Porous Hard Carbon Research Articles

Tailoring Conductive 3D Porous Hard Carbon for Supercapacitors

Hard carbon has attracted great attention for energy storage owing to low cost and extremely high microporosity, however, hindered by its low electrical conductivity. The common strategy to improve the conductivity is through graphitization process which requires temperatures as high as 3000 °C and inevitably destroys the porous structure. Herein, a balance between the specific surface area and electrical conductivity in a 3D porous hard carbon by in situ iron‐catalyzed graphitization process together with the Si–O–Si network is successfully achieved. The Fe can accelerate the localized graphitization at relatively low temperature (1000 °C) to form nanographite domains with enhanced conductivity, while the Si–O–Si network contributes to generating a 3D porous structure. As a result, the optimized hard carbon exhibits a 3D interconnected and hierarchical porous structure with extremely high specific surface area (2075 m2 g−1) and excellent electrical conductivity (12 S cm−1) which is comparable with that of artificial graphite. And thus, high capacitance of 315 F g−1 and excellent rate capability (174 F g−1 at 40 A g−1) are simultaneously achieved when used as electrodes for supercapacitors. The strategy is promising to build hard carbon materials with well‐tuned properties for high‐performance energy storage.

One-step sonochemical fabrication of biomass-derived porous hard carbons; towards tuned-surface anodes of sodium-ion batteries

A facile one-step sonochemical activation method is utilized to fabricate biomass-derived 3D porous hard carbon (PHC-1) with tuned-surface and is compared with the conventional two-step activation method. As raw biomass offers good KOH impregnation, ultrasonication power diffuses both K+ and OH– ions deep into its interior, creating various nanopores and attaching copious functional groups. In contrast, conventional activation lacks these features under the same carbonization/activation parameters. The high porosity (1599 m2/g), rich functional groups (O = 8.10%, N = 0.95%), and well-connected nanoporous network resulting from sonochemical activation, remarkably increased specific capacity, surface wettability, and electrode stability, consequently improved electrochemical performance. Benefiting from its suitable microstructure, PHC-1 possesses superior specific capacity (330 mAh/g at 20 mA/g), good capacity retention (89.5%), and excellent structural stability over 500 sodiation/desodiation cycles at high current density (1000 mA/g). Apart from modus operandi comparison, the two activation methods also provide mechanistic insights as the low-voltage plateau region and graphitic layers decrease simultaneously. This work suggests a scalable and economical approach for synthesizing large-scale activated porous carbons that are used in various applications, be it energy storage, water purification, or gas storage, to name a few.

Glucosamine derived hydrothermal carbon electrodes for aqueous electrolyte energy storage systems.

Nitrogen-doped porous hard carbons are synthesized by hydrothermal carbonization method (HTC) using glucosamine as biosource and treated at different carbonization temperatures in nitrogen environment (500, 750, 1000 °C). The electrochemical performances of hard carbons electrode materials for aqueous electrolyte sodium ion batteries are examined to observe the effect of two different voltage ranges (-0.8-0.0) V and (0.0-0.8) V in 1.0 M Na2SO4 aqueous electrolyte. The best electrochemical performances are acquired for the 1000 °C treated glucosamine (GA-1000) porous carbon sample that provides ~96 F/g capacitance value in the negative voltage range (between -0.8 and 0.0) V. The sodium diffusion coefficient of the GA-1000 carbon calculated by electrochemical impedance measurements is found to be 1.5 × 10-14 cm2/s.

Excellent Li/Garnet Interface Wettability Achieved by Porous Hard Carbon Layer for Solid State Li Metal Battery.

Garnet-type Li6.4 La3 Zr1.4 Ta0.6 O12 (LLZTO) electrolyte is considered as a promising solid electrolyte because of its relatively high ionic conductivity and excellent electrochemical stability. The surface contamination layer and poor Li/LLZTO interface contact cause large interfacial resistance and quick Li dendrite growth. In this paper, a porous hard carbon layer is introduced by the carbonization of a mixed layer of phenolic resin and polyvinyl butyral on the LLZTO surface to improve Li/garnet interfacial wettability. The multi-level pore structure of the hard carbon interlayer provides capillary force and large specific surface area, which, together with the chemical activity of the carbon material with Li, promote the molten Li infiltration with garnet electrolyte. The Li/LLZTO interface delivers a low interfacial resistance of 4.7 Ω∙cm2 at 40 °C and a higher critical current density, which can achieve stable Li+ conduction for over 800 h under current densities of 0.1 and 0.2 mA∙cm-2 . The solid-state battery coupled with Li and LiFePO4 exhibits excellent rate and cycling performance, demonstrating the application feasibility of the hard carbon interlayer for a solid state Li metal battery.

