We propose new insights into designing high-rate performance cathode materials for sodium-ion batteries through enlarging the interplanar spacing.

Rational design of efficient bifunctional oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) electrocatalysts are critical for rechargeable Li–O2 batteries. Here, we report inverse spinel Co­[Co,Fe]­O4/nitrogen-doped graphene (NG) composite used as a promising catalyst for rechargeable Li–O2 batteries. The cells with Co­[Co,Fe]­O4/NG catalyst exhibit high initial capacity, remarkable cyclability, and good rate capability. Moreover, the overpotential of the Li–O2 batteries is reduced significantly. The improved ORR/OER performances are attributed to the good property of Co­[Co,Fe]­O4 with an inverse spinel structure toward ORR and the improved electronic conductivity of N-doped graphene. The density functional theory (DFT) calculation shows the rate limitation step for ORR on the inverse spinel surface is the growth of the Li2O2 cluster while the rate limitation step for the OER pathway is the oxidation of Li2O2. The inverse spinel surface in Co­[Co,Fe]­O4/NG is more active than that of the normal spinel phases for the Li–O2 battery reactions. This work not only provides a promising bifunctional catalyst for practical metal air batteries but also offers a general strategy to rationally design catalysts for various applications.

The design and synthesis of efficient electrocatalysts are important for electrochemical energy conversion and storage technologies. Poor electrocatalytic activities of the cathode catalysts toward both the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are still two major challenges facing Li–O2 batteries. Here, we report ultralong porous perovskite La0.6Sr0.4Co0.8Mn0.2O3 nanofibers (LSCM NFs) loaded with RuO2 nanosheets (RuO2@LSCM NFs) used as a promising catalyst for Li–O2 batteries. The LSCM nanofibers were synthesized via an electrospinning technique followed by heat treatment. RuO2 nanosheets were loaded by a wet impregnation method. In comparison with that of the pristine LSCM NFs, the cell with RuO2@LSCM NFs catalyst exhibits good performances toward the ORR and OER with a higher specific discharge capacity (12741.7 mA h g–1), improved cyclability, and rate capability as well as low voltage gap. Moreover, the results of LSV indicate that LSCM NFs can efficiently catalyze the decomposition of the reaction side product Li2CO3 while RuO2@LSCM NFs are capable of decomposing LiOH. The enhanced cell performances are attributed to the merits of high catalytic activity and the porous structure of the RuO2@LSCM NF catalyst.

The development of paper–based triboelectric nanogenerator (P‐TENG) has gained increasing importance because of the growing demand for the next‐generation wearable and portable electronics. However, currently, the limited washability and breathability of P‐TENG have largely hindered its further development in wearable applications. Here, an air‐permeable and washable P‐TENG is successfully fabricated using highly flexible and robust multiwalled carbon nanotubes coated air‐laid paper electrodes. The good air permeability of the P‐TENG makes it comfortable when directly laminated onto human skin for wearable applications. Furthermore, the P‐TENG not only exhibits excellent flexibility and mechanical stability, but also shows remarkable washing durability. The P‐TENG can be utilized as self‐charging systems to drive electronic devices or self‐powered active sensor to monitor human body motions. This work presents a new possibility of the integration of paper‐based energy‐harvesting devices with cloth/skin for building low‐cost, green, and multifunctional wearable devices and systems.

Wearable triboelectric nanogenerators (TENGs) with both functionality and comfort have become an appealing field of research for portable electronic devices recently. Here, a breathable, stretchable, and tailorable TENG that enables both energy harvesting and biomechanical monitoring is designed. Two layers of nanofiber membranes, which consist of polyvinylidene fluoride supported by conducting fabric and thermoplastic polyurethanes (TPU) supported by Ag elastic fabric, are welded into arch structures through ultrasonic welding technique. As the bottom layer of the arch, the TPU/Ag layer with consistent stretchability guarantees the stretchable of the TENG. Therefore, the TENG can collect various types of irregular movements, such as stretching, pressing, and twisting motions, even the combination of the above all motions. Under twisting stretch, the open‐circuit voltage and short‐circuit current of one basic unit can reach up to 170 V and 4.5 µA, respectively. Besides, the welded TENG is tailorable and it still maintains certain output even if it is partially cut or damaged. The continuous arch‐structured TENGs can also be used as self‐powered motion sensors to constantly monitor the intensity and frequency of human body movements. Thus, this work opens up a new idea for preparation of wearable TENG with both multifunction and better comfort.