Hydroxyl-Decorated Carbon Cloth with High Potassium Affinity Enables Stable Potassium Metal Anodes.

Highly anticipated potassium metal batteries possess abundant potassium reserves and high theoretical capacity but currently suffer from poor cycling stability as a result of dendritic growth and volume expansion. Here, carbon cloths modified with different functional groups treated with ethylene glycol, ethanolamine, and ethylenediamine are designed as 3D hosts, exhibiting different wettability to molten potassium. Among them, the hydroxyl-decorated carbon cloth with a high affinity for potassium can achieve molten potassium perfusion (K@EG-CC) within 3 s. By efficiently inducing the uniform deposition of metal potassium, buffing its volume expansion, and lowering local current density, the developed K@EG-CC anode alleviates the dendrite growth issue. The K@EG-CC||K@EG-CC symmetric battery can be cycled stably for 2100 h and has only a small voltage hysteresis of ≈93 mV at 0.5 mA cm-2 . Moreover, the high-voltage plateau, high energy density, and long cycle life of K metal full batteries can be realized with a low-cost KFeSO4 F@carbon nanotube cathode. This study provides a simple strategy to promote the commercial applications of potassium metal batteries.

Recent Progress in Using Covalent Organic Frameworks to Stabilize Metal Anodes for Highly-Efficient Rechargeable Batteries.

Alkali metals (e.g. Li, Na, and K) and multivalent metals (e.g. Zn, Mg, Ca, and Al) have become star anodes for developing high-energy-density rechargeable batteries due to their high theoretical capacity and excellent conductivity. However, the inevitable dendrites and unstable interfaces of metal anodes pose challenges to the safety and stability of batteries. To address these issues, covalent organic frameworks (COFs), as emerging materials, have been widely investigated due to their regular porous structure, flexible molecular design, and high specific surface area. In this minireview, we summarize the research progress of COFs in stabilizing metal anodes. First, we present the research origins of metal anodes and delve into their advantages and challenges as anodes based on the physical/chemical properties of alkali and multivalent metals. Then, special attention has been paid to the application of COFs in the host design of metal anodes, artificial solid electrolyte interfaces, electrolyte additives, solid-state electrolytes, and separator modifications. Finally, a new perspective is provided for the research of metal anodes from the molecular design, pore modulation, and synthesis of COFs.

Implanting CuS Quantum Dots into Carbon Nanorods for Efficient Magnesium-Ion Batteries.

Magnesium-ion batteries (MIBs) are emerging as potential next-generation energy storage systems due to high security and high theoretical energy density. Nevertheless, the development of MIBs is limited by the lack of cathode materials with high specific capacity and cyclic stability. Currently, transition metal sulfides are considered as a promising class of cathode materials for advanced MIBs. Herein, a template-based strategy is proposed to successfully fabricate metal-organic framework-derived in-situ porous carbon nanorod-encapsulated CuS quantum dots (CuS-QD@C nanorods) via a two-step method of sulfurization and cation exchange. CuS quantum dots have abundant electrochemically active sites, which facilitate the contact between the electrode and the electrolyte. In addition, the tight combination of CuS quantum dots and porous carbon nanorods increases the electronic conductivity while accelerating the transport speed of ions and electrons. With these architectural and compositional advantages, when used as a cathode material for MIBs, the CuS-QD@C nanorods exhibit remarkable performance in magnesium storage, including a high reversible capacity of 323.7 mAh g-1 at 100 mA g-1 after 100 cycles, excellent long-term cycling stability (98.5 mAh g-1 after 1000 cycles at 1.0 A g-1 ), and satisfying rate performance (111.8 mA g-1 at 1.0 A g-1 ).

An ultrastable sodium-ion battery anode enabled by carbon-coated porous NaTi2(PO4)3 olive-like nanospheres.

NaTi2(PO4)3 (NTP) is a promising anode material for sodium-ion batteries (SIBs). It has drawn wide attention because of its stable three-dimensional NASICON-type structure, proper redox potential, and large accommodation space for Na+. However, the inherent low electronic conductivity of the phosphate framework reduces its charge transfer kinetics, thus limiting its exploitation. Therefore, this paper proposes a material with carbon-coated porous NTP olive-like nanospheres (p-NTP@C) to tackle the issues above. Based on experimental data and theoretical calculations, the porous structure of the material is found to be able to provide more active sites and shorten the Na+ diffusion distance. In addition, the carbon coating can effectively improve the electron and Na+ diffusion kinetics. As the anode material for SIBs, the p-NTP@C olive-like nanospheres exhibit a high reversible capacity (127.3 mAh g-1 at 0.1 C) and ultrastable cycling performance (84.8% capacity retention after 10,000 cycles at 5 C). Furthermore, the sodium-ion full cells, composed of p-NTP@C anode and Na3V2(PO4)2F3@carbon cathode, also deliver excellent performance (75.7% capacity retention after 1000 cycles at 1 C). In brief, this nanostructure design provides a viable approach for the future development of long-life and highly stable NASICON-type anode materials.

Implantation of Fe7S8 nanocrystals into hollow carbon nanospheres for efficient potassium storage.

As a desirable candidate for lithium-ion batteries, potassium-ion batteries (PIBs) have aroused great interest because of their low cost and high power and energy densities. However, the insertion/extraction of K+ with a large radius (1.38 Å) usually bring about the destruction of the electrode materials. Here, ultrafine Fe7S8 nanocrystals are successfully implanted into hollow carbon nanospheres (Fe7S8@HCSs) via a facile solvothermal method and subsequent novel low-temperature sulfurization, which avoid the aggregation of Fe7S8 nanoparticles produced during high-temperature sulfidation. The ultrafine Fe7S8 nanoparticles and hollow carbon spheres can not only buffer the severe expansion/shrinkage of electrode materials caused by the repeated insertion/extraction of K+, but also provide additional accessible pathways for the high-rate K+ transmission. When tested as an anode material for PIBs, Fe7S8@HCSs achieve impressive K+ storage capacity of 523.2 mAh g-1 at 0.1 A g-1 after 100 cycles and remarkable rate capacity of 176.3 mAh g-1 at 5 A g-1. Further, assembling this anode with a K2NiFe(CN)6 cathode yields stable cycling performance, revealing its great potential for large-scale energy storage applications.

Two new physalin derivatives from Physalis alkekengi L. var. franchetii (Mast.) Makino.

Two new physalin derivatives named 7ß-ethoxyl-isophysalin C (1) and 3ß-ethoxyl-2,3-dihydro-4,7-didehydrophysalin B (2) were isolated from Physalis alkekengi L. var. franchetii (Mast.) Makino. Their structures were determined by extensive NMR-spectroscopic analysis and HRESIMS data. Compounds 1 and 2 were tested for their cytotoxicity against PC-3 cancer cell lines. Compound 1 showed apparent moderate with IC50 values of 8.26 µM, whereas compound 2 exhibited no cytotoxicity against PC-3 cancer cell lines.