The recent discovery of reversible plating and alloying of calcium
has invoked considerable interest in calcium-based rechargeable batteries
toward overcoming the limitations of conventional Li-ion batteries.
However, only a few cathode materials have been tested thus far, and
these exhibit low energy-storage capability and poor cyclability.
Herein, the highly reversible Ca-intercalation capability of NASICON-type
NaV2(PO4)3 makes it a potential cathode
material for nonaqueous Ca-ion batteries, with high capacity and voltage
and good cyclability (90 mA h g–1 and ∼3.4
V at 11.7 mA g–1 and 75 °C; 70 mA h g–1 and ∼3.2 V at 5.85 mA g–1 and 25 °C).
Although this work shows only the capability of the cathode, not a
full-cell performance, it does demonstrate experimentally that a poly-oxyanionic
material can provide an outstanding host structure for Ca diffusion
at room temperature with high energy-storage capability.
Despite the attractive theoretical benefits of calcium-ion batteries (CIBs) as post-lithium-ion batteries, only a limited number of host materials are known to reversibly intercalate calcium ions to date, and their intercalation mechanism is barely understood. Herein, we report bilayered Ca 0.28 V 2 O 5 •H 2 O as a highcapacity CIB cathode material. It exhibits a capacity of 142 mA h g −1 at ∼3.0 V vs Ca/Ca 2+ and excellent cyclability. Ca 0.28 V 2 O 5 •H 2 O undergoes irreversible structural transformation to a two-fold superstructure during the first charge, which triggers its electrochemical activity from the subsequent cycling. Its intercalation mechanism is unique; upon charging, complete calcium extraction occurs from every two interlayers, maintaining only a fraction of calcium ions in the other interlayers; on discharge, calcium ions are irregularly inserted into the interlayers, resulting in stacking faults. This charge−discharge cycle is highly reversible. This work would be the first report that experimentally unveils the electrochemical calcium storage mechanism of an intercalation host material, providing valuable insights for developing high-performance CIB cathodes.
Calcium-ion batteries (CIBs) are getting increasing attention as post-lithium-ion batteries owing to their theoretical and potential advantages in terms of energy density and cost-effectiveness. However, most of the reported cathode...
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