On-surface conversion reaction realizes advanced red phosphorus/carbon anode for high-performance lithium-ion batteries.

Red phosphorus (RP), the one of the most prospective anodes in lithium-ion batteries (LIBs), has been severely limited due to the intrinsic defects of massive volume expansion and low electronic conductivity. The vaporization-condensation-conversion (VCC), which confines RP nanoparticles into carbon host, is the most widely used method to address the above drawbacks and prepare RP/C nanostructured composites. However, the volume effect-dominated RP caused by the inevitably deposition of RP vapor on the surface of carbon material suffers from the massive volume change and unstable solid electrolyte interface (SEI) film. Herein, we propose a simple interfacial modification method to eliminate the superficial RP and yield stable surface composed of ion-conducting Li3PS4 solid electrolyte, endowing RP/AC composites excellent cycling performance and ultrafast reaction kinetics. Therefore, the RP/AC@S composites exhibit 926 mAh/g after 320 cycles at 0.2 A/g (running over 181 days), with 81.6 % capacity retention and a corresponding capacity decay rate of as low as 0.059 %. When coupled with LiFePO4 cathode, the full cells present superior cycling performance (62.1 mAh/g after 500 cycles at 1 A/g) and excellent rate capability (81.1 mAh/g at 1.0 A/g).

Effect of Elevated Temperature Annealing on Nafion/SiO2 Composite Membranes for the All-Vanadium Redox Flow Battery.

Conducting Nafion/SiO2 composite membranes were successfully prepared using a simple electrostatic self-assembly method, followed by annealing at elevated temperatures of 240, 270, and 300 °C. Membrane performance was then investigated in vanadium redox flow batteries (VRB). These annealed composite membranes demonstrated lower vanadium permeability and a better selectivity coefficient than pure Nafion membranes. The annealing temperature of 270 °C created the highest proton conductivity in the Nafion/SiO2 composite membranes. The microstructures of these membranes were analyzed using transmission electron microscopy, small-angle X-ray scattering, and positron annihilation lifetime spectroscopy. This study revealed that exposure to high temperatures resulted in an increase in the free volumes of the composite membranes, resulting in improved mechanical and chemical behavior, with the single cell system containing composite membranes performing better than systems containing pure Nafion membranes.