Chemical Sciences and Engineering Division, Argonne National Laboratory, Argonne, IL, USA.
Phys Chem Chem Phys. 2013 Mar 21;15(11):3764-71. doi: 10.1039/c3cp00069a.
We report on the use of a petroleum coke-based activated carbon (AC) with very high surface area for a Li-O(2) battery cathode without the use of any additional metal catalysts. Electrochemical measurement in a tetra(ethylene) glycol dimethyl ether-lithium triflate (TEGDME-LiCF(3)SO(3)) electrolyte results in two voltage plateaus during charging at 3.2-3.5 and 4.2-4.3 V versus Li(+)/Li. Herein we present evidence from Raman and magnetic measurements that the lower plateau corresponds to a form of lithium peroxide with superoxide-like properties characterized by a low temperature magnetic phase transition and a high O-O stretching frequency (1125 cm(-1)). The magnetic phase transition and the high O-O stretching frequency disappear when charged to above 3.7 V. Theoretical calculations indicate that a surface superoxide structure on lithium peroxide clusters and some lithium peroxide surfaces have an unpaired electron and a high O-O stretching frequency that help explain the observations. These results provide evidence that the form of the lithium peroxide discharge product is important to obtaining a low charge overpotential, and thus improving the round-trip efficiency between discharge and charge.
我们报告了一种基于石油焦的活性炭（AC）的应用，该活性炭具有非常高的比表面积，可用于锂-氧（2）电池阴极，而无需使用任何额外的金属催化剂。在四甘醇二甲醚-三氟甲磺酸锂（TEGDME-LiCF（3）SO（3））电解质中的电化学测量在 3.2-3.5 和 4.2-4.3 V 对相对于 Li（+）/Li 充电时导致两个电压平台。在这里，我们从拉曼和磁性测量中提供证据表明，较低的平台对应于一种具有超氧化物性质的过氧化锂形式，其特征是低温磁相变和高 O-O 伸缩频率（1125 cm（-1））。当充电至 3.7 V 以上时，磁相变和高 O-O 伸缩频率消失。理论计算表明，过氧化锂簇表面上的超氧化物结构和一些过氧化锂表面具有未配对电子和高 O-O 伸缩频率，这有助于解释观察结果。这些结果表明，过氧化锂放电产物的形式对于获得低充电过电位很重要，从而提高放电和充电之间的往返效率。
