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Anodic dissolution of aluminum (commonly called aluminum corrosion) is a potential issue in sodium-ion batteries. Herein, it is demonstrated how different sodium-ion battery electrolyte solutions affect this phenomenon. The type of electrolyte was critical for the presence of anodic dissolution, while the solvent appeared to alter the dissolution process.

Knowledge about capacity losses related to the solid electrolyte interphase (SEI) in sodium-ion batteries (SIBs) is still limited. One major challenge in SIBs is that the solubility of SEI species in liquid electrolytes is comparatively higher than the corresponding species formed in Li-ion batteries. This study sheds new light on the associated capacity losses due to initial SEI formation, SEI dissolution and subsequent SEI reformation, charge leakage via SEI and subsequent SEI growth, and diffusion-controlled sodium trapping in electrode particles. By using a variety of electrochemical cycling protocols, synchrotron-based X-ray photoelectron spectroscopy (XPS), gas chromatography coupled with mass spectrometry (GC-MS), and proton nuclear magnetic resonance (¹H-NMR) spectroscopy, capacity losses due to changes in the SEI layer during different open circuit pause times are investigated in nine different electrolyte solutions. It is shown that the amount of capacity lost depends on the interplay between the electrolyte chemistry and the thickness and stability of the SEI layer. The highest capacity loss is measured in NaPF₆ in ethylene carboante mixed with diethylene carbonate electrolyte (i.e., 5 µAh h^−1/2_pause or 2.78 mAh g·h^−1/2_pause) while the lowest value is found in NaTFSI in ethylene carbonate mixed with dimethoxyethance electrolyte (i.e., 1.3 µAh h^−1/2_pause or 0.72 mAh g·h^−1/2_pause).

A wide array of carbon materials finds extensive utility across various industrial applications today. Nonetheless, the production processes for these materials continue to entail elevated temperatures, necessitate the use of inert atmospheres, and often involve the handling of aggressive and toxic chemicals. The prevalent method for large-scale carbon material production, namely the pyrolysis of waste biomass and polymers, typically unfolds within the temperature range of 500–700 °C under a nitrogen (N2) atmosphere. Unfortunately, this approach suffers from significant energy inefficiency due to substantial heat loss over extended processing durations. In this work, we propose an interesting alternative: the carbonization of photothermal nanocellulose/polypyrrole composite films through CO2 laser irradiation in the presence of air. This innovative technique offers a swift and energy-efficient means of preparing carbon materials. The unique interaction between nanocellulose and polypyrrole imparts the film with sufficient stability to retain its structural integrity post-carbonization. This breakthrough opens up new avenues for producing binder-free electrodes using a rapid and straightforward approach. Furthermore, the irradiated film demonstrates specific and areal capacitances of 159 F g−1 and 62 μF cm−2, respectively, when immersed in a 2 M NaOH electrolyte. These values significantly surpass those achieved by current commercial activated carbons. Together, these attributes render CO2-laser carbonization an environmentally sustainable and ecologically friendly method for carbon material production.

Hard X-ray photoelectron spectroscopy (HAXPES) was used to perform a non-destructive depth profile of AlCrNbYZrN_x (x = 0 to ∼50 at.%) thin films. The outermost native oxide of the pristine thin films contained the highest coordination oxides of every metal. Substoichiometric oxides or oxynitrides were found underneath. After exposure to 1.0 M HCl, increases in the most highly coordinated oxides of Cr, Nb, and Al in films with up to 37 at.% N were observed, suggesting that the low coordination oxides and oxynitrides in the subsurface had been further oxidised and were intermediary compounds in the passivation process. Al and Y oxides were lost to the HCl electrolyte, in agreement with their respective Pourbaix diagrams. The film with 49 at.% N showed little to no change in the data due to its high porosity which led to the oxide being detected at all probed depths. The metal core level spectra revealed a preferential order in which nitrogen bonded with the different metals. Nitrogen interacted first with Y, then Zr, then Al and Nb, and lastly Cr as the nitrogen content was increased.

