Long Straczekite δ‐Ca_0.24V₂O₅⋅H₂O Nanorods and Derived β‐Ca_0.24V₂O₅ Nanorods as Novel Host Materials for Lithium Storage with Excellent Cycling Stability

Abstract

Nanorods of δ-Ca V O ⋅H O, a straczekite group mineral with an open double-layered structure, have been successfully fabricated by a facile hydrothermal method and can be transformed into the tunnel β geometry (β-Ca V O ) through a vacuum annealing treatment. The generated β-Ca V O still preserves the nanorod construction of δ-Ca V O ⋅H O without substantial sintering and degradation of the nanostructure. As cathode materials, both calcium vanadium bronzes exhibit high reversible capacity, good rate capability, as well as superior cyclability. Compared with the hydrated vanadium bronze, the β-Ca V O nanorods show better cycling performance (81.68 and 97.93 % capacity retention after 200 cycles at 100 and 400 mA g , respectively) and excellent long-term cyclic stability with an average decay of 0.035 % per cycle over 500 cycles at 500 mA g . Note that the double-layered δ-Ca V O ⋅H O electrode irreversibly converts into β-Ca V O phase during the initial Li insertion/extraction process, while in contrast, the β-phase calcium vanadium bronze electrode shows excellent structural stability during cycling. The excellent electrochemical performance demonstrates that the two calcium vanadium bronzes are potential cathode candidates for rechargeable lithium-ion batteries.

(NH4)2V7O16 Microbricks as a Novel Anode for Aqueous Lithium‐Ion Battery with Good Cyclability

“…[10c] The gradual capacity increase in the second stage may have relation to high electrode polarization and Li + diffusion paths become more flexible with increased cycling numbers. [27] Similar phenomena have also been found in other vanadium bronze such as K 0.25 V 2 O 5 , [28] Mg 0.25 V 2 O 5 • H 2 O, [10b] Ca 0.24 V 2 O 5 [29] and NH 4 V 4 O 10. [11] In the meantime, it is observed that the Coulombic efficiency gradually increases along with the increment of current rate.…”

Flexible Zn‐Ion Batteries: Recent Progresses and Challenges

“…Compared with monovalent intercalated species (e.g., Li + , Na + ), the divalent metal ions bonded with oxygen atoms lead to stronger ionic bonds, which effectively prevents structural collapse. The Zn 0.25 V 2 O 5 · n H 2 O cathode was developed by Nazar and her co‐workers .…”

Highly Stable Aqueous Zinc‐Ion Storage Using a Layered Calcium Vanadium Oxide Bronze Cathode

“…[8] Unfortunately,these electrodes suffer from either limited capacity or very poor cycling stability.Very recently,layered and hydrated V 2 O 5 derivatives (e.g. In addition, compared with monovalent alkali metal cations (e.g.Li + , Na + ,K + ), the divalent metal ions bonded with oxygen atoms can bring about stronger ionic bonds, [9] better binding the layers together, which effectively prevents structural collapse; 2) Thet endency of vanadium to exist in multiple oxidation states,h ence making it high capacity in principle;3 )The charge shield effect of the crystal H 2 O, which could reduce the effective charges of intercalated Zn 2+ ions,and thus enhance the capacity and rate performance. In addition, compared with monovalent alkali metal cations (e.g.Li + , Na + ,K + ), the divalent metal ions bonded with oxygen atoms can bring about stronger ionic bonds, [9] better binding the layers together, which effectively prevents structural collapse; 2) Thet endency of vanadium to exist in multiple oxidation states,h ence making it high capacity in principle;3 )The charge shield effect of the crystal H 2 O, which could reduce the effective charges of intercalated Zn 2+ ions,and thus enhance the capacity and rate performance.…”