摘要
由高温分解 KMnO4制备层状 K-birnessite 前驱体, 再经过离子交换反应制备 Cr-birnessite. 在 2.5 mol/L LiOH 水溶液中研究了 Cr-birnessite 电极的可充性. 据 AAS 测试和锰的价态分析得 Cr-birnessite 的分子式为 Cr0.26Mn0.84O2+0.04.SEM 显示 Cr-birnessite 为片状颗粒, XRD 分析表明其层状结构在充放电前后没有明显变化. 恒电流充放电实验表明在2.5 mol/L LiOH 水溶液中以 1 C 大电流速率对 Cr-birnessite 进行全充全放循环可达 70 次而保持初始容量的 93%, 显示了良好的循环可逆性. AAS 表明在充放电过程中材料中的铬离子没有脱嵌, Li+脱嵌/嵌入. 循环伏安曲线表明在大约-0.3 和 0 V 出现两个氧化峰, 在-0.1 V 左右出现一个还原峰, 循环 20 周电流大小没有明显变化. 利用恒电位阶跃法测得 Li+在 Cr-birnessite 中的扩散系数平均值为 1.57×10-10 cm2·s-1.
The Cr-birnessite was prepared by ion exchange from K-birnessite, which was synthesized by calcination of KMnO4. Measurement methods of scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), atomic absorption spectrometry (AAS), slow-scanning cyclic voltammetric and galvanostatic discharge/charge characteristics of the Cr-birnessite were applied. Potentiostatic method was used for the determination of a chemical diffusion coefficient D. XRD patterns indicate that Cr-birnessite has layered structure. Slow-scanning voltammograms exhibit single peak occurring in the range of -0.2 to 0 V on discharge and two peaks at about -0.3 and 0 V on charge. The galvanostatic discharge/charge curves indicate that the Cr-birnessite has better rechargeability at a high discharge/charge rate. Li+ can reversibly intercalate into and de-intercalate from the Cr-birnessite during discharge and charge. The average value of the chemical diffusion coefficient D of Li+ intercalated into the Cr-birnessite is 1.57 x 10(-10) cm(2) . s(-1).
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2005年第3期229-233,共5页
Acta Chimica Sinica
基金
国家自然科学基金(No. 20077020)资助项目.
