Chunsong Zhao

Cycling of a Lithium‐Ion Battery with a Silicon Anode Drives Large Mechanical Actuation

Lithium-ion batteries with a Si anode can drive large mechanical actuation by utilizing the dramatic volume changes of the electrode during the charge/discharge cycles. A large loading of more than 10 MPa can be actuated by a LiFePO4 ||Si full battery with a rapid response while the driving voltage is lower than 4 V.

Buckled Tin Oxide Nanobelt Webs as Highly Stretchable and Transparent Photosensors.

Stretchable and transparent inorganic semiconductors play a key role for the next generation of wearable optoelectronics. Achieving stretchability in intrinsically rigid inorganic materials is far more challenging than in polymers and metals. Here, we present a low-cost and scalable strategy to engineer inorganic semiconductors into a buckling open-mesh configuration, by which extraordinary stretchability (≈160%) as well as high optical transparency (>86% at 550 nm) can be realized simultaneously in SnO2 nanofiber webs. Moreover, the mechanical stretchability of SnO2 nanowebs can be further improved along with the optical transparency by precisely controlling the nanofiber density. The as-prepared freestanding nanowebs can be laminated onto curved surfaces by conformal contact. It is demonstrated that the fully exposed SnO2 nanowebs can be used as wearable UV photodetectors, showing reliable optoelectronic performance and remarkable tolerance to repeated complex deformations with body movements.

Mass production of two-dimensional oxides by rapid heating of hydrous chlorides

Two-dimensional (2D) nanoscale oxides have attracted research interest owing to their electronic, magnetic optical and catalytic properties. If they could be manufactured on a large scale, 2D oxides would be attractive for applications ranging from electronics to energy conversion and storage. Herein, we report facile fabrication of oxide nanosheets by rapid thermal annealing of corresponding hydrous-chloride compounds. By heating CrCl3·6H2O, ZrOCl2·8H2O, AlCl3·6H2O and YCl3·6H2O crystals as precursors, we immediately collect large quantities of ultrathin Cr2O3, ZrO2, Al2O3 and Y2O3 nanosheets, respectively. The formation of layered nanosheets relies on exfoliation driven by rapid evaporation of water and/or other gas molecules generated under annealing. Our route allows simple, efficient and inexpensive production of 2D oxides. As a demonstration, we evaluate Cr2O3 nanosheets prepared by our method as anodes in lithium-ion batteries and find superior performance in comparison with their microcrystalline counterparts.

Ultralight, scalable, and high-temperature–resilient ceramic nanofiber sponges

Scalable synthesis of ultralight, multifunctional, and high-temperature resilient ceramic nanofiber sponges by blow-spinning. Ultralight and resilient porous nanostructures have been fabricated in various material forms, including carbon, polymers, and metals. However, the development of ultralight and high-temperature resilient structures still remains extremely challenging. Ceramics exhibit good mechanical and chemical stability at high temperatures, but their brittleness and sensitivity to flaws significantly complicate the fabrication of resilient porous ceramic nanostructures. We report the manufacturing of large-scale, lightweight, high-temperature resilient, three-dimensional sponges based on a variety of oxide ceramic (for example, TiO2, ZrO2, yttria-stabilized ZrO2, and BaTiO3) nanofibers through an efficient solution blow-spinning process. The ceramic sponges consist of numerous tangled ceramic nanofibers, with densities varying from 8 to 40 mg/cm3. In situ uniaxial compression in a scanning electron microscope showed that the TiO2 nanofiber sponge exhibits high energy absorption (for example, dissipation of up to 29.6 mJ/cm3 in energy density at 50% strain) and recovers rapidly after compression in excess of 20% strain at both room temperature and 400°C. The sponge exhibits excellent resilience with residual strains of only ~1% at 800°C after 10 cycles of 10% compression strain and maintains good recoverability after compression at ~1300°C. We show that ceramic nanofiber sponges can serve multiple functions, such as elasticity-dependent electrical resistance, photocatalytic activity, and thermal insulation.

Reduction of graphene oxide in Li-ion batteries

Graphene or graphene based composites are widely used in various fields. Reducing graphene oxide is a simple and common method to prepare graphene for energy storage fields such as Li-ion batteries. However, thermal reduction needs a high temperature under vacuum or inert gas conditions and chemical reduction needs hazardous reducing agents. Accordingly, we report an electrochemical method to reduce graphene oxide in Li-ion batteries. By this method, we could assemble graphene oxide based composite electrodes into cells and directly reduce the graphene oxide in situ. Compared to the conventional method to reduce graphene oxide, our work is simple and effective. In particular, when the reduced graphene oxide is used in Li-ion batteries, our method could greatly simplify the electrode fabrication process.

