Xueyi Lu

High-defect hydrophilic carbon cuboids anchored with Co/CoO nanoparticles as highly efficient and ultra-stable lithium-ion battery anodes

We propose an effective strategy to engineer a unique kind of porous carbon cuboid with tightly anchored cobalt/cobalt oxide nanoparticles (PCC–CoOx) that exhibit outstanding electrochemical performance for many key aspects of lithium-ion battery electrodes. The host carbon cuboid features an ultra-polar surface reflected by its high hydrophilicity and rich surface defects due to high heteroatom doping (N-/O-doping both higher than 10 atom%) as well as hierarchical pore systems. We loaded the porous carbon cuboid with cobalt/cobalt oxide nanoparticles through an impregnation process followed by calcination treatment. The resulting PCC–CoOx anode exhibits superior rate capability (195 mA h g−1 at 20 A g−1) and excellent cycling stability (580 mA h g−1 after 2000 cycles at 1 A g−1 with only 0.0067% capacity loss per cycle). Impressively, even after an ultra-long cycle life exceeding 10000 cycles at 5 A g−1, the battery can recover to 1050 mA h g−1 at 0.1 A g−1, perhaps the best performance demonstrated so far for lithium storage in cobalt oxide-based electrodes. This study provides a new perspective to engineer long-life, high-power metal oxide-based electrodes for lithium-ion batteries through controlling the surface chemistry of carbon host materials.

MoS2 nanosheets decorated with gold nanoparticles for rechargeable Li–O2 batteries

We demonstrate here a facile one-step hydrothermal synthesis to prepare molybdenum disulfide nanosheets decorated with gold nanoparticles (MoS2/AuNPs) for rechargeable Li–O2 batteries. The fabricated Li–O2 battery exhibits enhanced specific capacity and cycle efficiency, which are ascribed to the two-dimensional structure of MoS2/AuNP nanohybrids and the synergistic catalytic effects of both MoS2 nanosheets and AuNPs.

Tunable Pseudocapacitance in 3D TiO2−δ Nanomembranes Enabling Superior Lithium Storage Performance

Nanostructured TiO2 of different polymorphs, mostly prepared by hydro/solvothermal methods, have been extensively studied for more than a decade as anode materials in lithium ion batteries. Enormous efforts have been devoted to improving the electrical conductivity and lithium ion diffusivity in chemically synthesized TiO2 nanostructures. In this work we demonstrate that 3D Ti3+-self-doped TiO2 (TiO2-δ) nanomembranes, which are prepared by physical vapor deposition combined with strain-released rolled-up technology, have a great potential to address several of the long-standing challenges associated with TiO2 anodes. The intrinsic electrical conductivity of the TiO2 layer can be significantly improved by the in situ generated Ti3+, and the amorphous, thin TiO2 nanomembrane provides a shortened Li+ diffusion pathway. The fabricated material shows a favorable electrochemical reaction mechanism for lithium storage. Further, post-treatments are employed to adjust the Ti3+ concentration and crystallinity degree in TiO2 nanomembranes, providing an opportunity to investigate the important influences of Ti3+ self-doping and amorphous structures on the electrochemical processes. With these experiments, the pseudocapacitance contributions in TiO2 nanomembranes with different crystallinity degree are quantified and verified by an in-depth kinetics analysis. Additionally, an ultrathin metallic Ti layer can be included, which further improves the lithium storage properties of the TiO2, giving rise to the state-of-the-art capacity (200 mAh g-1 at 1 C), excellent rate capability (up to 50 C), and ultralong lifetime (for 5000 cycles at 10 C, with an extraordinary retention of 100%) of TiO2 anodes.

Bifunctional Au–Pd decorated MnOx nanomembranes as cathode materials for Li–O2 batteries

The search for new stable and efficient cathode materials for nonaqueous Li–O2 batteries has become an urgent task to satisfy the ever-growing needs for high capacity and high energy efficiency. To circumvent above issues, we have designed and synthesized isolated Au and Pd decorated MnOx nanomembranes, which act as bifunctional catalysts for Li–O2 batteries with a high specific capacity of 3200 mA h g−1 at 500 mA g−1 which is 9.8 and 3.2 times that of Super P and bare MnOx, respectively. In addition, with such novel structured catalysts, lithium ions, electrons and oxygen-containing intermediates can be rapidly transported, thus greatly improving the performance of Li–O2 batteries by significantly lowering the polarization and extending the cycle life to 120 times. The encouraging electrochemical property of such Au–Pd decorated MnOx nanomembranes leads to potential applications of the materials for high-performance Li–O2 batteries.

