Nana Wang

Double‐Walled Sb@TiO2−x Nanotubes as a Superior High‐Rate and Ultralong‐Lifespan Anode Material for Na‐Ion and Li‐Ion Batteries

Double-walled Sb@TiO2- x nanotubes take full advantage of the high capacity of Sb, the good stability of TiO2- x , and their unique interaction, realizing excellent electrochemical performance both in lithium-ion batteries and sodium-ion batteries.

General synthesis of hollow MnO2, Mn3O4 and MnO nanospheres as superior anode materials for lithium ion batteries

The use of manganese oxides as promising candidates for anode materials in lithium ion batteries has attracted a significant amount of attention recently. Here, we develop a general approach to synthesize hollow nanospheres of MnO2, Mn3O4 and MnO, using carbon nanospheres as a template and a reagent. Depending on the calcination temperature, time and atmosphere, hollow nanospheres of MnO2 assembled by randomly dispersed nanosheets, or hollow nanospheres of Mn3O4 and MnO composed of aggregated nanoparticles, are produced. The electrochemical properties of the three hollow nanoparticles are investigated in terms of cycling stability and rate capability. They deliver the specific capacities of 840, 1165 or 1515 mA h g−1 after 60 cycles at 100 mA g−1 for MnO2, Mn3O4 and MnO. Even at 500 mA g−1, the reversible capacities could be still kept at 637, 820, and 1050 mA h g−1 after 150 cycles. The outstanding performances might be related with their hollow structure, porous surface and nanoscale size.

Facile synthesis of hierarchically porous NiO micro-tubes as advanced anode materials for lithium-ion batteries

Hierarchically porous NiO microtubes are synthesized by a high-temperature calcination of Ni(dmg)2 microtubes obtained by a simple precipitation method. The porous NiO microtubes as an anode material for lithium ion batteries exhibit excellent performances, ∼640 mA h g−1 after 200 cycles at 1 A g−1.

Hydrogenated TiO2 Branches Coated Mn3O4 Nanorods as an Advanced Anode Material for Lithium Ion Batteries

Rational design and delicate control on the component, structure, and surface of electrodes in lithium ion batteries are highly important to their performances in practical applications. Compared with various components and structures for electrodes, the choices for their surface are quite limited. The most widespread surface for numerous electrodes, a carbon shell, has its own issues, which stimulates the desire to find another alternative surface. Here, hydrogenated TiO2 is exemplified as an appealing surface for advanced anodes by the growth of ultrathin hydrogenated TiO2 branches on Mn3O4 nanorods. High theoretical capacity of Mn3O4 is well matched with low volume variation (∼4%), enhanced electrical conductivity, good cycling stability, and rate capability of hydrogenated TiO2, as demonstrated in their electrochemical performances. The proof-of-concept reveals the promising potential of hydrogenated TiO2 as a next-generation material for the surface in high-performance hybrid electrodes.

Porous MnFe2O4 microrods as advanced anodes for Li-ion batteries with long cycle lifespan

Porous electrode materials with both high rate capabilities and long cycle lives are significant to satisfy the urgent demand of energy storage. Furthermore, a one dimensional structure can facilitate Li+ diffusion and accommodate the volume expansion. Here, porous MnFe2O4 microrods have been successfully synthesized by a room temperature reaction and then moderate annealing in an Ar atmosphere. The porous MnFe2O4 electrodes exhibit high reversible capacity and outstanding cycling stability (after 1000 cycles still maitain about 630 mA h g−1 at the current density of 1 A g−1), as well as high coulombic efficiency (>98%). Moreover, even at a high current density of 4 A g−1, the porous MnFe2O4 microrods can still maintain a reversible capacity of 420 mA h g−1. These results demonstrate that the porous MnFe2O4 microrods are promising anode materials for high performance Li-ion batteries.

Surface-Amorphous and Oxygen-Deficient Li3VO4-δ as a Promising Anode Material for Lithium-Ion Batteries.

Surface‐amorphous and oxygen‐deficient Li3VO4−δ synthesized by simple annealing of Li3VO4 powders in a vacuum shows great enhancements in both reversible capacity and coulombic efficiency for the first discharge/charge without delicate size control and carbon coating. The results are associated with the improved charge‐transfer kinetics caused by the amorphous surface of Li3VO4−δ.