Nitrogen and Oxygen Co-Doped Porous Hard Carbon Nanospheres with Core-Shell Architecture as Anode Materials for Superior Potassium-Ion Storage.

The investigation of carbonaceous-based anode materials will promote the fast application of low-cost potassium-ion batteries (PIBs). Here a nitrogen and oxygen co-doped yolk-shell carbon sphere (NO-YS-CS) is constructed as anode material for K-ion storage. The novel architecture, featuring with developed porous structure and high surface specific area, is beneficial to achieving excellent electrochemical kinetics behavior and great electrode stability from buffering the large volume expansion. Furthermore, the N/O heteroatoms co-doping can not only boost the adsorption and intercalation ability of K-ion but also increase the electron transfer capability. It is also demonstrated by experimental results and DFT calculations that K-ion insertion/extraction proceeds through both intercalation and surface capacitive adsorption mechanisms. As expected, the NO-YS-CS electrodes show high initial charge capacity of 473.7 mAh g-1 at 20 mA g-1 , ultralong cycling life over 2500 cycles with the retention of 85.8% at 500 mA g-1 , and superior rate performance (183.3 mAh g-1 at 1.0 A g-1 ). The K-ion full cell, with a high energy density of 271.4 Wh kg-1 and an excellent cyclic stability over 500cycles, is successfully fabricated with K2 Fe[Fe(CN)6 ] cathode. This work will provide new insight on the synthesis and mechanism understanding of high-performance hard carbon anode for PIBs.

Joule Heating-Driven Transformation of Hard-Carbons to Onion-like Carbon Monoliths for Efficient Capture of Volatile Organic Compounds.

Soft graphitizable carbon-based multifunctional nanomaterials have found versatile applications ranging from energy storage to quantum computing. In contrast, their hard-carbon analogues have been poorly investigated from both fundamental and application-oriented perspectives. The predominant challenges have been (a) the lack of approaches to fabricate porous hard-carbons and (b) their thermally nongraphitizable nature, leading to inaccessibility for several potential applications. In this direction, we present design principles for fabrication of porous hard-carbon-based nanostructured carbon florets (NCFs) with a highly accessible surface area (∼936 m2/g), rivalling their soft-carbon counterparts. Subjecting such thermally stable hard-carbons to a synergistic combination of an electric field and Joule heating drives their transformation to free-standing macroscopic monoliths composed of onion-like carbons (OLCMs). This represents the first such structural transformation observed in sp2-based hard-carbon NCFs to sp2-networked OLCMs. Micro-Raman spectroscopy establishes the simultaneous increase in the intensity of D-, 2D-, and D + G-bands at 1341, 2712, and 2936 cm-1 and is correlated to the reorganization in the disordered graphitic domains of NCFs to curved concentric nested spheres in OLCMs. This therefore completely precludes the formation of a nanodiamond core that has been consistently observed in all previously reported OLCs. The Joule heating-driven formation of OLCMs is accompanied by ∼5700% enhancement in electrical conductivity that is brought about by the fusion of outermost graphitic shells of OLCs to result in monolithic OLC structures (OLCMs). The porous and inter-networked OLCMs exhibit an excellent adsorption-based capture of volatile organic compounds such as toluene at high efficiencies (∼99%) over a concentration range (0.22-1.86 ppm) that is relevant for direct applications such as smoke filters in cigarettes.

Porous hard carbon spheres derived from biomass for high-performance sodium/potassium-ion batteries

Hard carbon is the most attractive anode material for electrochemical sodium/potassium-ion storage. The preparation of hard carbon spheres directly from the broad sources of biomass is of great interest but barely reported. Herein, we developed a simple two-step hydrothermal method to construct porous carbon microspheres directly from the original waste biomass of camellia shells. The porous carbon microspheres have high specific capacities of 250 mAh g−1 and 264.5 mAh g−1 at a current density of 100 mA g−1 for sodium-ion batteries and potassium-ion batteries, respectively. And it has excellent cycle stability for sodium ions and potassium ions outperforming most reported hard carbons, which is mainly attributed to the microporous structure and spherical morphology. The work paves a way to prepare porous hard carbon spheres directly from biomass for alkali metal-ion batteries.