Highly dispersed metal and oxide nanoparticles on ultra-polar carbon as efficient cathode materials for Li–O2 batteries

Li–O2 batteries trigger worldwide interest as promising candidates for future energy supplies. One of the major challenges regarding current Li–O2 batteries is exploring highly efficient cathodes with sophisticated structures and compositions. Herein, highly dispersed metal (Pd) or oxide (RuO2) nanoparticles on ultra-polar carbon are synthesized and employed as cathode materials for Li–O2 batteries. The hierarchically porous structure of the carbon facilitates the oxygen diffusion and electrolyte impregnation and provides enough space to accommodate the discharge products. More importantly, the porous carbon with the ultra-polar surface serves as an efficient support for distinct dispersion of Pd or RuO2 nanoparticles which not only greatly enhances the catalytic activity but also eases side reactions by passivating the carbon defects. By virtue of the hierarchical structure associated with the extremely high dispersion of active particles, the battery performance is effectively enhanced by greatly prolonging the cycle life and significantly lowering the overvoltages especially for the charging process. The encouraging results suggest that such ultra-polar hierarchical carbon-based composites can be appealing materials for rechargeable Li–O2 batteries.

Advances on Microsized On‐Chip Lithium‐Ion Batteries

Development of microsized on-chip batteries plays an important role in the design of modern micro-electromechanical systems, miniaturized biomedical sensors, and many other small-scale electronic devices. This emerging field intimately correlates with the topics of rechargeable batteries, nanomaterials, on-chip microfabrication, etc. In recent years, a number of novel designs are proposed to increase the energy and power densities per footprint area, as well as other electrochemical performances of microsized lithium-ion batteries. These advances may guide the pathway for the future development of microbatteries.

Reinforcing Germanium Electrode with Polymer Matrix Decoration for Long Cycle Life Rechargeable Lithium Ion Batteries

Germanium is a promising anode material for lithium ion batteries because of its high theoretical specific capacity and low operation voltage. However, a significant challenge in using Ge-based anodes is the large volume variation during cycling that causes pulverization and capacity fade. Despite intense studies in the past decade, unsatisfactory cycling stability of the Ge-based electrodes still impedes their widespread applications. In this study, we demonstrate a high-performance electrode through the synergistic combination of a high-capacity Ge film grown on a three-dimensional current collector and an in situ formed poly(vinylidene fluoride)-hexafluoropropene/SiO2 protective layer. Specifically, the polymer matrix is in continuous contact with the surface of the Ge shell, which provides improved mechanical and ionic transport properties. As a highlight, we present impressive cycling stability over 3000 cycles at 1 C rate with a capacity retention as high as 95.7%. Furthermore, the LiCoO2-Ge full battery operates at an average voltage of 3.3 V at 0.5 C and maintains good electrochemical performance, suggesting great potential for applications in energy storage and conversion devices.

Ultralong-Discharge-Time Biobattery Based on Immobilized Enzymes in Bilayer Rolled-Up Enzymatic Nanomembranes

Glucose biofuel cells (GBFCs) are highly promising power sources for implantable biomedical and consumer electronics because they provide a high energy density and safety. However, it remains a great challenge to combine their high power density with reliable long-term stability. In this study, a novel GBFC design based on the enzyme biocatalysts glucose dehydrogenase, diaphorase, and bilirubin oxidase immobilized in rolled-up titanium nanomembranes is reported. The setup delivers a maximum areal power density of ≈3.7 mW cm-2 and a stable power output of ≈0.8 mW cm-2 . The power discharges over 452 h, which is considerably longer than reported previously. These results demonstrate that the GBFC design is in principle a feasible and effective approach to solve the long-term discharge challenge for implantable biomedical device applications.

In Situ Generation of Plasmonic Nanoparticles for Manipulating Photon–Plasmon Coupling in Microtube Cavities

In situ generation of silver nanoparticles for selective coupling between localized plasmonic resonances and whispering-gallery modes (WGMs) is investigated by spatially resolved laser dewetting on microtube cavities. The size and morphology of the silver nanoparticles are changed by adjusting the laser power and irradiation time, which in turn effectively tune the photon-plasmon coupling strength. Depending on the relative position of the plasmonic nanoparticles spot and resonant field distribution of WGMs, selective coupling between the localized surface plasmon resonances (LSPRs) and WGMs is experimentally demonstrated. Moreover, by creating multiple plasmonic-nanoparticle spots on the microtube cavity, the field distribution of optical axial modes is freely tuned due to multicoupling between LSPRs and WGMs. The multicoupling mechanism is theoretically investigated by a modified quasipotential model based on perturbation theory. This work provides an in situ fabrication of plasmonic nanoparticles on three-dimensional microtube cavities for manipulating photon-plasmon coupling which is of interest for optical tuning abilities and enhanced light-matter interactions.