Yun-Xiao Wang

Ultrafine SnO2 nanoparticle loading onto reduced graphene oxide as anodes for sodium-ion batteries with superior rate and cycling performances

A structured SnO2–reduced graphene oxide (RGO) nanocomposite has been synthesized with SnO2 nanoparticles (∼5 nm) anchored on a RGO framework. It has been successfully applied as an anode material in sodium-ion batteries. The electrode delivers a reversible Na-storage capacity of 330 mA h g−1 with an outstanding capacity retention of 81.3% over 150 cycles. Moreover, it possesses a relatively good rate capability, exhibiting a capacity retention of 25.8% at high rate (1000 mA h g−1). With its combined advantages of low cost and environmental benignity, the SnO2–RGO nanocomposite would be a promising anode for Na-ion batteries.

Uniform yolk-shell iron sulfide–carbon nanospheres for superior sodium–iron sulfide batteries

Sodium–metal sulfide battery holds great promise for sustainable and cost-effective applications. Nevertheless, achieving high capacity and cycling stability remains a great challenge. Here, uniform yolk-shell iron sulfide–carbon nanospheres have been synthesized as cathode materials for the emerging sodium sulfide battery to achieve remarkable capacity of ∼545 mA h g−1 over 100 cycles at 0.2 C (100 mA g−1), delivering ultrahigh energy density of ∼438 Wh kg−1. The proven conversion reaction between sodium and iron sulfide results in high capacity but severe volume changes. Nanostructural design, including of nanosized iron sulfide yolks (∼170 nm) with porous carbon shells (∼30 nm) and extra void space (∼20 nm) in between, has been used to achieve excellent cycling performance without sacrificing capacity. This sustainable sodium–iron sulfide battery is a promising candidate for stationary energy storage. Furthermore, this spatially confined sulfuration strategy offers a general method for other yolk-shell metal sulfide–carbon composites.

High-performance sodium-ion batteries and sodium-ion pseudocapacitors based on MoS2/graphene composites

Sodium-ion energy storage, including sodium-ion batteries (NIBs) and electrochemical capacitive storage (NICs), is considered as a promising alternative to lithium-ion energy storage. It is an intriguing prospect, especially for large-scale applications, owing to its low cost and abundance. MoS2 sodiation/desodiation with Na ions is based on the conversion reaction, which is not only able to deliver higher capacity than the intercalation reaction, but can also be applied in capacitive storage owing to its typically sloping charge/discharge curves. Here, NIBs and NICs based on a graphene composite (MoS2 /G) were constructed. The enlarged d-spacing, a contribution of the graphene matrix, and the unique properties of the MoS2 /G substantially optimize Na storage behavior, by accommodating large volume changes and facilitating fast ion diffusion. MoS2 /G exhibits a stable capacity of approximately 350 mAh g(-1) over 200 cycles at 0.25 C in half cells, and delivers a capacitance of 50 F g(-1) over 2000 cycles at 1.5 C in pseudocapacitors with a wide voltage window of 0.1-2.5 V.

Amorphous TiO2 Shells: A Vital Elastic Buffering Layer on Silicon Nanoparticles for High‐Performance and Safe Lithium Storage

Smart surface coatings of silicon (Si) nanoparticles are shown to be good examples for dramatically improving the cyclability of lithium-ion batteries. Most coating materials, however, face significant challenges, including a low initial Coulombic efficiency, tedious processing, and safety assessment. In this study, a facile sol-gel strategy is demonstrated to synthesize commercial Si nanoparticles encapsulated by amorphous titanium oxide (TiO2 ), with core-shell structures, which show greatly superior electrochemical performance and high-safety lithium storage. The amorphous TiO2 shell (≈3 nm) shows elastic behavior during lithium discharging and charging processes, maintaining high structural integrity. Interestingly, it is found that the amorphous TiO2 shells offer superior buffering properties compared to crystalline TiO2 layers for unprecedented cycling stability. Moreover, accelerating rate calorimetry testing reveals that the TiO2 -encapsulated Si nanoparticles are safer than conventional carbon-coated Si-based anodes.

Achieving High-Performance Room-Temperature Sodium–Sulfur Batteries With S@Interconnected Mesoporous Carbon Hollow Nanospheres

Despite the high theoretical capacity of the sodium-sulfur battery, its application is seriously restrained by the challenges due to its low sulfur electroactivity and accelerated shuttle effect, which lead to low accessible capacity and fast decay. Herein, an elaborate carbon framework, interconnected mesoporous hollow carbon nanospheres, is reported as an effective sulfur host to achieve excellent electrochemical performance. Based on in situ synchrotron X-ray diffraction, the mechanism of the room temperature Na/S battery is proposed to be reversible reactions between S8 and Na2S4, corresponding to a theoretical capacity of 418 mAh g-1. The cell is capable of achieving high capacity retention of ∼88.8% over 200 cycles, and superior rate capability with reversible capacity of ∼390 and 127 mAh g-1 at 0.1 and 5 A g-1, respectively.

