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State of Charge (SoC) estimation for Lithium‐Iron Phosphate (LFP) batteries is challenging due to a flat Open Circuit Voltage (OCV) curve and a well‐known hysteresis effect. The authors built upon a previous study, which has shown that hysteresis in LFP is not an inherent characteristic but a very slow relaxation process when compared to other battery chemistries. Distribution of Relaxation Times (DRT) is used to deconvolve Electro‐Impedance Spectroscopy (EIS) measurements and model the hysteresis effect. The extracted DRT parameters show good agreement at low frequencies with previous thermodynamic studies in both fresh and aged cell conditions. The proposed model, called hystimator, integrates the hysteresis characteristics into a physics‐based Electro‐Chemical Model (ECM). The validation results show a significant reduction in the Root Mean Square Error (RMSE) during real‐world laboratory testing. This approach holds promise for SoC estimation in LFP battery cells, especially in embedded Battery Management System (BMS). [ABSTRACT FROM AUTHOR]

This study explores the efficacy of employing P(VDF−TrFE), a ferroelectric copolymer, to mitigate the formation of dead lithium in Li‐metal anodes when paired with carbonate electrolytes. Employing non‐solvent induced phase separation (NIPS), self‐standing membranes and coatings on polypropylene (PP) separators were prepared, both demonstrating a homogenous cellular pore structure and excellent ionic conductivity. Rigorous evaluation in pouch cell formats, featuring a thin Li‐metal anode (50 μm), a high‐loading NMC532 cathode (3 mAhcm−2), and a carbonate electrolyte, reveals the superior performance of cells with P(VDF−TrFE)‐coated PP separators. Notably, these cells exhibit slower and more consistent capacity fading, as well as the weakest increase in impedance, as evidenced by Electrochemical Impedance Spectroscopy (EIS) investigations. This work underscores the promising role of P(VDF−TrFE) as a key material for addressing challenges associated with dead lithium, offering valuable insights for advancing Li‐metal battery technologies in practical applications. [ABSTRACT FROM AUTHOR]

Herein, a methodology to investigate aging of commercial cylindrical Li‐ion cells is introduced. Distribution of relaxation time (DRT) method is applied to deconvolute electrochemical impedance spectroscopy (EIS) measurements and separate those polarization effects that are usually overlapped in the frequency domain by means of a peak‐based representation. Half‐cells are built at the beginning and end of life to link the electrochemical and aging processes occurring at anode and/or the cathode sides. Moreover, lab‐made full‐cells are exploited to verify the reproducibility when compared with cylindrical cells. The results of an extensive analysis of around 500 EIS spectra return an unambiguous attribution of different electrochemical processes to different time constants and ultimately to different DRT peaks. Digital imaging validates graphite degradation, mainly related to lithium plating. Scanning electron microscopy validates the degradation at NMC cathode, mainly attributed to particle cracking. It is concluded that DRT peaks allow to characterize cell aging and their tracking can help to develop more reliable state of health estimators. [ABSTRACT FROM AUTHOR]