Power battery failure analysis method

Abstract

The invention relates to the technical field of batteries, in particular to a power battery failure analysis method. The invention provides a power battery failure analysis method which comprises the following steps: performing appearance detection on a failed power battery to obtain appearance information, and judging whether the appearance of the failed power battery is damaged or not; when the appearance of the failed power battery is not damaged, carrying out nondestructive detection and destructive detection on the failed power battery in sequence; when the appearance of the failed power battery is damaged, carrying out damage detection on the failed power battery; and analyzing the failure reason of the failed power battery according to the detection result. According to the power battery failure analysis method, the failure power battery can be comprehensively analyzed, the failure reason of the power battery can be obtained, the weak link in each component can be found out, the improvement of the power battery can be directly guided from the mechanism, the service life of the power battery can be prolonged, the safety of the power battery can be improved, and the commercial application of the power battery can be further promoted.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a power battery failure analysis method. Background Art

[0002] With the rapid popularization of electric vehicles, consumers and automakers are paying more and more attention to battery safety issues. Power batteries are not only the main power source and core components of electric vehicles, but also the main technical barrier to their rapid development. Lithium batteries are widely used in mobile phones, electric vehicles, mobile power supplies and other fields due to their high energy density, high cycle life and high environmental protection.

[0003] However, safety accidents such as lithium battery fires caused by thermal runaway and battery management systems have become a huge challenge for the development of new energy vehicles. The combustion of lithium-ion batteries is accompanied by a large amount of heat and gas, which is not only easy to cause explosions, but also produces a large amount of harmful gases during the combustion process, such as hydrogen fluoride, olefins, alkanes, ethers and other compounds, posing a threat to people's lives and property safety. In addition, as the energy density of positive electrode materials approaches its limit, it is difficult to significantly increase the capacity of lithium-ion batteries and it is difficult to meet the needs of the development of new energy vehicles.

[0004] Solid-state batteries are a new type of battery technology that uses solid electrolytes with high ion conductivity and high stability to replace flammable and explosive organic electrolytes. It can greatly improve the intrinsic safety performance of the battery and broaden the application scenarios of the battery. Data shows that the energy density of the current mainstream liquid lithium batteries is about 200 to 300Wh / kg, while the energy density of solid-state lithium batteries can reach up to 500Wh / kg, and the operating temperature range can be extended to -50 to 200°C. At the same time, its charging time is shortened to 1 / 3 of that of liquid lithium batteries. Solid-state batteries can continue to use the liquid lithium battery material system, and the mechanical and chemical properties are more stable, without technical problems such as electrolyte leakage and drying. It is expected that the mass production cost will be only 30% of the current liquid lithium-ion battery, and it is regarded as one of the best battery solutions for future new energy vehicles.

[0005] Traditional thermal runaway analysis of battery cells is to conduct a detailed analysis of the power battery cells after thermal runaway. This kind of analysis will inevitably cause damage to the battery cells during the analysis process. At the same time, in the process of disassembling the battery cells, interference factors will inevitably be introduced, leading to misleading and interference with the true cause analysis, which is neither scientific nor precise. At the same time, due to the drastic changes in the physical and chemical forms of the above-mentioned batteries, the above-mentioned disassembly and analysis methods have limitations such as complex methods, insufficient detection capabilities, and low accuracy, resulting in various problems in the process of power battery fault diagnosis, resulting in a large amount of personnel costs, time costs and equipment investment.

[0006] In view of this, this invention is proposed. Summary of the invention

[0007] The purpose of the present invention is to provide a power battery failure analysis method, which can comprehensively analyze the failed power battery, obtain the cause of the power battery failure, and then directly guide the improvement of the power battery from the mechanism.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0009] The present invention provides a power battery failure analysis method, comprising the following steps:

[0010] Perform appearance inspection on the failed power battery to obtain appearance information and determine whether the appearance of the failed power battery is damaged;

[0011] When the appearance of the failed power battery is not damaged, the failed power battery is subjected to nondestructive testing and destructive testing in sequence; when the appearance of the failed power battery is damaged, the failed power battery is subjected to destructive testing; and the failure cause of the failed power battery is analyzed based on the test results.

[0012] Furthermore, the power battery includes a lithium battery.

