrack positions, low-pressure impregnation or constant-flow injection methods can be combined, and a constant time is maintained in a certain temperature environment, so that the mercapto groups are firmly dispersed inside the material. The organic compound with a multi-mercapto structure forms a stable coordination bond with metal ions and will exhibit characteristic coordination behavior when contacting manganese ions subsequently. Therefore, the enrichment or diffusion process of manganese ions can be strengthened through this approach. After this step, the obtained internally modified sample will provide a more obvious coordination signal when contacting exogenous manganese ions subsequently.

[0064] In the second step, nano-scale metal particles are uniformly dispersed on the surface region of the internally modified sample by means of coating or spraying techniques, and stress-sensitive groups are attached to the surfaces of these metal particles. A spin coater or an inkjet deposition instrument can be used to control the coating thickness and uniformity, so that the stress-sensitive groups are stably combined with the metal particles and form a continuous or semi-continuous distribution on the surface. The type of metal particles can be selected according to the mechanical response requirements. For example, silver or gold-based nanostructures that are more sensitive to local stress changes can be used. The surface-modified sample formed in this step will undergo slight deformation in the particle layer when subjected to mechanical loads, and generate a recordable or quantifiable signal through the stress-sensitive groups, thereby reflecting the local stress concentration or deformation conditions.

[0065] In the third step, the surface-modified sample is further placed in a vacuum impregnation device, and the preset vacuum degree and temperature conditions are maintained, so that the multi-mercapto organic coordination groups and the nano metal particles penetrate and synergistically distribute at the interface. This process can be adjusted by stepped vacuum degree or assisted by a low-viscosity solvent treatment, so that the modified components inside and on the surface gradually come into contact and form a tight bond in the nano-pores or microstructures. After this operation, the modified sample has the dual signal response ability to the electrochemical environment and mechanical stress at the overall level, and also has the synergistic coupling effect between the internal coordination groups and the surface particles. After this step, the obtained modified sample can capture and feedback the signs of manganese ion migration and stress corrosion more stably in the subsequent environment.

[0066] Please continue to refer to Figure 1, apply cyclic thermal load and mechanical load to the modified sample to be tested, and simultaneously introduce an electrolyte containing phosphate groups into the modified sample to be tested. Obtain the migration and enrichment data of manganese ions in the modified sample to be tested through the dual-response system, and obtain manganese corrosion response data;

[0067] In one embodiment of the present invention, applying cyclic thermal load and mechanical load to the modified sample to be tested, and simultaneously introducing an electrolyte containing phosphate groups into the modified sample to be tested, obtaining the migration and enrichment data of manganese ions in the modified sample to be tested through the dual-response system, and obtaining manganese corrosion response data, includes:

[0068] Introduce an electrolyte containing phosphate groups into the modified sample to be tested, obtain the initial coordination signal of the organic coordination group, and obtain initial coordination data;

[0069] According to the initial coordination data, apply cyclic thermal load and mechanical load to the modified sample to be tested, obtain the change of the coordination signal of the organic coordination group and the deformation signal of the mechanically sensitive particles, and obtain response change data;

[0070] According to the response change data, determine the manganese ion enrichment region in the modified sample to be tested, obtain the stress distribution data of the manganese ion enrichment region, and obtain manganese corrosion response data.

[0071] The following specifically describes the steps involved in the above embodiments:

[0072] In the first step, place the modified sample to be tested in a sealed or open container, introduce an electrolyte solution or aerosol containing phosphate groups, and make the electrolyte fully contact with the organic coordination group. The injection method can use a constant pressure or flow injection device, combined with a soaking or flowing process for a certain period of time to ensure that the organic coordination group and the phosphate environment reach a stable binding state. Under this condition, record the starting signal corresponding to the organic coordination group through fluorescence, absorption spectroscopy or an electrochemical workstation, and obtain the initial coordination data for subsequent comparison and analysis. This step presents the basic binding degree between the internal modified structure and the external electrolyte by measuring the coordination state without external load.

