Nansheng Xu

A novel solid oxide redox flow battery for grid energy storage

In this work we report proof-of-concept of a novel redox flow battery consisting of a solid oxide electrochemical cell (SOEC) integrated with a redox-cycle unit. The charge/discharge characteristics were explicitly observed by operating between fuel cell and electrolysis modes of the SOEC along with “in-battery” generation and storage of H2 realized by an in situ closed-loop reversible steam-metal reaction in the redox-cycle unit. With Fe/FeO as the redox materials, the new storage battery can produce an energy capacity of 348 Wh/kg-Fe and round-trip efficiency of 91.5% over twenty stable charge/discharge cycles. This excellent performance combined with robustness, environmental friendliness and sustainability promise the new battery to be a transformational energy storage device for grid application.

Flexible solid-state supercapacitors based on a conducting polymer hydrogel with enhanced electrochemical performance

In this paper, a conducting polyaniline hydrogel instead of traditional solid electrode materials is used as an electrode material to prepare high performance flexible solid-state supercapacitors. Conducting polymer hydrogels combine the properties of hydrogel with electrical conductivity, thus offering intrinsic porous conducting frameworks and promoting the transport of charges, ions, and molecules. According to our results, the capacitance of the polyaniline hydrogel electrode is quite remarkable (430 F g−1) in this prototype, flexible solid-state supercapacitor with a two-electrode configuration. Furthermore, this supercapacitor shows excellent rate capability, cyclic stability and bendable performance. Moreover, this supercapacitor can drive a glow armlet to work very well, which demonstrates that the device has great potential to work as a power source in real-life applications.

Energy storage characteristics of a new rechargeable solid oxide iron–air battery

Cost effective and large scale energy storage is critical to renewable energy integration and smart-grid energy infrastructure. Rechargeable batteries have great potential to become a class of cost effective technology suited for large scale energy storage. In this paper, we report the energy storage characteristics of a newly developed rechargeable solid oxide iron–air battery. Investigations of the battery’s performance under various current densities and cycle durations show that iron utilization plays a determining role in storage capacity and round-trip efficiency. Further studies of the batterys cycle life reveal a unique charge-cycle originated degradation mechanism that can be interpreted by a combined vapor-phase transport and electrochemical condensation model. Overall, the energy capacity of the new solid oxide iron–air storage battery should be properly balanced with the round-trip efficiency at optimized iron utilization.

A two-step method for preparing Li4Ti5O12–graphene as an anode material for lithium-ion hybrid capacitors

Lithium-ion hybrid capacitors (LICs) are expected to fill the gap between lithium-ion batteries and electrochemical supercapacitors. In this paper, we synthesize Li4Ti5O12–graphene (LTO–G) by a two-step method and use it as the anode material in AC/LTO–G Li-ion hybrid capacitors. The LTO–G composite prepared by the two-step method shows the best electrochemical properties in various ways, and delivers a high specific capacity of 194 mA h g−1 at 0.1C, and 90 mA h g−1 at 28.6C. The AC/LTO–G capacitors can perform well between 1 and 2.5 V, and they deliver a reversible capacity of 80 mA h g−1 at 0.1C. The energy density based on the total active material for these capacitors is 15 W h kg−1 at 4000 W kg−1, and 30 W h kg−1 at 1000 W kg−1. After 10 000 cycles, these capacitors still deliver an energy density higher than 22 W h kg−1 at 1000 W kg−1. The highest energy density based the total mass of the device is 6.6 W h kg−1 and there is still much room for improvement, indicating that the LTO–G composite is a promising candidate anode material for Li-ion hybrid capacitors.

A Ti-V-based bcc phase alloy for use as metal hydride electrode with high discharge capacity.

The electrochemical characteristics of single bcc phase Ti-30V-15Cr-15Mn alloy were investigated. It was demonstrated that the single bcc phase alloy has high electrochemical discharge performance at high temperature. Its discharge capacity is closely related with temperature and discharge current. The first discharge capacities of 580-814 mAh g(-1) of the alloy powder were obtained at discharge current of 45-10 mA g(-1) in 6 M KOH solution at 353 K. Although the electrochemical cycle life of the alloy is unsatisfactory at present, it opens up prospects for developing a new hydrogen storage alloy with high hydrogen capacity for use as high performance metal hydride electrodes in rechargeable Ni-MH battery.

