Jinshuo Qiao

Three-dimensional graphene–Co3O4 cathodes for rechargeable Li–O2 batteries

A three-dimensional (3D) graphene–Co3O4 electrode was prepared by a two-step method in which graphene was initially deposited on a Ni foam with Co3O4 then grown on the resulting graphene structure. Cross-linked Co3O4 nanosheets with an open pore structure were fully and vertically distributed throughout the graphene skeleton. The free-standing and binder-free monolithic electrode was used directly as a cathode in a Li–O2 battery. This composite structure exhibited enhanced performance with a specific capacity of 2453 mA h g−1 at 0.1 mA cm−2 and 62 stable cycles with 583 mA h g−1 (1000 mA h gcarbon−1). The excellent electrochemical performance is associated with the unique architecture and superior catalytic activity of the 3D electrode.

Ultrastrong Polyoxyzole Nanofiber Membranes for Dendrite-Proof and Heat-Resistant Battery Separators

Polymeric nanomaterials emerge as key building blocks for engineering materials in a variety of applications. In particular, the high modulus polymeric nanofibers are suitable to prepare flexible yet strong membrane separators to prevent the growth and penetration of lithium dendrites for safe and reliable high energy lithium metal-based batteries. High ionic conductance, scalability, and low cost are other required attributes of the separator important for practical implementations. Available materials so far are difficult to comply with such stringent criteria. Here, we demonstrate a high-yield exfoliation of ultrastrong poly(p-phenylene benzobisoxazole) nanofibers from the Zylon microfibers. A highly scalable blade casting process is used to assemble these nanofibers into nanoporous membranes. These membranes possess ultimate strengths of 525 MPa, Youngs moduli of 20 GPa, thermal stability up to 600 °C, and impressively low ionic resistance, enabling their use as dendrite-suppressing membrane separators in electrochemical cells. With such high-performance separators, reliable lithium-metal based batteries operated at 150 °C are also demonstrated. Those polyoxyzole nanofibers would enrich the existing library of strong nanomaterials and serve as a promising material for large-scale and cost-effective safe energy storage.

Photoelectrochemical oxidation of glucose for sensing and fuel cell applications

We report the photoelectrochemical oxidation of glucose at an anatase TiO2 modified electrode for unique sensing application. Furthermore, electricity was extracted with a dual-functional photoelectrochemical glucose fuel cell.

Facile Synthesis of Hierarchical Porous Three-Dimensional Free-Standing MnCo2O4 Cathodes for Long-Life Li—O2 Batteries

Hierarchical porous three-dimensional MnCo2O4 nanowire bundles were obtained by a universal and low-cost hydrothermal method, which subsequently act as a carbon-free and binder-free cathode for Li-O2 cell applications. This system showed a high discharge capacity of up to 12 919 mAh g-1 at 0.1 mA cm-2 and excellent rate capability. Under constrained specific capacities of 500 and 1000 mAh g-1, Li-O2 batteries could be successfully operated for over 300 and 144 cycles, respectively. Moreover, their charge voltage was markedly decreased to about 3.5 V. Their excellent electrochemical performance is proposed to be related to the conductivity enhancements resulting from the hierarchical interconnected mesoporous/macroporous weblike structure of the hybrid MnCo2O4 cathode, which facilitated the electron and mass transport. More importantly, after 2 months of cycling, the microstructure of the cathode was maintained and a recyclability of over 200 cycles of the reassembled Li-O2 cells was achieved. The effects of the level of electrolyte and corrosion of the lithium anode during long-term cycling on the electrochemical property of Li-O2 cells have been explored. Furthermore, the nucleation process of the discharge product morphology has been investigated.

