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

## TL;DR

This paper shows that using nano-sized LLZTO particles in LiFePO4 cathodes improves the performance of solid-state lithium batteries by enhancing ion transport and stability.

## Contribution

The novelty lies in demonstrating that reducing LLZTO particle size enhances cathode performance in solid-state lithium batteries.

## Key findings

- Nano-LLZTO increases ionic conductivity to 6.48 × 10–5 S cm–1 compared to 1.03 × 10–5 S cm–1 for micro-LLZTO.
- The composite cathode achieves 99.6% Coulombic efficiency and 144 mAh g–1 at 1C.
- The cathode retains 95% of its initial capacity after 200 cycles at 0.2C.

## Abstract

Solid-state lithium batteries (SSLBs) offer improved
safety and
stability over conventional liquid-electrolyte systems but often suffer
from sluggish ion transport and poor interfacial contact within the
cathode. To address these limitations, we investigate the incorporation
of nanosized Li6.75La3Zr1.75Ta0.25O12 (nano-LLZTO) particles into a LiFePO4 cathode to enhance ionic conductivity and electrochemical
performance. Finite element method simulations and experiments reveal
that downsizing LLZTO from the microscale to the nanoscale substantially
enhances Li+ flux uniformity and ionic conductivity (6.48
× 10–5 S cm–1 vs 1.03 ×
10–5 S cm–1), forming more continuous
ion-transport networks. The LiFePO4/nano-LLZTO cathode
exhibits reduced polarization, higher Coulombic efficiency (99.6%),
and superior high-rate capability compared with the microsized LLZTO
counterpart, achieving 144 mAh g–1 at 1C. Cross-sectional
analyses confirm that nano-LLZTO forms homogeneous interfacial coatings,
improving ionic percolation and mitigating transport bottlenecks.
In situ X-ray absorption near edge structure and extended X-ray absorption
fine structure analyses further confirm enhanced redox reversibility
and structural stability of Fe sites. Consequently, the LiFePO4/nano-LLZTO composite cathode retains 95% of its initial capacity
(154 mAh g–1) after 200 cycles at 0.2C and 25 °C.
This work demonstrates that reducing LLZTO particle size effectively
enhances the cathode ion-transport network and ionic conductivity,
thereby improving the rate capability and cycling stability of LiFePO4-based SSLBs.