[0013] Further, based on the appearance information and the result of the nondestructive testing, the failure phenomenon and failure cause of the power battery are predicted; or, based on the appearance information, the failure phenomenon and failure cause of the power battery are predicted.

[0014] Furthermore, after predicting the failure phenomenon and failure cause of the power battery, destructive testing is performed to obtain the failure cause of the failed power battery.

[0015] Furthermore, the appearance information includes breakage, corrosion damage, combustion damage and flatulence.

[0016] Furthermore, the non-destructive testing includes electrochemical performance testing and / or in-situ testing characterization.

[0017] Further, the electrochemical performance test includes a capacity test and / or an impedance test;

[0018] And / or, the in-situ test characterization includes CT imaging test and / or X-ray imaging test.

[0019] Furthermore, the failure phenomenon includes at least one of capacity attenuation, impedance increase, flatulence, thermal runaway and internal short circuit.

[0020] Furthermore, the destructive detection includes: disassembling the failed power battery to obtain the internal components of the battery; testing the internal components of the battery; the internal components of the battery include at least one of a positive electrode sheet, a negative electrode sheet, a positive electrode active material, a negative electrode active material, a current collector, a separator, an electrolyte, a solid electrolyte, a gas and a binder.

[0021] Further, the tests performed on the internal components of the battery include at least one of energy dispersive X-ray spectroscopy test, inductively coupled plasma mass spectrometry test, X-ray photoelectron spectroscopy test, scanning electron microscopy test, transmission electron microscopy test, X-ray diffraction test, neutron diffraction test, nuclear magnetic resonance test, Raman scattering spectroscopy test, Fourier transform infrared spectroscopy test, scanning tunneling microscope test, atomic force microscope test, thermogravimetric-differential scanning calorimeter test, accelerated rate calorimetry test, gas chromatography test, gel permeation chromatography test, electrochemical impedance spectroscopy test and cyclic voltammetry test.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The power battery failure analysis method of the present invention can comprehensively analyze the failed power battery, obtain the cause of the power battery failure, find out the weak links in each component, and then directly guide the improvement of the power battery from the mechanism, which is helpful to improve the life and safety of the power battery and further promote its commercial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 It is a schematic diagram of the process of the power battery failure analysis method of the present invention.

[0026] Figure 2 Schematic diagram of the SEI film overgrowth process of the present invention.

[0027] Figure 3 This is a SEM image of the LGPS sulfide solid electrolyte of the present invention.

[0028] Figure 4 This is a graph showing the relationship between the ionic conductivity of the LGPS sulfide solid electrolyte of the present invention and temperature.

[0029] Figure 5 This is the XRD diagram of the LGPS sulfide solid electrolyte of the present invention. DETAILED DESCRIPTION

[0030] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0031] A power battery failure analysis method according to an embodiment of the present invention is described in detail below.

[0032] In some embodiments of the present invention, a power battery failure analysis method is provided, comprising the following steps:

[0033] Perform appearance inspection on the failed power battery to obtain appearance information and determine whether the appearance of the failed power battery is damaged;

[0034] When the appearance of the failed power battery is not damaged, the failed power battery is subjected to nondestructive testing and destructive testing in sequence; when the appearance of the failed power battery is damaged, the failed power battery is subjected to destructive testing; and the failure cause of the failed power battery is analyzed based on the test results.

[0035] In some embodiments of the present invention, the power battery includes but is not limited to a lithium battery.

[0036] In some embodiments of the present invention, the failure phenomenon and failure cause of the power battery are predicted based on the appearance information and the results of non-destructive testing; or, the failure phenomenon and failure cause of the power battery are predicted based on the appearance information.

[0037] In some embodiments of the present invention, after predicting the failure phenomenon and failure cause of the power battery, a destructive test is performed to obtain the failure cause of the failed power battery. The present invention comprehensively analyzes the failure cause of the power battery based on the results of appearance testing, nondestructive testing and destructive testing to determine the final failure cause.

[0038] In some embodiments of the present invention, the appearance information includes breakage, corrosion damage, combustion damage, and flatulence.

[0039] In some embodiments of the present invention, non-destructive testing includes electrochemical performance testing and / or in-situ testing characterization.

[0040] In some embodiments of the present invention, the electrochemical performance test (see Table 4) includes a capacity test and / or an impedance test.

