A simple and universal method for preparing N, S co-doped biomass derived carbon with superior performance in supercapacitors

Construction of Microporous Zincophilic Interface for Stable Zn Anode

Aqueous zinc ion batteries (AZIBs) are promising electrochemical energy storage devices due to their high theoretical specific capacity, low cost, and environmental friendliness. However, uncontrolled dendrite growth poses a serious threat to the reversibility of Zn plating/stripping, which impacts the stability of batteries. Therefore, controlling the disordered dendrite growth remains a considerable challenge in the development of AZIBs. Herein, a ZIF-8-derived ZnO/C/N composite (ZOCC) interface layer was constructed on the surface of the Zn anode. The homogeneous distribution of zincophilic ZnO and the N element in the ZOCC facilitates directional Zn deposition on the (002) crystal plane. Moreover, the conductive skeleton with a microporous structure accelerates Zn²⁺ transport kinetics, resulting in a reduction in polarization. As a result, the stability and electrochemical properties of AZIBs are improved. Specifically, the ZOCC@Zn symmetric cell sustains over 1150 h at 0.5 mA cm^-2 with 0.25 mA h cm^-2, while the ZOCC@Zn half-cell achieves an outstanding Coulombic efficiency of 99.79% over 2000 cycles. This work provides a simple and effective strategy for improving the lifespan of AZIBs.

Rational design of pyrrolic-N dominated carbon material derived from aminated lignin for Zn-ion supercapacitors

Developing highly efficient, sustainable carbon cathodes is essential for emerging Zn-ion hybrid supercapacitors (ZICs). Herein, lignin's novel chemical modification (amination) has been developed to produce high quantity pyrrolic-N moieties as active sites. Furthermore, chemically modified amine moieties in lignin are vital as a natural self-activating template to generate hierarchical porosity in the 2D (graphene-like) architecture with exceedingly high surface area (2926.4 m²g^-1). The rationally introduced dominated pyrrolic-N moieties boost the Zn-ion storage capacity and reaction kinetics due to the dual energy storage mechanism and efficient charge transfer between pyrrolic-N and Zn⁺² ions. Furthermore, the pyrrolic-N species are energetically favorable for the adsorption of Zn⁺² ions by the formation of N-Zn⁺² chemical bonds. Besides, the nitrogen oxides reduce the intrinsic resistance and induce a more polarized surface, resulting in high wettability and efficient transfer of electrolytes into the pores of hydrophobic carbon materials. Subsequently, the chemically modified lignin-derived activated carbon material (Chem-ACM) as a cathode in ZICs delivers a high capacity of 161.2 mA h g^-1 at 1 A g^-1 with the admirable energy density of 106.7 W h kg^-1 at 897 W kg^-1 and excellent retention capacity (94%) after 10,000 cycles. Mainly, the assembled quasi solid-state ZICs using Chem-ACM retains the remarkable storage capacity (202 mA h g^-1 at 0.2 Ag^-1) even at a high bending angle. Notably, the Chem-ACM has been further employed in symmetric supercapacitors as an electrode, and it displays exceptional specific capacitance of 354 Fg^-1 at 0.5 Ag^-1 with tremendous energy (43.5 W h kg^-1) and the power density (0.53 kW kg^-1). Additionally, the charge storage capability of Chem-ACM is positively dependent on high nitrogen contents, and it is extrapolated that pyrrolic-N moieties are dominant active sites. Hence, the designed amination-assisted biocarbon synthesis provides a new way to prepare high nitrogen-containing biocarbon for ZICs and further understand pyrrolic-N species' impact on Zn-ion storage.

Transforming waste polypropylene face masks into S-doped porous carbon as the cathode electrode for supercapacitors

The spread of COVID-19 has led to an explosive increase in the number of waste polypropylene face masks worldwide, landfill and incineration of which will cause serious pollution and resource waste. This study aims to develop a new method for the safe and high-added value reuse of materials for polypropylene face masks based on carbonization of porous polymer. The waste masks were first sulfonated in an autoclave, then used as carbon source and turned into a dense hollow fiber porous structure after a one-step heat treatment. This porous structure has a high specific capacitance, namely 328.9 F g-1 at a current density of 1 A g-1. Besides, the assembled solid-state capacitor possesses a good energy density of 10.4 W h kg-1 at a power density of 600 W kg-1, and excellent cycling stability with a capacitance retention rate of 81.1% after 3000 cycles. These findings indicate that the novel carbonization technology in this study can not only be used to obtain high-performance supercapacitor electrode materials but also provide a new idea for the recycling and utilization of wastes such as medical devices.

