Dual‐Redox Sites Guarantee High‐Capacity Sodium Storage in Two‐Dimension Conjugated Metal–Organic Frameworks

Abstract

2D π-d conjugated metal-organic frameworks (c-MOFs) are promising anode candidates for sodium-ion batteries (SIBs) due to their high intrinsic conductivity and stability in organic electrolytes. However, the development of c-MOFs with multi-redox sites to improve the overall performance of SIBs is highly desired but remains a great challenge. Herein, this work reports the electrochemically active hexaazatrinaphthylene-based 2D π-d c-MOFs (HATN-XCu, X = O or S) as advanced anode materials with dual-redox sites for SIBs. The ordered porous and layer-stacked structure can provide fast transmission and diffusion channels for ions along the stacking directions. Ex situ Fourier transformed infrared spectra together with X-ray photoelectron spectroscopy reveal the dual-redox site storage mechanism of HATN-XCu, namely, the continuous multi-electron reactions occurring on the redox-active CN group and [CuX 4 ]unit, respectively. Based on the synergistic effect of dual-redox sites, HATN-OCu anode exhibits impressive reversible capacity (500 mAh g −1 at 0.1 A g −1 ) and high-rate performance (151 mAh g −1 at 5 A g −1 ). Significantly, a sodium-ion full battery assembled using a HATN-OCu anode and Na 3 V 2 (PO 4 ) 2 O 2 F cathode also displays high-rate performance (117 mAh g −1 at 5 A g −1 ) and stable long-cycle life (the capacity retention of 80% after 500 cycles at 2 A g −1 ).

Achieving Ultrahigh-Rate and Low-Temperature Sodium Storage of FePS3 via In Situ Construction of Graphitized Porous N-Doped Carbon

“…39,40 The proportion of pseudocapacitance at different scan rates can be calculated according to i = k 1 v + k 2 v 1/2 , in which k 1 v and k 2 v 1/2 are related to pseudocapacitance and the diffusion process, repspectively. 41,42 The proportion of pseudocapacitance at the scan rates of 0.2−3 mV s −1 were calculated to be 71.6−92.2% (Figure 5c,d), which confirm again that Na + in the FPS/GPNC electrode is a pseudocapacitive-dominated process. Such a high proportion of pseudocapacitance endows FPS/GPNC with superior rate performance.…”

“…The CV curves at 0.2–3 mV s –1 are displayed in Figure a, where the shift of peak with the rise of scan rate means polarization increase. Based on the relation of the peak current and scan speed i = av b , b values can be calculated as 0.97, 0.83, 0.77, and 0.99, revealing that the Na + diffusion in the FPS/GPNC electrode is a pseudocapacitive-dominated process (Figure b). , The proportion of pseudocapacitance at different scan rates can be calculated according to i = k 1 v + k 2 v 1/2 , in which k 1 v and k 2 v 1/2 are related to pseudocapacitance and the diffusion process, repspectively. , The proportion of pseudocapacitance at the scan rates of 0.2–3 mV s –1 were calculated to be 71.6–92.2% (Figure c,d), which confirm again that Na + in the FPS/GPNC electrode is a pseudocapacitive-dominated process. Such a high proportion of pseudocapacitance endows FPS/GPNC with superior rate performance.…”

Confined replacement synthesis of SnSe nanoplates in N-doped hollow carbon nanocages for high-performance sodium–ion batteries

“…More specifically, the capacitive contribution at a fixed scan rate can be further quantified based on the current (i) measured at a specific potential (V), according to the following equations. 51,52 iðVÞ…”

Symbiotically Reinforced Bimetallic Photocatalysis in Conjugated Metal−Organic Framework Nanosheets

“…Linker precursor HTHATN-R was synthesized according to our previous report [17] and characterized by 1 H and 13 C NMR (Figure S1, Supporting Information). HTHATN-R and Ni(OAc) 2 were heated solvothermally in the mixture of N,Ndimethylacetamide, sodium tert-butoxide (tBuONa) and ethylenediamine (EDA) to afford black solid of HTHATN-Ni (Figure 1a,b).…”