The surface decoration of CoS₂ on SPAN–CNT nanofibers endows lithium–sulfur (Li–S) batteries with outstanding capacity reversibility and high energy density.

For a next-generation sodium battery to replace lithium ion batteries, it is essential to develop an anode with a long cycle life and high rate. Sn is considered to be an ideal candidate for the anode of sodium ion batteries. Here, we report a Sn anode that exhibits ultra-long-term cycle stability with a high capacity of 554 mA h g⁻¹ at 10C-rate for 5000 cycles. The optimized cell configuration consists of 1,2-dimethoxyethane as the electrolyte, a double separator including a nanoporous membrane, and a Sn anode with MWCNT as a conductive additive. Its capacity retention reaches up to 99.8% and its coulombic efficiency is near 100% for 5000 cycles. Surprisingly, we have discovered that the Sn powder exhibits a self-healing phenomenon during cycling. Sn is initially pulverized into a nanometer-sized powder, and then forms a three-dimensional porous coral-like structure in which ligament-shaped micrometer-sized Sn particles are connected with a low coordination number by room temperature sintering. The coral-like structure is mechanically stable towards volume change and electrically connected. The self-healing structure and mechanism provide a direction for the design of other electrodes with alloying mechanisms.

To enhance the stability of sulfur cathode for a high energy lithium–sulfur battery, sulfur–activated carbon (S–AC) composite was prepared by encapsulating sulfur into micropores of activated carbon using a solution-based processing technique. In the analysis using the prepared specimen of S–AC composite by the focused ion beam (FIB) technique, the elemental sulfur exists in a highly dispersed state inside the micropores of activated carbon, which has a large surface area and a narrow pore distribution. The S–AC composite was characterized through X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) method, selected area electron diffraction (SAED), energy dispersive X-ray spectrometry (EDX), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry analysis (TGA), and field emission scanning electron microscopy (FESEM). A lithium–sulfur cell using the S–AC composite has a high first discharge capacity over 800 mA h g⁻¹ S even at a high current density such as 2C (3200 mA g⁻¹ S) and has good cycleability around 500 mA h g⁻¹ S discharge capacity at the 50^th cycle at the same current density.