High performance hollow carbon@SnO 2 @graphene composite based on internal-external double protection strategy for lithium ion battery

Construction of Carbon Nanofiber-Wrapped SnO2 Hollow Nanospheres as Flexible Integrated Anode for Half/Full Li-Ion Batteries

SnO2 is deemed a potential candidate for high energy density (1494 mAh g-1) anode materials for Li-ion batteries (LIBs). However, its severe volume variation and low intrinsic electrical conductivity result in poor long-term stability and reversibility, limiting the further development of such materials. Therefore, we propose a novel strategy, that is, to prepare SnO2 hollow nanospheres (SnO2-HNPs) by a template method, and then introduce these SnO2-HNPs into one-dimensional (1D) carbon nanofibers (CNFs) uniformly via electrospinning technology. Such a sugar gourd-like construction effectively addresses the limitations of traditional SnO2 during the charging and discharging processes of LIBs. As a result, the optimized product (denoted SnO2-HNP/CNF), a binder-free integrated electrode for half and full LIBs, displays superior electrochemical performance as an anode material, including high reversible capacity (~735.1 mAh g-1 for half LIBs and ~455.3 mAh g-1 at 0.1 A g-1 for full LIBs) and favorable long-term cycling stability. This work confirms that sugar gourd-like SnO2-HNP/CNF flexible integrated electrodes prepared with this novel strategy can effectively improve battery performance, providing infinite possibilities for the design and development of flexible wearable battery equipment.

Carbon-coated SnO2 riveted on a reduced graphene oxide composite (C@SnO2/RGO) as an anode material for lithium-ion batteries

The research on graphene-based anode materials for high-performance lithium-ion batteries (LIBs) has been prevalent in recent years. In the present work, carbon-coated SnO₂ riveted on a reduced graphene oxide sheet composite (C@SnO₂/RGO) was fabricated using GO solution, SnCl₄, and glucose via a hydrothermal method after heat treatment. When the composite was exploited as an anode material for LIBs, the electrodes were found to exhibit a stable reversible discharge capacity of 843 mA h g⁻¹ at 100 mA g⁻¹ after 100 cycles with 99.5% coulombic efficiency (CE), and a specific capacity of 485 mA h g⁻¹ at 1000 mA g⁻¹ after 200 cycles; these values were higher than those for a sample without glucose (SnO₂/RGO) and a pure SnO₂ sample. The favourable electrochemical performances of the C@SnO₂/RGO electrodes may be attributed to the special double-carbon structure of the composite, which can effectively suppress the volume expansion of SnO₂ nanoparticles and facilitate the transfer rates of Li⁺ and electrons during the charge/discharge process.

The combined action of GO and glucose makes the SnO₂ dispersed uniformly. The synergistic effect of the unique double-carbon structure can effectively improve the electrical conductivity of the SnO₂ and strengthen lithium storage capability.

Improving Lithium-Ion Half-/Full-Cell Performance of WO3 -Protected SnO2 Core-Shell Nanoarchitectures

Anodes derived from SnO₂ offer a greater specific capacity comparative to graphitic carbon in lithium-ion batteries (LIBs); hence, it is imperative to find a simple but effective approach for the fabrication of SnO₂ . The intelligent surfacing of transition metal oxides is one of the favorite strategies to dramatically boost cycling efficiency, and currently most work is primarily aimed at coating and/or compositing with carbon-based materials. Such coating materials, however, face major challenges, including tedious processing and low capacity. This study successfully reports a new and simple WO₃ coating to produce a core-shell structure on the surface of SnO₂ . The empty space permitted natural expansion for the SnO₂ nanostructures, retaining a higher specific capacity for over 100 cycles that did not appear in the pristine SnO₂ without WO₃ shell. Using WO₃ -protected SnO₂ nanoparticles as anode, a coin half-cell battery was designed with Li-foil as counter-electrode. Furthermore, the anode was paired with commercial LiFePO₄ as cathode for a coin-type full cell and tested for lithium storage performance. The WO₃ shell proved to be an effective and strong enhancer for both current rate and specific capacity of SnO₂ nanoarchitectures; additionally, an enhancement of cyclic stability was achieved. The findings demonstrate that the WO₃ can be used for the improvement of cyclic characteristics of other metal oxide materials as a new coating material.