Preparation of rice husk-derived porous hard carbon: A self-template method for biomass anode material used for high-performance lithium-ion battery

A self-template is used to prepare graded porous carbon materials from the rice husks. The porous carbon material hydrothermally treated for 24h exhibits excellent electrochemical performance. The discharge specific capacity can reach 679.9 mAh g-1 after 100 cycles at a current density of 0.2C. • A self-template method is used to prepare porous hard carbon materials from the rice husks. • The biomass-derived carbon hydrothermally treated for 24 h exhibits excellent electrochemical performance. • The discharge specific capacity of biomass hard carbon can reach 679.9 mAh g −1 after 100 cycles at 0.2C. Hard carbon materials are employed as a novel anode material in lithium ion batteries (LIBs) due to its large specific surface area, high specific capacity and stable cycle performance. In this work, we report the use of SiO 2 as a template to prepare porous hard carbon materials from the environmental-friendly rice husks (RHs), among which the porous carbon material hydrothermally treated for 24 h exhibits splendid micro-morphology and excellent electrochemical performance. The charge specific capacity can still reach 679.9 mAh g −1 after 100 cycles at a current density of 0.2C. Such significant improvement in electrochemical performance is attributed to the edges, defects and large specific surface area possessed by the porous structure.

Biomass-derived N/S dual-doped porous hard-carbon as high-capacity anodes for lithium/sodium ions batteries

The N/S dual-doped porous hard-carbon (N/S-PC) material is obtained by simple heat treatment. The N/S-PC material has the characteristics of hierarchical pore structure, high SSA and porous channels. These features can provide more active sites and space for lithium/sodium ion storage, which is conducive to lithium/sodium ion transfer. The N/S-PC material is characterized by instrument and equipment (SEM, TEM, XPS, Raman, XRD). The N1S1 has excellent rate performance and cycle stability. For LIBs anode materials, the capacity remains at 1060 mAh g-1 after 50 cycles, additionally, it has a capacity of 546 mAh g-1 at 5 A g-1. When N1S1 used as SIBs anode, the capacity can reach 801mAh g-1 at 0.1 A g-1 and 402 mAh g-1 at 5 A g-1, it also shows the same cycle stability and electrochemical performance.

Biomass Feedstock of Waste Mango-Peel-Derived Porous Hard Carbon for Sustainable High-Performance Lithium-Ion Energy Storage Devices

Biomass Feedstock of Waste Mango-Peel-Derived Porous Hard Carbon for Sustainable High-Performance Lithium-Ion Energy Storage Devices

Microstructure-Dependent K+ Storage in Porous Hard Carbon.

Hard carbons (HCs) are emerging as promising anodes for potassium-ion batteries (PIBs) due to overwhelming advantages including cost effectiveness and outstanding physicochemical properties. However, the fundamental K+ storage mechanism in HCs and the key structural parameters that determining K+ storage behaviors remain unclear and require further exploration. Herein, HC materials with controllable micro/mesopore structures are first synthesized by template-assisted spray pyrolysis technology. Detailed experimental analyses including in situ Raman and in situ electrochemical impedance spectroscopy analysis reveal two different K+ storage ways in the porous hard carbon (p-HC), e.g., the adsorption mechanism at high potential region and the intercalation mechanism at low potential region. Both are strongly dependent on the evolution of microstructure and significantly affect the electrochemical performance. Specifically, the adequate micropores act as the active sites for efficient K+ storage and ion-buffering reservoir to relieve the volume expansion, ensuring enhanced specific capacity and good structural stability. The abundant mesopores in the porous structure provide conductive pathways for ion diffusion and/or electrolyte infiltration, endowing fast ionic/electronic transport kinetics. All these together contribute to the high energy density of activated carbon//p-HCs potassium ion hybrid capacitors (74.5Whkg-1 , at 184.4Wkg-1 ).

