Alkali-Etched NiCoAl-LDH with Improved Electrochemical Performance for Asymmetric Supercapacitors.

Hydrotalcite, first found in natural ores, has important applications in supercapacitors. NiCoAl-LDH, as a hydrotalcite-like compound with good crystallinity, is commonly synthesized by a hydrothermal method. Al3+ plays an important role in the crystallization of hydrotalcite and can provide stable trivalent cations, which is conducive to the formation of hydrotalcite. However, aluminum and its hydroxides are unstable in a strong alkaline electrolyte; therefore, a secondary alkali treatment is proposed in this work to produce cation vacancies. The hydrophilicity of the NiCoAl-OH surface with cation vacancy has been greatly improved, which is conducive to the wetting and infiltration of electrolyte in water-based supercapacitors. At the same time, cation vacancies generate a large number of defects as active sites for energy storage. As a result, the specific capacity of the NiCoAl-OH electrode after 10,000 cycles can be maintained at 94.1%, which is much better than the NiCoAl-LDH material of 74%.

High Durability of Fe-N-C Single-Atom Catalysts with Carbon Vacancies toward the Oxygen Reduction Reaction in Alkaline Media.

Single-atom catalysts (SACs) have attracted extensive interest to catalyze the oxygen reduction reaction (ORR) in fuel cells and metal-air batteries. However, the development of SACs with high selectivity and long-term stability is a great challenge. In this work, carbon vacancy modified Fe-N-C SACs (FeH -N-C) are practically designed and synthesized through microenvironment modulation, achieving high-efficient utilization of active sites and optimization of electronic structures. The FeH -N-C catalyst exhibits a half-wave potential (E1/2 ) of 0.91 V and sufficient durability of 100 000 voltage cycles with 29 mV E1/2 loss. Density functional theory (DFT) calculations confirm that the vacancies around metal-N4 sites can reduce the adsorption free energy of OH*, and hinder the dissolution of metal center, significantly enhancing the ORR kinetics and stability. Accordingly, FeH -N-C SACs presented a high-power density and long-term stability over 1200 h in rechargeable zinc-air batteries (ZABs). This work will not only guide for developing highly active and stable SACs through rational modulation of metal-N4 sites, but also provide an insight into the optimization of the electronic structure to boost electrocatalytical performances.

Spectroscopic Monitoring of the Electrode Process of MnO2@rGO Nanospheres and Its Application in High-Performance Flexible Micro-Supercapacitors.

Structural instability is a major obstacle to realizing the high performance of a MnO2-based pseudocapacitor material. Understanding its structure transformation in the process of electrochemical reaction, therefore, plays an important role in the efficient enhancement of rate capacity and stability. Herein, a stable MnO2@rGO core-shell nanosphere is first synthesized by a liquid-liquid interface deposition further combined with the electrostatic self-assembly method. The structural transformation process of the MnO2@rGO electrode is monitored by ex situ Raman and X-ray diffraction spectroscopy during the charging-discharging process. It is found in the first discharging process that layered-MnO2 transforms into the spinel-Mn3O4 phase with K+ ion intercalation. From the second charging, the spinel-Mn3O4 phase is gradually adjusted to a more stable λ-MnO2 with a three-dimensional tunnel structure, finally realizing the reversible intercalation/deintercalation of K+ ions in the λ-MnO2 tunnel structure during subsequent cycling, which can be attributed to the presence of oxygen vacancies formed by the lengthening of the Mn-O bond and losing oxygen in the MnO6 octahedral unit with K+ ion intercalation/deintercalation. Meanwhile, the MnO2@rGO electrode demonstrates a high specific capacitance of 378 F g-1 at 1 A g-1 and excellent cycling stability with a capacitance retention of up to 89.5% after 10 000 cycles at 10 A g-1. Furthermore, the assembled symmetric micro-supercapacitor delivers a high areal energy density of 1.01 µWh cm-2, superior cycling stability with no significant capacity decay after 8700 cycles, and a capacity retention rate of almost 100% after 2000 bending cycles, showing great mechanical flexibility and practicability.

Designing a Functional CNT+PB@MXene-Coated Separator for High-Capacity and Long-Life Lithium-Sulfur Batteries.

