• Energy Research

AbstractThe 2D graphyne‐related scaffolds linked by carbon–carbon triple bonds have demonstrated promising applications in the field of catalysis and energy storage due to their unique features including high conductivity, permanent porosity, and electron‐rich properties. However, the construction of related scaffolds is still mainly limited to the cross‐linking of CaC2 with multiple substituted aromatic halogens and there is still a lack of efficient methodology capable of introducing high‐concentration heteroatoms within the architectures. The development of alternative and facile synthesis procedures to afford nitrogen‐abundant graphyne materials is highly desirable yet challenging in the field of energy storage, particularly via the facile mechanochemical procedure under neat and ambient conditions. Herein, graphyne materials with abundant nitrogen‐containing species (nitrogen content of 6.9–29.3 wt.%), tunable surface areas (43–865 m2 g−1), and hierarchical porosity are produced via the mechanochemistry‐driven pathway by deploying highly electron‐deficient multiple substituted aromatic nitriles as the precursors, which can undergo cross‐linking reaction with CaC2 to afford the desired nitrogen‐doped graphyne scaffolds efficiently. Unique structural features of the as‐synthesized materials contributed to promising performance in supercapacitor‐related applications, delivering high capacitance of 254.5 F g−1 at 5 mV s−1, attractive rate performance, and good long‐term stability.

A dual-template strategy for facile preparation of a bifunctional oxygen electrocatalyst for high-performance rechargeable zinc–air batteries has been reported.

Homogenized Sb2O3/WTC composite anode exhibited encapsulated surface morphology and revealed stable redox peaks at 0.21/0.26 V and 0.80/0.76 V. Thus, the sodium half-cell delivered the discharge-charge capacities of 218/ 207 mA h g–1 at 37 mA g–1.

The key to understanding the cycling mechanism of lithium-ion battery electrodes is to develop methods to monitor the dynamic cell chemistry, but the complexity of the problem has continued to pose an obstacle.

Quasi-liquid solid electrolytes are a promising alternative for next-generation Li batteries. These systems combine the safety of solid electrolytes with the desired properties of liquids and are typically formed by solutions of Li salts in ionic liquids incorporated into solid matrices. Here, we present a fundamental understanding of the transport properties in solutions of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Emim][TFSI]), either in bulk form or incorporated in a boron nitride (BN) matrix. We performed a series of quasi-elastic neutron scattering experiments that, given the high incoherent neutron scattering cross section of hydrogen, allowed us to focus on the Emim+ dynamics. First, [Emim][TFSI]/LiTFSI solutions (0.5 and 2.5 mol·kg-1) were investigated and we show how the increase in the concentration reduces the Emim+ mobility and increases the activation energy of their long-range motions. Then, the 0.5 mol·kg-1 solution was incorporated into the BN matrix and we report that the diffusivities of the Emim+ cations that remain mobile under confinement are highly accelerated in comparison with the bulk sample and the activation energy of these motions is drastically reduced. We present the experimental evidence that this effect is related to the content of the Emim+ cations immobilized near the surfaces of the BN pores.

Electrical double-layer capacitors (EDLCs) are of increasing importance in energy storage from renewable sources. The properties of the electrode and electrolyte materials influence the energy and power densities of EDLCs. We examined the specific capacitance and ion dynamics of a protic ionic liquid confined in pre-intercalated Ti3C2Tx MXene. Our electrochemical measurements demonstrated that the creation of a protic ionic liquid, 1-butyl-3-H-imidazolium bis(trifluoromethanesulfonyl)imide (BuIMH-NTf2), using a mixture of ionic liquid, 1-butyl imidazole (BuIM), and salt, bis(trifluoromethanesulfonyl)imide (HNTf2), in a ratio of 0.8:0.2 led to the optimal capacitance. Remarkably, quasi-elastic neutron scattering measurements revealed increased particle mobility at this composition, attributed to the more efficient accumulation of BuIMH+ on the electrode surface. This deposit of additional ions results in fewer BuIM molecules away from the surface, enhancing their mobility due to reduced crowding. This composition-dependent electrochemical behavior will guide the formulation of more efficient protic ionic liquid systems, enabling faster ion transport in energy storage devices.

The development of new electrolyte and electrode designs and compositions has led to advances in electrochemical energy-storage (EES) devices over the past decade. However, focusing on either the electrode or electrolyte separately is insufficient for developing safer and more efficient EES devices in various working environments, as the energy-storage ability is determined by the ion arrangement and charge and/or electron transfer at the electrode–electrolyte interface. In this Review, we assess the fundamental physicochemical and electrochemical properties at the electrode–electrolyte interfaces in Li-ion batteries and supercapacitors using safe and electrochemically stable ionic-liquid electrolytes. Key reactions and interactions at the electrode–electrolyte interface, as well as geometric constraints and temperature effects, are highlighted. Building on the fundamental understanding of interfacial processes, we suggest potential strategies for designing stable and efficient ionic-liquid-based EES devices with emerging electrode materials. The development of efficient, high-energy and high-power electrochemical energy-storage devices requires a systems-level holistic approach, rather than focusing on the electrode or electrolyte separately. In this Review, we discuss the interfacial reactions and ion transport in ionic-liquid-based Li-ion batteries and supercapacitors, and summarize their impact on device performance.

Abstract Molten chlorides are a good choice for fast-spectrum molten salt reactors, but many of their thermophysical and transport properties are not available. In this work we use classical molecular dynamics simulations based on the polarizable-ion model to investigate the structural and transport properties of NaCl-UCl3 at various U3+ mole fractions. Molar volume, coordination structure and number, network structure, heat capacity, diffusivity, and ion conductivity have been simulated. We find strong variation of the second coordination shells (U-U and Cl-Cl) with U3+ mole fraction. This is consistent with the increasing network formation or oligomerization of UCl63− and UCl74− units via shared Cl− ions. The movement of Cl− is strongly coupled with U3+ as the U-Cl network structures become dominant in the mixture when the mole fraction of UCl3 is >0.25. Evaluation of a heat-transfer figure-of-merit suggests that 0.20 to 0.30 is an optimal mole fraction of UCl3 to achieve both lower operating temperatures and better heat transfer.