Phase-selective defects engineering in dual-phase high entropy oxide for Li-ion storage

• Published in: Chemical engineering journal (Lausanne, Switzerland : 1996) Switzerland : 1996), 2024-05, Vol.488, p.151113, Article 151113
• Main Authors: Yang, Hengming, He, Linxin, Chen, Qingchun, Zhu, Junchao, Jiang, Guoquan, Qiu, Nan, Wang, Yuan
• Format: Article
• Language: English
• Subjects: Defective structure; Dual-phase structure; High entropy oxides; Intergrown interfaces; Phase-selective regulated
• ISSN: 1385-8947; 1873-3212
• DOI: 10.1016/j.cej.2024.151113

•By controlling the concentration of Li-ions, the phase composition of high entropy oxide (HEO) can be regulated.•A high concentration of point defects (i.e., oxygen vacancies) and extended defects (such as dislocations and stacking faults) can be introduced into the spinel phase.•Successful control over defect engineering in spinel-rocksalt dual-phase HEO has been achieved through phase-selective regulation.•The incorporation of an intergrown interface improves the conductivity and structural stability of electrode materials. This paper presents the effectiveness of phase-selective regulation in the Mg-Co-Ni-Mn-Zn-O-based spinel-rocksalt dual-phase high entropy oxide (HEO) for achieving novel electrochemical properties. The key factor distinguishing spinel from rocksalt in response to Li-ion incorporation is the separation of ions at tetrahedral sites, which offers greater structural adjustability and enables incoordinate defect regulation of individual phases. The optimized Li incorporation facilitates a high concentration of point defects (specifically oxygen vacancies) and appropriately extended defects (such as dislocations and stacking fault) in the spinel phase, accompanied by a spinel-rocksalt intergrown interface. These exquisite adjustments improve the conductivity, structural stability, and specific capacity of the HEO electrode material. Nevertheless, the ever-increasing Li content triggers the transformation from a spinel-rocksalt dual-phase HEO to a single-phase rocksalt HEO, resulting in serious lattice distortion and excessive defects that hinder the efficient transport of Li-ion, ultimately leading to unsatisfactory electrochemical performance. Thus, phase-selective engineering facilitates the determination of appropriate defects that synergistically interact with the intergrown interface and the dual-phase structure. The optimized HEO20 exhibits outstanding electrochemical performance, with a high initial discharge capacity of 2049.8 mAh g−1 at 0.1C and a high-rate capability of 502.9 mAh g−1 at 2C. Moreover, it demonstrates remarkable battery capacity retention of 99.5% after 1300 cycles at 0.5C and a stable cycle performance of 717.3 mAh g−1.