Lithiophilic MXene‐Guided Lithium Metal Nucleation and Growth Behavior

Abstract

The positive effects of a lithiophilic substrate on the electrochemical performance of lithium metal anodes are confirmed in several reports, while the understanding of lithiophilic substrate‐guided lithium metal nucleation and growth behavior is still insufficient. In this study, the effect of a lithiophilic surface on lithium metal nucleation and growth behaviors is investigated using a large‐area Ti3C2Tx MXene substrate with a large number of oxygen and fluorine dual heteroatoms. The use of the MXene substrate results in a high lithium‐ion concentration as well as the formation of uniform solid–electrolyte‐interface (SEI) layers on the lithiophilic surface. The solid–solid interface (MXene‐SEI layer) significantly affects the surface tension of the deposited lithium metal nuclei as well as the nucleation overpotential, resulting in the formation of uniformly dispersed lithium nanoparticles (≈10–20 nm in diameter) over the entire MXene surface. The primary lithium nanoparticles preferentially coalesce and agglomerate into larger secondary particles while retaining their primary particle shapes. Subsequently, they form close‐packed structures, resulting in a dense metal layer composed of particle‐by‐particle microstructures. This distinctive lithium metal deposition behavior leads to highly reversible cycling performance with high Columbic efficiencies > 99.0% and long cycle lives of over 1000 cycles.

Understanding the Effects of Interfacial Lithium Ion Concentration on Lithium Metal Anode

“…where V m and F are the molar volume of lithium and the Faraday's constant, respectively. [26] The relationship between the nucleation overpotential and free-energy is schematically depicted in Figure 2g-i. On the pyridinic nitrogen sites of the PNCs, ∆G V can be significantly reduced by the catalytic effect, which means a large reduction in 𝜂 n .…”

“…A noticeable improvement in the electrochemical performance can be achieved by designing (1) 3D-structured lithiophilic electrode materials (3D-LEMs) and (2) better SEI layers, having high chemical/mechanical stabilities and high ionic conductivities. [20][21][22][23][24][25][26][27][28][29][30][31][32] The high active surface areas and catalytic nucleation sites in 3D-LEMs can simultaneously cause extensive lithium metal growth on the electrode surfaces, which can remarkably reduce the effective current density, leading to kineticcontrolled lithium metal deposition. The explosive growth of lithium dendrites in a specific region can be mitigated by inducing lithium ion deconcentration.…”

“…The explosive growth of lithium dendrites in a specific region can be mitigated by inducing lithium ion deconcentration. [20][21][22][23][24][25][26] Several studies have also revealed that lithium-rich inorganic SEI (L-I-SEI) layers such as Li 2 O, Li 2 CO 3 , and LiF can induce uniform lithium ion transport in the interfacial area. The stable L-I-SEI layer can mitigate continuous electrolyte decomposition, even under harsh conditions, with infinite volume expansion, leading to homogeneous lithium metal deposition/dissolution cycles.…”

“…The stable L-I-SEI layer can mitigate continuous electrolyte decomposition, even under harsh conditions, with infinite volume expansion, leading to homogeneous lithium metal deposition/dissolution cycles. [26][27][28][29][30][31][32] Accordingly, the effects of various electrolyte additives have been actively studied in attempts to form better SEI layers with large numbers of inorganic components, where positive effects have been demonstrated, particularly on the surface of 3D-LEMs. [26] Hence, previous reports suggest that high-performance LMAs can be realized by a synergistic combination of 3D-LEMs and L-I-SEI layers.…”

“…[26][27][28][29][30][31][32] Accordingly, the effects of various electrolyte additives have been actively studied in attempts to form better SEI layers with large numbers of inorganic components, where positive effects have been demonstrated, particularly on the surface of 3D-LEMs. [26] Hence, previous reports suggest that high-performance LMAs can be realized by a synergistic combination of 3D-LEMs and L-I-SEI layers. However, despite their effectiveness, fundamental understanding of the key factors determining the high electrochemical performance of LMAs is still elusive.…”