Information contained in lithium battery discharge curves

　　The discharge curve refers to the curve that changes with time such as the voltage, current, and capacity of the battery during discharge. The information contained in the charging curve is very rich, including the relationship between capacity, energy, work voltage and voltage platforms, the relationship between electrode potential and load state. The main data recorded during the discharge test is the evolution of the current and voltage. From these basic data, many parameters can be obtained. The following detailed introduction of the parameters that can be obtained by the discharge curve can be obtained.

　　(1) Voltage

　　In the lithium -ion battery discharge test, the voltage parameters mainly include voltage platforms, median voltage, average voltage, cut -off voltage.

　　The platform voltage refers to the corresponding voltage value when the voltage is minimized and the capacity change is large, which can be worth emerging through the peak of DQ/DV.

　　The median voltage is the corresponding voltage value when the battery capacity is half. For materials with obvious platforms, such as lithium iron phosphate and lithium titanate, the median voltage is the platform voltage.

　　The average voltage is the effective area of the voltage-capacity curve (that is, the battery discharge energy) divided by the capacity, and the calculation formula is ü = ∫U (t)*i (t) DT /

　　。I (T) DT.

　　The deadline of the deadline refers to the minimum voltage allowed during battery discharge. If the voltage is lower than the discharge intercept voltage, the voltage at both ends of the battery will drop rapidly to form excessive discharge. The battery life is shortened.

　　As mentioned in the first part, the voltage of the battery is associated with the load and electrode potential of the positive and negative electrode material.

　　(2) Capacity and ratio capacity

　　The battery capacity refers to a certain discharge system (at a certain discharge current I, discharge temperature T, discharge deeper voltage V condition), the power released by the battery, which characterizes the capacity of the battery storage energy. The unit is AH or C. The capacity is affected by many citations, such as: discharge current, discharge temperature, etc. The capacity is determined by the number of active substances in the positive and negative poles.

　　Theoretical capacity: The capacity given by all active substances participating in the reaction. Actual capacity: actual capacity released under a certain discharge system. Rating capacity: refers to the minimum power given by the battery under the discharge conditions of the battery.

　　During the discharge test, the capacity is calculated on the time accumulation of the overcatisher, that is, C = ∫i (T) DT, the current current constant when the current discharge is unchanged, C =

　　I (t) dt = IT; when the constant resistance r is discharged, C = ∫i (t) dt = (1/r)*∫U (t) dt ≈ (1/r)*üt (ü is the average voltage discharge voltage voltage , T is the discharge time).

　　Comparison capacity: In order to compare different batteries, the concept of capacity is introduced. The capacity of the ratio refers to the capacity given by the unit mass or unit volume electrode active material, which is called the mass ratio or volume ratio capacity. The usual calculation method is: comparison capacity = the first discharge capacity of the battery /

　　(Quality material quality*active material utilization) factors affecting battery capacity

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