FeS_2和CoS_2正极材料的自放电性能比较

FeS_2和CoS_2是锂系热电池最常用的两种正极材料。经X射线衍射(XRD),扫描电子显微镜(SEM)以及热重分析(TGA)表征发现:二者具有相同的立方晶体结构,CoS_2的热分解温度比FeS_2高100℃左右。以LiB合金为负极材料、LiF-LiCl-LiBr低温共熔盐为电解质,分别采用CoS_2和FeS_2作为正极材料制备热电池,在500℃的温度下进行恒流放电实验。结果发现:在放电初期LiB/FeS_2体系的工作电压高于LiB/CoS_2体系,但在工作一段时间后被LiB/CoS_2体系反超;随着工作时间的延长,热电池可释放的电容量逐渐减少,LiB/FeS_2体系容量衰减的速率比LiB/CoS_2体系快。将热电池空载不同时间后再进行恒流放电,发现热电池实际可释放的电容量与工作时间呈现一元线性关系,以此计算出LiB/FeS_2电池和LiB/CoS_2电池的容量衰减率分别为17.7和3.92 C/min。

Self-discharge of FeS2 and CoS2 cathode materials

FeS2 and CoS2 are two common cathode materials for thermal batteries.After being characterized by XRD,SEM and TGA,the results shows that they have the identical cubic crystal structure,while the thermal decomposition temperature of CoS2 is about 100 ℃ higher than FeS2.Thermal batteries were prepared using LiB alloy as anode,LiF-LiCl-LiBr molten salts as electrolyte,either FeS2 or CoS2 as cathode.After being discharged at 500 ℃,it is found that LiB/FeS2 couple works at higher potential than LiB/CoS2 couple at the beginning of discharge,but the discharge potential for LiB/FeS2 couple decreases sharply and is overtaken by LiB/CoS2 couple after a period of discharge.The results also indicate that less and less capacity can be released with the increase of the working time,and the trend of capacity decay for LiB/FeS2 couple is greater than LiB/CoS2 couple.By changing time on open circuit before discharge at constant current,it is found that the capacity released has a linear relationship with the working time,from which it can be deduced that the rate of the capacity loss for LiB/FeS2 couple and LiB/CoS2 couple are 17.7 and 3.92 C/min,respectively.