在石榴石固体电解质中达到所需的锂浓度；加工对物理和电化学性能的影响,Chemistry of Materials

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在石榴石固体电解质中达到所需的锂浓度；加工对物理和电化学性能的影响
Chemistry of Materials ( IF 7.2 ) Pub Date : 2022-10-20 , DOI: 10.1021/acs.chemmater.2c01915
Matthew A. Limpert _{1,

2} , Terrill B. Atwater ₁ , Tanner Hamann ₂ , Griffin Luh Godbey ₂ , Gregory T. Hitz ₂ , Dennis Wayne McOwen ₂ , Eric D. Wachsman ₂

Affiliation

锂离子导电石榴石是最有前途的固态电解质之一，可替代锂电池中的液态有机电解质，导致石榴石出版物和商业活动的数量迅速增加。然而，这些出版物通常基于标称锂含量，并添加过量锂以定性地补充煅烧和烧结过程中的锂损失，导致锂成分不精确，直接影响烧结石榴石的物理和电化学性能。在这项研究中，我们系统地改变了 Li _{6.75± X} La _2.75 Ca _0.25 Zr _1.75 Nb _0.5 O _{12加工过程中的锂含量}(LLCZN)，然后测量实际锂含量，并确定密度、二次相形成以及对电化学性能的影响。对于所需的 6.75 化学计量 LLCZN Li 组合物，烧结后的摩尔锂含量在每摩尔 5.5 至 7.3 锂的范围内，这取决于起始锂含量和使用的烧结条件。当锂含量超出设计的化学计量时，会检测到二次相，从而阻碍烧结。在 MgO 坩埚中烧结的样品获得了高体积电导率 (>10 ^–4 S cm ^–1 )。然而，由于次生相，它们表现出较低的晶界电导率，导致总电导率约为 10 ^–5 S cm ^–1。相比之下，当在 Al 中烧结时₂ O ₃坩埚、体电导率 (2.0 × 10 ^–4 S cm ^–1 ) 和晶界电导 (1.07 × 10 ^–3 S cm ^–1 ) 在 6.37 锂/mol LLCZN 时达到最大值，总电导率为 1.68 × 10 ^–4 S cm ^–1。_{虽然在 MgO 坩埚中烧结时获得了相似的体积电导率，但在被来自 Al 2} O ₃坩埚的百万分之几铝污染的样品中获得了最高的总电导率。

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Achieving Desired Lithium Concentration in Garnet Solid Electrolytes; Processing Impacts on Physical and Electrochemical Properties

Lithium-ion-conducting garnets are one of the most promising solid-state electrolytes to replace liquid organic electrolytes in lithium batteries, resulting in a tremendous and rapidly increasing number of garnet publications and commercial activity. However, these publications are typically based on a nominal lithium content with the addition of excess lithium to qualitatively supplement lithium losses during calcining and sintering, resulting in an inexact lithium composition that directly influences the sintered garnet’s physical and electrochemical properties. In this study, we systematically varied the lithium content during the processing of Li_6.75±XLa_2.75Ca_0.25Zr_1.75Nb_0.5O₁₂ (LLCZN), then measured the actual lithium content, and determined density, secondary phase formation, and the impact on electrochemical properties. The molar lithium content after sintering ranged from 5.5 to 7.3 lithium per mol for a desired 6.75 stoichiometric LLCZN Li-composition, depending on the starting lithium content and sintering conditions utilized. Secondary phases were detected when lithium content was outside of the designed stoichiometry, hindering sintering. Samples sintered in MgO crucibles obtained high bulk conductivities (>10^–4 S cm^–1). However, they exhibited low grain boundary conductance due to secondary phases, resulting in total conductivities on the order of 10^–5 S cm^–1. In comparison, when sintered in Al₂O₃ crucibles, bulk conductivity (2.0 × 10^–4 S cm^–1) and grain boundary conductance (1.07 × 10^–3 S cm^–1) reached their maximum at 6.37 lithium per mol of LLCZN for a total conductivity of 1.68 × 10^–4 S cm^–1. While similar bulk conductivities were attained when sintered in MgO crucibles, the highest total conductivities were achieved in samples contaminated with parts per million levels of aluminum from the Al₂O₃ crucible.

更新日期：2022-10-20

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