[0073] In the second step, based on the initial coordination data obtained above, cyclic thermal loads and mechanical loads are applied to the modified sample to be tested. For the cyclic thermal load, a high and low temperature alternating test chamber can be used to set a reciprocating temperature change from a lower temperature to a higher temperature, and a predetermined time is maintained in each temperature range; the mechanical load is applied by a loading platform or a material fatigue testing machine to apply a pressure or tensile force of a specific magnitude and frequency. During this process, spectroscopic or electrochemical means are used to monitor the drift amount of the organic coordination group signal, while a strain gauge or a nanoparticle sensor is used to collect the deformation data of the mechanically sensitive particles, and the coordination signal change and the deformation signal are recorded and correlated with each other to obtain response change data. This step helps to observe the coupling effect presented by the internal coordination system and the surface mechanically sensitive structure under the superposition condition of thermal stress and mechanical stress.

[0074] In the third step, according to the aforementioned response change data, the position of the region with manganese ion enrichment in the modified sample to be tested can be determined by analyzing the spatial distribution and the trend of change with the load of the coordination signal and the deformation signal. To further quantify the mechanical state of these regions, a stress distribution test system (such as micro-area Raman stress measurement or high-resolution strain sensor) can be used to perform point-by-point or regional scanning on the specified positions, so as to obtain the stress distribution data corresponding to the manganese ion enrichment, and the two are combined to generate manganese corrosion response data. Through this process, the correlation between manganese ion diffusion enrichment and local stress concentration can be understood at the macroscopic and microscopic levels, providing a scientific basis for subsequent forming process control or failure prevention measures.

[0075] In an embodiment of the present invention, applying cyclic thermal loads and mechanical loads to the modified sample to be tested according to the initial coordination data, obtaining the coordination signal change of the organic coordination group and the deformation signal of the mechanically sensitive particles, and obtaining response change data includes:

[0076] Determine the detection area according to the initial coordination data, perform thermal cycling on the detection area at a heating rate of 2 °C / min in the temperature range of 25 °C to 45 °C, obtain the change in the coordination signal intensity of the organic coordination group, and obtain thermal response data;

[0077] Select a high signal response area according to the thermal response data, perform thermal cycling at a heating rate of 3 °C / min in the temperature range of 45 °C to 65 °C, and simultaneously apply a periodic compressive stress of 0.5 MPa to 2 MPa to obtain the coordination signal change curve of the organic coordination group and the stress-strain curve of the mechanically sensitive particles, and obtain load response data;

[0078] According to the load response data, calculate the first ratio of the signal intensity value of each detection point in the coordination signal change curve to the initial coordination data, and the second ratio of the displacement of each detection point in the stress-strain curve to the reference displacement measured at 25°C. Calibrate the overlapping part of the area where the first ratio is greater than 1.5 and the second ratio is greater than 1.002 to obtain the response change data.

[0079] The following specifically describes the steps involved in the above embodiments:

[0080] In the first step, based on the previous coordination data, select a detection area with obvious coordination signal differences at room temperature (around 25°C), and use a controllable temperature device or a high and low temperature test chamber to increase the temperature from 25°C to 45°C at a heating rate of 2°C / min. The consideration for this range and heating rate setting is to preliminarily explore the thermosensitive characteristics of the organic coordination groups in the material, and the range from 25°C to 45°C usually covers the transition stage of the sample from room temperature to slightly higher than the conventional operating environment. During this heating process, the coordination signal may tend to gradually increase or decay with the increase in temperature. By collecting the signal intensity changes through spectroscopic or electrochemical methods, the preliminary thermal response law presented in the low to medium temperature range can be identified. The thermal response data obtained in this stage provides a reference threshold for subsequent tests in a larger temperature range to more accurately define the high signal response area.

