In the context of energy crisis and environmental pollution, lithium camper batteries are receiving increasing attention as an ideal energy source for the development of the 21st century. However, some failure phenomena may occur during the production, transportation, and use of lithium camper batteries. Moreover, the failure of a single battery can affect the performance and reliability of the entire battery pack, and even cause the battery pack to stop working or other safety problems.
The causes of failure of lithium camper batteries can be divided into internal and external factors. The internal factors mainly refer to the physical and chemical changes that lead to failure, and the research scale can be traced back to the atomic and molecular level, studying the thermodynamic and kinetic changes in the failure process. External factors include impact, puncture, corrosion, high-temperature combustion, and human destruction.
Capacity attenuation failure: 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 times. Or when the number of cycles reaches 1000 times, the discharge capacity should not be lower than 80% of the initial capacity. If a sharp drop in capacity occurs within the standard cycle range, it is considered a capacity attenuation failure.
The root cause of battery capacity attenuation failure lies in the failure of materials, which is closely related to battery manufacturing processes, battery usage environment, and other objective factors. From a material perspective, the main reasons for failure are structural failure of positive electrode materials, excess growth of negative electrode surface SEI, decomposition and deterioration of electrolyte, corrosion of current collector, trace impurities in the system, etc.
Increased internal resistance: The increase in internal resistance of lithium camper batteries is accompanied by failure problems such as energy density reduction, voltage and power reduction, and battery heat generation. The important factors that cause the increase of internal resistance of lithium camper batteries are key battery materials and battery usage environment.
Key battery materials: micro-cracks and fractures in the positive electrode material, damage and excessive SEI on the negative electrode material surface, electrolyte aging, detachment of active materials and current collectors, deterioration of contact between active materials and conductive additives (including the loss of conductive additives), and clogging of diaphragm pores, abnormal welding of battery poles, etc.
Battery usage environment: high/low ambient temperature, overcharge/discharge, high-rate charge/discharge, manufacturing processes, battery design structure, etc.
Internal short circuit: Internal short circuit often causes self-discharge, capacity attenuation, localized thermal runaway, and safety accidents of lithium camper batteries.
Short circuit between copper/aluminum current collectors: Untrimmed metal foreign bodies puncture the diaphragm during battery production or use; displacement of electrodes or electrode ear in the battery packaging causes contact between positive and negative electrode current collectors.
Short circuit caused by diaphragm failure: Aging, collapsing and corrosion of diaphragm can cause diaphragm failure. The failed diaphragm loses its electronic insulation or the gap increases, causing micro-contact between positive and negative electrodes, which then causes serious local heating. Continuing to charge and discharge will spread to the surroundings, causing thermal runaway.