High-performance Sodium-ion Capacitors Research Articles

Engineering multiple heterogeneous Co/CoSe/MoSe2 embedded in carbon nanofibers with Co/Mo–Se–C bonding towards high performance sodium ion capacitors

MoSe2, as a representative two-dimensional transition selenide with a broad interlayer distance of 0.65 nm and a high theoretical capacity of 422 mAh g−1, is considered an optimal anode material for sodium-ion batteries (SIBs). However, its unsatisfactory electrical conduction and structural instability often lead to severe capacity decay during cycling, hindering its large-scale application in SIBs. To overcome these challenges, coupling heterostructures has been identified as an effective solution. The establishment of multiple heterointerfaces can minimize interface diffusion resistance, significantly enhancing ion and electron delivery dynamics compared to a single component. In this work, multiple heterogeneous Co/CoSe/MoSe2 uniformly distributed in carbon nanofibers (CNF) via Co/Mo–Se–C bonding are successfully synthesized using electrospinning and subsequent calcination. Importantly, the Co/CoSe and Co/MoSe2 heterointerfaces can greatly accelerate charge transfer and improve Na + adsorption capability compared to the CoSe/MoSe2 heterostructure, as corroborated by theoretical calculations. Given the high rate performance of Co/CoSe/MoSe2@CNF as an anode in SIBs (267.9 mAh g−1 at 5 A g−1), a rocking-chair sodium-ion capacitor (SIC) incorporating a Co/CoSe/MoSe2@CNF anode and a Na3V2(PO4)3 cathode is proposed, delivering high energy densities of 199.1 Wh kg−1 at 180 W kg−1 and 126.8 Wh kg−1 at 3280 W kg−1.

Coal-derived boron and phosphorus co-doped activated carbon with expanded interlayer space for high performance sodium ion capacitor anode

Aiming at the key problem of Na+ insertion difficulty and low charge transfer efficiency of activated carbon materials. It is an effective strategy to increase the lattice spacing and defect concentration by doping to reduce the ion diffusion resistance and improve the kinetics. Hence, anthracitic coal is used to prepare activated carbon (AC) and B,P-doped activated carbon (B,P-AC) as the cathode and anode materials for high-performance all-carbon SICs, respectively. AC cathode material has high specific surface area and reasonable micropore structure, which shows excellent capacitance performance. B,P-AC anode material has the advantages of extremely high specific surface area (1856.1 m2/g), expanded interlayer spacing (0.40 nm) and uniform distribution of B and P heteroatoms. Hence, B,P-AC anode achieves a highly reversible Na+ storage capacity of 243 mAh/g at a current density of 0.05 A/g. Density functional theory (DFT) calculations further verify that B,P-AC has stronger Na+ storage performance. The final assembled B,P-AC//AC SIC offers a high energy density of 109.78 Wh kg−1 and a high-power density of 10.03 kW kg−1. The high-performance coal-derived activated carbon of this work provides a variety of options for industrial production of electrode materials for sodium ion capacitors.

“Nano Reservoir” of Dual Energy Storage Mechanism for High-Performance Sodium Ion Capacitors

“Nano Reservoir” of Dual Energy Storage Mechanism for High-Performance Sodium Ion Capacitors

Enhancing pseudocapacitive behavior of MOF-derived TiO2-x@Carbon nanocubes via Mo-doping for high-performance sodium-ion capacitors

