Why is the lithium ion battery fail? What should I pay attention to?

　　Author ：Iflowpower – Nhà cung cấp trạm điện di động

Commercial lithium-ion batteries often have certain failure during use or storage, including capacity attenuation, increased internal resistance, decrease in magnification, gas production, leakage, short circuit, deformed, thermal out of control, lithium analysis, etc. Performance, reliability and safety of lithium-ion batteries. These failure phenomena is caused by a series of complex chemical and physical mechanisms inside the battery.

The correct analysis and understanding of the failure phenomenon is an important purpose for the promotion of the performance of lithium-ion battery. This paper uses the failure of the battery as the starting point. For the failure mechanism, the design of the failed analysis method, the design of the failure analysis process is simple introduction, and the correlation analysis case in terms of capacity attenuation, thermal out-of control and gas production.

1. Lithium-ion battery failure performance and failure mechanism (1) Capacity attenuation: the capacity attenuation of ion batteries Important points reversible capacity attenuation and irreversible capacity attenuation. Reversible capacity attenuation can restore the capacity of the loss by adjusting the battery charge and discharge system and improving the battery usage environment; and non-reversible capacity attenuation is an irreversible change in the battery internally, there is an unrecoverable capacity loss.

The root of battery capacity attenuation failure is the failure of the material, and it is closely related to the objective factors such as battery manufacturing process, battery usage. From the perspective of material, the cause of failure is important. The structural failure of the positive electrode material is invalid, the negative surface SEI transition growth, electrolyte decomposition and deterioration, collective fluid corrosion, system micro impurities, etc.

[2]. (2) Internal resistance increase: The internal resistance of the lithium-ion battery is related to the electron transport and ion transmission process in the battery system. It is important to divide ohmic resistance and polarized internal resistance, including the polarized internal resistance Important caused by electrochemical polarization, Two of electrochemical polarization and concentration.

Important factors leading to increased lithium-ion batteries are divided into battery-key materials and battery usage environments. my country's Science and Technology University, Yongchun, etc. [3] Use synchronous radiation technology to propose transitional elements to the transition element.

The reason for potential lag and voltage attenuation: illustrates that the abnormality of key materials is increasing and battery polarization in the battery system. Influencing factors. (3) Short-circuit: Short-circuit performance can be divided into: 1 short circuit between copper / aluminum agglomeration; 2 diaphragm failure loss of electron insulation or gap is positive, negative is slightly contacted, there is a partial heating, further charge and discharge In the process, it may spread to the four weeks, forming thermal out of control [4]; 3 Transition metal impurities in the positive slurry do not remove clean, pierced through the diaphragm, or cause the negative electrode lithium delegated crystal production to cause internal short circuits; 4 lithium delegra causes internal short circuits [5-7].

In addition, in the battery design, manufacturing or battery pack assembly process, unreasonable design and local pressure will also cause internal short circuits. For example, the cause of the internal extrusion caused by the internal extrusion caused by South Korea Media SBS, which causes internal and negative contacts to cause internal short circuits, which can cause thermal out of control of the battery. Under the induction of battery overcharge and overhang, there will be inner short circuits.

It is important because of the concentration of fluid corrosion, and sedimentary phenomenon in the surface of the electrode. (4) Yield: Lithium-ion battery gas is important to normal gas production and abnormal gas production [9]. Consuming electrolyte formation in the process of battery formation, the gas generating gas generated by the formation of a stable SEI film is normal gas production.

The normal production gas is important for the ester single / dual electron reaction, and H2, CO2, C2H2, etc. [10-11]. The abnormal gas production is important to release the gas or positive electrode material to release the gas or positive electrode material release in the battery cycle, and often appear in the soft bag battery, which causes the internal pressure of the battery.

Ball contact problem, etc. (5) Heat out-of-control: thermal out-of control means that the internal or overall temperature of the lithium ion battery cannot be scattered in time, and a large number of accumulated internally, and induce further side effect [12-14]. Table 1 lists common hot rows within the internal part of the lithium ion battery.

In order to prevent lithium ion batteries from causing serious safety problems in thermal loss, PTC, safety valve, heat-conducting film and other measures are often used, while the battery design, battery manufacturing process, battery management system, battery use environment, etc. should be systematic. Consideration [15-17].

(6) Lithium: lithium lithium is a relatively common expiration of lithium ion battery aging. The form of expression is important to have a layer of gray, grayish or gray blue substance on the surface of the negative electrode plate, which is a metal lithium precipitated in the surface of the negative electrode. Figure 3 is a common lithium phenomenon.

Figure 4 analyzes the cause of lithium lithium lithium in the battery from two aspects, and analyzes the occurrence of lithium generation and battery manufacturing process, battery usage environment (including charge and discharge system and charge and discharge environment). Tsinghua University Zhang Qiang et al [18] pointed out that important factors affecting the growth of dendrites is the current density, temperature and power, by adding an electrolyte additive, artificial SEI, high salt concentration electrolyte, structured negative electrode, optimizing battery configuration design, etc. Inhibit the growth of dendrites.

The failure of lithium-ion batteries is important from the following directions: constitutes materials, design and manufacturing, and environments. From the angle of forming material, various failure phenomena can be attributed to the battery composition. Figure 5 Multi-to-many relationships of the nature of the positive and negative electrode material shown in Figure 5.

