README

READM

FeF₃@Thin Nickel Ammine Nitrate Matrix: Smart Configurations and Applications as Superior Cathodes for Li-Ion Batteries

Iron fluorides (FeF_<i>x</i>) for Li-ion battery cathodes are still in the stage of intensive research due to their low delivery capacity and limited lifetime. One critical reason for cathode degradation is the severe aggregation of FeF_<i>x</i> nanocrystals upon long-term cycling. To maximize the capacity and cyclability of these cathodes, we propose herein a novel and applicable method using a thin-layered nickel ammine nitrate (NAN) matrix as a feasible encapsulation material to disperse the FeF₃ nanoparticles. Such core–shell hybrids with smart configurations are constructed via a green, scalable, in situ encapsulation approach. The outer thin-film NAN matrix with prominent electrochemical stability can keep the FeF₃ nanoactives encapsulated throughout the cyclic testing, protecting them from adverse aggregation into bulk crystals and thus leading to drastic improvements of electrode behaviors (e.g., high electrode capacity up to ∼423 mA h g^–1, greatly prolonged cyclic period, and promoted rate capabilities). This present work may set up a new and general platform to develop intriguing core–shell hybrid cathodes for Li-ion batteries, not only for FeF_<i>x</i> but also for a wide spectrum of other cathode materials

Smart Magnetic Interaction Promotes Efficient and Green Production of High-Quality Fe₃O₄@Carbon Nanoactives for Sustainable Aqueous Batteries

Efficient and green production of monodispersed Fe₃O₄@carbon (C) nanoactives for commercial aqueous battery usage still remains a great challenge due to issues related to tedious hybrid fabrication and purification procedures. Herein, we put forward an interesting applicable synthetic strategy via a general polymeric process and simple magnetic purification treatments, enabling low-cost and massive production of high-quality Fe₃O₄@C hybrids. In such core–shell configurations, all Fe₃O₄ nanoparticles are tightly encapsulated in permeable <i>N</i>-doped C nanoreactors, showing notable nanostructured superiorities as feasible anodes for aqueous batteries. When tested, the Fe₃O₄@C nanoactives exhibit outstanding anodic performance comprising pretty high electrochemical activity/capacity, greatly prolonged cyclic lifespan in contrast to bare Fe₃O₄ counterparts, and prominent rate capabilities. The as-assembled Ni/Fe full cells can even deliver a high energy/power density up to ∼135 Wh kg^–1/11.5 kW kg^–1, further demonstrating their good potential in practical applications. Our smart magnetic purification strategy may hold great promise in addressing critical issues of producing high-quality and affordable Fe₃O₄@C hybrids, not only for energy-storage fields but also in other broad ranges covering catalysts and biosensors

Selenium Encapsulated into Metal–Organic Frameworks Derived N‑Doped Porous Carbon Polyhedrons as Cathode for Na–Se Batteries

The substitution of Se for S as cathode for rechargeable batteries, which confine selenium in porous carbon, attracts much attention as a potential area of research for energy storage systems. To date, there are no reports about metal–organic frameworks (MOFs) to use for Na–Se batteries. Herein, MOFs-derived nitrogen-doped porous carbon polyhedrons (NPCPs) have been obtained via facile synthesis and annealing treatment. Se is encapsulated into the mesopores of carbon polyhedrons homogeneously by melt-diffusion process to form Se/NPCPs composite, using as cathode for advanced Na–Se batteries. Se/NPCPs cathode exhibits excellent rate capabilities of 351.6 and 307.8 at 0.5C and 2C, respectively, along with good cycling performance with high Coulombic efficiency of 99.7% and slow decay rate of 0.05% per cycle after 1000 cycles at 2C, which result from the NPCPs having a unique porous structure to accommodate volumetric expansion of Se during discharge–charge processes. Nitrogen doping could enhance the electrical conductivity of carbon matrix and facilitate rapid charge transfer

Selenium Embedded in Metal–Organic Framework Derived Hollow Hierarchical Porous Carbon Spheres for Advanced Lithium–Selenium Batteries

Metal–organic framework derived hollow hierarchical porous carbon spheres (MHPCS) have been fabricated via a facile hydrothermal method combined with a subsequent annealing treatment. Such MHPCS are composed of masses of small hollow carbon bubbles with a size of ∼20 nm and shells of ∼5 nm thickness interconnected to each other. MHPCS/Se composite is developed as a cathode for Li–Se cells and delivers an initial specific capacity up to 588.2 mA h g^–1 at a current density of 0.5 C, exhibiting an outstanding cycling stability over 500 cycles with a decay rate even down to 0.08% per cycle. This material is capable of retaining up to 200 mA h g^–1 even after 1000 cycles at a current density of 1 C. Such good electrochemical performance may be ascribed to the distinct hollow structure of the carbon spheres and a large amount of Se wrapped within small carbon bubbles, thus not only enhancing the electronic/ionic transport but also providing additional buffer space to adjust volume changes of Se during charge/discharge processes

