Fabrication of N-doped carbon-coated MnO/ZnMn2O4 cathode materials for high-capacity aqueous zinc-ion batteries.

Rechargeable aqueous zinc-ion batteries (ZIBs) are highly promising energy storage devices due to their advantages of high energy density, low cost, environmental friendliness, and excellent safety. Investigation of advanced cathode materials featuring high capacity is desired for their applications in high-capacity ZIBs. In this study, a porous N-doped carbon-coated manganese oxide/zinc manganate (MZM@N-C) composite was successfully prepared as an advanced cathode material for aqueous ZIBs. The MZM@N-C cathode demonstrated a superior specific capacity of 772.8 mA h g-1 at 50 mA g-1 and maintained a high specific capacity of 205 mA h g-1 after 300 cycles at a high current density of 500 mA g-1. As compared to the unmodified MnOx cathode, MZM@N-C has a higher reversible capacity and cycling stability which could be assigned to the robust one-dimensional (1D) structure and the synergistic effect of MZM@N-C, providing instructive insight into the design of high-capacity manganese-based cathodes for rechargeable aqueous ZIBs. Furthermore, a soft-pack battery was assembled using the MZM@N-C cathode, demonstrating its potential applications in various devices.

Ultrafast Synthesis of Layered Transition-Metal Oxide Cathodes from Metal-Organic Frameworks for High-Capacity Sodium-Ion Batteries.

Layered transition-metal oxides are promising candidate cathode materials for sodium-ion batteries due to their abundant raw materials and high theoretical capacity. Nevertheless, a long-time high-temperature heat treatment is required in traditional preparation methods, leading to low synthesis efficiency and waste of energy. Herein, an ultrafast preparation method of layered transition-metal oxides was proposed through minute calcination of metal-organic frameworks (MOFs). The homogeneous distribution of different atoms in MOFs allows fast phase transition during the calcination process. P'2-phase layered sodium manganese oxide was successfully obtained and demonstrated excellent electrochemical performance, with a high reversible capacity of 212 mA h g-1 and a cycling performance of 84% capacity retention after 100 cycles. Furthermore, this method can be expanded to a wide variety of MOF precursors and oxide electrode materials for different types of batteries. Our findings provide an efficient and cost-effective synthesis method for high-performance layered transition-metal oxide cathodes.

Soluble Organic Cathodes Enable Long Cycle Life, High Rate, and Wide-Temperature Lithium-Ion Batteries.

Organic electrode materials free of rare transition metal elements are promising for sustainable, cost-effective, and environmentally benign battery chemistries. However, severe shuttling effect caused by the dissolution of active materials in liquid electrolytes results in fast capacity decay, limiting their practical applications. Here, using a gel polymer electrolyte (GPE) that is in situ formed on Nafion-coated separators, the shuttle reaction of organic electrodes is eliminated while maintaining the electrochemical performance. The synergy of physical confinement by GPE with tunable polymer structure and charge repulsion of the Nafion-coated separator substantially prevents the soluble organic electrode materials with different molecular sizes from shuttling. A soluble small-molecule organic electrode material of 1,3,5-tri(9,10-anthraquinonyl)benzene demonstrates exceptional electrochemical performance with an ultra-long cycle life of 10 000 cycles, excellent rate capability of 203 mAh g-1 at 100 C, and a wide working temperature range from -70 to 100 °C based on the solid-liquid conversion chemistry, which outperforms all previously reported organic cathode materials. The shielding capability of GPE can be designed and tailored toward organic electrodes with different molecular sizes, thus providing a universal resolution to the shuttling effect that all soluble electrode materials suffer.

Flexible PDMS-Based SERS Substrates Replicated from Beetle Wings for Water Pollutant Detection.

The flexible surface-enhanced Raman scattering (SERS) sensor, which has the bionic 3D nanoarray structure of a beetle-wing substrate (BWS), was successfully prepared by replicated technology and thermal evaporation. The bionic structure was replicated with polydimethylsiloxane (PDMS) and then silver (Ag) nanoisland thin films were deposited by thermal evaporation. The deposition times and thicknesses (25-40 nm) of the Ag thin films were manipulated to find the optimal SERS detection capability. The Ag nanoisland arrays on the surface of the bionic replicated PDMS were observed by scanning electron microscope (SEM), X-ray diffraction (XRD), and contact angle, which can generate strong and reproducible three-dimensional hotspots (3D hotspots) to enhance Raman signals. The water pollutant, rhodamine 6G (R6G), was used as a model molecule for SERS detection. The results show that 35 nm Ag deposited on a PDMS-BWS SERS substrate displays the strongest SERS intensity, which is 10 times higher than that of the pristine BWS with 35 nm Ag coating, due to the excellent 3D bionic structure. Our results demonstrate that bionic 3D SERS sensors have the potential to be applied in wearable devices and sensors to detect biomolecules and environmental pollutants, such as industrial wastewater, in the future.

Highly Potassiophilic Carbon Nanofiber Paper Derived from Bacterial Cellulose Enables Ultra-Stable Dendrite-Free Potassium Metal Anodes.

