Stable Voltage Window Research Articles

Graphene‐based Supercapacitor Using Microemulsion Electrolyte

AbstractGraphene‐like material prepared by a facile combustion synthesis was investigated as an electrode material in a microemulsion electrolyte. Notably, a stable voltage window of 2.2–2.4 V was achieved, surpassing previous reports for aqueous‐based electrolytes on similar materials. The fabricated supercapacitor device exhibited a commendable specific capacitance values of 59 F g−1 at 0.1 A g−1 and 32 F g−1 at 5 A g−1, indicating its potential for high‐current applications. Mechanistic examination revealed that the charge storage primarily relies on electric double‐layer formation, with minor non‐capacitive contribution from electrode surface functionalities and the supporting electrolyte. Further analysis showed significant capacitive contributions of 85 % at 2.2 V and 67 % at 2.4 V, underscoring the dominance of the capacitive process. The fabricated supercapacitor's stability indicated a decrease as the non‐capacitive process intensified, suggesting that electrode surface functionalities predominantly contribute to cell deterioration at elevated potentials. These results highlight the potential efficacy of microemulsion electrolytes in energy storage applications.

Can Aqueous Na2SO4-Based Neutral Electrolyte Increase Energy Density of Monolithic Wood Biochar Electrode Supercapacitor?

The performance of supercapacitors is significantly influenced by both the nature and the concentration of the electrolyte employed. This study investigates the impact of a neutral electrolyte on the electrochemical properties of the maple-derived monolithic wood biochar (MWB)–sodium sulfate (Na2SO4) supercapacitor. The goal is to determine if a neutral electrolyte, in this case Na2SO4, can increase the supercapacitor energy density compared to a previous study employing a KOH electrolyte. Starting from examining the ion sizes and conductivities of salt species in KOH and Na2SO4 electrolytes, the difference in voltage window, measured specific capacitance, and resistance are discussed. By switching the electrolyte from 4 M KOH to 0.5/1 M Na2SO4, the voltage stability window was extended from 0.8 V to 1.4 V. For 1 M Na2SO4, the supercapacitor attains a specific capacitance of 46 F/g at 5 mA/g, accompanied by an energy density of 12.5 Wh/kg and a maximum power density of 300 W/kg. The MWB electrode, derived from naturally abundant wood, when combined with the non-toxic Na2SO4 electrolyte, offers an environmentally friendly and cost-effective energy storage solution. With a prolonged lifetime and minimal maintenance requirements, MWB-Na2SO4 supercapacitors emerge as a promising choice for diverse applications.

Regulating Water Activity for All‐Climate Aqueous Zinc‐Ion Batteries

AbstractSuppressing the water activity is challenging to achieve high‐performing aqueous zinc ion batteries (AZIBs), especially for its practical climate adaptability. Reconstructing the H‐bond network and repealing the solvation water can effectively reinforce the covalency inside water molecular. Here, a hydrogel electrolyte formula utilizing ClO4− anions and hydrophilic ─NH2 on polyacrylamide chains is shown to bond with water molecules, while the zincophilic glucose preferentially regulate Zn2+ solvation. The multifunctional hydrogel structure can effectively disrupt the intrinsic H‐bond network and inhibit the interface side‐reactions induced by active water. Finally, the delayed freezing point and expanded voltage stability window are realized, which promotes the ZIBs steady operate in a wide temperature range. When operating at 70 and −30 ˚C, the Zn//NVO battery achieves high specific capacity of 488 and 254 mAh g−1, respectively, surpassing most of the previously reported results. Remarkably, the pouch battery delivers the state‐of‐the‐art specific capacity of 438.1 mAh g−1 and realizes a capacity retention of 76.3% after 400 cycles at 200 mA g−1.

Flexible Supercapacitor with Wide Electrochemical Stable Window Based on Hydrogel Electrolyte.

