Otoyama Misae, Kuratani Kentaro, Kobayashi Hironori
Department of Energy and Environment, Research Institute of Electrochemical Energy, National Institute of Advanced Industrial Science and Technology (AIST) 1-8-31, Midorigaoka, Ikeda Osaka 563-8577 Japan
RSC Adv. 2021 Dec 3;11(61):38880-38888. doi: 10.1039/d1ra06466e. eCollection 2021 Nov 29.
Sulfide solid electrolytes with high ionic conductivity and high air stability must be developed for manufacturing sulfide all-solid-state batteries. LiGePS-type and argyrodite-type solid electrolytes exhibit a high ionic conductivity of ∼10 S cm at room temperature, while emitting toxic HS gas when exposed to air. We focused on hexagonal LiSnS prepared by mechanochemical treatment because it comprises air-stable SnS tetrahedra and shows higher ionic conductivity than orthorhombic LiSnS prepared by solid-phase synthesis. Herein, to enhance the ionic conductivity of hexagonal LiSnS, LiI was added to LiSnS by mechanochemical treatment. The ionic conductivity of 0.43LiI·0.57LiSnS increased by 3.6 times compared with that of LiSnS. XRD patterns of LiSnS with LiI showed peak-shifting to lower angles, indicating that introduction of I, which has a large ionic radius, expanded the Li conduction paths. Furthermore, LiPS, which is the most air-stable in the LiS-PS system and has higher ionic conductivity than LiSnS, was added to the LiI-LiSnS system. We found that 0.37LiI·0.25LiPS·0.38LiSnS sintered at 200 °C showed the highest ionic conductivity of 5.5 × 10 S cm at 30 °C in the hexagonal LiSnS-based solid electrolytes. The rate performance of an all-solid-state battery using 0.37LiI·0.25LiPS·0.38LiSnS heated at 200 °C was higher than those obtained using LiSnS and 0.43LiI·0.57LiSnS. In addition, it exhibited similar air stability to LiSnS by formation of LiI·3HO in air. Therefore, addition of LiI and LiPS to hexagonal LiSnS by mechanochemical treatment is an effective way to enhance ionic conductivity without decreasing the air stability of LiSnS.
为了制造硫化物全固态电池，必须开发具有高离子电导率和高空气稳定性的硫化物固体电解质。LiGePS型和硫银锗矿型固体电解质在室温下表现出约10 S cm的高离子电导率，但暴露于空气中时会释放有毒的HS气体。我们关注通过机械化学处理制备的六方LiSnS，因为它由空气稳定的SnS四面体组成，并且比通过固相合成制备的正交LiSnS具有更高的离子电导率。在此，为了提高六方LiSnS的离子电导率，通过机械化学处理将LiI添加到LiSnS中。0.43LiI·0.57LiSnS的离子电导率与LiSnS相比提高了3.6倍。含LiI的LiSnS的XRD图谱显示峰向低角度移动，表明具有大离子半径的I的引入扩展了Li传导路径。此外，将LiS-PS体系中空气稳定性最高且离子电导率高于LiSnS的LiPS添加到LiI-LiSnS体系中。我们发现，在基于六方LiSnS的固体电解质中，在200 °C烧结的0.37LiI·0.25LiPS·0.38LiSnS在30 °C时表现出最高离子电导率5.5×10 S cm。使用在200 °C加热的0.37LiI·0.25LiPS·0.38LiSnS的全固态电池的倍率性能高于使用LiSnS和0.43LiI·0.57LiSnS获得的倍率性能。此外，它通过在空气中形成LiI·3HO表现出与LiSnS相似的空气稳定性。因此，通过机械化学处理向六方LiSnS中添加LiI和LiPS是提高离子电导率而不降低LiSnS空气稳定性的有效方法。