Sodium-ion capacitors (SICs) have been viewed as promising energy storage devices because of their high power/energy density, cycling stability and cost-efficiency, but they are also restricted by the unmatched reaction kinetics between the battery-type anode and capacitor-type cathode. Herein, we present a novel way to enhance the pseudocapacitive storage behavior and reaction kinetics of TiO2-based anode via Mo-doping and carbon hybridization, using the Mo-doped titanium metal-organic framework (Ti-MOF, MIL-125) as the precursor. Appropriate amount of Mo-doping (Mo:Ti = 1:9) induces the shape evolution from the round MIL-125 nanotablets to square Mo-MIL-125 nanocubes, which can be readily converted to Mo-doped TiO2-x@carbon composite with conformal morphology (namely, Mo0.1-TiO2-x@C). Mo-doping increases the concentration of Ti3+/oxygen vacancy and decreases its crystallinity, which greatly enhances the reaction kinetics and sodium storage performance. When examined in half-cells, the Mo0.1-TiO2-x@C anode exhibits higher pseudocapacitive contribution (∼85%), higher reversible capacity (216 mAh g−1 at 0.5 A g−1), and better cycling and rate capability (185 mAh g−1 even after 3000 cycles at 1 A g−1). When paired with commercial activated carbon (AC) as cathode, the Mo0.1-TiO2-x@C//AC SICs deliver a maximum energy density of 269.37 Wh kg−1 at a power density of 80.4 W kg−1 and 61.75 Wh kg−1 even at a high power density of 5421.95 W kg−1.

Galvanic Replacement Synthesis of Graphene Coupled Amorphous Antimony Nanoparticles for High-Performance Sodium-Ion Capacitor

Galvanic Replacement Synthesis of Graphene Coupled Amorphous Antimony Nanoparticles for High-Performance Sodium-Ion Capacitor

Synergistic effect of NaTi2(PO4)3 and MXene synthesized in situ for high-performance sodium-ion capacitors

The rapid growth of industries that use electrical energy requires novel energy storage systems that are low-cost, reliable, and have improved capacity and power. Sodium-ion capacitors (SICs) have attracted considerable attention as next-generation energy storage systems because they comprise sodium, which is a relatively inexpensive resource, and have high energy and power. Battery-type materials for SICs need to be studied due to their poor rate performance and lifespan. This study reports a NaTi2(PO4)3/MXene (NTP/MXene) composite as a battery-type anode material for high-performance SICs. The NTP/MXene composite is synthesized via the in situ growth of NTP, with poor electrical conductivity, on the surface of MXene, with a two-dimensional structure and high electrical conductivity. The in situ synthesized NTP/MXene composite exhibits better rate performance and cyclic stability than NTP or MXene. These improved electrochemical properties are attributed to the synergistic effect of the pseudocapacitive characteristics of MXene and the battery characteristics of NTP. An SIC assembled with the NTP/MXene composite and activated carbon affords a high energy density of 112.1 Wh kg−1 and a high power density of 9.5 kW kg−1. Furthermore, it exhibits excellent long-term capacity retention of 78 % even after 10,000 cycles.

Nitrogen-doped carbon encapsulating Fe7Se8 anode with core-shell structure enables high-performance sodium-ion capacitors

With the associated advantages of low costs and abundant resources, sodium-ion capacitors (SICs) present a suitable means for large-scale energy storage. However, their practical application is still significantly limited by the sluggish electrochemical reaction kinetics of battery-type anodes. Herein, the nitrogen-doped carbon-encapsulated Fe7Se8 nanorods (Fe7Se8@NC) with a core–shell structure were prepared via an in-situ self-polymerization and carbonization–selenization approach, which improves ion transport and maintains the structural stability of the nanorods. The designed Fe7Se8@NC nanorods exhibit desirable rate capability with a capacity of 290.7 mAh/g at 10 A/g and long-term cyclability with 84.6 % retention over 6000 cycles at 5 A/g. Moreover, research has shown that the diffusion dynamics of Na+ is improved in ether-based electrolytes and that the irreversible reactions at low voltages can be inhibited by a high discharge cut-off voltage. Furthermore, we demonstrated the specific sodium storage mechanism and excellent electrochemical reversibility of the Fe7Se8@NC electrode through in-situ and ex-situ characterization techniques. As expected, the assembled SICs with the Fe7Se8@NC anode and active carbon cathode deliver prominent energy/power densities and an ultra-long cycle life over 5000 cycles, shedding new light on the design of transition metal dichalcogenides as anode materials for advanced energy storage systems.