[0041] In some embodiments of the invention, the in-situ test characterization (see Table 1) includes a CT imaging test and / or an X-ray imaging test.

[0042] In some embodiments of the present invention, the failure phenomenon in predicting the failure phenomenon and failure cause of the power battery includes at least one of capacity decay, impedance increase, flatulence, thermal runaway and internal short circuit.

[0043] In some embodiments of the present invention, destructive testing includes: disassembling a failed power battery to obtain internal components of the battery; testing the internal components of the battery; the internal components of the battery include at least one of a positive electrode sheet, a negative electrode sheet, a positive electrode active material, a negative electrode active material, a current collector, a separator, an electrolyte, a solid electrolyte, a gas and a binder.

[0044] In some embodiments of the present invention, the tests performed on the internal components of the battery include at least one of energy dispersive X-ray spectroscopy testing, inductively coupled plasma mass spectrometry testing, X-ray photoelectron spectroscopy testing, scanning electron microscopy testing, transmission electron microscopy testing, X-ray diffraction testing, neutron diffraction testing, nuclear magnetic resonance testing, Raman scattering spectroscopy testing, Fourier transform infrared spectroscopy testing, scanning tunneling microscopy testing, atomic force microscopy testing, thermogravimetric-differential scanning calorimeter testing, accelerated rate calorimetry testing, gas chromatography testing, gel permeation chromatography testing, electrochemical impedance spectroscopy testing, and cyclic voltammetry testing.

[0045] The power battery failure analysis method of the present invention studies the causes and mechanisms of battery failure. Through the failure analysis of the power battery, it can provide guidance for fundamental improvements to the power battery. The power battery failure analysis method is generally divided into four parts, namely, determination of the failure analysis process, identification of the failure phenomenon, failure analysis test, and failure mechanism analysis, for detailed description.

[0046] Determination of failure analysis process:

[0047] For power batteries that have obviously failed, it is necessary to predict the cause of the failure based on the failure phenomena that have occurred, and determine the tests and characterizations that need to be performed from the outside to the inside.

[0048] Since the number of sample batteries that can be used for testing is limited, and the components inside that can provide relevant failure information are also related to the battery itself, the testing and characterization of the battery needs to consider whether it will destroy its original state after failure and cause the loss of some information. According to the impact of the test characterization on the sample, the test method can be divided into two categories: "destructive" and "non-destructive". Non-destructive testing is the testing and characterization of the sample without destroying its overall integrity and failure state. It mainly includes direct testing of the electrochemical properties of the battery and in-situ characterization that can be performed without disassembling the battery (such as in-situ X-ray diffraction). Destructive testing requires disassembling the battery and obtaining the components therein for targeted testing, including the need to directly test and characterize the active materials, pole pieces, diaphragms, electrolytes, etc. The information obtained in each step can assist in predicting the cause of battery failure and guide the test method that should be used in the next step. The flow chart of the power battery failure analysis method of the present invention is shown in the figure. Figure 1 shown.

[0049] Through appearance inspection, it can be determined whether the power battery has damage, damage caused by corrosion, damage caused by combustion and flatulence, and it can also be determined whether the power battery has experienced some external environmental conditions, such as puncture, extrusion, overheating, etc. If not, non-destructive testing can be continued; if it is, it is difficult to characterize the electrochemical performance, and only partial in-situ test characterization or direct destructive testing can be performed. Through non-destructive testing, it is determined that the battery is intact and there are no problems that seriously affect its operation or safety. It can be tested for electrochemical performance, such as its remaining capacity, internal impedance, etc., and some key data can be obtained through electrochemical performance tests to help determine the cause of its failure. In addition, some in-situ test methods can be used to obtain as much internal information as possible without destroying the battery (such as whether it is damaged and the physical phase of the internal active material, etc.) to help determine the possible cause of its failure and determine the subsequent test characterization method. Through appearance inspection and non-destructive testing, the general direction of the failure phenomenon of the battery can be predicted. As shown in Table 1, some possible failure phenomena corresponding to the results of appearance inspection and non-destructive testing are listed.

