This is the first report of a multifunctional separator for potassium‐metal batteries (KMBs). Double‐coated tape‐cast microscale AlF3on polypropylene (AlF3@PP) yields state‐of‐the‐art electrochemical performance: symmetric cells are stable after 1000 cycles (2000 h) at 0.5 mA cm−2and 0.5 mAh cm−2, with 0.042 V overpotential. Stability is maintained at 5.0 mA cm−2for 600 cycles (240 h), with 0.138 V overpotential. Postcycled plated surface is dendrite‐free, while stripped surface contains smooth solid electrolyte interphase (SEI). Conventional PP cells fail rapidly, with dendrites at plating, and “dead metal” and SEI clumps at stripping. Potassium hexacyanoferrate(III) cathode KMBs with AlF3@PP display enhanced capacity retention (91% at 100 cycles vs 58%). AlF3partially reacts with K to form an artificial SEI containing KF, AlF3, and Al2O3phases. The AlF3@PP promotes complete electrolyte wetting and enhances uptake, improves ion conductivity, and increases ion transference number. The higher of K+transference number is ascribed to the strong interaction between AlF3and FSI−anions, as revealed through19F NMR. The enhancement in wetting and performance is general, being demonstrated with ester‐ and ether‐based solvents, with K‐, Na‐, or Li‐ salts, and with different commercial separators. In full batteries, AlF3prevents Fe crossover and cycling‐induced cathode pulverization.
Sodium‐metal batteries (SMBs) are considered as a compliment to lithium‐metal batteries for next‐generation high‐energy batteries because of their low cost and the abundance of sodium (Na). Herein, a 3D nanostructured porous carbon particle containing carbon‐shell‐coated Fe nanoparticles (PC‐CFe) is employed as a highly reversible Na‐metal host. PC‐CFe has a unique 3D hierarchy based on sub‐micrometer‐sized carbon particles, ordered open channels, and evenly distributed carbon‐coated Fe nanoparticles (CFe) on the surface. PC‐CFe achieves high reversibility of Na plating/stripping processes over 500 cycles with a Coulombic efficiency of 99.6% at 10 mA cm–2with 10 mAh cm–2in Na//Cu asymmetric cells, as well as over 14 400 cycles at 60 mA cm–2in Na//Na symmetric cells. Density functional theory calculations reveal that the superior cycling performance of PC‐CFe stems from the stronger adsorption of Na on the surface of the CFe, providing initial nucleation sites more favorable to Na deposition. Moreover, the full cell with a PC‐CFe host without Na metal and a high‐loading Na3V2(PO4)3cathode (10 mg cm–2) maintains a high capacity of 103 mAh g–1at 1 mA cm–2even after 100 cycles, demonstrating the operation of anode‐free SMBs.
more » « less- NSF-PAR ID:
- 10365564
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials
- Volume:
- 34
- Issue:
- 14
- ISSN:
- 0935-9648
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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