1：Experimental Design and Method Selection:

The study uses conventional solid-state synthesis to prepare Li+-doped BaTiO3 ceramics with different Li+ doping amounts (4%, 6%, 8%). Aging experiments involve comparing fresh (air-quenched from 200°C) and aged (room temperature for ten days) samples. Ferroelectric hysteresis loops and dielectric properties are measured to analyze the electrocaloric effect using Maxwell's equations (indirect method).

2：Sample Selection and Data Sources:

Samples include BaTiO3 and Li+-doped BaTiO3 (LBT4, LBT6, LBT8) ceramics synthesized from high-purity BaCO3, TiO2, and Li2CO3 powders. Data are collected from XRD, SEM, dielectric constant measurements, and ferroelectric hysteresis loops.

3：List of Experimental Equipment and Materials:

Equipment includes planetary ball mill (Retsch PM 100), Rigaku Miniflex 600 XRD, Philips XL 30SFEG SEM, Keysight Technologies E4980AL LCR meter, AixACCT TF1000 Ferroelectric Analyzer. Materials include BaCO3 (>99.5%, Enteknomaterials), TiO2 (>99.5%, Enteknomaterials), Li2CO3 (99.999%, Sigma-Aldrich), PVA binder, yttria-stabilized zirconia balls, high-density polyethylene jar, silver paste.

4：5%, Enteknomaterials), TiO2 (>5%, Enteknomaterials), Li2CO3 (999%, Sigma-Aldrich), PVA binder, yttria-stabilized zirconia balls, high-density polyethylene jar, silver paste. Experimental Procedures and Operational Workflow:

4. Experimental Procedures and Operational Workflow: Synthesis involves mixing powders in ethanol for 18 hours, calcining at 1000°C for 5 hours, adding Li2CO3 and binder, ball-milling, drying, pressing into discs, binder burnout at 600°C, sintering at 1200°C for 5 hours. Density measured by Archimedes method. XRD and SEM for structural analysis. Dielectric constant measured from 40-200°C at 1 kHz. Ferroelectric hysteresis loops measured at 10 Hz from 30-150°C. Aging: fresh samples prepared by holding at 200°C for one day and air quenching; aged samples kept at room temperature for ten days before measurement.

5：Data Analysis Methods:

XRD patterns analyzed using GSAS-II software for profile fitting. Grain size determined by linear intercept method from SEM. Electrocaloric temperature change (ΔT) calculated using Maxwell's equations with small linear increments formula, assuming specific heat capacity of 500 J/(kg K) and measured densities.