Enhancement in the Detection Ability of Metal Oxide Sensors Using Defect-Rich Polycrystalline Nanofiber Devices

The development of SnO2 and TiO2 polycrystalline nanofiber devices (PNFDs) has been widely researched as a method of protecting humans from household air pollution. PNFDs have three significant advantages. The nanofibers before the annealing process are polymer-rich materials, which can be used as particulate material (PM) filters. The multiporous nanofibers fabricated by the annealing process have numerous defects that can serve as generation-recombination centers for electron-hole pairs, enabling the PNFDs to serve as multiple-wavelength light (from 365 to 940 nm) detectors. Lastly, the numerous surface/interface defects can drastically enhance the toxic gas detection ability. The toxic gas detection range of PNFDs for CO(g) and NO(g) is from 400 to 50 ppm and 400 to 50 ppb, respectively. Quick response times and recovery properties are key parameters for commercial applications. The recovery time of NO(g) detection can be improved from 1 ks to 40 s and the PNFD operating temperature lowered to 50 °C. These results indicate that SnO2 and TiO2 PNFDs have good potential for commercialization and use as toxic gas and photon sensors in daily lives.

Influence of phase variation of ZnMn2O4/carbon electrodes on cycling performances of Li-ion batteries

Due to the high specific capacity and low cost, transition metal oxides (TMOs) exhibit huge potential as anode materials for high-performance Li-ion batteries.

Dual Carbon-Confined SnO2 Hollow Nanospheres Enabling High Performance for the Reversible Storage of Alkali Metal Ions

To explore a universal electrode material for the high-performance electrochemical storage of Li⁺, Na⁺, and K⁺ ions remains a big challenge. Herein, we propose a "trinity" strategy to coat the SnO₂ hollow nanospheres using the dual carbon layer from the polydopamine-derived nitrogen-doped carbon and graphene. Thereinto, hollow structures with sufficient void space could buffer the volume expansion, whereas dual carbon-confined strategy could not only elastically prevent the aggregation of nanoparticle and ensure the structural integrity but also immensely improve the conductivity and endow high rate properties. Benefiting from the effective strategy and specific structure, the dual carbon-confined SnO₂ hollow nanosphere (denoted as G@C@SnO₂) can serve as the universal host material for alkali metal ions and enable their rapid and reversible storage. As expected, the resulting G@C@SnO₂ as a universal anode material shows reversible alkali-metal-ion storage with high performance. We believe this that strategy could pave the way for constructing other metal-oxide-based dual carbon-confined high-performance materials for the future energy storage applications.

Large-Scale Fabrication of Core-Shell Structured C/SnO2 Hollow Spheres as Anode Materials with Improved Lithium Storage Performance

Due to the high theoretical capacity as high as 1494 mAh g^-1 , SnO₂ is considered as a potential anode material for high-capacity lithium-ion batteries (LIBs). Therefore, the simple but effective method focused on fabrication of SnO₂ is imperative. To meet this, a facile and efficient strategy to fabricate core-shell structured C/SnO₂ hollow spheres by a solvothermal method is reported. Herein, the solid and hollow structure as well as the carbon content can be controlled. Very importantly, high-yield C/SnO₂ spheres can be produced by this method, which suggest potential business applications in LIBs field. Owing to the dual buffer effect of the carbon layer and hollow structures, the core-shell structured C/SnO₂ hollow spheres deliver a high reversible discharge capacity of 1007 mAh g^-1 at a current density of 100 mA g^-1 after 300 cycles and a superior discharge capacity of 915 mAh g^-1 at 500 mA g^-1 after 500 cycles. Even at a high current density of 1 and 2 A g^-1 , the core-shell structured C/SnO₂ hollow spheres electrode still exhibits excellent discharge capacity in the long life cycles. Consideration of the superior performance and high yield, the core-shell structured C/SnO₂ hollow spheres are of great interest for the next-generation LIBs.

Metal-Organic Framework Template Synthesis of NiCo2S4@C Encapsulated in Hollow Nitrogen-Doped Carbon Cubes with Enhanced Electrochemical Performance for Lithium Storage

Owing to its richer redox reaction and remarkable electrical conductivity, bimetallic nickel cobalt sulfide (NiCo₂S₄) is considered as an advanced electrode material for energy-storage applications. Herein, nanosized NiCo₂S₄@C encapsulated in a hollow nitrogen-doped carbon cube (NiCo₂S₄@D-NC) has been fabricated using a core@shell Ni₃[Co(CN)₆]₂@polydopamine (PDA) nanocube as the precursor. In this composite, the NiCo₂S₄ nanoparticles coated with conformal carbon layers are homogeneously embedded in a 3D high-conduction carbon shell from PDA. Both the inner and the outer carbon coatings are helpful in increasing the electrical conductivity of the electrode materials and prohibit the polysulfide intermediates from dissolving in the electrolyte. When researched as electrode materials for lithium storage, owing to the unique structure with double layers of nitrogen-doped carbon coating, the as-obtained NiCo₂S₄@D-NC electrode maintains an excellent specific capacity of 480 mAh g^-1 at 100 mA g^-1 after 100 cycles. Even after 500 cycles at 500 mA g^-1, a reversible capacity of 427 mAh g^-1 can be achieved, suggesting an excellent rate capability and an ultralong cycling life. This remarkable lithium storage property indicates its potential application for future lithium-ion batteries.

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.