Stamminger Andreas R, Ziebarth Benedikt, Mrovec Matous, Hammerschmidt Thomas, Drautz Ralf
Robert Bosch GmbH, Corporate Research 71272 Renningen Germany
Ruhr-Universität Bochum, Interdisciplinary Centre for Advanced Materials Simulation Universitätsstraβe 150 44801 Bochum Germany.
RSC Adv. 2020 Mar 13;10(18):10715-10722. doi: 10.1039/d0ra00932f. eCollection 2020 Mar 11.
The synthesis of Li superionic conductor LiPS may be accompanied by the formation of a detrimental LiPS phase due to a high mixing sensitivity of precursor materials. This phase exhibits a poor ionic conductivity whose origins are not fully understood. Recently Dietrich investigated the energetics of Li ion migration in LiPS with nudged elastic band (NEB) calculations. The observed large migration barrier of 0.51 eV for purely interstitial diffusion leads to an interpretation of the low ionic conductivity by kinetic limitations. Based on molecular dynamics simulations (AIMD) we propose a new and energetically much more favorable diffusion path available to interstitial Li ion charge carriers that has not been considered so far. It consists of a concerted process in which a second lithium atom is pushed out from its equilibrium lattice position by the diffusing lithium ion. A detailed analysis with NEB calculations shows that the energy barrier for this concerted diffusion is only 0.08 eV, an order of magnitude lower than the previously reported value for purely interstitial diffusion. Therefore, the observed low ionic conductivity of LiPS is likely not originating from kinetic limitations due to high diffusion barriers but rather from thermodynamic reasons associated with a low concentration of free charge carriers. We therefore expect that increasing the charge carrier concentration by doping is a viable design route to optimize the ionic conductivity of this material.
由于前驱体材料具有较高的混合敏感性，锂超离子导体LiPS的合成可能伴随着有害LiPS相的形成。该相表现出较差的离子电导率，其起源尚未完全明了。最近，迪特里希用推挤弹性带（NEB）计算研究了LiPS中锂离子迁移的能量学。对于纯间隙扩散，观察到的0.51 eV的大迁移势垒导致通过动力学限制来解释低离子电导率。基于分子动力学模拟（AIMD），我们提出了一种新的、能量上更有利的间隙锂离子载流子可用扩散路径，该路径迄今尚未被考虑。它由一个协同过程组成，其中扩散的锂离子将第二个锂原子从其平衡晶格位置推出。用NEB计算进行的详细分析表明，这种协同扩散的能垒仅为0.08 eV，比先前报道的纯间隙扩散值低一个数量级。因此，观察到的LiPS低离子电导率可能并非源于高扩散势垒导致的动力学限制，而是源于与自由电荷载流子浓度低相关的热力学原因。因此，我们预计通过掺杂增加电荷载流子浓度是优化该材料离子电导率的可行设计途径。