Three-dimensional hierarchical porous hard carbon for excellent sodium/potassium storage and mechanism investigation

Hard carbons are one of the most promising anode materials for sodium/potassium-ion batteries (SIBs/PIBs), which demonstrate favorable long charge/discharge plateaus, but suffer from low rate performance. Herein, we report a new design of N–P codoped hard carbon (NPHC) with three-dimensional (3D) hierarchical porous frameworks. Such unique structure provides bicontinuous ion/electron transportation paths, regulated electronic structure, enlarged interlayer spacing, and moderate surface area. The as prepared NPHC demonstrates a high reversible specific capacity (336 mAh g−1 for SIBs, 339 mAh g−1 for PIBs), along with a good rate performance of ~5.3 C. Particularly, an in-depth study on the charge storage mechanism for both SIBs and PIBs is conducted by combining in-situ Raman spectra and quasi in-situ synchrotron X-ray diffraction analysis, whereby the coexistence of physical adsorption/graphitic layer intercalation, or intercalation/pore filling within certain potential ranges is detected, and the ion storage behavior at different charge/discharge stages is precisely identified.

Porous hard carbon microtubes from renewable cotton as high-performance anode material for lithium-ion batteries

Consumer electronics or electric vehicles/power grids requires lithium-ion batteries (LIBs) with an increasingly outstanding energy-storage performance. However, the present graphite anode still faces significant challenges on relatively low specific capacity and poor rate performance. Herein, porous hard carbon microtubes (HCMs) were prepared by an activation method using natural cotton as a precursor, and their performance as an anode electrode. The electrochemical results of HCMs showed high performance on initial Coulomb efficiency, rate performance and cycle stability. The micro structure of HCMs were characterized, and the mechanism of high-performance generation of HCMs was analyzed. This article may provide an effective method to improve the electrochemical performance of hard carbon, which is also benefit to further understanding the lithium storage mechanism in porous hard carbon materials.

High stability gel electrolytes for long life lithium ion solid state supercapacitor

Lithium ion capacitors with liquid electrolyte are prone to leakage, combustion, explosion and other dangerous accidents. To solve these problems, the solid gel separator prepared by polyvinylidene fluoride - six fluoropropene (PVDF-HFP) is used in this work to improve the safety and stability of lithium ion supercapacitors. The PVDF-HFP based gel separator was used to replace the commercial separator and electrolyte in the lithium ion capacitor. The solid-state lithium ion supercapacitor was matched with porous carbon (PC) and hard carbon (HC). The maximum energy density of the device is 148.76 wh/kg, even at the power density of 33.6 kW/kg, which still retains 20.6 wh/kg. In addition, 83.3% capacity of solid-state lithium-ion supercapacitor is retained after 8000 times of charge and discharge. The requirements of high power energy density, high cycle stability and high safety are realized.

Pseudocapacitive porous hard carbon anode with controllable pyridinic nitrogen and thiophene sulfur co-doping for high-power dual-carbon sodium ion hybrid capacitors

A new and efficient method to regulate the configuration of nitrogen dopants, increase the content of thiophene sulfur, create micropores and adjust the defect intensity synchronously.

Insight into the rapid sodium storage mechanism of the fiber-like oxygen-doped hierarchical porous biomass derived hard carbon

Biomass, as a continuously available raw material, is widely used to produce hard carbon. However, many researchers have ignored the natural special morphology of biomass and the influence of oxygen on the sodium storage performance. Here, we use the cilia of the setaria viridis as the precursor to obtain a fiber-like oxygen-doped hierarchical porous hard carbon (SVC). The sodium storage mechanism of SVC is studied by controlling the pyrolysis temperature. Studies have shown that the natural fibrous structure and vertical holes of SVC can provide channels for the rapid penetration of electrolyte. The appropriate nanocrystal size affords commodious circumstances for the insertion of Na+. More importantly, the increase in carbonization temperature will change the bonding mode of carbon and oxygen, promote the rupture of single bonds and retain the existence of double bonds, which is beneficial to the improvement of coulombic efficiency and reversible capacity. The hybrid sodium storage mechanism composed of insertion behavior and capacitance behavior promotes SVC to have higher reversible capacity (285.4 mAh g−1 at 0.05 A g−1) and excellent rate performance (90.7 mAh g−1 at 5 A g−1). This research provides some new ideas for the study of hard carbon.

