What are the performance indicators of lithium-ion batteries for new energy vehicles?

1. Capacity: The capacity of the battery refers to the amount of power stored in the battery. Commonly used expressions are the relationship between Ah and KWh, and Ah and KWh, which can be analogous to P equals UI, and power equals voltage multiplied by current. 2. Internal resistance: The internal resistance of the battery refers to the resistance that the current flows through the battery when the battery is working, and the unit is milliohm. It includes ohmic internal resistance and polarization internal resistance, which also includes electrochemical polarization internal resistance and concentration polarization internal resistance. The ohmic internal resistance is related to the size, structure and assembly of the battery; the internal polarization resistance is the internal resistance caused by the polarization when the positive electrode and the negative electrode of the battery undergo an electrochemical reaction. The influence of internal resistance on the battery: When charging and discharging a battery with a large internal resistance, the internal power consumption is large and the heating is serious, which will cause the accelerated aging and life decay of the lithium-ion battery, and also limit the large-rate charging and discharging. Therefore, the smaller the internal resistance, the better the life and rate of the lithium-ion battery. 3. Energy density: refers to the electric energy that the battery can release per unit volume or mass. Battery weight energy density u003d battery capacity × discharge platform/weight, the basic unit is Wh/kg; battery volume energy density u003d battery capacity × discharge platform/volume, the basic unit is Wh/L, the new energy density is a new addition to lithium-ion batteries As an important research direction of cruising range, national policies are also guiding battery processing companies to actively increase the energy density of batteries. The following figure shows the battery energy density of common vehicles. 4. Charge and discharge rate: It is used to indicate the ratio of battery charge and discharge current, that is, the rate, in C; for example, for a 60Ah battery, 1C means charging and discharging using 60A current, and 0.5C means using 30A current charge and discharge, 2C means 120A current charge and discharge. The figure below shows the relationship between the charge-discharge rate and battery voltage and battery capacity. Reliability performance indicators 1. Cycle life: The life of a high-voltage battery is generally defined by the number of cycles. The country has some regulatory requirements on battery life, that is, when the battery capacity decays below 80%, it must be forced to recycle and continue to be used in cascades. The factors that affect the life of the battery in normal use are: charging and discharging will reduce the active materials in the battery and cause changes in chemical materials, which will increase the internal resistance of the battery and permanent loss of capacity; when the temperature rises and the voltage is fully charged, the permanent capacity The biggest loss. Life-span influencing factors caused by abnormal use: over-discharge or long-term storage without use, when the battery voltage is lower than a certain value, it will cause irreversible damage; over-charging that exceeds the charge termination voltage, will seriously affect the life. 2 Self-discharge rate: also known as charge retention capacity, refers to the retention capacity of the battery under certain conditions when the battery is in an open circuit state, which is mainly affected by factors such as battery manufacturing technology, materials, and storage conditions. The self-discharge rate of lithium-ion batteries is less than 3%/month; the positive use of the self-discharge rate: predict problem cells, pair batteries in groups, and estimate and correct battery SOC. 3. Depth of discharge: the ratio of the discharge capacity of the lithium-ion battery to the total storage capacity (nominal capacity). The smaller the number, the shallower the discharge. For example: the depth of discharge is 80%, which means that 20% of the capacity is left. The reason for limiting the depth of discharge: the cycle life decreases sharply with the increase of the depth of discharge; the lower the capacity, the greater the internal resistance, and the energy consumption is wasted in the form of heat, which will also bring great safety hazards. The figure below shows the relationship between cycle life and depth of discharge. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous post: What is the difference between polymer lithium ion battery and lithium ion battery