Low Energy Density Research Articles

Tailored Yolk-Shell Design to Silicon Microparticles via Scalable and Template-Free Synthesis for Superior Lithium Storage.

Micrometer-sized Si particles are beneficial to practical lithium-ion batteries in regard to low cost and high volumetric energy density in comparison with nanostructured Si anodes. However, both the issues of electrical contact loss and overgrowth of solid electrolyte interface for microscale Si induced by colossal volume change still remain to be addressed. Herein, a scalable and template-free method is introduced to fabricate yolk-shell structured Si anode from commercially available Si microparticles. The void is created via a one-step alkali etching process with the remaining silicon core as the yolk, and a double-walled shell is formed from simultaneous in situ growth of the conformal native oxide layer and subsequent carbon coating. In this configuration, the well-defined void spaces allow the Si core to expand without compromising structural integrity, while the double-walled shell acts as a static capsule to confine silicon fragments despite likely particle fracture. Therefore, electrical connectivity is maintained on both the particle and electrode level during deep galvanostatic cycling, and the solid-electrolyte interface is stabilized on the shell surface. Owing to the benefits of tailored design, excellent cycling stability (capacity retention of 95% after 100 cycles) and high coulombic efficiency (99.5%) are realized in a practical full-cell demonstration.

Construction of controllable multicomponent ZnO-ZnCo/MOF-PANI composites for supercapacitor applications

Supercapacitors, as new electrochemical energy storage (EES) devices, with the lower energy density seriously hinder their realization of the requirements for future high energy storage devices. Thus, It is crucial to develop straightforward and efficient approaches to address the aforementioned challenges in future EES devices. In this paper, controllable multi-component composites are designed and ZnO is used as a conductive carrier in preparing layered structured ZnO-Zn/Co-metal-organic framework-polyaniline (ZnO-Zn/Co-MOF-PANI, ZZCMP) electrode materials by solvothermal and electrodeposition methods. The abundant active sites and the high specific surface area of the MOF are used to create the conditions for the loading of PANI, while it can establish an effective ion/electron transport channel with PANI to enhance the material utilisation and the electrochemical performance of the overall material. Add to that, the advantages of flexibility and rigidity of pristine MOF are made use of to provide sufficient space during the process of long-term charging and discharging, thus facilitating resistance to the structural deformation and enhancing the mechanical stability of the material. The optimized integrated electrode ZZCMP-10 exhibits a capacitance of 458.9 F.g−1 when operated at a current density of 1 A.g−1. The asymmetric supercapacitor (ASC) is constructed with ZZCMP-10 as the positive electrode material and active carbon is used as the material for the negative electrode, which shows an energy density of 26 Wh.kg−1 at a current density of 1 A.g−1 and a retention of 75.3 % capacitance is achieved after 5000 cycles of long-term charging and discharging. This study provides a reasonable exploration for designing high-energy-density electrochemical energy storage devices.

Sodium acetate-based thermochemical energy storage with low charging temperature and enhanced power density

The electrification of heat necessitates the development of innovative domestic heat batteries to effectively balance energy demand with renewable power supply. Thermochemical heat storage systems show great promise in supporting the electrification of heating, thanks to their high thermal energy storage density and minimal thermal losses. Among these systems, salt hydrate-based thermochemical systems are particularly appealing. However, they do suffer from slow hydration kinetics in the presence of steam, which limits the achievable power density. Additionally, their relatively high dehydration temperature hinders their application in supporting heating systems. Furthermore, there are still challenges regarding the appropriate thermodynamic, physical, kinetic, chemical, and economic requirements for implementing these systems in heating applications. This study analyzes a proposal for thermochemical energy storage based on the direct hydration of sodium acetate with liquid water. The proposed scheme satisfies numerous requirements for heating applications. By directly adding liquid water to the salt, an unprecedented power density of 5.96 W/g is achieved, nearly two orders of magnitude higher than previously reported for other salt-based systems that utilize steam. Albeit the reactivity drops as a consequence of deliquescence and particle aggregation, it has been shown that this deactivation can be effectively mitigated by incorporating 10 % silica, achieving lower but stable energy and power density values. Furthermore, unlike other salts studied previously, sodium acetate can be fully dehydrated at temperatures within the ideal range for electrified heating systems such as heat pumps (40 °C – 60 °C). The performance of the proposed scheme in terms of dehydration, hydration, and multicyclic behavior is determined through experimental analysis.

