Constructing PVDF-based composite polymer electrolytes with polymorphic Ce-MOFs for quasi-solid-state Li/LMFP batteries

The PVDF-based polymer electrolyte has the disadvantages of low ionic conductivity and low Li + migration number at room temperature, which hinders its application in lithium-ion batteries. Herein, polymer composite electrolytes were constructed utilizing three polymorphic Ce-MOFs as functional fillers to enhance its performance. The homogeneously dispersed Ce-MOF fillers restricted the reorganization of PVDF-HFP chains, thereby led to the change in crystallization and aggregation state of the polymer. Moreover, their porous structure and active sites also promoted the Lewis acid–base interactions with the polymer and TFSI − , promoting ion dissociation. Temperature-induced phase variation produced distinct porous crystalline structures formed the tetragonal-phase MOF-76-Ce exhibiting excellent properties with a room-temperature ionic conductivity of 7.89×10⁻ 4  S cm⁻ 1 and a Li + transference number of 0.79. The full cell assembled with this electrolyte and high-energy-density polyanionic LiMn 0.6 Fe 0.4 PO 4 cathodes demonstrated good cycling stability. It could reach discharge capacity of 147 mAh g⁻ 1 at 0.2 C and a capacity retention of 91% after 200 cycles at 0.5 C under a high cutoff voltage of 4.5 V. This work offers an effective filler strategy for developing high-performance quasi-solid-state polymer electrolytes and highlights the crucial role of metal–organic framework topology in advancing safe and durable lithium metal batteries. Graphical abstract