Galvanostatic Oxidation Research Articles

Radical Cation Salts of Hetera‐Buckybowls: Polar Crystals, Negative Thermal Expansion and Phase Transition

AbstractRadical cation salts of π‐conjugated polycycles are rich in physical properties. Herein, two kinds of hetera‐buckybowls, ethoxy‐substituted trithiasumanene (3SEt) and triselenasumanene (3SeEt), are synthesized as electron donors. Galvanostatic oxidation of them affords radical cation salts (3SEt)5(TTFMPB)3, (3SeEt)5(TTFMPB)3, (3SEt)4PMA, and (3SeEt)4PMA, where PMA is Keggin‐type phosphomolybdate and TTFMPB is tetrakis[3,5‐bis(trifluoromethyl)‐phenyl]borate. In these salts, 3SEt/3SeEt are partially charged and show distinct conformation change with the site charge and counter anions. In TTFMPB salts, (TTFMPB)− forms hexagonal channels that accommodate the packing columns of 3SEt/3SeEt. In particular, (3SEt)5(TTFMPB)3 adopts the R3c space group and is a polar crystal with the columns of 3SEt all in the up‐bowl direction. The PMA salts of 3SEt/3SeEt are polar crystals (C2 space group) with 3SEt/3SeEt being planar and forming columnar stacks. (3SeEt)4PMA shows a structural modulation below 200 K, namely, negative thermal expansion (NTE) of the unit cell volume and enlargement of the intermolecular distances between neighboring 3SeEt molecules. The four salts are semiconductors with an activation energy of 0.18–0.38 eV. The conductivity of (3SeEt)4PMA shows a reversible transition upon cooling and heating, in accordance to the NTE structural modulation. This work paves the way toward conducting materials based on hetera‐buckybowls.

Radical Cation Salts of Hetera-Buckybowls: Polar Crystals, Negative Thermal Expansion and Phase Transition.

Radical cation salts of π-conjugated polycycles are rich in physical properties. Herein, two kinds of hetera-buckybowls, ethoxy-substituted trithiasumanene (3SEt) and triselenasumanene (3SeEt), are synthesized as electron donors. Galvanostatic oxidation of them affords radical cation salts (3SEt)5 (TTFMPB)3 , (3SeEt)5 (TTFMPB)3 , (3SEt)4 PMA, and (3SeEt)4 PMA, where PMA is Keggin-type phosphomolybdate and TTFMPB is tetrakis[3,5-bis(trifluoromethyl)-phenyl]borate. In these salts, 3SEt/3SeEt are partially charged and show distinct conformation change with the site charge and counter anions. In TTFMPB salts, (TTFMPB)- forms hexagonal channels that accommodate the packing columns of 3SEt/3SeEt. In particular, (3SEt)5 (TTFMPB)3 adopts the R3c space group and is a polar crystal with the columns of 3SEt all in the up-bowl direction. The PMA salts of 3SEt/3SeEt are polar crystals (C2 space group) with 3SEt/3SeEt being planar and forming columnar stacks. (3SeEt)4 PMA shows a structural modulation below 200 K, namely, negative thermal expansion (NTE) of the unit cell volume and enlargement of the intermolecular distances between neighboring 3SeEt molecules. The four salts are semiconductors with an activation energy of 0.18-0.38 eV. The conductivity of (3SeEt)4 PMA shows a reversible transition upon cooling and heating, in accordance to the NTE structural modulation. This work paves the way toward conducting materials based on hetera-buckybowls.

Tuning the Valence of MnOx Cathodes Reveals the Universality of the Proton‐Coupled Electrodissolution/Electrodeposition Mechanism in Rechargeable Aqueous Zn Batteries

AbstractThe charge storage mechanism of manganese oxides (MnOx) in rechargeable mild aqueous Zn batteries is still a matter of debate, with no consensus on mechanism and charge carriers. In this work, this issue is addressed by relying on a quantitative and comparative electrochemical study of low‐valence crystalline MnOx cathodes in a range of aqueous electrolytes, with a primary focus on spinel Mn3O4. The results demonstrate that the oxidation state of Mn in MnOx structures as well as their degree of crystallinity have little impact on the electrochemical reactivity, all MnOx being fully converted into soluble Mn2+ upon discharge. It is further revealed that this electrodissolution mechanism is affected by Mn3O4 dismutation in the most acidic electrolytes. Accordingly, the true thermodynamics and kinetics of Mn3O4 are only accessible at mildly acidic to neutral pHs. In addition, the study confirms the phase transformation of Mn3O4 to Mn5O8 upon galvanostatic oxidation, and demonstrates that this transformation only proceeds in Mn2+‐free electrolytes, since otherwise amorphous MnO2 electrodeposits on top of Mn3O4. Finally, it is concluded that regardless of the starting MnOx material, after the first discharge or a first charge/discharge cycle, subsequent charge/discharge cycles rely on a reversible proton‐coupled electrodeposition of amorphous MnO2.

