Microstructure and Charge－Discharge Mechanism of a Li3CuS2 Positive Electrode Material for All-Solid-State Lithium-Ion Batteries
Microstructure and Charge－Discharge Mechanism of a Li3CuS2 Positive Electrode Material for All-Solid-State Lithium-Ion Batteries
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全固态锂离子电池Li3CuS2正极材料的微观结构及充放电机理
DOI：
10.1021/acsaem.1c01074
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发表时间：
2021
影响因子：
6.4
通讯作者：
S. Mori
中科院分区：
文献类型：
--
作者：
T. Ayama;H. Tsukasaki;Y. Kawasaki;H. Nakajima;M. Tatsumisago;A. Sakuda;A. Hayashi;S. Mori
要发展全固态锂电池，需要高容量正极材料。反萤石型材料Li 2S表现出高的理论容量。然而，Li 2S由于其绝缘性能而不能用作全固态电池的正极。为了提供电子和离子传导，最近，通过Cu取代活化Li 2S开发了反萤石型Li 3CuS 2。Li 3CuS 2是一种很好的正极材料，因为含有Li 3CuS 2的硫化物基全固态电池表现出很高的充放电性能。然而，在充放电循环过程中的结构变化和氧化还原物种还没有被理解。为了阐明Li 3CuS 2的充放电机理，采用透射电子显微镜（TEM）研究了Li 3CuS 2-Li 3 PS4正极复合材料在充放电过程中的微观结构变化。空心锥暗场成像技术被用来评估晶粒尺寸分布。结果表明，Li 3CuS 2的晶粒尺寸在充放电过程中分别可逆地减小和增大。电子衍射图谱表明，在充电过程中形成了LiCuS 2，这归因于Li+从Li 3CuS 2中提取。在放电状态下，微晶尺寸增加，Li 3CuS 2再生。TEM结果表明，Li 3CuS 2 → LiCuS 2 + 2Li++2e-的可逆结构变化有助于提高材料的充放电性能。
To develop all-solid-state lithium batteries, high-capacity positive electrode materials are necessary. An antifluorite-type material, Li2S, exhibits a high theoretical capacity. However, Li2S cannot be used as a positive electrode for the all-solid-state cell because of its insulating behavior. To provide electronic and ionic conduction, recently, antifluorite-type Li3CuS2has been developed by activation of Li2S by Cu substitution. Li3CuS2is a favorable candidate for positive electrodes as sulfide-based all-solid-state cells with Li3CuS2exhibit high charge–discharge performance. However, structural changes and redox species during the charge–discharge cycle have not been understood yet. To clarify the charge–discharge mechanism of Li3CuS2, in this study, we examined the microstructural changes in a Li3CuS2–Li3PS4positive electrode composite during charge and discharge by transmission electron microscopy (TEM). The hollow-cone dark-field imaging technique was employed to evaluate the crystallite size distribution. The result shows that the crystallite size of Li3CuS2reversibly decreases and increases in the charging and discharging states, respectively. The electron diffraction pattern shows that LiCuS2was formed during charging, which is attributed to Li+extraction from Li3CuS2. In the discharging state, the crystallite size increased and Li3CuS2was reproduced. The TEM results suggest that the reversible structural changes (Li3CuS2⇆ LiCuS2+ 2Li++ 2e–) would contribute to high charge–discharge characteristics.