Conversion of Surface Residual Alkali to Solid Electrolyte to Enable Na-Ion Full Cells with Robust Interfaces.
basic_science · Level V
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- Record sourced from PubMed, PMID 37040259.
- Also identified by DOI 10.1002/adma.202301314.
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Abstract
The deposition of volatilized Na<sup>+</sup> on the surface of the cathode during sintering results in the formation of surface residual alkali (NaOH/Na<sub>2</sub> CO<sub>3</sub> NaHCO<sub>3</sub> ) in layered cathode materials, leading to serious interfacial reactions and performance degradation. This phenomenon is particularly evident in O3-NaNi<sub>0.4</sub> Cu<sub>0.1</sub> Mn<sub>0.4</sub> Ti<sub>0.1</sub> O<sub>2</sub> (NCMT). In this study, a strategy is proposed to transform waste into treasure by converting residual alkali into a solid electrolyte. Mg(CH<sub>3</sub> COO)<sub>2</sub> and H<sub>3</sub> PO<sub>4</sub> are reacted with surface residual alkali to generate the solid electrolyte NaMgPO<sub>4</sub> on the surface of NCMT, which can be labeled as NaMgPO4@NaNi<sub>0.4</sub> Cu<sub>0.1</sub> Mn<sub>0.4</sub> Ti<sub>0.1</sub> O<sub>2</sub> -X (NMP@NCMT-X, where X indicates the different amounts of Mg<sup>2+</sup> and PO<sub>4</sub> <sup>3-</sup> ). NaMgPO<sub>4</sub> acts as a special ionic conductivity channel on the surface to improve the kinetics of the electrode reactions, remarkably improving the rate capability of the modified cathode at a high current density in the half-cell. Additionally, NMP@NCMT-2 enables a reversible phase transition from the P3 to OP2 phase in the charge-discharge process above 4.2 V and achieves a high specific capacity of 157.3 mAh g<sup>-1</sup> and outstanding capacity retention in the full cell. The strategy can effectively and reliably stabilize the interface and improve the performance of layered cathodes for Na-ion batteries (NIBs).