The Increasing Number of Electron Reservoirs in Nonporous, High-Conducting Coordination Polymers Cux BHT (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, Cux BHT(x=3, 4, 5.5). They show excellent capacitance of 312.1Fg-1 (374.5Cg-1 ) (Cu3 BHT), 186.7Fg-1 (224.0Cg-1 ) (Cu4 BHT) and 89.2Fg-1 (107.0Cg-1 ) (Cu5.5 BHT) at 0.5Ag-1 in a sequence related to the number of electron storage units in structures and outstanding rate performance and cycle stability. Furthermore, the constructed Cu3 BHT//MnO2 ASC device exhibits capacity retention of 92% (after 1500 cycles at 3Ag-1 ) and delivers a high energy density of 39.1Whkg-1 at power density of 549.6Wkg-1 within a large working potential window of 0-2.2V.