[0050] Table 1

[0051]

[0052] It should be noted that since thermal runaway is a very serious and rapidly developing failure phenomenon, in a battery pack module composed of a large number of lithium-ion batteries, often only one or a few lithium-ion batteries will experience thermal runaway at the beginning, and due to the domino effect, it will quickly develop into thermal runaway of all lithium-ion batteries in the module. Therefore, real-time detection is required for thermal runaway. Since thermal runaway is often accompanied by short circuit, high temperature and gas production, it is generally carried out: 1) Real-time detection of cell / module terminal voltage and surface temperature; 2) Real-time detection of lithium-ion battery internal temperature and strain; 3) Detection of characteristic gas production components that may occur in lithium-ion batteries. The main detection process of thermal runaway is shown in Table 2.

[0053] Table 2

[0054]

[0055] After the appearance inspection and non-destructive inspection, destructive inspection is carried out to obtain the internal components of the battery, and then targeted testing and characterization are carried out. It is important to note the pretreatment of the internal components of the battery, which requires the following conditions: 1) Inert atmosphere protection is required when disassembling the battery; 2) Separation and cleaning of active materials, current collectors, and adhesives; 3) When removing residual electrolyte from the diaphragm, prevent the removal of possible attached byproducts; 4) Collection of electrolyte / gas during disassembly, etc.

[0056] The internal components (test objects) of the disassembled battery include positive electrode sheets, negative electrode sheets, positive electrode active materials, negative electrode active materials, current collectors, diaphragms, electrolytes, solid electrolytes, generated gases, binders and other components. Among them, the properties (morphology, structure, composition, etc.) of the positive and negative electrode active materials need to be characterized for the positive and negative electrode sheets, and then they are assembled into button half-cells for performance (gram capacity, impedance, etc.) testing. In addition, according to the performance of failure, the binder, active materials, etc. can be separated for specific analysis. The diaphragm needs to be analyzed for morphology and surface elements, and it can also be assembled into a button cell for performance (analyzing its ionic conductivity through impedance, etc.) testing. For electrolytes, gases, and possible residues on the surface of the pole pieces and diaphragms, it is necessary to conduct component analysis, combined with analysis of possible reactions inside the battery.

[0057] After completing the destructive testing, the failure type and specific causes of the battery failure are comprehensively analyzed in combination with the overall battery performance test (if any) and the test and characterization of each component.

[0058] The test process of the power battery failure analysis method is shown in Table 3.

[0059] Table 3

[0060]

[0061]

[0062] Table 3 shows the steps of the power battery failure analysis method and the tests and characterizations performed. However, specific samples still need to be selected and combined according to actual conditions. Finally, after all tests are completed, the results of various aspects are analyzed to determine the cause of battery failure and the role of each component in the process.

[0063] Identification of failure phenomena:

[0064] According to the main properties affected by the failure of lithium-ion batteries, they can be divided into two aspects: battery performance and safety. Failure phenomena in battery performance mainly include capacity decay and / or impedance increase, and failure phenomena in safety include at least one of flatulence, thermal runaway and internal short circuit.

[0065] During the use of lithium-ion batteries, capacity decay is the most obvious feature of their aging and failure, which can be divided into two categories: reversible capacity decay and irreversible capacity decay.

[0066] Reversible capacity decay is mainly caused by the battery's usage conditions and can be restored to normal after adjusting the battery's usage and improving the environment. For reversible capacity decay, the battery's charge and discharge voltage range, operating temperature, etc. can be adjusted to the best state according to specific usage conditions, and the battery can be left to rest for a period of time after continuous use to alleviate capacity decay caused by polarization, etc.

[0067] Irreversible capacity decay is caused by some irreversible changes in its internal components, resulting in an irreversible decline in performance. For irreversible capacity decay, the main reasons are lithium ion inventory loss and failure of positive and negative electrode active materials. Generally speaking, the charging and discharging process of lithium-ion batteries is related to the embedding / extraction of lithium ions in positive and negative electrode active materials, so the capacity of the battery directly depends on the amount of active materials and available lithium ions. For the failure reasons of active materials, the main reasons for the failure of positive electrode materials include particle crushing, irreversible phase change, and mixing of metal elements and lithium in the materials. The main reasons for the failure of negative electrode materials include excessive growth of surface SEI film and huge volume expansion. Lithium ion inventory loss is mainly caused by the reaction and decomposition of electrolytes, which causes the available active lithium ions to become byproducts such as lithium fluoride and lithium carbonate. In addition, the corrosion of current collectors such as aluminum foil and copper foil will cause the active material to fall off, resulting in irreversible capacity loss.