Figure 6 is a diagram of the relationship between the use conditions, failure mechanism and failure phenomenon of lithium ion battery. 2. Failure analysis Common Test Analysis Method Lithium Ion Battery Failure Analysis is from battery test analysis technology, but the detection analysis of general testing centers.

Test analysis of failure analysis is to establish appropriate failure strategies for different failure phenomena, select the appropriate test method, and accurately obtain battery failure analysis. Figure 7 is a test method involved in the internal key material of a lithium ion battery [19]. In order to achieve failure analysis in practical applications, some test technologies that do not have universal and easy promotion should be prevented, such as Exafs, ABF-STEM, etc.

To this end, the test content is divided into necessary testing and auxiliary tests, such as Table 2 lists some commonly used failure analysis test analysis technology. In order to ensure the accuracy, timeliness, coherence of lithium-ion battery failure analysis, China Academy of Physics Lithium-Ion Battery Failure Analysis Team relies on the cleaning energy laboratory, built an interconnected inert atmosphere battery testing platform. A failure lithium-ion battery can be disassembled from battery disassembly, collection of by-products, various analyzes of key materials to the remaining materials to keep the entire process can be carried out in an orderly manner in the glove box, preventing multiple metastasis to make battery materials.

Pollution, denaturation, failure. Figure 8 is a schematic diagram of an interconnected inert atmosphere test analysis platform. 3.

The design of the failure analysis process for the unaffective analysis of the cell failure analysis can be summarized as the audio detection of the battery, battery non-destructive testing, battery damage testing, and comprehensive analysis report, as shown in Figure 9. The test content and method of each analysis phase are selected and combined according to the failure performance of the battery. However, in order to optimize the test path, the battery failure phenomenon can be classified, the design failure analysis process, as shown in Figure 10, the different failure phenomenon corresponds to different failure analysis, which can shorten the analysis cycle.

4. Case Analysis (1) Capacity Attenuation Failure Analysis Case 2016. Figure 11 shows the charge and discharge behavior of the battery pole piece, and determines according to the correlation curve of the fresh battery.

The cathode material of the whole battery has changed larger in the whole battery cycle, which is one of the main causes of failure. (2) Thermostat Analysis Case 2015 Finegandonalp et al. [21] Combined with the in-situ high-frequency X-ray tomography, combined thermal imaging technology, the two commercial batteries LG18650 change the internal structure of the internal structure after heating in this study.

Supply a variety of factors that may cause the failure of lithium-ion batteries, such as structural deformation, rupture, and material detachment, these can predict the key factors of heat generation and dissipation. (3) Yield Analysis Case 1999, Kumai et al [12] on the 18650 type cylindrical commercial lithium ion battery normally used potential range (4.2 ~ 2.

5V), over-discharge potential ( <2.5V)以及过充电电位(>4.2V) of gas gas phenomenon.

Over-rechargeable gas is important as CO2. The gas that appears in the normal potential range is important as the alkane as generated by several esters, and the over-discharge is similar to the principle of gas intake in the normal potential, and it is important to form alkane gases, CO and CO2. The specific mechanism is shown in Figure 13.

(4) Analysis of lithium analysis case failure battery will have different forms of lithium-graphic ribbed, which has the same mechanism and caused factors. At the LCO / MCMB battery system, ZHANG et al [22] uses a three-electrode method, and the lithium potential is directly studied by monitoring the lithium potential in the battery charge and discharge process. Li is a reference electrode, the electrolyte is 1.

0 mol / llibf4 dissolution. At 1: 1: 3 (mass ratio) EC / BL / EMC, the research conditions were different current ratios and temperatures. Figure 14 shows the result of charging and discharging the battery with a three-electrode method at different temperatures, through the negative electrode to Li + / Li The potential change can be clearly seen that the longer the temperature is, the easily analyzing lithium during the full battery charging process, and the same research method is used.

The more the charging current is, the more easily analyzed the lithium conclusion. In the high voltage high energy density system, an inappropriate charging cutoff voltage in the battery cycle will also cause lithium production of battery. ZHANG et al [23] studied the capacity attenuation mechanism of LCO / MCMB battery system under different cutoff voltage conditions.

During the circulation process, the charging cutoff voltage is 4.4V, 4.5V, 4.

6V, 4.7V, and the battery dismantling, the use of XAS, SEM / EDX and other methods, and found that the 4.7V battery is obvious.

Capacity attenuation and polarization, as shown in Figure 15. After the dismantling, there is a negative electrode SEM to show that there is more lithium delegra, as shown in Figure 16. The study shows that under 4.

7V overcharge conditions, the important cause of LCO / MCMB capacity attenuation is lithium, and the positive electrode CO is dissolved. Conclusion Lithium-ion battery applications are very broad, small to mobile terminals such as mobile phone, large-scale energy storage. Since the fire explosion accidents of many mobile phone electric vehicles at home and abroad, reliability, safety is the same as their performance.

This paper briefly introduces the failure performance of the lithium-ion battery, and analyzes the failure analysis of lithium ion battery from the development of the failure mechanism research, test analysis method, and failure analysis process design. Lithium-ion battery failure analysis plays feedback in the development of new high-performance batteries, which is conducive to its development research. .