Remarkable Capacitive Performance Research Articles

Graphene-intercalated P4Se3@CNF hybrid electrode for sustainable energy storage solution: Enabling high energy density and ultra-long cyclic stability

Non-metal-based compounds have emerged as promising electrodes in recent years to replace scarce and expensive transition-metals for energy storage applications. Herein, a simple electro-spinning technique followed by carbonization is used to create tetraphosphorus triselenide (P4Se3) nano-flakes encapsulated in carbon nanofiber (P4Se3@CNF) to obtain a binder-free, metal-free and flexible hybrid electrode with high electrical conductivity and cyclic stability. A remarkable capacitive performance (5.5-folds@P4Se3) of 810 F g-1/112.5 mAhg−1@0.9 A g-1 has been obtained using P4Se3@CNF electrode with an excellent rate capability compared to pristine (P4Se3) which is further supported by theoretical calculations via intercalating graphene within bare P4Se3 flakes inducing partial charge redistribution in hetero-structure. A flexible pouch-type hybrid-supercapacitor followed by coin-cell has been manufactured offering exceptional energy density without sacrificing power density and ultra-long durability over 35,000 and 1,00,000-cycles with capacitance-retention of 99.77 % and 100 %, respectively. It has been demonstrated that as-fabricated device has practical usefulness towards renewable energy harvesting and storage via integrating commercial solar cell module with supercapattery array that can enlighten the blue LED approximately for 31 min, rotate the homemade windmill device, power Arduino and glow “INST” against 2 min of charging. This work demonstrates a facile route towards the development of metal-free electrochemical renewable energy storage/transfer devices offering an inevitable adoption in industrial platforms.

Exploring the Photocatalytic and Supercapacitive Potential of CuZr2S4 Thin Films: A Key to Cleaner and Safer Environments

In this research, an extensive exploration of bimetallic sulfide, CuZr2S4, is delved into. It involves the utilization of diethyldithiocarbamate as a sulfur source. The resulting thin film exhibits a well‐defined crystalline structure, characterized by an average crystallite size of 33 nm, indicating a commendable crystallinity of 87%. Bandgap energy through optical characterization is unveiled to be 2.5 eV, shedding light on the metal sulfide optical behavior. Furthermore, the elemental composition and chemical bonding of the thin film are elucidated using X‐ray photoelectron spectroscopy, revealing distinctive core‐level peaks associated with Cu 2p, Zr 3d, and S 2p. Electrochemical evaluations employing voltammetry measurements showcase remarkable specific capacitive performance, achieving an impressive value of 479 Fg−1. The thin film demonstrates exceptional stability over multiple cycles, underscoring its immense potential for diverse energy‐storage applications. A thorough assessment of the synthesized material's photocatalytic capabilities, namely its ability to degrade several types of environmental contaminants, is conducted.

Bacterial cellulose derived carbon nanofiber aerogel assembled with redox active hydrogel and alpha-MoO3 nanoplate for high-performance supercapacitors

Dual-asymmetric supercapacitors (DASCs) with high capacitive performance were developed in this work through carefully design and configuration of all the capacitor components. Free-standing carbon aerogel was directly utilized as the positive electrode, which was fabricated by pyrolyzing bacterial cellulose (BC) aerogel. Its porous structure afforded it excellent interface with the redox active electrolyte. Redox active hydrogel electrolyte based on mixed-valence iron ions (PVA/H2SO4/Fe3+/2+) was prepared with a freezing-thawing method and combined with the carbon aerogel to form the positive compartment of the capacitors. Meanwhile, α-MoO3 nanoplates were fabricated by hydrothermal method and used for the fabrication of negative electrodes, which were assembled with conventional PVA/H2SO4 hydrogel electrolyte to form the negative compartment. The as-assembled DASCs showed a specific capacitance of 560.8 F g−1 at 1 A g−1 and energy density of 131.6 Wh kg−1, indicating its remarkable capacitive performance. Moreover, the optimized DASC displayed a remarkable long-term cycling stability. This work on the design and assembly of the battery-like supercapacitor with carbon aerogel electrodes combined with their corresponding hydrogel electrolytes afforded a new configuration to fabricate the devices with high performance.

