Interpretation of the Na + Ionic Conductivity in Na 4 P 2 S 7–x O x Mixed Oxy-Sulfide Glasses: Effects of Oxygen Doping
Interpretation of the Na + Ionic Conductivity in Na 4 P 2 S 7–x O x Mixed Oxy-Sulfide Glasses: Effects of Oxygen Doping
复制标题
Na 4 P 2 S 7âx O x 混合硫氧化物玻璃中 Na 离子电导率的解释：氧掺杂的影响
DOI：
10.1021/acs.chemmater.2c01934
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发表时间：
2022
影响因子：
8.6
通讯作者：
Martin, Steve W.
中科院分区：
文献类型：
--
作者：
Kmiec, Steven;Olson, Madison;Kenney, Matthew;Martin, Steve W.
世界各地的许多研究人员正在努力使全固态电池的众多优势，特别是安全性和能量密度成为市场现实。主要挑战之一是开发新型固体电解质，这些电解质具有高导电性，但在高电压和低电压下化学和电化学稳定。近年来，人们开发了新型的混合硫氧化物（MOS）玻璃态固体电解质（GSE），以改善纯硫化物GSE的化学和电化学不稳定性。氧的加入显著提高了纯硫化物GSE的化学和电化学稳定性，但降低了离子电导率。为了更好地理解MOS GSE中氧离子电导率降低的确切原因，本研究采用熔体淬冷技术制备了新型MOS Na 4P 2S 7-xOx，0 ≤x≤ 5 GSE（NPSO GSE）。正如所预期的，随着氧的掺入，钠离子电导率通常降低，并且平均活化能通常增加。然而，如在其他MOS GSE中已经发现的，在氧的稀释极限下，这里对于0 <x< 1.5的值，电导率增加并且活化能降低，分别在电导率和活化能中产生局部最大值和最小值。该行为与在该相同组成范围内GSE的摩尔自由体积中的相应局部最大值相关联。Christensen-Martin-Anderson-Stuart（CMAS）模型首次用于MOS GSE，以深入了解电导率和活化能的共价（体积应变）和离子（库仑）部分如何受到这些MOS反相玻璃中硫和氧阴离子混合的影响。为了准确地模拟这些玻璃中的体积应变能，有必要仔细分析Na+阳离子的配位环境的变化。在富含硫化物的玻璃中，钠主要以四面体（T）配位（NaS 4）存在，而在富含氧化物的玻璃中，钠以三角双锥配位（NaO 5）存在。在没有可调参数的情况下，CMS计算的活化能与测量的实验值在10%以内。与所有先前研究的GSE类似，发现库仑力似乎主导活化能，并且该行为表明这些玻璃可以被认为是“弱”电解质，其中移动的Na+离子大部分是通过“晃动和跳跃”机制传导的离子结合电荷，其中跳跃事件之间的驻留时间与移动的阳离子跳跃事件时间相比长。电导激活能ΔEact= ΔEB+ ΔES（Δ ES为体积应变部分）中库仑结合能部分ΔEB的增加是导致NPSO GSE的Δ Eact总体增加和Na+电导率总体下降的根本原因。
Many researchers around the world are working to make the numerous advantages, in particular, safety and energy density, of all-solid-state-batteries a marketplace reality. One of the main challenges is to develop new solid electrolytes that are highly conducting yet chemically and electrochemically stable at high and low voltages. New mixed oxy-sulfide (MOS) glassy solid electrolytes (GSEs) have been developed recently in this effort to improve upon pure sulfide GSEs which are notoriously chemically and electrochemically unstable. The addition of oxygen dramatically improves the chemical and electrochemical stability of pure sulfide GSEs, but decreases the ionic conductivity. In this study, new MOS Na4P2S7–xOx, 0 ≤x≤ 5 GSEs (NPSO GSEs) were prepared by the melt quench technique to develop a better understanding of the exact causes for the decrease in the ionic conductivity with added oxygen in MOS GSEs. As expected, with the incorporation of oxygen, the sodium ion conductivity generally decreases, and the average activation energy generally increases. However, as has been found in other MOS GSEs, at the dilute limit of oxygen, here for values of 0 <x< 1.5, the conductivity increases and the activation energy decreases, producing a local maximum and minimum in the conductivity and activation energy, respectively. This behavior is associated with a corresponding local maximum in the molar free volume of the GSE in this same compositional range. The Christensen–Martin–Anderson–Stuart (CMAS) model was used for the first time on MOS GSEs to provide insights into how the covalent (volumetric strain) and ionic (Coulombic) parts of the conductivity and activation energy are affected by the mixing of sulfur and oxygen anions in these MOS invert glasses. To accurately model the volumetric strain energy in these glasses, it was necessary to carefully analyze the changing coordination environments of the Na+cations. In sulfide-rich glasses, sodium is predominantly in tetrahedral (T) coordination (NaS4), while in oxide-rich glasses, sodium is found in the trigonal bipyramidal coordination (NaO5). The CMAS-calculated activation energies agree to within 10% of the measured experimental values with no adjustable parameters. Similar to all previously studied GSEs, it was found that the Coulombic forces appear to dominate the activation energy, and this behavior suggests that these glasses can be considered “weak” electrolytes where the mobile Na+ions are for the most part ionically bound charges conducting by a “rattle and jump” mechanism where the resident time between jump events is long compared to the mobile cation jump event time. The increase in the Coulombic binding energy part, ΔEB, of the conductivity activation energy, ΔEact= ΔEB+ ΔES, where ΔESis the volumetric strain part, is found to be the root cause for the overall increase in ΔEactand the concomitant overall decrease in the Na+conductivity of the NPSO GSEs.