Capacitance Of Supercapacitor Research Articles

Tailored mesoporous structures of lignin-derived nano-carbons for multiple applications

This work uses a one-step KOH activation for lignin precursors to produce ultra-high mesoporous activated carbons (ACs) with an unprecedented combination of the surface area of 3207 m2 g−1 and mesopore ratio of 76%. The ACs are applied for supercapacitors (SCs) and methylene blue (MB) adsorption. The capacitance of the SCs in the three-electrode system reaches 812.3 F g−1 and demonstrates a remarkable maximum MB adsorption capacity of 1250 mg g−1. By modifying the process conditions, the mesopore ratio of ACs could be controlled from 10% to 80%. Compared with one-step activation, a two-step method produced microporous carbons with a lower surface area of 1227 m2 g−1 and a high micropore ratio of 73%. The capacitance of SCs with two-step ACs reached 228.1 F g−1 and the maximum adsorption capacity of 476.19 mg g−1 for MB adsorption. The two-step method limited the surface area but had a higher oxygen surface functionality, benefiting its electrochemical performance. A techno-economic analysis reveals that the one-step KOH activation-based process develops ACs with a minimum selling price of $7648/ton. This work demonstrates tuning the processing-structure-property-performance relationship of lignin-based ACs to make an economically viable domestic carbon source.

Vertical growth of compact and large-area MoS2 nanosheet arrays on Ti3C2Tx for efficient bifunctional electrochemical energy storage and hydrogen evolution

The developments in hydrogen evolution reaction (HER) and supercapacitor technologies for electrochemical energy storage and conversion have received considerable attention. Although MoS2 is electrochemically active for both HER and supercapacitors, limited active sites, slow ionic transport, and poor conductivity lead to its poor capacitance and electrocatalytic activity. Herein, hierarchical Ti3C2Tx/MoS2/Ti3C2Tx@CC (TMT@CC) composites were well-designed as electrodes for both HER and supercapacitors. Flexible TMT@CC electrodes with an area as large as ∼ 80 cm2 and optimal mass-loading of 17.9 mg cm−2 were achieved. The inner layer Ti3C2Tx in the composites provides ideal nucleation sites for the growth of MoS2 arrays, and the outermost Ti3C2Tx effectively anchors the vertically arrayed MoS2. The hierarchically vertical structure provides strong interfacial coupling and shortens ion diffusion paths, leading to high stability and fast ion/electron transport kinetics. Due to such a synergistic effect, the flexible binder-free TMT@CC electrodes exhibited high areal capacitance (5.06 F cm−2 at 5 mA cm−2) for supercapacitors and low overpotential (119 mV versus RHE at 10 mA cm−2) for HER catalyst. Furthermore, a high energy density of 0.125 mWh cm−2 at a power density of 1.5 mW cm−2 has been achieved from the TMT@CC-based symmetric supercapacitor. Our strategy can be expanded to other vertically arrayed hierarchical structures as electrode materials of efficient HER and supercapacitors.

Hybrids of porous NiMoO4@Reduced graphene oxide composites for asymmetric supercapacitor applications

A major factor in improving the specific capacitance of supercapacitors is the shape of NiMoO4. In general, it is important to have a morphology with a large surface area and thin electrolytic dielectric characteristic. In this study, a hydrothermal technique was used to create a reduced graphene oxide/nickel molybdate (NiMoO4/rGO) nanocomposite, which was then heated to 450 °C for annealing. Analyses using X-ray diffraction, Raman, and X-ray photoelectron spectroscopy proved that the NiMoO4/rGO nanocomposite was formed. A study using field emission scanning electron microscopy revealed that the rGO surface was embellished with rod-like NiMoO4 nanostructures that ranged in length from 1 to 5 m. The NiMoO4/rGO electrode, when used in the aqueous basic electrolyte, demonstrated remarkable electrochemical properties by obtaining a high capacity of 1516 Fg-1 at current densities of 1 Ag-1 with high degree of rate capability. More intriguingly, during the charge-discharge process, the NiMoO4/rGO electrode showed outstanding cycling stability of 95.8% after 10,000 cycles. In order to create a supercapattery with a large operating potential window of 1.8 V, NiMoO4/rGO is used as a positive electrode and activated carbon (AC) as a negative electrode. at 1 Ag-1 current density, an energy density of 48.2 Whkg-1 and a power density of 878 Wkg-1 were attained, showing tremendous promise for this material's use in supercapacitors.

