哈工大张乃庆AFM：拓扑绝缘材料加速锂硫电池正极反应

【研究背景】

锂硫电池具有高的理论能量密度，是最有希望应用的下一代能量存储体系之一。然而，多硫化锂的溶解和穿梭以及缓慢的转化动力学限制了锂硫电池的实际应用。在正极中引入催化剂是加速硫物种转化反应的有效手段，理想的催化剂应能够与表面吸附的硫物种发生快速的电子交换。

【工作介绍】

近日，哈尔滨工业大学的张乃庆教授团队将Bi₂Te₃这一拓扑绝缘材料作为催化剂引入锂硫电池。研究发现，Bi₂Te₃能够通过发生Bi-S和Te-Li相互作用有效锚定多硫化锂。而且，Bi₂Te₃对硫还原反应和硫化锂氧化反应都具有本征催化作用。更重要的是，Bi₂Te₃能够与吸附的硫物种建立有效的电荷转移通道，有利于发生快速的电子交换。因而锂硫电池展现出优异的电化学性能。相关工作以“Accelerating Sulfur Redox Reactions by Topological Insulator Bi₂Te₃for High-Performance Li-S Batteries”为标题发表在Advanced Functional Materials期刊上。

【文章图表】

图1 Bi₂Te₃的形貌表征

Figure 1. a-c) SEM, d,e) TEM, f) HRTEM, g) HAADF-STEM images, and h-j) elemental mappings of Bi₂Te₃.

图2 Bi₂Te₃的结构表征

Figure 2. a) HRTEM image (inset is the corresponding FFT pattern), b) IFFT pattern, c) lattice spacing profiles, d) XRD pattern, e) EDS spectrum, and f) Raman spectrum of Bi₂Te₃.

图3 Bi₂Te₃的催化性能测试

Figure 3. CV curves of symmetric cells with a) Bi₂Te₃and b) graphene electrodes with Li₂S₆in the electrolyte; c) CV curves and d-f) Tafel plots of the Bi₂Te₃/S and Graphene/S cathodes.

图4 Bi₂Te₃/S的电化学性能测试

Figure 4. a) Rate performance, b) galvanostatic charge-discharge profiles, c) statistics of the plateau capacity ratio and charge potential barrier of the Bi₂Te₃/S and Graphene/S cathodes; d) long-term cycling performance of the Bi₂Te₃/S cathode.

图5 第一性原理计算

Figure 5. a) Adsorption energies between catalysts and sulfur species; b) adsorption energies between catalysts and solvated Li⁺; DOS of c) the Bi₂Te₃-Li₂S₄and f) the Graphene-Li₂S₄adsorption systems (the Fermi energy is set to zero); d) top-view and e) side-view of band-decomposed charge density distribution of the Bi₂Te₃-Li₂S₄adsorption system near Fermi energy (±1 eV); g) top-view and h) side-view of band-decomposed charge density distribution of the Graphene-Li₂S₄adsorption system. The Li, S, C, Bi, and Te atoms are denoted by green, yellow, chocolate, magenta, and brass balls, respectively.

图6 第一性原理计算

Figure 6. a) Energy profiles for the reduction of sulfur species on Bi₂Te₃and graphene; b) decomposition energy barriers of Li₂S on Bi₂Te₃and graphene; c) summary of Gibbs free energy changes and decomposition energy barriers with those of graphene set as the base point; d) schematic diagram of the rapid redox kinetics of sulfur species on Bi₂Te₃.

Song, X., Tian, D., Qiu, Y., Sun, X., Jiang, B., Zhao, C., Zhang, Y., Fan, L., Zhang, N., Accelerating Sulfur Redox Reactions by Topological Insulator Bi₂Te₃for High-Performance Li-S Batteries. Adv. Funct. Mater. 2021, 2109413. https://doi.org/10.1002/adfm.202109413