Yang Seunga, Lee SangYup, Nogales Paul Maldonado, Kim Yangsoo, Jeong Soon-Ki
Department of Future Convergence Technology, Graduate School, Soonchunhyang University, Soonchunhyang-ro 22-gil, Sinchang-myeon, Asan-si 31538, Chungcheongnam-do, Republic of Korea.
Korea Basic Science Institute, Jeonju Center, Jeonju-si 54907, Jeollabuk-do, Republic of Korea.
Int J Mol Sci. 2025 Aug 19;26(16):8005. doi: 10.3390/ijms26168005.
Tungsten disulfide (WS), a two-dimensional layered material with favorable electronic properties, has been explored as a promising negative electrode material for calcium-ion batteries (CIBs). Despite its use in monovalent systems, its performance in divalent Ca intercalation remains poorly understood. Herein, a combined theoretical and experimental framework is used to elucidate the electronic mechanisms underlying Ca intercalation. Theoretical insights were obtained through density functional theory calculations, incorporating periodic simulations using the Vienna Ab initio Simulation Package, and localized orbital-level analysis using the discrete variational Xα method. These approaches reveal that Ca insertion induces significant interlayer expansion, lowers diffusion barriers, and narrows the bandgap compared to Li. Orbital analysis revealed strengthened W-S bonding and diminished antibonding interactions, which may contribute to the improved structural resilience. Electrochemical tests validated these predictions; the CaWS electrode delivered an initial discharge capacity of 208 mAh·g at 0.1C, with 61% retention after 50 cycles at 1C. The voltage profile exhibits a distinct plateau near 0.7 V, consistent with a two-phase-like intercalation mechanism, contrasting with the gradual slope observed for Li. These findings suggest that Ca intercalation facilitates both rapid ion transport and enhanced structural robustness. This study offers mechanistic insights into multivalent-ion storage and supports the design of high-performance CIB electrodes.
二硫化钨（WS）是一种具有良好电子特性的二维层状材料，已被探索作为一种有前景的钙离子电池（CIBs）负极材料。尽管它在一价体系中有所应用，但其在二价钙嵌入方面的性能仍知之甚少。在此，采用理论与实验相结合的框架来阐明钙嵌入背后的电子机制。通过密度泛函理论计算获得理论见解，其中包括使用维也纳从头算模拟包进行周期性模拟，以及使用离散变分Xα方法进行局域轨道水平分析。这些方法表明，与锂相比，钙的插入会引起显著的层间膨胀，降低扩散势垒，并使带隙变窄。轨道分析表明W - S键增强且反键相互作用减弱，这可能有助于提高结构弹性。电化学测试验证了这些预测；CaWS电极在0.1C时的初始放电容量为208 mAh·g，在1C下循环50次后保留率为61%。电压曲线在0.7 V附近呈现出明显的平台，这与两相状嵌入机制一致，与锂嵌入时观察到 的逐渐斜率形成对比。这些发现表明钙嵌入既促进了快速离子传输又增强了结构稳健性。本研究为多价离子存储提供了机理见解，并支持高性能CIB电极的设计。