Facile Synthesis of Novel Networked Ultralong Cobalt Sulfide Nanotubes and Its Application in Supercapacitors

Ultralong cobalt sulfide (CoS_1.097) nanotube networks are synthesized by a simple one-step solvothermal method without any surfactant or template. A possible formation mechanism for the growth processes is proposed. Owing to the hollow structure and large specific area, the novel CoS_1.097 materials present outstanding electrochemical properties. Electrochemical measurements for supercapacitors show that the as-prepared ultralong CoS_1.097 nanotube networks exhibit high specific capacity, good capacity retention, and excellent Coulombic efficiency

One-Dimensional Integrated MnS@Carbon Nanoreactors Hybrid: An Alternative Anode for Full-Cell Li-Ion and Na-Ion Batteries

Manganese sulfide (MnS) has triggered great interest as an anode material for rechargeable Li-ion/Na-ion batteries (LIBs/SIBs) because of its low cost, high electrochemical activity, and theoretical capacity. Nevertheless, the practical application is greatly hindered by its rapid capacity decay lead by inevitable active dissolutions and volume expansions in charge/discharge cycles. To resolve the above issues in LIBs/SIBs, we herein put forward the smart construction of MnS nanowires embedded in carbon nanoreactors (MnS@C NWs) via a facile solution method followed by a scalable in situ sulfuration treatment. This engineering protocol toward electrode architectures/configurations endows integrated MnS@C NWs anodes with large specific capacity (with a maximum value of 847 mA h g^–1 in LIBs and 720 mA h g^–1 in SIBs), good operation stability, excellent rate capabilities, and prolonged cyclic life span. To prove their potential real applications, we have established the full cells (for LIBs, MnS@C//LiFePO₄; for SIBs, MnS@C//Na₃V₂(PO₄)₃), both of which are capable of showing remarkable specific capacities, outstanding rate performance, and superb cyclic endurance. This work offers a scalable, simple, and efficient evolution method to produce the integrated hybrid of MnS@C NWs, providing useful inspiration/guidelines for anodic applications of metal sulfides in next-generation power sources

Efficient Production of Coaxial Core–Shell MnO@Carbon Nanopipes for Sustainable Electrochemical Energy Storage Applications

Adverse structural changes and poor intrinsic electrical conductivity as well as the lack of an environmentally benign synthesis for MnO species are major factors to limit their further progress on electrochemical energy storage applications. To overcome the above constraints, the development of reliable and scalable techniques to confine MnO within a conductive matrix is highly desired. We herein propose an efficient and reliable way to fabricate coaxial core–shell hybrids of MnO@carbon nanopipes merely via simple ultrasonication and calcination treatments. The evolved MnO nanowires disconnected/confined in pipe-like carbon nanoreactors show great promise in sustainable supercapacitors (SCs) and Li-ion battery (LIB) applications. When used in SCs, such core–shell MnO@carbon configurations exhibit outstanding positive and negative capacitive behaviors in distinct aqueous electrolyte systems. This hybrid can also function as a prominent LIB electrode, demonstrating a high reversible capacity, excellent rate capability, long lifespan, and stable battery operation. The present work may shed light on effective and scalable production of Mn-based hybrids for practical applications, not merely for energy storage but also in other broad fields such as catalysts and biosensors

Improving the Performance of Hard Carbon//Na₃V₂O₂(PO₄)₂F Sodium-Ion Full Cells by Utilizing the Adsorption Process of Hard Carbon

Hard carbon has been regarded as a promising anode material for Na-ion batteries. Here, we show, for the first time, the effects of two Na⁺ uptake/release routes, i.e., adsorption and intercalation processes, on the electrochemical performance of half and full sodium batteries. Various Na⁺-storage processes are isolated in full cells by controlling the capacity ratio of anode/cathode and the sodiation state of hard carbon anode. Full cells utilizing adsorption region of hard carbon anode show better cycling stability and high rate capability compared to those utilizing intercalation region of hard carbon anode. On the other hand, the intercalation region promises a high working voltage full cell because of the low Na⁺ intercalation potential. We believe this work is enlightening for the further practical application of hard carbon anode