Jiangfeng Ni

Self‐Supported Nanotube Arrays of Sulfur‐Doped TiO2 Enabling Ultrastable and Robust Sodium Storage

Self-supported nanotube arrays of sulfur-doped TiO2 on metal substrates are fabricated using electrochemical anodization and subsequent sulfidation. The nanotube arrays can serve as an efficient anode for sodium storage, enabling ultrastable cycling (retaining 91% of the 2nd capacity up to 4400 cycles) and robust rate capability (167 mA h g(-1) at 3350 mA g(-1)), remarkably outperforming any other reported TiO2 -based electrodes.

One-pot facile fabrication of carbon-coated Bi2S3 nanomeshes with efficient Li-storage capability

AbstractLayered bismuth sulfide (Bi2S3) has emerged as an important type of Li-storage material due to its high theoretical capacity and intriguing reaction mechanism. The engineering and fabrication of Bi2S3 materials with large capacity and stable cyclability via a facile approach is essential, but still remains a great challenge. Herein, we employ a one-pot hydrothermal route to fabricate carbon-coated Bi2S3 nanomeshes (Bi2S3/C) as an efficient Li-storage material. The nanomeshes serve as a highly conducting and porous scaffold facilitating electron and ion transport, while the carbon coating layer provides flexible space for efficient reduction of mechanical strain upon electrochemical cycling. Consequently, the fabricated Bi2S3/C exhibits a high and stable capacity delivery in the 0.01–2.5 V region, notably outperforming previously reported Bi2S3 materials. It is able to discharge 472 mA·h·g−1 at 120 mA·g−1 over 50 full cycles, and to retain 301 mA·h·g−1 in the 40th cycle at 600 mA·g−1, demonstrating the potential of Bi2S3 as electrode materials for rechargeable batteries.

Grapecluster-like Fe3O4@C/CNT nanostructures with stable Li-storage capability

Magnetite Fe3O4 has emerged as an important type of Li-storage electrode material for rechargeable battery applications. The engineering and synthesis of high-performance Fe3O4 with large capacity and stable cyclability via a facile approach is desirable but remains challenging. Here, we adopt a simple three-step method to synthesize a carbon coated magnetite/carbon nanotube (CNT) grapecluster nanostructure as an efficient Li-storage electrode material. The CNT network serves as a highly conducting and porous scaffold facilitating electron and ion transport, while the carbon coating layer provides a flexible space for buffering of strain and stress upon electrochemical cycling. The prepared Fe3O4@C/CNT grapecluster structures show a much improved performance compared with the Fe3O4@C counterpart. Specifically, the Fe3O4@C/CNT hybrid structure with 20 wt% CNT loading delivers a reversible capacity exceeding 900 mA h g−1 at 60 mA g−1, and retains 693 mA h g−1 at 300 mA g−1 after 200 cycles. The Fe3O4@C/CNT structure also exhibits a favourable rate capability, demonstrating the potential of Fe3O4@C/CNT hybrids as an electrode material for rechargeable batteries.

Branch-structured Bi2S3–CNT hybrids with improved lithium storage capability

Bismuth sulfide (Bi2S3) is a promising Li-storage material due to its high gravimetric and volumetric capacities. However, this intrinsic merit has often been compromised by the poor cycle and rate capability due to the lack of structural integrity upon the Li insertion/extraction process. Here, we engineer a branch-structured bismuth sulfide–carbon nanotube (CNT) hybrid by growing Bi2S3 nanorods onto CNTs to mitigate this issue. The hierarchical Bi2S3–CNT hybrids possess high surface areas, rich porosity for electrolyte infiltration, and direct electron transport pathways, and can be employed as efficient electrode materials for Li storage. These electrochemical results show that the Bi2S3–CNT hybrid exhibits a high reversible capacity (671 mA h g−1 at 120 mA g−1), stable cycling retention (534 mA h g−1 after 90 cycles), and remarkable rate capability (399 mA h g−1 at 3000 mA g−1), notably outperforming other reported Bi2S3 materials. Such superb Li storage capabilities suggest that the Bi2S3–CNT branches could be potential electrodes for rechargeable batteries.

Na0.44MnO2–CNT electrodes for non-aqueous sodium batteries

Crystalline Na0.44MnO2 materials are readily synthesized via a solid state method followed by mixing with carbon nanotubes (CNTs). The obtained Na0.44MnO2–CNT composites consist of rod-like Na0.44MnO2 particles entangled with CNTs. Their electrochemical properties were thoroughly investigated in assembled non-aqueous Na0.44MnO2–CNT//Na cells using cyclic voltammetry, galvanostatic testing, and electrochemical impedance spectroscopy. The results show that the Na0.44MnO2–CNT material can deliver a high capacity over 113 mAh g−1 with stable cycling performance over 40 cycles. In addition, it exhibits an excellent rate capability, delivering a capacity of 95 mAh g−1 at a high rate of 5 C. The high capacity retention combined with remarkable high-rate capability makes Na0.44MnO2–CNT a promising electrode material for advanced Na-ion batteries.

