Assessment on the Use of High Capacity “Sn₄P₃”/NHC Composite Electrodes for Sodium‐Ion Batteries with Ether and Carbonate Electrolytes

Abstract

This work reports the facile synthesis of a Sn-P composite combined with nitrogen doped hard carbon (NHC) obtained by ball-milling and its use as electrode material for sodium ion batteries (SIBs). The "Sn 4 P 3 "/NHC electrode (with nominal composition "Sn 4 P 3 ":NHC = 75:25 wt%) when coupled with a diglyme-based electrolyte rather than the most commonly employed carbonatebased systems, exhibits a reversible capacity of 550 mAh g electrode −1 at 50 mA g −1 and 440 mAh g electrode −1 over 500 cycles (83% capacity retention). Morphology and solid electrolyte interphase formation of cycled "Sn 4 P 3 "/NHC electrodes is studied via electron microscopy and X-ray photoelectron spectroscopy. The expansion of the electrode upon sodiation (300 mAh g electrode −1) is only about 12-14% as determined by in situ electrochemical dilatometry, giving a reasonable explanation for the excellent cycle life despite the conversion-type storage mechanism. In situ X-ray diffraction shows that the discharge product is Na 15 Sn 4. The formation of mostly amorphous Na 3 P is derived from the overall (electro)chemical reactions. Upon charge the formation of Sn is observed while amorphous P is derived, which are reversibly alloying with Na in the subsequent cycles. However, the formation of Sn 4 P 3 can be certainly excluded.

Tunable Hollow Nanoreactors for In Situ Synthesis of GeP Electrodes towards High‐Performance Sodium Ion Batteries

“…c) Rate capability for all GeP/CN‐ x ( x =0, 1, 2, 3) electrodes. d) The rate performance of GeP/CN‐3 electrode in comparison with previous reported transition metal phosphates [4, 7, 30a–i] . e) Long‐term cycling performance for all GeP/CN− x electrodes at 0.5 A g −1 over 350 cycles.…”

“…Notably,t he rate performance of the flexible free-standing GeP/CN-3 electrode in this work is much better than that of the other three electrodes,a sw ell as the previously reported GeP-based materials and other kinds of phosphides for sodium storage (Figure 5d;S upporting Information, Table S1). [4,7,30] Thes uperior rate capability could be originated from the facilitated Na + diffusion kinetics rooting in the hollow structure tuning as well as the fast electron transport resulting from the special 3D conductive networking free-standing electrode design.…”

Conversion‐Alloying Anode Materials for Sodium Ion Batteries

“…Subsequently, the as‐prepared Sn 4 P 3 particles mixed with nitrogen‐doped hard carbon in a 75:25 mass ratio to fabricate the final Sn 4 P 3 /NHC composites under the same reaction conditions. [ 116 ]…”

Advances in metal phosphides for sodium‐ion batteries

“…However, the large volume expansion (490% from P to Na 3 P and 525% from Sn to Na 15 Sn 4 ) induced severe structural collapse of Sn 4 P 3 during Na insertion/extraction processes, causing the loss of electrical activity, pulverization of electrode materials along with the rapid performance deterioration 49 . Rational structural design and surface modification with conductive carbonaceous materials are effective ways to eliminate these concerns.…”