Important factors affecting the cycle life of lithium batteries

Introduction to the structure and principle of ion batteries During the first charge and discharge of lithium batteries, a passivation film can be formed on the interface between the negative electrode and the electrolyte. It serves as a diaphragm between the electrode and the electrolyte. It is an electronic insulator but an excellent conductor of lithium ions. Lithium ions can be inserted and extracted freely through the passivation layer. It has the characteristics of a solid electrolyte, so this passivation film It is called solid electrolyte interface membrane (solidelectrolyteinterface), abbreviated as SEI. Lithium batteries are mainly composed of anode and cathode materials, electrolyte, separator, current collector and battery casing. The anode and cathode materials are composed of two different lithium ion intercalation compounds. When charging, lithium ions are extracted from the positive electrode and inserted into the negative electrode through the separator through the electrolyte. The opposite is true when discharging. The aging and degradation of battery materials affects the process of charging and discharging cycles of lithium batteries, which is the process of deintercalation and movement of lithium ions back and forth between the positive and negative materials through the electrolyte. In the lithium battery cycle process, in addition to the oxidation-reduction reaction at the positive and negative electrodes, there are also a large number of side reactions. If the side reactions of the lithium battery can be reduced to a low level, so that the lithium ions can always smoothly go back and forth between the positive and negative materials through the electrolyte, the cycle life of the lithium battery can be increased. When a lithium battery is overcharged, the excess lithium ions extracted from the positive electrode will be deposited or embedded on the negative electrode, and the deposited active lithium easily reacts with the solvent, releasing heat to increase the battery temperature. The positive electrode heat analysis releases oxygen to make the electrolyte easy to analyze and generate a lot of heat [25]. When the discharge voltage of the lithium battery is lower than the discharge cut-off voltage, overdischarge is formed. In the process of over-discharge, lithium ions will be excessively extracted from the negative electrode, and it will be more difficult to re-intercalate during the next charge. Yu Zhongbao et al. [26] overdischarged the battery with MCMB as the negative electrode and LiCoO2 as the positive electrode to 0V, the copper foil current collector was severely corroded, the negative electrode SEI film was damaged, and the SEI film formed again had poor performance, which made the negative electrode impedance. Increase and polarization. The discharge capacity and charge-discharge efficiency of the battery are greatly reduced during the cycle after over-discharge. The influence of design and manufacturing process In the battery design process, the choice of materials is the most important factor. Different materials have different performance characteristics, and there are also gaps in the performance of the batteries developed. The cycle performance of the positive and negative materials is good, and the cycle life of the battery will be long. The electrolyte is also a very important factor in the influence of the reversible capacity of the battery. The process of removing and inserting lithium ions from the electrode material is always a process of mutual use with the electrolyte, and this mutual use has a major impact on the change of the interface condition and internal structure of the electrode material [3]. The electrolyte will be lost during the interaction with the positive and negative materials. In addition, part of the electrolyte will be consumed when the battery is formed into an SEI film and pre-charged. Therefore, the type of electrolyte and the amount of electrolyte also affect the battery life. In terms of ingredients, pay attention to the amount of positive and negative materials added. Generally speaking, the capacity of the negative electrode is generally required to be excessive relative to that of the positive electrode during the design and assembly process. If it is not excessive, lithium will be precipitated out of the negative electrode during the charging process, forming lithium dendrites, which affects safety. There is too much excess of the negative electrode relative to the positive electrode, and the positive electrode may be excessively delithified, causing the structure to collapse. The manufacturing process of lithium batteries includes: positive and negative electrode ingredients, coating, sheeting, winding, shelling, liquid injection, sealing, forming, etc. In the battery processing process, the requirements for each step of the process are very strict. Any process that is not well controlled may affect the battery cycle performance. In the process of mixing positive and negative electrodes, pay attention to the amount of binder added, stirring speed, slurry concentration, temperature and humidity, and ensure that the materials can be evenly dispersed. The impact of the charge and discharge system during the cycle. The use process of the lithium battery is the process of the charge and discharge cycle, the size of the charge and discharge current, the choice of the charge and discharge cut-off voltage, and the charge and discharge method used, etc. The charge and discharge system also affects the cycle life of the lithium battery. Very important influence. Blindly increasing the working current of the battery, adding a new charge cut-off voltage, lowering the discharge cut-off voltage, etc. will degrade the battery performance. Through the decomposition, we can see that there are many factors that affect the cycle life of lithium batteries, no matter in the process of design, manufacture or use. Lithium batteries are used more and more widely, and the demand for lithium batteries puts forward higher requirements in terms of quantity and quality. The cycle life directly affects the service time and quality of lithium batteries, so it is necessary for the processor to study its influencing factors. Only by properly grasping the various factors affecting cycle life during Ru0026D and processing can the company take the initiative in the fierce market competition. Consumers should pay attention to the characteristics of lithium batteries during use, and use the batteries correctly according to the instructions in the manual. 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: What are the advantages of medical lithium battery packs?