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The electrocatalytic sulfur reduction reaction (SRR) and sulfur evolution reaction (SER), two fundamental multistep conversion processes in lithium–sulfur batteries (LSBs), are root-cause solutions to overcome sluggish redox kinetics and the polysulfide shuttling effect. Metal–organic framework (MOF) electrocatalysts have emerged as good platforms for catalyzing SRR and SER, but their catalytic performance is challenged by poor electrical conductivity and limited chemical stability. Functionalized MOFs and their hybrids may be beneficial for stabilizing and improving the desired catalytic properties to achieve high-performance LSBs. This review provides a detailed overview of engineering principles for improving the activity, selectivity, and stability of MOF-related electrocatalysts via composition modulation and nanostructure design as well as hybrid assembly. It presents and discusses the various advances achieved by using in situ characterization techniques, simulations, and theoretical calculations to reveal the dynamic evolution of MOF-related electrocatalysts, enabling an in-depth understanding of the catalysis mechanism at the molecular/atomic level. Lastly, prospects and possible research directions for MOF-related sulfur electrocatalysts are proposed.

Blue-emission (∼480 ​nm) CsPbBr₃ nanoparticles with ultra-small size (∼2.1 ​nm) are synthesized using the liquid nitrogen freezing with the ligand of dodecylbenzene sulfonic acid (DBSA). Asymmetric narrow emissions at the low energy side, with the full width at half-maximum of ∼20 ​nm, are observed in solution and film at room temperature. The spectral asymmetry is mainly ascribed to phonon vibronic replica with averaged phonon energy of ∼40 ​meV. Moreover, exciting this CsPbBr₃ nanoparticles solution using linearly polarized 6 ns pulsed laser at 355 ​nm, we observe polarized emission with polarization degree (P_PL) of ∼7%, and P_PL decreases more than 20% in the vibronic progression. However, the P_PL goes to zero in frozen solutions as well as in films. Thus we speculate the polarized emission is due to the photoinduced re-alignment of nanoparticles, and the diminished P_PL at the phonon side band may be due to the non-adiabatic electronic-to-vibronic transitions. The novel phenomena from the ultra-small CsPbBr₃ nanoparticle demonstrated in this work may provide fundamental insights into its photophysics with direct implications for optoelectronics.

Aqueous electrolytes offer superior prospects for advanced energy storage. “Water-in-salt” (WIS) electrolytes exhibit a wide electrochemical stability window (ESW), but their low conductivity, high viscosity, and precipitation at low temperatures restrict their application. Herein, we report a novel localized “water-in-pyrrolidinium chloride” electrolyte (LWIP; 1 ​mol/L, N-propyl-N-methylpyrrolidinium chloride/(water and N,N-dimethylformamide, 1:4 by molality)) enabling high-voltage, low-temperature supercapacitors (SCs). The greatly improved ESW (3.451 ​V) is mainly attributed to the strong solvation between Cl⁻ and water molecules, which broadens the negative stability. This water-binding mechanism is very different from that of a WIS electrolyte based on alkali metal salt. SCs using LWIP electrolytes not only yield a high operating voltage of 2.4 ​V and excellent capacity retention (82.8% after 15,000 cycles at 5 ​A ​g⁻¹) but also operate stably at −20 ​°C. This work provides new approaches for the design and preparation of novel electrolytes.

With the growing concern around the sustainability and supply of lithium, the need for alternative rechargeable energy storage technologies has become ever more pressing. Sodium-, potassium-, magnesium-, and zinc-ion batteries are fast becoming viable alternatives but are held back by capacity, rate and stability problems that have not developed comparably to lithium-ion batteries. To overcome these shortcomings and reduce the reliance on lithium, electrode materials used for these post-lithium batteries must be improved. Pre-intercalation of foreign species into the lattice of promising electrode materials can enhance their electrochemical performance in comparison to the un-pre-intercalated counterparts, closing the performance gap with lithium-ion batteries. This review article covers the common methods of pre-intercalating foreign species into electrode materials, the resulting structural effects and the improvements that are observed in the materials' electrochemical performance for post-lithium batteries. Timely and impactful work reported previously are summarised as examples of these improvements, demonstrating the value and ever-growing importance of pre-intercalation in today's battery landscape.

Present-day Li⁺ storage materials generally suffer from sluggish low-temperature electrochemical kinetics and poor high-temperature cycling stability. Herein, based on a Ca²⁺ substituted Mg₂Nb₃₄O₈₇ anode material, we demonstrate that decreasing the ionic packing factor is a two-fold strategy to enhance the low-temperature electrochemical kinetics and high-temperature cyclic stability. The resulting Mg_1.5Ca_0.5Nb₃₄O₈₇ shows the smallest ionic packing factor among Wadsley–Roth niobate materials. Compared with Mg₂Nb₃₄O₈₇, Mg_1.5Ca_0.5Nb₃₄O₈₇ delivers a 1.6 times faster Li​⁺ ​diffusivity at −20 ​°C, leading to 56% larger reversible capacity and 1.5 times higher rate capability. Furthermore, Mg_1.5Ca_0.5Nb₃₄O₈₇ exhibits an 11% smaller maximum unit-cell volume expansion upon lithiation at 60 ​°C, resulting in better cyclic stability; at 10C after 500 cycles, it has a 7.1% higher capacity retention, and its reversible capacity at 10C is 57% larger. Therefore, Mg_1.5Ca_0.5Nb₃₄O₈₇ is an all-climate anode material capable of working at harsh temperatures, even when its particle sizes are in the order of micrometers.