[0081] In the second step, select the detection points that show obvious coordination signal changes or high curve fluctuations in the above thermal response data, and use the same or similar controllable temperature device to continue increasing the temperature from 45°C to 65°C at a heating rate adjusted to 3°C / min. This temperature range and heating rate are higher and faster than the previous stage, aiming to simulate a more severe working environment and simultaneously amplify the thermosensitive reaction of the organic coordination groups. During the heating process, apply a periodic compressive stress of 0.5 MPa to 2 MPa through a loading platform or a material mechanics testing machine. The periodic stress usually simulates the mechanical shock or fatigue load that the material may encounter in the use scenario. Use a strain gauge or other mechanical sensing devices to record the stress-strain curve of the particles and simultaneously monitor the intensity change of the coordination signal curve to obtain the load response data. This is to identify the potential areas in the material that are more prone to coupled stress corrosion under the combined action of temperature and stress, and to judge the signal performance of the organic coordination groups at different stress levels.

[0082] In the third step, based on the aforementioned load response data, calculate the signal intensity ratio of each detection point in the coordination signal curve of the organic coordination group relative to the initial coordination data, and the ratio of the displacement amount of each detection point in the stress-strain curve of the mechanically sensitive particles relative to the displacement amount under the reference condition of 25°C. Through comparative analysis, determine the overlapping part of the regions where the signal intensity ratio exceeds 1.5 times and the displacement amount ratio exceeds 1.002 times. These overlapping regions indicate that both obvious coordination signal fluctuations and mechanical responses beyond the normal range occur at these locations, meaning that under the combined action of increasing temperature and periodic compressive stress, these regions exhibit abnormal activity. The response change data obtained through this quantitative ratio analysis method can accurately identify potential corrosion and stress concentration risk regions in the material, providing clear target regions for subsequent regulation or accelerated aging treatment.

[0083] Please continue to refer to Figure 1 , and according to the manganese corrosion response data, obtain the diffusion parameter and stress distortion parameter of the manganese ions, and perform decoupling analysis on the manganese corrosion response data to obtain stress corrosion data induced by manganese ions;

[0084] In an embodiment of the present invention, the step of obtaining the diffusion parameter and stress distortion parameter of the manganese ions according to the manganese corrosion response data, and performing decoupling analysis on the manganese corrosion response data to obtain stress corrosion data induced by manganese ions includes:

[0085] According to the manganese corrosion response data, extract the coordination signal intensity change rate of the organic coordination group in the temperature range of 25°C to 65°C and the deformation response rate of the mechanically sensitive particles in the stress range of 0.5 MPa to 2 MPa to obtain dual-response change data;

[0086] According to the dual-response change data, determine the target region where the ratio of the coordination signal intensity change rate to the deformation response rate is greater than 1.5, and obtain the diffusion coefficient of manganese ions in the target region;

[0087] Analyze the change trend of the diffusion coefficient in the temperature range of 45°C to 65°C to obtain the acceleration factor of the diffusion coefficient with the increase of temperature;

[0088] Determine the high-risk region where the acceleration factor is greater than 2.0, and obtain the stress concentration coefficient under the stress action of 0.5 MPa to 2 MPa in the high-risk region to obtain stress corrosion data induced by manganese ions.

[0089] The following specifically describes the steps involved in the above embodiments:

[0090] In the first step, based on the manganese corrosion response data obtained from previous detections and analyses, the coordination signals of organic ligand groups collected at temperature conditions ranging from 25°C to 65°C are selected, and combined with the deformation records of mechanically sensitive particles within the stress range of 0.5 MPa to 2 MPa. The slopes of the change in coordination signal intensity with temperature and the change in particle deformation degree with stress are calculated respectively. The temperature range covers normal temperature to the moderate heating range, and a high and low temperature cycling chamber or a controllable environmental chamber can be used to gradually increase the temperature and record spectral or electrochemical signals; the stress range covers moderate mechanical loads, and a materials testing machine or a strain gauge acquisition device can be used to adjust the load and measure in real time. By separately differentiating or taking the difference of the coordination signals and deformation data, the change rates of the coordination signal intensity and the deformation response rate can be intuitively obtained, and the synchronous evolution of the chemical coordination process and the mechanical deformation process in the material is confirmed at this stage.