Defect sites-rich porous carbon with pseudocapacitive behaviors as an ultrafast and long-term cycling anode for sodium-ion batteries

Room-temperature sodium-ion batteries have been regarded as promising candidates for grid-scale energy storage due to their low cost and the wide distribution of sodium sources. The main scientific challenge for their practical application is to develop suitable anodes with long-term cycling stability and high rate capacity. Here, novel hierarchical three-dimensional porous carbon materials are synthesized through an in situ template carbonization process. Electrochemical examination demonstrates that carbonization temperature is a key factor that affects Na+-ion-storage performance, owing to the consequent differences in surface area, pore volume, and degree of crystallinity. The sample obtained at 600 °C delivers the best sodium-storage performance, including long-term cycling stability (15 000 cycles) and high rate capacity (126 mAh g-1 at 20 A g-1). Pseudocapacitive behavior in the Na+-ion-storage process has been confirmed and studied via cyclic voltammetry. Full cells based on the porous carbon anode and Na3V2(PO4)3-C cathode also deliver good cycling stability (400 cycles). Porous carbon, combining the merits of high energy density and extraordinary pseudocapacitive behavior after cycling stability, can be a promising replacement for battery/supercapacitors hybrid and suggest a design strategy for new energy-storage materials.

In Situ Grown S Nanosheets on Cu Foam: An Ultrahigh Electroactive Cathode for Room-Temperature Na–S Batteries

Room-temperature sodium-sulfur batteries are competitive candidates for large-scale stationary energy storage because of their low price and high theoretical capacity. Herein, pure S nanosheet cathodes can be grown in situ on three-dimensional Cu foam substrate with the condensation between binary polymeric binders, serving as a model system to investigate the formation and electrochemical mechanism of unique S nanosheets on the Cu current collectors. On the basis of the confirmed conversion reactions to Na2S, The constructed cathode exhibits ultrahigh initial discharge/charge capacity of 3189/1403 mAh g-1. These results suggest that there is great potential to optimize S cathode by exploiting low-cost Cu substrates instead of conventional Al current collectors.

New monatomic layer clusters for advanced catalysis materials

摘要“单原子层团簇”催化剂这一新概念, 不同于单原子催化剂和传统的纳米颗粒催化, 是由单原子建造新型的二维单原子层催化剂. 单原子层团簇催化剂的活性中心明确, 且原子间的相互作用会极大提高催化反应的选择性. 因此该催化剂材料不仅具有优异的催化性能, 还具有良好的选择性. 基于此, 作者同时分析和指出了未来的单原子层团簇催化剂的可能重点研究方向以及挑战.

Atomic cobalt as an efficient electrocatalyst in sulfur cathodes for superior room-temperature sodium-sulfur batteries

The low-cost room-temperature sodium-sulfur battery system is arousing extensive interest owing to its promise for large-scale applications. Although significant efforts have been made, resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging. Here, a sulfur host comprised of atomic cobalt-decorated hollow carbon nanospheres is synthesized to enhance sulfur reactivity and to electrocatalytically reduce polysulfide into the final product, sodium sulfide. The constructed sulfur cathode delivers an initial reversible capacity of 1081 mA h g−1 with 64.7% sulfur utilization rate; significantly, the cell retained a high reversible capacity of 508 mA h g−1 at 100 mA g−1 after 600 cycles. An excellent rate capability is achieved with an average capacity of 220.3 mA h g−1 at the high current density of 5 A g−1. Moreover, the electrocatalytic effects of atomic cobalt are clearly evidenced by operando Raman spectroscopy, synchrotron X-ray diffraction, and density functional theory.Room-temperature sodium-sulfur batteries hold promise, but are hindered by low reversible capacity and fast capacity fade. Here the authors construct a multifunctional sulfur host comprised of cobalt-decorated carbon nanospheres that impart attractive performance as a cathode in a sodium sulfide battery.

Self-Assembling Hollow Carbon Nanobeads into Double-Shell Microspheres as a Hierarchical Sulfur Host for Sustainable Room-Temperature Sodium–Sulfur Batteries

We report the use of passion fruit-like double-carbon-shell porous carbon microspheres (PCMs) as the sulfur substrate in room-temperature sodium-sulfur batteries. The PCMs are covered by microsized carbon shells on the outside and consisted of carbon nanobeads with hollow structure inside, leading to a unique multidimensional scaling double-carbon-shell structure with high electronic conductivity and strengthened mechanical properties. Sulfur is filled inside the PCMs (PCMs-S) and protected by the unique double-carbon-shell, which means the subsequently generated intermediate sodium polysulfide species cannot be exposed to the electrolyte directly and well protected inside. In addition, the inner interconnected porous structure provides room for the volume expansion of sulfur during discharge processes. It is found that the PCMs-S with a 63.6% initial Coulombic efficiency contributed to the 290 mA h g-1 at the current density of 100 mA g-1 after 350 cycles. More importantly, PCMs-S exhibited good rate performance with a capacity of 113 and 56 mA h g-1 at the current densities of 1000 and 2000 mA g-1, respectively.