Hydrogel electrolyte can endow supercapacitors with excellent flexibility, which has developed rapidly in recent years. However, the water-rich structures of hydrogel electrolyte are easy to freeze at subfreezing and dry at high temperatures, which will affect its energy storage characteristics. The low energy density of micro supercapacitors also hinders their development. Herein, a strategy is proposed to reduce the free water activity in the hydrogel to improve the operating voltage and the energy density of the device, which is achieved through the synergistic effect of the hydrogel skeleton, N, N'-dimethylformamide (DMF), NaClO4 and water. High concentrations of DMF and NaClO4 are introduced into sodium alginate/polyacrylamide (SA/PAAM) hydrogel through solvent exchange to obtain SA/PAAM/DMF/NaClO4 hydrogel electrolyte, which exhibited a high ionic conductivity of 82.1 mS cm-1, a high breaking strength of 563.2kPa, and a wide voltage stability window of 3.5V. The supercapacitor devices are assembled by the process of direct adhesion of the hydrogel electrolyte and laser induced graphene (LIG). The micro-supercapacitor exhibited an operating voltage of 2.0V, with a specific capacitance of 2.41 mF cm-2 and a high energy density of 1.34 µWh cm-2, and it also exhibit a high cycle stability, good flexibility, and integration performance.

Volume contractible Antimony bromide electrode as negative electrode for long-lasting Li-ion batteries

Antimony is one of the promising anode materials for lithium-ion batteries due to its high volumetric and gravimetric capacity (theoretical specific capacity 660 mAh g-1) and stable voltage window (0.87-0.91V vs Li/Li+). However, a high-volume expansion ( ∼130%) of Sb on lithiation degrades the electrochemical performance and restricts its application. In this work, a novel strategy is explored to use antimony halide (SbBr3) instead of Sb as the starting anode material. In the first step, Li will react with SbBr3 to form LiBr and pure Sb, leading to a 78% contraction in volume, and then this pure Sb further lithiates to form Li3Sb expanding the volume (of the lithiated Sb by 130%). LiBr, which is a byproduct of the first reaction, dissolves into the solvent, leaving a porous Sb. In a nutshell, the two-step lithiation process results in a net volume-contacted porous antimony, ideal as an electrode to counter volumetric stress in subsequent charge-discharge cycles. The electrochemical performance of this electrode is much superior when compared with the pure antimony electrode, taking advantage of initial volume reduction and porous scaffold. It achieves a high specific discharge capacity of 345 mAh g-1 at a rate of 100mAg-1 even after the end of the 100th cycle and losing only 20% of its capacity. This shows that this volume contractible technique can be successfully employed for metals and metallic alloys having drastically higher Li-storing capacities than graphite.

Decoupling electrolyte strategy for a high-voltage Na-ion hybrid capacitor based on NaFeO2 and activated carbon

Sodium iron dioxide (NaFeO2) with high specific capacity, has been widely used as a kind of electrode materials for Na-ion batteries. When NaFeO2 is used as the battery-type electrode for aqueous Na-ion hybrid capacitors, there are a lot of technical challenges to meet, especially the narrow voltage window limited by the thermodynamic decomposition of water. We propose a novel decoupling electrolyte strategy to suppress the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) on the NaFeO2 anode and the activated carbon (AC) cathode respectively, in order to expand the voltage window of the aqueous AC//NaFeO2 Na-ion hybrid capacitor. The alkaline anolyte (2 M NaOH) and the neutral catholyte (1 M Na2SO4) can be decoupled by the cation exchange membrane, which selectively allows the Na+ ions through the membrane to carry the electric currents in the charge/discharge process. The NaFeO2 sample with the stable crystal structure and oxygen vacancy defects, can provide a gravimetric specific capacitance of 101.1 F g−1 at 1 A g−1. Electrochemical kinetic analysis indicates that the capacitor-type behaviour is predominant in the electrochemical energy storage process of the AC//NaFeO2 Na-ion capacitor at the scan rates higher than 40 mV s−1. The AC//NaFeO2 Na-ion capacitor with the stable voltage window of 2 V, can provide an energy density of 12.6 Wh kg−1 at 1 kW kg−1. Due to its inhibiting effects on HER and OER, this decoupling electrolyte strategy holds great potential for constructing high-voltage aqueous energy storage devices.

A Green Asymmetric Bicyclic Co-Solvent Molecule for High-Voltage Aqueous Lithium-Ion Batteries.

