Perez Arnaud J, Vasylenko Andrij, Surta T Wesley, Niu Hongjun, Daniels Luke M, Hardwick Laurence J, Dyer Matthew S, Claridge John B, Rosseinsky Matthew J
Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom.
Stephenson Institute for Renewable Energy, University of Liverpool, Chadwick Building, Peach Street, Liverpool L69 7ZF, United Kingdom.
Inorg Chem. 2021 Dec 20;60(24):19022-19034. doi: 10.1021/acs.inorgchem.1c02882. Epub 2021 Dec 6.
Li-rich rocksalt oxides are promising candidates as high-energy density cathode materials for next-generation Li-ion batteries because they present extremely diverse structures and compositions. Most reported materials in this family contain as many cations as anions, a characteristic of the ideal cubic closed-packed rocksalt composition. In this work, a new rocksalt-derived structure type is stabilized by selecting divalent Cu and pentavalent Sb cations to favor the formation of oxygen vacancies during synthesis. The structure and composition of the oxygen-deficient LiCuSbO□ phase is characterized by combining X-ray and neutron diffraction, ICP-OES, XAS, and magnetometry measurements. The ordering of cations and oxygen vacancies is discussed in comparison with the related LiCuO□ and LiSbO□ phases. The electrochemical properties of this material are presented, with only 0.55 Li extracted upon oxidation, corresponding to a limited utilization of cationic and/or anionic redox, whereas more than 2 Li ions can be reversibly inserted upon reduction to 1 V vs Li/Li, a large capacity attributed to a conversion reaction and the reduction of Cu to Cu. Control of the formation of oxygen vacancies in Li-rich rocksalt oxides by selecting appropriate cations and synthesis conditions affords a new route for tuning the electrochemical properties of cathode materials for Li-ion batteries. Furthermore, the development of material models of the required level of detail to predict phase diagrams and electrochemical properties, including oxygen release in Li-rich rocksalt oxides, still relies on the accurate prediction of crystal structures. Experimental identification of new accessible structure types stabilized by oxygen vacancies represents a valuable step forward in the development of predictive models.
富锂岩盐氧化物作为下一代锂离子电池高能量密度阴极材料具有很大潜力，因为它们具有极其多样的结构和组成。该家族中大多数已报道的材料阳离子和阴离子数量相同，这是理想立方密堆积岩盐组成的一个特征。在这项工作中，通过选择二价铜和五价锑阳离子来促进合成过程中氧空位的形成，从而稳定了一种新的源自岩盐的结构类型。通过结合X射线和中子衍射、电感耦合等离子体发射光谱法（ICP - OES）、X射线吸收光谱法（XAS）和磁测量，对缺氧的LiCuSbO□相的结构和组成进行了表征。与相关的LiCuO□和LiSbO□相比较，讨论了阳离子和氧空位的有序排列。展示了这种材料的电化学性能，氧化时仅脱出0.55个锂，这对应于阳离子和/或阴离子氧化还原的有限利用，而在相对于Li/Li还原至1 V时，有超过2个锂离子可以可逆地嵌入，这一大容量归因于转化反应以及铜还原为铜。通过选择合适的阳离子和合成条件来控制富锂岩盐氧化物中氧空位的形成，为调整锂离子电池阴极材料的电化学性能提供了一条新途径。此外，开发能够预测相图和电化学性能（包括富锂岩盐氧化物中的氧释放）所需详细程度的材料模型，仍然依赖于晶体结构的准确预测。通过氧空位稳定的新可及结构类型实验鉴定是预测模型开发中向前迈出的有价值一步。