Dual redox electrolytes for improving the performance of asymmetric supercapacitors constructed from heteroatom-doped green carbon spheres

Although supercapacitors benefit from both long-cycle durability and extraordinary power density, unmet energy demands still remain the key challenge on the path of their practical applications. Boosting energy densities without sacrificing the remarkable power densities and long cycle life is of special significance in developing high-performance energy storage systems. Herein, the synergy between reversible redox mediator addition and heteroatom-doping of carbon-based electrode active materials represents an enhanced electrochemical performance of the fabricated energy storage devices. Green carbon spheres (CSs) were synthesized through the eco-benign hydrothermal carbonization (HTC) approach. CSs were then chemically decorated by metal nanoparticles. A carbothermic reduction, in which metallic nano particles nanoparticles played a role as a sacrificial agent, was conducted to prepare highly porous CSs (PCSs). The carbothermic reduction process was followed by heteroatom doping of the PCSs. Nitrogen- and boron-doped PCSs were then utilized as positive and negative electrode active materials, respectively. A combination of potassium iodide (KI) and sodium anthraquinone-2-sulfonic acid (AQSA) was employed as dual-redox mediators to boost the electrochemical performance of the fabricated N-PCS//B-PCS ASC devices. The assembled ASCs coupled with AQSA/KI dual redox additives rendered not only remarkable energy density (86.3 W h kg−1) at a reasonable power density of 340 W kg−1 but also exhibited outstanding cyclic stability (only 22 % decay of initial capacitance observed after 5000 charge/discharge cycle). The encouraging features parallel to the remarkable capacitive performance of the fabricated ASCs make these supercapacitors immensely promising for practical applications.

Response Surface Methodology Optimization in High-Performance Solid-State Supercapattery Cells Using NiCo2S4-Graphene Hybrids.

In this work, NiCo2S4–graphene hybrids (NCS@G) with high electrochemical performance were prepared using a hydrothermal method. The response surface methodology (RSM), along with a central composite design (CCD), was used to investigate the effect of independent variables (G/NCS, hydrothermal time, and S/Ni) on the specific capacitances of the NCS@G/Ni composite electrodes. RSM analysis revealed that the developed quadratic model with regression coefficient values of more than 0.95 could be well adapted to represent experimental results. Optimized preparation conditions for NCS@G were G/NCS = 6.0%, hydrothermal time = 10.0, and S/Ni = 6.0 of NCS@G (111) sample. The maximum specific capacitance of NCS@G (111)/Ni fabricated at the optimal condition is about 216% higher than the best result obtained using the conventional experimental method. The enhanced capacitive performance of the NCS@G (111) sample can be attributed to the synergistic effect between NCS nanoparticles and graphene, which has the meso/macropores conductive network and low diffusion resistance. Notably, the NCS@G (111) could not only provide numerous reaction sites but also prevent the restacking of graphene layers. Furthermore, a supercapattery cell was fabricated with an (G + AC)/Ni anode, a NCS@G (111)/Ni cathode, and a carboxymethyl cellulose–potassium hydroxide (CMC-KOH) gel electrolyte. The NCS@G (111)//(G + AC) demonstrates an outstanding energy density of 80 Wh kg−1 at a power density of 4 kW kg−1, and a good cycling performance of 75% after 5000 cycles at 2 A g−1. Applying the synthesis strategy of RSM endows remarkable capacitive performance of the hybrid materials, providing an economical pathway to design promising composite electrode material and fabricate high-performance energy storage devices.