[0068] As a parameter directly related to the electron and ion transport inside lithium-ion batteries, the internal resistance of lithium-ion batteries is related to many factors such as its state of charge (SOC), number of cycles and use environment. In addition, an increase in internal resistance will also lead to battery capacity decay. Under the condition that the charge and discharge cut-off voltage remains unchanged, the available capacity of the battery will decrease. Generally speaking, from the perspective of internal battery components, the main reasons for the increase in impedance are: destruction of positive and negative electrode active materials, excessive growth of SEI / CEI membranes, electrolyte reaction and decomposition, binder failure and diaphragm failure; among them, the schematic diagram of the overgrowth process of SEI membrane is shown in the figure below. Figure 2 As shown. The destruction of the positive and negative active materials will naturally lead to the destruction of some of the existing lithium ion transmission paths, resulting in a decrease in ionic conductivity and an increase in the impedance of lithium ion diffusion and migration; and the excessive growth of SEI and CEI films will first lead to the length of the path length during the transmission of lithium ions, resulting in an increase in the impedance of passage. In addition, the continued growth of SEI and CEI films will consume the active lithium ions in the electrolyte. At the same time, the ionic conductivity will decrease in the later stages of electrolyte reaction and decomposition aging, resulting in an increase in the resistance to the transfer of lithium ions in the electrolyte; the failure of the binder will cause the active material to fall off from the current collector and the contact with the conductive additive to deteriorate, resulting in a decrease in electronic conductivity; the aging of the diaphragm will cause the pores through which ions pass to shrink or even become directly blocked, and the byproducts of the electrolyte may also adhere to it, resulting in an increase in the resistance to the passage of lithium ions. Among them,

[0069] Gas production is mainly caused by high temperature of the battery system, overcharge and over discharge, etc. At high temperatures, different electrode materials and electrolytes of different components undergo electrochemical decomposition to produce different gases, including methane, ethylene, propylene, hydrogen, carbon dioxide, etc.

[0070] Thermal runaway refers to the rapid accumulation of heat inside a lithium-ion battery without timely heat dissipation, which causes the temperature to rise rapidly and triggers further reactions. Generally, the main cause of thermal runaway is that the battery operates under abnormal conditions, including short circuit, high temperature and external pressure. Since most of the components inside the battery are in an unstable state at high temperature, the battery is prone to combustion or even explosion in the thermal runaway state.

[0071] Short circuit is a very dangerous situation in electricity. For lithium-ion batteries, internal short circuit will not only lead to self-discharge, but also cause thermal runaway, and more seriously, it will develop into a safety accident of fire and explosion. The main causes of internal short circuit in lithium-ion batteries are short circuit between current collectors, diaphragm failure and lithium dendrites. Direct short circuit of current collector mainly occurs during the production process. Mistakes in battery packaging cause displacement of the diaphragm, which fails to separate the positive and negative pole pieces, causing a short circuit. Diaphragm failure is caused by aging of the diaphragm due to high temperature or electrolyte reaction, causing the diaphragm to lose its ability to separate the positive and negative pole pieces. During long-term cycling, the formation of lithium dendrites may pierce the diaphragm, causing a short circuit. This situation is more obvious for negative electrode materials with a lower discharge platform like graphite. In addition, overcharging and over-discharging during use may cause corrosion of the current collector and deposition on the electrode surface, causing a short circuit.

[0072] Failure analysis test:

[0073] Analysis of the causes of lithium-ion battery failure. Based on the above common manifestations of lithium-ion battery failure, there will be some subtle phenomena. Therefore, it is necessary to test the electrochemical properties of the battery as a whole to understand the main phenomena of battery failure.