High energy storage performance in poly(vinylidene fluoride)-based all-organic composites via optimizing the structure of semiconductive filler

The great demand for miniaturization and lightweight energy equipment stimulates the fast development of polymer-based dielectrics with low density and easy processability. Unfortunately, the low energy density puts barriers to the development of polymer dielectrics in the new energy industry. In this work, poly(vinylidene fluoride) (PVDF)-based blending films are prepared and the energy storage properties are explored by regulating the content and structure of semiconductive polymer fillers. The experiment results show that when poly{2-((3,6,7,10,11-pentakis(hexyloxy)triphenylene-2-yl)oxy)ethyl methacrylate} (P6) filler is added, 0.25 wt%-P6/PVDF film attains the maximal discharge energy density (Ud) of 19.1 J cm−3 at 624 MV m−1. Compared with poly{2-((3,6,7,10,11-pentabutoxytriphenylen-2-yl)oxy)ethyl methacrylate} (P4) filler, the P6 filler possesses better compatibility with PVDF and creates deeper traps to suppress the carrier migration and achieve the higher breakdown strength. This research offers useful references for the design of polymer-based composites with excellent energy density through blending triphenylene semiconductive fillers.

From waste to watts: Investigating teak biomass waste for bioenergy

The appropriate use of forest biomass can support the transition to a society with clean and renewable energy. In this context, the research aimed to evaluate the waste biomass from Tectona grandis L.f. for energy purposes. Seven teak wood waste types were used, accessible from the harvesting stage to wood processing. Physical attributes (moisture and basic density) and proximate analysis (volatile materials, ashes, and fixed carbon content) were evaluated, which were used to estimate the energy attributes (higher, lower, and net heating value and energy density). It was found that most waste components had moisture content averages below 30% and did not differentiate statistically. For the basic density, values varied between 366 and 519 kg.m-3. Proximate analysis and energetic attributes of the teak wastes support its feasibility for bioenergy use, focused on trimmings and thin logs. It was concluded that teak waste has the potential for energy purposes if its specific characteristics are considered and appropriate ways of use and conversion are chosen.

Unlocking Double Redox Reaction of Metal–Organic Framework for Aqueous Zinc‐Ion Battery

AbstractMetal–organic frameworks (MOFs) show wide application as the cathode of aqueous zinc‐ion batteries (AZIBs) in the future owning to their high porosity, diverse structures, abundant species, and controllable morphology. However, the low energy density and poor cycling stability hinder the feasibility in practical application. Herein, an innovative strategy of organic/inorganic double electroactive sites is proposed and demonstrated to obtain extra capacity and enhance the energy density in a manganese‐based metal–organic framework (Mn‐MOF‐74). Simultaneously, its energy storage mechanism is systematically investigated. Moreover, profiting from the coordination effect, the Mn‐MOF‐74 features with stable structure in ZnSO4 electrolyte. Therefore, the Zn/Mn‐MOF‐74 batteries exhibit a high energy density and superior cycling stability. This work aids in the future development of MOFs in AZIBs.

Unlocking Double Redox Reaction of Metal-Organic Framework for Aqueous Zinc-Ion Battery.

Metal-organic frameworks (MOFs) show wide application as the cathode of aqueous zinc-ion batteries (AZIBs) in the future owning to their high porosity, diverse structures, abundant species, and controllable morphology. However, the low energy density and poor cycling stability hinder the feasibility in practical application. Herein, an innovative strategy of organic/inorganic double electroactive sites is proposed and demonstrated to obtain extra capacity and enhance the energy density in a manganese-based metal-organic framework (Mn-MOF-74). Simultaneously, its energy storage mechanism is systematically investigated. Moreover, profiting from the coordination effect, the Mn-MOF-74 features with stable structure in ZnSO4 electrolyte. Therefore, the Zn/Mn-MOF-74 batteries exhibit a high energy density and superior cycling stability. This work aids in the future development of MOFs in AZIBs.

Mn Cluster-Embedded N/F Co-Doped Carbon toward Mild Aqueous Supercapacitors.

