物理化学学报 >> 2023, Vol. 39 >> Issue (8): 2212037.doi: 10.3866/PKU.WHXB202212037

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水系锌离子电池嵌入负极材料TiX2 (X = S, Se)的储锌机制

唐生龙1, 王春蕾1, 蒲想俊2, 顾向奎1, 陈重学1,*()   

  1. 1 武汉大学动力与机械学院, 水力机械过渡过程教育部重点实验室, 武汉 430072
    2 香港理工大学工业与系统工程系, 香港 999077
  • 收稿日期:2022-12-23 录用日期:2023-02-07 发布日期:2023-03-23
  • 通讯作者: 陈重学 E-mail:zxchen_pmc@whu.edu.cn
  • 基金资助:
    国家自然科学基金(U22A20438);国家自然科学基金(21875171);中央高校基本科研业务费专项资助项目

Unravelling Zn2+ Intercalation Mechanism in TiX2 (X = S, Se) Anodes for Aqueous Zn-Ion Batteries

Shenglong Tang1, Chunlei Wang1, Xiangjun Pu2, Xiangkui Gu1, Zhongxue Chen1,*()   

  1. 1 Key Laboratory of Hydraulic Machinery Transients, Ministry of Education, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China
    2 Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hong Kong 999077, China
  • Received:2022-12-23 Accepted:2023-02-07 Published:2023-03-23
  • Contact: Zhongxue Chen E-mail:zxchen_pmc@whu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(U22A20438);the National Natural Science Foundation of China(21875171);the Fundamental Research Funds for the Central Universities

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摘要：

水系锌离子电池(ZIBs)以其低成本、高安全性和环境友好的优点受到了研究者的广泛关注，成为大规模电化学储能系统的理想选择之一。然而锌金属负极在应用时面临着锌枝晶生长、腐蚀反应和副反应等难以克服的障碍，严重制约了水系锌离子电池的发展。探索可替代锌金属的储锌负极是应对上述问题的有效策略，因此研究者围绕过渡金属氧化物、硫化物和导电聚合物开展了深入研究。以TiX2 (X = S, Se)为代表的二维过渡金属硫族化合物(TMDs)具有较大的层间距和快速的离子传输通道，可作为锌离子电池的负极，但其储锌反应机制尚未得到完整的揭示。在本文中，我们使用密度泛函理论(DFT)计算方法系统地研究锌离子在TiX2中的嵌入反应。首先我们采用群论去描述嵌锌TiX2的稳定层间构型的特点，定义了一个依赖于超胞并且只涉及平移旋转两种对称操作的群，其子群可以用来描述层间构型的对称性，而且用来描述最稳定构型的子群总是倾向于有最大的阶数。基于该计算得到的一系列对应于不同放电深度的TiX2的稳定结构，我们发现TiS2和TiSe2两种材料在锌嵌入/脱出过程中的开路电压(OCV)均低于0.5 V。态密度(DOS)的计算结果表明TiX2具有很好的电子导电性，而分波态密度(PDOS)的结果显示随着锌的嵌入闭壳层的Ti4+还原成开壳层的Ti3+，并且伴随着Zn―X键的生成。Bader电荷分析的结果表明随着X的嵌入，X相比Ti得到了更多的负电荷，意味着X也参与了TiX2的氧化还原过程。爬坡弹性带方法(CINEB)计算的结果证实了Zn2+在TiX2中具有较低的扩散能垒(对于TiS2是0.333 eV，对于TiSe2是0.338 eV)。本文的研究结果不仅从本质上证明了TiX2适合作为锌离子电池的嵌锌负极材料，而且为其他高性能TMDs电池材料的DFT研究提供了新的见解。

关键词: 锌离子电池, TiX2负极, 第一性原理计算, 群论

Abstract:

In recent years, increased attention has been paid to aqueous Zn-ion batteries (ZIBs) owing to their low cost, inherent safety, and environmental benignity, which enable them to become promising electrochemical energy storage systems for grid-scale applications. However, some critical issues in zinc metal anode, like zinc dendrites growth, corrosion, and side reactions, act as obstacles to developing aqueous ZIBs. Exploring zinc-storage anodes to replace zinc-metal anodes is proposed as an effective strategy to promote the practical application of ZIBs. Therefore, several transition metal oxides, sulfides, and conductive polymers have been intensively studied as zinc-metal-free anodes. Two-dimensional metal dichalcogenides (TMDs), especially TiX2 (X = S, Se), are the most appealing candidates because of their sizeable interlayer space and facile 2D ion-transport channels. However, the reaction mechanism of these TiX2 in ZIBs still needs fundamental study. In this work, density functional theory (DFT) calculations are performed to investigate the behavior of zinc intercalation reaction in TiX2 systematically. First, the most stable interlayer configurations of zinc-intercalated TiX2 are characterized by group theory. We define a supercell-dependent group that only involves translation and rotation operation and find that the subgroup of the group that describes the symmetry of the most stable interlayer configurations possesses the highest order. So, the most stable configuration can be fast screened out among thousands of candidates. Calculations based on a series of those stable configurations at different discharge depths reveal the low open circuit voltage (OCV) of < 0.5 V for both ZnxTiS2 and ZnxTiSe2. The density of states (DOS) result suggests the good electronic conductivity of TiX2, and the partial density of states (PDOS) result indicates the closed-shell Ti(IV) is reduced to open-shell Ti(III), and the formation of Zn―X bonds as zinc ions intercalate into the interlayer of TiX2. Interestingly, Bader charge analysis demonstrates that X anions also participate in the redox process during charge and discharge because X gains more negative charge than Ti as zinc intercalates into TiX2. The climbing image nudged elastic band (CINEB) calculations reveal the low zinc ion diffusion barriers (0.333 and 0.338 eV for TiS2 and TiSe2, respectively). This study proves that TiX2 is suitable as zinc intercalating anode materials for ZIBs and provides new insights into the DFT investigation of other TMDs as high-performance battery materials.

Key words: Zn-ion battery, TiX2 anode, First-principle calculation, Group theory