Zhou Zizhen, Chu Dewei, Gao Bo, Momma Toshiyuki, Tateyama Yoshitaka, Cazorla Claudio
School of Materials Science and Engineering, UNSW Australia, Sydney, NSW 2052, Australia.
Graduate School of Advanced Science and Engineering, Waseda University, 3-4-1, Okubo, Shinjuku-ku, Tokyo 169-8555, Japan.
ACS Appl Mater Interfaces. 2022 Aug 17;14(32):37009-37018. doi: 10.1021/acsami.2c07560. Epub 2022 Aug 5.
Lithium-rich manganese-based oxides (LRMO) are regarded as promising cathode materials for powering electric applications due to their high capacity (250 mAh g) and energy density (∼900 Wh kg). However, poor cycle stability and capacity fading have impeded the commercialization of this family of materials as battery components. Surface modification based on coating has proven successful in mitigating some of these problems, but a microscopic understanding of how such improvements are attained is still lacking, thus impeding systematic and rational design of LRMO-based cathodes. In this work, first-principles density functional theory (DFT) calculations are carried out to fill out such a knowledge gap and to propose a promising LRMO-coating material. It is found that SrTiO (STO), an archetypal and highly stable oxide perovskite, represents an excellent coating material for LiNiMnO (LNMO), a prototypical member of the LRMO family. An accomplished atomistic model is constructed to theoretically estimate the structural, electronic, oxygen vacancy formation energy, and lithium-transport properties of the LNMO/STO interface system, thus providing insightful comparisons with the two integrating bulk materials. It is found that (i) electronic transport in the LNMO cathode is enhanced due to partial closure of the LNMO band gap (∼0.4 eV) and (ii) the lithium ions can easily diffuse near the LNMO/STO interface and within STO due to the small size of the involved ion-hopping energy barriers. Furthermore, the formation energy of oxygen vacancies notably increases close to the LNMO/STO interface, thus indicating a reduction in oxygen loss at the cathode surface and a potential inhibition of undesirable structural phase transitions. This theoretical work therefore opens up new routes for the practical improvement of cost-affordable lithium-rich cathode materials based on highly stable oxide perovskite coatings.
富锂锰基氧化物（LRMO）因其高容量（250 mAh/g）和能量密度（约900 Wh/kg）而被视为为电力应用提供动力的有前景的阴极材料。然而，较差的循环稳定性和容量衰减阻碍了这类材料作为电池组件的商业化。基于涂层的表面改性已被证明在缓解其中一些问题方面是成功的，但仍缺乏对如何实现这种改进的微观理解，从而阻碍了基于LRMO的阴极的系统和合理设计。在这项工作中，进行了第一性原理密度泛函理论（DFT）计算，以填补这一知识空白并提出一种有前景的LRMO涂层材料。发现典型且高度稳定的氧化物钙钛矿SrTiO₃（STO）是LRMO家族的典型成员LiNiMnO₃（LNMO）的优异涂层材料。构建了一个完整的原子模型，从理论上估计LNMO/STO界面系统的结构、电子、氧空位形成能和锂传输特性，从而与两种整合的块状材料进行有见地的比较。结果发现：（i）由于LNMO带隙（约0.4 eV）部分闭合，LNMO阴极中的电子传输得到增强；（ii）由于所涉及的离子跳跃能垒较小，锂离子可以在LNMO/STO界面附近以及STO内部轻松扩散。此外，靠近LNMO/STO界面处氧空位的形成能显著增加，从而表明阴极表面的氧损失减少，并且可能抑制不期望的结构相变。因此，这项理论工作为基于高度稳定的氧化物钙钛矿涂层实际改进经济实惠的富锂阴极材料开辟了新途径。