Aqueous supercapacitors have occupied a significant position among various types of stationary energy storage equipment, while their widespread application is hindered by the relatively low energy density. Herein, N/F co-doped carbon materials activated by manganese clusters (NCM) are constructed by the straightforward experimental routine. Benefiting from the elevated conductivity structure at the microscopic level, the optimized NCM-0.5 electrodes exhibited a remarkable specific capacitance of 653 F g-1 at 0.4 A g-1 and exceptional cycling stability (97.39% capacity retention even after 40,000 cycles at the scanning rate of 100 mV s-1) in a neutral 5 M LiCl electrolyte. Moreover, we assembled an asymmetric device pairing with a VOx anode (NCM-0.5//VOx), which delivered a durable life span of 95% capacity retention over 30,000 cycles and an impressive energy density of 77.9 Wh kg-1. This study provides inspiration for transition metal element doping engineering in high-energy storage equipment.

Superior electric displacement and energy storage density in dielectric polymer via inserting thermoplastic polyurethane

Dielectric polymers have been broadly applied in film energy storage capacitors owing to their excellent insulating characteristics. However, low electric displacement (D) and available energy densities (Ue) of existing polymer systems restrict them for miniaturized and integration applications. Herein, thermoplastic polyurethane (TPU) is utilized as the central layer to provide high D, and poly (methyl methacrylate) (PMMA) is used as the coating layer to maintain insulating characteristics. The electric displacement difference (Dmax-Dr) value and Ue values of the all-organic composites were optimized by modifying the relative ratios of the intermediate layer TPU. Notably, the all-organic composites with optimized relative ratio (26.13 vol%) of the TPU layer exhibits the largest Dmax-Dr of 8.27 μC/cm2 at highest breakdown strength of 450 MV/m, which is 89 % higher than that of PMMA at 4.37 μC/cm2, and thus a maximum Ue of 16.23 J/cm3 is obtained, far exceeding the values for advanced polymer and their composites. This strategy provides an effective approach for the development of dielectric polymer with high energy storage capabilities.

Investigation of the microstructural evolution and mechanical properties of bimodal TiN-reinforced 316L stainless steel composite fabricated by SLM

ABSTRACT Selective Laser Melting (SLM) preparation of TiN-reinforced 316L stainless steel effectively addresses the weaknesses of 316L stainless steel in terms of strength and hardness. While ensuring the flowability of the composite powder, this study employs dual-sized TiN particles to enhance 316L stainless steel. Experimental results indicate that micrometre-sized TiN particles are embedded in the matrix, and other TiN particles dissolve and re-form into cubic TiN particles with a diameter of around 200 nm. Samples produced at high laser energy density exhibit high density, consistently above 99%. The average grain size of the austenite is refined to 2.38 μm, and the tensile samples with a 90° interlayer rotation angle and island size of 60 × 10mm2 exhibit a maximum yield strength of 661 MPa, ultimate tensile strength of 950 MPa and elongation of 35.5%. Samples with lower laser energy density demonstrate the highest microhardness, reaching 365 HV. The corrosion resistance of samples with different scanning strategies is similar to pure 316L stainless steel, with the 67° interlayer rotation angle strategy showing the optimal corrosion resistance.

Investigation of the electrochemical performance of solid oxide fuel cells with methanol internal reforming

Hydrogen is a sought-after environmentally friendly energy source for the fuel of SOFC. However, it is difficult to liquefy, has low energy density, and is flammable, making it difficult to promote its use. Methanol is easy to obtain, can be stored as a liquid, and has a high hydrogen-to-carbon ratio. This makes it an ideal alternative hydrogen energy source. To assess the advantages and disadvantages of using methanol as the SOFC fuel, a comparison was made between methanol-fueled SOFC and hydrogen-fueled SOFC. The maximum power of the hydrogen SOFC is only slightly higher than that of the methanol SOFC. The study also analyzed the effects of key influencing factors on current density, component distribution temperature, and other factors. The inlet temperature of 1173 K differs by up to 0.1 V from the activation overpotential at 1073 K. The water-to-carbon ratio has a greater impact on the performance of the fuel cell. At the inlet temperature of 800℃, the power density is 4630 W/m2 higher when the carbon-to-water ratio is 1 than when that is 4. At the fuel flow rate of 0.25 m/s, the fuel utilization rate can reach 100%. These findings are important for understanding and optimizing energy conversion systems for SOFC technologies based on internal reforming.

