Ultrahigh-mass-loading flexible LiFePO4 cathode with the drop-shaped low-tortuosity architecture for high-performance flexible lithium-ion batteries

Ultrahigh-mass-loading design of the active materials shows great potentials to enhance their energy density of flexible lithium-ion batteries (FLIBs) from the device level, yet troubled by the sluggish Li⁺ transport and inferior mechanical flexibility. Herein, a drop-shaped low-tortuosity LiFePO₄-based flexible cathode with a tri-continuous networks is demonstrated by a water-induced phase separation method. The continuous hierarchical pores, particularly the vertically aligned drop-shaped pores, continuous conductive networks and continuous PVDF-HFP networks are deliberately constructed, which makes it possible to significantly improve its charge transport capability and mechanical flexibility simultaneously, even at ultra-high mass loading. Owing to its structural advantages, the electrode with a high mass loading of 13 mg cm^-2 presents remarkable rate capacities (162.87 mAh g^-1 at 0.1 C; 122.21 mAh g^-1 at 2 C) and cycling stability (a capacity retention of 88.58 % at 1 C after 100 cycles). Even at an ultra-high mass loading of 115 mg cm^-2, an impressive areal capacity of 13.20 mAh cm^-2 is successfully achieved. The research provides a potential solution for the design and optimization of ultrahigh-mass-loading flexible electrodes, which will give great impetus to the development of advanced FLIBs with high energy/power density.