Separators, as indispensable parts of LSBs (lithium-sulfur batteries), play a cucial role in inhibiting dendrite growth and suppressing the shuttle of lithium polysulfide (LiPSs). Herein, we prepared a functional carbon nanotube (CNT) and Fe-based Prussian blue (PB)@MXene/polypropylene (PP) composite separator using a facile vacuum filtration approach. The CNTs and MXene nanosheets are excellent electronic conductors that can enhance the composite separator electrical conductivity, while Fe-based Prussian blue with a rich pore structure can effectively suppress the migration by providing physical space to anchor soluble LiPSs and retain it as cathode active material. Additionally, MXene nanosheets can be well attached to Fe-based Prussian blue by an electrostatic interaction and contribute to the physical barriers that inhibit the shuttle of long-chain soluble Li2Sn (4 ≤ n ≤ 8). When used as a lithium-sulfur (Li-S) cell membrane with a functional coating layer of CNT+PB@MXene facing the cathode side, the batteries reveal a high initial discharge capacity (1042.6 mAh g-1 at 0.2 C), outstanding rate capability (90% retention of capacity at 1.0 C) and high reversible capacity (674.1 mAh g-1 after 200 cycles at 1.0 V). Of note, separator modification is a feasible method to improve the electrochemical performance of LSBs.

Electrodeposited Co-W-P ternary catalyst for hydrogen evolution reaction.

In order to reduce the overpotential of hydrogen evolution reaction (HER), the ternary coating Co-W-P was deposited on the surface of the nickel foam by electrochemical deposition to obtain a highly active electrode. Based on the measured double layer capacitance (Cdl) and HER activity, there is volcanic behavior between the intrinsic activity of Co-W-P and the Co:W ratio in the electrolyte. W and P play different roles in the formation of nanoparticles, and work together to achieve the large electrochemical surface area and excellent activity. When applied to the modification of other catalysts (Ni-P and Fe-P), the higher intrinsic activity was obtained after the introduction of W.

Single-atom catalysts for high-energy rechargeable batteries.

Clean and sustainable electrochemical energy storage has attracted extensive attention. It remains a great challenge to achieve next-generation rechargeable battery systems with high energy density, good rate capability, excellent cycling stability, efficient active material utilization, and high coulombic efficiency. Many catalysts have been explored to promote electrochemical reactions during the charge and discharge process. Among reported catalysts, single-atom catalysts (SACs) have attracted extensive attention due to their maximum atom utilization efficiency, homogenous active centres, and unique reaction mechanisms. In this perspective, we summarize the recent advances of the synthesis methods for SACs and highlight the recent progress of SACs for a new generation of rechargeable batteries, including lithium/sodium metal batteries, lithium/sodium-sulfur batteries, lithium-oxygen batteries, and zinc-air batteries. The challenges and perspectives for the future development of SACs are discussed to shed light on the future research of SACs for boosting the performances of rechargeable batteries.

High Li-Ion Conductivity Artificial Interface Enabled by Li-Grafted Graphene Oxide for Stable Li Metal Pouch Cell.

The fragile electrolyte/Li interface is responsible for the long-lasting consumption of Li resources and fast failure of Li metal batteries. The polymer artificial interface with high mechanical flexibility is a promising candidate to maintain the stability of the electrolyte/Li interface; however, sluggish Li-ion transportation of the conventional polymer interface hinders the application. In this work, Li-functionalized graphene oxide (GO-ADP-Li3), which is synthesized by covalent grafting of adenosine 5'-diphosphate lithium on GO nanosheets, is used as a functional additive to improve the Li-ion conductivity of the polymer artificial interface based on PVDF-HFP/LiTFSI. The enhanced Li-ion conductivity is contributed by accelerated Li-ion hopping at the surface between polymer chains and functionalized GO as well as the reduced crystallization degree of PVDF-HFP by this novel additive. The use of this modified polymer as an artificial interface on Li foil enables highly reversible Li stripping/plating and a high capacity retention of 78.4% after 150 cycles for a 0.2 A h Li metal pouch cell (Li/NCM811, strictly following practical conditions). This Li-grafted strategy on GO sheets provides an alternative for designing a compatible electrolyte/Li interface for practical Li metal batteries.

Soft X-ray Ptychography Chemical Imaging of Degradation in a Composite Surface-Reconstructed Li-Rich Cathode.

