Tao Qian

A Sustainable Route from Biomass Byproduct Okara to High Content Nitrogen‐Doped Carbon Sheets for Efficient Sodium Ion Batteries

A sustainable route from the biomass byproduct okara as a natural nitrogen fertilizer to high-content N-doped carbon sheets is demonstrated. The as-prepared unique structure exhibits high specific capacity (292 mAh g(-1) ) and extremely long cycle life (exceeding 2000 cycles). A full battery is devised for the practical use of materials with a flexible/wearable LED screen.

A New Type of Multifunctional Polar Binder: Toward Practical Application of High Energy Lithium Sulfur Batteries

A new type of amino polar binder with 3D network flexibility structure for high energy Li-S batteries is synthesized and successfully used with commercial sulfur powder cathodes. The binder shows significant performance improvement in capacity retention and high potential for practical application, which arouse the battery communitys interest in the commercial application of high energy Li-S battery.

Interconnected three-dimensional V2O5/polypyrrole network nanostructures for high performance solid-state supercapacitors

Supercapacitor electrodes composed of a 3D V2O5 network with polypyrrole (PPy) uniformly decorated onto each nanowire were fabricated to enhance their pseudocapacitive performance. The continuous 3D network creates channels for better ion transport, and the high degree of pore connectivity in the network enhances the mass transport. The PPy shell could enhance the electric conductivity and prevent the dissolution of vanadium. These merits together with the ideal synergy between V2O5 and PPy lead to a high specific capacitance of 448 F g−1, which is three times higher than that of the stacked V2O5. The all-solid-state symmetric supercapacitor device assembled by the V2O5/PPy core/shell 3D network exhibits a high energy density (14.2 W h kg−1) at a power density of 250 W kg−1 and good cyclic stability (capacitance retention of 81% after 1000 cycles). Furthermore, the prepared device could power a red light-emitting diode indicator efficiently after charging for only 10 s.

Greatly Suppressed Shuttle Effect for Improved Lithium Sulfur Battery Performance through Short Chain Intermediates

The high solubility of long-chain lithium polysulfides and their infamous shuttle effect in lithium sulfur battery lead to rapid capacity fading along with low Coulombic efficiency. To address above issues, we propose a new strategy to suppress the shuttle effect for greatly enhanced lithium sulfur battery performance mainly through the formation of short-chain intermediates during discharging, which allows significant improvements including high capacity retention of 1022 mAh/g with 87% retention for 450 cycles. Without LiNO3-containing electrolytes, the excellent Coulombic efficiency of ∼99.5% for more than 500 cycles is obtained, suggesting the greatly suppressed shuttle effect. In situ UV/vis analysis of electrolyte during cycling reveals that the short-chain Li2S2 and Li2S3 polysulfides are detected as main intermediates, which are theoretically verified by density functional theory (DFT) calculations. Our strategy may open up a new avenue for practical application of lithium sulfur battery.

Molecularly Imprinted Polymer Enables High-Efficiency Recognition and Trapping Lithium Polysulfides for Stable Lithium Sulfur Battery

Using molecularly imprinted polymer to recognize various target molecules emerges as a fascinating research field. Herein, we applied this strategy for the first time to efficiently recognize and trap long-chain polysulfides (Li2Sx, x = 6-8) in lithium sulfur battery to minimize the polysulfide shuttling between anode and cathode, which enables us to achieve remarkable electrochemical performance including a high specific capacity of 1262 mAh g-1 at 0.2 C and superior capacity retention of over 82.5% after 400 cycles at 1 C. The outstanding performance is attributed to the significantly reduced concentration of long-chain polysulfides in electrolyte as evidenced by in situ UV/vis spectroscopy and Li2S nucleation tests, which were further confirmed by density functional theory calculations. The molecular imprinting is demonstrated as a promising approach to effectively prevent the free diffusion of long-chain polysulfides, providing a new avenue to efficiently recognize and trap lithium polysulfides for high-performance lithium sulfur battery with greatly suppressed shuttle effect.

A new approach towards the synthesis of nitrogen-doped graphene/MnO2 hybrids for ultralong cycle-life lithium ion batteries

A new approach using polypyrrole as the nitrogen source has been demonstrated for the fabrication of nitrogen-doped graphene, which subsequently served as nucleation centers for the growth of metal oxides. The thin layers of the nitrogen-doped graphene are not only used as conductive pathways accelerating the electrical conductivity of metal oxides but also serve as buffer layers to improve the electrical contact with metal oxide nanostructures during the delithiation/lithiation of lithium ions. As anodes for lithium ion batteries, the nitrogen-doped graphene and their hybrids with MnO2 nanorods exhibit exceptionally excellent capacity retention for 3000 cycles at 2500 mA g−1, and ultrafast rate capability, which pave the way for developing electrode materials for long cycle-life energy storage devices.