Hybridizing aqueous electrolytes with organic co-solvents can effectively expand the voltage window of aqueous electrolytes while reducing salt usage, but most reported co-solvents are usually flammable and toxic, hardly achieving compatibility between safety and electrochemical performance. Here, a new non-flammable and non-toxic low-salt-concentration (1.85 m) aqueous electrolyte is reported using the green co-solvent isosorbide dimethyl ether (IDE). Owing to its unique 3D molecular structure, IDE can form a five-membered ring structure by binding the Li ion. The steric hindrance effect from IDE weakens its solvation ability, generating anion-participated solvation structures that produce a robust and uniform LiF-rich solid electrolyte interphase layer while containing elastic IDE-derived organics. Moreover, the multiple O atoms in IDE can effectively regulate the intermolecular hydrogen bonding networks, reducing H2O molecule activity and expanding the electrochemical window. Such unique solvation structures and optimized hydrogen bonding networks enabled by IDE effectively suppress electrode/electrolyte interfacial side reactions, achieving a 4.3 V voltage window. The as-developed Li4Ti5O12(LTO)||LiMn2O4(LMO) full cell delivers outstanding cycling performance over 450 cycles at 2 C. The proposed green hybrid aqueous electrolyte provides a new pathway for developing high-voltage aqueous lithium batteries.

Acetamide-Caprolactam Deep Eutectic Solvent-Based Electrolyte for Stable Zn-Metal Batteries.

Aqueous Zn-ion batteries (AZIBs) are promising for grid-scale energy storage. However, conventional AZIBs face challenges including hydrogen evolution reaction (HER), leading to high local pH, and by-product formation on the anode. Hereby the hydrogen bonds in the aqueous electrolyte are reconstructed by using a deep eutectic co-solvent (DES) made of acetamide (H-bond donor) and caprolactam (H-bond acceptor), which effectively suppresses the reactivity of water and broadens the electrochemical voltage stability window. The coordination between Zn2+ and acetamide-caprolactam in DES-based electrolytes produces a unique solvation structure that promotes the preferential growth of Zn crystals along the (002) plane. This will inhibit the formation of Zn dendrites and ensure the uniform deposition of Zn-ions on the anode surface. In addition, it is found that this DES-based electrolyte can form a protective membrane on the anode surface, reducing the risks of Zn corrosion. Compared to conventional electrolytes, the DES-based electrolyte shows a long-term stable plating/stripping performance with a significantly improved Coulombic efficiency from 78.18% to 98.37%. It is further demonstrated that a Zn||VS2 full-cell with the DES-based electrolyte exhibits enhanced stability after 500 cycles with 85.4% capacity retention at 0.5Ag-1 .

A “Polymer‐in‐Salt” Solid Electrolyte Enabled by Fast Phase Transition Route for Stable Zn Batteries

AbstractSolid polymer electrolyte‐based batteries show great promise because of their safe operating properties, wide voltage window and suitable flexibility. However, low ionic conductivity, low cation transfer number, weak oxidation/reduction resistance and low mechanical strength limit their implementation in Zn ion batteries. Here, w e developed a “polymer‐in‐salt” Zn2+‐conductive solid electrolyte (denoted as 70% salt‐SPE) constructed by a simple and fast phase transition method. The room‐temperature ionic conductivity and the transfer number of the 70% salt‐SPE reaches 1.6 mS cm−1 and 0.78, respectively. Meanwhile, the ZnF2‐rich inorganic/organic hybrid solid electrolyte interface is formed, and the stable voltage window reaches 9.35 V. In consequence, the Zn||Zn symmetric cell continuously cycles over 700 hours at current density of 2 mA cm−2 and the Zn||Cu symmetric battery runs with Coulombic efficiency of >99%. The Zn||MnPBA full battery delivers a discharge specific capacity of 109 mAh g−1 at room temperature and 190 mAh g−1 at 60 °C. Meanwhile, impressive cyclic stability of 6000 cycles with capacity retention of 80% is achieved, which originates from the effectively optimized ion transport action and dendrite‐free Zn plating/stripping.