The capability in spatially resolving the interactions between components in lithium (Li)-ion battery cathodes, especially correlating chemistry and electronic structure, is challenging but critical for a better understanding of complex degradation mechanisms for rational developments. X-ray spectro-ptychography and conventional synchrotron-based scanning transmission X-ray microscopy image stacks are the most powerful probes for studying the distribution and chemical state of cations in degraded Li-rich cathodes. Herein, we propose a chemical approach with a spatial resolution of around 5.6 nm to imaging degradation heterogeneities and interplay among components in degraded Li-rich cathodes. Through the chemical imaging reconstruction of the degraded Li-rich cathodes, fluorine (F) ions incorporated into the lattice during charging/discharging processes are proved and strongly correlate with the manganese (Mn) dissolution and oxygen loss within the secondary particles and impact the electronic structure. Otherwise, the electrode-electrolyte interphase component, scattered LiF particles (100-500 nm) along with the MnF2 layer, is also visualized between the primary particles inside the secondary particles of the degraded cathodes. The results provide direct visual evidence for the Li-rich cathode degradation mechanisms and demonstrate that the low-energy ptychography technique offers a superior approach for high-resolution battery material characterization.

Stable Electrochemical Li Plating/Stripping Behavior by Anchoring MXene Layers on Three-Dimensional Conductive Skeletons.

The ultrahigh specific capacity of lithium (Li) metal makes it possible to serve as the ultimate candidate for an anode in high-energy density secondary batteries, whereas the safety hazards caused by Li dendrite growth severely hamper the commercialization process of a lithium metal anode. Here, we propose a 3D conductive skeleton by anchoring MXene on Cu foam (MXene@CF) to significantly improve the electrochemical Li plating/stripping behavior. Li metal tends to nucleate uniformly and grow horizontally along the MXene nanosheets under the strong Coulomb interaction between adsorbed Li and MXene. Moreover, the abundant fluorine termination groups in MXene contribute to forming a stable fluorinated solid electrolyte interphase (SEI) and thus effectively regulating the Li deposition behaviors and prolonging the stability of the Li metal anode. Therefore, the MXene@CF skeleton maintains a high Coulombic efficiency (CE) of 98.5% after 200 cycles at 1 mA cm-2. The MXene@CF-based symmetric cells can run for more than 1000 h without intense voltage fluctuation and demonstrates remarkable deep charge/discharge abilities. The MXene@CF-Li|LiFePO4 full cell exhibits outstanding long-term cycling stability (95% capacity retention after 300 cycles). Our research suggests that MXene could effectively regulate the Li plating behavior that might provide a feasible solution for a dendrite-free Li anode.

Core-Shell-Structured Sulfur Cathode: Ultrathin δ-MnO2 Nanosheets as the Catalytic Conversion Shell for Lithium Polysulfides in High Sulfur Content Lithium-Sulfur Batteries.

Owing to their low cost and high theoretical energy density, lithium-sulfur (Li-S) batteries are highly promising as a contender for the post-lithium-ion battery era. However, the intrinsic low reversible conversion ability of lithium polysulfides to sulfur/Li2S during charging/discharging seriously hinders the sulfur utilization, resulting in poor cycling life of batteries. Herein, we report an improvement of core-shell-structured sulfur nanospheres@ultrathin δ-MnO2 nanosheet electrode materials prepared by a simple precipitation reaction method, in which the ultrathin δ-MnO2 nanosheets as a catalytic layer can promote the chemical adsorption of lithium polysulfides and their conversion rates to sulfur/Li2S. Using a combination of the UV-visible adsorption spectra and first-principles calculation, the results indicate that the Mn-O coordination center on the surface of the MnO2 structure plays an efficient catalytic role in the conversion reaction of lithium polysulfides to insoluble S/Li2S. The sulfur nanospheres@ultrathin δ-MnO2 nanosheet composite with a high S mass ratio of 82 wt % reveals a high specific capacity of 846 mA h g-1 at 1 C rate and good cycling stability. Moreover, the areal capacity of the electrode with a high sulfur loading mass of 10 mg cm-2 is 5.2 mA h cm-2, approaching the practical application standard at a current density of 1 mA cm-2.

In Situ Li3PO4/PVA Solid Polymer Electrolyte Protective Layer Stabilizes the Lithium Metal Anode.

