Detailed reason for the failure of lithium battery

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1 Lithium ion battery failure classification In order to prevent the above-mentioned performance attenuation and battery safety issues, the failure decomposition of lithium-ion batteries is bound to. The failure of the lithium-ion battery refers to the failure and safety failure of the battery performance attenuated by certain essential properties or abnormal use of performance. 2 The original lithium ion battery failure can be divided into endome and external causes.

The internal principle is the physical and chemical variation of the invalidation, the research scale can be traced back to the thermodynamics of the atomic, molecular scale, and the research failure process. External factors including impact, acupuncture, corrosion, high temperature combustion, human failure, etc. 3 Common failure performance of lithium ion batteries and its failure mechanism decomposition capacity attenuation failure: When the standard circulation life detection, the number of cycles reaches 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 fact that the fails to fail, the structural failure of the positive electrode material, the transition growth of the negative surface SEI, the electrolytic liquid and the deterioration, the fluid corrosion, the system trace impurities, etc. The structural failure of the positive electrode material: the structural failure of the positive electrode material includes cathode material particles, irreversible transformation, material dissemination, etc. LIMN2O4 will cause distortion to the Jahn-Teller effect during the charge and discharge process, and even particle rupture, resulting in electrical contact between particles.

LiMn1.5Ni0.5O4 material The four-square crystal system in the charge and discharge process, LiCoO2 material caused CO into the Li layer due to the transition of Li, caused the layered structure, restricting the layered structure during charge and discharge.

Capacity. The negative electrode material failure: the failure of the graphite electrode occurs in the surface of the graphite, the graphite surface is reacted with the electrolytic solution, and the solid electrolyte interface phase (SEI) is machined. If excessive growth can cause the lithium ion content in the internal system, the result is caused by capacity attenuation.

The failure of silicon negative electrode materials is the cycle performance problem caused by its huge volume expansion. Electrolyte failure: LIPF6 stability is poor, easy to analyze to reduce the migration of Li + content in electrolyte. It is also easy to form HF with trace reactions in the electrolyte, 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 increase: The lithium ion battery internal resistance conference accompanied by energy density, voltage and power decrease, battery heat and other failure problems.

Metal factors leading to increased lithium-ion battery internal resistance are divided into battery-key materials and batteries. Battery Key Material: The microcrack and rupture of the positive electrode material, the damage of the negative electrode material is too thick, the electrolytic solution aging, the active material is detached from the current, and the contact of the active material and the conductive additive is worse (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. Internal short circuit: internal short circuit tends to cause self-discharge, capacity attenuation, local thermal out of control, and cause safety accidents. Short-circuit between copper / aluminum concentration: battery processing or metal foreign body puncture diaphragm or electrode, battery pack in the battery package, causes positive, negative set fluid contact.

The short circuit caused by the diaphragm failure, the diaphragm, diaphragm, diaphragm corrosion, etc. can result in failure of the diaphragm, the failure diaphragm loss of electron insulation or gap is positive, negative electrode micro contact, then the local fever is severe, continuous charge and discharge will be 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 dendrites: a lithium lactary crystal, dendritic crystal pass through diaphragm, during the long cycle. Battery design, manufacturing or battery pack assembly, 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 out in this soft bag battery, it will cause excessive pressure in the battery, and stroke the encapsulation aluminum membrane, internal battery contact problem, 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.