Highly Reversible and Durable Na Storage in Niobium Pentoxide through Optimizing Structure, Composition, and Nanoarchitecture

Amorphous, hydrogenated, and self-ordered nanoporous Nb2 O5 films serve as an excellent binder-free electrode for sodium batteries, affording a high and sustainable capacity delivery and robust high-rate capability. This collaborative material engineering of structural order (amorphization), composition (hydrogenation), and architecture (ordered nanopore) opens up new possibilities to develop an energy storage solution that is more accessible, sustainable, and producible.

3D porous hierarchical Li2FeSiO4/C for rechargeable lithium batteries

Lithium iron silicates (Li2FeSiO4) are promising cathodes for rechargeable lithium batteries owing to their high capacity, low cost, and superior stability. However, Li2FeSiO4 suffers from extremely low electronic and ionic conductivity. Herein, we used a two-step method to fabricate carbon-painted, three-dimensional (3D) porous hierarchical Li2FeSiO4 (3D Li2FeSiO4/C) as an efficient cathode, based on a facile hydrothermal reaction followed by carbon nanopainting. The hierarchical porous structure endows the Li2FeSiO4/C with efficient electrolyte storage and penetration, whereas the 3D carbon nanopainting provides an expressway for rapid electron transport. As a result, this 3D Li2FeSiO4/C exhibits a high electrochemical activity towards Li cycling, outperforming its counterpart without carbon painting and other Li2FeSiO4 materials. This research highlights the potential of engineering 3D porous structure to circumvent the poor conductivity in battery materials.

Graphene wrapped ordered LiNi0.5Mn1.5O4 nanorods as promising cathode material for lithium-ion batteries.

LiNi0.5Mn1.5O4 nanorods wrapped with graphene nanosheets have been prepared and investigated as high energy and high power cathode material for lithium-ion batteries. The structural characterization by X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy indicates the LiNi0.5Mn1.5O4 nanorods prepared from β-MnO2 nanowires have ordered spinel structure with P4332 space group. The morphological characterization by scanning electron microscopy and transmission electron microscopy reveals that the LiNi0.5Mn1.5O4 nanorods of 100–200 nm in diameter are well dispersed and wrapped in the graphene nanosheets for the composite. Benefiting from the highly conductive matrix provided by graphene nanosheets and one-dimensional nanostructure of the ordered spinel, the composite electrode exhibits superior rate capability and cycling stability. As a result, the LiNi0.5Mn1.5O4-graphene composite electrode delivers reversible capacities of 127.6 and 80.8 mAh g−1 at 0.1 and 10 C, respectively, and shows 94% capacity retention after 200 cycles at 1 C, greatly outperforming the bare LiNi0.5Mn1.5O4 nanorod cathode. The outstanding performance of the LiNi0.5Mn1.5O4-graphene composite makes it promising as cathode material for developing high energy and high power lithium-ion batteries.

Engineering Bi2O3-Bi2S3 heterostructure for superior lithium storage.

Bismuth oxide may be a promising battery material due to the high gravimetric (690 mAh g−1) and volumetric capacities (6280 mAh cm−3). However, this intrinsic merit has been compromised by insufficient Li-storage performance due to poor conductivity and structural integrity. Herein, we engineer a heterostructure composed of bismuth oxide (Bi2O3) and bismuth sulphide (Bi2S3) through sulfurization of Bi2O3 nanosheets. Such a hierarchical Bi2O3-Bi2S3 nanostructure can be employed as efficient electrode material for Li storage, due to the high surface areas, rich porosity, and unique heterogeneous phase. The electrochemical results show that the heterostructure exhibits a high Coulombic efficiency (83.7%), stable capacity delivery (433 mAh g−1 after 100 cycles at 600 mA g−1) and remarkable rate capability (295 mAh g−1 at 6 A g−1), notably outperforming reported bismuth based materials. Such superb performance indicates that constructing heterostructure could be a promising strategy towards high-performance electrodes for rechargeable batteries.

Boosting Sodium Storage in TiO2 Nanotube Arrays through Surface Phosphorylation

Sodium-ion batteries (SIBs) offer a promise of a scalable, low-cost, and environmentally benign means of renewable energy storage. However, the low capacity and poor rate capability of anode materials present an unavoidable challenge. In this work, it is demonstrated that surface phosphorylated TiO2 nanotube arrays grown on Ti substrate can be efficient anode materials for SIBs. Fabrication of the phosphorylated nanoarray film is based on the electrochemical anodization of Ti metal in NH4 F solution and subsequent phosphorylation using sodium hypophosphite. The phosphorylated TiO2 nanotube arrays afford a reversible capacity of 334 mA h g-1 at 67 mA g-1 , a superior rate capability of 147 mA h g-1 at 3350 mA g-1 , and a stable cycle performance up to 1000 cycles. In situ X-ray diffraction and transmission electron microscopy reveal the near-zero strain response and robust mechanical behavior of the TiO2 host upon (de)sodiation, suggesting its excellent structural stability in the Na+ storage application.