Abstract:
Conducting polymers (CPs) are by far the most studied organic
materials for supercapacitors. Yet, their structural instability stemming
from volumetric expansion/contraction during charge/discharge
results in capacitance loss after moderate cycling that limits their
applications. Here, we show that the remarkable cycling stability,
capacitance, and rate performance can be achieved by replacing
conventional electrode additives (carbon black or insulating polymer
binder) with titanium carbide (Ti3C2Tx) MXene. Using polyaniline (PANI)
as a model system, an addition of only 15 wt% of Ti3C2Tx MXene binder
delivered remarkable capacitance retention of 96% after 10 000 cycles
at 50 mV s 1 and high-rate capability with a capacitance of 434 F g 1
.
Using density functional theory (DFT) calculations, we show that,
unlike insulating polymer binders, surface groups of MXene bond to
PANI with a significantly high binding energy (up to 2.11 eV) via
a charge transfer mechanism. This is one of the key mechanisms to
achieve a high electrochemical performance of the CP-based electrodes when MXene is used as a binder. We expect that a similar
approach can be used for stabilizing other organic electrode materials.
