The Increasing Number of Electron Reservoirs in Nonporous, High‐Conducting Coordination Polymers Cu_xBHT (x = 3, 4, and 5, BHT = Benzenehexathiol) for Improved Faradaic Capacitance

Abstract

Although asymmetric supercapacitors (ASCs) can achieve high energy density, the lifespan and power density are severely suppressed due to the low conductivity of using pseudocapacitive or battery‐type electrode materials. Recently, nonporous conductive coordination polymers (c‐CPs) have sparked interests in supercapacitors. However, their performance is expected to be limited by the nonporous features, low specific surface area and absence of ion‐diffusion channels. Here, it is demonstrated that the capacity of nonporous CPs will be significantly enhanced by maximizing the number of faradaic redox sites in their structures through a comparative investigation on three highly conductive nonporous c‐CPs, CuxBHT(x = 3, 4, 5.5). They show excellent capacitance of 312.1 F g‐1 (374.5 C g‐1) (Cu3BHT), 186.7 F g‐1 (224.0 C g‐1) (Cu4BHT) and 89.2 F g‐1 (107.0 C g‐1) (Cu5.5BHT) at 0.5 A g‐1 in a sequence related to the number of electron storage units in structures and outstanding rate performance and cycle stability. Furthermore, the constructed Cu3BHT//MnO2 ASC device exhibits capacity retention of 92% (after 1500 cycles at 3 A g‐1) and delivers a high energy density of 39.1 Wh kg‐1 at power density of 549.6 W kg‐1 within a large working potential window of 0‐2.2 V.

Revealing the Mechanism of Pressure‐Induced Emission in Layered Silver‐Bismuth Double Perovskites

“…The slow component is ascribed to the nonradiative recombination of the dark STEs, which should be responsible for the nonemission at ambient conditions. At 7.5 GPa, the lifetime of two fast components was prolonged (τ 1 ≈6.53 ps and τ 2 ≈115.42 ps) compared to its initial state due to the deepening of the defect state and the increase of defect density under high pressure [17] . The slow component of τ 3 ≈3.73 ns is assigned to the emissive decay of the bright STEs, corresponding to the efficient broadband emission and the long‐lived process of TRPL [14b, 18] .…”

Nonporous, conducting bimetallic coordination polymers with an advantageous electronic structure for boosted faradaic capacitance

“…It is worth noting that the M-dithiolene units consisting of planar tetra-coordinated Ag/Cu atoms with the benzene rings and the extended Ag–S networks can be deemed as the faradaic redox sites. 27,37,38 Overall, the well-defined layered structures of Ag 5 BHT and CuAg 4 BHT and their high electrical conductivities and hydrolytic stabilities as well as dense redox sites stimulated us to evaluate their performance in electrochemical capacitors.…”

“…15,23,24 Recent studies have demonstrated that the faradaic redox processes are commonly not limited by solid-state ion diffusion and that the energy storage capacity of nonporous c-CPs is mainly related to the built-in redox sites in their structure. 25–27 Remarkably, the introduction of heterometallic atoms in c-CPs can regulate their electronic structures, redox activities, morphologies, and enhance the charge transfer between different metal sites, which has emerged as an attractive tactic for lowering the kinetic energy barrier of the electrochemical processes. 28–31 For instance, Co–Ni, Co–Zn, and Fe–Co MOFs have been developed as efficient pseudocapacitive or battery-type electrode materials.…”

Synergistic Enhancement of Capacitance of Amorphous CuBHT/MoS2 Hybrids

“…This further confirms the importance of A-CuBHT for improving the capacitance performance of hybrid materials. Here, we assume that the main reasons for the improvement of the performance of hybrid materials are the excellent charge storage capacity of A-CuBHT and the synergistic effect between MoS 2 and A-CuBHT, namely, the possible existence of Cu plane fourcoordination structure units in A-CuBHT can store charges (Figure S6), 34 which creates conditions for the improvement of the performance of hybrid materials. Second, MoS 2 nanosheets can provide a large number of attachment sites for the formation of A-CuBHT, resulting in more redox-active sites of A-CuBHT exposed in the electrolyte.…”

“…To the best of our knowledge, the research on metal−organic coordination polymers and MoS 2 hybrid materials in the field of electrochemical energy storage is still very rare. Here, amorphous Cu 3 BHT (A-CuBHT), which is an amorphous form of metal− organic coordination polymer Cu 3 BHT with high conductivity 33 and high electrochemical energy storage capacity, 34 is used to hybridize with MoS 2 to improve its performance. The results indicate that hybridizing of A-CuBHT and the prepared 1T(H) phase MoS 2 with a 1T phase concentration of 76.6% at a proper weight ratio can effectively improve the conductivity of the hybrids and stabilize 1T phase MoS 2 , resulting in a significant increase in the rate performance and capacitance of the electrode based on this hybrid material.…”