Enhanced charge circuitry for indoor photovoltaic energy harvesting with fast activation and high efficiency

AbstractUsing batteries in low‐power Internet of Things (IoT) devices poses a risk of environmental pollution. Energy harvesting (EH) systems are needed to capture ambient energy and charge supercapacitors to address this issue. Indoor photovoltaic (PV) panels are a promising power source, but their weak ambient energy makes it challenging to activate IoT end nodes quickly. Here, an EH system enhanced charge circuitry with fast activation is proposed that reduces IoT end nodes activation time to less than 2 s, compared to the traditional 19.8 h, if an indoor PV panel supplying 28 µA to charge a 1 F capacity supercapacitor from 0 to 2 V. This system also offers high‐efficiency charging, enabling supercapacitors to replace batteries, particularly when charging from 0 to 1.2 V, with a charge time improvement ratio of 64%. These breakthroughs address long‐standing challenges in IoT power systems and reduce environmental pollution.

Facile synthesis strategy for phthalocyanine-titanium dioxide/multi-walled carbon nanotube/poly(3,4-ethylenedioxythiophene) ternary composite electrodes via one-step electrochemical method for supercapacitor applications

Recent advances in the construction of ternary composite electrodes have revealed new strategies for energy storage applications. For energy storage applications, supercapacitors have attracted significant attention owing to their fascinating electrochemical performance and combining advantages. In this study, a facile and one-step electrochemical method was used for synthesis of metallo phthalocyanine-titanium dioxide/functionalized-multiwalled carbon nanotube/poly(3,4-ethylenedioxythiophene) ternary composite on pencil graphite electrode (MPc-TiO2/f-MWCNT/PEDOT/PGE) with high specific capacitance and long cycle life for supercapacitors. In this context, ZnPc-TiO2/f-MWCNT/PEDOT/PGE and NiPc-TiO2/f-MWCNT/PEDOT/PGE materials were produced by cyclic voltammetry method for the first time in the literature. The results of this study have revealed that multiwalled carbon nanotube/poly(3,4-ethylenedioxythiophene) when functionalized with metallo phthalocyanine-titanium dioxide shows higher specific capacitance than multiwalled carbon nanotube/poly(3,4-ethylenedioxythiophene) forms. Among the modified electrodes containing ternary composite, ZnPc-TiO2/f-MWCNT/PEDOT/PGE electrode showed highest specific capacitance (395.98 F.g−1) value. Additionally, both ZnPc-TiO2/f-MWCNT/PEDOT/PGE and NiPc-TiO2/f-MWCNT/PEDOT/PGE have long-cycle life and have highly maintained their capacitance after 1000 charge/discharge cycles. The developed simple and efficient strategy in this work is the first report on the electrochemical synthesis of MPc-TiO2/f-MWCNT/PEDOT, which opens up new perspective for synthesizing electrode materials for energy storage applications.

Fabrication of hydrophilic porous carbon from polyvinylidene chloride-resin via synergetic activation of ZnO and tetrahydrofuran for aqueous supercapacitors