[0091] In the second step, based on the dual-response change data obtained in the first paragraph, by comparing the ratio of the change rate of the coordination signal intensity to the deformation response rate, the regions with a ratio higher than 1.5 are selected as the target regions, and then the manganese ion diffusion process within the target regions is measured. If further analysis of the diffusion coefficient is required, the known Fick diffusion equation or other common electrochemical analysis models in the field of materials science can be combined to fit or interpolate the evolution trend of the concentration distribution of manganese ions with time or space in the target regions. Such diffusion models are usually widely used in the fields of materials science and corrosion analysis to describe the transport behavior of ions in solid or liquid media. Based on this method, the diffusion coefficient of manganese ions within the target regions can be obtained, laying a numerical foundation for evaluating the potential corrosion sensitivity.

[0092] In the third step, using the diffusion coefficient determined in the previous step, the acceleration effect of the diffusion rate with the increase in temperature is evaluated within the temperature range of 45°C to 65°C. The Arrhenius relationship or other common temperature-dependent models can be combined to analyze the change trend of the diffusion rate, so as to extract the acceleration factor. Such models are usually regarded as mature theoretical means to describe the doubling of diffusion or reaction rates in different temperature ranges, and help to quickly quantify the corrosion risk faced by materials under higher temperature conditions. The consideration for setting the upper temperature limit at 65°C is to cover the upper temperature limit of common application scenarios and reveal the potential of high-temperature accelerated corrosion within a safe range.

[0093] In the fourth step, regions with an acceleration factor greater than 2.0 are screened and identified as high-risk regions. Then, a stress of 0.5 MPa to 2 MPa is applied within this range, and the stress concentration coefficient of the mechanically sensitive particles is measured. Finally, stress corrosion data induced by manganese ions are obtained. The acceleration factor threshold can be understood as a demarcation point for the enhanced diffusion phenomenon. If the value increases significantly, it indicates a higher risk of manganese migration inside the material under this temperature condition. At this time, by comparing the changes in the stress concentration coefficient at different load levels, the corresponding relationship between corrosion intensity and mechanical distortion can be established. This step is completed using strain gauges or high-resolution stress distribution testing equipment. The recorded stress concentration information combined with the previous diffusion analysis can clearly identify the distribution of coupled corrosion hazards in the material due to manganese activation behavior.

[0094] In one embodiment of the present invention, determining the target region where the ratio of the coordination signal intensity change rate to the deformation response rate is greater than 1.5 according to the dual-response change data and obtaining the diffusion coefficient of manganese ions in the target region includes:

[0095] Calculating the ratio of the coordination signal intensity change rate to the deformation response rate for each detection point in the dual-response change data, and screening out the set of detection points with a ratio greater than 1.5;

[0096] Performing adjacent point connection analysis on the set of detection points, and dividing adjacent detection points with a spacing less than 100 microns into the same target region;

[0097] Obtaining the manganese ion concentration gradient data at 25 °C and 45 °C temperatures respectively in the target region, and calculating the diffusion coefficient of manganese ions in the target region according to the change rate of the concentration gradient over time.

[0098] The following specifically describes the steps involved in the above embodiment:

[0099] In the first step, it is necessary to extract the coordination signal intensity change rate and the deformation response rate point by point from the dual-response change data, and divide these two values to obtain the corresponding ratio. This calculation process can be batch processed using numerical analysis software or script writing methods, and each detection point is assigned a ratio. During the operation, the coordination signal and deformation data are first calibrated for the baseline to ensure the comparability between different measurement conditions. For detection points with a ratio exceeding 1.5, they can be marked in the data table or classified separately, and finally a set of detection points is formed. A too high ratio often represents that the response of the organic ligand at this position is significantly higher than the mechanical deformation level, indicating more obvious chemical activity or corrosion sensitivity.

[0100] In the second step, adjacent point connection analysis needs to be performed based on the spatial coordinate information of the detection point set. This process can cluster the detection points or calculate the nearest neighbor distance through two-dimensional or three-dimensional data visualization tools, and consider the distance between any two points less than 100 microns as continuous distribution, and then classify these adjacent points into the same target area. The above approach is conducive to aggregating scattered high-value points into a coherent area, making subsequent positioning and processing more targeted. For application scenarios that may require extremely high resolution, relevant analysis can combine micro-area microscopy techniques to accurately calibrate the positions of the detection points, thereby further improving the data accuracy.

