Range of current values for battery aging test
The values of charging current and discharging current in aging testing have a significant impact on battery life, as follows:
1、 The influence of charging current size
The impact of larger charging currents
1. Accelerated electrode material aging: When the charging current is high, the chemical reaction rate inside the battery accelerates. This may lead to structural changes in electrode materials, such as lattice distortion of positive and negative electrode materials in lithium-ion batteries. Long term exposure to this state will gradually render the electrode material inactive, thereby shortening the lifespan of the battery. For example, under high rate charging, lithium ions may not have enough time to uniformly embed into the negative electrode material, but instead form lithium dendrites locally, which not only reduces battery capacity but may also puncture the separator and cause safety issues.
2. Excessive heat generation: High current charging can generate a large amount of heat inside the battery. If the heat cannot be dissipated in time, it will cause the battery temperature to rise. High temperature can accelerate various side reactions inside the battery, such as electrolyte decomposition and side reactions between electrode materials and electrolyte. These side reactions will consume the active substances in the battery, reducing its performance and lifespan. For example, in some cases of fast charging, the battery temperature may quickly rise above 50 ℃, which can significantly affect the battery's lifespan.
3. Increase battery internal resistance: A larger charging current may cause the internal resistance of the battery to rapidly increase in a short period of time. An increase in internal resistance can lead to increased energy loss during the charging and discharging process of the battery, as well as more severe heating during operation, further affecting the battery's lifespan. For example, after multiple high current charges, the internal resistance of the battery may increase by more than 30% compared to its initial state.
The impact of smaller charging current
1. Slowing down the aging of electrode materials: During low current charging, the chemical reactions inside the battery are relatively mild, and the structural changes of the electrode materials are minimal. This helps to maintain the activity of electrode materials and extend the lifespan of the battery. For example, by using a low current slow charging method, lithium ions can be more evenly embedded in the negative electrode material, reducing damage to the electrode material.
2. Reduce heat generation: Low current charging generates less heat and the battery temperature is relatively low. This can reduce the probability of side reactions, thereby extending the lifespan of the battery. For example, in some low-power application scenarios, using low current charging can keep the battery temperature within a relatively safe range and extend the battery's lifespan.
3. The impact on battery internal resistance is relatively small: low current charging usually does not cause significant changes in battery internal resistance. This is beneficial for the battery to maintain stable performance during long-term use. For example, after a long period of low current charging and discharging cycles, the internal resistance of the battery may only slightly increase.
2、 The Influence of Discharge Current Size
The impact of larger discharge currents
1. Accelerated electrode material loss: High rate discharge will accelerate the migration speed of ions inside the battery and intensify the structural changes of electrode materials. This may lead to particle breakage and detachment of electrode materials, thereby reducing the effective capacity of the battery. For example, in high-power applications such as electric tools, the battery is often in a high current discharge state, and the loss rate of electrode materials is fast, resulting in a relatively short battery life.
2. Increase internal pressure of the battery: High current discharge will cause significant pressure changes inside the battery. This may cause damage to the packaging structure of the battery, affecting its sealing and safety. Meanwhile, pressure changes may also lead to poor contact between electrode materials and current collectors, increasing the internal resistance of the battery. For example, in some high-power discharge situations, the pressure inside the battery may instantly increase, causing a certain amount of pressure on the battery's outer shell.
3. Reduce the discharge depth of the battery: During high current discharge, the voltage of the battery drops rapidly. In order to ensure the normal operation of the equipment, it may be necessary to stop discharging before the battery voltage is completely depleted. This will result in a decrease in the depth of discharge of the battery, and prolonged exposure to shallow charging and discharging can also affect the battery's lifespan. For example, in some devices that require high power output, in order to avoid the impact of low battery voltage on device performance, the discharge may be stopped when the battery is still more than 20% charged.
The influence of smaller discharge current
1. Reduce electrode material loss: During low current discharge, the structural changes of the electrode material are relatively small, and there are fewer cases of particle breakage and detachment. This helps to maintain the integrity of electrode materials and extend the lifespan of the battery. For example, in some low-power electronic devices, batteries typically discharge at low currents, resulting in slower electrode material loss and relatively longer battery life.
2. Reduce internal pressure of the battery: The pressure change caused by low current discharge is relatively small, and it has little impact on the packaging structure of the battery. At the same time, it is also beneficial to maintain good contact between the electrode material and the current collector, reducing the internal resistance of the battery. For example, in some small electronic devices, the discharge current of the battery is small, and the internal pressure changes can be almost negligible.
3. Increase the discharge depth of the battery: When discharging with low current, the voltage drop rate of the battery is slower, and it can continue to discharge at a lower voltage, thereby increasing the discharge depth of the battery. Although deep discharge can also have a certain impact on battery life, increasing the discharge depth appropriately within a reasonable range can improve the energy utilization efficiency of the battery, while the impact on life is relatively small. For example, in some energy storage systems, low current deep discharge is used to fully utilize the battery capacity.