For high capacitance, aqueous supercapacitors use large-area porous carbon electrode based on the charging principle of ion adsorption. Nonpolar hydrophobic carbon prevents ion adsorption, limiting the exploitation of porous surfaces. A carbon synthesis method was developed from pyrolysis of a polyvinylidene chloride-resin precursor and excess ZnO to derive a highly porous structure with a high surface area. Ion adsorption is limited by the small, newly formed pores. Added tetrahydrofuran expands the reaction region between the precursor and etchant during pyrolysis by dissolving the precursor. Moreover, tetrahydrofuran activates oxygen in the precursor and ZnO during pyrolysis, forming hydrophilic phenol and carboxylic acid. The hydrophilicity and pore expansion induced during pyrolysis convert the extra surface area into active charging sites. Hydrophilic carbon with enlarged pores increases the specific capacitance by 5.7 times to 126 F g−1 (at 5 mV s−1) and the rate capability by 2.7 times to 62% (50 mV s−1 vs. 5 mV s−1) in neutral K2SO4 solution compared to carbon made from polyvinylidene chloride-resin. Notably, the synthesized functional groups yielded a high capacitance of 243 F g−1 based on the faradaic charging in the KOH electrolyte. Hydrophilic carbon originating from polyvinylidene chloride-resin can be a potential electrode with a high capacitance for aqueous supercapacitors.

The effect of phosphorus and nitrogen dopants on structural, microstructural, and electrochemical characteristics of 3D reduced graphene oxide as an efficient supercapacitor electrode material

Supercapacitors are environmentally friendly and safe energy storage devices for diverse applications. The electrode material's structural, microstructural, and electrochemical properties are crucial determinants of supercapacitor capacity. One effective method to improve electrode performance is introducing doping heteroatoms or synthesizing composite materials. In this study, three-dimensional reduced graphene oxide (3D rGO) doped with Phosphorus, Nitrogen, or both (N/P co-doped) was synthesized for high-efficiency, supercapacitors using a facile, fast, and cost-effective hydrothermal process. The hydrothermal reduction of graphene oxide involved substituting Phosphorus and Nitrogen elements with carbon atoms. Moreover, the effect of dopants on structural and microstructural characteristics of 3D rGO was evaluated using different techniques, and the electrochemical characteristics were evaluated by cyclic voltammetric (CV) analysis, galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS). The specific capacitance of 3DN/PrGO on Ni foam reached 648 F g−1 at 1 Ag−1, in a voltage range of −0.6 –0.6 V (vs. Ag/AgCl), using 6 M KOH as the electrolyte. High energy density and power density of 6.1 wh/kg and 513 w/kg were obtained, respectively. The stability test was also conducted, and appropriate stability over 100 charging and discharging cycles was observed. The considerable performances are mainly due to the combined effect of pseudocapacitive properties of Nitrogen and Phosphorus dopants, improved wettability, and the porous structure of 3D rGO, which provides suitable electroactive sites and simplifies the electron/ion transfer for the electrochemical reactions.

Valorization of Biomass-Derived Polymers to Functional Biochar Materials for Supercapacitor Applications via Pyrolysis: Advances and Perspectives.

Polymers from biomass waste including plant/forest waste, biological industrial process waste, municipal solid waste, algae, and livestock are potential sources for renewable and sustainable resources. Converting biomass-derived polymers to functional biochar materials via pyrolysis is a mature and promising approach as these products can be widely utilized in many areas such as carbon sequestration, power production, environmental remediation, and energy storage. With abundant sources, low cost, and special features, the biochar derived from biological polymeric substances exhibits great potential to be an alternative electrode material of high-performance supercapacitors. To extend this scope of application, synthesis of high-quality biochar will be a key issue. This work systematically reviews the char formation mechanisms and technologies from polymeric substances in biomass waste and introduces energy storage mechanisms of supercapacitors to provide overall insight into the biological polymer-based char material for electrochemical energy storage. Aiming to enhance the capacitance of biochar-derived supercapacitor, recent progress in biochar modification approaches including surface activation, doping, and recombination is also summarized. This review can provide guidance for valorizing biomass waste to functional biochar materials for supercapacitor to meet future needs.