[0101] In the third step, for the identified target areas, manganese ion concentration gradients are collected at 25 °C and 45 °C respectively. The measurement method of the concentration gradient can be selected from micro-area electrochemical probes, X-ray energy spectra, or other common composition distribution analysis methods. By performing differential or slope operations on the concentration distribution curves at different time points at the same temperature, the change rate of the concentration gradient with time can be obtained, and the diffusion coefficient of manganese ions in the target area can be calculated in combination with materials science knowledge or recognized diffusion models. Selecting 25 °C and 45 °C is to compare the differences in the diffusion ability of manganese in this area under normal temperature and moderate temperature rise conditions, making subsequent evaluations of corrosion risks and process adjustments more valuable for reference.

[0102] Please continue to refer to Figure 1 , according to the stress corrosion data, perform accelerated aging treatment on the modified sample to be tested, obtain spectral response data, local stress data, and interfacial electrochemical data, and regulate the forming process parameters of the remaining metal matrix according to the obtained data.

[0103] In an embodiment of the present invention, the performing accelerated aging treatment on the modified sample to be tested according to the stress corrosion data, obtaining spectral response data, local stress data, and interfacial electrochemical data, and regulating the forming process parameters of the remaining metal matrix according to the obtained data includes:

[0104] According to the distribution of high-risk areas induced by manganese ions in the stress corrosion data, perform cyclic temperature rise treatment on the modified sample to be tested from 65 °C to 85 °C to obtain the spectral response data of the organic coordination groups;

[0105] During the cyclic temperature rise treatment, apply a cyclic stress load of 2 MPa to 5 MPa to the high-risk areas to obtain the local stress data of the mechanically sensitive particles;

[0106] Inject an electrolyte with a pH value of 3 to 4 into the sample to be tested, and apply a potential scan of -0.5 V to 1.0 V to the high-risk areas to obtain interfacial electrochemical data;

[0107] Determine the accelerated corrosion rate of the high-risk area based on the spectral response data, local stress data, and interfacial electrochemical data, and establish the corresponding relationship between the manganese corrosion risk and the forming process parameters;

[0108] Adjust the forming temperature, stress distribution, and surface treatment process parameters of the remaining metal matrix according to the corresponding relationship to achieve process control of the manganese corrosion risk.

[0109] The following is a specific description of the steps involved in the above embodiments:

[0110] In the first step, it is necessary to first clarify the specific location of the high-risk area based on the stress corrosion data obtained previously, and then place the modified sample to be tested in a programmable thermal cycling device or a high and low temperature test chamber, so that its temperature changes reciprocally between 65°C and 85°C, and collect the spectral signals of the organic coordination groups at specified time intervals. Spectral analysis can be completed by an absorption spectroscopy or fluorescence spectroscopy device, and the response amplitude of the coordination groups with temperature changes can be observed in real time according to the characteristic peak positions of different coordination groups. The reason for performing cyclic heating in the range of 65°C to 85°C is to amplify the possible corrosion phenomena in a higher temperature range, facilitate identifying the sensitivity of the high-risk parts to the thermal environment, and obtain the coordination behavior data under high temperature conditions.

[0111] In the second step, while performing cyclic heating, a stress of 2 MPa to 5 MPa needs to be applied to the high-risk area, and the loading method is set to pulsed or intermittent cycling. The mechanical loading equipment can be a material mechanics testing machine or a multi-channel mechanical load platform, and the load is applied and unloaded at regular intervals through a pre-programmed control program. The mechanically sensitive particles will undergo significant deformation under stress, and the local stress data can be collected by strain gauges or other micro-area sensors. The range of 2 MPa to 5 MPa is selected considering that a certain degree of mechanical stress can often exacerbate the defect expansion of the material, thereby amplifying the corrosion response in a high temperature environment, so as to obtain more discriminative data information.

