Poly(ethylene glycol) brush on Li6.4La3Zr1.4Ta0.6O12 towards intimate interfacial compatibility in composite polymer electrolyte for flexible all-solid-state lithium metal batteries

Polyethylene oxide (PEO)/Li 6.4 La 3 Zr 1.4 Ta 0.6 O 12 (LLZTO) composite solid electrolyte is considered as a promising electrolyte for lithium batteries . However, LLZTO nanoparticles tend to agglomerate in PEO/LLZTO composite polymer electrolyte due to interfacial incompatibility between PEO and LLZTO nanoparticles , which leads to low ionic conductivity , poor interface stability with the electrode, and inferior batteries cycling stability. In order to enhance interfacial compatibility, herein, LLZTO nanoparticles are modified through firstly surface-functionalizing by dopamine coating and then grafting poly (ethylene glycol) (PEG) brush on it via amino and epoxy reaction. As a consequence, the ionic conductivity of LLZTO/PEO composite polymer electrolyte filled with 2 wt% modified LLZTO increases up to 1.1 × 10 − 4 S cm −1 , which is about twice and 20 times in comparison with LLZTO/PEO filled with 2 wt% unmodified LLZTO and PEO electrolytes, respectively. Moreover, high oxidation potential of around 4.8 V and ionic transference number of 0.34 as well as good interface stability with lithium anode are also achieved. Thus, LiFePO 4 ||Li all-solid-state lithium metal batteries based on LLZTO/PEO composite polymer electrolyte filled with 2 wt% modified LLZTO exhibit excellent cyclic stability of 152.3 mAh g −1 with capacity retention of 90.35% at 0.5 C after 500 cycles under 60 °C.