Effect of boron content on the electrochemical properties of layered Lix(ByC1-y)2 anodes with 5-, 6-, and 8-membered-ring structure

• Published in: Computational materials science Vol. 231; p. 112595
• Main Authors: Peng, Fanglin, Zheng, Feng, Fang, Yimei, Lü, Tie-Yu, Cao, Xinrui, Zhu, Zi-Zhong, Wu, Shunqing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05-01-2024
• ISSN: 0927-0256; 1879-0801
• DOI: 10.1016/j.commatsci.2023.112595

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Using the crystal structure prediction combined with element substitution, several new layered Lix(ByC1-y)2 structures with 5-, 6-, and 8-membered BC/C rings are proposed. Phonon calculations and ab initio molecular dynamics simulations confirm that they are all dynamically and thermodynamically stable. To investigate the effect of boron content on electrochemical properties in these layered Lix(ByC1-y)2 (y = 0, 0.1, 0.2, 0.3, and 0.4) anode materials, we study their theoretical voltages, capacities, and Li diffusion mechanism by the first-principles calculations. Our calculated results show that high boron content structures have high theoretical capacities within the 0–2 V potential window. Li0.8(B0.3C0.7)2 has the highest capacity among them, with a capacity of 557 mAh/g, which is about 1.5 times higher than that of graphite (372 mAh/g). While they also have high average voltages, which is detrimental to the open circuit voltage of cells. Moreover, calculated ionic diffusions also show that boron carbon structures have higher activation barriers (>0.48 eV) than that of pure carbon (∼0.36 eV), indicating a poorer Li diffusion. However, the analysis of electronic properties reveals that these 5-, 6-, and 8-membered-ring Lix(ByC1-y)2 are all metallic, which suggests they may all have good electronic conductivity. Their calculated volume changes are all less than 6.73 %, indicating they will have excellent structural stability during the charge/discharge process. Our results broaden the current understanding of non-hexagonal boron carbides and provide guidelines for the future design of new boron carbides as anode materials.