Hydrothermal assisted synthesis of novel NiSe2/CuO nanocomposite: Extremely stable and exceptional energy storage performance for faradaic hybrid supercapacitors

• NiSe 2 /CuO composite was synthesized via the hydrothermal method for the first time for energy storage applications. • The composite ST-1 electrode exhibits a remarkable capacitive performance (396 C g −1 ) compared to their pure counterparts in capacity, e.g., NiSe 2 (330 C g −1 ), CuO (265 C g −1 ) • An ASC assembly delivers an incredible energy storage performance with durable stability. This work portrays the synthesis of NiSe 2 , CuO, and their nanocomposite NiSe 2 /CuO (ST-1) via a cost-effective, simple, co-precipitation and hydrothermal method for the first time to explore its performance for sustainable faradaic hybrid supercapacitor. The electrochemical investigation revealed that the ST-1 electrode exhibits a remarkable capacitive performance (396 C g −1 ) compared to their pure counterparts in capacity, e.g., NiSe 2 (330 C g −1 ), CuO (265 C g −1 ), and the lowest charge transfer resistance. Inspired by its durable energy storage performance, we further assembled the ST-1//AC/3M KOH faradaic hybrid supercapacitor, which effectively operates in a broad and stable voltage window of 1.6 V. The optimum voltage contributed to enhancing the capacitance of ST-1//AC/KOH faradaic hybrid supercapacitor up to 120 F/g at 1 A g −1. It maintained as high as 69 F/g when the current discharge rates upsurged to 15 A g −1 , denoting the excellent rate performance. Additionally, a high energy density of 29 Wh g −1 was attained at a maximum power of 4950 W kg −1 with excellent cycling stability of 86 % till 10,000 cycles. These fascinating results pave the way to construct other new electrode materials based on transition metal selenides and CuO for next-generation, long-lasting durability for sustainable supercapacitors.

TMP/Pd complex immobilized on graphene oxide for efficient pseudocapacitive energy storage with combined experimental and DFT study

Designing sophisticated energy sources that can offer a large amount of electricity for various energy storage uses is a pressing need. In this study, Trimethoprim (TMP) was functionalized as a rich supply of nitrogen and oxygen on graphene oxide (FGO-TMP), using graphene oxide layers adorned with trimethoprim functional groups. Then, using a simple approach to synthesize FGO-TMP/Pd complex for supercapacitor applications, palladium ions were reacted and fixed on the FGO-TMP composite surface. The FGO-TMP/Pd composite produced was characterized as a symmetric capacitor with a capacitance of 330F/g at 5 mV s−1 and high energy and power densities of 60.3 W h Kg−1 and 1200 W kg−1, respectively. After 10,000 cycles at 8 A/g, this symmetric device retained 93.7 percent of its original capacitance, proving the remarkable capacitive performance of the developed platform as well as ultra-stability for such sophisticated energy storage devices. Topological analysis of the electron density distribution and its Laplacian at the bonding critical points and Bader atomic charges of the GO layer in both FGO-TMP and FGO-TMP/Pd composites confirms more concentrated bond charges in FGO-TMP/Pd, indicating effective improvement in electrode material behavior in a supercapacitor.

Supercapacitor performance of nitrogen doped graphene synthesized via DMF assisted single-step solvothermal method

We report a single step dymethyleformamide (DMF) assisted solvothermally synthesized nitrogen-doped reduced graphene oxide (N-RGO) as a novel electrode material. DMF effectively acts as a nitrogen dopant cum reducing agent for graphene which remarkably enhances its electrochemical properties. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, FTIR spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed to characterize the structure and properties of the N-RGO. XRD study confirms effective reduction of GO in the N-RGO. SEM image shows the formation of fluffy and highly porous N-RGO. EDX, XPS and FTIR spectroscopic studies confirm the doping of nitrogen atom into the resultant material (N-RGO). The highest specific capacitance of N-RGO is found to be 516 Fg−1 at a scan rate of 2 mVs−1 along with a good cyclic stability and stable coulombic efficiency. Such a remarkable capacitive performance is attributed to its porous structure and effective nitrogen doping which facilitates the migration of electrolyte ions and provides abundant active sites for such electrochemical behaviour. The electrochemical impedance spectroscopy study showed a typical capacitive behavior of the N-RGO and a faster frequency response with a relaxation time constant of 0.4 s. Thus, the synthesized N-RGO using this simple, cost-effective, environment friendly method could be a potential candidate for high performance energy-storage applications.