Triple-walled SnO2@N-doped carbon@SnO2 nanotubes as an advanced anode material for lithium and sodium storage

Triple-walled SnO2@N-doped carbon@SnO2 nanotubes are synthesized by a facile process with high-quality PPy nanotubes as the template. This structure has SnO2 nanoparticles closely attached to both the external and internal surfaces of N-doped carbon nanotubes, thus assuring good charge-transfer kinetics to all the SnO2 nanoparticles. Meanwhile, it doubles the loading density of SnO2 in the nanocomposite, and offers adequate room to accommodate the volume deformation of SnO2 on/in the nanotubes. All these features make the nanocomposite well fitted for lithium or sodium storage. It is found that this nanocomposite as an anode material for lithium ion batteries can deliver a reversible capacity of 935 mA h g−1 after 100 cycles at 200 mA g−1, or 658 mA h g−1 after 300 cycles at 2000 mA g−1. In the case of sodium ion batteries, its capacity could be still preserved at 492 mA h g−1 after 50 cycles at a current density of 25 mA g−1.

One-Dimensional Yolk–Shell Sb@Ti–O–P Nanostructures as a High-Capacity and High-Rate Anode Material for Sodium Ion Batteries

Development of high energy/power density and long cycle life of anode materials is highly desirable for sodium ion batteries, because graphite anode cannot be used directly. Sb stands out from the potential candidates, due to high capacity, good electronic conductivity, and moderate sodiation voltage. Here, one-dimensional yolk-shell Sb@Ti-O-P nanostructures are synthesized by reducing core-shell Sb2O3@TiO2 nanorods with NaH2PO2. This structure has Sb nanorod as the core to increase the capacity and Ti-O-P as the shell to stabilize the interface between electrolyte and electrode material. The gap between the core and the shell accommodates the volume change during sodiation/desodiation. These features endow the structure outstanding performances. It could deliver a capacity of about 760 mA h g-1 after 200 cycles at 500 mA g-1, with a capacity retention of about 94%. Even at 10 A g-1, the reversible capacity is still at 360 mA h g-1. The full battery of Sb@Ti-O-P//Na3V2(PO4)3-C presents a high output voltage (∼2.7 V) and a capacity of 392 mA h g-1anode after 150 cycles at 1 A g-1anode.

Simple synthesis of a porous Sb/Sb2O3 nanocomposite for a high-capacity anode material in Na-ion batteries

High-capacity anode materials are highly desirable for sodium ion batteries. Here, a porous Sb/Sb2O3 nanocomposite is successfully synthesized by the mild oxidization of Sb nanocrystals in air. In the composite, Sb contributes good conductivity and Sb2O3 improves cycling stability, particularly within the voltage window of 0.02–1.5 V. It remains at a reversible capacity of 540 mAh·g–1 after 180 cycles at 0.66 A·g–1. Even at 10 A·g–1, the reversible capacity is still preserved at 412 mAh·g–1, equivalent to 71.6% of that at 0.066 A·g–1. These results are much better than Sb nanocrystals with a similar size and structure. Expanding the voltage window to 0.02–2.5 V includes the conversion reaction between Sb2O3 and Sb into the discharge/charge profiles. This would induce a large volume change and high structure strain/stress, deteriorating the cycling stability. The identification of a proper voltage window for Sb/Sb2O3 paves the way for its development in sodium ion batteries.

Biphase-Interface Enhanced Sodium Storage and Accelerated Charge Transfer: Flower-like Anatase/Bronze TiO2/C as an Advanced Anode Material for Na-Ion Batteries

Flower-like assembly of ultrathin nanosheets composed of anatase and bronze TiO2 embedded in carbon is successfully synthesized by a simple solvothermal reaction, followed with a high-temperature annealing. As an anode material in sodium-ion batteries, this composite exhibits outstanding electrochemical performances. It delivers a reversible capacity of 120 mA h g-1 over 6000 cycles at 10 C. Even at 100 C, there is still a capacity of 104 mA h g-1. Besides carbon matrix and hierarchical structure, abundant interfaces between anatase and bronze greatly enhance the performance by offering additional sites for reversible Na+ storage and improving the charge-transfer kinetics. The interface enhancements are confirmed by discharge/charge profiles, rate performances, electrochemical impedance spectra, and first-principle calculations. These results offer a new pathway to upgrade the performances of anode materials in sodium-ion batteries.