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Thermally Driven Interfacial Degradation between Li7La3Zr2O12 Electrolyte and LiNi0.6Mn0.2Co0.2O2 Cathode
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-11-05 , DOI: 10.1021/acs.chemmater.0c02261 Younggyu Kim 1 , Dongha Kim 1 , Roland Bliem 2 , Gülin Vardar 2 , Iradwikanari Waluyo 3 , Adrian Hunt 3 , Joshua T. Wright 4 , John P. Katsoudas 4 , Bilge Yildiz 2, 5
Chemistry of Materials ( IF 7.2 ) Pub Date : 2020-11-05 , DOI: 10.1021/acs.chemmater.0c02261 Younggyu Kim 1 , Dongha Kim 1 , Roland Bliem 2 , Gülin Vardar 2 , Iradwikanari Waluyo 3 , Adrian Hunt 3 , Joshua T. Wright 4 , John P. Katsoudas 4 , Bilge Yildiz 2, 5
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Solid-state batteries offer higher energy density and enhanced safety compared to the present lithium-ion batteries using liquid electrolytes. A challenge to implement them is the high resistances, especially at the solid electrolyte interface with the cathode. Sintering at elevated temperature is needed in order to get good contact between the ceramic solid electrolyte and oxide cathodes and thus to reduce contact resistances. Many solid electrolyte and cathode materials react to form secondary phases. It is necessary to find out which phases arise as a result of interface sintering and evaluate their effect on electrochemical properties. In this work, we assessed the interfacial reactions between LiNi0.6Mn0.2Co0.2O2 (NMC622) and Li7La3Zr2O12 (LLZO) as a function of temperature in air. We prepared model systems by depositing thin-film NMC622 cathode layers on LLZO pellets. The thin-film cathode approach enabled us to use interface-sensitive techniques such as X-ray absorption spectroscopy in the near-edge as well as the extended regimes and identify the onset of detrimental reactions. We found that the Ni and Co chemical environments change already at moderate temperatures, on-setting from 500 °C and becoming especially prominent at 700 °C. By analyzing spectroscopy results along with X-ray diffraction, we identified Li2CO3, La2Zr2O7, and La(Ni,Co)O3 as the secondary phases that formed at 700 °C. The interfacial resistance for Li transfer, measured by electrochemical impedance spectroscopy, increases significantly upon the onset and evolution of the detected interface chemistry. Our findings suggest that limiting the bonding temperature and avoiding CO2 in the sintering environment can help to remedy the interfacial degradation.
中文翻译：
Li 7 La 3 Zr 2 O 12电解质与LiNi 0.6 Mn 0.2 Co 0.2 O 2阴极之间的热驱动界面降解
与目前使用液体电解质的锂离子电池相比，固态电池具有更高的能量密度和更高的安全性。实现它们的挑战是高电阻，尤其是在与阴极的固体电解质界面处。为了在陶瓷固体电解质和氧化物阴极之间获得良好的接触并因此降低接触电阻，需要在高温下进行烧结。许多固体电解质和阴极材料反应形成次级相。有必要找出由于界面烧结而产生的相，并评估它们对电化学性能的影响。在这项工作中，我们评估了LiNi 0.6 Mn 0.2 Co 0.2 O 2（NMC622）与Li之间的界面反应。7 La 3 Zr 2 O 12（LLZO）与空气温度的关系。我们通过在LLZO颗粒上沉积薄膜NMC622阴极层来准备模型系统。薄膜阴极方法使我们能够在近边缘以及扩展方案中使用诸如X射线吸收光谱等界面敏感技术，并确定有害反应的发生。我们发现，Ni和Co的化学环境已经在中等温度下发生了变化，从500°C开始，并且在700°C时尤为突出。通过分析光谱结果和X射线衍射，我们鉴定出Li 2 CO 3，La 2 Zr 2 O 7，和La（Ni，Co）O 3作为第二相，在700°C形成。通过电化学阻抗谱测量的Li转移的界面电阻在检测到的界面化学物质发生和发展时会显着增加。我们的发现表明，限制粘结温度并避免在烧结环境中产生CO 2有助于纠正界面降解。
更新日期：2020-11-25
中文翻译：
Li 7 La 3 Zr 2 O 12电解质与LiNi 0.6 Mn 0.2 Co 0.2 O 2阴极之间的热驱动界面降解
与目前使用液体电解质的锂离子电池相比，固态电池具有更高的能量密度和更高的安全性。实现它们的挑战是高电阻，尤其是在与阴极的固体电解质界面处。为了在陶瓷固体电解质和氧化物阴极之间获得良好的接触并因此降低接触电阻，需要在高温下进行烧结。许多固体电解质和阴极材料反应形成次级相。有必要找出由于界面烧结而产生的相，并评估它们对电化学性能的影响。在这项工作中，我们评估了LiNi 0.6 Mn 0.2 Co 0.2 O 2（NMC622）与Li之间的界面反应。7 La 3 Zr 2 O 12（LLZO）与空气温度的关系。我们通过在LLZO颗粒上沉积薄膜NMC622阴极层来准备模型系统。薄膜阴极方法使我们能够在近边缘以及扩展方案中使用诸如X射线吸收光谱等界面敏感技术，并确定有害反应的发生。我们发现，Ni和Co的化学环境已经在中等温度下发生了变化，从500°C开始，并且在700°C时尤为突出。通过分析光谱结果和X射线衍射，我们鉴定出Li 2 CO 3，La 2 Zr 2 O 7，和La（Ni，Co）O 3作为第二相，在700°C形成。通过电化学阻抗谱测量的Li转移的界面电阻在检测到的界面化学物质发生和发展时会显着增加。我们的发现表明，限制粘结温度并避免在烧结环境中产生CO 2有助于纠正界面降解。
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