An Efficient Bifunctional Electrocatalyst for a Zinc–Air Battery Derived from Fe/N/C and Bimetallic Metal–Organic Framework Composites

Efficient bifunctional electrocatalysts with desirable oxygen activities are closely related to practical applications of renewable energy systems including metal-air batteries, fuel cells, and water splitting. Here a composite material derived from a combination of bimetallic zeolitic imidazolate frameworks (denoted as BMZIFs) and Fe/N/C framework was reported as an efficient bifunctional catalyst. Although BMZIF or Fe/N/C alone exhibits undesirable oxygen reaction activity, a combination of these materials shows unprecedented ORR (half-wave potential of 0.85 V as well as comparatively superior OER activities (potential@10 mA cm-2 of 1.64 V), outperforming not only a commercial Pt/C electrocatalyst but also most reported bifunctional electrocatalysts. We then tested its practical application in Zn-air batteries. The primary batteries exhibit a high peak power density of 235 mW cm-2, and the batteries are able to be operated smoothly for 100 cycles at a curent density of 10 mA cm-2. The unprecedented catalytic activity can be attritued to chemical coupling effects between Fe/N/C and BMZIF and will aid the development of highly active electrocatalysts and applications for electrochemical energy devices.

Selenium‐Doped Cathodes for Lithium–Organosulfur Batteries with Greatly Improved Volumetric Capacity and Coulombic Efficiency

For the first time a new strategy is reported to improve the volumetric capacity and Coulombic efficiency by selenium doping for lithium-organosulfur batteries. Selenium-doped cathodes with four sulfur atoms and one selenium atom (as the doped heteroatom) in the confined structure are designed and synthesized; this structure exhibits greatly improved volumetric/areal capacities, and a Coulombic efficiency of almost 100% for highly stable lithium-organosulfur batteries. The doping of Se significantly enhances the electronic conductivity of battery electrodes by a factor of 6.2 compared to pure sulfur electrodes, and completely restricts the production of long-chain lithium polysulfides. This allows achievement of a high gravimetric capacity of 700 mAh g-1 close to its theoretical mass capacity, an exceptional volumetric capacity of 2457 mAh cm-3 , and excellent capacity retention of 92% after 400 cycles. Shuttle effect is efficiently weakened since no long-chain polysulfides are detected from in situ UV/vis results throughout the entire cycling process arising from selenium doping, which is theoretically confirmed by density functional theory calculations.

Nanomeshes of highly crystalline nitrogen-doped carbon encapsulated Fe/Fe3C electrodes as ultrafast and stable anodes for Li-ion batteries

Fe/Fe3C homogeneously dispersed in 2D porous nitrogen-doped graphitic carbon nanomeshes (N-Fe/Fe3C@C nanomeshes) was prepared by a novel template-free method using the polypyrrole–Fe (PPy–Fe) coordination complex as a precursor. The designed architecture is beneficial to electron transport and accommodation of the strains of Li insertion/extraction. As an anode material for Li-ion batteries, the as-prepared composite exhibits a reversible capacity of 1316 mA h g−1 (normalized to the mass of Fe/Fe3C in the composite) with extremely excellent cycling performance at high rate (nearly 100% capacity retention after 500 cycles) and good rate capability. The synthesis approach presents a promising route for a large-scale production of N-Fe/Fe3C@C nanomesh composites as an extremely durable high-rate anode material for Li-ion batteries.

Highly Flexible Full Lithium Batteries with Self-Knitted α-MnO2 Fabric Foam.

Flexible/bendable electronic equipment has attracted great interest recently, while the development is hindered by fabricating flexible/bendable power sources due to the lack of reliable materials that combine both electronically superior conductivity and mechanical flexibility. Here, a novel structure of manganese oxide, like fabric foam, was constructed, which was then cocooned with a carbon shell via chemical vapor deposition. Serving as a binder-free anode, the self-knitted MnO2@Carbon Foam (MCF) exhibits high specific capacitance (850-950 mAh/g), excellent cycling stability (1000 cycles), and good rate capability (60 C, 1 C = 1 A/g). Moreover, a flexible full lithium battery was designed based on an MCF anode and a LiCoO2/Al cathode, and the outstanding performance (energy density of 2451 Wh/kg at a power density of 4085 W/kg) demonstrates its promising potential of the practical applications.