Xinhua Zhu

Université Libre de Bruxelles | ULB · Department of Chemistry

Kelvin probe force microscope (KPFM) is an AFM-based technique, which can be used for studying lithium ion batteries (LIBs). The capabilities of this technique for practical applications have been explored further in this work. A direct correlation between the local surface potential measured by KPFM and the electrochemical potential of LiNi0.80Co0...

A comprehensive post-mortem study is conducted on the power-optimized LiNi0.80Co0.15Al0.05O2 (NCA) cathode material harvested from large-format commercial pouch cells with different aging conditions. Uneven degradation phenomena are observed in the harvested NCA electrode during the post-mortem analysis. A schematic model, which is associated with...

High voltage cathodes suffer from degradation phenomena that are challenging to observe and identify during cell operation. Dense and smooth sputtered thin films electrodes with an absence of binders and conductive additives allow a direct study of the active material upon Li insertion and extraction at surface and bulk. Using an operando spectrosc...

Electrochemical impedance spectroscopy (EIS) is a powerful technique for characterization of lithium-ion batteries (LIBs). It has extensively been used in laboratory research, but seldom in industrial applications, e.g., electrical vehicles (EVs). This is because the latter needs EIS measurements during operation, but achieving valid EIS measuremen...

Anomalous diffusion impedance due to the solid-state Li⁺ diffusion in Li-ion batteries is often troublesome for the analysis. In this work, we propose a novel analytical Parallel-diffusion Warburg (PDW) model and couple it with the conventional equivalent electrical circuit model (EECM) analysis to tackle this long-standing challenge. The analytica...

Anomalous diffusion impedance due to the solid-state Li+ diffusion in Li-ion batteries is often troublesome for the analysis. In this work, we propose a novel analytical Parallel-diffusion Warburg (PDW) model and couple it with the conventional equivalent electrical circuit model (EECM) analysis to tackle this long-standing challenge. The analytica...

Electrochemical impedance spectroscopy (EIS) is a powerful non-invasive tool for characterising electrochemical systems. Applied to Li-ion batteries, EIS is shown to be an informative indicator for their state-of-health (SoH) [1,2,3]. However, EIS is limited by the constraints of linearity and stationarity, while Li-ion batteries inherently behave...

Electrochemical impedance spectroscopy (EIS) is a non-invasive technique for examining kinetics of electrochemical systems. Applied to energy storage devices, the impedance contains information about the state-of-charge and state-of-health of a battery. Classical EIS measurements, as implemented in many cyclers, are restricted by two important assu...

Equilibria evolving over time, also called trends, are often present in ongoing measurements of real-life systems. These trends are considered as disturbances when computing the Best Linear Time-varying Approximation (BLTVA) of the system. Current techniques for dealing with trends in BLTVA measurements consist of modelling the trend with a finite...

The solid–electrolyte interphase (SEI), the passivation layer formed on anode particles during the initial cycles, affects the performance of lithium-ion batteries (LIBs) in terms of capacity, power output, and cycle life. SEI features are dependent on the electrolyte content, as this complex layer originates from electrolyte decomposition products...

The class of nonlinear time-varying (NLTV) systems includes all possible systems and, hence, is difficult to identify. Still, when the nonlinearities are not too strong then, depending on the application, a linear model might be sufficient for approximating the true response. To quantify the approximation error of the linear model, detecting and qu...

A systematic post-mortem analysis on a batch of power-optimized commercial LiNi 0.80 Co 0.15 Al 0.05 O 2 (NCA) electrodes with different aging conditions was conducted. This aging study provides direct evidence that the intrinsic surface heterogeneity, resulting in locally overcharge reactions, plays a critical role in the degradation of NCA electr...

A comprehensive electrochemical impedance study is conducted on LiNi0.80Co0.15Al0.05O2 electrode material as a function of state-of-charge and aging. Electrodes are harvested from four commercial batteries with different state-of-health conditions. Odd random phase electrochemical impedance spectroscopy and the symmetric cell approach are applied i...

Higher power output requires faster charge transfer reactions in the charge/discharge process. Lower activation energy directly correlates to faster Li ion diffusion. Morphology of active materials, binders, separators and electrolytes play an important role in determining the activation energy of a battery system. In [1] the authors showed through...

Several electrochemical energy technologies (batteries, fuel cells, supercapacitors, …) have been developed. Many have been commercialized, but a large number is still under development. Systems are optimized in terms of life time, performance and cost, and new systems are being designed. The electrode and electrolyte materials must have the requir...