RESUMO
Alloying-type anodes show capacity and density advantages for sodium/potassium-ion batteries (SIBs/PIBs), but they encounter serious structural degradation upon cycling, which cannot be resolved through conventional nanostructuring techniques. Herein, we present an in-depth study to reveal the intrinsic reason for the pulverization of bismuth (Bi) materials upon (de)alloying, and report a novel particle-in-bulk architecture with Bi nanospheres inlaid in the bulk carbon (BiNC) to achieve durable Na/K storage. We simulate the volume-expansion-resistant mechanism of Bi during the (de)alloying reaction, and unveil that the irreversible phase transition upon (de)alloying underlies the fundamental origin for the structural degradation of Bi anode, while a proper compressive stress (~10 %) raised by the bulk carbon can trigger a "domino-like" Bi crystal recovering. Consequently, the as obtained BiNC exhibits a record high volumetric capacity (823.1â mAh cm-3 for SIBs, 848.1â mAh cm-3 for PIBs) and initial coulombic efficiency (95.3 % for SIBs, 96.4 % for PIBs), and unprecedented cycling stability (15000â cycles for SIBs with only 0.0015 % degradation per cycle), outperforming the state-of-the-art literature. This work provides new insights on the undesirable structural evolution, and proposes basic guidelines for design of the anti-degradation structure for alloy-type electrode materials.
RESUMO
Resin derived hard carbons (HCs) generally demonstrate remarkable electrochemical performance for both sodium ion batteries (SIBs) and potassium-ion batteries (KIBs), but their practical applications are hindered by their high price and high temperature pyrolysis (≈1500 °C). Herein, low-cost pitch is coated on the resin surface to compromise the cost, and meanwhile manipulate the microstructure at a relatively low pyrolysis temperature (1000 °C). HC-0.2P-1000 has a large number of short graphitic layer structures and a relatively large interlayer spacing of 0.3743 nm, as well as ≈1 nm sized nanopores suitable for sodium storage. Consequently, the as produced material demonstrates a superior reversible capacity (349.9 mAh g-1 for SIBs and 321.9 mAh g-1 for KIBs) and excellent rate performance (145.1 mAh g-1 at 20 A g-1 for SIBs, 48.5 mAh g-1 at 20 A g-1 for KIBs). Furthermore, when coupled with Na3 V2 (PO4 )3 as cathode, the full cell exhibits a high energy density of 251.1 Wh kg-1 and excellent stability with a capacity retention of 73.3% after 450 cycles at 1 A g-1 .
Assuntos
Grafite , Sódio , Carbono , Eletrodos , ÍonsRESUMO
Design of non-noble metal electrocatalysts with high catalytic activity and stability to replace commercial Pt/C is crucial in the commercialization development of Zn-air batteries (ZABs). In this work, Co catalyst nanoparticles coupled with nitrogen-doped hollow carbon nanoboxes were well designed through zeolite-imidazole framework (ZIF-67) carbonization. As a result, the 3D hollow nanoboxes reduced the charge transport resistance, and the Co nanoparticles loaded on nitrogen-doped carbon supports exhibited excellent electrocatalytic performance for oxygen reduction reaction (ORR, E1/2 =0.823â V vs. RHE), similar to that of commercial Pt/C. Moreover, the designed catalysts showed an excellent peak density of 142â mW cm-2 when applied on ZABs. This work provides a promising strategy for the rational design of non-noble electrocatalysts with high performance for ZABs and fuel cells.