双电层形成过程中的可逆产热敏感地依赖于电解质及其储层
Reversible heat production during electric double layer buildup depends sensitively on the electrolyte and its reservoir
摘要：
用于能量存储和转换的若干现代技术基于通过相邻电解质中的离子屏蔽多孔电极表面上的电荷。这种所谓的双电层（EDL）表现出与电解质温度的复杂相互作用，这是最近几项研究的重点。在其中之一中，Janssen等人[Phys. Rev. Lett. 119，166002（2017）]通过实验确定了在等温充电过程中流入超级电容器的可逆热的比率$\mathcal{Q}_\text{rev}/W_\text{el}$和施加在其中的电功。为了使这些数据合理化，在这里，我们使用密度泛函理论（DFT）以及分子动力学模拟等理论方法在不同的EDL模型中确定$\mathcal{Q}_\text{rev}/W_\text{el}$。主要应用受限原始模型，我们发现定量支持Janssen等人的推测，即空间离子相互作用是比例$\mathcal{Q}_\text{rev}/W_\text{el}$的关键。在这里，我们确定了某些DFT泛函的熵贡献，它允许直接访问可逆热。我们进一步展示了如何$\mathcal{Q}_\text{rev}/W_\text{el}$的变化时，在不同的热力学合奏和过程计算。我们表明，Janssen等人的实验。最好的解释在固定的体积密度，或在一个“半正则”系统的充电过程。最后，我们发现，$\mathcal{Q}_\text{rev}/W_\text{el}$显着依赖于参数，如孔和离子的大小，盐浓度，和价的猫和阴离子的电解质。我们的研究结果可以指导进一步的产热测量，并可以应用于神经传导等研究，其中可逆热是一个关键因素。
英文摘要：
Several modern technologies for energy storage and conversion are based on the screening of electric charge on the surface of porous electrodes by ions in an adjacent electrolyte. This so-called electric double layer (EDL) exhibits an intricate interplay with the electrolyte's temperature that was the focus of several recent studies. In one of them, Janssen et al. [Phys. Rev. Lett. 119, 166002 (2017)] experimentally determined the ratio $\mathcal{Q}_\text{rev}/W_\text{el}$ of reversible eat flowing into a supercapacitor during an isothermal charging process and the electric work applied therein. To rationalize that data, here, we determine $\mathcal{Q}_\text{rev}/W_\text{el}$ within different models of the EDL using theoretical approaches like density functional theory (DFT) as well as molecular dynamics simulations. Applying mainly the restricted primitive model, we find quantitative support for a speculation of Janssen et al. that steric ion interactions are key to the ratio $\mathcal{Q}_\text{rev}/W_\text{el}$. Here, we identified the entropic contribution of certain DFT functionals, which grants direct access to the reversible heat. We further demonstrate how $\mathcal{Q}_\text{rev}/W_\text{el}$ changes when calculated in different thermodynamic ensembles and processes. We show that the experiments of Janssen et al. are explained best by a charging process at fixed bulk density, or in a "semi-canonical" system. Finally, we find that $\mathcal{Q}_\text{rev}/W_\text{el}$ significantly depends on parameters as pore and ion size, salt concentration, and valencies of the cat- and anions of the electrolyte. Our findings can guide further heat production measurements and can be applied in studies on, for instance, nervous conduction, where reversible heat is a key element.
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