期刊
ADVANCED ENERGY MATERIALS
卷 9, 期 21, 页码 -出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/aenm.201900671
关键词
critical current density; garnet electrolytes; grain boundaries; interfacial modifications; solid-state batteries
类别
资金
- National Key R&D Program of China [2016YFB0700600]
- Guangdong Innovation Team Project [2013N080]
- Shenzhen Science and Technology Research Grant [JCYJ20160531141048950]
- Guangdong Key Lab Project [2017B0303010130]
Garnet-type solid-state electrolytes (SSEs) have been widely studied as a promising candidate for Li metal batteries. Despite the common belief that inorganic SSEs can prevent dendrite propagation, garnet SSEs suffer from relatively low critical current density (CCD) at which the SSEs are abruptly short-circuited by Li dendrites. In this study, the short-circuiting mechanism of garnet Li7La2.75Ca0.25Zr1.75Nb0.25O12 (LLCZN) is investigated. It is found that instead of propagating uniaxially from one electrode to other in a dendritic form, metallic lithium is formed within the SSE. This can be attributed to the fact that electrons combine with Li ions at the grain boundary, which exhibits relatively high electronic conductivity, and then reduce Li+ to Li-0 to cause short circuits. In order to reduce the electronic conductivity at the grain boundary, a thin layer of LiAlO2 is coated on the grain surface of LLCZN, which results in an improved CCD value. It is also found that under higher external voltages, the electronic conductivity of SSE becomes more significant, which is believed to be the origin of CCD. These findings not only shed light on the short-circuiting mechanism of garnet-type SSEs but also offer a novel perspective and useful guidance on their designs and modifications.
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