Resistance is the resistance that the lithium battery receives when the current flows inside the battery when it is working. Internal resistance is an important factor that affects the power performance and discharge efficiency of lithium batteries. Its initial size is mainly determined by the structural design of the battery, the performance of the raw materials and the manufacturing process. The change of the internal resistance of lithium batteries is affected by various usage conditions such as temperature and depth of discharge.
What is the internal resistance of lithium batteries?
Internal resistance is one of the key characteristics of lithium batteries. Generally, the internal resistance of lithium batteries is divided into ohmic internal resistance and polarized internal resistance. The ohmic internal resistance is composed of electrode material, electrolyte, diaphragm resistance and the contact resistance of each part. Polarization internal resistance refers to the resistance caused by polarization during electrochemical reaction, including electrochemical polarization internal resistance and concentration polarization internal resistance. The ohmic internal resistance of the battery is determined by the total conductivity of the battery, and the polarization internal resistance of the battery is determined by the solid phase diffusion coefficient of lithium ions in the electrode active material.
Internal resistance is an important factor that affects the power performance and discharge efficiency of lithium batteries. As the storage time of lithium-ion batteries increases, the batteries continue to age, and their internal resistance continues to increase. Different types of lithium batteries have different degrees of change in internal resistance.
What is the impact on the battery if the internal resistance of the lithium battery is too large or too small?
The internal resistance of the lithium battery is too large or too small, and the impact on the battery is as follows:
The internal resistance of a lithium battery is high and cannot be discharged with a large current. The lower the theoretical internal resistance, the better, and the internal resistance is directly related to the capacity. The general lithium battery assumes 1 ampere hour, the internal resistance is about 30 to 80 milliohms, while a good power lithium battery can be below 15 milliohms. As the internal resistance increases, its own heat loss will increase, and the temperature will worsen the performance of the battery during use. After being used in series with other batteries, there will be a problem of mismatch, resulting in a decrease in the overall battery pack capacity and performance.
Is the internal resistance of a lithium battery larger or smaller, the better?
The internal resistance is most sensitive to temperature, and the value of internal resistance can vary greatly at different temperatures. One of the important reasons for the degradation of lithium battery performance at low temperature is the excessive internal resistance of the battery at low temperature. Lithium battery as a power source, from the outside, the internal resistance must be as small as possible. Especially in the case of power applications, small internal resistance is a necessary condition.
Lithium battery as a power source, from the outside, the internal resistance must be as small as possible. The smaller the internal resistance, the less power is wasted for the battery, and it is helpful for the heat generation and rate of the battery.
Summary: In recent years, new energy vehicles have higher and higher requirements for high-rate charge and discharge performance of power batteries. According to experience, the larger the volume of lithium-ion batteries, the lower the internal resistance; and vice versa. The internal resistance of the lithium battery must be tested when needed, so that the battery can be used more safely and reasonably.