Chen Zhenlian, Schwarz Bjoern, Zhang Xianhui, Du Wenqiang, Zheng Lirong, Tian Ailing, Zhang Ying, Zhang Zhiyong, Zeng Xiao Cheng, Zhang Zhifeng, Huai Liyuan, Wu Jinlei, Ehrenberg Helmut, Wang Deyu, Li Jun
Key Laboratory of Optoelectronic Chemical Materials and Devices, School of Chemical and Environmental Engineering, Jianghan University, Wuhan, China.
Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, China.
Angew Chem Int Ed Engl. 2021 Apr 26;60(18):10056-10063. doi: 10.1002/anie.202100730. Epub 2021 Mar 24.
Oxygen redox in Li-rich oxides may boost the energy density of lithium-ion batteries by incorporating oxygen chemistry in solid cathodes. However, oxygen redox in the bulk usually entangles with voltage hysteresis and oxygen release, resulting in a prolonged controversy in literature on oxygen transformation. Here, we report spectroscopic evidence of peroxo species formed and confined in silicate cathodes amid oxygen redox at high voltage, accompanied by Co /Co redox dominant at low voltage. First-principles calculations reveal that localized electrons on dangling oxygen drive the O-O dimerization. The covalence between the binding cation and the O-O dimer determines the degree of electron transfer in oxygen transformation. Dimerization induces irreversible structural distortion and slow kinetics. But peroxo formation can minimize the voltage drop and volume expansion in cumulative cationic and anionic redox. These findings offer insights into oxygen redox in the bulk for the rational design of high-energy-density cathodes.
富锂氧化物中的氧氧化还原反应可通过在固态阴极中引入氧化学来提高锂离子电池的能量密度。然而，本体中的氧氧化还原反应通常与电压滞后和氧释放纠缠在一起，导致文献中关于氧转化的争论持续不断。在此，我们报告了在高压氧氧化还原反应过程中，过氧物种在硅酸盐阴极中形成并受限的光谱证据，同时在低电压下以Co/Co氧化还原为主。第一性原理计算表明，悬空氧上的局域电子驱动O-O二聚化。结合阳离子与O-O二聚体之间的共价性决定了氧转化过程中的电子转移程度。二聚化会导致不可逆的结构畸变和缓慢的动力学过程。但是过氧物种的形成可以使累积的阳离子和阴离子氧化还原反应中的电压降和体积膨胀最小化。这些发现为高能密度阴极的合理设计提供了关于本体中氧氧化还原反应的见解。
