High-Performance PEO-Based All-Solid-State Battery Achieved by Li- Conducting High Entropy Oxides

A rock-salt-structured Li-conducting high entropy oxide was prepared and utilized as an active filler in a polyethylene oxide (PEO)-based solid-state composite electrolyte. X-ray diffraction and high-resolution transmission electron microscopy were adopted to analyze the crystal structure of the high entropy oxide containing 20% of Li ions (HL20). The HL20 was crystallized in the Fm (3) over barm space group with Li+ ions located at the center of the MO6 octahedra. The ionic conductivity of the composite membrane at 30 degrees C reaches 3.44 x 10(-5) S cm(-1). The inflection point of activation energy of the membrane with HL20 decreases by 5 degrees C compared with that of the pure PEO membrane. In the galvanostatic plating/ stripping test, the Li||Li symmetric batteries could be cycled at a current density of 200 mu A cm(-2) for over 1200 h with an overpotential of 140 mV. The Li||LiFePO4 full battery could be charged/discharged at 0.5 C for 100 circles with a high capacity retention rate of 91%. Excellent rate performance is also achieved at lower temperatures and higher rates, showing the superiority of HL20 as an active filler. This work sheds light on the development of high entropy oxide as a new type of fast ionic conductor, promoting the practical application of all-solid-state batteries at a lower temperature.

Automated summary

A rock-salt-structured Li-conducting high entropy oxide was prepared and used as an active filler in a PEO-based solid-state composite electrolyte. The study demonstrated that the high entropy oxide significantly improved the ionic conductivity of the composite membrane and reduced its activation energy. The Li||Li symmetric batteries and Li||LiFePO4 full batteries with the high entropy oxide showed excellent rate performance at different temperatures and rates, suggesting its superiority as an active filler. This research contributes to the development of all-solid-state batteries at lower temperatures.