β″-Al_2O_3在钠硫电池钠电极中表面退化的交流阻抗研究

Study of A.C.Impedance due to Surface Degradation of β″-Al_2O_3 on the Sodium Electrode Utilized in Sodium-Sulfur Cells

钠硫电池中 Na/β″-Al_2O_3界面上的极化可以出现电阻增加、非欧姆电池电阻、不对称电池电阻以及瞬态高电池电阻。应用低频交流法测量了电池阻抗对频率的依从性,研究了电池充放电过程中阻抗膜在 Na/β″-Al_2O_3界面上的形成过程。实验结果表明在电池放电中电阻的增加、瞬态的高电阻与β″-Al_2O_3管的内表面富钠以及β″-Al_2O_3在钠电极中的表面退化有关。β″-Al_2O_3的表面退化,因形成局部高的充电电流密度,导致固体电解质钠沉积的贯穿而损坏。提山了各种机理解释了β″-Al_2O_3表面退化现象。

Interfacial polariszation on the Na/β″-Al_2O_3 interface can manifest itself in thesodium-sulfur cells as resistance rise,non ohmic cell resistance,asymmetric cells re-sistance and transient high cell resistance.Using an a.c.method at low frequencies,the dependence of cells impedance on frequencies were measured and the formativeprocess of the resistive surface film on the Na/β″-Al_2O_3 interface was studied duringcharge-discharge cycles.These results shew that the observed resistance rise andtransient high cell resistance on cell discharge were associated with the soda richon the inner surface of β″-Al_2O_3 tube and the surface degradation of β″Al_2O_3in the Sodium electrode.The surface degradation of β″-Al_2O_3 may lead to thefailure of the solid electrolyte by sodium deposition penetration due to locally highcharging current density.Various mechanisms have been proposed to explain thedegradation phenomena.