A lithium metal anode is regarded as the most promising anode material for the next generation of high-energy density batteries because of its high specific capacity and low reduction potential. However, dendritic deposition and severe side reactions in continuous Li plating/stripping inevitably hinder the practical application of Li metal batteries. A solid polymer electrolyte protective layer with synergistic Li3PO4/polyvinyl alcohol (PVA) features is in situ constructed on a lithium metal anode to obtain a stable interface during charge/discharge cycles. The protective layer can adapt to volume changes and inhibit lithium dendrites. The in situ reaction guaranteed the uniformity of ion transport and a tight interface between the protective layer and the lithium metal, so that the lithium deposition behavior was effectively regulated. The PP-Li anode presented a stable Li plating/stripping for 1000 h in a symmetrical cell system and exhibited an enhanced performance of the lithium titanium oxide cell. The in situ Li3PO4/PVA solid polymer electrolyte protective layer provided a promising strategy to tackle the challenges raised by the intrinsic properties of the lithium metal anode.

Na Superionic Conductor-Type TiNb(PO4)3 Anode with High Energy Density and Long Cycle Life Enables Aqueous Alkaline-Ion Batteries.

High energy density aqueous alkaline-ion batteries have drawn significant attention because of their intrinsic high security and low cost. As suitable anode materials with satisfying capacity and proper operating potential in an aqueous electrolyte are limited, it is of urgent need to find candidate materials to build aqueous alkaline-ion batteries for practical applications. For the first time, highly crystalline Na superionic conductor-type phase TiNb(PO4)3 (TNPO) was explored as an alkali-ion intercalation host in the aqueous battery technology. The TNPO material manifests a high specific capacity of 94 mA h g-1 at 5 C rate together with superior cyclic stability and remarkable rate capacity in aqueous electrolytes, which is assigned to its super stable three-dimensional tunnel structure. Furthermore, the aqueous lithium-ion battery based on the TNPO anode and LiMn2O4 (LMO) cathode delivers a high specific energy of 121 W h kg-1 and a specific power of 189 W kg-1 with a voltage output of 2.1 V, while it exhibits excellent cycling performance (82% capacity retention after 1000 times at 5 C rate). The remarkable overall electrochemical performances of the TNPO anode have clearly suggested that TNPO can be used as a promising electrode material of aqueous alkali-ion batteries with high energy density and long cycle life for energy storage in future.

Enhanced Bifunctional Catalytic Activity of Manganese Oxide/Perovskite Hierarchical Core-Shell Materials by Adjusting the Interface for Metal-Air Batteries.

LaMnO3 perovskite is one of the most promising catalysts for oxygen reduction reaction (ORR) in metal-air batteries and can be compared to Pt/C. However, the low catalytic activity toward oxygen evolution reaction (OER) limits its practical application in rechargeable metal-air batteries. In this work, the MnO2/La0.7Sr0.3MnO3 hierarchical core-shell composite materials with a special interface structure have been designed via the selective dissolution method. The core of La0.7Sr0.3MnO3 particles is wrapped by the porous and loose MnO2 nanoparticles. The as-prepared MnO2/La0.7Sr0.3MnO3 materials have excellent catalytic activity toward ORR/OER and are used as bifunctional oxygen electrocatalysts for metal-air batteries. Based on results of transmission electron microscopy, X-ray photoelectron spectroscopy, valence-band spectroscopy, and O2 temperature-programmed desorption analysis, we conclude that the bifunctional catalytic activity of the MnO2/La0.7Sr0.3MnO3 materials can be effectively promoted due to the specific interface structure between the La1-xSrxMnO3 core and the MnO2 shell. This can be attributed to three aspects: (a) the electronic conductivity, which is beneficial for providing the faster charge-transfer paths and kinetics at the oxide/solution interface than that of the MnO2 sample; (b) the enhancement of oxygen adsorption capacity due to surface defects (oxygen vacancies) and chemical adsorption, which is helpful to improve the reaction kinetics during the process of oxygen catalysis; and (c) the tuning of oxygen adsorption ability via the moderate Mn-O bond strength, which may be conducive to getting for obtain an enhanced Mn-O bond strength on the surfaces for ORR and a weakened Mn-O bond in the lattice for OER.

Reactivating Li2 O with Nano-Sn to Achieve Ultrahigh Initial Coulombic Efficiency SiO Anodes for Li-Ion Batteries.