Fabrication of High-Performance Asymmetric Supercapacitors Using Rice Husk-Activated Carbon and MnFe2O4 Nanostructures

To meet the growing demand for efficient and sustainable power sources, it is crucial to develop high-performance energy storage systems. Additionally, they should be cost-effective and able to operate without any detrimental environmental side effects. In this study, rice husk-activated carbon (RHAC), which is known for its abundance, low cost, and excellent electrochemical performance, was combined with MnFe2O4 nanostructures to improve the overall capacitance of asymmetric supercapacitors (ASCs) and their energy density. A series of activation and carbonization steps are involved in the fabrication process for RHAC from rice husk. Furthermore, the BET surface area for RHAC was determined to be 980 m2 g−1 and superior porosities (average pore diameter of 7.2 nm) provide abundant active sites for charge storage. Additionally, MnFe2O4 nanostructures were effective pseudocapacitive electrode materials due to their combined Faradic and non-Faradic capacitances. In order to assess the electrochemical performance of ASCs extensively, several characterization techniques were employed, including galvanostatic charge –discharge, cyclic voltammetry, and electrochemical impedance spectroscopy. Comparatively, the ASC demonstrated a maximum specific capacitance of ~420 F/g at a current density of 0.5 A/g. The as-fabricated ASC possesses remarkable electrochemical characteristics, including high specific capacitance, superior rate capability, and long-term cycle stability. The developed asymmetric configuration retained 98% of its capacitance even after 12,000 cycles performed at a current density of 6A/g, demonstrating its stability and reliability for supercapacitors. The present study demonstrates the potential of synergistic combinations of RHAC and MnFe2O4 nanostructures in improving supercapacitor performance, as well as providing a sustainable method of using agricultural waste for energy storage.

Secondary utilization of jujube shell bio-waste into biomass carbon for supercapacitor electrode materials study

Currently, the final destination of waste jujube shells from the deep processing of jujubes is usually burnt or simply thrown away, which has a significant impact on the natural environment. In this work, we established a strategy for the secondary use of waste jujube shells to solve the problems above. The jujube shell biomass carbon materials were prepared by using waste jujube shell residue after extraction of essential oils as carbon source, ZnCl2 as activator, boric acid and urea as dopants. In the three-electrode system, the specific capacitance of the boron-nitrogen co-doped carbon supercapacitor is 535F/g at the current density of 1 A/g, and the capacitance retention rate is 62.8%, Moreover, the assembled symmetrical two-electrode supercapacitor in an aqueous KOH electrolyte presented considerable synergetic energy–power output properties with an energy density of 13.97 Wh/kg at a power density of 250.0 W/kg, and 5.58 Wh/kg at 2.5 kW/kg.

Nanoneedles anchored ultrathin petals of CuCo layered double hydroxide with high areal capacitance and long cycle life for high-performance hybrid supercapacitors

Nanoneedles anchored ultrathin petals of CuCo layered double hydroxide with high areal capacitance and long cycle life for high-performance hybrid supercapacitors

Preparation of photo-rechargeable asymmetric supercapacitors using S,W-codoped titania: Experimental and theoretical insights

Photo-assisted charging has been shown to be a sustainable, highly efficient, cheap, and environmentally benign method for the successful enhancement of the capacitance of supercapacitors with low cost and good efficiency. Despite being promising supercapacitor electrode compounds, TiO2 nanotubes (TN) have poor electronic conductivity, which restricts their practical applications. Sulfur doped, tungsten doped and different S,W-codoped TN were prepared and applied as electrodes for supercapacitors with photo-assisted charging. A high average specific capacitance of 179 mF/cm2 at a 0.4 mA/cm2 current density, which is about 5 times the corresponding value for the pristine TN electrodes, is shown by codoped TN electrodes. To explain, the improvement of the capacitance of the fabricated doped and co-doped TN compared to the un-doped TNs, the density functional theory (DFT) calculations were employed. The higher capacitance of the doped and co-doped TNs compared to un-doped TiO2, was attributed to the presence of the occupied and unoccupied molecular orbitals which are related only to the doped elements (S and W) or have the contribution from both doped elements and TiO2 part of the nanotubes. The contribution of these molecular orbitals in the electron excitation due to the light illumination decreases the rate of the electron-hole recombination in the doped TN compared to un-doped TN. A photo-rechargeable SW(75:25)TN//polypyrrole/FTO structure asymmetric supercapacitor (ASC) device has also been fabricated, in which TN are used as the active material to provide direct charging by light in the absence of any external photovoltaic devices. This yields a high specific capacitance of 31 mF/cm2 at a 0.23 mA/cm2 current density.