Ultrafast laser micromachining of hard carbon/fumed silica anodes for high-performance sodium-ion capacitors

The slow sodium-ion storage kinetics of battery-type electrodes limits the performance of sodium-ion capacitors (SICs) operating under high-power conditions. In this study, ultrafast laser micromachining was utilized to accelerate the sodium-ion storage kinetics of hard carbon/fumed silica (HC/f-SiO2) anodes. The ablation process involving an ultrafast femtosecond laser source enabled three-dimensional microstructuring of hot-short HC/f-SiO2 anodes with minimal photothermal damage. The microporous structure of the HC/f-SiO2 anodes facilitated the electrolyte wetting of the active materials as well as the diffusion-limited supply of sodium-ions from the bulk electrolytes. The microstructured HC/f-SiO2 anode exhibited a sodium-ion storage capacity of 370 mAh g−1, which was higher than those of unstructured HC/f-SiO2 anodes of comparable mass (298 mAh g−1) or thickness (248 mAh g−1). In addition, the rate capability of the microstructured HC/f-SiO2 anode was superior to that of the unstructured samples. Comparative full-cell tests with oxidized single-walled carbon nanotube cathodes confirmed that micromachining of the HC/f-SiO2 anode was crucial for improving the performance of the SIC full cells. This study demonstrates that ultrafast laser micromachining of HC/f-SiO2 electrodes is a facile and reliable strategy for the development of high-performance SICs.

A Novel Hybrid Point Defect of Oxygen Vacancy and Phosphorus Doping in TiO2 Anode for High-Performance Sodium Ion Capacitor

HighlightsA novel hybrid point defect design (HPD) with oxygen vacancies and P-dopant is proposed to solve the insufficient kinetic and low specific capacity problems of TiO2.Through density functional theory calculation and sodium storage characterization, the synergistic effect of HPD is beneficial to improve the conductivity and sodium storage performance of TiO2.The prepared sodium ion capacitors show outstanding power/energy density, ultra-long life and good capacity retention.

Layered Fe2(MoO4)3 assemblies with pseudocapacitive properties as advanced materials for high-performance sodium-ion capacitors

Sodium-ion capacitors (SICs) show great potential for large-scale energy storage devices due to their high energy-power density, long cycling life, and low cost of sodium. Nevertheless, a daunting challenge to this technology is the sluggish sodium ion diffusion kinetics of the faradaic anode materials, which impede the widespread development of SICs. Herein, uniformly layered Fe2(MoO4)3 (L-FMO) assemblies are prepared though a facile solvothermal-assisted route and used as anode material of SICs for the first time. Benefiting from the improved extrinsic pseudocapacitive contribution, the L-FMO assemblies exhibit fast kinetics, high sodium storage capacity as well as long-term lifetime. Moreover, an initial intercalation-subsequent conversion sodium storage mechanism of L-FMO assemblies is further demonstrated though a series of techniques including in-situ X-ray diffraction, ex-situ transmission electron microscopy as well as ex-situ X-ray photoelectron spectroscopy. When the L-FMO assemblies was applied into SICs, the assembled devices achieve a high-energy-power density (227.2 Wh kg−1, 20.05 kW kg−1) along with good cycling stability (a low capacity decay of only 0.0062% per cycle during 3000 cycles at the current density of 1 A g−1). The present work pioneers alkaline earth metal molybdates for SICs anodes and will push the development of energy storage systems.

