Ji Xiao, Hou Singyuk, Wang Pengfei, He Xinzi, Piao Nan, Chen Ji, Fan Xiulin, Wang Chunsheng
Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD, 20742, USA.
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, 20742, USA.
Adv Mater. 2020 Nov;32(46):e2002741. doi: 10.1002/adma.202002741. Epub 2020 Oct 9.
All-solid-state Li metal batteries have attracted extensive attention due to their high safety and high energy density. However, Li dendrite growth in solid-state electrolytes (SSEs) still hinders their application. Current efforts mainly aim to reduce the interfacial resistance, neglecting the intrinsic dendrite-suppression capability of SSEs. Herein, the mechanism for the formation of Li dendrites is investigated, and Li-dendrite-free SSE criteria are reported. To achieve a high dendrite-suppression capability, SSEs should be thermodynamically stable with a high interface energy against Li, and they should have a low electronic conductivity and a high ionic conductivity. A cold-pressed Li N-LiF composite is used to validate the Li-dendrite-free design criteria, where the highly ionic conductive Li N reduces the Li plating/stripping overpotential, and LiF with high interface energy suppresses dendrites by enhancing the nucleation energy and suppressing the Li penetration into the SSEs. The Li N-LiF layer coating on Li PS SSE achieves a record-high critical current of >6 mA cm even at a high capacity of 6.0 mAh cm . The Coulombic efficiency also reaches a record 99% in 150 cycles. The Li N-LiF/Li PS SSE enables LiCoO cathodes to achieve 101.6 mAh g for 50 cycles. The design principle opens a new opportunity to develop high-energy all-solid-state Li metal batteries.
全固态锂金属电池因其高安全性和高能量密度而备受关注。然而，固态电解质（SSE）中锂枝晶的生长仍然阻碍了它们的应用。目前的努力主要旨在降低界面电阻，而忽略了SSE固有的枝晶抑制能力。在此，研究了锂枝晶形成的机制，并报道了无锂枝晶的SSE标准。为了实现高枝晶抑制能力，SSE应具有热力学稳定性，与锂的界面能高，并且应具有低电子电导率和高离子电导率。采用冷压的LiN-LiF复合材料来验证无锂枝晶的设计标准，其中高离子导电的LiN降低了锂电镀/剥离过电位，具有高界面能的LiF通过提高成核能和抑制锂渗透到SSE中来抑制枝晶。即使在6.0 mAh cm的高容量下，LiN-LiF层涂覆在LiPSSSE上也实现了创纪录的>6 mA cm的临界电流。在150次循环中，库仑效率也达到了创纪录的99%。LiN-LiF/LiPSSSE使LiCoO阴极在50次循环中能够达到101.6 mAh g。该设计原理为开发高能量全固态锂金属电池提供了新的机会。