Advanced Lithium-sulfur batteries enabled by a flexible electrocatalytic membrane of TiO2 and SiO2 co-decorated necklace-like carbon nanofibers

Lithium-sulfur (Li-S) batteries are regarded as new energy storage systems due to their low cost and high specific energy density; however, their commercial prospects are hindered by the shuttle effect of lithium polysulfides (LiPSs). Herein, the fabricating necklace-like carbon nanofibers membrane co-decorated by TiO2 and SiO2 (TiO2@SiO2/CNF) is prepared by the electrospinning technique as an interlayer to catalyze the conversion of LiPSs in Li-S batteries. The necklace-like nanofibers provide a three-dimensional conductive network, enabling SiO2 synergy with TiO2 to accelerate the redox kinetics of LiPSs through an enhanced interfacial effect. The Li-S batteries based on TiO2@SiO2/CNF interlayers exhibit an impressive specific capacity of 658 mAh g−1 at 3.0C, and their performances are decayed only 0.05 % per cycle at 1.0C within 500cycles. Our study reveals that the shuttle effect addition of LiPSs can be significantly improved by rational structural design, thus enhancing the electrochemical performance of Li-S batteries. The synthesis of necklace-like TiO2@SiO2/CNF presents a promising strategy for designing functional interlayers for advanced Li-S batteries.

Fine-Tuning Melt Pools and Microstructures: Taming Cracks in Powder Bed Fusion—Laser Beam of a non-weldable Ni-base Superalloy

Powder Bed Fusion – Laser Beam (PBF-LB) of high γ’ strengthened Ni-base superalloys, such as CM247LC, is of great interest for high temperature applications in gas turbines. However, PBF-LB of CM247LC is challenging due to the high cracking susceptibility during PBF-LB processing (solidification cracking) and heat treatment (strain age cracking, mostly caused by residual stresses). This study focuses on understanding the impact of process parameters on microstructure, residual stresses and solidification cracking. Laser power (P), speed (v) and hatch spacing (h) were varied while the layer thickness (t) was fixed. The melt pool size and shape were found to be key factors in minimizing solidification cracking. Narrower and shallower melt pools, achieved using a low line energy density (LED = P/v ≤ 0.1 J/mm), gave low crack densities (0.7 mm/mm2). A tight hatch spacing (h = 0.03 mm) resulted in reduced lack of fusion porosity. Electron backscatter diffraction investigations revealed that parameters giving finer microstructure with 〈100〉 crystallographic texture had low crack densities provided they were processed with a low LED. Atom probe tomography elucidated early stages of spinodal decomposition in the as-built condition, where Cr and Al cluster separately. The extent of spinodal decomposition was found to be affected by the LED and the hatch spacing. Samples with low LED and small hatch spacing showed higher degrees of spinodal decomposition. X-ray diffraction residual stress investigations revealed that the residual stress is proportional to the volumetric energy density (VED = P/(v. h. t)). Although low residual stresses can be achieved by using low VED, there is a high risk of lack of fusion. Hence, other parameters such as modified scan strategy, build plate pre-heating and pulsed laser mode, must be further explored to minimize the residual stresses to reduce the strain age cracking susceptibility.

Building Stable Solid-State Potassium Metal Batteries.

Solid-state potassium metal batteries (SPMBs) are promising candidates for the next generation of energy storage systems for their low cost, safety, and high energy density. However, full SPMBs are not yet reported due to the K dendrites, interfacial incompatibility, and limited availability of suitable solid-state electrolytes. Here, stable SPMBs using a new iodinated solid polymer electrolyte (ISPE) are presented. The functional ions reconstruct ion transport channels, providing efficient potassium ion transport. ISPE shows a combination of high ionic conductivity, superior interfacial compatibility, and electrochemical stability. In situ alloying and iodinated interlayer increase K metal compatibility for prolonged cycling with low polarization. Moreover, the ISPE enables SPMBs with Prussian blue cathode stable operation at a high voltage of 4.5V, a superior rate capability, and long-term cycling over 3000 cycles (4.2V vs K+/K) with an ultra-high coulombic efficiency of 99.94%. More importantly, a classic solid-state potassium metal pouch cell achieves 4.2V stable cycling over 800 cycles with a high retention of 93.6%, presenting a new development strategy for secure and high-performance rechargeable solid-state potassium metal batteries.

