The superior lithium storage performance of commercially available Cu 2 S under ultra-low temperature (−60 °C) is uncovered. The detailed reaction mechanism and mechanistic understanding of the excellent low-temperature performances are proposed.
Abstract Potassium-ion batteries (KIBs) are promising electrochemical energy storage systems because of their low cost and high energy density. However, practical exploitation of KIBs is hampered by the lack of high-performance cathode materials. Here we report a potassium manganese hexacyanoferrate (K 2 Mn[Fe(CN) 6 ]) material, with a negligible content of defects and water, for efficient high-voltage K-ion storage. When tested in combination with a K metal anode, the K 2 Mn[Fe(CN) 6 ]-based electrode enables a cell specific energy of 609.7 Wh kg −1 and 80% capacity retention after 7800 cycles. Moreover, a K-ion full-cell consisting of graphite and K 2 Mn[Fe(CN) 6 ] as anode and cathode active materials, respectively, demonstrates a specific energy of 331.5 Wh kg −1 , remarkable rate capability, and negligible capacity decay for 300 cycles. The remarkable electrochemical energy storage performances of the K 2 Mn[Fe(CN) 6 ] material are attributed to its stable frameworks that benefit from the defect-free structure.
The application of a layered K0.5MnO2 cathode in potassium-ion batteries is limited by its poor cycling performance when charged above 4.0 V (vs K+/K), and the underlying mechanism for this electrochemical instability is still unclear. Here, it is discovered that ethylene carbonate (EC) will intercalate into the depotassiated K0.5MnO2, causing the exfoliation of the layered compound and the capacity decay under high charge cutoff voltage. When the carbonates are replaced with a nonflammable phosphate, the electrochemical performance of K0.5MnO2 above 4.0 V (vs K+/K) is significantly enhanced with a large reversible capacity (120 mAh g–1) and high capacity retention of 84% after 400 cycles. This phosphate-based electrolyte also demonstrates good compatibility with the commercial graphite anode, enabling the encouraging electrochemical performance of the K0.5MnO2|graphite full-cell. The present study provides new insights on further exploration of other electrolytes to advance the emerging low-cost and high-performance potassium-ion batteries.
Potassium (K) metal is a promising anode for potential low-cost and high-energy-density K-ion batteries. However, its application is hampered by serious dendrite growth and large volume change. Herein, a Co nanoparticle-embedded nitrogen-doped nanoporous carbon nanofiber paper is prepared by carbonizing the electrospun fiber paper of metal–organic framework (MOF) nanoparticles and polyacrylonitrile, which displays a high potassiophilicity due to the incorporation of Co nanoparticles and N doping. As a three-dimensional host, excellent electrochemical performance is demonstrated for the K metal anode with a high average Coulombic efficiency of 98.75% for 400 cycles and a long lifespan of 1300 h in symmetric cells. Furthermore, enhanced electrochemical performance with good cycling stability and rate capability is achieved in full cells that are paired with organic cathodes. Our findings highlight a promising strategy for fabricating high-performance K metal anodes using MOF-based materials.
The capacity degradation mechanism of layered potassium vanadium oxide K0.5V2O5 towards K-ion storage was unveiled and the cycling stability of this material was enhanced by reducing its long-range structural order.
Abstract The development of high‐voltage Lithium‐metal batteries (LMBs) is hindered by suitable electrolytes that are simultaneously compatible with both high‐voltage cathodes and Li anodes. Herein, a novel localized high‐concentration electrolyte with ethoxy(pentafluoro)cyclotriphosphazene (PFPN) as a nonflammable diluent is developed. The inorganic‐dominate diluent improves the safety of the organic electrolyte, and helps to construct robust passivation interphases on both electrodes. Specifically, PFPN accelerates the complete reduction of anions, leading to a stable anion‐derived interphase layer on Li anode. Meanwhile, PFPN and anions co‐participate in the formation of cathode‐electrolyte interphase, suppressing side reactions and the structural damage of high‐voltage Ni‐rich cathodes. As a result, PFPN‐based electrolyte prolongs the cycling life of LMBs based on high‐voltage LiNi 0.6 Co 0.2 Mn 0.2 (NCM622) and LiNi 0.8 Co 0.1 Mn 0.1 (NCM811) cathodes. Specially, 25‐µm‐thick Li paired with NCM622 with a N/P ratio of 1.3 (4.4 V) exhibits excellent capacity retention of above 90% after 200 cycles. This study highlights the important role of diluent in tailoring electrode/electrolyte interphases and provides a new strategy for designing high‐safety electrolytes toward high‐voltage LMBs.
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