Wu Wei,Zhihong Wang,Liyun Yao,Hao Jiang,Chunzhong Li
Development of Ni-rich and Co-poor cathodes (Ni ≥ 80%, Co ≤ 5%) is indispensable for the next-generation lithium-ion batteries (LIBs) owing to the serious impact of scarce resources and fragile supply chain of cobalt, but they suffer from a more prominent lattice oxygen emission with serious Li/Ni intermixing as well as worsening crystal and interface structure. Herein, CeO2−x-coated LiNi0.9Co0.045Mn0.045Al0.01O2 has been demonstrated to stabilize lattice oxygen by the well-dispersed Al–O bonds and the reversible oxygen-storage protective layer. The in situ DEMS and ex situ spectral analyses verified the negligible O2 and CO2 emission, even charging to 4.4 V, and the formation of stable cathode–electrolyte interfacial membrane. The as-obtained cathode exhibited a reversible specific capacity as high as 223 mA h g−1 at 0.1C and 140 mA h g−1 even at 10C with 96.7% capacity retention at 1C after 100 cycles in a coin-type half-cell. About 90.1% capacity retention could still be obtained at 1C in a pouch-type full-cell after 300 cycles. This work provides a viable cathode for durable LIBs by stabilizing the lattice oxygen of Ni-rich and Co-poor cathodes.
Wei Zhang,Zhiwei Gu,Bingbing Zong,Yueju Fu,Kai Zhang,Yubao Li
Defects is of special importance in tuning the structure and physical properties of layered materials. Here the influence of transition metal Co vacancies on the structure and magnetism in collapsed tetragonal CaCo 2- x As 2 (0 ≤ x ≤ 0.3) solid solutions are systematically investigated. The electrical properties show metallicity in all compounds. The crystal structure refinement exhibits that the lattice constant of the c axis and c / a ratio decreases as Co vacancies increase, revealing the formation of a more collapsed tetragonal structure in CaCo 2- x As 2 . Moreover, these introduced Co vacancies suppress the antiferromagnetic Néel temperature from 80 K down to 18 K until it disappears above 10 K in CaCo 1 · 7 As 2 . X-ray photoelectron spectroscopy reveals increased Co 3+ /Co 2+ value in CaCo 2- x As 2 with higher Co vacancies, which may result in the charge balance and the gradually suppressed T N . This study offers insights into tuning and understanding the magneto-structural characteristics in ThCr 2 Si 2 -type layered materials through transition metal vacancies.
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