Self-assembled RuO2 nanoneedles on Ta/Cu foil for a robust and high-performance supercapacitor electrode

High-density self-assembled RuO2 nanoneedles (NNs) are successfully fabricated on a tantalum (Ta)-coated copper (Cu) substrate via a mild hydrothermal reaction for an electrochemical supercapacitor electrode with a superior energy storage capacity and excellent electrochemical stability. The electrochemical properties of the RuO2 NNs based electrode in a diluted H2SO4 electrolyte are investigated. The extremely thin Ta insertion layer enhances the adhesion between the RuO2 NNs and the copper foil charge collector, thereby significantly enhancing the mechanical and electrochemical energy storage characteristics of the RuO2 NNs electrode. The proposed electrode exhibits a remarkable capacitive storage performance of 1420 F g−1 at a scan rate of 5 mV s−1 and excellent long-term cycling stability (∼ 98% of capacitance is retained at 100 mV s−1 after several hundred cycles). Moreover, the electrode shows a high energy density of ∼ 13 Wh kg−1 at a power density of 27 kW kg−1. The proposed strategy can facilitate the design of binder-free robust nanostructured oxide/hydroxide electrodes and can be extended to prepare high-performance catalysts and battery anodes.

Fabrication of 5 V High-Performance Solid-State Asymmetric Supercapacitor Device Based on MnO2/Graphene/Ni Electrodes

To reach high energy density and excellent cycle stability, an asymmetric supercapacitor device combining a high-power electric double-layer capacitor (EDLC) anode and high energy density battery-type cathode has been designed and fabricated. A binder-free strategy was used to prepare cathode by coating graphene (G) on Ni foam (Ni), then electrodepositing MnO2, followed by calcination process. The potentiodynamic (PD) electrodeposition cycles of MnO2 onto graphene significantly impact the electrochemical properties. Benefiting from the hierarchical structure and binder-free process of the designed 75 C/G/Ni hybrid cathode, potentiostatic (PS) electrodeposition followed by PD electrodeposition for 75 cycles demonstrates a high specific capacitance of 691 F g−1 at 2 A g−1. The enhanced capacitive performance can be attributed to the synergistic effect between MnO2 nanosheets and graphene, in which graphene can serve as ideal support matrix and conductive channels. Furthermore, an asymmetric supercapacitor was fabricated with 75 C/G/Ni and (G + AC)/Ni as the cathode and anode, respectively, and a carboxymethyl cellulose–potassium hydroxide (CMC-KOH) gel electrolyte. The 75 C/G/Ni//(G + AC)/Ni asymmetric supercapacitor (ASC) exhibits a maximum energy density of 43 kW kg−1 at a power density of 302 W kg−1 with a potential window of 1.6 V and maintains good cycling stability of 88% capacitance retention at 2 A g−1 (over 5000 cycles). Four solid-state asymmetric supercapacitors stack connected in series display an effective 5.0 V working potential to increase the voltage and output energy as a device. The device was charged using a 18,650 Li battery with a voltage of +3.8 V for 30 s and discharged six white LEDs for 20 min. The facile fabrication and remarkable capacitive performance of the MnO2/G/Ni hybrid make it a promising electrode candidate in electrochemical energy conversion/storage devices.