Optoelectronic artificial synapses (OEASs) are essential for realizing artificial neural networks (ANNs) in next-generation information processing that has high transmission speed, high bandwidth, and low power consumption. Two-dimensional (2D) materials endowed with strong light-matter interactions and atomically thin dangling-bond-free surfaces are candidates for achieving versatile optoelectronics. Developing 2D OEASs for future neuromorphic applications is significant to break the bottleneck of von Neumann architecture and achieve future artificial intelligence systems. This review primarily focuses on recent developments in advanced 2D OEASs, discussing their working mechanism as well as potential applications. Common materials, device structures, and their synthesis and construction methods are also summarized. Finally, the prospects for future 2D OEASs from the perspectives of materials, performance, and applications are briefly described.

Ultra-thick, dense alloy-type anodes are promising for achieving large areal and volumetric performance in potassium-ion batteries (PIBs), but severe volume expansion as well as sluggish ion and electron diffusion kinetics heavily impede their widespread application. Herein, we design highly dense (3.1 ​g ​cm⁻³) Ti₃C₂T_x MXene and graphene dual-encapsulated nano-Sb monolith architectures (HD-Sb@Ti₃C₂T_x-G) with high-conductivity elastic networks (1560 ​S ​m⁻¹) and compact dually encapsulated structures, which exhibit a large volumetric capacity of 1780.2 ​mAh cm⁻³ (gravimetric capacity: 565.0 ​mAh g⁻¹), a long-term stable lifespan of 500 cycles with 82% retention, and a large areal capacity of 8.6 ​mAh cm⁻² (loading: 31 ​mg ​cm⁻²) in PIBs. Using ex-situ SEM, in-situ TEM, kinetic investigations, and theoretical calculations, we reveal that the excellent areal and volumetric performance mechanism stems from the three dimensional (3D) high-conductivity elastic networks and the dual-encapsulated Sb architecture of Ti₃C₂T_x and graphene; these effectively mitigate against volume expansion and the pulverization of Sb, offering good electrolyte penetration and rapid ionic/electronic transmission. Ti₃C₂T_x also decreases the K⁺ diffusion energy barrier, and the ultra-thick compact electrode ensures volumetric and areal performance. These findings provide a feasible strategy for fabricating ultra-thick, dense alloy-type electrodes to achieve high areal and volumetric capacity energy storage via highly-dense, dual-encapsulated architectures with conductive elastic networks.

Developing cost-effective and reliable solid-state sodium batteries with superior performance is crucial for stationary energy storage. A key component in facilitating their application is a solid-state electrolyte with high conductivity and stability. Herein, we employed aliovalent cation substitution to enhance ionic conductivity while preserving the crystal structure. Optimized substitution of Y³⁺ with Zr⁴⁺ in Na₅YSi₄O₁₂ introduced Na⁺ ​ion vacancies, resulting in high bulk and total conductivities of up to 6.5 and 3.3 ​mS ​cm⁻¹, respectively, at room temperature with the composition Na_4.92Y_0.92Zr_0.08Si₄O₁₂ (NYZS). NYZS shows exceptional electrochemical stability (up to 10 ​V vs. Na⁺/Na), favorable interfacial compatibility with Na, and an excellent critical current density of 2.4 ​mA ​cm⁻². The enhanced conductivity of Na⁺ ​ions in NYZS was elucidated using solid-state nuclear magnetic resonance techniques and theoretical simulations, revealing two migration routes facilitated by the synergistic effect of increased Na⁺ ​ion vacancies and improved chemical environment due to Zr⁴⁺ substitution. NYZS extends the list of suitable solid-state electrolytes and enables the facile synthesis of stable, low-cost Na⁺ ion silicate electrolytes.

Nonaqueous Li metal batteries (LMBs) and aqueous Zn metal batteries (ZMBs) are promising next-generation secondary batteries owing to their high energy density. Selecting an appropriate electrolyte is critical for addressing the safety issues nonaqueous and aqueous metal batteries can encounter. Ionic liquids (ILs) have been widely used in secondary metal batteries because they are non-flammable, present good thermal stability, and have wide electrochemical windows. This review highlights the research progress on IL-based electrolytes for stable Li/Zn metal anodes. We focus particularly on these electrolytes' electrochemistry and functionalities at the electrolyte/anode interface for inhibiting dendrite growth, preventing side reactions, and enhancing electrochemical performance. It is expected that this review will shed some light on the development of ILs for next-generation metal batteries.

Alongside the pursuit of high energy density and long service life, the urgent demand for low-temperature performance remains a long-standing challenge for a wide range of Li-ion battery applications, such as electric vehicles, portable electronics, large-scale grid systems, and special space/seabed/military purposes. Current Li-ion batteries suffer a major loss of capacity and power and fail to operate normally when the temperature decreases to −20 ​°C. This deterioration is mainly attributed to poor Li-ion transport in a bulk carbonated ester electrolyte and its derived solid–electrolyte interphase (SEI). In this mini-review discussing the limiting factors in the Li-ion diffusion process, we propose three basic requirements when formulating electrolytes for low-temperature Li-ion batteries: low melting point, poor Li⁺ affinity, and a favorable SEI. Then, we briefly review emerging progress, including liquefied gas electrolytes, weakly solvating electrolytes, and localized high-concentration electrolytes. The proposed novel electrolytes effectively improve the reaction kinetics via accelerating Li-ion diffusion in the bulk electrolyte and interphase. The final part of the paper addresses future challenges and offers perspectives on electrolyte designs for low-temperature Li-ion batteries.