Lithium metal batteries (LMBs) are one of the most promising energy storage technologies that would overcome the limitations of current Li‐ion batteries, based on their low density (0.534 g cm−3), ...low reduction potential (−3.04 V vs Standard Hydrogen Electrode) as well as their high theoretical capacities (3860 mAh g−1 and 2061 mAh cm−3). The overall cell mass and volume would be reduced while both gravimetric and volumetric energy densities would be greatly improved. Their electrochemical performance, however, is hampered by the low efficiency at high current densities and continuous degradation, which are related, among other factors, to the properties of the lithium metal anode (LMA). Hence, the production and processing of LMAs is crucial to obtain the desired properties that would enable LMBs. Here, the conventional method used for the production of LMAs, which is the combination of extraction, electrowinning, extrusion, and rolling processes, is reviewed. Then, the advances in the different alternative methods that can be used to produce and improve the properties of LMAs are described, which are divided into vapor phase, liquid phase, and electrodeposition. Within this last method, the anode‐less concept, for which different approaches to the development of advanced current collectors are illustrated, is included.
Lithium metal batteries (LMBs) are one of the most promising energy storage technologies that would overcome the limitations of current Li‐ion batteries. Their electrochemical performance, however, is hampered by the continuous degradation of the lithium metal anode (LMA). Hence, the production and processing of LMAs is crucial to obtain the desired properties that would enable LMBs.
The use of gel polymer electrolytes (GPEs) is of great interest to build high-performing rechargeable lithium metal batteries (LMBs) owing to the combination of good electrochemical properties and ...improved safety. Herein, we report a facile and scalable one-pot preparation method of a GPE based on highly safe polyethylene glycol dimethyl ether (PEGDME) plasticizer in a poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) polymer matrix. The prepared GPE exhibits excellent safety (nonflammability and thermal stability up to 250 °C) and outstanding electrochemical properties at room temperature (high ionic conductivity of 3.4 × 10–4 S cm–1 and high lithium transference number). Moreover, high loading LiFePO4 (6–7 mg cm–2) LMB using such GPE delivers a good C-rate response and high capacity (ca. 1 mAh cm–2 at C/10) with an excellent retention of 98% after 60 cycles in coin cell configuration. Notably, the prototype pouch cell (ca. 19 mAh at C/10) provides remarkable safety, mechanical flexibility, and strong tolerance toward bending and cutting. These results suggest that the prepared GPE is a promising candidate for the development of high performance, flexible, and safe LMBs that operate at room temperature, as well as for other energy storage systems beyond lithium-ion technologies.
Here, a platform for the development of highly responsive organic–inorganic enzyme hybrids is provided. The approach entails a first step of protein engineering, in which individual enzymes are ...armored with a porous nanogel decorated with imidazole motifs. In a second step, by mimicking the biomineralization mechanism, the assembly of the imidazole nanogels with CuSO4 and phosphate salts is triggered. A full characterization of the new composites reveals the first reported example in which the assembly mechanism is triggered by the sum of Cu(II)–imidazole interaction and Cu3(PO4)2 inorganic salt formation. It is demonstrated that the organic component of the hybrids, namely the imidazole‐modified polyacrylamide hydrogel, provides a favorable spatial distribution for the enzyme. This results in enhanced conversion rates, robustness of the composite at low pH values, and a remarkable thermal stability at 65 °C, exhibiting 400% of the activity of the mineralized enzyme lacking the organic constituent. Importantly, unlike in previous works, the protocol applies to the use of a broad range of transition metal cations (including mono‐, di‐, and trivalent cations) to trigger the mineralization mechanism, which eventually broadens the chemical and structural diversity of organic–inorganic protein hybrids.
A new platform for the assembly of organic–inorganic protein hybrids based on imidazole‐grafted enzyme nanogels is presented. The ability of the imidazole nanogels to mimic the biomineralization mechanism with a broad number of metallic salts allows the fabrication of protein hybrids on demand. Particularly, the use of enzyme nanogels leads to highly active, robust, and thermostable heterogeneous catalysts.