MXene-polypyrrole electrodes for asymmetric supercapacitors

Despite the tremendous progress in the development and applications of flexible high-performance MXene-polypyrrole (PPy) composites for supercapacitor (SC) technology, current research in this area is limited to symmetric devices with low active mass loading (AML) and operating in limited voltage windows of 0.5–1 V in acidic electrolytes. Here, we propose an asymmetric SC device operating in a neutral 0.5 M Na2SO4 electrolyte in a voltage window of 1.7 V. We report high capacitance of 1.37 F cm−2 from the cyclic voltammetry (CV) data and 1.18 F cm−2 from the galvanostatic charge-discharge (GCD) data. A useful strategy is provided for the fabrication of MXene-PPy composites, which allows their application in negative electrodes and facilitates remarkable capacitive performance at AML of 40 mg cm−2. We optimize composition and performance of the negative electrodes and report high capacitance of 2.11 F cm−2 from CV data and 2.49 F cm−2 from GCD data, which is achieved at low electrode resistance. One of the key factors for the enhanced negative electrode performance is the use a conceptually new strategy for in-situ PPy polymerization on the MXene surface, which is based on the application of an efficient catecholate-type dispersant for electrostatic dispersion of MXene. The adsorbed dispersant acts as an anionic dopant for PPy, promoting PPy polymerization on the MXene surface. PPy coated multiwalled carbon nanotubes (MCNT) are formed by in-situ polymerization of PPy on dispersed MCNT for charge storage in positive electrodes of the SC devices. The positive electrodes were designed to match capacitive properties of the negative electrodes in a complementary potential window.

Facile and Scalable Fabrication of High-Performance Microsupercapacitors Based on Laser-Scribed In Situ Heteroatom-Doped Porous Graphene.

This study proposes an efficient, facile, and scalable strategy to synthesize in situ heteroatom-doped porous graphene via laser direct writing on the precursor-doped polyimide (PI) film, which is fabricated for the first time through incorporating PI powder and precursors with sodium carboxymethyl cellulose (CMC) binder by a drop-casting and low-temperature drying process. The resulting microsupercapacitors (MSCs) based on the as-prepared heteroatom-doped porous graphene exhibit remarkable capacitive performance. The typical boron-doped MSC prepared on borax-doped polyimide film possesses an ultrahigh areal capacitance of 60.6 mF cm-2 at 0.08 mA cm-2, which is approximately 20 times larger than that of undoped MSC. Furthermore, the boron-doped MSC has impressive cycling stability (with the capacitance retention of 96.3% after 20 000 cycles), exceptional mechanical flexibility, tunable capacitance, and voltage output through arbitrary modular serial and parallel integration. Besides, the nitrogen-doped porous graphene with excellent capacitive performance is also prepared by laser direct scribing on the sulfonated melamine-doped polyimide film, demonstrating excellent scalability and generality of this strategy. Hence, one-step laser direct writing on precursor-doped polyimide films can realize in situ heteroatom doping and generation of hierarchical porous graphene electrodes simultaneously, which opens a new avenue for the facile, cost-effective, and scalable fabrication of heteroatom-doped porous graphene, thus promising for MSCs and various flexible and wearable electronics at large-scale production.

Pt enhanced capacitive performance of Cr2N electrode toward flexible asymmetric supercapacitor

In the present work, the Pt-Cr2N composite and carbon thin film electrodes were directly deposited on a flexible 304 stainless steel current collector by the one-step sputtering technique. The inclusion of platinum (Pt) in chromium nitride (Cr2N) provides a significant enhancement in the electrochemical properties of Cr2N. The prepared Pt-Cr2N composite-based electrode demonstrates a high specific capacitance and cyclic life compared to the pristine Cr2N electrode. The designed Pt-Cr2N//carbon flexible asymmetric supercapacitor (FASC) has been examined for practical applications. The FASC (at 80° bend state) shows excellent capacitance retention of 82.6% for 30 000 charging/discharging cycles with a high specific capacitance of 106 Fg−1 and a specific energy of 48 Wh kg−1. The remarkable capacitive performance of this designed FASC makes it a potential candidate for energy storage applications, long life span, and flexible electronic devices.

Remarkable capacitive performance in novel tungsten bronze ceramics.