Electrochemical Flux Synthesis of Type-I Na8Si46 Clathrates: Particle Size Control Using a Solid or Molten Na–Sn Mass Transport Mediator

Sodium-filled silicon clathrates have a host of interesting properties for thermoelectric, photovoltaic, and battery applications. However, the metastability of the clathrates has made it difficult to synthesize them with the desired morphology and crystallite size. Herein, we demonstrate an electrochemical method whereby Na4Si4 dissolved in a Sn-based flux is converted to the Na8Si46 type-I clathrate using galvanostatic (constant current) oxidation. The temperature has a large influence on the products, with the reactions at 485 °C resulting in clathrates with small particle sizes (1-2 μm), while larger single crystals are obtained at 538 °C. The difference in microstructure is attributed to the solid vs liquid state of the Na-Sn phase at the reaction temperature, which is supported by the observed voltage profiles. The demonstrated method is promising for the tunable growth of Si clathrates and could be applicable to a broad range of intermetallic compounds.

Synthesis of Type II Ge and Ge-Si Alloyed Clathrates Using Solid-State Electrochemical Oxidation of Zintl Phase Precursors.

Germanium clathrates with the type II structure are open-framework materials that show promise for various applications, but the difficulty of achieving phase-pure products via traditional synthesis routes has hindered their development. Herein, we demonstrate the synthesis of type II Ge clathrates in a two-electrode electrochemical cell using Na4Ge4-ySiy (y = 0, 1) Zintl phase precursors as the working electrode, Na metal as the counter/reference electrode, and Na-ion conducting β″-alumina as the solid electrolyte. The galvanostatic oxidation of Na4Ge4 resulted in voltage plateaus around 0.34-0.40 V vs Na/Na+ with the formation of different products depending on the reaction temperature. When using Na4Ge3Si as a precursor, nearly phase-pure, alloyed type II Ge-Si clathrate was obtained at 350 °C. The Na atoms in the large (Ge,Si)28 cages of the clathrate occupied off-centered positions according to Rietveld refinement and density functional theory calculations. The results indicate that electrochemical oxidation of Zintl phase precursors is a promising pathway for synthesizing Ge clathrates with type II structure and that Si alloying of the Zintl phase precursor can promote selective clathrate product formation over other phases.

Gas free oxidation of NaCN for presodiating and stabilizing the anodic host of sodium-ion capacitors

Sodium-ion capacitors (NICs) trigger considerable attention due to their higher specific energy than electrical double-layer capacitors (EDLCs) at comparable specific power. However, the presodiation process of the anodic host is extremely crucial for the construction of high-performance NICs. Herein, a positive EDL electrode containing activated carbon (AC) mixed with sodium cyanide (NaCN) as a sacrificial material was electrochemically oxidized to presodiate a Sn4P3 anodic host buffered by hard carbon (HC). The oxidation of CN− occurred ca. 2.9 V vs. Na/Na+ and finished by a short region of linearly increasing potential with a total capacity close to the theoretical value of 547 mAh g−1. The operando electrochemical mass spectrometry (EMS) analysis of the atmosphere in the cell together with the internal pressure measurements realized during the galvanostatic oxidation of a YP80F-NaCN electrode demonstrate that the process occurs without any gas evolution. A precursor cell of an NIC was constructed in a pouch with YP80F-NaCN and HC/Sn4P3 electrodes. After the oxidative sodium transfer from NaCN to HC/Sn4P3, the realized YP80F//Nax(HC/Sn4P3) NIC demonstrated a discharge capacitance retention higher than 80% for 8900 cycles in the voltage range from 2.0 to 3.8 V. The infrared analysis of the anode obtained by the herein described transfer process detected polycyanogen, which stabilizes the electrode structure during cycling, and thereof is at the origin of the enhanced life span of the NIC.

