High-Rate Polymeric Redox in MXene-Based Superlattice-Like Heterostructure for Ammonium Ion Storage
Chaofan Chen (TU Delft - RST/Storage of Electrochemical Energy)
Glenn Quek (National University of Singapore)
Hongjun Liu (VanderBilt University)
L. J. Bannenberg (TU Delft - RID/TS/Instrumenten groep)
Ruipeng Li (Brookhaven National Laboratory)
Jaehoon Choi (Helmholtz-Institute Ulm, Ulm, Karlsruhe Institut für Technologie)
D. Ren (TU Delft - ImPhys/Adam group, Norwegian University of Science and Technology (NTNU))
Ricardo Vázquez (National University of Singapore)
B. Boshuizen (TU Delft - ChemE/O&O groep)
Bjørn Ove Fimland (Norwegian University of Science and Technology (NTNU))
Simon Fleischmann (Helmholtz-Institute Ulm, Ulm, Karlsruhe Institut für Technologie)
M Wagemaker (TU Delft - RST/Storage of Electrochemical Energy)
De en Jiang (VanderBilt University)
Guillermo C. Bazan (National University of Singapore)
Xuehang Wang (TU Delft - RST/Storage of Electrochemical Energy)
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Abstract
Achieving both high redox activity and rapid ion transport is a critical and pervasive challenge in electrochemical energy storage applications. This challenge is significantly magnified when using large-sized charge carriers, such as the sustainable ammonium ion (NH4+). A self-assembled MXene/n-type conjugated polyelectrolyte (CPE) superlattice-like heterostructure that enables redox-active, fast, and reversible ammonium storage is reported. The superlattice-like structure persists as the CPE:MXene ratio increases, accompanied by a linear increase in the interlayer spacing of MXene flakes and a greater overlap of CPEs. Concurrently, the redox activity per unit of CPE unexpectedly intensifies, a phenomenon that can be explained by the enhanced de-solvation of ammonium due to the increased volume of 3 Å-sized pores, as indicated by molecular dynamic simulations. At the maximum CPE mass loading (MXene:CPE ratio = 2:1), the heterostructure demonstrates the strongest polymeric redox activity with a high ammonium storage capacity of 126.1 C g−1 and a superior rate capability at 10 A g−1. This work unveils an effective strategy for designing tunable superlattice-like heterostructures to enhance redox activity and achieve rapid charge transfer for ions beyond lithium.
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