Boron-Doped, Carbon-Coated SnO2/Graphene Nanosheets for Enhanced Lithium Storage

High-performance K-ion half/full batteries with superb rate capability and cycle stability

SignificanceThe present work might be significant for exploring advanced K-ion batteries with superb rate capability and cycle stability toward practical applications. The as-assembled K-ion half cell exhibits an excellent rate capability of 428 mA h g-1 at 100 mA g-1 and a high reversible specific capacity of 330 mA h g-1 with 120% specific capacity retention after 2,000 cycles at 2,000 mA g-1, which is the best among those based on carbon materials. The as-constructed full cell delivers 98% specific capacity retention over 750 cycles at 500 mA g-1, superior to most of those based on carbon materials that have been reported thus far.

Microalgae-Templated Spray Drying for Hierarchical and Porous Fe3O4/C Composite Microspheres as Li-ion Battery Anode Materials

A method of microalgae-templated spray drying to develop hierarchical porous Fe₃O₄/C composite microspheres as anode materials for Li-ion batteries was developed. During the spray-drying process, individual microalgae serve as building blocks of raspberry-like hollow microspheres via self-assembly. In the present study, microalgae-derived carbon matrices, naturally doped heteroatoms, and hierarchical porous structural features synergistically contributed to the high electrochemical performance of the Fe₃O₄/C composite microspheres, enabling a discharge capacity of 1375 mA·h·g^-1 after 700 cycles at a current density of 1 A/g. Notably, the microalgal frameworks of the Fe₃O₄/C composite microspheres were maintained over the course of charge/discharge cycling, thus demonstrating the structural stability of the composite microspheres against pulverization. In contrast, the sample fabricated without microalgal templating showed significant capacity drops (up to ~40% of initial capacity) during the early cycles. Clearly, templating of microalgae endows anode materials with superior cycling stability.

Metal Cation-Assisted Synthesis of Amorphous B, N Co-Doped Carbon Nanotubes for Superior Sodium Storage

Nearly inexhaustible sodium sources on earth make sodium ion batteries (SIBs) the best candidate for large-scale energy storage. However, the main obstacles faced by SIBs are the low rate performance and poor cycle stability caused by the large size of Na⁺ ions. Herein, a universal strategy for synthesizing amorphous metals encapsulated into amorphous B, N co-doped carbon (a-M@a-BCN; M = Co, Ni, Mn) nanotubes by metal cation-assisted carbonization is explored. The methodology allows tailoring the structures (e.g., length, wall thickness, and metals doping) of a-M@a-BCN nannotubes at the molecular level. Furthermore, the amorphous metal sulfide encapsulated into a-BCN (a-MS_x @a-BCN; MS_x : CoS, Ni₃ S₂ , MnS) nanotubes are obtained by one-step sulfidation process. The a-M@a-BCN and a-MS_x @a-BCN possess the larger interlayer spacing (0.40 nm) amorphous carbon nanotube rich in heteroatoms active sites, making them exhibit excellent Na⁺ ions diffusion kinetics and capacitive storage behavior. As SIBs anodes, they show high capacity, excellent rate performance, and long cycle stability.

Seeding Iron Trifluoride Nanoparticles on Reduced Graphite Oxide for Lithium-Ion Batteries with Enhanced Loading and Stability

Development of electric vehicles and portable electronic devices during the past decade calls for lithium-ion batteries (LIBs) with enhanced energy density and higher stability. Integration of FeF₃ phases and carbon structures leads to promising cathode materials for LIBs with high voltage, capacity, and power. In this study, FeF₃·0.33H₂O nanoparticles were synthesized on reduced graphite oxide (rGO) nanosheets using an in situ approach. By chemically tuning the interfacial bonding between FeF₃·0.33H₂O and rGO, we successfully achieved high particle loading and enhanced cycling stability. Specifically, a discharge capacity of ∼208.3 mAh g^-1 was observed at a current density of 0.5 C. The FeF₃·0.33H₂O/rGO nanocomposites also demonstrate great cycle capability with a reversible discharge capacity of 133.1 mAh g^-1 after 100 cycles at 100 mA g^-1; the capacity retention is about 97%. This study provides an alternative strategy to further improve the stability and performance of iron fluoride/carbon nanocomposite materials for LIB applications.