Lithium/sodium-ion capacitors based on 3D graphene-based materials

Metal ionic capacitors (MICs) are a new type of hybrid electrochemical energy storage (EES) devices that integrate the advantages of high-power output in supercapacitors and high energy density in batteries. These materials show potential to be commercialized, but their practical application is still limited due to the imbalance of kinetics and capacity between the electrodes, the slow ion/electron diffusion rate and the poor structural stability of the electrodes. 3D graphene-based materials with unique structure and appealing properties have recently received attentions for application in MICs due to their remarkable improvement from charge storage capacity to reaction kinetics. In this article, we reviewed the research progress of 3D graphene-based materials in lithium-ion capacitors (LICs) and sodium ion capacitors (SICs). Firstly, the energy storage principle and development requirements of LICs and SICs are introduced. The fabrication of 3D graphene materials is then summarized. The key advantages and important roles of 3D graphene-based materials in the construction of LICs and SICs are discussed. Finally, the challenges and prospects regarding the application of 3D graphene-based materials in high-performance LICs and SICs are presented.

A safe, low-cost and high-efficiency presodiation strategy for pouch-type sodium-ion capacitors with high energy density

Sodium-ion capacitors (SICs) have attracted appreciable attention in virtue of the higher energy and power densities compared with their rivals, supercapacitors and sodium-ion batteries. Due to the lack of sodium resources in cathode, presodiation is critical for SICs to further augment performances. However, current presodiation strategy utilizes metallic sodium as the presodiation material. In this strategy, assembling/disassembling of half-cells is required, which is dangerous and increases the time and cost of SIC leading to the restriction of their industrialization and commercialization. Herein we present a safe, low-cost and high-efficiency presodiation strategy by first employing Na2C2O4 as the sacrificial salt applied in SICs. Na2C2O4 is environmentally friendly and possesses considerably low expenditure. No additional residues remain after sodium extraction ascribed to its “zero dead mass” property. When paired with commercial activated carbon as the cathode and commercial hard carbon as the anode, the constructed pouch-type SICs exhibit high energy and power densities of 91.7 Wh/kg and 13.1 kW/kg, respectively. This work shows a prospect of realizing the safe and low-cost manufacturing for high-performance SICs commercially.

High content anion (S/Se/P) doping assisted by defect engineering with fast charge transfer kinetics for high-performance sodium ion capacitors

The rate-determining process for sodium storage in TiO2 is greatly depending on charge transfer happening in the electrode materials owing to its inferior diffusion coefficient and electronic conductivity. Apart from reducing the diffusion distance of ion/electron, the increasement of ionic/electronic mobility in the crystal lattice is also very important for charge transport. Here, an oxygen vacancy (OV) engineering assisted in high-content anion (S/Se/P) doping strategy to enhance charge transfer kinetics for ultrafast sodium-storage performance is proposed. Theoretical calculations indicate that OV-engineering evokes spontaneous S doping into the TiO2 phase and achieves high dopant concentration to bring about impurity state electron donor and electronic delocalization over S occupied sites, which can largely reduce the migration barrier of Na+. To realize the speculation, high-content anion doped anatase TiO2/C composites (9.82 at% for S in A-TiO2–x-S/C) are elaborately designed. The optimized A-TiO2–x-S/C anode exhibits extraordinarily high-rate capability with 209.6 mAh g−1 at 5000 mA g−1. The assembled sodium ion capacitors deliver an ultrahigh energy density of 150.1 Wh kg−1 at a power density of 150 W kg−1 when applied as anode materials. This work provides a new strategy to realize high content anion doping concentration, and enhances the charge transfer kinetics for TiO2, which delivers an efficient approach for the design of electrode materials with fast kinetic.

Functional carbon materials processed by NH3 plasma for advanced full-carbon sodium-ion capacitors

