Spatial engineering of electrode architectures with conducting polymer for high-performance lithium hybrid capacitors: interior 3D networks versus outer 2D layers

Abstract

In this study, we investigate the strategic spatial integration of a conducting polymer into lithium electrodes for energy storage applications. Poly(3,4-ethylenedioxythiophene) (PEDOT) was incorporated into 2D graphene-molybdenum disulfide (GM) heterolayers to enhance their electrochemical performance in lithium-ion hybrid capacitors (LHCs). Two design strategies were explored: (i) N-PGM with an intra-embedded 3D PEDOT network via vapor-phase polymerization (VDP), and (ii) L-PGM with an outer 2D PEDOT layer deposited in the final fabrication step. N-PGM exhibited improved rate capability over GM, while L-PGM achieved the highest specific capacity and excellent cycling stability, retaining over 95.3% of its capacity after 2000 cycles. PEDOT introduced an additional surface-driven charge storage mechanism, complementing the diffusion-limited redox behavior of MoS₂. Molecular dynamics simulations further revealed that PEDOT weakened direct Li⁺ binding but improved electrolyte compatibility and ion mobility. Notably, the spatial configuration of PEDOT critically influenced these effects: surface-localized PEDOT in L-PGM reduced Li⁺ adsorption energy and promoted faster ion diffusion, whereas embedded PEDOT in N-PGM maintained a balance between ion transport and retention. These findings highlight that spatially controlled polymer incorporation offers a promising route to optimizing ionic accessibility and charge transport in nanostructured electrodes.