Synthesis of hierarchically porous boron-doped carbon material with enhanced surface hydrophobicity and porosity for improved supercapacitor performance

A Laser-Processed Carbon-Titanium Carbide Heterostructure Electrode for High-Frequency Micro-Supercapacitors

Micro-supercapacitors (MSCs) are an important energy storage component for future miniaturized electronic systems, yet their key performance indexes such as high-frequency response, energy density, and cycle life still have a large room to be improved. Herein, a laser-processed carbon-titanium carbide heterostructure (LCTH) electrode is demonstrated, which can excellently address the above key challenges by employing a unique one-step laser-processing fabrication method. Different from the other reported electrode structures, this LCTH electrode shows a heterogeneous structure, featuring the carbon nanofoam layer which provides extremely short ion transport channels and abundant electrochemical active sites, and the underlying titanium carbide layer which can provide excellent electron conductivity and contribute to the pseudo-capacitance. The assembled symmetric supercapacitor can stably work at the voltage window of 3.5 V at an ultra-high frequency of approximately 1121.3 Hz, exhibiting an ultra-high areal specific energy density of 721 µFV² cm^-2 at 120 Hz and a cycle life of 140 000 cycles with capacitance retention of 100.95%, which is superior to most reported MSCs. The as-fabricated MSC is compatible with the contemporary embedded electronic component fabrication processes, which shows significant advantages in large-scale fabrication and system integration, demonstrating a broad prospect for future system-in-package applications.

Natural Halloysite-Templated Synthesis of Highly Graphitic Boron-Doped Hollow Carbon Nanocapsule Webs

Hollow carbon nanocapsules have been attracting growing interest due to their fascinating characteristics and extensive potential applications. In this work, a novel natural halloysite-templated synthesis approach for highly graphitic boron-doped hollow carbon nanocapsule webs (B-HCNCWs) using glucose as the carbon source and boric acid as the heteroatom dopant was first reported. The formation process and physicochemical properties of B-HCNCWs were revealed by SEM, TEM, XRD, Raman, Brunauer–Emmett–Teller (BET), and XPS characterization techniques. The outcomes showed that the as-obtained B-HCNCWs with hollow nanocapsule network architecture had a specific surface area of 263 m² g⁻¹, a pore volume of 0.8 cm³ g⁻¹, a high degree of graphitization (81.4%), graphite-like interplanar spacing (0.3370 nm), and B-containing functional groups (0.77 at%). The density function theory (DFT) calculation demonstrated that the adsorption energies of Li on B-HCNCWs were much higher than that of HCNCWs, which proved that B-doping in a carbon matrix could increase the lithium intercalation capacity.

B, O and N Codoped Biomass-Derived Hierarchical Porous Carbon for High-Performance Electrochemical Energy Storage

High specific surface area, reasonable pore structure and heteroatom doping are beneficial to enhance charge storage, which all depend on the selection of precursors, activators and reasonable preparation methods. Here, B, O and N codoped biomass-derived hierarchical porous carbon was synthesized by using KCl/ZnCl2 as a combined activator and porogen and H3BO3 as both boron source and porogen. Moreover, the cheap, environmentally friendly and heteroatom-rich laver was used as a precursor, and impregnation and freeze-drying methods were used to make the biological cells of laver have sufficient contact with the activator so that the layer was deeply activated. The as-prepared carbon materials exhibit high surface area (1514.3 m2 g−1), three-dimensional (3D) interconnected hierarchical porous structure and abundant heteroatom doping. The synergistic effects of these properties promote the obtained carbon materials with excellent specific capacitance (382.5 F g−1 at 1 A g−1). The symmetric supercapacitor exhibits a maximum energy density of 29.2 W h kg−1 at a power density of 250 W kg−1 in 1 M Na2SO4, and the maximum energy density can reach to 51.3 W h kg−1 at a power density of 250 W kg−1 in 1 M BMIMBF4/AN. Moreover, the as-prepared carbon materials as anode for lithium-ion batteries possess high reversible capacity of 1497 mA h g−1 at 1 A g−1 and outstanding cycling stability (no decay after 2000 cycles).

A Novel Dendrite-Free Lithium Metal Anode via Oxygen and Boron Codoped Honeycomb Carbon Skeleton

Lithium (Li) metal is an excellent anode of Li ion batteries because of its high theoretical capacity and the low redox potential compared to other anodes. However, the uncontrollable growth of Li dendrites still incurs serious safety issues and poor electrochemical performances, leading to its limited practical application. An oxygen and boron codoped honeycomb carbon skeleton (OBHcCs) is reported and a stable Li metal-based anode is realized. It can be coated on a copper foil substrate to be used as a current collector for a dendrite-free Li metal anode. OBHcCs effectively reduces the local current density owing to the high surface area and inhibits Li dendrite growth, which is explored by scanning electron microscopy and an X-ray photoelectron spectra depth profile. The abundant lithiophilic oxygen and boron-containing functional groups reduce the potential barrier of nucleation and lead to the homogeneous Li ions flux as confirmed by the density functional theories. Therefore, the Li metal anode based on OBHcCs (OBHcCs@Li) stably runs for 700 h in a symmetric cell with a Li stripping capacity of 1 mAh cm^-2 at 1 mA cm^-2 . Furthermore, the OBHcCs@Li|LiFePO₄ full cell shows a good capacity retention of 84.6% with a high coulombic efficiency of 99.6% at 0.5 C for 500 cycles.

Preparation of N/O co-doped porous carbon by a one-step activation method for supercapacitor electrode materials

Heteroatom-doped carbon materials used in supercapacitors are low in cost and demonstrate extraordinary performance. Here, ethylenediamine tetraacetic acid (EDTA) with intrinsic N and O elements is selected as a raw material for the preparation of heteroatom self-doped porous carbon. Furthermore, N/O self-doped porous carbon with a large surface area has been successfully prepared using K₂CO₃ as the activator. The derived sample with a 1 : 2 molar ratio of EDTA to K₂CO₃ (EK-2) demonstrates a porous structure, rich defects, a large surface area of 2057 m² g⁻¹ and a micropore volume of 0.25 cm³ g⁻¹. Benefiting from high N content (2.89 at%) and O content (10.75 at%), EK-2 exhibits superior performance, including high capacitance of 325 F g⁻¹ at 1 A g⁻¹ and outstanding cycling stability with 96.8% retention after 8000 cycles at 10 A g⁻¹, which strongly confirms its immense potential toward many applications. Additionally, the maximum energy density of EK-2 reaches was 17.01 W h kg⁻¹ at a power density of 350 W kg⁻¹ in a two-electrode system. This facile and versatile strategy provides a scalable approach for the batch synthesis of N/O co-doped carbonaceous electrode materials for energy storage.

Heteroatom-doped carbon materials used in supercapacitors are low in cost and demonstrate extraordinary performance.

N-doped graphitized porous carbon derived from N-rich polymer for improved supercapacitor performance

Porous carbons with the large specific surface area, high electrical conductivity as well as abundant heteroatom doping are regarded as a promising candidate for supercapacitor applications. In this report, a...