Yamijala Sharma S R K C, Kwon Hyuna, Guo Juchen, Wong Bryan M
ACS Appl Mater Interfaces. 2021 Mar 24;13(11):13114-13122. doi: 10.1021/acsami.0c21716. Epub 2021 Mar 10.
Multivalent batteries, such as magnesium-ion, calcium-ion, and zinc-ion batteries, have attracted significant attention as next-generation electrochemical energy storage devices to complement conventional lithium-ion batteries (LIBs). Among them, calcium-ion batteries (CIBs) are the least explored due to difficult reversible Ca deposition-dissolution. In this work, we examined the stability of four different Ca salts with weakly coordinating anions and three different solvents commonly employed in existing battery technologies to identify suitable candidates for CIBs. By employing Born-Oppenheimer molecular dynamics (BOMD) simulations on salt-Ca and solvent-Ca interfaces, we find that the tetraglyme solvent and carborane salt are promising candidates for CIBs. Due to the strong reducing nature of the calcium surface, the other salts and solvents readily decompose. We explain the microscopic mechanisms of salt/solvent decomposition on the Ca surface using time-dependent projected density of states, time-dependent charge-transfer plots, and climbing-image nudged elastic band calculations. Collectively, this work presents the first mechanistic assessment of the dynamical stability of candidate salts and solvents on a Ca surface using BOMD simulations, and provides a predictive path toward designing stable electrolytes for CIBs.
多价电池，如镁离子电池、钙离子电池和锌离子电池，作为补充传统锂离子电池（LIBs）的下一代电化学储能装置，已引起了广泛关注。其中，钙离子电池（CIBs）由于其钙的可逆沉积-溶解困难，研究最少。在这项工作中，我们研究了四种具有弱配位阴离子的不同钙盐和现有电池技术中常用的三种不同溶剂的稳定性，以确定适合CIBs的候选物。通过对盐-Ca和溶剂-Ca界面进行玻恩-奥本海默分子动力学（BOMD）模拟，我们发现四甘醇二甲醚溶剂和碳硼烷盐是CIBs很有前景的候选物。由于钙表面具有很强的还原性，其他盐和溶剂很容易分解。我们使用含时投影态密度、含时电荷转移图和爬坡图像推挤弹性带计算来解释盐/溶剂在Ca表面分解的微观机制。总的来说，这项工作首次使用BOMD模拟对候选盐和溶剂在Ca表面的动力学稳定性进行了机理评估，并为设计用于CIBs的稳定电解质提供了一条预测途径。
