Lithium–sulfur (Li–S) batteries are strong contenders among lithium batteries due to superior capacity and energy density, but the polysulfide shuttling effect limits the cycle life and reduces energy efficiency due to a voltage gap between charge and discharge. Here, we demonstrate that graphene foam impregnated with single-atom catalysts (SACs) can be coated on a commercial polypropylene separator to catalyze polysulfide conversion, leading to a reduced voltage gap and a much improved cycle life. Also, among Fe/Co/Ni SACs, Fe SACs may be a better option to be used in Li–S systems. By deploying SACs in the battery separator, cycling stability improves hugely, especially considering relatively high sulfur loading and ultralow SAC contents. Even at a metal loading of ∼2 μg in the whole cell, an Fe SAC-modified separator delivers superior Li–S battery performance even at high sulfur loading (891.6 mAh g–1, 83.7% retention after 750 cycles at 0.5C). Our work further enriches and expands the application of SACs catalyzing polysulfide blocking and conversion and improving round trip efficiencies in batteries, without side effects such as electrolyte and electrode decomposition.

Lithium metal is the “holy grail” of anodes, capable of unlocking the full potential of cathodes in next‐generation batteries. However, the use of pure lithium anodes faces several challenges in terms of safety, cycle life, and rate capability. Herein, a solution‐processable conjugated microporous thermosetting polymer (CMP) is developed. The CMP can be further converted into a large‐scale membrane with nanofluidic channels (5–6 Å). These channels can serve as facile and selective Li‐ion diffusion pathways on the surfaces of lithium anodes, thereby ensuring stable lithium stripping/plating even at high areal current densities. CMP‐modified lithium anodes (CMP‐Li) exhibit cycle stability of 2550 h at an areal current density of 20 mA cm−2. Furthermore, CMP is readily amenable to solution‐processing and spray coating, rendering it highly applicable to continuous roll‐to‐roll lithium metal treatment processes. Pouch cells with CMP‐Li as the anode and LiNi0.8Co0.1Mn0.1O2 (NCM811) as the cathode exhibits a stable energy density of 400 Wh kg−1.

No abstract

The voltage and capacity of cathodes are critical factors for energy density of batteries. However, the cutoff voltage of cathode materials in potassium‐ion batteries (PIBs) is usually 4.0 V, causing structural transformations in the electrode materials in the course of repeated insertion/extraction of K+ ions with a large radius (1.38 Å). Materials with large interlayer spacing and short ion diffusion paths show promise to overcome this issue. K0.486V2O5 nanobelts, prepared by preinserting K+ ions into V2O5, are used as cathode materials in high‐voltage PIBs. Various analysis methods are used to understand the insertion/extraction behavior of K+ ions in K0.486V2O5 cathodes cycled between 1.5 and 4.2 V. The analyses reveal the highly reversible structural evolution of K0.486V2O5, in which the chemically inserted K+ ions partially remain between VO layers charged at high voltage serving as stabilizing species to prevent phase transformations. K0.486V2O5 cathodes exhibit a high specific capacity of 159 mAh g−1 at 20 mA g−1 with good cycling stability of 67.4% after 100 cycles at 100 mAh g−1 in the half K‐ion cell. The results provide guidelines for designing layered transition metal oxides to be used as cathode materials for high‐voltage PIBs with high energy density.

No abstract