Analysis of the three major characteristics of lithium ion batteries

Source: 2020 - 04 - 12 20:58 hits: time analysis the three major characteristics of a lithium ion battery, the battery capacity characteristics of battery discharge voltage and capacity under the different rate curve is shown in figure 3. Can be seen from the diagram, the lithium ion battery in the process of the discharge voltage curve can be divided into three stages: 1) Battery terminal voltage drops rapidly in the initial stage, the discharge ratio, the greater the voltage drop in the faster; 2) The battery voltage entered the stage of slow change. This paragraph of time is called the platform area of the battery. The smaller the flow, platform area of the longer duration. In actual use lithium ion battery, the battery should work as far as possible in the platform area. 3) When the battery at the end of the discharge, close to the battery load voltage start fell sharply, until discharge cut-off voltage is reached. From capacity test results can also get the curve of the discharge current and the capacity of the relationship, as shown in figure 4. Can be seen from the diagram, the discharge current of the battery will directly affect the actual capacity of the battery. The smaller the discharge current, the greater the battery capacity, shows that the discharge current, the greater the reach the shorter the time of termination voltage. Therefore, when talking about the battery capacity, shall specify the discharge current ( Discharge rate) 。 Ii. Battery open circuit voltage characteristic of lithium ion battery open circuit voltage and battery SOC relation curve is shown in figure 5. Can be seen from the diagram, battery ocv - Curve and the discharge voltage of the battery soc curve with the same trend. In the middle of the SOC interval ( < 20% SOC < 80%) , battery OCV changed little, the battery is located in the platform area. In the ends of the SOC ( SOC < 10% and SOC & gt; 90%) OCV bigger change. The lithium iron phosphate battery ocv - Soc curve in the central area is flat, in the head and tail ends are steep. Lithium ion battery ocv - Soc relation curve affected by temperature, discharge rate and degree of aging [ 7] The influence of such factors as small, but in the condition of two kinds of charging and discharging, its characteristic curve have certain differences. 3. Battery internal resistance properties of lithium iron phosphate battery ohm resistance curve presents the following features: in a broad range of SOC surrounded in figure 6, SOC = 100% ( 10%) Within the scope of battery ohm resistance is small, and in the SOC interval is lower, and SOC ohm resistor is substantial reduction, this is because the battery discharge battery internal chemical activity; Within the scope of the whole SOC, charging ohm resistance generally greater than the discharge ohm internal resistance. This is because the lithium ion battery discharge is a spontaneous reaction, are more likely to happen. Charging is done via an external power source, this may make it harder for lithium ion to embed the cathode. It is important to note that the battery internal resistance is very complex, and by the depth, temperature, discharge to charge and discharge rate, cycles and other factors. Same type battery monomer is different, also do not agree with battery manufacturers, different working environment.