[0112] In the third step, after completing the above-mentioned thermal and mechanical coupling operations, an electrolyte with a pH of 3 to 4 is introduced into the sample to be tested, and a potential scan of -0.5 V to 1.0 V is performed on the high-risk area. The pH range of 3 to 4 can make the environment show strong acidic characteristics, thereby further accelerating the corrosion process to evaluate the actual performance of the high-risk area in a strong corrosion environment. The potential scan can be performed by an electrochemical workstation. During the operation, a forward or reverse scan is performed in the above potential range, and the current response curve is recorded. The interfacial electrochemical data obtained in this way can reflect the corrosion kinetic characteristics of the modified layer or the metal matrix in an acidic environment.

[0113] In the fourth step, comprehensively compare the above spectral response data, local stress data, and interfacial electrochemical data, and summarize them into the same analysis platform or perform multi-dimensional correlation with the aid of data processing software to calculate the corrosion rate of high-risk areas under the interaction conditions of temperature rise, stress, and acidic environment. The spectral response can reveal the chemical state changes of coordination groups, the mechanical data can reflect the degree of local deformation, and the electrochemical results can present redox or ion migration behaviors. Through vertical or horizontal numerical comparison, a rapid assessment of the manganese corrosion risk can be made under different load and temperature conditions, and a corresponding relationship between the manganese corrosion risk and the forming process parameters can be formed, facilitating the identification of the most vulnerable corrosion-triggering links under specific parameter combinations.

[0114] In the fifth step, according to the above corresponding relationship, start to adjust the forming process conditions of the remaining metal matrix. The temperature curve during forming can be finely tuned, a more appropriate pressure distribution strategy can be selected, or the material formula and treatment sequence during surface treatment can be changed, thereby weakening the corrosion inducement of high-risk areas at the source. The adjustment strategy can be implemented when the temperature control equipment cooperates with the mechanical loading platform, or the cleaning or activation parameters can be changed before surface treatment to reduce the impact of manganese ion diffusion and stress concentration on the material safety. By appropriately modifying the forming process parameters, the effects of reducing potential corrosion failures and improving overall reliability can be achieved.

[0115] The present invention also provides a lithium iron manganese phosphate battery, which includes a housing. The preparation method of the housing adopts the housing forming method of any one of the above embodiments for the lithium iron manganese phosphate battery. Therefore, the lithium iron manganese phosphate battery at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.

[0116] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the description and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A shell forming method for a lithium manganese iron phosphate battery, characterized in that: include: In the liquid or semi-solid forming stage of the metal matrix, a part of the metal matrix is ​​obtained as a sample to be tested, and a dual response system is added to the sample to be tested, wherein the dual response system includes an organic coordination group with a manganese ion coordination function and mechanically sensitive particles, and the dual response system is distributed in the interior and surface areas of the sample to be tested to obtain a modified sample to be tested; A phosphate-containing electrolyte is introduced into the modified sample to be tested to obtain an initial coordination signal of the organic coordination group and obtain initial coordination data; a detection area is determined according to the initial coordination data, and a thermal cycle treatment is performed on the detection area at a temperature range of 25°C to 45°C at a heating rate of 2°C / min to obtain a change in the coordination signal intensity of the organic coordination group and obtain thermal response data; a high signal response area is selected according to the thermal response data, and a thermal cycle is performed at a heating rate of 3°C / min in a temperature range of 45°C to 65°C, and a periodic compressive stress of 0.5MPa to 2MPa is applied to obtain the coordination signal of the organic coordination group. The load response data is obtained by comparing the signal change curve of the coordination signal change curve with the stress-strain curve of the mechanically sensitive particle; according to the load response data, a first ratio of the signal intensity value of each detection point in the coordination signal change curve to the initial coordination data, and a second ratio of the displacement of each detection point in the stress-strain curve to the reference displacement measured at 25°C are calculated, and the overlapping part of the region where the first ratio is greater than 1.5 and the second ratio is greater than 1.002 is calibrated to obtain response change data; according to the response change data, the manganese ion enrichment region in the modified sample to be tested is determined, and the stress distribution data of the manganese ion enrichment region is obtained to obtain manganese corrosion response data; According to the manganese corrosion response data, the coordination signal intensity change rate of the organic coordination group in the temperature range of 25°C to 65°C and the deformation response rate of the mechanically sensitive particle in the stress range of 0.5MPa to 2MPa are extracted to obtain dual response change data; the ratio of the coordination signal intensity change rate to the deformation response rate of each detection point in the dual response change data is calculated, and a set of detection points with a ratio greater than 1.5 is screened out; Performing adjacent point connection analysis on the detection point set, dividing adjacent detection points with a spacing of less than 100 microns into the same target area; acquiring manganese ion concentration gradient data at temperatures of 25° C. and 45° C. in the target area, respectively, and calculating the diffusion coefficient of manganese ions in the target area according to the rate of change of the concentration gradient over time; Analyze the change trend of the diffusion coefficient in the temperature range of 45°C to 65°C to obtain the acceleration factor of the diffusion coefficient with increasing temperature; Determine the high-risk area where the acceleration factor is greater than 2.0, obtain the stress concentration coefficient of the high-risk area under the stress of 0.5 MPa to 2 MPa, and obtain the stress corrosion data induced by manganese ions; According to the stress corrosion data, the modified sample to be tested is subjected to accelerated aging treatment to obtain spectral response data, local stress data and interface electrochemical data, and the molding process parameters of the remaining metal matrix are adjusted according to the obtained data.

