Mixed Cationic and Anionic Redox in Ni and Co Free Chalcogen-Based Cathode Chemistry for Li-Ion Batteries
Mixed Cationic and Anionic Redox in Ni and Co Free Chalcogen-Based Cathode Chemistry for Li-Ion Batteries
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DOI：
10.1021/jacs.1c06828
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发表时间：
2021-09-15
影响因子：
15
通讯作者：
Arava, Leela Mohana Reddy
中科院分区：
文献类型：
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作者：
Nagarajan, Sudhan;Hwang, Sooyeon;Arava, Leela Mohana Reddy
随着基于过渡金属的层状氧化物的传统阳离子氧化还原中心达到其理论容量极限，混合阳离子和阴离子氧化还原阴极化学正在兴起。然而，由于金属-氧配体共价性较弱，过渡金属氧化物基阴极中通过吸收过量锂离子实现的这些阴离子氧化还原反应导致了稳定性问题。在这里，我们提出了一种改善金属-配体共价性的替代方法，即在阴极结构框架中引入电负性较小的硫族配体（硫），其中金属 d 带渗透到配体 p 带中，从而利用可逆混合阴离子和阳离子氧化还原化学。通过这种设计策略，我们报告了当在锂离子导电相（Li2SnS3）中引入部分填充的 d 轨道氧化还原电对（如 Fe2+/3+）时，开发新型层状正极材料系列的可能性。此外，电子能量损失光谱和 X 射线吸收近边缘结构分析用于定性识别 Li+ 提取过程中金属和配体位点的电荷贡献者。详细的高分辨率透射电子显微镜和高环形暗场扫描透射电子显微镜研究揭示了循环过程中多重氧化还原诱导的结构修饰及其表面非晶化和纳米孔的形成。这项研究的结果将为设计不含镍和钴的硫属元素阴极以及基于硫属元素的双阴离子和阳离子氧化还原阴极途径中的各种功能材料提供线索。
Mixed cationic and anionic redox cathode chemistry is emerging as the conventional cationic redox centers of transition-metal-based layered oxides are reaching their theoretical capacity limit. However, these anionic redox reactions in transition metal oxide-based cathodes attained by taking excess lithium ions have resulted in stability issues due to weak metal-oxygen ligand covalency. Here, we present an alternative approach of improving metal-ligand covalency by introducing a less electronegative chalcogen ligand (sulfur) in the cathode structural framework where the metal d band penetrates into the ligand p band, thereby utilizing reversible mixed anionic and cationic redox chemistry. Through this design strategy, we report the possibility of developing a new family of layered cathode materials when partially filled d orbital redox couples like Fe2+/3+ are introduced in the Li-ion conducting phase (Li2SnS3). Further, the electron energy loss spectroscopy and X-ray absorption near-edge structure analyses are used to qualitatively identify the charge contributors at the metal and ligand sites during Li+ extraction. The detailed high-resolution transmission electron microscopy and high annular dark field-scanning transmission electron microscopy investigations reveal the multi-redox induced structural modifications and its surface amorphization with nanopore formation during cycling. Findings from this study will shed light on designing Ni and Co free chalcogen cathodes and various functional materials in the chalcogen-based dual anionic and cationic redox cathode avenue.