Pristine Poly(3‐hexylthiophene) as an On‐Demand Conductive Binder and Redox Mediator for Carbon‐Additive‐Free, High‐Volumetric‐Energy‐Density, LiFePO 4 Cathodes without Calendaring

Abstract

ABSTRACT Poly(3‐hexylthiophene) (P3HT) is introduced as a multifunctional conductive binder and redox mediator to fundamentally improve the performance and volumetric energy density of carbon‐free LiFePO 4 (LFP) cathodes. Unlike conventional Super P (SP):PVDF systems, P3HT can be electrochemically doped within the LFP operating potential range, forming an internal percolating conductive network that precedes and facilitates the LFP redox reaction. Strong π–π interactions and P3HT–Fe coordination enable P3HT to uniformly coat LFP particles, yielding intimate interfacial contact, enhanced adhesion, and an ultrathin, stable cathode–electrolyte interphase. As a result, P3HT‐based LFP cathodes exhibit significantly improved packing density (2.70 g cm −3 ), delivering volumetric energy densities up to 1402 Wh L − 1 , far surpassing SP:PVDF‐based counterparts (1.43 g cm −3 ; 738 Wh L −1 ). The P3HT‐based LFP cathodes achieve long‐term cycling stability and high‐rate capability comparable to or better than SP:PVDF‐based LFP electrodes. Density functional theory further reveals strong P3HT–LFP adsorption (−80 to −170 kJ mol − 1 ), substantial charge transfer, and narrowed bandgap at the P3HT‐LFP interface, confirming enhanced electronic coupling. This work shows that P3HT as a highly efficient binder can integrate conductivity, redox mediation, and interfacial stabilization, offering a compelling strategy for constructing next‐generation high‐density, long‐life LFP cathodes.