The real life of energy storage lithium iron phosphate battery pack

Energy storage lithium iron phosphate batteries are widely used in the field of energy storage, but there are not many batteries that can really make it work stably for a long time. The actual life of the lithium-ion battery is affected by a variety of factors, including the physical characteristics of the cell, the ambient temperature, use methods and so on. Among them, the physical characteristics of the cell have the greatest impact on the actual life of lithium-ion batteries. If the physical characteristics of the cell do not meet the actual situation or if the battery has certain problems during use, it will affect its real life and actual function.


1. Overcharge

Under normal use, the number of charging cycles of lithium iron phosphate battery should be 8-12 times, otherwise it will cause overcharging. Overcharging will cause the active material of the cell to be consumed in the discharge process and fail. Service life decreases as the battery capacity gradually decreases. At the same time, too high charging depth will lead to increased polarization, increasing the battery decay rate and shortening the battery life; overcharging will lead to electrolyte decomposition and increase the corrosion of the internal electrochemical system of the battery. Therefore, the charging depth should be controlled during the use of the battery to avoid overcharging.

2. The battery cell is damaged

Lithium iron phosphate battery in the actual application will also be affected by the external environment. For example, by impact or human factors, such as short-circuit or capacity decay inside the core; core in the charging and discharging process by external voltage, temperature, resulting in internal structure damage, internal material erosion, etc.. Therefore, it is necessary to conduct scientific and reasonable testing and maintenance of the battery cells. In the process of using the battery discharge capacity decay phenomenon needs to be charged in a timely manner, when it is forbidden to deflate charging should be discharged first after charging; cell in the process of charging and discharging abnormalities should stop charging or replace the cell in a timely manner long time without use or charging too fast will cause the internal structure of the battery damage deformation and lead to cell water loss. In addition, you need to pay attention to the quality of the battery cells and safety issues and other factors on the battery life and function.

3. Insufficient battery unit life

The low temperature of the monomer will lead to short cell life, in general, the monomer in the use of the process temperature can not be lower than 100 ℃, if the temperature is lower than 100 ℃ will lead to the transfer of electrons within the cell from the cathode to the anode, resulting in the battery electrons can not be effectively compensated, resulting in increased cell capacity decay, resulting in battery failure (energy density reduction). Changes in the structural parameters of the monomer will also cause internal resistance, volume changes and voltage changes, etc. affect the battery cycle life, most of the lithium iron phosphate batteries currently used in the field of energy storage is a primary battery, secondary battery or three battery systems used together. Secondary battery system life is shorter and cycle times less (generally 1 to 2 times) after the need to replace, which will increase the battery itself consumption costs and secondary pollution problems (the lower the temperature inside the cell will release more energy and make the battery voltage drop) probability; three in one battery system life is longer and cycle times more (up to tens of thousands of times) after the cost advantage (compared to ternary lithium batteries) (with higher energy density). The shorter service life and less cycles between the single cell will have a larger energy density drop (this is due to the low internal resistance of the single cell) to bring about the high internal resistance of the battery; the longer service life and more cycles between the single cell will cause the high internal resistance of the battery and reduce its energy density (this is due to the internal short circuit of the battery) to cause a drop in energy density.

4. The ambient temperature is too high and too low, will also affect the battery life.

Lithium-ion batteries have no effect on the conductivity of lithium ions in the operating temperature range, but when the ambient temperature is too high or too low, the charge density on the surface of lithium ions decreases. As the charge density decreases it will lead to lithium ions in the negative electrode surface deembedding and discharge. The longer the discharge time, the more likely the battery will be overcharged or overdischarged. Therefore, the battery should have a good storage environment and reasonable charging conditions. Generally speaking, the ambient temperature should be controlled between 25℃~35℃ not to exceed 35℃; the charging current should not be less than 10 A/V; not to exceed 20 hours; each charge should be discharged 5~10 times; the remaining capacity should not exceed 20% of the rated capacity after use; do not store in the temperature below 5℃ for a long time after charging; the battery set should not be short-circuited or burned out during the charging and discharging process The battery pack should not be short-circuited or burned during charging and discharging.

5. Poor performance of the battery cell causes low life expectancy and low energy utilization inside the battery cell.

In the selection of cathode material, the difference in performance of cathode material causes different energy utilization rate of the battery. In general, the longer the cycle life of the battery, the higher the energy ratio capacity of the cathode material and the higher the energy ratio capacity of the monomer, the higher the energy utilization rate inside the battery. However, with the improvement of electrolyte, additive content increases, etc., the energy density is high and the monomer energy density is low, which will have an impact on the battery cathode material performance. The higher the content of nickel and cobalt elements in the cathode material, the higher the possibility of forming more oxides in the cathode; while the possibility of forming oxides in the cathode is small. Due to this phenomenon, the cathode material has high internal resistance and rapid volume expansion rate, etc.

Post time: Nov-08-2022