General fast charging for high-power DC charging, half an hour can be filled with 80% of the power, fast charging DC charging voltage is generally greater than the battery voltage. So what are the risks of lithium battery fast charging regarding the technical problems of lithium battery fast charging?
What are the risks associated with fast charging lithium batteries?
The three basic ways to realize fast charging are: keep the voltage constant and increase the current; keep the current constant and increase the voltage; and increase the current and voltage at the same time. However, to truly realize fast charging, not only to improve the current and voltage can be, fast charging technology is a complete set of systems, including fast charging adapter and intelligent power management system.
Long-term fast charging affects the life of lithium batteries, lithium batteries fast charging is at the expense of the cycle life of the battery, because the battery is a device that generates electricity through electrochemical reactions, charging is the occurrence of a reverse chemical reaction, and fast charging will be in the instantaneous input of high current to the battery, the frequent use of fast charging mode will reduce the battery’s reducing capacity, reduce the number of battery charging and discharging cycles.
Lithium battery fast charging brings three effects: thermal effect, lithium precipitation and mechanical effect
1. Frequent fast charging accelerates the polarization of the battery cell
When the continuous charging current is large, the ion concentration at the electrode rises, polarization increases, and the battery terminal voltage cannot correspond directly and linearly to the amount of electricity charged. At the same time, high-current charging, the increase in internal resistance will lead to increased Joule heating effect brought about by side effects, such as electrolyte reaction decomposition, gas production and a series of problems, the risk factor suddenly increased, the impact on battery safety, the life of the non-powered batteries is bound to be significantly shortened.
2. Frequent fast charging may lead to crystalization of the battery core
Lithium battery fast charging means that lithium ions are quickly discharged and “swim to” the anode, which requires the anode material to have fast lithium embedding capacity, due to the embedded lithium potential and lithium precipitation potential is almost the same, in the fast charging or low-temperature conditions, lithium ions may precipitate on the surface of the formation of dendritic lithium. Dendritic lithium will pierce the diaphragm and cause secondary loss, reducing battery capacity. When the lithium crystal reaches a certain amount, it will grow from the negative electrode to the diaphragm, causing the danger of battery short circuit.
3. Frequent fast charging will shorten battery life
Frequent charging also tends to accelerate the depletion of battery life, and even lead to problems such as reduced battery activity and shorter battery life. Especially after the addition of fast charging technology, although the speed of charging in the early stage is very fast, but did not charge to 100% on the unplugging, resulting in multiple charging, increasing the number of cycles of the battery, long-term use of such a way will reduce the activity of the battery, thereby accelerating the aging of the battery.
High temperature is the biggest killer of lithium battery aging, fast charging of high power will make the battery in a short period of time to heat up, non-fast charging although the power is low, low heat per unit of time, but need a longer power-on time. In this way the battery heat will also accumulate over time, and the difference in heat generated during charging is not enough to cause a difference in the aging rate of the battery.
Summarizing the above, we can conclude that fast charging has high quality requirements for the battery, has a greater loss of battery life, and the safety factor will be significantly reduced, so try to do it as little as possible when it is not necessary. Frequent fast charging of the battery will cause harm to the battery, but due to the differences in battery cell density, materials, ambient temperature and battery management system, the battery suffers different degrees of injury during fast charging.
Post time: Oct-26-2023