The mixed ionic and electronic conductor (MIEC), as a classical family of high-performance cathode materials, is essential for ensuring the low-temperature operation performance and high efficiency of solid oxide fuel cells. The Fe-based double perovskites get the advantages of low cost, good thermal compatibility with the electrolyte, and good high-temperature stability, showing good application promise. However, due to the unsatisfactory electrochemical properties, Fe-based double perovskite MIECs are generally not sufficiently active for the oxygen reduction reaction. Herein, the consequences indicate that Zr-substitution of the Fe sites in the NdBaFe2O6-δ(NBF) lattice can obtain a higher oxygen vacancy concentration and a more high-lying position of the O p-band center simultaneously. Then, the Zr-doped NBF cathode obtains a higher oxygen-ion diffusion and oxygen surface exchange coefficients. The lower polarization resistance for NdBaFe1.9Zr0.1O6-δmeasured at 700 °C is 0.066 Ω·cm2 compared to 0.104 Ω·cm2 for NBF.
Wenjin Li,Zongyi Chen,Yansen Chen,Wenjie Duan,Guodong Liu,Youming Lv,Haitao Yang,Lei Yao
Chloride solid electrolytes (CSEs) have good compatibility with commercial oxide cathode materials and show great potential for application in all-solid-state Li metal batteries (ASSLMBs). However, achieving simultaneously low cost, high ionic conductivity, excellent moisture tolerance, and robust electrochemical stability with >4 V-class cathodes for CSEs remains challenging. Herein, we report a facile Zr substitution strategy to increase the degree of preferred orientation and lower the Li + diffusion barrier of the (001) plane, i.e. the ab plane, of Li 3 ScCl 6 , thus boosting the ion conduction kinetics and framework stability. As such, Li 2.5 Sc 0.5 Zr 0.5 Cl 6 exhibits a high conductivity of 2.23 mS cm −1 and low activation energy of 0.26 eV at room temperature (RT). ASSLMBs are constructed using a LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode, Li 2.5 Sc 0.5 Zr 0.5 Cl 6 electrolyte, and Li-In anode, and deliver an exceptional initial Coulombic efficiency of 89.6 % at RT and can run stably over 200 cycles with 90 % capacity retention at 0.2C. In-situ electrochemical impedance inspection of the battery further reveals a high interfacial stability between Li 2.5 Sc 0.5 Zr 0.5 Cl 6 and LiNi 0.8 Co 0.1 Mn 0.1 O 2 . Moreover, Li 2.5 Sc 0.5 Zr 0.5 Cl 6 demonstrates high wet fatness with a preserved structure stability and high ionic conductivity after exposure to atmosphere with 5 % relative humidity. Such humidity tolerance and cost-effectiveness solve two major obstacles for the application of CSEs.
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