Yubin Niu

Exploration of K2Ti8O17 as an anode material for potassium-ion batteries

Novel K2Ti8O17 is successfully fabricated via a facile hydrothermal method combined with a subsequent annealing treatment and further evaluated as an anode material for potassium-ion batteries for the first time. This study may provide a broader vision into developing anode materials for potassium-ion batteries.

Facile Synthesis of Novel Networked Ultralong Cobalt Sulfide Nanotubes and Its Application in Supercapacitors

Ultralong cobalt sulfide (CoS(1.097)) nanotube networks are synthesized by a simple one-step solvothermal method without any surfactant or template. A possible formation mechanism for the growth processes is proposed. Owing to the hollow structure and large specific area, the novel CoS(1.097) materials present outstanding electrochemical properties. Electrochemical measurements for supercapacitors show that the as-prepared ultralong CoS(1.097) nanotube networks exhibit high specific capacity, good capacity retention, and excellent Coulombic efficiency.

Solvent-mediated directionally self-assembling MoS2 nanosheets into a novel worm-like structure and its application in sodium batteries

Ultralong worm-like MoS2 nanostructures were assembled with a solvent-mediated solvothermal process by controlling the composition ratio of the miscible precursors in solution. The formation mechanism of worm-like MoS2 nanostructures was proposed and the as-prepared materials as anodes in sodium ion batteries delivered a good discharge–charge capacity, superior cycling stability and excellent coulombic efficiency. This work provides an efficient and economic approach to tailor the nanostructure of layered transition metal oxides and transition-metal dichalcogenides simply by controlling the chemical composition and physical properties in a solvothermal process.

Nanocubic KTi2(PO4)3 electrodes for potassium-ion batteries

Novel nanocubic KTi2(PO4)3 was successfully fabricated via a facile hydrothermal method combined with a subsequent annealing treatment and further evaluated as an electrode material for potassium-ion batteries for the first time. For comparison, carbon-coated KTi2(PO4)3 obtained by a normal cane sugar-assisted method reveals improved electrochemical performances in potassium-ion batteries. This work may give a new insight into developing electrode materials for potassium-ion batteries.

Na3.12Fe2.44(P2O7)2/multi-walled carbon nanotube composite as a cathode material for sodium-ion batteries

Na3.12Fe2.44(P2O7)2/multi-walled carbon nanotube (MWCNT) composite was fabricated by a solid state reaction and was further used to fabricate a cathode for sodium-ion batteries. The electrochemical behaviors were thoroughly investigated in assembled non-aqueous Na3.12Fe2.44(P2O7)2/MWCNT//Na cells, showing higher specific capacity (over 100 mA h g−1 at a rate of 0.15C) and better stable cycle performance than those of the pristine Na3.12Fe2.44(P2O7)2-based one. It is noted that with increased charge–discharge cycles, the specific capacity of Na3.12Fe2.44(P2O7)2/MWCNT gets close to the theoretical capacity (ca. 117.4 mA h g−1). These good performances could be attributed to the incorporated MWCNTs, which improve the conductivity for lower charge transfer resistance and shorten the diffusion length for faster Na+ diffusion to access the reaction sites. Through systematic studies of EIS at different states of charge and discharge, it is discovered that Rct decreases with the increase of voltage and reaches a minimum value at redox sites, but Re and DNa+ show the opposite trend. Moreover, a full cell test using a carbon black negative electrode also demonstrates good capacity retention up to 50 cycles and a reversible capacity of 145 mA h g−1 with the average operation voltage of 2.8 V.

Synthesis and application of ultra-long Na0.44MnO2 submicron slabs as a cathode material for Na-ion batteries

Novel ultra-long Na0.44MnO2 submicron slabs were fabricated through the sol–gel method, followed by high-temperature calcination. The material has a thickness ranging from 100 to 250 nm and a length varying from 10 μm to 40 μm. Electrochemical characterization indicates that the material can deliver a high capacity, larger than 120 mA h g−1 with stable cycling over 100 cycles in assembled non-aqueous Na-ion cells, the good performance of which is mainly attributed to the reduced sodium ion diffusion distance.