Integration of Si in a metal foam current collector for stable electrochemical cycling in Li-ion batteries

Here we designed and fabricated an integrated Li-ion battery electrode by trapping electrochemically active materials inside a three-dimensional (3D) metal current collector. Silicon microparticles have been sealed into a compressed 3D Cu foam matrix, which has interconnected pores for electrolyte wetting and also for providing enough empty space for the volume expansion of Si during lithiation. Such an electrode design can effectively trap the active materials inside the metal framework during dynamic electrochemical cycles, preventing particle escape from the current collector. Having these advantages, the electrode exhibits greatly improved electrochemical stability. The initial capacity reaches 2500 mA h g−1 and remains more than 1000 mA h g−1 over 200 cycles. While setting a constant charge capacity by 500 mA h g−1, the capacity does not reduce after 600 cycles.

Sol–gel synthesis of mesoporous spherical zirconia

Mesoporous spherical zirconia (ZrO2) with a surface area of 113 m2 g−1 and average pore size of 5.0 nm is prepared by a sol–gel method with ZrOCl2·8H2O precursors and Sodium Dodecyl Sulfonate (SDS) templates with subsequent annealing at 500 °C in air. After calcination at 700 °C, the tetragonal phase transfers to monoclinic zirconia and the surface area is reduced to 26 m2 g−1. The mesoporous spherical structure, which is assembled by aggregation of the ZrO2 nanoparticles, is confirmed by characterization using low and wide-angle X-ray diffraction, Transmission Electron Microscopy (TEM) and Scanning Electron Microscopy (SEM). Mesoporous ZrO2 with a surface area of 113 m2 g−1 has a higher adsorption for Cs ion (357 mg g−1). For the 700 °C calcinated ZrO2, the absorption capacity at equilibrium is only 188 mg g−1.

A heatproof separator for lithium-ion battery based on nylon66 nanofibers

The safety of lithium-ion battery is closely related to the anti-shrink and heatproof stability of the separator. In this paper, electrospun nylon66 (PA66) nanofiber-based membrane is used as lithium-ion battery separator, showing good thermodynamics properties via thermogravimetric analysis (TG), thermal shrinkage experiment, and tension test. Furthermore, electrospun nylon66 separator based battery exhibits better safety than the battery applying Celgard commerce separator under the condition of high temperature and severe vibration. Meanwhile, the electrochemical properties of both batteries are nearly identical. These facts prove that the electrospun nylon66 separator is an ideal separator candidate for power lithium-ion battery of electric vehicles. In addition, the nylon66 separator annealed in the air has higher tensile strength and better property of elongation than the unannealed one.

Sucrose-templated nanoporous BiFeO3 for promising magnetically recoverable multifunctional environment-purifying applications: adsorption and photocatalysis

Bismuth ferrite (BiFeO3), which acts as a significant multiferroic material, exhibits unique magnetic and ferroelectric properties. Here, we adopted a sol–gel method to synthesize disordered nanoporous BFO with a sucrose template. By different characterization methods such as powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 physisorption measurements, the large BET (Brunauer–Emmett–Teller) surface area (34.25 m2 g−1) and disordered pores (20–40 nm) of the sucrose-templated nanoporous BFO (SN-BFO) materials were determined. These SN-BFO materials exhibited high magnetic performance (Ms = 6.37 emu g−1) and a favorable magnetic recycling ratio. In addition, SN-BFO displayed appropriate adsorption characteristics and good photocatalytic stability, which demonstrates that SN-BFO is a candidate for promising recoverable multifunctional environment-purifying applications in the future.

Aerodynamic levitated laser annealing method to defective titanium dioxide with enhanced photocatalytic performance

Defective TiO2 has attracted increasing attention for use in photocatalytic and electrochemical materials because of its narrowed band-gap and improved visible-light photocatalytic activity. However, a facile and efficient approach for obtaining defect-rich TiO2 still remains a challenge. Herein, we demonstrate such an approach to narrow its bandgap and improve visible-light absorption through implanting abundant defects by aerodynamic levitated laser annealing (ALLA) treatment. Note that the ALLA method not only provides rapid annealing, solidifying and cooling process, but also exhibits high efficiency for homogeneous and defective TiO2 nanoparticles. The laser-annealed TiO2 achieves a high hydrogen evolution rate of 8.54 mmol·h–1·g–1, excellent decomposition properties within 60 min, and outstanding recyclability and stability, all of which are superior to the corresponding properties of commercial P25.