Shaojun Shi,Panye Jin,Zhixiong Huang,Jialei Kou,Hongmei Ji,Wenyu Yin,Xiaoyan Tang,Han Mao
With the development of sodium ion battery which is considered as the alternative of lithium ion battery, better performance is required. However, its poor structure stability and rate capability due to the Jahn–Teller distortion of Mn 3+ and poor charge transfer between transition metal and oxygen-ion limit its application. Here, Sm-doped P2-type layered oxide Na 0.67 Li 0.1 Mn 0.62 Fe 0.18 Cu 0.09 Sm 0.01 O 2 with spherical secondary hierarchy was obtained through microwave-assisted method. Pure P2-shaped layered oxide is obtained. And the tiny shift of the diffraction spectrum indicates the effect of doping. The electrochemical performance of the doped oxide improves obviously. Even at a high current density of 1.0A g −1 , the capacity is still as high as 60.3 mAh g −1 , much higher than that of undoped one. The cycle stability is also improved. Electrochemical impedance spectroscopy (EIS) and Distribution of relaxation times (DRT) are taken to further study the mechanism. It reveals that the doped samarium not only serves as the pillar to stable the structure of the layered oxide, but also makes faster charge transfer between transition metal ions and oxide ions due to the Multielectron structure of samarium. Thus, such Sm-doping strategy may offer a solution toward the application bottleneck of layered oxides for sodium-ion batteries.
Enyi Hu,Jun Wang,Muhammad Yousaf,Faze Wang,Bin Zhu,Peter D. Lund
Ceramic fuel cells (CFCs) employing lithium compounds, that is, Ni0.8Co0.15Al0.05LiO2 (NCAL) as symmetrical electrodes demonstrate remarkable ionic conductivity and power density at a temperature range of 400–600 °C. However, the stability issue of this type of CFCs has not been well investigated. In this work, we have demonstrated a commercially available samarium oxide (CSM) via a sodium doping method, that is, Na-doped samarium oxide (NDS) materials as functional electrolytes for robust CFCs. Results disclose that during the fuel cell operation, CSM could in situ-react with LiOH from the NCAL anode to cause cell degradation. Doped sodium ions in NDS could confine the LiOH that forms at the grain boundaries, which can result in several benefits, for example, to make the NDS electrolyte denser to prevent gas leakage, to enhance the CFC performance, and to ensure the CFC stability without the need for high-temperature sintering. The NCAL/NDS/NCAL-based fuel cell delivers a stable open circuit voltage over 1.0 V and maximum power density around 200 mW cm–2 for 144 h at 500 °C. Moreover, the optimized cell gives a stable power density of 140 mW cm–2 for 75 h at 500 °C. This work presents a methodology for developing advanced low-temperature CFCs using commercial samarium oxide as the functional electrolyte.
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