Analysis of the common failure performance of lithium batteries and its failure mechanism

　　Capacity attenuation failure:

　　"When the standard cycle life test, the discharge capacity of the loop reaches 500 times should not be less than 90%of the initial capacity. Or the discharge capacity should not be lower than the initial capacity of the initial capacity when the number of cycles reaches 1,000 times." Inside, the phenomenon of sharp decline in capacity is a capacity attenuation failure. The root cause of battery capacity attenuation is the failure of the material, and it is closely related to objective factors such as battery manufacturing process and battery use environment. From the perspective of material, the main causes of failure are the structural failure of the positive electrode material, the transition growth of the negative surface SEI, the electrolyte division and the deterioration, the stream corrosion, and the trace impurities of the system.

　　The structure of the positive electrode material fails:

　　The failure of the positive material structure includes the crushing of the positive material particles, the transformation of the irreversible phase, and the disorderly material. The Limn2O4 will cause the structure to disturb the structure due to the Jahn-Teller effect during the charging and discharge process, and even the particle crushing will occur, causing the electrical contact between the particles to fail. Limn1.5NI0.5O4 Materials will change during the charging and discharge process. The transformation of the "square crystal system-cubic crystal system" will occur. Due to the transition from the LI transition from the charging and discharge process , Restrict its capacity play.

　　The negative electrode material fails:

　　The failure of graphite electrode occurs mainly on the surface of graphite, the surface of the graphite is reacted with the electrolyte, and the production of solid electrolyte interface (SEI). If it is excessively growing, it will cause the lithium ion content in the battery internal system to decrease, and the result is the capacity attenuation. The failure of silicon negative materials is mainly due to its huge volume expansion.

　　Electrolytic liquid failure:

　　The stability of LIPF6 is poor, and it is easy to decompose to reduce the li+content in the electrolyte. It is also easy to generate HF with trace reactions in the electrolyte, causing corrosion inside the battery. Poor gas tightness causes the electrolyte deterioration, and the electrolyte viscosity and chromaticity change, which eventually leads to a sharp decline in transmission of ionic performance.

　　Faculture of the collector:

　　The streaming of the stream and the aggregation of the collector decrease. The HF generated by the failure of the electrolytes will cause corrosion to the collector and generate a compound with poor conductivity, causing an increased contact or active substance to fail. During the charging process, the CU foil is dissolved under the low potential and deposited on the positive pole surface. This is the so -called "analysis copper". The common form of a collection of streams is that the binding force between the stream and the active object is not enough to cause the active substance to peel off, and it cannot provide a capacity for the battery.

　　Internal resistance increases:

　　The internal resistance of lithium batteries is accompanied by failure such as decreased energy density, voltage and power decrease, and battery production. The main factors that lead to an increased internal resistance in lithium -ion battery are divided into key materials and battery use environment.

　　Key materials for battery: micro -cracks and crushing of positive electrode materials, destruction of negative materials and excessive surface SEI, electrolyte aging, active substances from the flowing of the streaming body, the difference in contact with the active material and conductive additives (including the loss of conductive additives), the loss of electrical additives), The diaphragm shrinking hole is blocked, and the battery polar ear welding is abnormal.

　　Battery use environment: excessive environmental temperature, overcharge, high power charging, manufacturing process and battery design structure.

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