Gradient-free thermo-electrochemical energy conversion based on ceramic intercalation materials

尽管技术设施、地热资源和人类自身永久地散发出相当大的热量，但这些热源的温度水平太低，无法使用直接热电转换的普通技术进行经济回收。最近，电化学过程作为现有热电转换技术的可能替代方案引起了人们的强烈关注，因为它们具有更有效和更便宜的潜力。在提出的项目框架内，基于非常有希望的初步测试，研究了一种利用陶瓷插层化合物进行热电转换的新型电化学电池概念。亚化学计量插入化合物（如基于Li， Na， K）具有相似的电极电位和尽可能高的相反的反应熵被用作阳极和阴极材料。电池温度的变化（没有梯度！）根据阳极和阴极反应的各自熵诱导出电池电压。电池实际上是通过温度变化充电的（类似于热释电材料）。在放电（发电）过程中，插层化合物的主晶格分别被氧化和还原，同时碱金属离子被萃取和插入，直到电池电压趋于0 V。这个过程是完全可逆的。极性反转并恢复到初始温度后，电池可再次放电，恢复初始状态。与现有的余热利用和能量收集技术相比，所描述的工作原理可能具有显著的优势。然而，考虑到它的新颖性和缺乏基础研究和实验数据，这种说法目前还不能得到证实。基于非常有前途的初步调查，申请人努力对使用典型陶瓷插入材料的热电化学热到电转换有一个基本的了解。这包括关于工作原理的机理研究，以及所使用的插层化合物的性质与所产生的热电化学电池之间的基本关系。最后，基于实验的见解，将建立一个描述电化学热到电转换的模型，该模型可能用于确定合适的材料和设计性能。

Although technical facilities, geothermal sources and humans themselves permanently emit heat of considerable power, the temperature level of these heat sources is too low for economic recovery using common technologies for direct heat to electricity conversion. Recently, electrochemical processes attracted intense attention as a possible alternative to existing technologies for heat to electricity conversion, since they have the potential to be much more effective and less expensive. In the framework of the proposed project and based on very promising preliminary tests, a novel electrochemical cell-concept for heat to electricity conversion using ceramic intercalation compounds is investigated. Substoichiometric intercalation compounds (e.g. based on Li, Na, K) with similar electrode potentials and as high as possible opposite reaction entropy are used as the anode and cathode material. A change in the cells’ temperature (no gradient!) induces a cell voltage according to the respective entropies of the anode and cathode reaction. The cell is literally charged by the temperature change (analogously to a pyroelectric material). During discharging (power generation), the host lattices of the intercalation compounds are oxidized and reduced, respectively, accompanied with the extraction and insertion of the alkali metal ion, until the cell voltage tends towards 0 V. This process is completely reversible. After polarity reversal and return to the initial temperature, the cell can be discharged again and the initial state is restored. The described working principle might have significant benefits compared to existing technologies for waste heat utilization and energy harvesting. However, in light of its novelty and the absence of basic research and experimental data, this statement cannot be confirmed at the moment. Based on very promising preliminary investigations, the applicants strive for a fundamental understanding of the thermo-electrochemical heat to electricity conversion using typical ceramic intercalation materials. This includes mechanistic studies regarding the working principle as well as basic relationships between the properties of the intercalation compounds used and the resulting thermo-electrochemical cells. Finally, based on the experimental insights, a model will be developed describing the thermo-electrochemical heat to electricity conversion, which might be used prospectively for the identification of suitable material and design properties.