Glass Electrolyte Infiltrated Cathode in an All Solid State Lithium Cell

Ion conducting glasses have been known for more than half a century, but their effective application in batteries is limited. Johnson Energy Storage is demonstrating a novel all solid state lithium battery construction which utilizes a lithium ion conducting glass to transport ions from deep within a structured cathode network. The unique application of the glass electrolyte is dependent upon a networked cathode structure, infiltration of the glass into the cathode and developing a glass with both sufficient ionic transport and a large voltage stability window. The advantages provided include continuity of transport channels and large contact surfaces between the active cathode material and the glass electrolyte. Both are required for effective transport and low impedance. Cells are shown with the potential for long cycle life and stability cycling from 3.0-4.3 volts utilizing a metallic lithium anode.

Solid State Zinc and Aluminum ion batteries: Challenges and Opportunities.

Solid state zinc ion batteries (ZIBs) and aluminum ion batteries (AIBs) are deemed as promising candidates for supplying power in wearable devices due to merits of low-cost, high safety, and tunable flexibility. However, their wide-scale practical application is limited by various challenges, down to the material level. This review begins with elaboration of the root causes and their detrimental effect for four main limitations: electrode-electrolyte interface contact, electrolyte ionic conductivity, mechanical strength and electrolyte voltage stability window. Thereafter, various strategies to mitigate each of the described limitation are discussed along with future research direction perspectives. Finally, to estimate the viability of these technologies for wearable applications, economic-performance metrics are compared against Li-ion batteries.

Manipulating chaotropic anion enables lacked H-bond aqueous electrolyte for lithium-ion hybrid capacitor

Aqueous electrochemical energy storages have multiple advantages especially safety performance in the energy storage process. The high concentration aqueous electrolytes with a wide electrochemical stable voltage window (ESW) solves the key problems of aqueous electrochemical energy storages. It effectively breaks the limitation of H2O molecule decomposition to realize aqueous electrochemical energy storage with high operating voltage. However, the slow ion transport and high cost limit their application in power-type storages. Here, the lacked H-bond aqueous electrolyte (LHE) is proposed by investigating the structures and properties of aqueous electrolytes with various chaotropic anions. The LHE achieves high conductivity, low viscosity, and low cost while ensuring a wide ESW. These excellent properties originate from the OTf− effect on the solvation structure of cations and the number of H-bonds. An aqueous Li-ion hybrid capacitor (LHC) with the LHE exhibits high operating voltage of 2.5 V and high ESW utilization of 92.6 %. The aqueous cathode electrolyte interphase formed by anions on the cathode surface also achieved a long cycle life for the LHC. It has guided the development of novel electrolytes for electrochemical energy storage.

Cr-doped Na3V2(PO4)3@C enables high-capacity with V2+/V5+ reaction and stable sodium storage

Due to its abundant sodium content and low cost, sodium-ion battery (SIB) has become an effective substitute and supplement for lithium-ion batteries, which has a broad development prospect in large-scale energy storage systems. Na-super-ionic conductor (NASICON) structural materials have stable 3D skeleton structures and open Na+ transport channels, which is a very promising SIB cathode material. But in the typical NASICON material Na3V2(PO4)3 (NVP), the number of electrons involved in NVP per formula unit is less than 2 at the stable voltage window, which limits the further improvement of battery performance. In this work, we report another NASICON structured Na3V4/3Cr2/3(PO4)3@C (NVCP@C), which is obtained by Cr-doped NVP through spray drying. By taking full advantage of the voltage platforms of V5+/4+, V4+/3+, and V3+/2+ in the window of 1.5–4.4 V, NVCP@C delivered a high discharge capacity (175 mAh g–1) and durable cyclability (86% capacity retention for 2000 cycles). In-situ X-ray diffraction results demonstrate that the reversible structural evolution accompanies by solid-solution reaction and two-phase reaction mechanisms co-exist during charge/discharge processes. When coupled with Na+ pre-embedded hard carbon (HC), the assembled NVCP@C//HC full cell delivers a high capacity (105 mAh g–1) and long cycling performance (70% after 1000 cycles). This Cr-doped NVP method offers new insights into the design of high-energy NASICON-structured cathode materials.

