Metal organic framework reinforced polymer electrolyte with high cation transference number to enable dendrite-free solid state Li metal conversion batteries

Solid polymer electrolytes are intrinsically advantageous over rigid inorganic ones in terms of their easy processability and scalability by film-based battery technology. Here, a three-dimensional (3D) structured Ce-based metal organic framework (Ce-MOF) nano-filler with plentiful catalytic active sites is introduced into polyethylene oxide (PEO) based electrolyte. This unusual filler with abundant cavities enables the strong Lewis acid-base interactions with both ether oxygen in PEO and anion in Li salt, leading to significantly improved ionic conductivity and Li+ transference number as high as 0.75. Such an electrolyte compositing can remarkably improve the mechanical (stretching) and thermal stabilities and effectively suppress Li dendrites, and the Li/Li symmetrical cells can continuously cycle without short circuit even under long-term 1800 h or relatively high current density of 0.4 mA cm−2. The polymer electrolyte composited with 10 wt% Ce-MOF can endow the integrated all-solid-state batteries with superior cycling stability and rate performance (e.g. with capacities as high as 120 mAh g−1 after 3800 cycles for Li/LiFePO4 and 300 mAh g−1 after 240 cycles for Li/FeF3). The electrolyte modification by MOF planting is expected to well alleviate the volume extrusion and species dissolution from the cathode side and promote its interface confinement especially during conversion reaction.