In the standard cycle life test, the discharge capacity should not be lower than 90% of the initial capacity when the number of cycles reaches 500. Or when the number of cycles reaches 1000, the discharge capacity should not be lower than 80% of the initial capacity. If it is within the standard cycle range, the phenomenon of a sharp drop in capacity is a failure of capacity fading.
The root cause of battery capacity attenuation failure lies in the failure of materials, and is closely related to objective factors such as 24v 100ah lithium battery manufacturing process and battery use environment. From the perspective of materials, the main causes of failure are the structural failure of the positive electrode material, the excessive growth of SEI on the surface of the negative electrode, the decomposition and deterioration of the electrolyte, the corrosion of the current collector, and the trace impurities in the system.
Structural failure of positive electrode materials: structural failure of positive electrode materials includes particle breakage of positive electrode materials, irreversible phase transition, material disorder, etc. During the charge and discharge process of LiMn2O4, the structure will be distorted due to the Jahn-Teller effect, and even the particles will be broken, resulting in the failure of the electrical contact between the particles.
Internal short circuit often causes self-discharge of 24v 100ah lithium battery, capacity decay, local thermal runaway and safety accidents. Short circuit between copper/aluminum current collectors: untrimmed metal foreign matter pierces the separator or electrodes during battery production or use, and the displacement of pole pieces or tabs in the battery package causes positive and negative current collectors to contact.
Short circuit caused by diaphragm failure: Diaphragm aging, diaphragm collapse, diaphragm corrosion, etc. will lead to diaphragm failure, and the failed diaphragm will lose its electronic insulation or the gap will become larger so that the positive and negative electrodes are in micro contact, and then there will be severe local heating, and the charge and discharge will spread to the surroundings , leading to thermal runaway.
The increase of the internal resistance of the 24v 100ah lithium battery will be accompanied by failure problems such as the decrease of energy density, the decrease of voltage and power, and the heat generation of the battery. The important factors that lead to the increase of the internal resistance of lithium-ion batteries are divided into key materials of the battery and the environment in which the battery is used.
Key materials of 24v 100ah lithium battery: microcracks and fragmentation of positive electrode material, damage of negative electrode material and excessive thickness of surface SEI, aging of electrolyte, detachment of active material and current collector, poor contact between active material and conductive additive (including conductive additive Loss), diaphragm shrinkage cavities blocked, abnormal welding of battery tabs, etc.
24v 100ah lithium battery use environment: high/low ambient temperature, overcharge and overdischarge, high rate charge and discharge, manufacturing process and battery design structure, etc.