Poly(o-phenylenediamine)-Decorated V4C3Tx MXene/Poly(o-phenylenediamine) Blends as Electrode Materials to Boost Storage Capacity for Supercapacitors and Lithium-Ion Batteries

Two-dimensional transition-metal carbides/nitrides (MXenes), as pseudocapacitor materials, have attracted extensive attention in the field of energy storage in recent years. However, the MXene surface is prone to oxidation and their layered structure is easy to stack, which limit their practical application. Here, we propose a facile and cost-effective strategy to fabricate a blend of poly(o-phenylenediamine) (PoPD)-decorated vanadium carbide MXene (N–V4C3Tx) and PoPD as electrode materials to boost the storage capacity for supercapacitors and lithium-ion batteries. N–V4C3Tx nanosheets and PoPD nanoparticles were prepared by in situ oxidant-free polymerization and redox methods, respectively. The electrochemical performance of the blend shows that the introduction of PoPD nanoparticles can effectively improve the specific capacitance of N–V4C3Tx. The N–V4C3Tx/PoPD electrode exhibits excellent specific capacitance of up to 676.5 F g–1 at 1 A g–1 for supercapacitor application. Compared with the V4C3Tx-based device (276.3 F g–1), the capacitance reaches up to 2.48 times enhancement. In addition, the N–V4C3Tx/PoPD electrode also presents satisfactory cyclic stability, and the retention rate can remain unchanged after 10,000 cycles. As the electrode material for lithium-ion batteries, it also shows a high capacity of 561.2 mA h g–1 at 0.1 A g–1, excellent rate performance, and cyclic stability. Our work broadens the application of MXenes and conductive polymers as electrode materials in the field of energy storage and offers a simple and effective strategy to improve the capacity and stability of the pristine MXene.

Realizing high energy density supercapacitors assisted by light-induced charging

The increasing demand for energy storage devices has initiated research on alternative sustainable energy storage mechanisms, such as supercapacitors. Here, we report a skillful design strategy that harvests visible light energy and has immense potential applications in boosting the storage capacity of supercapacitors – one of the energy storage devices. A down-conversion phosphor layer is introduced over a reduced graphene oxide-based supercapacitor electrode having an optical window to harvest visible light. The fabricated cell exhibits an excellent areal energy density of 233 μWh/cm2 (at an areal current density of 4 mA/cm2 for the voltage ranging from 2 to 4.25 V) under optical illumination, which is 2.5 times higher than that achieved without illumination. Under light illumination, the cell operates across a high voltage range (0–4 V) and current density (40 mA/cm2) and shows a light-induced charging voltage of 354 mV, without any external bias. Thus, such exceptional supercapacitor performance generates significant possibilities for developing novel energy storage devices with high energy and power densities, through which portable devices can be charged using visible light.

Biomass Porous Carbon Derived from Celery Leaves with High Capacitance for Supercapacitor

AbstractTo develop environmentally friendly and high‐performance supercapacitors, the low‐cost, high‐capacitance renewable electrode material is at present viewed as one of the most challenging tasks for obtaining the next‐generation of energy storage devices. Therefore, in this study, Celery leaves, a common biomass vegetable, are used to prepare activated carbon for high voltage and high‐capacity supercapacitors through a simple method. Due to their high surface area and abundant nitrogen and sulfur heteroatoms, hierarchically porous carbon materials can simultaneously realize high capacity and long‐cycling durability. The specific capacitance has been recorded to be up to 753.0 F g−1 at 0.5 A g−1 with capacity retention as high as 96.7 % even after 5,000 cycles. Also, the assembled symmetric cell provided a high energy density of 17.36 Wh kg−1 at 250 W kg−1. The effects of yellow and green colors and different activation temperatures on the properties of electrode materials were systematically studied. The results showed an excellent electrochemical performance in biomass carbon electrode materials, which would facilitate the development of a high‐quality energy system and a green supercapacitor.