An architectural development for energy conversion materials: morphology-conserved transformation synthesis of manganese oxides and their application in lithium ion batteries

A facile and effective redox reaction is developed to build various morphologies and crystal phases of manganese-based compounds by using two kinds of raw material, D-maltose and KMnO4. Interestingly, not only different morphologies, but also different crystal phases could be precisely tailored by adjusting the mass ratio of D-maltose to KMnO4. After thorough analysis of the observations, a reasonable formation mechanism is proposed to offer physico-chemical insight, while promoting opportunities to explore novel properties of manganese oxides for the fabrication of important functional devices. To demonstrate the process–structure–property relationship of the as-prepared nanomaterials, various morphologies of α-Mn2O3, including cubic, spindle and fusiform were used for lithium ion batteries. The results indicate that the improved material morphology and porous structure can significantly improve the discharge capacity and cycling stability.

Detailed investigation of a NaTi2(PO4)3 anode prepared by pyro-synthesis for Na-ion batteries

NaTi2(PO4)3 nanoparticles were synthesized by a facile polyol-assisted pyro-synthetic reaction. The nitrogen sorption isotherm of the synthesized material shows a surface area of 110.787 m2 g−1, in comparison to 20.984 m2 g−1 for pristine material obtained by a solid state method. Moreover, the as-prepared material exhibits much higher capacity, better rate performance and lower electrochemical polarization, of which the excellent electrochemical performance is mainly attributed to uniform particle distribution, good structural stability, high specific surface area, significantly enhanced diffusion coefficient and good conductivity. Through systematic studies using a galvanostatic intermittent titration technique (GITT) and electrochemical impedance spectroscopy (EIS) at different states of charge and discharge, the Na+ diffusion coefficient shows a minimum value at the end of the two-phase region.

A 3D porous interconnected NaVPO4F/C network: preparation and performance for Na-ion batteries

A uniform carbon embedded nano-scale NaVPO4F precursor of 3–5 nm is fabricated by a hydrothermal method and using vitamin C as the carbon source and reducing agent, followed by a sintering process, the carbon embedded NaVPO4F precursors transformed into a kind of 3D porous interconnected NaVPO4F/C network. As a Na-ion battery cathode material, the NaVPO4F/C network obtained at 750 °C achieves a high discharge capacity of 121 mA h g−1 and the sample obtained at 800 °C shows a slightly lower discharge capacity of 101 mA h g−1, but better rate capability and long cycle life. These results indicate that the 3D porous NaVPO4F/C network not only improves the electronic conductivity of the active material, but also prevents the aggregation of particles, and its open porous structure allows electrolyte penetration, and reduces the diffusion path of the sodium ions, hence maximizing utilization of the electrochemically active NaVPO4F particles.

Fabrication of WS2-nanoflowers@rGO composite as an anode material for enhanced electrode performance in lithium-ion batteries

In this paper, we descried a simple method to fabricate three-dimensional (3D) composite materials, WS2-nanoflowers @ reduced graphene oxide (WS2-NF@rGO), in which rGO crossed-link the isolated WS2-NF to construct a 3D conductive network and provided protection against the volume changes of WS2 during electrochemical processes simultaneously. This unique structure of the WS2-NF@rGO composite could not only promote both ion and electron diffusion, but also enhance the electrode stability, thus obtaining a high-capacity and long-cycle anode material for lithium-ion batteries. As a result, the WS2-NF@rGO exhibited a reversible capacity of 730mAhg-1 after 150 cycles at 100mAg-1 and maintained a capacity of higher than 260mAhg-1 at 2Ag-1, thus exhibiting great potential as an anode material for lithium storage.