Electrochemical Oxidative Fluorination of an Oxide Perovskite

We report the successful electrochemical intercalation of F-ions into a densely packed perovskite oxide from a liquid electrolyte at room temperature. Using galvanostatic oxidation and electrochemical impedance spectroscopy coupled with operando X-ray diffraction, we show that roughly 0.5 equivalents of F-ions can be inserted onto the vacant A-site of the perovskite ReO3. Density functional theory calculations indicate that the intercalated phase is thermodynamically unfavorable compared to other less densely packed polymorphs of ReO3F. Pairing X-ray spectroscopy, neutron total scattering measurements, and magic-angle spinning 19F NMR confirms a rapid decomposition of the product on removal from the cell but nevertheless, these results clearly demonstrate that small anions like fluoride can be intercalated into solids as readily as alkali cations at room temperature, which opens new opportunities to electrochemically fluorinate many new materials.

Общая теория анодного окисления кремния и его соединений (аналитический обзор)

The identity of the mechanisms of anodic oxide films formation on silicon, silicon carbide, and silicon nitride is proved, which can be used as the basis for the General theory of anodic oxidation of these materials. The processes of galvanostatic anodic oxidation of Si, SiC and Si3N4 in the intervals of linear dependence of the formation voltage on time proceed with activation control. The limiting stages in all cases are the anodic reactions of the formation of intermediate SiO monoxide. Preference should be given to electrolytes with lower values of the potential environmental hazard criterion of the electrolyte, which have a higher degree of environmental safety.

Similarity in the Kinetics and Mechanisms of Galvanostatic Anodic Oxidation of Silicon, Silicon Carbide, and Nitride

It is shown that the formation of anodic oxides in the galvanostatic mode of electrolytic anodizing of Si, SiC, and Si3N4 proceeds with the activation control of the process. It is suggested that the limiting stage of the oxidation process of these materials is the anodic reaction of the formation of intermediate monoxide SiO.

Fabrication of Thin Film Silver/Silver Chloride Electrodes with Finely Controlled Single Layer Silver Chloride.

This paper aims to present a protocol to form smooth and well-controlled films of silver/silver chloride (Ag/AgCl) with designated coverage on top of thin film silver electrodes. Thin film silver electrodes sized 80 µm x 80 µm and 160 µm x 160 µm were sputtered on quartz wafers with a chromium/gold (Cr/Au) layer for adhesion. After passivation, polishing and cathodic cleaning processes, the electrodes underwent galvanostatic oxidation with consideration of Faraday's Law of Electrolysis to form smooth layers of AgCl with a designated degree of coverage on top of the silver electrode. This protocol is validated by inspection of scanning electron microscope (SEM) images of the surface of the fabricated Ag/AgCl thin film electrodes, which highlights the functionality and performance of the protocol. Sub-optimally fabricated electrodes are fabricated as well for comparison. This protocol can be widely used to fabricate Ag/AgCl electrodes with specific impedance requirements (e.g., probing electrodes for impedance sensing applications like impedance flow cytometry and interdigitated electrode arrays).

Synthesis and Study of a Polypyrrole–Aluminum Oxide Nanocomposite Film on an Aluminum Surface

Using the method of electrochemical anodization, aluminum oxide porous films are obtained in a sulfuric acid solution. The morphology of the aluminum oxide surface is studied by the method of scanning electron microscopy. The high-quality elemental analysis of the initial and oxidized Al films is performed using the method of electron microprobe analysis. A protective composite polypyrrole-aluminum oxide film is produced on the aluminum surface on top of a porous aluminum oxide film in the galvanostatic oxidation mode by the electrochemical synthesis method. The properties of the polypyrrole–aluminum oxide composite film are studied by the methods of voltammetry, as well as impedance and FTIR spectroscopy.

Combined Galvanostatic and Potentiostatic Plasma Electrolytic Oxidation of Titanium in Different Concentrations of H2SO4

We report on plasma electrolytic oxidation of titanium, employing a technique with combined potentiostatic and galvanostatic control. The effect of different H 2 SO 4 electrolyte concentrations on the titanium oxide formation was studied sytematically. The titanium oxide consisted of two distinguishable layers. The upper layer is porous, up to few micrometers thick and primarily rutile, while the interlayer is compact, comparatively thin and is associated to anatase formation. The electrolyte concentration changed substantially layer thickness, porosity and phase composition, as deduced from scanning electron microscopy, X-ray diffraction and Raman spectroscopy.

