Lithium dendrite formation has hindered the practical implementation of lithium metal batteries with higher energy densities compared with those of conventional lithium-ion batteries. Herein, a nanoconfinement strategy to access dendritefree lithium metal anodes comprising three-dimensional (3D) hollow porous multi-nanochannel carbon fiber embedded with TiO 2 nanocrystals (HTCNF) is reported. The transport of the lithium ions is facilitated by the 3D architecture. Functioning as nanoseeds, the TiO 2 nanocrystals guide the lithium ions toward forming uniform deposits, which are further confined inside the hollow carbon fibers and the 3D HTCNF layer. Site-selective deposition coupled with the nanoconfinement of lithium metal modifies the Li plating/stripping behavior and effectively suppresses the dendrite growth. The HTCNF-Li cell delivers a stable cycling performance of 1300 h with a voltage hysteresis as low as 6 mV. The assembled HTCNF-Li//LiFePO 4 full cell displays a compelling rate performance and enhanced cycling stability with high capacity retention (90% after 400 cycles at 0.5 C). Our results demonstrate a new and potentially scalable route to resolve the lithium dendrite growth issue for enhanced electrochemical performances, which can be further extended to other metal battery systems.

Hierarchical structure design of transition metal compounds is a promising method for improving the electrochemical properties of supercapacitors. In this work, a 3D electrode is obtained by in situ growing of NiMoO4@NiCo2O4 core–shell nanorods on Ni foam (NF) followed by an annealing process (NF@NiMoO4@NiCo2O4). The hierarchical structure with ordered pores on a surface enables a uniform charge distribution, provides effective electron/ion transfer channels, and maintains structural integrity over long periods of cycling, which collectively results in excellent electrochemical properties with an extraordinary specific capacitance of 1920 F g–1 at 1 A g–1 as well as 91.6% capacitance retention after 10 000 cycles. Furthermore, a flexible solid-state asymmetric supercapacitor fabricated with NF@NiMoO4@NiCo2O4 achieves a superior energy density of 54.5 Wh kg–1 (at 845 W kg–1) and an outstanding cycling stability with 83% capacity retention over 10 000 cycles. The hierarchical 3D electrode design in this work will contribute to the development of high-performance supercapacitors and shows promising prospects in flexible and portable energy storage systems.

The exploring of oxygen electrocatalysts with outstanding durability and efficiency toward the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is greatly desired for zinc-air flow batteries (ZAFBs). Herein, NiCo alloy-based nanoparticles anchored on carbon nanotube-decorated carbon nanorods (CNRs) used as a durable and efficient oxygen electrocatalyst for ZAFBs were obtained from the pyrolysis of NiCo metal−organic frameworks synthesized by a facile oil bath method. By tailoring the ratio of Ni 2+ and Co 2+ , the prepared sample, Ni 2 Co 2 -CNR, exhibits excellent ORR (E 1/2 = 0.80 V) and OER catalytic performances (a low overpotential of 310 mV at 10 mA cm −2 ). Impressively, the ZAFB assembled with a Ni 2 Co 2 -CNR catalyst shows a narrow voltage gap and remarkable operation durability with 1200 cycles at 5 mA cm −2 with every cycle of 20 min.

Quasi-solid-state flexible zinc–air batteries (FZABs) have received enormous attention due to their low cost and high safety. However, the constraints in lifetime resulting from the lack of stable quasi-solid-state electrolyte membranes and efficient bifunctional electrocatalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) hinder the large-scale manufacture and commercialization of FZABs to power electric devices. Herein, a polyacrylonitrile (PAN)-based membrane (HPPANP) fabricated via facile coaxial electrospinning, water dissolution, lyophilization, and KOH preimmersion method was utilized as the quasi-solid-state electrolyte membrane. The interconnected hollow porous structure based on PAN nanofibers endows HPPANP with outstanding electrolyte-uptake/retention capabilities for high ionic conductivity and nanolevel wetted electrolyte/anode interface for uniform Zn dissolution/deposition, thus prolonging the lifespan of the FZABs. In addition, the in situ alkaline hydrolysis of KOH solution supplies HPPANP with abundant oxygen-containing groups, which also improves its ionic conductivity. Additionally, we synthesized a Co/N-doped hollow carbon sphere (CoN-CS) electrocatalyst that exhibits superior ORR and OER electrocatalytic activities with a low potential difference (ΔE) of 0.73 V. Such favorable ORR and OER performances can be mainly attributed to the hierarchical hollow micro/nanostructures with abundant active sites, long-term stability, and favorable electron/ion diffusion pathway. As a result, the assembled FZAB equipped with the CoN-CS catalyst and HPPANP displays high power density (123.8 mW cm–2) and preferable long-term cycling performance (more than 50 h at 3 mA cm–2).

Lithium-ion batteries (LIBs) typically suffer from large irreversible capacities caused by active lithium loss during formation of a solid electrolyte interface (SEI) at the anode side. Cathode prelithiation with preloaded additives has emerged as an effective strategy to solve the above issue. With ultrahigh theoretical capacity, Li2O2 serves as an excellent cathode prelithiation additive, whereas poor ambient stability limits its further development. In this study, we report a surface protection strategy to enable ambient processing of the Li2O2 additive. Li2O2 is well confined in poly­(methyl methacrylate) (PMMA) nanofibers (P-Li2O2) via electrospinning, which exhibits greatly enhanced ambient stability compared with the unprotected one. Notably, when P-Li2O2 is preloaded in LiNi0.5Co0.2Mn0.3O2 cathodes (NCM-P-Li2O2), PMMA nanofibers remain stable during cathode slurry processing but readily dissolve in electrolytes and expose Li2O2 for effective electrochemical oxidation. Fabrication of P-Li2O2 allows systematic investigation of prelithiation behavior in full cells (NCM-P-Li2O2 cathodes paired with Si/Graphite anodes) and its impact on the electrochemical performance. Rational tuning of the prelithiation degree provides guidance for optimizing the amount of the cathode additive, which brings appealing cell lifetime and energy density.