Active sites enriched hard carbon porous nanobelts for stable and high-capacity potassium-ion storage

Abstract Hard carbon finds critical applications in potassium-ion batteries (PIBs) anodes because of its attractive advantages including low cost and high conductivity. However, the sluggish reaction kinetics and structural instability caused by large K+ intercalation/deintercalation limit their storage capability and cycling life. Herein, active sites enriched hard carbon porous nanobelts (NOCNBs) for enhanced K+ storage are constructed from mineralized shrimp shells via a self-template assisted pyrolysis strategy. The NOCNBs possess multiscale structure with hierarchical micro/meso/macro-pores, high-level pyrrolic/pyridinic-N and O dual-doping, and large interlayer spacing. Hence, the NOCNBs deliver a high capacity of 468 mAh g−1 at 50 mA g−1 and long cycling life (277 mAh g−1 at 1000 mA g−1 over 1600 cycles), representing one of the best storage capability and cycling stability among the reported carbonaceous electrodes. Density functional theory calculations and kinetic analysis demonstrate that the abundant active sites within NOCNBs can strengthen K adsorption and diffusion, facilitating capacitive-adsorbed storage. The in-situ X-ray diffraction reveals the potassium intercalation mechanism in hard carbon for the first time. Furthermore, they exhibit a superior capacity of 89 mAh g−1 at 100 mA g−1 for potassium dual-ion batteries (PDIBs). This work opens up a new avenue for constructing porous hard carbon to achieve excellent K+ storage.

Ultrahigh “Relative Energy Density” and Mass Loading of Carbon Cloth Anodes for K-Ion Batteries

Mass loading and potential plateau are the two most important issues of potassium (K)-ion batteries (KIBs), but they have long been ignored in previous studies. Herein, we report a simple and scala...

Nitrogen-doped porous hard carbons derived from shaddock peel for high-capacity lithium-ion battery anodes

Heteroatom doping is an effective strategy to optimize the electrochemical performance of biomass-derived carbon electrode materials. In this work, nitrogen-doped porous hard carbons derived from shaddock peel (N-d-SPC) are successfully synthesized by alkali activation and carbamide-induced N-doping procedure, and are applied as the anode material in lithium-ion batteries (LIBs) for the first time. The introduction of N drives the forming of NC bonds, the expanding of interlayer distance and the optimizing of pore structure, which leads to the increase of the surface adsorption sites with the subordinate increase of interlayer active sites and the enhancement of electrochemical kinetics. Particularly, N-d-SPC electrode exhibits high cycling and rate capacities with the reversible capacity of 673 mAhg−1 at 50 mAg−1 after 100 cycles, and 282 and 172 mAhg−1 even at 2000 and 5000 mAg−1, respectively. Furthermore, N-d-SPC electrode demonstrates the Li+ storage process determined by the surface-induced pseudocapacitive behavior with a capacitive contribution of 73% at 0.5 mVs−1, which results in the surface electroadsorption predominant Li+ storage with a capacity contribution of 63% at 50 mAg−1.

Lotus Leaf-Derived Hierarchically Porous Hard Carbon Nanosheets as Anode for Highly Robust Potassium-Ion Batteries

Owing to abundant resources, low redox potential, and low expense, potassium-ion batteries (PIBs) have received continuous attention as a rookie of renewable electricity storage equipment. To obtain high-performance PIBs based energy storage, the energy storage anode must provide a stable and suitable structure for large-sized active potassium ions. To this end, a lotus leaf-derived, hierarchically porous activated carbon (LHPAC) was mainly obtained by a bionic strategy. The prepared LHPAC with a hierarchically porous structure not only affords fast transportation for both electrons and potassium ions but also supplies the necessary void space to avoid structural instability incurred by volume dilatation in the process of electrode operation. Therefore, the LHPAC exhibited exceptional reversible capacity (170 mA · h · g–1 at 50 mA · g–1) and superb cycle solidity (0.016% tiny capacity attenuation per cycle at 200 mA · g–1, capacity retention rate of 86.3% after 870 cycles), as well as inimitable rate performance. This work demonstrates the great application prospects of biomass-derived carbon materials as anode for sturdy PIBs.