Development of lithium‐ion batteries (LIBs) with high energy density has brought a promising future for the next generation of electric vehicles (EV). In order to make EVs more competitive with combustion engine vehicles, development of an effective fast charging technique is inevitable. However, improper employment of fast charging can damage the battery and bring safety hazards. Herein, industry based along with our proposed internal resistance (IR) based fast charging techniques were performed on commercial Panasonic NCR 18650B cylindrical batteries. To further investigate the fast charging impact and electrode degradation mechanisms, electrochemical analysis and material characterization techniques including EIS (electrochemical impedance spectroscopy), GITT (galvanostatic intermittent titration technique), SEM (scanning electron microscopy), and XRD (X‐ray diffraction) were implemented. Batteries that were cycled under industry based fast charging showed 78% increase in internal resistance after 120 cycles along with rapid capacity fading. Mechanical distortion of the battery case occurred around the 60th cycle for industry based fast charging. In contrast, IR based fast charged batteries showed 29.4% increase in internal resistance over 120 cycles. In addition, mechanical distortion was not observed and the relative capacity fading was on a moderate level. Furthermore, this work could pave the way for the optimization of fast charging techniques to secure the lifespan and safety of various types of lithium‐ion batteries.
A detailed and in-depth prediction of the state-of-health of lithium ion batteries (LIB) remains a major challenge. Meanwhile, the dynamic changes in the thermal and electrochemical characteristics of the interphases are important for the determination of battery health. Herein, we performed electrochemical impedance spectroscopy (EIS) measurements and equivalent circuit analysis on Panasonic NCR 18650B batteries under different states of charge (SOC), overcharge, and overdischarge cycling conditions. Three indicators of the comprehensive state of health (CSOH) of the batteries were summarized based on the values of the resistances obtained from equivalent circuit analysis from the EIS measurements. CSOH represents the dynamic electrochemical characteristics of the LIBs. By evaluating the CSOH indicators, we have developed an artificial neural network (ANN) model which can provide an effective prediction of the future CSOH of the LIBs. Percent error estimations have been done by implementing the Tanh activation function, and the estimation results of predicted equivalent series resistance, charge-transfer resistance, and solidelectrolyte interphase resistance are 5%, 1.5%, and 1%, respectively. The ANN model based on EIS analysis is a straightforward and effective approach that can provide novel routes for CSOH prediction of LIBs.
The practical application of lithium−sulfur (Li−S) batteries is still an issue mainly due to the shuttle phenomenon originating from the migration of lithium polysulfides (LiPs) between the electrodes, which leads to low Columbic efficiency and rapid capacity fading. In this work, sulfur electrodes are coated with TiO 2 thin films via a magnetron sputtering technique at varying deposition times. A stable capacity contribution (66%) from the long-chain to short-chain LiPs reactions is achieved for the TiO 2 coated electrodes, whereas a decline from 66% to 62% is observed for the uncoated electrode. This indicates a reversible use of the long-chain LiPs for the TiO 2 coated electrodes, representing a more efficient utilization of the active material. Correspondingly, the capacity retention is improved from 68.8% to 88.5% after TiO 2 coating. The TiO 2 coated electrode delivers a capacity of 570 mAh/g after 120 cycles at 0.1 C, which is 40% greater than that of the uncoated electrode. Similarly, the TiO 2 coated electrode delivers a capacity of 427 mAh/g after 170 cycles at 0.5 C, which is 67% greater than that of the uncoated electrode. Analysis of the binding energies of LiPs that are adsorbed on the TiO 2 surface by theoretical calculations shows that strong Li−O bonds dominate the interactions between the LiPs and TiO 2 layer. It is suggested that magnetron sputtered TiO 2 at the electrode−electrolyte interface can be effective in suppressing the shuttle effect due to the strong polysulfide adsorbing properties of the TiO 2 thin film.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.