In this study, novel lead-free Sr1.75Ca0.25NaNb5O15 tungsten bronze ceramics were designed for potential energy storage applications. A remarkable energy storage density (∼3.23 J cm-3) along with a high energy storage efficiency (∼88.2%) was obtained simultaneously at an applied electric field of 290 kV cm-1. Moreover, the ceramic also showed exceptional discharging performance including a fast discharge rate (τ0.9 < 70 ns), an ultrahigh discharge current density (1104 A cm-2) and a high power density (82.8 MW cm-3). The achieved capacitive performance in this work indicates the great potential of the designed novel tungsten bronze ceramic for energy storage applications.

Nickel cobalt bimetallic metal-organic frameworks with a layer-and-channel structure for high-performance supercapacitors

Using L-malic and 4,4′-bipyridine as linkers and Ni and Co as metal centers, a series of bimetallic metal-organic frameworks (MOFs; NinComMOFs, n:m = 4:1, 2:1, 1:1 and 1:2) with a layer-and-channel structure were hydrothermally synthesized. Owing to the joint action of Co and Ni as well as internal crystal properties, the NinComMOFs presented a remarkable capacitive performance. The capacitance of Ni1Co1MOF could reach up 1333 F•g−1 at 2 A•g−1 and even at 10 A•g−1, the capacitance retained 83% of its performance, which was higher than that of its corresponding monometallic MOFs (NiMOF and CoMOF). Meanwhile, an asymmetric supercapacitor Ni1Co1MOF//activated carbon (AC) was developed. It had an outstanding capacitance of 97 F•g−1 at 0.5 A•g−1. Moreover, 83% retention capacitance after 2000 cycles suggested an excellent cycling lifespan. Ni1Co1MOF//AC also exhibited a high energy density of 28 Wh•kg−1 at 444 W•kg−1. To summarize, the bimetallic MOFs were promising electrode materials for supercapacitors owing to their excellent electrochemical properties.

Co-ZIF derived porous NiCo-LDH nanosheets/N doped carbon foam for high-performance supercapacitor

The three-dimensional (3D) interconnected structure is desirable for high-performance supercapacitor since it can provide more exposed electroactive sites as well as accelerate the electron and ion transfer. Herein, nitrogen doped carbon foams with good hydrophilicity and mechanical property are first prepared from cheap melamine foams via the heat-treatment at low temperature in the air, which can serve as an ideal substrate for growing nickel cobalt layered double hydroxide nanosheets (NiCo-LDH) derived from cobalt zeolitic imidazole frameworks (Co-ZIF). The as-prepared NiCo-LDH/N doped carbon foam (NiCo-LDH/NCF) exhibits high specific capacity of 756 C g−1 at a current density of 0.5 A g−1, and still retains the specific capacity of 414 C g−1 at a current density of 20 A g−1, indicating the excellent rate capability. Furthermore, the assembled NiCo-LDH@NCF//activated carbon asymmetrical supercapacitor device achieves a high energy density of 41.5 Wh kg−1 at a power density of 750 W kg−1, and an excellent cyclic stability of 80.4% retention over 10000 cycles. The remarkable capacitive performance of NiCo-LDH@NCF is assigned to the self-supporting 3D interconnected architecture of NCF that makes the uniform distribution of NiCo-LDH nanosheets and also provides the rapid channels for electron and ion transfer. The results indicate that NiCo-LDH@NCF will be a promising candidate for high-performance supercapacitors.

Mn3O4 tetragonal bipyramid laden nitrogen doped and hierarchically porous carbon composite as positive electrode for high-performance asymmetric supercapacitor

