Electrostatic Shielding Boosts Electrochemical Performance of Alloy‐Type Anode Materials of Sodium‐Ion Batteries

Abstract

The applications of alloy‐type anode materials for Na‐ion batteries are always obstructed by enormous volume variation upon cycles. Here, K+ ions are introduced as an electrolyte additive to improve the electrochemical performance via electrostatic shielding, using Sn microparticles (μ‐Sn) as a model. Theoretical calculations and experimental results indicate that K+ ions are not incorporated in the electrode, but accumulate on some sites. This accumulation slows down the local sodiation at the “hot spots”, promotes the uniform sodiation and enhances the electrode stability. Therefore, the electrode maintains a high specific capacity of 565 mAh g−1 after 3000 cycles at 2 A g−1, much better than the case without K+. The electrode also remains an areal capacity of ≈3.5 mAh cm−2 after 100 cycles. This method does not involve time‐consuming preparation, sophisticated instruments and expensive reagents, exhibiting the promising potential for other anode materials.

Double Restriction of Bismuth Nanoparticles by Carbon Matrixes for Ultralong−lifespan Sodium Storage

“…Recently, alloying-type anode materials (such as Bi, Sb, Sn, Ge) have received more attention due to their appropriate Na+ insertion potentials and attractive theoretical capacities. [5] Among them, Bi is considered to be a competitive candidate for high performance anode owing to its large interlayer spacing along the c-axis (d (003) = 0.395 nm), flat reaction plateaus (0.6 V vs. Na+/ Na), and high volumetric capacity (3750 mA h cm−3). [6] In previous reports, Bi was directly applied in the anode for SIBs by a two-step alloying reaction mechanism: Bi + Na+ + e− ↔ NaBi and NaBi+ 2Na+ +2e− ↔Na3Bi.…”