Latticed Cd²⁺ Doping for Enhanced Ionic Transport in Li₂ZrCl₆ Solid-State Electrolytes toward High-Performance...

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Chemistry

Background:

• Halide solid-state electrolytes (SSEs) are crucial for advanced all-solid-state lithium-ion batteries (ASSLBs) due to their stability and deformability.
• Li$_{2}$ZrCl$_{6}$ (LZC) shows promise as a cost-effective SSE but suffers from low ionic conductivity, hindering practical ASSLB applications.

Purpose of the Study:

• To enhance the ionic conductivity and electrochemical window of Li$_{2}$ZrCl$_{6}$ through cadmium doping.
• To investigate the structural and electrochemical properties of Cd$^{2+}$-doped Li$_{2+2x}$Zr$_{1-x}$Cd$_{x}$Cl$_{6}$ for ASSLB applications.

Main Methods:

• Synthesis of a series of Cd$^{2+}$-doped lithium-rich superionic conductors, Li$_{2+2x}$Zr$_{1-x}$Cd$_{x}$Cl$_{6}$ (0 ≤ x ≤ 0.2).
• Structural characterization using a Li$_{3}$YCl$_{6}$-like trigonal structure.
• Electrochemical testing of the optimized Li$_{2.1}$Zr$_{0.95}$Cd$_{0.05}$Cl$_{6}$ (LZC-5Cd) in an all-solid-state lithium-ion battery configuration.

Main Results:

• Cd$^{2+}$ incorporation led to anisotropic lattice expansion and enhanced carrier concentration.
• LZC-5Cd achieved a high ionic conductivity of 9.8 × 10$^{-4}$ S cm$^{-1}$ at 30 °C and an electrochemical window up to 4.11 V.
• The ASSLB with LZC-5Cd demonstrated a reversible capacity of 161.4 mAh g$^{-1}$ at 0.1 C and 80.69% capacity retention over 250 cycles.

Conclusions:

• Cd$^{2+}$ doping is an effective strategy to boost ionic conductivity and broaden the working potential of halide SSEs.
• The developed LZC-5Cd material shows potential for large-scale application in halide-based ASSLBs.
• This work provides a cost-effective structural engineering approach for advanced energy storage solutions.