Downstream analytics quantification of ion release during high-voltage anodisation of niobium

In operando quantification of field-assisted ion release during high-voltage anodisation (up to 100 V SHE) of Nb in 0.1 M sulphuric acid was performed. Electrochemical high-field oxide formation under both potential and current control was studied separately. The quantification of in situ ion release via ICP-MS revealed an increase of the oxide dissolution factor (from 337 to 422 fm V−1) when decreasing the potential scan rate from 200 to 100 mV s−1. Dissolution rates measured during galvanostatic oxide formation allowed measuring oxide dissolution factors of 719 and 837 fm V−1 for current densities of 1.0 and 0.5 mA cm−2, respectively. As compared to the potentiodynamic case, higher dissolution rates and oxide dissolution factors were measured for galvanostatic anodisation. The overall fraction of the charge used for generation of soluble Nb species was below 0.4% for all oxide growth regimes. Cross-sectional SEM imaging proofs an oxide formation factor of 2.1 nm V−1. The surface of anodised films was extremely smooth and featureless without any cracks or voids. Based on X-ray diffraction, the films were found to be amorphous, indicating that no field crystallisation is occurring under the applied oxide growth conditions even at higher voltages.Graphical abstractSchematic live immaging of Nb dissolution during anodization and its quantification via ICP-MS.

The study of electrochemical synthesis, properties and composite mechanism of PANI/PVA and PANI/PVA/Ag composite films

Purpose The purpose of this paper is to improve the conductivity and processability of polyaniline (PANI). Design/methodology/approach The study opted for synthesis of the conductive PANI/polyvinyl alcohol (PVA) composite film, co-doped with 5-sulphosalicylic acid and sulphuric acid. Using an electrochemical method, a small amount of silver (Ag) was electrodeposited on the film. The PVA/PANI and PVA/PANI/Ag composite films were characterised by scanning electron microscope, X-ray diffraction and infrared. The composite deposition mechanism of the composite film was investigated by cyclic voltammetry for the first time. Findings The conductivity of the optimum PVA/PANI composite film reached 21.2 S · cm−1.Then, a small amount of Ag was deposited on the PVA/PANI film, and the conductivity significantly increased by 1250 S · cm−1. Through appropriate degree of stretching, the conductivity of the films was enhanced. The results indicate that uniform PVA/PANI fibres and dendritic Ag can combine to form complete three-dimensional conductive networks that exhibit better conductivity and mechanical properties. The cyclic voltammetry curves reveal that the dedoping potential of PANI was more negative than the reduction potential of Ag. Therefore, the procedure for the deposition of Ag on the PANI/PVA composite film cannot decrease the conductivity. Practical implications This paper for the first time described and revealed the effective and practical synthesis approach and composite mechanism to prepare multi-types metal-conductive polymer composites and improve the conductivity of a conductive polymer with a less expense and one-step electrochemical method. Originality/value This paper first explored galvanostatic oxidation to synthesise a PANI composite film to resolve the processability and conductivity of PANI by co-doped with mixed acids and deposited Ag on film. Furthermore, for the first time, the composite mechanism of metal and conductive polymer was studied.

Electrochemical Na-Migration into Delithiated Phase LizNi1/3Mn1/3Co1/3O2: Structure and Electrochemical Properties

This work aims to investigate Na-migration into the delithiated phase LizNi1/3Mn1/3Co1/3O2 (LizNMC), which is prepared via galvanostatic oxidation from initial phase LiNi1/3Mn1/3Co1/3O2 (LiNMC). XRD patterns showed the structural conservation of the delithiated phase comparing to the origin state. In electrochemical study, a reversible 0.48 Na-migration ions per mole was observed (120 mAh/g) at rate C/10, corresponding to a partial oxidation state of Ni4+/Ni2+. The smooth charge-discharge curves indicated an essential role of inner remaining Li+ ions in the delithiated phase to prevent the drastic gliding octahedra layers during Na insertion/extraction. The cycling tests remarked the stable performances in long-term test at C/10 as well as rate capability (from C/10 to 1C). The discharge capacities were found out 100 mAh/g at C/5, 80 mAh/g at C/2 and 40 mAh/g at 1C; a capacity retention of 100% was observed after staircase. The diffusion coefficients DNa of 10−9-10−10 cm2/s obtained from GITT data suggest a high mobility of sodium ion in the delithiated phase LizNMC.

