Solid-state electrolytes are one of the most promising strategies to mitigate the safety concerns in lithium-ion batteries caused by the thermal and electrochemical instabilities of liquid electrolytes. Solid-state electrolytes are classified typically into three categories, viz polymer electrolytes, ceramic electrolytes, and polymer-ceramic composite electrolytes. Composite electrolytes combine the advantages of polymer and ceramic electrolytes to advance the performance of solid-state electrolytes. As such, composite electrolytes usually exhibit high ionic conductivities and lithium-ion transference numbers compared to those associated with polymer electrolytes. Composite electrolytes also possess better interfacial contact with the cathode and the anode compared to that provided by rigid ceramic electrolytes. Polyethylene oxide (PEO)-garnet Li₇La₃Zr₂O₁₂ (LLZO) composite is one of the widely studied composite electrolytes for all-solid-state batteries because of the electrochemical stability of LLZO with the lithium metal anode and the good mechanical properties and processability of PEO electrolytes. However, the PEO-LLZO interface is still a problem, as the transport of lithium ions across it is very slow because of the large impedance observed in correspondence of this interface [1]. This then results in low lithium-ion conductivities that sometimes are even lower than those of the polymer electrolyte alone, and this hinders the full development of the LLZO-PEO composite electrolytes in all-solid-state batteries. In this work, the effect of the modification of the LLZO surface with lithium oxalate species to improve the interfacial properties of the LLZO-PEO composite is investigated.

REFERENCES

[1]. Gupta A, Sakamoto J. The Electrochemical Society Interface. 2019,28(2):63.