Fabrication of 3D bi-functional binder-free electrode by hydrothermal growth of MIL-101(Fe) framework on nickel foam: A supersensitive electrochemical sensor and highly stable supercapacitor

In present investigation, we report unique and successful fabrication of 3D bi-functional binder free electrode by hydrothermal growth of Fe based metal organic frameworks on nickel foam (MIL-101(Fe)/NF) for supersensitive electrochemical sensor and high capacitance supercapacitor. The materials characteristics were investigated by XRD, FTIR, RAMAN, FE-SEM, and BET techniques. The FE-SEM results revealed the formation of octahedral spindles nanosheets of MIL-101(Fe) fully covered on the nickel foam. In applications involving an electrochemical sensor or a supercapacitor, the binder-free MIL-101(Fe)/NF electrode provided excellent results by modestly avoiding dead mass of binders. The determination capability of MIL-101(Fe)/NF electrode as an electrochemical sensor of lead (Pb2+) ions has been investigated by differential pulse voltammetry (DPV) technique. According to the findings, the MIL-101(Fe)/NF exhibits excellent sensing performance towards Pb2+ ions with low detection limit of 0.169 nM and high sensitivity of 22.6 µA/M. Moreover, the electrode exhibits ideal sensor characteristics such as good selectivity, reproducibility, repeatability and stability. In addition, the structure of MIL-101(Fe)/NF electrode provides elevated electro-active sites, which altogether provides shorter path for electron passage and electrolyte diffusion process, which resulted in a high specific capacitance. At a scan rate of 10 mVs−1, the MIL-101(Fe)/NF electrode exhibits a specific capacitance of 210 Fg−1. Capacitance retention of greater than 98% is demonstrated by the fabricated electrode, even after 1000 cycles. The present investigated results and novel strategies to develop multifunctional materials will open innovative avenues for material scientist.

Polypyrrole-decorated hierarchical carbon aerogel from liquefied wood enabling high energy density and capacitance supercapacitor

Carbon aerogels (CAs) from biomass have low energy density and specific capacitance due to underutilized structure, severely hindering their application in high-performance supercapacitors. Herein, we address this issue through a binary composite in which psudocapacitive polypyrrole (PPy) microparticles are in situ grown on the surfaces of hierarchical porous liquefied wood carbon aerogels (LWCA). The deposited pseudocapacitive PPy microparticles contributes to the high energy density and specific capacitance. The hierarchical structure of LWCA prevents aggregation of PPy microparticles and ensures rapid transfer of electrolyte ions. In three electrodes system, the optimized hybride capacitive LWCA-PPy-65 composite exhibites excellent capacitive performance of 421.45 F g−1 and cycle stability with 82.9% after 5000 cycles. In KOH electrolyte, the hybrid supercapacitor from LWCA-PPy-65 demonstrates a high energy density of 52.0 Wh kg−1 with a power density of 2012.8 W kg−1, and excellent cyclic performance of 92.81% retention after 5000 cycles at 5 A g−1. In H2SO4 electrolyte, the fabricated solid state supercapacitor displays prominent cyclic performance of 92.81% retention after 5000 cycles at 5 A g−1. Such three-dimensional biomass-based composite aerogels with high energy density and capacitance demonstrated a promising application prospect in energy storage devices.

