The solid-electrolyte interphase (SEI) plays a key role in the stability of lithium-ion batteries as the SEI prevents the continuous degradation of the electrolyte at the anode. We combine the feedback and multi-frequency alternating-current modes of scanning electrochemical microscopy (SECM) for the first time to assess quantitatively the local electronic and ionic properties of the SEI varying the SEI formation conditions and the used electrolytes in the field of Li-ion batteries (LIB).
In today’s cell production, the focus lies on maximizing productivity while maintaining product quality. To achieve this, the lamination of electrode and separator is one key process technology, as it bonds the electrode and separator to form mechanically resilient intermediate products.This paper addresses the investigation of interdependencies and proposes three characterization methods (grey scale analysis, high potential tests, electrochemical cycling and C-rate tests).
Advanced EIS was applied to characterize industrial Ni-Cd batteries and to investigate the electrochemical redox processes. A two-term calibration workflow was used for accurate complex impedance measurements across a broad frequency range of 10 mHz to 2 kHz, resulting in calibrated resistance and reactance values. The EIS calibration significantly improved the measurements, particularly at high frequencies above 200 Hz, with differences of 6–8% to the uncalibrated impedance.
An interlaboratory Round-Robin comparison between three-labs is conducted where calibrated electrochemical-impedance-spectroscopy (EIS) is measured on prismatic cell dummies and prismatic batteries. Advanced EIS calibration workflow is employed allowing for precise measurements of low micro-Ohm impedances in a broad frequency range of 50 mHz to 10 kHz. Significant systematic-error corrections are obtained from the calibration.
In this work, a new, cheap and easily-implementable methodology to analyzes the quality of the Solid Electrolyte Interphase (SEI) on the negative electrode of Li-ion batteries (LIBs) is proposed. First, a redox-mediator is added in the electrolyte after the SEI formation cycle, and the redox mediator leads to an internal self-discharge process that is inversely proportional to the electrically-insulating character of the SEI. Second, a few charge and discharge cycles are applied to the battery and the presence of the redox-mediator provokes a shuttle effect enables by the lack of electrically protecting character of the SEI which consumes charges decreasing the coulombic efficiencies, enhancing the sensibility to the SEI protecting nature. We believe that the findings based on the application of this mediator-enhanced coulometry can be used to accurately predict the cyclic behavior of LIBs under extended operating conditions, which is especially relevant for a better comprehension of future industrial needs for battery R&D in cell components and production fields.
Accurate measurement of the impedance over a broad frequency spectrum is of high relevance in battery tests, also requiring specific calibration methods and evaluation of error bounds. Here, we report for the first time a comprehensive uncertainty analysis of calibrated EIS for batteries. We aim to identify two uncertainty sources, the fixture repeatability and measurement noise, and evaluate their effect on the measured impedances.
Anatase TiO2 is a promising material for Li-ion (Li+) batteries with fast charging capability. However, Li+ (de)intercalation dynamics in TiO2 remain elusive and reported diffusivities span many orders of magnitude. Here, we develop a smart protocol for scanning electrochemical cell microscopy (SECCM) with in situ optical microscopy (OM) to enable the high-throughput charge/discharge analysis of single TiO2 nanoparticle clusters.
A 7 kWh automotive battery module with 396 interconnected cells was tested with electrochemical impedance spectroscopy (EIS) and time-domain pulsing over 260 charge-discharge cycles. An EIS calibration workflow was developed for low complex impedance values in a frequency range of 1 kHz to 50 mHz. Significant corrections on the resistance and the reactance were obtained from the calibration, particularly at frequencies above 100 Hz.