Composite of CoS1.97 nanoparticles decorated CuS hollow cubes with rGO as thin film electrode for high-performance all solid flexible supercapacitors

Stretchable flexible thin-film electrodes are extensively explored for developing new wearable energy storage devices. However, traditional carbon-based materials used in such independent electrodes have limited practical applications owing to their low energy storage capacity and energy density. To address this, a unique structure and remarkable mechanical stability thin-film flexible positive electrode comprising CoS1.97 nanoparticles decorated hollow CuS cubes and reduced graphene oxide (rGO), hereinafter referred to as CCSrGO, is prepared. Transition metal sulfide CoS1.97 and CuS shows high energy density owing to the synergistic effects of its active components. The electrode can simultaneously meet the high-energy density and safety requirements of new wearable energy storage devices. The electrode has excellent electrochemical performance (1380 F/g at 1 A/g) and ideal capacitance retention (93.8 % after 10,000 cycles) owing to its unique three-dimensional hollow structure and polymetallic synergies between copper and cobalt elements, which are attributed to their different energy storage mechanisms. Furthermore, a flexible asymmetric supercapacitor (FASC) was constructed using CCSrGO as the positive electrode and rGO as the negative electrode (CCSrGO//rGO), which delivers an energy density of 100 Wh kg−1 and a corresponding power density of 2663 W kg−1 within a voltage window of 0–1.5 V. The resulting FASC can power a light-emitting diode (LED) at different bending and twisting angles, exerting little effect on the capacitance. Therefore, the prepared CCSrGO//rGO FASC devices show great application prospects in energy storage.

Preparation and comparison of polyaniline composites with lotus leaf-derived carbon and lotus petiole-derived carbon for supercapacitor applications

Biomass carbon is a class of economical and sustainable materials for supercapacitor electrode materials, while the low energy density restricts its development. Herein, lotus leaf-derived carbon (LLDC) and lotus petiole-derived carbon (LPDC) were prepared via carbonization and KOH activation processes. Then LLDC and LPDC were further modified with polyaniline to synthesize the polyaniline@lotus leaf-derived carbon (PANI@LLDC) and polyaniline@lotus petiole-derived carbon (PANI@LPDC) composites by the in-situ polymerization approach. The synthesized PANI@LPDC exhibited an ultra-large specific capacitance of 1332.5 F·g−1 at 0.3 A·g−1 and outstanding electrochemical stability of 89.2 % after 5000 cycles in the KI active electrolyte (1 M H2SO4 + 0.05 M KI), showing better electrochemical performance than PANI@LLDC (1190.3 F·g−1 at 0.3 A·g−1; 87.1 % after 5000 cycles). This is mainly due to the natural tubular structure of LPDC being more conducive to the movement of electrons, the introduction of Faradic capacitance by PANI and KI, and the porous structure of LPDC providing enough space for performing redox reactions. Moreover, a symmetric supercapacitor device assembled with two PANI@LPDC electrodes showed a superb energy density of 75.7 Wh·kg−1 at the power density of 540 W·kg−1. This study provides guidance for selecting different parts of biomass to prepare high-performance supercapacitor electrode materials.

Enhancing energy storage performance of polyethylene via passivation with oxygen atoms through C–H vacancy carbonylation

Low energy density of polymer film capacitors is regarded as one of the most serious drawbacks facing growing demands for equipment integration and miniaturization. Herein, ultraviolet light and ozone (UVO) surface modification is utilized to simultaneously improve dielectric constant and breakdown strength of polyethylene (PE) films. As a result, after 3 min of UVO treatment, an enhanced recoverable energy density of 4.79 J/cm3 with a charge-discharge efficiency of >95% is obtained under 650 MV/m at room temperature (RT). Significantly, stable energy storage performance under 200 MV/m is maintained throughout a broad temperature range from −90 °C to 90 °C and during 20,000 cycles of charge-discharge procedures. According to first-principles calculations and thermally stimulated depolarization current measurements, formation of carbonyl groups (C=O) after UVO treatment could effectively passivate initial deep-level defect states caused by H vacancies, which explains the improvement in capacitive energy storage. Moreover, the metalized UVO-modified PE exhibits valuable breakdown self-clearing ability, and the self-cleared specimen maintains stable energy storage performance over 20,000 cycles at 200 MV/m and RT. This work offers an effective and user-friendly method for enhancing comprehensive dielectric characteristics of PE-based materials and potential for applications in modern power systems and electronic devices.