Electrolyte Solvation Structure Design for High Voltage Zinc‐Based Hybrid Batteries

Zinc (Zn) metal anodes have enticed substantial curiosity for large‐scale energy storage owing to inherent safety, high specific and volumetric energy capacities of Zn metal anodes. However, the aqueous electrolyte traditionally employed in Zn batteries suffers severe decomposition due to the narrow voltage stability window. Herein, we introduce N‐methylformamide (NMF) as an organic solvent and modulate the solvation structure to obtain a stable organic/aqueous hybrid electrolyte for high‐voltage Zn batteries. NMF is not only extremely stable against Zn metal anodes but also reduces the free water molecule availability by creating numerous hydrogen bonds, thereby accommodating high‐voltage Zn‖LiMn2O4 batteries. The introduction of NMF prevented hydrogen evolution reaction and promoted the creation of an F‐rich solid electrolyte interphase, which in turn hampered dendrite growth on Zn anodes. The Zn‖LiMn2O4 full cells delivered a high average Coulombic efficiency of 99.7% over 400 cycles.

Quasi-solid-state supercapacitors based on wide-temperature eutectogels

Carbon-based supercapacitors possess fast charge-discharge rate, superior power density, and excellent cyclic lifespan, but it is subject to some problems, such as low operating potential window and energy density. To address these issues, a ternary deep eutectic solvent with a freezing point below −85.6 °C was firstly prepared using lithium perchlorate trihydrate and urea and then used as a reaction solvent to take part in a free radical polymerization reaction to prepare eutectogels. The optimized eutectogel showed an ionic conductivity of 20 mS cm−1 at room temperature and could be still stretched and twisted even at −40 °C. The quasi-solid-state supercapacitor composed of a eutectogel and carbon electrodes demonstrated a stable voltage window of 0–2.0 V, an energy density of 10.76 Wh kg−1 at a power density of 465 W kg−1 and excellent cycling stability with ∼105 % capacitance retention after 10,000 cycles. The flexible quasi-solid-state supercapacitors with such a eutectogel not only could be operated from −40 to 60 °C, but also exhibited a moderate bendability. Moreover, the damaged flexible quasi-solid-state supercapacitor could be still charged and drive a mini-fan for ⁓60 s. Therefore, the eutectogels displayed a promising potential for enhancing the energy density of carbon-based supercapacitors and should also provide instructive guidance for the preparation of wide-temperature gel polymer electrolytes.

Construction of thickness-controllable bimetallic sulfides/reduced graphene oxide as a binder-free positive electrode for hybrid supercapacitors.

Devices for electrochemical energy storage with exceptional capacitance and rate performance, outstanding energy density, simple fabrication, long-term stability, and remarkable reversibility have always been in high demand. Herein, a high-performance binder-free electrode (3D NiCuS/rGO) was fabricated as a supercapacitor by a simple electrodeposition process on a Ni foam (NF) surface. The thickness of the deposited materials on the NF surface was adjusted by applying a low cycle number of cyclic voltammetry (5 cycles) which produced a thin layer and thus enabled the easier penetration of electrolytes to promote electron and charge transfer. The NiCuS was anchored by graphene layers producing nicely integrated materials leading to a higher electroconductivity and a larger surface area electrode. The as-fabricated electrode displayed a high specific capacitance (2211.029 F g-1 at 5 mV s-1). The NiCuS/rGO/NF//active carbon device can achieve a stable voltage window of 1.5 V with a highly specific capacitance of 84.3 F g-1 at a current density of 1 A g-1. At a power density of 749 W kg-1, a satisfactory energy density of 26.3 W h kg-1 was achieved, with outstanding coulombic efficiency of 100% and an admirable life span of 96.2% after 10 000 GCD cycles suggesting the significant potential of the as-prepared materials for practical supercapacitors.

