Enabling Multielectron Reaction of Polyanionic Cathodes Toward High-Energy Calcium Rechargeable Batteries.
basic_science · Level V
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- Record sourced from PubMed, PMID 40714796.
- Also identified by DOI 10.1002/adma.202506603.
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Abstract
Polyanionic cathode materials with robust structural stability and large Ca<sup>2+</sup> diffusion channels have aroused great interest in propelling the development of calcium-ion batteries (CIBs). However, polyanionic cathodes usually exhibit single-electron transfer per unit, rendering limited specific capacity and energy densities. Herein, a new polyanionic Ca<sub>x</sub>NaV<sub>1.5</sub>Cr<sub>0.5</sub>(PO<sub>4</sub>)<sub>3</sub> (0 ≤ x ≤ 1.4) cathode is proposed for high-capacity and ultra-stable CIBs by unlocking 1.87-electron transfer per vanadium redox center during Ca ion insertion. The Ca<sub>x</sub>NaV<sub>1.5</sub>Cr<sub>0.5</sub>(PO<sub>4</sub>)<sub>3</sub> cathode delivers a reversible calcium storage capacity of 162 mAh g<sup>-1</sup> at an average voltage of ≈2.5 V at 10 mA g<sup>-1</sup>, featuring a record-high energy density of ≈400 Wh kg<sup>-1</sup>. The low volume changes (∆V = 1.8%) and fast diffusion kinetics indicate excellent cycling stability of Ca<sub>x</sub>NaV<sub>1.5</sub>Cr<sub>0.5</sub>(PO<sub>4</sub>)<sub>3</sub> with capacity retentions of 98.2% and 80.8% over 600 and 5000 cycles, respectively. In Ca metal full cells made from a Ca metal anode and a compatible electrolyte, the Ca<sub>x</sub>NaV<sub>1.5</sub>Cr<sub>0.5</sub>(PO<sub>4</sub>)<sub>3</sub> presents a high energy density of 318 Wh kg<sup>-1</sup> over 50 cycles, which rivals the state-of-the-art CIB performance. This work sheds new light on the electrochemically activated multielectron redox reactions of polyanionic cathode materials for sustainable CIBs.