A New Composite Proton Conductor as a High-Performance Electrolyte toward Low-Temperature Protonic Ceramic Cells

Protonic ceramic cells (PCCs) have drawn great attention on account of their reversibility and high efficiency. We propose a strategy to design a composite proton conductor composed of BaZr0.1Ce0.7Y0.2O3−δ (BZCY) and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) sintered through ultrafast high-temperature sintering, showing a reduced sintering temperature of 1170 °C. BZCY particles are uniformly distributed within a continuously conformal framework formed by the low-melting LLZTO phase. The unique structural design avoids the sharp edge between BZCY particles caused by the soft LLZTO phase, resulting in faster proton migration at the grain boundary region. As a result, the new composite electrolyte exhibits a proton conductivity of 0.028 S cm–1 at 600 °C, 4.5 times that of BZCY. Furthermore, we demonstrate that LLZTO exhibits considerable proton conductivity by combining our experimental and simulation results. This research advances the potential of combining proton and lithium-ion conducting composites with high proton conductivity and low sintering temperature for PCCs.