A combination of atomic layer deposition and photolithography is applied to fabricate interdigitated electrodes of aluminum‐doped zinc oxide embedded in polyethylene terephthalate substrates. Various ...designs with different gap to widths ratios are realized and important characteristics of the electrodes, including thickness, surface roughness, and electrical properties with different ZnO:Al2O3 ratios are studied. Oxygen plasma is applied to etch the polyethylene terephthalate surface and to embed the electrodes, a methodology which is a breakthrough toward ultimately thin devices fabrication. Moreover, the influence of oxygen plasma on the electrical properties of aluminum‐doped zinc oxide is analyzed in more detail. Electrochemical impedance spectroscopy studies of two different stimuli responsive ionogels are performed using the fabricated electrodes. The results show the suitability of the use of the fabricated electrodes to monitor changes in ion motion and morphology of stimuli responsive materials. These electrodes and the process of characterization of the ionogels presented could be implemented to monitor electrochemical changes in real applications such as protective coatings.
Functional interdigitated electrodes made of aluminum‐doped ZnO and embedded inside polyethylene terephthalate substrates are patterned combining photolithography with atomic layer deposition and plasma oxygen. The electrochemical properties of the electrodes can be used to monitor the swelling/drying behavior of ionogels and allows for distinguishing between ionogels with different polarity. This provides a means of monitoring the presence of defects on protective coatings.
•Charge transfer resistance depends on the porosity and chemical structure of the ionogel.•Ionogels with polar ionic liquids are excellent for fast response applications.•Nonpolar ionic liquids ...result in ionogels with more robust actuator behavior.
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The characterization of thermo-responsive ionogels with electrochemical impedance spectroscopy using gold interdigitated electrodes is described. The ionogels are synthesized using poly(N-isopropylacrylamide) as thermo-responsive gel and polymerized in the presence of two ionic liquids: ethyl-3-methylimidazolium ethyl sulfate or trihexyltetradecyl-phosphonium dicyanamide. The changes on the charge-transfer resistance show a clear dependence on the porosity and on the chemical structure of the ionogel. Moreover, the charge-transfer resistance parameter can be used to track in real time the photopolymerization and the hydration process of the ionogels. After exposing them to several drying/rehydration cycles the switching performance is fully understood. The results show that the ionogel with 1-ethyl-3-methylimidazolium ethyl sulfate requires less time to absorb and release water and is excellent for fast response applications. On the contrary, the one with the trihexyltetradecyl-phosphonium dicyanamide ionic liquid presents a more robust actuator behavior and a huge potential to be included in long-term applications. Finally, the observed microstructures have been correlated with the measured charge-transfer resistance providing a better understanding of the actuator behavior of these smart materials.
Memristors have emerged as promising devices for neuromorphic applications, particularly as synaptic weight. Graphene oxide, a partially oxidised and electrically insulating form of graphene, has ...been employed in metal/insulator/metal devices, where resistance switching based on the filamentary growth of the contacting metals has been demonstrated. Here we demonstrate an alternative highly reproducible resistance switching mechanism based on solid-state reduction of GO thin-films mediated by adsorbed water. It is shown that distinguishable and highly stable resistance states can be controllably realised in graphene oxide metal/insulator/metal devices. We have unravelled the growth mechanism and determined the growth kinetic of reduced graphene oxide, which enables a deterministic way to tune the resistance in GO devices. The demonstration of highly reproducible memristors based on graphene oxide crossbar devices is very promising for the realisation of low-cost and environmentally benign solution-processable neuromorphic synaptic weight.
Humidity-mediated electrochemical reduction of graphene oxide yields memristors with controllable and highly stable resistance states that can be used in multibit memory applications. The obtained kinetic, enables a predictive resistance setting.
