Tricontinuous Sponge-like LiFePO₄ Cathode with Ultrahigh Areal Capacity for Flexible Lithium-Ion Batteries

Increasing the mass loading of active materials offers significant potential for enhancing the energy density of flexible lithium-ion batteries on the system scale. However, this approach is hindered by the impeded Li⁺ diffusion kinetics and insufficient mechanical flexibility. To address this, we developed a tricontinuous sponge-like LiFePO₄-based flexible cathode using an ethanol-induced phase separation technique. The continuous sponge-like micromesopores enhance electrolyte permeation and shorten the Li⁺ diffusion pathway and resistance while a continuous dual-scale electron-transporting network ensures excellent electron transport. Besides, a continuous PVDF-HFP network forms an integrated flexible porous electrode skeleton. This synergistic tricontinuous network simultaneously boosts charge transport efficiency and mechanical resilience, even under ultrahigh mass loading. Consequently, the cathode achieves a favorable mass loading of 14 mg cm^-2, delivering exceptional rate performances (159.85 mAh g^-1 at 0.2C and 120.14 mAh g^-1 at 2C) and cycling stability (79.93% capacity retention after 140 cycles at 1C). Remarkably, at an ultrahigh mass loading of 114 mg cm^-2, it attains a record areal capacity of 13.69 mAh cm^-2. This study offers a promising strategy for optimizing ultrahigh-mass-loading flexible electrodes, paving the way for advanced flexible lithium-ion batteries to practical applications.