2. The shell forming method of the lithium manganese iron phosphate battery according to claim 1, characterized in that: Before adding the dual response system to the sample to be tested, the method comprises: Performing plasma activation treatment on the sample to be tested to form a nanometer-scale rough structure on the surface of the sample to be tested, thereby obtaining the sample to be tested after surface pretreatment; An inert conductive polymer is introduced into the sample to be tested after the surface pretreatment to form a uniformly distributed conductive layer to obtain the pretreated sample to be tested.

3. The shell forming method of the lithium manganese iron phosphate battery according to claim 2, characterized in that: The dual response system is added to the sample to be tested, wherein the dual response system includes an organic coordination group having a manganese ion coordination function and mechanically sensitive particles, and the dual response system is distributed in the interior and surface areas of the sample to be tested to obtain a modified sample to be tested, including: Injecting an organic coordination group containing a multi-thiol group into the internal area of ​​the pretreated sample to be tested, wherein the organic coordination group containing a multi-thiol group forms a stable coordination structure with the manganese ion to obtain an internally modified sample to be tested; Coating nano-metal particles whose surfaces are modified with stress-sensitive groups to the surface area of ​​the internally modified sample to be tested, wherein the nano-metal particles are deformed under the action of mechanical stress to obtain a surface-modified sample to be tested; The surface-modified sample to be tested is subjected to vacuum impregnation treatment, so that the organic coordination groups containing polythiol groups and the nano-metal particles form a coordinated distribution structure, thereby obtaining the modified sample to be tested.

4. The shell forming method of the lithium manganese iron phosphate battery according to claim 1, characterized in that: According to the stress corrosion data, the modified sample to be tested is subjected to accelerated aging treatment to obtain spectral response data, local stress data and interface electrochemical data, and the molding process parameters of the remaining metal matrix are adjusted according to the obtained data, including: According to the distribution of high-risk areas induced by manganese ions in the stress corrosion data, the modified sample to be tested is subjected to a 65° C. to 85° C. cycle heating treatment to obtain spectral response data of the organic coordination group; During the cyclic temperature increase treatment, a cyclic stress load of 2 MPa to 5 MPa is applied to the high-risk area to obtain local stress data of the mechanically sensitive particles; Injecting an electrolyte with a pH value of 3 to 4 into the sample to be tested, applying a potential scan from -0.5 V to 1.0 V to the high-risk area, and acquiring interface electrochemical data; Determine the accelerated corrosion rate of the high-risk area according to the spectral response data, local stress data and interface electrochemical data, and establish a corresponding relationship between manganese corrosion risk and molding process parameters; According to the corresponding relationship, the forming temperature, stress distribution and surface treatment process parameters of the remaining metal matrix are adjusted to achieve process control of manganese corrosion risk.

5. A lithium manganese iron phosphate battery, characterized in that: The lithium manganese iron phosphate battery includes a shell, and the shell is prepared by the shell molding method of the lithium manganese iron phosphate battery according to any one of claims 1 to 4.

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