Memristive crossbar arrays (MCAs) offer parallel data storage and processing for energy-efficient neuromorphic computing. However, most wafer-scale MCAs that are compatible with complementary metal–oxide–semiconductor (CMOS) technology still suffer from substantially larger energy consumption than biological synapses, due to the slow kinetics of forming conductive paths inside the memristive units. Here we report wafer-scale Ag₂S-based MCAs realized using CMOS-compatible processes at temperatures below 160 oC. Ag₂S electrolytes supply highly mobile Ag+ ions, and provide the Ag/Ag₂S interface with low silver nucleation barrier to form silver filaments at low energy costs. By further enhancing Ag⁺ migration in Ag₂S electrolytes via microstructure modulation, the integrated memristors exhibit a record low threshold of approximately -0.1 V, and demonstrate ultra-low switching-energies reaching femtojoule values as observed in biological synapses. The low-temperature process also enables MCA integration on polyimide substrates for applications in flexible electronics. Moreover, the intrinsic nonidealities of the memristive units for deep learning can be compensated by employing an advanced training algorithm. An impressive accuracy of 92.6 % in image recognition simulations is demonstrated with the MCAs after the compensation. The demonstrated MCAs provide a promising device option for neuromorphic computing with ultra-high energy-efficiency.  

This study provides principles for designing new corrosion resistant high entropy alloys. The theoretical framework is a percolation model developed by Newman and Sieradzki that predicts the ability of an alloy to passivate, i.e., to form a protective surface oxide, based on its composition. Here, their model is applied to more complex materials than previously, namely amorphous CrFeNiTa and CrFeNiW alloys. Furthermore, the model describes a more complex passivation process: reforming the oxide layer above the transpassive potential of Cr. The model is used to predict the lowest concentration of Ta or W required to extend the passive region, yielding 11–14 at% Ta and 14–17 at% W. For CrFeNiTa, experiments reveal a threshold value of 13–15 at% Ta, which agrees with the prediction. For CrFeNiW, the experimentally determined threshold value is 37–45 at% W, far above the predicted value. Further investigations explore why the percolation model fails to describe the CrFeNiW system; key factors are the higher nobility and the pH sensitivity of W. These results demonstrate some limitations of the percolation model and offer complementary passivation criteria, while providing a design route for combining the properties of the 3d transition metal and refractory metal groups.

The development of “anode-free” lithium-metal batteries with high energy densities is, at present, mainly limited by the poor control of the nucleation of lithium directly on the copper current collector, especially in conventional carbonate electrolytes. It is therefore essential to improve the understanding of the lithium nucleation process and its interactions with the copper substrate. In this study, it is shown that diffusion of lithium into the copper substrate, most likely via the grain boundaries, can significantly influence the nucleation process. Such diffusion makes it more difficult to obtain a great number of homogeneously distributed lithium nuclei on the copper surface and thus leads to inhomogeneous electrodeposition. It is, however, demonstrated that the nucleation of lithium on copper is significantly improved if an initial chemical prelithiation of the copper surface is performed. This prelithiation saturates the copper surface with lithium and hence decreases the influence of lithium diffusion via the grain boundaries. In this way, the lithium nucleation can be made to take place more homogenously, especially when a short potentiostatic nucleation pulse that can generate a large number of nuclei on the surface of the copper substrate is applied.

Magnetron sputter deposition of metal/carbon nanocomposites has been explored for many metals and a few alloys. In this paper, the formation of nanocomposites based on complex high entropy alloys (HEAs) was explored, focusing on the effect of the average carbon affinity on the phase formation. Two HEA systems were compared: CoCrFeMnNi and Cr26Fe27Ni27Ta20. For each alloy, around 20-50 at% carbon was added through combinatorial co-sputtering. Thermodynamic calculations predicted decomposition of these materials into multiple alloy phases, metal carbides, and, at higher concentrations, free graphitic carbon. Free carbon was found in the coatings at carbon concentrations above 28 and 33 at% for the CoCrFeMnNi and Cr26Fe27Ni27Ta20 systems, respectively, which agreed with the theoretical predictions. However, the segregation of metallic ele-ments and the formation of crystalline carbides were suppressed by the rapid quenching during deposition. All coatings were, instead, amorphous and consisted of either a single metallic phase or a mixture of a metallic phase and sp2- and sp3-hybridized carbon. Mechanical and electrochemical tests were performed, including in-situ fragmentation tests to quantify the crack resistance. The presence of free carbon made the coatings softer than the corresponding single-phase materials. Under tensile strain, the nanocomposite coatings formed a larger number of narrower cracks and exhibited less delamination at high strains.