Metal Phosphides Embedded with In Situ‐Formed Metal Phosphate Impurities as Buffer Materials for High‐Performance Potassium‐Ion Batteries

Abstract

As anodes for metal-ion batteries, metal phosphides usually suffer from severe capacity degradation because of their huge volume expansion and unstable solid electrolyte interphase (SEI), especially for potassium-ion batteries (PIBs). To address these issues, this study proposes amorphous phosphates acting as buffer materials. Ten types of metal phosphide composites embedded with in situ-formed amorphous phosphates are prepared by one-step ball milling using red phosphorus (RP) and the corresponding metal oxides (MOs) as starting materials. A zinc phosphide composite is selected for further study as a PIB anode. Benefitting from the effective suppression of volume variation, a KF-rich SEI is formed on the electrode surface in the KFSI-based electrolyte. The zinc phosphide composite exhibits a high reversible specific capacity and outstanding long-term cycling stability (476 mAh g −1 over 350 cycles at 0.1 A g −1 after going through a rate capability test and 177 mAh g −1 after 6000 cycles at 1.0 A g −1 ) and thus achieves the best cycling performance among all reported metal phosphide-based anodes for PIBs. This study highlights a low-cost and effective strategy to guide the development of metal phosphides as high-performance anodes for PIBs.

Excellent Metal Phosphide Electrode for Potassium Ion Hybrid Capacitors: The Case of Carbon Nanotube-Wrapped AgP2

“…Furthermore, the EDS mappings (Figure f) show that Ag, P, and K elements are homogeneously distributed over the anode material. A similar K + -storage mechanism in metal phosphides was also reported. ,, On the basis of the above results, we conjecture the reaction mechanism that AgP 2 decomposes into Ag nanocrystals and K 3 P after discharge in the first cycle and the reversible reaction is K 3 P ↔ P + K. After cycling, the Ag has no volume change because it does not react with K + . However, the reversible reaction of K 3 P ↔ P + K has a significant volume change.…”

Dynamic Reversible Evolution of Solid Electrolyte Interface in Nonflammable Triethyl Phosphate Electrolyte Enabling Safe and Stable Potassium‐Ion Batteries

“…In our recent work, we demonstrated that metal phosphides prepared by using metal oxides exhibit enhanced cycling stability in ethylene carbonate/diethyl carbonate (EC/DEC)‐based electrolyte. [ 9 ] Zinc phosphate is inactive to K‐ion in nature, and pure ZnO, when used as the raw material at the molar ratio of ZnO to P of 2:3, introduced the maximum mass percentage of zinc phosphate of 37.7 wt%, which would reduce the theoretical specific capacities of the zinc phosphide composites. Therefore, we optimized the content of zinc phosphate by controlling the proportion of Zn, ZnO, and P raw materials to keep a balance between the cycling stability and high specific capacity of zinc phosphide.…”

“…These results indicated that the amorphization of zinc phosphide increased with the increase in the proportion of zinc phosphate and carbon and were consistent with our previous findings, which were obtained by using pure ZnO to prepare completely amorphous zinc phosphide. [ 9 ] As shown in Figure 1d–i, a high‐resolution transmission electron microscope (HRTEM) was also employed to confirm the existence of zinc phosphide. In ZnP 2 @ZPO(10) (Figure 1d), the measured interplanar spacings of 0.284 and 0.204 nm matched with the (114) and (214) lattice planes of ZnP 2 phase, respectively.…”

“…[ 8 ] Our recent work is the first to provide an experimental report on the application of conversion‐type zinc phosphides as PIB anodes with high theoretical capacity (1262 mA h g −1 ) but large volume expansion/contraction during the charge/discharge process. [ 9 ] Metal oxides have been proposed and used as the starting materials for the formation of in situ amorphous metal phosphate matrixes to buffer volume expansion and relieve the massive volume expansion of metal phosphides. Although such a strategy has been proven to be effective, it introduces large amounts of inactive components that inevitably reduce specific capacity.…”

Recent advances and perspectives in aqueous potassium-ion batteries

“…can undergo alloying reactions with K metal in organic KIBs to achieve efficient K storage. [106][107][108][109][110] These elements have attracted widespread attention for their low operating voltages and high capacities. However, it is rarely reported in AKIBs.…”