Triolo Claudia, Maisuradze Mariam, Li Min, Liu Yanchen, Ponti Alessandro, Pagot Gioele, Di Noto Vito, Aquilanti Giuliana, Pinna Nicola, Giorgetti Marco, Santangelo Saveria
Dipartimento di Ingegneria Civile, dell'Energia, dell'Ambiente e dei Materiali (DICEAM), Università "Mediterranea,", Via Zehender, Loc. Feo di Vito, Reggio Calabria, 89122, Italy.
National Reference Center for Electrochemical Energy Storage (GISEL), Consorzio Interuniversitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM), Firenze, 50121, Italy.
Small. 2023 Nov;19(46):e2304585. doi: 10.1002/smll.202304585. Epub 2023 Jul 19.
High-entropy oxides (HEOs) have emerged as promising anode materials for next-generation lithium-ion batteries (LIBs). Among them, spinel HEOs with vacant lattice sites allowing for lithium insertion and diffusion seem particularly attractive. In this work, electrospun oxygen-deficient (Mn,Fe,Co,Ni,Zn) HEO nanofibers are produced under environmentally friendly calcination conditions and evaluated as anode active material in LIBs. A thorough investigation of the material properties and Li storage mechanism is carried out by several analytical techniques, including ex situ synchrotron X-ray absorption spectroscopy. The lithiation process is elucidated in terms of lithium insertion, cation migration, and metal-forming conversion reaction. The process is not fully reversible and the reduction of cations to the metallic form is not complete. In particular, iron, cobalt, and nickel, initially present mainly as Fe , Co /Co , and Ni , undergo reduction to Fe , Co , and Ni to different extent (Fe < Co < Ni). Manganese undergoes partial reduction to Mn /Mn and, upon re-oxidation, does not revert to the pristine oxidation state (+4). Zn cations do not electrochemically participate in the conversion reaction, but migrating from tetrahedral to octahedral positions, they facilitate Li-ion transport within lattice channels opened by their migration. Partially reversible crystal phase transitions are observed.
高熵氧化物（HEOs）已成为下一代锂离子电池（LIBs）颇具前景的负极材料。其中，具有可用于锂嵌入和扩散的空位晶格位点的尖晶石型HEOs似乎特别有吸引力。在这项工作中，在环境友好的煅烧条件下制备了静电纺丝的缺氧（Mn、Fe、Co、Ni、Zn）HEO纳米纤维，并将其作为LIBs的负极活性材料进行评估。通过几种分析技术，包括非原位同步辐射X射线吸收光谱，对材料性能和锂存储机制进行了深入研究。从锂嵌入、阳离子迁移和金属形成转化反应方面阐明了锂化过程。该过程不完全可逆，阳离子还原为金属形式也不完全。特别是，最初主要以Fe、Co/Co和Ni形式存在的铁、钴和镍，会不同程度地还原为Fe、Co和Ni（Fe < Co < Ni）。锰部分还原为Mn/Mn，再氧化时不会恢复到原始氧化态（+4）。锌阳离子不参与电化学转化反应，但从四面体位置迁移到八面体位置时，它们促进了锂离子在由其迁移打开的晶格通道内的传输。观察到了部分可逆的晶相转变。
