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Abstract A dual‐layer interphase that consists of an in‐situ‐formed lithium carboxylate organic layer and a thin BF3‐doped monolayer Ti3C2MXene on Li metal is reported. The honeycomb‐structured organic layer increases the wetting of electrolyte, leading to a thin solid electrolyte interface (SEI). While the BF3‐doped monolayer MXene provides abundant active sites for lithium homogeneous nucleation and growth, resulting in about 50% reduced thickness of inorganic‐rich components among the SEI layer. A low overpotential of less than 30 mV over 1000 h cycling in symmetric cells is received. The functional BF3 groups, along with the excellent electronic conductivity and smooth surface of the MXene, greatly reduce the lithium plating/stripping energy barrier, enabling a dendrite‐free lithium‐metal anode. The battery with this dual‐layer coated lithium metal as the anode displays greatly improved electrochemical performance. A high capacity‐retention of 175.4 mAh g−1at 1.0 C is achieved after 350 cycles. In a pouch cell with a capacity of 475 mAh, the battery still exhibits a high discharge capacity of 165.6 mAh g−1with a capacity retention of 90.2% after 200 cycles. In contrast to the fast capacity decay of pure Li metal, the battery using NCA as the cathode also displays excellent capacity retention in both coin and pouch cells. The dual‐layer modified surface provides an effective approach in stabilizing the Li‐metal anode.
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Cryo‐Electron Tomography of Highly Deformable and Adherent Solid‐Electrolyte Interphase Exoskeleton in Li‐Metal Batteries with Ether‐Based Electrolyte
Abstract The 3D nanocomposite structure of plated lithium (LiMetal) and solid electrolyte interphases (SEI), including a polymer‐rich surficial passivation layer (SEI exoskeleton) and inorganic SEI “fossils” buried inside amorphous Li matrix, is resolved using cryogenic transmission electron microscopy. With ether‐based DOLDME‐LiTFSI electrolyte, LiF and Li2O nanocrystals are formed and embedded in a thin but tough amorphous polymer in the SEI exoskeleton. The fast Li‐stripping directions are along or , which produces eight exposed {111} planes at halfway charging. Full Li stripping produces completely sagging, empty SEI husks that can sustain large bending and buckling, with the smallest bending radius of curvature observed approaching tens of nanometers without apparent damage. In the 2nd round of Li plating, a thin LiBCCsheet first nucleates at the current collector, extends to the top end of the deflated SEI husk, and then expands its thickness. The apparent zero wetting angle between LiBCCand the SEI interior means that the heterogeneous nucleation energy barrier is zero. Due to its complete‐wetting property and chemo‐mechanical stability, the SEI largely prevents further reactions between the Li metal and the electrolyte, which explains the superior performance of Li‐metal batteries with ether‐based electrolytes. However, uneven refilling of the SEI husks results in dendrite protrusions and some new SEI formation during the 2nd plating. A strategy to form bigger SEI capsules during the initial cycle with higher energy density than the following cycles enables further enhanced Coulombic efficiency to above 99%.
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- PAR ID:
- 10446314
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 34
- Issue:
- 13
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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