Chemically modified self-doped biocarbon via novel sulfonation assisted sacrificial template method for high performance flexible all solid-state supercapacitor

The development of lignin-based carbon electrodes for high-performance flexible, solid-state supercapacitors in next-generation soft and portable electronics, has received much attention. Herein, a self-doped multi-porous lignin-based biocarbon (SUMBC) has been prepared via a simple sulfonation assisted sacrificial template method for the effective formation of oxygenated C-S-C moieties in the carbon network. In this proposed method, the sulfonate moieties in lignin are responsible for the successful decoration of oxygen enriched C-S-C moieties as well as for creating the optimal multilevel porous architecture (ultra-micropores, micropores and mesopores) in the carbon matrix with a large surface area (3149 m² g^-1). Because the sulfonate functionalities yield more sulfur species and induce further defects into carbon framework, in the activation process, these sulfur functionalities produce additional narrow micropores. Benefiting from the above unique feature, the supercapacitor (SC) with the SUMBC electrode delivers excellent capacitive behavior in both acidic (2 M H₂SO₄) and alkaline (6 M KOH) liquid electrolytes. More prominently, the all-solid state, symmetric supercapacitors assembled by SUMBC show outstanding capacitance of ~140 F g^-1 at 0.5 A g^-1 in two different devices and reveals high energy density (~5.41 W h kg^-1 at 0.5 k W kg^-1 power density) and excellent stability. In addition, the solid-state supercapacitors manifest a remarkable flexibility at different bending angles. Hence, the present work provides a new strategy for the preparation of efficient biocarbons via a facile sulfonation assisted sacrificial template method; moreover, the high-performance all-solid supercapacitors based on sulfonated modified lignin has great potential in the field of portable and wearable energy storage devices.

Naturally derived honeycomb-like N,S-codoped hierarchical porous carbon with MS2 (M = Co, Ni) decoration for high-performance Li-S battery

Even though lithium-sulfur batteries have appealing advantages including a high theoretical capacity and energy density, their commercial implementation has been seriously hindered by some notorious reasons, particularly the severe shuttling effect, the insulating nature of sulfur, the large volumetric variation during cycling and the sluggish redox reaction kinetics. To tackle these issues, a biomass (ginkgo-nut) derived N,S-codoped porous carbon (GC) with an interconnected honeycomb-like hierarchical structure is synthesized by a templated carbonization method, followed by hydrothermal growth of transition metal sulfide MS2 (M = Co, Ni) nanocrystals, giving rise to a hybrid 3D electrocatalyst. The unique structure constructed by N,S-codoping can expose more active sites and polar surfaces to physically confine and chemically adsorb polysulfides. Meanwhile, the embedded MS2 polyhedral-like nanoparticles further enhance the interaction with polysulfides and improve conversion and redox kinetics of polysulfides. Remarkably, with 80 wt% sulfur loading (∼2.5 mg cm-2), GC-CoS2 exhibits a reversible capacity of 988.8 mA h g-1 after 500 cycles at 0.1 C and an excellent capacity of 610.3 mA h g-1 after 1000 cycles at 2 C, outperforming bare GC and GC-NiS2. Compared with the electrochemical performances of the representative reported biomass-derived sulfur host for Li-S batteries, evidently, both the discharge capacity and cycling stability of our GC-CoS2 sample are superior. Density functional theory (DFT) calculation results suggest that CoS2 exhibits a higher binding energy towards lithium polysulfides and a lower energy barrier for Li+ diffusion on the surface compared to the NiS2 counterpart, suggesting that CoS2 is a better choice for lithium-sulfur batteries than NiS2. This work provides a new avenue to rationally design a carbonaceous catalyst host for high-performance lithium-sulfur batteries.

Structure Engineering in Biomass-Derived Carbon Materials for Electrochemical Energy Storage

Biomass-derived carbon materials (B-d-CMs) are considered as a group of very promising electrode materials for electrochemical energy storage (EES) by virtue of their naturally diverse and intricate microarchitectures, extensive and low-cost source, environmental friendliness, and feasibility to be produced in a large scale. However, the practical application of raw B-d-CMs in EES is limited by their relatively rare storage sites and low diffusion kinetics. In recent years, various strategies from structural design to material composite manipulation have been explored to overcome these problems. In this review, a controllable design of B-d-CM structures boosting their storage sites and diffusion kinetics for EES devices including SIBs, Li-S batteries, and supercapacitors is systematically summarized from the aspects of effects of pseudographic structure, hierarchical pore structure, surface functional groups, and heteroatom doping of B-d-CMs, as well as the composite structure of B-d-CMs, aiming to provide guidance for further rational design of the B-d-CMs for high-performance EES devices. Besides, the contemporary challenges and perspectives on B-d-CMs and their composites are also proposed for further practical application of B-d-CMs for EES devices.