The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium
The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium
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DOI：
10.1073/pnas.1911017116
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发表时间：
2020-01-07
影响因子：
11.1
通讯作者：
Gallant, Betar M.
中科院分区：
文献类型：
--
作者：
He, Mingfu;Guo, Rui;Gallant, Betar M.
锂是用于高能量密度可再充电电池的最有吸引力的阳极材料，但是其循环受到形态不可逆性和枝晶生长的困扰，所述形态不可逆性和枝晶生长部分地由其异质的“天然”固体电解质界面（SEI）引起。用氟化锂（LiF）富集SEI近来已得到普及以改善Li循环能力。然而，LiF的内在功能--无论是化学的、机械的还是动力学的--仍然是未知的。在本文中，我们研究了LiF在人工预形成或衍生自氟化电解质的模型LiF富集的SEIs中的稳定性，以及因此LiF源对Li电极行为的影响。我们发现LiF的机械完整性在电镀过程中很容易受到损害，使其本质上无法保护Li。随后通过电解质原位修复界面，再生LiF或形成额外的弹性体“外层”，被确定为Li电极性能的更关键的决定因素。我们的研究结果提出了一个最新的和动态的图片的LiF丰富的SEI和证明需要仔细考虑的离子和电解质衍生层在未来的设计策略的综合作用。
Lithium is the most attractive anode material for high-energy density rechargeable batteries, but its cycling is plagued by morphological irreversibility and dendrite growth that arise in part from its heterogeneous "native" solid electrolyte interphase (SEI). Enriching the SEI with lithium fluoride (LiF) has recently gained popularity to improve Li cyclability. However, the intrinsic function of LiF-whether chemical, mechanical, or kinetic in nature-remains unknown. Herein, we investigated the stability of LiF in model LiF-enriched SEls that are either artificially preformed or derived from fluorinated electrolytes, and thus, the effect of the LiF source on Li electrode behavior. We discovered that the mechanical integrity of LiF is easily compromised during plating, making it intrinsically unable to protect Li. The ensuing in situ repair of the interface by electrolyte, either regenerating LiF or forming an extra elastomeric "outer layer," is identified as the more critical determinant of Li electrode performance. Our findings present an updated and dynamic picture of the LiF-enriched SEI and demonstrate the need to carefully consider the combined role of ionic and electrolyte-derived layers in future design strategies.