Vacancy-mediated LaCl3-based superionic conductors for all-solid-state sodium batteries

Sodium-based halide solid electrolytes offer excellent electrochemical stability and favorable interfacial compatibility, yet their low ionic conductivity at room temperature limits their application in all-solid-state Na-ion batteries (ASSNIBs). Here, we develop a series of LaCl3-based sodium superionic conductors engineered through cation vacancy-concentration modulation, which facilitates the formation of a three-dimensional Na+ transport network and increases the density of ion-hopping sites. The optimized Na0.4Ta0.236La0.472Cl3 (NTLC) electrolyte achieves a Na+ conductivity of 1.38 × 10−3 S/cm at 30 ℃, with a reduced activation energy of 0.26 eV. It also exhibits excellent mechanical deformation and moderate high-voltage stability, resulting in enhanced interfacial compatibility. When paired directly with an uncoated NaCrO2 cathode, the NTLC catholyte enables ASSNIBs to cycle stably over 300 cycles with 89.7 % capacity retention at 0.3 C and room temperature. This work underscores the potential of vacancy-rich LaCl3-based sodium superionic conductors for advancing high-performance ASSNIBs.