Pillared MXene with Ultralarge Interlayer Spacing as a Stable Matrix for High Performance Sodium Metal Anodes

Abstract

Sodium (Na) metal is a promising alternative to lithium metal as an anode material for the next-generation energy storage systems due to its high theoretical capacity, low cost, and natural abundance. However, dendritic/mossy Na growth caused by uncontrollable plating/stripping results in serious safe concerns and rapid electrode degradation. This study presents Sn 2+ pillared Ti 3 C 2 MXene serving as a stable matrix for high-performance dendrite-free Na metal anode. The intercalated Sn 2+ between Ti 3 C 2 layers not only induces Na to nucleate and grow within Ti 3 C 2 interlayers, but also endows the Ti 3 C 2 with larger interlayer space to accommodate the deposited Na by taking advantage of the "pillar effect," contributing to uniform Na deposition. As a result, the pillar-structured MXene-based Na metal electrode could enable high current density (up to 10 mA cm −2 ) along with high areal capacity (up to 5 mAh cm −2 ) over long-term cycling (up to 500 cycles). The full cell using MXene-based Na metal anode exhibits superior electrochemical performance than that using host-less commercial Na. It is believed that the well-controlled MXene-based Na anode not only extends the application scope of MXene, but also provides guidance in designing high-performance Na metal batteries.

Atomic Sulfur Covalently Engineered Interlayers of Ti3C2 MXene for Ultra‐Fast Sodium‐Ion Storage by Enhanced Pseudocapacitance

“…It is noteworthy that the signal of S is uniformly distributed in the CT‐S@Ti 3 C 2 ‐450, even if there is a location between the layers, which indicates the stable existence of S bonds in the matrix after cycling. To further confirm the “pillar effect,” ex situ XRD phase analysis of CT‐S@Ti 3 C 2 ‐450 during the sodiation and de‐sodiation processes was studied (Figure S23, Supporting Information) . The results show that the interlayer spacing of CT‐S@Ti 3 C 2 ‐450 increases from 1.41 to 2.21 nm when the electrode discharge to 0 V, which is basically consistent with the TEM results, confirming the contribution of “pillar effect.” After the desodiation at 3 V, the interlayer spacing of CT‐S@Ti 3 C 2 ‐450 decreases to 1.54 nm, which confirms the reversible expansion and shrinkage for CT‐S@Ti 3 C 2 ‐450 during the charge and discharge processes.…”

Two‐Dimensional Transition Metal Carbides and Nitrides (MXenes): Synthesis, Properties, and Electrochemical Energy Storage Applications

“…Taking the abundant natural sources of the alkali metals on earth into consideration, it is anticipated that developing non‐Li metal ion batteries can lower down the cost, next to potentially improving the battery safety. Thus, questing suitable anodes for the non‐Li metal ion batteries have become the research focus in recent years . By adjusting the interlayer spacing of MXenes, the intercalation kinetics of bulkier ions (such as Na + , K + , and Al 3+ ) can be improved, enabling high performance of MXene‐based non‐Li metal ion batteries.…”

“…By adjusting the interlayer spacing of MXenes, the intercalation kinetics of bulkier ions (such as Na + , K + , and Al 3+ ) can be improved, enabling high performance of MXene‐based non‐Li metal ion batteries. Luo et al used a Sn 2+ pillared Ti 3 C 2 T x for Na metal ion batteries . The Sn 2+ pillars have been proved to be efficient in guiding the uniform deposition of Na within the expanded interlayer space.…”

“…Full‐cell configurations of Na 3 V 2 (PO 4 ) 3 /bare Na and Na 3 V 2 (PO 4 ) 3 /CT‐Sn(II)@Ti 3 C 2 /Na cells, and their cycling performance at 1 C (117 mA g −1 ) for 200 cycles. Reproduced with permission from ref . Copyright 2019, John Wiley & Sons.…”

Fluorination of MXene by Elemental F2 as Electrode Material for Lithium‐Ion Batteries

“…Regardless of the method used to prepare MXene, the etching results in F and OH surface functional groups owing to the presence of HF and water. Given the presence of 2D layers, MXene has been widely studied for its electrochemical applications and specifically for LIBs as an intercalation pseudocapacitor electrode . However, owing to the compact atomic arrangement of MXene that would hinder the diffusion of Li + perpendicular to the layer plane, the electrodes have a reduced power density .…”