Low-cost and environment-friendly dual-ion batteries (DIBs) with fast-charging characteristics facilitate the development of high-power energy storage devices. However, the incompatibility between the cathode and electrolyte at high voltage results in low Coulombic efficiency (CE) and short lifespan. Here, the addition of ≈0.5 wt% lithium difluoro(oxalate) borate salt into the electrolyte forms a robust and durable cathode-electrolyte interface (CEI) in situ on the graphite surface, which enables remarkable cycling of the graphite||Li battery with 87.5% capacity retention after 4000 cycles at 5 C and ultrafast rate capability with 88.8% capacity retention under 40 C (4 A g −1 ), delivering high-power of 0.4-18.8 kW kg −1 at energy densities of 422.7-318.8 Wh kg −1 . Taking advantage of this robust CEI, a graphite||graphite full battery demonstrates high reversible capacities of 97.6, 92.8, 88.7, and 85.4 mAh (g cathode) −1 at current rates of 10, 20, 30, and 40 C, respectively. The full battery also shows a long cycling life of over 6500 cycles with 92.4% capacity retention and an average CE of ≈99.4% at 1 A g −1 , which is superior to other dual-graphite (carbon) batteries in the literature. This work offers an effective interface-stabilizing strategy on protecting graphite cathodes and a promising approach for developing DIBs with high-power capability.

One of the main challenges in commercializing electrolyzer is to develop cheap and highly active electrocatalysts toward hydrogen evolution reaction (HER). Although low Pt loadings in PEM electrolyzers have been demonstrated, it's still worthwhile to remove the Pt in the long term. Herein, porous N-doped carbon nanofibers containing encapsulated Co nanoparticles are in situ obtained by electrospinning and subsequent carbonization as efficient electrocatalysts for HER. The optimized catalyst treated at 800 • C shows a remarkably high HER activity with an overpotential of only 159 mV at current density of 10 mA cm −2 in a 0.5 M H 2 SO 4 solution, which is better than most non-precious metal based and metal free catalysts. The carbonization temperature as well as the concentration of nitrogen precursors have significant effects on the structure and catalytic activity of the composites. This work shows the efficacy of preparing noble-metal-free electrocatalysts for HER using the facile electrospinning method.

Metal-containing macromolecules with extraordinary properties have attracted a great deal of interest owing to their potential application in the development of functional materials.