Enhanced Rate Capability in B-Site High-Entropy Perovskite Oxide Ceramics: The Case of La(Co0.2Cr0.2Ni0.2Ga0.2Ge0.2)O3

This study employed the solid-state method to prepare perovskite-type high-entropy oxide materials La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 and La(Co0.2Cr0.2Ni0.2Ga0.2Ge0.2)O3 with equimolar ratios at the B-site and explored the effects of sintering temperature on the phase structure and electrochemical properties of high-entropy oxide ceramics. The results show that after sintering at 1300°C, both samples exhibit orthorhombic perovskite structures. Both have a relative density of >97%, while La(Co0.2Cr0.2Ni0.2Ga0.2Ge0.2)O3 has a significantly larger grain size. Using these materials as electrodes, the cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) results indicate that the working electrode made of La(Co0.2Cr0.2Ni0.2Ga0.2Ge0.2)O3 shows higher oxidation reaction activity in CV measurements and achieved a specific capacitance of 74.3 F/g at a current density of 1 A/g in GCD measurements, which still maintained 73% of its initial specific capacitance (54.3 F/g) when the current density was increased to 10 A/g. Its capacitance retention rate is 10 percentage points higher than that of La(Co0.2Cr0.2Fe0.2Mn0.2Ni0.2)O3 at high current densities, demonstrating superior rate performance.