Chitosan as a suitable host for sustainable plasticized nanocomposite sodium ion conducting polymer electrolyte in EDLC applications: Structural, ion transport and electrochemical studies

The challenge in front of EDLC device is their low energy density compared to their battery counter parts. In the current study, a green plasticized nanocomposite sodium ion conducting polymer blend electrolytes (PNSPBE) was developed by incorporating plasticized Chitosan (CS) blended with polyvinyl alcohol (PVA), doped with NaBr salt with various concentration of CaTiO3 nanoparticles. The most optimized PNSPBE film was subsequently utilized in an EDLC device to evaluate its effectiveness both as an electrolyte and a separator. Structural and morphological changes were assessed using XRD and SEM techniques. The PNSPBE film demonstrated a peak ionic conductivity of 9.76×10−5 S/cm, as determined through EIS analysis. The dielectric and AC studies provided further confirmation of structural modifications within the sample. Both TNM and LSV analyses affirmed the suitability of the prepared electrolyte for energy device applications, evidenced by its adequate ion transference number and an electrochemical potential window of 2.86 V. Electrochemical properties were assessed via CV and GCD techniques, confirming non-Faradaic ion storage, indicated by the rectangular CV pattern at low scan rates. The parameters associated with the designed EDLC device including specific capacitance, ESR, power density (1950 W/kg) and energy density (12.3 Wh/kg) were determined over 1000 cycles.

Co/Al Co-Substituted Layered Manganese-Based Oxide Cathode for Stable and High-Rate Potassium-Ion Batteries.

Manganese-based layered oxides are promising cathode materials for potassium-ion batteries (PIBs) due to their low cost and high theoretical energy density. However, the Jahn-Teller effect of Mn3+ and sluggish diffusion kinetics lead to rapid electrode deterioration and a poor rate performance, greatly limiting their practical application. Here, we report a Co/Al co-substitution strategy to construct a P3-type K0.45Mn0.7Co0.2Al0.1O2 cathode material, where Co3+ and Al3+ ions occupy Mn3+ sites. This effectively suppresses the Jahn-Teller distortion and alleviates the severe phase transition during K+ intercalation/de-intercalation processes. In addition, the Co element contributes to K+ diffusion, while Al stabilizes the layer structure through strong Al-O bonds. As a result, the K0.45Mn0.7Co0.2Al0.1O2 cathode exhibits high capacities of 111 mAh g-1 and 81 mAh g-1 at 0.05 A g-1 and 1 A g-1, respectively. It also demonstrates a capacity retention of 71.6% after 500 cycles at 1 A g-1. Compared to the pristine K0.45MnO2, the K0.45Mn0.7Co0.2Al0.1O2 significantly alleviates severe phase transition, providing a more stable and effective pathway for K+ transport, as investigated by in situ X-ray diffraction. The synergistic effect of Co/Al co-substitution significantly enhances the structural stability and electrochemical performance, contributing to the development of new Mn-based cathode materials for PIBs.

Tailoring moldy-mulberry-derived carbons for ionic liquid-based supercapacitors with ultrahigh energy density

Developing low cost and renewable materials for energy storage is becoming critical for modern society. Biomass-derived porous carbons are promising candidates for constructing high-performance supercapacitors and batteries. To overcome challenges such as the low energy density of carbon, herein three-dimensional interconnected N/P/O co-doped hierarchical porous carbon is fabricated from moldy mulberry/melamine mixture, which possesses a large specific surface area, enhanced surface wettability and fast ions transportation. The thus-improved microstructural properties of N/P/O co-doped carbon boost their supercapacitive performances in aqueous and ionic liquid electrolytes, where specific capacitance of 340 F g−1 at 1.0 A g−1 in KOH solution and capacitance retention of 95.0 % after 25,000 cycles are achieved. Symmetric supercapacitors assembled with such carbon electrodes produce an energy density of 15.5 Wh kg−1 at the power density of 162.3 W kg−1 in KOH solution, and an ultrahigh energy density of 147.6 Wh kg−1 at 900 W kg−1 in EMIMBF4 electrolyte. DFT calculations illustrate that the high N/P doping enhances the electrical conductivity and promotes binding sites for EMIM+ adsorption, hence greatly boosting their supercapacitive capability. These gratifying results demonstrate the feasibility of significantly enhancing electrochemical properties of biomass-derived hierarchical porous carbons with a simple and scalable doping method.