Zhu Qinyu, Liu Yifan, Shepard Lauren B, Bhattacharya Debjyoti, Sinnott Susan B, Reinhart Wesley F, Cooper Valentino R, Kumar Rajeev
Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Materials Sciences and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Chem Mater. 2024 Dec 6;36(24):11934-11946. doi: 10.1021/acs.chemmater.4c02432. eCollection 2024 Dec 24.
Solid polymer electrolytes have yet to achieve the desired ionic conductivity (>1 mS/cm) near room temperature required for many applications. This target implies the need to reduce the effective energy barriers for ion transport in polymer electrolytes to around 20 kJ/mol. In this work, we combine information extracted from existing experimental results with theoretical calculations to provide insights into ion transport in single-ion conductors (SICs) with a focus on lithium ion SICs. Through the analysis of temperature-dependent ionic conductivity data obtained from the literature, we evaluate different methods of extracting energy barriers for lithium transport. The traditional Arrhenius fit to the temperature-dependent ionic conductivity data indicates that the Meyer-Neldel rule holds for SICs. However, the values of the fitting parameters remain unphysical. Our modified approach based on recent work ( , 15, 6051), which incorporates a fixed pre-exponential factor, reveals that the energy barriers exhibit temperature dependence over a wide range of temperatures. Using this approach, we identify anions leading to the energy barriers <30 kJ/mol, which include trifluoromethane sulfonimide (TFSI), fluoromethane sulfonimide (FSI), and boron-based organic anions. In our efforts to design the next generation of anions, which can exhibit the energy barriers <20 kJ/mol, we have performed density functional theory (DFT) based calculations to connect the chemical structures of boron-based anions via the binding energy of cation (lithium)-anion pairs with the experimentally derived effective energy barriers for ion hopping. Not only have we identified a correlation between the binding energy and the energy barriers, but we also propose a strategy to design new boron-based anions by using the correlation. This combined approach involving experiments and theoretical calculations is capable of facilitating the identification of promising new anions, which can exhibit ionic conductivity >1 mS/cm near room temperature, thereby expediting the development of novel superionic single-ion conducting polymer electrolytes.
固态聚合物电解质尚未在许多应用所需的室温附近实现所需的离子电导率（>1 mS/cm）。这一目标意味着需要将聚合物电解质中离子传输的有效能垒降低到约20 kJ/mol。在这项工作中，我们将从现有实验结果中提取的信息与理论计算相结合，以深入了解单离子导体（SIC）中的离子传输，重点是锂离子SIC。通过分析从文献中获得的温度依赖性离子电导率数据，我们评估了提取锂传输能垒的不同方法。对温度依赖性离子电导率数据进行传统的阿仑尼乌斯拟合表明，迈耶-内德尔规则适用于SIC。然而，拟合参数的值仍然不符合实际情况。我们基于近期工作（ ，15，6051）的改进方法，该方法包含一个固定的指前因子，结果表明能垒在很宽的温度范围内呈现出温度依赖性。使用这种方法，我们确定了能垒<30 kJ/mol的阴离子，其中包括三氟甲磺酰亚胺（TFSI）、氟甲磺酰亚胺（FSI）和硼基有机阴离子。在我们设计下一代能垒<20 kJ/mol的阴离子的过程中，我们进行了基于密度泛函理论（DFT）的计算，通过阳离子（锂）-阴离子对的结合能将硼基阴离子的化学结构与实验得出的离子跳跃有效能垒联系起来。我们不仅确定了结合能与能垒之间的相关性，还提出了一种利用该相关性设计新型硼基阴离子的策略。这种结合实验和理论计算的方法能够促进有前景的新阴离子的识别，这些新阴离子在室温附近能够表现出>1 mS/cm的离子电导率，从而加速新型超离子单离子传导聚合物电解质的开发。
