Degradation identification of LiNi0.8Co0.1Mn0.1O2/graphite lithium-ion batteries under fast charging conditions

Multi-dimensional, Multi-scale Analysis of Interphase Chemistry for Enhanced Fast-Charging of Lithium-Ion Batteries with Ion Mass Spectrometry

Understanding the fundamental properties of electrode-electrolyte interphases (EEIs) is essential for designing electrolytes that support stable operation under high charging rates. In this study, we benchmark our fast-charging electrolyte (FCE) against the commercial LP57 electrolyte to identify the EEI characteristics that enhance fast-charging performance. By utilizing the latest advances in time-of-flight secondary ion mass spectrometry (TOF-SIMS) and focused-ion beam (FIB) techniques, we reveal the complex chemical architecture of the cathode-electrolyte interphase (CEI). Our findings indicate that stable battery operation under fast-charging conditions requires reduced surface reactivity rather than stabilizing the bulk integrity of the cathode. While inorganic species are often cited as beneficial for EEI composition, their distribution within the EEI is equally critical. Additionally, dynamic interactions between the cathode material and conductive carbon significantly affect CEI formation and alter the passivation layer chemistry. A chemically homogeneous distribution of CEI components passivating preferentially the active material particles is desired for enhanced performance. Notably, the amount of electrolyte decomposition species in the solid-electrolyte interphase (SEI) far outweighs their distribution within the SEI in determining better electrochemical performance. An inorganic-rich SEI effectively protects graphite particles, suppresses the accumulation of metallic lithium, and prevents the formation of lithium dendrites. Overall, an enhanced fast-charging performance can be achieved by tuning the interphase chemistry and architecture on both the cathode and anode sides.

Fast Charging Impact on the Lithium-Ion Batteries’ Lifetime and Cost-Effective Battery Sizing in Heavy-Duty Electric Vehicles Applications

Fast charging is an essential stakeholder concern for achieving a deeper penetration of Electric Vehicles (EVs), as optimizing the charging times of conventional vehicles is as yet a bottleneck to be solved. An important drawback of EV’s fast charging lies in the degradation suffered by the Li-ion Batteries (LIBs) at high charging currents. A deep understanding of the how these fast-charging activities affect the LIBs’ degradation is necessary in order to design appropriate fast charging stations and EV powertrains for different scenarios and contexts. In this regard, the present paper analyzes the effect of fast charging on Libs’ degradation under operation profiles from real driving cycles. Specifically, Battery Electric Buses (BEBs) driving profiles from three demos in European Cities (Gothenburg, Osnabrück and Barcelona) have been used in this analysis. In order to deduce the best practices for the design of the charging stations, different sizes for the chargers have been simulated, focusing on the analysis of the LIB degradation under each situation. Besides, for the design of the EV powertrain, different LIB sizes and LIB chemistries (Lithium Nickel Manganese Cobalt-NMC, Lithium Iron Phosphate-LFP, and Lithium Titanate Oxide-LTO) have also been proposed and compared in terms of LIB degradation. The results demonstrated that LTO batteries exhibited the lowest degradation, with capacity fade values under 1.5%/year in the nominal scenario (nominal charger and LIB sizes). As long as a full charging is ensured, reducing the fast charger size has been found to be a cost-effective measure, as the LTO degradation can be reduced at least to 1.21%/year. In addition, increasing the battery (BT) size has also been found to be a cost-effective approach for LTO batteries. In this case, it was found that for a 66% increase in capacity, the degradation can be reduced at least to 0.74%/year (more than 50% reduction). The obtained conclusions are seen as useful for the design of charging stations and EV’s BT systems that undergo fast charging.