Potassium-metal batteries are attractive candidates for low-cost and large-scale energy storage systems due to the abundance of potassium. However, K metal dendrite growth as well as volume expansion of K metal anodes on cycling have significantly hindered its practical applications. Although enhanced performance has been reported using carbon hosts with complicated structure engineering, they are not suitable for mass production. Herein, a highly potassiophilic carbon nanofiber paper with abundant oxygen-containing functional groups on the surface and a 3D interconnected network architecture is fabricated through a facile, scalable, and environmental-friendly biosynthesis method. As a host for K metal anode, uniform K nucleation and stable plating/stripping performance are demonstrated, with a stable cycling of 1400 h and a low overpotential of 45 mV, which are much better than all carbon hosts without complicated structure engineering. Moreover, full cells pairing the carbon nanofiber paper/K composite anodes with K4Fe(CN)6 cathodes exhibit excellent cycle stability and rate capability. The results provide a promising way for realizing dendrite-free K metal anodes and high-performance potassium-ion batteries.

Bismuth Nanoparticle@Carbon Composite Anodes for Ultralong Cycle Life and High-Rate Sodium-Ion Batteries.

Bismuth has emerged as a promising anode material for sodium-ion batteries (SIBs), owing to its high capacity and suitable operating potential. However, large volume changes during alloying/dealloying processes lead to poor cycling performance. Herein, bismuth nanoparticle@carbon (Bi@C) composite is prepared via a facile annealing method using a commercial coordination compound precursor of bismuth citrate. The composite has a uniform structure with Bi nanoparticles embedded within a carbon framework. The nanosized structure ensures a fast kinetics and efficient alleviation of stress/strain caused by the volume change, and the resilient and conductive carbon matrix provides an interconnected electron transportation pathway. The Bi@C composite delivers outstanding sodium-storage performance with an ultralong cycle life of 30 000 cycles at a high current density of 8 A g-1 and an excellent rate capability of 71% capacity retention at an ultrahigh current rate of 60 A g-1 . Even at a high mass loading of 11.5 mg cm-2 , a stable reversible capacity of 280 mA h g-1 can be obtained after 200 cycles. More importantly, full SIBs by pairing with a Na3 V2 (PO4 )3 cathode demonstrates superior performance. Combining the facile synthesis and the commercial precursor, the exceptional performance makes the Bi@C composite very promising for practical large-scale applications.

Uniform Mesoporous MnO2 Nanospheres as a Surface Chemical Adsorption and Physical Confinement Polysulfide Mediator for Lithium-Sulfur Batteries.

The actual implementation of lithium-sulfur batteries is hindered by inferior cyclic stability and poor coulombic efficiency stemming from the notorious shuttling of soluble polysulfide intermediates. Herein, uniform mesoporous MnO2 nanospheres were prepared using a facile self-assembly and room-temperature reaction method. As a sulfur carrier of sulfur cathodes, the versatile architecture of MnO2 not only provides powerful chemical adsorption to anchor polysulfide intermediates on the large polar surface area but also restrains them within the nanopores by physical confinement. The mesoporous MnO2-stabilized sulfur cathode demonstrates a high initial reversible capacity of 1349.3 mA h g-1 and a capacity fading rate of 0.073% at 1.0 C over 500 cycles. Furthermore, a reversible areal capacity of 2.5 mA h cm-2 was achieved with stable cycling performance at a sulfur content of 80.7%. Our work offers a facile method to build efficient sulfur cathodes for high performance lithium-sulfur batteries.

A Polysulfide-Immobilizing Polymer Retards the Shuttling of Polysulfide Intermediates in Lithium-Sulfur Batteries.

Lithium-sulfur batteries are regarded as one of the most promising candidates for next-generation rechargeable batteries. However, the practical application of lithium-sulfur (Li-S) batteries is seriously impeded by the notorious shuttling of soluble polysulfide intermediates, inducing a low utilization of active materials, severe self-discharge, and thus a poor cycling life, which is particularly severe in high-sulfur-loading cathodes. Herein, a polysulfide-immobilizing polymer is reported to address the shuttling issues. A natural polymer of Gum Arabic (GA) with precise oxygen-containing functional groups that can induce a strong binding interaction toward lithium polysulfides is deposited onto a conductive support of a carbon nanofiber (CNF) film as a polysulfide shielding interlayer. The as-obtained CNF-GA composite interlayer can achieve an outstanding performance of a high specific capacity of 880 mA h g-1 and a maintained specific capacity of 827 mA h g-1 after 250 cycles under a sulfur loading of 1.1 mg cm-2 . More importantly, high reversible areal capacities of 4.77 and 10.8 mA h cm-2 can be obtained at high sulfur loadings of 6 and even 12 mg cm-2 , respectively. The results offer a facile and promising approach to develop viable lithium-sulfur batteries with high sulfur loading and high reversible capacities.

Red Phosphorus Nanoparticle@3D Interconnected Carbon Nanosheet Framework Composite for Potassium-Ion Battery Anodes.

Red phosphorus (P) has been recognized as a promising storage material for Li and Na. However, it has not been reported for K storage and the reaction mechanism remains unknown. Herein, a novel nanocomposite anode material is designed and synthesized by anchoring red P nanoparticles on a 3D carbon nanosheet framework for K-ion batteries (KIBs). The red P@CN composite demonstrates a superior electrochemical performance with a high reversible capacity of 655 mA h g-1 at 100 mA g-1 and a good rate capability remaining 323.7 mA h g-1 at 2000 mA g-1 , which outperform reported anode materials for KIBs. The transmission electron microscopy and theoretical calculation results suggest a one-electron reaction mechanism ofP + K+ + e- → KP, corresponding to a theoretical capacity of 843 mA h g-1 ,which is the highest value for anode materials investigated for KIBs. The study not only sheds light on the rational design of high performance red P anodes for KIBs but also offers a fundamental understanding of the potassium storage mechanism of red P.