Title : Charging/discharging rates dependences of Li+ Ion migration in all solid state Li+ Ion batteries
Abstract:
All-solid-state lithium (Li)-based batteries (ASSB) have been expected as next generation rechargeable batteries. The existing interfaces between positive and negative electrodes/solid electrolyte (SE) have the highest resistance for the Li+ ion migration in ASSB and dominate a significant portion of the characterization of ASSB. Therefore, understanding dynamic behaviors of Li+ ions at interfaces is essential to realize the development of ASSB. Thus far, it has been reported that fast charging/discharging conditions result in capacity decay in the battery. Thought the Li+ ion behavior at the interfaces may be probably related to it, the mechanism of the charging/discharging rates dependences on the Li+ ion migration and the Li accumulation in ASSB has not been clarified well yet. In this study, some ASSB samples consisting of LiCoO2 as the positive electrode and Li1+x+yAlxTi2-xSiyP3-yO12(LATP) as SE have been fabricated by a magnetron sputtering and the change in the Li concentration around the LiCoO2/LATP interface during slow and fast charging/discharging conditions of approximately ±0.31 and ±1.56 mV/s, respectively, was in-situ investigated using elastic recoil detection (ERD). The typical ERD spectra revealed that the amount of Li, x, in LixCoO2 gradually decreased/increased as the applied voltage increased/decreased at the slower charging/discharging conditions and eventually, reached to be approximately 0.10/1.00 mol at +2.8 V. On the other hand, during the faster charging/discharging conditions, the values of x in LixCoO2 became approximately 0.59/0.50 mol at -2.8 V. The charging/discharging rates dependences on the Li+ ion migration from the LixCoO2 positive electrode to the LATP negative one may occur due to the amounts of the Li+ ions accumulated at the LiCoO2/LATP interface, resulting in the collision between Li+ ions and the Li concentration gradient between the Au/LiCoO2 and LiCoO2/LATP interfaces.
