Klarbring Johan, Walsh Aron
Department of Materials, Imperial College London, Exhibition Road, London SW7 2AZ, U.K.
Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-581 83 Linköping, Sweden.
Chem Mater. 2024 Sep 19;36(19):9406-9413. doi: 10.1021/acs.chemmater.4c00936. eCollection 2024 Oct 8.
Solid-state sodium batteries require effective electrolytes that conduct at room temperature. The NaPnCh (Pn = P, Sb; Ch = S, Se) family has been studied for their high Na ion conductivity. The population of Na vacancies, which mediate ion diffusion in these materials, can be enhanced through aliovalent doping on the pnictogen site. To probe the microscopic role of extrinsic doping and its impact on diffusion and phase stability, we trained a machine learning force field for Na W Sb S based on an equivariant graph neural network. Analysis of large-scale molecular dynamics trajectories shows that an increased Na vacancy population stabilizes the global cubic phase at lower temperatures with enhanced Na ion diffusion and that the explicit role of the substitutional W dopants is limited. In the global cubic phase, we observe large and long-lived deviations of atoms from the averaged symmetry, echoing recent experimental suggestions. Evidence of correlated Na ion diffusion is also presented that underpins the suggested superionic nature of these materials.
固态钠电池需要在室温下具有传导性的有效电解质。NaPnCh（Pn = P、Sb；Ch = S、Se）家族因其高钠离子传导率而受到研究。介导这些材料中离子扩散的钠空位数量可通过在磷族元素位点进行异价掺杂来增加。为了探究外在掺杂的微观作用及其对扩散和相稳定性的影响，我们基于等变图神经网络训练了一种用于NaW SbS的机器学习力场。对大规模分子动力学轨迹的分析表明，增加的钠空位数量在较低温度下稳定了全局立方相，同时增强了钠离子扩散，并且替代型W掺杂剂的明确作用有限。在全局立方相中，我们观察到原子相对于平均对称性存在大且持久的偏差，这与最近的实验结果相符。还给出了相关钠离子扩散的证据，这支持了这些材料所具有的超离子性质。
