Garnet-Type Fast Li-Ion Conductors with High Ionic Conductivities for All-Solid-State Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• All-solid-state Li-ion batteries (ASSBs) promise higher energy density and safety than conventional batteries.
• Challenges include low ionic conductivity of solid electrolytes and high interfacial resistance.
• Garnet-type Li-ion conducting oxides are promising solid electrolyte candidates.

Purpose of the Study:

• To enhance Li-ion conductivity in garnet electrolytes by doping with large-radius Rb.
• To investigate the effect of Rb doping on the Li-ion conductivity of cubic Li6.10Ga0.30La3Zr2O12.
• To evaluate the performance of Rb-doped garnet electrolytes in ASSBs.

Main Methods:

• Doping cubic Li6.10Ga0.30La3Zr2O12 with Rb at the La site.
• Synthesizing Li6.20Ga0.30La2.95Rb0.05Zr2O12 solid electrolyte.
• Measuring ionic conductivity at room temperature.
• Constructing ASSBs with metallic Li anode, LiFePO4 cathode, and the synthesized electrolyte.
• Adding Li(CF3SO2)2N salt to the cathode to reduce interfacial resistance.

Main Results:

• The synthesized Li6.20Ga0.30La2.95Rb0.05Zr2O12 electrolyte achieved a record Li-ion conductivity of 1.62 mS cm-1 at room temperature.
• ASSBs demonstrated a high initial discharge capacity of 152 mAh g-1.
• Good cycling stability was observed, retaining 110 mAh g-1 after 20 cycles at 0.05 C and 60 °C.
• Addition of Li(CF3SO2)2N salt effectively reduced interfacial resistance.

Conclusions:

• Rb doping is a viable strategy to significantly enhance Li-ion conductivity in garnet solid electrolytes.
• The developed Rb-doped garnet electrolyte shows great potential for practical ASSBs.
• Reduced interfacial resistance is crucial for achieving high performance in ASSBs.