A composite of Fe3O4@C and multilevel porous carbon as high-rate and long-life anode materials for lithium ion batteries.

The iron oxide-based anode materials are widely studied and reported due to their abundance, low cost, high energy density and environmental friendliness for lithium ion batteries (LIBs). However, the application of LIBs is always limited by the poor rate capability and stability. In order to tackle these issues, a novel material with carbon-encapsulated Fe3O4 nanorods stuck together by multilevel porous carbon (Fe3O4@C/PC) is prepared through directly carbonizing the Fe-based metal-organic framework under a nitrogen atmosphere. This novel material shows a high specific capacity and rate performance. The initial specific capacity can reach 1789 mAh g-1 at a current density of 0.1 A g-1, and the specific capacity still remains 1105.3 mAh g-1 and 783.5 mAh g-1 after 150 cycles at the current densities of 0.1 A g-1 and 1 A g-1, respectively. Even under a current density as high as 12 A g-1, the specific capacity can achieve 309 mAh g-1 after 2000 cycles with an average attenuation rate of 0.019% per cycle. Overall, the simple strategy, low cost and high capacity can make the practical application possible.

Embedding FeS nanodots into carbon nanosheets to improve the electrochemical performance of anode in potassium ion batteries.

Potassium-ion batteries (PIBs) is one of the most promising alternatives for Lithium-ion batteries (LIBs) due to the low-cost and abundant potassium reserves. However, the electrochemical performances of PIBs were seriously hindered by the larger radius of potassium ions, resulting in a slow kinetic during the electrochemical reaction, especially in the PIB anodes. In the study, we propose FeS nanodots embedded S-doped porous carbon (FeS@SPC) synthesized by a simple self-template method for the storage of potassium-ions. The FeS nanodots with an average diameter of 5 nm are uniformly distributed in S-doped porous carbon nanosheets. When the FeS@SPC was used as the anode in PIBs, the unique structure of FeS@SPC can relieve the agglomeration and volume expansion of FeS effectively during the charge-discharge process. Even after 3000 cycles, the FeS nanodots are still uniformly embedded in porous carbon without agglomeration. Ascribed to the merits, the FeS@SPC exhibits a reversible capacity of 309 mAh g-1 at 0.1 A g-1 after 100 cycles and 232 mAh g-1 at 1 A g-1 after 3000 cycles. The excellent electrochemical performance of FeS@SPC is attributed to the synergistic effects of FeS nanodots and S-doped porous carbon, which facilitated the diffusion of electrolyte and accelerated the migration of potassium ions. Moreover, theoretical calculation results also suggest that the van der waals heterostructure of FeS@SPC displays higher adsorption energy for potassium ions than that of S-doped graphene, indicating the suitability of FeS@SPC for K storage.

Facile self-templating synthesis of heteroatom-doped 3D porous carbon materials from waste biomass for supercapacitors.

Heteroatom-doped 3D porous carbon materials have been synthesized by utilizing hydroxyapatite in pig bones as a self-template and used as electrode materials for symmetric supercapacitors, which exhibit ultra-high energy density both in an aqueous electrolyte and organic electrolyte, showing great potential applications in the next generation of energy storage and conversion devices.

Closed Pore Structured NiCo2O4-Coated Nickel Foams for Stable and Effective Oil/Water Separation.

To solve the serious problem caused by oily wastewater pollution, unique interface designs, for example, membranes with superwetting properties such as superhydrophobicity/superoleophilicity and superhydrophilicity/underwater superoleophobicity, provide a good way to achieve oil/water separation. Here, inspired by the liquid storage property of the honeycomb structure, we propose a strategy to fabricate NiCo2O4-coated nickel foams for stable and efficient oil/water separation. NiCo2O4 with a closed-pore structure was formed by assembling nanoflakes with a micro/nanoscale hierarchical structure. Compared with nickel foam coated by NiCo2O4 with an open-pore structure (NiCo2O4 nanowires), the enclosed nanostructure of NiCo2O4 nanoflakes can firmly hold water for a more stable superhydrophilic/underwater superoleophobic interface. As a consequence, the NiCo2O4-nanoflake-coated nickel foam has a larger oil breakthrough pressure than the NiCo2O4-nanowire-coated nickel foam because of a slightly larger oil advancing angle and a lower underwater oil adhesion force, which makes it more stable and efficient for oil/water separation. Moreover, the NiCo2O4-coated nickel foams have excellent chemical and mechanical stability, and they are reusable for oil-water separation. This work will be beneficial for the design and development of stable underwater superoleophobic self-cleaning materials and related device applications, such as oil/water separation.