Heat Treatment Effect on Microstrain and Electrochemical Performance of Nano-sized FeS₂ Cathode for Thermal Batteries

摘要

Iron pyrite (FeS2) is the most widely used material for cathodes in thermal batteries, attributed to itshigh specific energy density and natural abundance as well as low cost. In this study, nano-sized FeS2powders were synthesized by high-energy milling to improve electrochemical performance Li(Si)/FeS2thermal battery, and their particle sizes, microstrain, and thermal stabilities were investigated byparticle size analysis (PSA), X-ray diffraction (XRD), and thermogravimetric analysis (TGA).Electrochemical performance was evaluated by single-cell discharge tests. The average particle sizedecreased from 107 m to 261 nm after 10 h of dry milling, resulting in microstrain on FeS2. Thismicrostrain led to the thermal instability of the FeS2 powder, causing an increase of the open-circuitvoltage of Li(Si)/FeS2 single cells. The voltage was stabilized from 2.45 V to 1.93 V, and thermalinstability was mitigated by the heat treatment of the FeS2 powder up to 400C. The electrochemicalperformance of the single cells fabricated with nano-sized FeS2 thermally annealed at 400C improvedby 57% as compared with that of untreated ones at a cut-off voltage of 1.4 V.