Selectivity of Electrochemical Ion Insertion into Manganese Dioxide Polymorphs

The ion insertion redox chemistry of manganese dioxide has diverse applications in energy storage, catalysis, and chemical separations. Unique properties derive from the assembly of Mn-O octahedra into polymorphic structures that can host protons and nonprotonic cations in interstitial sites. Despite many reports on individual ion-polymorph couples, much less is known about the selectivity of electrochemical ion insertion in MnO2. In this work, we use density functional theory to holistically compare the electrochemistry of AxMnO2 (where A = H+, Li+, Na+, K+, Mg2+, Ca2+, Zn2+, Al3+) in aqueous and nonaqueous electrolytes. We develop an efficient computational scheme demonstrating that Hubbard-U correction has a greater impact on calculating accurate redox energetics than choice of exchange-correlation functional. Using PBE+U, we find that for nonprotonic cations, ion selectivity depends on the oxygen coordination environments inside a polymorph. When H+ is present, however, the driving force to form hydroxyl bonds is usually stronger. In aqueous electrolytes, only three ion-polymorph pairs are thermodynamically stable within water's voltage stability window (Na+ and K+ in α-MnO2, and Li+ in λ-MnO2), with all other ion insertion being metastable. We find Al3+ may insert into the δ, R, and λ polymorphs across the full 2-electron redox of MnO2 at high voltage; however, electrolytes for multivalent ions must be designed to impede the formation of insoluble precipitates and facilitate cation desolvation. We also show that small ions coinsert with water in α-MnO2 to achieve greater coordination by oxygen, while solvation energies and kinetic effects dictate water coinsertion in δ-MnO2. Taken together, these findings explain reports of mixed ion insertion mechanisms in aqueous electrolytes and highlight promising design strategies for safe, high energy density electrochemical energy storage, desalination batteries, and electrocatalysts.

Self-foaming strategy to fabricate sunflower plate-derived porous carbon framework for high energy density supercapacitor

Herein, sunflower plate-derived nitrogen-doped porous carbon framework (SPPC) has been prepared by a one-step self-foaming and nitrogen doping strategy with sodium bicarbonate (NaHCO3) as an activator and melamine as a nitrogen source. According to the self-foaming activation and abundant nitrogen doping effect produced by the thermal decomposition of NaHCO3 and melamine, the typical SPPC-SM material exhibits a well-developed porous carbon skeleton structure, high specific surface area and high nitrogen content (8.35 wt%), which significantly enhances the electrochemical properties. The symmetrical supercapacitor constructed by the SPPC-SM and 0.5 M Na2SO4 aqueous electrolyte has a wide and stable voltage window of 2 V, high energy density of 19.18 Wh kg−1 at a power density of 100.1 W kg−1. In addition, the supercapacitor constructed by the SPPC-SM and ionic liquid (EMIMBF4) electrolyte delivers ultra-wide operating voltage of 4 V and shows the high energy density of 74.04 Wh kg−1 at the power density of 400.1 W kg−1, as well as a superior stability with capacitance retention of 87.1 % after 30,000 cycles. The green preparation of biomass-based nitrogen-doped porous carbon frameworks presented in this work provides a promising strategy for realizing wide operating voltage and high energy density supercapacitors.

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.

MnO2 nanosheets synthesized on nitrogen-doped vertically aligned carbon nanotubes as a supercapacitor electrode material

In the present study, nitrogen-doped vertically aligned carbon nanotubes (N-VACNTs) were synthesized on carbon cloth (CC) using the floating catalyst chemical vapor deposition (FCCVD) method, and MnO2 nanosheets were grown on them using the hydrothermal method to produce an N-VACNT@MnO2 nanocomposite structure. In this structure, a synergistic effect was obtained by combining N-VACNTs, which allow high electrical conductivity and fast ion transfer. In the galvanostatic charge-discharge (GCD) measurements performed separately in a three-electrode test cell using 1 M of Na2SO4 electrolyte, the specific capacitance of the N-VACNTs was found to be 53.7 F g−1 at a current density of 0.5 A g−1, and the specific capacitance of the N-VACNT@MnO2 electrode structure was found to be 497 F g−1. In addition, after 10,000 charge-discharge cycles at a current density of 10 A g−1, the N-VACNT electrode retained 99 % of its initial specific capacitance, while the N-VACNT@MnO2 electrode exhibited outstanding cyclic stability with 76 % of its initial specific capacitance. Moreover, in the as-fabricated asymmetric supercapacitor (ASC) using N-VACNTs and N-VACNTs@MnO2, the negative and positive electrodes achieved a stable voltage window of 0–1.7 V, with a specific capacitance of 59.4 F g−1 at a current density of 1 A g−1. Additionally, this ASC showed good cycling stability retaining 84 % of its specific capacitance at the end of 10,000 cycles. Therefore, this ASC structure with an energy density of 24.7 Wh kg−1 and a power density of 15.7 kW kg−1 are promising electrode materials for energy storage.