Nanostructured metal oxides have shown outstanding promise for electrochemical energy storage, but are usually limited to low rate capability and poor cycling performance caused by irregular shapes and aggregation of nanoparticles at high mass loading (>1 mg cm−2). To solve these problems, we report the design of a novel Mn3O4 tetragonal bipyramid laden nitrogen doped and hierarchically porous carbon (Mn3O4 TB/NHPC) composite with higher mass loading (～5 mg cm−2) for high-performance energy storage. The homogeneous dispersion of Mn3O4 TBs on NHPC with 3D architecture provides excellent electron transfer, and its hierarchically porous structure with large mesopore volume facilitates rapid ion transport. To achieve wide working potential window, an asymmetric supercapacitor of 1.8 V is assembled with Mn3O4 TB/NHPC composite and NHPC as the positive and negative electrode, respectively. Benefiting from these advantages, the supercapacitor exhibits excellent rate capability (80% of the capacitance retention from 0.5 to 10.0 A g−1) and high energy density (34.7 Wh kg−1 at 450 W kg−1). More importantly, the assembled device demonstrates a splendid cycling performance (97% capacitance retention after 10000 cycles). Morphology controlled Mn3O4 laden porous carbon composites with remarkable capacitive performance inspire us to develop superior electrode materials for energy storage.

Synergistic conversion of coal char and methane for syngas and carbon-based supercapacitor electrodes

A facile one-pot process for synergistic conversion of coal char and methane is conducted by employing K2CO3 as the catalyst. Besides syngas production, valuable carbon products are obtained and used to serve for supercapacitor electrodes. Effect of the operating parameters (including the catalyst dosage, gas feed flow rate, reaction temperature and time) is evaluated on electrochemical performance of the as-prepared carbon. The appropriate surface and structural properties enable the prepared carbon electrode to have a remarkable capacitive performance, along with a specific capacitance up to 125 F/g at a scan rate of 5 mV/s and 133 F/g at a current density of 1 A/g. According to the potential capacitive contribution of the carbon species, the high capacitive performance is mainly attributed to formation and growth of abundant carbon fibers in the one-pot process.

Boron and Nitrogen Co-Doped Porous Carbons Synthesized from Polybenzoxazines for High-Performance Supercapacitors

Boron and nitrogen co-doped porous carbons (BNPC-X) were synthesized from boron-containing polybenzoxazines through carbonization and chemical activation, where X represents the weight ratio of boric acid to benzoxazine resin. The as-prepared BNPC-X were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, element analysis and electrochemical measurements. The results show that the BNPC-0.15 possesses relatively high weight fractions of boron (2.97 wt %) and nitrogen (2.43 wt %), a homogeneous pore distribution, and remarkable electrochemical capacitive performance. It exhibits high specific capacitance (286 F·g−1 at 0.05 A·g−1), excellent rate capability (at A·g−1), and good charge–discharge stability (&gt;92% capacitance retention after 1,000 cycles at 1.0 A·g−1) in 6 M KOH aqueous solution.

Etching-Assisted Crumpled Graphene and Graphene Wrapped Spiky Iron Oxide Particles for Li-Ion Hybrid Supercapacitor

From graphene oxide wrapped iron oxide particles with etching/reduction process, high-performance anode and cathode materials of lithium-ion hybrid supercapacitors are obtained in the same process with different etching conditions, which consist of partially etched crumpled graphene (CG) wrapped spiky iron oxide particles (CG@SF) for a battery-type anode, and fully etched CG for a capacitive-type cathode. The CG is formed along the shape of spikily etched particles, resulting in high specific surface area and electrical conductivity, thus the CG-based cathode exhibits remarkable capacitive performance of 210 F g−1 and excellent rate capabilities. The CG@SF can also be ideal anode materials owing to spiky and porous morphology of the particles and tightly attached crumpled graphene onto the spiky particles, which provides structural stability and low contact resistance during repetitive lithiation/delithiation processes. The CG@SF anode shows a particularly high capacitive performance of 1420 mAh g−1 after 270 cycles, continuously increases capacity beyond the 270th cycle, and also maintains a high capacity of 170 mAh g−1 at extremely high speeds of 100 oC. The full-cell exhibits a higher energy density up to 121 Wh kg−1 and maintains high energy density of 60.1 Wh kg−1 at 18.0 kW kg−1. This system could thus be a practical energy storage system to fill the gap between batteries and supercapacitors.