Nanostructured silicon anodes have shown extraordinary lithium storage properties for lithium-ion batteries (LIBs) but are usually achieved at low areal loadings (< 1.5 mg·cm⁻²) with low areal capacity. Sustaining sound electrochemical performance at high loading requires proportionally higher ion/electron currents and robust structural stability in the thicker electrode. Herein, we report a three-dimensional (3D) printed silicon-graphene-carbon nanotube (3D-Si/G/C) electrode for simultaneously achieving ultrahigh areal/gravimetric capacities at high mass loading. The periodically arranged vertical channels and hierarchically porous filaments facilitate sufficient electrolyte infiltration and rapid ion diffusion, and the carbonaceous network provides excellent electron transport properties and mechanical integrity, thus endowing the printed 3D-Si/G/C electrode with fast electrochemical reaction kinetics and reversibility at high mass loading. Consequently, the 3D-Si/G/C with high areal mass loading of 12.9 mg·cm⁻² exhibits excellent areal capacity of 12.8 mAh·cm⁻² and specific capacity of 1007 mAh·g⁻¹, respectively. In-situ optical microscope and ex-situ scanning electron microscope (SEM) confirm that the hierarchically porous filaments with interconnected carbon skeletons effectively suppress the volume change of silicon and maintain stable micro-lattice architecture. A 3D printed 3D-Si/G/C-1∥3D-LiFePO₄/G full cell holds excellent cyclic stability (capacity retention rate of 78% after 50 cycles) with an initial Coulombic efficiency (ICE) of 96%. This work validates the feasibility of 3D printing on constructing high mass loading silicon anode for practical high energy-density LIBs.

Heteroatom-doped carbon nanotubes (CNTs) have great potential in various fields owing to their extraordinary electronic, structural, and mechanical properties. However, large-scale production of heteroatom-doped CNTs in a simple, economical, and highly efficient manner still remains challenging. Here, we report a modified Pechini method (MPM) for high-yield synthesis of N- and O-codoped CNTs (N,O-CNTs), by rapid pyrolysis of a NiCo-polymer precursor forming via a simple sol–gel process. The carbon source (i.e., citric acid) is inexpensive, and the NiCo-polymer material is the single precursor for the preparation of N,O-CNTs via a thermolysis process without the introduction of additional catalysts or carrier gas. Appropriate NiCo-organic coordination and controlled pyrolysis (i.e. heating rate, pyrolysis temperature, and holding time) are demonstrated to play vital roles in this MPM, which are critical for quick generation of small NiCo nanocatalysts with high catalytic activity and simultaneous formation of sufficient space inside the material. The growth mechanism is well studied. Benefitting from the hierarchically porous structure and the synergistic effect of N,O-codoping in the CNTs, the as-synthesized N,O-CNTs manifest excellent electrochemical performance in both supercapacitors and electrocatalysis. Density functional theory simulations show that N and O dopants could increase the densities of states of CNTs near the Fermi level and charge densities of adjacent C atoms, thus leading to improved electrochemical activity. We anticipate that this work will open up a new avenue for a high-yield and economical synthesis of heteroatom-doped CNTs for energy-related applications and beyond.

Monolithic carbon electrodes with robust mechanical integrity and porous architecture are highly desired for capacitive deionization but remain challenging. Owing to the excellent mechanical strength and electroconductivity, commercial carbon fibers cloth demonstrates great potential as high‐performance electrodes for ions storage. Despite this, its direct application on capacitive deionization is rarely reported in terms of limited pore structure and natural hydrophobicity. Herein, a powerful metal‐organic framework‐engaged structural regulation strategy is developed to boost the desalination properties of carbon fibers. The obtained porous carbon fibers features hierarchical porous structure and hydrophilic surface providing abundant ions‐accessible sites, and continuous graphitized carbon core ensuring rapid electrons transport. The catalytic‐etching mechanism involving oxidation of Co and subsequent carbonthermal reduction is proposed and highly relies on annealing temperature and holding time. When directly evaluated as a current collector‐free capacitive deionization electrode, the porous carbon fibers demonstrates much superior desalination capability than pristine carbon fibers, and remarkable cyclic stability up to 20 h with negligible degeneration. Particularly, the PCF‐1000 showcases the highest areal salt adsorption capacity of 0.037 mg cm⁻² among carbon microfibers. Moreover, monolithic porous carbon fibers‐carbon nanotubes with increased active sites and good structural integrity by in‐situ growth of carbon nanotubes are further fabricated to enhance the desalination performance (0.051 mg cm⁻²). This work demonstrates the great potential of carbon fibers in constructing high‐efficient and robust monolithic electrode for capacitive deionization.