Interfacial Engineering with a Nanoparticle-Decorated Porous Carbon Structure on ß″-Alumina Solid-State Electrolytes for Molten Sodium Batteries.

We present a novel anode interface modification on the ß″-alumina solid-state electrolyte that improves the wetting behavior of molten sodium in battery applications. Heat treating a simple slurry, composed only of water, acetone, carbon black, and lead acetate, formed a porous carbon network decorated with PbOx (0 ≤ x ≤ 2) nanoparticles between 10 and 50 nm. Extensive performance analysis, through impedance spectroscopy and symmetric cycling, shows a stable, low-resistance interface for close to 6000 cycles. Furthermore, an intermediate temperature Na-S cell with a modified ß″-alumina solid-state electrolyte could achieve an average stable cycling capacity as high as 509 mA h/g. This modification drastically decreases the amount of Pb content to approximately 3% in the anode interface (6 wt % or 0.4 mol %) and could further eliminate the need for toxic Pb altogether by replacing it with environmentally benign Sn. Overall, in situ reduction of oxide nanoparticles created a high-performance anode interface, further enabling large-scale applications of liquid metal anodes with solid-state electrolytes.

The intrinsic electrochemical behavior of layered Cu2WSe4nanoparticles.

Nanoplates of Cu2WSe4(∼50 nm) were synthesized via a hot-injection method by one-pot selenation of WCl6and Cu(acac)2. This synthetic route provided another perspective towards the intrinsic electrochemical properties of Cu2MSe4(M = Mo or W), where their nanoparticles were previously synthesized via a metathesis route. Cations-dependent cathodic events and surface activation anodic events were identified by cyclic voltammetry in acetonitrile.

Recent Progress in Cathode Materials for Sodium-Metal Halide Batteries.

Transitioning from fossil fuels to renewable energy sources is a critical goal to address greenhouse gas emissions and climate change. Major improvements have made wind and solar power increasingly cost-competitive with fossil fuels. However, the inherent intermittency of renewable power sources motivates pairing these resources with energy storage. Electrochemical energy storage in batteries is widely used in many fields and increasingly for grid-level storage, but current battery technologies still fall short of performance, safety, and cost. This review focuses on sodium metal halide (Na-MH) batteries, such as the well-known Na-NiCl2 battery, as a promising solution to safe and economical grid-level energy storage. Important features of conventional Na-MH batteries are discussed, and recent literature on the development of intermediate-temperature, low-cost cathodes for Na-MH batteries is highlighted. By employing lower cost metal halides (e.g., FeCl2, and ZnCl2, etc.) in the cathode and operating at lower temperatures (e.g., 190 °C vs. 280 °C), new Na-MH batteries have the potential to offer comparable performance at much lower overall costs, providing an exciting alternative technology to enable widespread adoption of renewables-plus-storage for the grid.

High performance sodium-sulfur batteries at low temperature enabled by superior molten Na wettability.

Reducing the operating temperature of conventional molten sodium-sulfur batteries (∼350 °C) is critical to create safe and cost-effective large-scale storage devices. By raising the surface treatment temperature of lead acetate trihydrate, the sodium wettability on ß''-Al2O3 improved significantly at 120 °C. The low temperature Na-S cell can reach a capacity as high as 520.2 mA h g-1 and stable cycling over 1000 cycles.

2D nanocrystalline ternary selenides Cu2MSe4 (M = Mo/W).

A high-temperature metathesis reaction between CuBr and [Ph4P]2MSe4 (M = Mo or W) gave rise to nanocrystalline Cu2MSe4 with a phase-pure M = Mo compound that was obtained for the first time. After exploring the formation mechanism, we found that the sub-stoichiometric ratios of CuBr to MSe42- resulted in the formation of a linear byproduct impurity, [Ph4P]CuMSe4 (M = Mo or W). However, excess CuBr selectively steered the reaction to the desired Cu2MSe4. As a consequence of the newfound similarity in the reaction conditions for both metals, we have demonstrated the applicability of this method towards a mixed Mo/W quaternary composition.

Molecular chains of coordinated dimolybdenum isonicotinate paddlewheel clusters.

A growing focus on the use of coordination polymers for active device applications motivates the search for candidate materials with integrated and optimized charge transport modes. We show herein the synthesis of a linear coordination polymer comprised of Mo2(INA)4 (INA = isonicotinate) metal-organic clusters. Single-crystal X-ray structure determination shows that this cluster crystallizes into one-dimensional molecular chains, whose INA-linked Mo2 cores engage in alternate axial and equatorial binding motifs along the chain axis. Electron paramagnetic resonance spectra, absorption spectra, and density functional theory calculations show that the aforementioned linear coordination environment significantly modifies the electronic structure of the clusters. This work expands the synthetic foundation for assembly of coordination polymers with tailorable dimensionalities and charge transport properties.

Hierarchically Ordered Two-Dimensional Coordination Polymers Assembled from Redox-Active Dimolybdenum Clusters.

Coordination polymers (CPs) supporting tunable through-framework conduction and responsive properties are of significant interest for enabling a new generation of active devices. However, such architectures are rare. We report a redox-active CP composed of two-dimensional (2D) lattices of coordinatively bonded Mo2(INA)4 clusters (INA = isonicotinate). The 2D lattices are commensurately stacked and their ordering topology can be synthetically tuned. The material has a hierarchical pore structure (pore sizes distributed between 7 and 33 Å) and exhibits unique CO2 adsorption (nominally Type VI) for an isotherm collected at 195 K. Furthermore, cyclic voltammetry and electrokinetic analyses identify a quasi-reversible feature at E1/2 = -1.275 V versus ferrocene/ferrocenium that can be ascribed to the [Mo2(INA)4]0/-1 redox couple, with an associated standard heterogeneous electron transfer rate constant ks = 1.49 s-1. The tunable structure, porosity, and redox activity of our material may render it a promising platform for CPs with responsive properties.

Pt Electrodes Enable the Formation of µ4-O Centers in MOF-5 from Multiple Oxygen Sources.

The µ4-O2- ions in the Zn4O(O2C-)6 secondary building units of Zn4O(1,4-benzenedicarboxylate)3 (MOF-5) electrodeposited under cathodic bias can be sourced from nitrate, water, and molecular oxygen when using platinum gauze as working electrodes. The use of Zn(ClO4)2·6H2O, anhydrous Zn(NO3)2, or anhydrous Zn(CF3SO3)2 as Zn2+ sources under rigorous control of other sources of oxygen, including water and O2, confirm that the source of the µ4-O2- ions can be promiscuous. Although this finding reveals a relatively complicated manifold of electrochemical processes responsible for the crystallization of MOF-5 under cathodic bias, it further highlights the importance of hydroxide intermediates in the formation of the Zn4O(O2C-R) secondary building units in this iconic material and is illustrative of the complicated crystallization mechanisms of metal-organic frameworks in general.