СИНТЕЗ ОКИСНЕНОЇ ФОРМИ ДИТІЄНО-ТТФ МЕТОДОМ ЕЛЕКТРОКРИСТАЛІЗАЦІЇ

General principles of the electrocrystallization technique in application to organic molecules are shown, as some historical background. Based on this, we were able to rationalize main variables in the experiment which are needed in order to get crystals of the oxidized form, that are suitable for further applications such as for example single crystal x-ray diffraction analysis or conductivity measurements. The biggest impact comes from such factors as choice of solvent and supporting electrolyte, which influence directly the solubility of both the starting compound and its oxidized form. Purity of all components is also paramount. In order to avoid formation of by-products, experiment is usually performed in a sealed U-shaped electrochemical cell with a glass filter between the anodic and cathodic compartments and under inert atmosphere such as argon or nitrogen. Other parameters considered here, such as temperature of the solution and intensity of the current, help to fine-tune the result, but have less impact on whether the crystallization will occur at all. It is also critical to maintain both parameters at constant values in order to obtain high quality single crystals. Galvanostatic oxidation mode is more favourable comparing to the potentiostatic as it allows steady rate of oxidation by providing fixed intensity of the electrical current and subsequently more stable rate of crystal grows, although potentiostatic mode or alternating current can be used to grow bigger amounts when quality of the single crystal is less important. Further we used this approach to electrocrystalize previously obtained by our group dithieno-TTF, based on the exTTF scaffold. According to the literature cyclic voltammetry data, dithieno-TTF undergoes reversible single-wave two electron oxidation to form bis-cation similar to classic exTTF, but in our case only radical-cation salt was obtained in a form of shiny, dark-red, needle-like single crystals. This could be attributed to its extremely low solubility and corresponding formation of the kinetic product, which correlate well with relatively fast crystallization just within 3 days. Another possibility is a comproportionation reaction involving the starting neutral molecule and oxidized dication.

On the Role of the Support in Pt Anode Catalyst Degradation under Simulated H2 Fuel Starvation Conditions

In order to learn more about the effect of H2 fuel starvation on the degradation of Pt anode catalysts and in particular on the role of the support therein, we have investigated the impact of a simulated fuel starvation procedure on three different polymer electrolyte fuel cell anode catalysts, Pt/C, Pt/TiO2 and Pt/TiO2+C, by differential electrochemical mass spectrometry (DEMS) measurements. Monitoring the potential as well as the mass spectrometric signal transients of the possible reaction products CO2 (carbon oxidation reaction – COR) and O2 (oxygen evolution reaction – OER) upon switching from H2-saturated to N2-saturated electrolyte under galvanostatic oxidation conditions, we find a rapid increase of the potential to values at about 1.75 V upon electrolyte exchange, together with the onset of CO2 formation and O2 evolution, where the latter dominates at high potentials. The ratio of O2 evolution and carbon support oxidation differs significantly for different catalyst supports, with the COR contributing more for the carbon-containing catalysts in the initial stage of the fuel starvation period, and the OER prevailing for the Pt/TiO2 catalyst over the whole starvation time. The complex interplay between different catalyst degradation processes during fuel starvation is discussed.

Rrde Studies of Glycerol Electro-Oxidation: Local pH Variation and Oscillatory Dynamics

Based on the fast consumption and depletion of OH- that generate considerable local pH variations from reference bulk values during anodic processes on platinum, rotating ring-disk electrode (RRDE) studies are expected to contribute in elucidating mechanisms and pH implications on kinetics. As more recently demonstrated by Feliu and co-workers[1] , significant pH variations of up to 1.5 pH units during the voltammetric electro-oxidation of ethanol in alkaline media over platinum, even under hydrodynamic conditions, were detected. Using Ptdisk-Ptring electrodes we investigated glycerol electro-oxidation in alkaline media under both conventional (Figure 1) and oscillatory conditions. All ring currents were corrected by the collection efficiency of the electrode, N, of 25.6%. Importantly, the intrinsic ohmic drop of the system might bring about distortions on the ring currents that must be taken into account in order to rule out the cross-talk of the disk and ring electrodes. Parameters such as ionic strength, distance between working and reference electrodes, and, current magnitudes in the disk require special attention in order to avoid misleading conclusions. The detection of pH variation under voltammetric conditions was done by polarizing the ring electrode at 100mV vs. RHE. The local generation of H+ is seen by the cathodic currents registered at the ring (Fig.1,bottom) whose potential is shifted to lower values due to the well-known pH dependence on the equilibrium potential (Nernstian potential). In oscillatory conditions[2] the situation is rather complicated as many soluble intermediate species are produced at the disk, introducing relevant mass-transport limitations to the oscillatory dynamics being recorded. For example, galvanostatic oxidation of glycerol is only observable in stationary conditions: rotation of the electrode modifies importantly the population of intermediates necessary to sustain oscillations. A systematic study of the effects of rotation speed and of different ring polarizations was conducted. Additionally, the interaction of platinum oxides and glycerol in alkaline media, at open circuit potential, was also followed by collection experiments with the ring polarized at different potentials. The results so far demonstrate particular features for the glycerol system unseen for other model systems, yet to be understood. Acknowledgments: A.A.Z., P.B.P. E.G.M. and H.V. acknowledge São Paulo Research Foundation (FAPESP) and Sao Paulo University Research Office for the scholarships (grants #2013-06205-3 and #2012/07313-1) and financial support (grants #2009/07629-6, #2012/21204-0, and #2013/16930-7).

