1. Causes of reversible capacity loss: Reversible capacity loss is caused by a reversible discharge reaction, the principle of which is the same as the normal discharge reaction of a battery. The difference is that the electron path in normal discharge is the external circuit and the reaction speed is very fast; the electron path in self-discharge is the electrolyte and the reaction speed is very slow.
2. Causes of Irreversible Capacity Loss: Irreversible capacity loss occurs when an irreversible reaction occurs inside the battery. The types of irreversible reactions that occur include: irreversible reactions between the positive electrode and the electrolyte; irreversible reactions between the negative electrode material and the electrolyte; irreversible reactions caused by impurities in the electrolyte itself; and irreversible reactions caused by micro-short circuits resulting from impurities during manufacturing.
Self-discharge rate is a crucial parameter for measuring the lifespan of lithium-ion batteries. The self-discharge process occurs internally and is related to battery materials and manufacturing processes, varying with ambient temperature, storage time, and state of charge. Rapid detection of lithium-ion battery self-discharge can shorten the measurement time and improve accuracy. Self-discharge detection can be applied to battery pack technology, providing new theoretical data for battery consistency studies and sorting in practical applications, thereby improving lithium-ion battery performance.
When a battery is completely discharged and the voltage reaches a certain value, continuing to discharge will cause over-discharge. The discharge cutoff voltage is usually determined based on the discharge current. Over-discharge can have disastrous consequences for the battery, especially high-current over-discharge or repeated over-discharge, which have a greater impact on the battery. Generally speaking, over-discharge will increase the internal pressure of the battery, damage the reversibility of the active materials of the positive and negative electrodes, and even if it is charged, only part of the capacity can be restored and there will be a significant decrease.
To ensure that some lithium ions remain in the graphite layer after discharge, the minimum discharge termination voltage must be strictly limited; in other words, lithium-ion batteries cannot be over-discharged. The discharge termination voltage is typically 3.0V/cell, and should not be lower than 2.5V/cell. The battery discharge time is related to the battery capacity and the discharge current. Battery discharge time (hours) = battery capacity / discharge current; the discharge current of a lithium-ion battery should not exceed three times its capacity, otherwise the battery will be damaged.