The pseudocapacitive storage mechanism of ClO 4 − and Na ions in cathode and anode were explored for the first time with NH 3 plasma strategy. In-situ/ex-situ characterizations and density functional theory (DFT) calculations demonstrate that pyridinic-N and C O could efficiently increase the defects and tune the adsorb properties of ClO 4 − , and build up an expressway for fast Na ions transfer, which further illustrates the “adsorption-pseudocapacitive reactions ”processes of cathodes and “adsorption-pseudocapacitive reactions-intercalation” processes of anodes. • N/O pseudocapacitive sites can be controlled by NH 3 plasma. • Revealing the reversible evolution of Pyridinic-N/C O. • Classifying the different mechanism in SICs. High-performance sodium-ion capacitors (SICs) are regarded as new-generation electrochemical energy-storage systems that are critically restricted due to the kinetic and capacity mismatch between the capacitor-type cathode and battery-type anode derived from the low capacity of carbon cathodes and the weak charge transfer kinetics of the anodes. In this study, for the first time, we investigate the pseudocapacitive storage mechanism of both ClO 4 − and Na ions in carbon cathode/anode with a novel NH 3 plasma strategy at room temperature. Interestingly, the implementation of pseudocapacitance greatly enhances the capacity in cathodes and the kinetics in anodes, effectively reducing the mismatch between two electrodes. With the ingenious NH 3 plasma strategy, which breaks the barriers of conventional methods of synthesizing N-functional carbon materials, various types and substances of N/O pseudocapacitive sites can be controlled directionally and accurately. The time-sensitive NH 3 plasma treatment utilized in this work has been demonstrated to be a state-of-art method for producing high content of pyridinic-N/C O bond and introducing ultrafast pseudocapacitance on the surface of the samples. Impressively, in-situ/ex-situ characterizations demonstrate the highly reversible evolution of Pyridinic-N and C O during the charging/discharging processes in cathodes/anodes, which is well consistent with electrochemical results and DFT calculations, presenting the “adsorption-pseudocapacitive reactions” and “adsorption-pseudocapacitive reactions-intercalation” mechanisms for cathodes and anodes respectively. Furthermore, the SICs deliver an energy density of 107 W h kg −1 at a power density of 200 W kg −1 . The current results are expected to be a powerful tool and an exciting opportunity to accelerate the practical application of SICs and achieve high-performance cathodes and anode materials.

Development of porous carbon nanosheets from polyvinyl alcohol for sodium-ion capacitors

Hard carbon anodes are deemed to be the best choice for sodium-ion capacitors (SICs). However, hard carbon still suffers from low specific capacity and poor rate capability, arising from its bulk structure with nonporous surface. Herein, we disclose the importance of utilizing ascorbic acid (AA) with polyvinyl alcohol (PVA) to synthesize 3D porous carbon nanosheets (PCNs) for SIC. The physical studies reveal that AA is operative to increase the specific surface area (373.7 m2 g−1) as well as to enlarge the interlayer spacing (0.41 nm). As anode for sodium-ion storage, PCNs-C600 achieves a high specific capacity of 307 mAh g−1 at 0.1 A g−1, superior rate performance of 121 mAh g−1 at 10 A g−1, as well as outstanding cycling stability at 1.0 A g−1 with virtually no decay over 5000 cycles. Accordingly, the SIC device is assembled by using PCNs-C600 as anode, which displays high energy/power densities of 128 Wh Kg−1/17034 W Kg−1 with superior rate capability and remarkable cyclability (83% retention over 8000 cycles at 1.0 A g−1). These results open a new pathway towards generating a high-performance sodium-ion capacitor.

High-performance sodium-ion capacitors with SnS2/ZnS-reduced graphene oxide anodes and biomass waste-derived porous carbon cathodes

High-performance sodium-ion capacitors with SnS2/ZnS-reduced graphene oxide anodes and biomass waste-derived porous carbon cathodes

Nitrogen and oxygen co-doped mesoporous carbon spheres as capacitive anode for high performance sodium-ion capacitors

