Thermal safety associated with lithium-ion cells as power sources remains a critical industry concern. A comprehensive understanding of how internal exothermic side reactions contribute to temperature rise is fundamental for accurately analyzing thermal runaway processes and predicting the thermal safety of lithium-ion cells. While various side-reactions, such as decomposition of solid electrolyte interphase layer, reaction between anode materials and electrolyte, reaction between cathode materials and electrolyte, and electrolyte decomposition, have been identified as heat generation sources in previous studies, the quantification of these reactions remains insufficiently standardized. Particularly, the impact of heat generation from binder decomposition (most commonly polyvinylidene difluoride) at elevated temperatures on the thermal runaway process of lithium-ion cells has not been fully elucidated. Therefore, in this study, an electro-thermal coupled numerical model was developed for 18650-type lithium-ion cells to systematically investigate the synergistic effects of these five major side-reactions under high-temperature conditions leading to thermal runaway. Special emphasis was placed on precisely quantifying the contribution from binder decomposition heat during the thermal runaway process. The results demonstrate that once the ambient temperature exceeds the threshold required to initiate cascading exothermic side reactions, the inclusion or exclusion of the binder reaction in the model does not affect the overall assessment results of thermal runaway for lithium-ion cells. However, under these conditions, the heat contribution from binder decomposition to the total heat release increases significantly and therefore becomes one of the dominant heat sources for temperature rise during the thermal runaway propagation. Conversely, when ambient temperatures do not reach the threshold, the heat contribution from binder decomposition is negligible. Additionally, the improved electro-thermal coupling model serves as an effective simulation tool for designing battery systems with enhanced safety, selecting appropriate binder materials to mitigate the adverse effects of thermal runaway, and optimizing thermal management during battery development. This approach significantly reduces the research and development cycle. These findings establish appropriate heat source selection criteria for electro-thermal models under varying precision requirements and provide a theoretical foundation for both model simplification and high-fidelity optimization in lithium-ion battery design.

Fe-N-C catalysts have long suffered from kinetically sluggish oxygen reduction reaction (ORR) due to excessive adsorption strength toward oxygen intermediates and low site utilization. Heteroatom doping effectively accelerates ORR reaction kinetics through electronic structure modulation of metal sites for optimal intermediate adsorption, while chemical vapor deposition (CVD) enhances the turnover frequency (TOF) of active sites. Herein, we developed an FeSNC catalyst featuring abundant FeS₁N₄ sites via a dual-precursor CVD strategy. Experimental and theoretical analyses revealed that S incorporation disrupts the symmetric coordination of active sites, which optimizes OH* adsorption energies from 0.212 eV to 1.194 eV. Moreover, the TOF increased from 1.98 e^-1·site^-1·s^-1 to 6.32 e^-1·site^-1·s^-1, significantly enhancing the intrinsic activity of the catalyst. More notably, the hydrophilic character of S-containing species substantially improved hydrophilicity in the S-doped catalyst, thereby promoting mass transport of oxygen and proton delivery. As a result, the FeSNC catalyst exhibited an extremely high half-wave potential of 0.863 V in 0.1 mol·L^-1 HClO₄ and achieved a peak power density of 1.2 W·cm^-2 in H₂-O₂ PEMFCs. This work highlights the critical role of coordination engineering.

Entropy is a basic thermodynamic property of the electrical double layer (EDL) at metal/solution interfaces, yet, its definition, measurement, and theoretical treatment are dispersed in the literature, and, in some cases, ambiguous. In this paper, we revisit the thermodynamic theory of EDL, from which two variants of entropy, excess entropy and formation entropy, are obtained and compared. In terms of the formation entropy, two calculation routes are validated in the context of a primitive EDL model, namely, the Gouy-Chapman (GC) model. After clarifying the concepts and calculation routes, we investigate interfacial water effects on the EDL entropy, using a refined Gouy-Chapman-Stern (GCS) model accounting for chemical potential difference between oxygen- and hydrogen-down water molecules, denoted \delta \mu. The model-derived differential capacitance and entropy are compared with experimental data for the EDL at Au(111) in an aqueous electrolyte solution. The model reveals that the charge of maximum entropy (CME) is negative when water molecules have higher tendency to take oxygen-down configuration at the uncharged surface. Moreover, the formation entropy profile becomes asymmetric around the CME, when \delta \mu is potential-dependent. However, the model fails to simultaneously reproduce capacitance and entropy measurements on the same system taken from two separate studies, indicating deficiencies of the model or experimental errors. Nevertheless, this work stresses the importance of measuring both capacitance and entropy of EDLs at the same time.