The paper proposes an advanced continuum level modelling framework characterized by a more consistent virtual representation of electrode topology to enhance prediction capability and generality of porous electrode theory based models. The proposed modelling framework, therefore, establishes the missing link between the mesoscopic scale with a detailed 3D representation of electrode topology and the continuum single cell scale, where interrelation to the real electrode topology was missing. This link is established by elaborating a unified approach for modelling materials with significantly different topologies of active material by virtually creating agglomerates, representing secondary particles, from primary particles. Proposed approach relies on multi-particle size distribution of primary particles and particle-to-particle connectivity. Generality of the proposed modelling framework is demonstrated by simulating LFP and NMC materials featuring significantly different electrode topologies by the same modelling framework while adapting only virtual representation of electrode topologies and intrinsic material properties. Credibility of the proposed modelling framework is confirmed through good agreement with experimental results for various discharge tests. Insightful simulation results also reveal background of the topologically driven low Li utilization at high current densities of the LFP material and topologically driven voltage response difference during the memory effect of different LFP materials.

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An innovative computationally efficient method for the simultaneous determination of top dead centre (TDC) offset and pressure offset is presented. It is based on characteristic deviations of the rate of heat release (ROHR) that are specific for both offsets in compression phase and expansion phase after the end of combustion. These characteristic deviations of the ROHR are derived from first principles and they were also confirmed through manual shifts of the pressure trace. The ROHR is calculated based on the first law of thermodynamics using an in-cylinder pressure trace, engine geometrical parameters and operating point specific parameters. The method can be applied in off-line analyses using an averaged pressure trace or in on-line analyses using a single pressure trace. In both application areas the method simultaneously determines the TDC position and the pressure offset within a single processing of the pressure trace, whereas a second refinement step can be performed for obtaining more accurate results as correction factors are determined more accurately using nearly converged input data. Innovative analytic basis of the method allows for significant reduction of the computational times compared to the existing methods for the simultaneous determination of TDC offset and pressure offset in fired conditions. The method was validated on a heavy-duty and a light-duty diesel engine.

Hysteresis is a general phenomenon regularly observed in various materials. Usually, hysteretic behavior is an intrinsic property that cannot be circumvented in the nonequilibrium operation of the system. Herein, it is shown that, at least with regard to the hysteretic behavior of phase‐separating battery materials, it is possible to enter (deeply) the hysteretic loop at finite battery currents. This newly observed electric response of the electrode, which is inherent to phase‐separating materials, is related to its microscopic origin arising from a (significant) share of the active material residing in an intraparticle phase‐separated state. This intriguing observation is further generalized by revealing that a phase‐separating material can feature (significantly) different chemical potentials at the same bulk lithiation level and temperature when exposed to the same finite current and external voltage hysteresis. Therefore, the intraparticle phase‐separated state significantly affects the DC and AC characteristics of the battery. The experimental evidence for entering the intraparticle phase‐separated state is supported by thermodynamic reasoning and advanced modeling. The current findings will help advance the understanding, control, diagnostics, and monitoring of batteries composed of phase‐separating materials while also providing pertinent motivation for the enhancement of battery design and performance.

Phase separating Li-ion battery cell cathode materials feature a well-known phenomenon called the memory effect. It manifests itself as an abnormal change in working voltage being dependent on cell cycling history. It was only recently that plausible mechanistic reasoning of the memory effect in Li-ion batteries was proposed. However, the existing literature does still not consistently reveal a phenomenological background for the onset or absence of the memory effect. This paper provides strong experimental and theoretical evidence of the memory effect in phase separating Li-ion battery cathode materials. Specifically, the background leading to the onset or absence of the memory effect and the underlying causal chain of phenomena from the collective particle-by-particle intra-electrode phenomena to macroscopic voltage output of the battery are presented and discussed. The results, clearly reveal that no memory effect is observed and predicted for low cut off voltages, whereas the absence of the first rest in memory writing cycle does not result in the absence of the memory effect, as previously believed. In addition, excellent agreement between the simulated and measured results is shown which, on one hand confirms the credibility of the combined analyses and, on the other, provides clear causal relations from macroscopic experimental parameters to simulated phenomena on the particle level.