Rui Zeng

Biomass derived hard carbon used as a high performance anode material for sodium ion batteries

A porous hard carbon material was synthesized by the simple pyrolysis of H3PO4-treated biomass, i.e., pomelo peels, at 700 °C in N2. The as-obtained hard carbon had a 3D connected porous structure and a large specific surface area of 1272 m2 g−1. XPS analysis showed that the carbon material was functionalized by O-containing and P-containing groups. The porous hard carbon was used as an anode for sodium ion batteries and exhibited good cycling stability and rate capability, delivering a capacity of 181 mA h g−1 at 200 mA g−1 after 220 cycles and retaining a capacity of 71 mA h g−1 at 5 A g−1. The sodium storage mechanisms of the porous hard carbon can be explained by Na+ intercalation into the disordered graphene layers, redox reaction of the surface O-containing functional groups and Na+ storage in the nanoscale pores. However, the porous hard carbon demonstrated a low coulombic efficiency of 27%, resulting from the formation of a solid electrolyte interphase film and the side reactions of surface phosphorus groups.

High-performance lithium-selenium battery with Se/microporous carbon composite cathode and carbonate-based electrolyte

Selenium attracts increasing attention as cathode material for rechargeable lithium batteries due to its high conductivity and comparable volumetric capacity with sulfur. Microporous carbon spheres (MiPCS) are synthesized via a hydrothermal-annealing route followed by activation with KOH. The MiPCS are used as matrix for Se loading to form Se/MiPCS composite. Such composite delivers a high specific capacity close to the theoretical value of Se. In carbonate-based electrolyte, the capacity is as high as 733 mAh g−1 at a current density of 50 mA g−1, and 353 mAh g−1 at 5000 mA g−1. At 0.5 C, the capacity retains up to 515 mAh g-1 even after 100 cycles. Such outstanding electrochemical performance of the composite cathode in the carbonate electrolyte can be ascribed to the robust structure of MiPCS and to the “ solid-solid” electrode process.摘要因为硒的高电子电导, 以及和硫相近的体积能量密度, 锂硒电池继锂硫电池之后受到越来越多的关注. 本论文使用蔗糖作为碳源, 通过水热方法合成碳球, 经KOH造孔, 从而得到了具有微孔结构的多孔碳球. 进一步和单质硒进行热复合制备了Se/C复合材料作为锂硒电池的正极材料, 该复合材料在碳酸酯的电解液中表现出高的活性物质利用率、 稳定的循环性能和良好的倍率性能. 其优异的电化学性能主要得益于Se/C复合材料的电子导电能力的改善, 以及硒在碳酸酯电解液中的“固-固”电极过程. 本工作关于碳酸酯电解液和醚类电解液用于锂硒电池的系统研究对今后锂硒电池电解液的选择有一定的参考意义.

Evaluation of Ca3Co2O6 as cathode material for high-performance solid-oxide fuel cell

A cobalt-based thermoelectric compound Ca3Co2O6 (CCO) has been developed as new cathode material with superior performance for intermediate-temperature (IT) solid-oxide fuel cell (SOFC). Systematic evaluation has been carried out. Measurement of thermal expansion coefficient (TEC), thermal-stress (σ) and interfacial shearing stress (τ) with the electrolyte show that CCO matches well with several commonly-used IT electrolytes. Maximum power density as high as 1.47 W cm−2 is attained at 800°C, and an additional thermoelectric voltage of 11.7 mV is detected. The superior electrochemical performance, thermoelectric effect, and comparable thermal and mechanical behaviors with the electrolytes make CCO to be a promising cathode material for SOFC.

Novel double-cathode configuration to improve the cycling stability of lithium–sulfur battery

Unsatisfactory cycling lifespan is a key problem hindering the practical applications of the next-generation lithium–sulfur batteries. Herein, we report a facile method to improve the cycling stability through a novel double-cathode configuration. In addition to the traditional cathode based on sulfur composite confined in mesoporous CMK-3 (denoted as S/CMK-3), an additional cathode based on sulfur composite confined in microporous carbon sphere (denoted as S/MiPCS) is set between the S/CMK-3 cathode and separator, which not only functions as a physical barrier to suppress polysulfides immigrating to the lithium anode but also contributes to the overall capacity with a moderate sulfur loading. The double-cathode cell (denoted as DCC) demonstrates a greatly improved cycling stability. After 50 cycles with deep discharge to 1 V at 0.5C, the DCC shows a capacity retention of 70%, whereas the single S/CMK-3 cathode only retains 28%. Even on replacing S/CMK-3 by pure S, the double cathode containing S/MiPCS still exhibits a remarkable improved cyclability. This impressive enhancement mainly benefits from the stable property of MiPCS and its “blocking and reutilization effect”. It can be visually confirmed that no polysulfides were generated upon the discharge process when sulfur is confined within the microporous carbon.

Thermoelectric solid-oxide fuel cell with Ca2Co2O5 as cathode material

In a solid-oxide fuel cell (SOFC), a thermoelectric material used as the cathode can generate extra electric power from the temperature gradient caused by the cell ohmic energy loss. Such a thermoelectric SOFC is an effective strategy to enhance the efficiency of fuel utilization by consuming waste heat. In this work, Ca2Co2O5 (CCO) has been employed as the cathode material for the thermoelectric SOFC. A conventionally designed SOFC with CCO as cathode exhibits a power density of 522 mW cm−2 at 800 °C in H2 fuel. By fabricating a novel thermoelectric SOFC with a dense CCO elongated cathode, the detected open circuit voltage of the cell increases from 1.1289 V to 1.1384 V, indicative of the existence of an additional thermoelectric voltage of 9.4 mV.