Author ：Iflowpower – Portable Power Station Supplier
In the context of energy crisis and environmental pollution, lithium-ion batteries are the ideal energy of the 21st century, and they are more concerned. However, the lithium-ion battery will have some failure during production, transportation and use. Moreover, it will affect the performance and reliability of the entire battery pack after a single battery failure, and even cause the battery pack to stop working or other security issues.
1 Lithium ion battery failure classification In order to prevent the above performance attenuation and battery safety problems, the failure analysis of lithium ion batteries is imperative. The failure of lithium-ion batteries refers to cell performance attenuation or use performance abnormality by certain essential reasons, and is divided into performance failure and safety failure. Common lithium ion battery failure classification 2 Lithium ion battery failure causes lithium ion battery failure can be divided into endome and external cause.
The internal factor is the physical and chemical variation of the invalid, the research scale can be traced back to the atomic, molecular scale, the thermodynamics, kinetic changes in the development of the failure process. External factors including impact, acupuncture, corrosion, high temperature combustion, human failure, etc. Internal condition of lithium-ion battery Failure 3 Lithium ion batteries Common failure performance and its failure mechanism analysis capacity attenuation failure standard cycle life test, the number of cycles reached 500 times when the discharge capacity should not be less than 90% of the initial capacity.
Or the number of cycles reaches 1000 times, the discharge capacity should not be below 80% of the initial capacity. If the capacity has a sharp drop in the standard cycle, it belongs to the capacity attenuation failure. 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, the transition growth of the negative electrode surface, the decomposition and deterioration of electrolyte, the fluid corrosion, the micro impurity, etc. The structural failure of the positive electrode material: the structural failure of the positive electrode material includes cathode material particles, irreversible phase transition, material dissemination, etc. LIMN2O4 will cause distortion in the Jahn-Teller effect during the charge and discharge process, and even particles are broken, resulting in electrical contact between particles.
LiMn1.5Ni0.5O4 materials occur during charge and discharge process, the LiCoO2 material causes CO to enter the Li layer due to the transition of Li, causing a layered structure in a layered structure in the charging and discharge process.
Capacity. The negative electrode material failure: the failure of the graphite electrode is important in the surface of the graphite, the graphite surface is reacted with the electrolyte, and the solid electrolyte interface phase (SEI), if excessive growth can result in lowering the lithium ion content in the internal system of the battery, resulting in capacity attenuation. The failure of silicon negative electrode materials is important that its huge volume expansion caused by cyclic performance.
Electrolyte failure: LIPF6 stability is poor, easy to decompose to reduce the migration of Li + content in the electrolyte. It is also easy to react to the trace water in the electrolyte to generate HF, resulting in corrosion inside the battery. The airtightness is not good to cause the electrolyte deterioration, the viscosity and chromaticity of the electrolyte, and ultimately lead to a sharp drop in transmission ion performance.
The failure of the collector: collective fluid corrosion, the concentration of the collector decreased. The HF, which is faded by the above electrolyte, causes corrosion of the collector, generates a poor conductivity, resulting in an increase in ohmic contact or active material failure. During the charge and discharge process, the Cu foil is dissolved under low potential, deposited in the positive surface, which is the so-called copper.
Common forms of collective failures are not enough to cause the active substance to peeling between the agglomeration and the active material, and cannot supply capacity for the battery. Internal resistance increases the internal resistance of lithium-ion battery accompanying energy density, voltage and power decrease, battery heat and other failure issues. Important factors leading to increased lithium-ion batteries are divided into battery-key materials and battery usage environments.
Battery Key Material: Microclite and crushing of the positive electrode material, the damage of the negative electrode material is excessively thick, the electrolyte aging, the active material is detached from the current, and the contact of the active material and the conductive additive (including the loss of conductive additives), Diaphragm, blockage, battery extreme ear welding abnormalities, etc. Battery use environment: ambient temperature is too high / low, overcharge, high-magnification charge and discharge, manufacturing process and battery design structure, etc. Short-circuit short circuits often cause self-discharge, capacity attenuation, local thermal loss of lithium ion batteries, and cause safety accidents.
Short-circuit between copper / aluminum concentrate: battery production or metal foreign body puncture diaphragm or electrode, battery pack in battery pack, causing positive, negative set fluid contact. Short circuits caused by diaphragm failure, diaphragm, diaphragm collapse, diaphragm corrosion, etc. can result in failure of the diaphragm, the failure diaphragm loss of electron insulation or gap is positive, the negative electrode is slightly contacted, then the local fever is severe, continue to charge and discharge electricity will spread to four weeks , Cause heat loss.
Impurity causes short circuit: transition metal impurities in the positive electrode slurry can result in piercing diaphragm or promote negative electrode lithium delegra to cause internal short circuits. Short-circuit caused by lithium branch crystals: Lithium lactary crystals, dendritic crystal pass diaphragm caused by local charge during long cycle. Battery design and manufacturing or battery pack assembly process, design is unreasonable or local pressure will also cause internal short circuits.
During the induction of battery overshoot and overhang, there will also be short-circuited. The gas intake of the electrolytic solution in the process of battery changes in the process of battery formation is normal gas, but the transitional consumption electrolyte release gas or positive electrode material release oxygen is abnormal. Often in the soft bag battery, it will cause an internal pressure of the battery, and strike the encapsulation aluminum membrane, the internal battery contact problem, etc.
The normal electrical cell and the fail-to-cell gas component analysis electrolytic solution are not dried, resulting in a lithium salt decomposition in the electrolyte, causing the fluid AL and the destroying agent, and hydrogen. The electrochemical decomposition of the chain / cyclic ester or ether in the electrolyte caused in an inappropriate voltage range, and C2H4, C2H6, C3H6, C3H8, CO2, etc. The thermal out-of-control thermal out-of control means that the temperature of the lithium ion battery is local or overall temperature rise, and the heat cannot be dispersed in time, and a large amount accumulates inside and induces further side effects.
Factors induced by heat loss of lithium-ion batteries are abnormal operating conditions, that is, abuse, short circuit, high magnification, high temperature, squeezing, and acupuncture. Analysis of lithium in the negative surface of the battery, is a common lithium-ion battery aging failure phenomenon. Analysis of lithium reduces the internal active lithium ion in the battery, there is capacity failure, and the dendritic puncture can result in a local current and heat, and finally cause a battery safety problem.
my country's failure analysis has been systematically developed in the field of mechanical fields and the aviation, and in the field of lithium-ion battery has not yet been obtained. Battery companies and materials have carried out the failure analysis of lithium-ion batteries, but more than the research and development of battery manufacturing processes and materials to improve battery performance and reduce battery costs as direct goals. Future Research Institutes and related companies can strengthen cooperative exchanges, strive to establish and improve the failure fault tree and failure analysis of lithium-ion batteries.
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