[0074] Mainly include:

[0075] By at least one of potential relaxation technique (PRT) calculation, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), constant current intermittent titration (GITT) and constant potential intermittent titration (PITT), kinetic parameters related to the electrochemical process of the lithium ion battery are fitted, and the kinetic parameters include at least one of impedance parameters, lithium ion chemical diffusion coefficient, ionic conductivity and electrode reaction rate constant;

[0076] Characterizing the composition and / or elemental valence state of at least one of the positive electrode active material, the negative electrode active material, and the separator by at least one of energy dispersive X-ray spectroscopy (EDS), inductively coupled plasma mass spectrometry (ICP-MS), and X-ray photoelectron spectroscopy (XPS);

[0077] Characterizing the surface morphology of at least one of the positive electrode active material, the negative electrode active material and the separator by scanning electron microscopy (SEM) and / or transmission electron microscopy (TEM);

[0078] Characterizing the crystal structure of the positive electrode active material and / or the negative electrode active material by at least one of X-ray diffraction (XRD), neutron diffraction (ND) and nuclear magnetic resonance (NMR);

[0079] Characterizing the surface-attached substances of at least one of the positive electrode active material, the negative electrode active material, the separator and the electrolyte by Raman scattering spectroscopy (Raman) and / or Fourier transform infrared spectroscopy (FTIR);

[0080] Characterizing the thermal properties of at least one of the positive electrode active material, the negative electrode active material and the separator by thermogravimetric-differential scanning calorimetry (TGA-DSC) and / or accelerated rate calorimetry (ARC);

[0081] characterizing the transport path of ions in the material by at least one of neutron diffraction (ND), scanning tunneling microscopy (STM), and atomic force microscopy (AFM);

[0082] The components of the produced gas were characterized by gas chromatography (GC);

[0083] Characterizing the composition of the solid electrolyte by at least one of Raman scattering spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric-differential scanning calorimetry (TGA-DSC);

[0084] The relative molecular mass of the binder was characterized by gel permeation chromatography (GPC) combined with Raman scattering spectroscopy (Raman) and Fourier transform infrared spectroscopy (FTIR) of the electrode and diaphragm.

[0085] Characterize at least one of the gram capacity, impedance, ion diffusion coefficient and ion conductivity of the half-cell assembled by the positive and negative active materials by at least one of rate cycling, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV);

[0086] The ionic conductivity of the separator-assembled button cells was characterized by electrochemical impedance spectroscopy (EIS) and / or cyclic voltammetry (CV).

[0087] The relevant tests in the power battery failure analysis method are shown in Table 4.

[0088] Table 4

[0089]

[0090]

[0091] Tests in power battery failure analysis methods, such as:

[0092] Through the fixture, Li 10 GeP2S 12After the (LGPS) sulfide solid electrolyte sample was compacted and placed in the corresponding position of the scanning electron microscope (SEM, FE-SEM, JSM6330) and the sample chamber, the LGPS sulfide solid electrolyte was tested by SEM, and the magnification was adjusted to the specific morphology. At the 10μm size level, it was found that the solid electrolyte particles were uniform and had the morphology of small particle agglomeration, but the porosity was too high. The results are as follows Figure 3 shown.

[0093] The LGPS sulfide solid electrolyte was tested by potential relaxation technique (PRT) calculation, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), constant current intermittent titration (GITT), and constant potential intermittent titration (PITT), and the kinetic parameters related to the electrochemical process of lithium-ion batteries were fitted, that is, the relationship between ion conductivity and temperature. The results are shown in Figure 4 As shown; it has a higher ionic conductivity (2.56×10 -3 Scm -1 , 25℃), which is more conducive to conductivity.

[0094] The crystal structure of the material was characterized by X-ray diffraction (XRD) under copper Ka radiation (RigakuD / max-RB) in the range of 10 to 90° at 2θ. The crystal structure of the LGPS sulfide solid electrolyte material was characterized, and the results are as follows: Figure 5 shown.

[0095] Failure Cause Analysis:

[0096] After analyzing the failure of lithium-ion batteries through the above process and test methods, the failure causes obtained can usually be divided into two categories. One is the manufacturing defects of the lithium-ion battery itself, that is, the internal cause of failure, and the other is the external environment, including the use environment, working environment, etc., that is, the external cause of failure.

[0097] Internal causes of failure include:

[0098] Performance degradation includes failure of positive and negative electrode active materials, diaphragm aging, electrolyte consumption, binder failure and current collector corrosion;

[0099] The causes of gas generation include other active impurities in the slurry, corrosion of the current collector, etc.