The poor rate capability of battery-type anode is usually the bottleneck of the power-energy outputs of a hybrid alkaline metal ion capacitor. In this work, nitrogen and oxygen co-doped mesoporous carbon spheres with excellent rate performance and cycle stability are used as anode materials of sodium ion capacitors (SICs). The high N and O element doping levels as well as the amorphous and mesoporous structure have enabled prominent capacitive Na ion storage behavior, which in turn match well with the capacitive cathode in the hybrid device. Under optimum conditions, the SIC delivers a high energy density of 103.1 Wh kg−1 at a power density of 205.6 W kg−1. Even at a high power density of 7520 W kg−1, an energy density of 23.5 Wh kg−1 is still maintained. Moreover, a robust cycle stability with capacity retention of 84.6 % after 2500 cycles at 1 A g-1 is maintained. Such excellent electrochemical performances convincingly demonstrate that the all-carbon based SICs with the highly capacitive N and O co-doped mesoporous carbon anode can be promising Na ion-based energy storage devices alternative to their Li ion-based counterparts.

Sulfur and nitrogen dual-doped carbon nanofiber with enlarged interlayer distance as a superior anode material for sodium-ion capacitors

Sodium-ion capacitors (SICs) have attracted widespread attention due to their combination of high-energy batteries and high-power supercapacitors as well as low cost of sodium resources. However, the anodes exhibit low specific capacities and sluggish kinetics, thus limiting fast development of high-performance SICs. In the present work, the sulfur and nitrogen dual-doped carbon nanofiber (S-NCNF) membrane was synthesized as a novel anode material of SICs. Introduction of S atoms can result in an enlarged interlayer distance of 0.38 nm in S-NCNF, which is beneficial to Na+ ion insertion and the electron transport. As a result, the obtained S-NCNF electrode shows high sodium-storage capacity (298 mAh g−1 at 0.1 A g−1) and superior rate capability (188 mAh g−1 at 5 A g−1). The fabricated SIC delivers high energy density (97 Wh kg−1) and power density (17 kW kg−1) as well as long cycle life (3000 cycles).

Electrolyte Technologies for High Performance Sodium-Ion Capacitors.

Bridging the energy gap between batteries and capacitors, while in principle delivering a supercapacitor-like high power density and long lifespan, sodium-ion capacitors (SIC) have been considered promising energy storage devices that could be commercialized in the near future due to the natural abundance of sodium sources and the performance superiority of SIC devices. Therefore, in the past decade, substantial research efforts have been devoted to their structure and property improvements. With regard to the electrochemical performance of an ion capacitor, except for the electrode, the composition and structure of the electrolytes are also of great importance. Thus, in this mini review, we present a brief summary of the electrolytes developed recently for high performance SIC, including aqueous, organic, and ionic liquid based electrolytes. The influence factors such as ionic conductivities, electrolyte concentrations, electrochemical stable windows, as well as the cost and safety issues are discussed. Furthermore, the future perspectives and challenges in the science and engineering of new electrolytes are also considered. We hope that this review may be helpful to the energy storage community regarding the electrolytes of advanced SIC systems.

Nb2O5 nanotubes on carbon cloth for high performance sodium-ion capacitors

Hybrid sodium-ion capacitors (SICs) bridge the gap between the supercapacitors (SCs) and batteries and have huge potential applications in large-scale energy storage. However, designing appropriate anode materials with fast kinetics behavior as well as long cycle life to match with the cathode electrodes remains a crucial challenge. Herein, Nb2O5 nanotubes and nanowire-to-nanotube homo-junctions were directly grown on the carbon cloth (CC) via a simple hydrothermal process through regulating the pH value of solution. The as-prepared Nb2O5@CC nanotubes displayed a high reversible capacity of 175 mA h g−1 at the current density of 1 A g−1 with the coulombic efficiency of 97% after 1500 cycles. Besides, the SICs fabricated with Nb2O5@CC and activated carbon (AC) electrode materials showed a high energy density of 195 W h kg−1 at 120 W kg−1, a power density of 7328 W kg−1 at 28 W h kg−1 and 80% of the capacitance retention after 5000 cycles. Additionally, the flexible SIC devices can operate normally at various bendable conditions. The Nb2O5@CC nanotubes in this work can be promising electrode materials in flexible and wearable energy storage devices.