The application of SiO anodes in Li-ion batteries is greatly restricted by its low initial coulombic efficiency (ICE). Usually, a pre-lithiation procedure is necessary to improve the ICE, but the available technologies are associated with safety issues. Metal (M)-mixed SiO shows great promise to address these issues by reactivating Li2 O through the reaction M+Li2 O→MOx +Li+ , which is the inverse reaction to that occurring at MOx anodes. Sn is found to be a good choice of metal for this concept. Nanoscale Sn-mixed SiO composites are prepared by mechanical milling. Sn forms an outstanding conductive phase, which boosts the reaction kinetics and also reactivates the Li2 O byproduct. Sn/SiO (1:2 w/w) delivers a significant improvement in ICE from 66.5 % to 85.5 %. A higher ICE value of >90 % is obtained when the Sn content is ≥50 wt %. However, additional electrolyte decomposition occurs, which is catalyzed by Sn. In addition, coarsening of the nano-Sn material reduces the inverse conversion reactivity of Sn/Li2 O and subsequently results in rapid capacity fading. The quantitative analysis indicates that, in contrast to transition metals, the alloying and dealloying nature of Sn gives a 50 % improvement in reversible capacity, attributed to Sn/Li2 O. This work gives a general strategy to choose metals for increasing the ICE of SiOx and metal oxides.

High-Stability MnOx Nanowires@C@MnOx Nanosheet Core-Shell Heterostructure Pseudocapacitance Electrode Based on Reversible Phase Transition Mechanism.

A stable MnOx @C@MnOx core-shell heterostructure consisting of vertical MnOx nanosheets grown evenly on the surface of the MnOx @carbon nanowires are obtained by simple liquid phase method combined with thermal treatment. The hierarchical MnOx @C@MnOx heterostructure electrode possesses a high specific capacitance of 350 F g-1 and an excellent cycle performance owing to the existence of the pore structure among the ultrasmall MnOx nanoparticles and the rapid transmission of electrons between the active material and carbon coating layer. Particularly, according to the in situ Raman spectra analysis, no characteristic peaks corresponding to MnOOH are found during charging/discharging, indicating that pseudocapacitive behavior of the MnOx electrode have no relevance to the intercalation/deintercalation of protons (H+ ) in the electrolyte. Further combining in situ X-ray powder diffraction analysis, the diffraction peak of α-MnO2 can be detected in the process of charging, while Mn3 O4 phase is found in discharge products. Therefore, these results demonstrate that the MnOx undergoes a reversible phase transformation reaction of Mn3 O4 ↔α-MnO2 . Moreover, the assembled all-solid-state asymmetric supercapacitor with a MnOx @C@MnOx electrode delivers a high energy density of 23 Wh kg-1 , an acceptable power density of 2500 W kg-1 , and an excellent cyclic stability performance of 94% after 2000 cycles, showing the potential for practical application.

Datura-like Ni-HG-rGO as highly efficient electrocatalyst for hydrogen evolution reaction in alkaline conditions.

Development of highly-active and noble-metal-free electrocatalysts for hydrogen evolution reactions is a challenge, and optimizing the structure and the composition of the relative materials is critical to obtain the high-quality catalysts. Ni-based compounds are being explored as noble-metal-free electrocatalysts in hydrogen evolution reactions but the Ni-based needs to be modified effectively. In this work, we co-electrodeposited Ni nanoparticles, hydrophilic graphene and graphene oxide layers on Ni foam to synthesize Ni-HG-rGO/NF catalysts. It was presented a Datura-like shape allowing for high performance with current densities of -10 and -100 mA cm-2 for HER at overpotentials of -50 and -132 mV, a low Tafel slope of -48 mV dec-1 and excellent long-term stability in 1.0 M NaOH solution. These results demonstrate that the Ni-HG-rGO/NF electrode can be a competitive electrode materials for HER in alkaline conditions.

Mixed Lithium Oxynitride/Oxysulfide as an Interphase Protective Layer To Stabilize Lithium Anodes for High-Performance Lithium-Sulfur Batteries.

