# Li—Co Dual‐Doped Ceria‐Based Composite as a Promising Low‐Temperature Electrolyte for Metal‐Supported Solid Oxide Electrolyzers

## TL;DR

A new Li-Co doped electrolyte improves performance and lowers sintering temperatures in solid oxide electrolyzers for green energy.

## Contribution

A Li–Co dual-doped GDC electrolyte is developed with enhanced sinterability and ionic conductivity for low-temperature SOECs.

## Key findings

- Li–Co codoping reduces sintering temperature and improves grain connectivity in GDC.
- The optimized sample achieves an ionic conductivity of 2.17 × 10−2 S cm−1 at 750 °C.
- The electrolyte outperforms YSZ in electrochemical performance in symmetric SOECs.

## Abstract

Solid oxide electrolysis cells (SOECs) are among the most efficient energy‐conversion devices for power‐to‐X applications in green energy technologies. Here, we report a high‐level (5 mol%) Li‐ and Co‐dual‐doped gadolinium‐doped ceria (GDC) electrolyte synthesized under an inert atmosphere, suitable for fabricating SOECs using conventional ferritic steel supports. The doped GDC exhibits uniform dopant incorporation and a single‐phase cubic fluorite structure, achieving 98.18% relative density at 950 °C. Dilatometry and microstructural analyses reveal that Li–Co codoping significantly reduces sintering temperature and improves grain connectivity. Time‐of‐flight secondary ion mass spectrometry shows a Li,Co‐rich surface layer whose thickness depends on sintering conditions, while Raman spectroscopy confirms the presence of a LiCoO2 phase and temperature‐dependent oxygen‐vacancy concentration. Electrochemical impedance spectroscopy demonstrates enhanced ionic conductivity, particularly for the sample sintered at 950 °C (denoted 5LC‐4), which achieves increases of 269.5% at 450 °C and 138.85% at 750 °C compared with commercial GDC. The ionic conductivity reaches 2.17 × 10−2 S cm−1 with an activation energy of 0.32 eV. A symmetric five‐layer SOEC integrating 5LC‐GDC exhibits superior electrochemical performance to yttria‐stabilized zirconia (YSZ) support, achieving a peak power density of 267.5 mW cm−2 at 850 °C.

Enhanced sinterability and ionic conductivity are achieved with Li and Co dual‐doped GDC electrolytes for metal‐supported solid oxide electrolyzers. The optimized sample shows 2.17 × 102 S cm1 at 750 °C, which typically approaches the superionic solid electrolyte conductivity ranges. A tubular cell fabrication and analysis demonstrated its potential as a high‐performance electrolyte for metal‐supported SOCs.© 2026 WILEY‐VCH GmbH