Transition metal dichalcogenides (TMDs) have attracted great research interest as potential anode materials for lithium-ion batteries (LIBs), owing to their remarkable specific capacity and stable cycling performance. However, challenges, such as limited active sites, poor cyclic performance, and low-rate capability, hinder their broader application. In this study, Co0.1-NbSSe was synthesized by using chemical vapor transport and hydrothermal methods. The Co0.1-NbSSe electrodes show the best performance compared with NbS2, NbSe2, and NbSSe electrodes. Significantly, the Co0.1-NbSSe electrode has a specific capacity of approximately 1037 mA h g–1 at 1 A g–1 after 1000 cycles, indicating its large capacity. At the same time, it has an excellent rate performance of approximately 305 mA h g–1 at 5 A g–1. The improved specific capacity and rate performance are attributed to the enhanced conductivity and additional lithium storage sites. Theoretical and experimental results demonstrate that more defects and reactive sites resulting from doping improve the electrochemical performance. These findings suggest that Co0.1-NbSSe is a good candidate for high-performance LIB anode materials, which offer a pathway to overcome the current challenges in TMD-based electrodes.
Yaqi He,Xinhua Li,Lihua Zhang,Jiawei Xu,Songhua Chen,Zongqing Ma
In this article, a batch of high-performance Sn-doped Nb 3 Al superconductors is prepared through mechanical alloying and subsequent low-temperature sintering. This article comparatively analyzes the superconducting properties, phase structure, and microstructure of Sn-doped Nb 3 Al under different sintering temperatures and sintering times to determine the most suitable sintering process for Sn-doped Nb 3 Al. The results show that the optimum sintering temperature of Sn-doped Nb 3 Al bulks is 800 °C, with an optimal sintering time of 5 h. The T c value of Sn-doped Nb 3 Al bulk obtained under this sintering condition is 14.8 k, and the value of J c is as high as 6.2 × 10 4 A cm −2 (4.2 K, 5 T). The elevated sintering temperature (900 and 1000 °C) results in significant growth of both Nb 3 Al grain size and Nb 2 Al nanoparticles. This reduces the number of effective pinning centers in the superconducting phase of Sn-doped Nb 3 Al, which severely weakens the flux pinning effect. As a result, the J c performance deteriorates gradually as the sintering temperature increases from 800 to 1000 °C. The extended duration of sintering time results in the formation of sintering holes, which significantly disrupt the continuity of the Nb 3 Al superconducting phase matrix and degrade its superconducting properties.
Yaqi He,Xinhua Li,Zhu Qian,ZuPeng Yan,Guizhen Shi,Xia Sun,Zongqing Ma
In this paper, we innovatively introduced Sn and B into the Nb-Al system at the same time and successfully prepared high-performance Nb 3 Al bulks through mechanical alloying and subsequent low-temperature sintering processes. The influence of different doping amounts of B in the Sn-B co-doping on the superconducting properties of Nb 3 Al superconductors was also investigated. It was found that Sn-B co-doping greatly improves the superconducting properties of Nb 3 Al, especially the J c properties, compared with the undoped sample. The optimal doping amount of Sn-B co-doping is finally determined to be 4 at% Sn-2.6 at% B. At this time, the superconducting transition temperature of Nb 3 Al is up to 16.2 K, and the critical current density reaches up to 1.3 × 10 5 A⋅cm −2 (4.2 K, 5 T), which is almost twice higher than that of Sn-doped Nb 3 Al, and one order of magnitude higher than that of general undoped Nb 3 Al. Combined with the phase composition analysis and microstructure observation, we find that with the co-doping of Sn and B, the grain size of Nb 3 Al is refined, and the diffusely distributed Nb 2 Al nanoparticles are introduced, which greatly enhance the magnetic flux pinning effect of Nb 3 Al. Secondly, the intergranular connectivity of Nb 3 Al is significantly improved. The Sn-B co-doped Nb 3 Al superconductors combine the advantages of Sn doping to enhance flux pinning and B doping to improve intergranular connectivity, which synergistically promotes the dramatic improvement of Nb 3 Al superconductivity Nb 3 Al.
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