Li14Zn(GeO4)4基Li+/H+共传导中低温电解质-中国材料进展

文章信息/Info

Title:: Theoretical Calculation of an IntermediateTemperature H+/Li+ Conducting Electrolyte: Li14Zn(GeO4)4

Author(s):: LI Yining; WEI Tao; School of Material Science and Engineering, University of Jinan

Keywords:: SOFCs; low and intermediate temperature; lithium ion conduct; proton conduct; mechanism of Li+/H+ exchange

摘要:: 固体氧化物燃料电池技术已历经近150年的发展史，但目前仍在努力步入市场化进程中。过高的工作温度\[氧化钇稳定的氧化锆（YSZ）基>800 ℃\]是限制其商业化推广的主要原因，而研发低温电解质是降低其工作温度的关键步骤。本研究通过第一性原理计算，报道了一种中低温（200~600 ℃）基质子传输电解质 Li14Zn(GeO4)4（LZG），建立了质子在LZG内传输分子动力学模型。通过理论模拟，提出LZG为中低温基锂离子/质子混合传导电解质，质子经锂离子/质子交换机制，通过LZG内存在的锂离子空位而引入，并模拟了质子与锂离子在锂离子空位的传导机制。进一步通过计算得出，质子在LZG电解质内部以较高的离子迁移系数通过锂离子空位进行传输，并得到不同位点锂离子与质子迁移系数随温度变化曲线。最后给出不同离子在LZG电解质内迁移的电子态密度。本研究为新型电解质的研发提供了理论指导，有益于将固体氧化物燃料电池（SOFCs）工作温度从中高温区（>600 ℃）向中低温区（200~600 ℃）推进。

Abstract:: SOFCs can convert chemical energy directly to electric energy efficiently with minimum emissions. Unfortunately, the existing SOFC technologies are still too expensive for commercial use due to the high operating temperature. A critical step toward low-cost SOFC technologies is to develop materials with high conductivity of oxygen ions or protons (O2- or H+) at lower temperatures. Li+ in some lithium ion conductors can be replaced by H+ through a reversible ion-exchange (even just in water solution), implying that it is possible to turn a lithium-ion conductor to a proton conductor by H+/Li+ exchange. Here we demonstrate that Li14Zn(GeO4)4 (LZG) exhibits not only lithium ion (for LIBs) but also protons (for SOFCs). In order to elucidate the mechanism of Li+ and H+ conduction in LSZG electrolyte, abinitio molecular dynamics computation was used to investigate Li+ and H+ transport trajectories，the diffusivity and the electronic density of states (e-DOS) for each type of ions in Li14Zn(GeO4)4. And in turn, the obtained calculating data can guide future design for 200~600 ℃ based proton conductor.