An approach to unify capacitance measurements of electric double layer capacitors using sinusoidal potential scan

Measuring supercapacitor capacitance is essential to understanding their electrical characteristics. However, different techniques can provide significantly different capacitance values. This discrepancy makes it difficult to compare results and communicate new research findings, hindering the progress of supercapacitor technology, particularly electric double layer capacitors (EDLCs). Voltammetry techniques often assume an ideal capacitor, while electrochemical impedance spectroscopy (EIS) recognizes the need to model the non-ideal electrode behavior with a constant phase element (CPE). Through comparison with the responses of two commercial EDLCs, this study confirms that the time domain responses of EDLCs should be modeled with CPE rather than a pure capacitor. The derived equations are then used to examine the effects of experimental conditions and the CPE exponent on capacitance measurements in cyclic voltammetry (CV). The study shows that estimated capacitances are affected by several experimental conditions, not only the scan rate, highlighting the need for an alternative approach to unify the capacitance measured using different analytical methods and measuring techniques. Therefore, this study proposes an alternative approach to estimate the capacitance of a CPE using a sinusoidal potential scan in voltammetric measurements. This approach not only equalizes the capacitance measured using different analytical methods and measuring techniques but also significantly reduces the number of experimental parameters affecting the calculated capacitance to just the frequency (or scan rate). The findings of this study offer valuable insights into the estimation of capacitance via various methods and have potential implications for improving the performance of electrochemical devices, particularly EDLCs, in the pursuit of a clean energy future.

Modeling of capacitance for carbon-based supercapacitors using Super Learner algorithm

Due to some specifications such as high capacitance and power density, electrostatic double-layer capacitors (EDLCs) are more noticeable than other supercapacitors. Some physical and chemical properties, surface functional groups, and testing conditions affect the efficiency and in particular the capacitance of EDLCs with carbon-based electrodes. In this study, four machine learning models, including Super Learner (SL), Extremely Randomized Trees (Extra trees), Extreme learning machine (ELM), and Multivariate adaptive regression splines (MARS) were implemented to predict the EDLCs' capacitance based on different impressive properties. A large dataset was assigned to the 121 different carbonaceous electrodes collected under various conditions, including 13 physical and chemical properties: voltage window (V), specific surface area (SSA) and SSA of micropore, pore volume (PV), and micropore volume, the ratio of D-band and G-band (Id/Ig) and doping elements (inputs parameters). The results indicated that the SL model with the R2 values of 0.9781, 0.9717, and 0.9768 for training, testing, and total dataset, respectively, and the RSME value of 18.099 was the most accurate model in comparison with the others. Indeed, the sensitivity analysis results exhibited that SSA with the relevance factor of 0.323 is the most important feature in the capacitance of carbon-based electrodes, while the presence of boron, sulfur, fluorine, phosphorus doping elements and pore size can be ignored.

The impact of physicochemical features of carbon electrodes on the capacitive performance of supercapacitors: a machine learning approach

Hybrid electric vehicles and portable electronic systems use supercapacitors for energy storage owing to their fast charging/discharging rates, long life cycle, and low maintenance. Specific capacitance is regarded as one of the most important performance-related characteristics of a supercapacitor’s electrode. In the current study, Machine Learning (ML) algorithms were used to determine the impact of various physicochemical properties of carbon-based materials on the capacitive performance of electric double-layer capacitors. Published experimental datasets from 147 references (4899 data entries) were extracted and then used to train and test the ML models, to determine the relative importance of electrode material features on specific capacitance. These features include current density, pore volume, pore size, presence of defects, potential window, specific surface area, oxygen, and nitrogen content of the carbon-based electrode material. Additionally, categorical variables as the testing method, electrolyte, and carbon structure of the electrodes are considered as well. Among five applied regression models, an extreme gradient boosting model was found to best correlate those features with the capacitive performance, highlighting that the specific surface area, the presence of nitrogen doping, and the potential window are the most significant descriptors for the specific capacitance. These findings are summarized in a modular and open-source application for estimating the capacitance of supercapacitors given, as only inputs, the features of their carbon-based electrodes, the electrolyte and testing method. In perspective, this work introduces a new wide dataset of carbon electrodes for supercapacitors extracted from the experimental literature, also giving an instance of how electrochemical technology can benefit from ML models.