LiFePO₄/Nano-LLZTO Composite Cathodes for Enhanced Performance of Solid-State Lithium Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Solid-State Batteries

Background:

• Solid-state lithium batteries (SSLBs) offer enhanced safety but face challenges with ion transport and interfacial contact in cathodes.
• LiFePO4 cathodes are promising but require improved ionic conductivity for better performance.

Purpose of the Study:

• To investigate the impact of nanosized Li6.75La3Zr1.75Ta0.25O12 (nano-LLZTO) particles on LiFePO4 cathode performance in SSLBs.
• To enhance ionic conductivity and electrochemical performance by optimizing the ion-transport network.

Main Methods:

• Finite element method simulations to model ion transport.
• Experimental synthesis and characterization of LiFePO4/LLZTO composite cathodes with varying LLZTO particle sizes (nano vs. micro).
• Electrochemical testing (rate capability, cycling stability, Coulombic efficiency) and in situ/ex situ spectroscopic analyses (XAS).

Main Results:

• Downsizing LLZTO to nanoscale significantly increased ionic conductivity (6.48 × 10-5 S cm-1) and improved Li+ flux uniformity compared to microscale LLZTO (1.03 × 10-5 S cm-1).
• The LiFePO4/nano-LLZTO cathode demonstrated reduced polarization, higher Coulombic efficiency (99.6%), and superior high-rate capability (144 mAh g-1 at 1C).
• Homogeneous interfacial coatings formed by nano-LLZTO improved ionic percolation and structural stability, leading to 95% capacity retention after 200 cycles.

Conclusions:

• Reducing LLZTO particle size to the nanoscale is an effective strategy to enhance the ion-transport network and ionic conductivity in LiFePO4-based SSLBs.
• The nano-LLZTO incorporation significantly improves the rate capability and long-term cycling stability of SSLBs.
• This approach offers a pathway to developing safer and higher-performing solid-state batteries.