A new solid oxide molybdenum–air redox battery

A new type of rechargeable molybdenum–air battery based on the technologies of reversible solid oxide fuel cells and chemical looping is reported in this study. The reversible solid oxide fuel cell serves as the electrical unit to realize the charging and discharging cycles while a pair of Mo/MoO2 redox couple integrated with the reversible solid oxide fuel cell stores electrical energy via an H2–H2O oxygen shuttle. The specific charge of the new battery reaches 1117 A h per kg-Mo at 550 °C, which is 45% higher than the non-rechargeable Mo–air battery. The corresponding discharge specific energy is 974 W h per kg-Mo with a round trip efficiency of 61.7%. In addition, the new Mo–air redox battery also exhibits 13.9% and 24.5% higher charge density (A h L−1) and energy density (W h L−1) than the state-of-the-art solid oxide Fe–air redox battery, respectively.

A novel intermediate-temperature all ceramic iron–air redox battery: the effect of current density and cycle duration

We here report the energy storage characteristics of a new all ceramic iron–air redox battery comprising of a reversible solid oxide fuel cell as the charger/discharger and a Fe–FeOx redox couple as the chemical storage bed. The effects of current density and cycle duration on specific energy and round trip efficiency of the new battery have been systematically studied at 650 °C and 550 °C. The results explicitly show that current density is the most influential variable on the performance, signifying the importance of improving electrochemical performance of the reversible solid oxide fuel cell.

Electrochemical performance of Ti0.4V0.3Mn0.15Cr0.15 alloy surface-modified by ballmilling with LaNi3.55Co0.75Mn0.4Al0.3

The characteristics and mechanisms of enhanced electrochemical properties of Ti 0.4 V 0.3 Mn 0.15 Cr 0.15 + x wt % LaNi 3.55 Co 0.75 Mn 0.4 Al 0.3 composite alloys produced by ballmilling were investigated. Surface modification of Ti 0.4 V 0.3 Mn 0.15 Cr 0.15 alloy by ballmilling with LaNi 3.55 Co 0.75 Mn 0.4 Al 0.3 can significantly improve its electrochemical properties. After 30 min of ballmilling, the discharge capacity increases from 205 mAh g -1 for the plain Ti 0.4 V 0.3 Mn 0.15 Cr 0.15 alloy to 420 mAh g -1 for the Ti 0.4 V 0.3 Mn 0.15 Cr 0.15 + 50 wt % LaNi 3.55 Co 0.75 Mn 0.4 Al 0.3 composite alloy. The improvement of cycle life and high-rate dischargeability of the composite alloy may be attributed to good catalytic ability of the LaNi 3.55 Co 0.75 Mn 0.4 Al 0.3 alloy, which not only provides the alloy with electrochemical activity, but also hinders the formation of oxide film and decreases the dissolution of V into KOH electrolyte.

Synergism of nano ZnO for improvement of hydrogen absorption performance of Ti-V-based alloys

Effect of nano ZnO on the hydrogen absorption performance of Ti-30V-15Mn-15Cr alloy was investigated. It was found that a small amount addition of nano ZnO (3 wt%) drastically improves the hydrogen absorption property of this alloy powder. The modification enables the air-exposed powder to absorb hydrogen quickly without activation. It could be attributed to the synergetic action of nano ZnO, which might expedite the dissociation of hydrogen on the oxidized alloy surface and play as entrance for hydrogen into the bulk alloy. The fact that nano ZnO addition improves the hydrogen absorption performance of Ti-30V-15Mn-15Cr alloy pioneers a new way for developing highly active Ti-V-based body-centered-cubic phase alloys.

Measurement on a Sample of Fuel Cell at High Temperature

Solid Oxide Fuel Cells (SOFCs) can be designed in either a planar or non-planar configuration. Since modern fuel cell assemblies are constructed from several different materials and operate at relatively high temperatures, 550–750 °C, the experimental characterization of the in-situ response is of interest for model validation. This study employs stereo-vision and stereo-DIC to measure both full-field surface strains and the out-of-plane displacement on the surface of a heterogeneous cell during operation.