Syndiotactic 1,2-polybutadiene nanoparticles (volume average diameter 13 nm) were functionalized in aqueous dispersion by free radical mercaptan addition. By appropriate choice of both water-soluble ...radical initiator and mercaptan concentration, nanoparticles with a degree of functionalization of up to 85% were prepared using 3-mercaptopropionic acid methyl ester and 3-mercaptopropionic acid. Only a minor portion of double bonds formed cycles instead of the desired thiol−ene addition products. The composition and structure of the nanoparticles were elucidated by combination of elemental analysis, NMR, IR, DLS, and TEM. Highly hydrophilic mercaptans (3-mercaptopropanesulfonic acid sodium salts), in contrast, only reacted with surface accessible double bonds to afford stable and redispersible nanoparticles solely stabilized with covalently bound moieties on their surface. Analogous grafting of the tripeptide glutathione was demonstrated.
A room temperature benzene and formaldehyde gas sensor system with an ionogel as sensing material is presented. The sensing layer is fabricated employing poly(
N
-isopropylacrylamide) polymerized in ...the presence of 1-ethyl-3-methylimidazolium ethyl sulfate ionic liquid onto gold interdigitated electrodes. When the ionogel is exposed to increasing formaldehyde concentrations employing N
2
as a carrier gas, a more stable response is observed in comparison to the bare ionic liquid, but no difference in sensitivity occurs. On the other hand, when air is used as carrier gas the sensitivity of the system towards formaldehyde is decreased by one order of magnitude. At room temperature, the proposed sensor exhibited in air higher sensitivities to benzene, at concentrations ranging between 4 and 20 ppm resulting, in a limit of detection of 47 ppb, which is below the standard permitted concentrations. The selectivity of the IL towards HCHO and C
6
H
6
is demonstrated by the absence of response when another IL is employed. Humidity from the ambient air slightly affects the resistance of the system proving the protective role of the polymeric matrix. Furthermore, the gas sensor system showed fast response/recovery times considering the thickness of the material, suggesting that ionogel materials can be used as novel and highly efficient volatile organic compounds sensors operating at room temperature.
Graphical abstract
The electrical and electrochemical properties of two ionogel materials based on the poly(N-isopropylacrylamide) gel with 1-ethyl-3-methylimidazolium ethyl sulfate and trihexyltetradecyl-phosphonium ...dicyanamide ionic liquids are investigated. The current-voltage curves show a current rectification for both ionogels and ionic liquids after inducing ion adsorption on gold electrode surface. The polymer matrix of the ionogels mitigates ion adsorption, resulting in lower rectification ratios when comparing with the corresponding ionic liquids. The stability and the electrochemical window (ECW) of the ionogels are calculated from cyclic voltammograms and compared with the ones obtained for the ionic liquids. The widest electrochemical window is achieved by the phosphonium ionic liquid and its ionogel. Finally, the effect of the absorbed atmospheric water and the mutual coefficient diffusion of the redox active species inside the IO is calculated. This work widens the knowledge of the behavior of ionogel materials characterized on gold electrode interfaces.
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The electrical properties of dielectric thin layers deposited on conducting substrates still need to be thoroughly characterized for a wide variety of applications such as solar modules, flexible ...displays and sensor integration. In this work, thin dielectric films composed of layers and alternated multilayers of SiO2 and Al2O3 up to a total thickness of 3μm have been deposited on flexible rough stainless steel substrates by means of reactive magnetron sputtering. Their electrical properties have been studied focusing on important parameters such as leakage current density and disruptive field strengths. Moreover, temperature annealing and bending effects have been quantified. It is concluded that the best electrical properties with this type of materials are achieved with multilayered structures.
•SiO2 and Al2O3 thin layers have been deposited on stainless steel substrates.•Electrical insulation and breakdown properties have been characterized.•Multilayered barriers showed improved insulation properties.•The effect of a temperature annealing process has been quantified.
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