Synthesis and characterization of B-site Ni-doped perovskites Sr2Fe1.5−xNixMo0.5O6−δ (x = 0, 0.05, 0.1, 0.2, 0.4) as cathodes for SOFCs

Sr2Fe1.5−xNixMo0.5O6−δ (x = 0, 0.05, 0.1, 0.2, 0.4) (SFNM) materials have been synthesized by a sol–gel combustion method and studied towards application as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs). The crystal structure, microstructure, thermal expansion, element valence, conductivity and electrochemical properties have been characterized as a function of Ni content. The symmetrical structure of the cubic lattice in perovskite oxides is confirmed. SFNM powders possess the 3D interconnected network microstructure composed of nanoparticles. An increasing Ni substitution results in the unit cell shrinkage and the increase of thermal expansion coefficient (TEC). Furthermore, X-ray photoelectron spectroscopy (XPS) analysis shows that Ni basically exhibits a low oxidation state (Ni2+). Doped Ni2+ affects the equilibrium between Fe3+/Mo5+ and Fe2+/Mo6+, which is directly related to the conductivity. The SFNM conductivity was apparently improved, reaching 60 S cm−1 at 450 °C when x = 0.1, which is more than twice that of the Sr2Fe1.5Mo0.5O6−δ (SFM) sample. In addition, Sr2Fe1.4Ni0.1Mo0.5O6−δ (SFN0.1M) cathodes showed excellent electrochemical performance and lowest interface polarization resistance (Rp). The Rp of the SFN0.1M cathode was approximately 50% of that of the SFM cathode. Moreover, the maximum power densities of a single cell based on the SFN0.1M cathode were 0.92, 1.27 W cm−2 at 700, 750 °C, respectively. The SFNM material is a type of potential cathode for IT-SOFCs.

Investigation into the effect of Fe-site substitution on the performance of Sr2Fe1.5Mo0.5O6−δ anodes for SOFCs

Ni-substituted Sr2Fe1.5−xNixMo0.5O6−δ (SFNM) materials have been investigated as anode catalysts for intermediate temperature solid oxide fuel cells. Reduced samples (x = 0.05 and 0.1) maintained the initial perovskite structure after reduction in H2, while metallic nickel particles were detected on the grain surface for x = 0.2 and 0.3 using transmission electron microscopy. Temperature programmed reduction results indicate that the stable temperature for SFNM samples under reduction conditions decreases with Ni content. In addition, X-ray photoelectron spectroscopy analysis suggests that the incorporation of Ni affects the conductivity of SFNM through changing the ratios of Fe3+/Fe2+ and Mo6+/Mo5+. Sr2Fe1.4Ni0.1Mo0.5O6−δ shows the highest electrical conductivity of 20.6 S cm−1 at 800 °C in H2. The performance of this anode was further tested with electrolyte-supported cells, giving 380 mW cm−2 at 750 °C in H2, hence demonstrating that Ni doping in the B-site is beneficial for Sr2Fe1.5Mo0.5O6−δ anode performance.

Hierarchical hollow nanofiber networks for high-performance hybrid direct carbon fuel cells

Herein, we demonstrated a new strategy for the development of Ce0.6Mn0.3Fe0.1O2 hierarchically structured porous hollow nanofibers tailored as efficient anodes for hybrid direct carbon fuel cells. The cell based on the as-optimized anode delivered an excellent electrochemical performance and achieved a good long-term stability.

Dynamic Deformation Behaviors of an In Situ Ti-Based Metallic Glass Matrix Composite

Quasi-static and dynamic deformation behaviors, fracture characteristics, and microstructural evolution of an in situ dendrite-reinforced metallic glass matrix composite: Ti50Zr20V10Cu5Be15 within a wide range of strain rates are investigated. Compared with the quasi-static compression, the yielding stress increases, but the macroscopic plasticity significantly decreases upon dynamic compression. The effects of the strain rate on strain hardening upon quasi-static loading and flow stress upon dynamic loading are evaluated, respectively. The Zerilli-Armstrong (Z-A) model based on dendrite-dominated mechanism is employed to further uncover the dependence of the yielding stress on the strain rate.