[0100] Thermal runaway includes unstable decomposition of cathode materials to produce oxygen that reacts with the electrolyte to release heat, and the inability of components such as the diaphragm and casing to quickly dissipate heat, resulting in heat accumulation;

[0101] Internal short circuits include displacement of the current collector during assembly resulting in direct contact, aging and failure of the diaphragm to insulate, metal impurities in the slurry piercing the diaphragm, and insufficient negative electrode capacity during design resulting in the formation of lithium dendrites that pierce the diaphragm.

[0102] External causes of failure include:

[0103] Performance degradation includes operating temperature that is too high or too low, overcharging or over-discharging;

[0104] Gas generation includes excessive operating temperature and puncture;

[0105] Thermal runaway includes over-current, over-temperature, external short circuit, puncture, over-charge and over-discharge;

[0106] Internal short circuits include overcharging, over-discharging, puncture, and extrusion.

[0107] The power battery failure analysis method of the present invention can comprehensively analyze the failed power battery to understand the cause of its failure and find out the weak links in each component, and then can directly guide the improvement of the power battery from the mechanism, which is helpful to improve the life and safety of the power battery and further promote its commercial application.

[0108] The review of failure analysis processes and the summary of failure analysis test methods can be applied to the analysis of lithium-ion batteries and solid-state batteries.

[0109] The identification of application failure phenomena, analysis of failure mechanisms and subsequent research based on the application of this method can be combined with empirical models and applied to the design and optimization of battery fast charging strategies.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power battery failure analysis method, characterized in that: The steps include: Perform appearance inspection on the failed power battery to obtain appearance information and determine whether the appearance of the failed power battery is damaged; When the appearance of the failed power battery is not damaged, the failed power battery is subjected to nondestructive testing and destructive testing in sequence; when the appearance of the failed power battery is damaged, the failed power battery is subjected to destructive testing; and the failure cause of the failed power battery is analyzed based on the test results.

2. The power battery failure analysis method according to claim 1, characterized in that: The power battery includes a lithium battery.

3. The power battery failure analysis method according to claim 1, characterized in that: The failure phenomenon and failure cause of the power battery are predicted based on the appearance information and the result of the nondestructive testing; or, the failure phenomenon and failure cause of the power battery are predicted based on the appearance information.

4. The power battery failure analysis method according to claim 3, characterized in that: After predicting the failure phenomenon and failure cause of the power battery, destructive testing is performed to obtain the failure cause of the failed power battery.

5. The power battery failure analysis method according to claim 3, characterized in that: The appearance information includes breakage, corrosion damage, combustion damage and flatulence.

6. The power battery failure analysis method according to claim 3, characterized in that: The non-destructive testing includes electrochemical performance testing and / or in-situ testing characterization.

7. The power battery failure analysis method according to claim 6, characterized in that: The electrochemical performance test includes a capacity test and / or an impedance test; And / or, the in-situ test characterization includes CT imaging test and / or X-ray imaging test.

8. The power battery failure analysis method according to claim 3, characterized in that: The failure phenomenon includes at least one of capacity decay, impedance increase, gas expansion, thermal runaway and internal short circuit.

9. The power battery failure analysis method according to claim 4, characterized in that: The destructive testing includes: disassembling the failed power battery to obtain the internal components of the battery; testing the internal components of the battery; the internal components of the battery include at least one of a positive electrode sheet, a negative electrode sheet, a positive electrode active material, a negative electrode active material, a current collector, a separator, an electrolyte, a solid electrolyte, a gas and a binder.

10. The power battery failure analysis method according to claim 9, characterized in that: The tests performed on the internal components of the battery include at least one of energy dispersive X-ray spectroscopy test, inductively coupled plasma mass spectrometry test, X-ray photoelectron spectroscopy test, scanning electron microscopy test, transmission electron microscopy test, X-ray diffraction test, neutron diffraction test, nuclear magnetic resonance test, Raman scattering spectroscopy test, Fourier transform infrared spectroscopy test, scanning tunneling microscope test, atomic force microscope test, thermogravimetric-differential scanning calorimeter test, accelerated rate calorimetry test, gas chromatography test, gel permeation chromatography test, electrochemical impedance spectroscopy test and cyclic voltammetry test.

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