| In recent years, the development of redox shuttle additive witch used as an overcharge protection additive is becoming the R&D focus for the consistency improvement of lithium ion power battery. This method has the following advantages: (1) It can create an anti-overcharge electrochemical self-protection mechanism in lithium battery, the additive will not cause any irreversible damage to the battery while it plays a protective role in the process, and the protection of the battery is recoverability; (2) the electrochemical reaction caused by shuttle is reversible, therefore, the added quantity of shuttle is little and with a long service life; (3) simple manufacturing process, low production cost.Currently, the consistency of the battery problem has limited the development of our company in the lithium ion secondary battery in laptop computers, power tools, electric vehicles and other areas, especially the voltage consistency of large electric vehicles and other power battery system had became our urgent need to solve the problems. In view of the above, we carried out the redox shuttle additives research, aim to develop several kinds of redox shuttle additives for LiFePO4/C battery system.In the first stage of the research work, we discussed the role of redox shuttle dynamic electrochemistry process, the theory of its gain and loss electron in the graphite and actual effect in battery pack. Preliminary screening of ten kinds of 4V redox shuttle additives, respectively develop the experimental research on the electrochemical properties, physical properties, overcharge protection properties and the general performance of the battery with the shuttle. Comparison results show that thianthrene with the proper redox potential, higher decomposition reaction rate, little disadvantageous on battery performance and safety performance, is a good redox shuttle additive for LiFePO4/C battery electrolyte.In the second stage of the research work, we continue the further study of thianthrene to research overcharge protection, aging, restoration, influenced by outside factors, summarizes the application of thianthrene results in some practical applications of battery products, the experiment verified the thianthrene effect the performance of the battery little after general consumption. Studies have shown thianthreneis a suitable redox shuttle for batteries LiFePO4/C system as an overcharge protection additive, can significantly improve the consistency of single cells in series battery pack. Through the simulation of the notebook computer for a long time standby process experiment, we found that thianthrene, in the process of recycling, loss attenuation relatively slowly, has a good circulation service life, so as to make the battery pack has excellent cycle performance. Though, the function of thianthrene influenced by charging currents and environmental temperature, but can be improved by raising the additive concentration, reduce the pole piece and the separator thickness, increasing the molecular diffusion rate of redox shuttle, thus improving overcharge protection performance under different current and temperature. In addition, the introduction of thianthreneis in the battery system, not only for the regular properties of the battery (especially the self-discharge performance) without any adverse effects, and, when the effect of thianthreneis was consumed, the additive in the process of oxidation-reduction cycle of irreversible reaction by-products, also does not have any adverse influence on normal performance of battery. |
PDF Full Text Request