Do you know these key performance indicators of lithium-ion batteries?

Lithium-ion batteries are a common type of battery used in our daily life, but do you know the main performance indicators of lithium batteries?

Battery Capacity

Battery capacity is divided into rated capacity and actual capacity. The rated capacity of a battery refers to the amount of electricity it should provide when discharged at a 5-hour rate to the termination voltage under conditions of ambient temperature of 20°C ± 5°C, denoted as C5. The actual capacity of a battery refers to the actual amount of electricity discharged under certain discharge conditions, primarily influenced by discharge rate and temperature (thus, battery capacity should strictly specify charging and discharging conditions).

Capacity units: mAh, Ah (1Ah = 1000mAh).

Battery Internal Resistance

Battery internal resistance refers to the resistance encountered by the flow of current through the battery during operation. It consists of ohmic resistance and polarization resistance. A large internal resistance of the battery will lead to a decrease in the working voltage and shorten the discharge time. The magnitude of internal resistance is mainly influenced by factors such as battery materials, manufacturing processes, and battery structure. Battery internal resistance is an important parameter for measuring battery performance.

Voltage

①Open circuit voltage refers to the potential difference between the positive and negative poles of the battery when there is no current flowing through the circuit in a non-working state. In general, the open circuit voltage of lithium-ion batteries is around 4.1-4.2V when fully charged and around 3.0V when discharged. By detecting the open circuit voltage of the battery, the state of charge of the battery can be determined.

②Operating voltage, also known as terminal voltage, refers to the potential difference between the positive and negative poles of the battery when there is current flowing through the circuit during operation. In the discharge working state of the battery, when the current flows through the interior of the battery, there is no need to overcome the resistance caused by the internal resistance of the battery, so the operating voltage is always lower than the open circuit voltage, and vice versa during charging. The discharge working voltage of lithium-ion batteries is around 3.6V.

Discharge Platform Time

Discharge platform time refers to the discharge time of the battery from full charge to a certain voltage under certain conditions. For example, to measure the discharge platform time of a ternary battery at 3.6V, charge it to a voltage of 4.2V with constant voltage, stop charging when the charging current is less than 0.02C, and then let it stand for 10 minutes. The discharge time at 3.6V under any discharge current is the discharge platform time at that current.Because some electrical appliances using lithium-ion batteries have voltage requirements, if the voltage is lower than the specified value, they may not work. Therefore, the discharge platform is one of the important criteria for measuring battery performance.

Self-discharge Rate

Self-discharge rate, also known as charge retention capacity, refers to the ability of a battery to retain the stored charge under certain conditions when in an open circuit state. It is mainly affected by factors such as battery manufacturing processes, materials, and storage conditions. It is an important parameter for measuring battery performance.

Efficiency

①Charging efficiency refers to the degree to which the electrical energy consumed by the battery during the charging process is converted into chemical energy stored by the battery. It is mainly influenced by battery technology and operating environment temperature. Generally, the higher the ambient temperature, the lower the charging efficiency.

②Discharge efficiency refers to the ratio of the actual amount of electricity discharged to the rated capacity of the battery when discharged to the endpoint voltage under certain discharge conditions. It is mainly influenced by factors such as discharge rate, ambient temperature, and internal resistance. In general, the higher the discharge rate, the lower the discharge efficiency. The lower the temperature, the lower the discharge efficiency.