Anion-immobilized polymer electrolyte achieved by cationic metal-organic framework filler for dendrite-free solid-state batteries

Abstract

The practical application of solid-state batteries (SSBs) is restricted by the growth of lithium dendrites, which could be attributed to uneven Li deposition mainly caused by the barrier of free anions in solid polymer electrolytes (SPEs). Herein, a novel cationic metal-organic framework (CMOF) is proposed to immobilize anions and guide Li+ uniform distribution for constructing dendrite-free SSBs. The CMOF grafted with -NH2 group protects the ether oxygen of polymer chains by hydrogen bonds, which extends the electrochemical window to 4.97 V. Such CMOF tethers anions by electrostatic interaction of charge carriers and the specific surface area as high as 1082 m2 g−1 further strengthens the effect of anion absorption on the surface of CMOF, leading to a high Li+ transference number of 0.72. With the anion-immobilized composite electrolyte, the Li symmetrical cells can continuously operate for 400 h at 0.1 mA cm−2 and 200 h at 0.5 mA cm−2 without discernable dendrites, respectively. In addition, the SSBs constructed with LiFePO4 and LiFe0.15Mn0.85PO4 cathodes demonstrate excellent rate and cycle performances at 60 °C. These results indicate that anion immobilization by CMOF is a promising strategy to realize dendrite-free SSBs with high energy density and safety.