Lithium metal is strongly recognized as a promising anode material for next-generation high-energy-density systems. However, unstable solid electrolyte interphase and uncontrolled lithium dendrites growth induce severe capacity decay and short cycle life accompanied by high security risks. Here, we propose a simple method for constructing an artificial solid electrolyte interphase layer on the surface of lithium metal through spontaneous reaction, where ammonium persulfate and lithium nitrate are exploited as oxidants. The satisfactory artificial protective layer with uniform and dense morphology is composed of mixed lithium compounds, mainly including Li xSO y and Li xNO y species, which could effectively stabilize the interphase between electrolyte and lithium metal anode and restrain the "shuttle effect" of polysulfides. By employing the premodified lithium metal as anodes for lithium-sulfur batteries, the resulting cells exhibit excellent cycle stability (capacity decay of 0.09% per cycle over 300 cycles at 1 C and Coulombic efficiency of over 98%) and outstanding rate capability (850.8 mAh g-1 even at 4 C). Hence, introducing a stable artificial protective layer to protect lithium anode delivers a new strategy for solving the issues related to lithium-metal batteries.

Hierarchical Interconnected Expanded Graphitic Ribbons Embedded with Amorphous Carbon: An Advanced Carbon Nanostructure for Superior Lithium and Sodium Storage.

Carbon materials have attracted considerable attention as anodes for lithium-ion and sodium-ion batteries due to their low cost and environmental friendliness. This work reports an advanced carbon nanostructure that takes advantage of the chelation effect of glucose and metal ions, which ensures the uniform dispersion of metal in the precursor. Thus, an effective catalytic conversion from sp3 to sp2 carbon occurs, enabling simultaneously formation of pores with catalyzed graphitic structures. Due to the low carbonization temperature and short carbonization time as well as the different catalytic degree of various metals, a series of expanded graphitic layers from 0.34 to 0.44 nm with defects and amorphous carbon structure are obtained. The structure not only offers accessible graphitic spacings for reversible lithium/sodium ion insertion, but also provides abundant active sites for lithium/sodium ion adsorption in the defects and amorphous structure. Moreover, the hierarchical interconnected porous structure combining graphitic ribbons is beneficial for fast electronic/ionic transport and favorable electrolyte permeation. More importantly, such advanced carbon materials prove their feasibility for balancing the pore structure and degree of graphitization. When serving as the electrode material for lithium-ion and sodium-ion batteries, excellent electrochemical performance along with fast kinetics and long cycle life is achieved.

3D interconnected porous carbon nanosheets/carbon nanotubes as a polysulfide reservoir for high performance lithium-sulfur batteries.

Carbon materials have attracted considerable attention as the hosts for lithium-sulfur batteries, especially the 3D structural carbon matrix. Herein, novel 3D interconnected porous carbon nanosheets/carbon nanotubes (denoted as PC/CNT) as a polysulfide reservoir are synthesized by a simple one-pot pyrolysis method. In the designed hybrid carbon matrix, porous carbon nanosheets exhibit hierarchical porous structures for high sulfur loading and effectively strengthen the physical confinement to trap soluble polysulfides, while carbon nanotubes provide a highly robust conductive pathway which can facilitate electron transport and maintain structural integrity. Moreover, the 3D interconnected structure combining 1D carbon nanotubes and 2D porous carbon nanosheets is beneficial for rapid electrical/ionic transport and favorable electrolyte infiltration. As a result, the S-PC/CNT composite exhibits outstanding electrochemical performance, with a high active-sulfur utilization, high specific capacity (1485.4, 1300.3 and 1138 mA h g-1 at 0.5, 1 and 2 C, respectively), superior cycling stability (only 0.1% capacity decay per cycle over 400 cycles at 2 C) and excellent rate capability (the reversible capacity of 749 mA h g-1 even at 4 C).

Disodium citrate-assisted hydrothermal synthesis of V2O5 nanowires for high performance supercapacitors.

Orthorhombic vanadium pentoxide (V2O5) nanowires with uniform morphology were successfully fabricated via a facile hydrothermal process. The effect of disodium citrate dosage on the crystallinity, morphology and electrochemical properties of the products was analyzed. Experimental results indicate that orthorhombic V2O5 nanowires with high crystallinity and diameter of about 20 nm can be obtained at 180 °C for 24 h when the dosage of disodium citrate is 0.236 g. Furthermore, the prepared V2O5 nanowires demonstrate a high specific capacitance of 528.2 F g-1 at 0.5 A g-1 and capacitance retention of 85% after 1000 galvanostatic charge/discharge cycles at 1 A g-1 when used as supercapacitors electrode in 0.5 M K2SO4.