Electrochemical impedance spectroscopy (EIS) is widely used to probe the physical and chemical processes in lithium (Li)‐ion batteries (LiBs). The key parameters include state‐of‐charge, rate ...capacity or power fade, degradation and temperature dependence, which are needed to inform battery management systems as well as for quality assurance and monitoring. All‐solid‐state batteries using a solid‐state electrolyte (SE), promise greater energy densities via a Li metal anode as well as enhanced safety, but their development is in its nascent stages and the EIS measurement, cell set‐up and modelling approach can be vastly different for various SE chemistries and cell configurations. This review aims to condense the current knowledge of EIS in the context of state‐of‐the‐art solid‐state electrolytes and batteries, with a view to advancing their scale‐up from the laboratory to commercial deployment. Experimental and modelling best practices are highlighted, as well as emerging impedance methods for conventional LiBs as a guide for opportunities in the solid‐state.
Materials to devices: Electrochemical impedance spectroscopy (EIS) is a powerful technique used in electrochemical research to interrogate materials, full cell devices and packs. This review summarizes the latest developments in EIS for sulfur, oxide and polymer solid‐state electrolytes in blocking electrode, symmetric and full cell configurations, with an outlook on how its applicability in this field can be improved.
High surface area N-doped mesoporous carbon capsules with iron traces exhibit outstanding electrocatalytic activity for the oxygen reduction reaction in both alkaline and acidic media. In alkaline ...conditions, they exhibit more positive onset (0.94 V vs RHE) and half-wave potentials (0.83 V vs RHE) than commercial Pt/C, while in acidic media the onset potential is comparable to that of commercial Pt/C with a peroxide yield lower than 10%. The Fe–N-doped carbon catalyst combines high catalytic activity with remarkable performance stability (3500 cycles between 0.6 and 1.0 V vs RHE), which stems from the fact that iron is coordinated to nitrogen. Additionally, the newly developed electrocatalyst is unaffected by the methanol crossover effect in both acid and basic media, contrary to commercial Pt/C. The excellent catalytic behavior of the Fe–N-doped carbon, even in the more relevant acid medium, is attributable to the combination of chemical functions (N-pyridinic, N-quaternary, and Fe–N coordination sites) and structural properties (large surface area, open mesoporous structure, and short diffusion paths), which guarantees a large number of highly active and fully accessible catalytic sites and rapid mass-transfer kinetics. Thus, this catalyst represents an important step forward toward replacing Pt catalysts with cheaper alternatives. In this regard, an alkaline anion exchange membrane fuel cell was assembled with Fe–N-doped mesoporous carbon capsules as the cathode catalyst to provide current and power densities matching those of a commercial Pt/C, which indicates the practical applicability of the Fe–N-carbon catalyst.
Rational design and controllable synthesis of nanostructured materials with unique microstructure and excellent electrochemical performance for energy storage are crucially desired. In this paper, a ...facile method is reported for general synthesis of hierarchically core–shell structured Ni3S2@NiMoO4 nanowires (NWs) as a binder‐free electrode for asymmetric supercapacitors. Due to the intimate contact between Ni3S2 and NiMoO4, the hierarchical structured electrodes provide a promising unique structure for asymmetric supercapacitors. The as‐prepared binder‐free Ni3S2@NiMoO4 electrode can significantly improve the electrical conductivity between Ni3S2 and NiMoO4, and effectively avoid the aggregation of NiMoO4 nanosheets, which provide more active space for storing charge. The Ni3S2@NiMoO4 electrode presents a high areal capacity of 1327.3 µAh cm−2 and 67.8% retention of its initial capacity when current density increases from 2 to 40 mA cm−2. In a two‐electrode Ni3S2@NiMoO4//active carbon cell, the active materials deliver a high energy density of 121.5 Wh kg−1 at a power density of 2.285 kW kg−1 with excellent cycling stability.
A facile method for general synthesis of core–shell structured Ni3S2@NiMoO4 nanowires as a binder‐free electrode for asymmetric supercapacitors is described in this study. Due to the intimate contact between the materials, core–shell structured Ni3S2@NiMoO4 binder‐free electrodes provide a promising target structure for energy storage.
Prevention and mitigation of thermal runaway presents one of the greatest challenges for the safe operation of lithium-ion batteries. Here, we demonstrate for the first time the application of ...high-speed synchrotron X-ray computed tomography and radiography, in conjunction with thermal imaging, to track the evolution of internal structural damage and thermal behaviour during initiation and propagation of thermal runaway in lithium-ion batteries. This diagnostic approach is applied to commercial lithium-ion batteries (LG 18650 NMC cells), yielding insights into key degradation modes including gas-induced delamination, electrode layer collapse and propagation of structural degradation. It is envisaged that the use of these techniques will lead to major improvements in the design of Li-ion batteries and their safety features.
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