Poly(Vinylidene Fluoride)‐Wrapped LiFePO ₄ Microspheres as Highly Stable Dual Functional Cathode for Solid‐State Lithium Batteries

Solid polymer electrolytes hold great promise for achieving improved processability and safety in solid‐state lithium‐ion batteries (LIBs); however, several inherent challenges arise from the use of polymers. One critical issue is the ultrahigh interfacial resistance between the cathode and electrolyte, which has emerged as a main research focus in recent years. In this study, a dual functional cathode (DFC) is developed by uniformly dispersing the cathode material (LiFePO 4 ) into the polymer electrolyte poly(vinylidenfluorid ‐ co‐hexafluorpropylene):lithium bis(trifluoromethanesulfonyl)imide, resulting in a conformable lamella structure with embedded microspheres. Simultaneous enhancement of the interfacial contact and the ion transport efficiency is observed. Solid‐state LIBs incorporating the proposed DFC demonstrate exceptional electrochemical performance at room temperature, exhibiting a high discharge capacity of 138 mAh g −1 at 1 C, along with an impressive capacity retention of over 80% after 250 cycles, all while preserving the intricate spherical structure. The discharge capacity reaches 98 mAh g −1 even at a high rate of 5 C. At an elevated temperature of 60 °C, a capacity retention of 80% is obtained after 500 cycles. Therefore, this work provides a simple but effective design concept for improving interfacial compatibility between the cathodes and polymer electrodes in solid‐state LIBs.