The Electrochemical Behavior of Mg-Al-Zn-In-Ga Alloy as Anode Materials in Sodium Chloride Solution

The microstructures and electrochemical behavior of Mg-Al-Zn-In-Ga alloys are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), galvanostatic oxidation, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Their performances as anode for Mg-CuCl water-activated battery are also evaluated. It is found that appropriate Ga alloying (1 wt.%) could promote the electrochemical properties of Mg-Al-Zn-In alloy, but over alloying (2 wt.%) may increase the self-corrosion and decrease the discharge capability. The Mg-6% Al-3% Zn-1% In-1% Ga alloy with desirable corrosion resistance and discharge performance is a kind of promising anode materials for broadening the Mg power sources application.

Simplified Lithium-Ion Capacitors with Irreversible Lithiated Materials in the Positive Electrode

The lithium-ion capacitor (LIC) is a high energy hybrid system which combines an electrical double-layer (EDL) positive electrode made from nanoporous carbon with a negative intercalation electrode made from graphite or hard carbon [1,2]. The electrolyte is a lithium salt (LiPF6) which is generally dissolved in ethylene carbonate:dimethyl carbonate (EC:DMC) mixture. The most common concept of LIC uses an auxiliary metallic lithium electrode for graphite pre-lithiation [1,2]. Since this additional lithium electrode complicates the cell construction and might be the cause of thermal runaway during LIC operation, alternative strategies have been considered. Pre-lithiation has been proposed directly from the electrolyte [3], but it leads to a decrease of electrolyte concentration and conductivity, which might have a negative impact on the LIC power. A better strategy to lithiate the negative electrode consists in irreversible lithium de-intercalation from lithium metal oxide (Li2MoO3, Li5FeO6, Li0.65Ni1.35O2) incorporated together with activated carbon in the positive electrode [4,5]. However, for some of these oxides, the extraction potential of lithium ions exceeds 4.5 V vs. ref. Li/Li+, which causes detrimental electrochemical oxidation of the electrolyte. The first objective of this presentation is to design new materials from which high amounts of lithium can be irreversibly de-intercalated at potential lower than 4.2 V vs. Li/Li+. For example, we demonstrated that lithium can be irreversibly extracted at 3.3 V vs. Li/Li+ with a capacity of ca. 350 mAh/g during galvanostatic oxidation of the renewable organic derivative C6H3CN(OLi)2; the LIC cell based on the use of this material demonstrates an excellent cycle life in the potential range from 2.2 ~ 4.0 V. The second objective is to investigate materials with the lowest residual mass after the delithiation step. We will show that this can be achieved by selecting materials which liberate neutral gases simultaneously to lithium deintercalation. Hence, after this step, the positive electrode contains only activated carbon, leading the system to display much higher energy density. [1] N. Ando, S. Takasi, H. Taguchi, Y. Hato, Organic electrolyte capacitor, EP1400996A1 (2002) [2] T. Aida, K. Yamada and M. Morita, Electrochem. Solid-State Lett. 9 (2006) A534. [3] V. Khomenko, E. Raymundo-Piñero, F. Béguin, J. Power Sources 177 (2008) 643. [4] M.-S. Park, Y.-G. Lim, J.-H. Kim, Y.-J. Kim, J. Cho and J.-S. Kim, Adv. Energy Mater. 1 (2011) 1002. [5] P. Jeżowski, K. Fic, O. Crosnier, T. Brousse, F. Béguin, Electrochim. Acta (2016) http://dx.doi.org/10.1016/j.electacta.2015.12.034.