Three-Dimensional Graphene/Single-Walled Carbon Nanotube Aerogel Anchored with SnO2 Nanoparticles for High Performance Lithium Storage

A unique 3D graphene-single walled carbon nanotube (G-SWNT) aerogel anchored with SnO₂ nanoparticles (SnO₂@G-SWCNT) is fabricated by the hydrothermal self-assembly process. The influences of mass ratio of SWCNT to graphene on structure and electrochemical properties of SnO₂@G-SWCNT are investigated systematically. The SnO₂@G-SWCNT composites show excellent electrochemical performance in Li-ion batteries; for instance, at a current density of 100 mA g^-1, a specific capacity of 758 mAh g^-1 was obtained for the SnO₂@G-SWCNT with 50% SWCNT in G-SWCNT and the Coulombic efficiency is close to 100% after 200 cycles; even at current density of 1 A g^-1, it can still maintain a stable specific capacity of 537 mAh g^-1 after 300 cycles. It is believed that the 3D G-SWNT architecture provides a flexible conductive matrix for loading the SnO₂, facilitating the electronic and ionic transportation and mitigating the volume variation of the SnO₂ during lithiation/delithiation. This work also provides a facile and reasonable strategy to solve the pulverization and agglomeration problem of other transition metal oxides as electrode materials.

Mesoporous graphene/carbon framework embedded with SnO2 nanoparticles as a high-performance anode for lithium storage

A uniform graphene-based mesoporous carbon framework as a robust matrix for embedding SnO₂ nanoparticles for long-life lithium storage.

Electrophoretic Deposition of SnFe2O4–Graphene Hybrid Films as Anodes for Lithium Ion Batteries

Binder-free SnFe2O4–submillimetre (hundreds of micrometres)-sized reduced graphene oxide (SnFe2O4–srGO) hybrid films were synthesized through electrophoretic deposition and subsequent carbonization treatment. Scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy results revealed that SnFe2O4–srGO hybrid films exhibit both horizontal and vertical channels. SnFe2O4–srGO hybrid films were used as binder-free anodes for lithium ion half-cells and revealed a high capacity of ~1018.5 mA h g−1 at 0.1 A g−1 after 200 cycles. During rate performance tests, a high capacity of 464.1 mA h g−1 (~61.2 % retention) was maintained at a current density of 4 A g−1, indicating an excellent structural stability of SnFe2O4–srGO hybrid films at high current densities.

Nanoconfined nitrogen-doped carbon-coated MnO nanoparticles in graphene enabling high performance for lithium-ion batteries and oxygen reduction reaction

We prepared N-doped double carbon coated MnO composites and explored their applications in lithium ion batteries and oxygen reduction reaction.

To tackle the issues of inferior cycling stability and low conductivity for MnO as an anode material for lithium ion batteries (LIBs) and as a catalyst for oxygen reduction reaction (ORR), a facile and effective strategy is explored to confine N-doped carbon-coated MnO nanoparticles in a conductive graphene matrix. The synthesis of the GMNCs involves the two-step coating of Mn₃O₄ nanocrystals with polydopamine and graphene, followed by heat treatment to form the GNS@MnO@N-doped carbon composites (GMNCs). When evaluated as anode materials for LIBs, the as-prepared GMNCs exhibit an improved cycling stability (754.3 mA h g^–1 after 350 cycles at 0.1 A g^–1) compared to carbon-coated MnO and pure Mn₃O₄ due to the double carbon coating design. When evaluated as catalysts for ORR, the as-prepared GMNCs exhibit higher electrocatalytic activity than that of pure Mn₃O₄ and MnO catalysts, and superior stability to a commercial Pt/C catalyst due to the synergetic effect between the MnO and N-doped double carbon coating. The optimum design of the unique nanostructures with the synergetic effect provides a new route to design advanced materials as electrode/catalysts for energy conversion and storage.

Carbon coated SnO2 nanoparticles anchored on CNT as a superior anode material for lithium-ion batteries

Hierarchically structured carbon coated SnO2 nanoparticles well-anchored on the surface of a CNT (C-SnO2/CNT) material were synthesized by a facile hydrothermal process and subsequent carbonization. The as-obtained C-SnO2/CNT hybrid, when applied as an anode material for lithium ion batteries (LIBs), showed a high reversible capacity up to 1572 mA h g(-1) at 200 mA g(-1) with a superior rate capability (685 mA h g(-1) at 4000 mA g(-1)). Even after 100 charge/discharge cycles at 1000 mA g(-1), a specific capacity of 1100 mA h g(-1) can still be maintained. Such impressive electrochemical performance can be mainly attributed to the hierarchical sandwiched structure and strong synergistic effects of the ultrafine SnO2 nanoparticles and the carbon coating, and thus presents this material a promising anode material for LIBs.

Effect of Boron-Doping on the Graphene Aerogel Used as Cathode for the Lithium-Sulfur Battery

A porous interconnected 3D boron-doped graphene aerogel (BGA) was prepared via a one-pot hydrothermal treatment. The BGA material was first loaded with sulfur to serve as cathode in lithium-sulfur batteries. Boron was positively polarized on the graphene framework, allowing for chemical adsorption of negative polysufide species. Compared with nitrogen-doped and undoped graphene aerogel, the BGA-S cathode could deliver a higher capacity of 994 mA h g(-1) at 0.2 C after 100 cycles, as well as an outstanding rate capability, which indicated the BGA was an ideal cathode material for lithium-sulfur batteries.